diff --git a/crates/tui/src/commands/debug.rs b/crates/tui/src/commands/debug.rs
index 373c927f..b096b29f 100644
--- a/crates/tui/src/commands/debug.rs
+++ b/crates/tui/src/commands/debug.rs
@@ -74,7 +74,9 @@ pub fn tokens(app: &mut App) -> CommandResult {
         .replace("{total}", &app.session.total_tokens.to_string())
         .replace(
             "{cost}",
-            &app.format_cost_amount_precise(app.session_cost_for_currency(app.cost_currency)),
+            &app.format_cost_amount_precise(
+                app.displayed_session_cost_for_currency(app.cost_currency),
+            ),
         )
         .replace("{api_messages}", &message_count.to_string())
         .replace("{chat_messages}", &chat_count.to_string())
@@ -84,9 +86,10 @@ pub fn tokens(app: &mut App) -> CommandResult {
 
 /// Show session cost breakdown
 pub fn cost(app: &mut App) -> CommandResult {
+    let total = app.displayed_session_cost_for_currency(app.cost_currency);
     let report = tr(app.ui_locale, MessageId::CmdCostReport).replace(
         "{cost}",
-        &app.format_cost_amount_precise(app.session_cost_for_currency(app.cost_currency)),
+        &app.format_cost_amount_precise(total),
     );
     CommandResult::message(report)
 }
diff --git a/crates/tui/src/commands/rename.rs b/crates/tui/src/commands/rename.rs
index 705ec02f..e551cf61 100644
--- a/crates/tui/src/commands/rename.rs
+++ b/crates/tui/src/commands/rename.rs
@@ -58,6 +58,7 @@ fn rename_with_manager(
         u64::from(app.session.total_tokens),
         app.system_prompt.as_ref(),
     );
+    app.sync_cost_to_metadata(&mut session.metadata);
     session.metadata.title = new_title.to_string();
 
     match manager.save_session(&session) {
diff --git a/crates/tui/src/commands/session.rs b/crates/tui/src/commands/session.rs
index d6c9db6c..6f3a4257 100644
--- a/crates/tui/src/commands/session.rs
+++ b/crates/tui/src/commands/session.rs
@@ -28,6 +28,7 @@ pub fn save(app: &mut App, path: Option<&str>) -> CommandResult {
         app.system_prompt.as_ref(),
         Some(app.mode.label()),
     );
+    app.sync_cost_to_metadata(&mut session.metadata);
     session.artifacts = app.session_artifacts.clone();
 
     let sessions_dir = save_path
diff --git a/crates/tui/src/main.rs b/crates/tui/src/main.rs
index 54373758..5a84a625 100644
--- a/crates/tui/src/main.rs
+++ b/crates/tui/src/main.rs
@@ -3060,13 +3060,14 @@ fn fork_session(session_id: Option<String>, last: bool, workspace: &Path) -> Res
         .system_prompt
         .as_ref()
         .map(|text| SystemPrompt::Text(text.clone()));
-    let forked = create_saved_session(
+    let mut forked = create_saved_session(
         &saved.messages,
         &saved.metadata.model,
         &saved.metadata.workspace,
         saved.metadata.total_tokens,
         system_prompt.as_ref(),
     );
+    forked.metadata.copy_cost_from(&saved.metadata);
     manager.save_session(&forked)?;
 
     let source_title = saved.metadata.title.trim();
diff --git a/crates/tui/src/tui/app.rs b/crates/tui/src/tui/app.rs
index 4a74c6f7..d0bf153c 100644
--- a/crates/tui/src/tui/app.rs
+++ b/crates/tui/src/tui/app.rs
@@ -1784,6 +1784,18 @@ impl App {
         self.refresh_displayed_cost_high_water();
     }
 
+    /// Copy current session/subagent cost accumulators into session metadata
+    /// for persistence.
+    pub fn sync_cost_to_metadata(&self, metadata: &mut crate::session_manager::SessionMetadata) {
+        metadata.cost.session_cost_usd = self.session.session_cost;
+        metadata.cost.session_cost_cny = self.session.session_cost_cny;
+        metadata.cost.subagent_cost_usd = self.session.subagent_cost;
+        metadata.cost.subagent_cost_cny = self.session.subagent_cost_cny;
+        metadata.cost.displayed_cost_high_water_usd = self.session.displayed_cost_high_water;
+        metadata.cost.displayed_cost_high_water_cny =
+            self.session.displayed_cost_high_water_cny;
+    }
+
     /// Recompute the displayed cost high-water mark. Called any time a cost
     /// counter is mutated; never decreases.
     pub fn refresh_displayed_cost_high_water(&mut self) {
diff --git a/crates/tui/src/tui/session_picker.rs b/crates/tui/src/tui/session_picker.rs
index 9fd520b1..77b86964 100644
--- a/crates/tui/src/tui/session_picker.rs
+++ b/crates/tui/src/tui/session_picker.rs
@@ -17,8 +17,8 @@ use unicode_width::{UnicodeWidthChar, UnicodeWidthStr};
 
 use crate::palette;
 use crate::session_manager::{
-    SavedSession, SessionManager, SessionMetadata, extract_title, extract_user_prompt,
-    strip_thinking_tags,
+    SavedSession, SessionCostSnapshot, SessionManager, SessionMetadata, extract_title,
+    extract_user_prompt, strip_thinking_tags,
 };
 use crate::tui::views::{ModalKind, ModalView, ViewAction, ViewEvent};
 
@@ -801,7 +801,7 @@ mod tests {
             model: "deepseek-v4-pro".to_string(),
             workspace: std::path::PathBuf::from("/tmp"),
             mode: Some("agent".to_string()),
-            cost: crate::session_manager::SessionCostSnapshot::default(),
+            cost: SessionCostSnapshot::default(),
         }
     }
 
diff --git a/crates/tui/src/tui/sidebar.rs b/crates/tui/src/tui/sidebar.rs
index f2630f91..35b7b68d 100644
--- a/crates/tui/src/tui/sidebar.rs
+++ b/crates/tui/src/tui/sidebar.rs
@@ -1339,22 +1339,22 @@ fn render_context_panel(f: &mut Frame, area: Rect, app: &App) {
     )));
 
     // ── Session cost ─────────────────────────────────────────────
-    let total_cost = app.displayed_session_cost_for_currency(app.cost_currency);
+    let displayed_total = app.displayed_session_cost_for_currency(app.cost_currency);
     let session_cost = app.session_cost_for_currency(app.cost_currency);
     let agent_cost = app.subagent_cost_for_currency(app.cost_currency);
     let real_total = session_cost + agent_cost;
     // Only show the additive breakdown when it matches the displayed
     // total; when the high-water mark is in effect (post-reconciliation),
     // the breakdown would not sum to the displayed value (#244).
-    let cost_line = if (total_cost - real_total).abs() < COST_EQ_TOLERANCE {
+    let cost_line = if (displayed_total - real_total).abs() < COST_EQ_TOLERANCE {
         format!(
             "cost: {} (session {} + agents {})",
-            app.format_cost_amount(total_cost),
+            app.format_cost_amount(displayed_total),
             app.format_cost_amount(session_cost),
             app.format_cost_amount(agent_cost)
         )
     } else {
-        format!("cost: {}", app.format_cost_amount(total_cost),)
+        format!("cost: {}", app.format_cost_amount(displayed_total))
     };
     lines.push(Line::from(Span::styled(
         cost_line,
diff --git a/crates/tui/src/tui/ui.rs b/crates/tui/src/tui/ui.rs
index 055ed03c..366c65f6 100644
--- a/crates/tui/src/tui/ui.rs
+++ b/crates/tui/src/tui/ui.rs
@@ -3481,6 +3481,7 @@ fn build_session_snapshot(app: &App, manager: &SessionManager) -> SavedSession {
             app.system_prompt.as_ref(),
         );
         updated.metadata.mode = Some(app.mode.as_setting().to_string());
+        app.sync_cost_to_metadata(&mut updated.metadata);
         updated.context_references = app.session_context_references.clone();
         updated.artifacts = app.session_artifacts.clone();
         updated
@@ -3505,6 +3506,7 @@ fn build_session_snapshot(app: &App, manager: &SessionManager) -> SavedSession {
                 Some(app.mode.as_setting()),
             )
         };
+        app.sync_cost_to_metadata(&mut session.metadata);
         session.context_references = app.session_context_references.clone();
         session.artifacts = app.session_artifacts.clone();
         session
@@ -6874,10 +6876,10 @@ fn apply_loaded_session(app: &mut App, session: &SavedSession) -> bool {
     app.workspace.clone_from(&session.metadata.workspace);
     app.session.total_tokens = u32::try_from(session.metadata.total_tokens).unwrap_or(u32::MAX);
     app.session.total_conversation_tokens = app.session.total_tokens;
-    app.session.session_cost = 0.0;
-    app.session.session_cost_cny = 0.0;
-    app.session.subagent_cost = 0.0;
-    app.session.subagent_cost_cny = 0.0;
+    app.session.session_cost = session.metadata.cost.session_cost_usd;
+    app.session.session_cost_cny = session.metadata.cost.session_cost_cny;
+    app.session.subagent_cost = session.metadata.cost.subagent_cost_usd;
+    app.session.subagent_cost_cny = session.metadata.cost.subagent_cost_cny;
     app.session.subagent_cost_event_seqs.clear();
     // Restore the high-water marks from persisted metadata so the
     // monotonic cost guarantee (#244) survives session restarts.