Review with research

Review With Research

Overview

Reviews a branch by dispatching a code-review subagent in a worktree alongside a research subagent, then synthesizes their findings into an evidence-based verdict.

Core principle: Review in isolation (worktree), research the domain, compare against what established tools do. Never rubber-stamp, never just echo the user's hunch.

When to Use

• User questions whether an approach is sound
• Review involves a technique worth verifying (locking, caching, auth, crypto, concurrency)
• User explicitly asks to research best practices

Skip for: pure style reviews or quick thumbs-up on small changes.

Workflow

digraph review {
  rankdir=TB;
  node [shape=box];

  worktree [label="0. Create worktree\nfor the branch"];
  review [label="1. Dispatch review subagent\n(read diff + baseline in worktree)"];
  research [label="2. Dispatch research subagent\n(ecosystem, libraries, how major tools do it)"];
  parallel [label="Run 1 and 2\nin parallel" shape=diamond];
  synthesize [label="3. Synthesize + verdict:\ncompare impl vs best practices"];
  cleanup [label="4. Remove worktree"];

  worktree -> parallel;
  parallel -> review;
  parallel -> research;
  review -> synthesize;
  research -> synthesize;
  synthesize -> cleanup;
}

0. Create a worktree

git worktree add --detach .worktrees/review-<branch> <branch>

Why --detach? If <branch> is already checked out (e.g., it's the current branch), git worktree add will refuse. Using --detach creates the worktree in detached HEAD state, avoiding the "already checked out" error. The worktree still has the branch's content.

Check that .worktrees/ is in .gitignore. If not, add it before creating the worktree. This keeps the main session on its current branch. Clean up after the review.

0.5. Identify research topic

Before dispatching subagents, skim the diff briefly to identify the technique or domain to research:

git diff main..<branch> --stat
git diff main..<branch> | head -200

This is a quick read, not the full review — just enough to know the research topic (e.g., "file locking with advisory locks", "JWT refresh token rotation", "concurrent HashMap sharding"). If the diff is empty, short-circuit: report "nothing to review" and stop.

1. Dispatch review subagent (parallel with step 2)

Dispatch an Explore subagent (read-only) into the worktree.

Parameter	Value
subagent_type	Explore
run_in_background	true

The subagent should:

• cd <worktree-absolute-path> as its first action (the Agent tool starts subagents in the parent's working directory, not the worktree)
• Read the full diff (git diff main..<branch>)
• Use git show main:<path> to read baseline files on main for context
• Read files directly from the worktree path for the branch version
• Summarize what the branch does and flag any concerns

Subagent prompt template:

You are reviewing branch <branch>. First, cd <worktree-absolute-path>. Then read git diff main..<branch> and examine the changed files. Use git show main:<path> to read baseline files on main. Read files directly from the worktree for the branch version. Produce a detailed review: what the branch does, any correctness/design concerns with line numbers, and questions about the approach. Do NOT write code.

2. Dispatch research subagent (parallel with step 1)

Parameter	Value
subagent_type	general-purpose
model	"sonnet"
run_in_background	true

Dispatch a general-purpose subagent to:

• Find established libraries/packages for the problem domain
• Check how major tools in the ecosystem solve it
• Identify known failure modes of the approach used

Subagent prompt template:

Research best practices for [topic] in [language/ecosystem]. Find: (1) common libraries, (2) tradeoffs between approaches, (3) what well-known tools use, (4) known failure modes of [technique]. Do NOT write code.

3. Synthesize and deliver verdict

Compare the review subagent's findings against the research and produce a verdict with this structure:

• What the branch does — neutral summary
• What the ecosystem does — researched evidence
• Specific problems — line numbers and failure modes
• Recommendation — accept, reject, or revise with concrete alternative

Reconciliation guidance:

• If review and research agree, state the convergence and cite both.
• If review and research contradict, present both perspectives with specific evidence. Don't silently pick one — the user needs to see the tension.
• If research is inconclusive (topic too niche, conflicting sources), weight code review more heavily, evaluate on first principles, and note the gap explicitly.

Handoff: If the recommendation is "revise" and the user wants to proceed with fixes, hand off to review-and-fix.

4. Clean up

git worktree remove .worktrees/review-<branch>

Key Rules

Rule	Why
Don't just confirm user suspicions	They want independent verification, not validation
Don't just contradict either	If the approach is fine, say so with evidence
Cite specifics, not vibes	"PID reuse is a known failure mode" beats "PIDs seem unreliable"
Always suggest the alternative	Rejection without a path forward isn't useful
Review in a worktree, not main	Don't switch branches on the main session

Common Mistakes

Mistake	Fix
Reviewing on the main thread's branch	Always create a worktree — keep main session clean
Reviewing from memory, skipping research	Always dispatch research subagent — training data may be stale
Only reading the diff, not main	Need baseline context to judge what changed
Agreeing with user before researching	Research first, form opinion second