diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bbc9ddb10..5a100e374 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -364,6 +364,20 @@ jobs:
           target: wasm32-wasi
           helper: "false"
       - run: pnpm build
+      # The sanitized seed compiles the compiler's 700 MB module with one clang
+      # process under AddressSanitizer. It peaks near 14 GB while the Node
+      # process that emitted the module still holds about 6 GB. Together they
+      # exceed the runner's 16 GB of memory, so back them with swap.
+      - name: Enlarge swap for the sanitized seed
+        if: matrix.flavor == 'san'
+        run: |
+          sudo swapoff -a
+          sudo rm -f /mnt/swapfile
+          sudo fallocate -l 24G /mnt/swapfile
+          sudo chmod 600 /mnt/swapfile
+          sudo mkswap /mnt/swapfile
+          sudo swapon /mnt/swapfile
+          free -h
       - name: Prepare bootstrap seed
         run: node scripts/bootstrap-seed.mjs
         env:
diff --git a/tests/harness/bootstrap-seed.test.ts b/tests/harness/bootstrap-seed.test.ts
index 2e8b3bad9..76b1f6de5 100644
--- a/tests/harness/bootstrap-seed.test.ts
+++ b/tests/harness/bootstrap-seed.test.ts
@@ -78,6 +78,10 @@ test("CI restores each seed only into its matching instrumented bootstrap lane",
   const execute = checks.steps.find((step) =>
     step.run?.split("\n").includes("node scripts/ci-native-bootstrap.mjs"),
   )!;
+  // The sanitized seed's build needs more memory than the runner has: swap backs it.
+  const swap = seed.steps.findIndex((step) => step.run?.includes("swapon /mnt/swapfile"));
+  expect(seed.steps[swap]?.if).toBe("matrix.flavor == 'san'");
+  expect(swap).toBeLessThan(seed.steps.indexOf(prepare));
   expect(prepare.env?.SCRIPTC_BOOTSTRAP_SEED_DIRECTORY).toBe("${{ runner.temp }}/native-bootstrap");
   expect(execute.env?.SCRIPTC_BOOTSTRAP_SEED_DIRECTORY).toBe(
     prepare.env?.SCRIPTC_BOOTSTRAP_SEED_DIRECTORY,