httpx Specified timeout not enforced (using a proxy) (Fix)

The Fix

Upgrade to version 0.13.0 or later.

Based on closed encode/httpx issue #2073 · 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

@@ -1,11 +1,9 @@
@@ -1,11 +1,9 @@
 import asyncio
-import logging
 import os

repro.py

connect_request = Request(
                    method=b"CONNECT", url=connect_url, headers=connect_headers
                )
                connect_response = await self._connection.handle_async_request(
                    connect_request
                )

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\nUpgrade to version 0.13.0 or later.\nWhen NOT to use: Do not use this fix if the timeout behavior is intentionally designed to be longer.\n\n

Why This Fix Works in Production

Trigger: Specified timeout not enforced (using a proxy)
Mechanism: Timeout settings were not enforced due to missing extensions in the connect request
Why the fix works: Refactor debug and trace log tests to improve logging behavior in httpx. (first fixed release: 0.13.0).

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

Timeout settings were not enforced due to missing extensions in the connect request
Production symptom (often without a traceback): Specified timeout not enforced (using a proxy)

Proof / Evidence

GitHub issue: #2073
Fix PR: https://github.com/encode/httpcore/pull/506
First fixed release: 0.13.0
Reproduced locally: No (not executed)
Last verified: 2026-02-08
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

“Alrighty then - resolved in https://github.com/encode/httpcore/pull/506 You're welcome to test against that branch if you want to verify it for yourself”

@lovelydinosaur · 2022-02-09 · confirmation · source

“Hi @tomchristie Thanks for the VERY quick reply. I'm not to familiar with the code so it would be awesome if one of you guys…”

@esbenkolsbjerg · 2022-02-09 · source

“Great! I expect we'll push a new httpcore version out soon enough.”

@lovelydinosaur · 2022-02-09 · source

“Thanks for raising this @esbenkolsbjerg”

@lovelydinosaur · 2022-02-09 · source

Failure Signature (Search String)

Specified timeout not enforced (using a proxy)
In the process of upgrading some very old packages I noticed a huge performance drop of a specific proxy pool. I tracked the issue to the timeouts set not being enforced.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Specified timeout not enforced (using a proxy)
In the process of upgrading some very old packages I noticed a huge performance drop of a specific proxy pool. I tracked the issue to the timeouts set not being enforced.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Specified timeout not enforced (using a proxy)
In the process of upgrading some very old packages I noticed a huge performance drop of a specific proxy pool. I tracked the issue to the timeouts set not being enforced.

Minimal Reproduction

repro.py

connect_request = Request(
                    method=b"CONNECT", url=connect_url, headers=connect_headers
                )
                connect_response = await self._connection.handle_async_request(
                    connect_request
                )

What Broke

Requests failed to timeout, causing prolonged delays and errors from the proxy service.

Why It Broke

Timeout settings were not enforced due to missing extensions in the connect request

Fix Options (Details)

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

Upgrade to version 0.13.0 or later.

When NOT to use: Do not use this fix if the timeout behavior is intentionally designed to be longer.

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

Fix reference: https://github.com/encode/httpcore/pull/506

First fixed release: 0.13.0

Last verified: 2026-02-08. Validate in your environment.

When NOT to Use This Fix

Do not use this fix if the timeout behavior is intentionally designed to be longer.

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.
Make timeouts explicit and test them (unit + integration) to avoid silent behavior changes.
Instrument retries (attempt count + reason) and alert on spikes to catch dependency slowdowns.

Version Compatibility Table

Version	Status
0.13.0	Fixed

Related Issues

No related fixes found.

Cluster: httpx:configuration-error All hubs All clusters

Related clusters: Data consistency Other Timeout

Sources

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