PR #5569: feat(integrations): add optional Signet integration for signed tool-call receipts

• Repository: crewAIInc/crewAI
• Author: devin-ai-integration[bot]
• State: open | merged: False
• Link: https://github.com/crewAIInc/crewAI/pull/5569

Description (problem / solution / changelog)

Summary

Closes #5568.

Adds a new opt-in crewai.integrations.signet module that produces Ed25519-signed Signet receipts for every governed action emitted on the CrewAI event bus:

1. Structured tool calls — ToolUsageStartedEvent / ToolUsageFinishedEvent / ToolUsageErrorEvent
2. MCP tool executions — MCPToolExecutionStartedEvent / MCPToolExecutionCompletedEvent / MCPToolExecutionFailedEvent
3. A2A delegations — A2ADelegationStartedEvent / A2ADelegationCompletedEvent

User-facing API

from crewai.integrations.signet import install

listener = install(key_name="my-crew-agent", audit=True)
# Every tool call + MCP call + A2A delegation now produces a signed receipt
# available on listener.receipts and optionally appended to signet-auth's
# hash-chained audit log.

Per-surface toggles (tool_events=False, mcp_events=False, a2a_events=False) let callers opt out of surfaces they don't care about, and a signing_agent=... keyword accepts any object exposing sign(action, params=...) — useful for tests and alternative backends.

Dependency story

• signet-auth is not a required dependency. It is exposed as an optional extra: pip install 'crewai[signet]'.
• listener.py lazy-imports signet_auth only when a signing agent is actually needed. If the extra isn't installed and no signing_agent is injected, the listener raises a clear ImportError pointing to the extra.
• Users who don't opt in pay zero runtime cost — crewai.integrations is an empty package and crewai.integrations.signet is only loaded when explicitly imported.

Implementation notes

• The listener correlates Started → Completed events via CrewAI's existing event-scope stack (event.started_event_id), so each receipt's payload covers both the call input (from the Started event) and the call output (from the Completed event).
• State is kept under a threading.Lock so parallel tool/MCP/A2A calls don't interfere.
• Files added:
  • lib/crewai/src/crewai/integrations/__init__.py
  • lib/crewai/src/crewai/integrations/signet/__init__.py (public install())
  • lib/crewai/src/crewai/integrations/signet/config.py (SignetConfig)
  • lib/crewai/src/crewai/integrations/signet/listener.py (SignetEventListener, Receipt)
  • lib/crewai/tests/integrations/signet/test_signet_listener.py (18 tests)
  • lib/crewai/pyproject.toml — new signet extra → signet-auth>=0.5.0

All 18 new tests pass locally (uv run pytest lib/crewai/tests/integrations/signet -vv), ruff and mypy are clean.

Review & Testing Checklist for Human

• Confirm the public API shape (install(key_name=..., audit=..., policy_path=..., ...)) matches what you want long-term — this is the main user-facing surface and will be hard to change later.
• Verify the exact signet-auth call pattern (SigningAgent.create(name, owner=..., audit=..., policy_path=...) vs. direct constructor) matches the real library's API — tests mock the agent, so only a live pip install 'crewai[signet]' end-to-end run will surface a mismatch.
• Decide whether signet-auth>=0.5.0 is the right floor (0.9.1 is the latest on PyPI as of writing).
• Sanity-check the payload shape inside each receipt (_tool_payload, _mcp_payload, _a2a_payload in listener.py) — these are what downstream verifiers will see.

Suggested end-to-end test

pip install 'crewai[signet]'

from crewai.integrations.signet import install

listener = install(key_name="review-test")
# ... run a Crew that calls tools / MCP / A2A ...
for r in listener.receipts:
    print(r.kind, r.action, r.receipt)

Notes

• The listener deliberately does not modify any core event-system code; it only subscribes via the public @bus.on(...) decorator, matching the pattern used by TraceListener.
• Failed A2A delegations (status != "completed") and tool/MCP error events still produce receipts but are marked error=True, so the audit log captures attempted-but-failed governed actions too.

Link to Devin session: https://app.devin.ai/sessions/5496de89037e4058907d62e8aa8c4e02

[!NOTE] Medium Risk Introduces a new event-bus listener that correlates and signs action payloads; while opt-in and tested, it touches concurrency/event handling and depends on the runtime behavior of an external signing library.

Overview Adds a new opt-in crewai.integrations.signet package (behind the crewai[signet] extra) that registers a SignetEventListener to sign a receipt for each governed action by pairing Started/Completed (and error) events for structured tool calls, MCP tool executions, and A2A delegations.

The listener lazy-imports signet_auth only when needed (or accepts an injected signing_agent), stores signed receipts in-memory on listener.receipts, and supports per-surface enable/disable toggles; comprehensive tests validate event pairing, error handling, toggles, and the lazy-import failure mode. Dependency metadata is updated in pyproject.toml and uv.lock to expose the new signet extra.

^{Reviewed by Cursor Bugbot for commit c001517b4835f25da74fb918ab4243ac71d4a53d. Bugbot is set up for automated code reviews on this repo. Configure here.}

Changed files

• lib/crewai/pyproject.toml (modified, +3/-0)
• lib/crewai/src/crewai/integrations/__init__.py (added, +6/-0)
• lib/crewai/src/crewai/integrations/signet/__init__.py (added, +83/-0)
• lib/crewai/src/crewai/integrations/signet/config.py (added, +34/-0)
• lib/crewai/src/crewai/integrations/signet/listener.py (added, +326/-0)
• lib/crewai/tests/integrations/__init__.py (added, +0/-0)
• lib/crewai/tests/integrations/signet/__init__.py (added, +0/-0)
• lib/crewai/tests/integrations/signet/test_signet_listener.py (added, +418/-0)
• uv.lock (modified, +18/-2)