PR Summary

Low Risk
Mostly registry, documentation, and opt-in integration tests; no changes to core routing or auth logic beyond exposing a new model id.

Overview
Adds anthropic/claude-opus-5 to models.yaml ($5/$25, 1M context, vision/tools/reasoning) and the generated Model literal in models.py, with notes on default thinking, effort limits, and optional Fast mode pricing.

Docs and guidance are updated across docs/models/anthropic.mdx, overview.mdx, and CLAUDE.md: a new Opus 5 card in the Latest section, Opus 4.8 framed as the previous generation, and production/deprecation fallback pointers moved from Opus 4.8 to Opus 5 (including Fable 5 and Opus 4.1 notes).

Integration tests add Opus 5 to the frontier live matrix (Agent.collect and _llm_router streaming) and raise shared max_tokens from 512 to 2048 so default-thinking Opus 5 can emit visible text before the budget is spent on reasoning.

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