diff --git a/src/testing/lemmyv1/builders.ts b/src/testing/lemmyv1/builders.ts
index 3470288..207e6e3 100644
--- a/src/testing/lemmyv1/builders.ts
+++ b/src/testing/lemmyv1/builders.ts
@@ -92,10 +92,11 @@ export function createLemmyV1Builders({
     return { downvotes, score: upvotes - downvotes, upvotes };
   }
 
-  // v1 conveys the logged-in user's vote/save via *_actions; absent (`{}`)
-  // when there's no interaction.
-  function actions(myVote: -1 | 0 | 1, saved: boolean) {
+  // v1 conveys the logged-in user's vote/save/read via *_actions; absent
+  // (`{}`) when there's no interaction.
+  function actions(myVote: -1 | 0 | 1, saved: boolean, read = false) {
     return {
+      read_at: read ? now : undefined,
       saved_at: saved ? now : undefined,
       vote_is_upvote: myVote === 0 ? undefined : myVote === 1,
       voted_at: myVote === 0 ? undefined : now,
@@ -147,6 +148,7 @@ export function createLemmyV1Builders({
     id: number;
     myVote?: -1 | 0 | 1;
     name: string;
+    read?: boolean;
     saved?: boolean;
     score?: number;
     url?: string;
@@ -162,7 +164,11 @@ export function createLemmyV1Builders({
       creator_is_admin: false,
       creator_is_moderator: false,
       post: post({ ...over, community: resolvedCommunity }),
-      post_actions: actions(over.myVote ?? 0, over.saved ?? false),
+      post_actions: actions(
+        over.myVote ?? 0,
+        over.saved ?? false,
+        over.read ?? false,
+      ),
       tags: [],
     };
   }
diff --git a/src/testing/lemmyv1/index.ts b/src/testing/lemmyv1/index.ts
index 9d72c7b..581e9a8 100644
--- a/src/testing/lemmyv1/index.ts
+++ b/src/testing/lemmyv1/index.ts
@@ -6,7 +6,7 @@ import {
   OperationDef,
   RecordedCall,
 } from "../FakeInstance";
-import { depthOf, paginateByCursor } from "../pagination";
+import { CursorTokens, depthOf, paginateByCursor } from "../pagination";
 import { searchSeed, SeedSearchType } from "../search";
 import {
   SeedComment,
@@ -283,6 +283,7 @@ export class FakeLemmyV1Instance extends FakeInstance {
         id: subject.id,
         myVote: subject.myVote,
         name: subject.name,
+        read: subject.read,
         saved: subject.saved,
         score: subject.score,
         url: subject.url,
@@ -322,12 +323,17 @@ export class FakeLemmyV1Instance extends FakeInstance {
           });
 
     // v1 pages with opaque cursors the server round-trips
+    const cursors = new CursorTokens();
     const pageOf = <T>(items: T[], call: RecordedCall) => {
       const limit = call.query.get("limit");
-      return paginateByCursor(items, {
-        cursor: call.query.get("page_cursor") ?? undefined,
-        limit: limit === null ? undefined : Number(limit),
-      });
+      return paginateByCursor(
+        items,
+        {
+          cursor: call.query.get("page_cursor") ?? undefined,
+          limit: limit === null ? undefined : Number(limit),
+        },
+        cursors,
+      );
     };
     const pagedFrom = <T, W>(
       items: T[],
@@ -508,9 +514,14 @@ export class FakeLemmyV1Instance extends FakeInstance {
       return { json: pagedFrom(notifications, call, notificationView) };
     });
 
-    // Fire-and-forget side effect of many logged-in interactions
-    this.mock("POST /api/v4/post/mark_as_read/many", {
-      json: { success: true },
+    this.mock("POST /api/v4/post/mark_as_read/many", (call) => {
+      const { post_ids, read } = call.body as {
+        post_ids: number[];
+        read: boolean;
+      };
+      for (const post of seed.posts)
+        if (post_ids.includes(post.id)) post.read = read;
+      return { json: { success: true } };
     });
 
     // Vote/save writes mutate the seed store, so the returned view — and
diff --git a/src/testing/pagination.ts b/src/testing/pagination.ts
index 1fa38b7..1a8b1e1 100644
--- a/src/testing/pagination.ts
+++ b/src/testing/pagination.ts
@@ -14,15 +14,41 @@
  * fails to advance, so a consumer's paging loop can't spin forever.
  */
 
-/** Prefix marks fake cursors as opaque: nothing should parse them */
-const CURSOR_PREFIX = "seed-offset:";
-
 export interface Page<T> {
   items: T[];
   /** Wire `next_page` value; absent when the last page was served */
   nextPage?: string;
 }
 
+/**
+ * Hands out cursors a client cannot derive.
+ *
+ * A cursor that encodes its own offset (`offset:40`) lets a buggy consumer
+ * fabricate the next one and still page correctly, so tests can't tell
+ * "echoes the server's cursor" from "invents one". Tokens here are opaque
+ * counter values resolved through this map — echoing what the server sent
+ * is the only way to advance. Counter, not random, so runs stay
+ * reproducible.
+ */
+export class CursorTokens {
+  #next = 1;
+
+  #offsets = new Map<string, number>();
+
+  /** Mint a cursor pointing at `offset` */
+  issue(offset: number): string {
+    const token = `seed-cursor-${this.#next++}`;
+    this.#offsets.set(token, offset);
+    return token;
+  }
+
+  /** The offset a cursor refers to; unknown cursors start from the top */
+  offsetOf(cursor: string | undefined): number {
+    if (cursor === undefined) return 0;
+    return this.#offsets.get(cursor) ?? 0;
+  }
+}
+
 /**
  * Depth of a comment from its materialized path (`0.24.27` → 2); top-level
  * comments are depth 1.
@@ -37,24 +63,19 @@ export function depthOf(path: string): number {
 export function paginateByCursor<T>(
   items: T[],
   { cursor, limit }: { cursor?: string; limit?: number },
+  tokens: CursorTokens,
 ): Page<T> {
-  const offset = cursor?.startsWith(CURSOR_PREFIX)
-    ? Number(cursor.slice(CURSOR_PREFIX.length))
-    : 0;
+  const offset = tokens.offsetOf(cursor);
   const end = limit === undefined ? items.length : offset + limit;
   const page = items.slice(offset, end);
 
-  return {
-    items: page,
-    // Real Lemmy hands out a cursor whenever it filled the page — so the
-    // last full page is followed by an empty one, and consumers that stop
-    // on "no cursor" are exercised properly. `limit > 0` keeps a
-    // degenerate limit from emitting a cursor that never advances.
-    nextPage:
-      limit !== undefined && limit > 0 && page.length === limit
-        ? `${CURSOR_PREFIX}${end}`
-        : undefined,
-  };
+  // Real Lemmy hands out a cursor whenever it filled the page — so the last
+  // full page is followed by an empty one, and consumers that stop on "no
+  // cursor" are exercised properly. `limit > 0` keeps a degenerate limit
+  // from emitting a cursor that never advances.
+  const hasMore = limit !== undefined && limit > 0 && page.length === limit;
+
+  return { items: page, nextPage: hasMore ? tokens.issue(end) : undefined };
 }
 
 /**
diff --git a/src/testing/piefed/builders.ts b/src/testing/piefed/builders.ts
index 38a4620..df74092 100644
--- a/src/testing/piefed/builders.ts
+++ b/src/testing/piefed/builders.ts
@@ -141,6 +141,7 @@ export function createPiefedBuilders({
     deleted?: boolean;
     id: number;
     myVote?: -1 | 0 | 1;
+    read?: boolean;
     saved?: boolean;
     score?: number;
     title: string;
@@ -167,7 +168,7 @@ export function createPiefedBuilders({
       hidden: false,
       my_vote: myVote,
       post: post({ ...over, community: resolvedCommunity }),
-      read: false,
+      read: over.read ?? false,
       saved: over.saved ?? false,
       subscribed: "NotSubscribed",
       unread_comments: 0,
diff --git a/src/testing/piefed/index.ts b/src/testing/piefed/index.ts
index 8d92d73..2e8fc08 100644
--- a/src/testing/piefed/index.ts
+++ b/src/testing/piefed/index.ts
@@ -326,6 +326,7 @@ export class FakePiefedInstance extends FakeInstance {
         deleted: subject.deleted,
         id: subject.id,
         myVote: subject.myVote,
+        read: subject.read,
         saved: subject.saved,
         score: subject.score,
         title: subject.name,
@@ -557,6 +558,39 @@ export class FakePiefedInstance extends FakeInstance {
       };
     });
 
+    this.mock("GET /api/alpha/community/list", (call) => {
+      const { items, nextPage } = pageOf(seed.communities, call);
+      return {
+        json: {
+          communities: items.map((subject) =>
+            build.communityView({ community: community(subject) }),
+          ),
+          next_page: nextPage ?? null,
+        },
+      };
+    });
+
+    // Real PieFed serves this; the lemmyv1 adapter throws UnsupportedError
+    // before requesting, so only the piefed fake needs it
+    this.mock("GET /api/alpha/federated_instances", () => ({
+      json: { federated_instances: { allowed: [], blocked: [], linked: [] } },
+    }));
+
+    // Fire-and-forget on the app side, but a real server answers it — an
+    // unmocked 404 here made the shared mark-read spec vacuous on piefed
+    this.mock("POST /api/alpha/post/mark_as_read", (call) => {
+      // PieFed accepts either a single post_id or a post_ids array
+      const { post_id, post_ids, read } = call.body as {
+        post_id?: number;
+        post_ids?: number[];
+        read: boolean;
+      };
+      const ids = post_ids ?? (post_id === undefined ? [] : [post_id]);
+      for (const post of seed.posts)
+        if (ids.includes(post.id)) post.read = read;
+      return { json: { success: true } };
+    });
+
     this.mock("GET /api/alpha/search", (call) => {
       // PieFed capitalizes search types on the wire
       const wireType = call.query.get("type_");
diff --git a/src/testing/seed.ts b/src/testing/seed.ts
index b3f889f..461581d 100644
--- a/src/testing/seed.ts
+++ b/src/testing/seed.ts
@@ -70,6 +70,8 @@ export interface SeedPost {
   /** The logged-in user's vote (mutated by like writes) */
   myVote: -1 | 0 | 1;
   name: string;
+  /** Read by the logged-in user (mutated by mark-as-read writes) */
+  read: boolean;
   /** Saved by the logged-in user (mutated by save writes) */
   saved: boolean;
   /** Base score at `myVote` 0; the logged-in user's vote is added on top */
@@ -219,6 +221,7 @@ export class SeedStore {
     id?: number;
     myVote?: -1 | 0 | 1;
     name: string;
+    read?: boolean;
     saved?: boolean;
     score?: number;
     url?: string;
@@ -231,6 +234,7 @@ export class SeedStore {
       id: over.id ?? this.#nextId++,
       myVote: over.myVote ?? 0,
       name: over.name,
+      read: over.read ?? false,
       saved: over.saved ?? false,
       score: over.score ?? 1,
       url: over.url,
diff --git a/test/testing-seed-matrix.test.ts b/test/testing-seed-matrix.test.ts
index eeedf90..2180591 100644
--- a/test/testing-seed-matrix.test.ts
+++ b/test/testing-seed-matrix.test.ts
@@ -271,6 +271,17 @@ describe.each([
     expect(third.next_page).toBeUndefined();
   });
 
+  it("marks posts read, and later reads reflect it", async () => {
+    const { client, fake, post } = setup();
+    fake.seed.loggedInAs(fake.seed.person({ name: "me" }));
+
+    expect((await client.getPost({ id: post.id })).post_view.read).toBe(false);
+
+    await client.markPostAsRead({ post_ids: [post.id], read: true });
+
+    expect((await client.getPost({ id: post.id })).post_view.read).toBe(true);
+  });
+
   it("serves a trailing empty page when the last page was full", async () => {
     const { client, fake } = setup();
 
@@ -509,6 +520,33 @@ describe.each([
   });
 });
 
+describe("lemmyv1 cursors", () => {
+  it("hands out cursors a consumer cannot derive", async () => {
+    // Real Lemmy cursors are opaque tokens. If the fake's encoded its own
+    // offset, a consumer that ignored the server's cursor and computed one
+    // would still page correctly — and its tests would pass. (PieFed is
+    // exempt: page numbers genuinely are its API.)
+    const fake = new FakeLemmyV1Instance();
+    const alex = fake.seed.person({ name: "alex" });
+    for (const index of [1, 2, 3, 4])
+      fake.seed.post({ creator: alex, id: index, name: `Post ${index}` });
+
+    const client = new ThreadiverseClient(fake.origin, fake.clientOptions());
+
+    const first = await client.getPosts({ limit: 2 });
+    expect(String(first.next_page)).not.toContain("2");
+
+    const second = await client.getPosts({
+      limit: 2,
+      page_cursor: first.next_page,
+    });
+    expect(second.data.map((view) => view.post.name)).toEqual([
+      "Post 3",
+      "Post 4",
+    ]);
+  });
+});
+
 describe("seeded notifications (lemmyv1)", () => {
   it("derives inbox endpoints from seeded notifications", async () => {
     const fake = new FakeLemmyV1Instance();