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fix: prevent SVG data from being misidentified as PNG in MCP export (fixes #644)

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The fallback condition for PNG detection in the MCP export handler was too broad:
it would match any string longer than 100 chars that didn't start with '<', which
includes SVG data URLs (data:image/svg+xml;base64,...).

This caused a race condition where an autosave SVG export response could arrive
while a PNG export was pending, resulting in SVG data being sent to the MCP server
as the PNG export result. The server would then try to write it as binary PNG,
producing a corrupt file (broken image).

Fix: exclude strings starting with 'data:' from the fallback condition, so only
raw base64 strings (without a data URL prefix) match as PNG, while SVG data URLs
are correctly rejected.
This commit is contained in:
Octopus
2026-04-07 09:44:27 +08:00
parent 73788abff9
commit 8986217a73
1 changed files with 1 additions and 1 deletions
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packages/mcp-server/src/http-server.ts
+1 -1
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@@ -684,7 +684,7 @@ function getHtmlPage(sessionId: string): string {
// unrelated exports (autosave SVG, sync XML)
if (pendingMcpExport) {
const d = msg.data;
const isPng = pendingMcpExport === 'png' && (d.startsWith('data:image/png') || (typeof d === 'string' && d.length > 100 && !d.startsWith('<')));
const isPng = pendingMcpExport === 'png' && (d.startsWith('data:image/png') || (typeof d === 'string' && d.length > 100 && !d.startsWith('<') && !d.startsWith('data:')));
const isSvg = pendingMcpExport === 'svg' && (d.startsWith('data:image/svg') || d.startsWith('<svg'));
if (isPng || isSvg) {
pendingMcpExport = null;