diff --git a/scripts/creator-editing-recipes.test.mjs b/scripts/creator-editing-recipes.test.mjs
index 5d00b4423c..a1fa442b94 100644
--- a/scripts/creator-editing-recipes.test.mjs
+++ b/scripts/creator-editing-recipes.test.mjs
@@ -73,3 +73,78 @@ test("the Studio skill's safe boxes equal the preview's", async () => {
   assert.match(skill, new RegExp(`Action-safe\\s*\\|\\s*${action}%`));
   assert.match(skill, new RegExp(`Title-safe\\s*\\|\\s*${title}%`));
 });
+
+async function studioDefaultSeconds(kind) {
+  const helpers = await read("packages/studio/src/utils/studioHelpers.ts");
+  const block = helpers.match(/DEFAULT_TIMELINE_ASSET_DURATION[^=]*=\s*\{([^}]*)\}/);
+  const defaults = block ? block[1] : "";
+  const value = defaults.match(new RegExp(`${kind}:\\s*(\\d+(?:\\.\\d+)?)`));
+  return value ? value[1] : undefined;
+}
+
+async function addMediaSection() {
+  const doc = await read(OWNER);
+  const afterHeading = doc.split("## Add media")[1] ?? "";
+  const section = afterHeading.split("\n## ")[0];
+  const imageMatch = section.match(/<img[\s\S]*?\/>/);
+  const image = imageMatch ? imageMatch[0] : "";
+  return { section, image };
+}
+
+test("the add-media recipe uses Studio's default durations", async () => {
+  const { section, image } = await addMediaSection();
+  const imageSecs = await studioDefaultSeconds("image");
+  assert.ok(imageSecs, "could not read Studio's image default");
+  assert.match(section, new RegExp(`defaults to ${imageSecs} seconds`));
+  assert.match(section, /`data-start` is enough/);
+  assert.doesNotMatch(section, /ffprobe/);
+  assert.match(section, /root composition's `data-duration` is at least/);
+  assert.match(section, new RegExp(`${imageSecs} for an image unless you set another`));
+  assert.doesNotMatch(image, /data-duration/);
+});
+
+test("the add-media recipe uses Studio's full-frame geometry", async () => {
+  const { section, image } = await addMediaSection();
+  const dropOps = await read("packages/studio/src/hooks/useTimelineAssetDropOps.ts");
+  assert.match(
+    dropOps,
+    /fitTimelineAssetGeometry\(\s*null,/,
+    "Studio centres by natural size now; update the doc",
+  );
+  assert.match(section, /fill the whole frame/);
+  assert.match(image, /left: 0px; top: 0px; width: 1920px; height: 1080px/);
+});
+
+test("the add-media example carries every attribute Studio's drop writes", async () => {
+  const { image } = await addMediaSection();
+  const drop = await read("packages/studio/src/utils/timelineAssetDrop.ts");
+  for (const attr of ['class="clip"', "data-start", "data-duration", "data-track-index"]) {
+    assert.ok(drop.includes(attr), `Studio no longer writes ${attr}`);
+  }
+  for (const attr of ['class="clip"', "data-start", "data-track-index"]) {
+    assert.ok(image.includes(attr), `doc example lacks ${attr}`);
+  }
+});
+
+const CLIP_ATTRS = ["id=", 'class="clip"', "data-start", "data-track-index"];
+
+const mediaExample = (section, tag) =>
+  section.match(new RegExp(`<${tag}[\\s\\S]*?</${tag}>`))?.[0] ?? "";
+
+const assertNoAuthoredDuration = (example, tag) => {
+  assert.ok(example, `no <${tag}> example`);
+  assert.doesNotMatch(example, /data-duration/, `${tag} example must not author a duration`);
+};
+
+const assertHasAttrs = (example, tag, attrs) => {
+  for (const attr of attrs) assert.ok(example.includes(attr), `${tag} example lacks ${attr}`);
+};
+
+test("the video and audio add-media examples carry no data-duration and keep the clip attributes", async () => {
+  const { section } = await addMediaSection();
+  for (const tag of ["video", "audio"]) {
+    const example = mediaExample(section, tag);
+    assertNoAuthoredDuration(example, tag);
+    assertHasAttrs(example, tag, CLIP_ATTRS);
+  }
+});
diff --git a/skills-manifest.json b/skills-manifest.json
index 0f9e21c193..b1789536e0 100644
--- a/skills-manifest.json
+++ b/skills-manifest.json
@@ -34,7 +34,7 @@
       "files": 11
     },
     "hyperframes-core": {
-      "hash": "ca3bc11c4e163225",
+      "hash": "99a07539f407ca0d",
       "files": 11
     },
     "hyperframes-creative": {
diff --git a/skills/hyperframes-core/references/creator-editing-recipes.md b/skills/hyperframes-core/references/creator-editing-recipes.md
index 74932476a5..6977324653 100644
--- a/skills/hyperframes-core/references/creator-editing-recipes.md
+++ b/skills/hyperframes-core/references/creator-editing-recipes.md
@@ -2,6 +2,8 @@
 
 Use these copyable contracts after `tracks-and-clips.md`. Global math: **consumed source = timeline duration × rate**; **natural timeline duration = remaining source / rate**.
 
+Before any edit, run `npx hyperframes timeline` (add `--json` for a machine-readable list) to see the project's tracks and clips instead of reading the HTML.
+
 These recipes keep sound on a separate `<audio>` element with the `<video>` muted, which is the pattern to reach for when picture and sound are cut independently. An unmuted `<video>` that declares `data-has-audio="true"` is also mixed, so a separate track is a choice, not a requirement.
 
 **Every `<video>` and `<audio>` below carries an `id`, and that is not cosmetic**: `lint` errors with `media_missing_id` on timed media without one, and an id-less `<audio>` is never picked up by the mixer, so the render comes out silent. Keep the ids when you copy a recipe.
@@ -417,6 +419,56 @@ Timeline math: an audio element in the root composition has `data-start` in abso
 
 Timeline math: pick the clips first and say which ones you picked (by id) if the request does not match the file exactly; then add one `delta` to every member's `data-start`, so relative spacing is preserved (here `delta = 40`). Give each copy a new unique `id` and the next unused `data-track-index`; keep `src`, `data-duration`, `data-media-start`, `data-volume` and any `data-automation` as they are. Leave the originals untouched. Check the copies still end inside the composition's duration. Owner: `/hyperframes-core`. Limit: copies of a `<video>` or a sub-composition host follow the same rule, and a copied sub-composition needs its own host `id`.
 
+## Add media (image, video, audio)
+
+Write what Studio writes when a person drops a file on the timeline, so an agent-added clip behaves the same as a dropped one; the one difference is that video and audio need no `data-duration`. Studio's source of truth is `DEFAULT_TIMELINE_ASSET_DURATION` in `packages/studio/src/utils/studioHelpers.ts` and `buildTimelineAssetInsertHtml` in `packages/studio/src/utils/timelineAssetDrop.ts`; a test keeps this section equal to them.
+
+- **Image: `data-duration` is optional and defaults to 3 seconds**, the same as a dropped image, because a still has no length of its own. Write it only for another length. A test keeps the 3 equal to the default in code.
+- **Video and audio: `data-start` is enough.** The length comes from the media itself. An authored `data-duration` shorter than the file is a trim, never a requirement; leave it out unless the request asks for a shorter clip.
+- **Start: the playhead or the requested time, never a silent `0`.** Studio's asset-panel Add uses the playhead time on track `0`; a drop uses the drop point.
+- Give every clip `id`, `class="clip"`, `data-start` and `data-track-index`. Video is `muted playsinline`; audio carries `data-volume="1"`.
+- Then make sure the root composition's `data-duration` is at least the clip's end (`data-start` plus its length: 3 for an image unless you set another, the media's length for video and audio): Studio raises a declared root duration to cover the new clip, so an agent must too, or the clip lies past the end and never plays.
+- **Images and video fill the whole frame**: absolutely positioned at `left: 0; top: 0`, `width` and `height` equal to the composition's `data-width` and `data-height`, `object-fit: contain`. Studio does not know a dropped file's natural size, so it does not centre a smaller one.
+- `z-index` is the number of top-level clips already in that file plus one (at least `1`); later clips stack above earlier ones.
+- Several files dropped together share the drop's track and run end to end.
+
+```html
+<img
+  id="photo"
+  class="clip"
+  src="assets/photo.png"
+  data-start="4"
+  data-track-index="1"
+  style="position: absolute; left: 0px; top: 0px; width: 1920px; height: 1080px; object-fit: contain; z-index: 2"
+/>
+```
+
+```html
+<video
+  id="broll"
+  class="clip"
+  src="assets/broll.mp4"
+  data-start="4"
+  data-track-index="2"
+  muted
+  playsinline
+  style="position: absolute; left: 0px; top: 0px; width: 1920px; height: 1080px; object-fit: contain; z-index: 3"
+></video>
+```
+
+```html
+<audio
+  id="whoosh"
+  class="clip"
+  src="assets/whoosh.mp3"
+  data-start="4"
+  data-track-index="3"
+  data-volume="1"
+></audio>
+```
+
+Inside a sub-composition file, `data-start` is scene-local (see `## Align a sound to an on-screen event`). Owner: `/hyperframes-core`.
+
 ## Swap a media file
 
 ```html
diff --git a/skills/hyperframes-core/references/tracks-and-clips.md b/skills/hyperframes-core/references/tracks-and-clips.md
index 9d0996c692..e9231d0131 100644
--- a/skills/hyperframes-core/references/tracks-and-clips.md
+++ b/skills/hyperframes-core/references/tracks-and-clips.md
@@ -10,7 +10,7 @@ A clip is any DOM element with `data-start` and, where required, `data-duration`
 - **Sub-composition hosts** — `<div>` with `data-composition-src`. Always require `data-duration`.
 - **Video clips** — `<video>` with `muted` and `playsinline`. Duration can default to media length.
 - **Audio clips** — `<audio>`. Duration can default to media length.
-- **Image clips** — `<img>`. Always require `data-duration`.
+- **Image clips** — `<img>`. `data-duration` is optional and defaults to 3 seconds; write it only for another length.
 
 Add `class="clip"` to authored visual clips. The runtime does not read it, but the scaffold's shared `.clip { position: absolute; inset: 0 }` rule is what gives a scene its full-frame box, Studio treats it as an edit hint, and `lint` warns without it.