diff --git a/karma.conf.cjs b/karma.conf.cjs
index dcdf6e3694..12ec027d8d 100644
--- a/karma.conf.cjs
+++ b/karma.conf.cjs
@@ -1,15 +1,18 @@
 const webpack = require("webpack");
-const playwright = require('playwright');
+const playwright = require("playwright");
 
 process.env.CHROME_BIN = playwright.chromium.executablePath();
 process.env.FIREFOX_BIN = playwright.firefox.executablePath();
 
+const path = require("path");
+const tsConfigFile = path.resolve(__dirname, "./tsconfig.dev.json");
+
 module.exports = function (config) {
   config.set({
     frameworks: ["webpack", "mocha"],
     files: ["src/**/!(node).spec.ts"],
     preprocessors: {
-      "src/**/!(node).spec.ts": ["webpack"]
+      "src/**/!(node).spec.ts": ["webpack"],
     },
     envPreprocessor: ["CI"],
     reporters: ["progress"],
@@ -17,13 +20,19 @@ module.exports = function (config) {
     singleRun: true,
     client: {
       mocha: {
-        timeout: 6000 // Default is 2s
-      }
+        timeout: 6000, // Default is 2s
+      },
     },
     webpack: {
       mode: "development",
       module: {
-        rules: [{ test: /\.([cm]?ts|tsx)$/, loader: "ts-loader" }]
+        rules: [
+          {
+            test: /\.([cm]?ts|tsx)$/,
+            loader: "ts-loader",
+            options: { configFile: tsConfigFile },
+          },
+        ],
       },
       plugins: [
         new webpack.DefinePlugin({
@@ -31,19 +40,19 @@ module.exports = function (config) {
           "process.env.DISPLAY": "Browser",
         }),
         new webpack.ProvidePlugin({
-          process: "process/browser.js"
-        })
+          process: "process/browser.js",
+        }),
       ],
       resolve: {
         extensions: [".ts", ".tsx", ".js"],
         extensionAlias: {
           ".js": [".js", ".ts"],
           ".cjs": [".cjs", ".cts"],
-          ".mjs": [".mjs", ".mts"]
-        }
+          ".mjs": [".mjs", ".mts"],
+        },
       },
       stats: { warnings: false },
-      devtool: "inline-source-map"
-    }
+      devtool: "inline-source-map",
+    },
   });
 };
diff --git a/package.json b/package.json
index d7a89a8276..1861d56030 100644
--- a/package.json
+++ b/package.json
@@ -29,9 +29,9 @@
     "check": "run-s check:*",
     "check:workspaces": "npm run check --workspaces --if-present",
     "check:ws": "[ $(ls -1 ./packages|wc -l) -eq $(cat package.json | jq '.workspaces | length') ] || exit 1 # check no packages left behind",
-    "test": "NODE_ENV=test npm run test --workspaces --if-present",
-    "test:browser": "NODE_ENV=test npm run test:browser --workspaces --if-present",
-    "test:node": "NODE_ENV=test npm run test:node --workspaces --if-present",
+    "test": "npm run test --workspaces --if-present",
+    "test:browser": "npm run test:browser --workspaces --if-present",
+    "test:node": "npm run test:node --workspaces --if-present",
     "proto": "npm run proto --workspaces --if-present",
     "deploy": "node ci/deploy.js",
     "doc": "run-s doc:*",
diff --git a/packages/core/package.json b/packages/core/package.json
index 30edd99477..0218dfe8a9 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -57,12 +57,12 @@
     "fix": "run-s fix:*",
     "fix:lint": "eslint src *.js --fix",
     "check": "run-s check:*",
-    "check:tsc": "tsc -p tsconfig.dev.json",
+    "check:tsc": "tsc -p tsconfig.json",
     "check:lint": "eslint src *.js",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "test": "NODE_ENV=test run-s test:*",
+    "test": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json run-s test:*",
     "test:node": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json mocha",
-    "test:browser": "NODE_ENV=test karma start karma.conf.cjs",
+    "test:browser": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json karma start karma.conf.cjs",
     "watch:build": "tsc -p tsconfig.json -w",
     "watch:test": "mocha --watch",
     "prepublish": "npm run build",
diff --git a/packages/core/src/lib/filter/index.ts b/packages/core/src/lib/filter/index.ts
index cadf1720c2..b3089b527f 100644
--- a/packages/core/src/lib/filter/index.ts
+++ b/packages/core/src/lib/filter/index.ts
@@ -110,7 +110,7 @@ class Subscription {
           async (source) => await all(source)
         );
 
-        if (!res || !res.length) {
+        if (!res?.[0]) {
           throw Error(
             `No response received for request ${request.requestId}: ${res}`
           );
@@ -203,7 +203,7 @@ class Subscription {
           async (source) => await all(source)
         );
 
-        if (!res || !res.length) {
+        if (!res?.[0]) {
           throw Error(
             `No response received for request ${request.requestId}: ${res}`
           );
@@ -246,7 +246,7 @@ class Subscription {
           async (source) => await all(source)
         );
 
-        if (!res || !res.length) {
+        if (!res?.[0]) {
           throw Error(
             `No response received for request ${request.requestId}: ${res}`
           );
diff --git a/packages/core/src/lib/filterPeers.ts b/packages/core/src/lib/filterPeers.ts
index 816c3bd5b5..1ac1ef76b9 100644
--- a/packages/core/src/lib/filterPeers.ts
+++ b/packages/core/src/lib/filterPeers.ts
@@ -43,7 +43,10 @@ export function filterPeersByDiscovery(
   // Fill up to numPeers with remaining random peers if needed
   while (selectedPeers.length < numPeers && nonBootstrapPeers.length > 0) {
     const randomIndex = Math.floor(Math.random() * nonBootstrapPeers.length);
-    const randomPeer = nonBootstrapPeers.splice(randomIndex, 1)[0];
+    const randomPeer = nonBootstrapPeers[randomIndex];
+    if (!randomPeer) {
+      continue;
+    }
     selectedPeers.push(randomPeer);
   }
 
diff --git a/packages/core/src/lib/store/index.ts b/packages/core/src/lib/store/index.ts
index 8b77adb605..cf6f8b01e2 100644
--- a/packages/core/src/lib/store/index.ts
+++ b/packages/core/src/lib/store/index.ts
@@ -237,9 +237,12 @@ class Store extends BaseProtocol implements IStore {
       );
     }
 
-    // we can be certain that there is only one pubsub topic in the query
     const pubsubTopicForQuery = uniquePubsubTopicsInQuery[0];
 
+    if (!pubsubTopicForQuery) {
+      throw Error("Cannot find a pubsub topic to use for query.");
+    }
+
     ensurePubsubTopicIsConfigured(pubsubTopicForQuery, this.pubsubTopics);
 
     // check that the pubsubTopic from the Cursor and Decoder match
@@ -287,6 +290,10 @@ class Store extends BaseProtocol implements IStore {
       })
     )[0];
 
+    if (!peer) {
+      throw Error("Failed executing query: missing a peer.");
+    }
+
     for await (const messages of paginate<T>(
       this.getStream.bind(this, peer),
       queryOpts,
diff --git a/packages/core/src/lib/wait_for_remote_peer.ts b/packages/core/src/lib/wait_for_remote_peer.ts
index ae5d5cf849..7ae1a35fe9 100644
--- a/packages/core/src/lib/wait_for_remote_peer.ts
+++ b/packages/core/src/lib/wait_for_remote_peer.ts
@@ -89,7 +89,7 @@ async function waitForConnectedPeer(
 
   if (peers.length) {
     if (!metadataService) {
-      log.info(`${codec} peer found: `, peers[0].id.toString());
+      log.info(`${codec} peer found: `, peers[0]?.id.toString());
       return;
     }
 
diff --git a/packages/dns-discovery/package.json b/packages/dns-discovery/package.json
index e0f7aee34f..77f6521b00 100644
--- a/packages/dns-discovery/package.json
+++ b/packages/dns-discovery/package.json
@@ -40,12 +40,12 @@
     "check": "run-s check:*",
     "check:lint": "eslint src --ext .ts",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "check:tsc": "tsc -p tsconfig.dev.json",
+    "check:tsc": "tsc -p tsconfig.json",
     "prepublish": "npm run build",
     "reset-hard": "git clean -dfx -e .idea && git reset --hard && npm i && npm run build",
-    "test": "NODE_ENV=test run-s test:*",
+    "test": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json run-s test:*",
     "test:node": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json mocha",
-    "test:browser": "NODE_ENV=test karma start karma.conf.cjs"
+    "test:browser": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json karma start karma.conf.cjs"
   },
   "engines": {
     "node": ">=18"
diff --git a/packages/dns-discovery/src/dns.ts b/packages/dns-discovery/src/dns.ts
index b17b25d4c5..04d0d6b88b 100644
--- a/packages/dns-discovery/src/dns.ts
+++ b/packages/dns-discovery/src/dns.ts
@@ -8,7 +8,7 @@ import type {
 import { Logger } from "@waku/utils";
 
 import { DnsOverHttps } from "./dns_over_https.js";
-import { ENRTree } from "./enrtree.js";
+import { ENRTree, ENRTreeValues } from "./enrtree.js";
 import {
   fetchNodesUntilCapabilitiesFulfilled,
   yieldNodesUntilCapabilitiesFulfilled
@@ -41,8 +41,7 @@ export class DnsNodeDiscovery {
     enrTreeUrls: string[],
     wantedNodeCapabilityCount: Partial<NodeCapabilityCount>
   ): Promise<IEnr[]> {
-    const networkIndex = Math.floor(Math.random() * enrTreeUrls.length);
-    const { publicKey, domain } = ENRTree.parseTree(enrTreeUrls[networkIndex]);
+    const { publicKey, domain } = DnsNodeDiscovery.parseTree(enrTreeUrls);
     const context: SearchContext = {
       domain,
       publicKey,
@@ -78,8 +77,7 @@ export class DnsNodeDiscovery {
     enrTreeUrls: string[],
     wantedNodeCapabilityCount: Partial<NodeCapabilityCount>
   ): AsyncGenerator<IEnr> {
-    const networkIndex = Math.floor(Math.random() * enrTreeUrls.length);
-    const { publicKey, domain } = ENRTree.parseTree(enrTreeUrls[networkIndex]);
+    const { publicKey, domain } = DnsNodeDiscovery.parseTree(enrTreeUrls);
     const context: SearchContext = {
       domain,
       publicKey,
@@ -149,8 +147,9 @@ export class DnsNodeDiscovery {
     subdomain: string,
     context: SearchContext
   ): Promise<string> {
-    if (this._DNSTreeCache[subdomain]) {
-      return this._DNSTreeCache[subdomain];
+    const currentCache = this._DNSTreeCache[subdomain];
+    if (currentCache) {
+      return currentCache;
     }
 
     // Location is either the top level tree entry host or a subdomain of it.
@@ -161,9 +160,13 @@ export class DnsNodeDiscovery {
 
     const response = await this.dns.resolveTXT(location);
 
-    if (!response.length)
+    if (!response.length) {
       throw new Error("Received empty result array while fetching TXT record");
-    if (!response[0].length) throw new Error("Received empty TXT record");
+    }
+
+    if (!response[0]?.length) {
+      throw new Error("Received empty TXT record");
+    }
 
     // Branch entries can be an array of strings of comma delimited subdomains, with
     // some subdomain strings split across the array elements
@@ -172,6 +175,17 @@ export class DnsNodeDiscovery {
     this._DNSTreeCache[subdomain] = result;
     return result;
   }
+
+  private static parseTree(enrTreeUrls: string[]): ENRTreeValues {
+    const networkIndex = Math.floor(Math.random() * enrTreeUrls.length);
+    const enrTree = enrTreeUrls[networkIndex];
+
+    if (!enrTree) {
+      throw Error(`Failed to read ENR tree for the network: ${networkIndex}`);
+    }
+
+    return ENRTree.parseTree(enrTree);
+  }
 }
 
 function getEntryType(entry: string): string {
@@ -211,5 +225,5 @@ function selectRandomPath(branches: string[], context: SearchContext): string {
     index = Math.floor(Math.random() * branches.length);
   } while (circularRefs[index]);
 
-  return branches[index];
+  return branches[index] as string;
 }
diff --git a/packages/dns-discovery/src/enrtree.ts b/packages/dns-discovery/src/enrtree.ts
index 7a1412c29b..f6023bb912 100644
--- a/packages/dns-discovery/src/enrtree.ts
+++ b/packages/dns-discovery/src/enrtree.ts
@@ -40,6 +40,10 @@ export class ENRTree {
     // (Trailing recovery bit must be trimmed to pass `ecdsaVerify` method)
     const signedComponent = root.split(" sig")[0];
 
+    if (!signedComponent) {
+      throw Error(`Signature component is missing, got: ${signedComponent}`);
+    }
+
     const signedComponentBuffer = utf8ToBytes(signedComponent);
     const signatureBuffer = fromString(rootValues.signature, "base64url").slice(
       0,
@@ -113,11 +117,18 @@ export class ENRTree {
    * either further branch entries or ENR records.
    */
   static parseBranch(branch: string): string[] {
-    if (!branch.startsWith(this.BRANCH_PREFIX))
-      throw new Error(
+    if (!branch.startsWith(this.BRANCH_PREFIX)) {
+      throw Error(
         `ENRTree branch entry must start with '${this.BRANCH_PREFIX}'`
       );
+    }
+
+    const enrPart = branch.split(this.BRANCH_PREFIX)[1];
+
+    if (!enrPart) {
+      throw Error(`ENRTree branch does not have data`);
+    }
 
-    return branch.split(this.BRANCH_PREFIX)[1].split(",");
+    return enrPart.split(",");
   }
 }
diff --git a/packages/enr/package.json b/packages/enr/package.json
index 77fcf5ff8f..eda46bfc37 100644
--- a/packages/enr/package.json
+++ b/packages/enr/package.json
@@ -40,10 +40,10 @@
     "check": "run-s check:*",
     "check:lint": "eslint src --ext .ts",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "check:tsc": "tsc -p tsconfig.dev.json",
-    "test": "NODE_ENV=test run-s test:*",
+    "check:tsc": "tsc -p tsconfig.json",
+    "test": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json run-s test:*",
     "test:node": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json mocha",
-    "test:browser": "NODE_ENV=test karma start karma.conf.cjs",
+    "test:browser": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json karma start karma.conf.cjs",
     "prepublish": "npm run build",
     "reset-hard": "git clean -dfx -e .idea && git reset --hard && npm i && npm run build"
   },
diff --git a/packages/enr/src/decoder.ts b/packages/enr/src/decoder.ts
index e01cd5f189..06e3571b74 100644
--- a/packages/enr/src/decoder.ts
+++ b/packages/enr/src/decoder.ts
@@ -30,7 +30,7 @@ async function fromValues(values: Uint8Array[]): Promise<ENR> {
   const obj: Record<ENRKey, ENRValue> = {};
   for (let i = 0; i < kvs.length; i += 2) {
     try {
-      obj[bytesToUtf8(kvs[i])] = kvs[i + 1];
+      obj[bytesToUtf8(kvs[i] as Uint8Array)] = kvs[i + 1] as Uint8Array;
     } catch (e) {
       log.error("Failed to decode ENR key to UTF-8, skipping it", kvs[i], e);
     }
diff --git a/packages/enr/src/enr.ts b/packages/enr/src/enr.ts
index edc02f8a08..93c8c7bfa2 100644
--- a/packages/enr/src/enr.ts
+++ b/packages/enr/src/enr.ts
@@ -73,25 +73,23 @@ export class ENR extends RawEnr implements IEnr {
 
   setLocationMultiaddr(multiaddr: Multiaddr): void {
     const protoNames = multiaddr.protoNames();
-    if (
-      protoNames.length !== 2 &&
-      protoNames[1] !== "udp" &&
-      protoNames[1] !== "tcp"
-    ) {
+    const protocol = protoNames[1];
+    if (protoNames.length !== 2 && protocol !== "udp" && protocol !== "tcp") {
       throw new Error("Invalid multiaddr");
     }
+
     const tuples = multiaddr.tuples();
-    if (!tuples[0][1] || !tuples[1][1]) {
+    if (!tuples[0]?.[1] || !tuples[1]?.[1] || !protocol) {
       throw new Error("Invalid multiaddr");
     }
 
     // IPv4
     if (tuples[0][0] === 4) {
       this.set("ip", tuples[0][1]);
-      this.set(protoNames[1], tuples[1][1]);
+      this.set(protocol, tuples[1][1]);
     } else {
       this.set("ip6", tuples[0][1]);
-      this.set(protoNames[1] + "6", tuples[1][1]);
+      this.set(protocol + "6", tuples[1][1]);
     }
   }
 
diff --git a/packages/enr/src/raw_enr.ts b/packages/enr/src/raw_enr.ts
index b7c607880e..b1e828a7e9 100644
--- a/packages/enr/src/raw_enr.ts
+++ b/packages/enr/src/raw_enr.ts
@@ -153,7 +153,7 @@ export class RawEnr extends Map<ENRKey, ENRValue> {
    */
   get waku2(): Waku2 | undefined {
     const raw = this.get("waku2");
-    if (raw) return decodeWaku2(raw[0]);
+    if (raw) return decodeWaku2(raw[0] as number);
 
     return;
   }
diff --git a/packages/interfaces/package.json b/packages/interfaces/package.json
index 8b0a51c5a5..da62669a23 100644
--- a/packages/interfaces/package.json
+++ b/packages/interfaces/package.json
@@ -39,7 +39,7 @@
     "check": "run-s check:*",
     "check:lint": "eslint src",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "check:tsc": "tsc -p tsconfig.dev.json",
+    "check:tsc": "tsc -p tsconfig.json",
     "prepublish": "npm run build",
     "reset-hard": "git clean -dfx -e .idea && git reset --hard && npm i && npm run build"
   },
diff --git a/packages/message-encryption/package.json b/packages/message-encryption/package.json
index 6cc43e9b10..27cd7b54cb 100644
--- a/packages/message-encryption/package.json
+++ b/packages/message-encryption/package.json
@@ -61,10 +61,10 @@
     "check": "run-s check:*",
     "check:lint": "eslint src *.js",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "check:tsc": "tsc -p tsconfig.dev.json",
-    "test": "NODE_ENV=test run-s test:*",
+    "check:tsc": "tsc -p tsconfig.json",
+    "test": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json run-s test:*",
     "test:node": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json mocha",
-    "test:browser": "NODE_ENV=test karma start karma.conf.cjs",
+    "test:browser": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json karma start karma.conf.cjs",
     "prepublish": "npm run build",
     "reset-hard": "git clean -dfx -e .idea && git reset --hard && npm i && npm run build"
   },
diff --git a/packages/message-encryption/src/crypto/ecies.ts b/packages/message-encryption/src/crypto/ecies.ts
index a53d3ef558..5fc04141ee 100644
--- a/packages/message-encryption/src/crypto/ecies.ts
+++ b/packages/message-encryption/src/crypto/ecies.ts
@@ -185,8 +185,12 @@ export async function decrypt(
       (macKey) => [hash.slice(0, 16), macKey]
     );
 
+    if (!encryptionKey || !macKey) {
+      throw Error("Failed to get parameters from the hash.");
+    }
+
     if (!(await hmacSha256Verify(macKey, cipherAndIv, msgMac))) {
-      throw new Error("Incorrect MAC");
+      throw Error("Incorrect MAC");
     }
 
     return aesCtrDecrypt(iv, encryptionKey, ciphertext);
diff --git a/packages/message-hash/package.json b/packages/message-hash/package.json
index fd420f6156..d4e1bdde5d 100644
--- a/packages/message-hash/package.json
+++ b/packages/message-hash/package.json
@@ -35,12 +35,12 @@
     "fix": "run-s fix:*",
     "fix:lint": "eslint src *.js --fix",
     "check": "run-s check:*",
-    "check:tsc": "tsc -p tsconfig.dev.json",
+    "check:tsc": "tsc -p tsconfig.json",
     "check:lint": "eslint src *.js",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "test": "NODE_ENV=test run-s test:*",
+    "test": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json run-s test:*",
     "test:node": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json mocha",
-    "test:browser": "NODE_ENV=test karma start karma.conf.cjs",
+    "test:browser": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json karma start karma.conf.cjs",
     "watch:build": "tsc -p tsconfig.json -w",
     "watch:test": "mocha --watch",
     "prepublish": "npm run build",
diff --git a/packages/peer-exchange/package.json b/packages/peer-exchange/package.json
index 624cd23d14..3c9f221c0f 100644
--- a/packages/peer-exchange/package.json
+++ b/packages/peer-exchange/package.json
@@ -40,7 +40,7 @@
     "check": "run-s check:*",
     "check:lint": "eslint src *.js",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "check:tsc": "tsc -p tsconfig.dev.json",
+    "check:tsc": "tsc -p tsconfig.json",
     "prepublish": "npm run build",
     "reset-hard": "git clean -dfx -e .idea && git reset --hard && npm i && npm run build"
   },
diff --git a/packages/proto/package.json b/packages/proto/package.json
index eba220e078..ddf35ef771 100644
--- a/packages/proto/package.json
+++ b/packages/proto/package.json
@@ -36,7 +36,7 @@
     "build:esm": "tsc",
     "build:bundle": "rollup --config rollup.config.js",
     "proto": "rimraf src/lib/*.ts; protons src/lib/*.proto",
-    "check:tsc": "tsc -p tsconfig.dev.json",
+    "check:tsc": "tsc -p tsconfig.json",
     "prepublish": "npm run build",
     "reset-hard": "git clean -dfx -e .idea && git reset --hard && npm i && npm run build"
   },
diff --git a/packages/relay/package.json b/packages/relay/package.json
index 9576b053c6..59798148d1 100644
--- a/packages/relay/package.json
+++ b/packages/relay/package.json
@@ -35,11 +35,11 @@
     "fix": "run-s fix:*",
     "fix:lint": "eslint src *.js --fix",
     "check": "run-s check:*",
-    "check:tsc": "tsc -p tsconfig.dev.json",
+    "check:tsc": "tsc -p tsconfig.json",
     "check:lint": "eslint src *.js",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "test": "NODE_ENV=test run-s test:*",
-    "test:node": "TS_NODE_PROJECT=./tsconfig.dev.json mocha",
+    "test": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json run-s test:*",
+    "test:node": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json mocha",
     "watch:build": "tsc -p tsconfig.json -w",
     "watch:test": "mocha --watch",
     "prepublish": "npm run build",
diff --git a/packages/relay/src/constants.ts b/packages/relay/src/constants.ts
index 067084d991..6c02e4d59b 100644
--- a/packages/relay/src/constants.ts
+++ b/packages/relay/src/constants.ts
@@ -4,7 +4,7 @@ export const minute = 60 * second;
 /**
  * RelayCodec is the libp2p identifier for the waku relay protocol
  */
-export const RelayCodecs = ["/vac/waku/relay/2.0.0"];
+export const RelayCodec = "/vac/waku/relay/2.0.0";
 
 /**
  * RelayGossipFactor affects how many peers we will emit gossip to at each heartbeat.
diff --git a/packages/relay/src/index.ts b/packages/relay/src/index.ts
index a5f6f241f7..1fc224e9b6 100644
--- a/packages/relay/src/index.ts
+++ b/packages/relay/src/index.ts
@@ -28,7 +28,7 @@ import { isWireSizeUnderCap, toAsyncIterator } from "@waku/utils";
 import { pushOrInitMapSet } from "@waku/utils";
 import { Logger } from "@waku/utils";
 
-import { RelayCodecs } from "./constants.js";
+import { RelayCodec } from "./constants.js";
 import { messageValidator } from "./message_validator.js";
 import { TopicOnlyDecoder } from "./topic_only_message.js";
 
@@ -50,7 +50,7 @@ class Relay implements IRelay {
   public readonly pubsubTopics: Set<PubsubTopic>;
   private defaultDecoder: IDecoder<IDecodedMessage>;
 
-  public static multicodec: string = RelayCodecs[0];
+  public static multicodec: string = RelayCodec;
   public readonly gossipSub: GossipSub;
 
   /**
@@ -292,7 +292,7 @@ export function wakuGossipSub(
       fallbackToFloodsub: false
     };
     const pubsub = new GossipSub(components, init);
-    pubsub.multicodecs = RelayCodecs;
+    pubsub.multicodecs = [RelayCodec];
     return pubsub;
   };
 }
diff --git a/packages/sdk/package.json b/packages/sdk/package.json
index 9181543b16..56d2230acb 100644
--- a/packages/sdk/package.json
+++ b/packages/sdk/package.json
@@ -53,7 +53,7 @@
     "check": "run-s check:*",
     "check:lint": "eslint src *.js",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "check:tsc": "tsc -p tsconfig.dev.json",
+    "check:tsc": "tsc -p tsconfig.json",
     "prepublish": "npm run build",
     "reset-hard": "git clean -dfx -e .idea && git reset --hard && npm i && npm run build"
   },
diff --git a/packages/tests/package.json b/packages/tests/package.json
index 9fbb1ab196..e61436f54f 100644
--- a/packages/tests/package.json
+++ b/packages/tests/package.json
@@ -41,9 +41,9 @@
     "check:lint": "eslint src tests",
     "check:spelling": "cspell \"{README.md,{tests,src}/**/*.ts}\"",
     "check:tsc": "tsc -p tsconfig.dev.json",
-    "test": "NODE_ENV=test run-s test:*",
-    "test:node": "NODE_ENV=test node ./src/run-tests.js \"tests/**/!(*.optional).spec.ts\"",
-    "test:optional": "NODE_ENV=test node ./src/run-tests.js \"tests/**/@(*.optional).spec.ts\"",
+    "test": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json run-s test:*",
+    "test:node": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json node ./src/run-tests.js \"tests/**/!(*.optional).spec.ts\"",
+    "test:optional": "NODE_ENV=test TS_NODE_PROJECT=./tsconfig.dev.json node ./src/run-tests.js \"tests/**/@(*.optional).spec.ts\"",
     "reset-hard": "git clean -dfx -e .idea && git reset --hard && npm i && npm run build"
   },
   "engines": {
diff --git a/packages/tests/tests/store/multiple_pubsub.spec.ts b/packages/tests/tests/store/multiple_pubsub.spec.ts
index cfac638e96..e76494f100 100644
--- a/packages/tests/tests/store/multiple_pubsub.spec.ts
+++ b/packages/tests/tests/store/multiple_pubsub.spec.ts
@@ -3,8 +3,7 @@ import type { ContentTopicInfo, IMessage, LightNode } from "@waku/interfaces";
 import { createLightNode, Protocols } from "@waku/sdk";
 import {
   contentTopicToPubsubTopic,
-  pubsubTopicToSingleShardInfo,
-  singleShardInfosToShardInfo
+  pubsubTopicToSingleShardInfo
 } from "@waku/utils";
 import { expect } from "chai";
 
@@ -31,6 +30,7 @@ import {
   sendMessagesAutosharding,
   shardInfo1,
   shardInfoBothShards,
+  singleShardInfosToShardInfo,
   startAndConnectLightNode,
   totalMsgs
 } from "./utils.js";
diff --git a/packages/tests/tests/store/utils.ts b/packages/tests/tests/store/utils.ts
index d1b88161d0..e1225358c8 100644
--- a/packages/tests/tests/store/utils.ts
+++ b/packages/tests/tests/store/utils.ts
@@ -148,3 +148,23 @@ export const adjustDate = (baseDate: Date, adjustMs: number): Date => {
   adjusted.setTime(adjusted.getTime() + adjustMs);
   return adjusted;
 };
+
+export const singleShardInfosToShardInfo = (
+  singleShardInfos: SingleShardInfo[]
+): ShardInfo => {
+  if (singleShardInfos.length === 0) throw new Error("Invalid shard");
+
+  const clusterIds = singleShardInfos.map((shardInfo) => shardInfo.clusterId);
+  if (new Set(clusterIds).size !== 1) {
+    throw new Error("Passed shard infos have different clusterIds");
+  }
+
+  const shards = singleShardInfos
+    .map((shardInfo) => shardInfo.shard)
+    .filter((shard): shard is number => shard !== undefined);
+
+  return {
+    clusterId: singleShardInfos[0].clusterId,
+    shards
+  };
+};
diff --git a/packages/tests/tsconfig.json b/packages/tests/tsconfig.json
index 693102ecc2..36c4347b3b 100644
--- a/packages/tests/tsconfig.json
+++ b/packages/tests/tsconfig.json
@@ -3,7 +3,8 @@
   "compilerOptions": {
     "outDir": "dist/",
     "rootDir": "src",
-    "tsBuildInfoFile": "dist/.tsbuildinfo"
+    "tsBuildInfoFile": "dist/.tsbuildinfo",
+    "noUncheckedIndexedAccess": false,
   },
   "include": ["src", "src/run-tests.js"],
   "exclude": ["src/**/*.spec.ts", "src/test_utils"]
diff --git a/packages/utils/package.json b/packages/utils/package.json
index 77341da5aa..f36ce82b3c 100644
--- a/packages/utils/package.json
+++ b/packages/utils/package.json
@@ -57,7 +57,7 @@
     "check": "run-s check:*",
     "check:lint": "eslint src *.js",
     "check:spelling": "cspell \"{README.md,src/**/*.ts}\"",
-    "check:tsc": "tsc -p tsconfig.dev.json",
+    "check:tsc": "tsc -p tsconfig.json",
     "prepublish": "npm run build",
     "reset-hard": "git clean -dfx -e .idea && git reset --hard && npm i && npm run build",
     "test": "NODE_ENV=test run-s test:*",
diff --git a/packages/utils/src/common/random_subset.ts b/packages/utils/src/common/random_subset.ts
index 20d0ca83ce..84ad1d306f 100644
--- a/packages/utils/src/common/random_subset.ts
+++ b/packages/utils/src/common/random_subset.ts
@@ -22,8 +22,8 @@ function shuffle<T>(arr: T[]): T[] {
 
   for (let i = 0; i < arr.length; i++) {
     const j = randInt();
-    const tmp = arr[i];
-    arr[i] = arr[j];
+    const tmp = arr[i] as T;
+    arr[i] = arr[j] as T;
     arr[j] = tmp;
   }
   return arr;
diff --git a/packages/utils/src/common/relay_shard_codec.ts b/packages/utils/src/common/relay_shard_codec.ts
index 91dea7b4ea..063dd3be8a 100644
--- a/packages/utils/src/common/relay_shard_codec.ts
+++ b/packages/utils/src/common/relay_shard_codec.ts
@@ -52,7 +52,7 @@ export const encodeRelayShard = (shardInfo: ShardInfo): Uint8Array => {
     // rs format (Index List)
     view.setUint8(2, shards.length);
     for (let i = 0, offset = 3; i < shards.length; i++, offset += 2) {
-      view.setUint16(offset, shards[i]);
+      view.setUint16(offset, shards[i] as number);
     }
   }
 
diff --git a/packages/utils/src/common/sharding.ts b/packages/utils/src/common/sharding.ts
index 236ebc0f1f..67c7c48da4 100644
--- a/packages/utils/src/common/sharding.ts
+++ b/packages/utils/src/common/sharding.ts
@@ -19,26 +19,6 @@ export const singleShardInfoToPubsubTopic = (
   return `/waku/2/rs/${shardInfo.clusterId}/${shardInfo.shard}`;
 };
 
-export const singleShardInfosToShardInfo = (
-  singleShardInfos: SingleShardInfo[]
-): ShardInfo => {
-  if (singleShardInfos.length === 0) throw new Error("Invalid shard");
-
-  const clusterIds = singleShardInfos.map((shardInfo) => shardInfo.clusterId);
-  if (new Set(clusterIds).size !== 1) {
-    throw new Error("Passed shard infos have different clusterIds");
-  }
-
-  const shards = singleShardInfos
-    .map((shardInfo) => shardInfo.shard)
-    .filter((shard): shard is number => shard !== undefined);
-
-  return {
-    clusterId: singleShardInfos[0].clusterId,
-    shards
-  };
-};
-
 export const shardInfoToPubsubTopics = (
   shardInfo: Partial<ShardingParams>
 ): PubsubTopic[] => {
@@ -80,15 +60,15 @@ export const pubsubTopicToSingleShardInfo = (
   const parts = pubsubTopics.split("/");
 
   if (
-    parts.length != 6 ||
+    parts.length !== 6 ||
     parts[1] !== "waku" ||
     parts[2] !== "2" ||
     parts[3] !== "rs"
   )
     throw new Error("Invalid pubsub topic");
 
-  const clusterId = parseInt(parts[4]);
-  const shard = parseInt(parts[5]);
+  const clusterId = parseInt(parts[4] as string);
+  const shard = parseInt(parts[5] as string);
 
   if (isNaN(clusterId) || isNaN(shard))
     throw new Error("Invalid clusterId or shard");
@@ -131,7 +111,7 @@ export function ensureValidContentTopic(contentTopic: string): ContentTopic {
   // Validate generation field if present
   let generation = 0;
   if (parts.length == 6) {
-    generation = parseInt(parts[1]);
+    generation = parseInt(parts[1] as string);
     if (isNaN(generation)) {
       throw new Error("Invalid generation field in content topic");
     }
@@ -141,29 +121,33 @@ export function ensureValidContentTopic(contentTopic: string): ContentTopic {
   }
   // Validate remaining fields
   const fields = parts.splice(-4);
-  // Validate application field
-  if (fields[0].length == 0) {
+
+  const application = fields[0];
+  if (!application || application?.length == 0) {
     throw new Error("Application field cannot be empty");
   }
-  // Validate version field
-  if (fields[1].length == 0) {
+
+  const version = fields[1];
+  if (!version || version?.length == 0) {
     throw new Error("Version field cannot be empty");
   }
-  // Validate topic name field
-  if (fields[2].length == 0) {
+
+  const topicName = fields[2];
+  if (!topicName || topicName?.length == 0) {
     throw new Error("Topic name field cannot be empty");
   }
-  // Validate encoding field
-  if (fields[3].length == 0) {
+
+  const encoding = fields[3];
+  if (!encoding || encoding?.length == 0) {
     throw new Error("Encoding field cannot be empty");
   }
 
   return {
     generation,
-    application: fields[0],
-    version: fields[1],
-    topicName: fields[2],
-    encoding: fields[3]
+    application,
+    version,
+    topicName,
+    encoding
   };
 }
 
diff --git a/packages/utils/src/libp2p/index.ts b/packages/utils/src/libp2p/index.ts
index 04c37c7d6d..348cc0278c 100644
--- a/packages/utils/src/libp2p/index.ts
+++ b/packages/utils/src/libp2p/index.ts
@@ -61,7 +61,7 @@ export async function getPeersForProtocol(
   const peers: Peer[] = [];
   await peerStore.forEach((peer) => {
     for (let i = 0; i < protocols.length; i++) {
-      if (peer.protocols.includes(protocols[i])) {
+      if (peer.protocols.includes(protocols[i] as string)) {
         peers.push(peer);
         break;
       }
diff --git a/tsconfig.dev.json b/tsconfig.dev.json
index 17eb953a8b..02ffa814d0 100644
--- a/tsconfig.dev.json
+++ b/tsconfig.dev.json
@@ -3,6 +3,6 @@
   "compilerOptions": {
     "module": "ESNext",
     "moduleResolution": "Bundler",
-    "noEmit": true
+    "noUncheckedIndexedAccess": false,
   }
 }
diff --git a/tsconfig.json b/tsconfig.json
index 5a268831bf..bbf3bcf06b 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -37,6 +37,7 @@
     /* Experimental Options */
     // "experimentalDecorators": true /* Enables experimental support for ES7 decorators. */,
     // "emitDecoratorMetadata": true /* Enables experimental support for emitting type metadata for decorators. */,
+    "noUncheckedIndexedAccess": true,
 
     "lib": ["es2022", "dom"],
     "types": ["node", "mocha"],