Composer

Composer groups related changes across multiple files into a session you review as a unified diff, then apply or reject atomically. Uses the compose_files tool.

When the agent reaches for it

Agent mode picks Composer when work is genuinely multi-file:

Scaffold a new feature (component + tests + types + styles)
Refactor a function signature + update all callers
Apply a pattern consistently across the codebase
Create or restructure boilerplate

You don’t invoke Composer directly — the agent decides.

Tool shape

{
  "files": [
    {
      "filePath": "src/auth/login.ts",
      "mode": "replace",
      "search": "function login(user: string)",
      "content": "function login(user: string, mfa?: string)"
    },
    {
      "filePath": "src/auth/login.test.ts",
      "mode": "replace",
      "search": "login('admin')",
      "content": "login('admin', '123456')"
    },
    {
      "filePath": "src/types/auth.ts",
      "mode": "overwrite",
      "content": "export interface LoginOptions { user: string; mfa?: string; }"
    }
  ]
}

Modes:

Mode	Behavior
`overwrite`	Replace the entire file content (or create a new file)
`replace`	Find the `search` string in the file and replace with `content`

Review panel

After the tool call, the Composer panel opens in the sidebar with:

Session status badge (active / applied / rejected / partial)
Each file with an expandable diff view
Per-file and whole-session actions

Diff uses DiffReviewService — same syntax-highlighted inline diff as Diff Review.

Actions:

Action	Effect
Apply session	Writes all file changes to disk
Reject session	Discards everything; no files modified
Partial	Apply some files, reject others → session status becomes `partial`

Session lifecycle

stateDiagram-v2 [*] --> active : compose_files call active --> review : Diff panel open review --> applied : Apply all review --> rejected : Discard all review --> partial : Apply some, reject others

Sessions managed by ComposerService, persisted for the editor window’s lifetime. Each has a unique ID and tracks per-file status independently.

Commands

Command	Effect
`CodeBuddy: Review Composer Session`	Open the diff panel for the current session
`CodeBuddy: Apply Composer Session`	Apply all pending changes to disk
`CodeBuddy: Reject Composer Session`	Discard all pending changes

Tips

Large refactors — ask “refactor X and update all references”; the agent will use Composer naturally.
Review before applying — the diff panel shows exactly what will change. Especially for overwrite mode.
Partial applies — if most changes look good but one file needs work, apply the good, reject the bad, ask the agent to fix just that file.

Diff review — the underlying diff engine
Tools — compose_files in the full tool list