fix(core): preserve workflow input after finish (#1362)

WorkflowStateManager.finish() reassigned the stored input to the current
data, so reading state.input after a workflow completed returned the final
output instead of the initial input it documents. update() already preserves
the input during a run; finish() now does too. state.data still reflects the
final value. Adds a regression test.

Author: VihaanAgarwal

.changeset/workflow-input-preserved-after-finish.md

@@ -0,0 +1,5 @@
+---
+"@voltagent/core": patch
+---
+
+Fixed workflow `state.input` being overwritten with the final output once a workflow finished. `finish()` reassigned the stored input to the current data, so reading `state.input` after completion returned the final result instead of the initial input it documents. The initial input is now preserved through completion; `state.data` still reflects the final value.

packages/core/src/workflow/internal/state.spec.ts

@@ -128,6 +128,17 @@ describe("WorkflowStateManager", () => {
       expect(result.status).toBe("completed");
     });
 
+    it("should preserve the original input after the workflow finishes", () => {
+      stateManager.start({ value: "original" });
+      stateManager.update({ data: { value: "final" } });
+      stateManager.finish();
+
+      // `input` is documented as the initial input and must survive completion;
+      // only `data` should reflect the final value.
+      expect(stateManager.state.input).toEqual({ value: "original" });
+      expect(stateManager.state.data).toEqual({ value: "final" });
+    });
+
     it("should transition from suspended to failed", () => {
       stateManager.start({ data: "test" });
       stateManager.suspend("Pause");

packages/core/src/workflow/internal/state.ts

@@ -167,7 +167,6 @@ class WorkflowStateManagerInternal<DATA, RESULT> implements WorkflowStateManager
 
   finish() {
     assertCanMutate(this.#state);
-    this.#input = this.#state.data as DATA;
     this.#internalUpdate({
       endAt: new Date(),
       status: "completed",