The regression
def refund(order, payment):
payment.refund(order.total)
order.status = "refunded"
return order
1 check, 1 broken. Refunded orders cannot be refunded again.
Perch checks the agent’s working file against a saved English requirement. The same check can verify a repair before the change becomes a public or private pull request.
perch check reads working files; perch scan reads Git HEAD. Relevant source is sent to TypeSafe’s hosted models. The MIT CLI does not run model inference offline.
A saved requirement makes a recurring mistake checkable. In this Perch capture from September 20, 2026, the same rule flags a missing guard and passes after the guard is restored.
def refund(order, payment):
payment.refund(order.total)
order.status = "refunded"
return order
1 check, 1 broken. Refunded orders cannot be refunded again.
def refund(order, payment):
if order.status == "refunded":
return order
payment.refund(order.total)
order.status = "refunded"
return order
1 check, nothing to report.
Source: public order-service checkout.py at the linked commit. The captured standalone file is refund.py. Perch command output and timestamp. This saved-rule demonstration does not measure Devin Review's detection rate.
Perch turns project behavior into focused checks that agents can run before committing. Use these differences to choose the review workflow and billing model your team needs.
| Capability | Perch | Devin Review |
|---|---|---|
| Billing | 10¢ per 1,000 fresh rule checks. Cached checks free. No seat fees. | Enterprise review draws from an ACU usage pool; a current flat per-review dollar price was not published.Vendor documentation ↗ |
| Before commit | perch check reads the files on disk, including uncommitted edits. | The launch documented npx devin-review for a PR URL; local working-tree review was not verified.Vendor documentation ↗ |
| Custom requirements | English ensure rules in perch.yaml: project, file or method scope. No paid custom-rule tier. | REVIEW.md, AGENTS.md and repository review guidance.Vendor documentation ↗ |
| Coverage | Each parsed non-test application method in the selected scan scope is read, with caller and callee context. No method-count cap. | PR review across supported Git providers; public PRs can be reviewed without an account.Vendor documentation ↗ |
| Open source | MIT-licensed CLI. Hosted model analysis is a paid service. | Commercial Cognition service.Vendor documentation ↗ |
Devin Review works on pull requests. Perch checks the working file before the PR exists, using an English requirement the agent can rerun after each relevant edit. Its public CLI and check-based bill make that saved requirement portable across agent workflows.
Devin Review: The launch documented npx devin-review for a PR URL; local working-tree review was not verified. Devin Review workflow documentation.
Perch reads the current working file with perch check. For a known requirement, select its rule name and method instead of requesting another broad review. A local CLI describes where the command runs; Perch sends relevant source to hosted TypeSafe models for analysis.
Devin Review: REVIEW.md, AGENTS.md and repository review guidance. Devin Review rule documentation.
Perch stores English ensure rules in perch.yaml or .perch/rules/. Project, file and method scopes determine what is checked. Run the named check after an edit and after the repair; a rule finding can fail the command and a CI gate. Perch rules · Working-file checks.
Compare Devin Review's billing unit and Perch's usage estimate
Devin Review: Commercial Cognition service. Devin Review product or license source.
Perch’s CLI is MIT-licensed; hosted model inference is a separate paid service included in its published check rate. It does not run the model offline. Unchanged requests can reuse cached answers for free. Fresh judgments can vary, and a passing requirement check does not prove application correctness. Perch MIT license.
Devin Review documents PR-oriented review and enterprise usage controls. Its launch-era free access and PR-URL command do not establish current working-tree support or a fixed review price.
Perch and Devin Review: pricing, allowances and workload calculator
npm install -g @lakeday/perchperch rules add refund-once \
--where refund.py --each method \
--ensure "Refunded orders cannot be refunded again."The captured rule checks the requirement shown above. Rule syntax and selectors
perch check refund.py::refund --rules refund-onceRun the check after an edit and after the fix. Working-tree check documentation
Use perch scan for repository code at Git HEAD and changed-code CI checks for pull requests. New model judgments can vary. Repeatability comes from cached answers for unchanged requests; a pass does not prove application correctness.
Choose Perch when you want an MIT CLI, English behavior rules and usage pricing that stays independent of team size. Give your coding agent a saved check it can run after every relevant edit.
Install PerchPublished by Perch. Vendor facts were reviewed on 2026-10-14; plans and allowances can change. Vendor marks belong to their owners.