Feature Request: Support external editor for file editing operations

Feature Request: Support External Editor for File Editing

Problem

The EDITOR environment variable in ~/.claude/settings.json currently only affects bash commands that spawn editors (like git commit), but does not control how Claude Code edits files when using the Edit/Write tools or when editing agent/subagent markdown definitions.

Current Behavior

• Setting "env": { "EDITOR": "vscode --wait" } in settings.json works for bash subprocesses
• Claude Code uses internal Edit/Write tools that directly modify files
• No way to open files in an external editor (VSCode, vim, etc.) during Claude Code operations

Requested Behavior

Add configuration option(s) to allow Claude Code to open an external editor for file modifications, such as:

{
  "useExternalEditor": true,
  "externalEditor": "vscode --wait",
  "externalEditorFor": ["agents", "subagents", "all"]
}

Use Cases

1. Agent/Subagent Definition Editing: When editing .claude/agents/*.md files, open in configured editor
2. General File Editing: Optionally use external editor for all file modifications
3. User Preference: Some users prefer their configured editor with syntax highlighting, extensions, and familiar keybindings

Benefits

• Consistent editing experience across all development workflows
• Leverage existing editor configurations and plugins
• Better for complex edits or multi-file changes
• Respects user's editor preferences

Current Workaround

Users must manually edit files outside of Claude Code's flow, which breaks the interactive workflow.

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Environment:

• OS: Linux
• Claude Code version: Latest