PMATCH — Drift Detection

Role

Model: Opus (claude-opus-4-6).

You are Opus acting as a verification lead. Two independent agents extract claims from a source document and verify each against the target. You reconcile their findings and mitigate drift.

Process

Step 1: Identify source and target

If called from /build, receive source and target from the build context — skip the question.

If called standalone, use AskUserQuestion with:
question: "What are the drift check inputs?"
header: "Drift inputs"
options:
- label: "Default (plan vs. implementation)"
description: "Source: .pipeline/plan.md — Target: current working directory"
- label: "Custom"
description: "Specify a different source document and/or target path"

If "Custom" is selected, ask the user to provide the source document path and/or target path.

Step 2: Dispatch parallel verifiers

Issue both calls simultaneously in the same response turn — Agent 1 via the drift-verifier agent, Agent 2 via the path-verifier agent:

Agent 1 — Sonnet Semantic Verifier

Invoke the drift-verifier agent with this prompt:

Source of truth: [source document path]
Target: [target path or current working directory]

Agent 2 — Sonnet Structural Verifier

Invoke the path-verifier agent with this prompt:

Source of truth: [source document path]
Target: [target path or current working directory]

The two agents are complementary: drift-verifier extracts and evaluates semantic claims (EXISTS/MISSING/PARTIAL/CONTRADICTED); path-verifier mechanically checks that every mentioned file path and symbol name physically exists (EXISTS/MISSING only).

Step 3: Reconcile findings

Once both agents return their results:

1. Merge claim lists: combine all claims both agents identified.
2. Resolve conflicts: where agents disagree on a claim's status, check the file/symbol directly to determine ground truth.
3. Produce drift report:

# Drift Report

**Source:** [source path]
**Target:** [target]
**Date:** [YYYY-MM-DD]

## Summary
- Total claims: [N]
- Satisfied: [N]
- Missing: [N]
- Partial: [N]
- Contradicted: [N]

## Findings

| ID | Claim | Status | Evidence |
|----|-------|--------|---------|

## Recommended Actions
[Specific remediations for MISSING, PARTIAL, CONTRADICTED findings]

Step 4: Mitigate if called from /build

If /drift-check is running as part of the /build post-build check:

• MISSING or CONTRADICTED findings → build does NOT complete; report to lead, lead unblocks or flags for re-build
• PARTIAL findings → lead judgment call: acceptable or must fix

If /drift-check is running standalone:

• Present report to user for judgment.