feat(agent): add AI summarization for conversation history compacting

apps/infrastructure/src/agent/mod.rs

@@ -3,4 +3,4 @@
 
 pub mod runner;
 
-pub use runner::{spawn_agent_turn, AgentTurnParams};
+pub use runner::{compact_messages_with_ai, spawn_agent_turn, AgentTurnParams};

apps/infrastructure/src/agent/runner.rs

@@ -53,11 +53,12 @@ fn run_turn(params: &mut AgentTurnParams) {
     let tools = all_tools();
     let defs = tool_defs(&tools);
 
-    let mut sys_prompt = "You are Zesdex, an AI coding assistant. You have access to various tools via native function calling to help the user. \
-         For complex problems, use `seq_think` to reason step-by-step. \
-         For any non-trivial tasks, you MUST prioritize creating a structured plan (using `plan_enter`) and a list of TODOs (using `todowrite`) BEFORE executing any other tools or modifying files. \
-         For large multi-step operations or delegating tasks, you MUST prioritize using `workflow_run` (to run a yaml workflow script) or `hive_mind` (to orchestrate multiple agents) to complete the task efficiently. \
-         Use other tools when necessary. If a tool returns an error, fix the issue before retrying. \
+    let mut sys_prompt = "You are Zesdex, an AI coding assistant. You have access to various tools via native function calling to help the user.\n\n\
+         CRITICAL DIRECTIVES & PRIORITY HIERARCHY:\n\
+         1. WORKFLOW FIRST: For any multi-step, complex, or non-trivial task, you MUST prioritize using `workflow_run` (to construct and execute a multi-phase YAML workflow) or `hive_mind` (to orchestrate parallel autonomous agents). Workflows are your primary strategy.\n\
+         2. PLANNING & TODOS: Use `plan_enter` to establish high-level architectural plans and `todowrite` to maintain granular task checklists.\n\
+         3. REASONING: Use `seq_think` for deep step-by-step analysis.\n\
+         4. TOOL EXECUTION: Execute individual tools (file edits, terminal commands) within or guided by your workflows. If an error occurs, analyze and fix it.\n\n\
          Respond conversationally, concisely, and helpfully.".to_string();
 
     if let Some(root) = params.workspace_roots.first() {
@@ -71,6 +72,22 @@ fn run_turn(params: &mut AgentTurnParams) {
         sys_prompt.push_str(&rich_ctx);
     }
 
+    // Auto-compact if conversation history is getting long (>24 messages)
+    if params.messages.len() > 24 {
+        push_event(
+            &params.turn_events,
+            TurnEvent::SystemNote {
+                kind: "info".into(),
+                message: "Auto-compacting context window via AI Summarization...".into(),
+            },
+        );
+        let _ = compact_messages_with_ai(&mut params.messages, &client);
+        push_event(
+            &params.turn_events,
+            TurnEvent::Compacted(params.messages.clone()),
+        );
+    }
+
     let sys_msg = ChatMessage::system(sys_prompt);
 
     let tool_ctx = ToolCtx::builder()
@@ -214,3 +231,52 @@ fn push_event(queue: &Arc<Mutex<VecDeque<TurnEvent>>>, event: TurnEvent) {
 fn mark_done(flag: &Arc<AtomicBool>) {
     flag.store(false, Ordering::SeqCst);
 }
+
+/// Compacts conversation history using AI summarization.
+///
+/// Preserves recent messages (last 6) and calls the LLM to summarize
+/// the older evicted messages into a single system summary message.
+pub fn compact_messages_with_ai(messages: &mut Vec<ChatMessage>, client: &LlmClient) -> anyhow::Result<()> {
+    const KEEP_TAIL: usize = 6;
+    if messages.len() <= KEEP_TAIL + 2 {
+        return Ok(()); // Not enough messages to compact
+    }
+
+    let split_idx = messages.len() - KEEP_TAIL;
+    let evicted: Vec<_> = messages.drain(..split_idx).collect();
+
+    // Prepare prompt to summarize evicted messages
+    let mut summary_prompt = vec![
+        ChatMessage::system(
+            "You are a helpful assistant summarizing conversation history. \
+             Provide a concise summary of the key user requests, decisions, tools executed, and modified files. \
+             Format as a clear bulleted list."
+                .to_string(),
+        ),
+    ];
+    summary_prompt.extend(evicted);
+    summary_prompt.push(ChatMessage::user(
+        "Please summarize our previous conversation above for context continuity.".to_string(),
+    ));
+
+    match client.chat_with_tools_non_streaming(&summary_prompt, None, Some(1024), Some(0.3), None) {
+        Ok((summary_msg, _)) => {
+            let summary_text = summary_msg.content.unwrap_or_else(|| "Previous context summarized.".to_string());
+            let summary_node = ChatMessage::system(format!(
+                "[AI Summary of Previous Conversation]\n{}",
+                summary_text.trim()
+            ));
+            messages.insert(0, summary_node);
+            Ok(())
+        }
+        Err(e) => {
+            warn!("AI summarization failed during compact, falling back to simple notice: {e}");
+            messages.insert(
+                0,
+                ChatMessage::system("[Earlier conversation messages compacted to save context window]".to_string()),
+            );
+            Ok(())
+        }
+    }
+}
+