Claude Opus 5.5 in Foundry: the Opus 5 migration cost math
Claude Opus 5.5 is GA in Microsoft Foundry at $4/$20 per million tokens with cache reads at $0.20, which cuts a cache-heavy 60-turn agent session from $8.63 on Opus 5 to $5.10 and brings it within 1.5x of Sonnet 5. The saving can reverse on uncached endpoints that ran Opus 5 with thinking disabled, because thinking is now always on, the default effort dropped to medium, and Foundry still offers no EU data zone, batch pricing or fast mode.