diff --git a/CHANGELOG.md b/CHANGELOG.md
index b4bb82a8..26ad8832 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -38,8 +38,11 @@ Spec version: `0.3.0`
 - Removed the `additions`, `deletions`, and `files` fields from
   `ChangesetSummary`. Aggregate counts now live on `SessionSummary.changes`;
   per-changeset views derive their own totals from `ChangesetState.files`.
-- Renamed the `ChangesetSummary` interface to `Changeset` (catalogue entry
-  on `SessionSummary.changesets`). The on-the-wire shape is unchanged.
+- Moved the `changesets` catalogue from `SessionSummary` to
+  `SessionState`. The `session/changesetsChanged` action now updates
+  `state.changesets` directly instead of `state.summary.changesets`.
+- Renamed the `ChangesetSummary` interface to `Changeset`. The
+  on-the-wire shape is unchanged.
 - Renamed the `UserMessage` type to `Message` and surfaced it consistently
   across turn state (`Turn.message`, `ActiveTurn.message`, `PendingMessage.message`)
   and the actions that carry it (`session/turnStarted`,
diff --git a/clients/go/CHANGELOG.md b/clients/go/CHANGELOG.md
index c9fd35ad..23fd26d1 100644
--- a/clients/go/CHANGELOG.md
+++ b/clients/go/CHANGELOG.md
@@ -25,7 +25,8 @@ tag whose matching `## [X.Y.Z]` heading is missing from this file.
 
 ### Changed
 
-- Renamed the `ChangesetSummary` type to `Changeset` (catalogue entry on `SessionSummary.changesets`). The on-the-wire shape is unchanged.
+- Renamed the `ChangesetSummary` type to `Changeset`. The on-the-wire shape is unchanged.
+- Moved the `changesets` catalogue from `SessionSummary` to `SessionState`. The `session/changesetsChanged` action now updates `state.changesets` directly instead of `state.summary.changesets`.
 
 ### Removed
 
diff --git a/clients/go/ahp/reducers.go b/clients/go/ahp/reducers.go
index e081790c..6f6c4eb4 100644
--- a/clients/go/ahp/reducers.go
+++ b/clients/go/ahp/reducers.go
@@ -499,7 +499,11 @@ func ApplyActionToSession(state *ahptypes.SessionState, action ahptypes.StateAct
 		state.Summary.Activity = a.Activity
 		return ReduceOutcomeApplied
 	case *ahptypes.SessionChangesetsChangedAction:
-		state.Summary.Changesets = append([]ahptypes.Changeset(nil), a.Changesets...)
+		if a.Changesets == nil {
+			state.Changesets = nil
+		} else {
+			state.Changesets = append([]ahptypes.Changeset(nil), a.Changesets...)
+		}
 		return ReduceOutcomeApplied
 	case *ahptypes.SessionConfigChangedAction:
 		if state.Config == nil {
diff --git a/clients/go/ahptypes/actions.generated.go b/clients/go/ahptypes/actions.generated.go
index 0f13bda5..452aec88 100644
--- a/clients/go/ahptypes/actions.generated.go
+++ b/clients/go/ahptypes/actions.generated.go
@@ -443,8 +443,9 @@ type SessionActivityChangedAction struct {
 
 // The {@link Changeset | catalogue of changesets} the agent host
 // advertises for this session changed. Replaces
-// `state.summary.changesets` entirely (full-replacement semantics) — set
-// to `undefined` to clear the catalogue.
+// {@link SessionState.changesets | `state.changesets`} entirely
+// (full-replacement semantics) — set to `undefined` to clear the
+// catalogue.
 //
 // Producers dispatch this whenever entries are added or removed. The
 // fan-out happens through this action so observers see catalogue
diff --git a/clients/go/ahptypes/notifications.generated.go b/clients/go/ahptypes/notifications.generated.go
index e7b96979..3d37cdc7 100644
--- a/clients/go/ahptypes/notifications.generated.go
+++ b/clients/go/ahptypes/notifications.generated.go
@@ -70,8 +70,7 @@ type SessionRemovedParams struct {
 //     {@link SessionSummary | `SessionSummary`} changes for a session the
 //     server has surfaced via `listSessions()` or `root/sessionAdded`.
 //     Servers MAY coalesce or debounce updates for noisy fields (for example,
-//     `modifiedAt` bumps while a turn is streaming, or rapidly changing
-//     `changesets`) at their discretion.
+//     `modifiedAt` bumps while a turn is streaming) at their discretion.
 //   - Clients that have no cached entry for `session` MAY ignore the
 //     notification; it is not a substitute for `root/sessionAdded`.
 type SessionSummaryChangedParams struct {
@@ -185,12 +184,6 @@ type PartialSessionSummary struct {
 	Agent *AgentSelection `json:"agent,omitempty"`
 	// The working directory URI for this session
 	WorkingDirectory *URI `json:"workingDirectory,omitempty"`
-	// Catalogue of changesets the server can produce for this session. Each
-	// entry advertises a subscribable view of file changes (uncommitted,
-	// session-wide, per-turn, etc.) and the URI template the client expands
-	// before subscribing. See {@link Changeset} for the full shape and
-	// {@link /guide/changesets | Changesets} for an overview of the model.
-	Changesets []Changeset `json:"changesets,omitempty"`
 	// Aggregate summary of file changes associated with this session. Servers
 	// may populate this to give clients a quick at-a-glance view of the
 	// session's footprint (e.g., for list rendering) without requiring the
diff --git a/clients/go/ahptypes/state.generated.go b/clients/go/ahptypes/state.generated.go
index 5cde6456..9e8a8354 100644
--- a/clients/go/ahptypes/state.generated.go
+++ b/clients/go/ahptypes/state.generated.go
@@ -555,6 +555,12 @@ type SessionState struct {
 	// and the host propagates them into this list (typically with the
 	// container's `clientId` set and `children` populated).
 	Customizations []Customization `json:"customizations,omitempty"`
+	// Catalogue of changesets the server can produce for this session. Each
+	// entry advertises a subscribable view of file changes (uncommitted,
+	// session-wide, per-turn, etc.) and the URI template the client expands
+	// before subscribing. See {@link Changeset} for the full shape and
+	// {@link /guide/changesets | Changesets} for an overview of the model.
+	Changesets []Changeset `json:"changesets,omitempty"`
 	// Additional provider-specific metadata for this session.
 	//
 	// Clients MAY look for well-known keys here to provide enhanced UI.
@@ -609,12 +615,6 @@ type SessionSummary struct {
 	Agent *AgentSelection `json:"agent,omitempty"`
 	// The working directory URI for this session
 	WorkingDirectory *URI `json:"workingDirectory,omitempty"`
-	// Catalogue of changesets the server can produce for this session. Each
-	// entry advertises a subscribable view of file changes (uncommitted,
-	// session-wide, per-turn, etc.) and the URI template the client expands
-	// before subscribing. See {@link Changeset} for the full shape and
-	// {@link /guide/changesets | Changesets} for an overview of the model.
-	Changesets []Changeset `json:"changesets,omitempty"`
 	// Aggregate summary of file changes associated with this session. Servers
 	// may populate this to give clients a quick at-a-glance view of the
 	// session's footprint (e.g., for list rendering) without requiring the
diff --git a/clients/kotlin/CHANGELOG.md b/clients/kotlin/CHANGELOG.md
index a1bc4578..365f76eb 100644
--- a/clients/kotlin/CHANGELOG.md
+++ b/clients/kotlin/CHANGELOG.md
@@ -26,7 +26,8 @@ versions (`*-SNAPSHOT`) are explicitly rejected by the publish pipeline; bump
 
 ### Changed
 
-- Renamed the `ChangesetSummary` type to `Changeset` (catalogue entry on `SessionSummary.changesets`). The on-the-wire shape is unchanged.
+- Renamed the `ChangesetSummary` type to `Changeset`. The on-the-wire shape is unchanged.
+- Moved the `changesets` catalogue from `SessionSummary` to `SessionState`. The `session/changesetsChanged` action now updates `state.changesets` directly instead of `state.summary.changesets`.
 
 ### Removed
 
diff --git a/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/Reducers.kt b/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/Reducers.kt
index f7c009b1..5c58e74d 100644
--- a/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/Reducers.kt
+++ b/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/Reducers.kt
@@ -924,9 +924,7 @@ public fun sessionReducer(state: SessionState, action: StateAction): SessionStat
     )
 
     is StateActionSessionChangesetsChanged -> state.copy(
-        // Clear the field entirely when no changesets are provided, matching
-        // TS `{ ...summaryWithoutChangesets }` semantics (omits the key).
-        summary = state.summary.copy(changesets = action.value.changesets),
+        changesets = action.value.changesets,
     )
 
     is StateActionSessionConfigChanged -> {
diff --git a/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/Notifications.generated.kt b/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/Notifications.generated.kt
index 9ba67479..425ef812 100644
--- a/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/Notifications.generated.kt
+++ b/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/Notifications.generated.kt
@@ -192,14 +192,6 @@ data class PartialSessionSummary(
      * The working directory URI for this session
      */
     val workingDirectory: String? = null,
-    /**
-     * Catalogue of changesets the server can produce for this session. Each
-     * entry advertises a subscribable view of file changes (uncommitted,
-     * session-wide, per-turn, etc.) and the URI template the client expands
-     * before subscribing. See {@link Changeset} for the full shape and
-     * {@link /guide/changesets | Changesets} for an overview of the model.
-     */
-    val changesets: List<Changeset>? = null,
     /**
      * Aggregate summary of file changes associated with this session. Servers
      * may populate this to give clients a quick at-a-glance view of the
diff --git a/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt b/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt
index ee2b2f84..0ebd79d8 100644
--- a/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt
+++ b/clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt
@@ -899,6 +899,14 @@ data class SessionState(
      * container's `clientId` set and `children` populated).
      */
     val customizations: List<Customization>? = null,
+    /**
+     * Catalogue of changesets the server can produce for this session. Each
+     * entry advertises a subscribable view of file changes (uncommitted,
+     * session-wide, per-turn, etc.) and the URI template the client expands
+     * before subscribing. See {@link Changeset} for the full shape and
+     * {@link /guide/changesets | Changesets} for an overview of the model.
+     */
+    val changesets: List<Changeset>? = null,
     /**
      * Additional provider-specific metadata for this session.
      * 
@@ -984,14 +992,6 @@ data class SessionSummary(
      * The working directory URI for this session
      */
     val workingDirectory: String? = null,
-    /**
-     * Catalogue of changesets the server can produce for this session. Each
-     * entry advertises a subscribable view of file changes (uncommitted,
-     * session-wide, per-turn, etc.) and the URI template the client expands
-     * before subscribing. See {@link Changeset} for the full shape and
-     * {@link /guide/changesets | Changesets} for an overview of the model.
-     */
-    val changesets: List<Changeset>? = null,
     /**
      * Aggregate summary of file changes associated with this session. Servers
      * may populate this to give clients a quick at-a-glance view of the
diff --git a/clients/rust/CHANGELOG.md b/clients/rust/CHANGELOG.md
index 4ced95cc..399a16ec 100644
--- a/clients/rust/CHANGELOG.md
+++ b/clients/rust/CHANGELOG.md
@@ -26,7 +26,8 @@ matching `## [X.Y.Z]` heading is missing from this file.
 
 ### Changed
 
-- Renamed the `ChangesetSummary` type to `Changeset` (catalogue entry on `SessionSummary.changesets`). The on-the-wire shape is unchanged.
+- Renamed the `ChangesetSummary` type to `Changeset`. The on-the-wire shape is unchanged.
+- Moved the `changesets` catalogue from `SessionSummary` to `SessionState`. The `session/changesetsChanged` action now updates `state.changesets` directly instead of `state.summary.changesets`.
 
 ### Removed
 
diff --git a/clients/rust/crates/ahp-types/src/actions.rs b/clients/rust/crates/ahp-types/src/actions.rs
index b0d250a3..49fdd8e9 100644
--- a/clients/rust/crates/ahp-types/src/actions.rs
+++ b/clients/rust/crates/ahp-types/src/actions.rs
@@ -577,8 +577,9 @@ pub struct SessionActivityChangedAction {
 
 /// The {@link Changeset | catalogue of changesets} the agent host
 /// advertises for this session changed. Replaces
-/// `state.summary.changesets` entirely (full-replacement semantics) — set
-/// to `undefined` to clear the catalogue.
+/// {@link SessionState.changesets | `state.changesets`} entirely
+/// (full-replacement semantics) — set to `undefined` to clear the
+/// catalogue.
 ///
 /// Producers dispatch this whenever entries are added or removed. The
 /// fan-out happens through this action so observers see catalogue
diff --git a/clients/rust/crates/ahp-types/src/notifications.rs b/clients/rust/crates/ahp-types/src/notifications.rs
index 06064129..f1a55a22 100644
--- a/clients/rust/crates/ahp-types/src/notifications.rs
+++ b/clients/rust/crates/ahp-types/src/notifications.rs
@@ -79,8 +79,7 @@ pub struct SessionRemovedParams {
 ///   {@link SessionSummary | `SessionSummary`} changes for a session the
 ///   server has surfaced via `listSessions()` or `root/sessionAdded`.
 ///   Servers MAY coalesce or debounce updates for noisy fields (for example,
-///   `modifiedAt` bumps while a turn is streaming, or rapidly changing
-///   `changesets`) at their discretion.
+///   `modifiedAt` bumps while a turn is streaming) at their discretion.
 /// - Clients that have no cached entry for `session` MAY ignore the
 ///   notification; it is not a substitute for `root/sessionAdded`.
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
@@ -218,13 +217,6 @@ pub struct PartialSessionSummary {
     /// The working directory URI for this session
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub working_directory: Option<Uri>,
-    /// Catalogue of changesets the server can produce for this session. Each
-    /// entry advertises a subscribable view of file changes (uncommitted,
-    /// session-wide, per-turn, etc.) and the URI template the client expands
-    /// before subscribing. See {@link Changeset} for the full shape and
-    /// {@link /guide/changesets | Changesets} for an overview of the model.
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub changesets: Option<Vec<Changeset>>,
     /// Aggregate summary of file changes associated with this session. Servers
     /// may populate this to give clients a quick at-a-glance view of the
     /// session's footprint (e.g., for list rendering) without requiring the
diff --git a/clients/rust/crates/ahp-types/src/state.rs b/clients/rust/crates/ahp-types/src/state.rs
index 73447c55..2770b915 100644
--- a/clients/rust/crates/ahp-types/src/state.rs
+++ b/clients/rust/crates/ahp-types/src/state.rs
@@ -716,6 +716,13 @@ pub struct SessionState {
     /// container's `clientId` set and `children` populated).
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub customizations: Option<Vec<Customization>>,
+    /// Catalogue of changesets the server can produce for this session. Each
+    /// entry advertises a subscribable view of file changes (uncommitted,
+    /// session-wide, per-turn, etc.) and the URI template the client expands
+    /// before subscribing. See {@link Changeset} for the full shape and
+    /// {@link /guide/changesets | Changesets} for an overview of the model.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub changesets: Option<Vec<Changeset>>,
     /// Additional provider-specific metadata for this session.
     ///
     /// Clients MAY look for well-known keys here to provide enhanced UI.
@@ -782,13 +789,6 @@ pub struct SessionSummary {
     /// The working directory URI for this session
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub working_directory: Option<Uri>,
-    /// Catalogue of changesets the server can produce for this session. Each
-    /// entry advertises a subscribable view of file changes (uncommitted,
-    /// session-wide, per-turn, etc.) and the URI template the client expands
-    /// before subscribing. See {@link Changeset} for the full shape and
-    /// {@link /guide/changesets | Changesets} for an overview of the model.
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub changesets: Option<Vec<Changeset>>,
     /// Aggregate summary of file changes associated with this session. Servers
     /// may populate this to give clients a quick at-a-glance view of the
     /// session's footprint (e.g., for list rendering) without requiring the
diff --git a/clients/rust/crates/ahp/src/hosts/runtime.rs b/clients/rust/crates/ahp/src/hosts/runtime.rs
index a8a2f92d..941bbd85 100644
--- a/clients/rust/crates/ahp/src/hosts/runtime.rs
+++ b/clients/rust/crates/ahp/src/hosts/runtime.rs
@@ -720,9 +720,6 @@ fn apply_summary_changes(
     if let Some(v) = &changes.working_directory {
         existing.working_directory = Some(v.clone());
     }
-    if let Some(v) = &changes.changesets {
-        existing.changesets = Some(v.clone());
-    }
 }
 
 // ─── Random helpers (no external dep on `rand`) ─────────────────────────────
diff --git a/clients/rust/crates/ahp/src/reducers.rs b/clients/rust/crates/ahp/src/reducers.rs
index 3b680848..5599bb83 100644
--- a/clients/rust/crates/ahp/src/reducers.rs
+++ b/clients/rust/crates/ahp/src/reducers.rs
@@ -619,7 +619,7 @@ pub fn apply_action_to_session(state: &mut SessionState, action: &StateAction) -
             ReduceOutcome::Applied
         }
         StateAction::SessionChangesetsChanged(a) => {
-            state.summary.changesets = a.changesets.clone();
+            state.changesets = a.changesets.clone();
             ReduceOutcome::Applied
         }
         StateAction::SessionConfigChanged(a) => {
@@ -1219,7 +1219,6 @@ mod tests {
                 model: None,
                 agent: None,
                 working_directory: None,
-                changesets: None,
                 changes: None,
             },
             lifecycle: SessionLifecycle::Creating,
@@ -1233,6 +1232,7 @@ mod tests {
             input_requests: None,
             config: None,
             customizations: None,
+            changesets: None,
             meta: None,
         }
     }
diff --git a/clients/rust/crates/ahp/tests/hosts.rs b/clients/rust/crates/ahp/tests/hosts.rs
index 9a6a8afd..cf5e9da7 100644
--- a/clients/rust/crates/ahp/tests/hosts.rs
+++ b/clients/rust/crates/ahp/tests/hosts.rs
@@ -1032,7 +1032,6 @@ fn make_summary(uri: &str, title: &str, modified_at: i64) -> ahp_types::state::S
         model: None,
         agent: None,
         working_directory: None,
-        changesets: None,
         changes: None,
     }
 }
diff --git a/clients/rust/crates/ahp/tests/multi_host_state_mirror.rs b/clients/rust/crates/ahp/tests/multi_host_state_mirror.rs
index 313fba76..5f830bd7 100644
--- a/clients/rust/crates/ahp/tests/multi_host_state_mirror.rs
+++ b/clients/rust/crates/ahp/tests/multi_host_state_mirror.rs
@@ -56,7 +56,6 @@ fn session_state(title: &str, resource: &str) -> SessionState {
             model: None,
             agent: None,
             working_directory: None,
-            changesets: None,
             changes: None,
         },
         lifecycle: SessionLifecycle::Ready,
@@ -70,6 +69,7 @@ fn session_state(title: &str, resource: &str) -> SessionState {
         input_requests: None,
         config: None,
         customizations: None,
+        changesets: None,
         meta: None,
     }
 }
@@ -364,7 +364,6 @@ fn non_action_event_is_ignored() {
                 model: None,
                 agent: None,
                 working_directory: None,
-                changesets: None,
                 changes: None,
             },
         }),
diff --git a/clients/swift/AHPApp/AHPApp/Store/AppStore.swift b/clients/swift/AHPApp/AHPApp/Store/AppStore.swift
index 0bf3a193..7e01ae47 100644
--- a/clients/swift/AHPApp/AHPApp/Store/AppStore.swift
+++ b/clients/swift/AHPApp/AHPApp/Store/AppStore.swift
@@ -1283,7 +1283,6 @@ final class AppStore {
         if let v = changes.project { summary.project = v }
         if let v = changes.model { summary.model = v }
         if let v = changes.workingDirectory { summary.workingDirectory = v }
-        if let v = changes.changesets { summary.changesets = v }
         sessionSummariesCache[uri] = summary
     }
 
diff --git a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/Notifications.generated.swift b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/Notifications.generated.swift
index cecc034c..e5f9ff00 100644
--- a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/Notifications.generated.swift
+++ b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/Notifications.generated.swift
@@ -164,12 +164,6 @@ public struct PartialSessionSummary: Codable, Sendable {
     public var agent: AgentSelection?
     /// The working directory URI for this session
     public var workingDirectory: String?
-    /// Catalogue of changesets the server can produce for this session. Each
-    /// entry advertises a subscribable view of file changes (uncommitted,
-    /// session-wide, per-turn, etc.) and the URI template the client expands
-    /// before subscribing. See {@link Changeset} for the full shape and
-    /// {@link /guide/changesets | Changesets} for an overview of the model.
-    public var changesets: [Changeset]?
     /// Aggregate summary of file changes associated with this session. Servers
     /// may populate this to give clients a quick at-a-glance view of the
     /// session's footprint (e.g., for list rendering) without requiring the
@@ -188,7 +182,6 @@ public struct PartialSessionSummary: Codable, Sendable {
         model: ModelSelection? = nil,
         agent: AgentSelection? = nil,
         workingDirectory: String? = nil,
-        changesets: [Changeset]? = nil,
         changes: ChangesSummary? = nil
     ) {
         self.resource = resource
@@ -202,7 +195,6 @@ public struct PartialSessionSummary: Codable, Sendable {
         self.model = model
         self.agent = agent
         self.workingDirectory = workingDirectory
-        self.changesets = changesets
         self.changes = changes
     }
 }
diff --git a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift
index de23729c..d6fbd9cb 100644
--- a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift
+++ b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift
@@ -687,6 +687,12 @@ public struct SessionState: Codable, Sendable {
     /// and the host propagates them into this list (typically with the
     /// container's `clientId` set and `children` populated).
     public var customizations: [Customization]?
+    /// Catalogue of changesets the server can produce for this session. Each
+    /// entry advertises a subscribable view of file changes (uncommitted,
+    /// session-wide, per-turn, etc.) and the URI template the client expands
+    /// before subscribing. See {@link Changeset} for the full shape and
+    /// {@link /guide/changesets | Changesets} for an overview of the model.
+    public var changesets: [Changeset]?
     /// Additional provider-specific metadata for this session.
     /// 
     /// Clients MAY look for well-known keys here to provide enhanced UI.
@@ -707,6 +713,7 @@ public struct SessionState: Codable, Sendable {
         case inputRequests
         case config
         case customizations
+        case changesets
         case meta = "_meta"
     }
 
@@ -723,6 +730,7 @@ public struct SessionState: Codable, Sendable {
         inputRequests: [SessionInputRequest]? = nil,
         config: SessionConfigState? = nil,
         customizations: [Customization]? = nil,
+        changesets: [Changeset]? = nil,
         meta: [String: AnyCodable]? = nil
     ) {
         self.summary = summary
@@ -737,6 +745,7 @@ public struct SessionState: Codable, Sendable {
         self.inputRequests = inputRequests
         self.config = config
         self.customizations = customizations
+        self.changesets = changesets
         self.meta = meta
     }
 }
@@ -795,12 +804,6 @@ public struct SessionSummary: Codable, Sendable {
     public var agent: AgentSelection?
     /// The working directory URI for this session
     public var workingDirectory: String?
-    /// Catalogue of changesets the server can produce for this session. Each
-    /// entry advertises a subscribable view of file changes (uncommitted,
-    /// session-wide, per-turn, etc.) and the URI template the client expands
-    /// before subscribing. See {@link Changeset} for the full shape and
-    /// {@link /guide/changesets | Changesets} for an overview of the model.
-    public var changesets: [Changeset]?
     /// Aggregate summary of file changes associated with this session. Servers
     /// may populate this to give clients a quick at-a-glance view of the
     /// session's footprint (e.g., for list rendering) without requiring the
@@ -819,7 +822,6 @@ public struct SessionSummary: Codable, Sendable {
         model: ModelSelection? = nil,
         agent: AgentSelection? = nil,
         workingDirectory: String? = nil,
-        changesets: [Changeset]? = nil,
         changes: ChangesSummary? = nil
     ) {
         self.resource = resource
@@ -833,7 +835,6 @@ public struct SessionSummary: Codable, Sendable {
         self.model = model
         self.agent = agent
         self.workingDirectory = workingDirectory
-        self.changesets = changesets
         self.changes = changes
     }
 }
diff --git a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Reducers.swift b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Reducers.swift
index f6524a86..042af8a3 100644
--- a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Reducers.swift
+++ b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Reducers.swift
@@ -376,7 +376,7 @@ public func sessionReducer(state: SessionState, action: StateAction) -> SessionS
 
     case .sessionChangesetsChanged(let a):
         var next = state
-        next.summary.changesets = a.changesets
+        next.changesets = a.changesets
         return next
 
     case .sessionConfigChanged(let a):
diff --git a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocolClient/Hosts/HostRuntime.swift b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocolClient/Hosts/HostRuntime.swift
index 42d1d0e4..f4d3a463 100644
--- a/clients/swift/AgentHostProtocol/Sources/AgentHostProtocolClient/Hosts/HostRuntime.swift
+++ b/clients/swift/AgentHostProtocol/Sources/AgentHostProtocolClient/Hosts/HostRuntime.swift
@@ -829,7 +829,6 @@ private func applySummaryChanges(
     if let v = changes.project { existing.project = v }
     if let v = changes.model { existing.model = v }
     if let v = changes.workingDirectory { existing.workingDirectory = v }
-    if let v = changes.changesets { existing.changesets = v }
 }
 
 /// Protocol version offered on `initialize`. Mirrors the Rust SDK's use of
diff --git a/clients/swift/CHANGELOG.md b/clients/swift/CHANGELOG.md
index 5617f9fb..4a4408e2 100644
--- a/clients/swift/CHANGELOG.md
+++ b/clients/swift/CHANGELOG.md
@@ -28,7 +28,8 @@ the tag matches the version pinned in [`VERSION`](VERSION).
 
 ### Changed
 
-- Renamed the `ChangesetSummary` type to `Changeset` (catalogue entry on `SessionSummary.changesets`). The on-the-wire shape is unchanged.
+- Renamed the `ChangesetSummary` type to `Changeset`. The on-the-wire shape is unchanged.
+- Moved the `changesets` catalogue from `SessionSummary` to `SessionState`. The `session/changesetsChanged` action now updates `state.changesets` directly instead of `state.summary.changesets`.
 
 ### Removed
 
diff --git a/clients/typescript/CHANGELOG.md b/clients/typescript/CHANGELOG.md
index 3e7104d4..5d80d4e7 100644
--- a/clients/typescript/CHANGELOG.md
+++ b/clients/typescript/CHANGELOG.md
@@ -31,7 +31,8 @@ hotfix escape hatch.
 
 ### Changed
 
-- Renamed the `ChangesetSummary` type to `Changeset` (catalogue entry on `SessionSummary.changesets`). The on-the-wire shape is unchanged.
+- Renamed the `ChangesetSummary` type to `Changeset`. The on-the-wire shape is unchanged.
+- Moved the `changesets` catalogue from `SessionSummary` to `SessionState`. The `session/changesetsChanged` action now updates `state.changesets` directly instead of `state.summary.changesets`.
 
 ### Removed
 
diff --git a/clients/typescript/src/client/hosts/runtime.ts b/clients/typescript/src/client/hosts/runtime.ts
index 6c98bb44..f1927e24 100644
--- a/clients/typescript/src/client/hosts/runtime.ts
+++ b/clients/typescript/src/client/hosts/runtime.ts
@@ -882,6 +882,5 @@ function applySummaryChange(
   if (changes.project !== undefined) merged.project = changes.project;
   if (changes.model !== undefined) merged.model = changes.model;
   if (changes.workingDirectory !== undefined) merged.workingDirectory = changes.workingDirectory;
-  if (changes.changesets !== undefined) merged.changesets = changes.changesets;
   cache.set(params.session, merged);
 }
diff --git a/docs/guide/changesets.md b/docs/guide/changesets.md
index 2113511b..70f55c3b 100644
--- a/docs/guide/changesets.md
+++ b/docs/guide/changesets.md
@@ -11,13 +11,13 @@ each with its own URI, lifecycle, and update stream.
 
 ### Changeset Catalogue
 
-Each session's `SessionSummary` advertises the set of changesets the
-server can produce. The summary entry is intentionally lightweight —
+Each session's `SessionState` advertises the set of changesets the
+server can produce. The catalogue entry is intentionally lightweight —
 just enough to render a chip or list row without subscribing — and
 references a full subscribable `ChangesetState` by URI.
 
 ```typescript
-SessionSummary {
+SessionState {
   // ...existing fields...
   changesets?: Changeset[]
 }
@@ -148,9 +148,9 @@ a JSON-RPC error.
 
 ## Lifecycle
 
-1. The server publishes the catalogue on `SessionSummary.changesets`.
-   Updates ride on `root/sessionSummaryChanged`.
-2. The client picks summary entries whose template variables it can
+1. The server publishes the catalogue on `SessionState.changesets`.
+   Updates ride on the `session/changesetsChanged` action.
+2. The client picks catalogue entries whose template variables it can
    satisfy and subscribes to the resulting URIs.
 3. The server returns a `ChangesetState` snapshot (`status: 'computing'`
    is allowed if scanning is async) and pushes `changeset/*` actions as
diff --git a/docs/guide/state-model.md b/docs/guide/state-model.md
index 44c59a20..8bb4cd29 100644
--- a/docs/guide/state-model.md
+++ b/docs/guide/state-model.md
@@ -378,7 +378,7 @@ The session list can be arbitrarily large and is **not** part of the state tree.
 - Clients fetch the list imperatively via `listSessions()` RPC.
 - The server sends lightweight **notifications** to keep connected clients' caches in sync without re-fetching:
   - `root/sessionAdded` and `root/sessionRemoved` signal lifecycle (creation and disposal).
-  - `root/sessionSummaryChanged` streams partial updates to an existing session's summary (title, status, `modifiedAt`, project, model, working directory, `changesets`) so clients that are displaying a session list can stay in sync without subscribing to every session URI individually. Only fields present in `changes` carry new values; omitted fields are unchanged. The server SHOULD emit this notification whenever any mutable summary field changes, and MAY coalesce or debounce noisy updates (for example, rapid `modifiedAt` bumps while a turn is streaming) at its discretion.
+  - `root/sessionSummaryChanged` streams partial updates to an existing session's summary (title, status, `modifiedAt`, project, model, working directory) so clients that are displaying a session list can stay in sync without subscribing to every session URI individually. Only fields present in `changes` carry new values; omitted fields are unchanged. The server SHOULD emit this notification whenever any mutable summary field changes, and MAY coalesce or debounce noisy updates (for example, rapid `modifiedAt` bumps while a turn is streaming) at its discretion.
 
 Notifications are ephemeral — not processed by reducers, not stored in state, not replayed on reconnect. On reconnect, clients re-fetch the list.
 
diff --git a/plugins/channels-migration-plugin/skills/channels-migration/SKILL.md b/plugins/channels-migration-plugin/skills/channels-migration/SKILL.md
index 7e525029..bfaaab3b 100644
--- a/plugins/channels-migration-plugin/skills/channels-migration/SKILL.md
+++ b/plugins/channels-migration-plugin/skills/channels-migration/SKILL.md
@@ -433,7 +433,7 @@ After the migration, your code should:
 - [ ] Resolve a session's provider via `SessionSummary.provider`, not via
       the URI scheme.
 - [ ] No `SessionDiffsChangedAction` / `summary.diffs` references; consume
-      `summary.changesets` plus the `changeset/*` action family instead.
+      `SessionState.changesets` plus the `changeset/*` action family instead.
 - [ ] Every command's params carries `channel: URI`. Channel-scoped
       commands (`createSession`, `disposeSession`, `createTerminal`,
       `disposeTerminal`, `fetchTurns`, `completions`,
diff --git a/schema/actions.schema.json b/schema/actions.schema.json
index ec8b6508..5eed1229 100644
--- a/schema/actions.schema.json
+++ b/schema/actions.schema.json
@@ -809,7 +809,7 @@
     },
     "SessionChangesetsChangedAction": {
       "type": "object",
-      "description": "The {@link Changeset | catalogue of changesets} the agent host\nadvertises for this session changed. Replaces\n`state.summary.changesets` entirely (full-replacement semantics) — set\nto `undefined` to clear the catalogue.\n\nProducers dispatch this whenever entries are added or removed. The\nfan-out happens through this action so observers see catalogue\nmutations in the same {@link ChangesetAction | per-changeset} action\nstream they already follow for file-level updates.",
+      "description": "The {@link Changeset | catalogue of changesets} the agent host\nadvertises for this session changed. Replaces\n{@link SessionState.changesets | `state.changesets`} entirely\n(full-replacement semantics) — set to `undefined` to clear the\ncatalogue.\n\nProducers dispatch this whenever entries are added or removed. The\nfan-out happens through this action so observers see catalogue\nmutations in the same {@link ChangesetAction | per-changeset} action\nstream they already follow for file-level updates.",
       "properties": {
         "type": {
           "$ref": "#/$defs/ActionType.SessionChangesetsChanged"
@@ -2173,6 +2173,13 @@
           },
           "description": "Top-level customizations active in this session.\n\nAlways container customizations — {@link PluginCustomization} or\n{@link DirectoryCustomization}. Children (agents, skills, prompts,\nrules, hooks, MCP servers) live in each container's\n{@link ContainerCustomizationBase.children | `children`} array.\n\nClient-published plugins arrive via\n{@link SessionActiveClient.customizations | `activeClient.customizations`}\nand the host propagates them into this list (typically with the\ncontainer's `clientId` set and `children` populated)."
         },
+        "changesets": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/Changeset"
+          },
+          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
+        },
         "_meta": {
           "type": "object",
           "additionalProperties": {},
@@ -2282,13 +2289,6 @@
           "$ref": "#/$defs/URI",
           "description": "The working directory URI for this session"
         },
-        "changesets": {
-          "type": "array",
-          "items": {
-            "$ref": "#/$defs/Changeset"
-          },
-          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
-        },
         "changes": {
           "$ref": "#/$defs/ChangesSummary",
           "description": "Aggregate summary of file changes associated with this session. Servers\nmay populate this to give clients a quick at-a-glance view of the\nsession's footprint (e.g., for list rendering) without requiring the\nclient to subscribe to a changeset."
diff --git a/schema/commands.schema.json b/schema/commands.schema.json
index b9ea5bc4..4b2bbac0 100644
--- a/schema/commands.schema.json
+++ b/schema/commands.schema.json
@@ -1824,6 +1824,13 @@
           },
           "description": "Top-level customizations active in this session.\n\nAlways container customizations — {@link PluginCustomization} or\n{@link DirectoryCustomization}. Children (agents, skills, prompts,\nrules, hooks, MCP servers) live in each container's\n{@link ContainerCustomizationBase.children | `children`} array.\n\nClient-published plugins arrive via\n{@link SessionActiveClient.customizations | `activeClient.customizations`}\nand the host propagates them into this list (typically with the\ncontainer's `clientId` set and `children` populated)."
         },
+        "changesets": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/Changeset"
+          },
+          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
+        },
         "_meta": {
           "type": "object",
           "additionalProperties": {},
@@ -1933,13 +1940,6 @@
           "$ref": "#/$defs/URI",
           "description": "The working directory URI for this session"
         },
-        "changesets": {
-          "type": "array",
-          "items": {
-            "$ref": "#/$defs/Changeset"
-          },
-          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
-        },
         "changes": {
           "$ref": "#/$defs/ChangesSummary",
           "description": "Aggregate summary of file changes associated with this session. Servers\nmay populate this to give clients a quick at-a-glance view of the\nsession's footprint (e.g., for list rendering) without requiring the\nclient to subscribe to a changeset."
@@ -5526,7 +5526,7 @@
     },
     "SessionChangesetsChangedAction": {
       "type": "object",
-      "description": "The {@link Changeset | catalogue of changesets} the agent host\nadvertises for this session changed. Replaces\n`state.summary.changesets` entirely (full-replacement semantics) — set\nto `undefined` to clear the catalogue.\n\nProducers dispatch this whenever entries are added or removed. The\nfan-out happens through this action so observers see catalogue\nmutations in the same {@link ChangesetAction | per-changeset} action\nstream they already follow for file-level updates.",
+      "description": "The {@link Changeset | catalogue of changesets} the agent host\nadvertises for this session changed. Replaces\n{@link SessionState.changesets | `state.changesets`} entirely\n(full-replacement semantics) — set to `undefined` to clear the\ncatalogue.\n\nProducers dispatch this whenever entries are added or removed. The\nfan-out happens through this action so observers see catalogue\nmutations in the same {@link ChangesetAction | per-changeset} action\nstream they already follow for file-level updates.",
       "properties": {
         "type": {
           "$ref": "#/$defs/ActionType.SessionChangesetsChanged"
diff --git a/schema/errors.schema.json b/schema/errors.schema.json
index 6d8f9d84..7bfa2977 100644
--- a/schema/errors.schema.json
+++ b/schema/errors.schema.json
@@ -756,6 +756,13 @@
           },
           "description": "Top-level customizations active in this session.\n\nAlways container customizations — {@link PluginCustomization} or\n{@link DirectoryCustomization}. Children (agents, skills, prompts,\nrules, hooks, MCP servers) live in each container's\n{@link ContainerCustomizationBase.children | `children`} array.\n\nClient-published plugins arrive via\n{@link SessionActiveClient.customizations | `activeClient.customizations`}\nand the host propagates them into this list (typically with the\ncontainer's `clientId` set and `children` populated)."
         },
+        "changesets": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/Changeset"
+          },
+          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
+        },
         "_meta": {
           "type": "object",
           "additionalProperties": {},
@@ -865,13 +872,6 @@
           "$ref": "#/$defs/URI",
           "description": "The working directory URI for this session"
         },
-        "changesets": {
-          "type": "array",
-          "items": {
-            "$ref": "#/$defs/Changeset"
-          },
-          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
-        },
         "changes": {
           "$ref": "#/$defs/ChangesSummary",
           "description": "Aggregate summary of file changes associated with this session. Servers\nmay populate this to give clients a quick at-a-glance view of the\nsession's footprint (e.g., for list rendering) without requiring the\nclient to subscribe to a changeset."
diff --git a/schema/notifications.schema.json b/schema/notifications.schema.json
index 9408126b..b93d9cda 100644
--- a/schema/notifications.schema.json
+++ b/schema/notifications.schema.json
@@ -65,7 +65,7 @@
     },
     "SessionSummaryChangedParams": {
       "type": "object",
-      "description": "Broadcast to all clients subscribed to the root channel when an existing\nsession's summary changes (title, status, `modifiedAt`, model, working\ndirectory, read/done state, or diff statistics).\n\nThis notification lets clients that maintain a cached session list — for\nexample, the result of a previous `listSessions()` call — stay in sync with\nin-flight sessions without having to subscribe to every session URI\nindividually. It is complementary to, not a replacement for,\n`root/sessionAdded` and `root/sessionRemoved`: those signal lifecycle\n(creation/disposal), while this signals summary-level mutations on an\nalready-known session.\n\nSemantics:\n\n- Only fields present in `changes` have new values; omitted fields are\n  unchanged on the client's cached summary.\n- Identity fields (`resource`, `provider`, `createdAt`) never change and\n  are not carried.\n- Like all protocol notifications, this is ephemeral: it is **not**\n  replayed on reconnect. On reconnect, clients should re-fetch the full\n  catalog via `listSessions()` as usual.\n- The server SHOULD emit this notification whenever any mutable field on\n  {@link SessionSummary | `SessionSummary`} changes for a session the\n  server has surfaced via `listSessions()` or `root/sessionAdded`.\n  Servers MAY coalesce or debounce updates for noisy fields (for example,\n  `modifiedAt` bumps while a turn is streaming, or rapidly changing\n  `changesets`) at their discretion.\n- Clients that have no cached entry for `session` MAY ignore the\n  notification; it is not a substitute for `root/sessionAdded`.",
+      "description": "Broadcast to all clients subscribed to the root channel when an existing\nsession's summary changes (title, status, `modifiedAt`, model, working\ndirectory, read/done state, or diff statistics).\n\nThis notification lets clients that maintain a cached session list — for\nexample, the result of a previous `listSessions()` call — stay in sync with\nin-flight sessions without having to subscribe to every session URI\nindividually. It is complementary to, not a replacement for,\n`root/sessionAdded` and `root/sessionRemoved`: those signal lifecycle\n(creation/disposal), while this signals summary-level mutations on an\nalready-known session.\n\nSemantics:\n\n- Only fields present in `changes` have new values; omitted fields are\n  unchanged on the client's cached summary.\n- Identity fields (`resource`, `provider`, `createdAt`) never change and\n  are not carried.\n- Like all protocol notifications, this is ephemeral: it is **not**\n  replayed on reconnect. On reconnect, clients should re-fetch the full\n  catalog via `listSessions()` as usual.\n- The server SHOULD emit this notification whenever any mutable field on\n  {@link SessionSummary | `SessionSummary`} changes for a session the\n  server has surfaced via `listSessions()` or `root/sessionAdded`.\n  Servers MAY coalesce or debounce updates for noisy fields (for example,\n  `modifiedAt` bumps while a turn is streaming) at their discretion.\n- Clients that have no cached entry for `session` MAY ignore the\n  notification; it is not a substitute for `root/sessionAdded`.",
       "properties": {
         "channel": {
           "$ref": "#/$defs/URI",
@@ -122,13 +122,6 @@
               "$ref": "#/$defs/URI",
               "description": "The working directory URI for this session"
             },
-            "changesets": {
-              "type": "array",
-              "items": {
-                "$ref": "#/$defs/Changeset"
-              },
-              "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
-            },
             "changes": {
               "$ref": "#/$defs/ChangesSummary",
               "description": "Aggregate summary of file changes associated with this session. Servers\nmay populate this to give clients a quick at-a-glance view of the\nsession's footprint (e.g., for list rendering) without requiring the\nclient to subscribe to a changeset."
@@ -888,6 +881,13 @@
           },
           "description": "Top-level customizations active in this session.\n\nAlways container customizations — {@link PluginCustomization} or\n{@link DirectoryCustomization}. Children (agents, skills, prompts,\nrules, hooks, MCP servers) live in each container's\n{@link ContainerCustomizationBase.children | `children`} array.\n\nClient-published plugins arrive via\n{@link SessionActiveClient.customizations | `activeClient.customizations`}\nand the host propagates them into this list (typically with the\ncontainer's `clientId` set and `children` populated)."
         },
+        "changesets": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/Changeset"
+          },
+          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
+        },
         "_meta": {
           "type": "object",
           "additionalProperties": {},
@@ -997,13 +997,6 @@
           "$ref": "#/$defs/URI",
           "description": "The working directory URI for this session"
         },
-        "changesets": {
-          "type": "array",
-          "items": {
-            "$ref": "#/$defs/Changeset"
-          },
-          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
-        },
         "changes": {
           "$ref": "#/$defs/ChangesSummary",
           "description": "Aggregate summary of file changes associated with this session. Servers\nmay populate this to give clients a quick at-a-glance view of the\nsession's footprint (e.g., for list rendering) without requiring the\nclient to subscribe to a changeset."
diff --git a/schema/state.schema.json b/schema/state.schema.json
index 7da12efb..52e5371f 100644
--- a/schema/state.schema.json
+++ b/schema/state.schema.json
@@ -667,6 +667,13 @@
           },
           "description": "Top-level customizations active in this session.\n\nAlways container customizations — {@link PluginCustomization} or\n{@link DirectoryCustomization}. Children (agents, skills, prompts,\nrules, hooks, MCP servers) live in each container's\n{@link ContainerCustomizationBase.children | `children`} array.\n\nClient-published plugins arrive via\n{@link SessionActiveClient.customizations | `activeClient.customizations`}\nand the host propagates them into this list (typically with the\ncontainer's `clientId` set and `children` populated)."
         },
+        "changesets": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/Changeset"
+          },
+          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
+        },
         "_meta": {
           "type": "object",
           "additionalProperties": {},
@@ -776,13 +783,6 @@
           "$ref": "#/$defs/URI",
           "description": "The working directory URI for this session"
         },
-        "changesets": {
-          "type": "array",
-          "items": {
-            "$ref": "#/$defs/Changeset"
-          },
-          "description": "Catalogue of changesets the server can produce for this session. Each\nentry advertises a subscribable view of file changes (uncommitted,\nsession-wide, per-turn, etc.) and the URI template the client expands\nbefore subscribing. See {@link Changeset} for the full shape and\n{@link /guide/changesets | Changesets} for an overview of the model."
-        },
         "changes": {
           "$ref": "#/$defs/ChangesSummary",
           "description": "Aggregate summary of file changes associated with this session. Servers\nmay populate this to give clients a quick at-a-glance view of the\nsession's footprint (e.g., for list rendering) without requiring the\nclient to subscribe to a changeset."
diff --git a/types/channels-root/notifications.ts b/types/channels-root/notifications.ts
index b7f15662..32fea359 100644
--- a/types/channels-root/notifications.ts
+++ b/types/channels-root/notifications.ts
@@ -103,8 +103,7 @@ export interface SessionRemovedParams {
  *   {@link SessionSummary | `SessionSummary`} changes for a session the
  *   server has surfaced via `listSessions()` or `root/sessionAdded`.
  *   Servers MAY coalesce or debounce updates for noisy fields (for example,
- *   `modifiedAt` bumps while a turn is streaming, or rapidly changing
- *   `changesets`) at their discretion.
+ *   `modifiedAt` bumps while a turn is streaming) at their discretion.
  * - Clients that have no cached entry for `session` MAY ignore the
  *   notification; it is not a substitute for `root/sessionAdded`.
  *
diff --git a/types/channels-session/actions.ts b/types/channels-session/actions.ts
index 02be1a5b..4881eca5 100644
--- a/types/channels-session/actions.ts
+++ b/types/channels-session/actions.ts
@@ -494,8 +494,9 @@ export interface SessionActivityChangedAction {
 /**
  * The {@link Changeset | catalogue of changesets} the agent host
  * advertises for this session changed. Replaces
- * `state.summary.changesets` entirely (full-replacement semantics) — set
- * to `undefined` to clear the catalogue.
+ * {@link SessionState.changesets | `state.changesets`} entirely
+ * (full-replacement semantics) — set to `undefined` to clear the
+ * catalogue.
  *
  * Producers dispatch this whenever entries are added or removed. The
  * fan-out happens through this action so observers see catalogue
diff --git a/types/channels-session/reducer.ts b/types/channels-session/reducer.ts
index ea162676..3273ad2a 100644
--- a/types/channels-session/reducer.ts
+++ b/types/channels-session/reducer.ts
@@ -568,11 +568,10 @@ export function sessionReducer(state: SessionState, action: SessionAction, log?:
       };
 
     case ActionType.SessionChangesetsChanged: {
-      const { changesets: _omit, ...summaryWithoutChangesets } = state.summary;
-      const newSummary = action.changesets
-        ? { ...summaryWithoutChangesets, changesets: action.changesets }
-        : summaryWithoutChangesets;
-      return { ...state, summary: newSummary };
+      const { changesets: _omit, ...stateWithoutChangesets } = state;
+      return action.changesets
+        ? { ...stateWithoutChangesets, changesets: action.changesets }
+        : stateWithoutChangesets;
     }
 
     case ActionType.SessionConfigChanged:
diff --git a/types/channels-session/state.ts b/types/channels-session/state.ts
index d2bf6a42..488ed6d8 100644
--- a/types/channels-session/state.ts
+++ b/types/channels-session/state.ts
@@ -17,8 +17,8 @@ import type {
   TextSelection,
   UsageInfo,
 } from '../common/state.js';
-import type { Changeset } from '../channels-changeset/state.js';
 import type { ModelSelection } from '../channels-root/state.js';
+import type { Changeset } from '../channels-changeset/state.js';
 
 // ─── Pending Message Types ───────────────────────────────────────────────────
 
@@ -129,6 +129,14 @@ export interface SessionState {
    * container's `clientId` set and `children` populated).
    */
   customizations?: Customization[];
+  /**
+   * Catalogue of changesets the server can produce for this session. Each
+   * entry advertises a subscribable view of file changes (uncommitted,
+   * session-wide, per-turn, etc.) and the URI template the client expands
+   * before subscribing. See {@link Changeset} for the full shape and
+   * {@link /guide/changesets | Changesets} for an overview of the model.
+   */
+  changesets?: Changeset[];
   /**
    * Additional provider-specific metadata for this session.
    *
@@ -208,14 +216,6 @@ export interface SessionSummary {
   agent?: AgentSelection;
   /** The working directory URI for this session */
   workingDirectory?: URI;
-  /**
-   * Catalogue of changesets the server can produce for this session. Each
-   * entry advertises a subscribable view of file changes (uncommitted,
-   * session-wide, per-turn, etc.) and the URI template the client expands
-   * before subscribing. See {@link Changeset} for the full shape and
-   * {@link /guide/changesets | Changesets} for an overview of the model.
-   */
-  changesets?: Changeset[];
   /**
   * Aggregate summary of file changes associated with this session. Servers
   * may populate this to give clients a quick at-a-glance view of the
diff --git a/types/test-cases/reducers/145-session-changesetschanged-sets-catalogue.json b/types/test-cases/reducers/145-session-changesetschanged-sets-catalogue.json
index 9f6cb3fc..7bdb0405 100644
--- a/types/test-cases/reducers/145-session-changesetschanged-sets-catalogue.json
+++ b/types/test-cases/reducers/145-session-changesetschanged-sets-catalogue.json
@@ -1,5 +1,5 @@
 {
-  "description": "session/changesetsChanged replaces summary.changesets with the new catalogue",
+  "description": "session/changesetsChanged replaces state.changesets with the new catalogue",
   "reducer": "session",
   "initial": {
     "summary": {
@@ -31,15 +31,15 @@
       "title": "Test Session",
       "status": 1,
       "createdAt": 1000,
-      "modifiedAt": 1000,
-      "changesets": [
-        {
-          "label": "Session Changes",
-          "uriTemplate": "copilot:/test-session/changeset/session"
-        }
-      ]
+      "modifiedAt": 1000
     },
     "lifecycle": "ready",
-    "turns": []
+    "turns": [],
+    "changesets": [
+      {
+        "label": "Session Changes",
+        "uriTemplate": "copilot:/test-session/changeset/session"
+      }
+    ]
   }
 }
diff --git a/types/test-cases/reducers/146-session-changesetschanged-clears-catalogue.json b/types/test-cases/reducers/146-session-changesetschanged-clears-catalogue.json
index 37d01991..78c6c5b1 100644
--- a/types/test-cases/reducers/146-session-changesetschanged-clears-catalogue.json
+++ b/types/test-cases/reducers/146-session-changesetschanged-clears-catalogue.json
@@ -1,5 +1,5 @@
 {
-  "description": "session/changesetsChanged with undefined clears summary.changesets",
+  "description": "session/changesetsChanged with undefined clears state.changesets",
   "reducer": "session",
   "initial": {
     "summary": {
@@ -8,16 +8,16 @@
       "title": "Test Session",
       "status": 1,
       "createdAt": 1000,
-      "modifiedAt": 1000,
-      "changesets": [
-        {
-          "label": "Session Changes",
-          "uriTemplate": "copilot:/test-session/changeset/session"
-        }
-      ]
+      "modifiedAt": 1000
     },
     "lifecycle": "ready",
-    "turns": []
+    "turns": [],
+    "changesets": [
+      {
+        "label": "Session Changes",
+        "uriTemplate": "copilot:/test-session/changeset/session"
+      }
+    ]
   },
   "actions": [
     {