diff --git a/lanes/A-stage.md b/lanes/A-stage.md
index 13c8ba9..c99989b 100644
--- a/lanes/A-stage.md
+++ b/lanes/A-stage.md
@@ -120,3 +120,20 @@ retargeted clip + timeline scrub, all through the real Stage). Answers + M2 orde
    backdrop rebuild-on-param-change, drag-from-dock onto viewport.
 Test assets now live in `assets/{characters,animations,backdrops}/test/`
 (man.fbx, hiphop.fbx, carrying.fbx, street.jpg — gitignored, on ultra).
+
+### 2026-07-18 — M2 ACCEPTED, SYNC 2 PASSED. **M3-polish unlocked.**
+Your entity-mirror seam report was exactly right and well-diagnosed. Resolution:
+Lane B's Timeline now subscribes to `stage.onChange` and mirrors adds/removes
+into its model (orchestrator implemented, `timeline.js _mirror`) — your
+onChange-on-every-add fix is what made that possible; no dedicated
+entityadd/remove events needed. Verified live: 6 dock-added entities all
+keyframable, full sunset demo saved as scene `sync2-sunset`.
+M3-polish list (order):
+1. **PiP is enormous** — it covered ~70% of the viewport in the SYNC 2
+   screenshot. Cap it (~24% width, bottom-right corner, click to swap
+   director/active-cam views or a size toggle).
+2. lady.glb (non-mixamo rig, `assets/characters/test/lady.glb`) renders
+   flat white — her textures didn't come through the GLB load path. Check
+   whether it's the asset or a loader/material issue (compare in rigroom).
+3. Keep `renderActiveCamera`/`pause`/`resume` stable — the finalRender
+   client drives them now (SYNC 3).
diff --git a/lanes/B-timeline.md b/lanes/B-timeline.md
index db612ac..f9f979a 100644
--- a/lanes/B-timeline.md
+++ b/lanes/B-timeline.md
@@ -105,3 +105,18 @@ clip retarget playback verified frame-exact via `step()`. Notes:
 6. Injected `<style id=laneB-tl-css>` is fine permanently — keep it.
 Then per plan: crossfade fade-IN polish, params + camera-cut lane UI,
 snapping config, box-select multi-drag (undo already wired).
+
+### 2026-07-18 — M2 ACCEPTED, SYNC 2 PASSED. **Session 3 (polish) granted.**
+Your flagged dock-entity gap is closed: orchestrator added `_mirror` to
+`timeline.js` (ctor subscribes `stage.onChange`; upserts an entity with empty
+tracks, removes when gone from stage — removal detected via
+`stage.getEntity(id) === null`). Verified live: 6 dock-added entities entered
+the model, clipdrop landed a 4.47s block, sunset param lerp + camera cuts all
+frame-exact. Session 3 items:
+1. **Absorb `_mirror`** — review it, then add a timeline_test.mjs case
+   (stub add → mutate → remove; assert entity+tracks lifecycle). The stub
+   needs `getEntity` to return null after removal for this to test honestly.
+2. Programmatic `scene.duration = x` doesn't refresh the scene bar (only
+   `load()` fires onLoad). Add a `setDuration(x)` mutator that clamps
+   existing keys' visibility and notifies the UI; wire the dur field to it.
+3. Your listed polish: snapping increment config, keyable-param add UI.
diff --git a/lanes/C-server.md b/lanes/C-server.md
index 63053f8..0779c51 100644
--- a/lanes/C-server.md
+++ b/lanes/C-server.md
@@ -106,3 +106,21 @@ solid), go straight into §C5 — implement `/render/begin|frame|end|status|out`
 4. uvicorn for local dev: `.venv/bin/uvicorn scenegod.server:app --port 8020`
    — there's also a launch entry in MESHGOD/.claude/launch.json ("scenegod")
    used by the orchestrator's browser preview.
+
+### 2026-07-18 — M2+M3 ACCEPTED, **SYNC 3 PASSED. M4 is UNLOCKED.**
+Orchestrator ran your `finalRender` end-to-end in the integrated app against
+Lane A's `renderActiveCamera`: 240 frames @1920×1080 → ffmpeg → out.mp4,
+h264, exactly 8.000s, with camera cuts and sunset light lerp visible in
+extracted frames. The browser client path you couldn't exercise is now
+verified — no changes needed. Proceed with M4 in this order:
+1. ffmpeg audio mux from scene `audio[]` (the sync2-sunset scene in
+   `scenes/` is your fixture; add a wav to `assets/audio/test/`).
+2. `scripts/graft_limb.py` (spec in §C6 — blender binary is on ultra's PATH
+   as `blender`; verify with a mixamo body + any rigged hand GLB, and add
+   the refusal-path test).
+3. `/mb/submit` MODELBEAST proxy last (needs `SCENEGOD_MB=1` gating like
+   riggermore; test only that auth/upload contract matches meshgod/ops.py —
+   don't burn farm jobs on repeat runs).
+One render-quality note for your backlog, not urgent: draft webm via
+MediaRecorder is untested in the embedded preview (rAF suspension) — verify
+it once in a real Chrome window before calling it done.
diff --git a/scenegod/web/timeline.js b/scenegod/web/timeline.js
index 6f1a1be..70ff1bb 100644
--- a/scenegod/web/timeline.js
+++ b/scenegod/web/timeline.js
@@ -99,6 +99,27 @@ export class Timeline {
         if (e.detail && e.detail.id) this.addClipDrop(e.detail);
       });
     }
+    // SYNC2 seam: mirror live stage adds/removes into scene.entities so
+    // dock-added entities can be keyframed without a scene load.
+    if (stage && stage.onChange) stage.onChange((en) => this._mirror(en));
+  }
+
+  _mirror(en) {
+    if (!en || !en.id) return;
+    const list = this.scene.entities;
+    const i = list.findIndex((x) => x.id === en.id);
+    if (!this.stage.getEntity(en.id)) {         // gone from stage → drop entity + its tracks
+      if (i >= 0) list.splice(i, 1);
+      return;
+    }
+    if (i >= 0) return;                          // known — timeline already owns its tracks
+    list.push({
+      id: en.id, kind: en.kind, label: en.label,
+      source: en.source ? structuredClone(en.source) : { type: 'upload' },
+      params: en.params ? structuredClone(en.params) : {},
+      transform: this.stage.entityTransform(en.id),
+      tracks: { transform: [], params: [], clips: [] },
+    });
   }
 
   get fps() { return this.scene.fps; }