diff --git a/apps/web/components/task-create-dialog-selectors.test.tsx b/apps/web/components/task-create-dialog-selectors.test.tsx
index a9fe157680..7a39d57322 100644
--- a/apps/web/components/task-create-dialog-selectors.test.tsx
+++ b/apps/web/components/task-create-dialog-selectors.test.tsx
@@ -4,6 +4,7 @@ import { afterEach, describe, expect, it, vi } from "vitest";
 import { TooltipProvider } from "@kandev/ui/tooltip";
 import { ToastProvider } from "@/components/toast-provider";
 import { MAX_FILES, MAX_TOTAL_SIZE, processFile } from "@/components/task/chat/file-attachment";
+import { formatBytes } from "@/lib/utils/format-bytes";
 import { TaskFormInputs } from "./task-create-dialog-selectors";
 import type { TaskFormInputsHandle } from "./task-create-dialog-types";
 
@@ -292,7 +293,7 @@ describe("TaskFormInputs attachment feedback", () => {
     const warning = await screen.findByTestId(TOAST_MESSAGE_TEST_ID);
     expect(warning.textContent).toContain("Attachment limit reached");
     expect(warning.textContent).toContain(
-      `Attachments can total up to ${MAX_TOTAL_SIZE / 1024 / 1024} MB.`,
+      `Attachments can total up to ${formatBytes(MAX_TOTAL_SIZE)}.`,
     );
   });
 
@@ -312,7 +313,7 @@ describe("TaskFormInputs attachment feedback", () => {
     const warning = await screen.findByTestId(TOAST_MESSAGE_TEST_ID);
     expect(warning.textContent).toContain("Attachment is too large");
     expect(warning.textContent).toContain(
-      "copied-image.png is 14 MB. The maximum file size is 10 MB.",
+      "copied-image.png is 14.0 MB. The maximum file size is 10.0 MB.",
     );
   });
 
diff --git a/apps/web/components/task-create-dialog-selectors.tsx b/apps/web/components/task-create-dialog-selectors.tsx
index ed0a88cbd2..1ca9a42dd5 100644
--- a/apps/web/components/task-create-dialog-selectors.tsx
+++ b/apps/web/components/task-create-dialog-selectors.tsx
@@ -8,9 +8,9 @@ import { IconPaperclip } from "@tabler/icons-react";
 import { Combobox } from "./combobox";
 import { scoreBranch } from "@/lib/utils/branch-filter";
 import { BranchRefreshButton } from "./branch-refresh-button";
+import { formatBytes } from "@/lib/utils/format-bytes";
 import {
   processFile,
-  formatBytes,
   MAX_FILES,
   MAX_TOTAL_SIZE,
   type FileAttachment,
diff --git a/apps/web/components/task/chat/context-items/file-attachment-item.tsx b/apps/web/components/task/chat/context-items/file-attachment-item.tsx
index 17aee6776f..bc892d53c3 100644
--- a/apps/web/components/task/chat/context-items/file-attachment-item.tsx
+++ b/apps/web/components/task/chat/context-items/file-attachment-item.tsx
@@ -2,7 +2,7 @@
 
 import { memo } from "react";
 import type { FileAttachmentContextItem } from "@/lib/types/context";
-import { formatBytes } from "../file-attachment";
+import { formatBytes } from "@/lib/utils/format-bytes";
 import { ContextChip } from "./context-chip";
 
 export const FileAttachmentItem = memo(function FileAttachmentItem({
diff --git a/apps/web/components/task/chat/file-attachment-preview.tsx b/apps/web/components/task/chat/file-attachment-preview.tsx
index daf9de0e38..a4ce99cea2 100644
--- a/apps/web/components/task/chat/file-attachment-preview.tsx
+++ b/apps/web/components/task/chat/file-attachment-preview.tsx
@@ -3,7 +3,8 @@
 import { memo } from "react";
 import { IconFile, IconX } from "@tabler/icons-react";
 import { cn } from "@/lib/utils";
-import { formatBytes, type FileAttachment } from "./file-attachment";
+import { formatBytes } from "@/lib/utils/format-bytes";
+import { type FileAttachment } from "./file-attachment";
 
 type FileAttachmentPreviewProps = {
   attachments: FileAttachment[];
diff --git a/apps/web/components/task/chat/file-attachment.ts b/apps/web/components/task/chat/file-attachment.ts
index d33b9789f8..5048efaf15 100644
--- a/apps/web/components/task/chat/file-attachment.ts
+++ b/apps/web/components/task/chat/file-attachment.ts
@@ -4,6 +4,7 @@
  */
 
 import { generateUUID } from "@/lib/utils";
+import { formatBytes } from "@/lib/utils/format-bytes";
 
 export type FileAttachment = {
   id: string;
@@ -22,14 +23,6 @@ export const MAX_FILE_SIZE = 10 * 1024 * 1024; // 10MB per file
 export const MAX_TOTAL_SIZE = 20 * 1024 * 1024; // 20MB total
 export const MAX_FILES = 10;
 
-export function formatBytes(bytes: number): string {
-  if (bytes === 0) return "0 B";
-  const k = 1024;
-  const sizes = ["B", "KB", "MB", "GB"];
-  const i = Math.floor(Math.log(bytes) / Math.log(k));
-  return `${parseFloat((bytes / Math.pow(k, i)).toFixed(1))} ${sizes[i]}`;
-}
-
 function isPreviewableImage(mimeType: string): boolean {
   return PREVIEWABLE_IMAGE_TYPES.includes(mimeType);
 }
diff --git a/apps/web/components/task/chat/image-attachment-preview.tsx b/apps/web/components/task/chat/image-attachment-preview.tsx
index 1cf3dc1b19..18fc2c7448 100644
--- a/apps/web/components/task/chat/image-attachment-preview.tsx
+++ b/apps/web/components/task/chat/image-attachment-preview.tsx
@@ -3,6 +3,7 @@
 import { memo } from "react";
 import { IconX } from "@tabler/icons-react";
 import { cn, generateUUID } from "@/lib/utils";
+import { formatBytes } from "@/lib/utils/format-bytes";
 
 export type ImageAttachment = {
   id: string;
@@ -22,14 +23,6 @@ export const MAX_IMAGE_SIZE = 10 * 1024 * 1024; // 10MB per image
 export const MAX_TOTAL_SIZE = 20 * 1024 * 1024; // 20MB total
 export const MAX_IMAGES = 10;
 
-export function formatBytes(bytes: number): string {
-  if (bytes === 0) return "0 B";
-  const k = 1024;
-  const sizes = ["B", "KB", "MB", "GB"];
-  const i = Math.floor(Math.log(bytes) / Math.log(k));
-  return `${parseFloat((bytes / Math.pow(k, i)).toFixed(1))} ${sizes[i]}`;
-}
-
 type ImageAttachmentPreviewProps = {
   attachments: ImageAttachment[];
   onRemove: (id: string) => void;
diff --git a/apps/web/components/task/chat/use-attachment-file-feedback.ts b/apps/web/components/task/chat/use-attachment-file-feedback.ts
index af0d44ff21..3a24255869 100644
--- a/apps/web/components/task/chat/use-attachment-file-feedback.ts
+++ b/apps/web/components/task/chat/use-attachment-file-feedback.ts
@@ -1,6 +1,7 @@
 import { useCallback } from "react";
 import { useToast } from "@/components/toast-provider";
-import { formatBytes, MAX_FILES, MAX_FILE_SIZE, MAX_TOTAL_SIZE } from "./file-attachment";
+import { formatBytes } from "@/lib/utils/format-bytes";
+import { MAX_FILES, MAX_FILE_SIZE, MAX_TOTAL_SIZE } from "./file-attachment";
 
 export function useAttachmentCountFeedback() {
   const { toast } = useToast();
diff --git a/apps/web/components/task/chat/use-chat-input-state.test.ts b/apps/web/components/task/chat/use-chat-input-state.test.ts
index a8a39242f8..ce4496fbd8 100644
--- a/apps/web/components/task/chat/use-chat-input-state.test.ts
+++ b/apps/web/components/task/chat/use-chat-input-state.test.ts
@@ -4,6 +4,7 @@ import React from "react";
 import { ToastProvider } from "@/components/toast-provider";
 import { useChatInputState } from "./use-chat-input-state";
 import { MAX_FILES, MAX_FILE_SIZE, MAX_TOTAL_SIZE } from "./file-attachment";
+import { formatBytes } from "@/lib/utils/format-bytes";
 import type { TipTapInputHandle } from "./tiptap-input";
 import type { EntityReference } from "@/lib/types/entity-reference";
 
@@ -234,9 +235,7 @@ describe("useChatInputState attachment feedback", () => {
     expect(result.current.attachments).toHaveLength(2);
     expect(screen.getAllByTestId("toast-message")).toHaveLength(1);
     expect(toastMessage()).toContain("Attachment limit reached");
-    expect(toastMessage()).toContain(
-      `Attachments can total up to ${MAX_TOTAL_SIZE / 1024 / 1024} MB.`,
-    );
+    expect(toastMessage()).toContain(`Attachments can total up to ${formatBytes(MAX_TOTAL_SIZE)}.`);
   });
 
   it("warns when a pasted attachment exceeds the file size limit", async () => {
@@ -250,7 +249,7 @@ describe("useChatInputState attachment feedback", () => {
 
     expect(toastMessage()).toContain("Attachment is too large");
     expect(toastMessage()).toContain(
-      `recording.mov is 11 MB. The maximum file size is ${MAX_FILE_SIZE / 1024 / 1024} MB.`,
+      `recording.mov is 11.0 MB. The maximum file size is ${formatBytes(MAX_FILE_SIZE)}.`,
     );
     expect(result.current.attachments).toEqual([]);
   });
diff --git a/apps/web/components/task/chat/use-chat-input-state.ts b/apps/web/components/task/chat/use-chat-input-state.ts
index 259e6fc372..f3caaad69b 100644
--- a/apps/web/components/task/chat/use-chat-input-state.ts
+++ b/apps/web/components/task/chat/use-chat-input-state.ts
@@ -18,13 +18,8 @@ import {
   setChatDraftContent,
   restoreAttachmentPreview,
 } from "@/lib/local-storage";
-import {
-  processFile,
-  formatBytes,
-  MAX_FILES,
-  MAX_TOTAL_SIZE,
-  type FileAttachment,
-} from "./file-attachment";
+import { formatBytes } from "@/lib/utils/format-bytes";
+import { processFile, MAX_FILES, MAX_TOTAL_SIZE, type FileAttachment } from "./file-attachment";
 import {
   useAttachmentCountFeedback,
   useAttachmentFileFeedback,
diff --git a/apps/web/components/task/session-dialog-shared.test.tsx b/apps/web/components/task/session-dialog-shared.test.tsx
index 41f1da30b3..bc4f53c1a2 100644
--- a/apps/web/components/task/session-dialog-shared.test.tsx
+++ b/apps/web/components/task/session-dialog-shared.test.tsx
@@ -3,6 +3,7 @@ import React from "react";
 import { afterEach, describe, expect, it, vi } from "vitest";
 import { ToastProvider } from "@/components/toast-provider";
 import { MAX_FILES, MAX_FILE_SIZE, MAX_TOTAL_SIZE } from "./chat/file-attachment";
+import { formatBytes } from "@/lib/utils/format-bytes";
 import { useDialogAttachments } from "./session-dialog-shared";
 
 afterEach(cleanup);
@@ -114,7 +115,7 @@ describe("useDialogAttachments", () => {
     ]);
     expect(screen.getAllByTestId(toastMessageTestId)).toHaveLength(1);
     expect(screen.getByTestId(toastMessageTestId).textContent).toContain(
-      `Attachments can total up to ${MAX_TOTAL_SIZE / 1024 / 1024} MB.`,
+      `Attachments can total up to ${formatBytes(MAX_TOTAL_SIZE)}.`,
     );
   });
 });
diff --git a/apps/web/components/task/session-dialog-shared.tsx b/apps/web/components/task/session-dialog-shared.tsx
index ed83af7900..624cf591dd 100644
--- a/apps/web/components/task/session-dialog-shared.tsx
+++ b/apps/web/components/task/session-dialog-shared.tsx
@@ -14,9 +14,9 @@ import {
 import { Tooltip, TooltipContent, TooltipTrigger } from "@kandev/ui/tooltip";
 import { IconGitBranch, IconPaperclip } from "@tabler/icons-react";
 import { AgentLogo } from "@/components/agent-logo";
+import { formatBytes } from "@/lib/utils/format-bytes";
 import {
   processFile,
-  formatBytes,
   MAX_FILES,
   MAX_TOTAL_SIZE,
   type FileAttachment,
diff --git a/apps/web/e2e/tests/chat/mobile-attachment-size-warning.spec.ts b/apps/web/e2e/tests/chat/mobile-attachment-size-warning.spec.ts
index 1aaf840431..f8ee6966e2 100644
--- a/apps/web/e2e/tests/chat/mobile-attachment-size-warning.spec.ts
+++ b/apps/web/e2e/tests/chat/mobile-attachment-size-warning.spec.ts
@@ -42,7 +42,9 @@ test.describe("oversized attachment feedback on mobile", () => {
     const warning = testPage
       .getByTestId("toast-message")
       .filter({ hasText: "Attachment is too large" });
-    await expect(warning).toContainText("recording.mov is 11 MB. The maximum file size is 10 MB.");
+    await expect(warning).toContainText(
+      "recording.mov is 11.0 MB. The maximum file size is 10.0 MB.",
+    );
 
     await expect
       .poll(async () => {
diff --git a/apps/web/e2e/tests/task/create-task-attachment-warning.spec.ts b/apps/web/e2e/tests/task/create-task-attachment-warning.spec.ts
index 7afcf7d584..c32eebf07f 100644
--- a/apps/web/e2e/tests/task/create-task-attachment-warning.spec.ts
+++ b/apps/web/e2e/tests/task/create-task-attachment-warning.spec.ts
@@ -25,7 +25,9 @@ test("warns when a pasted image is too large for a new task", async ({ testPage
   const warning = testPage
     .getByTestId("toast-message")
     .filter({ hasText: "Attachment is too large" });
-  await expect(warning).toContainText("copied-image.png is 14 MB. The maximum file size is 10 MB.");
+  await expect(warning).toContainText(
+    "copied-image.png is 14.0 MB. The maximum file size is 10.0 MB.",
+  );
 
   const overlay = testPage.locator('[data-slot="dialog-overlay"]:visible');
   await expect(overlay).toBeVisible();
diff --git a/apps/web/lib/utils/format-bytes.test.ts b/apps/web/lib/utils/format-bytes.test.ts
index 794ff77b10..1a234cca83 100644
--- a/apps/web/lib/utils/format-bytes.test.ts
+++ b/apps/web/lib/utils/format-bytes.test.ts
@@ -27,4 +27,15 @@ describe("formatBytes", () => {
     expect(formatBytes(1024 * 1024 * 1024)).toBe("1.0 GB");
     expect(formatBytes(1024 ** 4)).toBe("1.0 TB");
   });
+
+  it("clamps to TB above the largest unit", () => {
+    expect(formatBytes(1024 ** 5)).toBe("1024.0 TB");
+    expect(formatBytes(1024 ** 6)).toBe("1048576.0 TB");
+  });
+
+  it("returns '-' for non-finite input", () => {
+    expect(formatBytes(NaN)).toBe("-");
+    expect(formatBytes(Infinity)).toBe("-");
+    expect(formatBytes(-Infinity)).toBe("-");
+  });
 });