@occasiolabs/occasio
Advanced tools
Occasio — cryptographically verifiable behavioral attestation for AI coding agents. Tool-call interception + policy enforcement + tamper-evident audit chain + Sigstore-signed in-toto attestations + windowed EDR detection. Same engine for Claude Code and M
Cryptographically verifiable behavioral attestation for AI coding agents.
When an AI agent writes code in your CI, the question a reviewer or auditor will ask is not "what did it produce" — it is "what did it actually do". Which files did it read. Which it was blocked from reading. Which secrets it tried to leak. Which policy was in effect. Whether that record can be trusted six months later.
Occasio sits between the agent and the cloud on your own machine, decides every tool call against one human-readable policy, writes a tamper-evident audit chain of every decision, and produces signed attestations that a third party can verify offline using only cosign or a 200-line Python script.
npm install -g @occasiolabs/occasio
occasio demo audit # Auditor scenario: signed attestation + cross-verifier proof (10s, no API key)
occasio demo attest # End-to-end attestation pipeline against a synthetic chain
occasio demo anomalies # Live EDR detection on a synthetic adversarial chain
occasio harness # Real Claude Code attacking a denied path — defense holds
The first three demos run against synthetic data so you can see the full pipeline in seconds with no external dependencies. The fourth spawns a real Claude Code subordinate under your Anthropic login (bundled auth — no API key required) and proves the defense end-to-end. Start with demo audit — it answers the only question that actually matters: "prove what your AI agent did in CI."
Layer 1 — Tool-call interception. A local proxy sits between the agent and the Anthropic API. Read, Glob, Grep, TodoRead/TodoWrite, and a curated set of read-only shell commands (cat, head, git status, git log --oneline -N, ls, find) run in-process on your machine. The file bytes never enter the outbound request.
Layer 2 — Policy enforcement. Every tool call hits one decision: LOCAL / PASS / BLOCK / TRANSFORM, driven by policy.yml. deny_paths is enforced on the realpath-resolved absolute path so symlinks and traversal variants resolve to the same denial. block_secrets_in_tool_results redacts API keys and JWTs out of any tool output before it re-enters the prompt. Hot-reload: edits to policy.yml take effect on the next call, with a policy_loaded row written to the audit chain.
Layer 3 — Behavioral attestation. occasio attest --run-id <uuid> produces a self-contained JSON predicate that commits to the full audit-chain slice for one agent session: every tool call, every block, every transform, every redacted secret, plus the active policy's SHA-256 hash and rules digest. --sign wraps it in an in-toto Statement v1 and Sigstore-signs it using GitHub Actions OIDC (no key management). The predicate type URI is agent-attestation/v1. Two independent reference verifiers ship — Node (occasio attest verify) and Python (docs/attest_verify.py) — and the test suite asserts they agree byte-for-byte on the same payload.
Layer 4 — Anomaly detection (EDR). occasio anomalies runs four detectors over a time window of the audit chain: deny-rate spike, file-read-volume burst, previously-unseen tool-input shape, secret-redaction-rate spike. Severity escalates against your historical baseline — a ×500 deviation from normal triggers HIGH; see docs/edr-demo.md for the reproducible defense-in-depth walkthrough.
Three regulatory drivers, all converging on the same requirement: runtime evidence of AI-agent behavior must be cryptographically verifiable.
There is currently no off-the-shelf product producing a signed, third-party-verifiable artifact for what an AI coding agent did inside your CI. Occasio fills that gap with an open schema (Apache-2.0) and ships the reference implementations for it.
Requires Node.js ≥ 18. Works on Windows, macOS, Linux.
npm install -g @occasiolabs/occasio # Install
occasio doctor # Verify setup (Node, claude CLI, port, profile)
occasio policy init # Write ~/.occasio/policy.yml (dev-default)
occasio register # Add 'claude' shell alias (one-time)
claude "read package.json and tell me the version"
After the alias is registered, every claude invocation routes through Occasio transparently. Audit-chain rows accumulate at ~/.occasio/pipeline-events.jsonl.
Inspect the run:
occasio status # Session totals
occasio replay --detail # Run-level audit
occasio audit verify # Re-walk the hash chain end-to-end
occasio anomalies # Run EDR detectors over the last 15 minutes
occasio attest --run-id <uuid> # Build a behavioral attestation for one session
| Command | What it does |
|---|---|
occasio claude [args] | Start Claude Code with Occasio proxy active |
occasio register | Register claude shell alias |
occasio doctor | Setup health-check |
occasio status | Session totals + savings breakdown |
occasio replay | Run-level audit (--detail, --run <id>, --attribute) |
occasio inspect | Per-request cloud-boundary manifest |
occasio boundary | Three-column view: produced / re-entered / prevented |
occasio ledger | Per-request token ledger |
occasio distill | Inspect distilled tool outputs |
occasio dashboard | Live browser dashboard at http://localhost:3001 (session metrics) |
occasio eyes | Browser UI at http://127.0.0.1:3002 (per-exchange traffic, capture opt-in via --eyes) |
occasio audit verify | Re-walk the SHA-256 audit chain end-to-end |
occasio audit repair --file <path> | Truncate a crash-partial trailing line (writes .bak) |
occasio report | Governance summary export (--days N, --format csv) |
occasio anomalies | EDR detection over the audit chain (--window 15m, --json) |
occasio attest --run-id <uuid> | Build a behavioral attestation predicate v1 |
occasio attest --sign | Sigstore-sign via GitHub Actions OIDC |
occasio attest verify <file> | Re-verify a signed attestation end-to-end |
occasio policy [show | validate | init | doctor] | Policy authoring + diagnosis |
occasio harness | Run scripted adversarial scenarios against your policy |
occasio redteam | Autonomous tester-LLM probes a subject Claude Code session |
occasio computer-use --dry-run | Apply a Computer-Use policy to synthetic tool_use blocks |
occasio demo attest | End-to-end attestation pipeline against a synthetic chain |
occasio demo anomalies | EDR smoke test: synthetic adversarial chain → all 4 detectors |
occasio selftest | In-process governance self-checks on a scratch chain |
occasio baseline [learn | compare] | Per-project behavior baseline + drift detection |
occasio preflight | Read-only mine of recent activity for policy suggestions |
Session-level overrides on top of policy.yml:
| Flag | Effect |
|---|---|
--preset strict | Forces block_secrets_in_tool_results on for the session |
--preset off | Pure passthrough, log only |
--budget <N> | Hard cap: HTTP 402 once session cost reaches $N |
--hardened | Routes Read/Glob/Grep through unified runtime + distill + secret scan |
--eyes | Capture outbound + inbound payloads for occasio eyes browser UI |
The four layers above answer "what did the agent do, prove it" — the auditor's question. Sometimes you also want the simpler one: "what is the agent doing right now?" What is leaving your machine in this HTTP request. Which files have already gone to Anthropic in this session. What the system prompt looks like. What got redacted before it shipped.
occasio eyes is a local browser UI on http://127.0.0.1:3002 that shows exactly that. Capture is opt-in via --eyes on the proxy; nothing leaves the machine, all storage stays under ~/.occasio/eyes/.
occasio eyes --demo # synthetic data, no proxy needed (10-second tour)
occasio claude --eyes # then in another terminal:
occasio eyes # browser tab opens automatically
What you see:
Both run as local browser UIs but answer different questions:
occasio dashboard (3001) | occasio eyes (3002) | |
|---|---|---|
| Focus | Session-level metrics: cost, savings, tokens | Per-exchange traffic: what went out, what came back |
| Granularity | Aggregate counters + per-request summary table | Full HTTP bodies, decoded SSE, local tool outputs |
| Capture needed | No — reads session.json + daily logs | Yes — pass --eyes to the proxy (opt-in) |
| Data scope | Metadata only | Full payload bytes (kept locally under ~/.occasio/eyes/) |
| Best for | "How much have I spent today?" | "What did the agent actually send to Anthropic?" |
Both live on 127.0.0.1 only. No CORS, no auth, no external network.
Three independent checks, all required for a verified attestation:
cosign verify-blob, sigstore-js, sigstore-python).signature metadata field).prev_hash → hash link from the GENESIS sentinel, then assert the attestation's first_hash and last_hash appear in the chain in the right relative order.Two reference verifiers ship side by side:
occasio attest verify <file>python docs/attest_verify.py <file> — stdlib + optional sigstore-python, reuses docs/audit_walker.py for the chain step. See docs/python-verifier.md.Cross-language invariant (asserted in the test suite as xlang: and xlang-float: cases): both verifiers agree byte-for-byte on the predicate-equivalence and audit-chain steps for the same payload, including tamper-detection cases. Non-integer numbers are rejected by both canonicalize implementations so a future schema cannot silently introduce divergence.
The Sigstore signature step uses the standard DSSE-wrapped in-toto Statement format; any sigstore-conformant tool verifies it (cosign verify-blob, sigstore-js, sigstore-python). The test suite mocks the signing path; a real-OIDC end-to-end signed-and-verified round-trip requires a GitHub Actions environment and is exercised by the integrations/attest-action/ workflow in CI.
A third partial verifier runs in-browser at integrations/attest-view/ for drag-and-drop inspection. The browser performs the predicate-equivalence and audit-chain steps but defers Sigstore certificate-chain verification to one of the two CLIs (bundling Fulcio/Rekor trust roots in-browser is intentionally not done; the page is explicit about it).
agent (Claude Code / Cline / MCP / Computer Use)
│
▼ tool call
┌──────────────────────────────────────────────────────────────┐
│ Occasio proxy │
│ │
│ Layer 1: adapter parse → canonical event │
│ Layer 2: policy decision (LOCAL / PASS / BLOCK / TRANSFORM) │
│ Layer 2: deny_paths + deny_patterns + secret redaction │
│ Layer 2: native dispatch for LOCAL/TRANSFORM tools │
│ ──► row appended, SHA-256-chained │
│ Layer 4: anomaly detectors (windowed, on-demand or live) │
└──────────────────────────────────────────────────────────────┘
│
▼ cloud-bound: only PASS calls, with shaped result if TRANSFORM
Anthropic API
End of session
│
▼ occasio attest --run-id … --sign
Layer 3: signed in-toto Statement → Sigstore bundle → GitHub Check Run
│
▼ independent verifier
Node / Python / cosign — all must agree
All data is stored locally at ~/.occasio/:
~/.occasio/
pipeline-events.jsonl # tamper-evident audit chain (SHA-256 linked)
policy.yml # active policy
session.json # current run_id, totals
logs/YYYY-MM-DD.jsonl # per-request log
baseline/<cwd-hash>.json # per-project behavior baseline (opt-in)
eyes/ # `occasio eyes` capture (opt-in via --eyes)
payload-NNNNNN.json # per-exchange metadata + extracted blocks
content/<sha> # content-addressed blob store (file bytes,
# tool outputs) — dedup by SHA-256
The audit-chain row schema is documented in docs/AUDIT.md. Each row carries prev_hash and hash (SHA-256 hex), with the first row chained from a fixed GENESIS sentinel (64 zeros). occasio audit verify and docs/audit_walker.py are independent implementations of the walker.
deny_paths rule producing identical BLOCK rows under Claude Code's HTTP proxy and the MCP server.spec/agent-attestation/v1/README.md — predicate type specificationschemas/agent-attestation-v1.json — authoritative JSON Schemadocs/AUDIT.md — audit-chain row schema and canonical-serialisation rulesdocs/compliance-mapping.md — SOC 2 Common-Criteria mappingdocs/python-verifier.md — independent Python verifierdocs/edr-demo.md — defense-in-depth walkthroughdocs/reference-pipeline.md — end-to-end CI pipelineintegrations/attest-action/ — GitHub Action that signs + posts a Check Runintegrations/attest-view/ — static browser viewer for attestation filesnpm install -g @anthropic-ai/claude-code) — or any agent that respects ANTHROPIC_BASE_URLsigstore-python (optional) — adds the cryptographic Sigstore step to the Python verifierOccasio is open source under the Apache License 2.0, including an explicit patent grant for safe enterprise use. Versions 0.6.6 and earlier were released under the MIT License and remain MIT in perpetuity for those releases.
Contributions are accepted under Apache-2.0; please sign off your commits per the DCO (git commit -s).
FAQs
Occasio — cryptographically verifiable behavioral attestation for AI coding agents. Tool-call interception + policy enforcement + tamper-evident audit chain + Sigstore-signed in-toto attestations + windowed EDR detection. Same engine for Claude Code and M
The npm package @occasiolabs/occasio receives a total of 25 weekly downloads. As such, @occasiolabs/occasio popularity was classified as not popular.
We found that @occasiolabs/occasio demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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