Sol

Overview

GPT-5.6 Sol is OpenAI’s flagship model tier in the GPT-5.6 family—not a separate browser, wallet, or accounting product. Launched for general availability on 9 July 2026 (limited partner preview from 26 June 2026), Sol sits above two durable siblings: Terra (balanced, GPT-5.5-competitive cost/performance) and Luna (fastest, lowest cost). The generation number (5.6) and the Sol/Terra/Luna labels are independent: capability tiers can advance on their own cadence.

Sol is routed for hard professional work: multi-step coding and terminal agents, long-horizon knowledge work, science, defensive cybersecurity, computer use, and design. In ChatGPT it powers Medium, High, Extra High, and on higher plans Sol Pro. API model id: gpt-5.6-sol (alias gpt-5.6 also routes to Sol). Everyday chat still defaults to GPT-5.5 Instant—Sol is the deliberate “think harder” option.

Key features

• Flagship GPT-5.6 tier — Highest capability in the Sol / Terra / Luna stack. OpenAI positions Sol for complex professional workflows; Terra for everyday agent work; Luna for high-volume, cost-sensitive jobs.
• Reasoning effort ladder — In ChatGPT: Instant (GPT-5.5), Medium, High, Extra High (Sol), plus Sol Pro on Pro/Business/Enterprise for the hardest tasks. In API and Work/Codex: effort levels including max (longer single-agent reasoning than xhigh) and ultra (default multi-agent coordination, often four parallel agents).
• Coding & terminal agents — Artificial Analysis Coding Agent Index: Sol max scored 80 in Codex (leads DeepSWE / Terminal-Bench-class evals). Strong Terminal-Bench 2.1 results. Partners (Cursor, Qodo, Cognition, Shopify, Ramp) cited persistence, PR quality, and token efficiency vs GPT-5.5.
• Programmatic tool calling — Responses API can run lightweight programs that coordinate tools, filter intermediate data, and adapt the workflow without shipping every tool blob back through the model—fewer tokens and round trips on tool-heavy jobs.
• Multi-agent / ultra — ultra trades more tokens for stronger results and faster wall-clock on BrowseComp, SEC-Bench Pro, and Terminal-Bench-class work by coordinating parallel agents. API builders can approximate this with the multi-agent beta.
• Knowledge work artifacts — Stronger decks, documents, and spreadsheets; better template/Slide Master fidelity; high Presentation Elo on Artificial Analysis Briefcase. Designed to pull messy context from Slack, Notion, Microsoft 365, Google Drive, and similar connectors into shareable outputs.
• Computer use & design judgment — Inspects rendered UIs, refines visual/functional issues, and produces more polished frontends and interactive explainers in ChatGPT Work—not just raw HTML/CSS dumps.
• Long context API — Official model card: 1,050,000 context window, 128,000 max output tokens, knowledge cutoff 16 Feb 2026. Text + image input; text output. Tools: web search, file search, code interpreter, hosted shell, apply patch, skills, computer use, MCP, tool search, image generation.
• Prompt caching (GPT-5.6 generation) — Explicit cache breakpoints, 30-minute minimum cache life; cache reads at 90% discount; cache writes at 1.25× uncached input (first OpenAI generation with cache-write pricing).
• Surfaces — ChatGPT (Plus+ for Sol in standard chat), ChatGPT Work, Codex (CLI/IDE/desktop/cloud), OpenAI API / Responses API, third-party gateways (e.g. OpenRouter), and Microsoft 365 Copilot preference routing after the July 2026 launch.

Pricing

Sol is sold two ways: included (with caps) in ChatGPT plans, and pay-per-token on the API. Figures below are official OpenAI listings as of mid-July 2026—re-check chatgpt.com/pricing and the API pricing page before budgeting.

ChatGPT access (where Sol appears)

Plan	Typical price (USD)	GPT-5.6 Sol	Sol Pro / Extra High	Notes
Free / Go	$0 / ~$8 mo	No (standard chat)	No	Default GPT-5.5 Instant; Terra available in Work/Codex with limits. Go may include ads.
Plus	$20 / month	Medium & High	Not included	Entry plan for Sol in standard ChatGPT. Reasoning quotas still apply.
Pro (5× / 20×)	$100 / $200 / month	Unlimited*	Included (Sol Pro, Extra High)	Usage headroom + highest-quality Sol Pro. *Subject to abuse guardrails.
Business	$20 / user / mo annual; $25 monthly	Flexible (credits)	Flexible (credits)	2+ users; SSO, admin, no training on business data by default.
Enterprise	Custom	Flexible (credits)	Flexible (credits)	Residency, SCIM, EKM, SLA, expanded controls.

ChatGPT reasoning context windows (product table): roughly 256K on Plus/Business and up to 400K on Pro for reasoning modes; Instant windows are smaller (e.g. 54K Plus, 128K Pro). Product context is not identical to the full 1.05M API window.

API pricing (per 1M tokens, standard short context)

Model	Input	Cached input	Cache write	Output
gpt-5.6-sol	$5.00	$0.50	$6.25 (1.25×)	$30.00
gpt-5.6-terra	$2.50	$0.25	$3.125	$15.00
gpt-5.6-luna	$1.00	$0.10	$1.25	$6.00

• Long context surcharge — Prompts with >272K input tokens are billed at 2× input and 1.5× output for the full request (Sol long-context list: $10 in / $45 out standard).
• Batch / Flex — About half of standard rates on supported tiers (e.g. Sol short-context Batch/Flex ~$2.50 / $15).
• Priority — Higher list rates (Sol priority short-context roughly $10 in / $60 out class) for lower latency capacity.
• Tools — Web search, containers, file search, etc. add per-call or storage fees on top of model tokens.
• Independent cost signal — Artificial Analysis reported Sol (max) ~$1.04 per Intelligence Index task—about one-third the task cost of Claude Fable 5 at similar intelligence.

Limits & gotchas

• Not on Free/Go standard chat — Free and Go do not get GPT-5.6 Sol in ordinary ChatGPT conversations. They stay on GPT-5.5 Instant (and limited Terra in Work/Codex). Logged-out users have no Sol access.
• Plus vs Pro gap — Plus includes Medium/High Sol but not Extra High or Sol Pro. Heavy agent jobs frequently hit Plus reasoning caps; Reddit users reported Ultra exhausting quotas after one or two serious tasks at launch.
• Product context ≠ API 1.05M — API advertises ~1.05M context / 128K max out; Codex/ChatGPT often expose lower effective windows (~258K–353K with autocompaction). GitHub Codex issues track catalog caps below the model card.
• Long-context billing cliff — Crossing 272K input doubles input rates (and lifts output) for the whole request—easy to miss when agents grow context silently.
• Cache-write cost — New 1.25× write pricing means “always cache everything” is not free; design breakpoints for reused prefixes.
• Safeguards & dual-use — Layered cyber/bio safeguards may refuse, delay, or re-check dual-use security and biology requests. Legitimate defensive work sometimes needs retries or rephrasing; offensive exploit assistance is constrained by design.
• Latency at high effort — Max and ultra can be slow (multi-agent wall clock still can beat weak single-pass quality, but they are not Instant). Use Medium/High for interactive work.
• Hallucination tradeoffs — Independent AA notes modest accuracy gains vs GPT-5.5 with some increase in hallucination rate on omniscience-style indexes—still verify high-stakes facts.
• Rollout / workspace admin gates — Help Center notes gradual rollout; Business/Enterprise admins can disable models per workspace.
• Residency caveats — GPT-5.6 is not supported for UAE inference residency configs; UAE-located users can still use it without that residency setting.

Community sentiment

Launch-week discussion (r/ChatGPT, r/ClaudeAI, r/codex, Artificial Analysis, partner blogs) is unusually positive on coding-agent quality and cost-per-task, mixed on ChatGPT Plus quotas.

What people praise: Sol (max) leading the AA Coding Agent Index; roughly Claude Fable 5-level intelligence at about one-third task cost; fewer output tokens than many peers; strong Codex/terminal persistence; partner notes on PR-review efficiency vs GPT-5.5. Many Claude-heavy users report multi-model workflows because Sol is nearly as capable with better limits and price.

What people complain about: Plus feeling like a Pro demo under Ultra/max; high-effort usage drain; Codex context below the 1.05M model card; safety false positives on dual-use cyber; ultra latency in interactive chat.

Treat Sol as the expensive, high-yield reasoning engine—not the default Instant model. Medium for most paid ChatGPT work; max/ultra when the task is worth the quota; Terra/Luna when you are looping agents all day.

Who should use it

• Software engineers & agent builders running Codex, Cursor, or custom Responses API agents who need frontier coding, terminal, and multi-step tool use.
• Knowledge workers producing decks, financial research memos, legal document workflows, and multi-source briefs where presentation quality and long-horizon accuracy matter.
• Security & science teams doing defensive vuln research, patch development, and long biology analysis—with awareness of stricter safeguards.
• Teams already on ChatGPT Plus/Pro/Business who want the best OpenAI reasoning option without managing another vendor for primary chat.
• API cost optimizers who will route hard steps to Sol and volume steps to Terra/Luna (or Batch/Flex) with caching.

Skip or de-emphasize Sol if you only need fast everyday chat (use Instant/Terra/Luna), if you require open weights and full self-host control, or if your workload is pure high-volume classification where Luna or cheaper open models win on unit economics.

Alternatives

• ChatGPT — Full OpenAI product surface (Instant default, memory, apps, voice, images). Sol is the reasoning model inside ChatGPT, not a replacement for the product.
• Claude — Often preferred for careful writing, some long coding agents, and pushback style; Fable/Opus-class models compete with Sol on intelligence but usually cost more per completed hard task.
• Gemini — Google stack strength (Workspace, multimodal research, price/performance on some benches); different ecosystem and agent harnesses.
• OpenAI Codex — The coding agent product where Sol (and Terra/Luna) run for repo-scale engineering; choose Sol when quality beats cost.
• Cursor — IDE-native agent that can host Sol alongside other models; best when you live in the editor.
• DeepSeek — Far cheaper API / open weights when “good enough” coding and thinking modes beat OpenAI procurement price.
• Perplexity — Better default for citation-heavy web research UX than raw Sol chat without tools.

Verdict

As of mid-July 2026, GPT-5.6 Sol is OpenAI’s real flagship reasoning model: the Sol tier of GPT-5.6 that powers ChatGPT’s higher efforts, Codex’s top coding runs, and gpt-5.6-sol on the API. Coding-agent scores and partner evals put it at or near the frontier, often with better tokens-per-success than Claude’s top tiers. Caveats: Free/Go lack Sol in standard chat, Plus quotas can vanish under Ultra/max, and the 1.05M API window is not what every Codex/ChatGPT session exposes. On Plus/Pro, use Sol for hard work and Instant for the rest; on the API, route hard spans to Sol, volume to Terra/Luna, and design around the 272K long-context cliff and cache-write pricing.