Difference between GPT-5.6 Terra and Claude Sonnet 5

Difference between GPT-5.6 Terra and Claude Sonnet 5

GPT-5.6 Terra and Claude Sonnet 5 are the default mid-range models of OpenAI and Anthropic, with a price difference of less than a dollar. So between GPT-5.6 Terra and Claude Sonnet 5which AI should you choose? The article can give you the answer.

If you’re choosing a mid-range model to run an agent that’s active all day, the two best candidates today are the GPT-5.6 Terra and Claude Sonnet 5. Both are the vendor’s default models for free users, both support a context window of about 1 million tokens, and have an input token cost no more than a dollar different from each other.

However, these two models still have their own differences and advantages and disadvantages. The comparison information below can help you make the choice that best suits your needs.

Table of Contents

Compare GPT-5.6 and Claude Sonnet 5

Features	GPT-5.6 Terra	Claude Sonnet 5
Supplier	OpenAI	Anthropic
Location	Mid range	Mid range
Context window	1,050,000 tokens	1M tokens
Maximum output	128K tokens	128K tokens
Price per 1M tokens	$2.00 in / $12.00 out	$3.00 in / $15.00 out
Additional charge for long context	2x input, 1.5x output/272K input tokens	There is no specific data yet; constant at 1M
Outstanding features	Programmatic Tool Calling in Responses API	Mindset adapts to selectable levels of effort
Cyber security posture	Trained in cybersecurity; Defense capabilities based on Trusted Access mechanism	No training in cybersecurity; Protections are enabled by default.
Free level	Default for free and Go users in ChatGPT Work & Codex	Default for free and Pro plan users
API model ID	`gpt-5.6-terra`	`claude-sonnet-5`

When should you choose GPT-5.6 Terra and Claude Sonnet 5?

Use case	Should be used	Why?
Terminal and CLI coding agents	GPT-5.6 Terra	87.4% on Terminal-Bench 2.1 over 80.4% on Sonnet 5.
Fix Repository level error	Either one	The result of 63.4% versus 63.2% on SWE-Bench Pro is considered even; choose based on price and ecosystem.
Huge context (300K+ tokens)	Claude Sonnet 5	There is no additional charge for long contexts, while Terra charges double for input data exceeding 272,000 tokens.
Processing processes rely heavily on tools with high call frequency in each execution.	GPT-5.6 Terra	Programmatic Tool Calling reduces the number of prompt tokens for Clio’s document processing by 38%.
Defensive security and vulnerability prioritization	GPT-5.6 Terra	Scored 91.8% on the Capture-the-Flag exam and accessed through Trusted Access for Cyber.
Products where creating exploit code is a risk	Claude Sonnet 5	Achieved 0.0% development of Firefox exploits and implementation of cybersecurity protections by default.
Workloads requiring high content creation capacity by September 2026	Claude Sonnet 5	The initial preferential price of $2/$10 is lower than Terra’s price of $8 for a monthly cycle of 1 million units imported and 4 million units exported.
Workloads need custom sampling parameters	GPT-5.6 Terra	Sonnet 5 refuses `temperature` , `top_p` and `top_k` with error 400 error.

How to start using GPT-5.6 Terra and Claude Sonnet 5

Field	GPT-5.6 Terra	Claude Sonnet 5
App and user level	ChatGPT Work: Default for Free and Pro users; You can choose Plus, Pro, Business, Enterprise	App Claude: default on Free and Pro; Available for Max, Team, Enterprise
Internal API	OpenAI API, via Responses and Chat Completions	Claude API on Claude Platform
Cloud platform	Amazon Bedrock (GA) and Microsoft Foundry (GA, incl. APAC Data Zone); Not yet available on Google Vertex	Claude Platform on AWS and Claude in Microsoft Foundry
Coding agent	Codex: default for Free and Go, can choose from Plus package or higher	Claude Code
API model ID	`gpt-5.6-terra`	`claude-sonnet-5`