[mxschmitt]

What

Implements Option B from #2: a native --rerun-failed[=N] flag that brings upstream-Playwright retry semantics to go test — stay green on a transient flake, but still surface it as flaky on Flakiness.io.

After the first go test -json pass, flakiness-go re-invokes go test on only the still-failing tests (scoped via an anchored -run regex + -count=1), up to N more times. Every round feeds the same converter, so each rerun becomes an extra RunAttempt — a fail-then-pass is recorded as mixed attempts (flaky) while the job stays green.

flakiness-go --rerun-failed -timeout 15m --race ./...   # bare flag → 2 reruns
flakiness-go --rerun-failed=3 ./...                     # up to 3 reruns

Outcome	Exit code
A failed test passes on some attempt	0 (green-on-transient)
A test fails every attempt	non-zero (real regression)
Build/setup failure, panic/timeout, benchmark, usage error	non-zero (never masked)

Design

• Per-test gating. The verdict is keyed by full test name: the job goes green only once every test that failed in round 0 has passed on some attempt. Rerunning a parent func re-executes already-passing sibling subtests as collateral — those outcomes are explicitly not allowed to gate the job.
• Safeguards (borrowed from gotestsum): --rerun-failed-max-failures (default 10 — skip reruns on broad breakage) and --rerun-failed-abort-on-data-race (default true).
• Wrapper-mode only. Warns (no-op) under --stdin. Flags also resolve from FLAKINESS_RERUN_FAILED[_MAX_FAILURES|_ABORT_ON_DATA_RACE].
• Rerun flags are inserted before any -args/-- separator so they reach go test, not the test binary.

Tests

• Scripted-runner unit tests (synthetic event streams) cover: fail-then-pass green, fails-every-attempt red, clean-pass no-rerun, early-stop on recovery, max-failures skip + =0 unlimited, data-race abort (and =false no-abort), build-fail not retried, collateral passing sibling doesn't gate, failing subtest not masked by passing sibling, unexplained rerun failure not masked, -args separator handling, space-separated-value rejection, stdin warning.
• Real end-to-end test (testdata/flaky) drives actual go test -json through the rerun loop: fail-then-pass → exit 0 + [failed, passed]; stable test never rerun.
• go test -race -count=1 ./..., go vet ./..., and gofmt all clean.

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