GPT-6.1 Sol Guide: Near-Astra AI at 1/5 Cost

Last updated: October 3, 2026

If you build with ChatGPT Work, Codex, or the OpenAI API, GPT-6.1 Sol is the model OpenAI wants you to try first for serious work. Announced at DevDay 2026 on 29 September 2026, it is pitched as near-Astra intelligence for coding, computer use, and professional workflows at one-fifth of Astra’s standard token price. This guide shows what Sol actually does, what it costs, how to switch to it, and where paying for Astra still makes sense.

Quick answer: GPT-6.1 Sol matches Astra on coding at one-fifth the cost. Learn when to switch, how to set it up in Work and Codex, and where Astra still wins.

What is GPT-6.1 Sol?

GPT-6.1 Sol is an upgrade to GPT-6 Sol built for agentic coding, computer use, and multi-step professional work. OpenAI describes it as delivering performance close to its more capable Astra model while costing far less to run (OpenAI launch coverage via Analytics Insight, 29 September 2026). It supports a 1.05-million-token context window with up to 128,000 output tokens, and it can use web search, file search, code interpreter, computer use, image generation, and hosted shell through the Responses API (Analytics Insight, September 2026). It is available as gpt-6.1-sol in the API and inside ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu users — not yet in standard Chat. In plain terms: Sol is the cost-efficient workhorse, Astra remains the ceiling.

How much does GPT-6.1 Sol cost compared with Astra?

Sol costs $2 per million input tokens, $0.10 per million cached input tokens, and $10 per million output tokens under standard API pricing. GPT-6 Astra costs $10 per million input tokens and $50 per million output tokens, so Sol is priced at one-fifth of Astra’s standard rates (OpenAI pricing reported by Times of India and Analytics Insight, 29–30 September 2026). Cached input at $0.10 per million is 95% below standard input pricing and 50% below GPT-6 Sol’s cached price (Times of India, September 2026), which matters most for long-running agents that reuse the same context.

ModelInput (per 1M)Cached input (per 1M)Output (per 1M)
GPT-6.1 Sol$2$0.10$10
GPT-6 Astra$10—$50
GPT-6 Luna (for reference)$0.10—$0.50

Pricing as reported at DevDay 2026 launch, 29 September 2026 (Times of India; Analytics Insight). Check OpenAI’s pricing page before production use, as launch pricing changes.

How close is Sol to Astra on real benchmarks?

On DeepSWE v1.1, a software-engineering benchmark, GPT-6.1 Sol matches GPT-6 Astra at roughly one-fifth of the cost, and it improves on GPT-6 Sol’s best score by 6.4 percentage points at lower reasoning effort (OpenAI results reported by Times of India, September 2026). On OSWorld 2.0, a computer-use benchmark of long-horizon workflows, Sol scores seven percentage points higher than GPT-6 Sol at maximum reasoning effort and comes within 2.1 points of Astra while costing about one-seventh as much per task (Times of India, September 2026). On Terminal-Bench Science 0.1, Sol more than doubled GPT-6 Sol’s score at maximum reasoning effort, at an average cost of $5.47 per task versus $23.80 for Astra (Times of India, September 2026). The gap has not closed everywhere: on HealthBench Professional Sol scored 64.2 versus Astra’s 64.7, and on SEC-Bench Pro it scored 78.8% versus Astra’s 85.4% (Analytics Insight, September 2026). OpenAI also reports Sol’s factual error rate on difficult prompts fell from 11.4% with GPT-6 Sol to 7.7% with GPT-6.1 Sol (Times of India, September 2026). These are OpenAI-reported launch evaluations, not independent controlled studies, so treat them as vendor benchmarks to verify on your own workload.

“GPT-6.1 Sol is an upgrade to GPT-6 Sol that delivers performance close to its more capable Astra model. The model focuses on agentic coding, computer use, and professional workloads that require multi-step reasoning and tool use.”

OpenAI, via Analytics Insight (September 2026)

When should you use Sol, and when should you still pay for Astra?

Use Sol as your default for repeated, long-running work: agentic coding in Codex, document-heavy professional tasks, and computer-use workflows where you will run hundreds of tasks and cached context keeps costs down. Its 1.05M-token window and cheap cached input reward agents that revisit the same files and instructions. Keep Astra for the hardest single-shot problems where its remaining edge on benchmarks such as SEC-Bench Pro (85.4% versus Sol’s 78.8%, Analytics Insight, September 2026) justifies five times the token price, and for Pro 500 / Enterprise workflows that need Astra Ultrafast (up to 300 tokens per second in Codex, OpenAI via Analytics Insight, September 2026). Our take — the original element of this guide — is a simple rule built only from the launch figures above: start every new coding or professional workflow on Sol, measure cost per completed task on 10–20 real jobs, and promote to Astra only the steps where Sol fails or needs repeated retries. That per-task check is more useful than headline token prices, because a cheaper model that needs three attempts can cost more than Astra doing it once. We have not hands-on tested Sol for this guide; the comparison table and decision rule are built from dated OpenAI launch data so you can test the claim yourself. For wider context on this month’s launches, see our October tools roundup, and for a different agent use case entirely, read our guide to making money with AI voice agents.

How do you switch to GPT-6.1 Sol?

  1. Check your plan. Sol is live in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu. It is not yet in standard Chat, so do not look for it in the regular chat model picker (Times of India, September 2026).
  2. Choose Sol in Codex or Work. In Codex or Work, open the model selector and choose GPT-6.1 Sol (API name: gpt-6.1-sol). If you use the API, update your model parameter to gpt-6.1-sol and keep your existing Responses API tools (web search, file search, code interpreter, computer use) as they are.
  3. Turn on context reuse. Structure prompts so stable instructions and files are cached; cached input at $0.10 per million (OpenAI, September 2026) is where the largest savings appear for agents.
  4. Run a 10-task bake-off. Take 10 representative jobs you currently run on Astra or GPT-6 Sol, run them on Sol, and record success rate and cost per completed task (not cost per token). Include at least two tasks that previously needed retries.
  5. Promote selectively. Keep Sol as the default and route only the failing step types to Astra. Re-check after a week, because OpenAI says GPT-6.1 Sol Ultrafast (up to 8× faster token generation in Codex) is coming soon (Times of India, September 2026).

What are the limits to know before you commit?

Sol is not a universal Astra replacement. It trails Astra on some professional benchmarks (HealthBench Professional 64.2 vs 64.7; SEC-Bench Pro 78.8% vs 85.4%; ExploitGym 35.1% vs 42.4%, Analytics Insight, September 2026), and its launch benchmarks are vendor-reported, not independently replicated. Availability is also staged: Work and Codex first, API as gpt-6.1-sol, standard Chat later. If your workflow depends on Astra Ultrafast today (300 tokens/second in Codex on Pro 500 and Enterprise, Analytics Insight, September 2026), Sol Ultrafast is announced as coming soon, not live at launch. Finally, re-check pricing and context limits (1,050,000-token window, 128,000 max output, OpenTools model listing checked September 2026) on OpenAI’s docs before you budget a migration.

Frequently asked questions

Is GPT-6.1 Sol available in regular ChatGPT Chat?

No. At launch it is available in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu, and via the API as gpt-6.1-sol. OpenAI states it is not yet available in Chat (Times of India, September 2026).

How much cheaper is Sol than Astra in practice?

On token price, Sol is one-fifth of Astra ($2/$10 vs $10/$50 per million input/output). On OpenAI’s per-task launch figures, Sol cost $5.47 per Terminal-Bench Science task versus $23.80 for Astra, and about one-seventh as much per OSWorld 2.0 task (Times of India, September 2026). Your real saving depends on retries and cached-context share.

Should I migrate everything from Astra to Sol?

Start new and repeated workflows on Sol and promote only failing steps to Astra. Keep Astra for the hardest single-shot work where its benchmark edge matters and for Ultrafast-dependent workflows until Sol Ultrafast ships.

Has OpenAIMaster tested GPT-6.1 Sol hands-on?

No. This guide is built from OpenAI’s DevDay 2026 launch data and same-week reporting (29–30 September 2026), with every figure kept beside its source. Run the 10-task bake-off above on your own workload before committing. If you want ready-made structures for those jobs, use our copy-paste AI prompts for work.

Sources and methodology

This guide rests on OpenAI’s DevDay 2026 launch claims (29 September 2026) as reported the same week, checked on 3 October 2026. Benchmark and pricing figures are vendor-reported launch evaluations, not independent controlled findings; per-task costs are OpenAI-reported averages, not guarantees for your workload.

Have a burning question about this topic?
Feel free to email us at contact@openaimaster.ai — we are happy to help!