Saving a record as a CouchDB document does a HTTP POST request to the database and should read back the resulting JSON message that contains the ID for the newly-generated document. This used to be the case for Lift 2.2, but broke for the 2.3 release. The cause seems to be the DatabaseHelpers.handleUpdateResult method -- it expects a JObject containing JFields of JBool/JString values. Now the \ operator that is used returns the JBool/JString values directly which greatly simplifies the pattern matching code.

Here's the current (broken code):

def handleUpdateResult(original: JObject)(json: JValue): Box[JObject] = 
  for { 
    obj <- Full(json).asA[JObject] ?~ ("update result is not a JObject: " + 
json) 
    ok  <- Full(json \ "ok" 
).asA[JField].map(_.value).asA[JBool].filter(_.value) ?~ ("ok not present in 
reply or not true: "+json) 
    id  <- Full(json \ "id" ).asA[JField].map(_.value).asA[JString].map(_.s) 
   ?~ ("id not present or not a string: " + json) 
    rev <- Full(json \ "rev").asA[JField].map(_.value).asA[JString].map(_.s) 
   ?~ ("rev not present or not a string: " + json) 
  } yield updateIdAndRev(original, id, rev)

And here's the working version:

def handleUpdateResult(original: JObject)(json: JValue): Box[JObject] = {
  for {
    obj <- Full(json).asA[JObject] ?~ ("update result is not a JObject: " + json)
    ok  <- Full(json \ "ok" ).asA[JBool].filter(_.value) ?~ ("ok not present in reply or not true: "+json)
    id  <- Full(json \ "id" ).asA[JString].map(_.s)    ?~ ("id not present or not a string: " + json)
    rev <- Full(json \ "rev").asA[JString].map(_.s)    ?~ ("rev not present or not a string: " + json)
  } yield updateIdAndRev(original, id, rev)
}

Details, and the whole story on how I stumbled upon this are available in this mailing list thread. Here is a sample project demonstrating the problem and here is a branch that works around it by overriding the JSON parsing mechanism in the same way as described above. I hope this helps.