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Tui runtime reference

TUI environment variables

Symbol Variable Purpose
FAST_AGENT_SHELL_CHILD_ENV FAST_AGENT_SHELL_CHILD Set to 1 in child shells opened from the TUI with !.
Setting Environment variable Type Default Description
logger.streaming LOGGER__STREAMING Literal['markdown', 'plain', 'none'] markdown Streaming renderer for assistant responses.
logger.enable_prompt_marks LOGGER__ENABLE_PROMPT_MARKS bool True Emit OSC 133 prompt marks for supported terminals.
logger.progress_display LOGGER__PROGRESS_DISPLAY bool True Enable or disable progress display.
logger.show_chat LOGGER__SHOW_CHAT bool True Show user and assistant messages on the console.
logger.show_tools LOGGER__SHOW_TOOLS bool True Show MCP server tool calls on the console.
logger.truncate_tools LOGGER__TRUNCATE_TOOLS bool True Truncate long tool call display.
logger.theme_file LOGGER__THEME_FILE str \| None None Optional Rich theme file for console styles.
logger.code_theme LOGGER__CODE_THEME str native Pygments/Rich syntax theme for Markdown code rendering.
logger.render_fences_with_syntax LOGGER__RENDER_FENCES_WITH_SYNTAX bool True Render Markdown code fences with Rich Syntax.
logger.code_word_wrap LOGGER__CODE_WORD_WRAP bool True Wrap Syntax-rendered code blocks instead of cropping.
logger.apply_patch_preview_max_lines LOGGER__APPLY_PATCH_PREVIEW_MAX_LINES int \| None 120 Maximum lines to show in apply_patch and compact write_text_file previews.
logger.tool_display.layout LOGGER__TOOL_DISPLAY__LAYOUT Literal['compact', 'full'] compact Compact summary-first or full legacy tool rendering.
logger.tool_display.arguments LOGGER__TOOL_DISPLAY__ARGUMENTS Literal['auto', 'all', 'none'] auto Tool argument visibility; auto shows redacted six-row JSON previews and specialized bodies.
logger.tool_display.results LOGGER__TOOL_DISPLAY__RESULTS Literal['auto', 'all', 'none'] auto Tool result body visibility.
logger.tool_display.show_successful_file_reads LOGGER__TOOL_DISPLAY__SHOW_SUCCESSFUL_FILE_READS bool False Show successful complete file-read activity in compact layout.
logger.tool_display.stream_edit_previews LOGGER__TOOL_DISPLAY__STREAM_EDIT_PREVIEWS Literal['off', 'primary', 'all'] primary Stream apply_patch/edit_file previews for the primary agent or all agents.
logger.tool_display.aggregate_parallel LOGGER__TOOL_DISPLAY__AGGREGATE_PARALLEL bool True Aggregate safe parallel generic calls when argument bodies are disabled.
logger.terminal_images.enabled LOGGER__TERMINAL_IMAGES__ENABLED bool True Render image content in capable terminals.
logger.terminal_images.backend LOGGER__TERMINAL_IMAGES__BACKEND Literal['auto', 'textual-image', 'kitty', 'sixel', 'halfcell', 'unicode', 'none'] auto Auto uses reported terminal support, including Kitty in Herdr; use halfcell to opt out. Automatic Sixel rendering is fitted to the viewport.
logger.terminal_images.width LOGGER__TERMINAL_IMAGES__WIDTH TerminalImageSize 80% Image render width.
logger.terminal_images.height LOGGER__TERMINAL_IMAGES__HEIGHT TerminalImageSize auto Image render height.
shell_execution.tool_profile SHELL_EXECUTION__TOOL_PROFILE ShellToolProfile auto Model-specific shell/process contract.
shell_execution.output_display_lines SHELL_EXECUTION__OUTPUT_DISPLAY_LINES int \| None 5 Maximum shell/read_text_file lines to display.
shell_execution.show_bash SHELL_EXECUTION__SHOW_BASH bool True Show shell command output on the console.
shell_execution.interactive_use_pty SHELL_EXECUTION__INTERACTIVE_USE_PTY bool True Use a PTY for interactive prompt shell commands.
shell_execution.timeout_seconds SHELL_EXECUTION__TIMEOUT_SECONDS int 90 Maximum seconds without command output before termination.
shell_execution.warning_interval_seconds SHELL_EXECUTION__WARNING_INTERVAL_SECONDS int 30 Show timeout warnings every N seconds.
shell_execution.process_poll_max_wait_seconds SHELL_EXECUTION__PROCESS_POLL_MAX_WAIT_SECONDS int 260 Maximum managed-process wait.
shell_execution.foreground_auto_await_max_seconds SHELL_EXECUTION__FOREGROUND_AUTO_AWAIT_MAX_SECONDS int 30 Maximum total foreground runtime before returning a live process.
shell_execution.managed_process_poll_history_folding SHELL_EXECUTION__MANAGED_PROCESS_POLL_HISTORY_FOLDING Literal['auto', 'on', 'off'] auto Fold repetitive quiet managed-process polling.
tui.completion_menu_reserved_lines TUI__COMPLETION_MENU_RESERVED_LINES int 6 Prompt-toolkit lines reserved below the input for completion menus.