Long-context mode (~180k-token prompt, real 213k–285k by each tokenizer). Here TTFB is the whole story — it's now the prefill tax for reading the giant prompt, and it fans out from 0.6s (codex) to 27s (gemini-3.1-pro). The codex sub-second numbers are suspiciously fast for a 200k prefill and likely reflect ChatGPT-side prompt caching, not a true full read. TPS here is overall out ÷ total. gpt-oss-120b exceeded its context limit; codex-spark returned empty; fable-5 was rate-limited.