uvicorn Remove pinning of httptools==0.2.*

The Fix

Upgrade to version 0.16.0 or later.

Based on closed Kludex/uvicorn issue #1242 · 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

@@ -56,7 +56,7 @@ def get_packages(package):
     "websockets>=9.1; " + env_marker_below_37,
     "websockets>=10.0; " + env_marker_gte_37,
-    "httptools==0.2.*",
+    "httptools>=0.2.0,<0.4.0",
     "uvloop>=0.14.0,!=0.15.0,!=0.15.1; " + env_marker_cpython,

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 0.16.0 or later.\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: Remove pinning of httptools==0.2.* - this blocks wheel usage of httptools on Python 3.10 for uvicorn[standard]
Mechanism: Removes the pinning of httptools at version 0.2.*, allowing for the use of httptools>=0.2.0,<0.4.0, which supports Python 3.10 wheels.
Why the fix works: Removes the pinning of httptools at version 0.2.*, allowing for the use of httptools>=0.2.0,<0.4.0, which supports Python 3.10 wheels. (first fixed release: 0.16.0).

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 3.10 in real deployments (not just unit tests).

Proof / Evidence

GitHub issue: #1242
Fix PR: https://github.com/kludex/uvicorn/pull/1243
First fixed release: 0.16.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.74

Discussion

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

Jump to Sources Open on GitHub

“PR welcome with "httptools>=0.2.0,<0.4.0",. :kissing: EDIT: Actually, maybe we want a marker for httptools==0.3.0 and Python 3.10.”

@Kludex · 2021-11-08 · source

“@Kludex I added a PR removing the 0.2 pinning, but setting the 0.4 limit as requested”

@quantumtec · 2021-11-08 · source

“I meant a marker to httptools==0.3.*, the 0 at the end was a mistake. But I guess your PR is fine :+1:”

@Kludex · 2021-11-08 · source

Failure Signature (Search String)

Remove pinning of httptools==0.2.* - this blocks wheel usage of httptools on Python 3.10 for uvicorn[standard]

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Remove pinning of httptools==0.2.* - this blocks wheel usage of httptools on Python 3.10 for uvicorn[standard]

Environment

Python: 3.10

Fix Options (Details)

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

Upgrade to version 0.16.0 or later.

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/kludex/uvicorn/pull/1243

First fixed release: 0.16.0

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.

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

Capture the exact failing error string in logs and tests so you can reproduce via a minimal script.
Pin production dependencies and upgrade only with a reproducible test that hits the failing path.

Version Compatibility Table

Version	Status
0.16.0	Fixed

Related Issues

No related fixes found.

Cluster: uvicorn:configuration-error All hubs All clusters

Related clusters: Data consistency Race condition SSL handshake

Sources

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

uvicorn Remove pinning of httptools==0.2.* - this blocks wheel usage of httptools on Python 3.10 (Fix)