Add canvas artifact RPC foundation for A2UI

src/gateway/canvas-store.test.ts

@@ -0,0 +1,58 @@
+import { describe, expect, it } from 'vitest';
+import { CanvasStore } from './canvas-store.js';
+
+describe('CanvasStore', () => {
+  it('stores and retrieves artifacts per session', () => {
+    const store = new CanvasStore();
+    const artifact = store.put('ws:1', {
+      id: 'a1',
+      type: 'note',
+      content: { text: 'hello' },
+    });
+
+    expect(artifact.id).toBe('a1');
+    expect(store.get('ws:1', 'a1')?.type).toBe('note');
+    expect(store.list('ws:1')).toHaveLength(1);
+  });
+
+  it('updates existing artifacts while preserving createdAt', async () => {
+    const store = new CanvasStore();
+    const first = store.put('ws:1', {
+      id: 'a1',
+      type: 'note',
+      content: { text: 'one' },
+    });
+    await new Promise((resolve) => setTimeout(resolve, 2));
+    const second = store.put('ws:1', {
+      id: 'a1',
+      type: 'note',
+      content: { text: 'two' },
+    });
+
+    expect(second.createdAt).toBe(first.createdAt);
+    expect(second.updatedAt).toBeGreaterThanOrEqual(first.updatedAt);
+    expect(store.get('ws:1', 'a1')?.content).toEqual({ text: 'two' });
+  });
+
+  it('deletes and clears session artifacts', () => {
+    const store = new CanvasStore();
+    store.put('ws:1', { id: 'a1', type: 'note', content: 'x' });
+    store.put('ws:1', { id: 'a2', type: 'note', content: 'y' });
+
+    expect(store.delete('ws:1', 'a1')).toBe(true);
+    expect(store.delete('ws:1', 'missing')).toBe(false);
+    expect(store.list('ws:1')).toHaveLength(1);
+    expect(store.clear('ws:1')).toBe(1);
+    expect(store.list('ws:1')).toEqual([]);
+  });
+
+  it('evicts oldest artifact when per-session cap is exceeded', () => {
+    const store = new CanvasStore(2);
+    store.put('ws:1', { id: 'a1', type: 'note', content: 1 });
+    store.put('ws:1', { id: 'a2', type: 'note', content: 2 });
+    store.put('ws:1', { id: 'a3', type: 'note', content: 3 });
+
+    expect(store.get('ws:1', 'a1')).toBeUndefined();
+    expect(store.list('ws:1').map((a) => a.id).sort()).toEqual(['a2', 'a3']);
+  });
+});

src/gateway/canvas-store.ts

@@ -0,0 +1,99 @@
+export interface CanvasArtifact {
+  id: string;
+  type: string;
+  title?: string;
+  content: unknown;
+  metadata?: Record<string, unknown>;
+  createdAt: number;
+  updatedAt: number;
+}
+
+interface CanvasPutInput {
+  id?: string;
+  type: string;
+  title?: string;
+  content: unknown;
+  metadata?: Record<string, unknown>;
+}
+
+/**
+ * Ephemeral in-memory canvas store keyed by sessionId.
+ * Intended as a gateway runtime foundation for A2UI/canvas surfaces.
+ */
+export class CanvasStore {
+  private readonly sessions = new Map<string, Map<string, CanvasArtifact>>();
+
+  constructor(private readonly maxArtifactsPerSession = 200) {}
+
+  list(sessionId: string): CanvasArtifact[] {
+    const entries = this.sessions.get(sessionId);
+    if (!entries) {
+      return [];
+    }
+    return Array.from(entries.values()).sort((a, b) => b.updatedAt - a.updatedAt);
+  }
+
+  get(sessionId: string, artifactId: string): CanvasArtifact | undefined {
+    return this.sessions.get(sessionId)?.get(artifactId);
+  }
+
+  put(sessionId: string, input: CanvasPutInput): CanvasArtifact {
+    const id = sanitizeArtifactId(input.id);
+    const now = Date.now();
+    let entries = this.sessions.get(sessionId);
+    if (!entries) {
+      entries = new Map();
+      this.sessions.set(sessionId, entries);
+    }
+
+    const existing = entries.get(id);
+    const artifact: CanvasArtifact = {
+      id,
+      type: input.type.trim(),
+      title: input.title?.trim() || undefined,
+      content: input.content,
+      metadata: input.metadata,
+      createdAt: existing?.createdAt ?? now,
+      updatedAt: now,
+    };
+    entries.set(id, artifact);
+
+    if (entries.size > this.maxArtifactsPerSession) {
+      const oldest = Array.from(entries.values()).sort((a, b) => a.updatedAt - b.updatedAt)[0];
+      if (oldest) {
+        entries.delete(oldest.id);
+      }
+    }
+    return artifact;
+  }
+
+  delete(sessionId: string, artifactId: string): boolean {
+    const entries = this.sessions.get(sessionId);
+    if (!entries) {
+      return false;
+    }
+    const removed = entries.delete(artifactId);
+    if (entries.size === 0) {
+      this.sessions.delete(sessionId);
+    }
+    return removed;
+  }
+
+  clear(sessionId: string): number {
+    const entries = this.sessions.get(sessionId);
+    if (!entries) {
+      return 0;
+    }
+    const count = entries.size;
+    this.sessions.delete(sessionId);
+    return count;
+  }
+}
+
+function sanitizeArtifactId(raw?: string): string {
+  const value = (raw ?? '').trim();
+  if (value) {
+    return value.slice(0, 128);
+  }
+  return `art_${Date.now()}_${Math.random().toString(36).slice(2, 10)}`;
+}

src/gateway/handlers/canvas.ts

@@ -0,0 +1,89 @@
+import type { GatewayRequest, OutboundMessage } from '../protocol.js';
+import { makeError, makeResponse, ErrorCode } from '../protocol.js';
+import type { CanvasStore } from '../canvas-store.js';
+
+export interface CanvasHandlerDeps {
+  store: CanvasStore;
+}
+
+export function createCanvasHandlers(deps: CanvasHandlerDeps) {
+  return {
+    'canvas.list': async (request: GatewayRequest): Promise<OutboundMessage> => {
+      const params = request.params as { sessionId?: string } | undefined;
+      if (!params?.sessionId) {
+        return makeError(request.id, ErrorCode.InvalidRequest, 'sessionId is required');
+      }
+
+      const artifacts = deps.store.list(params.sessionId);
+      return makeResponse(request.id, { artifacts });
+    },
+
+    'canvas.get': async (request: GatewayRequest): Promise<OutboundMessage> => {
+      const params = request.params as { sessionId?: string; artifactId?: string } | undefined;
+      if (!params?.sessionId) {
+        return makeError(request.id, ErrorCode.InvalidRequest, 'sessionId is required');
+      }
+      if (!params?.artifactId) {
+        return makeError(request.id, ErrorCode.InvalidRequest, 'artifactId is required');
+      }
+
+      const artifact = deps.store.get(params.sessionId, params.artifactId);
+      if (!artifact) {
+        return makeError(request.id, ErrorCode.SessionNotFound, 'Canvas artifact not found');
+      }
+      return makeResponse(request.id, { artifact });
+    },
+
+    'canvas.put': async (request: GatewayRequest): Promise<OutboundMessage> => {
+      const params = request.params as {
+        sessionId?: string;
+        artifactId?: string;
+        type?: string;
+        title?: string;
+        content?: unknown;
+        metadata?: Record<string, unknown>;
+      } | undefined;
+      if (!params?.sessionId) {
+        return makeError(request.id, ErrorCode.InvalidRequest, 'sessionId is required');
+      }
+      if (!params?.type || typeof params.type !== 'string' || !params.type.trim()) {
+        return makeError(request.id, ErrorCode.InvalidRequest, 'type is required');
+      }
+      if (params.content === undefined) {
+        return makeError(request.id, ErrorCode.InvalidRequest, 'content is required');
+      }
+
+      const artifact = deps.store.put(params.sessionId, {
+        id: params.artifactId,
+        type: params.type,
+        title: params.title,
+        content: params.content,
+        metadata: params.metadata,
+      });
+      return makeResponse(request.id, { artifact, upserted: true });
+    },
+
+    'canvas.delete': async (request: GatewayRequest): Promise<OutboundMessage> => {
+      const params = request.params as { sessionId?: string; artifactId?: string } | undefined;
+      if (!params?.sessionId) {
+        return makeError(request.id, ErrorCode.InvalidRequest, 'sessionId is required');
+      }
+      if (!params?.artifactId) {
+        return makeError(request.id, ErrorCode.InvalidRequest, 'artifactId is required');
+      }
+
+      const deleted = deps.store.delete(params.sessionId, params.artifactId);
+      return makeResponse(request.id, { deleted });
+    },
+
+    'canvas.clear': async (request: GatewayRequest): Promise<OutboundMessage> => {
+      const params = request.params as { sessionId?: string } | undefined;
+      if (!params?.sessionId) {
+        return makeError(request.id, ErrorCode.InvalidRequest, 'sessionId is required');
+      }
+
+      const cleared = deps.store.clear(params.sessionId);
+      return makeResponse(request.id, { cleared });
+    },
+  };
+}

src/gateway/handlers/handlers.test.ts

@@ -7,10 +7,12 @@ import { createAgentHandlers } from './agent.js';
 import { createIntentHandlers } from './intents.js';
 import { createRoutingHandlers } from './routing.js';
 import { createHistoryHandlers } from './history.js';
+import { createCanvasHandlers } from './canvas.js';
 import { createConfigHandlers, redactConfig } from './config.js';
 import { createPairingHandlers } from './pairing.js';
 import { PairingManager } from '../../channels/pairing.js';
 import { LaneQueue } from '../lane-queue.js';
+import { CanvasStore } from '../canvas-store.js';
 import { ErrorCode } from '../protocol.js';
 import type { GatewayRequest, GatewayResponse, GatewayError, GatewayEvent, OutboundMessage } from '../protocol.js';
 import { ComponentRegistry } from '../../intents/index.js';
@@ -350,6 +352,82 @@ describe('session handlers', () => {
   });
 });
 
+describe('canvas handlers', () => {
+  it('supports put/get/list/delete/clear lifecycle', async () => {
+    const handlers = createCanvasHandlers({ store: new CanvasStore() });
+
+    const putReq: GatewayRequest = {
+      id: 1,
+      method: 'canvas.put',
+      params: {
+        sessionId: 'ws:abc',
+        artifactId: 'card-1',
+        type: 'note',
+        title: 'Draft',
+        content: { text: 'hello' },
+      },
+    };
+    const putRes = await handlers['canvas.put'](putReq) as GatewayResponse;
+    expect(getPath(putRes.result, 'artifact', 'id')).toBe('card-1');
+
+    const getRes = await handlers['canvas.get']({
+      id: 2,
+      method: 'canvas.get',
+      params: { sessionId: 'ws:abc', artifactId: 'card-1' },
+    }) as GatewayResponse;
+    expect(getPath(getRes.result, 'artifact', 'title')).toBe('Draft');
+
+    const listRes = await handlers['canvas.list']({
+      id: 3,
+      method: 'canvas.list',
+      params: { sessionId: 'ws:abc' },
+    }) as GatewayResponse;
+    expect((getPath(listRes.result, 'artifacts') as unknown[]).length).toBe(1);
+
+    const delRes = await handlers['canvas.delete']({
+      id: 4,
+      method: 'canvas.delete',
+      params: { sessionId: 'ws:abc', artifactId: 'card-1' },
+    }) as GatewayResponse;
+    expect(getPath(delRes.result, 'deleted')).toBe(true);
+
+    await handlers['canvas.put']({
+      id: 5,
+      method: 'canvas.put',
+      params: { sessionId: 'ws:abc', artifactId: 'card-2', type: 'note', content: 'a' },
+    });
+    await handlers['canvas.put']({
+      id: 6,
+      method: 'canvas.put',
+      params: { sessionId: 'ws:abc', artifactId: 'card-3', type: 'note', content: 'b' },
+    });
+    const clearRes = await handlers['canvas.clear']({
+      id: 7,
+      method: 'canvas.clear',
+      params: { sessionId: 'ws:abc' },
+    }) as GatewayResponse;
+    expect(getPath(clearRes.result, 'cleared')).toBe(2);
+  });
+
+  it('validates required params', async () => {
+    const handlers = createCanvasHandlers({ store: new CanvasStore() });
+
+    const missingSession = await handlers['canvas.list']({
+      id: 8,
+      method: 'canvas.list',
+      params: {},
+    }) as GatewayError;
+    expect(missingSession.error.code).toBe(ErrorCode.InvalidRequest);
+
+    const missingContent = await handlers['canvas.put']({
+      id: 9,
+      method: 'canvas.put',
+      params: { sessionId: 'ws:abc', type: 'note' },
+    }) as GatewayError;
+    expect(missingContent.error.code).toBe(ErrorCode.InvalidRequest);
+  });
+});
+
 describe('tool handlers', () => {
   const mockTool = {
     name: 'test.tool',

src/gateway/handlers/index.ts

@@ -17,5 +17,7 @@ export { createRoutingHandlers } from './routing.js';
 export type { RoutingHandlerDeps } from './routing.js';
 export { createHistoryHandlers } from './history.js';
 export type { HistoryHandlerDeps } from './history.js';
+export { createCanvasHandlers } from './canvas.js';
+export type { CanvasHandlerDeps } from './canvas.js';
 export { createNodeHandlers } from './node.js';
 export type { NodeHandlerDeps, NodeRegistration, NodeConnectionState, NodeLocation } from './node.js';

src/gateway/server.test.ts

@@ -234,6 +234,46 @@ describe('GatewayServer integration', () => {
     expect(methods).toContain('sessions.create');
     expect(methods).toContain('tools.list');
     expect(methods).toContain('tools.invoke');
+    expect(methods).toContain('canvas.put');
+    expect(methods).toContain('canvas.list');
+  });
+
+  it('supports canvas artifact lifecycle via gateway RPC', async () => {
+    if (!LISTEN_ALLOWED) {
+      return;
+    }
+    const ws = await createClient();
+    try {
+      const put = await sendAndReceive(ws, {
+        id: 31,
+        method: 'canvas.put',
+        params: {
+          sessionId: 'ws:test-canvas',
+          artifactId: 'a1',
+          type: 'note',
+          content: { text: 'draft' },
+        },
+      });
+      expect((put as GatewayResponse).id).toBe(31);
+
+      const list = await sendAndReceive(ws, {
+        id: 32,
+        method: 'canvas.list',
+        params: { sessionId: 'ws:test-canvas' },
+      });
+      const artifacts = ((list as GatewayResponse).result as { artifacts: Array<{ id: string }> }).artifacts;
+      expect(artifacts).toHaveLength(1);
+      expect(artifacts[0]?.id).toBe('a1');
+
+      const clear = await sendAndReceive(ws, {
+        id: 33,
+        method: 'canvas.clear',
+        params: { sessionId: 'ws:test-canvas' },
+      });
+      expect(((clear as GatewayResponse).result as { cleared: number }).cleared).toBe(1);
+    } finally {
+      ws.close();
+    }
   });
 
   // ── HTTP static file serving tests ────────────────────────────

src/gateway/server.ts

@@ -7,6 +7,7 @@ import { SessionBridge } from './session-bridge.js';
 import type { SessionBridgeConfig } from './session-bridge.js';
 import { LaneQueue } from './lane-queue.js';
 import type { LaneQueueConfig } from './lane-queue.js';
+import { CanvasStore } from './canvas-store.js';
 import { MetricsCollector } from './metrics.js';
 import { authenticateRequest, authorizeNodeMethod } from './auth.js';
 import type { AuthConfig } from './auth.js';
@@ -28,6 +29,7 @@ import {
   createIntentHandlers,
   createRoutingHandlers,
   createHistoryHandlers,
+  createCanvasHandlers,
   createNodeHandlers,
 } from './handlers/index.js';
 import { discoverServices } from './handlers/services.js';
@@ -133,6 +135,7 @@ export class GatewayServer {
   private router: Router;
   private sessionBridge: SessionBridge;
   private laneQueue: LaneQueue;
+  private canvasStore: CanvasStore;
   private metrics: MetricsCollector;
   private discoveryHandle: GatewayDiscoveryHandle | null = null;
   private connectionMap: Map<WebSocket, string> = new Map();
@@ -160,6 +163,7 @@ export class GatewayServer {
     });
 
     this.laneQueue = new LaneQueue(config.queue);
+    this.canvasStore = new CanvasStore();
     this.metrics = new MetricsCollector({
       getQueueDepth: () => this.laneQueue.totalPending(),
     });
@@ -235,6 +239,10 @@ export class GatewayServer {
       sessionManager: this.config.sessionManager,
     });
 
+    const canvasHandlers = createCanvasHandlers({
+      store: this.canvasStore,
+    });
+
     const toolHandlers = createToolHandlers({
       toolRegistry: this.config.toolRegistry,
       toolExecutor: this.config.toolExecutor,
@@ -365,6 +373,9 @@ export class GatewayServer {
     for (const [method, handler] of Object.entries(historyHandlers)) {
       this.router.register(method, handler);
     }
+    for (const [method, handler] of Object.entries(canvasHandlers)) {
+      this.router.register(method, handler);
+    }
     for (const [method, handler] of Object.entries(toolHandlers)) {
       this.router.register(method, handler);
     }