What model ID should you use for gpt-5.5?

Use the exact model ID `gpt-5.5` in the request. Keep the ID unchanged when comparing results across routing tests.

How do you call gpt-5.5 through MixRoute?

The model record lists OpenAI-compatible access via POST /v1/chat/completions with model ID gpt-5.5.

What is the max output length for gpt-5.5?

gpt-5.5 supports up to 128000 output tokens per request. Plan your prompts to stay within this limit, and use the max_tokens or max_completion_tokens parameter to control output length.

Which input modalities are listed for gpt-5.5?

The current model record lists no modality list. Confirm the current record before relying on a specific input type in production.

How should you evaluate gpt-5.5 before production?

Run representative quality, latency, and cost tests with `gpt-5.5` before moving production traffic.

How do you get a cache hit on gpt-5.5?

To get a cache hit on gpt-5.5, send requests with identical prompt prefixes. The cache is keyed by the beginning of your prompt; as long as the prefix matches a previous request, subsequent calls benefit from the lower cached rate. Keep system messages and initial context consistent across calls for best results.

Does gpt-5.5 charge more for long inputs?

Yes — gpt-5.5 uses tiered pricing for long-context requests. Inputs exceeding a token threshold are billed at a higher per-token rate. Check the model page for the exact threshold and long-context pricing tier applicable to gpt-5.5.

Model detail

GPT-5.5

Provided by OpenAI

Pay-as-you-go Dynamic pricing 2 tiers

GPT-5.5 is OpenAI’s frontier model designed for complex professional workloads, building on GPT-5.4 with stronger reasoning, higher reliability, and improved token efficiency on hard tasks. It features a 1M+ token context window (922K input, 128K output) with support for text and image inputs, enabling large-scale reasoning, coding, and multimodal workflows within a single system.

Model specs

Model ID: gpt-5.5

Context length: 1.05M
Max output: 128K
I/O modalities
Released: 2026-04

API endpoints

One MixRoute gateway, OpenAI-compatible

OpenAI-compatible /v1/chat/completions POST

Tiered pricing

Unit: /1M Tokens

Tier	Input /1M Tokens	Output /1M Tokens	Cache read /1M Tokens
standard Length ≤ 272K	$5.0000	$30.0000	$0.5000
long_context Length > 272K	$10.0000	$45.0000	$1.0000

Selection summary

Quickly judge whether it fits your workload

What is this model good for?

Flagship model for complex reasoning and agentic workflows

GPT-5.5: GPT-5.5 is a flagship model for the most complex professional work. Learn more in our GPT-5.5 model guidance. Reasoning.effort supports: none, low, medium (default), high and xhigh. 1,050,000-token context.

What should you check before using it?

1,050,000 context, 128,000 output

OpenAI model. Supports tool calling, structured outputs, function calling. Knowledge cutoff: 2025-12-01.

Why use it through MixRoute?

Swap the base URL, keep the GPT-5.5 client

MixRoute serves GPT-5.5 on the OpenAI-compatible endpoint /v1/chat/completions; point your existing client at https://api.mixroute.ai/v1 with the model ID gpt-5.5 and re-run your integration tests.

Capabilities & compatibility

Unconfirmed capabilities stay "Unknown," no guesses

Tool calling

GPT-5.5 supports function and tool calls.

EX Send a tools definition; the response returns tool_calls to execute and feed results back.

Structured output

GPT-5.5 can produce JSON-formatted output on demand.

EX response_format: { type: "json_schema" } forces valid JSON output.

Streaming

GPT-5.5 supports streamed responses.

EX stream: true streams tokens incrementally, so chat UIs render as they arrive.

Prompt caching

GPT-5.5 supports prompt caching under supported routing conditions.

EX Keep the system prompt and tool definitions at the start of the request; repeated prefixes are automatically billed at the cache-read rate.

Vision input

GPT-5.5 can process image inputs alongside text.

EX Pass a base64-encoded image in a image_url content part alongside text messages.

OpenAI SDK

Call GPT-5.5 through MixRoute's OpenAI-compatible endpoint.

EX Change base_url to https://api.mixroute.ai/v1; everything else follows the OpenAI style.

Token cost estimator

Live estimate from this page's pricing, not an actual bill

Input tokens Max per request 1.05M

Output tokens Max per request 128K

Requests / month

Cache hit rate 0%

Share of the same prefix read repeatedly, up to 100%

FAQ

Before moving production traffic to gpt-5.5, verify pricing, rate limits, and output quality on your specific tasks. Run a pilot with a representative sample of your workload, check latency at your expected concurrency, and confirm that the model handles your edge cases reliably.

Get started

01

Create an API key

Generate a key in the Console; one key calls every model.
02

Set the base URL

Fully OpenAI SDK-compatible; just swap the URL to connect.

https://api.mixroute.ai/v1
03

Specify the model ID

In the request's model field, enter:

gpt-5.5

Create an API key

New users get $5 in free credits

Test this model and alternate routes with the same request format

Start from a real workload, then let quality, total cost, and failure conditions decide whether to send production traffic.

Create an API key View integration docs