docs(retro): v6.3.1 PreCompact Codex empty-JSON fix (#66)#68
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Pull request overview
Adds a post-merge retrospective documenting the v6.3.1 PreCompact “empty stdout → invalid JSON on Codex” incident (#66), including the root cause, the “always emit JSON” invariant, and notes from adversarial review/test updates.
Changes:
- Add a new retro file describing the Codex invalid-JSON failure mode and the
{}no-op invariant. - Document what was caught during adversarial review (including test expectations around empty output) and remaining limitations/caveats.
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| # Retro: v6.3.1 — PreCompact invalid-JSON on Codex (#66) | ||
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| **PR:** #67 — fix(hooks): PreCompact emits {} no-op (never empty) so Codex accepts the JSON | ||
| **Merged / Released:** 2026-06-01 · v6.3.1 (Latest) | ||
| **Issue:** #66 (regression/uncovered-path of #41) | ||
| **Design:** docs/plans/2026-06-01-precompact-codex-empty-json-design.md (adversarial PASS @ cycle 1+revision) | ||
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| ## Project guidance updates | ||
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| | File | Change | Reason | | ||
| |---|---|---| | ||
| | (none) | no change | The invariant is encoded as the fix + regression tests + this retro; no separate guidance file exists yet. | |
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Closes the #66/v6.3.1 loop: retro capturing the root cause (empty PreCompact stdout rejected by Codex), the backprop invariant (every hook emits valid JSON on every exit path; empty→{}), the adversarial-review catch of 3 existing empty-asserting tests, and the honest can't-repro-on-Codex caveat. Docs-only.