diff --git a/.github/workflows/pr-build.yml b/.github/workflows/pr-build.yml
index 28e5f98d..02ccb32c 100644
--- a/.github/workflows/pr-build.yml
+++ b/.github/workflows/pr-build.yml
@@ -107,6 +107,7 @@ jobs:
           packages/ui/src/components/session-list-visibility.test.ts
           packages/ui/src/components/unified-picker-path.test.ts
           packages/ui/src/lib/hooks/use-app-session-capture.test.ts
+          packages/ui/src/lib/launch-errors.test.ts
           packages/ui/src/lib/message-selection-position.test.ts
           packages/ui/src/lib/trailing-resync.test.ts
           packages/ui/src/stores/abort-created-workspace-cleanup.test.ts
diff --git a/packages/server/src/workspaces/manager.test.ts b/packages/server/src/workspaces/manager.test.ts
index 7b9a66e4..e7f6061a 100644
--- a/packages/server/src/workspaces/manager.test.ts
+++ b/packages/server/src/workspaces/manager.test.ts
@@ -59,11 +59,13 @@ class ControlledRuntime {
 }
 
 function createHarness(options: {
+  stubReadiness?: boolean
   shutdownTimeoutMs?: number
   launchTimeoutMs?: number
   setTimeout?: (callback: () => void, delayMs: number) => ReturnType<typeof setTimeout>
   clearTimeout?: (timer: ReturnType<typeof setTimeout>) => void
 } = {}) {
+  const { stubReadiness = true, ...managerOptions } = options
   const eventBus = new EventBus()
   const runtime = new ControlledRuntime()
   const readiness = deferred<string | undefined>()
@@ -79,16 +81,18 @@ function createHarness(options: {
     logger: pino({ level: "silent" }),
     getServerBaseUrl: () => "http://127.0.0.1:4000",
     runtime,
-    ...options,
+    ...managerOptions,
   })
-  ;(manager as any).waitForWorkspaceReadiness = ({ signal }: { signal?: AbortSignal }) => Promise.race([
-    readiness.promise,
-    new Promise<never>((_resolve, reject) => {
-      const cancel = () => reject(signal?.reason)
-      signal?.addEventListener("abort", cancel, { once: true })
-      if (signal?.aborted) cancel()
-    }),
-  ])
+  if (stubReadiness) {
+    ;(manager as any).waitForWorkspaceReadiness = ({ signal }: { signal?: AbortSignal }) => Promise.race([
+      readiness.promise,
+      new Promise<never>((_resolve, reject) => {
+        const cancel = () => reject(signal?.reason)
+        signal?.addEventListener("abort", cancel, { once: true })
+        if (signal?.aborted) cancel()
+      }),
+    ])
+  }
   return { manager, runtime, readiness, started, stopped }
 }
 
@@ -102,6 +106,49 @@ async function createReady(harness: ReturnType<typeof createHarness>) {
 }
 
 describe("workspace manager lifecycle", () => {
+  it("rejects a healthy workspace whose OpenCode configuration is invalid", async () => {
+    const originalFetch = globalThis.fetch
+    const requests: string[] = []
+    const configError = JSON.stringify({
+      name: "ConfigInvalidError",
+      data: {
+        path: "C:\\Users\\dev\\.config\\opencode\\agents\\invalid.md",
+        issues: [{ path: ["tools", "bash"], message: 'Expected boolean, got "ask"' }],
+      },
+    })
+    globalThis.fetch = (async (input: URL | RequestInfo) => {
+      const url = String(input)
+      requests.push(url)
+      if (url.includes("/global/health")) {
+        return new Response(JSON.stringify({ healthy: true, version: "1.18.5" }), {
+          headers: { "Content-Type": "application/json" },
+        })
+      }
+      return new Response(configError, { status: 400, headers: { "Content-Type": "application/json" } })
+    }) as typeof fetch
+
+    try {
+      const harness = createHarness({ stubReadiness: false })
+      ;(harness.manager as any).waitForPortAvailability = async () => undefined
+      const creation = harness.manager.create(process.cwd())
+      const workspaceId = await harness.runtime.launchCalled.promise
+      harness.runtime.resolveLaunch()
+
+      await assert.rejects(creation, (error: unknown) => {
+        assert.ok(error instanceof Error)
+        assert.equal(error.message, configError)
+        return true
+      })
+      assert.deepEqual(requests.map((url) => new URL(url).pathname), ["/global/health", "/config"])
+      assert.equal(new URL(requests[1]).search, "")
+      assert.equal(harness.runtime.active.has(workspaceId), false)
+      assert.deepEqual(harness.started, [])
+      assert.deepEqual(harness.manager.list(), [])
+    } finally {
+      globalThis.fetch = originalFetch
+    }
+  })
+
   for (const boundary of ["launch", "readiness", "shutdown"] as const) {
     it(`cancels and cleans a workspace during ${boundary}`, async () => {
       const harness = createHarness()
diff --git a/packages/server/src/workspaces/manager.ts b/packages/server/src/workspaces/manager.ts
index 6966f705..6d39c919 100644
--- a/packages/server/src/workspaces/manager.ts
+++ b/packages/server/src/workspaces/manager.ts
@@ -713,6 +713,11 @@ export class WorkspaceManager {
 
     const version = await this.waitForInstanceHealth(params)
 
+    await Promise.race([
+      this.validateInstanceConfiguration(params),
+      this.exitDuringStartup(params, "exited during configuration validation"),
+    ])
+
     await Promise.race([
       delay(STARTUP_STABILITY_DELAY_MS, undefined, { signal: params.signal }),
       this.exitDuringStartup(params, "exited shortly after start"),
@@ -753,13 +758,7 @@ export class WorkspaceManager {
     const url = `http://${LOOPBACK_HOST}:${port}/global/health`
 
     try {
-      const headers: Record<string, string> = {}
-      const authHeader = this.opencodeAuth.get(workspaceId)?.authorization
-      if (authHeader) {
-        headers["Authorization"] = authHeader
-      }
-
-      const response = await fetch(url, { headers, signal })
+      const response = await fetch(url, { headers: this.getInstanceRequestHeaders(workspaceId), signal })
       if (!response.ok) {
         const reason = `/global/health returned HTTP ${response.status}`
         this.options.logger.debug({ workspaceId, status: response.status }, "Health probe returned server error")
@@ -784,6 +783,25 @@ export class WorkspaceManager {
     }
   }
 
+  private async validateInstanceConfiguration(params: WorkspaceReadiness): Promise<void> {
+    const response = await fetch(`http://${LOOPBACK_HOST}:${params.port}/config`, {
+      headers: this.getInstanceRequestHeaders(params.workspaceId),
+      signal: params.signal,
+    })
+    if (response.ok) {
+      await response.body?.cancel()
+      return
+    }
+
+    const body = (await response.text()).trim()
+    throw new Error(body || `OpenCode /config returned HTTP ${response.status}`)
+  }
+
+  private getInstanceRequestHeaders(workspaceId: string): Record<string, string> {
+    const authorization = this.opencodeAuth.get(workspaceId)?.authorization
+    return authorization ? { Authorization: authorization } : {}
+  }
+
   private buildStartupError(
     workspaceId: string,
     phase: string,
diff --git a/packages/ui/src/App.tsx b/packages/ui/src/App.tsx
index 189957c7..04f28790 100644
--- a/packages/ui/src/App.tsx
+++ b/packages/ui/src/App.tsx
@@ -303,7 +303,11 @@ const App: Component = () => {
         port: instances().get(result.instanceId)?.port,
       })
     } catch (error) {
-      const message = formatLaunchErrorMessage(error, t("app.launchError.fallbackMessage"))
+      const message = formatLaunchErrorMessage(
+        error,
+        t("app.launchError.fallbackMessage"),
+        t("app.launchError.invalidConfig"),
+      )
       const missingBinary = isMissingBinaryMessage(message)
       showLaunchError({ source: "create", message, binaryPath: selectedBinary, missingBinary })
       log.error("Failed to create instance", error)
diff --git a/packages/ui/src/lib/i18n/messages/de/app.ts b/packages/ui/src/lib/i18n/messages/de/app.ts
index d01d7689..8472d652 100644
--- a/packages/ui/src/lib/i18n/messages/de/app.ts
+++ b/packages/ui/src/lib/i18n/messages/de/app.ts
@@ -1,12 +1,13 @@
 export const appMessages = {
   "app.launchError.title": "OpenCode konnte nicht gestartet werden",
-  "app.launchError.description": "Die ausgewählte OpenCode-Binärdatei konnte nicht gestartet werden. Überprüfen Sie die Fehlerausgabe unten oder wählen Sie eine andere Binärdatei in den OpenCode-Einstellungen.",
+  "app.launchError.description": "OpenCode konnte diesen Arbeitsbereich nicht starten. Überprüfen Sie die Fehlerausgabe unten oder Ihre OpenCode-Einstellungen.",
   "app.launchError.binaryPathLabel": "Binärpfad",
   "app.launchError.errorOutputLabel": "Fehlerausgabe",
   "app.launchError.openAdvancedSettings": "OpenCode-Einstellungen öffnen",
   "app.launchError.close": "Schließen",
   "app.launchError.closeTitle": "Schließen (Esc)",
   "app.launchError.fallbackMessage": "Arbeitsbereich konnte nicht gestartet werden",
+  "app.launchError.invalidConfig": "Die OpenCode-Konfiguration ist ungültig",
 
   "app.stopInstance.confirmMessage": "OpenCode-Instanz stoppen? Dies wird den Server beenden.",
   "app.stopInstance.title": "Instanz stoppen",
diff --git a/packages/ui/src/lib/i18n/messages/en/app.ts b/packages/ui/src/lib/i18n/messages/en/app.ts
index 1fd95247..edcaf57d 100644
--- a/packages/ui/src/lib/i18n/messages/en/app.ts
+++ b/packages/ui/src/lib/i18n/messages/en/app.ts
@@ -1,12 +1,13 @@
 export const appMessages = {
   "app.launchError.title": "Unable to launch OpenCode",
-  "app.launchError.description": "We couldn't start the selected OpenCode binary. Review the error output below or choose a different binary from OpenCode settings.",
+  "app.launchError.description": "OpenCode could not start this workspace. Review the error output below or check your OpenCode settings.",
   "app.launchError.binaryPathLabel": "Binary path",
   "app.launchError.errorOutputLabel": "Error output",
   "app.launchError.openAdvancedSettings": "Open OpenCode Settings",
   "app.launchError.close": "Close",
   "app.launchError.closeTitle": "Close (Esc)",
   "app.launchError.fallbackMessage": "Failed to launch workspace",
+  "app.launchError.invalidConfig": "OpenCode configuration is invalid",
 
   "app.stopInstance.confirmMessage": "Stop OpenCode instance? This will stop the server.",
   "app.stopInstance.title": "Stop instance",
diff --git a/packages/ui/src/lib/i18n/messages/es/app.ts b/packages/ui/src/lib/i18n/messages/es/app.ts
index 95dfde99..99ce5f67 100644
--- a/packages/ui/src/lib/i18n/messages/es/app.ts
+++ b/packages/ui/src/lib/i18n/messages/es/app.ts
@@ -1,12 +1,13 @@
 export const appMessages = {
   "app.launchError.title": "No se pudo iniciar OpenCode",
-  "app.launchError.description": "No pudimos iniciar el binario de OpenCode seleccionado. Revisa la salida de error abajo o elige un binario distinto en la configuración de OpenCode.",
+  "app.launchError.description": "OpenCode no pudo iniciar este espacio de trabajo. Revisa la salida de error o la configuración de OpenCode.",
   "app.launchError.binaryPathLabel": "Ruta del binario",
   "app.launchError.errorOutputLabel": "Salida de error",
   "app.launchError.openAdvancedSettings": "Abrir Configuración de OpenCode",
   "app.launchError.close": "Cerrar",
   "app.launchError.closeTitle": "Cerrar (Esc)",
   "app.launchError.fallbackMessage": "No se pudo iniciar el workspace",
+  "app.launchError.invalidConfig": "La configuración de OpenCode no es válida",
 
   "app.stopInstance.confirmMessage": "¿Detener la instancia de OpenCode? Esto detendrá el servidor.",
   "app.stopInstance.title": "Detener instancia",
diff --git a/packages/ui/src/lib/i18n/messages/fr/app.ts b/packages/ui/src/lib/i18n/messages/fr/app.ts
index b2d0fd31..e5c9ae5c 100644
--- a/packages/ui/src/lib/i18n/messages/fr/app.ts
+++ b/packages/ui/src/lib/i18n/messages/fr/app.ts
@@ -1,12 +1,13 @@
 export const appMessages = {
   "app.launchError.title": "Impossible de lancer OpenCode",
-  "app.launchError.description": "Nous n'avons pas pu démarrer le binaire OpenCode sélectionné. Consultez la sortie d'erreur ci-dessous ou choisissez un autre binaire dans les paramètres OpenCode.",
+  "app.launchError.description": "OpenCode n'a pas pu démarrer cet espace de travail. Consultez la sortie d'erreur ci-dessous ou vérifiez vos paramètres OpenCode.",
   "app.launchError.binaryPathLabel": "Chemin du binaire",
   "app.launchError.errorOutputLabel": "Sortie d'erreur",
   "app.launchError.openAdvancedSettings": "Ouvrir les paramètres OpenCode",
   "app.launchError.close": "Fermer",
   "app.launchError.closeTitle": "Fermer (Esc)",
   "app.launchError.fallbackMessage": "Échec du lancement de l'espace de travail",
+  "app.launchError.invalidConfig": "La configuration OpenCode n'est pas valide",
 
   "app.stopInstance.confirmMessage": "Arrêter l'instance OpenCode ? Cela arrêtera le serveur.",
   "app.stopInstance.title": "Arrêter l'instance",
diff --git a/packages/ui/src/lib/i18n/messages/he/app.ts b/packages/ui/src/lib/i18n/messages/he/app.ts
index e00b6963..4a6501e7 100644
--- a/packages/ui/src/lib/i18n/messages/he/app.ts
+++ b/packages/ui/src/lib/i18n/messages/he/app.ts
@@ -1,12 +1,13 @@
 export const appMessages = {
   "app.launchError.title": "לא ניתן להפעיל את OpenCode",
-  "app.launchError.description": "לא הצלחנו להפעיל את קובץ ה-OpenCode שנבחר. בדוק את פלט השגיאה למטה או בחר קובץ בינארי אחר מהגדרות OpenCode.",
+  "app.launchError.description": "OpenCode לא הצליח להפעיל את סביבת העבודה הזו. בדוק את פלט השגיאה למטה או את הגדרות OpenCode.",
   "app.launchError.binaryPathLabel": "נתיב הקובץ הבינארי",
   "app.launchError.errorOutputLabel": "פלט שגיאה",
   "app.launchError.openAdvancedSettings": "פתח הגדרות OpenCode",
   "app.launchError.close": "סגור",
   "app.launchError.closeTitle": "סגור (Esc)",
   "app.launchError.fallbackMessage": "הפעלת סביבת העבודה נכשלה",
+  "app.launchError.invalidConfig": "תצורת OpenCode אינה תקינה",
 
   "app.stopInstance.confirmMessage": "לעצור את מופע OpenCode? פעולה זו תעצור את השרת.",
   "app.stopInstance.title": "עצור מופע",
diff --git a/packages/ui/src/lib/i18n/messages/ja/app.ts b/packages/ui/src/lib/i18n/messages/ja/app.ts
index e0b24dca..ece3e28b 100644
--- a/packages/ui/src/lib/i18n/messages/ja/app.ts
+++ b/packages/ui/src/lib/i18n/messages/ja/app.ts
@@ -1,12 +1,13 @@
 export const appMessages = {
   "app.launchError.title": "OpenCode を起動できません",
-  "app.launchError.description": "選択された OpenCode バイナリを起動できませんでした。下のエラー出力を確認するか、OpenCode 設定から別のバイナリを選択してください。",
+  "app.launchError.description": "OpenCode はこのワークスペースを起動できませんでした。下のエラー出力または OpenCode 設定を確認してください。",
   "app.launchError.binaryPathLabel": "バイナリのパス",
   "app.launchError.errorOutputLabel": "エラー出力",
   "app.launchError.openAdvancedSettings": "OpenCode 設定を開く",
   "app.launchError.close": "閉じる",
   "app.launchError.closeTitle": "閉じる (Esc)",
   "app.launchError.fallbackMessage": "ワークスペースの起動に失敗しました",
+  "app.launchError.invalidConfig": "OpenCode の設定が無効です",
 
   "app.stopInstance.confirmMessage": "OpenCode インスタンスを停止しますか？サーバーが停止します。",
   "app.stopInstance.title": "インスタンスを停止",
diff --git a/packages/ui/src/lib/i18n/messages/ne/app.ts b/packages/ui/src/lib/i18n/messages/ne/app.ts
index 9bcf7ace..ce78b306 100644
--- a/packages/ui/src/lib/i18n/messages/ne/app.ts
+++ b/packages/ui/src/lib/i18n/messages/ne/app.ts
@@ -1,12 +1,13 @@
 export const appMessages = {
   "app.launchError.title": "OpenCode सुरु गर्न असमर्थ",
-  "app.launchError.description": "हामीले चयन गरिएको OpenCode बाइनरी सुरु गर्न सकेनौं। तलको त्रुटि आउटपुट समीक्षा गर्नुहोस् वा OpenCode सेटिङहरूबाट फरक बाइनरी छनौट गर्नुहोस्।",
+  "app.launchError.description": "OpenCode ले यो कार्यस्थान सुरु गर्न सकेन। तलको त्रुटि आउटपुट वा OpenCode सेटिङहरू जाँच गर्नुहोस्।",
   "app.launchError.binaryPathLabel": "बाइनरी मार्ग (Binary path)",
   "app.launchError.errorOutputLabel": "त्रुटि आउटपुट (Error output)",
   "app.launchError.openAdvancedSettings": "OpenCode सेटिङहरू खोल्नुहोस्",
   "app.launchError.close": "बन्द गर्नुहोस्",
   "app.launchError.closeTitle": "बन्द गर्नुहोस् (Esc)",
   "app.launchError.fallbackMessage": "कार्यस्थान सुरु गर्न असफल",
+  "app.launchError.invalidConfig": "OpenCode कन्फिगरेसन अमान्य छ",
 
   "app.stopInstance.confirmMessage": "OpenCode उदाहरण रोक्ने? यसले सर्भर बन्द गर्नेछ।",
   "app.stopInstance.title": "उदाहरण रोक्नुहोस्",
diff --git a/packages/ui/src/lib/i18n/messages/ru/app.ts b/packages/ui/src/lib/i18n/messages/ru/app.ts
index 3fefb3f7..e14a60fd 100644
--- a/packages/ui/src/lib/i18n/messages/ru/app.ts
+++ b/packages/ui/src/lib/i18n/messages/ru/app.ts
@@ -1,12 +1,13 @@
 export const appMessages = {
   "app.launchError.title": "Не удалось запустить OpenCode",
-  "app.launchError.description": "Не удалось запустить выбранный бинарник OpenCode. Просмотрите вывод ошибки ниже или выберите другой бинарник в настройках OpenCode.",
+  "app.launchError.description": "OpenCode не удалось запустить это рабочее пространство. Проверьте вывод ошибки ниже или настройки OpenCode.",
   "app.launchError.binaryPathLabel": "Путь к бинарнику",
   "app.launchError.errorOutputLabel": "Вывод ошибки",
   "app.launchError.openAdvancedSettings": "Открыть настройки OpenCode",
   "app.launchError.close": "Закрыть",
   "app.launchError.closeTitle": "Закрыть (Esc)",
   "app.launchError.fallbackMessage": "Не удалось запустить рабочее пространство",
+  "app.launchError.invalidConfig": "Конфигурация OpenCode недействительна",
 
   "app.stopInstance.confirmMessage": "Остановить экземпляр OpenCode? Это остановит сервер.",
   "app.stopInstance.title": "Остановить экземпляр",
diff --git a/packages/ui/src/lib/i18n/messages/zh-Hans/app.ts b/packages/ui/src/lib/i18n/messages/zh-Hans/app.ts
index 0cc9d917..3a502e47 100644
--- a/packages/ui/src/lib/i18n/messages/zh-Hans/app.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-Hans/app.ts
@@ -1,12 +1,13 @@
 export const appMessages = {
   "app.launchError.title": "无法启动 OpenCode",
-  "app.launchError.description": "我们无法启动所选的 OpenCode 可执行文件。请查看下面的错误输出，或在 OpenCode 设置中选择其他可执行文件。",
+  "app.launchError.description": "OpenCode 无法启动此工作区。请查看下面的错误输出或检查 OpenCode 设置。",
   "app.launchError.binaryPathLabel": "可执行文件路径",
   "app.launchError.errorOutputLabel": "错误输出",
   "app.launchError.openAdvancedSettings": "打开 OpenCode 设置",
   "app.launchError.close": "关闭",
   "app.launchError.closeTitle": "关闭 (Esc)",
   "app.launchError.fallbackMessage": "启动工作区失败",
+  "app.launchError.invalidConfig": "OpenCode 配置无效",
 
   "app.stopInstance.confirmMessage": "停止 OpenCode 实例？这将停止服务器。",
   "app.stopInstance.title": "停止实例",
diff --git a/packages/ui/src/lib/launch-errors.test.ts b/packages/ui/src/lib/launch-errors.test.ts
new file mode 100644
index 00000000..f11bb7d4
--- /dev/null
+++ b/packages/ui/src/lib/launch-errors.test.ts
@@ -0,0 +1,52 @@
+import assert from "node:assert/strict"
+import { describe, it } from "node:test"
+
+import { formatLaunchErrorMessage } from "./launch-errors"
+
+describe("formatLaunchErrorMessage", () => {
+  it("formats OpenCode configuration validation details", () => {
+    const error = new Error(JSON.stringify({
+      name: "ConfigInvalidError",
+      data: {
+        path: "C:\\Users\\dev\\.config\\opencode\\agents\\invalid.md",
+        issues: [
+          { path: ["tools", "bash"], message: 'Expected boolean, got "ask"' },
+          { path: ["tools", "webfetch"], message: 'Expected boolean, got "ask"' },
+        ],
+      },
+    }))
+
+    assert.equal(formatLaunchErrorMessage(error, "fallback", "OpenCode configuration is invalid"), [
+      "OpenCode configuration is invalid",
+      "C:\\Users\\dev\\.config\\opencode\\agents\\invalid.md",
+      'tools.bash: Expected boolean, got "ask"',
+      'tools.webfetch: Expected boolean, got "ask"',
+    ].join("\n"))
+  })
+
+  it("preserves message-only tagged configuration errors", () => {
+    const error = JSON.stringify({
+      _tag: "ConfigInvalidError",
+      path: "/home/dev/.config/opencode/opencode.json",
+      message: "Missing environment variable",
+    })
+
+    assert.equal(formatLaunchErrorMessage(error, "fallback", "Invalid configuration"), [
+      "Invalid configuration",
+      "/home/dev/.config/opencode/opencode.json",
+      "Missing environment variable",
+    ].join("\n"))
+  })
+
+  it("preserves configuration directory typo suggestions", () => {
+    const error = JSON.stringify({
+      name: "ConfigDirectoryTypoError",
+      data: { dir: "/project/.opencod", suggestion: "/project/.opencode" },
+    })
+
+    assert.equal(formatLaunchErrorMessage(error, "fallback", "Invalid configuration"), [
+      "Invalid configuration",
+      "/project/.opencod → /project/.opencode",
+    ].join("\n"))
+  })
+})
diff --git a/packages/ui/src/lib/launch-errors.ts b/packages/ui/src/lib/launch-errors.ts
index 0d495f97..9397c074 100644
--- a/packages/ui/src/lib/launch-errors.ts
+++ b/packages/ui/src/lib/launch-errors.ts
@@ -1,4 +1,4 @@
-export function formatLaunchErrorMessage(error: unknown, fallbackMessage: string): string {
+export function formatLaunchErrorMessage(error: unknown, fallbackMessage: string, invalidConfigMessage: string): string {
   if (!error) {
     return fallbackMessage
   }
@@ -7,6 +7,8 @@ export function formatLaunchErrorMessage(error: unknown, fallbackMessage: string
 
   try {
     const parsed = JSON.parse(raw) as unknown
+    const configError = formatConfigError(parsed, invalidConfigMessage)
+    if (configError) return configError
     if (parsed && typeof parsed === "object" && "error" in parsed && typeof (parsed as any).error === "string") {
       return (parsed as any).error
     }
@@ -17,6 +19,41 @@ export function formatLaunchErrorMessage(error: unknown, fallbackMessage: string
   return raw
 }
 
+function formatConfigError(value: unknown, invalidConfigMessage: string): string | undefined {
+  if (!value || typeof value !== "object") return undefined
+  type ConfigErrorDetails = {
+    path?: unknown
+    message?: unknown
+    issues?: unknown
+    dir?: unknown
+    suggestion?: unknown
+  }
+  const error = value as ConfigErrorDetails & { name?: unknown; _tag?: unknown; data?: ConfigErrorDetails }
+  const name = typeof error.name === "string" ? error.name : error._tag
+  if (!["ConfigInvalidError", "ConfigJsonError", "ConfigFrontmatterError", "ConfigDirectoryTypoError"].includes(String(name))) return undefined
+  const details = error.data && typeof error.data === "object" ? error.data : error
+
+  const lines = [invalidConfigMessage]
+  if (typeof details.path === "string" && details.path.trim()) lines.push(details.path.trim())
+  if (typeof details.message === "string" && details.message.trim()) lines.push(details.message.trim())
+  const dir = typeof details.dir === "string" ? details.dir.trim() : ""
+  const suggestion = typeof details.suggestion === "string" ? details.suggestion.trim() : ""
+  if (dir && suggestion) lines.push(`${dir} → ${suggestion}`)
+  else if (dir || suggestion) lines.push(dir || suggestion)
+  if (Array.isArray(details.issues)) {
+    for (const issue of details.issues) {
+      if (!issue || typeof issue !== "object") continue
+      const candidate = issue as { path?: unknown; message?: unknown }
+      const location = Array.isArray(candidate.path) ? candidate.path.map(String).join(".") : ""
+      const message = typeof candidate.message === "string" ? candidate.message.trim() : ""
+      if (location && message) lines.push(`${location}: ${message}`)
+      else if (message) lines.push(message)
+    }
+  }
+
+  return lines.join("\n")
+}
+
 export function isMissingBinaryMessage(message: string): boolean {
   const normalized = message.toLowerCase()
   return (
diff --git a/packages/ui/src/stores/launch-errors.ts b/packages/ui/src/stores/launch-errors.ts
index 814790f8..3513aa0b 100644
--- a/packages/ui/src/stores/launch-errors.ts
+++ b/packages/ui/src/stores/launch-errors.ts
@@ -29,7 +29,11 @@ export function clearLaunchError() {
 export function showWorkspaceLaunchError(workspace: WorkspaceDescriptor) {
   const instanceId = workspace.id
   const rawMessage = workspace.error
-  const message = formatLaunchErrorMessage(rawMessage, tGlobal("app.launchError.fallbackMessage"))
+  const message = formatLaunchErrorMessage(
+    rawMessage,
+    tGlobal("app.launchError.fallbackMessage"),
+    tGlobal("app.launchError.invalidConfig"),
+  )
 
   const previous = lastWorkspaceErrorByInstanceId.get(instanceId)
   if (previous && previous === message) {