Pi 的不朽生命：在 Temporal 上运行 Pi 编程 Agent

转录记录是唯一的对话状态。Worker 会从会话文件中重建回合。我们通过在 sealStep Activity 的写入落盘后将其杀死，然后在新进程中重试它，来测试这一点。步骤边界处的钩子只会触发一次。

sealStep 是某个步骤工具结果的唯一写入者。Pi 的会话文件是一棵树，因此并发追加可能会创建不同分支。通过 sealStep 写入结果，可以保持它们的顺序。

工具被调用前会记录一项声明。发现该声明的竞争尝试不会再次调用相同的工具调用。

失去租约的 Worker 无法追加会话文件。我们通过在 Worker 调用过程中将其冻结、再让另一台 Worker 接管会话来测试这一点。当我们恢复第一台 Worker 时，写入保护机制拒绝了它的延迟追加。该租约要求在共享目录中进行独占文件创建和一致性读取。其时间窗口考虑了时钟差异，但并未设定最大时钟偏差。拒绝追加可阻止转录记录写入；工具仍可能产生外部副作用。磁盘上的声明可防止系统自动重新执行相同工具调用。

操作人员可为每个回合和每个会话配置 token 与耗时预算。执行器会实施这些预算，其中包括回合的硬截止时间。

The transcript is the only conversation state. A Worker reconstructs the turn from the session file. We test this by killing the sealStep Activity after its writes land, then retrying it in a fresh process. The hooks at the step boundary fire once.

sealStep is the only writer of a step’s tool results. Pi’s session file is a tree, so concurrent appends could create separate branches. Writing the results through sealStep preserves their order.

A claim is recorded before a tool is invoked. A competing attempt that finds the claim does not invoke the same tool call again.

A Worker that lost its lease cannot append to the session file. We tested this by freezing a Worker mid-call and letting another take over the session. When we resumed the first Worker, the write guard rejected its late append. The lease requires exclusive file creation and coherent reads in the shared directory. Its timing windows account for clock differences, but do not establish a maximum clock skew. Rejecting the append prevents the transcript write; the tool may still produce external effects. The claim on disk prevents automatic re-execution of the same tool call.

The operator configures token and elapsed-time budgets per turn and per session. The executor enforces those budgets, including a hard deadline for the turn.