diff --git a/common/bootstrap.js b/common/bootstrap.js
index 93f4d658..e029387c 100755
--- a/common/bootstrap.js
+++ b/common/bootstrap.js
@@ -207,6 +207,7 @@ function init() {
     let pref = "extensions.dactyl.cacheFlushCheck";
     let val  = addon.version + "-" + hardSuffix;
     if (!Services.prefs.prefHasUserValue(pref) || Services.prefs.getCharPref(pref) != val) {
+        var cacheFlush = true;
         Services.obs.notifyObservers(null, "startupcache-invalidate", "");
         Services.prefs.setCharPref(pref, val);
     }
@@ -244,6 +245,7 @@ function init() {
     JSMLoader.load(BOOTSTRAP_JSM, global);
 
     JSMLoader.init(suffix);
+    JSMLoader.cacheFlush = cacheFlush;
     JSMLoader.load("base.jsm", global);
 
     if (!(BOOTSTRAP_CONTRACT in Cc)) {
diff --git a/common/content/buffer.js b/common/content/buffer.js
index 156eb049..f6c8eb75 100644
--- a/common/content/buffer.js
+++ b/common/content/buffer.js
@@ -1291,6 +1291,10 @@ var Buffer = Module("buffer", {
         if (!DOM(elem).isScrollable(horizontal ? "horizontal" : "vertical"))
             return false;
 
+        return this.canScroll(elem, dir, horizontal);
+    },
+
+    canScroll: function canScroll(elem, dir, horizontal) {
         let pos = "scrollTop", size = "clientHeight", max = "scrollHeight", layoutSize = "offsetHeight",
             overflow = "overflowX", border1 = "borderTopWidth", border2 = "borderBottomWidth";
         if (horizontal)
diff --git a/common/content/dactyl.js b/common/content/dactyl.js
index f368786d..474f533b 100644
--- a/common/content/dactyl.js
+++ b/common/content/dactyl.js
@@ -111,6 +111,13 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
         }
     },
 
+    signals: {
+        "io.source": function ioSource(context, file, modTime) {
+            if (context.INFO)
+                help.flush("help/plugins.xml", modTime);
+        }
+    },
+
     profileName: deprecated("config.profileName", { get: function profileName() config.profileName }),
 
     /**
@@ -484,8 +491,7 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
 
         if (fileName && fileName[0] == "[")
             fileName = "dactyl://command-line/";
-
-        if (!context && fileName && fileName[0] !== "[")
+        else if (!context)
             context = ctxt || _userContext;
 
         if (isinstance(context, ["Sandbox"]))
@@ -659,82 +665,11 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
      * @private
      * Initialize the help system.
      */
-    initHelp: function initHelp(force) {
+    initHelp: function initHelp() {
         if ("noscriptOverlay" in window)
             noscriptOverlay.safeAllow("dactyl:", true, false);
 
-        if (!force && help.initialized)
-            return;
-
-        help.initialize(force);
-
-        // Process plugin help entries.
-        XML.ignoreWhiteSpace = XML.prettyPrinting = false;
-
-        let body = XML();
-        for (let [, context] in Iterator(plugins.contexts))
-            try {
-                let info = contexts.getDocs(context);
-                if (info instanceof XML) {
-                    if (info.*.@lang.length()) {
-                        let lang = config.bestLocale(String(a) for each (a in info.*.@lang));
-
-                        info.* = info.*.(function::attribute("lang").length() == 0 || @lang == lang);
-
-                        for each (let elem in info.NS::info)
-                            for each (let attr in ["@name", "@summary", "@href"])
-                                if (elem[attr].length())
-                                    info[attr] = elem[attr];
-                    }
-                    body += <h2 xmlns={NS.uri} tag={info.@name + '-plugin'}>{info.@summary}</h2> +
-                        info;
-                }
-            }
-            catch (e) {
-                util.reportError(e);
-            }
-
-        help.files["plugins"] = function () ['text/xml;charset=UTF-8',
-            '<?xml version="1.0"?>\n' +
-            '<?xml-stylesheet type="text/xsl" href="dactyl://content/help.xsl"?>\n' +
-            '<!DOCTYPE document SYSTEM "resource://dactyl-content/dactyl.dtd">\n' +
-            <document xmlns={NS}
-                name="plugins" title={config.appName + " Plugins"}>
-                <h1 tag="using-plugins">{_("help.title.Using Plugins")}</h1>
-                <toc start="2"/>
-
-                {body}
-            </document>.toXMLString()];
-
-
-        default xml namespace = NS;
-
-        help.overlays["index"] = ['text/xml;charset=UTF-8',
-            '<?xml version="1.0"?>\n' +
-            <overlay xmlns={NS}>{
-            template.map(dactyl.indices, function ([name, iter])
-                <dl insertafter={name + "-index"}>{
-                    template.map(iter(), util.identity)
-                }</dl>, <>{"\n\n"}</>)
-            }</overlay>];
-
-        help.overlays["gui"] = ['text/xml;charset=UTF-8',
-            '<?xml version="1.0"?>\n' +
-            <overlay xmlns={NS}>
-                <dl insertafter="dialog-list">{
-                template.map(config.dialogs, function ([name, val])
-                    (!val[2] || val[2]())
-                        ? <><dt>{name}</dt><dd>{val[0]}</dd></>
-                        : undefined,
-                    <>{"\n"}</>)
-                }</dl>
-            </overlay>];
-
-        help.tags["plugins"] = help.tags["plugins.xml"] = "plugins";
-        help.tags["index"] = help.tags["index.xml"] = "index";
-
-        help.addTags("plugins", util.httpGet("dactyl://help/plugins").responseXML);
-        help.addTags("index", util.httpGet("dactyl://help-overlay/index").responseXML);
+        help.initialize();
     },
 
     stringifyXML: function (xml) {
@@ -1280,6 +1215,73 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
 }, {
     toolbarHidden: function hidden(elem) (elem.getAttribute("autohide") || elem.getAttribute("collapsed")) == "true"
 }, {
+    cache: function () {
+        cache.register("help/plugins.xml", function () {
+            // Process plugin help entries.
+            XML.ignoreWhiteSpace = XML.prettyPrinting = false;
+
+            let body = XML();
+            for (let [, context] in Iterator(plugins.contexts))
+                try {
+                    let info = contexts.getDocs(context);
+                    if (info instanceof XML) {
+                        if (info.*.@lang.length()) {
+                            let lang = config.bestLocale(String(a) for each (a in info.*.@lang));
+
+                            info.* = info.*.(function::attribute("lang").length() == 0 || @lang == lang);
+
+                            for each (let elem in info.NS::info)
+                                for each (let attr in ["@name", "@summary", "@href"])
+                                    if (elem[attr].length())
+                                        info[attr] = elem[attr];
+                        }
+                        body += <h2 xmlns={NS.uri} tag={info.@name + '-plugin'}>{info.@summary}</h2> +
+                            info;
+                    }
+                }
+                catch (e) {
+                    util.reportError(e);
+                }
+
+            return '<?xml version="1.0"?>\n' +
+                   '<?xml-stylesheet type="text/xsl" href="dactyl://content/help.xsl"?>\n' +
+                   '<!DOCTYPE document SYSTEM "resource://dactyl-content/dactyl.dtd">\n' +
+                   <document xmlns={NS}
+                       name="plugins" title={config.appName + " Plugins"}>
+                       <h1 tag="using-plugins">{_("help.title.Using Plugins")}</h1>
+                       <toc start="2"/>
+
+                       {body}
+                   </document>.toXMLString();
+        });
+
+        cache.register("help/index.xml", function () {
+            default xml namespace = NS;
+
+            return '<?xml version="1.0"?>\n' +
+                   <overlay xmlns={NS}>{
+                   template.map(dactyl.indices, function ([name, iter])
+                       <dl insertafter={name + "-index"}>{
+                           template.map(iter(), util.identity)
+                       }</dl>, <>{"\n\n"}</>)
+                   }</overlay>;
+        });
+
+        cache.register("help/gui.xml", function () {
+            default xml namespace = NS;
+
+            return '<?xml version="1.0"?>\n' +
+                   <overlay xmlns={NS}>
+                       <dl insertafter="dialog-list">{
+                       template.map(config.dialogs, function ([name, val])
+                           (!val[2] || val[2]())
+                               ? <><dt>{name}</dt><dd>{val[0]}</dd></>
+                               : undefined,
+                           <>{"\n"}</>)
+                       }</dl>
+                   </overlay>;
+        });
+    },
     events: function () {
         events.listen(window, dactyl, "events", true);
     },
diff --git a/common/content/modes.js b/common/content/modes.js
index ae26b090..7443873d 100644
--- a/common/content/modes.js
+++ b/common/content/modes.js
@@ -213,57 +213,18 @@ var Modes = Module("modes", {
 
             }
         });
-
-        function makeTree() {
-            let list = modes.all.filter(function (m) m.name !== m.description);
-
-            let tree = {};
-
-            for (let mode in values(list))
-                tree[mode.name] = {};
-
-            for (let mode in values(list))
-                for (let base in values(mode.bases))
-                    tree[base.name][mode.name] = tree[mode.name];
-
-            let roots = iter([m.name, tree[m.name]] for (m in values(list)) if (!m.bases.length)).toObject();
-
-            default xml namespace = NS;
-            function rec(obj) {
-                XML.ignoreWhitespace = XML.prettyPrinting = false;
-
-                let res = <ul dactyl:highlight="Dense" xmlns:dactyl={NS}/>;
-                Object.keys(obj).sort().forEach(function (name) {
-                    let mode = modes.getMode(name);
-                    res.* += <li><em>{mode.displayName}</em>: {mode.description}{
-                        rec(obj[name])
-                    }</li>;
-                });
-
-                if (res.*.length())
-                    return res;
-                return <></>;
-            }
-
-            return rec(roots);
-        }
-
-        util.timeout(function () {
-            // Waits for the add-on to become available, if necessary.
-            config.addon;
-            config.version;
-
-            services["dactyl:"].pages["modes.dtd"] = services["dactyl:"].pages["modes.dtd"]();
-        });
-
-        services["dactyl:"].pages["modes.dtd"] = function () [null,
-            util.makeDTD(iter({ "modes.tree": makeTree() },
-                              config.dtd))];
     },
+
     cleanup: function cleanup() {
         modes.reset();
     },
 
+    signals: {
+        "io.source": function ioSource(context, file, modTime) {
+            cache.flushEntry("modes.dtd", modTime);
+        }
+    },
+
     _getModeMessage: function _getModeMessage() {
         // when recording a macro
         let macromode = "";
@@ -604,6 +565,45 @@ var Modes = Module("modes", {
         }, desc));
     }
 }, {
+    cache: function initCache() {
+        function makeTree() {
+            let list = modes.all.filter(function (m) m.name !== m.description);
+
+            let tree = {};
+
+            for (let mode in values(list))
+                tree[mode.name] = {};
+
+            for (let mode in values(list))
+                for (let base in values(mode.bases))
+                    tree[base.name][mode.name] = tree[mode.name];
+
+            let roots = iter([m.name, tree[m.name]] for (m in values(list)) if (!m.bases.length)).toObject();
+
+            default xml namespace = NS;
+            function rec(obj) {
+                XML.ignoreWhitespace = XML.prettyPrinting = false;
+
+                let res = <ul dactyl:highlight="Dense" xmlns:dactyl={NS}/>;
+                Object.keys(obj).sort().forEach(function (name) {
+                    let mode = modes.getMode(name);
+                    res.* += <li><em>{mode.displayName}</em>: {mode.description}{
+                        rec(obj[name])
+                    }</li>;
+                });
+
+                if (res.*.length())
+                    return res;
+                return <></>;
+            }
+
+            return rec(roots);
+        }
+
+        cache.register("modes.dtd", function ()
+            util.makeDTD(iter({ "modes.tree": makeTree() },
+                              config.dtd)));
+    },
     mappings: function initMappings() {
         mappings.add([modes.BASE, modes.NORMAL],
             ["<Esc>", "<C-[>"],
diff --git a/common/content/mow.js b/common/content/mow.js
index 90c3001d..9f17fa23 100644
--- a/common/content/mow.js
+++ b/common/content/mow.js
@@ -21,7 +21,7 @@ var MOW = Module("mow", {
             if (modes.have(modes.OUTPUT_MULTILINE)) {
                 this.resize(true);
 
-                if (options["more"] && this.isScrollable(1)) {
+                if (options["more"] && this.canScroll(1)) {
                     // start the last executed command's output at the top of the screen
                     let elements = this.document.getElementsByClassName("ex-command-output");
                     DOM(elements[elements.length - 1]).scrollIntoView(true);
@@ -219,7 +219,7 @@ var MOW = Module("mow", {
     onKeyPress: function onKeyPress(eventList) {
         const KILL = false, PASS = true;
 
-        if (options["more"] && mow.isScrollable(1))
+        if (options["more"] && mow.canScroll(1))
             this.updateMorePrompt(false, true);
         else {
             modes.pop();
@@ -279,7 +279,7 @@ var MOW = Module("mow", {
 
         if (showHelp)
             this.widgets.message = ["MoreMsg", _("mow.moreHelp")];
-        else if (force || (options["more"] && Buffer.isScrollable(elem, 1)))
+        else if (force || (options["more"] && Buffer.canScroll(elem, 1)))
             this.widgets.message = ["MoreMsg", _("mow.more")];
         else
             this.widgets.message = ["Question", _("mow.continue")];
@@ -341,36 +341,36 @@ var MOW = Module("mow", {
 
         bind(["j", "<C-e>", "<Down>"], "Scroll down one line",
              function ({ count }) { mow.scrollVertical("lines", 1 * (count || 1)); },
-             function () mow.isScrollable(1), BEEP);
+             function () mow.canScroll(1), BEEP);
 
         bind(["k", "<C-y>", "<Up>"], "Scroll up one line",
              function ({ count }) { mow.scrollVertical("lines", -1 * (count || 1)); },
-             function () mow.isScrollable(-1), BEEP);
+             function () mow.canScroll(-1), BEEP);
 
         bind(["<C-j>", "<C-m>", "<Return>"], "Scroll down one line, exit on last line",
              function ({ count }) { mow.scrollVertical("lines", 1 * (count || 1)); },
-             function () mow.isScrollable(1), DROP);
+             function () mow.canScroll(1), DROP);
 
         // half page down
         bind(["<C-d>"], "Scroll down half a page",
              function ({ count }) { mow.scrollVertical("pages", .5 * (count || 1)); },
-             function () mow.isScrollable(1), BEEP);
+             function () mow.canScroll(1), BEEP);
 
         bind(["<C-f>", "<PageDown>"], "Scroll down one page",
              function ({ count }) { mow.scrollVertical("pages", 1 * (count || 1)); },
-             function () mow.isScrollable(1), BEEP);
+             function () mow.canScroll(1), BEEP);
 
         bind(["<Space>"], "Scroll down one page",
              function ({ count }) { mow.scrollVertical("pages", 1 * (count || 1)); },
-             function () mow.isScrollable(1), DROP);
+             function () mow.canScroll(1), DROP);
 
         bind(["<C-u>"], "Scroll up half a page",
              function ({ count }) { mow.scrollVertical("pages", -.5 * (count || 1)); },
-             function () mow.isScrollable(-1), BEEP);
+             function () mow.canScroll(-1), BEEP);
 
         bind(["<C-b>", "<PageUp>"], "Scroll up half a page",
              function ({ count }) { mow.scrollVertical("pages", -1 * (count || 1)); },
-             function () mow.isScrollable(-1), BEEP);
+             function () mow.canScroll(-1), BEEP);
 
         bind(["gg"], "Scroll to the beginning of output",
              function () { mow.scrollToPercent(null, 0); });
diff --git a/common/locale/en-US/all.xml b/common/locale/en-US/all.xml
index 59c18308..7f6281f5 100644
--- a/common/locale/en-US/all.xml
+++ b/common/locale/en-US/all.xml
@@ -35,6 +35,7 @@
 <include href="developer" tag="developer.xml"/>
 <include href="various" tag="various.xml"/>
 <include href="plugins" tag="plugins.xml"/>
+<include href="versions" tag="versions.xml"/>
 <include href="faq" tag="faq.xml"/>
 <include href="index" tag="index.xml"/>
 
diff --git a/common/locale/en-US/map.xml b/common/locale/en-US/map.xml
index 3b0251d4..f7c7305a 100644
--- a/common/locale/en-US/map.xml
+++ b/common/locale/en-US/map.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <?xml-stylesheet type="text/xsl" href="dactyl://content/help.xsl"?>
 
-<!DOCTYPE document SYSTEM "dactyl://content/modes.dtd">
+<!DOCTYPE document SYSTEM "dactyl://cache/modes.dtd">
 
 <document
     name="map"
diff --git a/common/locale/en-US/options.xml b/common/locale/en-US/options.xml
index 26c40db8..7ad36e9c 100644
--- a/common/locale/en-US/options.xml
+++ b/common/locale/en-US/options.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <?xml-stylesheet type="text/xsl" href="dactyl://content/help.xsl"?>
 
-<!DOCTYPE document SYSTEM "dactyl://content/options.dtd">
+<!DOCTYPE document SYSTEM "dactyl://cache/options.dtd">
 
 <document
     name="options"
diff --git a/common/modules/cache.jsm b/common/modules/cache.jsm
new file mode 100644
index 00000000..72556bc7
--- /dev/null
+++ b/common/modules/cache.jsm
@@ -0,0 +1,232 @@
+// Copyright (c) 2011 by Kris Maglione <maglione.k@gmail.com>
+//
+// This work is licensed for reuse under an MIT license. Details are
+// given in the LICENSE.txt file included with this file.
+"use strict";
+
+Components.utils.import("resource://dactyl/bootstrap.jsm");
+defineModule("cache", {
+    exports: ["Cache", "cache"],
+    require: ["config", "services", "util"]
+}, this);
+
+var Cache = Module("Cache", XPCOM(Ci.nsIRequestObserver), {
+    init: function init() {
+        this.queue = [];
+        this.cache = {};
+        this.providers = {};
+        this.localProviders = {};
+
+        if (JSMLoader.cacheFlush)
+            this.flush();
+
+        update(services["dactyl:"].providers, {
+            "cache": function (uri, path) {
+                // TODO: Return zip reader stream
+
+                let result = cache.force(path);
+                if (isArray(result))
+                    return result;
+
+                try {
+                    return [services.mime.getTypeFromURI(uri), result];
+                }
+                catch (e) {
+                    return ["text/plain", result];
+                }
+            }
+        });
+    },
+
+    Local: function Local(dactyl, modules, window) ({
+        init: function init() {
+            delete this.instance;
+            this.providers = {};
+        },
+
+        isLocal: true
+    }),
+
+    compression: 9,
+
+    cacheFile: Class.Memoize(function () {
+        let dir = File(services.directory.get("ProfD", Ci.nsIFile))
+                    .child("dactyl");
+        if (!dir.exists())
+            dir.create(dir.DIRECTORY_TYPE, octal(777));
+        return dir.child("cache.zip");
+    }),
+
+    get cacheReader() {
+        if (!this._cacheReader && this.cacheFile.exists()
+                && !this.inQueue)
+            try {
+                this._cacheReader = services.ZipReader(this.cacheFile);
+            }
+            catch (e if e.result == Cr.NS_ERROR_FILE_CORRUPTED) {
+                util.reportError(e);
+                this.cacheFile.remove(false);
+            }
+
+        return this._cacheReader;
+    },
+
+    get inQueue() this._cacheWriter && this._cacheWriter.inQueue(),
+
+    getCacheWriter: function () {
+        if (!this._cacheWriter)
+            try {
+                let mode = File.MODE_RDWR;
+                if (!this.cacheFile.exists())
+                    mode |= File.MODE_CREATE;
+
+                cache._cacheWriter = services.ZipWriter(this.cacheFile, mode);
+            }
+            catch (e if e.result == Cr.NS_ERROR_FILE_CORRUPTED) {
+                util.reportError(e);
+                this.cacheFile.remove(false);
+
+                mode |= File.MODE_CREATE;
+                cache._cacheWriter = services.ZipWriter(this.cacheFile, mode);
+            }
+        return this._cacheWriter;
+    },
+
+    closeReader: function closeReader() {
+        if (cache._cacheReader) {
+            this.cacheReader.close();
+            delete cache._cacheReader;
+        }
+    },
+
+    closeWriter: function closeWriter() {
+        this.closeReader();
+
+        if (this._cacheWriter) {
+            this._cacheWriter.close();
+            delete cache._cacheWriter;
+
+            // ZipWriter bug.
+            if (this.cacheFile.fileSize <= 22)
+                this.cacheFile.remove(false);
+        }
+    },
+
+    flush: function flush() {
+        cache.cache = {};
+        if (this.cacheFile.eists()) {
+            this.closeReader();
+
+            this.flushJAR(this.cacheFile);
+            this.cacheFile.remove(false);
+        }
+    },
+
+    flushAll: function flushAll(file) {
+        this.flushStartup();
+        this.flush();
+    },
+
+    flushEntry: function flushEntry(name, time) {
+        if (this.cacheReader && this.cacheReader.hasEntry(name)) {
+            if (time && this.cacheReader.getEntry(name).lastModifiedTime / 1000 >= time)
+                return;
+
+            this.queue.push([null, name]);
+            cache.processQueue();
+        }
+
+        delete this.cache[name];
+    },
+
+    flushJAR: function flushJAR(file) {
+        services.observer.notifyObservers(file, "flush-cache-entry", "");
+    },
+
+    flushStartup: function flushStartup() {
+        services.observer.notifyObservers(null, "startupcache-invalidate", "");
+    },
+
+    force: function force(name, localOnly) {
+        if (this.cacheReader && this.cacheReader.hasEntry(name)) {
+            return JSON.parse(File.readStream(
+                this.cacheReader.getInputStream(name)));
+        }
+
+        if (Set.has(this.localProviders, name) && !this.isLocal) {
+            for each (let { cache } in overlay.modules)
+                if (cache.has(name))
+                    return cache.force(name, true);
+        }
+
+        if (Set.has(this.providers, name)) {
+            let [func, self] = this.providers[name];
+            this.cache[name] = func.call(self || this, name);
+
+            cache.queue.push([Date.now(), name]);
+            cache.processQueue();
+
+            return this.cache[name];
+        }
+
+        if (this.isLocal && !localOnly)
+            return cache.force(name);
+    },
+
+    get: function get(name) {
+        if (!Set.has(this.cache, name)) {
+            this.cache[name] = this.force(name);
+            util.assert(this.cache[name] !== undefined,
+                        "No such cache key", false);
+        }
+
+        return this.cache[name];
+    },
+
+    has: function has(name) Set.has(this.providers, name) || set.has(this.cache, name),
+
+    register: function register(name, callback, self) {
+        if (this.isLocal)
+            Set.add(this.localProviders, name);
+
+        this.providers[name] = [callback, self];
+    },
+
+    processQueue: function processQueue() {
+        this.closeReader();
+        this.closeWriter();
+
+        if (this.queue.length && !this.inQueue) {
+            // removeEntry does not work properly with queues.
+            for each (let [, entry] in this.queue)
+                if (this.getCacheWriter().hasEntry(entry)) {
+                    this.getCacheWriter().removeEntry(entry, false);
+                    this.closeWriter();
+                }
+
+            this.queue.splice(0).forEach(function ([time, entry]) {
+                if (time && Set.has(this.cache, entry)) {
+                    let stream = services.CharsetConv("UTF-8")
+                                         .convertToInputStream(JSON.stringify(this.cache[entry]));
+
+                    this.getCacheWriter().addEntryStream(entry, time * 1000,
+                                                         this.compression, stream,
+                                                         true);
+                }
+            }, this);
+
+            if (this._cacheWriter)
+                this.getCacheWriter().processQueue(this, null);
+        }
+    },
+
+    onStopRequest: function onStopRequest() {
+        this.processQueue();
+    }
+});
+
+endModule();
+
+// catch(e){ if (typeof e === "string") e = Error(e); dump(e.fileName+":"+e.lineNumber+": "+e+"\n" + e.stack); }
+
+// vim: set fdm=marker sw=4 sts=4 et ft=javascript:
diff --git a/common/modules/config.jsm b/common/modules/config.jsm
index c13f910f..20c70987 100644
--- a/common/modules/config.jsm
+++ b/common/modules/config.jsm
@@ -14,6 +14,7 @@ defineModule("config", {
 }, this);
 
 this.lazyRequire("addons", ["AddonManager"]);
+this.lazyRequire("cache", ["cache"]);
 this.lazyRequire("highlight", ["highlight"]);
 this.lazyRequire("messages", ["_"]);
 
@@ -54,9 +55,11 @@ var ConfigBase = Class("ConfigBase", {
                      "resource://dactyl-content/")));
 
         this.timeout(function () {
-            services["dactyl:"].pages.dtd = function () [null, util.makeDTD(config.dtd)];
+            cache.register("config.dtd", function () util.makeDTD(config.dtd));
         });
 
+        services["dactyl:"].pages["dtd"] = function () [null, cache.get("config.dtd")];
+
         update(services["dactyl:"].providers, {
             "locale": function (uri, path) LocaleChannel("dactyl-locale", config.locale, path, uri),
             "locale-local": function (uri, path) LocaleChannel("dactyl-local-locale", config.locale, path, uri)
@@ -101,6 +104,7 @@ var ConfigBase = Class("ConfigBase", {
         global: ["addons",
                  "base",
                  "io",
+                 "cache",
                  "commands",
                  "completion",
                  "config",
diff --git a/common/modules/help.jsm b/common/modules/help.jsm
index c5e0b8f9..4841564a 100644
--- a/common/modules/help.jsm
+++ b/common/modules/help.jsm
@@ -7,21 +7,79 @@
 Components.utils.import("resource://dactyl/bootstrap.jsm");
 defineModule("help", {
     exports: ["help"],
-    require: ["dom", "javascript", "protocol", "services", "util"]
+    require: ["cache", "dom", "javascript", "protocol", "services", "util"]
 }, this);
 
+var HelpBuilder = Class("HelpBuilder", {
+    init: function init() {
+        try {
+            help._data = this;
+
+            this.files = {};
+            this.tags = {};
+            this.overlays = {};
+
+            // Scrape the list of help files from all.xml
+            this.tags["all"] = this.tags["all.xml"] = "all";
+            let files = this.findHelpFile("all").map(function (doc)
+                    [f.value for (f in DOM.XPath("//dactyl:include/@href", doc))]);
+
+            // Scrape the tags from the rest of the help files.
+            array.flatten(files).forEach(function (file) {
+                this.tags[file + ".xml"] = file;
+                this.findHelpFile(file).forEach(function (doc) {
+                    this.addTags(file, doc);
+                }, this);
+            }, this);
+        }
+        finally {
+            delete help._data;
+        }
+    },
+
+    toJSON: function toJSON() ({
+        files: this.files,
+        overlays: this.overlays,
+        tags: this.tags
+    }),
+
+    // Find the tags in the document.
+    addTags: function addTags(file, doc) {
+        for (let elem in DOM.XPath("//@tag|//dactyl:tags/text()|//dactyl:tag/text()", doc))
+                for (let tag in values((elem.value || elem.textContent).split(/\s+/)))
+            this.tags[tag] = file;
+    },
+
+    bases: ["dactyl://locale-local/", "dactyl://locale/", "dactyl://cache/help/"],
+
+    // Find help and overlay files with the given name.
+    findHelpFile: function findHelpFile(file) {
+        let result = [];
+        for (let base in values(this.bases)) {
+            let url = [base, file, ".xml"].join("");
+            let res = util.httpGet(url);
+            if (res) {
+                if (res.responseXML.documentElement.localName == "document")
+                    this.files[file] = url;
+                if (res.responseXML.documentElement.localName == "overlay")
+                    this.overlays[file] = url;
+                result.push(res.responseXML);
+            }
+        }
+        return result;
+    }
+});
+
 var Help = Module("Help", {
     init: function init() {
         this.initialized = false;
-        this.files = {};
-        this.overlays = {};
-        this.tags = {};
 
         function Loop(fn)
             function (uri, path) {
                 if (!help.initialized)
                     return RedirectChannel(uri.spec, uri, 2,
                                            "Initializing. Please wait...");
+
                 return fn.apply(this, arguments);
             }
 
@@ -36,8 +94,136 @@ var Help = Module("Help", {
                     return RedirectChannel("dactyl://help/" + help.tags[tag] + "#" + tag.replace(/#/g, encodeURIComponent), uri);
             })
         });
+
+        cache.register("help", HelpBuilder);
+
+        cache.register("help/versions.xml", function () {
+            let NEWS = util.httpGet(config.addon.getResourceURI("NEWS").spec,
+                                    { mimeType: "text/plain;charset=UTF-8" })
+                           .responseText;
+
+            let re = util.regexp(UTF8(<![CDATA[
+                  ^ (?P<comment> \s* # .*\n)
+
+                | ^ (?P<space> \s*)
+                    (?P<char>  [-•*+]) \ //
+                  (?P<content> .*\n
+                     (?: \2\ \ .*\n | \s*\n)* )
+
+                | (?P<par>
+                      (?: ^ [^\S\n]*
+                          (?:[^-•*+\s] | [-•*+]\S)
+                          .*\n
+                      )+
+                  )
+
+                | (?: ^ [^\S\n]* \n) +
+            ]]>), "gmxy");
+
+            let betas = util.regexp(/\[(b\d)\]/, "gx");
+
+            let beta = array(betas.iterate(NEWS))
+                        .map(function (m) m[1]).uniq().slice(-1)[0];
+
+
+            default xml namespace = NS;
+            function rec(text, level, li) {
+                XML.ignoreWhitespace = XML.prettyPrinting = false;
+
+                let res = <></>;
+                let list, space, i = 0;
+
+
+                for (let match in re.iterate(text)) {
+                    if (match.comment)
+                        continue;
+                    else if (match.char) {
+                        if (!list)
+                            res += list = <ul/>;
+                        let li = <li/>;
+                        li.* += rec(match.content.replace(RegExp("^" + match.space, "gm"), ""), level + 1, li);
+                        list.* += li;
+                    }
+                    else if (match.par) {
+                        let [, par, tags] = /([^]*?)\s*((?:\[[^\]]+\])*)\n*$/.exec(match.par);
+                        let t = tags;
+                        tags = array(betas.iterate(tags)).map(function (m) m[1]);
+
+                        let group = !tags.length                       ? "" :
+                                    !tags.some(function (t) t == beta) ? "HelpNewsOld" : "HelpNewsNew";
+                        if (i === 0 && li) {
+                            li.@highlight = group;
+                            group = "";
+                        }
+
+                        list = null;
+                        if (level == 0 && /^.*:\n$/.test(match.par)) {
+                            let text = par.slice(0, -1);
+                            res += <h2 tag={"news-" + text}>{template.linkifyHelp(text, true)}</h2>;
+                        }
+                        else {
+                            let [, a, b] = /^(IMPORTANT:?)?([^]*)/.exec(par);
+                            res += <p highlight={group + " HelpNews"}>{
+                                !tags.length ? "" :
+                                <hl key="HelpNewsTag">{tags.join(" ")}</hl>
+                            }{
+                                a ? <hl key="HelpWarning">{a}</hl> : ""
+                            }{
+                                template.linkifyHelp(b, true)
+                            }</p>;
+                        }
+                    }
+                    i++;
+                }
+                for each (let attr in res..@highlight) {
+                    attr.parent().@NS::highlight = attr;
+                    delete attr.parent().@highlight;
+                }
+                return res;
+            }
+
+            XML.ignoreWhitespace = XML.prettyPrinting = false;
+            let body = rec(NEWS, 0);
+            for each (let li in body..li) {
+                let list = li..li.(@NS::highlight == "HelpNewsOld");
+                if (list.length() && list.length() == li..li.(@NS::highlight != "").length()) {
+                    for each (let li in list)
+                        li.@NS::highlight = "";
+                    li.@NS::highlight = "HelpNewsOld";
+                }
+            }
+
+
+            return '<?xml version="1.0"?>\n' +
+                   '<?xml-stylesheet type="text/xsl" href="dactyl://content/help.xsl"?>\n' +
+                   '<!DOCTYPE document SYSTEM "resource://dactyl-content/dactyl.dtd">\n' +
+                   <document xmlns={NS} xmlns:dactyl={NS}
+                       name="versions" title={config.appName + " Versions"}>
+                       <h1 tag="versions news NEWS">{config.appName} Versions</h1>
+                       <toc start="2"/>
+
+                       {body}
+                   </document>.toXMLString()
+        });
     },
 
+    initialize: function initialize() {
+        help.initialized = true;
+    },
+
+    flush: function flush(entries, time) {
+        cache.flushEntry("help", time);
+
+        for (let entry in values(Array.concat(entries || [])))
+            cache.flushEntry(entry, time);
+    },
+
+    get data() this._data || cache.get("help"),
+
+    get files() this.data.files,
+    get overlays() this.data.overlays,
+    get tags() this.data.tags,
+
     Local: function Local(dactyl, modules, window) ({
         init: function init() {
             dactyl.commands["dactyl.help"] = function (event) {
@@ -81,6 +267,7 @@ var Help = Module("Help", {
          */
         help: function (topic, consolidated) {
             dactyl.initHelp();
+
             if (!topic) {
                 let helpFile = consolidated ? "all" : modules.options["helpfile"];
 
@@ -210,176 +397,7 @@ var Help = Module("Help", {
                 zip.close();
         }, [function (context, args) completion.file(context)]),
 
-    }),
-
-    // Find the tags in the document.
-    addTags: function addTags(file, doc) {
-        for (let elem in DOM.XPath("//@tag|//dactyl:tags/text()|//dactyl:tag/text()", doc))
-                for (let tag in values((elem.value || elem.textContent).split(/\s+/)))
-            this.tags[tag] = file;
-    },
-
-    namespaces: ["locale-local", "locale"],
-
-    // Find help and overlay files with the given name.
-    findHelpFile: function findHelpFile(file) {
-        let result = [];
-        for (let namespace in values(this.namespaces)) {
-            let url = ["dactyl://", namespace, "/", file, ".xml"].join("");
-            let res = util.httpGet(url);
-            if (res) {
-                if (res.responseXML.documentElement.localName == "document")
-                    this.files[file] = url;
-                if (res.responseXML.documentElement.localName == "overlay")
-                    this.overlays[file] = url;
-                result.push(res.responseXML);
-            }
-        }
-        return result;
-    },
-
-    initialize: function initialize(force) {
-        // Waits for the add-on to become available, if necessary.
-        config.addon;
-        config.version;
-
-        if (force || !this.initialized) {
-
-            this.files["versions"] = function () {
-                let NEWS = util.httpGet(config.addon.getResourceURI("NEWS").spec,
-                                        { mimeType: "text/plain;charset=UTF-8" })
-                               .responseText;
-
-                let re = util.regexp(UTF8(<![CDATA[
-                      ^ (?P<comment> \s* # .*\n)
-
-                    | ^ (?P<space> \s*)
-                        (?P<char>  [-•*+]) \ //
-                      (?P<content> .*\n
-                         (?: \2\ \ .*\n | \s*\n)* )
-
-                    | (?P<par>
-                          (?: ^ [^\S\n]*
-                              (?:[^-•*+\s] | [-•*+]\S)
-                              .*\n
-                          )+
-                      )
-
-                    | (?: ^ [^\S\n]* \n) +
-                ]]>), "gmxy");
-
-                let betas = util.regexp(/\[(b\d)\]/, "gx");
-
-                let beta = array(betas.iterate(NEWS))
-                            .map(function (m) m[1]).uniq().slice(-1)[0];
-
-
-                default xml namespace = NS;
-                function rec(text, level, li) {
-                    XML.ignoreWhitespace = XML.prettyPrinting = false;
-
-                    let res = <></>;
-                    let list, space, i = 0;
-
-
-                    for (let match in re.iterate(text)) {
-                        if (match.comment)
-                            continue;
-                        else if (match.char) {
-                            if (!list)
-                                res += list = <ul/>;
-                            let li = <li/>;
-                            li.* += rec(match.content.replace(RegExp("^" + match.space, "gm"), ""), level + 1, li);
-                            list.* += li;
-                        }
-                        else if (match.par) {
-                            let [, par, tags] = /([^]*?)\s*((?:\[[^\]]+\])*)\n*$/.exec(match.par);
-                            let t = tags;
-                            tags = array(betas.iterate(tags)).map(function (m) m[1]);
-
-                            let group = !tags.length                       ? "" :
-                                        !tags.some(function (t) t == beta) ? "HelpNewsOld" : "HelpNewsNew";
-                            if (i === 0 && li) {
-                                li.@highlight = group;
-                                group = "";
-                            }
-
-                            list = null;
-                            if (level == 0 && /^.*:\n$/.test(match.par)) {
-                                let text = par.slice(0, -1);
-                                res += <h2 tag={"news-" + text}>{template.linkifyHelp(text, true)}</h2>;
-                            }
-                            else {
-                                let [, a, b] = /^(IMPORTANT:?)?([^]*)/.exec(par);
-                                res += <p highlight={group + " HelpNews"}>{
-                                    !tags.length ? "" :
-                                    <hl key="HelpNewsTag">{tags.join(" ")}</hl>
-                                }{
-                                    a ? <hl key="HelpWarning">{a}</hl> : ""
-                                }{
-                                    template.linkifyHelp(b, true)
-                                }</p>;
-                            }
-                        }
-                        i++;
-                    }
-                    for each (let attr in res..@highlight) {
-                        attr.parent().@NS::highlight = attr;
-                        delete attr.parent().@highlight;
-                    }
-                    return res;
-                }
-
-                XML.ignoreWhitespace = XML.prettyPrinting = false;
-                let body = rec(NEWS, 0);
-                for each (let li in body..li) {
-                    let list = li..li.(@NS::highlight == "HelpNewsOld");
-                    if (list.length() && list.length() == li..li.(@NS::highlight != "").length()) {
-                        for each (let li in list)
-                            li.@NS::highlight = "";
-                        li.@NS::highlight = "HelpNewsOld";
-                    }
-                }
-
-
-                return ["application/xml",
-                    '<?xml version="1.0"?>\n' +
-                    '<?xml-stylesheet type="text/xsl" href="dactyl://content/help.xsl"?>\n' +
-                    '<!DOCTYPE document SYSTEM "resource://dactyl-content/dactyl.dtd">\n' +
-                    <document xmlns={NS} xmlns:dactyl={NS}
-                        name="versions" title={config.appName + " Versions"}>
-                        <h1 tag="versions news NEWS">{config.appName} Versions</h1>
-                        <toc start="2"/>
-
-                        {body}
-                    </document>.toXMLString()
-                ];
-            }
-
-
-
-            // Scrape the list of help files from all.xml
-            // Manually process main and overlay files, since XSLTProcessor and
-            // XMLHttpRequest don't allow access to chrome documents.
-            this.tags["all"] = this.tags["all.xml"] = "all";
-            let files = this.findHelpFile("all").map(function (doc)
-                    [f.value for (f in DOM.XPath("//dactyl:include/@href", doc))]);
-
-            // Scrape the tags from the rest of the help files.
-            array.flatten(files).forEach(function (file) {
-                this.tags[file + ".xml"] = file;
-                this.findHelpFile(file).forEach(function (doc) {
-                    this.addTags(file, doc);
-                }, this);
-            }, this);
-
-            this.tags["versions"] = this.tags["versions.xml"] = "versions";
-
-            this.addTags("versions", util.httpGet("dactyl://help/versions").responseXML);
-
-            help.initialized = true;
-        }
-    },
+    })
 }, {
 }, {
     commands: function init_commands(dactyl, modules, window) {
diff --git a/common/modules/io.jsm b/common/modules/io.jsm
index 32e25843..0587ea40 100644
--- a/common/modules/io.jsm
+++ b/common/modules/io.jsm
@@ -175,7 +175,7 @@ var IO = Module("io", {
                                 util.flushCache();
 
                             dactyl.loadScript(uri.spec, context);
-                            help.initialized = false;
+                            dactyl.triggerObserver("io.source", context, file, file.lastModifiedTime);
                         }
                         catch (e) {
                             if (e.fileName && !(e instanceof FailedAssertion))
@@ -200,6 +200,7 @@ var IO = Module("io", {
                             group: context.GROUP,
                             line: 1
                         });
+                        dactyl.triggerObserver("io.source", context, file, file.lastModifiedTime);
                     }
 
                     Set.add(this._scriptNames, file.path);
diff --git a/common/modules/options.jsm b/common/modules/options.jsm
index f3fefc98..98ad8a12 100644
--- a/common/modules/options.jsm
+++ b/common/modules/options.jsm
@@ -794,7 +794,7 @@ var Options = Module("options", {
                     opt.set(opt.globalValue, Option.SCOPE_GLOBAL, true);
             }, window);
 
-            services["dactyl:"].pages["options.dtd"] = function () [null,
+            modules.cache.register("options.dtd", function ()
                 util.makeDTD(
                     iter(([["option", o.name, "default"].join("."),
                            o.type === "string" ? o.defaultValue.replace(/'/g, "''") :
@@ -804,7 +804,13 @@ var Options = Module("options", {
 
                          ([["option", o.name, "type"].join("."), o.type] for (o in self)),
 
-                         config.dtd))];
+                         config.dtd)));
+        },
+
+        signals: {
+            "io.source": function ioSource(context, file, modTime) {
+                cache.flushEntry("options.dtd", modTime);
+            }
         },
 
         dactyl: dactyl,
diff --git a/common/modules/overlay.jsm b/common/modules/overlay.jsm
index e4e23911..14d29fea 100644
--- a/common/modules/overlay.jsm
+++ b/common/modules/overlay.jsm
@@ -371,6 +371,9 @@ var Overlay = Module("Overlay", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReferen
         };
     },
 
+    get activeModules() this.activeWindow && this.activeWindow.dactyl.modules,
+
+    get modules() this.windows.map(function (w) w.dactyl.modules),
 
     /**
      * The most recently active dactyl window.
diff --git a/common/modules/services.jsm b/common/modules/services.jsm
index 0364f492..30e7482a 100644
--- a/common/modules/services.jsm
+++ b/common/modules/services.jsm
@@ -106,8 +106,8 @@ var Services = Module("Services", {
         this.addClass("Xmlhttp",      "@mozilla.org/xmlextras/xmlhttprequest;1",   "nsIXMLHttpRequest", "open");
         this.addClass("XPathEvaluator", "@mozilla.org/dom/xpath-evaluator;1",      "nsIDOMXPathEvaluator");
         this.addClass("XMLDocument",  "@mozilla.org/xml/xml-document;1",           ["nsIDOMXMLDocument", "nsIDOMNodeSelector"]);
-        this.addClass("ZipReader",    "@mozilla.org/libjar/zip-reader;1",          "nsIZipReader", "open");
-        this.addClass("ZipWriter",    "@mozilla.org/zipwriter;1",                  "nsIZipWriter", "open");
+        this.addClass("ZipReader",    "@mozilla.org/libjar/zip-reader;1",          "nsIZipReader", "open", false);
+        this.addClass("ZipWriter",    "@mozilla.org/zipwriter;1",                  "nsIZipWriter", "open", false);
     },
     reinit: function () {},