diff --git a/apps/web/src/components/files/FileBrowserPanel.tsx b/apps/web/src/components/files/FileBrowserPanel.tsx
index dc3cfcef0137..d5a1bf7fca7b 100644
--- a/apps/web/src/components/files/FileBrowserPanel.tsx
+++ b/apps/web/src/components/files/FileBrowserPanel.tsx
@@ -12,6 +12,7 @@ import { Button } from "~/components/ui/button";
 import { InputGroup, InputGroupInput } from "~/components/ui/input-group";
 import { toastManager } from "~/components/ui/toast";
 import { Tooltip, TooltipPopup, TooltipTrigger } from "~/components/ui/tooltip";
+import { isBrowserPreviewFile } from "~/browser/openFileInPreview";
 import { useComposerHandleContext } from "~/composerHandleContext";
 import { writeTextToClipboard } from "~/hooks/useCopyToClipboard";
 import { useTheme } from "~/hooks/useTheme";
@@ -37,6 +38,8 @@ interface FileBrowserPanelProps {
   onOpenFile: (relativePath: string) => void;
   onRefreshSelectedFile?: () => void;
   workspaceMutationId: string | null;
+  /** Present when the runtime can open a workspace file in the integrated browser. */
+  onOpenInBrowser?: ((relativePath: string) => void) | undefined;
 }
 
 function treePath(entry: ProjectEntry): string {
@@ -101,6 +104,7 @@ export default function FileBrowserPanel({
   onOpenFile,
   onRefreshSelectedFile,
   workspaceMutationId,
+  onOpenInBrowser,
 }: FileBrowserPanelProps) {
   const { resolvedTheme } = useTheme();
   const composerRef = useComposerHandleContext();
@@ -144,6 +148,10 @@ export default function FileBrowserPanel({
     }
     const relativePath = item.path.replace(/\/$/, "");
     const mention = serializeComposerFileLink(relativePath);
+    const canOpenInBrowser =
+      onOpenInBrowser !== undefined &&
+      entryKindsRef.current.get(relativePath) === "file" &&
+      isBrowserPreviewFile(relativePath);
     const pointer = contextMenuPointerRef.current;
     const pointerIsFresh = pointer !== null && performance.now() - pointer.at < 1000;
     const anchorRect = context.anchorElement.getBoundingClientRect();
@@ -153,11 +161,18 @@ export default function FileBrowserPanel({
     try {
       const clicked = await api.contextMenu.show(
         [
+          ...(canOpenInBrowser
+            ? [{ id: "open-in-browser" as const, label: "Open in browser" }]
+            : []),
           { id: "copy-mention", label: "Copy mention" },
           { id: "add-to-chat", label: "Add to chat" },
         ],
         position,
       );
+      if (clicked === "open-in-browser") {
+        onOpenInBrowser?.(relativePath);
+        return;
+      }
       if (clicked === "copy-mention") {
         try {
           await writeTextToClipboard(mention);
diff --git a/apps/web/src/components/files/FilePreviewPanel.tsx b/apps/web/src/components/files/FilePreviewPanel.tsx
index 0ad18434d7e7..a7607b4d092a 100644
--- a/apps/web/src/components/files/FilePreviewPanel.tsx
+++ b/apps/web/src/components/files/FilePreviewPanel.tsx
@@ -36,7 +36,7 @@ import { DIFF_SURFACE_THEME_UNSAFE_CSS, resolveDiffThemeName } from "~/lib/diffR
 import { PREFERRED_HIGHLIGHTER } from "~/lib/syntaxHighlighting";
 import { cn } from "~/lib/utils";
 import { isPreviewSupportedInRuntime } from "~/previewStateStore";
-import { isAbsolutePath, resolvePathLinkTarget } from "~/terminal-links";
+import { isAbsolutePath, resolveWorkspaceFilePath } from "~/terminal-links";
 import { ScrollArea } from "~/components/ui/scroll-area";
 import { Toggle } from "~/components/ui/toggle";
 import { Tooltip, TooltipPopup, TooltipTrigger } from "~/components/ui/tooltip";
@@ -1066,7 +1066,7 @@ export default function FilePreviewPanel({
     isPreviewSupportedInRuntime() &&
     isBrowserPreviewFile(relativePath);
   const absolutePath =
-    relativePath && attachment === undefined ? resolvePathLinkTarget(relativePath, cwd) : null;
+    relativePath && attachment === undefined ? resolveWorkspaceFilePath(relativePath, cwd) : null;
   const onFilePostRender = useFileLineReveal(relativePath, revealLine, revealRequestId);
   useWorkspaceMutationRefresh({
     enabled:
@@ -1099,30 +1099,35 @@ export default function FilePreviewPanel({
     });
   };
 
-  const handleOpenInBrowser = useCallback(() => {
-    if (!absolutePath || !environmentHttpBaseUrl) return;
-    void (async () => {
-      const result = await openFileInPreview({
-        threadRef,
-        filePath: absolutePath,
-        workspaceRoot: cwd,
-        httpBaseUrl: environmentHttpBaseUrl,
-        createAssetUrl,
-        openPreview,
-      });
-      if (result._tag === "Success" || isAtomCommandInterrupted(result)) {
-        return;
-      }
-      const error = squashAtomCommandFailure(result);
-      toastManager.add(
-        stackedThreadToast({
-          type: "error",
-          title: "Unable to open file in browser",
-          description: error instanceof Error ? error.message : "An error occurred.",
-        }),
-      );
-    })();
-  }, [absolutePath, createAssetUrl, cwd, environmentHttpBaseUrl, openPreview, threadRef]);
+  const handleOpenInBrowser = useCallback(
+    (filePath: string) => {
+      if (!environmentHttpBaseUrl) return;
+      void (async () => {
+        const result = await openFileInPreview({
+          threadRef,
+          // Tree and preview-header paths are workspace-relative; resolve them
+          // against the workspace root without terminal-link `~/` expansion.
+          filePath: resolveWorkspaceFilePath(filePath, cwd),
+          workspaceRoot: cwd,
+          httpBaseUrl: environmentHttpBaseUrl,
+          createAssetUrl,
+          openPreview,
+        });
+        if (result._tag === "Success" || isAtomCommandInterrupted(result)) {
+          return;
+        }
+        const error = squashAtomCommandFailure(result);
+        toastManager.add(
+          stackedThreadToast({
+            type: "error",
+            title: "Unable to open file in browser",
+            description: error instanceof Error ? error.message : "An error occurred.",
+          }),
+        );
+      })();
+    },
+    [createAssetUrl, cwd, environmentHttpBaseUrl, openPreview, threadRef],
+  );
 
   return (
     <div className="flex min-h-0 flex-1 flex-col overflow-hidden bg-background">
@@ -1205,7 +1210,7 @@ export default function FilePreviewPanel({
                   <Toggle
                     className="shrink-0"
                     pressed={false}
-                    onPressedChange={handleOpenInBrowser}
+                    onPressedChange={() => handleOpenInBrowser(relativePath)}
                     aria-label="Open file in preview browser"
                     variant="ghost"
                     size="sm"
@@ -1368,6 +1373,11 @@ export default function FilePreviewPanel({
               {...(relativePath && !isMedia && !isPdf
                 ? { onRefreshSelectedFile: file.refresh }
                 : {})}
+              onOpenInBrowser={
+                isPreviewSupportedInRuntime() && environmentHttpBaseUrl
+                  ? (browserPath) => handleOpenInBrowser(browserPath)
+                  : undefined
+              }
             />
           </aside>
         ) : null}
diff --git a/apps/web/src/terminal-links.ts b/apps/web/src/terminal-links.ts
index 204d0a742a05..ec2733a463a7 100644
--- a/apps/web/src/terminal-links.ts
+++ b/apps/web/src/terminal-links.ts
@@ -264,3 +264,14 @@ export function resolvePathLinkTarget(rawPath: string, cwd: string): string {
 
   return formatFilePathPosition({ ...position, path: resolvedPath });
 }
+
+/**
+ * Resolves a workspace-relative file path against the workspace root. Unlike
+ * terminal links, a leading `~/` is a literal folder name inside the
+ * workspace, not the user's home directory.
+ */
+export function resolveWorkspaceFilePath(rawPath: string, cwd: string): string {
+  if (isAbsolutePath(rawPath)) return rawPath;
+  const separator: "/" | "\\" = isWindowsPathStyle(cwd) ? "\\" : "/";
+  return joinPath(cwd, rawPath, separator);
+}