diff --git a/toolkit/devtools/debugger/dbg-client.jsm b/toolkit/devtools/debugger/dbg-client.jsm
index 8c5ab00308f4..0c0e219e940e 100644
--- a/toolkit/devtools/debugger/dbg-client.jsm
+++ b/toolkit/devtools/debugger/dbg-client.jsm
@@ -487,6 +487,7 @@ function ThreadClient(aClient, aActor) {
   this._frameCache = [];
   this._scriptCache = {};
   this._pauseGrips = {};
+  this._threadGrips = {};
 }
 
 ThreadClient.prototype = {
@@ -861,30 +862,74 @@ ThreadClient.prototype = {
   },
 
   /**
-   * Return an instance of LongStringClient for the given long string grip.
+   * Get or create a long string client, checking the grip client cache if it
+   * already exists.
+   *
+   * @param aGrip Object
+   *        The long string grip returned by the protocol.
+   * @param aGripCacheName String
+   *        The property name of the grip client cache to check for existing
+   *        clients in.
+   */
+  _longString: function TC__longString(aGrip, aGripCacheName) {
+    if (aGrip.actor in this[aGripCacheName]) {
+      return this[aGripCacheName][aGrip.actor];
+    }
+
+    let client = new LongStringClient(this._client, aGrip);
+    this[aGripCacheName][aGrip.actor] = client;
+    return client;
+  },
+
+  /**
+   * Return an instance of LongStringClient for the given long string grip that
+   * is scoped to the current pause.
    *
    * @param aGrip Object
    *        The long string grip returned by the protocol.
    */
-  longString: function TC_longString(aGrip) {
-    if (aGrip.actor in this._pauseGrips) {
-      return this._pauseGrips[aGrip.actor];
-    }
+  pauseLongString: function TC_pauseLongString(aGrip) {
+    return this._longString(aGrip, "_pauseGrips");
+  },
 
-    let client = new LongStringClient(this._client, aGrip);
-    this._pauseGrips[aGrip.actor] = client;
-    return client;
+  /**
+   * Return an instance of LongStringClient for the given long string grip that
+   * is scoped to the thread lifetime.
+   *
+   * @param aGrip Object
+   *        The long string grip returned by the protocol.
+   */
+  threadLongString: function TC_threadLongString(aGrip) {
+    return this._longString(aGrip, "_threadGrips");
+  },
+
+  /**
+   * Clear and invalidate all the grip clients from the given cache.
+   *
+   * @param aGripCacheName
+   *        The property name of the grip cache we want to clear.
+   */
+  _clearGripClients: function TC_clearGrips(aGripCacheName) {
+    for each (let grip in this[aGripCacheName]) {
+      grip.valid = false;
+    }
+    this[aGripCacheName] = {};
   },
 
   /**
    * Invalidate pause-lifetime grip clients and clear the list of
    * current grip clients.
    */
-  _clearPauseGrips: function TC_clearPauseGrips(aPacket) {
-    for each (let grip in this._pauseGrips) {
-      grip.valid = false;
-    }
-    this._pauseGrips = {};
+  _clearPauseGrips: function TC_clearPauseGrips() {
+    this._clearGripClients("_pauseGrips");
+  },
+
+  /**
+   * Invalidate pause-lifetime grip clients and clear the list of
+   * current grip clients.
+   */
+  _clearThreadGrips: function TC_clearPauseGrips() {
+    this._clearGripClients("_threadGrips");
   },
 
   /**
@@ -895,6 +940,7 @@ ThreadClient.prototype = {
     this._state = ThreadStateTypes[aPacket.type];
     this._clearFrames();
     this._clearPauseGrips();
+    aPacket.type === ThreadStateTypes.detached && this._clearThreadGrips();
     this._client._eventsEnabled && this.notify(aPacket.type, aPacket);
   },
 };
diff --git a/toolkit/devtools/debugger/server/dbg-script-actors.js b/toolkit/devtools/debugger/server/dbg-script-actors.js
index e8a8598c8c24..51955dd27e79 100644
--- a/toolkit/devtools/debugger/server/dbg-script-actors.js
+++ b/toolkit/devtools/debugger/server/dbg-script-actors.js
@@ -787,7 +787,7 @@ ThreadActor.prototype = {
     let type = typeof(aValue);
 
     if (type === "string" && this._stringIsLong(aValue)) {
-      return this.longStringGrip(aValue);
+      return this.longStringGrip(aValue, this._pausePool);
     }
 
     if (type === "boolean" || type === "string" || type === "number") {
@@ -881,26 +881,44 @@ ThreadActor.prototype = {
    *
    * @param aString String
    *        The string we are creating a grip for.
+   * @param aPool ActorPool
+   *        The actor pool where the new actor will be added.
    */
-  longStringGrip: function TA_longStringGrip(aString) {
-    if (!this._pausePool) {
-      throw new Error("LongString grip requested while not paused.");
+  longStringGrip: function TA_longStringGrip(aString, aPool) {
+    if (!aPool.longStringActors) {
+      aPool.longStringActors = {};
     }
 
-    if (!this._pausePool.longStringActors) {
-      this._pausePool.longStringActors = {};
-    }
-
-    if (this._pausePool.longStringActors.hasOwnProperty(aString)) {
-      return this._pausePool.longStringActors[aString].grip();
+    if (aPool.longStringActors.hasOwnProperty(aString)) {
+      return aPool.longStringActors[aString].grip();
     }
 
     let actor = new LongStringActor(aString, this);
-    this._pausePool.addActor(actor);
-    this._pausePool.longStringActors[aString] = actor;
+    aPool.addActor(actor);
+    aPool.longStringActors[aString] = actor;
     return actor.grip();
   },
 
+  /**
+   * Create a long string grip that is scoped to a pause.
+   *
+   * @param aString String
+   *        The string we are creating a grip for.
+   */
+  pauseLongStringGrip: function TA_pauseLongStringGrip (aString) {
+    return this.longStringGrip(aString, this._pausePool);
+  },
+
+  /**
+   * Create a long string grip that is scoped to a thread.
+   *
+   * @param aString String
+   *        The string we are creating a grip for.
+   */
+  threadLongStringGrip: function TA_pauseLongStringGrip (aString) {
+    return this.longStringGrip(aString, this._threadLifetimePool);
+  },
+
   /**
    * Returns true if the string is long enough to use a LongStringActor instead
    * of passing the value directly over the protocol.
diff --git a/toolkit/devtools/debugger/tests/unit/test_longstringgrips-01.js b/toolkit/devtools/debugger/tests/unit/test_longstringgrips-01.js
index bdebd8578bf1..1e93aad24e57 100644
--- a/toolkit/devtools/debugger/tests/unit/test_longstringgrips-01.js
+++ b/toolkit/devtools/debugger/tests/unit/test_longstringgrips-01.js
@@ -48,7 +48,7 @@ function test_longstring_grip()
       do_check_eq(grip.length, longString.length);
       do_check_eq(grip.initial, longString.substr(0, DebuggerServer.LONG_STRING_INITIAL_LENGTH));
 
-      let longStringClient = gThreadClient.longString(grip);
+      let longStringClient = gThreadClient.pauseLongString(grip);
       longStringClient.substring(22, 28, function (aResponse) {
         try {
           do_check_eq(aResponse.substring, "monkey");
diff --git a/toolkit/devtools/debugger/tests/unit/test_longstringgrips-02.js b/toolkit/devtools/debugger/tests/unit/test_longstringgrips-02.js
index 5c49ce059f3f..1bb7271406d6 100644
--- a/toolkit/devtools/debugger/tests/unit/test_longstringgrips-02.js
+++ b/toolkit/devtools/debugger/tests/unit/test_longstringgrips-02.js
@@ -36,7 +36,7 @@ function test_longstring_grip()
         actor: "123fakeActor123",
         initial: ""
       };
-      let longStringClient = gThreadClient.longString(fakeLongStringGrip);
+      let longStringClient = gThreadClient.pauseLongString(fakeLongStringGrip);
       longStringClient.substring(22, 28, function (aResponse) {
         try {
           do_check_true(!!aResponse.error,