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feat(app-server): support mcp elicitations in v2 api (#13425)

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This adds a first-class server request for MCP server elicitations:
`mcpServer/elicitation/request`.

Until now, MCP elicitation requests only showed up as a raw
`codex/event/elicitation_request` event from core. That made it hard for
v2 clients to handle elicitations using the same request/response flow
as other server-driven interactions (like shell and `apply_patch`
tools).

This also updates the underlying MCP elicitation request handling in
core to pass through the full MCP request (including URL and form data)
so we can expose it properly in app-server.

### Why not `item/mcpToolCall/elicitationRequest`?
This is because MCP elicitations are related to MCP servers first, and
only optionally to a specific MCP tool call.

In the MCP protocol, elicitation is a server-to-client capability: the
server sends `elicitation/create`, and the client replies with an
elicitation result. RMCP models it that way as well.

In practice an elicitation is often triggered by an MCP tool call, but
not always.

### What changed
- add `mcpServer/elicitation/request` to the v2 app-server API
- translate core `codex/event/elicitation_request` events into the new
v2 server request
- map client responses back into `Op::ResolveElicitation` so the MCP
server can continue
- update app-server docs and generated protocol schema
- add an end-to-end app-server test that covers the full round trip
through a real RMCP elicitation flow
- The new test exercises a realistic case where an MCP tool call
triggers an elicitation, the app-server emits
mcpServer/elicitation/request, the client accepts it, and the tool call
resumes and completes successfully.

### app-server API flow
- Client starts a thread with `thread/start`.
- Client starts a turn with `turn/start`.
- App-server sends `item/started` for the `mcpToolCall`.
- While that tool call is in progress, app-server sends
`mcpServer/elicitation/request`.
- Client responds to that request with `{ action: "accept" | "decline" |
"cancel" }`.
- App-server sends `serverRequest/resolved`.
- App-server sends `item/completed` for the mcpToolCall.
- App-server sends `turn/completed`.
- If the turn is interrupted while the elicitation is pending,
app-server still sends `serverRequest/resolved` before the turn
finishes.
This commit is contained in:
Owen Lin
2026-03-05 07:20:20 -08:00
committed by GitHub
parent 5e92f4af12
commit 926b2f19e8
32 changed files with 1472 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

117
codex-rs/app-server/src/bespoke_event_handling.rs
View File

@@ -45,6 +45,9 @@ use codex_app_server_protocol::InterruptConversationResponse;
use codex_app_server_protocol::ItemCompletedNotification;
use codex_app_server_protocol::ItemStartedNotification;
use codex_app_server_protocol::JSONRPCErrorError;
use codex_app_server_protocol::McpServerElicitationAction;
use codex_app_server_protocol::McpServerElicitationRequestParams;
use codex_app_server_protocol::McpServerElicitationRequestResponse;
use codex_app_server_protocol::McpToolCallError;
use codex_app_server_protocol::McpToolCallResult;
use codex_app_server_protocol::McpToolCallStatus;
@@ -609,6 +612,38 @@ pub(crate) async fn apply_bespoke_event_handling(
}
}
}
EventMsg::ElicitationRequest(request) => {
if matches!(api_version, ApiVersion::V2) {
let permission_guard = thread_watch_manager
.note_permission_requested(&conversation_id.to_string())
.await;
let turn_id = {
let state = thread_state.lock().await;
state.active_turn_snapshot().map(|turn| turn.id)
};
let params = McpServerElicitationRequestParams {
thread_id: conversation_id.to_string(),
turn_id,
server_name: request.server_name.clone(),
request: request.request.into(),
};
let (pending_request_id, rx) = outgoing
.send_request(ServerRequestPayload::McpServerElicitationRequest(params))
.await;
tokio::spawn(async move {
on_mcp_server_elicitation_response(
request.server_name,
request.id,
pending_request_id,
rx,
conversation,
thread_state,
permission_guard,
)
.await;
});
}
}
EventMsg::DynamicToolCallRequest(request) => {
if matches!(api_version, ApiVersion::V2) {
let call_id = request.call_id;
@@ -1989,6 +2024,68 @@ async fn on_request_user_input_response(
}
}
async fn on_mcp_server_elicitation_response(
server_name: String,
request_id: codex_protocol::mcp::RequestId,
pending_request_id: RequestId,
receiver: oneshot::Receiver<ClientRequestResult>,
conversation: Arc<CodexThread>,
thread_state: Arc<Mutex<ThreadState>>,
permission_guard: ThreadWatchActiveGuard,
) {
let response = receiver.await;
resolve_server_request_on_thread_listener(&thread_state, pending_request_id).await;
drop(permission_guard);
let response = mcp_server_elicitation_response_from_client_result(response);
if let Err(err) = conversation
.submit(Op::ResolveElicitation {
server_name,
request_id,
decision: response.action.to_core(),
content: response.content,
})
.await
{
error!("failed to submit ResolveElicitation: {err}");
}
}
fn mcp_server_elicitation_response_from_client_result(
response: std::result::Result<ClientRequestResult, oneshot::error::RecvError>,
) -> McpServerElicitationRequestResponse {
match response {
Ok(Ok(value)) => serde_json::from_value::<McpServerElicitationRequestResponse>(value)
.unwrap_or_else(|err| {
error!("failed to deserialize McpServerElicitationRequestResponse: {err}");
McpServerElicitationRequestResponse {
action: McpServerElicitationAction::Decline,
content: None,
}
}),
Ok(Err(err)) if is_turn_transition_server_request_error(&err) => {
McpServerElicitationRequestResponse {
action: McpServerElicitationAction::Cancel,
content: None,
}
}
Ok(Err(err)) => {
error!("request failed with client error: {err:?}");
McpServerElicitationRequestResponse {
action: McpServerElicitationAction::Decline,
content: None,
}
}
Err(err) => {
error!("request failed: {err:?}");
McpServerElicitationRequestResponse {
action: McpServerElicitationAction::Decline,
content: None,
}
}
}
}
const REVIEW_FALLBACK_MESSAGE: &str = "Reviewer failed to output a response.";
fn render_review_output_text(output: &ReviewOutputEvent) -> String {
@@ -2334,6 +2431,7 @@ mod tests {
use anyhow::Result;
use anyhow::anyhow;
use anyhow::bail;
use codex_app_server_protocol::JSONRPCErrorError;
use codex_app_server_protocol::TurnPlanStepStatus;
use codex_protocol::mcp::CallToolResult;
use codex_protocol::plan_tool::PlanItemArg;
@@ -2378,6 +2476,25 @@ mod tests {
assert_eq!(completion_status, None);
}
#[test]
fn mcp_server_elicitation_turn_transition_error_maps_to_cancel() {
let error = JSONRPCErrorError {
code: -1,
message: "client request resolved because the turn state was changed".to_string(),
data: Some(serde_json::json!({ "reason": "turnTransition" })),
};
let response = mcp_server_elicitation_response_from_client_result(Ok(Err(error)));
assert_eq!(
response,
McpServerElicitationRequestResponse {
action: McpServerElicitationAction::Cancel,
content: None,
}
);
}
#[test]
fn collab_resume_begin_maps_to_item_started_resume_agent() {
let event = CollabResumeBeginEvent {