diff --git a/site/src/pages/AgentsPage/components/ChatConversation/AttachmentBlocks.tsx b/site/src/pages/AgentsPage/components/ChatConversation/AttachmentBlocks.tsx
index 0ffc8b10a94..0516cabf2c6 100644
--- a/site/src/pages/AgentsPage/components/ChatConversation/AttachmentBlocks.tsx
+++ b/site/src/pages/AgentsPage/components/ChatConversation/AttachmentBlocks.tsx
@@ -17,6 +17,7 @@ import {
 	type AttachmentFailure,
 	attachmentFailureFromError,
 	getChatFileURL,
+	handleAttachmentDownloadClick,
 	isAbortError,
 	probeAttachmentFailure,
 } from "../../utils/chatAttachments";
@@ -54,17 +55,40 @@ const ATTACHMENT_FALLBACK_EXTENSIONS: Record<string, string> = {
 	"application/vnd.openxmlformats-officedocument.wordprocessingml.document":
 		"docx",
 	"application/x-tar": "tar",
+	"application/xml": "xml",
 	"image/jpeg": "jpg",
+	"image/svg+xml": "svg",
+	"text/csv": "csv",
 	"text/markdown": "md",
 	"text/plain": "txt",
 };
 
-const sanitizeAttachmentExtension = (value: string): string => {
-	const sanitized = value
+const sanitizeAttachmentExtension = (value: string): string =>
+	value
 		.replace(/[^a-z0-9]/gi, "")
 		.slice(0, 4)
-		.toLowerCase();
-	return sanitized || "file";
+		.toLowerCase() || "file";
+
+const getMediaTypeExtension = (mediaType: string): string | null => {
+	if (mediaType === "application/octet-stream") {
+		return null;
+	}
+	const mapped = ATTACHMENT_FALLBACK_EXTENSIONS[mediaType];
+	if (mapped) {
+		return mapped;
+	}
+	const [type, subtype = ""] = mediaType.split("/");
+	// Unmapped non-image subtypes are not assumed to be filename extensions.
+	return type === "image" && /^[a-z0-9]{1,8}$/i.test(subtype)
+		? subtype.toLowerCase()
+		: null;
+};
+
+const getNameExtension = (name: string): string | null => {
+	const lastDot = name.lastIndexOf(".");
+	return lastDot > 0 && lastDot < name.length - 1
+		? name.slice(lastDot + 1)
+		: null;
 };
 
 const getAttachmentExtension = (
@@ -74,20 +98,14 @@ const getAttachmentExtension = (
 	if (mapped) {
 		return mapped;
 	}
-	const trimmedName = block.name?.trim();
-	if (trimmedName) {
-		const lastDot = trimmedName.lastIndexOf(".");
-		// Keep dotfiles like `.env` out of the extension path, while still
-		// allowing ordinary `name.ext` filenames to contribute a fallback.
-		if (lastDot > 0 && lastDot < trimmedName.length - 1) {
-			return sanitizeAttachmentExtension(trimmedName.slice(lastDot + 1));
-		}
-	}
-	const subtype = block.media_type.split("/")[1] ?? "";
-	if (subtype.endsWith("+json")) {
-		return "json";
+	const nameExtension = getNameExtension(block.name?.trim() ?? "");
+	if (nameExtension) {
+		return sanitizeAttachmentExtension(nameExtension);
 	}
-	return sanitizeAttachmentExtension(subtype);
+	return (
+		getMediaTypeExtension(block.media_type) ??
+		sanitizeAttachmentExtension(block.media_type.split("/")[1] ?? "")
+	);
 };
 
 const isTextPreviewAttachmentMediaType = (mediaType: string): boolean =>
@@ -123,11 +141,16 @@ const getAttachmentDownloadName = (
 	block: Pick<FileAttachmentBlock, "media_type" | "name">,
 ): string => {
 	const name = block.name?.trim();
-	if (name) {
+	if (!name) {
+		const extension = getAttachmentExtension(block);
+		return extension === "file" ? "attachment" : `attachment.${extension}`;
+	}
+	// Kept even when the name's extension disagrees with the media type.
+	if (name.startsWith(".") || getNameExtension(name)) {
 		return name;
 	}
-	const extension = getAttachmentExtension(block);
-	return extension === "file" ? "attachment" : `attachment.${extension}`;
+	const mediaExtension = getMediaTypeExtension(block.media_type);
+	return mediaExtension ? `${name}.${mediaExtension}` : name;
 };
 
 const getAttachmentBadgeLabel = (
@@ -141,24 +164,35 @@ const DownloadOverlay: FC<{
 	href: string;
 	displayName: string;
 	downloadName: string;
-}> = ({ href, displayName, downloadName }) => (
-	<a
-		href={href}
-		download={downloadName}
-		onClick={(event) => event.stopPropagation()}
-		aria-label={`Download ${displayName}`}
-		className="invisible absolute right-1 top-1 flex size-6 items-center justify-center rounded bg-surface-primary/80 text-content-secondary opacity-0 shadow-sm backdrop-blur-sm transition-opacity hover:text-content-primary group-hover/attachment:visible group-hover/attachment:opacity-100 group-focus-within/attachment:visible group-focus-within/attachment:opacity-100 [@media(hover:none)]:visible [@media(hover:none)]:opacity-100 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-content-link"
-	>
-		<DownloadIcon aria-hidden="true" className="size-3.5" />
-	</a>
-);
+	mediaType: string;
+}> = ({ href, displayName, downloadName, mediaType }) => {
+	return (
+		<a
+			href={href}
+			download={downloadName}
+			onClick={(event) => {
+				event.stopPropagation();
+				void handleAttachmentDownloadClick(event, {
+					href,
+					fileName: downloadName,
+					mediaType,
+				});
+			}}
+			aria-label={`Download ${displayName}`}
+			className="invisible absolute right-1 top-1 flex size-6 items-center justify-center rounded bg-surface-primary/80 text-content-secondary opacity-0 shadow-sm backdrop-blur-sm transition-opacity hover:text-content-primary group-hover/attachment:visible group-hover/attachment:opacity-100 group-focus-within/attachment:visible group-focus-within/attachment:opacity-100 [@media(hover:none)]:visible [@media(hover:none)]:opacity-100 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-content-link"
+		>
+			<DownloadIcon aria-hidden="true" className="size-3.5" />
+		</a>
+	);
+};
 
 const AttachmentPreviewFrame: FC<{
 	href: string | null;
 	displayName: string;
 	downloadName: string;
+	mediaType: string;
 	children: ReactNode;
-}> = ({ href, displayName, downloadName, children }) => {
+}> = ({ href, displayName, downloadName, mediaType, children }) => {
 	return (
 		<div className="group/attachment relative inline-flex flex-col items-start">
 			{children}
@@ -167,6 +201,7 @@ const AttachmentPreviewFrame: FC<{
 					href={href}
 					displayName={displayName}
 					downloadName={downloadName}
+					mediaType={mediaType}
 				/>
 			) : null}
 		</div>
@@ -385,6 +420,7 @@ const RemoteTextAttachmentButton: FC<{
 			href={frameHref}
 			displayName={fileName ?? "Pasted text"}
 			downloadName={downloadName}
+			mediaType={mediaType ?? ""}
 		>
 			{button}
 		</AttachmentPreviewFrame>
@@ -530,7 +566,14 @@ const FileCard: FC<{
 		<a
 			href={href}
 			download={downloadName}
-			onClick={(event) => event.stopPropagation()}
+			onClick={(event) => {
+				event.stopPropagation();
+				void handleAttachmentDownloadClick(event, {
+					href,
+					fileName: downloadName,
+					mediaType: block.media_type,
+				});
+			}}
 			aria-label={`Download ${displayName}`}
 			className="inline-flex h-16 max-w-sm items-center gap-3 rounded-md border border-solid border-border-default bg-surface-tertiary px-3 py-2 no-underline transition-colors hover:bg-surface-quaternary"
 		>
@@ -616,6 +659,7 @@ export const AttachmentBlock: FC<{
 				href={href}
 				displayName={displayName}
 				downloadName={downloadName}
+				mediaType={block.media_type}
 			>
 				{button}
 			</AttachmentPreviewFrame>
@@ -641,6 +685,7 @@ export const AttachmentBlock: FC<{
 				href={href}
 				displayName={displayName}
 				downloadName={downloadName}
+				mediaType={block.media_type}
 			>
 				{image}
 			</AttachmentPreviewFrame>
diff --git a/site/src/pages/AgentsPage/components/ChatConversation/ConversationTimeline.stories.tsx b/site/src/pages/AgentsPage/components/ChatConversation/ConversationTimeline.stories.tsx
index a08c233e5d3..c525904099c 100644
--- a/site/src/pages/AgentsPage/components/ChatConversation/ConversationTimeline.stories.tsx
+++ b/site/src/pages/AgentsPage/components/ChatConversation/ConversationTimeline.stories.tsx
@@ -147,6 +147,11 @@ const ATTACHMENT_RESPONSES = new Map<string, AttachmentResponse>([
 		},
 	],
 	["storybook-text-error", { body: "Temporary failure", status: 503 }],
+	[
+		"storybook-ios-share-report",
+		{ status: 200, body: "pdf-bytes", contentType: "application/pdf" },
+	],
+	["storybook-ios-error-report", { status: 500, body: "" }],
 ]);
 
 let attachmentFetchCounts = new Map<string, number>();
@@ -1294,6 +1299,83 @@ export const AssistantMessageWithUnnamedDownloadableFile: Story = {
 	},
 };
 
+export const AssistantMessageWithMismatchedExtensionFile: Story = {
+	args: {
+		...defaultArgs,
+		parsedMessages: buildMessages([
+			{
+				...baseMessage,
+				id: 1,
+				role: "assistant",
+				content: [
+					{ type: "text", text: "Here are the release notes." },
+					{
+						type: "file",
+						media_type: "application/pdf",
+						file_id: "storybook-mismatched-notes",
+						name: "release-notes.txt",
+					},
+				],
+			},
+		]),
+	},
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+		const downloadLink = canvas.getByRole("link", {
+			name: "Download release-notes.txt",
+		});
+		expect(downloadLink).toHaveAttribute("download", "release-notes.txt");
+	},
+};
+
+const iosDownloadStoryArgs: Story["args"] = buildStoryArgs(
+	buildUserMessage({
+		text: "I attached the deployment report.",
+		files: [
+			buildFilePart({
+				media_type: "application/pdf",
+				file_id: "storybook-ios-share-report",
+				name: "deployment-report.pdf",
+			}),
+		],
+	}),
+);
+
+export const DownloadInIOSStandaloneSharesFile: Story = {
+	args: iosDownloadStoryArgs,
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+		const share = fn().mockResolvedValue(undefined);
+		// Read-only Navigator values must be shadowed with removable own
+		// properties.
+		const overrides: Record<string, unknown> = {
+			userAgent:
+				"Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X) AppleWebKit/605.1.15",
+			standalone: true,
+			share,
+			canShare: fn().mockReturnValue(true),
+		};
+		for (const [key, value] of Object.entries(overrides)) {
+			Object.defineProperty(navigator, key, { value, configurable: true });
+		}
+		try {
+			await userEvent.click(
+				canvas.getByRole("link", { name: "Download deployment-report.pdf" }),
+			);
+			await waitFor(() => expect(share).toHaveBeenCalledTimes(1));
+			const shared: { files: File[] } = share.mock.calls[0][0];
+			expect(shared.files).toHaveLength(1);
+			expect(shared.files[0].name).toBe("deployment-report.pdf");
+			expect(shared.files[0].type).toBe("application/pdf");
+			expect(getAttachmentFetchCount("storybook-ios-share-report")).toBe(1);
+		} finally {
+			for (const key of Object.keys(overrides)) {
+				Reflect.deleteProperty(navigator, key);
+			}
+		}
+	},
+};
+
 /** Images and file-references coexist without interfering. */
 export const UserMessageWithImagesAndFileRefs: Story = {
 	args: {
diff --git a/site/src/pages/AgentsPage/utils/chatAttachments.test.ts b/site/src/pages/AgentsPage/utils/chatAttachments.test.ts
index 19647576869..12d1cffd5f8 100644
--- a/site/src/pages/AgentsPage/utils/chatAttachments.test.ts
+++ b/site/src/pages/AgentsPage/utils/chatAttachments.test.ts
@@ -1,10 +1,251 @@
-import { describe, expect, it } from "vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+vi.mock("sonner", () => ({
+	toast: {
+		error: vi.fn(),
+	},
+}));
+
+import { toast } from "sonner";
 import {
+	handleAttachmentDownloadClick,
 	isChatAttachmentFile,
 	renameChatFileForUpload,
 	sanitizeChatFileName,
 } from "./chatAttachments";
 
+describe("handleAttachmentDownloadClick", () => {
+	const overriddenNavigatorKeys = new Set<string>();
+	const iPhoneUserAgent =
+		"Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X) AppleWebKit/605.1.15";
+	const target = {
+		href: "/api/experimental/chats/files/file-1",
+		fileName: "01-agents-list.png",
+		mediaType: "image/png",
+	};
+
+	const overrideNavigator = (key: string, value: unknown) => {
+		Object.defineProperty(navigator, key, { value, configurable: true });
+		overriddenNavigatorKeys.add(key);
+	};
+
+	const enterIOSStandalonePWA = () => {
+		overrideNavigator("userAgent", iPhoneUserAgent);
+		overrideNavigator("standalone", true);
+	};
+
+	const mockFileSharing = (share: ReturnType<typeof vi.fn>) => {
+		overrideNavigator("share", share);
+		overrideNavigator(
+			"canShare",
+			vi.fn(() => true),
+		);
+	};
+
+	const mockAttachmentFetch = (body = "png-bytes", mediaType = "image/png") =>
+		vi
+			.spyOn(globalThis, "fetch")
+			.mockResolvedValue(
+				new Response(new Blob([body], { type: mediaType }), { status: 200 }),
+			);
+
+	const click = (downloadTarget = target) => {
+		const event = { preventDefault: vi.fn() };
+		return {
+			event,
+			pending: handleAttachmentDownloadClick(event, downloadTarget),
+		};
+	};
+
+	afterEach(() => {
+		for (const key of overriddenNavigatorKeys) {
+			Reflect.deleteProperty(navigator, key);
+		}
+		overriddenNavigatorKeys.clear();
+		vi.restoreAllMocks();
+		vi.mocked(toast.error).mockClear();
+	});
+
+	it.each([
+		["outside iOS", () => {}],
+		[
+			"in the iOS browser",
+			() => overrideNavigator("userAgent", iPhoneUserAgent),
+		],
+	])("keeps the native anchor download %s", (_label, setup) => {
+		setup();
+		const { event, pending } = click();
+
+		expect(pending).toBeUndefined();
+		expect(event.preventDefault).not.toHaveBeenCalled();
+	});
+
+	it("shares the fetched attachment in an iOS standalone PWA", async () => {
+		enterIOSStandalonePWA();
+		const share = vi.fn().mockResolvedValue(undefined);
+		mockFileSharing(share);
+		mockAttachmentFetch();
+
+		const { event, pending } = click();
+		await pending;
+
+		expect(event.preventDefault).toHaveBeenCalled();
+		expect(globalThis.fetch).toHaveBeenCalledWith(target.href);
+		const shared: { files: File[] } = share.mock.calls[0][0];
+		expect(shared.files).toHaveLength(1);
+		expect(shared.files[0]).toMatchObject({
+			name: "01-agents-list.png",
+			type: "image/png",
+		});
+	});
+
+	it("recognizes iPadOS with a macOS user agent", async () => {
+		overrideNavigator(
+			"userAgent",
+			"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15",
+		);
+		overrideNavigator("maxTouchPoints", 5);
+		overrideNavigator("standalone", true);
+		const share = vi.fn().mockResolvedValue(undefined);
+		mockFileSharing(share);
+		mockAttachmentFetch();
+
+		const { event, pending } = click();
+		await pending;
+
+		expect(event.preventDefault).toHaveBeenCalled();
+		expect(share).toHaveBeenCalledTimes(1);
+	});
+
+	it("keeps the native anchor when file sharing is unavailable", () => {
+		enterIOSStandalonePWA();
+		const fetchSpy = vi.spyOn(globalThis, "fetch");
+
+		const { event, pending } = click();
+
+		expect(pending).toBeUndefined();
+		expect(event.preventDefault).not.toHaveBeenCalled();
+		expect(fetchSpy).not.toHaveBeenCalled();
+	});
+
+	it("stays quiet when the user dismisses the share sheet", async () => {
+		enterIOSStandalonePWA();
+		mockFileSharing(
+			vi.fn().mockRejectedValue(new DOMException("canceled", "AbortError")),
+		);
+		mockAttachmentFetch();
+
+		await click().pending;
+
+		expect(toast.error).not.toHaveBeenCalled();
+	});
+
+	it("shows the fetch failure", async () => {
+		enterIOSStandalonePWA();
+		const share = vi.fn().mockResolvedValue(undefined);
+		mockFileSharing(share);
+		vi.spyOn(globalThis, "fetch").mockResolvedValue(
+			new Response("nope", { status: 503 }),
+		);
+
+		await click().pending;
+
+		expect(share).not.toHaveBeenCalled();
+		expect(toast.error).toHaveBeenCalledWith(
+			"Couldn't download 01-agents-list.png",
+			{ description: "HTTP 503" },
+		);
+	});
+
+	it("offers a Save retry when user activation expires", async () => {
+		enterIOSStandalonePWA();
+		const share = vi
+			.fn()
+			.mockRejectedValueOnce(
+				new DOMException("activation expired", "NotAllowedError"),
+			)
+			.mockResolvedValue(undefined);
+		mockFileSharing(share);
+		mockAttachmentFetch();
+
+		await click().pending;
+
+		expect(toast.error).toHaveBeenCalledWith(
+			"Couldn't download 01-agents-list.png",
+			expect.objectContaining({
+				description: "The file is ready to save.",
+				action: expect.objectContaining({ label: "Save" }),
+			}),
+		);
+
+		const action: unknown = vi.mocked(toast.error).mock.calls[0][1]?.action;
+		if (
+			action === null ||
+			typeof action !== "object" ||
+			!("onClick" in action) ||
+			typeof action.onClick !== "function"
+		) {
+			throw new Error("expected the toast to carry a Save action");
+		}
+		action.onClick();
+		expect(share).toHaveBeenCalledTimes(2);
+		const first: { files: File[] } = share.mock.calls[0][0];
+		const retry: { files: File[] } = share.mock.calls[1][0];
+		expect(retry.files[0]).toBe(first.files[0]);
+	});
+
+	it("shows a plain failure toast after a permanent share failure", async () => {
+		enterIOSStandalonePWA();
+		mockFileSharing(vi.fn().mockRejectedValue(new Error("share failed")));
+		mockAttachmentFetch();
+
+		await click().pending;
+
+		expect(toast.error).toHaveBeenCalledWith(
+			"Couldn't download 01-agents-list.png",
+			{ description: "share failed" },
+		);
+	});
+
+	it("shares inline data without fetching", async () => {
+		enterIOSStandalonePWA();
+		const share = vi.fn().mockResolvedValue(undefined);
+		mockFileSharing(share);
+		const fetchSpy = vi.spyOn(globalThis, "fetch");
+
+		await click({
+			href: `data:image/png;base64,${btoa("png-bytes")}`,
+			fileName: "inline.png",
+			mediaType: "image/png",
+		}).pending;
+
+		expect(fetchSpy).not.toHaveBeenCalled();
+		const shared: { files: File[] } = share.mock.calls[0][0];
+		expect(shared.files[0]).toMatchObject({
+			name: "inline.png",
+			type: "image/png",
+			size: "png-bytes".length,
+		});
+	});
+
+	it("shows a decode error for corrupt inline data", async () => {
+		enterIOSStandalonePWA();
+		const share = vi.fn().mockResolvedValue(undefined);
+		mockFileSharing(share);
+
+		await click({
+			href: "data:image/png;base64,%%%",
+			fileName: "inline.png",
+			mediaType: "image/png",
+		}).pending;
+
+		expect(share).not.toHaveBeenCalled();
+		expect(toast.error).toHaveBeenCalledWith("Couldn't download inline.png", {
+			description: "The attachment data could not be decoded.",
+		});
+	});
+});
+
 describe("isChatAttachmentFile", () => {
 	it("accepts allowlisted MIME types", () => {
 		const file = new File(["png"], "image.png", { type: "image/png" });
diff --git a/site/src/pages/AgentsPage/utils/chatAttachments.ts b/site/src/pages/AgentsPage/utils/chatAttachments.ts
index 956753ffea5..9f3c65ce33c 100644
--- a/site/src/pages/AgentsPage/utils/chatAttachments.ts
+++ b/site/src/pages/AgentsPage/utils/chatAttachments.ts
@@ -1,5 +1,7 @@
-import { isApiErrorResponse } from "#/api/errors";
+import { toast } from "sonner";
+import { getErrorMessage, isApiErrorResponse } from "#/api/errors";
 import { ChatAttachmentMediaTypes } from "#/api/typesGenerated";
+import { decodeDataURL } from "./dataUrls";
 
 const undisplayableAttachmentDetail = "File exists but could not be displayed.";
 
@@ -62,6 +64,122 @@ export async function probeAttachmentFailure(
 	return classifyAttachmentFailureResponse(response);
 }
 
+type IOSNavigator = Navigator & { standalone?: boolean };
+
+const isIOS = (): boolean =>
+	/iPad|iPhone|iPod/.test(navigator.userAgent) ||
+	// iPadOS 13+ reports a macOS user agent; the touchscreen is the tell.
+	(navigator.userAgent.includes("Mac") && navigator.maxTouchPoints > 1);
+
+const isStandaloneDisplayMode = (): boolean => {
+	const nav: IOSNavigator = navigator;
+	return (
+		matchMedia("(display-mode: standalone)").matches || nav.standalone === true
+	);
+};
+
+const canShareFile = (file: File): boolean =>
+	typeof navigator.share === "function" &&
+	typeof navigator.canShare === "function" &&
+	navigator.canShare({ files: [file] });
+
+type AttachmentDownloadTarget = {
+	href: string;
+	fileName: string;
+	mediaType: string;
+};
+
+const fileFromDataURL = ({
+	href,
+	fileName,
+	mediaType,
+}: AttachmentDownloadTarget): File | null => {
+	const decoded = decodeDataURL(href);
+	return decoded
+		? new File([decoded.bytes], fileName, {
+				type: decoded.mediaType || mediaType || "application/octet-stream",
+			})
+		: null;
+};
+
+const shareFileViaSheet = (file: File, fileName: string): Promise<void> =>
+	navigator.share({ files: [file] }).catch((error: unknown) => {
+		if (error instanceof DOMException && error.name === "AbortError") {
+			return;
+		}
+		if (error instanceof DOMException && error.name === "NotAllowedError") {
+			// Fetching may outlast transient user activation. The toast action
+			// supplies a fresh gesture for the retry.
+			toast.error(`Couldn't download ${fileName}`, {
+				description: "The file is ready to save.",
+				action: {
+					label: "Save",
+					onClick: () => void shareFileViaSheet(file, fileName),
+				},
+			});
+			return;
+		}
+		toast.error(`Couldn't download ${fileName}`, {
+			description: getErrorMessage(error, "Sharing failed."),
+		});
+	});
+
+const shareAttachmentFile = async (
+	target: AttachmentDownloadTarget,
+): Promise<void> => {
+	let file: File;
+	if (target.href.startsWith("data:")) {
+		const decoded = fileFromDataURL(target);
+		if (!decoded) {
+			toast.error(`Couldn't download ${target.fileName}`, {
+				description: "The attachment data could not be decoded.",
+			});
+			return;
+		}
+		file = decoded;
+	} else {
+		try {
+			const response = await fetch(target.href);
+			if (!response.ok) {
+				throw new Error(
+					response.statusText
+						? `${response.status} ${response.statusText}`
+						: `HTTP ${response.status}`,
+				);
+			}
+			const blob = await response.blob();
+			file = new File([blob], target.fileName, {
+				type: blob.type || target.mediaType || "application/octet-stream",
+			});
+		} catch (error) {
+			toast.error(`Couldn't download ${target.fileName}`, {
+				description: getErrorMessage(error, "The file could not be fetched."),
+			});
+			return;
+		}
+	}
+	await shareFileViaSheet(file, target.fileName);
+};
+
+/**
+ * Uses the share sheet in iOS standalone mode to avoid a QuickLook navigation
+ * with no reliable return path. Otherwise, the native anchor handles the download.
+ */
+export const handleAttachmentDownloadClick = (
+	event: { preventDefault: () => void },
+	target: AttachmentDownloadTarget,
+): Promise<void> | undefined => {
+	if (!isIOS() || !isStandaloneDisplayMode()) {
+		return undefined;
+	}
+	const probe = new File(["0"], target.fileName, { type: target.mediaType });
+	if (!canShareFile(probe)) {
+		return undefined;
+	}
+	event.preventDefault();
+	return shareAttachmentFile(target);
+};
+
 // Filename extensions to list in the file-picker's `accept` attribute
 // alongside the MIME types. Browsers and operating systems do not always
 // map these extensions to a registered MIME type (Markdown is the common
diff --git a/site/src/pages/AgentsPage/utils/chatDraftAttachmentStorage.ts b/site/src/pages/AgentsPage/utils/chatDraftAttachmentStorage.ts
index 586ecd6267c..aa38557407e 100644
--- a/site/src/pages/AgentsPage/utils/chatDraftAttachmentStorage.ts
+++ b/site/src/pages/AgentsPage/utils/chatDraftAttachmentStorage.ts
@@ -1,3 +1,5 @@
+import { decodeDataURL } from "./dataUrls";
+
 type ChatDraftAttachmentRecord = {
 	clientId: string;
 	fileName: string;
@@ -279,35 +281,22 @@ const fileFromDataURL = (
 	payload: string,
 	metadata: { fileName: string; fileType: string; lastModified: number },
 ): File | null => {
-	const commaIndex = payload.indexOf(",");
-	if (commaIndex === -1 || !payload.startsWith("data:")) {
-		return null;
-	}
-	const header = payload.slice(0, commaIndex);
-	if (!header.toLowerCase().includes(";base64")) {
+	const decoded = decodeDataURL(payload);
+	// FileReader stores drafts as base64, so other encodings indicate corruption.
+	if (!decoded?.isBase64) {
 		return null;
 	}
-	const payloadMediaType = header.slice("data:".length).split(";")[0];
 	if (
 		metadata.fileType &&
-		payloadMediaType &&
-		payloadMediaType.toLowerCase() !== metadata.fileType.toLowerCase()
+		decoded.mediaType &&
+		decoded.mediaType.toLowerCase() !== metadata.fileType.toLowerCase()
 	) {
 		return null;
 	}
-	try {
-		const binary = atob(payload.slice(commaIndex + 1));
-		const bytes = new Uint8Array(binary.length);
-		for (let index = 0; index < binary.length; index++) {
-			bytes[index] = binary.charCodeAt(index);
-		}
-		return new File([bytes], metadata.fileName, {
-			type: metadata.fileType,
-			lastModified: metadata.lastModified,
-		});
-	} catch {
-		return null;
-	}
+	return new File([decoded.bytes], metadata.fileName, {
+		type: metadata.fileType,
+		lastModified: metadata.lastModified,
+	});
 };
 
 const fileForRecord = (record: ChatDraftAttachmentRecord): File | null => {
diff --git a/site/src/pages/AgentsPage/utils/dataUrls.ts b/site/src/pages/AgentsPage/utils/dataUrls.ts
new file mode 100644
index 00000000000..e4280c3601b
--- /dev/null
+++ b/site/src/pages/AgentsPage/utils/dataUrls.ts
@@ -0,0 +1,31 @@
+type DecodedDataURL = {
+	mediaType: string;
+	isBase64: boolean;
+	bytes: Uint8Array<ArrayBuffer>;
+};
+
+// Data URLs are decoded by hand because the production CSP excludes data:
+// from connect-src (so fetch cannot read them) and the Safari 16 support
+// baseline predates Uint8Array.fromBase64.
+export const decodeDataURL = (url: string): DecodedDataURL | null => {
+	const commaIndex = url.indexOf(",");
+	const scheme = url.slice(0, "data:".length).toLowerCase();
+	if (scheme !== "data:" || commaIndex === -1) {
+		return null;
+	}
+	const params = url.slice("data:".length, commaIndex).split(";");
+	const payload = url.slice(commaIndex + 1);
+	const isBase64 = params.at(-1)?.toLowerCase() === "base64";
+	try {
+		const bytes = isBase64
+			? Uint8Array.from(atob(payload), (char) => char.charCodeAt(0))
+			: new TextEncoder().encode(decodeURIComponent(payload));
+		return {
+			mediaType: params[0].trim(),
+			isBase64,
+			bytes,
+		};
+	} catch {
+		return null;
+	}
+};