diff --git a/tools/commands-cordova.js b/tools/commands-cordova.js
index addad6edec..319faf8d92 100644
--- a/tools/commands-cordova.js
+++ b/tools/commands-cordova.js
@@ -2909,6 +2909,12 @@ main.registerCommand({
     ensureCordovaPlatforms(projectContext);
   });
 
+  // If this was the first Cordova platform, we may need to rebuild all of the
+  // local packages to add the web.cordova unibuild to the IsopackCache.
+  main.captureAndExit("=> Errors while initializing project:", function () {
+    projectContext.prepareProjectForBuild();
+  });
+
   _.each(platforms, function (platform) {
     Console.info(platform + ": added platform");
   });
@@ -2959,6 +2965,12 @@ main.registerCommand({
   var appName = path.basename(projectContext.projectDir);
   ensureCordovaProject(projectContext, appName);
   ensureCordovaPlatforms(projectContext);
+
+  // If this was the last Cordova platform, we may need to rebuild all of the
+  // local packages to remove the web.cordova unibuild from the IsopackCache.
+  main.captureAndExit("=> Errors while initializing project:", function () {
+    projectContext.prepareProjectForBuild();
+  });
 });
 
 main.registerCommand({
diff --git a/tools/commands-packages.js b/tools/commands-packages.js
index 8a6a8149b9..5d10be170f 100644
--- a/tools/commands-packages.js
+++ b/tools/commands-packages.js
@@ -221,7 +221,10 @@ main.registerCommand({
       packageMapFilename: path.join(options.packageDir, '.versions'),
       // We always want to write our '.versions' package map, overriding a
       // comparison against the value of a release file that doesn't exist.
-      alwaysWritePackageMap: true
+      alwaysWritePackageMap: true,
+      // When we publish, we should always include web.cordova unibuilds, even
+      // though this temporary directory does not have any cordova platforms
+      forceIncludeCordovaUnibuild: true
     });
   } else {
     // We're in an app; let the app be our context, but make sure we don't
@@ -229,7 +232,10 @@ main.registerCommand({
     // ensure that we can actually build the package and its tests).
     projectContext = new projectContextModule.ProjectContext({
       projectDir: options.appDir,
-      neverWriteProjectConstraintsFile: true
+      neverWriteProjectConstraintsFile: true,
+      // When we publish, we should always include web.cordova unibuilds, even
+      // if this project does not have any cordova platforms
+      forceIncludeCordovaUnibuild: true
     });
   }
 
@@ -536,7 +542,10 @@ main.registerCommand({
   // Set up the project.
   var projectContext = new projectContextModule.ProjectContext({
     projectDir: tempProjectDir,
-    explicitlyAddedLocalPackageDirs: [packageDir]
+    explicitlyAddedLocalPackageDirs: [packageDir],
+    // When we publish, we should always include web.cordova unibuilds, even
+    // though this temporary directory does not have any cordova platforms
+    forceIncludeCordovaUnibuild: true
   });
   // Just get up to initializing the catalog. We're going to mutate the
   // constraints file a bit before we prepare the build.
@@ -735,7 +744,10 @@ main.registerCommand({
     var projectContext = new projectContextModule.ProjectContext({
       projectDir: tempProjectDir,  // won't have a packages dir, that's OK
       // seriously, we only want checkout packages
-      ignorePackageDirsEnvVar: true
+      ignorePackageDirsEnvVar: true,
+      // When we publish, we should always include web.cordova unibuilds, even
+      // though this temporary directory does not have any cordova platforms
+      forceIncludeCordovaUnibuild: true
     });
 
     // Read metadata and initialize catalog.
diff --git a/tools/compiler.js b/tools/compiler.js
index c918bb0df8..ad8154c745 100644
--- a/tools/compiler.js
+++ b/tools/compiler.js
@@ -33,6 +33,7 @@ compiler.compile = function (packageSource, options) {
 
   var packageMap = options.packageMap;
   var isopackCache = options.isopackCache;
+  var includeCordovaUnibuild = options.includeCordovaUnibuild;
 
   var pluginWatchSet = packageSource.pluginWatchSet.clone();
   var plugins = {};
@@ -124,6 +125,9 @@ compiler.compile = function (packageSource, options) {
   });
 
   _.each(packageSource.architectures, function (unibuild) {
+    if (unibuild.arch === 'web.cordova' && ! includeCordovaUnibuild)
+      return;
+
     var unibuildResult = compileUnibuild({
       isopack: isopk,
       sourceArch: unibuild,
diff --git a/tools/isopack-cache.js b/tools/isopack-cache.js
index a2590969fd..f3a0d0b940 100644
--- a/tools/isopack-cache.js
+++ b/tools/isopack-cache.js
@@ -15,6 +15,12 @@ exports.IsopackCache = function (options) {
   // cacheDir may be null; in this case, we just don't ever save things to disk.
   self.cacheDir = options.cacheDir;
 
+  // This is a bit of a hack, but basically: we really don't want to spend time
+  // building web.cordova unibuilds in a project that doesn't have any Cordova
+  // platforms. (Note that we need to be careful with 'meteor publish' to still
+  // publish a web.cordova unibuild!)
+  self._includeCordovaUnibuild = !! options.includeCordovaUnibuild;
+
   // Defines the versions of packages that we build. Must be set.
   self._packageMap = options.packageMap;
 
@@ -212,7 +218,8 @@ _.extend(exports.IsopackCache.prototype, {
         var compilerResult = compiler.compile(packageInfo.packageSource, {
           packageMap: self._packageMap,
           isopackCache: self,
-          noLineNumbers: self._noLineNumbers
+          noLineNumbers: self._noLineNumbers,
+          includeCordovaUnibuild: self._includeCordovaUnibuild
         });
         // Accept the compiler's result, even if there were errors (since it at
         // least will have a useful WatchSet and will allow us to keep going and
@@ -243,6 +250,14 @@ _.extend(exports.IsopackCache.prototype, {
     // up to date!
     if (! isopackBuildInfoJson)
       return false;
+
+    // If we include Cordova but this Isopack doesn't, or via versa, then we're
+    // not up to date.
+    if (self._includeCordovaUnibuild !==
+        isopackBuildInfoJson.includeCordovaUnibuild) {
+      return false;
+    }
+
     // If any of the direct dependencies changed their version or location, we
     // aren't up to date.
     if (!self._packageMap.isSupersetOfJSON(
diff --git a/tools/isopack.js b/tools/isopack.js
index 07cf644793..2628ecf33b 100644
--- a/tools/isopack.js
+++ b/tools/isopack.js
@@ -766,7 +766,10 @@ _.extend(Isopack.prototype, {
           // our package.js (because modifications to package.js could add a new
           // plugin), as well as any files making up plugins in our package.
           pluginDependencies: self.pluginWatchSet.toJSON(),
-          pluginProviderPackageMap: options.pluginProviderPackageMap.toJSON()
+          pluginProviderPackageMap: options.pluginProviderPackageMap.toJSON(),
+          includeCordovaUnibuild: _.any(self.unibuilds, function (unibuild) {
+            return unibuild.arch === 'web.cordova';
+          })
         };
       }
 
diff --git a/tools/isopackets.js b/tools/isopackets.js
index d0172fee2d..e6c24502cc 100644
--- a/tools/isopackets.js
+++ b/tools/isopackets.js
@@ -239,6 +239,7 @@ var makeIsopacketBuildContext = function () {
   // access to versioned packages.
   context.isopackCache = new isopackCacheModule.IsopackCache({
     packageMap: context.packageMap,
+    includeCordovaUnibuild: false,
     // When linking JS files, don't include the padding spaces and line number
     // comments. Since isopackets are loaded as part of possibly very short
     // 'meteor' tool command invocations, we care more about startup time than
diff --git a/tools/project-context.js b/tools/project-context.js
index 2e10642d61..48a5197ab1 100644
--- a/tools/project-context.js
+++ b/tools/project-context.js
@@ -107,6 +107,11 @@ _.extend(exports.ProjectContext.prototype, {
     // Set when deploying to a previous Galaxy prototype.
     self._requireControlProgram = options.requireControlProgram;
 
+    // Set by publishing commands to ensure that published packages always have
+    // a web.cordova slice (because we aren't yet smart enough to just default
+    // to using the web.browser slice instead or make a common 'web' slice).
+    self._forceIncludeCordovaUnibuild = options.forceIncludeCordovaUnibuild;
+
     // If explicitly specified as null, use no release for constraints.
     // If specified non-null, should be a release version catalog record.
     // If not specified, defaults to release.current.
@@ -656,6 +661,8 @@ _.extend(exports.ProjectContext.prototype, {
 
     self.isopackCache = new isopackCacheModule.IsopackCache({
       packageMap: self.packageMap,
+      includeCordovaUnibuild: (self._forceIncludeCordovaUnibuild
+                               || self.platformList.usesCordova()),
       cacheDir: self.getProjectLocalDirectory('isopacks'),
       tropohouse: self.tropohouse,
       previousIsopackCache: self._previousIsopackCache
@@ -1039,6 +1046,11 @@ _.extend(exports.PlatformList.prototype, {
                         exports.PlatformList.DEFAULT_PLATFORMS);
   },
 
+  usesCordova: function () {
+    var self = this;
+    return ! _.isEmpty(self.getCordovaPlatforms());
+  },
+
   getWebArchs: function () {
     var self = this;
     var archs = [ "web.browser" ];
diff --git a/tools/selftest.js b/tools/selftest.js
index be90012c76..1fc587b90f 100644
--- a/tools/selftest.js
+++ b/tools/selftest.js
@@ -126,7 +126,8 @@ var setUpBuiltPackageTropohouse = function () {
   // Make an isopack cache that doesn't automatically save isopacks to disk and
   // has no access to versioned packages.
   tropohouseIsopackCache = new isopackCacheModule.IsopackCache({
-    packageMap: packageMap
+    packageMap: packageMap,
+    includeCordovaUnibuild: true
   });
   doOrThrow(function () {
     buildmessage.enterJob("building self-test packages", function () {