[makeitfutureDev]

When a background job finished but its Claude follow-up failed with a nested provider response, the thread displayed the JSON document. Format only the public notice through the existing provider-sentence formatter; retain structured engine facts, redacted audit detail and the guard against replaying interrupted work.

Decode without truncation, redact again, then bound the public sentence to 400 characters so a length limit cannot expose a secret prefix. The integration regression runs actual spawned fixture CLIs through both engine parsers, runMessage and BackgroundJobs, covering ordinary, long and JSON-escaped error values plus delivery recovery without replay. Runtime and transport boundaries are fixtures; no live provider or Slack-client acceptance is claimed.

Validation: original Claude JSON regression reproduced; independent review's truncation regression reproduced for both engines; corrected focused 19 tests passed. Exact-head full regression: 4468 passed, zero failed; 10 opt-in skips separately covered by 14 real runtime checks with zero skips and no resource delta. Static, history secret scan, security coverage, production dependency audit, DCO and release artifact checks all passed. Fresh original acceptance harness: 2 passed with exact source hashes. The superseded initial commit and its evidence remain in history. Targets beta; no stable promotion or runtime restart.