tau-biggz 0.1.9

A Python implementation of a minimalist Pi-style coding-agent harness.

A small, readable terminal coding agent — and a working example of how coding agents are built.

GitHub · PyPI · Issues

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What is Tau?

Tau is a coding agent that lives in your terminal. You type requests like "explain this repo", "add tests", or "fix this stack trace"; Tau can read files, edit code, run commands, and keep a durable session history while streaming what it is doing.

Tau is also meant to be read. It is a teaching project for understanding the shape of a coding-agent system without starting from a giant production codebase.

tau_coding  →  tau_agent  →  tau_ai

• tau_ai translates model providers into Tau's provider-neutral stream.
• tau_agent owns the portable brain: messages, tools, events, loop, harness, and session primitives.
• tau_coding wraps the brain as a real coding app: CLI, TUI, file/shell tools, provider config, project instructions, skills, and on-disk sessions.

The important boundary is:

AgentHarness = reusable brain
CodingSession = coding-agent environment
TUI = one possible frontend

The core does not know about Textual, Rich, local config paths, slash commands, or rendering. Frontends consume events.

Install

Tau is published on PyPI as tau-biggz and installs a tau command. It requires Python 3.12 or newer.

Install with uv (recommended)

uv tool install tau-biggz
tau --version

Don't have uv? Install it first:

curl -LsSf https://astral.sh/uv/install.sh | sh

Install with pipx

pipx install tau-biggz

Install with pip

python -m pip install tau-biggz

One-command install script

Linux / macOS:

curl -fsSL https://raw.githubusercontent.com/biggs-100/tau-biggz/main/install.sh | sh

Windows (PowerShell):

irm https://raw.githubusercontent.com/biggs-100/tau-biggz/main/install.ps1 | iex

The script detects your Python, installs with pip, and adds tau to your PATH if needed.

Install from source (local development)

git clone https://github.com/biggs-100/tau-biggz.git
cd tau-biggz
uv sync --dev
uv run tau --version

Or install the local checkout as a regular package:

pip install .
# or
uv tool install --reinstall .

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Update / Upgrade

From PyPI (latest published version):

# With uv tool
uv tool upgrade tau-biggz

# With pip
python -m pip install --upgrade tau-biggz

# With pipx
pipx upgrade tau-biggz

From source (after git pull):

pip install --upgrade .
# or
uv tool install --reinstall .

The install scripts always pull the latest version, so you can re-run them:

curl -fsSL https://raw.githubusercontent.com/biggs-100/tau-biggz/main/install.sh | sh

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Uninstall

# If installed with uv tool
uv tool uninstall tau-biggz

# If installed with pip
python -m pip uninstall tau-biggz

# If installed with pipx
pipx uninstall tau-biggz

All methods remove the tau command and the tau-biggz package from your system. Session history and configuration under ~/.tau/ are preserved — delete that directory manually if you want a full cleanup.

Quickstart

Run Tau from the project you want it to work on:

cd my-project
tau

Then type a request and press Enter:

explain what this project does

One-shot print mode is useful for scripts and quick prompts:

tau -p "summarize the architecture"
tau --cwd /path/to/project -p "find the CLI entry point"

Tau needs a model provider. Start Tau and connect one with /login:

tau

/login
/login openai
/login openai-codex
/model

Tau ships with support for OpenAI, Anthropic, OpenAI Codex subscription auth, OpenRouter, Hugging Face, and custom OpenAI-compatible endpoints, including local models. See the providers guide.

The built-in catalog lives in src/tau_coding/data/catalog.toml; add your own providers and models by dropping a ~/.tau/catalog.toml with the same schema — no code changes required.

What Tau can do

• Interactive Textual TUI and non-interactive print mode.
• Built-in coding tools: read, write, edit, and bash.
• Durable JSONL sessions under ~/.tau/sessions/ with resume and branching.
• Slash commands for login, model selection, sessions, compaction, export, theme, trust, and more.
• Project instructions from AGENTS.md, .tau/, and .agents/ resources.
• User skills and prompt templates.
• Context accounting, manual compaction, and optional automatic compaction.
• Provider-neutral event rendering for Rich, plain text, JSON, transcripts, and custom frontends.
• --offline flag to skip network calls on startup.
• --rpc mode for non-Python integrations (JSONL over stdin/stdout).
• --harness / --list-harnesses for loading and listing agent harnesses.
• tau models sync to sync model metadata from the model registry.
• tau package to install, list, and remove community packages.

Philosophy

Tau follows a few rules:

• Small layers beat magic. Each package has one job and can be read alone.
• Events are the contract. Providers, renderers, the TUI, and custom frontends meet at a typed event stream.
• The core stays portable. The reusable harness does not depend on the CLI, Textual, Rich, or Tau's file layout.
• Tools are ordinary typed functions. A tool is a schema plus an async executor returning a structured result.
• Sessions are durable and inspectable. History is append-only JSONL; active context can be compacted without rewriting the record.
• Documentation follows implementation. The public docs explain the result; dev-notes/ preserves the phase-by-phase build journal.

Use Tau as a library

from tau_agent import AgentHarness, AgentHarnessConfig

harness = AgentHarness(
    AgentHarnessConfig(
        provider=provider,
        model="my-model",
        system="You are a helpful coding agent.",
        tools=tools,
    )
)

async for event in harness.prompt("Explain this package"):
    print(event)

Because the harness emits events instead of rendering UI directly, the same core can drive the built-in TUI, print mode, or a frontend you build yourself.

Development

See CONTRIBUTING.md for project philosophy, layer boundaries, testing expectations, and pull request guidelines.

uv sync --dev
uv run pytest
uv run ruff check .
uv run ruff format --check .
uv run mypy

Run Tau from the checkout:

uv run tau
uv run tau -p "explain this repo"

Run the Hugo documentation site:

cd website
hugo server -D

Open http://localhost:1313/. Build with hugo --minify.

Documentation

User docs live in website/content/. Build and view them locally:

cd website
hugo server -D

Useful entry points:

• What is Tau?
• Quickstart
• Core concepts
• Architecture overview
• The agent loop & events
• CLI reference

Tau is under active development. The implementation roadmap is tracked in GitHub issues.

License

Tau is released under the MIT License.