diff --git a/supacode/Clients/Git/GitClient.swift b/supacode/Clients/Git/GitClient.swift
index d71d5112..0ea37f03 100644
--- a/supacode/Clients/Git/GitClient.swift
+++ b/supacode/Clients/Git/GitClient.swift
@@ -434,10 +434,10 @@ struct GitClient {
       )
       async let untrackedOutput = runGit(
         operation: .untrackedFilePaths,
-        arguments: ["-C", path, "-c", "core.quotePath=false", "ls-files", "--others", "--exclude-standard"]
+        arguments: ["-C", path, "-c", "core.quotePath=false", "ls-files", "--others", "--exclude-standard", "-z"]
       )
       let tracked = parseShortstat(try await diffOutput)
-      let untrackedPaths = parseFileList(try await untrackedOutput)
+      let untrackedPaths = parseNULFileList(try await untrackedOutput)
       let untrackedLines = Self.countLinesInFiles(untrackedPaths, relativeTo: worktreeURL)
       return (added: tracked.added + untrackedLines, removed: tracked.removed)
     } catch {
@@ -452,21 +452,63 @@ struct GitClient {
     guard let handle = try? FileHandle(forReadingFrom: indexURL) else { return nil }
     defer { try? handle.close() }
     guard let header = try? handle.read(upToCount: 12), header.count == 12 else { return nil }
-    return header[8...11].withUnsafeBytes { Int($0.load(as: UInt32.self).bigEndian) }
+    guard header.prefix(4).elementsEqual("DIRC".utf8) else { return nil }
+    let version = Self.bigEndianUInt32(from: header, offset: 4)
+    guard (2...4).contains(version) else { return nil }
+    return Int(Self.bigEndianUInt32(from: header, offset: 8))
   }
 
   nonisolated static func countLinesInFiles(_ relativePaths: [String], relativeTo base: URL) -> Int {
     var total = 0
     for relativePath in relativePaths {
       let fileURL = base.appending(path: relativePath)
-      guard let data = try? Data(contentsOf: fileURL, options: .mappedIfSafe) else { continue }
-      let prefixCount = min(data.count, 8192)
-      if data.prefix(prefixCount).contains(0x00) { continue }
-      total += data.reduce(0) { $0 + ($1 == 0x0A ? 1 : 0) }
+      total += Self.countLines(in: fileURL) ?? 0
     }
     return total
   }
 
+  nonisolated private static func bigEndianUInt32(from data: Data, offset: Int) -> UInt32 {
+    data[offset..<(offset + 4)].reduce(UInt32(0)) { ($0 << 8) | UInt32($1) }
+  }
+
+  nonisolated private static func countLines(in fileURL: URL) -> Int? {
+    guard let handle = try? FileHandle(forReadingFrom: fileURL) else { return nil }
+    defer { try? handle.close() }
+
+    let binaryProbeByteCount = 8_192
+    let chunkByteCount = 64 * 1_024
+    var probedByteCount = 0
+    var lineCount = 0
+    var isEmpty = true
+    var lastByte: UInt8?
+
+    while true {
+      let chunk: Data
+      do {
+        guard let readChunk = try handle.read(upToCount: chunkByteCount) else { break }
+        chunk = readChunk
+      } catch {
+        return nil
+      }
+      guard !chunk.isEmpty else { break }
+
+      isEmpty = false
+      if probedByteCount < binaryProbeByteCount {
+        let remainingProbeCount = binaryProbeByteCount - probedByteCount
+        let probe = chunk.prefix(remainingProbeCount)
+        if probe.contains(0x00) { return nil }
+        probedByteCount += probe.count
+      }
+      lineCount += chunk.reduce(0) { $0 + ($1 == 0x0A ? 1 : 0) }
+      lastByte = chunk.last
+    }
+
+    if !isEmpty, lastByte != 0x0A {
+      lineCount += 1
+    }
+    return lineCount
+  }
+
   nonisolated private static func resolveGitDirectory(for worktreeURL: URL) -> URL? {
     let gitURL = worktreeURL.appending(path: ".git")
     var isDirectory = ObjCBool(false)
@@ -806,6 +848,12 @@ struct GitClient {
       .filter { !$0.isEmpty }
   }
 
+  nonisolated private func parseNULFileList(_ output: String) -> [String] {
+    output
+      .split(separator: "\0", omittingEmptySubsequences: true)
+      .map(String.init)
+  }
+
   nonisolated private func parseFileListCount(_ output: String) -> Int {
     parseFileList(output).count
   }
diff --git a/supacode/Features/Repositories/Views/WorktreeDetailTitleView.swift b/supacode/Features/Repositories/Views/WorktreeDetailTitleView.swift
index 657309b2..8b46ec94 100644
--- a/supacode/Features/Repositories/Views/WorktreeDetailTitleView.swift
+++ b/supacode/Features/Repositories/Views/WorktreeDetailTitleView.swift
@@ -56,7 +56,8 @@ struct WorktreeDetailTitleView: View {
         ))
     } else {
       // Button wrapper gives folder/workspace the same toolbar padding as the branch button.
-      Button {} label: {
+      Button {
+      } label: {
         labelContent
       }
     }
diff --git a/supacodeTests/GitClientLineChangesTests.swift b/supacodeTests/GitClientLineChangesTests.swift
index 689be317..fa1a62e8 100644
--- a/supacodeTests/GitClientLineChangesTests.swift
+++ b/supacodeTests/GitClientLineChangesTests.swift
@@ -41,6 +41,7 @@ struct GitClientLineChangesTests {
     let untrackedArgs = try #require(calls.first { $0.contains("ls-files") })
     #expect(untrackedArgs.contains("--others"))
     #expect(untrackedArgs.contains("--exclude-standard"))
+    #expect(untrackedArgs.contains("-z"))
   }
 
   @Test func lineChangesHandlesMissingDeletions() async {
@@ -112,7 +113,7 @@ struct GitClientLineChangesTests {
             stdout: " 1 file changed, 10 insertions(+), 2 deletions(-)\n", stderr: "", exitCode: 0)
         }
         if arguments.contains("ls-files") {
-          return ShellOutput(stdout: "new_file.swift\n", stderr: "", exitCode: 0)
+          return ShellOutput(stdout: "new_file.swift\0", stderr: "", exitCode: 0)
         }
         return ShellOutput(stdout: "", stderr: "", exitCode: 0)
       },
@@ -150,7 +151,39 @@ struct GitClientLineChangesTests {
           return ShellOutput(stdout: "", stderr: "", exitCode: 0)
         }
         if arguments.contains("ls-files") {
-          return ShellOutput(stdout: "image.png\nreadme.txt\n", stderr: "", exitCode: 0)
+          return ShellOutput(stdout: "image.png\0readme.txt\0", stderr: "", exitCode: 0)
+        }
+        return ShellOutput(stdout: "", stderr: "", exitCode: 0)
+      },
+      runLoginImpl: { _, _, _, _ in ShellOutput(stdout: "", stderr: "", exitCode: 0) }
+    )
+    let client = GitClient(shell: shell)
+
+    let changes = await client.lineChanges(at: tempRoot)
+
+    #expect(changes?.added == 2)
+    #expect(changes?.removed == 0)
+  }
+
+  @Test func lineChangesParsesNULSeparatedUntrackedFilePaths() async throws {
+    let fileManager = FileManager.default
+    let tempRoot = fileManager.temporaryDirectory.appending(path: UUID().uuidString)
+    defer { try? fileManager.removeItem(at: tempRoot) }
+    let gitDirectory = tempRoot.appending(path: ".git")
+    try fileManager.createDirectory(at: gitDirectory, withIntermediateDirectories: true)
+    let headURL = gitDirectory.appending(path: "HEAD")
+    try "ref: refs/heads/main\n".write(to: headURL, atomically: true, encoding: .utf8)
+
+    let relativePath = " leading space\nname.txt"
+    try "alpha\nbeta".write(to: tempRoot.appending(path: relativePath), atomically: true, encoding: .utf8)
+
+    let shell = ShellClient(
+      run: { _, arguments, _ in
+        if arguments.contains("--shortstat") {
+          return ShellOutput(stdout: "", stderr: "", exitCode: 0)
+        }
+        if arguments.contains("ls-files") {
+          return ShellOutput(stdout: "\(relativePath)\0", stderr: "", exitCode: 0)
         }
         return ShellOutput(stdout: "", stderr: "", exitCode: 0)
       },
@@ -198,18 +231,32 @@ struct GitClientLineChangesTests {
     let gitDirectory = tempRoot.appending(path: ".git")
     try fileManager.createDirectory(at: gitDirectory, withIntermediateDirectories: true)
 
-    var header = Data()
-    header.append(contentsOf: "DIRC".utf8)
-    var version = UInt32(2).bigEndian
-    header.append(Data(bytes: &version, count: 4))
-    var entryCount = UInt32(42_000).bigEndian
-    header.append(Data(bytes: &entryCount, count: 4))
-    try header.write(to: gitDirectory.appending(path: "index"))
+    try writeGitIndexHeader(entryCount: 42_000, to: gitDirectory.appending(path: "index"))
 
     let count = GitClient.indexEntryCount(at: tempRoot)
     #expect(count == 42_000)
   }
 
+  @Test func indexEntryCountRejectsInvalidHeader() throws {
+    let fileManager = FileManager.default
+    let tempRoot = fileManager.temporaryDirectory.appending(path: UUID().uuidString)
+    defer { try? fileManager.removeItem(at: tempRoot) }
+    let gitDirectory = tempRoot.appending(path: ".git")
+    try fileManager.createDirectory(at: gitDirectory, withIntermediateDirectories: true)
+
+    var invalidMagic = Data()
+    invalidMagic.append(contentsOf: "NOPE".utf8)
+    invalidMagic.append(contentsOf: [0, 0, 0, 2])
+    invalidMagic.append(contentsOf: [0, 0, 0, 1])
+    try invalidMagic.write(to: gitDirectory.appending(path: "index"))
+
+    #expect(GitClient.indexEntryCount(at: tempRoot) == nil)
+
+    try writeGitIndexHeader(version: 99, entryCount: 1, to: gitDirectory.appending(path: "index"))
+
+    #expect(GitClient.indexEntryCount(at: tempRoot) == nil)
+  }
+
   @Test func indexEntryCountReturnsNilForMissingIndex() {
     let count = GitClient.indexEntryCount(at: URL(fileURLWithPath: "/nonexistent"))
     #expect(count == nil)
@@ -227,6 +274,18 @@ struct GitClientLineChangesTests {
     #expect(count == 5)
   }
 
+  @Test func countLinesInFilesCountsFinalLineWithoutTrailingNewline() throws {
+    let fileManager = FileManager.default
+    let tempRoot = fileManager.temporaryDirectory.appending(path: UUID().uuidString)
+    defer { try? fileManager.removeItem(at: tempRoot) }
+    try fileManager.createDirectory(at: tempRoot, withIntermediateDirectories: true)
+    try "hello".write(to: tempRoot.appending(path: "single.txt"), atomically: true, encoding: .utf8)
+    try "a\nb".write(to: tempRoot.appending(path: "multi.txt"), atomically: true, encoding: .utf8)
+
+    let count = GitClient.countLinesInFiles(["single.txt", "multi.txt"], relativeTo: tempRoot)
+    #expect(count == 3)
+  }
+
   @Test func countLinesInFilesSkipsBinaryFiles() throws {
     let fileManager = FileManager.default
     let tempRoot = fileManager.temporaryDirectory.appending(path: UUID().uuidString)
@@ -252,4 +311,22 @@ struct GitClientLineChangesTests {
     let count = GitClient.countLinesInFiles(["exists.txt", "gone.txt"], relativeTo: tempRoot)
     #expect(count == 2)
   }
+
+  private func writeGitIndexHeader(
+    version: UInt32 = 2,
+    entryCount: UInt32,
+    to url: URL
+  ) throws {
+    var header = Data()
+    header.append(contentsOf: "DIRC".utf8)
+    header.append(UInt8((version >> 24) & 0xff))
+    header.append(UInt8((version >> 16) & 0xff))
+    header.append(UInt8((version >> 8) & 0xff))
+    header.append(UInt8(version & 0xff))
+    header.append(UInt8((entryCount >> 24) & 0xff))
+    header.append(UInt8((entryCount >> 16) & 0xff))
+    header.append(UInt8((entryCount >> 8) & 0xff))
+    header.append(UInt8(entryCount & 0xff))
+    try header.write(to: url)
+  }
 }