diff --git a/blockly_uncompressed.js b/blockly_uncompressed.js
index b89c8d7c9..b7f60f7d9 100644
--- a/blockly_uncompressed.js
+++ b/blockly_uncompressed.js
@@ -95,8 +95,8 @@ goog.addDependency("../../../" + dir + "/core/rendered_connection.js", ['Blockly
 goog.addDependency("../../../" + dir + "/core/renderers/block_rendering_rewrite/block_render_draw.js", ['Blockly.blockRendering.Drawer'], ['Blockly.blockRendering.Debug', 'Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.TopRow']);
 goog.addDependency("../../../" + dir + "/core/renderers/block_rendering_rewrite/block_render_draw_debug.js", ['Blockly.blockRendering.Debug'], ['Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.TopRow']);
 goog.addDependency("../../../" + dir + "/core/renderers/block_rendering_rewrite/block_render_info.js", ['Blockly.blockRendering.RenderInfo'], ['Blockly.blockRendering.Measurable', 'Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.TopRow', 'Blockly.blockRendering.InlineInput', 'Blockly.blockRendering.ExternalValueInput', 'Blockly.blockRendering.StatementInput', 'Blockly.blockRendering.PreviousConnection', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.OutputConnection', 'Blockly.RenderedConnection']);
-goog.addDependency("../../../" + dir + "/core/renderers/block_rendering_rewrite/block_rendering.js", ['Blockly.blockRendering'], ['Blockly.blockRendering.Debug', 'Blockly.blockRendering.Drawer', 'Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.ConstantProvider', 'Blockly.geras.HighlightConstantProvider', 'Blockly.geras.RenderInfo', 'Blockly.geras.Drawer', 'Blockly.thrasos.RenderInfo', 'Blockly.zelos.RenderInfo']);
-goog.addDependency("../../../" + dir + "/core/renderers/block_rendering_rewrite/block_rendering_constants.js", ['Blockly.blockRendering.ConstantProvider'], ['Blockly.utils.svgPaths']);
+goog.addDependency("../../../" + dir + "/core/renderers/block_rendering_rewrite/block_rendering.js", ['Blockly.blockRendering'], ['Blockly.blockRendering.Debug', 'Blockly.blockRendering.Drawer', 'Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.ConstantProvider', 'Blockly.geras.HighlightConstantProvider', 'Blockly.geras.RenderInfo', 'Blockly.geras.Drawer', 'Blockly.thrasos.RenderInfo', 'Blockly.zelos.RenderInfo', 'Blockly.zelos.ConstantProvider']);
+goog.addDependency("../../../" + dir + "/core/renderers/block_rendering_rewrite/constants.js", ['Blockly.blockRendering.ConstantProvider'], ['Blockly.utils.svgPaths']);
 goog.addDependency("../../../" + dir + "/core/renderers/block_rendering_rewrite/measurables.js", ['Blockly.blockRendering.InRowSpacer'], ['Blockly.blockRendering.Measurable']);
 goog.addDependency("../../../" + dir + "/core/renderers/geras/drawer.js", ['Blockly.geras.Drawer'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.blockRendering.Drawer', 'Blockly.geras.Highlighter', 'Blockly.geras.RenderInfo']);
 goog.addDependency("../../../" + dir + "/core/renderers/geras/highlight_constants.js", ['Blockly.geras.HighlightConstantProvider'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.utils.svgPaths']);
@@ -107,6 +107,7 @@ goog.addDependency("../../../" + dir + "/core/renderers/measurables/connections.
 goog.addDependency("../../../" + dir + "/core/renderers/measurables/inputs.js", ['Blockly.blockRendering.InputConnection', 'Blockly.blockRendering.InlineInput', 'Blockly.blockRendering.StatementInput', 'Blockly.blockRendering.ExternalValueInput'], ['Blockly.blockRendering.Connection', 'Blockly.blockRendering.Measurable']);
 goog.addDependency("../../../" + dir + "/core/renderers/measurables/rows.js", ['Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.TopRow'], ['Blockly.blockRendering.InputConnection', 'Blockly.blockRendering.InRowSpacer', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.PreviousConnection', 'Blockly.RenderedConnection']);
 goog.addDependency("../../../" + dir + "/core/renderers/thrasos/info.js", ['Blockly.thrasos', 'Blockly.thrasos.RenderInfo'], ['Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.TopRow', 'Blockly.blockRendering.InlineInput', 'Blockly.blockRendering.ExternalValueInput', 'Blockly.blockRendering.StatementInput', 'Blockly.blockRendering.PreviousConnection', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.OutputConnection', 'Blockly.RenderedConnection']);
+goog.addDependency("../../../" + dir + "/core/renderers/zelos/constants.js", ['Blockly.zelos.ConstantProvider'], ['Blockly.blockRendering.ConstantProvider', 'Blockly.utils.svgPaths']);
 goog.addDependency("../../../" + dir + "/core/renderers/zelos/info.js", ['Blockly.zelos', 'Blockly.zelos.RenderInfo'], ['Blockly.blockRendering.RenderInfo', 'Blockly.blockRendering.Measurable', 'Blockly.blockRendering.BottomRow', 'Blockly.blockRendering.InputRow', 'Blockly.blockRendering.Row', 'Blockly.blockRendering.SpacerRow', 'Blockly.blockRendering.TopRow', 'Blockly.blockRendering.InlineInput', 'Blockly.blockRendering.ExternalValueInput', 'Blockly.blockRendering.StatementInput', 'Blockly.blockRendering.PreviousConnection', 'Blockly.blockRendering.NextConnection', 'Blockly.blockRendering.OutputConnection', 'Blockly.RenderedConnection']);
 goog.addDependency("../../../" + dir + "/core/scrollbar.js", ['Blockly.Scrollbar', 'Blockly.ScrollbarPair'], ['Blockly.Touch', 'Blockly.utils', 'Blockly.utils.Coordinate', 'Blockly.utils.dom']);
 goog.addDependency("../../../" + dir + "/core/theme.js", ['Blockly.Theme'], []);
@@ -314,6 +315,7 @@ goog.require('Blockly.utils.uiMenu');
 goog.require('Blockly.utils.userAgent');
 goog.require('Blockly.utils.xml');
 goog.require('Blockly.zelos');
+goog.require('Blockly.zelos.ConstantProvider');
 goog.require('Blockly.zelos.RenderInfo');
 
 delete root.BLOCKLY_DIR;
diff --git a/core/renderers/block_rendering_rewrite/block_rendering.js b/core/renderers/block_rendering_rewrite/block_rendering.js
index 4880cc942..41ae85a42 100644
--- a/core/renderers/block_rendering_rewrite/block_rendering.js
+++ b/core/renderers/block_rendering_rewrite/block_rendering.js
@@ -40,6 +40,7 @@ goog.require('Blockly.geras.RenderInfo');
 goog.require('Blockly.geras.Drawer');
 goog.require('Blockly.thrasos.RenderInfo');
 goog.require('Blockly.zelos.RenderInfo');
+goog.require('Blockly.zelos.ConstantProvider');
 
 // TODO (#2702): Pick an API for choosing a renderer.
 Blockly.blockRendering.rendererName = 'geras';
@@ -49,12 +50,22 @@ Blockly.blockRendering.rendererName = 'geras';
  * @package
  */
 Blockly.blockRendering.init = function() {
-  Blockly.blockRendering.constants =
+  if (Blockly.blockRendering.rendererName == 'geras') {
+    Blockly.blockRendering.constants =
       new Blockly.blockRendering.ConstantProvider();
-  // No one else has a highlight provider.  It's possible this should only be
-  // created if we're rendering with geras.
-  Blockly.blockRendering.highlightConstants =
-      new Blockly.geras.HighlightConstantProvider();
+    Blockly.blockRendering.constants.init();
+    // No one else has a highlight provider.
+    Blockly.blockRendering.highlightConstants =
+        new Blockly.geras.HighlightConstantProvider();
+  } else if (Blockly.blockRendering.rendererName == 'thrasos') {
+    Blockly.blockRendering.constants =
+      new Blockly.blockRendering.ConstantProvider();
+    Blockly.blockRendering.constants.init();
+  } else if (Blockly.blockRendering.rendererName == 'zelos') {
+    Blockly.blockRendering.constants =
+      new Blockly.zelos.ConstantProvider();
+    Blockly.blockRendering.constants.init();
+  }
 };
 
 /**
diff --git a/core/renderers/block_rendering_rewrite/block_rendering_constants.js b/core/renderers/block_rendering_rewrite/constants.js
similarity index 97%
rename from core/renderers/block_rendering_rewrite/block_rendering_constants.js
rename to core/renderers/block_rendering_rewrite/constants.js
index 760119c8c..e485f6d14 100644
--- a/core/renderers/block_rendering_rewrite/block_rendering_constants.js
+++ b/core/renderers/block_rendering_rewrite/constants.js
@@ -75,8 +75,7 @@ Blockly.blockRendering.ConstantProvider = function() {
 
   // Offset from the left side of a block or the inside of a statement input to
   // the left side of the notch.
-  this.NOTCH_OFFSET_LEFT =
-      this.NOTCH_WIDTH;
+  this.NOTCH_OFFSET_LEFT = 15;
 
   this.STATEMENT_BOTTOM_SPACER = 5;
   this.STATEMENT_INPUT_PADDING_LEFT = 20;
@@ -133,6 +132,13 @@ Blockly.blockRendering.ConstantProvider = function() {
    * @const
    */
   this.JAGGED_TEETH_WIDTH = 6;
+};
+
+/**
+ * Initialize shape objects based on the constants set in the constructor.
+ * @package
+ */
+Blockly.blockRendering.ConstantProvider.prototype.init = function() {
 
   /**
    * An object containing sizing and path information about collapsed block
diff --git a/core/renderers/zelos/constants.js b/core/renderers/zelos/constants.js
new file mode 100644
index 000000000..d4bbe214a
--- /dev/null
+++ b/core/renderers/zelos/constants.js
@@ -0,0 +1,81 @@
+/**
+ * @license
+ * Visual Blocks Editor
+ *
+ * Copyright 2019 Google Inc.
+ * https://developers.google.com/blockly/
+ *
+ * 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.
+ */
+
+/**
+ * @fileoverview Methods for graphically rendering a block as SVG.
+ * @author fenichel@google.com (Rachel Fenichel)
+ */
+'use strict';
+
+goog.provide('Blockly.zelos.ConstantProvider');
+
+goog.require('Blockly.blockRendering.ConstantProvider');
+goog.require('Blockly.utils.svgPaths');
+
+/**
+ * An object containing all sizing information needed to draw this block.
+ *
+ * This measure pass does not propagate changes to the block (although fields
+ * may choose to rerender when getSize() is called).  However, calling it
+ * repeatedly may be expensive.
+ *
+ * @constructor
+ * @package
+ * @extends {Blockly.blockRendering.ConstantProvider}
+ */
+Blockly.zelos.ConstantProvider = function() {
+  Blockly.zelos.ConstantProvider.superClass_.constructor.call(this);
+};
+goog.inherits(Blockly.zelos.ConstantProvider,
+    Blockly.blockRendering.ConstantProvider);
+
+/**
+ * @override
+ */
+Blockly.zelos.ConstantProvider.prototype.makePuzzleTab = function() {
+  // Example replacement of one connection shape with another.
+  // Eventually this will be replaced by a lookup based on connection type.
+  // For now this just makes Zelos visibly different from Thrasos.
+  return this.makeTriangle();
+};
+
+Blockly.zelos.ConstantProvider.prototype.makeTriangle = function() {
+  var width = 20;
+  var height = 20;
+  // The 'up' and 'down'  versions of the paths are the same, but the Y sign
+  // flips.  Forward and back are the signs to use to move the cursor in the
+  // direction that the path is being drawn.
+  function makeMainPath(up) {
+    var forward = up ? -1 : 1;
+
+    return Blockly.utils.svgPaths.lineTo(-width, forward * height / 2) +
+        Blockly.utils.svgPaths.lineTo(width, forward * height / 2);
+  }
+
+  var pathUp = makeMainPath(true);
+  var pathDown = makeMainPath(false);
+
+  return {
+    width: width,
+    height: height,
+    pathDown: pathDown,
+    pathUp: pathUp
+  };
+};