From 3752f1c34cdbd98b19b263d0d613c9ceb9b36876 Mon Sep 17 00:00:00 2001
From: Stephen Belanger <stephen.belanger@braintrustdata.com>
Date: Thu, 2 Jul 2026 23:53:14 +0800
Subject: [PATCH] Track implicit skill loads

---
 src/event-processor.ts | 24 +++++++++++++++++++++++-
 src/tracing.test.ts    | 39 +++++++++++++++++++++++++++++++++++++++
 src/tracing.ts         | 24 +++++++++++++++++++++++-
 3 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/src/event-processor.ts b/src/event-processor.ts
index ae66997..64b9ec6 100644
--- a/src/event-processor.ts
+++ b/src/event-processor.ts
@@ -16,6 +16,26 @@ function generateUUID(): string {
   return crypto.randomUUID()
 }
 
+function skillLoadMetadata(tool: string, args: unknown): Record<string, unknown> | undefined {
+  if (tool !== "skill") return undefined
+  const name =
+    args && typeof args === "object" && "name" in args && typeof args.name === "string"
+      ? args.name
+      : undefined
+  return {
+    skill_name: name,
+  }
+}
+
+function skillToolSpanName(tool: string, title: string, args: unknown, fallback: string): string {
+  if (tool !== "skill") return fallback
+  const name =
+    args && typeof args === "object" && "name" in args && typeof args.name === "string"
+      ? args.name
+      : undefined
+  return name ? `skill: ${name}` : title || "skill"
+}
+
 // State management for tracing
 interface SessionState {
   rootSpanId: string
@@ -311,6 +331,7 @@ export class EventProcessor {
     // MCP tools return { content: [{ type: "text", text: "..." }] } instead of a plain
     // output value, so extract the text from content[] as a last resort.
     const rawOutput = capturedOutput !== undefined ? capturedOutput : extractToolOutput(output)
+    const formattedName = this.formatToolName(tool, title)
     const toolSpan: SpanData = {
       id: generateUUID(),
       span_id: toolSpanId,
@@ -323,13 +344,14 @@ export class EventProcessor {
         call_id: callID,
         title,
         reasoning: reasoning || undefined,
+        ...skillLoadMetadata(tool, toolArgs),
       },
       metrics: {
         start: startTime,
         end: endTime,
       },
       span_attributes: {
-        name: this.formatToolName(tool, title),
+        name: skillToolSpanName(tool, title, toolArgs, formattedName),
         type: "tool",
       },
     }
diff --git a/src/tracing.test.ts b/src/tracing.test.ts
index 8948f4a..2d38004 100644
--- a/src/tracing.test.ts
+++ b/src/tracing.test.ts
@@ -241,6 +241,45 @@ describe("Event to Span Transformation", () => {
     )
   })
 
+  it("normalizes native skill tool calls as skill load spans", async () => {
+    const sessionId = "ses_skill_tool"
+    const messageId = "msg_1"
+
+    await assertEventsProduceTree(
+      session(
+        sessionId,
+        sessionCreated(sessionId),
+        chatMessage("Use the review skill"),
+        toolCallPart(sessionId, messageId, "call_skill", "skill", { name: "review" }),
+        toolExecute("call_skill", "skill", "review", { name: "review" }, "Loaded skill review"),
+        textPart(sessionId, messageId, "Loaded the review skill."),
+        messageCompleted(sessionId, messageId, { tokens: { input: 20, output: 15 } }),
+        sessionIdle(sessionId),
+      ),
+      {
+        span_attributes: { name: "OpenCode: test-project", type: "task" },
+        children: [
+          {
+            span_attributes: { name: "Turn 1", type: "task" },
+            children: [
+              {
+                span_attributes: { name: "skill: review", type: "tool" },
+                metadata: {
+                  tool_name: "skill",
+                  call_id: "call_skill",
+                  skill_name: "review",
+                },
+              },
+              {
+                span_attributes: { name: "anthropic/claude-3-haiku", type: "llm" },
+              },
+            ],
+          },
+        ],
+      },
+    )
+  })
+
   it("session -> turn -> multiple tool calls", async () => {
     const sessionId = "ses_multi_tool"
     const messageId = "msg_1"
diff --git a/src/tracing.ts b/src/tracing.ts
index ef50a29..48f5bf1 100644
--- a/src/tracing.ts
+++ b/src/tracing.ts
@@ -22,6 +22,26 @@ function generateUUID(): string {
   return crypto.randomUUID()
 }
 
+function skillLoadMetadata(tool: string, args: unknown): Record<string, unknown> | undefined {
+  if (tool !== "skill") return undefined
+  const name =
+    args && typeof args === "object" && "name" in args && typeof args.name === "string"
+      ? args.name
+      : undefined
+  return {
+    skill_name: name,
+  }
+}
+
+function skillToolSpanName(tool: string, title: string, args: unknown, fallback: string): string {
+  if (tool !== "skill") return fallback
+  const name =
+    args && typeof args === "object" && "name" in args && typeof args.name === "string"
+      ? args.name
+      : undefined
+  return name ? `skill: ${name}` : title || "skill"
+}
+
 // State management for tracing
 interface SessionState {
   rootSpanId: string
@@ -1018,6 +1038,7 @@ export function createTracingHooks(
         const rawOutput =
           capturedOutput !== undefined ? capturedOutput : extractToolOutput(result.output ?? result)
         const toolOutput = typeof rawOutput === "string" ? rawOutput.substring(0, 10000) : rawOutput
+        const formattedName = formatToolName(tool, result.title)
         const toolSpan: SpanData = {
           id: generateUUID(),
           span_id: toolSpanId,
@@ -1030,13 +1051,14 @@ export function createTracingHooks(
             call_id: callID,
             title: result.title,
             reasoning: reasoning || undefined,
+            ...skillLoadMetadata(tool, toolArgs),
           },
           metrics: {
             start: startTime,
             end: endTime,
           },
           span_attributes: {
-            name: formatToolName(tool, result.title),
+            name: skillToolSpanName(tool, result.title, toolArgs, formattedName),
             type: "tool",
           },
         }