feat(app-server): add history_mode to thread

codex-rs/analytics/src/analytics_client_tests.rs

@@ -198,6 +198,7 @@ fn sample_thread_with_metadata(
         parent_thread_id,
         preview: "first prompt".to_string(),
         ephemeral,
+        history_mode: Default::default(),
         model_provider: "openai".to_string(),
         created_at: 1,
         updated_at: 2,

codex-rs/analytics/src/client_tests.rs

@@ -283,6 +283,7 @@ fn sample_thread(thread_id: &str) -> Thread {
         parent_thread_id: None,
         preview: "first prompt".to_string(),
         ephemeral: false,
+        history_mode: Default::default(),
         model_provider: "openai".to_string(),
         created_at: 1,
         updated_at: 2,

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -2580,6 +2580,7 @@ mod tests {
                     parent_thread_id: None,
                     preview: "first prompt".to_string(),
                     ephemeral: true,
+                    history_mode: Default::default(),
                     model_provider: "openai".to_string(),
                     created_at: 1,
                     updated_at: 2,
@@ -2630,6 +2631,7 @@ mod tests {
                         "parentThreadId": null,
                         "preview": "first prompt",
                         "ephemeral": true,
+                        "historyMode": "legacy",
                         "modelProvider": "openai",
                         "createdAt": 1,
                         "updatedAt": 2,

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

@@ -174,6 +174,7 @@ fn thread_resume_response_round_trips_initial_turns_page() {
             parent_thread_id: None,
             preview: String::new(),
             ephemeral: false,
+            history_mode: Default::default(),
             model_provider: "openai".to_string(),
             created_at: 1,
             updated_at: 1,

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

@@ -4,6 +4,7 @@ use super::AskForApproval;
 use super::SandboxMode;
 use super::SandboxPolicy;
 use super::Thread;
+use super::ThreadHistoryMode;
 use super::ThreadItem;
 use super::ThreadSource;
 use super::Turn;
@@ -105,6 +106,10 @@ pub struct ThreadStartParams {
     pub multi_agent_mode: Option<MultiAgentMode>,
     #[ts(optional = nullable)]
     pub ephemeral: Option<bool>,
+    /// Persisted thread history contract to use for this new thread.
+    #[experimental("thread/start.historyMode")]
+    #[ts(optional = nullable)]
+    pub history_mode: Option<ThreadHistoryMode>,
     #[ts(optional = nullable)]
     pub session_start_source: Option<ThreadStartSource>,
     /// Optional client-supplied analytics source classification for this thread.

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

@@ -5,6 +5,7 @@ use super::TurnStatus;
 use codex_experimental_api_macros::ExperimentalApi;
 use codex_protocol::protocol::SessionSource as CoreSessionSource;
 use codex_protocol::protocol::SubAgentSource as CoreSubAgentSource;
+use codex_protocol::protocol::ThreadHistoryMode as CoreThreadHistoryMode;
 use codex_protocol::protocol::ThreadSource as CoreThreadSource;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use schemars::JsonSchema;
@@ -64,6 +65,33 @@ impl From<SessionSource> for CoreSessionSource {
     }
 }
 
+#[derive(Default, Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "lowercase")]
+#[ts(rename_all = "lowercase", export_to = "v2/")]
+pub enum ThreadHistoryMode {
+    #[default]
+    Legacy,
+    Paginated,
+}
+
+impl From<CoreThreadHistoryMode> for ThreadHistoryMode {
+    fn from(value: CoreThreadHistoryMode) -> Self {
+        match value {
+            CoreThreadHistoryMode::Legacy => Self::Legacy,
+            CoreThreadHistoryMode::Paginated => Self::Paginated,
+        }
+    }
+}
+
+impl From<ThreadHistoryMode> for CoreThreadHistoryMode {
+    fn from(value: ThreadHistoryMode) -> Self {
+        match value {
+            ThreadHistoryMode::Legacy => Self::Legacy,
+            ThreadHistoryMode::Paginated => Self::Paginated,
+        }
+    }
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, TS)]
 #[serde(try_from = "String", into = "String")]
 #[ts(type = "string")]
@@ -155,6 +183,10 @@ pub struct Thread {
     pub preview: String,
     /// Whether the thread is ephemeral and should not be materialized on disk.
     pub ephemeral: bool,
+    /// Persisted thread history contract selected when this thread was created.
+    #[experimental("thread.historyMode")]
+    #[serde(default)]
+    pub history_mode: ThreadHistoryMode,
     /// Model provider used for this thread (for example, 'openai').
     pub model_provider: String,
     /// Unix timestamp (in seconds) when the thread was created.

codex-rs/app-server/src/bespoke_event_handling.rs

@@ -2284,6 +2284,7 @@ mod tests {
             cwd: test_path_buf("/tmp").abs().into(),
             cli_version: "0.0.0".to_string(),
             source: SessionSource::Cli,
+            history_mode: Default::default(),
             thread_source: None,
             agent_nickname: None,
             agent_role: None,

codex-rs/app-server/src/request_processors.rs

@@ -206,6 +206,8 @@ use codex_app_server_protocol::ThreadGoalSetResponse;
 use codex_app_server_protocol::ThreadGoalStatus;
 use codex_app_server_protocol::ThreadGoalUpdatedNotification;
 use codex_app_server_protocol::ThreadHistoryBuilder;
+#[cfg(test)]
+use codex_app_server_protocol::ThreadHistoryMode;
 use codex_app_server_protocol::ThreadIncrementElicitationParams;
 use codex_app_server_protocol::ThreadIncrementElicitationResponse;
 use codex_app_server_protocol::ThreadInjectItemsParams;

codex-rs/app-server/src/request_processors/external_agent_session_import.rs

@@ -15,6 +15,7 @@ use codex_models_manager::manager::RefreshStrategy;
 use codex_protocol::ThreadId;
 use codex_protocol::models::BaseInstructions;
 use codex_protocol::protocol::MultiAgentVersion;
+use codex_protocol::protocol::ThreadHistoryMode;
 use codex_protocol::protocol::ThreadMemoryMode;
 use codex_rollout::is_persisted_rollout_item;
 use codex_thread_store::AppendThreadItemsParams;
@@ -221,6 +222,7 @@ impl ExternalAgentSessionImporter {
             dynamic_tools: Vec::new(),
             selected_capability_roots: Vec::new(),
             multi_agent_version: Some(MultiAgentVersion::V1),
+            history_mode: ThreadHistoryMode::Legacy,
             initial_window_id: uuid::Uuid::now_v7().to_string(),
             metadata: ThreadPersistenceMetadata {
                 cwd: Some(cwd.clone()),