uvicorn process stop after any exception with developing

The Fix

Upgrade to version 0.17.0 or later.

Based on closed Kludex/uvicorn issue #1295 · 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

@@ -122,21 +122,6 @@ def test_cli_incomplete_app_parameter() -> None:
 
 
-def test_cli_reloader_incomplete_app_parameter(
-    capfd: pytest.CaptureFixture[str],
-) -> None:

repro

the bug

verify

Follow the reproduction steps, confirm the failure, apply the fix, and repeat the same steps to verify the behavior changes.

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 0.17.0 or later.\nWhen NOT to use: This fix is not suitable if you require immediate process termination on errors.\n\n

Why This Fix Works in Production

Trigger: process stop after any exception with developing with reload feature
Mechanism: The reload process exits unexpectedly when an exception occurs during startup
Why the fix works: Fixes the reload process behavior when an exception is raised, ensuring the server does not exit unexpectedly. (first fixed release: 0.17.0).

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

Shows up under Python 3.8 in real deployments (not just unit tests).
The reload process exits unexpectedly when an exception occurs during startup
Production symptom (often without a traceback): process stop after any exception with developing with reload feature

Proof / Evidence

GitHub issue: #1295
Fix PR: https://github.com/encode/uvicorn/pull/1313
First fixed release: 0.17.0
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

“watchgod support executing a function after any fs event. Add a new flag like --dev and add a thin wrapper to dispatch other flag like…”

@trim21 · 2021-12-18 · source

“After checking changes between 0.15.0 and 0.16.0, looks like it's expected behavior now? https://github.com/encode/uvicorn/pull/1278 But it brings a realy bad user experience”

@trim21 · 2021-12-17 · source

“That PR doesn't change what you described. But I'm aware of the PR you're talking about (I'm on my phone, so I'll not search for…”

@Kludex · 2021-12-17 · source

“I understand your issue, and I think it's a valid point. Let's see if we can find a solution that satisfies this issue, and can…”

@Kludex · 2021-12-18 · source

Failure Signature (Search String)

process stop after any exception with developing with reload feature
edit your server.py with any change with it raise a error when startup

Copy-friendly signature

signature.txt

Failure Signature
-----------------
process stop after any exception with developing with reload feature
edit your server.py with any change with it raise a error when startup

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
process stop after any exception with developing with reload feature
edit your server.py with any change with it raise a error when startup

Minimal Reproduction

the bug

Environment

Python: 3.8

What Broke

Uvicorn process exits instead of waiting for reload after an exception, disrupting development.

Why It Broke

The reload process exits unexpectedly when an exception occurs during startup

Fix Options (Details)

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

Upgrade to version 0.17.0 or later.

When NOT to use: This fix is not suitable if you require immediate process termination on errors.

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

Fix reference: https://github.com/encode/uvicorn/pull/1313

First fixed release: 0.17.0

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

When NOT to Use This Fix

This fix is not suitable if you require immediate process termination on errors.

Verify Fix

verify

Follow the reproduction steps, confirm the failure, apply the fix, and repeat the same steps to verify the behavior changes.

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

Make timeouts explicit and test them (unit + integration) to avoid silent behavior changes.
Instrument retries (attempt count + reason) and alert on spikes to catch dependency slowdowns.

Version Compatibility Table

Version	Status
0.17.0	Fixed

Related Issues

No related fixes found.

Cluster: uvicorn:configuration-error All hubs All clusters

Related clusters: Data consistency Race condition SSL handshake

Sources

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

uvicorn process stop after any exception with developing with reload feature (Fix)