# Claude Sonnet 5.5 not always working **URL:** \ **Category:** Bug Reports\ **Created:** [October 1, 2026, 2:49pm UTC](https://community.mindstudio.ai/t/claude-sonnet-5-5-not-always-working/2154 "2026-10-01T14:49:45Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Kuane](https://avatars.discourse-cdn.com/v4/letter/k/e68b1a/32.png) [@Kuane](https://community.mindstudio.ai/u/Kuane)\ **Post date:** [October 1, 2026, 2:49pm UTC](https://community.mindstudio.ai/t/claude-sonnet-5-5-not-always-working/2154/1 "2026-10-01T14:49:45Z")
It is returning empty message from time to time. My settings were reasoning enabled, cache enabled or disabled, reasoning level medium or high. ---
**Author:** ![Alex\_MindStudio](https://yyz2.discourse-cdn.com/flex008/user_avatar/community.mindstudio.ai/alex_mindstudio/32/27_2.png) [@Alex\_MindStudio](https://community.mindstudio.ai/u/Alex_MindStudio)\ **Post date:** [October 1, 2026, 5:08pm UTC](https://community.mindstudio.ai/t/claude-sonnet-5-5-not-always-working/2154/2 "2026-10-01T17:08:17Z")
Hi @Kuane, Thanks for flagging that, and apologies for the inconvenience. Could you share the debugger log links to runs where you saw this behavior? ---
**Author:** ![Kuane](https://avatars.discourse-cdn.com/v4/letter/k/e68b1a/32.png) [@Kuane](https://community.mindstudio.ai/u/Kuane)\ **Post date:** [October 2, 2026, 12:03am UTC](https://community.mindstudio.ai/t/claude-sonnet-5-5-not-always-working/2154/3 "2026-10-02T00:03:48Z")
Please see dm ---
**Author:** ![Alex\_MindStudio](https://yyz2.discourse-cdn.com/flex008/user_avatar/community.mindstudio.ai/alex_mindstudio/32/27_2.png) [@Alex\_MindStudio](https://community.mindstudio.ai/u/Alex_MindStudio)\ **Post date:** [October 2, 2026, 11:39am UTC](https://community.mindstudio.ai/t/claude-sonnet-5-5-not-always-working/2154/4 "2026-10-02T11:39:16Z")
Hi @Kuane, Thanks for sharing the link. From what I can see, Claude Sonnet 5.5 refuses to generate a response, but the same prompt works fine on its own, so the system prompt may be causing the issue. Could you share the system prompt so I can take a closer look? ---
**Author:** ![Kuane](https://avatars.discourse-cdn.com/v4/letter/k/e68b1a/32.png) [@Kuane](https://community.mindstudio.ai/u/Kuane)\ **Post date:** [October 4, 2026, 2:02pm UTC](https://community.mindstudio.ai/t/claude-sonnet-5-5-not-always-working/2154/5 "2026-10-04T14:02:17Z")
It is not my system prompt: It is not receive any response. Is there something wrong with the API settings? I go back to Sonnet 5 and it works completely fine ![image](https://canada1.discourse-cdn.com/flex008/uploads/mindstudio/original/2X/3/368cd90ac7ac3852e9ab6bf37e00917852bd911f.png) ---
**Author:** ![Alex\_MindStudio](https://yyz2.discourse-cdn.com/flex008/user_avatar/community.mindstudio.ai/alex_mindstudio/32/27_2.png) [@Alex\_MindStudio](https://community.mindstudio.ai/u/Alex_MindStudio)\ **Post date:** [October 5, 2026, 11:55am UTC](https://community.mindstudio.ai/t/claude-sonnet-5-5-not-always-working/2154/6 "2026-10-05T11:55:42Z")
Hi @Kuane, Thanks for checking that. I can confirm there’s nothing wrong with the API settings. The empty message comes from Claude Sonnet 5.5 itself declining to generate a response for those runs, not from MindStudio. Different model versions can respond differently to the same input, which is why you’re getting a response from Claude Sonnet 5 but not 5.5. ---
**Author:** ![Kuane](https://avatars.discourse-cdn.com/v4/letter/k/e68b1a/32.png) [@Kuane](https://community.mindstudio.ai/u/Kuane)\ **Post date:** [October 5, 2026, 12:09pm UTC](https://community.mindstudio.ai/t/claude-sonnet-5-5-not-always-working/2154/7 "2026-10-05T12:09:32Z")
Hi Alex, That’s weird. Generally when a model declines, it will say why and not just return an empty message. ---
**Author:** ![Alex\_MindStudio](https://yyz2.discourse-cdn.com/flex008/user_avatar/community.mindstudio.ai/alex_mindstudio/32/27_2.png) [@Alex\_MindStudio](https://community.mindstudio.ai/u/Alex_MindStudio)\ **Post date:** [October 5, 2026, 1:46pm UTC](https://community.mindstudio.ai/t/claude-sonnet-5-5-not-always-working/2154/8 "2026-10-05T13:46:23Z")
Hi @Kuane, That’s right, when a run errors out, you can see the details in the debugger. However, in your run, the model simply didn’t generate any output