diff --git a/apps/mobile/src/features/files/ThreadFilesRouteScreen.tsx b/apps/mobile/src/features/files/ThreadFilesRouteScreen.tsx
index a95f8ea8e997..bd9105e8b849 100644
--- a/apps/mobile/src/features/files/ThreadFilesRouteScreen.tsx
+++ b/apps/mobile/src/features/files/ThreadFilesRouteScreen.tsx
@@ -1,3 +1,5 @@
+import { formatFilePathForClipboard } from "@t3tools/client-runtime/media-actions";
+import { resolvePathLinkTarget } from "@t3tools/shared/fileLinks";
 import { resolveFilesystemReadAccess } from "@t3tools/client-runtime/state/filesystem";
 import { environmentSession } from "../../state/session";
 import { NativeStackScreenOptions } from "../../native/StackHeader";
@@ -783,7 +785,13 @@ export function ThreadFileScreen(props: ThreadFileRouteScreenProps) {
               title: "Copy path",
               icon: "doc.on.doc",
               inline: false,
-              onPress: () => copyTextWithHaptic(relativePath),
+              onPress: () =>
+                copyTextWithHaptic(
+                  formatFilePathForClipboard(
+                    relativePath,
+                    resolvePathLinkTarget(relativePath, cwd ?? ""),
+                  ),
+                ),
             } as const,
           ]),
       fileData?.contents != null
diff --git a/apps/mobile/src/features/threads/ThreadFeed.tsx b/apps/mobile/src/features/threads/ThreadFeed.tsx
index 46d9fccac17f..2b45fc547afc 100644
--- a/apps/mobile/src/features/threads/ThreadFeed.tsx
+++ b/apps/mobile/src/features/threads/ThreadFeed.tsx
@@ -230,7 +230,7 @@ import {
 } from "../files/filePath";
 import { waitForThreadShellReady } from "./threadForkNavigation";
 import { resolveUserMessageIntentBadge } from "./userMessageIntentBadge";
-import { fileChipMenu, resolveFileChipTarget, type FileChipAction } from "./fileChipMenu";
+import { fileChipClipboardPath, fileChipMenu, resolveFileChipTarget } from "./fileChipMenu";
 import { useFileChipShare } from "./useFileChipShare";
 import {
   MarkdownImageAvailableWidthContext,
@@ -1869,13 +1869,13 @@ export const ThreadFeed = memo(function ThreadFeed(props: ThreadFeedProps) {
     onFileContextMenuAction: (href, actionId) => {
       const target = resolveFileChipTarget(href, props.workspaceRoot);
       if (!target) return;
-      switch (actionId as FileChipAction) {
+      switch (actionId) {
         case "copy-full-path":
-          if (target.fullPath) copyTextWithHaptic(target.fullPath);
-          return;
-        case "copy-relative-path":
-          if (target.relativePath) copyTextWithHaptic(target.relativePath);
+        case "copy-relative-path": {
+          const clipboardPath = fileChipClipboardPath(target, actionId);
+          if (clipboardPath !== undefined) copyTextWithHaptic(clipboardPath);
           return;
+        }
         case "open-file":
           onMarkdownLinkPress(href);
           return;
diff --git a/apps/mobile/src/features/threads/fileChipMenu.test.ts b/apps/mobile/src/features/threads/fileChipMenu.test.ts
index 1627a72da5de..999c403964b3 100644
--- a/apps/mobile/src/features/threads/fileChipMenu.test.ts
+++ b/apps/mobile/src/features/threads/fileChipMenu.test.ts
@@ -1,7 +1,23 @@
 import { ThreadId } from "@t3tools/contracts";
 import { describe, expect, it } from "vite-plus/test";
 
-import { fileChipMenu, fileChipShareSource, resolveFileChipTarget } from "./fileChipMenu";
+import {
+  fileChipClipboardPath,
+  fileChipMenu,
+  fileChipShareSource,
+  resolveFileChipTarget,
+} from "./fileChipMenu";
+
+it("copies native paths from a relative file chip in a Windows workspace", () => {
+  const target = resolveFileChipTarget("reports/Device Users.csv", "C:/repo");
+  if (!target) throw new Error("File-chip target unavailable");
+  expect(fileChipClipboardPath(target, "copy-full-path")).toBe(
+    String.raw`C:\repo\reports\Device Users.csv`,
+  );
+  expect(fileChipClipboardPath(target, "copy-relative-path")).toBe(
+    String.raw`reports\Device Users.csv`,
+  );
+});
 
 describe("resolveFileChipTarget", () => {
   it("resolves a workspace-relative link to both paths", () => {
diff --git a/apps/mobile/src/features/threads/fileChipMenu.ts b/apps/mobile/src/features/threads/fileChipMenu.ts
index d55d3e4b5964..d020e5f542a3 100644
--- a/apps/mobile/src/features/threads/fileChipMenu.ts
+++ b/apps/mobile/src/features/threads/fileChipMenu.ts
@@ -1,3 +1,4 @@
+import { formatFilePathForClipboard } from "@t3tools/client-runtime/media-actions";
 import { fileBasename } from "@t3tools/shared/path";
 import type { ThreadId } from "@t3tools/contracts";
 import { resolveMarkdownLinkPresentation } from "../../lib/markdownLinks";
@@ -10,13 +11,19 @@ import {
   resolveWorkspaceRelativeFilePath,
 } from "../files/filePath";
 
-export type FileChipAction = "copy-full-path" | "copy-relative-path" | "open-file" | "save";
-
 export interface FileChipTarget {
   readonly fullPath?: string;
   readonly relativePath?: string;
 }
 
+export function fileChipClipboardPath(
+  target: FileChipTarget,
+  action: "copy-full-path" | "copy-relative-path",
+): string | undefined {
+  const path = action === "copy-full-path" ? target.fullPath : target.relativePath;
+  return path === undefined ? undefined : formatFilePathForClipboard(path, target.fullPath);
+}
+
 export function resolveFileChipTarget(
   href: string,
   workspaceRoot: string | null | undefined,
diff --git a/apps/mobile/src/lib/mediaActions.test.ts b/apps/mobile/src/lib/mediaActions.test.ts
index e270f723d8d6..6670587b1ca2 100644
--- a/apps/mobile/src/lib/mediaActions.test.ts
+++ b/apps/mobile/src/lib/mediaActions.test.ts
@@ -5,6 +5,7 @@ import {
   type AuthSessionState,
 } from "@t3tools/contracts";
 import { AsyncResult } from "effect/reactivity";
+import { mediaFileReference } from "@t3tools/client-runtime/media-reference";
 import { beforeEach, expect, it, vi } from "vite-plus/test";
 
 const state = vi.hoisted(() => ({
@@ -96,6 +97,56 @@ beforeEach(() => {
   state.copy.mockReset();
 });
 
+it.each([
+  [
+    "C:/repo/assets/shot.png",
+    "C:/repo",
+    String.raw`C:\repo\assets\shot.png`,
+    String.raw`assets\shot.png`,
+  ],
+  [
+    String.raw`\\server\share\repo/assets/clip.mp4`,
+    String.raw`\\server\share\repo`,
+    String.raw`\\server\share\repo\assets\clip.mp4`,
+    String.raw`assets\clip.mp4`,
+  ],
+] as const)("copies full and relative media paths for %s", (path, root, full, relative) => {
+  const media = useMediaActions({
+    environmentId,
+    threadId,
+    resource: { _tag: "media-file", threadId, path },
+    reference: mediaFileReference(path, root),
+    name: path.split(/[\\/]/).at(-1)!,
+    mimeType: path.endsWith(".mp4") ? "video/mp4" : "image/png",
+  });
+  for (const [actionId, expected] of [
+    ["copy-full-path", full],
+    ["copy-relative-path", relative],
+  ] as const) {
+    const action = media.actions.find(({ id }) => id === actionId);
+    if (!action) throw new Error(`Missing media action: ${actionId}`);
+    action.run();
+    expect(state.copy).toHaveBeenLastCalledWith(expected);
+  }
+  expect(state.refresh).not.toHaveBeenCalled();
+  expect(state.download).not.toHaveBeenCalled();
+});
+
+it("preserves media URLs when copying", () => {
+  const url = "https://cdn.test/assets/media?path=C:/repo/media";
+  const media = useMediaActions({
+    uri: url,
+    name: "media",
+    mimeType: "video/mp4",
+    reference: { kind: "url", url },
+  });
+  const action = media.actions.find(({ id }) => id === "copy-url");
+  if (!action) throw new Error("Copy URL action missing");
+  action.run();
+  expect(state.copy).toHaveBeenCalledWith(url);
+  expect(state.refresh).not.toHaveBeenCalled();
+});
+
 it.each(["workspace-file", "media-file"] as const)(
   "waits for the %s grant before enabling host menu actions",
   (_tag) => {
diff --git a/apps/mobile/src/state/mediaActions.ts b/apps/mobile/src/state/mediaActions.ts
index a0a9a678205f..dde7e2fe6b5b 100644
--- a/apps/mobile/src/state/mediaActions.ts
+++ b/apps/mobile/src/state/mediaActions.ts
@@ -2,7 +2,10 @@ import { settlePromise, squashAtomCommandFailure } from "@t3tools/client-runtime
 import * as Dialog from "../components/ui/Dialog";
 import type { MediaActionsSource } from "../lib/mediaActionsSource";
 import { useNavigation } from "@react-navigation/native";
-import type { MediaActionId } from "@t3tools/client-runtime/media-actions";
+import {
+  formatFilePathForClipboard,
+  type MediaActionId,
+} from "@t3tools/client-runtime/media-actions";
 import {
   AuthFilesystemReadScope,
   type EnvironmentId,
@@ -108,16 +111,17 @@ export function useMediaActions(source: MediaActionsSource | undefined, onOpenFi
                 {
                   id: "copy-full-path" as const,
                   title: "Copy full path",
-                  run: () => copyTextWithHaptic(reference.path),
+                  run: () => copyTextWithHaptic(formatFilePathForClipboard(reference.path)),
                 },
               ]
             : []),
-          ...(relativePath
+          ...(relativePath && reference?.kind === "file"
             ? [
                 {
                   id: "copy-relative-path" as const,
                   title: "Copy relative path",
-                  run: () => copyTextWithHaptic(relativePath),
+                  run: () =>
+                    copyTextWithHaptic(formatFilePathForClipboard(relativePath, reference.path)),
                 },
               ]
             : []),
diff --git a/apps/web/src/components/BranchToolbar.panel.browser.test.tsx b/apps/web/src/components/BranchToolbar.panel.browser.test.tsx
index 0c0a20593305..51ce200a53e6 100644
--- a/apps/web/src/components/BranchToolbar.panel.browser.test.tsx
+++ b/apps/web/src/components/BranchToolbar.panel.browser.test.tsx
@@ -132,6 +132,7 @@ it.each([
   ["local", null, "/tmp/project"],
   ["worktree", null, null],
   ["worktree", "/tmp/worktree", "/tmp/worktree"],
+  ["worktree", "C:/repo/worktree", String.raw`C:\repo\worktree`],
 ] as const)(
   "copies only an existing workspace path with mode %s and worktree %s",
   async (envMode, worktreePath, copiedPath) => {
diff --git a/apps/web/src/components/BranchToolbar.tsx b/apps/web/src/components/BranchToolbar.tsx
index 4d6fbef50a6e..d27dc428ac3e 100644
--- a/apps/web/src/components/BranchToolbar.tsx
+++ b/apps/web/src/components/BranchToolbar.tsx
@@ -1,4 +1,5 @@
 import { writeTextToClipboard } from "../hooks/useCopyToClipboard";
+import { formatFilePathForClipboard } from "@t3tools/client-runtime/media-actions";
 import { readLocalApi } from "../localApi";
 import { stackedThreadToast, toastManager } from "./ui/toast";
 import { ComposerContextLabel } from "./ComposerContextLabel";
@@ -118,13 +119,14 @@ function showWorkspaceContextMenu(event: ReactMouseEvent, workspacePath: string)
     })
     .then((action) => {
       if (action !== "copy-path") return;
-      void writeTextToClipboard(workspacePath, "workspace path").then(
+      const clipboardPath = formatFilePathForClipboard(workspacePath);
+      void writeTextToClipboard(clipboardPath, "workspace path").then(
         (didCopy) => {
           if (didCopy) {
             toastManager.add({
               type: "success",
               title: "Path copied",
-              description: workspacePath,
+              description: clipboardPath,
             });
           }
         },
diff --git a/apps/web/src/components/ChatMarkdown.browser.test.tsx b/apps/web/src/components/ChatMarkdown.browser.test.tsx
index 361b114250c4..05a900387724 100644
--- a/apps/web/src/components/ChatMarkdown.browser.test.tsx
+++ b/apps/web/src/components/ChatMarkdown.browser.test.tsx
@@ -11,6 +11,8 @@ import "../index.css";
 import { useTheme } from "../hooks/useTheme";
 import { applyThemeColorPreview, getStandardThemeColors } from "../themePalette";
 
+import { readLocalApi } from "../localApi";
+import { toastManager } from "./ui/toast";
 import { filesystemEnvironment } from "../state/filesystem";
 import { useRightPanelStore } from "../rightPanelStore";
 import { getSyntaxHighlighterPromise } from "../lib/syntaxHighlighting";
@@ -1262,6 +1264,60 @@ describe("ChatMarkdown thread find", () => {
   );
 });
 
+it.each([
+  {
+    name: "Windows drive paths on a Mac client",
+    platform: "MacIntel",
+    cwd: "C:/repo",
+    href: "C:/repo/reports/Device Users.csv:12:3",
+    full: String.raw`C:\repo\reports\Device Users.csv:12:3`,
+    relative: String.raw`reports\Device Users.csv:12:3`,
+  },
+  {
+    name: "UNC paths on a Mac client",
+    platform: "MacIntel",
+    cwd: String.raw`\\server\share\repo`,
+    href: "file://server/share/repo/reports/report.csv",
+    full: String.raw`\\server\share\repo\reports\report.csv`,
+    relative: String.raw`reports\report.csv`,
+  },
+  {
+    name: "POSIX paths on a Windows client",
+    platform: "Win32",
+    cwd: "/home/repo",
+    href: "/home/repo/reports/report.csv",
+    full: "/home/repo/reports/report.csv",
+    relative: "reports/report.csv",
+  },
+])("copies $name and shows the copied text", async ({ platform, cwd, href, full, relative }) => {
+  vi.spyOn(navigator, "platform", "get").mockReturnValue(platform);
+  vi.stubGlobal("ClipboardItem", undefined);
+  const writeText = vi.spyOn(navigator.clipboard, "writeText").mockResolvedValue(undefined);
+  const toast = vi.spyOn(toastManager, "add");
+  const api = readLocalApi();
+  if (!api) throw new Error("Local API unavailable");
+  const choose = vi.spyOn(api.contextMenu, "show");
+  const container = await renderText(`[File](<${href}>)`, {
+    cwd,
+    environmentId: EnvironmentId.make("env-file-copy"),
+  });
+  const link = container.querySelector(".chat-markdown-file-link");
+  if (!link) throw new Error("File link unavailable");
+  for (const [action, expected] of [
+    ["copy-full", full],
+    ["copy-relative", relative],
+  ] as const) {
+    choose.mockResolvedValue(action);
+    await act(async () => {
+      link.dispatchEvent(new MouseEvent("contextmenu", { bubbles: true }));
+    });
+    expect(writeText).toHaveBeenLastCalledWith(expected);
+    expect(toast).toHaveBeenLastCalledWith(
+      expect.objectContaining({ type: "success", description: expected }),
+    );
+  }
+});
+
 describe("ChatMarkdown math", () => {
   const renderMath = async (
     text: string,
diff --git a/apps/web/src/components/ChatMarkdown.tsx b/apps/web/src/components/ChatMarkdown.tsx
index 000a3617953e..baf23d2b4cec 100644
--- a/apps/web/src/components/ChatMarkdown.tsx
+++ b/apps/web/src/components/ChatMarkdown.tsx
@@ -1,3 +1,4 @@
+import { formatFilePathForClipboard } from "@t3tools/client-runtime/media-actions";
 import { MarkdownFindContext, findRevealRef } from "./chat/markdownFindContext";
 import {
   buildFileLinkParentSuffixByPath,
@@ -2119,7 +2120,7 @@ const MarkdownFileLink = memo(function MarkdownFileLink({
       return;
     }
 
-    const value = resolveValue();
+    const value = resolveValue().then((text) => formatFilePathForClipboard(text, targetPath));
     // Start the write before workspace lookup finishes so Safari retains the user gesture.
     const write =
       typeof navigator.clipboard.write === "function" && typeof ClipboardItem !== "undefined"
diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
index 43fd030f8e18..49a84f9900d8 100644
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -1,3 +1,5 @@
+import { formatFilePathForClipboard } from "@t3tools/client-runtime/media-actions";
+import { resolvePathLinkTarget } from "@t3tools/shared/fileLinks";
 import { ThreadFind, ThreadFindCanvas, type ThreadFindControls } from "./chat/ThreadFindProvider";
 import { THREAD_FIND_BAR_RESERVED_HEIGHT } from "./chat/ThreadFindBar";
 import { usageLimitRecoveryBannerItem } from "./chat/UsageLimitRecoveryBanner";
@@ -3941,12 +3943,16 @@ export default function ChatView(props: ChatViewProps) {
       return;
     }
 
-    void navigator.clipboard.writeText(relativePath).then(
+    const clipboardPath = formatFilePathForClipboard(
+      relativePath,
+      resolvePathLinkTarget(relativePath, gitCwd ?? activeProjectCwd ?? ""),
+    );
+    void navigator.clipboard.writeText(clipboardPath).then(
       () => {
         toastManager.add({
           type: "success",
           title: "Path copied",
-          description: relativePath,
+          description: clipboardPath,
         });
       },
       (error) => {
diff --git a/apps/web/src/components/media/MediaActions.test.tsx b/apps/web/src/components/media/MediaActions.test.tsx
index bcf2d64db418..1b12a92e74c9 100644
--- a/apps/web/src/components/media/MediaActions.test.tsx
+++ b/apps/web/src/components/media/MediaActions.test.tsx
@@ -5,6 +5,7 @@ import {
   type AuthSessionState,
 } from "@t3tools/contracts";
 import { AsyncResult } from "effect/reactivity";
+import { mediaFileReference } from "@t3tools/client-runtime/media-reference";
 import { createElement, isValidElement, type ReactNode } from "react";
 import { afterEach, beforeEach, expect, it, vi } from "vite-plus/test";
 
@@ -24,6 +25,7 @@ const state = vi.hoisted(() => ({
   showMenu: vi.fn(),
   openFile: vi.fn(),
   clipboard: vi.fn(),
+  copyText: vi.fn(),
   menuFinished: null as (() => void) | null,
 }));
 
@@ -33,7 +35,7 @@ vi.mock("react", async (importOriginal) => ({
   useRef: <A,>(current: A) => ({ current }),
   useState: <A,>(initial: A) => [initial, () => {}],
 }));
-vi.mock("../../hooks/useCopyToClipboard", () => ({ writeTextToClipboard: vi.fn() }));
+vi.mock("../../hooks/useCopyToClipboard", () => ({ writeTextToClipboard: state.copyText }));
 vi.mock("../../localApi", () => ({
   readLocalApi: () => ({ contextMenu: { show: state.showMenu } }),
 }));
@@ -128,6 +130,7 @@ beforeEach(() => {
   state.png.mockReset().mockResolvedValue(new Blob(["png"], { type: "image/png" }));
   state.showMenu.mockReset().mockResolvedValue(null);
   state.openFile.mockReset();
+  state.copyText.mockReset().mockResolvedValue(true);
   state.menuFinished = null;
   class TestClipboardItem {
     constructor(readonly items: Record<string, Promise<Blob>>) {}
@@ -141,6 +144,56 @@ beforeEach(() => {
 
 afterEach(() => vi.unstubAllGlobals());
 
+it.each([
+  [
+    "image",
+    "C:/repo/assets/shot.png",
+    "C:/repo",
+    String.raw`C:\repo\assets\shot.png`,
+    String.raw`assets\shot.png`,
+  ],
+  [
+    "video",
+    String.raw`\\server\share\repo/assets/clip.mp4`,
+    String.raw`\\server\share\repo`,
+    String.raw`\\server\share\repo\assets\clip.mp4`,
+    String.raw`assets\clip.mp4`,
+  ],
+] as const)(
+  "copies full and relative paths for %s %s",
+  async (kind, path, root, full, relative) => {
+    const source: MediaActionSource = {
+      ...hostSource(),
+      kind,
+      reference: mediaFileReference(path, root),
+    };
+    for (const [action, expected] of [
+      ["copy-full-path", full],
+      ["copy-relative-path", relative],
+    ] as const) {
+      const completed = deferred<void>();
+      state.menuFinished = () => completed.resolve();
+      state.showMenu.mockResolvedValue(action);
+      openMenu(source);
+      await completed.promise;
+      expect(state.copyText).toHaveBeenLastCalledWith(expected, "file path");
+    }
+    expect(state.mint).not.toHaveBeenCalled();
+    expect(state.download).not.toHaveBeenCalled();
+  },
+);
+
+it("preserves media URLs when copying", async () => {
+  const url = "https://cdn.test/assets/clip.mp4?path=C:/repo/media";
+  const completed = deferred<void>();
+  state.menuFinished = () => completed.resolve();
+  state.showMenu.mockResolvedValue("copy-url");
+  openMenu({ ...hostSource(), kind: "video", src: url, reference: { kind: "url", url } });
+  await completed.promise;
+  expect(state.copyText).toHaveBeenCalledWith(url, "URL");
+  expect(state.mint).not.toHaveBeenCalled();
+});
+
 it.each(["workspace-file", "media-file"] as const)(
   "waits for the %s grant before enabling host menu actions",
   (_tag) => {
diff --git a/apps/web/src/components/media/MediaActions.tsx b/apps/web/src/components/media/MediaActions.tsx
index 45b273e21305..314f7a6435d2 100644
--- a/apps/web/src/components/media/MediaActions.tsx
+++ b/apps/web/src/components/media/MediaActions.tsx
@@ -1,4 +1,7 @@
-import type { MediaActionId } from "@t3tools/client-runtime/media-actions";
+import {
+  formatFilePathForClipboard,
+  type MediaActionId,
+} from "@t3tools/client-runtime/media-actions";
 import {
   mediaReferenceFileName,
   type MediaReference,
@@ -166,7 +169,9 @@ export function MediaActions({
               ? reference.url
               : undefined;
       if (text !== undefined) {
-        await writeTextToClipboard(text, reference?.kind === "file" ? "file path" : "URL");
+        const clipboardText =
+          reference?.kind === "file" ? formatFilePathForClipboard(text, reference.path) : text;
+        await writeTextToClipboard(clipboardText, reference?.kind === "file" ? "file path" : "URL");
         toastManager.add({
           type: "success",
           title: action === "copy-url" ? "URL copied" : "Path copied",
diff --git a/packages/client-runtime/src/mediaActions.ts b/packages/client-runtime/src/mediaActions.ts
index fda507b17bb1..85bdcf67812b 100644
--- a/packages/client-runtime/src/mediaActions.ts
+++ b/packages/client-runtime/src/mediaActions.ts
@@ -1,3 +1,10 @@
+import { isWindowsAbsolutePath } from "@t3tools/shared/path";
+
+// The file host can use a different path style from the client.
+export function formatFilePathForClipboard(path: string, hostPath = path): string {
+  return isWindowsAbsolutePath(hostPath) ? path.replaceAll("/", "\\") : path;
+}
+
 export type MediaActionId =
   | "copy-full-path"
   | "copy-relative-path"