diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 0000000..87d3e3c
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,16 @@
+.git
+.gitignore
+.idea
+.vscode
+.venv
+.python-version
+.pre-commit-config.yaml
+docs
+tests
+examples
+**/__pycache__
+**/*.pyc
+**/.pytest_cache
+**/.ruff_cache
+**/.ty_cache
+README.md
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..6e51acb
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,18 @@
+repos:
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.15.13
+    hooks:
+      - id: ruff-check
+        types_or: [python, pyi]
+        args: [--fix]
+      - id: ruff-format
+        types_or: [python, pyi]
+
+  - repo: local
+    hooks:
+      - id: ty
+        name: ty check
+        entry: uvx ty check
+        language: python
+        types_or: [python, pyi]
+        pass_filenames: false
diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..da89a78
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,56 @@
+# syntax=docker/dockerfile:1.7
+#
+# Two stages: a uv-based builder that resolves the venv, and a thin
+# python:3.13-slim runtime with bun + the `claude` CLI baked in.
+#
+# Alpine is intentionally avoided: @anthropic-ai/claude-code ≥ 2.1.113
+# ships a glibc-only native binary (anthropics/claude-code#50270).
+#
+# This image is deliberately un-opinionated about ports and command —
+# the consumer's compose file decides what to publish and how to invoke.
+
+# ---- Builder: uv + Python deps ----
+FROM ghcr.io/astral-sh/uv:python3.13-bookworm-slim AS builder
+ENV UV_LINK_MODE=copy \
+    UV_COMPILE_BYTECODE=1 \
+    UV_PYTHON_DOWNLOADS=never
+# `git` is required at build time: the `prod` extra resolves
+# raycast-api / claude-code-api from git URLs.
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends git \
+ && rm -rf /var/lib/apt/lists/*
+WORKDIR /app
+
+RUN --mount=type=cache,target=/root/.cache/uv \
+    --mount=type=bind,source=uv.lock,target=uv.lock \
+    --mount=type=bind,source=pyproject.toml,target=pyproject.toml \
+    uv sync --frozen --no-dev --no-install-project --extra prod
+
+COPY . /app
+RUN --mount=type=cache,target=/root/.cache/uv \
+    uv sync --frozen --no-dev --extra prod
+
+# ---- Runtime ----
+FROM python:3.13-slim AS runtime
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends ca-certificates git \
+ && rm -rf /var/lib/apt/lists/*
+
+# Bun native binary (glibc) — fast `npm install` replacement, only used
+# to drop the claude CLI into the image. Not invoked at runtime.
+COPY --from=oven/bun:1-slim /usr/local/bin/bun /usr/local/bin/bun
+RUN ln -s /usr/local/bin/bun /usr/local/bin/bunx
+
+# `--trust` is required: without it bun skips the postinstall step that
+# fetches claude's native binary (anthropics/claude-code#50203).
+ENV BUN_INSTALL=/usr/local/bun-global \
+    PATH=/usr/local/bun-global/bin:/app/.venv/bin:$PATH
+RUN bun install -g --trust @anthropic-ai/claude-code \
+ && claude --version
+
+COPY --from=builder /app/.venv /app/.venv
+COPY --from=builder /app /app
+WORKDIR /app
+
+ENTRYPOINT ["python", "-m"]
+CMD ["beaver_gateway"]
diff --git a/examples/config.py b/examples/config.py
new file mode 100644
index 0000000..91cb630
--- /dev/null
+++ b/examples/config.py
@@ -0,0 +1,18 @@
+# Stub user config for the Phase 0 DoD.
+#
+# Loader (beaver_gateway/config_loader.py) execs this file with
+# ClaudeAgent, RaycastAgent, McpServer, ExposedMcp, Gateway already
+# bound. The top-level `gateway = Gateway(...)` is what gets picked up.
+
+gateway = Gateway(  # type: ignore[name-defined]  # noqa: F821
+    agents=[
+        ClaudeAgent(  # type: ignore[name-defined]  # noqa: F821
+            name="stub",
+            model="claude-sonnet-4-5",
+            system_prompt="You are a stub agent used to validate the Phase 0 skeleton.",
+            cwd="/tmp",
+        ),
+    ],
+    mcps=[],
+    frontends=[],
+)
diff --git a/examples/docker-compose.yml b/examples/docker-compose.yml
new file mode 100644
index 0000000..caa5b8f
--- /dev/null
+++ b/examples/docker-compose.yml
@@ -0,0 +1,20 @@
+# Minimal compose for the Phase 0 DoD: build the image, mount a
+# single-file user config, watch the process print its summary line
+# and exit cleanly.
+#
+# Real deployments add a postgres service, raycast-config.json bind,
+# ~/.config/claude bind, etc. — Phase 5 lives in a separate example
+# repo (see PLAN §5.1).
+
+services:
+  gateway:
+    build:
+      context: ..
+      dockerfile: Dockerfile
+    environment:
+      DATABASE_URL: "sqlite:///./gateway.db"
+      ADMIN_USER: "admin"
+      ADMIN_PASS: "change-me"
+      SESSION_SECRET: "dev-secret-change-me"
+    volumes:
+      - ./config.py:/config/config.py:ro
diff --git a/pyproject.toml b/pyproject.toml
index 5907d07..1b0b23e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -2,7 +2,6 @@
 name = "beaver-gateway"
 version = "0.1.0"
 description = "Agentic registry, gateway and head of operations for Beaver agent"
-readme = "README.md"
 authors = [
     { name = "h", email = "h@kotikot.com" }
 ]
diff --git a/src/beaver_gateway/__init__.py b/src/beaver_gateway/__init__.py
index 03f146b..b0e3deb 100644
--- a/src/beaver_gateway/__init__.py
+++ b/src/beaver_gateway/__init__.py
@@ -1,2 +1,7 @@
-def main() -> None:
-    print("Hello from beaver-gateway!")
+"""Beaver Gateway — personal AI agent gateway."""
+
+from __future__ import annotations
+
+from beaver_gateway.cli import main
+
+__all__ = ["main"]
diff --git a/src/beaver_gateway/__main__.py b/src/beaver_gateway/__main__.py
new file mode 100644
index 0000000..97c8e42
--- /dev/null
+++ b/src/beaver_gateway/__main__.py
@@ -0,0 +1,8 @@
+"""Allow ``python -m beaver_gateway``."""
+
+from __future__ import annotations
+
+from beaver_gateway.cli import main
+
+if __name__ == "__main__":
+    main()
diff --git a/src/beaver_gateway/agents/__init__.py b/src/beaver_gateway/agents/__init__.py
new file mode 100644
index 0000000..7d5020b
--- /dev/null
+++ b/src/beaver_gateway/agents/__init__.py
@@ -0,0 +1,9 @@
+"""Agent type definitions exposed to user config."""
+
+from __future__ import annotations
+
+from beaver_gateway.agents.base import BaseAgent, ExposedMcp
+from beaver_gateway.agents.claude import ClaudeAgent
+from beaver_gateway.agents.raycast import RaycastAgent
+
+__all__ = ["BaseAgent", "ClaudeAgent", "ExposedMcp", "RaycastAgent"]
diff --git a/src/beaver_gateway/agents/base.py b/src/beaver_gateway/agents/base.py
new file mode 100644
index 0000000..19ef84e
--- /dev/null
+++ b/src/beaver_gateway/agents/base.py
@@ -0,0 +1,33 @@
+"""Shared agent surface.
+
+``BaseAgent`` is the structural contract every backend-specific agent
+honours. Subclasses add **capabilities as fields** (``ClaudeAgent.cwd``,
+``RaycastAgent.streaming``) — backends dispatch on type, not on a runtime
+matrix.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from pydantic import BaseModel, ConfigDict
+
+
+@dataclass(frozen=True, slots=True)
+class ExposedMcp:
+    """Reference to an ``McpServer`` (by name) exposed to a single agent."""
+
+    name: str
+    tools: tuple[str, ...] | None = None
+
+
+class BaseAgent(BaseModel):
+    """Common fields. Concrete backends subclass and add capabilities."""
+
+    model_config = ConfigDict(frozen=True, arbitrary_types_allowed=True)
+
+    name: str
+    model: str
+    system_prompt: str
+    expose_mcps: tuple[ExposedMcp, ...] = ()
+    accept_client_tools: bool = False
diff --git a/src/beaver_gateway/agents/claude.py b/src/beaver_gateway/agents/claude.py
new file mode 100644
index 0000000..aa7d7c9
--- /dev/null
+++ b/src/beaver_gateway/agents/claude.py
@@ -0,0 +1,17 @@
+"""Claude Code agent definition.
+
+Notice the absence of a ``streaming`` field — claude-code does not emit
+token-level deltas, and that fact is encoded in the type, not in a
+runtime branch.
+"""
+
+from __future__ import annotations
+
+from beaver_gateway.agents.base import BaseAgent
+
+
+class ClaudeAgent(BaseAgent):
+    """Agent backed by ``claude-code-api``."""
+
+    cwd: str
+    available_native_tools: tuple[str, ...] = ()
diff --git a/src/beaver_gateway/agents/raycast.py b/src/beaver_gateway/agents/raycast.py
new file mode 100644
index 0000000..4360124
--- /dev/null
+++ b/src/beaver_gateway/agents/raycast.py
@@ -0,0 +1,15 @@
+"""Raycast agent definition."""
+
+from __future__ import annotations
+
+from raycast_api import Source
+
+from beaver_gateway.agents.base import BaseAgent
+
+
+class RaycastAgent(BaseAgent):
+    """Agent backed by ``raycast-api``."""
+
+    streaming: bool = True
+    available_native_tools: tuple[str, ...] = ()
+    source: Source = Source.AI_CHAT
diff --git a/src/beaver_gateway/cli.py b/src/beaver_gateway/cli.py
new file mode 100644
index 0000000..f02d1dc
--- /dev/null
+++ b/src/beaver_gateway/cli.py
@@ -0,0 +1,28 @@
+"""Process entrypoint.
+
+Phase 0.3 — load the user's ``/config/config.py`` via
+``config_loader``, build registries, print the
+``loaded N agents, M mcps, K frontends`` line from the Phase 0 DoD,
+exit cleanly. Phase 0.4 will install uvloop and start uvicorn(s) for
+the frontends and the internal MCP app.
+"""
+
+from __future__ import annotations
+
+from beaver_gateway import config_loader
+from beaver_gateway.core.registry import AgentRegistry, McpRegistry
+from beaver_gateway.settings import Settings
+
+
+def main() -> None:
+    settings = Settings()  # ty: ignore[missing-argument]
+
+    gateway = config_loader.load(settings.config_path)
+
+    agents = AgentRegistry(gateway.agents)
+    mcps = McpRegistry(gateway.mcps)
+
+    print(
+        f"beaver-gateway: loaded {len(agents)} agents, "
+        f"{len(mcps)} mcps, {len(gateway.frontends)} frontends"
+    )
diff --git a/src/beaver_gateway/config_loader.py b/src/beaver_gateway/config_loader.py
new file mode 100644
index 0000000..87876e8
--- /dev/null
+++ b/src/beaver_gateway/config_loader.py
@@ -0,0 +1,99 @@
+"""Load the user's ``/config/config.py``.
+
+The config file is regular Python. We ``exec`` it in a namespace seeded
+with the public surface the user is expected to use (``ClaudeAgent``,
+``RaycastAgent``, ``McpServer``, ``ExposedMcp``, ``Gateway``). The file
+must assign a top-level ``gateway = Gateway(...)``.
+
+Element-level validation already happens at construction time — agents
+and ``McpServer`` factories are pydantic models that reject garbage.
+What we *can't* validate at construction is the ``Gateway`` container
+itself (deliberately a plain dataclass per PRD), so we type-check its
+contents here before handing it back.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any
+
+from beaver_gateway.agents.base import BaseAgent, ExposedMcp
+from beaver_gateway.agents.claude import ClaudeAgent
+from beaver_gateway.agents.raycast import RaycastAgent
+from beaver_gateway.core.registry import Gateway
+from beaver_gateway.frontends.base import Frontend
+from beaver_gateway.mcp.types import HttpMcp, McpServer, PythonToolMcp, StdioMcp
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
+class ConfigError(Exception):
+    """User config file is missing, unreadable, or structurally wrong."""
+
+
+_PUBLIC_NAMES: dict[str, Any] = {
+    "ClaudeAgent": ClaudeAgent,
+    "RaycastAgent": RaycastAgent,
+    "McpServer": McpServer,
+    "ExposedMcp": ExposedMcp,
+    "Gateway": Gateway,
+}
+
+_McpInstance = StdioMcp | HttpMcp | PythonToolMcp
+
+
+def load(path: Path) -> Gateway:
+    """Execute ``path`` and return its top-level ``gateway`` object."""
+    try:
+        source = path.read_text(encoding="utf-8")
+    except FileNotFoundError as exc:
+        msg = f"config file not found: {path}"
+        raise ConfigError(msg) from exc
+    except OSError as exc:
+        msg = f"could not read config file {path}: {exc}"
+        raise ConfigError(msg) from exc
+
+    code = compile(source, str(path), "exec")
+    namespace: dict[str, Any] = {"__file__": str(path), **_PUBLIC_NAMES}
+    exec(code, namespace)  # noqa: S102 - exec'ing user config is the feature
+
+    try:
+        gw = namespace["gateway"]
+    except KeyError as exc:
+        msg = f"{path}: no top-level `gateway = Gateway(...)` found"
+        raise ConfigError(msg) from exc
+
+    if not isinstance(gw, Gateway):
+        msg = (
+            f"{path}: top-level `gateway` must be a Gateway instance, "
+            f"got {type(gw).__name__}"
+        )
+        raise ConfigError(msg)
+
+    _validate(gw, path)
+    return gw
+
+
+def _validate(gw: Gateway, path: Path) -> None:
+    for i, a in enumerate(gw.agents):
+        if not isinstance(a, BaseAgent):
+            msg = (
+                f"{path}: gateway.agents[{i}] must be a ClaudeAgent / "
+                f"RaycastAgent instance, got {type(a).__name__}"
+            )
+            raise ConfigError(msg)
+    for i, m in enumerate(gw.mcps):
+        if not isinstance(m, _McpInstance):
+            msg = (
+                f"{path}: gateway.mcps[{i}] must be built via "
+                f"McpServer.stdio/.http/.python_tool, "
+                f"got {type(m).__name__}"
+            )
+            raise ConfigError(msg)
+    for i, f in enumerate(gw.frontends):
+        if not isinstance(f, Frontend):
+            msg = (
+                f"{path}: gateway.frontends[{i}] must be a Frontend, "
+                f"got {type(f).__name__}"
+            )
+            raise ConfigError(msg)
diff --git a/src/beaver_gateway/core/__init__.py b/src/beaver_gateway/core/__init__.py
new file mode 100644
index 0000000..63d3592
--- /dev/null
+++ b/src/beaver_gateway/core/__init__.py
@@ -0,0 +1,7 @@
+"""Cross-cutting machinery: registries, event protocol, auth, sessions."""
+
+from __future__ import annotations
+
+from beaver_gateway.core.registry import AgentRegistry, Gateway, McpRegistry
+
+__all__ = ["AgentRegistry", "Gateway", "McpRegistry"]
diff --git a/src/beaver_gateway/core/registry.py b/src/beaver_gateway/core/registry.py
new file mode 100644
index 0000000..d45c365
--- /dev/null
+++ b/src/beaver_gateway/core/registry.py
@@ -0,0 +1,83 @@
+"""Agent / MCP registries + the user-facing ``Gateway`` collector.
+
+The user's ``/config/config.py`` ends with::
+
+    gateway = Gateway(agents=[...], mcps=[...], frontends=[...])
+
+``cli.main`` picks that object up and builds the registries.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from collections.abc import Iterable, Iterator
+
+    from beaver_gateway.agents.base import BaseAgent
+    from beaver_gateway.frontends.base import Frontend
+    from beaver_gateway.mcp.types import McpServerT
+
+
+class AgentRegistry:
+    """Name → agent lookup with duplicate detection."""
+
+    def __init__(self, agents: Iterable[BaseAgent]) -> None:
+        self._agents: dict[str, BaseAgent] = {}
+        for a in agents:
+            if a.name in self._agents:
+                msg = f"duplicate agent name: {a.name!r}"
+                raise ValueError(msg)
+            self._agents[a.name] = a
+
+    def __getitem__(self, name: str) -> BaseAgent:
+        return self._agents[name]
+
+    def get(self, name: str) -> BaseAgent | None:
+        return self._agents.get(name)
+
+    def __iter__(self) -> Iterator[BaseAgent]:
+        return iter(self._agents.values())
+
+    def __len__(self) -> int:
+        return len(self._agents)
+
+    def __contains__(self, name: object) -> bool:
+        return name in self._agents
+
+
+class McpRegistry:
+    """Name → MCP server lookup with duplicate detection."""
+
+    def __init__(self, mcps: Iterable[McpServerT]) -> None:
+        self._mcps: dict[str, McpServerT] = {}
+        for m in mcps:
+            if m.name in self._mcps:
+                msg = f"duplicate mcp name: {m.name!r}"
+                raise ValueError(msg)
+            self._mcps[m.name] = m
+
+    def __getitem__(self, name: str) -> McpServerT:
+        return self._mcps[name]
+
+    def get(self, name: str) -> McpServerT | None:
+        return self._mcps.get(name)
+
+    def __iter__(self) -> Iterator[McpServerT]:
+        return iter(self._mcps.values())
+
+    def __len__(self) -> int:
+        return len(self._mcps)
+
+    def __contains__(self, name: object) -> bool:
+        return name in self._mcps
+
+
+@dataclass(slots=True)
+class Gateway:
+    """Top-level object the user assembles in ``/config/config.py``."""
+
+    agents: list[BaseAgent] = field(default_factory=list)
+    mcps: list[McpServerT] = field(default_factory=list)
+    frontends: list[Frontend] = field(default_factory=list)
diff --git a/src/beaver_gateway/frontends/__init__.py b/src/beaver_gateway/frontends/__init__.py
new file mode 100644
index 0000000..71f4f31
--- /dev/null
+++ b/src/beaver_gateway/frontends/__init__.py
@@ -0,0 +1,7 @@
+"""Frontend protocols and (later) concrete app implementations."""
+
+from __future__ import annotations
+
+from beaver_gateway.frontends.base import Frontend
+
+__all__ = ["Frontend"]
diff --git a/src/beaver_gateway/frontends/base.py b/src/beaver_gateway/frontends/base.py
new file mode 100644
index 0000000..03ed04f
--- /dev/null
+++ b/src/beaver_gateway/frontends/base.py
@@ -0,0 +1,24 @@
+"""Frontend ABC.
+
+A frontend is anything that listens on a port and routes inbound traffic
+into the agent/MCP registries. ``configure`` is called once after the
+``Gateway`` is built; ``serve`` runs the listening loop.
+"""
+
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from beaver_gateway.core.registry import Gateway
+
+
+class Frontend(ABC):
+    """Listens on a port, dispatches into the gateway."""
+
+    @abstractmethod
+    def configure(self, gateway: Gateway) -> None: ...
+
+    @abstractmethod
+    async def serve(self) -> None: ...
diff --git a/src/beaver_gateway/mcp/__init__.py b/src/beaver_gateway/mcp/__init__.py
new file mode 100644
index 0000000..345f34e
--- /dev/null
+++ b/src/beaver_gateway/mcp/__init__.py
@@ -0,0 +1,13 @@
+"""MCP server definitions and (later) the internal aggregator app."""
+
+from __future__ import annotations
+
+from beaver_gateway.mcp.types import (
+    HttpMcp,
+    McpServer,
+    McpServerT,
+    PythonToolMcp,
+    StdioMcp,
+)
+
+__all__ = ["HttpMcp", "McpServer", "McpServerT", "PythonToolMcp", "StdioMcp"]
diff --git a/src/beaver_gateway/mcp/types.py b/src/beaver_gateway/mcp/types.py
new file mode 100644
index 0000000..5ba17d5
--- /dev/null
+++ b/src/beaver_gateway/mcp/types.py
@@ -0,0 +1,77 @@
+"""User-facing MCP server declarations.
+
+Three flavours, one factory facade (``McpServer``). The factory returns
+discriminated-union members so downstream code can ``match`` on ``kind``.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Callable  # noqa: TC003 — runtime use by pydantic
+from typing import TYPE_CHECKING, Annotated, Literal
+
+from pydantic import BaseModel, ConfigDict, Field
+
+if TYPE_CHECKING:
+    from collections.abc import Iterable
+
+
+class _BaseMcp(BaseModel):
+    model_config = ConfigDict(frozen=True, arbitrary_types_allowed=True)
+
+    name: str
+
+
+class StdioMcp(_BaseMcp):
+    """Subprocess MCP server we spawn and connect to over stdio."""
+
+    kind: Literal["stdio"] = "stdio"
+    command: tuple[str, ...]
+    env: dict[str, str] | None = None
+    cwd: str | None = None
+
+
+class HttpMcp(_BaseMcp):
+    """Remote MCP server reached over streamable HTTP."""
+
+    kind: Literal["http"] = "http"
+    url: str
+    auth: str | None = None
+
+
+class PythonToolMcp(_BaseMcp):
+    """Bundle of Python callables exposed as one FastMCP namespace."""
+
+    kind: Literal["python_tool"] = "python_tool"
+    tools: tuple[Callable[..., object], ...]
+
+
+McpServerT = Annotated[
+    StdioMcp | HttpMcp | PythonToolMcp, Field(discriminator="kind")
+]
+
+
+class McpServer:
+    """Factory facade matching the PRD-documented config surface."""
+
+    @classmethod
+    def stdio(
+        cls,
+        *,
+        name: str,
+        command: Iterable[str],
+        env: dict[str, str] | None = None,
+        cwd: str | None = None,
+    ) -> StdioMcp:
+        return StdioMcp(name=name, command=tuple(command), env=env, cwd=cwd)
+
+    @classmethod
+    def http(
+        cls, *, name: str, url: str, auth: str | None = None
+    ) -> HttpMcp:
+        return HttpMcp(name=name, url=url, auth=auth)
+
+    @classmethod
+    def python_tool(
+        cls, *, name: str, tools: Iterable[Callable[..., object]]
+    ) -> PythonToolMcp:
+        return PythonToolMcp(name=name, tools=tuple(tools))
diff --git a/src/beaver_gateway/settings.py b/src/beaver_gateway/settings.py
new file mode 100644
index 0000000..cba48e4
--- /dev/null
+++ b/src/beaver_gateway/settings.py
@@ -0,0 +1,31 @@
+"""Process-wide configuration loaded from environment (`.env`).
+
+Everything that varies between deployments (creds, paths, ports) lives here.
+User-facing agent/MCP/frontend definitions live in ``/config/config.py``
+and are loaded by ``config_loader`` (Phase 0.3).
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    """Runtime environment for the gateway process."""
+
+    model_config = SettingsConfigDict(
+        env_file=".env", env_file_encoding="utf-8", extra="ignore"
+    )
+
+    database_url: str
+    admin_user: str
+    admin_pass: str
+    session_secret: str
+
+    internal_mcp_port: int = 8765
+    config_path: Path = Path("/config/config.py")
+
+    raycast_bearer: str | None = None
+    raycast_config_path: Path = Path("/config/raycast.json")