diff --git a/src-tauri/src/proxy/providers/streaming_codex_chat.rs b/src-tauri/src/proxy/providers/streaming_codex_chat.rs
index 7039c1b27a..a5326ab137 100644
--- a/src-tauri/src/proxy/providers/streaming_codex_chat.rs
+++ b/src-tauri/src/proxy/providers/streaming_codex_chat.rs
@@ -429,8 +429,10 @@ impl ChatToResponsesState {
             if let Some(id) = id_delta {
                 state.call_id = id;
             }
-            if let Some(name) = name_delta {
-                state.name = name;
+            if let Some(ref name) = name_delta {
+                if !name.is_empty() {
+                    state.name.clone_from(name);
+                }
             }
             if !args_delta.is_empty() {
                 state.arguments.push_str(&args_delta);
@@ -442,7 +444,7 @@ impl ChatToResponsesState {
                 }
             }
 
-            if !state.added && (!state.call_id.is_empty() || !state.name.is_empty()) {
+            if !state.added && !state.call_id.is_empty() && !state.name.is_empty() {
                 should_add = true;
                 pending_arguments = state.arguments.clone();
             } else if state.added {
@@ -464,9 +466,6 @@ impl ChatToResponsesState {
             if state.call_id.is_empty() {
                 state.call_id = format!("call_{chat_index}");
             }
-            if state.name.is_empty() {
-                state.name = "unknown_tool".to_string();
-            }
             state.output_index = Some(assigned);
             let is_custom_tool = self.tool_context.is_custom_tool_chat_name(&state.name);
             state.item_id = response_tool_call_item_id_from_chat_name(
@@ -699,6 +698,21 @@ impl ChatToResponsesState {
                 continue;
             }
 
+            // Skip tool calls with missing names (defensive: some models generate
+            // tool call deltas without providing a valid function name)
+            let has_bad_name = self
+                .tools
+                .get(&key)
+                .map(|state| state.name.is_empty())
+                .unwrap_or(true);
+            if has_bad_name {
+                if let Some(state) = self.tools.get_mut(&key) {
+                    state.done = true;
+                }
+                log::warn!("[Codex] Skipping streaming tool call with missing name");
+                continue;
+            }
+
             if self
                 .tools
                 .get(&key)
@@ -713,9 +727,6 @@ impl ChatToResponsesState {
                 if state.call_id.is_empty() {
                     state.call_id = format!("call_{key}");
                 }
-                if state.name.is_empty() {
-                    state.name = "unknown_tool".to_string();
-                }
                 state.output_index = Some(assigned);
                 state.item_id = response_tool_call_item_id_from_chat_name(
                     &state.call_id,
diff --git a/src-tauri/src/proxy/providers/transform_codex_chat.rs b/src-tauri/src/proxy/providers/transform_codex_chat.rs
index d43809f0fa..1edc23d701 100644
--- a/src-tauri/src/proxy/providers/transform_codex_chat.rs
+++ b/src-tauri/src/proxy/providers/transform_codex_chat.rs
@@ -1398,6 +1398,14 @@ fn chat_tool_calls_to_response_output_items(
 
     if let Some(tool_calls) = message.get("tool_calls").and_then(|v| v.as_array()) {
         for (index, tool_call) in tool_calls.iter().enumerate() {
+            // Skip tool calls with missing function names (defensive: some models
+            // may generate tool calls without providing a valid name)
+            let function = tool_call.get("function").unwrap_or(&Value::Null);
+            let name = function.get("name").and_then(|v| v.as_str()).unwrap_or("");
+            if name.is_empty() {
+                log::warn!("[Codex] Skipping tool call with missing name");
+                continue;
+            }
             output.push(chat_tool_call_to_response_item(
                 tool_call,
                 index,
@@ -1406,11 +1414,13 @@ fn chat_tool_calls_to_response_output_items(
             ));
         }
     } else if let Some(function_call) = message.get("function_call") {
-        output.push(chat_legacy_function_call_to_response_item(
+        if let Some(item) = chat_legacy_function_call_to_response_item(
             function_call,
             reasoning,
             tool_context,
-        ));
+        ) {
+            output.push(item);
+        }
     }
 
     output
@@ -1448,7 +1458,7 @@ fn chat_legacy_function_call_to_response_item(
     function_call: &Value,
     reasoning: Option<&str>,
     tool_context: &CodexToolContext,
-) -> Value {
+) -> Option<Value> {
     let call_id = function_call
         .get("id")
         .and_then(|v| v.as_str())
@@ -1458,10 +1468,18 @@ fn chat_legacy_function_call_to_response_item(
         .get("name")
         .and_then(|v| v.as_str())
         .unwrap_or("");
+
+    // Skip legacy function calls with missing names (defensive: some models
+    // may generate function_call without providing a valid name)
+    if name.is_empty() {
+        log::warn!("[Codex] Skipping legacy function_call with missing name");
+        return None;
+    }
+
     let arguments = canonicalize_tool_arguments(function_call.get("arguments"));
 
     let item_id = response_tool_call_item_id_from_chat_name(call_id, name, tool_context);
-    response_tool_call_item_from_chat_name(
+    Some(response_tool_call_item_from_chat_name(
         &item_id,
         "completed",
         call_id,
@@ -1469,7 +1487,7 @@ fn chat_legacy_function_call_to_response_item(
         &arguments,
         reasoning,
         tool_context,
-    )
+    ))
 }
 
 pub(crate) fn response_tool_call_item_id_from_chat_name(