deepseek-ai/deepseek-harness · error · Error

tool arguments must be lossless JSON (call the tool with an

Error message

tool arguments must be lossless JSON (call the tool with an arguments object, e.g. `{}`)

What it means

Error "tool arguments must be lossless JSON (call the tool with an arguments object, e.g. `{}`)" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/core/tools/src/code-mode.ts:161

    super(message, 'CODE_RUN_FAILED')
    this.name = 'CodeRunFailedError'
  }
}

/**
 * Snapshot one binding call's argument as lossless JSON, then snapshot that
 * detached value again so dispatch and logging stay independent without
 * reintroducing structured-clone's platform-specific nesting limit.
 */
function jsonNormalizeArgs(value: unknown): { dispatched: unknown; logged: unknown } {
  let snapshot: JsonValue | undefined
  try {
    snapshot = snapshotJsonValue(value) as JsonValue | undefined
  } catch (error: unknown) {
    throw new Error(`tool arguments must be lossless JSON: ${error instanceof Error ? error.message : String(error)}`)
  }
  if (snapshot === undefined) {
    throw new Error('tool arguments must be lossless JSON (call the tool with an arguments object, e.g. `{}`)')
  }
  const logged = snapshotJsonValue(snapshot)
  /* v8 ignore next -- snapshot is already a detached lossless JSON value. */
  if (logged === undefined) {
    throw new Error('tool arguments could not be detached for durable logging')
  }
  return { dispatched: snapshot, logged }
}

/** Two-space JSON presentation, matching the existing shallow `run_code` text contract. */
const JSON_INDENT = '  '

/**
 * ECMAScript caps `JSON.stringify`'s `space` string at ten characters. The
 * renderer also caps TOTAL indentation there, compacting deeper subtrees, so
 * formatted output remains linear in the canonical JSON size.
 */
const MAX_JSON_INDENT_CHARS = 10

View on GitHub (pinned to b150a551b8)

When it happens

Trigger: Thrown at packages/core/tools/src/code-mode.ts:161 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of deepseek-ai/deepseek-harness@b150a551b8 (2026-08-24). Data as JSON: /api/errors/b680283921b9a63f. Report an issue: GitHub.