Pydantic `deprecated_instance_property` doesn't work with

The Fix

pip install pydantic==1.10.20

Based on closed pydantic/pydantic issue #11637 · 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%.

Jump to Verify Open PR/Commit

@@ -9,11 +9,11 @@ Pydantic models are simply classes which inherit from `BaseModel` and define fie
           - __init__
           - model_config
+          - model_fields
           - model_computed_fields
+          - __pydantic_core_schema__

repro.py

pydantic version: 2.11.0
        pydantic-core version: 2.33.0
          pydantic-core build: profile=release pgo=false
                 install path: /Users/jamesbraza/code/paper-qa/.venv/lib/python3.12/site-packages/pydantic
               python version: 3.12.8 (main, Jan 28 2025, 10:06:03) [Clang 16.0.0 (clang-1600.0.26.4)]
                     platform: macOS-15.3.2-arm64-arm-64bit
             related packages: mypy-1.15.0 pydantic-settings-2.8.1 typing_extensions-4.13.0
                       commit: unknown

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 pydantic==1.10.20\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: `deprecated_instance_property` doesn't work with `pylint`
Mechanism: `deprecated_instance_property` does not function correctly with `pylint` due to compatibility issues
Why the fix works: `deprecated_instance_property` was introduced to improve compliance with static type checking. (first fixed release: 1.10.20).

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 3.12 in real deployments (not just unit tests).
`deprecated_instance_property` does not function correctly with `pylint` due to compatibility issues
Production symptom (often without a traceback): `deprecated_instance_property` doesn't work with `pylint`

Proof / Evidence

GitHub issue: #11637
Fix PR: https://github.com/pydantic/pydantic/pull/11169
First fixed release: 1.10.20
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.95
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.58

Discussion

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

Jump to Sources Open on GitHub

“This is a pylint issue. deprecated_instance_property is standards compliant with respect to static type checking, and supported by major type checkers.”

@Viicos · 2025-03-27 · source

“Thanks @Viicos, figured I would notify just in case it wasn't on your radar”

@jamesbraza · 2025-03-27 · source

“Thanks for letting me know, in general it seems like pylint implement many rules that overlap with static type checkers, but such checkers have become…”

@Viicos · 2025-03-27 · source

Failure Signature (Search String)

`deprecated_instance_property` doesn't work with `pylint`

Copy-friendly signature

signature.txt

Failure Signature
-----------------
`deprecated_instance_property` doesn't work with `pylint`

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
`deprecated_instance_property` doesn't work with `pylint`

Minimal Reproduction

repro.py

pydantic version: 2.11.0
        pydantic-core version: 2.33.0
          pydantic-core build: profile=release pgo=false
                 install path: /Users/jamesbraza/code/paper-qa/.venv/lib/python3.12/site-packages/pydantic
               python version: 3.12.8 (main, Jan 28 2025, 10:06:03) [Clang 16.0.0 (clang-1600.0.26.4)]
                     platform: macOS-15.3.2-arm64-arm-64bit
             related packages: mypy-1.15.0 pydantic-settings-2.8.1 typing_extensions-4.13.0
                       commit: unknown

Environment

Python: 3.12
Pydantic: 2

What Broke

Users experience linting errors when using `deprecated_instance_property` with `pylint`.

Why It Broke

`deprecated_instance_property` does not function correctly with `pylint` due to compatibility issues

Fix Options (Details)

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

pip install pydantic==1.10.20

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.

Fix reference: https://github.com/pydantic/pydantic/pull/11169

First fixed release: 1.10.20

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.

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

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
1.10.20	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 `deprecated_instance_property` doesn't work with `pylint` (Fix)