diff --git a/src/lib/roadmap/band.test.ts b/src/lib/roadmap/band.test.ts
new file mode 100644
index 0000000..8056545
--- /dev/null
+++ b/src/lib/roadmap/band.test.ts
@@ -0,0 +1,117 @@
+import { describe, it, expect } from "vitest";
+import { deriveBand, type BandInput } from "@/lib/roadmap/band";
+
+const today = new Date("2026-09-17T12:00:00Z");
+
+/** Default board: Backlog(0), To Do(1), In Progress(2), Review(3). */
+function card(overrides: Partial<BandInput> = {}): BandInput {
+  return {
+    archived: false,
+    isInbox: false,
+    isDone: false,
+    columnIndex: 0,
+    workingColumnCount: 4,
+    priority: "medium",
+    targetDate: "",
+    ...overrides,
+  };
+}
+
+describe("deriveBand — exclusions", () => {
+  it("excludes archived cards", () => {
+    expect(deriveBand(card({ archived: true }), today)).toBeNull();
+  });
+
+  it("excludes Inbox cards", () => {
+    // An unaccepted request is not committed work.
+    expect(deriveBand(card({ isInbox: true, priority: "critical" }), today)).toBeNull();
+  });
+
+  it("excludes Done cards", () => {
+    expect(deriveBand(card({ isDone: true, columnIndex: 3 }), today)).toBeNull();
+  });
+});
+
+describe("deriveBand — dates outrank position", () => {
+  it("puts an overdue card in Now wherever it sits", () => {
+    expect(
+      deriveBand(card({ columnIndex: 0, targetDate: "2026-09-10" }), today)
+    ).toBe("now");
+  });
+
+  it("puts a card due within seven days in Now", () => {
+    expect(deriveBand(card({ targetDate: "2026-09-22" }), today)).toBe("now");
+  });
+
+  it("does not promote a card due further out", () => {
+    expect(deriveBand(card({ targetDate: "2026-10-30" }), today)).toBe("later");
+  });
+
+  it("treats a date exactly seven days out as imminent", () => {
+    expect(deriveBand(card({ targetDate: "2026-09-24" }), today)).toBe("now");
+  });
+});
+
+describe("deriveBand — the board's own order is the signal", () => {
+  it("puts the later half of the working columns in Now", () => {
+    expect(deriveBand(card({ columnIndex: 2 }), today)).toBe("now"); // In Progress
+    expect(deriveBand(card({ columnIndex: 3 }), today)).toBe("now"); // Review
+  });
+
+  it("puts the second column in Next", () => {
+    expect(deriveBand(card({ columnIndex: 1 }), today)).toBe("next"); // To Do
+  });
+
+  it("puts the first column in Later", () => {
+    expect(deriveBand(card({ columnIndex: 0 }), today)).toBe("later"); // Backlog
+  });
+
+  it("adapts when the owner adds a column", () => {
+    // Six working columns: the later half is 3, 4, 5.
+    const six = { workingColumnCount: 6 };
+    expect(deriveBand(card({ ...six, columnIndex: 3 }), today)).toBe("now");
+    expect(deriveBand(card({ ...six, columnIndex: 2 }), today)).toBe("next");
+    expect(deriveBand(card({ ...six, columnIndex: 0 }), today)).toBe("later");
+  });
+
+  it("handles a board with a single working column", () => {
+    expect(
+      deriveBand(card({ workingColumnCount: 1, columnIndex: 0 }), today)
+    ).toBe("now");
+  });
+});
+
+describe("deriveBand — priority", () => {
+  it("promotes critical to Now from anywhere", () => {
+    expect(deriveBand(card({ columnIndex: 0, priority: "critical" }), today)).toBe("now");
+  });
+
+  it("promotes high to Next from the backlog", () => {
+    expect(deriveBand(card({ columnIndex: 0, priority: "high" }), today)).toBe("next");
+  });
+
+  it("leaves low priority in Later", () => {
+    expect(deriveBand(card({ columnIndex: 0, priority: "low" }), today)).toBe("later");
+  });
+});
+
+describe("deriveBand — robustness", () => {
+  it("tolerates a PocketBase datetime", () => {
+    expect(
+      deriveBand(card({ targetDate: "2026-09-10 00:00:00.000Z" }), today)
+    ).toBe("now");
+  });
+
+  it("ignores an unparseable date rather than throwing", () => {
+    expect(deriveBand(card({ targetDate: "not a date" }), today)).toBe("later");
+  });
+
+  it("never returns a band for an excluded card, whatever else is set", () => {
+    expect(
+      deriveBand(
+        card({ isDone: true, priority: "critical", targetDate: "2026-09-01" }),
+        today
+      )
+    ).toBeNull();
+  });
+});
diff --git a/src/lib/roadmap/band.ts b/src/lib/roadmap/band.ts
new file mode 100644
index 0000000..92acd1e
--- /dev/null
+++ b/src/lib/roadmap/band.ts
@@ -0,0 +1,73 @@
+/**
+ * Now / Next / Later.
+ *
+ * Derived, never stored. A stored band would be a third thing to keep in sync
+ * with the column and the priority, and it would drift from both without
+ * anyone noticing.
+ *
+ * Column POSITION is used rather than column name, so a renamed or newly added
+ * column still works. The board's own order is the signal; this reads it rather
+ * than holding a parallel opinion about what "in progress" means.
+ */
+
+import type { Priority } from "@/lib/pb/types";
+
+export type Band = "now" | "next" | "later";
+
+/** A date this close counts as imminent regardless of board position. */
+const IMMINENT_DAYS = 7;
+
+export interface BandInput {
+  archived: boolean;
+  isInbox: boolean;
+  isDone: boolean;
+  /** Index among the working columns — those that are neither inbox nor done. */
+  columnIndex: number;
+  workingColumnCount: number;
+  priority: Priority;
+  /** ISO date or PocketBase datetime, or "". */
+  targetDate: string;
+}
+
+function daysUntil(targetDate: string, now: Date): number | null {
+  if (!targetDate) return null;
+
+  const iso = targetDate.replace(" ", "T");
+  const target = Date.UTC(
+    Number(iso.slice(0, 4)),
+    Number(iso.slice(5, 7)) - 1,
+    Number(iso.slice(8, 10))
+  );
+  if (Number.isNaN(target)) return null;
+
+  const reference = Date.UTC(
+    now.getUTCFullYear(),
+    now.getUTCMonth(),
+    now.getUTCDate()
+  );
+
+  return Math.round((target - reference) / 86_400_000);
+}
+
+export function deriveBand(card: BandInput, now: Date = new Date()): Band | null {
+  // Not committed work, finished work, or removed work.
+  if (card.archived || card.isInbox || card.isDone) return null;
+
+  const days = daysUntil(card.targetDate, now);
+  if (days !== null && days <= IMMINENT_DAYS) return "now";
+
+  // A one-column board is degenerate: with nothing to compare against, every
+  // card is in the only column that exists. Treat it as in flight.
+  if (card.workingColumnCount === 1) return "now";
+
+  // The later half of the working columns is work in flight.
+  const half = Math.ceil(card.workingColumnCount / 2);
+  if (card.workingColumnCount > 0 && card.columnIndex >= half) return "now";
+
+  if (card.priority === "critical") return "now";
+
+  if (card.columnIndex >= 1) return "next";
+  if (card.priority === "high") return "next";
+
+  return "later";
+}