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`mcp.ts`

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2c2163eClaude	1	/**
	2	* Model Context Protocol HTTP transport.
	3	*
	4	* POST /mcp — JSON-RPC 2.0 requests; body is a single request
	5	* or an array (batch). Response shape mirrors.
	6	* GET /mcp — Lightweight discovery: returns server info +
	7	* protocol version + tool count.
	8	*
	9	* Auth: softAuth — `userId` in the McpContext is the cookie/PAT/OAuth
	10	* user when present, null otherwise. v1 tools are read-only and public-
	11	* only, so anonymous works; write tools (v2) will require requireAuth +
	12	* write-access on the target repo.
	13	*
	14	* Streamable-HTTP-mode is the recommended MCP transport for stateless
	15	* cloud servers. We don't emit server-sent notifications yet, so the
	16	* route is plain JSON in / JSON out.
	17	*/
	18
	19	import { Hono } from "hono";
8ed88f2ccantynz-alt	20	import type { Context } from "hono";
2c2163eClaude	21	import { softAuth } from "../middleware/auth";
	22	import type { AuthEnv } from "../middleware/auth";
	23	import {
	24	routeMcpRequest,
	25	MCP_PROTOCOL_VERSION,
	26	MCP_SERVER_NAME,
	27	MCP_SERVER_VERSION,
	28	} from "../lib/mcp";
	29	import { defaultTools } from "../lib/mcp-tools";
0a6ebcdccanty labs	30	import { config } from "../lib/config";
2c2163eClaude	31
	32	const mcp = new Hono<AuthEnv>();
	33
	34	mcp.use("*", softAuth);
	35
0a6ebcdccanty labs	36	/**
	37	* MCP authorization challenge (MCP auth spec + RFC 9728).
	38	*
	39	* When an anonymous client attempts to CALL a tool, respond 401 with a
	40	* `WWW-Authenticate: Bearer resource_metadata="…"` header pointing at our
	41	* protected-resource metadata. This is the signal a remote connector
	42	* (claude.ai, Cursor, Copilot, …) follows to start the OAuth flow — so adding
	43	* `<host>/mcp` as a connector and invoking a tool prompts sign-in, then works
	44	* end to end.
	45	*
	46	* The handshake (initialize / tools/list / ping / notifications) stays open so
	47	* any client can introspect the server unauthenticated — only `tools/call`
	48	* requires an identity. Session cookie / PAT (`glc_`) / OAuth bearer (`glct_`)
	49	* all satisfy it, so token clients (.mcp.json, CLI, VS Code extension) are
	50	* unaffected. GET /mcp discovery also stays open.
	51	*/
b5a7bb3ccanty labs	52	function authChallenge(
8ed88f2ccantynz-alt	53	c: Context<AuthEnv>,
b5a7bb3ccanty labs	54	id: unknown,
	55	opts?: { invalidToken?: boolean }
	56	) {
0a6ebcdccanty labs	57	const rm = `${config.appBaseUrl}/.well-known/oauth-protected-resource`;
b5a7bb3ccanty labs	58	if (opts?.invalidToken) {
	59	// RFC 6750 §3.1: `error="invalid_token"` tells the client its token is
	60	// expired/revoked, so it runs the refresh_token grant (or re-authorizes)
	61	// instead of replaying the dead token forever. The anonymous challenge
	62	// below deliberately omits `error=` — its absence means "no credentials
	63	// at all, start first-time auth".
	64	c.header(
	65	"WWW-Authenticate",
	66	`Bearer error="invalid_token", error_description="The access token is expired or invalid", resource_metadata="${rm}"`
	67	);
	68	return c.json(
	69	{
	70	jsonrpc: "2.0",
	71	id: id ?? null,
	72	error: {
	73	code: -32001,
	74	message: "Invalid or expired access token — refresh or re-authorize",
	75	},
	76	},
	77	401
	78	);
	79	}
0a6ebcdccanty labs	80	c.header("WWW-Authenticate", `Bearer resource_metadata="${rm}"`);
	81	return c.json(
	82	{
	83	jsonrpc: "2.0",
	84	id: id ?? null,
	85	error: { code: -32001, message: "Authentication required" },
	86	},
	87	401
	88	);
	89	}
	90
b5a7bb3ccanty labs	91	/** Extract the JSON-RPC id from a single (non-batch) envelope, else null. */
	92	function idOf(body: unknown): unknown {
	93	return !Array.isArray(body) && body && typeof body === "object"
	94	? (body as { id?: unknown }).id ?? null
	95	: null;
	96	}
	97
0a6ebcdccanty labs	98	/** True when the JSON-RPC envelope (single or batch) invokes a tool. */
	99	function invokesTool(body: unknown): boolean {
	100	const isCall = (e: unknown): boolean =>
	101	!!e &&
	102	typeof e === "object" &&
	103	(e as { method?: unknown }).method === "tools/call";
	104	if (Array.isArray(body)) return body.some(isCall);
	105	return isCall(body);
	106	}
	107
2c2163eClaude	108	mcp.get("/mcp", (c) => {
b5a7bb3ccanty labs	109	// A dead bearer on discovery gets the invalid_token signal too (plain JSON
	110	// — this endpoint is not JSON-RPC). Anonymous discovery stays open.
	111	if (c.get("bearerInvalid")) {
	112	const rm = `${config.appBaseUrl}/.well-known/oauth-protected-resource`;
	113	c.header(
	114	"WWW-Authenticate",
	115	`Bearer error="invalid_token", error_description="The access token is expired or invalid", resource_metadata="${rm}"`
	116	);
	117	return c.json(
	118	{ error: "invalid_token", message: "Access token expired or invalid — refresh or re-authorize" },
	119	401
	120	);
	121	}
2c2163eClaude	122	const tools = defaultTools();
	123	return c.json({
	124	protocolVersion: MCP_PROTOCOL_VERSION,
	125	serverInfo: { name: MCP_SERVER_NAME, version: MCP_SERVER_VERSION },
	126	transport: "http",
	127	toolCount: Object.keys(tools).length,
	128	docs:
	129	"POST /mcp with a JSON-RPC 2.0 envelope to call. See https://spec.modelcontextprotocol.io/",
	130	});
	131	});
	132
	133	mcp.post("/mcp", async (c) => {
	134	const user = c.get("user") ?? null;
0feb720Claude	135	// Scope derivation mirrors the API-auth middleware:
	136	// - OAuth bearer (glct_) → oauthScopes from middleware
	137	// - PAT (glc_) → oauthScopes from middleware
	138	// - Session cookie → full ["repo","user","admin"]
	139	// - Anonymous → []
	140	const oauthScopes = c.get("oauthScopes");
	141	let scopes: string[] = [];
	142	if (Array.isArray(oauthScopes)) {
	143	scopes = oauthScopes;
	144	} else if (user) {
	145	scopes = ["repo", "user", "admin"];
	146	}
	147	const ctx = { userId: user?.id ?? null, scopes };
2c2163eClaude	148	const tools = defaultTools();
	149
	150	let body: unknown;
	151	try {
	152	body = await c.req.json();
	153	} catch {
	154	return c.json(
	155	{
	156	jsonrpc: "2.0",
	157	id: null,
	158	error: { code: -32700, message: "Parse error" },
	159	},
	160	400
	161	);
	162	}
	163
b5a7bb3ccanty labs	164	// A bearer token was presented but rejected (expired/revoked/unknown).
	165	// Challenge EVERY method — including initialize — with invalid_token, so a
	166	// client reconnecting on a dead token fails loudly and refreshes or
	167	// re-authorizes, instead of getting a false-healthy handshake and then
	168	// looping on tools/call. Truly-anonymous handshake stays open below.
	169	if (c.get("bearerInvalid")) {
	170	return authChallenge(c, idOf(body), { invalidToken: true });
	171	}
	172
0a6ebcdccanty labs	173	// Anonymous tool calls trigger the OAuth discovery challenge so connectors
	174	// sign in. The handshake (initialize/tools-list/ping/notifications) is left
	175	// open above so clients can introspect without a token.
	176	if (!user && invokesTool(body)) {
b5a7bb3ccanty labs	177	return authChallenge(c, idOf(body));
0a6ebcdccanty labs	178	}
	179
2c2163eClaude	180	if (Array.isArray(body)) {
	181	// Batched request — pass each through, drop nulls (notifications).
	182	const out = await Promise.all(
	183	body.map((entry) => routeMcpRequest(entry, { ctx, tools }))
	184	);
	185	const filtered = out.filter((r): r is NonNullable<typeof r> => r !== null);
	186	if (filtered.length === 0) return c.body(null, 204);
	187	return c.json(filtered);
	188	}
	189
	190	const result = await routeMcpRequest(body, { ctx, tools });
	191	if (result === null) {
	192	// Notification — no response body, 204.
	193	return c.body(null, 204);
	194	}
	195	return c.json(result);
	196	});
	197
	198	export default mcp;