starlette Consider moving to `request.kwargs` (Fix)

The Fix

Upgrade to version 0.13.4 or later.

Based on closed Kludex/starlette issue #127 · PR/commit linked

Open PR/Commit

@@ -19,7 +19,8 @@ def homepage(request):
 
 @app.route('/user/{username}')
-def user(request, username):
+def user(request):
+    username = request.path_params['username']

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 0.13.4 or later.\nWhen NOT to use: Do not use this fix if you require backward compatibility with existing endpoint signatures.\n\n

Why This Fix Works in Production

Trigger: Endpoints had inconsistent signatures, causing confusion and potential errors in handling requests.
Mechanism: The routing interface was inconsistent, using both **kwargs and explicit parameters
Why the fix works: Refines the routing interface by making path parameters accessible directly from the request object, simplifying endpoint signatures. (first fixed release: 0.13.4).

Why This Breaks in Prod

The routing interface was inconsistent, using both **kwargs and explicit parameters
Production symptom (often without a traceback): Endpoints had inconsistent signatures, causing confusion and potential errors in handling requests.

Proof / Evidence

GitHub issue: #127
Fix PR: https://github.com/kludex/starlette/pull/144
First fixed release: 0.13.4
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.80

Discussion

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

Jump to Sources Open on GitHub

“In both our function and class-based endpoints, we're currently using function signatures like: Which are sometimes expanded to include the actual path keyword arguments that are being routed, eg... I think we should possibly move against t”

Issue thread · issue description · source

Failure Signature (Search String)

Endpoints had inconsistent signatures, causing confusion and potential errors in handling requests.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Endpoints had inconsistent signatures, causing confusion and potential errors in handling requests.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Endpoints had inconsistent signatures, causing confusion and potential errors in handling requests.

What Broke

Endpoints had inconsistent signatures, causing confusion and potential errors in handling requests.

Why It Broke

The routing interface was inconsistent, using both **kwargs and explicit parameters

Fix Options (Details)

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

Upgrade to version 0.13.4 or later.

When NOT to use: Do not use this fix if you require backward compatibility with existing endpoint signatures.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/kludex/starlette/pull/144

First fixed release: 0.13.4

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

When NOT to Use This Fix

Do not use this fix if you require backward compatibility with existing endpoint signatures.

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.

Version Compatibility Table

Version	Status
0.13.4	Fixed

Related Issues

No related fixes found.

Cluster: starlette:webhook All hubs All clusters

Related clusters: Configuration error Data consistency SSL handshake

Sources

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