aer1-haystack

One-line install, no API key, free forever: wrap one pipeline and every Haystack 2.x run emits a hash-chained, offline-verifiable verifiable workflow receipt (AER-1, an IETF Internet-Draft, Section 8). What each component did, in what order, with per-step hashes and a Merkle root over the whole run. No network calls, no behavior changes, the collector only observes. Receipt chain heads can anchor to Nostr and Bitcoin, so anyone can later confirm the record was not changed, without trusting any server.

The AER-1 framework collector family

The Haystack 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-haystack, Haystack 2.x pipelines via run wrapping
• aer1-langchain, LangChain chains, agents, tools, and retrievers via callback handler
• aer1-llamaindex, LlamaIndex agents via callback handler
• 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
• aer1-pydantic, Pydantic AI agents via run wrapping and manual tool-call recording
• aer1-strands, Strands Agents via the typed hook system

See the AER-1 implementation registry for every implementation.

Install

pip install aer1-haystack

Use it (copy, paste, run, no API keys needed)

# pip install aer1-haystack
from haystack import Pipeline, component
from aer1_haystack import AER1ReceiptCollector


@component
class Adder:
    @component.output_types(total=int)
    def run(self, a: int, b: int):
        return {"total": a + b}


@component
class Doubler:
    @component.output_types(doubled=int)
    def run(self, total: int):
        return {"doubled": total * 2}


pipeline = Pipeline()
pipeline.add_component("adder", Adder())
pipeline.add_component("doubler", Doubler())
pipeline.connect("adder.total", "doubler.total")

collector = AER1ReceiptCollector(goal="add and double")
collector.wrap_pipeline(pipeline)  # line 1: pipeline.run is now observed

result = pipeline.run({"adder": {"a": 2, "b": 3}})
receipt = collector.finalize(final_answer=result)  # line 2
assert collector.verify(receipt) == []  # VALID
collector.save("receipt.json", workflow=receipt)

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

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 component, 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 component actually did: component name, input values, output values, and error if any. The hash commits to the content; the receipt stays compact. The wrapper asks the pipeline to include every component's outputs (include_outputs_from), so intermediate components are recorded, not just leaf outputs.

Verification

collector.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 collector.verify(receipt) != []  # fails, as it should

Manual instrumentation

For components that need finer control, skip wrap_pipeline and record steps from inside a component's own run() method:

collector = AER1ReceiptCollector(goal="manual run")

@component
class LoudAdder:
    @component.output_types(total=int)
    def run(self, a: int, b: int):
        out = {"total": a + b}
        collector.record_component(
            "loud_adder", inputs={"a": a, "b": b}, outputs=out)
        return out

record_component(name, inputs, outputs, error=None) takes the component name as the step's tool field. If the wrapped pipeline.run raises, a single error step named pipeline is recorded and the exception is re-raised unchanged.

Notes

• Works with any Haystack 2.x Pipeline. The collector never touches the network and never changes pipeline behavior; it only observes.
• Pass goal= to the collector; it becomes the receipt's goal field.
• session_id defaults to a fresh UUID per collector; 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.
• Steps accumulate across runs on the same wrapped pipeline; call collector.reset() between runs to start fresh.

Spec

AER-1: Agent Execution Receipts, draft-zambo-aer1 (IETF Internet-Draft), 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