developer

Build a automated code reviewer in YAML

An agent that reads a PR diff, surfaces risks, and posts a structured review.

filesystemwebtriggers.webhookbehavior

The pattern

A coding agent that watches for new pull requests, fetches the diff, runs lint and security checks, and posts a structured review with risk tags. Works with GitHub, GitLab, or any system that fires a webhook. Cost-controlled by behaviour rules so a freak 5000-line PR cannot drain your budget.

What good looks like

Posts within 2 minutes of PR open
Cites file:line for every comment
Tags severity (blocker, warning, nit) consistently
Stays under N tool calls per PR

Common pitfalls

Reviewing every commit instead of every PR (noisy)
Missing the read-before-edit guard, hallucinating file contents
No turn cap, runaway cost on huge PRs
Generic prose without file:line citations

The minimum YAML to ship this

app.yaml

1modules:2  filesystem: { config: { read_before_edit: true } }3  web: {}45triggers:6  - id: pr-opened7    kind: webhook8    path: /hooks/github-pr9    target: { agent: reviewer, message: "{{event.body.pull_request.title}}" }1011behavior:12  rules:13    - condition: tool_calls > 3014      action: gate1516agents:17  - id: reviewer18    modules: [filesystem, {web: [fetch]}]19    brain: { model: claude-sonnet-4-6 }20    system_prompt: "Review the diff. Tag severity. Cite file:line for each comment."

Ship in 5 minutes

Install Digitorn and deploy this agent

# 1. install runtime
curl -sSL https://digitorn.ai/install | sh

# 2. save the YAML above to ~/.digitorn/apps/my-code-review/app.yaml
mkdir -p ~/.digitorn/apps/my-code-review
# paste the YAML into app.yaml

# 3. deploy
digitorn deploy my-code-review

Read the deep dive

How to build a Claude Code clone in YAML

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Engineering notes from the Digitorn team. No marketing, no launch announcements, no "10 prompts that will change your life". Just the things we write that we'd want to read.

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The minimum YAML to ship this

app.yaml

1modules:2  filesystem: { config: { read_before_edit: true } }3  web: {}45triggers:6  - id: pr-opened7    kind: webhook8    path: /hooks/github-pr9    target: { agent: reviewer, message: "{{event.body.pull_request.title}}" }1011behavior:12  rules:13    - condition: tool_calls > 3014      action: gate1516agents:17  - id: reviewer18    modules: [filesystem, {web: [fetch]}]19    brain: { model: claude-sonnet-4-6 }20    system_prompt: "Review the diff. Tag severity. Cite file:line for each comment."

# 1. install runtime curl -sSL https://digitorn.ai/install | sh # 2. save the YAML above to ~/.digitorn/apps/my-code-review/app.yaml mkdir -p ~/.digitorn/apps/my-code-review # paste the YAML into app.yaml # 3. deploy digitorn deploy my-code-review