How is GPT-6 Sol different from GPT-6.1 Sol?

Context window, max output and input modalities are the same. Three things differ: 6 Sol accepts reasoning_effort: none and 6.1 Sol does not; 6 Sol's knowledge cutoff is April 20, 2026 against 6.1 Sol's April 30; and OpenAI's reasoning guide lists 6.1 Sol, not 6 Sol, as supporting all_turns. OpenAI says 6.1 Sol comes close to Astra on complex coding and professional work.

Is GPT-6 Sol the same tier as GPT-5.6 Sol?

No, they only share a name. GPT-5.6 Sol is the flagship of the July 2026 GPT-5.6 generation, which OpenAI says roughly corresponds to the unsuffixed tier of earlier GPT-5 families. In GPT-6 the top tier is Astra, and Sol sits in the middle.

How do I choose between Astra, Sol and Luna?

By OpenAI's positioning: Astra is for the most demanding reasoning, coding and professional work; Sol is for complex coding and agentic workflows; Luna is for focused, high-volume tasks. All three have a 1.05M context window, so switching is a change to the model field.

Does the price change for very long inputs?

Yes. A request whose input exceeds 272K tokens is billed entirely at the long-context rate, not just the part above the threshold. The pricing section above lists both tiers.

GPT-6 Sol

Save 85%Official

openai/gpt-6-sol

The mid tier of GPT-6 for complex coding and professional work.

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Live model playground

Try GPT-6 Sol here

Tune the request, see the current price ceiling, and inspect the real response without leaving this model page.

streamchat

1Configure input

Prompt

136 / 20,000

Add images

Maximum estimated cost—

2Live resultExample

GPT-6 Sol

Production-Ready Retries and Timeouts for LLM Calls
Making LLM Calls Resilient with Retries and Timeouts
Reliable LLM Inference: Retries, Timeouts, and Backoff
Hardening Production LLM Calls Against Failures
Designing Robust LLM Calls for Production Systems

Context window: 1.05M
Max output: 128K
Input modalities: TextImage
Output modalities: Text
Capabilities: Vision · Reasoning · Tool calling · Coding · Prompt cache · Paid cache writes
Upstream release: 2026-09-22
RouteMux name: openai/gpt-6-sol

What is GPT-6 Sol

GPT-6 Sol was released by OpenAI on September 22, 2026, the same day as GPT-6 Luna, and sits in the middle of the GPT-6 family, between Astra at the top and Luna for volume work. OpenAI's model page describes it as built to power complex coding and agentic workflows.

The specs: a 1.05M-token context window (up to 922K input), 128K max output, text and image in, text out, and a knowledge cutoff of April 20, 2026. Reasoning effort takes none, low, medium, high, xhigh or max, with medium as the default. Accepting none is the most practical difference from Astra and 6.1 Sol: one deployment can answer simple turns with no reasoning at all and raise effort only for the hard steps. On RouteMux it supports tool calling and explicit prompt caching, and it is reachable over OpenAI Chat Completions, OpenAI Responses and Anthropic Messages.

A week later, on September 29, OpenAI released the upgraded GPT-6.1 Sol. The 6 Sol model page calls it the newer Sol model, and OpenAI's GPT-6 guide features 6.1 Sol rather than 6 Sol. New integrations should generally start on 6.1 Sol. Pin 6 Sol when your requests need reasoning_effort: none, or when your prompts and evals were tuned against it and you want behavior to stay put.

At the standard tier (input up to 272K tokens) it bills $0.3 per 1M input tokens and $1.5 per 1M output tokens, with cached input at $0.03 per 1M tokens. OpenAI lists $2, $10 and $0.2 for the same three.

Before you choose

How is GPT-6 Sol different from GPT-6.1 Sol?: Context window, max output and input modalities are the same. Three things differ: 6 Sol accepts reasoning_effort: none and 6.1 Sol does not; 6 Sol's knowledge cutoff is April 20, 2026 against 6.1 Sol's April 30; and OpenAI's reasoning guide lists 6.1 Sol, not 6 Sol, as supporting all_turns. OpenAI says 6.1 Sol comes close to Astra on complex coding and professional work.
Is GPT-6 Sol the same tier as GPT-5.6 Sol?: No, they only share a name. GPT-5.6 Sol is the flagship of the July 2026 GPT-5.6 generation, which OpenAI says roughly corresponds to the unsuffixed tier of earlier GPT-5 families. In GPT-6 the top tier is Astra, and Sol sits in the middle.
How do I choose between Astra, Sol and Luna?: By OpenAI's positioning: Astra is for the most demanding reasoning, coding and professional work; Sol is for complex coding and agentic workflows; Luna is for focused, high-volume tasks. All three have a 1.05M context window, so switching is a change to the model field.
Does the price change for very long inputs?: Yes. A request whose input exceeds 272K tokens is billed entirely at the long-context rate, not just the part above the threshold. The pricing section above lists both tiers.

GPT-6 Sol API pricing

Prices verified 2026-10-18

InputOfficial $2 / M tokens

$0.3/ M tokensSave 85%

OutputOfficial $10 / M tokens

$1.5/ M tokensSave 85%

Fast $0.6 / $3 /M

Cache read $0.03/M · Cache write $0.375/M

Tier	Input	Cache read	Cache write	Output
Standard ≤272K	$0.3$2−85%	$0.03~~$0.2~~−85%	$0.375~~$2.5~~−85%	$1.5~~$10~~−85%
Standard >272K	$0.6$4−85%	$0.06~~$0.4~~−85%	$0.75$5−85%	$2.25~~$15~~−85%
Priority ≤272K	$0.6$4−85%	$0.06~~$0.4~~−85%	$0.75$5−85%	$3~~$20~~−85%
Priority >272K	$1.2$8−85%	$0.12~~$0.8~~−85%	$1.5~~$10~~−85%	$4.5~~$30~~−85%

Estimate cost

Input tokensOutput tokens

Estimated cost$0.0045

Key capabilities

Reasoning can be switched off: reasoning_effort accepts all six levels from none to max, defaulting to medium. GPT-6 Astra and GPT-6.1 Sol do not accept none.
Complex coding and agent workflows: That is how OpenAI's model page positions GPT-6 Sol.
1.05M context: Up to 922K input tokens and 128K output tokens, with a knowledge cutoff of April 20, 2026.
Vision and tools: Image input, tool calling and explicit prompt caching are supported.

Limited time10% extra Credits on your first top-up — up to 200 bonus Credits

Applies to your first top-up within 72 hours of signing up. Minimum $20, once per account.

Interface and protocols

OpenAI Chat CompletionsStreamingOpenAI ResponsesStreamingAnthropic MessagesStreaming

Use any of these IDs to call this model via the API.

RouteMux nameopenai/gpt-6-sol

Replace the ROUTEMUX_KEY placeholder with your API key. Create one →

from openai import OpenAI

client = OpenAI(
    base_url="https://api.routemux.com/v1",
    api_key="<ROUTEMUX_KEY>",
)

completion = client.chat.completions.create(
    model="openai/gpt-6-sol",
    messages=[{"role": "user", "content": "What is the meaning of life?"}],
)
print(completion.choices[0].message.content)

base_url: https://api.routemux.com/v1

Performance (last 30 days)

5,083 requests · last 30 days

Total usage422.24M

P50 first-token latency6.26s

Avg throughput27 tok/s

Success rate100.0%

Uptime · 24htested via openai_chat

100.00%

Success rate · 60d · from real requests

GPT-6 Sol FAQ

›What is GPT-6 Sol?

The mid tier of GPT-6 for complex coding and professional work.

›How large is the context window of GPT-6 Sol?

GPT-6 Sol supports a context window of up to 1.05M tokens, with up to 128K output tokens per request.

›How much does the GPT-6 Sol API cost?

Through RouteMux, GPT-6 Sol costs $0.3 for input and $1.5 for output (USD per 1M tokens), below the official list price.

›How do I call GPT-6 Sol via API?

GPT-6 Sol is OpenAI-compatible: point your base URL at RouteMux and set the model field to openai/gpt-6-sol — no code changes needed.

›Which input and output modalities does GPT-6 Sol support?

GPT-6 Sol accepts text, image as input and produces text as output.

›When was GPT-6 Sol released?

GPT-6 Sol was released on September 22, 2026.

Sources

Reviewed by the RouteMux team on 2026-10-24

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