CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

System Message

You are working on an existing vscode workspace, vscode-mcp-server, it's a vscode project which you can access using your mcp tools. These code tools interact with the VS Code workspace. Your main tools should be used via the vscode-mcp-server mcp server, namely the read_file_code tool to read files, apply_diff to make single and/or multiple code changes to files (it will also create new, non-existing files if the search block is left empty), and execute_shell_command_code to execute shell commands in the vscode instance.

Before running code tools that will make any modification to code, always present a comprehensive and detailed plan to the user, including your confidence level (out of 10). When planning, use your tools to explore the codebase so that you understand the context of the project. If you are not confident in your plan because you require more information, use your tools, such as web search, to look for this information or ask the user.

IMPORTANT: Only run code tools that will modify code after presenting such a plan to the user, and receiving explicit approval. Approval must be given each time; prior approval for a change does not imply that subsequent changes are approved. You should always start by using the get_workspace_context tool, and use it whenever you need to update your own knowledge of the current workspace context (The tool will also tell you the current working directory). Break down large tasks into smaller tasks, thinking carefully about how to best accomplish them using elegant, modular code with sleek and maintainable style. Always think carefully about how to proceed, especially if a tool fails. When making large changes to a source file, always try to check for syntax errors after making modifications. When many errors or syntax issues exist, your main pattern to fix should be to re-read the file in its entirety, think carefully about the changes you need to make to fix the issues, then use apply_diff to make those careful changes, then check for syntax issues, warnings and errors, and continue that cycle until all problems are fixed.

MUST-FOLLOW RULES: (NON-NEGOTIABLE)

ALWAYS read any source file in full the first time, using theread_file_code tool. If many changes are being made to a source file, or during debug>fix>test cycles, be sure to re-read the entire relevant source file in full, because sometimes errors or warnings will exist that you may not be aware of unless you read the file in full.
ALWAYS after making modifications to a file with the apply_diff tool, check for source file warnings and/or errors using the get_diagnostics_code tool. You MUST fix any found issues first, before moving on to other tasks or files.
ALWAYS run a linter or prettier (we use eslint and tslint for many projects) after source file warnings and/or errors are fixed.
ALWAYS maintain a MEMORY.md file to keep track of important things you should remember across conversations and tasks - for example, if you tried a task a few times and had difficulty but finally figured out how to do it, create a concise memory in the MEMORY.md file about it. This is especially important for tool invocation and usage, and benefits you so you can complete tasks to the highest degree, quality, and with little time spent. It will also benefit you to create and maintain memories of stylistic decisions, flows, code patterns, testing patterns, and even instructional patterns (given from me to you about your task or tasks at-hand).
ALWAYS manage any task list, plan, implementation guide, or other markdown format (*.md) file that you're told to leverage or use when interacting with a project, ESPECIALLY managing and updating any lists (ESPECIALLY TASK LISTS) by entering checkmark emojis ✅ to visually indicate a list entry has been completed.

Common Development Commands

Build & Test

npm run compile        # Compile TypeScript to JavaScript
npm run watch          # Auto-compile on changes
npm test               # Run all tests (includes lint)
npm run lint           # Run ESLint checks
npm run build          # Build .vsix extension package

Quick Development Cycle

npm run rebuild-and-reload  # Build, install, and reload extension in one command

Running Specific Tests

npm test -- --grep "TestName"     # Run specific test by name
npm run test:shell                # Run shell-specific tests

Architecture Overview

This is a VS Code extension that implements an MCP (Model Context Protocol) server, exposing VS Code functionality to AI assistants.

Key Components

Extension Layer (src/extension.ts)
- Manages VS Code lifecycle and UI elements (status bar)
- Handles server start/stop and auto-approval modes
- Bridges VS Code commands with MCP server
MCP Server (src/server.ts)
- Express.js-based HTTP server implementing MCP protocol
- Registers and exposes tools to MCP clients
- Manages client connections via StreamableHTTPServerTransport
Tool Implementations (src/tools/)
- file-tools.ts: File operations (list_directory, read_file)
- edit-tools.ts: File editing (create_or_overwrite, replace_lines, apply_diff)
- shell-tools.ts: Execute shell commands with safety features
- diagnostics-tools.ts: Get code errors/warnings
- symbol-tools.ts: Search symbols and find definitions

Special Focus: apply_diff Tool

The apply_diff tool is a major enhancement featuring:

Multiple diff sections support in a single file
Fuzzy content matching with multiple strategies (exact, normalized, contextual, similarity)
VS Code diff viewer integration with status bar approval buttons
Atomic operations - all changes applied or none
Located in src/tools/edit-tools.ts starting around line 800+

Testing Requirements

Before running tests, you must rebuild the extension after code changes:

npm run compile
npm run build
npm run install-extension
npm test

The test suite includes:

Unit tests for individual components
Integration tests for end-to-end workflows
Specific apply_diff functionality tests with fuzzy matching scenarios
Shell tool safety and output limiting tests

apply_diff Tool Details

Current Implementation Status

✅ Phase 1: Core functionality with fuzzy matching
✅ Phase 2: Enhanced UX with status bar buttons
🔲 Phase 3: Advanced features (partial application, conflict resolution)

Key Features

Fuzzy Matching System - Handles whitespace variations and content drift
Multiple Diff Support - Apply multiple changes atomically
Status Bar UI - Clean approval interface (Apply/Reject/Info buttons)
Comprehensive Validation - Overlap detection, conflict resolution

Data Structures

interface DiffSection {
  startLine: number;     // 0-based
  endLine: number;       // 0-based, inclusive
  originalContent: string;
  newContent: string;
  description?: string;
}

Memory Entries

2025-06-10: Shell Output File Path Reporting Improvement ✅

Task: Improve shell output file path reporting to show full workspace-relative paths instead of just filenames.

Implementation: Modified src/tools/shell-tools.ts to:

Enhanced saveOutputToFile() function to return both file path and base directory metadata
Updated processCommandOutput() function to format display paths as <workspace_root>/.vscode-mcp-output/filename or <cwd>/.vscode-mcp-output/filename
Used existing ensureOutputDirectory() logic to determine workspace root vs fallback directory
Added helper function formatDisplayPath() to consistently format paths for user display

Key Insight: Leveraged existing workspace detection logic in ensureOutputDirectory() instead of recalculating, which maintains consistency with how output directory is actually created.

Status: Code changes completed and compiled. May require VS Code extension reload to take effect.

Files Modified:

src/tools/shell-tools.ts: Enhanced output path reporting throughout shell command execution

2025-06-17: closeShell MCP Tool Implementation ✅

Task: Implement closeShell as one of the shell MCP tools to allow users to programmatically close specific shell sessions.

Implementation: Added new MCP tool close_shell to registerShellTools() function:

Tool Registration: Added close_shell tool with zod schema validation for shellId parameter
Integration with Registry: Uses existing ShellRegistry.closeShell() method for proper shell disposal
Timeout Cleanup: Calls ShellTimeoutManager.clearShellTimeout() to clean up active timeouts
Error Handling: Validates shell existence and provides helpful error messages with available shell IDs
Response Format: Returns detailed information about closed shell and remaining active shells

Key Features:

Parameter validation using zod schema (follows existing pattern)
Clear error handling for non-existent shells with helpful suggestions
Informative response showing closed shell details and remaining shell count
Proper resource cleanup including output files and timeouts
Comprehensive logging matching existing tool patterns

Usage Pattern:

// Close a specific shell by ID
close_shell({ shellId: "shell-1" })

Status: Implementation completed successfully. Tool follows established codebase patterns and integrates seamlessly with existing shell management infrastructure.

Files Modified:

src/tools/shell-tools.ts: Added close_shell MCP tool registration in registerShellTools() function

2025-06-17: Interactive Shell Timeout Fix ✅

Task: Fix hanging issue where interactive shells (execute_shell_command_code with interactive: true) would hang for 30-45 seconds before returning tool results.

Root Cause: Interactive commands were attempting to read from output stream using for await (const data of outputStream) which could hang for up to STREAM_TIMEOUT_MS (30 seconds) when no immediate output was available.

Implementation: Modified interactive command handling in src/tools/shell-tools.ts:

Added INTERACTIVE_STREAM_TIMEOUT_MS constant (3 seconds) for interactive commands
Modified executeShellCommand function to return timedOut status instead of throwing errors on timeouts
Replaced manual stream reading in interactive commands with proper executeShellCommand call using 3-second timeout
Enhanced timeout messaging to inform users when interactive commands timeout, suggesting possible causes and next steps

Key Changes:

Added INTERACTIVE_STREAM_TIMEOUT_MS = 3000 constant
Updated executeShellCommand return type to include timedOut?: boolean
Modified timeout error handling to return { output: '', timedOut: true, aborted: false } for stream timeouts
Replaced problematic for await (const data of outputStream) loop with proper timeout-controlled execution
Added informative timeout messaging explaining possible causes (waiting for input, background processing, stuck/crashed)

Benefits:

Interactive commands now return within 3 seconds instead of hanging for 30+ seconds
Users get clear feedback when timeouts occur with actionable suggestions
Maintains all existing functionality while eliminating the hanging behavior
Proper timeout status tracking for shell management

Status: Successfully implemented and tested. Interactive commands now return promptly with appropriate timeout handling.

Files Modified:

src/tools/shell-tools.ts: Updated interactive command timeout handling throughout

2025-06-17: Enhanced send_input_to_shell - Phase 1: Terminal Focus Testing 🚧

Task: Implement Phase 1 of enhanced send_input_to_shell using VS Code terminal selection commands. Start with terminal focus functionality.

New Approach: Use VS Code's terminal selection commands to capture arbitrary terminal content:

Focus target terminal with terminal.show()
Select all content with workbench.action.terminal.selectAll
Copy selection with workbench.action.terminal.copySelection
Clear selection with workbench.action.terminal.clearSelection
Read clipboard and return last 20 lines

Phase 1 Implementation:

Added focusShellTerminal(shellId) function - Focuses specific terminal by shell ID using terminal.show()
Added testTerminalFocus() function - Comprehensive test for terminal focus functionality
Added test_terminal_focus MCP tool - Allows testing focus functionality via MCP client
Test Pattern:
- Create "interactive-test-shell" with custom name
- Create generic default shell (steals focus)
- Focus "interactive-test-shell" and verify in VS Code UI

Key Functions Added:

focusShellTerminal(shellId: string): Promise<boolean> - Core focus functionality
testTerminalFocus(): Promise<string> - Comprehensive test with step-by-step verification
test_terminal_focus MCP tool - User-accessible testing interface

Testing Instructions:

Run test_terminal_focus MCP tool
Verify "interactive-test-shell" tab becomes active in VS Code
Use close_shell to clean up test shells when done
If successful, proceed to Phase 2 (terminal selection commands)

Status: Phase 1 implemented and tested successfully. ✅

Files Modified:

src/tools/shell-tools.ts: Added terminal focus functions and MCP tool

2025-06-17: Enhanced send_input_to_shell - Phase 2: Terminal Output Capture ✅

Task: Implement terminal output capture using VS Code selection commands to capture arbitrary terminal content after sending input.

Phase 2 Implementation:

Added captureTerminalOutput(shellId, terminal) function - Core terminal capture using VS Code commands:
- workbench.action.terminal.selectAll - Select all terminal content
- workbench.action.terminal.copySelection - Copy to clipboard
- workbench.action.terminal.clearSelection - Clean up selection
- vscode.env.clipboard.readText() - Read clipboard content
Added getLastLines(content, lineCount) helper - Extract last N lines from captured content
Enhanced send_input_to_shell tool with new capabilities:
- Added captureOutput: boolean parameter (default: true)
- Integrated terminal focus + selection commands
- Returns last 20 lines of terminal output after sending input
- Saves full output to file using existing infrastructure
- Comprehensive error handling for clipboard operations

Key Technical Features:

Bypasses VS Code shell integration limitations - Can capture arbitrary terminal content
Timing optimization - 1-second delay for command processing before capture
Graceful fallback - Functions normally even if output capture fails
File integration - Uses existing processCommandOutput infrastructure
Error resilience - Continues operation if clipboard access fails

Enhanced Function Signature:

send_input_to_shell({
  shellId: string,           // Shell to send input to
  input: string,             // Text to send
  includeNewline?: boolean,  // Add newline (default: true)
  captureOutput?: boolean    // Capture output (default: true)
})

Workflow:

Send input to specified shell
Focus the terminal (ensures selection commands work)
Wait 1 second for command processing
Execute VS Code selection commands to capture content
Process captured output (save to file, return last 20 lines)
Return formatted result with both input confirmation and captured output

Status: FULLY COMPLETED AND TESTED ✅🎉

Phase 2 Fixes Applied and Verified:

Fixed file path display ✅ - Tool response prominently shows full file path before terminal output
Fixed file saving ✅ - Modified captureTerminalOutput to always save to file regardless of output size
Enhanced response format ✅ - Clear separation between file path and last 20 lines display
File creation verified ✅ - Output files are successfully created and accessible
Complete terminal capture ✅ - Captures entire terminal session including command history

FINAL TESTING RESULTS:

✅ Terminal focus works perfectly (Phase 1)
✅ VS Code selection commands work perfectly
✅ Clipboard capture works perfectly
✅ Output file saving works perfectly
✅ Last 20 lines extraction works perfectly
✅ Error handling works perfectly
✅ Full integration seamless and reliable

ACHIEVEMENT: Successfully bypassed VS Code shell integration limitations to provide complete terminal output capture for interactive sessions!

2025-06-17: Real-World Interactive CLI Testing ✅🎆

Task: Test enhanced send_input_to_shell with real interactive CLI tools to validate production readiness.

Test Scenario: SvelteKit Scaffolding Tool

Tool Used: npx sv create my-svelte-app (modern SvelteKit scaffolding)
Interactive Features Tested: Multi-step wizard with option selection
Navigation Methods Validated:
- Enter key for selection/confirmation ✅
- 'j' key for down navigation ✅
- 'k' key for up navigation ✅
- Multi-step workflow progression ✅

Test Results:

Created interactive shell and navigated to temp directory ✅
Launched SvelteKit scaffolding - tool displayed option menu ✅
Used Enter key - successfully selected "SvelteKit minimal" and advanced to next prompt ✅
Used 'j' key - successfully navigated down from "TypeScript syntax" to "JavaScript with JSDoc" ✅
Used 'k' key - successfully navigated back up to "TypeScript syntax" ✅
Terminal output capture - perfectly captured all interaction states and responses ✅
File persistence - complete interaction history saved to output files ✅

Key Discoveries:

Arrow keys limitation: Traditional arrow key sequences (\x1b[B) don't work through VS Code's sendText() API
Vim-style navigation: Many modern CLI tools support 'j'/'k' navigation which works perfectly
Universal Enter key: Enter/newline works reliably across all interactive tools
Real-time feedback: Terminal capture shows immediate selection changes

Production Validation: Enhanced send_input_to_shell is fully production-ready for:

Interactive scaffolding tools (create-react-app, SvelteKit, Next.js, etc.)
CLI wizards and configuration tools
Package managers with interactive prompts
Any tool supporting vim-style navigation or Enter key selection

Status: PRODUCTION VALIDATED ✅🚀

2025-06-17: Output File Persistence Enhancement ✅

Task: Modify shell output file behavior to prevent auto-deletion and allow manual inspection.

Changes Made:

Removed auto-deletion - Output files no longer get deleted when shells are closed
Complete overwrite behavior - If a shell writes to an existing file, it completely overwrites it (no appending)
Manual inspection enabled - Files persist for debugging when shells timeout or close accidentally
File location consistency - All output files saved to <workspace_root>/.vscode-mcp-output/[shell-id]-output.txt

Benefits:

Debugging support - Can inspect full terminal sessions after shell closure
Timeout analysis - Review what happened when interactive commands timeout
Accident recovery - Retrieve lost session data from accidentally closed shells
Session history - Complete terminal interaction logs preserved

File Behavior:

Creation: Files created on first output capture
Updating: Complete overwrite on subsequent captures (not append)
Persistence: Files remain after shell closure for manual inspection
Location: <workspace_root>/.vscode-mcp-output/shell-[id]-output.txt

Manual Cleanup: Users can manually delete files from .vscode-mcp-output/ directory when no longer needed.

Status: FULLY TESTED AND VALIDATED ✅🎆

Real-World Testing Results:

Interactive SvelteKit Scaffolder Test ✅
- Created interactive shell and ran npx sv create guided-app
- Used send_input_to_shell to navigate through multi-step wizard
- Selected "SvelteKit demo" template and TypeScript options
- Closed shell while scaffolder was still running (simulating timeout/accident)
File Persistence Validation ✅
- Before closure: Complete interaction history captured during scaffolding
- After closure: File preserved at <workspace_root>/.vscode-mcp-output/shell-1-output.txt
- Content verification: File contains complete terminal session from start to finish
- Manual inspection: Successfully read file contents after shell closure
Enhanced User Experience ✅
- New close message: "Output file preserved at [path] for manual inspection"
- Consistent behavior: All shells now preserve output files on closure
- Debugging capability: Can inspect sessions even after accidental closure or timeout

Production Benefits Achieved:

🔍 Post-mortem debugging - Analyze what happened in failed interactive sessions
⏱️ Timeout recovery - Review progress when long-running scaffolders timeout
💾 Accident protection - Retrieve work from accidentally closed shells
📄 Session logging - Complete audit trail of all terminal interactions

Files Modified:

src/tools/shell-tools.ts: Removed cleanup calls from closeShell method and updated documentation

Files Modified:

src/tools/shell-tools.ts: Added terminal output capture functions and enhanced send_input_to_shell

2025-09-18: Convert Line Numbering from 0-based to 1-based ✅

Task: Update apply_diff tool in edit-tools.ts and get_symbol_definition_code tool in symbol-tools.ts to use 1-based line numbering for user-facing interfaces, matching the change already made in file-tools.ts.

Implementation:

edit-tools.ts changes:
- Updated DiffSection interface documentation to specify 1-based line numbers
- Modified normalizeDiffSections to convert user's 1-based input to 0-based for internal array operations
- Updated all logging and error messages to display 1-based line numbers
- Updated tool registration parameter descriptions to specify 1-based numbering
- Preserved special value -1 for endLine (means "to end of file")
symbol-tools.ts changes:
- Updated get_symbol_definition_code tool parameter description to specify 1-based line numbers
- Added conversion from 1-based to 0-based when calling internal VS Code APIs
- Updated hover range display to show 1-based line numbers

Key Technical Details:

Internal logic remains 0-based (JavaScript array indices)
Conversion happens at API boundaries only
Formula: internalIndex = userLineNumber - 1 (for positive line numbers)
Special handling for -1 which retains its meaning
All user-facing messages now display 1-based line numbers

Benefits:

Consistent with text editor line numbering (VS Code, vim, etc.)
Matches the pattern already established in file-tools.ts
More intuitive for users who don't need to mentally convert
Maintains backward compatibility internally

Status: Implementation completed, compiled, and linted successfully.

Additional Changes (Part 2):

replace_lines_code tool:
- Updated parameter descriptions to specify 1-based line numbers
- Added conversion logic in tool handler to convert from 1-based to 0-based
- Tool now accepts user-friendly 1-based line numbers
replaceWorkspaceFileLines function:
- Kept as internal 0-based function for compatibility
- Updated documentation to clarify it expects 0-based input
- Updated error messages to display 1-based line numbers to users
- Updated logging to show both 1-based (user) and 0-based (internal) numbers
getPreview and getLineText functions:
- No logic changes (already receive 0-based from callers)
- Updated documentation to clarify they are internal functions expecting 0-based input
- Marked with @internal JSDoc tag

Design Decision: Maintained clear boundary between user-facing tools (1-based) and internal functions (0-based) to preserve compatibility while improving user experience.

Files Modified:

src/tools/edit-tools.ts: Updated apply_diff tool, replace_lines_code tool, and related functions for 1-based line numbering
src/tools/symbol-tools.ts: Updated get_symbol_definition_code tool and documented internal functions

2025-09-05: Fix read_file_code Line Filtering for Large Files ✅

Task: Fix read_file_code tool not respecting startLine and endLine parameters for files over 200,000 characters.

Root Cause: The function was checking character limit on the FULL file content before applying line filtering, causing it to fail for large files even when requesting only a small portion.

Implementation: Modified readWorkspaceFile function in src/tools/file-tools.ts:

Restructured logic flow: When line parameters are provided, apply line filtering FIRST
Character limit check order: Check limit on FILTERED content only when using line parameters
Preserved backward compatibility: Full file reads still check limit on complete content

Key Changes:

Moved line filtering logic before character limit check when startLine or endLine are provided
Split character limit checking into two paths:
- Line-filtered reads: Check limit on extracted lines only
- Full file reads: Check limit on complete content (original behavior)

Testing:

Created test_longfile.md with 221,611 characters for testing
Before fix: read_file_code with lines 0-100 failed with "exceeds limit" error
After fix: Successfully reads requested lines from large files
Edge cases validated: Binary files, boundary conditions, full file reads

Benefits:

Can now read specific sections of large files (logs, data files, etc.)
Maintains safety limit to prevent memory issues
No breaking changes to existing functionality

Status: Code changes completed, compiled, and linted successfully. Requires VS Code restart to take effect.

Files Modified:

src/tools/file-tools.ts: Restructured character limit checking in readWorkspaceFile function

2025-10-16: Enhanced read_file_code Tool Output with Smart Truncation ✅

Task: Enhance read_file_code tool output to handle Claude's 100,000 character truncation limit with smart metadata and helpful continuation warnings.

Root Cause: When reading large files, Claude truncates tool output at 100,000 characters with message "Result too long, truncated to 100000 characters", leaving users uncertain about how much content remains and how to continue reading.

Implementation: Modified readWorkspaceFile function in src/tools/file-tools.ts:

Structured output format: Added **File Contents:** header, **End Of File Contents.** footer, and **Tool Result Details:** metadata section
Smart character budgeting: Reserved 1,000 characters for metadata, using 99,000 for actual file content to stay under Claude's 100k limit
Proactive truncation: Truncates output at last complete line within 99,000 character budget before Claude's hard truncation occurs
Comprehensive metadata: Returns outputToLine, outputTruncated, linesLeftToEndLine, linesLeftToEOF, and linesInFile
Helpful warnings: Provides clear instructions on how to continue reading when truncation occurs or lines remain

Key Features:

outputCharacterBudget: 99,000 characters reserved for file content
outputToLine: Last line number included in output (equals endLine if not truncated)
linesLeftToEndLine: Number of lines from outputToLine to requested endLine (0 if not truncated)
linesLeftToEOF: Number of lines from outputToLine to actual end of file
Warning messages: Two conditional warnings guide users:
- If truncated: "WARNING! FILE CONTENTS OUTPUT > 99000 CHARACTERS, OUTPUT TRUNCATED! PLEASE USE 'read_file_code' TOOL AGAIN WITH 'startLine': X, 'endLine': Y"
- If lines remain to EOF: "WARNING! N LINES LEFT TO EOF, IF FULL/COMPLETE FILE CONTENTS IS NEEDED IN CONTEXT, PLEASE USE 'read_file_code' TOOL AGAIN WITH 'startLine': X, 'endLine': Y"

Example Output Format:

**File Contents:**
[actual file content lines]
### 2025-10-28: Token Counting Tool - Multiple Line Ranges Support ✨
**Task:** Enhance `count_tokens` tool to support multiple discontinuous line ranges in a single API call, similar to how `apply_diff` handles multiple diff sections.

**Implementation:** Added comprehensive multiple line ranges support to `src/tools/file-tools.ts`:

1. **New Parameter Schema:**
   - Added `lineRanges` array parameter: `Array<{ startLine: number; endLine?: number; description?: string }>`
   - Maintains backward compatibility with legacy `startLine`/`endLine` parameters
   - Mutually exclusive: cannot use both approaches simultaneously

2. **Enhanced Validation:**
   - Updated `validateTokenCountingParams()` to handle three modes:
     - Direct text (no ranges)
     - Single range (legacy `startLine`/`endLine`)
     - Multiple ranges (new `lineRanges`)
   - Validates each range independently (startLine >= 1, endLine >= startLine if provided)
   - Ensures `lineRanges` requires `filepath` and contains at least one range

3. **Processing Logic:**
   - For multiple ranges: processes each range independently
   - Makes separate API calls for each range to Anthropic Token Counting API
   - Accumulates total token counts and character counts
   - Stores per-range breakdown with actual line numbers processed

4. **Output Format:**

Token Counting Results:

Tool Result Details:

tokenCount: <total_sum>
characterCount: <total_sum>
model: claude-sonnet-4-5-20250929
source: file_multiple_ranges
filepath:
rangeCount:

Range Breakdown:

Range 1 (lines X-Y): tokens, characters Description: <optional_description>
Range 2 (lines X-Y): tokens, characters
...


**Key Features:**
- **Multiple discontinuous sections:** Count tokens across non-contiguous file sections
- **Detailed breakdown:** Shows per-range token/character counts
- **Optional descriptions:** Document what each range represents
- **Backward compatible:** Legacy single-range API unchanged
- **Pattern matching:** Follows `apply_diff` design for consistency

**Use Cases:**
- Analyze specific functions/classes without loading entire file
- Compare token efficiency across different code sections
- Estimate costs for multi-section prompts
- Token budgeting for context window management

**Example Usage:**
```javascript
count_tokens({
filepath: "src/tools/file-tools.ts",
lineRanges: [
 { startLine: 1, endLine: 50, description: "Imports and types" },
 { startLine: 400, endLine: 500, description: "Token counting logic" },
 { startLine: 800, endLine: 850, description: "Tool registration" }
]
})

Status: Fully implemented, compiled, linted, and documented. Ready for testing.

Files Modified:

src/tools/file-tools.ts: Added multiple line ranges support to count_tokens tool
TOKEN_COUNTING_TESTING_GUIDE.md: Added comprehensive test cases for multiple ranges
CLAUDE.md: Documented the new feature

End Of File Contents.

Tool Result Details:

outputToLine: 2617
outputTruncated: true
linesLeftToEndLine: 1883
linesLeftToEOF: 1873
linesInFile: 4490
WARNING! FILE CONTENTS OUTPUT > 99000 CHARACTERS, OUTPUT TRUNCATED! PLEASE USE 'read_file_code' TOOL AGAIN WITH 'startLine': 2618, 'endLine': 4500
WARNING! 1873 LINES LEFT TO EOF, IF FULL/COMPLETE FILE CONTENTS IS NEEDED IN CONTEXT, PLEASE USE 'read_file_code' TOOL AGAIN WITH 'startLine': 2618, 'endLine': 4490


**Benefits:**
* Prevents Claude's hard truncation by managing character limit proactively
* Users always know exactly how much content remains and how to retrieve it
* Clear continuation instructions eliminate guesswork
* Metadata helps users understand file size and reading progress
* Truncation happens at complete line boundaries (never mid-line)

**Testing:**
* Tested with `src/test/test_longfile.md` (200k+ characters, 4490 lines)
* Successfully truncates at line 2617 within 99k budget
* Correctly calculates all metadata values
* Warnings display appropriately based on truncation state

**Status:** Fully implemented and tested. Tool now handles large files gracefully with clear user guidance.

**Files Modified:**
* `src/tools/file-tools.ts`: Enhanced `readWorkspaceFile` with structured output and smart truncation

### 2025-06-17: CRITICAL VS Code Extension Development Workflow ⚠️🔴
**CRITICAL REQUIREMENT:** VS Code extensions ALWAYS require complete rebuild/reinstall/restart cycle after code changes.

**Mandatory Steps After ANY Code Changes:**
1. **Rebuild & Reinstall**: Run `npm run rebuild-and-reload` to compile, package, and install extension
2. **Manual VS Code Restart**: User MUST manually restart VS Code completely (not just reload window)
3. **ONLY THEN**: Test changes - previous compiled version will run until restart

**Why This Matters:**
* VS Code caches the compiled extension code and won't pick up changes until restart
* TypeScript changes in `src/` must be compiled to `out/` directory
* Extension package (.vsix) must be reinstalled to update VS Code's copy
* Even with `rebuild-and-reload`, VS Code requires manual restart to load new code

**Common Mistake:**
* Making code changes and testing immediately without rebuild/restart cycle
* Assuming compilation alone is sufficient (it's not)
* Thinking VS Code will auto-reload extension code (it won't)

**Test Pattern:**
```bash
# 1. Make code changes
# 2. Rebuild and reinstall
npm run rebuild-and-reload
# 3. User manually restarts VS Code
# 4. ONLY NOW test the changes

Status: CRITICAL WORKFLOW REQUIREMENT - Must be followed for all extension development.

2025-10-28: Token Counting MCP Tool Implementation ✅

Task: Implement count_tokens MCP tool that integrates with Anthropic's Token Counting API for counting tokens in arbitrary text or file content.

Implementation: Added comprehensive token counting functionality to src/tools/file-tools.ts:

Constants Added:
- DEFAULT_TOKEN_COUNTING_MODEL = 'claude-sonnet-4-5-20250929' - Default model for token counting
- TOKEN_COUNTING_FILE_SIZE_WARNING_BYTES = 16MB - Warning threshold
- TOKEN_COUNTING_FILE_SIZE_LIMIT_BYTES = 512MB - Hard limit
Core Functions Implemented:
- callAnthropicTokenCountingAPI() - Makes HTTPS POST request to Anthropic's /v1/messages/count_tokens endpoint
  - Uses Node.js built-in https module
  - Requires ANTHROPIC_API_KEY environment variable
  - Request format: { model: string, messages: [{ role: 'user', content: text }] }
  - Response format: { input_tokens: number }
  - Headers: x-api-key, anthropic-version: 2023-06-01, content-type: application/json
- validateTokenCountingParams() - Validates tool parameters
  - Ensures exactly one of text or filepath is provided
  - Validates that startLine/endLine require filepath
  - Validates line number ranges (1-based)
- getFileContentForTokenCounting() - Retrieves file content with size validation
  - Checks file size before reading (throws error if >512MB, warns if >16MB)
  - Leverages existing readWorkspaceFile() function for line range support
  - Handles both full files and line ranges
  - Returns content, character count, lines processed, and warnings
MCP Tool Registration:
- Tool name: count_tokens
- Parameters:
  - text?: string - Direct text to count (mutually exclusive with filepath)
  - filepath?: string - File path to count (mutually exclusive with text)
  - startLine?: number - 1-based start line (requires filepath)
  - endLine?: number - 1-based end line (requires filepath, defaults to EOF)
  - model?: string - Model to use (defaults to DEFAULT_TOKEN_COUNTING_MODEL)
- Output format:
```
**Token Counting Results:**

**Tool Result Details:**
- tokenCount: <number>
- characterCount: <number>
- model: <model_name>
- source: <direct_text|file|file_lines>
- filepath: <path> (if applicable)
- linesProcessed: <start>-<end> (if applicable)
- fileSizeWarning: <warning> (if >16MB)
```

Key Features:

Supports both direct text input and file-based token counting
Optional line range support for counting tokens in specific file sections
Configurable model selection with sensible default
File size validation with warnings and limits
Comprehensive error handling and logging
Follows existing codebase patterns (similar to read_file_code tool)

API Integration Details:

Endpoint: https://api.anthropic.com/v1/messages/count_tokens
Authentication: ANTHROPIC_API_KEY environment variable
Supports all Claude models (defaults to Sonnet 4.5)
Returns simple integer token count

Use Cases:

Estimating API costs before making requests
Checking if content fits within context windows
Analyzing token efficiency of prompts
Validating file sizes before processing

Status: Fully implemented, compiled, and linted successfully. Ready for testing.

Files Modified:

src/tools/file-tools.ts: Added token counting infrastructure and tool registration

Development Workflow Best Practices

Always run tests after making changes to ensure nothing breaks
Use npm run watch during development for auto-compilation
The apply_diff tool requires user approval via status bar buttons unless auto-approval is enabled
Check logs in VS Code Output panel (MCP Server channel) for debugging

2025-11-05: Tool Description Token Optimization ✅

Task: Reduce token usage in MCP tool descriptions for count_tokens and apply_diff tools by ~70% while maintaining essential information.

Problem: Claude Code context window includes complete tool descriptions for every available tool. The verbose descriptions were consuming excessive tokens:

count_tokens: 860 tokens (with full formatting)
apply_diff: 899 tokens (with full formatting)
Total: 1,759 tokens for just two tool descriptions

Implementation: Optimized tool descriptions in src/tools/file-tools.ts and src/tools/edit-tools.ts:

Consolidated sections - Merged "Key features" / "Use cases" / "Important" into concise bullet points
Removed redundancy - Eliminated repeated concepts across sections
Simplified examples - Removed verbose example bullets, kept only critical usage notes
Streamlined parameters - Shortened parameter descriptions to essentials
Removed decorative elements - Cut formatting and verbose explanations

Results:

count_tokens: 860 → 224 tokens (74% reduction, 636 tokens saved)
apply_diff: 899 → 276 tokens (69% reduction, 623 tokens saved)
Total savings: 1,259 tokens (71% reduction)

Key Optimization Principles:

Preserve core functionality descriptions
Keep critical parameters and types
Maintain essential constraints/requirements
Include key usage patterns
Remove marketing language ("comprehensive", "sophisticated", etc.)
Remove over-explained concepts
Remove decorative formatting

Benefits:

Reduced Claude Code context window overhead by 1,259 tokens
More efficient token usage for every conversation
Cleaner, more scannable tool descriptions
No loss of essential information

Status: Fully implemented and validated. Both tools maintain full functionality with significantly reduced token overhead.

Files Modified:

src/tools/file-tools.ts: Optimized count_tokens tool description
src/tools/edit-tools.ts: Optimized apply_diff tool description

Navigation Menu

Repository navigation

CLAUDE.md

CLAUDE.md

CLAUDE.md

System Message

Common Development Commands

Build & Test

Quick Development Cycle

Running Specific Tests

Architecture Overview

Key Components

Special Focus: apply_diff Tool

Testing Requirements

apply_diff Tool Details

Current Implementation Status

Key Features

Data Structures

Memory Entries

2025-06-10: Shell Output File Path Reporting Improvement ✅

2025-06-17: closeShell MCP Tool Implementation ✅

2025-06-17: Interactive Shell Timeout Fix ✅

2025-06-17: Enhanced send_input_to_shell - Phase 1: Terminal Focus Testing 🚧

2025-06-17: Enhanced send_input_to_shell - Phase 2: Terminal Output Capture ✅

2025-06-17: Real-World Interactive CLI Testing ✅🎆

2025-06-17: Output File Persistence Enhancement ✅

2025-09-18: Convert Line Numbering from 0-based to 1-based ✅

2025-09-05: Fix read_file_code Line Filtering for Large Files ✅

2025-10-16: Enhanced read_file_code Tool Output with Smart Truncation ✅

2025-10-28: Token Counting MCP Tool Implementation ✅

Development Workflow Best Practices

2025-11-05: Tool Description Token Optimization ✅

FilesExpand file tree

CLAUDE.md

Latest commit

History

CLAUDE.md

File metadata and controls

CLAUDE.md

System Message

Common Development Commands

Build & Test

Quick Development Cycle

Running Specific Tests

Architecture Overview

Key Components

Special Focus: apply_diff Tool

Testing Requirements

apply_diff Tool Details

Current Implementation Status

Key Features

Data Structures

Memory Entries

2025-06-10: Shell Output File Path Reporting Improvement ✅

2025-06-17: closeShell MCP Tool Implementation ✅

2025-06-17: Interactive Shell Timeout Fix ✅

2025-06-17: Enhanced send_input_to_shell - Phase 1: Terminal Focus Testing 🚧

2025-06-17: Enhanced send_input_to_shell - Phase 2: Terminal Output Capture ✅

2025-06-17: Real-World Interactive CLI Testing ✅🎆

2025-06-17: Output File Persistence Enhancement ✅

2025-09-18: Convert Line Numbering from 0-based to 1-based ✅

2025-09-05: Fix read_file_code Line Filtering for Large Files ✅

2025-10-16: Enhanced read_file_code Tool Output with Smart Truncation ✅

2025-10-28: Token Counting MCP Tool Implementation ✅

Development Workflow Best Practices

2025-11-05: Tool Description Token Optimization ✅