diff --git a/src/client/App.tsx b/src/client/App.tsx
index f2f51c6..dba30a5 100644
--- a/src/client/App.tsx
+++ b/src/client/App.tsx
@@ -26,8 +26,8 @@ import {
 } from "./state/lens.ts";
 import { clockFor, DAY, formatRemaining } from "../shared/time.ts";
 import { dailySummary, isDaily, resolveDaily } from "../shared/daily.ts";
-import { gameMeta } from "../shared/games.ts";
-import type { GameId } from "../shared/schema.ts";
+import { useGameMeta } from "./state/gameMeta.tsx";
+import type { LaneId } from "../shared/custom.ts";
 
 type View = "soon" | "calendar";
 
@@ -70,6 +70,7 @@ export function App() {
   // The event most recently ignored, so it can be put back without hunting for
   // a row that just disappeared.
   const [lastIgnored, setLastIgnored] = useState<{ id: string; title: string } | null>(null);
+  const gameMeta = useGameMeta();
   const now = useNow();
   const online = useOnline();
   const { prefs, update, toggleGame } = usePrefs();
@@ -151,7 +152,7 @@ export function App() {
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [state, prefs.region, Math.floor(now / 60_000)]);
 
-  const games = useMemo<GameId[]>(
+  const games = useMemo<LaneId[]>(
     () => [...new Set(allRows.map((r) => r.event.game))],
     [allRows],
   );
diff --git a/src/client/components/Controls.tsx b/src/client/components/Controls.tsx
index 6cb2220..29a81bd 100644
--- a/src/client/components/Controls.tsx
+++ b/src/client/components/Controls.tsx
@@ -1,5 +1,6 @@
-import type { GameId, Region } from "../../shared/schema.ts";
-import { gameMeta } from "../../shared/games.ts";
+import type { LaneId } from "../../shared/custom.ts";
+import type { Region } from "../../shared/schema.ts";
+import { useGameMeta } from "../state/gameMeta.tsx";
 import type { Prefs } from "../state/usePrefs.ts";
 
 const REGIONS: Array<{ id: Region; label: string }> = [
@@ -17,14 +18,15 @@ export function Controls({
   onExport,
   onImport,
 }: {
-  games: GameId[];
+  games: LaneId[];
   prefs: Prefs;
-  onToggleGame: (g: GameId) => void;
+  onToggleGame: (g: LaneId) => void;
   onUpdate: (p: Partial<Prefs>) => void;
   ignoredCount: number;
   onExport: () => void;
   onImport: (file: File) => void;
 }) {
+  const gameMeta = useGameMeta();
   return (
     <section className="border-t border-hairline px-4 py-5">
       <p className="eyebrow">Games</p>
diff --git a/src/client/components/Dailies.tsx b/src/client/components/Dailies.tsx
index 832858d..b191a95 100644
--- a/src/client/components/Dailies.tsx
+++ b/src/client/components/Dailies.tsx
@@ -1,7 +1,8 @@
 import { useEffect, useRef, useState } from "react";
 import { dailiesId, dayKey, msUntilReset, streakOf } from "../../shared/daily.ts";
-import { gameMeta } from "../../shared/games.ts";
-import type { GachaEvent, GameId, Region } from "../../shared/schema.ts";
+import { useGameMeta } from "../state/gameMeta.tsx";
+import type { DisplayEvent, LaneId } from "../../shared/custom.ts";
+import type { GameId, Region } from "../../shared/schema.ts";
 import { formatRemaining } from "../../shared/time.ts";
 import { Fireworks } from "./Fireworks.tsx";
 
@@ -29,23 +30,27 @@ export function Dailies({
   daysFor,
   onToggleDay,
 }: {
-  games: GameId[];
+  games: LaneId[];
   /**
    * Live events that repeat daily — detected, or marked by the reader — and
    * that the reader has not already finished or ignored. An event they marked
    * done has no line left to tick, and listing it is the app arguing with them.
    */
-  events: GachaEvent[];
+  events: DisplayEvent[];
   region: Region;
   now: number;
   daysFor: (id: string) => string[];
   onToggleDay: (id: string, day: string) => void;
 }) {
+  const gameMeta = useGameMeta();
   // Each game rolls on its own server clock, so "today" is asked per game
   // rather than once for the section — Endfield's European day can still be
   // yesterday's while every HoYo game has already turned over.
+  // Only tracked games have a standing chore — a lane the reader invented has
+  // no routine we could name for them (docs/DATA-MODEL.md § Reader-authored key
+  // spaces), so App passes tracked lanes here and this stays a total mapping.
   const chores = games.map((id) => ({
-    key: dailiesId(id),
+    key: dailiesId(id as GameId),
     game: gameMeta(id),
     today: dayKey(now, region, id),
     resetsIn: msUntilReset(now, region, id),
diff --git a/src/client/components/DailyChecklist.tsx b/src/client/components/DailyChecklist.tsx
index 9406b7a..81a11d9 100644
--- a/src/client/components/DailyChecklist.tsx
+++ b/src/client/components/DailyChecklist.tsx
@@ -3,7 +3,8 @@ import {
   msUntilReset,
   type DailySummary,
 } from "../../shared/daily.ts";
-import type { GameId, Region } from "../../shared/schema.ts";
+import type { LaneId } from "../../shared/custom.ts";
+import type { Region } from "../../shared/schema.ts";
 import { formatRemaining } from "../../shared/time.ts";
 
 /**
@@ -32,7 +33,7 @@ export function DailyChecklist({
   endsMs: number | null;
   region: Region;
   /** Whose reset clock the days are counted on — not every game shares one. */
-  game: GameId;
+  game: LaneId;
   now: number;
   logged: string[];
   onToggleDay: (day: string) => void;
diff --git a/src/client/components/EventDetail.tsx b/src/client/components/EventDetail.tsx
index 8e2dd18..0471279 100644
--- a/src/client/components/EventDetail.tsx
+++ b/src/client/components/EventDetail.tsx
@@ -1,5 +1,5 @@
 import { useEffect } from "react";
-import { gameMeta } from "../../shared/games.ts";
+import { useGameMeta } from "../state/gameMeta.tsx";
 import { formatAbsolute, formatRemaining } from "../../shared/time.ts";
 import type { RowEvent } from "./EventRow.tsx";
 import { pressure, pressureReason, type Effort } from "../../shared/effort.ts";
@@ -52,6 +52,7 @@ export function EventDetail({
   onNote: (id: string, n: string) => void;
   onClose: () => void;
 }) {
+  const gameMeta = useGameMeta();
   const { event, clock } = row;
   const game = gameMeta(event.game);
   const heat = URGENCY_COLOR[clock.urgency];
@@ -217,14 +218,19 @@ export function EventDetail({
           >
             {completed ? "Mark not done" : "Mark done"}
           </button>
-          <a
-            href={event.sourceUrl}
-            target="_blank"
-            rel="noreferrer noopener"
-            className="rounded-lg border border-hairline px-4 py-2.5 text-sm text-muted transition-colors hover:text-ink"
-          >
-            Source
-          </a>
+          {/* Nothing to link to when the reader typed this themselves, and a
+              dead "Source" button would imply somebody else vouched for the
+              date. Provenance is stated above instead. */}
+          {event.sourceUrl !== null && (
+            <a
+              href={event.sourceUrl}
+              target="_blank"
+              rel="noreferrer noopener"
+              className="rounded-lg border border-hairline px-4 py-2.5 text-sm text-muted transition-colors hover:text-ink"
+            >
+              Source
+            </a>
+          )}
         </div>
 
         {/* Ignoring is not completing. "Done" keeps an event visible and
diff --git a/src/client/components/EventRow.tsx b/src/client/components/EventRow.tsx
index 55a3f21..649c707 100644
--- a/src/client/components/EventRow.tsx
+++ b/src/client/components/EventRow.tsx
@@ -1,5 +1,5 @@
-import { gameMeta } from "../../shared/games.ts";
-import type { GachaEvent } from "../../shared/schema.ts";
+import type { DisplayEvent } from "../../shared/custom.ts";
+import { useGameMeta } from "../state/gameMeta.tsx";
 import {
   formatRemaining,
   windowCaption,
@@ -10,7 +10,7 @@ import type { Status } from "../state/useProgress.ts";
 import { Meter, URGENCY_COLOR } from "./Meter.tsx";
 
 export interface RowEvent {
-  event: GachaEvent;
+  event: DisplayEvent;
   clock: EventClock;
 }
 
@@ -44,6 +44,7 @@ export function EventRow({
   onRestore,
   onOpen,
 }: EventRowProps) {
+  const gameMeta = useGameMeta();
   const { event, clock } = row;
   const game = gameMeta(event.game);
   const heat = URGENCY_COLOR[clock.urgency];
diff --git a/src/client/components/GameFocus.tsx b/src/client/components/GameFocus.tsx
index cba2eb9..355e65e 100644
--- a/src/client/components/GameFocus.tsx
+++ b/src/client/components/GameFocus.tsx
@@ -1,5 +1,5 @@
-import { gameMeta } from "../../shared/games.ts";
-import type { GameId } from "../../shared/schema.ts";
+import { useGameMeta } from "../state/gameMeta.tsx";
+import type { LaneId } from "../../shared/custom.ts";
 
 /**
  * One game at a time.
@@ -24,16 +24,17 @@ export function GameFocus({
   onAdvance,
 }: {
   /** Games the reader has switched on, in feed order. */
-  games: GameId[];
-  focus: GameId | null;
+  games: LaneId[];
+  focus: LaneId | null;
   /** Outstanding rows per game, so a chip says whether it is worth a visit. */
-  counts: Partial<Record<GameId, number>>;
+  counts: Partial<Record<LaneId, number>>;
   total: number;
   /** Where "next" goes — null means back to all games. */
-  next: GameId | null;
-  onFocus: (game: GameId | null) => void;
+  next: LaneId | null;
+  onFocus: (game: LaneId | null) => void;
   onAdvance: () => void;
 }) {
+  const gameMeta = useGameMeta();
   // With one game there is nothing to focus down to, and the bar would just be
   // a chip that does nothing.
   if (games.length < 2) return null;
diff --git a/src/client/components/NextUp.tsx b/src/client/components/NextUp.tsx
index 78f4131..b1ed5fe 100644
--- a/src/client/components/NextUp.tsx
+++ b/src/client/components/NextUp.tsx
@@ -1,4 +1,4 @@
-import { gameMeta } from "../../shared/games.ts";
+import { useGameMeta } from "../state/gameMeta.tsx";
 import { formatRemaining } from "../../shared/time.ts";
 import type { RowEvent } from "./EventRow.tsx";
 import { Meter, URGENCY_COLOR } from "./Meter.tsx";
@@ -26,6 +26,7 @@ export function NextUp({
   focused: string | null;
   onOpen: (id: string) => void;
 }) {
+  const gameMeta = useGameMeta();
   if (row === null) {
     return (
       <section className="border-b border-hairline px-4 py-8">
diff --git a/src/client/components/Timeline.tsx b/src/client/components/Timeline.tsx
index 770dd0f..d4a42f8 100644
--- a/src/client/components/Timeline.tsx
+++ b/src/client/components/Timeline.tsx
@@ -1,6 +1,6 @@
 import { useEffect, useRef } from "react";
-import { gameMeta } from "../../shared/games.ts";
-import type { GameId } from "../../shared/schema.ts";
+import { useGameMeta } from "../state/gameMeta.tsx";
+import type { LaneId } from "../../shared/custom.ts";
 import { DAY } from "../../shared/time.ts";
 import type { RowEvent } from "./EventRow.tsx";
 import { URGENCY_COLOR } from "./Meter.tsx";
@@ -42,6 +42,7 @@ export function Timeline({
    */
   isDone: (id: string) => boolean;
 }) {
+  const gameMeta = useGameMeta();
   const scroller = useRef<HTMLDivElement>(null);
 
   const ends = rows.map((r) => r.clock.endsMs ?? r.clock.startsMs + 14 * DAY);
@@ -75,7 +76,7 @@ export function Timeline({
     );
   }
 
-  const byGame = new Map<GameId, RowEvent[]>();
+  const byGame = new Map<LaneId, RowEvent[]>();
   for (const row of rows) {
     byGame.set(row.event.game, [...(byGame.get(row.event.game) ?? []), row]);
   }
diff --git a/src/client/components/Welcome.tsx b/src/client/components/Welcome.tsx
index 7b9a17d..fbbe3b1 100644
--- a/src/client/components/Welcome.tsx
+++ b/src/client/components/Welcome.tsx
@@ -1,6 +1,6 @@
 import { useState } from "react";
-import { gameMeta } from "../../shared/games.ts";
-import type { GameId } from "../../shared/schema.ts";
+import { useGameMeta } from "../state/gameMeta.tsx";
+import type { LaneId } from "../../shared/custom.ts";
 
 /**
  * First run: pick your games.
@@ -15,12 +15,13 @@ export function Welcome({
   available,
   onConfirm,
 }: {
-  available: GameId[];
-  onConfirm: (chosen: GameId[]) => void;
+  available: LaneId[];
+  onConfirm: (chosen: LaneId[]) => void;
 }) {
-  const [chosen, setChosen] = useState<GameId[]>([]);
+  const gameMeta = useGameMeta();
+  const [chosen, setChosen] = useState<LaneId[]>([]);
 
-  const toggle = (id: GameId) =>
+  const toggle = (id: LaneId) =>
     setChosen((prev) =>
       prev.includes(id) ? prev.filter((g) => g !== id) : [...prev, id],
     );
diff --git a/src/client/state/gameMeta.tsx b/src/client/state/gameMeta.tsx
new file mode 100644
index 0000000..b877121
--- /dev/null
+++ b/src/client/state/gameMeta.tsx
@@ -0,0 +1,36 @@
+import { createContext, useContext } from "react";
+import type { CustomGames, LaneId } from "../../shared/custom.ts";
+import { metaFor, type GameMeta } from "../../shared/games.ts";
+
+/**
+ * How a component turns a lane id into a name, a short label and a hue.
+ *
+ * It used to be a direct import of `gameMeta`, which could only answer for the
+ * games in `GAMES`. Now a lane can also be one the reader invented (PRD F13),
+ * and those live in their browser rather than in a module — so the resolver has
+ * to come from somewhere with access to that state.
+ *
+ * A context rather than module-level mutable state: `metaFor` stays pure and
+ * takes the reader's games as an argument, and nothing renders off a registry
+ * that some other part of the app has been quietly writing to.
+ */
+export type MetaResolver = (id: LaneId) => GameMeta;
+
+const NO_CUSTOM_GAMES: CustomGames = {};
+
+const GameMetaContext = createContext<MetaResolver>((id) =>
+  metaFor(id, NO_CUSTOM_GAMES),
+);
+
+export const GameMetaProvider = GameMetaContext.Provider;
+
+/**
+ * The lane resolver for this tree.
+ *
+ * The default answers for tracked games only, which is the correct answer
+ * anywhere the reader's own games cannot appear — and a safe one everywhere
+ * else, since `metaFor` is total.
+ */
+export function useGameMeta(): MetaResolver {
+  return useContext(GameMetaContext);
+}
diff --git a/src/client/state/lens.ts b/src/client/state/lens.ts
index 47c19d7..85d5f81 100644
--- a/src/client/state/lens.ts
+++ b/src/client/state/lens.ts
@@ -1,4 +1,4 @@
-import type { GameId } from "../../shared/schema.ts";
+import type { LaneId } from "../../shared/custom.ts";
 
 /**
  * Which rows each part of the page gets to see.
@@ -13,7 +13,7 @@ import type { GameId } from "../../shared/schema.ts";
 
 /** The shape every lens here needs. Structural so this module stays cheap. */
 interface Row {
-  event: { id: string; game: GameId };
+  event: { id: string; game: LaneId };
   clock: { msRemaining: number | null };
 }
 
@@ -71,9 +71,9 @@ export function firstToExpire<T extends Row>(rows: readonly T[]): T | null {
  * whose reason is a setting two screens away.
  */
 export function resolveFocus(
-  focus: GameId | null,
-  enabled: readonly GameId[],
-): GameId | null {
+  focus: LaneId | null,
+  enabled: readonly LaneId[],
+): LaneId | null {
   return focus !== null && enabled.includes(focus) ? focus : null;
 }
 
@@ -85,9 +85,9 @@ export function resolveFocus(
  * of the rotation except finding the "all" chip again.
  */
 export function advanceFocus(
-  focus: GameId | null,
-  enabled: readonly GameId[],
-): GameId | null {
+  focus: LaneId | null,
+  enabled: readonly LaneId[],
+): LaneId | null {
   if (enabled.length === 0) return null;
   const at = focus === null ? -1 : enabled.indexOf(focus);
   // An unknown focus (switched-off game) restarts the rotation rather than
@@ -98,8 +98,8 @@ export function advanceFocus(
 /** How many rows each game still has outstanding, for the focus chips. */
 export function countByGame<T extends Row>(
   rows: readonly T[],
-): Partial<Record<GameId, number>> {
-  const out: Partial<Record<GameId, number>> = {};
+): Partial<Record<LaneId, number>> {
+  const out: Partial<Record<LaneId, number>> = {};
   for (const row of rows) {
     out[row.event.game] = (out[row.event.game] ?? 0) + 1;
   }
diff --git a/src/client/state/usePrefs.ts b/src/client/state/usePrefs.ts
index 00c468b..b184653 100644
--- a/src/client/state/usePrefs.ts
+++ b/src/client/state/usePrefs.ts
@@ -1,5 +1,6 @@
 import { useCallback, useEffect, useState } from "react";
-import type { GameId, Region } from "../../shared/schema.ts";
+import type { LaneId } from "../../shared/custom.ts";
+import type { Region } from "../../shared/schema.ts";
 import { guessRegion } from "../../shared/time.ts";
 import type { SortMode } from "./sort.ts";
 import { KEYS, readJson, writeJson } from "./storage.ts";
@@ -7,7 +8,7 @@ import { KEYS, readJson, writeJson } from "./storage.ts";
 export interface Prefs {
   region: Region;
   /** Games the reader has switched off. Stored as hidden so a newly added game shows up by default. */
-  hiddenGames: GameId[];
+  hiddenGames: LaneId[];
   /**
    * One game to look at right now, or null for all of them.
    *
@@ -16,7 +17,7 @@ export interface Prefs {
    * obeyed (`resolveFocus`), so it can never leave the reader on a blank page
    * with no visible cause.
    */
-  focusGame: GameId | null;
+  focusGame: LaneId | null;
   /** How the list is ordered. Deadline order is the default and the fallback. */
   sort: SortMode;
   /**
@@ -66,7 +67,7 @@ export function usePrefs() {
     setPrefs((prev) => ({ ...prev, ...patch }));
   }, []);
 
-  const toggleGame = useCallback((game: GameId) => {
+  const toggleGame = useCallback((game: LaneId) => {
     setPrefs((prev) => ({
       ...prev,
       hiddenGames: prev.hiddenGames.includes(game)
diff --git a/src/shared/custom.ts b/src/shared/custom.ts
new file mode 100644
index 0000000..d5698be
--- /dev/null
+++ b/src/shared/custom.ts
@@ -0,0 +1,202 @@
+import { z } from "zod";
+import { EventType, GachaEvent, Precision, slugify } from "./schema.ts";
+
+/**
+ * Games and events the reader entered themselves (PRD F13).
+ *
+ * No source publishes these, nothing fetches them, and they never enter the
+ * ingest pipeline — `sanitize.ts` and `merge.ts` exist for pages we do not
+ * control, and a reader's own typing is neither untrusted markup nor a second
+ * opinion to reconcile. What they *do* share with scraped events is everything
+ * downstream: the same lists, the same clock, the same progress, ignore and
+ * daily-checklist stores, keyed by the ids below.
+ */
+
+/**
+ * Reserved first segments. None of these may ever become a `GameId`.
+ *
+ * Every id in this app is colon-separated and the first segment decides which
+ * space it belongs to: `dailies:<game>` is a standing chore, `mygame:` and
+ * `myevent:` are the reader's own, and anything else is `<game>:<slug>:<date>`
+ * from a source. The day one of these becomes a game id is the day two key
+ * spaces merge silently, so a test pins it against `GameId.options`.
+ */
+export const RESERVED_ID_SEGMENTS = ["dailies", "mygame", "myevent"] as const;
+
+const GAME_PREFIX = "mygame";
+const EVENT_PREFIX = "myevent";
+
+export const CustomGameId = z.string().regex(/^mygame:[a-z0-9-]{1,60}$/);
+export const CustomEventId = z.string().regex(/^myevent:[a-z0-9]{6,32}$/);
+
+/**
+ * Anything that can key a lane: a tracked game or one the reader defined.
+ *
+ * Deliberately a plain string rather than a union — it is read by filters,
+ * focus, counts and day keys, none of which care which kind it is, and a union
+ * would push a narrowing at every one of those call sites for no safety.
+ */
+export type LaneId = string;
+
+export function isCustomGameId(id: string): boolean {
+  return id.startsWith(`${GAME_PREFIX}:`);
+}
+
+/**
+ * Whether this event is the reader's own.
+ *
+ * The id is the authority, not `extractionMethod` — that says a human entered
+ * the value, which is also true of an event approved through the review gate.
+ * This says *this* reader entered it, which is what the UI must not get wrong:
+ * their own date is never attributed to a source.
+ */
+export function isCustomEventId(id: string): boolean {
+  return id.startsWith(`${EVENT_PREFIX}:`);
+}
+
+export const CustomGame = z.object({
+  id: CustomGameId,
+  name: z.string().min(1).max(40),
+  /**
+   * Reaches a `style` attribute, and an imported file is not necessarily one
+   * this reader wrote — so the shape is checked rather than trusted.
+   */
+  hue: z.string().regex(/^#[0-9a-fA-F]{6}$/),
+  at: z.string().datetime(),
+});
+export type CustomGame = z.infer<typeof CustomGame>;
+
+export const CustomEvent = z
+  .object({
+    id: CustomEventId,
+    /** A tracked game, or one of theirs — a source can miss an event too. */
+    game: z.string().min(1),
+    title: z.string().min(1).max(200),
+    type: EventType,
+    summary: z.string().max(500).nullable(),
+
+    startsAt: z.string().datetime(),
+    startPrecision: Precision,
+    endsAt: z.string().datetime().nullable(),
+    endPrecision: Precision,
+
+    at: z.string().datetime(),
+    updatedAt: z.string().datetime(),
+  })
+  // The same invariants the feed is held to. "I don't know when this ends" has
+  // to be expressible here too, or entering an unannounced event would force
+  // the reader to invent a date — the one thing this product refuses to do.
+  .refine((e) => (e.endsAt === null) === (e.endPrecision === "unknown"), {
+    message: "endsAt null must pair with endPrecision 'unknown'",
+    path: ["endPrecision"],
+  })
+  .refine((e) => e.endsAt === null || e.endsAt > e.startsAt, {
+    message: "endsAt must be after startsAt",
+    path: ["endsAt"],
+  });
+export type CustomEvent = z.infer<typeof CustomEvent>;
+
+export const CustomGames = z.record(z.string(), CustomGame);
+export const CustomEvents = z.record(z.string(), CustomEvent);
+export type CustomGames = z.infer<typeof CustomGames>;
+export type CustomEvents = z.infer<typeof CustomEvents>;
+
+/**
+ * What every view in the client actually reads.
+ *
+ * A feed event satisfies this as-is; a reader's event is projected into it by
+ * `asDisplayEvent`. Only two fields widen, and both for the same reason — the
+ * reader's events are not from a source:
+ *
+ *   game       may be a lane they invented, so not a `GameId`
+ *   sourceUrl  is null, because there is no page to send a sceptic to
+ */
+export type DisplayEvent = Omit<GachaEvent, "game" | "sourceUrl"> & {
+  game: LaneId;
+  sourceUrl: string | null;
+};
+
+/**
+ * Project a reader's event into the shape the views read.
+ *
+ * `extractionMethod: "manual"` and `confidence: 1` are the existing vocabulary
+ * for "a human asserted this", so nothing new is invented to describe it. The
+ * region fields say false/null because the reader entered one instant, not a
+ * per-region map — turning one timestamp into three would fabricate two of them.
+ */
+export function asDisplayEvent(event: CustomEvent): DisplayEvent {
+  return {
+    id: event.id,
+    game: event.game,
+    title: event.title,
+    type: event.type,
+    summary: event.summary,
+    startsAt: event.startsAt,
+    startPrecision: event.startPrecision,
+    endsAt: event.endsAt,
+    endPrecision: event.endPrecision,
+    regionScoped: false,
+    regionEnds: null,
+    sourceUrl: null,
+    sourceId: "you",
+    status: "published",
+    confidence: 1,
+    extractionMethod: "manual",
+    version: 1,
+    firstSeenAt: event.at,
+    updatedAt: event.updatedAt,
+  };
+}
+
+/**
+ * A stable id for a game the reader named, unique among the ones they have.
+ *
+ * Slug-derived so it reads in an export, and suffixed on collision rather than
+ * overwriting — two games called "Nikke" are two games.
+ */
+export function mintCustomGameId(
+  name: string,
+  taken: Iterable<string> = [],
+): string {
+  const base = slugify(name).slice(0, 60) || "game";
+  const used = new Set(taken);
+  let id = `${GAME_PREFIX}:${base}`;
+  for (let n = 2; used.has(id); n += 1) id = `${GAME_PREFIX}:${base}-${n}`;
+  return id;
+}
+
+/**
+ * A random id for an event the reader entered.
+ *
+ * Random, not derived from the title, for two reasons. It cannot collide with
+ * `${game}:${slug}:${date}` even when they type a scraped event's exact name and
+ * date — that collision would silently share one completion mark and one streak
+ * between two events. And it does not move when they rename their own event, so
+ * editing a typo in a title never costs them the marks attached to it.
+ */
+export function mintCustomEventId(random: () => number = Math.random): string {
+  let token = "";
+  while (token.length < 10) {
+    token += Math.floor(random() * 36 ** 6)
+      .toString(36)
+      .padStart(6, "0");
+  }
+  return `${EVENT_PREFIX}:${token.slice(0, 10)}`;
+}
+
+/**
+ * The precision a reader's boundary actually has.
+ *
+ * A date typed with no time of day is `"day"`, exactly as a source that printed
+ * one would be — so the detail sheet's existing "accurate to the day only" note
+ * is honest about their input too, rather than presenting midnight as a time
+ * they chose.
+ */
+export function precisionOf(hasTime: boolean): Extract<Precision, "exact" | "day"> {
+  return hasTime ? "exact" : "day";
+}
+
+/** True when `id` is a game this reader defined and still has. */
+export function knownLane(id: LaneId, games: CustomGames): boolean {
+  return !isCustomGameId(id) || games[id] !== undefined;
+}
diff --git a/src/shared/daily.ts b/src/shared/daily.ts
index 8f8bf06..c352abc 100644
--- a/src/shared/daily.ts
+++ b/src/shared/daily.ts
@@ -1,4 +1,5 @@
 import { GAMES } from "./games.ts";
+import type { LaneId } from "./custom.ts";
 import type { GachaEvent, GameId, Region } from "./schema.ts";
 import { DAY, HOUR, REGION_RESET_UTC_OFFSET } from "./time.ts";
 
@@ -127,8 +128,12 @@ export function dailyOverride(
  * that *do* have their own server onto somebody else's clock, which is a
  * different bug in the same place.
  */
-export function serverOffsetUtc(region: Region, game?: GameId): number {
-  const override = game === undefined ? undefined : GAMES[game].resetOffsets?.[region];
+export function serverOffsetUtc(region: Region, game?: LaneId): number {
+  // A lane the reader invented (PRD F13) has no server map to know about, and
+  // neither does an id that has outlived its game, so both take the regional
+  // default rather than being looked up and crashing.
+  const override =
+    game === undefined ? undefined : GAMES[game as GameId]?.resetOffsets?.[region];
   return override ?? REGION_RESET_UTC_OFFSET[region];
 }
 
@@ -141,7 +146,7 @@ export function serverOffsetUtc(region: Region, game?: GameId): number {
  * but it is still the reader's streak moving under them. Treat a change here as
  * a data change, not a constant.
  */
-function shift(region: Region, game?: GameId): number {
+function shift(region: Region, game?: LaneId): number {
   return serverOffsetUtc(region, game) * HOUR - RESET_HOUR_LOCAL * HOUR;
 }
 
@@ -155,18 +160,18 @@ function shift(region: Region, game?: GameId): number {
  * generic "what day is it here?" — still gets the regional answer. Anything
  * that reads or writes a tick should pass it.
  */
-export function dayKey(ms: number, region: Region, game?: GameId): string {
+export function dayKey(ms: number, region: Region, game?: LaneId): string {
   return new Date(ms + shift(region, game)).toISOString().slice(0, 10);
 }
 
 /** The next reset instant strictly after `ms`. */
-export function nextResetMs(ms: number, region: Region, game?: GameId): number {
+export function nextResetMs(ms: number, region: Region, game?: LaneId): number {
   const s = shift(region, game);
   return Math.floor((ms + s) / DAY) * DAY + DAY - s;
 }
 
 /** How long the reader has left to do today's dailies. */
-export function msUntilReset(ms: number, region: Region, game?: GameId): number {
+export function msUntilReset(ms: number, region: Region, game?: LaneId): number {
   return nextResetMs(ms, region, game) - ms;
 }
 
@@ -181,7 +186,7 @@ export function dailyDays(
   startsMs: number,
   endsMs: number | null,
   region: Region,
-  game?: GameId,
+  game?: LaneId,
 ): string[] | null {
   if (endsMs === null) return null;
 
@@ -230,7 +235,7 @@ export function dailySummary(input: {
   endsMs: number | null;
   region: Region;
   /** Whose reset clock this runs on. Omitted falls back to the region's. */
-  game?: GameId | undefined;
+  game?: LaneId | undefined;
   now: number;
   logged: readonly string[];
 }): DailySummary {
diff --git a/src/shared/games.ts b/src/shared/games.ts
index 3b80661..33e9384 100644
--- a/src/shared/games.ts
+++ b/src/shared/games.ts
@@ -1,3 +1,4 @@
+import type { CustomGames, LaneId } from "./custom.ts";
 import type { GameId, Region } from "./schema.ts";
 
 export interface GameMeta {
@@ -72,3 +73,48 @@ export const GAME_LIST: GameMeta[] = Object.values(GAMES);
 export function gameMeta(id: GameId): GameMeta {
   return GAMES[id];
 }
+
+/**
+ * Meta for any lane, including one the reader invented (PRD F13).
+ *
+ * Pure, and total. Total matters: a lane id can outlive the game it names —
+ * an import can carry an event whose game did not come with it, and a reader
+ * can delete a game a stale render is still holding. Returning a neutral
+ * placeholder keeps that a visible oddity rather than a blank screen, which is
+ * the trade this codebase makes everywhere else in the client.
+ */
+export function metaFor(id: LaneId, custom: CustomGames): GameMeta {
+  const tracked = GAMES[id as GameId];
+  if (tracked !== undefined) return tracked;
+
+  const own = custom[id];
+  if (own !== undefined) {
+    return {
+      id: own.id as GameId,
+      name: own.name,
+      short: shortLabel(own.name),
+      hue: own.hue,
+      // Not credited in the colophon and contributing no standing chore: the
+      // colophon lists the sources we fetch, and this game has none. See
+      // docs/DATA-MODEL.md § Reader-authored key spaces.
+      studio: "",
+      dailyTasks: "",
+    };
+  }
+
+  return {
+    id: id as GameId,
+    name: "Unknown game",
+    short: "?",
+    hue: "#9AA3B8",
+    studio: "",
+    dailyTasks: "",
+  };
+}
+
+/** A name that still fits a narrow lane label or a chip. */
+export function shortLabel(name: string): string {
+  if (name.length <= 12) return name;
+  const first = name.split(/\s+/)[0] ?? name;
+  return first.length <= 12 ? first : `${name.slice(0, 11)}…`;
+}
diff --git a/src/shared/time.ts b/src/shared/time.ts
index 8cc338d..e9e14a9 100644
--- a/src/shared/time.ts
+++ b/src/shared/time.ts
@@ -1,4 +1,5 @@
-import type { GachaEvent, Region } from "./schema.ts";
+import type { DisplayEvent } from "./custom.ts";
+import type { Region } from "./schema.ts";
 
 /**
  * Time is this product's entire subject, so the vocabulary lives in one place:
@@ -28,8 +29,23 @@ export function guessRegion(
   return "europe";
 }
 
+/**
+ * The boundary fields these helpers read.
+ *
+ * Structural rather than `GachaEvent` so a reader's own event (PRD F13) runs on
+ * exactly the same clock as a scraped one — there is no second countdown
+ * implementation to keep honest.
+ */
+export type EndBearing = Pick<
+  DisplayEvent,
+  "endsAt" | "regionScoped" | "regionEnds"
+>;
+
 /** The end instant to show this user, honouring a region-scoped event. */
-export function effectiveEnd(event: GachaEvent, region: Region): string | null {
+export function effectiveEnd(
+  event: EndBearing,
+  region: Region,
+): string | null {
   if (event.endsAt === null) return null;
   if (!event.regionScoped || event.regionEnds === null) return event.endsAt;
   return event.regionEnds[region] ?? event.endsAt;
@@ -96,7 +112,7 @@ export interface EventClock {
 }
 
 export function clockFor(
-  event: GachaEvent,
+  event: EndBearing & Pick<DisplayEvent, "startsAt">,
   region: Region,
   now: number,
 ): EventClock {
diff --git a/test/custom.test.ts b/test/custom.test.ts
new file mode 100644
index 0000000..a69b560
--- /dev/null
+++ b/test/custom.test.ts
@@ -0,0 +1,246 @@
+import { describe, expect, test } from "bun:test";
+import {
+  asDisplayEvent,
+  CustomEvent,
+  CustomGame,
+  isCustomEventId,
+  isCustomGameId,
+  knownLane,
+  mintCustomEventId,
+  mintCustomGameId,
+  precisionOf,
+  RESERVED_ID_SEGMENTS,
+  type CustomGames,
+} from "../src/shared/custom.ts";
+import { metaFor } from "../src/shared/games.ts";
+import { dailiesId } from "../src/shared/daily.ts";
+import { eventId, GameId } from "../src/shared/schema.ts";
+import { clockFor } from "../src/shared/time.ts";
+
+const AT = "2026-08-17T12:00:00.000Z";
+
+function ownEvent(over: Partial<CustomEvent> = {}): CustomEvent {
+  return CustomEvent.parse({
+    id: "myevent:k3f9qa2m01",
+    game: "mygame:limbus-company",
+    title: "Walpurgisnacht",
+    type: "banner",
+    summary: null,
+    startsAt: "2026-08-20T00:00:00.000Z",
+    startPrecision: "day",
+    endsAt: "2026-09-03T00:00:00.000Z",
+    endPrecision: "day",
+    at: AT,
+    updatedAt: AT,
+    ...over,
+  });
+}
+
+describe("reserved id segments", () => {
+  test("no game id can ever occupy a reserved first segment", () => {
+    // Every id in the app is colon-separated and the first segment decides
+    // which key space it belongs to. The day a GameId is called "mygame" is the
+    // day two spaces merge silently, and localStorage has no other copy.
+    for (const reserved of RESERVED_ID_SEGMENTS) {
+      expect(GameId.options as readonly string[]).not.toContain(reserved);
+    }
+  });
+
+  test("the three spaces cannot produce the same key", () => {
+    const feed = eventId("genshin", "Walpurgisnacht", "2026-08-20T00:00:00.000Z");
+    const chore = dailiesId("genshin");
+    const own = mintCustomEventId(() => 0.5);
+    const ownGame = mintCustomGameId("Limbus Company");
+
+    const keys = [feed, chore, own, ownGame];
+    expect(new Set(keys).size).toBe(keys.length);
+    for (const key of keys) {
+      expect(key.split(":").length).toBeGreaterThanOrEqual(2);
+    }
+  });
+
+  test("a reader's event never collides with the scraped event it names", () => {
+    // The whole reason for a random suffix: they can type a tracked event's
+    // exact title and date. Under the feed's scheme that is byte-identical.
+    const scraped = eventId("genshin", "Windblume Festival", "2026-03-14T00:00:00.000Z");
+    const mine = mintCustomEventId(() => 0.123456);
+    expect(mine).not.toBe(scraped);
+    expect(isCustomEventId(mine)).toBe(true);
+    expect(isCustomEventId(scraped)).toBe(false);
+  });
+});
+
+describe("minting ids", () => {
+  test("a game id is slug-derived and disambiguated rather than overwritten", () => {
+    expect(mintCustomGameId("Limbus Company")).toBe("mygame:limbus-company");
+    // Two games called Nikke are two games.
+    expect(mintCustomGameId("Nikke", ["mygame:nikke"])).toBe("mygame:nikke-2");
+    expect(mintCustomGameId("Nikke", ["mygame:nikke", "mygame:nikke-2"])).toBe(
+      "mygame:nikke-3",
+    );
+  });
+
+  test("a game whose name slugifies to nothing still gets an id", () => {
+    expect(mintCustomGameId("???")).toBe("mygame:game");
+  });
+
+  test("event ids match their schema and vary with the source of randomness", () => {
+    const a = mintCustomEventId(() => 0.1);
+    const b = mintCustomEventId(() => 0.9);
+    expect(a).toMatch(/^myevent:[a-z0-9]{10}$/);
+    expect(b).toMatch(/^myevent:[a-z0-9]{10}$/);
+    expect(a).not.toBe(b);
+    expect(isCustomGameId(a)).toBe(false);
+  });
+});
+
+describe("CustomEvent", () => {
+  test("an unannounced end is expressible, and must pair with unknown", () => {
+    // A reader entering an event nobody has dated must not be forced to invent
+    // one — that is the failure this whole product is built against.
+    const open = ownEvent({ endsAt: null, endPrecision: "unknown" });
+    expect(open.endsAt).toBeNull();
+
+    expect(() =>
+      CustomEvent.parse({ ...ownEvent(), endsAt: null, endPrecision: "day" }),
+    ).toThrow();
+    expect(() =>
+      CustomEvent.parse({
+        ...ownEvent(),
+        endsAt: "2026-09-03T00:00:00.000Z",
+        endPrecision: "unknown",
+      }),
+    ).toThrow();
+  });
+
+  test("rejects an end before its start", () => {
+    expect(() =>
+      CustomEvent.parse({ ...ownEvent(), endsAt: "2026-08-19T00:00:00.000Z" }),
+    ).toThrow();
+  });
+
+  test("rejects an empty or oversized title", () => {
+    expect(() => CustomEvent.parse({ ...ownEvent(), title: "" })).toThrow();
+    expect(() =>
+      CustomEvent.parse({ ...ownEvent(), title: "x".repeat(201) }),
+    ).toThrow();
+  });
+});
+
+describe("CustomGame", () => {
+  test("a hue must be a hex colour, because it reaches a style attribute", () => {
+    // An imported file is not necessarily one this reader wrote.
+    const ok = CustomGame.parse({
+      id: "mygame:limbus-company",
+      name: "Limbus Company",
+      hue: "#C74B50",
+      at: AT,
+    });
+    expect(ok.hue).toBe("#C74B50");
+
+    for (const hue of ["red", "url(javascript:alert(1))", "#fff", "#12345g", ""]) {
+      expect(() =>
+        CustomGame.parse({ id: "mygame:x", name: "X", hue, at: AT }),
+      ).toThrow();
+    }
+  });
+
+  test("rejects an id from another key space", () => {
+    expect(() =>
+      CustomGame.parse({ id: "genshin", name: "Genshin", hue: "#4EA8DE", at: AT }),
+    ).toThrow();
+  });
+});
+
+describe("asDisplayEvent", () => {
+  test("carries no source and claims no region split", () => {
+    const shown = asDisplayEvent(ownEvent());
+    // Never attributed to a source: there is no page to send a sceptic to.
+    expect(shown.sourceUrl).toBeNull();
+    // One instant was entered, so inventing three would fabricate two of them.
+    expect(shown.regionScoped).toBe(false);
+    expect(shown.regionEnds).toBeNull();
+    expect(shown.extractionMethod).toBe("manual");
+    expect(shown.status).toBe("published");
+  });
+
+  test("runs on the same clock as a scraped event", () => {
+    // Not a second countdown implementation — the identical one.
+    const clock = clockFor(
+      asDisplayEvent(ownEvent()),
+      "europe",
+      Date.parse("2026-08-27T00:00:00.000Z"),
+    );
+    expect(clock.live).toBe(true);
+    expect(clock.msRemaining).toBe(7 * 24 * 60 * 60 * 1000);
+  });
+
+  test("an unannounced end yields no countdown, exactly as the feed's does", () => {
+    const clock = clockFor(
+      asDisplayEvent(ownEvent({ endsAt: null, endPrecision: "unknown" })),
+      "europe",
+      Date.parse("2026-08-27T00:00:00.000Z"),
+    );
+    expect(clock.msRemaining).toBeNull();
+    expect(clock.urgency).toBe("calm");
+  });
+});
+
+describe("precisionOf", () => {
+  test("a date with no time of day is day precision", () => {
+    // So the detail sheet's "accurate to the day only" note is honest about
+    // the reader's input too, rather than presenting midnight as their choice.
+    expect(precisionOf(false)).toBe("day");
+    expect(precisionOf(true)).toBe("exact");
+  });
+});
+
+describe("metaFor", () => {
+  const mine: CustomGames = {
+    "mygame:limbus-company": {
+      id: "mygame:limbus-company",
+      name: "Limbus Company",
+      hue: "#C74B50",
+      at: AT,
+    },
+  };
+
+  test("answers for a tracked game unchanged", () => {
+    expect(metaFor("genshin", mine).name).toBe("Genshin Impact");
+    expect(metaFor("genshin", mine).studio).toBe("HoYoverse");
+  });
+
+  test("answers for one the reader defined, with no studio or chore", () => {
+    const meta = metaFor("mygame:limbus-company", mine);
+    expect(meta.name).toBe("Limbus Company");
+    expect(meta.hue).toBe("#C74B50");
+    // Nothing to credit in the colophon and no routine we could name for them.
+    expect(meta.studio).toBe("");
+    expect(meta.dailyTasks).toBe("");
+  });
+
+  test("is total, so a lane that outlived its game cannot blank the page", () => {
+    // An import can carry an event whose game did not come with it.
+    const meta = metaFor("mygame:deleted", mine);
+    expect(meta.name).toBe("Unknown game");
+    expect(meta.hue).toMatch(/^#[0-9A-Fa-f]{6}$/);
+  });
+
+  test("shortens a long name rather than overflowing a chip", () => {
+    const long: CustomGames = {
+      "mygame:x": { id: "mygame:x", name: "Chaos Zero Nightmare", hue: "#123456", at: AT },
+    };
+    expect(metaFor("mygame:x", long).short.length).toBeLessThanOrEqual(12);
+  });
+});
+
+describe("knownLane", () => {
+  test("a tracked lane is always known; a reader's lane must still exist", () => {
+    const mine: CustomGames = {
+      "mygame:a": { id: "mygame:a", name: "A", hue: "#123456", at: AT },
+    };
+    expect(knownLane("genshin", mine)).toBe(true);
+    expect(knownLane("mygame:a", mine)).toBe(true);
+    expect(knownLane("mygame:gone", mine)).toBe(false);
+  });
+});