fix: avoid utf8 panic in string preview truncation

src/apps/cli/src/root_handlers.rs

@@ -6,6 +6,7 @@ use std::path::Path;
 use crate::{
     config::CliConfig,
     modes::exec::{ExecMode, ExecOutputFormat, ExecSessionOptions},
+    ui::string_utils::truncate_str,
     ConfigAction, SessionAction,
 };
 
@@ -202,7 +203,7 @@ pub async fn handle_session_action(action: SessionAction) -> Result<Option<Strin
                         } => format!("[Tool result: {}]", tool_name),
                     };
                     let preview = if content_preview.len() > 80 {
-                        format!("{}...", &content_preview[..77])
+                        truncate_str(&content_preview, 77)
                     } else {
                         content_preview
                     };
@@ -237,10 +238,9 @@ pub async fn handle_session_action(action: SessionAction) -> Result<Option<Strin
                 .ok_or_else(|| anyhow::anyhow!("Session has no persisted turns to fork"))?;
             let path_manager = bitfun_core::infrastructure::try_get_path_manager_arc()
                 .map_err(|error| anyhow::anyhow!(error.to_string()))?;
-            let persistence_manager = bitfun_core::agentic::persistence::PersistenceManager::new(
-                path_manager,
-            )
-            .map_err(|error| anyhow::anyhow!(error.to_string()))?;
+            let persistence_manager =
+                bitfun_core::agentic::persistence::PersistenceManager::new(path_manager)
+                    .map_err(|error| anyhow::anyhow!(error.to_string()))?;
             let result = persistence_manager
                 .branch_session(
                     &workspace_path,

src/apps/relay-server/src/routes/websocket.rs

@@ -20,6 +20,18 @@ use tracing::{debug, error, info, warn};
 use crate::relay::room::{ConnId, OutboundMessage, ResponsePayload, RoomManager};
 use crate::routes::api::AppState;
 
+fn truncate_preview(text: &str, max_bytes: usize) -> &str {
+    if text.len() <= max_bytes {
+        return text;
+    }
+
+    let mut end = max_bytes;
+    while end > 0 && !text.is_char_boundary(end) {
+        end -= 1;
+    }
+    &text[..end]
+}
+
 /// Messages received from the desktop via WebSocket.
 #[derive(Debug, Deserialize)]
 #[serde(tag = "type", rename_all = "snake_case")]
@@ -120,7 +132,7 @@ fn handle_text_message(
 ) {
     debug!(
         "Received from conn_id={conn_id}: {}",
-        &text[..text.len().min(200)]
+        truncate_preview(text, 200)
     );
     let msg: InboundMessage = match serde_json::from_str(text) {
         Ok(m) => m,
@@ -193,6 +205,18 @@ fn handle_text_message(
     }
 }
 
+#[cfg(test)]
+mod tests {
+    use super::truncate_preview;
+
+    #[test]
+    fn truncate_preview_respects_utf8_boundaries() {
+        let text = format!("{}{}", "a".repeat(199), "你");
+
+        assert_eq!(truncate_preview(&text, 200), "a".repeat(199));
+    }
+}
+
 fn send_json<T: Serialize>(tx: &mpsc::UnboundedSender<OutboundMessage>, msg: &T) {
     if let Ok(json) = serde_json::to_string(msg) {
         let _ = tx.send(OutboundMessage { text: json });

src/crates/core/src/service/remote_ssh/manager.rs

@@ -7,6 +7,7 @@ use crate::service::remote_ssh::types::{
     SSHAuthMethod, SSHCommandOptions, SSHCommandResult, SSHConfigEntry, SSHConfigLookupResult,
     SSHConnectionConfig, SSHConnectionResult, SavedConnection, ServerInfo,
 };
+use crate::util::truncate_at_char_boundary;
 use anyhow::{anyhow, Context};
 use async_trait::async_trait;
 use russh::client::{DisconnectReason, Handle, Handler, Msg};
@@ -1396,7 +1397,7 @@ impl SSHConnectionManager {
     ) -> std::result::Result<SSHCommandResult, anyhow::Error> {
         let execution_started_at = Instant::now();
         let command_preview = if command.len() > 160 {
-            format!("{}...", &command[..160])
+            format!("{}...", truncate_at_char_boundary(command, 160))
         } else {
             command.to_string()
         };