Modernize MCP Server

.gitattributes

@@ -0,0 +1,3 @@
+# Ensure diff test data uses LF line endings on all platforms
+*.diff eol=lf
+tests/test_data/** eol=lf

docs/design.md

@@ -10,6 +10,8 @@ MCP server that chunks large diff files for efficient LLM navigation. Uses file-
 Diff File → Canonicalize Path → Hash Content → Cache Check → Parse → Filter → Chunk → Index → Tools
 ```
 
+The server uses FastMCP with module-level `@mcp.tool()` decorated sync functions (not a class). Resources use `@mcp.resource()`. Error handling is automatic: `ValueError` raised in any tool function is caught by FastMCP and returned as `CallToolResult(isError=True)`. All tools have `annotations={"readOnlyHint": True}` and `structured_output=False` (to prevent `outputSchema` generation).
+
 ## Tools
 
 ### load_diff (Optional)
@@ -156,14 +158,15 @@ class DiffStats:
 - File existence validation
 - Diff format verification
 - Graceful handling of malformed sections
-- Clear error messages for invalid patterns
+- Actionable error messages that guide LLMs to self-correct
+- `ValueError` automatically surfaces as `isError=True` through FastMCP
 
 ## Project Structure
 
 ```
 src/
 ├── main.py           # CLI entry point
-├── server.py         # MCP server (DiffChunkServer)
+├── server.py         # MCP server (FastMCP module-level tools)
 ├── tools.py          # MCP tools (DiffChunkTools)
 ├── models.py         # Data models
 ├── parser.py         # Diff parsing (DiffParser)
@@ -172,7 +175,12 @@ src/
 
 ## Resources
 
-- `diffchunk://current` - Overview of loaded diffs via MCP resource protocol
+- `diffchunk://current` - Overview of loaded diffs via `@mcp.resource("diffchunk://current")` decorator
+
+### File Matching
+
+- Pattern matching (glob) is case-insensitive, matching macOS/Windows filesystem behavior
+- Both `find_chunks_for_files` and `get_file_diff` use case-insensitive comparison
 
 ## Performance
 

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "diffchunk"
-version = "0.1.8"
+version = "0.1.9"
 description = "MCP server for navigating large diff files with intelligent chunking"
 readme = "README.md"
 requires-python = ">=3.10"
@@ -25,7 +25,7 @@ classifiers = [
 ]
 dependencies = [
     "click>=8.2.1",
-    "mcp>=1.10.0",
+    "mcp>=1.7.0,<2.0.0",
     "chardet>=4.0.0",
 ]
 

scripts/pre-push

@@ -1,41 +1,17 @@
-#!/bin/bash
+#!/bin/sh
+# Pre-push hook - runs the same checks as CI to catch issues early
 
-# Comprehensive code quality check script
-# Can be used manually or copied to .git/hooks/pre-push
+set -e
 
-set -e  # Exit on any error
+echo "Running pre-push checks..."
 
-echo "🚀 Running pre-push checks..."
-echo "================================"
+echo "Checking ruff lint..."
+uv run ruff check src/
 
-# Function to run a check and report results
-run_check() {
-    local name="$1"
-    local command="$2"
-
-    echo "🔍 Running $name..."
-    if eval "$command"; then
-        echo "✅ $name passed!"
-    else
-        echo "❌ $name failed!"
-        echo "Please fix the issues before pushing."
-        exit 1
-    fi
-    echo ""
-}
+echo "Checking code formatting..."
+uv run ruff format --check src/
 
-# 1. Code formatting check
-run_check "Ruff format check" "uv run ruff format --check"
+echo "Running tests..."
+uv run pytest tests/ -x -q
 
-# 2. Linting check
-run_check "Ruff linting" "uv run ruff check"
-
-# 3. Type checking
-run_check "MyPy type checking" "uv run mypy src/"
-
-# 4. Test suite
-run_check "Test suite" "uv run pytest -x -q"
-
-echo "🎉 All pre-push checks passed!"
-echo "✅ Code is ready to push"
-echo "================================"
+echo "All checks passed."

src/__init__.py

@@ -1,3 +1,3 @@
 """diffchunk - MCP server for navigating large diff files."""
 
-__version__ = "0.1.0"
+__version__ = "0.1.9"

src/chunker.py

@@ -20,8 +20,13 @@ def chunk_diff(
         skip_generated: bool = True,
         include_patterns: List[str] | None = None,
         exclude_patterns: List[str] | None = None,
+        max_chunk_lines: int | None = None,
     ) -> None:
         """Chunk a diff file into the session."""
+        if max_chunk_lines is None:
+            max_chunk_lines = self.max_chunk_lines
+        elif not isinstance(max_chunk_lines, int) or max_chunk_lines <= 0:
+            raise ValueError("max_chunk_lines must be a positive integer")
         chunk_number = 1
         current_chunk_lines = 0
         current_chunk_content: List[str] = []
@@ -55,7 +60,7 @@ def chunk_diff(
             file_name = files[-1]
 
             # Check if this file needs to be split
-            if content_lines > self.max_chunk_lines:
+            if content_lines > max_chunk_lines:
                 # Save current chunk if it has content
                 if current_chunk_content:
                     self._save_chunk(
@@ -73,7 +78,9 @@ def chunk_diff(
                     current_chunk_file_line_counts = {}
 
                 # Split the large file
-                file_chunks = self._split_large_file(files, content, content_lines)
+                file_chunks = self._split_large_file(
+                    files, content, content_lines, max_chunk_lines
+                )
                 parent_file = files[0] if len(files) == 1 else f"{len(files)} files"
 
                 for sub_index, (sub_files, sub_content, sub_lines) in enumerate(
@@ -95,7 +102,7 @@ def chunk_diff(
                 # Check if we need to start a new chunk
                 if (
                     current_chunk_content
-                    and current_chunk_lines + content_lines > self.max_chunk_lines
+                    and current_chunk_lines + content_lines > max_chunk_lines
                 ):
                     # Save current chunk
                     self._save_chunk(
@@ -172,10 +179,10 @@ def _save_chunk(
         session.add_chunk(chunk)
 
     def _split_large_file(
-        self, files: List[str], content: str, file_line_count: int
+        self, files: List[str], content: str, file_line_count: int, max_chunk_lines: int
     ) -> List[Tuple[List[str], str, int]]:
         """Split a large file's diff content at hunk boundaries."""
-        if file_line_count <= self.max_chunk_lines:
+        if file_line_count <= max_chunk_lines:
             return [(files, content, file_line_count)]
 
         # Pattern to match hunk headers like @@ -1,4 +1,6 @@
@@ -192,7 +199,7 @@ def _split_large_file(
 
         # Be very aggressive about staying under the limit
         target_chunk_size = max(
-            self.max_chunk_lines * 0.8, 200
+            max_chunk_lines * 0.8, 200
         )  # 80% of limit or 200 lines minimum
 
         for i, line in enumerate(lines):
@@ -236,10 +243,7 @@ def _split_large_file(
                 current_chunk_line_count += 1
 
             # STRICT enforcement: split immediately if we exceed limit
-            if (
-                current_chunk_line_count + len(file_header_lines)
-                >= self.max_chunk_lines
-            ):
+            if current_chunk_line_count + len(file_header_lines) >= max_chunk_lines:
                 # Find the last hunk header in current chunk to split there
                 last_hunk_idx = None
                 for j in range(len(current_chunk_lines) - 1, -1, -1):

src/main.py

@@ -4,7 +4,8 @@
 import asyncio
 import sys
 from importlib.metadata import version
-from .server import DiffChunkServer
+
+from .server import mcp
 
 
 def main():
@@ -35,12 +36,17 @@ def main():
 
     try:
         print(
-            f"Starting diffchunk MCP server v{version('diffchunk')}...", file=sys.stderr
+            f"Starting diffchunk MCP server v{version('diffchunk')}...",
+            file=sys.stderr,
+            flush=True,
+        )
+        print(
+            "Server ready - waiting for MCP client connection",
+            file=sys.stderr,
+            flush=True,
         )
-        print("Server ready - waiting for MCP client connection", file=sys.stderr)
-        server = DiffChunkServer()
-        asyncio.run(server.run())
-    except KeyboardInterrupt:
+        mcp.run()
+    except (KeyboardInterrupt, asyncio.CancelledError):
         print("Server shutdown requested", file=sys.stderr)
         sys.exit(0)
     except Exception as e:

src/models.py

@@ -103,7 +103,7 @@ def find_chunks_for_files(self, pattern: str) -> List[int]:
         matching_chunks = set()
 
         for file_path, chunk_numbers in self.file_to_chunks.items():
-            if fnmatch.fnmatch(file_path, pattern):
+            if fnmatch.fnmatch(file_path.lower(), pattern.lower()):
                 matching_chunks.update(chunk_numbers)
 
         return sorted(matching_chunks)

src/parser.py

@@ -1,9 +1,12 @@
 """Diff file parsing functionality."""
 
 import fnmatch
+import logging
 import re
 from typing import List, Tuple, Iterator
 
+logger = logging.getLogger("diffchunk")
+
 
 class DiffParser:
     """Parser for unified diff files."""
@@ -135,6 +138,12 @@ def _read_diff_file(self, file_path: str) -> List[str]:
         encoding = (
             result.get("encoding") if result.get("confidence", 0) > 0.7 else "utf-8"
         )
+        logger.debug(
+            "Detected encoding %s (confidence %.1f) for %s",
+            encoding,
+            result.get("confidence", 0),
+            file_path,
+        )
 
         try:
             with open(file_path, "r", encoding=encoding) as f: