diff --git a/src/features/tmux-subagent/manager.ts b/src/features/tmux-subagent/manager.ts
index 05199f4d1f..c1a11a9a82 100644
--- a/src/features/tmux-subagent/manager.ts
+++ b/src/features/tmux-subagent/manager.ts
@@ -71,7 +71,11 @@ export class TmuxSessionManager {
     this.tmuxConfig = tmuxConfig
     this.deps = deps
     const defaultPort = process.env.OPENCODE_PORT ?? "4096"
-    this.serverUrl = ctx.serverUrl?.toString() ?? `http://localhost:${defaultPort}`
+    try {
+      this.serverUrl = ctx.serverUrl?.toString() ?? `http://localhost:${defaultPort}`
+    } catch {
+      this.serverUrl = `http://localhost:${defaultPort}`
+    }
     this.sourcePaneId = deps.getCurrentPaneId()
     this.pollingManager = new TmuxPollingManager(
       this.client,