diff --git a/workflow/builder.go b/workflow/builder.go
index 358816d8..dc3bb14a 100644
--- a/workflow/builder.go
+++ b/workflow/builder.go
@@ -145,7 +145,12 @@ func (wb *Builder) AddDirectEdge(source ExecutorBinding, target ExecutorBinding,
 	}
 	applyEdgeOptions(&edge, opts)
 	wb.addEdgeForSource(source.ID, edge)
-	wb.conditionlessConnections = append(wb.conditionlessConnections, conn)
+	// Only conditionless edges participate in the conditionless-edge dedup set;
+	// appending conditional edges here would wrongly make a later conditionless
+	// edge on the same source→target pair look like a duplicate.
+	if condition == nil {
+		wb.conditionlessConnections = append(wb.conditionlessConnections, conn)
+	}
 	return wb
 }
 
diff --git a/workflow/builder_conditional_edge_test.go b/workflow/builder_conditional_edge_test.go
new file mode 100644
index 00000000..3dc85a6d
--- /dev/null
+++ b/workflow/builder_conditional_edge_test.go
@@ -0,0 +1,55 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+package workflow_test
+
+import (
+	"testing"
+
+	"github.com/microsoft/agent-framework-go/workflow"
+)
+
+// A conditional edge on a source→target pair must not populate the
+// conditionless-edge dedup set: adding a legitimate conditionless edge on the
+// same pair afterwards should succeed, not be rejected as a duplicate.
+func TestBuilder_ConditionalEdgeDoesNotBlockConditionlessEdge(t *testing.T) {
+	start := newNoOpExecutor("start")
+	target := newNoOpExecutor("target")
+
+	_, err := workflow.NewBuilder(start).
+		AddDirectEdge(start, target, false, func(any) bool { return true }).
+		AddEdge(start, target).
+		Build()
+	if err != nil {
+		t.Fatalf("conditionless edge after a conditional edge on the same pair should be allowed, got error: %v", err)
+	}
+}
+
+// The idempotent path (AddChain / idempotent=true) must likewise not silently
+// drop a conditionless edge just because a conditional edge preceded it.
+func TestBuilder_ConditionalEdgeDoesNotDropIdempotentConditionlessEdge(t *testing.T) {
+	start := newNoOpExecutor("start")
+	target := newNoOpExecutor("target")
+
+	wf, err := workflow.NewBuilder(start).
+		AddDirectEdge(start, target, false, func(any) bool { return true }).
+		AddDirectEdge(start, target, true, nil). // idempotent conditionless edge
+		Build()
+	if err != nil {
+		t.Fatalf("unexpected build error: %v", err)
+	}
+
+	// The idempotent conditionless edge must actually be present, not silently
+	// dropped by the poisoned dedup set: expect both a conditional and a
+	// conditionless edge from start.
+	var conditional, conditionless int
+	for _, e := range wf.Edges()["start"] {
+		if e.Condition == nil {
+			conditionless++
+		} else {
+			conditional++
+		}
+	}
+	if conditional != 1 || conditionless != 1 {
+		t.Fatalf("edges from start: conditional=%d conditionless=%d, want 1 and 1", conditional, conditionless)
+	}
+}