fix(agent): address critical issues from PR #1485 review

1. Prevent double-close panic on Stop() by using sync.Once in Scheduler,
   Brain, and Sentinel; remove duplicate Stop() call in main.go
2. Add trade quantity (100k) and leverage (125x) sanity caps to prevent
   LLM hallucinations or input errors from reaching the exchange
3. Mask secrets in onboarding setup state — only store "****" markers in
   SystemConfig instead of plaintext API keys/secrets

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

agent/brain.go

@@ -17,6 +17,7 @@ type Brain struct {
 	logger        *slog.Logger
 	http          *http.Client
 	stopCh        chan struct{}
+	stopOnce      sync.Once
 	recentSignals sync.Map // debounce
 }
 
@@ -29,7 +30,7 @@ func NewBrain(agent *Agent, logger *slog.Logger) *Brain {
 	}
 }
 
-func (b *Brain) Stop() { close(b.stopCh) }
+func (b *Brain) Stop() { b.stopOnce.Do(func() { close(b.stopCh) }) }
 
 // cleanStaleSignals removes debounce entries older than 30 minutes.
 func (b *Brain) cleanStaleSignals() {

agent/onboard.go

@@ -64,13 +64,24 @@ func (a *Agent) saveSetupState(userID int64, s *SetupState) {
 	a.store.SetSystemConfig(fmt.Sprintf("setup_step_%d", userID), s.Step)
 	setConfig(a.store, userID, "exchange", s.Exchange)
 	setConfig(a.store, userID, "exchange_id", s.ExchangeID)
-	setConfig(a.store, userID, "api_key", s.APIKey)
-	setConfig(a.store, userID, "api_secret", s.APISecret)
-	setConfig(a.store, userID, "passphrase", s.Passphrase)
+	// Store only a masked marker for secrets — full values stay in memory only.
+	// This prevents plaintext credentials from lingering in the config store
+	// if the setup flow is interrupted before clearSetupState runs.
+	if s.APIKey != "" {
+		setConfig(a.store, userID, "api_key", "****")
+	}
+	if s.APISecret != "" {
+		setConfig(a.store, userID, "api_secret", "****")
+	}
+	if s.Passphrase != "" {
+		setConfig(a.store, userID, "passphrase", "****")
+	}
 	setConfig(a.store, userID, "ai_provider", s.AIProvider)
 	setConfig(a.store, userID, "ai_model", s.AIModel)
 	setConfig(a.store, userID, "ai_model_id", s.AIModelID)
-	setConfig(a.store, userID, "ai_key", s.AIKey)
+	if s.AIKey != "" {
+		setConfig(a.store, userID, "ai_key", "****")
+	}
 	setConfig(a.store, userID, "ai_base_url", s.AIBaseURL)
 }
 

agent/scheduler.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 	"nofx/safe"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -13,6 +14,7 @@ type Scheduler struct {
 	agent    *Agent
 	logger   *slog.Logger
 	stopCh   chan struct{}
+	stopOnce sync.Once
 }
 
 func NewScheduler(a *Agent, l *slog.Logger) *Scheduler {
@@ -51,7 +53,7 @@ func (s *Scheduler) Start(ctx context.Context) {
 	})
 }
 
-func (s *Scheduler) Stop() { close(s.stopCh) }
+func (s *Scheduler) Stop() { s.stopOnce.Do(func() { close(s.stopCh) }) }
 
 func (s *Scheduler) dailyReport() {
 	if s.agent.traderManager == nil { return }

agent/sentinel.go

@@ -41,6 +41,7 @@ type Sentinel struct {
 	http     *http.Client
 	logger   *slog.Logger
 	stopCh   chan struct{}
+	stopOnce sync.Once
 }
 
 type pricePt struct {
@@ -76,7 +77,7 @@ func (s *Sentinel) Start() {
 	})
 }
 
-func (s *Sentinel) Stop()                            { close(s.stopCh) }
+func (s *Sentinel) Stop()                            { s.stopOnce.Do(func() { close(s.stopCh) }) }
 func (s *Sentinel) SymbolCount() int                  { s.mu.RLock(); defer s.mu.RUnlock(); return len(s.symbols) }
 func (s *Sentinel) AddSymbol(sym string)              { s.mu.Lock(); defer s.mu.Unlock(); for _, x := range s.symbols { if x == sym { return } }; s.symbols = append(s.symbols, sym) }
 func (s *Sentinel) RemoveSymbol(sym string)           { s.mu.Lock(); defer s.mu.Unlock(); for i, x := range s.symbols { if x == sym { s.symbols = append(s.symbols[:i], s.symbols[i+1:]...); return } } }

agent/trade.go

@@ -194,17 +194,31 @@ func (a *Agent) executeTrade(ctx context.Context, trade *TradeAction) error {
 		return fmt.Errorf("no running trader supports trade execution")
 	}
 
+	// Sanity caps to prevent LLM hallucinations or input errors from causing damage.
+	const maxQuantity = 100000.0
+	const maxLeverage = 125
+
+	if trade.Leverage > maxLeverage {
+		return fmt.Errorf("leverage %dx exceeds maximum allowed (%dx)", trade.Leverage, maxLeverage)
+	}
+
 	switch trade.Action {
 	case "open_long":
 		if trade.Quantity <= 0 {
 			return fmt.Errorf("quantity must be > 0")
 		}
+		if trade.Quantity > maxQuantity {
+			return fmt.Errorf("quantity %.4f exceeds maximum allowed (%.0f)", trade.Quantity, maxQuantity)
+		}
 		_, err := underlyingTrader.OpenLong(trade.Symbol, trade.Quantity, trade.Leverage)
 		return err
 	case "open_short":
 		if trade.Quantity <= 0 {
 			return fmt.Errorf("quantity must be > 0")
 		}
+		if trade.Quantity > maxQuantity {
+			return fmt.Errorf("quantity %.4f exceeds maximum allowed (%.0f)", trade.Quantity, maxQuantity)
+		}
 		_, err := underlyingTrader.OpenShort(trade.Symbol, trade.Quantity, trade.Leverage)
 		return err
 	case "close_long":

main.go

@@ -169,8 +169,7 @@ func main() {
 	}
 	logger.Info("✅ HTTP server stopped")
 
-	nofxiAgent.Stop()
-	logger.Info("✅ NOFXi agent stopped")
+	// nofxiAgent.Stop() is handled by defer above
 
 	// Stop all traders
 	traderManager.StopAll()