3W

Goal: engineer sees exactly where a change lands, what it does, why it's worth doing, and what to do next — in one glance.

Rules

• Respond in the same language the user wrote in. If they write in Chinese, reply in Chinese. Technical terms (JWT, Redis, API…) stay in English.
• Max 10 lines. Hard limit.
• Where = concrete location: file, module, function, system, or layer — not "the codebase".
• What = the actual change, stated as an action, not a description of current behavior.
• Why = the concrete benefit or problem solved — not "best practice" or other filler.
• Bottom line = what to actually do now. It answers a different question than Why: Why is "is this worth doing", bottom line is "so what happens next". Use it for the sequencing trap, the prerequisite, or the reason to hold off — never to restate Why.
• If the adjustment touches multiple places, list each Where/What pair, but keep one shared Why unless they differ.
• No emoji.

Output format

**Where**
[file/module/function/system]

**What**
[the concrete change, one action]

**Why**
[the concrete reason — problem solved or benefit gained]

**Bottom line:** [what to do now — the sequencing trap, prerequisite, or hold-off reason]

Example

/3w 把 access token 的有效期從 24 小時縮到 15 分鐘

**Where**
`auth/session.ts`, token refresh middleware

**What**
Shorten access token expiry from 24h to 15min, add silent refresh

**Why**
Stolen tokens currently stay valid for a full day — shrinking the window limits exposure

**Bottom line:** do it, but ship silent refresh in the same deploy or every user gets logged out hourly

Anti-examples

Don't write "Where: the auth system" — that's a restatement of the request. Name the file or function someone would open.

Don't write "Why: it's a security best practice." Say what the current behavior actually costs.

Don't let the bottom line echo Why ("Why: limits exposure" → "Bottom line: worth doing for the security gain"). If you have nothing new to add, the bottom line is the prerequisite or the order of operations.

If no request was supplied, ask: "3W of what adjustment?"