cw-slice

cw-slice

The expensive mistake in this repo is not a bad implementation — it is a second implementation. A new model_*, *_config, provider_*, or "bridge" module beside the one that already does the job ships two systems and a comment that is no longer true. This skill is the ponytail ladder's rung 2 with commands attached: find the thing that already exists, then edit it.

Stage 2 of the loop: cw-orient → slice → cw-gates → cw-dogfood → cw-land → cw-handoff.

When to use

• Any feature, upgrade, refactor, or "make X work like Y" request.
• Before creating a new module, trait, config struct, or command.
• When a plan or issue tells you to build something and you have not yet confirmed it does not already exist.

Workflow

1. Walk the ladder, out loud, before opening an editor. Stop at the first rung that answers, and say which one you stopped at:

   1. Does this need to exist? → skip it.
   2. Already in this codebase? → reuse it.
   3. Stdlib does it? → use it.
   4. Native platform feature? → use it.
   5. Installed dependency? → use it.
   6. One line? → one line.
   7. Only then: the minimum that works.

   The ladder runs after reading the code, never instead of it. A short diff written without reading the call sites is a guess, not a small change.

2. Grep for the predecessor. This is the step that gets skipped and the one that costs the most:

   grep -rn "<the concept, in the words the code would use>" crates --include='*.rs' | head -40
   ls crates
   grep -rln 'model_\|_config\|provider_' crates/*/src --include='*.rs' | head -30
   

   Search behavior and symbols, not just filenames. If you find an owner, edit it. If you are still adding a new layer, its module doc must name the predecessor it replaces — otherwise you are editing the wrong file.

3. Check the contracts you are about to walk into. These are the ones this repo actively guards, and a guard test fails if you duplicate them:

   • One turn loop: crates/tui/src/core/engine/turn_loop.rs, guarded by crates/core/tests/single_turn_loop.rs. Do not add a second.
   • One base prompt: BASE_PROMPT in crates/tui/src/prompts/text.rs.
   • The subagent tool is agent. Do not revive agent_open / agent_eval / agent_close / delegate_to_agent.
   • The system prompt + tool catalog are a session-pinned KV-cache prefix (docs/CACHE.md). Any new session-context contributor must state its cache effect — frozen prefix vs. append-only history. Never splice a volatile fact into the prefix.
   • crates/tui/src/core/ is a module inside the TUI crate. crates/core is a different crate that runs no turns. Do not confuse them.
   • Repeatedly misidentified as dead, verify consumers before removing: tui/src/context_budget.rs, tui/src/model_registry.rs, tui/src/prompt_zones.rs, tui/src/tools/remember.rs, config/src/route/.