refactor(agent-service): remove dead checkout/headChange path

agent-service/src/agent/texera-agent.ts

@@ -75,7 +75,7 @@ type ReActStepCallback = (step: ReActStep) => void;
 /**
  * A single Texera agent instance.
  *
- * Owns the conversation (ReAct step tree with HEAD/checkout semantics), the
+ * Owns the conversation (ReAct step tree with HEAD tracking), the
  * workflow being edited (`WorkflowState`), cached operator execution results
  * (`WorkflowResultState`), and the tool surface exposed to the LLM. Each call
  * to `sendMessage` drives one multi-step generation via the Vercel AI SDK,
@@ -298,16 +298,6 @@ export class TexeraAgent {
     return Array.from(this.stepsById.values()).filter(s => s.id !== INITIAL_STEP_ID);
   }
 
-  checkout(stepId: string): boolean {
-    const step = this.stepsById.get(stepId);
-    if (!step && stepId !== INITIAL_STEP_ID) return false;
-    this.head = stepId;
-    if (step?.afterWorkflowContent) {
-      this.workflowState.setWorkflowContent(step.afterWorkflowContent);
-    }
-    return true;
-  }
-
   setStepCallback(callback: ReActStepCallback | null): void {
     this.stepCallback = callback;
   }

agent-service/src/server.spec.ts

@@ -354,32 +354,6 @@ describe("agent read routes", () => {
   });
 });
 
-describe("checkout route", () => {
-  test("broadcasts and survives a websocket whose send throws", async () => {
-    const id = (await readJson<{ id: string }>(await createAgent())).id;
-    const agent = _getAgentForTests(id)!;
-    (agent as any).checkout = () => true;
-    (agent as any).getAllSteps = () => [];
-    // A failing socket must be dropped inside broadcastToAgentClients, not crash the request.
-    agent.addClient({
-      send: () => {
-        throw new Error("send failed");
-      },
-    } as any);
-
-    const res = await postJson(`${API}/agents/${id}/checkout`, { stepId: "step-1" });
-    expect(res.status).toBe(200);
-    expect((await readJson<{ headId: string }>(res)).headId).toBe("step-1");
-  });
-
-  test("returns 500 when the step cannot be found", async () => {
-    const id = (await readJson<{ id: string }>(await createAgent())).id;
-    (_getAgentForTests(id) as any).checkout = () => false;
-    const res = await postJson(`${API}/agents/${id}/checkout`, { stepId: "missing" });
-    expect(res.status).toBe(500);
-  });
-});
-
 describe("non-router routes", () => {
   test("unknown routes fall through to the catch-all error handler", async () => {
     const res = await getJson("/no-such-route");

agent-service/src/server.ts

@@ -41,13 +41,7 @@ import type {
 } from "./types/agent";
 import { AgentState, OperatorResultSerializationMode } from "./types/agent";
 import type { WsClientCommand, WsServerEvent } from "./types/ws";
-import {
-  WsServerSnapshotEvent,
-  WsServerStepEvent,
-  WsServerStatusEvent,
-  WsServerErrorEvent,
-  WsServerHeadChangeEvent,
-} from "./types/ws";
+import { WsServerSnapshotEvent, WsServerStepEvent, WsServerStatusEvent, WsServerErrorEvent } from "./types/ws";
 import type { OperatorResultSummary } from "./types/execution";
 
 const agentStore = new Map<string, TexeraAgent>();
@@ -317,25 +311,6 @@ const agentsRouter = new Elysia({ prefix: "/agents" })
     return { status: "cleared" };
   })
 
-  .post("/:id/checkout", ({ params: { id }, body }) => {
-    const agent = getAgent(id);
-    const { stepId } = body as { stepId: string };
-    if (!stepId) throw new Error("stepId is required");
-
-    const success = agent.checkout(stepId);
-    if (!success) throw new Error(`Step ${stepId} not found or checkout failed`);
-
-    const allSteps = agent.getAllSteps();
-    const workflowContent = agent.getWorkflowState().getWorkflowContent();
-
-    broadcastToAgentClients(id, new WsServerHeadChangeEvent(stepId, allSteps, workflowContent));
-
-    return {
-      status: "checked out",
-      headId: stepId,
-    };
-  })
-
   .get("/:id/operator-types", ({ params: { id } }) => {
     const agent = getAgent(id);
     const metadataStore = agent.getMetadataStore();
@@ -614,7 +589,7 @@ function printStartupMessage(app: ReturnType<typeof buildApp>) {
     console.log("         Send: { type: 'WsClientPromptCommand', content: '...' }");
     console.log("         Send: { type: 'WsClientStopCommand' }");
     console.log(
-      "         Recv: { type: 'WsServerSnapshotEvent' | 'WsServerStepEvent' | 'WsServerStatusEvent' | 'WsServerErrorEvent' | 'WsServerHeadChangeEvent', ... }"
+      "         Recv: { type: 'WsServerSnapshotEvent' | 'WsServerStepEvent' | 'WsServerStatusEvent' | 'WsServerErrorEvent', ... }"
     );
   }
 

agent-service/src/types/ws/server.ts

@@ -23,7 +23,6 @@
 // for you. `WsServerEvent` is their discriminated union.
 
 import type { AgentState, ReActStep } from "../agent";
-import type { WorkflowContent } from "../workflow";
 
 /**
  * Full state pushed once when a client connects: the agent's current lifecycle
@@ -60,27 +59,5 @@ export class WsServerErrorEvent {
   constructor(readonly error: string) {}
 }
 
-/**
- * Emitted after a checkout: HEAD moved, carrying the full step list and the
- * workflow snapshot at the new head.
- *
- * @deprecated Unused by the frontend/UI — nothing invokes the client's
- * `checkoutStep()`. The `/agents/:id/checkout` route (and its tests) still
- * broadcast it, so it remains reachable; do not build new UI on it.
- */
-export class WsServerHeadChangeEvent {
-  readonly type = "WsServerHeadChangeEvent";
-  constructor(
-    readonly headId: string,
-    readonly steps: ReActStep[],
-    readonly workflowContent?: WorkflowContent
-  ) {}
-}
-
 /** Discriminated union of every server -> client frame. */
-export type WsServerEvent =
-  | WsServerSnapshotEvent
-  | WsServerStepEvent
-  | WsServerStatusEvent
-  | WsServerErrorEvent
-  | WsServerHeadChangeEvent;
+export type WsServerEvent = WsServerSnapshotEvent | WsServerStepEvent | WsServerStatusEvent | WsServerErrorEvent;

frontend/src/app/workspace/service/agent/agent.service.ts

@@ -519,26 +519,6 @@ export class AgentService {
         }
         break;
 
-      case "WsServerHeadChangeEvent":
-        // HEAD moved (checkout) — update HEAD, visible steps, and workflow
-        if (message.headId !== undefined) {
-          tracking.headIdSubject.next(message.headId);
-        }
-        if (message.steps && Array.isArray(message.steps)) {
-          const steps = message.steps.map((s: any) => this.convertApiReActStep(s));
-          tracking.reActStepsSubject.next(steps);
-        }
-        // Update workflow content from agent service (ground truth)
-        if (message.workflowContent) {
-          tracking.wsWorkflowActive = true;
-          const workflow: Workflow = {
-            ...(message.workflowMetadata || tracking.workflowSubject.getValue() || {}),
-            content: message.workflowContent,
-          };
-          tracking.workflowSubject.next(workflow as Workflow);
-        }
-        break;
-
       case "WsServerErrorEvent":
         // Error occurred
         console.error(`Agent ${agentId} error:`, message.error);
@@ -1006,14 +986,6 @@ export class AgentService {
     return tracking ? tracking.headIdSubject.getValue() : null;
   }
 
-  /**
-   * Checkout to a specific step (move HEAD, restore workflow).
-   * The backend broadcasts headChange + visible steps via WebSocket to all clients.
-   */
-  public checkoutStep(agentId: string, stepId: string): Observable<any> {
-    return this.http.post(`${this.AGENT_API_BASE}/agents/${agentId}/checkout`, { stepId });
-  }
-
   /**
    * Get visible steps for an agent (current snapshot).
    */