diff --git a/tests/routes/canvas-chat-helpers.test.ts b/tests/routes/canvas-chat-helpers.test.ts
index ed1e358e8..66605df32 100644
--- a/tests/routes/canvas-chat-helpers.test.ts
+++ b/tests/routes/canvas-chat-helpers.test.ts
@@ -114,6 +114,7 @@ import {
   buildCanvasSaveRequestBody,
   mergeCanvasSaveRevisionOptions,
 } from "@/lib/canvas/canvas-save-request";
+import { canvasService } from "@/services/canvas";
 import {
   hasCanvasAgentNonGenerativeControlIntent,
   shouldBypassCanvasImagePointsPrecheckForAgentControl,
@@ -388,6 +389,84 @@ test.describe("canvas chat pure helpers", () => {
     });
   });
 
+  test("canvas service save uses store revision fallback when options are omitted", async () => {
+    const canvasData = {
+      nodes: [],
+      edges: [],
+      selectedNodeIds: [],
+      viewport: { x: 0, y: 0, zoom: 1 },
+      tool: "select" as const,
+    };
+    const originalFetch = globalThis.fetch;
+    const hadWindow = Object.prototype.hasOwnProperty.call(globalThis, "window");
+    const originalWindow = (globalThis as typeof globalThis & { window?: unknown })
+      .window;
+    const bodies: Array<Record<string, unknown>> = [];
+
+    useCanvasStore
+      .getState()
+      .setCanvasRevision(
+        "2026-06-22T00:00:10.000Z",
+        "2026-06-22T00:00:10.000Z"
+      );
+    Object.defineProperty(globalThis, "window", {
+      configurable: true,
+      value: {},
+      writable: true,
+    });
+    globalThis.fetch = (async (_input: RequestInfo | URL, init?: RequestInit) => {
+      bodies.push(JSON.parse(String(init?.body || "{}")));
+      return {
+        ok: true,
+        status: 200,
+        json: async () => ({
+          success: true,
+          data: { updatedAt: "2026-06-22T00:00:11.000Z" },
+        }),
+      } as Response;
+    }) as typeof fetch;
+
+    try {
+      await canvasService.saveCanvasState(
+        "11111111-1111-4111-8111-111111111111",
+        canvasData
+      );
+      await canvasService.saveCanvasState(
+        "11111111-1111-4111-8111-111111111111",
+        canvasData,
+        "canvas",
+        {
+          baseCanvasRevision: "2026-06-22T00:00:12.000Z",
+        }
+      );
+    } finally {
+      globalThis.fetch = originalFetch;
+      if (hadWindow) {
+        Object.defineProperty(globalThis, "window", {
+          configurable: true,
+          value: originalWindow,
+          writable: true,
+        });
+      } else {
+        Reflect.deleteProperty(globalThis, "window");
+      }
+      useCanvasStore.getState().setCanvasRevision(null, null);
+    }
+
+    expect(bodies).toHaveLength(2);
+    expect(bodies[0]).toMatchObject({
+      canvasData,
+      baseCanvasRevision: "2026-06-22T00:00:10.000Z",
+      baseCanvasUpdatedAt: "2026-06-22T00:00:10.000Z",
+    });
+    expect(bodies[1]).toMatchObject({
+      canvasData,
+      workspaceType: "canvas",
+      baseCanvasRevision: "2026-06-22T00:00:12.000Z",
+      baseCanvasUpdatedAt: "2026-06-22T00:00:10.000Z",
+    });
+  });
+
   const plannerContext: CanvasAgentContext = {
     version: 1,
     source: "canvas",