Insert the FastAPI benchmark probe as an APIRouter method instead of a top-level function before an indented method declaration. The old mutation produced invalid Python and contaminated scoped-LSP overlay diagnostics with parser fallout.
Compile the mutated source before writing it so future FastAPI probe changes fail fast with a precise error instead of producing misleading benchmark data.
Validation: uv run python -m py_compile scripts/benchmark-incremental-speed.py; uv run python -m py_compile /private/tmp/cbm-fastapi-valid-probe-current-20260704T2250/fastapi_insert_probe/repo/fastapi/routing.py; bash scripts/check-source-safety.sh; git diff --check; FastAPI matrix /private/tmp/cbm-fastapi-valid-probe-current-20260704T2250.json passed with canonical_equal=true and publish_kind=full.
Signed-off-by: Andrew Hundt <ATHundt@gmail.com>
Andrew Hundt
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