diff --git a/CLAUDE.md b/CLAUDE.md
index fcadd08..2f47a67 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -126,6 +126,7 @@ token.companyId; // string | undefined
 token.internalUserId; // string | undefined
 token.isClientUser; // boolean
 token.isInternalUser; // boolean
+token.isProxying; // boolean — internal user previewing as a client (both IDs present)
 
 const client = token.ensureIsClient(); // ClientTokenPayload (throws if not client)
 const internal = token.ensureIsInternalUser(); // InternalUserTokenPayload (throws if not internal)
diff --git a/README.md b/README.md
index c26411c..cc4804b 100644
--- a/README.md
+++ b/README.md
@@ -358,8 +358,9 @@ token.tokenId; // string | undefined — present in some marketplace tokens
 token.baseUrl; // string | undefined — overrides the API base URL if set
 
 // Identity checks
-token.isClientUser; // true if clientId + companyId are present
+token.isClientUser; // true if clientId is present
 token.isInternalUser; // true if internalUserId is present
+token.isProxying; // true if BOTH are present — internal user previewing as a client via CRM
 
 // Throwing guards — return narrowed payload type or throw AssemblyUnauthorizedError
 const clientPayload = token.ensureIsClient(); // ClientTokenPayload
diff --git a/src/token/assembly-token.ts b/src/token/assembly-token.ts
index 8e9942c..92d6611 100644
--- a/src/token/assembly-token.ts
+++ b/src/token/assembly-token.ts
@@ -117,6 +117,15 @@ export class AssemblyToken {
     return this.payload.internalUserId !== undefined;
   }
 
+  /**
+   * `true` when an internal user is proxying as a client (CRM "preview as client"):
+   * both `internalUserId` and `clientId` are present. Both `isClientUser` and
+   * `isInternalUser` are also `true` in this case — branch on this getter first.
+   */
+  get isProxying(): boolean {
+    return this.payload.internalUserId !== undefined && this.payload.clientId !== undefined;
+  }
+
   /**
    * Assert that the token belongs to a client user and return the narrowed payload.
    * @throws {AssemblyUnauthorizedError} If the token does not represent a client user.
diff --git a/tests/fixtures/tokens.ts b/tests/fixtures/tokens.ts
index b2fd1f4..2a33155 100644
--- a/tests/fixtures/tokens.ts
+++ b/tests/fixtures/tokens.ts
@@ -103,3 +103,13 @@ if (paddedWsId === undefined) {
   throw new Error("workspaceId missing in padded payload");
 }
 export const BLOCK_ALIGNED_WORKSPACE_ID: string = paddedWsId;
+
+// ---------------------------------------------------------------------------
+// Proxy token: internal user acting as a client via CRM
+// ---------------------------------------------------------------------------
+export const PROXY_TOKEN: string = encryptPayload(TEST_API_KEY, {
+  clientId: TEST_CLIENT_ID,
+  companyId: TEST_COMPANY_ID,
+  internalUserId: TEST_INTERNAL_USER_ID,
+  workspaceId: TEST_WORKSPACE_ID,
+});
diff --git a/tests/token.test.ts b/tests/token.test.ts
index f763b4b..f7bf916 100644
--- a/tests/token.test.ts
+++ b/tests/token.test.ts
@@ -13,6 +13,7 @@ import {
   BLOCK_ALIGNED_WORKSPACE_ID,
   CLIENT_TOKEN,
   INTERNAL_USER_TOKEN,
+  PROXY_TOKEN,
   TEST_API_KEY,
   TEST_BASE_URL,
   TEST_CLIENT_ID,
@@ -192,6 +193,22 @@ describe("AssemblyToken getters", () => {
 // Identity checks
 // ---------------------------------------------------------------------------
 describe("AssemblyToken identity checks", () => {
+  it("proxy token (internalUserId + clientId) is flagged as proxying", () => {
+    const t = new AssemblyToken({ apiKey: TEST_API_KEY, token: PROXY_TOKEN });
+    expect(t.isProxying).toBe(true);
+    expect(t.isClientUser).toBe(true);
+    expect(t.isInternalUser).toBe(true);
+    expect(t.ensureIsClient().clientId).toBe(TEST_CLIENT_ID);
+    expect(t.ensureIsInternalUser().internalUserId).toBe(TEST_INTERNAL_USER_ID);
+  });
+
+  it("isProxying is false for single-identity tokens", () => {
+    expect(new AssemblyToken({ apiKey: TEST_API_KEY, token: CLIENT_TOKEN }).isProxying).toBe(false);
+    expect(new AssemblyToken({ apiKey: TEST_API_KEY, token: INTERNAL_USER_TOKEN }).isProxying).toBe(
+      false,
+    );
+  });
+
   it("isClientUser is true for client tokens", () => {
     const t = new AssemblyToken({ apiKey: TEST_API_KEY, token: CLIENT_TOKEN });
     expect(t.isClientUser).toBe(true);