diff --git a/scripts/livecoding_video_pipeline.py b/scripts/livecoding_video_pipeline.py
index 7c728df97c..b609a8cc06 100644
--- a/scripts/livecoding_video_pipeline.py
+++ b/scripts/livecoding_video_pipeline.py
@@ -767,7 +767,7 @@ def run_pipeline(
     playwright_url: str = "https://strudel.cc/",
     ffmpeg_loudnorm_lufs: float = -14.0,
     capture: bool = False,
-    capture_seconds: int = 30,
+    capture_seconds: Optional[int] = None,
     headless: bool = False,
     narration_engine: str = "template",
     narration_json_path: Optional[str] = None,
@@ -806,6 +806,11 @@ def run_pipeline(
     dicts segments), 'tts', 'browser_capture', 'visualizer',
     'final_mix', 'verdict'.
     """
+    # Defaut coherent : sans --capture-seconds explicite, la capture suit
+    # --duration (mesure c.1528 : le defaut fige 30 tronquait une demo
+    # de 180 s a 30,9 s avec 4/11 segments mixes).
+    capture_seconds = _resolve_capture_seconds(capture_seconds, duration_seconds)
+
     strudel = compose_strudel(
         style_name=style_name,
         duration_seconds=duration_seconds,
@@ -1229,6 +1234,43 @@ def mix_final_ffmpeg(
     return cmd
 
 
+def _resolve_capture_seconds(
+    capture_seconds: Optional[int], duration_seconds: int
+) -> int:
+    """Defaut coherent de la duree de capture (etape 4, #15604).
+
+    Sans valeur explicite, la capture suit ``duration_seconds`` : le
+    defaut fige 30 tronquait silencieusement une demo de 180 s a
+    30,9 s (mesure c.1528, 4/11 segments mixes). Une valeur explicite
+    (capture plus courte que la musique) reste respectee.
+    """
+    if capture_seconds is not None:
+        return capture_seconds
+    return duration_seconds
+
+
+def _click_play(page: object, url: str, attempts: int = 3) -> None:
+    """Clic play robuste : re-navigation entre tentatives (etape 4).
+
+    Mesure c.1528 : le clic play echoue par timeout ~1 run sur 3
+    (``Locator.click: Timeout 10000ms``) — etat de page variable au
+    chargement du hash strudel. Un re-chargement de l'URL de partage
+    recharge le REPL avec le pattern et suffit a retablir le clic.
+    La derniere tentative echouee remonte telle quelle (echec explicite,
+    pas de fallback silencieux). Orchestration pure : le verdict de
+    capture reste porte par le checksum canvas en aval.
+    """
+    for attempt in range(1, attempts + 1):
+        try:
+            page.get_by_role("button", name="play").first.click(timeout=10_000)
+            return
+        except Exception:
+            if attempt == attempts:
+                raise
+            page.goto(url)
+            page.wait_for_timeout(5000)
+
+
 def capture_repl_session(
     pattern: str,
     output_dir: Path,
@@ -1269,7 +1311,7 @@ def capture_repl_session(
         try:
             page.goto(url)
             page.wait_for_timeout(5000)
-            page.get_by_role("button", name="play").first.click(timeout=10_000)
+            _click_play(page, url)
             page.wait_for_timeout(int(warmup_seconds * 1000))
 
             h1 = page.evaluate(_CANVAS_CHECKSUM_JS)
@@ -1389,14 +1431,16 @@ def _build_arg_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--capture-seconds",
         type=int,
-        default=30,
-        help="duree de capture video en secondes (default: 30)",
+        default=None,
+        help="duree de capture video en secondes (default: suit --duration "
+             "— le defaut fige 30 tronquait la demo, mesure c.1528)",
     )
     parser.add_argument(
         "--headless",
         action="store_true",
-        help="lancer Chromium headless (DECONSEILLE : le canvas REPL ne "
-             "s'anime pas sans fenetre compositée — mesure c.580)",
+        help="lancer Chromium headless (mesure c.1528 : capture 180 s "
+             "verifiee headless, le checksum canvas en aval reste le "
+             "garde contre un canvas immobile — cf mesure c.580 anterieure)",
     )
     parser.add_argument(
         "--narration-engine",
diff --git a/scripts/tests/test_livecoding_video_pipeline.py b/scripts/tests/test_livecoding_video_pipeline.py
index 8ab44bde08..6784698f46 100644
--- a/scripts/tests/test_livecoding_video_pipeline.py
+++ b/scripts/tests/test_livecoding_video_pipeline.py
@@ -41,6 +41,9 @@
     STYLES,
     StrudelStyle,
     _load_env_files,
+    _build_arg_parser,
+    _click_play,
+    _resolve_capture_seconds,
     build_repl_url,
     compose_narration,
     compose_strudel,
@@ -1074,3 +1077,117 @@ def _probe_fail(media):
         fc = cmd[cmd.index("-filter_complex") + 1]
         assert "st=87.850" in fc  # 90.85 - 3.0
         assert cmd[cmd.index("-t") + 1] == "90.850"
+
+
+class TestResolveCaptureSeconds:
+    """Defaut coherent capture/duration (mesure c.1528 : demo 180 s
+    tronquee a 30,9 s, 4/11 segments mixes, sans drapeau explicite)."""
+
+    def test_none_suit_duration(self):
+        assert _resolve_capture_seconds(None, 180) == 180
+
+    def test_explicite_respecte(self):
+        """Une capture plus courte que la musique reste legale
+        (verification rapide, capture de test)."""
+        assert _resolve_capture_seconds(45, 180) == 45
+
+
+class TestCliCaptureSecondsDefault:
+    def test_parser_defaut_none(self):
+        """Le parser ne fixe plus 30 : None traverse jusqu'a la
+        resolution dans run_pipeline, la capture reste coherente avec
+        --duration (cycles, narration, mix)."""
+        args = _build_arg_parser().parse_args(["--duration", "90"])
+        assert args.capture_seconds is None
+        assert args.duration == 90
+
+    def test_run_pipeline_transmet_duration_a_la_capture(self, tmp_path, monkeypatch):
+        """Wiring : sans capture_seconds explicite, capture_repl_session
+        recoit duration_seconds."""
+        import scripts.livecoding_video_pipeline as pl
+
+        seen = {}
+
+        def _fake_capture(pattern, output_dir, capture_seconds, cycles, headless):
+            seen["capture_seconds"] = capture_seconds
+            return {
+                "video_webm": str(tmp_path / "capture.webm"),
+                "audio_wav": str(tmp_path / "capture.wav"),
+                "final_mp4": str(tmp_path / "capture_final.mp4"),
+                "video_bytes": 1,
+                "wav_bytes": 1,
+                "mp4_bytes": 1,
+                "cycles": cycles,
+            }
+
+        monkeypatch.setattr(pl, "capture_repl_session", _fake_capture)
+        pl.run_pipeline(
+            style_name="trance",
+            duration_seconds=90,
+            output_path=str(tmp_path / "out.mp4"),
+            capture=True,
+            headless=True,
+        )
+        assert seen["capture_seconds"] == 90
+
+
+class _FakePlayPage:
+    """Page fake minimale pour l'orchestration _click_play : le clic
+    echoue les ``fail_first`` premiers essais puis reussit. Precedent
+    _FakeClient (LLM) : on valide la SEQUENCE retry, pas un verdict de
+    capture — la capture reelle reste provee par l'execution documentee
+    dans le body de la PR."""
+
+    def __init__(self, fail_first: int = 0):
+        self.clicks = 0
+        self.gotos = 0
+        self.waits = 0
+        self.last_url = None
+        self._fail_first = fail_first
+        outer = self
+
+        class _First:
+            @staticmethod
+            def click(timeout=None):
+                outer.clicks += 1
+                if outer.clicks <= outer._fail_first:
+                    raise RuntimeError(f"Locator.click: Timeout {timeout}ms")
+
+        self._first = _First()
+
+    def get_by_role(self, role, name=None):
+        return SimpleNamespace(first=self._first)
+
+    def goto(self, url):
+        self.gotos += 1
+        self.last_url = url
+
+    def wait_for_timeout(self, ms):
+        self.waits += 1
+
+
+class TestClickPlayRetry:
+    """Retry du clic play (timeout flaky 1 run sur 3, mesure c.1528) :
+    re-navigation de l'URL de partage entre tentatives, echec explicite
+    au dernier essai."""
+
+    def test_succes_immediat_sans_reload(self):
+        page = _FakePlayPage(fail_first=0)
+        _click_play(page, "https://strudel.cc/#HASH")
+        assert page.clicks == 1
+        assert page.gotos == 0
+
+    def test_timeout_puis_succes_apres_reload(self):
+        page = _FakePlayPage(fail_first=1)
+        _click_play(page, "https://strudel.cc/#HASH")
+        assert page.clicks == 2
+        assert page.gotos == 1
+        assert page.last_url == "https://strudel.cc/#HASH"
+        assert page.waits == 1  # attente post-navigation avant le 2e essai
+
+    def test_epuise_leve_la_derniere_erreur(self):
+        page = _FakePlayPage(fail_first=99)
+        with pytest.raises(RuntimeError, match="Timeout 10000ms"):
+            _click_play(page, "https://strudel.cc/#HASH", attempts=3)
+        assert page.clicks == 3
+        assert page.gotos == 2