Bring Back Runtime Deprecation Warnings in MUI v6

Summary

The removal of runtime deprecation warnings in MUI v6 is a significant regression in developer experience.

Previously, deprecation warnings provided immediate, actionable feedback during development. They made it clear when APIs were outdated and guided developers toward the correct replacements in real time. This was especially valuable in large or evolving codebases where manually tracking breaking changes is impractical.

In v6, deprecated APIs continue to function silently, but there is no longer any indication that they are deprecated. This creates a situation where developers unknowingly accumulate technical debt and only discover issues later—often during upgrades or after behavior changes.

Relying solely on codemods and migration documentation is not an adequate replacement:

• Codemods are not comprehensive and do not cover all cases.
• Documentation requires developers to proactively search for issues they may not even realize exist.
• There is no built-in mechanism to surface deprecated usage during normal development workflows.

Deprecation warnings are a standard and expected part of modern developer tooling. Removing them without providing an equivalent real-time feedback mechanism makes upgrades more difficult and error-prone.

Please reintroduce deprecation warnings (or an equivalent opt-in mechanism) so developers can identify and address deprecated usage as they work, rather than after the fact.

Examples

No response

Motivation

No response

Search keywords: warnings

The issue names no implementation files, tests, or entry points. First clarify which deprecated APIs and warning mechanism are in scope, then locate the existing v6 deprecation handling and related tests. Done means deprecated usage again produces actionable runtime feedback, or an agreed opt-in equivalent, with coverage for the selected cases.