claude-code - 💡(How to fix) Fix MCP server JSONL logs: timestamp should be first field [1 participants]

{"error":"Server stderr: [idle-manager] started (idle timeout: 30min)\n","timestamp":"2026-04-27T05:31:29.942Z","sessionId":"c962fdc3-...","cwd":"C:\path\to\project"} Timestamp is the primary key when reading logs — it's what you correlate, filter, and sort by. When it appears mid-object after a potentially long error string, the log lines become jagged and unreadable without a JSON pretty-printer. A wall of MCP log output is already dense; burying the timestamp makes it a tool-required read rather than a human-readable one. {"timestamp":"2026-04-27T05:31:29.942Z","error":"Server stderr: ...","sessionId":"c962fdc3-...","cwd":"C:\path\to\project"}

TL;DR

Reorder the key sequence in the MCP log serializer to place the timestamp field first.

Guidance

• Verify the current log format by checking the JSONL log files for the timestamp field position.
• Identify the log serialization code in Claude Code and apply the suggested one-line change to reorder the object literal to { timestamp, ...rest }.
• Test the updated log format to ensure the timestamp field appears as the first field in each log entry.
• Consider reviewing other log types in Claude for similar issues, as this may not be limited to MCP logs.

Example

// Before
{"error":"Server stderr: [idle-manager] started (idle timeout: 30min)\n","timestamp":"2026-04-27T05:31:29.942Z","sessionId":"c962fdc3-...","cwd":"C:\path\to\project"}

// After
{"timestamp":"2026-04-27T05:31:29.942Z","error":"Server stderr: [idle-manager] started (idle timeout: 30min)\n","sessionId":"c962fdc3-...","cwd":"C:\path\to\project"}

Notes

This fix assumes that the log serialization code is accessible and modifiable. If the issue is caused by an open-source library, patching that library may require additional steps.

Recommendation

Apply the workaround by reordering the key sequence in the MCP log serializer, as this is a targeted fix for the specific issue described.