diff --git a/src/json-crdt-extensions/peritext/__tests__/setup.ts b/src/json-crdt-extensions/peritext/__tests__/setup.ts
index 267e8f91a2..7a2e2832f1 100644
--- a/src/json-crdt-extensions/peritext/__tests__/setup.ts
+++ b/src/json-crdt-extensions/peritext/__tests__/setup.ts
@@ -14,8 +14,9 @@ const schema = (text: string) =>
 export const setupKit = (
   initialText: string = '',
   edits: (model: Model<SchemaToJsonNode<Schema>>) => void = () => {},
+  sid?: number,
 ) => {
-  const model = ModelWithExt.create(schema(initialText));
+  const model = ModelWithExt.create(schema(initialText), sid);
   edits(model);
   const api = model.api;
   const peritextApi = model.s.text.toExt();
@@ -65,35 +66,40 @@ export const setupNumbersKit = (): Kit => {
  * Creates a Peritext instance with text "0123456789", with single-char and
  * block-wise chunks, as well as with plenty of tombstones.
  */
-export const setupNumbersWithTombstonesKit = (): Kit => {
-  return setupKit('1234', (model) => {
-    const str = model.s.text.toExt().text();
-    str.ins(0, '234');
-    str.ins(1, '234');
-    str.ins(2, '345');
-    str.ins(3, '456');
-    str.ins(4, '567');
-    str.ins(5, '678');
-    str.ins(6, '789');
-    str.del(7, 1);
-    str.del(8, 1);
-    str.ins(0, '0');
-    str.del(1, 4);
-    str.del(2, 1);
-    str.ins(1, '1');
-    str.del(0, 1);
-    str.ins(0, '0');
-    str.ins(2, '234');
-    str.del(4, 7);
-    str.del(4, 2);
-    str.del(7, 3);
-    str.ins(6, '6789');
-    str.del(7, 2);
-    str.ins(7, '78');
-    str.del(10, 2);
-    str.del(2, 3);
-    str.ins(2, '234');
-    str.del(10, 3);
-    if (str.view() !== '0123456789') throw new Error('Invalid text');
-  });
+export const setupNumbersWithTombstonesKit = (sid?: number): Kit => {
+  return setupKit(
+    '1234',
+    (model) => {
+      const str = model.s.text.toExt().text();
+      str.ins(0, '234');
+      str.ins(1, '234');
+      str.ins(2, '345');
+      str.ins(3, '456');
+      str.ins(4, '567');
+      str.ins(5, '678');
+      str.ins(6, '789');
+      str.del(7, 1);
+      str.del(8, 1);
+      str.ins(0, '0');
+      str.del(1, 4);
+      str.del(2, 1);
+      str.ins(1, '1');
+      str.del(0, 1);
+      str.ins(0, '0');
+      str.ins(2, '234');
+      str.del(4, 7);
+      str.del(4, 2);
+      str.del(7, 3);
+      str.ins(6, '6789');
+      str.del(7, 2);
+      str.ins(7, '78');
+      str.del(10, 2);
+      str.del(2, 3);
+      str.ins(2, 'x234');
+      str.del(2, 1);
+      str.del(10, 3);
+      if (str.view() !== '0123456789') throw new Error('Invalid text');
+    },
+    sid,
+  );
 };
diff --git a/src/json-crdt-extensions/peritext/block/Inline.ts b/src/json-crdt-extensions/peritext/block/Inline.ts
new file mode 100644
index 0000000000..3296e99238
--- /dev/null
+++ b/src/json-crdt-extensions/peritext/block/Inline.ts
@@ -0,0 +1,152 @@
+import {printTree} from 'tree-dump/lib/printTree';
+import {OverlayPoint} from '../overlay/OverlayPoint';
+import {stringify} from '../../../json-text/stringify';
+import {SliceBehavior} from '../slice/constants';
+import {Range} from '../rga/Range';
+import {ChunkSlice} from '../util/ChunkSlice';
+import {updateNum} from '../../../json-hash';
+import type {AbstractRga} from '../../../json-crdt/nodes/rga';
+import type {Printable} from 'tree-dump/lib/types';
+import type {PathStep} from '../../../json-pointer';
+import type {Slice} from '../slice/types';
+import type {Peritext} from '../Peritext';
+
+export type InlineAttributes = Record<string | number, unknown>;
+
+/**
+ * The `Inline` class represents a range of inline text within a block, which
+ * has the same annotations and formatting for all of its text contents, i.e.
+ * its text contents can be rendered as a single (`<span>`) element. However,
+ * the text contents might still be composed of multiple {@link ChunkSlice}s,
+ * which are the smallest units of text and need to be concatenated to get the
+ * full text content of the inline.
+ */
+export class Inline extends Range implements Printable {
+  public static create(txt: Peritext, start: OverlayPoint, end: OverlayPoint) {
+    const texts: ChunkSlice[] = [];
+    txt.overlay.chunkSlices0(undefined, start, end, (chunk, off, len) => {
+      if (txt.overlay.isMarker(chunk.id)) return;
+      texts.push(new ChunkSlice(chunk, off, len));
+    });
+    return new Inline(txt.str, start, end, texts);
+  }
+
+  constructor(
+    rga: AbstractRga<string>,
+    public start: OverlayPoint,
+    public end: OverlayPoint,
+
+    /**
+     * @todo PERF: for performance reasons, we should consider not passing in
+     * this array. Maybe pass in just the initial chunk and the offset. However,
+     * maybe even the just is not necessary, as the `.start` point should have
+     * its chunk cached, or will have it cached after the first access.
+     */
+    public readonly texts: ChunkSlice[],
+  ) {
+    super(rga, start, end);
+  }
+
+  /**
+   * @returns A stable unique identifier of this *inline* within a list of other
+   *     inlines of the parent block. Can be used for UI libraries to track the
+   *     identity of the inline across renders.
+   */
+  public key(): number {
+    return updateNum(this.start.refresh(), this.end.refresh());
+  }
+
+  /**
+   * @returns The full text content of the inline, which is the concatenation
+   *     of all the underlying {@link ChunkSlice}s.
+   */
+  public str(): string {
+    let str = '';
+    for (const slice of this.texts) str += slice.view();
+    return str;
+  }
+
+  /**
+   * @returns The position of the inline withing the text.
+   */
+  public pos(): number {
+    const chunkSlice = this.texts[0];
+    if (!chunkSlice) return -1;
+    const chunk = chunkSlice.chunk;
+    const pos = this.rga.pos(chunk);
+    return pos + chunkSlice.off;
+  }
+
+  /**
+   * @returns Returns the attributes of the inline, which are the slice
+   *     annotations and formatting applied to the inline.
+   */
+  public attr(): InlineAttributes {
+    const attr: InlineAttributes = {};
+    const point = this.start as OverlayPoint;
+    const slices: Slice[] = this.texts.length ? point.layers : point.markers;
+    const length = slices.length;
+    for (let i = 0; i < length; i++) {
+      const slice = slices[i];
+      const type = slice.type as PathStep;
+      switch (slice.behavior) {
+        case SliceBehavior.Cursor:
+        case SliceBehavior.Stack: {
+          let dataList: unknown[] = (attr[type] as unknown[]) || (attr[type] = []);
+          if (!Array.isArray(dataList)) dataList = attr[type] = [dataList];
+          let data = slice.data();
+          if (data === undefined) data = 1;
+          dataList.push(data);
+          break;
+        }
+        case SliceBehavior.Overwrite: {
+          let data = slice.data();
+          if (data === undefined) data = 1;
+          attr[type] = data;
+          break;
+        }
+        case SliceBehavior.Erase: {
+          delete attr[type];
+          break;
+        }
+      }
+    }
+    // TODO: Iterate over the markers...
+    return attr;
+  }
+
+  // ---------------------------------------------------------------- Printable
+
+  public toString(tab: string = ''): string {
+    const str = this.str();
+    const truncate = str.length > 32;
+    const text = JSON.stringify(truncate ? str.slice(0, 32) : str) + (truncate ? ' …' : '');
+    const startFormatted = this.start.toString(tab, true);
+    const range =
+      this.start.cmp(this.end) === 0 ? startFormatted : `${startFormatted} ↔ ${this.end.toString(tab, true)}`;
+    const header = `${this.constructor.name} ${range} ${text}`;
+    const marks = this.attr();
+    const markKeys = Object.keys(marks);
+    return (
+      header +
+      printTree(tab, [
+        !marks
+          ? null
+          : (tab) =>
+              'attributes' +
+              printTree(
+                tab,
+                markKeys.map((key) => () => key + ' = ' + stringify(marks[key])),
+              ),
+        !this.texts.length
+          ? null
+          : (tab) =>
+              'texts' +
+              printTree(
+                tab,
+                this.texts.map((text) => (tab) => text.toString(tab)),
+              ),
+      ])
+    );
+  }
+}
diff --git a/src/json-crdt-extensions/peritext/block/__tests__/Inline.key.spec.ts b/src/json-crdt-extensions/peritext/block/__tests__/Inline.key.spec.ts
new file mode 100644
index 0000000000..d4b6dcf7ca
--- /dev/null
+++ b/src/json-crdt-extensions/peritext/block/__tests__/Inline.key.spec.ts
@@ -0,0 +1,98 @@
+import {Timestamp} from '../../../../json-crdt-patch';
+import {updateId} from '../../../../json-crdt/hash';
+import {updateNum} from '../../../../json-hash';
+import {Kit, setupKit, setupNumbersKit, setupNumbersWithTombstonesKit} from '../../__tests__/setup';
+import {Point} from '../../rga/Point';
+import {Inline} from '../Inline';
+
+describe('range hash', () => {
+  test('computes unique hash - 1', () => {
+    const {peritext} = setupKit();
+    const p1 = new Point(peritext.str, new Timestamp(12313123, 41), 0);
+    const p2 = new Point(peritext.str, new Timestamp(12313123, 41), 1);
+    const p3 = new Point(peritext.str, new Timestamp(12313123, 43), 0);
+    const p4 = new Point(peritext.str, new Timestamp(12313123, 43), 1);
+    const hash1 = updateNum(p1.refresh(), p2.refresh());
+    const hash2 = updateNum(p3.refresh(), p4.refresh());
+    expect(hash1).not.toBe(hash2);
+  });
+
+  test('computes unique hash - 2', () => {
+    const {peritext} = setupKit();
+    const p1 = new Point(peritext.str, new Timestamp(12313123, 61), 0);
+    const p2 = new Point(peritext.str, new Timestamp(12313123, 23), 1);
+    const p3 = new Point(peritext.str, new Timestamp(12313123, 60), 0);
+    const p4 = new Point(peritext.str, new Timestamp(12313123, 56), 1);
+    const hash1 = updateNum(p1.refresh(), p2.refresh());
+    const hash2 = updateNum(p3.refresh(), p4.refresh());
+    expect(hash1).not.toBe(hash2);
+  });
+
+  test('computes unique hash - 3', () => {
+    const {peritext} = setupKit();
+    const p1 = new Point(peritext.str, new Timestamp(12313123, 43), 0);
+    const p2 = new Point(peritext.str, new Timestamp(12313123, 61), 1);
+    const p3 = new Point(peritext.str, new Timestamp(12313123, 43), 0);
+    const p4 = new Point(peritext.str, new Timestamp(12313123, 60), 1);
+    const hash1 = updateNum(p1.refresh(), p2.refresh());
+    const hash2 = updateNum(p3.refresh(), p4.refresh());
+    expect(hash1).not.toBe(hash2);
+  });
+
+  test('computes unique hash - 4', () => {
+    const hash1 = updateNum(updateId(0, new Timestamp(2, 7)), updateId(1, new Timestamp(2, 7)));
+    const hash2 = updateNum(updateId(0, new Timestamp(2, 6)), updateId(1, new Timestamp(2, 40)));
+    expect(hash1).not.toBe(hash2);
+  });
+});
+
+const runKeyTests = (setup: () => Kit) => {
+  describe('.key()', () => {
+    test('construct unique keys for all ranges', () => {
+      const {peritext} = setup();
+      const overlay = peritext.overlay;
+      const length = peritext.strApi().length();
+      const keys = new Map<number | string, Inline>();
+      let cnt = 0;
+      for (let i = 0; i < length; i++) {
+        for (let j = 1; j <= length - i; j++) {
+          peritext.editor.cursor.setAt(i, j);
+          overlay.refresh();
+          const [start, end] = [...overlay.points()];
+          const inline = Inline.create(peritext, start, end);
+          if (keys.has(inline.key())) {
+            const inline2 = keys.get(inline.key())!;
+            // tslint:disable-next-line:no-console
+            console.error('DUPLICATE HASH:', inline.key());
+            // tslint:disable-next-line:no-console
+            console.log('INLINE 1:', inline.start.id, inline.start.anchor, inline.end.id, inline.end.anchor);
+            // tslint:disable-next-line:no-console
+            console.log('INLINE 2:', inline2.start.id, inline2.start.anchor, inline2.end.id, inline2.end.anchor);
+            throw new Error('Duplicate key');
+          }
+          keys.set(inline.key(), inline);
+          cnt++;
+        }
+      }
+      expect(keys.size).toBe(cnt);
+    });
+  });
+};
+
+describe('Inline', () => {
+  describe('lorem ipsum', () => {
+    runKeyTests(() => setupKit('lorem ipsum dolor sit amet consectetur adipiscing elit'));
+  });
+
+  describe('numbers "0123456789", no edits', () => {
+    runKeyTests(setupNumbersKit);
+  });
+
+  describe('numbers "0123456789", with default schema and tombstones', () => {
+    runKeyTests(setupNumbersWithTombstonesKit);
+  });
+
+  describe('numbers "0123456789", with default schema and tombstones and constant sid', () => {
+    runKeyTests(() => setupNumbersWithTombstonesKit(12313123));
+  });
+});
diff --git a/src/json-crdt-extensions/peritext/block/__tests__/Inline.str.spec.ts b/src/json-crdt-extensions/peritext/block/__tests__/Inline.str.spec.ts
new file mode 100644
index 0000000000..62ee4f634f
--- /dev/null
+++ b/src/json-crdt-extensions/peritext/block/__tests__/Inline.str.spec.ts
@@ -0,0 +1,124 @@
+import {Kit, setupKit, setupNumbersKit, setupNumbersWithTombstonesKit} from '../../__tests__/setup';
+import {Inline} from '../Inline';
+
+const runStrTests = (setup: () => Kit) => {
+  describe('.str()', () => {
+    test('concatenates parts of Inline correctly', () => {
+      const {peritext} = setup();
+      const overlay = peritext.overlay;
+      const length = peritext.strApi().length();
+      for (let i = 0; i < length; i++) {
+        for (let j = 1; j <= length - i; j++) {
+          peritext.editor.cursor.setAt(i, j);
+          overlay.refresh();
+          const [start, end] = [...overlay.points()];
+          const inline = Inline.create(peritext, start, end);
+          const str = inline.str();
+          expect(str).toBe(
+            peritext
+              .strApi()
+              .view()
+              .slice(i, i + j),
+          );
+        }
+      }
+    });
+  });
+
+  describe('.pos()', () => {
+    test('returns correct offset in text', () => {
+      const {peritext} = setup();
+      const overlay = peritext.overlay;
+      const length = peritext.strApi().length();
+      for (let i = 0; i < length; i++) {
+        for (let j = 1; j <= length - i; j++) {
+          peritext.editor.cursor.setAt(i, j);
+          overlay.refresh();
+          const [start, end] = [...overlay.points()];
+          const inline = Inline.create(peritext, start, end);
+          const pos = inline.pos();
+          expect(pos).toBe(i);
+        }
+      }
+    });
+  });
+
+  describe('.attr()', () => {
+    test('returns all STACK annotations of a slice', () => {
+      const {peritext} = setup();
+      const overlay = peritext.overlay;
+      peritext.editor.cursor.setAt(3, 3);
+      peritext.editor.saved.insStack('bold', 1);
+      peritext.editor.saved.insStack('bold', 2);
+      peritext.editor.saved.insStack('em', 1);
+      overlay.refresh();
+      const [start, end] = [...overlay.points()];
+      const inline = Inline.create(peritext, start, end);
+      const attr = inline.attr();
+      expect(attr.bold).toEqual([1, 2]);
+      expect(attr.em).toEqual([1]);
+    });
+
+    test('returns latest OVERWRITE annotation', () => {
+      const {peritext} = setup();
+      const overlay = peritext.overlay;
+      peritext.editor.cursor.setAt(3, 3);
+      peritext.editor.saved.insOverwrite('bold', 1);
+      peritext.editor.saved.insOverwrite('bold', 2);
+      peritext.editor.saved.insOverwrite('em', 1);
+      overlay.refresh();
+      const [start, end] = [...overlay.points()];
+      const inline = Inline.create(peritext, start, end);
+      const attr = inline.attr();
+      expect(attr.bold).toBe(2);
+      expect(attr.em).toBe(1);
+    });
+
+    test('hides annotation hidden with another ERASE annotation', () => {
+      const {peritext} = setup();
+      const overlay = peritext.overlay;
+      peritext.editor.cursor.setAt(3, 3);
+      peritext.editor.saved.insOverwrite('bold');
+      peritext.editor.saved.insErase('bold');
+      peritext.editor.saved.insOverwrite('em');
+      overlay.refresh();
+      const [start, end] = [...overlay.points()];
+      const inline = Inline.create(peritext, start, end);
+      const attr = inline.attr();
+      expect(attr.bold).toBe(undefined);
+      expect(attr.em).toBe(1);
+    });
+
+    test('concatenates with "," steps of nested Path type annotations', () => {
+      const {peritext} = setup();
+      const overlay = peritext.overlay;
+      peritext.editor.cursor.setAt(3, 3);
+      peritext.editor.saved.insStack(['bold', 'very'], 1);
+      peritext.editor.saved.insStack(['bold', 'normal'], 2);
+      overlay.refresh();
+      const [start, end] = [...overlay.points()];
+      const inline = Inline.create(peritext, start, end);
+      const attr = inline.attr();
+      expect(attr['bold,very']).toEqual([1]);
+      expect(attr['bold,normal']).toEqual([2]);
+    });
+  });
+};
+
+describe('Inline', () => {
+  describe('lorem ipsum', () => {
+    runStrTests(() => setupKit('lorem ipsum dolor sit amet'));
+  });
+
+  describe('numbers "0123456789", no edits', () => {
+    runStrTests(setupNumbersKit);
+  });
+
+  describe('numbers "0123456789", with default schema and tombstones', () => {
+    runStrTests(setupNumbersWithTombstonesKit);
+  });
+
+  describe('numbers "0123456789", with default schema and tombstones and constant sid', () => {
+    runStrTests(() => setupNumbersWithTombstonesKit(12313123));
+  });
+});
diff --git a/src/json-crdt-extensions/peritext/rga/Point.ts b/src/json-crdt-extensions/peritext/rga/Point.ts
index 9e5edf94e4..03d61dcd97 100644
--- a/src/json-crdt-extensions/peritext/rga/Point.ts
+++ b/src/json-crdt-extensions/peritext/rga/Point.ts
@@ -6,6 +6,7 @@ import {Position} from '../constants';
 import type {AbstractRga, Chunk} from '../../../json-crdt/nodes/rga';
 import type {Stateful} from '../types';
 import type {Printable} from 'tree-dump/lib/types';
+import {CONST, updateNum} from '../../../json-hash';
 
 /**
  * A "point" in a rich-text Peritext document. It is a combination of a
@@ -443,9 +444,7 @@ export class Point<T = string> implements Pick<Stateful, 'refresh'>, Printable {
   // ----------------------------------------------------------------- Stateful
 
   public refresh(): number {
-    let state = this.anchor;
-    state = updateId(state, this.id);
-    return state;
+    return updateId(this.anchor, this.id);
   }
 
   // ---------------------------------------------------------------- Printable
diff --git a/src/json-crdt/hash.ts b/src/json-crdt/hash.ts
index 8d998ecbc8..e16bdbd747 100644
--- a/src/json-crdt/hash.ts
+++ b/src/json-crdt/hash.ts
@@ -7,10 +7,9 @@ import type {ITimestampStruct} from '../json-crdt-patch/clock';
 import type {Model} from './model';
 
 export const updateId = (state: number, id: ITimestampStruct): number => {
-  const sid = id.sid;
-  state = updateNum(state, sid >>> 0);
-  // state = updateNum(state, Math.round(sid / 0x100000000));
-  state = updateNum(state, id.time);
+  const time = id.time;
+  state = updateNum(state, state ^ time);
+  state = updateNum(state, id.sid ^ time);
   return state;
 };