Design Debate

Design Debate

Decide whether to do something — before writing a plan for it — by making independent subagents genuinely disagree, not politely converge. The value isn't in getting three opinions; it's in the friction between them, and in a final verdict that says which argument actually held up.

Prerequisites

• A concrete decision or idea to debate, not yet written as a plan file (if it already is, use plan-review instead)
• Enough repo/codebase access to gather real facts before the debate starts
• The context-file skill, to persist the verdict as a finding
• The plan-create skill, as the next step if the verdict is "proceed"

When to Use

• "Should we split/merge/replace X?" — a decision with real tradeoffs on more than one side
• The user explicitly asks for pushback, a second opinion, or a collegial review
• A decision surfaced from real pain and it's unclear whether the fix is worth its cost

When NOT to Use

• A plan file already exists for this work — use plan-review
• The question needs narrowing before it's even debatable — use socratic-method first
• There's only one reasonable answer — AVOID manufacturing debate where none is warranted

Workflow

1. State the decision precisely

Write it as a yes/no or A-vs-B choice, not a vague topic.

2. Ground the debate in real facts BEFORE assigning positions

UNLESS you already have hard numbers, ALWAYS investigate first: current scale, who consumes the thing in question, what a proposed change would actually touch.

wc -l path/to/thing/in/question
grep -rl "the/consumer/pattern" . | wc -l

This confirms the actual size and blast radius before anyone argues about it — an ungrounded debate produces confident conclusions built on guessed facts.

3. Compose one identical brief for every reviewer

Every reviewer gets the same decision, the same grounding facts, and any candidate designs already on the table — differences in conclusions must come from role, not information.

4. Assign genuinely opposing roles

PREFER two roles (Advocate, Skeptic) as the minimum for real tension. ALWAYS add a Migration/Risk role when the change touches multiple files or downstream consumers. See references/role-design.md for the full role table and sample instructions.

5. Model selection

BY DEFAULT, diverse models catch different blind spots — see plan-review's model routing guidance for environment-specific pairs. A single model is acceptable for lower-stakes debates; the role framing alone still produces more tension than one pass.

6. Spawn all reviewers in parallel

# single message, N parallel Agent/Task calls — never sequential
# each call gets the identical brief plus its own role instruction

# wrong: spawn advocate -> wait -> spawn skeptic -> wait
# right: spawn advocate + skeptic (+ migration_risk) in one message

This produces both reviews in the time of the slowest single one, not their sum.

Never spawn sequentially — that triples wall-clock time for no benefit, since the reviews are fully independent.

7. Synthesize a verdict

The step most likely to be skipped under time pressure, and the one that matters most:

• Say which argument holds up under the others' scrutiny, and why.
• If the Skeptic's case rests on an existing mitigation, check whether the Advocate's case accounts for it.
• Render an actual recommendation — proceed, do_not_proceed_for_now, or proceed_with_modification. "It depends" is only acceptable when the brief genuinely lacked a fact needed to decide; if so, name exactly which fact.
• If the verdict is do_not_proceed_for_now, ALWAYS name a concrete revisit trigger — "revisit if X crosses N", never "revisit later".

Run the validation script to check the verdict conforms to schema:

./scripts/validate-debate-verdict.sh path/to/verdict.yaml
# expected: OK: 1 file(s) validated against debate-verdict schema

A missing revisit_trigger on a do_not_proceed_for_now verdict produces this instead:

Debate verdict validation errors:
  path/to/verdict.yaml: verdict 'do_not_proceed_for_now' must set 'revisit_trigger' ...

This confirms the verdict is complete before it ships or gets persisted.

8. Always record the outcome — the verdict decides which artifact

ALWAYS persist the outcome and ALWAYS ask explicitly before doing so — never decide silently, and never skip recording just because the main question got resolved. A verdict discussed and then left only in chat is the same failure mode session-reflection exists to prevent — RECOMMENDED is not the same as done.

Which artifact is a rule of thumb, not a free choice: if it's an issue that won't be fixed, it's a known-issue; otherwise, it's a finding. Record either way.

• Verdict is proceed or proceed_with_modification — something is being acted on. Use context-file to write a finding capturing the decision, the grounding facts, and why the losing arguments didn't hold up.
• Verdict is do_not_proceed_for_now — this is, by definition, a real issue being consciously left unfixed. Use context-file's KNOWN_ISSUE type (severity: CRITICAL|HIGH|MEDIUM|LOW) instead of a finding, with the revisit trigger from Step 7 as its eventual fix condition.
• The same rule applies to any individual role's finding, not just the overall verdict: if a role (commonly Migration/Risk, but not exclusively) surfaced a separate concrete gap that won't be fixed this session — even on an otherwise proceed verdict — that specific gap is its own known-issue, independent of how the main decision gets recorded.

./scripts/validate-context-frontmatter.sh <path-to-finding>
# confirms that the finding's frontmatter is valid before it's committed

If the verdict reveals a binding architectural decision, use adr-capture too.

9. Hand off

If the verdict is proceed, use plan-create next with the debate's grounding facts and chosen design as input — do not re-derive them from scratch.

Anti-Patterns

NEVER assign all reviewers a "balanced/neutral" framing. WHY: Neutral reviewers converge toward consensus, which reads as validation but is just multiple copies of the same unopposed take. GOOD: Assign explicit, opposing stances (Step 4).

NEVER skip Step 2 and let reviewers debate from assumption. WHY: An ungrounded debate produces confident conclusions built on guessed facts. GOOD: Investigate real numbers/consumers first; put them in the brief.

NEVER present raw reviewer output as the final answer. WHY: Opinions without a synthesized verdict push the actual decision back onto the user — the work this skill exists to do. GOOD: A verdict that names which argument won and what to do next (Step 7).

NEVER let a "not now" verdict omit a revisit trigger. WHY: "Not now" with no trigger silently becomes "never" by default. GOOD: Name a concrete, checkable condition (Step 7).

Mindset

• The value is real disagreement, not the appearance of thoroughness
• Ground everything in the actual repo — an argument equally true of any codebase isn't a real argument about this decision
• A well-run debate can end with "no, and here's why the strongest case for yes didn't hold up" — that's success, not failure to reach consensus
• Losing arguments are still worth recording — future readers benefit from knowing what was considered and rejected

Troubleshooting

Templates

References