story-kit: merge 245_bug_chat_history_persistence_lost_on_page_refresh_story_145_regression

server/src/llm/chat.rs

@@ -179,6 +179,44 @@ pub fn set_anthropic_api_key(store: &dyn StoreOps, api_key: String) -> Result<()
     set_anthropic_api_key_impl(store, &api_key)
 }
 
+/// Build a prompt for Claude Code that includes prior conversation history.
+///
+/// When a Claude Code session cannot be resumed (no session_id), we embed
+/// the prior messages as a structured preamble so the LLM retains context.
+/// If there is only one user message (the current one), the content is
+/// returned as-is with no preamble.
+fn build_claude_code_context_prompt(messages: &[Message], latest_user_content: &str) -> String {
+    // Collect prior messages (everything except the trailing user message).
+    let prior: Vec<&Message> = messages
+        .iter()
+        .rev()
+        .skip(1) // skip the latest user message
+        .collect::<Vec<_>>()
+        .into_iter()
+        .rev()
+        .collect();
+
+    if prior.is_empty() {
+        return latest_user_content.to_string();
+    }
+
+    let mut parts = Vec::new();
+    parts.push("<conversation_history>".to_string());
+    for msg in &prior {
+        let label = match msg.role {
+            Role::User => "User",
+            Role::Assistant => "Assistant",
+            Role::Tool => "Tool",
+            Role::System => continue,
+        };
+        parts.push(format!("[{}]: {}", label, msg.content));
+    }
+    parts.push("</conversation_history>".to_string());
+    parts.push(String::new());
+    parts.push(latest_user_content.to_string());
+    parts.join("\n")
+}
+
 #[allow(clippy::too_many_arguments)]
 pub async fn chat<F, U, T, A>(
     messages: Vec<Message>,
@@ -224,13 +262,25 @@ where
     if is_claude_code {
         use crate::llm::providers::claude_code::ClaudeCodeProvider;
 
-        let user_message = messages
+        let latest_user_content = messages
             .iter()
             .rev()
             .find(|m| m.role == Role::User)
             .map(|m| m.content.clone())
             .ok_or_else(|| "No user message found".to_string())?;
 
+        // When resuming with a session_id, Claude Code loads its own transcript
+        // from disk — the latest user message is sufficient.  Without a
+        // session_id (e.g. after a page refresh) the prior conversation context
+        // would be lost because Claude Code only receives a single prompt
+        // string.  In that case, prepend the conversation history so the LLM
+        // retains full context even though the session cannot be resumed.
+        let user_message = if config.session_id.is_some() {
+            latest_user_content
+        } else {
+            build_claude_code_context_prompt(&messages, &latest_user_content)
+        };
+
         let project_root = state
             .get_project_root()
             .unwrap_or_else(|_| std::path::PathBuf::from("."));
@@ -404,7 +454,7 @@ where
     }
 
     Ok(ChatResult {
-        messages: new_messages,
+        messages: current_history[2..].to_vec(),
         session_id: None,
     })
 }
@@ -1095,4 +1145,102 @@ mod tests {
         let result = execute_tool(&call, &state).await;
         assert!(result.starts_with("Error:"), "unexpected result: {result}");
     }
+
+    // ---------------------------------------------------------------------------
+    // build_claude_code_context_prompt (Bug 245)
+    // ---------------------------------------------------------------------------
+
+    #[test]
+    fn context_prompt_single_message_returns_content_as_is() {
+        let messages = vec![Message {
+            role: Role::User,
+            content: "hello".to_string(),
+            tool_calls: None,
+            tool_call_id: None,
+        }];
+        let result = build_claude_code_context_prompt(&messages, "hello");
+        assert_eq!(result, "hello");
+    }
+
+    #[test]
+    fn context_prompt_includes_prior_conversation() {
+        let messages = vec![
+            Message {
+                role: Role::User,
+                content: "What is Rust?".to_string(),
+                tool_calls: None,
+                tool_call_id: None,
+            },
+            Message {
+                role: Role::Assistant,
+                content: "Rust is a systems language.".to_string(),
+                tool_calls: None,
+                tool_call_id: None,
+            },
+            Message {
+                role: Role::User,
+                content: "Tell me more".to_string(),
+                tool_calls: None,
+                tool_call_id: None,
+            },
+        ];
+        let result = build_claude_code_context_prompt(&messages, "Tell me more");
+        assert!(
+            result.contains("<conversation_history>"),
+            "should have history preamble"
+        );
+        assert!(
+            result.contains("[User]: What is Rust?"),
+            "should include prior user message"
+        );
+        assert!(
+            result.contains("[Assistant]: Rust is a systems language."),
+            "should include prior assistant message"
+        );
+        assert!(
+            result.contains("</conversation_history>"),
+            "should close history block"
+        );
+        assert!(
+            result.ends_with("Tell me more"),
+            "should end with latest user message"
+        );
+    }
+
+    #[test]
+    fn context_prompt_skips_system_messages() {
+        let messages = vec![
+            Message {
+                role: Role::System,
+                content: "You are a helpful assistant.".to_string(),
+                tool_calls: None,
+                tool_call_id: None,
+            },
+            Message {
+                role: Role::User,
+                content: "hi".to_string(),
+                tool_calls: None,
+                tool_call_id: None,
+            },
+            Message {
+                role: Role::Assistant,
+                content: "hello".to_string(),
+                tool_calls: None,
+                tool_call_id: None,
+            },
+            Message {
+                role: Role::User,
+                content: "bye".to_string(),
+                tool_calls: None,
+                tool_call_id: None,
+            },
+        ];
+        let result = build_claude_code_context_prompt(&messages, "bye");
+        assert!(
+            !result.contains("helpful assistant"),
+            "should not include system messages"
+        );
+        assert!(result.contains("[User]: hi"));
+        assert!(result.contains("[Assistant]: hello"));
+    }
 }