diff --git a/CHANGELOG.md b/CHANGELOG.md
index d4aca17..5f5d725 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,16 @@ and the project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+### Fixed
+- `step(text, fn, options)` now honors flat caption display options (e.g.
+  `{ position }`, by analogy with `caption()`) instead of silently dropping
+  anything outside `options.captionOptions`.
+- `lintDemoStoryboard()` no longer emits a spurious "missing mp4" warning when
+  the demo config sets `mp4`/`crop`/`zoom` — the public caller need not pass
+  `mp4Requested`.
+- A thumbnail-only demo (no mp4/crop/zoom/trim) no longer re-muxes and
+  overwrites the source `.webm`; the thumbnail is taken from the original clip.
+
 ## [1.3.0] - 2026-06-18
 
 ### Added
diff --git a/src/demo.js b/src/demo.js
index e052a7f..ff78eaf 100644
--- a/src/demo.js
+++ b/src/demo.js
@@ -155,7 +155,11 @@ function analyzeDemoStoryboard(demoConfig, { viewport, mp4Requested } = {}) {
     ));
   }
 
-  if (!mp4Requested) {
+  // Honor an explicit mp4Requested (only the caller knows about the CLI --mp4
+  // flag) but also infer it from the demo config, so public callers like
+  // lintDemoStoryboard() don't emit a spurious warning when demo.mp4 is set.
+  const wantsMp4 = mp4Requested || !!(demoConfig.mp4 || demoConfig.crop || demoConfig.zoom);
+  if (!wantsMp4) {
     warnings.push(storyboardWarning(
       'missing-mp4',
       'X/SNS demo clips should emit mp4',
@@ -511,9 +515,13 @@ function createDemoController({ page, captions = [], captionOptions = {} }) {
     caption: (text, options = {}) => render(text, options),
 
     async step(text, action, options = {}) {
-      await render(text, options.captionOptions || {});
+      // Caption display options may be passed explicitly (captionOptions) or flat
+      // (e.g. step(text, fn, { position }) by analogy with caption()); honor both
+      // so they are not silently dropped. holdMs is the only step-control key.
+      const { holdMs, captionOptions, ...displayOptions } = options;
+      await render(text, { ...displayOptions, ...(captionOptions || {}) });
       const result = typeof action === 'function' ? await action() : undefined;
-      const hold = normalizeDelayMs(options.holdMs == null ? DEFAULT_STEP_HOLD_MS : options.holdMs, 'step holdMs');
+      const hold = normalizeDelayMs(holdMs == null ? DEFAULT_STEP_HOLD_MS : holdMs, 'step holdMs');
       if (hold > 0) await page.waitForTimeout(hold);
       return result;
     },
diff --git a/src/video.js b/src/video.js
index 1fa3cf6..543dc89 100644
--- a/src/video.js
+++ b/src/video.js
@@ -147,7 +147,7 @@ function postProcessDemo({ webmPath, mp4, trim, crop, zoom, thumbnail, log, env
     if (crop) notes.push('cropped');
     if (zoom) notes.push('zoomed');
     log(`✓ ${path.basename(mp4Path)} (${notes.join(', ')})`);
-  } else {
+  } else if (trim) {
     // Trim-only: stream-copy to a sibling temp file, then swap in place.
     const tmp = `${webmPath}.trim.webm`;
     execFileSync(bin, buildFfmpegArgs({ input: webmPath, output: tmp, trim, copy: true }), {
@@ -156,6 +156,8 @@ function postProcessDemo({ webmPath, mp4, trim, crop, zoom, thumbnail, log, env
     fs.renameSync(tmp, webmPath);
     log(`✓ ${path.basename(webmPath)} trimmed in place`);
   }
+  // else: thumbnail-only (no mp4/crop/zoom/trim) — nothing to re-encode; the
+  // thumbnail below is taken from the original webm without rewriting it.
   if (thumbnail) {
     const at = typeof thumbnail === 'object' && thumbnail.at != null ? thumbnail.at : 1;
     const thumbPath = typeof thumbnail === 'object' && thumbnail.name
diff --git a/test/validation-and-readiness.test.js b/test/validation-and-readiness.test.js
index 2abced6..b4ad51c 100644
--- a/test/validation-and-readiness.test.js
+++ b/test/validation-and-readiness.test.js
@@ -7,7 +7,7 @@
  */
 
 const { buildVideoFilter, buildFfmpegArgs } = require('../src/video');
-const { normalizeDemoConfigs } = require('../src/demo');
+const { normalizeDemoConfigs, lintDemoStoryboard } = require('../src/demo');
 const { buildHandoffRecommendations } = require('../src/integrations');
 const { assetRecord } = require('../src/handoff');
 
@@ -36,6 +36,20 @@ describe('demo config fails fast', () => {
   });
 });
 
+describe('storyboard lint mp4 warning reflects the demo config', () => {
+  const captions = [{ at: 1, text: 'before' }, { at: 4, text: 'restore original' }];
+
+  it('no spurious missing-mp4 when demo.mp4 is set (public caller passes no mp4Requested)', () => {
+    const lines = lintDemoStoryboard({ name: 'd', mp4: { crf: 18 }, trim: { duration: 25 }, captions });
+    expect(lines.some((l) => /mp4/i.test(l))).toBe(false);
+  });
+
+  it('still warns when neither the config nor a flag requests mp4', () => {
+    const lines = lintDemoStoryboard({ name: 'd', trim: { duration: 25 }, captions });
+    expect(lines.some((l) => /mp4/i.test(l))).toBe(true);
+  });
+});
+
 describe('handoff readiness reflects whether a clip exists', () => {
   const cwd = '/tmp';
   const outDir = '/tmp/store-assets';