Coding-Easy-Group-By-Key

The model receives the prompt (and optional system message). The run uses scorer javascript_function_tests with the JSON configuration below. Pass/fail and partial credit are determined entirely by that scorer against the model output; no human grading.

Return JSON only with a string field named code. The code must be dependency-free JavaScript, define the requested function in the top level or module.exports, and include no markdown, imports, require, timers, network, filesystem, eval, or placeholders.

Implement function groupByKey(items, key) that groups objects by the string value at key and returns an object of arrays.

Your JSON must look like {"code":"function groupByKey(...) { ... }"}.

{
  "function_name": "groupByKey",
  "timeout_ms": 100,
  "test_pass_threshold": 1,
  "partial_credit_threshold": 0.5,
  "tests": "[hidden executable tests]"
}