Closes #170

packages/archive/src/dashboard.ts

@@ -74,6 +74,28 @@ function mean(values: number[]): number | null {
   return sum / values.length;
 }
 
+/**
+ * Build one per-session index row from a parsed session. Pure and derived solely
+ * from `session`, so a row always carries ITS OWN session's numbers — callers can
+ * pair an entry with a session by identity (e.g. keyed by file name) rather than
+ * by array position (#170). NaN-guarded like the aggregate.
+ */
+export function toSessionIndexEntry(session: ParsedSession): SessionIndexEntry {
+  const { meta, metrics, isRecording } = session;
+  return {
+    title: meta.title,
+    date: meta.headerDate,
+    startClock: meta.startClock,
+    durationMin: finite(meta.durationMin),
+    sourceLang: meta.sourceLang,
+    targetLang: meta.targetLang,
+    costUsd: roundCents(finite(meta.costUsd)),
+    talkRatioMic: metrics ? finite(metrics.talkRatioMic) : null,
+    smoothScore: metrics ? finite(metrics.smoothScore) : null,
+    isRecording,
+  };
+}
+
 /** Chronological order: by header date, then start clock, stable for ties. */
 function chronological(a: ParsedSession, b: ParsedSession): number {
   if (a.meta.headerDate !== b.meta.headerDate) {
@@ -120,18 +142,7 @@ export function aggregateSessions(sessions: readonly ParsedSession[]): Dashboard
       smoothScoreTrend.push({ date: meta.headerDate, startClock: meta.startClock, value: smoothScore });
     }
 
-    index.push({
-      title: meta.title,
-      date: meta.headerDate,
-      startClock: meta.startClock,
-      durationMin: finite(meta.durationMin),
-      sourceLang: meta.sourceLang,
-      targetLang: meta.targetLang,
-      costUsd: roundCents(finite(meta.costUsd)),
-      talkRatioMic,
-      smoothScore,
-      isRecording,
-    });
+    index.push(toSessionIndexEntry(session));
   }
 
   return {

packages/archive/src/index.ts

@@ -33,5 +33,5 @@ export type {
 // Issue #98 — Dashboard data layer: parse saved sessions + aggregate stats (headless).
 export { parseSession } from "./parse";
 export type { ParsedSession, ParsedSessionMeta } from "./parse";
-export { aggregateSessions } from "./dashboard";
+export { aggregateSessions, toSessionIndexEntry } from "./dashboard";
 export type { DashboardStats, SessionIndexEntry, TrendPoint } from "./dashboard";

src/dashboard.ts

@@ -21,7 +21,7 @@ import { invoke } from "@tauri-apps/api/core";
 // Import the #98 data layer DIRECTLY from its source modules rather than the
 // package barrel: `parse`/`dashboard` are pure (they only touch `./types`), so
 // the webview never pulls the package's Node-only `fs` writer into the bundle.
-import { aggregateSessions, type DashboardStats } from "@livecap/archive/src/dashboard.ts";
+import { aggregateSessions, toSessionIndexEntry, type DashboardStats } from "@livecap/archive/src/dashboard.ts";
 import { parseSession, type ParsedSession } from "@livecap/archive/src/parse.ts";
 import type { SessionIndexEntry } from "@livecap/archive/src/dashboard.ts";
 import type { CaptionEntry } from "@livecap/archive/src/types.ts";
@@ -57,6 +57,10 @@ export interface IndexedSession {
   name: string;
   /** Front-matter parse: meta/summary/board/metrics populated, entries empty. */
   session: ParsedSession;
+  /** The history-row index entry derived from THIS session (#170) — carried with
+   *  the session so a row shows its own duration/langs/cost, never a tied
+   *  session's (no positional pairing). */
+  entry: SessionIndexEntry;
 }
 
 /** A parsed session paired with the dashboard index entry derived from it, so a
@@ -87,12 +91,16 @@ const BACK_ICON =
  */
 export function buildDashboardModel(index: readonly SessionHeader[]): DashboardModel {
   const parsed = index
-    .map((h) => ({ name: h.name, session: parseSession(h.markdown) }))
+    .map((h) => {
+      const session = parseSession(h.markdown);
+      // Derive each session's index entry HERE, alongside its file name (#170),
+      // so a history row pairs with its OWN entry by identity — not by a fragile
+      // positional reversal that swaps sessions tied on (date, startClock).
+      return { name: h.name, session, entry: toSessionIndexEntry(session) };
+    })
     .filter((p) => !p.session.isRecording);
   const stats = aggregateSessions(parsed.map((p) => p.session));
-  // `stats.index` is chronological (oldest first); the history list shows newest
-  // first. Sort the parsed sessions the same way the aggregator orders the index
-  // so a row's position maps to the same session.
+  // History shows newest-first; each session already carries its own entry.
   const sessions = [...parsed].sort((a, b) => compareChronological(b.session, a.session));
   return { stats, sessions };
 }
@@ -437,16 +445,11 @@ export function buildDashboard(callbacks: DashboardCallbacks): DashboardSurface
     h.textContent = "History";
     wrap.appendChild(h);
 
-    // Pair each header session with its index entry + file name ONCE.
-    // `m.sessions` is newest-first; the chronological index is oldest-first, so
-    // read it in reverse. The name backs the lazy detail load + search (#144).
-    const index = m.stats.index;
-    const pairs: { name: string; session: ParsedSession; entry: SessionIndexEntry | undefined }[] = [];
-    for (let i = 0; i < m.sessions.length; i++) {
-      const indexed = m.sessions[i];
-      if (indexed === undefined) continue;
-      pairs.push({ name: indexed.name, session: indexed.session, entry: index[index.length - 1 - i] });
-    }
+    // Each session carries its OWN index entry (built alongside it in
+    // buildDashboardModel, #170), so a row shows its own duration/langs/cost —
+    // never a tied session's, as the old positional index reversal did. The name
+    // backs the lazy detail load + search (#144).
+    const pairs = m.sessions;
 
     // Search box (#131): case-insensitive substring over title/summary/board/
     // transcript, debounced. Title/summary/board are already in the header

test/dashboard.test.ts

@@ -93,6 +93,24 @@ const RECORDING = `# (recording)
 ## Transcript
 `;
 
+// #170: two sessions saved in the SAME clock-minute (back-to-back captures / the
+// "(2)" filename-collision case). They TIE on (headerDate, startClock) but have
+// distinct duration/languages/cost, so a positional index pairing would swap
+// their history-row subtitles.
+const TIED_ALPHA = `# Alpha
+> 2026-06-10 09:00–09:45 (45 min) · EN → KO · engine: Claude CLI ($0.30)
+
+## Summary
+- alpha notes
+`;
+
+const TIED_BETA = `# Beta
+> 2026-06-10 09:00–09:10 (10 min) · JA → FR · engine: Claude CLI ($0.05)
+
+## Summary
+- beta notes
+`;
+
 describe("formatDuration", () => {
   it("renders minutes, hours, and combinations", () => {
     expect(formatDuration(0)).toBe("0m");
@@ -170,6 +188,41 @@ describe("buildDashboardModel (#144: front-matter index)", () => {
     // The transcript entries are absent in a header parse (they load lazily).
     expect(indexed?.session.entries).toHaveLength(0);
   });
+
+  it("pairs each session with its OWN index entry when two tie on date+clock (#170)", () => {
+    // Regression: renderHistory used to read the chronological index in reverse
+    // by position; on a (date, startClock) tie both stable sorts keep the SAME
+    // relative order (not mirrored), so the reversal swapped tied sessions'
+    // duration/langs/cost subtitles. Each IndexedSession now carries its OWN entry.
+    const index: SessionHeader[] = [
+      { name: "2026-06-10 0900 — Alpha.md", markdown: TIED_ALPHA },
+      { name: "2026-06-10 0900 — Beta (2).md", markdown: TIED_BETA },
+    ];
+    const model = buildDashboardModel(index);
+    expect(model.sessions).toHaveLength(2);
+
+    const byTitle = new Map(model.sessions.map((s) => [s.session.meta.title, s]));
+    const alpha = byTitle.get("Alpha");
+    const beta = byTitle.get("Beta");
+
+    // Alpha's row shows Alpha's numbers, Beta's shows Beta's — not swapped.
+    expect(alpha?.entry.durationMin).toBe(45);
+    expect(alpha?.entry.sourceLang).toBe("EN");
+    expect(alpha?.entry.targetLang).toBe("KO");
+    expect(alpha?.entry.costUsd).toBeCloseTo(0.3, 5);
+    expect(beta?.entry.durationMin).toBe(10);
+    expect(beta?.entry.sourceLang).toBe("JA");
+    expect(beta?.entry.targetLang).toBe("FR");
+    expect(beta?.entry.costUsd).toBeCloseTo(0.05, 5);
+
+    // Invariant: every session's entry is derived from that same session's meta.
+    for (const s of model.sessions) {
+      expect(s.entry.title).toBe(s.session.meta.title);
+      expect(s.entry.date).toBe(s.session.meta.headerDate);
+      expect(s.entry.startClock).toBe(s.session.meta.startClock);
+      expect(s.entry.durationMin).toBe(s.session.meta.durationMin);
+    }
+  });
 });
 
 describe("sessionMatches (#131)", () => {