Celery task_id must not be empty with chain as body of a

The Fix

pip install celery==5.6.0

Based on closed celery/celery issue #9773 · 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.

Jump to Verify Open PR/Commit

@@ -2234,7 +2234,8 @@ def run(self, header, body, partial_args, app=None, interval=None,
             body.options.update(options)
 
-        bodyres = body.freeze(task_id, root_id=root_id)
+        body_task_id = task_id or uuid()
+        bodyres = body.freeze(body_task_id, group_id=group_id, root_id=root_id)

repro.py

# bug_task.py

"""
Bug reproduction tasks for the pytest-celery bug report.

These tasks are used to reproduce the ValueError: task_id must not be empty
that occurs when a group with a failing task is part of a chain.
"""

import time
from celery import shared_task


@shared_task
def add(x, y):
    """Simple addition task with sleep to simulate work"""
    print(f"Adding {x} + {y}")
    time.sleep(1)
    result = x + y
    print(f"Result: {result}")
    return result


@shared_task
def failc():
    """Task that always fails to trigger the bug"""
    print("About to fail...")
    raise ValueError("failc - intentional failure")

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==5.6.0\nWhen NOT to use: This fix is not applicable if task IDs are managed externally and must remain None.\n\n

Why This Fix Works in Production

Trigger: -------------- [email protected] v5.5.3 (immunity)
Mechanism: The task_id can be None when a chord is called without an explicit ID, causing errors
Why the fix works: Fixes the issue where the task_id must not be empty when using a chain as the body of a chord. (first fixed release: 5.6.0).

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

Shows up under Python 3.11 in real deployments (not just unit tests).
The task_id can be None when a chord is called without an explicit ID, causing errors
Surfaces as: -------------- [email protected] v5.5.3 (immunity)

Proof / Evidence

GitHub issue: #9773
Fix PR: https://github.com/celery/celery/pull/9774
First fixed release: 5.6.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.35

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“ # Checklist  - [x] I hav”

Issue thread · issue description · source

Failure Signature (Search String)

-------------- [email protected] v5.5.3 (immunity)

Error Message

Stack trace

error.txt

Error Message
-------------
-------------- [email protected] v5.5.3 (immunity)
--- ***** ----- 
-- ******* ---- macOS-15.5-arm64-arm-64bit 2025-06-19 23:39:11
- *** --- * --- 
- ** ---------- [config]
- ** ---------- .> app:         celery_failing:0x104befdd0
- ** ---------- .> transport:   redis://localhost:6379//
- ** ---------- .> results:     redis://localhost:6379/
- *** --- * --- .> concurrency: 10 (prefork)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** ----- 
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery
                

[tasks]
  . tasks.add
  . tasks.failc

[2025-06-19 23:39:11,730: INFO/MainProcess] Connected to redis://localhost:6379//
[2025-06-19 23:39:11,750: INFO/MainProcess] mingle: searching for neighbors
[2025-06-19 23:39:12,789: INFO/MainProcess] mingle: all alone
[2025-06-19 23:39:12,824: INFO/MainProcess] [email protected] ready.
[2025-06-19 23:39:16,731: INFO/MainProcess] Task tasks.add[2069eb9f-b57e-48e4-98d8-595efd5f5922] received
[2025-06-19 23:39:16,735: INFO/MainProcess] Task tasks.failc[f9032a00-4ee6-4430-bf27-eb04f3d66cd7] received
[2025-06-19 23:39:16,748: ERROR/ForkPoolWorker-1] Task tasks.failc[f9032a00-4ee6-4430-bf27-eb04f3d66cd7] raised unexpected: Exception('failc')
Traceback (most recent call last):
  File "/Users/diego/Development/my_celery_project/
... (truncated) ...

Minimal Reproduction

repro.py

# bug_task.py

"""
Bug reproduction tasks for the pytest-celery bug report.

These tasks are used to reproduce the ValueError: task_id must not be empty
that occurs when a group with a failing task is part of a chain.
"""

import time
from celery import shared_task


@shared_task
def add(x, y):
    """Simple addition task with sleep to simulate work"""
    print(f"Adding {x} + {y}")
    time.sleep(1)
    result = x + y
    print(f"Result: {result}")
    return result


@shared_task
def failc():
    """Task that always fails to trigger the bug"""
    print("About to fail...")
    raise ValueError("failc - intentional failure")

Environment

Python: 3.11

What Broke

Error handling fails with 'task_id must not be empty' when using a chord with a failing group task.

Why It Broke

The task_id can be None when a chord is called without an explicit ID, causing errors

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install celery==5.6.0

When NOT to use: This fix is not applicable if task IDs are managed externally and must remain None.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/celery/celery/pull/9774

First fixed release: 5.6.0

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

This fix is not applicable if task IDs are managed externally and must remain None.

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
5.6.0	Fixed

Related Issues

No related fixes found.

Cluster: celery:configuration-error Celery hub Celery best practices All hubs All clusters

Related clusters: Data consistency Duplicates Duplicate processing

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

Celery task_id must not be empty with chain as body of a chord (Fix)