diff --git a/app/src-tauri/src/models/mod.rs b/app/src-tauri/src/models/mod.rs
index a868bff..10e2c0f 100644
--- a/app/src-tauri/src/models/mod.rs
+++ b/app/src-tauri/src/models/mod.rs
@@ -1,15 +1,17 @@
-pub mod project;
-pub mod container_config;
 pub mod app_settings;
+pub mod container_config;
 pub mod gateway_settings;
 pub mod migration;
+pub mod note;
+pub mod project;
 pub mod settings_export;
 pub mod update_info;
 
-pub use project::*;
-pub use container_config::*;
 pub use app_settings::*;
+pub use container_config::*;
 pub use gateway_settings::*;
 pub use migration::*;
+pub use note::*;
+pub use project::*;
 pub use settings_export::*;
 pub use update_info::*;
diff --git a/app/src-tauri/src/models/note.rs b/app/src-tauri/src/models/note.rs
new file mode 100644
index 0000000..f2c07b3
--- /dev/null
+++ b/app/src-tauri/src/models/note.rs
@@ -0,0 +1,34 @@
+use serde::{Deserialize, Serialize};
+
+/// One note. A scratchpad entry the user can also fire at a running Claude
+/// session.
+///
+/// Deliberately has no `kind`/`type` field. What makes a note "for the agent"
+/// is that the user pressed Send, not a mode chosen when it was written — a
+/// classification decision at writing time is one the user is least willing to
+/// make, and it would turn one pane into two features.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct Note {
+    pub id: String,
+    pub title: String,
+    pub body: String,
+    /// Pinned notes sort first, then by `updated_at` descending.
+    #[serde(default)]
+    pub pinned: bool,
+    pub created_at: String,
+    pub updated_at: String,
+}
+
+impl Note {
+    pub fn new(title: String, body: String) -> Self {
+        let now = chrono::Utc::now().to_rfc3339();
+        Self {
+            id: uuid::Uuid::new_v4().to_string(),
+            title,
+            body,
+            pinned: false,
+            created_at: now.clone(),
+            updated_at: now,
+        }
+    }
+}
diff --git a/app/src-tauri/src/storage/mod.rs b/app/src-tauri/src/storage/mod.rs
index fda731f..82d8588 100644
--- a/app/src-tauri/src/storage/mod.rs
+++ b/app/src-tauri/src/storage/mod.rs
@@ -1,4 +1,5 @@
 pub mod migration_store;
+pub mod notes_store;
 pub mod pending_cleanup;
 pub mod projects_store;
 pub mod secure;
diff --git a/app/src-tauri/src/storage/notes_store.rs b/app/src-tauri/src/storage/notes_store.rs
new file mode 100644
index 0000000..9a5afd0
--- /dev/null
+++ b/app/src-tauri/src/storage/notes_store.rs
@@ -0,0 +1,337 @@
+//! Host-side persistence for per-project notes.
+//!
+//! One JSON file per project under `<data_dir>/triple-c/notes/`, on the same
+//! free-function shape as `migration_store` — no struct, nothing in
+//! `AppState`, no in-memory copy. `ProjectsStore` holds a `Mutex` because it
+//! caches the project list; a store that reads and writes the file per call
+//! has nothing to cache and nothing to guard.
+//!
+//! Deliberately *not* a field on `Project`. `projects.json` is rewritten on
+//! every blur by the debounced-nothing save path in `useSaveState`, so notes
+//! there would mean the whole project list is rewritten per edit, and a note
+//! save racing a Config save would silently drop one of them.
+
+use std::fs;
+use std::path::{Path, PathBuf};
+use std::sync::{Mutex, OnceLock};
+
+use crate::models::Note;
+
+/// Serialises the read-modify-write half of an upsert or delete.
+///
+/// Nothing here is cached, so there is no shared state to protect — but an
+/// upsert reads the whole file, edits one entry and writes it back, and two of
+/// those interleaving would lose whichever note was written first. The read
+/// path does not take it.
+fn write_lock() -> &'static Mutex<()> {
+    static LOCK: OnceLock<Mutex<()>> = OnceLock::new();
+    LOCK.get_or_init(|| Mutex::new(()))
+}
+
+/// `<data_dir>/triple-c/notes`, created on demand.
+pub fn notes_dir() -> Result<PathBuf, String> {
+    let dir = dirs::data_dir()
+        .ok_or_else(|| {
+            "Could not determine data directory. Set XDG_DATA_HOME on Linux.".to_string()
+        })?
+        .join("triple-c")
+        .join("notes");
+    fs::create_dir_all(&dir).map_err(|e| format!("Failed to create notes directory: {}", e))?;
+    Ok(dir)
+}
+
+/// Project ids are UUIDs, but they arrive over IPC, so refuse to let one steer
+/// the write anywhere but the notes directory.
+fn sanitize(project_id: &str) -> String {
+    project_id
+        .chars()
+        .map(|c| if c.is_ascii_alphanumeric() || c == '-' || c == '_' { c } else { '_' })
+        .collect()
+}
+
+fn notes_path_in(dir: &Path, project_id: &str) -> PathBuf {
+    dir.join(format!("{}.json", sanitize(project_id)))
+}
+
+// ── Public API. Each resolves the real directory, then defers to the `_in`
+// variant, which is what the tests exercise against a temp dir. `ProjectsStore`
+// hardcodes `dirs::data_dir()` in its constructor and is therefore untestable
+// as a unit; this store does not inherit that. ─────────────────────────────
+
+pub fn load(project_id: &str) -> Result<Vec<Note>, String> {
+    load_in(&notes_dir()?, project_id)
+}
+
+pub fn upsert(project_id: &str, note: Note) -> Result<Note, String> {
+    upsert_in(&notes_dir()?, project_id, note)
+}
+
+pub fn delete(project_id: &str, note_id: &str) -> Result<(), String> {
+    delete_in(&notes_dir()?, project_id, note_id)
+}
+
+/// Remove a project's notes file entirely. Missing is success.
+pub fn clear(project_id: &str) -> Result<(), String> {
+    clear_in(&notes_dir()?, project_id)
+}
+
+// ── Implementation ─────────────────────────────────────────────────────────
+
+/// Read a project's notes. A missing file is an empty list.
+///
+/// **An unparseable file is copied aside and left in place**, then reported as
+/// empty. Erroring instead would make the Notes tab permanently unusable for
+/// that project with no way out through the UI; deleting instead would destroy
+/// the only copy of what the user wrote. The copy is timestamped so a second
+/// corruption cannot overwrite the first — which is the one taken before
+/// anything rewrote the file, and therefore the one worth having.
+fn load_in(dir: &Path, project_id: &str) -> Result<Vec<Note>, String> {
+    let path = notes_path_in(dir, project_id);
+    if !path.exists() {
+        return Ok(Vec::new());
+    }
+    let data = fs::read_to_string(&path).map_err(|e| format!("Failed to read notes: {}", e))?;
+    match serde_json::from_str::<Vec<Note>>(&data) {
+        Ok(notes) => Ok(notes),
+        Err(e) => {
+            keep_corrupt_copy(&path, &chrono::Utc::now());
+            log::error!(
+                "Failed to parse notes for project {}: {} — treating as empty; the file is \
+                 left in place and a copy was kept beside it",
+                project_id,
+                e
+            );
+            Ok(Vec::new())
+        }
+    }
+}
+
+fn keep_corrupt_copy(path: &Path, now: &chrono::DateTime<chrono::Utc>) {
+    let backup = path.with_extension(format!("json.corrupt-{}.bak", now.format("%Y%m%d-%H%M%S")));
+    if backup.exists() {
+        return;
+    }
+    if let Err(e) = fs::copy(path, &backup) {
+        log::error!("Could not keep a copy of the unreadable notes file: {}", e);
+    }
+}
+
+/// Insert or replace one note, leaving the rest untouched.
+///
+/// `created_at` and `id` are the store's, not the caller's: the webview sends
+/// a whole `Note` back and must not be able to rewrite when a note was made.
+/// `updated_at` is stamped here for the same reason.
+fn upsert_in(dir: &Path, project_id: &str, mut note: Note) -> Result<Note, String> {
+    let _guard = write_lock().lock().unwrap_or_else(|e| e.into_inner());
+    let mut notes = load_in(dir, project_id)?;
+    note.updated_at = chrono::Utc::now().to_rfc3339();
+    match notes.iter_mut().find(|n| n.id == note.id) {
+        Some(existing) => {
+            note.created_at = existing.created_at.clone();
+            *existing = note.clone();
+        }
+        None => notes.push(note.clone()),
+    }
+    save_all(dir, project_id, &notes)?;
+    Ok(note)
+}
+
+/// Remove one note. Removing one that is already gone is success — the UI can
+/// retry a delete whose result it never saw.
+fn delete_in(dir: &Path, project_id: &str, note_id: &str) -> Result<(), String> {
+    let _guard = write_lock().lock().unwrap_or_else(|e| e.into_inner());
+    let mut notes = load_in(dir, project_id)?;
+    let before = notes.len();
+    notes.retain(|n| n.id != note_id);
+    if notes.len() == before {
+        return Ok(());
+    }
+    save_all(dir, project_id, &notes)
+}
+
+fn clear_in(dir: &Path, project_id: &str) -> Result<(), String> {
+    let path = notes_path_in(dir, project_id);
+    match fs::remove_file(&path) {
+        Ok(()) => Ok(()),
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(()),
+        Err(e) => Err(format!("Failed to remove notes: {}", e)),
+    }
+}
+
+/// Atomically **and durably** write the whole list.
+///
+/// Write-temp-then-rename alone is only half of it. `fs::write` returns once
+/// the bytes are in the page cache; the rename is atomic with respect to other
+/// readers, not to power loss. Losing power in that window leaves the rename
+/// applied and the data not written — a truncated file, produced by the code
+/// whose job is to prevent one. So the file is fsynced before the rename and
+/// the directory after it, since the rename is directory metadata. Notes are
+/// prose the user typed and nothing else holds a copy.
+fn save_all(dir: &Path, project_id: &str, notes: &[Note]) -> Result<(), String> {
+    let path = notes_path_in(dir, project_id);
+    let data = serde_json::to_string_pretty(notes)
+        .map_err(|e| format!("Failed to serialize notes: {}", e))?;
+    let tmp = path.with_extension("json.tmp");
+
+    {
+        use std::io::Write;
+        let mut file =
+            fs::File::create(&tmp).map_err(|e| format!("Failed to write notes: {}", e))?;
+        file.write_all(data.as_bytes())
+            .map_err(|e| format!("Failed to write notes: {}", e))?;
+        file.sync_all()
+            .map_err(|e| format!("Failed to flush notes to disk: {}", e))?;
+    }
+
+    fs::rename(&tmp, &path).map_err(|e| format!("Failed to commit notes: {}", e))?;
+    sync_dir(&path);
+    Ok(())
+}
+
+/// fsync the directory holding `path`, so the rename survives power loss.
+///
+/// Best effort only where it is meaningless: Windows has no directory handle
+/// to sync and returns an error for the attempt, so a failure is logged rather
+/// than propagated. The file's own `sync_all` carries the data and is not best
+/// effort.
+fn sync_dir(path: &Path) {
+    let Some(dir) = path.parent() else { return };
+    if let Err(e) = fs::File::open(dir).and_then(|d| d.sync_all()) {
+        log::debug!(
+            "Could not fsync the notes directory {}: {} — the file itself was flushed",
+            dir.display(),
+            e
+        );
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn temp_dir(tag: &str) -> std::path::PathBuf {
+        let dir = std::env::temp_dir().join(format!(
+            "triple-c-notes-{}-{}",
+            tag,
+            uuid::Uuid::new_v4().simple()
+        ));
+        std::fs::create_dir_all(&dir).expect("temp dir");
+        dir
+    }
+
+    #[test]
+    fn project_ids_cannot_escape_the_notes_directory() {
+        // The id arrives over IPC. It must not be able to steer the write.
+        assert_eq!(sanitize("../../etc/passwd"), "______etc_passwd");
+        assert_eq!(sanitize("a/b"), "a_b");
+        assert_eq!(sanitize("a\\b"), "a_b");
+        // A real UUID must survive untouched, or every note file would move
+        // the first time this function changed.
+        assert_eq!(
+            sanitize("ab62cd24-51aa-4645-8f5c-17a124062050"),
+            "ab62cd24-51aa-4645-8f5c-17a124062050"
+        );
+    }
+
+    #[test]
+    fn a_missing_file_is_an_empty_list_not_an_error() {
+        let dir = temp_dir("missing");
+        assert_eq!(load_in(&dir, "nobody").unwrap(), Vec::<Note>::new());
+        std::fs::remove_dir_all(&dir).ok();
+    }
+
+    #[test]
+    fn an_upserted_note_round_trips() {
+        let dir = temp_dir("roundtrip");
+        let note = Note::new("Deploy steps".into(), "one\ntwo".into());
+        let saved = upsert_in(&dir, "p1", note.clone()).unwrap();
+        assert_eq!(saved.id, note.id);
+
+        let loaded = load_in(&dir, "p1").unwrap();
+        assert_eq!(loaded.len(), 1);
+        assert_eq!(loaded[0].body, "one\ntwo");
+        std::fs::remove_dir_all(&dir).ok();
+    }
+
+    #[test]
+    fn upserting_an_existing_id_replaces_it_and_keeps_created_at() {
+        let dir = temp_dir("replace");
+        let mut note = Note::new("Title".into(), "first".into());
+        upsert_in(&dir, "p1", note.clone()).unwrap();
+
+        note.body = "second".into();
+        note.created_at = "1999-01-01T00:00:00Z".into(); // a client must not rewrite this
+        let saved = upsert_in(&dir, "p1", note.clone()).unwrap();
+
+        let loaded = load_in(&dir, "p1").unwrap();
+        assert_eq!(loaded.len(), 1, "an upsert must not append a duplicate");
+        assert_eq!(loaded[0].body, "second");
+        assert_ne!(
+            saved.created_at, "1999-01-01T00:00:00Z",
+            "created_at is owned by the store, not by whatever the webview sent"
+        );
+        std::fs::remove_dir_all(&dir).ok();
+    }
+
+    #[test]
+    fn deleting_a_note_leaves_the_others_and_a_missing_one_is_success() {
+        let dir = temp_dir("delete");
+        let keep = upsert_in(&dir, "p1", Note::new("keep".into(), "".into())).unwrap();
+        let drop = upsert_in(&dir, "p1", Note::new("drop".into(), "".into())).unwrap();
+
+        delete_in(&dir, "p1", &drop.id).unwrap();
+        let loaded = load_in(&dir, "p1").unwrap();
+        assert_eq!(loaded.len(), 1);
+        assert_eq!(loaded[0].id, keep.id);
+
+        // Idempotent: removing what is already gone is not an error, because
+        // the UI can retry a delete it never saw the result of.
+        delete_in(&dir, "p1", &drop.id).unwrap();
+        std::fs::remove_dir_all(&dir).ok();
+    }
+
+    #[test]
+    fn an_unreadable_file_is_copied_aside_and_reads_as_empty() {
+        // Same reasoning as migration_store: a corrupt file must not make the
+        // tab permanently unusable, and the bytes must not be destroyed.
+        let dir = temp_dir("corrupt");
+        let path = notes_path_in(&dir, "p1");
+        std::fs::write(&path, b"{ not json").unwrap();
+
+        assert_eq!(load_in(&dir, "p1").unwrap(), Vec::<Note>::new());
+        assert!(path.exists(), "the unreadable file is left in place");
+
+        let copies: Vec<_> = std::fs::read_dir(&dir)
+            .unwrap()
+            .flatten()
+            .filter(|e| e.file_name().to_string_lossy().contains(".corrupt-"))
+            .collect();
+        assert_eq!(copies.len(), 1, "the bytes must be kept exactly once");
+        std::fs::remove_dir_all(&dir).ok();
+    }
+
+    #[test]
+    fn a_write_leaves_no_temp_file_behind() {
+        let dir = temp_dir("tmp");
+        upsert_in(&dir, "p1", Note::new("t".into(), "b".into())).unwrap();
+        let leftovers: Vec<_> = std::fs::read_dir(&dir)
+            .unwrap()
+            .flatten()
+            .filter(|e| e.file_name().to_string_lossy().ends_with(".tmp"))
+            .collect();
+        assert!(leftovers.is_empty(), "the rename must have consumed the temp file");
+        std::fs::remove_dir_all(&dir).ok();
+    }
+
+    #[test]
+    fn clearing_a_project_removes_its_file_and_missing_is_success() {
+        let dir = temp_dir("clear");
+        upsert_in(&dir, "p1", Note::new("t".into(), "b".into())).unwrap();
+        assert!(notes_path_in(&dir, "p1").exists());
+
+        clear_in(&dir, "p1").unwrap();
+        assert!(!notes_path_in(&dir, "p1").exists());
+        clear_in(&dir, "p1").unwrap(); // idempotent
+        std::fs::remove_dir_all(&dir).ok();
+    }
+}