fix: dedupe aiui:prefill-composer listener across chat re-navigations (fixes #209)

Register the Code Studio prefill listener as a module-scope singleton via
ensurePrefillListener() and remove it in cleanup(), preventing duplicate
window handlers from stacking on repeated SPA navigation between /chat and
/code-studio.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

src/praisonaiui/templates/frontend/plugins/views/chat.js

@@ -22,6 +22,7 @@ let agents = [];
 let messageQueue = [];
 let focusMode = false;
 let sessionSelectHandler = null;
+let prefillHandler = null;
 let containerRef = null;
 let currentDeltaEl = null;
 let currentDeltaBodyEl = null;
@@ -739,6 +740,26 @@ function setupResizeHandles(wrapper) {
   });
 }
 
+// ── Prefill Composer Listener (singleton) ───────────────────────
+// Code Studio's "Send to Agent" dispatches a window-level
+// 'aiui:prefill-composer' event. This SPA calls render() on every
+// visit to /chat, so the listener is installed once at module scope
+// and guarded to avoid stacking duplicate handlers across navigations.
+function ensurePrefillListener() {
+  if (prefillHandler) return;
+  prefillHandler = (e) => {
+    const text = e.detail && e.detail.text;
+    if (!text) return;
+    const el = document.getElementById('chat-input');
+    if (!el) return;
+    el.value = text;
+    el.style.height = 'auto';
+    el.style.height = Math.min(el.scrollHeight, 150) + 'px';
+    el.focus();
+  };
+  window.addEventListener('aiui:prefill-composer', prefillHandler);
+}
+
 // ── Main render (ES module entry point) ─────────────────────────
 export async function render(container) {
   injectStyles();
@@ -881,16 +902,7 @@ export async function render(container) {
     if (e.key === 'Enter' && !e.shiftKey) { e.preventDefault(); sendMessage(); }
   });
 
-  window.addEventListener('aiui:prefill-composer', (e) => {
-    const text = e.detail && e.detail.text;
-    if (!text) return;
-    const el = document.getElementById('chat-input');
-    if (!el) return;
-    el.value = text;
-    el.style.height = 'auto';
-    el.style.height = Math.min(el.scrollHeight, 150) + 'px';
-    el.focus();
-  });
+  ensurePrefillListener();
   input.addEventListener('input', () => {
     input.style.height = 'auto';
     input.style.height = Math.min(input.scrollHeight, 150) + 'px';
@@ -967,6 +979,10 @@ export function cleanup() {
     window.removeEventListener('aiui:session-select', sessionSelectHandler);
     sessionSelectHandler = null;
   }
+  if (prefillHandler) {
+    window.removeEventListener('aiui:prefill-composer', prefillHandler);
+    prefillHandler = null;
+  }
   currentSessionId = null;
   currentAgentName = null;
   isStreaming = false;

tests/unit/test_chat_prefill_listener.py

@@ -0,0 +1,32 @@
+"""Tests for the chat prefill-composer listener lifecycle (issue #209).
+
+The 'aiui:prefill-composer' listener must be registered as a module-scope
+singleton and torn down in cleanup(), so repeated SPA navigations between
+/code-studio and /chat do not stack duplicate handlers on window.
+"""
+
+from pathlib import Path
+
+VIEWS = Path("src/praisonaiui/templates/frontend/plugins/views")
+
+
+class TestChatPrefillListenerLifecycle:
+    def test_module_scope_handler_declared(self):
+        src = (VIEWS / "chat.js").read_text()
+        assert "let prefillHandler = null;" in src
+
+    def test_ensure_prefill_listener_guard(self):
+        src = (VIEWS / "chat.js").read_text()
+        assert "function ensurePrefillListener()" in src
+        assert "if (prefillHandler) return;" in src
+
+    def test_render_uses_singleton_not_inline_addlistener(self):
+        src = (VIEWS / "chat.js").read_text()
+        assert "ensurePrefillListener();" in src
+        # The listener is added exactly once, inside the guard helper.
+        assert src.count("window.addEventListener('aiui:prefill-composer'") == 1
+
+    def test_cleanup_removes_listener(self):
+        src = (VIEWS / "chat.js").read_text()
+        assert "window.removeEventListener('aiui:prefill-composer', prefillHandler)" in src
+        assert src.count("prefillHandler = null;") >= 2