OpenAI、GPT 5.6 Sol/Terra/Luna を発表

a quiet day.

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AI Twitter Recap

OpenAI launched a new three-model GPT‑5.6 family and simultaneously expanded the product stack around it.

• OpenAI announced GPT‑5.6 Sol, Terra, and Luna rolling out across ChatGPT, Codex, and the API via @OpenAI and @OpenAIDevs

• In ChatGPT, Plus, Pro, Business, and Enterprise users get access to GPT‑5.6 Sol through medium+ effort settings, while Pro and Enterprise can select GPT‑5.6 Pro for highest-quality results on complex tasks, per @OpenAI

• API pricing introduced a tiered lineup: Sol $5 / $30 per million input/output tokens, Terra $2.5 / $15, Luna $1 / $6, with cache-write pricing added for the first time and 90% cache-read discount retained, according to @ArtificialAnlys

• OpenAI framed the family around a price-performance ladder: Sol = flagship/highest ceiling, Terra = GPT‑5.5-like capability at lower cost, Luna = fastest/cheapest high-volume option, via @OpenAIDevs

• The launch bundled major app-layer changes: ChatGPT Work, a new desktop app merging Codex + ChatGPT, Sites beta, programmatic tool calling, and multi-agent beta in the Responses API, via @OpenAI, @OpenAIDevs, and @OpenAIDevs

Official claims and benchmark results

OpenAI’s official message emphasized strong agentic/coding performance, better artifact quality, and improved economics.

• Sam Altman called it “obviously the best model we have ever produced” in the launch post, linking the release blog, via @sama

• Altman also highlighted enterprise economics: “5.6 sol is a huge step forward for dollars-per-task,” via @sama

• Greg Brockman said the goal is “the best price for any level of target performance” and the highest possible ceiling, via @gdb

• OpenAI claimed GPT‑5.6 Sol sets a new high of 53.6 on Agents’ Last Exam, beating Claude Fable 5 adaptive by 13.1 points; at medium reasoning it beats Fable by 11.4 points at roughly one-quarter the estimated cost, while Terra and Luna also outperform Fable at around one-sixteenth the cost, via @OpenAI

• OpenAI said GPT‑5.6 improves artifact quality across presentations, documents, and spreadsheets, with outputs exportable into existing enterprise tools, via @OpenAI

• OpenAI positioned GPT‑5.6 as state of the art for reasoning through complex tasks and for producing materials matched to templates, reference files, and preferred style inside ChatGPT Work, via @OpenAI

• OpenAI also said GPT‑5.6 is its most capable model yet on cyber and bio-related tasks, with some API calls potentially blocked or paused for extra safety review in dual-use areas, via @OpenAIDevs

• OpenAI highlighted better Computer Use performance: faster, more token-efficient, support for batching and parallel operations across multi-step tasks, plus picture-in-picture supervision, via @OpenAIDevs

Independent evaluations and third-party measurements

Independent evals broadly placed Sol near or at the frontier, especially on coding-agent workloads, while also surfacing caveats.

• @ArtificialAnlys reported GPT‑5.6 Sol (max) scores 59 on its Intelligence Index, 1 point below Claude Fable 5 (max), at about one-third of Fable’s cost per task

• On the same analysis, Terra and Luna score 55 and 51 on the Intelligence Index, with ~50% and ~80% lower cost per task than Sol, respectively, via @ArtificialAnlys

• Artificial Analysis said Sol leads the Coding Agent Index at 80, ahead of Fable 5 and Opus 4.8, and is also cheaper per task than both on their harnesses, via @ArtificialAnlys

• It also noted Sol defines a new Pareto frontier of intelligence vs output tokens, while Terra and Luna are not on that frontier, via @ArtificialAnlys

• Artificial Analysis found minor improvement over GPT‑5.5 in AA‑Omniscience but with a higher hallucination rate than GPT‑5.5 max, via @ArtificialAnlys

• It reported similar GDPval-AA v2 performance to Claude Fable 5, suggesting comparable ability on economically valuable tasks, via @ArtificialAnlys

• @ValsAI ranked GPT‑5.6 #2 on Vals Index and Vals Multimodal Index, saying Fable 5 remains ahead on several benchmarks but GPT‑5.6 is “clearly in the same class”

• Vals also said Sol is #1 on CyberBench and Excel Modeling Benchmark, and #1 on Legal Research Bench, ProofBench, SWE-bench, and Terminal-Bench 2.1, adding that Fable had a nearly 100% refusal rate on CyberBench, via @ValsAI

• @arcprize said GPT‑5.6 Sol scores 7.8% on ARC‑AGI‑3 and is the first verified frontier model to ever beat an ARC‑AGI‑3 game

• @GregKamradt noted 92.5% on ARC‑AGI‑2, calling it SOTA while costing an order of magnitude less than GPT‑5.5 Pro three months earlier

• @ArtificialAnlys later reported GPT‑5.6 Sol (max) leads CritPt, a benchmark of unpublished research-level physics problems, by roughly 4 points over Claude Fable 5

• @llama_index said day-0 ParseBench results show GPT‑5.6 continues to do well on text and tables but still struggles on charts and layout, and that Luna is ~6× cheaper than Sol with only minor degradations

• @jerryjliu0 similarly said ParseBench shows no high-level change versus GPT‑5.5 on tables/text/charts/layout, stressing persistent weakness on complex text layouts, chart transcription, and source-element bounding boxes

Technical details

The technical story of GPT‑5.6 is as much about inference orchestration and token efficiency as raw capability.

• OpenAI shipped three model tiers with multiple reasoning effort levels; users discussed Light, Medium, High, Extra High, Ultra, leading to a large configuration matrix, via @rasbt

• OpenAI added Programmatic Tool Calling in the Responses API and Multi-agent beta, indicating more explicit support for orchestrated tool use and agent decomposition, via @OpenAIDevs

• OpenAI’s app layer now uses Codex as the core of the new Work product, per @sama and @gdb

• Several posts stress parallel agents/subagents as a major capability lever; @aidan_mclau explicitly mentions users can increase the number of 5.6 subagents

• @LiorOnAI summarized likely drivers as adaptive reasoning, parallel agents, programmatic tool use, and higher token efficiency

• Artificial Analysis reported Sol max uses ~15k output tokens per Intelligence Index task vs 16k for GPT‑5.5, and fewer than Opus 4.8, GLM‑5.2, and Gemini 3.5 Flash at comparable intelligence, via @ArtificialAnlys

• @OpenRouter said early testing found the 5.6 models more token efficient, lowering both cost and time-to-task completion

• The desktop/app layer brought a Chrome extension, revamped in-app browser, authenticated sites, persistent multi-tab sessions, file downloads, and tighter cross-device handoffs, via @OpenAIDevs, @OpenAIDevs, and @OpenAIDevs

• Sites entered beta for paid users, offering hosting, storage, and optional auth for GPT-built apps, via @OpenAIDevs and @OpenAIDevs

The “Sol autonomously post-trained Luna” claim

This was the most provocative technical claim around the launch, but its interpretation became contested almost immediately.

• Multiple accounts amplified the statement that OpenAI says GPT‑5.6 Sol autonomously post-trained GPT‑5.6 Luna, via @scaling01, @tejalpatwardhan, and @dejavucoder

• The claim fueled RSI/autoresearch speculation; @tenobrus said if true as stated, it would be a “pretty large update” for automated researcher timelines

• @eliebakouch framed it as OpenAI asking Sol to post-train Luna “with 100k GPUs” for an experiment

• @gdb said the implication is easy to overlook for accelerating engineering workflows, reinforcing that OpenAI wants this read as more than a marketing flourish

• But skeptical clarifications emerged quickly: @nikolaj2030 asked whether this actually meant Sol completed a small controlled post-training task—modifying a config, editing a scheduler file, and launching a run—rather than end-to-end real-world post-training of Luna

• @nrehiew_ interpreted the screenshot similarly: Sol could go from high-level ideas to editing configs and launching experiments, not fully owning Luna’s end-to-end post-training

• @scaling01 argued that what’s probably happening is a model implementing LLM-as-a-judge graders, reward-shaping logic, or small training configs on top of existing OpenAI RL infrastructure—not autonomous end-to-end research or training systems

• @scaling01 explicitly said we should distance these statements from literal autonomous end-to-end post-training or research, which models still cannot do

• Counterbalancing that skepticism, @aidan_mclau said it is routine for him to have 5.6 e2e do an entire RL run, suggesting meaningful internal workflow automation even if not self-sufficient research

• The consensus across technical observers was not that Sol independently invented and trained Luna, but that GPT‑5.6 may now be capable of executing meaningful chunks of model-improvement workflows inside mature internal infrastructure

Internal productivity and recursive improvement signals

OpenAI also used internal-usage data to argue that GPT‑5.6 materially changes researcher throughput.

• @scaling01 highlighted an OpenAI claim that it doubled experiment throughput per researcher since the start of the year

• @eliebakouch quoted OpenAI saying average daily output tokens per active researcher were more than twice the highest level observed for GPT‑5.5 during internal testing

• Another OpenAI stat, relayed by @eliebakouch, said over six months the share of research compute devoted to internal coding inference grew 100-fold, while internal agentic token usage increased ~22-fold

• @FakePsyho linked these developments to OpenAI’s performance in top programming contests, describing systems close to GPT‑5.6 plus custom harnesses as decisively beating elite human competitors

• This fed broader RSI/autoresearch discussion, especially from people who see long-horizon coding and heuristic optimization as proxies for model-improvement capability

Product implications: ChatGPT Work, Codex merge, desktop, and Sites

The model launch doubled as a product strategy reset: OpenAI is pushing from “chatbot” to “work OS.”

• OpenAI launched ChatGPT Work, an agent powered by Codex + GPT‑5.6 that can act across apps and files, stay on tasks for hours, and turn a goal into finished work, via @OpenAI

• Work can ingest context from docs, Slack, Notion, Microsoft 365, and Google Drive and produce decks, docs, spreadsheets, dashboards, visualizations, and interactive explanations, summarized by @kimmonismus

• The Codex app merged into the new ChatGPT desktop app, confirmed by @avstorm and @OpenAIDevs

• Developers now get inline diff editing, PR review side panel, better SSH video rendering, and stronger computer use, via @romainhuet and @reach_vb

• Sites lets users turn work into shareable hosted apps/websites from ChatGPT, via @OpenAIDevs and @simpsoka

• @OpenAI, @OpenAI, and @OpenAI marketed GPT‑5.6 through case studies: a broccoli farmer, a mathematician, and a family cereal business

• This product reframing was read by some as OpenAI’s answer to Anthropic’s Cowork / Claude Code stack, via @jerryjliu0 and @kimmonismus

Facts vs opinions

Facts / directly sourced claims

• GPT‑5.6 family names, rollout channels, and access tiers: @OpenAI, @OpenAI, @OpenAIDevs

• API prices and cache-write policy: @ArtificialAnlys

• OpenAI’s benchmark claims on Agents’ Last Exam: @OpenAI

• Artificial Analysis and Vals leaderboard placements: @ArtificialAnlys, @ValsAI

• ARC‑AGI‑3 7.8% claim: @arcprize

• ParseBench caveats: @llama_index, @jerryjliu0

• Safety testing finding jailbreaks on GPT‑5.6 Sol: @alxndrdavies

Opinions / interpretation / hype<