diff --git a/bin/gstack-gbrain-sync.ts b/bin/gstack-gbrain-sync.ts
index 61d9e677f7..b8e4d2848a 100644
--- a/bin/gstack-gbrain-sync.ts
+++ b/bin/gstack-gbrain-sync.ts
@@ -289,11 +289,14 @@ function gbrainSupportsSourcesRename(env?: NodeJS.ProcessEnv): boolean {
  * helper can be exercised without a real gbrain CLI.
  */
 export function sourceLocalPath(sourceId: string, env?: NodeJS.ProcessEnv): string | null {
-  const list = execGbrainJson<Array<{ id: string; local_path?: string }>>(
-    ["sources", "list", "--json"],
-    { baseEnv: env },
-  );
-  if (!list) return null;
+  const raw = execGbrainJson<
+    | Array<{ id: string; local_path?: string }>
+    | { sources?: Array<{ id: string; local_path?: string }> }
+  >(["sources", "list", "--json"], { baseEnv: env });
+  if (!raw) return null;
+  // gbrain v0.18.0+ returns {sources: [...]}; older versions returned a raw array.
+  // Defensive against both shapes so this works on any gbrain version.
+  const list = Array.isArray(raw) ? raw : raw.sources ?? [];
   const found = list.find((s) => s.id === sourceId);
   return found?.local_path ?? null;
 }
diff --git a/test/gstack-gbrain-sync.test.ts b/test/gstack-gbrain-sync.test.ts
index 0f1edec214..0fc710b3a1 100644
--- a/test/gstack-gbrain-sync.test.ts
+++ b/test/gstack-gbrain-sync.test.ts
@@ -812,7 +812,24 @@ describe("sourceLocalPath", () => {
     rmSync(bindir, { recursive: true, force: true });
   });
 
-  it("returns local_path when the source exists", () => {
+  // gbrain v0.18.0+ returns {sources: [...]}; this is the live contract.
+  it("returns local_path when the source exists (gbrain v0.18.0+ wrapped shape)", () => {
+    makeShim(bindir, {
+      "sources list --json": {
+        stdout: JSON.stringify({
+          sources: [
+            { id: "other-source", local_path: "/x" },
+            { id: "target-id", local_path: "/repo/match" },
+          ],
+        }),
+      },
+    });
+    expect(sourceLocalPath("target-id", envWithBindir(bindir))).toBe("/repo/match");
+  });
+
+  // Pre-v0.18.0 gbrain returned a raw array. Keep back-compat so the helper
+  // works regardless of which gbrain the user has on PATH.
+  it("returns local_path when the source exists (pre-v0.18.0 raw-array shape)", () => {
     makeShim(bindir, {
       "sources list --json": {
         stdout: JSON.stringify([
@@ -824,7 +841,14 @@ describe("sourceLocalPath", () => {
     expect(sourceLocalPath("target-id", envWithBindir(bindir))).toBe("/repo/match");
   });
 
-  it("returns null when the source is missing", () => {
+  it("returns null when the source is missing (wrapped shape)", () => {
+    makeShim(bindir, {
+      "sources list --json": { stdout: JSON.stringify({ sources: [] }) },
+    });
+    expect(sourceLocalPath("missing-id", envWithBindir(bindir))).toBeNull();
+  });
+
+  it("returns null when the source is missing (raw-array shape)", () => {
     makeShim(bindir, {
       "sources list --json": { stdout: "[]" },
     });