GPT-5.5

Learning Objectives

• Understand how GPT-5.5 differs from GPT-5.4 and where it changes the practical defaults
• Compare the three GPT-5.5 variants (standard, Thinking, Pro) and identify the right one for different use cases
• Evaluate GPT-5.5 against competing frontier models (Claude Opus 4.7, Gemini 3.1 Pro)

What Is GPT-5.5?

GPT-5.5 is OpenAI's flagship general-purpose model, released April 23, 2026 — just six weeks after GPT-5.4. OpenAI describes it as "a new class of intelligence built specifically for real work and for powering agents," and it replaces GPT-5.4 as the default model in ChatGPT for Plus, Pro, Business, and Enterprise users.

The headline shift from 5.4: GPT-5.5 is engineered for agentic workflows — multi-step tasks where the model plans, uses tools, executes commands, checks its own output, and recovers from mistakes with fewer human iterations. It also uses significantly fewer tokens than GPT-5.4 on the same Codex tasks at matched latency, which lowers the cost of long agent runs.

Key Capabilities

Agentic Coding and Computer Use

GPT-5.5's biggest jumps over GPT-5.4 are on the benchmarks that measure real agent work:

• Terminal-Bench 2.0: 82.7% (GPT-5.4: 75.1%) — multi-tool command-line workflows requiring planning and error recovery; the metric most coding-agent builders are paying attention to
• OSWorld-Verified: 78.7% (GPT-5.4: 75.0%) — desktop UI automation across mixed software tasks
• BrowseComp: 90.1% (GPT-5.5 Pro) — web research agent capability for locating hard-to-find information

The token-efficiency gain compounds with capability: agents that used to burn through context on retries finish the same task in fewer steps.

Knowledge Work

• GDPval: 84.9% (GPT-5.4: 83.0%) — economically valuable knowledge-work tasks measured against expert humans
• Stronger handling of unstructured prompts: GPT-5.5 plans workflows from a one-line goal where GPT-5.4 needed scaffolding

Scientific and Mathematical Reasoning

• FrontierMath Tier 4: 35.4% (Claude Opus 4.7: 22.9%, Gemini 3.1 Pro: 16.7%) — the hardest open math benchmark, where GPT-5.5 currently leads frontier models by a wide margin
• Meaningful gains on technical research workflows; OpenAI cites drug-discovery scenarios as an early use case

Context Window

GPT-5.5 carries forward a roughly 1 million token context window (922K effective) for the standard API. The Codex variant ships with a 400K context tuned for long-running coding sessions.

GPT-5.5 Variants

Choosing between variants:

• Default to GPT-5.5 Instant for most tasks — same low-latency profile users expect from chat, now with materially fewer hallucinations on sensitive professional domains
• GPT-5.5 Thinking when the task requires extended reasoning (complex math, multi-step logic, hard coding tickets)
• GPT-5.5 Pro when accuracy on the hardest research, browsing, or computer-use tasks justifies the higher compute cost

May 5, 2026 — Instant becomes default across every tier

OpenAI swapped ChatGPT's default model from GPT-5.3 Instant to GPT-5.5 Instant for free, Plus, Pro, Business, and Enterprise users on May 5, 2026, while keeping the same low-latency profile. The company says the new model substantially reduces hallucinations in sensitive professional domains (law, medicine, finance) and posts an AIME 2025 math score of 81.2 versus the prior 65.4, alongside improvements in multimodal reasoning. GPT-5.3 will remain available to paid API users for three more months before the older default is fully retired. The Instant variant is exposed to API users immediately as chat-latest; named gpt-5.5 and gpt-5.5-pro endpoints continue their separate rollout.

OpenAI did not ship a mini or nano variant alongside the GPT-5.5 launch. Older 5.x models (5.1, 5.2, 5.3, plus the existing GPT-5.4 mini) remain on the menu for cost-sensitive serving.

Pricing

ChatGPT Subscription Tiers

API Pricing

Third-party reporting at launch (Apr 23, 2026) cites the following per-million-token pricing for the upcoming gpt-5.5 and gpt-5.5-pro API endpoints:

API access is rolling out "in the coming weeks" per OpenAI; check platform.openai.com/pricing for the official rate card once endpoints are live.

GPT-5.5 vs. Competing Frontier Models

GPT-5.5 leads on agentic and mathematical benchmarks (Terminal-Bench, GDPval, OSWorld, FrontierMath). Claude Opus 4.7 still leads on SWE-bench Pro (64.3%) for the hardest software-engineering tickets — pick Claude when you need a model that can grind through complex GitHub issues end-to-end.

Strategic Context: The "Super App"

GPT-5.5 is the model OpenAI's leadership has framed as a step toward a "super app" — a single product that bundles ChatGPT, Codex, and the AI browser into one assistant that can carry a task across tools without handing it off. The fact that 5.5 ships only six weeks after 5.4 underscores how aggressively OpenAI is iterating to defend share against Claude and Gemini in the enterprise market.

Strengths

• Best-in-class agentic coding — Terminal-Bench 2.0 score of 82.7% leads the field by a wide margin
• Strongest knowledge-work model — GDPval 84.9% beats Claude Opus 4.7 and Gemini 3.1 Pro
• Token-efficient — uses fewer tokens than GPT-5.4 for the same Codex tasks at matched latency, lowering long-agent-run cost
• Scientific reasoning leap — FrontierMath Tier 4 35.4% nearly doubles Claude Opus 4.7 on the hardest open math benchmark
• Largest developer ecosystem — same OpenAI API, SDKs, tutorials, and community as the rest of the GPT-5 family

Limitations & Considerations

• API not live yet — endpoints roll out in the coming weeks; budget around ChatGPT-only access in the interim
• Higher API price than GPT-5.4 — reported at $5 in and $30 out per million tokens, roughly twice the cost of gpt-5.4; recheck math before migrating high-volume jobs
• Free and Go tiers do not include GPT-5.5 — those tiers stay on older 5.x mini models
• Claude Opus 4.7 still leads SWE-bench Pro — for the hardest end-to-end software-engineering tasks, Opus 4.7 is the safer default
• Closed model — API-only access; no weights available for self-hosting
• Rapid release cadence — OpenAI shipped 5.4 and 5.5 within six weeks; assume the model behind your prompts can change again on a similar timeline

Lineage

• GPT-5.5 (April 23, 2026) — current flagship; the page above
• GPT-5.4 (March 5, 2026) — prior flagship; introduced 1 million token context, native computer-use, and the GPT-5.4 Pro / Thinking / mini / nano variant lineup. Still available via the gpt-5.4 API endpoint and as the underlying Free / Go tier model
• GPT-5.3-Codex — dedicated coding model that powers the OpenAI Codex platform
• GPT-5.3-Codex-Spark — real-time coding variant on Cerebras hardware (1,000+ tokens/sec)
• GPT-OSS — OpenAI's open-weight model under Apache 2.0
• GPT-5.1 was deprecated on March 11, 2026; GPT-5.2 and GPT-5.3 remain on the menu for cost-sensitive serving

Key Takeaways

• GPT-5.5 (April 23, 2026) is OpenAI's new flagship — built specifically for agentic work, with record scores on Terminal-Bench 2.0 (82.7%), GDPval (84.9%), OSWorld (78.7%), and FrontierMath Tier 4 (35.4%)
• Three variants ship: Instant (May 5, 2026 default ChatGPT model across every tier; reduced hallucinations on law / medicine / finance; AIME 2025 81.2 vs prior 65.4), Thinking, and Pro — no mini or nano this time
• The Instant variant is live in the API as chat-latest; GPT-5.3 Instant stays available to paid API users for three more months; named gpt-5.5 / gpt-5.5-pro endpoints continue their separate rollout at a reported $5 in / $30 out per million tokens
• Now generally available on Amazon Bedrock (June 2026, after an earlier limited preview) — the first non-Azure cloud distribution of OpenAI frontier models since 2019, after the Microsoft-OpenAI agreement amendment ended exclusive cloud rights through 2032
• Claude Opus 4.7 still leads SWE-bench Pro (64.3% vs. 58.6%) — pick Claude for the hardest end-to-end software-engineering tasks; pick GPT-5.5 for everything else agentic