feat(app-server): include turns page on thread resume (#23534)

## Summary

The client currently calls `thread/resume` to establish live updates and
immediately follows it with `thread/turns/list` to hydrate recent turns.
This lets `thread/resume` return that page directly, eliminating a round
trip and the ordering/deduplication gap between the two calls.

Experimental clients opt in with `initialTurnsPage: { limit,
sortDirection, itemsView }`. The response returns `initialTurnsPage` as
a `TurnsPage`, including cursors for paging further back in history.
Keeping the controls in a nested opt-in object provides the useful
`thread/turns/list` knobs without spreading page-specific parameters
across `thread/resume`.

## Verification

- `just fmt`
- `just write-app-server-schema --experimental`
- `just write-app-server-schema`
- `cargo test -p codex-app-server-protocol`
- `cargo test -p codex-app-server
thread_resume_initial_turns_page_matches_requested_turns_list_page
--tests`
- `cargo test -p codex-app-server
thread_resume_rejoins_running_thread_even_with_override_mismatch
--tests`
- `just fix -p codex-app-server-protocol -p codex-app-server`

codex-rs/app-server-protocol/schema/json/ClientRequest.json

@@ -3543,6 +3543,42 @@
         }
       ]
     },
+    "ThreadResumeInitialTurnsPageParams": {
+      "properties": {
+        "itemsView": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/TurnItemsView"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "description": "How much item detail to include for each returned turn; defaults to summary."
+        },
+        "limit": {
+          "description": "Optional turn page size.",
+          "format": "uint32",
+          "minimum": 0.0,
+          "type": [
+            "integer",
+            "null"
+          ]
+        },
+        "sortDirection": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/SortDirection"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "description": "Optional turn pagination direction; defaults to descending."
+        }
+      },
+      "type": "object"
+    },
     "ThreadResumeParams": {
       "description": "There are three ways to resume a thread: 1. By thread_id: load the thread from disk by thread_id and resume it. 2. By history: instantiate the thread from memory and resume it. 3. By path: load the thread from disk by path and resume it.\n\nFor non-running threads, the precedence is: history > non-empty path > thread_id. If using history or a non-empty path for a non-running thread, the thread_id param will be ignored.\n\nIf thread_id identifies a running thread, app-server rejoins that thread and treats a non-empty path as a consistency check against the active rollout path. Empty string path values are treated as absent.\n\nPrefer using thread_id whenever possible.",
       "properties": {

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -17150,6 +17150,42 @@
         "title": "ThreadRealtimeTranscriptDoneNotification",
         "type": "object"
       },
+      "ThreadResumeInitialTurnsPageParams": {
+        "properties": {
+          "itemsView": {
+            "anyOf": [
+              {
+                "$ref": "#/definitions/v2/TurnItemsView"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "How much item detail to include for each returned turn; defaults to summary."
+          },
+          "limit": {
+            "description": "Optional turn page size.",
+            "format": "uint32",
+            "minimum": 0.0,
+            "type": [
+              "integer",
+              "null"
+            ]
+          },
+          "sortDirection": {
+            "anyOf": [
+              {
+                "$ref": "#/definitions/v2/SortDirection"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Optional turn pagination direction; defaults to descending."
+          }
+        },
+        "type": "object"
+      },
       "ThreadResumeParams": {
         "$schema": "http://json-schema.org/draft-07/schema#",
         "description": "There are three ways to resume a thread: 1. By thread_id: load the thread from disk by thread_id and resume it. 2. By history: instantiate the thread from memory and resume it. 3. By path: load the thread from disk by path and resume it.\n\nFor non-running threads, the precedence is: history > non-empty path > thread_id. If using history or a non-empty path for a non-running thread, the thread_id param will be ignored.\n\nIf thread_id identifies a running thread, app-server rejoins that thread and treats a non-empty path as a consistency check against the active rollout path. Empty string path values are treated as absent.\n\nPrefer using thread_id whenever possible.",
@@ -18488,6 +18524,32 @@
         "title": "TurnSteerResponse",
         "type": "object"
       },
+      "TurnsPage": {
+        "properties": {
+          "backwardsCursor": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "data": {
+            "items": {
+              "$ref": "#/definitions/v2/Turn"
+            },
+            "type": "array"
+          },
+          "nextCursor": {
+            "type": [
+              "string",
+              "null"
+            ]
+          }
+        },
+        "required": [
+          "data"
+        ],
+        "type": "object"
+      },
       "UserInput": {
         "oneOf": [
           {

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json

@@ -14974,6 +14974,42 @@
       "title": "ThreadRealtimeTranscriptDoneNotification",
       "type": "object"
     },
+    "ThreadResumeInitialTurnsPageParams": {
+      "properties": {
+        "itemsView": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/TurnItemsView"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "description": "How much item detail to include for each returned turn; defaults to summary."
+        },
+        "limit": {
+          "description": "Optional turn page size.",
+          "format": "uint32",
+          "minimum": 0.0,
+          "type": [
+            "integer",
+            "null"
+          ]
+        },
+        "sortDirection": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/SortDirection"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "description": "Optional turn pagination direction; defaults to descending."
+        }
+      },
+      "type": "object"
+    },
     "ThreadResumeParams": {
       "$schema": "http://json-schema.org/draft-07/schema#",
       "description": "There are three ways to resume a thread: 1. By thread_id: load the thread from disk by thread_id and resume it. 2. By history: instantiate the thread from memory and resume it. 3. By path: load the thread from disk by path and resume it.\n\nFor non-running threads, the precedence is: history > non-empty path > thread_id. If using history or a non-empty path for a non-running thread, the thread_id param will be ignored.\n\nIf thread_id identifies a running thread, app-server rejoins that thread and treats a non-empty path as a consistency check against the active rollout path. Empty string path values are treated as absent.\n\nPrefer using thread_id whenever possible.",
@@ -16312,6 +16348,32 @@
       "title": "TurnSteerResponse",
       "type": "object"
     },
+    "TurnsPage": {
+      "properties": {
+        "backwardsCursor": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "data": {
+          "items": {
+            "$ref": "#/definitions/Turn"
+          },
+          "type": "array"
+        },
+        "nextCursor": {
+          "type": [
+            "string",
+            "null"
+          ]
+        }
+      },
+      "required": [
+        "data"
+      ],
+      "type": "object"
+    },
     "UserInput": {
       "oneOf": [
         {

codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json

@@ -983,6 +983,74 @@
         "danger-full-access"
       ],
       "type": "string"
+    },
+    "SortDirection": {
+      "enum": [
+        "asc",
+        "desc"
+      ],
+      "type": "string"
+    },
+    "ThreadResumeInitialTurnsPageParams": {
+      "properties": {
+        "itemsView": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/TurnItemsView"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "description": "How much item detail to include for each returned turn; defaults to summary."
+        },
+        "limit": {
+          "description": "Optional turn page size.",
+          "format": "uint32",
+          "minimum": 0.0,
+          "type": [
+            "integer",
+            "null"
+          ]
+        },
+        "sortDirection": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/SortDirection"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "description": "Optional turn pagination direction; defaults to descending."
+        }
+      },
+      "type": "object"
+    },
+    "TurnItemsView": {
+      "oneOf": [
+        {
+          "description": "`items` was not loaded for this turn. The field is intentionally empty.",
+          "enum": [
+            "notLoaded"
+          ],
+          "type": "string"
+        },
+        {
+          "description": "`items` contains only a display summary for this turn.",
+          "enum": [
+            "summary"
+          ],
+          "type": "string"
+        },
+        {
+          "description": "`items` contains every ThreadItem available from persisted app-server history for this turn.",
+          "enum": [
+            "full"
+          ],
+          "type": "string"
+        }
+      ]
     }
   },
   "description": "There are three ways to resume a thread: 1. By thread_id: load the thread from disk by thread_id and resume it. 2. By history: instantiate the thread from memory and resume it. 3. By path: load the thread from disk by path and resume it.\n\nFor non-running threads, the precedence is: history > non-empty path > thread_id. If using history or a non-empty path for a non-running thread, the thread_id param will be ignored.\n\nIf thread_id identifies a running thread, app-server rejoins that thread and treats a non-empty path as a consistency check against the active rollout path. Empty string path values are treated as absent.\n\nPrefer using thread_id whenever possible.",

codex-rs/app-server-protocol/schema/json/v2/ThreadResumeResponse.json

@@ -1995,6 +1995,32 @@
       ],
       "type": "string"
     },
+    "TurnsPage": {
+      "properties": {
+        "backwardsCursor": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "data": {
+          "items": {
+            "$ref": "#/definitions/Turn"
+          },
+          "type": "array"
+        },
+        "nextCursor": {
+          "type": [
+            "string",
+            "null"
+          ]
+        }
+      },
+      "required": [
+        "data"
+      ],
+      "type": "object"
+    },
     "UserInput": {
       "oneOf": [
         {

codex-rs/app-server-protocol/schema/typescript/v2/ThreadResumeInitialTurnsPageParams.ts

@@ -0,0 +1,19 @@
+// GENERATED CODE! DO NOT MODIFY BY HAND!
+
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+import type { SortDirection } from "./SortDirection";
+import type { TurnItemsView } from "./TurnItemsView";
+
+export type ThreadResumeInitialTurnsPageParams = {
+/**
+ * Optional turn page size.
+ */
+limit?: number | null,
+/**
+ * Optional turn pagination direction; defaults to descending.
+ */
+sortDirection?: SortDirection | null,
+/**
+ * How much item detail to include for each returned turn; defaults to summary.
+ */
+itemsView?: TurnItemsView | null, };

codex-rs/app-server-protocol/schema/typescript/v2/TurnsPage.ts

@@ -0,0 +1,6 @@
+// GENERATED CODE! DO NOT MODIFY BY HAND!
+
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+import type { Turn } from "./Turn";
+
+export type TurnsPage = { data: Array<Turn>, nextCursor: string | null, backwardsCursor: string | null, };

codex-rs/app-server-protocol/schema/typescript/v2/index.ts

@@ -398,6 +398,7 @@ export type { ThreadRealtimeStartTransport } from "./ThreadRealtimeStartTranspor
 export type { ThreadRealtimeStartedNotification } from "./ThreadRealtimeStartedNotification";
 export type { ThreadRealtimeTranscriptDeltaNotification } from "./ThreadRealtimeTranscriptDeltaNotification";
 export type { ThreadRealtimeTranscriptDoneNotification } from "./ThreadRealtimeTranscriptDoneNotification";
+export type { ThreadResumeInitialTurnsPageParams } from "./ThreadResumeInitialTurnsPageParams";
 export type { ThreadResumeParams } from "./ThreadResumeParams";
 export type { ThreadResumeResponse } from "./ThreadResumeResponse";
 export type { ThreadRollbackParams } from "./ThreadRollbackParams";
@@ -450,6 +451,7 @@ export type { TurnStartedNotification } from "./TurnStartedNotification";
 export type { TurnStatus } from "./TurnStatus";
 export type { TurnSteerParams } from "./TurnSteerParams";
 export type { TurnSteerResponse } from "./TurnSteerResponse";
+export type { TurnsPage } from "./TurnsPage";
 export type { UserInput } from "./UserInput";
 export type { WarningNotification } from "./WarningNotification";
 export type { WebSearchAction } from "./WebSearchAction";

codex-rs/app-server-protocol/src/protocol/v2/tests.rs

@@ -111,6 +111,85 @@ fn thread_turns_list_params_accepts_items_view() {
     assert_eq!(params.items_view, Some(TurnItemsView::NotLoaded));
 }
 
+#[test]
+fn thread_resume_params_accept_turns_page_bootstrap() {
+    let params = serde_json::from_value::<ThreadResumeParams>(json!({
+        "threadId": "thr_123",
+        "initialTurnsPage": {
+            "limit": 25,
+            "sortDirection": "asc",
+            "itemsView": "full",
+        },
+    }))
+    .expect("thread resume params should deserialize");
+
+    assert_eq!(params.thread_id, "thr_123");
+    assert_eq!(
+        params.initial_turns_page,
+        Some(ThreadResumeInitialTurnsPageParams {
+            limit: Some(25),
+            sort_direction: Some(SortDirection::Asc),
+            items_view: Some(TurnItemsView::Full),
+        })
+    );
+}
+
+#[test]
+fn thread_resume_response_round_trips_initial_turns_page() {
+    let response = ThreadResumeResponse {
+        thread: Thread {
+            id: "thr_123".to_string(),
+            session_id: "thr_123".to_string(),
+            forked_from_id: None,
+            preview: String::new(),
+            ephemeral: false,
+            model_provider: "openai".to_string(),
+            created_at: 1,
+            updated_at: 1,
+            status: ThreadStatus::Idle,
+            path: None,
+            cwd: absolute_path("tmp"),
+            cli_version: "0.0.0".to_string(),
+            source: SessionSource::Exec,
+            thread_source: None,
+            agent_nickname: None,
+            agent_role: None,
+            git_info: None,
+            name: None,
+            turns: Vec::new(),
+        },
+        model: "gpt-5".to_string(),
+        model_provider: "openai".to_string(),
+        service_tier: None,
+        cwd: absolute_path("tmp"),
+        runtime_workspace_roots: Vec::new(),
+        instruction_sources: Vec::new(),
+        approval_policy: AskForApproval::OnFailure,
+        approvals_reviewer: ApprovalsReviewer::User,
+        sandbox: SandboxPolicy::DangerFullAccess,
+        active_permission_profile: None,
+        reasoning_effort: None,
+        initial_turns_page: Some(TurnsPage {
+            data: Vec::new(),
+            next_cursor: Some("cursor_next".to_string()),
+            backwards_cursor: Some("cursor_back".to_string()),
+        }),
+    };
+
+    let value = serde_json::to_value(&response).expect("serialize thread resume response");
+    assert_eq!(
+        value.get("initialTurnsPage"),
+        Some(&json!({
+            "data": [],
+            "nextCursor": "cursor_next",
+            "backwardsCursor": "cursor_back",
+        }))
+    );
+    let decoded = serde_json::from_value::<ThreadResumeResponse>(value)
+        .expect("deserialize thread resume response");
+    assert_eq!(decoded, response);
+}
+
 #[test]
 fn thread_turns_items_list_round_trips() {
     let params = ThreadTurnsItemsListParams {
@@ -3406,6 +3485,7 @@ fn thread_lifecycle_responses_default_missing_optional_fields() {
     assert_eq!(fork.instruction_sources, Vec::<AbsolutePathBuf>::new());
     assert_eq!(start.active_permission_profile, None);
     assert_eq!(resume.active_permission_profile, None);
+    assert_eq!(resume.initial_turns_page, None);
     assert_eq!(fork.active_permission_profile, None);
 }
 

codex-rs/app-server-protocol/src/protocol/v2/thread.rs

@@ -397,6 +397,11 @@ pub struct ThreadResumeParams {
     #[experimental("thread/resume.excludeTurns")]
     #[serde(default, skip_serializing_if = "std::ops::Not::not")]
     pub exclude_turns: bool,
+    /// When present, include a `thread/turns/list` page in the resume response
+    /// so clients can bootstrap recent turns without a second request.
+    #[experimental("thread/resume.initialTurnsPage")]
+    #[ts(optional = nullable)]
+    pub initial_turns_page: Option<ThreadResumeInitialTurnsPageParams>,
     /// Deprecated and ignored by app-server. Kept only so older clients can
     /// continue sending the field while rollout persistence always uses the
     /// limited history policy.
@@ -435,6 +440,44 @@ pub struct ThreadResumeResponse {
     #[serde(default)]
     pub active_permission_profile: Option<ActivePermissionProfile>,
     pub reasoning_effort: Option<ReasoningEffort>,
+    /// `thread/turns/list` page returned when requested by `initialTurnsPage`.
+    #[experimental("thread/resume.initialTurnsPage")]
+    #[serde(default)]
+    pub initial_turns_page: Option<TurnsPage>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadResumeInitialTurnsPageParams {
+    /// Optional turn page size.
+    #[ts(optional = nullable)]
+    pub limit: Option<u32>,
+    /// Optional turn pagination direction; defaults to descending.
+    #[ts(optional = nullable)]
+    pub sort_direction: Option<SortDirection>,
+    /// How much item detail to include for each returned turn; defaults to summary.
+    #[ts(optional = nullable)]
+    pub items_view: Option<TurnItemsView>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct TurnsPage {
+    pub data: Vec<Turn>,
+    pub next_cursor: Option<String>,
+    pub backwards_cursor: Option<String>,
+}
+
+impl From<ThreadTurnsListResponse> for TurnsPage {
+    fn from(response: ThreadTurnsListResponse) -> Self {
+        Self {
+            data: response.data,
+            next_cursor: response.next_cursor,
+            backwards_cursor: response.backwards_cursor,
+        }
+    }
 }
 
 #[derive(