Plan mode can use a Claude Doc as the plan you approve

Plan mode is a mode where Claude works out a plan first and waits for your approval before changing anything. Claude ends it with the ExitPlanMode tool. Before, the plan was always passed as text or a plan file.

When a Claude Doc service is available, a Claude Doc being a document shown beside the chat, Claude is now told to write or revise the plan in a Claude Doc. While planning, the only writes allowed are to that Doc. Then:

• You approve the plan on an approval card that says the plan is the Doc.
• Claude calls ExitPlanMode with nothing attached.
• Claude carries out the Doc as it reads at the moment you approve, and is told to read it again before starting work.

There are also new error messages for cases such as a missing Doc, a Doc plan sent together with extra plan text, and ending up with two Docs. Without a Doc service, plan mode works as before. The tool's own description was unchanged in the prompt capture taken under this release.