refactor: streamline token counting and message shaping logic

crates/zesdex-backend/src/app/runtime/actions/handlers.rs

@@ -2,6 +2,8 @@
 //! `apply_action` in the root module. Each handler mutates `AppStateRest`
 //! in place.
 
+use crate::app::runtime::context::tokens::count_tokens;
+use crate::app::runtime::context::window;
 use crate::app::state::rest::{AppStateRest, ChatMessageDisplay};
 use crate::app::state::runtime::TurnEvent;
 use crate::app::state::types::{Overlay, Toast, ToastKind};
@@ -205,24 +207,15 @@ pub(super) fn handle_abort_turn(state: &mut AppStateRest) {
 }
 
 pub(super) fn handle_compact(state: &mut AppStateRest) {
-    let max_wire_tokens = state
+    let max_wire_tokens = window::resolve(&state.app_config, &state.settings);
-        .app_config
-        .model_roles
-        .values()
-        .find(|role| {
-            role.provider == state.settings.provider && role.model == state.settings.model
-        })
-        .and_then(|role| role.context_window)
-        .unwrap_or(state.app_config.default_context_window) as usize;
 
     if let Some(ref mut rt) = state.session_runtime {
-        let total_chars: usize = rt
+        let token_estimate: usize = rt
             .messages
             .iter()
             .filter_map(|m| m.content.as_deref())
-            .map(str::len)
+            .map(count_tokens)
             .sum();
-        let token_estimate = total_chars / 3;
         rt.messages =
             crate::app::runtime::context::shaping::shape_messages(
                 &rt.messages,
@@ -230,6 +223,7 @@ pub(super) fn handle_compact(state: &mut AppStateRest) {
                 max_wire_tokens,
                 true,
                 None,
+                None,
             );
         state.push_toast(Toast::new(
             ToastKind::Success,

crates/zesdex-backend/src/app/runtime/actions/turn.rs

@@ -13,6 +13,7 @@ use sha2::Digest;
 use zesdex_cms::domain::repository::EditLogRepository;
 
 use crate::app::guard::Verdict;
+use crate::app::runtime::context::tokens::count_tokens;
 use crate::app::state::runtime::TurnEvent;
 use zesdex_cms::domain::repository::MemoryRepository;
 use crate::dto::chat::message::ChatMessage;
@@ -326,12 +327,11 @@ pub(super) fn run_agent_turn(
     let mut todo_retry_count = 0usize;
 
     loop {
-        let total_chars: usize = msgs
+        let token_estimate: usize = msgs
             .iter()
             .filter_map(|m| m.content.as_deref())
-            .map(str::len)
+            .map(count_tokens)
             .sum();
-        let token_estimate = total_chars / 4;
         let max_wire_tokens = tc.context_window;
 
         // Skip message compaction if abort was requested — the non-streaming
@@ -352,6 +352,7 @@ pub(super) fn run_agent_turn(
                     max_wire_tokens,
                     false,
                     Some(&tc.client),
+                    Some(&tc.abort_flag),
                 );
 
             // Dispatch the compacted messages to the main thread so the local session history
@@ -488,12 +489,12 @@ pub(super) fn run_agent_turn(
 
         let (mut tok_in, mut tok_out) = final_usage.unwrap_or((0, 0));
         if tok_in == 0 {
-            let total_chars: usize = wire_msgs
+            let total_tokens: usize = wire_msgs
                 .iter()
                 .filter_map(|m| m.content.as_deref())
-                .map(str::len)
+                .map(count_tokens)
                 .sum();
-            tok_in = (total_chars / 4).max(1) as u64;
+            tok_in = total_tokens.max(1) as u64;
         }
         if tok_out == 0 {
             let response_chars = response.content.as_deref().map_or(0, str::len);

crates/zesdex-backend/src/app/runtime/context/shaping.rs

@@ -3,6 +3,8 @@
 //! the LLM API. Ported from the former `runtime::shortsend` — behavior
 //! is unchanged, only its token-counting now goes through
 //! `context::tokens` instead of an inline heuristic.
+use std::sync::atomic::{AtomicBool, Ordering};
+
 use super::tokens::count_tokens;
 use crate::dto::chat::message::ChatMessage;
 
@@ -37,6 +39,11 @@ pub fn should_shape(token_estimate: usize, max_wire_tokens: usize, prev_shaped:
 /// `[prior conversation compacted]` (or LLM-generated summary, if
 /// `client` is `Some`) system message in between.
 ///
+/// The LLM summarization checks the abort flag before calling the LLM,
+/// so a user-requested abort is respected promptly. The turn loop already
+/// runs on a background thread (spawned in `spawn_turn`), so the blocking
+/// summarization call does not freeze the UI.
+///
 /// Why: keeps context-size overhead roughly constant regardless of
 /// session length.
 ///
@@ -48,6 +55,7 @@ pub fn shape_messages(
     max_wire_tokens: usize,
     force: bool,
     client: Option<&crate::service::provider::LlmClient>,
+    abort_flag: Option<&AtomicBool>,
 ) -> Vec<ChatMessage> {
     if !force && (token_count <= max_wire_tokens || messages.len() < 5) {
         return messages.to_vec();
@@ -88,12 +96,46 @@ pub fn shape_messages(
         let mut summary_text = "[prior conversation compacted]".to_string();
 
         if let Some(llm) = client {
+            // Check abort before starting the blocking LLM summarization call.
+            // The turn loop already runs on a background thread (spawned in
+            // `spawn_turn`), so this blocking call does not freeze the UI.
+            let aborted = abort_flag.is_some_and(|f| f.load(Ordering::SeqCst));
+            if !aborted {
                 let prompt = format!(
-                "Summarize the following dropped conversation history briefly. Focus on main goals, decisions made, and files modified, so the context is preserved for future turns. Keep it concise.\n\nHistory:\n{}",
+                    "You are a context-preservation summarizer. The following conversation \
+                     history is being dropped to free up context window space. \
+                     Produce a structured summary that preserves the information the AI \
+                     agent needs to continue working seamlessly.\n\n\
+                     Structure your summary into these sections:\n\
+                     1. **Goals & Objectives** — what the user asked for, what tasks remain\n\
+                     2. **Key Decisions** — architectural choices, design decisions, approach changes\n\
+                     3. **Files Modified/Created** — paths and brief description of changes\n\
+                     4. **Findings & State** — important discoveries, test results, current state\n\
+                     5. **Open Items** — unresolved issues, pending tasks, next steps\n\n\
+                     Be concise but thorough. Preserve file paths, error messages, and \
+                     specific details the agent needs to continue.\n\n\
+                     History to summarize:\n{}",
                     dropped_msgs.iter()
-                    .map(|m| format!("[{}]: {}", if m.role == crate::dto::chat::message::Role::User { "User" } else { "Assistant" }, m.content.as_deref().unwrap_or("")))
+                        .map(|m| {
+                            let role_label = match m.role {
+                                crate::dto::chat::message::Role::User => "User",
+                                crate::dto::chat::message::Role::Assistant => "Assistant",
+                                crate::dto::chat::message::Role::System => "System",
+                                crate::dto::chat::message::Role::Tool => "Tool",
+                            };
+                            let has_tool_calls = m.tool_calls.is_some()
+                                && m.tool_calls.as_ref().is_some_and(|c| !c.is_empty());
+                            let mut entry = format!("[{role_label}]: {}", m.content.as_deref().unwrap_or(""));
+                            if has_tool_calls {
+                                if let Some(calls) = &m.tool_calls {
+                                    let names: Vec<&str> = calls.iter().map(|c| c.function.name.as_str()).collect();
+                                    entry.push_str(&format!("\n  [tool calls: {}]", names.join(", ")));
+                                }
+                            }
+                            entry
+                        })
                         .collect::<Vec<_>>()
-                    .join("\n\n")
+                        .join("\n\n---\n\n")
                 );
 
                 let req_msgs = vec![ChatMessage::user(prompt)];
@@ -107,14 +149,13 @@ pub fn shape_messages(
                     Err(e) => {
                         tracing::warn!(
                             "[context::shaping] LLM summarization failed: {}. \
-                         Prior conversation history is lost — no summary available. \
+                             Falling back to static placeholder.",
-                         This means the model will lose context about earlier parts of \
-                         the conversation.",
                             e,
                         );
                     }
                 }
             }
+        }
 
         result.push(ChatMessage::system(summary_text));
     }
@@ -150,7 +191,7 @@ mod tests {
             ChatMessage::user("hi"),
             ChatMessage::assistant(Some("hello".to_string())),
         ];
-        let result = shape_messages(&messages, 10, 1000, false, None);
+        let result = shape_messages(&messages, 10, 1000, false, None, None);
         assert_eq!(result.len(), messages.len());
     }
 
@@ -178,7 +219,7 @@ mod tests {
         for i in 0..20 {
             messages.push(ChatMessage::user(padded_message(i)));
         }
-        let result = shape_messages(&messages, 100_000, 1000, true, None);
+        let result = shape_messages(&messages, 100_000, 1000, true, None, None);
         assert_eq!(result[0].content.as_deref(), Some("system prompt"));
     }
 
@@ -188,7 +229,7 @@ mod tests {
         for i in 0..20 {
             messages.push(ChatMessage::user(padded_message(i)));
         }
-        let result = shape_messages(&messages, 100_000, 1000, true, None);
+        let result = shape_messages(&messages, 100_000, 1000, true, None, None);
         let has_placeholder = result
             .iter()
             .any(|m| m.content.as_deref() == Some("[prior conversation compacted]"));
@@ -201,7 +242,7 @@ mod tests {
         for i in 0..20 {
             messages.push(ChatMessage::user(padded_message(i)));
         }
-        let result = shape_messages(&messages, 100_000, 1000, true, None);
+        let result = shape_messages(&messages, 100_000, 1000, true, None, None);
         let last_content = messages.last().unwrap().content.clone();
         assert!(
             result.iter().any(|m| m.content == last_content),