Cursor Composer vs Agent mode: when to use which

Cursor's Composer (introduced 2024) and Agent mode (added shortly after) look similar from the chat panel. They optimize for different workflows. Picking the right one per task is a real productivity gain.

This is the practical decision tree from running both daily.

TL;DR

• Composer for multi-file edits where you want to review each change before it lands.
• Agent for delegated tasks where you trust the agent to run tools and report back.
• Cmd+K inline for single-file single-edit (unchanged).

What each one is

Composer

Multi-file edit assistant with explicit approval per change.

Workflow:

1. Open Composer (Cmd+I or via the panel).
2. Describe the change in natural language.
3. Cursor proposes diffs across multiple files.
4. You review each file's diff, approve or reject individually.
5. Approved diffs land in the editor.

Composer doesn't run terminal commands or do open-ended exploration. It's a focused edit-proposal tool.

Agent mode

Autonomous task runner that can read files, run terminal commands, edit, and iterate.

Workflow:

1. Open Agent (Cmd+L or panel).
2. Describe the task.
3. Agent decides what to read, what to change, what tools to invoke.
4. Agent reports progress as it goes.
5. You can stop mid-flight or let it complete.
6. Final state is in the editor; review and commit.

Agent is for tasks where you don't want to babysit each step.

Cmd+K inline (for context)

Not part of this comparison but worth mentioning: Cmd+K does single-file inline edit. You highlight code, Cmd+K, prompt, accept the diff. Faster than Composer for simple edits in one file.

When to use Composer

Coordinated multi-file edit

"Add a new prop disabled to the Button component, update its TypeScript types, update the storybook story, and update tests."

This touches 4 files. The edits are coordinated (the prop name has to match across all four). Composer is right because:

• You want to see all 4 changes before any lands.
• You want to verify the prop name is consistent.
• You don't need exploration — you know exactly what to change.

Refactor with predictable shape

"Extract this auth logic from users-controller.ts into a new file auth-helpers.ts."

Predictable: split one file into two. Composer proposes the diffs; you confirm both.

When you want explicit control

If the codebase is sensitive (production code, security-critical), Composer's per-change approval gives you the audit trail. Agent might run a sed-like transformation across files; Composer makes you confirm each.

Short multi-file work

Anything under ~30 minutes of expected agent time. Composer keeps you engaged; Agent is overkill.

When to use Agent

Investigation + change

"The flaky test in tests/auth/login.test.ts is failing. Investigate and fix."

This requires exploration (read the test, read what it tests, hypothesize). Composer can't do this — it can only propose edits to files you specify. Agent can.

Multi-step with unknown shape

"Migrate all usages of the old request library to fetch. Find them first."

You don't know how many files yet. Agent searches, finds, edits. Composer would require you to pre-list the files.

Delegated work

"Set up a basic Express server with /health, /version endpoints, and write Jest tests for both."

You don't want to watch each file get created. Agent does the whole thing; you review when done.

Long-running tasks (with caveats)

For tasks expected to take >30 minutes, Agent's autonomy is needed (you don't want to approve 50 separate diffs). However, Cursor's Agent blocks the editor — for genuinely long tasks (hours), Claude Code in a terminal is better because it doesn't block your editing flow.

When to use neither (just Cmd+K)

For single-file, single-edit, in-flow:

"Refactor this function to use async/await instead of promises."

Highlight the function. Cmd+K. Prompt. Accept. Done in 30 seconds.

Composer is overkill (only one file). Agent is overkill (no exploration needed).

A decision tree

Task in scope:
│
├── Single file, single edit, you know the change?
│   → Cmd+K inline
│
├── Multiple files, coordinated edits, you know the files?
│   → Composer
│
├── Investigation + change, unknown scope?
│   → Agent
│
├── Multi-step, you don't want to watch?
│   → Agent (or Claude Code if expected to take >30 min)
│
└── Long-running, complex, multi-hour?
    → Claude Code in a terminal (Cursor's Agent blocks editor)

Concrete examples

Example 1: change a function signature

"Add a third parameter options: AuthOptions to loginUser in auth/login.ts. Update all callers."

Approach: Composer (multi-file, but the shape is predictable — you know it's the function and its callers).

If the callers number is unknown across many files, Agent might be better (let it find the callers).

Example 2: bug investigation

"Users report login sometimes fails with a 500. Find the cause."

Agent. Investigation-heavy, no specific files in mind.

Example 3: write a script

"Write a script in scripts/ that takes a folder and outputs a CSV of file sizes."

Either works. If you have a strong opinion on file structure → Composer. If you want it done with minimal input → Agent.

Example 4: convert TypeScript types

"Convert these JSDoc types in lib/types.js to TypeScript in lib/types.ts."

Composer. Specific files, specific transformation, you want to see the result before it lands.

What Composer doesn't do well

For balance:

Open-ended exploration

Composer needs you to tell it what files to look at. It won't go discover files in your repo it doesn't have open.

Long-running tasks

Composer's flow is conversational; long tasks become tedious approvals.

Tool invocation

Composer doesn't run terminal commands or invoke tests. If your task needs "run npm test, fix what fails, repeat," use Agent.

What Agent doesn't do well

Sensitive edits without review

Agent applies changes autonomously. You review at the end. For production-critical code, this is more risk than Composer's per-change approval.

Very long tasks (>1 hour)

Agent blocks the editor. You can't keep working in Cursor while Agent runs a 2-hour migration. Use Claude Code in a separate terminal for genuinely long tasks.

Tasks that need very specific output

If your task is "produce exactly this diff," Composer is better — it shows you the diff and you accept. Agent might decide on a different approach.

File-manager setup

For users running Cursor + agent workflows, mq-dir's quad-pane works:

• Pane 1: project root.
• Pane 2: artifacts/notes.
• Pane 3: cmux pane (for Claude Code if you also use it for long tasks).
• Pane 4: scratch.

Composer and Agent both run inside Cursor; you don't need mq-dir to invoke them. mq-dir is helpful for navigating the broader work the agent produces (artifacts, notes, related files) while Cursor handles the active edit.

Verdict

Cursor's Composer and Agent serve different workflows:

• Composer: multi-file, coordinated, you-know-the-files, want-explicit-approval.
• Agent: investigation, delegation, multi-step, autonomous.
• Cmd+K: single-file in-flow.

Most users default to Cmd+K (fast, low friction), escalate to Composer for multi-file changes, escalate to Agent for investigation.

For very long tasks (>1 hour), step out of Cursor entirely and use Claude Code in a terminal session. Cursor's Agent blocks the editor; Claude Code lets you keep working.

The right combination is task-dependent. After a few days of using both deliberately, the choice becomes automatic.

mq-dir pairs with any Cursor workflow as the GUI navigation layer; the agent decisions happen in Cursor itself.