diff --git a/dsl-reference.md b/dsl-reference.md
index 4bef65cb..118776f4 100644
--- a/dsl-reference.md
+++ b/dsl-reference.md
@@ -2132,7 +2132,7 @@ An event object typically includes details such as the event type, source, times
 | Property | Type | Required | Description |
 |----------|:----:|:--------:|-------------|
 | id | `string` | `no` | Identifies the event. `source` + `id` is unique for each distinct event.<br>*Required when emitting an event using `emit.event.with`, generated by runtime implementations (e.g., UUID) at emission time.* |
-| source | `string` | `no` | An URI formatted string, or [runtime expression](dsl.md#runtime-expressions), that identifies the context in which an event happened. `source` + `id` is unique for each distinct event.<br>*Required when emitting an event using `emit.event.with`.* |
+| source | `string` | `no` | An URI formatted string, or [runtime expression](dsl.md#runtime-expressions), that identifies the context in which an event happened. `source` + `id` is unique for each distinct event.<br>*Required when emitting an event using `emit.event.with`, generated by runtime implementations (e.g., from the workflow identity `/{namespace}/{name}/{version}`) at emission time. When explicitly provided by the workflow author, the supplied value takes precedence over the auto-generated one.* |
 | type | `string` | `no` | Describes the type of event related to the originating occurrence.<br>*Required when emitting an event using `emit.event.with`.* |
 | time | `string` | `no` | A string, or [runtime expression](dsl.md#runtime-expressions), representing the timestamp of when the occurrence happened. |
 | subject | `string` | `no` | Describes the subject of the event in the context of the event producer. |
diff --git a/schema/workflow.yaml b/schema/workflow.yaml
index a443ed50..eaef7c38 100644
--- a/schema/workflow.yaml
+++ b/schema/workflow.yaml
@@ -671,7 +671,7 @@ $defs:
                   $ref: '#/$defs/eventProperties'
                   title: EmitEventWith
                   description: Defines the properties of event to emit.
-                  required: [ source, type ]
+                  required: [ type ]
               additionalProperties: true
           required: [ event ]
   forTask:
@@ -1483,7 +1483,7 @@ $defs:
         description: The event's unique identifier.
       source:
         title: EventSource
-        description: Identifies the context in which an event happened.
+        description: Identifies the context in which an event happened. If not explicitly provided, runtime implementations generate it at emission time (e.g., from the workflow identity). If explicitly provided by the workflow author, the supplied value takes precedence.
         oneOf:
           - $ref: '#/$defs/uriTemplate'
           - $ref: '#/$defs/runtimeExpression'