fix(app-server): set originator header from initialize (re-revert) (#8988)

Reapplies https://github.com/openai/codex/pull/8873 which was reverted
due to merge conflicts

codex-rs/app-server/tests/suite/v2/initialize.rs

@@ -0,0 +1,137 @@
+use anyhow::Result;
+use app_test_support::McpProcess;
+use app_test_support::create_mock_responses_server_sequence_unchecked;
+use app_test_support::to_response;
+use codex_app_server_protocol::ClientInfo;
+use codex_app_server_protocol::InitializeResponse;
+use codex_app_server_protocol::JSONRPCMessage;
+use pretty_assertions::assert_eq;
+use std::path::Path;
+use tempfile::TempDir;
+use tokio::time::timeout;
+
+const DEFAULT_READ_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(10);
+
+#[tokio::test]
+async fn initialize_uses_client_info_name_as_originator() -> Result<()> {
+    let responses = Vec::new();
+    let server = create_mock_responses_server_sequence_unchecked(responses).await;
+    let codex_home = TempDir::new()?;
+    create_config_toml(codex_home.path(), &server.uri(), "never")?;
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+
+    let message = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.initialize_with_client_info(ClientInfo {
+            name: "codex_vscode".to_string(),
+            title: Some("Codex VS Code Extension".to_string()),
+            version: "0.1.0".to_string(),
+        }),
+    )
+    .await??;
+
+    let JSONRPCMessage::Response(response) = message else {
+        anyhow::bail!("expected initialize response, got {message:?}");
+    };
+    let InitializeResponse { user_agent } = to_response::<InitializeResponse>(response)?;
+
+    assert!(user_agent.starts_with("codex_vscode/"));
+    Ok(())
+}
+
+#[tokio::test]
+async fn initialize_respects_originator_override_env_var() -> Result<()> {
+    let responses = Vec::new();
+    let server = create_mock_responses_server_sequence_unchecked(responses).await;
+    let codex_home = TempDir::new()?;
+    create_config_toml(codex_home.path(), &server.uri(), "never")?;
+    let mut mcp = McpProcess::new_with_env(
+        codex_home.path(),
+        &[(
+            "CODEX_INTERNAL_ORIGINATOR_OVERRIDE",
+            Some("codex_originator_via_env_var"),
+        )],
+    )
+    .await?;
+
+    let message = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.initialize_with_client_info(ClientInfo {
+            name: "codex_vscode".to_string(),
+            title: Some("Codex VS Code Extension".to_string()),
+            version: "0.1.0".to_string(),
+        }),
+    )
+    .await??;
+
+    let JSONRPCMessage::Response(response) = message else {
+        anyhow::bail!("expected initialize response, got {message:?}");
+    };
+    let InitializeResponse { user_agent } = to_response::<InitializeResponse>(response)?;
+
+    assert!(user_agent.starts_with("codex_originator_via_env_var/"));
+    Ok(())
+}
+
+#[tokio::test]
+async fn initialize_rejects_invalid_client_name() -> Result<()> {
+    let responses = Vec::new();
+    let server = create_mock_responses_server_sequence_unchecked(responses).await;
+    let codex_home = TempDir::new()?;
+    create_config_toml(codex_home.path(), &server.uri(), "never")?;
+    let mut mcp = McpProcess::new_with_env(
+        codex_home.path(),
+        &[("CODEX_INTERNAL_ORIGINATOR_OVERRIDE", None)],
+    )
+    .await?;
+
+    let message = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.initialize_with_client_info(ClientInfo {
+            name: "bad\rname".to_string(),
+            title: Some("Bad Client".to_string()),
+            version: "0.1.0".to_string(),
+        }),
+    )
+    .await??;
+
+    let JSONRPCMessage::Error(error) = message else {
+        anyhow::bail!("expected initialize error, got {message:?}");
+    };
+
+    assert_eq!(error.error.code, -32600);
+    assert_eq!(
+        error.error.message,
+        "Invalid clientInfo.name: 'bad\rname'. Must be a valid HTTP header value."
+    );
+    assert_eq!(error.error.data, None);
+    Ok(())
+}
+
+// Helper to create a config.toml pointing at the mock model server.
+fn create_config_toml(
+    codex_home: &Path,
+    server_uri: &str,
+    approval_policy: &str,
+) -> std::io::Result<()> {
+    let config_toml = codex_home.join("config.toml");
+    std::fs::write(
+        config_toml,
+        format!(
+            r#"
+model = "mock-model"
+approval_policy = "{approval_policy}"
+sandbox_mode = "read-only"
+
+model_provider = "mock_provider"
+
+[model_providers.mock_provider]
+name = "Mock provider for test"
+base_url = "{server_uri}/v1"
+wire_api = "responses"
+request_max_retries = 0
+stream_max_retries = 0
+"#
+        ),
+    )
+}