diff --git a/src/pty_worker.rs b/src/pty_worker.rs
index dbdd73a67..fd9eed991 100644
--- a/src/pty_worker.rs
+++ b/src/pty_worker.rs
@@ -29,6 +29,28 @@ const STARTUP_BUFFER_KEEP: usize = 8_000;
 const PROMPT_WINDOW_BYTES: usize = 800;
 const RELAYCAST_BOOT_MARKER: &str = "booting mcp server: relaycast";
 
+/// Detect the relaycast MCP boot marker in output. Different CLIs emit
+/// different boot messages:
+/// - Claude: "booting mcp server: relaycast"
+/// - Codex:  "Starting MCP servers (0/2): relay, relaycast"
+///
+/// Returns the byte offset of the end of the marker, or None if not found.
+fn find_relaycast_boot_marker(lower_output: &str) -> Option<usize> {
+    // Claude-style marker
+    if let Some(idx) = lower_output.find(RELAYCAST_BOOT_MARKER) {
+        return Some(idx + RELAYCAST_BOOT_MARKER.len());
+    }
+    // Codex-style marker: "starting mcp server" with "relaycast" nearby
+    if let Some(idx) = lower_output.find("starting mcp server") {
+        // Look for "relaycast" within the same line (next ~200 chars)
+        let search_end = floor_char_boundary(lower_output, (idx + 200).min(lower_output.len()));
+        if let Some(rc_idx) = lower_output[idx..search_end].find("relaycast") {
+            return Some(idx + rc_idx + "relaycast".len());
+        }
+    }
+    None
+}
+
 fn append_bounded(buf: &mut String, text: &str, max: usize, keep: usize) {
     buf.push_str(text);
     if buf.len() > max {
@@ -408,13 +430,13 @@ pub(crate) async fn run_pty_worker(cmd: PtyCommand) -> Result<()> {
                             let mut just_saw_relaycast_boot = false;
                             if !saw_relaycast_boot {
                                 let lower_startup = startup_output.to_ascii_lowercase();
-                                if let Some(marker_idx) = lower_startup.find(RELAYCAST_BOOT_MARKER)
+                                if let Some(marker_end_offset) = find_relaycast_boot_marker(&lower_startup)
                                 {
                                     saw_relaycast_boot = true;
                                     just_saw_relaycast_boot = true;
                                     let marker_end = floor_char_boundary(
                                         &startup_output,
-                                        marker_idx + RELAYCAST_BOOT_MARKER.len(),
+                                        marker_end_offset,
                                     );
                                     post_boot_output.clear();
                                     append_bounded(