fix(core): per-property-group keyframe foundations (#1354)

Add PropertyGroupName type system (position/scale/size/rotation/visual/other),
PROPERTY_GROUPS constant, classifyPropertyGroup/classifyTweenPropertyGroup
functions. Parser generates group-aware animation IDs, resolves position strings
(+=, -=, <, >), uses numeric matching with 2% tolerance, and preserves IDs
across all mutations.

packages/core/src/parsers/__goldens__/complex.parsed.json

@@ -1,41 +1,5 @@
 {
   "animations": [
-    {
-      "targetSelector": ".ambient-line",
-      "method": "from",
-      "position": 0.16,
-      "properties": {
-        "scaleX": 0,
-        "opacity": 0
-      },
-      "duration": 0.42,
-      "extras": {
-        "stagger": "__raw:0.08"
-      },
-      "id": ".ambient-line-from-160"
-    },
-    {
-      "targetSelector": ".ambient-word",
-      "method": "from",
-      "position": 0.08,
-      "properties": {
-        "scale": 0.92,
-        "opacity": 0
-      },
-      "duration": 0.5,
-      "id": ".ambient-word-from-80"
-    },
-    {
-      "targetSelector": ".headline .sub",
-      "method": "from",
-      "position": 0.2,
-      "properties": {
-        "y": 20,
-        "opacity": 0
-      },
-      "duration": 0.28,
-      "id": ".headline .sub-from-200"
-    },
     {
       "targetSelector": ".headline span",
       "method": "from",
@@ -49,7 +13,50 @@
       "extras": {
         "stagger": "__raw:0.055"
       },
+      "resolvedStart": 0.05,
       "id": ".headline span-from-50"
+    },
+    {
+      "targetSelector": ".headline .sub",
+      "method": "from",
+      "position": 0.2,
+      "properties": {
+        "y": 20,
+        "opacity": 0
+      },
+      "duration": 0.28,
+      "ease": "power3.out",
+      "resolvedStart": 0.2,
+      "id": ".headline .sub-from-200"
+    },
+    {
+      "targetSelector": ".ambient-word",
+      "method": "from",
+      "position": 0.08,
+      "properties": {
+        "scale": 0.92,
+        "opacity": 0
+      },
+      "duration": 0.5,
+      "ease": "power3.out",
+      "resolvedStart": 0.08,
+      "id": ".ambient-word-from-80"
+    },
+    {
+      "targetSelector": ".ambient-line",
+      "method": "from",
+      "position": 0.16,
+      "properties": {
+        "scaleX": 0,
+        "opacity": 0
+      },
+      "duration": 0.42,
+      "ease": "power3.out",
+      "extras": {
+        "stagger": "__raw:0.08"
+      },
+      "resolvedStart": 0.16,
+      "id": ".ambient-line-from-160"
     }
   ],
   "timelineVar": "tl",

packages/core/src/parsers/__goldens__/complex.serialized.js

@@ -3,8 +3,8 @@
 gsap.defaults({ force3D: true });
 const tl = gsap.timeline({ paused: true, defaults: { duration: 0.45, ease: "power3.out" } });
     tl.from(".headline span", { y: 46, opacity: 0, duration: 0.38, ease: "back.out(1.35)", stagger: 0.055 }, 0.05);
-    tl.from(".ambient-word", { scale: 0.92, opacity: 0, duration: 0.5 }, 0.08);
-    tl.from(".ambient-line", { scaleX: 0, opacity: 0, duration: 0.42, stagger: 0.08 }, 0.16);
-    tl.from(".headline .sub", { y: 20, opacity: 0, duration: 0.28 }, 0.2);
+    tl.from(".ambient-word", { scale: 0.92, opacity: 0, duration: 0.5, ease: "power3.out" }, 0.08);
+    tl.from(".ambient-line", { scaleX: 0, opacity: 0, duration: 0.42, ease: "power3.out", stagger: 0.08 }, 0.16);
+    tl.from(".headline .sub", { y: 20, opacity: 0, duration: 0.28, ease: "power3.out" }, 0.2);
     window.__timelines["vpn-youtube-spot"] = tl;
   

packages/core/src/parsers/__goldens__/fromto.parsed.json

@@ -14,6 +14,7 @@
       },
       "duration": 0.6,
       "ease": "power3.out",
+      "resolvedStart": 0.1,
       "id": "#hero-fromTo-100"
     },
     {
@@ -29,6 +30,7 @@
         "opacity": 0
       },
       "duration": 0.45,
+      "resolvedStart": 0.5,
       "id": "#caption-fromTo-500"
     }
   ],

packages/core/src/parsers/__goldens__/minimal.parsed.json

@@ -10,6 +10,7 @@
       },
       "duration": 0.5,
       "ease": "power3.out",
+      "resolvedStart": 0.2,
       "id": "#notification-to-200"
     },
     {
@@ -22,6 +23,7 @@
       },
       "duration": 0.3,
       "ease": "power3.in",
+      "resolvedStart": 4.2,
       "id": "#notification-to-4200"
     }
   ],

packages/core/src/parsers/__goldens__/moderate.parsed.json

@@ -10,6 +10,7 @@
       },
       "duration": 0.5,
       "ease": "power3.out",
+      "resolvedStart": 0.1,
       "id": "#card-to-100"
     },
     {
@@ -21,7 +22,9 @@
       },
       "duration": 0.15,
       "ease": "power2.out",
-      "id": "#subscribe-btn-to-1000"
+      "propertyGroup": "scale",
+      "resolvedStart": 1,
+      "id": "#subscribe-btn-to-1000-scale"
     },
     {
       "targetSelector": "#subscribe-btn",
@@ -32,7 +35,9 @@
       },
       "duration": 0.4,
       "ease": "elastic.out(1, 0.4)",
-      "id": "#subscribe-btn-to-1150"
+      "propertyGroup": "scale",
+      "resolvedStart": 1.15,
+      "id": "#subscribe-btn-to-1150-scale"
     },
     {
       "targetSelector": "#btn-subscribe",
@@ -43,7 +48,9 @@
       },
       "duration": 0.08,
       "ease": "none",
-      "id": "#btn-subscribe-to-1150"
+      "propertyGroup": "visual",
+      "resolvedStart": 1.15,
+      "id": "#btn-subscribe-to-1150-visual"
     },
     {
       "targetSelector": "#btn-subscribed",
@@ -54,7 +61,9 @@
       },
       "duration": 0.08,
       "ease": "none",
-      "id": "#btn-subscribed-to-1180"
+      "propertyGroup": "visual",
+      "resolvedStart": 1.18,
+      "id": "#btn-subscribed-to-1180-visual"
     },
     {
       "targetSelector": "#card",
@@ -66,6 +75,7 @@
       },
       "duration": 0.25,
       "ease": "power3.in",
+      "resolvedStart": 3.8,
       "id": "#card-to-3800"
     }
   ],

packages/core/src/parsers/gsapConstants.ts

@@ -45,6 +45,46 @@ export const SUPPORTED_PROPS = [
   "innerText",
 ];
 
+// ── Property Groups ─────────────────────────────────────────────────────────
+// Each group maps to an independent GSAP tween so editing one property
+// (e.g. drag → x/y) never contaminates another (e.g. scale, rotation).
+
+export type PropertyGroupName = "position" | "scale" | "size" | "rotation" | "visual" | "other";
+
+export const PROPERTY_GROUPS: Record<PropertyGroupName, ReadonlySet<string>> = {
+  position: new Set(["x", "y", "xPercent", "yPercent"]),
+  scale: new Set(["scale", "scaleX", "scaleY"]),
+  size: new Set(["width", "height"]),
+  rotation: new Set(["rotation", "skewX", "skewY"]),
+  visual: new Set(["opacity", "autoAlpha"]),
+  other: new Set<string>(),
+};
+
+const PROP_TO_GROUP = new Map<string, PropertyGroupName>();
+for (const [group, props] of Object.entries(PROPERTY_GROUPS) as [
+  PropertyGroupName,
+  ReadonlySet<string>,
+][]) {
+  for (const p of props) PROP_TO_GROUP.set(p, group);
+}
+
+export function classifyPropertyGroup(prop: string): PropertyGroupName {
+  return PROP_TO_GROUP.get(prop) ?? "other";
+}
+
+export function classifyTweenPropertyGroup(
+  properties: Record<string, unknown>,
+): PropertyGroupName | undefined {
+  const groups = new Set<PropertyGroupName>();
+  for (const key of Object.keys(properties)) {
+    if (key === "transformOrigin") continue;
+    const g = classifyPropertyGroup(key);
+    groups.add(g);
+  }
+  if (groups.size === 1) return groups.values().next().value;
+  return undefined;
+}
+
 export const SUPPORTED_EASES = [
   "none",
   "power1.in",

packages/core/src/parsers/gsapParser.stress.test.ts

@@ -658,9 +658,9 @@ describe("14. ID collision", () => {
     const ids = result.animations.map((a) => a.id);
     // All IDs must be unique
     expect(new Set(ids).size).toBe(3);
-    expect(ids[0]).toBe("#el-to-0");
-    expect(ids[1]).toBe("#el-to-0-2");
-    expect(ids[2]).toBe("#el-to-0-3");
+    expect(ids[0]).toBe("#el-to-0-visual");
+    expect(ids[1]).toBe("#el-to-0-position");
+    expect(ids[2]).toBe("#el-to-0-position-2");
   });
 
   it("disambiguated IDs are stable across parses", () => {
@@ -932,7 +932,7 @@ describe("Additional edge cases", () => {
     `;
     const result = parseGsapScript(script);
     // ID uses Math.round(position * 1000) for numeric positions
-    expect(result.animations[0].id).toBe("#el-to--2500");
+    expect(result.animations[0].id).toBe("#el-to--2500-position");
   });
 
   it("fromTo with no position arg defaults to 0", () => {

packages/core/src/parsers/gsapParser.test.ts

@@ -18,8 +18,10 @@ import {
   removeAllKeyframesFromScript,
   addAnimationWithKeyframesToScript,
   splitAnimationsInScript,
+  splitIntoPropertyGroups,
 } from "./gsapParser.js";
 import type { GsapAnimation } from "./gsapParser.js";
+import { classifyPropertyGroup, classifyTweenPropertyGroup } from "./gsapConstants.js";
 import type { Keyframe } from "../core.types";
 import {
   parseAndSerialize,
@@ -260,8 +262,8 @@ describe("parseGsapScript", () => {
     expect(result1.animations[1].id).toBe(result2.animations[1].id);
 
     // IDs encode selector, method, and position
-    expect(result1.animations[0].id).toBe("#el1-to-0");
-    expect(result1.animations[1].id).toBe("#el2-to-1000");
+    expect(result1.animations[0].id).toBe("#el1-to-0-visual");
+    expect(result1.animations[1].id).toBe("#el2-to-1000-position");
   });
 
   it("disambiguates colliding IDs with a suffix", () => {
@@ -272,8 +274,8 @@ describe("parseGsapScript", () => {
     `;
     const result = parseGsapScript(script);
 
-    expect(result.animations[0].id).toBe("#el1-to-0");
-    expect(result.animations[1].id).toBe("#el1-to-0-2");
+    expect(result.animations[0].id).toBe("#el1-to-0-visual");
+    expect(result.animations[1].id).toBe("#el1-to-0-visual-2");
   });
 
   it("uses string position in ID for relative positions", () => {
@@ -283,7 +285,219 @@ describe("parseGsapScript", () => {
     `;
     const result = parseGsapScript(script);
 
-    expect(result.animations[0].id).toBe("#el1-to-+=1");
+    expect(result.animations[0].id).toBe("#el1-to-+=1-visual");
+  });
+});
+
+describe("resolvedStart — timeline position resolution", () => {
+  it("resolves chained from() tweens with relative positions (sdk-test pattern)", () => {
+    const script = `
+      const tl = gsap.timeline({ defaults: { ease: "power3.out" } });
+      tl.from("#headline", { duration: 0.6, scale: 0.92, transformOrigin: "left center" })
+        .from("#subtext",  { duration: 0.5, scale: 0.92, transformOrigin: "left center" }, "-=0.3")
+        .from("#box",      { duration: 0.5, scale: 0.5,  transformOrigin: "center center" }, "-=0.3");
+    `;
+    const result = parseGsapScript(script);
+
+    expect(result.animations).toHaveLength(3);
+    // Execution order: #headline, #subtext, #box
+    expect(result.animations[0].targetSelector).toBe("#headline");
+    expect(result.animations[1].targetSelector).toBe("#subtext");
+    expect(result.animations[2].targetSelector).toBe("#box");
+
+    // #headline: implicit position → starts at 0, ends at 0.6
+    expect(result.animations[0].resolvedStart).toBe(0);
+    expect(result.animations[0].implicitPosition).toBe(true);
+
+    // #subtext: "-=0.3" from cursor (0.6) → 0.6 - 0.3 = 0.3
+    expect(result.animations[1].resolvedStart).toBe(0.3);
+
+    // #box: "-=0.3" from cursor (max(0.6, 0.3+0.5=0.8) = 0.8) → 0.8 - 0.3 = 0.5
+    expect(result.animations[2].resolvedStart).toBe(0.5);
+  });
+
+  it("resolves += and < positions", () => {
+    const script = `
+      const tl = gsap.timeline({ paused: true });
+      tl.to("#el1", { opacity: 1, duration: 0.5 }, "+=1");
+      tl.to("#el2", { x: 100, duration: 1 }, "<");
+      tl.to("#el3", { y: 50, duration: 0.3 }, "-=0.5");
+    `;
+    const result = parseGsapScript(script);
+
+    // #el1: "+=1" from cursor (0) → 0 + 1 = 1, ends at 1.5
+    expect(result.animations[0].resolvedStart).toBe(1);
+
+    // #el2: "<" = previous start → 1
+    expect(result.animations[1].resolvedStart).toBe(1);
+
+    // #el3: "-=0.5" from cursor (max(1.5, 1+1=2) = 2) → 2 - 0.5 = 1.5
+    expect(result.animations[2].resolvedStart).toBe(1.5);
+  });
+
+  it("resolves numeric positions directly", () => {
+    const script = `
+      const tl = gsap.timeline({ paused: true });
+      tl.to("#el1", { opacity: 1, duration: 0.5 }, 0);
+      tl.to("#el2", { x: 100, duration: 1 }, 2);
+    `;
+    const result = parseGsapScript(script);
+
+    expect(result.animations[0].resolvedStart).toBe(0);
+    expect(result.animations[1].resolvedStart).toBe(2);
+  });
+
+  it("resolves implicit sequential positions", () => {
+    const script = `
+      const tl = gsap.timeline({ paused: true });
+      tl.to("#el1", { opacity: 1, duration: 0.5 })
+        .to("#el2", { x: 100, duration: 1 })
+        .to("#el3", { y: 50, duration: 0.3 });
+    `;
+    const result = parseGsapScript(script);
+
+    // #el1: implicit → cursor=0, ends at 0.5
+    expect(result.animations[0].resolvedStart).toBe(0);
+    expect(result.animations[0].implicitPosition).toBe(true);
+
+    // #el2: implicit → cursor=0.5, ends at 1.5
+    expect(result.animations[1].resolvedStart).toBe(0.5);
+    expect(result.animations[1].implicitPosition).toBe(true);
+
+    // #el3: implicit → cursor=1.5, ends at 1.8
+    expect(result.animations[2].resolvedStart).toBe(1.5);
+    expect(result.animations[2].implicitPosition).toBe(true);
+  });
+
+  it("clamps negative resolvedStart to 0", () => {
+    const script = `
+      const tl = gsap.timeline({ paused: true });
+      tl.to("#el1", { opacity: 1, duration: 0.2 });
+      tl.to("#el2", { x: 100, duration: 1 }, "-=5");
+    `;
+    const result = parseGsapScript(script);
+
+    expect(result.animations[1].resolvedStart).toBe(0);
+  });
+
+  it("uses GSAP default duration (0.5) for tweens with no explicit duration", () => {
+    const script = `
+      const tl = gsap.timeline({ paused: true });
+      tl.to("#el1", { opacity: 1 })
+        .to("#el2", { x: 100 });
+    `;
+    const result = parseGsapScript(script);
+
+    // #el1: starts at 0, duration defaults to 0.5 → cursor at 0.5
+    expect(result.animations[0].resolvedStart).toBe(0);
+    // #el2: starts at cursor = 0.5
+    expect(result.animations[1].resolvedStart).toBe(0.5);
+  });
+
+  it("treats set() as zero-duration", () => {
+    const script = `
+      const tl = gsap.timeline({ paused: true });
+      tl.set("#el1", { opacity: 0 });
+      tl.to("#el2", { opacity: 1, duration: 1 });
+    `;
+    const result = parseGsapScript(script);
+
+    // set() at 0, zero duration → cursor stays at 0
+    expect(result.animations[0].resolvedStart).toBe(0);
+    // next tween starts at cursor = 0
+    expect(result.animations[1].resolvedStart).toBe(0);
+  });
+});
+
+describe("timeline defaults inheritance", () => {
+  it("inherits ease and duration from timeline defaults onto tweens", () => {
+    const script = `
+      const tl = gsap.timeline({ defaults: { ease: "power3.out", duration: 0.6 } });
+      tl.from("#headline", { scale: 0.92, transformOrigin: "left center" })
+        .from("#subtext", { scale: 0.92 }, "-=0.3");
+    `;
+    const result = parseGsapScript(script);
+
+    expect(result.animations[0].ease).toBe("power3.out");
+    expect(result.animations[0].duration).toBe(0.6);
+    expect(result.animations[1].ease).toBe("power3.out");
+    expect(result.animations[1].duration).toBe(0.6);
+  });
+
+  it("does not override explicit ease/duration on individual tweens", () => {
+    const script = `
+      const tl = gsap.timeline({ defaults: { ease: "power3.out", duration: 0.6 } });
+      tl.to("#el1", { opacity: 1, duration: 1, ease: "none" });
+    `;
+    const result = parseGsapScript(script);
+
+    expect(result.animations[0].ease).toBe("none");
+    expect(result.animations[0].duration).toBe(1);
+  });
+
+  it("uses inherited duration for position resolution", () => {
+    const script = `
+      const tl = gsap.timeline({ defaults: { duration: 0.8 } });
+      tl.from("#a", { scale: 0.5 })
+        .from("#b", { scale: 0.5 });
+    `;
+    const result = parseGsapScript(script);
+
+    // #a starts at 0, duration 0.8 → cursor at 0.8
+    expect(result.animations[0].resolvedStart).toBe(0);
+    // #b starts at cursor = 0.8
+    expect(result.animations[1].resolvedStart).toBe(0.8);
+  });
+});
+
+describe("property group classification", () => {
+  it("classifies individual properties into groups", () => {
+    expect(classifyPropertyGroup("x")).toBe("position");
+    expect(classifyPropertyGroup("y")).toBe("position");
+    expect(classifyPropertyGroup("xPercent")).toBe("position");
+    expect(classifyPropertyGroup("scale")).toBe("scale");
+    expect(classifyPropertyGroup("scaleX")).toBe("scale");
+    expect(classifyPropertyGroup("width")).toBe("size");
+    expect(classifyPropertyGroup("height")).toBe("size");
+    expect(classifyPropertyGroup("rotation")).toBe("rotation");
+    expect(classifyPropertyGroup("skewX")).toBe("rotation");
+    expect(classifyPropertyGroup("opacity")).toBe("visual");
+    expect(classifyPropertyGroup("autoAlpha")).toBe("visual");
+    expect(classifyPropertyGroup("borderRadius")).toBe("other");
+    expect(classifyPropertyGroup("fontSize")).toBe("other");
+  });
+
+  it("classifies a pure position tween", () => {
+    expect(classifyTweenPropertyGroup({ x: 100, y: 50 })).toBe("position");
+  });
+
+  it("classifies a pure scale tween", () => {
+    expect(classifyTweenPropertyGroup({ scale: 0.5 })).toBe("scale");
+  });
+
+  it("classifies scale + transformOrigin as scale (transformOrigin follows group)", () => {
+    expect(classifyTweenPropertyGroup({ scale: 0.5, transformOrigin: "center center" })).toBe(
+      "scale",
+    );
+  });
+
+  it("returns undefined for mixed-group tweens", () => {
+    expect(classifyTweenPropertyGroup({ x: 100, scale: 0.5 })).toBeUndefined();
+    expect(classifyTweenPropertyGroup({ x: 100, opacity: 0 })).toBeUndefined();
+  });
+
+  it("classifies tweens during parsing", () => {
+    const script = `
+      const tl = gsap.timeline({ paused: true });
+      tl.to("#a", { x: 100, y: 50, duration: 1 }, 0);
+      tl.to("#b", { scale: 0.5, duration: 0.5 }, 0);
+      tl.to("#c", { x: 100, scale: 0.5, opacity: 0, duration: 1 }, 0);
+    `;
+    const result = parseGsapScript(script);
+
+    expect(result.animations[0].propertyGroup).toBe("position");
+    expect(result.animations[1].propertyGroup).toBe("scale");
+    expect(result.animations[2].propertyGroup).toBeUndefined();
   });
 });
 
@@ -1223,11 +1437,12 @@ describe("native GSAP keyframes parsing", () => {
     const kfs = expectKeyframesFormat(anim, "object-array", 3);
 
     // Total duration = 0.5 + 1 + 0.8 = 2.3
-    expectKeyframe(kfs[0], 0, { x: 0, opacity: 1 });
-    // Second: cumulative = 0.5, pct = round(0.5/2.3 * 100) = 22
-    expectKeyframe(kfs[1], 22, { x: 100 }, "power2.out");
-    // Third: cumulative = 1.5, pct = round(1.5/2.3 * 100) = 65
-    expectKeyframe(kfs[2], 65, { x: 200 });
+    // First: cumulative = 0.5, pct = round(0.5/2.3 * 100) = 22
+    expectKeyframe(kfs[0], 22, { x: 0, opacity: 1 });
+    // Second: cumulative = 1.5, pct = round(1.5/2.3 * 100) = 65
+    expectKeyframe(kfs[1], 65, { x: 100 }, "power2.out");
+    // Third: cumulative = 2.3, pct = round(2.3/2.3 * 100) = 100
+    expectKeyframe(kfs[2], 100, { x: 200 });
   });
 
   it("parses simple array keyframes format", () => {
@@ -1944,3 +2159,119 @@ tl.to("#el1", { y: 200, duration: 1 }, 3);`;
     expect(result.skippedSelectors).toEqual([".el1"]);
   });
 });
+
+describe("splitIntoPropertyGroups", () => {
+  const baseScript = `const tl = gsap.timeline({ paused: true });`;
+
+  it("splits flat to({x, y, scale, rotation}) into 3 group tweens", () => {
+    const script = `${baseScript}\ntl.to("#el", { x: 100, y: 50, scale: 1.5, rotation: 45, duration: 1 }, 0);`;
+    const parsed = parseGsapScript(script);
+    const animId = parsed.animations[0]!.id;
+
+    const result = splitIntoPropertyGroups(script, animId);
+    const reParsed = parseGsapScript(result.script);
+
+    // Should produce 3 tweens: position (x,y), scale, rotation
+    expect(reParsed.animations).toHaveLength(3);
+    expect(result.ids).toHaveLength(3);
+
+    const groups = new Set(reParsed.animations.map((a) => a.propertyGroup));
+    expect(groups.has("position")).toBe(true);
+    expect(groups.has("scale")).toBe(true);
+    expect(groups.has("rotation")).toBe(true);
+
+    const posAnim = reParsed.animations.find((a) => a.propertyGroup === "position")!;
+    expect(posAnim.properties.x).toBe(100);
+    expect(posAnim.properties.y).toBe(50);
+    expect(posAnim.properties.scale).toBeUndefined();
+
+    const scaleAnim = reParsed.animations.find((a) => a.propertyGroup === "scale")!;
+    expect(scaleAnim.properties.scale).toBe(1.5);
+    expect(scaleAnim.properties.x).toBeUndefined();
+
+    const rotAnim = reParsed.animations.find((a) => a.propertyGroup === "rotation")!;
+    expect(rotAnim.properties.rotation).toBe(45);
+  });
+
+  it("splits flat from({scale, opacity}) into 2 group tweens", () => {
+    const script = `${baseScript}\ntl.from("#el", { scale: 0.5, opacity: 0, duration: 0.5 }, 1);`;
+    const parsed = parseGsapScript(script);
+    const animId = parsed.animations[0]!.id;
+
+    const result = splitIntoPropertyGroups(script, animId);
+    const reParsed = parseGsapScript(result.script);
+
+    expect(reParsed.animations).toHaveLength(2);
+    expect(result.ids).toHaveLength(2);
+
+    const groups = new Set(reParsed.animations.map((a) => a.propertyGroup));
+    expect(groups.has("scale")).toBe(true);
+    expect(groups.has("visual")).toBe(true);
+  });
+
+  it("returns same ID for single-group tween (no split)", () => {
+    const script = `${baseScript}\ntl.to("#el", { x: 100, y: 50, duration: 1 }, 0);`;
+    const parsed = parseGsapScript(script);
+    const animId = parsed.animations[0]!.id;
+
+    const result = splitIntoPropertyGroups(script, animId);
+    expect(result.ids).toEqual([animId]);
+    // Script should be unchanged
+    const reParsed = parseGsapScript(result.script);
+    expect(reParsed.animations).toHaveLength(1);
+  });
+
+  it("preserves position, duration, ease on split tweens", () => {
+    const script = `${baseScript}\ntl.to("#el", { x: 100, scale: 2, duration: 0.8, ease: "power2.out" }, 1.5);`;
+    const parsed = parseGsapScript(script);
+    const animId = parsed.animations[0]!.id;
+
+    const result = splitIntoPropertyGroups(script, animId);
+    const reParsed = parseGsapScript(result.script);
+
+    expect(reParsed.animations).toHaveLength(2);
+    for (const anim of reParsed.animations) {
+      expect(anim.position).toBe(1.5);
+      expect(anim.duration).toBe(0.8);
+      expect(anim.ease).toBe("power2.out");
+    }
+  });
+
+  it("splits keyframed tween: each group gets only its properties per keyframe", () => {
+    const script = `${baseScript}\ntl.to("#el", { keyframes: { "0%": { x: 0, scale: 1 }, "50%": { x: 50, scale: 1.5 }, "100%": { x: 100, scale: 2 } }, duration: 2 }, 0);`;
+    const parsed = parseGsapScript(script);
+    const animId = parsed.animations[0]!.id;
+
+    const result = splitIntoPropertyGroups(script, animId);
+    const reParsed = parseGsapScript(result.script);
+
+    expect(reParsed.animations).toHaveLength(2);
+    expect(result.ids).toHaveLength(2);
+
+    // Both tweens are keyframed — identify them by the properties inside their keyframes.
+    const xAnim = reParsed.animations.find((a) =>
+      a.keyframes?.keyframes.some((kf) => "x" in kf.properties),
+    )!;
+    const scaleAnim = reParsed.animations.find((a) =>
+      a.keyframes?.keyframes.some((kf) => "scale" in kf.properties),
+    )!;
+
+    expect(xAnim).toBeDefined();
+    expect(xAnim.keyframes).toBeDefined();
+    expect(xAnim.keyframes!.keyframes).toHaveLength(3);
+    // Position keyframes should have x but not scale
+    for (const kf of xAnim.keyframes!.keyframes) {
+      expect(kf.properties.x).toBeDefined();
+      expect(kf.properties.scale).toBeUndefined();
+    }
+
+    expect(scaleAnim).toBeDefined();
+    expect(scaleAnim.keyframes).toBeDefined();
+    expect(scaleAnim.keyframes!.keyframes).toHaveLength(3);
+    // Scale keyframes should have scale but not x
+    for (const kf of scaleAnim.keyframes!.keyframes) {
+      expect(kf.properties.scale).toBeDefined();
+      expect(kf.properties.x).toBeUndefined();
+    }
+  });
+});

packages/core/src/parsers/gsapParser.ts

@@ -39,6 +39,14 @@ export {
   SUPPORTED_PROPS,
   SUPPORTED_EASES,
 } from "./gsapSerialize";
+export type { PropertyGroupName } from "./gsapConstants";
+export {
+  PROPERTY_GROUPS,
+  classifyPropertyGroup,
+  classifyTweenPropertyGroup,
+} from "./gsapConstants";
+import { classifyPropertyGroup, classifyTweenPropertyGroup } from "./gsapConstants";
+import type { PropertyGroupName } from "./gsapConstants";
 export { generateSpringEaseData, SPRING_PRESETS } from "./springEase";
 export type { SpringPreset } from "./springEase";
 
@@ -343,19 +351,47 @@ function isGsapTimelineCall(node: any): boolean {
   );
 }
 
+interface TimelineDefaults {
+  ease?: string;
+  duration?: number;
+}
+
 interface TimelineDetection {
   timelineVar: string | null;
   timelineCount: number;
+  defaults?: TimelineDefaults;
 }
 
-function findTimelineVar(ast: any): TimelineDetection {
+function extractTimelineDefaults(
+  callNode: any,
+  scope: ScopeBindings,
+): TimelineDefaults | undefined {
+  const arg = callNode.arguments?.[0];
+  if (!arg || arg.type !== "ObjectExpression") return undefined;
+  const defaultsProp = arg.properties?.find(
+    (p: any) => isObjectProperty(p) && propKeyName(p) === "defaults",
+  );
+  if (!defaultsProp?.value || defaultsProp.value.type !== "ObjectExpression") return undefined;
+  const record = objectExpressionToRecord(defaultsProp.value, scope);
+  const result: TimelineDefaults = {};
+  if (typeof record.ease === "string") result.ease = record.ease;
+  if (typeof record.duration === "number") result.duration = record.duration;
+  return Object.keys(result).length > 0 ? result : undefined;
+}
+
+function findTimelineVar(ast: any, scope?: ScopeBindings): TimelineDetection {
   let timelineVar: string | null = null;
   let timelineCount = 0;
+  let defaults: TimelineDefaults | undefined;
+  const emptyScope: ScopeBindings = scope ?? new Map();
   recast.types.visit(ast, {
     visitVariableDeclarator(path: any) {
       if (isGsapTimelineCall(path.node.init)) {
         timelineCount += 1;
-        if (!timelineVar) timelineVar = path.node.id?.name ?? null;
+        if (!timelineVar) {
+          timelineVar = path.node.id?.name ?? null;
+          defaults = extractTimelineDefaults(path.node.init, emptyScope);
+        }
       }
       this.traverse(path);
     },
@@ -365,12 +401,13 @@ function findTimelineVar(ast: any): TimelineDetection {
         if (!timelineVar) {
           const left = path.node.left;
           if (left?.type === "Identifier") timelineVar = left.name;
+          defaults = extractTimelineDefaults(path.node.right, emptyScope);
         }
       }
       this.traverse(path);
     },
   });
-  return { timelineVar, timelineCount };
+  return { timelineVar, timelineCount, defaults };
 }
 
 // ── Find All Tween Calls ────────────────────────────────────────────────────
@@ -632,13 +669,13 @@ function parseObjectArrayKeyframes(node: any, scope: ScopeBindings): GsapKeyfram
   if (totalDuration > 0) {
     let cumulative = 0;
     for (const entry of raw) {
+      cumulative += entry.duration ?? 0;
       const percentage = Math.round((cumulative / totalDuration) * 100);
       keyframes.push({
         percentage,
         properties: entry.properties,
         ...(entry.ease ? { ease: entry.ease } : {}),
       });
-      cumulative += entry.duration ?? 0;
     }
   } else {
     for (let i = 0; i < raw.length; i++) {
@@ -872,7 +909,8 @@ function tweenCallToAnimation(
     }
   }
 
-  const posVal = call.positionArg ? extractLiteralValue(call.positionArg, scope) : 0;
+  const hasPositionArg = !!call.positionArg;
+  const posVal = hasPositionArg ? extractLiteralValue(call.positionArg, scope) : 0;
   const position: number | string =
     typeof posVal === "number" ? posVal : typeof posVal === "string" ? posVal : 0;
   let duration = typeof vars.duration === "number" ? vars.duration : undefined;
@@ -891,6 +929,16 @@ function tweenCallToAnimation(
     duration,
     ease,
   };
+  if (!hasPositionArg) anim.implicitPosition = true;
+  let group = classifyTweenPropertyGroup(properties);
+  if (!group && keyframesData) {
+    const kfProps: Record<string, unknown> = {};
+    for (const kf of keyframesData.keyframes) {
+      for (const k of Object.keys(kf.properties)) kfProps[k] = true;
+    }
+    group = classifyTweenPropertyGroup(kfProps);
+  }
+  if (group) anim.propertyGroup = group;
   if (Object.keys(extras).length > 0) anim.extras = extras;
   if (keyframesData) anim.keyframes = keyframesData;
   if (motionPathResult) anim.arcPath = motionPathResult.arcPath;
@@ -899,8 +947,96 @@ function tweenCallToAnimation(
   return anim;
 }
 
+// ── Timeline Position Resolution ──────────────────────────────────────────
+
+const GSAP_DEFAULT_DURATION = 0.5;
+
+// NOTE: Label-based positions (e.g. "myLabel+=0.5") are not yet resolved —
+// they fall through to parseFloat which returns null for non-numeric strings.
+function resolvePositionString(pos: string, cursor: number, prevStart: number): number | null {
+  const trimmed = pos.trim();
+  if (trimmed === "") return cursor;
+  if (trimmed.startsWith("+=")) {
+    const n = Number.parseFloat(trimmed.slice(2));
+    return Number.isFinite(n) ? cursor + n : null;
+  }
+  if (trimmed.startsWith("-=")) {
+    const n = Number.parseFloat(trimmed.slice(2));
+    return Number.isFinite(n) ? cursor - n : null;
+  }
+  if (trimmed === "<") return prevStart;
+  if (trimmed === ">") return cursor;
+  if (trimmed.startsWith("<")) {
+    const n = Number.parseFloat(trimmed.slice(1));
+    return Number.isFinite(n) ? prevStart + n : null;
+  }
+  if (trimmed.startsWith(">")) {
+    const n = Number.parseFloat(trimmed.slice(1));
+    return Number.isFinite(n) ? cursor + n : null;
+  }
+  const n = Number.parseFloat(trimmed);
+  return Number.isFinite(n) ? n : null;
+}
+
+function applyTimelineDefaults(
+  anims: Omit<GsapAnimation, "id">[],
+  defaults?: TimelineDefaults,
+): void {
+  if (!defaults) return;
+  for (const anim of anims) {
+    if (anim.method === "set") continue;
+    if (anim.duration === undefined && defaults.duration !== undefined) {
+      anim.duration = defaults.duration;
+    }
+    if (anim.ease === undefined && defaults.ease !== undefined) {
+      anim.ease = defaults.ease;
+    }
+  }
+}
+
+function resolveTimelinePositions(anims: Omit<GsapAnimation, "id">[]): void {
+  let cursor = 0;
+  let prevStart = 0;
+  for (const anim of anims) {
+    const duration = anim.method === "set" ? 0 : (anim.duration ?? GSAP_DEFAULT_DURATION);
+    let start: number | null;
+
+    if (anim.implicitPosition) {
+      start = cursor;
+    } else if (typeof anim.position === "number") {
+      start = anim.position;
+    } else if (typeof anim.position === "string") {
+      start = resolvePositionString(anim.position, cursor, prevStart);
+    } else {
+      start = cursor;
+    }
+
+    if (start != null) {
+      anim.resolvedStart = Math.max(0, start);
+      prevStart = anim.resolvedStart;
+      cursor = Math.max(cursor, anim.resolvedStart + duration);
+    }
+  }
+}
+
+function sortBySourcePosition(calls: TweenCallInfo[]): void {
+  calls.sort((a, b) => {
+    const aLoc = a.node.callee?.property?.loc?.start;
+    const bLoc = b.node.callee?.property?.loc?.start;
+    if (!aLoc || !bLoc) return 0;
+    return aLoc.line - bLoc.line || aLoc.column - bLoc.column;
+  });
+}
+
 // ── Stable ID Generation ───────────────────────────────────────────────────
 
+/**
+ * IDs are transient — recomputed on every parse, never persisted across sessions.
+ * They exist only in ephemeral request/response payloads, React component state,
+ * and the in-memory keyframe cache (rebuilt on every page load). No database,
+ * localStorage, or file stores animation IDs, so changing the ID format (e.g.
+ * adding a `-scale`/`-position` suffix) is safe.
+ */
 function assignStableIds(anims: Omit<GsapAnimation, "id">[]): GsapAnimation[] {
   const counts = new Map<string, number>();
   return anims.map((anim) => {
@@ -908,7 +1044,8 @@ function assignStableIds(anims: Omit<GsapAnimation, "id">[]): GsapAnimation[] {
       typeof anim.position === "number"
         ? String(Math.round(anim.position * 1000))
         : String(anim.position);
-    const base = `${anim.targetSelector}-${anim.method}-${posKey}`;
+    const groupSuffix = anim.propertyGroup ? `-${anim.propertyGroup}` : "";
+    const base = `${anim.targetSelector}-${anim.method}-${posKey}${groupSuffix}`;
     const count = (counts.get(base) ?? 0) + 1;
     counts.set(base, count);
     const id = count === 1 ? base : `${base}-${count}`;
@@ -937,10 +1074,14 @@ function parseGsapAst(script: string): ParsedGsapAst {
   const ast = parseScript(script);
   const scope = collectScopeBindings(ast);
   const targetBindings = collectTargetBindings(ast, scope);
-  const detection = findTimelineVar(ast);
+  const detection = findTimelineVar(ast, scope);
   const timelineVar = detection.timelineVar ?? "tl";
   const calls = findAllTweenCalls(ast, timelineVar, scope, targetBindings);
-  const animations = assignStableIds(calls.map((call) => tweenCallToAnimation(call, scope)));
+  sortBySourcePosition(calls);
+  const rawAnims = calls.map((call) => tweenCallToAnimation(call, scope));
+  applyTimelineDefaults(rawAnims, detection.defaults);
+  resolveTimelinePositions(rawAnims);
+  const animations = assignStableIds(rawAnims);
   const located = animations.map((animation, i) => ({
     id: animation.id,
     call: calls[i]!,
@@ -1300,7 +1441,11 @@ export function removeAnimationFromScript(script: string, animationId: string):
     console.warn("[gsap-parser] removeAnimationFromScript parse failed:", e);
     return script;
   }
-  const target = parsed.located.find((l) => l.id === animationId);
+  let target = parsed.located.find((l) => l.id === animationId);
+  if (!target) {
+    const convertedId = animationId.replace(/-from-|-fromTo-/, "-to-");
+    target = parsed.located.find((l) => l.id === convertedId);
+  }
   if (!target) return script;
   const node = target.call.node;
   const stmtPath = findStatementPath(target.call.path);
@@ -1514,6 +1659,21 @@ function percentageFromKey(key: string): number {
   return m ? Number.parseFloat(m[1]!) : Number.NaN;
 }
 
+const PCT_TOLERANCE = 2;
+
+function findKeyframePropByPct(kfNode: any, percentage: number): { idx: number; prop: any } | null {
+  const props = kfNode.properties;
+  for (let i = 0; i < props.length; i++) {
+    if (!isObjectProperty(props[i])) continue;
+    const key = propKeyName(props[i]);
+    if (typeof key !== "string") continue;
+    const parsed = percentageFromKey(key);
+    if (Number.isNaN(parsed)) continue;
+    if (Math.abs(parsed - percentage) <= PCT_TOLERANCE) return { idx: i, prop: props[i] };
+  }
+  return null;
+}
+
 /** Build a keyframe value AST node from properties and optional ease. */
 function buildKeyframeValueNode(properties: Record<string, number | string>, ease?: string): any {
   const entries = Object.entries(properties).map(([k, v]) => `${safeKey(k)}: ${valueToCode(v)}`);
@@ -1571,7 +1731,11 @@ function collapseKeyframesToFlat(varsArg: any, record: Record<string, unknown>):
  * updateKeyframeInScript.
  */
 function locateKeyframeCtx(script: string, animationId: string, percentage: number) {
-  const loc = locateAnimation(script, animationId);
+  let loc = locateAnimation(script, animationId);
+  if (!loc) {
+    const convertedId = animationId.replace(/-from-|-fromTo-/, "-to-");
+    loc = locateAnimation(script, convertedId);
+  }
   if (!loc) return null;
   const kfNode = findKeyframesObjectNode(loc.target.call.varsArg);
   if (!kfNode) return null;
@@ -1613,12 +1777,20 @@ export function addKeyframeToScript(
 
   const newValueNode = buildKeyframeValueNode(properties, ease);
 
-  // Replace if this percentage already exists
-  const existingIdx = kfNode.properties.findIndex(
-    (p: any) => isObjectProperty(p) && propKeyName(p) === pctKey,
-  );
-  if (existingIdx !== -1) {
-    kfNode.properties[existingIdx].value = newValueNode;
+  // Merge into existing keyframe at this percentage, or insert new
+  const existing = findKeyframePropByPct(kfNode, percentage);
+  if (existing) {
+    if (existing.prop.value?.type === "ObjectExpression") {
+      const existingRecord = objectExpressionToRecord(existing.prop.value, loc.parsed.scope);
+      const merged = { ...existingRecord };
+      for (const [k, v] of Object.entries(properties)) merged[k] = v;
+      existing.prop.value = buildKeyframeValueNode(
+        merged as Record<string, number | string>,
+        ease ?? (typeof existingRecord.ease === "string" ? existingRecord.ease : undefined),
+      );
+    } else {
+      existing.prop.value = newValueNode;
+    }
   } else {
     // Build the new property node with a quoted percentage key
     const newProp = parseExpr(`{ ${JSON.stringify(pctKey)}: {} }`).properties[0];
@@ -1703,12 +1875,11 @@ export function removeKeyframeFromScript(
 ): string {
   const ctx = locateKeyframeCtx(script, animationId, percentage);
   if (!ctx) return script;
-  const { loc, kfNode, pctKey } = ctx;
+  const { loc, kfNode } = ctx;
 
-  const removeIdx = kfNode.properties.findIndex(
-    (p: any) => isObjectProperty(p) && propKeyName(p) === pctKey,
-  );
-  if (removeIdx === -1) return script;
+  const match = findKeyframePropByPct(kfNode, percentage);
+  if (!match) return script;
+  const removeIdx = match.idx;
 
   kfNode.properties.splice(removeIdx, 1);
 
@@ -1736,14 +1907,12 @@ export function updateKeyframeInScript(
 ): string {
   const ctx = locateKeyframeCtx(script, animationId, percentage);
   if (!ctx) return script;
-  const { loc, kfNode, pctKey } = ctx;
+  const { loc, kfNode } = ctx;
 
-  const existing = kfNode.properties.find(
-    (p: any) => isObjectProperty(p) && propKeyName(p) === pctKey,
-  );
-  if (!existing) return script;
+  const match = findKeyframePropByPct(kfNode, percentage);
+  if (!match) return script;
 
-  existing.value = buildKeyframeValueNode(properties, ease);
+  match.prop.value = buildKeyframeValueNode(properties, ease);
   return recast.print(loc.parsed.ast).code;
 }
 
@@ -1760,32 +1929,47 @@ function cssIdentityValue(prop: string): number {
   return CSS_IDENTITY[prop] ?? 0;
 }
 
+/**
+ * Resolve the 0% (from) and 100% (to) property maps for a tween being
+ * converted to percentage keyframes.
+ *
+ * @param resolvedFromValues — Despite the "from" in the name (historical), these
+ *   are runtime-captured DOM values that override the conversion endpoint:
+ *   - For to():    overrides fromProps (the 0% state / where the element is now).
+ *   - For from():  overrides toProps  (the 100% state / where the element rests).
+ *   - For fromTo(): merges into toProps (the 100% endpoint the user is editing).
+ */
 function resolveConversionProps(
   anim: GsapAnimation,
   resolvedFromValues?: Record<string, number | string>,
 ): { fromProps: Record<string, number | string>; toProps: Record<string, number | string> } {
   if (anim.method === "to") {
-    if (resolvedFromValues) {
-      return { fromProps: resolvedFromValues, toProps: { ...anim.properties } };
-    }
     const identityFrom: Record<string, number | string> = {};
     for (const [key, val] of Object.entries(anim.properties)) {
       if (val != null) identityFrom[key] = typeof val === "number" ? cssIdentityValue(key) : val;
     }
-    return { fromProps: identityFrom, toProps: { ...anim.properties } };
+    const fromProps = resolvedFromValues
+      ? { ...identityFrom, ...resolvedFromValues }
+      : identityFrom;
+    return { fromProps, toProps: { ...anim.properties } };
   }
   if (anim.method === "from") {
-    if (resolvedFromValues) {
-      return { fromProps: { ...anim.properties }, toProps: resolvedFromValues };
-    }
     const identityTo: Record<string, number | string> = {};
     for (const [key, val] of Object.entries(anim.properties)) {
       if (val != null) identityTo[key] = typeof val === "number" ? cssIdentityValue(key) : val;
     }
-    return { fromProps: { ...anim.properties }, toProps: identityTo };
+    const toProps = resolvedFromValues ? { ...identityTo, ...resolvedFromValues } : identityTo;
+    return { fromProps: { ...anim.properties }, toProps };
   }
-  // fromTo
-  return { fromProps: { ...(anim.fromProperties ?? {}) }, toProps: { ...anim.properties } };
+  // fromTo(fromVars, toVars): anim.fromProperties = fromVars (0% state),
+  // anim.properties = toVars (100% state). resolvedFromValues contains the
+  // current DOM position from a drag — it represents the NEW destination, so
+  // it merges into toProps (the 100% endpoint the user is editing), NOT into
+  // fromProps. This is intentional and not inverted.
+  const toProps = resolvedFromValues
+    ? { ...anim.properties, ...resolvedFromValues }
+    : { ...anim.properties };
+  return { fromProps: { ...(anim.fromProperties ?? {}) }, toProps };
 }
 
 /** Strip editable properties and ease/keyframes keys from a varsArg. */
@@ -1827,7 +2011,11 @@ export function convertToKeyframesInScript(
   animationId: string,
   resolvedFromValues?: Record<string, number | string>,
 ): string {
-  const loc = locateAnimation(script, animationId);
+  let loc = locateAnimation(script, animationId);
+  if (!loc) {
+    const convertedId = animationId.replace(/-from-|-fromTo-/, "-to-");
+    loc = locateAnimation(script, convertedId);
+  }
   if (!loc) return script;
 
   const anim = loc.target.animation;
@@ -1858,7 +2046,11 @@ export function convertToKeyframesInScript(
  * last keyframe's properties.
  */
 export function removeAllKeyframesFromScript(script: string, animationId: string): string {
-  const loc = locateAnimation(script, animationId);
+  let loc = locateAnimation(script, animationId);
+  if (!loc) {
+    const convertedId = animationId.replace(/-from-|-fromTo-/, "-to-");
+    loc = locateAnimation(script, convertedId);
+  }
   if (!loc) return script;
   const kfNode = findKeyframesObjectNode(loc.target.call.varsArg);
   if (!kfNode) return script;
@@ -1894,7 +2086,11 @@ export function materializeKeyframesInScript(
   easeEach?: string,
   resolvedSelector?: string,
 ): string {
-  const loc = locateAnimation(script, animationId);
+  let loc = locateAnimation(script, animationId);
+  if (!loc) {
+    const convertedId = animationId.replace(/-from-|-fromTo-/, "-to-");
+    loc = locateAnimation(script, convertedId);
+  }
   if (!loc) return script;
 
   const varsArg = loc.target.call.varsArg;
@@ -2143,6 +2339,156 @@ export function removeArcPathFromScript(script: string, animationId: string): st
   });
 }
 
+// ── Split Into Property Groups ────────────────────────────────────────────
+
+/**
+ * Split a multi-group tween into separate per-group tweens. Each resulting
+ * tween contains only properties belonging to one property group (position,
+ * scale, rotation, visual, etc.). `transformOrigin` stays with the group that
+ * has the most properties. If the tween already belongs to a single group,
+ * returns the script unchanged with the original ID.
+ */
+// fallow-ignore-next-line complexity
+export function splitIntoPropertyGroups(
+  script: string,
+  animationId: string,
+): { script: string; ids: string[] } {
+  let loc = locateAnimation(script, animationId);
+  if (!loc) {
+    const convertedId = animationId.replace(/-from-|-fromTo-/, "-to-");
+    loc = locateAnimation(script, convertedId);
+  }
+  if (!loc) return { script, ids: [animationId] };
+
+  const anim = loc.target.animation;
+
+  // Collect the properties to partition. For keyframed tweens, gather the
+  // union of all properties across all keyframes. For flat tweens, use the
+  // tween's own properties map.
+  const allPropKeys = new Set<string>();
+  if (anim.keyframes) {
+    for (const kf of anim.keyframes.keyframes) {
+      for (const k of Object.keys(kf.properties)) allPropKeys.add(k);
+    }
+  } else {
+    for (const k of Object.keys(anim.properties)) allPropKeys.add(k);
+  }
+
+  // Partition properties into groups (excluding transformOrigin — handled below).
+  const groupProps = new Map<PropertyGroupName, string[]>();
+  for (const key of allPropKeys) {
+    if (key === "transformOrigin") continue;
+    const group = classifyPropertyGroup(key);
+    let arr = groupProps.get(group);
+    if (!arr) {
+      arr = [];
+      groupProps.set(group, arr);
+    }
+    arr.push(key);
+  }
+
+  // Only one group (or zero) — no split needed.
+  if (groupProps.size <= 1) return { script, ids: [anim.id] };
+
+  // Assign transformOrigin to the group with the most properties.
+  if (allPropKeys.has("transformOrigin")) {
+    let largestGroup: PropertyGroupName | undefined;
+    let largestCount = 0;
+    for (const [group, props] of groupProps) {
+      if (props.length > largestCount) {
+        largestCount = props.length;
+        largestGroup = group;
+      }
+    }
+    if (largestGroup) {
+      groupProps.get(largestGroup)!.push("transformOrigin");
+    }
+  }
+
+  // Build per-group tweens and insert them, then remove the original.
+  let result = script;
+
+  // Remove the original tween first.
+  result = removeAnimationFromScript(result, anim.id);
+
+  // Insert one tween per group. Iteration order of the Map follows insertion
+  // order, which mirrors the order properties were encountered.
+  for (const [, props] of groupProps) {
+    const propSet = new Set(props);
+
+    if (anim.keyframes) {
+      // Build keyframes containing only this group's properties per keyframe.
+      const groupKeyframes: Array<{
+        percentage: number;
+        properties: Record<string, number | string>;
+        ease?: string;
+        auto?: boolean;
+      }> = [];
+
+      for (const kf of anim.keyframes.keyframes) {
+        const filtered: Record<string, number | string> = {};
+        for (const [k, v] of Object.entries(kf.properties)) {
+          if (propSet.has(k)) filtered[k] = v;
+        }
+        // Skip keyframes where this group has zero properties.
+        if (Object.keys(filtered).length === 0) continue;
+        groupKeyframes.push({
+          percentage: kf.percentage,
+          properties: filtered,
+          ...(kf.ease ? { ease: kf.ease } : {}),
+        });
+      }
+
+      if (groupKeyframes.length === 0) continue;
+
+      const addResult = addAnimationWithKeyframesToScript(
+        result,
+        anim.targetSelector,
+        typeof anim.position === "number" ? anim.position : 0,
+        anim.duration ?? 0.5,
+        groupKeyframes,
+        anim.keyframes.easeEach ?? anim.ease,
+      );
+      result = addResult.script;
+    } else {
+      // Flat tween — filter properties to this group.
+      const groupProperties: Record<string, number | string> = {};
+      for (const [k, v] of Object.entries(anim.properties)) {
+        if (propSet.has(k)) groupProperties[k] = v;
+      }
+      if (Object.keys(groupProperties).length === 0) continue;
+
+      let fromProperties: Record<string, number | string> | undefined;
+      if (anim.method === "fromTo" && anim.fromProperties) {
+        fromProperties = {};
+        for (const [k, v] of Object.entries(anim.fromProperties)) {
+          if (propSet.has(k)) fromProperties[k] = v;
+        }
+      }
+
+      const addResult = addAnimationToScript(result, {
+        targetSelector: anim.targetSelector,
+        method: anim.method,
+        position: anim.position,
+        duration: anim.duration,
+        ease: anim.ease,
+        properties: groupProperties,
+        fromProperties,
+        extras: anim.extras,
+      });
+      result = addResult.script;
+    }
+  }
+
+  // Re-parse to collect the new IDs.
+  const reParsed = parseGsapAst(result);
+  const newIds = reParsed.located
+    .filter((l) => l.animation.targetSelector === anim.targetSelector)
+    .map((l) => l.id);
+
+  return { script: result, ids: newIds };
+}
+
 /**
  * Replace a dynamic loop that generates multiple tween calls with individual
  * static `tl.to()` calls — one per element. Finds the loop containing the
@@ -2213,7 +2559,7 @@ export function unrollDynamicAnimations(
       kfEntries.push(`easeEach: ${JSON.stringify(el.easeEach)}`);
     }
     calls.push(
-      `tl.to(${JSON.stringify(el.selector)}, { keyframes: { ${kfEntries.join(", ")} }, duration: ${duration}, ease: ${JSON.stringify(ease)} }, ${posCode});`,
+      `${loc.parsed.timelineVar}.to(${JSON.stringify(el.selector)}, { keyframes: { ${kfEntries.join(", ")} }, duration: ${duration}, ease: ${JSON.stringify(ease)} }, ${posCode});`,
     );
   }
 

packages/core/src/parsers/gsapSerialize.ts

@@ -7,6 +7,7 @@
  * parsing of GSAP source lives in the Node-only `./gsapParser` module.
  */
 import type { Keyframe, KeyframeProperties, ValidationResult } from "../core.types";
+import type { PropertyGroupName } from "./gsapConstants";
 
 export type GsapMethod = "set" | "to" | "from" | "fromTo";
 
@@ -29,6 +30,13 @@ export interface GsapAnimation {
   hasUnresolvedKeyframes?: boolean;
   /** True when the tween's target selector couldn't be statically resolved (dynamic). */
   hasUnresolvedSelector?: boolean;
+  /** Absolute start time computed by walking the timeline chain (handles +=, -=, <, >, labels). */
+  resolvedStart?: number;
+  /** True when no position arg was authored — the tween is sequentially placed by GSAP. */
+  implicitPosition?: boolean;
+  /** Which property group this tween belongs to (position, scale, size, rotation, visual, other).
+   *  Undefined for legacy mixed tweens that bundle multiple groups. */
+  propertyGroup?: PropertyGroupName;
 }
 
 export interface GsapPercentageKeyframe {
@@ -77,8 +85,10 @@ export function serializeGsapAnimations(
   options?: { includeMediaSync?: boolean; preamble?: string; postamble?: string },
 ): string {
   const sorted = [...animations].sort((a, b) => {
-    const aNum = typeof a.position === "number" ? a.position : Number.MAX_SAFE_INTEGER;
-    const bNum = typeof b.position === "number" ? b.position : Number.MAX_SAFE_INTEGER;
+    const aNum =
+      a.resolvedStart ?? (typeof a.position === "number" ? a.position : Number.MAX_SAFE_INTEGER);
+    const bNum =
+      b.resolvedStart ?? (typeof b.position === "number" ? b.position : Number.MAX_SAFE_INTEGER);
     return aNum - bNum;
   });
   const lines = sorted.map((anim) => {