@@ -42,7 +42,9 @@ export function RuntimeErrorTooltip({
         side="bottom"
         sideOffset={12}
       >
-        <span className="leading-4">{detail}</span>
+        <span className="block max-h-48 overflow-y-auto overflow-x-hidden break-words whitespace-pre-line leading-4">
+          {detail}
+        </span>
       </TooltipContent>
     </Tooltip>
   );
 
@@ -463,19 +463,56 @@ function RuntimeAuthError({ runtime }: { runtime: AcpRuntimeCatalogEntry }) {
 }
 
 function RuntimeCard({
-  installError,
-  isInstalling,
-  onInstall,
+  installResults,
+  onInstallResultsChange,
   runtime,
 }: {
-  installError: string | null;
-  isInstalling: boolean;
-  onInstall: () => void;
+  installResults: InstallResultsState;
+  onInstallResultsChange: React.Dispatch<
+    React.SetStateAction<InstallResultsState>
+  >;
   runtime: AcpRuntimeCatalogEntry;
 }) {
+  // Each card owns its own mutation instance so concurrent installs on
+  // different cards each track their own isPending state and callbacks
+  // independently (react-query v5 per-mutate callbacks only fire for the
+  // latest mutate() call on a shared instance, silently dropping earlier ones).
+  const installMutation = useInstallAcpRuntimeMutation();
+  const installError = installResults[runtime.id]?.error ?? null;
+  const isInstalling = installMutation.isPending;
   const isAvailable = runtime.availability === "available";
   const isReady = runtimeIsReadyForOnboarding(runtime);
 
+  function handleInstall() {
+    onInstallResultsChange((current) => ({
+      ...current,
+      [runtime.id]: { error: null, success: false },
+    }));
+
+    installMutation.mutate(runtime.id, {
+      onSuccess: (result) => {
+        onInstallResultsChange((current) => ({
+          ...current,
+          [runtime.id]: result.success
+            ? { error: null, success: true }
+            : {
+                error: getInstallErrorMessage(result.steps),
+                success: false,
+              },
+        }));
+      },
+      onError: (error) => {
+        onInstallResultsChange((current) => ({
+          ...current,
+          [runtime.id]: {
+            error: error instanceof Error ? error.message : "Install failed.",
+            success: false,
+          },
+        }));
+      },
+    });
+  }
+
   return (
     <Card
       className={cn(
@@ -499,7 +536,7 @@ function RuntimeCard({
         <RuntimeStatus
           installError={installError}
           isInstalling={isInstalling}
-          onInstall={onInstall}
+          onInstall={handleInstall}
           runtime={runtime}
         />
         {!isAvailable && runtimeDetailText(runtime) ? (
@@ -517,7 +554,7 @@ function RuntimeCard({
       {installError ? (
         <RuntimeErrorTooltip
           className="absolute inset-x-3 bottom-2 flex min-w-0 items-center justify-center gap-1.5 overflow-hidden whitespace-nowrap text-xs leading-4 text-destructive"
-          detail="Installation couldn’t be completed. Try again."
+          detail={installError}
           label="Installation failed"
           showIcon
           testId={`onboarding-runtime-error-${runtime.id}`}
@@ -560,34 +597,6 @@ function RuntimeProvidersSection({
 }) {
   const { errorMessage, isChecking, items } = runtimeProviders;
   const orderedItems = getVisibleOnboardingRuntimes(items);
-  const installMutation = useInstallAcpRuntimeMutation();
-
-  function handleInstall(runtimeId: string) {
-    onInstallResultsChange((current) => ({
-      ...current,
-      [runtimeId]: { error: null, success: false },
-    }));
-
-    installMutation.mutate(runtimeId, {
-      onSuccess: (result) => {
-        onInstallResultsChange((current) => ({
-          ...current,
-          [runtimeId]: result.success
-            ? { error: null, success: true }
-            : { error: getInstallErrorMessage(result.steps), success: false },
-        }));
-      },
-      onError: (error) => {
-        onInstallResultsChange((current) => ({
-          ...current,
-          [runtimeId]: {
-            error: error instanceof Error ? error.message : "Install failed.",
-            success: false,
-          },
-        }));
-      },
-    });
-  }
 
   return (
     <section className="flex min-h-full w-full flex-col items-center">
@@ -606,13 +615,9 @@ function RuntimeProvidersSection({
           <div className="grid min-w-0 w-full max-w-[592px] grid-cols-1 gap-4 md:grid-cols-2">
             {orderedItems.map((runtime) => (
               <RuntimeCard
-                installError={installResults[runtime.id]?.error ?? null}
-                isInstalling={
-                  installMutation.isPending &&
-                  installMutation.variables === runtime.id
-                }
+                installResults={installResults}
                 key={runtime.id}
-                onInstall={() => handleInstall(runtime.id)}
+                onInstallResultsChange={onInstallResultsChange}
                 runtime={runtime}
               />
             ))}
 
@@ -279,22 +279,56 @@ function RuntimeHeader({
 }
 
 function RuntimeRow({
-  installError,
-  installSuccess,
-  isInstalling,
-  onInstall,
+  resetEpoch,
   runtime,
 }: {
-  installError: string | null;
-  installSuccess: boolean;
-  isInstalling: boolean;
-  onInstall: () => void;
+  resetEpoch: number;
   runtime: AcpRuntimeCatalogEntry;
 }) {
   const [terminalLaunchMethodId, setTerminalLaunchMethodId] = React.useState<
     string | null
   >(null);
   const [isUpdateWarningOpen, setIsUpdateWarningOpen] = React.useState(false);
+  // Each row owns its mutation instance so concurrent installs each track
+  // their own isPending / result state independently.
+  const installMutation = useInstallAcpRuntimeMutation();
+  const [installResult, setInstallResult] = React.useState<{
+    success: boolean;
+    error: string | null;
+  } | null>(null);
+  // Clear stale install results when the parent triggers a catalog refresh
+  // (Check again) — the runtime may now be healthy and stale failure state
+  // would linger because keyed rows don't remount on refetch.
+  // biome-ignore lint/correctness/useExhaustiveDependencies: resetEpoch is an intentional trigger only; its value is not consumed in the effect body
+  React.useEffect(() => {
+    setInstallResult(null);
+  }, [resetEpoch]);
+  const isInstalling = installMutation.isPending;
+  const installError = installResult?.error ?? null;
+  const installSuccess = installResult?.success ?? false;
+
+  function handleInstall() {
+    setInstallResult(null);
+    installMutation.mutate(runtime.id, {
+      onSuccess: (result) => {
+        if (result.success) {
+          setInstallResult({ success: true, error: null });
+        } else {
+          setInstallResult({
+            success: false,
+            error: getInstallErrorMessage(result.steps),
+          });
+        }
+      },
+      onError: (error) => {
+        setInstallResult({
+          success: false,
+          error: error instanceof Error ? error.message : "Install failed.",
+        });
+      },
+    });
+  }
+
   const canConnectAccount =
     runtime.availability === "available" &&
     runtime.authStatus.status === "logged_out";
@@ -352,7 +386,7 @@ function RuntimeRow({
               setIsUpdateWarningOpen(true);
               return;
             }
-            onInstall();
+            handleInstall();
           }}
           runtime={runtime}
         />
@@ -372,7 +406,10 @@ function RuntimeRow({
           </p>
         ) : null}
         {installError ? (
-          <p className="mt-2 whitespace-pre-line rounded-lg border border-destructive/30 bg-destructive/10 px-3 py-1.5 text-sm text-destructive">
+          <p
+            className="mt-2 whitespace-pre-line rounded-lg border border-destructive/30 bg-destructive/10 px-3 py-1.5 text-sm text-destructive"
+            data-testid={`doctor-runtime-install-error-${runtime.id}`}
+          >
             {installError}
           </p>
         ) : null}
@@ -410,7 +447,7 @@ function RuntimeRow({
           <AlertDialogFooter>
             <AlertDialogCancel>Cancel</AlertDialogCancel>
             <AlertDialogAction
-              onClick={onInstall}
+              onClick={handleInstall}
               data-testid={`doctor-runtime-confirm-update-${runtime.id}`}
             >
               Update
@@ -491,59 +528,9 @@ export function DoctorSettingsPanel() {
     [runtimesQuery.data],
   );
   const isRefreshing = runtimesQuery.isFetching;
-  const installMutation = useInstallAcpRuntimeMutation();
-  const [installResults, setInstallResults] = React.useState<
-    Record<string, { success: boolean; error: string | null }>
-  >({});
-  // Per-runtime installing state: tracks which runtime IDs have an in-flight
-  // install so concurrent installs each show their own spinner correctly.
-  const [installingIds, setInstallingIds] = React.useState<Set<string>>(
-    new Set(),
-  );
-
-  function handleInstall(runtimeId: string) {
-    // Clear any previous result for this runtime before retrying.
-    setInstallResults((prev) => ({
-      ...prev,
-      [runtimeId]: { success: false, error: null },
-    }));
-    setInstallingIds((prev) => new Set(prev).add(runtimeId));
-
-    installMutation.mutate(runtimeId, {
-      onSuccess: (result) => {
-        if (result.success) {
-          setInstallResults((prev) => ({
-            ...prev,
-            [runtimeId]: { success: true, error: null },
-          }));
-        } else {
-          setInstallResults((prev) => ({
-            ...prev,
-            [runtimeId]: {
-              success: false,
-              error: getInstallErrorMessage(result.steps),
-            },
-          }));
-        }
-      },
-      onError: (error) => {
-        setInstallResults((prev) => ({
-          ...prev,
-          [runtimeId]: {
-            success: false,
-            error: error instanceof Error ? error.message : "Install failed.",
-          },
-        }));
-      },
-      onSettled: () => {
-        setInstallingIds((prev) => {
-          const next = new Set(prev);
-          next.delete(runtimeId);
-          return next;
-        });
-      },
-    });
-  }
+  // Incremented each time the user clicks "Check again" so RuntimeRow
+  // useEffect clears stale install results from before the refresh.
+  const [resetEpoch, setResetEpoch] = React.useState(0);
 
   return (
     <section
@@ -558,7 +545,7 @@ export function DoctorSettingsPanel() {
           <Button
             disabled={isRefreshing}
             onClick={() => {
-              setInstallResults({});
+              setResetEpoch((e) => e + 1);
               void runtimesQuery.refetch();
               void gitBashQuery.refetch();
             }}
@@ -598,11 +585,8 @@ export function DoctorSettingsPanel() {
             <div className="space-y-3" data-testid="doctor-runtime-list">
               {runtimes.map((runtime) => (
                 <RuntimeRow
-                  installError={installResults[runtime.id]?.error ?? null}
-                  installSuccess={installResults[runtime.id]?.success ?? false}
-                  isInstalling={installingIds.has(runtime.id)}
                   key={runtime.id}
-                  onInstall={() => handleInstall(runtime.id)}
+                  resetEpoch={resetEpoch}
                   runtime={runtime}
                 />
               ))}
 
@@ -67,3 +67,47 @@ test("getInstallErrorMessage: failed step with empty stderr falls back to stdout
   ]);
   assert.match(message, /some stdout output/);
 });
+
+test("getInstallErrorMessage: hint and step detail are separated by double newline for whitespace-pre-line rendering", () => {
+  const hint = "Git Bash is required. Install it from git-scm.com.";
+  const message = getInstallErrorMessage([
+    {
+      step: "shell",
+      command: "bash -l -c 'npm install'",
+      success: false,
+      stdout: "",
+      stderr: "bash: command not found",
+      exitCode: 127,
+      hint,
+    },
+  ]);
+  assert.ok(
+    message.includes("\n\n"),
+    "hint and step detail should be separated by a blank line",
+  );
+  assert.ok(message.startsWith(hint));
+});
+
+test("getInstallErrorMessage: only reports the last (failing) step when multiple steps present", () => {
+  const message = getInstallErrorMessage([
+    {
+      step: "node",
+      command: "node --version",
+      success: true,
+      stdout: "v20.0.0",
+      stderr: "",
+      exitCode: 0,
+    },
+    {
+      step: "adapter",
+      command: "npm install -g @agentclientprotocol/claude-code-acp",
+      success: false,
+      stdout: "",
+      stderr: "npm ERR! code E404",
+      exitCode: 1,
+    },
+  ]);
+  assert.match(message, /Step "adapter" failed:/);
+  assert.match(message, /npm ERR! code E404/);
+  assert.doesNotMatch(message, /Step "node"/);
+});