diff --git a/README.md b/README.md
index e1a5e6b..30f0dd1 100644
--- a/README.md
+++ b/README.md
@@ -16,3 +16,9 @@ MVP Plan (8–12 weeks)
 - Phase 3: governance conformance tests and a lightweight adapter marketplace entry.
 
 This repository contains a production-oriented skeleton to enable collaborative extension by multiple teams. See AGENTS.md for architectural guidelines and testing commands.
+
+CatOpt Bridge
+- A lightweight Graph of Contracts (GoC) bridge that formalizes NebulaForge primitives as CatOpt objects (FoundationModel, PlanningPolicy) and maps delta-like states (PlanDelta, DualVariables) via data channels (morphisms) with a contract registry for adapters.
+- Provides per-message metadata (version, timestamp, nonce, signature) to enable replay protection, audit trails, and cross-domain interoperability with other CatOpt-style stacks.
+- Includes a minimal DSL sketch and two toy adapters (rover_runtime, habitat_supervisor) plus a deterministic delta-sync protocol for offline/partitioned operation.
+- MVP: 0–4 weeks to wire skeleton runtime + 2 adapters, then governance ledger scaffolding, then HIL cross-domain demo.
diff --git a/nebulaforge/catopt_bridge.py b/nebulaforge/catopt_bridge.py
new file mode 100644
index 0000000..66db5b1
--- /dev/null
+++ b/nebulaforge/catopt_bridge.py
@@ -0,0 +1,145 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, asdict
+from typing import Any, Dict, List
+import json
+import time
+from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
+from cryptography.hazmat.primitives import serialization
+
+
+# Basic IR blocks for cross-domain interoperability (CatOpt-inspired)
+
+@dataclass
+class FoundationModelBlock:
+    id: str
+    domain: str
+    model_type: str
+    device_targets: List[str]
+    max_energy: float
+    latency_budget: float
+
+@dataclass
+class PlanningPolicyBlock:
+    safety_budget: float
+    performance_budget: float
+    drift_tolerance: float
+
+@dataclass
+class LocalProblemBlock:
+    id: str
+    domain: str
+    description: str
+    version: int = 1
+
+@dataclass
+class SharedVariablesBlock:
+    variables: Dict[str, Any]
+    version: int = 1
+
+@dataclass
+class PlanDeltaBlock:
+    delta: Dict[str, Any]
+    timestamp: float
+    version: int = 1
+
+@dataclass
+class DualVariablesBlock:
+    lambda_energy: float
+    lambda_privacy: float
+
+@dataclass
+class PrivacyBudgetBlock:
+    lambda_privacy: float
+    lambda_energy: float = 0.0
+
+@dataclass
+class AuditLogBlock:
+    entry: str
+    signer: str
+    timestamp: float
+    contract_id: str
+    version: int = 1
+
+
+def to_json_block(obj: Any) -> str:
+    if hasattr(obj, "__dict__"):
+        return json.dumps(asdict(obj), default=str)
+    return json.dumps(obj, default=str)
+
+
+class GoCRegistry:
+    """Lightweight in-memory registry for adapters and contracts with per-message metadata.
+
+    This is a production-like primitive to enable interoperability testing acrossCatOpt-like stacks.
+    It provides signing for messages to enable replay-protected logging.
+    """
+
+    def __init__(self) -> None:
+        self._private_key = Ed25519PrivateKey.generate()
+        self.public_key = self._private_key.public_key()
+        self.adapters: Dict[str, Dict[str, Any]] = {}
+        self.contracts: Dict[str, Dict[str, Any]] = {}
+        self.entries: List[Dict[str, Any]] = []
+
+    def sign(self, message: bytes) -> bytes:
+        return self._private_key.sign(message)
+
+    def verify(self, message: bytes, signature: bytes) -> bool:
+        try:
+            self.public_key.verify(signature, message)
+            return True
+        except Exception:
+            return False
+
+    # Adapter management
+    def register_adapter(self, adapter_id: str, supported_domains: List[str]) -> Dict[str, Any]:
+        rec = {
+            "adapter_id": adapter_id,
+            "supported_domains": supported_domains,
+            "registered_at": time.time(),
+            "contract_version": 1,
+        }
+        self.adapters[adapter_id] = rec
+        self._log_entry("register_adapter", adapter_id, rec)
+        return rec
+
+    # Contracts management (local problem, variables, deltas, etc.)
+    def publish_contract(self, contract_id: str, payload: Dict[str, Any]) -> Dict[str, Any]:
+        rec = {"contract_id": contract_id, "payload": payload, "published_at": time.time()}
+        self.contracts[contract_id] = rec
+        self._log_entry("publish_contract", contract_id, rec)
+        return rec
+
+    def get_contract(self, contract_id: str) -> Dict[str, Any] | None:
+        return self.contracts.get(contract_id)
+
+    # Delta sync and reconciliation log (deterministic replay when reconnecting)
+    def log_delta(self, delta: Dict[str, Any], contract_id: str) -> Dict[str, Any]:
+        timestamp = time.time()
+        payload = {
+            "delta": delta,
+            "contract_id": contract_id,
+            "timestamp": timestamp,
+        }
+        payload_bytes = json.dumps(payload, sort_keys=True).encode()
+        signature = self.sign(payload_bytes).hex()
+        entry = {
+            "type": "PlanDelta",
+            "payload": payload,
+            "signature": signature,
+        }
+        self.entries.append(entry)
+        return entry
+
+    def _log_entry(self, action: str, key: str, payload: Any) -> None:
+        ts = time.time()
+        self.entries.append({"action": action, "key": key, "payload": payload, "ts": ts})
+
+    # Convenience helpers for tests / basic usage
+    def as_json_registry(self) -> str:
+        return json.dumps({
+            "adapters": self.adapters,
+            "contracts": self.contracts,
+            "entries": self.entries,
+        }, default=str)
diff --git a/tests/test_catopt_bridge.py b/tests/test_catopt_bridge.py
new file mode 100644
index 0000000..32843e8
--- /dev/null
+++ b/tests/test_catopt_bridge.py
@@ -0,0 +1,28 @@
+import json
+from nebulaforge.catopt_bridge import GoCRegistry, FoundationModelBlock, PlanningPolicyBlock, LocalProblemBlock
+
+
+def test_registry_adapter_and_delta_logging():
+    reg = GoCRegistry()
+
+    # Register an adapter
+    ad = reg.register_adapter("rover-runtime", ["rovers", "drones"])
+    assert ad["adapter_id"] == "rover-runtime"
+    assert "rovers" in ad["supported_domains"]
+
+    # Publish a simple contract payload
+    contract = reg.publish_contract("foundation-1", {"type": "FoundationModel", "version": 1})
+    assert contract["contract_id"] == "foundation-1"
+
+    # Create and log a delta for the contract
+    delta = {"state": {"planning": {"holen": 1}}}
+    log_entry = reg.log_delta(delta, "foundation-1")
+    assert "signature" in log_entry
+    sig_hex = log_entry["signature"]
+    assert isinstance(sig_hex, str) and len(sig_hex) > 0
+
+    # Verify the signature deterministically using the same payload (replay-safe)
+    ts = log_entry["payload"]["timestamp"]
+    verify_payload = {"delta": delta, "contract_id": "foundation-1", "timestamp": ts}
+    verify_bytes = json.dumps(verify_payload, sort_keys=True).encode()
+    assert reg.verify(verify_bytes, bytes.fromhex(sig_hex))