The Fix
Upgrade to version 0.24.1 or later.
Based on closed encode/httpx issue #2670 · 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%.
@@ -399,7 +399,7 @@ def normalize_path(path: str) -> str:
def percent_encode(char: str) -> str:
"""
- Replace every character in a string with the percent-encoded representation.
+ Replace a single character with the percent-encoded representation.
repro.py
from urllib.parse importparse_qs
from httpx._urls import urlencode
parse_qs( urlencode((('u', "http://example.com?q=foo%2Fa%20b%2Ac"),)))
# -> {'u': ['http://example.com?q=foo/a b*c']}
# Incorrect url decoded from the query string
from urllib.parse import urlencode
parse_qs( urlencode((('u', "http://example.com?q=foo%2Fa%20b%2Ac"),)))
# -> {'u': ['http://example.com?q=foo%2Fa%20b%2Ac']}
# Correct original url decoded from the query string
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 0.24.1 or later.\nWhen NOT to use: This fix should not be applied if the application relies on the previous encoding behavior.\n\n
Why This Fix Works in Production
- Trigger: Since httpx 0.24 the behavior regarding query params changed, and possibly contains a bug.
- Mechanism: Fixes the optional percent encoding behavior in query parameters, ensuring that pre-signed URLs are correctly encoded.
- Why the fix works: Fixes the optional percent encoding behavior in query parameters, ensuring that pre-signed URLs are correctly encoded. (first fixed release: 0.24.1).
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
- Production symptom (often without a traceback): Since httpx 0.24 the behavior regarding query params changed, and possibly contains a bug.
Proof / Evidence
- GitHub issue: #2670
- Fix PR: https://github.com/encode/httpx/pull/2671
- First fixed release: 0.24.1
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.75
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.54
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“If understand correctly, the new code still leaves query parameters which look like already percent-escapes as-is? I think this is not a good idea, because…”
“This is related to the changes here: https://github.com/encode/httpx/pull/2543”
“Also for forward-slashes https://github.com/encode/httpx/discussions/2661”
“+1 for @dlange-hima I belive that urlparse(urlencode(x)) shoud be equal to x. This won't be true for parameter values like %20. With current solution it's…”
Failure Signature (Search String)
- Since httpx 0.24 the behavior regarding query params changed, and possibly contains a bug.
- This is related to the changes here: https://github.com/encode/httpx/pull/2543
Copy-friendly signature
signature.txt
Failure Signature
-----------------
Since httpx 0.24 the behavior regarding query params changed, and possibly contains a bug.
This is related to the changes here: https://github.com/encode/httpx/pull/2543
Error Message
Signature-only (no traceback captured)
error.txt
Error Message
-------------
Since httpx 0.24 the behavior regarding query params changed, and possibly contains a bug.
This is related to the changes here: https://github.com/encode/httpx/pull/2543
Minimal Reproduction
repro.py
from urllib.parse importparse_qs
from httpx._urls import urlencode
parse_qs( urlencode((('u', "http://example.com?q=foo%2Fa%20b%2Ac"),)))
# -> {'u': ['http://example.com?q=foo/a b*c']}
# Incorrect url decoded from the query string
from urllib.parse import urlencode
parse_qs( urlencode((('u', "http://example.com?q=foo%2Fa%20b%2Ac"),)))
# -> {'u': ['http://example.com?q=foo%2Fa%20b%2Ac']}
# Correct original url decoded from the query string
Environment
- httpx: 0.24
What Broke
Query parameters containing percent-escaped sequences were not encoded correctly, leading to incorrect URL handling.
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
Upgrade to version 0.24.1 or later.
When NOT to use: This fix should not be applied if the application relies on the previous encoding behavior.
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/2671
First fixed release: 0.24.1
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- This fix should not be applied if the application relies on the previous encoding behavior.
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.
Version Compatibility Table
| Version | Status |
|---|---|
| 0.24.1 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.