[FEATURE] Vim-style word completion (Ctrl+P/Ctrl+N) in insert mode

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When composing prompts in Claude Code with Vim mode enabled, there's no way to auto-complete words from the conversation history or current prompt buffer. This is a standard feature in Vim's insert mode that significantly speeds up editing, especially when working with long technical terms, file paths, or previously mentioned concepts that appear multiple times in a conversation.

Current Behavior:

• Vim mode supports navigation (h/j/k/l), text objects (ciw, diw), and basic editing
• No word completion available in insert mode
• Users must manually retype long or technical terms that appeared earlier in the conversation

Why This Matters:
When iterating on prompts or referencing concepts from earlier in the conversation, users frequently need to type the same technical terms, file names, or domain-specific vocabulary repeatedly. In standard Vim, Ctrl+P and Ctrl+N provide word completion from the current buffer, which is muscle memory for Vim users and dramatically improves editing efficiency.

Proposed Solution

Implement Vim-style word completion in insert mode:

Ctrl+P: Search backward through conversation history for word completions
Ctrl+N: Search forward through conversation history for word completions

Completion Sources (in priority order):

1. Current prompt input (words already typed in the current prompt)
2. Conversation history (words from previous messages in the session)
3. Optionally: Project file names and common terms

Behavior:

• Pressing Ctrl+P while typing a partial word shows matching completions from history
• Repeated presses cycle through matches
• Escape or Ctrl+[ cancels completion and returns to normal insert mode
• Tab or Enter accepts the completion

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

Example Use Case

Scenario: Working on a project with long technical terms

> Please refactor the AuthenticationService to use dependency injection

[Claude responds with code changes]

> Now update the tests for Authent<Ctrl+P>
                              ^
                              Auto-completes to "AuthenticationService"

Another scenario: Referencing file paths mentioned earlier

> Check the error in src/components/UserDashboard/ProfileSettings.tsx

[Discussion continues...]

> Now apply the same pattern to src/compo<Ctrl+P>
                                   ^
                                   Cycles through:
                                   - src/components/UserDashboard/ProfileSettings.tsx
                                   - src/components/...

Benefits

1. Consistency: Matches Vim behavior that users already know
2. Efficiency: Reduces repetitive typing of long terms
3. Accuracy: Avoids typos when reusing complex terms
4. Muscle Memory: Vim users instinctively use Ctrl+P/Ctrl+N
5. Cognitive Load: Less mental effort remembering exact spelling of terms from earlier in conversation

Additional Context

Alternative Considered

Using shell-style history completion (Ctrl+R for reverse search) could work, but:

• Less intuitive for Vim users
• Doesn't match the Vim editing paradigm Claude Code has already adopted
• Word completion is more granular and flexible than full command history

Related Issues

• #10016 - Enhanced Vim Mode: Support for Text Objects
• #1204 - Implement more Vim motions and shortcuts
• #8471 - Add Vi/Vim Mode to Prompt Input Area

These issues focus on Vim navigation and editing primitives, while this request addresses insert-mode completion—a complementary feature that completes the Vim editing experience.

Implementation Notes

This feature should:

• Only activate when Vim mode is enabled in settings
• Respect the current insert mode state
• Work seamlessly with multiline prompts
• Handle Shift+Enter for newlines correctly
• Not interfere with existing Tab completion for files/commands