Requests Proxy authentication broken with 0.76 -> 0.83

The Fix

This specific case is fixed in.

Based on closed psf/requests issue #293

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%.

fix.md

Option A — Apply the official fix\nThis specific case is fixed in.\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: Proxy authentication broken with 0.76 -> 0.83 upgrade.
Mechanism: This specific case is fixed in.

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

Surfaces as: Traceback (most recent call last):\n File "req.py", line 10, in <module>\n print get('http://ipcheckit.com', proxies=p).content\n File "build\bdist.win32\egg\requests\api.py",…

Proof / Evidence

GitHub issue: #293
Reproduced locally: No (not executed)
Last verified: 2026-02-04
Confidence: 0.00
Did this fix it?: No (no upstream fix linked)
Own content ratio: 0.46

Discussion

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

Jump to Sources Open on GitHub

“This specific case is fixed in https://github.com/shazow/urllib3/commit/e5c2c193a0a93f97202ad76749231723f8d60156”

@shazow · 2011-12-04 · confirmation · source

“This may be an unexpected side effect of @shazow's hated for the urlparse module :)”

@kennethreitz · 2011-11-29 · source

“You are correct”

@shazow · 2011-11-29 · source

Failure Signature (Search String)

Proxy authentication broken with 0.76 -> 0.83 upgrade.

Error Message

Stack trace

error.txt

Error Message
-------------
Traceback (most recent call last):\n  File "req.py", line 10, in <module>\n    print get('http://ipcheckit.com', proxies=p).content\n  File "build\bdist.win32\egg\requests\api.py", line 80, in get\n  File "build\bdist.win32\egg\requests\api.py", line 67, in request\n  File "build\bdist.win32\egg\requests\sessions.py", line 191, in request\n  File "build\bdist.win32\egg\requests\models.py", line 409, in send\n  File "build\bdist.win32\egg\requests\packages\urllib3\poolmanager.py", line 127, in proxy_from_url\n  File "build\bdist.win32\egg\requests\packages\urllib3\connectionpool.py", line 521, in connection_from_url\n  File "build\bdist.win32\egg\requests\packages\urllib3\connectionpool.py", line 497, in get_host

Fix Options (Details)

Option A — Apply the official fix

This specific case is fixed in.

When NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.

Fix reference: https://github.com/psf/requests/issues/293

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

Track RSS + object counts after deployments; alert on monotonic growth and GC pressure.
Add a long-running test that repeats the failing call path and asserts stable memory.

Related Issues

No related fixes found.

Cluster: requests:configuration-error Requests hub Requests best practices All hubs All clusters

Related clusters: Data consistency SSL handshake Other

Sources

GitHub issue #293

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

Requests Proxy authentication broken with 0.76 -> 0.83 upgrade. (Fix)