openai/codex · error · anyhow::Error

unknown MCP server '{CODEX_APPS_MCP_SERVER_NAME}'

Error message

unknown MCP server '{CODEX_APPS_MCP_SERVER_NAME}'

What it means

Error "unknown MCP server '{CODEX_APPS_MCP_SERVER_NAME}'" thrown in openai/codex.

Source

Thrown at codex-rs/core/src/session/mcp.rs:302

                executor_capability_discovery.as_deref(),
            )
            .await;
        let mcp_projection = self
            .project_selected_environment_mcp_servers(
                &desired.session_source,
                &desired.config,
                &desired.environments,
                mcp_projection,
            )
            .await;
        let selected_plugins = mcp_projection.selected_plugins.clone();
        let input = self.build_mcp_runtime_input(
            &desired,
            mcp_projection,
            &ready_selected_capability_roots,
            Some(self.mcp_elicitation_reviewer()),
        );
        anyhow::ensure!(
            input.mcp_servers.contains_key(CODEX_APPS_MCP_SERVER_NAME),
            "unknown MCP server '{CODEX_APPS_MCP_SERVER_NAME}'"
        );
        let refreshed = self.services.mcp_runtime.replace_fresh(input).await;
        self.services.thread_extension_data.insert(selected_plugins);
        refreshed
    }

    pub(super) fn mark_mcp_runtime_dirty(&self) {
        self.mcp_refresh.invalidate();
    }

    #[tracing::instrument(name = "mcp.runtime.resolve_for_step", skip_all)]
    pub(crate) async fn mcp_runtime_for_step(
        self: &Arc<Self>,
        turn_context: &TurnContext,
        selected_capability_roots: &[ResolvedSelectedCapabilityRoot],
        required_servers: &[String],

View on GitHub (pinned to 339751715c)

Solutions

1. Ensure the Codex apps MCP server is configured and connected.

When it happens

Trigger: Thrown at codex-rs/core/src/session/mcp.rs:302 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of openai/codex@339751715c (2026-08-25). Data as JSON: /api/errors/212c37838b4f0bf2. Report an issue: GitHub.