diff --git a/services/shellexecutor/java/androidx/test/services/shellexecutor/BUILD b/services/shellexecutor/java/androidx/test/services/shellexecutor/BUILD
index 897bc547a..91bf1da4d 100644
--- a/services/shellexecutor/java/androidx/test/services/shellexecutor/BUILD
+++ b/services/shellexecutor/java/androidx/test/services/shellexecutor/BUILD
@@ -64,6 +64,7 @@ kt_android_library(
         "ShellCommandExecutor.java",
         "ShellCommandExecutorServer.java",
         "ShellCommandFileObserverExecutorServer.kt",
+        "ShellCommandLocalSocketExecutorServer.kt",
         "ShellExecSharedConstants.java",
         "ShellMain.java",
     ],
@@ -72,6 +73,8 @@ kt_android_library(
     deps = [
         ":coroutine_file_observer",
         ":file_observer_protocol",
+        ":local_socket_protocol",
+        ":local_socket_protocol_pb_java_proto_lite",
         "//services/speakeasy/java/androidx/test/services/speakeasy:protocol",
         "//services/speakeasy/java/androidx/test/services/speakeasy/client",
         "//services/speakeasy/java/androidx/test/services/speakeasy/client:tool_connection",
diff --git a/services/shellexecutor/java/androidx/test/services/shellexecutor/ShellCommandLocalSocketExecutorServer.kt b/services/shellexecutor/java/androidx/test/services/shellexecutor/ShellCommandLocalSocketExecutorServer.kt
new file mode 100644
index 000000000..775f81d89
--- /dev/null
+++ b/services/shellexecutor/java/androidx/test/services/shellexecutor/ShellCommandLocalSocketExecutorServer.kt
@@ -0,0 +1,245 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.test.services.shellexecutor
+
+import android.net.LocalServerSocket
+import android.net.LocalSocket
+import android.net.LocalSocketAddress
+import android.os.Process as AndroidProcess
+import android.util.Log
+import androidx.test.services.shellexecutor.LocalSocketProtocol.asBinderKey
+import androidx.test.services.shellexecutor.LocalSocketProtocol.readRequest
+import androidx.test.services.shellexecutor.LocalSocketProtocol.sendResponse
+import androidx.test.services.shellexecutor.LocalSocketProtocolProto.RunCommandRequest
+import java.io.IOException
+import java.io.InterruptedIOException
+import java.security.SecureRandom
+import java.util.concurrent.Executors
+import java.util.concurrent.atomic.AtomicBoolean
+import kotlin.time.Duration
+import kotlin.time.Duration.Companion.milliseconds
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.TimeoutCancellationException
+import kotlinx.coroutines.asCoroutineDispatcher
+import kotlinx.coroutines.async
+import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.runInterruptible
+import kotlinx.coroutines.withTimeout
+
+/** Server that run shell commands for a client talking over a LocalSocket. */
+final class ShellCommandLocalSocketExecutorServer
+@JvmOverloads
+constructor(
+  private val scope: CoroutineScope =
+    CoroutineScope(Executors.newCachedThreadPool().asCoroutineDispatcher())
+) {
+  // Use the same secret generation as SpeakEasy does.
+  private val secret = java.lang.Long.toHexString(SecureRandom().nextLong())
+  lateinit var socket: LocalServerSocket
+  lateinit var address: LocalSocketAddress
+  // Since LocalServerSocket.accept() has to be interrupted, we keep that in its own Job...
+  lateinit var serverJob: Job
+  // ...while all the child jobs are under a single SupervisorJob that we can join later.
+  val shellJobs = SupervisorJob()
+  val running = AtomicBoolean(true)
+
+  /** Returns the binder key to pass to client processes. */
+  fun binderKey(): String {
+    // The address can contain spaces, and since it gets passed through a command line, we need to
+    // encode it. java.net.URLEncoder is conveniently available in all SDK versions.
+    return address.asBinderKey(secret)
+  }
+
+  /** Runs a simple server. */
+  private suspend fun server() = coroutineScope {
+    while (running.get()) {
+      val connection =
+        try {
+          runInterruptible { socket.accept() }
+        } catch (x: Exception) {
+          // None of my tests have managed to trigger this one.
+          Log.e(TAG, "LocalServerSocket.accept() failed", x)
+          break
+        }
+      launch(scope.coroutineContext + shellJobs) { handleConnection(connection) }
+    }
+  }
+
+  /**
+   * Relays the output of process to connection with a series of RunCommandResponses.
+   *
+   * @param process The process to relay output from.
+   * @param connection The connection to relay output to.
+   * @return false if there was a problem, true otherwise.
+   */
+  private suspend fun relay(process: Process, connection: LocalSocket): Boolean {
+    // Experiment shows that 64K is *much* faster than 4K, especially on API 21-23. Streaming 1MB
+    // takes 3s with 4K buffers and 2s with 64K on API 23. 22 is a bit faster (2.6s -> 1.5s),
+    // 21 faster still (630ms -> 545ms). Higher API levels are *much* faster (24 is 119 ms ->
+    // 75ms).
+    val buffer = ByteArray(65536)
+    var size: Int
+
+    // LocalSocket.isOutputShutdown() throws UnsupportedOperationException, so we can't use
+    // that as our loop constraint.
+    while (true) {
+      try {
+        size = runInterruptible { process.inputStream.read(buffer) }
+        if (size < 0) return true // EOF
+        if (size == 0) {
+          delay(1.milliseconds)
+          continue
+        }
+      } catch (x: InterruptedIOException) {
+        // We start getting these at API 24 when the timeout handling kicks in.
+        Log.i(TAG, "Interrupted while reading from ${process}: ${x.message}")
+        return false
+      } catch (x: IOException) {
+        Log.i(TAG, "Error reading from ${process}; did it time out?", x)
+        return false
+      }
+
+      if (!connection.sendResponse(buffer = buffer, size = size)) {
+        return false
+      }
+    }
+  }
+
+  /** Handle one connection. */
+  private suspend fun handleConnection(connection: LocalSocket) {
+    // connection.localSocketAddress is always null, so no point in logging it.
+
+    // Close the connection when done.
+    connection.use {
+      val request = connection.readRequest()
+
+      if (request.secret.compareTo(secret) != 0) {
+        Log.w(TAG, "Ignoring request with wrong secret: $request")
+        return
+      }
+
+      val pb = request.toProcessBuilder()
+      pb.redirectErrorStream(true)
+
+      val process: Process
+      try {
+        process = pb.start()
+      } catch (x: IOException) {
+        Log.e(TAG, "Failed to start process", x)
+        connection.sendResponse(
+          buffer = x.stackTraceToString().toByteArray(),
+          exitCode = EXIT_CODE_FAILED_TO_START,
+        )
+        return
+      }
+
+      // We will not be writing anything to the process' stdin.
+      process.outputStream.close()
+
+      // Close the process' stdout when we're done reading.
+      process.inputStream.use {
+        // Launch a coroutine to relay the process' output to the client. If it times out, kill the
+        // process and cancel the job. This is more coroutine-friendly than using waitFor() to
+        // handle timeouts.
+        val ioJob = scope.async { relay(process, connection) }
+
+        try {
+          withTimeout(request.timeout()) {
+            if (!ioJob.await()) {
+              Log.w(TAG, "Relaying ${process} output failed")
+            }
+            runInterruptible { process.waitFor() }
+          }
+        } catch (x: TimeoutCancellationException) {
+          Log.e(TAG, "Process ${process} timed out after ${request.timeout()}")
+          process.destroy()
+          ioJob.cancel()
+          connection.sendResponse(exitCode = EXIT_CODE_TIMED_OUT)
+          return
+        }
+
+        connection.sendResponse(exitCode = process.exitValue())
+      }
+    }
+  }
+
+  /** Starts the server. */
+  fun start() {
+    socket = LocalServerSocket("androidx.test.services ${AndroidProcess.myPid()}")
+    address = socket.localSocketAddress
+    Log.i(TAG, "Starting server on ${address.name}")
+
+    // Launch a coroutine to call socket.accept()
+    serverJob = scope.launch { server() }
+  }
+
+  /** Stops the server. */
+  fun stop(timeout: Duration) {
+    running.set(false)
+    // Closing the socket does not interrupt accept()...
+    socket.close()
+    runBlocking(scope.coroutineContext) {
+      try {
+        // ...so we simply cancel that job...
+        serverJob.cancel()
+        // ...and play nicely with all the shell jobs underneath.
+        withTimeout(timeout) {
+          shellJobs.complete()
+          shellJobs.join()
+        }
+      } catch (x: TimeoutCancellationException) {
+        Log.w(TAG, "Shell jobs did not stop after $timeout", x)
+        shellJobs.cancel()
+      }
+    }
+  }
+
+  private fun RunCommandRequest.timeout(): Duration =
+    if (timeoutMs <= 0) {
+      Duration.INFINITE
+    } else {
+      timeoutMs.milliseconds
+    }
+
+  /**
+   * Sets up a ProcessBuilder with information from the request; other configuration is up to the
+   * caller.
+   */
+  private fun RunCommandRequest.toProcessBuilder(): ProcessBuilder {
+    val pb = ProcessBuilder(argvList)
+    val redacted = argvList.map { it.replace(secret, "(SECRET)") } // Don't log the secret!
+    Log.i(TAG, "Command to execute: [${redacted.joinToString("] [")}] within ${timeout()}")
+    if (environmentMap.isNotEmpty()) {
+      pb.environment().putAll(environmentMap)
+      val env = environmentMap.entries.map { (k, v) -> "$k=$v" }.joinToString(", ")
+      Log.i(TAG, "Environment: $env")
+    }
+    return pb
+  }
+
+  private companion object {
+    const val TAG = "SCLSEServer" // up to 23 characters
+
+    const val EXIT_CODE_FAILED_TO_START = -1
+    const val EXIT_CODE_TIMED_OUT = -2
+  }
+}
diff --git a/services/shellexecutor/javatests/androidx/test/services/shellexecutor/BUILD b/services/shellexecutor/javatests/androidx/test/services/shellexecutor/BUILD
index 0b69391ab..ff90f5063 100644
--- a/services/shellexecutor/javatests/androidx/test/services/shellexecutor/BUILD
+++ b/services/shellexecutor/javatests/androidx/test/services/shellexecutor/BUILD
@@ -109,6 +109,23 @@ axt_android_library_test(
     ],
 )
 
+axt_android_library_test(
+    name = "ShellCommandLocalSocketExecutorServerTest",
+    srcs = [
+        "ShellCommandLocalSocketExecutorServerTest.kt",
+    ],
+    deps = [
+        "//runner/monitor",
+        "//services/shellexecutor:exec_server",
+        "//services/shellexecutor/java/androidx/test/services/shellexecutor:local_socket_protocol",
+        "//services/shellexecutor/java/androidx/test/services/shellexecutor:local_socket_protocol_pb_java_proto_lite",
+        "@com_google_protobuf//:protobuf_javalite",
+        "@maven//:com_google_truth_truth",
+        "@maven//:junit_junit",
+        "@maven//:org_jetbrains_kotlinx_kotlinx_coroutines_android",
+    ],
+)
+
 axt_android_library_test(
     name = "ShellExecutorTest",
     srcs = [
diff --git a/services/shellexecutor/javatests/androidx/test/services/shellexecutor/ShellCommandLocalSocketExecutorServerTest.kt b/services/shellexecutor/javatests/androidx/test/services/shellexecutor/ShellCommandLocalSocketExecutorServerTest.kt
new file mode 100644
index 000000000..230ea9820
--- /dev/null
+++ b/services/shellexecutor/javatests/androidx/test/services/shellexecutor/ShellCommandLocalSocketExecutorServerTest.kt
@@ -0,0 +1,104 @@
+package androidx.test.services.shellexecutor
+
+import android.net.LocalSocket
+import android.os.Build
+import androidx.test.services.shellexecutor.LocalSocketProtocol.addressFromBinderKey
+import androidx.test.services.shellexecutor.LocalSocketProtocol.hasExited
+import androidx.test.services.shellexecutor.LocalSocketProtocol.readResponse
+import androidx.test.services.shellexecutor.LocalSocketProtocol.secretFromBinderKey
+import androidx.test.services.shellexecutor.LocalSocketProtocol.sendRequest
+import androidx.test.services.shellexecutor.LocalSocketProtocolProto.RunCommandResponse
+import com.google.common.truth.Truth.assertThat
+import kotlin.time.Duration.Companion.milliseconds
+import kotlinx.coroutines.runBlocking
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+@RunWith(JUnit4::class)
+class ShellCommandLocalSocketExecutorServerTest {
+
+  @Test
+  fun success_simple() {
+    val responses = mutableListOf<RunCommandResponse>()
+    runBlocking {
+      val server = ShellCommandLocalSocketExecutorServer()
+      server.start()
+      val client = LocalSocket(LocalSocket.SOCKET_STREAM)
+      client.connect(addressFromBinderKey(server.binderKey()))
+      client.sendRequest(
+        secretFromBinderKey(server.binderKey()),
+        listOf("echo", "\${POTRZEBIE}"),
+        mapOf("POTRZEBIE" to "furshlugginer"),
+        1000.milliseconds,
+      )
+      do {
+        client.readResponse()?.let { responses.add(it) }
+      } while (!responses.last().hasExited())
+      server.stop(100.milliseconds)
+    }
+    if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.LOLLIPOP_MR1) {
+      // On API 21 and 22, echo only exists as a shell builtin!
+      assertThat(responses).hasSize(1)
+      assertThat(responses[0].exitCode).isEqualTo(-1)
+      assertThat(responses[0].buffer.toStringUtf8()).contains("Permission denied")
+    } else {
+      // On rare occasions, the output of the command will come back in two packets! So to keep
+      // this test from being 1% flaky:
+      val stdout = buildString {
+        for (response in responses) {
+          if (response.buffer.size() > 0) append(response.buffer.toStringUtf8())
+        }
+      }
+      assertThat(stdout).isEqualTo("\${POTRZEBIE}\n")
+      assertThat(responses.last().hasExited()).isTrue()
+      assertThat(responses.last().exitCode).isEqualTo(0)
+    }
+  }
+
+  @Test
+  fun success_shell_expansion() {
+    val responses = mutableListOf<RunCommandResponse>()
+    runBlocking {
+      val server = ShellCommandLocalSocketExecutorServer()
+      server.start()
+      val client = LocalSocket(LocalSocket.SOCKET_STREAM)
+      client.connect(addressFromBinderKey(server.binderKey()))
+      client.sendRequest(
+        secretFromBinderKey(server.binderKey()),
+        listOf("sh", "-c", "echo \${POTRZEBIE}"),
+        mapOf("POTRZEBIE" to "furshlugginer"),
+        1000.milliseconds,
+      )
+      do {
+        client.readResponse()?.let { responses.add(it) }
+      } while (!responses.last().hasExited())
+      server.stop(100.milliseconds)
+    }
+    val stdout = buildString {
+      for (response in responses) {
+        if (response.buffer.size() > 0) append(response.buffer.toStringUtf8())
+      }
+    }
+    assertThat(stdout).isEqualTo("furshlugginer\n")
+    assertThat(responses.last().hasExited()).isTrue()
+    assertThat(responses.last().exitCode).isEqualTo(0)
+  }
+
+  @Test
+  fun failure_bad_secret() {
+    runBlocking {
+      val server = ShellCommandLocalSocketExecutorServer()
+      server.start()
+      val client = LocalSocket(LocalSocket.SOCKET_STREAM)
+      client.connect(addressFromBinderKey(server.binderKey()))
+      client.sendRequest(
+        "potrzebie!",
+        listOf("sh", "-c", "echo \${POTRZEBIE}"),
+        mapOf("POTRZEBIE" to "furshlugginer"),
+        1000.milliseconds,
+      )
+      assertThat(client.inputStream.read()).isEqualTo(-1)
+    }
+  }
+}