fix: initial state for session creation

core/src/main/java/com/google/adk/flows/llmflows/Identity.java

@@ -35,12 +35,10 @@ public Single<RequestProcessor.RequestProcessingResult> processRequest(
     StringBuilder builder =
         new StringBuilder()
             .append("You are an agent. Your internal name is ")
-            .append("\"")
             .append(agent.name())
-            .append("\"")
             .append(".");
     if (!Strings.isNullOrEmpty(agent.description())) {
-      builder.append(" The description about you is \"").append(agent.description()).append("\".");
+      builder.append(" The description about you is ").append(agent.description());
     }
     return Single.just(
         RequestProcessor.RequestProcessingResult.create(

core/src/main/java/com/google/adk/models/LlmRequest.java

@@ -16,8 +16,6 @@
 
 package com.google.adk.models;
 
-import static com.google.common.base.Preconditions.checkArgument;
-import static com.google.common.base.Preconditions.checkState;
 import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.common.collect.ImmutableMap.toImmutableMap;
 
@@ -172,29 +170,14 @@ public final Builder appendInstructions(List<String> instructions) {
       return liveConnectConfig(liveCfg.toBuilder().systemInstruction(newLiveSi).build());
     }
 
-    private Content addInstructions(
-        Optional<Content> currentSystemInstruction, List<String> additionalInstructions) {
-      checkArgument(
-          currentSystemInstruction.isEmpty()
-              || currentSystemInstruction.get().parts().map(parts -> parts.size()).orElse(0) <= 1,
-          "At most one instruction is supported.");
-
-      // Either append to the existing instruction, or create a new one.
-      String instructions = String.join("\n\n", additionalInstructions);
-
-      Optional<Part> part =
-          currentSystemInstruction
-              .flatMap(Content::parts)
-              .flatMap(parts -> parts.stream().findFirst());
-      if (part.isEmpty() || part.get().text().isEmpty()) {
-        part = Optional.of(Part.fromText(instructions));
-      } else {
-        part = Optional.of(Part.fromText(part.get().text().get() + "\n\n" + instructions));
-      }
-      checkState(part.isPresent(), "Failed to create instruction.");
+    private Content addInstructions(Optional<Content> currentSi, List<String> newInst) {
+      ImmutableList.Builder<Part> parts = ImmutableList.builder();
+      currentSi.flatMap(Content::parts).ifPresent(parts::addAll);
+
+      newInst.stream().map(Part::fromText).forEach(parts::add);
 
-      String role = currentSystemInstruction.flatMap(Content::role).orElse("user");
-      return Content.builder().parts(part.get()).role(role).build();
+      String role = currentSi.flatMap(Content::role).orElse("user");
+      return Content.builder().parts(parts.build()).role(role).build();
     }
 
     @CanIgnoreReturnValue

core/src/test/java/com/google/adk/flows/llmflows/InstructionsTest.java

@@ -257,6 +257,7 @@ public void processRequest_agentInstructionAndGlobalInstruction_bothAreAppendedT
         instructionsProcessor.processRequest(context, initialRequest).blockingGet();
 
     assertThat(result.updatedRequest().getSystemInstructions())
-        .containsExactly("Global instruction.\n\nAgent instruction.");
+        .containsExactly("Global instruction.", "Agent instruction.")
+        .inOrder();
   }
 }

core/src/test/java/com/google/adk/models/LlmRequestTest.java

@@ -120,9 +120,9 @@ public void appendInstructions_existingInstruction_appendsNewInstructionCorrectl
     assertThat(request.config()).isPresent();
     Content systemInstruction = request.config().get().systemInstruction().get();
     assertThat(systemInstruction.role()).hasValue("system");
-    assertThat(systemInstruction.parts().get()).hasSize(1);
-    assertThat(systemInstruction.parts().get().get(0).text())
-        .hasValue(initialInstructionText + "\n\n" + newInstructionText);
+    assertThat(systemInstruction.parts().get()).hasSize(2);
+    assertThat(systemInstruction.parts().get().get(0).text()).hasValue(initialInstructionText);
+    assertThat(systemInstruction.parts().get().get(1).text()).hasValue(newInstructionText);
 
     assertThat(request.liveConnectConfig().systemInstruction()).isPresent();
     Content liveSystemInstruction = request.liveConnectConfig().systemInstruction().get();
@@ -154,9 +154,10 @@ public void appendInstructions_existingInstruction_appendsNewInstructionCorrectl
     assertThat(request.liveConnectConfig().systemInstruction()).isPresent();
     Content liveSystemInstruction = request.liveConnectConfig().systemInstruction().get();
     assertThat(liveSystemInstruction.role()).hasValue("system"); // Role preserved
-    assertThat(liveSystemInstruction.parts().get()).hasSize(1);
+    assertThat(liveSystemInstruction.parts().get()).hasSize(2);
     assertThat(liveSystemInstruction.parts().get().get(0).text())
-        .hasValue(initialLiveInstructionText + "\n\n" + newInstructionText);
+        .hasValue(initialLiveInstructionText);
+    assertThat(liveSystemInstruction.parts().get().get(1).text()).hasValue(newInstructionText);
 
     // Assertions for main config (should get the new instruction with default role)
     assertThat(request.config()).isPresent();
@@ -195,16 +196,16 @@ public void appendInstructions_multipleInstructions_appendsAllInOrder() {
 
     assertThat(request.config()).isPresent();
     Content systemInstruction = request.config().get().systemInstruction().get();
-    assertThat(systemInstruction.parts().get()).hasSize(1);
-    assertThat(systemInstruction.parts().get().get(0).text())
-        .hasValue(instruction1 + "\n\n" + instruction2);
+    assertThat(systemInstruction.parts().get()).hasSize(2);
+    assertThat(systemInstruction.parts().get().get(0).text()).hasValue(instruction1);
+    assertThat(systemInstruction.parts().get().get(1).text()).hasValue(instruction2);
 
     assertThat(request.liveConnectConfig().systemInstruction()).isPresent();
     Content liveSystemInstruction = request.liveConnectConfig().systemInstruction().get();
     assertThat(liveSystemInstruction.role()).hasValue("user");
-    assertThat(liveSystemInstruction.parts().get()).hasSize(1);
-    assertThat(liveSystemInstruction.parts().get().get(0).text())
-        .hasValue(instruction1 + "\n\n" + instruction2);
+    assertThat(liveSystemInstruction.parts().get()).hasSize(2);
+    assertThat(liveSystemInstruction.parts().get().get(0).text()).hasValue(instruction1);
+    assertThat(liveSystemInstruction.parts().get().get(1).text()).hasValue(instruction2);
   }
 
   @Test
@@ -305,7 +306,7 @@ public void getSystemInstructions_whenPresent_returnsList() {
             .appendInstructions(ImmutableList.of(instruction1, instruction2))
             .build();
     assertThat(request.getSystemInstructions())
-        .containsExactly(instruction1 + "\n\n" + instruction2)
+        .containsExactly(instruction1, instruction2)
         .inOrder();
   }
 }

dev/src/main/java/com/google/adk/web/controller/SessionController.java

@@ -21,6 +21,7 @@
 import com.google.adk.sessions.BaseSessionService;
 import com.google.adk.sessions.ListSessionsResponse;
 import com.google.adk.sessions.Session;
+import com.google.adk.web.dto.SessionRequest;
 import io.reactivex.rxjava3.core.Maybe;
 import io.reactivex.rxjava3.core.Single;
 import java.util.Collections;
@@ -167,13 +168,15 @@ public Session createSessionWithId(
       @PathVariable String appName,
       @PathVariable String userId,
       @PathVariable String sessionId,
-      @RequestBody(required = false) Map<String, Object> state) {
+      @RequestBody(required = false) SessionRequest body) {
     log.info(
-        "Request received for POST /apps/{}/users/{}/sessions/{} with state: {}",
+        "Request received for POST /apps/{}/users/{}/sessions/{} with request body: {}",
         appName,
         userId,
         sessionId,
-        state);
+        body);
+
+    Map<String, Object> initialState = (body != null) ? body.getState() : Collections.emptyMap();
 
     try {
       findSessionOrThrow(appName, userId, sessionId);
@@ -190,7 +193,6 @@ public Session createSessionWithId(
       log.info("Session {} not found, proceeding with creation.", sessionId);
     }
 
-    Map<String, Object> initialState = (state != null) ? state : Collections.emptyMap();
     try {
       Session createdSession =
           sessionService
@@ -228,18 +230,18 @@ public Session createSessionWithId(
   public Session createSession(
       @PathVariable String appName,
       @PathVariable String userId,
-      @RequestBody(required = false) Map<String, Object> state) {
+      @RequestBody(required = false) SessionRequest body) {
 
     log.info(
-        "Request received for POST /apps/{}/users/{}/sessions (service generates ID) with state:"
-            + " {}",
+        "Request received for POST /apps/{}/users/{}/sessions (service generates ID) with request"
+            + " body: {}",
         appName,
         userId,
-        state);
+        body);
 
-    Map<String, Object> initialState = (state != null) ? state : Collections.emptyMap();
-    try {
+    Map<String, Object> initialState = (body != null) ? body.getState() : Collections.emptyMap();
 
+    try {
       Session createdSession =
           sessionService
               .createSession(appName, userId, new ConcurrentHashMap<>(initialState), null)

dev/src/main/java/com/google/adk/web/dto/SessionRequest.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.adk.web.dto;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import java.util.Collections;
+import java.util.Map;
+
+/**
+ * Data Transfer Object (DTO) for POST /apps/{appName}/users/{userId}/sessions and POST
+ * /apps/{appName}/users/{userId}/sessions/{sessionId} equests. Contains information for a session.
+ */
+public class SessionRequest {
+  @JsonProperty("state")
+  public Map<String, Object> state;
+
+  public SessionRequest() {}
+
+  public Map<String, Object> getState() {
+    if (state == null) {
+      return Collections.emptyMap();
+    }
+    return state;
+  }
+}