Pi Agent extensions 的选择与权衡

最近在考虑从 opencode 转 pi，也阅读了很多佬友分享的配置和经验。

但是在实际上手配置之后，我发现其实很多…经常被提起的ext，实际上都有一些不太容易察觉的问题。有些ext使用了之后会大幅提高 system-prompt 的 token 用量。有些会影响原有的自带的工具（或者是对应的system prompt）。

• 首先是 pi-tool-display，理论上他只是一个 UI 美化的包，但是实际上因为是通过重写 read write edit 那些 tools 实现的，导致了一个很奇怪的现象。在使用这个 package 之前，我的 pi 的system prompt 是：```

Available tools:

read: Read file contents
bash: Execute bash commands (ls, grep, find, etc.)
edit: Make precise file edits with exact text replacement, including multiple disjoint edits in one call
write: Create or overwrite files
todo: Manage a task list to track multi-step progress
ask_user_question: Ask the user up to 4 structured questions (2-4 options each) when requirements are ambiguous
web_search: Search the web for up-to-date information
web_fetch: Fetch and read content from a specific URL
ffgrep: Grep contents
fffind: Find files by path or glob

In addition to the tools above, you may have access to other custom tools depending on the project.
...
``使用了之后就变成``
Available tools:

bash: Execute bash commands (ls, grep, find, etc.)
todo: Manage a task list to track multi-step progress
web_search: Search the web for up-to-date information
web_fetch: Fetch and read content from a specific URL
ffgrep: Grep contents
fffind: Find files by path or glob

In addition to the tools above, you may have access to other custom tools depending on the project.
```也就是 read write edit 那些的 snippet 不见了。理论上不是什么问题，不过还是提一下，有些 ext 可能会有意想不到的side effect。

• 然后是 @juicesharp/rpiv-todo，这个 todo 工具已经算是比较简洁的了（不是 claude code 那种带 subagent task assign 的重量级工具），本身的工具的定义也只需要几百token，但是注入到 system prompt 里的 guideline 却是不少：```

-Use todo for complex work with 3+ steps, when the user gives you a list of tasks, or immediately after receiving new instructions to capture requirements. Skip it for single trivial tasks and purely conversational requests.
-When starting any task, mark it in_progress BEFORE beginning work. Mark it completed IMMEDIATELY when done — never batch completions. Exactly one task should be in_progress at a time.
-Never mark a task completed if tests are failing, the implementation is partial, or you hit unresolved errors — keep it in_progress and create a new task for the blocker instead.
-Task status is a 4-state machine: pending → in_progress → completed, plus deleted as a tombstone. Pass activeForm (present-continuous label, e.g. 'researching existing tool') when marking in_progress.
-To change a task's status, call update with the task id and the target status, e.g. {"action":"update","id":3,"status":"completed"} or {"action":"update","id":3,"status":"in_progress","activeForm":"writing tests"}. status is the field that changes the task; an update without a mutable field (status or another) is rejected.
-Use blockedBy to express dependencies (A is blocked by B). On create, pass blockedBy as the initial set. On update, use addBlockedBy / removeBlockedBy (additive merge — do not resend the full array). Cycles are rejected.
-list hides tombstoned (deleted) tasks by default; pass includeDeleted:true to see them. Pass status to filter by a single status.
-Subject must be short and imperative (e.g. 'Research existing tool'); description is for long-form detail. activeForm is a present-continuous label shown while in_progress.
```更大的问题是。。。这个注入的内容，没有表明是使用什么工具的时候要注意。我其实有点怀疑到底有多大的用处，会不会影响agent做其他事情的效果。同一个作者的 @juicesharp/rpiv-ask-user-question 和 @juicesharp/rpiv-web-tools 也有一样的问题。

• 相比起来，@ff-labs/pi-fff 的 guideline 就明显规范一点。有工具名，也很简洁。```
• ffgrep: prefer bare identifiers as patterns. Literal queries are most efficient.
• ffgrep: use path for include ('src/', '.ts') and exclude for noise ('test/,.min.js').
• ffgrep: caseSensitive: true when you need exact case (smart-case otherwise).
• ffgrep: after 1-2 greps, read the top match instead of more greps.
• fffind: matches the WHOLE path, not just the filename — profile hits chrome/browser/profiles/x.cc too.
• fffind: keep queries to 1-2 terms; extra words narrow.
• fffind: use for paths, not content. Use ffgrep for content.
• fffind: for exact path matches use a glob in path — e.g. path: '/profile.h' for exact filename, or path: 'src//profile.h' scoped to a subtree. Bare patterns are fuzzy.
• fffind: to list everything inside a directory, pass path: 'dir/**' with an empty or wildcard pattern instead of using pattern alone.
• fffind: use exclude: 'test/,*.min.js' to cut noise in large repos.

```说这些的目的就是。。提醒各位佬，在挑选pi的插件的时候，可能不止要看看用的人多不多，实际上可能也要看看实现是否符合各位佬自己的需求和想法。然后。。。可能有些插件的实现水平还是比较参差，具体好不好用还是要多多测试，体验。