zed-industries/zed · error · anyhow::Error

Context server not found

Error message

Context server not found

What it means

An MCP (context-server) tool was invoked, but `ContextServerStore::get_running_server` returned None for the server id — no running server is registered under it. The tool never executes; `run` immediately returns a ready error task.

Source

Thrown at crates/agent/src/tools/context_server_registry.rs:345

        Ok(match schema {
            serde_json::Value::Null => {
                serde_json::json!({ "type": "object", "properties": [] })
            }
            serde_json::Value::Object(map) if map.is_empty() => {
                serde_json::json!({ "type": "object", "properties": [] })
            }
            _ => schema,
        })
    }

    fn run(
        self: Arc<Self>,
        input: ToolInput<serde_json::Value>,
        event_stream: ToolCallEventStream,
        cx: &mut App,
    ) -> Task<Result<AgentToolOutput, AgentToolOutput>> {
        let Some(server) = self.store.read(cx).get_running_server(&self.server_id) else {
            return Task::ready(Err(anyhow::anyhow!("Context server not found").into()));
        };
        let tool_name = self.tool.name.clone();
        let tool_id = mcp_tool_id(&self.server_id.0, &self.tool.name);
        let display_name = self.tool.name.clone();
        let initial_title = self.initial_title(serde_json::Value::Null, cx);
        let authorize =
            event_stream.authorize_third_party_tool(initial_title, tool_id, display_name, cx);

        cx.spawn(async move |cx| {
            let input = input
                .recv()
                .await
                .map_err(|e| anyhow::anyhow!(e.to_string()))?;

            authorize
                .await
                .map_err(|e| anyhow::anyhow!(e.to_string()))?;

View on GitHub (pinned to bc538def45)

Solutions

1. Open context-server/extension settings and confirm the server is installed and its command runs in a terminal.
2. Check agent/extension logs for the server's startup error and fix it (install the runtime, correct path/args/env).
3. Restart or re-enable the server, wait for it to reach the running state, then retry the tool once.
4. Remove references to uninstalled servers so their stale tools stop reaching the model.

Example fix

// before
let server = self.store.read(cx).get_running_server(&self.server_id); // None → error at run time
// after
let Some(server) = self.store.read(cx).get_running_server(&self.server_id) else {
    return Task::ready(Err(anyhow::anyhow!("server {} is not running — start it before calling tools", self.server_id.0).into()));
};

let server_running = cx
    .update(|cx| store.read(cx).get_running_server(&server_id).is_some())?;
if !server_running {
    anyhow::bail!("context server '{server_id}' is not running — start it before calling tools");
}

fn is_context_server_running(
    store: &Entity<ContextServerStore>,
    server_id: &ContextServerId,
    cx: &App,
) -> bool {
    store.read(cx).get_running_server(server_id).is_some()
}

When it happens

Trigger: Calling an MCP tool when the server failed to start (bad command, missing runtime), crashed, was stopped or deleted, or has not completed its first startup; also stale tool advertisements after uninstalling the providing extension.

Common situations: npx/uvx-based servers failing because Node/Python is missing or installs run offline; server entry removed from settings while the model still recalls its tools; dev servers not yet spawned when the agent acts.

Related errors

• Context server not initialized
• Project state not found for session
• {e}
• {error_message}
• Could not find UNIT_DATA in the file

AI-assisted analysis of zed-industries/zed@bc538def45 (2026-08-16). Data as JSON: /api/errors/3ae42a6cf561a739. Report an issue: GitHub.