ChatGPT developer MCP works initially, then becomes unavailable in long-running conversation

ChatGPT users are reporting that Developer Mode MCP connectors work in new conversations but later fail with the error "FORBIDDEN: This conversation does not support developer MCPs," according to a support thread posted on the Hugging Face forum. The reported workaround is toggling Developer Mode off and back on in ChatGPT's settings and starting a fresh conversation, since existing threads appear to lose the flag permanently, and the issue affects scheduled tasks whose later runs can also lose MCP access. The behavior is described as conversation- or session-specific rather than an MCP server availability problem, and respondents directed the report to OpenAI's own community forum or support channel.

I’m supporting a customer who is experiencing a recurring Developer MCP issue in ChatGPT. The MCP connector works correctly at first and continues to work in brand-new chats. However, after a conversation has been running for some time, ChatGPT begins returning: FORBIDDEN: This conversation does not support developer MCPs Developer Mode remains enabled, and the same connector continues to function in a fresh conversation. We have also observed similar behavior with scheduled tasks: an initial run can succeed, while later runs may lose access to the MCP. This appears to be conversation/session-specific rather than an MCP server availability problem. Has anyone seen MCP tool availability disappear or fail to persist across long-running ChatGPT conversations or session transitions? If so, is there a known cause or workaround other than starting a new conversation? Any insight into MCP tool registration, session persistence, rehydration, or tool-state behavior would be appreciated. Heads up, this isn’t a Hugging Face issue, Developer Mode MCP connectors are a ChatGPT/OpenAI feature so this forum won’t have much visibility into it. A few people have reported the same “FORBIDDEN: This conversation does not support developer MCPs” behavior recently, and the workaround that’s worked for others is toggling Developer Mode off and back on in ChatGPT’s settings, then starting a fresh conversation, existing threads seem to lose the flag permanently and don’t recover on their own. You’d get a more reliable answer posting this on OpenAI’s own community forum or support channel.