GPT-5 in 2026: Features, Benchmarks, Pricing, and How to Use It in Slack | Runbear

GPT-5 is OpenAI's flagship language model, generally available since August 2025. It runs as the default ChatGPT model across all plans and ships in four API variants: gpt-5, gpt-5-mini, gpt-5-pro, and a 'thinking' mode picked automatically by a router. Per OpenAI's GPT-5 system card, the model hallucinates roughly 80% less than GPT-4o and scores 74.9% on SWE-bench Verified, the highest result of any major foundation model in 2026.

May 2026 Update

GPT-5 has been generally available since August 2025 and is now nine months into production. ChatGPT users got a smarter default model. Developers got three API tiers (mini, standard, pro) plus a router that picks 'thinking mode' automatically when a question is hard.

Runbear now runs on GPT-5 via the OpenAI API, powering context assembly and automated actions across 2,000+ connected tools in Slack. The improvement in instruction following (GPT-5 scored 99% on COLLIE vs earlier baselines) shows up directly in how precisely Runbear agents route requests, draft responses, and take action.

See the Aloware case study for a real example: a Zoom transcript agent that logs CRM deals with a single emoji, built on this model layer.

The rest of this post covers everything you need to know: what GPT-5 is, how it compares to prior models, availability, pricing, and what it means for ops teams using AI in Slack.

What Is GPT-5?

GPT-5 is OpenAI's most advanced language model yet—built to be more robust, reliable, and helpful than any of its predecessors. It delivers state-of-the-art accuracy on real-world tasks while significantly reducing hallucinations and deceptive responses. Designed with real workflows in mind, it powers real-time AI agents, developer tools, and enterprise copilots across platforms like Slack, HubSpot, and Microsoft Teams.

Key Improvements in GPT-5

• State-of-the-art performance on leading AI benchmarks:
• Fewer hallucinations: GPT-5 responses are up to 80% more factual than previous models like GPT-4o or o3.
• Safer and more honest: Reduced deceptive behavior in edge cases or underspecified prompts.
• Improved instruction following: More reliable for agents, workflows, and multi-step tasks.
• Multimodal reasoning: Enhanced capabilities across text, image, video, and charts.

What makes GPT-5 different?

Rather than a single monolithic model, GPT-5 introduces a router-based model architecture:

• GPT-5: Fast, general-purpose response generation
• GPT-5 Thinking: Deep reasoning for complex tasks
• GPT-5 Pro: Long-context, high-precision model tuned for advanced applications

These models are deployed intelligently behind the scenes, depending on query difficulty, user intent, and context. This allows GPT-5 to feel both fast and deeply capable—delivering expert-level answers where needed, while still handling everyday queries with speed and grace.

Evaluations: How Smart Is GPT-5?

Math Mastery

GPT-5 dominates math evaluations:

• AIME 2025: 94.6% (no tools) — new state-of-the-art.
• HMMT: 96.7% (no tools), 100% (with tools).
• FrontierMath: 26.3% → 32.1% with tool support.
• GPQA (PhD-level): 88.4% (no tools) → 89.4% (with thinking).

Real-World Coding

On practical software engineering and code editing benchmarks:

• SWE-bench Verified: 74.9% accuracy (GPT-5) vs 69.1% (OpenAI o3) and 30.8% (GPT-4o).
• Aider Polyglot: 88% accuracy (GPT-5), far ahead of all previous models.

Instruction Following & Tool Use

GPT-5 is vastly better at multi-step reasoning and agentic behaviors:

• Scale MultiChallenge (multi-turn): 69.6% vs GPT-4o's 40.3%.
• BrowseComp (search + browsing): 54.9% vs 49.7%.
• COLLIE (freeform following): 99.0% accuracy.

Multimodal Understanding

GPT-5 outperforms on visual, video, and diagram-based tasks:

• MMMU: 84.2% vs GPT-4o's 72.2%.
• ERQA: 65.7% vs 35.2% (GPT-4o).

Health Conversations

GPT-5 is the most accurate and least hallucinatory model for medical applications:

• HealthBench: 67.2% vs GPT-4o's 32.0%.
• Hallucination Rate: 1.6% (with thinking), down from GPT-4o's 15.8%.

Economically Valuable Tasks

GPT-5 beats both o3 and ChatGPT Agent on complex, real-world professional tasks:

• Achieves 47.1% wins over industry experts in internal benchmarks.

Faster, More Efficient Thinking

GPT-5 achieves better performance with fewer output tokens than OpenAI o3:

• 50–80% fewer tokens across reasoning, coding, and scientific benchmarks.

Detailed Benchmarks

Who is GPT-5 for?

• Business leaders & teams: Analyze documents, monitor operations, and plan strategy with better context awareness and safer outputs.
• Developers: Use GPT-5 to generate production-quality frontends, debug codebases, and automate software tasks.
• Healthcare professionals & patients: Understand diagnoses and treatment options with greater clarity and proactive reasoning.
• Knowledge workers & writers: Get help crafting thoughtful reports, articles, or even poetry—with deeper structure and emotional impact.

Final Thoughts

GPT-5 sets a new standard in reasoning, reliability, and real-world AI performance. With better benchmarks and lower hallucination rates, it's shaping up to be the most capable foundation model to date.

Runbear agents are powered by GPT-5 via the OpenAI API. That means every context assembly, Slack response, and automated action your team runs through Runbear benefits from GPT-5's improved reasoning and lower hallucination rates.