Bub

A common shape for agents that live alongside people.

Bub started in group chats. Not as a demo or a personal assistant, but as a teammate that had to coexist with real humans and other agents in the same messy conversations — concurrent tasks, incomplete context, and nobody waiting.

It is hook-first, built on pluggy, with a small core (~200 lines) and builtins that are just default plugins you can replace. Context comes from tape, not session accumulation. The same pipeline runs across CLI, Telegram, and any channel you add.

Website · GitHub

Quick Start

pip install bub

Or from source:

git clone https://github.com/bubbuild/bub.git
cd bub
uv sync

uv run bub chat                         # interactive session
uv run bub run "summarize this repo"    # one-shot task
uv run bub gateway                      # channel listener mode

How It Works

Every inbound message goes through one turn pipeline. Each stage is a hook.

resolve_session → load_state → build_prompt → run_model
                                                   ↓
              dispatch_outbound ← render_outbound ← save_state

Builtins are plugins registered first. Later plugins override earlier ones. No special cases.

If AGENTS.md exists in the workspace, it is appended to the system prompt automatically.

Key source files:

• Turn orchestrator: src/bub/framework.py
• Hook contract: src/bub/hookspecs.py
• Builtin hooks: src/bub/builtin/hook_impl.py
• Skill discovery: src/bub/skills.py

What Sets It Apart

Bub grew up in multi-person chats with multiple agents running at the same time. Single-user flows hide structural problems; shared environments expose them fast. That shaped a few things:

• Context from tape. History is append-only facts. Anchors mark phase transitions. Context is assembled on demand — not accumulated, not compressed into lossy summaries.
• Hooks all the way down. The turn pipeline is hooks. Override build_prompt, run_model, or render_outbound to change behavior. The core does not privilege its own builtins.
• One pipeline across channels. CLI and Telegram share the same process_inbound() path. Hooks don't know which channel they're in.
• Skills as documents. Skills are SKILL.md files with validated frontmatter, not code modules with magic registration.

Extend It

from bub import hookimpl

class EchoPlugin:
    @hookimpl
    def build_prompt(self, message, session_id, state):
        return f"[echo] {message['content']}"

    @hookimpl
    async def run_model(self, prompt, session_id, state):
        return prompt

[project.entry-points."bub"]
echo = "my_package.plugin:EchoPlugin"

See the Extension Guide for hook semantics and plugin packaging.

CLI

Command	Description
bub chat	Interactive REPL
bub run MESSAGE	One-shot turn
bub gateway	Channel listener (Telegram, etc.)
bub login openai	OpenAI Codex OAuth
bub hooks	Print hook-to-plugin bindings

Lines starting with , enter internal command mode (,help, ,skill name=my-skill, ,fs.read path=README.md).

Configuration

Variable	Default	Description
BUB_MODEL	openrouter:qwen/qwen3-coder-next	Model identifier
BUB_API_KEY	—	Provider key (optional with bub login openai)
BUB_API_BASE	—	Custom provider endpoint
BUB_API_FORMAT	completion	completion, responses, or messages
BUB_MAX_STEPS	50	Max tool-use loop iterations
BUB_MAX_TOKENS	1024	Max tokens per model call
BUB_MODEL_TIMEOUT_SECONDS	—	Model call timeout (seconds)

Background

We care less about whether an agent can finish a demo task, and more about whether it can coexist with real people under real conditions. Context is not baggage to carry forever — it is a working set, constructed when needed and let go when done.

Read more: Context from Tape · Socialized Evaluation and Agent Partnership

Docs

• Architecture — lifecycle, hook precedence, error handling
• Features — what ships today and current boundaries
• Channels — CLI, Telegram, and custom adapters
• Skills — discovery and authoring
• Extension Guide — hooks, tools, plugin packaging
• Deployment — Docker, environment, upgrades
• Posts — design notes

Development

uv run ruff check .
uv run mypy src
uv run pytest -q

See CONTRIBUTING.md.

License

Apache-2.0