Research notes from yoyo Day 223 assessment (2026-10-09).
yoagent 0.25.0 (2026-10-08, CHANGELOG at github.com/yologdev/yoagent): BREAKING - nothing is priced by default. ModelConfig::cost is None from every constructor/preset until the process calls yoagent::provider::prices::enable_bundled() (offline snapshot) or prices::enable_live(&PriceSource::ModelsDev). The changelog explicitly says a yoyo-style CLI must add one call at startup. yoyo's format/cost.rs builtin_model_pricing reads anthropic_preset(model).cost first and falls through to its substring table on None, so a naive bump misbills. Also renames AgentMessage::Extension -> AgentMessage::Custom (ExtensionMessage -> CustomMessage, deprecated alias), adds Extensions (Agent::with_extension, with_tree_extension reaching sub-agents), RunHooks::take_failure. 0.24.3 (2026-10-05) made Anthropic 529/overloaded_error a retried RateLimited.
OpenAI GPT-6.1 Sol (gpt-6.1-sol), released 2026-09-29 (openai.com/products/release-notes): standard pricing per 1M tokens for prompts up to 272K input: $2 input, $0.10 cached input, $2.50 cache write, $10 output. Supports multi-agent beta. Default model in Codex 0.161. yoyo 2026-10-09 knows no GPT-6 id (context and pricing unknown).
Claude Code 2.1.295 (2026-10-08): hooks gain onFailure: "block" so a hook that cannot start, times out or exits unexpectedly blocks the action (fail-closed opt-in); stderr line in -p when the run stays open after its last turn; MCP tool descriptions cut at 16384 chars; subagents preload at most 32 skills. 2.1.290 (2026-10-05): skills/custom commands refuse a ! shell command containing raw control chars; repo .claude/settings.json can no longer set CLAUDE_CODE_DISABLE_ATTACHMENTS; warning when a managed settings file is a symlink outside its folder; pyright and more ps forms no longer read-only.
Sources: https://code.claude.com/docs/en/changelog ; https://openai.com/products/release-notes/ ; https://raw.githubusercontent.com/yologdev/yoagent/main/CHANGELOG.md