Replace serial LLM-wait-TTS with overlapped execution:
- LLM streams via background thread → asyncio.Queue (non-blocking event loop)
- _sentence_split() detects sentence boundaries in the token stream
- asyncio.create_task fires TTS for each sentence immediately — TTS for
sentence 1 runs while LLM is still generating sentences 2, 3, …
- Audio chunks stream to frontend in order as each task completes
- Time-to-first-audio drops from (LLM total + TTS total) to
roughly (LLM time-to-first-sentence + TTS latency for one sentence)
Frontend audio queue:
- enqueueAudio() / playNextAudio() chain multi-chunk responses seamlessly
- clearAudio() stops playback and cancels queue on new turn or mic click
- scheduleAutoMic() waits for queue to drain before restarting mic
- Error paths clear the queue to avoid stale audio playing after failure
Also fix missing contextlib import (silent bug when audio temp files
needed cleanup in the STT path).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Perceived startup speed:
- index.html: animated shimmer skeleton (header + toolbar + 8 voice cards)
visible immediately; fades out when loader.js finishes
- WaveSurfer (57KB) and MDI icon font (394KB woff2) now served from
static/vendor/ — removes 3 render-blocking external requests from <head>
- Flag-icons CSS loaded async (rel=preload onload trick) — non-blocking
loader.js:
- Fade out skeleton + remove from DOM (300ms transition)
- Reveal page-sections after JS finishes loading
Conversation playground:
- Qwen3 thinking mode fix: fall back to delta.reasoning_content when
delta.content is empty so think-only LLM turns produce visible output
- Better error message with /no-think hint when LLM returns empty
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
UploadFile | None = File(None) with from __future__ import annotations
caused FastAPI to still treat audio as required when omitted.
Changed to Optional[UploadFile] = None (no File() wrapper) so the
field is genuinely optional for text-input turns.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Frontend:
- Add pill-shaped text input + send button (→) to the left of the mic button
- Enter key or → click sends text directly without recording audio
- Input is disabled while a turn is processing; cleared on submit
- Welcome message updated to mention both input methods
- New CSS: .conv-input-bar, .conv-text-row, .conv-text-inp, .conv-send-btn,
.conv-divider (visual separator between text and mic sections)
Backend:
- /api/conversation/turn: audio is now optional (UploadFile | None)
- New text form field — when provided, STT step is skipped and text is
used as the transcript directly; SSE emits transcript event with stt_ms=null
- Raises 400 if neither audio nor text is supplied
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
