Codex Cloud threads API: reading a local Codex thread fails with "unsupported placement format version 2"; cloud_threads_create returns invalid argument on a connected & authorized environment #50780

Environment

• OS: Windows 11 (Build 26200)
• Client: ChatGPT web, driving the Codex app tools through a connector ("dot")
• Target environment: WIN-7H47KIN0TIU
• list_environments reports: connected: true (status connected), attached: true, is_authorized_for_tasks: true
• The same thread is readable by the local Codex client, but the cloud threads read API fails.

1. Reading an existing thread fails

Tool: mcp__codex_apps__cloud_threads_read

Input:

{"threadId":"01a0ffa8-c433-79a3-8a11-a1a771cc8903","limit":1}

Full error:

AppServerBackendRequestError: Client specified an invalid argument: post-cutover thread ID 01a0ffa8-c433-79a3-8a11-a1a771cc8903 has unsupported placement format version 2

• error_code: UNKNOWN
• No request ID was returned.
• Last reproduced: 2026-10-04 03:17:06–03:17:14 UTC
• The thread returns no content. Some other ChatGPT conversations can be read, so this is not a global read failure.

2. Minimal local task creation fails

Tool: mcp__codex_apps__cloud_threads_create

Input:

{"environmentId":"ccarenv_b64_Y2NhcmVudl82YWJkMDg0ZWQ4NWM4MTkxYTZkMzEzYzI3NmVjOTBjMw","title":"验证 DOT_CREATE_OK 通信","prompt":"只回复 DOT_CREATE_OK，不读取或修改项目文件。"}

• environmentId matches the corresponding list_environments output exactly.
• No model, thinking, cwd, environmentConfigId, or fork_turns were passed.

Full error:

AppServerBackendRequestError: Something went wrong. Request ID: 2ba63be3-ce8e-4344-a42d-d8b51b27ad72

• error_code: UNKNOWN
• Time: 2026-10-03 06:59:53–07:00:17 UTC
• A subsequent mcp__codex_apps__cloud_threads_list_threads with {"limit":10} returned threads=[], nextCursor=null. No new task ID and no DOT_CREATE_OK reply.
• A previous create failure returned request ID: wfr_01a0ffbadfee79c58ca129c43a355f2a (2026-10-03 03:07 UTC).

Impact

Cannot set up the intended workflow (Codex delivers → dot hands off to a GPT command session → instructions return to Codex). Only a limited number of minimal tests were performed; no project files, task database, or security permissions were modified. Whether the read failure and the create failure share the same root cause is currently unknown.

Requests

1. Is reading / following local Codex threads like this supported by the cloud threads API?
2. Is unsupported placement format version 2 a known thread routing / format compatibility issue? Is the fix server-side, or does it require a specific client version?
3. Please look up the create-failure request IDs above and explain why a minimal task cannot be created even though the machine is online and authorized under the default model configuration.
4. Are there any verified workarounds, required versions, or an ETA for a fix?

Related public reproductions (not confirmed to share the same root cause)

• read failure report Dot cannot read existing remote Codex sessions: unsupported placement format versions 1 and 2 #50157
• task interop report Dot cannot create or follow up with local Codex tasks in saved projects #49729