diff --git a/docs/protocol/v1/draft/extensibility.mdx b/docs/protocol/v1/draft/extensibility.mdx
index 31441013..8046050e 100644
--- a/docs/protocol/v1/draft/extensibility.mdx
+++ b/docs/protocol/v1/draft/extensibility.mdx
@@ -132,3 +132,7 @@ Implementations **SHOULD** use the `_meta` field in capability objects to advert
 ```
 
 This allows implementations to negotiate custom features during initialization without breaking compatibility with standard Clients and Agents.
+
+## Unrecognized Session Update Variants
+
+Every `session/update` notification carries a `sessionUpdate` field that identifies the variant. Future protocol versions may define new variants. Clients are encouraged to ignore variants they do not recognize rather than treating them as errors. The [`SessionUpdate`](/protocol/v1/draft/schema#sessionupdate) schema reference lists the variants defined in this version.
diff --git a/docs/protocol/v1/draft/prompt-turn.mdx b/docs/protocol/v1/draft/prompt-turn.mdx
index 3a5d3e30..ef314524 100644
--- a/docs/protocol/v1/draft/prompt-turn.mdx
+++ b/docs/protocol/v1/draft/prompt-turn.mdx
@@ -105,6 +105,13 @@ Upon receiving the prompt request, the Agent processes the user's message and se
 
 The Agent reports the model's output to the Client via `session/update` notifications. This may include the Agent's plan for accomplishing the task:
 
+<Note>
+  This page walks through the `session/update` variants most common in a prompt
+  turn. It is not the full set. See the
+  [`SessionUpdate`](/protocol/v1/draft/schema#sessionupdate) schema reference
+  for every variant defined in this version.
+</Note>
+
 ```json expandable
 {
   "jsonrpc": "2.0",
diff --git a/docs/protocol/v1/extensibility.mdx b/docs/protocol/v1/extensibility.mdx
index 31441013..3515b40e 100644
--- a/docs/protocol/v1/extensibility.mdx
+++ b/docs/protocol/v1/extensibility.mdx
@@ -132,3 +132,7 @@ Implementations **SHOULD** use the `_meta` field in capability objects to advert
 ```
 
 This allows implementations to negotiate custom features during initialization without breaking compatibility with standard Clients and Agents.
+
+## Unrecognized Session Update Variants
+
+Every `session/update` notification carries a `sessionUpdate` field that identifies the variant. Future protocol versions may define new variants. Clients are encouraged to ignore variants they do not recognize rather than treating them as errors. The [`SessionUpdate`](/protocol/v1/schema#sessionupdate) schema reference lists the variants defined in this version.
diff --git a/docs/protocol/v1/prompt-turn.mdx b/docs/protocol/v1/prompt-turn.mdx
index d459f55b..0fe5ba9e 100644
--- a/docs/protocol/v1/prompt-turn.mdx
+++ b/docs/protocol/v1/prompt-turn.mdx
@@ -105,6 +105,13 @@ Upon receiving the prompt request, the Agent processes the user's message and se
 
 The Agent reports the model's output to the Client via `session/update` notifications. This may include the Agent's plan for accomplishing the task:
 
+<Note>
+  This page walks through the `session/update` variants most common in a prompt
+  turn. It is not the full set. See the
+  [`SessionUpdate`](/protocol/v1/schema#sessionupdate) schema reference for
+  every variant defined in this version.
+</Note>
+
 ```json expandable
 {
   "jsonrpc": "2.0",