Feat: port FirestoreSessionService from adk-python to @google/adk-integrations

core/src/sessions/base_session_service.ts

@@ -236,6 +236,37 @@ export function trimTempState(
   return filteredState;
 }
 
+/**
+ * Splits a state map into its app-scoped, user-scoped and session-scoped
+ * parts, stripping the `app:` and `user:` prefixes and dropping `temp:` keys.
+ *
+ * The inverse of {@link mergeStates}, which re-applies the prefixes.
+ *
+ * @param state The state to split.
+ * @return The app, user and session buckets.
+ */
+export function splitStateDelta(state: Record<string, unknown> | undefined): {
+  app: Record<string, unknown>;
+  user: Record<string, unknown>;
+  session: Record<string, unknown>;
+} {
+  const app: Record<string, unknown> = {};
+  const user: Record<string, unknown> = {};
+  const session: Record<string, unknown> = {};
+
+  for (const [key, value] of Object.entries(state ?? {})) {
+    if (key.startsWith(State.APP_PREFIX)) {
+      app[key.slice(State.APP_PREFIX.length)] = value;
+    } else if (key.startsWith(State.USER_PREFIX)) {
+      user[key.slice(State.USER_PREFIX.length)] = value;
+    } else if (!key.startsWith(State.TEMP_PREFIX)) {
+      session[key] = value;
+    }
+  }
+
+  return {app, user, session};
+}
+
 /**
  * Merges app state, user state, and session state.
  *

core/src/sessions/database_session_service.ts

@@ -22,6 +22,7 @@ import {
   ListSessionsRequest,
   ListSessionsResponse,
   mergeStates,
+  splitStateDelta,
   trimTempDeltaState,
 } from './base_session_service.js';
 import {
@@ -37,7 +38,6 @@ import {
   StorageUserState,
 } from './db/schema.js';
 import {createSession, Session} from './session.js';
-import {State} from './state.js';
 
 /**
  * Checks if a URI is a database connection URI.
@@ -140,21 +140,11 @@ export class DatabaseSessionService extends BaseSessionService {
       em.persist(userStateModel);
     }
 
-    const appStateDelta: Record<string, unknown> = {};
-    const userStateDelta: Record<string, unknown> = {};
-    const sessionState: Record<string, unknown> = {};
-
-    if (state) {
-      for (const [key, value] of Object.entries(state)) {
-        if (key.startsWith(State.APP_PREFIX)) {
-          appStateDelta[key.replace(State.APP_PREFIX, '')] = value;
-        } else if (key.startsWith(State.USER_PREFIX)) {
-          userStateDelta[key.replace(State.USER_PREFIX, '')] = value;
-        } else if (!key.startsWith(State.TEMP_PREFIX)) {
-          sessionState[key] = value;
-        }
-      }
-    }
+    const {
+      app: appStateDelta,
+      user: userStateDelta,
+      session: sessionState,
+    } = splitStateDelta(state);
 
     if (Object.keys(appStateDelta).length > 0) {
       appStateModel.state = {...appStateModel.state, ...appStateDelta};
@@ -442,19 +432,11 @@ export class DatabaseSessionService extends BaseSessionService {
       }
 
       if (event.actions && event.actions.stateDelta) {
-        const appDelta: Record<string, unknown> = {};
-        const userDelta: Record<string, unknown> = {};
-        const sessionDelta: Record<string, unknown> = {};
-
-        for (const [key, value] of Object.entries(event.actions.stateDelta)) {
-          if (key.startsWith(State.APP_PREFIX)) {
-            appDelta[key.replace(State.APP_PREFIX, '')] = value;
-          } else if (key.startsWith(State.USER_PREFIX)) {
-            userDelta[key.replace(State.USER_PREFIX, '')] = value;
-          } else if (!key.startsWith(State.TEMP_PREFIX)) {
-            sessionDelta[key] = value;
-          }
-        }
+        const {
+          app: appDelta,
+          user: userDelta,
+          session: sessionDelta,
+        } = splitStateDelta(event.actions.stateDelta);
 
         if (Object.keys(appDelta).length > 0) {
           appStateModel.state = {...appStateModel.state, ...appDelta};

core/test/sessions/base_session_service_test.ts

@@ -0,0 +1,48 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {mergeStates, splitStateDelta} from '@google/adk';
+import {describe, expect, it} from 'vitest';
+
+describe('splitStateDelta', () => {
+  it('routes each key by prefix and drops temporary keys', () => {
+    expect(
+      splitStateDelta({
+        'app:theme': 'dark',
+        'user:locale': 'en',
+        'temp:scratch': 1,
+        turn: 2,
+      }),
+    ).toEqual({
+      app: {theme: 'dark'},
+      user: {locale: 'en'},
+      session: {turn: 2},
+    });
+  });
+
+  it('returns empty buckets for undefined state', () => {
+    expect(splitStateDelta(undefined)).toEqual({
+      app: {},
+      user: {},
+      session: {},
+    });
+  });
+
+  it('strips only the leading prefix', () => {
+    expect(splitStateDelta({'app:app:nested': 1})).toEqual({
+      app: {'app:nested': 1},
+      user: {},
+      session: {},
+    });
+  });
+
+  it('round-trips through mergeStates for non-temporary keys', () => {
+    const state = {'app:theme': 'dark', 'user:locale': 'en', turn: 2};
+    const {app, user, session} = splitStateDelta(state);
+
+    expect(mergeStates(app, user, session)).toEqual(state);
+  });
+});

integrations/package.json

@@ -40,6 +40,7 @@
     "prepublishOnly": "npm run build"
   },
   "dependencies": {
+    "@google-cloud/firestore": "^8.7.0",
     "@google/adk": "^1.5.0"
   }
 }