flask CHANGES.rst on master is not UTF-8 -- appares to be

The Fix

Upgrade to version 1.0.3 or later.

Based on closed pallets/flask issue #3279 · 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

@@ -7,81 +7,81 @@ Unreleased
 -   Bump minimum Werkzeug version to >= 0.15.
 -   Drop support for Python 3.4.
--   Error handlers for ��InternalServerError�� or ��500�� will always be
-    passed an instance of ��InternalServerError��. If they are invoked
+-   Error handlers for ``InternalServerError`` or ``500`` will always be

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 1.0.3 or later.\nWhen NOT to use: This fix is not applicable if the file is already UTF-8 encoded.\n\n

Why This Fix Works in Production

Trigger: CHANGES.rst on master is not UTF-8 -- appares to be some windows encoding
Mechanism: Makes the changelog UTF-8 compatible by replacing non-UTF-8 characters.
Why the fix works: Makes the changelog UTF-8 compatible by replacing non-UTF-8 characters. (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): CHANGES.rst on master is not UTF-8 -- appares to be some windows encoding

Proof / Evidence

GitHub issue: #3279
Fix PR: https://github.com/pallets/flask/pull/3281
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: 0.64

Discussion

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

Jump to Sources Open on GitHub

“oops, looks like someone wrote this file on windows! I'll fix it to be UTF-8 (my editor was very unhappy trying to edit it!)”

Issue thread · issue description · source

Failure Signature (Search String)

CHANGES.rst on master is not UTF-8 -- appares to be some windows encoding

Copy-friendly signature

signature.txt

Failure Signature
-----------------
CHANGES.rst on master is not UTF-8 -- appares to be some windows encoding

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
CHANGES.rst on master is not UTF-8 -- appares to be some windows encoding

What Broke

Users experienced issues editing the changelog file due to encoding errors.

Fix Options (Details)

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

Upgrade to version 1.0.3 or later.

When NOT to use: This fix is not applicable if the file is already UTF-8 encoded.

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/3281

First fixed release: 1.0.3

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

When NOT to Use This Fix

This fix is not applicable if the file is already UTF-8 encoded.

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.

flask CHANGES.rst on master is not UTF-8 -- appares to be some windows encoding (Fix)