Pydantic Changing `model_copy.update`'s type hint from

The Fix

pip install pydantic==1.10.19

Based on closed pydantic/pydantic issue #10750 · PR/commit linked

Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.

Open PR/Commit

@@ -351,7 +351,7 @@ def model_construct(cls, _fields_set: set[str] | None = None, **values: Any) ->
         return m
 
-    def model_copy(self, *, update: dict[str, Any] | None = None, deep: bool = False) -> Self:
+    def model_copy(self, *, update: Mapping[str, Any] | None = None, deep: bool = False) -> Self:
         """Usage docs: https://docs.pydantic.dev/2.10/concepts/serialization/#model_copy

fix.md

Option A — Upgrade to fixed release\npip install pydantic==1.10.19\nWhen NOT to use: This fix should not be used if strict type checking for dictionaries is required.\n\n

Why This Fix Works in Production

Trigger: Changing `model_copy.update`'s type hint from `dict[str, Any]` to `Mapping[str, Any]`
Mechanism: Changed the type hint of `model_copy.update` from `dict[str, Any]` to `Mapping[str, Any]` to allow for more general mapping types.
Why the fix works: Changed the type hint of `model_copy.update` from `dict[str, Any]` to `Mapping[str, Any]` to allow for more general mapping types. (first fixed release: 1.10.19).

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): Changing `model_copy.update`'s type hint from `dict[str, Any]` to `Mapping[str, Any]`

Proof / Evidence

GitHub issue: #10750
Fix PR: https://github.com/pydantic/pydantic/pull/10751
First fixed release: 1.10.19
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.95
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.61

Discussion

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

Jump to Sources Open on GitHub

“### Initial Checks - [X] I have searched Google & GitHub for similar requests and couldn't find anything - [X] I have read and followed the docs and still think this feature is missing ### Description https://github.com/pydantic/pydantic/bl”

Issue thread · issue description · source

Failure Signature (Search String)

Changing `model_copy.update`'s type hint from `dict[str, Any]` to `Mapping[str, Any]`
- [ ] [Compatibility between releases](https://docs.pydantic.dev/changelog/)

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Changing `model_copy.update`'s type hint from `dict[str, Any]` to `Mapping[str, Any]`
- [ ] [Compatibility between releases](https://docs.pydantic.dev/changelog/)

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Changing `model_copy.update`'s type hint from `dict[str, Any]` to `Mapping[str, Any]`
- [ ] [Compatibility between releases](https://docs.pydantic.dev/changelog/)

What Broke

Users could not use other mapping types with `model_copy` leading to type errors.

Fix Options (Details)

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

pip install pydantic==1.10.19

When NOT to use: This fix should not be used if strict type checking for dictionaries is required.

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/10751

First fixed release: 1.10.19

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

When NOT to Use This Fix

This fix should not be used if strict type checking for dictionaries is required.

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
1.10.19	Fixed

Related Issues

No related fixes found.

Cluster: pydantic:configuration-error Pydantic hub Pydantic best practices All hubs All clusters

Related clusters: Data consistency OpenAPI schema Serialization

Sources

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

Pydantic Changing `model_copy.update`'s type hint from `dict[str, Any]` to `Mapping[str, Any]` (Fix)