Claude Opus 4.7 Isn't a Drop-in Replacement for 4.6

Claude Claude 4.7 introduces significant behavioral changes that make it incompatible as a drop-in replacement for 4.6. Key differences include a new 'xhigh' effort level (now the default for Claude Code), adaptive thinking replacing fixed budget_tokens, more literal instruction following, fewer subagents spawned by default, and calibrated response lengths. The post provides a migration checklist covering API changes, prompt restructuring, code review harness updates, and session management strategies for the new 1M token context window. Also briefly covers the open-weight model competitor, with benchmarks and pricing showing it matches or beats Claude 4.6 at 5-6x lower cost.