feat: decision tree visualization with React Flow + Dagre auto-layout

apps/web/src/app/api/traces/[id]/route.ts

@@ -38,7 +38,44 @@ export async function GET(
       return NextResponse.json({ error: "Trace not found" }, { status: 404 });
     }
 
-    return NextResponse.json({ trace }, { status: 200 });
+    // Transform data to match frontend expectations
+    const transformedTrace = {
+      ...trace,
+      decisionPoints: trace.decisionPoints.map((dp) => ({
+        id: dp.id,
+        type: dp.type,
+        chosenAction: typeof dp.chosen === "string" ? dp.chosen : JSON.stringify(dp.chosen),
+        alternatives: dp.alternatives.map((alt) => (typeof alt === "string" ? alt : JSON.stringify(alt))),
+        reasoning: dp.reasoning,
+        contextSnapshot: dp.contextSnapshot as Record<string, unknown> | null,
+        confidence: null, // Not in schema, default to null
+        timestamp: dp.timestamp.toISOString(),
+        parentSpanId: dp.parentSpanId,
+      })),
+      spans: trace.spans.map((span) => ({
+        id: span.id,
+        name: span.name,
+        type: span.type,
+        status: span.status === "COMPLETED" ? "OK" : span.status === "ERROR" ? "ERROR" : "CANCELLED",
+        startedAt: span.startedAt.toISOString(),
+        endedAt: span.endedAt?.toISOString() ?? null,
+        durationMs: span.durationMs,
+        input: span.input,
+        output: span.output,
+        metadata: (span.metadata as Record<string, unknown>) ?? {},
+        parentSpanId: span.parentSpanId,
+      })),
+      events: trace.events.map((event) => ({
+        id: event.id,
+        type: event.type,
+        name: event.name,
+        timestamp: event.timestamp.toISOString(),
+        metadata: (event.metadata as Record<string, unknown>) ?? {},
+        spanId: event.spanId,
+      })),
+    };
+
+    return NextResponse.json({ trace: transformedTrace }, { status: 200 });
   } catch (error) {
     console.error("Error retrieving trace:", error);
     return NextResponse.json({ error: "Internal server error" }, { status: 500 });

apps/web/src/app/dashboard/traces/[id]/page.tsx

@@ -1,18 +1,17 @@
 import { notFound } from "next/navigation";
 import { TraceDetail } from "@/components/trace-detail";
 
-interface TraceResponse {
-  trace: {
-    id: string;
-    name: string;
-    status: "RUNNING" | "COMPLETED" | "ERROR";
-    startedAt: string;
-    endedAt: string | null;
-    durationMs: number | null;
-    tags: string[];
-    metadata: Record<string, unknown>;
-    costUsd: number | null;
-  };
+interface TraceData {
+  id: string;
+  name: string;
+  status: "RUNNING" | "COMPLETED" | "ERROR";
+  startedAt: string;
+  endedAt: string | null;
+  durationMs: number | null;
+  tags: string[];
+  metadata: Record<string, unknown>;
+  costUsd: number | null;
+  totalCost: number | null;
   decisionPoints: Array<{
     id: string;
     type: string;
@@ -22,6 +21,7 @@ interface TraceResponse {
     contextSnapshot: Record<string, unknown> | null;
     confidence: number | null;
     timestamp: string;
+    parentSpanId: string | null;
   }>;
   spans: Array<{
     id: string;
@@ -34,6 +34,7 @@ interface TraceResponse {
     input: unknown;
     output: unknown;
     metadata: Record<string, unknown>;
+    parentSpanId: string | null;
   }>;
   events: Array<{
     id: string;
@@ -41,9 +42,14 @@ interface TraceResponse {
     name: string;
     timestamp: string;
     metadata: Record<string, unknown>;
+    spanId: string | null;
   }>;
 }
 
+interface TraceResponse {
+  trace: TraceData;
+}
+
 async function getTrace(id: string): Promise<TraceResponse | null> {
   try {
     const res = await fetch(`http://localhost:3000/api/traces/${id}`, {
@@ -76,12 +82,24 @@ export default async function TraceDetailPage({ params }: TraceDetailPageProps)
     notFound();
   }
 
+  const { trace } = data;
+
   return (
     <TraceDetail
-      trace={data.trace}
-      decisionPoints={data.decisionPoints}
-      spans={data.spans}
-      events={data.events}
+      trace={{
+        id: trace.id,
+        name: trace.name,
+        status: trace.status,
+        startedAt: trace.startedAt,
+        endedAt: trace.endedAt,
+        durationMs: trace.durationMs,
+        tags: trace.tags,
+        metadata: trace.metadata,
+        costUsd: trace.costUsd ?? trace.totalCost,
+      }}
+      decisionPoints={trace.decisionPoints}
+      spans={trace.spans}
+      events={trace.events}
     />
   );
 }

apps/web/src/components/decision-tree.tsx

@@ -0,0 +1,797 @@
+"use client";
+
+import { useCallback, useMemo, useState } from "react";
+import {
+  ReactFlow,
+  useNodesState,
+  useEdgesState,
+  addEdge,
+  type Connection,
+  type Edge,
+  type Node,
+  Handle,
+  Position,
+  MiniMap,
+  Controls,
+  Background,
+  BackgroundVariant,
+  ConnectionLineType,
+} from "@xyflow/react";
+import "@xyflow/react/dist/style.css";
+import dagre from "@dagrejs/dagre";
+import {
+  GitBranch,
+  Activity,
+  Zap,
+  Terminal,
+  AlertCircle,
+  CheckCircle,
+  XCircle,
+  Clock,
+  ChevronDown,
+  ChevronRight,
+  Lightbulb,
+  Layers,
+} from "lucide-react";
+import { cn, formatDuration } from "@/lib/utils";
+
+// Types matching trace-detail.tsx
+type TraceStatus = "RUNNING" | "COMPLETED" | "ERROR";
+
+interface DecisionPoint {
+  id: string;
+  type: string;
+  chosenAction: string;
+  alternatives: string[];
+  reasoning: string | null;
+  contextSnapshot: Record<string, unknown> | null;
+  confidence: number | null;
+  timestamp: string;
+  parentSpanId?: string | null;
+}
+
+interface Span {
+  id: string;
+  name: string;
+  type: string;
+  status: "OK" | "ERROR" | "CANCELLED";
+  startedAt: string;
+  endedAt: string | null;
+  durationMs: number | null;
+  input: unknown;
+  output: unknown;
+  metadata: Record<string, unknown>;
+  parentSpanId?: string | null;
+}
+
+interface Event {
+  id: string;
+  type: string;
+  name: string;
+  timestamp: string;
+  metadata: Record<string, unknown>;
+  spanId?: string | null;
+}
+
+interface Trace {
+  id: string;
+  name: string;
+  status: TraceStatus;
+  startedAt: string;
+  endedAt: string | null;
+  durationMs: number | null;
+  tags: string[];
+  metadata: Record<string, unknown>;
+  costUsd: number | null;
+}
+
+interface DecisionTreeProps {
+  trace: Trace;
+  decisionPoints: DecisionPoint[];
+  spans: Span[];
+  events: Event[];
+}
+
+// Color configurations
+const spanTypeColors: Record<string, { bg: string; text: string; border: string }> = {
+  LLM_CALL: {
+    bg: "bg-purple-500/10",
+    text: "text-purple-400",
+    border: "border-purple-500/20",
+  },
+  TOOL_CALL: {
+    bg: "bg-blue-500/10",
+    text: "text-blue-400",
+    border: "border-blue-500/20",
+  },
+  CHAIN: {
+    bg: "bg-amber-500/10",
+    text: "text-amber-400",
+    border: "border-amber-500/20",
+  },
+  AGENT: {
+    bg: "bg-cyan-500/10",
+    text: "text-cyan-400",
+    border: "border-cyan-500/20",
+  },
+  MEMORY_OP: {
+    bg: "bg-pink-500/10",
+    text: "text-pink-400",
+    border: "border-pink-500/20",
+  },
+  CUSTOM: {
+    bg: "bg-neutral-700/30",
+    text: "text-neutral-400",
+    border: "border-neutral-600/30",
+  },
+};
+
+const spanStatusColors: Record<string, { dot: string; pulse?: boolean }> = {
+  OK: { dot: "bg-emerald-400" },
+  ERROR: { dot: "bg-red-400" },
+  CANCELLED: { dot: "bg-amber-400", pulse: true },
+};
+
+const decisionTypeColors: Record<string, { bg: string; text: string; border: string }> = {
+  TOOL_SELECTION: {
+    bg: "bg-blue-500/10",
+    text: "text-blue-400",
+    border: "border-blue-500/20",
+  },
+  PATH_SELECTION: {
+    bg: "bg-purple-500/10",
+    text: "text-purple-400",
+    border: "border-purple-500/20",
+  },
+  RESPONSE_FORMULATION: {
+    bg: "bg-emerald-500/10",
+    text: "text-emerald-400",
+    border: "border-emerald-500/20",
+  },
+  DEFAULT: {
+    bg: "bg-neutral-700/30",
+    text: "text-neutral-400",
+    border: "border-neutral-600/30",
+  },
+};
+
+const eventTypeIcons: Record<string, React.ComponentType<{ className?: string }>> = {
+  LLM_CALL: Zap,
+  TOOL_CALL: Terminal,
+  ERROR: AlertCircle,
+  DEFAULT: Activity,
+};
+
+// Node data types
+type TraceNodeData = {
+  trace: Trace;
+} & Record<string, unknown>;
+
+type SpanNodeData = {
+  span: Span;
+  maxDuration: number;
+} & Record<string, unknown>;
+
+type DecisionNodeData = {
+  decision: DecisionPoint;
+} & Record<string, unknown>;
+
+type EventNodeData = {
+  event: Event;
+} & Record<string, unknown>;
+
+// Custom Node Components
+function TraceNode({ data, selected }: { data: TraceNodeData; selected?: boolean }) {
+  const { trace } = data;
+
+  const statusConfig: Record<TraceStatus, { icon: React.ComponentType<{ className?: string }>; color: string }> = {
+    RUNNING: { icon: Activity, color: "text-amber-400" },
+    COMPLETED: { icon: CheckCircle, color: "text-emerald-400" },
+    ERROR: { icon: XCircle, color: "text-red-400" },
+  };
+
+  const status = statusConfig[trace.status];
+  const StatusIcon = status.icon;
+
+  return (
+    <div
+      className={cn(
+        "w-[300px] p-4 rounded-xl bg-neutral-900 border-2 transition-all",
+        selected
+          ? "border-emerald-500 shadow-[0_0_20px_rgba(16,185,129,0.3)]"
+          : "border-emerald-500/50 hover:border-emerald-400/70"
+      )}
+    >
+      <Handle type="target" position={Position.Top} className="!bg-emerald-500" />
+      <div className="flex items-center gap-3">
+        <div className="p-2 rounded-lg bg-emerald-500/10">
+          <GitBranch className="w-5 h-5 text-emerald-400" />
+        </div>
+        <div className="flex-1 min-w-0">
+          <h3 className="font-semibold text-neutral-100 truncate">{trace.name}</h3>
+          <div className="flex items-center gap-2 mt-1">
+            <StatusIcon className={cn("w-3 h-3", status.color)} />
+            <span className={cn("text-xs", status.color)}>{trace.status}</span>
+          </div>
+        </div>
+      </div>
+      <div className="flex items-center gap-2 mt-3 pt-3 border-t border-neutral-700">
+        <Clock className="w-3 h-3 text-neutral-500" />
+        <span className="text-xs text-neutral-400">{formatDuration(trace.durationMs)}</span>
+      </div>
+      <Handle type="source" position={Position.Bottom} className="!bg-emerald-500" />
+    </div>
+  );
+}
+
+function SpanNode({ data, selected }: { data: SpanNodeData; selected?: boolean }) {
+  const { span, maxDuration } = data;
+  const colors = spanTypeColors[span.type] || spanTypeColors.CUSTOM;
+  const statusColor = spanStatusColors[span.status] || spanStatusColors.CANCELLED;
+  const durationPercent = maxDuration > 0 ? ((span.durationMs || 0) / maxDuration) * 100 : 0;
+
+  return (
+    <div
+      className={cn(
+        "w-[260px] p-3 rounded-xl bg-neutral-900 border transition-all",
+        selected
+          ? "border-emerald-500 shadow-[0_0_20px_rgba(16,185,129,0.3)]"
+          : "border-neutral-700 hover:border-neutral-600"
+      )}
+    >
+      <Handle type="target" position={Position.Top} className="!bg-neutral-500" />
+      <div className="flex items-start gap-2">
+        <div className={cn("w-2 h-2 rounded-full mt-1.5", statusColor.dot, statusColor.pulse && "animate-pulse")} />
+        <div className="flex-1 min-w-0">
+          <h4 className="font-medium text-neutral-100 text-sm truncate">{span.name}</h4>
+          <div
+            className={cn(
+              "inline-flex items-center px-1.5 py-0.5 rounded text-[10px] font-medium mt-1 border",
+              colors.bg,
+              colors.text,
+              colors.border
+            )}
+          >
+            {span.type}
+          </div>
+        </div>
+      </div>
+      <div className="mt-2">
+        <div className="flex items-center gap-2">
+          <div className="flex-1 h-1.5 bg-neutral-800 rounded-full overflow-hidden">
+            <div
+              className="h-full bg-emerald-500 rounded-full transition-all"
+              style={{ width: `${durationPercent}%` }}
+            />
+          </div>
+          <span className="text-xs text-neutral-400">{formatDuration(span.durationMs)}</span>
+        </div>
+      </div>
+      <Handle type="source" position={Position.Bottom} className="!bg-neutral-500" />
+    </div>
+  );
+}
+
+function DecisionNode({ data, selected }: { data: DecisionNodeData; selected?: boolean }) {
+  const { decision } = data;
+  const [expanded, setExpanded] = useState(false);
+  const colors = decisionTypeColors[decision.type] || decisionTypeColors.DEFAULT;
+
+  return (
+    <div
+      className={cn(
+        "w-[240px] rounded-xl bg-neutral-900 border transition-all overflow-hidden",
+        selected
+          ? "border-emerald-500 shadow-[0_0_20px_rgba(16,185,129,0.3)]"
+          : "border-neutral-700 hover:border-neutral-600"
+      )}
+    >
+      <Handle type="target" position={Position.Top} className="!bg-neutral-500" />
+      <div className="p-3">
+        <div className="flex items-center gap-2 mb-2">
+          <div
+            className={cn(
+              "px-1.5 py-0.5 rounded text-[10px] font-medium border",
+              colors.bg,
+              colors.text,
+              colors.border
+            )}
+          >
+            {decision.type}
+          </div>
+          {decision.confidence !== null && (
+            <span className="text-[10px] text-emerald-400 font-medium">
+              {Math.round(decision.confidence * 100)}%
+            </span>
+          )}
+        </div>
+        <p className="text-sm text-neutral-100 truncate">{decision.chosenAction}</p>
+        {decision.alternatives.length > 0 && (
+          <button
+            onClick={() => setExpanded(!expanded)}
+            className="flex items-center gap-1 mt-2 text-[10px] text-neutral-400 hover:text-neutral-200 transition-colors"
+          >
+            {expanded ? (
+              <ChevronDown className="w-3 h-3" />
+            ) : (
+              <ChevronRight className="w-3 h-3" />
+            )}
+            {decision.alternatives.length} alternative{decision.alternatives.length !== 1 ? "s" : ""}
+          </button>
+        )}
+        {expanded && decision.alternatives.length > 0 && (
+          <div className="mt-2 space-y-1">
+            {decision.alternatives.map((alt, idx) => (
+              <div
+                key={idx}
+                className="flex items-center gap-1 text-[10px] text-neutral-500 px-2 py-1 bg-neutral-800/50 rounded"
+              >
+                <span className="text-neutral-600">#{idx + 1}</span>
+                <span className="truncate">{alt}</span>
+              </div>
+            ))}
+          </div>
+        )}
+        {decision.reasoning && (
+          <div className="mt-2 pt-2 border-t border-neutral-800">
+            <div className="flex items-center gap-1 text-[10px] text-neutral-500">
+              <Lightbulb className="w-3 h-3" />
+              <span className="truncate">{decision.reasoning}</span>
+            </div>
+          </div>
+        )}
+      </div>
+      <Handle type="source" position={Position.Bottom} className="!bg-neutral-500" />
+    </div>
+  );
+}
+
+function EventNode({ data, selected }: { data: EventNodeData; selected?: boolean }) {
+  const { event } = data;
+  const Icon = eventTypeIcons[event.type] || eventTypeIcons.DEFAULT;
+
+  return (
+    <div
+      className={cn(
+        "w-[180px] p-2 rounded-xl bg-neutral-900 border transition-all",
+        selected
+          ? "border-emerald-500 shadow-[0_0_20px_rgba(16,185,129,0.3)]"
+          : "border-neutral-700 hover:border-neutral-600"
+      )}
+    >
+      <Handle type="target" position={Position.Top} className="!bg-neutral-500" />
+      <div className="flex items-center gap-2">
+        <div className="p-1.5 rounded-lg bg-neutral-800">
+          <Icon className="w-3 h-3 text-neutral-400" />
+        </div>
+        <div className="flex-1 min-w-0">
+          <p className="text-xs text-neutral-100 truncate">{event.name}</p>
+          <p className="text-[10px] text-neutral-500">{event.type}</p>
+        </div>
+      </div>
+      <Handle type="source" position={Position.Bottom} className="!bg-neutral-500" />
+    </div>
+  );
+}
+
+// Node types must be defined outside the component to avoid re-renders
+const nodeTypes = {
+  trace: TraceNode,
+  span: SpanNode,
+  decision: DecisionNode,
+  event: EventNode,
+};
+
+// Build the tree layout using Dagre
+function buildTreeLayout(
+  trace: Trace,
+  spans: Span[],
+  decisionPoints: DecisionPoint[],
+  events: Event[]
+): { nodes: Node[]; edges: Edge[] } {
+  const g = new dagre.graphlib.Graph();
+  g.setDefaultEdgeLabel(() => ({}));
+  g.setGraph({
+    rankdir: "TB",
+    ranksep: 80,
+    nodesep: 40,
+  });
+
+  const nodes: Node[] = [];
+  const edges: Edge[] = [];
+
+  // Add root trace node
+  const traceNodeId = `trace-${trace.id}`;
+  g.setNode(traceNodeId, { width: 300, height: 100 });
+  nodes.push({
+    id: traceNodeId,
+    type: "trace",
+    data: { trace } as TraceNodeData,
+    position: { x: 0, y: 0 },
+  });
+
+  // Calculate max duration for span bars
+  const maxDuration = Math.max(...spans.map((s) => s.durationMs || 0), 1);
+
+  // Add span nodes and build parent-child relationships
+  const spanMap = new Map<string, string>(); // spanId -> nodeId
+  const childSpans = new Map<string, string[]>(); // parentSpanId -> spanIds
+
+  spans.forEach((span) => {
+    const nodeId = `span-${span.id}`;
+    spanMap.set(span.id, nodeId);
+
+    if (span.parentSpanId) {
+      const siblings = childSpans.get(span.parentSpanId) || [];
+      siblings.push(span.id);
+      childSpans.set(span.parentSpanId, siblings);
+    }
+
+    g.setNode(nodeId, { width: 260, height: 80 });
+    nodes.push({
+      id: nodeId,
+      type: "span",
+      data: { span, maxDuration } as SpanNodeData,
+      position: { x: 0, y: 0 },
+    });
+  });
+
+  // Connect spans to their parents or to trace root
+  spans.forEach((span) => {
+    const nodeId = spanMap.get(span.id)!;
+    if (span.parentSpanId && spanMap.has(span.parentSpanId)) {
+      const parentId = spanMap.get(span.parentSpanId)!;
+      g.setEdge(parentId, nodeId);
+      edges.push({
+        id: `e-${parentId}-${nodeId}`,
+        source: parentId,
+        target: nodeId,
+        type: ConnectionLineType.SmoothStep,
+        animated: true,
+        style: { stroke: span.status === "ERROR" ? "#f87171" : "#34d399" },
+      });
+    } else {
+      // Top-level span - connect to trace root
+      g.setEdge(traceNodeId, nodeId);
+      edges.push({
+        id: `e-${traceNodeId}-${nodeId}`,
+        source: traceNodeId,
+        target: nodeId,
+        type: ConnectionLineType.SmoothStep,
+        animated: true,
+        style: { stroke: span.status === "ERROR" ? "#f87171" : "#34d399" },
+      });
+    }
+  });
+
+  // Add decision nodes
+  decisionPoints.forEach((decision) => {
+    const nodeId = `decision-${decision.id}`;
+    g.setNode(nodeId, { width: 240, height: 90 });
+    nodes.push({
+      id: nodeId,
+      type: "decision",
+      data: { decision } as DecisionNodeData,
+      position: { x: 0, y: 0 },
+    });
+
+    // Connect to parent span or trace root
+    if (decision.parentSpanId && spanMap.has(decision.parentSpanId)) {
+      const parentId = spanMap.get(decision.parentSpanId)!;
+      g.setEdge(parentId, nodeId);
+      edges.push({
+        id: `e-${parentId}-${nodeId}`,
+        source: parentId,
+        target: nodeId,
+        type: ConnectionLineType.SmoothStep,
+        animated: true,
+        style: { stroke: "#60a5fa" },
+      });
+    } else {
+      g.setEdge(traceNodeId, nodeId);
+      edges.push({
+        id: `e-${traceNodeId}-${nodeId}`,
+        source: traceNodeId,
+        target: nodeId,
+        type: ConnectionLineType.SmoothStep,
+        animated: true,
+        style: { stroke: "#60a5fa" },
+      });
+    }
+  });
+
+  // Add event nodes
+  events.forEach((event) => {
+    const nodeId = `event-${event.id}`;
+    g.setNode(nodeId, { width: 180, height: 50 });
+    nodes.push({
+      id: nodeId,
+      type: "event",
+      data: { event } as EventNodeData,
+      position: { x: 0, y: 0 },
+    });
+
+    // Connect to span or trace root
+    if (event.spanId && spanMap.has(event.spanId)) {
+      const parentId = spanMap.get(event.spanId)!;
+      g.setEdge(parentId, nodeId);
+      edges.push({
+        id: `e-${parentId}-${nodeId}`,
+        source: parentId,
+        target: nodeId,
+        type: ConnectionLineType.SmoothStep,
+        animated: true,
+        style: { stroke: "#a78bfa" },
+      });
+    } else {
+      g.setEdge(traceNodeId, nodeId);
+      edges.push({
+        id: `e-${traceNodeId}-${nodeId}`,
+        source: traceNodeId,
+        target: nodeId,
+        type: ConnectionLineType.SmoothStep,
+        animated: true,
+        style: { stroke: "#a78bfa" },
+      });
+    }
+  });
+
+  // Calculate layout
+  dagre.layout(g);
+
+  // Update node positions from Dagre
+  nodes.forEach((node) => {
+    const dagreNode = g.node(node.id);
+    node.position = {
+      x: dagreNode.x - dagreNode.width / 2,
+      y: dagreNode.y - dagreNode.height / 2,
+    };
+  });
+
+  return { nodes, edges };
+}
+
+export function DecisionTree({ trace, spans, decisionPoints, events }: DecisionTreeProps) {
+  const { nodes: initialNodes, edges: initialEdges } = useMemo(
+    () => buildTreeLayout(trace, spans, decisionPoints, events),
+    [trace, spans, decisionPoints, events]
+  );
+
+  const [nodes, _, onNodesChange] = useNodesState(initialNodes);
+  const [edges, setEdges, onEdgesChange] = useEdgesState(initialEdges);
+  const [selectedNode, setSelectedNode] = useState<Node | null>(null);
+
+  const onConnect = useCallback(
+    (params: Connection) => {
+      setEdges((eds) => addEdge(params, eds));
+    },
+    [setEdges]
+  );
+
+  const onNodeClick = useCallback((_: React.MouseEvent, node: Node) => {
+    setSelectedNode((prev) => (prev?.id === node.id ? null : node));
+  }, []);
+
+  // Empty state
+  if (spans.length === 0 && decisionPoints.length === 0 && events.length === 0) {
+    return (
+      <div className="flex flex-col items-center justify-center min-h-[600px] text-center">
+        <Layers className="w-12 h-12 text-neutral-600 mb-4" />
+        <h3 className="text-lg font-medium text-neutral-300 mb-2">No trace data available</h3>
+        <p className="text-sm text-neutral-500 max-w-md">
+          This trace does not contain any spans, decisions, or events to visualize.
+        </p>
+      </div>
+    );
+  }
+
+  return (
+    <div className="flex gap-4 h-[600px]">
+      <div className="flex-1 rounded-xl border border-neutral-800 overflow-hidden bg-neutral-950">
+        <ReactFlow
+          nodes={nodes}
+          edges={edges}
+          onNodesChange={onNodesChange}
+          onEdgesChange={onEdgesChange}
+          onConnect={onConnect}
+          onNodeClick={onNodeClick}
+          nodeTypes={nodeTypes}
+          connectionLineType={ConnectionLineType.SmoothStep}
+          fitView
+          minZoom={0.1}
+          maxZoom={2}
+          colorMode="dark"
+          attributionPosition="bottom-right"
+        >
+          <Background variant={BackgroundVariant.Dots} gap={20} size={1} color="#404040" />
+          <MiniMap
+            nodeColor={(node) => {
+              switch (node.type) {
+                case "trace":
+                  return "#10b981";
+                case "span":
+                  return "#3b82f6";
+                case "decision":
+                  return "#8b5cf6";
+                case "event":
+                  return "#f59e0b";
+                default:
+                  return "#6b7280";
+              }
+            }}
+            maskColor="rgba(23, 23, 23, 0.8)"
+            className="!bg-neutral-900/80 !border-neutral-700"
+          />
+          <Controls className="!bg-neutral-900 !border-neutral-700 [&>button]:!bg-neutral-800 [&>button]:!border-neutral-700 [&>button]:!text-neutral-300 [&>button:hover]:!bg-neutral-700" />
+        </ReactFlow>
+      </div>
+
+      {/* Details Panel */}
+      {selectedNode && (
+        <div className="w-80 rounded-xl border border-neutral-800 bg-neutral-900 p-4 overflow-y-auto">
+          <div className="flex items-center justify-between mb-4">
+            <h3 className="font-semibold text-neutral-100">Details</h3>
+            <button
+              onClick={() => setSelectedNode(null)}
+              className="text-neutral-400 hover:text-neutral-200 transition-colors"
+            >
+              <XCircle className="w-5 h-5" />
+            </button>
+          </div>
+          <NodeDetails node={selectedNode} />
+        </div>
+      )}
+    </div>
+  );
+}
+
+function NodeDetails({ node }: { node: Node }) {
+  switch (node.type) {
+    case "trace": {
+      const data = node.data as unknown as TraceNodeData;
+      return (
+        <div className="space-y-4">
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Name</span>
+            <p className="text-sm text-neutral-100 mt-1">{data.trace.name}</p>
+          </div>
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Status</span>
+            <p className="text-sm text-neutral-100 mt-1">{data.trace.status}</p>
+          </div>
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Duration</span>
+            <p className="text-sm text-neutral-100 mt-1">{formatDuration(data.trace.durationMs)}</p>
+          </div>
+          {data.trace.costUsd !== null && (
+            <div>
+              <span className="text-xs text-neutral-500 uppercase tracking-wide">Cost</span>
+              <p className="text-sm text-neutral-100 mt-1">${data.trace.costUsd.toFixed(4)}</p>
+            </div>
+          )}
+          {data.trace.tags.length > 0 && (
+            <div>
+              <span className="text-xs text-neutral-500 uppercase tracking-wide">Tags</span>
+              <div className="flex flex-wrap gap-2 mt-1">
+                {data.trace.tags.map((tag) => (
+                  <span key={tag} className="px-2 py-1 rounded bg-neutral-800 text-xs text-neutral-300">
+                    {tag}
+                  </span>
+                ))}
+              </div>
+            </div>
+          )}
+        </div>
+      );
+    }
+    case "span": {
+      const data = node.data as unknown as SpanNodeData;
+      return (
+        <div className="space-y-4">
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Name</span>
+            <p className="text-sm text-neutral-100 mt-1">{data.span.name}</p>
+          </div>
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Type</span>
+            <p className="text-sm text-neutral-100 mt-1">{data.span.type}</p>
+          </div>
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Status</span>
+            <p className="text-sm text-neutral-100 mt-1">{data.span.status}</p>
+          </div>
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Duration</span>
+            <p className="text-sm text-neutral-100 mt-1">{formatDuration(data.span.durationMs)}</p>
+          </div>
+          {Boolean(data.span.input) && (
+            <div>
+              <span className="text-xs text-neutral-500 uppercase tracking-wide">Input</span>
+              <pre className="mt-1 p-2 bg-neutral-950 rounded text-xs text-neutral-300 overflow-x-auto">
+                {JSON.stringify(data.span.input, null, 2)}
+              </pre>
+            </div>
+          )}
+          {Boolean(data.span.output) && (
+            <div>
+              <span className="text-xs text-neutral-500 uppercase tracking-wide">Output</span>
+              <pre className="mt-1 p-2 bg-neutral-950 rounded text-xs text-neutral-300 overflow-x-auto">
+                {JSON.stringify(data.span.output, null, 2)}
+              </pre>
+            </div>
+          )}
+        </div>
+      );
+    }
+    case "decision": {
+      const data = node.data as unknown as DecisionNodeData;
+      return (
+        <div className="space-y-4">
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Type</span>
+            <p className="text-sm text-neutral-100 mt-1">{data.decision.type}</p>
+          </div>
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Chosen Action</span>
+            <p className="text-sm text-neutral-100 mt-1">{data.decision.chosenAction}</p>
+          </div>
+          {data.decision.confidence !== null && (
+            <div>
+              <span className="text-xs text-neutral-500 uppercase tracking-wide">Confidence</span>
+              <p className="text-sm text-emerald-400 mt-1">{Math.round(data.decision.confidence * 100)}%</p>
+            </div>
+          )}
+          {data.decision.alternatives.length > 0 && (
+            <div>
+              <span className="text-xs text-neutral-500 uppercase tracking-wide">
+                Alternatives ({data.decision.alternatives.length})
+              </span>
+              <div className="space-y-1 mt-1">
+                {data.decision.alternatives.map((alt, idx) => (
+                  <p key={idx} className="text-xs text-neutral-400">
+                    {idx + 1}. {alt}
+                  </p>
+                ))}
+              </div>
+            </div>
+          )}
+          {data.decision.reasoning && (
+            <div>
+              <span className="text-xs text-neutral-500 uppercase tracking-wide">Reasoning</span>
+              <p className="text-sm text-neutral-300 mt-1 italic">&ldquo;{data.decision.reasoning}&rdquo;</p>
+            </div>
+          )}
+        </div>
+      );
+    }
+    case "event": {
+      const data = node.data as unknown as EventNodeData;
+      return (
+        <div className="space-y-4">
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Name</span>
+            <p className="text-sm text-neutral-100 mt-1">{data.event.name}</p>
+          </div>
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Type</span>
+            <p className="text-sm text-neutral-100 mt-1">{data.event.type}</p>
+          </div>
+          <div>
+            <span className="text-xs text-neutral-500 uppercase tracking-wide">Timestamp</span>
+            <p className="text-sm text-neutral-100 mt-1">{new Date(data.event.timestamp).toLocaleString()}</p>
+          </div>
+          {Object.keys(data.event.metadata).length > 0 && (
+            <div>
+              <span className="text-xs text-neutral-500 uppercase tracking-wide">Metadata</span>
+              <pre className="mt-1 p-2 bg-neutral-950 rounded text-xs text-neutral-300 overflow-x-auto">
+                {JSON.stringify(data.event.metadata, null, 2)}
+              </pre>
+            </div>
+          )}
+        </div>
+      );
+    }
+    default:
+      return null;
+  }
+}

apps/web/src/components/trace-detail.tsx

@@ -20,9 +20,10 @@ import {
   Terminal,
 } from "lucide-react";
 import { cn, formatDuration, formatRelativeTime } from "@/lib/utils";
+import { DecisionTree } from "./decision-tree";
 
 type TraceStatus = "RUNNING" | "COMPLETED" | "ERROR";
-type TabType = "decisions" | "spans" | "events";
+type TabType = "tree" | "decisions" | "spans" | "events";
 
 interface DecisionPoint {
   id: string;
@@ -33,6 +34,7 @@ interface DecisionPoint {
   contextSnapshot: Record<string, unknown> | null;
   confidence: number | null;
   timestamp: string;
+  parentSpanId?: string | null;
 }
 
 interface Span {
@@ -46,6 +48,7 @@ interface Span {
   input: unknown;
   output: unknown;
   metadata: Record<string, unknown>;
+  parentSpanId?: string | null;
 }
 
 interface Event {
@@ -54,6 +57,7 @@ interface Event {
   name: string;
   timestamp: string;
   metadata: Record<string, unknown>;
+  spanId?: string | null;
 }
 
 interface Trace {
@@ -138,7 +142,7 @@ export function TraceDetail({
   spans,
   events,
 }: TraceDetailProps) {
-  const [activeTab, setActiveTab] = useState<TabType>("decisions");
+  const [activeTab, setActiveTab] = useState<TabType>("tree");
   const status = statusConfig[trace.status];
   const StatusIcon = status.icon;
 
@@ -243,6 +247,12 @@ export function TraceDetail({
       {/* Tabs */}
       <div className="border-b border-neutral-800">
         <div className="flex gap-1">
+          <TabButton
+            active={activeTab === "tree"}
+            onClick={() => setActiveTab("tree")}
+            icon={GitBranch}
+            label="Tree"
+          />
           <TabButton
             active={activeTab === "decisions"}
             onClick={() => setActiveTab("decisions")}
@@ -265,7 +275,15 @@ export function TraceDetail({
       </div>
 
       {/* Tab Content */}
-      <div className="min-h-[400px]">
+      <div className="min-h-[600px]">
+        {activeTab === "tree" && (
+          <DecisionTree
+            trace={trace}
+            spans={spans}
+            decisionPoints={decisionPoints}
+            events={events}
+          />
+        )}
         {activeTab === "decisions" && (
           <DecisionsTab decisionPoints={decisionPoints} />
         )}