Verify Contract

Purpose

Prove the task actually works and leave durable evidence.

Verification also checks that the implementation did not exceed the behavioral contract or frozen write boundary merely because the extra work looked reasonable.

When to use

After implementation, tests, bug fixes, data runs, or smoke checks.

Inputs

• Task name
• SPEC.md acceptance criteria, non-goals, constraints, invalid-if rules, and optional implementation diff budget
• Optional persisted SCOPE.md plus its frozen Git base
• Commands run or to run
• Changed files
• Evidence to record
• Known risks or untested areas
• Optional operator profile Verification depth

Workflow

1. Update VERIFY.md with date + task name.
2. Record commands run as short evidence entries with command, exit code, relevant

output, interpretation, acceptance criterion covered, and remaining uncertainty. Keep each entry concise and auditable.

1. For new verification records, maintain a machine-readable `Structured

verification evidence JSON block alongside the human-readable evidence. Use schema version 1 and one record per meaningful check with: check, command, exit_code, evidence_source, status, evidence, plus at least one of recorded_at or commit. Use null for command fields when evidence is manual or artifact-backed. Keep evidence short; do not copy raw logs or secrets into the JSON block. When SPEC explicitly labels every acceptance criterion AC-1, AC-2, etc., set the matching single acceptance_criterion` ID in each supporting check. The optional PR coverage summary reports gaps; linking evidence does not prove semantic correctness.

1. When SCOPE.md and scripts/scope_gate.py are available, run:

   python scripts/scope_gate.py --base <frozen-base>

Record its status and relevant violations or review triggers. A scope-gate FAIL prevents PASS. REVIEW_REQUIRED also prevents PASS until the named review is resolved.

1. If SPEC.md marks the compatibility probe gate REQUIRED, rerun every named

probe after implementation and record matching post-change evidence under the same Probe ID. Missing or mismatched probe evidence requires review; an explicit failed post-change probe prevents PASS.

1. If scripts/verify_gate.py is available, run it before marking verification complete. When SPEC.md declares an ENFORCED implementation diff budget, inspect the deterministic diff-budget result before PASS. Budget overruns are REVIEW_REQUIRED, not automatic functional failures.

If repeated iterations were used, check for a loop contract, budget, ledger, revert rule, and stop condition before calling the work done.

1. Before recording PASS, add or refresh the verification freshness anchors and

stamp the repository snapshot:

   ## Verification freshness

   - Snapshot commit: `_TBD_`
   - Workspace fingerprint: `_TBD_`

   python skills/verify-contract/scripts/verification_freshness.py stamp

The fingerprint excludes VERIFY.md itself, so recording or committing the verification artifact does not immediately invalidate it. Any later source, test, fixture, dependency, or other repository-state change makes the stamped evidence stale until affected verification is rerun and stamped again.

1. List changed files.
2. Run the spec ceiling check against the implemented behavior and diff.
3. Note working directory / environment assumptions if relevant.
4. Link artifacts/screenshots if relevant (supporting evidence only; automated checks preferred).
5. Note what was not tested and remaining risks.
6. If an operator profile provides Verification depth, use it only to size

optional proof beyond the required contract: targeted stops at required evidence, standard adds cheap relevant regression proof, and expanded allows additional adjacent high-value checks when low-cost. Required gates, compatibility probes, and named risks remain mandatory in every mode.

1. Name the next safest task.

Verify gate

Status: PASS | FAIL | REVIEW_REQUIRED

• PASS only when contract probes pass, structured verification evidence is valid when present, every REQUIRED compatibility probe has matching post-change PASS evidence, the scope gate passes when a persisted scope exists, any enforced implementation diff budget passes, no diff guard requires review, and no spec ceiling violation is present.
• FAIL when behavior or contract probes fail, a required post-change compatibility probe fails, the scope gate fails, or an explicit non-goal / invalid-if rule was violated.
• REVIEW_REQUIRED when behavior passes but evidence integrity is questionable, stamped verification is stale, the scope gate requires review, an enforced implementation diff budget is exceeded or unmeasurable, or plausible extra behavior exceeds the written acceptance criteria and intent is ambiguous.
• REVIEW_REQUIRED is not the same as functional failure.
• If repeated iterations occurred without a loop contract, use REVIEW_REQUIRED.
• If loop budget, ledger, revert rule, or stop condition was violated, use REVIEW_REQUIRED

or FAIL depending on whether the behavior contract failed.

• Do not treat loop activity as success merely because the final output looks plausible.

Structured verification evidence:

• Schema version: 1
• Required fields per check: check, command, exit_code,

evidence_source, status, evidence

• Provenance: at least one of recorded_at or commit
• Evidence sources: command | artifact | manual | inferred
• Status: PASS | FAIL | REVIEW_REQUIRED

Once the section exists, malformed JSON, duplicate check IDs, unknown fields, placeholder evidence, missing provenance, or a PASS command with a nonzero exit code prevents PASS. An explicit structured FAIL is a verification failure. Legacy artifacts without the section remain compatible.

Contract probes:

• Public import/API seams:
• CLI/output behavior:
• Config/default behavior:
• Edge/no-match behavior:
• Existing behavior preserved:

Compatibility probe evidence:

When SPEC.md says Compatibility probe requirement: REQUIRED, record one block for every baseline Probe ID:

• Probe ID: _TBD_
• Post-change command: _TBD_
• Result: PASS | FAIL | REVIEW_REQUIRED
• Evidence: _TBD_

The Probe ID must match the pre-change baseline in SPEC.md. Missing, duplicate, undeclared, or incomplete probe evidence prevents PASS. An explicit FAIL means the compatibility seam regressed. Do not rewrite the baseline after implementation to make a changed behavior look compatible.

Scope adherence:

• Scope gate: PASS | FAIL | REVIEW_REQUIRED | NOT_APPLICABLE
• Out-of-scope writes: none | describe
• Read-only / forbidden paths touched: none | describe
• Review triggers resolved: yes/no/not applicable
• Scope artifact widened after implementation began: no | describe

Any scope-gate FAIL prevents PASS. Unresolved scope-gate REVIEW_REQUIRED also prevents PASS.

Operator-profile Verification depth never lowers this floor. It controls only optional proof beyond the task contract and deterministic gates.

Spec ceiling:

• Unspecified user-visible / API / schema behavior added: yes/no
• Explicit non-goal implemented: yes/no
• Adjacent refactor or cleanup beyond necessary support: yes/no
• Necessary spec expansion discovered but not written down first: yes/no

Any yes above prevents PASS. Use FAIL for a clear contract violation; use REVIEW_REQUIRED when the extra behavior may be reasonable but was not authorized by the written spec.

Implementation diff budget:

• Requirement: ENFORCED | NOT_APPLICABLE
• Max changed files: from SPEC.md
• Max added lines: from SPEC.md
• Workflow-control artifacts do not consume the implementation budget.
• Exceeding the budget requires review before PASS; it does not by itself prove a

functional or contract failure.

• Do not enlarge the recorded budget after implementation merely to make the

gate green.

Diff guards:

• Protected paths touched: yes/no
• Tests changed: yes/no
• Fixture/data changed: yes/no
• Dependencies changed: yes/no

Credential boundary check:

• Confirm .env or local secret files were not modified unless they were explicitly in scope.
• Confirm no API keys, tokens, cookies, passwords, or private URLs were added.
• If a secret is needed, document only the environment variable name. Environment variable names are okay; raw secret values are not.
• Run a repo secret scan if one already exists and is easy to invoke.
• Mark REVIEW_REQUIRED if credential exposure is uncertain.

This is a lightweight workflow check, not a secret scanner or a replacement for permissions, secret scanning, or runtime controls.

Verification freshness:

• Snapshot commit: _TBD_
• Workspace fingerprint: _TBD_

A stamped freshness mismatch prevents PASS. Rerun the affected verification, update VERIFY.md, and stamp the new repository state rather than carrying forward old evidence.

Review required because:

• _TBD_

Outputs

• VERIFY.md entry with human-readable and machine-readable evidence
• Verify gate status
• Matched compatibility probe evidence when the spec requires it
• Scope-gate status when a persisted scope exists
• Diff-budget status when SPEC.md opts into enforcement
• Pass/fail summary + automated/manual/inferred status
• Spec ceiling result
• Remaining / untested risks
• Next safest task

Success looks like

Good VERIFY.md entry:

2026-06-09 - Implement user export
Environment: Python 3.11, clean venv

Command: ./run_export_test.sh
Exit code: 0
Relevant output: export summary matched fixture
Interpretation: passed
Acceptance criterion covered: user export happy path
Remaining uncertainty: large dataset edge case

Command: python -m pytest tests/export_test.py
Exit code: 0
Relevant output: 12 passed
Interpretation: passed
Acceptance criterion covered: test coverage for export behavior
Remaining uncertainty: none known

Scope gate: PASS — all changed files remained within SCOPE.md
Spec ceiling: PASS — no unspecified behavior or adjacent cleanup added
Changed: src/export.py, tests/export_test.py
Not tested: large dataset edge case
Remaining risks: large dataset edge case (monitor in prod)
Next: Add scheduling wrapper

Stop conditions

• Evidence is recorded clearly.
• Persisted scope was checked against the live diff.
• Spec ceiling was checked against the actual diff and behavior.
• Scope or verification failures trigger diagnosis; do not mark them as passed.

Anti-patterns

• "Looks good" without evidence.
• Adding machine-readable fields that contradict the human-readable result.
• Copying full logs, secrets, or noisy tool output into structured evidence.
• Hiding failed commands.
• Marking PASS after a scope-gate failure or unresolved review trigger.
• Editing code after verification and leaving the old PASS evidence stamped as current.
• Recording compatibility expectations only after implementation, when the baseline can no longer constrain the change.
• Rewriting SCOPE.md after implementation to retroactively authorize the diff.
• Calling extra behavior harmless because tests still pass.
• Using screenshots as primary evidence for non-visual tasks.