The Fix
Upgrade to version 0.7.5 or later.
Based on closed encode/httpx issue #391 · 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%.
@@ -136,6 +136,10 @@ def scheme(self) -> str:
return self._uri_reference.authority or ""
+ @property
+ def userinfo(self) -> str:
+ return self._uri_reference.userinfo or ""
Option A — Upgrade to fixed release\nUpgrade to version 0.7.5 or later.\nWhen NOT to use: Do not apply this fix if the userinfo component is required for authentication.\n\n
Why This Fix Works in Production
- Trigger: Requests fail to reach the intended host due to incorrect Host header formatting.
- Mechanism: Fixes the issue by ensuring that the userinfo component is removed from the Host header when preparing the request.
- Why the fix works: Fixes the issue by ensuring that the userinfo component is removed from the Host header when preparing the request. (first fixed release: 0.7.5).
- 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): Requests fail to reach the intended host due to incorrect Host header formatting.
Proof / Evidence
- GitHub issue: #391
- Fix PR: https://github.com/encode/httpx/pull/417
- First fixed release: 0.7.5
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.75
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“Do we want a URL.host_with_port property, or something similar? Are there any prior art examples of URL libraries giving an explicit naming to the host+explicit-port-if-it-exists…”
“host_with_port sounds more relevant for the CONNECT case. I've seen "hostname" used for host and port if it's non-default.”
“You're right, was misremembering the stdlib. Totally agree with the port not returning a value via inference and then have a method/property to resolve the…”
“Reviewing stdlib, furl, purl, hyperlink, I don't see any prior art (and stdlib uses hostname as just the host component.) We might want to switch…”
Failure Signature (Search String)
- Requests fail to reach the intended host due to incorrect Host header formatting.
Copy-friendly signature
Failure Signature
-----------------
Requests fail to reach the intended host due to incorrect Host header formatting.
Error Message
Signature-only (no traceback captured)
Error Message
-------------
Requests fail to reach the intended host due to incorrect Host header formatting.
What Broke
Requests fail to reach the intended host due to incorrect Host header formatting.
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
Upgrade to version 0.7.5 or later.
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/417
First fixed release: 0.7.5
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- Do not apply this fix if the userinfo component is required for 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.
Version Compatibility Table
| Version | Status |
|---|---|
| 0.7.5 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.