new file mode 100644
--- /dev/null
+++ b/b2g/dev/config/mozconfigs/linux64/mulet_dbg
@@ -0,0 +1,14 @@
+MOZ_AUTOMATION_L10N_CHECK=0
+MOZ_AUTOMATION_UPLOAD_SYMBOLS=0
+MOZ_AUTOMATION_UPDATE_PACKAGING=0
+MOZ_AUTOMATION_SDK=0
+. "$topsrcdir/browser/config/mozconfigs/linux64/nightly"
+
+ac_add_options --enable-application=b2g/dev
+ac_add_options --enable-debug
+MOZ_DEMANGLE_SYMBOLS=1
+MOZ_DEBUG=1
+MOZ_DEBUG_SYMBOLS=1
+
+# Include Firefox OS fonts.
+MOZTTDIR=$topsrcdir/moz-tt

--- a/taskcluster/ci/legacy/tasks/branches/base_jobs.yml
+++ b/taskcluster/ci/legacy/tasks/branches/base_jobs.yml
@@ -15,16 +15,18 @@ builds:
       debug:
         task: tasks/builds/android_api_15_debug.yml
   linux64-mulet:
     platforms:
       - Mulet Linux
     types:
       opt:
         task: tasks/builds/mulet_linux.yml
+      debug:
+        task: tasks/builds/mulet_linux_dbg.yml
   linux:
     platforms:
       - Linux
     extra-builds:  # see RIDEALONG_BUILDS in `mach taskgraph`
       - linux-l10n
     types:
       opt:
         task: tasks/builds/opt_linux32.yml
@@ -288,16 +290,52 @@ tests:
   firefox-ui-functional-remote-e10s:
     allowed_build_tasks:
       tasks/builds/opt_linux64.yml:
         task: tasks/tests/fx_linux64_fxui_functional_remote_e10s_opt.yml
       tasks/builds/dbg_linux64.yml:
         task: tasks/tests/fx_linux64_fxui_functional_remote_e10s_dbg.yml
       tasks/builds/opt_linux64_pgo.yml:
         task: tasks/tests/fx_linux64_fxui_functional_remote_e10s_opt.yml
+  gaia-build:
+    allowed_build_tasks:
+      tasks/builds/mulet_linux.yml:
+        task: tasks/tests/mulet_build_test.yml
+      tasks/builds/mulet_linux_dbg.yml:
+        task: tasks/tests/mulet_build_test.yml
+  gaia-build-unit:
+    allowed_build_tasks:
+      tasks/builds/mulet_linux.yml:
+        task: tasks/tests/mulet_build_unit.yml
+      tasks/builds/mulet_linux_dbg.yml:
+        task: tasks/tests/mulet_build_unit.yml
+  gaia-js-integration:
+    allowed_build_tasks:
+      tasks/builds/mulet_linux.yml:
+        task: tasks/tests/mulet_gaia_js_integration_tests.yml
+      tasks/builds/mulet_linux_dbg.yml:
+        task: tasks/tests/mulet_gaia_js_integration_tests.yml
+  gaia-linter:
+    allowed_build_tasks:
+      tasks/builds/mulet_linux.yml:
+        task: tasks/tests/mulet_linter.yml
+      tasks/builds/mulet_linux_dbg.yml:
+        task: tasks/tests/mulet_linter.yml
+  gaia-unit:
+    allowed_build_tasks:
+      tasks/builds/mulet_linux.yml:
+        task: tasks/tests/mulet_gaia_unit.yml
+      tasks/builds/mulet_linux_dbg.yml:
+        task: tasks/tests/mulet_gaia_unit.yml
+  gaia-unit-oop:
+    allowed_build_tasks:
+      tasks/builds/mulet_linux.yml:
+        task: tasks/tests/mulet_gaia_unit_oop.yml
+      tasks/builds/mulet_linux_dbg.yml:
+        task: tasks/tests/mulet_gaia_unit_oop.yml
   gtest:
     allowed_build_tasks:
       tasks/builds/opt_linux64.yml:
         task: tasks/tests/fx_linux64_gtest_opt.yml
       tasks/builds/dbg_linux64.yml:
         task: tasks/tests/fx_linux64_gtest_dbg.yml
       tasks/builds/opt_linux64_pgo.yml:
         task: tasks/tests/fx_linux64_gtest_opt.yml
@@ -356,16 +394,18 @@ tests:
       tasks/builds/opt_linux64_pgo.yml:
         task: tasks/tests/fx_linux64_marionette_e10s_opt.yml
       tasks/builds/opt_linux64-asan.yml:
         task: tasks/tests/fx_linux64_marionette_e10s_opt.yml
   mochitest:
     allowed_build_tasks:
       tasks/builds/mulet_linux.yml:
         task: tasks/tests/mulet_mochitests.yml
+      tasks/builds/mulet_linux_dbg.yml:
+        task: tasks/tests/mulet_mochitests.yml
       tasks/builds/opt_linux64.yml:
         task: tasks/tests/fx_linux64_mochitest_plain_opt.yml
       tasks/builds/dbg_linux64.yml:
         task: tasks/tests/fx_linux64_mochitest_plain_dbg.yml
       tasks/builds/opt_linux64_pgo.yml:
         task: tasks/tests/fx_linux64_mochitest_plain_opt.yml
       tasks/builds/opt_linux64-asan.yml:
         task: tasks/tests/fx_linux64_mochitest_plain_opt.yml
@@ -548,16 +588,18 @@ tests:
       tasks/builds/opt_linux64_pgo.yml:
         task: tasks/tests/fx_linux64_mochitest_clipboard_e10s_opt.yml
       tasks/builds/opt_linux64-asan.yml:
         task: tasks/tests/fx_linux64_mochitest_clipboard_e10s_opt.yml
   reftest:
     allowed_build_tasks:
       tasks/builds/mulet_linux.yml:
         task: tasks/tests/mulet_reftests.yml
+      tasks/builds/mulet_linux_dbg.yml:
+        task: tasks/tests/mulet_reftests.yml
       tasks/builds/opt_linux64.yml:
         task: tasks/tests/fx_linux64_reftest_opt.yml
       tasks/builds/dbg_linux64.yml:
         task: tasks/tests/fx_linux64_reftest_dbg.yml
       tasks/builds/opt_linux64_pgo.yml:
         task: tasks/tests/fx_linux64_reftest_opt.yml
       tasks/builds/android_api_15.yml:
         task: tasks/tests/fx_android-api-15_reftest_opt.yml

--- a/taskcluster/ci/legacy/tasks/branches/try/job_flags.yml
+++ b/taskcluster/ci/legacy/tasks/branches/try/job_flags.yml
@@ -76,16 +76,24 @@ builds:
       opt:
         task: tasks/builds/opt_linux64_st-an.yml
   linux64-pgo:
     platforms:
       - Linux64 PGO
     types:
       opt:
         task: tasks/builds/opt_linux64_pgo.yml
+  linux64-mulet:
+    platforms:
+      - Mulet Linux
+    types:
+      opt:
+        task: tasks/builds/mulet_linux.yml
+      debug:
+        task: tasks/builds/mulet_linux_dbg.yml
   linux64-mulet-haz:
     platforms:
       - Mulet Linux
     types:
       debug:
         task: tasks/builds/mulet_haz_linux.yml
   macosx64:
     platforms:

new file mode 100644
--- /dev/null
+++ b/taskcluster/ci/legacy/tasks/builds/mulet_linux_dbg.yml
@@ -0,0 +1,60 @@
+$inherits:
+  from: 'tasks/builds/b2g_base.yml'
+  variables:
+    build_name: 'mulet'
+    build_type: 'dbg'
+task:
+  metadata:
+    name: '[TC] Mulet Linux Dbg'
+    description: Mulet Linux Dbg
+
+  workerType: mulet-debug
+
+  routes:
+    - 'index.buildbot.branches.{{project}}.linux64-mulet'
+    - 'index.buildbot.revisions.{{head_rev}}.{{project}}.linux64-mulet'
+
+  scopes:
+    - 'docker-worker:cache:level-{{level}}-{{project}}-build-mulet-dbg-linux-workspace'
+    - 'docker-worker:cache:tooltool-cache'
+    - 'docker-worker:relengapi-proxy:tooltool.download.public'
+
+  payload:
+    cache:
+      level-{{level}}-{{project}}-build-mulet-dbg-linux-workspace: '/home/worker/workspace'
+      tooltool-cache: '/home/worker/tools/tooltool-cache'
+
+    features:
+      relengAPIProxy: true
+
+    env:
+      MOZCONFIG: 'b2g/dev/config/mozconfigs/linux64/mulet_dbg'
+      TOOLTOOL_MANIFEST: 'b2g/dev/config/tooltool-manifests/linux64/releng.manifest'
+
+    maxRunTime: 3600
+
+    command:
+      - /bin/bash
+      - -c
+      - >
+        checkout-gecko workspace &&
+        cd ./workspace/gecko/testing/taskcluster/scripts/builder &&
+        buildbot_step 'Build' ./build-mulet-linux.sh $HOME/workspace
+
+  extra:
+    treeherderEnv:
+      - production
+      - staging
+    treeherder:
+      # Disable "TC" prefix...
+      groupSymbol: "?"
+      machine:
+        platform: mulet-linux64
+      collection:
+        debug: true
+    # Rather then enforcing particular conventions we require that all build
+    # tasks provide the "build" extra field to specify where the build and tests
+    # files are located.
+    locations:
+      build: 'public/build/target.tar.bz2'
+      test_packages: 'public/build/target.test_packages.json'

--- a/taskcluster/ci/legacy/tasks/tests/mulet_gaia_js_integration_tests.yml
+++ b/taskcluster/ci/legacy/tasks/tests/mulet_gaia_js_integration_tests.yml
@@ -18,17 +18,17 @@ task:
       - --application=firefox
       - {"task-reference": "--installer-url=https://queue.taskcluster.net/v1/task/<{{build_slugid}}>/artifacts/{{build_location}}"}
       - {"task-reference": "--test-packages-url=https://queue.taskcluster.net/v1/task/<{{build_slugid}}>/artifacts/{{test_packages_location}}"}
       - --total-chunk={{total_chunks}}
       - --this-chunk={{chunk}}
 
   extra:
     chunks:
-      total: 40
+      total: 10
     treeherderEnv:
       - production
       - staging
     treeherder:
       groupName: Gaia JS Integration Test
       groupSymbol: Gij
       symbol: '{{chunk}}'
       productName: b2g