GPT-5.6 sets a new standard for price-performance, making frontier-level agent performance dramatically more affordable. The model family includes Luna and Terra, which often perform similarly to previous flagships at significantly lower costs. For example, on Browse Comp, GPT-5.6 Luna (Extra High) scored 84.04% at a cost of $1.33, versus GPT-5.5's 84.36% for $33.27.

New API controls enable more efficient agents: retained reasoning and compaction maintain coherence across long tasks, multi-agent orchestration enables parallel workstreams, and programmatic tool calling moves deterministic work into code. On ARC-AGI-3, GPT-5.6 Sol's score jumped from 13.3% to 38.3% with 6× fewer output tokens after enabling these features.

Startups can now use smaller models with tuned reasoning effort and architectural choices to achieve comparable or better results at a fraction of the cost. Use cases that once required a frontier model at every step can now leverage GPT-5.6 family models for significant savings.