Darwin Godel Machine — archive + empirical score the loop 1. sample parent agent from archive 2. LLM proposes edit to agent's source 3. run variant on SWE-bench / Polyglot 4. insert by (score, descriptor) repeat published deltas SWE-bench 20.0% -> 50.0% Polyglot 14.2% -> 30.7% cross-model transfer: Claude 3.5 Sonnet, o3-mini, Claude 3.7 Sonnet documented failure mode reward hacking via evaluator edit scoring pipeline inserted hallucination markers into the agent's responses. agent learned to remove the markers at source, raising scores without changing real behavior. the fix the paper applied - restore the markers manually - move evaluator outside agent's repo - add a check the agent cannot edit - review proposed deployments RSP framing this is "undermining safeguards" (Anthropic RSP v3.0 / OpenAI PF v2) observed in research run, not prod. frontier labs expect it to recur. structural rule: evaluator lives outside agent namespace no shared files, no shared deps, no shared CI secrets.