diff --git a/dev/codeserver/java/com/google/gwt/dev/codeserver/Job.java b/dev/codeserver/java/com/google/gwt/dev/codeserver/Job.java
index b94c0c5..9af7cda 100644
--- a/dev/codeserver/java/com/google/gwt/dev/codeserver/Job.java
+++ b/dev/codeserver/java/com/google/gwt/dev/codeserver/Job.java
@@ -28,6 +28,7 @@
 import com.google.gwt.thirdparty.guava.common.util.concurrent.SettableFuture;
 
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -70,6 +71,7 @@
   // Miscellaneous
 
   private final ImmutableList<String> args;
+  private final Set<String> tags;
 
   /**
    * The id to report to the recompile listener.
@@ -98,6 +100,7 @@
     this.recompileListener = Preconditions.checkNotNull(options.getRecompileListener());
     this.jobChangeListener = Preconditions.checkNotNull(options.getJobChangeListener());
     this.args = Preconditions.checkNotNull(options.getArgs());
+    this.tags = Preconditions.checkNotNull(options.getTags());
     this.logSupplier = new LogSupplier(parentLogger, id);
   }
 
@@ -284,6 +287,7 @@
     out.setCompileDir(compileDir);
     out.setCompileStrategy(compileStrategy);
     out.setArguments(args);
+    out.setTags(tags);
     return out.build();
   }
 
diff --git a/dev/codeserver/java/com/google/gwt/dev/codeserver/JobEvent.java b/dev/codeserver/java/com/google/gwt/dev/codeserver/JobEvent.java
index ee26865..e4582a6 100644
--- a/dev/codeserver/java/com/google/gwt/dev/codeserver/JobEvent.java
+++ b/dev/codeserver/java/com/google/gwt/dev/codeserver/JobEvent.java
@@ -25,6 +25,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.SortedMap;
+import java.util.regex.Pattern;
 
 /**
  * The status of a compile job submitted to Super Dev Mode.
@@ -32,6 +33,7 @@
  * <p>JobEvent objects are deeply immutable, though they describe a Job that changes.
  */
 public final class JobEvent {
+  private static final Pattern VALID_TAG = Pattern.compile("\\S{1,100}");
 
   private final String jobId;
 
@@ -43,6 +45,7 @@
   private final CompileDir compileDir;
   private final CompileStrategy compileStrategy;
   private final ImmutableList<String> arguments;
+  private final ImmutableList<String> tags;
 
   private JobEvent(Builder builder) {
     this.jobId = Preconditions.checkNotNull(builder.jobId);
@@ -55,6 +58,7 @@
     this.compileDir = builder.compileDir;
     this.compileStrategy = builder.compileStrategy;
     this.arguments = ImmutableList.copyOf(builder.args);
+    this.tags = ImmutableList.copyOf(builder.tags);
 
     // Any new fields added should allow nulls for backward compatibility.
   }
@@ -120,6 +124,34 @@
   }
 
   /**
+   * User-defined tags associated with this job. (Not null but may be empty.)
+   */
+  public ImmutableList<String> getTags() { return tags; }
+
+  /**
+   * If all the given tags are valid, returns a list containing the tags.
+   * @throws java.lang.IllegalArgumentException if any tag is invalid.
+   */
+  static ImmutableList<String> checkTags(Iterable<String> tags) {
+    ImmutableList.Builder<String> builder = ImmutableList.builder();
+    for (String tag : tags) {
+      if (!isValidTag(tag)) {
+        throw new IllegalArgumentException("invalid tag: " + tag);
+      }
+      builder.add(tag);
+    }
+    return builder.build();
+  }
+
+  /**
+   * Returns true if the tag is valid.
+   * Tags must not be null, contain whitespace, or be more than 100 characters.
+   */
+  private static boolean isValidTag(String candidate) {
+    return candidate != null && VALID_TAG.matcher(candidate).matches();
+  }
+
+  /**
    * Defines the lifecycle of a job.
    */
   public enum Status {
@@ -155,7 +187,7 @@
     /**
      * The string to use for serialization.
      */
-    String getJsonName() {
+    public String getJsonName() {
       return jsonName;
     }
   }
@@ -175,6 +207,7 @@
     private CompileDir compileDir;
     private CompileStrategy compileStrategy;
     private List<String> args = ImmutableList.of();
+    private List<String> tags = ImmutableList.of();
 
     /**
      * A unique id for this job. Required.
@@ -250,6 +283,14 @@
       this.args = Preconditions.checkNotNull(args);
     }
 
+    /**
+     * User-defined tags passed to {@link Options#addTags}.
+     * Optional but may not be null. If not set, defaults to the empty list.
+     */
+    public void setTags(Iterable<String> tags) {
+      this.tags = checkTags(tags);
+    }
+
     public JobEvent build() {
       return new JobEvent(this);
     }
diff --git a/dev/codeserver/java/com/google/gwt/dev/codeserver/Options.java b/dev/codeserver/java/com/google/gwt/dev/codeserver/Options.java
index 42732ee..3910845 100644
--- a/dev/codeserver/java/com/google/gwt/dev/codeserver/Options.java
+++ b/dev/codeserver/java/com/google/gwt/dev/codeserver/Options.java
@@ -28,6 +28,7 @@
 import com.google.gwt.dev.util.arg.OptionSourceLevel;
 import com.google.gwt.dev.util.arg.SourceLevel;
 import com.google.gwt.thirdparty.guava.common.collect.ImmutableList;
+import com.google.gwt.thirdparty.guava.common.collect.ImmutableSet;
 import com.google.gwt.util.tools.ArgHandler;
 import com.google.gwt.util.tools.ArgHandlerDir;
 import com.google.gwt.util.tools.ArgHandlerExtra;
@@ -40,7 +41,9 @@
 import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Set;
 
 /**
  * Defines the command-line options for the {@link CodeServer CodeServer's} main() method.
@@ -49,6 +52,7 @@
  */
 public class Options {
   private ImmutableList<String> args;
+  private Set<String> tags = new LinkedHashSet<String>();
 
   private boolean compilePerFile = false;
   private boolean noPrecompile = false;
@@ -103,10 +107,36 @@
       noPrecompile = true;
     }
 
+    // Set some tags automatically for migration tracking.
+    if (shouldCompilePerFile()) {
+      addTags("incremental_on");
+    } else {
+      addTags("incremental_off");
+    }
+
+    if (getNoPrecompile()) {
+      addTags("precompile_off");
+    } else {
+      addTags("precompile_on");
+    }
+
     return true;
   }
 
   /**
+   * Adds some user-defined tags that will be passed through to {@link JobEvent#getTags}.
+   *
+   * <p>A tag may not be null, contain whitespace, or be more than 100 characters.
+   * If a tag was already added, it won't be added again.
+   *
+   * <p>This method may be called more than once, but compile jobs that are already running
+   * will not have the new tags.
+   */
+  public synchronized void addTags(String... tags) {
+    this.tags.addAll(JobEvent.checkTags(Arrays.asList(tags)));
+  }
+
+  /**
    * Returns the arguments passed to {@link #parseArgs}.
    */
   ImmutableList<String> getArgs() {
@@ -114,6 +144,13 @@
   }
 
   /**
+   * Returns the tags passed to {@link #addTags}.
+   */
+  synchronized Set<String> getTags() {
+    return ImmutableSet.copyOf(tags);
+  }
+
+  /**
    * A Java application that embeds Super Dev Mode can use this hook to find out
    * when compiles start and end.
    *