developerintermediate

Pull request reviewer

Fires on a real inbound webhook, fetches the diff, reviews it, and posts severity-tagged comments (blocker, warning, nit) with file:line citations. A hook gates the session once it passes 30 tool calls, so a freak 5000-line PR can't drain the budget.

lines 46cost ~$0.05 per typical PRapp id pr-reviewer

Install it locally

# save the YAML below as app.yaml in a new folder
digitorn install ./pr-reviewer

This is a local install: the folder you create is the source. No Hub package to publish first.

What you get

Reviews a PR within moments of the webhook firing
Severity-tagged comments with file:line citations
A tool-call cap so a freak PR can't blow the budget
The webhook path is real: adapter: webhook, config.inbound_path

Credentials this template uses

Anthropic Claude

Click each one for the credential setup command, scope guidance, and provider details.

The full YAML, ready to fork

app.yaml

1schema_version: 223app:4  app_id: pr-reviewer5  name: "PR reviewer"6  version: "1.0.0"7  category: "developer-tools"89runtime:10  mode: background11  entry_agent: reviewer12  hooks:13    - id: pr_budget_cap14      "on": tool_start15      condition:16        type: expression17        expr: "session.tool_calls.total >= 30"18      action:19        type: gate20        reason: "PR review budget cap reached. Ask a human to extend."2122tools:23  modules:24    web: {}25    bash: {}26    channels:27      config:28        providers:29          github_pr:30            adapter: webhook31            config:32              inbound_path: /hooks/github-pr33            activation:34              agent: reviewer35              message: "{{event.payload.pull_request.title}}\n\n{{event.payload.pull_request.body}}"3637agents:38  - id: reviewer39    modules: [{web: [fetch]}, {bash: [run]}]40    brain:41      provider: anthropic42      model: claude-sonnet-543      credential: { ref: anthropic_main, scope: per_user, provider: anthropic }44    system_prompt: |45      Review the PR diff. Tag each comment with severity (blocker, warning, nit).46      Cite file:line for every comment. Be terse.

How it works

a real webhook provider, not a fake trigger type

adapter: webhook with config.inbound_path is the actual, compiler-verified shape - point your GitHub webhook at the URL Setup shows you once this is installed, no guessing at trigger syntax.

a gate hook for the cost ceiling

The hook fires on tool_start, checks session.tool_calls.total >= 30 via an expression condition, and its action is type: gate with a reason (not message - that's the field the gate action actually reads).

activation.message templates the PR payload in

{{event.payload.pull_request.title}} pulls straight from the webhook body, so the reviewer agent starts its turn already knowing what it's looking at.

Read the deep dive

Hooks: 4 production patterns we ship today on Digitorn

Read article

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