Module: ClaudeAgentSDK::SessionMutations

Defined in:
lib/claude_agent_sdk/session_mutations.rb

Overview

Session mutation functions: rename, tag, delete, and fork sessions.

Ported from Python SDK’s _internal/session_mutations.py. Appends typed metadata entries to the session’s JSONL file, matching the CLI pattern. Safe to call from any SDK host process.

Constant Summary collapse

TRANSCRIPT_TYPES =

Transcript entry types kept in fork output. Mirrors Python’s ‘_TRANSCRIPT_TYPES`. Other types (custom-title, tag, aiTitle, permission-mode, etc.) carry session metadata and must not bleed into the fork’s transcript body — they are reconstructed for the fork’s own sessionId after the body is written.

%w[user assistant attachment system progress].freeze
UNICODE_STRIP_RE =

Unicode sanitization — ported from Python SDK / TS sanitization.ts

Iteratively applies NFKC normalization and strips format/private-use/ unassigned characters until stable (max 10 iterations).

/[\u200b-\u200f\u202a-\u202e\u2066-\u2069\ufeff\ue000-\uf8ff]/
FORMAT_CATEGORIES = 
%w[Cf Co Cn].freeze

Class Method Summary collapse

Class Method Details

.delete_session(session_id:, directory: nil) ⇒ Object

Delete a session by removing its JSONL file.

This is a hard delete — the file is removed permanently. For soft-delete semantics, use tag_session(id, ‘__hidden’) and filter on listing instead.

Parameters:

  • session_id (String) —

    UUID of the session to delete

  • directory (String, nil) (defaults to: nil) —

    Project directory path

Raises:

  • (ArgumentError) —

    if session_id is invalid

  • (Errno::ENOENT) —

    if the session file cannot be found



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# File 'lib/claude_agent_sdk/session_mutations.rb', line 81

def delete_session(session_id:, directory: nil)
  raise ArgumentError, "Invalid session_id: #{session_id}" unless session_id.match?(Sessions::UUID_RE)

  result = find_session_file_with_dir(session_id, directory)
  raise Errno::ENOENT, "Session #{session_id} not found#{" in project directory for #{directory}" if directory}" unless result

  path = result[0]

  begin
    File.delete(path)
  rescue Errno::ENOENT
    raise Errno::ENOENT, "Session #{session_id} not found"
  end

  # Subagent transcripts live in a sibling directory named after the
  # session ID. Without removing it, the CLI would later pick up
  # orphaned subagent state if the same session ID happened to be
  # reused. Matches Python's `shutil.rmtree(path.parent / session_id)`.
  subagent_dir = File.join(File.dirname(path), session_id)
  FileUtils.rm_rf(subagent_dir) if File.directory?(subagent_dir)
end

.fork_session(session_id:, directory: nil, up_to_message_id: nil, title: nil) ⇒ ForkSessionResult

Fork a session into a new branch with fresh UUIDs.

Creates a copy of the session transcript (or a prefix up to up_to_message_id) with remapped UUIDs and a new session ID. Sidechains are filtered out, progress entries are excluded from the written output but used for parentUuid chain walking.

Parameters:

  • session_id (String) —

    UUID of the session to fork

  • directory (String, nil) (defaults to: nil) —

    Project directory path

  • up_to_message_id (String, nil) (defaults to: nil) —

    Truncate the fork at this message UUID

  • title (String, nil) (defaults to: nil) —

    Custom title for the fork (auto-generated if omitted)

Returns:

Raises:

  • (ArgumentError) —

    if session_id or up_to_message_id is invalid

  • (Errno::ENOENT) —

    if the session file cannot be found



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# File 'lib/claude_agent_sdk/session_mutations.rb', line 117

def fork_session(session_id:, directory: nil, up_to_message_id: nil, title: nil) # rubocop:disable Metrics/MethodLength
  raise ArgumentError, "Invalid session_id: #{session_id}" unless session_id.match?(Sessions::UUID_RE)

  raise ArgumentError, "Invalid up_to_message_id: #{up_to_message_id}" if up_to_message_id && !up_to_message_id.match?(Sessions::UUID_RE)

  result = find_session_file_with_dir(session_id, directory)
  raise Errno::ENOENT, "Session #{session_id} not found#{" in project directory for #{directory}" if directory}" unless result

  file_path, project_dir = result
  file_size = File.size(file_path)
  raise ArgumentError, "Session #{session_id} has no messages to fork" if file_size.zero?

  transcript, content_replacements = parse_fork_transcript(file_path, session_id)
  transcript.reject! { |e| e['isSidechain'] }
  raise ArgumentError, "Session #{session_id} has no messages to fork" if transcript.empty?

  if up_to_message_id
    cutoff = transcript.index { |e| e['uuid'] == up_to_message_id }
    raise ArgumentError, "Message #{up_to_message_id} not found in session #{session_id}" unless cutoff

    transcript = transcript[0..cutoff]
  end

  # Build UUID mapping (including progress entries for parentUuid chain walk)
  uuid_mapping = {}
  transcript.each { |e| uuid_mapping[e['uuid']] = SecureRandom.uuid }

  by_uuid = transcript.to_h { |e| [e['uuid'], e] }

  # Filter out progress messages from written output
  writable = transcript.reject { |e| e['type'] == 'progress' }
  raise ArgumentError, "Session #{session_id} has no messages to fork" if writable.empty?

  forked_session_id = SecureRandom.uuid
  now = Time.now.utc.strftime('%Y-%m-%dT%H:%M:%S.%3NZ')

  lines = writable.each_with_index.map do |original, i|
    build_forked_entry(original, i, writable.size, uuid_mapping, by_uuid,
                       forked_session_id, session_id, now)
  end

  # Append content-replacement entry if any. The entry needs `uuid` and
  # `timestamp` so a *second* fork of this forked session can re-ingest
  # it — `parse_fork_transcript` gates content-replacement on the entry
  # being a valid hash with a matching `sessionId`, and the CLI's own
  # tools index entries by uuid. Matches Python's `_emit_fork_to_disk`.
  if content_replacements && !content_replacements.empty?
    lines << JSON.generate({
                             'type' => 'content-replacement',
                             'sessionId' => forked_session_id,
                             'replacements' => content_replacements,
                             'uuid' => SecureRandom.uuid,
                             'timestamp' => now
                           })
  end

  # Derive title — only read head/tail chunks when we need to generate one
  fork_title = title&.strip
  fork_title = "#{derive_fork_title(file_path, file_size)} (fork)" if fork_title.nil? || fork_title.empty?

  lines << JSON.generate({
                           'type' => 'custom-title',
                           'sessionId' => forked_session_id,
                           'customTitle' => fork_title,
                           'uuid' => SecureRandom.uuid,
                           'timestamp' => now
                         })

  fork_path = File.join(project_dir, "#{forked_session_id}.jsonl")
  io = nil
  fd = IO.sysopen(fork_path, File::WRONLY | File::CREAT | File::EXCL, 0o600)
  begin
    io = IO.new(fd)
    io.write("#{lines.join("\n")}\n")
  ensure
    if io
      io.close
    else
      IO.for_fd(fd).close rescue nil # rubocop:disable Style/RescueModifier
    end
  end

  ForkSessionResult.new(session_id: forked_session_id)
end

.rename_session(session_id:, title:, directory: nil) ⇒ Object

Rename a session by appending a custom-title entry.

list_sessions reads the LAST custom-title from the file tail, so repeated calls are safe — the most recent wins.

Parameters:

  • session_id (String) —

    UUID of the session to rename

  • title (String) —

    New session title (whitespace stripped)

  • directory (String, nil) (defaults to: nil) —

    Project directory path

Raises:

  • (ArgumentError) —

    if session_id is invalid or title is empty

  • (Errno::ENOENT) —

    if the session file cannot be found



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# File 'lib/claude_agent_sdk/session_mutations.rb', line 34

def rename_session(session_id:, title:, directory: nil)
  raise ArgumentError, "Invalid session_id: #{session_id}" unless session_id.match?(Sessions::UUID_RE)

  stripped = title.strip
  raise ArgumentError, 'title must be non-empty' if stripped.empty?

  data = "#{JSON.generate({ type: 'custom-title', customTitle: stripped, sessionId: session_id },
                          space_size: 0)}\n"

  append_to_session(session_id, data, directory)
end

.tag_session(session_id:, tag:, directory: nil) ⇒ Object

Tag a session. Pass nil to clear the tag.

Appends a type:‘tag’,tag:<tag>,sessionId:<id> JSONL entry. Tags are Unicode-sanitized before storing.

Parameters:

  • session_id (String) —

    UUID of the session to tag

  • tag (String, nil) —

    Tag string, or nil to clear

  • directory (String, nil) (defaults to: nil) —

    Project directory path

Raises:

  • (ArgumentError) —

    if session_id is invalid or tag is empty after sanitization

  • (Errno::ENOENT) —

    if the session file cannot be found



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# File 'lib/claude_agent_sdk/session_mutations.rb', line 56

def tag_session(session_id:, tag:, directory: nil)
  raise ArgumentError, "Invalid session_id: #{session_id}" unless session_id.match?(Sessions::UUID_RE)

  if tag
    sanitized = sanitize_unicode(tag).strip
    raise ArgumentError, 'tag must be non-empty (use nil to clear)' if sanitized.empty?

    tag = sanitized
  end

  data = "#{JSON.generate({ type: 'tag', tag: tag || '', sessionId: session_id },
                          space_size: 0)}\n"

  append_to_session(session_id, data, directory)
end