OPEN SOURCE / MIT Independent verification for AI-coded software

Test whatyour AI didn’t.

THE TRUST GAP

AI can change the implementation and the tests that judge it.

MaruCheck keeps an independent record of approved behavior, then challenges every change against it.

Verify your first change Contribute on GitHub ↗See the decision unfold ↓

AI SAID “DONE” / MARU STARTED CHECKING RELEASE BLOCKED

MARU / VERIFYfeat/subscription-limits ANALYZING

AGENT PATCH2 files changed

src/subscriptions/limits.ts+1 −1

 export const limits = {- FREE_LIMIT: 5,+ FREE_LIMIT: 10, PRO_LIMIT: Infinity }

CODING AGENT

Implementation updated. Existing tests pass.

VERIFICATION SEQUENCERUN-1048

01
Diff classifiedbusiness-logic · billing
DONE
02
Risk assessedcontract + historical signals
HIGH · 72
03
Contract checkedsubscription-management#SUB-001
CONFLICT
04
Evidence normalizedexpected 5 · observed 10
1 FINDING

$maru verify --diffAnalyzing changed behaviorVERIFICATION GATE: BLOCKED

Fits the tools already doing the work

Codex

Claude Code

Cursor

GitHub Actions

Vitest

Playwright

02 — UNDER PRESSURE

One change enters.
Every assumption gets challenged.

Scroll through a real MaruCheck decision. The proof changes because the state changes.

MARU / LIVE VERIFICATION RUNNING

00.00 / Patch capturedThe agent changes the limit.

2 files · billing logic

00.00 / Patch captured

The agent changes the limit.

The implementation moves from five to ten. The existing tests still pass.

2 files · billing logic

00.17 / Intent loaded

The contract remembers five.

Approved behavior remains independent of whatever the implementation currently returns.

subscription-management#SUB-001

00.31 / Risk compounded

The change is not treated equally.

Path sensitivity, contract criticality, and changed-test coverage produce an explainable score.

contract + billing + blast radius

01.08 / Memory recalled

An old failure returns to the plan.

A confirmed historical bug forces its regression test back into verification.

MEM-0143 · related regression

03.42 / Decision reached

The release stops with a reason.

MaruCheck reports the semantic conflict instead of silently changing approved intent.

expected 5 · observed 10

03 — SEMANTIC DRIFT

The tests adapted.
The promise did not.

src/billing/limits.ts1 semantic change

− FREE_LIMIT = 5+ FREE_LIMIT = 10

SEMANTIC CHANGE DETECTED

Expected: Free users may create 5 projects.
Observed: Free users may create 10 projects.

OWNER APPROVAL REQUIRED

04 — QA MEMORY

A bug should only surprise you once.

When related code changes again, MaruCheck recalls the failure and forces its regression back into the plan.

How memory is matched

03 APRMEM-0143

Invoice ownership bypass

Missing server-side account check.

RELATED PATH CHANGED

NOWREGRESSION RECALLED

cross-account.test.ts

Forced into this verification plan.

05 — AGENT BOUNDARY

Let the agent call the verifier.
Don’t let it approve itself.

Codex, Claude Code, Cursor, and compatible MCP clients can run MaruCheck and read structured evidence. Approval remains human-owned.

Connect an MCP client

CODEX → MARU MCP CONNECTED

CODING AGENTI changed invoice authorization. Existing tests pass.

TOOL CALLmaru_run_verification

{ "diff": "working-tree", "evidence": true }

RESULT / 1.42sBLOCKED

Cross-account regression reproduced.

invoice-access#INV-001 · critical

06 — LOCAL EXECUTION

The check runs where
the change lives.

Source and secrets stay in the repository or CI runner. MaruCheck produces reviewable evidence under .maru/.

maru — local verificationstdio / trusted

~/project main*

$maru verify --diff

01Verification gate: BLOCKED

02[CRITICAL] BLOCKING · invoice-access#INV-001

03Expected: Users can only read invoices owned by their account.

04Actual: Cross-account invoice payload returned.

05Reproduce: npx vitest run tests/regressions/cross-account.test.ts

06Report: .maru/artifacts/runs/RUN-1048/report.json

07 — RELEASE PROOF

Not another confidence score.
A decision with receipts.

YOUR REPOSITORYCode · tests · secretsLOCAL

MARUCHECKContracts · findings · evidenceINSPECTABLE

Verify your first change Inspect the proof console