The Fix
Upgrade to version 0.16.0 or later.
Based on closed Kludex/uvicorn issue #693 · PR/commit linked
@@ -7,6 +7,13 @@ equivalent keyword arguments, eg. `uvicorn.run("example:app", port=5000, reload=
you should put `uvicorn.run` into `if __name__ == '__main__'` clause in the main module.
+You can also configure Uvicorn using environment variables with the prefix `UVICORN_`.
+For example, in case you want to run the app on port `5000`, just set the environment variable `UVICORN_PORT` to `5000`.
+
Option A — Upgrade to fixed release\nUpgrade to version 0.16.0 or later.\nWhen NOT to use: This fix is not suitable for static configurations that do not require dynamic changes.\n\n
Why This Fix Works in Production
- Trigger: Include a environment variable to change arg commands
- Mechanism: Uvicorn did not support reading configuration from environment variables
- Why the fix works: Enables Uvicorn to read settings from environment variables, allowing for dynamic configuration without rebuilding containers. (first fixed release: 0.16.0).
Why This Breaks in Prod
- Uvicorn did not support reading configuration from environment variables
- Production symptom (often without a traceback): Include a environment variable to change arg commands
Proof / Evidence
- GitHub issue: #693
- Fix PR: https://github.com/kludex/uvicorn/pull/1279
- First fixed release: 0.16.0
- Reproduced locally: No (not executed)
- Last verified: 2026-02-09
- Confidence: 0.95
- Did this fix it?: Yes (upstream fix exists)
- Own content ratio: 0.62
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“https://github.com/encode/uvicorn/blob/d9d7bc6b38d07a4187882a2d49d92f1640c2446c/uvicorn/__main__.py#L4 maybe instead of: use”
“reading click pypi, maybe something could be done here: https://click.palletsprojects.com/en/7.x/options/#values-from-environment-variables”
Failure Signature (Search String)
- Include a environment variable to change arg commands
- this is very usefull when using docker compose, or k8s. without rebuild the container i can change how it starts (more debug messages instead of only critical)
Copy-friendly signature
Failure Signature
-----------------
Include a environment variable to change arg commands
this is very usefull when using docker compose, or k8s. without rebuild the container i can change how it starts (more debug messages instead of only critical)
Error Message
Signature-only (no traceback captured)
Error Message
-------------
Include a environment variable to change arg commands
this is very usefull when using docker compose, or k8s. without rebuild the container i can change how it starts (more debug messages instead of only critical)
What Broke
Users had to rebuild containers to change Uvicorn's startup configuration.
Why It Broke
Uvicorn did not support reading configuration from environment variables
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
Upgrade to version 0.16.0 or later.
Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.
Fix reference: https://github.com/kludex/uvicorn/pull/1279
First fixed release: 0.16.0
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- This fix is not suitable for static configurations that do not require dynamic changes.
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 |
|---|---|
| 0.16.0 | Fixed |
Related Issues
No related fixes found.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.