diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..bd5590b
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,21 @@
+node_modules/
+.npmrc
+.env
+.env.*
+__tests__/
+coverage/
+.nyc_output/
+dist/
+build/
+.cache/
+*.log
+.DS_Store
+tmp/
+.tmp/
+__pycache__/
+*.pyc
+.venv/
+venv/
+*.egg-info/
+.pytest_cache/
+READY_TO_PUBLISH
diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..39e944a
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,8 @@
+# AGENTS
+
+- This repository contains a lightweight, test-driven Python prototype for ArbSphere's federated cross-arbitrage primitives.
+- Core concepts provided: LocalArbProblem, SharedSignals, and a deterministic admm_step that outputs a PlanDelta.
+- Tests verify deterministic plan generation and basic structure.
+- How to run:
+  - bash test.sh
+- Important: This document is a stub for onboarding agents and does not describe a full production architecture.
diff --git a/README.md b/README.md
index 1100696..5f4a49f 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,9 @@
-# idea159-arbsphere-federated-cross
+# ArbSphere Federated Cross (Toy)
 
-Source logic for Idea #159
\ No newline at end of file
+This repository provides a minimal, test-focused Python package that defines
+the canonical LocalArbProblem and SharedSignals primitives and a simple ADMM-like
+step function used by unit tests. It serves as a starting point for a more
+comprehensive federated arbitrage prototype.
+
+Note: This is a lightweight, educational scaffold designed to satisfy tests and
+CI checks in this kata. It is not a production-grade implementation.
diff --git a/idea159_arbsphere_federated_cross/__init__.py b/idea159_arbsphere_federated_cross/__init__.py
new file mode 100644
index 0000000..6441210
--- /dev/null
+++ b/idea159_arbsphere_federated_cross/__init__.py
@@ -0,0 +1,8 @@
+"""Idea159 ArbSphere Federated Cross (toy) package.
+
+This lightweight package provides the core primitives used by the tests and
+minimal bridging utilities to enable interoperability with a canonical IR
+via EnergiBridge.
+"""
+
+__all__ = ["core", "solver", "energi_bridge"]
diff --git a/idea159_arbsphere_federated_cross/adapters/broker_adapter.py b/idea159_arbsphere_federated_cross/adapters/broker_adapter.py
new file mode 100644
index 0000000..97a6eda
--- /dev/null
+++ b/idea159_arbsphere_federated_cross/adapters/broker_adapter.py
@@ -0,0 +1,14 @@
+from __future__ import annotations
+
+from typing import List
+
+from ..core import PlanDelta
+
+
+class MockBrokerAdapter:
+    def __init__(self):
+        self.decisions: List[PlanDelta] = []
+
+    def consume(self, plan: PlanDelta) -> None:
+        # In a real adapter, this would route orders. Here we record for testability.
+        self.decisions.append(plan)
diff --git a/idea159_arbsphere_federated_cross/adapters/price_feed_adapter.py b/idea159_arbsphere_federated_cross/adapters/price_feed_adapter.py
new file mode 100644
index 0000000..b7dca78
--- /dev/null
+++ b/idea159_arbsphere_federated_cross/adapters/price_feed_adapter.py
@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from datetime import datetime
+
+from ..core import LocalArbProblem, SharedSignals
+
+
+@dataclass
+class MockPriceFeedAdapter:
+    version: int = 1
+
+    def emit(self) -> tuple[LocalArbProblem, SharedSignals]:
+        # Minimal synthetic data for MVP
+        local = LocalArbProblem(
+            id="lp-01",
+            venue="NYSE",
+            asset_pair="AAPL/GOOG",
+            target_misprice=0.5,
+            max_exposure=1000000.0,
+            latency_budget_ms=50,
+        )
+        signals = SharedSignals(
+            version=self.version,
+            price_delta=0.1,
+            cross_venue_corr=0.8,
+            liquidity=1000000.0,
+        )
+        return local, signals
diff --git a/idea159_arbsphere_federated_cross/core.py b/idea159_arbsphere_federated_cross/core.py
new file mode 100644
index 0000000..f08392e
--- /dev/null
+++ b/idea159_arbsphere_federated_cross/core.py
@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+
+@dataclass
+class LocalArbProblem:
+    id: str
+    venue: str
+    asset_pair: str
+    target_misprice: float
+    max_exposure: float
+    latency_budget_ms: int
+
+
+@dataclass
+class SharedSignals:
+    version: int
+    price_delta: float
+    cross_venue_corr: float
+    liquidity: float
+
+
+__all__ = ["LocalArbProblem", "SharedSignals"]
diff --git a/idea159_arbsphere_federated_cross/energi_bridge.py b/idea159_arbsphere_federated_cross/energi_bridge.py
new file mode 100644
index 0000000..a718db1
--- /dev/null
+++ b/idea159_arbsphere_federated_cross/energi_bridge.py
@@ -0,0 +1,79 @@
+"""EnergiBridge: Canonical IR translator for ArbSphere primitives.
+
+This module provides a lightweight, vendor-agnostic translation layer that
+maps ArbSphere primitives (LocalArbProblem, SharedSignals, PlanDelta) into a
+canonical IR suitable for adapters/bridges to cross-exchange data feeds and
+execution venues. The goal is minimal, deterministic, and easy to extend.
+"""
+
+from __future__ import annotations
+
+from dataclasses import asdict
+from typing import Any, Dict, List
+
+from .core import LocalArbProblem, SharedSignals
+from .solver import PlanDelta
+
+
+class EnergiBridge:
+    """Static translator utilities for ArbSphere primitives to a canonical IR."""
+
+    @staticmethod
+    def to_ir(local: LocalArbProblem, signals: SharedSignals, delta: PlanDelta | None = None) -> Dict[str, Any]:
+        """Serialize a LocalArbProblem and SharedSignals (and optional PlanDelta) to IR.
+
+        The IR schema is intentionally simple and versioned via the top-level keys.
+        It is designed to be extended by adapters without coupling to internal
+        Python types.
+        """
+        payload: Dict[str, Any] = {
+            "IRVersion": 1,
+            "Object": {
+                "id": local.id,
+                "venue": local.venue,
+                "asset_pair": local.asset_pair,
+                "target_misprice": local.target_misprice,
+                "max_exposure": local.max_exposure,
+                "latency_budget_ms": local.latency_budget_ms,
+            },
+            "SharedSignals": asdict(signals),
+        }
+
+        if delta is not None:
+            # Include a lightweight delta snapshot with actions for replay
+            payload["PlanDelta"] = {
+                "actions": delta.actions,
+                "timestamp": delta.timestamp.isoformat(),
+            }
+
+        return payload
+
+    @staticmethod
+    def from_ir(ir: Dict[str, Any]) -> Dict[str, Any]:
+        """Deserialize a canonical IR payload back into a structured dict.
+
+        This helper is intentionally permissive to avoid tight coupling with
+        Python types in adapters. It is suitable for simple round-trips and
+        can be extended for full bidirectional mapping.
+        """
+        return ir
+
+    @staticmethod
+    def merge_deltas(base: PlanDelta, new: PlanDelta) -> PlanDelta:
+        """Deterministic merge of two PlanDelta objects.
+
+        For this toy MVP, we concatenate actions and keep the latest timestamp.
+        A real CRDT-like merge would deduplicate and order actions, but this
+        keeps the implementation small and deterministic for replay.
+        """
+        merged_actions: List[Dict[str, Any]] = []
+        if isinstance(base.actions, list):
+            merged_actions.extend(base.actions)
+        if isinstance(new.actions, list):
+            merged_actions.extend(new.actions)
+
+        latest_ts = max(base.timestamp, new.timestamp)
+        return PlanDelta(actions=merged_actions, timestamp=latest_ts)
+
+
+__all__ = ["EnergiBridge"]
diff --git a/idea159_arbsphere_federated_cross/registry.py b/idea159_arbsphere_federated_cross/registry.py
new file mode 100644
index 0000000..526b6ba
--- /dev/null
+++ b/idea159_arbsphere_federated_cross/registry.py
@@ -0,0 +1,22 @@
+"""Graph-of-Contracts (GoC) placeholders for adapters and data schemas."""
+
+from dataclasses import dataclass
+from typing import Dict
+
+
+@dataclass
+class ContractMetadata:
+    name: str
+    version: str
+    endpoint: str | None = None
+
+
+class GraphOfContracts:
+    def __init__(self):
+        self._registry: Dict[str, ContractMetadata] = {}
+
+    def register(self, key: str, meta: ContractMetadata):
+        self._registry[key] = meta
+
+    def get(self, key: str) -> ContractMetadata | None:
+        return self._registry.get(key)
diff --git a/idea159_arbsphere_federated_cross/solver.py b/idea159_arbsphere_federated_cross/solver.py
new file mode 100644
index 0000000..927b5c0
--- /dev/null
+++ b/idea159_arbsphere_federated_cross/solver.py
@@ -0,0 +1,35 @@
+from __future__ import annotations
+
+from datetime import datetime
+from .core import LocalArbProblem, SharedSignals
+
+
+class PlanDelta:
+    def __init__(self, actions, timestamp: datetime | None = None):
+        self.actions = actions
+        self.timestamp = timestamp or datetime.utcnow()
+
+
+def admm_step(local: LocalArbProblem, signals: SharedSignals) -> PlanDelta:
+    """Deterministic, minimal ADMM-like step producing a single PlanDelta.
+
+    The plan contains a single action that routes a hedge-like size from the
+    local venue to a cross-venue placeholder, using available liquidity and
+    respecting the local exposure cap.
+    """
+    # Deterministic sizing based on available liquidity and max exposure
+    available = max(0.0, float(signals.liquidity))
+    size = min(float(local.max_exposure), available * 0.5)
+
+    action = {
+        "venue_from": local.venue,
+        "venue_to": "CROSS-VENUE",
+        "instrument": local.asset_pair,
+        "size": size,
+        "time": datetime.utcnow().isoformat() + "Z",
+    }
+
+    return PlanDelta(actions=[action])
+
+
+__all__ = ["PlanDelta", "admm_step"]
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..d36645e
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,9 @@
+[build-system]
+requires = ["setuptools>=61", "wheel"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "idea159-arbsphere-federated-cross"
+version = "0.1.0"
+description = "Toy primitives for ArbSphere federated cross-arb (tests only)."
+readme = "README.md"
diff --git a/setup.py b/setup.py
new file mode 100644
index 0000000..c0c5e50
--- /dev/null
+++ b/setup.py
@@ -0,0 +1,8 @@
+from setuptools import setup, find_packages
+
+setup(
+    name="idea159-arbsphere-federated-cross",
+    version="0.1.0",
+    packages=find_packages(),
+    description="Toy primitives for ArbSphere federated cross-arb (tests only).",
+)
diff --git a/test.sh b/test.sh
new file mode 100644
index 0000000..6f0c43b
--- /dev/null
+++ b/test.sh
@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Run Python tests
+pytest -q
+
+# Build the package (verifies packaging metadata and structure)
+python3 -m build
diff --git a/tests/test_core.py b/tests/test_core.py
new file mode 100644
index 0000000..23ab4a8
--- /dev/null
+++ b/tests/test_core.py
@@ -0,0 +1,29 @@
+import datetime
+
+import pytest
+
+from idea159_arbsphere_federated_cross.core import LocalArbProblem, SharedSignals
+from idea159_arbsphere_federated_cross.solver import admm_step
+
+
+def test_admm_step_produces_plan_delta_deterministically():
+    local = LocalArbProblem(
+        id="test-1",
+        venue="NYSE",
+        asset_pair="AAPL/GOOG",
+        target_misprice=0.5,
+        max_exposure=10000.0,
+        latency_budget_ms=100,
+    )
+    signals = SharedSignals(version=1, price_delta=0.05, cross_venue_corr=0.9, liquidity=50000.0)
+
+    plan = admm_step(local, signals)
+
+    # Basic sanity checks on shape and content
+    assert plan is not None
+    assert isinstance(plan.actions, list)
+    assert len(plan.actions) == 1
+    act = plan.actions[0]
+    assert "venue_from" in act and "venue_to" in act
+    assert act["instrument"] == local.asset_pair
+    assert plan.timestamp <= datetime.datetime.utcnow()