Coding agents are most useful when the task has a clear boundary. "Improve the editor" is not a boundary. "Add autosave, preserve unsaved-change prompts, and do not change the document format" is one.
Xcode 27 makes planning a first-class part of the agent workflow. The plan appears as an editable Markdown artifact alongside the conversation, and the agent can collect project context before making changes. That makes the plan the handoff between product intent and implementation, not a polite preamble before an uncontrolled diff.
Start with constraints, not implementation guesses
Use the planning step for work that crosses more than one file, touches persistence, or could create a hard-to-see regression. State the behaviour to preserve, the files or systems that are in scope, and the checks that decide whether the work is complete.
A useful request has three parts:
- the user-visible outcome;
- the constraints that must remain true;
- the evidence required before the change is accepted.
For example, a request to add search can name the expected empty state, say that filtering must not mutate the source collection, and require the existing keyboard navigation tests to pass. It gives the agent something it can verify instead of asking it to infer product policy from the codebase.
/plan Add in-memory search to the article list.
Keep the original sort order when the query is empty.
Do not add a server dependency or change article URLs.
Include the files you expect to change, edge cases for an empty result,
and the checks you will run before implementation.The prompt does not need to prescribe a state object or a specific SwiftUI modifier. Leaving room for the agent to inspect the architecture is useful. The constraints are the part a reviewer should be unwilling to compromise.
Review the plan like a small design document
Before approving implementation, read the plan for omissions rather than for prose quality. A sound plan names the source of truth, notes any migration or compatibility impact, and separates data changes from view changes. It should also identify tests or manual verification that are proportional to the risk.
Ask follow-up questions directly on the plan when something is unclear:
- Which model owns the new state?
- What happens when the value is absent or stale?
- Does this alter a public type or persisted file format?
- Which test proves the previous behaviour still works?
In Xcode, plans can be annotated and revised before the agent proceeds. That is especially valuable for a SwiftUI change that looks local but affects navigation, observation, or preview setup several layers away.
Keep implementation and evidence visible together
Agent conversations now live in the editor, so a plan, the relevant source file, and the generated diff can sit in tabs or split panes. Keep the diff visible while the task runs. A tool call succeeding is not evidence that the implementation matches the plan.
Review additions in the same order that a maintainer would review a human change: data ownership first, public APIs next, UI behaviour after that, and generated files last. If a change expands past the approved scope, stop and update the plan instead of treating the extra files as a free improvement.
The artifacts view also makes screenshots and generated files available beside the conversation. Treat them as supporting evidence. A screenshot can show that a layout renders, but it cannot prove that state remains stable after relaunch or that an accessibility action is reachable.
Use parallel work for independent questions
The planning tool can investigate independent questions in parallel. This is a good fit for gathering context, such as locating existing localization conventions while another task maps the settings flow. It is a poor fit for two agents changing the same feature area at once.
Split research by responsibility, then make one implementation path responsible for the final diff. This avoids a common failure mode where two plausible edits make incompatible assumptions about ownership or naming.
Key takeaway
The best use of an agent plan is not to make a task sound detailed. It is to establish a reviewable contract before code changes begin. Write down the outcome, the constraints, and the proof of completion. Then use the plan to keep the diff honest.