Slipmark

Slipmark

*A Reply Intelligence Group project.*

Make AI agents prove what they checked.

Add it to a workflow:

- uses: actions/checkout@v4

• uses: founder-ship-it/Slipmark@v0.6.2 with: require: | specs/your-spec.md

When a file changes after an agent signed it off, the build refuses:

Slipmark verify: 1 verified · 1 refused

✓ verified review-agent verified examples/attestation/brief.md ✗ hash_mismatch security-audit-agent gave "cleared" for a different version of examples/attestation/spec.md. The file changed after the verdict.

Set it up in one command: npx slipmark init. Your coding agents then write their sign-off with slipmark attest (see Works with your coding agent). No model calls, no account, one GitHub Action.

A slip mark is the paint line engineers draw across a bolt once it has been tightened and checked. If the bolt ever moves, the line breaks and everyone can see it. Slipmark does the same for AI agent verdicts: once an agent signs off a file, any change after that breaks the mark.

Agents now review code, audit specs and sign off their own work. The weak point is the verdict. An agent can report "passed" about a file that has since changed, or that it never looked at, and nothing downstream can tell.

Slipmark does two things:

1. Verdict attestation. Every agent verdict is bound to a SHA-256 hash of the exact files the agent read. Before anything ships, the gate re-hashes them. Mismatch, missing file, failing verdict, or nothing attested at all: it refuses. Deterministic, no model calls, one GitHub Action.
2. Drift diagnosis. Behavioural "locks" for your AI features. When a change breaks one, Slipmark says what likely broke it, how sure it is (and refuses to fake confidence it doesn't have), and hands your coding agent a repair prompt.

Status: v0.6.2, early. Apache-2.0. Optional hosted layer: Slipmark Cloud.

Why the gate exists

We run a nightly pipeline of 20+ agents: research, architecture, security audit, build, QA. Every morning they reported what passed.

Then we found the final verification job had been checking the wrong branch for months. It could not fail, so it never did. Months of green ticks, proving nothing.

So we built the gate: bind every verdict to the hash of what it read, and re-check before shipping. Pointed at 23 open agent pull requests, it refused all 23.

What Slipmark proves, and what it doesn't

Slipmark doesn't decide whether your agent is right. It makes sure the verdict you are trusting is about the code you are shipping.

It proves:

• The verdict was given on these exact bytes. Change one and the verdict stops counting.
• Every file you require has a current, passing verdict. A missing verdict is a refusal, not a silent pass.
• The answer is the same every time. No model calls, no scoring, no judgement.

It doesn't prove:

• That the agent was smart. If an agent misses a bug on day one, Slipmark will pass that file for as long as it stays unchanged. That is the agent's verdict, faithfully kept.
• Who wrote an unsigned attestation. Anyone who can push can write "by": "security-reviewer". Require signed verdicts and only verdicts signed by a workflow you trust count.

So pair it with the checks you already trust. Slipmark is the lock on the verdict, not the verdict. If you want stronger verdicts, require more of them: coverage of every changed file, checks Slipmark runs itself, or a re-review when the model changes. Those are on main now (docs/attestation.md). Two independent reviewers on sensitive paths, and the rest of attestation v2, are next.

Quick start

In the repository you want to protect (Node 22.6 or later):

npx slipmark init

  + create .slipmark/attestations/.gitkeep      attestation directory, committed with the repo

• create .github/workflows/slipmark.yml report-only gate on pull requests
• create AGENTS.md agent instructions for attesting verdicts ~ update CLAUDE.md agent instructions for attesting verdicts

That is the whole setup:

• A workflow that runs the gate on every pull request. It starts in report-only mode, because a repo with no verdicts yet would otherwise fail. Set fail-on-refusal: "true" once your agents are attesting.
• Agent instructions in AGENTS.md, plus CLAUDE.md, Cursor rules or Copilot instructions if your repo already has them. Re-running init updates the block in place and never touches anything else in those files.

Check any time with npx slipmark verify. Commit .slipmark/attestations/.

Works with your coding agent

The instructions init writes are enough for agents to attest on their own. We gave Claude Code a plain review task in a fresh repo, with no mention of Slipmark:

Review src/export.ts against specs/invoice-export.md. Does it meet the spec?

It read both files, found the export was not CSV, and recorded:

{

"by": "reviewer", "verdict": "fail", "subjects": [ { "path": "src/export.ts", "sha256": "0ea6029f…" }, { "path": "specs/invoice-export.md", "sha256": "81994e0f…" } ], "note": "Tenant filter and 10k limit OK; no CSV output, returns raw query result" }

Both files it based the verdict on, not just the one under review. When the code is fixed, the old verdict stops counting until the agent reads it again.

Setup notes for Claude Code, Cursor, Copilot and Codex are in docs/agents.md.

Claude Code plugin

For Claude Code there is also a plugin. It adds a skill so Claude records verdicts without any repo instructions, /slipmark:verify and /slipmark:setup commands, and a stop check that asks Claude to re-read and re-attest when a file it signed off has changed since.

/plugin marketplace add founder-ship-it/Slipmark

/plugin install slipmark@slipmark

Details, including exactly what it runs, in claude-plugin/.

MCP server: Codex, Cursor, Copilot, Gemini

slipmark mcp serves slipmark_attest and slipmark_verify as MCP tools, so any agent that speaks MCP can record and check verdicts. For OpenAI Codex, in ~/.codex/config.toml:

[mcp_servers.slipmark]

command = "npx" args = ["-y", "slipmark@0.6.2", "mcp"]

Setup for Claude Code, Cursor, Copilot in VS Code and Gemini CLI is in docs/mcp.md. Agents can't record a human approval through it.

Verdict attestation

1. The agent attests what it read. Call this at the end of any agent step that gives a verdict:

slipmark attest --by security-audit-agent --verdict cleared \

--subject specs/invoice-export.md --subject src/export.ts

That writes .slipmark/attestations/ -- .json:

{

"schema": "slipmark/attestation@1", "by": "security-audit-agent", "verdict": "cleared", "at": "2026-10-17T09:00:00.000Z", "subjects": [ { "path": "specs/invoice-export.md", "sha256": "cf89da70…" } ] }

2. The gate checks it before anything ships.

slipmark verify --require specs/invoice-export.md

Passing verdicts are pass and cleared. An empty gate is a refusal, never a silent pass. --json prints the full report for other tools.

Stronger verdicts (on main, unreleased). Record what the verdict was checked against, and let Slipmark run the checks itself:

slipmark attest --by reviewer --verdict pass --subject src/export.ts \

--against specs/invoice-export.md --run "npm test"

A failing --run refuses a passing verdict. Then require a verdict for every changed file, not just the ones you listed:

slipmark verify --coverage diff --base origin/main

Details in docs/attestation.md.

Agent context

Your reviewer passed the code. But who wrote the reviewer's instructions? The coding-agent attacks of 2026 changed AGENTS.md, skills and MCP configs and left the reviewed code alone. Add "context": {} to .slipmark/policy.json and Slipmark binds each verdict to the agent's instructions too:

• a verdict given under instructions that later changed stops counting
• a change to AGENTS.md, CLAUDE.md, a skill or an MCP config needs an approver's verdict (pair it with CODEOWNERS, or require signed approvals)
• changed instructions must be plain Markdown that GitHub shows in full: an allow-list refuses anything else (HTML, comments, images, diagrams, anything GitHub adds later), and in GitHub Actions each file is checked against GitHub's own renderer
• context files that link outside the watched set are refused

The policy is read from the base branch, so a pull request can't switch this off. What it doesn't cover yet is listed in the docs. Details in docs/attestation.md.

See it refuse five real attack patterns (Ghostcommit, Deadbugz, hidden comments, invisible Unicode, a PR switching the checks off) as open pull requests in slipmark-context-demo.

Signed verdicts

Prove who gave the verdict, not just what it was about (on main, unreleased). Run the review agent in a GitHub Actions job and sign as it attests:

slipmark attest --by security-reviewer --verdict pass --subject src/auth/session.ts --sign

The verdict is signed with the job's own GitHub identity through Sigstore: no keys to manage, and every signature is in a public transparency log. Then only count verdicts from the workflow you trust:

- uses: founder-ship-it/Slipmark@main

with: require-signed: "true" trusted-signers: | https://github.com/acme/api/.github/workflows/agent-review.yml@refs/heads/main

A verdict typed by hand, made by another workflow, or edited after signing is refused. Details, including which ref to trust, in docs/attestation.md.

As a GitHub Action:

- uses: actions/checkout@v4

• uses: founder-ship-it/Slipmark@v0.6.2 with: require: | specs/invoice-export.md

Rolling it out gently? Set fail-on-refusal: "false" to report refusals as warnings without failing the build. The step's result output is passed or refused either way.

Formatters. A formatter run changes the bytes, so it breaks a verdict like any other change. Run formatters before your agent attests (first in your pre-commit hooks) and most of this goes away. Formatting-tolerant hash modes and re-reviewing only the diff are planned for v0.5.

Run it on the branch you are about to merge. Because it checks content, not branch names, a verdict produced on one branch can't clear a different tree.

More in docs/attestation.md.

Slipmark Cloud

The gate above is free, open source and needs no account. Slipmark Cloud is the optional hosted layer for teams that need the record, not just the build result:

• An append-only, hash-chained ledger o