Model comparison
GPT-5.5 Pro vs GPT-5.6 Sol
Two OpenAI tiers compared on the figures that decide which one a workload actually needs.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: High — see receipts below
OpenAI
GPT-5.5 Pro
Frontier
OpenAI
GPT-5.6 Sol
Frontier
| Specification | GPT-5.5 Pro | GPT-5.6 Sol |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Tier | Frontier | Frontier |
| Context window | 1.05M | 1.05M |
| Max output | 128K | 128K |
| Input / 1M tokens | $30 | Winner: $4 |
| Output / 1M tokens | $180 | Winner: $20 |
| Weights | Closed | Closed |
| Parameters | Not disclosedUnverified | flagship reasoning + coding model |
| Reasoning levels | none, low, medium, high, xhigh, max | none, low, medium, high, xhigh, max |
| Modalities | text, image | text, image |
| API model id | gpt-5.5-pro | gpt-5.6-sol |
| Released | April 23, 2026 | July 9, 2026 |
| Artificial Analysis Intelligence Index [xhigh] (2026-08-14) | 60 | Not verifiedUnverified |
| Artificial Analysis Intelligence Index [max] (2026-08-14) | Not verifiedUnverified | 61 |
| Terminal-Bench 2.1 (2026-07-09) | Not verifiedUnverified | 88.8 |
| GPQA Diamond (2026-07-09) | Not verifiedUnverified | 94.6 |
Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.
Benchmark receipts
- 2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
- 2026-07-09: OpenAI — GPT-5.6 evals table (vendor)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
Pricing tiers: GPT-5.5 Pro: Standard $30/$180 per MTok; no cached-input discount. Batch $15/$90. · GPT-5.6 Sol: Launch list was $5/$30; cut to $4/$20 on 2026-08-21, promo held at least through 2026-11-21. Cached input $0.40/MTok; batch $2/$10. Knowledge cutoff Feb 16 2026.
GPT-5.5 Pro
GPT-5.5 Pro is OpenAI's highest-effort tier for maximal accuracy on the hardest tasks.
Best for
- Maximum-accuracy reasoning
- Research
- Hard enterprise workloads
Watch out
At $30/$180 per MTok it is the most expensive OpenAI tier; reserve for work that needs it.
GPT-5.6 Sol
OpenAI's GPT-5.6 flagship for complex reasoning and coding with a 1.05M-token context — top-tier but no longer the agentic-coding leader on the tracked boards.
Best for
- Complex reasoning
- Agentic coding
- Hard knowledge work
Watch out
At $4/$20 per MTok it is the priciest GPT-5.6 tier; 'max' effort and 'ultra' multi-agent mode multiply token use.
When the cheaper one wins
GPT-5.6 Sol is cheaper on output at $20 per million tokens against $180 for GPT-5.5 Pro — about 9.0×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.
Run the model pickerEvidence confidence: High
How strong and complete the evidence behind this comparison is — not a prediction of which model is better.
- Pricing verified on both sides — Input and output rates are verified for both models.
- 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
- 1 shared named benchmark (scores match) — Measured on: Artificial Analysis Intelligence Index — scores are equivalent, so the benchmark does not separate the pair.
- Verified within the last 90 days — Newest catalog check was 8 days ago.
- Both models carry source citations — Each side has at least two catalog sources on record.
Source receipts
Each catalog figure was checked against the provider or an independent second source on the date shown.
- GPT-5.5 Pro: OpenAI — Introducing GPT-5.5 (accessed 2026-08-29)
- GPT-5.5 Pro: OpenAI API pricing (gpt-5.5-pro $30/$180) (accessed 2026-08-29)
- GPT-5.6 Sol: OpenAI — GPT-5.6 (accessed 2026-08-29)
- GPT-5.6 Sol: OpenAI API pricing (gpt-5.6-sol $4/$20) (accessed 2026-08-29)
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- Claude Fable 5.1 vs GPT-5.5 Pro
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Diving deeper on one model? GPT-5.5 Pro · GPT-5.6 Sol
Common questions
GPT-5.5 Pro vs GPT-5.6 Sol
Answered from the verified figures on this page rather than general guidance.
Is GPT-5.5 Pro or GPT-5.6 Sol cheaper for input?
GPT-5.6 Sol is cheaper at $4 per million input tokens, against $30 for GPT-5.5 Pro — roughly 7.5× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.5 Pro has tiered pricing: Standard $30/$180 per MTok; no cached-input discount. Batch $15/$90. GPT-5.6 Sol has tiered pricing: Launch list was $5/$30; cut to $4/$20 on 2026-08-21, promo held at least through 2026-11-21. Cached input $0.40/MTok; batch $2/$10. Knowledge cutoff Feb 16 2026.
Is GPT-5.5 Pro or GPT-5.6 Sol cheaper for output?
GPT-5.6 Sol is cheaper at $20 per million output tokens, against $180 for GPT-5.5 Pro — roughly 9.0× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.5 Pro has tiered pricing: Standard $30/$180 per MTok; no cached-input discount. Batch $15/$90. GPT-5.6 Sol has tiered pricing: Launch list was $5/$30; cut to $4/$20 on 2026-08-21, promo held at least through 2026-11-21. Cached input $0.40/MTok; batch $2/$10. Knowledge cutoff Feb 16 2026.
Which has the larger context window, GPT-5.5 Pro or GPT-5.6 Sol?
Both accept about 1.05M tokens of context, so document length will not decide between them.
Do GPT-5.5 Pro and GPT-5.6 Sol support the same reasoning levels?
Yes — both accept the same effort settings: "none", "low", "medium", "high", "xhigh", "max". Higher effort costs more and takes longer, so start low and raise it only where output quality actually improves.
Should I use GPT-5.5 Pro or GPT-5.6 Sol?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. GPT-5.5 Pro suits maximum-accuracy reasoning; GPT-5.6 Sol suits complex reasoning.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
- Input price: GPT-5.6 Sol costs $4 per 1M tokens versus $30 for GPT-5.5 Pro — a 7.5x difference at the headline tier.
- Measured capability: GPT-5.6 Sol leads Artificial Analysis Intelligence Index 61 to 60 (measured 2026-08-14).
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.