From f4b1d8bb534e7e937d979fa2bf64f4c869b72038 Mon Sep 17 00:00:00 2001
From: Guilhem Lemouel <guilhemlemouel@gmail.com>
Date: Thu, 10 Sep 2026 15:06:23 +0200
Subject: [PATCH] fix: clone a remote MCP schema before normalizing it

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JgzuxyafKNF2uaEeL35XQw
---
 .../copilot/chat/global/mcpTools.test.ts      | 20 +++++++++++++++++++
 .../copilot/chat/global/mcpTools.ts           |  6 +++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/frontend/src/lib/components/copilot/chat/global/mcpTools.test.ts b/frontend/src/lib/components/copilot/chat/global/mcpTools.test.ts
index ca4f2a906d..5192dd8d2c 100644
--- a/frontend/src/lib/components/copilot/chat/global/mcpTools.test.ts
+++ b/frontend/src/lib/components/copilot/chat/global/mcpTools.test.ts
@@ -260,6 +260,26 @@ describe('loaded remote tools', () => {
 		expect(loadedMcpTools(OWNER)).toEqual([])
 	})
 
+	// The sanitized schema must not alias the listing cache: the normalize pass rewrites
+	// nested nodes in place, so a shallow copy would edit the entry `summarizeTool` and
+	// the failed-call schema echo read from, and that every other chat shares.
+	it('does not mutate the remote schema it was given', () => {
+		const remote = {
+			name: 'aliased',
+			description: 'x',
+			inputSchema: {
+				type: 'object',
+				properties: { a: { type: 'string', format: '' } },
+				required: ['a', 'a']
+			}
+		} as any
+
+		registerMcpTools(OWNER, mcpRegistryGeneration(OWNER), server, [remote])
+
+		expect(remote.inputSchema.properties.a.format).toBe('')
+		expect(remote.inputSchema.required).toEqual(['a', 'a'])
+	})
+
 	it('falls back to an empty object schema when the remote sends no usable one', () => {
 		registerMcpTools(OWNER, mcpRegistryGeneration(OWNER), server, [
 			{ name: 'nada', description: 'x', inputSchema: null } as any
diff --git a/frontend/src/lib/components/copilot/chat/global/mcpTools.ts b/frontend/src/lib/components/copilot/chat/global/mcpTools.ts
index 1b92fbb13f..844c9017dc 100644
--- a/frontend/src/lib/components/copilot/chat/global/mcpTools.ts
+++ b/frontend/src/lib/components/copilot/chat/global/mcpTools.ts
@@ -646,7 +646,11 @@ function safeInputSchema(schema: unknown): Record<string, unknown> {
 				)
 			]
 		: []
-	const safe = { ...rest, type: 'object', properties, required }
+	// Cloned, not spread: the spread would leave `properties` and any `items`/`allOf`
+	// carried through `rest` pointing at the listing cache's own objects, and the
+	// normalize pass below rewrites nested nodes in place. A registered tool is
+	// supposed to be a frozen copy — sharing that structure makes it one in name only.
+	const safe = structuredClone({ ...rest, type: 'object', properties, required })
 	// The same pass `createToolDef` runs on every other tool, so a remote schema is not
 	// the one that reaches a provider unnormalized. It recurses, which this does not:
 	// Windmill's own MCP server emits `format: ""` on untyped fields.