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Gpt Image 2.5 Sunburst vs Flux 1.1 Pro Ultra: Which AI Model Should You Choose?

Pricing, context windows, latency, capabilities, and a one-line code switch — everything you need to pick the right model.

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Image Generation
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Image Generation
Verdict

Gpt Image 2.5 Sunburst and Flux 1.1 Pro Ultra are closely matched on pricing and context. The right choice depends on your specific workload — see the table below for the full breakdown.

Side-by-side specs

SpecGpt Image 2.5 SunburstFlux 1.1 Pro Ultra
ProviderReplicateReplicate
CategoryImage GenerationImage Generation
Input cost / 1M tokensn/an/a
Output cost / 1M tokensn/an/a
Context window——
Max output tokens——
Avg. latency—15.0s
Featured—Yes
NewYes—
Capabilities
text
jpg
png

Pricing example

A typical chat workload of 100,000 input tokens plus 50,000 output tokens.

Gpt Image 2.5 Sunburst
n/a

100K in × n/a + 50K out × n/a

Flux 1.1 Pro Ultra
n/a

100K in × n/a + 50K out × n/a

Switch in one line

Both models live behind Railwail's OpenAI-compatible endpoint. Replace the model string and you are done.

JavaScript / TypeScript
import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.RAILWAIL_API_KEY,
  baseURL: "https://railwail.com/v1",
});

// Before — using Gpt Image 2.5 Sunburst
let r = await client.chat.completions.create({
  model: "openai/gpt-image-2.5-sunburst",
  messages: [{ role: "user", content: "Hello" }],
});

// After — switched to Flux 1.1 Pro Ultra
r = await client.chat.completions.create({
  model: "black-forest-labs/flux-1.1-pro-ultra",
  messages: [{ role: "user", content: "Hello" }],
});
Python
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["RAILWAIL_API_KEY"],
    base_url="https://railwail.com/v1",
)

# Before — using Gpt Image 2.5 Sunburst
r = client.chat.completions.create(
    model="openai/gpt-image-2.5-sunburst",
    messages=[{"role": "user", "content": "Hello"}],
)

# After — switched to Flux 1.1 Pro Ultra
r = client.chat.completions.create(
    model="black-forest-labs/flux-1.1-pro-ultra",
    messages=[{"role": "user", "content": "Hello"}],
)
cURL
# Before — using Gpt Image 2.5 Sunburst
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-image-2.5-sunburst",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

# After — switched to Flux 1.1 Pro Ultra
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "black-forest-labs/flux-1.1-pro-ultra",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

Which one wins for...

Quick verdicts derived from public specs. Always validate on your own workload.

Coding
Gpt Image 2.5 Sunburst

Higher coding category match or larger context wins.

Writing
Gpt Image 2.5 Sunburst

Bigger context window helps maintain long-form coherence.

Long documents
Gpt Image 2.5 Sunburst

The larger context window is the deciding factor.

Vision
Tie

Multimodal/vision support is required for image inputs.

Real-time chat
Flux 1.1 Pro Ultra

Lower average latency wins for interactive UX.

Cost-sensitive
Tie

The model with the lower input-token price wins.

Frequently asked questions

Which is cheaper, Gpt Image 2.5 Sunburst or Flux 1.1 Pro Ultra?
Gpt Image 2.5 Sunburst and Flux 1.1 Pro Ultra cannot be compared on per-token price: at least one of them has no per-token price listed (it is priced per run or not yet priced). See each model page for its current price.
Which has more context, Gpt Image 2.5 Sunburst or Flux 1.1 Pro Ultra?
Gpt Image 2.5 Sunburst and Flux 1.1 Pro Ultra have similar context windows (— vs —).
Is Gpt Image 2.5 Sunburst better than Flux 1.1 Pro Ultra for coding?
For coding-heavy workloads we lean toward Gpt Image 2.5 Sunburst on this comparison — it scores higher on the relevant heuristics (category, tags, or context window). Both models are usable for code via Railwail's OpenAI-compatible endpoint, so the safest path is to A/B test on your own prompts.
Can I use both Gpt Image 2.5 Sunburst and Flux 1.1 Pro Ultra via Railwail?
Yes. Both Gpt Image 2.5 Sunburst and Flux 1.1 Pro Ultra are accessible through a single Railwail API key and the OpenAI-compatible /v1/chat/completions endpoint. You only change the "model" parameter to switch between them — no SDK swap, no separate billing.
How do I switch from Gpt Image 2.5 Sunburst to Flux 1.1 Pro Ultra?
Replace the model identifier "openai/gpt-image-2.5-sunburst" with "black-forest-labs/flux-1.1-pro-ultra" in your request payload. Everything else — API key, base URL, request shape — stays the same. See the code example on this page for the exact one-line change.

Try Gpt Image 2.5 Sunburst and Flux 1.1 Pro Ultra side by side

One API key, one endpoint, both models. Start free — no credit card required.

Get Started FreeView Gpt Image 2.5 SunburstView Flux 1.1 Pro Ultra