provider fallback: switch to proxy_fallbacks on API failure in message/system loops

pkg/agent/loop.go

@@ -58,6 +58,8 @@ type AgentLoop struct {
 	intentHints           map[string]string
 	sessionRunMu          sync.Mutex
 	sessionRunLocks       map[string]*sync.Mutex
+	providerNames         []string
+	providerPool          map[string]providers.LLMProvider
 }
 
 // StartupCompactionReport provides startup memory/session maintenance stats.
@@ -236,6 +238,35 @@ func NewAgentLoop(cfg *config.Config, msgBus *bus.MessageBus, provider providers
 		sessionRunLocks:       map[string]*sync.Mutex{},
 	}
 
+	// Initialize provider fallback chain (primary + proxy_fallbacks).
+	loop.providerPool = map[string]providers.LLMProvider{}
+	loop.providerNames = []string{}
+	primaryName := cfg.Agents.Defaults.Proxy
+	if primaryName == "" {
+		primaryName = "proxy"
+	}
+	loop.providerPool[primaryName] = provider
+	loop.providerNames = append(loop.providerNames, primaryName)
+	for _, name := range cfg.Agents.Defaults.ProxyFallbacks {
+		if name == "" {
+			continue
+		}
+		dup := false
+		for _, existing := range loop.providerNames {
+			if existing == name {
+				dup = true
+				break
+			}
+		}
+		if dup {
+			continue
+		}
+		if p2, err := providers.CreateProviderByName(cfg, name); err == nil {
+			loop.providerPool[name] = p2
+			loop.providerNames = append(loop.providerNames, name)
+		}
+	}
+
 	// Inject recursive run logic so subagents can use full tool-calling flows.
 	subagentManager.SetRunFunc(func(ctx context.Context, task, channel, chatID string) (string, error) {
 		sessionKey := fmt.Sprintf("subagent:%d", os.Getpid()) // Use PID/randomized key to reduce session key collisions.
@@ -309,6 +340,27 @@ func (al *AgentLoop) lockSessionRun(sessionKey string) func() {
 	return func() { mu.Unlock() }
 }
 
+func (al *AgentLoop) tryFallbackProviders(ctx context.Context, messages []providers.Message, toolDefs []providers.ToolDefinition, options map[string]interface{}, primaryErr error) (*providers.LLMResponse, error) {
+	if len(al.providerNames) <= 1 {
+		return nil, primaryErr
+	}
+	lastErr := primaryErr
+	for i := 1; i < len(al.providerNames); i++ {
+		name := al.providerNames[i]
+		p, ok := al.providerPool[name]
+		if !ok || p == nil {
+			continue
+		}
+		resp, err := p.Chat(ctx, messages, toolDefs, al.model, options)
+		if err == nil {
+			logger.WarnCF("agent", "LLM fallback provider switched", map[string]interface{}{"provider": name})
+			return resp, nil
+		}
+		lastErr = err
+	}
+	return nil, lastErr
+}
+
 func (al *AgentLoop) processInbound(ctx context.Context, msg bus.InboundMessage) {
 	taskID := fmt.Sprintf("%s-%d", shortSessionKey(msg.SessionKey), time.Now().Unix()%100000)
 	started := time.Now()
@@ -686,6 +738,14 @@ func (al *AgentLoop) processMessage(ctx context.Context, msg bus.InboundMessage)
 			response, err = al.provider.Chat(ctx, messages, providerToolDefs, al.model, options)
 		}
 
+		if err != nil {
+			if fb, ferr := al.tryFallbackProviders(ctx, messages, providerToolDefs, options, err); ferr == nil && fb != nil {
+				response = fb
+				err = nil
+			} else {
+				err = ferr
+			}
+		}
 		if err != nil {
 			errText := strings.ToLower(err.Error())
 			if strings.Contains(errText, "no tool call found for function call output") {
@@ -1015,11 +1075,20 @@ func (al *AgentLoop) processSystemMessage(ctx context.Context, msg bus.InboundMe
 				"tools_json":    formatToolsForLog(providerToolDefs),
 			})
 
-		response, err := al.provider.Chat(ctx, messages, providerToolDefs, al.model, map[string]interface{}{
+		options := map[string]interface{}{
 			"max_tokens":  8192,
 			"temperature": 0.7,
-		})
+		}
+		response, err := al.provider.Chat(ctx, messages, providerToolDefs, al.model, options)
 
+		if err != nil {
+			if fb, ferr := al.tryFallbackProviders(ctx, messages, providerToolDefs, options, err); ferr == nil && fb != nil {
+				response = fb
+				err = nil
+			} else {
+				err = ferr
+			}
+		}
 		if err != nil {
 			errText := strings.ToLower(err.Error())
 			if strings.Contains(errText, "no tool call found for function call output") {