The Fix
pip install celery==5.2.0rc2
Based on closed celery/celery issue #6859 · PR/commit linked
Production note: This usually shows up under retries/timeouts. Treat it as a side-effect risk until you can verify behavior with a canary + real traffic.
@@ -27,7 +27,7 @@
__all__ = (
- 'Celery', 'bugreport', 'shared_task', 'task', 'Task',
+ 'Celery', 'bugreport', 'shared_task', 'Task',
'current_app', 'current_task', 'maybe_signature',
repro.py
$ python3 -m venv .
$ . ./bin/activate
$ python3 -m pip install celery
[...]
$ python3 -m pydoc celery
No module named 'celery.task'
$
verify
Re-run the minimal reproduction on your broken version, then apply the fix and re-run.
fix.md
Option A — Upgrade to fixed release\npip install celery==5.2.0rc2\nWhen NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.\n\n
Why This Fix Works in Production
- Trigger: Missing celery.task is not innocuous, breaks pydoc
- Mechanism: Removes lingering references to `celery.task` in both the Celery module code and documentation to prevent failures when displaying in-module documentation using `pydoc`.
- Why the fix works: Removes lingering references to `celery.task` in both the Celery module code and documentation to prevent failures when displaying in-module documentation using `pydoc`. (first fixed release: 5.2.0rc2).
Production impact:
- If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.
Why This Breaks in Prod
- Production symptom (often without a traceback): Missing celery.task is not innocuous, breaks pydoc
Proof / Evidence
- GitHub issue: #6859
- Fix PR: https://github.com/celery/celery/pull/6869
- First fixed release: 5.2.0rc2
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.65
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“you can come with a half baked pr as well to kickstart”
“Hey @ferdnyc :wave:, Thank you for opening an issue”
“https://github.com/celery/celery/issues/6558#issuecomment-750281219 celery.task was removed so try new API”
“@auvipy I understand that, the issue is not that the API has changed”
Failure Signature (Search String)
- Missing celery.task is not innocuous, breaks pydoc
- In #6558 the lack of `celery.task` was closed as "not a bug", but because `task` is still in the `__all__` for the `celery` <s>module</s> package (in `celery/__init__.py`), among
Copy-friendly signature
signature.txt
Failure Signature
-----------------
Missing celery.task is not innocuous, breaks pydoc
In #6558 the lack of `celery.task` was closed as "not a bug", but because `task` is still in the `__all__` for the `celery` <s>module</s> package (in `celery/__init__.py`), among other things the missing module breaks `pydoc`:
Error Message
Signature-only (no traceback captured)
error.txt
Error Message
-------------
Missing celery.task is not innocuous, breaks pydoc
In #6558 the lack of `celery.task` was closed as "not a bug", but because `task` is still in the `__all__` for the `celery` <s>module</s> package (in `celery/__init__.py`), among other things the missing module breaks `pydoc`:
Minimal Reproduction
repro.py
$ python3 -m venv .
$ . ./bin/activate
$ python3 -m pip install celery
[...]
$ python3 -m pydoc celery
No module named 'celery.task'
$
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install celery==5.2.0rc2
When NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Option D — Guard side-effects with OnceOnly Guardrail for side-effects
Mitigate duplicate external side-effects under retries/timeouts/agent loops by gating the operation before calling external systems.
- Place OnceOnly between your code/agent and real side-effects (Stripe, emails, CRM, APIs).
- Use a stable key per side-effect (e.g., customer_id + action + idempotency_key).
- Fail-safe: configure fail-open vs fail-closed based on blast radius and spend risk.
Show example snippet (optional)
onceonly.py
from onceonly import OnceOnly
import os
once = OnceOnly(api_key=os.environ["ONCEONLY_API_KEY"], fail_open=True)
# Stable idempotency key per real side-effect.
# Use a request id / job id / webhook delivery id / Stripe event id, etc.
event_id = "evt_..." # replace
key = f"stripe:webhook:{event_id}"
res = once.check_lock(key=key, ttl=3600)
if res.duplicate:
return {"status": "already_processed"}
# Safe to execute the side-effect exactly once.
handle_event(event_id)
When NOT to use: Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.
Fix reference: https://github.com/celery/celery/pull/6869
First fixed release: 5.2.0rc2
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- Do not use if it changes public behavior or if the failure cannot be reproduced.
- Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.
Verify Fix
verify
Re-run the minimal reproduction on your broken version, then apply the fix and re-run.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Capture the exact failing error string in logs and tests so you can reproduce via a minimal script.
- Pin production dependencies and upgrade only with a reproducible test that hits the failing path.
Version Compatibility Table
| Version | Status |
|---|---|
| 5.2.0rc2 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.