seonghobae · Aug 31, 2026 · Aug 31, 2026 · Aug 31, 2026 · Aug 31, 2026 · Aug 31, 2026
@@ -1,7 +1,7 @@
 # AGENTS.md
 
 ## Project overview
-- BandScope is a local-first desktop app for rehearsal prep: a practical song view with likely harmony by section and by instrument or vocal role, form and groove cues, stems, playable ranges, simplification guidance, transposition or setup cues, part-overlap cues, visible confidence, and rehearsal priorities.
+- BandScope is a local-first desktop app for rehearsal prep: a practical song view with likely harmony by section and by instrument or vocal role, form and groove cues, stems, playable ranges, leftover sit-out cues after a partial return, simplification guidance, transposition or setup cues, part-overlap cues, visible confidence, and rehearsal priorities.
 - Authoritative delivery rules live in `ARCHITECTURE.md`, `docs/plans/`, and the root verification scripts.
 - Brand, tone, UX copy, and prioritization rules live in `docs/brand-story.md` and must be applied to PRDs, TRDs, UI copy, onboarding, empty states, and error messages.
 - App security rules live in `docs/security/app-security.md` and must be applied to file handling, URL intake, subprocesses, IPC, WebView usage, model loading, updates, logging, cache handling, and export behavior.

@@ -82,7 +82,7 @@ Last updated: 2026-03-11
   - likely harmony by section and by role
   - section roadmap with entries, dropouts, pickups, stops, tags, and handoffs
   - groove and timing cues relevant to locking the band together
-  - playable ranges and density or overlap warnings, with the ready workspace naming tonight's first span and the next instrument check
+  - playable ranges and density or overlap warnings, with the ready workspace naming tonight's first span and tonight's first leftover sit-out after a partial return
   - simplification, transposition, capo, tuning, or setup cues where applicable
   - role-specific rehearsal priorities and confidence flags
   - cue-sheet or chart-style exports that summarize the analysis in rehearsal-friendly form

@@ -4,6 +4,7 @@
 
 ### Added
 
+- Name tonight's first leftover sit-out on the ready rehearsal map and tell returning parts to play without waiting, or the leftover part to stay out.
 - Name tonight's first playable range on the ready rehearsal map and tell the player to check that span on their instrument before the section.
 - Display the analyzed song tempo (BPM) as a badge in the rehearsal workspace.
 - 각 합주 역할(Role)별 개인 연습 진행도를 0~100% 범위로 기록 및 시각화할 수 있는 연습 진척도(`practiceProgress`) 트래커 기능 추가. UI 컨트롤(슬라이더 및 +/- 버튼)과 한/영 다국어 지원 포함.

@@ -51,7 +51,7 @@ BandScope is a local-first desktop app for rehearsal prep: it turns a song into
 
 Three layers, decoupled through shared contracts:
 
-- `apps/desktop` — Tauri 2 + Vite + React 19 shell (Tailwind 4, Base UI, Storybook). Feature screens live in `src/features/` (home, workspace, chords, ranges, player, settings). The ready workspace names tonight's first playable range and the next instrument check. `src/lib/analysis.ts` and `src/lib/job_runner.ts` call typed Tauri IPC commands, with a browser fallback that serves demo data when not running inside Tauri.
+- `apps/desktop` — Tauri 2 + Vite + React 19 shell (Tailwind 4, Base UI, Storybook). Feature screens live in `src/features/` (home, workspace, chords, ranges, player, settings). The ready workspace names tonight's first playable range and tonight's first leftover sit-out after a partial return. `src/lib/analysis.ts` and `src/lib/job_runner.ts` call typed Tauri IPC commands, with a browser fallback that serves demo data when not running inside Tauri.
 - `apps/desktop/src-tauri/src/main.rs` — the Rust orchestration boundary. Tauri commands (`start_analysis_job`, `get_analysis_job_status`, `select_local_audio_source`, `import_youtube_url`) validate untrusted input (project IDs, file paths, URLs) and spawn the Python engine as a subprocess. There is no loopback HTTP listener and no network path for local analysis.
 - `services/analysis-engine` — Python package `bandscope_analysis` (librosa/numpy). Entry point `cli.py` reads a JSON job request on stdin and prints a structured job-status JSON envelope on stdout (`--progress-jsonl` streams progress lines). `api.py` orchestrates the pipeline across the `separation`, `sections`, `roles`, `chords`, `ranges`, `temporal`, `transcription`, and `youtube` modules.
 

@@ -196,6 +196,82 @@ describe("Workspace", () => {
     );
   });
 
+  it("names tonight's first leftover sit-out after a partial return", () => {
+    setNavigatorLanguage("en-US");
+    const song = createDemoRehearsalSong();
+    const verse = song.sections[0]!;
+    song.sections = [
+      {
+        ...verse,
+        partGraph: verse.partGraph.map((node) =>
+          node.role_id === "bass-guitar" || node.role_id === "keys-right"
+            ? { ...node, is_active: false }
+            : node
+        )
+      },
+      {
+        ...verse,
+        id: "chorus-1",
+        label: "chorus",
+        timeRange: { start: verse.timeRange.end, end: verse.timeRange.end + 20 },
+        partGraph: verse.partGraph.map((node) =>
+          node.role_id === "keys-right" ? { ...node, is_active: false } : node
+        )
+      }
+    ];
+
+    render(<Workspace song={song} />);
+
+    const callout = screen.getByTestId("first-leftover");
+    expect(callout).toHaveTextContent("Tonight's first leftover sit-out");
+    expect(callout).toHaveTextContent(
+      "Keyboard 1 Right Hand stays tacet in chorus after verse. Play chorus without waiting for Keyboard 1 Right Hand."
+    );
+  });
+
+  it("tells the leftover part to stay out of the partial return", () => {
+    setNavigatorLanguage("en-US");
+    const song = createDemoRehearsalSong();
+    const verse = song.sections[0]!;
+    song.sections = [
+      {
+        ...verse,
+        partGraph: verse.partGraph.map((node) =>
+          node.role_id === "bass-guitar" || node.role_id === "keys-right"
+            ? { ...node, is_active: false }
+            : node
+        )
+      },
+      {
+        ...verse,
+        id: "chorus-1",
+        label: "chorus",
+        timeRange: { start: verse.timeRange.end, end: verse.timeRange.end + 20 },
+        partGraph: verse.partGraph.map((node) =>
+          node.role_id === "keys-right" ? { ...node, is_active: false } : node
+        )
+      }
+    ];
+
+    render(<Workspace song={song} />);
+    fireEvent.click(screen.getByRole("tab", { name: "Keyboard 1 Right Hand" }));
+
+    expect(screen.getByTestId("first-leftover")).toHaveTextContent(
+      "Keyboard 1 Right Hand stays tacet in chorus after verse. Stay out of chorus."
+    );
+  });
+
+  it("asks the player to confirm the leftover sit-out when every part stays active", () => {
+    setNavigatorLanguage("en-US");
+    const song = createDemoRehearsalSong();
+
+    render(<Workspace song={song} />);
+
+    expect(screen.getByTestId("first-leftover")).toHaveTextContent(
+      "Tonight's first leftover sit-out still needs a named part that stays out after others return. Confirm who stays tacet before the first section."
+    );
+  });
+
   it("falls back from blank planning copy and tolerates partial collaboration payloads", () => {
     setNavigatorLanguage("en-US");
     const song = createDemoRehearsalSong();

@@ -5,6 +5,7 @@ import { SectionRoadmap } from "./SectionRoadmap";
 import { GrooveMap } from "./GrooveMap";
 import { PracticeProgress } from "./PracticeProgress";
 import { fillRangeCopy, firstRangeSqueeze } from "./firstRangeSqueeze";
+import { firstLeftover } from "./firstLeftover";
 import { createTranslator, detectPreferredLocale } from "../../i18n";
 import { generateCueSheetCsv, generateChartSummaryJson, generateMetadataHandoffJson, sanitizeFilename } from "../../lib/export";
 import { Button } from "@/components/ui/button";
@@ -163,6 +164,21 @@ export function Workspace({ song, sourceBootstrap = null, onSongUpdate }: Worksp
         }
       )
     : t("workspaceFirstRangeMissing");
+  const namedLeftover = useMemo(() => firstLeftover(song, activeRole), [activeRole, song]);
+  const firstLeftoverCopy = namedLeftover
+    ? fillRangeCopy(
+        t(
+          activeRole && activeRole === namedLeftover.leftoverRoleId
+            ? "workspaceFirstLeftoverStayOut"
+            : "workspaceFirstLeftoverNamed"
+        ),
+        {
+          leftoverRoleName: namedLeftover.leftoverRoleName,
+          sectionLabel: namedLeftover.sectionLabel,
+          fromSectionLabel: namedLeftover.fromSectionLabel
+        }
+      )
+    : t("workspaceFirstLeftoverMissing");
 
   /** Handle the practice progress change internally by immutably updating the song state. */
   const handlePracticeProgressChange = (newProgress: number) => {
@@ -309,6 +325,14 @@ export function Workspace({ song, sourceBootstrap = null, onSongUpdate }: Worksp
             <p className="text-xs font-black uppercase tracking-[0.24em] text-fuchsia-200">{t("workspaceFirstRangeTitle")}</p>
             <p className="mt-2 text-sm leading-6 text-slate-100">{firstRangeCopy}</p>
           </section>
+          <section
+            className="rounded-2xl border border-amber-300/20 bg-amber-300/[0.07] p-4"
+            data-testid="first-leftover"
+            aria-label={t("workspaceFirstLeftoverTitle")}
+          >
+            <p className="text-xs font-black uppercase tracking-[0.24em] text-amber-200">{t("workspaceFirstLeftoverTitle")}</p>
+            <p className="mt-2 text-sm leading-6 text-slate-100">{firstLeftoverCopy}</p>
+          </section>
 
           <div className="grid gap-4 md:grid-cols-2 xl:grid-cols-4">
             <section className="rounded-2xl border border-cyan-300/20 bg-cyan-300/[0.06] p-4 md:col-span-2">

@@ -0,0 +1,204 @@
+import { createDemoRehearsalSong, type RehearsalSong } from "@bandscope/shared-types";
+import { describe, expect, it } from "vitest";
+import { fillRangeCopy } from "./firstRangeSqueeze";
+import { firstLeftover } from "./firstLeftover";
+
+function withChorus(song: RehearsalSong): RehearsalSong {
+  const verse = song.sections[0]!;
+  const chorus = {
+    ...verse,
+    id: "chorus-1",
+    label: "chorus" as RehearsalSong["sections"][number]["label"],
+    timeRange: {
+      start: verse.timeRange.end,
+      end: verse.timeRange.end + 20
+    }
+  };
+  return { ...song, sections: [verse, chorus] };
+}
+
+function withPartialReturn(
+  song: RehearsalSong,
+  returningRoleId: string,
+  leftoverRoleId: string,
+  leftoverActive: boolean | "omit" = false
+): RehearsalSong {
+  const twoSection = withChorus(song);
+  return {
+    ...twoSection,
+    sections: twoSection.sections.map((section, index) => ({
+      ...section,
+      partGraph: section.partGraph.map((node) => {
+        if (index === 0) {
+          if (node.role_id === returningRoleId || node.role_id === leftoverRoleId) {
+            return { ...node, is_active: false };
+          }
+          return node;
+        }
+        if (node.role_id === leftoverRoleId) {
+          if (leftoverActive === "omit") {
+            const rest: Record<string, unknown> = {
+              role_id: node.role_id,
+              handoff_to: node.handoff_to,
+              handoff_from: node.handoff_from
+            };
+            return rest as RehearsalSong["sections"][number]["partGraph"][number];
+          }
+          return { ...node, is_active: leftoverActive };
+        }
+        return node;
+      })
+    }))
+  };
+}
+
+describe("firstLeftover", () => {
+  it("returns null on the demo song where every graph node is active", () => {
+    expect(firstLeftover(createDemoRehearsalSong())).toBeNull();
+    expect(firstLeftover(withChorus(createDemoRehearsalSong()))).toBeNull();
+  });
+
+  it("names the leftover sit-out after a partial return", () => {
+    expect(
+      firstLeftover(withPartialReturn(createDemoRehearsalSong(), "bass-guitar", "keys-right"))
+    ).toEqual({
+      sectionLabel: "chorus",
+      fromSectionLabel: "verse",
+      leftoverRoleId: "keys-right",
+      leftoverRoleName: "Keyboard 1 Right Hand"
+    });
+  });
+
+  it("skips blank leftover labels until a named partial return exists", () => {
+    const song = withPartialReturn(createDemoRehearsalSong(), "bass-guitar", "keys-right");
+    song.sections[1] = {
+      ...song.sections[1]!,
+      label: "none" as RehearsalSong["sections"][number]["label"]
+    };
+    expect(firstLeftover(song)).toBeNull();
+  });
+
+  it("keeps the selected active part on tonight's first leftover", () => {
+    const song = withPartialReturn(createDemoRehearsalSong(), "bass-guitar", "keys-right");
+    expect(firstLeftover(song, "keys-right")).toEqual({
+      sectionLabel: "chorus",
+      fromSectionLabel: "verse",
+      leftoverRoleId: "keys-right",
+      leftoverRoleName: "Keyboard 1 Right Hand"
+    });
+    expect(firstLeftover(song, "bass-guitar")).toEqual({
+      sectionLabel: "chorus",
+      fromSectionLabel: "verse",
+      leftoverRoleId: "keys-right",
+      leftoverRoleName: "Keyboard 1 Right Hand"
+    });
+    expect(firstLeftover(song, "missing-role")).toBeNull();
+  });
+
+  it("ignores inherited is_active evidence", () => {
+    const song = withChorus(createDemoRehearsalSong());
+    const inherited = Object.create({
+      is_active: false,
+      role_id: "keys-right"
+    }) as RehearsalSong["sections"][number]["partGraph"][number];
+    song.sections[0] = {
+      ...song.sections[0]!,
+      partGraph: [inherited, ...song.sections[0]!.partGraph]
+    };
+    expect(firstLeftover(song)).toBeNull();
+  });
+
+  it("does not treat a missing is_active flag as a leftover", () => {
+    expect(
+      firstLeftover(withPartialReturn(createDemoRehearsalSong(), "bass-guitar", "keys-right", "omit"))
+    ).toBeNull();
+  });
+
+  it("does not treat a continued sit-out with nobody returning as a leftover", () => {
+    const song = withChorus(createDemoRehearsalSong());
+    song.sections = song.sections.map((section) => ({
+      ...section,
+      partGraph: section.partGraph.map((node) =>
+        node.role_id === "keys-right" ? { ...node, is_active: false } : node
+      )
+    }));
+    expect(firstLeftover(song)).toBeNull();
+  });
+
+  it("does not treat a full-band return as a leftover", () => {
+    const song = withPartialReturn(createDemoRehearsalSong(), "bass-guitar", "keys-right", true);
+    expect(firstLeftover(song)).toBeNull();
+  });
+
+  it("does not treat a new dropout after every original sit-out returns as a leftover", () => {
+    const song = withPartialReturn(createDemoRehearsalSong(), "bass-guitar", "keys-right", true);
+    song.sections[1] = {
+      ...song.sections[1]!,
+      partGraph: song.sections[1]!.partGraph.map((node) =>
+        node.role_id === "lead-vocal" ? { ...node, is_active: false } : node
+      )
+    };
+    expect(firstLeftover(song)).toBeNull();
+  });
+
+  it("fails closed when the later section has no named leftover role", () => {
+    const song = withPartialReturn(createDemoRehearsalSong(), "bass-guitar", "keys-right");
+    song.sections[1] = {
+      ...song.sections[1]!,
+      roles: song.sections[1]!.roles.map((role) => ({ ...role, name: "   " }))
+    };
+    expect(firstLeftover(song)).toBeNull();
+  });
+
+  it("fails closed when the later section has no named graph", () => {
+    const song = withPartialReturn(createDemoRehearsalSong(), "bass-guitar", "keys-right");
+    song.sections[1] = {
+      ...song.sections[1]!,
+      partGraph: []
+    };
+    expect(firstLeftover(song)).toBeNull();
+  });
+
+  it("fails closed on malformed runtime roots", () => {
+    for (const malformed of [null, {}, { sections: {} }, { sections: [null] }]) {
+      expect(firstLeftover(malformed as unknown as RehearsalSong)).toBeNull();
+    }
+  });
+
+  it("isolates blank role ids, non-boolean flags, and unnamed graph members", () => {
+    const song = withPartialReturn(createDemoRehearsalSong(), "bass-guitar", "keys-right");
+    song.sections[0] = {
+      ...song.sections[0]!,
+      partGraph: [
+        { role_id: "   ", is_active: false, handoff_to: [], handoff_from: [] },
+        { role_id: "ghost", is_active: false, handoff_to: [], handoff_from: [] },
+        { role_id: "keys-right", is_active: "no" as unknown as boolean, handoff_to: [], handoff_from: [] },
+        ...song.sections[0]!.partGraph
+      ]
+    };
+    const inheritedId = Object.create({ id: "keys-right", name: "Inherited Keys" });
+    song.sections[0] = {
+      ...song.sections[0]!,
+      roles: [inheritedId as RehearsalSong["sections"][number]["roles"][number], ...song.sections[0]!.roles]
+    };
+    expect(
+      firstLeftover({
+        ...song,
+        sections: [song.sections[0]!, { ...song.sections[1]!, roles: "broken" as unknown as RehearsalSong["sections"][number]["roles"] }]
+      })
+    ).toBeNull();
+    expect(firstLeftover({ ...song, sections: [song.sections[0]!, { ...song.sections[1]!, partGraph: null }] })).toBeNull();
+  });
+});
+
+describe("leftover copy filling", () => {
+  it("keeps rehearsal values literal", () => {
+    expect(
+      fillRangeCopy("{leftoverRoleName} stays tacet in {sectionLabel} after {fromSectionLabel}.", {
+        leftoverRoleName: "Keyboard 1 Right Hand {sectionLabel}",
+        sectionLabel: "chorus",
+        fromSectionLabel: "verse"
+      })
+    ).toBe("Keyboard 1 Right Hand {sectionLabel} stays tacet in chorus after verse.");
+  });
+});