GPT or Claude in 2026: comparing price, index, caching and API format

GPT or Claude — there's no answer "in general," but there is one for a specific task and budget. Below is a comparison of the lineups on what can be checked: prices as of October 7, 2026, intelligence index, how caching works, API format and tool support. At the end, a method for choosing a model on your own data in an hour.

The Claude and GPT lineups on Zukko

Prices as of October 7, 2026, USD per 1M tokens. The last column is 1,000 requests at 2,000 input and 500 output tokens: 2 × input + 0.5 × output.

The intelligence index is the Artificial Analysis Intelligence Index in the Zukko catalog. A dash in the write column means GPT cache writes aren't billed separately. All models in the table have a 1M-token context; only GPT-6 Luna and GPT-5.6 Luna don't accept image input. For the current list and prices, call GET https://api.zukko.pro/v1/models or open the Models page in the dashboard.

GPT or Claude: price and index

What the table shows:

• Top tier. Claude Opus 5.5 has the highest index in the catalog (58) at 0.8 / 4. GPT-6 Astra has 53 and is a bit cheaper: 0.62 / 3.05.
• Mid tier. GPT-6.1 Sol scores 52 at 0.27 / 1.32. Claude Sonnet 5 costs 0.4 / 2, with no index data.
• Budget tier. GPT has more options here: 6 Sol, 5.6 Terra, both Lunas (more on the lineup in the article GPT-6 via API↗). The cheapest Claude model in the table is Sonnet 5.
• Fable 5.1, at index 53, is far more expensive than everything else — use it only if testing on your tasks justifies it.

The index is an average benchmark score. A gap of a few points doesn't tell you which model will handle your specific task better.

Caching: the key difference for agents and long chats

The models bill prompt caching differently, and for agents this often matters more than the input price.

Claude:

• both cache reads and writes are billed: a read costs about a tenth of the input price (0.05 vs 0.4 for Sonnet 5), a write costs more than input (0.5);
• the discount only works in the Anthropic format (/v1/messages, Anthropic SDK, Claude Code). In the OpenAI format (/v1/chat/completions) all Claude input is billed at the input price.

GPT:

• the gateway only sees cache reads (prompt_tokens_details.cached_tokens); writes aren't billed separately — the first request is billed at the input price;
• caching shows up in both formats.

Example agent session: 2M cache-read tokens, 200K cache write, 50K fresh input, 100K output. GPT has no write line, so those 200K are billed at the input price together with the fresh 50K.

Volumes in millions of tokens, prices as of October 7, 2026. Caveat: models use different tokenizers, so the same text yields different token counts, and the cache hit rate depends on the client. This is an example calculation, not a forecast of your bill. More on caching in the key limits and cache docs↗ and the article on cache reads and writes↗.

API format

Through Zukko any model can be called in either format — the gateway converts the request. In practice:

• if your code already uses the OpenAI SDK, you can compare Claude and GPT by changing only model;
• if you use Claude with a large repeated context, switch to the Anthropic format for caching.

Claude with caching through the official Anthropic SDK:

import os
from anthropic import Anthropic

client = Anthropic(base_url="https://api.zukko.pro", api_key=os.environ["ZUKKO_API_KEY"])
LONG_INSTRUCTIONS = open("instructions.md", encoding="utf-8").read()

msg = client.messages.create(
    model="claude-sonnet-5",
    max_tokens=1024,
    system=[{"type": "text", "text": LONG_INSTRUCTIONS, "cache_control": {"type": "ephemeral"}}],
    messages=[{"role": "user", "content": "Check this contract against the checklist."}],
)
print(msg.content[0].text)
print("cache read:", msg.usage.cache_read_input_tokens, "written:", msg.usage.cache_creation_input_tokens)

The Anthropic SDK address has no /v1 — the SDK adds it. For the OpenAI SDK it's https://api.zukko.pro/v1. How to choose the format is covered in the docs↗.

Tools

• Claude Code uses the Anthropic format — the natural choice for Claude models.
• Codex goes through the Responses API: GPT and Claude models work.
• Cline, Kilo Code, Continue, Zed connect as OpenAI-compatible: both lineups are available, but Claude gets no cache discount there.
• Roo Code with the Anthropic provider and OpenCode with the anthropic provider use the Anthropic format and suit Claude.

How to choose by testing on your own tasks

1. Collect 30–100 real examples with reference answers.
2. Take one or two models from each lineup in your price range, for example claude-sonnet-5 and gpt-6.1-sol, plus claude-opus-5-5 as the upper bar.
3. Use the same prompt and answer format.
4. Score blind: automatically if the answer can be checked by code, or manually on a scale without the model name.
5. Compute cost from usage including caching, and pick the cheapest model that clears your bar.

import os
from openai import OpenAI

client = OpenAI(base_url="https://api.zukko.pro/v1", api_key=os.environ["OPENAI_API_KEY"])
PRICES = {"claude-sonnet-5": (0.4, 2), "gpt-6.1-sol": (0.27, 1.32)}  # USD per 1M, Oct 7, 2026
CASES = [{"q": "Return the date from the text 'pay by 15.11.2026' as YYYY-MM-DD", "a": "2026-11-15"}]

for model, (p_in, p_out) in PRICES.items():
    ok, cost = 0, 0.0
    for case in CASES:
        r = client.chat.completions.create(model=model, messages=[{"role": "user", "content": case["q"]}])
        ok += r.choices[0].message.content.strip() == case["a"]
        cost += (r.usage.prompt_tokens * p_in + r.usage.completion_tokens * p_out) / 1_000_000
    print(f"{model}: {ok}/{len(CASES)}, ${cost:.5f}")

The script ignores caching — for short independent requests that's close to reality. For agents, compare the actual charges in the dashboard.

One key covers all models for this comparison — create it in the dashboard↗.

FAQ

Which is cheaper, GPT or Claude?

At prices as of October 7, 2026, GPT models are cheaper: GPT-6.1 Sol (0.27 / 1.32) costs less than Claude Sonnet 5 (0.4 / 2), and GPT-6 Astra (0.62 / 3.05) less than Claude Opus 5.5 (0.8 / 4), on every line including cache reads. For Claude the total also depends on the API format: outside the Anthropic format there's no cache discount — run the formula on your own profile.

Which model is stronger?

By the catalog's intelligence index, Claude Opus 5.5 is the highest at 58. GPT-6 Astra has 53 and GPT-6.1 Sol 52. The index is a benchmark average; test models on real examples for your task.

Can I switch between GPT and Claude without rewriting code?

Yes. Any model can be called in the OpenAI or Anthropic format; only model changes in your code. Keep in mind Claude gets the cache discount only in the Anthropic format.

Why is Claude more expensive in the OpenAI format?

In the OpenAI format the gateway can't see which part of Claude's input came from cache, so all input is billed at the input price. GPT has no such difference.