flask Define reloader extra_files in `flask run` CLI (Fix)

The Fix

Upgrade to version 1.0.3 or later.

Based on closed pallets/flask issue #2897 · 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%.

Open PR/Commit

@@ -49,6 +49,9 @@ Unreleased
 -   Signaling support has a stub for the ``connect_via`` method when
     the Blinker library is not installed. :pr:`3208`
+-   Add an ``--extra-files`` option to the ``flask run`` CLI command to
+    specify extra files that will trigger the reloader on change.
+    :issue:`2897`

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 1.0.3 or later.\nWhen NOT to use: Do not use this fix if you do not require additional file watching.\n\n

Why This Fix Works in Production

Trigger: The reloader does not watch additional files for changes, leading to missed updates.
Mechanism: Added an `--extra-files` option to the `flask run` CLI command to specify extra files that will trigger the reloader on change.
Why the fix works: Added an `--extra-files` option to the `flask run` CLI command to specify extra files that will trigger the reloader on change. (first fixed release: 1.0.3).

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

Production symptom (often without a traceback): The reloader does not watch additional files for changes, leading to missed updates.

Proof / Evidence

GitHub issue: #2897
Fix PR: https://github.com/pallets/flask/pull/2898
First fixed release: 1.0.3
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.68

Discussion

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

Jump to Sources Open on GitHub

“i believe adding a argument/cli option for the extra files should fit the expectations well i'd like @davidism 's input on this as well”

@RonnyPfannschmidt · 2018-08-31 · source

“I can provide a Pull Request to add this, just let me know what you think about it.”

@rochacbruno · 2018-08-31 · source

Failure Signature (Search String)

The reloader does not watch additional files for changes, leading to missed updates.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
The reloader does not watch additional files for changes, leading to missed updates.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
The reloader does not watch additional files for changes, leading to missed updates.

What Broke

The reloader does not watch additional files for changes, leading to missed updates.

Fix Options (Details)

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

Upgrade to version 1.0.3 or later.

When NOT to use: Do not use this fix if you do not require additional file watching.

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

Fix reference: https://github.com/pallets/flask/pull/2898

First fixed release: 1.0.3

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

When NOT to Use This Fix

Do not use this fix if you do not require additional file watching.

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
1.0.3	Fixed

Related Issues

No related fixes found.

Cluster: flask:configuration-error All hubs All clusters

Related clusters: Data consistency Other Duplicate processing

Sources

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