diff --git a/src/PharoLink/PharoLinkErrorRequestSignal.class.st b/src/PharoLink/PharoLinkErrorRequestSignal.class.st
index c6d7819..1545c11 100644
--- a/src/PharoLink/PharoLinkErrorRequestSignal.class.st
+++ b/src/PharoLink/PharoLinkErrorRequestSignal.class.st
@@ -1,6 +1,6 @@
 Class {
 	#name : #PharoLinkErrorRequestSignal,
-	#superclass : #BeaconSignal,
+	#superclass : #PharoLinkSignal,
 	#instVars : [
 		'dictionary'
 	],
diff --git a/src/PharoLink/PharoLinkRegistry.class.st b/src/PharoLink/PharoLinkRegistry.class.st
index f0c1d6a..74babf0 100644
--- a/src/PharoLink/PharoLinkRegistry.class.st
+++ b/src/PharoLink/PharoLinkRegistry.class.st
@@ -3,7 +3,8 @@ Class {
 	#superclass : #Object,
 	#instVars : [
 		'idToObjMap',
-		'objToIdMap'
+		'objToIdMap',
+		'oldIds'
 	],
 	#classVars : [
 		'Default'
@@ -46,11 +47,15 @@ PharoLinkRegistry >> createNewObjId [
 { #category : #registry }
 PharoLinkRegistry >> deregister: anObjId [
 	"Remove the supplied id"
-	| object |
+	| object olds |
 
-	object := idToObjMap at: anObjId ifAbsent: [ ^ nil ].
+	olds := oldIds at: anObjId ifAbsentPut: [ OrderedCollection new ].
+	object := idToObjMap at: anObjId ifAbsent: 
+		[ olds add: DateAndTime now -> #missing.
+		^ nil ].
 	idToObjMap removeKey: anObjId.
 	objToIdMap removeKey: object.
+	olds add: DateAndTime now -> object class name.
 	^ nil.
 ]
 
@@ -67,6 +72,7 @@ PharoLinkRegistry >> initialize [
 	super initialize.
 	idToObjMap := Dictionary new.
 	objToIdMap := Dictionary new.
+	oldIds := Dictionary new.
 ]
 
 { #category : #registry }
@@ -135,7 +141,9 @@ PharoLinkRegistry >> register: anObject withId: newObjId [
 PharoLinkRegistry >> resolve: objId [
 	"Answer the object with the supplied id"
 
-	^ idToObjMap 
-		at: objId
-		ifAbsent: [ PharoLinkRegistryUnknownObjectError signalId: objId ]
+	^ idToObjMap at: objId ifAbsent: 
+		[ PharoLinkRegistryUnknownIdSignal new
+			unknownId: objId;
+			isOld: (oldIds includes: objId).
+		PharoLinkRegistryUnknownObjectError signalId: objId ]
 ]
diff --git a/src/PharoLink/PharoLinkRegistryDifferentIdError.class.st b/src/PharoLink/PharoLinkRegistryDifferentIdError.class.st
index 2f0eaf2..8a0a2d3 100644
--- a/src/PharoLink/PharoLinkRegistryDifferentIdError.class.st
+++ b/src/PharoLink/PharoLinkRegistryDifferentIdError.class.st
@@ -20,21 +20,21 @@ PharoLinkRegistryDifferentIdError class >> signalId: objId object: anObject [
 ]
 
 { #category : #accessing }
-PharoLinkRegistryDifferentIdError >> object [
-	^ object
+PharoLinkRegistryDifferentIdError >> objId [
+	^ objId
 ]
 
 { #category : #accessing }
-PharoLinkRegistryDifferentIdError >> object: anObject [
-	object := anObject
+PharoLinkRegistryDifferentIdError >> objId: anObject [
+	objId := anObject
 ]
 
 { #category : #accessing }
-PharoLinkRegistryDifferentIdError >> objId [
-	^ objId
+PharoLinkRegistryDifferentIdError >> object [
+	^ object
 ]
 
 { #category : #accessing }
-PharoLinkRegistryDifferentIdError >> objId: anObject [
-	objId := anObject
+PharoLinkRegistryDifferentIdError >> object: anObject [
+	object := anObject
 ]
diff --git a/src/PharoLink/PharoLinkRegistryUnknownIdSignal.class.st b/src/PharoLink/PharoLinkRegistryUnknownIdSignal.class.st
new file mode 100644
index 0000000..36b29f8
--- /dev/null
+++ b/src/PharoLink/PharoLinkRegistryUnknownIdSignal.class.st
@@ -0,0 +1,29 @@
+Class {
+	#name : #PharoLinkRegistryUnknownIdSignal,
+	#superclass : #PharoLinkServerSignal,
+	#instVars : [
+		'unknownId',
+		'isOld'
+	],
+	#category : #'PharoLink-Registry'
+}
+
+{ #category : #accessing }
+PharoLinkRegistryUnknownIdSignal >> isOld [
+	^ isOld
+]
+
+{ #category : #accessing }
+PharoLinkRegistryUnknownIdSignal >> isOld: anObject [
+	isOld := anObject
+]
+
+{ #category : #accessing }
+PharoLinkRegistryUnknownIdSignal >> unknownId [
+	^ unknownId
+]
+
+{ #category : #accessing }
+PharoLinkRegistryUnknownIdSignal >> unknownId: anObject [
+	unknownId := anObject
+]
diff --git a/src/PharoLink/PharoLinkServerConnection.class.st b/src/PharoLink/PharoLinkServerConnection.class.st
index 20e8c2c..5bc59bd 100644
--- a/src/PharoLink/PharoLinkServerConnection.class.st
+++ b/src/PharoLink/PharoLinkServerConnection.class.st
@@ -45,6 +45,28 @@ PharoLinkServerConnection >> globals [
 	^ server globals
 ]
 
+{ #category : #private }
+PharoLinkServerConnection >> handlEnqueue: aDictionary [
+	"Process the supplied statements"
+	| command bindings |
+
+	bindings := Dictionary new.
+	(aDictionary at: #bindings) keysAndValuesDo: [ :key :value |
+		bindings
+			at: key asSymbol
+			put: (self deserialize: value) ].
+	command := PharoLinkEvalCommand
+		           source: (aDictionary at: #statements)
+		           bindings: bindings
+		           id: (aDictionary at: #commandId).
+	command connection: self.
+	processes add: ([ 
+		 PharoLinkServerCurrentConnection
+			 value: self
+			 during: [ command execute: self globals ] ] forkAt:
+			 Processor userSchedulingPriority)
+]
+
 { #category : #'error handling' }
 PharoLinkServerConnection >> handleError: aDictionary [
 
@@ -106,28 +128,6 @@ PharoLinkServerConnection >> handleNextRequestSafely [
 			do: [ :ex | self notifyError: ex in: request ]
 ]
 
-{ #category : #private }
-PharoLinkServerConnection >> handlEnqueue: aDictionary [
-	"Process the supplied statements"
-	| command bindings |
-
-	bindings := Dictionary new.
-	(aDictionary at: #bindings) keysAndValuesDo: [ :key :value |
-		bindings
-			at: key asSymbol
-			put: (self deserialize: value) ].
-	command := PharoLinkEvalCommand
-		           source: (aDictionary at: #statements)
-		           bindings: bindings
-		           id: (aDictionary at: #commandId).
-	command connection: self.
-	processes add: ([ 
-		 PharoLinkServerCurrentConnection
-			 value: self
-			 during: [ command execute: self globals ] ] forkAt:
-			 Processor userSchedulingPriority)
-]
-
 { #category : #public }
 PharoLinkServerConnection >> handleRequest: aDictionary [
 	| type syncId registryEntry |
diff --git a/src/PharoLink/PharoLinkServerSignal.class.st b/src/PharoLink/PharoLinkServerSignal.class.st
new file mode 100644
index 0000000..bc18f03
--- /dev/null
+++ b/src/PharoLink/PharoLinkServerSignal.class.st
@@ -0,0 +1,5 @@
+Class {
+	#name : #PharoLinkServerSignal,
+	#superclass : #PharoLinkSignal,
+	#category : #'PharoLink-Signals'
+}
diff --git a/src/PharoLink/PharoLinkTestCaseEndAnnouncement.class.st b/src/PharoLink/PharoLinkTestCaseEndAnnouncement.class.st
index e7c8291..70e364a 100644
--- a/src/PharoLink/PharoLinkTestCaseEndAnnouncement.class.st
+++ b/src/PharoLink/PharoLinkTestCaseEndAnnouncement.class.st
@@ -61,6 +61,12 @@ PharoLinkTestCaseEndAnnouncement class >> testCase: aTestCase startTimestamp: aD
 		yourself
 ]
 
+{ #category : #adding }
+PharoLinkTestCaseEndAnnouncement >> addToTestResult: aTestResult [
+
+	self subclassResponsibility
+]
+
 { #category : #accessing }
 PharoLinkTestCaseEndAnnouncement >> additionalProperties [
 	^ additionalProperties
@@ -71,12 +77,6 @@ PharoLinkTestCaseEndAnnouncement >> additionalProperties: aDictionary [
 	^ additionalProperties := aDictionary
 ]
 
-{ #category : #adding }
-PharoLinkTestCaseEndAnnouncement >> addToTestResult: aTestResult [
-
-	self subclassResponsibility
-]
-
 { #category : #accessing }
 PharoLinkTestCaseEndAnnouncement >> asGtExampleResult [
 	"Answer the receiver wrapped in the appropriate GtExampleResultX class."
diff --git a/src/PharoLink/PharoLinkTraceGroup.class.st b/src/PharoLink/PharoLinkTraceGroup.class.st
index d1d59ef..e89e14e 100644
--- a/src/PharoLink/PharoLinkTraceGroup.class.st
+++ b/src/PharoLink/PharoLinkTraceGroup.class.st
@@ -31,6 +31,14 @@ PharoLinkTraceGroup >> populateTree [
 	self traces do: [ :trace | self addToTreeTrace: trace ]
 ]
 
+{ #category : #initialization }
+PharoLinkTraceGroup >> traceStrings: aCollection [
+
+	self traces: (aCollection collect: [ :string |
+		PharoLinkTrace new traceString: string ]).
+
+]
+
 { #category : #accessing }
 PharoLinkTraceGroup >> traces [
 
@@ -43,11 +51,3 @@ PharoLinkTraceGroup >> traces: aCollection [
 	traces := aCollection.
 	self populateTree.
 ]
-
-{ #category : #initialization }
-PharoLinkTraceGroup >> traceStrings: aCollection [
-
-	self traces: (aCollection collect: [ :string |
-		PharoLinkTrace new traceString: string ]).
-
-]
diff --git a/src/PharoLink/TGtPharoLinkPlayground.trait.st b/src/PharoLink/TGtPharoLinkPlayground.trait.st
index 8bc73e7..56be532 100644
--- a/src/PharoLink/TGtPharoLinkPlayground.trait.st
+++ b/src/PharoLink/TGtPharoLinkPlayground.trait.st
@@ -77,13 +77,6 @@ TGtPharoLinkPlayground >> gtPlaygroundText [
 	^ self gtPlaygroundString asRopedText attributesBuilder
 ]
 
-{ #category : #'ui - accessing' }
-TGtPharoLinkPlayground >> gtPlaygroundXdocStore [
-	"Answer the XDoc store for the receiver."
-
-	^ XdKeyDocumentStore forKey: self gtPlaygroundXDocStoreKey
-]
-
 { #category : #'ui - accessing' }
 TGtPharoLinkPlayground >> gtPlaygroundXDocStoreKey [
 	"Answer the key to be used for storing documents.
@@ -91,3 +84,10 @@ TGtPharoLinkPlayground >> gtPlaygroundXDocStoreKey [
 
 	^ self class name
 ]
+
+{ #category : #'ui - accessing' }
+TGtPharoLinkPlayground >> gtPlaygroundXdocStore [
+	"Answer the XDoc store for the receiver."
+
+	^ XdKeyDocumentStore forKey: self gtPlaygroundXDocStoreKey
+]