Claude Opus 5.5 vs GPT-5.6 Sol: Pricing, Benchmarks & Which to Pick (2026)

The short answer: GPT-5.6 Sol is the better value for everyday coding and reasoning at volume. Claude Opus 5.5 is clearly the more capable model, and it earns its higher rate on long agentic tasks, terminal automation and knowledge work where quality matters more than cost per call.

This isn't a matchup of equals — it's a choice between a frontier model and a cost-efficient workhorse. Both are available on HiAPI behind the same API, so the smart move is often to use both: Sol for the bulk of requests, Opus for the hard ones.

At a Glance

Prices are as of October 2026 — check the pricing page for current rates.

Context and output limits are effectively the same, so neither model will box you in on long documents or large codebases. The decision comes down to two things: how hard your task is, and how many times you need to run it.

Benchmarks

Public head-to-head data for this pair is thin, and what exists is vendor-reported by each side, so treat it as directional.

The gap is large. Terminal-Bench 4.0 measures how well a model completes multi-step tasks in a real terminal — exactly the kind of work coding agents do — and Opus 5.5 scores far higher. The Artificial Analysis Intelligence Index tells the same story across a broader set of evaluations.

That doesn't make Sol weak. Third-party reviews consistently describe it as a strong, cost-efficient model for everyday coding and reasoning. It simply isn't built to compete with Opus on the hardest agentic work.

Cost on HiAPI

Sol is the cheaper model on every line: $1.25 vs $2.02 per million input tokens, $7.50 vs $10.08 per million output tokens. Opus has the edge on cached reads ($0.10 vs $0.125), which narrows the gap for agents that resend a large, stable context on every turn.

For a sample workload of 1,000 requests a day, 3,000 input and 800 output tokens each, for 30 days, with no caching:

Both are priced well below their published list prices on HiAPI — Opus 5.5 at roughly half, GPT-5.6 Sol at roughly a third. Billing is per token on ordinary real-time requests, with no monthly plan and no minimum.

Key Differences

Hard agentic tasks. If the model has to plan, run commands, read results and keep going for many steps, Opus 5.5 is in a different league (66.4 vs 37.3 on Terminal-Bench 4.0). Cheaper per call doesn't help if the cheaper model needs several retries or a human to finish the job.

Everyday coding and reasoning. For writing a function, explaining an error, generating tests or answering technical questions, Sol is the cost-efficient workhorse. At high volume, the savings add up fast.

Knowledge work and writing. Third-party reviews rate Opus 5.5 highly for knowledge work and say its writing is easier to read. One caveat: on very long tasks it can occasionally lose focus or be slow to wrap up, so give it clear stopping criteria. Our Claude Opus 5.5 API quickstart shows how to get started.

Freshness. Opus 5.5's knowledge cutoff is 2026-06, Sol's is 2026-02. If your prompts depend on recent libraries or events without retrieval, Opus has a few more months of knowledge.

How to Choose

• High-volume pipeline, routine tasks? GPT-5.6 Sol.
• Coding assistant for day-to-day edits and explanations? GPT-5.6 Sol.
• Autonomous coding agent or terminal automation? Claude Opus 5.5.
• Reports, analysis or long-form writing where quality matters? Claude Opus 5.5.
• Mixed workload? Route by difficulty: send most traffic to Sol and escalate to Opus when a task is long, ambiguous or fails on the first attempt.
• Need stronger math, science or prompt-injection resistance in the OpenAI family? See GPT-6 Astra vs GPT-5.6 Sol and Claude Opus 5.5 vs GPT-6 Astra.

Try Both With One Key

HiAPI serves both models through one OpenAI-compatible endpoint. Change the model field to switch.

curl https://api.hiapi.ai/v1/chat/completions \
  -H "Authorization: Bearer $HIAPI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-opus-5-5",
    "messages": [
      {"role": "user", "content": "Write unit tests for this function, covering edge cases."}
    ]
  }'
# Swap "claude-opus-5-5" for "gpt-5.6-sol" to run the same request on GPT-5.6 Sol.

Three prompts that show where the two diverge:

1. Routine task: "Explain what this error message means and suggest the most likely fix."
2. Multi-step agent task: "Given this repository layout and the failing CI log, work out the root cause, propose a patch, and list the steps to verify it."
3. Long-form writing: "Turn these meeting notes into a one-page decision memo with context, options considered and a recommendation."

Model pages: Claude Opus 5.5 · GPT-5.6 Sol

FAQ

Which is better, Claude Opus 5.5 or GPT-5.6 Sol?

Claude Opus 5.5 is the more capable model — it scores 66.4 vs 37.3 on Terminal-Bench 4.0 and 58 vs 47 on the Artificial Analysis Intelligence Index. GPT-5.6 Sol is the better value for everyday coding and reasoning where you don't need frontier-level performance.

Which is cheaper, Claude Opus 5.5 or GPT-5.6 Sol?

GPT-5.6 Sol. On HiAPI it costs $1.25 / $7.50 per million input/output tokens vs $2.02 / $10.08 for Opus 5.5. For a sample workload of 1,000 requests a day, that is about $292/month vs $424/month.

Why is it cheaper on HiAPI than the list price?

HiAPI buys capacity at volume and passes the saving on as a plain per-token rate on ordinary real-time requests. There is no batch queue, no minimum and no monthly plan — your balance is pay-as-you-go and never expires.

Do I need to change my code to use these models on HiAPI?

Very little. HiAPI provides an OpenAI-compatible endpoint, so you change the base URL, the API key and the model name. Switching between Opus 5.5 and Sol is then a one-field change.

Can I use both in the same app?

Yes. Because both models share one endpoint and one key on HiAPI, you can route easy requests to Sol and hard ones to Opus without managing separate accounts or SDKs.

Conclusion

GPT-5.6 Sol is the sensible default when you're running lots of routine coding and reasoning requests. Claude Opus 5.5 is the model to escalate to for long agentic work and output where quality really counts. On HiAPI both are priced well under their list prices and share one API, so you can combine them and pay only for what each task needs. Check current rates on the pricing page.

Related Reading

• Claude Opus 5.5 vs GPT-6 Astra
• GPT-6 Astra vs GPT-5.6 Sol
• Claude Opus 5.5 vs Kimi K3
• Claude Opus 5.5 vs Claude Sonnet 4.6
• Claude Opus 5.5 API Quickstart