fix(producer): probe variable-bound media sources (#2444)

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

@@ -1,5 +1,9 @@
 import { describe, expect, it, mock } from "bun:test";
-import { hasAutoStartVideos, hasScriptedAudioVolumeAutomation } from "./probeStage.js";
+import {
+  hasAutoStartVideos,
+  hasScriptedAudioVolumeAutomation,
+  hasVariableBoundMedia,
+} from "./probeStage.js";
 
 // ── Mocks for runProbeStage tests ────────────────────────────────────────────
 // Capture the cfg passed to createCaptureSession so we can assert it carries
@@ -244,7 +248,36 @@ describe("hasAutoStartVideos", () => {
   });
 });
 
+describe("hasVariableBoundMedia", () => {
+  it("requires a browser probe when an audio src is overridden by render variables", () => {
+    const html = `<audio id="voice" src="fallback.wav" data-var-src="voice_src"></audio>`;
+
+    expect(hasVariableBoundMedia(html, { voice_src: "row-02.wav" })).toBe(true);
+  });
+
+  it("does not probe unrelated overrides or image-only bindings", () => {
+    const audio = `<audio src="fallback.wav" data-var-src="voice_src"></audio>`;
+    const image = `<img src="fallback.png" data-var-src="hero_src" />`;
+
+    expect(hasVariableBoundMedia(audio, { title: "Row 02" })).toBe(false);
+    expect(hasVariableBoundMedia(image, { hero_src: "row-02.png" })).toBe(false);
+  });
+});
+
 describe("runProbeStage — forceScreenshot threading", () => {
+  it("launches a probe for a static-duration composition with variable-bound audio", async () => {
+    capturedCfgs.length = 0;
+    const { runProbeStage } = await import("./probeStage.js");
+    const input = makeProbeInput({});
+    input.composition.duration = 5;
+    input.compiled.html = `<audio id="voice" src="fallback.wav" data-var-src="voice_src"></audio>`;
+    input.job.config.variables = { voice_src: "row-02.wav" };
+
+    await runProbeStage(input);
+
+    expect(capturedCfgs.length).toBeGreaterThan(0);
+  });
+
   it("passes forceScreenshot:true to createCaptureSession when stage input carries it but cfg does not (low-memory mode fix #1236)", async () => {
     capturedCfgs.length = 0;
 

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

@@ -135,6 +135,25 @@ export function hasAutoStartVideos(html: string): boolean {
   return document.querySelector("video[data-hf-auto-start]") !== null;
 }
 
+/**
+ * Variable-bound audio/video sources are resolved by the browser runtime, not
+ * the static compiler. Probe them whenever the current render overrides the
+ * referenced variable so media extraction follows the resolved row value.
+ */
+export function hasVariableBoundMedia(
+  html: string,
+  variables: Record<string, unknown> | undefined,
+): boolean {
+  if (!variables || Object.keys(variables).length === 0) return false;
+  const { document } = parseHTML(html);
+  return Array.from(
+    document.querySelectorAll("audio[data-var-src], video[data-var-src], source[data-var-src]"),
+  ).some((element) => {
+    const variableId = element.getAttribute("data-var-src")?.trim();
+    return Boolean(variableId && Object.hasOwn(variables, variableId));
+  });
+}
+
 export async function runProbeStage(input: ProbeStageInput): Promise<ProbeStageResult> {
   const {
     projectDir,
@@ -166,11 +185,13 @@ export async function runProbeStage(input: ProbeStageInput): Promise<ProbeStageR
     compiled.html,
     composition.audios.length,
   );
+  const hasVariableMedia = hasVariableBoundMedia(compiled.html, job.config.variables);
   const needsBrowser =
     composition.duration <= 0 ||
     compiled.unresolvedCompositions.length > 0 ||
     hasAutoStart ||
-    hasScriptedAudio;
+    hasScriptedAudio ||
+    hasVariableMedia;
 
   if (needsBrowser) {
     const reasons = [];
@@ -179,6 +200,7 @@ export async function runProbeStage(input: ProbeStageInput): Promise<ProbeStageR
       reasons.push(`${compiled.unresolvedCompositions.length} unresolved composition(s)`);
     if (hasAutoStart) reasons.push("auto-start video(s)");
     if (hasScriptedAudio) reasons.push("scripted audio volume");
+    if (hasVariableMedia) reasons.push("variable-bound media source(s)");
 
     log.info("Launching browser for composition probe...", {
       reasons,