refactor(tailshare): address feedback

- Extract useSharedWorkerAvailable() into @webnet/react
- Add explicit defaults (useWorker: true, fileOps: "memory") in parseConfig
  so consumers don't repeat them
- Restore markAutostart tri-state: undefined → latches to true on first
  Running, false → never autostart, true → autostart

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/react/src/index.ts

@@ -1,2 +1,3 @@
 export { useClient } from "./useClient.js"
 export { useLocalStorage } from "./useLocalStorage.js"
+export { useSharedWorkerAvailable } from "./useSharedWorkerAvailable.js"

packages/react/src/useSharedWorkerAvailable.ts

@@ -0,0 +1,9 @@
+import { useSyncExternalStore } from "react"
+
+const sub = () => () => void 0
+const getClient = () => typeof SharedWorker !== "undefined"
+const getServer = () => false
+
+export function useSharedWorkerAvailable(): boolean {
+  return useSyncExternalStore(sub, getClient, getServer)
+}

packages/tailshare/src/contexts/IpnContext.tsx

@@ -25,11 +25,10 @@ import {
   useMemo,
   useRef,
   useState,
-  useSyncExternalStore,
 } from "react"
 import { initIPN, InMemoryFileOps, InMemoryState } from "@webnet/tsconnect"
 import type { IpnClient } from "@webnet/tsconnect"
-import { useLocalStorage } from "@webnet/react"
+import { useLocalStorage, useSharedWorkerAvailable } from "@webnet/react"
 import wasmUrl from "@webnet/tsconnect/main.wasm"
 import type { WorkerConfig } from "@webnet/tsconnect-worker"
 
@@ -52,10 +51,10 @@ export type TailshareConfig = {
 }
 
 function parseConfig(raw: string): TailshareConfig {
+  const cfg: TailshareConfig = { useWorker: true, fileOps: "memory" }
   try {
     const parsed = JSON.parse(raw)
-    if (typeof parsed !== "object" || parsed === null || Array.isArray(parsed)) return {}
-    const cfg: TailshareConfig = {}
+    if (typeof parsed !== "object" || parsed === null || Array.isArray(parsed)) return cfg
     if (typeof parsed.hostname === "string") cfg.hostname = parsed.hostname
     if (typeof parsed.controlURL === "string") cfg.controlURL = parsed.controlURL
     if (typeof parsed.authKey === "string") cfg.authKey = parsed.authKey
@@ -63,16 +62,12 @@ function parseConfig(raw: string): TailshareConfig {
     if (typeof parsed.autostart === "boolean") cfg.autostart = parsed.autostart
     if (typeof parsed.useWorker === "boolean") cfg.useWorker = parsed.useWorker
     if (parsed.fileOps === "memory" || parsed.fileOps === "opfs") cfg.fileOps = parsed.fileOps
-    return cfg
   } catch {
-    return {}
+    // return defaults
   }
+  return cfg
 }
 
-const workerAvailableSub = () => () => void 0
-const workerAvailableClient = () => typeof SharedWorker !== "undefined"
-const workerAvailableServer = () => false
-
 export const IpnPrepareContext = createContext<{
   config: TailshareConfig
   setConfig: (patch: Partial<TailshareConfig>) => void
@@ -89,11 +84,7 @@ export function IpnProvider({ children }: { children: ReactNode }) {
   }
   const localStore = storeRef.current
 
-  const workerAvailable = useSyncExternalStore(
-    workerAvailableSub,
-    workerAvailableClient,
-    workerAvailableServer,
-  )
+  const workerAvailable = useSharedWorkerAvailable()
 
   const [configRaw, setConfigRaw] = useLocalStorage("tailshare:config")
   const config = useMemo(() => parseConfig(configRaw), [configRaw])
@@ -104,7 +95,7 @@ export function IpnProvider({ children }: { children: ReactNode }) {
     [setConfigRaw],
   )
 
-  const useWorker = config.useWorker !== false && workerAvailable
+  const useWorker = !!config.useWorker && workerAvailable
 
   const [willBuild, setWillBuild] = useState(false)
   const build = useCallback(() => setWillBuild(true), [])
@@ -184,7 +175,7 @@ export function IpnProvider({ children }: { children: ReactNode }) {
           <AutoExitNode ipn={ipn} config={config} setConfig={setConfig} />
         </>
       )}
-      <AutoInit build={build} config={config} />
+      <AutoInit build={build} config={config} setConfig={setConfig} />
       <IpnContext value={ipn}>
         <IpnPrepareContext value={prepare}>{children}</IpnPrepareContext>
       </IpnContext>
@@ -237,7 +228,24 @@ function AutoExitNode({
   return null
 }
 
-function AutoInit({ build, config }: { build: () => void; config: TailshareConfig }) {
+function AutoInit({
+  build,
+  config,
+  setConfig,
+}: {
+  build: () => void
+  config: TailshareConfig
+  setConfig: (patch: Partial<TailshareConfig>) => void
+}) {
+  const state = useIpnSelector(getIpnState)
+
+  const markAutostart = useEffectEvent(() => {
+    if (config.autostart !== false) setConfig({ autostart: true })
+  })
+  useEffect(() => {
+    if (state === "Running") markAutostart()
+  }, [state])
+
   useEffect(() => {
     if (!config.autostart) return
     const timeout = window.setTimeout(build, 1000)

packages/tailshare/src/pages/tailscale.tsx

@@ -171,7 +171,7 @@ function TailscaleConfig() {
               ? "OPFS: files persist across reloads. Requires SharedWorker mode."
               : "Memory: files are lost on reload."
           }
-          value={config.fileOps ?? "memory"}
+          value={config.fileOps}
           onChange={(e) => setConfig({ fileOps: e.target.value as "memory" | "opfs" })}
           data={[
             { label: "Memory (volatile)", value: "memory" },
@@ -192,7 +192,7 @@ function TailscaleConfig() {
           <Checkbox
             mt="md"
             label="Use SharedWorker (enables multi-tab support)"
-            checked={config.useWorker !== false}
+            checked={!!config.useWorker}
             onChange={(e) => setConfig({ useWorker: e.target.checked })}
           />
         )}