diff --git a/src/graph/construction.ts b/src/graph/construction.ts
index 3f8b6dd..1f48c22 100644
--- a/src/graph/construction.ts
+++ b/src/graph/construction.ts
@@ -8,6 +8,7 @@ import {
   NodeNotFoundError,
   CycleError,
   InvalidInputError,
+  InvalidTransitionError,
 } from "../error/index.js";
 import type { CallStatus, AnyValidationError, ValidationError } from "../error/index.js";
 import {
@@ -20,8 +21,10 @@ import {
   OperationEdgeAttrs as OperationEdgeAttrsSchema,
   OperationGraphSerialized,
   CallGraphSerialized,
+  CallNodeAttrs as CallNodeAttrsSchema,
+  CallEdgeAttrs as CallEdgeAttrsSchema,
 } from "../schema/index.js";
-import type { OperationNodeAttrs, FlowGraphSerialized } from "../schema/index.js";
+import type { OperationNodeAttrs, FlowGraphSerialized, CallNodeAttrs } from "../schema/index.js";
 import { typeCompat, type TypeCompatResult } from "../analysis/type-compat.js";
 
 export interface FlowGraphOptions {
@@ -41,8 +44,55 @@ export interface OperationSpec {
   tags?: string[];
 }
 
+export interface CallRequestedEvent {
+  type: "call.requested";
+  requestId: string;
+  operationId: string;
+  input: unknown;
+  timestamp: string;
+  parentRequestId?: string;
+  identity?: { id: string; scopes: string[]; resources?: Record<string, string[]> };
+  startedAt?: 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;
+
 type OperationGraph = FlowGraph<typeof OperationNodeAttrsSchema, typeof OperationEdgeAttrsSchema>;
 
+type CallGraph = FlowGraph<typeof CallNodeAttrsSchema, typeof CallEdgeAttrsSchema>;
+
 type TypedEdgeAttrs = {
   edgeType: "typed";
   compatible: boolean;
@@ -52,6 +102,14 @@ type TypedEdgeAttrs = {
 
 type Attrs = Record<string, unknown>;
 
+const VALID_TRANSITIONS: Record<CallStatus, CallStatus[]> = {
+  pending: ["running", "aborted"],
+  running: ["completed", "failed", "aborted"],
+  completed: [],
+  failed: [],
+  aborted: [],
+};
+
 export class FlowGraph<
   NodeAttrs extends TSchema = TSchema,
   EdgeAttrs extends TSchema = TSchema,
@@ -318,6 +376,145 @@ export class FlowGraph<
     return chain;
   }
 
+  updateFromEvent(event: CallEventMapValue): void {
+    switch (event.type) {
+      case "call.requested": {
+        const attrs: CallNodeAttrs = {
+          requestId: event.requestId,
+          operationId: event.operationId,
+          status: "pending",
+          input: event.input,
+          ...(event.parentRequestId !== undefined ? { parentRequestId: event.parentRequestId } : {}),
+          ...(event.identity !== undefined ? { identity: event.identity } : {}),
+          ...(event.startedAt !== undefined ? { startedAt: event.startedAt } : {}),
+        };
+        this.addCall(attrs);
+        break;
+      }
+      case "call.responded": {
+        if (!this._graph.hasNode(event.requestId)) return;
+        const current = this._graph.getNodeAttributes(event.requestId) as Record<string, unknown>;
+        const currentStatus = current.status as CallStatus;
+        if (currentStatus === "completed" || currentStatus === "failed" || currentStatus === "aborted") return;
+        this._graph.mergeNodeAttributes(event.requestId, {
+          status: "completed",
+          output: event.output,
+          completedAt: event.timestamp,
+        } as Attrs);
+        break;
+      }
+      case "call.error": {
+        if (!this._graph.hasNode(event.requestId)) return;
+        const current = this._graph.getNodeAttributes(event.requestId) as Record<string, unknown>;
+        const currentStatus = current.status as CallStatus;
+        if (currentStatus === "completed" || currentStatus === "failed" || currentStatus === "aborted") return;
+        this._graph.mergeNodeAttributes(event.requestId, {
+          status: "failed",
+          error: event.error,
+          completedAt: event.timestamp,
+        } as Attrs);
+        break;
+      }
+      case "call.aborted": {
+        if (!this._graph.hasNode(event.requestId)) return;
+        const current = this._graph.getNodeAttributes(event.requestId) as Record<string, unknown>;
+        const currentStatus = current.status as CallStatus;
+        if (currentStatus === "completed" || currentStatus === "failed" || currentStatus === "aborted") return;
+        this._graph.mergeNodeAttributes(event.requestId, {
+          status: "aborted",
+          completedAt: event.timestamp,
+        } as Attrs);
+        break;
+      }
+      case "call.completed": {
+        if (!this._graph.hasNode(event.requestId)) return;
+        const current = this._graph.getNodeAttributes(event.requestId) as Record<string, unknown>;
+        const currentStatus = current.status as CallStatus;
+        if (currentStatus === "completed") {
+          if (!current.completedAt) {
+            this._graph.mergeNodeAttributes(event.requestId, { completedAt: event.timestamp } as Attrs);
+          }
+          return;
+        }
+        if (currentStatus === "failed" || currentStatus === "aborted") return;
+        this._graph.mergeNodeAttributes(event.requestId, {
+          status: "completed",
+          ...(event.output !== undefined ? { output: event.output } : {}),
+          completedAt: event.timestamp,
+        } as Attrs);
+        break;
+      }
+    }
+  }
+
+  addCall(attrs: CallNodeAttrs): void {
+    if (this._graph.hasNode(attrs.requestId)) return;
+    this._graph.addNode(attrs.requestId, attrs as Attrs);
+    if (attrs.parentRequestId !== undefined) {
+      if (this._graph.hasNode(attrs.parentRequestId)) {
+        if (willCreateCycle(this._graph, attrs.parentRequestId, attrs.requestId)) {
+          this._graph.dropNode(attrs.requestId);
+          const path = this._findPath(attrs.requestId, attrs.parentRequestId);
+          const cycle = [attrs.parentRequestId, ...path, attrs.parentRequestId];
+          throw new CycleError([cycle]);
+        }
+        const edgeKey = this._edgeKey(attrs.parentRequestId, attrs.requestId);
+        this._graph.addEdgeWithKey(edgeKey, attrs.parentRequestId, attrs.requestId, { edgeType: "triggered" } as Attrs);
+      }
+    }
+  }
+
+  addDependency(source: string, target: string): void {
+    if (!this._graph.hasNode(source)) {
+      throw new NodeNotFoundError(source);
+    }
+    if (!this._graph.hasNode(target)) {
+      throw new NodeNotFoundError(target);
+    }
+    const edgeKey = `${source}->${target}:depends_on`;
+    if (this._graph.hasEdge(edgeKey)) return;
+    if (willCreateCycle(this._graph, source, target)) {
+      const path = this._findPath(target, source);
+      const cycle = [source, ...path, source];
+      throw new CycleError([cycle]);
+    }
+    this._graph.addEdgeWithKey(edgeKey, source, target, { edgeType: "depends_on" } as Attrs);
+  }
+
+  updateStatus(requestId: string, status: CallStatus, extra?: Partial<CallNodeAttrs>): void {
+    if (!this._graph.hasNode(requestId)) {
+      throw new NodeNotFoundError(requestId);
+    }
+    const current = this._graph.getNodeAttributes(requestId) as Record<string, unknown>;
+    const currentStatus = current.status as CallStatus;
+    if (currentStatus === status) return;
+    const allowed = VALID_TRANSITIONS[currentStatus];
+    if (!allowed || !allowed.includes(status)) {
+      throw new InvalidTransitionError(requestId, currentStatus, status);
+    }
+    const update: Record<string, unknown> = { status };
+    if (extra) {
+      for (const [key, value] of Object.entries(extra)) {
+        if (value !== undefined) {
+          update[key] = value;
+        }
+      }
+    }
+    this._graph.mergeNodeAttributes(requestId, update as Attrs);
+  }
+
+  updateCall(requestId: string, attrs: Partial<CallNodeAttrs>): void {
+    if (!this._graph.hasNode(requestId)) {
+      throw new NodeNotFoundError(requestId);
+    }
+    this._graph.mergeNodeAttributes(requestId, attrs as Attrs);
+  }
+
+  removeCall(requestId: string): void {
+    if (!this._graph.hasNode(requestId)) return;
+    this._graph.dropNode(requestId);
+  }
+
   validate(schema: TSchema): AnyValidationError[] {
     return _validate(this, schema as NodeAttrs);
   }
@@ -365,10 +562,12 @@ export class FlowGraph<
     return graph;
   }
 
-  static fromCallEvents(
-    _events: unknown[],
-  ): FlowGraph<TSchema, TSchema> {
-    throw new Error("not implemented");
+  static fromCallEvents(events: CallEventMapValue[]): CallGraph {
+    const graph = new FlowGraph<typeof CallNodeAttrsSchema, typeof CallEdgeAttrsSchema>();
+    for (const event of events) {
+      graph.updateFromEvent(event);
+    }
+    return graph;
   }
 
   export(): FlowGraphSerialized {
diff --git a/src/graph/index.ts b/src/graph/index.ts
index 9a2f18e..6d249ff 100644
--- a/src/graph/index.ts
+++ b/src/graph/index.ts
@@ -1,4 +1,4 @@
-export { FlowGraph, buildTypeEdges, type FlowGraphOptions, type OperationSpec } from "./construction.js";
+export { FlowGraph, buildTypeEdges, type FlowGraphOptions, type OperationSpec, type CallEventMapValue, type CallRequestedEvent, type CallRespondedEvent, type CallErrorEvent, type CallAbortedEvent, type CallCompletedEvent } from "./construction.js";
 export {
   topologicalOrder,
   hasCycles,
diff --git a/src/index.ts b/src/index.ts
index 37319a2..978b0ab 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,6 +1,6 @@
 export * from "./error/index.js";
 
-export { FlowGraph, buildTypeEdges, type FlowGraphOptions, type OperationSpec } from "./graph/index.js";
+export { FlowGraph, buildTypeEdges, type FlowGraphOptions, type OperationSpec, type CallEventMapValue, type CallRequestedEvent, type CallRespondedEvent, type CallErrorEvent, type CallAbortedEvent, type CallCompletedEvent } from "./graph/index.js";
 export {
   validateSchema,
   validateGraph,
diff --git a/src/reactive/workflow.ts b/src/reactive/workflow.ts
index dfd0ad3..d10a5a2 100644
--- a/src/reactive/workflow.ts
+++ b/src/reactive/workflow.ts
@@ -88,6 +88,7 @@ export class WorkflowReactiveRoot implements EventLogProjection {
   blockedByFailure: Map<string, ReadonlySignal<boolean>>;
   resultMap: Map<string, ReadonlySignal<CallResult | undefined>>;
   nodeKeyToRequestId: Map<string, string>;
+  requestIdToNodeKey: Map<string, string>;
 
   private graph: DirectedGraph;
   private effectDisposers: (() => void)[];
@@ -106,10 +107,16 @@ export class WorkflowReactiveRoot implements EventLogProjection {
     this.effectDisposers = [];
     this.eventLog = [];
     this.nodeKeyToRequestId = new Map();
+    this.requestIdToNodeKey = new Map();
     this._failurePolicy = options?.failurePolicy ?? "continue-running";
     this.initializeSignals();
   }
 
+  setRequestId(nodeKey: string, requestId: string): void {
+    this.nodeKeyToRequestId.set(nodeKey, requestId);
+    this.requestIdToNodeKey.set(requestId, nodeKey);
+  }
+
   private initializeSignals(): void {
     for (const node of this.graph.nodes()) {
       const predecessors: string[] = this.graph.inNeighbors(node) ?? [];
@@ -213,15 +220,29 @@ export class WorkflowReactiveRoot implements EventLogProjection {
 
     if (!("requestId" in event)) return;
 
-    const nodeId = this.findNodeByRequestId(event.requestId);
+    let nodeId = this.requestIdToNodeKey.get(event.requestId);
+
+    if (nodeId === undefined) {
+      for (const [nId, rid] of this.nodeKeyToRequestId) {
+        if (rid === event.requestId) {
+          nodeId = nId;
+          this.requestIdToNodeKey.set(event.requestId, nId);
+          break;
+        }
+      }
+    }
+
     if (nodeId === undefined) return;
 
-    const statusSignal = this.statusMap.get(nodeId);
-    if (!statusSignal) return;
+    const currentRequestId = this.nodeKeyToRequestId.get(nodeId);
+    if (currentRequestId === event.requestId) {
+      const statusSignal = this.statusMap.get(nodeId);
+      if (!statusSignal) return;
 
-    const derived = EVENT_TO_STATUS[event.type];
-    if (derived !== undefined) {
-      statusSignal.value = derived;
+      const derived = EVENT_TO_STATUS[event.type];
+      if (derived !== undefined) {
+        statusSignal.value = derived;
+      }
     }
   }
 
@@ -254,12 +275,17 @@ export class WorkflowReactiveRoot implements EventLogProjection {
   }
 
   getEvents(nodeId: string): CallEventMapValue[] {
-    const requestId = this.nodeKeyToRequestId.get(nodeId);
-    if (!requestId) return [];
+    const requestIds = new Set<string>();
+    for (const [rid, nId] of this.requestIdToNodeKey) {
+      if (nId === nodeId) {
+        requestIds.add(rid);
+      }
+    }
+    if (requestIds.size === 0) return [];
 
     const events: CallEventMapValue[] = [];
     for (const e of this.eventLog) {
-      if ("requestId" in e && e.requestId === requestId) {
+      if ("requestId" in e && requestIds.has(e.requestId)) {
         events.push(e);
       }
     }
@@ -325,13 +351,7 @@ export class WorkflowReactiveRoot implements EventLogProjection {
     this.blockedByFailure.clear();
     this.resultMap.clear();
     this.nodeKeyToRequestId.clear();
+    this.requestIdToNodeKey.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/graph/construction.test.ts b/test/graph/construction.test.ts
index 19c99ac..76e049d 100644
--- a/test/graph/construction.test.ts
+++ b/test/graph/construction.test.ts
@@ -1,13 +1,15 @@
 import { describe, it, expect } from "vitest";
 import { Type } from "@alkdev/typebox";
 import { FlowGraph, buildTypeEdges } from "../../src/graph/construction.js";
-import type { OperationSpec } from "../../src/graph/construction.js";
+import type { OperationSpec, CallEventMapValue } from "../../src/graph/construction.js";
 import {
   DuplicateNodeError,
   DuplicateEdgeError,
   NodeNotFoundError,
   CycleError,
+  InvalidTransitionError,
 } from "../../src/error/index.js";
+import type { CallStatus } from "../../src/error/index.js";
 
 describe("FlowGraph constructor", () => {
   it("creates an empty graph", () => {
@@ -300,8 +302,13 @@ describe("FlowGraph query methods", () => {
 });
 
 describe("FlowGraph static stubs", () => {
-  it("fromCallEvents throws not implemented", () => {
-    expect(() => FlowGraph.fromCallEvents([])).toThrow("not implemented");
+  it("fromCallEvents returns empty graph for empty events", () => {
+    const graph = FlowGraph.fromCallEvents([]);
+    expect(graph.order).toBe(0);
+    expect(graph.size).toBe(0);
+  });
+  it("fromJSON throws not implemented", () => {
+    expect(() => FlowGraph.fromJSON({} as never)).toThrow();
   });
 });
 
@@ -634,4 +641,520 @@ describe("FlowGraph cycle detection", () => {
     fg.addEdge("a", "c");
     expect(() => fg.addEdge("b", "c")).not.toThrow();
   });
+});
+
+describe("FlowGraph.fromCallEvents", () => {
+  const requestedEvent: CallEventMapValue = {
+    type: "call.requested",
+    requestId: "req-1",
+    operationId: "task.classify",
+    input: { text: "hello" },
+    timestamp: "2026-01-01T00:00:00Z",
+  };
+
+  const requestedWithParent: CallEventMapValue = {
+    type: "call.requested",
+    requestId: "req-2",
+    operationId: "task.enrich",
+    input: { label: "greeting" },
+    timestamp: "2026-01-01T00:00:01Z",
+    parentRequestId: "req-1",
+  };
+
+  const respondedEvent: CallEventMapValue = {
+    type: "call.responded",
+    requestId: "req-1",
+    output: { label: "greeting" },
+    timestamp: "2026-01-01T00:00:02Z",
+  };
+
+  const errorEvent: CallEventMapValue = {
+    type: "call.error",
+    requestId: "req-1",
+    error: { code: "INTERNAL", message: "Something went wrong" },
+    timestamp: "2026-01-01T00:00:03Z",
+  };
+
+  const abortedEvent: CallEventMapValue = {
+    type: "call.aborted",
+    requestId: "req-1",
+    timestamp: "2026-01-01T00:00:04Z",
+  };
+
+  const completedEvent: CallEventMapValue = {
+    type: "call.completed",
+    requestId: "req-1",
+    output: { label: "greeting" },
+    timestamp: "2026-01-01T00:00:05Z",
+  };
+
+  it("adds node from call.requested event", () => {
+    const graph = FlowGraph.fromCallEvents([requestedEvent]);
+    expect(graph.order).toBe(1);
+    expect(graph.hasNode("req-1")).toBe(true);
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("pending");
+    expect(attrs.operationId).toBe("task.classify");
+  });
+
+  it("creates triggered edge from parentRequestId", () => {
+    const graph = FlowGraph.fromCallEvents([requestedEvent, requestedWithParent]);
+    expect(graph.order).toBe(2);
+    expect(graph.hasNode("req-2")).toBe(true);
+    expect(graph.hasEdge("req-1", "req-2")).toBe(true);
+    const edgeAttrs = graph.getEdgeAttributes("req-1", "req-2") as Record<string, unknown>;
+    expect(edgeAttrs.edgeType).toBe("triggered");
+  });
+
+  it("updates status to completed on call.responded", () => {
+    const graph = FlowGraph.fromCallEvents([requestedEvent, respondedEvent]);
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("completed");
+    expect(attrs.output).toEqual({ label: "greeting" });
+    expect(attrs.completedAt).toBe("2026-01-01T00:00:02Z");
+  });
+
+  it("updates status to failed on call.error", () => {
+    const graph = FlowGraph.fromCallEvents([requestedEvent, errorEvent]);
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("failed");
+    expect(attrs.error).toEqual({ code: "INTERNAL", message: "Something went wrong" });
+    expect(attrs.completedAt).toBe("2026-01-01T00:00:03Z");
+  });
+
+  it("updates status to aborted on call.aborted", () => {
+    const graph = FlowGraph.fromCallEvents([requestedEvent, abortedEvent]);
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("aborted");
+    expect(attrs.completedAt).toBe("2026-01-01T00:00:04Z");
+  });
+
+  it("updates status to completed on call.completed", () => {
+    const graph = FlowGraph.fromCallEvents([requestedEvent, completedEvent]);
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("completed");
+    expect(attrs.completedAt).toBe("2026-01-01T00:00:05Z");
+  });
+
+  it("is idempotent — duplicate events have no effect", () => {
+    const graph = FlowGraph.fromCallEvents([requestedEvent, requestedEvent, respondedEvent, respondedEvent]);
+    expect(graph.order).toBe(1);
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("completed");
+  });
+
+  it("ignores responded/error/aborted for unknown requestId", () => {
+    const graph = FlowGraph.fromCallEvents([respondedEvent, errorEvent, abortedEvent]);
+    expect(graph.order).toBe(0);
+  });
+
+  it("creates node for unknown operationId", () => {
+    const unknownOpEvent: CallEventMapValue = {
+      type: "call.requested",
+      requestId: "req-unknown",
+      operationId: "unknown.op",
+      input: {},
+      timestamp: "2026-01-01T00:00:00Z",
+    };
+    const graph = FlowGraph.fromCallEvents([unknownOpEvent]);
+    expect(graph.order).toBe(1);
+    const attrs = graph.getNodeAttributes("req-unknown") as Record<string, unknown>;
+    expect(attrs.status).toBe("pending");
+    expect(attrs.operationId).toBe("unknown.op");
+  });
+
+  it("processes full event sequence", () => {
+    const req1: CallEventMapValue = {
+      type: "call.requested",
+      requestId: "req-parent",
+      operationId: "task.parent",
+      input: {},
+      timestamp: "2026-01-01T00:00:00Z",
+    };
+    const req2: CallEventMapValue = {
+      type: "call.requested",
+      requestId: "req-child",
+      operationId: "task.child",
+      input: {},
+      timestamp: "2026-01-01T00:00:01Z",
+      parentRequestId: "req-parent",
+    };
+    const resp: CallEventMapValue = {
+      type: "call.responded",
+      requestId: "req-parent",
+      output: "done",
+      timestamp: "2026-01-01T00:00:02Z",
+    };
+    const graph = FlowGraph.fromCallEvents([req1, req2, resp]);
+    expect(graph.order).toBe(2);
+    expect(graph.hasEdge("req-parent", "req-child")).toBe(true);
+    const parentAttrs = graph.getNodeAttributes("req-parent") as Record<string, unknown>;
+    expect(parentAttrs.status).toBe("completed");
+    const childAttrs = graph.getNodeAttributes("req-child") as Record<string, unknown>;
+    expect(childAttrs.status).toBe("pending");
+  });
+
+  it("stores identity and startedAt from call.requested", () => {
+    const event: CallEventMapValue = {
+      type: "call.requested",
+      requestId: "req-id",
+      operationId: "task.op",
+      input: {},
+      timestamp: "2026-01-01T00:00:00Z",
+      identity: { id: "user-1", scopes: ["read"] },
+      startedAt: "2026-01-01T00:00:01Z",
+    };
+    const graph = FlowGraph.fromCallEvents([event]);
+    const attrs = graph.getNodeAttributes("req-id") as Record<string, unknown>;
+    expect(attrs.identity).toEqual({ id: "user-1", scopes: ["read"] });
+    expect(attrs.startedAt).toBe("2026-01-01T00:00:01Z");
+  });
+
+  it("skips triggered edge if parent node does not exist", () => {
+    const orphanEvent: CallEventMapValue = {
+      type: "call.requested",
+      requestId: "req-orphan",
+      operationId: "task.child",
+      input: {},
+      timestamp: "2026-01-01T00:00:00Z",
+      parentRequestId: "req-nonexistent",
+    };
+    const graph = FlowGraph.fromCallEvents([orphanEvent]);
+    expect(graph.order).toBe(1);
+    expect(graph.hasNode("req-orphan")).toBe(true);
+    expect(graph.size).toBe(0);
+  });
+});
+
+describe("FlowGraph.updateFromEvent", () => {
+  it("processes single event for real-time pattern", () => {
+    const graph = new FlowGraph();
+    graph.updateFromEvent({
+      type: "call.requested",
+      requestId: "req-1",
+      operationId: "task.classify",
+      input: { text: "hello" },
+      timestamp: "2026-01-01T00:00:00Z",
+    });
+    expect(graph.hasNode("req-1")).toBe(true);
+
+    graph.updateFromEvent({
+      type: "call.responded",
+      requestId: "req-1",
+      output: { label: "hi" },
+      timestamp: "2026-01-01T00:00:02Z",
+    });
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("completed");
+    expect(attrs.output).toEqual({ label: "hi" });
+  });
+
+  it("ignores events for unknown requestId", () => {
+    const graph = new FlowGraph();
+    graph.updateFromEvent({
+      type: "call.responded",
+      requestId: "unknown",
+      output: "x",
+      timestamp: "2026-01-01T00:00:00Z",
+    });
+    expect(graph.order).toBe(0);
+  });
+
+  it("ignores terminal event re-processing", () => {
+    const graph = new FlowGraph();
+    graph.updateFromEvent({
+      type: "call.requested",
+      requestId: "req-1",
+      operationId: "task.op",
+      input: {},
+      timestamp: "2026-01-01T00:00:00Z",
+    });
+    graph.updateFromEvent({
+      type: "call.responded",
+      requestId: "req-1",
+      output: "done",
+      timestamp: "2026-01-01T00:00:01Z",
+    });
+    graph.updateFromEvent({
+      type: "call.error",
+      requestId: "req-1",
+      error: { code: "X", message: "Y" },
+      timestamp: "2026-01-01T00:00:02Z",
+    });
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("completed");
+  });
+});
+
+describe("FlowGraph.addCall", () => {
+  it("adds a call node", () => {
+    const graph = new FlowGraph();
+    graph.addCall({
+      requestId: "req-1",
+      operationId: "task.classify",
+      status: "pending",
+      input: { text: "hello" },
+    });
+    expect(graph.hasNode("req-1")).toBe(true);
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("pending");
+  });
+
+  it("adds triggered edge when parentRequestId is present", () => {
+    const graph = new FlowGraph();
+    graph.addCall({
+      requestId: "req-parent",
+      operationId: "task.parent",
+      status: "pending",
+      input: {},
+    });
+    graph.addCall({
+      requestId: "req-child",
+      operationId: "task.child",
+      status: "pending",
+      input: {},
+      parentRequestId: "req-parent",
+    });
+    expect(graph.hasEdge("req-parent", "req-child")).toBe(true);
+    const edgeAttrs = graph.getEdgeAttributes("req-parent", "req-child") as Record<string, unknown>;
+    expect(edgeAttrs.edgeType).toBe("triggered");
+  });
+
+  it("is idempotent — duplicate addCall is ignored", () => {
+    const graph = new FlowGraph();
+    graph.addCall({
+      requestId: "req-1",
+      operationId: "task.op",
+      status: "pending",
+      input: {},
+    });
+    graph.addCall({
+      requestId: "req-1",
+      operationId: "task.op",
+      status: "pending",
+      input: {},
+    });
+    expect(graph.order).toBe(1);
+  });
+
+  it("does not throw if parentRequestId node does not exist", () => {
+    const graph = new FlowGraph();
+    graph.addCall({
+      requestId: "req-child",
+      operationId: "task.child",
+      status: "pending",
+      input: {},
+      parentRequestId: "nonexistent",
+    });
+    expect(graph.hasNode("req-child")).toBe(true);
+    expect(graph.size).toBe(0);
+  });
+});
+
+describe("FlowGraph.addDependency", () => {
+  it("creates depends_on edge", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.a", status: "pending", input: {} });
+    graph.addCall({ requestId: "req-2", operationId: "task.b", status: "pending", input: {} });
+    graph.addDependency("req-1", "req-2");
+    const edgeKey = "req-1->req-2:depends_on";
+    expect(graph.graph.hasEdge(edgeKey)).toBe(true);
+    const attrs = graph.graph.getEdgeAttributes(edgeKey) as Record<string, unknown>;
+    expect(attrs.edgeType).toBe("depends_on");
+  });
+
+  it("is idempotent — duplicate addDependency is ignored", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.a", status: "pending", input: {} });
+    graph.addCall({ requestId: "req-2", operationId: "task.b", status: "pending", input: {} });
+    graph.addDependency("req-1", "req-2");
+    graph.addDependency("req-1", "req-2");
+    expect(graph.graph.hasEdge("req-1->req-2:depends_on")).toBe(true);
+  });
+
+  it("throws NodeNotFoundError if source doesn't exist", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-2", operationId: "task.b", status: "pending", input: {} });
+    expect(() => graph.addDependency("missing", "req-2")).toThrow(NodeNotFoundError);
+  });
+
+  it("throws NodeNotFoundError if target doesn't exist", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.a", status: "pending", input: {} });
+    expect(() => graph.addDependency("req-1", "missing")).toThrow(NodeNotFoundError);
+  });
+
+  it("throws CycleError if adding would create cycle", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.a", status: "pending", input: {} });
+    graph.addCall({ requestId: "req-2", operationId: "task.b", status: "pending", input: {} });
+    graph.addCall({ requestId: "req-3", operationId: "task.c", status: "pending", input: {} });
+    graph.addEdge("req-1", "req-2");
+    graph.addEdge("req-2", "req-3");
+    expect(() => graph.addDependency("req-3", "req-1")).toThrow(CycleError);
+  });
+});
+
+describe("FlowGraph.updateStatus", () => {
+  it("transitions pending to running", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "running");
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("running");
+  });
+
+  it("transitions running to completed", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "running");
+    graph.updateStatus("req-1", "completed", { completedAt: "2026-01-01T00:00:01Z" });
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("completed");
+    expect(attrs.completedAt).toBe("2026-01-01T00:00:01Z");
+  });
+
+  it("transitions running to failed", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "running");
+    graph.updateStatus("req-1", "failed");
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("failed");
+  });
+
+  it("transitions pending to aborted", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "aborted");
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("aborted");
+  });
+
+  it("transitions running to aborted", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "running");
+    graph.updateStatus("req-1", "aborted");
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("aborted");
+  });
+
+  it("is no-op if status is already the target", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "pending");
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("pending");
+  });
+
+  it("throws InvalidTransitionError for completed to running", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "running");
+    graph.updateStatus("req-1", "completed", { completedAt: "2026-01-01T00:00:01Z" });
+    expect(() => graph.updateStatus("req-1", "running")).toThrow(InvalidTransitionError);
+  });
+
+  it("throws InvalidTransitionError for failed to running", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "running");
+    graph.updateStatus("req-1", "failed");
+    expect(() => graph.updateStatus("req-1", "running")).toThrow(InvalidTransitionError);
+  });
+
+  it("throws InvalidTransitionError for aborted to running", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "aborted");
+    expect(() => graph.updateStatus("req-1", "running")).toThrow(InvalidTransitionError);
+  });
+
+  it("throws InvalidTransitionError for pending to completed", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    expect(() => graph.updateStatus("req-1", "completed")).toThrow(InvalidTransitionError);
+  });
+
+  it("throws InvalidTransitionError for pending to failed", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    expect(() => graph.updateStatus("req-1", "failed")).toThrow(InvalidTransitionError);
+  });
+
+  it("throws NodeNotFoundError for unknown requestId", () => {
+    const graph = new FlowGraph();
+    expect(() => graph.updateStatus("missing", "running")).toThrow(NodeNotFoundError);
+  });
+
+  it("InvalidTransitionError contains from/to info", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "running");
+    graph.updateStatus("req-1", "completed", { completedAt: "2026-01-01T00:00:01Z" });
+    try {
+      graph.updateStatus("req-1", "running");
+      expect.unreachable("should throw");
+    } catch (e) {
+      expect(e).toBeInstanceOf(InvalidTransitionError);
+      const ite = e as InvalidTransitionError;
+      expect(ite.requestId).toBe("req-1");
+      expect(ite.from).toBe("completed" as CallStatus);
+      expect(ite.to).toBe("running" as CallStatus);
+    }
+  });
+
+  it("merges extra attributes on transition", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.op", status: "pending", input: {} });
+    graph.updateStatus("req-1", "running");
+    graph.updateStatus("req-1", "completed", {
+      output: { result: 42 },
+      completedAt: "2026-01-01T00:00:01Z",
+    });
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.status).toBe("completed");
+    expect(attrs.output).toEqual({ result: 42 });
+    expect(attrs.completedAt).toBe("2026-01-01T00:00:01Z");
+  });
+});
+
+describe("FlowGraph.updateCall", () => {
+  it("partially merges call attributes", () => {
+    const graph = new FlowGraph();
+    graph.addCall({
+      requestId: "req-1",
+      operationId: "task.op",
+      status: "pending",
+      input: {},
+    });
+    graph.updateCall("req-1", { output: "some result" });
+    const attrs = graph.getNodeAttributes("req-1") as Record<string, unknown>;
+    expect(attrs.output).toBe("some result");
+    expect(attrs.status).toBe("pending");
+  });
+
+  it("throws NodeNotFoundError for unknown requestId", () => {
+    const graph = new FlowGraph();
+    expect(() => graph.updateCall("missing", { output: "x" })).toThrow(NodeNotFoundError);
+  });
+});
+
+describe("FlowGraph.removeCall", () => {
+  it("removes node and attached edges", () => {
+    const graph = new FlowGraph();
+    graph.addCall({ requestId: "req-1", operationId: "task.parent", status: "pending", input: {} });
+    graph.addCall({ requestId: "req-2", operationId: "task.child", status: "pending", input: {}, parentRequestId: "req-1" });
+    expect(graph.size).toBe(1);
+    graph.removeCall("req-2");
+    expect(graph.hasNode("req-2")).toBe(false);
+    expect(graph.size).toBe(0);
+    expect(graph.hasNode("req-1")).toBe(true);
+  });
+
+  it("is a no-op if requestId doesn't exist", () => {
+    const graph = new FlowGraph();
+    expect(() => graph.removeCall("missing")).not.toThrow();
+  });
 });
\ No newline at end of file
diff --git a/test/reactive/workflow.test.ts b/test/reactive/workflow.test.ts
index 1975831..f02ab08 100644
--- a/test/reactive/workflow.test.ts
+++ b/test/reactive/workflow.test.ts
@@ -159,7 +159,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -177,7 +177,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -201,7 +201,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -225,7 +225,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -265,7 +265,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
 
       const respondedEvent: CallEventMapValue = {
         type: "call.responded",
@@ -304,7 +304,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -353,7 +353,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -380,7 +380,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -408,7 +408,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -434,7 +434,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -452,7 +452,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-2");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -466,6 +466,7 @@ describe("WorkflowReactiveRoot", () => {
         error: { code: "ERR", message: "first attempt failed" },
         timestamp: "2026-01-01T00:00:01Z",
       });
+      root.setRequestId("a", "req-2");
       root.append({
         type: "call.requested",
         requestId: "req-2",
@@ -503,7 +504,7 @@ describe("WorkflowReactiveRoot", () => {
       const graph = makeSimpleGraph();
       const root = new WorkflowReactiveRoot(graph);
 
-      root.nodeKeyToRequestId.set("a", "req-1");
+      root.setRequestId("a", "req-1");
       root.append({
         type: "call.requested",
         requestId: "req-1",
@@ -840,9 +841,9 @@ describe("WorkflowReactiveRoot", () => {
       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");
+      root.setRequestId("a", "req-a");
+      root.setRequestId("b", "req-b");
+      root.setRequestId("c", "req-c");
 
       expect(root.getStatus("a")).toBe("idle");
       expect(root.getStatus("b")).toBe("idle");