diff --git a/apps/server/src/assets/AssetAccess.test.ts b/apps/server/src/assets/AssetAccess.test.ts
index 71a2c769ef4e..a596ca55c32a 100644
--- a/apps/server/src/assets/AssetAccess.test.ts
+++ b/apps/server/src/assets/AssetAccess.test.ts
@@ -713,6 +713,49 @@ describe("AssetAccess", () => {
     }).pipe(Effect.provide(testLayer)),
   );
 
+  it.effect("previews workspace files with literal fragment characters in their paths", () =>
+    Effect.gen(function* () {
+      const fileSystem = yield* FileSystem.FileSystem;
+      const path = yield* Path.Path;
+      const root = yield* fileSystem.makeTempDirectoryScoped({ prefix: "t3-preview-literal-" });
+      const directory = path.join(root, "assets#archive");
+      yield* fileSystem.makeDirectory(directory);
+
+      for (const name of ["icon#v2.png", "report#draft.pdf"]) {
+        const filePath = path.join(directory, name);
+        yield* fileSystem.writeFileString(filePath, "preview fixture");
+        const canonicalFile = yield* fileSystem.realPath(filePath);
+        const result = yield* issueAssetUrl({
+          resource: {
+            _tag: "workspace-file",
+            threadId: ThreadId.make("thread-1"),
+            path: filePath,
+          },
+          workspaceRoot: root,
+        });
+        const suffix = result.relativeUrl.slice(`${ASSET_ROUTE_PREFIX}/`.length);
+        const token = suffix.slice(0, suffix.indexOf("/"));
+
+        expect(yield* resolveAsset(token, name)).toEqual({ kind: "file", path: canonicalFile });
+        if (name.endsWith(".png")) {
+          expect(yield* resolveAsset(token, "other.png")).toBeNull();
+        }
+      }
+
+      const disguisedPath = path.join(root, "image.png#notes.txt");
+      yield* fileSystem.writeFileString(disguisedPath, "not an image");
+      const error = yield* issueAssetUrl({
+        resource: {
+          _tag: "workspace-file",
+          threadId: ThreadId.make("thread-1"),
+          path: disguisedPath,
+        },
+        workspaceRoot: root,
+      }).pipe(Effect.flip);
+      expect(error).toBeInstanceOf(AssetPreviewTypeValidationError);
+    }).pipe(Effect.provide(testLayer)),
+  );
+
   it.effect("issues exact attachment capabilities by attachment id", () =>
     Effect.gen(function* () {
       const config = yield* ServerConfig.ServerConfig;
diff --git a/docs/user/composer.md b/docs/user/composer.md
index 59efc3c30f01..8cb8d7805ac9 100644
--- a/docs/user/composer.md
+++ b/docs/user/composer.md
@@ -274,5 +274,8 @@ On web and desktop, HTML and PDF files open as rendered pages. Switch an HTML
 file to source view to read its markup; a link to a specific line opens source
 automatically. HTML previews cannot access your T3 Code session.
 
+The file viewer recognizes images, HTML, and PDF files by their filename extension,
+including filenames or folders containing `#` or `?`.
+
 On mobile, select a PDF attachment or link to open it. iOS uses the native viewer;
 Android opens a compatible installed file viewer.
diff --git a/packages/shared/src/filePreview.test.ts b/packages/shared/src/filePreview.test.ts
index 34d619e7a782..602fb8299cdd 100644
--- a/packages/shared/src/filePreview.test.ts
+++ b/packages/shared/src/filePreview.test.ts
@@ -14,7 +14,7 @@ import {
 } from "./filePreview.ts";
 
 describe("workspace file previews", () => {
-  it.each(["report.html", "report.HTM", "document.pdf?download=1"])(
+  it.each(["report.html", "report.HTM", "document#draft.pdf", "reports?old/document.pdf"])(
     "recognizes browser preview path %s",
     (path) => {
       expect(isWorkspaceBrowserPreviewPath(path)).toBe(true);
@@ -26,7 +26,9 @@ describe("workspace file previews", () => {
     "icon.png",
     "photo.JPEG",
     "animation.gif",
-    "vector.svg#mark",
+    "vector#mark.svg",
+    "photo?edited.JPEG",
+    "images#archive/icon.png",
     "texture.webp",
     "image.avif",
   ])("recognizes image preview path %s", (path) => {
@@ -34,12 +36,19 @@ describe("workspace file previews", () => {
     expect(isWorkspacePreviewEntryPath(path)).toBe(true);
   });
 
-  it.each(["README.md", "src/index.ts", "image.png.ts", "png"])(
-    "rejects non-preview path %s",
-    (path) => {
-      expect(isWorkspacePreviewEntryPath(path)).toBe(false);
-    },
-  );
+  it.each([
+    "README.md",
+    "src/index.ts",
+    "image.png.ts",
+    "png",
+    "image.png#notes.txt",
+    "image.svg?notes.txt",
+    "document.pdf?download=1",
+    "report.html#notes.txt",
+    "image%2Epng",
+  ])("rejects non-preview path %s", (path) => {
+    expect(isWorkspacePreviewEntryPath(path)).toBe(false);
+  });
 
   it("serves audio in place from the host like video and browser documents", () => {
     expect(isWorkspaceAudioPreviewPath("notes/recording.WAV")).toBe(true);
diff --git a/packages/shared/src/filePreview.ts b/packages/shared/src/filePreview.ts
index da62d2e689ec..04e285eff224 100644
--- a/packages/shared/src/filePreview.ts
+++ b/packages/shared/src/filePreview.ts
@@ -171,8 +171,8 @@ export function mediaKindFromPath(path: string): "image" | "video" | null {
 }
 
 function hasPreviewExtension(path: string, extensions: ReadonlyArray<string>): boolean {
-  const pathWithoutQuery = path.split(/[?#]/, 1)[0]?.toLowerCase() ?? "";
-  return extensions.some((extension) => pathWithoutQuery.endsWith(extension));
+  const literalPath = path.toLowerCase();
+  return extensions.some((extension) => literalPath.endsWith(extension));
 }
 
 export function isWorkspaceBrowserPreviewPath(path: string): boolean {