feat: add sessionMode parameter to send_agent_prompt and currentModeId to activity

Allow setting session mode when sending prompts, and include current mode in activity output.

Changes:
- sendPrompt now accepts options object with maxWait and sessionMode
- If sessionMode specified, sets mode before sending prompt
- send_agent_prompt MCP tool exposes sessionMode parameter
- get_agent_activity now returns currentModeId in output
- Enables workflow: send_agent_prompt({ sessionMode: "plan", prompt: "..." })

🤖 Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

packages/voice-assistant/src/server/acp/agent-manager.ts

@@ -212,13 +212,13 @@ export class AgentManager {
    * Send a prompt to an agent
    * @param agentId - Agent ID
    * @param prompt - The prompt text
-   * @param maxWait - Optional max milliseconds to wait for completion. If not provided, returns immediately without waiting.
+   * @param options - Optional settings: maxWait (ms), sessionMode to set before sending
    * @returns Object with didComplete boolean indicating if agent finished within maxWait time
    */
   async sendPrompt(
     agentId: string,
     prompt: string,
-    maxWait?: number
+    options?: { maxWait?: number; sessionMode?: string }
   ): Promise<{ didComplete: boolean; stopReason?: string }> {
     const agent = this.agents.get(agentId);
     if (!agent) {
@@ -229,6 +229,11 @@ export class AgentManager {
       throw new Error(`Agent ${agentId} is ${agent.status}`);
     }
 
+    // Set session mode if specified
+    if (options?.sessionMode) {
+      await this.setSessionMode(agentId, options.sessionMode);
+    }
+
     agent.status = "processing";
     this.notifySubscribers(agentId);
 
@@ -270,6 +275,8 @@ export class AgentManager {
         );
       });
 
+    const maxWait = options?.maxWait;
+
     // If no maxWait specified, return immediately
     if (maxWait === undefined) {
       console.log(`[Agent ${agentId}] Prompt sent (non-blocking, use get_agent_status to check completion)`);

packages/voice-assistant/src/server/acp/mcp-server.ts

@@ -118,7 +118,7 @@ export async function createAgentMcpServer(
     {
       title: "Send Agent Prompt",
       description:
-        "Sends a task or prompt to an existing agent. By default, returns immediately without waiting (non-blocking). The agent will process the prompt in the background. Use get_agent_status or get_agent_activity to check progress. Optionally, you can specify maxWait to wait up to that many milliseconds for completion before returning.",
+        "Sends a task or prompt to an existing agent. By default, returns immediately without waiting (non-blocking). The agent will process the prompt in the background. Use get_agent_status or get_agent_activity to check progress. Optionally specify maxWait to wait for completion, or sessionMode to switch modes before sending.",
       inputSchema: {
         agentId: z.string().describe("Agent ID returned from create_coding_agent"),
         prompt: z
@@ -126,6 +126,12 @@ export async function createAgentMcpServer(
           .describe(
             "The task, instruction, or feedback to send to the agent. Be specific about what you want the agent to accomplish."
           ),
+        sessionMode: z
+          .string()
+          .optional()
+          .describe(
+            "Optional: Session mode to set before sending the prompt (e.g., 'plan', 'code', 'default'). If specified, the agent's mode will be changed before processing the prompt."
+          ),
         maxWait: z
           .number()
           .optional()
@@ -139,8 +145,11 @@ export async function createAgentMcpServer(
         stopReason: z.string().nullable().describe("Reason agent stopped if it completed: 'end_turn', 'max_tokens', 'max_turn_requests', 'refusal', 'cancelled'"),
       },
     },
-    async ({ agentId, prompt, maxWait }) => {
-      const response = await agentManager.sendPrompt(agentId, prompt, maxWait);
+    async ({ agentId, prompt, sessionMode, maxWait }) => {
+      const response = await agentManager.sendPrompt(agentId, prompt, {
+        maxWait,
+        sessionMode,
+      });
 
       const result = {
         success: true,
@@ -330,6 +339,7 @@ export async function createAgentMcpServer(
         agentId: z.string(),
         format: z.enum(["curated", "raw"]),
         updateCount: z.number().describe("Total number of updates available"),
+        currentModeId: z.string().nullable().describe("Current session mode of the agent"),
         content: z.string().describe("Formatted activity content (if curated) or empty string (if raw)"),
         updates: z.array(
           z.object({
@@ -342,6 +352,7 @@ export async function createAgentMcpServer(
     },
     async ({ agentId, format = "curated", limit }) => {
       const updates = agentManager.getAgentUpdates(agentId);
+      const currentModeId = agentManager.getCurrentMode(agentId);
 
       if (format === "curated") {
         // Return curated, human-readable format
@@ -353,6 +364,7 @@ export async function createAgentMcpServer(
             agentId,
             format: "curated" as const,
             updateCount: updates.length,
+            currentModeId,
             content: curatedText,
             updates: null,
           },
@@ -369,6 +381,7 @@ export async function createAgentMcpServer(
             agentId,
             format: "raw" as const,
             updateCount: updates.length,
+            currentModeId,
             content: "",
             updates: selectedUpdates.map((update) => ({
               timestamp: update.timestamp.toISOString(),