diff --git a/packages/cli/src/commands/compositions.test.ts b/packages/cli/src/commands/compositions.test.ts
index 50c4456ff1..32c30caa1c 100644
--- a/packages/cli/src/commands/compositions.test.ts
+++ b/packages/cli/src/commands/compositions.test.ts
@@ -1,6 +1,46 @@
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
 import { describe, expect, it, beforeEach } from "vitest";
 import { ensureDOMParser } from "../utils/dom.js";
-import { parseSubComposition } from "./compositions.js";
+import { parseCompositions, parseSubComposition } from "./compositions.js";
+
+describe("parseCompositions", () => {
+  beforeEach(() => {
+    ensureDOMParser();
+  });
+
+  it("resolves relative sub-composition starts when computing host duration", () => {
+    const baseDir = mkdtempSync(join(tmpdir(), "hyperframes-compositions-"));
+
+    try {
+      const compositionsDir = join(baseDir, "compositions");
+      mkdirSync(compositionsDir);
+
+      const subCompositionHtml = `
+<template id="scene-template">
+  <div data-composition-id="scene" data-width="1920" data-height="1080" data-duration="3">
+    <div class="clip" data-start="0" data-duration="3"></div>
+  </div>
+</template>`;
+      writeFileSync(join(compositionsDir, "scene.html"), subCompositionHtml);
+
+      const html = `
+<div data-composition-id="host" data-width="1920" data-height="1080">
+  <div id="s1" data-composition-id="s1" data-composition-src="compositions/scene.html" data-start="0" data-duration="3" data-track="main"></div>
+  <div data-composition-id="s2" data-composition-src="compositions/scene.html" data-start="s1" data-duration="3" data-track="main"></div>
+</div>`;
+
+      const host = parseCompositions(html, baseDir).find(
+        (composition) => composition.id === "host",
+      );
+
+      expect(host?.duration).toBe(6);
+    } finally {
+      rmSync(baseDir, { recursive: true, force: true });
+    }
+  });
+});
 
 describe("parseSubComposition", () => {
   beforeEach(() => {
diff --git a/packages/cli/src/commands/compositions.ts b/packages/cli/src/commands/compositions.ts
index b31645ee5a..f962640dc7 100644
--- a/packages/cli/src/commands/compositions.ts
+++ b/packages/cli/src/commands/compositions.ts
@@ -1,4 +1,5 @@
 import { defineCommand } from "citty";
+import { parseNumeric, parseStartExpression } from "@hyperframes/core";
 import type { Example } from "./_examples.js";
 import { existsSync, readFileSync } from "node:fs";
 import { resolve, dirname } from "node:path";
@@ -45,12 +46,78 @@ function estimateDurationFromScripts(root: ParentNode): number {
   return duration;
 }
 
-function parseCompositions(html: string, baseDir: string): CompositionInfo[] {
+function findReferenceTargetEl(doc: Document, refId: string): Element | null {
+  return doc.getElementById(refId) ?? doc.querySelector(`[data-composition-id="${refId}"]`);
+}
+
+function resolveStart(
+  doc: Document,
+  el: Element,
+  startCache: Map<Element, number>,
+  visiting: Set<Element>,
+): number {
+  const cached = startCache.get(el);
+  if (cached !== undefined) return cached;
+  if (visiting.has(el)) return 0;
+  visiting.add(el);
+
+  try {
+    const expression = parseStartExpression(el.getAttribute("data-start"));
+    if (!expression) {
+      startCache.set(el, 0);
+      return 0;
+    }
+
+    if (expression.kind === "absolute") {
+      const value = Math.max(0, expression.value);
+      startCache.set(el, value);
+      return value;
+    }
+
+    const target = findReferenceTargetEl(doc, expression.refId);
+    if (!target) {
+      startCache.set(el, 0);
+      return 0;
+    }
+
+    const targetStart = resolveStart(doc, target, startCache, visiting);
+    const targetDuration = resolveReferencedDuration(doc, target, startCache, visiting);
+    const resolved =
+      targetDuration != null && targetDuration > 0
+        ? Math.max(0, targetStart + targetDuration + expression.offset)
+        : Math.max(0, targetStart + expression.offset);
+    startCache.set(el, resolved);
+    return resolved;
+  } finally {
+    visiting.delete(el);
+  }
+}
+
+function resolveReferencedDuration(
+  doc: Document,
+  el: Element,
+  startCache: Map<Element, number>,
+  visiting: Set<Element>,
+): number | null {
+  const durationAttr = parseNumeric(el.getAttribute("data-duration"));
+  if (durationAttr != null && durationAttr > 0) return durationAttr;
+  const endAttr = parseNumeric(el.getAttribute("data-end"));
+  if (endAttr != null) {
+    const start = resolveStart(doc, el, startCache, visiting);
+    const delta = endAttr - start;
+    if (Number.isFinite(delta) && delta > 0) return delta;
+  }
+  return null;
+}
+
+export function parseCompositions(html: string, baseDir: string): CompositionInfo[] {
   const parser = new DOMParser();
   const doc = parser.parseFromString(html, "text/html");
 
   const compositionDivs = doc.querySelectorAll("[data-composition-id]");
   const compositions: CompositionInfo[] = [];
+  const startCache = new Map<Element, number>();
+  const visiting = new Set<Element>();
 
   compositionDivs.forEach((div) => {
     const id = div.getAttribute("data-composition-id") ?? "unknown";
@@ -75,7 +142,7 @@ function parseCompositions(html: string, baseDir: string): CompositionInfo[] {
 
     timedChildren.forEach((el) => {
       elementCount++;
-      const start = parseFloat(el.getAttribute("data-start") ?? "0");
+      const start = resolveStart(doc, el, startCache, visiting);
       const endAttr = el.getAttribute("data-end");
       const durationAttr = el.getAttribute("data-duration");
 
@@ -141,9 +208,11 @@ export function parseSubComposition(
   // Also check timed children for max end time
   if (compDiv) {
     const timedEls = compDiv.querySelectorAll("[data-start]");
+    const startCache = new Map<Element, number>();
+    const visiting = new Set<Element>();
     timedEls.forEach((el) => {
       elementCount = Math.max(elementCount, timedEls.length);
-      const start = parseFloat(el.getAttribute("data-start") ?? "0");
+      const start = resolveStart(doc, el, startCache, visiting);
       const endAttr = el.getAttribute("data-end");
       const durAttr = el.getAttribute("data-duration");