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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 below OpenAI's published rate on both input and output.

Highlights
Reasoning effort tiers · tools & JSON mode
Best for
Long-form analysis, agent workflows
Input
Chat messages (OpenAI-compatible)
Output
Text, streaming optional
GPT-5.6 Terra

Ask GPT-5.6 Terra

Start with the prompt in the composer or choose an example.

Enter to send · Shift+Enter for a new line

Pricing

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

First test cost
$0.011211.2 credits

One 1K-token prompt with a 1K-token answer at the cheapest tier.

Testing budget guide
Add credits
$10
≈ 892 tests
$50
≈ 4464 tests
$100
≈ 8928 tests
Category
Token pricing
Long context · prompts over 272K tokens
Input
$1.6
Price · 1M tokens
$3.2
Price · 1M tokens
Output
$9.6
Price · 1M tokens
$14.5
Price · 1M tokens

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 /api/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.

Why reAPI for GPT-5.6 Terra

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 below both, and the rates on this page are updated live. No subscription underneath it, no minimum commitment, pay-as-you-go from your reAPI 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 `/api/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 reapi.ai. No SDK swap, no bespoke client.

One key across the whole ladder

The same reAPI 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

  1. step 01

    Create a reAPI API key

    Sign in to reAPI and create a key under API keys. That one key reaches GPT-5.6 Terra and every other model on the platform, billed from a single balance.

    Open
  2. step 02

    Point your client at reapi.ai

    Set your base URL to reapi.ai's API 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
  3. 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://reapi.ai/api/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.6-terra",
    "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 per token from your reAPI balance, with separate input and output rates and no subscription. Both sit below OpenAI's published per-token rate. Current numbers are in the pricing table on this page.

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