httpx AnyIO is missing in "Supported async environments"

The Fix

Upgrade to version 0.18.2 or later.

Based on closed encode/httpx issue #1419 · PR/commit linked

Open PR/Commit

@@ -190,6 +190,29 @@ curio.run(main)
     The `curio` package must be installed to use the Curio backend.
 
+
+### [AnyIO](https://github.com/agronholm/anyio)
+

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 0.18.2 or later.\nWhen NOT to use: This fix is not applicable if the documentation is already updated.\n\n

Why This Fix Works in Production

Trigger: AnyIO is missing in "Supported async environments"
Mechanism: Documentation for AnyIO support in HTTPX was missing
Why the fix works: Added documentation for AnyIO under supported async environments in HTTPX. (first fixed release: 0.18.2).

Why This Breaks in Prod

Documentation for AnyIO support in HTTPX was missing
Production symptom (often without a traceback): AnyIO is missing in "Supported async environments"

Proof / Evidence

GitHub issue: #1419
Fix PR: https://github.com/encode/httpx/pull/1673
First fixed release: 0.18.2
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.79

Discussion

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

Jump to Sources Open on GitHub

“HTTPCore has support for anyio, but we don't document it yet: https://www.python-httpx.org/async/#supported-async-environments IMO there are two things to document: * HTTPX can work with programs that run under anyio, since it'll auto-detec”

Issue thread · issue description · source

Failure Signature (Search String)

AnyIO is missing in "Supported async environments"

Copy-friendly signature

signature.txt

Failure Signature
-----------------
AnyIO is missing in "Supported async environments"

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
AnyIO is missing in "Supported async environments"

What Broke

Users were unaware that HTTPX supports AnyIO, leading to confusion.

Why It Broke

Documentation for AnyIO support in HTTPX was missing

Fix Options (Details)

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

Upgrade to version 0.18.2 or later.

When NOT to use: This fix is not applicable if the documentation is already updated.

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/1673

First fixed release: 0.18.2

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

When NOT to Use This Fix

This fix is not applicable if the documentation is already updated.

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
0.18.2	Fixed

Related Issues

No related fixes found.

Cluster: httpx:other All hubs All clusters

Related clusters: Configuration error Data consistency Timeout

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

httpx AnyIO is missing in "Supported async environments" (Fix)