verify

Arguments. [<claim or target>]. e.g. /performance:verify the 4-to-1 spawn reduction

Purpose

Answers "is this result real, and what does it actually say?"

This phase is where blocking correctness defects that the implementer, the implementer's own test suite, and a full green CI run all missed get caught. That is why it is a separate phase from measurement and not a step inside it.

Read ${CLAUDE_PLUGIN_ROOT}/reference/harness-integrity.md first.

1. Fresh context, and adversarial by construction

Dispatch a verifier that does not inherit the implementer's numbers. Give it the trees and the claim; withhold the reasoning that produced the figures. A verifier shown the expected answer verifies the answer, not the work.

The brief should say, in substance: distrust the reported numbers, re-derive them yourself, and report what you actually observe including the ways you could not reproduce it.

The brief also sets a turn budget, a limit the verifier keeps for itself: 30 turns, stop gathering and re-measuring by turn 22, and spend the remaining turns writing the report. Run the highest-value checks first: re-derive the headline number and the differential before any secondary check. A report that ends short names what it did not reach under Not covered:. A verification that ran out of turns is not complete, so anything unreached stays NOT MET or unverified.

Two independent verifiers routinely find different defects, so one verifier is the floor, not the target.

2. Prove behavior did not change, with a differential

A passing test suite is not a behavior proof. It proves nothing asserted broke. It does not prove behavior is unchanged, because it only checks what someone thought to assert.

Run a differential: the pre-change and post-change subject over a harvested corpus of real inputs, requiring byte-identical output. Use the bundled one rather than writing one: python3 "${CLAUDE_PLUGIN_ROOT}/scripts/differential.py" --baseline <path> --candidate <path> --config <json>. Its config takes a matrix of modes, and it refuses a run where neither arm ever produced output. Run it from the Bash tool, whose shell resolves python3 (type -P python3 names the one it found); a bare name inside another process's subprocess call searches a different PATH (harness-integrity rule 6). The module docstring documents the config.