Custom models may break MCP calls in Codex CLI
returns an “unsupported call” error when a different model is configured instead of the default one. The same error appears across multiple MCP setups, so the issue may be either a local problem or a bug. The available details only show the error and the condition that triggers it; the exact and are not provided.
Key points
- was configured to use a .
- MCP calls then failed with an “unsupported call” error.
- The same failure happened across multiple MCP setups.
- It is unclear whether the cause is user or a bug.