diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index f891d297c0a..4ce40e07992 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -55,15 +55,15 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v3
-        if: github.event_name != 'issue_comment'
+        if: github.event_name != 'issue_comment' && github.event_name != 'pull_request_target'
         with:
           fetch-depth: 2
       # This is necessary to checkout the pull request if this run was triggered
       # via an `issue_comment` action on a pull request.
       - uses: actions/checkout@v3
-        if: github.event_name == 'issue_comment'
+        if: github.event_name == 'issue_comment' || github.event_name == 'pull_request_target'
         with:
-          ref: refs/pull/${{ github.event.issue.number }}/head
+          ref: refs/pull/${{ github.event.issue.number || github.event.number }}/head
           fetch-depth: 2
       - name: Run sccache-cache
         uses: mozilla-actions/sccache-action@v0.0.3
diff --git a/.github/workflows/mac.yml b/.github/workflows/mac.yml
index dda92fdcbdd..83d820bef9e 100644
--- a/.github/workflows/mac.yml
+++ b/.github/workflows/mac.yml
@@ -48,15 +48,15 @@ jobs:
     runs-on: macos-13
     steps:
       - uses: actions/checkout@v3
-        if: github.event_name != 'issue_comment'
+        if: github.event_name != 'issue_comment' && github.event_name != 'pull_request_target'
         with:
           fetch-depth: 2
       # This is necessary to checkout the pull request if this run was triggered
       # via an `issue_comment` action on a pull request.
       - uses: actions/checkout@v3
-        if: github.event_name == 'issue_comment'
+        if: github.event_name == 'issue_comment' || github.event_name == 'pull_request_target'
         with:
-          ref: refs/pull/${{ github.event.issue.number }}/head
+          ref: refs/pull/${{ github.event.issue.number || github.event.number }}/head
           fetch-depth: 2
       - name: Run sccache-cache
         uses: mozilla-actions/sccache-action@v0.0.3
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index cedb03b4c8f..c3eb7ef78ba 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -13,21 +13,15 @@ on:
     types: [checks_requested]
   workflow_call:
     inputs:
-      platform:
+      configuration:
         required: true
         type: string
-      layout:
-        required: true
-        type: string
-      unit-tests:
-        required: true
-        type: boolean
   workflow_dispatch:
     inputs:
       platform:
         required: false
         type: choice
-        options: ["none", "linux", "windows", "macos", "all", "sync"]
+        options: ["linux", "windows", "macos", "all"]
       layout:
         required: false
         type: choice
@@ -48,6 +42,14 @@ jobs:
         uses: actions/github-script@v6
         with:
           script: |
+            // If this is a workflow call with a configuration object,
+            // then just return it immediately.
+            let configuration = ${{ inputs.configuration || '""' }};
+            if (configuration != "") {
+              console.log("Using configuration: " + JSON.stringify(configuration));
+              return configuration;
+            }
+
             // We need to pick defaults if the inputs are not provided. Unprovided inputs
             // are empty strings in this template.
             let platform = "${{ inputs.platform }}" || "linux";
@@ -61,18 +63,26 @@ jobs:
               unit_tests = true;
             }
 
+            let platforms = [];
+            if (platform == "all") {
+              platforms = [ "linux", "windows", "macos" ];
+            } else {
+              platforms = [ platform ];
+            }
+
             let returnValue =  {
-              platform,
+              platforms,
               layout,
               unit_tests,
             };
+
             console.log("Using configuration: " + JSON.stringify(returnValue));
             return returnValue;
 
   build-win:
     name: Windows
     needs: ["decision"]
-    if: ${{ contains(fromJson('["windows", "all"]'), fromJson(needs.decision.outputs.configuration).platform) }}
+    if: ${{ contains(fromJson(needs.decision.outputs.configuration).platforms, 'windows') }}
     uses: ./.github/workflows/windows.yml
     with:
       unit-tests: ${{ fromJson(needs.decision.outputs.configuration).unit_tests }}
@@ -80,7 +90,7 @@ jobs:
   build-mac:
     name: Mac
     needs: ["decision"]
-    if: ${{ contains(fromJson('["macos", "all"]'), fromJson(needs.decision.outputs.configuration).platform) }}
+    if: ${{ contains(fromJson(needs.decision.outputs.configuration).platforms, 'macos') }}
     uses: ./.github/workflows/mac.yml
     with:
       unit-tests: ${{ fromJson(needs.decision.outputs.configuration).unit_tests }}
@@ -88,7 +98,7 @@ jobs:
   build-linux:
     name: Linux
     needs: ["decision"]
-    if: ${{ contains(fromJson('["linux", "all"]'), fromJson(needs.decision.outputs.configuration).platform) }}
+    if: ${{ contains(fromJson(needs.decision.outputs.configuration).platforms, 'linux') }}
     uses: ./.github/workflows/linux.yml
     with:
       wpt: 'test'
@@ -108,7 +118,7 @@ jobs:
 
     steps:
       - name: Mark skipped jobs as successful
-        if: ${{ fromJson(needs.decision.outputs.configuration).platform == 'none' }}
+        if: ${{ fromJson(needs.decision.outputs.configuration).platforms[0] != null }}
         run: exit 0
       - name: Mark the job as successful
         if: ${{ !contains(needs.*.result, 'failure') && !contains(needs.*.result, 'cancelled') }}
diff --git a/.github/workflows/try.yml b/.github/workflows/try.yml
index 88936b8f59b..f6e40cf1b55 100644
--- a/.github/workflows/try.yml
+++ b/.github/workflows/try.yml
@@ -1,13 +1,15 @@
 name: Try
 
 on:
+  pull_request_target:
+    types: [labeled]
   issue_comment:
     types: [created]
 
 jobs:
   parse-comment:
-    name: Process Comment
-    if: ${{ github.event.issue.pull_request }}
+    name: Trigger Try (${{ github.event.name }})
+    if: ${{ github.event_name == 'pull_request_target' || github.event.issue.pull_request  }}
     runs-on: ubuntu-latest
     outputs:
       configuration: ${{ steps.configuration.outputs.result }}
@@ -26,62 +28,140 @@ jobs:
                 })
             }
 
-            let tokens = context.payload.comment.body.split(/\s+/);
-            let tagIndex = tokens.indexOf("@bors-servo");
-            if (tagIndex == -1 || tagIndex + 1 >= tokens.length) {
-              return { try: false };
+            function combineWPTLayoutOptions(layout, newLayout) {
+                let has2013 = layout == "2013" || layout == "all";
+                let has2020 = layout == "2020" || layout == "all";
+                let adding2013 = newLayout == "2013";
+                let adding2020 = newLayout == "2020";
+
+                if ((adding2020 && has2020) || (adding2013 && has2013)) {
+                  return layout;
+                }
+                if (adding2020) {
+                  return has2013 ? "all" : "2020";
+                }
+                if (adding2013) {
+                  return has2020 ? "all" : "2013";
+                }
+                return layout;
             }
 
-            let tryString = tokens[tagIndex + 1];
-            console.log("Found try string: '" + tryString + "'");
-            let returnValue = { try: false };
-            if (tryString == "try") {
-              returnValue = { try: true, platform: 'all', layout: 'all', unit_tests: true, };
-            } else if (tryString == "try=wpt") {
-              returnValue = { try: true, platform: 'linux', layout: '2013', unit_tests: false };
-            } else if (tryString == "try=wpt-2020") {
-              returnValue = { try: true, platform: 'linux', layout: '2020', unit_tests: false };
-            } else if (tryString == "try=linux") {
-              returnValue = { try: true, platform: 'linux', layout: 'none', unit_tests: true };
-            } else if (tryString == "try=mac") {
-              returnValue = { try: true, platform: 'macos', layout: 'none', unit_tests: true };
-            } else if (tryString == "try=windows") {
-              returnValue = { try: true, platform: 'windows', layout: 'none', unit_tests: true };
-            } else {
-              makeComment("🤔 Unknown try string '" + tryString + "'");
-              return returnValue;
-            }
-
-            if (returnValue.try) {
-              let username = context.payload.comment.user.login;
-              let result = await github.rest.repos.getCollaboratorPermissionLevel({
-                owner: context.repo.owner,
-                repo: context.repo.repo,
-                username
-              });
-              if (!result.data.user.permissions.push) {
-                makeComment('🔒 User @' + username + ' does not have permission to trigger try jobs.');
-                return { try: false };
+            function addPlatformToConfiguration(platform, configuration) {
+              if (!configuration.platforms.includes(platform)) {
+                configuration.platforms.push(platform);
               }
             }
 
+            function updateConfigurationFromString(tryString, configuration) {
+                if (tryString.includes("full")) {
+                  configuration.platforms = ["linux", "macos", "windows"];
+                  configuration.unit_tests = true;
+                  configuration.layout = "all";
+                  return configuration;
+                }
+
+                if (tryString.includes("linux")) {
+                  addPlatformToConfiguration("linux", configuration);
+                  configuration.unit_tests = true;
+                } else if (tryString.includes("macos")) {
+                  addPlatformToConfiguration("macos", configuration);
+                  configuration.unit_tests = true;
+                } else if (tryString.includes("win")) {
+                  addPlatformToConfiguration("windows", configuration);
+                  configuration.unit_tests = true;
+                }
+
+                if (tryString.includes("wpt")) {
+                  addPlatformToConfiguration("linux", configuration);
+                  if (tryString.includes("2020")) {
+                    configuration.layout = combineWPTLayoutOptions(configuration.layout, "2020");
+                  } else {
+                    configuration.layout = combineWPTLayoutOptions(configuration.layout, "2013");
+                  }
+                }
+            }
+
+            let configuration = {
+              platforms: [],
+              layout: "none",
+              unit_tests: false,
+            };
+
+            if (context.eventName == "pull_request_target") {
+              let try_labels = [];
+              for (const label of context.payload.pull_request.labels) {
+                if (!label.name.startsWith("T-")) {
+                  continue;
+                }
+
+                // Try to remove the label. If that fails, it's likely that another
+                // workflow has already processed it or a user has removed it.
+                try {
+                  await github.rest.issues.removeLabel({
+                    owner: context.repo.owner,
+                    repo: context.repo.repo,
+                    issue_number: context.issue.number,
+                    name: label.name,
+                  });
+                } catch (exception) {
+                  console.log("Assuming '" + label.name + "' is already removed: " + exception);
+                  continue;
+                }
+
+                console.log("Found label: " + label.name);
+                updateConfigurationFromString(label.name, configuration);
+              }
+            } else {
+              let tokens = context.payload.comment.body.split(/\s+/);
+              let tagIndex = tokens.indexOf("@bors-servo");
+              if (tagIndex == -1 || tagIndex + 1 >= tokens.length) {
+                return { platforms: [] };
+              }
+
+
+              let tryString = tokens[tagIndex + 1];
+              console.log("Found try string: '" + tryString + "'");
+              if (tryString == "try") {
+                updateConfigurationFromString("full", configuration);
+              } else {
+                updateConfigurationFromString(tryString, configuration);
+              }
+            }
+
+            console.log(JSON.stringify(configuration));
+
+            if (configuration.platforms.length == 0) {
+                return { platforms: [] };
+            }
+
+            let username = context.payload.sender.login;
+            let result = await github.rest.repos.getCollaboratorPermissionLevel({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              username
+            });
+            if (!result.data.user.permissions.push) {
+              makeComment('🔒 User @' + username + ' does not have permission to trigger try jobs.');
+              return { platforms: [] };
+            }
+
             const url = context.serverUrl +
               "/" + context.repo.owner +
               "/" + context.repo.repo +
               "/actions/runs/" + context.runId;
             const formattedURL = "[#" + context.runId + "](" + url + ")";
-            makeComment("🔨 Triggering try run (" + formattedURL + ") with platform=" + returnValue.platform + " and layout=" + returnValue.layout);
-            return returnValue;
+            let platformsString = configuration.platforms.toString();
+            makeComment("🔨 Triggering try run (" + formattedURL + ") with platforms=" +
+                        platformsString + " and layout=" + configuration.layout);
+            return configuration;
 
   run-try:
     name: Run Try
     needs: ["parse-comment"]
-    if: ${{ fromJson(needs.parse-comment.outputs.configuration).try}}
+    if: ${{ fromJson(needs.parse-comment.outputs.configuration).platforms[0] != null }}
     uses: ./.github/workflows/main.yml
     with:
-      platform: ${{ fromJson(needs.parse-comment.outputs.configuration).platform }}
-      layout: ${{ fromJson(needs.parse-comment.outputs.configuration).layout }}
-      unit-tests: ${{ fromJson(needs.parse-comment.outputs.configuration).unit_tests }}
+      configuration: ${{ needs.parse-comment.outputs.configuration }}
 
   results:
     name: Results
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index e416cde2707..0b7e31ecc03 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -43,15 +43,15 @@ jobs:
     runs-on: windows-2019
     steps:
       - uses: actions/checkout@v3
-        if: github.event_name != 'issue_comment'
+        if: github.event_name != 'issue_comment' && github.event_name != 'pull_request_target'
         with:
           fetch-depth: 2
       # This is necessary to checkout the pull request if this run was triggered
       # via an `issue_comment` action on a pull request.
       - uses: actions/checkout@v3
-        if: github.event_name == 'issue_comment'
+        if: github.event_name == 'issue_comment' || github.event_name == 'pull_request_target'
         with:
-          ref: refs/pull/${{ github.event.issue.number }}/head
+          ref: refs/pull/${{ github.event.issue.number || github.event.number }}/head
           fetch-depth: 2
       - name: ccache
         uses: hendrikmuhs/ccache-action@v1.2
diff --git a/etc/ci/report_aggregated_expected_results.py b/etc/ci/report_aggregated_expected_results.py
index f0046456c27..21c2d6b2431 100755
--- a/etc/ci/report_aggregated_expected_results.py
+++ b/etc/ci/report_aggregated_expected_results.py
@@ -173,6 +173,11 @@ def get_pr_number() -> Optional[str]:
     if "issue" in github_context["event"]:
         return str(github_context["event"]["issue"]["number"])
 
+    # If we have an 'number' in the context, this was triggered by "pull_request" or
+    # "pull_request_target" event.
+    if "number" in github_context["event"]:
+        return str(github_context["event"]["number"])
+
     return None