reelier
Record an agent's MCP tool-call workflow once, replay it deterministically for zero tokens, and get a receipt — a snapshot-testing and deterministic-execution layer for Agent Skills.
README
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<img src="https://www.reelier.com/avatar.svg" width="72" alt="Reelier" />
Reelier
Agents make claims. Reelier writes receipts.
A dependency bump shouldn't silently break your agent. Reelier re-runs your recorded workflows against the new version at zero LLM cost and diffs them — so you see exactly what changed before you merge.
Think of it as CI + snapshot tests for your agent's tool-call workflows.
<img src="https://raw.githubusercontent.com/seldonframe/reelier/main/docs/assets/reelier-demo.gif" width="760" alt="Reelier: Dependabot bumps a dependency, Reelier replays your recorded agent run at 0 tokens and diffs it, catching the drift on the PR before you merge" />
<sub><a href="https://www.reelier.com/reelier-explainer.mp4">▶ watch with sound (27s)</a></sub>
<a href="https://glama.ai/mcp/servers/seldonframe/reelier"><img width="380" height="200" src="https://glama.ai/mcp/servers/seldonframe/reelier/badge" alt="Reelier MCP server on Glama" /></a>
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Why
AI agents are non-deterministic — the same prompt, a different result every run — and they'll claim they did the work whether they did or not. Reelier records the run that worked, replays it deterministically at $0, and writes a signed receipt that proves it. Point it at your existing CI in one workflow — it adds a verifiable receipt, it doesn't replace your stack.
Measured on a real head-to-head benchmark, same task, same data (full method):
- 1,000 / 1,000 replays byte-identical
- ~50× cheaper
- ~59× faster
Install
npm i -g reelier && reelier init
# No Node install needed — same commands via Docker:
docker run --rm ghcr.io/seldonframe/reelier --help
reelier init scans work you've already done (Claude Code, Codex, OpenClaw) into a real skill, or falls back to a zero-setup demo with a real receipt in under 60 seconds.
How to use it
reelier init # 60s: record → compile → replay → your receipt
reelier run <name>.skill.md # replay deterministically — 0 tokens (read-only by default)
reelier diff <name> # SAME or DRIFTED, per step — exit 1 on drift
reelier push <name>.skill.md # sync receipts to your ledger (opt-in)
reelier ci # write a workflow: drift-CI + PR receipts, one command
- Record.
reelier mcp --wrap "<mcp server>"proxies your tools live, or pull a session viareelier scan/from-session, or run the guidedreelier init. - Compile.
reelier compileturns a trace into aSKILL.md— 0 LLM calls, minimal assertions, honest gaps printed as Open questions. - Replay.
reelier runreplays it at Level 0 — no LLM, byte-identical, read-only by default (writes need--allow-writes). - Diff.
reelier diffreports SAME or DRIFTED per step, with the failing assertion as the why — exit 1 on drift. - Log in.
reelier loginconnects this machine to Reelier Cloud with a device code in your browser — or setREELIER_CLOUD_URL/REELIER_CLOUD_KEYfor CI and self-hosting. - Push. Every run is a receipt;
reelier pushoptionally syncs it to a ledger for a permalink and an embeddable verified-replay badge.
Already have an Agent Skill? Convert it — your skill, minus the model:
reelier compile trace.jsonl --from-skill ./my-skill/SKILL.md
Three tests, one skill
| Test | Command | Answers |
|---|---|---|
| Determinism | reelier run <skill.md> |
Does this still do what it did? |
| Recovery | reelier run <skill.md> --fail N |
If this broke, would the skill notice and heal? |
| Drift | reelier run <skill.md> --wrap "<your mcp server>" |
Has the world moved out from under this skill? |
Taxonomy due to Mads Hansen's review of the launch post. Full semantics for each test, including recovery injection and manifest guardrails: docs/REFERENCE.md.
Gate Dependabot / Renovate bump PRs
Dependabot and Renovate open the PR and run your test suite — but neither knows what your agent actually does at runtime, so a dependency bump that silently changes a tool call's shape (a renamed field, a new default, a different error) sails through with green unit tests. This is the check they don't run.
Copy .github/workflows/reelier-bump-check.yml into your repo, point skill: at your own recorded .skill.md file(s), and it will: gate to PRs from dependabot[bot]/renovate[bot] (or a dependencies label), install the bumped dependency, replay your recorded skill live against it at --max-level 0 (0 tokens), and fail the check on the exact step that drifted.
This tests dependency and MCP-tool-call behavior — it does not test model upgrades; --max-level 0 never calls an LLM. Full listing copy and setup: docs/marketplace-listing.md.
Prove it
A pushed receipt carries a ladder of independently-verifiable claims — not one blanket "verified." Depending on what you turn on, it can be signed, timestamped, CI-attested, and carry cross-checkable provider request-ids. reelier verify recomputes every claim offline, and a claim you haven't enabled just renders as an honest gap, never a shamed one.
See a real one: reelier.com/r/HWBdmGob9KeHRqXi-OEaRD0z.
Full 8-rung ladder, what each rung does and doesn't prove: docs/REFERENCE.md.
Who it's for
- Solo dev / OSS maintainer — a real regression test again; drift can't pass silently.
- Team shipping agent changes — "it ran clean" becomes a checkable PR artifact, not a claim.
- Agency running agents for clients — signed, timestamped proof-of-delivery a client can verify.
- Marketplace buyer or seller — corroborated receipts are reviews that can't be astroturfed.
- Audit-facing ops — a signed, CI-attested trail of every write, idempotency key included.
MIT, free forever (versions ≤0.16.0 remain AGPL-3.0). Your data — skills, traces, runs — is specified in SPEC.md, so leaving is copying a folder.
Contributing: issues and PRs welcome — SPEC.md is the source of truth for formats; fix the code, not the spec. npm test before a PR.
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If Reelier saved you a re-run, star it ⭐ — it's how other builders find it.
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