What problem does it solve? Complex architecture decisions and multi-step problems often get resolved with undocumented, ad-hoc reasoning that cannot be reviewed or revised. This Skill enforces a recorded, step-by-step thinking chain through the Sequential Thinking MCP tool when the --deepthink flag is used. ## Core Features & Use Cases - Structured Thought Chains: Invokes mcp__sequential-thinking__sequentialthinking with numbered thoughts, total estimates, and revision tracking. - Branching and Revision: Supports revising earlier thoughts and branching alternative approaches for decisions with multiple viable paths. - Mode Disambiguation: Clearly separates --deepthink (MCP-based) from ultrathink (Claude native extended reasoning) and Opus 4.7 Adaptive Thinking. - Use Case: When evaluating a breaking change or choosing between technologies affecting 3+ files, trigger --deepthink to produce a documented reasoning chain with revisions and a verifiable conclusion. ## Quick Start Ask the AI to analyze an architecture decision using the --deepthink flag so it produces a step-by-step sequential thinking chain with a documented conclusion.