> ## Documentation Index
> Fetch the complete documentation index at: https://docs.trysixth.com/llms.txt
> Use this file to discover all available pages before exploring further.

# /deep-planning Command

> Have Sixth investigate the codebase and write a full implementation plan before coding.

`/deep-planning` tells Sixth to understand your codebase thoroughly and produce a complete implementation plan **before writing any code**. Use it for features that touch many files, risky refactors, or anything where a wrong first step is expensive.

```
/deep-planning add multi-tenant support to the billing service
```

## The four steps

1. **Silent investigation.** Sixth reads the relevant source, configuration and docs, and runs read-only commands to map the project structure, definitions, imports, dependencies and existing TODOs. It doesn't change anything.
2. **Discussion.** Sixth asks only the questions it needs answered, such as unclear requirements, a choice between equally valid approaches, or assumptions about how the system behaves. Questions are brief and come one at a time.
3. **The plan document.** Sixth writes `implementation_plan.md` with these sections:
   * **Overview**: the goal, scope and overall approach
   * **Types**: new or changed types, interfaces and data structures
   * **Files**: files to create, modify, delete or move, including config
   * **Functions**: signatures, purpose and key details of new or changed functions
   * **Changes**: the step-by-step implementation order
   * **Tests**: unit and integration tests, test data and edge cases
4. **The implementation task.** Sixth uses `new_task` to start a fresh task that carries the plan and a step-by-step checklist (see [Focus Chain](/features/focus-chain)). The new task reads the plan section by section as it implements.

<Tip>Review `implementation_plan.md` before you approve the new task. Editing the plan is the cheapest point to change direction.</Tip>

## Related

* [Interactive Planning](/features/interactive-planning) (`/interactive-planning`): plans the task as an interactive flowchart before running it.
* [Plan & Act](/features/plan-and-act): switch to Plan mode to discuss an approach without a formal plan document.


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