feat(short): la paleta de audio viva — GET /audio en el contrato, el prompt y el bucle de edición

shortsmith ya compone la banda sonora (sonar); ahora publica una paleta
(pulse, static) y este repo la consume en vivo: el prompt la ofrece con sus
notas de mood, validate_spec la usa como fuente de verdad para audio.preset,
y editar el preset en /short_spec es la manera gratis de escucharlas. Sin
/audio (404 o caída) todo cae a la paleta base y nada deja de renderizar.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -92,6 +92,13 @@ saves the edited spec as a new output, and renders. No LLM in that path: it is
 free. The session comes from the filename, so it works even if the chat has
 researched something else since.
 
+**Soundtrack:** every Short carries a synthesized score — shortsmith composes
+it deterministically, no samples, no licensing. The palette comes live from
+`GET /audio` (the audio half of what `GET /templates` does for shots): `sonar`
+for case files, `pulse` for debunks, `static` for document drops. The model
+picks one to match the narrative shape, and the cheapest way to audition them
+is the edit loop — change `audio.preset` in the spec file and re-send it.
+
 Full spec of the phase: `docs/shortsmith-phase2-spec.md`.
 
 ## YouTube (`/upload_short`)

docs/shortsmith-phases-4-6.md

@@ -34,26 +34,34 @@ the expected outcome (audio first), but the gate can reorder them.
 
 ## Phase 4 — sound
 
-The largest single lever. A silent Short is penalised de facto: retention is the
-algorithm's primary signal and silence invites the swipe at second one. Three deliverables,
-shipped in this order because each is useful without the next.
+> **Corrected after reading the shortsmith source** (the first draft of this section
+> assumed silent renders and proposed royalty-free tracks on disk — both wrong).
+> shortsmith has synthesized audio by design: numpy only, no samples, no licensing
+> exposure, deterministic to the sample, with the spec's `audio: {preset, silence}`
+> block and the validated `sonar` composition guarded by a reference gate. The right
+> 4a for that architecture is a wider palette of synthesized presets, not files.
 
-### 4a. Music bed + transition SFX
+### 4a. The preset palette — **shipped 2026-08-06**
 
-- shortsmith: new **optional** top-level spec block:
+- shortsmith: `pulse` (sub-bass heartbeat tightening past the midpoint — tension, for
+  debunks) and `static` (shortwave noise bed, seeded crackles, faint drone — document
+  drops) joined `sonar` and `none`. Same arc grammar (nothing starts inside a `silence`
+  window, closing swell, same limiter chain); `static`'s noise comes from seeded legacy
+  `RandomState` streams, which NEP 19 froze — deterministic on any numpy. `GET /audio`
+  publishes the palette with one-line mood notes.
+- researchowl: the client fetches the palette (404 → the baseline pair, fallback
+  convention), `validate_spec` takes it as the live source of truth for
+  `audio.preset`, and the prompt offers it with the mood notes so the model matches
+  preset to narrative shape. The edit loop accepts it too: changing `audio.preset` in
+  the `/short_spec` file and re-sending is the free way to audition the palette.
 
-  ```json
-  "audio": { "track": "static_dread", "volume_db": -14 }
-  ```
+### Deferred from 4a: shot-boundary transition accents
 
-  A small curated set of royalty-free tracks (3–5, matching the channel's tone) baked
-  into the shortsmith image as assets. Track names are advertised in the `GET /templates`
-  response (a new `audio.tracks` key) so the prompt can list them without hardcoding —
-  same reasoning as the template schemas. ffmpeg mixes at final assembly; a short whoosh
-  on each shot boundary comes free from the same mix.
-- researchowl: **zero code**. The prompt gains one line ("pick a track from: …",
-  fed from the contract fetch). Old specs without `audio` render silent, as today.
-- Determinism holds: same spec, same output.
+A synthesized whoosh at each cut. Deliberately not done yet: `audio.py`'s presets are
+fixed compositions that know nothing about the shots, and that one-way line is worth
+keeping until the palette itself proves its value. If it happens, it is an opt-in
+`Audio.transitions` flag with boundaries passed alongside `silence` — additive, and
+`sonar`'s reference gate must not notice.
 
 ### 4b. Narration (TTS) + burned-in captions
 
@@ -172,8 +180,8 @@ One change at a time, verified before the next — and phase-gated by the Analyt
 from §0.
 
 1. Publish 3–4 Shorts with the current pipeline. Read the retention curves.
-2. Phase 4a (music). Smallest change, immediate feel upgrade, proves the `audio` contract
-   extension end to end.
+2. ~~Phase 4a~~ — done (the preset palette, see above; the user chose to skip the gate
+   for the mechanism and let the published Shorts test the palette itself).
 3. Phase 4b (narration + captions), grounding extension in researchowl **first** — build
    the check before the thing it checks, same reasoning as phase 2 §12.
 4. Free-work templates whenever convenient; they ride along.

src/bot/bot.py

@@ -605,7 +605,8 @@ async def cmd_short_spec(update: Update, ctx: ContextTypes.DEFAULT_TYPE):
             filename=f"short_{session['id']}_spec.json",
             caption=f"🎬 Shot spec — {session['topic']}\n{created} UTC\n\n"
                     f"Edítalo y mándamelo de vuelta como fichero para "
-                    f"re-renderizar sin pagar otra generación.",
+                    f"re-renderizar sin pagar otra generación. La banda sonora "
+                    f"también: audio.preset acepta sonar, pulse o static.",
         )
     except Exception as e:
         logger.error("short_spec failed", error=str(e))

src/generator/short.py

@@ -28,7 +28,8 @@ from src.config import settings
 from src.db.database import OutputType, ResearchDB
 from src.generator.grounding import GroundingReport, check_grounding
 from src.generator.shortsmith import (
-    ShortsmithClient, ShortsmithError, ShortsmithRejected, ShortsmithUnavailable,
+    BASELINE_PRESETS, ShortsmithClient, ShortsmithError, ShortsmithRejected,
+    ShortsmithUnavailable,
 )
 from src.generator.shortspec import ShortSpecWriter, SpecWriteFailed
 from src.generator.spec_contract import SpecInvalid, editorial_notes, validate_spec
@@ -138,6 +139,15 @@ class ShortProducer:
         directory.mkdir(parents=True, exist_ok=True)
         return directory / f"{session_id}.mp4"
 
+    async def _presets(self) -> dict[str, str]:
+        """La paleta de audio, en vivo. Nunca tumba nada: sin ella se ofrece la
+        base y el Short sale con sonar, que es lo que salía siempre."""
+        try:
+            return await self.client.audio_presets()
+        except Exception as e:
+            logger.warning("GET /audio falló — paleta base", error=str(e))
+            return dict(BASELINE_PRESETS)
+
     # --- pipeline -----------------------------------------------------------
 
     async def produce(self, session_id: int,
@@ -171,15 +181,19 @@ class ShortProducer:
             logger.warning("Short sin URL de artículo — se sigue con el dominio pelado",
                            session_id=session_id)
 
-        # 2. El contrato, en vivo. Sin él no hay prompt que escribir.
+        # 2. El contrato, en vivo. Sin él no hay prompt que escribir. La paleta
+        #    de audio mejora el prompt pero no lo define: si /audio falla, se
+        #    ofrece la paleta base y el render sale igual.
         templates = await self.client.templates()
+        presets = await self._presets()
 
         # 3. El spec.
         started = time.monotonic()
         llm_call = self.llm_override or self._llm_call(session_id)
         writer = ShortSpecWriter(
             llm_call, templates,
-            refresh_templates=lambda: self.client.templates(refresh=True))
+            refresh_templates=lambda: self.client.templates(refresh=True),
+            presets=presets)
         try:
             written = await writer.write(
                 topic, context, article_url=result.article_url,
@@ -251,9 +265,12 @@ class ShortProducer:
         result = ShortResult(topic=topic, spec=spec)
 
         # 1. El contrato, en vivo — las mismas rutas verbatim que ve el modelo.
+        #    La paleta también: editar audio.preset a "pulse" es justo el tipo
+        #    de retoque para el que existe este camino.
         templates = await self.client.templates()
+        presets = await self._presets()
         try:
-            validate_spec(spec, templates)
+            validate_spec(spec, templates, presets=presets)
         except SpecInvalid as e:
             result.failure = ("El spec editado no pasa el contrato: "
                               + "; ".join(e.errors[:6]))

src/generator/shortsmith.py

@@ -42,10 +42,20 @@ __all__ = [
     "ShortsmithUnavailable",
     "ShortsmithRejected",
     "JobResult",
+    "BASELINE_PRESETS",
     "POLL_INTERVAL",
     "POLL_CEILING",
 ]
 
+#: La paleta que existía antes de que shortsmith publicara `GET /audio`. Es el
+#: fallback cuando el endpoint no está (404 = shortsmith anterior) o no se pudo
+#: consultar: la paleta mejora el spec, no lo define, y quedarse en sonar nunca
+#: rompe un render.
+BASELINE_PRESETS = {
+    "sonar": "low drone and sonar pings tightening toward the close",
+    "none": "digital silence",
+}
+
 
 class ShortsmithError(Exception):
     """Cualquier fallo hablando con shortsmith."""
@@ -86,6 +96,7 @@ class JobResult:
 #: petición cuando una validación falla, por si el renderizador se actualizó a
 #: mitad de una run.
 _templates_cache: dict[str, dict[str, Any]] = {}
+_presets_cache: dict[str, dict[str, str]] = {}
 
 
 class ShortsmithClient:
@@ -136,6 +147,37 @@ class ShortsmithClient:
         logger.info("shortsmith templates fetched", n=len(data))
         return data
 
+    async def audio_presets(self, refresh: bool = False) -> dict[str, str]:
+        """La paleta de audio: nombre de preset -> nota de una línea (`GET /audio`).
+
+        La mitad de audio del contrato vivo: shortsmith añade un preset y el
+        prompt lo ofrece sin tocar este repo. Un 404 es un shortsmith anterior
+        al endpoint y devuelve la paleta base, sin error — fallbacks siempre.
+        """
+        if not refresh and self.base_url in _presets_cache:
+            return _presets_cache[self.base_url]
+        try:
+            async with self._session(30) as sess:
+                async with sess.get(f"{self.base_url}/audio") as resp:
+                    if resp.status == 404:
+                        data = dict(BASELINE_PRESETS)
+                    elif resp.status != 200:
+                        body = await resp.text()
+                        raise ShortsmithError(
+                            f"GET /audio devolvió {resp.status}: {body[:200]}")
+                    else:
+                        payload = await resp.json()
+                        presets = payload.get("presets")
+                        data = (presets if isinstance(presets, dict) and presets
+                                else dict(BASELINE_PRESETS))
+        except aiohttp.ClientError as e:
+            raise ShortsmithUnavailable(f"shortsmith inalcanzable: {e}") from e
+        except asyncio.TimeoutError as e:
+            raise ShortsmithUnavailable("shortsmith no respondió a /audio") from e
+        _presets_cache[self.base_url] = data
+        logger.info("shortsmith audio presets fetched", presets=sorted(data))
+        return data
+
     async def render(self, spec: dict[str, Any]) -> str:
         """`POST /render`. Devuelve el job_id. 422 -> ShortsmithRejected."""
         try:

src/generator/shortspec.py

@@ -98,7 +98,9 @@ and your whole answer becomes unparseable. This is the single most common way \
 this task fails.
 - meta.id is a lowercase slug (letters, digits, - and _). meta.title is the \
 title a human reads, not a filename.
-- version is 1. Keep meta at 1080x1920 and audio preset "sonar".
+- version is 1. Keep meta at 1080x1920.
+- audio.preset — pick the one whose mood fits the shape you chose:
+{presets}
 - The closing shot carries the domain, uppercase, no protocol: {domain}
 
 # 4. Grounding — this is the part that matters
@@ -144,6 +146,14 @@ Return the JSON object now."""
 
 PALETTE_FALLBACK = "ink, amber, amber_dark, muted, dim, red"
 
+#: Si el caller no trae la paleta de audio, el prompt solo ofrece lo que
+#: cualquier shortsmith renderiza.
+PRESETS_FALLBACK = {"sonar": "low drone and sonar pings", "none": "digital silence"}
+
+
+def _describe_presets(presets: dict[str, str]) -> str:
+    return "\n".join(f'  "{name}" — {note}' for name, note in sorted(presets.items()))
+
 
 @dataclass
 class SpecResult:
@@ -305,12 +315,14 @@ LLMCall = Callable[[str, str], Awaitable[str]]
 
 class ShortSpecWriter:
     def __init__(self, llm_call: LLMCall, templates: dict[str, dict],
-                 refresh_templates: Optional[Callable[[], Awaitable[dict]]] = None):
+                 refresh_templates: Optional[Callable[[], Awaitable[dict]]] = None,
+                 presets: Optional[dict[str, str]] = None):
         self.llm_call = llm_call
         self.templates = templates
         #: Se vuelve a pedir el contrato si una validación falla: el
         #: renderizador puede haberse actualizado a mitad de la run.
         self.refresh_templates = refresh_templates
+        self.presets = presets or dict(PRESETS_FALLBACK)
 
     def build_prompt(self, topic: str, context: str, article_url: Optional[str],
                      domain: str) -> str:
@@ -322,6 +334,7 @@ class ShortSpecWriter:
             shapes=NARRATIVE_SHAPES,
             templates=describe_templates(self.templates),
             colors=_palette(self.templates),
+            presets=_describe_presets(self.presets),
             domain=domain,
             target_min=TARGET_MIN_DURATION,
             target_max=TARGET_MAX_DURATION,
@@ -359,7 +372,7 @@ class ShortSpecWriter:
 
             last_spec = spec
             try:
-                validate_spec(spec, self.templates)
+                validate_spec(spec, self.templates, presets=self.presets)
             except SpecInvalid as e:
                 history.append(e.errors)
                 feedback = _format_errors(e.errors)

src/generator/spec_contract.py

@@ -21,7 +21,7 @@ cubierto.
 from __future__ import annotations
 
 import re
-from typing import Any, Optional
+from typing import Any, Iterable, Optional
 
 __all__ = [
     "SpecInvalid",
@@ -183,14 +183,23 @@ def _check_meta(meta: Any) -> list[str]:
     return errors
 
 
-def _check_audio(audio: Any, total: float) -> list[str]:
+#: Los presets que existían antes de `GET /audio`. Solo es el default cuando el
+#: caller no pasa la paleta viva; con ella, un preset nuevo en shortsmith llega
+#: aquí sin tocar este repo — el mismo pacto que las plantillas.
+BASELINE_PRESET_NAMES = ("sonar", "none")
+
+
+def _check_audio(audio: Any, total: float,
+                 presets: Optional[Iterable[str]] = None) -> list[str]:
     if audio is None:
         return []
     if not isinstance(audio, dict):
         return ["audio: se esperaba un objeto"]
     errors = []
-    if audio.get("preset", "sonar") not in ("sonar", "none"):
-        errors.append(f"audio.preset: {audio.get('preset')!r} no es 'sonar' ni 'none'")
+    known = tuple(presets) if presets else BASELINE_PRESET_NAMES
+    if audio.get("preset", "sonar") not in known:
+        errors.append(f"audio.preset: {audio.get('preset')!r} no existe "
+                      f"(los presets son: {', '.join(sorted(known))})")
     silence = audio.get("silence", [])
     if not isinstance(silence, list):
         return errors + ["audio.silence: se esperaba una lista de pares [inicio, fin]"]
@@ -223,12 +232,16 @@ def _total_duration(spec: dict) -> float:
     return total
 
 
-def validate_spec(spec: Any, templates: dict[str, dict]) -> None:
+def validate_spec(spec: Any, templates: dict[str, dict],
+                  presets: Optional[Iterable[str]] = None) -> None:
     """Lanza `SpecInvalid` con TODAS las rutas que fallan.
 
     Se devuelven todos los errores de golpe a propósito: el bucle de reintento
     se los da al modelo verbatim y arreglar cinco de una vez sale más barato
     que cinco vueltas.
+
+    `presets` es la paleta viva de `GET /audio`; sin ella se valida contra la
+    paleta base, que nunca acepta nada que un shortsmith viejo no renderice.
     """
     errors: list[str] = []
     if not isinstance(spec, dict):
@@ -284,7 +297,7 @@ def validate_spec(spec: Any, templates: dict[str, dict]) -> None:
     if total > MAX_TOTAL_DURATION:
         errors.append(f"shots: la duración total ({total:.2f}s) pasa del límite "
                       f"de {MAX_TOTAL_DURATION}s")
-    errors.extend(_check_audio(spec.get("audio"), total))
+    errors.extend(_check_audio(spec.get("audio"), total, presets))
 
     if errors:
         raise SpecInvalid(errors)

tests/test_short_producer.py

@@ -59,6 +59,14 @@ class FakeProcessor:
         return self.chunks
 
 
+PRESETS = {
+    "sonar": "low drone — the case-file mood",
+    "pulse": "sub-bass heartbeat — debunks",
+    "static": "shortwave static — document drops",
+    "none": "digital silence",
+}
+
+
 class FakeClient:
     """shortsmith de mentira. `fail_at` decide dónde se rompe."""
 
@@ -73,6 +81,11 @@ class FakeClient:
             raise ShortsmithUnavailable("no hay nadie al otro lado")
         return TEMPLATES
 
+    async def audio_presets(self, refresh=False):
+        if self.fail_at == "audio":
+            raise ShortsmithUnavailable("sin /audio")
+        return dict(PRESETS)
+
     async def render(self, spec):
         if self.fail_at == "render":
             raise ShortsmithUnavailable("conexión rechazada")
@@ -450,3 +463,48 @@ async def test_rerender_respects_the_kill_switch(tmp_path, monkeypatch):
 
     with pytest.raises(ShortsDisabled):
         await p.rerender(153, json.loads(json.dumps(SPEC)))
+
+
+# --- la paleta de audio (GET /audio) ----------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_an_edited_preset_from_the_live_palette_renders(tmp_path, monkeypatch):
+    """El retoque para el que existe el bucle de edición: cambiar la banda
+    sonora a "pulse" sin pagar otra generación."""
+    edited = json.loads(json.dumps(SPEC))
+    edited["audio"] = {"preset": "pulse"}
+    client = FakeClient()
+    p = producer(tmp_path, monkeypatch, client=client, llm=_llm_prohibido)
+
+    result = await p.rerender(153, edited)
+
+    assert result.has_video
+    assert client.rendered["audio"]["preset"] == "pulse"
+
+
+@pytest.mark.asyncio
+async def test_a_preset_the_renderer_does_not_know_is_rejected_with_the_palette(
+        tmp_path, monkeypatch):
+    edited = json.loads(json.dumps(SPEC))
+    edited["audio"] = {"preset": "vaporwave"}
+    client = FakeClient()
+    p = producer(tmp_path, monkeypatch, client=client, llm=_llm_prohibido)
+
+    result = await p.rerender(153, edited)
+
+    assert not result.has_video
+    assert "audio.preset" in result.failure and "pulse" in result.failure
+    assert client.rendered is None
+
+
+@pytest.mark.asyncio
+async def test_a_dead_audio_endpoint_never_blocks_a_sonar_render(tmp_path, monkeypatch):
+    """La paleta mejora el prompt, no lo define: sin /audio se cae a la base y
+    un spec con sonar renderiza igual."""
+    p = producer(tmp_path, monkeypatch, client=FakeClient(fail_at="audio"),
+                 llm=_llm_prohibido)
+
+    result = await p.rerender(153, json.loads(json.dumps(SPEC)))
+
+    assert result.has_video

tests/test_shortsmith_client.py

@@ -10,8 +10,8 @@ from pathlib import Path
 import pytest
 
 from src.generator.shortsmith import (
-    JobResult, ShortsmithClient, ShortsmithError, ShortsmithRejected,
-    ShortsmithUnavailable, _templates_cache,
+    BASELINE_PRESETS, JobResult, ShortsmithClient, ShortsmithError,
+    ShortsmithRejected, ShortsmithUnavailable, _presets_cache, _templates_cache,
 )
 
 EXAMPLE = Path(__file__).resolve().parents[1] / "src/generator/examples/jal1628.json"
@@ -100,6 +100,30 @@ async def test_templates_cached_per_process():
     _templates_cache.clear()
 
 
+@pytest.mark.asyncio
+async def test_audio_presets_come_from_the_service():
+    _presets_cache.clear()
+    client = ShortsmithClient("http://fake:8080")
+    palette = {"sonar": "drone", "pulse": "heartbeat"}
+    session = patch_session(client, {"/audio": FakeResp(200, {"presets": palette})})
+
+    assert await client.audio_presets() == palette
+    await client.audio_presets()
+    assert len(session.calls) == 1, "la segunda llamada debe salir de la caché"
+    _presets_cache.clear()
+
+
+@pytest.mark.asyncio
+async def test_a_shortsmith_without_audio_endpoint_yields_the_baseline():
+    """404 = shortsmith anterior a la paleta. Fallback, no error."""
+    _presets_cache.clear()
+    client = ShortsmithClient("http://fake:8080")
+    patch_session(client, {"/audio": FakeResp(404, body="not found")})
+
+    assert await client.audio_presets() == BASELINE_PRESETS
+    _presets_cache.clear()
+
+
 @pytest.mark.asyncio
 async def test_render_returns_job_id(spec):
     client = ShortsmithClient("http://fake:8080")

tests/test_shortspec.py

@@ -118,6 +118,23 @@ def test_prompt_says_out_loud_that_there_is_no_article_yet():
     assert "No article URL yet" in w.build_prompt("X", "m", None, "X.TEST")
 
 
+def test_prompt_offers_the_live_audio_palette():
+    """La mitad de audio del contrato vivo: los presets y sus notas de mood
+    vienen de GET /audio, no de este repo."""
+    palette = {"sonar": "the case-file mood", "pulse": "tension, built for debunks"}
+    w, _ = writer("{}", presets=palette)
+    prompt = w.build_prompt("X", "m", None, "X.TEST")
+    assert '"pulse" — tension, built for debunks' in prompt
+    assert "whose mood fits the shape" in prompt
+
+
+def test_prompt_without_a_palette_only_offers_the_baseline():
+    w, _ = writer("{}")
+    prompt = w.build_prompt("X", "m", None, "X.TEST")
+    assert '"sonar"' in prompt and '"none"' in prompt
+    assert '"pulse"' not in prompt
+
+
 # --- bucle ------------------------------------------------------------------
 
 @pytest.mark.asyncio

tests/test_spec_contract.py

@@ -184,6 +184,31 @@ def test_silence_window_cannot_run_past_the_end():
     assert any("se sale de la duración total" in e for e in errors_of(bad))
 
 
+def test_the_live_palette_widens_what_a_preset_may_be():
+    """Con la paleta de GET /audio, un preset nuevo en shortsmith llega aquí
+    sin tocar este repo — el mismo pacto que las plantillas."""
+    doc = spec_with(shot(duration=25.0))
+    doc["audio"] = {"preset": "pulse"}
+    validate_spec(doc, TEMPLATES, presets=("sonar", "pulse", "static", "none"))
+
+
+def test_without_the_palette_only_the_baseline_presets_pass():
+    """El default es conservador a propósito: nunca acepta lo que un shortsmith
+    viejo no renderice."""
+    doc = spec_with(shot(duration=25.0))
+    doc["audio"] = {"preset": "pulse"}
+    assert any("audio.preset" in e for e in errors_of(doc))
+
+
+def test_an_unknown_preset_error_names_the_palette():
+    doc = spec_with(shot(duration=25.0))
+    doc["audio"] = {"preset": "vaporwave"}
+    with pytest.raises(SpecInvalid) as exc:
+        validate_spec(doc, TEMPLATES, presets=("sonar", "pulse", "none"))
+    line = next(e for e in exc.value.errors if "audio.preset" in e)
+    assert "pulse" in line and "vaporwave" in line
+
+
 def test_extra_root_key_is_rejected():
     bad = spec_with(shot(duration=25.0)); bad["narrative_shape"] = "case_file"
     assert any(e.startswith("narrative_shape:") for e in errors_of(bad))