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 gives each requirement a name, selector and rerunnable check command. Its published fresh-check rate lets a team budget semantic checks separately from a broader cloud coding session.
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 Ellipsis'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 | Ellipsis |
|---|---|---|
| Billing | 10¢ per 1,000 fresh rule checks. Cached checks free. No seat fees. | Model token cost plus a 10% platform fee; compute is additionally metered. No seat fee.Vendor documentation ↗ |
| Before commit | perch check reads the files on disk, including uncommitted edits. | Open CLI and REST sessions invoke cloud workflows.Vendor documentation ↗ |
| Custom requirements | English ensure rules in perch.yaml: project, file or method scope. No paid custom-rule tier. | YAML prompts, models, budgets, paths and pass/fail configuration.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. | Code-review sessions and cloud coding workflows.Vendor documentation ↗ |
| Open source | MIT-licensed CLI. Hosted model analysis is a paid service. | MIT thin CLI; commercial review engine.Vendor documentation ↗ |
Ellipsis also offers usage pricing and an open CLI. Choose Perch for a direct rule-check unit, repository selectors and cached answers for unchanged checks. The agent can run one saved behavior requirement after each relevant edit instead of starting a broader coding session.
Ellipsis: Open CLI and REST sessions invoke cloud workflows. Ellipsis 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.
Ellipsis: YAML prompts, models, budgets, paths and pass/fail configuration. Ellipsis 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 Ellipsis's billing unit and Perch's usage estimate
Ellipsis: MIT thin CLI; commercial review engine. Ellipsis 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.
Ellipsis exposes CLI and API sessions for cloud workflows. Compute, memory, model tokens and session duration matter to its bill; the existence of a CLI does not imply local inference or a fixed review price.
Perch and Ellipsis: 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.