fix: start agents synchronously, and add examples setting data on start

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - feat: add kubernetes secrets provider and API to read secrets [#885](https://github.com/hypermodeinc/modus/pull/885)
 - feat: "start" and "stop" are now mutation prefixes [#889](https://github.com/hypermodeinc/modus/pull/889)
+- fix: start agents synchronously, and add examples setting data on start [#890](https://github.com/hypermodeinc/modus/pull/890)
 
 ## 2025-06-10 - Runtime 0.18.0-alpha.6
 

runtime/actors/actorsystem.go

@@ -93,11 +93,13 @@ func loadAgentActors(ctx context.Context, plugin *plugins.Plugin) error {
 	runningAgents := make(map[string]bool, len(actors))
 	for _, pid := range actors {
 		if actor, ok := pid.Actor().(*wasmAgentActor); ok {
-			runningAgents[actor.agentId] = true
-			actor.plugin = plugin
-			if err := pid.Restart(ctx); err != nil {
-				logger.Err(ctx, err).Msgf("Failed to restart actor for agent %s.", actor.agentId)
-			}
+			go func() {
+				runningAgents[actor.agentId] = true
+				actor.plugin = plugin
+				if err := pid.Restart(ctx); err != nil {
+					logger.Err(ctx, err).Msgf("Failed to restart actor for agent %s.", actor.agentId)
+				}
+			}()
 		}
 	}
 
@@ -112,7 +114,11 @@ func loadAgentActors(ctx context.Context, plugin *plugins.Plugin) error {
 	host := wasmhost.GetWasmHost(ctx)
 	for _, agent := range agents {
 		if !runningAgents[agent.Id] {
-			spawnActorForAgentAsync(host, plugin, agent.Id, agent.Name, false)
+			go func() {
+				if _, err := spawnActorForAgent(host, plugin, agent.Id, agent.Name, false); err != nil {
+					logger.Err(ctx, err).Msgf("Failed to spawn actor for agent %s.", agent.Id)
+				}
+			}()
 		}
 	}
 

runtime/actors/agents.go

@@ -67,26 +67,21 @@ func StartAgent(ctx context.Context, agentName string) (*AgentInfo, error) {
 
 	agentId := xid.New().String()
 	host := wasmhost.GetWasmHost(ctx)
-	spawnActorForAgentAsync(host, plugin, agentId, agentName, true)
+	pid, err := spawnActorForAgent(host, plugin, agentId, agentName, true)
+	if err != nil {
+		return nil, fmt.Errorf("error spawning actor for agent %s: %w", agentId, err)
+	}
 
+	actor := pid.Actor().(*wasmAgentActor)
 	info := &AgentInfo{
-		Id:     agentId,
-		Name:   agentName,
-		Status: AgentStatusStarting,
+		Id:     actor.agentId,
+		Name:   actor.agentName,
+		Status: actor.status,
 	}
 
 	return info, nil
 }
 
-func spawnActorForAgentAsync(host wasmhost.WasmHost, plugin *plugins.Plugin, agentId, agentName string, initializing bool) {
-	// We spawn the actor in a goroutine to avoid blocking while the actor is being spawned.
-	// This allows many agents to be spawned in parallel, if needed.
-	// Errors are logged but not returned, as the actor system will handle them.
-	go func() {
-		_, _ = spawnActorForAgent(host, plugin, agentId, agentName, initializing)
-	}()
-}
-
 func spawnActorForAgent(host wasmhost.WasmHost, plugin *plugins.Plugin, agentId, agentName string, initializing bool) (*goakt.PID, error) {
 	// The actor needs to spawn in its own context, so we don't pass one in to this function.
 	// If we did, then when the original context was cancelled or completed, the actor initialization would be cancelled too.

sdk/assemblyscript/examples/agents/assembly/index.ts

@@ -25,6 +25,16 @@ export function startCounterAgent(): AgentInfo {
   return agents.start("Counter");
 }
 
+/**
+ * Starts a counter agent with an initial count value,
+ * and returns info including its ID and status.
+ */
+export function startCounterAgentWithData(initialCount: i32): AgentInfo {
+  const info = agents.start("Counter");
+  updateCountAsync(info.id, initialCount);
+  return info;
+}
+
 /**
  * Stops the specified agent by ID, returning its status info.
  * This will terminate the agent, and it cannot be resumed or restarted.

sdk/go/examples/agents/main.go

@@ -30,6 +30,18 @@ func StartCounterAgent() (agents.AgentInfo, error) {
 	return agents.Start("Counter")
 }
 
+// Starts a counter agent with an initial count value,
+// and returns info including its ID and status.
+func StartCounterAgentWithData(initialCount int) (agents.AgentInfo, error) {
+	info, err := agents.Start("Counter")
+	if err != nil {
+		return agents.AgentInfo{}, err
+	}
+
+	err = UpdateCountAsync(info.Id, initialCount)
+	return info, err
+}
+
 // Stops the specified agent by ID, returning its status info.
 // This will terminate the agent, and it cannot be resumed or restarted.
 // However, a new agent with the same name can be started at any time.