GPT-5.5 vs Claude 4 Opus for Legal
Compare GPT-5.5 by OpenAI and Claude 4 Opus by Anthropic for legal tasks - pricing, context windows, and strengths, and see how to put either to work in Appaca.
GPT-5.5
OpenAI's smartest and most capable model yet for agentic coding, knowledge work, and computer use, delivering a new class of intelligence at GPT-5.4 latency.
View GPT-5.5Claude 4 Opus
The flagship model, focused on deep reasoning, large-scale coding and sustained multi-step agentic workflows.
View Claude 4 OpusGPT-5.5 vs Claude 4 Opus at a glance
Specs and pricing side by side, from the Appaca AI models directory.
| Spec | GPT-5.5 | Claude 4 Opus |
|---|---|---|
| Provider | OpenAI | Anthropic |
| Model type | Text | Text |
| Context window | 1M tokens | 200K tokens |
| Input price | $5 / 1M tokens | $15 / 1M tokens |
| Output price | $30 / 1M tokens | $75 / 1M tokens |
| Status | Current | Superseded by Claude 4.1 Opus |
What matters for Legal
Evaluation criteria and how GPT-5.5 and Claude 4 Opus compare on what legal tasks actually require.
Precision and accuracy in legal language
Ability to identify risks and ambiguous clauses
Appropriate caveats and professional disclaimers
Handling long documents within context window
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GPT-5.5 is 67% cheaper on input tokens ($5 vs $15 per million), which adds up quickly on high-volume legal workloads.
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GPT-5.5 is 60% cheaper on output tokens ($30 vs $75 per million) - the bigger factor for legal tasks that generate long responses.
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GPT-5.5's 1M tokens context window is roughly 5x larger than Claude 4 Opus's 200K tokens, so it can handle bigger inputs in a single legal pass.
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Claude 4 Opus has been superseded by Claude 4.1 Opus - for new legal builds, consider the newer model first.
Strengths side by side
Where each model shines, according to benchmarks and provider positioning.
GPT-5.5
1. Strongest Agentic Coding Model
- State-of-the-art on Terminal-Bench 2.0 (82.7%), Expert-SWE (73.1%), and SWE-Bench Pro (58.6%), outperforming GPT-5.4 on complex coding tasks.
- Holds context across large systems, reasons through ambiguous failures, and carries changes through surrounding codebases with fewer tokens.
2. Higher Intelligence at GPT-5.4 Latency
- Co-designed, trained, and served on NVIDIA GB200/GB300 NVL72 systems to match GPT-5.4 per-token latency while performing at a significantly higher level.
- Uses fewer tokens to complete the same tasks, making it more efficient as well as more capable.
3. Powerful for Knowledge Work & Computer Use
- Scores 84.9% on GDPval (44 occupations) and 78.7% on OSWorld-Verified for autonomous computer operation.
- Excels at generating documents, spreadsheets, and reports; naturally moves across finding information, using tools, and checking output.
4. Scientific Research Co-Scientist
- Leading performance on GeneBench, BixBench, and FrontierMath; helped discover a new proof about Ramsey numbers verified in Lean.
- Strong enough to meaningfully accelerate progress at the frontiers of biomedical and mathematical research.
Claude 4 Opus
- Highest capability in the family: described as “our most powerful model yet” by Anthropic.
- Exceptional at long-running tasks requiring thousands of steps and sustained focus (e.g., continuous codebase work for hours).
- Excellent performance on benchmarks: e.g., SWE-bench 72.5 % and Terminal-bench 43.2 %.
- Designed for complex agentic workflows, deep reasoning, tool use, and large context windows.
- Placed under a higher safety classification (ASL-3) due to its frontier capability and risk profile.
Use GPT-5.5 or Claude 4 Opus - or both
Appaca is the AI workspace for operators. Build internal legal tools and AI co-workers powered by GPT-5.5 or Claude 4 Opus - connected to your real data and ready for your whole team. No code, no deployment.
Describe it, and it's built
Tell the Appaca agent the internal tool you need for legal and it builds a working app powered by GPT-5.5 or Claude 4 Opus. No code, no API keys, no deployment.
Switch models without rebuilding
Start on GPT-5.5, test the same tool on Claude 4 Opus, and keep whichever performs better for your legal workflow - the rest of your app stays exactly as it is.
Automated for the whole team
Schedule tools to run on autopilot - daily digests, weekly reports, real-time triggers - and share them with your whole team from one workspace.
Describe it, and it's built
Tell the Appaca agent what your team needs for legal and it builds a working app powered by GPT-5.5 or Claude 4 Opus - connected to the tools you already use.
Keep comparing for Legal
More side-by-side model comparisons for legal tasks.
FAQs
Claude 4 Opus and GPT-5.5 are the top legal LLMs in 2026. Claude 4 Opus excels at identifying ambiguous clauses, drafting precise contract language, and handling nuanced legal reasoning with appropriate disclaimers. GPT-5.5 is preferred for structured document output and legal research synthesis. Both offer the large context windows needed for full contract review.
GPT-5.5 is generally cheaper: $5 input / $30 output per million tokens, versus $15 / $75 for Claude 4 Opus. Actual cost depends on how many tokens your legal workload reads and writes.
GPT-5.5 has the larger context window at 1M tokens, compared to 200K tokens for Claude 4 Opus. For legal tasks, a larger window means the model can consider more context at once without losing track.
Yes. Appaca is a no-code AI workspace: describe the internal tool your team needs for legal and the Appaca agent builds it as a working app powered by GPT-5.5, Claude 4 Opus, or any other model in the directory - with a built-in database, team access, and integrations. No API keys to wire up and nothing to deploy.
Build Legal tools with GPT-5.5 or Claude 4 Opus
Describe the legal tool your team needs and get a working app powered by the model you choose - with a built-in database, team access, and integrations. No code, no deployment.