diff --git a/bench/real-world.ts b/bench/real-world.ts
index 098a5c6..0e57ac4 100644
--- a/bench/real-world.ts
+++ b/bench/real-world.ts
@@ -90,7 +90,7 @@ function collectSourceFiles(root: string, cap: number): string[] {
     if (out.length >= cap) return;
     let entries: ReturnType<typeof readdirSync>;
     try {
-      entries = readdirSync(dir, { withFileTypes: true });
+      entries = readdirSync(dir, { withFileTypes: true, encoding: "utf-8" });
     } catch {
       return;
     }
diff --git a/src/miners/ast-miner.ts b/src/miners/ast-miner.ts
index 1857723..30b577b 100644
--- a/src/miners/ast-miner.ts
+++ b/src/miners/ast-miner.ts
@@ -612,7 +612,7 @@ export function extractDirectory(
 
     let entries: Dirent[];
     try {
-      entries = readdirSync(dir, { withFileTypes: true });
+      entries = readdirSync(dir, { withFileTypes: true, encoding: "utf-8" });
     } catch {
       return;
     }
diff --git a/src/miners/skills-miner.ts b/src/miners/skills-miner.ts
index 86d795a..a34c444 100644
--- a/src/miners/skills-miner.ts
+++ b/src/miners/skills-miner.ts
@@ -223,10 +223,7 @@ function discoverSkillFiles(skillsDir: string): string[] {
   // `.localeCompare`, `.startsWith`, and path join calls.
   let entries;
   try {
-    entries = readdirSync(skillsDir, {
-      withFileTypes: true,
-      encoding: "utf-8",
-    });
+    const entries = readdirSync(dir, { withFileTypes: true, encoding: "utf-8" });
   } catch {
     return [];
   }
diff --git a/tests/ast-miner.test.ts b/tests/ast-miner.test.ts
index 6bfd2fc..ac34258 100644
--- a/tests/ast-miner.test.ts
+++ b/tests/ast-miner.test.ts
@@ -1,6 +1,8 @@
 import { describe, it, expect } from "vitest";
 import { extractFile, extractDirectory, SUPPORTED_EXTENSIONS } from "../src/miners/ast-miner.js";
 import { join } from "node:path";
+import { mkdtempSync, rmSync, mkdirSync, writeFileSync } from "node:fs";
+import * as os from "node:os";
 
 const FIXTURES = join(import.meta.dirname, "fixtures");
 
@@ -138,4 +140,81 @@ describe("AST Miner", () => {
       expect(edges).toEqual([]);
     });
   });
+
+describe("depth limits", () => {
+    function mkdtemp(prefix: string): string {
+      return mkdtempSync(join(os.tmpdir(), prefix));
+    }
+
+    function cleanup(dir: string): void {
+      rmSync(dir, { recursive: true, force: true });
+    }
+
+    it("does not throw on directory nested 101 levels deep", () => {
+      // Build a path 101 levels deep within a temp root
+      const root = mkdtemp("engram-deep-");
+      let current = root;
+
+      for (let i = 1; i <= 101; i++) {
+        current = join(current, `level${i}`);
+      }
+      mkdirSync(current, { recursive: true });
+      writeFileSync(join(current, "deep.ts"), "export function deep() {}\n");
+
+      // extractDirectory should not throw — MAX_DEPTH guard prevents stack overflow
+      expect(() => extractDirectory(root)).not.toThrow();
+
+      cleanup(root);
+    });
+
+    it("extracts files at exactly MAX_DEPTH (100)", () => {
+      const root = mkdtemp("engram-exact-");
+      let current = root;
+
+      for (let i = 1; i <= 100; i++) {
+        current = join(current, `d${i}`);
+      }
+      mkdirSync(current, { recursive: true });
+      writeFileSync(join(current, "exact.ts"), "export function exact() {}\n");
+
+      const result = extractDirectory(root);
+
+      // File at depth 100 IS reachable (depth 0..100 inclusive)
+      expect(result.fileCount).toBeGreaterThanOrEqual(1);
+      expect(result.nodes.some((n) => n.label === "exact()")).toBe(true);
+
+      cleanup(root);
+    });
+
+    it("stops extraction beyond MAX_DEPTH (100)", () => {
+      const root = mkdtemp("engram-beyond-");
+      let current = root;
+
+      for (let i = 1; i <= 101; i++) {
+        current = join(current, `d${i}`);
+      }
+      mkdirSync(current, { recursive: true });
+      writeFileSync(join(current, "beyond.ts"), "export function beyond() {}\n");
+
+      const result = extractDirectory(root);
+
+      // File at depth 101 should NOT be extracted
+      expect(result.fileCount).toBe(0);
+      expect(result.nodes.some((n) => n.label === "beyond()")).toBe(false);
+
+      cleanup(root);
+    });
+
+    it("returns mtimes map for incremental indexing", () => {
+      const root = mkdtemp("engram-mtime-");
+      mkdirSync(join(root, "src"), { recursive: true });
+      writeFileSync(join(root, "src", "app.ts"), "export function app() {}\n");
+
+      const result = extractDirectory(root);
+      expect(result.mtimes.size).toBeGreaterThan(0);
+      expect(result.skippedCount).toBe(0);
+
+      cleanup(root);
+    });
+  });
 });
diff --git a/tests/git-miner.test.ts b/tests/git-miner.test.ts
new file mode 100644
index 0000000..a2a4351
--- /dev/null
+++ b/tests/git-miner.test.ts
@@ -0,0 +1,129 @@
+import { describe, it, expect } from "vitest";
+import { mkdtempSync, rmSync, mkdirSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import * as os from "node:os";
+import { execSync } from "node:child_process";
+import { mineGitHistory } from "../src/miners/git-miner.js";
+
+describe("git-miner", () => {
+  it("caps co-change edges at MAX_FILES_PER_COMMIT (50) for large commits", () => {
+    const tmpDir = mkdtempSync(join(os.tmpdir(), "engram-cap-"));
+    const gitDir = join(tmpDir, "repo");
+    mkdirSync(gitDir, { recursive: true });
+
+    execSync("git init", { cwd: gitDir });
+    execSync("git config user.email test@test.com", { cwd: gitDir });
+    execSync("git config user.name Test", { cwd: gitDir });
+
+    // Create 51 files and commit them all together
+    for (let i = 1; i <= 51; i++) {
+      writeFileSync(join(gitDir, `file${i}.ts`), `export const x${i} = ${i};\n`);
+    }
+
+    execSync("git add .", { cwd: gitDir });
+    execSync("git commit -m 'bulk: add 51 files'", { cwd: gitDir });
+
+    const result = mineGitHistory(gitDir);
+
+    // MAX_FILES_PER_COMMIT = 50 → files beyond limit are ignored
+    // With only 1 commit, no pair reaches the threshold of 3 co-changes
+    const coChangeEdges = result.edges.filter(
+      (e) => e.metadata?.coChangeCount !== undefined
+    );
+    expect(coChangeEdges.length).toBe(0);
+
+    rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it("handles commit with exactly MAX_FILES_PER_COMMIT (50) files", () => {
+    const tmpDir = mkdtempSync(join(os.tmpdir(), "engram-max-"));
+    const gitDir = join(tmpDir, "repo");
+    mkdirSync(gitDir, { recursive: true });
+
+    execSync("git init", { cwd: gitDir });
+    execSync("git config user.email test@test.com", { cwd: gitDir });
+    execSync("git config user.name Test", { cwd: gitDir });
+
+    for (let i = 1; i <= 50; i++) {
+      writeFileSync(join(gitDir, `f${i}.ts`), `const v${i} = ${i};\n`);
+    }
+
+    execSync("git add .", { cwd: gitDir });
+    execSync("git commit -m 'max files commit'", { cwd: gitDir });
+
+    const result = mineGitHistory(gitDir);
+
+    // 50 files at count=1 → no edges (threshold is 3)
+    const coChangeEdges = result.edges.filter(
+      (e) => e.metadata?.coChangeCount !== undefined
+    );
+    expect(coChangeEdges.length).toBe(0);
+
+    rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it("creates edges when files co-change 3+ times", () => {
+    const tmpDir = mkdtempSync(join(os.tmpdir(), "engram-edge-"));
+    const gitDir = join(tmpDir, "repo");
+    mkdirSync(gitDir, { recursive: true });
+
+    execSync("git init", { cwd: gitDir });
+    execSync("git config user.email test@test.com", { cwd: gitDir });
+    execSync("git config user.name Test", { cwd: gitDir });
+
+    // Create 10 files
+    for (let i = 1; i <= 10; i++) {
+      writeFileSync(join(gitDir, `lib${i}.ts`), "export function fn() {}\n");
+    }
+
+    // Commit all files together 3 times (modify ALL files each time)
+    for (let commit = 1; commit <= 3; commit++) {
+      // Update ALL files to ensure they're included in every commit
+      for (let i = 1; i <= 10; i++) {
+        writeFileSync(join(gitDir, `lib${i}.ts`), `// commit ${commit}\nexport function fn${i}() {}\n`);
+      }
+      execSync("git add .", { cwd: gitDir });
+      execSync(`git commit -m 'chore: update all libs ${commit}'`, { cwd: gitDir });
+    }
+
+    const result = mineGitHistory(gitDir);
+
+    // 10 files at count=3 → C(10,2) = 45 edges
+    const coChangeEdges = result.edges.filter(
+      (e) => e.metadata?.coChangeCount === 3
+    );
+    expect(coChangeEdges.length).toBe(45);
+    expect(coChangeEdges.every((e) => e.confidenceScore > 0.5)).toBe(true);
+
+    rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it("skips build/dist/node_modules prefixes", () => {
+    const tmpDir = mkdtempSync(join(os.tmpdir(), "engram-skip-"));
+    const gitDir = join(tmpDir, "repo");
+    mkdirSync(gitDir, { recursive: true });
+
+    execSync("git init", { cwd: gitDir });
+    execSync("git config user.email test@test.com", { cwd: gitDir });
+    execSync("git config user.name Test", { cwd: gitDir });
+
+    mkdirSync(join(gitDir, "src"), { recursive: true });
+    writeFileSync(join(gitDir, "src/a.ts"), "export const a = 1;\n");
+    mkdirSync(join(gitDir, "dist"), { recursive: true });
+    writeFileSync(join(gitDir, "dist/bundle.js"), "// generated");
+    mkdirSync(join(gitDir, "node_modules", "pkg"), { recursive: true });
+    writeFileSync(join(gitDir, "node_modules", "pkg", "index.js"), "// dep");
+
+    execSync("git add .", { cwd: gitDir });
+    execSync("git commit -m 'with build artifacts'", { cwd: gitDir });
+
+    const result = mineGitHistory(gitDir);
+
+    // Only src/a.ts should appear in the graph
+    const nodeLabels = result.nodes.map((n) => n.label);
+    expect(nodeLabels.some((l) => l.includes("dist"))).toBe(false);
+    expect(nodeLabels.some((l) => l.includes("node_modules"))).toBe(false);
+
+    rmSync(tmpDir, { recursive: true, force: true });
+  });
+});
\ No newline at end of file