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Add: Debug logging for MCP skill startup time #50

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Merged
FL4TLiN3 merged 1 commit into from
Dec 4, 2025
Merged

Add: Debug logging for MCP skill startup time #50

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6 changes: 6 additions & 0 deletions .changeset/add-mcp-debug-logging.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
---
"@perstack/runtime": patch
---

Add debug logging for MCP skill startup time

Empty file removed assets/image-c3bc156b-e84b-43b8-ac80-4f97a44fcaee.png
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14 changes: 13 additions & 1 deletion packages/runtime/src/skill-manager/mcp.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -72,9 +72,21 @@ export class McpSkillManager extends BaseSkillManager {
}
env[envName] = this._env[envName]
}
const startTime = Date.now()
console.log(`[MCP] Starting skill ${skill.name}...`)
const { command, args } = this._getCommandArgs(skill)
const transport = new StdioClientTransport({ command, args, env, stderr: "ignore" })
const transport = new StdioClientTransport({ command, args, env, stderr: "pipe" })
if (transport.stderr) {
transport.stderr.on("data", (chunk: Buffer) => {
console.log(`[MCP:${skill.name}:stderr] ${chunk.toString().trim()}`)
})
}
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@cursor cursor bot Dec 4, 2025

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Bug: Stderr listener attached before process starts, never receives data

The transport.stderr listener is attached at lines 79-82, but the child process isn't spawned until connect() is called at line 85. The StdioClientTransport.stderr property returns the spawned process's stderr stream, which is only available after start() (called internally by connect()). Since transport.stderr is null or undefined before the process starts, the if (transport.stderr) check fails silently, and the stderr listener is never attached. This defeats the main purpose of this PR - stderr output from the MCP skill will never be logged.

Fix in Cursor Fix in Web

const connectStartTime = Date.now()
await this._mcpClient!.connect(transport)
const connectTime = Date.now()
console.log(
`[MCP] Skill ${skill.name} connected in ${connectTime - connectStartTime}ms (total: ${connectTime - startTime}ms)`,
)
if (this._eventListener) {
const serverInfo = this._mcpClient!.getServerVersion()
const event = createRuntimeEvent("skillConnected", this._runId, {
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