diff --git a/backend/migrations/077_rollback_sonnet_to_original.sql b/backend/migrations/077_rollback_sonnet_to_original.sql
new file mode 100644
index 0000000000..13316e0b72
--- /dev/null
+++ b/backend/migrations/077_rollback_sonnet_to_original.sql
@@ -0,0 +1,18 @@
+-- 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-4-6": "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
+)
+WHERE platform = 'antigravity'
+  AND deleted_at IS NULL
+  AND credentials->'model_mapping' IS NOT NULL;