Preserve local project context across compaction and todo updates

This change makes compaction summaries durable under .claude/memory,
feeds those saved memory files back into prompt context, updates /memory
to report both instruction and project-memory files, and moves TodoWrite
persistence to a human-readable .claude/todos.md file.

Constraint: Reuse existing compaction, prompt loading, and slash-command plumbing rather than add a new subsystem
Constraint: Keep persisted project state under Claude-local .claude/ paths
Rejected: Introduce a dedicated memory service module | larger diff with no clear user benefit for this task
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Project memory files are loaded as prompt context, so future format changes must preserve concise readable content
Tested: cargo fmt --all --manifest-path rust/Cargo.toml
Tested: cargo clippy --manifest-path rust/Cargo.toml --all-targets --all-features -- -D warnings
Tested: cargo test --manifest-path rust/Cargo.toml --all
Not-tested: Long-term retention/cleanup policy for .claude/memory growth

rust/crates/runtime/src/compact.rs

@@ -1,3 +1,6 @@
+use std::fs;
+use std::time::{SystemTime, UNIX_EPOCH};
+
 use crate::session::{ContentBlock, ConversationMessage, MessageRole, Session};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -90,6 +93,7 @@ pub fn compact_session(session: &Session, config: CompactionConfig) -> Compactio
     let preserved = session.messages[keep_from..].to_vec();
     let summary = summarize_messages(removed);
     let formatted_summary = format_compact_summary(&summary);
+    persist_compact_summary(&formatted_summary);
     let continuation = get_compact_continuation_message(&summary, true, !preserved.is_empty());
 
     let mut compacted_messages = vec![ConversationMessage {
@@ -110,6 +114,35 @@ pub fn compact_session(session: &Session, config: CompactionConfig) -> Compactio
     }
 }
 
+fn persist_compact_summary(formatted_summary: &str) {
+    if formatted_summary.trim().is_empty() {
+        return;
+    }
+
+    let Ok(cwd) = std::env::current_dir() else {
+        return;
+    };
+    let memory_dir = cwd.join(".claude").join("memory");
+    if fs::create_dir_all(&memory_dir).is_err() {
+        return;
+    }
+
+    let path = memory_dir.join(compact_summary_filename());
+    let _ = fs::write(path, render_memory_file(formatted_summary));
+}
+
+fn compact_summary_filename() -> String {
+    let timestamp = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs();
+    format!("summary-{timestamp}.md")
+}
+
+fn render_memory_file(formatted_summary: &str) -> String {
+    format!("# Project memory\n\n{}\n", formatted_summary.trim())
+}
+
 fn summarize_messages(messages: &[ConversationMessage]) -> String {
     let user_messages = messages
         .iter()
@@ -378,14 +411,21 @@ fn collapse_blank_lines(content: &str) -> String {
 mod tests {
     use super::{
         collect_key_files, compact_session, estimate_session_tokens, format_compact_summary,
-        infer_pending_work, should_compact, CompactionConfig,
+        infer_pending_work, render_memory_file, should_compact, CompactionConfig,
     };
+    use std::fs;
+    use std::time::{SystemTime, UNIX_EPOCH};
+
     use crate::session::{ContentBlock, ConversationMessage, MessageRole, Session};
 
     #[test]
     fn formats_compact_summary_like_upstream() {
         let summary = "<analysis>scratch</analysis>\n<summary>Kept work</summary>";
         assert_eq!(format_compact_summary(summary), "Summary:\nKept work");
+        assert_eq!(
+            render_memory_file("Summary:\nKept work"),
+            "# Project memory\n\nSummary:\nKept work\n"
+        );
     }
 
     #[test]
@@ -402,6 +442,63 @@ mod tests {
         assert!(result.formatted_summary.is_empty());
     }
 
+    #[test]
+    fn persists_compacted_summaries_under_dot_claude_memory() {
+        let _guard = crate::test_env_lock();
+        let temp = std::env::temp_dir().join(format!(
+            "runtime-compact-memory-{}",
+            SystemTime::now()
+                .duration_since(UNIX_EPOCH)
+                .expect("time after epoch")
+                .as_nanos()
+        ));
+        fs::create_dir_all(&temp).expect("temp dir");
+        let previous = std::env::current_dir().expect("cwd");
+        std::env::set_current_dir(&temp).expect("set cwd");
+
+        let session = Session {
+            version: 1,
+            messages: vec![
+                ConversationMessage::user_text("one ".repeat(200)),
+                ConversationMessage::assistant(vec![ContentBlock::Text {
+                    text: "two ".repeat(200),
+                }]),
+                ConversationMessage::tool_result("1", "bash", "ok ".repeat(200), false),
+                ConversationMessage {
+                    role: MessageRole::Assistant,
+                    blocks: vec![ContentBlock::Text {
+                        text: "recent".to_string(),
+                    }],
+                    usage: None,
+                },
+            ],
+        };
+
+        let result = compact_session(
+            &session,
+            CompactionConfig {
+                preserve_recent_messages: 2,
+                max_estimated_tokens: 1,
+            },
+        );
+        let memory_dir = temp.join(".claude").join("memory");
+        let files = fs::read_dir(&memory_dir)
+            .expect("memory dir exists")
+            .flatten()
+            .map(|entry| entry.path())
+            .collect::<Vec<_>>();
+
+        assert_eq!(result.removed_message_count, 2);
+        assert_eq!(files.len(), 1);
+        let persisted = fs::read_to_string(&files[0]).expect("memory file readable");
+
+        std::env::set_current_dir(previous).expect("restore cwd");
+        fs::remove_dir_all(temp).expect("cleanup temp dir");
+
+        assert!(persisted.contains("# Project memory"));
+        assert!(persisted.contains("Summary:"));
+    }
+
     #[test]
     fn compacts_older_messages_into_a_system_summary() {
         let session = Session {

rust/crates/runtime/src/conversation.rs

@@ -408,13 +408,14 @@ mod tests {
                 .sum::<i32>();
             Ok(total.to_string())
         });
-        let permission_policy = PermissionPolicy::new(PermissionMode::Prompt);
+        let permission_policy = PermissionPolicy::new(PermissionMode::WorkspaceWrite);
         let system_prompt = SystemPromptBuilder::new()
             .with_project_context(ProjectContext {
                 cwd: PathBuf::from("/tmp/project"),
                 current_date: "2026-03-31".to_string(),
                 git_status: None,
                 instruction_files: Vec::new(),
+                memory_files: Vec::new(),
             })
             .with_os("linux", "6.8")
             .build();
@@ -487,7 +488,7 @@ mod tests {
             Session::new(),
             SingleCallApiClient,
             StaticToolExecutor::new(),
-            PermissionPolicy::new(PermissionMode::Prompt),
+            PermissionPolicy::new(PermissionMode::WorkspaceWrite),
             vec!["system".to_string()],
         );
 
@@ -536,7 +537,7 @@ mod tests {
             session,
             SimpleApi,
             StaticToolExecutor::new(),
-            PermissionPolicy::new(PermissionMode::Allow),
+            PermissionPolicy::new(PermissionMode::DangerFullAccess),
             vec!["system".to_string()],
         );
 
@@ -563,7 +564,7 @@ mod tests {
             Session::new(),
             SimpleApi,
             StaticToolExecutor::new(),
-            PermissionPolicy::new(PermissionMode::Allow),
+            PermissionPolicy::new(PermissionMode::DangerFullAccess),
             vec!["system".to_string()],
         );
         runtime.run_turn("a", None).expect("turn a");

rust/crates/runtime/src/prompt.rs

@@ -51,6 +51,7 @@ pub struct ProjectContext {
     pub current_date: String,
     pub git_status: Option<String>,
     pub instruction_files: Vec<ContextFile>,
+    pub memory_files: Vec<ContextFile>,
 }
 
 impl ProjectContext {
@@ -60,11 +61,13 @@ impl ProjectContext {
     ) -> std::io::Result<Self> {
         let cwd = cwd.into();
         let instruction_files = discover_instruction_files(&cwd)?;
+        let memory_files = discover_memory_files(&cwd)?;
         Ok(Self {
             cwd,
             current_date: current_date.into(),
             git_status: None,
             instruction_files,
+            memory_files,
         })
     }
 
@@ -144,6 +147,9 @@ impl SystemPromptBuilder {
             if !project_context.instruction_files.is_empty() {
                 sections.push(render_instruction_files(&project_context.instruction_files));
             }
+            if !project_context.memory_files.is_empty() {
+                sections.push(render_memory_files(&project_context.memory_files));
+            }
         }
         if let Some(config) = &self.config {
             sections.push(render_config_section(config));
@@ -186,7 +192,7 @@ pub fn prepend_bullets(items: Vec<String>) -> Vec<String> {
     items.into_iter().map(|item| format!(" - {item}")).collect()
 }
 
-fn discover_instruction_files(cwd: &Path) -> std::io::Result<Vec<ContextFile>> {
+fn discover_context_directories(cwd: &Path) -> Vec<PathBuf> {
     let mut directories = Vec::new();
     let mut cursor = Some(cwd);
     while let Some(dir) = cursor {
@@ -194,6 +200,11 @@ fn discover_instruction_files(cwd: &Path) -> std::io::Result<Vec<ContextFile>> {
         cursor = dir.parent();
     }
     directories.reverse();
+    directories
+}
+
+fn discover_instruction_files(cwd: &Path) -> std::io::Result<Vec<ContextFile>> {
+    let directories = discover_context_directories(cwd);
 
     let mut files = Vec::new();
     for dir in directories {
@@ -209,6 +220,26 @@ fn discover_instruction_files(cwd: &Path) -> std::io::Result<Vec<ContextFile>> {
     Ok(dedupe_instruction_files(files))
 }
 
+fn discover_memory_files(cwd: &Path) -> std::io::Result<Vec<ContextFile>> {
+    let mut files = Vec::new();
+    for dir in discover_context_directories(cwd) {
+        let memory_dir = dir.join(".claude").join("memory");
+        let Ok(entries) = fs::read_dir(&memory_dir) else {
+            continue;
+        };
+        let mut paths = entries
+            .flatten()
+            .map(|entry| entry.path())
+            .filter(|path| path.is_file())
+            .collect::<Vec<_>>();
+        paths.sort();
+        for path in paths {
+            push_context_file(&mut files, path)?;
+        }
+    }
+    Ok(dedupe_instruction_files(files))
+}
+
 fn push_context_file(files: &mut Vec<ContextFile>, path: PathBuf) -> std::io::Result<()> {
     match fs::read_to_string(&path) {
         Ok(content) if !content.trim().is_empty() => {
@@ -251,6 +282,12 @@ fn render_project_context(project_context: &ProjectContext) -> String {
             project_context.instruction_files.len()
         ));
     }
+    if !project_context.memory_files.is_empty() {
+        bullets.push(format!(
+            "Project memory files discovered: {}.",
+            project_context.memory_files.len()
+        ));
+    }
     lines.extend(prepend_bullets(bullets));
     if let Some(status) = &project_context.git_status {
         lines.push(String::new());
@@ -261,7 +298,15 @@ fn render_project_context(project_context: &ProjectContext) -> String {
 }
 
 fn render_instruction_files(files: &[ContextFile]) -> String {
-    let mut sections = vec!["# Claude instructions".to_string()];
+    render_context_file_section("# Claude instructions", files)
+}
+
+fn render_memory_files(files: &[ContextFile]) -> String {
+    render_context_file_section("# Project memory", files)
+}
+
+fn render_context_file_section(title: &str, files: &[ContextFile]) -> String {
+    let mut sections = vec![title.to_string()];
     let mut remaining_chars = MAX_TOTAL_INSTRUCTION_CHARS;
     for file in files {
         if remaining_chars == 0 {
@@ -453,8 +498,9 @@ fn get_actions_section() -> String {
 mod tests {
     use super::{
         collapse_blank_lines, display_context_path, normalize_instruction_content,
-        render_instruction_content, render_instruction_files, truncate_instruction_content,
-        ContextFile, ProjectContext, SystemPromptBuilder, SYSTEM_PROMPT_DYNAMIC_BOUNDARY,
+        render_instruction_content, render_instruction_files, render_memory_files,
+        truncate_instruction_content, ContextFile, ProjectContext, SystemPromptBuilder,
+        SYSTEM_PROMPT_DYNAMIC_BOUNDARY,
     };
     use crate::config::ConfigLoader;
     use std::fs;
@@ -519,6 +565,35 @@ mod tests {
         fs::remove_dir_all(root).expect("cleanup temp dir");
     }
 
+    #[test]
+    fn discovers_project_memory_files_from_ancestor_chain() {
+        let root = temp_dir();
+        let nested = root.join("apps").join("api");
+        fs::create_dir_all(root.join(".claude").join("memory")).expect("root memory dir");
+        fs::create_dir_all(nested.join(".claude").join("memory")).expect("nested memory dir");
+        fs::write(
+            root.join(".claude").join("memory").join("2026-03-30.md"),
+            "root memory",
+        )
+        .expect("write root memory");
+        fs::write(
+            nested.join(".claude").join("memory").join("2026-03-31.md"),
+            "nested memory",
+        )
+        .expect("write nested memory");
+
+        let context = ProjectContext::discover(&nested, "2026-03-31").expect("context should load");
+        let contents = context
+            .memory_files
+            .iter()
+            .map(|file| file.content.as_str())
+            .collect::<Vec<_>>();
+
+        assert_eq!(contents, vec!["root memory", "nested memory"]);
+        assert!(render_memory_files(&context.memory_files).contains("# Project memory"));
+        fs::remove_dir_all(root).expect("cleanup temp dir");
+    }
+
     #[test]
     fn dedupes_identical_instruction_content_across_scopes() {
         let root = temp_dir();