httpx Accept url-encoded characters in proxy authentication

The Fix

Handles URL quoting for username and password components in proxy authentication strings, allowing special characters to be properly encoded.

Based on closed encode/httpx issue #858 · 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

@@ -7,7 +7,7 @@
 from collections.abc import MutableMapping
 from http.cookiejar import Cookie, CookieJar
-from urllib.parse import parse_qsl, urlencode
+from urllib.parse import parse_qsl, quote, unquote, urlencode

fix.md

Option A — Apply the official fix\nHandles URL quoting for username and password components in proxy authentication strings, allowing special characters to be properly encoded.\nWhen NOT to use: This fix should not be used if the application does not require special character handling in proxy authentication.\n\n

Why This Fix Works in Production

Trigger: Certain characters such as @:!#$ break proxy authentication strings when included without url-encoding them.
Mechanism: Certain characters in proxy authentication strings are not properly URL-encoded, causing issues with URI parsing

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

Certain characters in proxy authentication strings are not properly URL-encoded, causing issues with URI parsing
Production symptom (often without a traceback): Certain characters such as @:!#$ break proxy authentication strings when included without url-encoding them.

Proof / Evidence

GitHub issue: #858
Fix PR: https://github.com/encode/httpx/pull/1159
Reproduced locally: No (not executed)
Last verified: 2026-02-11
Confidence: 0.70
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.75

Discussion

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

Jump to Sources Open on GitHub

“Certain characters such as @:!#$ break proxy authentication strings when included without url-encoding them. I'm dealing with a service account that has # in the password and httpx is unable handle this. # breaks the URI and %23 is sent lit”

Issue thread · issue description · source

Failure Signature (Search String)

Certain characters such as @:!#$ break proxy authentication strings when included without url-encoding them.
I'm dealing with a service account that has # in the password and httpx is unable handle this. # breaks the URI and %23 is sent literal.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Certain characters such as @:!#$ break proxy authentication strings when included without url-encoding them.
I'm dealing with a service account that has # in the password and httpx is unable handle this. # breaks the URI and %23 is sent literal.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Certain characters such as @:!#$ break proxy authentication strings when included without url-encoding them.
I'm dealing with a service account that has # in the password and httpx is unable handle this. # breaks the URI and %23 is sent literal.

What Broke

Proxy authentication fails when special characters are included without URL encoding, leading to connection errors.

Why It Broke

Certain characters in proxy authentication strings are not properly URL-encoded, causing issues with URI parsing

Fix Options (Details)

Option A — Apply the official fix

Handles URL quoting for username and password components in proxy authentication strings, allowing special characters to be properly encoded.

When NOT to use: This fix should not be used if the application does not require special character handling in proxy authentication.

Fix reference: https://github.com/encode/httpx/pull/1159

Last verified: 2026-02-11. Validate in your environment.

When NOT to Use This Fix

This fix should not be used if the application does not require special character handling in proxy authentication.

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.

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.

httpx Accept url-encoded characters in proxy authentication strings (Fix)