OpenAI
GPT-5.5
From $4.00 per 1M tokens
Chat
GPT-5.6 Sol — Frontier Tier, 1.05M Context, Max Effort
GPT-5.6 Sol is the frontier model of the GPT-5.6 family and what the bare `gpt-5.6` alias resolves to. GPT-5.6 Sol reads a 1,050,000-token context window, returns up to 128,000 tokens, and carries the family's full six-rung reasoning ladder including the new max setting. OpenAI rates its reasoning Highest and its speed Fast. On reAPI, GPT-5.6 Sol bills 20% below OpenAI's published rate on both input and output.
GPT-5.6 Solmodel
gpt-5.6-solGPT-5.6 Sol playground
Chat models run on the api.reapi.ai gateway, which has its own console and its own key. Open the console to run GPT-5.6 Sol through the OpenAI-compatible Chat Completions surface.
What you can build with this model
Real-world workflows and production use cases you can build and ship with this model.
The debugging and review work that has to be right
OpenAI's guidance for the top of the effort ladder names security and code review, complex debugging and deep planning — tasks where quality matters more than latency. GPT-5.6 Sol is the tier those settings were built for, and the shape of the work follows from the limits: a 1,050,000-token window means the service, its tests and its recent history all go into one request, so the model is reasoning about the actual system rather than a summary of it. Ask GPT-5.6 Sol to prove a cause before proposing a fix and the deep pass earns its cost; ask it to guess quickly and you are paying frontier rates for a cheap tier's job.
Read the API docs
Long-horizon agentic runs that do not drift
Deep research, asynchronous workflows and agentic tasks that require long runs are OpenAI's stated cases for xhigh, and this generation adds the pieces those runs need: programmatic tool calling, explicit prompt-caching controls and persisted reasoning. With functions, web search, file search and computer use all available, GPT-5.6 Sol is the tier you point at a task that will take many steps and many tool calls, where the failure you are buying protection against is not a wrong token but a plan that quietly falls apart at step thirty.
High-value judgement, where the cheap tier is the expensive choice
There is a class of request where a wrong answer costs more than the whole month's inference bill: a migration plan, a contract review, an architectural commitment, a security finding. On those, tier selection is not a cost decision. GPT-5.6 Sol is the model OpenAI puts at the top of this family — reasoning rated Highest, and the target of the bare `gpt-5.6` alias, which is a fair signal of where OpenAI expects the default to sit. Route the volume to a cheaper sibling and keep GPT-5.6 Sol for the calls you would want a senior engineer to make.
Pricing
Credit-based — 1 credit = $0.001 USD. Pay only for completed generations.
| Category | Unit | Price |
|---|---|---|
| Token pricing | ||
| Input | 1M tokens | $4 |
| Output | 1M tokens | $24 |
Why reAPI
20% below the published rate
OpenAI publishes a per-million-token rate for GPT-5.6 Sol input and output. On reAPI, GPT-5.6 Sol bills 20% below both — the same discount on each dimension, so an existing cost model scales down by a single figure. No subscription underneath it, no minimum commitment, pay-as-you-go in USD against your gateway balance. The exact numbers are in the pricing table on this page.
OpenAI-compatible drop-in
GPT-5.6 Sol is served from a standard `/v1/chat/completions` endpoint. If your code already speaks that shape, adopting GPT-5.6 Sol is a base URL, a key and a model string — the same SDKs work once the base URL points at the gateway. No SDK swap, no bespoke client.
One key across the whole ladder
The same api.reapi.ai key that calls GPT-5.6 Sol calls its cheaper siblings, the Claude and Gemini families, and the open-weight tiers. That is what makes a frontier tier affordable in practice: send the routine turns somewhere cheap and escalate to GPT-5.6 Sol by changing a model string, not by signing up with a second vendor.
GPT-5.6 Sol vs Claude Opus 5
Two frontier tiers, the same order of magnitude on price, and genuinely different contracts. GPT-5.6 Sol gives you a six-rung effort ladder that includes turning reasoning off entirely, image input, and a million-token window with a 128K output ceiling. Claude Opus 5 reasons by default, refuses the sampling parameters outright, and takes PDF rather than images. Neither is the general answer; the rows below are the ones that decide it for a given route.
Capability
GPT-5.6 Sol on reAPI
Claude Opus 5
Vendor positioning
Frontier model for complex professional work; reasoning rated Highest in its family
For complex agentic coding and enterprise work
Context and output limits
1,050,000-token context, 128,000-token maximum output
1M-token context, 128k maximum output
Reasoning default
Effort defaults to medium, and none turns reasoning off entirely
Thinking on by default; can be disabled only at effort high or lower
Effort ladder
Six rungs — none, low, medium, high, xhigh, max
Five rungs from low through max, defaulting to high
Sampling parameters
Reasoning effort is the intended control on this family
Sampling parameters removed — sending them returns an error
Non-text input
Images, at their original dimensions
Images and PDF
Comparison reflects behavior documented by each vendor at the time of writing. Rates are described as relationships rather than amounts; the live numbers for GPT-5.6 Sol are in the pricing table above.
Ship GPT-5.6 Sol in three steps
- step 01
Create an account and key on api.reapi.ai
Sign up at api.reapi.ai, open the console and generate an API key. That one key reaches GPT-5.6 Sol and every other model on the gateway, billed from a single balance.
Open - step 02
Point your client at the gateway
Set your base URL to api.reapi.ai and your key to the one you just created. Any client that already speaks OpenAI Chat Completions works unchanged — no SDK swap is needed to reach GPT-5.6 Sol.
Open - step 03
Send `gpt-5.6-sol` as the model
Set the model field to `gpt-5.6-sol` — with the dots — and post your messages. Turn on streaming, since a deep pass can be slow to first token, and set reasoning effort deliberately: the family default is medium, and this tier is worth paying for at high and above.
Open
Frequently asked questions
Common questions about this model.
GPT-5.6 Sol is billed pay-as-you-go in USD per token against your api.reapi.ai balance, with separate input and output rates and no subscription. Both sit 20% below OpenAI's published per-token rate. Current numbers are in the pricing table on this page.
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