diff --git a/package-lock.json b/package-lock.json
index 02032776..efaa0f51 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -17,7 +17,7 @@
         "@hyperswarm/secret-stream": "^6.6.3",
         "@mapeo/crypto": "1.0.0-alpha.10",
         "@mapeo/sqlite-indexer": "1.0.0-alpha.9",
-        "@sinclair/typebox": "^0.29.6",
+        "@sinclair/typebox": "^0.33.17",
         "@sindresorhus/merge-streams": "^4.0.0",
         "b4a": "^1.6.3",
         "bcp-47": "^2.1.0",
@@ -65,6 +65,7 @@
         "@bufbuild/buf": "^1.26.1",
         "@comapeo/cloud": "^0.1.0",
         "@comapeo/core2.0.1": "npm:@comapeo/core@2.0.1",
+        "@comapeo/ipc": "^2.1.0",
         "@mapeo/default-config": "5.0.0",
         "@mapeo/mock-data": "^2.1.1",
         "@sinonjs/fake-timers": "^10.0.2",
@@ -268,21 +269,15 @@
         "ws": "^8.18.0"
       }
     },
-    "node_modules/@comapeo/cloud/node_modules/@sinclair/typebox": {
-      "version": "0.33.17",
-      "resolved": "https://registry.npmjs.org/@sinclair/typebox/-/typebox-0.33.17.tgz",
-      "integrity": "sha512-75232GRx3wp3P7NP+yc4nRK3XUAnaQShxTAzapgmQrgs0QvSq0/mOJGoZXRpH15cFCKyys+4laCPbBselqJ5Ag==",
-      "dev": true,
-      "license": "MIT"
-    },
     "node_modules/@comapeo/core": {
-      "version": "2.1.0",
-      "resolved": "https://registry.npmjs.org/@comapeo/core/-/core-2.1.0.tgz",
-      "integrity": "sha512-Fvi/EO1RJIQfpmKFUs4QApM2TsV8JrKw3HbNZ3hmlXiPl1oVVvIce0KkfdPJOoYHbEznTc9dIN1A2vkaoi431A==",
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/@comapeo/core/-/core-2.3.0.tgz",
+      "integrity": "sha512-yH/GOKMGSRNbdo4mKf+XXw7TGzdK+e4Ze9QfojhKs2Gdmq6uXMGp74XbUBUyzLKxiUnYCyOM0dPIyQR+i08yqg==",
       "dev": true,
+      "license": "MIT",
       "dependencies": {
         "@comapeo/fallback-smp": "^1.0.0",
-        "@comapeo/schema": "1.2.0",
+        "@comapeo/schema": "1.3.0",
         "@digidem/types": "^2.3.0",
         "@fastify/error": "^3.4.1",
         "@fastify/type-provider-typebox": "^4.1.0",
@@ -290,6 +285,7 @@
         "@mapeo/crypto": "1.0.0-alpha.10",
         "@mapeo/sqlite-indexer": "1.0.0-alpha.9",
         "@sinclair/typebox": "^0.29.6",
+        "@sindresorhus/merge-streams": "^4.0.0",
         "b4a": "^1.6.3",
         "bcp-47": "^2.1.0",
         "better-sqlite3": "^8.7.0",
@@ -325,25 +321,20 @@
         "sub-encoder": "^2.1.1",
         "throttle-debounce": "^5.0.0",
         "tiny-typed-emitter": "^2.1.0",
-        "type-fest": "^4.5.0",
+        "type-fest": "^4.30.0",
         "undici": "^6.13.0",
+        "unix-path-resolve": "^1.0.2",
         "varint": "^6.0.0",
         "ws": "^8.18.0",
         "yauzl-promise": "^4.0.0"
       }
     },
-    "node_modules/@comapeo/core/node_modules/@comapeo/schema": {
-      "version": "1.2.0",
-      "resolved": "https://registry.npmjs.org/@comapeo/schema/-/schema-1.2.0.tgz",
-      "integrity": "sha512-LWrUSqtXmrEmE/B9V/zffKBbJmMo37AlvjXczvGx1+BbCAjOYCPDX6GCtnSKNsvtnNS2KQZDm9apg3mp92tFGA==",
+    "node_modules/@comapeo/core/node_modules/@sinclair/typebox": {
+      "version": "0.29.6",
+      "resolved": "https://registry.npmjs.org/@sinclair/typebox/-/typebox-0.29.6.tgz",
+      "integrity": "sha512-aX5IFYWlMa7tQ8xZr3b2gtVReCvg7f3LEhjir/JAjX2bJCMVJA5tIPv30wTD4KDfcwMd7DDYY3hFDeGmOgtrZQ==",
       "dev": true,
-      "license": "MIT",
-      "dependencies": {
-        "@comapeo/geometry": "^1.0.2",
-        "compact-encoding": "^2.12.0",
-        "protobufjs": "^7.2.5",
-        "type-fest": "^4.26.0"
-      }
+      "license": "MIT"
     },
     "node_modules/@comapeo/core2.0.1": {
       "name": "@comapeo/core",
@@ -412,6 +403,13 @@
         "type-fest": "^4.26.0"
       }
     },
+    "node_modules/@comapeo/core2.0.1/node_modules/@sinclair/typebox": {
+      "version": "0.29.6",
+      "resolved": "https://registry.npmjs.org/@sinclair/typebox/-/typebox-0.29.6.tgz",
+      "integrity": "sha512-aX5IFYWlMa7tQ8xZr3b2gtVReCvg7f3LEhjir/JAjX2bJCMVJA5tIPv30wTD4KDfcwMd7DDYY3hFDeGmOgtrZQ==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@comapeo/fallback-smp": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/@comapeo/fallback-smp/-/fallback-smp-1.0.0.tgz",
@@ -426,6 +424,24 @@
         "protobufjs": "^7.4.0"
       }
     },
+    "node_modules/@comapeo/ipc": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/@comapeo/ipc/-/ipc-2.1.0.tgz",
+      "integrity": "sha512-awrVjwI25wJVX1OoE4yBBdWP7rLO/lHeYfjne2wk7ecuuO5abekKUQ0QFoKLpvo94LNnK+K61jRrEN5A4FY9lw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "eventemitter3": "^5.0.1",
+        "p-defer": "^4.0.0",
+        "rpc-reflector": "^1.3.11"
+      },
+      "engines": {
+        "node": ">=18.17.1"
+      },
+      "peerDependencies": {
+        "@comapeo/core": "^2.2.0"
+      }
+    },
     "node_modules/@comapeo/schema": {
       "version": "1.3.0",
       "resolved": "https://registry.npmjs.org/@comapeo/schema/-/schema-1.3.0.tgz",
@@ -983,6 +999,16 @@
         "gl-style-validate": "dist/gl-style-validate.mjs"
       }
     },
+    "node_modules/@msgpack/msgpack": {
+      "version": "1.12.2",
+      "resolved": "https://registry.npmjs.org/@msgpack/msgpack/-/msgpack-1.12.2.tgz",
+      "integrity": "sha512-Vwhc3ObxmDZmA5hY8mfsau2rJ4vGPvzbj20QSZ2/E1GDPF61QVyjLfNHak9xmel6pW4heRt3v1fHa6np9Ehfeg==",
+      "dev": true,
+      "license": "ISC",
+      "engines": {
+        "node": ">= 10"
+      }
+    },
     "node_modules/@node-rs/crc32": {
       "version": "1.10.3",
       "resolved": "https://registry.npmjs.org/@node-rs/crc32/-/crc32-1.10.3.tgz",
@@ -1192,9 +1218,10 @@
       "dev": true
     },
     "node_modules/@sinclair/typebox": {
-      "version": "0.29.6",
-      "resolved": "https://registry.npmjs.org/@sinclair/typebox/-/typebox-0.29.6.tgz",
-      "integrity": "sha512-aX5IFYWlMa7tQ8xZr3b2gtVReCvg7f3LEhjir/JAjX2bJCMVJA5tIPv30wTD4KDfcwMd7DDYY3hFDeGmOgtrZQ=="
+      "version": "0.33.22",
+      "resolved": "https://registry.npmjs.org/@sinclair/typebox/-/typebox-0.33.22.tgz",
+      "integrity": "sha512-auUj4k+f4pyrIVf4GW5UKquSZFHJWri06QgARy9C0t9ZTjJLIuNIrr1yl9bWcJWJ1Gz1vOvYN1D+QPaIlNMVkQ==",
+      "license": "MIT"
     },
     "node_modules/@sindresorhus/merge-streams": {
       "version": "4.0.0",
@@ -2597,6 +2624,13 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/const-max-uint32": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/const-max-uint32/-/const-max-uint32-1.0.2.tgz",
+      "integrity": "sha512-T8/9bffg5RThuejasJWrwqxs3Q0fsJvyl7/33IB6svroD8JC93E7X60AuuOnDE8RlP6Jlb5FxmlrVDpl9KiU2Q==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/content-disposition": {
       "version": "0.5.4",
       "resolved": "https://registry.npmjs.org/content-disposition/-/content-disposition-0.5.4.tgz",
@@ -5679,6 +5713,25 @@
         "safe-buffer": "~5.1.0"
       }
     },
+    "node_modules/length-prefixed-stream": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/length-prefixed-stream/-/length-prefixed-stream-2.0.0.tgz",
+      "integrity": "sha512-dvjTuWTKWe0oEznQcG6a9osfiYknCs7DEFJMP88n9Y581IFhYh1sZIgAFcuDOojKB0G7ftPreKhh4D0kh/VPjQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "inherits": "^2.0.3",
+        "readable-stream": "^3.1.1",
+        "varint": "^5.0.0"
+      }
+    },
+    "node_modules/length-prefixed-stream/node_modules/varint": {
+      "version": "5.0.2",
+      "resolved": "https://registry.npmjs.org/varint/-/varint-5.0.2.tgz",
+      "integrity": "sha512-lKxKYG6H03yCZUpAGOPOsMcGxd1RHCu1iKvEHYDPmTyq2HueGhD73ssNBqqQWfvYs04G9iUFRvmAVLW20Jw6ow==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/levn": {
       "version": "0.4.1",
       "resolved": "https://registry.npmjs.org/levn/-/levn-0.4.1.tgz",
@@ -8332,6 +8385,49 @@
         "url": "https://github.com/sponsors/isaacs"
       }
     },
+    "node_modules/rpc-reflector": {
+      "version": "1.3.11",
+      "resolved": "https://registry.npmjs.org/rpc-reflector/-/rpc-reflector-1.3.11.tgz",
+      "integrity": "sha512-TIf/RHJy11q/xmNBj0Xj2Z4GVPP1aLeaZXSRtthcMnXNuK+tv7SpZldB5Jk6RFHzA9TgxhcWvLHdHrdlEDKH0w==",
+      "dev": true,
+      "license": "ISC",
+      "dependencies": {
+        "@msgpack/msgpack": "^1.12.1",
+        "@types/node": "^18.16.19",
+        "duplexify": "^4.1.2",
+        "eventemitter3": "^5.0.1",
+        "is-stream": "^2.0.1",
+        "length-prefixed-stream": "^2.0.0",
+        "p-timeout": "^4.1.0",
+        "pump": "^3.0.0",
+        "serialize-error": "^8.1.0",
+        "through2": "^4.0.2",
+        "validate.io-array-like": "^1.0.2"
+      }
+    },
+    "node_modules/rpc-reflector/node_modules/is-stream": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/is-stream/-/is-stream-2.0.1.tgz",
+      "integrity": "sha512-hFoiJiTl63nn+kstHGBtewWSKnQLpyb155KHheA1l39uvtO9nWIop1p3udqPcUd/xbF1VLMO4n7OI6p7RbngDg==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=8"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
+    },
+    "node_modules/rpc-reflector/node_modules/p-timeout": {
+      "version": "4.1.0",
+      "resolved": "https://registry.npmjs.org/p-timeout/-/p-timeout-4.1.0.tgz",
+      "integrity": "sha512-+/wmHtzJuWii1sXn3HCuH/FTwGhrp4tmJTxSKJbfS+vkipci6osxXM5mY0jUiRzWKMTgUT8l7HFbeSwZAynqHw==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=10"
+      }
+    },
     "node_modules/run-applescript": {
       "version": "7.0.0",
       "resolved": "https://registry.npmjs.org/run-applescript/-/run-applescript-7.0.0.tgz",
@@ -8446,6 +8542,35 @@
       "version": "2.7.0",
       "license": "BSD-3-Clause"
     },
+    "node_modules/serialize-error": {
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/serialize-error/-/serialize-error-8.1.0.tgz",
+      "integrity": "sha512-3NnuWfM6vBYoy5gZFvHiYsVbafvI9vZv/+jlIigFn4oP4zjNPK3LhcY0xSCgeb1a5L8jO71Mit9LlNoi2UfDDQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "type-fest": "^0.20.2"
+      },
+      "engines": {
+        "node": ">=10"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
+    },
+    "node_modules/serialize-error/node_modules/type-fest": {
+      "version": "0.20.2",
+      "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-0.20.2.tgz",
+      "integrity": "sha512-Ne+eE4r0/iWnpAxD852z3A+N0Bt5RN//NjJwRd2VFHEmrywxf5vsZlh4R6lixl6B+wz/8d+maTSAkN1FIkI3LQ==",
+      "dev": true,
+      "license": "(MIT OR CC0-1.0)",
+      "engines": {
+        "node": ">=10"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
+    },
     "node_modules/set-cookie-parser": {
       "version": "2.6.0",
       "license": "MIT"
@@ -9420,6 +9545,16 @@
         "node": ">=12.22"
       }
     },
+    "node_modules/through2": {
+      "version": "4.0.2",
+      "resolved": "https://registry.npmjs.org/through2/-/through2-4.0.2.tgz",
+      "integrity": "sha512-iOqSav00cVxEEICeD7TjLB1sueEL+81Wpzp2bY17uZjZN0pWZPuo4suZ/61VujxmqSGFfgOcNuTZ85QJwNZQpw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "readable-stream": "3"
+      }
+    },
     "node_modules/timeout-refresh": {
       "version": "2.0.1",
       "license": "MIT"
@@ -9907,6 +10042,32 @@
         "spdx-expression-parse": "^3.0.0"
       }
     },
+    "node_modules/validate.io-array-like": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/validate.io-array-like/-/validate.io-array-like-1.0.2.tgz",
+      "integrity": "sha512-rGLiN0cvY9OWzQcWP+RtqZR/MK9RUz3gKDTCcRLtEQ/BvlanMF5PyqtVIN+CgrIBCv/ypfme9v7r4yMJPYpbNA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "const-max-uint32": "^1.0.2",
+        "validate.io-integer-primitive": "^1.0.0"
+      }
+    },
+    "node_modules/validate.io-integer-primitive": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/validate.io-integer-primitive/-/validate.io-integer-primitive-1.0.0.tgz",
+      "integrity": "sha512-4ARGKA4FImVWJgrgttLYsYJmDGwxlhLfDCdq09gyVgohLKKRUfD3VAo1L2vTRCLt6hDhDtFKdZiuYUTWyBggwg==",
+      "dev": true,
+      "dependencies": {
+        "validate.io-number-primitive": "^1.0.0"
+      }
+    },
+    "node_modules/validate.io-number-primitive": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/validate.io-number-primitive/-/validate.io-number-primitive-1.0.0.tgz",
+      "integrity": "sha512-8rlCe7N0TRTd50dwk4WNoMXNbX/4+RdtqE3TO6Bk0GJvAgbQlfL5DGr/Pl9ZLbWR6CutMjE2cu+yOoCnFWk+Qw==",
+      "dev": true
+    },
     "node_modules/varint": {
       "version": "6.0.0",
       "resolved": "https://registry.npmjs.org/varint/-/varint-6.0.0.tgz",
diff --git a/package.json b/package.json
index 0aa54eca..8230fbc8 100644
--- a/package.json
+++ b/package.json
@@ -110,6 +110,7 @@
     "@bufbuild/buf": "^1.26.1",
     "@comapeo/cloud": "^0.1.0",
     "@comapeo/core2.0.1": "npm:@comapeo/core@2.0.1",
+    "@comapeo/ipc": "^2.1.0",
     "@mapeo/default-config": "5.0.0",
     "@mapeo/mock-data": "^2.1.1",
     "@sinonjs/fake-timers": "^10.0.2",
@@ -165,7 +166,7 @@
     "@hyperswarm/secret-stream": "^6.6.3",
     "@mapeo/crypto": "1.0.0-alpha.10",
     "@mapeo/sqlite-indexer": "1.0.0-alpha.9",
-    "@sinclair/typebox": "^0.29.6",
+    "@sinclair/typebox": "^0.33.17",
     "@sindresorhus/merge-streams": "^4.0.0",
     "b4a": "^1.6.3",
     "bcp-47": "^2.1.0",
diff --git a/test-e2e/forked-process.js b/test-e2e/forked-process.js
new file mode 100644
index 00000000..5276cd33
--- /dev/null
+++ b/test-e2e/forked-process.js
@@ -0,0 +1,95 @@
+import { createMapeoServer } from '@comapeo/ipc'
+import { Type } from '@sinclair/typebox'
+import { Value } from '@sinclair/typebox/value'
+import Fastify from 'fastify'
+import assert from 'node:assert/strict'
+import { randomBytes } from 'node:crypto'
+import * as process from 'node:process'
+import { isMainThread, MessagePort, workerData } from 'node:worker_threads'
+import RAM from 'random-access-memory'
+import { MapeoManager } from '../src/mapeo-manager.js'
+
+/**
+ * @internal
+ * @typedef {ConstructorParameters<typeof MapeoManager>[0]} MapeoManagerConstructorOptions
+ */
+
+const mapeoManagerConstructorOptionsType = Type.Partial(
+  Type.Object({
+    rootKey: Type.Uint8Array(),
+    dbFolder: Type.String(),
+    coreStorage: Type.String(),
+    projectMigrationsFolder: Type.String(),
+    clientMigrationsFolder: Type.String(),
+    defaultConfigPath: Type.String(),
+    customMapPath: Type.String(),
+    fallbackMapPath: Type.String(),
+    defaultOnlineStyleUrl: Type.String(),
+  })
+)
+
+/**
+ * @internal
+ * @typedef {object} ParsedWorkerData
+ * @prop {MessagePort} childPort
+ * @prop {Partial<MapeoManagerConstructorOptions>} managerConstructorOverrides
+ */
+
+/**
+ * Parse data passed to this worker. If the data is invalid (which can happen
+ * if run with `node --test`), returns `null`.
+ *
+ * @param {unknown} workerData
+ * @return {null | ParsedWorkerData}
+ */
+function parseWorkerData(workerData) {
+  try {
+    assert(
+      workerData &&
+        typeof workerData === 'object' &&
+        'childPort' in workerData &&
+        workerData.childPort instanceof MessagePort &&
+        'managerConstructorOverrides' in workerData
+    )
+    return {
+      childPort: workerData.childPort,
+      managerConstructorOverrides: Value.Parse(
+        mapeoManagerConstructorOptionsType,
+        workerData.managerConstructorOverrides
+      ),
+    }
+  } catch {
+    return null
+  }
+}
+
+async function main() {
+  if (isMainThread) return
+
+  const parsedWorkerData = parseWorkerData(workerData)
+  if (!parsedWorkerData) return
+  const { managerConstructorOverrides, childPort } = parsedWorkerData
+
+  const manager = new MapeoManager({
+    rootKey: randomBytes(16),
+    projectMigrationsFolder: new URL('../drizzle/project', import.meta.url)
+      .pathname,
+    clientMigrationsFolder: new URL('../drizzle/client', import.meta.url)
+      .pathname,
+    dbFolder: ':memory:',
+    coreStorage: () => new RAM(),
+    fastify: Fastify(),
+    ...managerConstructorOverrides,
+  })
+
+  // This `any` cast is needed because `@comapeo/ipc` expects a `MapeoManager`
+  // from the `@comapeo/core` install from npm, not our local development one.
+  createMapeoServer(/** @type {any} */ (manager), childPort)
+
+  childPort.start()
+}
+
+main().catch((err) => {
+  console.error(err)
+  process.exit(1)
+})
diff --git a/test-e2e/ipc-basic.js b/test-e2e/ipc-basic.js
new file mode 100644
index 00000000..2407ad1e
--- /dev/null
+++ b/test-e2e/ipc-basic.js
@@ -0,0 +1,22 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import { createIpcManager } from './utils.js'
+import { valueOf } from '@comapeo/schema'
+import { generate } from '@mapeo/mock-data'
+
+test('basic functionality of a manager in a separate process', async (t) => {
+  const manager = await createIpcManager('manager', t)
+  await manager.setDeviceInfo({ name: 'manager', deviceType: 'mobile' })
+
+  const projectId = await manager.createProject()
+  const project = await manager.getProject(projectId)
+
+  const { docId } = await project.observation.create(
+    valueOf(generate('observation')[0])
+  )
+
+  assert(
+    await project.observation.getByDocId(docId),
+    'can retrieve an observation we just created'
+  )
+})
diff --git a/test-e2e/utils.js b/test-e2e/utils.js
index d07fdf8d..0ab9621d 100644
--- a/test-e2e/utils.js
+++ b/test-e2e/utils.js
@@ -9,6 +9,8 @@ import { createRequire } from 'node:module'
 import { fileURLToPath } from 'node:url'
 import * as v8 from 'node:v8'
 import { pEvent } from 'p-event'
+import { createMapeoClient } from '@comapeo/ipc'
+import { Worker, MessageChannel } from 'node:worker_threads'
 import { MapeoManager as MapeoManager_2_0_1 } from '@comapeo/core2.0.1'
 
 import { MapeoManager, roles } from '../src/index.js'
@@ -267,6 +269,7 @@ export function createManager(seed, t, overrides = {}) {
     ...overrides,
   })
 }
+
 /**
  * @param {string} seed
  * @param {Partial<ConstructorParameters<typeof MapeoManager_2_0_1>[0]>} [overrides]
@@ -293,6 +296,37 @@ export async function createOldManagerOnVersion2_0_1(seed, overrides = {}) {
   })
 }
 
+/**
+ * @param {string} seed
+ * @param {import('node:test').TestContext} t
+ * @param {Partial<ConstructorParameters<typeof MapeoManager_2_0_1>[0]>} [overrides]
+ * @returns {Promise<ReturnType<typeof createMapeoClient>>}
+ */
+export async function createIpcManager(seed, t, overrides = {}) {
+  const { port1: parentPort, port2: childPort } = new MessageChannel()
+
+  const forkedProcessPath = fileURLToPath(
+    new URL('./forked-process.js', import.meta.url)
+  )
+  const worker = new Worker(forkedProcessPath, {
+    workerData: {
+      managerConstructorOverrides: { rootKey: getRootKey(seed), ...overrides },
+      childPort,
+    },
+    transferList: [childPort],
+  })
+
+  t.after(() => worker.terminate())
+
+  // As an optimization, we can prevent the worker from keeping the test
+  // process alive. This isn't necessary for correctness (the call to
+  // `worker.terminate()` should be enough), but it can speed up tests by
+  // letting the process end early.
+  worker.unref()
+
+  return createMapeoClient(parentPort)
+}
+
 /**
  * `ManagerCustodian` helps you test the creation of multiple managers accessing
  * the same underlying files.