urllib3 Collect mypy requirements in their own file (Fix)

The Fix

pip install urllib3==1.26.7

Based on closed urllib3/urllib3 issue #2377 · 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

@@ -0,0 +1,8 @@
@@ -0,0 +1,8 @@
+mypy==0.910
+idna>=2.0.0
+cryptography>=1.3.4

fix.md

Option A — Upgrade to fixed release\npip install urllib3==1.26.7\nWhen NOT to use: This fix should not be used if mypy dependencies need to be installed individually for specific reasons.\n\n

Why This Fix Works in Production

Trigger: Slower installation of mypy dependencies impacts development efficiency.
Mechanism: Mypy dependencies were installed individually, leading to slower installation times
Why the fix works: Collects mypy requirements into a separate file, improving installation efficiency and compatibility with tools like dependabot. (first fixed release: 1.26.7).

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

Mypy dependencies were installed individually, leading to slower installation times
Production symptom (often without a traceback): Slower installation of mypy dependencies impacts development efficiency.

Proof / Evidence

GitHub issue: #2377
Fix PR: https://github.com/urllib3/urllib3/pull/2379
First fixed release: 1.26.7
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.88

Discussion

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

Jump to Sources Open on GitHub

“We currently install mypy dependencies one by one: https://github.com/urllib3/urllib3/blob/0a4839af7103e9ad71d26bf5ba7914e765577efe/noxfile.py#L162-L169 It was fine initially, but we currently install 8 dependencies that way. That's slower”

Issue thread · issue description · source

Failure Signature (Search String)

Slower installation of mypy dependencies impacts development efficiency.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Slower installation of mypy dependencies impacts development efficiency.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Slower installation of mypy dependencies impacts development efficiency.

What Broke

Slower installation of mypy dependencies impacts development efficiency.

Why It Broke

Mypy dependencies were installed individually, leading to slower installation times

Fix Options (Details)

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

pip install urllib3==1.26.7

When NOT to use: This fix should not be used if mypy dependencies need to be installed individually for specific reasons.

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/2379

First fixed release: 1.26.7

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

When NOT to Use This Fix

This fix should not be used if mypy dependencies need to be installed individually for specific reasons.

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
1.26.7	Fixed

Related Issues

No related fixes found.

Cluster: urllib3:configuration-error urllib3 hub urllib3 best practices All hubs All clusters

Related clusters: Data consistency SSL handshake Other

Sources

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