fix(FN-2539): preserve dashboard API compatibility and harden proxy wildcard routing

- Replace app/api.ts with a compatibility barrel that re-exports the legacy client API surface from app/api/legacy.ts
- Move the existing dashboard API implementation into app/api/legacy.ts and update static-analysis tests to include the new module path
- Update proxy wildcard routing to use /proxy/:nodeId/{*splat}, keeping explicit proxy handlers ahead of the fallback route
- Reject proxying to local nodes with a consistent 400 response and expand proxy route tests plus route-ordering compatibility notes

packages/dashboard/app/__tests__/agent-runs-ui.test.ts

@@ -10,11 +10,12 @@ const agentsViewPath = path.join(__dirname, "../components/AgentsView.tsx");
 const agentDetailViewPath = path.join(__dirname, "../components/AgentDetailView.tsx");
 const agentRunHistoryPath = path.join(__dirname, "../components/AgentRunHistory.tsx");
 const apiPath = path.join(__dirname, "../api.ts");
+const apiLegacyPath = path.join(__dirname, "../api/legacy.ts");
 
 const agentsViewContent = fs.readFileSync(agentsViewPath, "utf-8");
 const agentDetailViewContent = fs.readFileSync(agentDetailViewPath, "utf-8");
 const agentRunHistoryContent = fs.readFileSync(agentRunHistoryPath, "utf-8");
-const apiContent = fs.readFileSync(apiPath, "utf-8");
+const apiContent = `${fs.readFileSync(apiPath, "utf-8")}\n${fs.existsSync(apiLegacyPath) ? fs.readFileSync(apiLegacyPath, "utf-8") : ""}`;
 
 describe("Agent runs UI — static analysis", () => {
   describe("startAgentRun API function", () => {

packages/dashboard/src/__tests__/proxy-routes.test.ts

@@ -206,14 +206,24 @@ describe("Proxy routes", () => {
       expect(res.body).toEqual({ error: "Node not found" });
     });
 
-    it("returns 400 when node is local (no url)", async () => {
+    it("returns 400 when node is local", async () => {
       const node = createMockRemoteNode({ type: "local", url: undefined });
       mockGetNode.mockResolvedValue(node);
 
       const res = await get(app, "/api/proxy/local-node/some-endpoint");
 
       expect(res.status).toBe(400);
-      expect(res.body).toEqual({ error: "Node has no URL" });
+      expect(res.body).toEqual({ error: "Cannot proxy to local node" });
+    });
+
+    it("returns 400 when local node has a URL", async () => {
+      const node = createMockRemoteNode({ type: "local", url: "http://local:4040" });
+      mockGetNode.mockResolvedValue(node);
+
+      const res = await get(app, "/api/proxy/local-node/some-endpoint");
+
+      expect(res.status).toBe(400);
+      expect(res.body).toEqual({ error: "Cannot proxy to local node" });
     });
 
     it("returns 502 on connection error (TypeError)", async () => {

packages/dashboard/src/routes.ts

@@ -2065,6 +2065,8 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
 
   // Registrar mount order is part of the API contract. Keep specific routes
   // before generic parameter/wildcard routes to preserve Express precedence.
+  // Proxy registrar must remain last so explicit /proxy handlers stay ahead
+  // of the fallback /proxy/:nodeId/{*splat} wildcard route.
   const routeContext = {
     router,
     store,

packages/dashboard/src/routes/register-proxy.ts

@@ -226,9 +226,10 @@ export function registerProxyRoutes(ctx: ApiRoutesContext): void {
 
   /**
    * Generic wildcard proxy route — forwards any HTTP request to a remote node.
+   * Keep this after specific /proxy routes so they retain precedence.
    * Matches /api/proxy/:nodeId/*
    */
-  router.all("/proxy/:nodeId/*splat", async (req: Request, res: Response) => {
+  router.all("/proxy/:nodeId/{*splat}", async (req: Request, res: Response) => {
     const nodeId = req.params.nodeId as string;
     const splat = req.params.splat as string | string[];
     const remainingPath = Array.isArray(splat) ? splat.join("/") : splat;
@@ -245,6 +246,11 @@ export function registerProxyRoutes(ctx: ApiRoutesContext): void {
         return;
       }
 
+      if (node.type === "local") {
+        res.status(400).json({ error: "Cannot proxy to local node" });
+        return;
+      }
+
       if (!node.url) {
         res.status(400).json({ error: "Node has no URL" });
         return;