feat(unstable-v2): add cancelled variant to tool call and plan item statuses

agent-client-protocol-schema/src/v2/conversion.rs

@@ -1603,6 +1603,9 @@ impl TryToV1 for super::PlanEntryStatus {
             Self::Pending => crate::v1::PlanEntryStatus::Pending,
             Self::InProgress => crate::v1::PlanEntryStatus::InProgress,
             Self::Completed => crate::v1::PlanEntryStatus::Completed,
+            Self::Cancelled => {
+                return Err(unknown_v2_enum_variant("PlanEntryStatus", "cancelled"));
+            }
             Self::Other(value) => return Err(unknown_v2_enum_variant("PlanEntryStatus", &value)),
         })
     }
@@ -3189,6 +3192,9 @@ impl TryToV1 for super::ToolCallStatus {
             Self::InProgress => crate::v1::ToolCallStatus::InProgress,
             Self::Completed => crate::v1::ToolCallStatus::Completed,
             Self::Failed => crate::v1::ToolCallStatus::Failed,
+            Self::Cancelled => {
+                return Err(unknown_v2_enum_variant("ToolCallStatus", "cancelled"));
+            }
             Self::Other(value) => return Err(unknown_v2_enum_variant("ToolCallStatus", &value)),
         })
     }
@@ -10648,6 +10654,18 @@ mod tests {
         );
     }
 
+    #[test]
+    fn v2_cancelled_statuses_do_not_convert_to_v1() {
+        assert_v2_to_v1_error(
+            v2::ToolCallStatus::Cancelled,
+            "v2 ToolCallStatus variant `cancelled` cannot be represented in v1",
+        );
+        assert_v2_to_v1_error(
+            v2::PlanEntryStatus::Cancelled,
+            "v2 PlanEntryStatus variant `cancelled` cannot be represented in v1",
+        );
+    }
+
     #[test]
     fn v2_collection_conversion_fails_on_unrepresentable_items() {
         let response = v2::InitializeResponse::new(

agent-client-protocol-schema/src/v2/plan.rs

@@ -514,6 +514,8 @@ pub enum PlanEntryStatus {
     InProgress,
     /// The task has been successfully completed.
     Completed,
+    /// The task was cancelled before it completed.
+    Cancelled,
     /// Custom or future plan entry status.
     ///
     /// Values beginning with `_` are reserved for implementation-specific
@@ -541,6 +543,13 @@ mod tests {
         assert_eq!(serde_json::to_value(&status).unwrap(), "blocked");
     }
 
+    #[test]
+    fn plan_entry_status_recognizes_cancelled_variant() {
+        let status: PlanEntryStatus = serde_json::from_str("\"cancelled\"").unwrap();
+        assert_eq!(status, PlanEntryStatus::Cancelled);
+        assert_eq!(serde_json::to_value(&status).unwrap(), "cancelled");
+    }
+
     #[test]
     fn plan_update_content_preserves_unknown_variant() {
         let content: PlanUpdateContent = serde_json::from_value(serde_json::json!({

agent-client-protocol-schema/src/v2/tool_call.rs

@@ -330,6 +330,8 @@ pub enum ToolCallStatus {
     Completed,
     /// The tool call failed with an error.
     Failed,
+    /// The tool call was cancelled before it completed.
+    Cancelled,
     /// Custom or future tool call status.
     ///
     /// Values beginning with `_` are reserved for implementation-specific
@@ -1244,6 +1246,13 @@ mod tests {
         assert_eq!(serde_json::to_value(&status).unwrap(), "deferred");
     }
 
+    #[test]
+    fn tool_call_status_recognizes_cancelled_variant() {
+        let status: ToolCallStatus = serde_json::from_str("\"cancelled\"").unwrap();
+        assert_eq!(status, ToolCallStatus::Cancelled);
+        assert_eq!(serde_json::to_value(&status).unwrap(), "cancelled");
+    }
+
     #[test]
     fn tool_call_content_preserves_unknown_variant() {
         let content: ToolCallContent = serde_json::from_value(serde_json::json!({

docs/protocol/v2/agent-plan.mdx

@@ -95,6 +95,7 @@ Custom or future priority values can be used for display hints. Custom prioritie
 - `pending`
 - `in_progress`
 - `completed`
+- `cancelled`
 
 Custom or future status values can be used when Clients can preserve or display a generic plan-entry state. Custom statuses **MUST** begin with `_`; unknown non-underscore statuses are reserved for future ACP variants.
 

docs/protocol/v2/draft/agent-plan.mdx

@@ -161,6 +161,7 @@ Custom or future priority values can be used for display hints. Custom prioritie
 - `pending`
 - `in_progress`
 - `completed`
+- `cancelled`
 
 Custom or future status values can be used when Clients can preserve or display a generic plan-entry state. Custom statuses **MUST** begin with `_`; unknown non-underscore statuses are reserved for future ACP variants.
 

docs/protocol/v2/draft/schema.mdx

@@ -6482,6 +6482,10 @@ See protocol docs: [Plan Entries](https://agentclientprotocol.com/protocol/v2/dr
   The task has been successfully completed.
 </ResponseField>
 
+<ResponseField name="cancelled" type="string">
+  The task was cancelled before it completed.
+</ResponseField>
+
 <ResponseField name="other" type="string">
 Custom or future plan entry status.
 
@@ -9225,6 +9229,10 @@ See protocol docs: [Status](https://agentclientprotocol.com/protocol/v2/draft/to
   The tool call failed with an error.
 </ResponseField>
 
+<ResponseField name="cancelled" type="string">
+  The tool call was cancelled before it completed.
+</ResponseField>
+
 <ResponseField name="other" type="string">
 Custom or future tool call status.
 

docs/protocol/v2/draft/tool-calls.mdx

@@ -339,6 +339,10 @@ Tool calls progress through different statuses during their lifecycle:
 
 <ResponseField name="failed">The tool call failed with an error</ResponseField>
 
+<ResponseField name="cancelled">
+  The tool call was cancelled before it completed
+</ResponseField>
+
 Custom or future status values can be used when Clients can display a generic progress state. Custom status values **MUST** begin with `_`; unknown non-underscore statuses are reserved for future ACP variants.
 
 ## Content

docs/protocol/v2/migration.mdx

@@ -348,7 +348,7 @@ v1 had `tool_call` (create) and `tool_call_update` (modify). In practice the spl
 }
 ```
 
-The patch semantics are the same three-state model as messages: omitted fields stay unchanged, `null` explicitly clears a field, and concrete values replace. Array fields such as `content` and `locations` are replaced wholesale when present. The field set (`title`, `kind`, `status`, `content`, `locations`, `rawInput`, `rawOutput`) and the `kind`/`status` values are unchanged from v1, though the enums are now extensible.
+The patch semantics are the same three-state model as messages: omitted fields stay unchanged, `null` explicitly clears a field, and concrete values replace. Array fields such as `content` and `locations` are replaced wholesale when present. The field set (`title`, `kind`, `status`, `content`, `locations`, `rawInput`, `rawOutput`) and `kind` values are unchanged from v1. The `status` enum adds `cancelled`, and both enums are now extensible.
 
 ### Streaming tool-call content
 
@@ -550,7 +550,7 @@ The v1 `plan` update was a flat entries list with no identity and no room to gro
 
 </CodeGroup>
 
-Stable v2 defines the `items` plan type. The entry shape (`content`, `priority`, `status`, all required) is unchanged from v1, and entry priorities and statuses are now extensible enums. Each `plan_update` for a given `planId` replaces that plan's entries, and the `planId` allows multiple plans per session and future plan content types (such as markdown or file-backed plans, which remain unstable) without another breaking change.
+Stable v2 defines the `items` plan type. The entry shape (`content`, `priority`, `status`, all required) is unchanged from v1. Entry priorities and statuses are now extensible enums, and `status` adds `cancelled`. Each `plan_update` for a given `planId` replaces that plan's entries, and the `planId` allows multiple plans per session and future plan content types (such as markdown or file-backed plans, which remain unstable) without another breaking change.
 
 ## Session setup and lifecycle
 

docs/protocol/v2/schema.mdx

@@ -2846,6 +2846,10 @@ See protocol docs: [Plan Entries](https://agentclientprotocol.com/protocol/v2/ag
   The task has been successfully completed.
 </ResponseField>
 
+<ResponseField name="cancelled" type="string">
+  The task was cancelled before it completed.
+</ResponseField>
+
 <ResponseField name="other" type="string">
 Custom or future plan entry status.
 
@@ -5010,6 +5014,10 @@ See protocol docs: [Status](https://agentclientprotocol.com/protocol/v2/tool-cal
   The tool call failed with an error.
 </ResponseField>
 
+<ResponseField name="cancelled" type="string">
+  The tool call was cancelled before it completed.
+</ResponseField>
+
 <ResponseField name="other" type="string">
 Custom or future tool call status.
 

docs/protocol/v2/tool-calls.mdx

@@ -339,6 +339,10 @@ Tool calls progress through different statuses during their lifecycle:
 
 <ResponseField name="failed">The tool call failed with an error</ResponseField>
 
+<ResponseField name="cancelled">
+  The tool call was cancelled before it completed
+</ResponseField>
+
 Custom or future status values can be used when Clients can display a generic progress state. Custom status values **MUST** begin with `_`; unknown non-underscore statuses are reserved for future ACP variants.
 
 ## Content

docs/rfds/v2/plan-variants.mdx

@@ -64,7 +64,7 @@ The stable v2 `plan_update` shape does not require a capability. The unstable pl
 
 When converting a v1 single-plan update to v2, implementations should use the item-based `plan_update` shape with a stable synthetic plan ID of `main`.
 
-When converting v2 back to a v1 surface that does not support unstable plan operations, an item-based `plan_update` can be represented as the old v1 `plan` update by dropping the plan ID. Other plan content variants cannot be represented without the unstable v1 plan operations surface.
+When converting v2 back to a v1 surface that does not support unstable plan operations, an item-based `plan_update` whose entries use v1-representable priorities and statuses can be represented as the old v1 `plan` update by dropping the plan ID. Other plan content variants cannot be represented without the unstable v1 plan operations surface.
 
 ## Shiny future
 

docs/rfds/v2/tool-call-updates.mdx

@@ -94,7 +94,7 @@ There is a single way to update a tool call, removing lots of confusion from how
 
 When converting v1 to v2, both v1 `tool_call` and v1 `tool_call_update` should map to v2 `tool_call_update`.
 
-When converting v2 back to v1, adapters can represent a v2 update as a v1 `ToolCallUpdate`. This is lossy for some explicit clear operations because v1 update fields cannot represent every distinction between omitted and `null`. Collection clears can be represented as empty arrays, but scalar/raw-field clears may have to be omitted when targeting v1. This will be a best-effort conversion.
+When converting v2 back to v1, adapters can represent compatible v2 updates as a v1 `ToolCallUpdate`. Conversion is also lossy for some explicit clear operations because v1 update fields cannot represent every distinction between omitted and `null`. Collection clears can be represented as empty arrays, but scalar/raw-field clears may have to be omitted when targeting v1. This will be a best-effort conversion.
 
 `tool_call_content_chunk` cannot be represented by the stateless v2-to-v1 conversion helper because v1 tool-call content updates replace the whole content array rather than appending one item. A stateful bridge can choose to accumulate chunks and emit replacement arrays to v1 clients.
 

schema/v2/schema.json

@@ -816,6 +816,11 @@
           "type": "string",
           "const": "failed"
         },
+        {
+          "description": "The tool call was cancelled before it completed.",
+          "type": "string",
+          "const": "cancelled"
+        },
         {
           "title": "other",
           "description": "Custom or future tool call status.\n\nValues beginning with `_` are reserved for implementation-specific\nextensions. Unknown values that do not begin with `_` are reserved for\nfuture ACP variants.",
@@ -4390,6 +4395,11 @@
           "type": "string",
           "const": "completed"
         },
+        {
+          "description": "The task was cancelled before it completed.",
+          "type": "string",
+          "const": "cancelled"
+        },
         {
           "title": "other",
           "description": "Custom or future plan entry status.\n\nValues beginning with `_` are reserved for implementation-specific\nextensions. Unknown values that do not begin with `_` are reserved for\nfuture ACP variants.",

schema/v2/schema.unstable.json

@@ -960,6 +960,11 @@
           "type": "string",
           "const": "failed"
         },
+        {
+          "description": "The tool call was cancelled before it completed.",
+          "type": "string",
+          "const": "cancelled"
+        },
         {
           "title": "other",
           "description": "Custom or future tool call status.\n\nValues beginning with `_` are reserved for implementation-specific\nextensions. Unknown values that do not begin with `_` are reserved for\nfuture ACP variants.",
@@ -6991,6 +6996,11 @@
           "type": "string",
           "const": "completed"
         },
+        {
+          "description": "The task was cancelled before it completed.",
+          "type": "string",
+          "const": "cancelled"
+        },
         {
           "title": "other",
           "description": "Custom or future plan entry status.\n\nValues beginning with `_` are reserved for implementation-specific\nextensions. Unknown values that do not begin with `_` are reserved for\nfuture ACP variants.",