Plan Mode separates research from execution in Claude Code¶
Insight: Plan Mode (Shift+Tab or /plan command) restricts Claude to read-only tools (Read, LS, Glob, Grep, Task, WebFetch, WebSearch) while blocking all modification tools (Edit, Write, Bash, MCP state changes). This forces consistently formatted, reasonably verbose planning output before any code changes are executed.
Detail: Opus Plan Mode (with Opus 4.6) introduces interactive planning with 1M context: Claude asks clarifying questions, creates plan.md files with task breakdown and dependencies, the user reviews/edits, then execution proceeds using Sonnet 4.5. The Plan Subagent Architecture (v2.0.28+) enables dynamic model selection and subagent resumption. An Explore Subagent (Haiku-powered) handles efficient codebase search. Plan files can be stored in a configurable directory via plansDirectory setting.
Sources
- ClaudeLog by InventorBlack — "Plan Mode" (2026-02-05)
Related: existing entry "Read-before-write and plan-before-code patterns" in external/claude-code.md — COMPLEMENTS