diff --git a/db.py b/db.py
index 68bd742..3c95553 100644
--- a/db.py
+++ b/db.py
@@ -65,9 +65,9 @@ CREATE TABLE IF NOT EXISTS assets (
     updated_at TIMESTAMPTZ
 );
 
--- Activities table
+-- Activities table (activity_id is content-addressable run_id hash)
 CREATE TABLE IF NOT EXISTS activities (
-    activity_id UUID PRIMARY KEY,
+    activity_id VARCHAR(64) PRIMARY KEY,
     activity_type VARCHAR(50) NOT NULL,
     actor_id TEXT NOT NULL,
     object_data JSONB NOT NULL,
@@ -83,8 +83,8 @@ CREATE TABLE IF NOT EXISTS anchors (
     tree_ipfs_cid VARCHAR(128),
     ots_proof_cid VARCHAR(128),
     activity_count INTEGER NOT NULL,
-    first_activity_id UUID,
-    last_activity_id UUID,
+    first_activity_id VARCHAR(64),
+    last_activity_id VARCHAR(64),
     created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
     confirmed_at TIMESTAMPTZ,
     bitcoin_txid VARCHAR(64)
@@ -243,6 +243,20 @@ async def get_asset_by_hash(content_hash: str) -> Optional[dict]:
         return None
 
 
+async def get_asset_by_run_id(run_id: str) -> Optional[dict]:
+    """Get asset by run_id stored in provenance."""
+    async with get_connection() as conn:
+        row = await conn.fetchrow(
+            """SELECT name, content_hash, ipfs_cid, asset_type, tags, metadata, url,
+                      provenance, description, origin, owner, created_at, updated_at
+               FROM assets WHERE provenance->>'run_id' = $1""",
+            run_id
+        )
+        if row:
+            return _parse_asset_row(row)
+        return None
+
+
 async def get_all_assets() -> dict[str, dict]:
     """Get all assets as a dict indexed by name."""
     async with get_connection() as conn:
diff --git a/server.py b/server.py
index e902e75..91ce35f 100644
--- a/server.py
+++ b/server.py
@@ -66,6 +66,26 @@ COOKIE_DOMAIN = _get_cookie_domain()
 DATA_DIR.mkdir(parents=True, exist_ok=True)
 (DATA_DIR / "assets").mkdir(exist_ok=True)
 
+
+def compute_run_id(input_hashes: list[str], recipe: str, recipe_hash: str = None) -> str:
+    """
+    Compute a deterministic run_id from inputs and recipe.
+
+    The run_id is a SHA3-256 hash of:
+    - Sorted input content hashes
+    - Recipe identifier (recipe_hash if provided, else "effect:{recipe}")
+
+    This makes runs content-addressable: same inputs + recipe = same run_id.
+    Must match the L1 implementation exactly.
+    """
+    data = {
+        "inputs": sorted(input_hashes),
+        "recipe": recipe_hash or f"effect:{recipe}",
+        "version": "1",  # For future schema changes
+    }
+    json_str = json.dumps(data, sort_keys=True, separators=(",", ":"))
+    return hashlib.sha3_256(json_str.encode()).hexdigest()
+
 # Load README
 README_PATH = Path(__file__).parent / "README.md"
 README_CONTENT = ""
@@ -1614,6 +1634,27 @@ async def get_asset(name: str, request: Request):
     return registry["assets"][name]
 
 
+@app.get("/assets/by-run-id/{run_id}")
+async def get_asset_by_run_id(run_id: str):
+    """
+    Get asset by content-addressable run_id.
+
+    Returns the asset info including output_hash and ipfs_cid for L1 recovery.
+    The run_id is stored in the asset's provenance when the run is recorded.
+    """
+    asset = await db.get_asset_by_run_id(run_id)
+    if not asset:
+        raise HTTPException(404, f"No asset found for run_id: {run_id}")
+
+    return {
+        "run_id": run_id,
+        "asset_name": asset.get("name"),
+        "output_hash": asset.get("content_hash"),
+        "ipfs_cid": asset.get("ipfs_cid"),
+        "provenance_cid": asset.get("provenance", {}).get("provenance_cid") if asset.get("provenance") else None,
+    }
+
+
 @app.patch("/assets/{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."""
@@ -1756,7 +1797,7 @@ async def _register_asset_impl(req: RegisterRequest, owner: str):
                 object_data["provenance"] = req.provenance
 
             activity = {
-                "activity_id": str(uuid.uuid4()),
+                "activity_id": req.content_hash,  # Content-addressable by content hash
                 "activity_type": "Create",
                 "actor_id": f"https://{DOMAIN}/users/{owner}",
                 "object_data": object_data,
@@ -1950,7 +1991,11 @@ async def record_run(req: RecordRunRequest, user: User = Depends(get_required_us
         recipe_cid = ipfs_client.add_json(recipe_data)
 
         # Build and store full provenance on IPFS
+        # Compute content-addressable run_id from inputs + recipe
+        recipe_name = recipe_data.get("name", "unknown") if isinstance(recipe_data, dict) else str(recipe_data)
+        run_id = compute_run_id(input_hashes, recipe_name)
         provenance = {
+            "run_id": run_id,  # Content-addressable run identifier
             "inputs": registered_inputs,
             "output": {
                 "content_hash": output_hash,
@@ -2036,7 +2081,7 @@ async def record_run(req: RecordRunRequest, user: User = Depends(get_required_us
             }
 
             activity = {
-                "activity_id": str(uuid.uuid4()),
+                "activity_id": provenance["run_id"],  # Content-addressable run_id
                 "activity_type": "Create",
                 "actor_id": f"https://{DOMAIN}/users/{user.username}",
                 "object_data": object_data,
@@ -2157,7 +2202,7 @@ async def publish_cache(req: PublishCacheRequest, user: User = Depends(get_requi
                 }
 
             activity = {
-                "activity_id": str(uuid.uuid4()),
+                "activity_id": req.content_hash,  # Content-addressable by content hash
                 "activity_type": "Create",
                 "actor_id": f"https://{DOMAIN}/users/{user.username}",
                 "object_data": object_data,