Trailmark Review Gate Agent Skill

Trailmark Review Gate

Apply deterministic security gate rules to Trailmark structural diff evidence.

This skill does not replace line-level review. It produces a compact structural

packet reviewers can cite while they inspect the code.

When to Use

• Reviewing a branch, pull request, release diff, or fix commit
• Checking whether a change expands attack surface
• Looking for removed validation or authorization on reachable paths
• Comparing before/after taint, privilege-boundary, blast-radius, or

complexity signals

• Producing graph evidence for a differential review

When NOT to Use

• Single-snapshot analysis. Use trailmark or trailmark-structural.
• Text-diff review only. Use differential-review.
• Full vulnerability discovery. Use an audit or bug-finding workflow.
• One static finding. Use trailmark-finding-triage.
• Tooling is unavailable and the user wants manual review only.

Rationalizations to Reject

| Rationalization | Why It Is Wrong | Required Action |

|---|---|---|

| "The line diff is small, so no graph gate is needed" | Small changes can create new call paths | Compare before/after graphs |

| "Graph gate passed, so the PR is secure" | The gate only checks structural regressions | Still perform line-level review |

| "Trailmark failed, so pass the gate" | Tool failure is unknown risk, not success | Emit UNKNOWN |

| "Tests pass, so removed validation is fine" | Tests may miss affected entrypoint paths | Review the removed path manually |

| "Only new code matters" | Removed auth, validation, and callers can be higher risk than additions | Review removals and path changes |

Workflow

Review Gate Progress:
- [ ] Step 1: Resolve before/after inputs
- [ ] Step 2: Build graph-evolution evidence
- [ ] Step 3: Normalize structural changes
- [ ] Step 4: Apply gate rules
- [ ] Step 5: Emit review packet and actions

Step 1: Resolve Inputs

Accept two refs, a branch name, a commit range, or before/after directories.

Do not check out branches unnecessarily. Prefer git diff, git show, and

git worktrees, following the graph-evolution snapshot workflow.

Step 2: Build Graph Evidence

Run graph-evolution or equivalent Trailmark before/after graph analysis.

Both snapshots must run engine.preanalysis() so taint, privilege-boundary,

blast-radius, complexity, and entrypoint signals are available.

Record Trailmark version and any feature probes. If graph construction fails,

emit UNKNOWN.

Step 3: Normalize Changes

Normalize evidence into:

• added, removed, and modified nodes
• added and removed edges
• entrypoint set changes
• taint membership changes
• privilege-boundary membership changes
• blast-radius changes
• complexity changes
• newly reachable sensitive sinks
• unresolved, proxy, or dynamic edge changes

Step 4: Apply Gate Rules

Apply the rules in references/gate-rules.md.

Gate verdicts are:

| Verdict | Meaning |

|---|---|

| FAIL | A high-risk structural regression needs review before acceptance |

| WARN | A meaningful graph change needs reviewer attention |

| PASS | No configured structural gate fired |

| UNKNOWN | Trailmark failed or evidence is too incomplete |

Step 5: Emit Packet

Write the packet using

references/output-format.md, then hand it to

the branch reviewer. Use

references/review-integration.md when

combining this packet with differential-review or another PR review process.

Requirements

• Never mutate the user's working branch while comparing refs.
• Never report PASS when Trailmark failed.
• Separate graph evidence from manual security judgment.
• Include exact changed nodes or paths for every FAIL and WARN.
• Include limitations when parser, proxy, unresolved-call, or dynamic-dispatch

uncertainty affects the verdict.