diff --git a/packages/shared/jsconfig.node.json b/packages/shared/jsconfig.node.json
new file mode 100644
index 0000000000..c9a3832f00
--- /dev/null
+++ b/packages/shared/jsconfig.node.json
@@ -0,0 +1,28 @@
+{
+	"$schema": "https://json.schemastore.org/tsconfig",
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": true,
+		"noEmit": true,
+		// ES2025 is the earliest that supports our API uses: https://node.green/#ES2025
+		// But TS doesn't implement it yet: https://github.com/microsoft/TypeScript/issues/61735
+		"target": "ESNext",
+		"module": "NodeNext",
+		"moduleResolution": "NodeNext",
+		"types": ["node"],
+		"lib": ["ESNext"],
+		"noLib": false,
+		"allowSyntheticDefaultImports": true,
+		"esModuleInterop": true,
+		"skipLibCheck": true,
+		"skipDefaultLibCheck": true,
+		"incremental": true
+	},
+	"compileOnSave": false,
+	"exclude": [
+		"node_modules",
+		"built",
+		"coverage",
+		"**/*.ts"
+	]
+}
diff --git a/packages/shared/jsconfig.web.json b/packages/shared/jsconfig.web.json
new file mode 100644
index 0000000000..3e17a5adfb
--- /dev/null
+++ b/packages/shared/jsconfig.web.json
@@ -0,0 +1,26 @@
+{
+	"$schema": "https://json.schemastore.org/tsconfig",
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": true,
+		"noEmit": true,
+		"target": "ES2022",
+		"module": "ES2022",
+		"moduleResolution": "Bundler",
+		"types": [],
+		"lib": ["ES2022", "DOM", "DOM.Iterable"],
+		"noLib": false,
+		"allowSyntheticDefaultImports": true,
+		"esModuleInterop": true,
+		"skipLibCheck": true,
+		"skipDefaultLibCheck": true,
+		"incremental": true
+	},
+	"compileOnSave": false,
+	"exclude": [
+		"node_modules",
+		"built",
+		"coverage",
+		"**/*.ts"
+	]
+}
diff --git a/packages/shared/jsconfig.webworker.json b/packages/shared/jsconfig.webworker.json
new file mode 100644
index 0000000000..68c1def539
--- /dev/null
+++ b/packages/shared/jsconfig.webworker.json
@@ -0,0 +1,11 @@
+{
+	"$schema": "https://json.schemastore.org/tsconfig",
+	"extends": "./jsconfig.web.json",
+	"compilerOptions": {
+		"lib": [
+			"ES2022",
+			"WebWorker",
+			"Webworker.Iterable"
+		]
+	}
+}
diff --git a/packages/shared/package.json b/packages/shared/package.json
index 15ea788f45..8ce9e6679b 100644
--- a/packages/shared/package.json
+++ b/packages/shared/package.json
@@ -2,5 +2,6 @@
 	"type": "module",
 	"devDependencies": {
 		"@misskey-dev/eslint-plugin": "2.1.0",
+		"typescript": "5.9.2"
 	}
 }
diff --git a/packages/shared/tsconfig.node.json b/packages/shared/tsconfig.node.json
new file mode 100644
index 0000000000..9183af505d
--- /dev/null
+++ b/packages/shared/tsconfig.node.json
@@ -0,0 +1,42 @@
+{
+	"$schema": "https://json.schemastore.org/tsconfig",
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": true,
+		"noEmitOnError": true,
+		// ES2025 is the earliest that supports our API uses: https://node.green/#ES2025
+		// But TS doesn't implement it yet: https://github.com/microsoft/TypeScript/issues/61735
+		"target": "ESNext",
+		"module": "NodeNext",
+		"moduleResolution": "NodeNext",
+		"types": ["node"],
+		"lib": ["ESNext"],
+		"noLib": false,
+		"noImplicitAny": true,
+		"noImplicitReturns": true,
+		"noUnusedParameters": false,
+		"noUnusedLocals": false,
+		"noFallthroughCasesInSwitch": true,
+		"declaration": false,
+		"sourceMap": false,
+		"allowSyntheticDefaultImports": true,
+		"esModuleInterop": true,
+		"strict": true,
+		"strictNullChecks": true,
+		"strictPropertyInitialization": false,
+		"skipLibCheck": true,
+		"skipDefaultLibCheck": true,
+		"experimentalDecorators": true,
+		"verbatimModuleSyntax": true,
+		"emitDecoratorMetadata": true,
+		"resolveJsonModule": true,
+		"isolatedModules": true,
+		"incremental": true
+	},
+	"compileOnSave": false,
+	"exclude": [
+		"node_modules",
+		"built",
+		"coverage"
+	]
+}
diff --git a/packages/shared/tsconfig.web.json b/packages/shared/tsconfig.web.json
new file mode 100644
index 0000000000..1865ef1c7b
--- /dev/null
+++ b/packages/shared/tsconfig.web.json
@@ -0,0 +1,39 @@
+{
+	"$schema": "https://json.schemastore.org/tsconfig",
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": true,
+		"noEmitOnError": false,
+		// TODO should we support an older standard?
+		"target": "ES2022",
+		"module": "ES2022",
+		"moduleResolution": "Bundler",
+		"lib": ["ES2022", "DOM", "DOM.Iterable"],
+		"noLib": false,
+		"strict": true,
+		"noImplicitAny": false,
+		"noImplicitReturns": true,
+		"noUnusedParameters": false,
+		"noUnusedLocals": false,
+		"noFallthroughCasesInSwitch": true,
+		"declaration": false,
+		"sourceMap": false,
+		"strictNullChecks": true,
+		"experimentalDecorators": true,
+		"resolveJsonModule": true,
+		"allowSyntheticDefaultImports": true,
+		"isolatedModules": true,
+		"useDefineForClassFields": true,
+		"esModuleInterop": true,
+		"verbatimModuleSyntax": true,
+		"skipLibCheck": true,
+		"skipDefaultLibCheck": true,
+		"incremental": true
+	},
+	"compileOnSave": false,
+	"exclude": [
+		"node_modules",
+		"built",
+		"coverage"
+	]
+}
diff --git a/packages/shared/tsconfig.webworker.json b/packages/shared/tsconfig.webworker.json
new file mode 100644
index 0000000000..cf60dbb9e2
--- /dev/null
+++ b/packages/shared/tsconfig.webworker.json
@@ -0,0 +1,11 @@
+{
+	"$schema": "https://json.schemastore.org/tsconfig",
+	"extends": "./tsconfig.web.json",
+	"compilerOptions": {
+		"lib": [
+			"ES2022",
+			"WebWorker",
+			"Webworker.Iterable"
+		]
+	}
+}