diff --git a/.github/workflows/_test.yml b/.github/workflows/_test.yml
index 0eddc1754..e1db65e32 100644
--- a/.github/workflows/_test.yml
+++ b/.github/workflows/_test.yml
@@ -460,7 +460,14 @@ jobs:
         run: scripts/ci/msan-lane.sh build
 
       - name: MSan suite (exclusions per scripts/msan.sh)
-        run: scripts/ci/msan-lane.sh run
+        # Reduce mmap ASLR entropy on the host first, as the TSan leg does: with
+        # the runner kernel's higher default the MSan runtime tries to re-exec
+        # itself with ADDR_NO_RANDOMIZE, which the container's seccomp profile
+        # refuses, and it aborts ("CHECK failed: msan_linux.cpp:193 ...
+        # personality") before any test runs. The container shares this kernel.
+        run: |
+          sudo sysctl -w vm.mmap_rnd_bits=28 || true
+          scripts/ci/msan-lane.sh run
 
   # macOS leak coverage. LeakSanitizer runs by default under ASan on Linux, so
   # test-unix's ubuntu legs have always had it; on macOS it is off by default
diff --git a/scripts/test-windows.ps1 b/scripts/test-windows.ps1
index 8c1a8358a..28739163d 100644
--- a/scripts/test-windows.ps1
+++ b/scripts/test-windows.ps1
@@ -18,6 +18,7 @@
                       * test_hook_augment.py      guards #618      (fixed by #619)
                       * test_ui_drive_listing.py  guards #548      (roots field)
                       * test_cli_non_ascii_arg.py guards #423/#20  (wide-argv main())
+                      * test_mcp_stdio.py         guards #654      (clean stdio stderr)
                       * test_daemon_stability.py guards the daemon parameter
                         surface, crash recovery, busy-stop refusal, and churn
                       * test_windows_update_handoff.py guards that `update`
@@ -166,6 +167,7 @@ $guards = @(
     "tests\windows\test_hook_augment.py",
     "tests\windows\test_ui_drive_listing.py",
     "tests\windows\test_cli_non_ascii_arg.py",
+    "tests\windows\test_mcp_stdio.py",
     "tests\windows\test_windows_update_handoff.py"
 )
 
diff --git a/src/cli/hook_augment.c b/src/cli/hook_augment.c
index 58e75c6d2..ac0b37eb3 100644
--- a/src/cli/hook_augment.c
+++ b/src/cli/hook_augment.c
@@ -65,8 +65,8 @@
  * Observability (#858): a fired deadline is otherwise indistinguishable from
  * "no matches", so the handler first write()s a pre-formatted breadcrumb to
  * <cache_dir>/logs/hook-augment-timeouts.log (by default
- * ~/.cache/codebase-memory-mcp/logs; fd and message prepared at arm time —
- * only async-signal-safe write/_exit in the handler). */
+ * ~/.cache/codebase-memory-mcp/logs) and to stderr (fd and message prepared at
+ * arm time — only async-signal-safe write/_exit in the handler). */
 #ifndef _WIN32
 #define HA_DEADLINE_DEFAULT_MS 2000 /* in-process budget; see ha_deadline_ms()  */
 #define HA_DEADLINE_MIN_MS 50
@@ -102,9 +102,16 @@ static size_t g_ha_crumb_len = 0;
 
 static void ha_deadline_exit(int sig) {
     (void)sig;
-    if (g_ha_crumb_fd >= 0 && g_ha_crumb_len > 0) {
-        ssize_t w = write(g_ha_crumb_fd, g_ha_crumb_msg, g_ha_crumb_len);
-        (void)w;
+    /* async-signal-safe only: write() the prepared breadcrumb to the timeouts
+     * log (when it opened) and ALWAYS to stderr, so a fired deadline is a
+     * visible event, never a silent 0-byte exit(0). */
+    if (g_ha_crumb_len > 0) {
+        if (g_ha_crumb_fd >= 0) {
+            ssize_t w = write(g_ha_crumb_fd, g_ha_crumb_msg, g_ha_crumb_len);
+            (void)w;
+        }
+        ssize_t e = write(STDERR_FILENO, g_ha_crumb_msg, g_ha_crumb_len);
+        (void)e;
     }
     _exit(0);
 }
@@ -115,6 +122,16 @@ static bool ha_fits(int written, size_t cap) {
 }
 
 static void ha_open_crumb_log(int deadline_ms) {
+    /* Pre-format the breadcrumb unconditionally: the handler may only write() a
+     * prepared buffer, and formatting it before the log path is resolved means
+     * stderr still gets the line even when the file cannot be opened (no HOME,
+     * unwritable cache dir) — the "never silent" guarantee holds regardless. */
+    int n = snprintf(g_ha_crumb_msg, sizeof(g_ha_crumb_msg),
+                     "hook-augment: deadline_exceeded ms=%d pid=%ld (raise via "
+                     "CBM_HOOK_DEADLINE_MS)\n",
+                     deadline_ms, (long)getpid());
+    g_ha_crumb_len = (n > 0 && n < (int)sizeof(g_ha_crumb_msg)) ? (size_t)n : 0;
+
     const char *override = getenv("CBM_HOOK_TIMEOUT_LOG"); /* tests + power users */
     char path[CBM_SZ_1K];
     /* A path cut off at the buffer names some other file, and O_CREAT would
@@ -136,18 +153,10 @@ static void ha_open_crumb_log(int deadline_ms) {
         cbm_mkdir_p_ex(dir, 0755, CBM_MKDIR_FOLLOW_OWNED);
     }
     /* Startup may re-arm after resolving saved settings. Keep the original
-     * diagnostic descriptor and refresh only the deadline text below. */
+     * diagnostic descriptor; the deadline text above is refreshed on every arm. */
     if (g_ha_crumb_fd < 0) {
         g_ha_crumb_fd = open(path, O_WRONLY | O_CREAT | O_APPEND, 0644);
     }
-    if (g_ha_crumb_fd < 0) {
-        return;
-    }
-    int n = snprintf(g_ha_crumb_msg, sizeof(g_ha_crumb_msg),
-                     "hook-augment: deadline_exceeded ms=%d pid=%ld (raise via "
-                     "CBM_HOOK_DEADLINE_MS)\n",
-                     deadline_ms, (long)getpid());
-    g_ha_crumb_len = (n > 0 && n < (int)sizeof(g_ha_crumb_msg)) ? (size_t)n : 0;
 }
 
 int cbm_hook_augment_deadline_ms_for_testing(void) {
diff --git a/src/daemon/frontend.c b/src/daemon/frontend.c
index e76c920b6..fa81cc06d 100644
--- a/src/daemon/frontend.c
+++ b/src/daemon/frontend.c
@@ -121,9 +121,11 @@ static atomic_uint_fast64_t frontend_test_worker_observation_count = ATOMIC_VAR_
 static atomic_uint_fast64_t frontend_test_worker_idle_count = ATOMIC_VAR_INIT(0);
 static atomic_uint_fast64_t frontend_test_routed_cancellation_count = ATOMIC_VAR_INIT(0);
 static atomic_uint_fast32_t frontend_test_replay_budget_ms = ATOMIC_VAR_INIT(0);
+static atomic_uint_fast32_t frontend_test_monitor_idle_sleep = ATOMIC_VAR_INIT(0);
 
 void cbm_daemon_frontend_test_observer_reset(bool hold_monitor) {
     atomic_store_explicit(&frontend_test_monitor_observation_count, 0, memory_order_release);
+    atomic_store_explicit(&frontend_test_monitor_idle_sleep, 0, memory_order_release);
     atomic_store_explicit(&frontend_test_worker_observation_count, 0, memory_order_release);
     atomic_store_explicit(&frontend_test_worker_idle_count, 0, memory_order_release);
     atomic_store_explicit(&frontend_test_monitor_is_waiting, false, memory_order_release);
@@ -157,6 +159,10 @@ uint64_t cbm_daemon_frontend_test_routed_cancellations(void) {
 uint32_t cbm_daemon_frontend_test_replay_timeout_ms(void) {
     return (uint32_t)atomic_load_explicit(&frontend_test_replay_budget_ms, memory_order_acquire);
 }
+
+uint32_t cbm_daemon_frontend_test_monitor_idle_sleep_ms(void) {
+    return (uint32_t)atomic_load_explicit(&frontend_test_monitor_idle_sleep, memory_order_acquire);
+}
 #endif
 
 static cbm_version_cohort_maintenance_presence_t frontend_observe_maintenance(
@@ -187,7 +193,11 @@ static void *frontend_maintenance_monitor_worker(void *opaque) {
         cbm_version_cohort_maintenance_presence_t presence =
             frontend_observe_maintenance(monitor->manager, true);
         if (presence == CBM_VERSION_COHORT_MAINTENANCE_ABSENT) {
-            cbm_usleep(FRONTEND_MAINTENANCE_IDLE_POLL_MS * 1000U);
+            uint32_t idle_ms = FRONTEND_MAINTENANCE_IDLE_POLL_MS;
+#if defined(CBM_ENABLE_TEST_SEAMS) && CBM_ENABLE_TEST_SEAMS
+            atomic_store_explicit(&frontend_test_monitor_idle_sleep, idle_ms, memory_order_release);
+#endif
+            cbm_usleep(idle_ms * 1000U);
             continue;
         }
 
diff --git a/src/daemon/frontend.h b/src/daemon/frontend.h
index 8ee33d276..4629644bb 100644
--- a/src/daemon/frontend.h
+++ b/src/daemon/frontend.h
@@ -83,6 +83,10 @@ uint64_t cbm_daemon_frontend_test_routed_cancellations(void);
  * settings requests. Recovery tests use distinct connect and startup budgets
  * and compare. */
 uint32_t cbm_daemon_frontend_test_replay_timeout_ms(void);
+/* Milliseconds the maintenance monitor last slept in its no-maintenance
+ * (ABSENT) branch, recorded from the exact value passed to the sleep; zero
+ * until the first idle cycle after reset. Pins the idle probe cadence. */
+uint32_t cbm_daemon_frontend_test_monitor_idle_sleep_ms(void);
 #endif
 
 /* Takes ownership of client and borrows cohort_manager for the complete call.
diff --git a/src/daemon/runtime.c b/src/daemon/runtime.c
index 64f6a05f4..eb2eddf70 100644
--- a/src/daemon/runtime.c
+++ b/src/daemon/runtime.c
@@ -798,6 +798,302 @@ static bool runtime_posix_stat_same_image(const struct stat *first, const struct
 
 #endif
 
+/* ── Executable-image fingerprint cache ──────────────────────────────────────
+ * The build-identity fingerprint is a SHA-256 over the entire executable
+ * (cbm_daemon_build_fingerprint_native_file), a full read of a ~300 MB image.
+ * A daemon process otherwise pays it twice for its own image at start (the
+ * supervisor's startup capture, then the runtime service's active-image check),
+ * so the digest of this process's OWN image is cached, keyed by the file
+ * identity the acquire path verifies as stable across the hash: device, inode,
+ * size, mtime and change time (on Windows FILE_BASIC_INFO.ChangeTime). A peer's
+ * image is never cached: it is hashed on every fingerprinting acquire
+ * (re-hashing of a verified peer copy is avoided separately, #1955).
+ *
+ * Limiting the cache to the own image is what makes that key sufficient. On
+ * POSIX the change time moves on every write and cannot be set back. A Windows
+ * change time can be set through SetFileInformationByHandle, but Windows keeps
+ * a running image locked against modification for as long as the process, and
+ * so this cache, exists. A rebuilt or replaced binary rolls the key and misses,
+ * so the cache never returns a stale digest and build-cohort admission keeps
+ * its exact meaning. One entry suffices: a process has one own image.
+ *
+ * The cache is process-local: a fresh process (a hook, a CLI call) still hashes
+ * its own image once. A hit does not weaken the identity proof: the acquire
+ * chain still brackets the held image with its before/after stat and
+ * process-maps checks, so the returned digest is bound to that same verified
+ * image; only the re-read of bytes whose identity is unchanged is skipped. A
+ * freshly hashed digest is committed only after that post-hash check has
+ * passed, under the identity observed after the hash, so an image that changed
+ * under the hash is never cached. */
+#if defined(_WIN32) || defined(__APPLE__) || defined(__linux__) || defined(__FreeBSD__) || \
+    defined(__NetBSD__)
+
+/* POSIX carries timespec fields; Windows stores FILETIME ticks in the seconds
+ * fields and leaves the nanoseconds fields zero. */
+typedef struct {
+    bool valid;
+    uint64_t device;
+    uint64_t inode;
+    uint64_t size;
+    int64_t mtime_seconds;
+    int64_t mtime_nanoseconds;
+    int64_t ctime_seconds;
+    int64_t ctime_nanoseconds;
+} runtime_fingerprint_key_t;
+
+/* The single entry: this process's own image. */
+static atomic_flag runtime_fingerprint_cache_lock = ATOMIC_FLAG_INIT;
+static runtime_fingerprint_key_t runtime_fingerprint_cache_key;
+static char runtime_fingerprint_cache_digest[CBM_DAEMON_BUILD_FINGERPRINT_SIZE];
+
+#ifdef CBM_ENABLE_TEST_SEAMS
+static atomic_int runtime_fingerprint_hash_call_count;
+static atomic_bool runtime_fingerprint_hash_stub_active;
+static char runtime_fingerprint_hash_stub_digest[CBM_DAEMON_BUILD_FINGERPRINT_SIZE];
+#endif
+
+static bool runtime_fingerprint_key_equal(const runtime_fingerprint_key_t *a,
+                                          const runtime_fingerprint_key_t *b) {
+    return a->valid && b->valid && a->device == b->device && a->inode == b->inode &&
+           a->size == b->size && a->mtime_seconds == b->mtime_seconds &&
+           a->mtime_nanoseconds == b->mtime_nanoseconds && a->ctime_seconds == b->ctime_seconds &&
+           a->ctime_nanoseconds == b->ctime_nanoseconds;
+}
+
+static void runtime_fingerprint_cache_enter(void) {
+    while (
+        atomic_flag_test_and_set_explicit(&runtime_fingerprint_cache_lock, memory_order_acquire)) {}
+}
+
+static void runtime_fingerprint_cache_leave(void) {
+    atomic_flag_clear_explicit(&runtime_fingerprint_cache_lock, memory_order_release);
+}
+
+static bool runtime_fingerprint_cache_lookup(const runtime_fingerprint_key_t *key,
+                                             char out[CBM_DAEMON_BUILD_FINGERPRINT_SIZE]) {
+    if (!key->valid) {
+        return false;
+    }
+    runtime_fingerprint_cache_enter();
+    bool hit = runtime_fingerprint_key_equal(&runtime_fingerprint_cache_key, key);
+    if (hit) {
+        memcpy(out, runtime_fingerprint_cache_digest, CBM_DAEMON_BUILD_FINGERPRINT_SIZE);
+    }
+    runtime_fingerprint_cache_leave();
+    return hit;
+}
+
+static void runtime_fingerprint_cache_store(
+    const runtime_fingerprint_key_t *key,
+    const char fingerprint[CBM_DAEMON_BUILD_FINGERPRINT_SIZE]) {
+    if (!key->valid || fingerprint[0] == '\0') {
+        return;
+    }
+    runtime_fingerprint_cache_enter();
+    runtime_fingerprint_cache_key = *key;
+    memcpy(runtime_fingerprint_cache_digest, fingerprint, CBM_DAEMON_BUILD_FINGERPRINT_SIZE);
+    runtime_fingerprint_cache_leave();
+}
+
+/* The single point where the expensive image hash is paid; a test seam counts
+ * calls and can substitute a stub digest so the cache's hit/miss behaviour is
+ * observable without a real full-image read. */
+static bool runtime_fingerprint_hash_native_file(uintptr_t native_file,
+                                                 char out[CBM_DAEMON_BUILD_FINGERPRINT_SIZE]) {
+#ifdef CBM_ENABLE_TEST_SEAMS
+    atomic_fetch_add_explicit(&runtime_fingerprint_hash_call_count, 1, memory_order_relaxed);
+    if (atomic_load_explicit(&runtime_fingerprint_hash_stub_active, memory_order_acquire)) {
+        memcpy(out, runtime_fingerprint_hash_stub_digest, CBM_DAEMON_BUILD_FINGERPRINT_SIZE);
+        return true;
+    }
+#endif
+    return cbm_daemon_build_fingerprint_native_file(native_file, out);
+}
+
+/* Resolve the digest for the image identity `key` of process `process_id`:
+ * from the cache when that process is this one and the cache already holds
+ * that identity, otherwise by hashing the held native image. `cached` reports
+ * which. Every acquire site resolves through here, so this is where the cache
+ * is limited to the own image: a peer's key is marked invalid, which is never
+ * looked up and never committed. A freshly hashed digest is deliberately not
+ * stored here: the acquire site commits it (runtime_fingerprint_cache_commit)
+ * only once its post-hash identity check has proven the hashed bytes belong to
+ * the identity they were keyed on. */
+static bool runtime_build_fingerprint_resolve(uintptr_t native_file, uint64_t process_id,
+                                              runtime_fingerprint_key_t *key,
+                                              char fingerprint[CBM_DAEMON_BUILD_FINGERPRINT_SIZE],
+                                              bool *cached) {
+    if (process_id != runtime_current_process_id()) {
+        key->valid = false;
+    }
+    *cached = runtime_fingerprint_cache_lookup(key, fingerprint);
+    return *cached || runtime_fingerprint_hash_native_file(native_file, fingerprint);
+}
+
+/* Commit a freshly hashed digest after the acquire chain has passed. The
+ * identity observed after the hash must equal the one the digest was resolved
+ * under; otherwise the bytes read belong to no single identity and are not
+ * cached. A cache hit has nothing to commit, and neither has a peer, whose
+ * resolved key is invalid. */
+static void runtime_fingerprint_cache_commit(
+    const runtime_fingerprint_key_t *before, const runtime_fingerprint_key_t *after, bool cached,
+    const char fingerprint[CBM_DAEMON_BUILD_FINGERPRINT_SIZE]) {
+    if (!cached && runtime_fingerprint_key_equal(before, after)) {
+        runtime_fingerprint_cache_store(after, fingerprint);
+    }
+}
+
+#ifdef _WIN32
+static int64_t runtime_fingerprint_filetime(FILETIME value) {
+    return (int64_t)(((uint64_t)value.dwHighDateTime << 32) | value.dwLowDateTime);
+}
+
+/* Key the held image by the snapshot identity the acquire path compares plus
+ * the kernel-maintained change time. An unreadable change time yields an
+ * invalid key, which never hits and is never stored: the image is simply
+ * hashed. */
+static void runtime_fingerprint_key_windows(HANDLE file,
+                                            const BY_HANDLE_FILE_INFORMATION *information,
+                                            const LARGE_INTEGER *size,
+                                            runtime_fingerprint_key_t *key) {
+    memset(key, 0, sizeof(*key));
+    FILE_BASIC_INFO basic;
+    memset(&basic, 0, sizeof(basic));
+    key->valid = information != NULL && size != NULL && size->QuadPart >= 0 &&
+                 file != INVALID_HANDLE_VALUE &&
+                 GetFileInformationByHandleEx(file, FileBasicInfo, &basic, sizeof(basic)) != 0;
+    if (key->valid) {
+        key->device = information->dwVolumeSerialNumber;
+        key->inode = ((uint64_t)information->nFileIndexHigh << 32) | information->nFileIndexLow;
+        key->size = (uint64_t)size->QuadPart;
+        key->mtime_seconds = runtime_fingerprint_filetime(information->ftLastWriteTime);
+        key->ctime_seconds = basic.ChangeTime.QuadPart;
+    }
+}
+
+static bool runtime_build_fingerprint_resolve_windows(
+    HANDLE file, uint64_t process_id, const BY_HANDLE_FILE_INFORMATION *information,
+    const LARGE_INTEGER *size, char fingerprint[CBM_DAEMON_BUILD_FINGERPRINT_SIZE],
+    runtime_fingerprint_key_t *key, bool *cached) {
+    runtime_fingerprint_key_windows(file, information, size, key);
+    return runtime_build_fingerprint_resolve((uintptr_t)file, process_id, key, fingerprint, cached);
+}
+
+static void runtime_fingerprint_cache_commit_windows(
+    HANDLE file, const BY_HANDLE_FILE_INFORMATION *information, const LARGE_INTEGER *size,
+    const runtime_fingerprint_key_t *key, bool cached,
+    const char fingerprint[CBM_DAEMON_BUILD_FINGERPRINT_SIZE]) {
+    runtime_fingerprint_key_t key_after;
+    runtime_fingerprint_key_windows(file, information, size, &key_after);
+    runtime_fingerprint_cache_commit(key, &key_after, cached, fingerprint);
+}
+#else
+static void runtime_fingerprint_key_posix(const struct stat *status,
+                                          runtime_fingerprint_key_t *key) {
+    memset(key, 0, sizeof(*key));
+    key->valid = status != NULL && S_ISREG(status->st_mode);
+    if (key->valid) {
+        key->device = (uint64_t)status->st_dev;
+        key->inode = (uint64_t)status->st_ino;
+        key->size = (uint64_t)status->st_size;
+#ifdef __APPLE__
+        key->mtime_seconds = status->st_mtimespec.tv_sec;
+        key->mtime_nanoseconds = status->st_mtimespec.tv_nsec;
+        key->ctime_seconds = status->st_ctimespec.tv_sec;
+        key->ctime_nanoseconds = status->st_ctimespec.tv_nsec;
+#else
+        key->mtime_seconds = status->st_mtim.tv_sec;
+        key->mtime_nanoseconds = status->st_mtim.tv_nsec;
+        key->ctime_seconds = status->st_ctim.tv_sec;
+        key->ctime_nanoseconds = status->st_ctim.tv_nsec;
+#endif
+    }
+}
+
+static bool runtime_build_fingerprint_resolve_posix(
+    uintptr_t native_file, uint64_t process_id, const struct stat *status,
+    char fingerprint[CBM_DAEMON_BUILD_FINGERPRINT_SIZE], runtime_fingerprint_key_t *key,
+    bool *cached) {
+    runtime_fingerprint_key_posix(status, key);
+    return runtime_build_fingerprint_resolve(native_file, process_id, key, fingerprint, cached);
+}
+
+static void runtime_fingerprint_cache_commit_posix(
+    const struct stat *status, const runtime_fingerprint_key_t *key, bool cached,
+    const char fingerprint[CBM_DAEMON_BUILD_FINGERPRINT_SIZE]) {
+    runtime_fingerprint_key_t key_after;
+    runtime_fingerprint_key_posix(status, &key_after);
+    runtime_fingerprint_cache_commit(key, &key_after, cached, fingerprint);
+}
+#endif
+
+#ifdef CBM_ENABLE_TEST_SEAMS
+void cbm_daemon_runtime_fingerprint_cache_reset_for_testing(void) {
+    runtime_fingerprint_cache_enter();
+    memset(&runtime_fingerprint_cache_key, 0, sizeof(runtime_fingerprint_cache_key));
+    memset(runtime_fingerprint_cache_digest, 0, sizeof(runtime_fingerprint_cache_digest));
+    runtime_fingerprint_cache_leave();
+    atomic_store_explicit(&runtime_fingerprint_hash_call_count, 0, memory_order_relaxed);
+    atomic_store_explicit(&runtime_fingerprint_hash_stub_active, false, memory_order_release);
+    memset(runtime_fingerprint_hash_stub_digest, 0, sizeof(runtime_fingerprint_hash_stub_digest));
+}
+
+void cbm_daemon_runtime_fingerprint_cache_set_hash_stub_for_testing(const char *digest) {
+    if (!digest) {
+        atomic_store_explicit(&runtime_fingerprint_hash_stub_active, false, memory_order_release);
+        return;
+    }
+    memset(runtime_fingerprint_hash_stub_digest, 0, sizeof(runtime_fingerprint_hash_stub_digest));
+    size_t length = strlen(digest);
+    if (length >= CBM_DAEMON_BUILD_FINGERPRINT_SIZE) {
+        length = CBM_DAEMON_BUILD_FINGERPRINT_SIZE - 1;
+    }
+    memcpy(runtime_fingerprint_hash_stub_digest, digest, length);
+    atomic_store_explicit(&runtime_fingerprint_hash_stub_active, true, memory_order_release);
+}
+
+int cbm_daemon_runtime_fingerprint_hash_call_count_for_testing(void) {
+    return atomic_load_explicit(&runtime_fingerprint_hash_call_count, memory_order_relaxed);
+}
+
+static runtime_fingerprint_key_t runtime_fingerprint_key_for_testing(
+    const cbm_daemon_runtime_fingerprint_identity_for_testing_t *identity) {
+    runtime_fingerprint_key_t key = {.valid = true,
+                                     .device = identity->device,
+                                     .inode = identity->inode,
+                                     .size = identity->size,
+                                     .mtime_seconds = identity->mtime_seconds,
+                                     .mtime_nanoseconds = identity->mtime_nanoseconds,
+                                     .ctime_seconds = identity->ctime_seconds,
+                                     .ctime_nanoseconds = identity->ctime_nanoseconds};
+    return key;
+}
+
+bool cbm_daemon_runtime_fingerprint_cache_resolve_for_testing(
+    const cbm_daemon_runtime_fingerprint_identity_for_testing_t *before,
+    const cbm_daemon_runtime_fingerprint_identity_for_testing_t *after,
+    char out[CBM_DAEMON_BUILD_FINGERPRINT_SIZE]) {
+    /* There is no native image behind a synthetic identity: only the stubbed
+     * hash may ever be reached from here. The identity stands for this
+     * process's own image, the only one the cache serves. */
+    if (!before || !after || !out ||
+        !atomic_load_explicit(&runtime_fingerprint_hash_stub_active, memory_order_acquire)) {
+        return false;
+    }
+    runtime_fingerprint_key_t key_before = runtime_fingerprint_key_for_testing(before);
+    runtime_fingerprint_key_t key_after = runtime_fingerprint_key_for_testing(after);
+    bool cached = false;
+    if (!runtime_build_fingerprint_resolve((uintptr_t)0, runtime_current_process_id(), &key_before,
+                                           out, &cached)) {
+        return false;
+    }
+    runtime_fingerprint_cache_commit(&key_before, &key_after, cached, out);
+    return true;
+}
+#endif
+
+#endif /* supported platform: executable-image fingerprint cache */
+
 /* Acquire one process instance's mapped image as a native object. Supplying a
  * fingerprint hashes that same held object; NULL performs metadata-only
  * acquisition for the HELLO fast path. Every platform brackets the process
@@ -826,6 +1122,8 @@ static bool runtime_process_image_reference_acquire(
     BY_HANDLE_FILE_INFORMATION file_after;
     LARGE_INTEGER size_before;
     LARGE_INTEGER size_after;
+    runtime_fingerprint_key_t fingerprint_key = {0};
+    bool fingerprint_cached = false;
     bool ok = runtime_windows_process_image_snapshot(process, &process_before);
     /* QueryFullProcessImageNameW returns a stable identity spelling for the
      * before/after comparison, but its Win32/DOS form may exceed MAX_PATH.
@@ -839,7 +1137,9 @@ static bool runtime_process_image_reference_acquire(
                       : INVALID_HANDLE_VALUE;
     free(open_path);
     ok = ok && runtime_windows_file_snapshot(file, &file_before, &size_before) &&
-         (!fingerprint || cbm_daemon_build_fingerprint_native_file((uintptr_t)file, fingerprint)) &&
+         (!fingerprint || runtime_build_fingerprint_resolve_windows(
+                              file, process_id, &file_before, &size_before, fingerprint,
+                              &fingerprint_key, &fingerprint_cached)) &&
          runtime_windows_file_snapshot(file, &file_after, &size_after) &&
          runtime_windows_file_snapshot_same(&file_before, &size_before, &file_after, &size_after) &&
          runtime_windows_process_image_snapshot(process, &process_after) &&
@@ -848,6 +1148,10 @@ static bool runtime_process_image_reference_acquire(
         ok = false;
     }
     if (ok) {
+        if (fingerprint) {
+            runtime_fingerprint_cache_commit_windows(
+                file, &file_after, &size_after, &fingerprint_key, fingerprint_cached, fingerprint);
+        }
         reference->held = true;
         reference->file = file;
         reference->information = file_after;
@@ -873,14 +1177,22 @@ static bool runtime_process_image_reference_acquire(
     int fd = ok ? open(path, O_RDONLY | O_CLOEXEC | O_NOFOLLOW | O_NONBLOCK) : -1;
     struct stat file_before;
     struct stat file_after;
+    runtime_fingerprint_key_t fingerprint_key = {0};
+    bool fingerprint_cached = false;
     ok = ok && fd >= 0 && fstat(fd, &file_before) == 0 && S_ISREG(file_before.st_mode) &&
          runtime_mac_process_maps_file_executable(pid, &file_before) &&
-         (!fingerprint || cbm_daemon_build_fingerprint_native_file((uintptr_t)fd, fingerprint)) &&
+         (!fingerprint || runtime_build_fingerprint_resolve_posix(
+                              (uintptr_t)fd, process_id, &file_before, fingerprint,
+                              &fingerprint_key, &fingerprint_cached)) &&
          fstat(fd, &file_after) == 0 && runtime_mac_stat_same(&file_before, &file_after) &&
          runtime_mac_process_maps_file_executable(pid, &file_after) &&
          runtime_mac_process_instance(pid, &process_after) &&
          runtime_mac_process_instance_same(&process_before, &process_after);
     if (ok) {
+        if (fingerprint) {
+            runtime_fingerprint_cache_commit_posix(&file_after, &fingerprint_key,
+                                                   fingerprint_cached, fingerprint);
+        }
         reference->held = true;
         reference->fd = fd;
         reference->status = file_after;
@@ -898,10 +1210,13 @@ static bool runtime_process_image_reference_acquire(
     int image_fd = process_fd >= 0 ? openat(process_fd, "exe", O_RDONLY | O_CLOEXEC) : -1;
     struct stat image_before;
     struct stat image_after;
+    runtime_fingerprint_key_t fingerprint_key = {0};
+    bool fingerprint_cached = false;
     bool ok = image_fd >= 0 && fstat(image_fd, &image_before) == 0 &&
               S_ISREG(image_before.st_mode) &&
-              (!fingerprint ||
-               cbm_daemon_build_fingerprint_native_file((uintptr_t)image_fd, fingerprint)) &&
+              (!fingerprint || runtime_build_fingerprint_resolve_posix(
+                                   (uintptr_t)image_fd, process_id, &image_before, fingerprint,
+                                   &fingerprint_key, &fingerprint_cached)) &&
               fstat(image_fd, &image_after) == 0 &&
               runtime_posix_stat_same_image(&image_before, &image_after);
     int verify_fd = ok ? openat(process_fd, "exe", O_RDONLY | O_CLOEXEC) : -1;
@@ -915,6 +1230,10 @@ static bool runtime_process_image_reference_acquire(
         ok = false;
     }
     if (ok) {
+        if (fingerprint) {
+            runtime_fingerprint_cache_commit_posix(&image_after, &fingerprint_key,
+                                                   fingerprint_cached, fingerprint);
+        }
         reference->held = true;
         reference->fd = image_fd;
         reference->status = image_after;
@@ -940,12 +1259,19 @@ static bool runtime_process_image_reference_acquire(
     int image_fd = ok ? open(path, O_RDONLY | O_CLOEXEC | O_NOFOLLOW | O_NONBLOCK) : -1;
     struct stat image_before;
     struct stat image_after;
+    runtime_fingerprint_key_t fingerprint_key = {0};
+    bool fingerprint_cached = false;
     ok = image_fd >= 0 && fstat(image_fd, &image_before) == 0 && S_ISREG(image_before.st_mode) &&
-         (!fingerprint ||
-          cbm_daemon_build_fingerprint_native_file((uintptr_t)image_fd, fingerprint)) &&
+         (!fingerprint || runtime_build_fingerprint_resolve_posix(
+                              (uintptr_t)image_fd, process_id, &image_before, fingerprint,
+                              &fingerprint_key, &fingerprint_cached)) &&
          fstat(image_fd, &image_after) == 0 &&
          runtime_posix_stat_same_image(&image_before, &image_after);
     if (ok) {
+        if (fingerprint) {
+            runtime_fingerprint_cache_commit_posix(&image_after, &fingerprint_key,
+                                                   fingerprint_cached, fingerprint);
+        }
         reference->held = true;
         reference->fd = image_fd;
         reference->status = image_after;
diff --git a/src/daemon/runtime.h b/src/daemon/runtime.h
index 76d168c73..361a7e781 100644
--- a/src/daemon/runtime.h
+++ b/src/daemon/runtime.h
@@ -499,6 +499,31 @@ typedef enum {
 } cbm_daemon_runtime_hello_point_t;
 typedef void (*cbm_daemon_runtime_hello_hook_t)(cbm_daemon_runtime_hello_point_t point);
 void cbm_daemon_runtime_set_hello_hook_for_testing(cbm_daemon_runtime_hello_hook_t hook);
+
+/* Executable-image fingerprint-cache seams. reset empties the cache, zeroes
+ * the hash counter and disarms the stub; a test that arms the stub must reset
+ * before its first assertion, because an armed stub replaces every later
+ * fingerprint in the process. resolve drives a synthetic file identity through
+ * the exact resolve-then-commit path the acquire sites use: `before` is the
+ * identity the digest is keyed on, `after` the identity observed after the
+ * hash, and the digest is committed only when the two agree. It refuses unless
+ * the stub is armed, since no native image backs a synthetic identity. */
+typedef struct {
+    uint64_t device;
+    uint64_t inode;
+    uint64_t size;
+    int64_t mtime_seconds;
+    int64_t mtime_nanoseconds;
+    int64_t ctime_seconds;
+    int64_t ctime_nanoseconds;
+} cbm_daemon_runtime_fingerprint_identity_for_testing_t;
+void cbm_daemon_runtime_fingerprint_cache_reset_for_testing(void);
+void cbm_daemon_runtime_fingerprint_cache_set_hash_stub_for_testing(const char *digest);
+int cbm_daemon_runtime_fingerprint_hash_call_count_for_testing(void);
+bool cbm_daemon_runtime_fingerprint_cache_resolve_for_testing(
+    const cbm_daemon_runtime_fingerprint_identity_for_testing_t *before,
+    const cbm_daemon_runtime_fingerprint_identity_for_testing_t *after,
+    char out[CBM_DAEMON_BUILD_FINGERPRINT_SIZE]);
 #endif
 
 #endif /* CBM_DAEMON_RUNTIME_H */
diff --git a/src/pipeline/pass_definitions.c b/src/pipeline/pass_definitions.c
index bb3954008..44678b76c 100644
--- a/src/pipeline/pass_definitions.c
+++ b/src/pipeline/pass_definitions.c
@@ -521,13 +521,16 @@ static void process_def(cbm_pipeline_ctx_t *ctx, const CBMDefinition *def, const
      * field resolution), Variable/Field (READS/WRITES resolution), and Table/View
      * (SQL FROM/JOIN lineage). pass_parallel.c and pipeline_incremental.c seed
      * through the same predicate, so the three registries cannot diverge.
-     * A generated member is registered by qualified name only, at all three. */
+     * A generated member is registered by qualified name only, at all three.
+     * The registry's test verdict is the extractor's OR the test-double path
+     * rule (cbm_registry_test_double_path) on the node's file, at all three. */
     if (node_id > 0 && cbm_label_is_registry_symbol(def->label)) {
         if (cbm_def_props_generated(def->extra_props)) {
             cbm_registry_add_qn_only(ctx->registry, def->qualified_name, def->label);
         } else {
             cbm_registry_add_lang_in_module(ctx->registry, def->name, def->qualified_name,
-                                            def->label, lang, module_prefix_len);
+                                            def->label, lang, module_prefix_len,
+                                            def->is_test || cbm_registry_test_double_path(def_rel));
         }
         if (def->qn_sig_off) {
             cbm_registry_set_swift_signature(ctx->registry, def->qualified_name,
diff --git a/src/pipeline/pass_parallel.c b/src/pipeline/pass_parallel.c
index 670347352..4ae2ea88f 100644
--- a/src/pipeline/pass_parallel.c
+++ b/src/pipeline/pass_parallel.c
@@ -1816,7 +1816,7 @@ int cbm_parallel_extract(cbm_pipeline_ctx_t *ctx, const cbm_file_info_t *files,
 /* `file_node_id` is the defining file's node id (0 when it has none), looked up
  * once per file by the caller: computing the file QN and finding its node for
  * every definition was 700 k allocations and lookups on the Go corpus. */
-static int register_and_link_def(cbm_pipeline_ctx_t *ctx, const CBMDefinition *def,
+static int register_and_link_def(cbm_pipeline_ctx_t *ctx, const CBMDefinition *def, const char *rel,
                                  int64_t file_node_id, CBMLanguage lang, size_t module_prefix_len,
                                  int *reg_entries) {
     int edges = 0;
@@ -1824,14 +1824,17 @@ static int register_and_link_def(cbm_pipeline_ctx_t *ctx, const CBMDefinition *d
         return 0;
     }
     /* Registry membership is defined ONCE by cbm_label_is_registry_symbol
-     * (helpers.c) — see pass_definitions.c for the per-label rationale, and
-     * for the generated member registered by qualified name only. */
+     * (helpers.c) — see pass_definitions.c for the per-label rationale, for
+     * the generated member registered by qualified name only, and for the
+     * test-double path rule, judged on the path the def's node stores. */
     if (cbm_label_is_registry_symbol(def->label)) {
         if (cbm_def_props_generated(def->extra_props)) {
             cbm_registry_add_qn_only(ctx->registry, def->qualified_name, def->label);
         } else {
+            const char *def_rel = def->file_path ? def->file_path : rel;
             cbm_registry_add_lang_in_module(ctx->registry, def->name, def->qualified_name,
-                                            def->label, lang, module_prefix_len);
+                                            def->label, lang, module_prefix_len,
+                                            def->is_test || cbm_registry_test_double_path(def_rel));
         }
         if (def->qn_sig_off) {
             cbm_registry_set_swift_signature(ctx->registry, def->qualified_name,
@@ -2050,7 +2053,7 @@ int cbm_build_registry_from_cache(cbm_pipeline_ctx_t *ctx, const cbm_file_info_t
                                        : 0;
             for (int d = 0; d < result->defs.count; d++) {
                 defines_edges +=
-                    register_and_link_def(ctx, &result->defs.items[d], file_node_id,
+                    register_and_link_def(ctx, &result->defs.items[d], rel, file_node_id,
                                           files[i].language, py_prefix_len, &reg_entries);
             }
         }
diff --git a/src/pipeline/pass_tests.c b/src/pipeline/pass_tests.c
index a763016fb..9972086ee 100644
--- a/src/pipeline/pass_tests.c
+++ b/src/pipeline/pass_tests.c
@@ -45,7 +45,7 @@ static const char *itoa_log(int val) {
 }
 
 /* Check if a node has is_test:true in its properties JSON. */
-static bool node_is_test(const cbm_gbuf_node_t *n) {
+bool cbm_node_is_test(const cbm_gbuf_node_t *n) {
     if (!n || !n->properties_json) {
         return false;
     }
@@ -270,13 +270,13 @@ static int create_tests_edges(cbm_pipeline_ctx_t *ctx) {
         }
 
         bool src_is_test =
-            node_is_test(src) || (src->file_path && cbm_is_test_path(src->file_path));
+            cbm_node_is_test(src) || (src->file_path && cbm_is_test_path(src->file_path));
         if (!src_is_test) {
             continue;
         }
 
         bool tgt_is_test =
-            node_is_test(tgt) || (tgt->file_path && cbm_is_test_path(tgt->file_path));
+            cbm_node_is_test(tgt) || (tgt->file_path && cbm_is_test_path(tgt->file_path));
         if (tgt_is_test) {
             continue;
         }
diff --git a/src/pipeline/pipeline.h b/src/pipeline/pipeline.h
index f877cdecc..83907ae4b 100644
--- a/src/pipeline/pipeline.h
+++ b/src/pipeline/pipeline.h
@@ -283,9 +283,24 @@ cbm_registry_t *cbm_registry_new(void);
 void cbm_registry_free(cbm_registry_t *r);
 
 /* Register a function/method/class. All strings are copied. The entry's
- * language is unknown, so name-based resolution never filters it out. */
+ * language is unknown, so name-based resolution never filters it out.
+ * `is_test` is the extractor's verdict for this symbol (CBMDefinition.is_test:
+ * the file's test-ness OR the definition's own test attributes). The registry
+ * stores it and scores with it; it does not derive test-ness from the QN. */
 void cbm_registry_add(cbm_registry_t *r, const char *name, const char *qualified_name,
-                      const char *label);
+                      const char *label, bool is_test);
+
+/* The test-double path rule, for the registry's ranking only: true when the
+ * repo-relative path of a symbol's defining file has a directory segment named
+ * exactly `fake`, `mock`, `mocks`, `testing` or `testutil`, or its file name
+ * matches `mock_*.go` or `fake_*.go`. Go projects keep generated fake
+ * clientsets and mock packages in ordinary files the extractor rightly does
+ * not call tests; a call should still prefer real code over them. The three
+ * registry seeders (pass_definitions.c, pass_parallel.c,
+ * pipeline_incremental.c) pass the extractor's verdict OR this, so full and
+ * incremental indexes rank alike. It never decides what a node is: the stored
+ * is_test property, TESTS edges and importance stay with cbm_is_test_path. */
+bool cbm_registry_test_double_path(const char *rel_path);
 
 /* Swift-only metadata and label-compatible overload selection. The returned
  * QNs are borrowed from the registry and all belong to one base callable.
@@ -306,7 +321,7 @@ int cbm_registry_swift_candidates_in_file(const cbm_registry_t *r, const CBMCall
  * function-local symbols: that needs the defining file's module QN, see
  * cbm_registry_add_lang_in_module. */
 void cbm_registry_add_lang(cbm_registry_t *r, const char *name, const char *qualified_name,
-                           const char *label, CBMLanguage lang);
+                           const char *label, CBMLanguage lang, bool is_test);
 
 /* As cbm_registry_add_lang. A Python symbol declared inside a function body of
  * its own file (cbm_registry_qn_is_function_local, bounded by
@@ -318,7 +333,7 @@ void cbm_registry_add_lang(cbm_registry_t *r, const char *name, const char *qual
  * indexes agree. 0 = no local detection. */
 void cbm_registry_add_lang_in_module(cbm_registry_t *r, const char *name,
                                      const char *qualified_name, const char *label,
-                                     CBMLanguage lang, size_t module_prefix_len);
+                                     CBMLanguage lang, size_t module_prefix_len, bool is_test);
 
 /* Register a symbol for exact (qualified-name) lookups only: it is never
  * offered to the short-name strategies (unique_name, suffix_match,
diff --git a/src/pipeline/pipeline_delta.c b/src/pipeline/pipeline_delta.c
index 63c5ef1d1..22573f8c8 100644
--- a/src/pipeline/pipeline_delta.c
+++ b/src/pipeline/pipeline_delta.c
@@ -623,6 +623,28 @@ static char *delta_generated_props(const char *props, const char *generated) {
     return out;
 }
 
+/* `props` (a JSON object) with the extractor's test verdict added as
+ * `"is_test":true` (CBM_MEM_CLASS_OTHER; the caller frees), NULL on allocation
+ * failure. The incremental registry seed reads the verdict back
+ * (cbm_node_is_test) so a re-resolved caller ranks a test definition below
+ * real code exactly as the full build does; an absent key reads as false. */
+static char *delta_test_props(const char *props) {
+    static const char member[] = "\"is_test\":true";
+    size_t pl = props ? strlen(props) : 0;
+    bool has_members = pl > PAIR_LEN && props[0] == '{' && props[pl - SKIP_ONE] == '}';
+    size_t cap = pl + sizeof(member) + CBM_SZ_4;
+    char *out = (char *)cbm_alloc(CBM_MEM_CLASS_OTHER, cap);
+    if (!out) {
+        return NULL;
+    }
+    if (has_members) {
+        snprintf(out, cap, "%.*s,%s}", (int)(pl - SKIP_ONE), props, member);
+    } else {
+        snprintf(out, cap, "{%s}", member);
+    }
+    return out;
+}
+
 int64_t cbm_delta_preseed(cbm_store_t *store, const char *project, cbm_gbuf_t *gbuf) {
     sqlite3 *db = cbm_store_get_db(store);
     if (!db) {
@@ -673,7 +695,13 @@ int64_t cbm_delta_preseed(cbm_store_t *store, const char *project, cbm_gbuf_t *g
      * And a generated member's mark (a Java record's implicit accessor, a
      * Method node): the registry seed reads it to register the member by
      * qualified name only, as the full build does (cbm_node_props_generated);
-     * without it the proxy came back into the short-name index. */
+     * without it the proxy came back into the short-name index.
+     *
+     * And the extractor's test verdict: the registry seed reads it back
+     * (cbm_node_is_test) to rank a test definition below real code, as the
+     * full build does with CBMDefinition.is_test; without it every proxy
+     * scored as production and a re-resolved caller could bind a test helper
+     * the full build ranks last. */
     sqlite3_stmt *stmt = NULL;
     if (sqlite3_prepare_v2(
             db,
@@ -702,7 +730,8 @@ int64_t cbm_delta_preseed(cbm_store_t *store, const char *project, cbm_gbuf_t *g
             " THEN json_extract(properties, '$.parent_class') END,"
             " CASE WHEN label = 'Method'"
             " AND instr(properties, '\"" CBM_PROP_GENERATED "\"') > 0"
-            " THEN json_extract(properties, '$." CBM_PROP_GENERATED "') END"
+            " THEN json_extract(properties, '$." CBM_PROP_GENERATED "') END,"
+            " instr(properties, '\"is_test\":true') > 0"
             " FROM nodes"
             " WHERE project = ?1 AND label NOT IN"
             " ('Macro','Comment','Section','Branch','Commit','Tag')"
@@ -727,14 +756,27 @@ int64_t cbm_delta_preseed(cbm_store_t *store, const char *project, cbm_gbuf_t *g
         int end_line = sqlite3_column_int(stmt, 7);
         const char *parent = (const char *)sqlite3_column_text(stmt, 8);
         const char *generated = (const char *)sqlite3_column_text(stmt, 9);
+        bool is_test = sqlite3_column_int(stmt, 10) != 0;
         char *owner_props =
             parent ? delta_owner_props(project, name, qn, parent, client_props) : NULL;
         const char *props = owner_props ? owner_props : (client_props ? client_props : "{}");
         char *generated_props = delta_generated_props(props, generated);
+        const char *seed_props = generated_props ? generated_props : props;
+        char *test_props = is_test ? delta_test_props(seed_props) : NULL;
+        if (is_test && !test_props) {
+            /* A proxy without its verdict would rank as production code;
+             * the run cannot be trusted, as with an id mismatch below. */
+            cbm_free(CBM_MEM_CLASS_OTHER, generated_props);
+            cbm_free(CBM_MEM_CLASS_OTHER, owner_props);
+            sqlite3_finalize(stmt);
+            cbm_log_error("delta.preseed_verdict_alloc_failed", "qn", qn ? qn : "");
+            return -1;
+        }
         /* Pin the gbuf id to the database id: proxies ARE their rows. */
         cbm_gbuf_set_next_id(gbuf, id);
         int64_t got = cbm_gbuf_upsert_node(gbuf, label, name, qn, fp ? fp : "", start_line,
-                                           end_line, generated_props ? generated_props : props);
+                                           end_line, test_props ? test_props : seed_props);
+        cbm_free(CBM_MEM_CLASS_OTHER, test_props);
         cbm_free(CBM_MEM_CLASS_OTHER, generated_props);
         cbm_free(CBM_MEM_CLASS_OTHER, owner_props);
         if (got != id) {
diff --git a/src/pipeline/pipeline_incremental.c b/src/pipeline/pipeline_incremental.c
index 58ac46d1a..9324314cd 100644
--- a/src/pipeline/pipeline_incremental.c
+++ b/src/pipeline/pipeline_incremental.c
@@ -1396,8 +1396,11 @@ static void registry_visitor(const cbm_gbuf_node_t *node, void *userdata) {
     size_t prefix_len = lang == CBM_LANG_PYTHON
                             ? cbm_pipeline_fqn_symbol_prefix_len(seed->project, node->file_path)
                             : 0;
+    /* The full index's verdict: the extractor's (stored as is_test) OR the
+     * test-double path rule on the node's file (pass_definitions.c). */
+    bool is_test = cbm_node_is_test(node) || cbm_registry_test_double_path(node->file_path);
     cbm_registry_add_lang_in_module(seed->registry, node->name, node->qualified_name, node->label,
-                                    lang, prefix_len);
+                                    lang, prefix_len, is_test);
     if (node->properties_json) {
         const char *mask = strstr(node->properties_json, "\"param_default_mask\":\"");
         const char *count = strstr(node->properties_json, "\"selector_param_count\":");
diff --git a/src/pipeline/pipeline_internal.h b/src/pipeline/pipeline_internal.h
index 930a2fe7a..cb8af8f02 100644
--- a/src/pipeline/pipeline_internal.h
+++ b/src/pipeline/pipeline_internal.h
@@ -260,7 +260,8 @@ cbm_resolution_t cbm_registry_resolve_lang(const cbm_registry_t *r, const char *
                                            CBMLanguage lang);
 /* The CALLS variant: as cbm_registry_resolve_lang, except that a bare C call
  * (no `.` / `->`) does not consider Field or Method nodes, which it can never
- * call. */
+ * call, and that in a C# file a built-in type keyword root (`int.TryParse`)
+ * names a type for the receiver chain check (#2121). */
 cbm_resolution_t cbm_registry_resolve_call_lang(const cbm_registry_t *r, const char *callee_name,
                                                 const char *module_qn, const char **import_map_keys,
                                                 const char **import_map_vals, int import_map_count,
@@ -656,6 +657,12 @@ static inline bool cbm_pipeline_test_force_def_modules_null(const cbm_pipeline_c
 typedef bool (*cbm_result_want_fn)(const CBMFileResult *header);
 CBMFileResult *cbm_pipeline_result_acquire(const cbm_pipeline_ctx_t *ctx, CBMFileResult **cache,
                                            int i, cbm_result_want_fn want, bool *loaded);
+/* True when a graph-buffer node carries is_test:true in its properties JSON.
+ * The incremental registry seed has only the persisted node, not the
+ * CBMDefinition the definition passes hand to cbm_registry_add, and both must
+ * give the registry the same verdict for the same symbol. */
+bool cbm_node_is_test(const cbm_gbuf_node_t *n);
+
 void cbm_pipeline_result_release(CBMFileResult *r, bool loaded);
 
 /* Log the store counters, close and delete the store, drop the latch. */
diff --git a/src/pipeline/registry.c b/src/pipeline/registry.c
index 93b4a16c1..ac1b8ce61 100644
--- a/src/pipeline/registry.c
+++ b/src/pipeline/registry.c
@@ -30,6 +30,7 @@ enum { REG_MAX_CANDIDATES = 256 };
 #include "foundation/compat.h" /* CBM_TLS */
 #include "foundation/hash_table.h"
 #include "foundation/arena.h"
+#include "foundation/log.h"
 #include "foundation/dyn_array.h"
 #include "foundation/mem_core.h"
 #include "foundation/platform.h"
@@ -81,16 +82,16 @@ const char *cbm_confidence_band(double score) {
 
 /* ── Internal types ──────────────────────────────────────────────── */
 
-/* Array of QN strings for byName index, with the test/mock verdict of each
- * name cached beside it: the scorer asked is_test_qn for every candidate of
- * every unresolved call, and the answer depends only on the name, which never
- * changes once registered (waste sanitizer scaling lane, 2026-09-17). Field
- * order and names match CBM_DYN_ARRAY(char *) so cbm_da_push works on it. */
+/* Array of QN strings for byName index, with each entry's test verdict beside
+ * it. The verdict is the extractor's, handed to cbm_registry_add by the caller
+ * that already computed it from the file path and the definition's attributes;
+ * it is stored rather than derived, so every entry always has one. Field order
+ * and names match CBM_DYN_ARRAY(char *) so cbm_da_push works on it. */
 typedef struct {
     char **items;
     int count;
     int cap;
-    uint8_t *is_test; /* is_test_qn(items[i]), one byte per entry */
+    uint8_t *is_test; /* the caller's verdict for items[i], one byte per entry */
     int is_test_cap;
     /* Language of the file that defined items[i] (a CBMLanguage; CBM_LANG_COUNT
      * = unknown, compatible with every caller), one byte per entry. Grown in
@@ -204,84 +205,64 @@ static int common_prefix_len(const char *a, const char *b) {
 
 enum { REG_TEST_PENALTY = 1000 };
 
-/* Check if a qualified name looks like a test/mock path: does it contain any of
- * Test, test, Mock, mock, Stub, stub, Fake, fake, Fixture, spec? One pass that
- * dispatches on the first character instead of ten strstr scans of the whole
- * name (this ran for every candidate of every unresolved call: the scaling
- * lane's x4.0, waste sanitizer 2026-09-17). */
-static bool is_test_qn(const char *qn) {
-    if (!qn) {
-        return false;
-    }
-    for (const char *p = qn; *p; p++) {
-        switch (*p) {
-        case 'T':
-            if (strncmp(p, "Test", 4) == 0) {
-                return true;
-            }
-            break;
-        case 't':
-            if (strncmp(p, "test", 4) == 0) {
-                return true;
-            }
-            break;
-        case 'M':
-            if (strncmp(p, "Mock", 4) == 0) {
-                return true;
-            }
-            break;
-        case 'm':
-            if (strncmp(p, "mock", 4) == 0) {
-                return true;
-            }
-            break;
-        case 'S':
-            if (strncmp(p, "Stub", 4) == 0) {
-                return true;
-            }
-            break;
-        case 's':
-            if (strncmp(p, "stub", 4) == 0 || strncmp(p, "spec", 4) == 0) {
-                return true;
-            }
-            break;
-        case 'F':
-            if (strncmp(p, "Fake", 4) == 0 || strncmp(p, "Fixture", 7) == 0) {
-                return true;
-            }
-            break;
-        case 'f':
-            if (strncmp(p, "fake", 4) == 0) {
-                return true;
-            }
-            break;
-        default:
-            break;
+/* A directory segment that, by name alone, holds test doubles: Go's generated
+ * fake clientsets and listers (pkg/client/.../fake), mock packages, and the
+ * testing / testutil helper packages. Whole segments only, compared exactly. */
+static bool test_double_dir_segment(const char *seg, size_t len) {
+    static const char *const dirs[] = {"fake", "mock", "mocks", "testing", "testutil"};
+    for (size_t i = 0; i < sizeof(dirs) / sizeof(dirs[0]); i++) {
+        if (strlen(dirs[i]) == len && memcmp(seg, dirs[i], len) == 0) {
+            return true;
         }
     }
     return false;
 }
 
-/* The cached test verdicts, only when they cover every entry: a failed growth
- * leaves the cache short, and then the scorer asks per candidate as before. */
-static const uint8_t *qn_test_flags(const qn_array_t *arr) {
-    return arr->is_test && arr->is_test_cap >= arr->count ? arr->is_test : NULL;
+/* `base` is a Go file named `prefix`*.go. */
+static bool go_file_with_prefix(const char *base, const char *prefix) {
+    static const char go_ext[] = ".go";
+    size_t blen = strlen(base);
+    size_t plen = strlen(prefix);
+    size_t elen = sizeof(go_ext) - SKIP_ONE;
+    return blen >= plen + elen && strncmp(base, prefix, plen) == 0 &&
+           strcmp(base + blen - elen, go_ext) == 0;
 }
 
-/* The cached candidate languages, under the same coverage rule: both side
- * arrays grow together and share is_test_cap. */
+bool cbm_registry_test_double_path(const char *rel_path) {
+    if (!rel_path) {
+        return false;
+    }
+    const char *seg = rel_path;
+    for (const char *slash = strchr(seg, '/'); slash; slash = strchr(seg, '/')) {
+        if (test_double_dir_segment(seg, (size_t)(slash - seg))) {
+            return true;
+        }
+        seg = slash + SKIP_ONE;
+    }
+    /* `seg` is the file name now. */
+    return go_file_with_prefix(seg, "mock_") || go_file_with_prefix(seg, "fake_");
+}
+
+/* The stored test verdicts. index_under_name drops an entry it cannot record a
+ * verdict for, so this covers every entry of a non-empty bucket. */
+static const uint8_t *qn_test_flags(const qn_array_t *arr) {
+    return arr->is_test;
+}
+
+/* The stored candidate languages. Both side arrays grow together and share
+ * is_test_cap, and index_under_name drops an entry that does not fit both, so
+ * this covers every entry of a non-empty bucket too. */
 static const uint8_t *qn_lang_flags(const qn_array_t *arr) {
-    return arr->lang && arr->is_test_cap >= arr->count ? arr->lang : NULL;
+    return arr->lang;
 }
 
 /* Score a candidate for tiebreaking. Higher = better.
  * Layer 1: Non-test code preferred over test code (+1000)
  * Layer 2: Namespace proximity via common prefix length (+plen)
- * `is_test` is the cached verdict when the caller has one (-1: ask). */
-static int candidate_score(const char *candidate_qn, const char *module_qn, int is_test) {
+ * `is_test` is the verdict stored for this candidate at registration. */
+static int candidate_score(const char *candidate_qn, const char *module_qn, bool is_test) {
     int score = 0;
-    bool test = is_test >= 0 ? is_test != 0 : is_test_qn(candidate_qn);
-    if (!test) {
+    if (!is_test) {
         score += REG_TEST_PENALTY;
     }
     score += common_prefix_len(candidate_qn, module_qn);
@@ -351,9 +332,10 @@ static bool candidate_outranks_on_tie(const cbm_registry_t *r, const char *candi
 }
 
 /* Pick candidate with highest composite score (test-deprioritization + namespace
- * proximity), ties settled by candidate_outranks_on_tie. `is_test_flags` and
- * `lang_flags` are the candidates' cached test verdicts and languages, or NULL
- * when the caller has none (a filtered subset carries its own copies). */
+ * proximity), ties settled by candidate_outranks_on_tie. `is_test_flags` are
+ * the candidates' stored test verdicts, always given: every by-name entry has
+ * one, and a filtered subset carries its own copies. `lang_flags` are their
+ * languages, or NULL when the caller has none. */
 static const char *best_by_import_distance(const cbm_registry_t *r, const char **candidates,
                                            const uint8_t *is_test_flags, const uint8_t *lang_flags,
                                            int count, const char *module_qn) {
@@ -361,8 +343,7 @@ static const char *best_by_import_distance(const cbm_registry_t *r, const char *
     uint8_t best_lang = (uint8_t)CBM_LANG_COUNT;
     int best_score = CBM_NOT_FOUND;
     for (int i = 0; i < count; i++) {
-        int score =
-            candidate_score(candidates[i], module_qn, is_test_flags ? (int)is_test_flags[i] : -1);
+        int score = candidate_score(candidates[i], module_qn, is_test_flags[i] != 0);
         uint8_t lang = lang_flags ? lang_flags[i] : (uint8_t)CBM_LANG_COUNT;
         if (score > best_score ||
             (score == best_score && best &&
@@ -485,6 +466,7 @@ typedef struct {
     cbm_resolution_t res;
     size_t scope_len;  /* raw and Python-scoped requests may share one file cache */
     bool skip_members; /* a C call and a C reference to the same name share it too */
+    bool cs_keywords;  /* a C# call and a C# reference to the same name share it too */
 } resolve_cache_entry_t;
 
 static CBM_TLS CBMHashTable *_resolve_cache = NULL;
@@ -1718,11 +1700,11 @@ void cbm_registry_free(cbm_registry_t *r) {
 /* ── Registration ────────────────────────────────────────────────── */
 
 /* Record `owned_qn` in the by-name bucket for `key`, keeping the bucket's
- * is_test flags in step with its entries.
+ * is_test and lang side arrays in step with its entries.
  *
  * No array dedup needed: cbm_registry_add's exact-map check guarantees the QN
  * is new, and it calls this at most once per distinct key. */
-static void index_under_name(cbm_registry_t *r, const char *key, const char *owned_qn,
+static void index_under_name(cbm_registry_t *r, const char *key, const char *owned_qn, bool is_test,
                              CBMLanguage lang) {
     qn_array_t *arr = cbm_ht_get(r->by_name, key);
     if (!arr) {
@@ -1732,7 +1714,7 @@ static void index_under_name(cbm_registry_t *r, const char *key, const char *own
     int before = arr->count;
     cbm_da_push(arr, (char *)owned_qn);
     if (arr->count == before) {
-        return; /* the name could not be recorded: no verdict to cache */
+        return; /* the name could not be recorded: no verdict to store */
     }
     if (arr->count > arr->is_test_cap) {
         int want = arr->cap > 0 ? arr->cap : arr->count;
@@ -1743,19 +1725,25 @@ static void index_under_name(cbm_registry_t *r, const char *key, const char *own
             uint8_t *grown_lang =
                 cbm_realloc(CBM_MEM_CLASS_DYN_ARRAY, arr->lang, (size_t)want * sizeof(uint8_t));
             /* Both side arrays share is_test_cap: on failure it stays below
-             * count, so this name serves neither cached test verdicts nor
-             * language filtering, exactly the unfiltered answer. */
+             * count, and the entry is dropped below. */
             if (grown_lang) {
                 arr->lang = grown_lang;
                 arr->is_test_cap = want;
             }
         }
     }
-    if (arr->count <= arr->is_test_cap) {
-        arr->is_test[arr->count - SKIP_ONE] = is_test_qn(owned_qn) ? 1 : 0;
-        arr->lang[arr->count - SKIP_ONE] =
-            (uint8_t)(lang >= 0 && lang < CBM_LANG_COUNT ? lang : CBM_LANG_COUNT);
+    if (arr->count > arr->is_test_cap) {
+        /* The verdict can no longer be recomputed from the QN, so an entry
+         * without one would be scored as non-test and outrank real code. Drop
+         * it instead: one missing candidate beats a wrong winner. The language
+         * shares is_test_cap, so the drop covers it as well. */
+        arr->count = before;
+        cbm_log_warn("registry.verdict_alloc_failed", "key", key);
+        return;
     }
+    arr->is_test[arr->count - SKIP_ONE] = is_test ? 1 : 0;
+    arr->lang[arr->count - SKIP_ONE] =
+        (uint8_t)(lang >= 0 && lang < CBM_LANG_COUNT ? lang : CBM_LANG_COUNT);
 }
 
 static bool registry_label_is_callable(const char *label) {
@@ -1843,13 +1831,13 @@ static const char *registry_add_exact(cbm_registry_t *r, const char *qualified_n
 }
 
 void cbm_registry_add(cbm_registry_t *r, const char *name, const char *qualified_name,
-                      const char *label) {
-    cbm_registry_add_lang_in_module(r, name, qualified_name, label, CBM_LANG_COUNT, 0);
+                      const char *label, bool is_test) {
+    cbm_registry_add_lang_in_module(r, name, qualified_name, label, CBM_LANG_COUNT, 0, is_test);
 }
 
 void cbm_registry_add_lang(cbm_registry_t *r, const char *name, const char *qualified_name,
-                           const char *label, CBMLanguage lang) {
-    cbm_registry_add_lang_in_module(r, name, qualified_name, label, lang, 0);
+                           const char *label, CBMLanguage lang, bool is_test) {
+    cbm_registry_add_lang_in_module(r, name, qualified_name, label, lang, 0, is_test);
 }
 
 /* Python nests defs: a def or class declared in a function body -- a closure,
@@ -1868,7 +1856,7 @@ void cbm_registry_add_lang(cbm_registry_t *r, const char *name, const char *qual
  * index seconds for nothing. */
 void cbm_registry_add_lang_in_module(cbm_registry_t *r, const char *name,
                                      const char *qualified_name, const char *label,
-                                     CBMLanguage lang, size_t module_prefix_len) {
+                                     CBMLanguage lang, size_t module_prefix_len, bool is_test) {
     if (!r || !qualified_name || !label) {
         return;
     }
@@ -1912,7 +1900,7 @@ void cbm_registry_add_lang_in_module(cbm_registry_t *r, const char *name,
     const char *derived = simple_name(qualified_name);
     const char *primary =
         name && cbm_qn_callable_base_len_named(owned_qn, name) < strlen(owned_qn) ? name : derived;
-    index_under_name(r, primary, owned_qn, lang);
+    index_under_name(r, primary, owned_qn, is_test, lang);
     /* '#' is a QN fence; no extractor mints one for a REGISTERED definition
      * today (Rust cfg twins are variants of one plain QN; a C macro's QN ends in
      * "#macro", but Macro is no registry label, so it never gets here). A
@@ -1924,7 +1912,7 @@ void cbm_registry_add_lang_in_module(cbm_registry_t *r, const char *name,
      * signature-qualified callable is filed under `name` already, and its
      * capped suffix may carry a '#' of its own. */
     if (name && name[0] && strchr(derived, '#') && strcmp(name, primary) != 0) {
-        index_under_name(r, name, owned_qn, lang);
+        index_under_name(r, name, owned_qn, is_test, lang);
     }
 }
 
@@ -2295,12 +2283,8 @@ static cbm_resolution_t resolve_multi_with_imports(const cbm_registry_t *r, cons
     int fcount = 0;
     for (int i = 0; i < arr->count && fcount < CBM_SZ_256; i++) {
         if (is_import_reachable(arr->items[i], import_vals, import_count)) {
-            if (flags) {
-                filtered_test[fcount] = flags[i];
-            }
-            if (langs) {
-                filtered_lang[fcount] = langs[i];
-            }
+            filtered_test[fcount] = flags[i];
+            filtered_lang[fcount] = langs[i];
             filtered[fcount] = arr->items[i];
             fcount++;
         }
@@ -2310,8 +2294,8 @@ static cbm_resolution_t resolve_multi_with_imports(const cbm_registry_t *r, cons
         return (cbm_resolution_t){filtered[0], "suffix_match", conf, arr->count};
     }
     if (fcount > SKIP_ONE) {
-        const char *best = best_by_import_distance(r, filtered, flags ? filtered_test : NULL,
-                                                   langs ? filtered_lang : NULL, fcount, module_qn);
+        const char *best =
+            best_by_import_distance(r, filtered, filtered_test, filtered_lang, fcount, module_qn);
         if (best) {
             double conf = candidate_count_penalty(CONF_SUFFIX_MATCH, fcount);
             return (cbm_resolution_t){best, "suffix_match", conf, fcount};
@@ -2384,6 +2368,26 @@ static const char *qualified_suffix_match(const qn_array_t *arr, const char *cal
     return match;
 }
 
+/* True when the first segment of the dotted chain `dotted` is one of C#'s
+ * built-in type keywords (int, string, bool, ...; nint and nuint since C# 9).
+ * Closed list: these words are grammar, not a naming heuristic. `dynamic` is
+ * not on it: the type has no static members, so `dynamic.X` is a variable
+ * named `dynamic` and stays an ordinary lower-case value root. */
+static bool cs_type_keyword_root(const char *dotted) {
+    static const char *const keywords[] = {
+        "bool",  "byte",   "char",  "decimal", "double", "float", "int",   "long",   "nint",
+        "nuint", "object", "sbyte", "short",   "string", "uint",  "ulong", "ushort", "void",
+    };
+    const char *dot = strchr(dotted, '.');
+    size_t len = dot ? (size_t)(dot - dotted) : strlen(dotted);
+    for (size_t i = 0; i < sizeof(keywords) / sizeof(keywords[0]); i++) {
+        if (strlen(keywords[i]) == len && strncmp(dotted, keywords[i], len) == 0) {
+            return true;
+        }
+    }
+    return false;
+}
+
 /* A dotted callee whose FIRST segment starts upper-case names a type — URLSession,
  * Calendar, JSONEncoder. That receiver chain is evidence the bare-name scorers
  * throw away, and throwing it away binds Foundation's URLSession.shared.data to
@@ -2397,9 +2401,17 @@ static const char *qualified_suffix_match(const qn_array_t *arr, const char *cal
  * show, so the chain proves nothing there and the call passes through
  * unchanged. A callee with no separator passes through as well.
  *
- * Language agnostic by design: the registry holds no language, and every
- * language that writes receiver chains gains the same protection. */
-static bool receiver_chain_admits(const char *callee_name, const char *candidate_qn) {
+ * One exception, for C# CALLS only (#2121): C# spells its built-in types as
+ * lower-case keywords, so in `int.TryParse` or `string.Join` the root names a
+ * type and gets the same check (cs_type_keyword_root). `lang` is the calling
+ * file's language on the CALLS path (cbm_registry_resolve_call_lang) and
+ * CBM_LANG_COUNT on every other resolve. In Python, JS or Go these words are
+ * ordinary identifiers, so a variable named `object` stays a value root there.
+ *
+ * Otherwise language agnostic by design: every language that writes receiver
+ * chains gains the same protection. */
+static bool receiver_chain_admits(const char *callee_name, const char *candidate_qn,
+                                  CBMLanguage lang) {
     /* Normalize "::" -> "." so the chain composes with dotted candidate QNs,
      * the same way qualified_suffix_match does. */
     char dotted[CBM_SZ_512];
@@ -2418,7 +2430,8 @@ static bool receiver_chain_admits(const char *callee_name, const char *candidate
     if (!last_dot) {
         return true; /* bare name — no receiver chain to judge */
     }
-    if (dotted[0] < 'A' || dotted[0] > 'Z') {
+    if ((dotted[0] < 'A' || dotted[0] > 'Z') &&
+        !(lang == CBM_LANG_CSHARP && cs_type_keyword_root(dotted))) {
         return true; /* lower-case root names a value, not a type */
     }
     /* A name written in capitals with underscores is a constant holding a
@@ -2477,14 +2490,13 @@ static bool receiver_chain_admits(const char *callee_name, const char *candidate
 
 /* The same-name candidates without the members -- Field and Method nodes --
  * in `view` (backed by the caller's buffers, at most REG_MAX_CANDIDATES
- * entries). The side arrays are carried over only when the bucket has them
- * for every entry. */
+ * entries). Every entry of a non-empty bucket has its stored verdict and
+ * language (index_under_name), and the view carries them over. */
 static void candidates_without_members(const cbm_registry_t *r, const qn_array_t *arr,
                                        qn_array_t *view, char **items, uint8_t *is_test,
                                        uint8_t *lang) {
     const uint8_t *flags = qn_test_flags(arr);
     const uint8_t *langs = qn_lang_flags(arr);
-    bool side = flags && langs;
     int n = 0;
     for (int i = 0; i < arr->count; i++) {
         const char *label = cbm_registry_label_of(r, arr->items[i]);
@@ -2492,24 +2504,20 @@ static void candidates_without_members(const cbm_registry_t *r, const qn_array_t
             continue;
         }
         items[n] = arr->items[i];
-        if (side) {
-            is_test[n] = flags[i];
-            lang[n] = langs[i];
-        }
+        is_test[n] = flags[i];
+        lang[n] = langs[i];
         n++;
     }
-    *view = (qn_array_t){.items = items,
-                         .count = n,
-                         .cap = n,
-                         .is_test = side ? is_test : NULL,
-                         .is_test_cap = side ? n : 0,
-                         .lang = side ? lang : NULL};
+    *view = (qn_array_t){
+        .items = items, .count = n, .cap = n, .is_test = is_test, .is_test_cap = n, .lang = lang};
 }
 
-/* Strategies 3.5, 3 and 4 over one same-name candidate set. */
+/* Strategies 3.5, 3 and 4 over one same-name candidate set. `lang` reaches
+ * receiver_chain_admits only (see there). */
 static cbm_resolution_t resolve_name_candidates(const cbm_registry_t *r, const qn_array_t *arr,
                                                 const char *callee_name, const char *module_qn,
-                                                const char **import_vals, int import_count) {
+                                                const char **import_vals, int import_count,
+                                                CBMLanguage lang) {
     /* Strategy 3.5: a qualified callee disambiguates among multiple same-name
      * candidates by full qualified tail, before bare-name scoring collapses
      * them onto a single winner. */
@@ -2522,7 +2530,7 @@ static cbm_resolution_t resolve_name_candidates(const cbm_registry_t *r, const q
 
     /* Strategy 3: unique name */
     if (arr->count == SKIP_ONE) {
-        if (!receiver_chain_admits(callee_name, arr->items[0])) {
+        if (!receiver_chain_admits(callee_name, arr->items[0], lang)) {
             return empty_result();
         }
         double conf = CONF_UNIQUE_NAME;
@@ -2540,7 +2548,7 @@ static cbm_resolution_t resolve_name_candidates(const cbm_registry_t *r, const q
     const char *best = best_by_import_distance(r, (const char **)arr->items, qn_test_flags(arr),
                                                qn_lang_flags(arr), arr->count, module_qn);
     if (best) {
-        if (!receiver_chain_admits(callee_name, best)) {
+        if (!receiver_chain_admits(callee_name, best, lang)) {
             return empty_result();
         }
         double conf = candidate_count_penalty(CONF_SUFFIX_MATCH, arr->count);
@@ -2558,7 +2566,7 @@ static cbm_resolution_t resolve_name_candidates(const cbm_registry_t *r, const q
  * libc `read()` the unique name of a C++ adapter's Method instead. */
 static cbm_resolution_t resolve_name_lookup(const cbm_registry_t *r, const char *callee_name,
                                             const char *module_qn, const char **import_vals,
-                                            int import_count, bool skip_members) {
+                                            int import_count, bool skip_members, CBMLanguage lang) {
     const char *lookup = simple_name(callee_name);
     const qn_array_t *arr = cbm_ht_get(r->by_name, lookup);
     if (!arr || arr->count == 0) {
@@ -2576,17 +2584,20 @@ static cbm_resolution_t resolve_name_lookup(const cbm_registry_t *r, const char
         if (view.count == 0) {
             return empty_result();
         }
-        return resolve_name_candidates(r, &view, callee_name, module_qn, import_vals, import_count);
+        return resolve_name_candidates(r, &view, callee_name, module_qn, import_vals, import_count,
+                                       lang);
     }
-    return resolve_name_candidates(r, arr, callee_name, module_qn, import_vals, import_count);
+    return resolve_name_candidates(r, arr, callee_name, module_qn, import_vals, import_count, lang);
 }
 
 /* The strategy chain shared by both public resolve variants (no caching here —
- * cbm_registry_resolve owns the per-file cache). */
+ * cbm_registry_resolve owns the per-file cache). `lang`: see
+ * receiver_chain_admits. */
 static cbm_resolution_t registry_resolve_chain(const cbm_registry_t *r, const char *callee_name,
                                                const char *module_qn, const char **import_map_keys,
                                                const char **import_map_vals, int import_map_count,
-                                               size_t scope_len, bool skip_members) {
+                                               size_t scope_len, bool skip_members,
+                                               CBMLanguage lang) {
     /* Split callee at the first path separator: "pkg.Func" → prefix="pkg",
      * suffix="Func".  Rust/C++ use "::" rather than ".", so honor whichever
      * separator appears first ("lib::square" → prefix="lib", suffix="square").
@@ -2624,7 +2635,7 @@ static cbm_resolution_t registry_resolve_chain(const cbm_registry_t *r, const ch
     if (!(res.qualified_name && res.qualified_name[0])) {
         /* Strategy 3+4: name lookup */
         res = resolve_name_lookup(r, callee_name, module_qn, import_map_vals, import_map_count,
-                                  skip_members);
+                                  skip_members, lang);
     }
     return res;
 }
@@ -2634,7 +2645,7 @@ static cbm_resolution_t registry_resolve_chain(const cbm_registry_t *r, const ch
  * at most REG_MAX_CANDIDATES long whenever a name strategy produced `qn`. */
 static CBMLanguage registry_entry_language(const cbm_registry_t *r, const char *qn) {
     const qn_array_t *arr = cbm_ht_get(r->by_name, simple_name(qn));
-    if (!arr || !arr->lang || arr->is_test_cap < arr->count) {
+    if (!arr) {
         return CBM_LANG_COUNT;
     }
     for (int i = 0; i < arr->count; i++) {
@@ -2672,25 +2683,31 @@ bool cbm_registry_name_guess_vetoed(const cbm_registry_t *r, CBMLanguage caller_
                                            registry_entry_language(r, res->qualified_name));
 }
 
+/* call_lang: the calling file's language for a CALLS resolve, CBM_LANG_COUNT
+ * for every other one (see receiver_chain_admits). */
 static cbm_resolution_t registry_resolve_scoped(const cbm_registry_t *r, const char *callee_name,
                                                 const char *module_qn, const char **import_map_keys,
                                                 const char **import_map_vals, int import_map_count,
-                                                size_t scope_len, bool skip_members) {
+                                                size_t scope_len, bool skip_members,
+                                                CBMLanguage call_lang) {
     if (!r || !callee_name) {
         return empty_result();
     }
 
     /* Per-file cache: same callee_name in N call sites → 1 chain walk
      * + N-1 O(1) hash hits. module_qn is constant per file so the
-     * cache key only needs callee_name. */
+     * cache key only needs callee_name. The chain reads call_lang only as
+     * "is it C#", so that one bit is all the entry has to record. */
+    bool cs_keywords = call_lang == CBM_LANG_CSHARP;
     resolve_cache_entry_t *cached =
         _resolve_cache ? (resolve_cache_entry_t *)cbm_ht_get(_resolve_cache, callee_name) : NULL;
-    if (cached && cached->scope_len == scope_len && cached->skip_members == skip_members)
+    if (cached && cached->scope_len == scope_len && cached->skip_members == skip_members &&
+        cached->cs_keywords == cs_keywords)
         return cached->res;
 
     cbm_resolution_t res =
         registry_resolve_chain(r, callee_name, module_qn, import_map_keys, import_map_vals,
-                               import_map_count, scope_len, skip_members);
+                               import_map_count, scope_len, skip_members, call_lang);
 
     /* Data relations (Table/View) are lineage-only registry members: common
      * table names (users, orders, config) collide with code identifiers across
@@ -2711,12 +2728,14 @@ static cbm_resolution_t registry_resolve_scoped(const cbm_registry_t *r, const c
         cached->res = res;
         cached->scope_len = scope_len;
         cached->skip_members = skip_members;
+        cached->cs_keywords = cs_keywords;
     } else if (_resolve_cache) {
         resolve_cache_entry_t *e = (resolve_cache_entry_t *)malloc(sizeof(*e));
         if (e) {
             e->res = res;
             e->scope_len = scope_len;
             e->skip_members = skip_members;
+            e->cs_keywords = cs_keywords;
             char *kdup = strdup(callee_name);
             if (kdup) {
                 cbm_ht_set(_resolve_cache, kdup, e);
@@ -3028,22 +3047,28 @@ static bool swift_signature_matches(const swift_signature_t *meta, const CBMCall
 }
 
 /* Keep receiver choice ahead of general import/name choice. Without a module,
- * this path still uses the deterministic distance tie-break, as before. */
-static const char *swift_choose_receiver(const cbm_registry_t *r, const char **matches, int matched,
-                                         const char *name, const CBMCall *call,
-                                         const char *module_qn, const char **import_vals,
-                                         int import_count, const char **scratch) {
+ * this path still uses the deterministic distance tie-break, as before.
+ * `match_test` holds the stored test verdict of each of `matches`, and
+ * `scratch_test` is the matching scratch, so every filtered list the scorer
+ * sees carries its own verdicts. */
+static const char *swift_choose_receiver(const cbm_registry_t *r, const char **matches,
+                                         const uint8_t *match_test, int matched, const char *name,
+                                         const CBMCall *call, const char *module_qn,
+                                         const char **import_vals, int import_count,
+                                         const char **scratch, uint8_t *scratch_test) {
     if (!strchr(call->callee_name, '.')) {
         return NULL;
     }
     size_t callee_len = strlen(call->callee_name);
     const char **receiver_matches = scratch;
+    uint8_t *receiver_test = scratch_test;
     int receiver_count = 0;
     for (int i = 0; i < matched; i++) {
         size_t base = cbm_qn_callable_base_len_named(matches[i], name);
         if (base >= callee_len &&
             memcmp(matches[i] + base - callee_len, call->callee_name, callee_len) == 0 &&
             (base == callee_len || matches[i][base - callee_len - SKIP_ONE] == '.')) {
+            receiver_test[receiver_count] = match_test[i];
             receiver_matches[receiver_count++] = matches[i];
         }
     }
@@ -3051,45 +3076,53 @@ static const char *swift_choose_receiver(const cbm_registry_t *r, const char **m
         return NULL;
     }
     const char **reachable = scratch + matched;
+    uint8_t *reachable_test = scratch_test + matched;
     int reachable_count = 0;
     if (import_vals) {
         for (int i = 0; i < receiver_count; i++) {
             if (is_import_reachable(receiver_matches[i], import_vals, import_count)) {
+                reachable_test[reachable_count] = receiver_test[i];
                 reachable[reachable_count++] = receiver_matches[i];
             }
         }
     }
     const char **preferred = reachable_count > 0 ? reachable : receiver_matches;
+    const uint8_t *preferred_test = reachable_count > 0 ? reachable_test : receiver_test;
     int preferred_count = reachable_count > 0 ? reachable_count : receiver_count;
-    return best_by_import_distance(r, preferred, NULL, NULL, preferred_count, module_qn);
+    return best_by_import_distance(r, preferred, preferred_test, NULL, preferred_count, module_qn);
 }
 
 static const char *swift_choose_candidate(const cbm_registry_t *r, const char **matches,
-                                          int matched, const char *name, const CBMCall *call,
-                                          const char *module_qn, const char **import_vals,
-                                          int import_count, const char **scratch) {
-    const char *chosen = swift_choose_receiver(r, matches, matched, name, call, module_qn,
-                                               import_vals, import_count, scratch);
+                                          const uint8_t *match_test, int matched, const char *name,
+                                          const CBMCall *call, const char *module_qn,
+                                          const char **import_vals, int import_count,
+                                          const char **scratch, uint8_t *scratch_test) {
+    const char *chosen =
+        swift_choose_receiver(r, matches, match_test, matched, name, call, module_qn, import_vals,
+                              import_count, scratch, scratch_test);
     if (chosen) {
         return chosen;
     }
     const char **reachable = scratch;
+    uint8_t *reachable_test = scratch_test;
     int reachable_count = 0;
     if (import_vals) {
         for (int i = 0; i < matched; i++) {
             if (is_import_reachable(matches[i], import_vals, import_count)) {
+                reachable_test[reachable_count] = match_test[i];
                 reachable[reachable_count++] = matches[i];
             }
         }
     }
     if (reachable_count > 0) {
-        chosen = module_qn
-                     ? best_by_import_distance(r, reachable, NULL, NULL, reachable_count, module_qn)
-                     : reachable[0];
+        chosen = module_qn ? best_by_import_distance(r, reachable, reachable_test, NULL,
+                                                     reachable_count, module_qn)
+                           : reachable[0];
     }
     if (!chosen) {
-        chosen = module_qn ? best_by_import_distance(r, matches, NULL, NULL, matched, module_qn)
-                           : matches[0];
+        chosen = module_qn
+                     ? best_by_import_distance(r, matches, match_test, NULL, matched, module_qn)
+                     : matches[0];
     }
     return chosen;
 }
@@ -3719,23 +3752,29 @@ int cbm_registry_swift_candidates(const cbm_registry_t *r, const CBMCall *call,
     if (!bucket) {
         return 0;
     }
+    /* Three QN lists (the matches and the choosers' two scratch lists), each
+     * with a parallel byte per entry for its stored test verdict, in one block. */
     enum { SWIFT_MATCH_BUFFERS = 3 };
-    if ((size_t)bucket->count > SIZE_MAX / sizeof(const char *) / SWIFT_MATCH_BUFFERS) {
+    const size_t slot = sizeof(const char *) + sizeof(uint8_t);
+    if ((size_t)bucket->count > SIZE_MAX / slot / SWIFT_MATCH_BUFFERS) {
         return SWIFT_INCOMPATIBLE;
     }
-    const char **matches = cbm_alloc(
-        CBM_MEM_CLASS_OTHER, (size_t)bucket->count * SWIFT_MATCH_BUFFERS * sizeof(*matches));
+    size_t slots = (size_t)bucket->count * SWIFT_MATCH_BUFFERS;
+    const char **matches = cbm_alloc(CBM_MEM_CLASS_OTHER, slots * slot);
     if (!matches) {
         return SWIFT_INCOMPATIBLE;
     }
+    uint8_t *match_test = (uint8_t *)(matches + slots);
+    const uint8_t *bucket_test = qn_test_flags(bucket);
     int matched = 0;
     bool has_swift = false;
     for (int i = 0; i < bucket->count; i++) {
         const char *qn = bucket->items[i];
         swift_signature_t *meta = cbm_ht_get(r->swift_signatures, qn);
         has_swift = has_swift || meta != NULL;
-        if (meta && receiver_chain_admits(call->callee_name, qn) &&
+        if (meta && receiver_chain_admits(call->callee_name, qn, CBM_LANG_SWIFT) &&
             swift_signature_matches(meta, call)) {
+            match_test[matched] = bucket_test[i];
             matches[matched++] = qn;
         }
     }
@@ -3743,8 +3782,9 @@ int cbm_registry_swift_candidates(const cbm_registry_t *r, const CBMCall *call,
         cbm_free(CBM_MEM_CLASS_OTHER, matches);
         return has_swift ? SWIFT_INCOMPATIBLE : 0;
     }
-    const char *chosen = swift_choose_candidate(r, matches, matched, name, call, module_qn,
-                                                import_vals, import_count, matches + bucket->count);
+    const char *chosen =
+        swift_choose_candidate(r, matches, match_test, matched, name, call, module_qn, import_vals,
+                               import_count, matches + bucket->count, match_test + bucket->count);
     if (!chosen) {
         cbm_free(CBM_MEM_CLASS_OTHER, matches);
         return 0;
@@ -4445,7 +4485,8 @@ cbm_resolution_t cbm_registry_resolve(const cbm_registry_t *r, const char *calle
                                       const char *module_qn, const char **import_map_keys,
                                       const char **import_map_vals, int import_map_count) {
     return registry_resolve_scoped(r, callee_name, module_qn, import_map_keys, import_map_vals,
-                                   import_map_count, module_qn ? strlen(module_qn) : 0, false);
+                                   import_map_count, module_qn ? strlen(module_qn) : 0, false,
+                                   CBM_LANG_COUNT);
 }
 
 static size_t lang_scope_len(const char *module_qn, CBMLanguage lang) {
@@ -4458,7 +4499,8 @@ cbm_resolution_t cbm_registry_resolve_lang(const cbm_registry_t *r, const char *
                                            const char **import_map_vals, int import_map_count,
                                            CBMLanguage lang) {
     return registry_resolve_scoped(r, callee_name, module_qn, import_map_keys, import_map_vals,
-                                   import_map_count, lang_scope_len(module_qn, lang), false);
+                                   import_map_count, lang_scope_len(module_qn, lang), false,
+                                   CBM_LANG_COUNT);
 }
 
 cbm_resolution_t cbm_registry_resolve_call_lang(const cbm_registry_t *r, const char *callee_name,
@@ -4472,7 +4514,8 @@ cbm_resolution_t cbm_registry_resolve_call_lang(const cbm_registry_t *r, const c
     bool skip_members = lang == CBM_LANG_C && callee_name && !strchr(callee_name, '.') &&
                         !strstr(callee_name, "->");
     return registry_resolve_scoped(r, callee_name, module_qn, import_map_keys, import_map_vals,
-                                   import_map_count, lang_scope_len(module_qn, lang), skip_members);
+                                   import_map_count, lang_scope_len(module_qn, lang), skip_members,
+                                   lang);
 }
 
 /* ── Class-qualified route handlers (PHP, #1146) ─────────────────── */
@@ -4640,7 +4683,8 @@ cbm_resolution_t cbm_registry_resolve_lineage(const cbm_registry_t *r, const cha
      * it would poison one variant with the other's semantics. SQL files hold
      * few distinct relation refs, so the chain walk stays cheap. */
     return registry_resolve_chain(r, callee_name, module_qn, import_map_keys, import_map_vals,
-                                  import_map_count, module_qn ? strlen(module_qn) : 0, false);
+                                  import_map_count, module_qn ? strlen(module_qn) : 0, false,
+                                  CBM_LANG_COUNT);
 }
 
 /* Python looks a bare name up in the calling def's own scope, then in each
@@ -4713,11 +4757,18 @@ cbm_resolution_t cbm_registry_resolve_call_scoped(const cbm_registry_t *r, const
 /* ── Fuzzy Resolve ──────────────────────────────────────────────── */
 
 /* Filter candidates by import reachability. Returns count of reachable. */
-static int filter_import_reachable(const char **candidates, int count, const char **import_vals,
-                                   int import_count, const char **out, int max_out) {
+/* Keeps `out_flags` and `out_langs` in step with `out`: the verdicts are
+ * stored per entry and cannot be recomputed from the QN, so a filtered view has
+ * to carry its own, and the languages travel with them. */
+static int filter_import_reachable(const char **candidates, const uint8_t *flags,
+                                   const uint8_t *langs, int count, const char **import_vals,
+                                   int import_count, const char **out, uint8_t *out_flags,
+                                   uint8_t *out_langs, int max_out) {
     int n = 0;
     for (int i = 0; i < count && n < max_out; i++) {
         if (is_import_reachable(candidates[i], import_vals, import_count)) {
+            out_flags[n] = flags[i];
+            out_langs[n] = langs[i];
             out[n++] = candidates[i];
         }
     }
@@ -4757,13 +4808,21 @@ cbm_fuzzy_result_t cbm_registry_fuzzy_resolve(const cbm_registry_t *r, const cha
 
     /* Multiple candidates: filter by import reachability */
     const char *filtered[CBM_SZ_256];
+    uint8_t filtered_flags[CBM_SZ_256];
+    uint8_t filtered_langs[CBM_SZ_256];
     int fcount = arr->count;
     const char **fptr = (const char **)arr->items;
+    const uint8_t *fflags = qn_test_flags(arr);
+    const uint8_t *flangs = qn_lang_flags(arr);
 
     if (have_imports) {
-        fcount = filter_import_reachable((const char **)arr->items, arr->count, import_map_vals,
-                                         import_map_count, filtered, CBM_SZ_256);
+        fcount = filter_import_reachable((const char **)arr->items, qn_test_flags(arr),
+                                         qn_lang_flags(arr), arr->count, import_map_vals,
+                                         import_map_count, filtered, filtered_flags, filtered_langs,
+                                         CBM_SZ_256);
         fptr = filtered;
+        fflags = filtered_flags;
+        flangs = filtered_langs;
     }
 
     if (fcount == 0) {
@@ -4783,9 +4842,7 @@ cbm_fuzzy_result_t cbm_registry_fuzzy_resolve(const cbm_registry_t *r, const cha
             {fptr[0], "fuzzy", candidate_count_penalty(CONF_FUZZY_SINGLE, arr->count), arr->count},
             true};
     }
-    const bool all = fptr == (const char **)arr->items;
-    const char *best = best_by_import_distance(r, fptr, all ? qn_test_flags(arr) : NULL,
-                                               all ? qn_lang_flags(arr) : NULL, fcount, module_qn);
+    const char *best = best_by_import_distance(r, fptr, fflags, flangs, fcount, module_qn);
     if (!best) {
         return no_match;
     }
diff --git a/tests/test_callable_sig.c b/tests/test_callable_sig.c
index 9f09e55d0..e981aa7ff 100644
--- a/tests/test_callable_sig.c
+++ b/tests/test_callable_sig.c
@@ -434,9 +434,9 @@ TEST(callable_sig_leaf_splitters_skip_suffix) {
  * keeps its historical key (last '.' or "::" segment). */
 TEST(callable_sig_registry_by_name_uses_base_leaf) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "upload", "p.Session.upload(_:Data,to:URL)", "Method");
-    cbm_registry_add(r, "upload", "p.Session.upload(_:Data,with:URLRequest)", "Method");
-    cbm_registry_add(r, "square", "p.Math::square", "Function");
+    cbm_registry_add(r, "upload", "p.Session.upload(_:Data,to:URL)", "Method", false);
+    cbm_registry_add(r, "upload", "p.Session.upload(_:Data,with:URLRequest)", "Method", false);
+    cbm_registry_add(r, "square", "p.Math::square", "Function", false);
     const char **out = NULL;
     int count = 0;
     cbm_registry_find_by_name(r, "upload", &out, &count);
diff --git a/tests/test_cli.c b/tests/test_cli.c
index a337cce4d..2be1371ed 100644
--- a/tests/test_cli.c
+++ b/tests/test_cli.c
@@ -18664,19 +18664,31 @@ TEST(cli_hook_augment_deadline_breadcrumb_issue858) {
     snprintf(logpath, sizeof(logpath), "%s/timeouts.log", tmpdir);
 
     int fds[2];
+    int errfds[2];
     if (pipe(fds) != 0) {
         test_rmdir_r(tmpdir);
         FAIL("pipe failed");
     }
+    if (pipe(errfds) != 0) {
+        close(fds[0]);
+        close(fds[1]);
+        test_rmdir_r(tmpdir);
+        FAIL("stderr pipe failed");
+    }
 
     fflush(NULL);
     pid_t pid = fork();
     if (pid == 0) {
         /* Child: hook-augment with a 60ms deadline and stdin that blocks
-         * forever (parent keeps the write end open, sends nothing). */
+         * forever (parent keeps the write end open, sends nothing). Its stderr
+         * is redirected so the parent can prove the deadline is also announced
+         * there, not only in the timeouts log. */
         close(fds[1]);
         dup2(fds[0], 0);
         close(fds[0]);
+        close(errfds[0]);
+        dup2(errfds[1], 2);
+        close(errfds[1]);
         setenv("CBM_HOOK_DEADLINE_MS", "60", 1);
         setenv("CBM_HOOK_TIMEOUT_LOG", logpath, 1);
         alarm(10); /* backstop: never hang the suite */
@@ -18684,6 +18696,19 @@ TEST(cli_hook_augment_deadline_breadcrumb_issue858) {
     }
     ASSERT_GT(pid, 0);
     close(fds[0]);
+    close(errfds[1]);
+
+    /* Drain the child's stderr before reaping, so a full pipe can never wedge
+     * it. EOF arrives once the child's deadline handler has run and _exit()ed. */
+    char errbuf[4096] = "";
+    size_t errlen = 0;
+    ssize_t rd;
+    while (errlen + 1 < sizeof(errbuf) &&
+           (rd = read(errfds[0], errbuf + errlen, sizeof(errbuf) - 1 - errlen)) > 0) {
+        errlen += (size_t)rd;
+    }
+    errbuf[errlen] = '\0';
+    close(errfds[0]);
 
     int status = 0;
     waitpid(pid, &status, 0);
@@ -18694,8 +18719,8 @@ TEST(cli_hook_augment_deadline_breadcrumb_issue858) {
     ASSERT_EQ(WEXITSTATUS(status), 0);
 
     /* RED before the fix: no breadcrumb existed — a fired deadline was
-     * indistinguishable from a no-match run. GREEN: the log names the
-     * deadline and the knob. */
+     * indistinguishable from a no-match run. GREEN: it is announced on BOTH
+     * the timeouts log and stderr, each naming the deadline and the knob. */
     FILE *f = fopen(logpath, "r");
     if (!f) {
         fprintf(stderr, "  [858] FAIL no timeout breadcrumb written to %s\n", logpath);
@@ -18708,6 +18733,9 @@ TEST(cli_hook_augment_deadline_breadcrumb_issue858) {
     ASSERT(strstr(line, "deadline_exceeded") != NULL);
     ASSERT(strstr(line, "CBM_HOOK_DEADLINE_MS") != NULL);
 
+    ASSERT(strstr(errbuf, "deadline_exceeded") != NULL);
+    ASSERT(strstr(errbuf, "CBM_HOOK_DEADLINE_MS") != NULL);
+
     cbm_unsetenv("CBM_HOOK_DEADLINE_MS");
     cbm_unsetenv("CBM_HOOK_TIMEOUT_LOG");
     test_rmdir_r(tmpdir);
diff --git a/tests/test_daemon_frontend.c b/tests/test_daemon_frontend.c
index aa49bf4c7..7e5c540ba 100644
--- a/tests/test_daemon_frontend.c
+++ b/tests/test_daemon_frontend.c
@@ -1641,6 +1641,32 @@ TEST(daemon_frontend_idle_uses_one_maintenance_observer) {
     ASSERT_TRUE(fixture_closed);
     PASS();
 }
+
+/* An idle monitor must not repeatedly perform the expensive presence probe
+ * while no maintenance request exists (#2093). The monitor records the exact
+ * value it sleeps on in its no-maintenance branch; once recorded that value is
+ * stable, so the verdict depends on neither elapsed time nor scheduler cadence.
+ * The deadline below is only a hang guard. */
+TEST(daemon_frontend_idle_maintenance_probe_is_bounded) {
+    frontend_maintenance_fixture_t fixture;
+    ASSERT_TRUE(frontend_maintenance_fixture_start(&fixture, "idle-cadence"));
+
+    cbm_daemon_frontend_test_observer_reset(false);
+    cbm_daemon_maintenance_monitor_t *monitor = cbm_daemon_maintenance_monitor_start(
+        fixture.manager, NULL, NULL, EXIT_SUCCESS, "idle cadence test");
+    ASSERT_TRUE(monitor != NULL);
+    uint64_t deadline = cbm_now_ms() + 10000U;
+    while (cbm_now_ms() < deadline && cbm_daemon_frontend_test_monitor_idle_sleep_ms() == 0) {
+        cbm_usleep(1000);
+    }
+    uint32_t idle_sleep_ms = cbm_daemon_frontend_test_monitor_idle_sleep_ms();
+    ASSERT_TRUE(cbm_daemon_maintenance_monitor_stop(&monitor));
+    frontend_maintenance_fixture_finish(&fixture);
+
+    ASSERT_TRUE(idle_sleep_ms != 0);
+    ASSERT_GTE(idle_sleep_ms, 250);
+    PASS();
+}
 #endif
 
 #ifndef _WIN32
@@ -1982,6 +2008,7 @@ SUITE(daemon_frontend) {
     RUN_TEST(daemon_frontend_rejects_non_notification_cancellation_shapes);
 #if defined(CBM_ENABLE_TEST_SEAMS) && CBM_ENABLE_TEST_SEAMS
     RUN_TEST(daemon_frontend_idle_uses_one_maintenance_observer);
+    RUN_TEST(daemon_frontend_idle_maintenance_probe_is_bounded);
 #endif
 #ifndef _WIN32
     RUN_TEST(daemon_frontend_maintenance_exits_while_stdio_reader_is_blocked);
diff --git a/tests/test_daemon_runtime.c b/tests/test_daemon_runtime.c
index 61488358c..c34c45f5b 100644
--- a/tests/test_daemon_runtime.c
+++ b/tests/test_daemon_runtime.c
@@ -5237,6 +5237,196 @@ TEST(daemon_runtime_process_fingerprint_never_hashes_replacement_path) {
 }
 #endif
 
+/* The executable-image fingerprint cache short-circuits the full-image hash for
+ * a repeated file identity, and rolls its key when the binary changes so a
+ * rebuild or atomic replacement never returns a stale digest. Results are
+ * gathered first and asserted only after the stub is disarmed: an assertion
+ * returns early, and an armed stub would replace every later fingerprint in
+ * this process. */
+TEST(daemon_runtime_fingerprint_cache_hit_miss_key_roll) {
+    /* 64-hex placeholders, distinct enough to tell "cached" from "recomputed". */
+    static const char digest_a[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] =
+        "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+    static const char digest_b[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] =
+        "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
+    const cbm_daemon_runtime_fingerprint_identity_for_testing_t image = {1,   2,   3,  100,
+                                                                         200, 300, 400};
+    cbm_daemon_runtime_fingerprint_identity_for_testing_t rolled = image;
+    char miss[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char hit[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char mtime_rolled[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char ctime_rolled[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char inode_rolled[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+
+    cbm_daemon_runtime_fingerprint_cache_reset_for_testing();
+    /* Miss: first sight of this identity pays the hash and stores digest_a. */
+    cbm_daemon_runtime_fingerprint_cache_set_hash_stub_for_testing(digest_a);
+    bool miss_ok = cbm_daemon_runtime_fingerprint_cache_resolve_for_testing(&image, &image, miss);
+    int hashes_after_miss = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    /* Hit: the same identity returns the cached digest without calling the
+     * hash, even though the stub would now yield a different value. */
+    cbm_daemon_runtime_fingerprint_cache_set_hash_stub_for_testing(digest_b);
+    bool hit_ok = cbm_daemon_runtime_fingerprint_cache_resolve_for_testing(&image, &image, hit);
+    int hashes_after_hit = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    /* Key roll: a changed mtime (a rebuilt binary) misses and recomputes. */
+    rolled = image;
+    rolled.mtime_seconds = 101;
+    bool mtime_ok =
+        cbm_daemon_runtime_fingerprint_cache_resolve_for_testing(&rolled, &rolled, mtime_rolled);
+    int hashes_after_mtime_roll = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    /* A changed change time (an in-place write, a metadata edit) rolls it too. */
+    rolled = image;
+    rolled.ctime_seconds = 301;
+    bool ctime_ok =
+        cbm_daemon_runtime_fingerprint_cache_resolve_for_testing(&rolled, &rolled, ctime_rolled);
+    int hashes_after_ctime_roll = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    /* A changed inode (atomic replacement) likewise rolls the key. */
+    rolled = image;
+    rolled.inode = 9;
+    bool inode_ok =
+        cbm_daemon_runtime_fingerprint_cache_resolve_for_testing(&rolled, &rolled, inode_rolled);
+    int hashes_after_inode_roll = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    cbm_daemon_runtime_fingerprint_cache_reset_for_testing();
+
+    ASSERT_TRUE(miss_ok);
+    ASSERT_STR_EQ(miss, digest_a);
+    ASSERT_EQ(hashes_after_miss, 1);
+    ASSERT_TRUE(hit_ok);
+    ASSERT_STR_EQ(hit, digest_a);
+    ASSERT_EQ(hashes_after_hit, 1);
+    ASSERT_TRUE(mtime_ok);
+    ASSERT_STR_EQ(mtime_rolled, digest_b);
+    ASSERT_EQ(hashes_after_mtime_roll, 2);
+    ASSERT_TRUE(ctime_ok);
+    ASSERT_STR_EQ(ctime_rolled, digest_b);
+    ASSERT_EQ(hashes_after_ctime_roll, 3);
+    ASSERT_TRUE(inode_ok);
+    ASSERT_STR_EQ(inode_rolled, digest_b);
+    ASSERT_EQ(hashes_after_inode_roll, 4);
+    PASS();
+}
+
+/* A digest is committed only when the identity observed after the hash is the
+ * one it was keyed on. An image that changed under the hash still yields the
+ * bytes read for that acquisition (the acquire chain's own post-hash stat check
+ * is what rejects it) but is never cached, so the next sight of the original
+ * identity hashes again. */
+TEST(daemon_runtime_fingerprint_cache_skips_image_changed_under_hash) {
+    static const char digest[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] =
+        "dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd";
+    const cbm_daemon_runtime_fingerprint_identity_for_testing_t image = {1,   2,   3,  100,
+                                                                         200, 300, 400};
+    cbm_daemon_runtime_fingerprint_identity_for_testing_t moved = image;
+    moved.ctime_seconds = 301;
+    char first[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char second[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+
+    cbm_daemon_runtime_fingerprint_cache_reset_for_testing();
+    cbm_daemon_runtime_fingerprint_cache_set_hash_stub_for_testing(digest);
+    bool first_ok = cbm_daemon_runtime_fingerprint_cache_resolve_for_testing(&image, &moved, first);
+    int hashes_after_first = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    bool second_ok =
+        cbm_daemon_runtime_fingerprint_cache_resolve_for_testing(&image, &image, second);
+    int hashes_after_second = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    cbm_daemon_runtime_fingerprint_cache_reset_for_testing();
+
+    ASSERT_TRUE(first_ok);
+    ASSERT_STR_EQ(first, digest);
+    ASSERT_EQ(hashes_after_first, 1);
+    ASSERT_TRUE(second_ok);
+    ASSERT_STR_EQ(second, digest);
+    ASSERT_EQ(hashes_after_second, 2);
+    PASS();
+}
+
+/* The real acquire path: fingerprinting this process twice pays the image hash
+ * once, and the second call is served from the cache inside the same bracketed
+ * identity checks. This drives cbm_daemon_runtime_process_build_fingerprint,
+ * not the seam, so a cache wired into the seam but not into the platform's
+ * acquire site fails here. */
+TEST(daemon_runtime_process_fingerprint_hashes_own_image_once_per_process) {
+    static const char digest[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] =
+        "eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee";
+    char first[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char second[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+
+    cbm_daemon_runtime_fingerprint_cache_reset_for_testing();
+    cbm_daemon_runtime_fingerprint_cache_set_hash_stub_for_testing(digest);
+    bool first_ok = cbm_daemon_runtime_process_build_fingerprint(runtime_test_process_id(), first);
+    int hashes_after_first = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    bool second_ok =
+        cbm_daemon_runtime_process_build_fingerprint(runtime_test_process_id(), second);
+    int hashes_after_second = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    cbm_daemon_runtime_fingerprint_cache_reset_for_testing();
+
+    ASSERT_TRUE(first_ok);
+    ASSERT_TRUE(second_ok);
+    ASSERT_STR_EQ(first, digest);
+    ASSERT_STR_EQ(second, digest);
+    ASSERT_EQ(hashes_after_first, 1);
+    ASSERT_EQ(hashes_after_second, 1);
+    PASS();
+}
+
+#if defined(__APPLE__) || defined(__linux__)
+/* Only this process's own image is cached. The peer here is this very runner
+ * spawned in holder mode, so its image has exactly the file identity the own
+ * image is cached under: a cache keyed on that identity alone would answer for
+ * the peer. A peer must be hashed on every fingerprint, before and after the
+ * own image is cached, while the own image still costs one hash. */
+TEST(daemon_runtime_process_fingerprint_caches_only_own_image) {
+    static const char digest[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] =
+        "cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc";
+    char image_path[RUNTIME_TEST_PATH_CAP] = {0};
+    char peer_first[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char peer_second[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char own_first[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char own_second[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    char peer_after_own[CBM_DAEMON_BUILD_FINGERPRINT_SIZE] = {0};
+    int release_fd = -1;
+    bool setup = runtime_test_self_image_path(image_path);
+    pid_t child = setup ? runtime_test_spawn_blocked_executable(image_path, &release_fd) : -1;
+    setup = setup && child > 0;
+
+    cbm_daemon_runtime_fingerprint_cache_reset_for_testing();
+    cbm_daemon_runtime_fingerprint_cache_set_hash_stub_for_testing(digest);
+    bool peer_first_ok =
+        setup && cbm_daemon_runtime_process_build_fingerprint((uint64_t)child, peer_first);
+    bool peer_second_ok =
+        setup && cbm_daemon_runtime_process_build_fingerprint((uint64_t)child, peer_second);
+    int hashes_after_peer = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    bool own_first_ok =
+        cbm_daemon_runtime_process_build_fingerprint(runtime_test_process_id(), own_first);
+    bool own_second_ok =
+        cbm_daemon_runtime_process_build_fingerprint(runtime_test_process_id(), own_second);
+    int hashes_after_own = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    bool peer_after_own_ok =
+        setup && cbm_daemon_runtime_process_build_fingerprint((uint64_t)child, peer_after_own);
+    int hashes_after_peer_again = cbm_daemon_runtime_fingerprint_hash_call_count_for_testing();
+    cbm_daemon_runtime_fingerprint_cache_reset_for_testing();
+    runtime_test_stop_blocked_executable(child, release_fd);
+
+    ASSERT_TRUE(setup);
+    ASSERT_TRUE(peer_first_ok);
+    ASSERT_TRUE(peer_second_ok);
+    ASSERT_TRUE(own_first_ok);
+    ASSERT_TRUE(own_second_ok);
+    ASSERT_TRUE(peer_after_own_ok);
+    ASSERT_STR_EQ(peer_first, digest);
+    ASSERT_STR_EQ(peer_second, digest);
+    ASSERT_STR_EQ(own_first, digest);
+    ASSERT_STR_EQ(own_second, digest);
+    ASSERT_STR_EQ(peer_after_own, digest);
+    /* Each peer fingerprint pays its own hash: a peer is never cached. */
+    ASSERT_EQ(hashes_after_peer, 2);
+    /* The own image is hashed once, then served from the cache. */
+    ASSERT_EQ(hashes_after_own, 3);
+    /* The cached own entry never answers for the peer's identical file. */
+    ASSERT_EQ(hashes_after_peer_again, 4);
+    PASS();
+}
+#endif
+
 TEST(daemon_runtime_close_begin_releases_admission_with_inflight_request) {
     static const uint8_t request[] = {'b', 'l', 'o', 'c', 'k'};
     cbm_daemon_build_identity_t identity =
@@ -5430,6 +5620,12 @@ SUITE(daemon_runtime) {
     RUN_TEST(daemon_runtime_copied_image_fallback_accepts_identical_and_rejects_changed);
 #if defined(_WIN32) || defined(__APPLE__) || defined(__linux__)
     RUN_TEST(daemon_runtime_process_fingerprint_never_hashes_replacement_path);
+#endif
+    RUN_TEST(daemon_runtime_fingerprint_cache_hit_miss_key_roll);
+    RUN_TEST(daemon_runtime_fingerprint_cache_skips_image_changed_under_hash);
+    RUN_TEST(daemon_runtime_process_fingerprint_hashes_own_image_once_per_process);
+#if defined(__APPLE__) || defined(__linux__)
+    RUN_TEST(daemon_runtime_process_fingerprint_caches_only_own_image);
 #endif
     RUN_TEST(daemon_runtime_convenience_service_owns_participant_guard);
     RUN_TEST(daemon_runtime_host_loop_stops_on_coordination_file_loss);
diff --git a/tests/test_fqn.c b/tests/test_fqn.c
index 013bea6a9..d2734df0d 100644
--- a/tests/test_fqn.c
+++ b/tests/test_fqn.c
@@ -630,6 +630,23 @@ TEST(project_name_encodes_unicode_segments_issue571) {
     PASS();
 }
 
+TEST(project_name_unicode_segments_do_not_collide_issue571) {
+    char *first = cbm_project_name_from_path("/Users/dev/\xe5\xbc\x80\xe5\x8f\x91");
+    char *second = cbm_project_name_from_path("/Users/dev/\xe5\x90\x8e\xe7\xab\xaf");
+    ASSERT_NOT_NULL(first);
+    ASSERT_NOT_NULL(second);
+    ASSERT_STR_NEQ(first, second);
+    /* Distinct is not enough: each name must carry the hex image of its own
+     * non-ASCII segment, so the segment is preserved rather than replaced. */
+    ASSERT_NOT_NULL(strstr(first, "e5bc80e58f91"));
+    ASSERT_NOT_NULL(strstr(second, "e5908ee7abaf"));
+    ASSERT_TRUE(cbm_validate_project_name(first));
+    ASSERT_TRUE(cbm_validate_project_name(second));
+    free(first);
+    free(second);
+    PASS();
+}
+
 /* issue #624: #571 preserves non-ASCII path segments by hex-encoding each byte
  * (1 byte -> 2 hex chars), so a DEEP non-ASCII path triples in length and can
  * blow past the filesystem's 255-byte filename-component limit. Then
@@ -802,6 +819,7 @@ SUITE(fqn) {
     RUN_TEST(project_name_deep_path);
     RUN_TEST(project_name_always_validator_safe_issue349);
     RUN_TEST(project_name_encodes_unicode_segments_issue571);
+    RUN_TEST(project_name_unicode_segments_do_not_collide_issue571);
     RUN_TEST(project_name_length_capped_issue624);
     RUN_TEST(project_name_colon_only);
     RUN_TEST(project_name_backslash_only);
diff --git a/tests/test_parallel.c b/tests/test_parallel.c
index 09815518a..59c8b9130 100644
--- a/tests/test_parallel.c
+++ b/tests/test_parallel.c
@@ -3331,6 +3331,100 @@ TEST(parallel_csharp_parse_damaged_namespace_is_not_global) {
     PASS();
 }
 
+/* #2121, the issue's own two files: C# spells its built-in types as lower-case
+ * keywords, so `int.TryParse(...)` calls the BCL, never the project's only
+ * TryParse. The LSP's answer (System.Int32.TryParse) has no graph node, so the
+ * call falls through to the registry, whose receiver chain check used to skip
+ * every lower-case root. Both resolvers must refuse the name guess (also for
+ * the C# 9 `nint`), and a real call to the project type must still bind. */
+TEST(parallel_csharp_keyword_receiver_no_name_guess_issue2121) {
+    static const char decoys_src[] =
+        "namespace Contoso.App;\n"
+        "\n"
+        "public class TsidNode\n"
+        "{\n"
+        "    public static bool TryParse(string text, out TsidNode n)\n"
+        "    {\n"
+        "        n = null;\n"
+        "        return false;\n"
+        "    }\n"
+        "}\n";
+    static const char demo_src[] = "using Microsoft.Extensions.Options;\n"
+                                   "\n"
+                                   "namespace Contoso.App;\n"
+                                   "\n"
+                                   "public class Demo\n"
+                                   "{\n"
+                                   "    public string M(string input)\n"
+                                   "    {\n"
+                                   "        _ = int.TryParse(input, out _);\n"
+                                   "        _ = nint.TryParse(input, out _);\n"
+                                   "        return input;\n"
+                                   "    }\n"
+                                   "\n"
+                                   "    public string Control(string input)\n"
+                                   "    {\n"
+                                   "        _ = TsidNode.TryParse(input, out _);\n"
+                                   "        return input;\n"
+                                   "    }\n"
+                                   "}\n";
+    const char *project = "cbm_cs_2121";
+    static const char *rels[] = {"src/Decoys.cs", "src/Demo.cs"};
+    const char *srcs[] = {decoys_src, demo_src};
+    enum { N_FILES = 2 };
+
+    char tmpdir[256];
+    snprintf(tmpdir, sizeof(tmpdir), "/tmp/cbm_par_cs_2121_XXXXXX");
+    if (!cbm_mkdtemp(tmpdir)) {
+        FAIL("mkdtemp failed");
+    }
+    char paths[N_FILES][512];
+    cbm_file_info_t files[N_FILES] = {0};
+    for (int i = 0; i < N_FILES; i++) {
+        snprintf(paths[i], sizeof(paths[i]), "%s/%s", tmpdir, rels[i]);
+        if (th_write_file(paths[i], srcs[i]) != 0) {
+            th_rmtree(tmpdir);
+            FAIL("failed to write #2121 fixture");
+        }
+        files[i].path = paths[i];
+        files[i].rel_path = (char *)rels[i];
+        files[i].language = CBM_LANG_CSHARP;
+    }
+
+    cbm_gbuf_t *graphs[2] = {run_sequential_with_lsp_cross(project, tmpdir, files, N_FILES), NULL};
+    g_harness_cs_registry = true;
+    graphs[1] = run_parallel(project, tmpdir, files, N_FILES, 2);
+    g_harness_cs_registry = false;
+    ASSERT_NOT_NULL(graphs[0]);
+    ASSERT_NOT_NULL(graphs[1]);
+
+    const char *tsid = "cbm_cs_2121.src.Decoys.TsidNode.TryParse";
+    bool ok[2][4];
+    bool all = true;
+    for (int g = 0; g < 2; g++) {
+        cbm_gbuf_t *gb = graphs[g];
+        /* The negative below must not pass because a node went missing. */
+        ok[g][0] = cbm_gbuf_find_by_qn(gb, tsid) != NULL;
+        ok[g][1] = find_unique_callable_node_by_tail(gb, "Demo.M") != NULL;
+        ok[g][2] = !has_edge_from_callable_to_qn(gb, "Demo.M", tsid, "CALLS");
+        ok[g][3] = has_edge_from_callable_to_qn(gb, "Demo.Control", tsid, "CALLS");
+        for (int k = 0; k < 4; k++) {
+            all = all && ok[g][k];
+        }
+    }
+    if (!all) {
+        for (int g = 0; g < 2; g++) {
+            printf("  #2121 diagnostic %s: target=%d caller=%d no_keyword_guess=%d control=%d\n",
+                   g == 0 ? "sequential" : "parallel", ok[g][0], ok[g][1], ok[g][2], ok[g][3]);
+        }
+    }
+    cbm_gbuf_free(graphs[0]);
+    cbm_gbuf_free(graphs[1]);
+    th_rmtree(tmpdir);
+    ASSERT_TRUE(all);
+    PASS();
+}
+
 /* External Kotlin protocol targets must not borrow a project method merely
  * because the final Class.method segments agree. Raw assertions prove that the
  * iterator/destructuring carriers and their stdlib semantic rows really exist;
@@ -6031,6 +6125,7 @@ SUITE(parallel) {
     RUN_TEST(parallel_csharp_same_name_class_binds_by_namespace);
     RUN_TEST(parallel_csharp_nested_type_and_global_namespace_binding);
     RUN_TEST(parallel_csharp_parse_damaged_namespace_is_not_global);
+    RUN_TEST(parallel_csharp_keyword_receiver_no_name_guess_issue2121);
     RUN_TEST(parallel_kotlin_external_protocol_does_not_use_project_class_method_tail);
     RUN_TEST(parallel_kotlin_nonbinary_operator_carriers_reach_graph);
     RUN_TEST(parallel_rust_cross_crate_worker_receives_workspace_manifest);
diff --git a/tests/test_pipeline.c b/tests/test_pipeline.c
index 71d423f50..baf2e34b7 100644
--- a/tests/test_pipeline.c
+++ b/tests/test_pipeline.c
@@ -6619,6 +6619,132 @@ TEST(pipeline_incremental_cross_file_call_reference_matches_fresh_full) {
     PASS();
 }
 
+/* #2427 rank probes: one bare call, two same-named candidates, and the
+ * registry's test ranking alone decides which one the call binds. Three runs
+ * on one database: a full index, then a comment-only edit of the caller on
+ * the closure-repair route, then another on the forced legacy-partial route.
+ * Both incremental routes re-resolve the caller against a registry seeded from
+ * stored nodes rather than the extractor's definitions, which is where a
+ * seeder that loses the verdict shows. */
+typedef struct {
+    int want[3];
+    int other[3];
+    cbm_incremental_route_t route[3];
+} rank_probe_t;
+
+static int rank_probe_count(const char *db, const char *project, const char *source,
+                            const char *target, const char *file) {
+    cbm_store_t *s = cbm_store_open_path(db);
+    if (!s) {
+        return -1;
+    }
+    int n = named_edge_to_file_count(s, project, "CALLS", source, target, file);
+    cbm_store_close(s);
+    return n;
+}
+
+static void rank_probe(const char *tmp, const char *caller_path, const char *caller_src,
+                       const char *source, const char *target, const char *want_file,
+                       const char *other_file, rank_probe_t *out) {
+    char db[512];
+    snprintf(db, sizeof(db), "%s/rank.db", tmp);
+    for (int run = 0; run < 3; run++) {
+        out->want[run] = -1;
+        out->other[run] = -1;
+        out->route[run] = CBM_INCREMENTAL_ROUTE_NONE;
+        if (run > 0) {
+            char edited[512];
+            snprintf(edited, sizeof(edited), "%s// edit %d\n", caller_src, run);
+            write_temp_file(tmp, caller_path, edited);
+        }
+        cbm_pipeline_incremental_test_reset_faults();
+#if defined(CBM_INCREMENTAL_TEST_API) && CBM_INCREMENTAL_TEST_API
+        if (run == 2) {
+            cbm_pipeline_incremental_test_force_legacy_partial_once();
+        }
+#endif
+        cbm_pipeline_t *p = cbm_pipeline_new(tmp, db, CBM_MODE_FULL);
+        if (!p) {
+            return;
+        }
+        int rc = cbm_pipeline_run(p);
+        out->route[run] = cbm_pipeline_incremental_test_last_route();
+        char project[256];
+        snprintf(project, sizeof(project), "%s", cbm_pipeline_project_name(p));
+        cbm_pipeline_free(p);
+        if (rc != 0) {
+            return;
+        }
+        out->want[run] = rank_probe_count(db, project, source, target, want_file);
+        out->other[run] = rank_probe_count(db, project, source, target, other_file);
+    }
+}
+
+/* "latest" spells "test", so the QN scan the extractor's verdict replaced
+ * ranked the production Parse below a helper in a _test.go file, whose Go QN
+ * names only its package and so spells nothing. The verdict ranks them the
+ * right way round, and both incremental routes must read the same verdict
+ * back from the stored nodes: the closure-repair proxies once carried no
+ * is_test, every candidate scored as production, and the smaller QN -- the
+ * test helper -- won. */
+TEST(pipeline_registry_ranks_by_extractor_verdict_full_and_incremental) {
+    char tmp[256];
+    snprintf(tmp, sizeof(tmp), "/tmp/cbm_rank_verdict_XXXXXX");
+    ASSERT_NOT_NULL(cbm_mkdtemp(tmp));
+    static const char caller[] = "package app\n\nfunc Run() int { return Parse() }\n";
+    write_temp_file(tmp, "go.mod", "module example.com/rank\n\ngo 1.22\n");
+    write_temp_file(tmp, "latest/parse.go", "package latest\n\nfunc Parse() int { return 1 }\n");
+    write_temp_file(tmp, "harness/parse_test.go",
+                    "package harness\n\nfunc Parse() int { return 2 }\n");
+    write_temp_file(tmp, "app/run.go", caller);
+    rank_probe_t r;
+    rank_probe(tmp, "app/run.go", caller, "Run", "Parse", "latest/parse.go",
+               "harness/parse_test.go", &r);
+    th_rmtree(tmp);
+    ASSERT_EQ(r.want[0], 1); /* full */
+    ASSERT_EQ(r.other[0], 0);
+    ASSERT_EQ(r.route[1], CBM_INCREMENTAL_ROUTE_CLOSURE_REPAIR);
+    ASSERT_EQ(r.want[1], 1);
+    ASSERT_EQ(r.other[1], 0);
+#if defined(CBM_INCREMENTAL_TEST_API) && CBM_INCREMENTAL_TEST_API
+    ASSERT_EQ(r.route[2], CBM_INCREMENTAL_ROUTE_LEGACY_PARTIAL);
+#endif
+    ASSERT_EQ(r.want[2], 1);
+    ASSERT_EQ(r.other[2], 0);
+    PASS();
+}
+
+/* A generated fake beside its callers: client/fake shares more of the caller's
+ * package path than the real store does, so on the extractor's verdict alone
+ * (a fake is not a test file) the fake wins on proximity. The test-double path
+ * rule ranks it last in the full index and, through the incremental seed's own
+ * use of the rule, on both incremental routes. */
+TEST(pipeline_registry_ranks_test_doubles_last_full_and_incremental) {
+    char tmp[256];
+    snprintf(tmp, sizeof(tmp), "/tmp/cbm_rank_double_XXXXXX");
+    ASSERT_NOT_NULL(cbm_mkdtemp(tmp));
+    static const char caller[] = "package client\n\nfunc Run() int { return Load() }\n";
+    write_temp_file(tmp, "go.mod", "module example.com/rank\n\ngo 1.22\n");
+    write_temp_file(tmp, "store/load.go", "package store\n\nfunc Load() int { return 1 }\n");
+    write_temp_file(tmp, "client/fake/load.go", "package fake\n\nfunc Load() int { return 2 }\n");
+    write_temp_file(tmp, "client/run.go", caller);
+    rank_probe_t r;
+    rank_probe(tmp, "client/run.go", caller, "Run", "Load", "store/load.go", "client/fake/load.go",
+               &r);
+    th_rmtree(tmp);
+    ASSERT_EQ(r.want[0], 1); /* full */
+    ASSERT_EQ(r.other[0], 0);
+    ASSERT_EQ(r.route[1], CBM_INCREMENTAL_ROUTE_CLOSURE_REPAIR);
+    ASSERT_EQ(r.want[1], 1);
+    ASSERT_EQ(r.other[1], 0);
+#if defined(CBM_INCREMENTAL_TEST_API) && CBM_INCREMENTAL_TEST_API
+    ASSERT_EQ(r.route[2], CBM_INCREMENTAL_ROUTE_LEGACY_PARTIAL);
+#endif
+    ASSERT_EQ(r.want[2], 1);
+    ASSERT_EQ(r.other[2], 0);
+    PASS();
+}
+
 /* A semantic control file can change an unchanged source file's exact target.
  * Both target modules deliberately export the same short name: without the
  * tsconfig path mapping, project-wide unique-name fallback is ambiguous and
@@ -21834,7 +21960,7 @@ static int python_typed_field_scope_case(bool external) {
     if (result && reg && gbuf && result->field_types.count == 1) {
         for (int i = 0; i < result->defs.count; i++) {
             const CBMDefinition *def = &result->defs.items[i];
-            cbm_registry_add(reg, def->name, def->qualified_name, def->label);
+            cbm_registry_add(reg, def->name, def->qualified_name, def->label, false);
         }
         const char **keys = NULL;
         const char **vals = NULL;
@@ -27801,8 +27927,8 @@ TEST(helm_parse_chart_many_dependencies) {
 
 TEST(registry_resolve_single_candidate) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "CreateOrder", "svcA.handlers.CreateOrder", "Function");
-    cbm_registry_add(reg, "ValidateOrder", "svcB.validators.ValidateOrder", "Function");
+    cbm_registry_add(reg, "CreateOrder", "svcA.handlers.CreateOrder", "Function", false);
+    cbm_registry_add(reg, "ValidateOrder", "svcB.validators.ValidateOrder", "Function", false);
 
     /* Normal resolve unique name */
     cbm_resolution_t r = cbm_registry_resolve(reg, "CreateOrder", "svcC.caller", NULL, NULL, 0);
@@ -27820,7 +27946,7 @@ TEST(registry_resolve_single_candidate) {
 
 TEST(registry_fuzzy_nonexistent) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "CreateOrder", "svcA.handlers.CreateOrder", "Function");
+    cbm_registry_add(reg, "CreateOrder", "svcA.handlers.CreateOrder", "Function", false);
 
     cbm_fuzzy_result_t fr =
         cbm_registry_fuzzy_resolve(reg, "NonExistent", "svcC.caller", NULL, NULL, 0);
@@ -27832,8 +27958,8 @@ TEST(registry_fuzzy_nonexistent) {
 
 TEST(registry_fuzzy_multiple_best_by_distance) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Process", "svcA.handlers.Process", "Function");
-    cbm_registry_add(reg, "Process", "svcB.handlers.Process", "Function");
+    cbm_registry_add(reg, "Process", "svcA.handlers.Process", "Function", false);
+    cbm_registry_add(reg, "Process", "svcB.handlers.Process", "Function", false);
 
     /* Caller in svcA → prefer svcA */
     cbm_fuzzy_result_t fr =
@@ -27852,7 +27978,7 @@ TEST(registry_fuzzy_multiple_best_by_distance) {
 
 TEST(registry_fuzzy_simple_name_extraction) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "DoWork", "myproject.utils.DoWork", "Function");
+    cbm_registry_add(reg, "DoWork", "myproject.utils.DoWork", "Function", false);
 
     /* Deeply qualified name → extract "DoWork" */
     cbm_fuzzy_result_t fr = cbm_registry_fuzzy_resolve(reg, "some.deep.module.DoWork",
@@ -27877,8 +28003,8 @@ TEST(registry_fuzzy_empty) {
 
 TEST(registry_exists) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Foo", "pkg.module.Foo", "Function");
-    cbm_registry_add(reg, "Bar", "pkg.module.Bar", "Method");
+    cbm_registry_add(reg, "Foo", "pkg.module.Foo", "Function", false);
+    cbm_registry_add(reg, "Bar", "pkg.module.Bar", "Method", false);
 
     ASSERT_TRUE(cbm_registry_exists(reg, "pkg.module.Foo"));
     ASSERT_TRUE(cbm_registry_exists(reg, "pkg.module.Bar"));
@@ -27891,7 +28017,7 @@ TEST(registry_exists) {
 
 TEST(registry_confidence_import_map) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Foo", "proj.other.Foo", "Function");
+    cbm_registry_add(reg, "Foo", "proj.other.Foo", "Function", false);
 
     const char *keys[] = {"other"};
     const char *vals[] = {"proj.other"};
@@ -27906,7 +28032,7 @@ TEST(registry_confidence_import_map) {
 
 TEST(registry_confidence_import_map_suffix) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Foo", "proj.other.sub.Foo", "Function");
+    cbm_registry_add(reg, "Foo", "proj.other.sub.Foo", "Function", false);
 
     const char *keys[] = {"other"};
     const char *vals[] = {"proj.other"};
@@ -27921,7 +28047,7 @@ TEST(registry_confidence_import_map_suffix) {
 
 TEST(registry_confidence_same_module) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Foo", "proj.pkg.Foo", "Function");
+    cbm_registry_add(reg, "Foo", "proj.pkg.Foo", "Function", false);
 
     cbm_resolution_t r = cbm_registry_resolve(reg, "Foo", "proj.pkg", NULL, NULL, 0);
     ASSERT_STR_EQ(r.qualified_name, "proj.pkg.Foo");
@@ -27934,7 +28060,7 @@ TEST(registry_confidence_same_module) {
 
 TEST(registry_confidence_unique_name) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Bar", "proj.pkg.Bar", "Function");
+    cbm_registry_add(reg, "Bar", "proj.pkg.Bar", "Function", false);
 
     cbm_resolution_t r = cbm_registry_resolve(reg, "Bar", "proj.unrelated", NULL, NULL, 0);
     ASSERT_STR_EQ(r.qualified_name, "proj.pkg.Bar");
@@ -27947,8 +28073,8 @@ TEST(registry_confidence_unique_name) {
 
 TEST(registry_confidence_suffix_match) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Process", "proj.svcA.Process", "Function");
-    cbm_registry_add(reg, "Process", "proj.svcB.Process", "Function");
+    cbm_registry_add(reg, "Process", "proj.svcA.Process", "Function", false);
+    cbm_registry_add(reg, "Process", "proj.svcB.Process", "Function", false);
 
     cbm_resolution_t r = cbm_registry_resolve(reg, "Process", "proj.svcA.caller", NULL, NULL, 0);
     ASSERT_STR_EQ(r.qualified_name, "proj.svcA.Process");
@@ -27964,7 +28090,7 @@ TEST(registry_confidence_suffix_match) {
  * wrong target — and with one candidate it won the top name-only confidence. */
 TEST(registry_receiver_chain_refuses_library_unique_name_issue1893) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "data", "HomeboxUI.PickedFile.data", "Variable");
+    cbm_registry_add(reg, "data", "HomeboxUI.PickedFile.data", "Variable", false);
 
     cbm_resolution_t r =
         cbm_registry_resolve(reg, "URLSession.shared.data", "HomeboxUI.Net", NULL, NULL, 0);
@@ -27978,8 +28104,8 @@ TEST(registry_receiver_chain_refuses_library_unique_name_issue1893) {
  * the final name and import distance picks the winner. */
 TEST(registry_receiver_chain_refuses_library_suffix_match_issue1893) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "data", "HomeboxUI.PickedFile.data", "Variable");
-    cbm_registry_add(reg, "data", "HomeboxUI.Payload.data", "Variable");
+    cbm_registry_add(reg, "data", "HomeboxUI.PickedFile.data", "Variable", false);
+    cbm_registry_add(reg, "data", "HomeboxUI.Payload.data", "Variable", false);
 
     cbm_resolution_t r =
         cbm_registry_resolve(reg, "URLSession.shared.data", "HomeboxUI.Net", NULL, NULL, 0);
@@ -27993,7 +28119,7 @@ TEST(registry_receiver_chain_refuses_library_suffix_match_issue1893) {
  * so Calendar really is in the receiver chain. */
 TEST(registry_receiver_chain_keeps_project_extension_issue1893) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "startOfDayUTC", "AuthDTOs.Calendar.startOfDayUTC", "Method");
+    cbm_registry_add(reg, "startOfDayUTC", "AuthDTOs.Calendar.startOfDayUTC", "Method", false);
 
     cbm_resolution_t r = cbm_registry_resolve(reg, "Calendar.utcGregorian.startOfDayUTC",
                                               "HomeboxUI.Stats", NULL, NULL, 0);
@@ -28013,7 +28139,7 @@ TEST(registry_receiver_chain_keeps_project_extension_issue1893) {
 TEST(registry_receiver_chain_admits_factory_chain_into_nested_type) {
     cbm_registry_t *reg = cbm_registry_new();
     cbm_registry_add(reg, "putList", "org.elasticsearch.common.settings.Settings.Builder.putList",
-                     "Method");
+                     "Method", false);
 
     cbm_resolution_t r = cbm_registry_resolve(
         reg, "Settings.builder().putList", "org.elasticsearch.index.IndexSettings", NULL, NULL, 0);
@@ -28024,7 +28150,7 @@ TEST(registry_receiver_chain_admits_factory_chain_into_nested_type) {
      * .toBuilder().setWarningsHandler -> RequestOptions.Builder.setWarningsHandler. */
     cbm_registry_add(reg, "setWarningsHandler",
                      "org.elasticsearch.client.RequestOptions.Builder.setWarningsHandler",
-                     "Method");
+                     "Method", false);
     r = cbm_registry_resolve(reg, "RequestOptions.DEFAULT.toBuilder().setWarningsHandler",
                              "org.elasticsearch.client.Rest", NULL, NULL, 0);
     ASSERT_STR_EQ(r.qualified_name,
@@ -28040,7 +28166,7 @@ TEST(registry_receiver_chain_admits_factory_chain_into_nested_type) {
 TEST(registry_receiver_chain_still_refuses_foreign_root_with_ancestry_rule) {
     cbm_registry_t *reg = cbm_registry_new();
     cbm_registry_add(reg, "getEncoder", "org.elasticsearch.index.codec.DocOffsetsCodec.getEncoder",
-                     "Method");
+                     "Method", false);
 
     cbm_resolution_t r = cbm_registry_resolve(
         reg, "Base64.getEncoder", "org.elasticsearch.index.IndexSettings", NULL, NULL, 0);
@@ -28050,7 +28176,7 @@ TEST(registry_receiver_chain_still_refuses_foreign_root_with_ancestry_rule) {
      * org.elasticsearch.common.Math.toIntExact through "Math" appearing as an
      * ancestry segment ONLY IF that segment really is the type — here it is, and
      * that is the correct outcome (the project's own Math.toIntExact). */
-    cbm_registry_add(reg, "toIntExact", "org.elasticsearch.common.Math.toIntExact", "Method");
+    cbm_registry_add(reg, "toIntExact", "org.elasticsearch.common.Math.toIntExact", "Method", false);
     r = cbm_registry_resolve(reg, "Math.toIntExact", "org.elasticsearch.index.IndexSettings", NULL,
                              NULL, 0);
     ASSERT_STR_EQ(r.qualified_name, "org.elasticsearch.common.Math.toIntExact");
@@ -28063,7 +28189,7 @@ TEST(registry_receiver_chain_still_refuses_foreign_root_with_ancestry_rule) {
  * must not look at it, or every ordinary vm.load style call would be refused. */
 TEST(registry_receiver_chain_ignores_lowercase_root_issue1893) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "load", "HomeboxUI.EntityListViewModel.load", "Method");
+    cbm_registry_add(reg, "load", "HomeboxUI.EntityListViewModel.load", "Method", false);
 
     cbm_resolution_t r = cbm_registry_resolve(reg, "vm.load", "HomeboxUI.Views", NULL, NULL, 0);
     ASSERT_STR_EQ(r.qualified_name, "HomeboxUI.EntityListViewModel.load");
@@ -28073,10 +28199,99 @@ TEST(registry_receiver_chain_ignores_lowercase_root_issue1893) {
     PASS();
 }
 
+/* Issue #2121: unlike vm.load's lower-case value root above, C#'s built-in
+ * type keywords (int, string, bool, nint, ...) DO name a type and must get the
+ * same chain-consistency check an upper-case root gets. The check belongs to
+ * the CALLS entry point both resolvers share, for a C# file. */
+TEST(registry_receiver_chain_refuses_lowercase_type_keyword_issue2121) {
+    cbm_registry_t *reg = cbm_registry_new();
+    cbm_registry_add(reg, "TryParse", "tmp.Decoys.TsidNode.TryParse", "Method", false);
+
+    cbm_resolution_t r = cbm_registry_resolve_call_lang(reg, "int.TryParse", "tmp.Demo", NULL, NULL,
+                                                        0, CBM_LANG_CSHARP);
+    ASSERT_NULL(r.qualified_name);
+    /* C# 9 native-sized integers are keywords in receiver position too. */
+    r = cbm_registry_resolve_call_lang(reg, "nint.TryParse", "tmp.Demo", NULL, NULL, 0,
+                                       CBM_LANG_CSHARP);
+    ASSERT_NULL(r.qualified_name);
+
+    cbm_registry_free(reg);
+    PASS();
+}
+
+/* The true positive the new keyword check must not eat: the project really
+ * does define a type literally named "int" (or similar) and the chain shows
+ * it, so the match must still go through. Resolved as a C# call, so this
+ * exercises the keyword branch's ancestry walk, not the non-C# early return
+ * (which would pass through for the wrong reason). */
+TEST(registry_receiver_chain_keeps_type_keyword_when_chain_matches_issue2121) {
+    cbm_registry_t *reg = cbm_registry_new();
+    cbm_registry_add(reg, "TryParse", "tmp.int.TryParse", "Method", false);
+
+    cbm_resolution_t r = cbm_registry_resolve_call_lang(reg, "int.TryParse", "tmp.Demo", NULL, NULL,
+                                                        0, CBM_LANG_CSHARP);
+    ASSERT_STR_EQ(r.qualified_name, "tmp.int.TryParse");
+
+    cbm_registry_free(reg);
+    PASS();
+}
+
+/* The type-keyword branch above is a C#-only rule (closed list, gated on the
+ * calling file's language) and must not trade away recall in a language where
+ * the same spellings are ordinary identifiers. `object` and `string` are
+ * ordinary lower-case variable names in Python/Go; a variable named `object`
+ * calling a method (`object.TryParse`, shaped exactly like the refusal test
+ * above) must still resolve as a value root there: the negative control
+ * pinning the other side of the gate. */
+TEST(registry_receiver_chain_keyword_list_gated_to_csharp_issue2121) {
+    cbm_registry_t *reg = cbm_registry_new();
+    cbm_registry_add(reg, "TryParse", "tmp.Decoys.TsidNode.TryParse", "Method", false);
+
+    cbm_resolution_t r = cbm_registry_resolve_call_lang(reg, "object.TryParse", "tmp.Demo", NULL,
+                                                        NULL, 0, CBM_LANG_PYTHON);
+    ASSERT_STR_EQ(r.qualified_name, "tmp.Decoys.TsidNode.TryParse");
+    ASSERT_STR_EQ(r.strategy, "unique_name");
+
+    /* A Go call and the language-blind cbm_registry_resolve read a second
+     * keyword spelling as a value root as well. */
+    cbm_registry_t *reg2 = cbm_registry_new();
+    cbm_registry_add(reg2, "Join", "tmp.Decoys.Joiner.Join", "Method", false);
+    cbm_resolution_t r2 =
+        cbm_registry_resolve_call_lang(reg2, "string.Join", "tmp.Demo", NULL, NULL, 0, CBM_LANG_GO);
+    ASSERT_STR_EQ(r2.qualified_name, "tmp.Decoys.Joiner.Join");
+    ASSERT_STR_EQ(r2.strategy, "unique_name");
+    r2 = cbm_registry_resolve(reg2, "string.Join", "tmp.Demo", NULL, NULL, 0);
+    ASSERT_STR_EQ(r2.qualified_name, "tmp.Decoys.Joiner.Join");
+    ASSERT_STR_EQ(r2.strategy, "unique_name");
+
+    cbm_registry_free(reg);
+    cbm_registry_free(reg2);
+    PASS();
+}
+
+/* `dynamic` is a contextual keyword in C#, not a reserved type keyword like
+ * `int`: in receiver position (`dynamic.Invoke(...)`) it is a variable that
+ * happens to be called `dynamic`, whose type the chain does not show. In a C#
+ * file it must stay an ordinary lower-case value root, like vm.load above, so
+ * the call still binds: the control that keeps the keyword list closed to
+ * words that can only name a type. */
+TEST(registry_receiver_chain_csharp_dynamic_variable_still_binds_issue2121) {
+    cbm_registry_t *reg = cbm_registry_new();
+    cbm_registry_add(reg, "Invoke", "tmp.Handlers.Handler.Invoke", "Method", false);
+
+    cbm_resolution_t r = cbm_registry_resolve_call_lang(reg, "dynamic.Invoke", "tmp.Demo", NULL,
+                                                        NULL, 0, CBM_LANG_CSHARP);
+    ASSERT_STR_EQ(r.qualified_name, "tmp.Handlers.Handler.Invoke");
+    ASSERT_STR_EQ(r.strategy, "unique_name");
+
+    cbm_registry_free(reg);
+    PASS();
+}
+
 /* An unqualified callee has no chain at all and must pass through unchanged. */
 TEST(registry_receiver_chain_ignores_bare_name_issue1893) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "helper", "proj.pkg.helper", "Function");
+    cbm_registry_add(reg, "helper", "proj.pkg.helper", "Function", false);
 
     cbm_resolution_t r = cbm_registry_resolve(reg, "helper", "proj.other", NULL, NULL, 0);
     ASSERT_STR_EQ(r.qualified_name, "proj.pkg.helper");
@@ -28088,7 +28303,7 @@ TEST(registry_receiver_chain_ignores_bare_name_issue1893) {
 
 TEST(registry_fuzzy_confidence_single) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Handler", "proj.svc.Handler", "Function");
+    cbm_registry_add(reg, "Handler", "proj.svc.Handler", "Function", false);
 
     cbm_fuzzy_result_t fr =
         cbm_registry_fuzzy_resolve(reg, "unknownPkg.Handler", "proj.caller", NULL, NULL, 0);
@@ -28102,8 +28317,8 @@ TEST(registry_fuzzy_confidence_single) {
 
 TEST(registry_fuzzy_confidence_distance) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Process", "proj.svcA.Process", "Function");
-    cbm_registry_add(reg, "Process", "proj.svcB.Process", "Function");
+    cbm_registry_add(reg, "Process", "proj.svcA.Process", "Function", false);
+    cbm_registry_add(reg, "Process", "proj.svcB.Process", "Function", false);
 
     cbm_fuzzy_result_t fr =
         cbm_registry_fuzzy_resolve(reg, "unknownPkg.Process", "proj.svcA.other", NULL, NULL, 0);
@@ -28117,8 +28332,8 @@ TEST(registry_fuzzy_confidence_distance) {
 
 TEST(registry_negative_import_rejects) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Process", "proj.billing.Process", "Function");
-    cbm_registry_add(reg, "Process", "proj.handler.Process", "Function");
+    cbm_registry_add(reg, "Process", "proj.billing.Process", "Function", false);
+    cbm_registry_add(reg, "Process", "proj.handler.Process", "Function", false);
 
     /* Import only handler's module → should prefer handler */
     const char *keys[] = {"handler"};
@@ -28132,7 +28347,7 @@ TEST(registry_negative_import_rejects) {
 
 TEST(registry_fuzzy_import_penalty) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Handler", "proj.billing.Handler", "Function");
+    cbm_registry_add(reg, "Handler", "proj.billing.Handler", "Function", false);
 
     /* Has imports but billing not imported → confidence halved */
     const char *keys[] = {"other"};
@@ -28149,7 +28364,7 @@ TEST(registry_fuzzy_import_penalty) {
 
 TEST(registry_fuzzy_no_import_map_passthrough) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Handler", "proj.billing.Handler", "Function");
+    cbm_registry_add(reg, "Handler", "proj.billing.Handler", "Function", false);
 
     /* NULL import map → no penalty, full fuzzy confidence */
     cbm_fuzzy_result_t fr =
@@ -28163,10 +28378,10 @@ TEST(registry_fuzzy_no_import_map_passthrough) {
 
 TEST(registry_find_by_name) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Foo", "proj.pkg.Foo", "Function");
-    cbm_registry_add(reg, "Bar", "proj.pkg.Bar", "Function");
-    cbm_registry_add(reg, "Foo", "proj.other.Foo", "Function");
-    cbm_registry_add(reg, "transform", "proj.utils.DataProcessor.transform", "Method");
+    cbm_registry_add(reg, "Foo", "proj.pkg.Foo", "Function", false);
+    cbm_registry_add(reg, "Bar", "proj.pkg.Bar", "Function", false);
+    cbm_registry_add(reg, "Foo", "proj.other.Foo", "Function", false);
+    cbm_registry_add(reg, "transform", "proj.utils.DataProcessor.transform", "Method", false);
 
     /* FindByName returns all entries for "Foo" */
     const char **foos = NULL;
@@ -29126,10 +29341,10 @@ TEST(registry_is_import_reachable) {
 /* Port of FindEndingWith portion from Go TestFunctionRegistry in pipeline_test.go */
 TEST(registry_find_ending_with) {
     cbm_registry_t *reg = cbm_registry_new();
-    cbm_registry_add(reg, "Foo", "proj.pkg.Foo", "Function");
-    cbm_registry_add(reg, "Bar", "proj.pkg.Bar", "Function");
-    cbm_registry_add(reg, "Foo", "proj.other.Foo", "Function");
-    cbm_registry_add(reg, "transform", "proj.utils.DataProcessor.transform", "Method");
+    cbm_registry_add(reg, "Foo", "proj.pkg.Foo", "Function", false);
+    cbm_registry_add(reg, "Bar", "proj.pkg.Bar", "Function", false);
+    cbm_registry_add(reg, "Foo", "proj.other.Foo", "Function", false);
+    cbm_registry_add(reg, "transform", "proj.utils.DataProcessor.transform", "Method", false);
 
     /* FindEndingWith "DataProcessor.transform" → 1 match */
     const char **matches = NULL;
@@ -34397,6 +34612,8 @@ SUITE(pipeline) {
     RUN_TEST(pipeline_call_reference_sequential_parallel_edge_set_parity);
     RUN_TEST(pipeline_complexity_props_independent_of_worker_order);
     RUN_TEST(pipeline_incremental_cross_file_call_reference_matches_fresh_full);
+    RUN_TEST(pipeline_registry_ranks_by_extractor_verdict_full_and_incremental);
+    RUN_TEST(pipeline_registry_ranks_test_doubles_last_full_and_incremental);
     RUN_TEST(pipeline_incremental_changed_target_invalidates_stale_inbound_call_reference);
     RUN_TEST(pipeline_incremental_parallel_registry_nodes_advance_shared_ids);
 #if defined(CBM_INCREMENTAL_TEST_API) && CBM_INCREMENTAL_TEST_API
@@ -34687,6 +34904,10 @@ SUITE(pipeline) {
     RUN_TEST(registry_receiver_chain_admits_factory_chain_into_nested_type);
     RUN_TEST(registry_receiver_chain_still_refuses_foreign_root_with_ancestry_rule);
     RUN_TEST(registry_receiver_chain_ignores_lowercase_root_issue1893);
+    RUN_TEST(registry_receiver_chain_refuses_lowercase_type_keyword_issue2121);
+    RUN_TEST(registry_receiver_chain_keeps_type_keyword_when_chain_matches_issue2121);
+    RUN_TEST(registry_receiver_chain_keyword_list_gated_to_csharp_issue2121);
+    RUN_TEST(registry_receiver_chain_csharp_dynamic_variable_still_binds_issue2121);
     RUN_TEST(registry_receiver_chain_ignores_bare_name_issue1893);
     RUN_TEST(registry_fuzzy_confidence_single);
     RUN_TEST(registry_fuzzy_confidence_distance);
diff --git a/tests/test_registry.c b/tests/test_registry.c
index 6e0e18f3a..10c9ef8e5 100644
--- a/tests/test_registry.c
+++ b/tests/test_registry.c
@@ -193,7 +193,7 @@ TEST(registry_free_null) {
 
 TEST(registry_add_and_exists) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "main", "proj.cmd.main", "Function");
+    cbm_registry_add(r, "main", "proj.cmd.main", "Function", false);
     ASSERT_EQ(cbm_registry_size(r), 1);
     ASSERT_TRUE(cbm_registry_exists(r, "proj.cmd.main"));
     ASSERT_FALSE(cbm_registry_exists(r, "proj.cmd.other"));
@@ -201,10 +201,114 @@ TEST(registry_add_and_exists) {
     PASS();
 }
 
+/* REG_TEST_PENALTY had no direct coverage. Of the registry call sites in this
+ * suite, none registered a symbol the scorer would treat as a test, so the
+ * layer that keeps production code ahead of test code was never exercised.
+ * These three pin it, and pin where the verdict comes from. */
+TEST(registry_prefers_non_test_over_test_candidate) {
+    cbm_registry_t *r = cbm_registry_new();
+    cbm_registry_add(r, "helper", "proj.app.helper", "Function", false);
+    cbm_registry_add(r, "helper", "proj.harness.helper", "Function", true);
+
+    cbm_resolution_t res = cbm_registry_resolve(r, "helper", "proj.other", NULL, NULL, 0);
+    ASSERT_STR_EQ(res.qualified_name, "proj.app.helper");
+    cbm_registry_free(r);
+    PASS();
+}
+
+/* The verdict is the caller's, not the QN's spelling. "latest" contains "test",
+ * so the scan this replaces read ordinary production code as a test and pushed
+ * it below a real one; "harness" spells nothing, so the same scan read a test
+ * as production. Both verdicts here are the extractor's, and both are right. */
+TEST(registry_test_verdict_comes_from_the_caller_not_the_qn) {
+    cbm_registry_t *r = cbm_registry_new();
+    cbm_registry_add(r, "parse", "proj.latest.parse", "Function", false);
+    cbm_registry_add(r, "parse", "proj.harness.parse", "Function", true);
+
+    cbm_resolution_t res = cbm_registry_resolve(r, "parse", "proj.other", NULL, NULL, 0);
+    ASSERT_STR_EQ(res.qualified_name, "proj.latest.parse");
+    cbm_registry_free(r);
+    PASS();
+}
+
+/* A bucket of one is returned whatever its verdict: the penalty orders
+ * candidates, it does not veto them. */
+TEST(registry_sole_test_candidate_still_resolves) {
+    cbm_registry_t *r = cbm_registry_new();
+    cbm_registry_add(r, "only", "proj.harness.only", "Function", true);
+
+    cbm_resolution_t res = cbm_registry_resolve(r, "only", "proj.other", NULL, NULL, 0);
+    ASSERT_STR_EQ(res.qualified_name, "proj.harness.only");
+    cbm_registry_free(r);
+    PASS();
+}
+
+/* The test-double path rule: whole directory segments named fake, mock, mocks,
+ * testing or testutil, and Go files named mock_*.go or fake_*.go. Anchored, so
+ * the substrings the old QN scan tripped on (inspect, latest, contest) and
+ * near-miss names (fakeroot, mockery, testingutil) stay ordinary code. */
+TEST(registry_test_double_path_table) {
+    static const char *const doubles[] = {
+        "pkg/client/fake/clientset.go",
+        "fake/x.go",
+        "internal/mocks/store.go",
+        "pkg/mock/store.go",
+        "pkg/testing/fixtures.go",
+        "internal/testutil/helpers.go",
+        "pkg/mock_store.go",
+        "pkg/fake_clock.go",
+        "mock_store.go",
+        "src/fake/deep/nested/util.py",
+    };
+    static const char *const ordinary[] = {
+        "pkg/inspect/x.go",      "pkg/latest/x.go",      "pkg/contest/x.go", "pkg/fakeroot/x.go",
+        "pkg/mockery/x.go",      "pkg/testingutil/x.go", "pkg/mocking.go",   "pkg/mock_store.py",
+        "pkg/fake_clock.golang", "pkg/fake.go",          "pkg/x/fake",       "pkg/Fake/x.go",
+        "pkg/myfake/x.go",       "pkg/fake-client/x.go", "testing.go",       "",
+    };
+    char why[256];
+    for (size_t i = 0; i < sizeof(doubles) / sizeof(doubles[0]); i++) {
+        if (!cbm_registry_test_double_path(doubles[i])) {
+            snprintf(why, sizeof(why), "expected a test-double path: %s", doubles[i]);
+            FAIL(why);
+        }
+    }
+    for (size_t i = 0; i < sizeof(ordinary) / sizeof(ordinary[0]); i++) {
+        if (cbm_registry_test_double_path(ordinary[i])) {
+            snprintf(why, sizeof(why), "expected an ordinary path: %s", ordinary[i]);
+            FAIL(why);
+        }
+    }
+    ASSERT_FALSE(cbm_registry_test_double_path(NULL));
+    PASS();
+}
+
+/* The Swift overload choosers score with the verdicts stored at registration,
+ * carried through their own filtered lists. Both overloads fit the call and tie
+ * on proximity; without the verdicts the smaller QN (the test double) would win
+ * the tie. */
+TEST(registry_swift_overload_choice_uses_stored_verdicts) {
+    cbm_registry_t *r = cbm_registry_new();
+    const char *double_qn = "proj.Fixtures.Store.load(path:String)";
+    const char *real_qn = "proj.Zeta.Store.load(path:String)";
+    cbm_registry_add(r, "load", double_qn, "Method", true);
+    cbm_registry_add(r, "load", real_qn, "Method", false);
+    cbm_registry_set_swift_signature(r, double_qn, 0, 1, NULL);
+    cbm_registry_set_swift_signature(r, real_qn, 0, 1, NULL);
+
+    CBMCallArg arg = {.keyword = "path"};
+    CBMCall call = {.callee_name = "load", .args = &arg, .arg_count = 1};
+    const char *out[4] = {0};
+    ASSERT_EQ(cbm_registry_swift_candidates(r, &call, "proj.Caller", NULL, 0, out, 4), 1);
+    ASSERT_STR_EQ(out[0], real_qn);
+    cbm_registry_free(r);
+    PASS();
+}
+
 TEST(registry_label_of) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Foo", "proj.pkg.Foo", "Class");
-    cbm_registry_add(r, "bar", "proj.pkg.bar", "Function");
+    cbm_registry_add(r, "Foo", "proj.pkg.Foo", "Class", false);
+    cbm_registry_add(r, "bar", "proj.pkg.bar", "Function", false);
 
     ASSERT_STR_EQ(cbm_registry_label_of(r, "proj.pkg.Foo"), "Class");
     ASSERT_STR_EQ(cbm_registry_label_of(r, "proj.pkg.bar"), "Function");
@@ -218,10 +322,10 @@ TEST(registry_label_of) {
  * method's fenced `#field` twin when the class has one; nothing else moves. */
 TEST(registry_value_target_field_twin) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "count", "p.C.count", "Method");
-    cbm_registry_add(r, "count", "p.C.count#field", "Field");
-    cbm_registry_add(r, "size", "p.C.size", "Method");
-    cbm_registry_add(r, "name", "p.C.name", "Field");
+    cbm_registry_add(r, "count", "p.C.count", "Method", false);
+    cbm_registry_add(r, "count", "p.C.count#field", "Field", false);
+    cbm_registry_add(r, "size", "p.C.size", "Method", false);
+    cbm_registry_add(r, "name", "p.C.name", "Field", false);
     ASSERT_STR_EQ(cbm_registry_value_target(r, "p.C.count"), "p.C.count#field");
     ASSERT_STR_EQ(cbm_registry_value_target(r, "p.C.size"), "p.C.size");
     ASSERT_STR_EQ(cbm_registry_value_target(r, "p.C.name"), "p.C.name");
@@ -237,9 +341,9 @@ TEST(registry_value_target_field_twin) {
 
 TEST(registry_find_by_name) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "main", "proj.cmd.main", "Function");
-    cbm_registry_add(r, "main", "proj.srv.main", "Function");
-    cbm_registry_add(r, "helper", "proj.util.helper", "Function");
+    cbm_registry_add(r, "main", "proj.cmd.main", "Function", false);
+    cbm_registry_add(r, "main", "proj.srv.main", "Function", false);
+    cbm_registry_add(r, "helper", "proj.util.helper", "Function", false);
 
     const char **out = NULL;
     int count = 0;
@@ -258,8 +362,8 @@ TEST(registry_find_by_name) {
 
 TEST(registry_no_duplicates) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "main", "proj.cmd.main", "Function");
-    cbm_registry_add(r, "main", "proj.cmd.main", "Function"); /* duplicate */
+    cbm_registry_add(r, "main", "proj.cmd.main", "Function", false);
+    cbm_registry_add(r, "main", "proj.cmd.main", "Function", false); /* duplicate */
     ASSERT_EQ(cbm_registry_size(r), 1);
 
     const char **out = NULL;
@@ -275,7 +379,7 @@ TEST(registry_no_duplicates) {
 
 TEST(resolve_same_module) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "helper", "proj.pkg.service.helper", "Function");
+    cbm_registry_add(r, "helper", "proj.pkg.service.helper", "Function", false);
 
     /* Call "helper" from the same module → should resolve */
     cbm_resolution_t res = cbm_registry_resolve(r, "helper", "proj.pkg.service", NULL, NULL, 0);
@@ -297,7 +401,7 @@ TEST(resolve_same_module) {
  * (false only for a this/super receiver). */
 TEST(resolve_same_module_only_on_self_receiver) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "get", "proj.pkg.service.get", "Function");
+    cbm_registry_add(r, "get", "proj.pkg.service.get", "Function", false);
     const CBMLanguage js = CBM_LANG_JAVASCRIPT;
     const char *mod = "proj.pkg.service";
     CBMImport axios_import = {.local_name = "axios", .module_path = "axios", .is_default = true};
@@ -457,11 +561,11 @@ TEST(resolve_qualified_receiver_awareness) {
     const CBMLanguage js = CBM_LANG_JAVASCRIPT;
 
     /* 1. Register a Method candidate under Class Service: proj.pkg.Service.get */
-    cbm_registry_add(r, "Service", "proj.pkg.Service", "Class");
-    cbm_registry_add(r, "get", "proj.pkg.Service.get", "Method");
+    cbm_registry_add(r, "Service", "proj.pkg.Service", "Class", false);
+    cbm_registry_add(r, "get", "proj.pkg.Service.get", "Method", false);
 
     /* 2. Register a Module axios */
-    cbm_registry_add(r, "axios", "proj.axios", "Module");
+    cbm_registry_add(r, "axios", "proj.axios", "Module", false);
 
     /* Test Case A: Unrelated receiver that is a known module/type -> name-only
      * guess, dropped by the member guard */
@@ -513,7 +617,7 @@ TEST(resolve_qualified_receiver_awareness) {
     /* Test Case F: Function candidate behind an unrelated receiver -> name-only
      * guess, dropped by the member guard */
     /* Register unique Function helper.compute */
-    cbm_registry_add(r, "compute", "proj.pkg.helper.compute", "Function");
+    cbm_registry_add(r, "compute", "proj.pkg.helper.compute", "Function", false);
     {
         cbm_resolution_t res =
             cbm_registry_resolve(r, "unrelated.compute", "proj.app", NULL, NULL, 0);
@@ -530,9 +634,9 @@ TEST(resolve_qualified_receiver_awareness) {
  * Foo::Bar::sub()) where the same sub name exists in multiple packages. */
 TEST(resolve_qualified_disambiguates_same_name) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "save", "proj.lib.App.Alpha.save", "Function");
-    cbm_registry_add(r, "save", "proj.lib.App.Beta.save", "Function");
-    cbm_registry_add(r, "save", "proj.lib.App.Gamma.save", "Function");
+    cbm_registry_add(r, "save", "proj.lib.App.Alpha.save", "Function", false);
+    cbm_registry_add(r, "save", "proj.lib.App.Beta.save", "Function", false);
+    cbm_registry_add(r, "save", "proj.lib.App.Gamma.save", "Function", false);
 
     /* Each fully-qualified call routes to its own package. */
     cbm_resolution_t a =
@@ -573,8 +677,8 @@ TEST(resolve_qualified_disambiguates_same_name) {
  * pick arbitrarily under the high-confidence qualified_suffix strategy. */
 TEST(resolve_qualified_ambiguous_tail_falls_through) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "run", "proj.svcA.Foo.Bar.run", "Function");
-    cbm_registry_add(r, "run", "proj.svcB.Foo.Bar.run", "Function");
+    cbm_registry_add(r, "run", "proj.svcA.Foo.Bar.run", "Function", false);
+    cbm_registry_add(r, "run", "proj.svcB.Foo.Bar.run", "Function", false);
 
     /* "Foo::Bar::run" tail matches BOTH candidates → not unique → fall through. */
     cbm_resolution_t res =
@@ -592,7 +696,7 @@ TEST(resolve_qualified_ambiguous_tail_falls_through) {
  * `add` callee could ever reach it. */
 TEST(registry_indexes_by_passed_name_not_qn_tail) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "add", "proj.lib.add#cfg(test)", "Function");
+    cbm_registry_add(r, "add", "proj.lib.add#cfg(test)", "Function", false);
 
     cbm_resolution_t res = cbm_registry_resolve(r, "add", "proj.lib.caller", NULL, NULL, 0);
     ASSERT_STR_EQ(res.qualified_name, "proj.lib.add#cfg(test)");
@@ -617,9 +721,9 @@ TEST(registry_indexes_by_passed_name_not_qn_tail) {
  * lookup a bare module reference needs. */
 TEST(registry_indexes_a_dotted_name_under_its_tail_too) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "resource.aws_instance.web", "proj.main.resource.aws_instance.web",
-                     "Class");
-    cbm_registry_add(r, "helper.py", "proj.pkg.helper", "Module");
+    cbm_registry_add(r, "resource.aws_instance.web", "proj.main.resource.aws_instance.web", "Class",
+                     false);
+    cbm_registry_add(r, "helper.py", "proj.pkg.helper", "Module", false);
 
     cbm_resolution_t tail = cbm_registry_resolve(r, "web", "proj.main", NULL, NULL, 0);
     ASSERT_STR_EQ(tail.qualified_name, "proj.main.resource.aws_instance.web");
@@ -637,7 +741,7 @@ TEST(registry_indexes_a_dotted_name_under_its_tail_too) {
 
 TEST(resolve_import_map) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Process", "proj.pkg.worker.Process", "Function");
+    cbm_registry_add(r, "Process", "proj.pkg.worker.Process", "Function", false);
 
     /* Import map: "worker" → "proj.pkg.worker" */
     const char *keys[] = {"worker"};
@@ -660,9 +764,9 @@ TEST(resolve_import_map) {
  * file. Regression for the @/lib/auth-style import case. */
 TEST(resolve_import_map_bare_function) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "requireAdmin", "proj.lib.authorization.requireAdmin", "Function");
+    cbm_registry_add(r, "requireAdmin", "proj.lib.authorization.requireAdmin", "Function", false);
     /* Same name in another module — without the fix this is what gets picked. */
-    cbm_registry_add(r, "requireAdmin", "proj.lib.users.requireAdmin", "Function");
+    cbm_registry_add(r, "requireAdmin", "proj.lib.users.requireAdmin", "Function", false);
 
     const char *keys[] = {"requireAdmin"};
     const char *vals[] = {"proj.lib.authorization"};
@@ -683,7 +787,7 @@ TEST(resolve_import_map_bare_function) {
  * Regression for #875. */
 TEST(resolve_import_map_bare_alias) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "scan_bash", "proj.security_scan.scan_bash", "Function");
+    cbm_registry_add(r, "scan_bash", "proj.security_scan.scan_bash", "Function", false);
     /* Import map: alias "_scan_bash" → FULL SYMBOL QN (not the module). */
     const char *keys[] = {"_scan_bash"};
     const char *vals[] = {"proj.security_scan.scan_bash"};
@@ -700,10 +804,10 @@ TEST(resolve_import_map_bare_alias) {
  * already on main via #875/#979; this locks the Yui G1 shape. */
 TEST(resolve_import_map_aliased_from_import) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "execute", "proj.services.satori_bridge.gate.execute", "Function");
+    cbm_registry_add(r, "execute", "proj.services.satori_bridge.gate.execute", "Function", false);
     /* Alias ghost must not win if somehow registered. */
     cbm_registry_add(r, "bridge_execute", "proj.services.satori_bridge.gate.bridge_execute",
-                     "Function");
+                     "Function", false);
 
     const char *keys[] = {"bridge_execute"};
     const char *vals[] = {"proj.services.satori_bridge.gate.execute"};
@@ -719,7 +823,7 @@ TEST(resolve_import_map_aliased_from_import) {
 
 TEST(resolve_unique_name) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "UniqueFunc", "proj.deep.path.UniqueFunc", "Function");
+    cbm_registry_add(r, "UniqueFunc", "proj.deep.path.UniqueFunc", "Function", false);
 
     /* Call "UniqueFunc" — only one candidate project-wide */
     cbm_resolution_t res =
@@ -733,7 +837,7 @@ TEST(resolve_unique_name) {
 
 TEST(resolve_unresolved) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "foo", "proj.pkg.foo", "Function");
+    cbm_registry_add(r, "foo", "proj.pkg.foo", "Function", false);
 
     /* Call "nonexistent" — not in registry */
     cbm_resolution_t res = cbm_registry_resolve(r, "nonexistent", "proj.other", NULL, NULL, 0);
@@ -750,7 +854,7 @@ TEST(resolve_many_nodes) {
         char name[32], qn[64];
         snprintf(name, sizeof(name), "func_%d", i);
         snprintf(qn, sizeof(qn), "proj.pkg.func_%d", i);
-        cbm_registry_add(r, name, qn, "Function");
+        cbm_registry_add(r, name, qn, "Function", false);
     }
     ASSERT_EQ(cbm_registry_size(r), 500);
 
@@ -788,8 +892,8 @@ TEST(confidence_band_speculative) {
 
 TEST(resolve_suffix_match) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Process", "proj.svcA.Process", "Function");
-    cbm_registry_add(r, "Process", "proj.svcB.Process", "Function");
+    cbm_registry_add(r, "Process", "proj.svcA.Process", "Function", false);
+    cbm_registry_add(r, "Process", "proj.svcB.Process", "Function", false);
 
     /* Caller in svcA — should prefer svcA via import distance */
     cbm_resolution_t res = cbm_registry_resolve(r, "Process", "proj.svcA.caller", NULL, NULL, 0);
@@ -812,7 +916,7 @@ TEST(resolve_caps_unresolvably_ambiguous_names) {
     for (int i = 0; i < 300; i++) {
         char qn[64];
         snprintf(qn, sizeof(qn), "proj.mod%d.flags", i);
-        cbm_registry_add(r, "flags", qn, "Variable");
+        cbm_registry_add(r, "flags", qn, "Variable", false);
     }
     cbm_resolution_t res = cbm_registry_resolve(r, "flags", "proj.other.caller", NULL, NULL, 0);
     ASSERT_TRUE(res.qualified_name == NULL || res.qualified_name[0] == '\0');
@@ -830,7 +934,7 @@ TEST(resolve_caps_unresolvably_ambiguous_names) {
 
 TEST(resolve_import_map_suffix) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Foo", "proj.other.sub.Foo", "Function");
+    cbm_registry_add(r, "Foo", "proj.other.sub.Foo", "Function", false);
 
     const char *keys[] = {"other"};
     const char *vals[] = {"proj.other"};
@@ -852,7 +956,7 @@ TEST(resolve_is_import_reachable) {
     /* Test import reachability through unique_name confidence penalty.
      * is_import_reachable is static, so we test it indirectly. */
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Helper", "proj.shared.utils.Helper", "Function");
+    cbm_registry_add(r, "Helper", "proj.shared.utils.Helper", "Function", false);
 
     /* With import covering the module → full confidence */
     const char *keys1[] = {"utils"};
@@ -875,7 +979,7 @@ TEST(resolve_is_import_reachable) {
 TEST(resolve_import_reachable_prefix) {
     /* "proj.handler.sub.Process" should be reachable via import "proj.handler" */
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Process", "proj.handler.sub.Process", "Function");
+    cbm_registry_add(r, "Process", "proj.handler.sub.Process", "Function", false);
 
     const char *keys[] = {"handler"};
     const char *vals[] = {"proj.handler"};
@@ -929,8 +1033,8 @@ TEST(reach_cache_memo_matches_uncached_across_files) {
 
 TEST(negative_import_rejects_unimported) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Process", "proj.billing.Process", "Function");
-    cbm_registry_add(r, "Process", "proj.handler.Process", "Function");
+    cbm_registry_add(r, "Process", "proj.billing.Process", "Function", false);
+    cbm_registry_add(r, "Process", "proj.handler.Process", "Function", false);
 
     /* Import only handler's module — suffix_match should prefer handler */
     const char *keys[] = {"handler"};
@@ -946,8 +1050,8 @@ TEST(negative_import_rejects_unimported) {
 
 TEST(fuzzy_resolve_single_candidate) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "CreateOrder", "svcA.handlers.CreateOrder", "Function");
-    cbm_registry_add(r, "ValidateOrder", "svcB.validators.ValidateOrder", "Function");
+    cbm_registry_add(r, "CreateOrder", "svcA.handlers.CreateOrder", "Function", false);
+    cbm_registry_add(r, "ValidateOrder", "svcB.validators.ValidateOrder", "Function", false);
 
     /* FuzzyResolve should find by simple name even with unknown prefix */
     cbm_fuzzy_result_t fr =
@@ -961,7 +1065,7 @@ TEST(fuzzy_resolve_single_candidate) {
 
 TEST(fuzzy_resolve_nonexistent) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "CreateOrder", "svcA.handlers.CreateOrder", "Function");
+    cbm_registry_add(r, "CreateOrder", "svcA.handlers.CreateOrder", "Function", false);
 
     cbm_fuzzy_result_t fr =
         cbm_registry_fuzzy_resolve(r, "NonExistent", "svcC.caller", NULL, NULL, 0);
@@ -973,8 +1077,8 @@ TEST(fuzzy_resolve_nonexistent) {
 
 TEST(fuzzy_resolve_multiple_best_by_distance) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Process", "svcA.handlers.Process", "Function");
-    cbm_registry_add(r, "Process", "svcB.handlers.Process", "Function");
+    cbm_registry_add(r, "Process", "svcA.handlers.Process", "Function", false);
+    cbm_registry_add(r, "Process", "svcB.handlers.Process", "Function", false);
 
     /* Caller in svcA — should prefer svcA */
     cbm_fuzzy_result_t fr =
@@ -993,7 +1097,7 @@ TEST(fuzzy_resolve_multiple_best_by_distance) {
 
 TEST(fuzzy_resolve_deep_name_extraction) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "DoWork", "myproject.utils.DoWork", "Function");
+    cbm_registry_add(r, "DoWork", "myproject.utils.DoWork", "Function", false);
 
     /* Deeply qualified callee — should extract "DoWork" */
     cbm_fuzzy_result_t fr =
@@ -1018,7 +1122,7 @@ TEST(fuzzy_resolve_empty_registry) {
 
 TEST(fuzzy_resolve_confidence_single) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Handler", "proj.svc.Handler", "Function");
+    cbm_registry_add(r, "Handler", "proj.svc.Handler", "Function", false);
 
     cbm_fuzzy_result_t fr =
         cbm_registry_fuzzy_resolve(r, "unknownPkg.Handler", "proj.caller", NULL, NULL, 0);
@@ -1032,8 +1136,8 @@ TEST(fuzzy_resolve_confidence_single) {
 
 TEST(fuzzy_resolve_confidence_distance) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Process", "proj.svcA.Process", "Function");
-    cbm_registry_add(r, "Process", "proj.svcB.Process", "Function");
+    cbm_registry_add(r, "Process", "proj.svcA.Process", "Function", false);
+    cbm_registry_add(r, "Process", "proj.svcB.Process", "Function", false);
 
     cbm_fuzzy_result_t fr =
         cbm_registry_fuzzy_resolve(r, "unknownPkg.Process", "proj.svcA.other", NULL, NULL, 0);
@@ -1047,7 +1151,7 @@ TEST(fuzzy_resolve_confidence_distance) {
 
 TEST(fuzzy_penalty_unreachable_import) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Handler", "proj.billing.Handler", "Function");
+    cbm_registry_add(r, "Handler", "proj.billing.Handler", "Function", false);
 
     /* Import for different module → confidence halved */
     const char *keys[] = {"other"};
@@ -1064,7 +1168,7 @@ TEST(fuzzy_penalty_unreachable_import) {
 
 TEST(fuzzy_no_import_map_passthrough) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "Handler", "proj.billing.Handler", "Function");
+    cbm_registry_add(r, "Handler", "proj.billing.Handler", "Function", false);
 
     /* nil import map → full confidence */
     cbm_fuzzy_result_t fr =
@@ -1173,8 +1277,8 @@ TEST(registry_tie_break_is_independent_of_registration_order) {
     cbm_registry_t *forward = cbm_registry_new();
     cbm_registry_t *backward = cbm_registry_new();
     for (int i = 0; i < n; i++) {
-        cbm_registry_add(forward, "dev_name", cands[i], labels[i]);
-        cbm_registry_add(backward, "dev_name", cands[n - 1 - i], labels[n - 1 - i]);
+        cbm_registry_add(forward, "dev_name", cands[i], labels[i], false);
+        cbm_registry_add(backward, "dev_name", cands[n - 1 - i], labels[n - 1 - i], false);
     }
 
     /* A far-away caller with no imports: every candidate scores the same. */
@@ -1192,10 +1296,10 @@ TEST(registry_tie_break_is_independent_of_registration_order) {
     /* Equal kind: the smaller QN, from either order. */
     cbm_registry_t *lex_a = cbm_registry_new();
     cbm_registry_t *lex_b = cbm_registry_new();
-    cbm_registry_add(lex_a, "sg_next", "proj.tools.virtio.scatterlist.sg_next", "Function");
-    cbm_registry_add(lex_a, "sg_next", "proj.include.linux.scatterlist.sg_next", "Function");
-    cbm_registry_add(lex_b, "sg_next", "proj.include.linux.scatterlist.sg_next", "Function");
-    cbm_registry_add(lex_b, "sg_next", "proj.tools.virtio.scatterlist.sg_next", "Function");
+    cbm_registry_add(lex_a, "sg_next", "proj.tools.virtio.scatterlist.sg_next", "Function", false);
+    cbm_registry_add(lex_a, "sg_next", "proj.include.linux.scatterlist.sg_next", "Function", false);
+    cbm_registry_add(lex_b, "sg_next", "proj.include.linux.scatterlist.sg_next", "Function", false);
+    cbm_registry_add(lex_b, "sg_next", "proj.tools.virtio.scatterlist.sg_next", "Function", false);
     cbm_resolution_t la =
         cbm_registry_resolve(lex_a, "sg_next", "proj.drivers.scsi.arm_scsi", NULL, NULL, 0);
     cbm_resolution_t lb =
@@ -1205,9 +1309,9 @@ TEST(registry_tie_break_is_independent_of_registration_order) {
 
     /* Proximity outranks the tie order: the sibling wins over a shallower stranger. */
     cbm_registry_t *proximity = cbm_registry_new();
-    cbm_registry_add(proximity, "vnic_rq_free", "proj.lib.vnic_rq_free", "Function");
+    cbm_registry_add(proximity, "vnic_rq_free", "proj.lib.vnic_rq_free", "Function", false);
     cbm_registry_add(proximity, "vnic_rq_free", "proj.drivers.scsi.fnic.vnic_rq.vnic_rq_free",
-                     "Function");
+                     "Function", false);
     cbm_resolution_t nr = cbm_registry_resolve(proximity, "vnic_rq_free",
                                                "proj.drivers.scsi.fnic.fnic_res", NULL, NULL, 0);
     ASSERT_STR_EQ(nr.qualified_name, "proj.drivers.scsi.fnic.vnic_rq.vnic_rq_free");
@@ -1231,13 +1335,14 @@ TEST(registry_tie_prefers_callable_over_property) {
     cbm_registry_add(
         r, "where",
         "proj.exposed-core.src.main.kotlin.org.jetbrains.exposed.v1.core.AbstractQuery.where",
-        "Variable");
+        "Variable", false);
     cbm_registry_add(r, "where",
                      "proj.exposed-jdbc.src.main.kotlin.org.jetbrains.exposed.v1.jdbc.Query.where",
-                     "Method");
+                     "Method", false);
     /* A deeper method still beats a shallower field: kind decides before order. */
-    cbm_registry_add(r, "limit", "proj.exposed-core.Table.limit", "Field");
-    cbm_registry_add(r, "limit", "proj.exposed-jdbc.src.main.kotlin.jdbc.Query.limit", "Method");
+    cbm_registry_add(r, "limit", "proj.exposed-core.Table.limit", "Field", false);
+    cbm_registry_add(r, "limit", "proj.exposed-jdbc.src.main.kotlin.jdbc.Query.limit", "Method",
+                     false);
 
     const char *caller =
         "proj.exposed-tests.src.test.kotlin.org.jetbrains.exposed.v1.tests.SelectTests";
@@ -1258,8 +1363,8 @@ TEST(registry_tie_prefers_callable_over_property) {
  * order alone, which is still a pure function of the candidate set (O9). */
 TEST(registry_tie_ignores_nesting_depth) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "filter", "proj.django.template.library.Library.filter", "Method");
-    cbm_registry_add(r, "filter", "proj.django.db.models.query.QuerySet.filter", "Method");
+    cbm_registry_add(r, "filter", "proj.django.template.library.Library.filter", "Method", false);
+    cbm_registry_add(r, "filter", "proj.django.db.models.query.QuerySet.filter", "Method", false);
     cbm_resolution_t f =
         cbm_registry_resolve(r, "filter", "proj.tests.lookup.tests", NULL, NULL, 0);
     ASSERT_STR_EQ(f.qualified_name, "proj.django.db.models.query.QuerySet.filter");
@@ -1281,23 +1386,25 @@ TEST(registry_tie_prefers_csharp_implementation_over_ref_stub) {
     cbm_registry_add_lang(
         r, "MemoryStream",
         "proj.src.libraries.System.Runtime.ref.System.Runtime.MemoryStream.MemoryStream", "Method",
-        CBM_LANG_CSHARP);
+        CBM_LANG_CSHARP, false);
     cbm_registry_add_lang(
         r, "MemoryStream",
         "proj.src.libraries.System.Private.CoreLib.src.System.IO.MemoryStream.MemoryStream",
-        "Method", CBM_LANG_CSHARP);
+        "Method", CBM_LANG_CSHARP, false);
     /* Equal depth, "ref" sorts before "src" (WithCancellation). */
     cbm_registry_add_lang(r, "WithCancellation",
                           "proj.src.libraries.System.Linq.Parallel.ref.System.Linq."
                           "ParallelEnumerable.WithCancellation",
-                          "Method", CBM_LANG_CSHARP);
+                          "Method", CBM_LANG_CSHARP, false);
     cbm_registry_add_lang(r, "WithCancellation",
                           "proj.src.libraries.System.Linq.Parallel.src.System.Linq."
                           "ParallelEnumerable.WithCancellation",
-                          "Method", CBM_LANG_CSHARP);
+                          "Method", CBM_LANG_CSHARP, false);
     /* Not C#: a `ref` directory gets no special treatment. */
-    cbm_registry_add_lang(r, "resolve", "proj.lib.ref.Resolver.resolve", "Method", CBM_LANG_JAVA);
-    cbm_registry_add_lang(r, "resolve", "proj.lib.src.Resolver.resolve", "Method", CBM_LANG_JAVA);
+    cbm_registry_add_lang(r, "resolve", "proj.lib.ref.Resolver.resolve", "Method", CBM_LANG_JAVA,
+                          false);
+    cbm_registry_add_lang(r, "resolve", "proj.lib.src.Resolver.resolve", "Method", CBM_LANG_JAVA,
+                          false);
 
     const char *caller = "proj.src.libraries.System.Security.Cryptography.src.CapiHelper";
     cbm_resolution_t ms = cbm_registry_resolve(r, "MemoryStream", caller, NULL, NULL, 0);
@@ -1353,10 +1460,10 @@ static cbm_resolution_t xl_resolve(const cbm_registry_t *r, CBMLanguage lang, co
 
 TEST(name_guess_vetoed_across_languages) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add_lang(r, "get", "builtins.dict.get", "Method", CBM_LANG_PYTHON);
-    cbm_registry_add_lang(r, "patch", "proj.web.Panel.patch", "Function", CBM_LANG_TSX);
-    cbm_registry_add_lang(r, "patch", "proj.api.client.patch", "Function", CBM_LANG_PYTHON);
-    cbm_registry_add(r, "legacy", "proj.x.legacy", "Function"); /* unknown language */
+    cbm_registry_add_lang(r, "get", "builtins.dict.get", "Method", CBM_LANG_PYTHON, false);
+    cbm_registry_add_lang(r, "patch", "proj.web.Panel.patch", "Function", CBM_LANG_TSX, false);
+    cbm_registry_add_lang(r, "patch", "proj.api.client.patch", "Function", CBM_LANG_PYTHON, false);
+    cbm_registry_add(r, "legacy", "proj.x.legacy", "Function", false); /* unknown language */
 
     /* JS `app.get`: the only "get" is Python's -> EMPTY, not unique_name. */
     cbm_resolution_t res = xl_resolve(r, CBM_LANG_JAVASCRIPT, "app.get", "proj.app");
@@ -1402,10 +1509,11 @@ TEST(name_guess_vetoed_across_languages) {
 TEST(same_module_vetoed_across_languages) {
     cbm_registry_t *r = cbm_registry_new();
     cbm_registry_add_lang(r, "reducer_worker", "proj.tests.cov.reducer_worker", "Function",
-                          CBM_LANG_PYTHON);
+                          CBM_LANG_PYTHON, false);
     cbm_registry_add_lang(r, "reducer_worker", "proj.other.reducer_worker", "Function",
-                          CBM_LANG_PYTHON);
-    cbm_registry_add_lang(r, "stat_child", "proj.tests.cov.stat_child", "Function", CBM_LANG_C);
+                          CBM_LANG_PYTHON, false);
+    cbm_registry_add_lang(r, "stat_child", "proj.tests.cov.stat_child", "Function", CBM_LANG_C,
+                          false);
 
     cbm_resolution_t res =
         cbm_registry_resolve(r, "reducer_worker", "proj.tests.cov", NULL, NULL, 0);
@@ -1562,11 +1670,11 @@ TEST(c_bare_call_does_not_weigh_field_namesakes) {
      * A bare C call never names a member, so its Field namesakes do not
      * compete: the function is the unique name it was in v0.11.0. */
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add_lang(r, "put_page", "proj.include.linux.mm.put_page", "Function",
-                          CBM_LANG_CPP);
+    cbm_registry_add_lang(r, "put_page", "proj.include.linux.mm.put_page", "Function", CBM_LANG_CPP,
+                          false);
     cbm_registry_add_lang(r, "put_page",
                           "proj.arch.arm64.include.asm.kvm_pgtable.kvm_pgtable_mm_ops.put_page",
-                          "Field", CBM_LANG_CPP);
+                          "Field", CBM_LANG_CPP, false);
     const char *mod = "proj.arch.arm64.kernel.elfcore";
     cbm_resolution_t res =
         cbm_registry_resolve_call_lang(r, "put_page", mod, NULL, NULL, 0, CBM_LANG_C);
@@ -1581,13 +1689,14 @@ TEST(c_bare_call_does_not_weigh_field_namesakes) {
     /* A name only members carry is no bare C call target at all -- neither a
      * struct member nor a C++ method: redis's libc `read()` became the unique
      * name of a Qt adapter's `read` Method once only Fields were set aside. */
-    cbm_registry_add_lang(r, "on_close", "proj.net.sock.sock_ops.on_close", "Field", CBM_LANG_C);
+    cbm_registry_add_lang(r, "on_close", "proj.net.sock.sock_ops.on_close", "Field", CBM_LANG_C,
+                          false);
     res = cbm_registry_resolve_call_lang(r, "on_close", mod, NULL, NULL, 0, CBM_LANG_C);
     ASSERT_TRUE(res.qualified_name == NULL || res.qualified_name[0] == '\0');
     cbm_registry_add_lang(r, "read", "proj.deps.hiredis.adapters.qt.RedisQtAdapter.read", "Method",
-                          CBM_LANG_CPP);
-    cbm_registry_add_lang(r, "read", "proj.src.connection.ConnectionType.read", "Field",
-                          CBM_LANG_C);
+                          CBM_LANG_CPP, false);
+    cbm_registry_add_lang(r, "read", "proj.src.connection.ConnectionType.read", "Field", CBM_LANG_C,
+                          false);
     res = cbm_registry_resolve_call_lang(r, "read", mod, NULL, NULL, 0, CBM_LANG_C);
     ASSERT_TRUE(res.qualified_name == NULL || res.qualified_name[0] == '\0');
     /* C++ still reaches the method by name. */
@@ -1652,12 +1761,12 @@ TEST(unique_field_qn_needs_exactly_one_field_of_that_name) {
      * the same name is not a candidate for a member at all. */
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "only_here", "proj.a.Alpha.only_here", "Field");
-    cbm_registry_add(r, "count", "proj.a.Alpha.count", "Field");
-    cbm_registry_add(r, "count", "proj.b.Beta.count", "Field");
-    cbm_registry_add(r, "close", "proj.cb.Callbacks.close", "Field");
-    cbm_registry_add(r, "close", "proj.io.close", "Function");
-    cbm_registry_add(r, "lonely_fn", "proj.io.lonely_fn", "Function");
+    cbm_registry_add(r, "only_here", "proj.a.Alpha.only_here", "Field", false);
+    cbm_registry_add(r, "count", "proj.a.Alpha.count", "Field", false);
+    cbm_registry_add(r, "count", "proj.b.Beta.count", "Field", false);
+    cbm_registry_add(r, "close", "proj.cb.Callbacks.close", "Field", false);
+    cbm_registry_add(r, "close", "proj.io.close", "Function", false);
+    cbm_registry_add(r, "lonely_fn", "proj.io.lonely_fn", "Function", false);
 
     const char *only = cbm_registry_unique_field_qn(r, "only_here");
     ASSERT_NOT_NULL(only);
@@ -1746,7 +1855,7 @@ TEST(generated_member_registers_by_qn_only) {
     ASSERT_EQ(n, 0);
     cbm_resolution_t res = cbm_registry_resolve(r, "v.y", "proj.app.Caller", NULL, NULL, 0);
     ASSERT_NULL(res.qualified_name);
-    cbm_registry_add(r, "x", "proj.geo.Point.Point.x", "Method");
+    cbm_registry_add(r, "x", "proj.geo.Point.Point.x", "Method", false);
     res = cbm_registry_resolve(r, "v.x", "proj.app.Caller", NULL, NULL, 0);
     ASSERT_STR_EQ(res.qualified_name, "proj.geo.Point.Point.x");
     /* Degenerate input registers nothing. */
@@ -2403,8 +2512,8 @@ TEST(go_suppress_keeps_typed_and_import_aware_matches) {
  * Signal.send). Regression guard for #1000. */
 TEST(resolve_import_map_alias_with_suffix_hits_method) {
     cbm_registry_t *r = cbm_registry_new();
-    cbm_registry_add(r, "user_logged_in", "proj.auth.signals.user_logged_in", "Variable");
-    cbm_registry_add(r, "send", "proj.auth.signals.user_logged_in.send", "Method");
+    cbm_registry_add(r, "user_logged_in", "proj.auth.signals.user_logged_in", "Variable", false);
+    cbm_registry_add(r, "send", "proj.auth.signals.user_logged_in.send", "Method", false);
     const char *keys[] = {"user_logged_in"};
     const char *vals[] = {"proj.auth.signals.user_logged_in"};
     cbm_resolution_t res =
@@ -2418,7 +2527,7 @@ TEST(resolve_import_map_alias_with_suffix_hits_method) {
 TEST(swift_overload_labels_defaults_and_trailing_closure) {
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "Service", "proj.Service", "Class");
+    cbm_registry_add(r, "Service", "proj.Service", "Class", false);
     const char *qns[] = {
         "proj.Service.work(flag:Bool)",
         "proj.Service.work(name:String)",
@@ -2449,7 +2558,7 @@ TEST(swift_overload_labels_defaults_and_trailing_closure) {
                            "combine", "repeated", "repeated", "unlabeled"};
     const uint8_t counts[] = {1, 1, 1, 1, 2, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 2, 2, 2};
     for (int i = 0; i < 22; i++) {
-        cbm_registry_add(r, names[i], qns[i], "Method");
+        cbm_registry_add(r, names[i], qns[i], "Method", false);
         uint64_t defaults = (i == 5 || i == 15)  ? UINT64_C(1) << 1
                             : i == 17 || i >= 19 ? UINT64_C(1)
                                                  : 0;
@@ -2460,7 +2569,7 @@ TEST(swift_overload_labels_defaults_and_trailing_closure) {
     const char *generic_qns[] = {"proj.Service.constrained<T;where T==()=>Void>(_:T)",
                                  "proj.Service.constrained<T>(_:T)async"};
     for (int i = 0; i < 2; i++) {
-        cbm_registry_add(r, "constrained", generic_qns[i], "Method");
+        cbm_registry_add(r, "constrained", generic_qns[i], "Method", false);
         cbm_registry_set_swift_signature(r, generic_qns[i], 0, 1, NULL);
     }
     CBMCallArg generic_arg = {0};
@@ -2468,7 +2577,7 @@ TEST(swift_overload_labels_defaults_and_trailing_closure) {
         .callee_name = "Service.constrained", .args = &generic_arg, .arg_count = 1};
     ASSERT_EQ(cbm_registry_swift_candidates(r, &generic_call, "proj.Caller", NULL, 0, out, 8), 2);
     const char *nested = "proj.Service.nested<T,U;where T==Box<[Int]>,U==()=>Void>(_:T)=>Int";
-    cbm_registry_add(r, "nested", nested, "Method");
+    cbm_registry_add(r, "nested", nested, "Method", false);
     cbm_registry_set_swift_signature(r, nested, 0, 1, NULL);
     generic_call.callee_name = "Service.nested";
     ASSERT_EQ(cbm_registry_swift_candidates(r, &generic_call, "proj.Caller", NULL, 0, out, 8), 1);
@@ -2476,7 +2585,7 @@ TEST(swift_overload_labels_defaults_and_trailing_closure) {
     const char *returns[] = {"proj.Service.pick()=>Int",
                              "proj.Service.pick()async=>(A/Item)=>B/Item"};
     for (int i = 0; i < 2; i++) {
-        cbm_registry_add(r, "pick", returns[i], "Method");
+        cbm_registry_add(r, "pick", returns[i], "Method", false);
         cbm_registry_set_swift_signature(r, returns[i], 0, 0, NULL);
     }
     CBMCall returned = {.callee_name = "Service.pick"};
@@ -2484,7 +2593,7 @@ TEST(swift_overload_labels_defaults_and_trailing_closure) {
     const char *malformed[] = {"proj.Service.bad()=>", "proj.Service.bad()=>[Int",
                                "proj.Service.bad()=>Int)"};
     for (int i = 0; i < 3; i++) {
-        cbm_registry_add(r, "bad", malformed[i], "Method");
+        cbm_registry_add(r, "bad", malformed[i], "Method", false);
         cbm_registry_set_swift_signature(r, malformed[i], 0, 0, NULL);
     }
     returned.callee_name = "Service.bad";
@@ -2493,7 +2602,7 @@ TEST(swift_overload_labels_defaults_and_trailing_closure) {
     for (int i = 0; i < 2; i++) {
         char qn[128];
         snprintf(qn, sizeof(qn), "proj.Service.%s(_:A,_:A)=>Bool", operators[i]);
-        cbm_registry_add(r, operators[i], qn, "Method");
+        cbm_registry_add(r, operators[i], qn, "Method", false);
         cbm_registry_set_swift_signature(r, qn, 0, 2, NULL);
         CBMCallArg operands[2] = {{0}};
         CBMCall operation = {.callee_name = operators[i], .args = operands, .arg_count = 2};
@@ -2657,14 +2766,14 @@ TEST(swift_manifest_root_targets_respect_nested_package_boundaries) {
     const char *methods[] = {"proj.Root.Ext.Service.run()", "proj.Nested.Ext.Service.run()",
                              "proj.Unknown.Ext.Service.run()"};
     for (int i = 0; i < 5; i++) {
-        cbm_registry_add(r, "Service", qns[i], "Class");
+        cbm_registry_add(r, "Service", qns[i], "Class", false);
         ASSERT_GT(cbm_gbuf_upsert_node(graph, "Class", "Service", qns[i], files[i], 1, 3,
                                        i == 0 || i == 2 ? "{\"swift_type_path\":\"Service\"}"
                                                         : "{\"swift_extension\":\"Service\"}"),
                   0);
     }
     for (int i = 0; i < 3; i++) {
-        cbm_registry_add(r, "run", methods[i], "Method");
+        cbm_registry_add(r, "run", methods[i], "Method", false);
         cbm_registry_set_swift_signature(r, methods[i], 0, 0, "()");
     }
     cbm_registry_build_swift_owners(r, graph, root, NULL, 0);
@@ -2701,12 +2810,12 @@ TEST(swift_receiver_resolution_is_independent_of_registration_order) {
     for (int reverse = 0; reverse < 2; reverse++) {
         cbm_registry_t *r = cbm_registry_new();
         ASSERT_NOT_NULL(r);
-        cbm_registry_add(r, "Service", "proj.alpha.Service", "Class");
-        cbm_registry_add(r, "Service", "proj.beta.Service", "Class");
+        cbm_registry_add(r, "Service", "proj.alpha.Service", "Class", false);
+        cbm_registry_add(r, "Service", "proj.beta.Service", "Class", false);
         const char *first = reverse ? beta : alpha;
         const char *second = reverse ? alpha : beta;
-        cbm_registry_add(r, "work", first, "Method");
-        cbm_registry_add(r, "work", second, "Method");
+        cbm_registry_add(r, "work", first, "Method", false);
+        cbm_registry_add(r, "work", second, "Method", false);
         cbm_registry_set_swift_signature(r, first, 0, 1, NULL);
         cbm_registry_set_swift_signature(r, second, 0, 1, NULL);
 
@@ -2725,11 +2834,11 @@ TEST(swift_receiver_resolution_is_independent_of_registration_order) {
 TEST(swift_multiple_trailing_closures_match_labels) {
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "Service", "proj.Service", "Class");
+    cbm_registry_add(r, "Service", "proj.Service", "Class", false);
     const char *one_qn = "proj.Service.handle(completion:()=>Void)";
     const char *two_qn = "proj.Service.handle(completion:()=>Void,onError:()=>Void)";
-    cbm_registry_add(r, "handle", one_qn, "Method");
-    cbm_registry_add(r, "handle", two_qn, "Method");
+    cbm_registry_add(r, "handle", one_qn, "Method", false);
+    cbm_registry_add(r, "handle", two_qn, "Method", false);
     cbm_registry_set_swift_signature(r, one_qn, 0, 1, NULL);
     cbm_registry_set_swift_signature(r, two_qn, 0, 2, NULL);
 
@@ -2762,7 +2871,7 @@ TEST(swift_multiple_trailing_closures_match_labels) {
      * closure can skip an earlier defaulted closure and bind the required one. */
     const char *delayed_qn =
         "proj.Service.delayed(onDismiss:(()=>Void)?,content:()=>Void,onError:(()=>Void)?)";
-    cbm_registry_add(r, "delayed", delayed_qn, "Method");
+    cbm_registry_add(r, "delayed", delayed_qn, "Method", false);
     cbm_registry_set_swift_signature(r, delayed_qn, (UINT64_C(1) << 0) | (UINT64_C(1) << 2), 3,
                                      NULL);
     call.callee_name = "Service.delayed";
@@ -2779,9 +2888,9 @@ TEST(swift_multiple_trailing_closures_match_labels) {
 TEST(swift_repeated_labels_skip_default_before_next_trailing_label) {
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "Service", "proj.Service", "Class");
+    cbm_registry_add(r, "Service", "proj.Service", "Class", false);
     const char *qn = "proj.Service.repeated(a:()=>Void,b:()=>Void,a:()=>Void,b:()=>Void)";
-    cbm_registry_add(r, "repeated", qn, "Method");
+    cbm_registry_add(r, "repeated", qn, "Method", false);
     cbm_registry_set_swift_signature(r, qn, (UINT64_C(1) << 0) | (UINT64_C(1) << 3), 4, NULL);
     const char *labels[3] = {NULL, "a", "b"};
     CBMCall call = {.callee_name = "Service.repeated",
@@ -2800,9 +2909,9 @@ TEST(swift_repeated_labels_skip_default_before_next_trailing_label) {
 TEST(swift_repeated_labels_do_not_skip_default_past_next_trailing_label) {
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "Service", "proj.Service", "Class");
+    cbm_registry_add(r, "Service", "proj.Service", "Class", false);
     const char *qn = "proj.Service.repeated(a:()=>Void,b:()=>Void,a:()=>Void,b:()=>Void)";
-    cbm_registry_add(r, "repeated", qn, "Method");
+    cbm_registry_add(r, "repeated", qn, "Method", false);
     cbm_registry_set_swift_signature(r, qn, (UINT64_C(1) << 0) | (UINT64_C(1) << 1), 4, NULL);
     const char *labels[2] = {NULL, "b"};
     CBMCall call = {.callee_name = "Service.repeated",
@@ -2822,9 +2931,9 @@ TEST(swift_repeated_labels_do_not_skip_default_past_next_trailing_label) {
 TEST(swift_variadic_trailing_closures_do_not_precede_parenthesized_argument) {
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "Service", "proj.Service", "Class");
+    cbm_registry_add(r, "Service", "proj.Service", "Class", false);
     const char *qn = "proj.Service.f(callbacks:(()=>Void)~,flag:Bool,done:()=>Void)";
-    cbm_registry_add(r, "f", qn, "Method");
+    cbm_registry_add(r, "f", qn, "Method", false);
     cbm_registry_set_swift_signature(r, qn, UINT64_C(1) << 1, 3, NULL);
     CBMCallArg arg = {.keyword = "flag"};
     const char *labels[2] = {NULL, "done"};
@@ -2845,17 +2954,17 @@ TEST(swift_variadic_trailing_closures_do_not_precede_parenthesized_argument) {
 TEST(swift_overloaded_bucket_fails_closed) {
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "Service", "proj.Service", "Class");
+    cbm_registry_add(r, "Service", "proj.Service", "Class", false);
     const char *first_qn = "proj.Service.work(flag:Bool)";
-    cbm_registry_add(r, "work", first_qn, "Method");
+    cbm_registry_add(r, "work", first_qn, "Method", false);
     cbm_registry_set_swift_signature(r, first_qn, 0, 1, NULL);
     const char *other = "proj.Other.work(flag:Bool)";
-    cbm_registry_add(r, "work", other, "Method");
+    cbm_registry_add(r, "work", other, "Method", false);
     cbm_registry_set_swift_signature(r, other, 0, 1, NULL);
     char qns[256][64];
     for (int i = 1; i < 256; i++) {
         snprintf(qns[i], sizeof(qns[i]), "proj.Other%d.work(flag:Bool)", i);
-        cbm_registry_add(r, "work", qns[i], "Method");
+        cbm_registry_add(r, "work", qns[i], "Method", false);
         cbm_registry_set_swift_signature(r, qns[i], 0, 1, NULL);
     }
     CBMCall call = {.callee_name = "Service.work"};
@@ -2921,11 +3030,11 @@ TEST(python_symbol_scope_len_preserves_file_identity) {
 TEST(registry_python_package_scope_is_explicit) {
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "Field", "proj.forms.fields.Field", "Class");
-    cbm_registry_add(r, "Field", "proj.db.fields.Field", "Class");
-    cbm_registry_add(r, "Field", "proj.db.fields.__init__.Field", "Class");
-    cbm_registry_add(r, "Field", "proj.db.plain.Field", "Class");
-    cbm_registry_add(r, "Field", "proj.db.index.Field", "Class");
+    cbm_registry_add(r, "Field", "proj.forms.fields.Field", "Class", false);
+    cbm_registry_add(r, "Field", "proj.db.fields.Field", "Class", false);
+    cbm_registry_add(r, "Field", "proj.db.fields.__init__.Field", "Class", false);
+    cbm_registry_add(r, "Field", "proj.db.plain.Field", "Class", false);
+    cbm_registry_add(r, "Field", "proj.db.index.Field", "Class", false);
     const char *keys[] = {"forms"};
     const char *vals[] = {"proj.forms"};
     const char *module = "proj.db.fields.__init__";
@@ -2957,11 +3066,11 @@ TEST(registry_python_package_scope_is_explicit) {
 TEST(registry_python_scope_keeps_import_precedence_and_raw_scoring) {
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "Field", "proj.vendor.Field", "Class");
-    cbm_registry_add(r, "Field", "proj.pkg.Field", "Class");
-    cbm_registry_add(r, "Field", "proj.pkg.__init__.Field", "Class");
-    cbm_registry_add(r, "choose", "proj.pkg.__init__.child.choose", "Function");
-    cbm_registry_add(r, "choose", "proj.pkg.peer.choose", "Function");
+    cbm_registry_add(r, "Field", "proj.vendor.Field", "Class", false);
+    cbm_registry_add(r, "Field", "proj.pkg.Field", "Class", false);
+    cbm_registry_add(r, "Field", "proj.pkg.__init__.Field", "Class", false);
+    cbm_registry_add(r, "choose", "proj.pkg.__init__.child.choose", "Function", false);
+    cbm_registry_add(r, "choose", "proj.pkg.peer.choose", "Function", false);
     const char *keys[] = {"Field"};
     const char *vals[] = {"proj.vendor.Field"};
     bool seeded = cbm_registry_size(r) == 5;
@@ -2985,14 +3094,14 @@ TEST(registry_python_scope_keeps_import_precedence_and_raw_scoring) {
 TEST(registry_python_scope_cache_modes_and_raw_lineage) {
     cbm_registry_t *r = cbm_registry_new();
     ASSERT_NOT_NULL(r);
-    cbm_registry_add(r, "Entry", "proj.pkg.Entry", "Function");
-    cbm_registry_add(r, "Entry", "proj.pkg.__init__.Entry", "Function");
-    cbm_registry_add(r, "Reject", "proj.pkg.Reject", "Table");
-    cbm_registry_add(r, "Reject", "proj.pkg.__init__.Reject", "Function");
-    cbm_registry_add(r, "Accept", "proj.pkg.Accept", "Function");
-    cbm_registry_add(r, "Accept", "proj.pkg.__init__.Accept", "Table");
-    cbm_registry_add(r, "Relation", "proj.pkg.Relation", "View");
-    cbm_registry_add(r, "Relation", "proj.pkg.__init__.Relation", "Table");
+    cbm_registry_add(r, "Entry", "proj.pkg.Entry", "Function", false);
+    cbm_registry_add(r, "Entry", "proj.pkg.__init__.Entry", "Function", false);
+    cbm_registry_add(r, "Reject", "proj.pkg.Reject", "Table", false);
+    cbm_registry_add(r, "Reject", "proj.pkg.__init__.Reject", "Function", false);
+    cbm_registry_add(r, "Accept", "proj.pkg.Accept", "Function", false);
+    cbm_registry_add(r, "Accept", "proj.pkg.__init__.Accept", "Table", false);
+    cbm_registry_add(r, "Relation", "proj.pkg.Relation", "View", false);
+    cbm_registry_add(r, "Relation", "proj.pkg.__init__.Relation", "Table", false);
     bool seeded = cbm_registry_size(r) == 8;
     bool correct = true;
     /* Each cache lifetime has one fixed module/import map. Alternate modes in
@@ -3070,12 +3179,12 @@ TEST(registry_python_scope_complete_candidate_boundaries) {
         int tn = snprintf(target, sizeof(target), "%s.%s", scope, name);
         bool shape = mn > 0 && (size_t)mn < sizeof(module) && tn > 0 && (size_t)tn == lengths[i] &&
                      (size_t)tn < sizeof(target);
-        cbm_registry_add(r, name, target, "Function");
+        cbm_registry_add(r, name, target, "Function", false);
         if (lengths[i] > 511) {
             char truncated[512];
             memcpy(truncated, target, sizeof(truncated) - 1);
             truncated[sizeof(truncated) - 1] = '\0';
-            cbm_registry_add(r, "truncated_decoy", truncated, "Function");
+            cbm_registry_add(r, "truncated_decoy", truncated, "Function", false);
         }
         const char *canonical = registry_scope_canonical(r, name, target);
         cbm_resolution_t python =
@@ -3102,7 +3211,7 @@ TEST(registry_python_scope_qualified_terminal_bucket_uncapped) {
         char qn[80];
         int n = snprintf(qn, sizeof(qn), "proj.noise%d.perform", i);
         shape = n > 0 && (size_t)n < sizeof(qn) && shape;
-        cbm_registry_add(r, "perform", qn, "Method");
+        cbm_registry_add(r, "perform", qn, "Method", false);
     }
     char scope[1024];
     memcpy(scope, "proj.", 5);
@@ -3120,7 +3229,7 @@ TEST(registry_python_scope_qualified_terminal_bucket_uncapped) {
         int pn = snprintf(prefixed, sizeof(prefixed), "receiver.%s", names[i]);
         shape = tn > 0 && (size_t)tn < sizeof(target) && pn > 0 && (size_t)pn < sizeof(prefixed) &&
                 shape;
-        cbm_registry_add(r, "perform", target, "Method");
+        cbm_registry_add(r, "perform", target, "Method", false);
         const char *canonical = registry_scope_canonical(r, "perform", target);
         cbm_resolution_t direct =
             cbm_registry_resolve_lang(r, names[i], module, NULL, NULL, 0, CBM_LANG_PYTHON);
@@ -3154,13 +3263,13 @@ TEST(registry_python_function_local_is_exact_only_issue1548) {
         {"Inner", "proj.web.Outer.Inner", "Class"},
     };
     for (size_t i = 0; i < sizeof(defs) / sizeof(defs[0]); i++) {
-        cbm_registry_add_lang_in_module(r, defs[i][0], defs[i][1], defs[i][2], CBM_LANG_PYTHON,
-                                        web);
+        cbm_registry_add_lang_in_module(r, defs[i][0], defs[i][1], defs[i][2], CBM_LANG_PYTHON, web,
+                                        false);
     }
     cbm_registry_add_lang_in_module(r, "f", "proj.ts.f", "Function", CBM_LANG_TYPESCRIPT,
-                                    strlen("proj.ts"));
+                                    strlen("proj.ts"), false);
     cbm_registry_add_lang_in_module(r, "g", "proj.ts.f.g", "Function", CBM_LANG_TYPESCRIPT,
-                                    strlen("proj.ts"));
+                                    strlen("proj.ts"), false);
 
     static const char *const local[] = {"proj.web.create_app.index", "proj.web.create_app.Settings",
                                         "proj.web.create_app.Settings.value"};
@@ -3212,7 +3321,7 @@ TEST(registry_resolve_lexical_walks_enclosing_defs_issue1548) {
     };
     for (size_t i = 0; i < sizeof(defs) / sizeof(defs[0]); i++) {
         cbm_registry_add_lang_in_module(r, defs[i][0], defs[i][1], defs[i][2], CBM_LANG_PYTHON,
-                                        strlen("proj.m"));
+                                        strlen("proj.m"), false);
     }
 
     /* In method Tree.visit, `visit` is its nested def; so it is inside that
@@ -3254,17 +3363,17 @@ TEST(registry_python_local_bound_at_own_file_issue1548) {
         cbm_registry_t *r = cbm_registry_new();
         if (order == 0) {
             cbm_registry_add_lang_in_module(r, "layout", "proj.pkg.layout", "Function",
-                                            CBM_LANG_PYTHON, init_prefix);
+                                            CBM_LANG_PYTHON, init_prefix, false);
         }
         cbm_registry_add_lang_in_module(r, "Layout", "proj.pkg.layout.Layout", "Class",
-                                        CBM_LANG_PYTHON, mod_prefix);
+                                        CBM_LANG_PYTHON, mod_prefix, false);
         cbm_registry_add_lang_in_module(r, "create", "proj.pkg.layout.Layout.create", "Method",
-                                        CBM_LANG_PYTHON, mod_prefix);
+                                        CBM_LANG_PYTHON, mod_prefix, false);
         cbm_registry_add_lang_in_module(r, "make", "proj.pkg.layout.make", "Function",
-                                        CBM_LANG_PYTHON, mod_prefix);
+                                        CBM_LANG_PYTHON, mod_prefix, false);
         if (order == 1) {
             cbm_registry_add_lang_in_module(r, "layout", "proj.pkg.layout", "Function",
-                                            CBM_LANG_PYTHON, init_prefix);
+                                            CBM_LANG_PYTHON, init_prefix, false);
         }
         static const char *const nameable[][2] = {{"Layout", "proj.pkg.layout.Layout"},
                                                   {"create", "proj.pkg.layout.Layout.create"},
@@ -3332,6 +3441,11 @@ SUITE(registry) {
     RUN_TEST(registry_create_free);
     RUN_TEST(registry_free_null);
     RUN_TEST(registry_add_and_exists);
+    RUN_TEST(registry_prefers_non_test_over_test_candidate);
+    RUN_TEST(registry_test_verdict_comes_from_the_caller_not_the_qn);
+    RUN_TEST(registry_sole_test_candidate_still_resolves);
+    RUN_TEST(registry_test_double_path_table);
+    RUN_TEST(registry_swift_overload_choice_uses_stored_verdicts);
     RUN_TEST(registry_label_of);
     RUN_TEST(registry_value_target_field_twin);
     RUN_TEST(registry_find_by_name);
diff --git a/tests/windows/mcp_stdio.py b/tests/windows/mcp_stdio.py
index 218e9a27f..d582d4c10 100644
--- a/tests/windows/mcp_stdio.py
+++ b/tests/windows/mcp_stdio.py
@@ -25,6 +25,8 @@ class McpServer:
         self._id = 0
         self.proc = None
         self._stderr = []
+        self._stderr_thread = None
+        self._stderr_eof = False
         env = dict(os.environ)
         if cache_dir:
             env["CBM_CACHE_DIR"] = cache_dir  # isolate the graph DB location
@@ -52,12 +54,27 @@ class McpServer:
         try:
             for line in self.proc.stderr:
                 self._stderr.append(line.decode("utf-8", "replace"))
+            self._stderr_eof = True
         except Exception:
             pass
 
     def stderr_text(self):
         return "".join(self._stderr)
 
+    def stderr_complete(self, timeout):
+        """Wait for the stderr reader to reach EOF; True once it has.
+
+        Only then is stderr_text() the whole capture. False means the reader
+        is still running (some process still holds the pipe) or stopped on a
+        read error, so the text may be partial: a caller that asserts on
+        stderr must treat False as a setup failure, never as a verdict. The
+        timeout is a liveness backstop, not part of any verdict.
+        """
+        if self._stderr_thread is None:
+            return False
+        self._stderr_thread.join(timeout)
+        return not self._stderr_thread.is_alive() and self._stderr_eof
+
     def _send(self, obj):
         data = json.dumps(obj, ensure_ascii=False).encode("utf-8")
         self.proc.stdin.write(data + b"\n")
@@ -148,6 +165,7 @@ class McpServer:
                 self.proc.kill()
             except Exception:
                 pass
+        self._stderr_thread.join(timeout=10)
 
 
 def wait_projects_with_stats(server, timeout=90.0, poll=1.0):
diff --git a/tests/windows/test_mcp_stdio.py b/tests/windows/test_mcp_stdio.py
new file mode 100644
index 000000000..7b7eee617
--- /dev/null
+++ b/tests/windows/test_mcp_stdio.py
@@ -0,0 +1,127 @@
+"""Regression guard for clean Windows MCP stdio startup (#654).
+
+A successful initialize + tools/list exchange must leave nothing on stderr but
+the server's own structured log lines. #654 reported the OS "path not found"
+message leaking to stderr on startup, in English and on a Spanish Windows. Those
+two messages are named cases; any other non-empty line that is not a structured
+`level=<name> msg=<event>` record fails as well, so the same leak on a machine
+in any other language is caught without listing its translation.
+
+The verdict is read only after the stderr reader has reached EOF. A reader that
+is still running after the server exited means the capture may be partial, and
+that is a setup failure, never a pass.
+
+Exit codes follow the guard contract of scripts/test-windows.ps1:
+0 = GREEN, 1 = RED (regression), 2 = SETUP / precondition.
+"""
+
+import os
+import re
+import subprocess
+import sys
+import tempfile
+
+from mcp_stdio import McpServer
+
+# The OS path-not-found message as reported in #654 (English and Spanish
+# Windows). Named so a RED says exactly which known leak came back.
+KNOWN_PATH_ERRORS = (
+    "The system cannot find the path specified.",
+    "El sistema no puede encontrar la ruta especificada.",
+)
+
+# The text-format record cbm_log writes (src/foundation/log.c):
+# "level=<debug|info|warn|error> msg=<event> key=value ...".
+STRUCTURED_LOG_LINE = re.compile(r"level=[a-z]+ msg=\S")
+
+# Liveness backstop for the stderr reader. The server has already exited when
+# this is waited on, so the reader is at EOF unless another process still holds
+# the pipe. Expiry is a SETUP failure; it never decides PASS or FAIL.
+STDERR_EOF_BACKSTOP_S = 60
+
+
+def classify_stderr(text):
+    """Return (known, raw): the named #654 messages found, and every other
+    non-empty stderr line that is not a structured log record."""
+    known = [message for message in KNOWN_PATH_ERRORS if message in text]
+    raw = []
+    for line in text.splitlines():
+        line = line.strip()
+        if not line or STRUCTURED_LOG_LINE.match(line):
+            continue
+        if any(message in line for message in KNOWN_PATH_ERRORS):
+            continue
+        raw.append(line)
+    return known, raw
+
+
+def main():
+    if os.name != "nt":
+        print("SKIP: Windows-only MCP stdio guard")
+        return 2
+
+    binary = sys.argv[1] if len(sys.argv) > 1 else os.environ.get("CBM_TEST_BINARY")
+    if not binary:
+        print("SETUP FAIL: CBM_TEST_BINARY is required", file=sys.stderr)
+        return 2
+
+    with tempfile.TemporaryDirectory(prefix="cbm-mcp-stdio-") as work:
+        cache = os.path.join(work, "cache")
+        runtime = os.path.join(work, "runtime")
+        os.makedirs(cache)
+        os.makedirs(runtime)
+        # The verdict reads the text log shape, so select it explicitly: an
+        # inherited CBM_LOG_FORMAT=json must not turn every record into a raw
+        # line.
+        server = McpServer(
+            binary,
+            cache_dir=cache,
+            extra_env={"CBM_RUNTIME_DIR": runtime, "CBM_LOG_FORMAT": "text"},
+        )
+        try:
+            with server:
+                server.initialize(timeout=30)
+                server.tools_list(timeout=30)
+        finally:
+            stop = subprocess.run(
+                [binary, "daemon", "stop"],
+                env=server.env,
+                capture_output=True,
+                timeout=30,
+            )
+            if stop.returncode != 0:
+                detail = (stop.stdout + stop.stderr).decode("utf-8", "replace")
+                raise RuntimeError(
+                    "daemon cleanup failed (%d): %s" % (stop.returncode, detail.strip())
+                )
+
+    if not server.stderr_complete(STDERR_EOF_BACKSTOP_S):
+        print(
+            "SETUP FAIL: the stderr reader did not reach EOF after the server "
+            "exited; refusing to judge a possibly partial capture",
+            file=sys.stderr,
+        )
+        return 2
+
+    known, raw = classify_stderr(server.stderr_text())
+    if known or raw:
+        if known:
+            print(
+                "FAIL: startup leaked an OS path error to stderr: " + ", ".join(known),
+                file=sys.stderr,
+            )
+        if raw:
+            print(
+                "FAIL: startup wrote %d stderr line(s) that are not structured "
+                "level= log records:" % len(raw),
+                file=sys.stderr,
+            )
+            for line in raw:
+                print("  " + line, file=sys.stderr)
+        return 1
+    print("PASS: successful MCP startup emitted only structured log lines on stderr")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())