scripts/precompact.js

#!/usr/bin/env node
/**
 * precompact.js — Nomad PreCompact hook (portable port of production
 * `hooks-core/precompact-core.js`, parameterized per team-skeleton.md §3/§5).
 *
 * Best-effort reminder to flush progress before context gets compacted — the
 * Stop hook (session-stop.js) is the primary flush mechanism, this is a
 * secondary nudge, not a guarantee. Never blocks compaction.
 *
 * PreCompact does NOT support hookSpecificOutput.additionalContext on
 * claude/codex (that schema is for SessionStart/UserPromptSubmit/PostToolUse/
 * Stop) — only the top-level `systemMessage` field is honored, so this script
 * always emits `{ systemMessage: ... }` on those platforms rather than routing
 * through emit.buildSessionStartPayload.
 *
 * Usage: node precompact.js [--platform claude|codex|cursor]
 */
'use strict';
const emit = require('./lib/emit');
const cfg = require('./lib/config');
const messages = require('./lib/messages');

async function main() {
  const platform = emit.getPlatform();
  try {
    const raw = await emit.readStdin(); // read in; content isn't otherwise used, only session_id for dedup
    const sid = emit.extractSessionId(raw);
    if (sid && emit.isDuplicateInvocation('PreCompact', sid)) {
      process.exit(0);
      return;
    }

    const cwd = emit.resolveCwd(raw, platform);
    const teamRoot = cfg.resolveTeamRoot(cwd || process.cwd());
    const config = cfg.loadTeamConfig(teamRoot);
    const lang = cfg.resolveLanguage(config);
    const msg = messages.get(lang);

    emit.writeJson(emit.buildPreCompactPayload(msg.precompactMessage, platform));
  } catch (e) {
    // Never block compaction: emit nothing on stdout. But surface an unexpected
    // exception on stderr rather than swallowing it silently — stderr is not
    // part of the compaction flow, so this keeps the "never block compaction"
    // contract while still leaving a trace when something genuinely broke.
    process.stderr.write('[precompact] non-fatal error, no message emitted (compaction not blocked): ' + ((e && e.stack) || e) + '\n');
  }
  process.exit(0);
}

if (require.main === module) {
  main();
}

module.exports = {};