Claude
4-tier model family: Sonnet 5.5 for daily code, Opus 5.5 for long-running agentic and knowledge work, Haiku 5.5 for fast high-volume tasks, Fable 5.1 for demanding reasoning and long-horizon runs. Opus 5.5 is the recommended starting point; Opus 5, Sonnet 5 and Opus 4.8 are now legacy. 1M token window on all four, top reasoning benchmarks.
Strengths
- Opus tops reasoning benchmarks
- 1M token context window, ingests entire codebases or document libraries
- Four-tier model family covering power, speed, cost and long-horizon runs
- Constitutional AI design, lowest prompt injection success rate in the industry
Limitations
- Opus, the top tier, is expensive: pricing limits high-volume production use
- Haiku unsuitable for complex reasoning or long-document analysis
- Slower than Gemini Flash for latency-critical, high-throughput pipelines
Best for
- Complex reasoning, long-form writing, and code generation at scale
- Agentic workflows with tool use, multi-step planning, and safety