diff --git a/packages/parsers/src/gsapParser.test.ts b/packages/parsers/src/gsapParser.test.ts
index 11b592f9ae..e931a95722 100644
--- a/packages/parsers/src/gsapParser.test.ts
+++ b/packages/parsers/src/gsapParser.test.ts
@@ -656,6 +656,27 @@ describe("stagger/yoyo/repeat round-trip", () => {
   });
 });
 
+describe("object keyframe per-step duration is not an animatable property", () => {
+  it("excludes `duration` from %-keyed keyframe properties (segment timing must not become a lane)", () => {
+    // A %-keyed object keyframe carrying a stray per-step `duration` — the shape
+    // a buggy array->object conversion produces. `duration` is GSAP segment
+    // timing, not a property; it must never surface as a keyframe lane or get
+    // round-tripped as an animatable value (which corrupts the tween on edit).
+    const script = `
+      const tl = gsap.timeline({ paused: true });
+      tl.to("#card", { keyframes: { "0%": { x: 0, duration: 0 }, "50%": { x: 100, duration: 6, ease: "power2.out" }, "100%": { x: 200, duration: 6 } } }, 0);
+    `;
+    const parsed = parseGsapScript(script);
+    const kfs = parsed.animations[0].keyframes?.keyframes ?? [];
+    expect(kfs.length).toBe(3);
+    for (const kf of kfs) {
+      expect(kf.properties).not.toHaveProperty("duration"); // the fix
+      expect(kf.properties).toHaveProperty("x"); // real animatable prop preserved
+    }
+    expect(kfs[1]?.ease).toBe("power2.out"); // per-keyframe ease still parsed
+  });
+});
+
 describe("unresolvable value round-trip", () => {
   it("preserves unresolvable property values through serialize", () => {
     const script = `
diff --git a/packages/parsers/src/gsapParser.ts b/packages/parsers/src/gsapParser.ts
index 315c238c8f..59bc432a85 100644
--- a/packages/parsers/src/gsapParser.ts
+++ b/packages/parsers/src/gsapParser.ts
@@ -686,6 +686,12 @@ function parsePercentageKeyframes(node: AstNode, scope: ScopeBindings): GsapKeyf
       for (const [k, v] of Object.entries(record)) {
         if (k === "ease" && typeof v === "string") {
           kfEase = v;
+        } else if (k === "duration") {
+          // `duration` is array-keyframe segment timing, not an animatable
+          // property. In a %-keyed object keyframe the % key owns timing, so a
+          // per-step `duration` is neither timing nor a property — skip it, or
+          // it surfaces as a bogus keyframe lane and corrupts the round-trip.
+          continue;
         } else if (typeof v === "number" || typeof v === "string") {
           properties[k] = v;
         }
diff --git a/packages/parsers/src/gsapParserAcorn.full.test.ts b/packages/parsers/src/gsapParserAcorn.full.test.ts
index eca4213a05..9eeab50737 100644
--- a/packages/parsers/src/gsapParserAcorn.full.test.ts
+++ b/packages/parsers/src/gsapParserAcorn.full.test.ts
@@ -84,6 +84,24 @@ const REAL_WORLD_SCRIPT = `(function () {
 // ── parseGsapScript ───────────────────────────────────────────────────────────
 
 describe("parseGsapScript", () => {
+  it("excludes per-step `duration` from %-keyed keyframe properties (segment timing is not a lane)", () => {
+    // A %-keyed object keyframe carrying a stray per-step `duration` — the shape
+    // a buggy array->object conversion produces. `duration` is GSAP segment
+    // timing, not an animatable property; it must not surface as a keyframe lane
+    // or round-trip as a property (which corrupts the tween on the next edit).
+    const script = `
+      const tl = gsap.timeline({ paused: true });
+      tl.to("#card", { keyframes: { "0%": { x: 0, duration: 0 }, "50%": { x: 100, duration: 6, ease: "power2.out" }, "100%": { x: 200, duration: 6 } } }, 0);
+    `;
+    const anim = parseGsapScript(script).animations[0]!;
+    const kfs = expectKeyframesFormat(anim, "percentage", 3);
+    for (const kf of kfs) {
+      expect(kf.properties).not.toHaveProperty("duration"); // the fix
+      expect(kf.properties).toHaveProperty("x"); // real animatable prop preserved
+    }
+    expect(kfs[1]!.ease).toBe("power2.out"); // per-keyframe ease still parsed
+  });
+
   it("parses a basic timeline with .to()", () => {
     const script = `
       const tl = gsap.timeline({ paused: true });
diff --git a/packages/parsers/src/gsapParserAcorn.ts b/packages/parsers/src/gsapParserAcorn.ts
index 048e0befd5..5e369e14ff 100644
--- a/packages/parsers/src/gsapParserAcorn.ts
+++ b/packages/parsers/src/gsapParserAcorn.ts
@@ -854,6 +854,14 @@ function parsePercentageKeyframes(
       for (const [k, v] of Object.entries(record)) {
         if (k === "ease" && typeof v === "string") {
           kfEase = v;
+        } else if (k === "duration") {
+          // `duration` is array-keyframe SEGMENT TIMING, not an animatable
+          // property. In a %-keyed object keyframe the % key owns timing, so a
+          // per-step `duration` is neither timing nor a property here. Skip it
+          // (parseObjectArrayKeyframes already does) — otherwise it surfaces as
+          // a bogus "duration" keyframe lane and gets round-tripped as a
+          // property, corrupting the tween on the next manual edit.
+          continue;
         } else if (typeof v === "number" || typeof v === "string") {
           properties[k] = v;
         }