diff --git a/src/wormhole/_rlcompleter.py b/src/wormhole/_rlcompleter.py
new file mode 100644
index 0000000..f72451c
--- /dev/null
+++ b/src/wormhole/_rlcompleter.py
@@ -0,0 +1,100 @@
+from __future__ import print_function, unicode_literals
+import six
+from attr import attrs, attrib
+from twisted.internet.defer import inlineCallbacks, returnValue
+from twisted.internet.threads import deferToThread, blockingCallFromThread
+
+@attrs
+class CodeInputter:
+    _input_helper = attrib()
+    _reactor = attrib()
+    def __attrs_post_init__(self):
+        self.used_completion = False
+        self._matches = None
+        self._committed_nameplate = None
+
+    def bcft(self, f, *a, **kw):
+        return blockingCallFromThread(self._reactor, f, *a, **kw)
+
+    def wrap_completer(self, text, state):
+        try:
+            return self.completer(text, state)
+        except Exception as e:
+            # completer exceptions are normally silently discarded, which
+            # makes debugging challenging
+            print("completer exception: %s" % e)
+            raise e
+
+    def completer(self, text, state):
+        self.used_completion = True
+        #if state == 0:
+        #    print("", file=sys.stderr)
+        #print("completer: '%s' %d '%d'" % (text, state,
+        #                                   readline.get_completion_type()),
+        #      file=sys.stderr)
+        #sys.stderr.flush()
+
+        if state > 0:
+            # just use the values we decided last time
+            if state >= len(self._matches):
+                return None
+            return self._matches[state]
+
+        if not self._committed_nameplate:
+            self.bcft(self._input_helper.refresh_nameplates)
+
+        # now figure out new matches
+        if not "-" in text:
+            completions = self.bcft(self._input_helper.get_nameplate_completions,
+                                    text)
+            # TODO: does rlcompleter want full strings, or the next suffix?
+            self._matches = sorted(completions)
+        else:
+            nameplate, words = text.split("-", 1)
+            if self._committed_nameplate:
+                if nameplate != self._committed_nameplate:
+                    # they deleted past the committment point: we can't use
+                    # this. For now, bail, but in the future let's find a
+                    # gentler way to encourage them to not do that.
+                    raise ValueError("nameplate (NN-) already entered, cannot go back")
+                # they've just committed to this nameplate
+                self.bcft(self._input_helper.choose_nameplate, nameplate)
+                self._committed_nameplate = nameplate
+            completions = self.bcft(self._input_helper.get_word_completions,
+                                    words)
+            self._matches = sorted(completions)
+
+        #print(" match: '%s'" % self._matches[state], file=sys.stderr)
+        #sys.stderr.flush()
+        return self._matches[state]
+
+def input_code_with_completion(prompt, input_helper, code_length):
+    try:
+        import readline
+        c = CodeInputter(input_helper)
+        if readline.__doc__ and "libedit" in readline.__doc__:
+            readline.parse_and_bind("bind ^I rl_complete")
+        else:
+            readline.parse_and_bind("tab: complete")
+        readline.set_completer(c.wrap_completer)
+        readline.set_completer_delims("")
+    except ImportError:
+        c = None
+    code = six.moves.input(prompt)
+    # Code is str(bytes) on py2, and str(unicode) on py3. We want unicode.
+    if isinstance(code, bytes):
+        code = code.decode("utf-8")
+    nameplate, words = code.split("-", 1)
+    input_helper.choose_words(words)
+    used_completion = c.used_completion if c else False
+    return (code, used_completion)
+
+@inlineCallbacks
+def rlcompleter_helper(prompt, input_helper, reactor):
+    def warn_readline():
+        pass
+    t = reactor.addSystemEventTrigger("before", "shutdown", warn_readline)
+    res = yield deferToThread(input_code_with_completion, prompt, input_helper)
+    (code, used_completion) = res
+    reactor.removeSystemEventTrigger(t)
+    returnValue(used_completion)