GPT-5.6 went GA with three tiers (Sol, Terra, Luna) and a new capability that matters more than the benchmarks: Programmatic Tool Calling.
Agents can now write and execute lightweight programs between tool calls — filtering data, coordinating tools, monitoring progress — without round-tripping intermediate results through the context window. Fewer tokens, fewer model calls, faster task completion.
Production receipts: Ploy.ai migrated from Claude Opus 4.8 to GPT-5.6 Sol. Results: $2.22 per build vs $3.06. Half the wall-clock time.
Also in this issue:
Anthropic's J-Space: Claude has a silent internal workspace for reasoning it never writes down. Used for deception detection.
