The Fix
Upgrade to version 0.7.3 or later.
Based on closed encode/httpx issue #318 · 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%.
@@ -148,7 +148,7 @@ def redirect_headers(self, request: AsyncRequest, url: URL, method: str) -> Head
# the origin.
del headers["Authorization"]
- del headers["Host"]
+ headers["Host"] = url.authority
Option A — Upgrade to fixed release\nUpgrade to version 0.7.3 or later.\nWhen NOT to use: Do not use this fix if the application relies on the original Host header for routing.\n\n
Why This Fix Works in Production
- Trigger: Requests to redirected URLs failed due to missing Host header, causing potential connectivity issues.
- Mechanism: Away-from-origin redirects were removing the Host header instead of setting it to the new URL authority
- Why the fix works: Sets the Host header to the URL authority when redirecting away from the origin, addressing issue #318. (first fixed release: 0.7.3).
- 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
- Away-from-origin redirects were removing the Host header instead of setting it to the new URL authority
- Production symptom (often without a traceback): Requests to redirected URLs failed due to missing Host header, causing potential connectivity issues.
Proof / Evidence
- GitHub issue: #318
- Fix PR: https://github.com/encode/httpx/pull/321
- First fixed release: 0.7.3
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.85
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.76
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“@gdhameeja Consider the task yours :) Thanks for taking this on!”
Failure Signature (Search String)
- Requests to redirected URLs failed due to missing Host header, causing potential connectivity issues.
Copy-friendly signature
Failure Signature
-----------------
Requests to redirected URLs failed due to missing Host header, causing potential connectivity issues.
Error Message
Signature-only (no traceback captured)
Error Message
-------------
Requests to redirected URLs failed due to missing Host header, causing potential connectivity issues.
What Broke
Requests to redirected URLs failed due to missing Host header, causing potential connectivity issues.
Why It Broke
Away-from-origin redirects were removing the Host header instead of setting it to the new URL authority
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
Upgrade to version 0.7.3 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/321
First fixed release: 0.7.3
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- Do not use this fix if the application relies on the original Host header for routing.
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 |
|---|---|
| 0.7.3 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.