Viewer: click a vault TIN to copy the full number

The party page's "TIN on file" and the W-9 card's TIN copy the full,
formatted number on click (right-click: digits only). The viewer reads
it from the vault only at that moment, with the server's key file in
force, never creates a key, refuses a key inside the books dir, and
never draws more than the last four. A locked vault copies nothing and
says why.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX

crates/ledger-gui/Cargo.toml

@@ -15,6 +15,7 @@ ledger-core = { path = "../ledger-core" }
 ledger-store = { path = "../ledger-store" }
 ledger-config = { path = "../ledger-config" }
 ledger-import = { path = "../ledger-import" }
+ledger-vault = { path = "../ledger-vault" }
 eframe = { version = "0.36", default-features = false, features = ["default_fonts", "wgpu", "wayland", "x11", "persistence"] }
 egui = "0.36"
 egui_extras = { version = "0.36", features = ["image", "datepicker", "serde"] }

crates/ledger-gui/src/books.rs

@@ -15,7 +15,7 @@ use ledger_store::{Attachment, JournalLine, Reconciliation, Snapshot, Statement,
 use rust_decimal::Decimal;
 use serde_json::Value;
 use std::collections::{BTreeMap, HashMap, HashSet};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 use crate::nav::Route;
 
@@ -1470,6 +1470,58 @@ impl Books {
         )
     }
 
+    /// The books dir: the folder holding `books-data/` (and `vault/`).
+    fn books_dir(&self) -> PathBuf {
+        let d = self
+            .data_dir
+            .canonicalize()
+            .unwrap_or_else(|_| self.data_dir.clone());
+        d.parent().map(Path::to_path_buf).unwrap_or(d)
+    }
+
+    /// A party's full TIN from the encrypted vault, formatted
+    /// ("123-45-6789" for an SSN or ITIN, "12-3456789" for an EIN), for the
+    /// clipboard only: never drawn on screen.
+    ///
+    /// ```text
+    /// INVARIANT 1: read only on demand (a click), never on load or paint.
+    /// INVARIANT 2: never creates a key file; a missing key is a locked
+    ///   vault ("restore it from your password manager").
+    /// INVARIANT 3: the key file in force is the server's: [vault]
+    ///   key_file, else ~/.config/wanderbooks/vault.key; one inside the
+    ///   books dir is refused, as the server refuses it.
+    /// INVARIANT 4: an error never carries the digits (the vault's errors
+    ///   are redacted); a party with no record is "not in the vault".
+    /// ```
+    pub fn tin_from_vault(&self, party: PartyId) -> Result<String, String> {
+        let key = self
+            .settings
+            .vault_key_file
+            .clone()
+            .unwrap_or_else(ledger_vault::default_key_file);
+        let books = self.books_dir();
+        if resolved(&key).starts_with(resolved(&books)) {
+            return Err(format!(
+                "The vault key file {} is inside the books folder: move it out and set [vault] key_file.",
+                key.display()
+            ));
+        }
+        let vault = ledger_vault::Vault::open(&books.join("vault"), &key, false).map_err(
+            |e| match e {
+                ledger_vault::Error::NoKey(k) => format!(
+                    "The vault is locked: its key file {} is missing. Restore it from your password manager.",
+                    k.display()
+                ),
+                other => other.to_string(),
+            },
+        )?;
+        match vault.tin(party) {
+            Ok(Some(t)) => Ok(t.formatted()),
+            Ok(None) => Err("Not in the vault on this computer.".into()),
+            Err(e) => Err(e.to_string()),
+        }
+    }
+
     /// One entry's what-for, for one party (see [`PartyFlow`] INVARIANT
     /// 3): its fraction of the entry's entry_flow what_for, summing to its
     /// money share exactly (zero when the entry moves no money, like a
@@ -1895,3 +1947,28 @@ fn origin(events: &[usize], journal: &[JournalLine], closing: bool) -> &'static
 fn cash_accounts(ledger: &Ledger, settings: &BooksSettings) -> Vec<AccountId> {
     ledger_store::reconcilable::cash_accounts(ledger, &settings.cash_accounts)
 }
+
+/// `path` made absolute through its nearest existing ancestor (symlinks
+/// resolved), so a path that doesn't exist yet can still be placed: the
+/// server's rule for where the vault key may live.
+fn resolved(path: &Path) -> PathBuf {
+    let abs = if path.is_absolute() {
+        path.to_path_buf()
+    } else {
+        std::env::current_dir().unwrap_or_default().join(path)
+    };
+    let mut base = abs.as_path();
+    let mut rest = Vec::new();
+    while !base.exists() {
+        match (base.file_name(), base.parent()) {
+            (Some(name), Some(up)) => {
+                rest.push(name.to_os_string());
+                base = up;
+            }
+            _ => return abs,
+        }
+    }
+    let mut out = base.canonicalize().unwrap_or_else(|_| base.to_path_buf());
+    out.extend(rest.into_iter().rev());
+    out
+}

crates/ledger-gui/src/pages/parties.rs

@@ -157,6 +157,9 @@ pub fn party_icon(p: &Party) -> &'static str {
     }
 }
 
+/// What a TIN kept in the vault says on hover.
+const TIN_COPY_HOVER: &str = "Click to copy the full number (right-click: digits only). It's read from the encrypted vault and never shown; the books keep only the last four.";
+
 /// The last four of a TIN, masked the way a truncated TIN is printed:
 /// "•••-••-1234". The books never hold more than these four digits.
 pub fn masked_tin(last4: &str) -> String {
@@ -774,7 +777,7 @@ pub fn show_party(ui: &mut Ui, b: &Books, id: PartyId, shell: &mut Shell<'_>) {
         });
         super::columns(ui, 860.0, &[1.0, 1.0], |col, ui| {
             if col == 0 {
-                facts_card(ui, party, &mut go);
+                facts_card(ui, b, party, &mut go);
             } else {
                 let mut any = false;
                 if b.files_1099(party) || party.w9.is_some() {
@@ -861,7 +864,7 @@ pub fn show_party(ui: &mut Ui, b: &Books, id: PartyId, shell: &mut Shell<'_>) {
 }
 
 /// Who they are: names, website, address, notes, ids.
-fn facts_card(ui: &mut Ui, party: &Party, go: &mut Option<Route>) {
+fn facts_card(ui: &mut Ui, b: &Books, party: &Party, go: &mut Option<Route>) {
     let p = pal(ui.ctx());
     widgets::titled_card(
         ui,
@@ -908,10 +911,18 @@ fn facts_card(ui: &mut Ui, party: &Party, go: &mut Option<Route>) {
                 ui.end_row();
                 k(ui, "Taxpayer ID");
                 match &party.tin {
+                    Some(t) if t.vault_record.is_some() => {
+                        widgets::secret_copyable(
+                            ui,
+                            RichText::new(tin_on_file(t)).monospace(),
+                            TIN_COPY_HOVER,
+                            || b.tin_from_vault(party.id),
+                        );
+                    }
                     Some(t) => {
                         ui.label(RichText::new(tin_on_file(t)).monospace())
                             .on_hover_text(
-                                "Only the last four digits are in the books; the full number is kept in the encrypted TIN vault, for the CPA package.",
+                                "Only the last four digits are in the books; the full number isn't in the vault.",
                             );
                     }
                     None => {
@@ -1008,10 +1019,19 @@ fn w9_card(ui: &mut Ui, b: &Books, party: &Party) {
                 ui.label(w.fatca_code.as_deref().unwrap_or("none"));
                 ui.end_row();
                 k(ui, "TIN");
-                ui.label(RichText::new(masked_tin(&w.tin_last4)).monospace())
-                    .on_hover_text(
-                        "Only the last four digits are in the books; the full number is kept in the vault.",
+                if w.vault_record.is_some() {
+                    widgets::secret_copyable(
+                        ui,
+                        RichText::new(masked_tin(&w.tin_last4)).monospace(),
+                        TIN_COPY_HOVER,
+                        || b.tin_from_vault(party.id),
                     );
+                } else {
+                    ui.label(RichText::new(masked_tin(&w.tin_last4)).monospace())
+                        .on_hover_text(
+                            "Only the last four digits are in the books; the full number isn't in the vault (the form is kept elsewhere).",
+                        );
+                }
                 ui.end_row();
                 k(ui, "Kept at");
                 ui.label(&w.kept_at);

crates/ledger-gui/src/widgets.rs

@@ -308,6 +308,90 @@ pub fn copyable(ui: &mut Ui, text: RichText, value: &str) -> Response {
     .inner
 }
 
+/// A secret that copies itself when clicked but is never drawn: `text` is
+/// its masked form; `fetch` reads the real value, only on a click (or the
+/// right-click menu's "Copy digits only"). A fetch that fails shows why,
+/// beside it, for a few seconds.
+pub fn secret_copyable(
+    ui: &mut Ui,
+    text: RichText,
+    hover: &str,
+    fetch: impl Fn() -> Result<String, String>,
+) -> Response {
+    let id = ui.id().with(("secret-copy", text.text()));
+    let err_id = id.with("error");
+    let p = pal(ui.ctx());
+    ui.horizontal(|ui| {
+        ui.spacing_mut().item_spacing.x = 4.0;
+        let r = ui.add(egui::Label::new(text).sense(Sense::click()));
+        let recent = recently_copied(ui, id);
+        let (slot, _) = ui.allocate_exact_size(vec2(14.0, 14.0), Sense::hover());
+        if r.hovered() || recent {
+            ui.painter().text(
+                slot.center(),
+                egui::Align2::CENTER_CENTER,
+                if recent {
+                    egui_phosphor::regular::CHECK
+                } else {
+                    egui_phosphor::regular::COPY
+                },
+                egui::FontId::proportional(12.0),
+                if recent { p.positive } else { p.muted },
+            );
+        }
+        if r.hovered() {
+            ui.ctx().set_cursor_icon(egui::CursorIcon::PointingHand);
+        }
+        let copy = |ui: &mut Ui, digits_only: bool| match fetch() {
+            Ok(v) => {
+                let v: String = if digits_only {
+                    v.chars().filter(char::is_ascii_digit).collect()
+                } else {
+                    v
+                };
+                ui.ctx().data_mut(|d| d.remove::<(f64, String)>(err_id));
+                copy_now(ui, id, &v);
+            }
+            Err(e) => {
+                let now = ui.input(|i| i.time);
+                ui.ctx().data_mut(|d| d.insert_temp(err_id, (now, e)));
+            }
+        };
+        let r = r.on_hover_text(if recent { "Copied" } else { hover });
+        if r.clicked() {
+            copy(ui, false);
+        }
+        r.context_menu(|ui| {
+            if ui
+                .button(format!("{} Copy", egui_phosphor::regular::COPY))
+                .clicked()
+            {
+                copy(ui, false);
+                ui.close();
+            }
+            if ui
+                .button(format!("{} Copy digits only", egui_phosphor::regular::COPY))
+                .clicked()
+            {
+                copy(ui, true);
+                ui.close();
+            }
+        });
+        let failed: Option<(f64, String)> = ui.ctx().data(|d| d.get_temp(err_id));
+        let now = ui.input(|i| i.time);
+        if let Some((at, e)) = failed.filter(|(at, _)| now - at < 6.0) {
+            ui.ctx()
+                .request_repaint_after(std::time::Duration::from_secs_f64(6.0 - (now - at)));
+            ui.add(
+                egui::Label::new(RichText::new(e).font(theme::regular(12.0)).color(p.warning))
+                    .wrap(),
+            );
+        }
+        r
+    })
+    .inner
+}
+
 /// A "Copy …" item for a right-click menu.
 pub fn copy_item(ui: &mut Ui, label: &str, value: &str) {
     if ui

crates/ledger-gui/tests/tin_copy.rs

@@ -0,0 +1,179 @@
+//! A TIN in the vault copies from the party page, and is never drawn.
+//!
+//! ```text
+//! GOAL: people can use a member's or payee's full TIN (paste it into a
+//!       form) without the viewer ever showing it.
+//! SOURCE: DECISION (Stephen, 2026-10-16: "the TIN on the party page
+//!         should have a click to copy too ... people still need to
+//!         actually access these things").
+//! INVARIANTS: Books::tin_from_vault 1-4, and
+//!   5. Clicking the masked TIN puts the full, formatted number on the
+//!      clipboard; nothing the viewer draws holds more than the last four.
+//!   6. A failed read (locked vault) copies nothing and says why.
+//! ```
+
+use egui::OutputCommand;
+use egui_kittest::Harness;
+use egui_kittest::kittest::Queryable;
+use ledger_core::{PartyId, Role, TinFacts, TinType};
+use ledger_gui::books::Books;
+use ledger_gui::nav::Route;
+use ledger_gui::{App, Source, data};
+use ledger_store::Store;
+use ledger_vault::{Tin, Vault};
+use std::path::{Path, PathBuf};
+
+const SSN: &str = "123-45-6789";
+
+struct Fixture {
+    root: PathBuf,
+    books: PathBuf,
+    key: PathBuf,
+    party: PartyId,
+}
+
+impl Drop for Fixture {
+    fn drop(&mut self) {
+        let _ = std::fs::remove_dir_all(&self.root);
+    }
+}
+
+/// Books with one member whose SSN is in the vault; the key lives outside
+/// the books dir, as the server requires.
+fn fixture(tag: &str) -> Fixture {
+    let root = std::env::temp_dir().join(format!("ledger-gui-tin-{tag}-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&root);
+    let books = root.join("books");
+    let key = root.join("keys/vault.key");
+    std::fs::create_dir_all(&books).unwrap();
+    let mut s = Store::create(&books.join("books-data"), ledger_core::Currency::USD).unwrap();
+    let party = s.add_party("Pat Lee", &[Role::Member]).unwrap();
+    let v = Vault::open(&books.join("vault"), &key, true).unwrap();
+    let hash = v
+        .put_tin(party, &Tin::new(SSN, ledger_vault::TinType::Ssn).unwrap())
+        .unwrap();
+    s.set_party_tin(
+        party,
+        Some(TinFacts {
+            tin_type: TinType::Ssn,
+            last4: "6789".into(),
+            vault_record: Some(hash),
+            purged: None,
+        }),
+    )
+    .unwrap();
+    Fixture {
+        root,
+        books,
+        key,
+        party,
+    }
+}
+
+fn load(f: &Fixture, key: Option<&Path>) -> Books {
+    let mut b = data::load_once(&Source {
+        data_dir: f.books.join("books-data"),
+        books_toml: None,
+        today: Some(chrono::NaiveDate::from_ymd_opt(2026, 10, 16).unwrap()),
+    })
+    .unwrap();
+    b.settings.vault_key_file = key.map(Path::to_path_buf);
+    b
+}
+
+fn copied(h: &Harness<'_, App>) -> Vec<String> {
+    h.output()
+        .platform_output
+        .commands
+        .iter()
+        .filter_map(|c| match c {
+            OutputCommand::CopyText(t) => Some(t.clone()),
+            _ => None,
+        })
+        .collect()
+}
+
+fn no_digits(s: &str) {
+    let digits: String = s.chars().filter(char::is_ascii_digit).collect();
+    assert!(!digits.contains("12345"), "{s}");
+}
+
+/// INVARIANTS 1, 3, 4: the vault's record, formatted; a party without
+/// one is "not in the vault".
+#[test]
+fn reads_the_vault_with_the_key_in_force() {
+    let f = fixture("read");
+    let b = load(&f, Some(&f.key));
+    assert_eq!(b.tin_from_vault(f.party).unwrap(), SSN);
+    let e = b.tin_from_vault(f.party + 1).unwrap_err();
+    assert!(e.contains("Not in the vault"), "{e}");
+}
+
+/// INVARIANT 2: a missing key is a locked vault, and none is created.
+#[test]
+fn a_missing_key_is_locked_and_never_created() {
+    let f = fixture("locked");
+    let gone = f.root.join("elsewhere/vault.key");
+    let b = load(&f, Some(&gone));
+    let e = b.tin_from_vault(f.party).unwrap_err();
+    assert!(e.contains("locked"), "{e}");
+    no_digits(&e);
+    assert!(!gone.exists(), "reading must never create a key");
+}
+
+/// INVARIANT 3: a key file inside the books dir is refused.
+#[test]
+fn a_key_inside_the_books_is_refused() {
+    let f = fixture("inside");
+    let inside = f.books.join("vault.key");
+    std::fs::copy(&f.key, &inside).unwrap();
+    let e = load(&f, Some(&inside)).tin_from_vault(f.party).unwrap_err();
+    assert!(e.contains("inside the books folder"), "{e}");
+}
+
+/// INVARIANT 4: a tampered record is unreadable, and says nothing of it.
+#[test]
+fn a_bad_record_is_an_error_without_digits() {
+    let f = fixture("tamper");
+    let rec = f.books.join(format!("vault/tin-{}.bin", f.party));
+    let mut raw = std::fs::read(&rec).unwrap();
+    let last = raw.len() - 1;
+    raw[last] ^= 1;
+    std::fs::write(&rec, raw).unwrap();
+    let e = load(&f, Some(&f.key)).tin_from_vault(f.party).unwrap_err();
+    no_digits(&e);
+}
+
+fn party_page(b: Books, party: PartyId) -> Harness<'static, App> {
+    let mut h = Harness::builder()
+        .with_size(egui::vec2(1280.0, 1000.0))
+        .build_eframe(move |cc| App::with_books(&cc.egui_ctx, b, false, Route::Party(party)));
+    h.run_steps(3);
+    h
+}
+
+/// INVARIANTS 5, 6, through the party page.
+#[test]
+fn clicking_the_masked_tin_copies_the_full_number() {
+    let f = fixture("click");
+    let shown = "TIN on file ••••6789 (SSN)";
+    let mut h = party_page(load(&f, Some(&f.key)), f.party);
+    assert!(
+        h.query_by_label_contains("12345").is_none(),
+        "the full number is never drawn"
+    );
+    h.get_by_label(shown).click();
+    h.step();
+    assert_eq!(copied(&h), [SSN]);
+    h.run_steps(2);
+    assert!(h.query_by_label_contains("12345").is_none());
+
+    // Locked: nothing copied; the reason shows beside it.
+    let gone = f.root.join("elsewhere/vault.key");
+    let mut h = party_page(load(&f, Some(&gone)), f.party);
+    h.get_by_label(shown).click();
+    h.step();
+    assert!(copied(&h).is_empty());
+    h.run_steps(2);
+    assert!(h.query_by_label_contains("The vault is locked").is_some());
+}