codex/codex-rs/rmcp-client/tests/streamable_http_recovery.rs

use std::net::TcpListener;
use std::path::PathBuf;
use std::time::Duration;
use std::time::Instant;

use codex_rmcp_client::ElicitationAction;
use codex_rmcp_client::ElicitationResponse;
use codex_rmcp_client::OAuthCredentialsStoreMode;
use codex_rmcp_client::RmcpClient;
use codex_utils_cargo_bin::CargoBinError;
use futures::FutureExt as _;
use pretty_assertions::assert_eq;
use rmcp::model::CallToolResult;
use rmcp::model::ClientCapabilities;
use rmcp::model::ElicitationCapability;
use rmcp::model::FormElicitationCapability;
use rmcp::model::Implementation;
use rmcp::model::InitializeRequestParams;
use rmcp::model::ProtocolVersion;
use serde_json::json;
use tokio::net::TcpStream;
use tokio::process::Child;
use tokio::process::Command;
use tokio::time::sleep;

const SESSION_POST_FAILURE_CONTROL_PATH: &str = "/test/control/session-post-failure";

fn streamable_http_server_bin() -> Result<PathBuf, CargoBinError> {
    codex_utils_cargo_bin::cargo_bin("test_streamable_http_server")
}

fn init_params() -> InitializeRequestParams {
    InitializeRequestParams {
        meta: None,
        capabilities: ClientCapabilities {
            experimental: None,
            extensions: None,
            roots: None,
            sampling: None,
            elicitation: Some(ElicitationCapability {
                form: Some(FormElicitationCapability {
                    schema_validation: None,
                }),
                url: None,
            }),
            tasks: None,
        },
        client_info: Implementation {
            name: "codex-test".into(),
            version: "0.0.0-test".into(),
            title: Some("Codex rmcp recovery test".into()),
            description: None,
            icons: None,
            website_url: None,
        },
        protocol_version: ProtocolVersion::V_2025_06_18,
    }
}

fn expected_echo_result(message: &str) -> CallToolResult {
    CallToolResult {
        content: Vec::new(),
        structured_content: Some(json!({
            "echo": format!("ECHOING: {message}"),
            "env": null,
        })),
        is_error: Some(false),
        meta: None,
    }
}

async fn create_client(base_url: &str) -> anyhow::Result<RmcpClient> {
    let client = RmcpClient::new_streamable_http_client(
        "test-streamable-http",
        &format!("{base_url}/mcp"),
        Some("test-bearer".to_string()),
        /*http_headers*/ None,
        /*env_http_headers*/ None,
        OAuthCredentialsStoreMode::File,
    )
    .await?;

    client
        .initialize(
            init_params(),
            Some(Duration::from_secs(5)),
            Box::new(|_, _| {
                async {
                    Ok(ElicitationResponse {
                        action: ElicitationAction::Accept,
                        content: Some(json!({})),
                        meta: None,
                    })
                }
                .boxed()
            }),
        )
        .await?;

    Ok(client)
}

async fn call_echo_tool(client: &RmcpClient, message: &str) -> anyhow::Result<CallToolResult> {
    client
        .call_tool(
            "echo".to_string(),
            Some(json!({ "message": message })),
            /*meta*/ None,
            Some(Duration::from_secs(5)),
        )
        .await
}

async fn arm_session_post_failure(
    base_url: &str,
    status: u16,
    remaining: usize,
) -> anyhow::Result<()> {
    let response = reqwest::Client::new()
        .post(format!("{base_url}{SESSION_POST_FAILURE_CONTROL_PATH}"))
        .json(&json!({
            "status": status,
            "remaining": remaining,
        }))
        .send()
        .await?;

    assert_eq!(response.status(), reqwest::StatusCode::NO_CONTENT);
    Ok(())
}

async fn spawn_streamable_http_server() -> anyhow::Result<(Child, String)> {
    let listener = TcpListener::bind("127.0.0.1:0")?;
    let port = listener.local_addr()?.port();
    drop(listener);

    let bind_addr = format!("127.0.0.1:{port}");
    let base_url = format!("http://{bind_addr}");
    let mut child = Command::new(streamable_http_server_bin()?)
        .kill_on_drop(true)
        .env("MCP_STREAMABLE_HTTP_BIND_ADDR", &bind_addr)
        .spawn()?;

    wait_for_streamable_http_server(&mut child, &bind_addr, Duration::from_secs(5)).await?;
    Ok((child, base_url))
}

async fn wait_for_streamable_http_server(
    server_child: &mut Child,
    address: &str,
    timeout: Duration,
) -> anyhow::Result<()> {
    let deadline = Instant::now() + timeout;

    loop {
        if let Some(status) = server_child.try_wait()? {
            return Err(anyhow::anyhow!(
                "streamable HTTP server exited early with status {status}"
            ));
        }

        let remaining = deadline.saturating_duration_since(Instant::now());
        if remaining.is_zero() {
            return Err(anyhow::anyhow!(
                "timed out waiting for streamable HTTP server at {address}: deadline reached"
            ));
        }

        match tokio::time::timeout(remaining, TcpStream::connect(address)).await {
            Ok(Ok(_)) => return Ok(()),
            Ok(Err(error)) => {
                if Instant::now() >= deadline {
                    return Err(anyhow::anyhow!(
                        "timed out waiting for streamable HTTP server at {address}: {error}"
                    ));
                }
            }
            Err(_) => {
                return Err(anyhow::anyhow!(
                    "timed out waiting for streamable HTTP server at {address}: connect call timed out"
                ));
            }
        }

        sleep(Duration::from_millis(50)).await;
    }
}

#[tokio::test(flavor = "multi_thread", worker_threads = 1)]
async fn streamable_http_404_session_expiry_recovers_and_retries_once() -> anyhow::Result<()> {
    let (_server, base_url) = spawn_streamable_http_server().await?;
    let client = create_client(&base_url).await?;

    let warmup = call_echo_tool(&client, "warmup").await?;
    assert_eq!(warmup, expected_echo_result("warmup"));

    arm_session_post_failure(&base_url, /*status*/ 404, /*remaining*/ 1).await?;

    let recovered = call_echo_tool(&client, "recovered").await?;
    assert_eq!(recovered, expected_echo_result("recovered"));

    Ok(())
}

#[tokio::test(flavor = "multi_thread", worker_threads = 1)]
async fn streamable_http_401_does_not_trigger_recovery() -> anyhow::Result<()> {
    let (_server, base_url) = spawn_streamable_http_server().await?;
    let client = create_client(&base_url).await?;

    let warmup = call_echo_tool(&client, "warmup").await?;
    assert_eq!(warmup, expected_echo_result("warmup"));

    arm_session_post_failure(&base_url, /*status*/ 401, /*remaining*/ 2).await?;

    let first_error = call_echo_tool(&client, "unauthorized").await.unwrap_err();
    assert!(first_error.to_string().contains("401"));

    let second_error = call_echo_tool(&client, "still-unauthorized")
        .await
        .unwrap_err();
    assert!(second_error.to_string().contains("401"));

    Ok(())
}

#[tokio::test(flavor = "multi_thread", worker_threads = 1)]
async fn streamable_http_404_recovery_only_retries_once() -> anyhow::Result<()> {
    let (_server, base_url) = spawn_streamable_http_server().await?;
    let client = create_client(&base_url).await?;

    let warmup = call_echo_tool(&client, "warmup").await?;
    assert_eq!(warmup, expected_echo_result("warmup"));

    arm_session_post_failure(&base_url, /*status*/ 404, /*remaining*/ 2).await?;

    let error = call_echo_tool(&client, "double-404").await.unwrap_err();
    assert!(
        error
            .to_string()
            .contains("handshaking with MCP server failed")
            || error.to_string().contains("Transport channel closed")
    );

    let recovered = call_echo_tool(&client, "after-double-404").await?;
    assert_eq!(recovered, expected_echo_result("after-double-404"));

    Ok(())
}

#[tokio::test(flavor = "multi_thread", worker_threads = 1)]
async fn streamable_http_non_session_failure_does_not_trigger_recovery() -> anyhow::Result<()> {
    let (_server, base_url) = spawn_streamable_http_server().await?;
    let client = create_client(&base_url).await?;

    let warmup = call_echo_tool(&client, "warmup").await?;
    assert_eq!(warmup, expected_echo_result("warmup"));

    arm_session_post_failure(&base_url, /*status*/ 500, /*remaining*/ 2).await?;

    let first_error = call_echo_tool(&client, "server-error").await.unwrap_err();
    assert!(first_error.to_string().contains("500"));

    let second_error = call_echo_tool(&client, "still-server-error")
        .await
        .unwrap_err();
    assert!(second_error.to_string().contains("500"));

    Ok(())
}