Claude Sonnet 5 shipped alongside the new model generation and took the familiar mid-tier spot: faster and cheaper than the flagship, strong enough for most production workloads.
The price, in numbers
claude-sonnet-5 costs $0.3 per million input tokens and $0.3 per million output tokens. The flagship claude-opus-5 costs the same.
At scale those cents add up, but picking a model on a gap that small is rarely the right call. What matters is whether Sonnet handles your task without Opus.
Where Sonnet 5 matches Opus
- everyday agentic coding: multi-file edits, tests, refactors that follow a clear plan
- API integrations, client code generation from docs
- answering over long context: PR review, ticket summarization, questions about a codebase
- routine agent steps where the task is already well specified
Sonnet 5 holds long context and follows instructions cleanly. That covers most pipelines.
Where Opus earns its keep
The flagship pays off when a task can't be broken into clear steps ahead of time: an unfamiliar architecture that needs to be understood as a whole, a race condition with no working hypothesis, planning under a pile of conflicting constraints. Opus reasons deeper there,, and at the same price there is nothing to weigh against it.
If you're not sure, start with Sonnet. It either solves the task or fails visibly, and switching to Opus after that costs one extra call.
A working example
Anthropic Messages API:
from anthropic import Anthropic
client = Anthropic(
api_key="sk_cdx_your_key_here",
base_url="https://api.claudexia.tech",
)
message = client.messages.create(
model="claude-sonnet-5",
max_tokens=1024,
messages=[{"role": "user", "content": "Split this PR into logical commits."}],
)
print(message.content[0].text)
The same key also works with OpenAI Chat Completions:
from openai import OpenAI
client = OpenAI(api_key="sk_cdx_your_key_here", base_url="https://api.claudexia.tech/v1")
resp = client.chat.completions.create(
model="claude-sonnet-5",
messages=[{"role": "user", "content": "Split this PR into logical commits."}],
)
print(resp.choices[0].message.content)
Both formats run on one endpoint with one key, no need to rebuild infrastructure around a specific SDK.
Sonnet 5 versus Sonnet 4.6
Sonnet 4.6 has been removed from the Claudexia catalog, so anyone still on it has to move: set model to claude-sonnet-5, same price. If your prompts were tuned for 4.6, run your typical requests on Sonnet 5 and compare against your own metric. Details in moving off Sonnet 4.6.
Checking it against your own numbers
Generic advice maps poorly onto a real budget. The site has a calculator: plug in your input and output volumes, compare models on your actual traffic. Per-key stats and budgets, set separately per user and per team, show who's spending what without reconciling a spreadsheet at month end.
In short
Sonnet 5 covers most production traffic at $0.3 per million tokens. Opus earns its place on tasks where the starting point isn't obvious. They cost the same, so decide by the task, not the bill.