Keep MCP tool callback updates inside host executors

[Aymericr]

Description

RegisteredTool.update({ callback }) could replace a regular tool handler after registration and bypass the host executor. Returned registrations from both registerTool() and deprecated tool() now re-wrap callback replacements.

String renames fail closed while executeTool is configured. The SDK updater closes over the original name, so repeated renames and later remove() cannot be made reliable through its public registration API. Failed rename attempts leave the original registered tool wrapped and removable. Experimental task-based tool registration remains outside this hook and is not used by createPascalMcpServer.

Validation

• bun test packages/mcp/src — 361 tests, 1,375 assertions passed.
• Both registration surfaces cover callback replacement, repeated rename refusal, continued wrapped execution, and removal after failed renames.
• bunx ultracite check packages/mcp/src/server.ts packages/mcp/src/server.test.ts
• git diff --check
• Package typecheck retains eight pre-existing scene-query.ts implicit-any diagnostics and has no changed-file diagnostics.

[pascal]

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Error id: 5fe01166-83a8-424e-8dc5-71eb7f2bf7f3