* fix(action): cap subprocess stdout/stderr retention to prevent RangeError crashes (#680)
unbounded `stdoutBuffer += chunk` / `stderrBuffer += chunk` in
`action/utils/subprocess.ts` previously crashed the wrapper with
`RangeError: Invalid string length` once V8's ~1 GiB kMaxLength was
breached on long-lived agent runs. multi-lens opencode Reviews on large
monorepos (e.g. tambo-ai/buildy) hit this consistently — 23 runs in the
last 24h, 100% of Review-mode hard failures on that repo.
- add `retain: "tail" | "none"` to SpawnOptions, defaulting to "tail"
with an 8 MiB cap. tail-mode prepends a `... [N MiB truncated] ...`
sentinel so downstream consumers can detect truncation.
- export `TailBuffer` helper for callers that need the same bounded
accumulator semantics at their own layer.
- wrap stream `data` listeners in try/catch as defense in depth — any
synchronous throw inside a stream handler is otherwise fatal.
- opencode + claude pass `retain: "none"` (they drain via onStdout /
onStderr) and switch their own `output` accumulators to TailBuffer.
their error paths read the agent-layer bounded mirrors instead of
the now-empty `result.stdout` / `result.stderr`.
- add `failure:string-length-overflow` heuristic to scripts/analyze-logs.ts
so post-fix recurrences are visible at a glance instead of bucketing
into `failure:unknown`.
- regression tests cover >1 MiB stderr without crash, retain:"none"
contract, and TailBuffer truncation semantics.
* fix: avoid TS parameter property syntax in TailBuffer for strip-only node loader
* address review: clarify try/catch scope + lock retain default to "tail"
- the original comment claimed the try/catch caught "any synchronous throw"
in the data listener, but `options.onStdout?.(chunk)` returns a Promise
in the agent callers (claude.ts:569, opencode.ts:933) — a throw inside
an async user callback surfaces as an unhandled Promise rejection, not
a synchronous exception. reword to describe the actual protection:
defense-in-depth for synchronous throws in the listener body, which is
exactly the shape of the original RangeError on `+= chunk`.
- add a test that locks `retain` default to "tail" by spawning without
the option and asserting `result.stderr` is non-empty. a future refactor
that flipped the default to "none" would silently break gitAuth,
package installs, and lifecycle hooks that read result.stderr for
failure messages, and the rest of the suite wouldn't catch it.
Colin McDonnell
5aabd1e4a9