tau

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v0.1.0 Latest Latest
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 Go to latest Published: Jul 29, 2026 License: MIT

README

tau

A coding agent for your terminal. tau is a Go reimplementation of Pi — same architecture, same feature surface, same minimalist philosophy — shipped as a single static binary with no runtime dependencies.

Status: early development. tau is being built in phases toward parity with Pi v0.82.1. The interactive agent works on Anthropic models; other providers, session trees, and the extension subprocess protocol are still landing.

tau does not ask before it acts. It edits files and runs shell commands without a confirmation prompt. Run it on a clean git tree or in a scratch directory until approval gating lands.

Goals

  • Single binary. No Node, no npm. brew install or download one file.
  • Pi parity. The agent loop, session trees, providers, extensions, themes, skills, and modes you know from Pi, in idiomatic Go.
  • Easy migration. tau reads your existing ~/.pi state (sessions, settings, auth, models) and imports it. Existing Pi TypeScript extensions run against tau via a host shim.
  • Libraries first. ai, agent, session, tools, and extension are importable Go packages, not just internals of the CLI.

Install

brew install ihavespoons/tap/tau
# or
go install github.com/ihavespoons/tau/cmd/tau@latest

Use

tau login                  # Claude Pro/Max OAuth, or an API key
tau                        # interactive session in the current directory
tau -c                     # …continuing the most recent one
tau -p "fix the failing test"    # one-shot, non-interactive
tau -p --mode json "…"     # JSONL events, for scripts and CI

Inside a session: Enter sends, Alt+Enter adds a newline, Esc stops the agent, Ctrl+P cycles models, Ctrl+T cycles thinking level, and /help lists the commands. Typing while the agent is working steers it — the message is delivered at the next turn boundary instead of starting a competing run.

The transcript is printed into your terminal's scrollback rather than an alternate screen, so scrolling, selection, and search keep working, and session length costs nothing to render.

MCP

tau speaks the Model Context Protocol through a bundled extension. Configure servers in ~/.tau/agent/mcp.json, using the same mcpServers shape other MCP hosts read:

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
    },
    "example": {
      "url": "https://example.com/mcp",
      "headers": { "Authorization": "Bearer …" }
    }
  }
}

A project may add servers in .tau/mcp.json, but only in a directory you have trusted — otherwise cloning a repository would be enough to make tau launch a process. Run /mcp to see what connected.

Everything MCP does goes through the public extension package, which is the point: it is the acceptance test for that API, not a privileged core feature.

License

MIT. tau is derived from Pi, MIT © 2025 Mario Zechner — see THIRD-PARTY-NOTICES.md.

Directories

Path Synopsis
Package agent is tau's agent runtime — the port of Pi's @earendil-works/pi-agent-core.
 Package agent is tau's agent runtime — the port of Pi's @earendil-works/pi-agent-core.
env
Package env is the capability abstraction tools execute against: a filesystem and a shell.
 Package env is the capability abstraction tools execute against: a filesystem and a shell.
env/osenv
Package osenv implements env.Env against the local operating system: the real filesystem and a real bash shell.
 Package osenv implements env.Env against the local operating system: the real filesystem and a real bash shell.
ai
Package ai is a unified multi-provider LLM API — the tau port of Pi's @earendil-works/pi-ai (snapshot v0.82.1).
 Package ai is a unified multi-provider LLM API — the tau port of Pi's @earendil-works/pi-ai (snapshot v0.82.1).
api/anthropic
Package anthropic implements the anthropic-messages wire API — the tau port of Pi's packages/ai/src/api/anthropic-messages.ts (snapshot v0.82.1), re-based from the @anthropic-ai/sdk onto net/http.
 Package anthropic implements the anthropic-messages wire API — the tau port of Pi's packages/ai/src/api/anthropic-messages.ts (snapshot v0.82.1), re-based from the @anthropic-ai/sdk onto net/http.
auth
Package auth implements provider credential storage and auth resolution — the tau port of Pi's packages/ai/src/auth (snapshot v0.82.1) plus the file-backed store from coding-agent's auth-storage.ts.
 Package auth implements provider credential storage and auth resolution — the tau port of Pi's packages/ai/src/auth (snapshot v0.82.1) plus the file-backed store from coding-agent's auth-storage.ts.
auth/oauth
Package oauth implements the provider OAuth flows — the tau port of Pi's packages/ai/src/auth/oauth.
 Package oauth implements the provider OAuth flows — the tau port of Pi's packages/ai/src/auth/oauth.
faux
Package faux is a scripted in-memory provider — the backbone of tau's offline test suite (tau's analogue of Pi's providers/faux.ts).
 Package faux is a scripted in-memory provider — the backbone of tau's offline test suite (tau's analogue of Pi's providers/faux.ts).
internal/sse
Package sse decodes Server-Sent Event streams.
 Package sse decodes Server-Sent Event streams.
partialjson
Package partialjson salvages tool-call arguments from incomplete or malformed JSON produced during streaming.
 Package partialjson salvages tool-call arguments from incomplete or malformed JSON produced during streaming.
provider
Package provider assembles wire APIs and model catalogs into named providers — the tau analogue of pi-ai's providers/ + models.ts collection.
 Package provider assembles wire APIs and model catalogs into named providers — the tau analogue of pi-ai's providers/ + models.ts collection.
cmd
tau command
Package coding wires the runtime pieces into a working coding agent: provider + agent loop + tools + session persistence.
 Package coding wires the runtime pieces into a working coding agent: provider + agent loop + tools + session persistence.
Package config resolves tau's on-disk locations.
 Package config resolves tau's on-disk locations.
Package extension is tau's in-process extension API — the Go port of Pi's ExtensionAPI.
 Package extension is tau's in-process extension API — the Go port of Pi's ExtensionAPI.
extensions
mcp
Package mcp is tau's bundled Model Context Protocol client, shipped as an extension rather than as a core feature.
 Package mcp is tau's bundled Model Context Protocol client, shipped as an extension rather than as a core feature.
Package frontmatter parses YAML frontmatter from markdown files, shared by skills and prompt templates.
 Package frontmatter parses YAML frontmatter from markdown files, shared by skills and prompt templates.
internal
tui
Package tui is tau's interactive terminal interface, built on Bubble Tea.
 Package tui is tau's interactive terminal interface, built on Bubble Tea.
Package models is tau's runtime model registry: the compiled provider catalog layered with user-supplied models.json (custom providers, extra models, and overrides of built-ins), plus Pi's model-reference grammar.
 Package models is tau's runtime model registry: the compiled provider catalog layered with user-supplied models.json (custom providers, extra models, and overrides of built-ins), plus Pi's model-reference grammar.
Package prompt builds tau's system prompt and discovers the project context files that feed it.
 Package prompt builds tau's system prompt and discovers the project context files that feed it.
Package prompttemplate loads and expands markdown prompt templates.
 Package prompttemplate loads and expands markdown prompt templates.
Package session implements tau's session store: an append-only JSONL tree (format version 3) that is byte-compatible with Pi's, so sessions written by either agent can be read by the other.
 Package session implements tau's session store: an append-only JSONL tree (format version 3) that is byte-compatible with Pi's, so sessions written by either agent can be read by the other.
Package settings is tau's two-scope configuration layer — the port of Pi's settings-manager.ts.
 Package settings is tau's two-scope configuration layer — the port of Pi's settings-manager.ts.
Package skills discovers and parses Agent Skills (SKILL.md files) and renders them for the system prompt.
 Package skills discovers and parses Agent Skills (SKILL.md files) and renders them for the system prompt.
Package slashcmd is tau's slash-command engine: parsing, a registry, and the built-in command set.
 Package slashcmd is tau's slash-command engine: parsing, a registry, and the built-in command set.
Package tools implements tau's built-in agent tools, ported from Pi's coding-agent tool set.
 Package tools implements tau's built-in agent tools, ported from Pi's coding-agent tool set.
Package trust gates project-local configuration — the port of Pi's trust-manager.ts and project-trust.ts.
 Package trust gates project-local configuration — the port of Pi's trust-manager.ts and project-trust.ts.

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