diff --git a/.eslintrc.json b/.eslintrc.json
index 293047dd7c..3fc7b0476e 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -98,6 +98,7 @@
         "stream_sort": false,
         "stream_list": false,
         "stream_popover": false,
+        "narrow_state": false,
         "narrow": false,
         "narrow_state": false,
         "admin_sections": false,
diff --git a/frontend_tests/node_tests/narrow.js b/frontend_tests/node_tests/narrow.js
index 7c092d6b3a..d95cdec147 100644
--- a/frontend_tests/node_tests/narrow.js
+++ b/frontend_tests/node_tests/narrow.js
@@ -3,12 +3,16 @@ global.stub_out_jquery();
 add_dependencies({
     hash_util: 'js/hash_util.js',
     hashchange: 'js/hashchange.js',
+    narrow_state: 'js/narrow_state.js',
     people: 'js/people.js',
     stream_data: 'js/stream_data.js',
     Filter: 'js/filter.js',
 });
 
 var narrow = require('js/narrow.js');
+
+var narrow_state = global.narrow_state;
+
 var Filter = global.Filter;
 var stream_data = global.stream_data;
 var _ = global._;
@@ -17,68 +21,68 @@ function set_filter(operators) {
     operators = _.map(operators, function (op) {
         return {operator: op[0], operand: op[1]};
     });
-    narrow._set_current_filter(new Filter(operators));
+    narrow_state.set_current_filter(new Filter(operators));
 }
 
 (function test_stream() {
     var test_stream = {name: 'Test', stream_id: 15};
     stream_data.add_sub('Test', test_stream);
 
-    assert(!narrow.is_for_stream_id(test_stream.stream_id));
+    assert(!narrow_state.is_for_stream_id(test_stream.stream_id));
 
     set_filter([['stream', 'Test'], ['topic', 'Bar'], ['search', 'yo']]);
 
-    assert.equal(narrow.stream(), 'Test');
-    assert.equal(narrow.topic(), 'Bar');
-    assert(narrow.is_for_stream_id(test_stream.stream_id));
+    assert.equal(narrow_state.stream(), 'Test');
+    assert.equal(narrow_state.topic(), 'Bar');
+    assert(narrow_state.is_for_stream_id(test_stream.stream_id));
 }());
 
 
 (function test_narrowed() {
-    narrow._set_current_filter(undefined); // not narrowed, basically
-    assert(!narrow.narrowed_to_pms());
-    assert(!narrow.narrowed_by_reply());
-    assert(!narrow.narrowed_by_pm_reply());
-    assert(!narrow.narrowed_by_topic_reply());
-    assert(!narrow.narrowed_to_search());
-    assert(!narrow.narrowed_to_topic());
+    narrow_state.reset_current_filter(); // not narrowed, basically
+    assert(!narrow_state.narrowed_to_pms());
+    assert(!narrow_state.narrowed_by_reply());
+    assert(!narrow_state.narrowed_by_pm_reply());
+    assert(!narrow_state.narrowed_by_topic_reply());
+    assert(!narrow_state.narrowed_to_search());
+    assert(!narrow_state.narrowed_to_topic());
 
     set_filter([['stream', 'Foo']]);
-    assert(!narrow.narrowed_to_pms());
-    assert(!narrow.narrowed_by_reply());
-    assert(!narrow.narrowed_by_pm_reply());
-    assert(!narrow.narrowed_by_topic_reply());
-    assert(!narrow.narrowed_to_search());
-    assert(!narrow.narrowed_to_topic());
+    assert(!narrow_state.narrowed_to_pms());
+    assert(!narrow_state.narrowed_by_reply());
+    assert(!narrow_state.narrowed_by_pm_reply());
+    assert(!narrow_state.narrowed_by_topic_reply());
+    assert(!narrow_state.narrowed_to_search());
+    assert(!narrow_state.narrowed_to_topic());
 
     set_filter([['pm-with', 'steve@zulip.com']]);
-    assert(narrow.narrowed_to_pms());
-    assert(narrow.narrowed_by_reply());
-    assert(narrow.narrowed_by_pm_reply());
-    assert(!narrow.narrowed_by_topic_reply());
-    assert(!narrow.narrowed_to_search());
-    assert(!narrow.narrowed_to_topic());
+    assert(narrow_state.narrowed_to_pms());
+    assert(narrow_state.narrowed_by_reply());
+    assert(narrow_state.narrowed_by_pm_reply());
+    assert(!narrow_state.narrowed_by_topic_reply());
+    assert(!narrow_state.narrowed_to_search());
+    assert(!narrow_state.narrowed_to_topic());
 
     set_filter([['stream', 'Foo'], ['topic', 'bar']]);
-    assert(!narrow.narrowed_to_pms());
-    assert(narrow.narrowed_by_reply());
-    assert(!narrow.narrowed_by_pm_reply());
-    assert(narrow.narrowed_by_topic_reply());
-    assert(!narrow.narrowed_to_search());
-    assert(narrow.narrowed_to_topic());
+    assert(!narrow_state.narrowed_to_pms());
+    assert(narrow_state.narrowed_by_reply());
+    assert(!narrow_state.narrowed_by_pm_reply());
+    assert(narrow_state.narrowed_by_topic_reply());
+    assert(!narrow_state.narrowed_to_search());
+    assert(narrow_state.narrowed_to_topic());
 
     set_filter([['search', 'grail']]);
-    assert(!narrow.narrowed_to_pms());
-    assert(!narrow.narrowed_by_reply());
-    assert(!narrow.narrowed_by_pm_reply());
-    assert(!narrow.narrowed_by_topic_reply());
-    assert(narrow.narrowed_to_search());
-    assert(!narrow.narrowed_to_topic());
+    assert(!narrow_state.narrowed_to_pms());
+    assert(!narrow_state.narrowed_by_reply());
+    assert(!narrow_state.narrowed_by_pm_reply());
+    assert(!narrow_state.narrowed_by_topic_reply());
+    assert(narrow_state.narrowed_to_search());
+    assert(!narrow_state.narrowed_to_topic());
 }());
 
 (function test_operators() {
     set_filter([['stream', 'Foo'], ['topic', 'Bar'], ['search', 'Yo']]);
-    var result = narrow.operators();
+    var result = narrow_state.operators();
     assert.equal(result.length, 3);
     assert.equal(result[0].operator, 'stream');
     assert.equal(result[0].operand, 'Foo');
@@ -123,19 +127,19 @@ function set_filter(operators) {
 
 (function test_muting_enabled() {
     set_filter([['stream', 'devel']]);
-    assert(narrow.muting_enabled());
+    assert(narrow_state.muting_enabled());
 
-    narrow._set_current_filter(undefined); // not narrowed, basically
-    assert(narrow.muting_enabled());
+    narrow_state.reset_current_filter(); // not narrowed, basically
+    assert(narrow_state.muting_enabled());
 
     set_filter([['stream', 'devel'], ['topic', 'mac']]);
-    assert(!narrow.muting_enabled());
+    assert(!narrow_state.muting_enabled());
 
     set_filter([['search', 'whatever']]);
-    assert(!narrow.muting_enabled());
+    assert(!narrow_state.muting_enabled());
 
     set_filter([['is', 'private']]);
-    assert(!narrow.muting_enabled());
+    assert(!narrow_state.muting_enabled());
 
 }());
 
@@ -143,7 +147,7 @@ function set_filter(operators) {
     set_filter([['stream', 'Foo'], ['topic', 'Bar']]);
 
     var opts = {};
-    narrow.set_compose_defaults(opts);
+    narrow_state.set_compose_defaults(opts);
     assert.equal(opts.stream, 'Foo');
     assert.equal(opts.subject, 'Bar');
 
@@ -151,7 +155,7 @@ function set_filter(operators) {
     set_filter([['stream', 'rome']]);
 
     opts = {};
-    narrow.set_compose_defaults(opts);
+    narrow_state.set_compose_defaults(opts);
     assert.equal(opts.stream, 'ROME');
 }());
 
@@ -191,7 +195,7 @@ function set_filter(operators) {
       return {hide: function () {hide_id = id;}, show: function () {show_id = id;}};
     };
 
-    narrow._set_current_filter(undefined);
+    narrow_state.reset_current_filter();
     narrow.show_empty_narrow_message();
     assert.equal(hide_id,'.empty_feed_notice');
     assert.equal(show_id, '#empty_narrow_message');
@@ -262,8 +266,8 @@ function set_filter(operators) {
         ['sender', 'steve@foo.com'],
         ['stream', 'steve@foo.com'], // try to be tricky
     ]);
-    narrow.update_email(steve.user_id, 'showell@foo.com');
-    var filter = narrow.filter();
+    narrow_state.update_email(steve.user_id, 'showell@foo.com');
+    var filter = narrow_state.filter();
     assert.deepEqual(filter.operands('pm-with'), ['showell@foo.com']);
     assert.deepEqual(filter.operands('sender'), ['showell@foo.com']);
     assert.deepEqual(filter.operands('stream'), ['steve@foo.com']);
diff --git a/frontend_tests/node_tests/search_suggestion.js b/frontend_tests/node_tests/search_suggestion.js
index 065436445e..ada2ad3773 100644
--- a/frontend_tests/node_tests/search_suggestion.js
+++ b/frontend_tests/node_tests/search_suggestion.js
@@ -14,7 +14,7 @@ add_dependencies({
     typeahead_helper: 'js/typeahead_helper.js',
     people: 'js/people.js',
     stream_data: 'js/stream_data.js',
-    narrow: 'js/narrow.js',
+    narrow_state: 'js/narrow_state.js',
 });
 
 var people = global.people;
@@ -46,7 +46,7 @@ global.stream_data.populate_stream_topics_for_tests({});
         return [];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return 'office';
     };
 
@@ -65,7 +65,7 @@ global.stream_data.populate_stream_topics_for_tests({});
         return [];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return undefined;
     };
 
@@ -85,7 +85,7 @@ global.stream_data.populate_stream_topics_for_tests({});
         return [];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return undefined;
     };
 
@@ -220,7 +220,7 @@ global.stream_data.populate_stream_topics_for_tests({});
         return [];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return undefined;
     };
 
@@ -332,7 +332,7 @@ init();
         return ['devel', 'office'];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return undefined;
     };
 
@@ -369,7 +369,7 @@ init();
         return [];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return undefined;
     };
 
@@ -428,7 +428,7 @@ init();
         return ['office'];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return 'office';
     };
 
@@ -496,7 +496,7 @@ init();
         return ['office'];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return;
     };
 
@@ -518,7 +518,7 @@ init();
         return ['office'];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return;
     };
 
@@ -541,7 +541,7 @@ init();
         return [];
     };
 
-    global.narrow.stream = function () {
+    global.narrow_state.stream = function () {
         return;
     };
 
diff --git a/frontend_tests/node_tests/unread.js b/frontend_tests/node_tests/unread.js
index bd93001b73..49815612f2 100644
--- a/frontend_tests/node_tests/unread.js
+++ b/frontend_tests/node_tests/unread.js
@@ -1,6 +1,6 @@
 // Unit test the unread.js module, which depends on these global variables:
 //
-//   _, narrow, current_msg_list, home_msg_list, subs
+//   _, narrow_state, current_msg_list, home_msg_list, subs
 //
 // These tests are framework-free and run sequentially; they are invoked
 // immediately after being defined.  The contract here is that tests should
@@ -29,8 +29,8 @@ var people = global.people;
 
 var unread = require('js/unread.js');
 
-var narrow = {};
-global.narrow = narrow;
+var narrow_state = {};
+global.narrow_state = narrow_state;
 
 var current_msg_list = {};
 global.current_msg_list = current_msg_list;
@@ -57,7 +57,7 @@ var zero_counts = {
 };
 
 (function test_empty_counts_while_narrowed() {
-    narrow.active = function () {
+    narrow_state.active = function () {
         return true;
     };
     current_msg_list.all_messages = function () {
@@ -69,7 +69,7 @@ var zero_counts = {
 }());
 
 (function test_empty_counts_while_home() {
-    narrow.active = function () {
+    narrow_state.active = function () {
         return false;
     };
     current_msg_list.all_messages = function () {
@@ -219,7 +219,7 @@ var zero_counts = {
 
 
 (function test_home_messages() {
-    narrow.active = function () {
+    narrow_state.active = function () {
         return false;
     };
     stream_data.is_subscribed = function () {
@@ -279,7 +279,7 @@ var zero_counts = {
 }());
 
 (function test_private_messages() {
-    narrow.active = function () {
+    narrow_state.active = function () {
         return false;
     };
     stream_data.is_subscribed = function () {
@@ -351,7 +351,7 @@ var zero_counts = {
 
 
 (function test_mentions() {
-    narrow.active = function () {
+    narrow_state.active = function () {
         return false;
     };
     stream_data.is_subscribed = function () {
diff --git a/static/js/compose_actions.js b/static/js/compose_actions.js
index a8d22219c7..e0f156ac40 100644
--- a/static/js/compose_actions.js
+++ b/static/js/compose_actions.js
@@ -304,7 +304,7 @@ exports.on_topic_narrow = function () {
         return;
     }
 
-    if (compose_state.stream_name() !== narrow.stream()) {
+    if (compose_state.stream_name() !== narrow_state.stream()) {
         // If we changed streams, then we only leave the
         // compose box open if there is content.
         if (compose_state.has_message_content()) {
@@ -333,12 +333,12 @@ exports.on_topic_narrow = function () {
     // stream filled in, and we just need to update the topic.
     // See #3300 for context--a couple users specifically asked
     // for this convenience.
-    compose_state.subject(narrow.topic());
+    compose_state.subject(narrow_state.topic());
     $('#new_message_content').focus().select();
 };
 
 exports.on_narrow = function () {
-    if (narrow.narrowed_by_topic_reply()) {
+    if (narrow_state.narrowed_by_topic_reply()) {
         exports.on_topic_narrow();
         return;
     }
@@ -348,7 +348,7 @@ exports.on_narrow = function () {
         return;
     }
 
-    if (narrow.narrowed_by_pm_reply()) {
+    if (narrow_state.narrowed_by_pm_reply()) {
         exports.start('private');
         return;
     }
diff --git a/static/js/echo.js b/static/js/echo.js
index d8919fe654..8f04fb6cf5 100644
--- a/static/js/echo.js
+++ b/static/js/echo.js
@@ -211,7 +211,7 @@ exports.try_deliver_locally = function try_deliver_locally(message_request) {
         return undefined;
     }
 
-    if (narrow.active() && !narrow.filter().can_apply_locally()) {
+    if (narrow_state.active() && !narrow_state.filter().can_apply_locally()) {
         return undefined;
     }
 
diff --git a/static/js/message_events.js b/static/js/message_events.js
index 2240b396b9..0a25340332 100644
--- a/static/js/message_events.js
+++ b/static/js/message_events.js
@@ -12,7 +12,7 @@ function maybe_add_narrowed_messages(messages, msg_list, messages_are_new, local
         url:      '/json/messages_in_narrow',
         idempotent: true,
         data:     {msg_ids: JSON.stringify(ids),
-                   narrow:  JSON.stringify(narrow.public_operators())},
+                   narrow:  JSON.stringify(narrow_state.public_operators())},
         timeout:  5000,
         success: function (data) {
             if (msg_list !== current_msg_list) {
@@ -63,8 +63,8 @@ exports.insert_new_messages = function insert_new_messages(messages, local_id) {
     message_util.add_messages(messages, home_msg_list, {messages_are_new: true});
     message_util.add_messages(messages, message_list.all, {messages_are_new: true});
 
-    if (narrow.active()) {
-        if (narrow.filter().can_apply_locally()) {
+    if (narrow_state.active()) {
+        if (narrow_state.filter().can_apply_locally()) {
             message_util.add_messages(messages, message_list.narrowed, {messages_are_new: true});
             notifications.possibly_notify_new_messages_outside_viewport(messages, local_id);
         } else {
@@ -78,7 +78,7 @@ exports.insert_new_messages = function insert_new_messages(messages, local_id) {
     activity.process_loaded_messages(messages);
     message_util.do_unread_count_updates(messages);
 
-    if (narrow.narrowed_by_reply()) {
+    if (narrow_state.narrowed_by_reply()) {
         // If you send a message when narrowed to a recipient, move the
         // pointer to it.
 
@@ -159,7 +159,7 @@ exports.update_messages = function update_messages(events) {
                 var selection_changed_topic = _.indexOf(event.message_ids, current_id) >= 0;
 
                 if (selection_changed_topic) {
-                    var current_filter = narrow.filter();
+                    var current_filter = narrow_state.filter();
                     if (current_filter && stream_name) {
                         if (current_filter.has_topic(stream_name, event.orig_subject)) {
                             var new_filter = current_filter.filter_with_new_topic(event.subject);
diff --git a/static/js/message_fetch.js b/static/js/message_fetch.js
index e9c5d265da..2ac22bffbe 100644
--- a/static/js/message_fetch.js
+++ b/static/js/message_fetch.js
@@ -82,8 +82,8 @@ exports.load_old_messages = function load_old_messages(opts) {
                 num_before: opts.num_before,
                 num_after: opts.num_after};
 
-    if (opts.msg_list.narrowed && narrow.active()) {
-        var operators = narrow.public_operators();
+    if (opts.msg_list.narrowed && narrow_state.active()) {
+        var operators = narrow_state.public_operators();
         if (page_params.narrow !== undefined) {
             operators = operators.concat(page_params.narrow);
         }
diff --git a/static/js/message_list.js b/static/js/message_list.js
index b3540d6d79..dd27b34180 100644
--- a/static/js/message_list.js
+++ b/static/js/message_list.js
@@ -362,7 +362,7 @@ exports.MessageList.prototype = {
         if (!this.narrowed) {
             return;
         }
-        var stream = narrow.stream();
+        var stream = narrow_state.stream();
         if (stream === undefined) {
             return;
         }
diff --git a/static/js/message_list_view.js b/static/js/message_list_view.js
index 8a083e6162..149f185bab 100644
--- a/static/js/message_list_view.js
+++ b/static/js/message_list_view.js
@@ -577,7 +577,7 @@ MessageListView.prototype = {
                 _.last(last_message_group.message_containers).msg.historical;
         }
 
-        var stream_name = narrow.stream();
+        var stream_name = narrow_state.stream();
         if (stream_name !== undefined) {
             // If user narrows to a stream, doesn't update
             // trailing bookend if user is subscribed.
diff --git a/static/js/narrow.js b/static/js/narrow.js
index 183aa2deea..3615c1d3fe 100644
--- a/static/js/narrow.js
+++ b/static/js/narrow.js
@@ -2,139 +2,8 @@ var narrow = (function () {
 
 var exports = {};
 
-var current_filter;
 var unnarrow_times;
 
-// A small concession to unit testing follows:
-exports._set_current_filter = function (filter) {
-    current_filter = filter;
-};
-
-exports.active = function () {
-    return current_filter !== undefined;
-};
-
-exports.filter = function () {
-    return current_filter;
-};
-
-exports.predicate = function () {
-    if (current_filter === undefined) {
-        return function () { return true; };
-    }
-    return current_filter.predicate();
-};
-
-exports.operators = function () {
-    if (current_filter === undefined) {
-        return new Filter(page_params.narrow).operators();
-    }
-    return current_filter.operators();
-};
-
-exports.update_email = function (user_id, new_email) {
-    if (current_filter !== undefined) {
-        current_filter.update_email(user_id, new_email);
-    }
-};
-
-
-/* Operators we should send to the server. */
-exports.public_operators = function () {
-    if (current_filter === undefined) {
-        return undefined;
-    }
-    return current_filter.public_operators();
-};
-
-exports.search_string = function () {
-    return Filter.unparse(exports.operators());
-};
-
-// Collect operators which appear only once into an object,
-// and discard those which appear more than once.
-function collect_single(operators) {
-    var seen   = new Dict();
-    var result = new Dict();
-    _.each(operators, function (elem) {
-        var key = elem.operator;
-        if (seen.has(key)) {
-            result.del(key);
-        } else {
-            result.set(key, elem.operand);
-            seen.set(key, true);
-        }
-    });
-    return result;
-}
-
-// Modify default compose parameters (stream etc.) based on
-// the current narrowed view.
-//
-// This logic is here and not in the 'compose' module because
-// it will get more complicated as we add things to the narrow
-// operator language.
-exports.set_compose_defaults = function (opts) {
-    var single = collect_single(exports.operators());
-
-    // Set the stream, subject, and/or PM recipient if they are
-    // uniquely specified in the narrow view.
-
-    if (single.has('stream')) {
-        opts.stream = stream_data.get_name(single.get('stream'));
-    }
-
-    if (single.has('topic')) {
-        opts.subject = single.get('topic');
-    }
-
-    if (single.has('pm-with')) {
-        opts.private_message_recipient = single.get('pm-with');
-    }
-};
-
-exports.stream = function () {
-    if (current_filter === undefined) {
-        return undefined;
-    }
-    var stream_operands = current_filter.operands("stream");
-    if (stream_operands.length === 1) {
-        return stream_operands[0];
-    }
-    return undefined;
-};
-
-exports.is_for_stream_id = function (stream_id) {
-    // This is not perfect, since we still track narrows by
-    // name, not id, but at least the interface is good going
-    // forward.
-    var sub = stream_data.get_sub_by_id(stream_id);
-
-    if (sub === undefined) {
-        blueslip.error('Bad stream id ' + stream_id);
-        return false;
-    }
-
-    var narrow_stream_name = exports.stream();
-
-    if (narrow_stream_name === undefined) {
-        return false;
-    }
-
-    return (sub.name === narrow_stream_name);
-};
-
-exports.topic = function () {
-    if (current_filter === undefined) {
-        return undefined;
-    }
-    var operands = current_filter.operands("topic");
-    if (operands.length === 1) {
-        return operands[0];
-    }
-    return undefined;
-};
-
 function report_narrow_time(initial_core_time, initial_free_time, network_time) {
     channel.post({
         url: '/json/report_narrow_time',
@@ -178,7 +47,7 @@ function report_unnarrow_time() {
 exports.narrow_title = "home";
 exports.activate = function (raw_operators, opts) {
     var start_time = new Date();
-    var was_narrowed_already = exports.active();
+    var was_narrowed_already = narrow_state.active();
     // most users aren't going to send a bunch of a out-of-narrow messages
     // and expect to visit a list of narrows, so let's get these out of the way.
     notifications.clear_compose_notifications();
@@ -248,8 +117,8 @@ exports.activate = function (raw_operators, opts) {
 
     // For legacy reasons, we need to set current_filter before calling
     // muting_enabled.
-    current_filter = filter;
-    var muting_enabled = exports.muting_enabled();
+    narrow_state.set_current_filter(filter);
+    var muting_enabled = narrow_state.muting_enabled();
 
     // Save how far from the pointer the top of the message list was.
     if (current_msg_list.selected_id() !== -1) {
@@ -274,10 +143,17 @@ exports.activate = function (raw_operators, opts) {
         home_msg_list.pre_narrow_offset = page_params.initial_offset;
     }
 
-    var msg_list = new message_list.MessageList('zfilt', current_filter, {
-        collapse_messages: ! current_filter.is_search(),
+    var msg_list_opts = {
+        collapse_messages: ! narrow_state.get_current_filter().is_search(),
         muting_enabled: muting_enabled,
-    });
+    };
+
+    var msg_list = new message_list.MessageList(
+        'zfilt',
+        narrow_state.get_current_filter(),
+        msg_list_opts
+    );
+
     msg_list.start_time = start_time;
 
     // Show the new set of messages.  It is important to set current_msg_list to
@@ -326,9 +202,11 @@ exports.activate = function (raw_operators, opts) {
     // Don't bother populating a message list when it won't contain
     // the message we want anyway or if the filter can't be applied
     // locally.
-    if (message_list.all.get(then_select_id) !== undefined && current_filter.can_apply_locally()) {
-        message_util.add_messages(message_list.all.all_messages(), message_list.narrowed,
-                                   {delay_render: true});
+    if (message_list.all.get(then_select_id) !== undefined) {
+        if (narrow_state.get_current_filter().can_apply_locally()) {
+            message_util.add_messages(message_list.all.all_messages(), message_list.narrowed,
+                                       {delay_render: true});
+        }
     }
 
     var defer_selecting_closest = message_list.narrowed.empty();
@@ -369,6 +247,7 @@ exports.activate = function (raw_operators, opts) {
 
     compose_actions.on_narrow();
 
+    var current_filter = narrow_state.get_current_filter();
     $(document).trigger($.Event('narrow_activated.zulip', {msg_list: message_list.narrowed,
                                                             filter: current_filter,
                                                             trigger: opts.trigger}));
@@ -395,8 +274,8 @@ exports.stream_topic = function () {
     // We may be in an empty narrow.  In that case we use
     // our narrow parameters to return the stream/topic.
     return {
-        stream: exports.stream(),
-        topic: exports.topic(),
+        stream: narrow_state.stream(),
+        topic: narrow_state.topic(),
     };
 };
 
@@ -491,7 +370,7 @@ exports.by_conversation_and_time = function (target_id, opts) {
 };
 
 exports.deactivate = function () {
-    if (current_filter === undefined) {
+    if (narrow_state.get_current_filter() === undefined) {
         return;
     }
     unnarrow_times = {start_time: new Date()};
@@ -509,7 +388,7 @@ exports.deactivate = function () {
         compose_actions.cancel();
     }
 
-    current_filter = undefined;
+    narrow_state.reset_current_filter();
 
     exports.hide_empty_narrow_message();
 
@@ -590,6 +469,9 @@ exports.restore_home_state = function () {
 
 function pick_empty_narrow_banner() {
     var default_banner = $('#empty_narrow_message');
+
+    var current_filter = narrow_state.get_current_filter();
+
     if (current_filter === undefined) {
         return default_banner;
     }
@@ -614,7 +496,7 @@ function pick_empty_narrow_banner() {
         }
     } else if ((first_operator === "stream") && !stream_data.is_subscribed(first_operand)) {
         // You are narrowed to a stream to which you aren't subscribed.
-        if (!stream_data.get_sub(narrow.stream())) {
+        if (!stream_data.get_sub(narrow_state.stream())) {
             return $("#nonsubbed_private_nonexistent_stream_narrow_message");
         }
         return $("#nonsubbed_stream_narrow_message");
@@ -692,58 +574,6 @@ exports.by_conversation_and_time_uri = function (message) {
         "/near/" + hash_util.encodeHashComponent(message.id);
 };
 
-// Are we narrowed to PMs: all PMs or PMs with particular people.
-exports.narrowed_to_pms = function () {
-    if (current_filter === undefined) {
-        return false;
-    }
-    return (current_filter.has_operator("pm-with") ||
-            current_filter.has_operand("is", "private"));
-};
-
-// We auto-reply under certain conditions, namely when you're narrowed
-// to a PM (or huddle), and when you're narrowed to some stream/subject pair
-exports.narrowed_by_reply = function () {
-    return (exports.narrowed_by_pm_reply() ||
-            exports.narrowed_by_topic_reply());
-};
-
-exports.narrowed_by_pm_reply = function () {
-    if (current_filter === undefined) {
-        return false;
-    }
-    var operators = current_filter.operators();
-    return (operators.length === 1 &&
-            current_filter.has_operator('pm-with'));
-};
-
-exports.narrowed_by_topic_reply = function () {
-    if (current_filter === undefined) {
-        return false;
-    }
-    var operators = current_filter.operators();
-    return (operators.length === 2 &&
-            current_filter.operands("stream").length === 1 &&
-            current_filter.operands("topic").length === 1);
-};
-
-exports.narrowed_to_topic = function () {
-    if (current_filter === undefined) {
-        return false;
-    }
-    return (current_filter.has_operator("stream") &&
-            current_filter.has_operator("topic"));
-};
-
-exports.narrowed_to_search = function () {
-    return (current_filter !== undefined) && current_filter.is_search();
-};
-
-exports.muting_enabled = function () {
-    return (!exports.narrowed_to_topic() && !exports.narrowed_to_search() &&
-            !exports.narrowed_to_pms());
-};
-
 return exports;
 
 }());
diff --git a/static/js/narrow_state.js b/static/js/narrow_state.js
new file mode 100644
index 0000000000..1538dddb91
--- /dev/null
+++ b/static/js/narrow_state.js
@@ -0,0 +1,194 @@
+var narrow_state = (function () {
+
+var exports = {};
+
+var current_filter;
+
+exports.reset_current_filter = function () {
+    current_filter = undefined;
+};
+
+exports.set_current_filter = function (filter) {
+    current_filter = filter;
+};
+
+exports.get_current_filter = function () {
+    return current_filter;
+};
+
+exports.active = function () {
+    return current_filter !== undefined;
+};
+
+exports.filter = function () {
+    return current_filter;
+};
+
+exports.operators = function () {
+    if (current_filter === undefined) {
+        return new Filter(page_params.narrow).operators();
+    }
+    return current_filter.operators();
+};
+
+exports.update_email = function (user_id, new_email) {
+    if (current_filter !== undefined) {
+        current_filter.update_email(user_id, new_email);
+    }
+};
+
+
+/* Operators we should send to the server. */
+exports.public_operators = function () {
+    if (current_filter === undefined) {
+        return undefined;
+    }
+    return current_filter.public_operators();
+};
+
+exports.search_string = function () {
+    return Filter.unparse(exports.operators());
+};
+
+// Collect operators which appear only once into an object,
+// and discard those which appear more than once.
+function collect_single(operators) {
+    var seen   = new Dict();
+    var result = new Dict();
+    _.each(operators, function (elem) {
+        var key = elem.operator;
+        if (seen.has(key)) {
+            result.del(key);
+        } else {
+            result.set(key, elem.operand);
+            seen.set(key, true);
+        }
+    });
+    return result;
+}
+
+// Modify default compose parameters (stream etc.) based on
+// the current narrowed view.
+//
+// This logic is here and not in the 'compose' module because
+// it will get more complicated as we add things to the narrow
+// operator language.
+exports.set_compose_defaults = function (opts) {
+    var single = collect_single(exports.operators());
+
+    // Set the stream, subject, and/or PM recipient if they are
+    // uniquely specified in the narrow view.
+
+    if (single.has('stream')) {
+        opts.stream = stream_data.get_name(single.get('stream'));
+    }
+
+    if (single.has('topic')) {
+        opts.subject = single.get('topic');
+    }
+
+    if (single.has('pm-with')) {
+        opts.private_message_recipient = single.get('pm-with');
+    }
+};
+
+exports.stream = function () {
+    if (current_filter === undefined) {
+        return undefined;
+    }
+    var stream_operands = current_filter.operands("stream");
+    if (stream_operands.length === 1) {
+        return stream_operands[0];
+    }
+    return undefined;
+};
+
+exports.topic = function () {
+    if (current_filter === undefined) {
+        return undefined;
+    }
+    var operands = current_filter.operands("topic");
+    if (operands.length === 1) {
+        return operands[0];
+    }
+    return undefined;
+};
+
+// Are we narrowed to PMs: all PMs or PMs with particular people.
+exports.narrowed_to_pms = function () {
+    if (current_filter === undefined) {
+        return false;
+    }
+    return (current_filter.has_operator("pm-with") ||
+            current_filter.has_operand("is", "private"));
+};
+
+exports.narrowed_by_pm_reply = function () {
+    if (current_filter === undefined) {
+        return false;
+    }
+    var operators = current_filter.operators();
+    return (operators.length === 1 &&
+            current_filter.has_operator('pm-with'));
+};
+
+exports.narrowed_by_topic_reply = function () {
+    if (current_filter === undefined) {
+        return false;
+    }
+    var operators = current_filter.operators();
+    return (operators.length === 2 &&
+            current_filter.operands("stream").length === 1 &&
+            current_filter.operands("topic").length === 1);
+};
+
+// We auto-reply under certain conditions, namely when you're narrowed
+// to a PM (or huddle), and when you're narrowed to some stream/subject pair
+exports.narrowed_by_reply = function () {
+    return (exports.narrowed_by_pm_reply() ||
+            exports.narrowed_by_topic_reply());
+};
+
+exports.narrowed_to_topic = function () {
+    if (current_filter === undefined) {
+        return false;
+    }
+    return (current_filter.has_operator("stream") &&
+            current_filter.has_operator("topic"));
+};
+
+exports.narrowed_to_search = function () {
+    return (current_filter !== undefined) && current_filter.is_search();
+};
+
+exports.muting_enabled = function () {
+    return (!exports.narrowed_to_topic() && !exports.narrowed_to_search() &&
+            !exports.narrowed_to_pms());
+};
+
+exports.is_for_stream_id = function (stream_id) {
+    // This is not perfect, since we still track narrows by
+    // name, not id, but at least the interface is good going
+    // forward.
+    var sub = stream_data.get_sub_by_id(stream_id);
+
+    if (sub === undefined) {
+        blueslip.error('Bad stream id ' + stream_id);
+        return false;
+    }
+
+    var narrow_stream_name = exports.stream();
+
+    if (narrow_stream_name === undefined) {
+        return false;
+    }
+
+    return (sub.name === narrow_stream_name);
+};
+
+return exports;
+
+}());
+if (typeof module !== 'undefined') {
+    module.exports = narrow_state;
+}
diff --git a/static/js/navigate.js b/static/js/navigate.js
index 49e8694a64..af1186ab59 100644
--- a/static/js/navigate.js
+++ b/static/js/navigate.js
@@ -118,12 +118,12 @@ exports.page_down = function () {
 exports.cycle_stream = function (direction) {
     var currentStream;
     var nextStream;
-    if (narrow.stream() !== undefined) {
-        currentStream = stream_list.get_stream_li(narrow.stream());
+    if (narrow_state.stream() !== undefined) {
+        currentStream = stream_list.get_stream_li(narrow_state.stream());
     }
     switch (direction) {
         case 'forward':
-            if (narrow.stream() === undefined) {
+            if (narrow_state.stream() === undefined) {
                 nextStream = $("#stream_filters").children('.narrow-filter').first();
             } else {
                 nextStream = currentStream.next('.narrow-filter');
@@ -133,7 +133,7 @@ exports.cycle_stream = function (direction) {
             }
             break;
         case 'backward':
-            if (narrow.stream() === undefined) {
+            if (narrow_state.stream() === undefined) {
                 nextStream = $("#stream_filters").children('.narrow-filter').last();
             } else {
                 nextStream = currentStream.prev('.narrow-filter');
diff --git a/static/js/pm_list.js b/static/js/pm_list.js
index 08c733f505..d952ff2bd1 100644
--- a/static/js/pm_list.js
+++ b/static/js/pm_list.js
@@ -152,12 +152,12 @@ exports.rebuild_recent = function (active_conversation) {
 exports.update_private_messages = function () {
     exports._build_private_messages_list();
 
-    if (! narrow.active()) {
+    if (! narrow_state.active()) {
         return;
     }
 
-    var is_pm_filter = _.contains(narrow.filter().operands('is'), "private");
-    var conversation = narrow.filter().operands('pm-with');
+    var is_pm_filter = _.contains(narrow_state.filter().operands('is'), "private");
+    var conversation = narrow_state.filter().operands('pm-with');
     if (conversation.length === 1) {
         exports.rebuild_recent(conversation[0]);
     } else if (conversation.length !== 0) {
diff --git a/static/js/popovers.js b/static/js/popovers.js
index 2ee6b7d42e..2e05d2f8a5 100644
--- a/static/js/popovers.js
+++ b/static/js/popovers.js
@@ -77,7 +77,7 @@ function show_message_info_popover(element, id) {
             user_time: people.get_user_time(message.sender_id),
             pm_with_uri: narrow.pm_with_uri(sender_email),
             sent_by_uri: narrow.by_sender_uri(sender_email),
-            narrowed: narrow.active(),
+            narrowed: narrow_state.active(),
             historical: message.historical,
             private_message_class: "respond_personal_button",
         };
@@ -275,7 +275,7 @@ exports.toggle_actions_popover = function (element, id) {
             should_display_add_reaction_option: message.sent_by_me,
             should_display_edit_history_option: should_display_edit_history_option,
             conversation_time_uri: narrow.by_conversation_and_time_uri(message),
-            narrowed: narrow.active(),
+            narrowed: narrow_state.active(),
         };
 
         var ypos = elt.offset().top;
diff --git a/static/js/reload.js b/static/js/reload.js
index 86e0411e47..f79d56f659 100644
--- a/static/js/reload.js
+++ b/static/js/reload.js
@@ -46,7 +46,7 @@ function preserve_state(send_after_reload, save_pointer, save_narrow, save_compo
 
     if (save_narrow) {
         var row = home_msg_list.selected_row();
-        if (!narrow.active()) {
+        if (!narrow_state.active()) {
             if (row.length > 0) {
                 url += "+offset=" + row.offset().top;
             }
diff --git a/static/js/search.js b/static/js/search.js
index 3e9cd6c6cf..eaa41327f6 100644
--- a/static/js/search.js
+++ b/static/js/search.js
@@ -25,7 +25,7 @@ function update_buttons_with_focus(focused) {
     // or we are narrowed.
     if (focused
         || search_query.val()
-        || narrow.active()) {
+        || narrow_state.active()) {
         $('.search_button').removeAttr('disabled');
     } else {
         $('.search_button').attr('disabled', 'disabled');
@@ -121,7 +121,7 @@ exports.initialize = function () {
         // really it would be OK if they did).
 
         setTimeout(function () {
-            var search_string = narrow.search_string();
+            var search_string = narrow_state.search_string();
             query.val(search_string);
             exports.update_button_visibility();
         }, 100);
diff --git a/static/js/search_suggestion.js b/static/js/search_suggestion.js
index fca8626157..562342dc57 100644
--- a/static/js/search_suggestion.js
+++ b/static/js/search_suggestion.js
@@ -311,7 +311,7 @@ function get_topic_suggestions(query_operators) {
         if (filter.has_operator('stream')) {
             stream = filter.operands('stream')[0];
         } else {
-            stream = narrow.stream();
+            stream = narrow_state.stream();
             query_operators.push({operator: 'stream', operand: stream});
         }
         break;
diff --git a/static/js/shim.js b/static/js/shim.js
deleted file mode 100644
index 8324b5b9b3..0000000000
--- a/static/js/shim.js
+++ /dev/null
@@ -1,11 +0,0 @@
-/*
-
-This module has shims to help us break circular dependencies.
-We eventually want to to move the actual implementations into
-new modules.  When we do this, you may need to fix node tests
-that still refer to the old name.
-*/
-
-var narrow_state = {}; // global, should be made into module
-narrow_state.set_compose_defaults = narrow.set_compose_defaults;
-
diff --git a/static/js/stream_edit.js b/static/js/stream_edit.js
index 4942e849c8..2a6edf491e 100644
--- a/static/js/stream_edit.js
+++ b/static/js/stream_edit.js
@@ -402,7 +402,7 @@ $(function () {
         e.preventDefault();
         e.stopPropagation();
 
-        var stream_name = narrow.stream();
+        var stream_name = narrow_state.stream();
         if (stream_name === undefined) {
             return;
         }
diff --git a/static/js/stream_events.js b/static/js/stream_events.js
index ae9d0f24a7..5fb7a477e7 100644
--- a/static/js/stream_events.js
+++ b/static/js/stream_events.js
@@ -99,7 +99,7 @@ exports.mark_subscribed = function (sub, subscribers, color) {
 
     subs.update_settings_for_subscribed(sub);
 
-    if (narrow.is_for_stream_id(sub.stream_id)) {
+    if (narrow_state.is_for_stream_id(sub.stream_id)) {
         current_msg_list.update_trailing_bookend();
     }
 
@@ -124,7 +124,7 @@ exports.mark_unsubscribed = function (sub) {
         return;
     }
 
-    if (narrow.is_for_stream_id(sub.stream_id)) {
+    if (narrow_state.is_for_stream_id(sub.stream_id)) {
         current_msg_list.update_trailing_bookend();
     }
 
diff --git a/static/js/stream_list.js b/static/js/stream_list.js
index c6cd99c3ed..9e29b7ee5d 100644
--- a/static/js/stream_list.js
+++ b/static/js/stream_list.js
@@ -144,7 +144,7 @@ function zoom_in() {
     popovers.hide_all();
     topic_list.zoom_in();
     $("#streams_list").expectOne().removeClass("zoom-out").addClass("zoom-in");
-    zoomed_stream = narrow.stream();
+    zoomed_stream = narrow_state.stream();
 
     // Hide stream list titles and pinned stream splitter
     $(".stream-filters-label").each(function () {
@@ -296,11 +296,11 @@ function rebuild_recent_topics(stream) {
 exports.update_streams_sidebar = function () {
     exports.build_stream_list();
 
-    if (! narrow.active()) {
+    if (! narrow_state.active()) {
         return;
     }
 
-    var op_stream = narrow.filter().operands('stream');
+    var op_stream = narrow_state.filter().operands('stream');
     if (op_stream.length !== 0) {
         if (stream_data.is_subscribed(op_stream[0])) {
             rebuild_recent_topics(op_stream[0]);
@@ -369,7 +369,7 @@ $(function () {
 
     $(document).on('narrow_activated.zulip', function (event) {
         deselect_top_left_corner_items();
-        reset_to_unnarrowed(narrow.stream() === zoomed_stream);
+        reset_to_unnarrowed(narrow_state.stream() === zoomed_stream);
 
         // TODO: handle confused filters like "in:all stream:foo"
         var op_in = event.filter.operands('in');
diff --git a/static/js/subs.js b/static/js/subs.js
index 98a5e0f29f..d01c9c20a0 100644
--- a/static/js/subs.js
+++ b/static/js/subs.js
@@ -644,7 +644,7 @@ $(function () {
         e.preventDefault();
 
         $('#subscription-status').hide();
-        var stream_name = narrow.stream();
+        var stream_name = narrow_state.stream();
         if (stream_name === undefined) {
             return;
         }
@@ -709,7 +709,7 @@ $(function () {
 });
 
 function focus_on_narrowed_stream() {
-    var stream_name = narrow.stream();
+    var stream_name = narrow_state.stream();
     if (stream_name === undefined) {
         return;
     }
diff --git a/static/js/tab_bar.js b/static/js/tab_bar.js
index 76a2372d18..b875eb70f9 100644
--- a/static/js/tab_bar.js
+++ b/static/js/tab_bar.js
@@ -13,7 +13,7 @@ function make_tab(title, hash, data, extra_class, home) {
 
 function make_tab_data() {
     var tabs = [];
-    var filter = narrow.filter();
+    var filter = narrow_state.filter();
 
     // Root breadcrumb item: Either Home or All Messages
     if (filter !== undefined &&
@@ -34,9 +34,9 @@ function make_tab_data() {
         tabs.push(make_tab('Home', "#", "home", "root", true));
     }
 
-    if (narrow.active() && narrow.operators().length > 0) {
+    if (narrow_state.active() && narrow_state.operators().length > 0) {
         var stream;
-        var ops = narrow.operators();
+        var ops = narrow_state.operators();
         // Second breadcrumb item
         var hashed = hashchange.operators_to_hash(ops.slice(0, 1));
         if (filter.has_operator("stream")) {
diff --git a/static/js/topic_list.js b/static/js/topic_list.js
index 80a37817fd..89bfc95ff0 100644
--- a/static/js/topic_list.js
+++ b/static/js/topic_list.js
@@ -157,7 +157,7 @@ exports.build_widget = function (parent_elem, stream, active_topic, max_topics)
 exports.rebuild = function (stream_li, stream) {
     var max_topics = 5;
 
-    var active_topic = narrow.topic();
+    var active_topic = narrow_state.topic();
     exports.remove_expanded_topics();
     active_widget = exports.build_widget(stream_li, stream, active_topic, max_topics);
 };
diff --git a/static/js/typing_events.js b/static/js/typing_events.js
index bd051c12ca..6e133f1df1 100644
--- a/static/js/typing_events.js
+++ b/static/js/typing_events.js
@@ -15,13 +15,15 @@ var TYPING_STARTED_EXPIRY_PERIOD = 15000; // 15s
 // that make typing indicators work.
 
 function get_users_typing_for_narrow() {
-    if (!narrow.narrowed_to_pms()) {
+    if (!narrow_state.narrowed_to_pms()) {
         // Narrow is neither pm-with nor is: private
         return [];
     }
-    if (narrow.operators()[0].operator === 'pm-with') {
+
+    var first_term = narrow_state.operators()[0];
+    if (first_term.operator === 'pm-with') {
         // Get list of users typing in this conversation
-        var narrow_emails_string = narrow.operators()[0].operand;
+        var narrow_emails_string = first_term.operand;
         // TODO: Create people.emails_strings_to_user_ids.
         var narrow_user_ids_string = people.emails_strings_to_user_ids_string(narrow_emails_string);
         var narrow_user_ids = narrow_user_ids_string.split(',').map(function (user_id_string) {
diff --git a/static/js/unread.js b/static/js/unread.js
index 2e6cd3cc7f..5488f29bb1 100644
--- a/static/js/unread.js
+++ b/static/js/unread.js
@@ -251,7 +251,7 @@ exports.get_counts = function () {
     res.private_message_count = pm_count;
     res.home_unread_messages += pm_count;
 
-    if (narrow.active()) {
+    if (narrow_state.active()) {
         res.unread_in_current_view = exports.num_unread_current_messages();
     } else {
         res.unread_in_current_view = res.home_unread_messages;
diff --git a/static/js/user_events.js b/static/js/user_events.js
index dd292f00df..f943e34013 100644
--- a/static/js/user_events.js
+++ b/static/js/user_events.js
@@ -20,7 +20,7 @@ exports.update_person = function update(person) {
         var user_id = person.user_id;
         var new_email = person.new_email;
 
-        narrow.update_email(user_id, new_email);
+        narrow_state.update_email(user_id, new_email);
         compose.update_email(user_id, new_email);
 
         if (people.is_my_user_id(person.user_id)) {
diff --git a/tools/js-dep-visualizer.py b/tools/js-dep-visualizer.py
index c08763da69..6555d20c39 100644
--- a/tools/js-dep-visualizer.py
+++ b/tools/js-dep-visualizer.py
@@ -140,6 +140,7 @@ def find_edges_to_remove(graph, methods):
         ('settings_notifications', 'stream_edit'),
         ('compose', 'stream_edit'),
         ('subs', 'stream_edit'),
+        ('narrow_state', 'stream_data'),
     ] # type: List[Edge]
 
     def is_exempt(edge):
diff --git a/zproject/settings.py b/zproject/settings.py
index d569066446..c0f216607b 100644
--- a/zproject/settings.py
+++ b/zproject/settings.py
@@ -854,6 +854,7 @@ JS_SPECS = {
             'js/message_list_view.js',
             'js/message_list.js',
             'js/message_live_update.js',
+            'js/narrow_state.js',
             'js/narrow.js',
             'js/reload.js',
             'js/compose_fade.js',
@@ -947,7 +948,6 @@ JS_SPECS = {
             'js/typing_data.js',
             'js/typing_events.js',
             'js/ui_init.js',
-            'js/shim.js',
             # JS bundled by webpack is also included here if PIPELINE_ENABLED setting is true
         ],
         'output_filename': 'min/app.js'