feat: move TODO lists to session-scoped directories

TODO lists are now stored in .g3/sessions/<session_id>/todo.g3.md instead
of the workspace root. This prevents different g3 sessions from accidentally
picking up or overwriting each other's TODOs.

Changes:
- Add get_session_todo_path() function in paths.rs
- Update todo_read/todo_write handlers to use session-specific paths
- Remove TODO loading at Agent initialization (sessions start fresh)
- Update prompts to reflect session-scoped behavior

Fallback behavior preserved for planner mode (G3_TODO_PATH env var).

crates/g3-core/src/lib.rs

@@ -51,7 +51,7 @@ pub use paths::{
     G3_WORKSPACE_PATH_ENV, ensure_session_dir, get_context_summary_file, get_g3_dir, get_logs_dir,
     get_session_file, get_session_logs_dir, get_thinned_dir, logs_dir,
 };
-use paths::get_todo_path;
+use paths::{get_todo_path, get_session_todo_path};
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ToolCall {
@@ -1114,23 +1114,9 @@ impl<W: UiWriter> Agent<W> {
             context_window.add_message(readme_message);
         }
 
-        // Load existing TODO list if present (after system prompt and README)
+        // NOTE: TODO lists are now session-scoped and stored in .g3/sessions/<session_id>/todo.g3.md
-        let todo_path = get_todo_path();
+        // We don't load any TODO at initialization since we don't have a session_id yet.
-        let initial_todo_content = if todo_path.exists() {
+        // The agent will use todo_read to load the TODO once a session is established.
-            std::fs::read_to_string(&todo_path).ok()
-        } else {
-            None
-        };
-
-        if let Some(ref todo_content) = initial_todo_content {
-            if !todo_content.trim().is_empty() {
-                let todo_message = Message::new(
-                    MessageRole::System,
-                    format!("📋 Existing TODO list (from todo.g3.md):\n\n{}", todo_content),
-                );
-                context_window.add_message(todo_message);
-            }
-        }
 
         // Initialize computer controller if enabled
         let computer_controller = if config.computer_control.enabled {
@@ -1160,11 +1146,8 @@ impl<W: UiWriter> Agent<W> {
             session_id: None,
             tool_call_metrics: Vec::new(),
             ui_writer,
-            todo_content: std::sync::Arc::new(tokio::sync::RwLock::new({
+            // TODO content starts empty - session-scoped TODOs are loaded via todo_read
-                // Initialize from TODO.md file if it exists
+            todo_content: std::sync::Arc::new(tokio::sync::RwLock::new(String::new())),
-                let todo_path = get_todo_path();
-                std::fs::read_to_string(&todo_path).unwrap_or_default()
-            })),
             is_autonomous,
             quiet,
             computer_controller,
@@ -2946,7 +2929,7 @@ impl<W: UiWriter> Agent<W> {
             },
             Tool {
                 name: "todo_read".to_string(),
-                description: "Read your current TODO list from todo.g3.md file in the workspace directory. Shows what tasks are planned and their status. Call this at the start of multi-step tasks to check for existing plans, and during execution to review progress before updating. TODO lists persist across g3 sessions.".to_string(),
+                description: "Read your current TODO list from todo.g3.md file in the session directory. Shows what tasks are planned and their status. Call this at the start of multi-step tasks to check for existing plans, and during execution to review progress before updating. TODO lists are scoped to the current session.".to_string(),
                 input_schema: json!({
                     "type": "object",
                     "properties": {},
@@ -2955,7 +2938,7 @@ impl<W: UiWriter> Agent<W> {
             },
             Tool {
                 name: "todo_write".to_string(),
-                description: "Create or update your TODO list in todo.g3.md file with a complete task plan. Use markdown checkboxes: - [ ] for pending, - [x] for complete. This tool replaces the entire file content, so always call todo_read first to preserve existing content. Essential for multi-step tasks. Changes persist across g3 sessions.".to_string(),
+                description: "Create or update your TODO list in todo.g3.md file with a complete task plan. Use markdown checkboxes: - [ ] for pending, - [x] for complete. This tool replaces the entire file content, so always call todo_read first to preserve existing content. Essential for multi-step tasks. TODO lists are scoped to the current session.".to_string(),
                 input_schema: json!({
                     "type": "object",
                     "properties": {
@@ -5331,8 +5314,13 @@ impl<W: UiWriter> Agent<W> {
             }
             "todo_read" => {
                 debug!("Processing todo_read tool call");
-                // Read from todo.g3.md file (uses G3_TODO_PATH env var if set, else current dir)
+                // Read from session-specific todo.g3.md if we have a session, else fall back to workspace
-                let todo_path = get_todo_path();
+                let todo_path = if let Some(ref session_id) = self.session_id {
+                    let _ = ensure_session_dir(session_id); // Ensure dir exists
+                    get_session_todo_path(session_id)
+                } else {
+                    get_todo_path()
+                };
 
                 if !todo_path.exists() {
                     // Also update in-memory content to stay in sync
@@ -5447,7 +5435,12 @@ impl<W: UiWriter> Agent<W> {
                         // If all todos are complete, delete the file instead of writing
                         // EXCEPT in planner mode (G3_TODO_PATH is set) - preserve for rename to completed_todo_*.md
                         let in_planner_mode = std::env::var("G3_TODO_PATH").is_ok();
-                        let todo_path = get_todo_path();
+                        let todo_path = if let Some(ref session_id) = self.session_id {
+                            let _ = ensure_session_dir(session_id); // Ensure dir exists
+                            get_session_todo_path(session_id)
+                        } else {
+                            get_todo_path()
+                        };
                         
                         if !in_planner_mode && !has_incomplete && (content_str.contains("- [x]") || content_str.contains("- [X]")) {
                             if todo_path.exists() {
@@ -5469,8 +5462,6 @@ impl<W: UiWriter> Agent<W> {
                             }
                         }
 
-                        // Write to todo.g3.md file (uses G3_TODO_PATH env var if set, else current dir)
-
                         match std::fs::write(&todo_path, content_str) {
                             Ok(_) => {
                                 // Also update in-memory content to stay in sync

crates/g3-core/src/paths.rs

@@ -27,6 +27,12 @@ pub fn get_todo_path() -> PathBuf {
     }
 }
 
+/// Get the path to the todo.g3.md file for a specific session.
+/// Returns .g3/sessions/<session_id>/todo.g3.md
+pub fn get_session_todo_path(session_id: &str) -> PathBuf {
+    get_session_logs_dir(session_id).join("todo.g3.md")
+}
+
 /// Get the path to the logs directory.
 ///
 /// Checks for G3_WORKSPACE_PATH environment variable first (used by planning mode),
@@ -110,15 +116,18 @@ mod tests {
         let thinned_dir = get_thinned_dir(session_id);
         let session_file = get_session_file(session_id);
         let summary_file = get_context_summary_file(session_id);
+        let todo_file = get_session_todo_path(session_id);
 
         // All paths should be under the session directory
         assert!(thinned_dir.starts_with(&session_dir));
         assert!(session_file.starts_with(&session_dir));
         assert!(summary_file.starts_with(&session_dir));
+        assert!(todo_file.starts_with(&session_dir));
 
         // Check expected filenames
         assert!(thinned_dir.ends_with("thinned"));
         assert!(session_file.ends_with("session.json"));
         assert!(summary_file.ends_with("context_summary.txt"));
+        assert!(todo_file.ends_with("todo.g3.md"));
     }
 }

crates/g3-core/src/prompts.rs

@@ -72,7 +72,7 @@ Every multi-step task follows this pattern:
 2. **During**: Execute steps, then todo_read and todo_write to mark progress
 3. **End**: Call todo_read to verify all items complete
     
-Note: todo_write replaces the entire todo.g3.md file, so always read first to preserve content. TODO lists persist across g3 sessions in the workspace directory.
+Note: todo_write replaces the entire todo.g3.md file, so always read first to preserve content. TODO lists are scoped to the current session and stored in the session directory.
 
 IMPORTANT: If you are provided with a SHA256 hash of the requirements file, you MUST include it as the very first line of the todo.g3.md file in the following format:
 `{{Based on the requirements file with SHA256: <SHA>}}`
@@ -270,11 +270,11 @@ Short description for providers without native calling specs:
 - **final_output**: Signal task completion with a detailed summary of work done in markdown format
   - Format: {\"tool\": \"final_output\", \"args\": {\"summary\": \"what_was_accomplished\"}
 
-- **todo_read**: Read the entire TODO list from todo.g3.md file in workspace directory
+- **todo_read**: Read the current session's TODO list from todo.g3.md (session-scoped)
   - Format: {\"tool\": \"todo_read\", \"args\": {}}
   - Example: {\"tool\": \"todo_read\", \"args\": {}}
 
-- **todo_write**: Write or overwrite the entire todo.g3.md file (WARNING: overwrites completely, always read first)
+- **todo_write**: Write or overwrite the session's todo.g3.md file (WARNING: overwrites completely, always read first)
   - Format: {\"tool\": \"todo_write\", \"args\": {\"content\": \"- [ ] Task 1\\n- [ ] Task 2\"}}
   - Example: {\"tool\": \"todo_write\", \"args\": {\"content\": \"- [ ] Implement feature\\n  - [ ] Write tests\\n  - [ ] Run tests\"}}