Haiku 5.5 matches Astra on hidden bugs with half the file changes
On the same messy production-style repo with a vague prompt, Haiku 5.5 and GPT-6 Astra both found 8 of 9 hidden defects, but Astra touched 68 files while Haiku changed only 34.
Never Confuse price with capability and Never underestimate Haiku 5.5! I tested it at Xhigh effort against the same messy, production-style repository I used for GPT-6 Astra, GPT-6.1 Sol, Opus 5.5 and Fable 5.1, to give you context I used same frozen baseline. Same vague prompt. No bug list. 9 hidden defects + 1 architectural trap. The results surprised me and for comparison: >Claude Haiku 5.5: 8/9, restraint preserved, 34 files touched >GPT-6 Astra: 8/9, restraint broken, 68 files touched. >GPT-6.1 Sol High: 8/9, restraint broken, 62 files touched. It didn't beat Fable 5.1 or Opus 5.5, which reached 9/9 and preserved restraint but in this experiment, Haiku demonstrated better engineering restraint than the highest-tier OpenAI models I tested, matching their hidden-defect signature coverage while modifying significantly fewer files.