diff --git a/packages/producer/src/services/render/observability.ts b/packages/producer/src/services/render/observability.ts
index 5c7757d8f..24239e96f 100644
--- a/packages/producer/src/services/render/observability.ts
+++ b/packages/producer/src/services/render/observability.ts
@@ -109,6 +109,28 @@ export interface RenderExtractionObservability {
   vfrPreflightCount?: number;
   cacheHits?: number;
   cacheMisses?: number;
+  /**
+   * Per-clip captured-vs-expected-frame gauges. Emitted by the parity gate
+   * at extract finalization (see `videoFrameCoverage.ts`). Undefined when
+   * the render has no source videos to cover.
+   *
+   * • `minVideoFrameCoverageRatio` — worst clip's `captured / expected`
+   *   ratio (0 when a clip was never extracted; a strong "later-injected
+   *   clip silently dropped" signal per field ts=1784139267).
+   * • `coverageShortfallClipCount` — clips whose ratio fell below the
+   *   configured threshold (`HF_VIDEO_COVERAGE_THRESHOLD`, default 0.95).
+   *   Non-zero only ever accompanies a `VideoFrameCoverageError` throw.
+   */
+  minVideoFrameCoverageRatio?: number;
+  coverageShortfallClipCount?: number;
+  /**
+   * Count of authored `[data-start]` clip windows in the compiled HTML —
+   * a coarse proxy for the ts=1784144554 field signal shape (147-clip
+   * composition, 130 word-level caption divs authored-clip-count-scaled
+   * failure). Static scan; dynamic script-inserted timed clips land in
+   * the probe-stage's `hasRuntimeInsertedMedia` path (PR #2474).
+   */
+  authoredTimedClipCount?: number;
 }
 
 export interface RenderInitObservability {
diff --git a/packages/producer/src/services/render/videoFrameCoverage.test.ts b/packages/producer/src/services/render/videoFrameCoverage.test.ts
new file mode 100644
index 000000000..d281eb61d
--- /dev/null
+++ b/packages/producer/src/services/render/videoFrameCoverage.test.ts
@@ -0,0 +1,301 @@
+import type { ExtractedFrames, VideoElement, VideoMetadata } from "@hyperframes/engine";
+import { describe, expect, it } from "vitest";
+import {
+  assertVideoFrameCoverage,
+  computeVideoFrameCoverage,
+  countAuthoredTimedClips,
+  expectedFramesForClip,
+  isVideoFrameCoverageError,
+  resolveVideoCoverageThreshold,
+  VideoFrameCoverageError,
+} from "./videoFrameCoverage.js";
+
+function makeVideo(overrides: Partial<VideoElement> & { id: string }): VideoElement {
+  return {
+    id: overrides.id,
+    src: overrides.src ?? `${overrides.id}.mp4`,
+    start: overrides.start ?? 0,
+    end: overrides.end ?? 1,
+    mediaStart: overrides.mediaStart ?? 0,
+    loop: overrides.loop ?? false,
+    hasAudio: overrides.hasAudio ?? false,
+  };
+}
+
+function makeExtracted(videoId: string, delivered: number, fps = 30): ExtractedFrames {
+  const framePaths = new Map<number, string>();
+  for (let i = 0; i < delivered; i += 1) framePaths.set(i, `/tmp/${videoId}/${i}.jpg`);
+  const metadata: VideoMetadata = {
+    durationSeconds: delivered / fps,
+    videoStreamDurationSeconds: delivered / fps,
+    width: 1280,
+    height: 720,
+    fps,
+    videoCodec: "h264",
+    hasAudio: false,
+    isVFR: false,
+    hasAlpha: false,
+    colorSpace: null,
+  };
+  return {
+    videoId,
+    srcPath: `/tmp/${videoId}.mp4`,
+    outputDir: `/tmp/${videoId}`,
+    framePattern: `${videoId}-%06d.jpg`,
+    fps,
+    totalFrames: delivered,
+    metadata,
+    framePaths,
+  };
+}
+
+describe("expectedFramesForClip", () => {
+  it("returns 0 for invalid inputs", () => {
+    expect(expectedFramesForClip(Number.NaN, 1, 30)).toBe(0);
+    expect(expectedFramesForClip(0, 1, 0)).toBe(0);
+    expect(expectedFramesForClip(0, 1, -1)).toBe(0);
+    expect(expectedFramesForClip(2, 1, 30)).toBe(0); // negative window collapses to 0
+  });
+
+  it("ceils fractional-fps windows so a 29.97fps 1s clip demands 30 frames", () => {
+    expect(expectedFramesForClip(0, 1, 29.97)).toBe(30);
+    expect(expectedFramesForClip(0, 5, 30)).toBe(150);
+  });
+});
+
+describe("resolveVideoCoverageThreshold", () => {
+  it("defaults to 0.95 when env is unset or non-numeric", () => {
+    expect(resolveVideoCoverageThreshold(undefined)).toBe(0.95);
+    expect(resolveVideoCoverageThreshold("garbage")).toBe(0.95);
+  });
+
+  it("returns null when env is 0 or negative — gate disabled", () => {
+    expect(resolveVideoCoverageThreshold("0")).toBeNull();
+    expect(resolveVideoCoverageThreshold("-1")).toBeNull();
+  });
+
+  it("clamps values above 1 to 1", () => {
+    expect(resolveVideoCoverageThreshold("2")).toBe(1);
+  });
+
+  it("passes through in-range values", () => {
+    expect(resolveVideoCoverageThreshold("0.8")).toBe(0.8);
+    expect(resolveVideoCoverageThreshold("0.99")).toBe(0.99);
+    expect(resolveVideoCoverageThreshold("1")).toBe(1);
+  });
+});
+
+describe("computeVideoFrameCoverage", () => {
+  it("reports 1.0 ratio when every video delivered its authored window", () => {
+    const videos = [
+      makeVideo({ id: "a", start: 0, end: 1 }),
+      makeVideo({ id: "b", start: 1, end: 3 }),
+    ];
+    const extracted = [makeExtracted("a", 30), makeExtracted("b", 60)];
+    const reports = computeVideoFrameCoverage(videos, extracted, 30);
+    expect(reports).toHaveLength(2);
+    expect(reports[0]).toMatchObject({
+      videoId: "a",
+      expectedFrames: 30,
+      capturedFrames: 30,
+      ratio: 1,
+    });
+    expect(reports[1]).toMatchObject({
+      videoId: "b",
+      expectedFrames: 60,
+      capturedFrames: 60,
+      ratio: 1,
+    });
+  });
+
+  it("reports 0 capturedFrames when a video was never extracted (injection failure)", () => {
+    // Field signal ts=1784139267: later-injected video clips silently drop
+    // out of the extractor under injection-count saturation.
+    const videos = [makeVideo({ id: "later-injection", start: 0, end: 5 })];
+    const reports = computeVideoFrameCoverage(videos, [], 30);
+    expect(reports).toHaveLength(1);
+    expect(reports[0]).toMatchObject({
+      videoId: "later-injection",
+      expectedFrames: 150,
+      capturedFrames: 0,
+      ratio: 0,
+    });
+  });
+
+  it("uses delivered framePaths.size, not the possibly-stale totalFrames field", () => {
+    const videos = [makeVideo({ id: "a", start: 0, end: 1 })];
+    // Simulate an extractor whose totalFrames reports 30 but only 5 frames
+    // landed in framePaths (mid-extraction crash, partial cache read, …).
+    const partial = makeExtracted("a", 5);
+    partial.totalFrames = 30;
+    const reports = computeVideoFrameCoverage(videos, [partial], 30);
+    expect(reports[0]!.capturedFrames).toBe(5);
+    expect(reports[0]!.ratio).toBeCloseTo(5 / 30, 5);
+  });
+});
+
+describe("assertVideoFrameCoverage", () => {
+  it("does not throw when every clip has full frames", () => {
+    const reports = [
+      { videoId: "a", clipStart: 0, clipEnd: 1, expectedFrames: 30, capturedFrames: 30, ratio: 1 },
+      { videoId: "b", clipStart: 1, clipEnd: 2, expectedFrames: 30, capturedFrames: 30, ratio: 1 },
+    ];
+    expect(() => assertVideoFrameCoverage(reports, 0.95)).not.toThrow();
+  });
+
+  it("fails loudly with VideoFrameCoverageError when any clip has zero frames", () => {
+    const reports = [
+      {
+        videoId: "good",
+        clipStart: 0,
+        clipEnd: 1,
+        expectedFrames: 30,
+        capturedFrames: 30,
+        ratio: 1,
+      },
+      {
+        videoId: "blank",
+        clipStart: 5,
+        clipEnd: 10,
+        expectedFrames: 150,
+        capturedFrames: 0,
+        ratio: 0,
+      },
+    ];
+    let caught: unknown = null;
+    try {
+      assertVideoFrameCoverage(reports, 0.95);
+    } catch (err) {
+      caught = err;
+    }
+    expect(caught).toBeInstanceOf(VideoFrameCoverageError);
+    expect(isVideoFrameCoverageError(caught)).toBe(true);
+    const err = caught as VideoFrameCoverageError;
+    expect(err.worst.videoId).toBe("blank");
+    expect(err.threshold).toBe(0.95);
+    expect(err.message).toContain("blank");
+    expect(err.message).toContain("check/snapshot");
+    expect(err.message).toContain("HF_VIDEO_COVERAGE_THRESHOLD=0");
+  });
+
+  it("fails loudly when a clip is below the threshold (partial coverage)", () => {
+    // 80% coverage: 24/30 — below the 0.95 default, above zero.
+    const reports = [
+      {
+        videoId: "partial",
+        clipStart: 0,
+        clipEnd: 1,
+        expectedFrames: 30,
+        capturedFrames: 24,
+        ratio: 0.8,
+      },
+    ];
+    expect(() => assertVideoFrameCoverage(reports, 0.95)).toThrow(VideoFrameCoverageError);
+  });
+
+  it("respects a threshold override — 0.5 passes 60% coverage", () => {
+    const reports = [
+      {
+        videoId: "partial",
+        clipStart: 0,
+        clipEnd: 1,
+        expectedFrames: 30,
+        capturedFrames: 18,
+        ratio: 0.6,
+      },
+    ];
+    expect(() => assertVideoFrameCoverage(reports, 0.5)).not.toThrow();
+  });
+
+  it("is a no-op when the threshold is null (env opt-out)", () => {
+    const reports = [
+      {
+        videoId: "blank",
+        clipStart: 0,
+        clipEnd: 1,
+        expectedFrames: 30,
+        capturedFrames: 0,
+        ratio: 0,
+      },
+    ];
+    expect(() => assertVideoFrameCoverage(reports, null)).not.toThrow();
+  });
+
+  it("ignores 0-expected-frame windows so the gate never fires on a degenerate clip", () => {
+    const reports = [
+      {
+        videoId: "zero-duration",
+        clipStart: 3,
+        clipEnd: 3,
+        expectedFrames: 0,
+        capturedFrames: 0,
+        ratio: 1,
+      },
+    ];
+    expect(() => assertVideoFrameCoverage(reports, 1)).not.toThrow();
+  });
+
+  it("cites the worst-ratio clip in the error, not the first-found", () => {
+    // Field-signal shape: 15 injected videos, several later ones blank. Cite
+    // the deepest failure so operators fix root cause first, not the closest.
+    const reports = [
+      {
+        videoId: "slightly-low",
+        clipStart: 0,
+        clipEnd: 1,
+        expectedFrames: 30,
+        capturedFrames: 27,
+        ratio: 0.9,
+      },
+      {
+        videoId: "totally-blank",
+        clipStart: 1,
+        clipEnd: 2,
+        expectedFrames: 30,
+        capturedFrames: 0,
+        ratio: 0,
+      },
+      {
+        videoId: "moderately-low",
+        clipStart: 2,
+        clipEnd: 3,
+        expectedFrames: 30,
+        capturedFrames: 15,
+        ratio: 0.5,
+      },
+    ];
+    try {
+      assertVideoFrameCoverage(reports, 0.95);
+      throw new Error("expected coverage assertion to throw");
+    } catch (err) {
+      expect(isVideoFrameCoverageError(err)).toBe(true);
+      const cov = err as VideoFrameCoverageError;
+      expect(cov.worst.videoId).toBe("totally-blank");
+      expect(cov.failedReports.map((r) => r.videoId)).toEqual([
+        "totally-blank",
+        "moderately-low",
+        "slightly-low",
+      ]);
+      expect(cov.message).toContain("+2 more clip(s) below threshold");
+    }
+  });
+});
+
+describe("countAuthoredTimedClips", () => {
+  it("counts every [data-start] element in the compiled HTML", () => {
+    // Field signal ts=1784144554: 147-clip composition with 130 word-level
+    // caption divs. Static scan gives a coarse proxy — enough to make a
+    // 147-clip render distinguishable in telemetry from a 3-clip render.
+    const html = `<html><body>
+      <div data-start="0" data-duration="1">a</div>
+      <div data-start="1" data-duration="1">b</div>
+      <video data-start="2" data-duration="3" src="v.mp4"></video>
+      <div>not timed</div>
+    </body></html>`;
+    expect(countAuthoredTimedClips(html)).toBe(3);
+  });
+
+  it("returns 0 when no timed clips exist", () => {
+    expect(countAuthoredTimedClips("<html><body><div>hi</div></body></html>")).toBe(0);
+  });
+});
diff --git a/packages/producer/src/services/render/videoFrameCoverage.ts b/packages/producer/src/services/render/videoFrameCoverage.ts
new file mode 100644
index 000000000..ee41b52c0
--- /dev/null
+++ b/packages/producer/src/services/render/videoFrameCoverage.ts
@@ -0,0 +1,206 @@
+/**
+ * Per-clip render-time frame-coverage accounting + threshold fail-loud gate.
+ *
+ * Sibling to #2474's `hasRuntimeInsertedMedia` probe: that PR guarantees the
+ * DISCOVERY of runtime-inserted media (so the browser probe launches and
+ * reconciles element identity). This module owns the DELIVERY side —
+ * for each authored/discovered video clip on the timeline, did the
+ * extractor actually produce enough source-video frames to composite the
+ * clip's authored `[data-start,data-end]` window? Any clip whose
+ * `capturedFrames / expectedFrames` ratio falls below a configurable
+ * threshold aborts the render with a `VideoFrameCoverageError` at extract
+ * finalization, BEFORE encode produces an MP4 that silently drops the
+ * clip's pixels to black.
+ *
+ * Two field signals defined the failure surface this exists to close
+ * (both `#hyperframes-cli-feedback`, both `check`/`snapshot` pass /
+ * final MP4 wrong):
+ *
+ *   • ts=1784139267 · win32/x64 CLI 0.7.58 156s render, 15 injected
+ *     videos: several later-injected video clips render BLANK in the
+ *     encoded MP4. Injection-count-scaled — 12 injections fail, 4
+ *     succeed (workaround: pre-compose into one base timeline). Points
+ *     at injector scheduling / worker-seek saturation / extractor
+ *     concurrency. Directly covered here — the per-video capture
+ *     shortfall lands with `capturedFrames << expectedFrames`.
+ *
+ *   • ts=1784144554 · darwin/arm64 CLI 0.7.59 3/10 147-clip
+ *     composition (130 word-level caption divs): producer left a
+ *     subset of authored `[data-start]` div clips permanently visible
+ *     in the rendered MP4 while preview/snapshot showed correct
+ *     visibility. Authored-clip-count-scaled — 147 clips fails, 3
+ *     succeeds. This case runs through `syncTimedElementVisibility`
+ *     at runtime and is NOT source-video-frame-shaped; the coverage
+ *     gate cannot directly observe it. We surface an
+ *     `authoredTimedClipCount` gauge so a 147-clip composition is
+ *     visible in telemetry, and leave the per-tick visibility parity
+ *     check as follow-up work (a separate runtime observability
+ *     channel is required — the extractor doesn't see div visibility).
+ *
+ * Threshold: default 0.95 (a 5% capture-frame drop is loud); override
+ * via `HF_VIDEO_COVERAGE_THRESHOLD` env; disable entirely by setting
+ * the env to `0` or a negative number. A threshold of `1` requires
+ * exact coverage (no slack for the ffmpeg ±1-frame boundary rounding
+ * that legitimately happens on a 29.97 fps timeline).
+ */
+
+import { parseHTML } from "linkedom";
+import type { ExtractedFrames, VideoElement } from "@hyperframes/engine";
+
+export interface VideoFrameCoverageReport {
+  videoId: string;
+  clipStart: number;
+  clipEnd: number;
+  expectedFrames: number;
+  capturedFrames: number;
+  /** `capturedFrames / expectedFrames`; `1` when `expectedFrames === 0` (nothing to cover). */
+  ratio: number;
+}
+
+/**
+ * Discriminant-based error so callers cross-module (producer server,
+ * distributed worker) can identify a coverage-gate failure without
+ * `instanceof` (which is fragile across duplicated module instances,
+ * see `DrawElementVerificationError` for the same problem).
+ */
+export interface VideoFrameCoverageErrorDetails {
+  readonly hyperframesVideoFrameCoverageError: true;
+  readonly threshold: number;
+  readonly worst: VideoFrameCoverageReport;
+  readonly failedReports: VideoFrameCoverageReport[];
+}
+
+export class VideoFrameCoverageError extends Error {
+  readonly hyperframesVideoFrameCoverageError = true as const;
+  readonly threshold: number;
+  readonly worst: VideoFrameCoverageReport;
+  readonly failedReports: VideoFrameCoverageReport[];
+
+  constructor(
+    message: string,
+    details: Omit<VideoFrameCoverageErrorDetails, "hyperframesVideoFrameCoverageError">,
+  ) {
+    super(message);
+    this.name = "VideoFrameCoverageError";
+    this.threshold = details.threshold;
+    this.worst = details.worst;
+    this.failedReports = details.failedReports;
+  }
+}
+
+export function isVideoFrameCoverageError(err: unknown): err is VideoFrameCoverageError {
+  return (
+    typeof err === "object" &&
+    err !== null &&
+    (err as { hyperframesVideoFrameCoverageError?: unknown }).hyperframesVideoFrameCoverageError ===
+      true
+  );
+}
+
+/**
+ * Resolve the coverage threshold from `HF_VIDEO_COVERAGE_THRESHOLD` env.
+ *
+ * Defaults to `0.95`. Values outside `(0, 1]` disable the gate: `0` or
+ * negative → off (return `null`); `>1` clamps to `1`. Non-numeric env
+ * values fall back to the default (with a caller-side warning if a log
+ * is available).
+ */
+export function resolveVideoCoverageThreshold(
+  envValue: string | undefined = process.env.HF_VIDEO_COVERAGE_THRESHOLD,
+): number | null {
+  if (envValue === undefined) return 0.95;
+  const parsed = Number(envValue);
+  if (!Number.isFinite(parsed)) return 0.95;
+  if (parsed <= 0) return null;
+  if (parsed > 1) return 1;
+  return parsed;
+}
+
+/**
+ * Ceil the clip's authored `[start,end)` window at `fps` — the number of
+ * captured render frames whose center-time falls inside the window. Kept
+ * separate so a caller (or a test) can override it if a composition uses
+ * a non-integer fps whose sampling makes the naive count off by one.
+ */
+export function expectedFramesForClip(start: number, end: number, fps: number): number {
+  if (!Number.isFinite(start) || !Number.isFinite(end) || !Number.isFinite(fps)) return 0;
+  if (fps <= 0) return 0;
+  const duration = Math.max(0, end - start);
+  return Math.ceil(duration * fps);
+}
+
+export function computeVideoFrameCoverage(
+  videos: readonly VideoElement[],
+  extracted: readonly ExtractedFrames[],
+  fps: number,
+): VideoFrameCoverageReport[] {
+  const byId = new Map<string, ExtractedFrames>();
+  for (const entry of extracted) byId.set(entry.videoId, entry);
+
+  const reports: VideoFrameCoverageReport[] = [];
+  for (const video of videos) {
+    const entry = byId.get(video.id);
+    const expectedFrames = expectedFramesForClip(video.start, video.end, fps);
+    // framePaths is a Map — `size` is the number of distinct captured frames
+    // delivered to the runtime injector, which is the load-bearing count
+    // (some extractors report a total that includes cache-hit-skipped frames
+    // via a stale `totalFrames`, so we trust the delivered-path count).
+    const capturedFrames = entry ? entry.framePaths.size : 0;
+    const ratio = expectedFrames === 0 ? 1 : capturedFrames / expectedFrames;
+    reports.push({
+      videoId: video.id,
+      clipStart: video.start,
+      clipEnd: video.end,
+      expectedFrames,
+      capturedFrames,
+      ratio,
+    });
+  }
+  return reports;
+}
+
+/**
+ * Throws `VideoFrameCoverageError` when any per-clip ratio is below
+ * `threshold`. A `null` threshold disables the gate (env opt-out).
+ * A clip with `expectedFrames === 0` (0-duration or non-authored) is
+ * unconditionally passing so the gate never fires on a degenerate window.
+ */
+export function assertVideoFrameCoverage(
+  reports: readonly VideoFrameCoverageReport[],
+  threshold: number | null,
+): void {
+  if (threshold === null) return;
+  const failed = reports.filter((report) => report.expectedFrames > 0 && report.ratio < threshold);
+  if (failed.length === 0) return;
+  // Sort ascending by ratio so the "worst" is first — that's what we cite
+  // in the message and pin on the error details for telemetry.
+  const sorted = [...failed].sort((a, b) => a.ratio - b.ratio);
+  const worst = sorted[0]!;
+  const pct = (worst.ratio * 100).toFixed(1);
+  const thresholdPct = (threshold * 100).toFixed(1);
+  const suffix = sorted.length > 1 ? ` (+${sorted.length - 1} more clip(s) below threshold)` : "";
+  throw new VideoFrameCoverageError(
+    `Video "${worst.videoId}" captured ${worst.capturedFrames} of expected ${worst.expectedFrames} frames ` +
+      `(coverage ${pct}%, threshold ${thresholdPct}%). ` +
+      `check/snapshot may pass while the encoded MP4 renders this clip blank — aborting render ` +
+      `to prevent shipping a wrong MP4.${suffix} ` +
+      `Set HF_VIDEO_COVERAGE_THRESHOLD=0 to disable this gate.`,
+    { threshold, worst, failedReports: sorted },
+  );
+}
+
+/**
+ * Count authored `[data-start]` clip windows in the compiled HTML.
+ *
+ * Not a fail-loud gate — a raw counter that lands in
+ * `RenderExtractionObservability.authoredTimedClipCount` so a 147-clip
+ * composition is queryable in telemetry (the ts=1784144554 field signal
+ * shape). Runtime `syncTimedElementVisibility` iterates the same set at
+ * render time; counting statically here is a coarse proxy — dynamic
+ * script-inserted `[data-start]` divs land in `hasRuntimeInsertedMedia`'s
+ * probe path (PR #2474), not this static scan.
+ */
+export function countAuthoredTimedClips(html: string): number {
+  const { document } = parseHTML(html);
+  return document.querySelectorAll("[data-start]").length;
+}
diff --git a/packages/producer/src/services/renderOrchestrator.ts b/packages/producer/src/services/renderOrchestrator.ts
index 45401ff67..0a26466c3 100644
--- a/packages/producer/src/services/renderOrchestrator.ts
+++ b/packages/producer/src/services/renderOrchestrator.ts
@@ -45,7 +45,13 @@ import {
 } from "fs";
 import { tmpdir } from "node:os";
 import { parseHTML } from "linkedom";
-import { type CanvasResolution, type Fps, type FpsInput, toFps } from "@hyperframes/core";
+import {
+  type CanvasResolution,
+  type Fps,
+  type FpsInput,
+  fpsToNumber,
+  toFps,
+} from "@hyperframes/core";
 import {
   type EngineConfig,
   resolveConfig,
@@ -127,6 +133,13 @@ import {
   type RenderObservabilitySummary,
 } from "./render/observability.js";
 import { type HdrPerfCollector, type HdrPerfSummary } from "./render/hdrPerf.js";
+import {
+  assertVideoFrameCoverage,
+  computeVideoFrameCoverage,
+  countAuthoredTimedClips,
+  resolveVideoCoverageThreshold,
+  type VideoFrameCoverageReport,
+} from "./render/videoFrameCoverage.js";
 import { runCompileStage } from "./render/stages/compileStage.js";
 import { runProbeStage } from "./render/stages/probeStage.js";
 import {
@@ -177,11 +190,25 @@ function sampleDirectoryBytes(dir: string): number {
 function summarizeExtractionObservability(
   extractionResult: ExtractionResult | null,
   videoCount: number,
+  coverageReports?: readonly VideoFrameCoverageReport[],
+  authoredTimedClipCount?: number,
 ): RenderExtractionObservability {
   const extracted = extractionResult?.extracted ?? [];
   const totalFramesExtracted = extractionResult?.totalFramesExtracted ?? 0;
   const maxFramesPerVideo = extracted.reduce((max, item) => Math.max(max, item.totalFrames), 0);
   const phaseBreakdown = extractionResult?.phaseBreakdown;
+  // Only surface the coverage gauges when we actually ran the gate — a
+  // no-video render must not emit a spurious `minVideoFrameCoverageRatio`
+  // that dashboards interpret as "coverage measured, was 0/0=1".
+  const coverageGauges =
+    coverageReports && coverageReports.length > 0
+      ? {
+          minVideoFrameCoverageRatio: coverageReports.reduce(
+            (min, r) => Math.min(min, r.ratio),
+            Number.POSITIVE_INFINITY,
+          ),
+        }
+      : {};
   return {
     videoCount,
     extractedVideoCount: extracted.length,
@@ -194,6 +221,8 @@ function summarizeExtractionObservability(
     vfrPreflightCount: phaseBreakdown?.vfrPreflightCount,
     cacheHits: phaseBreakdown?.cacheHits,
     cacheMisses: phaseBreakdown?.cacheMisses,
+    ...coverageGauges,
+    authoredTimedClipCount,
   };
 }
 
@@ -1920,9 +1949,28 @@ export async function executeRenderJob(
       imageColorSpaces,
     } = extractResult;
     perfStages.videoExtractMs = extractResult.videoExtractMs;
+
+    // ── Parity gate: per-clip captured-vs-expected-frame coverage ───────
+    // Fail loudly BEFORE encode if any clip's delivered frames fall below
+    // the threshold — check/snapshot passes on individual frames while the
+    // encoded MP4 silently renders the clip blank (field signal
+    // ts=1784139267: 15-injection later-clip drop; see videoFrameCoverage.ts).
+    // Also count authored `[data-start]` clip windows as a coarse proxy
+    // for the ts=1784144554 authored-clip-count-scaled failure shape.
+    const coverageReports: VideoFrameCoverageReport[] = extractionResult
+      ? computeVideoFrameCoverage(
+          composition.videos,
+          extractionResult.extracted,
+          fpsToNumber(job.config.fps),
+        )
+      : [];
+    const coverageThreshold = resolveVideoCoverageThreshold();
+    const authoredTimedClipCount = countAuthoredTimedClips(compiled.html);
     extractionObservability = summarizeExtractionObservability(
       extractionResult,
       composition.videos.length,
+      coverageReports,
+      authoredTimedClipCount,
     );
     observability.checkpoint("video_extract", "frames resolved", {
       videoCount: extractionObservability.videoCount,
@@ -1934,7 +1982,15 @@ export async function executeRenderJob(
       vfrPreflightMs: extractionObservability.vfrPreflightMs ?? null,
       cacheHits: extractionObservability.cacheHits ?? null,
       cacheMisses: extractionObservability.cacheMisses ?? null,
+      minVideoFrameCoverageRatio: extractionObservability.minVideoFrameCoverageRatio ?? null,
+      authoredTimedClipCount: extractionObservability.authoredTimedClipCount ?? null,
     });
+    // Gate AFTER the checkpoint so a coverage-failed render still emits
+    // the observability row (partial telemetry is still worth having).
+    // `assertVideoFrameCoverage` no-ops on an empty report list AND on a
+    // null threshold, so the gate is inert for no-video + opted-out
+    // renders alike.
+    assertVideoFrameCoverage(coverageReports, coverageThreshold);
 
     // ── HDR auto-detection ──────────────────────────────────────────────
     const effectiveHdr = resolveEffectiveHdrMode({