Week 2026-W40

The week in AI

GPT-6 tiers: OpenAI's lineup is now Astra, Sol, and Luna; GPT-6.1 Sol was reported on 2026-09-29. (source)
Gemini 4 Argon (2026-09-30), Google's most capable model, went first only to cybersecurity partners. (source)
Claude lineup: Fable 5.1, Opus 5.5, Sonnet 5.5, and Haiku 4.5. Thinking is always on for Fable and Opus, and forced tool_choice and prefill are gone. (source)
MCP 2026-07-28 spec: stateless core, MCP Apps, and Tasks; the largest revision since launch. (source)
Open weights: DeepSeek-V4-Pro (1.6T MoE, MIT) and Qwen3.5 (hybrid linear attention, Apache 2.0) lead the open field. (DeepSeek, Qwen)
Agent frameworks converge: Google ADK 2.11, OpenAI Agents SDK 0.23, and Pydantic AI 2.54 (all 2026-10-02) add sandboxes, tool approval, and newer MCP SDKs. (ADK, Agents SDK, Pydantic AI)

Links: 24 checked on the final pass, 0 dead, 0 moved. The Claude models overview moved to platform.claude.com/docs/en/models/overview; url updated. The OpenAI GPT-6 page blocks the checker (403); no action needed.
Consolidated models/claude: API behaviour changes folded into Key concepts. Corrected the page to say thinking is always on for Fable 5.1 as well as Opus 5.5, and added Haiku 4.5's 64K output limit and 2026-10-15 earliest retirement date.
Consolidated models/open-weight: the comparison table moved from Current state into a "Main families" section.
Consolidated fundamentals/transformers: the duplicated hybrid-attention entries were merged into the body.
Second pass after the framework release-notes run: consolidated frameworks/landscape (Agent Framework 1.0 and the shared framework direction moved into Key concepts) and tooling/mcp (2026-07-28 spec features moved into Key concepts; Current state keeps the deprecation window and adoption news). The MCP migration open question is partly answered by ADK 2.11.
No stale pages: all 22 topic pages were reviewed this week. No page has more than 8 Current state entries. Inbox empty. No duplicate tags found.