Brainstorm a Feature or Improvement

Brainstorming answers WHAT to build through dialogue; ce-plan then enriches the same unified plan artifact with HOW. This skill does not implement code. The current year is 2026, for dating the artifact.

Outcome: a result sized to the work that ce-plan can build on without inventing product behavior, scope boundaries, or success criteria: a chat paragraph for Lightweight work, or a requirements-only unified plan under <root>/plans/ when a file is earned.

Done, on the brainstorm path: that artifact is written and passes the Ready for Planning Check — or no file was written because the dialogue produced no decision that a later reader (the planner, a reviewer, or a future reader) needs recorded under a stable ID and the user asked for none — and Phase 4's handoff has been presented.

Lightweight work ends in chat. Phase 0.3 classifies the tier from the request and bounded inline reads before anything is dispatched; when the tier is uncertain, take the heavier one. Lightweight work — small, well-bounded, low ambiguity — ends in a chat paragraph with no file, no grounding scout, no approach generation, and no claim verifier. A file is earned only by a decision that a later reader needs recorded under a stable ID, or by the user asking for one.

Stop and route instead in three cases, decided by references/phase-0.md, not from memory. Each ends the run its own way, so the done condition above does not apply: non-software work, where references/universal-brainstorming.md replaces Phases 0.2–4; a verdict question about a named external candidate, where you offer the ce-pov handoff; and neither — quick help, a factual question, a single-step task — answered directly.

The feature description is what the invocation carries, whether the user wrote it or a calling skill passed it. If none came, ask the user what they want to explore and do not proceed until you have one.

mode:return-to-caller (a leading token a calling skill such as lfg sets): strip it, run the dialogue unchanged, and replace Phase 4 with the structured return references/handoff.md defines: no menu, no lfg or ce-plan invocation.

Artifact Root

Resolve <root> the first time you compose or read a <root>/ path, never earlier; a scratch-only or no-repo run that touches none skips this entirely.

Resolve the CE artifact root <root> before composing any artifact path.

• Read docs_root from <repo-root>/.compound-engineering/config.yaml only (<repo-root> = git rev-parse --show-toplevel). Do not read it from config.local.yaml. Unset -> <root> is docs, exactly as before.
• Validate a set value: a repo-relative directory whose real, symlink-resolved path stays inside the repo and is neither the repo root nor under .git/. Otherwise stop with an error naming docs_root and the value -- never fall back to docs.
• Use <root> as the sole artifact location: create it if absent, compose each path as <root>/<subdir> with this skill's own subdirectory, and never also read docs.

brainstorm_output and brainstorm_model resolve by this rule instead:

Resolve ordinary CE yaml keys from the two repo files.

• Read <repo-root>/.compound-engineering/config.local.yaml, then config.yaml (<repo-root> = git rev-parse --show-toplevel). Missing files are skipped. Gitignore does not change resolution.
• Win with the first active (non-commented) value. For scalars, empty is unset; an invalid value continues to the next layer, then the skill default. For lists and maps, a present key — including an empty list or map — replaces the whole key.
• Do not use this rule for docs_root — that key is config.yaml only.

Execution Flow

Phases run in this order. Each names the files it cannot run correctly without: read them when you reach it, and never do its work from this table alone.

These rules hold without any read:

OUTPUT_FORMAT is exclusive — markdown OR HTML, never both. The format is the first that applies: a request in this prompt, a preference the user stated earlier, config, then markdown, in every run including headless ones.

When a file is written on the brainstorm path the artifact contract does not change: write to <root>/plans/YYYY-MM-DD-HHMM-<type>-<topic>-plan.<md|html>, with HHMM from local wall-clock time at write; frontmatter carries artifact_contract: ce-unified-plan/v1 and product_contract_source: ce-brainstorm; the body is a Goal Capsule plus the Product Contract. Do not emit a Goal Launch Block or Reader Index. The non-software route writes none of this.

When a file is written, do not declare it written or enter Phase 4 while any check fails in the Ready for Planning Check; a chat result enters Phase 4 (the handoff) with no check to run. An improvised handoff menu is the other silent failure: it shows options that should be hidden and passes the wrong input to the next skill.

The Phase 1.1 grounding scout, the Phase 2.6 claim verifier, and the opt-in Slack researcher are tiered by task shape, never hardcoded to a model name; read references/model-tiers.md before dispatching one. Model elevation is a separate mechanism (references/reasoning-elevation.md).