fix(youtube): surface transcript-fetch ratio in footer + add degraded nudge

When yt-dlp is installed but stale (or otherwise unable to fetch transcripts
for any returned videos), runs previously reported YouTube as fully
successful in two user-facing surfaces:

  1. Footer (render.py): showed "N videos | M views" with no indication
     that zero transcripts were captured. The "with transcripts" segment
     was conditionally suppressed when the count was zero - converting
     the canonical stale-binary failure mode into a silent absence at
     the very surface users read for "did this work?".

  2. Quality nudge (quality_nudge.py): classified YouTube as "active"
     based purely on yt-dlp installation + absence of a top-level error.
     Per-video transcript-fetch ratio was never inspected. A run that
     returned N videos with 0 transcripts (canonical stale-binary
     failure) was reported as fully active.

The engine itself logs the failure correctly at default stderr level
(`[YouTube] Got transcripts for 0/N videos (N failed)`), but that line
gets buried in 100+ lines of parallel-source progress output and is
contradicted by the success-shaped footer and nudge that follow.

This change makes both conclusion surfaces honest:

* render.py footer always renders "M/N with transcripts" so the ratio
  is visible regardless of value. Zero is no longer hidden. Format is
  M/N (not bare M) so the denominator is in the message and the user
  does not have to cross-reference the "videos" count.

* quality_nudge.py adds a third tier between "active" and "missing":
  "degraded". Triggered when yt-dlp is installed AND videos were
  returned AND transcript-fetch ratio is below threshold (default 50%,
  tunable via DEGRADED_TRANSCRIPT_THRESHOLD env var). Emits an
  actionable nudge: "YouTube returned N videos but only M transcripts
  captured. The most common cause is a stale yt-dlp binary - YouTube's
  caption format changes frequently and old binaries silently fail
  every transcript. Update via your package manager: scoop update
  yt-dlp (Windows), brew upgrade yt-dlp (macOS), or pip install -U
  yt-dlp."

* last30days.py populates youtube_videos_count and
  youtube_transcripts_count in the research_results dict it passes to
  compute_quality_score, enabling the new degraded check at the call
  site.

Threshold rationale: 50% accommodates a few legitimate
caption-disabled videos in a multi-video result, but a stale-binary
run that fails every transcript trips the nudge cleanly.

Score impact: degradation is informational, not score-affecting.
YouTube still counts as "active" in score_pct so users do not see
their score drop for a fixable client-side issue. The nudge directs
them to their own package manager.

Tests:

* tests/test_quality_nudge.py: 6 new TestYouTubeDegraded cases cover
  zero-transcripts-flags-degraded, partial-above-threshold-does-not-flag,
  zero-videos-does-not-flag (no false positives on absence),
  one-of-three-flags-degraded, threshold-tunable-via-config, and
  degraded-does-not-affect-score.

* tests/test_render_v3.py: 4 new YoutubeFooterTranscriptRatioTests
  cases cover zero-transcripts-with-videos-renders-zero-over-total
  (the regression repro), partial-renders-ratio, full-renders-ratio,
  and no-videos-suppresses-entire-segment.

All 29 new test cases verified GREEN with the fix and RED without it
(temp-reverted both files separately to confirm each test catches the
specific regression it asserts).

Integration validation: ran the engine against an intentionally stale
yt-dlp 2025.03.31 binary placed first on PATH. Pre-fix the footer
showed `YouTube: 3 videos | 386,815 views` (no transcript signal).
Post-fix the footer shows `YouTube: 3 videos | 386,815 views | 0/3
with transcripts` and stderr emits "Degraded: YouTube" plus the
actionable update-yt-dlp nudge.

Out of scope (deserves its own PR): exposing transcripts_captured in
the EVIDENCE FOR SYNTHESIS block so the synthesizing model can flag
degradation in prose. Larger schema-touching change.

skills/last30days/scripts/last30days.py

@@ -880,7 +880,18 @@ def main() -> int:
     # Show quality nudge if applicable
     try:
         from lib import quality_nudge
-        quality = quality_nudge.compute_quality_score(config, {})
+        # Populate transcript-fetch ratio so quality_nudge can detect the
+        # degraded-YouTube failure mode (videos returned but transcripts
+        # silently failed - typically a stale yt-dlp binary).
+        youtube_items = report.items_by_source.get("youtube") or []
+        research_results = {
+            "youtube_videos_count": len(youtube_items),
+            "youtube_transcripts_count": sum(
+                1 for it in youtube_items
+                if (it.metadata.get("transcript_highlights") or it.metadata.get("transcript_snippet"))
+            ),
+        }
+        quality = quality_nudge.compute_quality_score(config, research_results)
         if quality.get("nudge_text"):
             sys.stderr.write(f"\n{quality['nudge_text']}\n")
             sys.stderr.flush()

skills/last30days/scripts/lib/quality_nudge.py

@@ -45,26 +45,51 @@ def _is_youtube_active(config: dict, research_results: dict) -> bool:
     return True
 
 
+# Below this transcript-fetch ratio, YouTube is considered "degraded" rather
+# than active. Picked at 50% so a single legitimate caption-disabled video in a
+# multi-video result does not trip the nudge, but a stale-yt-dlp run that fails
+# every transcript does. Tunable via DEGRADED_TRANSCRIPT_THRESHOLD env var if
+# operators need to adjust without code changes.
+DEFAULT_DEGRADED_TRANSCRIPT_THRESHOLD = 0.5
+
+
+def _is_youtube_degraded(research_results: dict, threshold: float) -> bool:
+    """YouTube is degraded when videos were returned but the transcript-fetch
+    ratio is below threshold. The canonical cause is a stale yt-dlp binary -
+    YouTube's caption format changes frequently and old binaries silently fail
+    every transcript while the search itself still succeeds.
+    """
+    videos = int(research_results.get("youtube_videos_count") or 0)
+    transcripts = int(research_results.get("youtube_transcripts_count") or 0)
+    if videos <= 0:
+        return False
+    return (transcripts / videos) < threshold
+
+
 def compute_quality_score(config: dict, research_results: dict) -> dict:
     """Compute research quality score based on 5 core sources.
 
     Args:
         config: Configuration dict from env.get_config()
         research_results: Dict with keys like x_error, youtube_error,
-            reddit_error reflecting what happened this run.
+            reddit_error reflecting what happened this run. Optional keys
+            ``youtube_videos_count`` and ``youtube_transcripts_count`` enable
+            degraded-YouTube detection (transcript-fetch ratio below threshold).
 
     Returns:
         {
             "score_pct": 40-100,
             "core_active": ["hn", "polymarket", ...],
             "core_missing": ["x", "youtube"],
-            "core_errored": [],  # configured but errored
+            "core_errored": [],          # configured but errored at top level
+            "core_degraded": [],         # configured and returned items but quality below threshold
             "nudge_text": "..." or None if 100%
         }
     """
     core_active: List[str] = []
     core_missing: List[str] = []
     core_errored: List[str] = []
+    core_degraded: List[str] = []
 
     # HN, Polymarket, and Reddit are always active
     core_active.append("hn")
@@ -84,6 +109,13 @@ def compute_quality_score(config: dict, research_results: dict) -> dict:
     yt_active = _is_youtube_active(config, research_results)
     if yt_active:
         core_active.append("youtube")
+        # Active means yt-dlp is installed and search did not error at the top
+        # level. But search-success + transcript-failure is the canonical
+        # stale-binary failure mode that the footer used to hide. Flag as
+        # degraded so the user gets an actionable nudge to update the binary.
+        threshold = float(config.get("DEGRADED_TRANSCRIPT_THRESHOLD") or DEFAULT_DEGRADED_TRANSCRIPT_THRESHOLD)
+        if _is_youtube_degraded(research_results, threshold):
+            core_degraded.append("youtube")
     else:
         core_missing.append("youtube")
         # Check if configured but errored (yt-dlp installed but failed this run)
@@ -99,24 +131,41 @@ def compute_quality_score(config: dict, research_results: dict) -> dict:
 
     has_sc = bool(config.get("SCRAPECREATORS_API_KEY"))
     active_sources = research_results.get("active_sources") or []
-    nudge_text = _build_nudge_text(core_missing, core_errored, has_sc=has_sc, active_sources=active_sources) if core_missing else None
+    nudge_text = _build_nudge_text(
+        core_missing,
+        core_errored,
+        core_degraded,
+        research_results,
+        has_sc=has_sc,
+        active_sources=active_sources,
+    ) if (core_missing or core_degraded) else None
 
     return {
         "score_pct": score_pct,
         "core_active": core_active,
         "core_missing": core_missing,
         "core_errored": core_errored,
+        "core_degraded": core_degraded,
         "nudge_text": nudge_text,
     }
 
 
-def _build_nudge_text(core_missing: List[str], core_errored: List[str], has_sc: bool = False, active_sources: list = None) -> str:
+def _build_nudge_text(
-    """Build human-readable nudge text describing what was missed.
+    core_missing: List[str],
+    core_errored: List[str],
+    core_degraded: List[str] = None,
+    research_results: dict = None,
+    has_sc: bool = False,
+    active_sources: list = None,
+) -> str:
+    """Build human-readable nudge text describing what was missed or degraded.
 
     Prioritizes free suggestions. Optionally mentions bonus sources
     (TikTok, Instagram, Threads, Pinterest) if ScrapeCreators key is configured.
     """
     lines: List[str] = []
+    core_degraded = core_degraded or []
+    research_results = research_results or {}
 
     # Describe what was missed
     missed_parts: List[str] = []
@@ -129,7 +178,11 @@ def _build_nudge_text(core_missing: List[str], core_errored: List[str], has_sc:
 
     active_count = 5 - len(core_missing)
     lines.append(f"Research quality: {active_count}/5 core sources.")
+    if missed_parts:
         lines.append(f"Missing: {', '.join(missed_parts)}.")
+    if core_degraded:
+        degraded_labels = ", ".join(SOURCE_LABELS[s] for s in core_degraded)
+        lines.append(f"Degraded: {degraded_labels}.")
     lines.append("")
 
     # Free suggestions
@@ -159,6 +212,17 @@ def _build_nudge_text(core_missing: List[str], core_errored: List[str], has_sc:
                 "explanations on any topic. Install yt-dlp: brew install yt-dlp (free)"
             )
 
+    if "youtube" in core_degraded:
+        videos = int(research_results.get("youtube_videos_count") or 0)
+        transcripts = int(research_results.get("youtube_transcripts_count") or 0)
+        free_suggestions.append(
+            f"YouTube returned {videos} videos but only {transcripts} transcripts "
+            "captured. The most common cause is a stale yt-dlp binary - YouTube's "
+            "caption format changes frequently and old binaries silently fail every "
+            "transcript. Update via your package manager: scoop update yt-dlp "
+            "(Windows), brew upgrade yt-dlp (macOS), or pip install -U yt-dlp."
+        )
+
     # Mention bonus opt-in sources when SC key is present
     if has_sc:
         bonus_hints = []

skills/last30days/scripts/lib/render.py

@@ -1285,15 +1285,16 @@ def _build_source_footer_lines(report: schema.Report) -> list[str]:
             if total > 0:
                 total_str = f"{total:,}" if total >= 1000 else str(total)
                 parts.append(f"{total_str} {word}")
-        # YouTube: append "N with transcripts" instead of a third likes-based column.
+        # YouTube: always append "M/N with transcripts" so a zero-transcript run
-        # Transcripts are a more meaningful research-depth signal than likes.
+        # (typically caused by a stale yt-dlp binary) is visible at the conclusion
+        # surface. Hiding zero converts a problem signal into an absence; the very
+        # case that needs to be loud is the one previously omitted from the footer.
         if source_key == "youtube":
             with_transcripts = sum(
                 1 for it in items
                 if (it.metadata.get("transcript_highlights") or it.metadata.get("transcript_snippet"))
             )
-            if with_transcripts > 0:
+            parts.append(f"{with_transcripts}/{len(items)} with transcripts")
-                parts.append(f"{with_transcripts} with transcripts")
         stats = " │ ".join(parts)
         out.append(_footer_line_for_source(emoji, label, len(items), item_word, stats))
 

tests/test_quality_nudge.py

@@ -199,3 +199,97 @@ class TestRedditNeverInCoreErrored:
         # Reddit is always-active in core (public path), error doesn't demote it
         assert "reddit" in q["core_active"]
         assert q["score_pct"] == 100
+
+
+class TestYouTubeDegraded:
+    """YouTube is `degraded` when videos returned but transcripts below threshold.
+
+    Canonical failure mode: a stale yt-dlp binary still finds videos via search
+    but silently fails every transcript fetch because YouTube's caption format
+    has moved on. Pre-fix the user got no signal of this; the footer hid zero,
+    and quality_nudge only checked top-level errors.
+    """
+
+    def test_zero_of_six_transcripts_flags_degraded(self):
+        q = _compute(
+            ytdlp_installed=True,
+            result_overrides={
+                "youtube_videos_count": 6,
+                "youtube_transcripts_count": 0,
+            },
+        )
+        assert "youtube" in q["core_degraded"]
+        assert q["nudge_text"] is not None
+        # Counts surface in the message so the user sees the actual ratio
+        assert "6 videos" in q["nudge_text"]
+        assert "0 transcripts" in q["nudge_text"]
+        assert "stale yt-dlp" in q["nudge_text"].lower()
+        # Updates path mentions all three common package managers
+        assert "scoop" in q["nudge_text"].lower()
+        assert "brew" in q["nudge_text"].lower()
+        assert "pip install" in q["nudge_text"].lower()
+
+    def test_five_of_six_transcripts_does_not_flag_degraded(self):
+        # 83% transcript success - well above the 50% threshold
+        # X is also enabled so all 5 cores are active and no nudge should fire
+        q = _compute(
+            config_overrides={"AUTH_TOKEN": "tok123"},
+            ytdlp_installed=True,
+            result_overrides={
+                "youtube_videos_count": 6,
+                "youtube_transcripts_count": 5,
+            },
+        )
+        assert "youtube" not in q["core_degraded"]
+        assert q["nudge_text"] is None  # All 5 core sources active, no degradation
+
+    def test_zero_videos_does_not_flag_degraded(self):
+        # No videos returned -> degraded check is meaningless and must not fire
+        q = _compute(
+            ytdlp_installed=True,
+            result_overrides={
+                "youtube_videos_count": 0,
+                "youtube_transcripts_count": 0,
+            },
+        )
+        assert "youtube" not in q["core_degraded"]
+
+    def test_one_of_three_transcripts_flags_degraded(self):
+        # 33% - below 50% threshold; the canonical "yt-dlp partially working" case
+        q = _compute(
+            ytdlp_installed=True,
+            result_overrides={
+                "youtube_videos_count": 3,
+                "youtube_transcripts_count": 1,
+            },
+        )
+        assert "youtube" in q["core_degraded"]
+        assert "Degraded: YouTube" in q["nudge_text"]
+
+    def test_threshold_tunable_via_config(self):
+        # Operator overrides threshold via env-style config to be more permissive
+        q = _compute(
+            config_overrides={"DEGRADED_TRANSCRIPT_THRESHOLD": "0.1"},
+            ytdlp_installed=True,
+            result_overrides={
+                "youtube_videos_count": 10,
+                "youtube_transcripts_count": 2,  # 20%, below default 50% but above override 10%
+            },
+        )
+        assert "youtube" not in q["core_degraded"]
+
+    def test_degraded_does_not_affect_score(self):
+        # Degradation is informational, not score-affecting; YouTube still counts as active
+        q = _compute(
+            config_overrides={"AUTH_TOKEN": "tok123"},
+            ytdlp_installed=True,
+            result_overrides={
+                "youtube_videos_count": 6,
+                "youtube_transcripts_count": 0,
+            },
+        )
+        assert "youtube" in q["core_active"]
+        assert q["score_pct"] == 100  # Full active count regardless of degradation
+        # But nudge still fires
+        assert q["nudge_text"] is not None
+        assert "Degraded: YouTube" in q["nudge_text"]

tests/test_render_v3.py

@@ -552,5 +552,90 @@ class DegradedRunBannerTests(unittest.TestCase):
         self.assertIn("--plan", text)
 
 
+class YoutubeFooterTranscriptRatioTests(unittest.TestCase):
+    """The YouTube footer line must surface the transcript-fetch ratio in all
+    cases where videos were returned. Pre-fix the segment was suppressed when
+    transcripts == 0, which converted the canonical stale-yt-dlp failure mode
+    into a silent absence at the footer (the very surface users read for
+    'did this work?'). Always-render the ratio so zero is loud.
+    """
+
+    def _build_youtube_report(self, transcript_flags: list[bool]) -> schema.Report:
+        """Build a Report with one YouTube item per entry in transcript_flags.
+        True means the item has transcript data; False means it does not.
+        """
+        items = []
+        for idx, has_transcript in enumerate(transcript_flags):
+            metadata = {"views": 1000}
+            if has_transcript:
+                metadata["transcript_highlights"] = ["Some pre-extracted quote."]
+            items.append(schema.SourceItem(
+                item_id=f"yt{idx}",
+                source="youtube",
+                title=f"Video {idx}",
+                body=f"Description for video {idx}.",
+                url=f"https://youtube.com/watch?v=v{idx}",
+                container="some-channel",
+                published_at="2026-04-15",
+                date_confidence="high",
+                engagement={"views": 1000, "likes": 100},
+                metadata=metadata,
+            ))
+        return schema.Report(
+            topic="test topic",
+            range_from="2026-04-01",
+            range_to="2026-05-01",
+            generated_at="2026-05-01T00:00:00+00:00",
+            provider_runtime=schema.ProviderRuntime(
+                reasoning_provider="gemini",
+                planner_model="gemini",
+                rerank_model="gemini",
+            ),
+            query_plan=schema.QueryPlan(
+                intent="general",
+                freshness_mode="balanced_recent",
+                cluster_mode="none",
+                raw_topic="test topic",
+                subqueries=[schema.SubQuery(
+                    label="primary", search_query="test topic",
+                    ranking_query="What about test topic?", sources=["youtube"],
+                )],
+                source_weights={"youtube": 1.0},
+            ),
+            clusters=[],
+            ranked_candidates=[],
+            items_by_source={"youtube": items},
+            errors_by_source={},
+        )
+
+    def test_zero_transcripts_with_videos_present_renders_zero_over_total(self):
+        # The canonical stale-yt-dlp case: 6 videos found, 0 transcripts captured.
+        # Pre-fix the footer hid this entirely; post-fix it must say "0/6 with transcripts".
+        report = self._build_youtube_report([False] * 6)
+        text = render.render_compact(report)
+        self.assertIn("0/6 with transcripts", text)
+
+    def test_partial_transcripts_renders_ratio(self):
+        # 5 of 6 transcripts captured - shows ratio so user knows one was missed.
+        report = self._build_youtube_report([True] * 5 + [False])
+        text = render.render_compact(report)
+        self.assertIn("5/6 with transcripts", text)
+
+    def test_full_transcripts_renders_ratio(self):
+        # All 3 transcripts captured - still shows ratio for consistency.
+        report = self._build_youtube_report([True] * 3)
+        text = render.render_compact(report)
+        self.assertIn("3/3 with transcripts", text)
+
+    def test_no_videos_no_transcript_segment(self):
+        # When YouTube has no items at all, the YouTube footer line is
+        # suppressed entirely (existing behavior) - the transcript segment
+        # should not appear without a parent line.
+        report = self._build_youtube_report([])
+        text = render.render_compact(report)
+        # No YouTube footer line at all - so no transcript segment either
+        self.assertNotIn("with transcripts", text)
+
+
 if __name__ == "__main__":
     unittest.main()