GPT-5.5 vs GPT-5.6 Sol
GPT-5.6 Sol is OpenAI's July 2026 GA successor to GPT-5.5 for frontier reasoning, long-horizon coding, agentic workflows, and multimodal API work. OpenAI positions Sol as the highest-capability GPT-5.6 tier, with Terra and Luna as lower-cost siblings competitive with GPT-5.5 on price-sensitive routes. Both models remain relevant: GPT-5.5 is the established baseline, while GPT-5.6 Sol is the new flagship path across ChatGPT, Codex, and the API.
Upgrade to GPT-5.6 Sol when you want OpenAI's July 2026 GA frontier route, new launch-table coding and agent rows, max reasoning effort, and the same 1.05M-class context window with refreshed benchmark evidence. Keep GPT-5.5 when stable incumbent pricing, existing prompt investments, or batch/flex economics still win in your harness, and use Terra or Luna when you need a lower-cost GPT-5.6 tier rather than full Sol capability. Do not treat GPT-5.5 as deprecated unless OpenAI publishes a separate deprecation notice.
Decision scorecard
Local evidence first| Signal | GPT-5.5 | GPT-5.6 Sol |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1.05m | 1.05m |
| Cheapest output | $30/1M tokens | $30/1M tokens |
| Provider routes | 4 tracked | 2 tracked |
| Shared benchmarks | 6 shared | SWE-bench Pro leader |
Decision tradeoffs
- GPT-5.5 holds a shared-benchmark lead on MMMU Pro, ahead by 5.3 points.
- GPT-5.5 has broader tracked provider coverage for fallback and procurement flexibility.
- GPT-5.5 uniquely exposes Structured outputs in local model data.
- Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
- GPT-5.6 Sol holds a shared-benchmark lead on SWE-bench Pro, ahead by 6.0 points.
- Local decision data tags GPT-5.6 Sol for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GPT-5.5
$11,500
Cheapest tracked route/tier: OpenAI API 0-272K input tokens
GPT-5.6 Sol
$11,500
Cheapest tracked route/tier: OpenAI API 0-272K input tokens
Estimated monthly gap: $0.00. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenAI API and OpenRouter; start route-level A/B tests there.
- Cheapest tracked output pricing is tied, so migration risk shifts to quality, latency, and provider packaging.
- Check replacement coverage for Structured outputs before moving production traffic.
- Provider overlap exists on OpenAI API and OpenRouter; start route-level A/B tests there.
- Cheapest tracked output pricing is tied, so migration risk shifts to quality, latency, and provider packaging.
- GPT-5.5 adds Structured outputs in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-23 | 2026-07-09 |
| Context window | 1.05m | 1.05m |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2025-12 | - |
Pricing and availability
| Pricing attribute | GPT-5.5 | GPT-5.6 Sol |
|---|---|---|
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| Output price |
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Capabilities
| Capability | GPT-5.5 | GPT-5.6 Sol |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | No |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | GPT-5.5 | GPT-5.6 Sol |
|---|---|---|
| SWE-bench Pro | 58.6 | 64.6 |
| Google-Proof Q&A | 93.6 | 94.6 |
| Terminal-Bench 2.1 | 78.2 | 88.8 |
| GeneBench-Pro | 12.0 | 31.5 |
| BrowseComp | 84.4 | 90.4 |
| MMMU Pro | 88.3 | 83.0 |
Deep dive
OpenAI frames GPT-5.6 as a family upgrade rather than a single SKU swap. Sol is the frontier tier, Terra is the balanced lower-cost tier positioned against GPT-5.5, and Luna is the fastest and most affordable GPT-5.6 tier. This route should compare Sol against GPT-5.5 while mentioning Terra and Luna in tier guidance.
Pricing is tier-dependent. GPT-5.6 Sol lists $5/$30 up to 272K input tokens and $10/$45 above that threshold. GPT-5.5 standard pricing remains $5/$30 up to 272K with its own long-context surcharge pattern in the OpenAI pricing table. Sol is not automatically cheaper; the upgrade case is capability and launch-table evidence, not a blanket price cut.
Benchmark coverage favors GPT-5.6 Sol on July 2026 GA rows such as DeepSWE 1.1, BrowseComp, OSWorld 2.0, GPQA Diamond, and MMMU Pro from OpenAI launch materials. GPT-5.5 retains strong incumbent rows including SWE-bench Verified and Terminal-Bench evidence from earlier OpenAI and third-party sources. Compare harness labels before citing a single score in procurement.
Availability is the practical reason to move now. OpenAI says GPT-5.6 is GA across ChatGPT, Codex, and the API on July 9, 2026, while GPT-5.5 remains a useful baseline route for teams that have not revalidated prompts on Sol yet.
Migration should be route-level A/B testing on overlapping OpenAI API infrastructure: system prompts, tool schemas, reasoning settings, and long-context surcharges can all shift when moving from GPT-5.5 to GPT-5.6 Sol even inside the same provider account.
FAQ
Is GPT-5.6 Sol worth switching to from GPT-5.5?
Switch when OpenAI's July 2026 GA launch rows and product features such as max reasoning effort or refreshed coding-agent evidence justify revalidation cost. Stay on GPT-5.5 when your incumbent prompts, batch/flex pricing, or benchmark-backed workflows still meet requirements and you do not need the newest GA tier yet.
What changed in GPT-5.6 pricing and tiers?
GPT-5.6 adds Sol, Terra, and Luna tiers rather than replacing GPT-5.5 with one SKU. Sol uses $5/$30 up to 272K input tokens and $10/$45 above that threshold in the tracked OpenAI API row. Terra and Luna are the lower-cost GPT-5.6 options OpenAI positions against GPT-5.5 for price-sensitive work.
When should teams use Terra or Luna instead of Sol?
Use Terra for balanced GPT-5.6 work when Sol-level frontier capability is unnecessary and cost should stay closer to GPT-5.5. Use Luna for the fastest and most affordable GPT-5.6 tier. Use Sol when you need the highest-capability GPT-5.6 route and OpenAI's frontier launch-table evidence.
Does GPT-5.6 Sol replace GPT-5.5 Pro?
Not automatically. Compare Sol against GPT-5.5 Pro on its own route when premium reasoning or long-context cost matters. This pair is the GPT-5.5 baseline upgrade path; do not collapse GPT-5.5 Pro pricing or benchmarks into GPT-5.5 baseline claims.
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Last reviewed: 2026-07-09. Data sourced from public model cards and provider documentation.