diff --git a/src/components/__tests__/WorkflowCanvas.test.tsx b/src/components/__tests__/WorkflowCanvas.test.tsx
index cb38db84..5fcde784 100644
--- a/src/components/__tests__/WorkflowCanvas.test.tsx
+++ b/src/components/__tests__/WorkflowCanvas.test.tsx
@@ -140,6 +140,7 @@ const createDefaultState = (overrides = {}) => ({
   markCommentViewed: vi.fn(),
   canvasNavigationSettings: { panMode: "space", zoomMode: "altScroll", selectionMode: "click" },
   dimmedNodeIds: new Set<string>(),
+  skippedNodeIds: new Set<string>(),
   captureSnapshot: vi.fn(),
   applyEditOperations: vi.fn(() => ({ applied: 0, skipped: [] })),
   setWorkflowMetadata: vi.fn(),
diff --git a/src/store/__tests__/skipPropagation.test.ts b/src/store/__tests__/skipPropagation.test.ts
new file mode 100644
index 00000000..e888f710
--- /dev/null
+++ b/src/store/__tests__/skipPropagation.test.ts
@@ -0,0 +1,475 @@
+/**
+ * Tests for optional input skip propagation in executeWorkflow.
+ *
+ * Covers:
+ * - Optional inputs with no data are skipped
+ * - Skip propagation cascades to downstream nodes (ANY policy)
+ * - Shared nodes (e.g. prompt connected to multiple generators) are not skipped
+ * - Backward compatibility: nodes without isOptional behave as before
+ * - Skipped status is cleared after workflow completes
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { useWorkflowStore } from "../workflowStore";
+import type { WorkflowNode, WorkflowEdge } from "@/types";
+
+// Mock the Toast hook
+vi.mock("@/components/Toast", () => ({
+  useToast: {
+    getState: () => ({
+      show: vi.fn(),
+    }),
+  },
+}));
+
+// Mock the logger
+vi.mock("@/utils/logger", () => ({
+  logger: {
+    info: vi.fn(),
+    warn: vi.fn(),
+    error: vi.fn(),
+    startSession: vi.fn().mockResolvedValue(undefined),
+    endSession: vi.fn().mockResolvedValue(undefined),
+    getCurrentSession: vi.fn().mockReturnValue(null),
+  },
+}));
+
+// Mock localStorage
+const mockLocalStorage: Record<string, string> = {};
+vi.stubGlobal("localStorage", {
+  getItem: vi.fn((key: string) => mockLocalStorage[key] || null),
+  setItem: vi.fn((key: string, value: string) => {
+    mockLocalStorage[key] = value;
+  }),
+  removeItem: vi.fn((key: string) => {
+    delete mockLocalStorage[key];
+  }),
+  clear: vi.fn(() => {
+    Object.keys(mockLocalStorage).forEach((key) => delete mockLocalStorage[key]);
+  }),
+});
+
+// Mock fetch for API calls
+vi.stubGlobal("fetch", vi.fn().mockResolvedValue({
+  ok: true,
+  json: () => Promise.resolve({ success: true, image: "data:image/png;base64,generated" }),
+  text: () => Promise.resolve(""),
+}));
+
+function resetStore() {
+  useWorkflowStore.getState().clearWorkflow();
+}
+
+function createTestNode(
+  id: string,
+  type: string,
+  data: Record<string, unknown> = {},
+  position = { x: 0, y: 0 }
+): WorkflowNode {
+  return {
+    id,
+    type: type as WorkflowNode["type"],
+    position,
+    data: data as WorkflowNode["data"],
+  };
+}
+
+function createTestEdge(
+  source: string,
+  target: string,
+  sourceHandle: string | null = null,
+  targetHandle: string | null = null
+): WorkflowEdge {
+  return {
+    id: `edge-${source}-${target}-${sourceHandle || "default"}-${targetHandle || "default"}`,
+    source,
+    target,
+    sourceHandle,
+    targetHandle,
+  };
+}
+
+describe("Skip propagation", () => {
+  beforeEach(() => {
+    resetStore();
+    vi.clearAllMocks();
+  });
+
+  afterEach(() => {
+    resetStore();
+  });
+
+  describe("Optional input with no data", () => {
+    it("should skip optional imageInput with no image", async () => {
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("img-1", "imageInput", { image: null, isOptional: true }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+        ],
+        edges: [
+          createTestEdge("img-1", "nb-1", "image", "image"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      // Workflow should complete without errors
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+
+      // The nanoBanana node should NOT have been executed (no API call for it)
+      // We verify by checking that its status was reset to idle (skip → cleanup → idle)
+      const nbNode = useWorkflowStore.getState().nodes.find(n => n.id === "nb-1");
+      expect(nbNode?.data).toBeDefined();
+      expect((nbNode?.data as any).status).toBe("idle");
+    });
+
+    it("should skip optional audioInput with no audio", async () => {
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("audio-1", "audioInput", { audioFile: null, isOptional: true }),
+          createTestNode("output-1", "output", {}),
+        ],
+        edges: [
+          createTestEdge("audio-1", "output-1", "audio", "audio"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+    });
+
+    it("should skip optional prompt with empty text", async () => {
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("prompt-1", "prompt", { prompt: "", isOptional: true }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+        ],
+        edges: [
+          createTestEdge("prompt-1", "nb-1", "text", "text"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+    });
+
+    it("should skip optional prompt with whitespace-only text", async () => {
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("prompt-1", "prompt", { prompt: "   ", isOptional: true }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+        ],
+        edges: [
+          createTestEdge("prompt-1", "nb-1", "text", "text"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+    });
+
+    it("should NOT skip optional imageInput when it has an image", async () => {
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("img-1", "imageInput", { image: "data:image/png;base64,test", isOptional: true }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+          createTestNode("prompt-1", "prompt", { prompt: "test" }),
+        ],
+        edges: [
+          createTestEdge("img-1", "nb-1", "image", "image"),
+          createTestEdge("prompt-1", "nb-1", "text", "text"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      // Workflow should complete — nanoBanana should execute (it won't be skipped)
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+      // skippedNodeIds should be cleared
+      expect(useWorkflowStore.getState().skippedNodeIds.size).toBe(0);
+    });
+  });
+
+  describe("Skip propagation (ANY merge policy)", () => {
+    it("should skip downstream node when its source is skipped", async () => {
+      // imageInput(optional, empty) → nanoBanana → output
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("img-1", "imageInput", { image: null, isOptional: true }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+          createTestNode("output-1", "output", {}),
+        ],
+        edges: [
+          createTestEdge("img-1", "nb-1", "image", "image"),
+          createTestEdge("nb-1", "output-1", "image", "image"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      // All three nodes should have been skipped
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+      // skippedNodeIds cleared after completion
+      expect(useWorkflowStore.getState().skippedNodeIds.size).toBe(0);
+    });
+
+    it("should skip node when ANY source is skipped (not requiring ALL)", async () => {
+      // imageInput(optional, empty) → nanoBanana ← prompt(has text)
+      // nanoBanana should be skipped because one source (imageInput) is skipped
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("img-1", "imageInput", { image: null, isOptional: true }),
+          createTestNode("prompt-1", "prompt", { prompt: "test prompt" }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+        ],
+        edges: [
+          createTestEdge("img-1", "nb-1", "image", "image"),
+          createTestEdge("prompt-1", "nb-1", "text", "text"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      // Workflow completes without error
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+      // skippedNodeIds should be cleared after completion
+      expect(useWorkflowStore.getState().skippedNodeIds.size).toBe(0);
+    });
+  });
+
+  describe("Shared nodes are NOT skipped", () => {
+    it("should only skip the branch with the empty input, not the shared prompt", async () => {
+      // Setup:
+      // prompt → nanoBanana1 ← imageInput1 (optional, empty)
+      // prompt → nanoBanana2 ← imageInput2 (optional, has image)
+      //
+      // Expected: prompt executes, nanoBanana1 is skipped, nanoBanana2 executes
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("prompt-1", "prompt", { prompt: "test prompt" }, { x: 0, y: 100 }),
+          createTestNode("img-1", "imageInput", { image: null, isOptional: true }, { x: 0, y: 0 }),
+          createTestNode("img-2", "imageInput", { image: "data:image/png;base64,test", isOptional: true }, { x: 0, y: 200 }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }, { x: 200, y: 0 }),
+          createTestNode("nb-2", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }, { x: 200, y: 200 }),
+        ],
+        edges: [
+          createTestEdge("prompt-1", "nb-1", "text", "text"),
+          createTestEdge("prompt-1", "nb-2", "text", "text"),
+          createTestEdge("img-1", "nb-1", "image", "image"),
+          createTestEdge("img-2", "nb-2", "image", "image"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      // Workflow should complete
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+      // Both skippedNodeIds should be cleared
+      expect(useWorkflowStore.getState().skippedNodeIds.size).toBe(0);
+    });
+  });
+
+  describe("Backward compatibility", () => {
+    it("should NOT skip non-optional imageInput with no image (errors as before)", async () => {
+      // imageInput without isOptional → nanoBanana
+      // The nanoBanana should attempt to execute (and likely fail on API call)
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("img-1", "imageInput", { image: null }),
+          createTestNode("prompt-1", "prompt", { prompt: "test" }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+        ],
+        edges: [
+          createTestEdge("img-1", "nb-1", "image", "image"),
+          createTestEdge("prompt-1", "nb-1", "text", "text"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      // Workflow should complete (nanoBanana attempted execution — wasn't skipped)
+      // We just need to verify it wasn't skipped, not that it succeeded
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+      // The skippedNodeIds should be empty — nothing was skipped
+      expect(useWorkflowStore.getState().skippedNodeIds.size).toBe(0);
+    });
+
+    it("should NOT skip when isOptional is explicitly false", async () => {
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("img-1", "imageInput", { image: null, isOptional: false }),
+          createTestNode("prompt-1", "prompt", { prompt: "test" }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+        ],
+        edges: [
+          createTestEdge("img-1", "nb-1", "image", "image"),
+          createTestEdge("prompt-1", "nb-1", "text", "text"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+      expect(useWorkflowStore.getState().skippedNodeIds.size).toBe(0);
+    });
+  });
+
+  describe("Skipped status cleanup", () => {
+    it("should clear skippedNodeIds after workflow completes", async () => {
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("img-1", "imageInput", { image: null, isOptional: true }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+        ],
+        edges: [
+          createTestEdge("img-1", "nb-1", "image", "image"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      // After completion, skippedNodeIds should be empty
+      expect(useWorkflowStore.getState().skippedNodeIds.size).toBe(0);
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+    });
+
+    it("should reset skipped node status back to idle after completion", async () => {
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("img-1", "imageInput", { image: null, isOptional: true }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }),
+        ],
+        edges: [
+          createTestEdge("img-1", "nb-1", "image", "image"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      // nanoBanana status should be "idle" (was set to "skipped" during execution, then reset)
+      const nbNode = useWorkflowStore.getState().nodes.find(n => n.id === "nb-1");
+      expect((nbNode?.data as any).status).toBe("idle");
+    });
+
+    it("should clear skippedNodeIds on stopWorkflow", () => {
+      // Manually set some skipped nodes
+      useWorkflowStore.setState({
+        skippedNodeIds: new Set(["node-1", "node-2"]),
+        isRunning: true,
+      });
+
+      const store = useWorkflowStore.getState();
+      store.stopWorkflow();
+
+      expect(useWorkflowStore.getState().skippedNodeIds.size).toBe(0);
+    });
+  });
+
+  describe("Multi-level cascade", () => {
+    it("should cascade skip through multiple levels", async () => {
+      // imageInput(optional, empty) → nanoBanana → output
+      // All three should be skipped
+      useWorkflowStore.setState({
+        nodes: [
+          createTestNode("img-1", "imageInput", { image: null, isOptional: true }, { x: 0, y: 0 }),
+          createTestNode("prompt-1", "prompt", { prompt: "test" }, { x: 0, y: 100 }),
+          createTestNode("nb-1", "nanoBanana", {
+            status: "idle",
+            aspectRatio: "1:1",
+            resolution: "1MP",
+            model: "nano-banana",
+          }, { x: 200, y: 0 }),
+          createTestNode("output-1", "output", {}, { x: 400, y: 0 }),
+        ],
+        edges: [
+          createTestEdge("img-1", "nb-1", "image", "image"),
+          createTestEdge("prompt-1", "nb-1", "text", "text"),
+          createTestEdge("nb-1", "output-1", "image", "image"),
+        ],
+      });
+
+      const store = useWorkflowStore.getState();
+      await store.executeWorkflow();
+
+      // Workflow completes without errors
+      expect(useWorkflowStore.getState().isRunning).toBe(false);
+      // All skipped node IDs cleaned up
+      expect(useWorkflowStore.getState().skippedNodeIds.size).toBe(0);
+    });
+  });
+});