Plan Mode & Ultraplan
In Claude Code, managing the boundary between Analysis and Action is handled through specialized modes and commands. This architecture ensures safety and architectural integrity in Spec-Driven Development.
Permission Modes
1. Plan Mode
- Command:
/planorShift + Tab - Behavior: Read-Only. Claude can read files, search the web, and browse the codebase but cannot write files or execute shell commands.
- Use Case: Researching legacy code, drafting implementation strategies, and identifying dependencies.
2. Normal Mode
- Behavior: Semi-Autonomous. Claude proposes edits and command executions, but requires explicit human approval for every individual action.
- Use Case: Targeted, small-scale bug fixes or UI tweaks where high oversight is required.
3. Act Mode (Auto-Accept)
- Behavior: Autonomous. Claude is authorized to execute a series of tasks without interruption.
- Use Case: Executing a previously approved plan or performing routine maintenance.
Ultraplan (/ultraplan)
Ultraplan is an advanced planning command that offloads complex reasoning to a remote environment.
Workflow
- Trigger: Developer runs
/ultraplan <feature_request>. - Provisioning: Claude Code spins up a remote cloud container and clones the project’s GitHub repository.
- Synthesis: A high-reasoning model analyzes the codebase and requirements to generate a multi-step implementation plan.
- Review: The developer reviews the plan in a dedicated browser-based UI, adding comments or requesting revisions.
- Sync: The finalized plan is synced back to the local terminal for execution.
Advantages
- Terminal Freedom: Local development is not blocked while the plan is being generated.
- Extended Thinking: Utilizes models with larger reasoning budgets.
- Persistence: Plans are documented and can be versioned alongside the code.
Plan Mode + SubAgent Architecture
A powerful workflow combines Plan Mode and SubAgents:
- Enter Plan Mode to research and draft a task decomposition.
- Review the decomposed task list.
- Switch to Act Mode; the orchestrator dispatches one SubAgent per task.
- SubAgents execute in isolation; parent context stays clean.
This pattern is the production-grade replacement for running all tasks sequentially in a single session, which causes context window bloat.
Integrating with SDD
Plan Mode is the primary tool for the Plan and Decompose phases of Spec-Driven Development.
| SDD Phase | Claude Code Feature |
|---|---|
| Specify | Human-led (using /plan for context) |
| Plan | /plan or /ultraplan |
| Decompose | /ultraplan task list |
| Implement | Act Mode |
| Validate | /plan (referencing spec.md) |