Regression: PreCompact hook returned invalid JSON output in Codex

[intel352]

Summary

Codex surfaced a PreCompact hook failure during an autodev workflow-compute run:

PreCompact hook (failed)
  error: hook returned invalid PreCompact hook JSON output

Context

• Date observed: 2026-06-05
• Host: Codex
• Workspace: /Users/jon/workspace
• Active repo/task: GoCodeAlone/workflow-compute, locked plan completion checkpoint for docs/plans/2026-05-31-outstanding-roadmap.md
• Autodev plugin path in hook prompt: /Users/jon/.codex/plugins/cache/autodev-marketplace/autodev/6.5.0/hooks/hooks.json

Notes

• The visible failure did not include the malformed JSON payload, only the hook runner error above.
• Similar older issues exist (#41, #66), but both are closed and this failure recurred under autodev 6.5.0/Codex.
• The workflow was able to continue after the hook error, but the hook output contract should be hardened so PreCompact always emits valid JSON or reports a structured failure.