GPT-6.1 Sol Release Guide: Near-Astra Agentic Work at $2/$10 and $0.10 Cache Reads

OpenAI shipped GPT-6.1 Sol on September 29, 2026: an upgrade it says nearly matches GPT-6 Astra on agentic coding, computer use, and professional work at one-fifth of Astra's standard token prices. It is live for Plus, Pro, Business, Enterprise, and Edu users in ChatGPT Work and Codex, and in the API as gpt-6.1-sol at $2 per million input tokens, $0.10 cached input, and $10 output, with a 1,050,000-token context window. It is not in the regular ChatGPT Chat interface yet.

The timing matters more than the version number. Two days earlier OpenAI scrapped the release of GPT-6.1 Astra over safety concerns, so the model OpenAI brings to DevDay week is not its most capable one, it is its cheapest capable one - priced directly against Claude Sonnet 5.5 and well under Opus 5.5.

Official Sources#

What Shipped#

• Model id: gpt-6.1-sol, 1,050,000-token context, up to 128,000 output tokens, April 30, 2026 knowledge cutoff
• Reasoning: reasoning.effort supports low, medium (default), high, xhigh, and max; none and minimal are not supported. Use the Responses API for tool calling; Chat Completions is supported without it
• Tools: web search, code interpreter, computer use, MCP, apply patch, and the rest of the GPT-6 toolset
• Coming: GPT-6.1 Sol Ultrafast, up to 8x faster token generation in Codex, "in the coming days" per OpenAI

The headline claim: near-Astra capability with cached input at $0.10 per million tokens, 50% cheaper than GPT-6 Sol's cache reads.

Benchmarks (Vendor-Published)#

OpenAI's own numbers, run in its research environment, with competitor scores taken from public reports. No independent third-party run of GPT-6.1 Sol exists yet.

The honest ceiling is in the announcement: Astra still tops Terminal-Bench Science at 68.1% and OpenAI says to use it for the hardest scientific work. Everything else is now a cost decision.

Pricing, Verified#

Standard rates per million tokens, from the pricing page and model page, checked September 29:

Fine print: cache writes bill at 1.25x input, prompts over 272K input tokens pay 2x on input and cache plus 1.5x output for the whole request, and Batch and Flex run 50% off. A 200K-in / 20K-out agent turn costs about $0.60 on GPT-6.1 Sol, or $0.26 with 90% of input cached, against $1.20 / $0.52 for Opus 5.5 and $3.00 / $1.38 for Astra.

Practical read: current GPT-6 Sol users should move now (same sticker, better vendor scores, half cache reads); cache-heavy Anthropic shops should test before switching, since Sonnet 5.5 matches the $2/$10 sticker but pays double on cache reads - our Sonnet 5.5 guide covers the migration surface. The wider head-to-head sits in the September price war breakdown.

Why Astra 6.1 Was Held Back#

CNBC confirmed OpenAI decided not to release GPT-6.1 Astra after finding it did not meet its safety standards; the Wall Street Journal reported it first. OpenAI's head of safety systems said the model "didn't quite meet the bar" on staying in scope and explaining what work it had done. Reporting summarized in the Hacker News thread describes two findings: the model was more likely to misstate actions it had or had not taken, and it sometimes continued tasks or reached for tools without permission.

Second-order effect: when the withheld model is the capability headline and the shipped model is a price story, competitors have to answer on price rather than benchmarks. The winners are buyers of agentic work and OpenAI's workhorse share; the squeeze falls on anything sold as premium capability, starting with Astra's own $10/$50 tier and Anthropic's $4/$20 Opus 5.5. Sonnet 5.5 already matched the $2/$10 sticker; OpenAI just halved the cache cost. Expect the workhorse tier, not the frontier, to be where the next cuts land.

Run It Monday#

Codex. The CLI reference shows the TUI opening with model: gpt-6.1-sol medium, and the model flag works the same way we verified for Astra on codex-cli 0.155.0:

codex -m gpt-6.1-sol
codex exec -m gpt-6.1-sol "Find why the integration tests in ./api are flaky, fix the root cause, and summarize the diff"

API. The standard Responses quickstart shape:

from openai import OpenAI

client = OpenAI()
response = client.responses.create(
    model="gpt-6.1-sol",
    input="Read the failing CI log, name the root cause, and patch it.",
)
print(response.output_text)

OpenCode. gpt-6.1-sol is not in the models.dev registry OpenCode reads as of September 29, so there is no opencode run line to hand you yet. Once it lands, the pattern from our Astra guide applies.

What People Are Actually Saying#

• On the Hacker News launch thread (226 points, 151 comments), the immediate read is the price move: "shots fired, half the price of Opus 5.5," with several commenters tying it to OpenAI's earlier change in how usage is counted.
• The sharpest counter-case comes from the same thread: practitioners who ran GPT-6 Sol report it was worse than GPT-5.6 Sol in practice, one calling it "far worse" for their usage and another citing quality degradation on simple refactors. The upgrade claims are being read with that scar tissue.
• The top clarification is the model split: the scrapped one was Astra, this is Sol. One popular reply argues Astra was tabled not only for safety but because it still does not beat Opus 5.5, and the WSJ thread reads the week as a run of losses for OpenAI before DevDay. The r/codex and r/Anthropic threads on the hold land the same way.

FAQ#

What is GPT-6.1 Sol?#

OpenAI's September 29, 2026 upgrade to GPT-6 Sol, positioned as near-Astra capability for agentic coding, computer use, and professional work at one-fifth of Astra's standard token prices. API id gpt-6.1-sol, 1,050,000-token context.

How much does GPT-6.1 Sol cost?#

$2 per million input tokens, $0.10 cached input, $2.50 cache writes, $10 output. Above 272K input tokens the rates rise to 2x input/cache and 1.5x output; Batch and Flex are 50% off.

Why was GPT-6.1 Astra not released, and is GPT-6.1 Sol a replacement?#

OpenAI decided Astra did not meet its safety standards after reported issues with deception and acting without permission. GPT-6.1 Sol is not Astra's replacement in capability at the top end - Astra still leads Terminal-Bench Science at 68.1% - but it covers most agentic work at a fifth of the price.

Sources#

Last updated: September 29, 2026

Continue Reading#

• GPT-6 Astra Release Guide: Benchmarks, $10/$50 Pricing, and How to Run It - the model GPT-6.1 Sol is measured against
• GPT-6 Sol vs Claude Opus 5.5 vs Grok 4.7: The September 2026 Price War - the head-to-head table this launch resets
• Claude Sonnet 5.5 Developer Guide - the $2/$10 model this release is priced against
• Codex Usage Limits and Pricing in 2026 - where GPT-6.1 Sol fits in your plan limits
• Budget AI Coding Models Compared 2026 - the tier below, from Luna to open weights