Log

The log component provides structured, append-only event logging scoped to the current agent and session.

append()

await harness.log().append({
  event: "tool_call",
  level: "info",
  data: { tool: "web_search", query: "TypeScript best practices" },
})

Field	Type	Required	Description
`event`	`string`	yes	Event name
`level`	`LogLevel`	yes	`"debug"`, `"info"`, `"warn"`, or `"error"`
`data`	`object`	no	Arbitrary event data

query()

const entries = await harness.log().query({
  event: "tool_call",
  level: "error",
  since: new Date("2024-01-01"),
  until: new Date(),
  limit: 100,
})

Field	Type	Required	Description
`event`	`string`	no	Filter by event name
`level`	`LogLevel`	no	Filter by minimum level
`since`	`Date`	no	Start time
`until`	`Date`	no	End time
`limit`	`number`	no	Max results

Each LogEntry contains:

interface LogEntry {
  id: string
  agentId: string
  sessionId: string
  event: string
  level: LogLevel
  data?: Record<string, unknown>
  createdAt: Date
}