The Fix
Introduces middleware support for the aiohttp client, allowing users to intercept and modify requests and responses. This enables powerful use cases like authentication, logging, retries, and request/response modification.
Based on closed aio-libs/aiohttp issue #10903 · PR/commit linked
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+Added client middleware support -- by :user:`bdraco` and :user:`Dreamsorcerer`.
+
+This change allows users to add middleware to the client session and requests, enabling features like
Option A — Apply the official fix\nIntroduces middleware support for the aiohttp client, allowing users to intercept and modify requests and responses. This enables powerful use cases like authentication, logging, retries, and request/response modification.\nWhen NOT to use: Avoid using middleware for simple use cases where request parameters suffice.\n\n
Why This Fix Works in Production
- Trigger: Middleware support enhances client capabilities but may introduce complexity in request handling.
- Mechanism: This change allows users to add middleware to the client session and requests, enabling features like authentication, logging, and request/response modification
Why This Breaks in Prod
- This change allows users to add middleware to the client session and requests, enabling features like authentication, logging, and request/response modification
- Production symptom (often without a traceback): Middleware support enhances client capabilities but may introduce complexity in request handling.
Proof / Evidence
- GitHub issue: #10903
- Fix PR: https://github.com/aio-libs/aiohttp/pull/9732
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.80
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.83
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“> I think we will likely want to ship some common patterns”
“Ideally we get on for SSRF as well but we don't need that to ship”
Failure Signature (Search String)
- Middleware support enhances client capabilities but may introduce complexity in request handling.
Copy-friendly signature
Failure Signature
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Middleware support enhances client capabilities but may introduce complexity in request handling.
Error Message
Signature-only (no traceback captured)
Error Message
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Middleware support enhances client capabilities but may introduce complexity in request handling.
What Broke
Middleware support enhances client capabilities but may introduce complexity in request handling.
Why It Broke
This change allows users to add middleware to the client session and requests, enabling features like authentication, logging, and request/response modification
Fix Options (Details)
Option A — Apply the official fix
Introduces middleware support for the aiohttp client, allowing users to intercept and modify requests and responses. This enables powerful use cases like authentication, logging, retries, and request/response modification.
Fix reference: https://github.com/aio-libs/aiohttp/pull/9732
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- Avoid using middleware for simple use cases where request parameters suffice.
Did This Fix Work in Your Case?
Quick signal helps us prioritize which fixes to verify and improve.
Prevention
- Capture the exact failing error string in logs and tests so you can reproduce via a minimal script.
- Pin production dependencies and upgrade only with a reproducible test that hits the failing path.
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.