bl_info Migration to the Extensions Platform

Trigger

Use this skill when the user:

Has an existing add-on with a bl_info = {...} dictionary at the top of __init__.py
Wants to publish to extensions.blender.org or distribute as a .zip for the Extensions Platform
Asks "is bl_info dead?" or "do I have to migrate?"
Sees a deprecation warning at install time about legacy add-ons
Mentions blender_manifest.toml, "Install legacy Add-on", or "the new extension system"

Yes, with caveats.

In 5.1 stable: bl_info is supported as a fallback for legacy add-ons. The Edit > Preferences > Add-ons panel still has "Install legacy Add-on" and recognizes bl_info dicts.
For the Extensions Platform (extensions.blender.org and the new add-ons UI): you need a blender_manifest.toml. bl_info is ignored.
Dual format is officially recognized: ship a blender_manifest.toml and keep the bl_info dict. The platform reads the manifest; legacy installers read bl_info. Both code paths work without conditional logic.