Opus 4.5 skips explicit plan instructions more often than previous models

Description

When given a detailed implementation plan with explicit file-level instructions (exact line numbers, code snippets, specific locations), Claude Opus 4.5 occasionally skips steps or takes shortcuts that deviate from the plan. This requires the user to re-read the plan and prompt Claude to follow it more carefully.

Example

A plan specified 4 files to modify with specific changes per file, including:

• Adding env var documentation to .env.vps.example
• Guarding 8 specific workers in main.go (with line numbers provided)
• Updating 3 specific lines in a shell script

Claude completed the work but needed prompting to verify all deployment steps were followed, suggesting it was ready to move on before confirming completeness.

Expected Behavior

When given a numbered plan with explicit instructions, Claude should methodically execute each step and self-verify completion before declaring done.

Environment

• Claude Code CLI
• Model: claude-opus-4-5-20251101
• Mode: Learning output style with plan execution