diff --git a/AGENTS.md b/AGENTS.md
index b9a67ce17..ebfb9e04e 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -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 (including tonight's first section-length change and the next count-in), stems, playable ranges, 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.
diff --git a/ARCHITECTURE.md b/ARCHITECTURE.md
index ca0df5ac4..5645f7a88 100644
--- a/ARCHITECTURE.md
+++ b/ARCHITECTURE.md
@@ -81,7 +81,7 @@ Last updated: 2026-03-11
- Core rehearsal artifacts should include:
- 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
+ - groove and timing cues relevant to locking the band together, with the ready workspace naming tonight's first section-length change and the next count-in
- playable ranges and density or overlap warnings, with the ready workspace naming tonight's first span and the next instrument check
- simplification, transposition, capo, tuning, or setup cues where applicable
- role-specific rehearsal priorities and confidence flags
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0b6f7e784..9afb72fa9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
### Added
- 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.
+- Name tonight's first section-length change on the ready rehearsal map and tell the player to count the new length in before that 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.
diff --git a/CLAUDE.md b/CLAUDE.md
index b5a34c1fa..2a0b079d5 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -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 the next instrument check, plus tonight's first section-length change and the next count-in. `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.
diff --git a/apps/desktop/src/features/workspace/SectionRoadmap.test.tsx b/apps/desktop/src/features/workspace/SectionRoadmap.test.tsx
index 5b32019d2..c1e4adb0f 100644
--- a/apps/desktop/src/features/workspace/SectionRoadmap.test.tsx
+++ b/apps/desktop/src/features/workspace/SectionRoadmap.test.tsx
@@ -34,6 +34,47 @@ describe("SectionRoadmap", () => {
expect(screen.getAllByText("음역").length).toBeGreaterThan(0);
expect(screen.getByText("C#2 — E3")).toBeTruthy();
expect(screen.getAllByText("verse 들어가기 전에 이 음역을 악기로 확인해 보세요.").length).toBeGreaterThan(0);
+ expect(screen.getByText("verse 들어가기 전에 이 길이를 세어 보세요.")).toBeTruthy();
+ });
+
+ it("names the next count-in on the section where the length changes", () => {
+ setNavigatorLanguage("en-US");
+ const song = createDemoRehearsalSong();
+ const verse = song.sections[0]!;
+ song.sections = [
+ verse,
+ {
+ ...verse,
+ id: "chorus-1",
+ label: "chorus",
+ timeRange: { start: 30, end: 62 },
+ roles: verse.roles.map((role) => ({ ...role, id: `${role.id}-chorus` }))
+ }
+ ];
+
+ render();
+
+ expect(screen.queryByTestId("duration-next-action-verse-1")).toBeNull();
+ expect(screen.getByTestId("duration-next-action-chorus-1")).toHaveTextContent(
+ "Count this new length in before chorus."
+ );
+ });
+
+ it("marks only the destination card when consecutive sections share a label", () => {
+ setNavigatorLanguage("en-US");
+ const song = createDemoRehearsalSong();
+ const verse = song.sections[0]!;
+ song.sections = [
+ { ...verse, id: "verse-a", label: "verse", timeRange: { start: 0, end: 16 } },
+ { ...verse, id: "verse-b", label: "verse", timeRange: { start: 16, end: 48 } }
+ ];
+
+ render();
+
+ expect(screen.queryByTestId("duration-next-action-verse-a")).toBeNull();
+ expect(screen.getByTestId("duration-next-action-verse-b")).toHaveTextContent(
+ "Count this new length in before verse."
+ );
});
it("omits the range row when both notes are unnamed", () => {
diff --git a/apps/desktop/src/features/workspace/SectionRoadmap.tsx b/apps/desktop/src/features/workspace/SectionRoadmap.tsx
index 834d1e8f0..99a2750dc 100644
--- a/apps/desktop/src/features/workspace/SectionRoadmap.tsx
+++ b/apps/desktop/src/features/workspace/SectionRoadmap.tsx
@@ -3,6 +3,7 @@ import { useId, useMemo } from "react";
import { createTranslator, detectPreferredLocale } from "../../i18n";
import { ConfidenceBadge } from "./ConfidenceBadge";
import { fillRangeCopy, playableRange } from "./firstRangeSqueeze";
+import { fillDurationCopy, firstDurationChange, isDurationChangeTarget } from "./firstDurationChange";
import { Card, CardContent, CardHeader } from "@/components/ui/card";
import { Badge } from "@/components/ui/badge";
import { Separator } from "@/components/ui/separator";
@@ -19,6 +20,7 @@ export function SectionRoadmap({ song, activeRole, onSongUpdate }: SectionRoadma
const sectionRoadmapTitleId = useId();
const locale = useMemo(() => detectPreferredLocale(), []);
const t = useMemo(() => createTranslator(locale), [locale]);
+ const durationChange = useMemo(() => firstDurationChange(song), [song]);
/** Documented. */
const editChordLabel = (role: RehearsalRole, sectionLabel: string): string => {
@@ -120,6 +122,14 @@ export function SectionRoadmap({ song, activeRole, onSongUpdate }: SectionRoadma
{t("sectionGrooveLabel")}
{section.groove}
+ {durationChange && isDurationChangeTarget(durationChange, section.id) ? (
+
+ {fillDurationCopy(
+ t(durationChange.kind === "change" ? "sectionDurationNextActionChange" : "sectionDurationNextActionHold"),
+ { sectionLabel: section.label }
+ )}
+
+ ) : null}
diff --git a/apps/desktop/src/features/workspace/Workspace.test.tsx b/apps/desktop/src/features/workspace/Workspace.test.tsx
index 7837bf80e..c0f850643 100644
--- a/apps/desktop/src/features/workspace/Workspace.test.tsx
+++ b/apps/desktop/src/features/workspace/Workspace.test.tsx
@@ -153,6 +153,41 @@ describe("Workspace", () => {
);
});
+ it("names tonight's held length and the next count-in when the form does not change duration", () => {
+ setNavigatorLanguage("en-US");
+ const song = createDemoRehearsalSong();
+
+ render();
+
+ const callout = screen.getByTestId("first-duration-change");
+ expect(callout).toHaveTextContent("Tonight's first length change");
+ expect(callout).toHaveTextContent(
+ "Tonight's section length stays 20 seconds through the form. Count that length in before the verse."
+ );
+ });
+
+ it("names tonight's first length change and the next count-in", () => {
+ setNavigatorLanguage("en-US");
+ const song = createDemoRehearsalSong();
+ const verse = song.sections[0]!;
+ song.sections = [
+ verse,
+ {
+ ...verse,
+ id: "chorus-1",
+ label: "chorus",
+ timeRange: { start: 30, end: 62 },
+ roles: verse.roles.map((role) => ({ ...role, id: `${role.id}-chorus` }))
+ }
+ ];
+
+ render();
+
+ expect(screen.getByTestId("first-duration-change")).toHaveTextContent(
+ "The section length changes at chorus: 32 seconds, after verse's 20 seconds. Count the new length in before the chorus."
+ );
+ });
+
it("asks for an ear check when the selected part has no named span", () => {
setNavigatorLanguage("en-US");
const song = createDemoRehearsalSong();
@@ -325,5 +360,18 @@ describe("Workspace", () => {
expect(screen.getByText("스템")).toBeTruthy();
expect(screen.getByText("합주 우선순위")).toBeTruthy();
expect(screen.getByText("역할과 화성")).toBeTruthy();
+ expect(screen.getByText("오늘 먼저 바뀌는 구간 길이")).toBeTruthy();
+ });
+
+ it("asks for an ear check when no named section length exists", () => {
+ setNavigatorLanguage("en-US");
+ const song = createDemoRehearsalSong();
+ song.sections[0] = { ...song.sections[0]!, label: " ", timeRange: { start: 10, end: 10 } };
+
+ render();
+
+ expect(screen.getByTestId("first-duration-change")).toHaveTextContent(
+ "Tonight's first length change still needs an ear check. Confirm how long the first two sections last before you count in."
+ );
});
});
diff --git a/apps/desktop/src/features/workspace/Workspace.tsx b/apps/desktop/src/features/workspace/Workspace.tsx
index d44e20777..9bcba9140 100644
--- a/apps/desktop/src/features/workspace/Workspace.tsx
+++ b/apps/desktop/src/features/workspace/Workspace.tsx
@@ -5,6 +5,7 @@ import { SectionRoadmap } from "./SectionRoadmap";
import { GrooveMap } from "./GrooveMap";
import { PracticeProgress } from "./PracticeProgress";
import { fillRangeCopy, firstRangeSqueeze } from "./firstRangeSqueeze";
+import { fillDurationCopy, firstDurationChange } from "./firstDurationChange";
import { createTranslator, detectPreferredLocale } from "../../i18n";
import { generateCueSheetCsv, generateChartSummaryJson, generateMetadataHandoffJson, sanitizeFilename } from "../../lib/export";
import { Button } from "@/components/ui/button";
@@ -163,6 +164,20 @@ export function Workspace({ song, sourceBootstrap = null, onSongUpdate }: Worksp
}
)
: t("workspaceFirstRangeMissing");
+ const firstDuration = useMemo(() => firstDurationChange(song), [song]);
+ const firstDurationCopy = firstDuration
+ ? firstDuration.kind === "change"
+ ? fillDurationCopy(t("workspaceFirstDurationChange"), {
+ fromSection: firstDuration.fromSectionLabel,
+ fromDuration: firstDuration.fromDuration,
+ toSection: firstDuration.toSectionLabel,
+ toDuration: firstDuration.toDuration
+ })
+ : fillDurationCopy(t("workspaceFirstDurationHold"), {
+ sectionLabel: firstDuration.toSectionLabel,
+ duration: firstDuration.toDuration
+ })
+ : t("workspaceFirstDurationMissing");
/** Handle the practice progress change internally by immutably updating the song state. */
const handlePracticeProgressChange = (newProgress: number) => {
@@ -310,6 +325,15 @@ export function Workspace({ song, sourceBootstrap = null, onSongUpdate }: Worksp
{firstRangeCopy}
+
+ {t("workspaceFirstDurationTitle")}
+ {firstDurationCopy}
+
+
{t("workspaceSongTimelineLabel")}
diff --git a/apps/desktop/src/features/workspace/firstDurationChange.test.ts b/apps/desktop/src/features/workspace/firstDurationChange.test.ts
new file mode 100644
index 000000000..35bd89a8f
--- /dev/null
+++ b/apps/desktop/src/features/workspace/firstDurationChange.test.ts
@@ -0,0 +1,240 @@
+import { createDemoRehearsalSong, type RehearsalSong } from "@bandscope/shared-types";
+import { describe, expect, it } from "vitest";
+import { parseRehearsalSongWithTimingEvidence } from "../../lib/rehearsalTimingEvidence";
+import {
+ fillDurationCopy,
+ firstDurationChange,
+ isDurationChangeTarget,
+ sectionDurationSeconds
+} from "./firstDurationChange";
+
+function cloneSong(song: RehearsalSong): RehearsalSong {
+ return {
+ ...song,
+ sections: song.sections.map((section) => ({
+ ...section,
+ roles: section.roles.map((role) => ({ ...role }))
+ }))
+ };
+}
+
+function appendSection(
+ song: RehearsalSong,
+ label: string,
+ timeRange: { start: number; end: number }
+): RehearsalSong {
+ const first = song.sections[0];
+ return {
+ ...song,
+ sections: [
+ ...song.sections,
+ {
+ ...first,
+ id: `${label}-section`,
+ label,
+ timeRange,
+ roles: first.roles.map((role) => ({ ...role, id: `${role.id}-${label}` }))
+ }
+ ]
+ };
+}
+
+describe("sectionDurationSeconds", () => {
+ it("returns the positive integer span for a valid time range", () => {
+ expect(sectionDurationSeconds({ start: 10, end: 30 })).toBe(20);
+ expect(sectionDurationSeconds({ start: 0, end: 1 })).toBe(1);
+ });
+
+ it("fails closed on missing, inverted, fractional, or unbounded ranges", () => {
+ expect(sectionDurationSeconds(null)).toBeNull();
+ expect(sectionDurationSeconds({ start: 30, end: 10 })).toBeNull();
+ expect(sectionDurationSeconds({ start: 10, end: 10 })).toBeNull();
+ expect(sectionDurationSeconds({ start: 10.5, end: 20 })).toBeNull();
+ expect(sectionDurationSeconds({ start: -1, end: 10 })).toBeNull();
+ expect(sectionDurationSeconds({ start: Number.NaN, end: 10 })).toBeNull();
+ });
+});
+
+describe("firstDurationChange", () => {
+ it("holds the demo song's one named length so the room does not reset the count", () => {
+ expect(firstDurationChange(createDemoRehearsalSong())).toEqual({
+ kind: "same",
+ fromSectionId: "verse-1",
+ fromSectionLabel: "verse",
+ fromDuration: "20",
+ toSectionId: "verse-1",
+ toSectionLabel: "verse",
+ toDuration: "20"
+ });
+ });
+
+ it("names the first consecutive length change in form order", () => {
+ const song = appendSection(
+ appendSection(createDemoRehearsalSong(), "pre-chorus", { start: 30, end: 50 }),
+ "chorus",
+ { start: 50, end: 82 }
+ );
+
+ expect(firstDurationChange(song)).toEqual({
+ kind: "change",
+ fromSectionId: "pre-chorus-section",
+ fromSectionLabel: "pre-chorus",
+ fromDuration: "20",
+ toSectionId: "chorus-section",
+ toSectionLabel: "chorus",
+ toDuration: "32"
+ });
+ });
+
+ it("skips unlabeled or invalid-duration sections until a named pair exists", () => {
+ const song = cloneSong(createDemoRehearsalSong());
+ song.sections[0] = {
+ ...song.sections[0]!,
+ label: " ",
+ timeRange: { start: 10, end: 10 }
+ };
+ const withChorus = appendSection(song, "chorus", { start: 30, end: 46 });
+ const withBridge = appendSection(withChorus, "bridge", { start: 46, end: 78 });
+
+ expect(firstDurationChange(withBridge)).toEqual({
+ kind: "change",
+ fromSectionId: "chorus-section",
+ fromSectionLabel: "chorus",
+ fromDuration: "16",
+ toSectionId: "bridge-section",
+ toSectionLabel: "bridge",
+ toDuration: "32"
+ });
+ });
+
+ it("fails closed instead of bridging across a named section with missing timing evidence", () => {
+ const song = createDemoRehearsalSong();
+ const verse = song.sections[0]!;
+ song.sections = [
+ { ...verse, id: "verse-a", label: "verse", timeRange: { start: 0, end: 16 } },
+ {
+ ...verse,
+ id: "chorus-gap",
+ label: "chorus",
+ timeRange: null
+ } as unknown as typeof verse,
+ { ...verse, id: "bridge-a", label: "bridge", timeRange: { start: 16, end: 48 } }
+ ];
+
+ expect(firstDurationChange(song)).toBeNull();
+ });
+
+ it("does not present legacy migration placeholders as measured section lengths", () => {
+ const legacySong = structuredClone(createDemoRehearsalSong()) as unknown as {
+ sections: Array>;
+ };
+ delete legacySong.sections[0]!.timeRange;
+
+ const parsedLegacySong = parseRehearsalSongWithTimingEvidence(legacySong);
+ expect(parsedLegacySong.sections[0]?.timeRange).toEqual({ start: 0, end: 1 });
+ expect(firstDurationChange(parsedLegacySong)).toBeNull();
+ });
+
+ it("keeps an explicit measured one-second section eligible for count-in guidance", () => {
+ const measuredSong = structuredClone(createDemoRehearsalSong());
+ measuredSong.sections[0]!.timeRange = { start: 0, end: 1 };
+
+ expect(firstDurationChange(parseRehearsalSongWithTimingEvidence(measuredSong))).toEqual({
+ kind: "same",
+ fromSectionId: "verse-1",
+ fromSectionLabel: "verse",
+ fromDuration: "1",
+ toSectionId: "verse-1",
+ toSectionLabel: "verse",
+ toDuration: "1"
+ });
+ });
+
+ it("fails closed on malformed runtime roots and members", () => {
+ expect(firstDurationChange(null as unknown as RehearsalSong)).toBeNull();
+ expect(firstDurationChange({ sections: "nope" } as unknown as RehearsalSong)).toBeNull();
+ expect(
+ firstDurationChange({
+ ...createDemoRehearsalSong(),
+ sections: [null, "skip", { label: "verse" }]
+ } as unknown as RehearsalSong)
+ ).toBeNull();
+ });
+
+ it("fails closed when repeated section ids cannot identify one destination card", () => {
+ const song = createDemoRehearsalSong();
+ const verse = song.sections[0]!;
+ song.sections = [
+ { ...verse, id: "duplicate", timeRange: { start: 0, end: 16 } },
+ { ...verse, id: "duplicate", timeRange: { start: 16, end: 48 } }
+ ];
+
+ expect(firstDurationChange(song)).toBeNull();
+ });
+
+ it("rejects a repeated section id even when one occurrence has no eligible duration evidence", () => {
+ const song = createDemoRehearsalSong();
+ const verse = song.sections[0]!;
+ song.sections = [
+ { ...verse, id: "duplicate", label: " ", timeRange: { start: 10, end: 10 } },
+ { ...verse, id: "duplicate", label: "chorus", timeRange: { start: 30, end: 46 } }
+ ];
+
+ expect(firstDurationChange(song)).toBeNull();
+ });
+
+ it("validates later section ids before returning an earlier duration transition", () => {
+ const song = createDemoRehearsalSong();
+ const verse = song.sections[0]!;
+ song.sections = [
+ { ...verse, id: "verse-a", label: "verse", timeRange: { start: 0, end: 16 } },
+ { ...verse, id: "chorus-a", label: "chorus", timeRange: { start: 16, end: 48 } },
+ { ...verse, id: "verse-a", label: "outro", timeRange: { start: 48, end: 64 } }
+ ];
+
+ expect(firstDurationChange(song)).toBeNull();
+ });
+});
+
+describe("isDurationChangeTarget", () => {
+ it("marks only the arrival section identity as the next-action card", () => {
+ const change: ReturnType = {
+ kind: "change",
+ fromSectionId: "verse-1",
+ fromSectionLabel: "verse",
+ fromDuration: "20",
+ toSectionId: "chorus-1",
+ toSectionLabel: "chorus",
+ toDuration: "32"
+ };
+
+ expect(isDurationChangeTarget(change, "chorus-1")).toBe(true);
+ expect(isDurationChangeTarget(change, " verse-1 ")).toBe(false);
+ expect(isDurationChangeTarget(change, " ")).toBe(false);
+ });
+
+ it("uses stable section identity when repeated labels would otherwise mark multiple cards", () => {
+ const song = createDemoRehearsalSong();
+ const verse = song.sections[0]!;
+ song.sections = [
+ { ...verse, id: "verse-a", label: "verse", timeRange: { start: 0, end: 16 } },
+ { ...verse, id: "verse-b", label: "verse", timeRange: { start: 16, end: 48 } }
+ ];
+
+ const change = firstDurationChange(song);
+ expect(change?.kind).toBe("change");
+ expect(isDurationChangeTarget(change!, "verse-a")).toBe(false);
+ expect(isDurationChangeTarget(change!, "verse-b")).toBe(true);
+ });
+});
+
+describe("fillDurationCopy", () => {
+ it("keeps rehearsal duration values literal while filling trusted tokens", () => {
+ expect(
+ fillDurationCopy("Count {toDuration} before the {toSection}.", {
+ toDuration: "32 {toSection}",
+ toSection: "chorus"
+ })
+ ).toBe("Count 32 {toSection} before the chorus.");
+ });
+});
diff --git a/apps/desktop/src/features/workspace/firstDurationChange.ts b/apps/desktop/src/features/workspace/firstDurationChange.ts
new file mode 100644
index 000000000..f38edb5b1
--- /dev/null
+++ b/apps/desktop/src/features/workspace/firstDurationChange.ts
@@ -0,0 +1,159 @@
+import { MAX_SECTION_TIME_SECONDS, type RehearsalSong } from "@bandscope/shared-types";
+import { hasSyntheticSectionTimeRange } from "../../lib/rehearsalTimingEvidence";
+import { fillRangeCopy, meaningfulRangeText } from "./firstRangeSqueeze";
+
+/** Tonight's first named section-length change, or a same-length hold through the form. */
+export type FirstDurationChange = {
+ kind: "change" | "same";
+ fromSectionId: string;
+ fromSectionLabel: string;
+ fromDuration: string;
+ toSectionId: string;
+ toSectionLabel: string;
+ toDuration: string;
+};
+
+type NamedDuration = {
+ sectionId: string;
+ sectionLabel: string;
+ duration: string;
+};
+
+/** Return whether an untrusted runtime value is a plain object record. */
+function isRuntimeObject(value: unknown): value is Record {
+ return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+/**
+ * Return a positive integer duration in seconds from untrusted time-range evidence.
+ *
+ * Mirrors the shared rehearsal-song contract: start and end must be finite
+ * integers, start must be in range, and end must be strictly after start.
+ */
+export function sectionDurationSeconds(timeRangeValue: unknown): number | null {
+ if (!isRuntimeObject(timeRangeValue)) {
+ return null;
+ }
+ const start = timeRangeValue.start;
+ const end = timeRangeValue.end;
+ if (
+ typeof start !== "number" ||
+ typeof end !== "number" ||
+ !Number.isFinite(start) ||
+ !Number.isFinite(end) ||
+ !Number.isInteger(start) ||
+ !Number.isInteger(end) ||
+ start < 0 ||
+ start > MAX_SECTION_TIME_SECONDS ||
+ end <= start ||
+ end > MAX_SECTION_TIME_SECONDS
+ ) {
+ return null;
+ }
+ return end - start;
+}
+
+/**
+ * Pick the first named section-length change a player should count in before the next section.
+ *
+ * Walks labeled sections in form order and returns the first consecutive pair
+ * whose integer duration differs. Unlabeled compatibility noise is ignored,
+ * while a named section without valid timing fails closed so unknown timing can
+ * never bridge two measured sections. Legacy compatibility placeholders are
+ * also rejected so migration data cannot become measured rehearsal guidance.
+ * When every named section holds the same length, the result is a same-length
+ * hold so the room does not reset the count. Stable section ids, rather than
+ * display labels, own roadmap targeting. All meaningful section ids are
+ * validated for uniqueness before duration evidence is derived so an
+ * ineligible or later duplicate cannot create ambiguous cards.
+ */
+export function firstDurationChange(song: RehearsalSong): FirstDurationChange | null {
+ const runtimeSong: unknown = song;
+ if (!isRuntimeObject(runtimeSong) || !Array.isArray(runtimeSong.sections)) {
+ return null;
+ }
+
+ const seenSectionIds = new Set();
+ for (const sectionValue of runtimeSong.sections) {
+ if (!isRuntimeObject(sectionValue)) {
+ continue;
+ }
+ const sectionId = meaningfulRangeText(sectionValue.id);
+ if (!sectionId) {
+ continue;
+ }
+ if (seenSectionIds.has(sectionId)) {
+ return null;
+ }
+ seenSectionIds.add(sectionId);
+ }
+
+ const namedDurations: NamedDuration[] = [];
+ for (const sectionValue of runtimeSong.sections) {
+ if (!isRuntimeObject(sectionValue)) {
+ continue;
+ }
+ const sectionId = meaningfulRangeText(sectionValue.id);
+ const sectionLabel = meaningfulRangeText(sectionValue.label);
+ if (!sectionId || !sectionLabel) {
+ continue;
+ }
+ if (hasSyntheticSectionTimeRange(sectionValue)) {
+ return null;
+ }
+ const durationSeconds = sectionDurationSeconds(sectionValue.timeRange);
+ if (durationSeconds === null) {
+ return null;
+ }
+ namedDurations.push({
+ sectionId,
+ sectionLabel,
+ duration: String(durationSeconds)
+ });
+ }
+
+ if (namedDurations.length === 0) {
+ return null;
+ }
+
+ const first = namedDurations[0];
+ if (!first) {
+ return null;
+ }
+ for (let index = 1; index < namedDurations.length; index += 1) {
+ const previous = namedDurations[index - 1];
+ const current = namedDurations[index];
+ if (previous.duration !== current.duration) {
+ return {
+ kind: "change",
+ fromSectionId: previous.sectionId,
+ fromSectionLabel: previous.sectionLabel,
+ fromDuration: previous.duration,
+ toSectionId: current.sectionId,
+ toSectionLabel: current.sectionLabel,
+ toDuration: current.duration
+ };
+ }
+ }
+
+ return {
+ kind: "same",
+ fromSectionId: first.sectionId,
+ fromSectionLabel: first.sectionLabel,
+ fromDuration: first.duration,
+ toSectionId: first.sectionId,
+ toSectionLabel: first.sectionLabel,
+ toDuration: first.duration
+ };
+}
+
+/** Fill trusted `{token}` placeholders for duration-change rehearsal copy. */
+export function fillDurationCopy(template: string, values: Record): string {
+ return fillRangeCopy(template, values);
+}
+
+/** True when this stable section identity is the map card owning the next duration action. */
+export function isDurationChangeTarget(change: FirstDurationChange, sectionId: string): boolean {
+ const identity = meaningfulRangeText(sectionId);
+ return Boolean(identity) && identity === change.toSectionId;
+}
diff --git a/apps/desktop/src/lib/analysis.test.ts b/apps/desktop/src/lib/analysis.test.ts
index e3347d1f5..7ff9b56f9 100644
--- a/apps/desktop/src/lib/analysis.test.ts
+++ b/apps/desktop/src/lib/analysis.test.ts
@@ -4,8 +4,10 @@ import {
MAX_YOUTUBE_URL_LENGTH,
getAnalysisJobStatus,
importYoutubeUrl,
+ loadProject,
startAnalysisJob
} from "./analysis";
+import { hasSyntheticSectionTimeRange } from "./rehearsalTimingEvidence";
type TauriWindow = Window & {
__TAURI_INTERNALS__?: unknown;
@@ -117,6 +119,20 @@ describe("analysis bridge", () => {
expect(status.result?.sections[0]?.timeRange).toEqual({ start: 0, end: 1 });
});
+ it("preserves synthetic timing provenance when a legacy project crosses the native load boundary", async () => {
+ const legacyProject = createDemoRehearsalSong() as unknown as {
+ sections: Array>;
+ };
+ delete legacyProject.sections[0]!.timeRange;
+ tauriWindow.__TAURI_INVOKE__ = vi.fn().mockResolvedValue(legacyProject);
+
+ const loaded = await loadProject();
+
+ expect(tauriWindow.__TAURI_INVOKE__).toHaveBeenCalledWith("load_project", undefined);
+ expect(loaded.sections[0]?.timeRange).toEqual({ start: 0, end: 1 });
+ expect(hasSyntheticSectionTimeRange(loaded.sections[0])).toBe(true);
+ });
+
it("reports staged browser fallback progress before returning the demo result", async () => {
const queued = await startAnalysisJob(createDemoAnalysisJobRequest());
diff --git a/apps/desktop/src/lib/analysis.ts b/apps/desktop/src/lib/analysis.ts
index bb750b34b..3b977d570 100644
--- a/apps/desktop/src/lib/analysis.ts
+++ b/apps/desktop/src/lib/analysis.ts
@@ -15,6 +15,7 @@ import {
type RehearsalSong
} from "@bandscope/shared-types";
import { listen } from "@tauri-apps/api/event";
+import { parseRehearsalSongWithTimingEvidence } from "./rehearsalTimingEvidence";
type TauriInvoke = (command: string, args?: Record) => Promise;
@@ -351,5 +352,5 @@ export async function saveProject(song: RehearsalSong): Promise {
/** Documented. */
export async function loadProject(): Promise {
const response = await invokeAnalysis("load_project");
- return parseRehearsalSong(response);
+ return parseRehearsalSongWithTimingEvidence(response);
}
diff --git a/apps/desktop/src/lib/rehearsalTimingEvidence.ts b/apps/desktop/src/lib/rehearsalTimingEvidence.ts
new file mode 100644
index 000000000..29648726c
--- /dev/null
+++ b/apps/desktop/src/lib/rehearsalTimingEvidence.ts
@@ -0,0 +1,53 @@
+import { parseRehearsalSong, type RehearsalSong } from "@bandscope/shared-types";
+
+const SYNTHETIC_SECTION_TIME_RANGE = Symbol("bandscope.syntheticSectionTimeRange");
+
+type RuntimeSectionRecord = Record & {
+ [SYNTHETIC_SECTION_TIME_RANGE]?: true;
+};
+
+/** Return whether an untrusted value can carry section timing evidence. */
+function isRuntimeSectionRecord(sectionValue: unknown): sectionValue is RuntimeSectionRecord {
+ return typeof sectionValue === "object" && sectionValue !== null && !Array.isArray(sectionValue);
+}
+
+/** Return whether a parsed section carries a compatibility-only synthetic time range. */
+export function hasSyntheticSectionTimeRange(sectionValue: unknown): boolean {
+ return isRuntimeSectionRecord(sectionValue) && sectionValue[SYNTHETIC_SECTION_TIME_RANGE] === true;
+}
+
+/**
+ * Parse a rehearsal song while retaining whether legacy migration synthesized a section time range.
+ *
+ * The marker is symbol-keyed, so it remains an application-internal adapter concern and is omitted
+ * from JSON/vendor contracts. It is enumerable so ordinary object-spread copies preserve the
+ * evidence while the song remains in memory.
+ */
+export function parseRehearsalSongWithTimingEvidence(songValue: unknown): RehearsalSong {
+ const sourceSections =
+ isRuntimeSectionRecord(songValue) && Array.isArray(songValue.sections) ? songValue.sections : null;
+ const parsedSong = parseRehearsalSong(songValue);
+
+ if (!sourceSections) {
+ return parsedSong;
+ }
+
+ parsedSong.sections.forEach((parsedSection, sectionIndex) => {
+ const sourceSection = sourceSections[sectionIndex];
+ if (!isRuntimeSectionRecord(sourceSection)) {
+ return;
+ }
+ const missingSourceTimeRange = !Object.prototype.hasOwnProperty.call(sourceSection, "timeRange");
+ if (!missingSourceTimeRange && !hasSyntheticSectionTimeRange(sourceSection)) {
+ return;
+ }
+ Object.defineProperty(parsedSection, SYNTHETIC_SECTION_TIME_RANGE, {
+ value: true,
+ enumerable: true,
+ configurable: false,
+ writable: false
+ });
+ });
+
+ return parsedSong;
+}
diff --git a/apps/desktop/src/locales/en/common.json b/apps/desktop/src/locales/en/common.json
index d803a765e..65029d056 100644
--- a/apps/desktop/src/locales/en/common.json
+++ b/apps/desktop/src/locales/en/common.json
@@ -153,6 +153,12 @@
"workspaceFirstRangeCheck": "{roleName} sits {lowestNote}–{highestNote} in {sectionLabel}. Check that span on your instrument before the {sectionLabel}.",
"workspaceFirstRangeClash": "{roleName} sits {lowestNote}–{highestNote} in {sectionLabel}. Hear that clash on your instrument before the {sectionLabel}.",
"workspaceFirstRangeMissing": "Tonight's first range still needs an ear check. Confirm the high and low notes on the selected part before the first section.",
+ "workspaceFirstDurationTitle": "Tonight's first length change",
+ "workspaceFirstDurationChange": "The section length changes at {toSection}: {toDuration} seconds, after {fromSection}'s {fromDuration} seconds. Count the new length in before the {toSection}.",
+ "workspaceFirstDurationHold": "Tonight's section length stays {duration} seconds through the form. Count that length in before the {sectionLabel}.",
+ "workspaceFirstDurationMissing": "Tonight's first length change still needs an ear check. Confirm how long the first two sections last before you count in.",
+ "sectionDurationNextActionChange": "Count this new length in before {sectionLabel}.",
+ "sectionDurationNextActionHold": "Count this length in before {sectionLabel}.",
"sectionRangeLabel": "Range",
"sectionRangeNextAction": "Check this span on your instrument before {sectionLabel}."
}
diff --git a/apps/desktop/src/locales/ko/common.json b/apps/desktop/src/locales/ko/common.json
index 0f6c6c66d..ee573a81c 100644
--- a/apps/desktop/src/locales/ko/common.json
+++ b/apps/desktop/src/locales/ko/common.json
@@ -153,6 +153,12 @@
"workspaceFirstRangeCheck": "{sectionLabel}의 {roleName}은 {lowestNote}–{highestNote}입니다. {sectionLabel} 들어가기 전에 그 음역을 악기로 확인해 보세요.",
"workspaceFirstRangeClash": "{sectionLabel}의 {roleName}은 {lowestNote}–{highestNote}이고 다른 파트와 겹칩니다. {sectionLabel} 들어가기 전에 그 충돌을 악기로 들어 보세요.",
"workspaceFirstRangeMissing": "오늘 먼저 볼 음역은 아직 귀로 확인이 필요합니다. 선택한 파트의 최저·최고음을 첫 구간 전에 확인해 보세요.",
+ "workspaceFirstDurationTitle": "오늘 먼저 바뀌는 구간 길이",
+ "workspaceFirstDurationChange": "{fromSection}의 {fromDuration}초 다음, {toSection}에서 {toDuration}초로 바뀝니다. {toSection} 들어가기 전에 새 길이를 세어 보세요.",
+ "workspaceFirstDurationHold": "오늘 구간 길이는 {duration}초로 끝까지 갑니다. {sectionLabel} 들어가기 전에 그 길이를 세어 보세요.",
+ "workspaceFirstDurationMissing": "오늘 먼저 바뀌는 구간 길이는 아직 귀로 확인이 필요합니다. 처음 두 구간의 길이를 확인한 뒤 카운트하세요.",
+ "sectionDurationNextActionChange": "{sectionLabel} 들어가기 전에 이 새 길이를 세어 보세요.",
+ "sectionDurationNextActionHold": "{sectionLabel} 들어가기 전에 이 길이를 세어 보세요.",
"sectionRangeLabel": "음역",
"sectionRangeNextAction": "{sectionLabel} 들어가기 전에 이 음역을 악기로 확인해 보세요."
}