C4Ch3L4 Pre Negotiation Brief with a PreToolUse Block

Описание: Block the bad write. Don't fix it after.

In Lesson 4, you'll build a PreToolUse hook that's stricter than the one from Lesson 3: it doesn't detect bad output, it prevents bad output from ever being written. If the pre-negotiation brief is missing a BATNA section or a walk-away price with a real dollar figure, the file never reaches the disk. No clean-up later. No revision request from your CPO. The bad state simply cannot exist.

What you'll learn:
The airport security analogy: why PreToolUse is the boarding gate, and why post-flight checks are too late
The architectural distinction that ties this whole chapter together: PreToolUse prevents bad states; PostToolUse detects them
How to write a validation script that reads the proposed write content, checks for a BATNA section and a walk-away price within 300 characters of a dollar figure, and exits 0 or 1
The proximity check trick: why "dollar sign anywhere in the document" is the wrong rule, and how the 300-character window catches it correctly
How to register both PreToolUse and PostToolUse hooks in settings.json as sibling keys without breaking either
The JSON validation discipline: run python -m json.tool before restarting Claude Code, because one trailing comma silently disables every hook
The deliberate test sequence: write an incomplete brief and confirm the block, then write the complete brief and confirm the approval, before trusting the system
The four mistakes that break PreToolUse: dollar sign anywhere check, short-circuit evaluation, wrong matcher case, unvalidated JSON

This is the lesson that turns "incomplete brief reaches CPO" from a recoverable problem into an impossible one.

Built for: procurement, sourcing, category, and supply chain professionals whose pre-negotiation briefs land on senior leaders' desks and must be complete the first time.

Lesson 4, Chapter 3: The Negotiation Intelligence System
From the course Run Better RFx Events: Sourcing and Negotiation Powered by Claude Code

Full course and more lessons: https://www.u2xai.academy/

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Found this useful? Let me know in the comments which document in your stack should never be allowed to exist without a key section.