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httpx AttributeError: 'AsyncLock' object has no attribute '_anyio_lock' (Fix)

Fixed
Spec
Package
httpx
Fixed In
0.25.1
Verdict
Status
Fixed
Safe for prod
No
Risk
Medium
Last verified
2026-02-09
Own content ratio
0.25
#2890 ai auth Updated: 2026-02-13
Issue #2890

The Fix

Upgrade to version 0.25.1 or later.

Based on closed encode/httpx issue #2890 · 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
@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/). * Add support for Python 3.12. (#2854) +* Add support for httpcore 1.0 (#2885) ### Fixed
repro.py
(.venv) E:\hcore1>python app.py Traceback (most recent call last): File "E:\hcore1\app.py", line 6, in main r = await client.get('https://www.example.com/') ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1757, in get return await self.request( ^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1530, in request return await self.send(request, auth=auth, follow_redirects=follow_redirects) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1617, in send response = await self._send_handling_auth( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1645, in _send_handling_auth response = await self._send_handling_redirects( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1682, in _send_handling_redirects response = await self._send_single_request(request) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1719, in _send_single_request response = await transport.handle_async_request(request) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_transports\default.py", line 366, in handle_async_request resp = await self._pool.handle_async_request(req) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpcore\_async\connection_pool.py", line 224, in handle_async_request async with self._pool_lock: File "E:\hcore1\.venv\Lib\site-packages\httpcore\_synchronization.py", line 62, in __aenter__ self.setup() File "E:\hcore1\.venv\Lib\site-packages\httpcore\_synchronization.py", line 55, in setup raise RuntimeError( RuntimeError: Running with asyncio requires installation of 'httpcore[asyncio]'. During handling of the above exception, another exception occurred: Traceback (most recent call last): File "E:\hcore1\app.py", line 8, in <module> asyncio.run(main()) File "C:\Users\Tester\.rye\py\[email protected]\install\Lib\asyncio\runners.py", line 194, in run return runner.run(main) ^^^^^^^^^^^^^^^^ File "C:\Users\Tester\.rye\py\[email protected]\install\Lib\asyncio\runners.py", line 118, in run return self._loop.run_until_complete(task) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Tester\.rye\py\[email protected]\install\Lib\asyncio\base_events.py", line 664, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "E:\hcore1\app.py", line 5, in main async with httpx.AsyncClient() as client: File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 2003, in __aexit__ await self._transport.__aexit__(exc_type, exc_value, traceback) File "E:\hcore1\.venv\Lib\site-packages\httpx\_transports\default.py", line 345, in __aexit__ await self._pool.__aexit__(exc_type, exc_value, traceback) File "E:\hcore1\.venv\Lib\site-packages\httpcore\_async\connection_pool.py", line 327, in __aexit__ await self.aclose() File "E:\hcore1\.venv\Lib\site-packages\httpcore\_async\connection_pool.py", line 312, in aclose async with self._pool_lock: File "E:\hcore1\.venv\Lib\site-packages\httpcore\_synchronization.py", line 67, in __aenter__ await self._anyio_lock.acquire() ^^^^^^^^^^^^^^^^ AttributeError: ... (truncated) ...
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 0.25.1 or later.\nWhen NOT to use: This fix is not applicable if anyio is intentionally removed for compatibility reasons.\n\n

Why This Fix Works in Production

  • Trigger: (.venv) E:\hcore1>python app.py
  • Mechanism: The AsyncLock in httpcore lacks the required attributes when anyio is not installed
  • Why the fix works: Supports newer versions of httpcore, addressing compatibility issues with httpx. (first fixed release: 0.25.1).
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

  • The AsyncLock in httpcore lacks the required attributes when anyio is not installed
  • Surfaces as: (.venv) E:\hcore1>python app.py

Proof / Evidence

  • GitHub issue: #2890
  • Fix PR: https://github.com/encode/httpx/pull/2885
  • First fixed release: 0.25.1
  • Reproduced locally: No (not executed)
  • Last verified: 2026-02-09
  • Confidence: 0.85
  • Did this fix it?: Yes (upstream fix exists)
  • Own content ratio: 0.25

Discussion

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

Jump to Sources Open on GitHub
“Try install httpx + httpcore 1.0 then remove anyio. Error: _Originally posted by @T-256 in https://github.com/encode/httpx/pull/2885#discussion_r1356548422_”
Issue thread · issue description · source

Failure Signature (Search String)

  • (.venv) E:\hcore1>python app.py

Error Message

Stack trace
error.txt
Error Message ------------- (.venv) E:\hcore1>python app.py Traceback (most recent call last): File "E:\hcore1\app.py", line 6, in main r = await client.get('https://www.example.com/') ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1757, in get return await self.request( ^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1530, in request return await self.send(request, auth=auth, follow_redirects=follow_redirects) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1617, in send response = await self._send_handling_auth( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1645, in _send_handling_auth response = await self._send_handling_redirects( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1682, in _send_handling_redirects response = await self._send_single_request(request) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1719, in _send_single_request response = await transport.handle_async_request(request) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ... (truncated) ...

Minimal Reproduction

repro.py
(.venv) E:\hcore1>python app.py Traceback (most recent call last): File "E:\hcore1\app.py", line 6, in main r = await client.get('https://www.example.com/') ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1757, in get return await self.request( ^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1530, in request return await self.send(request, auth=auth, follow_redirects=follow_redirects) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1617, in send response = await self._send_handling_auth( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1645, in _send_handling_auth response = await self._send_handling_redirects( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1682, in _send_handling_redirects response = await self._send_single_request(request) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 1719, in _send_single_request response = await transport.handle_async_request(request) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpx\_transports\default.py", line 366, in handle_async_request resp = await self._pool.handle_async_request(req) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "E:\hcore1\.venv\Lib\site-packages\httpcore\_async\connection_pool.py", line 224, in handle_async_request async with self._pool_lock: File "E:\hcore1\.venv\Lib\site-packages\httpcore\_synchronization.py", line 62, in __aenter__ self.setup() File "E:\hcore1\.venv\Lib\site-packages\httpcore\_synchronization.py", line 55, in setup raise RuntimeError( RuntimeError: Running with asyncio requires installation of 'httpcore[asyncio]'. During handling of the above exception, another exception occurred: Traceback (most recent call last): File "E:\hcore1\app.py", line 8, in <module> asyncio.run(main()) File "C:\Users\Tester\.rye\py\[email protected]\install\Lib\asyncio\runners.py", line 194, in run return runner.run(main) ^^^^^^^^^^^^^^^^ File "C:\Users\Tester\.rye\py\[email protected]\install\Lib\asyncio\runners.py", line 118, in run return self._loop.run_until_complete(task) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\Tester\.rye\py\[email protected]\install\Lib\asyncio\base_events.py", line 664, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "E:\hcore1\app.py", line 5, in main async with httpx.AsyncClient() as client: File "E:\hcore1\.venv\Lib\site-packages\httpx\_client.py", line 2003, in __aexit__ await self._transport.__aexit__(exc_type, exc_value, traceback) File "E:\hcore1\.venv\Lib\site-packages\httpx\_transports\default.py", line 345, in __aexit__ await self._pool.__aexit__(exc_type, exc_value, traceback) File "E:\hcore1\.venv\Lib\site-packages\httpcore\_async\connection_pool.py", line 327, in __aexit__ await self.aclose() File "E:\hcore1\.venv\Lib\site-packages\httpcore\_async\connection_pool.py", line 312, in aclose async with self._pool_lock: File "E:\hcore1\.venv\Lib\site-packages\httpcore\_synchronization.py", line 67, in __aenter__ await self._anyio_lock.acquire() ^^^^^^^^^^^^^^^^ AttributeError: ... (truncated) ...

What Broke

Users experience AttributeError when attempting to make asynchronous requests without anyio.

Why It Broke

The AsyncLock in httpcore lacks the required attributes when anyio is not installed

Fix Options (Details)

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

Upgrade to version 0.25.1 or later.

When NOT to use: This fix is not applicable if anyio is intentionally removed for compatibility reasons.

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/2885

First fixed release: 0.25.1

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

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When NOT to Use This Fix

  • This fix is not applicable if anyio is intentionally removed for compatibility reasons.

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

VersionStatus
0.25.1 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.

Source & Disclaimer: Analysis derived from GitHub Issue #2890. Not affiliated with the library maintainers. Verify before production use.