diff --git a/js/src/mux.js b/js/src/mux.js
index fd0e52a..70c274c 100644
--- a/js/src/mux.js
+++ b/js/src/mux.js
@@ -44,27 +44,43 @@ Mux.prototype.updateStream = function (pid, unclampedPatch) {
 	   deltaAggregate: deltaAggregate };
 };
 
+var atMetaEverything = Route.compilePattern(true, Patch.atMeta(Route.__));
+var atMetaBranchKeys = Immutable.List([Route.SOA, Patch.$AtMeta]);
+var onlyMeta = Immutable.Set.of("meta");
+
+function echoCancelledTrie(t) {
+  return Route.subtract(t, atMetaEverything, function (v1, v2) {
+    return v1.has("meta") ? onlyMeta : null;
+  });
+}
+
 function computeEvents(oldMux, newMux, updateStreamResult) {
   var actingPid = updateStreamResult.pid;
   var delta = updateStreamResult.delta;
   var deltaAggregate = updateStreamResult.deltaAggregate;
+  var deltaAggregateNoEcho = (actingPid === "meta")
+      ? delta // because echo-cancellation means that meta-SCNs are always new information
+      : new Patch.Patch(Route.triePruneBranch(deltaAggregate.added, atMetaBranchKeys),
+			Route.triePruneBranch(deltaAggregate.removed, atMetaBranchKeys));
   var oldRoutingTable = oldMux.routingTable;
   var newRoutingTable = newMux.routingTable;
-  var affectedPids = computeAffectedPids(oldRoutingTable, delta).add(actingPid).remove("meta");
+  var affectedPids =
+      computeAffectedPids(oldRoutingTable, deltaAggregateNoEcho).add(actingPid).remove("meta");
   return {
     eventMap: Immutable.Map().withMutations(function (result) {
       affectedPids.forEach(function (pid) {
 	var patchForPid;
 	if (pid === actingPid) {
-	  var part1 = new Patch.Patch(Patch.biasedIntersection(newRoutingTable, delta.added),
-				      Patch.biasedIntersection(oldRoutingTable, delta.removed));
-	  var part2 = new Patch.Patch(Patch.biasedIntersection(deltaAggregate.added,
+	  var part1 = new Patch.Patch(
+	    echoCancelledTrie(Patch.biasedIntersection(newRoutingTable, delta.added)),
+	    echoCancelledTrie(Patch.biasedIntersection(oldRoutingTable, delta.removed)));
+	  var part2 = new Patch.Patch(Patch.biasedIntersection(deltaAggregateNoEcho.added,
 							       newMux.interestsOf(pid)),
-				      Patch.biasedIntersection(deltaAggregate.removed,
+				      Patch.biasedIntersection(deltaAggregateNoEcho.removed,
 							       oldMux.interestsOf(pid)));
 	  patchForPid = part1.unsafeUnion(part2);
 	} else {
-	  patchForPid = updateStreamResult.deltaAggregate.viewFrom(oldMux.interestsOf(pid));
+	  patchForPid = deltaAggregateNoEcho.viewFrom(oldMux.interestsOf(pid));
 	}
 	if (patchForPid.isNonEmpty()) {
 	  result.set(pid, patchForPid);
diff --git a/js/test/test-syndicate.js b/js/test/test-syndicate.js
index b71f037..823a6b1 100644
--- a/js/test/test-syndicate.js
+++ b/js/test/test-syndicate.js
@@ -1,83 +1,135 @@
 "use strict";
 
 var expect = require('expect.js');
+var Immutable = require('immutable');
+
 var Syndicate = require('../src/main.js');
-
 var Network = Syndicate.Network;
+var Patch = Syndicate.Patch;
 
-// var sub = Syndicate.sub;
-// var pub = Syndicate.pub;
-// var __ = Syndicate.__;
-// var _$ = Syndicate._$;
+var __ = Syndicate.__;
+var _$ = Syndicate._$;
 
-// function configurationTrace(bootConfiguration) {
-//   var eventLog = [];
-//   function trace(item) {
-//     eventLog.push(item);
-//   }
+function configurationTrace(bootConfiguration) {
+  var eventLog = [];
+  function trace(item) {
+    eventLog.push(item);
+  }
 
-//   var G = new Syndicate.Ground(function () {
-//     bootConfiguration(trace);
-//   });
+  var G = new Syndicate.Ground(function () {
+    bootConfiguration(trace);
+  });
 
-//   while (G.step()) {
-//     // do nothing until G becomes inert
-//   }
+  while (G.step()) {
+    // do nothing until G becomes inert
+  }
 
-//   return eventLog;
-// }
+  return eventLog;
+}
 
-// function checkTrace(bootConfiguration, expected) {
-//   expect(configurationTrace(bootConfiguration)).to.eql(expected);
-// }
+function traceEvent(trace) {
+  return function(item) {
+    trace((item.type === "stateChange") ? item.patch.pretty() : item);
+  }
+}
 
-// describe("configurationTrace", function() {
-//   describe("with an inert configuration", function () {
-//     it("should yield an empty trace", function () {
-//       checkTrace(function (trace) {}, []);
-//     });
-//   });
+function checkTrace(bootConfiguration, expected) {
+  expect(configurationTrace(bootConfiguration)).to.eql(expected);
+}
 
-//   describe("with a single trace in an inert configuration", function () {
-//     it("should yield that trace", function () {
-//       checkTrace(function (trace) { trace(1) }, [1]);
-//     });
-//   });
+describe("configurationTrace", function() {
+  describe("with an inert configuration", function () {
+    it("should yield an empty trace", function () {
+      checkTrace(function (trace) {}, []);
+    });
+  });
 
-//   describe("with some traced communication", function () {
-//     it("should yield an appropriate trace", function () {
-//       checkTrace(function (trace) {
-// 	Network.spawn({
-// 	  boot: function () { return [sub(__)] },
-// 	  handleEvent: function (e) {
-// 	    trace(e);
-// 	  }
-// 	});
-// 	Network.send(123);
-// 	Network.send(234);
-//       }, [Syndicate.updateRoutes([]),
-// 	  Syndicate.sendMessage(123),
-// 	  Syndicate.sendMessage(234)]);
-//     });
-//   });
-// });
+  describe("with a single trace in an inert configuration", function () {
+    it("should yield that trace", function () {
+      checkTrace(function (trace) { trace(1) }, [1]);
+    });
+  });
 
-// describe("nonempty initial routes", function () {
-//   it("should be immediately signalled to the process", function () {
-//     // Specifically, no Syndicate.updateRoutes([]) first.
-//     checkTrace(function (trace) {
-//       Network.spawn({
-// 	boot: function () { return [pub(["A", __])] },
-// 	handleEvent: function (e) {
-// 	  Network.spawn({
-// 	    boot: function () { return [sub(["A", __], 0, 1)] },
-// 	    handleEvent: trace
-// 	  });
-// 	}
-//       });
-//     }, [Syndicate.updateRoutes([pub(["A", __]).label(1)])]);
-//   });
-// });
+  describe("with some traced communication", function () {
+    it("should yield an appropriate trace", function () {
+      checkTrace(function (trace) {
+	Network.spawn({
+	  boot: function () { return Syndicate.sub(__); },
+	  handleEvent: traceEvent(trace)
+	});
+	Network.send(123);
+	Network.send(234);
+      }, ['<<<<<<<< Removed:\n'+
+	  '::: nothing\n'+
+	  '======== Added:\n'+
+	  ' < $Observe ★ > >{[0]}\n'
+	  +'            >::: nothing\n'+
+	  '>>>>>>>>',
+	  Syndicate.message(123),
+	  Syndicate.message(234)]);
+    });
+  });
+});
+
+describe("nonempty initial routes", function () {
+  it("should be immediately signalled to the process", function () {
+    // Specifically, no Syndicate.updateRoutes([]) first.
+    checkTrace(function (trace) {
+      Network.spawn({
+	boot: function () { return Patch.assert(["A", __]); },
+	handleEvent: function (e) {}
+      });
+      Network.spawn({
+	boot: function () { return Patch.sub(["A", __]); },
+	handleEvent: traceEvent(trace)
+      });
+    }, ['<<<<<<<< Removed:\n'+
+	'::: nothing\n'+
+	'======== Added:\n'+
+	' < "A" ★ > >{[1]}\n'+
+	'>>>>>>>>']);
+  });
+});
+
+describe("nested actor with an echoey protocol", function () {
+  it("shouldn't see an echoed assertion", function () {
+    checkTrace(function (trace) {
+      Network.spawn(new Network(function () {
+	Network.spawn({
+	  boot: function () {
+	    Network.stateChange(Patch.retract("X", 1)); // happens after subs on next line!
+	    return Patch.sub("X", 1).andThen(Patch.assert("X", 1));
+	  },
+	  handleEvent: traceEvent(trace)
+	});
+      }));
+    }, ['<<<<<<<< Removed:\n'+
+	'::: nothing\n'+
+	'======== Added:\n'+
+	' < $AtMeta "X" > >{[0]}\n'+
+	'>>>>>>>>',
+	'<<<<<<<< Removed:\n'+
+	' < $AtMeta "X" > >{[0]}\n'+
+	'======== Added:\n'+
+	'::: nothing\n'+
+	'>>>>>>>>']);
+  })
+  it("shouldn't see an echoed message", function () {
+    checkTrace(function (trace) {
+      Network.spawn(new Network(function () {
+	Network.spawn({
+	  boot: function () {
+	    Network.send("X", 1); // happens after subs on next line!
+	    return Patch.sub("X", 1);
+	  },
+	  handleEvent: traceEvent(trace)
+	});
+      }));
+    }, [Syndicate.message(Patch.atMeta("X"))]);
+  });
+  it("shouldn't see an echoed assertion", function () {
+  });
+});
 
 // describe("actor with nonempty initial routes", function () {
 //   it("shouldn't see initial empty conversational context", function () {