diff --git a/packages/runtime/id-compressor/.eslintrc.cjs b/packages/runtime/id-compressor/.eslintrc.cjs
index 0cfb8c689f85..7551e98ea5d1 100644
--- a/packages/runtime/id-compressor/.eslintrc.cjs
+++ b/packages/runtime/id-compressor/.eslintrc.cjs
@@ -4,10 +4,7 @@
  */
 
 module.exports = {
-	extends: [
-		require.resolve("@fluidframework/eslint-config-fluid/minimal-deprecated"),
-		"prettier",
-	],
+	extends: [require.resolve("@fluidframework/eslint-config-fluid/recommended"), "prettier"],
 	parserOptions: {
 		project: ["./tsconfig.json", "./src/test/tsconfig.json"],
 	},
diff --git a/packages/runtime/id-compressor/src/appendOnlySortedMap.ts b/packages/runtime/id-compressor/src/appendOnlySortedMap.ts
index 1ee13c3a72fa..d6740193de04 100644
--- a/packages/runtime/id-compressor/src/appendOnlySortedMap.ts
+++ b/packages/runtime/id-compressor/src/appendOnlySortedMap.ts
@@ -3,7 +3,6 @@
  * Licensed under the MIT License.
  */
 
-/* eslint-disable tsdoc/syntax */
 /* eslint-disable no-bitwise */
 import { assert } from "@fluidframework/core-utils/internal";
 
@@ -20,6 +19,7 @@ export class AppendOnlySortedMap<K, V> {
 	public constructor(protected readonly comparator: (a: K, b: K) => number) {}
 
 	/**
+	 * Gets the size of the map.
 	 * @returns the number of entries in this map
 	 */
 	public get size(): number {
@@ -27,6 +27,7 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
+	 * Gets the min key in the map.
 	 * @returns the min key in the map.
 	 */
 	public minKey(): K | undefined {
@@ -34,6 +35,7 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
+	 * Gets the max key in the map.
 	 * @returns the max key in the map.
 	 */
 	public maxKey(): K | undefined {
@@ -41,6 +43,7 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
+	 * Gets the min value in the map.
 	 * @returns the min value in the map.
 	 */
 	public minValue(): V | undefined {
@@ -48,14 +51,16 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
-	 * @returns the min value in the map.
+	 * Gets the max value in the map.
+	 * @returns the max value in the map.
 	 */
 	public maxValue(): V | undefined {
 		return this.elements[this.elements.length - 1] as V | undefined;
 	}
 
 	/**
-	 * @returns the min key in the map.
+	 * Gets the first key/value pair in the map.
+	 * @returns the first pair if it exists, or undefined otherwise.
 	 */
 	public first(): [K, V] | undefined {
 		const { elements } = this;
@@ -67,7 +72,8 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
-	 * @returns the max key in the map.
+	 * Gets the last key/value pair in the map.
+	 * @returns the last pair if it exists, or undefined otherwise.
 	 */
 	public last(): [K, V] | undefined {
 		const { elements } = this;
@@ -80,7 +86,9 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
-	 * Returns the element at the insertion index.
+	 * Gets the entry at the specified index.
+	 * @param index - the entry index
+	 * @returns the key/value pair if it exists, or undefined otherwise.
 	 */
 	public getAtIndex(index: number): [K, V] | undefined {
 		const realIndex = index * 2;
@@ -92,6 +100,7 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
+	 * Gets the entries in the map.
 	 * @returns an iterable of the entries in the map.
 	 */
 	public *entries(): IterableIterator<readonly [K, V]> {
@@ -102,6 +111,7 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
+	 * Gets the keys in the map.
 	 * @returns an iterable of the keys in the map.
 	 */
 	public *keys(): IterableIterator<K> {
@@ -112,6 +122,7 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
+	 * Gets the values in the map.
 	 * @returns an iterable of the values in the map.
 	 */
 	public *values(): IterableIterator<V> {
@@ -122,6 +133,7 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
+	 * Gets the entries in the map, reversed.
 	 * @returns an iterable of the entries in the map, reversed.
 	 */
 	public *entriesReversed(): IterableIterator<readonly [K, V]> {
@@ -132,9 +144,9 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
-	 * Adds a new key/value pair to the map. `key` must be > to all keys in the map.
-	 * @param key - the key to add.
-	 * @param value - the value to add.
+	 * Appends a new key/value pair at the end of the map. `key` must be greater than all other keys in the map.
+	 * @param key - the key to add
+	 * @param value - the value to add
 	 */
 	public append(key: K, value: V): void {
 		const { elements } = this;
@@ -142,15 +154,14 @@ export class AppendOnlySortedMap<K, V> {
 		if (length !== 0 && this.comparator(key, this.maxKey() as K) <= 0) {
 			throw new Error("Inserted key must be > all others in the map.");
 		}
-		elements.push(key);
-		elements.push(value);
+		elements.push(key, value);
 	}
 
 	/**
-	 * Replaces the last key/value pair with the given one. If the map is empty, it simply appends.
-	 * `key` must be > to all keys in the map prior to the one replaced.
-	 * @param key - the key to add.
-	 * @param value - the value to add.
+	 * Replaces the last key/value pair with a new one. If the map is empty, the new pair is appended.
+	 * 'key' must be greater than all other keys in the map.
+	 * @param key - the key to set
+	 * @param value - the value to set
 	 */
 	public replaceLast(key: K, value: V): void {
 		const { elements, comparator } = this;
@@ -162,13 +173,13 @@ export class AppendOnlySortedMap<K, V> {
 				throw new Error("Inserted key must be > all others in the map.");
 			}
 		}
-		elements.push(key);
-		elements.push(value);
+		elements.push(key, value);
 	}
 
 	/**
-	 * @param key - the key to lookup.
-	 * @returns the value associated with `key` if such an entry exists, and undefined otherwise.
+	 * Gets the value associated with a given key.
+	 * @param key - the key to lookup
+	 * @returns the value if it exists, or undefined otherwise.
 	 */
 	public get(key: K): V | undefined {
 		const index = AppendOnlySortedMap.keyIndexOf(this.elements, key, this.comparator);
@@ -179,15 +190,16 @@ export class AppendOnlySortedMap<K, V> {
 	}
 
 	/**
-	 * @param key - the key to lookup.
-	 * @returns the entry associated with `key` if such an entry exists, the entry associated with the next lower key if such an entry
-	 * exists, and undefined otherwise.
+	 * Gets the pair associated with the given key or the next smaller key.
+	 * @param key - the key to lookup
+	 * @returns the pair if it exists, or undefined otherwise.
 	 */
 	public getPairOrNextLower(key: K): readonly [K, V] | undefined {
 		return this.getPairOrNextLowerBy(key, this.comparator);
 	}
 
 	/**
+	 * Gets the pair associated with the given key or the next higher key.
 	 * @param key - the key to lookup.
 	 * @returns the entry associated with `key` if such an entry exists, the entry associated with the next higher key if such an entry
 	 * exists, and undefined otherwise.
@@ -293,6 +305,12 @@ export class AppendOnlySortedMap<K, V> {
 		return keyIndex;
 	}
 
+	/**
+	 * Gets the pair associated with the given key or next higher key.
+	 * @param search - the search value
+	 * @param comparator - a comparison function
+	 * @returns the pair if it exists, or undefined otherwise.
+	 */
 	protected getPairOrNextHigherBy<T>(
 		search: T,
 		comparator: (search: T, key: K, value: V) => number,
diff --git a/packages/runtime/id-compressor/src/finalSpace.ts b/packages/runtime/id-compressor/src/finalSpace.ts
index ad9b6d4a2b36..46b05687d079 100644
--- a/packages/runtime/id-compressor/src/finalSpace.ts
+++ b/packages/runtime/id-compressor/src/finalSpace.ts
@@ -29,7 +29,7 @@ export class FinalSpace {
 		return this.clusterList[this.clusterList.length - 1];
 	}
 
-	public addCluster(newCluster: IdCluster) {
+	public addCluster(newCluster: IdCluster): void {
 		const lastCluster = this.getLastCluster();
 		assert(
 			lastCluster === undefined ||
@@ -40,7 +40,7 @@ export class FinalSpace {
 	}
 
 	/**
-	 * @returns the upper bound (exclusive) of finalized IDs in final space, i.e. one greater than the last final ID in the last cluster.
+	 * Gets the upper bound (exclusive) of finalized IDs in final space, i.e. one greater than the last final ID in the last cluster.
 	 * Note: this does not include allocated but unfinalized space in clusters.
 	 */
 	public getFinalizedIdLimit(): FinalCompressedId {
@@ -51,7 +51,7 @@ export class FinalSpace {
 	}
 
 	/**
-	 * @returns the upper bound (exclusive) of allocated IDs in final space, i.e. one greater than the last final ID in the last cluster.
+	 * Gets the upper bound (exclusive) of allocated IDs in final space, i.e. one greater than the last final ID in the last cluster.
 	 * Note: this does includes all allocated IDs in clusters.
 	 */
 	public getAllocatedIdLimit(): FinalCompressedId {
@@ -62,8 +62,9 @@ export class FinalSpace {
 	}
 
 	public equals(other: FinalSpace): boolean {
-		for (const [index, value] of Object.entries(this.clusterList)) {
-			if (!clustersEqual(value, other.clusterList[index])) {
+		for (let i = 0; i < this.clusterList.length; i++) {
+			const cluster = this.clusterList[i] as IdCluster;
+			if (!clustersEqual(cluster, other.clusterList[i] as IdCluster)) {
 				return false;
 			}
 		}
diff --git a/packages/runtime/id-compressor/src/idCompressor.ts b/packages/runtime/id-compressor/src/idCompressor.ts
index a4c4ec146fb8..d38ae7452ed9 100644
--- a/packages/runtime/id-compressor/src/idCompressor.ts
+++ b/packages/runtime/id-compressor/src/idCompressor.ts
@@ -64,7 +64,7 @@ import {
  * The version of IdCompressor that is currently persisted.
  * This should not be changed without careful consideration to compatibility.
  */
-const currentWrittenVersion = 2.0;
+const currentWrittenVersion = 2;
 
 function rangeFinalizationError(expectedStart: number, actualStart: number): LoggingError {
 	return new LoggingError("Ranges finalized out of order", {
@@ -202,7 +202,7 @@ export class IdCompressor implements IIdCompressor, IIdCompressorCore {
 	/**
 	 * {@inheritdoc IIdCompressorCore.beginGhostSession}
 	 */
-	public beginGhostSession(ghostSessionId: SessionId, ghostSessionCallback: () => void) {
+	public beginGhostSession(ghostSessionId: SessionId, ghostSessionCallback: () => void): void {
 		this.startGhostSession(ghostSessionId);
 		try {
 			ghostSessionCallback();
@@ -554,7 +554,8 @@ export class IdCompressor implements IIdCompressor, IIdCompressorCore {
 			!this.ongoingGhostSession,
 			0x8a9 /* IdCompressor should not be operated normally when in a ghost session */,
 		);
-		const { normalizer, finalSpace, sessions } = this;
+		const { normalizer, finalSpace, sessions, localGenCount, logger, nextRangeBaseGenCount } =
+			this;
 		const sessionIndexMap = new Map<Session, number>();
 		let sessionIndex = 0;
 		for (const session of sessions.sessions()) {
@@ -568,7 +569,7 @@ export class IdCompressor implements IIdCompressor, IIdCompressorCore {
 			? 1 + // generated ID count
 				1 + // next range base genCount
 				1 + // count of normalizer pairs
-				this.normalizer.idRanges.size * 2 // pairs
+				normalizer.idRanges.size * 2 // pairs
 			: 0;
 		// Layout size, in 8 byte increments
 		const totalSize =
@@ -592,7 +593,7 @@ export class IdCompressor implements IIdCompressor, IIdCompressorCore {
 			index = writeNumericUuid(serializedUint, index, session.sessionUuid);
 		}
 
-		finalSpace.clusters.forEach((cluster) => {
+		for (const cluster of finalSpace.clusters) {
 			index = writeNumber(
 				serializedFloat,
 				index,
@@ -600,11 +601,11 @@ export class IdCompressor implements IIdCompressor, IIdCompressorCore {
 			);
 			index = writeNumber(serializedFloat, index, cluster.capacity);
 			index = writeNumber(serializedFloat, index, cluster.count);
-		});
+		}
 
 		if (hasLocalState) {
-			index = writeNumber(serializedFloat, index, this.localGenCount);
-			index = writeNumber(serializedFloat, index, this.nextRangeBaseGenCount);
+			index = writeNumber(serializedFloat, index, localGenCount);
+			index = writeNumber(serializedFloat, index, nextRangeBaseGenCount);
 			index = writeNumber(serializedFloat, index, normalizer.idRanges.size);
 			for (const [leadingGenCount, count] of normalizer.idRanges.entries()) {
 				index = writeNumber(serializedFloat, index, leadingGenCount);
@@ -613,7 +614,7 @@ export class IdCompressor implements IIdCompressor, IIdCompressorCore {
 		}
 
 		assert(index === totalSize, 0x75b /* Serialized size was incorrectly calculated. */);
-		this.logger?.sendTelemetryEvent({
+		logger?.sendTelemetryEvent({
 			eventName: "RuntimeIdCompressor:SerializedIdCompressorSize",
 			size: serializedFloat.byteLength,
 			clusterCount: finalSpace.clusters.length,
@@ -652,12 +653,15 @@ export class IdCompressor implements IIdCompressor, IIdCompressorCore {
 		};
 		const version = readNumber(index);
 		switch (version) {
-			case 1.0:
+			case 1: {
 				throw new Error("IdCompressor version 1.0 is no longer supported.");
-			case 2.0:
+			}
+			case 2: {
 				return IdCompressor.deserialize2_0(index, sessionId, logger);
-			default:
+			}
+			default: {
 				throw new Error("Unknown IdCompressor serialized version.");
+			}
 		}
 	}
 
@@ -673,17 +677,17 @@ export class IdCompressor implements IIdCompressor, IIdCompressorCore {
 		// Sessions
 		let sessionOffset = 0;
 		const sessions: [NumericUuid, Session][] = [];
-		if (!hasLocalState) {
+		if (hasLocalState) {
+			assert(
+				sessionId === undefined,
+				0x75e /* Local state should not exist in serialized form. */,
+			);
+		} else {
 			// If !hasLocalState, there won't be a serialized local session ID so insert one at the beginning
 			assert(sessionId !== undefined, 0x75d /* Local session ID is undefined. */);
 			const localSessionNumeric = numericUuidFromStableId(sessionId);
 			sessions.push([localSessionNumeric, new Session(localSessionNumeric)]);
 			sessionOffset = 1;
-		} else {
-			assert(
-				sessionId === undefined,
-				0x75e /* Local state should not exist in serialized form. */,
-			);
 		}
 
 		for (let i = 0; i < sessionCount; i++) {
diff --git a/packages/runtime/id-compressor/src/identifiers.ts b/packages/runtime/id-compressor/src/identifiers.ts
index d394c51b812d..791474b16468 100644
--- a/packages/runtime/id-compressor/src/identifiers.ts
+++ b/packages/runtime/id-compressor/src/identifiers.ts
@@ -26,7 +26,7 @@ export type LocalCompressedId = number & {
 } & SessionSpaceCompressedId; // Same brand as CompressedId, as local IDs are always locally normalized
 
 /**
- * @returns true if the supplied ID is a final ID.
+ * Returns true if the supplied ID is a final ID.
  */
 export function isFinalId(
 	id: SessionSpaceCompressedId | OpSpaceCompressedId,
diff --git a/packages/runtime/id-compressor/src/sessions.ts b/packages/runtime/id-compressor/src/sessions.ts
index 377178848381..11b4e72af46f 100644
--- a/packages/runtime/id-compressor/src/sessions.ts
+++ b/packages/runtime/id-compressor/src/sessions.ts
@@ -131,7 +131,7 @@ export class Sessions {
 	}
 
 	public equals(other: Sessions, includeLocalState: boolean): boolean {
-		const checkIsSubset = (sessionsA: Sessions, sessionsB: Sessions) => {
+		const checkIsSubset = (sessionsA: Sessions, sessionsB: Sessions): boolean => {
 			const first = sessionsA.sessions().next();
 			const firstSessionThis = first.done ? undefined : first.value;
 			for (const [stableId, session] of sessionsA.sessionCache.entries()) {
@@ -296,7 +296,7 @@ export class Session {
 
 	public equals(other: Session): boolean {
 		for (const [index, value] of Object.entries(this.clusterChain)) {
-			if (!clustersEqual(value, other.clusterChain[index])) {
+			if (!clustersEqual(value, other.clusterChain[index] as IdCluster)) {
 				return false;
 			}
 		}
diff --git a/packages/runtime/id-compressor/src/test/appendOnlySortedMap.perf.spec.ts b/packages/runtime/id-compressor/src/test/appendOnlySortedMap.perf.spec.ts
index 2d2c2f3bb4f9..6ab99312e652 100644
--- a/packages/runtime/id-compressor/src/test/appendOnlySortedMap.perf.spec.ts
+++ b/packages/runtime/id-compressor/src/test/appendOnlySortedMap.perf.spec.ts
@@ -9,13 +9,15 @@ import { BenchmarkType, benchmark } from "@fluid-tools/benchmark";
 import { AppendOnlySortedMap } from "../appendOnlySortedMap.js";
 import { compareFiniteNumbers } from "../utilities.js";
 
-function runAppendOnlyMapPerfTests(mapBuilder: () => AppendOnlySortedMap<number, number>) {
+function runAppendOnlyMapPerfTests(
+	mapBuilder: () => AppendOnlySortedMap<number, number>,
+): void {
 	const type = BenchmarkType.Measurement;
 	let map: AppendOnlySortedMap<number, number>;
 	let rand: IRandom;
 	const keyChoices: number[] = [];
 	let localChoice = 0;
-	const before = () => {
+	const before = (): void => {
 		rand = makeRandom(42);
 		map = mapBuilder();
 		let curKey = 0;
diff --git a/packages/runtime/id-compressor/src/test/appendOnlySortedMap.spec.ts b/packages/runtime/id-compressor/src/test/appendOnlySortedMap.spec.ts
index 2377322083bf..b5e2482d25b2 100644
--- a/packages/runtime/id-compressor/src/test/appendOnlySortedMap.spec.ts
+++ b/packages/runtime/id-compressor/src/test/appendOnlySortedMap.spec.ts
@@ -5,14 +5,15 @@
 
 /* eslint-disable no-bitwise */
 
-import { strict as assert } from "assert";
+// eslint-disable-next-line import/no-nodejs-modules
+import { strict as assert } from "node:assert";
 
 import { AppendOnlySortedMap } from "../appendOnlySortedMap.js";
 import { compareFiniteNumbers } from "../utilities.js";
 
 import { assertNotUndefined } from "./testCommon.js";
 
-function runAppendOnlyMapTests(mapBuilder: () => AppendOnlySortedMap<number, number>) {
+function runAppendOnlyMapTests(mapBuilder: () => AppendOnlySortedMap<number, number>): void {
 	it("detects out-of-order keys", () => {
 		const map = mapBuilder();
 		map.append(0, 0);
@@ -74,7 +75,7 @@ function runAppendOnlyMapTests(mapBuilder: () => AppendOnlySortedMap<number, num
 	});
 
 	it("can get an entry or next lower by key", () => {
-		[99, 100].forEach((elementCount) => {
+		for (const elementCount of [99, 100]) {
 			const map = mapBuilder();
 			for (let i = 0; i < elementCount; i++) {
 				map.append(i * 2, i * 2);
@@ -86,11 +87,11 @@ function runAppendOnlyMapTests(mapBuilder: () => AppendOnlySortedMap<number, num
 			}
 			const maxKey = assertNotUndefined(map.maxKey());
 			assert.deepEqual(map.getPairOrNextLower(maxKey + 1), [maxKey, maxKey]);
-		});
+		}
 	});
 
 	it("can get an entry or next higher by key", () => {
-		[99, 100].forEach((elementCount) => {
+		for (const elementCount of [99, 100]) {
 			const map = mapBuilder();
 			for (let i = 0; i < elementCount; i++) {
 				map.append(i * 2, i * 2);
@@ -102,7 +103,7 @@ function runAppendOnlyMapTests(mapBuilder: () => AppendOnlySortedMap<number, num
 				assert.deepEqual(map.getPairOrNextHigher(i * 2 + 1), [i * 2 + 2, i * 2 + 2]);
 			}
 			assert.equal(map.getPairOrNextHigher(map.size * 2 + 1), undefined);
-		});
+		}
 	});
 
 	it("knows how big it is", () => {
diff --git a/packages/runtime/id-compressor/src/test/idCompressor.perf.spec.ts b/packages/runtime/id-compressor/src/test/idCompressor.perf.spec.ts
index 2b786aaca646..79042e514e11 100644
--- a/packages/runtime/id-compressor/src/test/idCompressor.perf.spec.ts
+++ b/packages/runtime/id-compressor/src/test/idCompressor.perf.spec.ts
@@ -94,17 +94,18 @@ describe("IdCompressor Perf", () => {
 		const log = network.getIdLog(client);
 		for (let i = log.length - 1; i > 0; i--) {
 			const { id, originatingClient } = log[i];
-			if (originatingClient === client) {
-				if ((eagerFinal && isFinalId(id)) || (!eagerFinal && isLocalId(id))) {
-					assert(eagerFinal === isFinalId(id), "Not local/final as requested.");
-					return id;
-				}
+			if (
+				originatingClient === client &&
+				((eagerFinal && isFinalId(id)) || (!eagerFinal && isLocalId(id)))
+			) {
+				assert(eagerFinal === isFinalId(id), "Not local/final as requested.");
+				return id;
 			}
 		}
 		fail("no ID found in log");
 	}
 
-	function benchmarkWithFlag(creator: (flag: boolean) => void) {
+	function benchmarkWithFlag(creator: (flag: boolean) => void): void {
 		for (const flag of [true, false]) {
 			creator(flag);
 		}
@@ -235,7 +236,7 @@ describe("IdCompressor Perf", () => {
 				for (let clusterCount = 0; clusterCount < 5; clusterCount++) {
 					network.allocateAndSendIds(
 						localClient,
-						// eslint-disable-next-line @typescript-eslint/dot-notation
+						// eslint-disable-next-line @typescript-eslint/dot-notation, @typescript-eslint/no-unsafe-argument
 						perfCompressor["nextRequestedClusterSize"],
 					);
 					network.allocateAndSendIds(
diff --git a/packages/runtime/id-compressor/src/test/idCompressor.spec.ts b/packages/runtime/id-compressor/src/test/idCompressor.spec.ts
index acc2e659efe3..47b9a1cfb11a 100644
--- a/packages/runtime/id-compressor/src/test/idCompressor.spec.ts
+++ b/packages/runtime/id-compressor/src/test/idCompressor.spec.ts
@@ -3,7 +3,8 @@
  * Licensed under the MIT License.
  */
 
-import { strict as assert } from "assert";
+/* eslint-disable import/no-nodejs-modules */
+import { strict as assert } from "node:assert";
 
 import { bufferToString, stringToBuffer } from "@fluid-internal/client-utils";
 import { take } from "@fluid-private/stochastic-test-utils";
@@ -229,10 +230,10 @@ describe("IdCompressor", () => {
 				// Assert everything is unique and consistent.
 				const ids = new Set<SessionSpaceCompressedId>();
 				const uuids = new Set<StableId | string>();
-				[id1_1, id1_2, id2_1, id2_2, id3_1, id3_2, id4_1, id4_2].forEach((id) => {
+				for (const id of [id1_1, id1_2, id2_1, id2_2, id3_1, id3_2, id4_1, id4_2]) {
 					ids.add(id);
 					uuids.add(compressor.decompress(id));
-				});
+				}
 				assert.equal(ids.size, 8);
 				assert.equal(uuids.size, 8);
 			});
@@ -274,7 +275,7 @@ describe("IdCompressor", () => {
 
 				// All generated IDs should have aligned finals (even though range3 has not been finalized)
 				const allIds: SessionSpaceCompressedId[] = [id1_1, id1_2, id2_1, id2_2, id2_3, id3_1];
-				allIds.forEach((id) => assert(isFinalId(compressor.normalizeToOpSpace(id))));
+				for (const id of allIds) assert(isFinalId(compressor.normalizeToOpSpace(id)));
 
 				compressor.finalizeCreationRange(range3);
 
@@ -286,10 +287,10 @@ describe("IdCompressor", () => {
 				// Assert everything is unique and consistent.
 				const ids = new Set<SessionSpaceCompressedId>();
 				const uuids = new Set<StableId | string>();
-				allIds.forEach((id) => {
+				for (const id of allIds) {
 					ids.add(id);
 					uuids.add(compressor.decompress(id));
-				});
+				}
 				assert.equal(ids.size, 7);
 				assert.equal(uuids.size, 7);
 			});
@@ -321,18 +322,18 @@ describe("IdCompressor", () => {
 			{ title: "with more IDs than fit in a cluster", idCount: clusterSize * 2 },
 		];
 
-		tests.forEach(({ title, idCount }) => {
+		for (const { title, idCount } of tests) {
 			it(title, () => {
 				const compressor = CompressorFactory.createCompressor(Client.Client1);
 				generateCompressedIds(compressor, idCount);
 				const range = compressor.takeNextCreationRange();
-				if (range.ids !== undefined) {
-					assert.equal(range.ids.count, idCount);
-				} else {
+				if (range.ids === undefined) {
 					assert.equal(idCount, 0);
+				} else {
+					assert.equal(range.ids.count, idCount);
 				}
 			});
-		});
+		}
 
 		it("with the correct local ranges", () => {
 			const compressor = CompressorFactory.createCompressor(Client.Client1, 1);
@@ -357,6 +358,7 @@ describe("IdCompressor", () => {
 			assert.deepEqual(ids3, [3, -5]);
 			assert.deepEqual(range3.ids?.localIdRanges, [[5, 1]]);
 
+			// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-explicit-any
 			(range3 as any).ids.requestedClusterSize = 4;
 			const ids4 = generateCompressedIds(compressor, 2);
 			compressor.finalizeCreationRange(range3);
@@ -470,7 +472,9 @@ describe("IdCompressor", () => {
 				() => compressor.finalizeCreationRange(batchRange),
 				(e: Error) =>
 					e.message === "Ranges finalized out of order" &&
+					// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-explicit-any
 					(e as any).expectedStart === -4 &&
+					// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-explicit-any
 					(e as any).actualStart === -1,
 			);
 		});
@@ -485,7 +489,9 @@ describe("IdCompressor", () => {
 				() => compressor.finalizeCreationRange(secondRange),
 				(e: Error) =>
 					e.message === "Ranges finalized out of order" &&
+					// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-explicit-any
 					(e as any).expectedStart === -1 &&
+					// eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-explicit-any
 					(e as any).actualStart === -2,
 			);
 		});
@@ -500,9 +506,9 @@ describe("IdCompressor", () => {
 					}
 					compressor.finalizeCreationRange(compressor.takeNextCreationRange());
 					const opIds = new Set<OpSpaceCompressedId>();
-					ids.forEach((id) => opIds.add(compressor.normalizeToOpSpace(id)));
+					for (const id of ids) opIds.add(compressor.normalizeToOpSpace(id));
 					assert.equal(ids.size, opIds.size);
-					opIds.forEach((id) => assert.equal(isFinalId(id), true));
+					for (const id of opIds) assert.equal(isFinalId(id), true);
 				}
 			}
 		});
@@ -957,7 +963,7 @@ describe("IdCompressor", () => {
 			const base64Content = compressor.serialize(false);
 			const floatView = new Float64Array(stringToBuffer(base64Content, "base64"));
 			// Change the version to 1.0
-			floatView[0] = 1.0;
+			floatView[0] = 1;
 			const docString1 = bufferToString(
 				floatView.buffer,
 				"base64",
@@ -1086,7 +1092,7 @@ describe("IdCompressor", () => {
 				const opSpaceIds = network.allocateAndSendIds(Client.Client1, 1);
 				// Mimic sending a reference to an ID that hasn't been acked yet, such as in a slow network
 				const id = opSpaceIds[0];
-				const getSessionNormalizedId = () =>
+				const getSessionNormalizedId = (): SessionSpaceCompressedId =>
 					compressor2.normalizeToSessionSpace(id, compressor1.localSessionId);
 				assert.throws(
 					getSessionNormalizedId,
@@ -1142,48 +1148,43 @@ describe("IdCompressor", () => {
 
 			// Client 1 makes three IDs
 			network.allocateAndSendIds(Client.Client1, 3);
-			network.getIdLog(Client.Client1).forEach(({ id }) => assert(isLocalId(id)));
+			for (const { id } of network.getIdLog(Client.Client1)) assert(isLocalId(id));
 
 			// Client 1's IDs have not been acked so have no op space equivalent
-			network
-				.getIdLog(Client.Client1)
-				.forEach((idData) => assert(isLocalId(compressor1.normalizeToOpSpace(idData.id))));
+			for (const idData of network.getIdLog(Client.Client1))
+				assert(isLocalId(compressor1.normalizeToOpSpace(idData.id)));
 
 			// Client 1's IDs are acked
 			network.deliverOperations(Client.Client1);
-			network.getIdLog(Client.Client1).forEach(({ id }) => assert(isLocalId(id)));
+			for (const { id } of network.getIdLog(Client.Client1)) assert(isLocalId(id));
 
 			// Client 2 makes three IDs
 			network.allocateAndSendIds(Client.Client2, 3);
 
-			network.getIdLog(Client.Client2).forEach(({ id }) => assert(isLocalId(id)));
+			for (const { id } of network.getIdLog(Client.Client2)) assert(isLocalId(id));
 
 			// Client 1 receives Client 2's IDs
 			network.deliverOperations(Client.Client1);
 
-			network
-				.getIdLog(Client.Client1)
-				.slice(-3)
-				.forEach(({ id }) => assert(isFinalId(id)));
+			for (const { id } of network.getIdLog(Client.Client1).slice(-3)) assert(isFinalId(id));
 
 			// All IDs have been acked or are from another client, and therefore have a final form in op space
-			network
-				.getIdLog(Client.Client1)
-				.forEach(({ id }) => assert(isFinalId(compressor1.normalizeToOpSpace(id))));
+			for (const { id } of network.getIdLog(Client.Client1))
+				assert(isFinalId(compressor1.normalizeToOpSpace(id)));
 
 			// Compression should preserve ID space correctness
-			network.getIdLog(Client.Client1).forEach((idData) => {
+			for (const idData of network.getIdLog(Client.Client1)) {
 				const roundtripped = compressor1.recompress(compressor1.decompress(idData.id));
 				assert.equal(Math.sign(roundtripped), Math.sign(idData.id));
-			});
+			}
 
-			network.getIdLog(Client.Client1).forEach((idData) => {
+			for (const idData of network.getIdLog(Client.Client1)) {
 				const opNormalized = compressor1.normalizeToOpSpace(idData.id);
 				assert.equal(
 					Math.sign(compressor1.normalizeToSessionSpace(opNormalized, idData.sessionId)),
 					Math.sign(idData.id),
 				);
-			});
+			}
 		});
 
 		itNetwork("produces consistent IDs with large fuzz input", (network) => {
@@ -1222,7 +1223,8 @@ describe("IdCompressor", () => {
 			});
 
 			itNetwork("can finalize a range when the current cluster is full", 5, (network) => {
-				const clusterCapacity = network.getCompressor(
+				// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+				const clusterCapacity: number = network.getCompressor(
 					Client.Client1,
 					// eslint-disable-next-line @typescript-eslint/dot-notation
 				)["nextRequestedClusterSize"];
@@ -1233,7 +1235,8 @@ describe("IdCompressor", () => {
 			});
 
 			itNetwork("can finalize a range that spans multiple clusters", 5, (network) => {
-				const clusterCapacity = network.getCompressor(
+				// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+				const clusterCapacity: number = network.getCompressor(
 					Client.Client1,
 					// eslint-disable-next-line @typescript-eslint/dot-notation
 				)["nextRequestedClusterSize"];
@@ -1314,7 +1317,8 @@ describe("IdCompressor", () => {
 				"can resume a session and interact with multiple other clients",
 				3,
 				(network) => {
-					const clusterSize = network.getCompressor(
+					// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+					const clusterSize: number = network.getCompressor(
 						Client.Client1,
 						// eslint-disable-next-line @typescript-eslint/dot-notation
 					)["nextRequestedClusterSize"];
@@ -1389,7 +1393,7 @@ function createNetworkTestFunction(
 function describeNetwork(
 	title: string,
 	its: (itFunc: NetworkTestFunction & NetworkTestFunctionWithCapacity) => void,
-) {
+): void {
 	describe(title, () => {
 		its(createNetworkTestFunction(false));
 	});
diff --git a/packages/runtime/id-compressor/src/test/idCompressorTestUtilities.ts b/packages/runtime/id-compressor/src/test/idCompressorTestUtilities.ts
index b8f82d83f082..83e1cf3d46c3 100644
--- a/packages/runtime/id-compressor/src/test/idCompressorTestUtilities.ts
+++ b/packages/runtime/id-compressor/src/test/idCompressorTestUtilities.ts
@@ -3,7 +3,8 @@
  * Licensed under the MIT License.
  */
 
-import { strict as assert } from "assert";
+// eslint-disable-next-line import/no-nodejs-modules
+import { strict as assert } from "node:assert";
 
 import {
 	BaseFuzzTestState,
@@ -51,19 +52,25 @@ export interface ClosedMap<K, V> extends Omit<Map<K, V>, "delete" | "clear"> {
 	get(key: K): V;
 }
 
-/** Identifies a compressor in a network */
+/**
+ * Identifies a compressor in a network
+ */
 export enum Client {
 	Client1 = "Client1",
 	Client2 = "Client2",
 	Client3 = "Client3",
 }
 
-/** Identifies categories of compressors */
+/**
+ * Identifies categories of compressors
+ */
 export enum MetaClient {
 	All = "All",
 }
 
-/** Identifies a compressor inside the network but outside the three specially tracked clients. */
+/**
+ * Identifies a compressor inside the network but outside the three specially tracked clients.
+ */
 export enum OutsideClient {
 	Remote = "Remote",
 }
@@ -75,7 +82,9 @@ export enum OutsideClient {
 export type OriginatingClient = Client | OutsideClient;
 export const OriginatingClient = { ...Client, ...OutsideClient };
 
-/** Identifies a compressor to which to send an operation */
+/**
+ * Identifies a compressor to which to send an operation
+ */
 export type DestinationClient = Client | MetaClient;
 export const DestinationClient = { ...Client, ...MetaClient };
 
@@ -171,7 +180,9 @@ function makeSessionIds(): ClientMap<SessionId> {
  */
 export const sessionIds = makeSessionIds();
 
-/** Information about a generated ID in a network to be validated by tests */
+/**
+ * Information about a generated ID in a network to be validated by tests
+ */
 export interface TestIdData {
 	readonly id: SessionSpaceCompressedId;
 	readonly originatingClient: OriginatingClient;
@@ -184,20 +195,30 @@ export interface TestIdData {
  * Not suitable for performance testing.
  */
 export class IdCompressorTestNetwork {
-	/** The compressors used in this network */
+	/**
+	 * The compressors used in this network
+	 */
 	private readonly compressors: ClientMap<IdCompressor>;
-	/** The log of operations seen by the server so far. Append-only. */
+	/**
+	 * The log of operations seen by the server so far. Append-only.
+	 */
 	private readonly serverOperations: [
 		creationRange: IdCreationRange,
 		opSpaceIds: OpSpaceCompressedId[],
 		clientFrom: OriginatingClient,
 		sessionIdFrom: SessionId,
 	][] = [];
-	/** An index into `serverOperations` for each client which represents how many operations have been delivered to that client */
+	/**
+	 * An index into `serverOperations` for each client which represents how many operations have been delivered to that client
+	 */
 	private readonly clientProgress: ClientMap<number>;
-	/** All ids (local and sequenced) that a client has created or received, in order. */
+	/**
+	 * All ids (local and sequenced) that a client has created or received, in order.
+	 */
 	private readonly idLogs: ClientMap<TestIdData[]>;
-	/** All ids that a client has received from the server, in order. */
+	/**
+	 * All ids that a client has received from the server, in order.
+	 */
 	private readonly sequencedIdLogs: ClientMap<TestIdData[]>;
 
 	public constructor(public readonly initialClusterSize = 5) {
@@ -341,6 +362,7 @@ export class IdCompressorTestNetwork {
 				ids: {
 					firstGenCount: 1,
 					count: numIds,
+					// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
 					requestedClusterSize: this.getCompressor(Client.Client1)[
 						// eslint-disable-next-line @typescript-eslint/dot-notation
 						"nextRequestedClusterSize"
@@ -391,9 +413,9 @@ export class IdCompressorTestNetwork {
 			opIndexBound = this.serverOperations.length;
 		} else {
 			opIndexBound =
-				opsToDeliver !== undefined
-					? this.clientProgress.get(clientTakingDelivery) + opsToDeliver
-					: this.serverOperations.length;
+				opsToDeliver === undefined
+					? this.serverOperations.length
+					: this.clientProgress.get(clientTakingDelivery) + opsToDeliver;
 		}
 		for (const [clientTo, compressorTo] of this.getTargetCompressors(clientTakingDelivery)) {
 			for (let i = this.clientProgress.get(clientTo); i < opIndexBound; i++) {
@@ -452,38 +474,38 @@ export class IdCompressorTestNetwork {
 		};
 
 		// Ensure creation ranges for clients we track contain the correct local ID ranges
-		this.serverOperations.forEach(([range, opSpaceIds, clientFrom]) => {
+		for (const [range, opSpaceIds, clientFrom] of this.serverOperations) {
 			if (clientFrom !== OriginatingClient.Remote) {
 				const localIdsInCreationRange = getLocalIdsInRange(range, opSpaceIds);
 				let localCount = 0;
-				opSpaceIds.forEach((id) => {
+				for (const id of opSpaceIds) {
 					if (isLocalId(id)) {
 						localCount++;
 						assert(localIdsInCreationRange.has(id), "Local ID not in creation range");
 					}
-				});
+				}
 				assert.strictEqual(
 					localCount,
 					localIdsInCreationRange.size,
 					"Local ID count mismatch",
 				);
 			}
-		});
+		}
 
 		const undeliveredRanges = new Map<Client, IdCreationRange[]>();
-		this.clientProgress.forEach((progress, client) => {
+		for (const [client, progress] of this.clientProgress.entries()) {
 			const ranges = this.serverOperations
 				.slice(progress)
 				.filter((op) => op[2] === client)
 				.map(([range]) => range);
 			undeliveredRanges.set(client, ranges);
-		});
-		undeliveredRanges.forEach((ranges, client) => {
+		}
+		for (const [client, ranges] of undeliveredRanges.entries()) {
 			const compressor = this.compressors.get(client);
 			let firstGenCount: number | undefined;
 			let totalCount = 0;
 			const unionedLocalRanges = new SessionSpaceNormalizer();
-			ranges.forEach((range) => {
+			for (const range of ranges) {
 				assert(range.sessionId === compressor.localSessionId);
 				if (range.ids !== undefined) {
 					// initialize firstGenCount if not set
@@ -491,18 +513,21 @@ export class IdCompressorTestNetwork {
 						firstGenCount = range.ids.firstGenCount;
 					}
 					totalCount += range.ids.count;
-					range.ids.localIdRanges.forEach(([genCount, count]) => {
+					for (const [genCount, count] of range.ids.localIdRanges) {
 						unionedLocalRanges.addLocalRange(genCount, count);
-					});
+					}
 				}
-			});
+			}
 
 			const retakenRange = compressor.takeUnfinalizedCreationRange();
-			if (retakenRange.ids !== undefined) {
+			if (retakenRange.ids === undefined) {
+				assert.strictEqual(totalCount, 0);
+				assert.strictEqual(unionedLocalRanges.idRanges.size, 0);
+			} else {
 				const retakenLocalIds = new SessionSpaceNormalizer();
-				retakenRange.ids.localIdRanges.forEach(([genCount, count]) => {
+				for (const [genCount, count] of retakenRange.ids.localIdRanges) {
 					retakenLocalIds.addLocalRange(genCount, count);
-				});
+				}
 				assert.strictEqual(
 					retakenLocalIds.equals(unionedLocalRanges),
 					true,
@@ -510,11 +535,8 @@ export class IdCompressorTestNetwork {
 				);
 				assert.strictEqual(retakenRange.ids.count, totalCount, "Count mismatch");
 				assert.strictEqual(retakenRange.ids.firstGenCount, firstGenCount, "Count mismatch");
-			} else {
-				assert.strictEqual(totalCount, 0);
-				assert.strictEqual(unionedLocalRanges.idRanges.size, 0);
 			}
-		});
+		}
 
 		// First, ensure all clients each generated a unique ID for each of their own calls to generate.
 		for (const [compressor, ids] of sequencedLogs) {
@@ -528,6 +550,7 @@ export class IdCompressorTestNetwork {
 
 		const maxLogLength = sequencedLogs
 			.map(([_, data]) => data.length)
+			// eslint-disable-next-line unicorn/no-array-reduce
 			.reduce((p, n) => Math.max(p, n));
 
 		function getNextLogWithEntryAt(logsIndex: number, entryIndex: number): number | undefined {
@@ -680,8 +703,8 @@ export function roundtrip(
 ] {
 	// preserve the capacity request as this property is normally private and resets
 	// to a default on construction (deserialization)
-	// eslint-disable-next-line @typescript-eslint/dot-notation
-	const capacity = compressor["nextRequestedClusterSize"];
+	// eslint-disable-next-line @typescript-eslint/dot-notation, @typescript-eslint/no-unsafe-assignment
+	const capacity: number = compressor["nextRequestedClusterSize"];
 	if (withSession) {
 		const serialized = compressor.serialize(withSession);
 		const roundtripped = IdCompressor.deserialize(serialized);
@@ -732,10 +755,10 @@ export function mergeArrayMaps<K, V>(
 ): Pick<Map<K, V[]>, "get" | "set"> {
 	for (const [key, value] of from.entries()) {
 		const entry = to.get(key);
-		if (entry !== undefined) {
-			entry.push(...value);
-		} else {
+		if (entry === undefined) {
 			to.set(key, [...value]);
+		} else {
+			entry.push(...value);
 		}
 	}
 	return to;
@@ -796,11 +819,17 @@ interface FuzzTestState extends BaseFuzzTestState {
 }
 
 export interface OperationGenerationConfig {
-	/** maximum cluster size of the network. Default: 25 */
+	/**
+	 * maximum cluster size of the network. Default: 25
+	 */
 	maxClusterSize?: number;
-	/** Number of ops between validation ops. Default: 200 */
+	/**
+	 * Number of ops between validation ops. Default: 200
+	 */
 	validateInterval?: number;
-	/** Fraction of ID allocations that are from an outside client (not Client1/2/3). */
+	/**
+	 * Fraction of ID allocations that are from an outside client (not Client1/2/3).
+	 */
 	outsideAllocationFraction?: number;
 }
 
diff --git a/packages/runtime/id-compressor/src/test/numericUuid.spec.ts b/packages/runtime/id-compressor/src/test/numericUuid.spec.ts
index 1954c5a76205..c75fecaa8cf9 100644
--- a/packages/runtime/id-compressor/src/test/numericUuid.spec.ts
+++ b/packages/runtime/id-compressor/src/test/numericUuid.spec.ts
@@ -3,7 +3,8 @@
  * Licensed under the MIT License.
  */
 
-import { strict as assert } from "assert";
+// eslint-disable-next-line import/no-nodejs-modules
+import { strict as assert } from "node:assert";
 
 import { StableId } from "../index.js";
 import { readNumericUuid, writeNumericUuid } from "../persistanceUtilities.js";
diff --git a/packages/runtime/id-compressor/src/test/sessionSpaceNormalizer.spec.ts b/packages/runtime/id-compressor/src/test/sessionSpaceNormalizer.spec.ts
index 46028bf1c416..5b737c50357a 100644
--- a/packages/runtime/id-compressor/src/test/sessionSpaceNormalizer.spec.ts
+++ b/packages/runtime/id-compressor/src/test/sessionSpaceNormalizer.spec.ts
@@ -3,7 +3,8 @@
  * Licensed under the MIT License.
  */
 
-import { strict as assert } from "assert";
+/* eslint-disable import/no-nodejs-modules */
+import { strict as assert } from "node:assert";
 
 import { SessionSpaceNormalizer } from "../sessionSpaceNormalizer.js";
 
diff --git a/packages/runtime/id-compressor/src/test/snapshots/summary.spec.ts b/packages/runtime/id-compressor/src/test/snapshots/summary.spec.ts
index 1e2673770868..4fa1944d03f6 100644
--- a/packages/runtime/id-compressor/src/test/snapshots/summary.spec.ts
+++ b/packages/runtime/id-compressor/src/test/snapshots/summary.spec.ts
@@ -5,9 +5,9 @@
 
 /* eslint-disable import/no-nodejs-modules */
 
-import { strict as assert } from "assert";
-import { existsSync, mkdirSync, readFileSync, rmSync, writeFileSync } from "fs";
-import path from "path";
+import { strict as assert } from "node:assert";
+import { existsSync, mkdirSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import path from "node:path";
 
 import { SessionId, createIdCompressor } from "../../index.js";
 
@@ -77,7 +77,7 @@ function takeSnapshot(data: string, suffix: string = ""): void {
 		writeFileSync(fullFile, data);
 	} else {
 		assert(exists, `test snapshot file does not exist: "${fullFile}"`);
-		const pastData = readFileSync(fullFile, "utf-8");
+		const pastData = readFileSync(fullFile, "utf8");
 		assert.equal(data, pastData, `snapshot different for "${currentTestName}"`);
 	}
 }
diff --git a/packages/runtime/id-compressor/src/test/testCommon.ts b/packages/runtime/id-compressor/src/test/testCommon.ts
index 60e624d831c0..4af38ddfb281 100644
--- a/packages/runtime/id-compressor/src/test/testCommon.ts
+++ b/packages/runtime/id-compressor/src/test/testCommon.ts
@@ -44,6 +44,7 @@ export type LocalCompressedId = number & {
 } & SessionSpaceCompressedId; // Same brand as CompressedId, as local IDs are always locally normalized
 
 /**
+ * Returns true if the supplied ID is a final ID.
  * @returns true if the supplied ID is a final ID.
  */
 export function isFinalId(id: CompressedId): id is FinalCompressedId {
@@ -51,6 +52,7 @@ export function isFinalId(id: CompressedId): id is FinalCompressedId {
 }
 
 /**
+ * Returns true if the supplied ID is a local ID.
  * @returns true if the supplied ID is a local ID.
  */
 export function isLocalId(id: CompressedId): id is LocalCompressedId {
@@ -91,7 +93,9 @@ export function incrementStableId(stableId: StableId, offset: number): StableId
 	return stableIdFromNumericUuid(offsetNumericUuid(numericUuidFromStableId(stableId), offset));
 }
 
-/** An immutable view of an `IdCompressor` */
+/**
+ * An immutable view of an `IdCompressor`
+ */
 export type ReadonlyIdCompressor = Omit<
 	IdCompressor,
 	| "generateCompressedId"
diff --git a/packages/runtime/id-compressor/src/utilities.ts b/packages/runtime/id-compressor/src/utilities.ts
index b41ec962ec68..66f570ab0348 100644
--- a/packages/runtime/id-compressor/src/utilities.ts
+++ b/packages/runtime/id-compressor/src/utilities.ts
@@ -10,7 +10,7 @@ import { v4 } from "uuid";
 import { LocalCompressedId, NumericUuid } from "./identifiers.js";
 import { SessionId, StableId } from "./types/index.js";
 
-const hexadecimalCharCodes = Array.from("09afAF").map((c) => c.charCodeAt(0)) as [
+const hexadecimalCharCodes = [..."09afAF"].map((c) => c.codePointAt(0)) as [
 	zero: number,
 	nine: number,
 	a: number,
@@ -76,17 +76,19 @@ export function isStableId(str: string): str is StableId {
 			case 8:
 			case 13:
 			case 18:
-			case 23:
+			case 23: {
 				if (str.charAt(i) !== "-") {
 					return false;
 				}
 				break;
+			}
 
-			case 14:
+			case 14: {
 				if (str.charAt(i) !== "4") {
 					return false;
 				}
 				break;
+			}
 
 			case 19: {
 				const char = str.charAt(i);
@@ -96,11 +98,14 @@ export function isStableId(str: string): str is StableId {
 				break;
 			}
 
-			default:
-				if (!isHexadecimalCharacter(str.charCodeAt(i))) {
+			default: {
+				const codePoint = str.codePointAt(i);
+				assert(codePoint !== undefined, "Unexpected undefined code point");
+				if (!isHexadecimalCharacter(codePoint)) {
 					return false;
 				}
 				break;
+			}
 		}
 	}
 
@@ -172,10 +177,10 @@ export function stableIdFromNumericUuid(numericUuid: NumericUuid): StableId {
 	const uuidU128 = upperMasked | versionMask | middieBittiesMasked | variantMask | lowerMasked;
 	// Pad to 32 characters, inserting leading zeroes if needed
 	const uuidString = uuidU128.toString(16).padStart(32, "0");
-	return `${uuidString.substring(0, 8)}-${uuidString.substring(8, 12)}-${uuidString.substring(
+	return `${uuidString.slice(0, 8)}-${uuidString.slice(8, 12)}-${uuidString.slice(
 		12,
 		16,
-	)}-${uuidString.substring(16, 20)}-${uuidString.substring(20, 32)}` as StableId;
+	)}-${uuidString.slice(16, 20)}-${uuidString.slice(20, 32)}` as StableId;
 }
 
 export function offsetNumericUuid(numericUuid: NumericUuid, offset: number): NumericUuid {