pi v0.87.1: Opus 5.5 and GPT-6 Sol/Luna across providers, Grok 4.7 as the xAI default

pi v0.87.1 was published on September 22, 2026, a day after v0.87.0. It is a model-availability release: three new frontier models are now selectable in pi across the providers that carry them.

Claude Opus 5.5, GPT-6 Sol, and GPT-6 Luna arrive through supported providers, including GitHub Copilot. The inheritance lines spell out the coverage: GitHub Copilot inherits all three; OpenAI API keys and OpenAI Codex subscriptions inherit GPT-6 Sol and GPT-6 Luna; Anthropic inherits Claude Opus 5.5 with adaptive thinking and a 1M context window.

xAI sessions get a new default: Grok 4.7 replaces the previous model for new sessions, so xAI users land on the current generation without changing settings.

The fix list carries one contributed fix worth noting: split-turn compaction summaries were being refused by Claude Fable 5.1, and the fix clearly separates the conversation and uses continuation-oriented instructions (#9908). Missing or invalid --mode values now report an error and exit nonzero instead of being silently ignored (#9045), inherited image-only user messages no longer carry an empty text part that some OpenAI-compatible providers rejected (#9797), and inherited Anthropic OAuth requests stop reporting an outdated Claude Code version.

The release page groups the changes under New Features, Added, Changed, and Fixed.