omarqureshi · omarqureshi · Jun 6, 2026 · Jun 10, 2026 · Jun 10, 2026 · Jun 11, 2026
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
@@ -433,6 +433,7 @@ jobs:
         rosetta:
           - latest
           - 5.9.x
+          - 6.0.x
     steps:
       # Check out the code
       - name: Download Artifact

diff --git a/.yarnrc.yml b/.yarnrc.yml
@@ -1,3 +1,7 @@
 nodeLinker: node-modules
 
 npmMinimalAgeGate: 3d
+
+npmPreapprovedPackages:
+  - "jsii-rosetta@^6.0.0"
+  - "jsii@^6.0.0"
diff --git a/package.json b/package.json
@@ -19,26 +19,26 @@
     "@jest/types": "^29.6.3",
     "@types/jest": "^30.0.0",
     "@types/node": "^18",
-    "@typescript-eslint/eslint-plugin": "^8.57.2",
-    "@typescript-eslint/parser": "^8.57.2",
+    "@typescript-eslint/eslint-plugin": "^8.60.1",
+    "@typescript-eslint/parser": "^8.60.1",
     "@yarnpkg/types": "^4.0.1",
     "all-contributors-cli": "^6.26.1",
     "eslint": "^9.39.4",
     "eslint-config-prettier": "^10.1.8",
     "eslint-import-resolver-node": "^0.4.0",
-    "eslint-import-resolver-typescript": "^4.4.4",
+    "eslint-import-resolver-typescript": "^4.4.5",
     "eslint-plugin-import": "2.31.0",
     "eslint-plugin-prettier": "^5.5.6",
     "jest": "^30.4.2",
     "jest-circus": "^30.4.2",
     "jest-config": "^30.4.2",
     "jest-expect-message": "^1.1.3",
     "lerna": "^9.0.7",
-    "npm-check-updates": "^22.2.1",
+    "npm-check-updates": "^22.2.3",
     "prettier": "^3.8.3",
     "standard-version": "^9.5.0",
     "ts-node": "^10.9.2",
-    "typescript": "5.9.x"
+    "typescript": "6.x"
   },
   "repository": {
     "type": "git",

diff --git a/packages/@jsii/check-node/package.json b/packages/@jsii/check-node/package.json
@@ -37,12 +37,12 @@
   },
   "dependencies": {
     "chalk": "^4.1.2",
-    "semver": "^7.8.1"
+    "semver": "^7.8.2"
   },
   "devDependencies": {
     "eslint": "^9.39.4",
     "jest": "^30.4.2",
     "jsii-build-tools": "^0.0.0",
-    "typescript": "5.9.x"
+    "typescript": "6.x"
   }
 }
diff --git a/packages/@jsii/dotnet-runtime-test/package.json b/packages/@jsii/dotnet-runtime-test/package.json
@@ -33,6 +33,6 @@
     "@jsii/dotnet-runtime": "^0.0.0",
     "jsii-calc": "^3.20.120",
     "jsii-pacmak": "^0.0.0",
-    "typescript": "5.9.x"
+    "typescript": "6.x"
   }
 }
diff --git a/packages/@jsii/dotnet-runtime/package.json b/packages/@jsii/dotnet-runtime/package.json
@@ -41,7 +41,7 @@
     "@jsii/runtime": "^0.0.0",
     "@types/semver": "^7.7.1",
     "jsii-build-tools": "^0.0.0",
-    "semver": "^7.8.1",
-    "typescript": "5.9.x"
+    "semver": "^7.8.2",
+    "typescript": "6.x"
   }
 }
diff --git a/packages/@jsii/go-runtime-test/package.json b/packages/@jsii/go-runtime-test/package.json
@@ -16,7 +16,7 @@
   "license": "Apache-2.0",
   "devDependencies": {
     "jsii-pacmak": "^0.0.0",
-    "typescript": "5.9.x"
+    "typescript": "6.x"
   },
   "dependencies": {
     "@jsii/go-runtime": "^0.0.0",

diff --git a/packages/@jsii/go-runtime/package.json b/packages/@jsii/go-runtime/package.json
@@ -27,6 +27,6 @@
     "fs-extra": "^10.1.0",
     "jsii-build-tools": "^0.0.0",
     "jsii-calc": "^3.20.120",
-    "typescript": "5.9.x"
+    "typescript": "6.x"
   }
 }
diff --git a/packages/@jsii/java-runtime/package.json b/packages/@jsii/java-runtime/package.json
@@ -34,6 +34,6 @@
   "devDependencies": {
     "@jsii/runtime": "^0.0.0",
     "jsii-build-tools": "^0.0.0",
-    "typescript": "5.9.x"
+    "typescript": "6.x"
   }
 }
diff --git a/packages/@jsii/kernel/package.json b/packages/@jsii/kernel/package.json
@@ -34,7 +34,7 @@
     "@jsii/spec": "0.0.0",
     "fs-extra": "^10.1.0",
     "lockfile": "^1.0.4",
-    "tar": "^7.5.15"
+    "tar": "^7.5.16"
   },
   "devDependencies": {
     "@scope/jsii-calc-base": "^0.0.0",
@@ -46,6 +46,6 @@
     "jest-expect-message": "^1.1.3",
     "jsii-build-tools": "^0.0.0",
     "jsii-calc": "^3.20.120",
-    "typescript": "5.9.x"
+    "typescript": "6.x"
   }
 }
diff --git a/packages/@jsii/kernel/src/kernel.ts b/packages/@jsii/kernel/src/kernel.ts
@@ -641,7 +641,7 @@ export class Kernel {
 
     switch (typeinfo.kind) {
       case spec.TypeKind.Class:
-        const classType = typeinfo as spec.ClassType;
+        const classType = typeinfo;
         this.#validateMethodArguments(classType.initializer, args);
         return {
           ctor: this.#findSymbol(fqn),
@@ -1248,11 +1248,11 @@ export class Kernel {
       let bases;
 
       if (spec.isClassType(typeInfo)) {
-        const classTypeInfo = typeInfo as spec.ClassType;
+        const classTypeInfo = typeInfo;
         properties = classTypeInfo.properties;
         bases = classTypeInfo.base ? [classTypeInfo.base] : [];
       } else if (spec.isInterfaceType(typeInfo)) {
-        const interfaceTypeInfo = typeInfo as spec.InterfaceType;
+        const interfaceTypeInfo = typeInfo;
         properties = interfaceTypeInfo.properties;
         bases = interfaceTypeInfo.interfaces ?? [];
       } else {

diff --git a/packages/@jsii/kernel/src/objects.ts b/packages/@jsii/kernel/src/objects.ts
@@ -1,5 +1,5 @@
 import * as spec from '@jsii/spec';
-import * as assert from 'assert';
+import assert from 'assert';
 import { inspect } from 'util';
 
 import * as api from './api';

diff --git a/packages/@jsii/kernel/src/on-exit.ts b/packages/@jsii/kernel/src/on-exit.ts
@@ -1,5 +1,5 @@
 import * as fs from 'fs-extra';
-import * as process from 'process';
+import process from 'process';
 
 const removeSyncPaths = new Array<string>();
 

diff --git a/packages/@jsii/kernel/src/serialization.ts b/packages/@jsii/kernel/src/serialization.ts
@@ -27,7 +27,7 @@
  */
 
 import * as spec from '@jsii/spec';
-import * as assert from 'assert';
+import assert from 'assert';
 import { inspect } from 'util';
 
 import {
@@ -1288,12 +1288,12 @@ function describeTypeOf(
         return 'an array';
       }
 
-      const fqn = jsiiTypeFqn(value as object, isVisibleType);
+      const fqn = jsiiTypeFqn(value, isVisibleType);
       if (fqn != null && fqn !== EMPTY_OBJECT_FQN) {
         return `an instance of ${fqn}`;
       }
 
-      const ctorName = (value as object).constructor.name;
+      const ctorName = value.constructor.name;
       if (ctorName != null && ctorName !== Object.name) {
         return `an instance of ${ctorName}`;
       }

diff --git a/packages/@jsii/python-runtime/package.json b/packages/@jsii/python-runtime/package.json
@@ -44,6 +44,7 @@
     "jsii-build-tools": "^0.0.0",
     "jsii-calc": "^3.20.120",
     "jsii-pacmak": "^0.0.0",
-    "pyright": "^1.1.410"
+    "pyright": "^1.1.410",
+    "ts-node": "^10.9.2"
   }
 }
diff --git a/packages/@jsii/python-runtime/tests/test_invoke_bin.py b/packages/@jsii/python-runtime/tests/test_invoke_bin.py
@@ -104,18 +104,29 @@ def test_invoke_script_with_line_flush(
                 current_dt = datetime.utcnow()
 
                 delay_s = round((current_dt - last_dt).total_seconds())
-                timed_lines.append([line, delay_s])
+                timed_lines.append((line, delay_s))
 
                 last_dt = current_dt
         exit_code = proc.wait()
 
         assert exit_code == 0
-        assert timed_lines == [
-            [b"Hello World!\n", 0],
-            [b"  arguments: arg1, delay\n", 0],
-            [b"sleeping 1s 1\n", 0],
-            [b"sleeping 1s 2\n", 1],
-            [b"sleeping 1s 3\n", 1],
-            [b"sleeping 1s 4\n", 1],
-            [b"sleeping 1s 5\n", 1],
+        expected_lines = [
+            b"Hello World!\n",
+            b"  arguments: arg1, delay\n",
+            b"sleeping 1s 1\n",
+            b"sleeping 1s 2\n",
+            b"sleeping 1s 3\n",
+            b"sleeping 1s 4\n",
+            b"sleeping 1s 5\n",
         ]
+
+        # Check we got the right lines
+        assert [item[0] for item in timed_lines] == expected_lines
+
+        # Check that we didn't receive all lines at once (which would happen if they were buffered)
+        # The first 3 lines are printed immediately, so their delays should be around 0.
+        # The subsequent lines should have delays > 0 since they sleep for 1s.
+        for line, delay in timed_lines[3:]:
+            assert (
+                int(delay) >= 1
+            ), f"Expected line {line!r} to be delayed, but got delay of {delay}s"
diff --git a/packages/@jsii/runtime/package.json b/packages/@jsii/runtime/package.json
@@ -46,7 +46,7 @@
     "jsii-build-tools": "^0.0.0",
     "jsii-calc": "^3.20.120",
     "source-map-loader": "^5.0.0",
-    "typescript": "5.9.x",
+    "typescript": "6.x",
     "webpack": "^5.107.2",
     "webpack-cli": "^7.0.3"
   }

diff --git a/packages/@jsii/spec/package.json b/packages/@jsii/spec/package.json
@@ -36,7 +36,7 @@
     "eslint": "^9.39.4",
     "jest": "^30.4.2",
     "jsii-build-tools": "^0.0.0",
-    "typescript": "5.9.x",
+    "typescript": "6.x",
     "typescript-json-schema": "^0.67.4"
   }
 }
diff --git a/packages/@scope/jsii-calc-base-of-base/package.json b/packages/@scope/jsii-calc-base-of-base/package.json
@@ -30,10 +30,10 @@
     "test:update": "yarn build && UPDATE_DIFF=1 yarn test"
   },
   "devDependencies": {
-    "jsii": "5.9.28",
+    "jsii": "6.0.1",
     "jsii-build-tools": "^0.0.0",
-    "jsii-rosetta": "^5.9.32",
-    "typescript": "5.9.x"
+    "jsii-rosetta": "^6.0.0",
+    "typescript": "6.x"
   },
   "jsii": {
     "outdir": "dist",

diff --git a/packages/@scope/jsii-calc-base-of-base/test/assembly.jsii b/packages/@scope/jsii-calc-base-of-base/test/assembly.jsii
@@ -9,7 +9,7 @@
   },
   "description": "An example transitive dependency for jsii-calc.",
   "homepage": "https://github.com/aws/jsii",
-  "jsiiVersion": "5.9.28",
+  "jsiiVersion": "6.0.1",
   "license": "Apache-2.0",
   "metadata": {
     "jsii": {
@@ -169,5 +169,5 @@
     }
   },
   "version": "2.1.1",
-  "fingerprint": "BjSsTpfAZrUOLnC8ASj2CZzF3hk7An9dtBfSV5UCVQQ="
+  "fingerprint": "n/Wnr2S8ZAsMAtxUqhEZ5jnX5qNcXyPhHAO1nWXclOM="
 }
diff --git a/packages/@scope/jsii-calc-base/package.json b/packages/@scope/jsii-calc-base/package.json
@@ -35,10 +35,10 @@
     "@scope/jsii-calc-base-of-base": "^2.1.1"
   },
   "devDependencies": {
-    "jsii": "5.9.28",
+    "jsii": "6.0.1",
     "jsii-build-tools": "^0.0.0",
-    "jsii-rosetta": "^5.9.32",
-    "typescript": "5.9.x"
+    "jsii-rosetta": "^6.0.0",
+    "typescript": "6.x"
   },
   "jsii": {
     "metadata": {

diff --git a/packages/@scope/jsii-calc-base/test/assembly.jsii b/packages/@scope/jsii-calc-base/test/assembly.jsii
@@ -39,7 +39,7 @@
   },
   "description": "An example direct dependency for jsii-calc.",
   "homepage": "https://github.com/aws/jsii",
-  "jsiiVersion": "5.9.28",
+  "jsiiVersion": "6.0.1",
   "license": "Apache-2.0",
   "metadata": {
     "jsii": {
@@ -210,5 +210,5 @@
     }
   },
   "version": "0.0.0",
-  "fingerprint": "6KIUIA93Vgu+WbV0lkhiIW7AzQP8IaESaRI8HrnLF5E="
+  "fingerprint": "OQw7pozGKvEAFpZzGYsGWDf1TP3ZajLf75a3XbmCQzY="
 }
diff --git a/packages/@scope/jsii-calc-lib/package.json b/packages/@scope/jsii-calc-lib/package.json
@@ -39,10 +39,10 @@
     "@scope/jsii-calc-base-of-base": "^2.1.1"
   },
   "devDependencies": {
-    "jsii": "5.9.28",
+    "jsii": "6.0.1",
     "jsii-build-tools": "^0.0.0",
-    "jsii-rosetta": "^5.9.32",
-    "typescript": "5.9.x"
+    "jsii-rosetta": "^6.0.0",
+    "typescript": "6.x"
   },
   "jsii": {
     "outdir": "dist",

diff --git a/packages/@scope/jsii-calc-lib/test/assembly.jsii b/packages/@scope/jsii-calc-lib/test/assembly.jsii
@@ -71,7 +71,7 @@
     "stability": "deprecated"
   },
   "homepage": "https://github.com/aws/jsii",
-  "jsiiVersion": "5.9.28",
+  "jsiiVersion": "6.0.1",
   "license": "Apache-2.0",
   "metadata": {
     "jsii": {
@@ -1164,5 +1164,5 @@
     }
   },
   "version": "0.0.0",
-  "fingerprint": "ggZ93wBIOHmjgXQQQJM2Ue2y3Hvh9OeTZxbyOyJRR40="
+  "fingerprint": "XupMZaY5jv/mSCaBUFt0DZT8ppuKuHvY1rEAQodH2Ys="
 }
diff --git a/packages/codemaker/package.json b/packages/codemaker/package.json
@@ -39,6 +39,6 @@
     "@types/fs-extra": "^9.0.13",
     "eslint": "^9.39.4",
     "jest": "^30.4.2",
-    "typescript": "5.9.x"
+    "typescript": "6.x"
   }
 }
diff --git a/packages/codemaker/src/case-utils.ts b/packages/codemaker/src/case-utils.ts
@@ -1,4 +1,4 @@
-import * as camelcase from 'camelcase';
+import camelcase from 'camelcase';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import decamelize = require('decamelize');
 

diff --git a/packages/jsii-calc/lib/cdk16625/index.ts b/packages/jsii-calc/lib/cdk16625/index.ts
@@ -1,4 +1,4 @@
-import * as assert from 'assert';
+import assert from 'assert';
 
 import { IRandomNumberGenerator } from '../calculator';
 import { UnimportedSubmoduleType } from './donotimport';

diff --git a/packages/jsii-calc/lib/compliance.ts b/packages/jsii-calc/lib/compliance.ts
@@ -477,6 +477,7 @@ export class SyncOverrideExtraArgs {
   public callProduceWithExtraArg(): string {
     // Cast to bypass TypeScript's parameter-count check — we deliberately
     // pass an argument that the declared signature does not accept.
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
     return (this.produce as (...args: unknown[]) => string)({
       ignoredExtra: true,
     });
@@ -1833,7 +1834,7 @@ export class ImplementsInterfaceWithInternalSubclass extends ImplementsInterface
   /**
    * @internal
    */
-  public _propertiesToo?: string;
+  declare public _propertiesToo: string | undefined;
 }
 
 //

diff --git a/packages/jsii-calc/package.json b/packages/jsii-calc/package.json
@@ -52,10 +52,10 @@
   },
   "devDependencies": {
     "eslint": "^9.39.4",
-    "jsii": "5.9.28",
+    "jsii": "6.0.1",
     "jsii-build-tools": "^0.0.0",
-    "jsii-rosetta": "^5.9.32",
-    "typescript": "5.9.x"
+    "jsii-rosetta": "^6.0.0",
+    "typescript": "6.x"
   },
   "jsii": {
     "outdir": "dist",
-Original file line number
+Diff line change
@@ Expand Up / @@ -433,6 +433,7 @@ jobs: @@
             rosetta:
               - latest
               - 5.9.x
+              - 6.0.x
         steps:
           # Check out the code
           - name: Download Artifact
@@ Expand Down @@