diff --git a/__tests__/cronJobTest/lgtmShortCircuits.test.ts b/__tests__/cronJobTest/lgtmShortCircuits.test.ts
new file mode 100644
index 0000000..bcff381
--- /dev/null
+++ b/__tests__/cronJobTest/lgtmShortCircuits.test.ts
@@ -0,0 +1,176 @@
+import { Buffer } from 'node:buffer'
+import { http } from 'msw'
+import { setupServer } from 'msw/node'
+import { afterAll, afterEach, beforeAll, describe, expect, it } from 'vitest'
+
+import { cronLgtm } from '../../src/cronJobs/lgtm'
+import labelFileContents from '../fixtures/labels/labelFileContentsResp.json'
+import listPullReqs from '../fixtures/pullReq/pullReqListPulls.json'
+import pullReqOpenedEvent from '../fixtures/pullReq/pullReqOpenedEvent.json'
+import * as utils from '../testUtils'
+
+// cronLgtm's contracts that no merge request can show: the count it resolves
+// to, and that a PR it skips before the shared merge path costs no further
+// request. Both are only visible by calling cronLgtm directly and by watching
+// the per-PR read that evaluateMerge would otherwise make.
+
+const repo = `${utils.api}/repos/Codertocat/Hello-World`
+
+function prowYaml(text: string) {
+  const file = structuredClone(labelFileContents)
+  file.content = Buffer.from(text).toString('base64')
+  return http.get(utils.contentsUrl('.github/prow.yaml'), utils.mockResponse(200, file))
+}
+
+function lgtmPr(number: number, ...extraLabels: string[]) {
+  const pr = structuredClone(listPullReqs[0])
+  pr.number = number
+  pr.labels = ['lgtm', ...extraLabels].map(name => ({ ...pr.labels[0], name }))
+  return pr
+}
+
+function withoutLgtm(number: number) {
+  const pr = lgtmPr(number)
+  pr.labels = [{ ...pr.labels[0], name: 'approved' }]
+  return pr
+}
+
+const server = setupServer(
+  ...utils.noOrgOrRepoConfigExcept(),
+  utils.defaultBranchTree(),
+  utils.lgtmStatus(),
+  // no merge queue on the base branch: a merged PR is a direct merge
+  utils.mergeQueueGraphql({ enabled: false }).handler,
+)
+beforeAll(() => server.listen(utils.failOnUnhandledRequest))
+afterEach(() => server.resetHandlers())
+afterAll(() => server.close())
+
+/** serves the listing page by page, an empty page after the last, and each listed PR as clean and mergeable */
+function routePages(pages: ReturnType<typeof lgtmPr>[][], listing?: utils.ObserveRequest) {
+  const all = pages.flat()
+  server.use(
+    http.get(`${repo}/pulls`, ({ request }) => {
+      if (listing)
+        listing.ref = request
+      const page = Number(new URL(request.url).searchParams.get('page'))
+      return utils.mockResponse(200, pages[page - 1] ?? [])({ request })
+    }),
+    http.get(`${repo}/pulls/:number`, ({ params }) => {
+      const pr = all.find(item => item.number === Number(params.number))
+      return pr === undefined
+        ? new Response(JSON.stringify({ message: 'Not Found' }), { status: 404, headers: { 'Content-Type': 'application/json' } })
+        : new Response(JSON.stringify({ ...pr, mergeable: true, mergeable_state: 'clean' }), { status: 200, headers: { 'Content-Type': 'application/json' } })
+    }),
+  )
+}
+
+function acceptMerge(number: number) {
+  server.use(http.put(`${repo}/pulls/${number}/merge`, utils.mockResponse(200, { merged: true })))
+}
+
+function observeRead(number: number) {
+  const read = new utils.ObserveRequest()
+  const merge = new utils.ObserveRequest()
+  server.use(
+    http.get(`${repo}/pulls/${number}`, utils.mockResponse(200, lgtmPr(number), read)),
+    http.put(`${repo}/pulls/${number}/merge`, utils.mockResponse(200, null, merge)),
+  )
+  return { read, merge }
+}
+
+describe('cronLgtm', () => {
+  it('resolves to the number of pull requests it merged across every page, not the number it saw', async () => {
+    utils.setupJobsEnv('lgtm')
+    const context = new utils.MockContext(pullReqOpenedEvent)
+    routePages([
+      [lgtmPr(11), withoutLgtm(12)],
+      [lgtmPr(13)],
+    ])
+    acceptMerge(11)
+    acceptMerge(13)
+
+    await expect(cronLgtm(1, context)).resolves.toBe(2)
+  })
+
+  it('resolves to zero when every listed pull request is skipped', async () => {
+    utils.setupJobsEnv('lgtm')
+    const context = new utils.MockContext(pullReqOpenedEvent)
+    routePages([[withoutLgtm(14), lgtmPr(15, 'do-not-merge/hold')]])
+
+    await expect(cronLgtm(1, context)).resolves.toBe(0)
+  })
+
+  it('carries the count of earlier pages into the pages that follow', async () => {
+    utils.setupJobsEnv('lgtm')
+    const context = new utils.MockContext(pullReqOpenedEvent)
+    routePages([[], [lgtmPr(16)]])
+    acceptMerge(16)
+
+    await expect(cronLgtm(2, context, { jobsDone: 3, failures: [] })).resolves.toBe(4)
+  })
+
+  it('lists only open pull requests', async () => {
+    utils.setupJobsEnv('lgtm')
+    const context = new utils.MockContext(pullReqOpenedEvent)
+    const listing = new utils.ObserveRequest()
+    routePages([], listing)
+
+    await expect(cronLgtm(1, context)).resolves.toBe(0)
+    expect(listing.ref).not.toBeNull()
+    expect(new URL(listing.ref!.url).searchParams.get('state')).toBe('open')
+  })
+
+  it.each([
+    ['missing lgtm', withoutLgtm(17)],
+    ['blocked by a do-not-merge label', lgtmPr(18, 'do-not-merge/work-in-progress')],
+  ])('does not read a pull request that fails the merge gate (%s)', async (_reason, pr) => {
+    utils.setupJobsEnv('lgtm')
+    const context = new utils.MockContext(pullReqOpenedEvent)
+    routePages([[pr]])
+    const { read, merge } = observeRead(pr.number)
+
+    await expect(cronLgtm(1, context)).resolves.toBe(0)
+    await expect(read.notCalled()).resolves.toBe('not called')
+    await expect(merge.notCalled()).resolves.toBe('not called')
+  })
+
+  it('does not read a locked pull request even when it passes the merge gate', async () => {
+    utils.setupJobsEnv('lgtm')
+    const context = new utils.MockContext(pullReqOpenedEvent)
+    const locked = lgtmPr(19)
+    locked.locked = true
+    routePages([[locked]])
+    const { read, merge } = observeRead(19)
+
+    await expect(cronLgtm(1, context)).resolves.toBe(0)
+    await expect(read.notCalled()).resolves.toBe('not called')
+    await expect(merge.notCalled()).resolves.toBe('not called')
+  })
+
+  it('honours the merge gate of the prow configuration before reading a pull request', async () => {
+    utils.setupJobsEnv('lgtm')
+    const context = new utils.MockContext(pullReqOpenedEvent)
+    server.use(prowYaml(`
+tide:
+  labels: [lgtm, approved]
+`))
+    routePages([[lgtmPr(20)]])
+    const { read, merge } = observeRead(20)
+
+    await expect(cronLgtm(1, context)).resolves.toBe(0)
+    await expect(read.notCalled()).resolves.toBe('not called')
+    await expect(merge.notCalled()).resolves.toBe('not called')
+  })
+
+  it('requires the github-token input before listing anything', async () => {
+    utils.setupJobsEnv('lgtm')
+    delete process.env['INPUT_GITHUB-TOKEN']
+    const context = new utils.MockContext(pullReqOpenedEvent)
+    const listing = new utils.ObserveRequest()
+    routePages([], listing)
+
+    await expect(cronLgtm(1, context)).rejects.toThrow('Input required and not supplied: github-token')
+    expect(listing.ref).toBeNull()
+  })
+})