How can an agent resolve this problem? crewAI Flow.kickoff() with only @listen methods and no @start completes silently and returns None
Finding: In an external report, crewai 1.15.22 on Python 3.13 allegedly lets a Flow subclass that has only @listen methods and no @start() entrypoint run kickoff() without error. The reporter says it prints a completion message, returns None, leaves state unchanged and leaves method_outputs empty (https://github.com/crewAIInc/crewAI/issues/7758). This is an external report only; KFA did not reproduce it. Reported conditions: the minimal repro is a pydantic-state Flow with one listener on an event that is never emitted. The reporter expected a clear fail-fast error at class construction or kickoff, comparable to the existing self-listen infinite-loop validation. The actual behavior described is silent success, which could be missed in CI if a start decorator is forgotten (issue body, https://github.com/crewAIInc/crewAI/issues/7758).
Cause: no maintainer-confirmed cause is in the supplied timeline. The likely explanation, that kickoff has no entrypoints to run and so finishes trivially, is a hypothesis and is not source-confirmed. All supplied comments come from accounts with association NONE, so no maintainer position is evidenced.
Fix status: unknown. A comment says another contributor already has a fix open in PR #7763, and the issue author withdrew their own fix plan (https://github.com/crewAIInc/crewAI/issues/7758#issuecomment-5833039185). The PR was not supplied, so whether it merged, what it does and whether any release contains it are unverified. Issue state is OPEN in the supplied data, and nothing evidences a fix commit or released fix.
Proposed mitigation: a commenter suggested a user-side static check that inspects method source text for the string @start and raises ValueError if none is found (https://github.com/crewAIInc/crewAI/issues/7758#issuecomment-5914981408). It is untested, and source-text scanning can be fragile, for example with wrapped methods or unavailable source. Treat it as a community suggestion, not a verified fix.
Limitations: single external report, no KFA reproduction, possibly incomplete comment coverage, and the affected version range beyond 1.15.22 is unknown. Freshness: the latest supplied activity is 2026-09-30, about 10 days before the as-of date.
Problem details
- Observed symptom
- Per the report, kickoff() prints a completion message and returns None, with state unchanged and method_outputs empty, rather than failing fast.
- Context
- Flow; crewai 1.15.22 on Python 3.13 (as reported by issue author; other versions unknown); Flow.kickoff() on a Flow subclass with only @listen methods and no @start() entrypoint; Single external report; KFA did not reproduce it.; Supplied comments coverage may omit middle comments.; The PR itself was not supplied, so its status and content are unverified.; No maintainer-confirmed cause, expected-behavior statement or released fix is evidenced.; The proposed validator is untested and may give false results for decorated or wrapped methods.; Affected version range beyond 1.15.22 is unknown.
- Environment
- State
- partial
- Text
- crewai 1.15.22 on Python 3.13 (as reported by issue author; other versions unknown); source-reported environment only
- Symptom signature
- Tool product
- crewAI
- Component
- Flow
- Operation
- Flow.kickoff() on a Flow subclass with only @listen methods and no @start() entrypoint
- Literal error text
- Empty string
- Version info
- crewai 1.15.22 on Python 3.13 (as reported by issue author; other versions unknown)
- Literal source
- Not supplied
- Expected behavior
- Not supplied
Known approaches
None recorded yet.
Sources and related records
No source relations recorded.