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[deep-report] Root-cause recurring 'failed to read prompt file ENOENT' copilot-engine crash across workflows #50304

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Description

Multiple copilot-engine workflow runs are crashing with [copilot-sdk-driver] error: failed to read prompt file /tmp/gh-aw/aw-prompts/prompt.txt: Error: ENOENT: no such file or directory. Freshest confirmed occurrence: CI Optimization Coach run 30915139809 (2026-08-04T13:55Z, issue #50274). The same signature also surfaces in incident notes for PR Code Quality Reviewer and Smoke Goose runs. This is a distinct failure signature from the already-tracked background task-tool sub-agent hang/model-allocation issue (#49022) — the prompt file is missing entirely before the agent even starts, rather than the agent session hanging or failing mid-run.

Expected Impact

Root-causing this removes a zero-turn, zero-output crash mode that currently burns a full scheduled run with no diagnostic value, across at least 3 distinct workflows on the copilot engine.

Suggested Agent

gh-aw core / copilot-sdk-driver and prompt-generation step maintainer

Estimated Effort

Medium (1-4 hours) — check for a race between the prompt-file-write step and the Execute Copilot CLI step (e.g. workspace cleanup, cache restore ordering, or a step timeout truncating the write) rather than assuming this is the same root cause as the existing sub-agent-hang ticket.

Data Source

DeepReport Intelligence Briefing 2026-08-04, cross-referencing issue #50274 and the 2026-08-03 Agentic Workflow Audit's copilot-sdk-driver-failures finding.

Generated by 🔬 Deep Report · agent · 197.5 AIC · ⌖ 40.2 AIC · ⊞ 11K ·

  • expires on Aug 6, 2026, 7:39 AM UTC-08:00

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