diff --git a/client/grpc-web-fake-transport/README.md b/client/grpc-web-fake-transport/README.md
index 5069b956..2950b8c8 100644
--- a/client/grpc-web-fake-transport/README.md
+++ b/client/grpc-web-fake-transport/README.md
@@ -3,6 +3,14 @@
 
 ## Usage
 
+`FakeTransportBuilder` builds a `Transport` that can be configured to send preset headers, messages, and trailers for testing.
+
+By default the `Transport` that `FakeTranportBuilder.build()` generates will trigger all of the specified response behaviours (`.withHeaders(metadata)`, `.withMessages([msgOne, msgTwo])`, `.withTrailers(metadata)`) when the client has finished sending. 
+
+This is usually the desired flow as all of the response behaviour is triggered only after the client has finished sending as would most commonly occur in production usage. 
+
+However, in the case of bi-directional or other complex usage it can be helpful to use `.withManualTrigger()` to disable automatic sending of messages or headers/trailers and trigger the sending manually using `sendHeaders()`, `sendMessages()` and `sendTrailers()`.
+
 ### With Service Stubs generated by ts-protoc-gen 
 ```typescript
 import { FakeTransportBuilder } from '@improbable-eng/grpc-web-fake-transport';
@@ -34,6 +42,30 @@ grpc.invoke(PingService.DoPing, {
 });
 ```
 
+### With `withManualTrigger()`
+```typescript
+import { grpc } from '@improbable-eng/grpc-web';
+import { FakeTransportBuilder } from '@improbable-eng/grpc-web-fake-transport';
+
+const fakeTransport = new FakeTransportBuilder()
+  .withManualTrigger()
+  .withHeaders(new grpc.Metadata({ headerKey: "value" }))
+  .withMessages([ new PingResponse() ])
+  .withTrailers(new grpc.Metadata({ trailerKey: "value" }))
+  .build();
+
+grpc.invoke(PingService.DoPing, {
+  host: "https://example.com",
+  transport: fakeTransport,
+  /* ... */
+});
+
+// Manually trigger the response behaviours
+fakeTransport.sendHeaders();
+fakeTransport.sendMessages();
+fakeTransport.sendTrailers();
+```
+
 Alternatively replace the Default Transport when initialising your tests:
 ```typescript
 import { grpc } from "@improbable-eng/grpc-web";
@@ -41,4 +73,4 @@ import { NodeHttpTransport } from "@improbable-eng/grpc-web-fake-transport";
 
 // Do this first, before you make any grpc requests!
 grpc.setDefaultTransport(fakeTransport);
-```  
\ No newline at end of file
+```  
diff --git a/client/grpc-web-fake-transport/src/index.spec.ts b/client/grpc-web-fake-transport/src/index.spec.ts
index a4b5e1ca..a8e102dd 100644
--- a/client/grpc-web-fake-transport/src/index.spec.ts
+++ b/client/grpc-web-fake-transport/src/index.spec.ts
@@ -115,7 +115,9 @@ describe("FakeTransportBuilder", () => {
         const expectedBytes = frameRequest(req);
 
         const transport = new FakeTransportBuilder()
-          .withMessageListener(messageSpy)
+          .withMessageListener(messageBytes => {
+            messageSpy(messageBytes);
+          })
           .build();
 
         doPingStreamRequest(transport, [ req ], () => {
@@ -227,7 +229,7 @@ describe("FakeTransportBuilder", () => {
   });
 
   describe("manual trigger", () => {
-    it("should allow the consumer to control the lifecycle of the server response", done => {
+    it("should allow the consumer to control the lifecycle of the server response", () => {
       const onHeadersSpy = jest.fn();
       const onMessageSpy = jest.fn();
       const onEndSpy = jest.fn();
@@ -258,30 +260,19 @@ describe("FakeTransportBuilder", () => {
 
       transport.sendHeaders();
 
-      // Note that we must defer the assertions as the grpc-web package detaches all callbacks, so they
-      // will not run immediately.
-      setTimeout(() => {
-        expect(onHeadersSpy).toHaveBeenCalled();
-        expect(onMessageSpy).not.toHaveBeenCalled();
-        expect(onEndSpy).not.toHaveBeenCalled();
-
-        transport.sendMessages();
-        setTimeout(() => {
-          expect(onHeadersSpy).toHaveBeenCalled();
-          expect(onMessageSpy).toHaveBeenCalled();
-          expect(onEndSpy).not.toHaveBeenCalled();
-
-          transport.sendTrailers();
-          setTimeout(() => {
-            expect(onHeadersSpy).toHaveBeenCalled();
-            expect(onMessageSpy).toHaveBeenCalled();
-            expect(onEndSpy).toHaveBeenCalled();
-
-            done();
-          }, 0);
-        }, 0);
-
-      }, 0);
+      expect(onHeadersSpy).toHaveBeenCalled();
+      expect(onMessageSpy).not.toHaveBeenCalled();
+      expect(onEndSpy).not.toHaveBeenCalled();
+
+      transport.sendMessages();
+      expect(onHeadersSpy).toHaveBeenCalled();
+      expect(onMessageSpy).toHaveBeenCalled();
+      expect(onEndSpy).not.toHaveBeenCalled();
+
+      transport.sendTrailers();
+      expect(onHeadersSpy).toHaveBeenCalled();
+      expect(onMessageSpy).toHaveBeenCalled();
+      expect(onEndSpy).toHaveBeenCalled();
     });
   });
 
@@ -352,4 +343,4 @@ describe("FakeTransportBuilder", () => {
     }
     client.finishSend();
   }
-});
\ No newline at end of file
+});
diff --git a/client/grpc-web-fake-transport/src/index.ts b/client/grpc-web-fake-transport/src/index.ts
index 1fcac86a..d41525e5 100644
--- a/client/grpc-web-fake-transport/src/index.ts
+++ b/client/grpc-web-fake-transport/src/index.ts
@@ -277,9 +277,6 @@ export class FakeTransportBuilder {
           if (mock.headersListener) {
             mock.headersListener(metadata);
           }
-          if (mock.autoTrigger) {
-            triggers.sendAll();
-          }
         },
         sendMessage: (msgBytes: ArrayBufferView) => {
           if (mock.messageListener) {
@@ -290,6 +287,9 @@ export class FakeTransportBuilder {
           if (mock.finishSendListener) {
             mock.finishSendListener();
           }
+          if (mock.autoTrigger) {
+            triggers.sendAll();
+          }
         },
         cancel: () => {
           if (mock.cancelListener) {
@@ -308,4 +308,4 @@ export interface TriggerableTransport extends grpc.TransportFactory {
   sendMessages(): boolean;
   sendTrailers(): boolean;
   sendAll(): void;
-}
\ No newline at end of file
+}
diff --git a/client/grpc-web/src/client.ts b/client/grpc-web/src/client.ts
index 15a54510..1f53e871 100644
--- a/client/grpc-web/src/client.ts
+++ b/client/grpc-web/src/client.ts
@@ -2,7 +2,6 @@ import {Metadata} from "./metadata";
 import {ChunkParser, Chunk, ChunkType} from "./ChunkParser";
 import {Code, httpStatusToCode} from "./Code";
 import {debug} from "./debug";
-import detach from "./detach";
 import {Transport, TransportFactory, makeDefaultTransport} from "./transports/Transport";
 import {MethodDefinition} from "./service";
 import {frameRequest} from "./util";
@@ -202,10 +201,14 @@ class GrpcClient<TRequest extends ProtobufMessage, TResponse extends ProtobufMes
     this.completed = true;
 
     this.onEndCallbacks.forEach(callback => {
-      detach(() => {
-        if (this.closed) return;
+      if (this.closed) return;
+      try {
         callback(code, message, trailers);
-      });
+      } catch (e) {
+        setTimeout(() => {
+          throw e;
+        })
+      }
     });
   }
 
@@ -213,9 +216,13 @@ class GrpcClient<TRequest extends ProtobufMessage, TResponse extends ProtobufMes
     this.props.debug && debug("rawOnHeaders", headers);
     if (this.completed) return;
     this.onHeadersCallbacks.forEach(callback => {
-      detach(() => {
+      try {
         callback(headers);
-      });
+      } catch (e) {
+        setTimeout(() => {
+          throw e;
+        })
+      }
     });
   }
 
@@ -224,10 +231,14 @@ class GrpcClient<TRequest extends ProtobufMessage, TResponse extends ProtobufMes
     if (this.completed) return;
     this.completed = true;
     this.onEndCallbacks.forEach(callback => {
-      detach(() => {
-        if (this.closed) return;
+      if (this.closed) return;
+      try {
         callback(code, msg, trailers);
-      });
+      } catch (e) {
+        setTimeout(() => {
+          throw e;
+        })
+      }
     });
   }
 
@@ -235,10 +246,14 @@ class GrpcClient<TRequest extends ProtobufMessage, TResponse extends ProtobufMes
     this.props.debug && debug("rawOnMessage", res.toObject());
     if (this.completed || this.closed) return;
     this.onMessageCallbacks.forEach(callback => {
-      detach(() => {
-        if (this.closed) return;
+      if (this.closed) return;
+      try {
         callback(res);
-      });
+      } catch (e) {
+        setTimeout(() => {
+          throw e;
+        })
+      }
     });
   }
 
diff --git a/client/grpc-web/src/detach.ts b/client/grpc-web/src/detach.ts
index 1513302d..ef6a5d04 100644
--- a/client/grpc-web/src/detach.ts
+++ b/client/grpc-web/src/detach.ts
@@ -1,43 +1,3 @@
-// awaitingExecution is null if there is no current timer
-let awaitingExecution: Array<() => void> | null = null;
-
-function runCallbacks() {
-  if (awaitingExecution) {
-    // Use a new reference to the awaitingExecution array to allow callbacks to add to the "new" awaitingExecution array
-    const thisCallbackSet = awaitingExecution;
-    awaitingExecution = null;
-    for (let i = 0; i < thisCallbackSet.length; i++) {
-      try {
-        thisCallbackSet[i]();
-      } catch (e) {
-        if (awaitingExecution === null) {
-          awaitingExecution = [];
-          setTimeout(() => {
-            runCallbacks();
-          }, 0);
-        }
-        // Add the remaining callbacks to the array so that they can be invoked on the next pass
-        for (let k = thisCallbackSet.length - 1; k > i; k--) {
-          awaitingExecution.unshift(thisCallbackSet[k]);
-        }
-        // rethrow the error
-        throw e;
-      }
-    }
-  }
-}
-
-// detach executes the callbacks in the order they are added with no context - this is used to avoid errors thrown
-// in user callbacks being caught by handlers such as fetch's catch. This function is necessary as setTimeout in
-// Safari is prone to switching the order of execution of setTimeout(0).
 export default function detach(cb: () => void) {
-  if (awaitingExecution !== null) {
-    // there is a timer running, add to the list and this function will be executed with that existing timer
-    awaitingExecution.push(cb);
-    return;
-  }
-  awaitingExecution = [cb];
-  setTimeout(() => {
-    runCallbacks();
-  }, 0);
+  cb();
 }
diff --git a/client/grpc-web/src/transports/http/fetch.ts b/client/grpc-web/src/transports/http/fetch.ts
index 29c76b0e..1dfc3e0b 100644
--- a/client/grpc-web/src/transports/http/fetch.ts
+++ b/client/grpc-web/src/transports/http/fetch.ts
@@ -1,7 +1,6 @@
 import {Metadata} from "../../metadata";
 import {Transport, TransportFactory, TransportOptions} from "../Transport";
 import {debug} from "../../debug";
-import detach from "../../detach";
 
 type Omit<T, K extends keyof T> = Pick<T, Exclude<keyof T, K>>
 export type FetchTransportInit = Omit<RequestInit, "headers" | "method" | "body" | "signal">;
@@ -44,14 +43,10 @@ class Fetch implements Transport {
     this.reader.read()
       .then((result: { done: boolean, value: Uint8Array }) => {
         if (result.done) {
-          detach(() => {
-            this.options.onEnd();
-          });
+          this.options.onEnd();
           return res;
         }
-        detach(() => {
-          this.options.onChunk(result.value);
-        });
+        this.options.onChunk(result.value);
         this.pump(this.reader, res);
         return;
       })
@@ -62,9 +57,7 @@ class Fetch implements Transport {
         }
         this.cancelled = true;
         this.options.debug && debug("Fetch.catch", err.message);
-        detach(() => {
-          this.options.onEnd(err);
-        });
+        this.options.onEnd(err);
       });
   }
 
@@ -77,9 +70,7 @@ class Fetch implements Transport {
       signal: this.controller && this.controller.signal
     }).then((res: Response) => {
       this.options.debug && debug("Fetch.response", res);
-      detach(() => {
-        this.options.onHeaders(new Metadata(res.headers as any), res.status);
-      });
+      this.options.onHeaders(new Metadata(res.headers as any), res.status);
       if (res.body) {
         this.pump(res.body.getReader(), res)
         return;
@@ -92,9 +83,7 @@ class Fetch implements Transport {
       }
       this.cancelled = true;
       this.options.debug && debug("Fetch.catch", err.message);
-      detach(() => {
-        this.options.onEnd(err);
-      });
+      this.options.onEnd(err);
     });
   }
 
diff --git a/client/grpc-web/src/transports/http/xhr.ts b/client/grpc-web/src/transports/http/xhr.ts
index 2f82a689..80756a96 100644
--- a/client/grpc-web/src/transports/http/xhr.ts
+++ b/client/grpc-web/src/transports/http/xhr.ts
@@ -1,7 +1,6 @@
 import {Metadata} from "../../metadata";
 import {Transport, TransportFactory, TransportOptions} from "../Transport";
 import {debug} from "../../debug";
-import detach from "../../detach";
 import {detectMozXHRSupport, detectXHROverrideMimeTypeSupport} from "./xhrUtil";
 
 export interface XhrTransportInit {
@@ -37,24 +36,18 @@ export class XHR implements Transport {
     const rawText = this.xhr.response.substr(this.index);
     this.index = this.xhr.response.length;
     const asArrayBuffer = stringToArrayBuffer(rawText);
-    detach(() => {
-      this.options.onChunk(asArrayBuffer);
-    });
+    this.options.onChunk(asArrayBuffer);
   }
 
   onLoadEvent() {
     this.options.debug && debug("XHR.onLoadEvent");
-    detach(() => {
-      this.options.onEnd();
-    });
+    this.options.onEnd();
   }
 
   onStateChange() {
     this.options.debug && debug("XHR.onStateChange", this.xhr.readyState);
     if (this.xhr.readyState === XMLHttpRequest.HEADERS_RECEIVED) {
-      detach(() => {
-        this.options.onHeaders(new Metadata(this.xhr.getAllResponseHeaders()), this.xhr.status);
-      });
+      this.options.onHeaders(new Metadata(this.xhr.getAllResponseHeaders()), this.xhr.status);
     }
   }
 
@@ -85,9 +78,7 @@ export class XHR implements Transport {
     xhr.addEventListener("loadend", this.onLoadEvent.bind(this));
     xhr.addEventListener("error", (err: ErrorEvent) => {
       this.options.debug && debug("XHR.error", err);
-      detach(() => {
-        this.options.onEnd(err.error);
-      });
+      this.options.onEnd(err.error);
     });
   }
 
@@ -114,9 +105,7 @@ export class MozChunkedArrayBufferXHR extends XHR {
   onProgressEvent() {
     const resp = this.xhr.response;
     this.options.debug && debug("MozXHR.onProgressEvent: ", new Uint8Array(resp));
-    detach(() => {
-      this.options.onChunk(new Uint8Array(resp));
-    });
+    this.options.onChunk(new Uint8Array(resp));
   }
 }
 
diff --git a/client/grpc-web/src/transports/websocket/websocket.ts b/client/grpc-web/src/transports/websocket/websocket.ts
index 8bb8b389..ff1c8306 100644
--- a/client/grpc-web/src/transports/websocket/websocket.ts
+++ b/client/grpc-web/src/transports/websocket/websocket.ts
@@ -1,7 +1,6 @@
 import {Metadata} from "../../metadata";
 import {Transport, TransportFactory, TransportOptions} from "../Transport";
 import {debug} from "../../debug";
-import detach from "../../detach";
 import {encodeASCII} from "../../ChunkParser";
 
 enum WebsocketSignal {
@@ -68,9 +67,7 @@ function websocketRequest(options: TransportOptions): Transport {
 
       ws.onclose = function (closeEvent) {
         options.debug && debug("websocketRequest.onclose", closeEvent);
-        detach(() => {
-          options.onEnd();
-        });
+        options.onEnd();
       };
 
       ws.onerror = function (error) {
@@ -78,17 +75,13 @@ function websocketRequest(options: TransportOptions): Transport {
       };
 
       ws.onmessage = function (e) {
-        detach(() => {
-          options.onChunk(new Uint8Array(e.data));
-        });
+        options.onChunk(new Uint8Array(e.data));
       };
 
     },
     cancel: () => {
       options.debug && debug("websocket.abort");
-      detach(() => {
-        ws.close();
-      });
+      ws.close();
     }
   };
 }
diff --git a/integration_test/ts/src/detach.spec.ts b/integration_test/ts/src/detach.spec.ts
deleted file mode 100644
index 2c3b4f75..00000000
--- a/integration_test/ts/src/detach.spec.ts
+++ /dev/null
@@ -1,131 +0,0 @@
-import {assert} from "chai";
-import detach from "../../../client/grpc-web/src/detach";
-import {UncaughtExceptionListener} from "./util";
-import { conditionallyRunTestSuite, SuiteEnum } from "../suiteUtils";
-
-conditionallyRunTestSuite(SuiteEnum.detach, () => {
-  describe("basic execution ordering", () => {
-    it("should invoke a function", (done) => {
-      detach(() => {
-        done();
-      });
-    });
-
-    it("should invoke multiple functions in the order they are added", (done) => {
-      let index = 0;
-      detach(() => {
-        assert.equal(index, 0);
-        index++;
-      });
-      detach(() => {
-        assert.equal(index, 1);
-        index++;
-      });
-      detach(() => {
-        assert.equal(index, 2);
-        index++;
-        done();
-      });
-    });
-
-    it("should invoke multiple functions in the order they are added after the current context", (done) => {
-      let index = 0;
-      detach(() => {
-        assert.equal(index, 5);
-        index++;
-      });
-      detach(() => {
-        assert.equal(index, 6);
-        index++;
-      });
-      detach(() => {
-        assert.equal(index, 7);
-        index++;
-        done();
-      });
-      index = 5; // This should be run before the first callback
-    });
-  });
-
-  describe("exception handling", () => {
-    let uncaughtHandler: UncaughtExceptionListener;
-    beforeEach(() => {
-      uncaughtHandler = new UncaughtExceptionListener();
-      uncaughtHandler.attach();
-    });
-
-    afterEach(() => {
-      uncaughtHandler.detach();
-    });
-
-    it("should invoke remaining function when exceptions are thrown", (done) => {
-      let index = 0;
-      detach(() => {
-        assert.equal(index, 0);
-        index++;
-      });
-      detach(() => {
-        assert.equal(index, 1);
-        index++;
-        throw new Error("Second callback threw error");
-      });
-      detach(() => {
-        assert.equal(index, 2);
-        index++;
-        throw new Error("Third callback threw error");
-      });
-      detach(() => {
-        uncaughtHandler.detach();
-        assert.equal(index, 3);
-        index++;
-        const exceptionsCaught = uncaughtHandler.getMessages();
-        assert.lengthOf(exceptionsCaught, 2);
-        assert.include(exceptionsCaught[0], "Second callback threw error");
-        assert.include(exceptionsCaught[1], "Third callback threw error");
-        done();
-      });
-    });
-
-    // This test is weakly-held. It is here to detect changes to execution ordering with other contexts, but detach
-    // should not be used in a manner that relies on this behaviour.
-    it("should invoke remaining function when exceptions are thrown", (done) => {
-      let index = 0;
-      detach(() => {
-        assert.equal(index, 0);
-        index++;
-      });
-      detach(() => {
-        assert.equal(index, 1);
-        index++;
-        throw new Error("Second callback threw error");
-      });
-      // setTimeout below will be called between the above and below functions
-      detach(() => {
-        assert.equal(index, 3);
-        index++;
-        setTimeout(() => {
-          assert.equal(index, 4);
-          index++;
-        }, 0);
-        throw new Error("Third callback threw error");
-      });
-      detach(() => {
-        uncaughtHandler.detach();
-        assert.equal(index, 5);
-        index++;
-        const exceptionsCaught = uncaughtHandler.getMessages();
-        assert.lengthOf(exceptionsCaught, 2);
-        assert.include(exceptionsCaught[0], "Second callback threw error");
-        assert.include(exceptionsCaught[1], "Third callback threw error");
-        done();
-      });
-
-      // This function will be called after the first exception is thrown. Throwing exceptions causes the subsequent
-      // callbacks to be run in a separate, subsequent timeout.
-      setTimeout(() => {
-        assert.equal(index, 2);
-        index++;
-      }, 0);
-    });
-  });
-});
\ No newline at end of file
diff --git a/integration_test/ts/src/spec.ts b/integration_test/ts/src/spec.ts
index b3efacc5..00f45a93 100644
--- a/integration_test/ts/src/spec.ts
+++ b/integration_test/ts/src/spec.ts
@@ -3,7 +3,6 @@ import "./client.websocket.spec";
 import "./invoke.spec";
 import "./unary.spec";
 import "./cancellation.spec";
-import "./detach.spec";
 import "./ChunkParser.spec";
 
-jasmine.DEFAULT_TIMEOUT_INTERVAL = 10000;
\ No newline at end of file
+jasmine.DEFAULT_TIMEOUT_INTERVAL = 10000;
diff --git a/integration_test/ts/suiteUtils.ts b/integration_test/ts/suiteUtils.ts
index 792830de..6339defd 100644
--- a/integration_test/ts/suiteUtils.ts
+++ b/integration_test/ts/suiteUtils.ts
@@ -5,7 +5,6 @@ export enum SuiteEnum {
   unary,
   ChunkParser,
   cancellation,
-  detach,
 }
 
 type enumMap = {[key: string]: number} & {[key: number]: string};