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/lc-build

Build an ASTRA analysis from spec to materialized results. Plans interactively, then loops autonomously via the ralph-wiggum stop hook until all outputs are materialized or --max-iterations is reached.

Source: claude/lightcone/skills/lc-build/SKILL.md.

Argument hint: [DESCRIPTION] [--universe NAME] [--max-iterations N]. Defaults: universe baseline, max-iterations 25.

Allowed tools

Read, Write, Edit, Glob, Grep,
Bash(astra:*), Bash(lc:*), Bash(python:*), Bash(git:*), Bash(pip:*), Bash(mkdir:*),
Bash(setup-lc-build:*),
Agent, AskUserQuestion

Phases

Phase 0 — Resume an interrupted loop

If .claude/ralph-loop.local.md exists, ask the user via AskUserQuestion whether to resume or start fresh. Resume runs setup-lc-build.sh --resume; fresh deletes the state file.

Phase 1 — Plan (interactive)

  1. Validate prerequisites via setup-lc-build.sh --validate --universe <U> --max-iterations <N>. Bails out with actionable error messages if astra.yaml, the universe file, or required tools are missing.
  2. Read context — astra.yaml, CLAUDE.md, .claude/guides/astra-reference.md, .claude/guides/lightcone-cli-reference.md, universes/<U>.yaml, any existing scripts/.
  3. Produce a plan at .lightcone/plans/build-plan-<U>.md with: analysis overview; dependency graph; decision selections; ordered build checklist with per-output script / decisions / dependencies / estimated cost; verification checklist.
  4. Get approval via AskUserQuestion: "Approve and start building" vs "Let me edit the plan first."

Rule: Phase 1 is read-only exploration. No code, no spec edits until the user approves.

Phase 2 — Loop (autonomous)

Once approved, setup-lc-build.sh --activate writes .claude/ralph-loop.local.md. The Claude Code stop hook intercepts session exits and re-injects the loop prompt (assets/loop-prompt.md) until the agent emits <promise>BUILD_COMPLETE</promise> or max-iterations is hit.

Each iteration: survey state, decide what to do next, work, commit, exit. The plan file persists across crashes for easy resumption and is deleted on successful completion.

State files

File Purpose
.lightcone/plans/build-plan-<universe>.md The user-approved plan. Persists across crashes. Deleted on completion.
.claude/ralph-loop.local.md Loop state: iteration count, max iterations, session id, universe. Used by the session-start hook to detect interruptions.

Cancellation

Mid-loop: /cancel-ralph (provided by the ralph-loop plugin).

Dependency on the ralph-loop plugin

The loop machinery (the stop hook, /cancel-ralph) ships in a separate Claude Code plugin. setup-lc-build.sh will attempt to install it on demand from the marketplace; if installation fails it errors out and cleans up.