Pydantic `pydantic` weekly project plan (Sydney Runkle) -

The Fix

pip install pydantic==1.10.18

Based on closed pydantic/pydantic issue #9804 · PR/commit linked

Open PR/Commit

@@ -198,6 +198,47 @@ except ValidationError as exc:
 ```
 
+## `complex_str_parsing`
+
+This error is raised when the input value is a string but cannot be parsed as a complex number because

fix.md

Option A — Upgrade to fixed release\npip install pydantic==1.10.18\nWhen NOT to use: Do not use this fix if complex number support is not required in your application.\n\n

Why This Fix Works in Production

Trigger: - [x] Finish up merging `json_schema_extra` via https://github.com/pydantic/pydantic/pull/9792
Mechanism: Merged the `json_schema_extra` dictionaries from annotated types, providing a more additive approach to merging
Why the fix works: Merged the `json_schema_extra` dictionaries from annotated types, providing a more additive approach to merging. (first fixed release: 1.10.18).

Why This Breaks in Prod

Merged the `json_schema_extra` dictionaries from annotated types, providing a more additive approach to merging
Production symptom (often without a traceback): - [x] Finish up merging `json_schema_extra` via https://github.com/pydantic/pydantic/pull/9792

Proof / Evidence

GitHub issue: #9804
Fix PR: https://github.com/pydantic/pydantic/pull/9654
First fixed release: 1.10.18
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.75
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.75

Discussion

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

Jump to Sources Open on GitHub

“@hramezani and @Kludex, Confirmed, I finally fixed the relnotes application thing. Here's a PR with proof: https://github.com/pydantic/pydantic/pull/9814”

@sydney-runkle · 2024-07-01 · source

“My work for this week will be catching up on everything I missed over my holiday, then will pivot to another weekly plan next Monday!”

@sydney-runkle · 2024-07-17 · source

Failure Signature (Search String)

- [x] Finish up merging `json_schema_extra` via https://github.com/pydantic/pydantic/pull/9792
- [ ] Backlog grooming for both `pydantic` and `pydantic-core`, as well as issue categorization to support easy access / entry for new contributors

Copy-friendly signature

signature.txt

Failure Signature
-----------------
- [x] Finish up merging `json_schema_extra` via https://github.com/pydantic/pydantic/pull/9792
- [ ] Backlog grooming for both `pydantic` and `pydantic-core`, as well as issue categorization to support easy access / entry for new contributors

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
- [x] Finish up merging `json_schema_extra` via https://github.com/pydantic/pydantic/pull/9792
- [ ] Backlog grooming for both `pydantic` and `pydantic-core`, as well as issue categorization to support easy access / entry for new contributors

What Broke

Complex numbers were not properly validated, leading to potential data integrity issues.

Why It Broke

Merged the `json_schema_extra` dictionaries from annotated types, providing a more additive approach to merging

Fix Options (Details)

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

pip install pydantic==1.10.18

When NOT to use: Do not use this fix if complex number support is not required in your application.

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

Fix reference: https://github.com/pydantic/pydantic/pull/9654

First fixed release: 1.10.18

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

When NOT to Use This Fix

Do not use this fix if complex number support is not required in your application.

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.
Track RSS + object counts after deployments; alert on monotonic growth and GC pressure.
Add a long-running test that repeats the failing call path and asserts stable memory.

Version Compatibility Table

Version	Status
1.10.18	Fixed

Related Issues

No related fixes found.

Cluster: pydantic:openapi-schema Pydantic hub Pydantic best practices All hubs All clusters

Related clusters: Configuration error Data consistency Serialization

Sources

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

Pydantic `pydantic` weekly project plan (Sydney Runkle) - July 1, 2024 (Fix)