Pick Claude Sonnet 4.5 for agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch or computer use and gui automation (61.4% osworld at launch). Pick GPT-5.6 Terra for balanced everyday work at roughly half of sol's price or competitive with gpt-5.5 quality at about 2x lower cost. On a tight budget at scale, GPT-5.6 Terra is the value pick.
Claude Sonnet 4.5 (Anthropic) and GPT-5.6 Terra (OpenAI) are two of the models people most often weigh against each other in 2026. Claude Sonnet 4.5 is september 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded. GPT-5.6 Terra is the mid-tier daily driver of the GPT-5.6 family — near-flagship quality at about half of Sol's cost. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences
Price: nearly identical — $3/$15 per 1M tokens vs $2.5/$15 per 1M tokens. Cost will not be the deciding factor here.
Context window: GPT-5.6 Terra holds 5× more — 1M (~1,500 pages) vs 200K (~300 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
Recency: GPT-5.6 Terra is the newer model by about 9 months (released July 9, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Claude Sonnet 4.5
GPT-5.6 Terra
Provider
Anthropic (US)
OpenAI (US)
Released
September 29, 2025
July 9, 2026
Context window
200K (~300 pages)
1M (~1,500 pages)
Price (in/out)
$3/$15 per 1M tokens
$2.5/$15 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, image, code
SWE-Bench Verified
77.2%
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Agentic coding — 77.2% on SWE-Bench Verified, the best score any model had posted at its launch: Claude Sonnet 4.5 — GPT-5.6 Terra is comparatively weak here — fewer independently verified benchmarks than Sol, and trails it across coding evals
Computer use and GUI automation (61.4% OSWorld at launch): Claude Sonnet 4.5 — Claude Sonnet 4.5 lists computer use and GUI automation (61.4% OSWorld at launch) among its strengths; GPT-5.6 Terra does not.
Long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks: Claude Sonnet 4.5 — Claude Sonnet 4.5 lists long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks among its strengths; GPT-5.6 Terra does not.
Balanced everyday work at roughly half of Sol's price: GPT-5.6 Terra — At $2.5/$15 per 1M tokens it undercuts Claude Sonnet 4.5 ($3/$15 per 1M tokens), and that gap compounds at volume.
Competitive with GPT-5.5 quality at about 2x lower cost: GPT-5.6 Terra — Claude Sonnet 4.5 is comparatively weak here — superseded twice — Sonnet 4.6 and Sonnet 5 match or beat it at the same or lower price
Solid agentic coding (Terminal-Bench 2.1 in the mid-80s): GPT-5.6 Terra — The mid-tier daily driver of the GPT-5.6 family — near-flagship quality at about half of Sol's cost — and it runs cheaper at $2.5/$15 per 1M tokens.
Lowest cost at scale: GPT-5.6 Terra — At $2.5/$15 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input: GPT-5.6 Terra — Its 1M window is about 5× larger than Claude Sonnet 4.5's 200K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: GPT-5.6 Terra — At $2.5/$15 per 1M tokens it undercuts Claude Sonnet 4.5, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases: GPT-5.6 Terra — Larger 1M window fits more in one prompt.
Anyone whose priority is agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch: Claude Sonnet 4.5 — It is specifically built for that.
Anyone whose priority is balanced everyday work at roughly half of sol's price: GPT-5.6 Terra — That is its strongest area.
Claude Sonnet 4.5: where it fits
September 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded. Released September 29, 2025 by Anthropic, it is built for agentic coding — 77.2% on SWE-Bench Verified, the best score any model had posted at its launch, computer use and GUI automation (61.4% OSWorld at launch), long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks, and tracking its own remaining token budget natively, which few models do.
Its trade-offs are real: superseded twice — Sonnet 4.6 and Sonnet 5 match or beat it at the same or lower price, capped at 200K since Anthropic retired its 1M beta in April 2026, while its successors ship 1M as standard, and missing the modern API surface: no adaptive thinking, no effort control, and half the max output of newer Sonnets. At $3 in / $15 out per million tokens, it sits in the mid price band.
GPT-5.6 Terra: where it fits
The mid-tier daily driver of the GPT-5.6 family — near-flagship quality at about half of Sol's cost. Released July 9, 2026 by OpenAI, it is built for balanced everyday work at roughly half of Sol's price, competitive with GPT-5.5 quality at about 2x lower cost, solid agentic coding (Terminal-Bench 2.1 in the mid-80s), and same 1M context and programmatic tool calling as Sol.
Its trade-offs: fewer independently verified benchmarks than Sol, and trails it across coding evals, and no open weights. At $2.5 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Claude Sonnet 4.5 and GPT-5.6 Terra overlap enough that the right pick depends on your specific job. GPT-5.6 Terra costs less per token; GPT-5.6 Terra holds the larger context; and each leads in its own area — Claude Sonnet 4.5 for agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch, GPT-5.6 Terra for balanced everyday work at roughly half of sol's price. Rather than crowning one, run the same hard task through both once and let the results decide.
Frequently asked questions
Is Claude Sonnet 4.5 or GPT-5.6 Terra better for coding?
Public SWE-Bench figures are not available for GPT-5.6 Terra, so the honest test is your own repository — run an identical real bug through both. By design, Claude Sonnet 4.5 leans toward agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch while GPT-5.6 Terra leans toward balanced everyday work at roughly half of sol's price, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Sonnet 4.5 or GPT-5.6 Terra?
GPT-5.6 Terra is cheaper — $3/$15 per 1M tokens vs $2.5/$15 per 1M tokens, roughly 1.2× apart on input.
Which has the bigger context window?
GPT-5.6 Terra — 1M vs 200K, about 5× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both Claude Sonnet 4.5 and GPT-5.6 Terra together?
Yes — a multi-model platform like LumiChats gives you Claude Sonnet 4.5, GPT-5.6 Terra and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, Claude Sonnet 4.5 or GPT-5.6 Terra?
GPT-5.6 Terra — released July 9, 2026, about 9 months after Claude Sonnet 4.5.
Claude Sonnet 4.5 vs GPT-5.6 Terra
Anthropic · US | OpenAI · US · Updated June 2026
Quick verdict
Pick Claude Sonnet 4.5 for agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch or computer use and gui automation (61.4% osworld at launch). Pick GPT-5.6 Terra for balanced everyday work at roughly half of sol's price or competitive with gpt-5.5 quality at about 2x lower cost. On a tight budget at scale, GPT-5.6 Terra is the value pick.
Claude Sonnet 4.5 (Anthropic) and GPT-5.6 Terra (OpenAI) are two of the models people most often weigh against each other in 2026. Claude Sonnet 4.5 is september 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded. GPT-5.6 Terra is the mid-tier daily driver of the GPT-5.6 family — near-flagship quality at about half of Sol's cost. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences at a glance
▸Price: nearly identical — $3/$15 per 1M tokens vs $2.5/$15 per 1M tokens. Cost will not be the deciding factor here.
▸Context window: GPT-5.6 Terra holds 5× more — 1M (~1,500 pages) vs 200K (~300 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
▸Recency: GPT-5.6 Terra is the newer model by about 9 months (released July 9, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Claude Sonnet 4.5
GPT-5.6 Terra
Provider
Anthropic (US)
OpenAI (US)
Released
September 29, 2025
July 9, 2026
Context window
200K (~300 pages)
1M (~1,500 pages)
Price (in/out)
$3/$15 per 1M tokens
$2.5/$15 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, image, code
SWE-Bench Verified
77.2%
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Agentic coding — 77.2% on SWE-Bench Verified, the best score any model had posted at its launch
Claude Sonnet 4.5
GPT-5.6 Terra is comparatively weak here — fewer independently verified benchmarks than Sol, and trails it across coding evals
Computer use and GUI automation (61.4% OSWorld at launch)
Claude Sonnet 4.5
Claude Sonnet 4.5 lists computer use and GUI automation (61.4% OSWorld at launch) among its strengths; GPT-5.6 Terra does not.
Long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks
Claude Sonnet 4.5
Claude Sonnet 4.5 lists long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks among its strengths; GPT-5.6 Terra does not.
Balanced everyday work at roughly half of Sol's price
GPT-5.6 Terra
At $2.5/$15 per 1M tokens it undercuts Claude Sonnet 4.5 ($3/$15 per 1M tokens), and that gap compounds at volume.
Competitive with GPT-5.5 quality at about 2x lower cost
GPT-5.6 Terra
Claude Sonnet 4.5 is comparatively weak here — superseded twice — Sonnet 4.6 and Sonnet 5 match or beat it at the same or lower price
Solid agentic coding (Terminal-Bench 2.1 in the mid-80s)
GPT-5.6 Terra
The mid-tier daily driver of the GPT-5.6 family — near-flagship quality at about half of Sol's cost — and it runs cheaper at $2.5/$15 per 1M tokens.
Lowest cost at scale
GPT-5.6 Terra
At $2.5/$15 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input
GPT-5.6 Terra
Its 1M window is about 5× larger than Claude Sonnet 4.5's 200K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ GPT-5.6 Terra
At $2.5/$15 per 1M tokens it undercuts Claude Sonnet 4.5, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ GPT-5.6 Terra
Larger 1M window fits more in one prompt.
Anyone whose priority is agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch
→ Claude Sonnet 4.5
It is specifically built for that.
Anyone whose priority is balanced everyday work at roughly half of sol's price
→ GPT-5.6 Terra
That is its strongest area.
Claude Sonnet 4.5: where it fits
September 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded. Released September 29, 2025 by Anthropic, it is built for agentic coding — 77.2% on SWE-Bench Verified, the best score any model had posted at its launch, computer use and GUI automation (61.4% OSWorld at launch), long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks, and tracking its own remaining token budget natively, which few models do.
Its trade-offs are real: superseded twice — Sonnet 4.6 and Sonnet 5 match or beat it at the same or lower price, capped at 200K since Anthropic retired its 1M beta in April 2026, while its successors ship 1M as standard, and missing the modern API surface: no adaptive thinking, no effort control, and half the max output of newer Sonnets. At $3 in / $15 out per million tokens, it sits in the mid price band.
GPT-5.6 Terra: where it fits
The mid-tier daily driver of the GPT-5.6 family — near-flagship quality at about half of Sol's cost. Released July 9, 2026 by OpenAI, it is built for balanced everyday work at roughly half of Sol's price, competitive with GPT-5.5 quality at about 2x lower cost, solid agentic coding (Terminal-Bench 2.1 in the mid-80s), and same 1M context and programmatic tool calling as Sol.
Its trade-offs: fewer independently verified benchmarks than Sol, and trails it across coding evals, and no open weights. At $2.5 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Claude Sonnet 4.5 and GPT-5.6 Terra overlap enough that the right pick depends on your specific job. GPT-5.6 Terra costs less per token; GPT-5.6 Terra holds the larger context; and each leads in its own area — Claude Sonnet 4.5 for agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch, GPT-5.6 Terra for balanced everyday work at roughly half of sol's price. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both Claude Sonnet 4.5 and GPT-5.6 Terra without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Is Claude Sonnet 4.5 or GPT-5.6 Terra better for coding?
Public SWE-Bench figures are not available for GPT-5.6 Terra, so the honest test is your own repository — run an identical real bug through both. By design, Claude Sonnet 4.5 leans toward agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch while GPT-5.6 Terra leans toward balanced everyday work at roughly half of sol's price, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Sonnet 4.5 or GPT-5.6 Terra?
GPT-5.6 Terra is cheaper — $3/$15 per 1M tokens vs $2.5/$15 per 1M tokens, roughly 1.2× apart on input.
Which has the bigger context window?
GPT-5.6 Terra — 1M vs 200K, about 5× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both Claude Sonnet 4.5 and GPT-5.6 Terra together?
Yes — a multi-model platform like LumiChats gives you Claude Sonnet 4.5, GPT-5.6 Terra and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, Claude Sonnet 4.5 or GPT-5.6 Terra?
GPT-5.6 Terra — released July 9, 2026, about 9 months after Claude Sonnet 4.5.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.