diff --git a/apps/mcp/src/server/auth/index.test.ts b/apps/mcp/src/server/auth/index.test.ts
index 62698e81..26f4a449 100644
--- a/apps/mcp/src/server/auth/index.test.ts
+++ b/apps/mcp/src/server/auth/index.test.ts
@@ -212,6 +212,34 @@ describe("MCP authentication", () => {
 		expect(error).not.toHaveBeenCalled()
 	})
 
+	it("rejects an API key whose session has no organization", async () => {
+		const warn = vi.spyOn(console, "warn").mockImplementation(() => {})
+		const error = vi.spyOn(console, "error").mockImplementation(() => {})
+		vi.stubGlobal(
+			"fetch",
+			vi.fn().mockResolvedValue(
+				Response.json({
+					user: { id: "user_test", email: "test@example.com", name: "Test" },
+					org: null,
+					session: null,
+					role: null,
+					accessType: "full",
+					containerTags: null,
+					scope: { type: "full", permission: "write" },
+				}),
+			),
+		)
+
+		await expect(
+			validateApiKey("sm_noorg_key_0123456789abcdef", API_URL),
+		).resolves.toBeNull()
+		expect(warn).toHaveBeenCalledTimes(1)
+		expect(warn).toHaveBeenCalledWith(
+			"API key rejected: session has no organization",
+		)
+		expect(error).not.toHaveBeenCalled()
+	})
+
 	it("rejects malformed API keys without an API request", async () => {
 		const fetchSpy = vi.fn()
 		vi.stubGlobal("fetch", fetchSpy)
@@ -239,48 +267,6 @@ describe("MCP authentication", () => {
 		expect(warn).not.toHaveBeenCalled()
 	})
 
-	it("surfaces a 200 session body that fails the session contract as TransientAuthError", async () => {
-		const warn = vi.spyOn(console, "warn").mockImplementation(() => {})
-		const error = vi.spyOn(console, "error").mockImplementation(() => {})
-		vi.stubGlobal(
-			"fetch",
-			vi.fn().mockResolvedValue(
-				new Response(JSON.stringify({}), {
-					status: 200,
-					headers: { "content-type": "application/json" },
-				}),
-			),
-		)
-
-		await expect(
-			validateApiKey("sm_badbody_key_0123456789abcd", API_URL),
-		).rejects.toThrow(TransientAuthError)
-		expect(error).toHaveBeenCalledTimes(1)
-		expect(error.mock.calls[0]?.[0]).toBe(
-			"Auth backend unavailable during API key validation: Invalid session response",
-		)
-		expect(warn).not.toHaveBeenCalled()
-	})
-
-	it("surfaces a non-JSON 200 session body as TransientAuthError", async () => {
-		const warn = vi.spyOn(console, "warn").mockImplementation(() => {})
-		const error = vi.spyOn(console, "error").mockImplementation(() => {})
-		vi.stubGlobal(
-			"fetch",
-			vi
-				.fn()
-				.mockResolvedValue(
-					new Response("<html>upstream error</html>", { status: 200 }),
-				),
-		)
-
-		await expect(
-			validateApiKey("sm_htmlbody_key_0123456789abc", API_URL),
-		).rejects.toThrow(TransientAuthError)
-		expect(error).toHaveBeenCalledTimes(1)
-		expect(warn).not.toHaveBeenCalled()
-	})
-
 	it("surfaces a session-endpoint timeout as TransientAuthError", async () => {
 		const warn = vi.spyOn(console, "warn").mockImplementation(() => {})
 		const error = vi.spyOn(console, "error").mockImplementation(() => {})
diff --git a/apps/mcp/src/server/auth/index.ts b/apps/mcp/src/server/auth/index.ts
index a68d7c9f..819e1f31 100644
--- a/apps/mcp/src/server/auth/index.ts
+++ b/apps/mcp/src/server/auth/index.ts
@@ -44,13 +44,9 @@ export async function fetchSession(
 		)
 	}
 
-	const body = await response.json().catch((error: unknown) => {
-		if (error instanceof SyntaxError) return undefined
-		throw error
-	})
-	const result = sessionInfoSchema.safeParse(body)
+	const result = sessionInfoSchema.safeParse(await response.json())
 	if (!result.success) {
-		throw new TransientAuthError("Invalid session response")
+		throw new Error("Invalid session response")
 	}
 
 	return result.data
@@ -90,7 +86,6 @@ const TRANSIENT_ERROR_NAMES = new Set([
 const TRANSIENT_JOSE_CODES = new Set(["ERR_JWKS_TIMEOUT", "ERR_JOSE_GENERIC"])
 
 function transientAuthErrorFor(error: unknown): TransientAuthError | null {
-	if (error instanceof TransientAuthError) return error
 	const status = (error as { status?: unknown } | null)?.status
 	if (typeof status === "number" && status !== 401 && status !== 403) {
 		return new TransientAuthError(`Session endpoint returned ${status}`, status)
@@ -122,7 +117,10 @@ export async function validateApiKey(
 	try {
 		const session = await fetchSession(token, apiUrl)
 		const organizationId = session.org?.id
-		if (!organizationId) return null
+		if (!organizationId) {
+			console.warn("API key rejected: session has no organization")
+			return null
+		}
 
 		const user: AuthUser = {
 			userId: session.user.id,
diff --git a/apps/mcp/src/shared/types.ts b/apps/mcp/src/shared/types.ts
index ad59a02b..67914630 100644
--- a/apps/mcp/src/shared/types.ts
+++ b/apps/mcp/src/shared/types.ts
@@ -37,8 +37,8 @@ export const sessionInfoSchema = z
 			email: z.string().optional(),
 			name: z.string().optional(),
 		}),
-		org: z.looseObject({ id: z.string().min(1) }).optional(),
-		role: z.string().optional(),
+		org: z.looseObject({ id: z.string().min(1) }).nullish(),
+		role: z.string().nullish(),
 		accessType: z.enum(["full", "restricted"]).optional(),
 		containerTags: z.array(sessionNamespaceAccessSchema).nullable().optional(),
 		scope: sessionScopeSchema.optional(),