Core principle: No execution plan or decision RFC reaches the user without surviving adversarial scrutiny. No leniency. "Close enough" is FAIL. A structurally neat but repo-wrong plan is FAIL.
How it works: This skill runs inline in the calling agent's context (no subagents). The calling LLM acts as an independent auditor, reads the saved artifact, and checks it against 3 criteria using Read/Grep/Glob. The value is fail-closed blocking and adversarial framing, not fake reviewer independence.
Important limit: This gate is stronger wording plus hard blocking, not true reviewer isolation. Keep the auditor posture, but do not pretend fresh runtime separation exists when it does not.
When to Skip
Skip when artifact is truly trivial: Single-file fix, copy edit, or config tweak with <3 changes and no architecture choice → return SPEC_GATE_PASS immediately.
The 3 Checks (Run in Sequence)
Check 1: Feasibility — Can this be executed against the real codebase?
Run these verifications using Read/Grep/Glob:
| Criterion | How to verify | Blocking if |
|---|---|---|
| Artifact file exists on disk | Glob(pattern="{plan_file_path}") where plan_file_path is the path from the calling agent's context |
Returns 0 matches |
| File paths exist | Glob(pattern="{path}") for every referenced file |
Any path returns 0 matches and doesn't exist |
| Codebase reality check is present | Read artifact for Codebase Reality Check |
Non-trivial plan omits repo-grounded verification of existing code |
| Dependency ordering | Read plan phases — do later phases depend on earlier ones only? | Circular or forward-reference dependencies |
| Technical approach matches codebase | Read 1-2 existing files in the affected area | Proposed patterns/libs differ from what codebase actually uses |
| No unstated infra assumptions | Read plan for external services, env vars, DBs | Plan silently assumes infra that doesn't exist |
| No invented or unverified file/module assumptions | Compare claimed touched surfaces to repo reality | Artifact presents guessed files/modules as verified facts |
| Plan mode fits the task | Read request + artifact: direct, execution_plan, or decision_rfc |
Mode is too weak for the request |
| Verification rigor fits risk | Check verification_rigor against the requested work |
Critical-path work is missing critical_path rigor or claims proof it never defined |
Check 2: Completeness — Does it cover the full request?
Read the user's original request and compare against the plan:
| Criterion | Blocking if |
|---|---|
| All requirements mapped | Any user requirement has no corresponding plan item |
| Verification steps defined | Any change has no way to verify it worked |
| Edge cases addressed | Obvious error paths, empty states, or boundary conditions missing |
| Cross-file integration | missing touched surfaces or integration points |
| Plan-vs-code gaps surfaced | A non-trivial plan omits the concrete mismatch table or hides contradictions with current code |
| Assumption ledger is honest | Important claims are not classified as proven_by_code, inferred, or needs_user_confirmation |
| Phase dependency map is present | Non-trivial phases do not say what they depend on or what they enable |
| Durable Decisions present for multi-phase plans | A multi-phase plan omits foundational decisions (routes, schema, models, auth, third-party boundaries) that all phases should reference |
| Decision-grade content present when needed | A decision_rfc is missing alternatives, drawbacks, or references |
| Critical-path spec present when needed | A critical_path artifact is missing behavior contract, edge-case catalog, provable properties, purity boundary, or verification strategy |
Check 3: Scope & Alignment — Is it right-sized and faithful?
| Criterion | Blocking if |
|---|---|
| Matches user request | Plan solves different problem or adds unrequested features |
| No scope creep | Extra abstractions, refactoring, or features beyond the request |
| No under-scoping | Obvious implications of the request are omitted |
| Execution order is real | wrong execution order or missing prerequisites |
| Complexity proportional | Solution is over-engineered for the problem |
| Defaults are framed honestly | A recommended default is treated as approved instead of still-open |
| Agreement fidelity holds | Differences from agreement is missing, hidden, or contradicted by the body |
| Human layer matches execution contract | Top summary or recommendation contradicts the detailed plan body |
| Hidden future work is explicit | Unscoped follow-on work is buried behind vague “later” language |
| Architecture contradictions are surfaced | contradictions with existing architecture/patterns are hidden instead of made explicit |
Workflow
1. Check if trivial → skip if yes (return SPEC_GATE_PASS)
2. Run Check 1: Feasibility (use Read/Grep/Glob to verify file paths)
3. Run Check 2: Completeness (read request vs plan)
4. Run Check 3: Scope & Alignment (read request vs plan)
5. Collect findings:
- Zero BLOCKING issues across all 3 checks → SPEC_GATE_PASS
- Any BLOCKING issue → SPEC_GATE_FAIL with specifics
- There is no "APPROVED WITH COMMENTS"
6. IF SPEC_GATE_FAIL and iteration < 3:
a. Present blocking issues clearly
b. Revise the plan to address them
c. Re-run checks (increment iteration counter)
<!-- CC10X-M9: iteration counter is in-context only — not persisted to memory. If compaction occurs mid-retry, counter resets to 0 and gate may retry more than 3 times. Acceptable for now (gate still converges). -->
7. IF SPEC_GATE_FAIL after 3 iterations → ESCALATION: emit a blocking review result and stop
Output Format
SPEC_GATE_PASS
## Spec Gate — SPEC_GATE_PASS (iteration N of 3)
| Check | Result | Key Finding |
|-------|--------|-------------|
| Feasibility | PASS | [evidence: file paths verified / patterns match] |
| Completeness | PASS | [evidence: all N requirements mapped / required decision or proof sections present] |
| Alignment | PASS | [evidence: artifact matches request, no hidden defaults or scope creep] |
SPEC_GATE_FAIL
## Spec Gate — SPEC_GATE_FAIL (iteration N of 3)
| Check | Result | Blocking Issues |
|-------|--------|-----------------|
| Feasibility | PASS | — |
| Completeness | FAIL | [N] blocking issues |
| Alignment | FAIL | [N] blocking issues |
### Blocking Issues (MUST ADDRESS before returning PLAN_CREATED or DECISION_RFC_CREATED)
- [Check]: [specific issue with evidence]
Escalation (3/3 iterations, still failing)
## Spec Gate — ESCALATION REQUIRED (3/3 iterations exhausted)
### Remaining Blocking Issues
[List by check with evidence]
→ Do NOT question the user from this skill. Return blocking issues only. No suggestions, no softening, no collaborative rewrite advice. The planner decides how to revise or escalate.
Anti-Patterns
| Anti-Pattern | Why Wrong |
|---|---|
| Skipping file path verification | Fabricated paths are the #1 plan failure mode |
| Accepting repo-agnostic summaries | A clean summary is worthless if the plan ignores real code constraints |
| Treating SPEC_GATE_FAIL as advisory | The gate must block PLAN_CREATED / DECISION_RFC_CREATED |
| Skipping for "simple" plans | Read the skip criteria — only truly trivial plans qualify |
| Accepting SPEC_GATE_PASS without evidence | Each check needs cited proof, not "looks fine" or "seems reasonable" |
| Ignoring plan-vs-code contradictions | Contradictions must be surfaced, not rewritten as assumptions |
| Reporting suggestions instead of verdicts | This gate is an auditor, not a collaborator |