What is the GPT-5.6 Terra context window?

1,050,000 tokens, with a maximum output of 128,000 tokens — identical to the other tiers in the GPT-5.6 family. Moving between tiers changes reasoning depth and price, not capacity.

What reasoning effort should I use on GPT-5.6 Terra?

Start with the default. Medium is what GPT-5.6 Terra uses when the field is omitted, and OpenAI calls it the well-balanced point on the curve of latency, performance and cost, naming agentic coding, research and delegated long-horizon work as its cases. Then sweep: low for speed on planning-shaped work, high when a route needs complex debugging or deep planning.

What reasoning effort levels does GPT-5.6 Terra accept?

GPT-5.6 Terra accepts six: none, low, medium, high, xhigh and max. There is no minimal on this family. Each rung is genuinely distinct rather than an alias for its neighbour, so a middle setting really does buy a middle cost.

Does GPT-5.6 Terra read images?

Yes. Input is text and image, output is text. This generation accepts images at their original dimensions with original or automatic detail, so no resizing step is needed before a screenshot goes in.

What is the GPT-5.6 Terra knowledge cutoff?

OpenAI lists February 16, 2026 for the whole GPT-5.6 family. For anything more recent, give GPT-5.6 Terra web search or put the material in the request.

Which endpoint and model string does GPT-5.6 Terra use on reAPI?

An OpenAI-compatible `/v1/chat/completions` endpoint on api.reapi.ai, with `gpt-5.6-terra` as the model string. OpenAI notes that its reasoning models work better on the newer Responses API while Chat Completions remains supported — the family's changelog lists both endpoints.

When should I move up to GPT-5.6 Sol?

When a route wants the top of the effort ladder every time. If your evals keep preferring xhigh or max, you are paying this tier for depth it was not priced for, and the frontier sibling is the better buy. Everything else — the window, the output ceiling, the tools, the endpoint — is the same, so the move is a model string. The versus table on this page compares them row by row.

Is GPT-5.6 Terra free or paid?

Paid. Usage is billed pay-as-you-go in USD from your api.reapi.ai token balance, based on input, output, and any applicable cache-token rates. See the live per-1M-token rates in the pricing table on this page; failed requests are not charged.

Does GPT-5.6 Terra require a monthly subscription?

No. There is no monthly subscription. Add funds to your api.reapi.ai token balance and pay in USD only for the input, output, and any applicable cache tokens each request uses. The live per-1M-token rates are in the pricing table on this page.

How do I get a GPT-5.6 Terra API key?

Sign up at api.reapi.ai and create a key under API Keys, then pass it as a Bearer token in the Authorization header. Chat keys and their token balance are separate from the reapi.ai image and video gateway.

GPT-5.6 Terra — the Balanced Tier at OpenAI's Default Effort

GPT-5.6 Terra is the tier OpenAI positions between intelligence and cost, and it lands exactly where the family's default reasoning effort sits. GPT-5.6 Terra reads a 1,050,000-token context window, returns up to 128,000 tokens, and takes all six effort rungs from off to max. OpenAI rates its reasoning Higher and its speed Fast. On reAPI, GPT-5.6 Terra bills 20% below OpenAI's published rate on both input and output.

GPT-5.6 Terramodelgpt-5.6-terra

GPT-5.6 Terra 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 Terra through the OpenAI-compatible Chat Completions surface.

Open console Token rates

What is the GPT-5.6 Terra API?

GPT-5.6 Terra is the tier of OpenAI's GPT-5.6 family that balances intelligence against cost, served on reAPI through an OpenAI-compatible /v1/chat/completions endpoint. It reads a 1,050,000-token context window, returns up to 128,000 tokens, takes all six reasoning-effort rungs from none to max, and sits exactly at medium — the family's default — with OpenAI rating its reasoning Higher and its speed Fast. Billing is per 1M tokens, with input and output priced separately; reasoning tokens count as output.

What you can build with this model

Real-world workflows and production use cases you can build and ship with this model.

GPT-5.6 Terra implementing a change across a repository with tests

Agentic coding as the everyday setting, not the special case

Read OpenAI's own description of medium effort and it names agentic coding first, then research, spreadsheets and slides, and delegating long-horizon work. That list is the job description of a workhorse, and GPT-5.6 Terra is the tier priced for running it all day rather than for the occasional hard call. The family's limits do not change here: GPT-5.6 Terra still reads 1,050,000 tokens and still returns up to 128,000, so an agent working from a whole repository does not need a different tier just to see its inputs.

Read the API docs

GPT-5.6 Terra producing a structured multi-part deliverable

Structured deliverables, not just answers

Spreadsheets with working formulas, slide decks that follow a convention, runbooks with owners and rollback points: OpenAI puts this class of work under the same default effort setting, and it is where a 128,000-token output ceiling stops being a specification and starts being the reason the deliverable arrives whole. Pair GPT-5.6 Terra with a JSON schema when the artefact is consumed by another system, and with plain prose when a person will read it — the model is the same either way, only the contract changes.

GPT-5.6 Terra being evaluated across several reasoning effort settings

The tier you sweep effort from, in both directions

Because GPT-5.6 Terra starts at the family default, it is the natural place to run the experiment that actually saves money: take a real route, try low, try high, and keep whichever your evals prefer. OpenAI's guidance for low is planning and multi-step decisions at speed, and for high it is complex debugging and deep planning — both reachable on this tier without changing models. When a route turns out to want max effort every time, that is the signal to move it up to the frontier sibling rather than pay for depth this tier was not priced for.

Pricing

Credit-based — 1 credit = $0.001 USD. Pay only for completed generations.

First test cost

$22,000 credits

One sample at the cheapest tier (1M tokens).

Testing budget guide

Add credits

$10

≈ 5 tests

$50

≈ 25 tests

$100

≈ 50 tests

Model	Category	Price
Token pricing	Input	$2 1M tokens
Token pricing	Output	$12 1M tokens

Why reAPI

20% below the published rate

OpenAI publishes a per-million-token rate for GPT-5.6 Terra input and output. On reAPI, GPT-5.6 Terra bills 20% below both — the same discount on each dimension, so an existing estimate scales down by one 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 Terra is served from a standard `/v1/chat/completions` endpoint. If your code already speaks that shape, adopting GPT-5.6 Terra 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 Terra calls the tier below it, the frontier tier above it, the Claude and Gemini families, and the open-weight models. Tiering a workload up or down is a model string rather than a second integration, a second invoice and a second set of credentials.

GPT-5.6 Terra vs GPT-5.6 Sol

Same family, adjacent tiers, and an unusually honest comparison because nearly every specification is shared: identical context window, identical output ceiling, identical effort ladder, identical tools, identical knowledge cutoff, identical endpoint. What differs is the reasoning rating OpenAI gives each, the earlier-generation tier they descend from, and the rate. The question the rows below answer is whether your route needs the top of the ladder often enough to pay for it.

Capability

GPT-5.6 Terra on reAPI

GPT-5.6 Sol

OpenAI's positioning

Balances intelligence and cost

Frontier model for complex professional work

Reasoning rating

Higher — the middle rating in the family

Highest

Earlier-generation lineage

Corresponds to the mini tier of earlier GPT-5 families

Corresponds to the unsuffixed tier, and the gpt-5.6 alias points at it

Rate on reAPI

The middle of the three tiers — see the pricing table above

The highest of the three

Context and output limits

1,050,000-token context, 128,000-token maximum output

Identical — the limits do not change across tiers

Effort ladder and tools

All six rungs, functions, web search, file search, computer use

Identical — the difference is how well the top rungs pay off

Comparison reflects behavior documented on OpenAI's own model pages at the time of writing. Rates are described as relationships rather than amounts; the live numbers for GPT-5.6 Terra are in the pricing table above.

Ship GPT-5.6 Terra 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 Terra 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 Terra.
Open
step 03
Send `gpt-5.6-terra` as the model
Set the model field to `gpt-5.6-terra` — with the dots — and post your messages. You can leave reasoning effort alone to start with, since the family default is medium and that is this tier's intended setting; turn on streaming for anything a person is watching.
Open

docs/api/gpt-5-6-terra

API reference

Drop-in code and the full parameter table.

View full reference

curl https://api.reapi.ai/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.6-terra",
    "group": "default",
    "messages": [
      { "role": "user", "content": "Hello" }
    ],
    "reasoning_effort": "medium",
    "stream": true
  }'

Parameter validation failed

Rejected synchronously with the failing field named. Check enum values, ranges, and URL fields — nothing is charged.

Authentication or balance issue

401 means a missing or invalid Bearer key; 402 means the reserve exceeds your balance. Manage keys and credits in the console.

Content or material rejected

Reference material and outputs pass automated moderation. Rejected tasks fail with a clear error and a full refund.

Task failed or timed out

A task that reaches a failed state is never charged — the reserve refunds automatically. Keep the task id and retry when ready.

Frequently asked questions

Common questions about this model.

GPT-5.6 Terra 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.