Shared State

  // Subscribe the component to agent state changes. Any time the agent  // mutates its state (e.g. via its `set_notes` tool) this hook fires,  // we re-render, and the sidebar panels reflect the new values.  const { agent } = useAgent({    agentId: "shared-state-read-write",    updates: [UseAgentUpdate.OnStateChanged],  });

  // WRITE: every edit in the sidebar goes straight into agent state.  // On the agent's next turn, `PreferencesInjectorMiddleware` reads this  // back out of state and adds it to the system prompt — so the UI's  // writes visibly steer the model.  const handlePreferencesChange = (next: Preferences) => {    agent.setState({      preferences: next,      notes: latestNotesRef.current, // preserve what the agent has written    } as RWAgentState);  };

// Read-side render: this card reflects the agent-authored `notes` slice// of shared state. The parent page passes `state.notes` in; we never// touch agent state ourselves — we just render it. The Clear button is// a small write-back, exposed as an `onClear` prop.export function NotesCard({ notes, onClear }: NotesCardProps) {  return (    <Card data-testid="notes-card" className="w-full">      <CardHeader>        <div className="flex items-start justify-between gap-3">          <div className="space-y-1.5">            <CardTitle>Agent Scratch pad</CardTitle>            <CardDescription>              The agent writes here via its{" "}              <code className="font-mono text-[11px] text-[#010507]">                set_notes              </code>{" "}              tool. The UI re-renders from shared state.            </CardDescription>          </div>          {notes.length > 0 && (            <Button              type="button"              onClick={onClear}              data-testid="notes-clear-button"              variant="destructive"              size="sm"              className="uppercase tracking-[0.14em] text-[10px]"            >              Clear            </Button>          )}        </div>      </CardHeader>      <CardContent>        {notes.length === 0 ? (          <div            data-testid="notes-empty"            className="text-sm text-[#838389] italic min-h-[160px] flex items-center justify-center text-center px-4 border border-dashed border-[#E9E9EF] rounded-xl bg-[#FAFAFC]"          >            the agent will make observations about you and note them here!          </div>        ) : (          <ul            data-testid="notes-list"            className="space-y-2 text-sm text-[#010507]"          >            {notes.map((note, i) => (              <li                key={i}                data-testid="note-item"                className="flex gap-2 rounded-lg border border-[#E9E9EF] bg-[#FAFAFC] px-3 py-2"              >                <span className="text-[#838389] font-mono text-xs leading-5 select-none">                  {String(i + 1).padStart(2, "0")}                </span>                <span className="flex-1">{note}</span>              </li>            ))}          </ul>        )}      </CardContent>    </Card>  );}

import { EventType } from "@ag-ui/core";import type Anthropic from "@anthropic-ai/sdk";type StreamingState = {  document?: string;};type ToolDeltaEvent = {  type: string;  content_block?: { type: string; name?: string };  delta?: { type: string; partial_json?: string };};export const WRITE_DOCUMENT_TOOL_SCHEMA: Anthropic.Tool = {  name: "write_document",  description: "Write a document into shared agent state.",  input_schema: {    type: "object",    properties: {      document: {        type: "string",        description: "The full document text to render in shared state.",      },    },    required: ["document"],  },};function partialJsonStringProperty(source: string, key: string): string | null {  // Hand-rolled partial-JSON string extraction with no external dependency  // (mirrors the Python sibling snippet). Reads the current value of a string  // property from a partial buffer, tolerating truncation mid-value.  const marker = JSON.stringify(key);  const keyPos = source.indexOf(marker);  if (keyPos < 0) return null;  const colonPos = source.indexOf(":", keyPos + marker.length);  if (colonPos < 0) return null;  const valueStart = source.indexOf('"', colonPos + 1);  if (valueStart < 0) return null;  const rawChars: string[] = [];  let escaped = false;  for (const char of source.slice(valueStart + 1)) {    if (escaped) {      rawChars.push("\\" + char);      escaped = false;    } else if (char === "\\") {      escaped = true;    } else if (char === '"') {      break;    } else {      rawChars.push(char);    }  }  // A buffer truncated mid-escape drops the dangling backslash (matching the  // Python sibling) so the partial value still parses instead of forcing null.  try {    return JSON.parse(`"${rawChars.join("")}"`) as string;  } catch {    return null;  }}export function emitStreamingDocumentState(  event: ToolDeltaEvent,  tracker: { toolName: string | null; argsJson: string; lastDocument: string },  state: StreamingState,  emit: (event: object) => void,) {  if (    event.type === "content_block_start" &&    event.content_block?.type === "tool_use"  ) {    tracker.toolName = event.content_block.name ?? null;    tracker.argsJson = "";    return;  }  if (    event.type !== "content_block_delta" ||    event.delta?.type !== "input_json_delta"  ) {    return;  }  tracker.argsJson += event.delta.partial_json ?? "";  if (tracker.toolName !== "write_document") {    return;  }  const streamedDocument = partialJsonStringProperty(    tracker.argsJson,    "document",  );  if (streamedDocument === null || streamedDocument === tracker.lastDocument) {    return;  }  // Mutate `state` in place but emit a fresh copy each delta, so a consumer  // that retains a snapshot doesn't see earlier snapshots mutate to the final  // text as streaming continues. (Mirrors the Python sibling snippet.)  const snapshot: StreamingState = { ...state, document: streamedDocument };  state.document = streamedDocument;  tracker.lastDocument = streamedDocument;  emit({ type: EventType.STATE_SNAPSHOT, snapshot });}