[kensai] skip .git dirs and binary extensions during walk

PathIndex walked every file including .git internals and
opened every file for line counting. On repos with millions
of files (e.g. game engines with binary assets), session_start
exceeded MCP tool timeout.

Two configurable constants control the behavior:
- WALK_EXCLUDE_DIRS: directories never descended into (.git)
- BINARY_EXTENSIONS: ~100 extensions that get stat-only
  indexing (size captured, marked isBinary, no fd opened)

Binary-extension files remain in the index for find_files
and grep -- only line counting is skipped.

Author: xobotyi

claude/kensai/mcp/review/src/repofs/pathindex/pathindex.test.ts

@@ -284,7 +284,7 @@ describe("PathIndex.new", () => {
 		expect(ix.length).toBe(4);
 	});
 
-	it("includes all files without exclusions", async () => {
+	it("excludes .git directory", async () => {
 		await createFiles(tempDir, [
 			"src/main.go",
 			".git/HEAD",
@@ -293,16 +293,9 @@ describe("PathIndex.new", () => {
 			".hidden",
 		]);
 		const ix = await PathIndex.new(tempDir);
-		expect(ix.paths).toEqual(
-			expect.arrayContaining([
-				"src/main.go",
-				".git/HEAD",
-				".git/objects/ab/cdef",
-				"node_modules/lib/index.js",
-				".hidden",
-			]),
-		);
-		expect(ix.length).toBe(5);
+		expect(ix.paths).toEqual(expect.arrayContaining(["src/main.go", "node_modules/lib/index.js", ".hidden"]));
+		expect(ix.paths.filter((p) => p.startsWith(".git/"))).toHaveLength(0);
+		expect(ix.length).toBe(3);
 	});
 
 	it("returns paths in sorted order", async () => {

claude/kensai/mcp/review/src/repofs/pathindex/pathindex.ts

@@ -8,6 +8,142 @@ import picomatch from "picomatch";
 
 import { ErrBinaryContent, LineIter } from "../lineiter/lineiter.ts";
 
+/** Directory names skipped during filesystem walk. Never descended into. */
+const WALK_EXCLUDE_DIRS: ReadonlySet<string> = new Set([".git"]);
+
+/** Extensions treated as binary without opening the file. Stat-only — no line counting, no fd consumed. */
+const BINARY_EXTENSIONS: ReadonlySet<string> = new Set([
+	// Images
+	".png",
+	".jpg",
+	".jpeg",
+	".gif",
+	".bmp",
+	".ico",
+	".svg",
+	".webp",
+	".tiff",
+	".tif",
+	".psd",
+	".dds",
+	".tga",
+	".hdr",
+	".exr",
+	".ktx",
+	".ktx2",
+	".astc",
+	".pvr",
+	".basis",
+	// Audio
+	".wav",
+	".mp3",
+	".ogg",
+	".flac",
+	".aac",
+	".wma",
+	".m4a",
+	".opus",
+	// Video
+	".mp4",
+	".avi",
+	".mkv",
+	".mov",
+	".wmv",
+	".webm",
+	".flv",
+	// 3D / geometry
+	".fbx",
+	".obj",
+	".gltf",
+	".glb",
+	".blend",
+	".dae",
+	".3ds",
+	".stl",
+	".usd",
+	".usda",
+	".usdc",
+	".usdz",
+	// Compiled / binary
+	".exe",
+	".dll",
+	".so",
+	".dylib",
+	".o",
+	".a",
+	".lib",
+	".pdb",
+	".wasm",
+	".class",
+	".jar",
+	".pyc",
+	".pyo",
+	// Archives
+	".zip",
+	".tar",
+	".gz",
+	".bz2",
+	".xz",
+	".7z",
+	".rar",
+	".zst",
+	".lz4",
+	// Fonts
+	".ttf",
+	".otf",
+	".woff",
+	".woff2",
+	".eot",
+	// Documents / data
+	".pdf",
+	".doc",
+	".docx",
+	".xls",
+	".xlsx",
+	".ppt",
+	".pptx",
+	".sqlite",
+	".db",
+	".mdb",
+	// Game engine assets (general)
+	".bin",
+	".pak",
+	".dat",
+	".res",
+	".asset",
+	".bundle",
+	".bank",
+	".bsp",
+	".nav",
+	".lightmap",
+	".cubemap",
+	".mdl",
+	".vtf",
+	".vpk",
+	".pck",
+	// Compiled shaders
+	".spv",
+	".cso",
+	".dxbc",
+	".metallib",
+	// Unreal Engine
+	".uasset",
+	".umap",
+	".ubulk",
+	".upk",
+	// Audio middleware (FMOD / Wwise)
+	".fsb",
+	".fev",
+	".bnk",
+	// Dagor Engine
+	".dag",
+	".dynmodel",
+	".rendinst",
+	".composit",
+	".gameobj",
+	".lod",
+]);
+
 export type IndexEntryFile = {
 	type: "file";
 	name: string;
@@ -168,6 +304,8 @@ export class PathIndex {
 		const work: Promise<void>[] = [];
 
 		for (const dirent of dirEntries) {
+			if (WALK_EXCLUDE_DIRS.has(dirent.name)) continue;
+
 			const relPath = path.join(dir, dirent.name);
 			const absPath = nativePath.join(this.absRoot, relPath);
 
@@ -194,21 +332,41 @@ export class PathIndex {
 				continue;
 			}
 
-			work.push(
-				Promise.all([fs.stat(absPath), this.#countLines(absPath)]).then(([s, lc]) => {
-					const entry: IndexEntryFile = {
-						type: "file",
-						name: dirent.name,
-						size: s.size,
-						lineCount: lc.lineCount,
-						maxLineLen: lc.maxLineLen,
-						isBinary: lc.isBinary,
-					};
-					dirEntry.children.push(entry);
-					this.paths.push(relPath);
-					this.#entries.set(relPath, entry);
-				}),
-			);
+			const ext = path.extname(dirent.name).toLowerCase();
+
+			if (BINARY_EXTENSIONS.has(ext)) {
+				work.push(
+					fs.stat(absPath).then((s) => {
+						const entry: IndexEntryFile = {
+							type: "file",
+							name: dirent.name,
+							size: s.size,
+							lineCount: 0,
+							maxLineLen: 0,
+							isBinary: true,
+						};
+						dirEntry.children.push(entry);
+						this.paths.push(relPath);
+						this.#entries.set(relPath, entry);
+					}),
+				);
+			} else {
+				work.push(
+					Promise.all([fs.stat(absPath), this.#countLines(absPath)]).then(([s, lc]) => {
+						const entry: IndexEntryFile = {
+							type: "file",
+							name: dirent.name,
+							size: s.size,
+							lineCount: lc.lineCount,
+							maxLineLen: lc.maxLineLen,
+							isBinary: lc.isBinary,
+						};
+						dirEntry.children.push(entry);
+						this.paths.push(relPath);
+						this.#entries.set(relPath, entry);
+					}),
+				);
+			}
 		}
 
 		await Promise.all(work);