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Fix VS Code MCP server initialization crash and multi-agent architecture

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CRITICAL FIX:
- Removed auto-registration during initialization that was causing crashes
- Fixed pattern match error with Inbox.start_link (already_started case)
- Changed architecture to require explicit agent registration with unique IDs

MULTI-AGENT SUPPORT:
- Agents must now register themselves with unique identifiers (e.g., 'Green Platypus')
- register_agent tool now works without requiring prior agent_id
- All other tools require agent_id parameter to identify the calling agent
- Proper error handling for missing agent_id in tool calls

ARCHITECTURE CHANGE:
- One MCP server instance serves multiple agents (as per VS Code design)
- Removed auto-registration of 'GitHub Copilot' agent during initialization
- Each agent must explicitly call register_agent before using other tools

This fixes the VS Code connection error:
MatchError: no match of right hand side value: {:error, {:already_started, #PID<0.215.0>}}
This commit is contained in:
Ra
2025-09-03 00:59:52 -07:00
parent 7cb42e4131
commit 004ba6ab55
3 changed files with 81 additions and 85 deletions
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158
lib/agent_coordinator/mcp_server.ex
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@@ -1,7 +1,7 @@
defmodule AgentCoordinator.MCPServer do
@moduledoc """
Unified MCP (Model Context Protocol) server for agent coordination.
This server provides:
- Agent coordination tools for task management and communication
- External MCP server management and unified tool access
@@ -16,7 +16,7 @@ defmodule AgentCoordinator.MCPServer do
# State for tracking external servers and agent sessions
defstruct [
:external_servers,
:server_processes,
:server_processes,
:tool_registry,
:agent_sessions,
:session_monitors,
@@ -26,7 +26,7 @@ defmodule AgentCoordinator.MCPServer do
@mcp_tools [
%{
"name" => "register_agent",
"description" => "Register a new agent with the coordination system",
"description" => "Register a new agent with the coordination system. Each agent must choose a unique identifier (e.g., 'Green Platypus', 'Blue Koala') and include their agent_id in all subsequent tool calls to identify themselves.",
"inputSchema" => %{
"type" => "object",
"properties" => %{
@@ -347,7 +347,7 @@ defmodule AgentCoordinator.MCPServer do
session_monitors: %{},
server_config: load_server_config()
}
# Start external MCP servers
{:ok, state, {:continue, :start_external_servers}}
end
@@ -381,36 +381,57 @@ defmodule AgentCoordinator.MCPServer do
def handle_call({:mcp_request, request}, from, state) do
# Extract agent context for automatic heartbeat management
agent_context = extract_agent_context(request, from, state)
# Send pre-operation heartbeat if we have agent context
if agent_context[:agent_id] do
TaskRegistry.heartbeat_agent(agent_context[:agent_id])
update_session_activity(agent_context[:agent_id])
end
# Process the request
response = process_mcp_request(request)
# Send post-operation heartbeat and update session activity
if agent_context[:agent_id] do
TaskRegistry.heartbeat_agent(agent_context[:agent_id])
update_session_activity(agent_context[:agent_id])
# Add heartbeat metadata to successful responses
enhanced_response = case response do
%{"result" => _} = success ->
Map.put(success, "_heartbeat_metadata", %{
agent_id: agent_context[:agent_id],
timestamp: DateTime.utc_now()
})
error_result ->
error_result
end
{:reply, enhanced_response, state}
else
{:reply, response, state}
case extract_agent_context(request, from, state) do
{:error, error_message} ->
# Return error if agent context extraction fails (unless this is register_agent)
method = Map.get(request, "method")
if method == "tools/call" and
Map.get(request, "params", %{}) |> Map.get("name") == "register_agent" do
# Allow register_agent to proceed without agent_id
response = process_mcp_request(request)
{:reply, response, state}
else
error_response = %{
"jsonrpc" => "2.0",
"id" => Map.get(request, "id"),
"error" => %{
"code" => -32602,
"message" => error_message
}
}
{:reply, error_response, state}
end
agent_context ->
# Send pre-operation heartbeat if we have agent context
if agent_context[:agent_id] do
TaskRegistry.heartbeat_agent(agent_context[:agent_id])
update_session_activity(agent_context[:agent_id])
end
# Process the request
response = process_mcp_request(request)
# Send post-operation heartbeat and update session activity
if agent_context[:agent_id] do
TaskRegistry.heartbeat_agent(agent_context[:agent_id])
update_session_activity(agent_context[:agent_id])
# Add heartbeat metadata to successful responses
enhanced_response = case response do
%{"result" => _} = success ->
Map.put(success, "_heartbeat_metadata", %{
agent_id: agent_context[:agent_id],
timestamp: DateTime.utc_now()
})
error_result ->
error_result
end
{:reply, enhanced_response, state}
else
{:reply, response, state}
end
end
end
@@ -464,7 +485,7 @@ defmodule AgentCoordinator.MCPServer do
} = request
) do
id = Map.get(request, "id", nil)
# Determine if this is a coordinator tool or external tool
result = route_tool_call(tool_name, args)
@@ -515,12 +536,18 @@ defmodule AgentCoordinator.MCPServer do
# Add agent to codebase registry
CodebaseRegistry.add_agent_to_codebase(agent.codebase_id, agent.id)
# Start inbox for the agent
{:ok, _pid} = Inbox.start_link(agent.id)
# Start inbox for the agent (handle already started case)
case Inbox.start_link(agent.id) do
{:ok, _pid} -> :ok
{:error, {:already_started, _pid}} -> :ok
{:error, reason} ->
Logger.warning("Failed to start inbox for agent #{agent.id}: #{inspect(reason)}")
:ok
end
# Track the session if we have caller info
track_agent_session(agent.id, name, capabilities)
{:ok, %{agent_id: agent.id, codebase_id: agent.codebase_id, status: "registered"}}
{:error, reason} ->
@@ -994,7 +1021,7 @@ defmodule AgentCoordinator.MCPServer do
end
# External MCP server management functions
defp start_external_server(name, %{type: :stdio} = config) do
case start_stdio_external_server(name, config) do
{:ok, os_pid, port, pid_file_path} ->
@@ -1045,7 +1072,7 @@ defmodule AgentCoordinator.MCPServer do
pid_file_path: nil,
config: config
}
Logger.info("Registering HTTP server: #{name} at #{Map.get(config, :url)}")
{:ok, server_info}
end
@@ -1279,21 +1306,21 @@ defmodule AgentCoordinator.MCPServer do
defp get_all_unified_tools do
# Combine coordinator tools with external server tools
coordinator_tools = @mcp_tools
# Get external tools from the current process state
external_tools =
external_tools =
case Process.get(:external_tool_registry) do
nil -> []
registry -> Map.values(registry) |> List.flatten()
end
coordinator_tools ++ external_tools
end
defp route_tool_call(tool_name, args) do
# Check if it's a coordinator tool first
coordinator_tool_names = Enum.map(@mcp_tools, & &1["name"])
if tool_name in coordinator_tool_names do
handle_coordinator_tool(tool_name, args)
else
@@ -1340,7 +1367,7 @@ defmodule AgentCoordinator.MCPServer do
registered_at: DateTime.utc_now(),
last_activity: DateTime.utc_now()
}
# Store in process dictionary for now (could be enhanced to track caller PID)
Process.put({:agent_session, agent_id}, session_info)
end
@@ -1364,40 +1391,15 @@ defmodule AgentCoordinator.MCPServer do
agent_id = request["params"]["arguments"]["agent_id"]
%{agent_id: agent_id}
# If no explicit agent_id, try to auto-register a default agent
# If no explicit agent_id, return error - agents must register first
true ->
default_agent_context()
{:error, "Missing agent_id. Agents must register themselves using register_agent before calling other tools."}
end
end
defp default_agent_context do
# Create or use a default agent session for GitHub Copilot
default_agent_id = "github_copilot_session"
# Check if we already have this agent in our session tracking
case Process.get({:agent_session, default_agent_id}) do
nil ->
# Auto-register GitHub Copilot as an agent
case register_agent(%{
"name" => "GitHub Copilot",
"capabilities" => ["coding", "analysis", "review", "documentation"]
}) do
{:ok, %{agent_id: agent_id}} ->
%{agent_id: agent_id}
_ ->
# Fallback to default ID even if registration fails
%{agent_id: default_agent_id}
end
_session_info ->
%{agent_id: default_agent_id}
end
end
defp load_server_config do
config_file = System.get_env("MCP_CONFIG_FILE", "mcp_servers.json")
if File.exists?(config_file) do
try do
case Jason.decode!(File.read!(config_file)) do
@@ -1417,12 +1419,12 @@ defmodule AgentCoordinator.MCPServer do
get_default_server_config()
end
end
defp normalize_server_config(config) do
config
|> Map.update("type", :stdio, fn
"stdio" -> :stdio
"http" -> :http
"http" -> :http
type when is_atom(type) -> type
type -> String.to_existing_atom(type)
end)
@@ -1431,7 +1433,7 @@ defmodule AgentCoordinator.MCPServer do
{key, value} -> {String.to_atom(key), value}
end)
end
defp get_default_server_config do
%{
servers: %{
@@ -1444,7 +1446,7 @@ defmodule AgentCoordinator.MCPServer do
},
"mcp_memory" => %{
type: :stdio,
command: "bunx",
command: "bunx",
args: ["-y", "@modelcontextprotocol/server-memory"],
auto_restart: true,
description: "Memory and knowledge graph server"