diff --git a/src/integrations/misc/__tests__/imageDataUrl.spec.ts b/src/integrations/misc/__tests__/imageDataUrl.spec.ts
index 4993303034..01b100afa8 100644
--- a/src/integrations/misc/__tests__/imageDataUrl.spec.ts
+++ b/src/integrations/misc/__tests__/imageDataUrl.spec.ts
@@ -18,40 +18,13 @@ describe("normalizeImageRefsToDataUrls", () => {
 		expect(result).toEqual([dataUrl])
 	})
 
-	it("should convert webview URIs to data URLs", async () => {
-		const webviewUri = "file:///path/to/test.png"
-		const mockBuffer = Buffer.from("test image data")
-
-		vi.mocked(fs.readFile).mockResolvedValue(mockBuffer)
-
-		const result = await normalizeImageRefsToDataUrls([webviewUri])
-
-		expect(result).toHaveLength(1)
-		expect(result[0]).toMatch(/^data:image\/png;base64,/)
-		expect(fs.readFile).toHaveBeenCalledWith("/path/to/test.png")
-	})
-
-	it("should handle mixed arrays of data URLs and webview URIs", async () => {
-		const dataUrl = "data:image/jpeg;base64,test123"
-		const webviewUri = "file:///path/to/test.png"
-		const mockBuffer = Buffer.from("test image data")
-
-		vi.mocked(fs.readFile).mockResolvedValue(mockBuffer)
-
-		const result = await normalizeImageRefsToDataUrls([dataUrl, webviewUri])
-
-		expect(result).toHaveLength(2)
-		expect(result[0]).toBe(dataUrl) // Data URL unchanged
-		expect(result[1]).toMatch(/^data:image\/png;base64,/) // Webview URI converted
-	})
-
 	it("should handle errors gracefully by skipping problematic images", async () => {
 		const validDataUrl = "data:image/png;base64,valid"
-		const invalidWebviewUri = "file:///nonexistent/test.png"
+		const invalidCdnUri = "vscode-file://vscode-app/nonexistent/test.png"
 
 		vi.mocked(fs.readFile).mockRejectedValue(new Error("File not found"))
 
-		const result = await normalizeImageRefsToDataUrls([validDataUrl, invalidWebviewUri])
+		const result = await normalizeImageRefsToDataUrls([validDataUrl, invalidCdnUri])
 
 		expect(result).toEqual([validDataUrl]) // Only valid ones returned
 	})
diff --git a/webview-ui/src/components/chat/ChatTextArea.tsx b/webview-ui/src/components/chat/ChatTextArea.tsx
index 63e1fd4a0a..4e8b1570b3 100644
--- a/webview-ui/src/components/chat/ChatTextArea.tsx
+++ b/webview-ui/src/components/chat/ChatTextArea.tsx
@@ -11,6 +11,7 @@ import { ExtensionMessage } from "@roo/ExtensionMessage"
 import { vscode } from "@src/utils/vscode"
 import { useExtensionState } from "@src/context/ExtensionStateContext"
 import { useAppTranslation } from "@src/i18n/TranslationContext"
+import { MAX_IMAGE_BYTES, estimateBytesFromBase64DataUrl } from "@src/utils/image"
 import {
 	ContextMenuOptionType,
 	getContextMenuOptions,
@@ -732,18 +733,11 @@ export const ChatTextArea = forwardRef<HTMLTextAreaElement, ChatTextAreaProps>(
 					if (dataUrls.length > 0) {
 						// Process each image: enforce 10MB limit and send to backend to save as temp file
 						for (const dataUrl of dataUrls) {
-							// Approximate bytes from base64 (ignore header and padding)
-							const commaIdx = dataUrl.indexOf(",")
-							let tooLarge = false
-							if (commaIdx !== -1) {
-								const base64 = dataUrl.slice(commaIdx + 1).replace(/=+$/, "")
-								const approxBytes = Math.floor((base64.length * 3) / 4)
-								if (approxBytes > 10 * 1024 * 1024) {
-									console.warn("Pasted image exceeds 10MB; skipping")
-									tooLarge = true
-								}
+							const approxBytes = estimateBytesFromBase64DataUrl(dataUrl)
+							if (approxBytes > MAX_IMAGE_BYTES) {
+								console.warn("Pasted image exceeds 10MB; skipping")
+								continue
 							}
-							if (tooLarge) continue
 
 							const requestId = Math.random().toString(36).substring(2, 9)
 
@@ -910,18 +904,11 @@ export const ChatTextArea = forwardRef<HTMLTextAreaElement, ChatTextAreaProps>(
 						if (dataUrls.length > 0) {
 							// Process each dropped image: enforce 10MB limit and send to backend to save as temp file
 							for (const dataUrl of dataUrls) {
-								// Approximate bytes from base64 (ignore header and padding)
-								const commaIdx = dataUrl.indexOf(",")
-								let tooLarge = false
-								if (commaIdx !== -1) {
-									const base64 = dataUrl.slice(commaIdx + 1).replace(/=+$/, "")
-									const approxBytes = Math.floor((base64.length * 3) / 4)
-									if (approxBytes > 10 * 1024 * 1024) {
-										console.warn("Dropped image exceeds 10MB; skipping")
-										tooLarge = true
-									}
+								const approxBytes = estimateBytesFromBase64DataUrl(dataUrl)
+								if (approxBytes > MAX_IMAGE_BYTES) {
+									console.warn("Dropped image exceeds 10MB; skipping")
+									continue
 								}
-								if (tooLarge) continue
 
 								const requestId = Math.random().toString(36).substring(2, 9)