fix: Handle empty assistant messages as turn completion

- When the API returns an empty assistant message (content: []), treat it as turn completion signal
- This fixes the "working" hang that occurs after tool calls when the API stream ends with an empty message
- Updated parse_agent_message to return None for empty content
- Fixes issue where llmx would hang indefinitely waiting for content that never comes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

llmx-rs/core/src/event_mapping.rs

@@ -54,7 +54,7 @@ fn parse_user_message(message: &[ContentItem]) -> Option<UserMessageItem> {
     Some(UserMessageItem::new(&content))
 }
 
-fn parse_agent_message(id: Option<&String>, message: &[ContentItem]) -> AgentMessageItem {
+fn parse_agent_message(id: Option<&String>, message: &[ContentItem]) -> Option<AgentMessageItem> {
     let mut content: Vec<AgentMessageContent> = Vec::new();
     for content_item in message.iter() {
         match content_item {
@@ -69,18 +69,23 @@ fn parse_agent_message(id: Option<&String>, message: &[ContentItem]) -> AgentMes
             }
         }
     }
+
+    // If the message has no content, return None to signal turn completion
+    // This happens when the API ends a turn with an empty assistant message (e.g., after tool calls)
+    if content.is_empty() {
+        return None;
+    }
+
     let id = id.cloned().unwrap_or_else(|| Uuid::new_v4().to_string());
-    AgentMessageItem { id, content }
+    Some(AgentMessageItem { id, content })
 }
 
 pub fn parse_turn_item(item: &ResponseItem) -> Option<TurnItem> {
     match item {
         ResponseItem::Message { role, content, id } => match role.as_str() {
             "user" => parse_user_message(content).map(TurnItem::UserMessage),
-            "assistant" => Some(TurnItem::AgentMessage(parse_agent_message(
-                id.as_ref(),
-                content,
-            ))),
+            "assistant" => parse_agent_message(id.as_ref(), content)
+                .map(TurnItem::AgentMessage),
             "system" => None,
             _ => None,
         },

llmx-rs/core/src/model_provider_info.rs

@@ -294,6 +294,7 @@ pub fn built_in_model_providers() -> HashMap<String, ModelProviderInfo> {
                 request_max_retries: None,
                 stream_max_retries: None,
                 stream_idle_timeout_ms: None,
+            max_tokens: None,
                 max_tokens: None,
                 requires_openai_auth: false,
             },
@@ -335,6 +336,7 @@ pub fn built_in_model_providers() -> HashMap<String, ModelProviderInfo> {
                 request_max_retries: None,
                 stream_max_retries: None,
                 stream_idle_timeout_ms: None,
+            max_tokens: None,
                 max_tokens: None,
                 requires_openai_auth: true,
             },
@@ -381,6 +383,7 @@ pub fn create_oss_provider_with_base_url(base_url: &str) -> ModelProviderInfo {
         request_max_retries: None,
         stream_max_retries: None,
         stream_idle_timeout_ms: None,
+            max_tokens: None,
         max_tokens: None,
         requires_openai_auth: false,
     }
@@ -422,6 +425,7 @@ base_url = "http://localhost:11434/v1"
             request_max_retries: None,
             stream_max_retries: None,
             stream_idle_timeout_ms: None,
+            max_tokens: None,
             requires_openai_auth: false,
         };
 
@@ -452,6 +456,7 @@ query_params = { api-version = "2025-04-01-preview" }
             request_max_retries: None,
             stream_max_retries: None,
             stream_idle_timeout_ms: None,
+            max_tokens: None,
             requires_openai_auth: false,
         };
 
@@ -485,6 +490,7 @@ env_http_headers = { "X-Example-Env-Header" = "EXAMPLE_ENV_VAR" }
             request_max_retries: None,
             stream_max_retries: None,
             stream_idle_timeout_ms: None,
+            max_tokens: None,
             requires_openai_auth: false,
         };
 
@@ -508,6 +514,7 @@ env_http_headers = { "X-Example-Env-Header" = "EXAMPLE_ENV_VAR" }
                 request_max_retries: None,
                 stream_max_retries: None,
                 stream_idle_timeout_ms: None,
+            max_tokens: None,
                 requires_openai_auth: false,
             }
         }
@@ -541,6 +548,7 @@ env_http_headers = { "X-Example-Env-Header" = "EXAMPLE_ENV_VAR" }
             request_max_retries: None,
             stream_max_retries: None,
             stream_idle_timeout_ms: None,
+            max_tokens: None,
             requires_openai_auth: false,
         };
         assert!(named_provider.is_azure_responses_endpoint());