Both are the flagship of their family. Both cost a small fortune at full retail. The right pick depends entirely on your workload — and the wrong pick costs 5x more than it should.
New tokenizer, advanced coding, the agent's choice.
Frontier reasoning + multimodal + 256k context.
Opus 4.7's tool-call cleanliness and long-chain coherence are exactly what agents need. Claude Code, Cline, OpenClaw, Cursor's agent mode all default to Opus or Sonnet for a reason.
If your task is 'solve this novel hard problem in one prompt,' GPT-5.5 has the edge. Math, scientific reasoning, obscure-fact synthesis — GPT-5.5 wins.
Opus 4.7's 128k max output crushes GPT-5.5's 32k. If you need to generate a novel chapter, full report, or large code file, Opus does it in one call. GPT requires chunking.
GPT-5.5 has better vision accuracy, native audio understanding, and image generation. Opus vision works but is more conservative.
256k beats 200k. For loading large codebases or long documents, GPT-5.5 has 28% more headroom.
Depends on input/output ratio. For typical coding (high input, moderate output), Opus is slightly cheaper because Opus has cheaper output. For chat (moderate input, low output), GPT is slightly cheaper because GPT has cheaper input. Through claudeapi.cheap Pro, both come down to under $1/M input — affordable enough to pick on capability.
Opus 4.7 for any agentic workload — coding agents, multi-step automation, long generation. GPT-5.5 for hard one-shot reasoning, multimodal tasks, or when 256k context is a hard requirement. Through claudeapi.cheap (80% off Pro), both are $1/M input or less — budget shouldn't drive the choice.
Claudeapi.cheap serves both at 80% off list. One sk-cc-... key, both endpoints (Anthropic-format + OpenAI-format), drop-in compatible. Run an A/B in 5 minutes — find your winner per task class.
Get a free API keyOpus 4.7 ships with an updated tokenizer that produces ~10% fewer tokens for typical English text vs Opus 4.6. Same input string, fewer billed input tokens. Real money on long-context use.
Depends on workload. For chat and tool-using agents, 32k is plenty per turn. For 'write me a 50-page report in one call' or 'output the full refactored 5000-line file,' GPT-5.5 will refuse or truncate. Opus 4.7's 128k handles those.
Yes. A common pattern: GPT-5.5 plans (best reasoning), Opus 4.7 executes (best tool-use). Aider's --architect mode does this natively. Both via one sk-cc-... key on claudeapi.cheap.
Pro plan ($19 lifetime, 80% off): Opus 4.7 = $1.00 input / $5.00 output per 1M tokens. GPT-5.5 = $0.80 input / $6.40 output per 1M. Both flagships run for under $1/M input — about 1/5 of direct retail.