codex/codex-rs/core/tests/suite/websocket_fallback.rs

use anyhow::Result;
use codex_core::features::Feature;
use core_test_support::responses;
use core_test_support::responses::ev_completed;
use core_test_support::responses::ev_response_created;
use core_test_support::responses::mount_sse_once;
use core_test_support::responses::mount_sse_sequence;
use core_test_support::responses::sse;
use core_test_support::skip_if_no_network;
use core_test_support::test_codex::test_codex;
use pretty_assertions::assert_eq;
use wiremock::Mock;
use wiremock::ResponseTemplate;
use wiremock::http::Method;
use wiremock::matchers::method;
use wiremock::matchers::path_regex;

#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
async fn websocket_fallback_switches_to_http_on_upgrade_required_connect() -> Result<()> {
    skip_if_no_network!(Ok(()));

    let server = responses::start_mock_server().await;
    Mock::given(method("GET"))
        .and(path_regex(".*/responses$"))
        .respond_with(ResponseTemplate::new(426))
        .mount(&server)
        .await;

    let response_mock = mount_sse_once(
        &server,
        sse(vec![ev_response_created("resp-1"), ev_completed("resp-1")]),
    )
    .await;

    let mut builder = test_codex().with_config({
        let base_url = format!("{}/v1", server.uri());
        move |config| {
            config.model_provider.base_url = Some(base_url);
            config.model_provider.wire_api = codex_core::WireApi::Responses;
            config.features.enable(Feature::ResponsesWebsockets);
            // If we don't treat 426 specially, the sampling loop would retry the WebSocket
            // handshake before switching to the HTTP transport.
            config.model_provider.stream_max_retries = Some(2);
            config.model_provider.request_max_retries = Some(0);
        }
    });
    let test = builder.build(&server).await?;

    test.submit_turn("hello").await?;

    let requests = server.received_requests().await.unwrap_or_default();
    let websocket_attempts = requests
        .iter()
        .filter(|req| req.method == Method::GET && req.url.path().ends_with("/responses"))
        .count();
    let http_attempts = requests
        .iter()
        .filter(|req| req.method == Method::POST && req.url.path().ends_with("/responses"))
        .count();

    // One websocket attempt comes from startup preconnect and one from the first turn's stream
    // attempt before fallback activates; after fallback, transport is HTTP. This matches the
    // retry-budget tradeoff documented in [`codex_core::client`] module docs.
    assert_eq!(websocket_attempts, 2);
    assert_eq!(http_attempts, 1);
    assert_eq!(response_mock.requests().len(), 1);

    Ok(())
}

#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
async fn websocket_fallback_switches_to_http_after_retries_exhausted() -> Result<()> {
    skip_if_no_network!(Ok(()));

    let server = responses::start_mock_server().await;
    let response_mock = mount_sse_once(
        &server,
        sse(vec![ev_response_created("resp-1"), ev_completed("resp-1")]),
    )
    .await;

    let mut builder = test_codex().with_config({
        let base_url = format!("{}/v1", server.uri());
        move |config| {
            config.model_provider.base_url = Some(base_url);
            config.model_provider.wire_api = codex_core::WireApi::Responses;
            config.features.enable(Feature::ResponsesWebsockets);
            config.model_provider.stream_max_retries = Some(2);
            config.model_provider.request_max_retries = Some(0);
        }
    });
    let test = builder.build(&server).await?;

    test.submit_turn("hello").await?;

    let requests = server.received_requests().await.unwrap_or_default();
    let websocket_attempts = requests
        .iter()
        .filter(|req| req.method == Method::GET && req.url.path().ends_with("/responses"))
        .count();
    let http_attempts = requests
        .iter()
        .filter(|req| req.method == Method::POST && req.url.path().ends_with("/responses"))
        .count();

    // One websocket attempt comes from startup preconnect.
    // The first turn then makes 3 websocket stream attempts (initial try + 2 retries),
    // after which fallback activates and the request is replayed over HTTP.
    assert_eq!(websocket_attempts, 4);
    assert_eq!(http_attempts, 1);
    assert_eq!(response_mock.requests().len(), 1);

    Ok(())
}

#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
async fn websocket_fallback_is_sticky_across_turns() -> Result<()> {
    skip_if_no_network!(Ok(()));

    let server = responses::start_mock_server().await;
    let response_mock = mount_sse_sequence(
        &server,
        vec![
            sse(vec![ev_response_created("resp-1"), ev_completed("resp-1")]),
            sse(vec![ev_response_created("resp-2"), ev_completed("resp-2")]),
        ],
    )
    .await;

    let mut builder = test_codex().with_config({
        let base_url = format!("{}/v1", server.uri());
        move |config| {
            config.model_provider.base_url = Some(base_url);
            config.model_provider.wire_api = codex_core::WireApi::Responses;
            config.features.enable(Feature::ResponsesWebsockets);
            config.model_provider.stream_max_retries = Some(2);
            config.model_provider.request_max_retries = Some(0);
        }
    });
    let test = builder.build(&server).await?;

    test.submit_turn("first").await?;
    test.submit_turn("second").await?;

    let requests = server.received_requests().await.unwrap_or_default();
    let websocket_attempts = requests
        .iter()
        .filter(|req| req.method == Method::GET && req.url.path().ends_with("/responses"))
        .count();
    let http_attempts = requests
        .iter()
        .filter(|req| req.method == Method::POST && req.url.path().ends_with("/responses"))
        .count();

    // WebSocket attempts all happen on the first turn:
    // 1 startup preconnect + 3 stream attempts (initial try + 2 retries) before fallback.
    // Fallback is sticky, so the second turn stays on HTTP and adds no websocket attempts.
    assert_eq!(websocket_attempts, 4);
    assert_eq!(http_attempts, 2);
    assert_eq!(response_mock.requests().len(), 2);

    Ok(())
}