diff --git a/src/reactive/index.ts b/src/reactive/index.ts
index 8cec2e9..efd2937 100644
--- a/src/reactive/index.ts
+++ b/src/reactive/index.ts
@@ -1 +1,12 @@
-export {};
\ No newline at end of file
+export {
+  WorkflowReactiveRoot,
+  type FailurePolicy,
+  type CallEventMapValue,
+  type CallRequestedEvent,
+  type CallRespondedEvent,
+  type CallErrorEvent,
+  type CallAbortedEvent,
+  type CallCompletedEvent,
+  type EventLogProjection,
+  type AggregateStatus,
+} from "./workflow.js";
diff --git a/src/reactive/workflow.ts b/src/reactive/workflow.ts
index 8cec2e9..dfd0ad3 100644
--- a/src/reactive/workflow.ts
+++ b/src/reactive/workflow.ts
@@ -1 +1,337 @@
-export {};
\ No newline at end of file
+import { signal, computed, effect } from "@preact/signals-core";
+import type { Signal, ReadonlySignal } from "@preact/signals-core";
+import type { DirectedGraph } from "graphology";
+import type { NodeStatus } from "../schema/enums.js";
+import type { CallResult } from "../schema/edge.js";
+
+export type FailurePolicy = "continue-running" | "abort-dependents";
+
+export interface CallRequestedEvent {
+  type: "call.requested";
+  requestId: string;
+  operationId: string;
+  input: unknown;
+  timestamp: string;
+}
+
+export interface CallRespondedEvent {
+  type: "call.responded";
+  requestId: string;
+  output: unknown;
+  timestamp: string;
+}
+
+export interface CallErrorEvent {
+  type: "call.error";
+  requestId: string;
+  error: { code: string; message: string; details?: unknown };
+  timestamp: string;
+}
+
+export interface CallAbortedEvent {
+  type: "call.aborted";
+  requestId: string;
+  timestamp: string;
+}
+
+export interface CallCompletedEvent {
+  type: "call.completed";
+  requestId: string;
+  output: unknown;
+  timestamp: string;
+}
+
+export type CallEventMapValue =
+  | CallRequestedEvent
+  | CallRespondedEvent
+  | CallErrorEvent
+  | CallAbortedEvent
+  | CallCompletedEvent;
+
+export interface EventLogProjection {
+  append(event: CallEventMapValue): void;
+  getStatus(nodeId: string): NodeStatus;
+  getResult(nodeId: string): CallResult | undefined;
+  getEvents(nodeId: string): CallEventMapValue[];
+}
+
+export interface AggregateStatus {
+  completed: number;
+  failed: number;
+  aborted: number;
+  skipped: number;
+  running: number;
+  waiting: number;
+  ready: number;
+  idle: number;
+  total: number;
+}
+
+const TERMINAL_STATUSES: Set<NodeStatus> = new Set([
+  "completed",
+  "failed",
+  "aborted",
+  "skipped",
+]);
+
+const EVENT_TO_STATUS: Record<string, NodeStatus> = {
+  "call.requested": "running",
+  "call.responded": "completed",
+  "call.error": "failed",
+  "call.aborted": "aborted",
+  "call.completed": "completed",
+};
+
+export class WorkflowReactiveRoot implements EventLogProjection {
+  statusMap: Map<string, Signal<NodeStatus>>;
+  preconditions: Map<string, ReadonlySignal<boolean>>;
+  blockedByFailure: Map<string, ReadonlySignal<boolean>>;
+  resultMap: Map<string, ReadonlySignal<CallResult | undefined>>;
+  nodeKeyToRequestId: Map<string, string>;
+
+  private graph: DirectedGraph;
+  private effectDisposers: (() => void)[];
+  private eventLog: CallEventMapValue[];
+  private _failurePolicy: FailurePolicy;
+
+  constructor(
+    graph: DirectedGraph,
+    options?: { failurePolicy?: FailurePolicy },
+  ) {
+    this.graph = graph;
+    this.statusMap = new Map();
+    this.preconditions = new Map();
+    this.blockedByFailure = new Map();
+    this.resultMap = new Map();
+    this.effectDisposers = [];
+    this.eventLog = [];
+    this.nodeKeyToRequestId = new Map();
+    this._failurePolicy = options?.failurePolicy ?? "continue-running";
+    this.initializeSignals();
+  }
+
+  private initializeSignals(): void {
+    for (const node of this.graph.nodes()) {
+      const predecessors: string[] = this.graph.inNeighbors(node) ?? [];
+
+      const status = signal<NodeStatus>("idle");
+
+      const preconditionsComputed = computed(() => {
+        return predecessors.every((pred: string) => {
+          const predStatus = this.statusMap.get(pred);
+          if (!predStatus) return false;
+          return (
+            predStatus.value === "completed" || predStatus.value === "skipped"
+          );
+        });
+      });
+
+      const blockedByFailureComputed = computed(() => {
+        return predecessors.some((pred: string) => {
+          const predStatus = this.statusMap.get(pred);
+          if (!predStatus) return false;
+          return (
+            predStatus.value === "failed" || predStatus.value === "aborted"
+          );
+        });
+      });
+
+      const resultComputed = computed(() => {
+        const requestId = this.nodeKeyToRequestId.get(node);
+        if (!requestId) return undefined;
+
+        let latestTerminalEvent: CallEventMapValue | undefined;
+        for (let i = this.eventLog.length - 1; i >= 0; i--) {
+          const e = this.eventLog[i]!;
+          if ("requestId" in e && e.requestId === requestId) {
+            if (
+              e.type === "call.responded" ||
+              e.type === "call.error" ||
+              e.type === "call.aborted"
+            ) {
+              latestTerminalEvent = e;
+              break;
+            }
+          }
+        }
+
+        if (!latestTerminalEvent) return undefined;
+
+        if (latestTerminalEvent.type === "call.error") {
+          return {
+            status: "failed" as NodeStatus,
+            output: undefined,
+            error: latestTerminalEvent.error,
+          } as CallResult;
+        }
+        if (latestTerminalEvent.type === "call.responded") {
+          return {
+            status: "completed" as NodeStatus,
+            output: latestTerminalEvent.output,
+          } as CallResult;
+        }
+        if (latestTerminalEvent.type === "call.aborted") {
+          return {
+            status: "aborted" as NodeStatus,
+            output: undefined,
+          } as CallResult;
+        }
+
+        return undefined;
+      });
+
+      this.statusMap.set(node, status);
+      this.preconditions.set(node, preconditionsComputed);
+      this.blockedByFailure.set(node, blockedByFailureComputed);
+      this.resultMap.set(node, resultComputed);
+    }
+
+    for (const node of this.graph.nodes()) {
+      const status = this.statusMap.get(node)!;
+      const blocked = this.blockedByFailure.get(node)!;
+
+      const disposer = effect(() => {
+        if (blocked.value) {
+          const current = status.value;
+          if (current === "idle" || current === "waiting" || current === "ready") {
+            if (this._failurePolicy === "abort-dependents") {
+              if (!TERMINAL_STATUSES.has(current)) {
+                status.value = "aborted";
+              }
+            } else {
+              status.value = "aborted";
+            }
+          }
+        }
+      });
+      this.effectDisposers.push(disposer);
+    }
+  }
+
+  append(event: CallEventMapValue): void {
+    this.eventLog.push(event);
+
+    if (!("requestId" in event)) return;
+
+    const nodeId = this.findNodeByRequestId(event.requestId);
+    if (nodeId === undefined) return;
+
+    const statusSignal = this.statusMap.get(nodeId);
+    if (!statusSignal) return;
+
+    const derived = EVENT_TO_STATUS[event.type];
+    if (derived !== undefined) {
+      statusSignal.value = derived;
+    }
+  }
+
+  getStatus(nodeId: string): NodeStatus {
+    const statusSignal = this.statusMap.get(nodeId);
+    if (!statusSignal) return "idle";
+
+    const requestId = this.nodeKeyToRequestId.get(nodeId);
+    if (requestId) {
+      let lastEventType: string | undefined;
+      for (let i = this.eventLog.length - 1; i >= 0; i--) {
+        const e = this.eventLog[i]!;
+        if ("requestId" in e && e.requestId === requestId) {
+          lastEventType = e.type;
+          break;
+        }
+      }
+      if (lastEventType && EVENT_TO_STATUS[lastEventType] !== undefined) {
+        return EVENT_TO_STATUS[lastEventType]!;
+      }
+    }
+
+    return statusSignal.value;
+  }
+
+  getResult(nodeId: string): CallResult | undefined {
+    const resultComputed = this.resultMap.get(nodeId);
+    if (!resultComputed) return undefined;
+    return resultComputed.value;
+  }
+
+  getEvents(nodeId: string): CallEventMapValue[] {
+    const requestId = this.nodeKeyToRequestId.get(nodeId);
+    if (!requestId) return [];
+
+    const events: CallEventMapValue[] = [];
+    for (const e of this.eventLog) {
+      if ("requestId" in e && e.requestId === requestId) {
+        events.push(e);
+      }
+    }
+    return events;
+  }
+
+  abortAll(): void {
+    for (const [_nodeId, status] of this.statusMap) {
+      if (!TERMINAL_STATUSES.has(status.value)) {
+        status.value = "aborted";
+      }
+    }
+  }
+
+  abortNode(nodeId: string): void {
+    const status = this.statusMap.get(nodeId);
+    if (!status) return;
+    if (!TERMINAL_STATUSES.has(status.value)) {
+      status.value = "aborted";
+    }
+  }
+
+  isComplete(): boolean {
+    for (const [_nodeId, status] of this.statusMap) {
+      if (!TERMINAL_STATUSES.has(status.value)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  getAggregateStatus(): AggregateStatus {
+    const counts: Record<string, number> = {
+      completed: 0,
+      failed: 0,
+      aborted: 0,
+      skipped: 0,
+      running: 0,
+      waiting: 0,
+      ready: 0,
+      idle: 0,
+      total: 0,
+    };
+
+    for (const [_nodeId, status] of this.statusMap) {
+      const s = status.value;
+      counts["total"]!++;
+      if (s in counts) {
+        counts[s]!++;
+      }
+    }
+
+    return counts as unknown as AggregateStatus;
+  }
+
+  dispose(): void {
+    for (const disposer of this.effectDisposers) {
+      disposer();
+    }
+    this.effectDisposers = [];
+    this.statusMap.clear();
+    this.preconditions.clear();
+    this.blockedByFailure.clear();
+    this.resultMap.clear();
+    this.nodeKeyToRequestId.clear();
+    this.eventLog = [];
+  }
+
+  private findNodeByRequestId(requestId: string): string | undefined {
+    for (const [nodeId, rid] of this.nodeKeyToRequestId) {
+      if (rid === requestId) return nodeId;
+    }
+    return undefined;
+  }
+}
diff --git a/test/reactive/workflow.test.ts b/test/reactive/workflow.test.ts
new file mode 100644
index 0000000..1975831
--- /dev/null
+++ b/test/reactive/workflow.test.ts
@@ -0,0 +1,910 @@
+import { describe, it, expect } from "vitest";
+import { DirectedGraph } from "graphology";
+import { WorkflowReactiveRoot } from "../../src/reactive/workflow.js";
+import type {
+  CallEventMapValue,
+  FailurePolicy,
+} from "../../src/reactive/workflow.js";
+
+function makeSimpleGraph(): DirectedGraph {
+  const graph = new DirectedGraph();
+  graph.addNode("a", { name: "a" });
+  graph.addNode("b", { name: "b" });
+  graph.addNode("c", { name: "c" });
+  graph.addEdgeWithKey("a->b", "a", "b", { edgeType: "sequential" });
+  graph.addEdgeWithKey("b->c", "b", "c", { edgeType: "sequential" });
+  return graph;
+}
+
+function makeDiamondGraph(): DirectedGraph {
+  const graph = new DirectedGraph();
+  graph.addNode("top", { name: "top" });
+  graph.addNode("left", { name: "left" });
+  graph.addNode("right", { name: "right" });
+  graph.addNode("bottom", { name: "bottom" });
+  graph.addEdgeWithKey("top->left", "top", "left", { edgeType: "sequential" });
+  graph.addEdgeWithKey("top->right", "top", "right", { edgeType: "sequential" });
+  graph.addEdgeWithKey("left->bottom", "left", "bottom", {
+    edgeType: "sequential",
+  });
+  graph.addEdgeWithKey("right->bottom", "right", "bottom", {
+    edgeType: "sequential",
+  });
+  return graph;
+}
+
+function makeForkJoinGraph(): DirectedGraph {
+  const graph = new DirectedGraph();
+  graph.addNode("source", { name: "source" });
+  graph.addNode("fail-node", { name: "fail-node" });
+  graph.addNode("run-node", { name: "run-node" });
+  graph.addNode("sink", { name: "sink" });
+  graph.addEdgeWithKey("source->fail-node", "source", "fail-node", { edgeType: "sequential" });
+  graph.addEdgeWithKey("source->run-node", "source", "run-node", { edgeType: "sequential" });
+  graph.addEdgeWithKey("fail-node->sink", "fail-node", "sink", { edgeType: "sequential" });
+  graph.addEdgeWithKey("run-node->sink", "run-node", "sink", { edgeType: "sequential" });
+  return graph;
+}
+
+describe("WorkflowReactiveRoot", () => {
+  describe("constructor and initializeSignals", () => {
+    it("initializes all nodes with idle status", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.statusMap.get("a")!.value).toBe("idle");
+      expect(root.statusMap.get("b")!.value).toBe("idle");
+      expect(root.statusMap.get("c")!.value).toBe("idle");
+
+      root.dispose();
+    });
+
+    it("creates precondition computeds for all nodes", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.preconditions.has("a")).toBe(true);
+      expect(root.preconditions.has("b")).toBe(true);
+      expect(root.preconditions.has("c")).toBe(true);
+
+      root.dispose();
+    });
+
+    it("root node has met preconditions (no predecessors)", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.preconditions.get("a")!.value).toBe(true);
+
+      root.dispose();
+    });
+
+    it("downstream nodes have unmet preconditions initially", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.preconditions.get("b")!.value).toBe(false);
+      expect(root.preconditions.get("c")!.value).toBe(false);
+
+      root.dispose();
+    });
+
+    it("creates blockedByFailure computeds for all nodes", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.blockedByFailure.has("a")).toBe(true);
+      expect(root.blockedByFailure.has("b")).toBe(true);
+      expect(root.blockedByFailure.has("c")).toBe(true);
+
+      root.dispose();
+    });
+
+    it("no nodes are blocked by failure initially", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.blockedByFailure.get("a")!.value).toBe(false);
+      expect(root.blockedByFailure.get("b")!.value).toBe(false);
+      expect(root.blockedByFailure.get("c")!.value).toBe(false);
+
+      root.dispose();
+    });
+
+    it("creates resultMap entries for all nodes", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.resultMap.has("a")).toBe(true);
+      expect(root.resultMap.has("b")).toBe(true);
+      expect(root.resultMap.has("c")).toBe(true);
+
+      root.dispose();
+    });
+
+    it("defaults failurePolicy to continue-running", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+      const policy = (root as unknown as { _failurePolicy: string })._failurePolicy;
+
+      expect(policy).toBe("continue-running");
+
+      root.dispose();
+    });
+
+    it("accepts custom failurePolicy", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph, {
+        failurePolicy: "abort-dependents",
+      });
+      const policy = (root as unknown as { _failurePolicy: string })._failurePolicy;
+
+      expect(policy).toBe("abort-dependents");
+
+      root.dispose();
+    });
+
+    it("initializes nodeKeyToRequestId as empty map", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.nodeKeyToRequestId.size).toBe(0);
+
+      root.dispose();
+    });
+  });
+
+  describe("append and status updates", () => {
+    it("updates status to running on call.requested", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+
+      expect(root.statusMap.get("a")!.value).toBe("running");
+
+      root.dispose();
+    });
+
+    it("updates status to completed on call.responded", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+      root.append({
+        type: "call.responded",
+        requestId: "req-1",
+        output: { result: 42 },
+        timestamp: "2026-01-01T00:00:01Z",
+      });
+
+      expect(root.statusMap.get("a")!.value).toBe("completed");
+
+      root.dispose();
+    });
+
+    it("updates status to failed on call.error", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+      root.append({
+        type: "call.error",
+        requestId: "req-1",
+        error: { code: "ERR", message: "something failed" },
+        timestamp: "2026-01-01T00:00:01Z",
+      });
+
+      expect(root.statusMap.get("a")!.value).toBe("failed");
+
+      root.dispose();
+    });
+
+    it("updates status to aborted on call.aborted", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+      root.append({
+        type: "call.aborted",
+        requestId: "req-1",
+        timestamp: "2026-01-01T00:00:01Z",
+      });
+
+      expect(root.statusMap.get("a")!.value).toBe("aborted");
+
+      root.dispose();
+    });
+
+    it("ignores events for unknown requestIds", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.append({
+        type: "call.requested",
+        requestId: "unknown-req",
+        operationId: "x",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+
+      expect(root.statusMap.get("a")!.value).toBe("idle");
+
+      root.dispose();
+    });
+
+    it("is idempotent - appending same event twice produces same state", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+
+      const respondedEvent: CallEventMapValue = {
+        type: "call.responded",
+        requestId: "req-1",
+        output: { result: 42 },
+        timestamp: "2026-01-01T00:00:01Z",
+      };
+
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+      root.append(respondedEvent);
+      root.append(respondedEvent);
+
+      expect(root.statusMap.get("a")!.value).toBe("completed");
+
+      root.dispose();
+    });
+  });
+
+  describe("getStatus", () => {
+    it("returns idle for nodes with no events", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.getStatus("a")).toBe("idle");
+
+      root.dispose();
+    });
+
+    it("returns event-derived status when requestId is mapped", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+
+      expect(root.getStatus("a")).toBe("running");
+
+      root.dispose();
+    });
+
+    it("falls back to signal value when no requestId is mapped", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "waiting";
+
+      expect(root.getStatus("a")).toBe("waiting");
+
+      root.dispose();
+    });
+
+    it("returns idle for unknown node", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.getStatus("nonexistent")).toBe("idle");
+
+      root.dispose();
+    });
+  });
+
+  describe("getResult", () => {
+    it("returns undefined when no requestId is mapped", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.getResult("a")).toBeUndefined();
+
+      root.dispose();
+    });
+
+    it("returns completed result from call.responded event", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+      root.append({
+        type: "call.responded",
+        requestId: "req-1",
+        output: { value: 99 },
+        timestamp: "2026-01-01T00:00:01Z",
+      });
+
+      const result = root.getResult("a");
+      expect(result).toBeDefined();
+      expect(result!.status).toBe("completed");
+      expect(result!.output).toEqual({ value: 99 });
+
+      root.dispose();
+    });
+
+    it("returns failed result from call.error event", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+      root.append({
+        type: "call.error",
+        requestId: "req-1",
+        error: { code: "TIMEOUT", message: "timed out" },
+        timestamp: "2026-01-01T00:00:01Z",
+      });
+
+      const result = root.getResult("a");
+      expect(result).toBeDefined();
+      expect(result!.status).toBe("failed");
+      expect(result!.output).toBeUndefined();
+      expect(result!.error).toEqual({ code: "TIMEOUT", message: "timed out" });
+
+      root.dispose();
+    });
+
+    it("returns aborted result from call.aborted event", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+      root.append({
+        type: "call.aborted",
+        requestId: "req-1",
+        timestamp: "2026-01-01T00:00:01Z",
+      });
+
+      const result = root.getResult("a");
+      expect(result).toBeDefined();
+      expect(result!.status).toBe("aborted");
+      expect(result!.output).toBeUndefined();
+
+      root.dispose();
+    });
+
+    it("returns undefined when only call.requested has been received", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+
+      expect(root.getResult("a")).toBeUndefined();
+
+      root.dispose();
+    });
+
+    it("uses most recent terminal event for retries", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-2");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+      root.append({
+        type: "call.error",
+        requestId: "req-1",
+        error: { code: "ERR", message: "first attempt failed" },
+        timestamp: "2026-01-01T00:00:01Z",
+      });
+      root.append({
+        type: "call.requested",
+        requestId: "req-2",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:02Z",
+      });
+      root.append({
+        type: "call.responded",
+        requestId: "req-2",
+        output: { ok: true },
+        timestamp: "2026-01-01T00:00:03Z",
+      });
+
+      const result = root.getResult("a");
+      expect(result).toBeDefined();
+      expect(result!.status).toBe("completed");
+      expect(result!.output).toEqual({ ok: true });
+
+      root.dispose();
+    });
+  });
+
+  describe("getEvents", () => {
+    it("returns empty array for unmapped node", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.getEvents("a")).toEqual([]);
+
+      root.dispose();
+    });
+
+    it("returns events for a mapped node", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-1");
+      root.append({
+        type: "call.requested",
+        requestId: "req-1",
+        operationId: "a",
+        input: null,
+        timestamp: "2026-01-01T00:00:00Z",
+      });
+      root.append({
+        type: "call.responded",
+        requestId: "req-1",
+        output: 42,
+        timestamp: "2026-01-01T00:00:01Z",
+      });
+
+      const events = root.getEvents("a");
+      expect(events).toHaveLength(2);
+      expect(events[0]!.type).toBe("call.requested");
+      expect(events[1]!.type).toBe("call.responded");
+
+      root.dispose();
+    });
+  });
+
+  describe("abort cascade", () => {
+    it("failed node causes downstream dependents to abort (continue-running default)", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "failed";
+
+      expect(root.statusMap.get("b")!.value).toBe("aborted");
+      expect(root.statusMap.get("c")!.value).toBe("aborted");
+
+      root.dispose();
+    });
+
+    it("aborted node causes downstream dependents to abort", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "aborted";
+
+      expect(root.statusMap.get("b")!.value).toBe("aborted");
+      expect(root.statusMap.get("c")!.value).toBe("aborted");
+
+      root.dispose();
+    });
+
+    it("sibling branches are independent - failure on one side does not abort the other", () => {
+      const graph = makeDiamondGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("top")!.value = "completed";
+      root.statusMap.get("left")!.value = "running";
+      root.statusMap.get("right")!.value = "failed";
+
+      expect(root.statusMap.get("left")!.value).toBe("running");
+      expect(root.statusMap.get("bottom")!.value).toBe("aborted");
+
+      root.dispose();
+    });
+
+    it("failed node does not abort already completed nodes", () => {
+      const graph = makeDiamondGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("top")!.value = "completed";
+      root.statusMap.get("left")!.value = "completed";
+      root.statusMap.get("right")!.value = "failed";
+
+      expect(root.statusMap.get("left")!.value).toBe("completed");
+
+      root.dispose();
+    });
+  });
+
+  describe("failurePolicy: abort-dependents", () => {
+    it("abort-dependents policy aborts idle dependents of a failed node", () => {
+      const graph = makeForkJoinGraph();
+      const root = new WorkflowReactiveRoot(graph, {
+        failurePolicy: "abort-dependents",
+      });
+
+      root.statusMap.get("source")!.value = "completed";
+      root.statusMap.get("fail-node")!.value = "running";
+      root.statusMap.get("run-node")!.value = "running";
+      root.statusMap.get("fail-node")!.value = "failed";
+
+      expect(root.statusMap.get("sink")!.value).toBe("aborted");
+
+      root.dispose();
+    });
+  });
+
+  describe("abortAll", () => {
+    it("sets all non-terminal nodes to aborted", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "completed";
+
+      root.abortAll();
+
+      expect(root.statusMap.get("a")!.value).toBe("completed");
+      expect(root.statusMap.get("b")!.value).toBe("aborted");
+      expect(root.statusMap.get("c")!.value).toBe("aborted");
+
+      root.dispose();
+    });
+
+    it("does not change already failed nodes", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "failed";
+
+      root.abortAll();
+
+      expect(root.statusMap.get("a")!.value).toBe("failed");
+
+      root.dispose();
+    });
+  });
+
+  describe("abortNode", () => {
+    it("aborts a specific non-terminal node", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.abortNode("b");
+
+      expect(root.statusMap.get("b")!.value).toBe("aborted");
+
+      root.dispose();
+    });
+
+    it("does not abort already completed nodes", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "completed";
+
+      root.abortNode("a");
+
+      expect(root.statusMap.get("a")!.value).toBe("completed");
+
+      root.dispose();
+    });
+
+    it("does not throw for unknown node", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(() => root.abortNode("nonexistent")).not.toThrow();
+
+      root.dispose();
+    });
+  });
+
+  describe("isComplete", () => {
+    it("returns false when any node is non-terminal", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.isComplete()).toBe(false);
+
+      root.dispose();
+    });
+
+    it("returns true when all nodes are in terminal state", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "completed";
+      root.statusMap.get("b")!.value = "skipped";
+      root.statusMap.get("c")!.value = "failed";
+
+      expect(root.isComplete()).toBe(true);
+
+      root.dispose();
+    });
+  });
+
+  describe("getAggregateStatus", () => {
+    it("returns correct counts", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "completed";
+      root.statusMap.get("b")!.value = "running";
+      root.statusMap.get("c")!.value = "idle";
+
+      const agg = root.getAggregateStatus();
+      expect(agg.completed).toBe(1);
+      expect(agg.running).toBe(1);
+      expect(agg.idle).toBe(1);
+      expect(agg.total).toBe(3);
+      expect(agg.failed).toBe(0);
+      expect(agg.aborted).toBe(0);
+      expect(agg.skipped).toBe(0);
+      expect(agg.waiting).toBe(0);
+      expect(agg.ready).toBe(0);
+
+      root.dispose();
+    });
+  });
+
+  describe("dispose", () => {
+    it("clears all maps", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.dispose();
+
+      expect(root.statusMap.size).toBe(0);
+      expect(root.preconditions.size).toBe(0);
+      expect(root.blockedByFailure.size).toBe(0);
+      expect(root.resultMap.size).toBe(0);
+      expect(root.nodeKeyToRequestId.size).toBe(0);
+    });
+
+    it("effects no longer fire after dispose", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      const bStatusValue = root.statusMap.get("b")!.value;
+      root.dispose();
+
+      expect(bStatusValue).toBeDefined();
+    });
+  });
+
+  describe("precondition reactivity", () => {
+    it("preconditions update when predecessor completes", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      expect(root.preconditions.get("b")!.value).toBe(false);
+
+      root.statusMap.get("a")!.value = "completed";
+
+      expect(root.preconditions.get("b")!.value).toBe(true);
+
+      root.dispose();
+    });
+
+    it("skipped predecessor satisfies preconditions", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "skipped";
+
+      expect(root.preconditions.get("b")!.value).toBe(true);
+
+      root.dispose();
+    });
+
+    it("failed predecessor does not satisfy preconditions", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "failed";
+
+      expect(root.preconditions.get("b")!.value).toBe(false);
+
+      root.dispose();
+    });
+
+    it("diamond graph: bottom requires both predecessors complete", () => {
+      const graph = makeDiamondGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("top")!.value = "completed";
+      root.statusMap.get("left")!.value = "completed";
+      root.statusMap.get("right")!.value = "completed";
+
+      expect(root.preconditions.get("bottom")!.value).toBe(true);
+
+      root.dispose();
+    });
+
+    it("diamond graph: bottom blocked when one predecessor fails", () => {
+      const graph = makeDiamondGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("top")!.value = "completed";
+      root.statusMap.get("left")!.value = "completed";
+      root.statusMap.get("right")!.value = "failed";
+
+      expect(root.preconditions.get("bottom")!.value).toBe(false);
+
+      root.dispose();
+    });
+  });
+
+  describe("blockedByFailure reactivity", () => {
+    it("detects failed predecessor", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "failed";
+
+      expect(root.blockedByFailure.get("b")!.value).toBe(true);
+      expect(root.blockedByFailure.get("c")!.value).toBe(true);
+
+      root.dispose();
+    });
+
+    it("detects aborted predecessor", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "aborted";
+
+      expect(root.blockedByFailure.get("b")!.value).toBe(true);
+
+      root.dispose();
+    });
+
+    it("completed predecessor does not block by failure", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.statusMap.get("a")!.value = "completed";
+
+      expect(root.blockedByFailure.get("b")!.value).toBe(false);
+
+      root.dispose();
+    });
+  });
+
+  describe("full workflow execution flow", () => {
+    it("simulates a simple linear workflow: a -> b -> c", () => {
+      const graph = makeSimpleGraph();
+      const root = new WorkflowReactiveRoot(graph);
+
+      root.nodeKeyToRequestId.set("a", "req-a");
+      root.nodeKeyToRequestId.set("b", "req-b");
+      root.nodeKeyToRequestId.set("c", "req-c");
+
+      expect(root.getStatus("a")).toBe("idle");
+      expect(root.getStatus("b")).toBe("idle");
+      expect(root.getStatus("c")).toBe("idle");
+
+      root.append({
+        type: "call.requested",
+        requestId: "req-a",
+        operationId: "a",
+        input: null,
+        timestamp: "t1",
+      });
+      expect(root.getStatus("a")).toBe("running");
+
+      root.append({
+        type: "call.responded",
+        requestId: "req-a",
+        output: "result-a",
+        timestamp: "t2",
+      });
+      expect(root.getStatus("a")).toBe("completed");
+      expect(root.preconditions.get("b")!.value).toBe(true);
+
+      root.append({
+        type: "call.requested",
+        requestId: "req-b",
+        operationId: "b",
+        input: null,
+        timestamp: "t3",
+      });
+      expect(root.getStatus("b")).toBe("running");
+
+      root.append({
+        type: "call.responded",
+        requestId: "req-b",
+        output: "result-b",
+        timestamp: "t4",
+      });
+      expect(root.getStatus("b")).toBe("completed");
+      expect(root.preconditions.get("c")!.value).toBe(true);
+
+      root.append({
+        type: "call.requested",
+        requestId: "req-c",
+        operationId: "c",
+        input: null,
+        timestamp: "t5",
+      });
+      root.append({
+        type: "call.responded",
+        requestId: "req-c",
+        output: "result-c",
+        timestamp: "t6",
+      });
+      expect(root.getStatus("c")).toBe("completed");
+      expect(root.isComplete()).toBe(true);
+
+      expect(root.getResult("a")!.output).toBe("result-a");
+      expect(root.getResult("b")!.output).toBe("result-b");
+      expect(root.getResult("c")!.output).toBe("result-c");
+
+      root.dispose();
+    });
+  });
+});