fix: rogue "s" next to roman numeral harmony labels

repro/harmony-roman-s.tla

@@ -0,0 +1,184 @@
+{
+  "file_path": "C:/Users/Felipe/dev/tilia-desktop/.claude/worktrees/tilia-app-dns-fix-cb44c6/repro/harmony-roman-s.tla",
+  "media_path": "",
+  "media_metadata": {
+    "title": "harmony-roman-s",
+    "notes": "",
+    "media length": 100,
+    "composer": "",
+    "tonality": "",
+    "time signature": "",
+    "performer": "",
+    "performance year": "",
+    "arranger": "",
+    "composition year": "",
+    "recording year": "",
+    "form": "",
+    "instrumentation": "",
+    "genre": "",
+    "lyrics": ""
+  },
+  "timelines": {
+    "0": {
+      "kind": "HARMONY_TIMELINE",
+      "level_count": 1,
+      "level_height": 35,
+      "is_visible": true,
+      "name": "",
+      "ordinal": 1,
+      "visible_level_count": 2,
+      "hash": "46fa9e532d92228f5688fb04a2cc17e9",
+      "components": {
+        "2": {
+          "time": 0.0,
+          "comments": "",
+          "step": 0,
+          "accidental": 0,
+          "quality": "major",
+          "inversion": 0,
+          "applied_to": 0,
+          "level": 1,
+          "display_mode": "roman",
+          "custom_text": "",
+          "custom_text_font_type": "analytic",
+          "kind": "HARMONY",
+          "hash": "6c48851babc6afa48936cdf65180bd61"
+        },
+        "3": {
+          "time": 10,
+          "comments": "",
+          "step": 0,
+          "accidental": 0,
+          "quality": "major",
+          "inversion": 1,
+          "applied_to": 0,
+          "level": 1,
+          "display_mode": "roman",
+          "custom_text": "",
+          "custom_text_font_type": "analytic",
+          "kind": "HARMONY",
+          "hash": "ca8fd969194756510648e632ea0be4a0"
+        },
+        "4": {
+          "time": 20,
+          "comments": "",
+          "step": 0,
+          "accidental": 0,
+          "quality": "major",
+          "inversion": 2,
+          "applied_to": 0,
+          "level": 1,
+          "display_mode": "roman",
+          "custom_text": "",
+          "custom_text_font_type": "analytic",
+          "kind": "HARMONY",
+          "hash": "2a58a41503d3d03fd02087b0738a5b58"
+        },
+        "5": {
+          "time": 30,
+          "comments": "",
+          "step": 4,
+          "accidental": 0,
+          "quality": "dominant-seventh",
+          "inversion": 1,
+          "applied_to": 0,
+          "level": 1,
+          "display_mode": "roman",
+          "custom_text": "",
+          "custom_text_font_type": "analytic",
+          "kind": "HARMONY",
+          "hash": "d522cbc0c607b8b4104f947f3c10a4f4"
+        },
+        "6": {
+          "time": 40,
+          "comments": "",
+          "step": 4,
+          "accidental": 0,
+          "quality": "dominant-seventh",
+          "inversion": 2,
+          "applied_to": 0,
+          "level": 1,
+          "display_mode": "roman",
+          "custom_text": "",
+          "custom_text_font_type": "analytic",
+          "kind": "HARMONY",
+          "hash": "631e562c66dc19c2e715d87a5aa5c22e"
+        },
+        "7": {
+          "time": 50,
+          "comments": "",
+          "step": 4,
+          "accidental": 0,
+          "quality": "dominant-seventh",
+          "inversion": 3,
+          "applied_to": 0,
+          "level": 1,
+          "display_mode": "roman",
+          "custom_text": "",
+          "custom_text_font_type": "analytic",
+          "kind": "HARMONY",
+          "hash": "8e48290e575fc9f7b4639c44456ee5ac"
+        },
+        "8": {
+          "time": 60,
+          "comments": "",
+          "step": 1,
+          "accidental": 0,
+          "quality": "dominant-seventh",
+          "inversion": 1,
+          "applied_to": 4,
+          "level": 1,
+          "display_mode": "roman",
+          "custom_text": "",
+          "custom_text_font_type": "analytic",
+          "kind": "HARMONY",
+          "hash": "04edd729caae353bf67a23f8171093aa"
+        },
+        "9": {
+          "time": 70,
+          "comments": "",
+          "step": 1,
+          "accidental": 0,
+          "quality": "minor-seventh",
+          "inversion": 1,
+          "applied_to": 0,
+          "level": 1,
+          "display_mode": "roman",
+          "custom_text": "",
+          "custom_text_font_type": "analytic",
+          "kind": "HARMONY",
+          "hash": "305e60532e03f546c8ff94b209d21034"
+        },
+        "10": {
+          "time": 80,
+          "comments": "",
+          "step": 4,
+          "accidental": 0,
+          "quality": "dominant-ninth",
+          "inversion": 3,
+          "applied_to": 0,
+          "level": 1,
+          "display_mode": "roman",
+          "custom_text": "",
+          "custom_text_font_type": "analytic",
+          "kind": "HARMONY",
+          "hash": "80a5eb6f96a6ee8e7df1f803e73978ad"
+        },
+        "1": {
+          "time": 0.0,
+          "step": 0,
+          "accidental": 0,
+          "type": "major",
+          "comments": "",
+          "level": 2,
+          "kind": "MODE",
+          "hash": "93165266d353cdc0a4b8df96d5d0f91d"
+        }
+      },
+      "components_hash": "1e052a4bd06b7a723f32d01cea45ea1f"
+    }
+  },
+  "timelines_hash": "0f9df940ab670331652bf4d39914e000",
+  "app_name": "TiLiA",
+  "version": "0.6.4"
+}

tests/repro_harmony_roman_s.py

@@ -0,0 +1,61 @@
+"""Throwaway generator for the repro bundle of the rogue-"s" harmony fix.
+
+Harmony is not covered by the CLI's `timelines add` / `components`, so the
+fixture is built through `commands.execute(...)` and saved with `file.save`,
+as `CLAUDE.md` prescribes for kinds the CLI cannot populate.
+
+Run from the repo root:
+
+    uv run --python 3.12 pytest tests/repro_harmony_roman_s.py -q
+
+Writes `repro/harmony-roman-s.tla`. Delete both this file and the `.tla`
+before merge — the durable artifact is
+`TestRomanNumeralDisplay::test_roman_label_has_no_blank_accidental_placeholder`.
+"""
+
+from pathlib import Path
+
+from tests.mock import Serve
+from tests.ui.timelines.harmony.test_harmony_timeline_ui import add_harmony, add_mode
+from tilia.requests import Get
+from tilia.ui import commands
+
+OUT = Path(__file__).resolve().parent.parent / "repro" / "harmony-roman-s.tla"
+
+# (time, step, quality, inversion, applied_to) -> what the label should read.
+# Every entry but the last two is a one- or two-figure figured bass, which is
+# where the blank-accidental placeholder leaks out of the "%" stack.
+HARMONIES = [
+    (0, 0, "major", 0, 0),  # I       — control, no figures
+    (10, 0, "major", 1, 0),  # I6
+    (20, 0, "major", 2, 0),  # I64
+    (30, 4, "dominant-seventh", 1, 0),  # V65
+    (40, 4, "dominant-seventh", 2, 0),  # V43
+    (50, 4, "dominant-seventh", 3, 0),  # V42
+    (60, 1, "dominant-seventh", 1, 4),  # V65/V  — applied chord
+    (70, 1, "minor-seventh", 1, 0),  # ii65
+    (80, 4, "dominant-ninth", 3, 0),  # V%sss432 — control, stacked form
+]
+
+
+def test_generate_fixture(harmony_tlui, tilia_state):
+    tilia_state.set_duration(100, "no")
+    add_mode(0, step=0, accidental=0, type="major")  # C major
+
+    for time, step, quality, inversion, applied_to in HARMONIES:
+        add_harmony(
+            time,
+            step=step,
+            quality=quality,
+            inversion=inversion,
+            applied_to=applied_to,
+            display_mode="roman",
+        )
+
+    OUT.parent.mkdir(parents=True, exist_ok=True)
+    with Serve(Get.FROM_USER_SAVE_PATH_TILIA, (True, OUT)):
+        commands.execute("file.save")
+
+    print("\nwrote", OUT)
+    for element in sorted(harmony_tlui.harmonies(), key=lambda e: e.get_data("time")):
+        print(f"  t={element.get_data('time'):>5} label={element.label!r}")

tests/ui/timelines/harmony/test_harmony_timeline_ui.py

@@ -131,6 +131,35 @@ def test_roman_label_does_not_start_with_accidental_when_root_is_diatonic_sharp_
 
         assert harmony_tlui[0].label.startswith(expected_start)
 
+    @pytest.mark.parametrize(
+        "step,quality,inversion,expected",
+        [
+            (0, "major", 1, "I6"),
+            (0, "major", 2, "I64"),
+            (1, "minor-seventh", 0, "ii7"),
+            (1, "minor-seventh", 1, "ii65"),
+            (4, "dominant-seventh", 1, "V65"),
+            (4, "dominant-seventh", 2, "V43"),
+            (4, "dominant-seventh", 3, "V42"),
+        ],
+    )
+    def test_roman_label_has_no_blank_accidental_placeholder(
+        self, step, quality, inversion, expected, harmony_tlui
+    ):
+        # "s" marks an accidental slot left blank; MusAnalysis only consumes it
+        # inside the three-figure "%" stack, so it must not reach shorter
+        # figures, where it would be drawn as a literal letter.
+        add_harmony(step=step, quality=quality, inversion=inversion)
+
+        assert harmony_tlui.harmonies()[0].label == expected
+
+    def test_roman_label_keeps_blank_accidental_placeholder_in_stacked_figures(
+        self, harmony_tlui
+    ):
+        add_harmony(step=4, quality="dominant-ninth", inversion=3)
+
+        assert harmony_tlui.harmonies()[0].label == "V%sss432"
+
     def test_roman_label_for_ninth_chord_high_inversion(self, harmony_tlui):
         # inversion=4 places the 9th in the bass; label is dynamically computed
         add_harmony(

tilia/ui/timelines/harmony/utils.py

@@ -134,8 +134,13 @@ def _fmt_mod(mod: str | None, none_str: str = "") -> str:
 
 
 def _figs_to_str(figures: list[tuple[int, str | None]]) -> str:
-    prefix = "%" if len(figures) > 2 else ""
-    accs = "".join(_fmt_mod(mod, "s") for _, mod in figures)
+    # MusAnalysis only consumes the "s" placeholder (an accidental slot left
+    # blank) inside the three-figure stack introduced by "%". Outside it there
+    # is no blank slot, so an unaccidented figure must contribute nothing —
+    # otherwise the "s" is rendered as a literal letter next to the numeral.
+    stacked = len(figures) > 2
+    prefix = "%" if stacked else ""
+    accs = "".join(_fmt_mod(mod, "s" if stacked else "") for _, mod in figures)
     nums = "".join(str(n) for n, _ in figures)
     return prefix + accs + nums