opensession: Skill for Claude Code

Figure it out

When the task matches no playbook, design one. The deliverable before any code is the workflow itself: a sequence of phases that scales rigor to the task, runs the scientific method, and leaves a decision trail a human can audit after stepping away. Bias toward more rigor. The cost of building the wrong thing dwarfs the cost of being careful.

Don't reinvent a playbook you already have. A focused single-unit task that matches Bug fix, Perf, Feature, Visual parity, Eval, or Multi-phase plan routes there. But a large or cross-cutting version of one (a migration across many call sites, an ambitious multi-part change), or work the user reviews after stepping away, belongs here even though a single-unit version would be a Feature. The rigor and the audit trail are the point.

Start

Keep a checklist whose first item is to read the Principles section of the canonical pstack skill. Then add the phases below as todos.

Phase A: Frame

Ground first, then commit. Don't start the run until you can state:

• The definition of done as a falsifiable predicate (the prove-it-works principle skill). "Done well" has to be checkable.
• Scope, quantified: rough units and effort, plus the blockers grounding surfaced. Raise them before spending hours, not after fifty doomed commits.
• The rigor level, biased high. One-way doors and high blast radius get more; reversible low-stakes steps get less. Rigor is gates and artifacts, not "try harder".

Present the framing and tradeoffs before committing to a long run. Reversible work proceeds (the never-block-on-the-human principle skill), but a multi-hour run earns one checkpoint.

Phase B: Design the workflow

Decompose into atomic, independently-landable units. Sequence riskiest-unknown-first so option value stays high. Scaffold and verification come before features (the foundational-thinking principle skill).

• Build the verification harness before the work, with the baseline captured from the pre-change state, so the check reads as "old value vs new value".
• For one-way-door design decisions, run the architect skill (it runs arena) with diverse, isolated, opinionated candidates and a read-only judge on a different model family. Skip it for mechanical work whose shape is already concrete. A second arena over a settled design is over-engineering (the laziness-protocol principle skill).
• Decide what fans out. Parallelize only across genuine seams, and give each worker its own worktree or branch (the separate-before-serializing-shared-state principle skill). Don't over-fan.
• Write the designed phase list down. That list is what the human reviews.