[aw-failures] Discussion Task Miner: sed read of agent's own scratch file denied, cascades to invocation-cap exhaustion #50682

Problem

Stop letting a single denied sed read burn the whole invocation budget — cap identical-intent permission denials the same way #49096 already asked for jq -Rs, but this time it's shell(sed ...) on an agent-owned scratch file. Discussion Task Miner's attempt 1 hit permission denied by workflow tool permissions: shell(sed -n '205,260p' /tmp/gh-aw/agent/50544.md), retried the identical command pattern, and tripped guard.tool_denials_exceeded (3/3) — max tool denials threshold reached (3/3); stopping SDK session early, then exhausted the run's invocation cap entirely.

Affected Workflows and Run IDs

• Discussion Task Miner - Code Quality Improvement Agent (scheduled workflow, .github/workflows/discussion-task-miner.md) — §31009371114 (2026-08-05 13:15 UTC)

Probable Root Cause

This is the same class of bug as #49096 (permission-denied retries exhausting the LLM invocation cap) but on a different surface: reading the agent's own scratch/context file (/tmp/gh-aw/agent/50544.md) via sed -n is blocked by workflow tool permissions, and the harness has no short-circuit for "same file, same denial, N attempts" — it keeps retrying until the 3-denial guard fires, then the whole session dies instead of degrading gracefully (e.g. falling back to a cat/Read-equivalent allowed tool, or reporting missing_tool).

Specific Proposed Remediation

1. Allow read-only access (sed -n, cat, head) to files the workflow itself wrote under /tmp/gh-aw/agent/** — these are the agent's own generated context, not untrusted external content, so denying reads of them serves no security purpose.
2. When guard.tool_denials_exceeded fires, exit with a clear missing_tool/report_incomplete signal rather than continuing to burn invocation budget on the same command shape.
3. Since this is a scheduled workflow, confirm the fix by re-running Discussion Task Miner on its next scheduled trigger and checking it completes without a permission-denial cascade.

Success Criteria / Verification

• Next scheduled run of Discussion Task Miner completes without guard.tool_denials_exceeded or invocation_cap_exceeded.
• sed -n/read-only shell access to /tmp/gh-aw/agent/** scratch files is no longer denied by workflow tool permissions.
• Related to [aw-failures] Design Decision Gate exhausts LLM invocation cap after permission-denied retries on shell-expanded file paths #49096 (same failure class, different workflow/command) — track both to closure together if the fix is a shared permission-policy change.
  Related to [aw-failures] [aw] Failure Investigator Report — 2026-08-05 (6h) #50518

Generated by 🔍 [aw] Failure Investigator (6h) · agent · 148.2 AIC · ⌖ 49.3 AIC · ⊞ 5.2K · ◷

• expires on Aug 12, 2026, 11:24 AM UTC-08:00