diff --git a/packages/core/src/oidc/grants/client-credentials.test.ts b/packages/core/src/oidc/grants/client-credentials.test.ts
new file mode 100644
index 000000000000..5fda1ab21337
--- /dev/null
+++ b/packages/core/src/oidc/grants/client-credentials.test.ts
@@ -0,0 +1,157 @@
+import { isKeyInObject } from '@silverhand/essentials';
+import { type KoaContextWithOIDC, errors, type Adapter } from 'oidc-provider';
+
+import { createOidcContext } from '#src/test-utils/oidc-provider.js';
+import { MockTenant } from '#src/test-utils/tenant.js';
+
+const { jest } = import.meta;
+
+jest.unstable_mockModule('oidc-provider/lib/shared/check_resource.js', () => ({
+  default: jest.fn(),
+}));
+
+jest.unstable_mockModule('oidc-provider/lib/helpers/weak_cache.js', () => ({
+  default: jest.fn().mockReturnValue({
+    configuration: jest.fn().mockReturnValue({
+      features: {
+        mTLS: { getCertificate: jest.fn() },
+      },
+      scopes: new Set(['foo', 'bar']),
+    }),
+  }),
+}));
+
+// eslint-disable-next-line @typescript-eslint/no-empty-function
+const noop = async () => {};
+
+const clientId = 'some_client_id';
+const requestScopes = ['foo', 'bar'];
+
+const mockAdapter: Adapter = {
+  upsert: jest.fn(),
+  find: jest.fn(),
+  findByUserCode: jest.fn(),
+  findByUid: jest.fn(),
+  consume: jest.fn(),
+  destroy: jest.fn(),
+  revokeByGrantId: jest.fn(),
+};
+
+type ClientCredentials = InstanceType<KoaContextWithOIDC['oidc']['provider']['ClientCredentials']>;
+type Client = InstanceType<KoaContextWithOIDC['oidc']['provider']['Client']>;
+
+const validClientCredentials: ClientCredentials = {
+  kind: 'ClientCredentials',
+  clientId,
+  aud: '',
+  tokenType: '',
+  isSenderConstrained: jest.fn().mockReturnValue(false),
+  iat: 0,
+  jti: '',
+  scope: requestScopes.join(' '),
+  scopes: new Set(requestScopes),
+  ttlPercentagePassed: jest.fn(),
+  isValid: false,
+  isExpired: false,
+  remainingTTL: 0,
+  expiration: 0,
+  save: jest.fn(),
+  adapter: mockAdapter,
+  destroy: jest.fn(),
+  emit: jest.fn(),
+};
+
+// @ts-expect-error
+const createValidClient = ({ scope }: { scope?: string } = {}): Client => ({
+  clientId,
+  grantTypeAllowed: jest.fn().mockResolvedValue(true),
+  clientAuthMethod: 'none',
+  scope,
+});
+
+const validOidcContext: Partial<KoaContextWithOIDC['oidc']> = {
+  params: {
+    refresh_token: 'some_refresh_token',
+    organization_id: 'some_org_id',
+    scope: requestScopes.join(' '),
+  },
+  client: createValidClient(),
+};
+
+const { buildHandler } = await import('./client-credentials.js');
+
+const mockHandler = (tenant = new MockTenant()) => {
+  return buildHandler(tenant.envSet, tenant.queries);
+};
+
+// The handler returns void so we cannot check the return value, and it's also not
+// straightforward to assert the token is issued correctly. Here we just do the sanity
+// check and basic token validation. Comprehensive token validation should be done in
+// integration tests.
+describe('client credentials grant', () => {
+  it('should throw an error if the client is not available', async () => {
+    const ctx = createOidcContext({ ...validOidcContext, client: undefined });
+    await expect(mockHandler()(ctx, noop)).rejects.toThrow(errors.InvalidClient);
+  });
+
+  it('should throw an error if the requested scope is not allowed', async () => {
+    const ctx = createOidcContext({
+      ...validOidcContext,
+      client: createValidClient({ scope: 'baz' }),
+    });
+    await expect(
+      mockHandler(
+        new MockTenant(undefined, {
+          organizations: {
+            relations: {
+              // @ts-expect-error
+              apps: {
+                exists: jest.fn().mockResolvedValue(true),
+              },
+            },
+          },
+        })
+      )(ctx, noop)
+    ).rejects.toThrow(errors.InvalidScope);
+  });
+
+  it('should throw an error if the app has not associated with the organization', async () => {
+    const ctx = createOidcContext(validOidcContext);
+    await expect(
+      mockHandler(
+        new MockTenant(undefined, {
+          organizations: {
+            relations: {
+              // @ts-expect-error
+              apps: {
+                exists: jest.fn().mockResolvedValue(false),
+              },
+            },
+          },
+        })
+      )(ctx, noop)
+    ).rejects.toThrow(errors.AccessDenied);
+  });
+
+  it('should be ok', async () => {
+    const ctx = createOidcContext(validOidcContext);
+    await expect(
+      mockHandler(
+        new MockTenant(undefined, {
+          organizations: {
+            relations: {
+              // @ts-expect-error
+              apps: {
+                exists: jest.fn().mockResolvedValue(true),
+              },
+              // @ts-expect-error
+              appsRoles: { getApplicationScopes: jest.fn().mockResolvedValue([{ name: 'foo' }]) },
+            },
+          },
+        })
+      )(ctx, noop)
+    ).resolves.toBeUndefined();
+
+    expect(isKeyInObject(ctx.body, 'scope') && ctx.body.scope).toBe('foo');
+  });
+});
diff --git a/packages/core/src/oidc/grants/client-credentials.ts b/packages/core/src/oidc/grants/client-credentials.ts
index 8e6346d8624c..badabf11d10a 100644
--- a/packages/core/src/oidc/grants/client-credentials.ts
+++ b/packages/core/src/oidc/grants/client-credentials.ts
@@ -20,6 +20,8 @@
  * The commit hash of the original file is `0c52469f08b0a4a1854d90a96546a3f7aa090e5e`.
  */
 
+import { buildOrganizationUrn } from '@logto/core-kit';
+import { cond } from '@silverhand/essentials';
 import type Provider from 'oidc-provider';
 import { errors } from 'oidc-provider';
 import epochTime from 'oidc-provider/lib/helpers/epoch_time.js';
@@ -27,17 +29,19 @@ import dpopValidate from 'oidc-provider/lib/helpers/validate_dpop.js';
 import instance from 'oidc-provider/lib/helpers/weak_cache.js';
 import checkResource from 'oidc-provider/lib/shared/check_resource.js';
 
-import { type EnvSet } from '#src/env-set/index.js';
+import { EnvSet } from '#src/env-set/index.js';
 import type Queries from '#src/tenants/Queries.js';
 import assertThat from '#src/utils/assert-that.js';
 
-const { InvalidClient, InvalidGrant, InvalidScope, InvalidTarget } = errors;
+import { getSharedResourceServerData, reversedResourceAccessTokenTtl } from '../resource.js';
+
+const { AccessDenied, InvalidClient, InvalidGrant, InvalidScope, InvalidTarget } = errors;
 
 /**
  * The valid parameters for the `client_credentials` grant type. Note the `resource` parameter is
  * not included here since it should be handled per configuration when registering the grant type.
  */
-export const parameters = Object.freeze(['scope']);
+export const parameters = Object.freeze(['scope', 'organization_id']);
 
 // We have to disable the rules because the original implementation is written in JavaScript and
 // uses mutable variables.
@@ -45,9 +49,9 @@ export const parameters = Object.freeze(['scope']);
 export const buildHandler: (
   envSet: EnvSet,
   queries: Queries
-  // eslint-disable-next-line complexity, unicorn/consistent-function-scoping
-) => Parameters<Provider['registerGrantType']>[1] = (_envSet, _queries) => async (ctx, next) => {
-  const { client } = ctx.oidc;
+  // eslint-disable-next-line complexity
+) => Parameters<Provider['registerGrantType']>[1] = (envSet, queries) => async (ctx, next) => {
+  const { client, params } = ctx.oidc;
   const { ClientCredentials, ReplayDetection } = ctx.oidc.provider;
 
   assertThat(client, new InvalidClient('client must be available'));
@@ -61,8 +65,40 @@ export const buildHandler: (
 
   const dPoP = await dpopValidate(ctx);
 
-  // eslint-disable-next-line @typescript-eslint/no-empty-function
-  await checkResource(ctx, async () => {});
+  /* === RFC 0001 === */
+  // The value type is `unknown`, which will swallow other type inferences. So we have to cast it
+  // to `Boolean` first.
+  const organizationId = cond(Boolean(params?.organization_id) && String(params?.organization_id));
+  // TODO: Remove
+  if (!EnvSet.values.isDevFeaturesEnabled && organizationId) {
+    throw new InvalidTarget('organization tokens are not supported yet');
+  }
+
+  if (
+    organizationId &&
+    !(await queries.organizations.relations.apps.exists({
+      organizationId,
+      applicationId: client.clientId,
+    }))
+  ) {
+    const error = new AccessDenied('app has not associated with the organization');
+    error.statusCode = 403;
+    throw error;
+  }
+  /* === End RFC 0001 === */
+
+  // Do not check the resource if the organization ID is provided and the resource is not. In this
+  // case, the default resource server will be ignored, and an organization token will be issued.
+  if (!(organizationId && !params?.resource)) {
+    // eslint-disable-next-line @typescript-eslint/no-empty-function
+    await checkResource(ctx, async () => {});
+  }
+
+  const { 0: resourceServer, length } = Object.values(ctx.oidc.resourceServers ?? {});
+
+  if (!organizationId && length === 0) {
+    throw new InvalidTarget('both `resource` and `organization_id` are not provided');
+  }
 
   const scopes = ctx.oidc.params?.scope
     ? [...new Set(String(ctx.oidc.params.scope).split(' '))]
@@ -83,7 +119,6 @@ export const buildHandler: (
     scope: scopes.join(' ') || undefined!,
   });
 
-  const { 0: resourceServer, length } = Object.values(ctx.oidc.resourceServers ?? {});
   if (resourceServer) {
     if (length !== 1) {
       throw new InvalidTarget(
@@ -96,6 +131,33 @@ export const buildHandler: (
       undefined;
   }
 
+  // Issue organization token only if resource server is not present.
+  // If it's present, the flow falls into the `checkResource` and `if (resourceServer)` block above.
+  if (organizationId && !resourceServer) {
+    /* === RFC 0001 === */
+    const audience = buildOrganizationUrn(organizationId);
+    const availableScopes = await queries.organizations.relations.appsRoles
+      .getApplicationScopes(organizationId, client.clientId)
+      .then((scope) => scope.map(({ name }) => name));
+
+    /** The intersection of the available scopes and the requested scopes. */
+    const issuedScopes = availableScopes.filter((scope) => scopes.includes(scope)).join(' ');
+
+    token.aud = audience;
+    // Note: the original implementation uses `new provider.ResourceServer` to create the resource
+    // server. But it's not available in the typings. The class is actually very simple and holds
+    // no provider-specific context. So we just create the object manually.
+    // See https://github.com/panva/node-oidc-provider/blob/cf2069cbb31a6a855876e95157372d25dde2511c/lib/helpers/resource_server.js
+    token.resourceServer = {
+      ...getSharedResourceServerData(envSet),
+      accessTokenTTL: reversedResourceAccessTokenTtl,
+      audience,
+      scope: availableScopes.join(' '),
+    };
+    token.scope = issuedScopes;
+    /* === End RFC 0001 === */
+  }
+
   if (client.tlsClientCertificateBoundAccessTokens) {
     const cert = getCertificate(ctx);
 
diff --git a/packages/core/src/oidc/grants/refresh-token.test.ts b/packages/core/src/oidc/grants/refresh-token.test.ts
index 55110e6b58de..69d8e21b77f2 100644
--- a/packages/core/src/oidc/grants/refresh-token.test.ts
+++ b/packages/core/src/oidc/grants/refresh-token.test.ts
@@ -154,7 +154,11 @@ afterAll(() => {
   Sinon.restore();
 });
 
-describe('organization token grant', () => {
+// The handler returns void so we cannot check the return value, and it's also not
+// straightforward to assert the token is issued correctly. Here we just do the sanity
+// check and basic token validation. Comprehensive token validation should be done in
+// integration tests.
+describe('refresh token grant', () => {
   it('should throw when client is not available', async () => {
     const ctx = createOidcContext({ ...validOidcContext, client: undefined });
     await expect(mockHandler()(ctx, noop)).rejects.toThrow(errors.InvalidClient);
@@ -307,10 +311,6 @@ describe('organization token grant', () => {
     );
   });
 
-  // The handler returns void so we cannot check the return value, and it's also not
-  // straightforward to assert the token is issued correctly. Here we just do the sanity
-  // check and basic token validation. Comprehensive token validation should be done in
-  // integration tests.
   it('should not explode when everything looks fine', async () => {
     const ctx = createPreparedContext();
     const tenant = new MockTenant();
diff --git a/packages/core/src/oidc/grants/refresh-token.ts b/packages/core/src/oidc/grants/refresh-token.ts
index 479e10da5a3e..87677f4f0345 100644
--- a/packages/core/src/oidc/grants/refresh-token.ts
+++ b/packages/core/src/oidc/grants/refresh-token.ts
@@ -216,7 +216,6 @@ export const buildHandler: (
   }
 
   /* === RFC 0001 === */
-
   if (organizationId) {
     // Check membership
     if (
@@ -325,7 +324,7 @@ export const buildHandler: (
   const scope = params.scope ? requestParamScopes : refreshToken.scopes;
 
   // Note, issue organization token only if `params.resource` is not present.
-  // If resource is set, will issue normal access token with extra claim "organization_id",
+  // If resource is set, we will issue normal access token with extra claim "organization_id",
   // the logic is handled in `getResourceServerInfo` and `extraTokenClaims`, see the init file of oidc-provider.
   if (organizationId && !params.resource) {
     /* === RFC 0001 === */
diff --git a/packages/core/src/oidc/init.ts b/packages/core/src/oidc/init.ts
index 22ce03e63376..9e6a12f6c946 100644
--- a/packages/core/src/oidc/init.ts
+++ b/packages/core/src/oidc/init.ts
@@ -131,7 +131,9 @@ export default function initOidc(
         enabled: true,
         defaultResource: async () => {
           const resource = await findDefaultResource();
-          return resource?.indicator ?? '';
+          // The default implementation returns `undefined` - https://github.com/panva/node-oidc-provider/blob/0c52469f08b0a4a1854d90a96546a3f7aa090e5e/lib/helpers/defaults.js#L195
+          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+          return resource?.indicator ?? undefined!;
         },
         // Disable the auto use of authorization_code granted resource feature
         useGrantedResource: () => false,
@@ -147,13 +149,6 @@ export default function initOidc(
           const { client, params, session, entities } = ctx.oidc;
           const userId = session?.accountId ?? entities.Account?.accountId;
 
-          /**
-           * In consent or code exchange flow, the organization_id is undefined,
-           * and all the scopes inherited from the all organization roles will be granted.
-           * In the flow of granting token for organization with api resource,
-           * this value is set to the organization id,
-           * and will then narrow down the scopes to the specific organization.
-           */
           const organizationId = params?.organization_id;
           const scopes = await findResourceScopes({
             queries,
@@ -228,7 +223,6 @@ export default function initOidc(
       },
     },
     extraParams: Object.values(ExtraParamsKey),
-
     extraTokenClaims: async (ctx, token) => {
       const organizationApiResourceClaims = await getExtraTokenClaimsForOrganizationApiResource(
         ctx,
diff --git a/packages/core/src/oidc/resource.ts b/packages/core/src/oidc/resource.ts
index ab51a0a181fa..d6f7bea8ea3c 100644
--- a/packages/core/src/oidc/resource.ts
+++ b/packages/core/src/oidc/resource.ts
@@ -20,9 +20,12 @@ export const getSharedResourceServerData = (
   },
 });
 
+// TODO: Refactor me. This function is too complex.
 /**
- * Find the scopes for a given resource indicator according to the subject in the
- * context. The subject can be either a user or an application.
+ * Find the scopes for a given resource indicator according to the subject in the context. The
+ * subject can be either a user or an application.
+ *
+ * When both `userId` and `applicationId` are provided, the function will prioritize the user.
  *
  * This function also handles the reserved resources.
  *
@@ -40,6 +43,15 @@ export const findResourceScopes = async ({
   queries: Queries;
   libraries: Libraries;
   indicator: string;
+  /**
+   * In consent or code exchange flow, the `organizationId` is `undefined`, and all the scopes
+   * inherited from the all organization roles should be granted.
+   *
+   * In the flow of granting token for a specific organization with API resource, `organizationId`
+   * is provided, and only the scopes inherited from that organization should be granted.
+   *
+   * Note: This value does not affect the reserved resources and application subjects.
+   */
   findFromOrganizations: boolean;
   userId?: string;
   applicationId?: string;
@@ -68,6 +80,14 @@ export const findResourceScopes = async ({
     );
   }
 
+  if (applicationId && organizationId) {
+    return queries.organizations.relations.appsRoles.getApplicationResourceScopes(
+      organizationId,
+      applicationId,
+      indicator
+    );
+  }
+
   if (applicationId) {
     return findApplicationScopesForResourceIndicator(applicationId, indicator);
   }
diff --git a/packages/core/src/queries/organization/application-role-relations.ts b/packages/core/src/queries/organization/application-role-relations.ts
index f576732c1fa3..17de5ecf38c3 100644
--- a/packages/core/src/queries/organization/application-role-relations.ts
+++ b/packages/core/src/queries/organization/application-role-relations.ts
@@ -3,6 +3,13 @@ import {
   OrganizationRoles,
   Applications,
   OrganizationRoleApplicationRelations,
+  type OrganizationScope,
+  OrganizationRoleScopeRelations,
+  OrganizationScopes,
+  OrganizationRoleResourceScopeRelations,
+  Scopes,
+  Resources,
+  type Scope,
 } from '@logto/schemas';
 import { type CommonQueryMethods, sql } from '@silverhand/slonik';
 
@@ -22,6 +29,61 @@ export class ApplicationRoleRelationQueries extends RelationQueries<
     );
   }
 
+  /**
+   * Get all the organization scopes of an application in an organization. Scopes are unique by
+   * their IDs.
+   */
+  async getApplicationScopes(
+    organizationId: string,
+    applicationId: string
+  ): Promise<readonly OrganizationScope[]> {
+    const { fields } = convertToIdentifiers(OrganizationRoleApplicationRelations, true);
+    const roleScopeRelations = convertToIdentifiers(OrganizationRoleScopeRelations, true);
+    const scopes = convertToIdentifiers(OrganizationScopes, true);
+
+    return this.pool.any<OrganizationScope>(sql`
+      select distinct on (${scopes.fields.id})
+        ${sql.join(Object.values(scopes.fields), sql`, `)}
+      from ${this.table}
+      join ${roleScopeRelations.table}
+        on ${roleScopeRelations.fields.organizationRoleId} = ${fields.organizationRoleId}
+      join ${scopes.table}
+        on ${scopes.fields.id} = ${roleScopeRelations.fields.organizationScopeId}
+      where ${fields.organizationId} = ${organizationId}
+      and ${fields.applicationId} = ${applicationId}
+    `);
+  }
+
+  /**
+   * Get all the resource scopes of an application in an organization. Scopes are unique by their
+   * IDs.
+   */
+  async getApplicationResourceScopes(
+    organizationId: string,
+    applicationId: string,
+    resourceIndicator: string
+  ): Promise<readonly Scope[]> {
+    const { fields } = convertToIdentifiers(OrganizationRoleApplicationRelations, true);
+    const roleScopeRelations = convertToIdentifiers(OrganizationRoleResourceScopeRelations, true);
+    const resources = convertToIdentifiers(Resources, true);
+    const scopes = convertToIdentifiers(Scopes, true);
+
+    return this.pool.any<Scope>(sql`
+      select distinct on (${scopes.fields.id})
+        ${sql.join(Object.values(scopes.fields), sql`, `)}
+      from ${this.table}
+      join ${roleScopeRelations.table}
+        on ${roleScopeRelations.fields.organizationRoleId} = ${fields.organizationRoleId}
+      join ${scopes.table}
+        on ${scopes.fields.id} = ${roleScopeRelations.fields.scopeId}
+      join ${resources.table}
+        on ${resources.fields.id} = ${scopes.fields.resourceId}
+      where ${fields.organizationId} = ${organizationId}
+      and ${fields.applicationId} = ${applicationId}
+      and ${resources.fields.indicator} = ${resourceIndicator}
+    `);
+  }
+
   /** Replace the roles of an application in an organization. */
   async replace(organizationId: string, applicationId: string, roleIds: readonly string[]) {
     const applications = convertToIdentifiers(Applications);
diff --git a/packages/integration-tests/src/api/api.ts b/packages/integration-tests/src/api/api.ts
index e3993997681e..5fcd0882e7ce 100644
--- a/packages/integration-tests/src/api/api.ts
+++ b/packages/integration-tests/src/api/api.ts
@@ -1,3 +1,4 @@
+import { formUrlEncodedHeaders } from '@logto/shared';
 import { appendPath } from '@silverhand/essentials';
 import ky from 'ky';
 
@@ -31,5 +32,6 @@ export const cloudApi = ky.extend({
 });
 
 export const oidcApi = ky.extend({
+  headers: formUrlEncodedHeaders,
   prefixUrl: appendPath(new URL(logtoUrl), 'oidc'),
 });
diff --git a/packages/integration-tests/src/api/application.ts b/packages/integration-tests/src/api/application.ts
index 055fa83b70d6..4a2a96125fd0 100644
--- a/packages/integration-tests/src/api/application.ts
+++ b/packages/integration-tests/src/api/application.ts
@@ -7,7 +7,6 @@ import {
   type ProtectedAppMetadata,
   type OrganizationWithRoles,
 } from '@logto/schemas';
-import { formUrlEncodedHeaders } from '@logto/shared';
 import { conditional } from '@silverhand/essentials';
 
 import { authedAdminApi, oidcApi } from './api.js';
@@ -101,7 +100,6 @@ export const generateM2mLog = async (applicationId: string) => {
 
   // This is a token request with insufficient parameters and should fail. We make the request to generate a log for the current machine to machine app.
   return oidcApi.post('token', {
-    headers: formUrlEncodedHeaders,
     body: new URLSearchParams({
       client_id: id,
       client_secret: secret,
diff --git a/packages/integration-tests/src/tests/api/application/application.roles.test.ts b/packages/integration-tests/src/tests/api/application/application.roles.test.ts
index 0e012e47b12e..5516339e0652 100644
--- a/packages/integration-tests/src/tests/api/application/application.roles.test.ts
+++ b/packages/integration-tests/src/tests/api/application/application.roles.test.ts
@@ -1,5 +1,5 @@
 import { ApplicationType, RoleType } from '@logto/schemas';
-import { generateStandardId, formUrlEncodedHeaders } from '@logto/shared';
+import { generateStandardId } from '@logto/shared';
 import { HTTPError } from 'ky';
 
 import {
@@ -175,7 +175,6 @@ describe('admin console application management (roles)', () => {
 
     const { access_token: accessToken } = await oidcApi
       .post('token', {
-        headers: formUrlEncodedHeaders,
         body: new URLSearchParams({
           client_id: m2mApp.id,
           client_secret: m2mApp.secret,
diff --git a/packages/integration-tests/src/tests/api/oidc/client-credentials-grant.test.ts b/packages/integration-tests/src/tests/api/oidc/client-credentials-grant.test.ts
new file mode 100644
index 000000000000..63c5dbaccf7f
--- /dev/null
+++ b/packages/integration-tests/src/tests/api/oidc/client-credentials-grant.test.ts
@@ -0,0 +1,300 @@
+import assert from 'node:assert';
+
+import { buildOrganizationUrn } from '@logto/core-kit';
+import {
+  type Application,
+  ApplicationType,
+  RoleType,
+  type Resource,
+  type Role,
+  type Scope,
+} from '@logto/schemas';
+import { appendPath } from '@silverhand/essentials';
+import { createRemoteJWKSet, jwtVerify } from 'jose';
+import { HTTPError } from 'ky';
+
+import { oidcApi } from '#src/api/api.js';
+import {
+  assignRolesToApplication,
+  createApplication,
+  deleteApplication,
+} from '#src/api/application.js';
+import {
+  createResource as createResourceApi,
+  deleteResource,
+  setDefaultResource,
+} from '#src/api/resource.js';
+import { assignScopesToRole, createRole as createRoleApi, deleteRole } from '#src/api/role.js';
+import { createScope as createScopeApi } from '#src/api/scope.js';
+import { isDevFeaturesEnabled, logtoUrl } from '#src/constants.js';
+import { OrganizationApiTest } from '#src/helpers/organization.js';
+import { devFeatureTest, randomString } from '#src/utils.js';
+
+type TokenResponse = {
+  access_token: string;
+  token_type: string;
+  expires_in: number;
+  scope: string;
+};
+
+const createApi = <R, Args extends unknown[]>(
+  run: (...args: Args) => Promise<R>,
+  storage: R[]
+): ((...args: Args) => Promise<R>) => {
+  return async (...args) => {
+    const result = await run(...args);
+    // eslint-disable-next-line @silverhand/fp/no-mutating-methods
+    storage.push(result);
+    return result;
+  };
+};
+
+describe('client credentials grant', () => {
+  const jwkSet = createRemoteJWKSet(appendPath(new URL(logtoUrl), 'oidc/jwks'));
+  const organizationApi = new OrganizationApiTest();
+  // eslint-disable-next-line @silverhand/fp/no-let
+  let client: Application;
+  const currentResources: Resource[] = [];
+  const currentRoles: Role[] = [];
+  const currentScopes: Scope[] = [];
+
+  const createResource = createApi(createResourceApi, currentResources);
+  const createRole = createApi(createRoleApi, currentRoles);
+  const createScope = createApi(createScopeApi, currentScopes);
+
+  const post = async (additionalParams: Record<string, string> = {}) =>
+    oidcApi
+      .post('token', {
+        body: new URLSearchParams({
+          client_id: client.id,
+          client_secret: client.secret,
+          grant_type: 'client_credentials',
+          ...additionalParams,
+        }),
+      })
+      .json<TokenResponse>();
+
+  const expectError = async (
+    additionalParams: Record<string, string>,
+    status: number,
+    json?: Record<string, unknown>
+  ) => {
+    const error = await post(additionalParams).catch((error: unknown) => error);
+    assert(error instanceof HTTPError);
+    expect(error.response.status).toBe(status);
+
+    if (json) {
+      expect(await error.response.json()).toMatchObject(json);
+    }
+  };
+
+  beforeAll(async () => {
+    // eslint-disable-next-line @silverhand/fp/no-mutation
+    client = await createApplication('client credentials test', ApplicationType.MachineToMachine);
+  });
+
+  afterAll(async () => {
+    await deleteApplication(client.id);
+  });
+
+  afterEach(async () => {
+    await Promise.all([
+      organizationApi.cleanUp(),
+      // eslint-disable-next-line @typescript-eslint/no-empty-function
+      ...currentResources.map(async ({ id }) => deleteResource(id).catch(() => {})),
+      // eslint-disable-next-line @typescript-eslint/no-empty-function
+      ...currentRoles.map(async ({ id }) => deleteRole(`roles/${id}`).catch(() => {})),
+    ]);
+  });
+
+  describe('general failed cases', () => {
+    it('should fail if the client is not found', async () => {
+      await expectError({ client_id: 'not-found', client_secret: 'not-found' }, 400, {
+        error: 'invalid_client',
+        error_description: 'invalid client not-found',
+      });
+    });
+
+    it('should fail if parameters are missing', async () => {
+      await expectError({}, 400, {
+        error: 'invalid_target',
+        error_description: 'both `resource` and `organization_id` are not provided',
+      });
+    });
+  });
+
+  describe('resource server', () => {
+    it('should fail if the resource server is not found', async () => {
+      await expectError({ resource: 'https://not-found' }, 400, {
+        error: 'invalid_target',
+        error_description: 'resource indicator is missing, or unknown',
+      });
+    });
+
+    it('should be able to get a token for a resource server', async () => {
+      const resource = await createResource();
+      const { access_token: accessToken, scope } = await post({ resource: resource.indicator });
+
+      expect(scope).toBe(undefined);
+
+      const verified = await jwtVerify(accessToken, jwkSet, { audience: resource.indicator });
+      expect(verified.payload.scope).toBe(undefined);
+    });
+
+    it('should be able to get a token for a resource server with valid scope', async () => {
+      const resource = await createResource();
+      const scope = await createScope(resource.id, 'test-scope');
+      const role = await createRole({
+        name: `cc-${randomString()}`,
+        type: RoleType.MachineToMachine,
+      });
+      await assignScopesToRole([scope.id], role.id);
+      await assignRolesToApplication(client.id, [role.id]);
+
+      const { access_token: accessToken, scope: returnedScope } = await post({
+        resource: resource.indicator,
+        scope: `${scope.name} ${randomString()}`,
+      });
+
+      expect(returnedScope).toBe(scope.name);
+
+      const verified = await jwtVerify(accessToken, jwkSet, { audience: resource.indicator });
+      expect(verified.payload.scope).toBe(scope.name);
+    });
+
+    it('should fall back to the default resource server if no `resource` parameter is provided', async () => {
+      const resource = await createResource();
+      await setDefaultResource(resource.id);
+      const { access_token: accessToken, scope } = await post();
+
+      expect(scope).toBe(undefined);
+
+      const verified = await jwtVerify(accessToken, jwkSet, { audience: resource.indicator });
+      expect(verified.payload.scope).toBe(undefined);
+    });
+  });
+
+  describe('organization token', () => {
+    it('should fail if dev feature is not enabled', async () => {
+      if (isDevFeaturesEnabled) {
+        return;
+      }
+
+      await expectError({ organization_id: 'not-found' }, 400, {
+        error: 'invalid_target',
+        error_description: 'organization tokens are not supported yet',
+      });
+    });
+  });
+
+  devFeatureTest.describe('organization token', () => {
+    it('should fail if the application is not associated with the organization', async () => {
+      await expectError({ organization_id: 'not-found' }, 403, {
+        error: 'access_denied',
+        error_description: 'app has not associated with the organization',
+      });
+    });
+
+    it('should be able to get an organization token', async () => {
+      const organization = await organizationApi.create({ name: 'test-organization' });
+      await organizationApi.applications.add(organization.id, [client.id]);
+      const { access_token: accessToken, scope } = await post({ organization_id: organization.id });
+
+      expect(scope).toBe('');
+
+      const verified = await jwtVerify(accessToken, jwkSet, {
+        audience: buildOrganizationUrn(organization.id),
+      });
+      expect(verified.payload.scope).toBe('');
+    });
+
+    it('should be able to get an organization token with valid scope', async () => {
+      const organization = await organizationApi.create({ name: 'test-organization' });
+      await organizationApi.applications.add(organization.id, [client.id]);
+      const scope = await organizationApi.scopeApi.create({ name: `test-scope-${randomString()}` });
+      const role = await organizationApi.roleApi.create({
+        name: `cc-${randomString()}`,
+        type: RoleType.MachineToMachine,
+        organizationScopeIds: [scope.id],
+      });
+      await organizationApi.addApplicationRoles(organization.id, client.id, [role.id]);
+
+      const { access_token: accessToken, scope: returnedScope } = await post({
+        organization_id: organization.id,
+        scope: `${scope.name} ${randomString()}`,
+      });
+
+      expect(returnedScope).toBe(scope.name);
+
+      const verified = await jwtVerify(accessToken, jwkSet, {
+        audience: buildOrganizationUrn(organization.id),
+      });
+      expect(verified.payload.scope).toBe(scope.name);
+    });
+
+    it('should be able to get an organization token with valid scope and resource', async () => {
+      const organization = await organizationApi.create({ name: 'test-organization' });
+      await organizationApi.applications.add(organization.id, [client.id]);
+
+      const resource = await createResource();
+      const [scope1, scope2, scope3] = await Promise.all([
+        createScope(resource.id, `test-scope-${randomString()}`),
+        createScope(resource.id, `test-scope-${randomString()}`),
+        createScope(resource.id, `test-scope-${randomString()}`),
+      ]);
+      const role = await organizationApi.roleApi.create({
+        name: `cc-${randomString()}`,
+        type: RoleType.MachineToMachine,
+        resourceScopeIds: [scope1.id, scope2.id],
+      });
+      await organizationApi.addApplicationRoles(organization.id, client.id, [role.id]);
+
+      const { access_token: accessToken, scope: returnedScope } = await post({
+        organization_id: organization.id,
+        resource: resource.indicator,
+        scope: `${scope1.name} ${scope2.name} ${scope3.name} ${randomString()}`,
+      });
+      expect(returnedScope).toBe(`${scope1.name} ${scope2.name}`);
+
+      const verified = await jwtVerify(accessToken, jwkSet, { audience: resource.indicator });
+      expect(verified.payload.scope).toBe(`${scope1.name} ${scope2.name}`);
+    });
+
+    it('should only issue requested scopes', async () => {
+      const organization = await organizationApi.create({ name: 'test-organization' });
+      await organizationApi.applications.add(organization.id, [client.id]);
+
+      const resource = await createResource();
+      const [scope1, scope2] = await Promise.all([
+        createScope(resource.id, `test-scope-${randomString()}`),
+        createScope(resource.id, `test-scope-${randomString()}`),
+      ]);
+      const role = await organizationApi.roleApi.create({
+        name: `cc-${randomString()}`,
+        type: RoleType.MachineToMachine,
+        resourceScopeIds: [scope1.id, scope2.id],
+      });
+      await organizationApi.addApplicationRoles(organization.id, client.id, [role.id]);
+
+      const { access_token: accessToken1, scope: returnedScope1 } = await post({
+        organization_id: organization.id,
+        resource: resource.indicator,
+        scope: `${scope1.name}`,
+      });
+      expect(returnedScope1).toBe(scope1.name);
+
+      const verified1 = await jwtVerify(accessToken1, jwkSet, { audience: resource.indicator });
+      expect(verified1.payload.scope).toBe(scope1.name);
+
+      const { access_token: accessToken2, scope: returnedScope2 } = await post({
+        organization_id: organization.id,
+        resource: resource.indicator,
+        scope: '',
+      });
+      expect(returnedScope2).toBe(undefined);
+
+      const verified2 = await jwtVerify(accessToken2, jwkSet, { audience: resource.indicator });
+      expect(verified2.payload.scope).toBe(undefined);
+    });
+  });
+});