fix(producer): tolerate rounded frame-boundary durations

packages/producer/src/services/render/stages/probeStage.test.ts

@@ -279,6 +279,30 @@ describe("runProbeStage — forceScreenshot threading", () => {
   });
 });
 
+describe("runProbeStage — decimal duration frame count", () => {
+  it("does not add a frame for a six-decimal duration rounded from an exact frame boundary", async () => {
+    const { runProbeStage } = await import("./probeStage.js");
+    const input = makeProbeInput({});
+    input.composition.duration = 32.866667;
+    input.compiled.staticDuration = 32.866667;
+
+    const result = await runProbeStage(input);
+
+    expect(result.totalFrames).toBe(986);
+  });
+
+  it("still ceilings a duration that genuinely extends into the next frame", async () => {
+    const { runProbeStage } = await import("./probeStage.js");
+    const input = makeProbeInput({});
+    input.composition.duration = 32.867;
+    input.compiled.staticDuration = 32.867;
+
+    const result = await runProbeStage(input);
+
+    expect(result.totalFrames).toBe(987);
+  });
+});
+
 describe("runProbeStage — transient browser error retry (#1687)", () => {
   it("retries once on a transient 'Navigating frame was detached' error and succeeds", async () => {
     resetRetryMocks();

packages/producer/src/services/render/stages/probeStage.ts

@@ -83,6 +83,16 @@ export interface ProbeStageInput {
   deviceScaleFactor: number;
 }
 
+const FRAME_BOUNDARY_EPSILON = 1e-3;
+
+function durationToFrameCount(duration: number, fps: number): number {
+  const rawFrameCount = duration * fps;
+  const nearestFrame = Math.round(rawFrameCount);
+  return Math.abs(rawFrameCount - nearestFrame) <= FRAME_BOUNDARY_EPSILON
+    ? nearestFrame
+    : Math.ceil(rawFrameCount);
+}
+
 export interface ProbeStageResult {
   /** May be reassigned from `recompileWithResolutions`. */
   compiled: CompiledComposition;
@@ -536,7 +546,7 @@ export async function runProbeStage(input: ProbeStageInput): Promise<ProbeStageR
   const browserProbeMs = Date.now() - probeStart;
 
   const duration = composition.duration;
-  const totalFrames = Math.ceil(duration * fpsToNumber(job.config.fps));
+  const totalFrames = durationToFrameCount(duration, fpsToNumber(job.config.fps));
 
   if (duration <= 0) {
     // Gather diagnostics to help users understand why the render would produce a black video.