diff --git a/server.py b/server.py
index 2e23eb7..97ca832 100644
--- a/server.py
+++ b/server.py
@@ -95,6 +95,25 @@ class RecordRunRequest(BaseModel):
     output_name: str
 
 
+class PublishCacheRequest(BaseModel):
+    """Request to publish a cache item from L1."""
+    content_hash: str
+    asset_name: str
+    asset_type: str = "image"
+    origin: dict  # {type: "self"|"external", url?: str, note?: str}
+    description: Optional[str] = None
+    tags: list[str] = []
+    metadata: dict = {}
+
+
+class UpdateAssetRequest(BaseModel):
+    """Request to update an existing asset."""
+    description: Optional[str] = None
+    tags: Optional[list[str]] = None
+    metadata: Optional[dict] = None
+    origin: Optional[dict] = None
+
+
 # ============ Storage ============
 
 def load_registry() -> dict:
@@ -889,6 +908,66 @@ async def get_asset(name: str):
     return registry["assets"][name]
 
 
+@app.patch("/registry/{name}")
+async def update_asset(name: str, req: UpdateAssetRequest, user: User = Depends(get_required_user)):
+    """Update an existing asset's metadata. Creates an Update activity."""
+    registry = load_registry()
+    if name not in registry.get("assets", {}):
+        raise HTTPException(404, f"Asset not found: {name}")
+
+    asset = registry["assets"][name]
+
+    # Check ownership
+    if asset.get("owner") != user.username:
+        raise HTTPException(403, f"Not authorized to update asset owned by {asset.get('owner')}")
+
+    # Update fields that were provided
+    if req.description is not None:
+        asset["description"] = req.description
+    if req.tags is not None:
+        asset["tags"] = req.tags
+    if req.metadata is not None:
+        asset["metadata"] = {**asset.get("metadata", {}), **req.metadata}
+    if req.origin is not None:
+        asset["origin"] = req.origin
+
+    asset["updated_at"] = datetime.now(timezone.utc).isoformat()
+
+    # Save registry
+    registry["assets"][name] = asset
+    save_registry(registry)
+
+    # Create Update activity
+    activity = {
+        "activity_id": str(uuid.uuid4()),
+        "activity_type": "Update",
+        "actor_id": f"https://{DOMAIN}/users/{user.username}",
+        "object_data": {
+            "type": asset.get("asset_type", "Object").capitalize(),
+            "name": name,
+            "id": f"https://{DOMAIN}/objects/{asset['content_hash']}",
+            "contentHash": {
+                "algorithm": "sha3-256",
+                "value": asset["content_hash"]
+            },
+            "attributedTo": f"https://{DOMAIN}/users/{user.username}",
+            "summary": req.description,
+            "tag": req.tags or asset.get("tags", [])
+        },
+        "published": asset["updated_at"]
+    }
+
+    # Sign activity
+    activity = sign_activity(activity)
+
+    # Save activity
+    activities = load_activities()
+    activities.append(activity)
+    save_activities(activities)
+
+    return {"asset": asset, "activity": activity}
+
+
 def _register_asset_impl(req: RegisterRequest, owner: str):
     """Internal implementation for registering an asset."""
     registry = load_registry()
@@ -989,6 +1068,99 @@ async def record_run(req: RecordRunRequest, user: User = Depends(get_required_us
     ), user.username)
 
 
+@app.post("/registry/publish-cache")
+async def publish_cache(req: PublishCacheRequest, user: User = Depends(get_required_user)):
+    """
+    Publish a cache item from L1 with metadata.
+
+    Requires origin to be set (self or external URL).
+    Creates a new asset and Create activity.
+    """
+    # Validate origin
+    if not req.origin or "type" not in req.origin:
+        raise HTTPException(400, "Origin is required for publishing (type: 'self' or 'external')")
+
+    origin_type = req.origin.get("type")
+    if origin_type not in ("self", "external"):
+        raise HTTPException(400, "Origin type must be 'self' or 'external'")
+
+    if origin_type == "external" and not req.origin.get("url"):
+        raise HTTPException(400, "External origin requires a URL")
+
+    # Check if asset name already exists
+    registry = load_registry()
+    if req.asset_name in registry.get("assets", {}):
+        raise HTTPException(400, f"Asset name already exists: {req.asset_name}")
+
+    # Create asset
+    now = datetime.now(timezone.utc).isoformat()
+    asset = {
+        "name": req.asset_name,
+        "content_hash": req.content_hash,
+        "asset_type": req.asset_type,
+        "tags": req.tags,
+        "description": req.description,
+        "origin": req.origin,
+        "metadata": req.metadata,
+        "owner": user.username,
+        "created_at": now
+    }
+
+    # Add to registry
+    if "assets" not in registry:
+        registry["assets"] = {}
+    registry["assets"][req.asset_name] = asset
+    save_registry(registry)
+
+    # Create ownership activity with origin info
+    object_data = {
+        "type": req.asset_type.capitalize(),
+        "name": req.asset_name,
+        "id": f"https://{DOMAIN}/objects/{req.content_hash}",
+        "contentHash": {
+            "algorithm": "sha3-256",
+            "value": req.content_hash
+        },
+        "attributedTo": f"https://{DOMAIN}/users/{user.username}",
+        "tag": req.tags
+    }
+
+    if req.description:
+        object_data["summary"] = req.description
+
+    # Include origin in ActivityPub object
+    if origin_type == "self":
+        object_data["generator"] = {
+            "type": "Application",
+            "name": "Art DAG",
+            "note": "Original content created by the author"
+        }
+    else:
+        object_data["source"] = {
+            "type": "Link",
+            "href": req.origin.get("url"),
+            "name": req.origin.get("note", "External source")
+        }
+
+    activity = {
+        "activity_id": str(uuid.uuid4()),
+        "activity_type": "Create",
+        "actor_id": f"https://{DOMAIN}/users/{user.username}",
+        "object_data": object_data,
+        "published": now
+    }
+
+    # Sign activity
+    activity = sign_activity(activity)
+
+    # Save activity
+    activities = load_activities()
+    activities.append(activity)
+    save_activities(activities)
+
+    return {"asset": asset, "activity": activity}
+
+
 # ============ Activities Endpoints ============
 
 @app.get("/activities")