# Fastest Response Time LLMs for Agentic Coding & Browser Automation (2026) ## By "Response Time" — There Are 3 Different Metrics, Each with a Different Winner --- ### 1. 🏆 API-Level Latency (TTFT — Time to First Token) *The fastest to *start responding* — crucial for interactive feel.* | Model | TTFT | |---|---| | **GPT-5.3 Codex** | **0.003s (3ms)** — *by far the fastest* | | Nova Micro | 0.30s | | Llama 4 Scout | 0.33s | | Gemini 2.0 Flash | 0.34s | | GPT-4o mini | 0.35s | **Winner: GPT-5.3 Codex** — 100x faster than the next-best model. It's a specialized coding model with absurdly low latency. --- ### 2. 🏆 Task Completion Speed (Wall-Clock Time for Agentic Browser Automation) *The fastest to *finish a multi-step task** — includes reasoning + tool calls.* **From Test-Lab.ai benchmark (April 2026)** — real production browser automation: | Tier | Model | Avg Duration | Pass Rate | Cost | |---|---|---|---|---| | **Light** | **Gemini 3 Flash** | **58s** | 100% | $0.06 | | Light | Gemini 3.1 Flash Lite | 60s | 50% | $0.03 | | Light | Kimi K2.6 | 136s | 100% | $0.07 | | Light | DeepSeek V3.2 | 250s | 100% | $0.04 | | **Smart** | **Claude Opus 4.7** | **88s** | 100% | $1.88 | | Smart | GPT-5.4 Mini | 86s | 50% | $0.07 | | Smart | **GPT-5.4** | **98s** | 100% | $0.17 | | Smart | Gemini 3.1 Pro | 100s | 100% | $0.24 | | Smart | Claude Sonnet 4.6 | 121s | 100% | $0.77 | **Winners:** - **Light tier (simple tasks): Gemini 3 Flash** — 58s avg, 100% pass rate, only $0.06/run - **Smart tier (complex multi-step): Claude Opus 4.7** — 88s avg (fastest smart model), 100% pass rate, but expensive at $1.88/run - **Best value sweet spot: GPT-5.4** — 98s avg, 100% pass rate, only $0.17/run (11x cheaper than Claude Opus 4.7) **From Browser Use BU Bench (June 2026)** — 100 hard browser tasks: - **Browser Use Cloud (bu-ultra)** — fastest throughput at ~14 tasks/hour (most accurate + fastest combined) - claude-fable-5 — highest accuracy at 80% but slower (more API calls per task) --- ### 3. 🏆 Best Combination of Speed + Quality for Agentic Coding | Agentic Coding (SWE-Bench) | Score | Browsing (BrowseComp) | Score | Computer Use (OSWorld) | Score | |---|---|---|---|---|---| | **Claude Mythos 5** | **95.5%** | **Claude Fable 5** | **88%** | **Claude Fable 5** | **85%** | | Claude Fable 5 | 95.0% | DeepSeek V4 Flash | 85.9% | Claude Opus 4.8 | 83.4% | | Claude Opus 4.8 | 88.6% | Gemini 3.1 Pro | 85.9% | Claude Sonnet 5 | 81.2% | --- ### 📊 Summary: Which Should You Use? | Use Case | Fastest Response Time Recommendation | |---|---| | **Agentic coding (interactive)** | **GPT-5.3 Codex** — 3ms TTFT is unmatched for feel. Or **Claude Mythos 5** for best SWE-Bench quality (95.5%) | | **Browser automation (simple tasks)** | **Gemini 3 Flash** — 58s avg, 100% pass, $0.06/run | | **Browser automation (complex)** | **Claude Opus 4.7** (88s fastest) or **GPT-5.4** (98s, best value at $0.17) | | **Browser automation (highest quality)** | **Claude Fable 5** — 80% on BU Bench, 88% on BrowseComp, 85% on OSWorld | | **Highest throughput (tasks/hour)** | **Browser Use Cloud (bu-ultra)** — ~14 tasks/hour | **The single best all-around answer** for "fastest response time LLM for agentic coding / browser automation" is **GPT-5.4** — it delivers 100% pass rate in production browser automation in 98s average (only 10s behind the speed champion), costs just $0.17/run, and is a top-tier coding model. For pure speed at any cost, **Claude Opus 4.7** (88s) or **GPT-5.3 Codex** (3ms TTFT) are the champions.