fix: send engine=edge from the first-party Edge callers

The settings UI writes localStorage immediately but persists the server
engine through a debounced save, so a first-party Edge selection could
fall through the new server default to a stale ElevenLabs/OpenAI
engine. Both WebUI Edge callers now pass engine explicitly; regressions
cover both call sites.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CNmJZVV9u6pBhcwVhwkPp6

static/boot.js

@@ -1901,7 +1901,7 @@ window.renderTranscript=function(container, messages, opts){
       fetch(new URL('api/tts', document.baseURI || location.href).href, {
         method: 'POST',
         headers: {'Content-Type': 'application/json'},
-        body: JSON.stringify({text: clean, voice, rate, pitch})
+        body: JSON.stringify({text: clean, voice, rate, pitch, engine: 'edge'})
       })
       .then(r => {
         if(!r.ok) throw new Error('TTS request failed: ' + r.status);

static/ui.js

@@ -9168,7 +9168,7 @@ function _playEdgeTtsChunked(text, btn){
     fetch(new URL('api/tts', document.baseURI || location.href).href, {
       method:'POST',
       headers:{'Content-Type':'application/json'},
-      body:JSON.stringify({text:chunk, voice:voice, rate:rate, pitch:pitch})
+      body:JSON.stringify({text:chunk, voice:voice, rate:rate, pitch:pitch, engine:'edge'})
     })
     .then(function(r){
       if(!r.ok){

tests/test_issue7391_first_party_edge_tts_engine.py

@@ -0,0 +1,143 @@
+"""G7394-1: first-party Edge callers must send engine:'edge' explicitly.
+
+The Settings selector writes localStorage immediately, then saves the server
+setting through a 350ms debounced autosave. During that window (or if the
+save fails) the WebUI dispatches the Edge branch while the server still holds
+ElevenLabs/OpenAI. Omitting engine lets the persisted-engine fallback silently
+play the stale provider.
+
+These tests execute the production ui.js / boot.js callers with a local Edge
+selection and assert the /api/tts request body carries the explicit override.
+"""
+
+from __future__ import annotations
+
+import json
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+from tests.js_source_extract import extract_function
+
+
+ROOT = Path(__file__).resolve().parents[1]
+UI_JS = (ROOT / "static" / "ui.js").read_text(encoding="utf-8")
+BOOT_JS = (ROOT / "static" / "boot.js").read_text(encoding="utf-8")
+NODE = shutil.which("node")
+
+pytestmark = pytest.mark.skipif(NODE is None, reason="node not on PATH")
+
+
+def _run_node(script: str) -> list[dict]:
+    result = subprocess.run(
+        [NODE, "-e", script],
+        cwd=ROOT,
+        capture_output=True,
+        text=True,
+        timeout=30,
+    )
+    assert result.returncode == 0, (
+        f"node subprocess failed:\n--- stdout ---\n{result.stdout}\n"
+        f"--- stderr ---\n{result.stderr}"
+    )
+    return json.loads(result.stdout.strip().splitlines()[-1])
+
+
+_UI_HARNESS = r"""
+const requests = [];
+const store = {
+  'hermes-tts-engine': 'edge',
+  'hermes-tts-voice': 'en-US-AriaNeural',
+};
+globalThis.window = globalThis;
+globalThis.speechSynthesis = { cancel() {}, getVoices() { return []; } };
+globalThis.localStorage = {
+  getItem: (k) => Object.prototype.hasOwnProperty.call(store, k) ? store[k] : null,
+};
+globalThis.document = {
+  baseURI: 'http://localhost:8787/',
+  querySelectorAll: () => [],
+};
+globalThis.location = { href: 'http://localhost:8787/' };
+globalThis.fetch = (url, opts) => {
+  requests.push({ url: String(url), body: JSON.parse(opts.body) });
+  return new Promise(() => {});
+};
+let _ttsSpeaking = false;
+let _playingEdgeAudio = null;
+let _ttsCurrentUtterance = null;
+let _ttsChunkQueue = [];
+let _ttsChunkIndex = 0;
+let _ttsActiveBtn = null;
+__UI_FNS__
+const row = { dataset: { rawText: 'Hello from Edge' } };
+const btn = { dataset: { speaking: '0' }, closest: () => row };
+speakMessage(btn);
+console.log(JSON.stringify(requests));
+"""
+
+
+_BOOT_HARNESS = r"""
+const requests = [];
+const store = {
+  'hermes-tts-engine': 'edge',
+  'hermes-tts-voice': 'en-US-AriaNeural',
+};
+globalThis.window = globalThis;
+globalThis.localStorage = {
+  getItem: (k) => Object.prototype.hasOwnProperty.call(store, k) ? store[k] : null,
+};
+globalThis.document = {
+  baseURI: 'http://localhost:8787/',
+  querySelectorAll: () => [{ dataset: { rawText: 'Hello from Edge' } }],
+};
+globalThis.location = { href: 'http://localhost:8787/' };
+globalThis.fetch = (url, opts) => {
+  requests.push({ url: String(url), body: JSON.parse(opts.body) });
+  return new Promise(() => {});
+};
+const S = { session: { session_id: 'sid-edge' } };
+let _voiceModeActive = true;
+let _voiceModeThinkingSid = null;
+let _ttsSpeaking = false;
+let _playingEdgeAudio = null;
+function _setState() {}
+function _startListening() {}
+__BOOT_FNS__
+_speakResponse();
+console.log(JSON.stringify(requests));
+"""
+
+
+def test_play_edge_tts_chunked_sends_explicit_engine_when_server_still_elevenlabs():
+    """Local Edge selection (Listen button) must override persisted ElevenLabs."""
+    fns = "\n".join(
+        [
+            extract_function(UI_JS, "_stripForTTS"),
+            extract_function(UI_JS, "_splitForTTS"),
+            extract_function(UI_JS, "_playEdgeTtsChunked"),
+            extract_function(UI_JS, "stopTTS"),
+            extract_function(UI_JS, "speakMessage"),
+        ]
+    )
+    requests = _run_node(_UI_HARNESS.replace("__UI_FNS__", fns))
+
+    assert len(requests) == 1
+    assert requests[0]["url"].endswith("/api/tts")
+    assert requests[0]["body"]["engine"] == "edge"
+    assert requests[0]["body"]["text"] == "Hello from Edge"
+    assert requests[0]["body"]["voice"] == "en-US-AriaNeural"
+
+
+def test_voice_mode_edge_branch_sends_explicit_engine_when_server_still_openai():
+    """Local Edge selection (voice-mode auto-read) must override persisted OpenAI."""
+    fns = extract_function(BOOT_JS, "_speakResponse")
+    requests = _run_node(_BOOT_HARNESS.replace("__BOOT_FNS__", fns))
+
+    assert len(requests) == 1
+    assert requests[0]["url"].endswith("/api/tts")
+    assert requests[0]["body"]["engine"] == "edge"
+    assert requests[0]["body"]["text"] == "Hello from Edge"
+    assert requests[0]["body"]["voice"] == "en-US-AriaNeural"