diff --git a/packages/core/src/debug.ts b/packages/core/src/debug.ts
index 91798bda0..20bae020d 100644
--- a/packages/core/src/debug.ts
+++ b/packages/core/src/debug.ts
@@ -2,8 +2,7 @@ export const stackTrace = (autolog = true) => {
   try {
     throw new Error()
   } catch (e) {
-    // @ts-ignore
-    const stack = e.stack
+    const stack = (e as Error).stack
 
     if (!autolog) {
       return stack
diff --git a/packages/react/src/Form.ts b/packages/react/src/Form.ts
index fb4a117b7..a67f38903 100644
--- a/packages/react/src/Form.ts
+++ b/packages/react/src/Form.ts
@@ -70,7 +70,7 @@ const Form = forwardRef<FormComponentRef, ComponentProps>(
     ref,
   ) => {
     const form = useForm<Record<string, any>>({})
-    const formElement = useRef<HTMLFormElement>(null)
+    const formElement = useRef<HTMLFormElement>(undefined)
 
     const resolvedMethod = useMemo(() => {
       return isUrlMethodPair(action) ? action.method : (method.toLowerCase() as Method)
@@ -96,13 +96,15 @@ const Form = forwardRef<FormComponentRef, ComponentProps>(
 
       const formEvents: Array<keyof HTMLElementEventMap> = ['input', 'change', 'reset']
 
-      formEvents.forEach((e) => formElement.current.addEventListener(e, updateDirtyState))
+      formEvents.forEach((e) => formElement.current!.addEventListener(e, updateDirtyState))
 
       return () => formEvents.forEach((e) => formElement.current?.removeEventListener(e, updateDirtyState))
     }, [])
 
     const reset = (...fields: string[]) => {
-      resetFormFields(formElement.current, defaultData.current, fields)
+      if (formElement.current) {
+        resetFormFields(formElement.current, defaultData.current, fields)
+      }
     }
 
     const resetAndClearErrors = (...fields: string[]) => {
diff --git a/packages/react/src/InfiniteScroll.ts b/packages/react/src/InfiniteScroll.ts
index ca5bcb140..986c64aa3 100644
--- a/packages/react/src/InfiniteScroll.ts
+++ b/packages/react/src/InfiniteScroll.ts
@@ -181,8 +181,8 @@ const InfiniteScroll = forwardRef<InfiniteScrollRef, ComponentProps>(
 
         // Elements
         getTriggerMargin: () => callbackPropsRef.current.buffer,
-        getStartElement: () => resolvedStartElement,
-        getEndElement: () => resolvedEndElement,
+        getStartElement: () => resolvedStartElement!,
+        getEndElement: () => resolvedEndElement!,
         getItemsElement: () => resolvedItemsElement,
         getScrollableParent: () => scrollableParent,
 
diff --git a/packages/react/src/Link.ts b/packages/react/src/Link.ts
index a16d25dba..8b10c3021 100755
--- a/packages/react/src/Link.ts
+++ b/packages/react/src/Link.ts
@@ -9,6 +9,7 @@ import {
   router,
   shouldIntercept,
   shouldNavigate,
+  VisitOptions,
 } from '@inertiajs/core'
 import { createElement, ElementType, forwardRef, useEffect, useMemo, useRef, useState } from 'react'
 
@@ -59,7 +60,7 @@ const Link = forwardRef<unknown, InertiaLinkProps>(
     ref,
   ) => {
     const [inFlightCount, setInFlightCount] = useState(0)
-    const hoverTimeout = useRef<number>(null)
+    const hoverTimeout = useRef<number>(undefined)
 
     const _method = useMemo(() => {
       return isUrlMethodPair(href) ? href.method : (method.toLowerCase() as Method)
@@ -82,7 +83,7 @@ const Link = forwardRef<unknown, InertiaLinkProps>(
     const url = useMemo(() => mergeDataArray[0], [mergeDataArray])
     const _data = useMemo(() => mergeDataArray[1], [mergeDataArray])
 
-    const baseParams = useMemo(
+    const baseParams = useMemo<VisitOptions>(
       () => ({
         data: _data,
         method: _method,
@@ -98,7 +99,7 @@ const Link = forwardRef<unknown, InertiaLinkProps>(
       [_data, _method, preserveScroll, preserveState, preserveUrl, replace, only, except, headers, async],
     )
 
-    const visitParams = useMemo(
+    const visitParams = useMemo<VisitOptions>(
       () => ({
         ...baseParams,
         onCancelToken,
diff --git a/packages/react/src/PageContext.ts b/packages/react/src/PageContext.ts
index eacc4a3c2..c12e8b8d8 100755
--- a/packages/react/src/PageContext.ts
+++ b/packages/react/src/PageContext.ts
@@ -1,6 +1,7 @@
+import { Page } from '@inertiajs/core'
 import { createContext } from 'react'
 
-const pageContext = createContext(undefined)
+const pageContext = createContext<Page | null>(null)
 pageContext.displayName = 'InertiaPageContext'
 
 export default pageContext
diff --git a/packages/react/src/useForm.ts b/packages/react/src/useForm.ts
index f40b26beb..28fc19fd7 100644
--- a/packages/react/src/useForm.ts
+++ b/packages/react/src/useForm.ts
@@ -1,5 +1,6 @@
 import {
   CancelToken,
+  Errors,
   ErrorValue,
   FormDataErrors,
   FormDataKeys,
@@ -7,6 +8,7 @@ import {
   FormDataValues,
   Method,
   Progress,
+  RequestPayload,
   router,
   UrlMethodPair,
   VisitOptions,
@@ -27,6 +29,8 @@ export type SetDataAction<TForm extends Record<any, any>> = SetDataByObject<TFor
   SetDataByKeyValuePair<TForm>
 
 type FormOptions = Omit<VisitOptions, 'data'>
+type SubmitArgs = [Method, string, FormOptions?] | [UrlMethodPair, FormOptions?]
+type TransformCallback<TForm> = (data: TForm) => object
 
 export interface InertiaFormProps<TForm extends object> {
   data: TForm
@@ -38,7 +42,7 @@ export interface InertiaFormProps<TForm extends object> {
   wasSuccessful: boolean
   recentlySuccessful: boolean
   setData: SetDataAction<TForm>
-  transform: (callback: (data: TForm) => object) => void
+  transform: (callback: TransformCallback<TForm>) => void
   setDefaults(): void
   setDefaults<T extends FormDataKeys<TForm>>(field: T, value: FormDataValues<TForm, T>): void
   setDefaults(fields: Partial<TForm>): void
@@ -47,7 +51,7 @@ export interface InertiaFormProps<TForm extends object> {
   resetAndClearErrors<K extends FormDataKeys<TForm>>(...fields: K[]): void
   setError<K extends FormDataKeys<TForm>>(field: K, value: ErrorValue): void
   setError(errors: FormDataErrors<TForm>): void
-  submit: (...args: [Method, string, FormOptions?] | [UrlMethodPair, FormOptions?]) => void
+  submit: (...args: SubmitArgs) => void
   get: (url: string, options?: FormOptions) => void
   patch: (url: string, options?: FormOptions) => void
   post: (url: string, options?: FormOptions) => void
@@ -66,23 +70,23 @@ export default function useForm<TForm extends FormDataType<TForm>>(
   rememberKeyOrInitialValues?: string | TForm | (() => TForm),
   maybeInitialValues?: TForm | (() => TForm),
 ): InertiaFormProps<TForm> {
-  const isMounted = useRef(null)
+  const isMounted = useRef(false)
   const rememberKey = typeof rememberKeyOrInitialValues === 'string' ? rememberKeyOrInitialValues : null
   const [defaults, setDefaults] = useState(
     (typeof rememberKeyOrInitialValues === 'string' ? maybeInitialValues : rememberKeyOrInitialValues) || ({} as TForm),
   )
   const cancelToken = useRef<CancelToken | null>(null)
-  const recentlySuccessfulTimeoutId = useRef(null)
+  const recentlySuccessfulTimeoutId = useRef<number>(undefined)
   const [data, setData] = rememberKey ? useRemember(defaults, `${rememberKey}:data`) : useState(defaults)
   const [errors, setErrors] = rememberKey
     ? useRemember({} as FormDataErrors<TForm>, `${rememberKey}:errors`)
     : useState({} as FormDataErrors<TForm>)
   const [hasErrors, setHasErrors] = useState(false)
   const [processing, setProcessing] = useState(false)
-  const [progress, setProgress] = useState(null)
+  const [progress, setProgress] = useState<Progress | null>(null)
   const [wasSuccessful, setWasSuccessful] = useState(false)
   const [recentlySuccessful, setRecentlySuccessful] = useState(false)
-  const transform = useRef((data) => data)
+  const transform = useRef<TransformCallback<TForm>>((data) => data)
   const isDirty = useMemo(() => !isEqual(data, defaults), [data, defaults])
 
   useEffect(() => {
@@ -97,16 +101,16 @@ export default function useForm<TForm extends FormDataType<TForm>>(
   const setDefaultsCalledInOnSuccess = useRef(false)
 
   const submit = useCallback(
-    (...args) => {
+    (...args: SubmitArgs) => {
       const objectPassed = args[0] !== null && typeof args[0] === 'object'
 
-      const method = objectPassed ? args[0].method : args[0]
-      const url = objectPassed ? args[0].url : args[1]
+      const method = objectPassed ? args[0].method : (args[0] as Method)
+      const url = objectPassed ? args[0].url : (args[1] as string)
       const options = (objectPassed ? args[1] : args[2]) ?? {}
 
       setDefaultsCalledInOnSuccess.current = false
 
-      const _options = {
+      const _options: VisitOptions = {
         ...options,
         onCancelToken: (token) => {
           cancelToken.current = token
@@ -132,7 +136,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
           }
         },
         onProgress: (event) => {
-          setProgress(event)
+          setProgress(event || null)
 
           if (options.onProgress) {
             return options.onProgress(event)
@@ -168,7 +172,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
           if (isMounted.current) {
             setProcessing(false)
             setProgress(null)
-            setErrors(errors)
+            setErrors(errors as FormDataErrors<TForm>)
             setHasErrors(true)
           }
 
@@ -200,10 +204,12 @@ export default function useForm<TForm extends FormDataType<TForm>>(
         },
       }
 
+      const transformedData = transform.current(data) as RequestPayload
+
       if (method === 'delete') {
-        router.delete(url, { ..._options, data: transform.current(data) })
+        router.delete(url, { ..._options, data: transformedData })
       } else {
-        router[method](url, transform.current(data), _options)
+        router[method](url, transformedData, _options)
       }
     },
     [data, setErrors, transform],
@@ -266,7 +272,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
   }, [dataAsDefaults])
 
   const reset = useCallback(
-    (...fields) => {
+    (...fields: string[]) => {
       if (fields.length === 0) {
         setData(defaults)
       } else {
@@ -300,12 +306,12 @@ export default function useForm<TForm extends FormDataType<TForm>>(
   )
 
   const clearErrors = useCallback(
-    (...fields) => {
+    (...fields: string[]) => {
       setErrors((errors) => {
         const newErrors = Object.keys(errors).reduce(
           (carry, field) => ({
             ...carry,
-            ...(fields.length > 0 && !fields.includes(field) ? { [field]: errors[field] } : {}),
+            ...(fields.length > 0 && !fields.includes(field) ? { [field]: (errors as Errors)[field] } : {}),
           }),
           {},
         )
@@ -317,16 +323,18 @@ export default function useForm<TForm extends FormDataType<TForm>>(
   )
 
   const resetAndClearErrors = useCallback(
-    (...fields) => {
+    (...fields: string[]) => {
       reset(...fields)
       clearErrors(...fields)
     },
     [reset, clearErrors],
   )
 
-  const createSubmitMethod = (method) => (url, options) => {
-    submit(method, url, options)
-  }
+  const createSubmitMethod =
+    (method: Method) =>
+    (url: string, options: VisitOptions = {}) => {
+      submit(method, url, options)
+    }
   const getMethod = useCallback(createSubmitMethod('get'), [submit])
   const post = useCallback(createSubmitMethod('post'), [submit])
   const put = useCallback(createSubmitMethod('put'), [submit])
@@ -339,7 +347,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
     }
   }, [])
 
-  const transformFunction = useCallback((callback) => {
+  const transformFunction = useCallback((callback: TransformCallback<TForm>) => {
     transform.current = callback
   }, [])
 
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index b476e56d5..a71a3320f 100644
--- a/packages/svelte/package.json
+++ b/packages/svelte/package.json
@@ -35,7 +35,7 @@
     }
   },
   "scripts": {
-    "build": "pnpm package && publint",
+    "build": "pnpm package && svelte-check --tsconfig ./tsconfig.json && publint",
     "build:with-deps": "svelte-kit sync && vite build --config vite-with-deps.config.js",
     "check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
     "check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
diff --git a/packages/svelte/src/components/Form.svelte b/packages/svelte/src/components/Form.svelte
index 194e4cf1e..2afc9fb8c 100644
--- a/packages/svelte/src/components/Form.svelte
+++ b/packages/svelte/src/components/Form.svelte
@@ -5,6 +5,7 @@
     mergeDataIntoQueryString,
     type Errors,
     type FormComponentProps,
+    type Method,
     type FormDataConvertible,
     type VisitOptions,
     isUrlMethodPair,
@@ -45,8 +46,8 @@
   let isDirty = false
   let defaultData: FormData = new FormData()
 
-  $: _method = isUrlMethodPair(action) ? action.method : (method.toLowerCase() as FormComponentProps['method'])
-  $: _action = isUrlMethodPair(action) ? action.url : action
+  $: _method = isUrlMethodPair(action) ? action.method : ((method ?? 'get').toLowerCase() as Method)
+  $: _action = isUrlMethodPair(action) ? action.url : (action as string)
 
   function getFormData(): FormData {
     return new FormData(formElement)
@@ -117,7 +118,7 @@
       ...options,
     }
 
-    $form.transform(() => transform(_data)).submit(_method, url, submitOptions)
+    $form.transform(() => transform!(_data)).submit(_method, url, submitOptions)
   }
 
   function handleSubmit(event: Event) {
diff --git a/packages/svelte/src/components/InfiniteScroll.svelte b/packages/svelte/src/components/InfiniteScroll.svelte
index 9ffb2e336..c21cad621 100644
--- a/packages/svelte/src/components/InfiniteScroll.svelte
+++ b/packages/svelte/src/components/InfiniteScroll.svelte
@@ -9,7 +9,7 @@
   } from '@inertiajs/core'
   import { onDestroy, onMount } from 'svelte'
 
-  export let data: InfiniteScrollComponentBaseProps['data'] = undefined
+  export let data: InfiniteScrollComponentBaseProps['data']
   export let buffer: InfiniteScrollComponentBaseProps['buffer'] = 0
   export let as: InfiniteScrollComponentBaseProps['as'] = 'div'
   export let manual: InfiniteScrollComponentBaseProps['manual'] = false
@@ -126,28 +126,28 @@
 
     infiniteScrollInstance = useInfiniteScroll({
       // Data
-      getPropName: () => data,
-      inReverseMode: () => reverse,
+      getPropName: () => data!,
+      inReverseMode: () => reverse ?? false,
       shouldFetchNext: () => !onlyPrevious,
       shouldFetchPrevious: () => !onlyNext,
-      shouldPreserveUrl: () => preserveUrl,
+      shouldPreserveUrl: () => preserveUrl ?? false,
 
       // Elements
-      getTriggerMargin: () => buffer,
-      getStartElement: () => resolvedStartElement,
-      getEndElement: () => resolvedEndElement,
-      getItemsElement: () => resolvedItemsElement,
+      getTriggerMargin: () => buffer ?? 0,
+      getStartElement: () => resolvedStartElement!,
+      getEndElement: () => resolvedEndElement!,
+      getItemsElement: () => resolvedItemsElement!,
       getScrollableParent: () => (resolvedItemsElement ? getScrollableParent(resolvedItemsElement) : null),
 
       // Request callbacks
       onBeforePreviousRequest: () => (loadingPrevious = true),
       onBeforeNextRequest: () => (loadingNext = true),
       onCompletePreviousRequest: () => {
-        requestCount = infiniteScrollInstance.dataManager.getRequestCount()
+        requestCount = infiniteScrollInstance!.dataManager.getRequestCount()
         loadingPrevious = false
       },
       onCompleteNextRequest: () => {
-        requestCount = infiniteScrollInstance.dataManager.getRequestCount()
+        requestCount = infiniteScrollInstance!.dataManager.getRequestCount()
         loadingNext = false
       },
     })
@@ -167,7 +167,7 @@
     }
   }
 
-  $: manualMode = manual || (manualAfter > 0 && requestCount >= manualAfter)
+  $: manualMode = manual || (manualAfter !== undefined && manualAfter > 0 && requestCount >= manualAfter)
   $: autoLoad = !manualMode
 
   $: headerAutoMode = autoLoad && !onlyNext
diff --git a/packages/svelte/src/link.ts b/packages/svelte/src/link.ts
index 2cf0b5598..d3b1cb262 100644
--- a/packages/svelte/src/link.ts
+++ b/packages/svelte/src/link.ts
@@ -136,7 +136,7 @@ function link(
       return 30_000
     })()
 
-    cacheTags = cacheTagValues
+    cacheTags = Array.isArray(cacheTagValues) ? cacheTagValues : [cacheTagValues]
 
     method = isUrlMethodPair(params.href) ? params.href.method : (params.method?.toLowerCase() as Method) || 'get'
     ;[href, data] = hrefAndData(method, params)
diff --git a/packages/svelte/src/useForm.ts b/packages/svelte/src/useForm.ts
index fe1c15586..eba526757 100644
--- a/packages/svelte/src/useForm.ts
+++ b/packages/svelte/src/useForm.ts
@@ -23,6 +23,8 @@ import { writable, type Writable } from 'svelte/store'
 type InertiaFormStore<TForm extends object> = Writable<InertiaForm<TForm>> & InertiaForm<TForm>
 
 type FormOptions = Omit<VisitOptions, 'data'>
+type SubmitArgs = [Method, string, FormOptions?] | [UrlMethodPair, FormOptions?]
+type TransformCallback<TForm> = (data: TForm) => object
 
 export interface InertiaFormProps<TForm extends object> {
   isDirty: boolean
@@ -35,7 +37,7 @@ export interface InertiaFormProps<TForm extends object> {
   setStore(data: TForm): void
   setStore<T extends FormDataKeys<TForm>>(key: T, value: FormDataValues<TForm, T>): void
   data(): TForm
-  transform(callback: (data: TForm) => object): this
+  transform(callback: TransformCallback<TForm>): this
   defaults(): this
   defaults(fields: Partial<TForm>): this
   defaults<T extends FormDataKeys<TForm>>(field: T, value: FormDataValues<TForm, T>): this
@@ -44,7 +46,7 @@ export interface InertiaFormProps<TForm extends object> {
   resetAndClearErrors<K extends FormDataKeys<TForm>>(...fields: K[]): this
   setError<K extends FormDataKeys<TForm>>(field: K, value: ErrorValue): this
   setError(errors: FormDataErrors<TForm>): this
-  submit: (...args: [Method, string, FormOptions?] | [UrlMethodPair, FormOptions?]) => void
+  submit: (...args: SubmitArgs) => void
   get(url: string, options?: FormOptions): void
   post(url: string, options?: FormOptions): void
   put(url: string, options?: FormOptions): void
@@ -78,6 +80,11 @@ export default function useForm<TForm extends FormDataType<TForm>>(
   // overriding user's custom defaults with automatic behavior.
   let defaultsCalledInOnSuccess = false
 
+  // Internal helper to update form state properties
+  const setFormState = <K extends keyof InertiaFormProps<TForm>>(key: K, value: InertiaFormProps<TForm>[K]) => {
+    store.update((form) => ({ ...form, [key]: value }))
+  }
+
   const store = writable<InertiaForm<TForm>>({
     ...(restored ? restored.data : data),
     isDirty: false,
@@ -97,7 +104,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
         return set(carry, key, get(this, key))
       }, {} as TForm)
     },
-    transform(callback) {
+    transform(callback: TransformCallback<TForm>) {
       transform = callback
       return this
     },
@@ -115,7 +122,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
 
       return this
     },
-    reset(...fields) {
+    reset(...fields: Array<FormDataKeys<TForm>>) {
       const clonedData = cloneDeep(defaults)
       if (fields.length === 0) {
         this.setStore(clonedData)
@@ -132,32 +139,32 @@ export default function useForm<TForm extends FormDataType<TForm>>(
       return this
     },
     setError(fieldOrFields: FormDataKeys<TForm> | FormDataErrors<TForm>, maybeValue?: ErrorValue) {
-      this.setStore('errors', {
+      setFormState('errors', {
         ...this.errors,
         ...((typeof fieldOrFields === 'string' ? { [fieldOrFields]: maybeValue } : fieldOrFields) as Errors),
       })
 
       return this
     },
-    clearErrors(...fields) {
-      this.setStore(
+    clearErrors(...fields: string[]) {
+      setFormState(
         'errors',
         Object.keys(this.errors).reduce(
           (carry, field) => ({
             ...carry,
-            ...(fields.length > 0 && !fields.includes(field) ? { [field]: this.errors[field] } : {}),
+            ...(fields.length > 0 && !fields.includes(field) ? { [field]: (this.errors as Errors)[field] } : {}),
           }),
           {},
-        ) as Errors,
+        ) as FormDataErrors<TForm>,
       )
       return this
     },
-    resetAndClearErrors(...fields) {
+    resetAndClearErrors(...fields: Array<FormDataKeys<TForm>>) {
       this.reset(...fields)
       this.clearErrors(...fields)
       return this
     },
-    submit(...args) {
+    submit(...args: SubmitArgs) {
       const objectPassed = args[0] !== null && typeof args[0] === 'object'
 
       const method = objectPassed ? args[0].method : args[0]
@@ -178,8 +185,8 @@ export default function useForm<TForm extends FormDataType<TForm>>(
           }
         },
         onBefore: (visit: PendingVisit) => {
-          this.setStore('wasSuccessful', false)
-          this.setStore('recentlySuccessful', false)
+          setFormState('wasSuccessful', false)
+          setFormState('recentlySuccessful', false)
           if (recentlySuccessfulTimeoutId) {
             clearTimeout(recentlySuccessfulTimeoutId)
           }
@@ -189,55 +196,58 @@ export default function useForm<TForm extends FormDataType<TForm>>(
           }
         },
         onStart: (visit: PendingVisit) => {
-          this.setStore('processing', true)
+          setFormState('processing', true)
 
           if (options.onStart) {
             return options.onStart(visit)
           }
         },
         onProgress: (event?: AxiosProgressEvent) => {
-          this.setStore('progress', event as any)
+          setFormState('progress', event || null)
 
           if (options.onProgress) {
             return options.onProgress(event)
           }
         },
         onSuccess: async (page: Page) => {
-          this.setStore('processing', false)
-          this.setStore('progress', null)
+          setFormState('processing', false)
+          setFormState('progress', null)
           this.clearErrors()
-          this.setStore('wasSuccessful', true)
-          this.setStore('recentlySuccessful', true)
-          recentlySuccessfulTimeoutId = setTimeout(() => this.setStore('recentlySuccessful', false), 2000)
+          setFormState('wasSuccessful', true)
+          setFormState('recentlySuccessful', true)
+          recentlySuccessfulTimeoutId = setTimeout(() => setFormState('recentlySuccessful', false), 2000)
 
           const onSuccess = options.onSuccess ? await options.onSuccess(page) : null
 
           if (!defaultsCalledInOnSuccess) {
-            this.defaults(cloneDeep(this.data()))
+            store.update((form) => {
+              this.defaults(cloneDeep(form.data()))
+              return form
+            })
           }
 
           return onSuccess
         },
         onError: (errors: Errors) => {
-          this.setStore('processing', false)
-          this.setStore('progress', null)
-          this.clearErrors().setError(errors)
+          setFormState('processing', false)
+          setFormState('progress', null)
+          this.clearErrors().setError(errors as FormDataErrors<TForm>)
 
           if (options.onError) {
             return options.onError(errors)
           }
         },
         onCancel: () => {
-          this.setStore('processing', false)
-          this.setStore('progress', null)
+          setFormState('processing', false)
+          setFormState('progress', null)
 
           if (options.onCancel) {
             return options.onCancel()
           }
         },
         onFinish: (visit: ActiveVisit) => {
-          this.setStore('processing', false)
-          this.setStore('progress', null)
+          setFormState('processing', false)
+          setFormState('progress', null)
           cancelToken = null
 
           if (options.onFinish) {
@@ -252,19 +262,19 @@ export default function useForm<TForm extends FormDataType<TForm>>(
         router[method](url, data, _options)
       }
     },
-    get(url, options) {
+    get(url: string, options: VisitOptions) {
       this.submit('get', url, options)
     },
-    post(url, options) {
+    post(url: string, options: VisitOptions) {
       this.submit('post', url, options)
     },
-    put(url, options) {
+    put(url: string, options: VisitOptions) {
       this.submit('put', url, options)
     },
-    patch(url, options) {
+    patch(url: string, options: VisitOptions) {
       this.submit('patch', url, options)
     },
-    delete(url, options) {
+    delete(url: string, options: VisitOptions) {
       this.submit('delete', url, options)
     },
     cancel() {
@@ -274,12 +284,12 @@ export default function useForm<TForm extends FormDataType<TForm>>(
 
   store.subscribe((form) => {
     if (form.isDirty === isEqual(form.data(), defaults)) {
-      form.setStore('isDirty', !form.isDirty)
+      setFormState('isDirty', !form.isDirty)
     }
 
     const hasErrors = Object.keys(form.errors).length > 0
     if (form.hasErrors !== hasErrors) {
-      form.setStore('hasErrors', !form.hasErrors)
+      setFormState('hasErrors', !form.hasErrors)
     }
 
     if (rememberKey) {
@@ -287,5 +297,5 @@ export default function useForm<TForm extends FormDataType<TForm>>(
     }
   })
 
-  return store
+  return store as InertiaFormStore<TForm>
 }
diff --git a/packages/vue3/src/deferred.ts b/packages/vue3/src/deferred.ts
index 89aa1f0b2..9557d5a33 100644
--- a/packages/vue3/src/deferred.ts
+++ b/packages/vue3/src/deferred.ts
@@ -15,6 +15,6 @@ export default defineComponent({
       throw new Error('`<Deferred>` requires a `<template #fallback>` slot')
     }
 
-    return keys.every((key) => this.$page.props[key] !== undefined) ? this.$slots.default() : this.$slots.fallback()
+    return keys.every((key) => this.$page.props[key] !== undefined) ? this.$slots.default?.() : this.$slots.fallback()
   },
 })
diff --git a/packages/vue3/src/form.ts b/packages/vue3/src/form.ts
index 84944d5c9..70935225b 100644
--- a/packages/vue3/src/form.ts
+++ b/packages/vue3/src/form.ts
@@ -1,4 +1,5 @@
 import {
+  Errors,
   FormComponentProps,
   FormComponentRef,
   FormComponentSlotProps,
@@ -180,8 +181,8 @@ const Form = defineComponent({
         onFinish: props.onFinish,
         onCancel: props.onCancel,
         onSuccess: (...args) => {
-          props.onSuccess(...args)
-          props.onSubmitComplete(exposed)
+          props.onSuccess?.(...args)
+          props.onSubmitComplete?.(exposed)
           maybeReset(props.resetOnSuccess)
 
           if (props.setDefaultsOnSuccess === true) {
@@ -189,7 +190,7 @@ const Form = defineComponent({
           }
         },
         onError: (...args) => {
-          props.onError(...args)
+          props.onError?.(...args)
           maybeReset(props.resetOnError)
         },
         ...props.options,
@@ -235,7 +236,7 @@ const Form = defineComponent({
       clearErrors: (...fields: string[]) => form.clearErrors(...fields),
       resetAndClearErrors,
       setError: (fieldOrFields: string | Record<string, string>, maybeValue?: string) =>
-        form.setError(typeof fieldOrFields === 'string' ? { [fieldOrFields]: maybeValue } : fieldOrFields),
+        form.setError((typeof fieldOrFields === 'string' ? { [fieldOrFields]: maybeValue } : fieldOrFields) as Errors),
       get isDirty() {
         return isDirty.value
       },
diff --git a/packages/vue3/src/infiniteScroll.ts b/packages/vue3/src/infiniteScroll.ts
index a422be757..acacaef9b 100644
--- a/packages/vue3/src/infiniteScroll.ts
+++ b/packages/vue3/src/infiniteScroll.ts
@@ -9,7 +9,10 @@ import {
 import { computed, defineComponent, Fragment, h, onMounted, onUnmounted, PropType, ref, SlotsType, watch } from 'vue'
 
 // Vue-specific element resolver
-const resolveHTMLElement = (value, fallback): HTMLElement | null => {
+const resolveHTMLElement = (
+  value: string | object | (() => HTMLElement | null),
+  fallback: HTMLElement | null,
+): HTMLElement | null => {
   if (!value) {
     return fallback
   }
@@ -38,6 +41,7 @@ const InfiniteScroll = defineComponent({
   props: {
     data: {
       type: String as PropType<InfiniteScrollComponentBaseProps['data']>,
+      required: true,
     },
     buffer: {
       type: Number as PropType<InfiniteScrollComponentBaseProps['buffer']>,
@@ -225,7 +229,7 @@ const InfiniteScroll = defineComponent({
               ? slots.previous(exposedPrevious)
               : loadingPrevious.value
                 ? slots.loading?.(exposedPrevious)
-                : null,
+                : undefined,
           ),
         )
       }
@@ -258,7 +262,7 @@ const InfiniteScroll = defineComponent({
           h(
             'div',
             { ref: endElementRef },
-            slots.next ? slots.next(exposedNext) : loadingNext.value ? slots.loading?.(exposedNext) : null,
+            slots.next ? slots.next(exposedNext) : loadingNext.value ? slots.loading?.(exposedNext) : undefined,
           ),
         )
       }
diff --git a/packages/vue3/src/link.ts b/packages/vue3/src/link.ts
index 66b69be7a..dfb09bb95 100755
--- a/packages/vue3/src/link.ts
+++ b/packages/vue3/src/link.ts
@@ -134,7 +134,7 @@ const Link: InertiaLink = defineComponent({
   },
   setup(props, { slots, attrs }) {
     const inFlightCount = ref(0)
-    const hoverTimeout = ref(null)
+    const hoverTimeout = ref<ReturnType<typeof setTimeout>>()
 
     const prefetchModes = computed<LinkPrefetchOption[]>(() => {
       if (props.prefetch === true) {
@@ -149,7 +149,7 @@ const Link: InertiaLink = defineComponent({
         return props.prefetch
       }
 
-      return [props.prefetch]
+      return [props.prefetch] as LinkPrefetchOption[]
     })
 
     const cacheForValue = computed(() => {
@@ -179,7 +179,7 @@ const Link: InertiaLink = defineComponent({
     })
 
     const method = computed(() =>
-      isUrlMethodPair(props.href) ? props.href.method : (props.method.toLowerCase() as Method),
+      isUrlMethodPair(props.href) ? props.href.method : ((props.method ?? 'get').toLowerCase() as Method),
     )
     const as = computed(() => {
       if (typeof props.as !== 'string' || props.as.toLowerCase() !== 'a') {
@@ -192,8 +192,8 @@ const Link: InertiaLink = defineComponent({
     const mergeDataArray = computed(() =>
       mergeDataIntoQueryString(
         method.value,
-        isUrlMethodPair(props.href) ? props.href.url : props.href,
-        props.data,
+        isUrlMethodPair(props.href) ? props.href.url : (props.href as string),
+        props.data || {},
         props.queryStringArrayFormat,
       ),
     )
@@ -231,12 +231,12 @@ const Link: InertiaLink = defineComponent({
       onBefore: props.onBefore,
       onStart: (visit: PendingVisit) => {
         inFlightCount.value++
-        props.onStart(visit)
+        props.onStart?.(visit)
       },
       onProgress: props.onProgress,
       onFinish: (visit: ActiveVisit) => {
         inFlightCount.value--
-        props.onFinish(visit)
+        props.onFinish?.(visit)
       },
       onCancel: props.onCancel,
       onSuccess: props.onSuccess,
@@ -312,7 +312,7 @@ const Link: InertiaLink = defineComponent({
 
     return () => {
       return h(
-        as.value,
+        as.value as string | Component,
         {
           ...attrs,
           ...elProps.value,
diff --git a/packages/vue3/src/useForm.ts b/packages/vue3/src/useForm.ts
index 480e298b4..2c0b677b2 100644
--- a/packages/vue3/src/useForm.ts
+++ b/packages/vue3/src/useForm.ts
@@ -7,6 +7,7 @@ import {
   FormDataValues,
   Method,
   Progress,
+  RequestPayload,
   router,
   UrlMethodPair,
   VisitOptions,
@@ -15,6 +16,8 @@ import { cloneDeep, get, has, isEqual, set } from 'lodash-es'
 import { reactive, watch } from 'vue'
 
 type FormOptions = Omit<VisitOptions, 'data'>
+type SubmitArgs = [Method, string, FormOptions?] | [UrlMethodPair, FormOptions?]
+type TransformCallback<TForm> = (data: TForm) => object
 
 export interface InertiaFormProps<TForm extends object> {
   isDirty: boolean
@@ -25,7 +28,7 @@ export interface InertiaFormProps<TForm extends object> {
   wasSuccessful: boolean
   recentlySuccessful: boolean
   data(): TForm
-  transform(callback: (data: TForm) => object): this
+  transform(callback: TransformCallback<TForm>): this
   defaults(): this
   defaults<T extends FormDataKeys<TForm>>(field: T, value: FormDataValues<TForm, T>): this
   defaults(fields: Partial<TForm>): this
@@ -34,7 +37,7 @@ export interface InertiaFormProps<TForm extends object> {
   resetAndClearErrors<K extends FormDataKeys<TForm>>(...fields: K[]): this
   setError<K extends FormDataKeys<TForm>>(field: K, value: ErrorValue): this
   setError(errors: FormDataErrors<TForm>): this
-  submit: (...args: [Method, string, FormOptions?] | [UrlMethodPair, FormOptions?]) => void
+  submit: (...args: SubmitArgs) => void
   get(url: string, options?: FormOptions): void
   post(url: string, options?: FormOptions): void
   put(url: string, options?: FormOptions): void
@@ -61,8 +64,8 @@ export default function useForm<TForm extends FormDataType<TForm>>(
     : null
   let defaults = typeof data === 'function' ? cloneDeep(data()) : cloneDeep(data)
   let cancelToken: CancelToken | null = null
-  let recentlySuccessfulTimeoutId = null
-  let transform = (data) => data
+  let recentlySuccessfulTimeoutId: ReturnType<typeof setTimeout>
+  let transform: TransformCallback<TForm> = (data) => data
 
   // Track if defaults was called manually during onSuccess to avoid
   // overriding user's custom defaults with automatic behavior.
@@ -82,7 +85,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
         return set(carry, key, get(this, key))
       }, {} as Partial<TForm>) as TForm
     },
-    transform(callback) {
+    transform(callback: TransformCallback<TForm>) {
       transform = callback
 
       return this
@@ -106,7 +109,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
 
       return this
     },
-    reset(...fields) {
+    reset(...fields: string[]) {
       const resolvedData = typeof data === 'function' ? cloneDeep(data()) : cloneDeep(defaults)
       const clonedData = cloneDeep(resolvedData)
       if (fields.length === 0) {
@@ -130,7 +133,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
 
       return this
     },
-    clearErrors(...fields) {
+    clearErrors(...fields: string[]) {
       this.errors = Object.keys(this.errors).reduce(
         (carry, field) => ({
           ...carry,
@@ -143,22 +146,21 @@ export default function useForm<TForm extends FormDataType<TForm>>(
 
       return this
     },
-    resetAndClearErrors(...fields) {
+    resetAndClearErrors(...fields: string[]) {
       this.reset(...fields)
       this.clearErrors(...fields)
       return this
     },
-    submit(...args) {
+    submit(...args: SubmitArgs) {
       const objectPassed = args[0] !== null && typeof args[0] === 'object'
 
-      const method = objectPassed ? args[0].method : args[0]
-      const url = objectPassed ? args[0].url : args[1]
+      const method = objectPassed ? args[0].method : (args[0] as Method)
+      const url = objectPassed ? args[0].url : (args[1] as string)
       const options = (objectPassed ? args[1] : args[2]) ?? {}
 
       defaultsCalledInOnSuccess = false
 
-      const data = transform(this.data())
-      const _options = {
+      const _options: VisitOptions = {
         ...options,
         onCancelToken: (token) => {
           cancelToken = token
@@ -235,25 +237,27 @@ export default function useForm<TForm extends FormDataType<TForm>>(
         },
       }
 
+      const transformedData = transform(this.data()) as RequestPayload
+
       if (method === 'delete') {
-        router.delete(url, { ..._options, data })
+        router.delete(url, { ..._options, data: transformedData })
       } else {
-        router[method](url, data, _options)
+        router[method](url, transformedData, _options)
       }
     },
-    get(url, options) {
+    get(url: string, options: VisitOptions) {
       this.submit('get', url, options)
     },
-    post(url, options) {
+    post(url: string, options: VisitOptions) {
       this.submit('post', url, options)
     },
-    put(url, options) {
+    put(url: string, options: VisitOptions) {
       this.submit('put', url, options)
     },
-    patch(url, options) {
+    patch(url: string, options: VisitOptions) {
       this.submit('patch', url, options)
     },
-    delete(url, options) {
+    delete(url: string, options: VisitOptions) {
       this.submit('delete', url, options)
     },
     cancel() {
@@ -265,7 +269,7 @@ export default function useForm<TForm extends FormDataType<TForm>>(
     __remember() {
       return { data: this.data(), errors: this.errors }
     },
-    __restore(restored) {
+    __restore(restored: { data: TForm; errors: FormDataErrors<TForm> }) {
       Object.assign(this, restored.data)
       this.setError(restored.errors)
     },
diff --git a/packages/vue3/src/usePrefetch.ts b/packages/vue3/src/usePrefetch.ts
index 6cdd7484f..07091fe18 100644
--- a/packages/vue3/src/usePrefetch.ts
+++ b/packages/vue3/src/usePrefetch.ts
@@ -19,8 +19,8 @@ export default function usePrefetch(options: VisitOptions = {}): {
   isPrefetching.value = inFlight !== null
   isPrefetched.value = cached !== null
 
-  let onPrefetchedListener
-  let onPrefetchingListener
+  let onPrefetchedListener: () => void
+  let onPrefetchingListener: () => void
 
   onMounted(() => {
     onPrefetchingListener = router.on('prefetching', (e) => {
diff --git a/packages/vue3/src/whenVisible.ts b/packages/vue3/src/whenVisible.ts
index ee1f5bff3..ad0774ed0 100644
--- a/packages/vue3/src/whenVisible.ts
+++ b/packages/vue3/src/whenVisible.ts
@@ -27,7 +27,7 @@ export default defineComponent({
     return {
       loaded: false,
       fetching: false,
-      observer: null,
+      observer: null as IntersectionObserver | null,
     }
   },
   unmounted() {
@@ -41,7 +41,7 @@ export default defineComponent({
         }
 
         if (!this.$props.always) {
-          this.observer.disconnect()
+          this.observer?.disconnect()
         }
 
         if (this.fetching) {