The Fix
pip install pydantic==1.10.15
Based on closed pydantic/pydantic issue #8990 · PR/commit linked
@@ -224,6 +224,9 @@ print(Model(x='test value').model_dump_json())
```
+!!! note
+ A single serializer can also be called on all fields by passing the special value '*' to the [`@field_serializer`][pydantic.functional_serializers.field_serializer] decorator.
+
Option A — Upgrade to fixed release\npip install pydantic==1.10.15\nWhen NOT to use: Do not use this fix if you require different serialization logic for individual fields.\n\n
Why This Fix Works in Production
- Trigger: this is a 2-lines change, i can submit a PR right away if this is indeed a missing feature.
- Mechanism: The absence of a field_serializer('*') feature limits serialization flexibility in Pydantic models
- Why the fix works: Allows the use of field_serializer('*') for defining a serializer for all fields in a model, addressing issue #8990. (first fixed release: 1.10.15).
Why This Breaks in Prod
- The absence of a field_serializer('*') feature limits serialization flexibility in Pydantic models
- Production symptom (often without a traceback): this is a 2-lines change, i can submit a PR right away if this is indeed a missing feature.
Proof / Evidence
- GitHub issue: #8990
- Fix PR: https://github.com/pydantic/pydantic/pull/9001
- First fixed release: 1.10.15
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.77
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“@ornariece, This seems reasonable to me! Thanks for pointing this out! Feel free to submit a PR + ping me when you need a review…”
Failure Signature (Search String)
- this is a 2-lines change, i can submit a PR right away if this is indeed a missing feature.
Copy-friendly signature
Failure Signature
-----------------
this is a 2-lines change, i can submit a PR right away if this is indeed a missing feature.
Error Message
Signature-only (no traceback captured)
Error Message
-------------
this is a 2-lines change, i can submit a PR right away if this is indeed a missing feature.
Environment
- Pydantic: 2
What Broke
Developers cannot define a serializer for all fields, leading to repetitive code.
Why It Broke
The absence of a field_serializer('*') feature limits serialization flexibility in Pydantic models
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install pydantic==1.10.15
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)
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)
Fix reference: https://github.com/pydantic/pydantic/pull/9001
First fixed release: 1.10.15
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- Do not use this fix if you require different serialization logic for individual fields.
- 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.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Add a CI check that diffs key outputs after upgrades (OpenAPI schema snapshots, JSON payload shapes, CLI output).
- Upgrade behind a canary and run integration tests against the canary before 100% rollout.
Version Compatibility Table
| Version | Status |
|---|---|
| 1.10.15 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.