How to Use GPT 5.6 Sol Fast Mode via the Moyi API API | Moyi API

Quick Answer

You enable GPT 5.6 Sol Fast mode through Moyi API the exact same way you would on OpenAI's API — add "service_tier": "fast" to your request body. Point your OpenAI SDK at Moyi API's endpoint (https://api.moyi-api.com/v1), use your sk-... key, and Fast mode runs up to 2.5x faster at ~2x the token rate. This guide covers Chat Completions, the Responses API, curl, Python, Node.js, setting a project default, verifying Fast mode is active, and the gotchas that trip people up.

Model ID, list price and curl examples: GPT-5.6 Sol API.

Why Use Fast Mode Through Moyi API

OpenAI renamed Priority processing to Fast mode on July 30, 2026. For GPT-5.6 Sol it is up to 2.5x faster than Standard, with steadier latency, for 2x the Standard token price. On service levels, OpenAI says Fast mode for GPT-5.6 and earlier gets the same SLA treatment as Scale Tier, while Fast mode for GPT-6 Astra has no latency SLA.

The reason to route it through Moyi API rather than calling OpenAI directly:

• One key for everything. The same sk-... key gives you gpt-5.6-sol (Fast or Standard), deepseek-v4-flash, claude-opus-4-8, gemini-3.5-flash, and 500+ more providers — no per-vendor accounts, no per-vendor billing.
• Discounted rates. Moyi API's pricing is typically well under OpenAI list prices, so even Fast mode's 2x premium lands at a lower absolute number than direct billing.
• Payment without an international card. Alipay and WeChat Pay are supported, which matters if you're accessing from China.
• Per-request routing. Because it's OpenAI-compatible, you can flip between gpt-5.6-sol Fast mode and a cheap model like deepseek-v4-flash on the same code path, per request.

Prerequisites

1. A Moyi API account.
2. Top up a small balance (Alipay, WeChat Pay, or bank transfer).
3. An API key from the dashboard — it starts with sk-.
4. An OpenAI SDK in your language (Python openai, Node openai, or plain curl).

That's it. No separate "Fast mode subscription" to buy, no special access request — the capability is on the account.

Step 1: Verify GPT 5.6 Sol Is Available

Confirm the model is on your account by listing models:

curl https://api.moyi-api.com/v1/models \
  -H "Authorization: Bearer sk-xxxxxx"

You should see gpt-5.6-sol in the returned list, alongside gpt-5.6-terra, gpt-5.6-luna, deepseek-v4-flash, claude-fable-5, and the rest. If gpt-5.6-sol is missing, refresh your model list in the dashboard — newly added providers propagate within minutes.

Step 2: Send a Fast Mode Request

The magic is one field: "service_tier": "fast".

curl (Responses API)

curl https://api.moyi-api.com/v1/responses \
  -H "Authorization: Bearer sk-xxxxxx" \
  -H "content-type: application/json" \
  -d '{
    "model": "gpt-5.6-sol",
    "input": "Write a Fast mode health check for our agent pipeline.",
    "service_tier": "fast"
  }'

curl (Chat Completions)

curl https://api.moyi-api.com/v1/chat/completions \
  -H "Authorization: Bearer sk-xxxxxx" \
  -H "content-type: application/json" \
  -d '{
    "model": "gpt-5.6-sol",
    "messages": [{"role": "user", "content": "Summarize Fast mode in one sentence."}],
    "service_tier": "fast"
  }'

Python (openai SDK)

from openai import OpenAI

client = OpenAI(
    api_key="sk-xxxxxx",
    base_url="https://api.moyi-api.com/v1",
)

# Responses API
resp = client.responses.create(
    model="gpt-5.6-sol",
    input="Explain the Fast mode downgrade caveat.",
    service_tier="fast",
)
print(resp.output_text)

# Chat Completions
chat = client.chat.completions.create(
    model="gpt-5.6-sol",
    messages=[{"role": "user", "content": "Give me a Fast mode activation checklist."}],
    service_tier="fast",
)
print(chat.choices[0].message.content)

Node.js

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: "sk-xxxxxx",
  baseURL: "https://api.moyi-api.com/v1",
});

const resp = await client.responses.create({
  model: "gpt-5.6-sol",
  input: "Draft a latency budget for a coding assistant.",
  service_tier: "fast",
});
console.log(resp.output_text);

Note the two differences from calling OpenAI directly: the base_url/baseURL is https://api.moyi-api.com/v1, and the key is sk-.... Your service_tier value works the same way: the gateway accepts "fast" or "priority" and forwards it upstream as "priority". On Moyi API, Fast mode works on gpt-5.6-sol, gpt-5.6-terra and gpt-6-astra; on other models the request runs and is billed at Standard.

Step 3: Set a Project Default (Optional)

If you want every request from a project to use Fast mode without editing each call, set the default service tier at the project level.

• Through OpenAI's platform: set the project default service tier to Fast/Priority in the Project settings. Requests from that project carry it automatically.
• Through Moyi API: OpenAI project defaults don't apply, so set service_tier on each request, or in your client's config (for Codex CLI, service_tier = "fast" in ~/.codex/config.toml).

Per-request service_tier always overrides the project default, so you can keep a global default of Fast mode and carve out exceptions (batch jobs, evals) with an explicit "service_tier": "standard" (or just omit it).

Step 4: Verify Fast Mode Is Actually Active

Fast mode is best-effort under extreme load, so verify it — don't assume it. The response object echoes the tier that was applied.

resp = client.responses.create(
    model="gpt-5.6-sol",
    input="ping",
    service_tier="fast",
)
print(resp.service_tier)  # "fast" in most cases

Two things to know about the response field:

• For GPT-5.6 and earlier models, the response may still return "priority" even when you sent "fast". This is expected — the field names in responses weren't all updated. It still means Fast mode was applied.
• If traffic spikes past 1M TPM with >50% growth in 15 minutes, OpenAI may downgrade some Fast requests to Standard. The response then shows service_tier: "default". Alert on this. If you see "default", that request was billed at Standard and ran at Standard priority.

if resp.service_tier == "default":
    # Fast mode was downgraded — adjust routing or investigate traffic spike
    log_warning("Fast mode downgraded to Standard")

Step 5: Route Fast Mode + Cheap Models Together

The whole point of a gateway is that you don't pick one model. Here's a realistic tiered setup on one key:

from openai import OpenAI

client = OpenAI(
    api_key="sk-xxxxxx",
    base_url="https://api.moyi-api.com/v1",
)

def run_interactive(prompt: str):
    """Human is waiting — flagship + fast lane."""
    return client.responses.create(
        model="gpt-5.6-sol",
        input=prompt,
        service_tier="fast",
    )

def run_background(prompt: str):
    """No human waiting — cheap executor."""
    return client.chat.completions.create(
        model="deepseek-v4-flash",
        messages=[{"role": "user", "content": prompt}],
    )

Same client, same key, two different economics. The interactive path gets GPT-5.6 Sol with Fast mode; the background path gets DeepSeek V4 Flash at $0.14/$0.28. This is the pattern that makes Fast mode's 2x premium rational — you pay it only where a human is actually waiting.

Common Gotchas

1. Wrong base URL

The most common failure. OpenAI SDKs need the /v1 suffix for Moyi API: https://api.moyi-api.com/v1. If you use the bare https://api.moyi-api.com, paths will 404. (Anthropic SDKs are the opposite — they use the bare base URL.)

2. Fast mode on a non-GPT model

service_tier: "fast" only applies to GPT models that support Fast mode. OpenAI lists Fast prices for the GPT-6 line, the GPT-5.6 family and older GPT-5.x models; on Moyi API, Fast mode works on gpt-5.6-sol, gpt-5.6-terra and gpt-6-astra, and on other models the request runs and is billed at Standard. Sending it for Claude or DeepSeek is ignored or rejected depending on the endpoint. Only pass it on GPT routes.

3. Batch workloads getting downgraded

Fast mode is for interactive traffic. If you point a batch job or eval harness at Fast mode, you risk automatic downgrade to Standard (and Standard billing). Use Fast mode for the interactive path only.

4. Legacy value still works

If your code already sends service_tier: "priority" (the pre-July-30 name), it still works and behaves identically. No urgent migration needed — but switch to "fast" when you touch the code for clarity.

Pricing Recap

These are OpenAI list prices; Sol's $4 / $20 is a promotional price, available at least through November 21, 2026 (see OpenAI's pricing page). Through Moyi API, a request processed in Fast mode is billed at 2x the Standard list price with your account discount unchanged, and it is marked with a Fast hint in your billing history (see Billing). If the upstream processes it at Standard speed, it is billed at Standard.

Bottom Line

GPT 5.6 Sol Fast mode via Moyi API is a five-minute setup: point your OpenAI SDK at https://api.moyi-api.com/v1, use your sk- key, and pass service_tier: "fast". You get the 2.5x fast lane on the same key that also serves Claude, Gemini, DeepSeek, and Kimi — so you can afford Fast mode precisely because the rest of your traffic runs on cheap models. One key, one dashboard, one bill, and Fast mode exactly where it pays off.

Ready to try it? Sign up at Moyi API, top up, generate a key, and your first Fast mode request will be flying in under two minutes. For more endpoint details, see the API integration docs.

FAQ

How do I enable Fast mode on Moyi API?

Add "service_tier": "fast" to your request body on the OpenAI-compatible endpoint (https://api.moyi-api.com/v1). The legacy value "priority" also works.

Is Fast mode more expensive?

Yes, exactly 2x the Standard token rate. At OpenAI list price GPT-5.6 Sol is $4 / $20 per million input / output tokens at Standard (promotional, at least through November 21, 2026) and $8 / $40 in Fast mode. On Moyi API, Fast requests are billed at 2x the Standard list price with your account discount unchanged.

Does Fast mode work on Chat Completions and Responses API?

Yes, both. The example above covers chat.completions.create and responses.create.

How do I know Fast mode is active?

Check the service_tier field in the response. If it returns "fast" (or the legacy "priority" for GPT-5.6-era models), Fast mode was applied. If it returns "default", the request was downgraded to Standard.

Can I set Fast mode as the default for my project?

On OpenAI directly, yes: set a project-level default service tier, and a per-request service_tier overrides it. Through Moyi API, set service_tier on each request or in your client's config, since OpenAI project defaults don't apply.

Do I need an international credit card?

No. Moyi API supports Alipay and WeChat Pay, so you can use GPT-5.6 Sol Fast mode from China without an overseas card or VPN.