# Live streaming preview

Added in `feat/live-streaming` branch.

## What's new

- **Incremental SVG parser** (`incremental_svg.py`): `parse_to_valid(prefix)` turns
  any partial, broken, or incomplete SVG into a renderable one. Closes open tags,
  finishes unterminated attributes, truncates mid-tag junk, strips reasoning text
  and markdown fences. Property-based tested against 100 random prefixes.
- **LM Studio streaming client** (`lm_client.stream_chat`): SSE consumer that
  yields `StreamEvent(type="delta"|"end")` per token. Yields reasoning + content
  together (qwen3.5 emits them in the same field).
- **Live UI** (`app.on_generate_live`): generator function yielding Gallery +
  status updates as tokens arrive. Throttled to ~150ms between updates
  (`time.monotonic()` check, skip-if-recent). Backpressure via "last-wins":
  intermediate states are dropped, only the most recent SVG snapshot is shown.
  Checkbox "Live-стрим" in UI defaults to ON.

## How it works

1. User clicks "Сгенерировать" with Live mode.
2. `on_generate_live` opens SSE connection to LM Studio.
3. Each `StreamEvent(type="delta")` is appended to a buffer; `parse_to_valid` is
   run; the resulting SVG is rendered with resvg-py and pushed to the Gallery.
4. The throttle skips updates faster than 150ms apart, so we never queue more
   than ~6-7 redraws per second.
5. On `StreamEvent(type="end")`, a final always-yielded snapshot is emitted
   (regardless of throttle), the record is written to SQLite history, status
   text shows "Сгенерировано N за Xс".

## Performance

- **Time to first preview:** typically 1-3 seconds (depends on the model's
  "thinking" speed — qwen3.5-35b-a3b spends time in reasoning before the first
  content token).
- **Updates per second:** capped at ~6-7 by the 150ms throttle.
- **PNG render time:** ~5-15ms per snapshot via resvg-py (no cairo dependency).

## Limitations

- Reasoning tokens are still rendered as part of the live preview. They appear
  as raw text until the model emits a real `<svg>` tag. Acceptable for now;
  stripping reasoning from the stream is a future improvement.
- `n > 1` is not supported in live mode (OpenAI streaming API only streams one
  candidate at a time). UI automatically uses `n=1` when Live is on.
- Network interruptions mid-stream result in a `gr.Error` and partial preview
  is discarded; the user must retry.

## Tests

- 34 tests in `tests/test_incremental_svg.py` (all passing)
- ~6 tests in `tests/test_lm_streaming.py` (all passing)
- 5+ tests in `tests/test_app.py` for live-UI behavior (all passing)
- **Total:** 183 passed, 1 skipped, 0 failed