Function compactFileReads

src/agent/read-cache.ts:111–169

(messages: Message[], opts: ReadCacheOptions = {})

 * mutated); array length and message order are preserved.
 */
export function compactFileReads(messages: Message[], opts: ReadCacheOptions = {}): Message[] {
  if (!Array.isArray(messages) || messages.length === 0) return messages;
  const recentWindow = opts.recentWindow ?? 24;

  // 1) tool_call_id -> ReadTarget, from assistant tool_calls that name a read tool.
  const targetById = new Map<string, ReadTarget>();
  for (const m of messages) {
    if (m.role !== 'assistant' || !Array.isArray(m.tool_calls)) continue;
    for (const tc of m.tool_calls) {
      if (!tc?.function || !READ_TOOLS.has(tc.function.name)) continue;
      const t = readTargetFor(parseArgs(tc.function.arguments));
      if (t) targetById.set(tc.id, t);
    }
  }
  if (targetById.size === 0) return messages;

  // 2) read tool-result messages, in order.
  const reads: Array<{ idx: number; t: ReadTarget }> = [];
  messages.forEach((m, idx) => {
    if (m.role === 'tool' && m.tool_call_id && targetById.has(m.tool_call_id)) {
      reads.push({ idx, t: targetById.get(m.tool_call_id)! });
    }
  });
  if (reads.length === 0) return messages;

  // 3) superseded: an earlier read covered by a LATER read of the same path
  //    (later full read, or later identical slice).
  const superseded = new Set<number>();
  for (let i = 0; i < reads.length; i++) {
    for (let j = i + 1; j < reads.length; j++) {
      if (reads[j].t.path !== reads[i].t.path) continue;
      if (reads[j].t.full || reads[j].t.key === reads[i].t.key) {
        superseded.add(reads[i].idx);
        break;
      }
    }
  }

  // 4) rewrite. Superseded → lossless stub (any age). Else, if aging is on and the
  //    read is older than the recent window → outline stub.
  const boundary = messages.length - recentWindow;
  const idxToTarget = new Map(reads.map(r => [r.idx, r.t]));
  let changed = false;
  const out = messages.map((m, idx) => {
    const t = idxToTarget.get(idx);
    if (!t) return m;
    if (isStub(m.content)) return m; // already compacted on a prior pass
    if (superseded.has(idx)) {
      changed = true;
      return { ...m, content: supersededStub(t.path) };
    }
    if (opts.agingOutline && idx < boundary) {
      changed = true;
      return { ...m, content: agedStub(t.path, m.content) };
    }
    return m;
  });
  return changed ? out : messages;