diff --git a/src/server/api/git-diffs.ts b/src/server/api/git-diffs.ts
index bcdeec0..38e43fd 100644
--- a/src/server/api/git-diffs.ts
+++ b/src/server/api/git-diffs.ts
@@ -14,7 +14,7 @@ export interface FileDiff {
   status: "added" | "deleted" | "modified";
 }
 
-function parseGitDiff(stdout: string): FileDiff[] {
+export function parseGitDiff(stdout: string): FileDiff[] {
   const files: FileDiff[] = [];
   // Split on diff --git headers
   const blocks = stdout.split(/\ndiff --git /).filter(Boolean);
@@ -29,12 +29,12 @@ function parseGitDiff(stdout: string): FileDiff[] {
     const patchContent = block;
 
     // Count additions/deletions
-    const additions = (patchContent.match(/^\+/gm) || []).length;
-    const deletions = (patchContent.match(/^-/gm) || []).length;
+    const additions = (patchContent.match(/^\+(?!\+\+)/gm) || []).length;
+    const deletions = (patchContent.match(/^-(?!--)/gm) || []).length;
 
     // Determine status
-    const isNew = /^new file mode/.test(patchContent);
-    const isDeleted = /^deleted file mode/.test(patchContent);
+    const isNew = /^new file mode/m.test(patchContent);
+    const isDeleted = /^deleted file mode/m.test(patchContent);
     const status = isNew ? "added" : isDeleted ? "deleted" : "modified";
 
     files.push({
diff --git a/tests/git-diffs.test.ts b/tests/git-diffs.test.ts
new file mode 100644
index 0000000..bd5f685
--- /dev/null
+++ b/tests/git-diffs.test.ts
@@ -0,0 +1,60 @@
+import { describe, expect, it } from "vitest";
+import { parseGitDiff } from "../src/server/api/git-diffs.js";
+
+describe("parseGitDiff", () => {
+  it("counts changed lines without counting diff file headers", () => {
+    const diff = [
+      "diff --git a/src/app.ts b/src/app.ts",
+      "index 1111111..2222222 100644",
+      "--- a/src/app.ts",
+      "+++ b/src/app.ts",
+      "@@ -1,3 +1,4 @@",
+      " const keep = true;",
+      "-const oldName = 'reasonix';",
+      "+const newName = 'carboncode';",
+      "+const enabled = true;",
+      " export { keep };",
+      "diff --git a/src/new.ts b/src/new.ts",
+      "new file mode 100644",
+      "index 0000000..3333333",
+      "--- /dev/null",
+      "+++ b/src/new.ts",
+      "@@ -0,0 +1,2 @@",
+      "+export const one = 1;",
+      "+export const two = 2;",
+      "diff --git a/src/old.ts b/src/old.ts",
+      "deleted file mode 100644",
+      "index 4444444..0000000",
+      "--- a/src/old.ts",
+      "+++ /dev/null",
+      "@@ -1,2 +0,0 @@",
+      "-export const gone = true;",
+      "-export const alsoGone = true;",
+      "",
+    ].join("\n");
+
+    expect(parseGitDiff(diff)).toEqual([
+      {
+        file: "src/app.ts",
+        additions: 2,
+        deletions: 1,
+        patch: expect.any(String),
+        status: "modified",
+      },
+      {
+        file: "src/new.ts",
+        additions: 2,
+        deletions: 0,
+        patch: expect.any(String),
+        status: "added",
+      },
+      {
+        file: "src/old.ts",
+        additions: 0,
+        deletions: 2,
+        patch: expect.any(String),
+        status: "deleted",
+      },
+    ]);
+  });
+});