aer1-crewai

AER-1 verifiable workflow receipts for CrewAI.

Attach one listener and every crew run emits a hash-chained, offline-verifiable verifiable workflow receipt (AER-1, Section 8): what the crew did, in what order, with per-step hashes and a Merkle root over the whole run. It hooks CrewAI's own event bus, so there is no monkey-patching, no behavior change, and no network calls. The listener only observes. It complements CrewAI's built-in observability; it does not replace it.

The AER-1 framework collector family

The CrewAI collector in the AER-1 framework collector family. Any agent running on these frameworks can emit verifiable AER-1 execution receipts: every step recorded, hash-chained, one Merkle root over the whole run.

• aer1-smolagents ��� SmolAgents agents via step callbacks
• aer1-openai-agents ��� the OpenAI Agents SDK via its TracingProcessor
• aer1-crewai ��� CrewAI crews via the event bus
• aer1-langgraph ��� LangGraph swarms via callback handler
• aer1-autogen ��� AutoGen multi-agent chats

Install

pip install aer1-crewai

Use it (two lines)

# pip install aer1-crewai
from aer1_crewai import AER1CrewAIListener
from crewai import Agent, Task, Crew

listener = AER1CrewAIListener(goal="Research AER-1 adoption")  # line 1

researcher = Agent(
    role="Researcher",
    goal="Find the latest AER-1 adoption numbers",
    backstory="You are a diligent research analyst.",
)
writer = Agent(
    role="Writer",
    goal="Turn research into a crisp summary",
    backstory="You write clearly and cite numbers.",
)
crew = Crew(
    agents=[researcher, writer],
    tasks=[
        Task(description="Find the latest AER-1 adoption numbers",
             expected_output="A bullet list of numbers with sources",
             agent=researcher),
        Task(description="Write a 3-sentence summary of the findings",
             expected_output="Three sentences",
             agent=writer),
    ],
)
result = crew.kickoff()
receipt = listener.finalize(final_answer=result.raw)  # line 2
assert listener.verify(receipt) == []  # VALID
listener.save("receipt.json", workflow=receipt)

CrewAI needs an LLM API key in your environment (for example OPENAI_API_KEY); the listener itself needs no model configuration. Keep the listener referenced for the whole process. Constructing it registers its handlers on CrewAI's global event bus; dropping the reference can unregister them.

That is the whole integration. The receipt is a plain JSON object you can store, ship to an auditor, or render in a UI.

What gets recorded

One receipt step per observed event, in arrival order:

• ToolUsageFinishedEvent becomes a step named for the tool, with the tool arguments, output, agent role, and task name hashed in, and started_at / ended_at taken from the event's own timestamps.
• ToolUsageErrorEvent becomes the same step with status: "error".
• TaskCompletedEvent / TaskFailedEvent become tool: "task" steps carrying the task name and output.

What the receipt contains

Workflow level (AER-1 Section 8, Table 2):

• type, version, workflow_id, receipt_id, session_id
• goal, status
• steps: one record per observed event, seq 1..n in order
• merkle_root: Section 8.1 root over the ordered step receipt ids
• output_hash: SHA-256 of the final answer
• verify_url: where the verification procedure is documented

Step level (AER-1 Section 8, Table 3):

• seq, receipt_id, tool, receipt_hash, started_at, ended_at, status

Each step receipt_hash is SHA-256 over the canonical JSON of what the step actually did. The hash commits to the content; the receipt stays compact.

Verification

listener.verify(receipt) runs the full offline check and returns a list of failure reasons, empty when valid:

• all Table 2 / Table 3 members present and well-formed
• seq values exactly 1..n in order, no gaps
• no two steps share a receipt_id (MM-1)
• merkle_root matches the recomputed Section 8.1 root
• strict RFC 3339 timestamps, lowercase UUIDs, 64-char hex digests

Tamper with any field and verification fails. Try it:

receipt["steps"][0]["tool"] = ""
assert listener.verify(receipt) != []  # fails, as it should

Notes

• One listener observes every crew run in the process. Call reset() between runs if you want one receipt per run from a shared listener.
• session_id defaults to a fresh UUID per listener; pass your own to correlate receipts across runs.
• verify_url defaults to the AER-1 specification page; point it at your own verifier in production.
• If final_answer is omitted, finalize() uses the output captured from the crew kickoff completed event when available.

Spec

AER-1: Agent Execution Receipts, draft-zambo-aer1, https://datatracker.ietf.org/doc/draft-zambo-aer1/

See it live

Your receipt is offline-verifiable, but you can also check it on the live verifier:

1. Copy the receipt JSON your code produced
2. Paste it at https://zambo.dev/verify
3. See the verification result with the Merkle root and step hashes

Or mint a live receipt directly: run any call at https://zambo.dev/demo and get a shareable receipt URL like https://zambo.dev/run/.

License

Apache-2.0