diff --git a/packages/studio-server/src/routes/files.test.ts b/packages/studio-server/src/routes/files.test.ts
index b6610146c5..306efb3f44 100644
--- a/packages/studio-server/src/routes/files.test.ts
+++ b/packages/studio-server/src/routes/files.test.ts
@@ -1307,30 +1307,40 @@ tl.fromTo("#box", { opacity: 0, x: -50 }, { opacity: 1, x: 0, duration: 1.5, eas
   });
 
   it("rejects a stale semantic no-op after a concurrent file write", async () => {
-    const projectDir = createProjectDir();
-    writeHtml(projectDir, "comp.html", FROMTO_COMP);
-    const app = new Hono();
-    registerFileRoutes(app, createAdapter(projectDir));
-    const successor = FROMTO_COMP.replace('data-duration="3"', 'data-duration="9"');
-    let releaseImport = () => {};
-    recastImportGate.wait = new Promise<void>((resolve) => {
-      releaseImport = resolve;
-    });
-    const parserEntered = new Promise<void>((resolve) => {
-      recastImportGate.onEnter = resolve;
-    });
+    // Pins the recast writer: this test's interleave seam is recast's LAZY module
+    // import, which the acorn default no longer performs (acorn is statically
+    // imported). The 409 revalidation under test is writer-independent.
+    const previousWriter = process.env.HYPERFRAMES_GSAP_WRITER;
+    process.env.HYPERFRAMES_GSAP_WRITER = "recast";
+    try {
+      const projectDir = createProjectDir();
+      writeHtml(projectDir, "comp.html", FROMTO_COMP);
+      const app = new Hono();
+      registerFileRoutes(app, createAdapter(projectDir));
+      const successor = FROMTO_COMP.replace('data-duration="3"', 'data-duration="9"');
+      let releaseImport = () => {};
+      recastImportGate.wait = new Promise<void>((resolve) => {
+        releaseImport = resolve;
+      });
+      const parserEntered = new Promise<void>((resolve) => {
+        recastImportGate.onEnter = resolve;
+      });
 
-    const pending = postGsapMutationBatch(app, "comp.html", {
-      mutations: [{ type: "shift-positions", targetSelector: "#missing", delta: 1 }],
-    });
-    await parserEntered;
-    writeHtml(projectDir, "comp.html", successor);
-    releaseImport();
-    const response = await pending;
+      const pending = postGsapMutationBatch(app, "comp.html", {
+        mutations: [{ type: "shift-positions", targetSelector: "#missing", delta: 1 }],
+      });
+      await parserEntered;
+      writeHtml(projectDir, "comp.html", successor);
+      releaseImport();
+      const response = await pending;
 
-    expect(response.status).toBe(409);
-    expect(await response.json()).toMatchObject({ conflict: true });
-    expect(readFileSync(join(projectDir, "comp.html"), "utf-8")).toBe(successor);
+      expect(response.status).toBe(409);
+      expect(await response.json()).toMatchObject({ conflict: true });
+      expect(readFileSync(join(projectDir, "comp.html"), "utf-8")).toBe(successor);
+    } finally {
+      if (previousWriter === undefined) delete process.env.HYPERFRAMES_GSAP_WRITER;
+      else process.env.HYPERFRAMES_GSAP_WRITER = previousWriter;
+    }
   });
 
   it("applies an ordered GSAP mutation batch with one before/after write result", async () => {
diff --git a/packages/studio-server/src/routes/gsapMutationCapabilities.test.ts b/packages/studio-server/src/routes/gsapMutationCapabilities.test.ts
index e004fcb583..02c427acb1 100644
--- a/packages/studio-server/src/routes/gsapMutationCapabilities.test.ts
+++ b/packages/studio-server/src/routes/gsapMutationCapabilities.test.ts
@@ -3,7 +3,7 @@ import { resolve } from "node:path";
 import { describe, expect, it } from "vitest";
 import {
   GSAP_MUTATION_CAPABILITIES,
-  acornDefaultBlockers,
+  behavioralParityOps,
   renderGsapMutationCapabilityReport,
   resolveGsapWriter,
 } from "./gsapMutationCapabilities.js";
@@ -61,14 +61,37 @@ describe("GSAP writer capability matrix", () => {
     );
   });
 
-  it("renders every classified operation and keeps default blocked until parity is differential", () => {
+  it("renders every classified operation and names the behavioral-only ops", () => {
     const report = renderGsapMutationCapabilityReport();
     for (const operation of operations) expect(report).toContain(`| ${operation} |`);
-    expect(acornDefaultBlockers().length).toBeGreaterThan(0);
+    expect(report).toContain("Behavioral-only parity");
+    expect(behavioralParityOps().sort()).toEqual(
+      [
+        "add-with-keyframes",
+        "consolidate-position-writes",
+        "convert-to-keyframes",
+        "delete-all-for-selector",
+        "materialize-keyframes",
+        "move-keyframe",
+        "remove-all-keyframes",
+        "remove-arc-path",
+        "replace-with-keyframes",
+        "resize-keyframed-tween",
+        "scale-positions",
+        "set-arc-path",
+        "shift-positions",
+        "shift-positions-batch",
+        "split-animations",
+        "split-into-property-groups",
+        "unroll-timeline",
+        "update-arc-segment",
+      ].sort(),
+    );
   });
 
-  it("defaults to Recast and requires an explicit Acorn canary selection", () => {
-    expect(resolveGsapWriter({})).toBe("recast");
+  it("defaults to Acorn; recast is an explicit fallback", () => {
+    expect(resolveGsapWriter({})).toBe("acorn");
+    expect(resolveGsapWriter({ HYPERFRAMES_GSAP_WRITER: "recast" })).toBe("recast");
     expect(resolveGsapWriter({ HYPERFRAMES_GSAP_WRITER: "acorn" })).toBe("acorn");
     expect(() => resolveGsapWriter({ HYPERFRAMES_GSAP_WRITER: "unknown" })).toThrow(
       "expected recast or acorn",
diff --git a/packages/studio-server/src/routes/gsapMutationCapabilities.ts b/packages/studio-server/src/routes/gsapMutationCapabilities.ts
index b59f2066ab..0980f47bd0 100644
--- a/packages/studio-server/src/routes/gsapMutationCapabilities.ts
+++ b/packages/studio-server/src/routes/gsapMutationCapabilities.ts
@@ -68,16 +68,17 @@ const GSAP_WRITER_MIGRATION = Object.freeze({
   owner: "studio-foundations",
   deadline: "2026-09-30",
   graduationCriteria:
-    "Every operation has differential parity, the Acorn path imports no Recast runtime, and canary divergence is zero for the agreed soak window.",
+    "Acorn is the default writer. Recast is retained one watch window as HYPERFRAMES_GSAP_WRITER=recast, then deleted (spec 2026-09-17 §5).",
 });
 
 export function resolveGsapWriter(env: { HYPERFRAMES_GSAP_WRITER?: string }): "recast" | "acorn" {
-  const configured = env.HYPERFRAMES_GSAP_WRITER ?? "recast";
+  const configured = env.HYPERFRAMES_GSAP_WRITER ?? "acorn";
   if (configured === "recast" || configured === "acorn") return configured;
   throw new Error(`Invalid ${GSAP_WRITER_MIGRATION.flag}=${configured}; expected recast or acorn`);
 }
 
-export function acornDefaultBlockers(): GsapMutationType[] {
+/** Ops whose acorn/recast parity rests on behavioral tests, not a byte-diff oracle. */
+export function behavioralParityOps(): GsapMutationType[] {
   return (
     Object.entries(GSAP_MUTATION_CAPABILITIES) as Array<[GsapMutationType, GsapMutationCapability]>
   )
@@ -97,13 +98,13 @@ export function renderGsapMutationCapabilityReport(): string {
     "",
     `Owner: ${GSAP_WRITER_MIGRATION.owner}`,
     `Deadline: ${GSAP_WRITER_MIGRATION.deadline}`,
-    `Flag: \`${GSAP_WRITER_MIGRATION.flag}=recast|acorn\``,
+    `Flag: \`${GSAP_WRITER_MIGRATION.flag}=recast|acorn\` (default: acorn)`,
     "",
     "| Operation | Family | Acorn | Recast | Parity evidence |",
     "| --- | --- | --- | --- | --- |",
     ...rows,
     "",
-    `Default blockers: ${acornDefaultBlockers().join(", ") || "none"}`,
+    `Behavioral-only parity (no byte-diff oracle): ${behavioralParityOps().join(", ") || "none"}`,
     "",
   ].join("\n");
 }
diff --git a/packages/studio/src/components/editor/manualEditingAvailability.test.ts b/packages/studio/src/components/editor/manualEditingAvailability.test.ts
index b661d1f2fc..0d7f583950 100644
--- a/packages/studio/src/components/editor/manualEditingAvailability.test.ts
+++ b/packages/studio/src/components/editor/manualEditingAvailability.test.ts
@@ -1,5 +1,6 @@
 import { afterEach, describe, expect, it, vi } from "vitest";
 import { resolveStudioBooleanEnvFlag } from "./manualEditingAvailability";
+import { STUDIO_SDK_OPERATION_FAMILIES } from "../../utils/sdkCutoverPolicy";
 
 async function loadAvailabilityWithEnv(env: Record<string, string | undefined>) {
   vi.resetModules();
@@ -88,4 +89,22 @@ describe("manual editing availability", () => {
     });
     expect(off.STUDIO_FLAT_INSPECTOR_ENABLED).toBe(false);
   });
+
+  it("defaults SDK cutover on for every family", async () => {
+    const all = await loadAvailabilityWithEnv({});
+    expect(all.STUDIO_SDK_CUTOVER_ENABLED).toBe(true);
+    expect(all.STUDIO_SDK_CUTOVER_FAMILIES).toEqual(new Set(STUDIO_SDK_OPERATION_FAMILIES));
+  });
+
+  it("honors the SDK cutover kill switches", async () => {
+    const off = await loadAvailabilityWithEnv({ VITE_STUDIO_SDK_CUTOVER_ENABLED: "false" });
+    expect(off.STUDIO_SDK_CUTOVER_ENABLED).toBe(false);
+    expect(off.STUDIO_SDK_CUTOVER_FAMILIES.size).toBe(0);
+
+    const subset = await loadAvailabilityWithEnv({
+      VITE_STUDIO_SDK_CUTOVER_FAMILIES: "dom,timing",
+    });
+    expect(subset.STUDIO_SDK_CUTOVER_ENABLED).toBe(true);
+    expect(subset.STUDIO_SDK_CUTOVER_FAMILIES).toEqual(new Set(["dom", "timing"]));
+  });
 });
diff --git a/packages/studio/src/components/editor/manualEditingAvailability.ts b/packages/studio/src/components/editor/manualEditingAvailability.ts
index d156bf6941..cc3c806f7a 100644
--- a/packages/studio/src/components/editor/manualEditingAvailability.ts
+++ b/packages/studio/src/components/editor/manualEditingAvailability.ts
@@ -38,16 +38,20 @@ const runtimeEnv =
     : {};
 const env = { ...(import.meta.env ?? {}), ...runtimeEnv } as StudioFeatureFlagEnv;
 
-// Stage 7 Step 3c: SDK cutover — routes inline-style ops through SDK dispatch
-// instead of the server patch-element API. Default false; enable via
-// VITE_STUDIO_SDK_CUTOVER_ENABLED=true. Requires SDK session to be open.
+// Stage 7 SDK cutover — routes Studio edits through SDK dispatch instead of the
+// server patch/mutation routes. Default TRUE as of the flip release (spec:
+// 2026-09-17-studio-sdk-cutover-flip-design.md). Kill switch:
+// VITE_STUDIO_SDK_CUTOVER_ENABLED=false (works at runtime via __HF_STUDIO_ENV__).
 export const STUDIO_SDK_CUTOVER_ENABLED = resolveStudioBooleanEnvFlag(
   env,
   ["VITE_STUDIO_SDK_CUTOVER_ENABLED"],
-  false,
+  true,
 );
 
-/** Explicit per-operation-family canary selection; the master flag alone enables nothing. */
+/**
+ * Per-family selection. Unset = every family (the master alone enables all).
+ * Set `VITE_STUDIO_SDK_CUTOVER_FAMILIES=dom,timing` to RESTRICT to a subset.
+ */
 export const STUDIO_SDK_CUTOVER_FAMILIES = resolveEnabledSdkFamilies(
   env,
   STUDIO_SDK_CUTOVER_ENABLED,
diff --git a/packages/studio/src/hooks/useSdkSession.lifecycle.test.tsx b/packages/studio/src/hooks/useSdkSession.lifecycle.test.tsx
index 7719b6d883..dd52400913 100644
--- a/packages/studio/src/hooks/useSdkSession.lifecycle.test.tsx
+++ b/packages/studio/src/hooks/useSdkSession.lifecycle.test.tsx
@@ -12,6 +12,17 @@ vi.mock("@hyperframes/sdk", () => ({
 import type { Composition } from "@hyperframes/sdk";
 import { useSdkSession, type SdkSessionHandle } from "./useSdkSession";
 
+vi.mock("../utils/studioTelemetry", () => ({ trackStudioEvent: vi.fn() }));
+
+import { trackStudioEvent } from "../utils/studioTelemetry";
+
+const trackMock = vi.mocked(trackStudioEvent);
+
+function Probe({ projectId }: { projectId: string }) {
+  useSdkSession(projectId, "index.html");
+  return null;
+}
+
 (globalThis as unknown as { IS_REACT_ACT_ENVIRONMENT: boolean }).IS_REACT_ACT_ENVIRONMENT = true;
 
 function fakeSession(): Composition {
@@ -135,3 +146,68 @@ describe("useSdkSession ownership", () => {
     expect(published.dispose).toHaveBeenCalledOnce();
   });
 });
+
+describe("useSdkSession unavailable telemetry", () => {
+  beforeEach(() => {
+    openComposition.mockReset();
+    trackMock.mockClear();
+    class FakeEventSource {
+      addEventListener(): void {}
+      close(): void {}
+    }
+    vi.stubGlobal("EventSource", FakeEventSource);
+  });
+
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  // Every cutover chokepoint silently takes the server path when there is no
+  // session, and the shadow never runs either — so a missing session is a total,
+  // otherwise-invisible SDK bypass. These three exits are its only origin.
+  it("reports an unreadable composition", async () => {
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async () => ({ ok: false, json: async () => ({}) }) as Response),
+    );
+    const root = createRoot(document.createElement("div"));
+    await act(async () => root.render(<Probe projectId="project-a" />));
+    await flushAsyncEffects();
+
+    expect(trackMock).toHaveBeenCalledWith("sdk_session_unavailable", { stage: "read" });
+    await act(async () => root.unmount());
+  });
+
+  it("reports a parse failure with its message", async () => {
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async () => response("PROJECT_A")),
+    );
+    openComposition.mockRejectedValue(new Error("unparseable composition"));
+
+    const root = createRoot(document.createElement("div"));
+    await act(async () => root.render(<Probe projectId="project-a" />));
+    await flushAsyncEffects();
+
+    expect(trackMock).toHaveBeenCalledWith("sdk_session_unavailable", {
+      stage: "open",
+      error: "unparseable composition",
+    });
+    await act(async () => root.unmount());
+  });
+
+  it("stays silent on the happy path", async () => {
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async () => response("PROJECT_A")),
+    );
+    openComposition.mockResolvedValue(fakeSession());
+
+    const root = createRoot(document.createElement("div"));
+    await act(async () => root.render(<Probe projectId="project-a" />));
+    await flushAsyncEffects();
+
+    expect(trackMock).not.toHaveBeenCalledWith("sdk_session_unavailable", expect.anything());
+    await act(async () => root.unmount());
+  });
+});
diff --git a/packages/studio/src/hooks/useSdkSession.ts b/packages/studio/src/hooks/useSdkSession.ts
index 278598376a..837b4d3b46 100644
--- a/packages/studio/src/hooks/useSdkSession.ts
+++ b/packages/studio/src/hooks/useSdkSession.ts
@@ -181,7 +181,15 @@ export function useSdkSession(
 
     readProjectFileOptional(projectId, activeCompPath)
       .then(async (content) => {
-        if (cancelled || typeof content !== "string") return;
+        if (cancelled) return;
+        if (typeof content !== "string") {
+          // No SDK session follows, so EVERY cutover chokepoint below takes the
+          // server path and emits nothing — the shadow never runs either. This
+          // is the only place a missing session can originate, so a broken read
+          // would otherwise be a silent, total SDK bypass.
+          trackStudioEvent("sdk_session_unavailable", { stage: "read" });
+          return;
+        }
         // No persist queue: Studio's writeProjectFile (via sdkCutover's
         // persistSdkSerialize) is the SINGLE writer. Wiring the SDK persist
         // queue too would double-write the file (queue auto-writes on every
@@ -206,6 +214,7 @@ export function useSdkSession(
           )
         ) {
           disposeSdkSession(comp);
+          trackStudioEvent("sdk_session_unavailable", { stage: "ownership" });
           return;
         }
         const displaced = ownedSessionRef.current;
@@ -215,8 +224,17 @@ export function useSdkSession(
         setOwnedSession(installed);
         if (displaced && displaced.session !== comp) disposeSdkSession(displaced.session);
       })
-      .catch(() => {
-        if (!cancelled && generationRef.current === generation) setOwnedSession(null);
+      .catch((error: unknown) => {
+        if (!cancelled && generationRef.current === generation) {
+          setOwnedSession(null);
+          // openComposition threw (unparseable composition, OOM) — same total
+          // bypass as the read failure above, but this one is a real defect
+          // rather than a missing file. Carry the message; it is the only clue.
+          trackStudioEvent("sdk_session_unavailable", {
+            stage: "open",
+            error: error instanceof Error ? error.message : String(error),
+          });
+        }
       });
 
     return () => {
diff --git a/packages/studio/src/utils/sdkCutover.gate.test.ts b/packages/studio/src/utils/sdkCutover.gate.test.ts
index c19085955b..e6b9531e69 100644
--- a/packages/studio/src/utils/sdkCutover.gate.test.ts
+++ b/packages/studio/src/utils/sdkCutover.gate.test.ts
@@ -1,11 +1,12 @@
 import { describe, expect, it, vi } from "vitest";
 
-// Dark-launch contract: with STUDIO_SDK_CUTOVER_ENABLED=false, EVERY cutover
+// Kill-switch contract: with VITE_STUDIO_SDK_CUTOVER_ENABLED=false, EVERY cutover
 // persist chokepoint must explicitly decline so the caller takes the legacy server
 // path — even when a valid SDK session exists (one always does, for
-// shadow/selection). This is the contract the prod flag-flip rests on; a future
-// refactor of the gate guards that silently re-enables cutover on flag-off
-// turns these red. (sdkCutover.test.ts mocks the flag TRUE; this is its sibling.)
+// shadow/selection). Default is ON (manualEditingAvailability.test.ts pins that);
+// this file pins that the env override still turns it fully off. A future
+// refactor of the gate guards that ignores the flag turns these red.
+// (sdkCutover.test.ts mocks the flag TRUE; this is its sibling.)
 vi.mock("../components/editor/manualEditingAvailability", () => ({
   STUDIO_SDK_CUTOVER_ENABLED: false,
   STUDIO_SDK_RESOLVER_SHADOW_ENABLED: false,
diff --git a/packages/studio/src/utils/sdkCutover.test.ts b/packages/studio/src/utils/sdkCutover.test.ts
index 4815ac4bc4..d5644bc0e3 100644
--- a/packages/studio/src/utils/sdkCutover.test.ts
+++ b/packages/studio/src/utils/sdkCutover.test.ts
@@ -23,6 +23,8 @@ vi.mock("./studioTelemetry", () => ({
   trackStudioEvent: vi.fn(),
 }));
 
+import { trackStudioEvent } from "./studioTelemetry";
+
 const styleOp = (property: string, value: string): PatchOperation => ({
   type: "inline-style",
   property,
@@ -202,6 +204,46 @@ describe("sdkCutoverPersist", () => {
     expect(result.status).toBe("declined");
   });
 
+  it("tags target_not_found with resolverDisagreement when dispatch could have resolved it", async () => {
+    // getElement is canonical-only for a bare id; resolveSnapshot mirrors what
+    // dispatch resolves (bare ids anywhere). An element present under a scoped
+    // id is dispatchable, so getElement refusing it is a resolver disagreement
+    // — and one the shadow event stays silent about.
+    const deps = makeDeps();
+    const session = makeSession(false);
+    (session as unknown as { getElements: () => unknown[] }).getElements = () => [
+      { id: "hf-abc", scopedId: "host/hf-abc" },
+    ];
+    const sel = { hfId: "hf-abc" } as never;
+
+    await sdkCutoverPersist(sel, [styleOp("color", "red")], "before", "/path.html", session, deps);
+
+    expect(trackStudioEvent).toHaveBeenCalledWith(
+      "sdk_cutover_declined",
+      expect.objectContaining({ reason: "target_not_found", resolverDisagreement: true }),
+    );
+  });
+
+  it("does not tag resolverDisagreement when the element is genuinely absent", async () => {
+    const deps = makeDeps();
+    const session = makeSession(false);
+    (session as unknown as { getElements: () => unknown[] }).getElements = () => [
+      { id: "hf-other", scopedId: "hf-other" },
+    ];
+    const sel = { hfId: "hf-abc" } as never;
+    vi.mocked(trackStudioEvent).mockClear();
+
+    await sdkCutoverPersist(sel, [styleOp("color", "red")], "before", "/path.html", session, deps);
+
+    expect(trackStudioEvent).toHaveBeenLastCalledWith(
+      "sdk_cutover_declined",
+      expect.objectContaining({ reason: "target_not_found" }),
+    );
+    expect(vi.mocked(trackStudioEvent).mock.lastCall?.[1]).not.toHaveProperty(
+      "resolverDisagreement",
+    );
+  });
+
   it("dispatches setStyle for inline-style ops", async () => {
     const deps = makeDeps();
     const session = makeSession(true);
diff --git a/packages/studio/src/utils/sdkCutover.ts b/packages/studio/src/utils/sdkCutover.ts
index 4839bc083b..faf33b4b1f 100644
--- a/packages/studio/src/utils/sdkCutover.ts
+++ b/packages/studio/src/utils/sdkCutover.ts
@@ -5,7 +5,11 @@ import * as studioAvailability from "../components/editor/manualEditingAvailabil
 import { trackStudioEvent } from "./studioTelemetry";
 import { patchOpsToSdkEditOps } from "./sdkOpMapping";
 import { recordResolverParity, recordAnimationResolverParity } from "./sdkResolverShadow";
-import { shouldDeclineTextCutoverForTarget, shouldUseSdkCutover } from "./sdkCutoverEligibility";
+import {
+  isResolverDisagreement,
+  shouldDeclineTextCutoverForTarget,
+  shouldUseSdkCutover,
+} from "./sdkCutoverEligibility";
 import {
   asCutoverError,
   declinedCutover,
@@ -78,15 +82,17 @@ export async function sdkCutoverPersist(
   options?: CutoverOptions,
 ): Promise<CutoverResult> {
   if (!shouldUseSdkCutover(sdkFamilyEnabled("dom"), !!sdkSession, selection.hfId, ops))
-    return declinedCutover("ineligible_operation");
-  if (!sdkSession) return declinedCutover("session_unavailable");
+    return declinedCutover("ineligible_operation", "dom");
+  if (!sdkSession) return declinedCutover("session_unavailable", "dom");
   const hfId = selection.hfId;
-  if (!hfId) return declinedCutover("target_unaddressable");
+  if (!hfId) return declinedCutover("target_unaddressable", "dom");
   const target = sdkSession.getElement(hfId);
-  if (!target) return declinedCutover("target_not_found");
+  if (!target)
+    return declinedCutover("target_not_found", "dom", isResolverDisagreement(sdkSession, hfId));
   if (shouldDeclineTextCutoverForTarget(target, ops))
-    return declinedCutover("unsupported_text_target");
-  if (wrongCompositionFile(deps, targetPath)) return declinedCutover("wrong_composition_file");
+    return declinedCutover("unsupported_text_target", "dom");
+  if (wrongCompositionFile(deps, targetPath))
+    return declinedCutover("wrong_composition_file", "dom");
   const result = await persistSdkCandidateMutation(
     sdkSession,
     targetPath,
@@ -122,10 +128,12 @@ export async function sdkTimingPersist(
   // Dark-launch gate: without this, timing cutover runs whenever an SDK session
   // exists (it always does, for shadow/selection) — flipping the flag OFF would
   // NOT disable it. Gate here so flag-off routes back to the legacy server path.
-  if (!sdkFamilyEnabled("timing")) return declinedCutover("feature_disabled");
-  if (!sdkSession) return declinedCutover("session_unavailable");
-  if (!sdkSession.getElement(hfId)) return declinedCutover("target_not_found");
-  if (wrongCompositionFile(deps, targetPath)) return declinedCutover("wrong_composition_file");
+  if (!sdkFamilyEnabled("timing")) return declinedCutover("feature_disabled", "timing");
+  if (!sdkSession) return declinedCutover("session_unavailable", "timing");
+  if (!sdkSession.getElement(hfId))
+    return declinedCutover("target_not_found", "timing", isResolverDisagreement(sdkSession, hfId));
+  if (wrongCompositionFile(deps, targetPath))
+    return declinedCutover("wrong_composition_file", "timing");
   try {
     const serializedBefore = sdkSession.serialize();
     const result = await persistSdkCandidateMutation(
@@ -166,11 +174,17 @@ export async function sdkTimingBatchPersist(
       { targetPath, compositionPath: deps.compositionPath },
     );
   }
-  if (!sdkFamilyEnabled("timing")) return declinedCutover("feature_disabled");
-  if (!sdkSession) return declinedCutover("session_unavailable");
-  if (wrongCompositionFile(deps, targetPath)) return declinedCutover("wrong_composition_file");
-  if (changes.some((change) => !sdkSession.getElement(change.hfId)))
-    return declinedCutover("target_not_found");
+  if (!sdkFamilyEnabled("timing")) return declinedCutover("feature_disabled", "timing");
+  if (!sdkSession) return declinedCutover("session_unavailable", "timing");
+  if (wrongCompositionFile(deps, targetPath))
+    return declinedCutover("wrong_composition_file", "timing");
+  const unresolved = changes.find((change) => !sdkSession.getElement(change.hfId));
+  if (unresolved)
+    return declinedCutover(
+      "target_not_found",
+      "timing",
+      isResolverDisagreement(sdkSession, unresolved.hfId),
+    );
   try {
     const serializedBefore = sdkSession.serialize();
     const result = await persistSdkCandidateMutation(
@@ -244,9 +258,9 @@ export function sdkGsapTweenPersist(
   // Leading dark-launch gate so flag-off does no SDK touch (getElement) at all —
   // matches the other three chokepoints' discipline.
   if (!sdkFamilyEnabled("gsap-animation"))
-    return Promise.resolve(declinedCutover("feature_disabled"));
+    return Promise.resolve(declinedCutover("feature_disabled", "gsap-animation"));
   if (op.kind === "add" && sdkSession && !sdkSession.getElement(op.target))
-    return Promise.resolve(declinedCutover("target_not_found"));
+    return Promise.resolve(declinedCutover("target_not_found", "gsap-animation"));
   // dispatchGsapOpAndPersist declines on before===after — that catches stale
   // animationIds and unsupported shapes (e.g. from-prop on a plain tween), falling
   // back to the server path. This subsumes explicit existence guards for set/remove.
@@ -285,9 +299,10 @@ async function dispatchGsapOpAndPersist(
   }
   // Dark-launch gate (shared chokepoint for every GSAP-op cutover persist):
   // flag OFF → explicit decline → caller falls back to the legacy server path.
-  if (!sdkFamilyEnabled(family)) return declinedCutover("feature_disabled");
-  if (!sdkSession) return declinedCutover("session_unavailable");
-  if (wrongCompositionFile(deps, targetPath)) return declinedCutover("wrong_composition_file");
+  if (!sdkFamilyEnabled(family)) return declinedCutover("feature_disabled", family);
+  if (!sdkSession) return declinedCutover("session_unavailable", family);
+  if (wrongCompositionFile(deps, targetPath))
+    return declinedCutover("wrong_composition_file", family);
   const session = sdkSession;
   // persistSdkCandidateMutation owns the shared per-project/file transaction
   // coordinator used by both SDK and legacy GSAP writes.
@@ -559,10 +574,16 @@ export async function sdkDeletePersist(
     { targetPath, compositionPath: deps.compositionPath },
   );
   // Dark-launch gate: flag OFF → legacy server delete path.
-  if (!sdkFamilyEnabled("lifecycle")) return declinedCutover("feature_disabled");
-  if (!sdkSession) return declinedCutover("session_unavailable");
-  if (!sdkSession.getElement(hfId)) return declinedCutover("target_not_found");
-  if (wrongCompositionFile(deps, targetPath)) return declinedCutover("wrong_composition_file");
+  if (!sdkFamilyEnabled("lifecycle")) return declinedCutover("feature_disabled", "lifecycle");
+  if (!sdkSession) return declinedCutover("session_unavailable", "lifecycle");
+  if (!sdkSession.getElement(hfId))
+    return declinedCutover(
+      "target_not_found",
+      "lifecycle",
+      isResolverDisagreement(sdkSession, hfId),
+    );
+  if (wrongCompositionFile(deps, targetPath))
+    return declinedCutover("wrong_composition_file", "lifecycle");
   const result = await persistSdkCandidateMutation(
     sdkSession,
     targetPath,
diff --git a/packages/studio/src/utils/sdkCutoverEligibility.ts b/packages/studio/src/utils/sdkCutoverEligibility.ts
index 4e779807bb..2dbc0aee63 100644
--- a/packages/studio/src/utils/sdkCutoverEligibility.ts
+++ b/packages/studio/src/utils/sdkCutoverEligibility.ts
@@ -4,8 +4,10 @@
  * sdkCutover.ts (which hit the packages/studio 600-line filesize cap) — this
  * block has no dependency on the persist/dispatch functions there.
  */
+import type { Composition } from "@hyperframes/sdk";
 import type { PatchOperation } from "./sourcePatcher";
 import { isAllowedHtmlAttribute, isSafeAttributeValue } from "./htmlAttrSafety";
+import { resolveSnapshot } from "./sdkResolverShadow";
 
 const CUTOVER_OP_TYPES = new Set<PatchOperation["type"]>([
   "inline-style",
@@ -102,6 +104,25 @@ export function shouldDeclineTextCutoverForTarget(target: unknown, ops: PatchOpe
   return tag !== null && NON_HTML_CHILD_TAGS.has(tag);
 }
 
+/**
+ * On a `target_not_found`, decide whether the miss is the known benign class
+ * (node genuinely absent from the session — nothing dispatch could have done)
+ * or a resolver disagreement: the shadow's broader resolver finds it, so
+ * dispatch could have made the edit and `getElement` refused it. The shadow
+ * event stays silent in that case, so this flag is the only signal for it.
+ *
+ * Diagnostic context only — it must never turn a clean decline into a throw, so
+ * a session shape without `getElements` reports "no disagreement" and the edit
+ * falls back exactly as it otherwise would have.
+ */
+export function isResolverDisagreement(session: Composition, hfId: string): boolean {
+  try {
+    return resolveSnapshot(session, hfId) !== null;
+  } catch {
+    return false;
+  }
+}
+
 export function shouldUseSdkCutover(
   flagEnabled: boolean,
   hasSession: boolean,
diff --git a/packages/studio/src/utils/sdkCutoverPolicy.test.ts b/packages/studio/src/utils/sdkCutoverPolicy.test.ts
index a23cbbd1c1..5c77a1d420 100644
--- a/packages/studio/src/utils/sdkCutoverPolicy.test.ts
+++ b/packages/studio/src/utils/sdkCutoverPolicy.test.ts
@@ -7,8 +7,17 @@ import {
 } from "./sdkCutoverPolicy";
 
 describe("Studio SDK operation-family policy", () => {
-  it("enables no family from the master switch alone", () => {
-    expect(resolveEnabledSdkFamilies({}, true).size).toBe(0);
+  it("enables every family when the master switch is on and no family list is set", () => {
+    const all = new Set(STUDIO_SDK_OPERATION_FAMILIES);
+    expect(resolveEnabledSdkFamilies({}, true)).toEqual(all);
+    expect(resolveEnabledSdkFamilies({ VITE_STUDIO_SDK_CUTOVER_FAMILIES: "" }, true)).toEqual(all);
+    expect(resolveEnabledSdkFamilies({ VITE_STUDIO_SDK_CUTOVER_FAMILIES: "  " }, true)).toEqual(
+      all,
+    );
+  });
+
+  it("enables no family when the master switch is off, regardless of the family list", () => {
+    expect(resolveEnabledSdkFamilies({}, false).size).toBe(0);
     expect(resolveEnabledSdkFamilies({ VITE_STUDIO_SDK_CUTOVER_FAMILIES: "dom" }, false).size).toBe(
       0,
     );
diff --git a/packages/studio/src/utils/sdkCutoverPolicy.ts b/packages/studio/src/utils/sdkCutoverPolicy.ts
index 25c7284462..da998c36af 100644
--- a/packages/studio/src/utils/sdkCutoverPolicy.ts
+++ b/packages/studio/src/utils/sdkCutoverPolicy.ts
@@ -54,7 +54,8 @@ export function resolveEnabledSdkFamilies(
 ): ReadonlySet<StudioSdkOperationFamily> {
   if (!masterEnabled) return new Set();
   const raw = env["VITE_STUDIO_SDK_CUTOVER_FAMILIES"];
-  if (typeof raw !== "string" || raw.trim() === "") return new Set();
+  // Unset/blank = every family. The list exists to RESTRICT (kill switch per family).
+  if (typeof raw !== "string" || raw.trim() === "") return new Set(STUDIO_SDK_OPERATION_FAMILIES);
   const requested = raw
     .split(",")
     .map((family) => family.trim())
@@ -85,8 +86,9 @@ export function renderStudioSdkCutoverReport(): string {
   return [
     "# Studio SDK cutover report",
     "",
-    "Master flag: `VITE_STUDIO_SDK_CUTOVER_ENABLED=true`",
-    "Family flag: `VITE_STUDIO_SDK_CUTOVER_FAMILIES=dom,timing,...`",
+    "Default: SDK persist ON for every family. Kill switches:",
+    "  `VITE_STUDIO_SDK_CUTOVER_ENABLED=false` (all families → server path)",
+    "  `VITE_STUDIO_SDK_CUTOVER_FAMILIES=dom,timing` (only listed families → SDK; rest → server)",
     "",
     "A family graduates only after zero unexplained resolver/serialization divergences over its agreed corpus and soak window.",
     "",
diff --git a/packages/studio/src/utils/sdkEditTransaction.decline.test.ts b/packages/studio/src/utils/sdkEditTransaction.decline.test.ts
new file mode 100644
index 0000000000..2de21a7916
--- /dev/null
+++ b/packages/studio/src/utils/sdkEditTransaction.decline.test.ts
@@ -0,0 +1,46 @@
+import { describe, expect, it, vi } from "vitest";
+
+vi.mock("./studioTelemetry", () => ({ trackStudioEvent: vi.fn() }));
+
+import { trackStudioEvent } from "./studioTelemetry";
+import { declinedCutover } from "./sdkEditTransaction";
+
+describe("declinedCutover telemetry", () => {
+  it("emits sdk_cutover_declined with reason and family, and returns the declined result", () => {
+    const result = declinedCutover("target_not_found", "timing");
+    expect(result).toEqual({ status: "declined", reason: "target_not_found" });
+    expect(trackStudioEvent).toHaveBeenCalledWith("sdk_cutover_declined", {
+      reason: "target_not_found",
+      family: "timing",
+    });
+  });
+
+  it("emits family:null when the decline happens before a family is known", () => {
+    declinedCutover("no_change");
+    expect(trackStudioEvent).toHaveBeenCalledWith("sdk_cutover_declined", {
+      reason: "no_change",
+      family: null,
+    });
+  });
+
+  it("omits resolverDisagreement when it is not set, and carries it when it is", () => {
+    declinedCutover("target_not_found", "timing");
+    expect(trackStudioEvent).toHaveBeenLastCalledWith("sdk_cutover_declined", {
+      reason: "target_not_found",
+      family: "timing",
+    });
+
+    declinedCutover("target_not_found", "timing", true);
+    expect(trackStudioEvent).toHaveBeenLastCalledWith("sdk_cutover_declined", {
+      reason: "target_not_found",
+      family: "timing",
+      resolverDisagreement: true,
+    });
+
+    declinedCutover("target_not_found", "timing", false);
+    expect(trackStudioEvent).toHaveBeenLastCalledWith("sdk_cutover_declined", {
+      reason: "target_not_found",
+      family: "timing",
+    });
+  });
+});
diff --git a/packages/studio/src/utils/sdkEditTransaction.ts b/packages/studio/src/utils/sdkEditTransaction.ts
index 2ecf9df19b..4e8f371d05 100644
--- a/packages/studio/src/utils/sdkEditTransaction.ts
+++ b/packages/studio/src/utils/sdkEditTransaction.ts
@@ -3,6 +3,7 @@ import type { EditHistoryKind } from "./editHistory";
 import { hashContent, markSelfWrite } from "../hooks/sdkSelfWriteRegistry";
 import { trackStudioEvent } from "./studioTelemetry";
 import { serializeStudioFileMutation } from "./studioFileMutationCoordinator";
+import type { StudioSdkOperationFamily } from "./sdkCutoverPolicy";
 
 export type CutoverResult =
   | { status: "declined"; reason: string }
@@ -66,7 +67,27 @@ interface CandidateEdit {
   after: string;
 }
 
-export function declinedCutover(reason: string): CutoverResult {
+/**
+ * Explicit fall-back to the legacy server path. Emits `sdk_cutover_declined` so
+ * post-flip we can distinguish "SDK took the edit" from "SDK bowed out"; payload
+ * is reason + family only (no hfId / path / content).
+ *
+ * `resolverDisagreement` is the one extra field with diagnostic value beyond the
+ * reason itself: on a `target_not_found`, the shadow's `resolveSnapshot` (what
+ * dispatch resolves) found the element that `getElement` could not. The shadow
+ * event stays silent in that case, so without this flag the case is invisible —
+ * and it is an adoption loss (a dispatchable edit refused), not a missing node.
+ */
+export function declinedCutover(
+  reason: string,
+  family?: StudioSdkOperationFamily,
+  resolverDisagreement?: boolean,
+): CutoverResult {
+  trackStudioEvent("sdk_cutover_declined", {
+    reason,
+    family: family ?? null,
+    ...(resolverDisagreement ? { resolverDisagreement: true } : {}),
+  });
   return { status: "declined", reason };
 }
 
diff --git a/packages/studio/src/utils/sdkResolverShadow.ts b/packages/studio/src/utils/sdkResolverShadow.ts
index 6508e683f8..e06167480c 100644
--- a/packages/studio/src/utils/sdkResolverShadow.ts
+++ b/packages/studio/src/utils/sdkResolverShadow.ts
@@ -96,7 +96,16 @@ function countHfIdInSource(source: string, id: string): number {
   );
 }
 
-function resolveSnapshot(session: Composition, id: string): FlatEl | null {
+/**
+ * Resolvability the SDK DISPATCH path actually has (mirrors `resolveScoped`):
+ * exact scoped-path match, then canonical bare match, then first bare match.
+ *
+ * Exported so the cutover path can distinguish its two `target_not_found` cases:
+ * `Composition.getElement` is narrower (canonical-only for a bare id) than what
+ * `dispatch` resolves, so an element can be genuinely dispatchable yet still
+ * fail `getElement` — a resolver disagreement worth fixing, not a missing node.
+ */
+export function resolveSnapshot(session: Composition, id: string): FlatEl | null {
   const els = session.getElements();
   const exact = els.find((el) => el.scopedId === id);
   if (exact) return exact;