diff --git a/packages/better-auth/src/plugins/organization/team.test.ts b/packages/better-auth/src/plugins/organization/team.test.ts
index 3d3df8242b..c45d9dd645 100644
--- a/packages/better-auth/src/plugins/organization/team.test.ts
+++ b/packages/better-auth/src/plugins/organization/team.test.ts
@@ -23,6 +23,15 @@ describe("team", async () => {
 		logger: {
 			level: "error",
 		},
+		databaseHooks: {
+			user: {
+				create: {
+					before: async (user) => ({
+						data: { ...user, emailVerified: true },
+					}),
+				},
+			},
+		},
 	});
 
 	const { headers } = await signInWithTestUser();
@@ -418,6 +427,15 @@ describe("team", async () => {
 			logger: {
 				level: "error",
 			},
+			databaseHooks: {
+				user: {
+					create: {
+						before: async (user) => ({
+							data: { ...user, emailVerified: true },
+						}),
+					},
+				},
+			},
 		});
 
 		const { headers } = await signInWithTestUser();
@@ -518,6 +536,15 @@ describe("setActiveTeam org scoping", async () => {
 		logger: {
 			level: "error",
 		},
+		databaseHooks: {
+			user: {
+				create: {
+					before: async (user) => ({
+						data: { ...user, emailVerified: true },
+					}),
+				},
+			},
+		},
 	});
 
 	const { headers } = await signInWithTestUser();
@@ -773,6 +800,15 @@ describe("multi team support", async () => {
 			logger: {
 				level: "error",
 			},
+			databaseHooks: {
+				user: {
+					create: {
+						before: async (user) => ({
+							data: { ...user, emailVerified: true },
+						}),
+					},
+				},
+			},
 		},
 		{
 			testWith: "sqlite",
@@ -1608,3 +1644,75 @@ describe("listUserTeams with organizationId parameter", async () => {
 		expect(res).toBeInstanceOf(Error);
 	});
 });
+
+describe("invitation with team id containing comma", async () => {
+	const { auth, signInWithTestUser } = await getTestInstance(
+		{
+			advanced: {
+				database: {
+					generateId: ({ model }) => {
+						if (model === "team") {
+							return `team,id,${crypto.randomUUID()}`;
+						}
+						return crypto.randomUUID();
+					},
+				},
+			},
+			plugins: [
+				organization({
+					async sendInvitationEmail() {},
+					teams: { enabled: true },
+				}),
+			],
+			logger: { level: "error" },
+			databaseHooks: {
+				user: {
+					create: {
+						before: async (user) => ({
+							data: { ...user, emailVerified: true },
+						}),
+					},
+				},
+			},
+		},
+		{ testWith: "sqlite" },
+	);
+
+	const admin = await signInWithTestUser();
+
+	const org = await auth.api.createOrganization({
+		headers: admin.headers,
+		body: { name: "Comma Org", slug: "comma-org" },
+	});
+	if (!org) throw new Error("failed to create organization");
+	const organizationId = org.id;
+
+	const team = await auth.api.createTeam({
+		headers: admin.headers,
+		body: { name: "Comma Team", organizationId },
+	});
+
+	it("seeds a team whose generated id contains the storage separator", () => {
+		expect(team.id).toContain(",");
+	});
+
+	it.each([
+		{ name: "string body", teamId: team.id },
+		{ name: "array body", teamId: [team.id] },
+	])("rejects createInvitation with $name", async ({ teamId }) => {
+		await expect(
+			auth.api.createInvitation({
+				headers: admin.headers,
+				body: {
+					email: "comma-invitee@email.com",
+					role: "member",
+					organizationId,
+					teamId,
+				},
+			}),
+		).rejects.toMatchObject({
+			status: "BAD_REQUEST",
+			body: { code: "INVALID_TEAM_ID" },
+		});
+	});
+});
diff --git a/packages/better-auth/src/plugins/username/username.test.ts b/packages/better-auth/src/plugins/username/username.test.ts
index 42923c869d..6babdbd32d 100644
--- a/packages/better-auth/src/plugins/username/username.test.ts
+++ b/packages/better-auth/src/plugins/username/username.test.ts
@@ -819,3 +819,52 @@ describe("immutable username", async () => {
 		expect(session?.user.displayUsername).toBe("Updated Display Name");
 	});
 });
+
+describe("username sign-in verify-email callbackURL", async () => {
+	/**
+	 * The verify-email link sent on username sign-in for an unverified user must
+	 * keep the caller's `callbackURL` intact. A raw interpolation truncates any
+	 * value containing `&` at the first ampersand.
+	 *
+	 * @see https://github.com/better-auth/better-auth/issues/6086
+	 */
+	it("encodes callbackURL in the verify-email link on username sign-in", async () => {
+		let capturedUrl = "";
+		const { client } = await getTestInstance(
+			{
+				emailAndPassword: { enabled: true, requireEmailVerification: true },
+				emailVerification: {
+					sendOnSignIn: true,
+					async sendVerificationEmail({ url }) {
+						capturedUrl = url;
+					},
+				},
+				plugins: [username()],
+			},
+			{
+				clientOptions: {
+					plugins: [usernameClient()],
+				},
+			},
+		);
+
+		await client.signUp.email({
+			email: "encode-username@example.com",
+			username: "encode_username",
+			password: "correct-password",
+			name: "Encode Username",
+		});
+
+		const callbackURL = "/welcome?ref=username&plan=pro";
+		await client.signIn.username({
+			username: "encode_username",
+			password: "correct-password",
+			callbackURL,
+		});
+
+		expect(capturedUrl).not.toBe("");
+		expect(new URL(capturedUrl).searchParams.get("callbackURL")).toBe(
+			callbackURL,
+		);
+	});
+});