GLM 5.1 vs GPT-5.1

Choose GLM 5.1 if you want…

• ✓Higher intelligence (Artificial Analysis index 51)
• ✓Lower price ($2.15 / 1M blended)

Choose GPT-5.1 if you want…

• ✓Faster output (~142.7 tokens/sec)
• ✓Larger context window (400K)

GLM 5.1

GLM-5.1 from Z.ai is built for one thing above all else: software engineering that runs on its own. A 754-billion parameter Mixture-of-Experts model, it tops the SWE-Bench Pro leaderboard at 58.4%, edging out both GPT-5.4 and Claude Opus 4.6 on real-world coding tasks. What sets it apart in practice is stamina — it can pursue a single engineering goal autonomously for up to eight hours, sustaining hundreds of iterations and thousands of tool calls without human intervention. Users consistently praise this long-horizon execution for agent-based workflows where other models stall. It also delivers fast responses, with a time-to-first-token of 1.33 seconds against a class median of 2.37 seconds. The honest trade-off: GLM-5.1 accepts text only, with no image input, making it a poor fit for visual debugging or UI-centric tasks. It also tends toward verbosity in practice, which can inflate token costs. For teams building autonomous coding pipelines, though, it earns its place at the top of the leaderboard.

GPT-5.1

GPT-5.1 earns its place through adaptive reasoning — a system that genuinely calibrates effort to the task, running roughly twice as fast on straightforward queries and digging deeper on complex ones. That mechanical intelligence shows up in the benchmarks: 94% on AIME 2025, 88.1% on GPQA Diamond, and a 76.3% solve rate on SWE-Bench Verified, making it one of the more capable off-the-shelf options for serious coding and research-level math. Users consistently praise how much cleaner the code output is — fewer logic errors, better edge-case handling — and the improved tool-calling reliability makes it a practical choice for production agentic pipelines. The catch is that the Auto-routing variant has frustrated users who found it silently redirecting requests through stricter safety filters without explanation, a criticism that turned OpenAI's own Reddit launch AMA into a notable PR setback. For teams willing to pick the right variant (Instant, Thinking, or Auto) and work within a September 2024 knowledge cutoff, GPT-5.1 offers strong price-to-capability value at $1.25 per million input tokens — cheaper than its GPT-5.2 successor while covering most production needs.