diff --git a/app/routers/cache.py b/app/routers/cache.py
index abf940b..13b10f5 100644
--- a/app/routers/cache.py
+++ b/app/routers/cache.py
@@ -221,8 +221,8 @@ async def upload_content(
         raise HTTPException(400, error)
 
     return {
-        "cid": ipfs_cid,
-        "cid": cid,  # Legacy, for backwards compatibility
+        "cid": ipfs_cid or cid,
+        "content_hash": cid,  # Legacy, for backwards compatibility
         "filename": file.filename,
         "size": len(content),
         "uploaded": True,
diff --git a/database.py b/database.py
index 21b5818..dc20af9 100644
--- a/database.py
+++ b/database.py
@@ -78,6 +78,25 @@ DO $$ BEGIN
 EXCEPTION WHEN others THEN NULL;
 END $$;
 
+-- Migration: rename content_hash to cid (for existing databases)
+DO $$ BEGIN
+    IF EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'cache_items' AND column_name = 'content_hash') THEN
+        ALTER TABLE cache_items RENAME COLUMN content_hash TO cid;
+    END IF;
+    IF EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'item_types' AND column_name = 'content_hash') THEN
+        ALTER TABLE item_types RENAME COLUMN content_hash TO cid;
+    END IF;
+    IF EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'l2_shares' AND column_name = 'content_hash') THEN
+        ALTER TABLE l2_shares RENAME COLUMN content_hash TO cid;
+    END IF;
+    IF EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'storage_pins' AND column_name = 'content_hash') THEN
+        ALTER TABLE storage_pins RENAME COLUMN content_hash TO cid;
+    END IF;
+    IF EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = 'run_cache' AND column_name = 'output_hash') THEN
+        ALTER TABLE run_cache RENAME COLUMN output_hash TO output_cid;
+    END IF;
+END $$;
+
 -- Run cache: maps content-addressable run_id to output
 -- run_id is a hash of (sorted inputs + recipe), making runs deterministic
 CREATE TABLE IF NOT EXISTS run_cache (