friday-ng

Next-generation AI coding harness. Single Node.js process, instant token streaming, pluggable everything.

The same agent core that powers the interactive Pi-style TUI also drives one-shot CLI prompts and pluggable programmatic integrations. The harness is designed around a few key principles:

• Harness-shaped architecture — every long-lived object (Agent, Tui, Session, Settings, slash-command registry, tool registry) is composed from small typed interfaces. Hosts wire them together; nothing is hard-coded.
• Streaming-first — Agent consumes an async StreamFn and emits a typed AgentEvent stream. The CLI, the TUI, the session recorder, and any external host all subscribe to the same stream.
• Pluggable everything — providers, tools, slash commands, settings keys, and hooks are all extension points.

What's in the harness

Subsystem	File(s)	What it does
Agent core	src/agent.ts, src/agent-loop.ts, src/event-stream.ts	State machine + event stream. Agent drives the loop, manages messages, calls tools, supports abort.
Tools	src/tools/shell.ts, src/tools/websearch.ts	read, write, edit, bash, glob, grep, websearch. Each tool has a TypeBox schema, and read-only tools carry an isReadOnly flag.
Sessions	src/sessions.ts	JSONL-per-message sessions, with createSession / loadSession / listSessions / deleteSession / recordMessage.
Compaction	src/compaction.ts	Token-budget transformer that drops old tool results when the transcript is too long. Pluggable via transformContext on the agent.
Settings	src/settings.ts	Namespaced persisted settings (UI, model, harness). Hot-reload via replaceConfig.
Slash commands	src/slash-commands.ts, src/commands/builtin.ts	Registry of typed SlashCommands + 14 built-ins (/help, /model, /cost, etc).
Permissions	src/permissions.ts	Allow/deny/ask policy with glob + regex pattern matching, per-tool and per-rule.
Lifecycle hooks	src/hooks.ts	pre_tool_use, post_tool_use, pre_user_message, post_assistant_message, pre_model_call, post_model_call, turn_end — each with veto/transform.
Extension loader	src/extension-loader.ts	Auto-discovers and runs ~/.friday-ng/extensions/*.js modules that can register commands, tools, and hooks.
Retry	src/retry.ts	Wraps a StreamFn with exponential-backoff retry for transient errors (overloaded, 5xx, 429, network).
TUI	src/tui.ts	Raw-mode Pi-style REPL with input history, multiline (shift+enter), command palette, model picker, status line, scroll, and markdown-aware rendering.
Console renderer	src/console-renderer.ts	Token-by-token console rendering; prints plain-text (ANSI-free) file diffs after write / edit / multi_edit. Set showDiffs: false to switch them off.
Markdown	src/markdown.ts	Tiny dependency-free markdown subset (code, bold, italic, links, lists, tables) with regex-level syntax highlighting and OSC 8 hyperlinks.
Diff	src/diff.ts	LCS line diff with prefix/suffix trimming, context collapsing, @@ -a,b +c,d @@ hunk headers, and a size guard. Renders write / edit / multi_edit results as hunks instead of dumping whole files.
Providers	src/providers/*.ts	OpenAI, Anthropic, Google, Ollama, Groq, OpenRouter, DeepSeek, Mistral, Together, Kilo, freecc, plus a faux mock.
Config	src/config.ts	Persisted ~/.friday-ng/config.json with API keys, last model, recent sessions, last session id.
Console setup	src/console-setup.ts	Windows console UTF-8 + VT helpers (--setup-utf8 / --revert-utf8).

Built-in slash commands

• /help [cmd] — list every command; or get detailed help for one.
• /model [name] — show current model; or pick a different one (with picker).
• /models — list available models for the current provider.
• /provider [name] — show current provider; or list available providers.
• /tools — list the tool names available in the current session.
• /settings [key] [value] — read or write a setting.
• /reload — re-read config from disk.
• /clear — wipe the in-memory chat history.
• /compact — force a compaction pass.
• /cost — show last-turn token usage and running totals.
• /usage — show cumulative token usage and limits.
• /sessions — list saved sessions.
• /exit, /quit — leave the TUI.

CLI flags

  --provider <id>        Provider to use (default: openai, or saved)
  --model <name>         Model name (skip picker)
  --api-key <key>        API key (skip prompt, don't save)
  --list-providers       Print providers and exit
  --list-models          Print available models for the selected provider
  --no-config            Don't save API key or model
  --force-key            Re-prompt for API key even if saved
  --repl, -i             Interactive TUI
  --setup-utf8           Make UTF-8 + VT the Windows default
  --revert-utf8          Undo --setup-utf8
  --utf8-status          Print current console codepage + VT state
  --resume <id>          Resume a saved session by id
  --list-sessions        Print every saved session and exit
  --delete-session <id>  Delete a saved session and exit
  --help, -h             Show help

Built-in tools

• read(path, limit?, offset?) — read a file with optional head/offset.
• write(path, content) — write a file (creates parents).
• edit(path, old_string, new_string, replace_all?) — surgical in-place edit.
• bash(command, timeout?) — run a shell command (with a 30s default timeout).
• glob(pattern, path?) — find files by pattern, returning sorted paths.
• grep(pattern, path?, glob_filter?, max_results?) — search file contents.
• websearch(query, numResults?) — real web search via the DuckDuckGo Instant Answer API with a Wikipedia fallback (keyless).

All file/shell tools honour a workingDir and refuse to leave it unless the host opts in. Read-only tools are tagged with isReadOnly: true so hosts can auto-approve them.

Quick start

npm install
npm run build
node dist/cli.js --list-providers
node dist/cli.js "What is 2+2?" --provider openai
node dist/cli.js -i --provider anthropic
node dist/cli.js -i --provider faux       # smoke test, no key needed

Tests

npm test

The suite covers agent state machine, tool execution, sessions, compaction, settings, slash-command registry, built-in commands, TUI rendering, markdown, permissions, hooks, extensions, retry, and provider smoke tests against Ollama (when available). 290+ tests, all green.

Layout

src/
  agent.ts                Agent class (event stream, tool loop, abort)
  event-stream.ts         AgentEvent types + helpers
  agent-loop.ts           Pure agent state machine (testable without I/O)
  cli.ts                  Entry point: parses argv, picks provider, runs REPL
  tui.ts                  Pi-style raw-mode REPL
  interactive.ts          Model picker + provider setup
  config.ts               Persisted config + API key storage
  settings.ts             Persisted named settings (UI, model, harness)
  console-setup.ts        Windows console UTF-8 helpers
  console-renderer.ts     Token-by-token console rendering
  markdown.ts             Tiny dependency-free markdown subset
  sessions.ts             JSONL session storage
  compaction.ts           Token-budget transcript compaction
  slash-commands.ts       Slash command registry
  commands/builtin.ts     Built-in slash commands (14)
  permissions.ts          Allow/deny/ask policy with glob+regex patterns
  hooks.ts                Lifecycle hook registry
  extension-loader.ts     Auto-load ~/.friday-ng/extensions/*.js
  retry.ts                Stream-function retry with exponential backoff
  tools.ts                Built-in tool exports
  tools/shell.ts          bash, read, write, edit, glob, grep
  tools/websearch.ts      websearch (DuckDuckGo Instant Answer + Wikipedia fallback)
  tools/path-safety.ts    Path-policy helpers
  types.ts                AgentMessage, Model, Tool, ToolResult, etc.
  providers/
    base.ts               ProviderMeta, StreamFn
    registry.ts           findProvider, listProviders
    openai.ts             OpenAI Chat Completions
    anthropic.ts          Anthropic Messages
    google.ts             Google Gemini
    ollama.ts             Ollama (OpenAI-compatible)
    openai-compat.ts      Groq, OpenRouter, DeepSeek, Mistral, Together, Kilo
    freecc.ts             freecc (Anthropic-compatible local proxy)
    faux.ts               Mock provider (no network) — for tests + smoke runs
tests/                    Vitest suite (unit + integration + provider smoke)
examples/extensions/      Example extension modules

Writing an extension

An extension is a small .js file with a default export. Drop it into ~/.friday-ng/extensions/ and friday-ng will discover and run it on startup. The host exposes:

• host.commands.register({ name, description, run }) — register a slash command
• host.hooks.on("pre_tool_use", payload => ...) — observe or veto a tool call
• host.getSetting(key), host.setSetting(key, value) — read/write settings
• host.log(msg) — surface diagnostics to the user

See examples/extensions/hello-world.js and examples/extensions/safe-rm.js for runnable demos.

License

MIT — see LICENSE.