Claude Sonnet 5.5 (Sep 28) ships 5 breaking changes: forced tool use returns 400, `thinking:disabled` is rejected, thinking blocks are model-bound, `computer_20251124` is gone on the Claude API, and advisor pairings are now 5.x-only.
Four breaking changes in Claude Opus 5.5: thinking can't be disabled, forced tool_choice returns 400, thinking blocks don't cross non-Fable/Mythos models, and computer_20251124 is gone. Each has a specific fix — three carry fallback routing implications the announcement skips.
GPT-6 Astra refuses Chat Completions tool calls, drops temperature and top_p, adds two new error codes operators must handle, and runs async misalignment monitoring that changes the latency contract for Responses API users.
OpenAI deprecated nine legacy audio and realtime model IDs on July 20, shutdown January 20, 2027. The migration is a model-string swap — but operators routing gpt-4o-audio, gpt-4o-realtime, or gpt-audio families need a full routing audit before the deadline.
Three experimental API endpoints that let you programmatically generate, improve, and templatize prompts are being removed alongside the legacy Workbench on August 17. No other major provider exposes equivalent endpoints — here is the operator migration plan.
Claude Sonnet 5 ships three silent production killers: adaptive thinking on by default, temperature/top_p/top_k now returns 400, and a new tokenizer that inflates token counts ~30%. Here's the operator checklist.
OpenAI Assistants API shuts down August 26, 2026 — 56 days away. Official migration replaces Threads/Runs/Assistants with Conversations/Responses/Prompts. Checklist covers grep patterns, thread state, tool schemas, routing proxy compatibility, and Azure timelines.
Claude Fable 5 ships a new tokenizer that produces ~30% more tokens from the same text versus pre-Opus-4.7 models. Here is what AI engineering teams must audit before migrating: token budgets, cost models, cache boundaries, and max_tokens headroom.
Google deprecated Vertex AI Extensions on May 26, 2026, with a hard shutdown on November 26. Teams routing agent workflows through Google must migrate their Code Interpreter, Search, and Custom Extensions to the Gemini Enterprise Agent Platform before the deadline.
TheRouter's legacy /v1/anthropic/messages paths are deprecated and will be removed on September 3, 2026. The canonical path is /v1/messages — the same path official Anthropic SDKs use. Migration is a one-line base-URL change.
Anthropic's Claude Opus 4.1 deprecation retires claude-opus-4-1-20250805 on August 5, 2026. Use this router-focused migration guide to replace aliases, audit fallback tiers, and avoid API failures.
OpenAI's evals platform deprecation, Agent Builder shutdown, and v1/prompts API removal all land November 30, 2026. Here's what operators need to migrate and how the routing layer absorbs the gap.
Official OpenAI gpt-image-2 migration checklist for teams still using gpt-image-1, gpt-image-1.5, gpt-image-1-mini, or chatgpt-image-latest before the Q4 2026 API shutdown.
Anthropic retires claude-sonnet-4-20250514 and claude-opus-4-20250514 on June 15, 2026. Any routing config still pointing to these model IDs will start returning errors in two weeks. Here's the migration map.
OpenAI's April 22 deprecation notice covers 25+ model IDs across two hard shutdown dates — July 23 and October 23, 2026. If your routing config still references gpt-4, gpt-3.5-turbo, o1, o3-mini, or o4-mini, you have a breaking change on the calendar.
