Claude Haiku 4.5 vs Claude Fable 5:2026年に勝つAIモデルはどっち?

“The precise localized edits are the underrated feature. It fixes the line that needs fixing and leaves the rest alone. GPT mini class models keep rewriting half my file.”

“Haiku 4.5 gives me about 90% of Sonnet agentic coding at a third of the price, and it is fast enough that edit loops feel instant. My default for quick fixes now.”

“I do medical imaging research and the bio classifier keeps flagging my MRI segmentation prompts, then it silently falls back to Opus 4.8 mid-session. At $50 per million output tokens I expect to at least know which model actually answered me.”

“Yes it's 2x the price of Opus and yes the turns are slow. But one overnight Fable run replaced what used to be a week of supervising shorter runs. On a per-task basis it's actually the cheapest model we use.”

“The 1M context is real, not marketing. I fed it our entire service mesh config plus six months of incident postmortems and it traced a flaky timeout to a retry policy nobody remembered writing. Opus 4.8 never connected those dots.”

“Gave it a monorepo migration that Opus 4.8 kept stalling on. It ran for about 40 minutes, came back with the whole thing done plus a test harness it wrote for itself. Felt like reviewing a senior engineer's PR, not babysitting a chatbot.”