fix(ci): surface collection errors behind invalid_payload truth-gate verdicts

[groupthinking]

Canonical issue

Closes #1286

Outcome

Every PR blocked by the agent-completion truth gate now learns why. The gate previously answered invalid_payload and nothing else for 47 of the 69 open PRs; it now returns the collector's own diagnostics alongside that verdict, so an author can act instead of guessing.

Before (real PR #1270 payload):

{"verdict":"blocked","reasons":["invalid_payload"],
 "details":{"invalid_fields":["policy.agent_login","policy.run_id"]}}

After, same payload:

{"verdict":"blocked","reasons":["invalid_payload"],
 "details":{"invalid_fields":["issue.number","policy.agent_login","policy.run_id"],
            "collection_errors":["missing_linked_issue","missing_closing_issue_reference",
                                 "missing_agent_run_id","missing_agent_login"]}}

Scope

• Included: scripts/ci/agent_completion_gate.py (extract _collection_errors(); attach it to the invalid_payload early return), tests/unit/test_agent_completion_gate.py (4 regression tests).
• Explicitly excluded: the agentTaskApplicable() branch-name heuristic in pr-checks.yml. It over-triggers on claude/*, codex/*, copilot/* worktree branches from human authors, but changing it changes which PRs are policed. This PR only changes what the gate says. Tracked as follow-up in Truth gate reports bare invalid_payload and discards the collector's diagnostics, stranding ~47 open PRs #1286.

Risk

• Risk level: low
• Failure mode: none identified. verdict and reasons are byte-identical for every input; the change is purely additive to details. No blocked verdict can become ready, and no field is dropped from validation, so the gate remains fail-closed. A malformed collection_errors (non-list, blank strings, None) is filtered rather than raised — covered by tests.
• Rollback: revert this commit. The gate returns to its prior, less informative output with no behavioural change to any verdict.

Verification

Against head 4001c8db5952ec2ee068bcc2d38e2eda2a7d9204:

$ .venv/bin/python -m pytest tests/unit/test_agent_completion_gate.py \
    tests/unit/test_agent_completion_enforcement.py -q
114 passed, 89 subtests passed in 1.86s

New tests: real-world invalid_payload cascade (reproduces PR #1270), empty-list omission, non-list tolerance (None / str / dict / int), blank-entry filtering, plus both early short-circuit paths.

Review follow-up (4001c8d): the diagnostic was initially attached only to the late field-validation return, so the three early short-circuits (payload not a dict, policy not a dict, invalid policy.applicable) stayed opaque. All four invalid_payload returns now route through a shared _invalid_payload() builder.

Backward compatibility asserted explicitly — a non-dict payload still returns details: {}, and policy/policy.applicable returns keep their exact prior invalid_fields:

non-dict payload       -> details={}
policy not dict        -> details={"invalid_fields": ["policy"]}
applicable missing     -> details={"invalid_fields": ["policy.applicable"]}
early-path diagnostic  -> {"invalid_fields": ["policy.applicable"], "collection_errors": ["missing_agent_login"]}

Manual: replayed the exact PR #1270 collector payload through evaluate() and confirmed the after-output above.

• Focused tests
• Required CI
• Review threads resolved

Production evidence

Not applicable — this changes a CI verdict-reporting path only. No runtime, application, or deployed surface is touched.

The gate itself is the evidence: this PR is on a fix/ branch rather than claude/*, and agent-completion/truth-gate/pr-1285 returns not_applicable: all rules passed, which is precisely the branch-heuristic asymmetry described in #1286.

Agent handoff

• One canonical issue is linked
• No competing PR implements the same issue
• Acceptance criteria are satisfied
• Required checks pass on the current head
• Human decision is requested only for product, security, irreversible infrastructure, or production approval

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
v0-uvai	Ready	Preview, v0	Aug 3, 2026 9:06pm

[coderabbitai]

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[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Snapshot Warnings

⚠️: No snapshots were found for the head SHA 4001c8d.

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Scanned Files

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[github-actions]

Agent Completion Truth Gate: NOT_APPLICABLE

Evidence agrees.

Machine-readable verdict

{
  "details": {},
  "reasons": [],
  "verdict": "not_applicable"
}

Workflow evidence

[Copilot]

Pull request overview

Surfaces evidence collection errors alongside invalid_payload verdicts while preserving fail-closed behavior.

Changes:

• Adds reusable collection-error normalization.
• Includes diagnostics in malformed-payload details.
• Adds regression coverage for filtering and malformed values.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
scripts/ci/agent_completion_gate.py	Surfaces collection diagnostics during validation failures.
tests/unit/test_agent_completion_gate.py	Tests diagnostic propagation and filtering.

[groupthinking]

Publish gate — HALTED(awaiting_merge_approval).

This PR is green and merge-ready: all required checks pass, CodeRabbit approved, Vercel deployed, agent-completion/truth-gate returned not_applicable: all rules passed, and mergeable_state is clean.

The automated remediation run does not auto-merge to main (protected default branch; no automerge label on this PR), so the merge is staged for a human. To publish:

gh pr merge 1285 --squash --delete-branch

No further automated action is needed here — only your sign-off.

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Generated by Claude Code

[groupthinking]

Closing as superseded by #1331.

#1331 cherry-picks both commits from this PR cleanly onto the current main (this PR's base had fallen behind) and carries the same fix for #1286, including the review follow-up in 4001c8d. Keeping both open leaves two competing implementations of #1286, which trips the canonical-delivery governance gate.

No work is lost — #1331 is the live continuation. Reopen this if #1331 is abandoned.

---

Generated by Claude Code