--- a/devtools/client/debugger/new/src/actions/pause/commands.js
+++ b/devtools/client/debugger/new/src/actions/pause/commands.js
@@ -9,29 +9,25 @@ import {
   isPaused,
   getCurrentThread,
   getSource,
   getTopFrame
 } from "../../selectors";
 import { PROMISE } from "../utils/middleware/promise";
 import { getNextStep } from "../../workers/parser";
 import { addHiddenBreakpoint } from "../breakpoints";
-import { evaluateExpressions } from "../expressions";
 import { features } from "../../utils/prefs";
 import { recordEvent } from "../../utils/telemetry";
 
 import type { Source } from "../../types";
 import type { ThunkArgs } from "../types";
 import type { Command } from "../../reducers/types";
 
 export function selectThread(thread: string) {
-  return async ({ dispatch, getState, client }: ThunkArgs) => {
-    await dispatch({ type: "SELECT_THREAD", thread });
-    await dispatch(evaluateExpressions());
-  };
+  return { type: "SELECT_THREAD", thread };
 }
 
 /**
  * Debugger commands like stepOver, stepIn, stepUp
  *
  * @param string $0.type
  * @memberof actions/pause
  * @static

--- a/devtools/client/debugger/new/src/actions/types/index.js
+++ b/devtools/client/debugger/new/src/actions/types/index.js
@@ -59,16 +59,35 @@ type AddTabAction = {|
 type UpdateTabAction = {|
   +type: "UPDATE_TAB",
   +url: string,
   +framework?: string,
   +isOriginal?: boolean,
   +sourceId?: string
 |};
 
+type ReplayAction =
+  | {|
+      +type: "TRAVEL_TO",
+      +data: {
+        paused: {
+          why: Why,
+          scopes: Scope[],
+          frames: Frame[],
+          selectedFrameId: string,
+          loadedObjects: Object
+        },
+        expressions?: Object[]
+      },
+      +position: number
+    |}
+  | {|
+      +type: "CLEAR_HISTORY"
+    |};
+
 type NavigateAction =
   | {| +type: "CONNECT", +mainThread: MainThread, +canRewind: boolean |}
   | {| +type: "NAVIGATE", +mainThread: MainThread |};
 
 export type FocusItem = {
   thread: string,
   item: TreeNode
 };
@@ -152,9 +171,10 @@ export type Action =
   | PauseAction
   | NavigateAction
   | UIAction
   | ASTAction
   | QuickOpenAction
   | FileTextSearchAction
   | ProjectTextSearchAction
   | DebugeeAction
+  | ReplayAction
   | SourceTreeAction;

--- a/devtools/client/debugger/new/src/reducers/expressions.js
+++ b/devtools/client/debugger/new/src/reducers/expressions.js
@@ -79,32 +79,52 @@ function update(
       );
 
     case "DELETE_EXPRESSION":
       return deleteExpression(state, action.input);
 
     case "CLEAR_EXPRESSION_ERROR":
       return state.set("expressionError", false);
 
+    // respond to time travel
+    case "TRAVEL_TO":
+      return travelTo(state, action);
+
     case "AUTOCOMPLETE":
       const { matchProp, matches } = action.result;
 
       return state
         .updateIn(["autocompleteMatches", matchProp], list => matches)
         .set("currentAutocompleteInput", matchProp);
 
     case "CLEAR_AUTOCOMPLETE":
       return state
         .updateIn(["autocompleteMatches", ""], list => [])
         .set("currentAutocompleteInput", "");
   }
 
   return state;
 }
 
+function travelTo(state, action) {
+  const { expressions } = action.data;
+  if (!expressions) {
+    return state;
+  }
+  return expressions.reduce(
+    (finalState, previousState) =>
+      updateExpressionInList(finalState, previousState.input, {
+        input: previousState.input,
+        value: previousState.value,
+        updating: false
+      }),
+    state
+  );
+}
+
 function restoreExpressions() {
   const exprs = prefs.expressions;
   if (exprs.length == 0) {
     return;
   }
   return exprs;
 }
 

--- a/devtools/client/debugger/new/src/reducers/pause.js
+++ b/devtools/client/debugger/new/src/reducers/pause.js
@@ -189,16 +189,19 @@ function update(
       return updateThreadState({
         frameScopes: {
           ...threadState().frameScopes,
           generated
         }
       });
     }
 
+    case "TRAVEL_TO":
+      return updateThreadState({ ...action.data.paused });
+
     case "MAP_SCOPES": {
       const { frame, status, value } = action;
       const selectedFrameId = frame.id;
 
       const original = {
         ...threadState().frameScopes.original,
         [selectedFrameId]: {
           pending: status !== "done",