What causes "Project state not found for session" in zed-industries/zed?

Create the session and await its completion before sending MCP prompts

Project state not found for session

Error message

Project state not found for session

What it means

send_mcp_prompt resolves per-session project state via session_project_state(&session_id); when the session id is not registered in the agent's in-memory sessions/projects map, it returns a ready Err 'Project state not found for session'. The MCP prompt never reaches the server store because there is no project context to resolve it against.

Source

Thrown at crates/agent/src/agent.rs:1837

                        .log_err();
                }
            }))
            .await;
        }
    }

    fn send_mcp_prompt(
        &self,
        client_user_message_id: ClientUserMessageId,
        session_id: acp::SessionId,
        prompt_name: String,
        server_id: ContextServerId,
        arguments: HashMap<String, String>,
        original_content: Vec<acp::ContentBlock>,
        cx: &mut Context<Self>,
    ) -> Task<Result<acp::PromptResponse>> {
        let Some(state) = self.session_project_state(&session_id) else {
            return Task::ready(Err(anyhow!("Project state not found for session")));
        };
        let server_store = state
            .context_server_registry
            .read(cx)
            .server_store()
            .clone();
        let path_style = state.project.read(cx).path_style(cx);

        cx.spawn(async move |this, cx| {
            let prompt =
                crate::get_prompt(&server_store, &server_id, &prompt_name, arguments, cx).await?;

            let (acp_thread, thread) = this.update(cx, |this, _cx| {
                let session = this
                    .sessions
                    .get(&session_id)
                    .context("Failed to get session")?;
                anyhow::Ok((session.acp_thread.clone(), session.thread.clone()))

View on GitHub (pinned to bc538def45)

Solutions

Create the session and await its completion before sending MCP prompts
On this error, recreate the session and re-invoke the prompt
Ensure prompts are routed to the agent instance that owns the session

Defensive patterns

Strategy: validation

Validate before calling

// Ensure the session is registered before sending an MCP prompt
if agent.session_project_state(&session_id).is_none() {
    let session = agent.create_session(project, cx).await?; // register first
    session_id = session.id;
}
send_mcp_prompt(client_id, session_id, prompt_name, server_id, args, content, cx)

Try / catch

match send_mcp_prompt(...).await {
    Err(error) if error.to_string().contains("Project state not found") => {
        // Session was never registered / was removed: recreate and retry once.
        let session = recreate_session(cx).await?;
        send_mcp_prompt(client_id, session.id, prompt_name, server_id, args, content, cx).await
    }
    other => other,
}

Prevention

Await session creation before enabling MCP prompt UI
Invalidate cached session ids whenever the agent restarts
Route prompts to the agent instance that created the session

When it happens

Trigger: Invoking an MCP prompt for a session id that was never created on this Agent, was removed (ended/rewound fully), or belongs to a different agent instance/process.

Common situations: Client fires the prompt before session creation resolves; agent restarted while the client kept its old session ids; two agent connections with crossed session ids; session torn down concurrently with the prompt.

Related errors

AI-assisted analysis of zed-industries/zed@bc538def45 (2026-08-16). Data as JSON: /api/errors/33d500e4cabfdad5. Report an issue: GitHub.