Add proactive assumption challenging to brainstorming skill

[thakoreh]

Description

Fixes #530 - Brainstorming skill should proactively challenge product assumptions

Problem

During product brainstorming sessions, the skill explores requirements and design well, but does not proactively challenge the assumptions embedded in the user's request. AI assistants tend to accept user framing and jump to implementation, missing opportunities to surface better product decisions early.

Solution

Added a new step "Challenge product assumptions" that runs after exploring project context and before asking clarifying questions. This mirrors what a founding product designer or senior PM would do naturally.

Changes

• Added new step to checklist
• Added "Challenging Product Assumptions" section with example challenge questions
• Updated process flow diagram to include new step
• Included concrete example of how challenge questioning saves implementation effort

Example Challenge Questions

• "Which user state/lifecycle does this feature serve?"
• "If we build this, what would users actually do with it?"
• "Is there a simpler or lower-cost alternative?"

Motivation

The cost of a wrong assumption is highest before any code is written. Challenging assumptions early saves implementation effort and surfaces better product decisions.

[coderabbitai]

📝 Walkthrough

Walkthrough

The brainstorming skill's planning workflow is enhanced by introducing a new "Challenge product assumptions" step positioned between "Explore project context" and "Ask clarifying questions." The process flow diagram is updated accordingly, and detailed guidance is added explaining how to challenge assumptions with example questions and scenarios before proceeding with design work.

Changes

Cohort / File(s)	Summary
Brainstorming Skill Workflow Enhancement skills/brainstorming/SKILL.md	Added "Challenge product assumptions" step to planning workflow. Updated process flow graph with new node and edges. Introduced "Challenging Product Assumptions" section with purpose, example questions, and scenario. Reworded existing "Understanding the idea" bullets to align with new workflow sequence.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• Enforce brainstorming workflow with hard gates and process flow #462: Modifies the same skills/brainstorming/SKILL.md file's planning workflow and process flow graph structure with workflow node adjustments.

Poem

🐰 A step to question first, before we leap,
Challenge the assumptions buried deep.
Is this the path, or just pretense?
Better to ask than skip the sense! 🌱

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	Title clearly summarizes the main change: adding proactive assumption challenging to the brainstorming skill, directly reflecting the core content modification.
Description check	✅ Passed	Description provides comprehensive context about the problem, solution, changes, and motivation, all directly related to the pull request's purpose of adding assumption-challenging functionality.
Linked Issues check	✅ Passed	Pull request fully addresses issue #530 by adding the 'Challenge product assumptions' step, including example challenge questions and documentation that align with all stated requirements.
Out of Scope Changes check	✅ Passed	All changes are within scope: the new checklist step, 'Challenging Product Assumptions' section, process flow diagram update, and concrete example are directly tied to addressing issue #530.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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🧹 Nitpick comments (1)

skills/brainstorming/SKILL.md (1)

12-12: Align the overview and “Understanding the idea” bullets with the new challenge step.

The overview and the “Understanding the idea” bullets still read as if clarifying questions come immediately after context, which contradicts the newly inserted “Challenge product assumptions” step. Consider updating those lines to explicitly mention the challenge step before clarifying questions.

✏️ Suggested text update

-Start by understanding the current project context, then ask questions one at a time to refine the idea. Once you understand what you're building, present the design and get user approval.
+Start by understanding the current project context, then challenge product assumptions before asking clarifying questions one at a time. Once you understand what you're building, present the design and get user approval.

-**Understanding the idea:**
-- Check out the current project state first (files, docs, recent commits)
-- Ask questions one at a time to refine the idea
+**Understanding the idea:**
+- Check out the current project state first (files, docs, recent commits)
+- Challenge product assumptions before clarifying
+- Ask questions one at a time to refine the idea

Also applies to: 84-90

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@skills/brainstorming/SKILL.md` at line 12, Update the SKILL.md bullets so the
Overview and the "Understanding the idea" section explicitly mention and
sequence the new "Challenge product assumptions" step before asking clarifying
questions; locate the Overview heading and the "Understanding the idea" bullet
list and insert or reword to: first contextualize the project, then perform the
"Challenge product assumptions" step (call out that you should critique
constraints and propose alternatives), and only after that proceed to ask
clarifying questions one at a time and present the design for approval—apply the
same change to the duplicate content around lines referenced as also applies to:
84-90.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@skills/brainstorming/SKILL.md`:
- Line 12: Update the SKILL.md bullets so the Overview and the "Understanding
the idea" section explicitly mention and sequence the new "Challenge product
assumptions" step before asking clarifying questions; locate the Overview
heading and the "Understanding the idea" bullet list and insert or reword to:
first contextualize the project, then perform the "Challenge product
assumptions" step (call out that you should critique constraints and propose
alternatives), and only after that proceed to ask clarifying questions one at a
time and present the design for approval—apply the same change to the duplicate
content around lines referenced as also applies to: 84-90.

---

ℹ️ Review info

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between e4a2375 and b762785.

📒 Files selected for processing (1)

• skills/brainstorming/SKILL.md

[obra]

Thanks for this! Challenging assumptions is a good instinct. v5.0.0 added scope assessment to brainstorming — it now catches oversized projects and decomposes them into sub-projects before speccing. That covers the most impactful case of assumption-challenging (building the wrong-sized thing). Closing as the brainstorming skill was substantially reworked in v5.

— Claude (claude-opus-4-6, Claude Code 2.1.71, session 64908a66-5c98-4c79-b0f7-1aa7eac2dcb0)