Track inherited paginated rollout prefixes

codex-rs/app-server/tests/common/rollout.rs

@@ -242,6 +242,7 @@ fn create_fake_rollout_with_source_and_parent_thread_id(
         selected_capability_roots: Vec::new(),
         memory_mode: None,
         history_mode: Default::default(),
+        history_base: None,
         subagent_history_start_ordinal: None,
         multi_agent_version: None,
         context_window: None,
@@ -333,6 +334,7 @@ pub fn create_fake_rollout_with_text_elements(
         selected_capability_roots: Vec::new(),
         memory_mode: None,
         history_mode: Default::default(),
+        history_base: None,
         subagent_history_start_ordinal: None,
         multi_agent_version: None,
         context_window: None,

codex-rs/app-server/tests/suite/v2/thread_resume.rs

@@ -2588,6 +2588,7 @@ stream_max_retries = 0
         selected_capability_roots: Vec::new(),
         memory_mode: None,
         history_mode: Default::default(),
+        history_base: None,
         subagent_history_start_ordinal: None,
         multi_agent_version: None,
         context_window: None,

codex-rs/core/tests/suite/sqlite_state.rs

@@ -375,6 +375,7 @@ async fn backfill_scans_existing_rollouts() -> Result<()> {
                     selected_capability_roots: Vec::new(),
                     memory_mode: None,
                     history_mode: Default::default(),
+                    history_base: None,
                     subagent_history_start_ordinal: None,
                     multi_agent_version: None,
                     context_window: None,

codex-rs/protocol/src/protocol.rs

@@ -3049,6 +3049,16 @@ impl SessionContextWindow {
     }
 }
 
+/// Exclusive position in another thread's paginated rollout history.
+#[derive(Serialize, Deserialize, Clone, Copy, Debug, PartialEq, Eq, JsonSchema, TS)]
+pub struct HistoryPosition {
+    pub thread_id: ThreadId,
+    /// First rollout ordinal not included from the prefix file.
+    pub end_ordinal_exclusive: u64,
+    /// Byte offset immediately after the last included JSONL record from the prefix file.
+    pub end_byte_offset: u64,
+}
+
 /// SessionMeta contains session-level data that doesn't correspond to a specific turn.
 ///
 /// NOTE: There used to be an `instructions` field here, which stored user_instructions, but we
@@ -3098,6 +3108,9 @@ pub struct SessionMeta {
     pub memory_mode: Option<String>,
     #[serde(default)]
     pub history_mode: ThreadHistoryMode,
+    /// Exclusive prefix of another paginated rollout inherited by this thread.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub history_base: Option<HistoryPosition>,
     /// First rollout ordinal that belongs to this subagent's own projected history.
     ///
     /// Earlier rollout records are inherited model context and stay out of child
@@ -3134,6 +3147,7 @@ impl Default for SessionMeta {
             selected_capability_roots: Vec::new(),
             memory_mode: None,
             history_mode: ThreadHistoryMode::default(),
+            history_base: None,
             subagent_history_start_ordinal: None,
             multi_agent_version: None,
             context_window: None,
@@ -5854,6 +5868,7 @@ mod tests {
         }))?;
 
         assert_eq!(session_meta.history_mode, ThreadHistoryMode::Legacy);
+        assert_eq!(session_meta.history_base, None);
         let serialized = serde_json::to_value(&session_meta)?;
         assert_eq!(serialized["history_mode"], json!("legacy"));
         let mut unknown = serialized;

codex-rs/rollout/src/compression_tests.rs

@@ -606,6 +606,7 @@ fn write_rollout(path: &std::path::Path, thread_id: ThreadId, message: &str) ->
             selected_capability_roots: Vec::new(),
             memory_mode: None,
             history_mode: Default::default(),
+            history_base: None,
             subagent_history_start_ordinal: None,
             multi_agent_version: None,
             context_window: None,

codex-rs/rollout/src/metadata_tests.rs

@@ -53,6 +53,7 @@ async fn extract_metadata_from_rollout_uses_session_meta() {
         selected_capability_roots: Vec::new(),
         memory_mode: None,
         history_mode: ThreadHistoryMode::Paginated,
+        history_base: None,
         subagent_history_start_ordinal: None,
         multi_agent_version: None,
         context_window: None,
@@ -150,6 +151,7 @@ async fn extract_metadata_from_rollout_returns_latest_memory_mode() {
         selected_capability_roots: Vec::new(),
         memory_mode: None,
         history_mode: Default::default(),
+        history_base: None,
         subagent_history_start_ordinal: None,
         multi_agent_version: None,
         context_window: None,
@@ -424,6 +426,7 @@ fn write_rollout_in_sessions_with_cwd(
         selected_capability_roots: Vec::new(),
         memory_mode: None,
         history_mode: Default::default(),
+        history_base: None,
         subagent_history_start_ordinal: None,
         multi_agent_version: None,
         context_window: None,

codex-rs/rollout/src/recorder.rs

@@ -831,6 +831,7 @@ impl RolloutRecorder {
                     selected_capability_roots,
                     memory_mode: (!config.generate_memories()).then_some("disabled".to_string()),
                     history_mode,
+                    history_base: None,
                     subagent_history_start_ordinal,
                     multi_agent_version,
                     context_window: initial_window_id.map(SessionContextWindow::new),

codex-rs/rollout/src/recorder_tests.rs

@@ -178,6 +178,7 @@ async fn state_db_init_backfills_before_returning() -> anyhow::Result<()> {
             selected_capability_roots: Vec::new(),
             memory_mode: None,
             history_mode: Default::default(),
+            history_base: None,
             subagent_history_start_ordinal: None,
             multi_agent_version: None,
             context_window: None,

codex-rs/rollout/src/session_index_tests.rs

@@ -45,6 +45,7 @@ fn write_rollout_with_metadata(path: &Path, thread_id: ThreadId) -> std::io::Res
                 selected_capability_roots: Vec::new(),
                 memory_mode: None,
                 history_mode: Default::default(),
+                history_base: None,
                 subagent_history_start_ordinal: None,
                 multi_agent_version: None,
                 context_window: None,

codex-rs/rollout/src/state_db_tests.rs

@@ -178,6 +178,7 @@ fn write_rollout_with_user_message(
                     selected_capability_roots: Vec::new(),
                     memory_mode: None,
                     history_mode: Default::default(),
+                    history_base: None,
                     subagent_history_start_ordinal: None,
                     multi_agent_version: None,
                     context_window: None,

codex-rs/rollout/src/tests.rs

@@ -1336,6 +1336,7 @@ async fn test_updated_at_uses_file_mtime() -> Result<()> {
                 selected_capability_roots: Vec::new(),
                 memory_mode: None,
                 history_mode: Default::default(),
+                history_base: None,
                 subagent_history_start_ordinal: None,
                 multi_agent_version: None,
                 context_window: None,

codex-rs/state/src/extract.rs

@@ -381,6 +381,7 @@ mod tests {
                     selected_capability_roots: Vec::new(),
                     memory_mode: None,
                     history_mode: Default::default(),
+                    history_base: None,
                     subagent_history_start_ordinal: None,
                     multi_agent_version: None,
                     context_window: None,
@@ -629,6 +630,7 @@ mod tests {
                     selected_capability_roots: Vec::new(),
                     memory_mode: None,
                     history_mode: ThreadHistoryMode::Legacy,
+                    history_base: None,
                     subagent_history_start_ordinal: None,
                     multi_agent_version: None,
                     context_window: None,

codex-rs/state/src/runtime/threads.rs

@@ -2183,6 +2183,7 @@ mod tests {
                 selected_capability_roots: Vec::new(),
                 memory_mode: Some("polluted".to_string()),
                 history_mode: Default::default(),
+                history_base: None,
                 subagent_history_start_ordinal: None,
                 multi_agent_version: None,
                 context_window: None,
@@ -2249,6 +2250,7 @@ mod tests {
                 selected_capability_roots: Vec::new(),
                 memory_mode: None,
                 history_mode: Default::default(),
+                history_base: None,
                 subagent_history_start_ordinal: None,
                 multi_agent_version: None,
                 context_window: None,

codex-rs/thread-store/src/in_memory.rs

@@ -443,6 +443,7 @@ impl InMemoryThreadStore {
             memory_mode: matches!(params.metadata.memory_mode, ThreadMemoryMode::Disabled)
                 .then_some("disabled".to_string()),
             history_mode: params.history_mode,
+            history_base: None,
             subagent_history_start_ordinal: params.subagent_history_start_ordinal,
             multi_agent_version: params.multi_agent_version,
             context_window: Some(SessionContextWindow::new(params.initial_window_id.clone())),