httpx urllib3.ProxyManager() instantiation is broken. (Fix)

The Fix

Upgrade to version 0.13.0 or later.

Based on closed encode/httpx issue #762 · 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

@@ -77,7 +77,7 @@ def init_pool_manager(
         else:
             return urllib3.ProxyManager(
-                proxy_url=proxy.url,
+                proxy_url=str(proxy.url),
                 proxy_headers=dict(proxy.headers),

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 0.13.0 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: urllib3.ProxyManager() instantiation is broken.
Mechanism: Fixes the instantiation issue of urllib3.ProxyManager by passing a string representation of the URL instead of an httpx.URL instance.
Why the fix works: Fixes the instantiation issue of urllib3.ProxyManager by passing a string representation of the URL instead of an httpx.URL instance. (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

Dependency interaction matters here: urllib3 v1.25.7.
Shows up under Python 3.7.5 in real deployments (not just unit tests).
Production symptom (often without a traceback): urllib3.ProxyManager() instantiation is broken.

Proof / Evidence

GitHub issue: #762
Fix PR: https://github.com/encode/httpx/pull/763
First fixed release: 0.13.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.78

Discussion

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

Jump to Sources Open on GitHub

“Besides, unlike most CLI tools, and unlike **requests**, httpx uses OS system proxy settings over envvar (at least on macOS), which is surprising and unexpected”

@ushuz · 2020-01-14 · source

“@yorushika - The issue only occurs when proxies are in use - presumably you've got some different HTTP_PROXY / HTTPS_PROXY / ALL_PROXY environment settings on…”

@lovelydinosaur · 2020-01-14 · source

“> @yorushika - The issue only occurs when proxies are in use - presumably you've got some different HTTP_PROXY / HTTPS_PROXY / ALL_PROXY environment settings…”

@miranquil · 2020-01-14 · source

“@yorushika Maybe try python -c "import urllib.request; print(urllib.request.getproxies())" to inspect your system proxy configuration.”

@lovelydinosaur · 2020-01-14 · source

Failure Signature (Search String)

urllib3.ProxyManager() instantiation is broken.
TypeError Traceback (most recent call last)

Copy-friendly signature

signature.txt

Failure Signature
-----------------
urllib3.ProxyManager() instantiation is broken.
TypeError                                 Traceback (most recent call last)

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
urllib3.ProxyManager() instantiation is broken.
TypeError                                 Traceback (most recent call last)

Environment

Python: 3.7.5
urllib3: 1.25.7
httpx: 0.11.0

What Broke

Users experienced TypeError when trying to instantiate ProxyManager with incorrect URL type.

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 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/encode/httpx/pull/763

First fixed release: 0.13.0

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

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.
Add a TLS smoke test that performs a real handshake in CI (include CA bundle validation and hostname checks).
Alert on handshake failures by error string and endpoint to catch cert/CA changes quickly.

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.