Python: [Python] MCP prompt refresh keeps removed or changed prompts

[jpalvarezl]

Current behavior

MCPTool._load_prompts_locked refreshes prompts append-only: it records existing function names, skips prompt names already loaded, and extends _functions only with unseen names.

Consequences:

• Prompts removed by the server remain exposed.
• A successful empty prompt snapshot does not clear previously loaded prompt functions.
• Changed prompt descriptions or arguments remain stale.

Expected behavior

Treat a successful, complete prompts/list fetch as the current prompt catalog, while preserving unrelated MCP tools and user-added functions. Build the refreshed prompt catalog without publishing partial results; if pagination fails, retain the previous catalog rather than applying an incomplete snapshot.

Scope

This is protocol-version independent and affects both legacy list-change notifications and modern subscriptions. It was discovered during the MCP v2 work, but is not caused by v2.

Related to #8245. This issue should not expand or block the base v2 migration unless maintainers choose otherwise.

Relevant source: python/packages/core/agent_framework/_mcp.py, method _load_prompts_locked.

[Anshuman-Prakash]

I'd like to pick this up. Plan: rebuild the prompt catalog from a complete prompts/list snapshot (all pages) and only then swap it into _functions, replacing previously loaded prompt functions while preserving MCP tools and user-added functions; on a pagination/list failure keep the previous catalog. Will add unit tests for removed, changed, empty-snapshot, and failed-pagination cases.