diff --git a/backend/migrations/077_rollback_sonnet_to_original.sql b/backend/migrations/077_rollback_sonnet_to_original.sql
index 5102727aba..13316e0b72 100644
--- a/backend/migrations/077_rollback_sonnet_to_original.sql
+++ b/backend/migrations/077_rollback_sonnet_to_original.sql
@@ -1,13 +1,15 @@
--- 077: Migrate Sonnet 4.5 → Sonnet 4.6 for all antigravity accounts
--- Sonnet 4.5 is no longer reliable on upstream, redirect to 4.6
+-- 077: Rollback Sonnet/Haiku mappings from Opus back to original values
+-- Reverts migration 077_migrate_sonnet_to_opus46_thinking.sql
+-- Restores: Sonnet→Sonnet, Haiku→Sonnet (original behavior)
 
 UPDATE accounts
 SET credentials = jsonb_set(
     credentials, '{model_mapping}',
     (credentials->'model_mapping')
-        || '{"claude-sonnet-4-5": "claude-sonnet-4-6"}'::jsonb
-        || '{"claude-sonnet-4-5-thinking": "claude-sonnet-4-6"}'::jsonb
-        || '{"claude-sonnet-4-5-20250929": "claude-sonnet-4-6"}'::jsonb
+        || '{"claude-sonnet-4-6": "claude-sonnet-4-6"}'::jsonb
+        || '{"claude-sonnet-4-5": "claude-sonnet-4-5"}'::jsonb
+        || '{"claude-sonnet-4-5-thinking": "claude-sonnet-4-5-thinking"}'::jsonb
+        || '{"claude-sonnet-4-5-20250929": "claude-sonnet-4-5"}'::jsonb
         || '{"claude-haiku-4-5": "claude-sonnet-4-6"}'::jsonb
         || '{"claude-haiku-4-5-20251001": "claude-sonnet-4-6"}'::jsonb
 )
diff --git a/backend/migrations/078_migrate_sonnet45_to_sonnet46.sql b/backend/migrations/078_migrate_sonnet45_to_sonnet46.sql
new file mode 100644
index 0000000000..d617ca4a16
--- /dev/null
+++ b/backend/migrations/078_migrate_sonnet45_to_sonnet46.sql
@@ -0,0 +1,16 @@
+-- 078: Migrate Sonnet 4.5 → Sonnet 4.6 for all antigravity accounts
+-- Sonnet 4.5 is no longer reliable on upstream, redirect to 4.6
+
+UPDATE accounts
+SET credentials = jsonb_set(
+    credentials, '{model_mapping}',
+    (credentials->'model_mapping')
+        || '{"claude-sonnet-4-5": "claude-sonnet-4-6"}'::jsonb
+        || '{"claude-sonnet-4-5-thinking": "claude-sonnet-4-6"}'::jsonb
+        || '{"claude-sonnet-4-5-20250929": "claude-sonnet-4-6"}'::jsonb
+        || '{"claude-haiku-4-5": "claude-sonnet-4-6"}'::jsonb
+        || '{"claude-haiku-4-5-20251001": "claude-sonnet-4-6"}'::jsonb
+)
+WHERE platform = 'antigravity'
+  AND deleted_at IS NULL
+  AND credentials->'model_mapping' IS NOT NULL;