diff --git a/spec/integ/crypto/crypto.spec.ts b/spec/integ/crypto/crypto.spec.ts
index 96d809aea9..af1142dfe0 100644
--- a/spec/integ/crypto/crypto.spec.ts
+++ b/spec/integ/crypto/crypto.spec.ts
@@ -3142,7 +3142,7 @@ describe.each(Object.entries(CRYPTO_BACKENDS))("crypto (%s)", (backend: string,
                     fetchMock.put(
                         "path:/_matrix/client/v3/room_keys/keys",
                         (url, request) => {
-                            const uploadPayload: KeyBackup = JSON.parse(request.body?.toString() ?? "{}");
+                            const uploadPayload: KeyBackup = JSON.parse((request.body as string) ?? "{}");
                             resolve(uploadPayload);
                             return {
                                 status: 200,
@@ -3209,7 +3209,7 @@ describe.each(Object.entries(CRYPTO_BACKENDS))("crypto (%s)", (backend: string,
                 fetchMock.post(
                     "path:/_matrix/client/v3/room_keys/version",
                     (url, request) => {
-                        const backupData: KeyBackupInfo = JSON.parse(request.body?.toString() ?? "{}");
+                        const backupData: KeyBackupInfo = JSON.parse((request.body as string) ?? "{}");
                         backupData.version = newVersion;
                         backupData.count = 0;
                         backupData.etag = "zer";
diff --git a/spec/integ/crypto/megolm-backup.spec.ts b/spec/integ/crypto/megolm-backup.spec.ts
index 05b5ff27b6..eff0ff567e 100644
--- a/spec/integ/crypto/megolm-backup.spec.ts
+++ b/spec/integ/crypto/megolm-backup.spec.ts
@@ -91,7 +91,7 @@ function mockUploadEmitter(
                     },
                 };
             }
-            const uploadPayload: KeyBackup = JSON.parse(request.body?.toString() ?? "{}");
+            const uploadPayload: KeyBackup = JSON.parse((request.body as string) ?? "{}");
             let count = 0;
             for (const [roomId, value] of Object.entries(uploadPayload.rooms)) {
                 for (const sessionId of Object.keys(value.sessions)) {
diff --git a/spec/test-utils/mockEndpoints.ts b/spec/test-utils/mockEndpoints.ts
index 988d6f13b6..7c16583885 100644
--- a/spec/test-utils/mockEndpoints.ts
+++ b/spec/test-utils/mockEndpoints.ts
@@ -88,7 +88,7 @@ export function mockSetupMegolmBackupRequests(backupVersion: string): void {
     });
 
     fetchMock.post("path:/_matrix/client/v3/room_keys/version", (url, request) => {
-        const backupData: KeyBackupInfo = JSON.parse(request.body?.toString() ?? "{}");
+        const backupData: KeyBackupInfo = JSON.parse((request.body as string) ?? "{}");
         backupData.version = backupVersion;
         backupData.count = 0;
         backupData.etag = "zer";
diff --git a/src/client.ts b/src/client.ts
index 2de41f2ca2..54f5309428 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -5065,7 +5065,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             if (this.canSupport.get(Feature.RelationBasedRedactions) === ServerSupport.Unsupported) {
                 throw new Error(
                     "Server does not support relation based redactions " +
-                        `roomId ${roomId} eventId ${eventId} txnId: ${txnId} threadId ${threadId}`,
+                        `roomId ${roomId} eventId ${eventId} txnId: ${txnId as string} threadId ${threadId}`,
                 );
             }
 
diff --git a/src/crypto/store/indexeddb-crypto-store-backend.ts b/src/crypto/store/indexeddb-crypto-store-backend.ts
index 55a3d5aaff..6705ce0ed1 100644
--- a/src/crypto/store/indexeddb-crypto-store-backend.ts
+++ b/src/crypto/store/indexeddb-crypto-store-backend.ts
@@ -776,7 +776,7 @@ export class Backend implements CryptoStore {
                 ev.preventDefault();
                 logger.log("Ignoring duplicate inbound group session: " + senderCurve25519Key + " / " + sessionId);
             } else {
-                abortWithException(txn, new Error("Failed to add inbound group session: " + addReq.error));
+                abortWithException(txn, new Error("Failed to add inbound group session: " + addReq.error?.name));
             }
         };
     }
diff --git a/src/store/indexeddb-local-backend.ts b/src/store/indexeddb-local-backend.ts
index 0367380386..04a58dd410 100644
--- a/src/store/indexeddb-local-backend.ts
+++ b/src/store/indexeddb-local-backend.ts
@@ -71,7 +71,7 @@ function selectQuery<T>(
     return new Promise((resolve, reject) => {
         const results: T[] = [];
         query.onerror = (): void => {
-            reject(new Error("Query failed: " + query.error));
+            reject(new Error("Query failed: " + query.error?.name));
         };
         // collect results
         query.onsuccess = (): void => {
@@ -360,7 +360,7 @@ export class LocalIndexedDBStoreBackend implements IIndexedDBBackend {
                 // in firefox, with indexedDB disabled, this fails with a
                 // DOMError. We treat this as non-fatal, so that we can still
                 // use the app.
-                logger.warn(`unable to delete js-sdk store indexeddb: ${req.error}`);
+                logger.warn(`unable to delete js-sdk store indexeddb: ${req.error?.name}`);
                 resolve();
             };
 
diff --git a/yarn.lock b/yarn.lock
index a7ea2491c3..f652440929 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1857,29 +1857,29 @@
     "@types/yargs-parser" "*"
 
 "@typescript-eslint/eslint-plugin@^8.0.0":
-  version "8.16.0"
-  resolved "https://registry.yarnpkg.com/@typescript-eslint/eslint-plugin/-/eslint-plugin-8.16.0.tgz#ac56825bcdf3b392fc76a94b1315d4a162f201a6"
-  integrity sha512-5YTHKV8MYlyMI6BaEG7crQ9BhSc8RxzshOReKwZwRWN0+XvvTOm+L/UYLCYxFpfwYuAAqhxiq4yae0CMFwbL7Q==
+  version "8.18.0"
+  resolved "https://registry.yarnpkg.com/@typescript-eslint/eslint-plugin/-/eslint-plugin-8.18.0.tgz#0901933326aea4443b81df3f740ca7dfc45c7bea"
+  integrity sha512-NR2yS7qUqCL7AIxdJUQf2MKKNDVNaig/dEB0GBLU7D+ZdHgK1NoH/3wsgO3OnPVipn51tG3MAwaODEGil70WEw==
   dependencies:
     "@eslint-community/regexpp" "^4.10.0"
-    "@typescript-eslint/scope-manager" "8.16.0"
-    "@typescript-eslint/type-utils" "8.16.0"
-    "@typescript-eslint/utils" "8.16.0"
-    "@typescript-eslint/visitor-keys" "8.16.0"
+    "@typescript-eslint/scope-manager" "8.18.0"
+    "@typescript-eslint/type-utils" "8.18.0"
+    "@typescript-eslint/utils" "8.18.0"
+    "@typescript-eslint/visitor-keys" "8.18.0"
     graphemer "^1.4.0"
     ignore "^5.3.1"
     natural-compare "^1.4.0"
     ts-api-utils "^1.3.0"
 
 "@typescript-eslint/parser@^8.0.0":
-  version "8.16.0"
-  resolved "https://registry.yarnpkg.com/@typescript-eslint/parser/-/parser-8.16.0.tgz#ee5b2d6241c1ab3e2e53f03fd5a32d8e266d8e06"
-  integrity sha512-D7DbgGFtsqIPIFMPJwCad9Gfi/hC0PWErRRHFnaCWoEDYi5tQUDiJCTmGUbBiLzjqAck4KcXt9Ayj0CNlIrF+w==
+  version "8.18.0"
+  resolved "https://registry.yarnpkg.com/@typescript-eslint/parser/-/parser-8.18.0.tgz#a1c9456cbb6a089730bf1d3fc47946c5fb5fe67b"
+  integrity sha512-hgUZ3kTEpVzKaK3uNibExUYm6SKKOmTU2BOxBSvOYwtJEPdVQ70kZJpPjstlnhCHcuc2WGfSbpKlb/69ttyN5Q==
   dependencies:
-    "@typescript-eslint/scope-manager" "8.16.0"
-    "@typescript-eslint/types" "8.16.0"
-    "@typescript-eslint/typescript-estree" "8.16.0"
-    "@typescript-eslint/visitor-keys" "8.16.0"
+    "@typescript-eslint/scope-manager" "8.18.0"
+    "@typescript-eslint/types" "8.18.0"
+    "@typescript-eslint/typescript-estree" "8.18.0"
+    "@typescript-eslint/visitor-keys" "8.18.0"
     debug "^4.3.4"
 
 "@typescript-eslint/scope-manager@8.14.0":
@@ -1898,13 +1898,21 @@
     "@typescript-eslint/types" "8.16.0"
     "@typescript-eslint/visitor-keys" "8.16.0"
 
-"@typescript-eslint/type-utils@8.16.0":
-  version "8.16.0"
-  resolved "https://registry.yarnpkg.com/@typescript-eslint/type-utils/-/type-utils-8.16.0.tgz#585388735f7ac390f07c885845c3d185d1b64740"
-  integrity sha512-IqZHGG+g1XCWX9NyqnI/0CX5LL8/18awQqmkZSl2ynn8F76j579dByc0jhfVSnSnhf7zv76mKBQv9HQFKvDCgg==
+"@typescript-eslint/scope-manager@8.18.0":
+  version "8.18.0"
+  resolved "https://registry.yarnpkg.com/@typescript-eslint/scope-manager/-/scope-manager-8.18.0.tgz#30b040cb4557804a7e2bcc65cf8fdb630c96546f"
+  integrity sha512-PNGcHop0jkK2WVYGotk/hxj+UFLhXtGPiGtiaWgVBVP1jhMoMCHlTyJA+hEj4rszoSdLTK3fN4oOatrL0Cp+Xw==
   dependencies:
-    "@typescript-eslint/typescript-estree" "8.16.0"
-    "@typescript-eslint/utils" "8.16.0"
+    "@typescript-eslint/types" "8.18.0"
+    "@typescript-eslint/visitor-keys" "8.18.0"
+
+"@typescript-eslint/type-utils@8.18.0":
+  version "8.18.0"
+  resolved "https://registry.yarnpkg.com/@typescript-eslint/type-utils/-/type-utils-8.18.0.tgz#6f0d12cf923b6fd95ae4d877708c0adaad93c471"
+  integrity sha512-er224jRepVAVLnMF2Q7MZJCq5CsdH2oqjP4dT7K6ij09Kyd+R21r7UVJrF0buMVdZS5QRhDzpvzAxHxabQadow==
+  dependencies:
+    "@typescript-eslint/typescript-estree" "8.18.0"
+    "@typescript-eslint/utils" "8.18.0"
     debug "^4.3.4"
     ts-api-utils "^1.3.0"
 
@@ -1918,6 +1926,11 @@
   resolved "https://registry.yarnpkg.com/@typescript-eslint/types/-/types-8.16.0.tgz#49c92ae1b57942458ab83d9ec7ccab3005e64737"
   integrity sha512-NzrHj6thBAOSE4d9bsuRNMvk+BvaQvmY4dDglgkgGC0EW/tB3Kelnp3tAKH87GEwzoxgeQn9fNGRyFJM/xd+GQ==
 
+"@typescript-eslint/types@8.18.0":
+  version "8.18.0"
+  resolved "https://registry.yarnpkg.com/@typescript-eslint/types/-/types-8.18.0.tgz#3afcd30def8756bc78541268ea819a043221d5f3"
+  integrity sha512-FNYxgyTCAnFwTrzpBGq+zrnoTO4x0c1CKYY5MuUTzpScqmY5fmsh2o3+57lqdI3NZucBDCzDgdEbIaNfAjAHQA==
+
 "@typescript-eslint/typescript-estree@8.14.0":
   version "8.14.0"
   resolved "https://registry.yarnpkg.com/@typescript-eslint/typescript-estree/-/typescript-estree-8.14.0.tgz#a7a3a5a53a6c09313e12fb4531d4ff582ee3c312"
@@ -1946,15 +1959,29 @@
     semver "^7.6.0"
     ts-api-utils "^1.3.0"
 
-"@typescript-eslint/utils@8.16.0", "@typescript-eslint/utils@^8.13.0":
-  version "8.16.0"
-  resolved "https://registry.yarnpkg.com/@typescript-eslint/utils/-/utils-8.16.0.tgz#c71264c437157feaa97842809836254a6fc833c3"
-  integrity sha512-C1zRy/mOL8Pj157GiX4kaw7iyRLKfJXBR3L82hk5kS/GyHcOFmy4YUq/zfZti72I9wnuQtA/+xzft4wCC8PJdA==
+"@typescript-eslint/typescript-estree@8.18.0":
+  version "8.18.0"
+  resolved "https://registry.yarnpkg.com/@typescript-eslint/typescript-estree/-/typescript-estree-8.18.0.tgz#d8ca785799fbb9c700cdff1a79c046c3e633c7f9"
+  integrity sha512-rqQgFRu6yPkauz+ms3nQpohwejS8bvgbPyIDq13cgEDbkXt4LH4OkDMT0/fN1RUtzG8e8AKJyDBoocuQh8qNeg==
+  dependencies:
+    "@typescript-eslint/types" "8.18.0"
+    "@typescript-eslint/visitor-keys" "8.18.0"
+    debug "^4.3.4"
+    fast-glob "^3.3.2"
+    is-glob "^4.0.3"
+    minimatch "^9.0.4"
+    semver "^7.6.0"
+    ts-api-utils "^1.3.0"
+
+"@typescript-eslint/utils@8.18.0":
+  version "8.18.0"
+  resolved "https://registry.yarnpkg.com/@typescript-eslint/utils/-/utils-8.18.0.tgz#48f67205d42b65d895797bb7349d1be5c39a62f7"
+  integrity sha512-p6GLdY383i7h5b0Qrfbix3Vc3+J2k6QWw6UMUeY5JGfm3C5LbZ4QIZzJNoNOfgyRe0uuYKjvVOsO/jD4SJO+xg==
   dependencies:
     "@eslint-community/eslint-utils" "^4.4.0"
-    "@typescript-eslint/scope-manager" "8.16.0"
-    "@typescript-eslint/types" "8.16.0"
-    "@typescript-eslint/typescript-estree" "8.16.0"
+    "@typescript-eslint/scope-manager" "8.18.0"
+    "@typescript-eslint/types" "8.18.0"
+    "@typescript-eslint/typescript-estree" "8.18.0"
 
 "@typescript-eslint/utils@^6.0.0 || ^7.0.0 || ^8.0.0":
   version "8.14.0"
@@ -1966,6 +1993,16 @@
     "@typescript-eslint/types" "8.14.0"
     "@typescript-eslint/typescript-estree" "8.14.0"
 
+"@typescript-eslint/utils@^8.13.0":
+  version "8.16.0"
+  resolved "https://registry.yarnpkg.com/@typescript-eslint/utils/-/utils-8.16.0.tgz#c71264c437157feaa97842809836254a6fc833c3"
+  integrity sha512-C1zRy/mOL8Pj157GiX4kaw7iyRLKfJXBR3L82hk5kS/GyHcOFmy4YUq/zfZti72I9wnuQtA/+xzft4wCC8PJdA==
+  dependencies:
+    "@eslint-community/eslint-utils" "^4.4.0"
+    "@typescript-eslint/scope-manager" "8.16.0"
+    "@typescript-eslint/types" "8.16.0"
+    "@typescript-eslint/typescript-estree" "8.16.0"
+
 "@typescript-eslint/visitor-keys@8.14.0":
   version "8.14.0"
   resolved "https://registry.yarnpkg.com/@typescript-eslint/visitor-keys/-/visitor-keys-8.14.0.tgz#2418d5a54669af9658986ade4e6cfb7767d815ad"
@@ -1982,6 +2019,14 @@
     "@typescript-eslint/types" "8.16.0"
     eslint-visitor-keys "^4.2.0"
 
+"@typescript-eslint/visitor-keys@8.18.0":
+  version "8.18.0"
+  resolved "https://registry.yarnpkg.com/@typescript-eslint/visitor-keys/-/visitor-keys-8.18.0.tgz#7b6d33534fa808e33a19951907231ad2ea5c36dd"
+  integrity sha512-pCh/qEA8Lb1wVIqNvBke8UaRjJ6wrAWkJO5yyIbs8Yx6TNGYyfNjOo61tLv+WwLvoLPp4BQ8B7AHKijl8NGUfw==
+  dependencies:
+    "@typescript-eslint/types" "8.18.0"
+    eslint-visitor-keys "^4.2.0"
+
 "@ungap/structured-clone@^1.2.0":
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/@ungap/structured-clone/-/structured-clone-1.2.0.tgz#756641adb587851b5ccb3e095daf27ae581c8406"
@@ -5846,7 +5891,16 @@ string-length@^4.0.1:
     char-regex "^1.0.2"
     strip-ansi "^6.0.0"
 
-"string-width-cjs@npm:string-width@^4.2.0", string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.3:
+"string-width-cjs@npm:string-width@^4.2.0":
+  version "4.2.3"
+  resolved "https://registry.yarnpkg.com/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
+  integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
+  dependencies:
+    emoji-regex "^8.0.0"
+    is-fullwidth-code-point "^3.0.0"
+    strip-ansi "^6.0.1"
+
+string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.3:
   version "4.2.3"
   resolved "https://registry.yarnpkg.com/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
   integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
@@ -6069,9 +6123,9 @@ tr46@~0.0.3:
   integrity sha512-N3WMsuqV66lT30CrXNbEjx4GEwlow3v6rr4mCcv6prnfwhS01rkgyFdjPNBYd9br7LpXV1+Emh01fHnq2Gdgrw==
 
 ts-api-utils@^1.3.0:
-  version "1.4.2"
-  resolved "https://registry.yarnpkg.com/ts-api-utils/-/ts-api-utils-1.4.2.tgz#a6a6dff26117ac7965624fc118525971edc6a82a"
-  integrity sha512-ZF5gQIQa/UmzfvxbHZI3JXN0/Jt+vnAfAviNRAMc491laiK6YCLpCW9ft8oaCRFOTxCZtUTE6XB0ZQAe3olntw==
+  version "1.4.3"
+  resolved "https://registry.yarnpkg.com/ts-api-utils/-/ts-api-utils-1.4.3.tgz#bfc2215fe6528fecab2b0fba570a2e8a4263b064"
+  integrity sha512-i3eMG77UTMD0hZhgRS562pv83RC6ukSAC2GMNWc+9dieh/+jDM5u5YG+NHX6VNDRHQcHwmsTHctP9LhbC3WxVw==
 
 ts-node@^10.9.2:
   version "10.9.2"
@@ -6445,7 +6499,16 @@ word-wrap@^1.2.5:
   resolved "https://registry.yarnpkg.com/word-wrap/-/word-wrap-1.2.5.tgz#d2c45c6dd4fbce621a66f136cbe328afd0410b34"
   integrity sha512-BN22B5eaMMI9UMtjrGd5g5eCYPpCPDUy0FJXbYsaT5zYxjFOckS53SQDE3pWkVoWpHXVb3BrYcEN4Twa55B5cA==
 
-"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0", wrap-ansi@^7.0.0:
+"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0":
+  version "7.0.0"
+  resolved "https://registry.yarnpkg.com/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
+  integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==
+  dependencies:
+    ansi-styles "^4.0.0"
+    string-width "^4.1.0"
+    strip-ansi "^6.0.0"
+
+wrap-ansi@^7.0.0:
   version "7.0.0"
   resolved "https://registry.yarnpkg.com/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
   integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==