fix: reply in user's thread and prevent git credential hangs

Pass thread name through Add-ons response wrapper so bot replies stay
in the user's thread instead of posting top-level messages. Add
GIT_TERMINAL_PROMPT=0 to Dockerfile to prevent git from hanging on
credential prompts, which was blocking all requests under concurrency=1.

.dockerignore

@@ -0,0 +1,15 @@
+.git
+.github
+.gcp
+bundle
+evals
+integration-tests
+docs
+packages/cli
+packages/vscode-ide-companion
+packages/test-utils
+**/*.test.ts
+**/*.test.js
+**/src/**/*.ts
+!packages/a2a-server/dist/**
+!packages/core/dist/**

package-lock.json

@@ -2255,6 +2255,7 @@
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       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@octokit/auth-token": "^6.0.0",
         "@octokit/graphql": "^9.0.2",
@@ -2435,6 +2436,7 @@
       "resolved": "https://registry.npmjs.org/@opentelemetry/api/-/api-1.9.0.tgz",
       "integrity": "sha512-3giAOQvZiH5F9bMlMiv8+GSPMeqg0dbaeo58/0SlA9sxSqZhnUtxzX9/2FzyhS9sWQf5S0GJE0AKBrFqjpeYcg==",
       "license": "Apache-2.0",
+      "peer": true,
       "engines": {
         "node": ">=8.0.0"
       }
@@ -2468,6 +2470,7 @@
       "resolved": "https://registry.npmjs.org/@opentelemetry/core/-/core-2.0.1.tgz",
       "integrity": "sha512-MaZk9SJIDgo1peKevlbhP6+IwIiNPNmswNL4AF0WaQJLbHXjr9SrZMgS12+iqr9ToV4ZVosCcc0f8Rg67LXjxw==",
       "license": "Apache-2.0",
+      "peer": true,
       "dependencies": {
         "@opentelemetry/semantic-conventions": "^1.29.0"
       },
@@ -2836,6 +2839,7 @@
       "resolved": "https://registry.npmjs.org/@opentelemetry/resources/-/resources-2.0.1.tgz",
       "integrity": "sha512-dZOB3R6zvBwDKnHDTB4X1xtMArB/d324VsbiPkX/Yu0Q8T2xceRthoIVFhJdvgVM2QhGVUyX9tzwiNxGtoBJUw==",
       "license": "Apache-2.0",
+      "peer": true,
       "dependencies": {
         "@opentelemetry/core": "2.0.1",
         "@opentelemetry/semantic-conventions": "^1.29.0"
@@ -2869,6 +2873,7 @@
       "resolved": "https://registry.npmjs.org/@opentelemetry/sdk-metrics/-/sdk-metrics-2.0.1.tgz",
       "integrity": "sha512-wf8OaJoSnujMAHWR3g+/hGvNcsC16rf9s1So4JlMiFaFHiE4HpIA3oUh+uWZQ7CNuK8gVW/pQSkgoa5HkkOl0g==",
       "license": "Apache-2.0",
+      "peer": true,
       "dependencies": {
         "@opentelemetry/core": "2.0.1",
         "@opentelemetry/resources": "2.0.1"
@@ -2921,6 +2926,7 @@
       "resolved": "https://registry.npmjs.org/@opentelemetry/sdk-trace-base/-/sdk-trace-base-2.0.1.tgz",
       "integrity": "sha512-xYLlvk/xdScGx1aEqvxLwf6sXQLXCjk3/1SQT9X9AoN5rXRhkdvIFShuNNmtTEPRBqcsMbS4p/gJLNI2wXaDuQ==",
       "license": "Apache-2.0",
+      "peer": true,
       "dependencies": {
         "@opentelemetry/core": "2.0.1",
         "@opentelemetry/resources": "2.0.1",
@@ -4136,6 +4142,7 @@
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       "devOptional": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "csstype": "^3.0.2"
       }
@@ -4430,6 +4437,7 @@
       "integrity": "sha512-6sMvZePQrnZH2/cJkwRpkT7DxoAWh+g6+GFRK6bV3YQo7ogi3SX5rgF6099r5Q53Ma5qeT7LGmOmuIutF4t3lA==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@typescript-eslint/scope-manager": "8.35.0",
         "@typescript-eslint/types": "8.35.0",
@@ -5422,6 +5430,7 @@
       "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.15.0.tgz",
       "integrity": "sha512-NZyJarBfL7nWwIq+FDL6Zp/yHEhePMNnnJ0y3qfieCrmNvYct8uvtiV41UvlSe6apAfk0fY1FbWx+NwfmpvtTg==",
       "license": "MIT",
+      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -8431,6 +8440,7 @@
       "integrity": "sha512-GsGizj2Y1rCWDu6XoEekL3RLilp0voSePurjZIkxL3wlm5o5EC9VpgaP7lrCvjnkuLvzFBQWB3vWB3K5KQTveQ==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@eslint-community/eslint-utils": "^4.2.0",
         "@eslint-community/regexpp": "^4.12.1",
@@ -8971,6 +8981,7 @@
       "resolved": "https://registry.npmjs.org/express/-/express-5.2.1.tgz",
       "integrity": "sha512-hIS4idWWai69NezIdRt2xFVofaF4j+6INOpJlVOLDO8zXGpUVEVzIYk12UUi2JzjEzWL3IOAxcTubgz9Po0yXw==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "accepts": "^2.0.0",
         "body-parser": "^2.2.1",
@@ -10584,6 +10595,7 @@
       "resolved": "https://registry.npmjs.org/@jrichman/ink/-/ink-6.4.8.tgz",
       "integrity": "sha512-v0thcXIKl9hqF/1w4HqA6MKxIcMoWSP3YtEZIAA+eeJngXpN5lGnMkb6rllB7FnOdwyEyYaFTcu1ZVr4/JZpWQ==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@alcalzone/ansi-tokenize": "^0.2.1",
         "ansi-escapes": "^7.0.0",
@@ -14368,6 +14380,7 @@
       "resolved": "https://registry.npmjs.org/react/-/react-19.2.0.tgz",
       "integrity": "sha512-tmbWg6W31tQLeB5cdIBOicJDJRR2KzXsV7uSK9iNfLWQ5bIZfxuPEHp7M8wiHyHnn0DD1i7w3Zmin0FtkrwoCQ==",
       "license": "MIT",
+      "peer": true,
       "engines": {
         "node": ">=0.10.0"
       }
@@ -14378,6 +14391,7 @@
       "integrity": "sha512-ePrwPfxAnB+7hgnEr8vpKxL9cmnp7F322t8oqcPshbIQQhDKgFDW4tjhF2wjVbdXF9O/nyuy3sQWd9JGpiLPvA==",
       "devOptional": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "shell-quote": "^1.6.1",
         "ws": "^7"
@@ -16614,6 +16628,7 @@
       "resolved": "https://registry.npmjs.org/picomatch/-/picomatch-4.0.3.tgz",
       "integrity": "sha512-5gTmgEY/sqK6gFXLIsQNH19lWb4ebPDLA4SdLP7dsWkIXHWlG66oPuVvXSGFPppYZz8ZDZq0dYYrbHfBCVUb1Q==",
       "license": "MIT",
+      "peer": true,
       "engines": {
         "node": ">=12"
       },
@@ -16837,7 +16852,8 @@
       "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.8.1.tgz",
       "integrity": "sha512-oJFu94HQb+KVduSUQL7wnpmqnfmLsOA/nAh6b6EH0wCEoK0/mPeXU6c3wKDV83MkOuHPRHtSXKKU99IBazS/2w==",
       "dev": true,
-      "license": "0BSD"
+      "license": "0BSD",
+      "peer": true
     },
     "node_modules/tsx": {
       "version": "4.20.3",
@@ -16845,6 +16861,7 @@
       "integrity": "sha512-qjbnuR9Tr+FJOMBqJCW5ehvIo/buZq7vH7qD7JziU98h6l3qGy0a/yPFjwO+y0/T7GFpNgNAvEcPPVfyT8rrPQ==",
       "devOptional": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "esbuild": "~0.25.0",
         "get-tsconfig": "^4.7.5"
@@ -17017,6 +17034,7 @@
       "integrity": "sha512-p1diW6TqL9L07nNxvRMM7hMMw4c5XOo/1ibL4aAIGmSAt9slTE1Xgw5KWuof2uTOvCg9BY7ZRi+GaF+7sfgPeQ==",
       "devOptional": true,
       "license": "Apache-2.0",
+      "peer": true,
       "bin": {
         "tsc": "bin/tsc",
         "tsserver": "bin/tsserver"
@@ -17224,6 +17242,7 @@
       "resolved": "https://registry.npmjs.org/vite/-/vite-7.2.2.tgz",
       "integrity": "sha512-BxAKBWmIbrDgrokdGZH1IgkIk/5mMHDreLDmCJ0qpyJaAteP8NvMhkwr/ZCQNqNH97bw/dANTE9PDzqwJghfMQ==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "esbuild": "^0.25.0",
         "fdir": "^6.5.0",
@@ -17337,6 +17356,7 @@
       "resolved": "https://registry.npmjs.org/picomatch/-/picomatch-4.0.3.tgz",
       "integrity": "sha512-5gTmgEY/sqK6gFXLIsQNH19lWb4ebPDLA4SdLP7dsWkIXHWlG66oPuVvXSGFPppYZz8ZDZq0dYYrbHfBCVUb1Q==",
       "license": "MIT",
+      "peer": true,
       "engines": {
         "node": ">=12"
       },
@@ -17349,6 +17369,7 @@
       "resolved": "https://registry.npmjs.org/vitest/-/vitest-3.2.4.tgz",
       "integrity": "sha512-LUCP5ev3GURDysTWiP47wRRUpLKMOfPh+yKTx3kVIEiu5KOMeqzpnYNsKyOoVrULivR8tLcks4+lga33Whn90A==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@types/chai": "^5.2.2",
         "@vitest/expect": "3.2.4",
@@ -18053,6 +18074,7 @@
       "resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",
       "integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
       "license": "MIT",
+      "peer": true,
       "funding": {
         "url": "https://github.com/sponsors/colinhacks"
       }
@@ -18075,6 +18097,7 @@
         "@google/gemini-cli-core": "file:../core",
         "express": "^5.1.0",
         "fs-extra": "^11.3.0",
+        "google-auth-library": "^9.11.0",
         "tar": "^7.5.2",
         "uuid": "^13.0.0",
         "winston": "^3.17.0"
@@ -18351,6 +18374,7 @@
       "resolved": "https://registry.npmjs.org/picomatch/-/picomatch-4.0.3.tgz",
       "integrity": "sha512-5gTmgEY/sqK6gFXLIsQNH19lWb4ebPDLA4SdLP7dsWkIXHWlG66oPuVvXSGFPppYZz8ZDZq0dYYrbHfBCVUb1Q==",
       "license": "MIT",
+      "peer": true,
       "engines": {
         "node": ">=12"
       },

packages/a2a-server/Dockerfile

@@ -0,0 +1,31 @@
+# Pre-built production image for a2a-server
+# Used with Cloud Build: npm install + build runs in step 1, then Docker copies artifacts
+FROM docker.io/library/node:20-slim
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+  python3 curl git jq ripgrep ca-certificates \
+  && apt-get clean && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+# Copy everything including pre-installed node_modules and pre-built dist
+COPY package.json package-lock.json ./
+COPY node_modules/ node_modules/
+COPY packages/core/ packages/core/
+COPY packages/a2a-server/ packages/a2a-server/
+
+# Create workspace directory for agent operations
+RUN mkdir -p /workspace && chown -R node:node /workspace
+
+USER node
+
+ENV CODER_AGENT_WORKSPACE_PATH=/workspace
+ENV CODER_AGENT_PORT=8080
+ENV NODE_ENV=production
+# Prevent git from prompting for credentials interactively — fails fast instead of hanging
+ENV GIT_TERMINAL_PROMPT=0
+ENV CODER_AGENT_HOST=0.0.0.0
+
+EXPOSE 8080
+
+CMD ["node", "packages/a2a-server/dist/src/http/server.js"]

packages/a2a-server/cloudbuild.yaml

@@ -0,0 +1,35 @@
+steps:
+  # Step 1: Install all dependencies and build
+  - name: 'node:20-slim'
+    entrypoint: 'bash'
+    args:
+      - '-c'
+      - |
+        apt-get update && apt-get install -y python3 make g++ git
+        npm pkg delete scripts.prepare
+        npm install
+        npm run build
+    env:
+      - 'HUSKY=0'
+
+  # Step 2: Build Docker image (using pre-built dist/ from step 1)
+  - name: 'gcr.io/cloud-builders/docker'
+    args:
+      - 'build'
+      - '-t'
+      - 'us-central1-docker.pkg.dev/$PROJECT_ID/gemini-a2a/a2a-server:latest'
+      - '-f'
+      - 'packages/a2a-server/Dockerfile'
+      - '.'
+
+  # Step 3: Push to Artifact Registry
+  - name: 'gcr.io/cloud-builders/docker'
+    args:
+      - 'push'
+      - 'us-central1-docker.pkg.dev/$PROJECT_ID/gemini-a2a/a2a-server:latest'
+
+images:
+  - 'us-central1-docker.pkg.dev/$PROJECT_ID/gemini-a2a/a2a-server:latest'
+timeout: '1800s'
+options:
+  machineType: 'E2_HIGHCPU_8'

packages/a2a-server/k8s/deployment.yaml

@@ -0,0 +1,74 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: gemini-a2a-server
+  labels:
+    app: gemini-a2a-server
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: gemini-a2a-server
+  template:
+    metadata:
+      labels:
+        app: gemini-a2a-server
+    spec:
+      containers:
+        - name: a2a-server
+          image: us-central1-docker.pkg.dev/adamfweidman-test/gemini-a2a/a2a-server:latest
+          ports:
+            - containerPort: 8080
+              protocol: TCP
+          env:
+            - name: CODER_AGENT_PORT
+              value: "8080"
+            - name: CODER_AGENT_HOST
+              value: "0.0.0.0"
+            - name: CODER_AGENT_WORKSPACE_PATH
+              value: "/workspace"
+            - name: GEMINI_API_KEY
+              valueFrom:
+                secretKeyRef:
+                  name: gemini-secrets
+                  key: api-key
+            - name: GEMINI_YOLO_MODE
+              value: "true"
+            - name: CHAT_BRIDGE_A2A_URL
+              value: "http://localhost:8080"
+            - name: NODE_ENV
+              value: "production"
+          resources:
+            requests:
+              cpu: "500m"
+              memory: "512Mi"
+            limits:
+              cpu: "2000m"
+              memory: "2Gi"
+          readinessProbe:
+            httpGet:
+              path: /.well-known/agent-card.json
+              port: 8080
+            initialDelaySeconds: 10
+            periodSeconds: 10
+          livenessProbe:
+            httpGet:
+              path: /.well-known/agent-card.json
+              port: 8080
+            initialDelaySeconds: 15
+            periodSeconds: 30
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: gemini-a2a-server
+  labels:
+    app: gemini-a2a-server
+spec:
+  type: ClusterIP
+  selector:
+    app: gemini-a2a-server
+  ports:
+    - port: 80
+      targetPort: 8080
+      protocol: TCP

packages/a2a-server/package.json

@@ -29,6 +29,7 @@
     "@google-cloud/storage": "^7.16.0",
     "@google/gemini-cli-core": "file:../core",
     "express": "^5.1.0",
+    "google-auth-library": "^9.11.0",
     "fs-extra": "^11.3.0",
     "tar": "^7.5.2",
     "uuid": "^13.0.0",

packages/a2a-server/src/a2ui/a2ui-components.ts

@@ -0,0 +1,157 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Builder functions for A2UI standard catalog components.
+ * These create the component objects that go into updateComponents messages.
+ */
+
+import type { A2UIComponent } from './a2ui-extension.js';
+
+// Layout components
+
+export function column(
+  id: string,
+  children: string[],
+  opts?: { align?: string; justify?: string; weight?: number },
+): A2UIComponent {
+  return {
+    id,
+    component: 'Column',
+    children,
+    ...opts,
+  };
+}
+
+export function row(
+  id: string,
+  children: string[],
+  opts?: { align?: string; justify?: string },
+): A2UIComponent {
+  return {
+    id,
+    component: 'Row',
+    children,
+    ...opts,
+  };
+}
+
+export function card(
+  id: string,
+  child: string,
+  opts?: Record<string, unknown>,
+): A2UIComponent {
+  return {
+    id,
+    component: 'Card',
+    child,
+    ...opts,
+  };
+}
+
+// Content components
+
+export function text(
+  id: string,
+  textContent: string | { path: string },
+  opts?: { variant?: string },
+): A2UIComponent {
+  return {
+    id,
+    component: 'Text',
+    text: textContent,
+    ...opts,
+  };
+}
+
+export function icon(id: string, name: string): A2UIComponent {
+  return {
+    id,
+    component: 'Icon',
+    name,
+  };
+}
+
+export function divider(
+  id: string,
+  axis: 'horizontal' | 'vertical' = 'horizontal',
+): A2UIComponent {
+  return {
+    id,
+    component: 'Divider',
+    axis,
+  };
+}
+
+// Interactive components
+
+export function button(
+  id: string,
+  child: string,
+  action: {
+    event?: { name: string; context: Record<string, unknown> };
+    functionCall?: { call: string; args: Record<string, unknown> };
+  },
+  opts?: { variant?: 'primary' | 'borderless' },
+): A2UIComponent {
+  return {
+    id,
+    component: 'Button',
+    child,
+    action,
+    ...opts,
+  };
+}
+
+export function textField(
+  id: string,
+  label: string,
+  valuePath: string,
+  opts?: {
+    variant?: 'shortText' | 'longText';
+    checks?: Array<{
+      call: string;
+      args: Record<string, unknown>;
+      message: string;
+    }>;
+  },
+): A2UIComponent {
+  return {
+    id,
+    component: 'TextField',
+    label,
+    value: { path: valuePath },
+    ...opts,
+  };
+}
+
+export function checkBox(
+  id: string,
+  label: string,
+  valuePath: string,
+): A2UIComponent {
+  return {
+    id,
+    component: 'CheckBox',
+    label,
+    value: { path: valuePath },
+  };
+}
+
+export function choicePicker(
+  id: string,
+  options: Array<{ label: string; value: string }>,
+  valuePath: string,
+  opts?: { variant?: 'mutuallyExclusive' | 'multiSelect' },
+): A2UIComponent {
+  return {
+    id,
+    component: 'ChoicePicker',
+    options,
+    value: { path: valuePath },
+    ...opts,
+  };
+}

packages/a2a-server/src/a2ui/a2ui-extension.ts

@@ -0,0 +1,194 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * A2UI (Agent-to-UI) Extension for A2A protocol.
+ * Implements the A2UI v0.10 specification for generating declarative UI
+ * messages that clients can render natively.
+ *
+ * @see https://a2ui.org/specification/v0_10/docs/a2ui_protocol.md
+ * @see https://a2ui.org/specification/v0_10/docs/a2ui_extension_specification.md
+ */
+
+import type { Part } from '@a2a-js/sdk';
+
+// Extension constants
+export const A2UI_EXTENSION_URI = 'https://a2ui.org/a2a-extension/a2ui/v0.10';
+export const A2UI_MIME_TYPE = 'application/json+a2ui';
+export const A2UI_VERSION = 'v0.10';
+export const STANDARD_CATALOG_ID =
+  'https://a2ui.org/specification/v0_10/standard_catalog.json';
+
+// Metadata keys
+export const MIME_TYPE_KEY = 'mimeType';
+export const A2UI_CLIENT_CAPABILITIES_KEY = 'a2uiClientCapabilities';
+export const A2UI_CLIENT_DATA_MODEL_KEY = 'a2uiClientDataModel';
+
+/**
+ * A2UI message types (server-to-client).
+ */
+export interface CreateSurfaceMessage {
+  version: typeof A2UI_VERSION;
+  createSurface: {
+    surfaceId: string;
+    catalogId: string;
+    theme?: Record<string, unknown>;
+    sendDataModel?: boolean;
+  };
+}
+
+export interface UpdateComponentsMessage {
+  version: typeof A2UI_VERSION;
+  updateComponents: {
+    surfaceId: string;
+    components: A2UIComponent[];
+  };
+}
+
+export interface UpdateDataModelMessage {
+  version: typeof A2UI_VERSION;
+  updateDataModel: {
+    surfaceId: string;
+    path?: string;
+    value?: unknown;
+  };
+}
+
+export interface DeleteSurfaceMessage {
+  version: typeof A2UI_VERSION;
+  deleteSurface: {
+    surfaceId: string;
+  };
+}
+
+export type A2UIServerMessage =
+  | CreateSurfaceMessage
+  | UpdateComponentsMessage
+  | UpdateDataModelMessage
+  | DeleteSurfaceMessage;
+
+/**
+ * A2UI component definition.
+ */
+export interface A2UIComponent {
+  id: string;
+  component: string;
+  [key: string]: unknown;
+}
+
+/**
+ * A2UI client-to-server action message.
+ */
+export interface A2UIActionMessage {
+  version: typeof A2UI_VERSION;
+  action: {
+    name: string;
+    surfaceId: string;
+    sourceComponentId: string;
+    timestamp: string;
+    context: Record<string, unknown>;
+  };
+}
+
+/**
+ * A2UI client capabilities sent in metadata.
+ */
+export interface A2UIClientCapabilities {
+  supportedCatalogIds: string[];
+  inlineCatalogs?: unknown[];
+}
+
+/**
+ * Creates an A2A DataPart containing A2UI messages.
+ * Per the spec, the data field contains an ARRAY of A2UI messages.
+ */
+export function createA2UIPart(messages: A2UIServerMessage[]): Part {
+   
+  return {
+    kind: 'data',
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+    data: messages as unknown as Record<string, unknown>,
+    metadata: {
+      [MIME_TYPE_KEY]: A2UI_MIME_TYPE,
+    },
+  } as Part;
+}
+
+/**
+ * Creates a single A2A DataPart from one A2UI message.
+ */
+export function createA2UISinglePart(message: A2UIServerMessage): Part {
+  return createA2UIPart([message]);
+}
+
+/**
+ * Checks if an A2A Part contains A2UI data.
+ */
+export function isA2UIPart(part: Part): boolean {
+  return (
+    part.kind === 'data' &&
+    part.metadata != null &&
+    part.metadata[MIME_TYPE_KEY] === A2UI_MIME_TYPE
+  );
+}
+
+/**
+ * Extracts A2UI action messages from an A2A Part.
+ */
+export function extractA2UIActions(part: Part): A2UIActionMessage[] {
+  if (!isA2UIPart(part)) return [];
+  // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+  const data = (part as unknown as { data?: unknown[] }).data;
+  if (!Array.isArray(data)) return [];
+  return data.filter(
+    (msg): msg is A2UIActionMessage =>
+      typeof msg === 'object' &&
+      msg !== null &&
+      'action' in msg &&
+      'version' in msg,
+  );
+}
+
+/**
+ * Creates the A2UI AgentExtension configuration for the AgentCard.
+ */
+export function getA2UIAgentExtension(
+  supportedCatalogIds: string[] = [STANDARD_CATALOG_ID],
+  acceptsInlineCatalogs = false,
+): {
+  uri: string;
+  description: string;
+  required: boolean;
+  params: Record<string, unknown>;
+} {
+  const params: Record<string, unknown> = {};
+  if (supportedCatalogIds.length > 0) {
+    params['supportedCatalogIds'] = supportedCatalogIds;
+  }
+  if (acceptsInlineCatalogs) {
+    params['acceptsInlineCatalogs'] = true;
+  }
+
+  return {
+    uri: A2UI_EXTENSION_URI,
+    description: 'Provides agent driven UI using the A2UI JSON format.',
+    required: false,
+    params,
+  };
+}
+
+/**
+ * Checks if the A2UI extension was requested via extension headers or message.
+ */
+export function isA2UIRequested(
+  requestedExtensions?: string[],
+  messageExtensions?: string[],
+): boolean {
+  return (
+    (requestedExtensions?.includes(A2UI_EXTENSION_URI) ?? false) ||
+    (messageExtensions?.includes(A2UI_EXTENSION_URI) ?? false)
+  );
+}

packages/a2a-server/src/a2ui/a2ui-surface-manager.ts

@@ -0,0 +1,468 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Manages A2UI surfaces for the Gemini CLI A2A server.
+ * Creates and updates surfaces for:
+ * - Tool call approval UIs
+ * - Agent text/thought streaming displays
+ * - Task status indicators
+ */
+
+import type { Part } from '@a2a-js/sdk';
+import { logger } from '../utils/logger.js';
+import {
+  A2UI_VERSION,
+  STANDARD_CATALOG_ID,
+  createA2UIPart,
+  type A2UIServerMessage,
+  type A2UIComponent,
+} from './a2ui-extension.js';
+import {
+  column,
+  row,
+  text,
+  button,
+  card,
+  icon,
+  divider,
+} from './a2ui-components.js';
+
+/**
+ * Generates A2UI parts for tool call approval surfaces.
+ */
+export function createToolCallApprovalSurface(
+  taskId: string,
+  toolCall: {
+    callId: string;
+    name: string;
+    displayName?: string;
+    description?: string;
+    args?: Record<string, unknown>;
+    kind?: string;
+  },
+): Part {
+  const surfaceId = `tool_approval_${taskId}_${toolCall.callId}`;
+  const toolDisplayName = toolCall.displayName || toolCall.name;
+  const argsPreview = toolCall.args
+    ? JSON.stringify(toolCall.args, null, 2).substring(0, 500)
+    : 'No arguments';
+
+  logger.info(
+    `[A2UI] Creating tool approval surface: ${surfaceId} for tool: ${toolDisplayName}`,
+  );
+
+  const messages: A2UIServerMessage[] = [
+    // 1. Create the surface
+    {
+      version: A2UI_VERSION,
+      createSurface: {
+        surfaceId,
+        catalogId: STANDARD_CATALOG_ID,
+        theme: {
+          primaryColor: '#1a73e8',
+          agentDisplayName: 'Gemini CLI Agent',
+        },
+        sendDataModel: true,
+      },
+    },
+    // 2. Define the components
+    {
+      version: A2UI_VERSION,
+      updateComponents: {
+        surfaceId,
+        components: buildToolApprovalComponents(
+          taskId,
+          toolCall.callId,
+          toolDisplayName,
+          toolCall.description || '',
+          argsPreview,
+          toolCall.kind || 'tool',
+        ),
+      },
+    },
+    // 3. Populate the data model
+    {
+      version: A2UI_VERSION,
+      updateDataModel: {
+        surfaceId,
+        value: {
+          tool: {
+            callId: toolCall.callId,
+            name: toolCall.name,
+            displayName: toolDisplayName,
+            description: toolCall.description || '',
+            args: argsPreview,
+            kind: toolCall.kind || 'tool',
+            status: 'awaiting_approval',
+          },
+          taskId,
+        },
+      },
+    },
+  ];
+
+  return createA2UIPart(messages);
+}
+
+function buildToolApprovalComponents(
+  taskId: string,
+  callId: string,
+  toolName: string,
+  description: string,
+  argsPreview: string,
+  kind: string,
+): A2UIComponent[] {
+  return [
+    // Root card
+    card('root', 'main_column'),
+
+    // Main vertical layout
+    column(
+      'main_column',
+      [
+        'header_row',
+        'description_text',
+        'divider_1',
+        'args_label',
+        'args_text',
+        'divider_2',
+        'action_row',
+      ],
+      { align: 'stretch' },
+    ),
+
+    // Header with icon and tool name
+    row('header_row', ['tool_icon', 'tool_name_text'], {
+      align: 'center',
+    }),
+    icon('tool_icon', kind === 'shell' ? 'terminal' : 'build'),
+    text('tool_name_text', `**${toolName}** requires approval`, {
+      variant: 'h3',
+    }),
+
+    // Description
+    text(
+      'description_text',
+      description || 'This tool needs your permission to execute.',
+    ),
+
+    divider('divider_1'),
+
+    // Arguments preview
+    text('args_label', '**Arguments:**', { variant: 'caption' }),
+    text('args_text', `\`\`\`\n${argsPreview}\n\`\`\``),
+
+    divider('divider_2'),
+
+    // Action buttons row
+    row(
+      'action_row',
+      ['approve_button', 'approve_always_button', 'reject_button'],
+      { justify: 'spaceBetween' },
+    ),
+
+    // Approve button
+    text('approve_label', 'Approve'),
+    button(
+      'approve_button',
+      'approve_label',
+      {
+        event: {
+          name: 'tool_confirmation',
+          context: {
+            taskId,
+            callId,
+            outcome: 'proceed_once',
+          },
+        },
+      },
+      { variant: 'primary' },
+    ),
+
+    // Approve always button
+    text('approve_always_label', 'Always Allow'),
+    button('approve_always_button', 'approve_always_label', {
+      event: {
+        name: 'tool_confirmation',
+        context: {
+          taskId,
+          callId,
+          outcome: 'proceed_always_tool',
+        },
+      },
+    }),
+
+    // Reject button
+    text('reject_label', 'Reject'),
+    button('reject_button', 'reject_label', {
+      event: {
+        name: 'tool_confirmation',
+        context: {
+          taskId,
+          callId,
+          outcome: 'cancel',
+        },
+      },
+    }),
+  ];
+}
+
+/**
+ * Creates an A2UI surface update for tool execution status.
+ */
+export function updateToolCallStatus(
+  taskId: string,
+  callId: string,
+  status: string,
+  output?: string,
+): Part {
+  const surfaceId = `tool_approval_${taskId}_${callId}`;
+
+  logger.info(
+    `[A2UI] Updating tool status surface: ${surfaceId} status: ${status}`,
+  );
+
+  const messages: A2UIServerMessage[] = [
+    {
+      version: A2UI_VERSION,
+      updateDataModel: {
+        surfaceId,
+        path: '/tool/status',
+        value: status,
+      },
+    },
+  ];
+
+  // If tool completed, update the UI to show result
+  if (['success', 'error', 'cancelled'].includes(status)) {
+    messages.push({
+      version: A2UI_VERSION,
+      updateComponents: {
+        surfaceId,
+        components: [
+          // Replace action row with status indicator
+          row('action_row', ['status_icon', 'status_text'], {
+            align: 'center',
+          }),
+          icon(
+            'status_icon',
+            status === 'success'
+              ? 'check_circle'
+              : status === 'error'
+                ? 'error'
+                : 'cancel',
+          ),
+          text(
+            'status_text',
+            status === 'success'
+              ? 'Tool executed successfully'
+              : status === 'error'
+                ? 'Tool execution failed'
+                : 'Tool execution cancelled',
+          ),
+        ],
+      },
+    });
+
+    if (output) {
+      messages.push({
+        version: A2UI_VERSION,
+        updateDataModel: {
+          surfaceId,
+          path: '/tool/output',
+          value: output,
+        },
+      });
+    }
+  }
+
+  return createA2UIPart(messages);
+}
+
+/**
+ * Creates an A2UI text content surface for agent messages.
+ */
+export function createTextContentPart(
+  taskId: string,
+  content: string,
+  surfaceId?: string,
+): Part {
+  const sid = surfaceId || `agent_text_${taskId}`;
+
+  const messages: A2UIServerMessage[] = [
+    {
+      version: A2UI_VERSION,
+      updateDataModel: {
+        surfaceId: sid,
+        path: '/content/text',
+        value: content,
+      },
+    },
+  ];
+
+  return createA2UIPart(messages);
+}
+
+/**
+ * Creates the initial agent response surface.
+ */
+export function createAgentResponseSurface(taskId: string): Part {
+  const surfaceId = `agent_response_${taskId}`;
+
+  logger.info(`[A2UI] Creating agent response surface: ${surfaceId}`);
+
+  const messages: A2UIServerMessage[] = [
+    {
+      version: A2UI_VERSION,
+      createSurface: {
+        surfaceId,
+        catalogId: STANDARD_CATALOG_ID,
+        theme: {
+          primaryColor: '#1a73e8',
+          agentDisplayName: 'Gemini CLI Agent',
+        },
+      },
+    },
+    {
+      version: A2UI_VERSION,
+      updateComponents: {
+        surfaceId,
+        components: [
+          card('root', 'response_column'),
+          column('response_column', ['response_text', 'status_text'], {
+            align: 'stretch',
+          }),
+          text('response_text', { path: '/response/text' }),
+          text(
+            'status_text',
+            { path: '/response/status' },
+            {
+              variant: 'caption',
+            },
+          ),
+        ],
+      },
+    },
+    {
+      version: A2UI_VERSION,
+      updateDataModel: {
+        surfaceId,
+        value: {
+          response: {
+            text: '',
+            status: 'Working...',
+          },
+        },
+      },
+    },
+  ];
+
+  return createA2UIPart(messages);
+}
+
+/**
+ * Updates the agent response surface with new text content.
+ */
+export function updateAgentResponseText(
+  taskId: string,
+  content: string,
+  status?: string,
+): Part {
+  const surfaceId = `agent_response_${taskId}`;
+
+  const messages: A2UIServerMessage[] = [
+    {
+      version: A2UI_VERSION,
+      updateDataModel: {
+        surfaceId,
+        path: '/response/text',
+        value: content,
+      },
+    },
+  ];
+
+  if (status) {
+    messages.push({
+      version: A2UI_VERSION,
+      updateDataModel: {
+        surfaceId,
+        path: '/response/status',
+        value: status,
+      },
+    });
+  }
+
+  return createA2UIPart(messages);
+}
+
+/**
+ * Creates an A2UI thought surface.
+ */
+export function createThoughtPart(
+  taskId: string,
+  subject: string,
+  description: string,
+): Part {
+  const surfaceId = `thought_${taskId}_${Date.now()}`;
+
+  const messages: A2UIServerMessage[] = [
+    {
+      version: A2UI_VERSION,
+      createSurface: {
+        surfaceId,
+        catalogId: STANDARD_CATALOG_ID,
+        theme: {
+          primaryColor: '#7c4dff',
+          agentDisplayName: 'Gemini CLI Agent',
+        },
+      },
+    },
+    {
+      version: A2UI_VERSION,
+      updateComponents: {
+        surfaceId,
+        components: [
+          card('root', 'thought_column'),
+          column('thought_column', ['thought_icon_row', 'thought_desc'], {
+            align: 'stretch',
+          }),
+          row('thought_icon_row', ['thought_icon', 'thought_subject'], {
+            align: 'center',
+          }),
+          icon('thought_icon', 'psychology'),
+          text('thought_subject', `*${subject}*`, { variant: 'h4' }),
+          text('thought_desc', description),
+        ],
+      },
+    },
+  ];
+
+  return createA2UIPart(messages);
+}
+
+/**
+ * Deletes a tool approval surface after resolution.
+ */
+export function deleteToolApprovalSurface(
+  taskId: string,
+  callId: string,
+): Part {
+  const surfaceId = `tool_approval_${taskId}_${callId}`;
+
+  logger.info(`[A2UI] Deleting tool approval surface: ${surfaceId}`);
+
+  const messages: A2UIServerMessage[] = [
+    {
+      version: A2UI_VERSION,
+      deleteSurface: {
+        surfaceId,
+      },
+    },
+  ];
+
+  return createA2UIPart(messages);
+}

packages/a2a-server/src/agent/executor.ts

@@ -36,6 +36,10 @@ import { loadExtensions } from '../config/extension.js';
 import { Task } from './task.js';
 import { requestStorage } from '../http/requestStorage.js';
 import { pushTaskStateFailed } from '../utils/executor_utils.js';
+import {
+  A2UI_CLIENT_CAPABILITIES_KEY,
+  A2UI_EXTENSION_URI,
+} from '../a2ui/a2ui-extension.js';
 
 /**
  * Provides a wrapper for Task. Passes data from Task to SDKTask.
@@ -73,6 +77,24 @@ class TaskWrapper {
       artifacts: [],
     };
     sdkTask.metadata!['_contextId'] = this.task.contextId;
+
+    // Persist conversation history for session resumability.
+    // GCSTaskStore saves this as a separate object and restores it on load.
+    try {
+      const conversationHistory = this.task.geminiClient.getHistory();
+      if (conversationHistory.length > 0) {
+        sdkTask.metadata!['_conversationHistory'] = conversationHistory;
+        logger.info(
+          `Task ${this.task.id}: Persisting ${conversationHistory.length} conversation history entries.`,
+        );
+      }
+    } catch {
+      // GeminiClient may not be initialized yet
+      logger.warn(
+        `Task ${this.task.id}: Could not get conversation history for persistence.`,
+      );
+    }
+
     return sdkTask;
   }
 }
@@ -127,7 +149,25 @@ export class CoderAgentExecutor implements AgentExecutor {
       agentSettings.autoExecute,
     );
     runtimeTask.taskState = persistedState._taskState;
-    await runtimeTask.geminiClient.initialize();
+
+    // Restore conversation history if available from the TaskStore.
+    // This enables session resumability — the LLM gets full context of
+    // prior interactions rather than starting with a blank slate.
+    const conversationHistory = metadata['_conversationHistory'];
+    if (Array.isArray(conversationHistory) && conversationHistory.length > 0) {
+      logger.info(
+        `Task ${sdkTask.id}: Resuming with ${conversationHistory.length} conversation history entries.`,
+      );
+      // History was serialized from GeminiClient.getHistory() which returns
+      // Content[]. After JSON round-trip it's structurally identical.
+      await runtimeTask.geminiClient.initialize();
+      runtimeTask.geminiClient.setHistory(
+         
+        conversationHistory,
+      );
+    } else {
+      await runtimeTask.geminiClient.initialize();
+    }
 
     const wrapper = new TaskWrapper(runtimeTask, agentSettings);
     this.tasks.set(sdkTask.id, wrapper);
@@ -435,6 +475,22 @@ export class CoderAgentExecutor implements AgentExecutor {
 
     const currentTask = wrapper.task;
 
+    // Detect A2UI extension activation from the request
+    // Check if user message metadata contains A2UI client capabilities
+    // or if the extensions header includes the A2UI URI
+    const messageMetadata = userMessage.metadata;
+    const hasA2UICapabilities =
+      messageMetadata?.[A2UI_CLIENT_CAPABILITIES_KEY] != null;
+    // Also check if extension URI is referenced in message extensions
+    const messageExtensions = messageMetadata?.['extensions'];
+    const hasA2UIExtension =
+      Array.isArray(messageExtensions) &&
+      messageExtensions.includes(A2UI_EXTENSION_URI);
+    if (hasA2UICapabilities || hasA2UIExtension) {
+      currentTask.a2uiEnabled = true;
+      logger.info(`[CoderAgentExecutor] A2UI enabled for task ${taskId}`);
+    }
+
     if (['canceled', 'failed', 'completed'].includes(currentTask.taskState)) {
       logger.warn(
         `[CoderAgentExecutor] Attempted to execute task ${taskId} which is already in state ${currentTask.taskState}. Ignoring.`,
@@ -552,6 +608,9 @@ export class CoderAgentExecutor implements AgentExecutor {
       logger.info(
         `[CoderAgentExecutor] Task ${taskId}: Agent turn finished, setting to input-required.`,
       );
+      // Finalize A2UI surfaces before marking complete
+      currentTask.finalizeA2UISurfaces();
+
       const stateChange: StateChange = {
         kind: CoderAgentEvent.StateChangeEvent,
       };

packages/a2a-server/src/agent/task.ts

@@ -56,6 +56,15 @@ import type {
   Citation,
 } from '../types.js';
 import type { PartUnion, Part as genAiPart } from '@google/genai';
+import {
+  createToolCallApprovalSurface,
+  updateToolCallStatus,
+  createAgentResponseSurface,
+  updateAgentResponseText,
+  createThoughtPart as createA2UIThoughtPart,
+  deleteToolApprovalSurface,
+} from '../a2ui/a2ui-surface-manager.js';
+import { isA2UIPart, extractA2UIActions } from '../a2ui/a2ui-extension.js';
 
 type UnionKeys<T> = T extends T ? keyof T : never;
 
@@ -75,6 +84,11 @@ export class Task {
   promptCount = 0;
   autoExecute: boolean;
 
+  // A2UI support
+  a2uiEnabled = false;
+  private accumulatedText = '';
+  private a2uiResponseSurfaceCreated = false;
+
   // For tool waiting logic
   private pendingToolCalls: Map<string, string> = new Map(); //toolCallId --> status
   private toolCompletionPromise?: Promise<void>;
@@ -391,6 +405,44 @@ export class Task {
             : { kind: CoderAgentEvent.ToolCallUpdateEvent };
         const message = this.toolStatusMessage(tc, this.id, this.contextId);
 
+        // Add A2UI parts for tool call updates if A2UI is enabled
+        if (this.a2uiEnabled) {
+          try {
+            if (tc.status === 'awaiting_approval') {
+              const a2uiPart = createToolCallApprovalSurface(this.id, {
+                callId: tc.request.callId,
+                name: tc.request.name,
+                displayName: tc.tool?.displayName || tc.tool?.name,
+                description: tc.tool?.description,
+                args: tc.request.args as Record<string, unknown> | undefined,
+                kind: tc.tool?.kind,
+              });
+              message.parts.push(a2uiPart);
+              logger.info(
+                `[Task] A2UI: Added tool approval surface for ${tc.request.callId}`,
+              );
+            } else if (['success', 'error', 'cancelled'].includes(tc.status)) {
+              const output =
+                'liveOutput' in tc ? String(tc.liveOutput) : undefined;
+              const a2uiPart = updateToolCallStatus(
+                this.id,
+                tc.request.callId,
+                tc.status,
+                output,
+              );
+              message.parts.push(a2uiPart);
+              logger.info(
+                `[Task] A2UI: Updated tool status for ${tc.request.callId}: ${tc.status}`,
+              );
+            }
+          } catch (a2uiError) {
+            logger.error(
+              '[Task] A2UI: Error generating tool call surface:',
+              a2uiError,
+            );
+          }
+        }
+
         const event = this._createStatusUpdateEvent(
           this.taskState,
           coderAgentMessage,
@@ -954,7 +1006,66 @@ export class Task {
     let anyConfirmationHandled = false;
     let hasContentForLlm = false;
 
+    // Reset A2UI accumulated text for new user turn
+    if (this.a2uiEnabled) {
+      this.accumulatedText = '';
+      this.a2uiResponseSurfaceCreated = false;
+    }
+
     for (const part of userMessage.parts) {
+      // Handle A2UI action messages (e.g., button clicks for tool approval)
+      if (this.a2uiEnabled && isA2UIPart(part)) {
+        const actions = extractA2UIActions(part);
+        for (const action of actions) {
+          if (action.action.name === 'tool_confirmation') {
+            const ctx = action.action.context;
+            // Convert A2UI action to a tool confirmation data part
+            const syntheticPart: Part = {
+              kind: 'data',
+              data: {
+                callId: ctx['callId'],
+                outcome: ctx['outcome'],
+              },
+            } as Part;
+            const handled =
+              await this._handleToolConfirmationPart(syntheticPart);
+            if (handled) {
+              anyConfirmationHandled = true;
+              // Emit a delete surface part for the approval UI
+              try {
+                const deletePart = deleteToolApprovalSurface(
+                  // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+                  (ctx['taskId'] as string) || this.id,
+                  // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+                  ctx['callId'] as string,
+                );
+                const deleteMessage: Message = {
+                  kind: 'message',
+                  role: 'agent',
+                  parts: [deletePart],
+                  messageId: uuidv4(),
+                  taskId: this.id,
+                  contextId: this.contextId,
+                };
+                const event = this._createStatusUpdateEvent(
+                  this.taskState,
+                  { kind: CoderAgentEvent.ToolCallUpdateEvent },
+                  deleteMessage,
+                  false,
+                );
+                this.eventBus?.publish(event);
+              } catch (a2uiError) {
+                logger.error(
+                  '[Task] A2UI: Error deleting approval surface:',
+                  a2uiError,
+                );
+              }
+            }
+          }
+        }
+        continue;
+      }
+
       const confirmationHandled = await this._handleToolConfirmationPart(part);
       if (confirmationHandled) {
         anyConfirmationHandled = true;
@@ -1020,6 +1131,33 @@ export class Task {
     }
     logger.info('[Task] Sending text content to event bus.');
     const message = this._createTextMessage(content);
+
+    // Add A2UI response surface parts if A2UI is enabled
+    if (this.a2uiEnabled) {
+      try {
+        this.accumulatedText += content;
+        if (!this.a2uiResponseSurfaceCreated) {
+          const surfacePart = createAgentResponseSurface(this.id);
+          message.parts.push(surfacePart);
+          this.a2uiResponseSurfaceCreated = true;
+          logger.info(
+            `[Task] A2UI: Created agent response surface for task ${this.id}`,
+          );
+        }
+        const updatePart = updateAgentResponseText(
+          this.id,
+          this.accumulatedText,
+          'Working...',
+        );
+        message.parts.push(updatePart);
+      } catch (a2uiError) {
+        logger.error(
+          '[Task] A2UI: Error generating text content surface:',
+          a2uiError,
+        );
+      }
+    }
+
     const textContent: TextContent = {
       kind: CoderAgentEvent.TextContentEvent,
     };
@@ -1041,15 +1179,35 @@ export class Task {
       return;
     }
     logger.info('[Task] Sending thought to event bus.');
+    const parts: Part[] = [
+      {
+        kind: 'data',
+        data: content,
+      } as Part,
+    ];
+
+    // Add A2UI thought surface if A2UI is enabled
+    if (this.a2uiEnabled) {
+      try {
+        const a2uiPart = createA2UIThoughtPart(
+          this.id,
+          content.subject || 'Thinking...',
+          content.description || '',
+        );
+        parts.push(a2uiPart);
+        logger.info(`[Task] A2UI: Added thought surface for task ${this.id}`);
+      } catch (a2uiError) {
+        logger.error(
+          '[Task] A2UI: Error generating thought surface:',
+          a2uiError,
+        );
+      }
+    }
+
     const message: Message = {
       kind: 'message',
       role: 'agent',
-      parts: [
+      parts,
-        {
-          kind: 'data',
-          data: content,
-        } as Part,
-      ],
       messageId: uuidv4(),
       taskId: this.id,
       contextId: this.contextId,
@@ -1070,6 +1228,43 @@ export class Task {
     );
   }
 
+  /**
+   * Finalizes A2UI surfaces when the agent turn is complete.
+   * Updates the response surface status to "Done".
+   */
+  finalizeA2UISurfaces(): void {
+    if (!this.a2uiEnabled || !this.a2uiResponseSurfaceCreated) {
+      return;
+    }
+    try {
+      const finalPart = updateAgentResponseText(
+        this.id,
+        this.accumulatedText,
+        'Done',
+      );
+      const message: Message = {
+        kind: 'message',
+        role: 'agent',
+        parts: [finalPart],
+        messageId: uuidv4(),
+        taskId: this.id,
+        contextId: this.contextId,
+      };
+      const event = this._createStatusUpdateEvent(
+        this.taskState,
+        { kind: CoderAgentEvent.TextContentEvent },
+        message,
+        false,
+      );
+      this.eventBus?.publish(event);
+      logger.info(
+        `[Task] A2UI: Finalized response surface for task ${this.id}`,
+      );
+    } catch (a2uiError) {
+      logger.error('[Task] A2UI: Error finalizing surfaces:', a2uiError);
+    }
+  }
+
   _sendCitation(citation: string) {
     if (!citation || citation.trim() === '') {
       return;

packages/a2a-server/src/chat-bridge/a2a-bridge-client.ts

@@ -0,0 +1,268 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * A2A client wrapper for the Google Chat bridge.
+ * Connects to the A2A server (local or remote) and sends/receives messages.
+ * Follows the patterns from core/agents/a2a-client-manager.ts and
+ * core/agents/remote-invocation.ts.
+ */
+
+import type { Message, Task, Part, MessageSendParams } from '@a2a-js/sdk';
+import {
+  type Client,
+  ClientFactory,
+  ClientFactoryOptions,
+  DefaultAgentCardResolver,
+  RestTransportFactory,
+  JsonRpcTransportFactory,
+} from '@a2a-js/sdk/client';
+import { v4 as uuidv4 } from 'uuid';
+import { logger } from '../utils/logger.js';
+import { A2UI_EXTENSION_URI, A2UI_MIME_TYPE } from '../a2ui/a2ui-extension.js';
+
+export type A2AResponse = Message | Task;
+
+/**
+ * Extracts contextId and taskId from an A2A response.
+ * Follows extractIdsFromResponse pattern from a2aUtils.ts.
+ */
+export function extractIdsFromResponse(result: A2AResponse): {
+  contextId?: string;
+  taskId?: string;
+} {
+  if (result.kind === 'message') {
+    return {
+      contextId: result.contextId,
+      taskId: result.taskId,
+    };
+  }
+
+  if (result.kind === 'task') {
+    const contextId = result.contextId;
+    let taskId: string | undefined = result.id;
+
+    // Clear taskId on terminal states so next interaction starts a fresh task
+    const state = result.status?.state;
+    if (state === 'completed' || state === 'failed' || state === 'canceled') {
+      taskId = undefined;
+    }
+
+    return { contextId, taskId };
+  }
+
+  return {};
+}
+
+/**
+ * Extracts all parts from an A2A response.
+ * For Tasks, checks history (accumulated from intermediate status-update events),
+ * the final status message, and artifacts. The blocking DefaultRequestHandler
+ * accumulates intermediate events into task.history, so the A2UI response content
+ * from "working" events lives there even if the final status message is empty.
+ */
+export function extractAllParts(result: A2AResponse): Part[] {
+  const parts: Part[] = [];
+
+  if (result.kind === 'message') {
+    parts.push(...(result.parts ?? []));
+  } else if (result.kind === 'task') {
+    // Parts from task history (accumulated intermediate status-update messages)
+    if (result.history) {
+      for (const msg of result.history) {
+        if (msg.parts) {
+          parts.push(...msg.parts);
+        }
+      }
+    }
+    // Parts from the final status message
+    if (result.status?.message?.parts) {
+      parts.push(...result.status.message.parts);
+    }
+    // Parts from artifacts
+    if (result.artifacts) {
+      for (const artifact of result.artifacts) {
+        parts.push(...(artifact.parts ?? []));
+      }
+    }
+  }
+
+  return parts;
+}
+
+/**
+ * Extracts plain text content from response parts.
+ */
+export function extractTextFromParts(parts: Part[]): string {
+  return parts
+    .filter((p) => p.kind === 'text')
+    .map(
+      (p) =>
+        // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+        (p as unknown as { text: string }).text,
+    )
+    .filter(Boolean)
+    .join('\n');
+}
+
+/**
+ * Extracts A2UI data parts from response parts.
+ * A2UI parts are DataParts with metadata.mimeType === 'application/json+a2ui'.
+ */
+export function extractA2UIParts(parts: Part[]): unknown[][] {
+  const a2uiMessages: unknown[][] = [];
+
+  for (const part of parts) {
+    if (
+      part.kind === 'data' &&
+      part.metadata != null &&
+      part.metadata['mimeType'] === A2UI_MIME_TYPE
+    ) {
+      // The data field is an array of A2UI messages
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+      const data = (part as unknown as { data: unknown }).data;
+      if (Array.isArray(data)) {
+        a2uiMessages.push(data);
+      }
+    }
+  }
+
+  return a2uiMessages;
+}
+
+/**
+ * A2A client for the chat bridge.
+ * Manages connection to the A2A server and provides message send/receive.
+ */
+export class A2ABridgeClient {
+  private client: Client | null = null;
+  private agentUrl: string;
+
+  constructor(agentUrl: string) {
+    this.agentUrl = agentUrl;
+  }
+
+  /**
+   * Initializes the client connection to the A2A server.
+   */
+  async initialize(): Promise<void> {
+    if (this.client) return;
+
+    const resolver = new DefaultAgentCardResolver({});
+    const options = ClientFactoryOptions.createFrom(
+      ClientFactoryOptions.default,
+      {
+        transports: [
+          new RestTransportFactory({}),
+          new JsonRpcTransportFactory({}),
+        ],
+        cardResolver: resolver,
+      },
+    );
+
+    const factory = new ClientFactory(options);
+    // createFromUrl expects the agent card URL, not just the base URL
+    const agentCardUrl =
+      this.agentUrl.replace(/\/$/, '') + '/.well-known/agent-card.json';
+    this.client = await factory.createFromUrl(agentCardUrl, '');
+
+    const card = await this.client.getAgentCard();
+    logger.info(
+      `[ChatBridge] Connected to A2A agent: ${card.name} (${card.url})`,
+    );
+  }
+
+  /**
+   * Sends a text message to the A2A server using blocking mode.
+   * The blocking DefaultRequestHandler accumulates all intermediate events
+   * (including A2UI content from "working" status updates) into the Task's
+   * history array, so extractAllParts can find them.
+   */
+  async sendMessage(
+    text: string,
+    options: { contextId?: string; taskId?: string },
+  ): Promise<A2AResponse> {
+    if (!this.client) {
+      throw new Error('A2A client not initialized. Call initialize() first.');
+    }
+
+    const params: MessageSendParams = {
+      message: {
+        kind: 'message',
+        role: 'user',
+        messageId: uuidv4(),
+        parts: [{ kind: 'text', text }],
+        contextId: options.contextId,
+        taskId: options.taskId,
+        // Signal A2UI support in message metadata
+        metadata: {
+          extensions: [A2UI_EXTENSION_URI],
+        },
+      },
+      configuration: {
+        blocking: true,
+      },
+    };
+
+    return this.client.sendMessage(params);
+  }
+
+  /**
+   * Sends a tool confirmation action back to the A2A server.
+   * The action is sent as a DataPart containing the A2UI action message.
+   */
+  async sendToolConfirmation(
+    callId: string,
+    outcome: string,
+    taskId: string,
+    options: { contextId?: string },
+  ): Promise<A2AResponse> {
+    if (!this.client) {
+      throw new Error('A2A client not initialized. Call initialize() first.');
+    }
+
+    // Build the A2UI action message as a DataPart
+    const actionPart: Part = {
+      kind: 'data',
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+      data: [
+        {
+          version: 'v0.10',
+          action: {
+            name: 'tool_confirmation',
+            surfaceId: `tool_approval_${taskId}_${callId}`,
+            sourceComponentId:
+              outcome === 'cancel' ? 'reject_button' : 'approve_button',
+            timestamp: new Date().toISOString(),
+            context: { callId, outcome, taskId },
+          },
+        },
+      ] as unknown as Record<string, unknown>,
+      metadata: {
+        mimeType: A2UI_MIME_TYPE,
+      },
+    } as Part;
+
+    const params: MessageSendParams = {
+      message: {
+        kind: 'message',
+        role: 'user',
+        messageId: uuidv4(),
+        parts: [actionPart],
+        contextId: options.contextId,
+        taskId,
+        metadata: {
+          extensions: [A2UI_EXTENSION_URI],
+        },
+      },
+      configuration: {
+        blocking: true,
+      },
+    };
+
+    return this.client.sendMessage(params);
+  }
+}

packages/a2a-server/src/chat-bridge/handler.ts

@@ -0,0 +1,329 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Google Chat webhook handler.
+ * Processes incoming Google Chat events, forwards them to the A2A server,
+ * and converts responses back to Google Chat format.
+ */
+
+import type { ChatEvent, ChatResponse, ChatBridgeConfig } from './types.js';
+import { SessionStore } from './session-store.js';
+import {
+  A2ABridgeClient,
+  extractIdsFromResponse,
+} from './a2a-bridge-client.js';
+import { renderResponse, extractToolApprovals } from './response-renderer.js';
+import { logger } from '../utils/logger.js';
+
+export class ChatBridgeHandler {
+  private sessionStore: SessionStore;
+  private a2aClient: A2ABridgeClient;
+  private initialized = false;
+
+  constructor(private config: ChatBridgeConfig) {
+    this.sessionStore = new SessionStore(config.gcsBucket);
+    this.a2aClient = new A2ABridgeClient(config.a2aServerUrl);
+  }
+
+  /**
+   * Initializes the A2A client connection and restores persisted sessions.
+   * Must be called before handling events.
+   */
+  async initialize(): Promise<void> {
+    if (this.initialized) return;
+    await this.a2aClient.initialize();
+    await this.sessionStore.restore();
+    this.initialized = true;
+    logger.info(
+      `[ChatBridge] Handler initialized, connected to ${this.config.a2aServerUrl}`,
+    );
+  }
+
+  /**
+   * Main entry point for handling Google Chat webhook events.
+   */
+  async handleEvent(event: ChatEvent): Promise<ChatResponse> {
+    if (!this.initialized) {
+      await this.initialize();
+    }
+
+    logger.info(
+      `[ChatBridge] Received event: type=${event.type}, space=${event.space.name}`,
+    );
+
+    switch (event.type) {
+      case 'MESSAGE':
+        return this.handleMessage(event);
+      case 'CARD_CLICKED':
+        return this.handleCardClicked(event);
+      case 'ADDED_TO_SPACE':
+        return this.handleAddedToSpace(event);
+      case 'REMOVED_FROM_SPACE':
+        return this.handleRemovedFromSpace(event);
+      default:
+        logger.warn(`[ChatBridge] Unknown event type: ${event.type}`);
+        return { text: 'Unknown event type.' };
+    }
+  }
+
+  /**
+   * Handles a MESSAGE event: user sent a text message in Chat.
+   */
+  private async handleMessage(event: ChatEvent): Promise<ChatResponse> {
+    const message = event.message;
+    if (!message?.thread?.name) {
+      return { text: 'Error: Missing thread information.' };
+    }
+
+    const text = message.argumentText || message.text || '';
+    if (!text.trim()) {
+      return { text: "I didn't receive any text. Please try again." };
+    }
+
+    const threadName = message.thread.name;
+    const spaceName = event.space.name;
+
+    // Handle slash commands
+    const trimmed = text.trim().toLowerCase();
+    if (
+      trimmed === '/reset' ||
+      trimmed === '/clear' ||
+      trimmed === 'reset' ||
+      trimmed === 'clear'
+    ) {
+      this.sessionStore.remove(threadName);
+      logger.info(`[ChatBridge] Session cleared for thread ${threadName}`);
+      return { text: 'Session cleared. Send a new message to start fresh.' };
+    }
+
+    const session = this.sessionStore.getOrCreate(threadName, spaceName);
+
+    if (trimmed === '/yolo') {
+      session.yoloMode = true;
+      logger.info(`[ChatBridge] YOLO mode enabled for thread ${threadName}`);
+      return {
+        text: 'YOLO mode enabled. All tool calls will be auto-approved.',
+      };
+    }
+
+    if (trimmed === '/safe') {
+      session.yoloMode = false;
+      logger.info(`[ChatBridge] YOLO mode disabled for thread ${threadName}`);
+      return { text: 'Safe mode enabled. Tool calls will require approval.' };
+    }
+
+    logger.info(
+      `[ChatBridge] MESSAGE from ${event.user.displayName}: "${text.substring(0, 100)}"`,
+    );
+
+    // Handle text-based tool approval responses
+    const lowerText = trimmed;
+    if (
+      session.pendingToolApproval &&
+      (lowerText === 'approve' ||
+        lowerText === 'yes' ||
+        lowerText === 'y' ||
+        lowerText === 'reject' ||
+        lowerText === 'no' ||
+        lowerText === 'n' ||
+        lowerText === 'always allow')
+    ) {
+      const approval = session.pendingToolApproval;
+      const isReject =
+        lowerText === 'reject' || lowerText === 'no' || lowerText === 'n';
+      const isAlwaysAllow = lowerText === 'always allow';
+      const outcome = isReject
+        ? 'cancel'
+        : isAlwaysAllow
+          ? 'proceed_always_tool'
+          : 'proceed_once';
+
+      logger.info(
+        `[ChatBridge] Text-based tool ${outcome}: callId=${approval.callId}, taskId=${approval.taskId}`,
+      );
+
+      session.pendingToolApproval = undefined;
+
+      try {
+        const response = await this.a2aClient.sendToolConfirmation(
+          approval.callId,
+          outcome,
+          approval.taskId,
+          { contextId: session.contextId },
+        );
+
+        const { contextId: newCtxId, taskId: newTaskId } =
+          extractIdsFromResponse(response);
+        if (newCtxId) session.contextId = newCtxId;
+        this.sessionStore.updateTaskId(threadName, newTaskId);
+
+        const threadKey = message.thread.threadKey || threadName;
+        return renderResponse(response, threadKey, threadName);
+      } catch (error) {
+        const errorMsg =
+          error instanceof Error ? error.message : 'Unknown error';
+        logger.error(
+          `[ChatBridge] Error sending tool confirmation: ${errorMsg}`,
+          error,
+        );
+        return { text: `Error processing tool confirmation: ${errorMsg}` };
+      }
+    }
+
+    try {
+      const response = await this.a2aClient.sendMessage(text, {
+        contextId: session.contextId,
+        taskId: session.taskId,
+      });
+
+      // Update session with new IDs from response
+      const { contextId, taskId } = extractIdsFromResponse(response);
+      if (contextId) {
+        session.contextId = contextId;
+      }
+      this.sessionStore.updateTaskId(threadName, taskId);
+
+      // Check for pending tool approvals and store for text-based confirmation
+      const approvals = extractToolApprovals(response);
+      if (approvals.length > 0) {
+        const firstApproval = approvals[0];
+        session.pendingToolApproval = {
+          callId: firstApproval.callId,
+          taskId: firstApproval.taskId,
+          toolName: firstApproval.displayName || firstApproval.name,
+        };
+        logger.info(
+          `[ChatBridge] Pending tool approval: ${firstApproval.displayName || firstApproval.name} callId=${firstApproval.callId}`,
+        );
+      } else {
+        session.pendingToolApproval = undefined;
+      }
+
+      // Convert A2A response to Chat format
+      const threadKey = message.thread.threadKey || threadName;
+      return renderResponse(response, threadKey, threadName);
+    } catch (error) {
+      const errorMsg = error instanceof Error ? error.message : 'Unknown error';
+      logger.error(`[ChatBridge] Error handling message: ${errorMsg}`, error);
+      return {
+        text: `Sorry, I encountered an error processing your request: ${errorMsg}`,
+      };
+    }
+  }
+
+  /**
+   * Handles a CARD_CLICKED event: user clicked a button on a card.
+   * Used for tool approval/rejection flows.
+   */
+  private async handleCardClicked(event: ChatEvent): Promise<ChatResponse> {
+    const action = event.action;
+    if (!action) {
+      return { text: 'Error: Missing action data.' };
+    }
+
+    const threadName = event.message?.thread?.name;
+    if (!threadName) {
+      return { text: 'Error: Missing thread information.' };
+    }
+
+    const session = this.sessionStore.get(threadName);
+    if (!session) {
+      return { text: 'Error: No active session found for this thread.' };
+    }
+
+    logger.info(
+      `[ChatBridge] CARD_CLICKED: function=${action.actionMethodName}`,
+    );
+
+    if (action.actionMethodName === 'tool_confirmation') {
+      return this.handleToolConfirmation(event, session.contextId);
+    }
+
+    return { text: `Unknown action: ${action.actionMethodName}` };
+  }
+
+  /**
+   * Handles tool confirmation actions from card button clicks.
+   */
+  private async handleToolConfirmation(
+    event: ChatEvent,
+    contextId: string,
+  ): Promise<ChatResponse> {
+    const params = event.action?.parameters || [];
+    const paramMap = new Map(params.map((p) => [p.key, p.value]));
+
+    const callId = paramMap.get('callId');
+    const outcome = paramMap.get('outcome');
+    const taskId = paramMap.get('taskId');
+
+    if (!callId || !outcome || !taskId) {
+      return { text: 'Error: Missing tool confirmation parameters.' };
+    }
+
+    logger.info(
+      `[ChatBridge] Tool confirmation: callId=${callId}, outcome=${outcome}, taskId=${taskId}`,
+    );
+
+    try {
+      const response = await this.a2aClient.sendToolConfirmation(
+        callId,
+        outcome,
+        taskId,
+        { contextId },
+      );
+
+      // Update session
+      const threadName = event.message?.thread?.name;
+      if (threadName) {
+        const { contextId: newContextId, taskId: newTaskId } =
+          extractIdsFromResponse(response);
+        if (newContextId) {
+          const session = this.sessionStore.get(threadName);
+          if (session) session.contextId = newContextId;
+        }
+        this.sessionStore.updateTaskId(threadName, newTaskId);
+      }
+
+      return renderResponse(response);
+    } catch (error) {
+      const errorMsg = error instanceof Error ? error.message : 'Unknown error';
+      logger.error(
+        `[ChatBridge] Error sending tool confirmation: ${errorMsg}`,
+        error,
+      );
+      return {
+        text: `Error processing tool confirmation: ${errorMsg}`,
+      };
+    }
+  }
+
+  /**
+   * Handles ADDED_TO_SPACE event: bot was added to a space or DM.
+   */
+  private handleAddedToSpace(event: ChatEvent): ChatResponse {
+    const spaceType = event.space.type === 'DM' ? 'DM' : 'space';
+    logger.info(`[ChatBridge] Bot added to ${spaceType}: ${event.space.name}`);
+    return {
+      text:
+        `Hello! I'm the Gemini CLI Agent. Send me a message to get started with code generation and development tasks.\n\n` +
+        `I can:\n` +
+        `- Generate code from natural language\n` +
+        `- Edit files and run commands\n` +
+        `- Answer questions about code\n\n` +
+        `I'll ask for your approval before executing tools.`,
+    };
+  }
+
+  /**
+   * Handles REMOVED_FROM_SPACE event: bot was removed from a space.
+   */
+  private handleRemovedFromSpace(event: ChatEvent): ChatResponse {
+    logger.info(`[ChatBridge] Bot removed from space: ${event.space.name}`);
+    // Clean up any sessions for this space
+    return {};
+  }
+}

packages/a2a-server/src/chat-bridge/response-renderer.ts

@@ -0,0 +1,413 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Converts A2A/A2UI responses into Google Chat messages and Cards V2.
+ *
+ * This renderer understands the A2UI v0.10 surface structures produced by our
+ * a2a-server (tool approval surfaces, agent response surfaces, thought surfaces)
+ * and converts them to Google Chat's Cards V2 format.
+ *
+ * Inspired by the A2UI web_core message processor pattern but simplified for
+ * server-side rendering to a constrained card format.
+ */
+
+import type {
+  ChatResponse,
+  ChatCardV2,
+  ChatCardSection,
+  ChatWidget,
+} from './types.js';
+import {
+  type A2AResponse,
+  extractAllParts,
+  extractTextFromParts,
+  extractA2UIParts,
+} from './a2a-bridge-client.js';
+
+export interface ToolApprovalInfo {
+  taskId: string;
+  callId: string;
+  name: string;
+  displayName: string;
+  description: string;
+  args: string;
+  kind: string;
+  status: string;
+}
+
+interface AgentResponseInfo {
+  text: string;
+  status: string;
+}
+
+/**
+ * Extracts tool approval info from an A2A response.
+ * Used by the handler to track pending approvals for text-based confirmation.
+ */
+export function extractToolApprovals(
+  response: A2AResponse,
+): ToolApprovalInfo[] {
+  const parts = extractAllParts(response);
+  const a2uiMessageGroups = extractA2UIParts(parts);
+  const toolApprovals: ToolApprovalInfo[] = [];
+  const agentResponses: AgentResponseInfo[] = [];
+  const thoughts: Array<{ subject: string; description: string }> = [];
+
+  for (const messages of a2uiMessageGroups) {
+    parseA2UIMessages(messages, toolApprovals, agentResponses, thoughts);
+  }
+
+  return deduplicateToolApprovals(toolApprovals);
+}
+
+/**
+ * Renders an A2A response as a Google Chat response.
+ * Extracts text content and A2UI surfaces, converting them to Chat format.
+ */
+export function renderResponse(
+  response: A2AResponse,
+  threadKey?: string,
+  threadName?: string,
+): ChatResponse {
+  const parts = extractAllParts(response);
+  const textContent = extractTextFromParts(parts);
+  const a2uiMessageGroups = extractA2UIParts(parts);
+
+  // Parse A2UI surfaces for known types
+  const toolApprovals: ToolApprovalInfo[] = [];
+  const agentResponses: AgentResponseInfo[] = [];
+  const thoughts: Array<{ subject: string; description: string }> = [];
+
+  for (const messages of a2uiMessageGroups) {
+    parseA2UIMessages(messages, toolApprovals, agentResponses, thoughts);
+  }
+
+  // Deduplicate tool approvals by surfaceId — A2UI history contains both
+  // initial 'awaiting_approval' and later 'success' events for auto-approved tools.
+  const dedupedApprovals = deduplicateToolApprovals(toolApprovals);
+
+  const cards: ChatCardV2[] = [];
+
+  // Only render tool approval cards for tools still awaiting approval.
+  // In YOLO mode, tools are auto-approved and their status becomes "success"
+  // so we skip rendering approval cards for those.
+  for (const approval of dedupedApprovals) {
+    if (approval.status === 'awaiting_approval') {
+      cards.push(renderToolApprovalCard(approval));
+    }
+  }
+
+  // Build text response from agent responses and plain text
+  const responseTexts: string[] = [];
+
+  // Add thought summaries
+  for (const thought of thoughts) {
+    responseTexts.push(`_${thought.subject}_: ${thought.description}`);
+  }
+
+  // Add agent response text (from A2UI surfaces).
+  // Use only the last non-empty response since later updates supersede earlier
+  // ones for the same surface (history contains multiple status-update messages).
+  for (let i = agentResponses.length - 1; i >= 0; i--) {
+    if (agentResponses[i].text) {
+      responseTexts.push(agentResponses[i].text);
+      break;
+    }
+  }
+
+  // Fall back to plain text content if no A2UI response text
+  if (responseTexts.length === 0 && textContent) {
+    responseTexts.push(textContent);
+  }
+
+  // Add task state info
+  if (response.kind === 'task' && response.status) {
+    const state = response.status.state;
+    if (state === 'input-required' && cards.length > 0) {
+      responseTexts.push('*Waiting for your approval to continue...*');
+    } else if (state === 'failed') {
+      responseTexts.push('*Task failed.*');
+    } else if (state === 'canceled') {
+      responseTexts.push('*Task was cancelled.*');
+    }
+  }
+
+  const chatResponse: ChatResponse = {};
+
+  if (responseTexts.length > 0) {
+    chatResponse.text = responseTexts.join('\n\n');
+  }
+
+  if (cards.length > 0) {
+    chatResponse.cardsV2 = cards;
+  }
+
+  if (threadKey || threadName) {
+    chatResponse.thread = {};
+    if (threadKey) chatResponse.thread.threadKey = threadKey;
+    if (threadName) chatResponse.thread.name = threadName;
+  }
+
+  // Ensure we always return something
+  if (!chatResponse.text && !chatResponse.cardsV2) {
+    chatResponse.text = '_Agent is processing..._';
+  }
+
+  return chatResponse;
+}
+
+/**
+ * Renders a CARD_CLICKED acknowledgment response.
+ */
+export function renderActionAcknowledgment(
+  action: string,
+  outcome: string,
+): ChatResponse {
+  const emoji =
+    outcome === 'cancel'
+      ? 'Rejected'
+      : outcome === 'proceed_always_tool'
+        ? 'Always Allowed'
+        : 'Approved';
+  return {
+    actionResponse: { type: 'UPDATE_MESSAGE' },
+    text: `*Tool ${emoji}* - Processing...`,
+  };
+}
+
+/** Safely extracts a string property from an unknown object. */
+function str(obj: Record<string, unknown>, key: string): string {
+  const v = obj[key];
+  return typeof v === 'string' ? v : '';
+}
+
+/** Safely checks if an unknown value is a record. */
+function isRecord(v: unknown): v is Record<string, unknown> {
+  return typeof v === 'object' && v !== null && !Array.isArray(v);
+}
+
+/** Safely extracts a nested object property. */
+function obj(
+  parent: Record<string, unknown>,
+  key: string,
+): Record<string, unknown> | undefined {
+  const v = parent[key];
+  return isRecord(v) ? v : undefined;
+}
+
+/**
+ * Deduplicates tool approvals by surfaceId, keeping the last entry per surface.
+ * In blocking mode, A2UI history accumulates ALL intermediate events — a tool
+ * surface may appear first as 'awaiting_approval' then as 'success' (YOLO mode).
+ * By keeping only the last entry per surfaceId, auto-approved tools show 'success'.
+ */
+function deduplicateToolApprovals(
+  approvals: ToolApprovalInfo[],
+): ToolApprovalInfo[] {
+  const byId = new Map<string, ToolApprovalInfo>();
+  for (const a of approvals) {
+    const key = `${a.taskId}_${a.callId}`;
+    byId.set(key, a);
+  }
+  return [...byId.values()];
+}
+
+/**
+ * Parses A2UI v0.10 messages to extract known surface types.
+ * Our server produces specific surfaces: tool approval, agent response, thought.
+ */
+function parseA2UIMessages(
+  messages: unknown[],
+  toolApprovals: ToolApprovalInfo[],
+  agentResponses: AgentResponseInfo[],
+  thoughts: Array<{ subject: string; description: string }>,
+): void {
+  for (const msg of messages) {
+    if (!isRecord(msg)) continue;
+
+    // Look for updateDataModel messages that contain tool approval or response data
+    const updateDM = obj(msg, 'updateDataModel');
+    if (updateDM) {
+      const surfaceId = str(updateDM, 'surfaceId');
+      const value = obj(updateDM, 'value');
+      const path = str(updateDM, 'path');
+
+      if (value && !path) {
+        // Full data model update (initial) - check for known structures
+        const tool = obj(value, 'tool');
+        if (surfaceId.startsWith('tool_approval_') && tool) {
+          toolApprovals.push({
+            taskId: str(value, 'taskId'),
+            callId: str(tool, 'callId'),
+            name: str(tool, 'name'),
+            displayName: str(tool, 'displayName'),
+            description: str(tool, 'description'),
+            args: str(tool, 'args'),
+            kind: str(tool, 'kind') || 'tool',
+            status: str(tool, 'status') || 'unknown',
+          });
+        }
+
+        const resp = obj(value, 'response');
+        if (surfaceId.startsWith('agent_response_') && resp) {
+          agentResponses.push({
+            text: str(resp, 'text'),
+            status: str(resp, 'status'),
+          });
+        }
+      }
+
+      // Partial data model updates (path-based)
+      if (path === '/response/text' && updateDM['value'] != null) {
+        agentResponses.push({
+          text: String(updateDM['value']),
+          status: '',
+        });
+      }
+
+      // Tool status updates (e.g., YOLO mode changes status to 'success')
+      if (
+        surfaceId.startsWith('tool_approval_') &&
+        path === '/tool/status' &&
+        typeof updateDM['value'] === 'string'
+      ) {
+        // Find existing tool approval for this surface and update its status
+        const existing = toolApprovals.find(
+          (a) => `tool_approval_${a.taskId}_${a.callId}` === surfaceId,
+        );
+        if (existing) {
+          existing.status = updateDM['value'];
+        }
+      }
+    }
+
+    // Look for updateComponents to extract thought text
+    const updateComp = obj(msg, 'updateComponents');
+    if (updateComp) {
+      const surfaceId = str(updateComp, 'surfaceId');
+      const components = updateComp['components'];
+
+      if (surfaceId.startsWith('thought_') && Array.isArray(components)) {
+        const subject = extractComponentText(components, 'thought_subject');
+        const desc = extractComponentText(components, 'thought_desc');
+        if (subject || desc) {
+          thoughts.push({
+            subject: subject || 'Thinking',
+            description: desc || '',
+          });
+        }
+      }
+    }
+  }
+}
+
+/**
+ * Extracts the text content from a named component in a component array.
+ * Components use our a2ui-components.ts builder format.
+ */
+function extractComponentText(
+  components: unknown[],
+  componentId: string,
+): string {
+  for (const comp of components) {
+    if (!isRecord(comp)) continue;
+    if (comp['id'] === componentId && comp['component'] === 'text') {
+      return str(comp, 'text');
+    }
+  }
+  return '';
+}
+
+/**
+ * Extracts a concise command summary from tool approval args.
+ * For shell tools, returns just the command string.
+ * For file tools, returns the file path.
+ */
+function extractCommandSummary(approval: ToolApprovalInfo): string {
+  if (!approval.args || approval.args === 'No arguments') return '';
+
+  try {
+    const parsed: unknown = JSON.parse(approval.args);
+    if (isRecord(parsed)) {
+      // Shell tool: {"command": "ls -F"}
+      if (typeof parsed['command'] === 'string') {
+        return parsed['command'];
+      }
+      // File tools: {"file_path": "/path/to/file", ...}
+      if (typeof parsed['file_path'] === 'string') {
+        const action =
+          approval.name || approval.displayName || 'File operation';
+        return `${action}: ${parsed['file_path']}`;
+      }
+    }
+  } catch {
+    // Not JSON, return as-is if short enough
+    if (approval.args.length <= 200) return approval.args;
+  }
+
+  return '';
+}
+
+/**
+ * Renders a tool approval surface as a Google Chat Card V2.
+ */
+function renderToolApprovalCard(approval: ToolApprovalInfo): ChatCardV2 {
+  const widgets: ChatWidget[] = [];
+
+  // Show a concise summary of what the tool will do.
+  // For shell commands, extract just the command string from the args JSON.
+  const commandSummary = extractCommandSummary(approval);
+  if (commandSummary) {
+    widgets.push({
+      decoratedText: {
+        text: `\`${commandSummary}\``,
+        topLabel: approval.displayName || approval.name,
+        startIcon: { knownIcon: 'DESCRIPTION' },
+        wrapText: true,
+      },
+    });
+  } else if (approval.args && approval.args !== 'No arguments') {
+    // Fallback: show truncated args
+    const truncatedArgs =
+      approval.args.length > 300
+        ? approval.args.substring(0, 300) + '...'
+        : approval.args;
+    widgets.push({
+      decoratedText: {
+        text: truncatedArgs,
+        topLabel: approval.displayName || approval.name,
+        startIcon: { knownIcon: 'DESCRIPTION' },
+        wrapText: true,
+      },
+    });
+  }
+
+  // Text-based approval instructions (card click buttons don't work
+  // with the current Add-ons routing configuration)
+  widgets.push({
+    textParagraph: {
+      text: 'Reply <b>approve</b>, <b>always allow</b>, or <b>reject</b>',
+    },
+  });
+
+  const sections: ChatCardSection[] = [
+    {
+      widgets,
+    },
+  ];
+
+  return {
+    cardId: `tool_approval_${approval.callId}`,
+    card: {
+      header: {
+        title: 'Tool Approval Required',
+        subtitle: approval.displayName || approval.name,
+      },
+      sections,
+    },
+  };
+}

packages/a2a-server/src/chat-bridge/routes.ts

@@ -0,0 +1,362 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Express routes for the Google Chat bridge webhook.
+ * Adds a POST /chat/webhook endpoint to the existing Express app.
+ * Includes JWT verification for Google Chat requests when configured.
+ */
+
+import type { Router, Request, Response, NextFunction } from 'express';
+import { Router as createRouter } from 'express';
+import { OAuth2Client } from 'google-auth-library';
+import type { ChatEvent, ChatBridgeConfig, ChatResponse } from './types.js';
+import { ChatBridgeHandler } from './handler.js';
+import { logger } from '../utils/logger.js';
+
+const CHAT_ISSUER = 'chat@system.gserviceaccount.com';
+
+/**
+ * Creates middleware that verifies Google Chat JWT tokens.
+ *
+ * On Cloud Run (detected via K_SERVICE env var), authentication is handled by
+ * Cloud Run's IAM layer — only principals with roles/run.invoker can reach the
+ * container. Cloud Run strips the Authorization header after validation, so our
+ * middleware cannot re-verify the token. We trust Cloud Run's IAM instead.
+ *
+ * When NOT on Cloud Run and projectNumber is set, requests must include a valid
+ * Bearer token signed by Google Chat with the correct audience.
+ *
+ * When neither condition applies, verification is skipped (local testing).
+ */
+function createAuthMiddleware(
+  projectNumber: string | undefined,
+): (req: Request, res: Response, next: NextFunction) => void {
+  // On Cloud Run, IAM handles auth — the Authorization header is stripped
+  // before reaching the container, so we cannot verify it ourselves.
+  if (process.env['K_SERVICE']) {
+    logger.info(
+      '[ChatBridge] Running on Cloud Run — auth delegated to Cloud Run IAM.',
+    );
+    return (_req: Request, _res: Response, next: NextFunction) => {
+      next();
+    };
+  }
+
+  if (!projectNumber) {
+    logger.warn(
+      '[ChatBridge] CHAT_PROJECT_NUMBER not set — JWT verification disabled. ' +
+        'Set it in production to verify requests come from Google Chat.',
+    );
+    return (_req: Request, _res: Response, next: NextFunction) => {
+      next();
+    };
+  }
+
+  const authClient = new OAuth2Client();
+
+  return (req: Request, res: Response, next: NextFunction) => {
+    const authHeader = req.headers['authorization'];
+    if (!authHeader || !authHeader.startsWith('Bearer ')) {
+      logger.warn('[ChatBridge] Missing or invalid Authorization header');
+      res.status(401).json({ error: 'Unauthorized: missing Bearer token' });
+      return;
+    }
+
+    const token = authHeader.substring(7);
+
+    // Debug: decode token payload without verification to inspect claims
+    try {
+      const payloadB64 = token.split('.')[1];
+      if (payloadB64) {
+        const decoded = JSON.parse(
+          Buffer.from(payloadB64, 'base64').toString(),
+        );
+        logger.info(
+          `[ChatBridge] Token claims: iss=${String(decoded.iss ?? 'none')} ` +
+            `aud=${String(decoded.aud ?? 'none')} ` +
+            `email=${String(decoded.email ?? 'none')} ` +
+            `sub=${String(decoded.sub ?? 'none')}`,
+        );
+      }
+    } catch {
+      logger.warn('[ChatBridge] Could not decode token for debug logging');
+    }
+
+    authClient
+      .verifyIdToken({
+        idToken: token,
+        audience: projectNumber,
+      })
+      .then((ticket) => {
+        const payload = ticket.getPayload();
+        if (payload?.iss !== CHAT_ISSUER) {
+          logger.warn(
+            `[ChatBridge] Invalid token issuer: ${payload?.iss ?? 'unknown'}`,
+          );
+          res.status(403).json({ error: 'Forbidden: invalid token issuer' });
+          return;
+        }
+        next();
+      })
+      .catch((err: unknown) => {
+        const msg = err instanceof Error ? err.message : 'Unknown error';
+        logger.warn(`[ChatBridge] Token verification failed: ${msg}`);
+        res.status(401).json({ error: 'Unauthorized: invalid token' });
+      });
+  };
+}
+
+/** Safely extract a string from an unknown record. */
+function str(obj: Record<string, unknown>, key: string): string {
+  const v = obj[key];
+  return typeof v === 'string' ? v : '';
+}
+
+/** Safely check if a value is a plain object. */
+function isObj(v: unknown): v is Record<string, unknown> {
+  return typeof v === 'object' && v !== null && !Array.isArray(v);
+}
+
+/**
+ * Normalizes a Google Chat event to the legacy ChatEvent format.
+ * Workspace Add-ons send: {chat: {messagePayload, user, ...}, commonEventObject}
+ * Legacy format: {type: "MESSAGE", message: {...}, space: {...}, user: {...}}
+ */
+function normalizeEvent(raw: Record<string, unknown>): ChatEvent | null {
+  // Already in legacy format
+  if (typeof raw['type'] === 'string') {
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+    return raw as unknown as ChatEvent;
+  }
+
+  // Workspace Add-ons format
+  const chat = raw['chat'];
+  if (!isObj(chat)) return null;
+
+  const user = isObj(chat['user']) ? chat['user'] : {};
+  const eventTime = str(chat, 'eventTime');
+
+  // Check for card click actions (button clicks) via commonEventObject
+  const common = raw['commonEventObject'];
+  if (isObj(common) && typeof common['invokedFunction'] === 'string') {
+    const invokedFunction = common['invokedFunction'];
+    const params = isObj(common['parameters']) ? common['parameters'] : {};
+
+    // Build action parameters array from commonEventObject.parameters
+    const actionParams = Object.entries(params)
+      .filter(([, v]) => typeof v === 'string')
+      .map(([key, value]) => ({ key, value: String(value) }));
+
+    // Extract message/thread/space from chat object
+    const message = isObj(chat['message']) ? chat['message'] : {};
+    const thread = isObj(message['thread']) ? message['thread'] : {};
+    const space = isObj(chat['space'])
+      ? chat['space']
+      : isObj(message['space'])
+        ? message['space']
+        : {};
+
+    logger.info(
+      `[ChatBridge] Add-ons CARD_CLICKED: function=${invokedFunction} ` +
+        `params=${JSON.stringify(params)} thread=${str(thread, 'name')}`,
+    );
+
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+    return {
+      type: 'CARD_CLICKED',
+      eventTime,
+      message: { ...message, thread, space },
+      space,
+      user,
+      action: {
+        actionMethodName: invokedFunction,
+        parameters: actionParams,
+      },
+    } as unknown as ChatEvent;
+  }
+
+  // Determine event type from which payload field is present
+  if (isObj(chat['messagePayload'])) {
+    const payload = chat['messagePayload'];
+    const message = isObj(payload['message']) ? payload['message'] : {};
+    const space = isObj(payload['space'])
+      ? payload['space']
+      : isObj(message['space'])
+        ? message['space']
+        : {};
+    const thread = isObj(message['thread']) ? message['thread'] : {};
+
+    logger.info(
+      `[ChatBridge] Add-ons MESSAGE: text="${str(message, 'text')}" ` +
+        `space=${str(space, 'name')} thread=${str(thread, 'name')}`,
+    );
+
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+    return {
+      type: 'MESSAGE',
+      eventTime,
+      message: {
+        ...message,
+        sender: message['sender'] ?? user,
+        thread,
+        space,
+      },
+      space,
+      user,
+    } as unknown as ChatEvent;
+  }
+
+  if (isObj(chat['addedToSpacePayload'])) {
+    const payload = chat['addedToSpacePayload'];
+    const space = isObj(payload['space']) ? payload['space'] : {};
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+    return {
+      type: 'ADDED_TO_SPACE',
+      eventTime,
+      space,
+      user,
+    } as unknown as ChatEvent;
+  }
+
+  if (isObj(chat['removedFromSpacePayload'])) {
+    const payload = chat['removedFromSpacePayload'];
+    const space = isObj(payload['space']) ? payload['space'] : {};
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+    return {
+      type: 'REMOVED_FROM_SPACE',
+      eventTime,
+      space,
+      user,
+    } as unknown as ChatEvent;
+  }
+
+  logger.warn(
+    `[ChatBridge] Unknown Add-ons event, chat keys: ${Object.keys(chat).join(',')}`,
+  );
+  return null;
+}
+
+/**
+ * Wraps a legacy ChatResponse in the Workspace Add-ons response format.
+ * Add-ons expects: {hostAppDataAction: {chatDataAction: {createMessageAction: {message}}}}
+ */
+function wrapAddOnsResponse(response: ChatResponse): Record<string, unknown> {
+  // Build the message object for the Add-ons format
+  const message: Record<string, unknown> = {};
+  if (response.text) {
+    message['text'] = response.text;
+  }
+  if (response.cardsV2) {
+    message['cardsV2'] = response.cardsV2;
+  }
+  // Include thread info so the reply goes to the user's thread
+  // instead of appearing as a top-level message
+  if (response.thread) {
+    const thread: Record<string, string> = {};
+    if (response.thread.name) thread['name'] = response.thread.name;
+    if (response.thread.threadKey)
+      thread['threadKey'] = response.thread.threadKey;
+    message['thread'] = thread;
+  }
+
+  // For action responses (like CARD_CLICKED acknowledgments), use updateMessageAction
+  if (response.actionResponse?.type === 'UPDATE_MESSAGE') {
+    return {
+      hostAppDataAction: {
+        chatDataAction: {
+          updateMessageAction: { message },
+        },
+      },
+    };
+  }
+
+  return {
+    hostAppDataAction: {
+      chatDataAction: {
+        createMessageAction: { message },
+      },
+    },
+  };
+}
+
+/**
+ * Creates Express routes for the Google Chat bridge.
+ */
+export function createChatBridgeRoutes(config: ChatBridgeConfig): Router {
+  const router = createRouter();
+  const handler = new ChatBridgeHandler(config);
+  const authMiddleware = createAuthMiddleware(config.projectNumber);
+
+  // Google Chat sends webhook events as POST requests
+  router.post(
+    '/chat/webhook',
+    authMiddleware,
+    async (req: Request, res: Response) => {
+      try {
+        // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
+        const rawBody = req.body as Record<string, unknown>;
+
+        // Normalize to legacy ChatEvent format. Google Chat HTTP endpoints
+        // configured as Workspace Add-ons send a different event structure:
+        //   {chat: {messagePayload, user, eventTime}, commonEventObject: {...}}
+        // We convert to the legacy format our handler expects:
+        //   {type: "MESSAGE", message: {...}, space: {...}, user: {...}}
+        const event = normalizeEvent(rawBody);
+
+        if (!event || !event.type) {
+          logger.warn(
+            `[ChatBridge] Could not parse event. Keys: ${Object.keys(rawBody).join(',')}`,
+          );
+          res.status(400).json({ error: 'Invalid event: missing type field' });
+          return;
+        }
+
+        logger.info(`[ChatBridge] Webhook received: type=${event.type}`);
+
+        // Detect if the request came in Add-ons format
+        const isAddOnsFormat = Boolean(rawBody['chat'] && !rawBody['type']);
+
+        const response = await handler.handleEvent(event);
+
+        // For CARD_CLICKED events, force UPDATE_MESSAGE so the card is
+        // replaced in-place rather than posting a new message.
+        if (event.type === 'CARD_CLICKED' && !response.actionResponse) {
+          response.actionResponse = { type: 'UPDATE_MESSAGE' };
+        }
+
+        if (isAddOnsFormat) {
+          // Wrap in Workspace Add-ons response format
+          const addOnsResponse = wrapAddOnsResponse(response);
+          logger.info(
+            `[ChatBridge] Add-ons response: ${JSON.stringify(addOnsResponse).substring(0, 200)}`,
+          );
+          res.json(addOnsResponse);
+        } else {
+          res.json(response);
+        }
+      } catch (error) {
+        const errorMsg =
+          error instanceof Error ? error.message : 'Unknown error';
+        logger.error(`[ChatBridge] Webhook error: ${errorMsg}`, error);
+        res.status(500).json({
+          text: `Internal error: ${errorMsg}`,
+        });
+      }
+    },
+  );
+
+  // Health check endpoint for the chat bridge (no auth required)
+  router.get('/chat/health', (_req: Request, res: Response) => {
+    res.json({
+      status: 'ok',
+      bridge: 'google-chat',
+      a2aServerUrl: config.a2aServerUrl,
+    });
+  });
+
+  return router;
+}

packages/a2a-server/src/chat-bridge/session-store.ts

@@ -0,0 +1,231 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Manages mapping between Google Chat threads and A2A sessions.
+ * Each Google Chat thread maintains a persistent contextId (conversation)
+ * and a transient taskId (active task within that conversation).
+ *
+ * Supports optional GCS persistence so session mappings survive
+ * Cloud Run instance restarts.
+ */
+
+import { v4 as uuidv4 } from 'uuid';
+import { logger } from '../utils/logger.js';
+
+export interface PendingToolApproval {
+  callId: string;
+  taskId: string;
+  toolName: string;
+}
+
+export interface SessionInfo {
+  /** A2A contextId - persists for the lifetime of the Chat thread. */
+  contextId: string;
+  /** A2A taskId - cleared on terminal states, reused on input-required. */
+  taskId?: string;
+  /** Space name for async messaging. */
+  spaceName: string;
+  /** Thread name for async messaging. */
+  threadName: string;
+  /** Last activity timestamp. */
+  lastActivity: number;
+  /** Pending tool approval waiting for text-based response. */
+  pendingToolApproval?: PendingToolApproval;
+  /** When true, all tool calls are auto-approved. */
+  yoloMode?: boolean;
+}
+
+/** Serializable subset of SessionInfo for GCS persistence. */
+interface PersistedSession {
+  contextId: string;
+  taskId?: string;
+  spaceName: string;
+  threadName: string;
+  lastActivity: number;
+  yoloMode?: boolean;
+}
+
+/**
+ * Session store mapping Google Chat thread names to A2A sessions.
+ * Optionally backed by GCS for persistence across restarts.
+ */
+export class SessionStore {
+  private sessions = new Map<string, SessionInfo>();
+  private gcsBucket?: string;
+  private gcsObjectPath = 'chat-bridge/sessions.json';
+  private dirty = false;
+  private flushTimer?: ReturnType<typeof setInterval>;
+
+  constructor(gcsBucket?: string) {
+    this.gcsBucket = gcsBucket;
+    if (gcsBucket) {
+      // Flush to GCS every 30 seconds if dirty
+      this.flushTimer = setInterval(() => {
+        if (this.dirty) {
+          this.persistToGCS().catch((err) =>
+            logger.warn(`[ChatBridge] GCS session flush failed:`, err),
+          );
+        }
+      }, 30000);
+    }
+  }
+
+  /**
+   * Restores sessions from GCS on startup.
+   */
+  async restore(): Promise<void> {
+    if (!this.gcsBucket) return;
+
+    try {
+      const { Storage } = await import('@google-cloud/storage');
+      const storage = new Storage();
+      const file = storage.bucket(this.gcsBucket).file(this.gcsObjectPath);
+      const [exists] = await file.exists();
+      if (!exists) {
+        logger.info('[ChatBridge] No persisted sessions found in GCS.');
+        return;
+      }
+
+      const [contents] = await file.download();
+      const persisted: PersistedSession[] = JSON.parse(contents.toString());
+      for (const s of persisted) {
+        this.sessions.set(s.threadName, {
+          contextId: s.contextId,
+          taskId: s.taskId,
+          spaceName: s.spaceName,
+          threadName: s.threadName,
+          lastActivity: s.lastActivity,
+          yoloMode: s.yoloMode,
+        });
+      }
+      logger.info(
+        `[ChatBridge] Restored ${persisted.length} sessions from GCS.`,
+      );
+    } catch (err) {
+      logger.warn(`[ChatBridge] Could not restore sessions from GCS:`, err);
+    }
+  }
+
+  /**
+   * Persists current sessions to GCS.
+   */
+  private async persistToGCS(): Promise<void> {
+    if (!this.gcsBucket) return;
+
+    try {
+      const { Storage } = await import('@google-cloud/storage');
+      const storage = new Storage();
+      const file = storage.bucket(this.gcsBucket).file(this.gcsObjectPath);
+
+      const persisted: PersistedSession[] = [];
+      for (const session of this.sessions.values()) {
+        persisted.push({
+          contextId: session.contextId,
+          taskId: session.taskId,
+          spaceName: session.spaceName,
+          threadName: session.threadName,
+          lastActivity: session.lastActivity,
+          yoloMode: session.yoloMode,
+        });
+      }
+
+      await file.save(JSON.stringify(persisted), {
+        contentType: 'application/json',
+      });
+      this.dirty = false;
+      logger.info(
+        `[ChatBridge] Persisted ${persisted.length} sessions to GCS.`,
+      );
+    } catch (err) {
+      logger.warn(`[ChatBridge] Failed to persist sessions to GCS:`, err);
+    }
+  }
+
+  /**
+   * Gets or creates a session for a Google Chat thread.
+   */
+  getOrCreate(threadName: string, spaceName: string): SessionInfo {
+    let session = this.sessions.get(threadName);
+    if (!session) {
+      session = {
+        contextId: uuidv4(),
+        spaceName,
+        threadName,
+        lastActivity: Date.now(),
+      };
+      this.sessions.set(threadName, session);
+      this.dirty = true;
+      logger.info(
+        `[ChatBridge] New session for thread ${threadName}: contextId=${session.contextId}`,
+      );
+    }
+    session.lastActivity = Date.now();
+    return session;
+  }
+
+  /**
+   * Gets an existing session by thread name.
+   */
+  get(threadName: string): SessionInfo | undefined {
+    return this.sessions.get(threadName);
+  }
+
+  /**
+   * Updates the taskId for a session.
+   */
+  updateTaskId(threadName: string, taskId: string | undefined): void {
+    const session = this.sessions.get(threadName);
+    if (session) {
+      session.taskId = taskId;
+      this.dirty = true;
+      logger.info(
+        `[ChatBridge] Session ${threadName}: taskId=${taskId ?? 'cleared'}`,
+      );
+    }
+  }
+
+  /**
+   * Removes a session (e.g. when bot is removed from space).
+   */
+  remove(threadName: string): void {
+    this.sessions.delete(threadName);
+    this.dirty = true;
+  }
+
+  /**
+   * Cleans up stale sessions older than the given max age (ms).
+   */
+  cleanup(maxAgeMs: number = 24 * 60 * 60 * 1000): void {
+    const now = Date.now();
+    for (const [threadName, session] of this.sessions.entries()) {
+      if (now - session.lastActivity > maxAgeMs) {
+        this.sessions.delete(threadName);
+        this.dirty = true;
+        logger.info(`[ChatBridge] Cleaned up stale session: ${threadName}`);
+      }
+    }
+  }
+
+  /**
+   * Forces an immediate flush to GCS.
+   */
+  async flush(): Promise<void> {
+    if (this.dirty) {
+      await this.persistToGCS();
+    }
+  }
+
+  /**
+   * Stops the periodic flush timer.
+   */
+  dispose(): void {
+    if (this.flushTimer) {
+      clearInterval(this.flushTimer);
+      this.flushTimer = undefined;
+    }
+  }
+}

packages/a2a-server/src/chat-bridge/types.ts

@@ -0,0 +1,141 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Google Chat HTTP endpoint event types.
+ * @see https://developers.google.com/workspace/chat/api/reference/rest/v1/Event
+ */
+
+export interface ChatUser {
+  name: string;
+  displayName: string;
+  type?: 'HUMAN' | 'BOT';
+}
+
+export interface ChatThread {
+  name: string;
+  threadKey?: string;
+}
+
+export interface ChatSpace {
+  name: string;
+  type: 'DM' | 'ROOM' | 'SPACE';
+  displayName?: string;
+}
+
+export interface ChatMessage {
+  name: string;
+  sender: ChatUser;
+  createTime: string;
+  text?: string;
+  argumentText?: string;
+  thread: ChatThread;
+  space: ChatSpace;
+  cardsV2?: ChatCardV2[];
+}
+
+export interface ChatActionParameter {
+  key: string;
+  value: string;
+}
+
+export interface ChatAction {
+  actionMethodName: string;
+  parameters: ChatActionParameter[];
+}
+
+export type ChatEventType =
+  | 'MESSAGE'
+  | 'CARD_CLICKED'
+  | 'ADDED_TO_SPACE'
+  | 'REMOVED_FROM_SPACE';
+
+export interface ChatEvent {
+  type: ChatEventType;
+  eventTime: string;
+  message?: ChatMessage;
+  space: ChatSpace;
+  user: ChatUser;
+  action?: ChatAction;
+  common?: Record<string, unknown>;
+  threadKey?: string;
+}
+
+// Google Chat Cards V2 response types
+
+export interface ChatCardV2 {
+  cardId: string;
+  card: ChatCard;
+}
+
+export interface ChatCard {
+  header?: ChatCardHeader;
+  sections: ChatCardSection[];
+}
+
+export interface ChatCardHeader {
+  title: string;
+  subtitle?: string;
+  imageUrl?: string;
+  imageType?: 'CIRCLE' | 'SQUARE';
+}
+
+export interface ChatCardSection {
+  header?: string;
+  widgets: ChatWidget[];
+  collapsible?: boolean;
+  uncollapsibleWidgetsCount?: number;
+}
+
+export type ChatWidget =
+  | { textParagraph: { text: string } }
+  | { decoratedText: ChatDecoratedText }
+  | { buttonList: { buttons: ChatButton[] } }
+  | { divider: Record<string, never> };
+
+export interface ChatDecoratedText {
+  text: string;
+  topLabel?: string;
+  bottomLabel?: string;
+  startIcon?: { knownIcon: string };
+  wrapText?: boolean;
+}
+
+export interface ChatButton {
+  text: string;
+  onClick: ChatOnClick;
+  color?: { red: number; green: number; blue: number; alpha?: number };
+  disabled?: boolean;
+}
+
+export interface ChatOnClick {
+  action: {
+    function: string;
+    parameters: ChatActionParameter[];
+  };
+}
+
+export interface ChatResponse {
+  text?: string;
+  cardsV2?: ChatCardV2[];
+  thread?: { threadKey?: string; name?: string };
+  actionResponse?: {
+    type: 'NEW_MESSAGE' | 'UPDATE_MESSAGE' | 'REQUEST_CONFIG';
+  };
+}
+
+// Bridge configuration
+
+export interface ChatBridgeConfig {
+  /** URL of the A2A server to connect to (e.g. http://localhost:8080) */
+  a2aServerUrl: string;
+  /** Google Chat project number for verification (optional) */
+  projectNumber?: string;
+  /** Whether to enable debug logging */
+  debug?: boolean;
+  /** GCS bucket name for session persistence (optional) */
+  gcsBucket?: string;
+}

packages/a2a-server/src/http/app.ts

@@ -28,6 +28,8 @@ import { commandRegistry } from '../commands/command-registry.js';
 import { debugLogger, SimpleExtensionLoader } from '@google/gemini-cli-core';
 import type { Command, CommandArgument } from '../commands/types.js';
 import { GitService } from '@google/gemini-cli-core';
+import { getA2UIAgentExtension } from '../a2ui/a2ui-extension.js';
+import { createChatBridgeRoutes } from '../chat-bridge/routes.js';
 
 type CommandResponse = {
   name: string;
@@ -46,11 +48,12 @@ const coderAgentCard: AgentCard = {
     url: 'https://google.com',
   },
   protocolVersion: '0.3.0',
-  version: '0.0.2', // Incremented version
+  version: '0.1.0', // A2UI-enabled version
   capabilities: {
     streaming: true,
-    pushNotifications: false,
+    pushNotifications: true,
     stateTransitionHistory: true,
+    extensions: [getA2UIAgentExtension()],
   },
   securitySchemes: undefined,
   security: undefined,
@@ -200,6 +203,28 @@ export async function createApp() {
       requestStorage.run({ req }, next);
     });
 
+    // Mount Google Chat bridge routes BEFORE A2A SDK routes.
+    // The A2A SDK's setupRoutes registers a catch-all jsonRpcHandler middleware
+    // at baseUrl="" that intercepts ALL POST requests and returns 400 for
+    // non-JSON-RPC payloads. Chat bridge must be registered first.
+    const chatBridgeUrl =
+      process.env['CHAT_BRIDGE_A2A_URL'] || process.env['CODER_AGENT_PORT']
+        ? `http://localhost:${process.env['CODER_AGENT_PORT'] || '8080'}`
+        : undefined;
+    if (chatBridgeUrl) {
+      expressApp.use(express.json());
+      const chatRoutes = createChatBridgeRoutes({
+        a2aServerUrl: chatBridgeUrl,
+        projectNumber: process.env['CHAT_PROJECT_NUMBER'],
+        debug: process.env['CHAT_BRIDGE_DEBUG'] === 'true',
+        gcsBucket: process.env['GCS_BUCKET_NAME'],
+      });
+      expressApp.use(chatRoutes);
+      logger.info(
+        `[CoreAgent] Google Chat bridge enabled at /chat/webhook (A2A: ${chatBridgeUrl})`,
+      );
+    }
+
     const appBuilder = new A2AExpressApp(requestHandler);
     expressApp = appBuilder.setupRoutes(expressApp, '');
     expressApp.use(express.json());
@@ -330,7 +355,8 @@ export async function main() {
     const expressApp = await createApp();
     const port = Number(process.env['CODER_AGENT_PORT'] || 0);
 
-    const server = expressApp.listen(port, 'localhost', () => {
+    const host = process.env['CODER_AGENT_HOST'] || 'localhost';
+    const server = expressApp.listen(port, host, () => {
       const address = server.address();
       let actualPort;
       if (process.env['CODER_AGENT_PORT']) {

packages/a2a-server/src/persistence/gcs.ts

@@ -18,7 +18,7 @@ import { setTargetDir } from '../config/config.js';
 import { getPersistedState, type PersistedTaskMetadata } from '../types.js';
 import { v4 as uuidv4 } from 'uuid';
 
-type ObjectType = 'metadata' | 'workspace';
+type ObjectType = 'metadata' | 'workspace' | 'conversation';
 
 const getTmpArchiveFilename = (taskId: string): string =>
   `task-${taskId}-workspace-${uuidv4()}.tar.gz`;
@@ -224,6 +224,28 @@ export class GCSTaskStore implements TaskStore {
           `Workspace directory ${workDir} not found, skipping workspace save for task ${taskId}.`,
         );
       }
+      // Save conversation history if present in metadata
+      const rawHistory = dataToStore?.['_conversationHistory'];
+      const conversationHistory = Array.isArray(rawHistory)
+        ? rawHistory
+        : undefined;
+      if (conversationHistory && conversationHistory.length > 0) {
+        const conversationObjectPath = this.getObjectPath(
+          taskId,
+          'conversation',
+        );
+        const historyJson = JSON.stringify(conversationHistory);
+        const compressedHistory = gzipSync(Buffer.from(historyJson));
+        const conversationFile = this.storage
+          .bucket(this.bucketName)
+          .file(conversationObjectPath);
+        await conversationFile.save(compressedHistory, {
+          contentType: 'application/gzip',
+        });
+        logger.info(
+          `Task ${taskId} conversation history saved to GCS: gs://${this.bucketName}/${conversationObjectPath} (${conversationHistory.length} entries)`,
+        );
+      }
     } catch (error) {
       logger.error(`Failed to save task ${taskId} to GCS:`, error);
       throw error;
@@ -280,6 +302,29 @@ export class GCSTaskStore implements TaskStore {
         logger.info(`Task ${taskId} workspace archive not found in GCS.`);
       }
 
+      // Restore conversation history if available
+      const conversationObjectPath = this.getObjectPath(taskId, 'conversation');
+      const conversationFile = this.storage
+        .bucket(this.bucketName)
+        .file(conversationObjectPath);
+      const [conversationExists] = await conversationFile.exists();
+      if (conversationExists) {
+        try {
+          const [compressedHistory] = await conversationFile.download();
+          const historyJson = gunzipSync(compressedHistory).toString();
+          const conversationHistory: unknown[] = JSON.parse(historyJson);
+          loadedMetadata['_conversationHistory'] = conversationHistory;
+          logger.info(
+            `Task ${taskId} conversation history restored from GCS (${conversationHistory.length} entries)`,
+          );
+        } catch (historyError) {
+          logger.warn(
+            `Task ${taskId} conversation history could not be restored:`,
+            historyError,
+          );
+        }
+      }
+
       return {
         id: taskId,
         contextId: loadedMetadata._contextId || uuidv4(),

packages/a2a-server/test-chat-bridge.sh

@@ -0,0 +1,48 @@
+#!/bin/bash
+# Test script for the Google Chat bridge webhook endpoint.
+# Simulates Google Chat events to verify the bridge works.
+#
+# Usage: ./test-chat-bridge.sh [PORT]
+# Default port: 9090 (for kubectl port-forward)
+
+PORT=${1:-9090}
+BASE_URL="http://localhost:${PORT}"
+
+echo "Testing chat bridge at ${BASE_URL}..."
+
+# 1. Test health endpoint
+echo -e "\n--- Health Check ---"
+curl -s "${BASE_URL}/chat/health" | jq .
+
+# 2. Test ADDED_TO_SPACE event
+echo -e "\n--- ADDED_TO_SPACE ---"
+curl -s -X POST "${BASE_URL}/chat/webhook" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "type": "ADDED_TO_SPACE",
+    "eventTime": "2026-01-01T00:00:00Z",
+    "space": { "name": "spaces/test123", "type": "DM" },
+    "user": { "name": "users/123", "displayName": "Test User" }
+  }' | jq .
+
+# 3. Test MESSAGE event
+echo -e "\n--- MESSAGE (Hello) ---"
+curl -s -X POST "${BASE_URL}/chat/webhook" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "type": "MESSAGE",
+    "eventTime": "2026-01-01T00:01:00Z",
+    "message": {
+      "name": "spaces/test123/messages/msg1",
+      "sender": { "name": "users/123", "displayName": "Test User" },
+      "createTime": "2026-01-01T00:01:00Z",
+      "text": "Hello, write me a python hello world",
+      "argumentText": "Hello, write me a python hello world",
+      "thread": { "name": "spaces/test123/threads/thread1" },
+      "space": { "name": "spaces/test123", "type": "DM" }
+    },
+    "space": { "name": "spaces/test123", "type": "DM" },
+    "user": { "name": "users/123", "displayName": "Test User" }
+  }' | jq .
+
+echo -e "\nDone."