Method recordTurn

src/session/store.ts:203–234

(
    sessionId: string,
    messages: Message[],
    usage: { input: number; output: number; costUsd: number },
    title?: string,
  )

  }

  /**
   * Create a session row with a caller-chosen id if it doesn't exist yet (idempotent).
   * Used for sub-agent sessions, whose ids are derived from the parent's
   * (`<parent>/sub-<ts>`, `<parent>/fanout-<n>`, …): messages.session_id has a FK to
   * sessions.id, so the row MUST exist before the sub-agent's first recordTurn —
   * otherwise every child write dies with "FOREIGN KEY constraint failed".
   */
  ensureSession(id: string, cwd: string, model: string): void {
    this.db.prepare(
      `INSERT OR IGNORE INTO sessions (id, cwd, model, title) VALUES (?, ?, ?, ?)`,
    ).run(id, cwd, model, null);
  }

  recordTurn(
    sessionId: string,
    messages: Message[],
    usage: { input: number; output: number; costUsd: number },
    title?: string,
  ): void {
    const hasUserMessage = messages.some(m => m.role === 'user');
    // Reuse the same turn_number for all messages in this batch.
    // Only bump to a new turn_number when this batch starts a new user turn.
    const currentMax = this.getCurrentTurnNumber(sessionId);
    const turnNumber = hasUserMessage ? currentMax + 1 : Math.max(currentMax, 1);

    const tx = this.db.transaction(() => {
      for (const msg of messages) {
        this.insertMessage.run(
          sessionId,
          turnNumber,
          msg.role,
          msg.content ?? null,
          msg.tool_calls ? JSON.stringify(msg.tool_calls) : null,
          msg.tool_call_id ?? null,
          msg.name ?? null,