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fix(claude-agent-sdk): Fix subagents span nesting and input #2119

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Merged
Luca Forstner (lforst) merged 4 commits into from
Jun 16, 2026
Merged

fix(claude-agent-sdk): Fix subagents span nesting and input #2119

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2466ca6
fix(claude-agent-sdk): Fix subagents span nesting and input
lforst Jun 15, 2026
6b83a39
cs
lforst Jun 15, 2026
1994823
fixes
lforst Jun 15, 2026
9971a7a
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lforst Jun 16, 2026
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5 changes: 5 additions & 0 deletions .changeset/funky-pigs-clap.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"braintrust": patch
---

fix(claude-agent-sdk): Fix subagents span nesting and input
244 changes: 90 additions & 154 deletions ...agent-sdk-instrumentation/__snapshots__/claude-agent-sdk-v0.2.76-auto-hook.span-tree.json
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Original file line number Diff line number Diff line change
Expand Up @@ -14,37 +14,7 @@
{
"name": "anthropic.messages.create",
"type": "llm",
"children": [
{
"name": "tool: calculator/calculator",
"type": "tool",
"children": [
{
"name": "calculator-local-handler-multiply",
"children": []
}
],
"input": {
"a": 15,
"b": 7,
"operation": "multiply"
},
"output": {
"content": [
{
"text": "multiply(15, 7) = 105",
"type": "text"
}
]
},
"metadata": {
"claude_agent_sdk.raw_tool_name": "mcp__calculator__calculator",
"gen_ai.tool.call.id": "toolu_01VxxkUqbM8wfd3hj1SmgRLd",
"gen_ai.tool.name": "calculator",
"mcp.server": "calculator"
}
}
],
"children": [],
"input": [
{
"content": "Use the calculator tool to multiply 15 by 7. Do not answer from memory.",
Expand Down Expand Up @@ -91,6 +61,35 @@
"tokens": 18794
}
},
{
"name": "tool: calculator/calculator",
"type": "tool",
"children": [
{
"name": "calculator-local-handler-multiply",
"children": []
}
],
"input": {
"a": 15,
"b": 7,
"operation": "multiply"
},
"output": {
"content": [
{
"text": "multiply(15, 7) = 105",
"type": "text"
}
]
},
"metadata": {
"claude_agent_sdk.raw_tool_name": "mcp__calculator__calculator",
"gen_ai.tool.call.id": "toolu_01VxxkUqbM8wfd3hj1SmgRLd",
"gen_ai.tool.name": "calculator",
"mcp.server": "calculator"
}
},
{
"name": "anthropic.messages.create",
"type": "llm",
Expand Down Expand Up @@ -390,59 +389,16 @@
{
"name": "anthropic.messages.create",
"type": "llm",
"children": [
{
"name": "tool: calculator/calculator",
"type": "tool",
"children": [
{
"name": "calculator-local-handler-add",
"children": []
}
],
"input": {
"a": 15,
"b": 27,
"operation": "add"
},
"output": {
"content": [
{
"text": "add(15, 27) = 42",
"type": "text"
}
]
},
"metadata": {
"claude_agent_sdk.raw_tool_name": "mcp__calculator__calculator",
"gen_ai.tool.call.id": "toolu_01BUZHbp64XJFUZRU2vuUrJ9",
"gen_ai.tool.name": "calculator",
"mcp.server": "calculator"
}
}
],
"children": [],
"input": [
{
"content": "Spawn a math-expert subagent to add 15 and 27 using the calculator tool. Report the result. Do not solve it yourself.",
"role": "user"
},
{
"content": [
{
"caller": {
"type": "direct"
},
"id": "<span:1>",
"input": {
"description": "Add 15 and 27 using calculator",
"prompt": "Please add 15 and 27 together using the calculator tool. Report the result to me.",
"subagent_type": "math-expert"
},
"name": "Agent",
"type": "tool_use"
"text": "Please add 15 and 27 together using the calculator tool. Report the result to me.",
"type": "text"
}
],
"role": "assistant"
"role": "user"
}
],
"output": [
Expand Down Expand Up @@ -475,6 +431,35 @@
"prompt_tokens": 22031,
"tokens": 22034
}
},
{
"name": "tool: calculator/calculator",
"type": "tool",
"children": [
{
"name": "calculator-local-handler-add",
"children": []
}
],
"input": {
"a": 15,
"b": 27,
"operation": "add"
},
"output": {
"content": [
{
"text": "add(15, 27) = 42",
"type": "text"
}
]
},
"metadata": {
"claude_agent_sdk.raw_tool_name": "mcp__calculator__calculator",
"gen_ai.tool.call.id": "toolu_01BUZHbp64XJFUZRU2vuUrJ9",
"gen_ai.tool.name": "calculator",
"mcp.server": "calculator"
}
}
],
"input": "Please add 15 and 27 together using the calculator tool. Report the result to me.",
Expand Down Expand Up @@ -569,24 +554,6 @@
}
],
"role": "assistant"
},
{
"content": [
{
"caller": {
"type": "direct"
},
"id": "<span:2>",
"input": {
"a": 15,
"b": 27,
"operation": "add"
},
"name": "mcp__calculator__calculator",
"type": "tool_use"
}
],
"role": "assistant"
}
],
"output": [
Expand Down Expand Up @@ -718,27 +685,14 @@
"type": "llm",
"children": [],
"input": [
{
"content": "You MUST call the Agent tool now with subagent_type=\"echo\" and description \"echo greeting\". Do not call Bash yourself. Do not answer with text yourself; delegate to the echo sub-agent.",
"role": "user"
},
{
"content": [
{
"caller": {
"type": "direct"
},
"id": "<span:1>",
"input": {
"description": "echo greeting",
"prompt": "Please echo a greeting message",
"subagent_type": "echo"
},
"name": "Agent",
"type": "tool_use"
"text": "Please echo a greeting message",
"type": "text"
}
],
"role": "assistant"
"role": "user"
}
],
"output": [
Expand Down Expand Up @@ -886,23 +840,6 @@
}
],
"role": "assistant"
},
{
"content": [
{
"caller": {
"type": "direct"
},
"id": "<span:2>",
"input": {
"command": "echo hello",
"description": "Echo hello message"
},
"name": "Bash",
"type": "tool_use"
}
],
"role": "assistant"
}
],
"output": [
Expand Down Expand Up @@ -975,31 +912,7 @@
{
"name": "anthropic.messages.create",
"type": "llm",
"children": [
{
"name": "tool: calculator/calculator",
"type": "tool",
"children": [
{
"name": "calculator-local-handler-divide",
"children": [],
"error": "division by zero\n\nError: division by zero\n at traced.name (<repo>/e2e/scenarios/claude-agent-sdk-instrumentation/scenario.impl.mjs:0:0)\n at <repo>/js/dist/index.mjs:0:0\n at AsyncLocalStorage.run (node:<internal>:0:0)\n at BraintrustContextManager.runInContext (<repo>/js/dist/index.mjs:0:0)\n at withCurrent (<repo>/js/dist/index.mjs:0:0)\n at <repo>/js/dist/index.mjs:0:0\n at runCatchFinally (<repo>/js/dist/index.mjs:0:0)\n at traced (<repo>/js/dist/index.mjs:0:0)\n at <repo>/e2e/scenarios/claude-agent-sdk-instrumentation/scenario.impl.mjs:0:0\n at runHandler (<repo>/js/dist/index.mjs:0:0)"
}
],
"input": {
"a": 2,
"b": 0,
"operation": "divide"
},
"metadata": {
"claude_agent_sdk.raw_tool_name": "mcp__calculator__calculator",
"gen_ai.tool.call.id": "toolu_01CMsRz4pP2m3xfVrPNDKi3r",
"gen_ai.tool.name": "calculator",
"mcp.server": "calculator"
},
"error": "division by zero"
}
],
"children": [],
"input": [
{
"content": "Use the calculator tool to divide 2 by 0. Do not recover from the error.",
Expand Down Expand Up @@ -1046,6 +959,29 @@
"tokens": 18802
}
},
{
"name": "tool: calculator/calculator",
"type": "tool",
"children": [
{
"name": "calculator-local-handler-divide",
"children": [],
"error": "division by zero\n\nError: division by zero\n at traced.name (<repo>/e2e/scenarios/claude-agent-sdk-instrumentation/scenario.impl.mjs:0:0)\n at <repo>/js/dist/index.mjs:0:0\n at AsyncLocalStorage.run (node:<internal>:0:0)\n at BraintrustContextManager.runInContext (<repo>/js/dist/index.mjs:0:0)\n at withCurrent (<repo>/js/dist/index.mjs:0:0)\n at <repo>/js/dist/index.mjs:0:0\n at runCatchFinally (<repo>/js/dist/index.mjs:0:0)\n at traced (<repo>/js/dist/index.mjs:0:0)\n at <repo>/e2e/scenarios/claude-agent-sdk-instrumentation/scenario.impl.mjs:0:0\n at runHandler (<repo>/js/dist/index.mjs:0:0)"
}
],
"input": {
"a": 2,
"b": 0,
"operation": "divide"
},
"metadata": {
"claude_agent_sdk.raw_tool_name": "mcp__calculator__calculator",
"gen_ai.tool.call.id": "toolu_01CMsRz4pP2m3xfVrPNDKi3r",
"gen_ai.tool.name": "calculator",
"mcp.server": "calculator"
},
"error": "division by zero"
},
{
"name": "anthropic.messages.create",
"type": "llm",
Expand Down
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