@@ -27,7 +27,7 @@ const TEST_BROWSER_ENV = "T3CODE_TEST_HEADLESS_SHELL";
 
 const layerHtmlRender = (
   executable?: string,
-  installed: Effect.Effect<Option.Option<string>> = Effect.succeed(
+  installed: PreviewBrowser.PreviewBrowser["Service"]["installed"] = Effect.succeed(
     Option.fromUndefinedOr(executable),
   ),
 ) =>
@@ -258,6 +258,27 @@ describe("HtmlRender", () => {
     }).pipe(Effect.provide(layerTest)),
   );
 
+  it.effect("rejects an invalid browser configuration without retaining the published page", () =>
+    Effect.gen(function* () {
+      const error = new PreviewBrowser.PreviewBrowserInstallError({
+        detail: "T3CODE_SERVER_BROWSER_EXECUTABLE must be an absolute path to an executable file.",
+      });
+      yield* Effect.gen(function* () {
+        const fileSystem = yield* FileSystem.FileSystem;
+        const config = yield* ServerConfig.ServerConfig;
+        const htmlRender = yield* HtmlRender.HtmlRender;
+        const mcpSessions = yield* McpProviderSessions.McpProviderSessions;
+        const threadId = ThreadId.make("thread-html-invalid-browser");
+        const page = { html: "<p>x</p>", title: "X", height: 200 };
+
+        expect(yield* htmlRender.publish({ threadId, ...page }).pipe(Effect.flip)).toEqual(error);
+        const stored = yield* fileSystem.readDirectory(config.attachmentsDir, { recursive: true });
+        expect(stored.filter((name) => name.endsWith(".html"))).toEqual([]);
+        expect(yield* mcpSessions.takeHtmlRender(threadId, page)).toBe(undefined);
+      }).pipe(Effect.provide(layerHtmlRender(undefined, Effect.fail(error))));
+    }),
+  );
+
   it.effect("removes the page when publishing is interrupted", () =>
     Effect.gen(function* () {
       const threadId = ThreadId.make("thread-html-cancel");
 
@@ -126,7 +126,10 @@ export class HtmlRender extends Context.Service<
       readonly html: string;
       readonly title: string;
       readonly height: number;
-    }) => Effect.Effect<HtmlRenderReference, HtmlRenderPrepareError | HtmlRenderStoreError>;
+    }) => Effect.Effect<
+      HtmlRenderReference,
+      HtmlRenderPrepareError | HtmlRenderStoreError | PreviewBrowser.PreviewBrowserInstallError
+    >;
     readonly preview: (input: {
       readonly html: string;
       readonly width?: number | undefined;
@@ -390,9 +393,11 @@ const make = Effect.gen(function* () {
       return heights.toSorted(([left], [right]) => left - right);
     },
     Effect.catch((cause) =>
-      Effect.logWarning("Could not measure an HTML render; publishing it without heights.", {
-        cause,
-      }).pipe(Effect.as(undefined)),
+      cause._tag === "PreviewBrowserInstallError"
+        ? Effect.fail(cause)
+        : Effect.logWarning("Could not measure an HTML render; publishing it without heights.", {
+            cause,
+          }).pipe(Effect.as(undefined)),
     ),
   );
 
 
@@ -165,7 +165,9 @@ it.layer(NodeServices.layer)("PreviewBrowser", (it) => {
         env: { T3CODE_SERVER_BROWSER_EXECUTABLE: configured },
       });
 
-      expect(yield* browser.installed).toEqual(Option.none());
+      const installedError = yield* browser.installed.pipe(Effect.flip);
+      expect(installedError._tag).toBe("PreviewBrowserInstallError");
+      expect(installedError.message).toContain("T3CODE_SERVER_BROWSER_EXECUTABLE");
       const error = yield* browser.executable.pipe(Effect.flip);
       expect(error._tag).toBe("PreviewBrowserInstallError");
       expect(error.message).toContain("T3CODE_SERVER_BROWSER_EXECUTABLE");
 
@@ -131,7 +131,7 @@ export class PreviewBrowser extends Context.Service<
       string,
       PreviewBrowserInstallError | PreviewBrowserInstallingError | PreviewBrowserUnsupportedError
     >;
-    readonly installed: Effect.Effect<Option.Option<string>>;
+    readonly installed: Effect.Effect<Option.Option<string>, PreviewBrowserInstallError>;
   }
 >()("t3/preview/PreviewBrowser") {}
 
@@ -175,23 +175,24 @@ export const makePreviewBrowser = Effect.fn("PreviewBrowser.make")(function* (
           Effect.orElseSucceed(() => Option.none<string>()),
         )
       : Effect.succeed(Option.none<string>());
-    return PreviewBrowser.of({
-      installed,
-      executable: installed.pipe(
-        Effect.flatMap(
-          Option.match({
-            onSome: Effect.succeed,
-            onNone: () =>
-              Effect.fail(
-                new PreviewBrowserInstallError({
-                  detail:
-                    "T3CODE_SERVER_BROWSER_EXECUTABLE must be an absolute path to an executable file.",
-                }),
-              ),
-          }),
-        ),
-        Effect.withSpan("PreviewBrowser.executable"),
+    const executable = installed.pipe(
+      Effect.flatMap(
+        Option.match({
+          onSome: Effect.succeed,
+          onNone: () =>
+            Effect.fail(
+              new PreviewBrowserInstallError({
+                detail:
+                  "T3CODE_SERVER_BROWSER_EXECUTABLE must be an absolute path to an executable file.",
+              }),
+            ),
+        }),
       ),
+      Effect.withSpan("PreviewBrowser.executable"),
+    );
+    return PreviewBrowser.of({
+      installed: executable.pipe(Effect.map(Option.some)),
+      executable,
     });
   }
   const http = yield* HttpClient.HttpClient;
 
@@ -238,7 +238,8 @@ For a background service, put the variable in `service.env` inside the server's
 T3 home, normally `~/.t3/service.env`, then restart the service. Set the path on
 the machine running the server, including when you connect from another device.
 An unset or blank variable keeps the bundled browser. A relative, missing,
-non-file or non-executable path produces an error rather than downloading a fallback.
+non-file or non-executable path produces an error for browser tabs and HTML
+publishing rather than downloading a fallback.
 
 Profiles stay in T3's data folder. You maintain the selected browser and its
 required libraries. This option does not change sandbox settings; on Linux,