[BUG]: Setting a custom agent does not appear to work

[robintegg-createfuture]

What happened?

Firstly, great work on the SDK 👍

I'm trying to set a custom agent on my session following the custom agent documentation - https://copilot-community-sdk.github.io/copilot-sdk-java/snapshot/advanced.html#Custom_Agents

After creating a list of custom agents and settings on my session, the setAgent() doesn't appear to be taking and even after explicitly setting I don't see the agent prompt being applied.

Here's my jbang code and the output follows

//DEPS io.github.copilot-community-sdk:copilot-sdk:1.0.12-SNAPSHOT
import com.github.copilot.sdk.*;
import com.github.copilot.sdk.json.*;

import java.util.ArrayList;
import java.util.List;

class hello {
    public static void main(String[] args) throws Exception {

        List<CustomAgentConfig> customAgents = new ArrayList<>();
        customAgents.add(new CustomAgentConfig()
                .setName("test")
                .setDescription("Test agent for trying out the agent framework.")
                .setPrompt(
                        """
                                You are a helpful assistant. Always start every response with the phrase "🤖 AGENT ACTIVE 🤖" on its own line, followed by a blank line. This must appear in every reply without exception.
                                """));
        try (var client = new CopilotClient()) {

            client.start().get();

            var session = client.createSession(new SessionConfig()
                    .setCustomAgents(customAgents)
                    .setAgent("test")
                    .setOnPermissionRequest(PermissionHandler.APPROVE_ALL)).get();

            var availableAgents = session.listAgents().get();
            System.out.println("Available agents:");
            for (var agent : availableAgents) {
                System.out.println("- name=" + agent.getName()
                        + " displayName=" + agent.getDisplayName());
            }

            var current = session.getCurrentAgent().get();
            System.out.println(
                    "Current agent after createSession: " + (current == null ? "<default>" : current.getName()));

            var response1 = session.sendAndWait(new MessageOptions().setPrompt("Say hello!")).get().getData().content();

            System.out.println("Response to 'Say hello!':\n" + response1);

            // Try explicit select
            var selected = session.selectAgent("test").get();
            System.out.println("selectAgent(\"test\") returned: " + (selected == null ? "<null>" : selected.getName()));

            current = session.getCurrentAgent().get();
            System.out
                    .println("Current agent after selectAgent: " + (current == null ? "<default>" : current.getName()));

            var response2 = session.sendAndWait(new MessageOptions().setPrompt("Say hello again!")).get().getData().content();
            System.out.println("Response to 'Say hello again!':\n" + response2);

        }
    }

}

Output is the following:

[jbang] Building jar for hello-copilot.java...
Mar 13, 2026 10:45:49 AM com.github.copilot.sdk.CopilotClient lambda$1
INFO: Copilot client connected
Available agents:
- name=test displayName=test
Current agent after createSession: <default>
Response to 'Say hello!':
Hello! 👋 How can I help you today?
selectAgent("test") returned: test
Current agent after selectAgent: test
Response to 'Say hello again!':
Hello again! 😄 What can I help you with?  

I'm expecting the response to contain the AGENT ACTIVE wording as I do in the vscode chat mode.

Versions

SDK 1.0.12-SNAPSHOT latest from main, needed for compatibility with CLI
GitHub Copilot CLI 1.0.5.

Relevant log output

[jbang] Building jar for hello-copilot.java...
Mar 13, 2026 10:45:49 AM com.github.copilot.sdk.CopilotClient lambda$1
INFO: Copilot client connected
Available agents:
- name=test displayName=test
Current agent after createSession: <default>
Response to 'Say hello!':
Hello! 👋 How can I help you today?
selectAgent("test") returned: test
Current agent after selectAgent: test
Response to 'Say hello again!':
Hello again! 😄 What can I help you with?

Code of Conduct

• I agree to follow this project's Code of Conduct

[robintegg-createfuture]

FYI, same behaviour with io.github.copilot-community-sdk:copilot-sdk:1.0.11