fix(providers): add iteration cap to performAgentChain to prevent infinite loops

backend/pkg/providers/helpers.go

@@ -25,8 +25,9 @@ import (
 )
 
 const (
-	RepeatingToolCallThreshold   = 3
-	maxQASectionsAfterRestore    = 3
+	RepeatingToolCallThreshold          = 3
+	MaxConsecutiveRepeatingDetections   = 5
+	maxQASectionsAfterRestore           = 3
 	keepQASectionsAfterRestore   = 1
 	lastSecBytesAfterRestore     = 16 * 1024 // 16 KB
 	maxBPBytesAfterRestore       = 8 * 1024  // 8 KB
@@ -36,7 +37,8 @@ const (
 )
 
 type repeatingDetector struct {
-	funcCalls []llms.FunctionCall
+	funcCalls            []llms.FunctionCall
+	consecutiveDetections int
 }
 
 func (rd *repeatingDetector) detect(toolCall llms.ToolCall) bool {
@@ -59,7 +61,16 @@ func (rd *repeatingDetector) detect(toolCall llms.ToolCall) bool {
 
 	rd.funcCalls = append(rd.funcCalls, funcCall)
 
-	return len(rd.funcCalls) >= RepeatingToolCallThreshold
+	if len(rd.funcCalls) >= RepeatingToolCallThreshold {
+		rd.consecutiveDetections++
+		return true
+	}
+
+	return false
+}
+
+func (rd *repeatingDetector) shouldError() bool {
+	return rd.consecutiveDetections >= MaxConsecutiveRepeatingDetections
 }
 
 func (rd *repeatingDetector) clearCallArguments(toolCall *llms.FunctionCall) llms.FunctionCall {

backend/pkg/providers/performer.go

@@ -30,6 +30,7 @@ const (
 	maxRetriesToCallAgentChain  = 3
 	maxRetriesToCallFunction    = 3
 	maxReflectorCallsPerChain   = 3
+	maxAgentChainIterations     = 100
 	delayBetweenRetries         = 5 * time.Second
 )
 
@@ -91,7 +92,7 @@ func (fp *flowProvider) performAgentChain(
 	groupID := fmt.Sprintf("flow-%d", fp.flowID)
 	toolTypeMapping := tools.GetToolTypeMapping()
 
-	for {
+	for iteration := 0; iteration < maxAgentChainIterations; iteration++ {
 		result, err := fp.callWithRetries(ctx, chain, optAgentType, executor)
 		if err != nil {
 			logger.WithError(err).Error("failed to call agent chain")
@@ -219,6 +220,9 @@ func (fp *flowProvider) performAgentChain(
 			}
 		}
 	}
+
+	logger.Error("agent chain exceeded maximum iterations")
+	return fmt.Errorf("agent chain exceeded maximum iterations (%d)", maxAgentChainIterations)
 }
 
 func (fp *flowProvider) execToolCall(
@@ -271,6 +275,12 @@ func (fp *flowProvider) execToolCall(
 			langfuse.WithEventLevel(langfuse.ObservationLevelError),
 			langfuse.WithEventOutput(response),
 		)
+
+		if detector.shouldError() {
+			logger.Error("tool call repeated too many times, aborting agent chain")
+			return "", fmt.Errorf("tool call '%s' repeated %d consecutive times, aborting", funcName, detector.consecutiveDetections)
+		}
+
 		logger.Warn("failed to exec function: tool call is repeating")
 
 		return response, nil

backend/pkg/providers/performer_test.go

@@ -0,0 +1,84 @@
+package providers
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/vxcontrol/langchaingo/llms"
+)
+
+func TestAgentChainIterationCap(t *testing.T) {
+	t.Run("maxAgentChainIterations is set", func(t *testing.T) {
+		assert.Equal(t, 100, maxAgentChainIterations,
+			"maxAgentChainIterations should be 100 to prevent infinite loops")
+	})
+}
+
+func TestRepeatingDetectorShouldError(t *testing.T) {
+	makeToolCall := func(name, args string) llms.ToolCall {
+		return llms.ToolCall{
+			FunctionCall: &llms.FunctionCall{
+				Name:      name,
+				Arguments: args,
+			},
+		}
+	}
+
+	t.Run("no error before threshold", func(t *testing.T) {
+		rd := &repeatingDetector{}
+		tc := makeToolCall("test_tool", `{"key":"value"}`)
+
+		// First RepeatingToolCallThreshold calls build up to first detection
+		for i := 0; i < RepeatingToolCallThreshold; i++ {
+			rd.detect(tc)
+		}
+		assert.Equal(t, 1, rd.consecutiveDetections)
+		assert.False(t, rd.shouldError(),
+			"should not error after only 1 consecutive detection")
+	})
+
+	t.Run("error after max consecutive detections", func(t *testing.T) {
+		rd := &repeatingDetector{}
+		tc := makeToolCall("test_tool", `{"key":"value"}`)
+
+		// Each detection requires RepeatingToolCallThreshold identical calls.
+		// But after the first detection the counter keeps growing, so every
+		// subsequent identical call is also a detection.
+		// We need enough calls to reach MaxConsecutiveRepeatingDetections.
+		totalCallsNeeded := RepeatingToolCallThreshold + MaxConsecutiveRepeatingDetections - 1
+		for i := 0; i < totalCallsNeeded; i++ {
+			rd.detect(tc)
+		}
+
+		require.Equal(t, MaxConsecutiveRepeatingDetections, rd.consecutiveDetections)
+		assert.True(t, rd.shouldError(),
+			"should error after %d consecutive detections", MaxConsecutiveRepeatingDetections)
+	})
+
+	t.Run("different tool call resets detection", func(t *testing.T) {
+		rd := &repeatingDetector{}
+		tc1 := makeToolCall("tool_a", `{"key":"value"}`)
+		tc2 := makeToolCall("tool_b", `{"key":"value"}`)
+
+		// Build up detections for tool_a
+		for i := 0; i < RepeatingToolCallThreshold; i++ {
+			rd.detect(tc1)
+		}
+		assert.Equal(t, 1, rd.consecutiveDetections)
+
+		// Switch to a different tool - should reset funcCalls
+		rd.detect(tc2)
+		assert.Equal(t, 1, rd.consecutiveDetections,
+			"consecutive detections should not increase after a different tool call")
+	})
+
+	t.Run("nil function call does not trigger", func(t *testing.T) {
+		rd := &repeatingDetector{}
+		tc := llms.ToolCall{FunctionCall: nil}
+
+		detected := rd.detect(tc)
+		assert.False(t, detected)
+		assert.False(t, rd.shouldError())
+	})
+}