diff --git a/apps/server/src/preview/PortScanner.test.ts b/apps/server/src/preview/PortScanner.test.ts
index 6c48f6d5c8b..69b5729164d 100644
--- a/apps/server/src/preview/PortScanner.test.ts
+++ b/apps/server/src/preview/PortScanner.test.ts
@@ -3,14 +3,48 @@ import * as NodeNet from "node:net";
 import { it as effectIt } from "@effect/vitest";
 import { HostProcessPlatform } from "@t3tools/shared/hostProcess";
 import * as Net from "@t3tools/shared/Net";
-import { Effect, Layer } from "effect";
+import * as Cause from "effect/Cause";
+import * as Effect from "effect/Effect";
+import * as Exit from "effect/Exit";
+import * as Layer from "effect/Layer";
+import * as PlatformError from "effect/PlatformError";
 import { expect } from "vite-plus/test";
 
 import * as ProcessRunner from "../processRunner.ts";
 import * as PortScanner from "./PortScanner.ts";
 const TestProcessRunner = Layer.succeed(ProcessRunner.ProcessRunner, {
-  run: () => Effect.die("ProcessRunner should not be used by Windows TCP probe tests"),
+  run: (input) =>
+    Effect.fail(
+      new ProcessRunner.ProcessSpawnError({
+        command: input.command,
+        argumentCount: input.args.length,
+        cwd: input.cwd,
+        cause: PlatformError.systemError({
+          _tag: "NotFound",
+          module: "ChildProcess",
+          method: "spawn",
+          description: "PowerShell is not installed in the test environment",
+        }),
+      }),
+    ),
 });
+
+const makeProbeFailureLayer = (run: ProcessRunner.ProcessRunner["Service"]["run"]) =>
+  PortScanner.layer.pipe(
+    Layer.provide(
+      Layer.mergeAll(
+        Layer.succeed(ProcessRunner.ProcessRunner, { run }),
+        Layer.succeed(Net.NetService, {
+          canListenOnHost: () => Effect.succeed(true),
+          isPortAvailableOnLoopback: () => Effect.succeed(true),
+          reserveLoopbackPort: () => Effect.succeed(40_000),
+          findAvailablePort: (preferred) => Effect.succeed(preferred),
+        }),
+        Layer.succeed(HostProcessPlatform, "linux"),
+      ),
+    ),
+  );
+
 const TestPortDiscoveryLive = PortScanner.layer.pipe(
   Layer.provide(
     Layer.mergeAll(TestProcessRunner, Net.layer, Layer.succeed(HostProcessPlatform, "win32")),
@@ -87,3 +121,37 @@ effectIt.layer(TestPortDiscoveryLive)("PortDiscovery integration (TCP probe fall
     }),
   );
 });
+
+effectIt("does not swallow process probe defects", () =>
+  Effect.gen(function* () {
+    const defect = new Error("unexpected process probe defect");
+    const layer = makeProbeFailureLayer(() => Effect.die(defect));
+
+    const exit = yield* Effect.flatMap(PortScanner.PortDiscovery, (scanner) => scanner.scan()).pipe(
+      Effect.provide(layer),
+      Effect.exit,
+    );
+
+    expect(Exit.isFailure(exit)).toBe(true);
+    if (Exit.isFailure(exit)) {
+      expect(Cause.hasDies(exit.cause)).toBe(true);
+      expect(Cause.squash(exit.cause)).toBe(defect);
+    }
+  }),
+);
+
+effectIt("does not swallow process probe interruption", () =>
+  Effect.gen(function* () {
+    const layer = makeProbeFailureLayer(() => Effect.interrupt);
+
+    const exit = yield* Effect.flatMap(PortScanner.PortDiscovery, (scanner) => scanner.scan()).pipe(
+      Effect.provide(layer),
+      Effect.exit,
+    );
+
+    expect(Exit.isFailure(exit)).toBe(true);
+    if (Exit.isFailure(exit)) {
+      expect(Cause.hasInterruptsOnly(exit.cause)).toBe(true);
+    }
+  }),
+);
diff --git a/apps/server/src/preview/PortScanner.ts b/apps/server/src/preview/PortScanner.ts
index 16ff0fed58f..c306fca2b33 100644
--- a/apps/server/src/preview/PortScanner.ts
+++ b/apps/server/src/preview/PortScanner.ts
@@ -221,6 +221,14 @@ export const make = Effect.gen(function* PortDiscoveryMake() {
       }));
   });
 
+  const recoverProcessProbeFailure =
+    (probe: "lsof" | "windows-listeners") => (error: ProcessRunner.ProcessRunError) =>
+      Effect.logDebug("preview port process probe failed; falling back to common-port probes", {
+        cause: error,
+        probe,
+        platform: hostPlatform,
+      }).pipe(Effect.as(null));
+
   const scanOnce = Effect.fn("PortDiscovery.scan")(function* () {
     const state = yield* Ref.get(stateRef);
     const terminalByProcessId = new Map<number, TerminalProcessOwner>();
@@ -230,6 +238,7 @@ export const make = Effect.gen(function* PortDiscoveryMake() {
       }
     }
     if (hostPlatform === "win32") {
+      const recoverWindowsProbeFailure = recoverProcessProbeFailure("windows-listeners");
       const command =
         'Get-NetTCPConnection -State Listen -ErrorAction Stop | ForEach-Object { $processName = (Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue).ProcessName; Write-Output "$($_.LocalAddress)|$($_.LocalPort)|$($_.OwningProcess)|$processName" }';
       const listeners = yield* processRunner
@@ -242,11 +251,18 @@ export const make = Effect.gen(function* PortDiscoveryMake() {
         })
         .pipe(
           Effect.map((result) => parseWindowsListenerOutput(result.stdout, terminalByProcessId)),
-          Effect.catchCause(() => Effect.succeed(null)),
+          Effect.catchTags({
+            ProcessSpawnError: recoverWindowsProbeFailure,
+            ProcessStdinError: recoverWindowsProbeFailure,
+            ProcessOutputLimitError: recoverWindowsProbeFailure,
+            ProcessReadError: recoverWindowsProbeFailure,
+            ProcessTimeoutError: recoverWindowsProbeFailure,
+          }),
         );
       if (listeners !== null) return listeners;
       return yield* probeCommonPorts();
     }
+    const recoverLsofProbeFailure = recoverProcessProbeFailure("lsof");
     const lsofResult = yield* processRunner
       .run({
         command: "lsof",
@@ -257,7 +273,13 @@ export const make = Effect.gen(function* PortDiscoveryMake() {
       })
       .pipe(
         Effect.map((result) => parseLsofOutput(result.stdout, terminalByProcessId)),
-        Effect.catchCause(() => Effect.succeed(null)),
+        Effect.catchTags({
+          ProcessSpawnError: recoverLsofProbeFailure,
+          ProcessStdinError: recoverLsofProbeFailure,
+          ProcessOutputLimitError: recoverLsofProbeFailure,
+          ProcessReadError: recoverLsofProbeFailure,
+          ProcessTimeoutError: recoverLsofProbeFailure,
+        }),
       );
     if (lsofResult !== null) return lsofResult;
     return yield* probeCommonPorts();