diff --git a/crates/tui/src/client.rs b/crates/tui/src/client.rs
index 76f71a52..30c710f6 100644
--- a/crates/tui/src/client.rs
+++ b/crates/tui/src/client.rs
@@ -61,7 +61,10 @@ pub(super) fn from_api_tool_name(name: &str) -> String {
                     break;
                 }
             }
-            if let Ok(code) = u32::from_str_radix(&hex, 16)
+            // Only decode if we got exactly 6 hex digits (matching encoder output).
+            // Fewer digits means a truncated/malformed sequence — pass through as-is.
+            if hex.len() == 6
+                && let Ok(code) = u32::from_str_radix(&hex, 16)
                 && let Some(decoded) = std::char::from_u32(code)
             {
                 if let Some('-') = iter.peek().copied() {
@@ -1395,8 +1398,8 @@ pub(super) fn parse_usage(usage: Option<&Value>) -> Usage {
     });
 
     Usage {
-        input_tokens: input_tokens as u32,
-        output_tokens: output_tokens as u32,
+        input_tokens: input_tokens.min(u64::from(u32::MAX)) as u32,
+        output_tokens: output_tokens.min(u64::from(u32::MAX)) as u32,
         prompt_cache_hit_tokens,
         prompt_cache_miss_tokens,
         reasoning_tokens,
diff --git a/crates/tui/src/client/chat.rs b/crates/tui/src/client/chat.rs
index a338170d..f8e2b984 100644
--- a/crates/tui/src/client/chat.rs
+++ b/crates/tui/src/client/chat.rs
@@ -1990,6 +1990,8 @@ fn provider_accepts_reasoning_content(provider: ApiProvider) -> bool {
             | ApiProvider::Novita
             | ApiProvider::Fireworks
             | ApiProvider::Siliconflow
+            | ApiProvider::SiliconflowCn
+            | ApiProvider::Volcengine
             | ApiProvider::Arcee
             | ApiProvider::Sglang
     )
diff --git a/crates/tui/src/commands/mod.rs b/crates/tui/src/commands/mod.rs
index 5478ee4a..0f8ffb53 100644
--- a/crates/tui/src/commands/mod.rs
+++ b/crates/tui/src/commands/mod.rs
@@ -682,8 +682,8 @@ pub fn execute(cmd: &str, app: &mut App) -> CommandResult {
         _ => {
             // Third source: skills (lowest precedence after native and user-config).
             // Try to run a skill whose name matches the command.
-            if skills::run_skill_by_name(app, command, arg).is_some() {
-                return skills::run_skill_by_name(app, command, arg).unwrap();
+            if let Some(result) = skills::run_skill_by_name(app, command, arg) {
+                return result;
             }
             let suggestions = suggest_command_names(command, 3);
             if suggestions.is_empty() {
diff --git a/crates/tui/src/tools/file.rs b/crates/tui/src/tools/file.rs
index f02124da..2ca1ca0c 100644
--- a/crates/tui/src/tools/file.rs
+++ b/crates/tui/src/tools/file.rs
@@ -114,7 +114,11 @@ impl ToolSpec for ReadFileTool {
                     "start_line must be 1-based and greater than 0".to_string(),
                 ));
             }
-            Some(v) => v as usize,
+            Some(v) => usize::try_from(v).map_err(|_| {
+                ToolError::invalid_input(
+                    "start_line exceeds platform addressable range".to_string(),
+                )
+            })?,
             None => 1,
         };
 
@@ -124,7 +128,14 @@ impl ToolSpec for ReadFileTool {
                     "max_lines must be greater than 0".to_string(),
                 ));
             }
-            Some(v) => std::cmp::min(v as usize, HARD_MAX_READ_LINES),
+            Some(v) => {
+                let converted = usize::try_from(v).map_err(|_| {
+                    ToolError::invalid_input(
+                        "max_lines exceeds platform addressable range".to_string(),
+                    )
+                })?;
+                std::cmp::min(converted, HARD_MAX_READ_LINES)
+            }
             None => DEFAULT_READ_LINES,
         };
 
@@ -292,7 +303,9 @@ fn clean_pdf_text(raw: &str) -> String {
     if any_content {
         let start = out.find(|c: char| c != '\n').unwrap_or(0);
         // Walk back from end to find the last non-newline character.
-        let end = out.rfind(|c: char| c != '\n').map_or(out.len(), |i| i + 1);
+        let end = out.rfind(|c: char| c != '\n').map_or(out.len(), |i| {
+            i + out[i..].chars().next().map_or(1, |c| c.len_utf8())
+        });
         out[start..end].to_string()
     } else {
         String::new()
diff --git a/crates/tui/src/tools/search.rs b/crates/tui/src/tools/search.rs
index 221d760b..0174011a 100644
--- a/crates/tui/src/tools/search.rs
+++ b/crates/tui/src/tools/search.rs
@@ -100,8 +100,9 @@ impl ToolSpec for GrepFilesTool {
     async fn execute(&self, input: Value, context: &ToolContext) -> Result<ToolResult, ToolError> {
         let pattern_str = required_str(&input, "pattern")?;
         let path_str = optional_str(&input, "path").unwrap_or(".");
-        let context_lines =
-            usize::try_from(optional_u64(&input, "context_lines", 2)).unwrap_or(usize::MAX);
+        let context_lines = usize::try_from(optional_u64(&input, "context_lines", 2))
+            .unwrap_or(usize::MAX)
+            .min(1000);
         let case_insensitive = optional_bool(&input, "case_insensitive", false);
         let max_results = usize::try_from(optional_u64(&input, "max_results", MAX_RESULTS as u64))
             .unwrap_or(MAX_RESULTS);