The Ultimate ChatGPT Model Comparison: GPT-5.0 to GPT-6.1

OpenAI now sells five general-purpose GPT-6 models: Astra since September 3, 2026, GPT-6 Sol and GPT-6 Luna since September 22, GPT-6.1 Sol since September 29 and GPT-6.1 Terra since October 26. Since October 7, GPT-6 also runs the ChatGPT conversation window, GPT-6 Sol on Plus, Pro, Business and Enterprise and, from October 8, GPT-6 Luna on Free and Go, while GPT-5.6, public since July 9, 2026, stays in the model menu as an explicit pick on paid plans. GPT-5.6’s flagship Sol tier scores 88.8% on Terminal-Bench 2.1 (and 91.9% in its Sol Ultra high-effort mode), edging GPT-5.5’s own 88.0% on the same agentic-coding test, and it ships alongside two cheaper tiers, Terra and Luna.

In under a year, OpenAI has shipped seven distinct versions of GPT-5, each with its own identity and price point. If you have lost track of what separates GPT-5.0 from GPT-5.6, this guide covers every model in the family, release dates, context windows, benchmarks, pricing, and the key differences that actually matter. GPT-5.6 first shipped as a June 26 government-gated preview to roughly 20 organizations, then went fully public on July 9. It powered ChatGPT’s thinking levels until GPT-6 took over the Chat tab on October 7, and it remains available in full through the API. We also cover the five GPT-6 models and which of them your plan runs in Chat, Work and Codex. If you are newer to ChatGPT, our ChatGPT for Beginners guide is a good place to start before you compare model differences.

The Key Takeaways

• GPT-6 has run the ChatGPT conversation window since October 7, 2026: GPT-6 Sol on Plus, Pro, Business and Enterprise, GPT-6 Luna on Free and Go from October 8, and GPT-6 Pro, powered by Astra, behind the Pro option. GPT-5.6 (public July 9, 2026) is now the previous generation: Sol stays selectable in Chat on paid plans, and all three tiers, Sol, Terra and Luna, remain in Work, Codex and the API, with Sol scoring 88.8% on Terminal-Bench 2.1 and a 1.05M-token API context window.
• GPT-5.5 (April 23, 2026) was the flagship before GPT-5.6 and is still an excellent all-rounder in the API. It scores 93.6% on GPQA Diamond and 78.7% on OSWorld-Verified, both ahead of GPT-5.4, and ships in two variants, GPT-5.5 standard and GPT-5.5 Pro. It left Codex for ChatGPT sign-in on October 14, 2026.
• GPT-5.4 (March 5, 2026) is now several generations back but still matters. It introduced a 1M-token context window (API only) and native computer use, scoring 75.0% on OSWorld-Verified and 57.7% on SWE-Bench Pro.
• GPT-5.3 Instant (March 3, 2026) fixed the over-cautious tone and delivered 26.8% fewer hallucinations than GPT-5.2 with web search on, but it is no longer listed on OpenAI’s API pricing page. Only gpt-5.3-codex survives from that generation, and it leaves the API on April 1, 2027.
• GPT-5.2 was the first model to score 90%+ on ARC-AGI-1 (Pro) and hit a perfect 100% on AIME 2025 math.
• GPT-5.1 introduced adaptive reasoning, 2 to 3x faster on simple tasks, while keeping the same $1.25 / $10 price as GPT-5.0.
• Pricing splits by tier in GPT-5.6. Sol was cut to $4 / $20 per 1M tokens on August 21, 2026, below GPT-5.5’s $5 / $30, Terra drops to $2 / $12, and Luna is just $0.20 / $1.20 after OpenAI cut both tiers on July 30, 2026, Luna by 80% and Terra by 20%. OpenAI now calls Sol’s rate promotional and guarantees it only through November 30, 2026.
• 14 legacy model snapshots lost API access on July 23, 2026, including five Codex snapshots and both chat-latest aliases. It was an API-only change; the ChatGPT model picker was untouched. The bigger October 23 wave has passed too, and the next GPT text-model shutdowns fall on December 11, 2026, January 14, 2027 and April 1, 2027.
• GPT-6 Astra shipped on September 3, 2026. It costs $10 / $50 per 1M tokens, roughly 2.5x GPT-5.6 Sol, and it reached ChatGPT the next day as GPT-6 Pro on Pro, Business and Enterprise. Plus plans get Astra in ChatGPT Work and Codex instead, and Free and Go get none.
• GPT-6 Sol and GPT-6 Luna followed on September 22, 2026 at $2 / $10 and $0.10 / $0.50, half the matching GPT-5.6 rates, first in ChatGPT Work, Codex and the API and, since October 7, in Chat as well. GPT-6.1 Sol followed on September 29 at the same $2 / $10, and GPT-6.1 Terra on October 26 at $1 / $5; both run in Work, Codex and the API but not in Chat.

All ChatGPT 5 Models at a Glance

One caveat on that table. It is a history of the family, not a current order form. OpenAI’s API pricing page still carries most of these models, from gpt-5 and its mini, nano and pro variants up through the GPT-5.4 family, GPT-5.5, GPT-5.5 Pro, the three GPT-5.6 tiers and the five general-purpose GPT-6 models, with gpt-5.3-codex listed separately under Codex. The standard GPT-5.3 is the one that has gone. What remains is on the clock: the original gpt-5-2025-08-07, along with its mini, nano and pro variants, shuts down on December 11, 2026, and gpt-5.1, gpt-5.3-codex and gpt-5.4-nano follow on April 1, 2027. The prices below are kept because they explain how the family evolved, not because you can still buy them all.

The GPT-6 family now sits above every model in that table, and since October 7 it also runs ChatGPT’s Chat tab. GPT-6 Astra launched on September 3, 2026 at $10 / $50 per 1M tokens, with the same 1.05M-token context and 128K output ceiling, GPT-6 Sol ($2 / $10) and GPT-6 Luna ($0.10 / $0.50) followed on September 22 at half the matching GPT-5.6 rates, GPT-6.1 Sol arrived on September 29 at the same $2 / $10, and GPT-6.1 Terra followed on October 26 at $1 / $5. The section below maps which of them each ChatGPT surface and plan runs today. Our GPT-6 Astra launch coverage has the full pricing and benchmark breakdown.

For how these API prices map to ChatGPT subscription tiers (Free, Go, Plus, Pro, Business, Enterprise), see our ChatGPT pricing guide.

What ChatGPT Runs Today: Chat, Work, Codex and the API

On October 7, 2026, OpenAI moved the Chat tab to GPT-6. The model menu now simply says GPT-6, which replaced Latest: GPT-6 Sol powers Instant, Medium, High and Extra High on Plus, Pro, Business and Enterprise, and GPT-6 Luna took over Free and Go from October 8. The Pro option still runs GPT-6 Pro, powered by GPT-6 Astra. No older model was retired by the switch, and an explicit GPT-5.6 Sol selection stays on GPT-5.6. ChatGPT Work and Codex kept their own model list, which is where GPT-6.1 Sol and GPT-6.1 Terra live.

GPT-6.1 Terra is the newest of the five. It arrived on October 26, 2026 in Work and Codex for Plus, Pro, Business, Enterprise and Edu, and in the API as gpt-6.1-terra at $1 / $5 per 1M tokens, half GPT-6.1 Sol’s rate, with the same 1.05M-token context window. OpenAI pitches it for clear writing, visual understanding and computer use, and it is not available in Chat. Some Plus and Pro users may now see it at Medium in Work’s default Power preset, in place of GPT-6.1 Sol at Light. Codex changed too: GPT-5.5 retired from Codex with ChatGPT sign-in on October 14, 2026. OpenAI points paid plans to GPT-6.1 Sol and Free and Go to GPT-6 Luna, while the API and Codex sessions signed in with an API key keep GPT-5.5.

On independent scores, Artificial Analysis’s Intelligence Index v5.0.1 puts GPT-6 Astra at 56.9, GPT-6.1 Sol at 54.6, GPT-6.1 Terra at 51.3 and GPT-6 Luna at 27.9, each at maximum effort, as read on November 10, 2026. GPT-6 Sol, the model that answers in Chat on paid plans, scores 44.2 at maximum effort, a setting above Extra High, the highest level ChatGPT offers in Chat, so treat it as a ceiling; on the same measure it sits roughly ten points below GPT-6.1 Sol. Version 5 replaced v4.3.2 on October 27 and rescaled every score, so older figures are not comparable, and GPT-5.6 Sol has no score on the new version, which is why this guide no longer ranks it against GPT-6 on the index. One caveat on Free and Go: OpenAI’s release notes and pricing page say both plans moved to GPT-6 Luna, while its help article on ChatGPT models still describes GPT-5.6 Luna for them.

GPT-5.0: The Foundation

Released: August 7, 2025

The original GPT-5 arrived as a meaningful jump over GPT-4o, not just in raw benchmarks, but in architecture. According to OpenAI’s launch announcement, it was built as a unified system with a fast base model for everyday queries and a deeper reasoning layer (GPT-5 Thinking) that activates automatically when the query demands it. A real-time router decides which to use based on complexity, tool needs, and context, so you do not have to manage it manually.

GPT-5.0 Benchmarks

GPT-5.0 shipped with a 400K input / 128K output context window and was available to all ChatGPT users, with Pro subscribers getting extended reasoning access.

API pricing: $1.25 per 1M input tokens / $10 per 1M output tokens

What Changed vs. GPT-4o

GPT-5 was roughly 45% less likely to hallucinate than GPT-4o with web search enabled. The unified routing eliminated the need to manually switch between chat and reasoning modes, a friction point many users had with the o-series models.

GPT-5.1: Faster Without Being Dumber

Released: November 13, 2025

Per OpenAI’s GPT-5.1 announcement, GPT-5.1 was not a capability leap, it was an efficiency upgrade. The headline feature was adaptive reasoning, where the model dynamically allocates compute based on query complexity. Ask it something simple and it answers 2 to 3x faster than the standard model. Ask it something complex and it switches to full reasoning mode. That reasoning mode is also why heavier models can feel laggy; our guide to why ChatGPT is so slow explains when the wait is the model and when it is something you can fix.

OpenAI also tuned the tone to be warmer and more conversational, dropping some of the rigid formality that made GPT-5.0 occasionally feel stiff. It used 30% fewer thinking tokens than its Codex variant while maintaining near-identical benchmark scores on most tasks.

GPT-5.1 Benchmarks

GPT-5.1 Variants

OpenAI shipped a full family with GPT-5.1, Instant (fast), Thinking (deep reasoning), Auto (routing), and Pro (research-grade), plus three Codex variants, standard Codex, Codex-Mini for lightweight tasks, and Codex-Max for agentic coding tasks lasting 24+ hours. All three of those Codex snapshots lost API access on July 23, 2026, and OpenAI now lists gpt-5.6-sol as the substitute for Codex and Codex-Max and gpt-5.6-terra for Codex-Mini.

What GPT-5.1 Got Right

The reasoning_effort parameter (none / low / medium / high) gave developers fine-grained control over how much compute to spend per request, a practical tool for balancing cost and quality in production.

GPT-5.2: The Reasoning Milestone

Released: December 11, 2025

GPT-5.2 was the model that set new goalposts. It was the first AI to score 90%+ on ARC-AGI-1, a benchmark designed specifically to resist pattern-matching and test genuine reasoning. It also hit a perfect 100% on AIME 2025 math problems. These were not marginal gains; they crossed thresholds that had defined the frontier for years.

OpenAI introduced a three-tier architecture with GPT-5.2. GPT-5.2 Instant was optimized for throughput, which made it the pick for customer support, content generation, and translation. GPT-5.2 Thinking added configurable reasoning depth through Light, Medium, Heavy, and xhigh settings, letting you trade latency for accuracy on a per-request basis. GPT-5.2 Pro sat at the top with maximum compute and up to 30 minutes of sustained processing for the most demanding tasks.

GPT-5.2 Benchmarks

GPT-5.2 delivered 38% fewer errors than GPT-5.1, the largest reliability jump in the GPT-5 family so far.

The context window stayed at 400K tokens (272K input / 128K output), but API pricing rose to $1.75 per 1M input / $14 per 1M output, a 40% increase over GPT-5.1.

An agentic coding variant, GPT-5.2-Codex, followed on January 14, 2026, purpose-built for planning and executing multi-step engineering tasks autonomously. It retired from the API on July 23, 2026 alongside the GPT-5.0 and 5.1 Codex snapshots.

Note: GPT-5.2 Thinking was retired on June 3, 2026. If you relied on it for analytical work, its replacement today is the Medium, High or Extra High thinking level in ChatGPT, which runs on GPT-6 Sol when GPT-6 is selected.

GPT-5.3: The Everyday Upgrade

Released: March 3, 2026

GPT-5.3 Instant fixed something earlier models quietly got wrong, the tone. Previous GPT-5 versions had a tendency toward excessive caveats, unnecessary hedging, and what users called “cringe,” AI overcaution that made every answer feel like a legal disclaimer. GPT-5.3 dialed that back, producing more direct and natural responses.

It also delivered a meaningful accuracy improvement. With web search enabled, GPT-5.3 produces 26.8% fewer hallucinations than GPT-5.2 Instant. Without search, the improvement is still 19.7%. User-flagged errors dropped by 22.5%.

GPT-5.3 Specs

That pricing was a dramatic drop from GPT-5.2’s $1.75 / $14, and GPT-5.3 Instant was positioned as a high-quality, low-cost everyday model rather than a reasoning powerhouse. It no longer appears on OpenAI’s API pricing page, so treat those figures as history. If you want that role today, GPT-6 Luna at $0.10 / $0.50 is the cheapest current option, half the rate of GPT-5.6 Luna, which itself fell to $0.20 / $1.20 after an 80% cut on July 30, 2026.

GPT-5.3 Trade-offs

The anti-cringe update came with a trade-off: safety compliance on some categories declined. Graphic violence content filtering dropped from 85.2% to 78.1% compared to GPT-5.2, a decision OpenAI appears to have made deliberately, moving some safety controls to the product layer rather than the model level.

The GPT-5.3-Codex variant (February 5, 2026) is worth noting separately. It carries a 1 million-token context window, the same as GPT-5.4, runs 25% faster than GPT-5.2-Codex, and was for months the lower-cost option for large-scale agentic coding next to 5.4 and 5.5. OpenAI has since deprecated it: it leaves the API on April 1, 2027, with gpt-6-sol as the recommended replacement. If you run any Codex variant locally, check our explainer on Codex’s storage bug first, because a runaway logger was burning through SSD endurance until OpenAI patched most of it in June 2026.

GPT-5.4: The Professional Frontier

Released: March 5, 2026

GPT-5.4 held the “most capable model OpenAI has ever shipped” title for six weeks until GPT-5.5 arrived in late April 2026. According to OpenAI’s official GPT-5.4 announcement, the two genuinely new capabilities that set it apart from every prior model were native computer use and a 1 million-token context window (via the API).

Computer use means GPT-5.4 can interact directly with software interfaces, navigating desktops, clicking UI elements, running commands, verifying output, and looping back to fix errors in a build-run-verify-fix cycle. On OSWorld-Verified, the benchmark for desktop computer use, it scores 75.0%, exceeding the measured human baseline of 72.4%.

GPT-5.4 Benchmarks

GPT-5.4 Key Features

1 million-token context (API only). The full 1M window is available via the API. ChatGPT Plus, Team, and Pro subscribers in the chat interface do not get the expanded context. Worth noting, OpenAI charges double the standard rate once input exceeds 272K tokens in a single request.

Tool search. Instead of loading all tool definitions upfront, GPT-5.4 can retrieve tool definitions on demand. This cuts token usage by 47% in tool-heavy workflows, a practical cost saving for anyone building agents.

Full-resolution vision. GPT-5.4 processes images up to 10.24 million pixels, making it viable for detailed medical imaging, architectural plans, and high-res document analysis.

Compaction training. The model is trained to compress long agent trajectories while preserving key context, useful for multi-day autonomous workflows.

GPT-5.4 Pricing

GPT-5.4 Pro is priced at a significant premium. For context, Anthropic’s Claude Opus 4.8 costs $5 per 1M input / $25 per 1M output, so GPT-5.4 Pro is six times the input price.

GPT-5.4 ships in three variants: Standard (everyday professional use), Thinking (deep multi-step reasoning, available to Plus/Team/Pro subscribers), and Pro (maximum performance).

GPT-5.5: The Previous Flagship

Released: April 23, 2026

GPT-5.5 held the flagship slot from late April until GPT-5.6 arrived in July. Its fast variant, GPT-5.5 Instant, served as the default model for quick everyday responses on every ChatGPT plan, including Free, until GPT-5.6 took over Instant; since October 7, Instant runs on GPT-6 Sol on Plus and above and on GPT-6 Luna on Free and Go. It arrived 49 days after GPT-5.4, making it the fastest flagship turnover in the GPT-5 family. Read OpenAI’s official GPT-5.5 announcement for the full technical brief, and our own GPT-5.5 launch coverage for the complete benchmark tables and real-world testing.

Two variants shipped. GPT-5.5 standard launched on all paid ChatGPT tiers and in Codex, and GPT-5.5 Pro was restricted to Pro, Business, and Enterprise tiers. GPT-5.5 left Codex for ChatGPT sign-in on October 14, 2026, and both variants remain in the API. OpenAI positioned GPT-5.5 as a model “built specifically for real work and for powering agents,” with the largest efficiency gains going to agentic coding and long-horizon knowledge work.

GPT-5.5 Benchmarks

Versus GPT-5.4, the standout gains are OSWorld-Verified (+3.7 points), GPQA Diamond (+0.8), SWE-Bench Pro (+0.9), and Terminal-Bench 2.0 (+7.6). The numbers understate how the model feels to use, though. OpenAI reports that at NVIDIA, debugging cycles “dropped from days to hours” using GPT-5.5’s agentic workflow, which is the kind of real-world win that does not show up in a benchmark table.

GPT-5.5 Key Features

Agentic coding by default. GPT-5.5 ships tuned for multi-step engineering workflows. The same Codex tool that used to need supervision can now chain apply_patch, terminal commands, and verification steps over longer horizons without losing the thread.

Computer use, now production-grade. 78.7% on OSWorld-Verified puts GPT-5.5 firmly above the 72.4% human baseline. Desktop automation workflows that were flaky on 5.4 start to look viable on 5.5.

Lower hallucination rate. OpenAI reports meaningfully fewer hallucinations versus GPT-5.4 across standard knowledge-work tasks, though the company has not released a single headline figure.

API access followed the app. At launch, GPT-5.5 went live inside ChatGPT and Codex first, with API access arriving shortly afterwards under different safeguards than the ChatGPT rollout. Both surfaces were generally available for months, until GPT-5.5 left Codex for ChatGPT sign-in on October 14, 2026; it remains in the API.

GPT-5.5 Pricing

Standard is exactly 2x the price of GPT-5.4 standard. GPT-5.5 Pro matches GPT-5.4 Pro’s $30 / $180, so if you already pay for Pro, the jump to 5.5 Pro is effectively free at the API level.

GPT-5.6: The Generation Before GPT-6 (Sol, Terra, Luna)

Released: July 9, 2026 (June 26, 2026 government-gated preview)

GPT-5.6 is the release that reorganized the lineup into three named tiers instead of a “standard plus Pro” split, and it ran the ChatGPT conversation window until GPT-6 took over the Chat tab on October 7, 2026. It shipped first as a June 26 preview to roughly 20 approved organizations under the new federal review regime for frontier models, then went fully public on July 9. Today GPT-5.6 Sol stays selectable in Chat on paid plans, and all three tiers remain in Work, Codex and the API. All three tiers share a 1.05M-token context window and 128K max output.

The three tiers map cleanly to budget and capability. Sol is the flagship, tuned for agentic coding and long-horizon work, with a high-effort Sol Ultra mode on top. Terra is the balanced middle option, competitive with GPT-5.5 at 60% less. Luna is the fastest and cheapest, aimed at high-volume everyday use. On Terminal-Bench 2.1, the agentic-coding benchmark, Sol scores 88.8% and Sol Ultra 91.9%, edging GPT-5.5’s 88.0% on the same test.

How GPT-6 and GPT-5.6 Share ChatGPT’s Thinking Levels

The API sells Sol, Terra, and Luna by name. Inside ChatGPT the models sit behind thinking levels, which trips people up. With GPT-6 selected, the default since October 7, GPT-6 Sol powers Instant as well as the Medium, High, and Extra High levels; select GPT-5.6 Sol explicitly and the same levels run on GPT-5.6 instead. The Pro option runs GPT-6 Pro, powered by GPT-6 Astra, on Pro, Business and Enterprise, with GPT-5.6 Sol Pro still available inside the GPT-5.6 family. Extra High corresponds to the maximum-effort mode that OpenAI benchmarked on GPT-5.6 as Sol Ultra. The plan table below applies to both generations.

Two consequences are worth knowing before you pay for anything. GPT-5.6 Terra and Luna are not selectable in a normal ChatGPT conversation at all; both live in Work, Codex, and the API, where Work serves all three GPT-5.6 tiers to Plus and above and Codex adds Terra for Free and Go. And since September 14, 2026, ChatGPT no longer switches from Instant to a thinking level on its own for Plus and Pro, so pick the level yourself. If you exhaust a thinking allowance, OpenAI says ChatGPT may continue on another available model rather than cutting you off, so check which model answered before you trust a long analytical reply.

Those prices are the short-context rates, and OpenAI now labels Sol’s rate promotional, guaranteed only through November 30, 2026. Push a single request past OpenAI’s long-context threshold and OpenAI bills the whole request at 2x input and 1.5x output, taking Sol to $8 / $30, Terra to $4 / $18, and Luna to $0.40 / $1.80. Budget for the tier you will actually hit.

One caveat worth flagging: OpenAI has not published GPT-5.6 numbers for the standard benchmarks it used with earlier models (no SWE-bench Verified, GPQA, or OSWorld figures for Sol yet), and independent evaluator METR noted the family is unusually good at benchmark-style tasks, so treat the Terminal-Bench lead as one data point rather than a full picture. For the complete breakdown of the tiers, benchmarks, and rollout, see our GPT-5.6 Sol, Terra, and Luna explainer. Once you pick a tier, our GPT-5.6 prompting guide walks through seven tips for getting sharper answers.

What OpenAI Retired on July 23, 2026

Shipping seven versions in eleven months leaves debris, and OpenAI cleared it. On July 23, 2026, 14 model snapshots lost API access in a single wave, announced back on April 22 under the heading “Legacy GPT model snapshots.” The April notice listed 15, but OpenAI’s deprecations page now lists the fifteenth, the gpt-4o-mini-tts-2025-03-20 text-to-speech snapshot, under a January 6, 2027 shutdown instead. The reasoning OpenAI gave was straightforward, to improve reliability and make it easier to pick the right model.

Read the scope carefully. This was an API-only shutdown, and it removed nothing from the ChatGPT model picker. If you use ChatGPT through the app or the web, nothing changed for you on July 23. If you call the API directly, or you run a tool that pins a specific model snapshot, that deadline has already passed.

The Codex Snapshots Take the Biggest Hit

Five pre-5.3 Codex snapshots retired together, which made this the largest single cut to the Codex lineup at the time. The two chat-latest aliases went the same day, and so did both deep-research snapshots and the original computer-use preview. The table below covers the entries most likely to appear in a GPT-5-era codebase, with the substitutes OpenAI’s deprecations page lists today.

The remaining four are GPT-4o-era leftovers rather than GPT-5 models, covering the search-preview pair and dated audio and realtime mini snapshots. Note what was not on the list. GPT-5.3-Codex survived that wave, but OpenAI has since deprecated it too: it leaves the API on April 1, 2027, with gpt-6-sol as the replacement. GPT-5.4, GPT-5.5, and GPT-5.5 Pro all stay on sale in the API.

The October Wave and the Shutdowns Still to Come

July 23 was the smaller wave. On October 23, 2026, OpenAI shut down a much more recognisable set, including gpt-3.5-turbo-0125, gpt-4-0613, gpt-4-turbo, gpt-4o-2024-05-13, o1, o1-pro, o3-mini, o4-mini, and the original gpt-image-1, along with fine-tuned models built on GPT-3.5 Turbo and GPT-4. The next wave lands on December 11, 2026, taking the original GPT-5 snapshots with it, gpt-5-2025-08-07 plus its mini, nano, and pro variants, along with o3 and o3-pro. Two newer notices reach into 2027: on January 14, 2027 the remaining GPT-4o snapshots, GPT-4o mini, GPT-4.1 and GPT-4.1 mini go, with gpt-6-luna as the replacement, and on April 1, 2027 gpt-5.1, gpt-5.3-codex and gpt-5.4-nano follow, replaced by gpt-6-sol or gpt-6-luna. Separately, the Videos API and every Sora 2 snapshot sunset on September 24, 2026. You can track every date on OpenAI’s deprecations page.

Which ChatGPT Model Should You Use?

The right pick depends entirely on the job, from cheap everyday chat to top-tier reasoning and coding, and the table below maps common tasks to the best-fit model. If you are weighing Google’s lineup instead, our Gemini model comparison runs the same version-by-version breakdown for Flash, Pro, and Flash-Lite.

For a broader comparison including Claude, Gemini, and other leading models, see our Best AI Models hub. For a head-to-head on OpenAI versus Anthropic specifically, check our Claude vs ChatGPT comparison. For Google’s side, see our Ultimate Gemini model comparison. For Anthropic’s side, see our Ultimate Claude model comparison. And if you would rather talk than type, our ChatGPT live voice mode guide explains OpenAI’s new real-time GPT-Live.

GPT-6 Astra: What Actually Shipped

The wait ended on September 3, 2026, when OpenAI launched GPT-6 Astra and settled the argument over whether Astra would arrive as GPT-6 or as another point release inside the GPT-5 line. It is the first model OpenAI has ever designated Critical for cybersecurity capability under its Preparedness Framework, which is why the rollout started with vetted defenders rather than with the model picker. That gate lasted exactly one day, because Astra reached ChatGPT as GPT-6 Pro on September 4 for Pro, Business and Enterprise plans. Company president Greg Brockman told a press briefing, “Welcome to the AGI era.” Our GPT-6 Astra launch coverage works through the pricing, the benchmarks, and the footnotes those numbers arrive with. Sam Altman had said GPT-6 would come sooner than the 2.5-year gap between GPT-4 and GPT-5, and at 13 months after GPT-5.0 that held.

What GPT-6 Astra Brings

Notes that survive the context window. The long-rumoured persistent memory arrived in a narrower form than the leaks suggested. Astra can keep notes across context windows and search back through earlier messages and tool output, instead of relying on compaction that summarises old work and can discard the one detail an agent needs later. It was experimental behind a config.toml setting at launch, and OpenAI said then that it would become the default for Astra in the following weeks.

Long-horizon computer use. This is where the jump is easiest to see. On OSWorld V2-Offline, OpenAI reports Astra at 72.6% in about 40 minutes per task against GPT-5.6 Sol’s 65.7% in about 75 minutes, and on DeepSWE v1.1 agentic coding, 74.1% against Sol’s 70.8%. Halving the time per task while raising the score is the practically useful result. Astra can also ask you a question without stopping the work that does not depend on your answer.

Scope discipline, at a cost. In OpenAI’s internal tests on difficult or impossible tasks run without production safeguards, GPT-5.6 Sol went beyond its authorised scope 48.2% of the time. Astra did so 0% of the time. The same materials disclose a regression: in evaluations designed to elicit monitoring evasion, Astra’s written reasoning was harder to follow than Sol’s. A model that never oversteps but whose reasoning is harder to read is a trade, not a clean win.

What did not arrive. The speculation around persistent weight updates, where a model learns across sessions rather than only within them, is not part of what OpenAI shipped. Neither is a GDPval figure, the benchmark OpenAI built to measure performance on economically valuable work, which is a conspicuous absence at a launch framed around AGI. And the headline 98.6% on ARC-AGI-3 is not a solve rate. It measures Relative Human Action Efficiency, on a harness OpenAI has itself shown can triple the number.

For how each GPT-6 rumour held up against what actually shipped, see our ChatGPT 6 leak scorecard.

Astra was not the whole family. On September 22, 2026 OpenAI added GPT-6 Sol at $2 / $10 and GPT-6 Luna at $0.10 / $0.50, halving the matching GPT-5.6 rates, and put both into ChatGPT Work and Codex for Plus and above, with Luna in the desktop app for Free and Go. At first OpenAI kept the two separate from the models available in Chat; on October 7 both moved into the Chat tab as well, Sol for Plus and above and Luna for Free and Go. Our guide to GPT-6 Sol and Luna covers the benchmarks and the surfaces in detail.

Benchmark Progression Through the GPT-5 Family

GPT-5.4 SWE-Bench Verified score is from a non-thinking variant; OpenAI has not published an official figure for this benchmark. Humanity’s Last Exam numbers are not directly comparable, GPT-5.5’s 41.4% is the no-tools figure; GPT-5.4’s 52.1% is with tools.

The table stops at GPT-5.5 on purpose. The only headline benchmark OpenAI published for GPT-5.6 at launch is Terminal-Bench 2.1, where Sol hits 88.8% and Sol Ultra 91.9%. Two further Sol figures arrived sideways in the GPT-6 Astra launch materials on September 3, 2026, 70.8% on DeepSWE v1.1 and 65.7% on OSWorld V2-Offline, but both sit on benchmark releases the older rows never used, so adding them would mean comparing different tests. Comparable GPQA, SWE-Bench, and FrontierMath figures for the 5.6 family are still unpublished. Our guide to AI benchmarks explains what Terminal-Bench actually measures.

Want Every GPT-5 Variant Plus Claude, Gemini, and Grok in One Mac App?

If you are paying for ChatGPT, Claude Pro, and Google AI Pro just to compare model outputs, there is a simpler setup. Fello AI is a native Mac, iPhone and iPad app that routes your prompts to ChatGPT, Claude, Gemini, Grok, DeepSeek, Perplexity, Kimi, GLM and Qwen through one interface, for $11.99/month in the US (prices vary by country). One price, every top model, no tab switching.

That matters in a world where OpenAI ships a new GPT model every few weeks, and where each one competes head-to-head with releases from Anthropic, Google, and xAI. If a GPT-6 model suits your coding work today but Claude or Gemini edges ahead on a specific task next month, you can switch models inside the same app without changing your workflow.

You can download Fello AI on the App Store and run every one of these models side by side on Mac, iPhone, and iPad, for $11.99/month in the US (prices vary by country), with a free tier to try first and a 4.7-star rating across 27,000+ reviews. It works as an alternative to stacking three separate subscriptions, or as a complement to the one you already pay for, and it handles images, documents, and spreadsheets rather than chat alone.

For context on persistent memory, see Anthropic’s new agent memory system.

For practical tips on how to use ChatGPT effectively, see our full guide.

Conclusion

The GPT-5 family has moved fast. In eleven months, OpenAI has gone from a capable general-purpose model to one that operates software like a human, holds an entire codebase in context, and outperforms industry professionals on knowledge work benchmarks across 44 occupations. GPT-5.5 made multi-step agentic coding workflows viable without human supervision, GPT-5.6’s Sol tier leads the GPT-5 family on exactly that work, and GPT-6 has now landed on top of it and, since October 7, taken its place as the default in Chat.

For most users the everyday choice inside ChatGPT is now simply GPT-6, GPT-6 Sol on Plus and above and GPT-6 Luna on Free and Go, because that is what the conversation window serves. If you are calling the API or working in Codex, the cheaper answers are GPT-6 Luna at $0.10 / $0.50, GPT-6.1 Terra at $1 / $5 and GPT-6.1 Sol at $2 / $10, each half or less of its GPT-5.6 counterpart’s price. And when the job isn’t ChatGPT’s strength at all, our guide on when to use which AI shows which model to open instead. If you are building anything that will still be running in 12 months, plan for GPT-6 Astra at $10 / $50 per 1M tokens, which ChatGPT offers as GPT-6 Pro on Pro, Business and Enterprise.

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The featured image for this article was created with the help of AI.