urllib3 Python 3.14 CI failures due to httpcore issue (Fix)

The Fix

pip install urllib3==2.5.0

Based on closed urllib3/urllib3 issue #3576 · PR/commit linked

Open PR/Commit

@@ -1,4 +1,5 @@
@@ -1,4 +1,5 @@
 version = 1
+revision = 1
 requires-python = ">=3.9"
 resolution-markers = [

fix.md

Option A — Upgrade to fixed release\npip install urllib3==2.5.0\nWhen NOT to use: Do not apply this fix if not using httpcore or if not affected by the CI issue.\n\n

Why This Fix Works in Production

Trigger: Tests with CPython 3.14.0a6 [fail](https://github.com/urllib3/urllib3/actions/runs/14046308016/job/39327778144?pr=3575) because of an issue documented in
Mechanism: Bump httpcore to fix Python 3.14 tests, resolving the issue documented in the linked discussions.
Why the fix works: Bump httpcore to fix Python 3.14 tests, resolving the issue documented in the linked discussions. (first fixed release: 2.5.0).

Why This Breaks in Prod

Shows up under Python 3.14 in real deployments (not just unit tests).
Production symptom (often without a traceback): Python 3.14 CI failures due to httpcore issue

Proof / Evidence

GitHub issue: #3576
Fix PR: https://github.com/urllib3/urllib3/pull/3592
First fixed release: 2.5.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.68

Discussion

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

Jump to Sources Open on GitHub

“You can use this monkey-patch I did to fix the issue meanwhile: https://github.com/encode/httpx/issues/3548#issuecomment-2795327545”

@codebydivine · 2025-04-11 · source

Failure Signature (Search String)

Tests with CPython 3.14.0a6 [fail](https://github.com/urllib3/urllib3/actions/runs/14046308016/job/39327778144?pr=3575) because of an issue documented in

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Python 3.14 CI failures due to httpcore issue
Tests with CPython 3.14.0a6 [fail](https://github.com/urllib3/urllib3/actions/runs/14046308016/job/39327778144?pr=3575) because of an issue documented in https://github.com/encode/httpcore/discussions/995.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Python 3.14 CI failures due to httpcore issue
Tests with CPython 3.14.0a6 [fail](https://github.com/urllib3/urllib3/actions/runs/14046308016/job/39327778144?pr=3575) because of an issue documented in https://github.com/encode/httpcore/discussions/995.

Environment

Python: 3.14

Fix Options (Details)

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

pip install urllib3==2.5.0

When NOT to use: Do not apply this fix if not using httpcore or if not affected by the CI issue.

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/3592

First fixed release: 2.5.0

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

When NOT to Use This Fix

Do not apply this fix if not using httpcore or if not affected by the CI issue.

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
2.5.0	Fixed

Related Issues

No related fixes found.

Cluster: urllib3:other urllib3 hub urllib3 best practices All hubs All clusters

Related clusters: Configuration error Data consistency SSL handshake

Sources

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