Claude Sonnet 5 vs GPT-5.6 Terra
The balanced everyday tier of each family compared across price, context, coding standing, and access.
Updated August 28, 2026 · Independent comparison — Claude Sonnet 5, GPT-5.6 Terra are separate products.
Claude Sonnet 5
Near-Opus quality in Anthropic's balanced tier
Claude Sonnet 5 is Anthropic's best blend of speed and intelligence, reaching near-Opus quality on coding and agentic work. Released June 30, 2026, it carries a 1M-token context window and up to 128K output, with adaptive thinking on by default, the effort ladder from low through max, and high-resolution vision. At $2/$10 per million tokens — a cheaper introductory rate than Sonnet 4.5's $3/$15, with a $0.20 cache-read rate — it is one of the strongest value picks in its tier, and both OpenCode Zen and Cursor list it at $2/$10.
GPT-5.6 Terra
OpenAI's balanced everyday GPT-5.6 tier
GPT-5.6 Terra is the balanced middle tier of OpenAI's GPT-5.6 family, sitting between the flagship Sol and the low-cost Luna. It targets everyday coding, reasoning, and agentic tasks at roughly half of Sol's cost, with a ~1.05M-token context window, 128K max output, and a February 2026 knowledge cutoff. After a July 30, 2026 price cut it costs $2/$12 per million tokens with a $0.20 cache-read rate; requests over the long-context threshold are billed at $4/$18. It is available through the OpenAI API and inside ChatGPT Work and Codex — Free and Go users can reach Terra there, and Plus and above can pick Terra or Luna directly.
Bottom line
The balanced everyday tier of each family compared across price, context, coding standing, and access. Choose Claude Sonnet 5 if you want near-Opus coding quality in a balanced, high-throughput tier; choose GPT-5.6 Terra if you want the balanced tier that ChatGPT Work/Codex users (including Free/Go) can reach.
Context & Limits
| Feature | Claude Sonnet 5 | GPT-5.6 Terra |
|---|---|---|
| Context window | 1M (1,000,000 tokens) | ~1.05M (1,050,000 tokens) |
| Max output tokens | 128K | 128K |
| Image / vision input | Yes (high-resolution) | ✓ |
| Knowledge cutoff | Not published | February 2026 |
Pricing (per 1M tokens)
| Feature | Claude Sonnet 5 | GPT-5.6 Terra |
|---|---|---|
| Input | $2.00 | $2.00 |
| Output | $10.00 | $12.00 |
| Cached input read | $0.20 | $0.20 |
| Long-context rate | Flat (no long-context tier) | $4 / $18 above the long-context threshold |
| Batch API discount | 50% | 50% |
Coding & Agentic Standing
| Feature | Claude Sonnet 5 | GPT-5.6 Terra |
|---|---|---|
| Positioning | Near-Opus quality in Anthropic's balanced, high-throughput tier | OpenAI's balanced everyday tier for coding, reasoning, and agentic tasks |
| Agentic / tool use | Strong agentic and terminal work close to the Opus tier | Solid everyday tool use at roughly half of Sol's cost |
| Vendor benchmark suites reported | SWE-bench (Verified / Pro), Terminal-Bench | TAU-bench, GPQA Diamond |
| Directly comparable head-to-head score | No shared vendor-published benchmark | No shared vendor-published benchmark |
Access & Openness
| Feature | Claude Sonnet 5 | GPT-5.6 Terra |
|---|---|---|
| Open weights | ✗ | ✗ |
| Where you can run it | Claude API, Claude apps, Bedrock, Vertex, Foundry; OpenCode Zen, Cursor | OpenAI API; ChatGPT Work/Codex (Free/Go), Plus and above (Terra or Luna) |
| Reasoning control | Adaptive thinking on by default; effort low-max | reasoning.effort none-max |
| Structured outputs | ✓ | ✓ |
Speed & Fit
| Feature | Claude Sonnet 5 | GPT-5.6 Terra |
|---|---|---|
| Speed tier | Fast, balanced — near-Opus quality without Opus cost | Balanced everyday tier (~half of Sol's cost) |
| Best-fit workload | High-volume coding and agentic work that wants near-frontier quality | Everyday coding, reasoning, and agentic tasks at value pricing |
| Value note | Cheaper intro rate than Sonnet 4.5's $3/$15 | Output priced above Sonnet 5 ($12 vs $10) |
The Verdict
Choose Claude Sonnet 5 if...
- ✓You want near-Opus coding quality in a balanced, high-throughput tier
- ✓You want the lower output rate ($10 vs $12 per 1M) and high-resolution vision
- ✓You're in the Anthropic ecosystem (Claude apps, Bedrock, Vertex, Foundry) or use OpenCode Zen / Cursor
- ✓You value a stable price cheaper than the prior Sonnet generation
Choose GPT-5.6 Terra if...
- ✓You want the balanced tier that ChatGPT Work/Codex users (including Free/Go) can reach
- ✓You already live in the OpenAI API or ChatGPT and want to step up to Sol or down to Luna in-family
- ✓A ~1.05M context and February 2026 knowledge cutoff fit your workload
- ✓You want OpenAI's reasoning-effort controls on everyday coding tasks
- ✓Your long-context work fits within the $4/$18 tier economics
Frequently Asked Questions
What is the difference between Claude Sonnet 5 and GPT-5.6 Terra?
Claude Sonnet 5 is Anthropic's best blend of speed and intelligence, reaching near-Opus quality on coding and agentic work. GPT-5.6 Terra is the balanced middle tier of OpenAI's GPT-5.6 family, sitting between the flagship Sol and the low-cost Luna.
How much do Claude Sonnet 5 and GPT-5.6 Terra cost?
Claude Sonnet 5: $2.00. GPT-5.6 Terra: $2.00. See the pricing table above for full plan details.
Should I choose Claude Sonnet 5 or GPT-5.6 Terra?
Choose Claude Sonnet 5 if you want near-Opus coding quality in a balanced, high-throughput tier. Choose GPT-5.6 Terra if you want the balanced tier that ChatGPT Work/Codex users (including Free/Go) can reach.
1DevToolRun either mid-tier model from one workspace
Claude Sonnet 5 and GPT-5.6 Terra are both closed models reached through an agent or API. 1DevTool runs Claude Code, Codex, and Gemini CLI side by side in persistent terminals, so you can drive Sonnet 5 and GPT-5.6 Terra from the same workspace on your own keys or subscriptions — no lock-in to either lab. It adds a built-in HTTP client, 13-engine database client, and embedded browser, all wired into Send-to-AI. One-time $29, no subscription.