Claude Code Ultraplan: Plan, Review, and Hand Off the Work

Claude Code Ultraplan is a planning mode that directs Claude Code to think through an implementation in more depth before writing a line of code. Instead of moving directly from your instruction to a change, it produces a structured plan: the steps, the files affected, the tradeoffs, and the checks needed before finishing.

A plan is only useful if a person reviews it. The steps and tradeoffs an extended thinking pass produces still need human judgment before becoming instructions. Tools like fenbs keep the reviewed plan and the decisions behind it, so the session that actually implements the work begins from an approved starting point.

What is Claude Code Ultraplan?

Ultraplan activates the extended thinking capability available on Claude's higher-tier plans. In planning mode, Claude Code applies more computation to the problem before responding, which typically produces a more thorough breakdown of the task: corner cases it would otherwise miss, dependencies between steps, and explicit assumptions that are worth confirming.

The extended thinking happens before Claude Code touches any file. The output is a plan, not code. You read it, adjust it, and approve it before telling Claude Code to proceed. This is the key difference from a standard session: you have a checkpoint between the plan and the implementation.

How do you access Ultraplan?

Use the /ultraplan command followed by your task description. Anthropic's Claude Code documentation↗ (opens in a new tab) describes the available slash commands and which plan levels include extended thinking. Check your current plan before expecting Ultraplan behavior; it is not available on all tiers.

/ultraplan Add rate limiting to the API endpoints.

The result is a written plan, not code. Claude Code will wait for your confirmation before implementing. Use that pause to review what it intends to do.

What should you check before accepting the plan?

Extended thinking produces a more detailed plan, but it does not make the plan correct. Read it as you would read a proposal from a capable but fallible colleague.

• Scope. Does the plan stay inside the task boundary, or does it propose changes you did not ask for? Reject additions that are outside the agreed scope, even if they seem sensible.
• Assumptions. The plan will state or imply assumptions about the codebase, the environment, or the requirements. Check each one against what you actually know.
• Missing checks. What does the plan say should be verified? What does it leave out? Add explicit test steps for any behavior the plan touches but does not cover.
• Decisions that need a person. If the plan reaches a point where two valid approaches exist, that is a choice for you, not for Claude Code to resolve alone. Mark it and decide before proceeding.

How do you turn the plan into implementation safely?

Once you have reviewed and adjusted the plan, confirm it clearly before Claude Code implements it. "Proceed with this plan as written" is unambiguous. If you changed a step during review, restate the amended plan so Claude Code works from your version, not its original output.

For larger plans, consider breaking the implementation into stages. Ask Claude Code to complete the first stage and pause for review before continuing. The Claude Code checkpoints guide covers saving state at each stage so you can restore if a later step goes wrong.

After each stage, ask Claude Code to summarize what it did and compare that summary with the corresponding plan step before approving the next one. A stage that produced something different from the plan is a reason to pause and align, not to continue automatically.

How do you hand off a plan that takes more than one session?

An Ultraplan output can be long, and implementation may span several sessions or involve a teammate. The plan itself is ephemeral; once the session window closes, it is gone unless you saved it. Copy the reviewed and approved plan into a task plan before implementation begins.

Where we left off in fenbs records which stages are complete, what was verified at each stage, and what the next session should pick up. A teammate or a different AI session can start from a clear position rather than re-reading a closed transcript.

How to do this with fenbs

1. Create a free account and open the task you are planning with Ultraplan.
2. Run /ultraplan with your task description and read the full output before approving anything.
3. Copy the reviewed and approved plan into the fenbs task plan field. Note any changes you made during review as decisions.
4. Tell Claude Code to proceed. Ask it to pause after each stage and save progress to fenbs before continuing to the next.
5. Record any choices made during implementation — an approach selected over an alternative — as decisions in fenbs so the reason is available to future sessions.

fenbs does not run Ultraplan or control Claude Code's planning mode. It keeps the approved plan and the decisions it produced. For understanding how Claude Code behaves during a standard planning session before extended thinking, the Claude Code plan mode guide is the starting point. See also Claude Code update to confirm your version supports extended thinking.