ChatGPT vs Claude vs Gemini vs Grok

OpenAI's ChatGPT remains the most widely-used AI assistant in the world. GPT-5.5 (April 23, 2026) held #1 on the Artificial Analysis Intelligence Index at 60.2 until Anthropic retook the crown, and after the June 9 release of Claude Fable 5 (64.9) it now sits behind both Fable 5 and Claude Opus 4.8 (61.4), still the strongest non-Claude model. It dominates shell automation (Terminal-Bench 2.0: 82.7%, +13 over Opus 4.7) and advanced math (FrontierMath Tier 4: 35.4%). API pricing doubled vs 5.4 to $5/$30 per million tokens; a new GPT-5.5 Pro variant for longer reasoning sits at $30/$180. Codex now has a 1M-token context window with optional fast-mode at 2.5x cost. Honest caveats: GPT-5.5 still loses SWE-Bench Pro to Claude Opus 4.8 (58.6% vs 69.2%), loses MCP-Atlas tool use to both Opus (82.2%) and Gemini (83.6%), and posts an 86% hallucination rate on AA-Omniscience. The ecosystem advantage remains unmatched: DALL-E, Codex, Atlas browser, 60+ connectors, Memory, Projects, GPT Store, and Microsoft 365 Copilot integration. Sora video app/API is being discontinued (web/app April 26, 2026; API September 24, 2026).

Anthropic's Claude Fable 5 (June 9, 2026) is the most capable model the company has ever made generally available, and it tops the Artificial Analysis Intelligence Index at 64.9, nearly five points clear of any other lab's best model and ahead of Anthropic's own Opus 4.8 (61.4) and GPT-5.5 (60.2). It is the production, safeguarded version of the same weights as the restricted Claude Mythos 5. On coding it posts 95.0% on SWE-bench Verified and 80.3% on SWE-bench Pro, beating Opus 4.8 (69.2%), GPT-5.5 (58.6%), and Gemini (54.2%), and on GDPval-AA, the benchmark for real economic-value work, it leads at 1,932 Elo. It is built for long-horizon autonomy, working for days at a time in an agent harness and testing its own output, plus state-of-the-art vision for diagrams, charts, and tables inside PDFs. New wrinkle for developers: Fable 5 ships safety classifiers that can decline a request (returned as stop_reason "refusal", with server, client, or manual fallback to Opus 4.8), reroute in under 5% of sessions, and require 30-day data retention. Fable 5 prices at $10/$50 per million tokens with a 1M-token context and 128K output. Sitting alongside it, the cheaper, faster Claude Opus 4.8 ($5/$25, optional fast mode at $10/$50) remains the everyday workhorse. Honest caveats: Fable runs slower per turn, costs double Opus 4.8, and its classifiers have refused some innocuous prompts near security and biology topics.

Google's Gemini 3.5 Flash (May 19, 2026) is the new headline model: a Flash-tier model that beats last generation's flagship 3.1 Pro on coding and agentic work. It posts 76.2% on Terminal-Bench 2.1, 83.6% on MCP Atlas tool-use, and 1656 Elo on GDPval-AA, while running ~280 tokens/sec (one of the fastest models measured) at $1.50/$9.00 per million tokens. On the Artificial Analysis Intelligence Index it scores 55, behind Claude Fable 5 (64.9), Claude Opus 4.8 (61.4), and GPT-5.5 (60.2) but sitting on the speed-intelligence frontier. Honest caveat: 3.1 Pro still wins some of the hardest abstract-reasoning tests like ARC-AGI-2, and 3.5 Flash costs 3x the previous Gemini 3 Flash. Native multimodal across text, image, audio, and video with 1M-token context. Gemini 3.5 Pro is slated for next month. Deep integration across Google Workspace, NotebookLM, Veo 3.1, and the new Google Antigravity 2.0 agent platform.

xAI's Grok 4.3 (public launch April 30, 2026, after an April 17 beta on the SuperGrok Heavy tier) replaces the multi-variant Grok 4.20 lineup with a single value-priced flagship, API ID grok-4.3, that is cheaper and faster than its predecessor. Flagship API pricing dropped to $1.25/$2.50 per million tokens (cached input $0.20), roughly 38% cheaper input and 58% cheaper output than Grok 4.20, with a 1M-token context window (down from the 2M some 4.20 variants offered) and new native video input. On the Artificial Analysis Intelligence Index it scores 53, about 4 points above Grok 4.20 and just above Claude Sonnet 4.6, but clearly behind the frontier: Claude Fable 5 (64.9), Claude Opus 4.8 (61.4), GPT-5.5 (60.2), and Gemini 3.5 Flash (55.0). Its standout gain is agentic performance, where its GDPval-AA Elo jumped 321 points to 1500, beating Gemini 3.1 Pro Preview and Muse Spark, though it still trails GPT-5.5 by about 276 Elo. Honest caveat: accuracy rose roughly 8 points but the non-hallucination rate fell about 8 points versus Grok 4.20, so the older model still leads on factual reliability, and xAI published no SWE-bench numbers so coding comparisons stay inferential. xAI is now a SpaceX subsidiary, with Grok 5 in training on Colossus 2.