diff --git a/src/main/java/com/google/devtools/build/lib/BUILD b/src/main/java/com/google/devtools/build/lib/BUILD
index 0ea5446..b6bf332 100644
--- a/src/main/java/com/google/devtools/build/lib/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/BUILD
@@ -233,6 +233,7 @@
             "util/BlazeClock.java",
             "util/Clock.java",
             "util/ExitCode.java",
+            "util/FailureDetailUtil.java",
             "util/FileType.java",
             "util/FileTypeSet.java",
             "util/JavaClock.java",
@@ -319,6 +320,7 @@
     ],
     deps = [
         "//third_party:guava",
+        "//third_party:jsr305",
     ],
 )
 
@@ -328,6 +330,17 @@
     deps = ["//third_party:jsr305"],
 )
 
+java_library(
+    name = "failure_detail_util",
+    srcs = ["util/FailureDetailUtil.java"],
+    deps = [
+        ":exitcode-external",
+        "//src/main/protobuf:failure_details_java_proto",
+        "//third_party:guava",
+        "//third_party/protobuf:protobuf_java",
+    ],
+)
+
 # Event reporting infrastructure.
 java_library(
     name = "events",
@@ -1172,6 +1185,7 @@
     deps = [
         ":bug-report",
         ":exitcode-external",
+        ":failure_detail_util",
         ":os_util",
         ":out-err",
         ":runtime",
@@ -1244,6 +1258,7 @@
         ":custom-exit-code-publisher",
         ":events",
         ":exitcode-external",
+        ":failure_detail_util",
         ":io",
         ":keep-going-option",
         ":loading-phase-threads-option",
@@ -1288,6 +1303,7 @@
         "//src/main/protobuf:command_line_java_proto",
         "//src/main/protobuf:command_server_java_proto",
         "//src/main/protobuf:extra_actions_base_java_proto",
+        "//src/main/protobuf:failure_details_java_proto",
         "//src/main/protobuf:invocation_policy_java_proto",
         "//src/main/protobuf:option_filters_java_proto",
         "//src/main/protobuf:test_status_java_proto",
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandResult.java b/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandResult.java
index 8be6f9f..da17258 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandResult.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandResult.java
@@ -18,7 +18,9 @@
 import com.google.common.base.Preconditions;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.server.CommandProtos.ExecRequest;
+import com.google.devtools.build.lib.server.FailureDetails.FailureDetail;
 import com.google.devtools.build.lib.util.ExitCode;
+import com.google.devtools.build.lib.util.FailureDetailUtil;
 import javax.annotation.Nullable;
 
 /**
@@ -28,12 +30,17 @@
 @Immutable
 public final class BlazeCommandResult {
   private final ExitCode exitCode;
-  @Nullable
-  private final ExecRequest execDescription;
+  @Nullable private final FailureDetail failureDetail;
+  @Nullable private final ExecRequest execDescription;
   private final boolean shutdown;
 
-  private BlazeCommandResult(ExitCode exitCode, ExecRequest execDescription, boolean shutdown) {
+  private BlazeCommandResult(
+      ExitCode exitCode,
+      @Nullable FailureDetail failureDetail,
+      ExecRequest execDescription,
+      boolean shutdown) {
     this.exitCode = Preconditions.checkNotNull(exitCode);
+    this.failureDetail = failureDetail;
     this.execDescription = execDescription;
     this.shutdown = shutdown;
   }
@@ -42,6 +49,11 @@
     return exitCode;
   }
 
+  @Nullable
+  public FailureDetail getFailureDetail() {
+    return failureDetail;
+  }
+
   public boolean shutdown() {
     return shutdown;
   }
@@ -55,21 +67,27 @@
   public String toString() {
     return MoreObjects.toStringHelper(this)
         .add("exitCode", exitCode)
+        .add("failureDetail", failureDetail)
         .add("execDescription", execDescription)
         .add("shutdown", shutdown)
         .toString();
   }
 
   public static BlazeCommandResult shutdown(ExitCode exitCode) {
-    return new BlazeCommandResult(exitCode, null, true);
+    return new BlazeCommandResult(exitCode, null, null, true);
   }
 
   public static BlazeCommandResult exitCode(ExitCode exitCode) {
-    return new BlazeCommandResult(exitCode, null, false);
+    return new BlazeCommandResult(exitCode, null, null, false);
+  }
+
+  public static BlazeCommandResult failureDetail(FailureDetail failureDetail) {
+    return new BlazeCommandResult(
+        FailureDetailUtil.getExitCode(failureDetail), failureDetail, null, false);
   }
 
   public static BlazeCommandResult execute(ExecRequest execDescription) {
     return new BlazeCommandResult(
-        ExitCode.SUCCESS, Preconditions.checkNotNull(execDescription), false);
+        ExitCode.SUCCESS, null, Preconditions.checkNotNull(execDescription), false);
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/server/GrpcServerImpl.java b/src/main/java/com/google/devtools/build/lib/server/GrpcServerImpl.java
index 6276d4e..e831e62 100644
--- a/src/main/java/com/google/devtools/build/lib/server/GrpcServerImpl.java
+++ b/src/main/java/com/google/devtools/build/lib/server/GrpcServerImpl.java
@@ -36,7 +36,9 @@
 import com.google.devtools.build.lib.server.CommandProtos.RunResponse;
 import com.google.devtools.build.lib.server.CommandProtos.ServerInfo;
 import com.google.devtools.build.lib.server.CommandProtos.StartupOption;
+import com.google.devtools.build.lib.server.FailureDetails.Interrupted.InterruptedCode;
 import com.google.devtools.build.lib.util.ExitCode;
+import com.google.devtools.build.lib.util.FailureDetailUtil;
 import com.google.devtools.build.lib.util.Pair;
 import com.google.devtools.build.lib.util.io.OutErr;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
@@ -611,7 +613,9 @@
         result = BlazeCommandResult.exitCode(ExitCode.COMMAND_LINE_ERROR);
       }
     } catch (InterruptedException e) {
-      result = BlazeCommandResult.exitCode(ExitCode.INTERRUPTED);
+      result =
+          BlazeCommandResult.failureDetail(
+              FailureDetailUtil.interrupted(InterruptedCode.UNSPECIFIED));
       commandId = ""; // The default value, the client will ignore it
     }
 
@@ -626,6 +630,9 @@
       response.setExecRequest(result.getExecRequest());
     } else {
       response.setExitCode(result.getExitCode().getNumericExitCode());
+      if (result.getFailureDetail() != null) {
+        response.setFailureDetail(result.getFailureDetail());
+      }
     }
 
     try {
diff --git a/src/main/java/com/google/devtools/build/lib/util/ExitCode.java b/src/main/java/com/google/devtools/build/lib/util/ExitCode.java
index 34b7bbb..fda79d9 100644
--- a/src/main/java/com/google/devtools/build/lib/util/ExitCode.java
+++ b/src/main/java/com/google/devtools/build/lib/util/ExitCode.java
@@ -17,6 +17,7 @@
 import com.google.common.base.Objects;
 import java.util.Collection;
 import java.util.HashMap;
+import javax.annotation.Nullable;
 
 /**
  *  <p>Anything marked FAILURE is generally from a problem with the source code
@@ -134,6 +135,18 @@
     }
   }
 
+  /**
+   * Returns a registered {@link ExitCode} with the given {@code code}.
+   *
+   * <p>Note that there *are* unregistered ExitCodes. This will never return them.
+   */
+  @Nullable
+  static ExitCode forCode(int code) {
+    synchronized (exitCodeRegistry) {
+      return exitCodeRegistry.get(code);
+    }
+  }
+
   private final int numericExitCode;
   private final String name;
   private final boolean infrastructureFailure;
diff --git a/src/main/java/com/google/devtools/build/lib/util/FailureDetailUtil.java b/src/main/java/com/google/devtools/build/lib/util/FailureDetailUtil.java
new file mode 100644
index 0000000..4aec6eb
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/util/FailureDetailUtil.java
@@ -0,0 +1,68 @@
+// Copyright 2020 The Bazel Authors. All rights reserved.
+//
+// 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 com.google.devtools.build.lib.util;
+
+import com.google.common.base.Preconditions;
+import com.google.devtools.build.lib.server.FailureDetails;
+import com.google.devtools.build.lib.server.FailureDetails.FailureDetail;
+import com.google.devtools.build.lib.server.FailureDetails.Interrupted;
+import com.google.devtools.build.lib.server.FailureDetails.Interrupted.InterruptedCode;
+import com.google.protobuf.ProtocolMessageEnum;
+
+/** Utilities for constructing and managing {@link FailureDetail}s. */
+public class FailureDetailUtil {
+
+  private FailureDetailUtil() {}
+
+  /**
+   * Returns a {@link FailureDetail} specifying {@code code} in its {@link Interrupted} submessage.
+   */
+  public static FailureDetail interrupted(InterruptedCode code) {
+    return FailureDetail.newBuilder()
+        .setInterrupted(Interrupted.newBuilder().setCode(code))
+        .build();
+  }
+
+  /** Returns the registered {@link ExitCode} associated with a {@link FailureDetail} message. */
+  public static ExitCode getExitCode(FailureDetail failureDetail) {
+    // TODO(mschaller): Consider specializing for unregistered exit codes here, if absolutely
+    //  necessary.
+    int numericExitCode = FailureDetailUtil.getNumericExitCode(failureDetail);
+    return Preconditions.checkNotNull(
+        ExitCode.forCode(numericExitCode), "No ExitCode for numericExitCode %s", numericExitCode);
+  }
+
+  /** Returns the numeric exit code associated with a {@link FailureDetail} message. */
+  private static int getNumericExitCode(FailureDetail failureDetail) {
+    // TODO(mschaller): generalize this for arbitrary FailureDetail messages.
+    Preconditions.checkArgument(failureDetail.hasInterrupted());
+    return getNumericExitCode(failureDetail.getInterrupted().getCode());
+  }
+
+  /**
+   * Returns the numeric exit code associated with a {@link FailureDetail} submessage's subcategory
+   * enum value.
+   */
+  private static int getNumericExitCode(ProtocolMessageEnum code) {
+    Preconditions.checkArgument(
+        code.getValueDescriptor().getOptions().hasExtension(FailureDetails.metadata),
+        "Enum value %s has no FailureDetails.metadata",
+        code);
+    return code.getValueDescriptor()
+        .getOptions()
+        .getExtension(FailureDetails.metadata)
+        .getExitCode();
+  }
+}
diff --git a/src/main/protobuf/failure_details.proto b/src/main/protobuf/failure_details.proto
index f4095f1..79adce5 100644
--- a/src/main/protobuf/failure_details.proto
+++ b/src/main/protobuf/failure_details.proto
@@ -33,7 +33,71 @@
   FailureDetailMetadata metadata = 1078;
 }
 
+// The FailureDetail message type is designed such that consumers can extract a
+// basic classification of a FailureDetail message even if the consumer was
+// built with a stale definition. This forward compatibility is implemented via
+// conventions on FailureDetail and its submessage types, as follows.
+//
+// *** FailureDetail field numbers
+//
+// Field numbers 1 through 100 (inclusive) are reserved for generally applicable
+// values. Any number of these fields may be set on a FailureDetail message.
+//
+// Field numbers 101 through 10,000 (inclusive) are reserved for use inside the
+// "oneof" structure. Only one of these values should be set on a FailureDetail
+// message.
+//
+// Additional fields numbers are unlikely to be needed, but, for extreme future-
+// proofing purposes, field numbers 10,001 through 1,000,000 (inclusive;
+// excluding protobuf's reserved range 19000 through 19999) are reserved for
+// additional generally applicable values.
+//
+// *** FailureDetail's "oneof" submessages
+//
+// Each field in the "oneof" structure is a submessage corresponding to a
+// category of failure.
+//
+// In each of these submessage types, field number 1 is an enum whose values
+// correspond to a subcategory of the failure. Generally, the enum's constant
+// which maps to 0 should be interpreted as "unspecified", though this is not
+// required.
+//
+// *** Recommended forward compatibility strategy
+//
+// The recommended forward compatibility strategy is to reduce a FailureDetail
+// message to a pair of integers.
+//
+// The first integer corresponds to the field number of the submessage set
+// inside FailureDetail's "oneof", which corresponds with the failure's
+// category.
+//
+// The second integer corresponds to the value of the enum at field number 1
+// within that submessage, which corresponds with the failure's subcategory.
+//
+// WARNING: This functionality is experimental and should not be relied on at
+// this time.
+// TODO(mschaller): remove experimental warning
 message FailureDetail {
   // A short human-readable message describing the failure, for debugging.
+  //
+  // This value is *not* intended to be used algorithmically.
   string message = 1;
+
+  // Reserved for future generally applicable values. Any of these may be set.
+  reserved 2 to 100;
+
+  oneof category {
+    Interrupted interrupted = 101;
+  }
+}
+
+message Interrupted {
+  enum InterruptedCode {
+    // Interrupted at an unspecified time.
+    UNSPECIFIED = 0 [(metadata) = { exit_code: 8 }];
+    // TODO(mschaller): Add subcategories that specify what was happening at the
+    //  time of interruption.
+  }
+
+  InterruptedCode code = 1;
 }
diff --git a/src/test/java/com/google/devtools/build/lib/BUILD b/src/test/java/com/google/devtools/build/lib/BUILD
index bbe241f..97365d9 100644
--- a/src/test/java/com/google/devtools/build/lib/BUILD
+++ b/src/test/java/com/google/devtools/build/lib/BUILD
@@ -1075,6 +1075,7 @@
         "//src/main/java/com/google/devtools/build/lib/vfs/inmemoryfs",
         "//src/main/protobuf:command_server_java_grpc",
         "//src/main/protobuf:command_server_java_proto",
+        "//src/main/protobuf:failure_details_java_proto",
         "//src/main/protobuf:invocation_policy_java_proto",
         "//third_party:jsr305",
         "//third_party:mockito",
diff --git a/src/test/java/com/google/devtools/build/lib/server/GrpcServerTest.java b/src/test/java/com/google/devtools/build/lib/server/GrpcServerTest.java
index d64c35d7..71d50f1 100644
--- a/src/test/java/com/google/devtools/build/lib/server/GrpcServerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/server/GrpcServerTest.java
@@ -25,6 +25,7 @@
 import com.google.devtools.build.lib.server.CommandProtos.RunRequest;
 import com.google.devtools.build.lib.server.CommandProtos.RunResponse;
 import com.google.devtools.build.lib.server.CommandServerGrpc.CommandServerStub;
+import com.google.devtools.build.lib.server.FailureDetails.Interrupted.InterruptedCode;
 import com.google.devtools.build.lib.server.GrpcServerImpl.BlockingStreamObserver;
 import com.google.devtools.build.lib.testutil.Suite;
 import com.google.devtools.build.lib.testutil.TestSpec;
@@ -155,6 +156,7 @@
     assertThat(responses.get(0).getCookie()).isNotEmpty();
     assertThat(responses.get(1).getFinished()).isTrue();
     assertThat(responses.get(1).getExitCode()).isEqualTo(0);
+    assertThat(responses.get(1).hasFailureDetail()).isFalse();
   }
 
   @Test
@@ -261,6 +263,7 @@
     }
     assertThat(responses.get(11).getFinished()).isTrue();
     assertThat(responses.get(11).getExitCode()).isEqualTo(0);
+    assertThat(responses.get(11).hasFailureDetail()).isFalse();
   }
 
   @Test
@@ -321,7 +324,6 @@
 
   @Test
   public void testCancel() throws Exception {
-    CountDownLatch done = new CountDownLatch(1);
     CommandDispatcher dispatcher =
         new CommandDispatcher() {
           @Override
@@ -332,30 +334,34 @@
               LockingMode lockingMode,
               String clientDescription,
               long firstContactTimeMillis,
-              Optional<List<Pair<String, String>>> startupOptionsTaggedWithBazelRc) {
+              Optional<List<Pair<String, String>>> startupOptionsTaggedWithBazelRc)
+              throws InterruptedException {
             synchronized (this) {
-              try {
-                this.wait();
-              } catch (InterruptedException expected) {
-                // Expected
-              }
+              this.wait();
             }
-            done.countDown();
-            return BlazeCommandResult.exitCode(ExitCode.INTERRUPTED);
+            // Interruption expected before this is reached.
+            throw new IllegalStateException();
           }
         };
     createServer(dispatcher);
 
     AtomicReference<String> commandId = new AtomicReference<>();
-    CountDownLatch inResponse = new CountDownLatch(1);
+    CountDownLatch gotCommandId = new CountDownLatch(1);
+    AtomicReference<RunResponse> secondResponse = new AtomicReference<>();
+    CountDownLatch gotSecondResponse = new CountDownLatch(1);
     CommandServerStub stub = CommandServerGrpc.newStub(channel);
     stub.run(
         createRequest("Foo"),
         new StreamObserver<RunResponse>() {
           @Override
           public void onNext(RunResponse value) {
-            commandId.set(value.getCommandId());
-            inResponse.countDown();
+            String previousCommandId = commandId.getAndSet(value.getCommandId());
+            if (previousCommandId == null) {
+              gotCommandId.countDown();
+            } else {
+              secondResponse.set(value);
+              gotSecondResponse.countDown();
+            }
           }
 
           @Override
@@ -365,7 +371,7 @@
           public void onCompleted() {}
         });
     // Wait until we've got the command id.
-    inResponse.await();
+    gotCommandId.await();
 
     CountDownLatch cancelRequestComplete = new CountDownLatch(1);
     CancelRequest cancelRequest =
@@ -385,9 +391,16 @@
           }
         });
     cancelRequestComplete.await();
-    done.await();
+    gotSecondResponse.await();
     server.shutdown();
     server.awaitTermination();
+
+    assertThat(secondResponse.get().getFinished()).isTrue();
+    assertThat(secondResponse.get().getExitCode()).isEqualTo(8);
+    assertThat(secondResponse.get().hasFailureDetail()).isTrue();
+    assertThat(secondResponse.get().getFailureDetail().hasInterrupted()).isTrue();
+    assertThat(secondResponse.get().getFailureDetail().getInterrupted().getCode())
+        .isEqualTo(InterruptedCode.UNSPECIFIED);
   }
 
   @Test