diff --git a/crates/fonts-build/src/tests.rs b/crates/fonts-build/src/tests.rs
--- a/crates/fonts-build/src/tests.rs
+++ b/crates/fonts-build/src/tests.rs
@@ -376,7 +376,10 @@ fn for_ui_embeds_cjk_faces_only_as_cut_interface_faces() {
     assert_eq!(warnings(&r), Vec::<String>::new());
     let r = run(Embed::documents(&["Noto Sans TC UI", "Noto Sans TC"]), Some(&dir), Some("1"));
     assert_eq!(r.result.as_ref().unwrap(), &["Noto Sans TC Regular", "Noto Sans TC UI Regular"]);
-    assert!(r.table.contains("fonts/1.ttf"), "{}", r.table);
+    // Generated Rust escapes native separators (and Windows' canonical path prefix).
+    // Match the selected file's complete include expression on every platform.
+    let interface_face = dir.join("fonts/1.ttf").canonicalize().unwrap();
+    assert!(r.table.contains(&format!("include_bytes!({interface_face:?})")), "{}", r.table);
 }
 
 #[test]
diff --git a/crates/keymap/README.md b/crates/keymap/README.md
--- a/crates/keymap/README.md
+++ b/crates/keymap/README.md
@@ -7,6 +7,8 @@ supplies its command catalog, its file-format readers and its UI.
 
 ## Boundaries
 
+For contextual ribbon/menu letter allocation, see [contextual keytips](docs/contextual-keytips.md).
+
 - Data and logic, plus a shared Keyboard Shortcuts dialog behind the `ui` feature. The apps keep
   the command catalog (ids, labels, menu paths, defaults), the readers for other applications'
   files, file dialogs and running the commands.
diff --git a/crates/keymap/docs/contextual-keytips.md b/crates/keymap/docs/contextual-keytips.md
new file mode 100644
--- /dev/null
+++ b/crates/keymap/docs/contextual-keytips.md
@@ -0,0 +1,19 @@
+# Contextual keytip allocation
+
+`craft_keymap::keytips::allocate` shares the collision-free letter allocation from
+[WordCraft #3855](https://github.com/storytold/wordcraft/pull/3855). It is useful for contextual
+ribbon tabs and menus in other Craft apps while leaving their command catalogs and Alt-key
+handling in each host.
+
+Pass labels in stable order and reserve every fixed tab/search/legacy-menu prefix. Multi-key
+sequences reserve their first letter, so a generated single-letter tip cannot shadow them.
+Allocation prefers an available letter from the label, then the first free A-Z letter.
+
+Allocate over all possible contextual tabs once, then display the active subset. This keeps
+letters stable as selections change. Stable source labels or localized labels are both possible
+host policies; non-Latin labels use the A-Z fallback. No transliteration is attempted. Exhausted
+letters return `None`, meaning the control stays usable without a generated keytip.
+
+The result covers at most 4096 labels and reports omitted choices; at most 256 characters per
+label are scanned. Reserved prefixes are all inspected. This adds no global state, bindings or
+app-specific legacy key reservations, and it does not change existing `Keymap` shortcut dispatch.
diff --git a/crates/keymap/src/keytips.rs b/crates/keymap/src/keytips.rs
new file mode 100644
--- /dev/null
+++ b/crates/keymap/src/keytips.rs
@@ -0,0 +1,76 @@
+//! Deterministic single-letter keytips for contextual menus and tabs.
+//!
+//! This shares allocation policy, not an application's Alt-key state machine or command catalog.
+//! Allocate over the full ordered set of possible contextual tabs, then display its active subset;
+//! allocating only visible tabs can change their letters when another tab appears.
+
+const MAX_CHOICES: usize = 4096;
+const MAX_LABEL_CHARS: usize = 256;
+
+/// One optional ASCII A-Z letter per considered label, in input order. `None` means all letters
+/// are reserved or already assigned; the host should keep the control available without a badge.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Allocation {
+    pub letters: Vec<Option<char>>,
+    /// Labels after the first 4096 are not considered. Report this if exposing imported catalogs.
+    pub omitted: usize,
+}
+
+/// Prefer the first unused ASCII letter in each label, then the first free A-Z letter.
+/// Reserved sequences protect their first letter, case-insensitively, including prefixes of
+/// multi-key tips. Empty/non-letter prefixes reserve no A-Z key. Assignments never duplicate
+/// another result or shadow a reserved prefix. Exhaustion is explicit, not a fabricated key.
+///
+/// The caller supplies its reserved fixed tabs, search and legacy-menu prefixes. Labels may be
+/// localized or stable source labels according to host policy; non-Latin names fall back to A-Z
+/// rather than attempting transliteration. At most 4096 choices and 256 characters per label are
+/// scanned. All reserved prefixes are inspected so truncation cannot introduce a collision.
+pub fn allocate(labels: &[&str], reserved: &[&str]) -> Allocation {
+    let mut taken = [false; 26];
+    let index = |c: char| {
+        if c.is_ascii_alphabetic() { Some((c.to_ascii_uppercase() as u8 - b'A') as usize) } else { None }
+    };
+    for text in reserved {
+        if let Some(i) = text.chars().next().and_then(index) {
+            taken[i] = true;
+        }
+    }
+    let mut letters = Vec::with_capacity(labels.len().min(MAX_CHOICES));
+    for label in labels.iter().take(MAX_CHOICES) {
+        let preferred = label.chars().take(MAX_LABEL_CHARS).filter_map(index).find(|&i| !taken[i]);
+        let free = preferred.or_else(|| taken.iter().position(|used| !used));
+        letters.push(free.map(|i| {
+            taken[i] = true;
+            char::from(b'A' + i as u8)
+        }));
+    }
+    Allocation { letters, omitted: labels.len().saturating_sub(MAX_CHOICES) }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn contextual_letters_avoid_fixed_and_legacy_prefixes_even_when_labels_repeat() {
+        let allocation = allocate(&["Picture Format", "Shape Format", "Shape Format", "图表"], &["P", "S", "jT", "Q", "fO"]);
+        let letters = allocation.letters.iter().flatten().copied().collect::<Vec<_>>();
+        assert_eq!(letters.len(), 4);
+        let unique = letters.iter().copied().collect::<std::collections::HashSet<_>>();
+        assert_eq!(unique.len(), 4);
+        assert!(letters.iter().all(|c| !"PSJQF".contains(*c)));
+        assert_eq!(allocate(&["Picture Format", "Shape Format", "Shape Format", "图表"], &["P", "S", "jT", "Q", "fO"]), allocation);
+    }
+    #[test]
+    fn exhausted_alphabet_is_explicit_and_large_catalogs_are_reported() {
+        let labels = vec!["A"; 5000];
+        let allocation = allocate(&labels, &[]);
+        assert_eq!(allocation.letters.len(), MAX_CHOICES);
+        assert_eq!(allocation.omitted, 5000 - MAX_CHOICES);
+        assert_eq!(allocation.letters.iter().filter(|c| c.is_some()).count(), 26);
+        let reserved = allocate(
+            &["Anything"],
+            &["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"],
+        );
+        assert_eq!(reserved.letters, vec![None]);
+    }
+}
diff --git a/crates/keymap/src/lib.rs b/crates/keymap/src/lib.rs
--- a/crates/keymap/src/lib.rs
+++ b/crates/keymap/src/lib.rs
@@ -142,6 +142,7 @@ pub mod editor;
 pub mod egui;
 pub mod import;
 pub mod keymap;
+pub mod keytips;
 pub mod layout;
 pub mod profiles;
 pub mod reserved;