bvandeusenandClaude Opus 5.5
3984f639e8
Second step of milestone 461. An MCP client (Claude Code, Claude Desktop via mcp-remote, Open WebUI) connects to /mcp with a personal API token. - mcp>=2.2 (SDK v2 MCPServer). Mounted by wrapping app.asgi_app, so /mcp never enters Quart's pipeline; stateless streamable HTTP so a redeploy never strands a client on a session id the new process didn't issue. - Auth: Authorization: Bearer stw_… resolves to a Caller (user + effective role) in a ContextVar; 401 with WWW-Authenticate otherwise. The web pipeline's database gate runs first, so a DB restart answers 503 instead of failing inside a tool. - Registry, default-deny: register_tool(fn, role=, read_only=) is the only door; role and read_only are required. Tools above the caller's role, or from a disabled plugin, are neither listed nor callable. Undeclared arguments are refused (not silently dropped); a tool's ValueError reaches the agent as its reason; a DB failure mid-tool says so. - Plugins contribute tools via an optional register_mcp_tools(register) export, all-or-nothing, replaced on hot-reload. Documented in docs/plugins/writing-a-plugin.md. - First tool: whoami. - Tests drive app.asgi_app directly (Quart's test client never reaches /mcp); the integration test mints a real token against Postgres and runs initialize → tools/list → whoami → revoke → 401. Task #4966 "MCP-2 — /mcp transport". Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
39 lines
1.3 KiB
Python
39 lines
1.3 KiB
Python
"""Per-request MCP context: who is calling, and which app they are calling.
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The /mcp transport bypasses Quart's request pipeline, so neither `session`
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nor `current_app` exists inside a tool. The ASGI auth wrapper in server.py
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sets these from the resolved bearer token before dispatching; tools read them
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through `current_caller()` and `mcp_app()`.
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Neither falls back to a default: a tool reached without an authenticated
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caller is a bug in the transport, and it raises rather than acting for nobody.
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"""
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from __future__ import annotations
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from contextvars import ContextVar
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from typing import TYPE_CHECKING
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if TYPE_CHECKING:
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from quart import Quart
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from steward.core.api_tokens import Caller
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_caller_ctx: ContextVar["Caller | None"] = ContextVar("steward_mcp_caller", default=None)
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_app_ctx: ContextVar["Quart | None"] = ContextVar("steward_mcp_app", default=None)
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def current_caller() -> "Caller":
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caller = _caller_ctx.get()
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if caller is None:
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raise RuntimeError("no MCP caller in context: the request was not bearer-authenticated")
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return caller
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def current_caller_or_none() -> "Caller | None":
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return _caller_ctx.get()
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def mcp_app() -> "Quart":
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app = _app_ctx.get()
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if app is None:
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raise RuntimeError("no Steward app in MCP context")
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return app
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