Pydantic AliasChoices Unhashable When Comparing Models (Fix)

The Fix

pip install pydantic==2.7.1

Based on closed pydantic/pydantic issue #9220 · 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

@@ -2,7 +2,9 @@
 
 import dataclasses
-from typing import Callable, Literal
+from typing import Any, Callable, Literal
+

repro.py

from pydantic import AliasChoices, BaseModel, Field

class MyModel(BaseModel):
    data: str
    our_id: str | None = Field(
        default=None,
        validation_alias=AliasChoices("their_id", "theirId", "our_id", "id"),
    )

def test_cardmodel_eq():
    model1 = MyModel.model_construct(data="test data")
    model2 = MyModel.model_construct(data="test data")
    model3 = MyModel.model_construct(data="other data")
    assert model1 == model2
    assert not model1 == model3

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==2.7.1\nWhen NOT to use: This fix should not be used if the model comparison logic is fundamentally altered.\n\n

Why This Fix Works in Production

Trigger: validation_alias=AliasChoices("their_id", "theirId", "our_id", "id"),
Mechanism: The validation alias behavior was not correctly implemented for model comparisons, leading to a TypeError
Why the fix works: Fixes the validation alias behavior with model construction for AliasChoices and AliasPath, addressing a TypeError encountered during model comparisons. (first fixed release: 2.7.1).

Production impact:

If left unfixed, retries/timeouts can trigger duplicate external side-effects (double charges, duplicate emails, repeated writes).

Why This Breaks in Prod

Shows up under Python 3.11 in real deployments (not just unit tests).
The validation alias behavior was not correctly implemented for model comparisons, leading to a TypeError
Production symptom (often without a traceback): validation_alias=AliasChoices("their_id", "theirId", "our_id", "id"),

Proof / Evidence

GitHub issue: #9220
Fix PR: https://github.com/pydantic/pydantic/pull/9223
First fixed release: 2.7.1
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.65

Discussion

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

Jump to Sources Open on GitHub

“@sydney-runkle I see I have made a typo when writing my example code 🤦🏼~~I will fix it.~~ It should be fixed now”

@iambroadband · 2024-04-12 · confirmation · source

“Closing this as a dupe of https://github.com/pydantic/pydantic/issues/9216, but will make sure to resolve this in the patch release!”

@sydney-runkle · 2024-04-12 · confirmation · source

“@iambroadband, Thanks for reporting this! We'll roll a fix out with a patch release early next week!”

@sydney-runkle · 2024-04-12 · source

“@iambroadband, I don't think your test as it stands should pass - model1 and model2 aren't equivalent, unless I'm missing something?”

@sydney-runkle · 2024-04-12 · source

Failure Signature (Search String)

validation_alias=AliasChoices("their_id", "theirId", "our_id", "id"),
assert model1 == model2

Copy-friendly signature

signature.txt

Failure Signature
-----------------
validation_alias=AliasChoices("their_id", "theirId", "our_id", "id"),
assert model1 == model2

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
validation_alias=AliasChoices("their_id", "theirId", "our_id", "id"),
assert model1 == model2

Minimal Reproduction

repro.py

from pydantic import AliasChoices, BaseModel, Field

class MyModel(BaseModel):
    data: str
    our_id: str | None = Field(
        default=None,
        validation_alias=AliasChoices("their_id", "theirId", "our_id", "id"),
    )

def test_cardmodel_eq():
    model1 = MyModel.model_construct(data="test data")
    model2 = MyModel.model_construct(data="test data")
    model3 = MyModel.model_construct(data="other data")
    assert model1 == model2
    assert not model1 == model3

Environment

Python: 3.11
Pydantic: 2

What Broke

Model comparisons failed with a TypeError, causing test failures in production.

Why It Broke

The validation alias behavior was not correctly implemented for model comparisons, leading to a TypeError

Fix Options (Details)

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

pip install pydantic==2.7.1

When NOT to use: This fix should not be used if the model comparison logic is fundamentally altered.

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/9223

First fixed release: 2.7.1

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

When NOT to Use This Fix

This fix should not be used if the model comparison logic is fundamentally altered.

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
2.7.1	Fixed

Related Issues

No related fixes found.

Cluster: pydantic:duplicate-processing Pydantic hub Pydantic best practices All hubs All clusters

Related clusters: Configuration error Data consistency OpenAPI schema

Sources

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