httpx Document using a custom SSL Context (Fix)

The Fix

Upgrade to version 0.13.0 or later.

Based on closed encode/httpx issue #926 · 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%.

Jump to Verify Open PR/Commit

@@ -399,6 +399,22 @@ client = httpx.Client(timeout=timeout)
 ```
 
+## Pool limit configuration
+
+You can control the connection pool size using the `pool_limits` keyword

repro.py

>> import httpx
>> import ssl
>> import certifi
>> context = ssl.create_default_context()
>> context.load_verify_locations(cafile=certifi.where())
>> httpx.get('https://www.example.com', verify=context)
<Response [200 OK]>

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 0.13.0 or later.\nWhen NOT to use: This fix is not applicable if you do not require a custom SSL context.\n\n

Why This Fix Works in Production

Trigger: Document using a custom SSL Context
Mechanism: The documentation did not include examples for using a custom SSL context with HTTPX
Why the fix works: Documents the use of a custom SSL context in the HTTPX library, providing an example for users. (first fixed release: 0.13.0).

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

The documentation did not include examples for using a custom SSL context with HTTPX
Production symptom (often without a traceback): Document using a custom SSL Context

Proof / Evidence

GitHub issue: #926
Fix PR: https://github.com/encode/httpx/pull/942
First fixed release: 0.13.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.71

Discussion

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

Jump to Sources Open on GitHub

“Prompted by #924 Our SSL docs don't include any examples of using a custom SSL context. See: https://www.python-httpx.org/advanced/#ssl-certificates I think we ought to include a minimal example, such as...”

Issue thread · issue description · source

Failure Signature (Search String)

Document using a custom SSL Context
Our SSL docs don't include any examples of using a custom SSL context.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Document using a custom SSL Context
Our SSL docs don't include any examples of using a custom SSL context.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Document using a custom SSL Context
Our SSL docs don't include any examples of using a custom SSL context.

Minimal Reproduction

repro.py

>> import httpx
>> import ssl
>> import certifi
>> context = ssl.create_default_context()
>> context.load_verify_locations(cafile=certifi.where())
>> httpx.get('https://www.example.com', verify=context)
<Response [200 OK]>

What Broke

Users were unable to configure custom SSL contexts, leading to potential security issues.

Why It Broke

The documentation did not include examples for using a custom SSL context with HTTPX

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

Upgrade to version 0.13.0 or later.

When NOT to use: This fix is not applicable if you do not require a custom SSL context.

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/942

First fixed release: 0.13.0

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

This fix is not applicable if you do not require a custom SSL context.

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.
Add a TLS smoke test that performs a real handshake in CI (include CA bundle validation and hostname checks).
Alert on handshake failures by error string and endpoint to catch cert/CA changes quickly.

Version Compatibility Table

Version	Status
0.13.0	Fixed

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.