init claude-code

2026-04-01 17:32:37 +02:00
commit 73b208c009
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+import * as fs from 'fs'
+import {
+  mkdir as mkdirPromise,
+  open,
+  readdir as readdirPromise,
+  readFile as readFilePromise,
+  rename as renamePromise,
+  rmdir as rmdirPromise,
+  rm as rmPromise,
+  stat as statPromise,
+  unlink as unlinkPromise,
+} from 'fs/promises'
+import { homedir } from 'os'
+import * as nodePath from 'path'
+import { getErrnoCode } from './errors.js'
+import { slowLogging } from './slowOperations.js'
+
+/**
+ * Simplified filesystem operations interface based on Node.js fs module.
+ * Provides a subset of commonly used sync operations with type safety.
+ * Allows abstraction for alternative implementations (e.g., mock, virtual).
+ */
+export type FsOperations = {
+  // File access and information operations
+  /** Gets the current working directory */
+  cwd(): string
+  /** Checks if a file or directory exists */
+  existsSync(path: string): boolean
+  /** Gets file stats asynchronously */
+  stat(path: string): Promise<fs.Stats>
+  /** Lists directory contents with file type information asynchronously */
+  readdir(path: string): Promise<fs.Dirent[]>
+  /** Deletes file asynchronously */
+  unlink(path: string): Promise<void>
+  /** Removes an empty directory asynchronously */
+  rmdir(path: string): Promise<void>
+  /** Removes files and directories asynchronously (with recursive option) */
+  rm(
+    path: string,
+    options?: { recursive?: boolean; force?: boolean },
+  ): Promise<void>
+  /** Creates directory recursively asynchronously. */
+  mkdir(path: string, options?: { mode?: number }): Promise<void>
+  /** Reads file content as string asynchronously */
+  readFile(path: string, options: { encoding: BufferEncoding }): Promise<string>
+  /** Renames/moves file asynchronously */
+  rename(oldPath: string, newPath: string): Promise<void>
+  /** Gets file stats */
+  statSync(path: string): fs.Stats
+  /** Gets file stats without following symlinks */
+  lstatSync(path: string): fs.Stats
+
+  // File content operations
+  /** Reads file content as string with specified encoding */
+  readFileSync(
+    path: string,
+    options: {
+      encoding: BufferEncoding
+    },
+  ): string
+  /** Reads raw file bytes as Buffer */
+  readFileBytesSync(path: string): Buffer
+  /** Reads specified number of bytes from file start */
+  readSync(
+    path: string,
+    options: {
+      length: number
+    },
+  ): {
+    buffer: Buffer
+    bytesRead: number
+  }
+  /** Appends string to file */
+  appendFileSync(path: string, data: string, options?: { mode?: number }): void
+  /** Copies file from source to destination */
+  copyFileSync(src: string, dest: string): void
+  /** Deletes file */
+  unlinkSync(path: string): void
+  /** Renames/moves file */
+  renameSync(oldPath: string, newPath: string): void
+  /** Creates hard link */
+  linkSync(target: string, path: string): void
+  /** Creates symbolic link */
+  symlinkSync(
+    target: string,
+    path: string,
+    type?: 'dir' | 'file' | 'junction',
+  ): void
+  /** Reads symbolic link */
+  readlinkSync(path: string): string
+  /** Resolves symbolic links and returns the canonical pathname */
+  realpathSync(path: string): string
+
+  // Directory operations
+  /** Creates directory recursively. Mode defaults to 0o777 & ~umask if not specified. */
+  mkdirSync(
+    path: string,
+    options?: {
+      mode?: number
+    },
+  ): void
+  /** Lists directory contents with file type information */
+  readdirSync(path: string): fs.Dirent[]
+  /** Lists directory contents as strings */
+  readdirStringSync(path: string): string[]
+  /** Checks if the directory is empty */
+  isDirEmptySync(path: string): boolean
+  /** Removes an empty directory */
+  rmdirSync(path: string): void
+  /** Removes files and directories (with recursive option) */
+  rmSync(
+    path: string,
+    options?: {
+      recursive?: boolean
+      force?: boolean
+    },
+  ): void
+  /** Create a writable stream for writing data to a file. */
+  createWriteStream(path: string): fs.WriteStream
+  /** Reads raw file bytes as Buffer asynchronously.
+   *  When maxBytes is set, only reads up to that many bytes. */
+  readFileBytes(path: string, maxBytes?: number): Promise<Buffer>
+}
+
+/**
+ * Safely resolves a file path, handling symlinks and errors gracefully.
+ *
+ * Error handling strategy:
+ * - If the file doesn't exist, returns the original path (allows for file creation)
+ * - If symlink resolution fails (broken symlink, permission denied, circular links),
+ *   returns the original path and marks it as not a symlink
+ * - This ensures operations can continue with the original path rather than failing
+ *
+ * @param fs The filesystem implementation to use
+ * @param filePath The path to resolve
+ * @returns Object containing the resolved path and whether it was a symlink
+ */
+export function safeResolvePath(
+  fs: FsOperations,
+  filePath: string,
+): { resolvedPath: string; isSymlink: boolean; isCanonical: boolean } {
+  // Block UNC paths before any filesystem access to prevent network
+  // requests (DNS/SMB) during validation on Windows
+  if (filePath.startsWith('//') || filePath.startsWith('\\\\')) {
+    return { resolvedPath: filePath, isSymlink: false, isCanonical: false }
+  }
+
+  try {
+    // Check for special file types (FIFOs, sockets, devices) before calling realpathSync.
+    // realpathSync can block on FIFOs waiting for a writer, causing hangs.
+    // If the file doesn't exist, lstatSync throws ENOENT which the catch
+    // below handles by returning the original path (allows file creation).
+    const stats = fs.lstatSync(filePath)
+    if (
+      stats.isFIFO() ||
+      stats.isSocket() ||
+      stats.isCharacterDevice() ||
+      stats.isBlockDevice()
+    ) {
+      return { resolvedPath: filePath, isSymlink: false, isCanonical: false }
+    }
+
+    const resolvedPath = fs.realpathSync(filePath)
+    return {
+      resolvedPath,
+      isSymlink: resolvedPath !== filePath,
+      // realpathSync returned: resolvedPath is canonical (all symlinks in
+      // all path components resolved). Callers can skip further symlink
+      // resolution on this path.
+      isCanonical: true,
+    }
+  } catch (_error) {
+    // If lstat/realpath fails for any reason (ENOENT, broken symlink,
+    // EACCES, ELOOP, etc.), return the original path to allow operations
+    // to proceed
+    return { resolvedPath: filePath, isSymlink: false, isCanonical: false }
+  }
+}
+
+/**
+ * Check if a file path is a duplicate and should be skipped.
+ * Resolves symlinks to detect duplicates pointing to the same file.
+ * If not a duplicate, adds the resolved path to loadedPaths.
+ *
+ * @returns true if the file should be skipped (is duplicate)
+ */
+export function isDuplicatePath(
+  fs: FsOperations,
+  filePath: string,
+  loadedPaths: Set<string>,
+): boolean {
+  const { resolvedPath } = safeResolvePath(fs, filePath)
+  if (loadedPaths.has(resolvedPath)) {
+    return true
+  }
+  loadedPaths.add(resolvedPath)
+  return false
+}
+
+/**
+ * Resolve the deepest existing ancestor of a path via realpathSync, walking
+ * up until it succeeds. Detects dangling symlinks (link entry exists, target
+ * doesn't) via lstat and resolves them via readlink.
+ *
+ * Use when the input path may not exist (new file writes) and you need to
+ * know where the write would ACTUALLY land after the OS follows symlinks.
+ *
+ * Returns the resolved absolute path with non-existent tail segments
+ * rejoined, or undefined if no symlink was found in any existing ancestor
+ * (the path's existing ancestors all resolve to themselves).
+ *
+ * Handles: live parent symlinks, dangling file symlinks, dangling parent
+ * symlinks. Same core algorithm as teamMemPaths.ts:realpathDeepestExisting.
+ */
+export function resolveDeepestExistingAncestorSync(
+  fs: FsOperations,
+  absolutePath: string,
+): string | undefined {
+  let dir = absolutePath
+  const segments: string[] = []
+  // Walk up using lstat (cheap, O(1)) to find the first existing component.
+  // lstat does not follow symlinks, so dangling symlinks are detected here.
+  // Only call realpathSync (expensive, O(depth)) once at the end.
+  while (dir !== nodePath.dirname(dir)) {
+    let st: fs.Stats
+    try {
+      st = fs.lstatSync(dir)
+    } catch {
+      // lstat failed: truly non-existent. Walk up.
+      segments.unshift(nodePath.basename(dir))
+      dir = nodePath.dirname(dir)
+      continue
+    }
+    if (st.isSymbolicLink()) {
+      // Found a symlink (live or dangling). Try realpath first (resolves
+      // chained symlinks); fall back to readlink for dangling symlinks.
+      try {
+        const resolved = fs.realpathSync(dir)
+        return segments.length === 0
+          ? resolved
+          : nodePath.join(resolved, ...segments)
+      } catch {
+        // Dangling: realpath failed but lstat saw the link entry.
+        const target = fs.readlinkSync(dir)
+        const absTarget = nodePath.isAbsolute(target)
+          ? target
+          : nodePath.resolve(nodePath.dirname(dir), target)
+        return segments.length === 0
+          ? absTarget
+          : nodePath.join(absTarget, ...segments)
+      }
+    }
+    // Existing non-symlink component. One realpath call resolves any
+    // symlinks in its ancestors. If none, return undefined (no symlink).
+    try {
+      const resolved = fs.realpathSync(dir)
+      if (resolved !== dir) {
+        return segments.length === 0
+          ? resolved
+          : nodePath.join(resolved, ...segments)
+      }
+    } catch {
+      // realpath can still fail (e.g. EACCES in ancestors). Return
+      // undefined — we can't resolve, and the logical path is already
+      // in pathSet for the caller.
+    }
+    return undefined
+  }
+  return undefined
+}
+
+/**
+ * Gets all paths that should be checked for permissions.
+ * This includes the original path, all intermediate symlink targets in the chain,
+ * and the final resolved path.
+ *
+ * For example, if test.txt -> /etc/passwd -> /private/etc/passwd:
+ * - test.txt (original path)
+ * - /etc/passwd (intermediate symlink target)
+ * - /private/etc/passwd (final resolved path)
+ *
+ * This is important for security: a deny rule for /etc/passwd should block
+ * access even if the file is actually at /private/etc/passwd (as on macOS).
+ *
+ * @param path - The path to check (will be converted to absolute)
+ * @returns An array of absolute paths to check permissions for
+ */
+export function getPathsForPermissionCheck(inputPath: string): string[] {
+  // Expand tilde notation defensively - tools should do this in getPath(),
+  // but we normalize here as defense in depth for permission checking
+  let path = inputPath
+  if (path === '~') {
+    path = homedir().normalize('NFC')
+  } else if (path.startsWith('~/')) {
+    path = nodePath.join(homedir().normalize('NFC'), path.slice(2))
+  }
+
+  const pathSet = new Set<string>()
+  const fsImpl = getFsImplementation()
+
+  // Always check the original path
+  pathSet.add(path)
+
+  // Block UNC paths before any filesystem access to prevent network
+  // requests (DNS/SMB) during validation on Windows
+  if (path.startsWith('//') || path.startsWith('\\\\')) {
+    return Array.from(pathSet)
+  }
+
+  // Follow the symlink chain, collecting ALL intermediate targets
+  // This handles cases like: test.txt -> /etc/passwd -> /private/etc/passwd
+  // We want to check all three paths, not just test.txt and /private/etc/passwd
+  try {
+    let currentPath = path
+    const visited = new Set<string>()
+    const maxDepth = 40 // Prevent runaway loops, matches typical SYMLOOP_MAX
+
+    for (let depth = 0; depth < maxDepth; depth++) {
+      // Prevent infinite loops from circular symlinks
+      if (visited.has(currentPath)) {
+        break
+      }
+      visited.add(currentPath)
+
+      if (!fsImpl.existsSync(currentPath)) {
+        // Path doesn't exist (new file case). existsSync follows symlinks,
+        // so this is also reached for DANGLING symlinks (link entry exists,
+        // target doesn't). Resolve symlinks in the path and its ancestors
+        // so permission checks see the real destination. Without this,
+        // `./data -> /etc/cron.d/` (live parent symlink) or
+        // `./evil.txt -> ~/.ssh/authorized_keys2` (dangling file symlink)
+        // would allow writes that escape the working directory.
+        if (currentPath === path) {
+          const resolved = resolveDeepestExistingAncestorSync(fsImpl, path)
+          if (resolved !== undefined) {
+            pathSet.add(resolved)
+          }
+        }
+        break
+      }
+
+      const stats = fsImpl.lstatSync(currentPath)
+
+      // Skip special file types that can cause issues
+      if (
+        stats.isFIFO() ||
+        stats.isSocket() ||
+        stats.isCharacterDevice() ||
+        stats.isBlockDevice()
+      ) {
+        break
+      }
+
+      if (!stats.isSymbolicLink()) {
+        break
+      }
+
+      // Get the immediate symlink target
+      const target = fsImpl.readlinkSync(currentPath)
+
+      // If target is relative, resolve it relative to the symlink's directory
+      const absoluteTarget = nodePath.isAbsolute(target)
+        ? target
+        : nodePath.resolve(nodePath.dirname(currentPath), target)
+
+      // Add this intermediate target to the set
+      pathSet.add(absoluteTarget)
+      currentPath = absoluteTarget
+    }
+  } catch {
+    // If anything fails during chain traversal, continue with what we have
+  }
+
+  // Also add the final resolved path using realpathSync for completeness
+  // This handles any remaining symlinks in directory components
+  const { resolvedPath, isSymlink } = safeResolvePath(fsImpl, path)
+  if (isSymlink && resolvedPath !== path) {
+    pathSet.add(resolvedPath)
+  }
+
+  return Array.from(pathSet)
+}
+
+export const NodeFsOperations: FsOperations = {
+  cwd() {
+    return process.cwd()
+  },
+
+  existsSync(fsPath) {
+    using _ = slowLogging`fs.existsSync(${fsPath})`
+    return fs.existsSync(fsPath)
+  },
+
+  async stat(fsPath) {
+    return statPromise(fsPath)
+  },
+
+  async readdir(fsPath) {
+    return readdirPromise(fsPath, { withFileTypes: true })
+  },
+
+  async unlink(fsPath) {
+    return unlinkPromise(fsPath)
+  },
+
+  async rmdir(fsPath) {
+    return rmdirPromise(fsPath)
+  },
+
+  async rm(fsPath, options) {
+    return rmPromise(fsPath, options)
+  },
+
+  async mkdir(dirPath, options) {
+    try {
+      await mkdirPromise(dirPath, { recursive: true, ...options })
+    } catch (e) {
+      // Bun/Windows: recursive:true throws EEXIST on directories with the
+      // FILE_ATTRIBUTE_READONLY bit set (Group Policy, OneDrive, desktop.ini).
+      // Bun's directoryExistsAt misclassifies DIRECTORY+READONLY as not-a-dir
+      // (bun-internal src/sys.zig existsAtType). The dir exists; ignore.
+      // https://github.com/anthropics/claude-code/issues/30924
+      if (getErrnoCode(e) !== 'EEXIST') throw e
+    }
+  },
+
+  async readFile(fsPath, options) {
+    return readFilePromise(fsPath, { encoding: options.encoding })
+  },
+
+  async rename(oldPath, newPath) {
+    return renamePromise(oldPath, newPath)
+  },
+
+  statSync(fsPath) {
+    using _ = slowLogging`fs.statSync(${fsPath})`
+    return fs.statSync(fsPath)
+  },
+
+  lstatSync(fsPath) {
+    using _ = slowLogging`fs.lstatSync(${fsPath})`
+    return fs.lstatSync(fsPath)
+  },
+
+  readFileSync(fsPath, options) {
+    using _ = slowLogging`fs.readFileSync(${fsPath})`
+    return fs.readFileSync(fsPath, { encoding: options.encoding })
+  },
+
+  readFileBytesSync(fsPath) {
+    using _ = slowLogging`fs.readFileBytesSync(${fsPath})`
+    return fs.readFileSync(fsPath)
+  },
+
+  readSync(fsPath, options) {
+    using _ = slowLogging`fs.readSync(${fsPath}, ${options.length} bytes)`
+    let fd: number | undefined = undefined
+    try {
+      fd = fs.openSync(fsPath, 'r')
+      const buffer = Buffer.alloc(options.length)
+      const bytesRead = fs.readSync(fd, buffer, 0, options.length, 0)
+      return { buffer, bytesRead }
+    } finally {
+      if (fd) fs.closeSync(fd)
+    }
+  },
+
+  appendFileSync(path, data, options) {
+    using _ = slowLogging`fs.appendFileSync(${path}, ${data.length} chars)`
+    // For new files with explicit mode, use 'ax' (atomic create-with-mode) to avoid
+    // TOCTOU race between existence check and open. Fall back to normal append if exists.
+    if (options?.mode !== undefined) {
+      try {
+        const fd = fs.openSync(path, 'ax', options.mode)
+        try {
+          fs.appendFileSync(fd, data)
+        } finally {
+          fs.closeSync(fd)
+        }
+        return
+      } catch (e) {
+        if (getErrnoCode(e) !== 'EEXIST') throw e
+        // File exists — fall through to normal append
+      }
+    }
+    fs.appendFileSync(path, data)
+  },
+
+  copyFileSync(src, dest) {
+    using _ = slowLogging`fs.copyFileSync(${src} → ${dest})`
+    fs.copyFileSync(src, dest)
+  },
+
+  unlinkSync(path: string) {
+    using _ = slowLogging`fs.unlinkSync(${path})`
+    fs.unlinkSync(path)
+  },
+
+  renameSync(oldPath: string, newPath: string) {
+    using _ = slowLogging`fs.renameSync(${oldPath} → ${newPath})`
+    fs.renameSync(oldPath, newPath)
+  },
+
+  linkSync(target: string, path: string) {
+    using _ = slowLogging`fs.linkSync(${target} → ${path})`
+    fs.linkSync(target, path)
+  },
+
+  symlinkSync(
+    target: string,
+    path: string,
+    type?: 'dir' | 'file' | 'junction',
+  ) {
+    using _ = slowLogging`fs.symlinkSync(${target} → ${path})`
+    fs.symlinkSync(target, path, type)
+  },
+
+  readlinkSync(path: string) {
+    using _ = slowLogging`fs.readlinkSync(${path})`
+    return fs.readlinkSync(path)
+  },
+
+  realpathSync(path: string) {
+    using _ = slowLogging`fs.realpathSync(${path})`
+    return fs.realpathSync(path).normalize('NFC')
+  },
+
+  mkdirSync(dirPath, options) {
+    using _ = slowLogging`fs.mkdirSync(${dirPath})`
+    const mkdirOptions: { recursive: boolean; mode?: number } = {
+      recursive: true,
+    }
+    if (options?.mode !== undefined) {
+      mkdirOptions.mode = options.mode
+    }
+    try {
+      fs.mkdirSync(dirPath, mkdirOptions)
+    } catch (e) {
+      // Bun/Windows: recursive:true throws EEXIST on directories with the
+      // FILE_ATTRIBUTE_READONLY bit set (Group Policy, OneDrive, desktop.ini).
+      // Bun's directoryExistsAt misclassifies DIRECTORY+READONLY as not-a-dir
+      // (bun-internal src/sys.zig existsAtType). The dir exists; ignore.
+      // https://github.com/anthropics/claude-code/issues/30924
+      if (getErrnoCode(e) !== 'EEXIST') throw e
+    }
+  },
+
+  readdirSync(dirPath) {
+    using _ = slowLogging`fs.readdirSync(${dirPath})`
+    return fs.readdirSync(dirPath, { withFileTypes: true })
+  },
+
+  readdirStringSync(dirPath) {
+    using _ = slowLogging`fs.readdirStringSync(${dirPath})`
+    return fs.readdirSync(dirPath)
+  },
+
+  isDirEmptySync(dirPath) {
+    using _ = slowLogging`fs.isDirEmptySync(${dirPath})`
+    const files = this.readdirSync(dirPath)
+    return files.length === 0
+  },
+
+  rmdirSync(dirPath) {
+    using _ = slowLogging`fs.rmdirSync(${dirPath})`
+    fs.rmdirSync(dirPath)
+  },
+
+  rmSync(path, options) {
+    using _ = slowLogging`fs.rmSync(${path})`
+    fs.rmSync(path, options)
+  },
+
+  createWriteStream(path: string) {
+    return fs.createWriteStream(path)
+  },
+
+  async readFileBytes(fsPath: string, maxBytes?: number) {
+    if (maxBytes === undefined) {
+      return readFilePromise(fsPath)
+    }
+    const handle = await open(fsPath, 'r')
+    try {
+      const { size } = await handle.stat()
+      const readSize = Math.min(size, maxBytes)
+      const buffer = Buffer.allocUnsafe(readSize)
+      let offset = 0
+      while (offset < readSize) {
+        const { bytesRead } = await handle.read(
+          buffer,
+          offset,
+          readSize - offset,
+          offset,
+        )
+        if (bytesRead === 0) break
+        offset += bytesRead
+      }
+      return offset < readSize ? buffer.subarray(0, offset) : buffer
+    } finally {
+      await handle.close()
+    }
+  },
+}
+
+// The currently active filesystem implementation
+let activeFs: FsOperations = NodeFsOperations
+
+/**
+ * Overrides the filesystem implementation. Note: This function does not
+ * automatically update cwd.
+ * @param implementation The filesystem implementation to use
+ */
+export function setFsImplementation(implementation: FsOperations): void {
+  activeFs = implementation
+}
+
+/**
+ * Gets the currently active filesystem implementation
+ * @returns The currently active filesystem implementation
+ */
+export function getFsImplementation(): FsOperations {
+  return activeFs
+}
+
+/**
+ * Resets the filesystem implementation to the default Node.js implementation.
+ * Note: This function does not automatically update cwd.
+ */
+export function setOriginalFsImplementation(): void {
+  activeFs = NodeFsOperations
+}
+
+export type ReadFileRangeResult = {
+  content: string
+  bytesRead: number
+  bytesTotal: number
+}
+
+/**
+ * Read up to `maxBytes` from a file starting at `offset`.
+ * Returns a flat string from Buffer — no sliced string references to a
+ * larger parent. Returns null if the file is smaller than the offset.
+ */
+export async function readFileRange(
+  path: string,
+  offset: number,
+  maxBytes: number,
+): Promise<ReadFileRangeResult | null> {
+  await using fh = await open(path, 'r')
+  const size = (await fh.stat()).size
+  if (size <= offset) {
+    return null
+  }
+  const bytesToRead = Math.min(size - offset, maxBytes)
+  const buffer = Buffer.allocUnsafe(bytesToRead)
+
+  let totalRead = 0
+  while (totalRead < bytesToRead) {
+    const { bytesRead } = await fh.read(
+      buffer,
+      totalRead,
+      bytesToRead - totalRead,
+      offset + totalRead,
+    )
+    if (bytesRead === 0) {
+      break
+    }
+    totalRead += bytesRead
+  }
+
+  return {
+    content: buffer.toString('utf8', 0, totalRead),
+    bytesRead: totalRead,
+    bytesTotal: size,
+  }
+}
+
+/**
+ * Read the last `maxBytes` of a file.
+ * Returns the whole file if it's smaller than maxBytes.
+ */
+export async function tailFile(
+  path: string,
+  maxBytes: number,
+): Promise<ReadFileRangeResult> {
+  await using fh = await open(path, 'r')
+  const size = (await fh.stat()).size
+  if (size === 0) {
+    return { content: '', bytesRead: 0, bytesTotal: 0 }
+  }
+  const offset = Math.max(0, size - maxBytes)
+  const bytesToRead = size - offset
+  const buffer = Buffer.allocUnsafe(bytesToRead)
+
+  let totalRead = 0
+  while (totalRead < bytesToRead) {
+    const { bytesRead } = await fh.read(
+      buffer,
+      totalRead,
+      bytesToRead - totalRead,
+      offset + totalRead,
+    )
+    if (bytesRead === 0) {
+      break
+    }
+    totalRead += bytesRead
+  }
+
+  return {
+    content: buffer.toString('utf8', 0, totalRead),
+    bytesRead: totalRead,
+    bytesTotal: size,
+  }
+}
+
+/**
+ * Async generator that yields lines from a file in reverse order.
+ * Reads the file backwards in chunks to avoid loading the entire file into memory.
+ * @param path - The path to the file to read
+ * @returns An async generator that yields lines in reverse order
+ */
+export async function* readLinesReverse(
+  path: string,
+): AsyncGenerator<string, void, undefined> {
+  const CHUNK_SIZE = 1024 * 4
+  const fileHandle = await open(path, 'r')
+  try {
+    const stats = await fileHandle.stat()
+    let position = stats.size
+    // Carry raw bytes (not a decoded string) across chunk boundaries so that
+    // multi-byte UTF-8 sequences split by the 4KB boundary are not corrupted.
+    // Decoding per-chunk would turn a split sequence into U+FFFD on both sides,
+    // which for history.jsonl means JSON.parse throws and the entry is dropped.
+    let remainder = Buffer.alloc(0)
+    const buffer = Buffer.alloc(CHUNK_SIZE)
+
+    while (position > 0) {
+      const currentChunkSize = Math.min(CHUNK_SIZE, position)
+      position -= currentChunkSize
+
+      await fileHandle.read(buffer, 0, currentChunkSize, position)
+      const combined = Buffer.concat([
+        buffer.subarray(0, currentChunkSize),
+        remainder,
+      ])
+
+      const firstNewline = combined.indexOf(0x0a)
+      if (firstNewline === -1) {
+        remainder = combined
+        continue
+      }
+
+      remainder = Buffer.from(combined.subarray(0, firstNewline))
+      const lines = combined.toString('utf8', firstNewline + 1).split('\n')
+
+      for (let i = lines.length - 1; i >= 0; i--) {
+        const line = lines[i]!
+        if (line) {
+          yield line
+        }
+      }
+    }
+
+    if (remainder.length > 0) {
+      yield remainder.toString('utf8')
+    }
+  } finally {
+    await fileHandle.close()
+  }
+}