urllib3 imprecise types on `urllib3.Retry.new` /

The Fix

pip install urllib3==2.2.2

Based on closed urllib3/urllib3 issue #3363 · 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

@@ -0,0 +1 @@
@@ -0,0 +1 @@
+Consistently used ``typing.Self`` for return types representing copying actions.
diff --git a/src/urllib3/_collections.py b/src/urllib3/_collections.py
index 55b0324797..8a4409a122 100644

repro.py

from typing import Any, Self
import urllib3
class MyRetry(urllib3.Retry):
    def increment(self, *a: Any, **k: Any) -> Self:  # type error on this line!
        return super().increment(*a, **k)

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 urllib3==2.2.2\nWhen NOT to use: This fix should not be used if backward compatibility with older Python versions is required.\n\n

Why This Fix Works in Production

Trigger: t.py:5: error: Incompatible return value type (got "Retry", expected "Self") [return-value]
Mechanism: Resolves issue #3363 by using `Self` from `typing_extensions` for return types in the `urllib3.Retry` class methods.
Why the fix works: Resolves issue #3363 by using `Self` from `typing_extensions` for return types in the `urllib3.Retry` class methods. (first fixed release: 2.2.2).

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

Triggered by an upgrade/regression window: 3.11 breaks; 2.2.2 is the first fixed release.
Shows up under Python 3.11 in real deployments (not just unit tests).
Production symptom (often without a traceback): def increment(self, *a: Any, **k: Any) -> Self: # type error on this line!

Proof / Evidence

GitHub issue: #3363
Fix PR: https://github.com/urllib3/urllib3/pull/3364
First fixed release: 2.2.2
Affected versions: 3.11
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.64

Discussion

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

Jump to Sources Open on GitHub

“Thanks for reporting this! > if the codebase were python 3.11+ I would use from typing import Self -- it appears elsewhere in the codebase…”

@illia-v · 2024-03-13 · source

Failure Signature (Search String)

t.py:5: error: Incompatible return value type (got "Retry", expected "Self") [return-value]

Copy-friendly signature

signature.txt

Failure Signature
-----------------
def increment(self, *a: Any, **k: Any) -> Self:  # type error on this line!
t.py:5: error: Incompatible return value type (got "Retry", expected "Self")  [return-value]

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
def increment(self, *a: Any, **k: Any) -> Self:  # type error on this line!
t.py:5: error: Incompatible return value type (got "Retry", expected "Self")  [return-value]

Minimal Reproduction

repro.py

from typing import Any, Self
import urllib3
class MyRetry(urllib3.Retry):
    def increment(self, *a: Any, **k: Any) -> Self:  # type error on this line!
        return super().increment(*a, **k)

Environment

Python: 3.11

Fix Options (Details)

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

pip install urllib3==2.2.2

When NOT to use: This fix should not be used if backward compatibility with older Python versions is required.

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

Fix reference: https://github.com/urllib3/urllib3/pull/3364

First fixed release: 2.2.2

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

When NOT to Use This Fix

This fix should not be used if backward compatibility with older Python versions is required.

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
3.11	Broken
2.2.2	Fixed

Related Issues

No related fixes found.

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Related clusters: Data consistency SSL handshake Other

Sources

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

urllib3 imprecise types on `urllib3.Retry.new` / `urllib3.Retry.increment` (Fix)