fission-ai__openspec/openspec/changes/add-antigravity-support/proposal.md

Why

Google is rolling out Antigravity, a Windsurf-derived IDE that discovers workflows from .agent/workflows/*.md. Today OpenSpec can only scaffold slash commands for Windsurf directories, so Antigravity users cannot run the proposal/apply/archive flows from the IDE.

What Changes

• Add Antigravity as a selectable native tool in openspec init so it creates .agent/workflows/openspec-proposal.md, openspec-apply.md, and openspec-archive.md with YAML frontmatter containing only a description field plus the standard OpenSpec-managed body.
• Ensure openspec update refreshes the body of any existing Antigravity workflows inside .agent/workflows/ without creating missing files, mirroring the Windsurf behavior.
• Share e2e/template coverage confirming the generator writes the proper directory, filename casing, and frontmatter format so Antigravity picks up the workflows.

Impact

• Affected specs: specs/cli-init, specs/cli-update
• Expected code: CLI init/update tool registries, slash-command templates, associated tests