GPT-6 Astra vs GPT-5.6 Sol
This is the upgrade question for anyone already on OpenAI, and the honest framing is that it is a price increase with a capability argument attached. GPT-5.6 Sol has cost $4 per million input tokens and $20 output since the August 21, 2026 cut, a rate OpenAI lists as promotional through at least November 21. GPT-6 Astra arrived September 3 at $10 and $50. That is two and a half times the input rate and two and a half times output, so a workload that moves over sees its token bill multiply before anything else changes, and the promotional Sol rate expiring in November does not close the gap. Astra does buy real headroom. The context window goes from 1,000,000 to 1,050,000 tokens, but the number that actually matters is what happens deep in it: OpenAI reports MRCR v2 8-needle at 100 percent in the 256K to 512K band and 96.3 from 512K to 1M, against 91.5 and 73.8 for Sol. That 73.8 is the case for upgrading in one figure, since it means Sol drops roughly a quarter of the needles in the top half of its own window. SRE-Bench first-attempt incident resolution goes 55.9 to 88.0. GPQA Diamond moves 94.6 to 96.0, which is a saturated benchmark and not a reason to spend anything. Against that, Astra bills prompts above 272,000 input tokens at 2x input and cache rates and 1.5x output, so the long-context advantage is exactly where the surcharge lives. All figures are OpenAI-reported.
Head-to-Head Specs
| Spec | GPT-6 Astra | GPT-5.6 Sol |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Input Price | $10.00/1M | $4.00/1M |
| Output Price | $50.00/1M | $20.00/1M |
| Context Window | 1M | 1M |
| Released | 2026-09 | 2026-07 |
| Capabilities | text, vision, tool-use, code, reasoning | text, vision, tool-use, code, reasoning |
Benchmark Scores
| Benchmark | GPT-6 Astra | GPT-5.6 Sol | Winner |
|---|---|---|---|
| GPQA Diamond | 96.0 | 94.6 | GPT-6 |
| BrowseComp | 91.5 | 90.4 | GPT-6 |
See the full benchmark leaderboard for all models.
Category Breakdown
Sol is $4/$20 against Astra at $10/$50, a 2.5x difference on both sides
Sol caches at $0.40 per 1M against $1 for Astra
MRCR v2 from 512K to 1M is 96.3 for Astra against 73.8 for Sol, a 22.5 point gap where Sol is least reliable
SRE-Bench first-attempt resolution at 88.0 against 55.9
GPQA Diamond 96.0 against 94.6, a 1.4 point move on a benchmark near saturation
Sol prices its full 1M window at one rate; Astra doubles input and cache rates above 272K, taxing the workloads it is best at
Sol is generally available across the API and ChatGPT tiers; Astra rolled out through a partner preview into a restricted build with staged API and AWS availability
1,050,000 tokens against 1,000,000, a 5 percent nominal increase
Choose GPT-6 Astra when:
- ▸Prompts that regularly run past 512K tokens where Sol recall collapses
- ▸Production incident triage where first-attempt resolution has a dollar value
- ▸Work that has measurably failed on Sol, not work that might improve
- ▸Budgets that can absorb a 2.5x token cost increase
Choose GPT-5.6 Sol when:
- ▸Everything under roughly 256K tokens, where the recall gap largely disappears
- ▸High-volume production traffic where cost per token dominates
- ▸Workloads already meeting quality targets on Sol
- ▸Teams that want generally available capacity without preview restrictions
Frequently Asked Questions
Which is better, GPT-6 Astra or GPT-5.6 Sol?
It depends on your use case. GPT-6 Astra from OpenAI excels at prompts that regularly run past 512k tokens where sol recall collapses, while GPT-5.6 Sol from OpenAI is better for everything under roughly 256k tokens, where the recall gap largely disappears. See the full comparison above for detailed benchmarks and pricing.
How much does GPT-6 Astra cost compared to GPT-5.6 Sol?
GPT-6 Astra costs $10.00 input and $50.00 output per 1M tokens. GPT-5.6 Sol costs $4.00 input and $20.00 output per 1M tokens.
What is the context window difference between GPT-6 Astra and GPT-5.6 Sol?
GPT-6 Astra supports 1M tokens, while GPT-5.6 Sol supports 1M tokens.