diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index db0aea637f..5f4ee4122a 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -68,6 +68,8 @@ This installs a `commit-msg` hook that adds the sign-off trailer automatically f
 
 We review as capacity allows — focused PRs that follow this guide move fastest.
 
+Hosted community vs Buzz identity questions (Builderlab email vs nsec) are covered in [docs/hosted-community-identity.md](docs/hosted-community-identity.md).
+
 ---
 
 ## Setting Up the Development Environment
diff --git a/desktop/src/features/communities/ui/HostedCommunityOnboarding.tsx b/desktop/src/features/communities/ui/HostedCommunityOnboarding.tsx
index 1152cd8fec..a214586e30 100644
--- a/desktop/src/features/communities/ui/HostedCommunityOnboarding.tsx
+++ b/desktop/src/features/communities/ui/HostedCommunityOnboarding.tsx
@@ -517,15 +517,26 @@ export function HostedCommunityOnboarding({
               </DialogTitle>
               <DialogDescription className="mt-2 text-sm leading-6 text-foreground">
                 Your Builderlab account
-                {auth.email ? ` (${auth.email})` : ""} is ready. Connect this
-                device’s Buzz identity to finish setup. Your private key stays
-                on this device.
+                {auth.email ? ` (${auth.email})` : ""} is ready. Connect the
+                Buzz identity already on this device to finish setup. Your
+                private key stays on this device — Builderlab never receives
+                it.
               </DialogDescription>
+              <p
+                className="mt-4 w-full text-left text-xs leading-5 text-foreground/55"
+                data-testid="hosted-connect-identity-hint"
+              >
+                Need a different Buzz private key for this email? Close this
+                dialog, open Settings → Account, sign out of the current
+                identity (back up the nsec first), then import or create a new
+                key and return here to connect.
+              </p>
               {errorBox ? <div className="mt-5 w-full">{errorBox}</div> : null}
               <Button
                 className={`mt-6 ${MODAL_PRIMARY_ACTION_CLASS}`}
                 disabled={busy}
                 onClick={() => void connectIdentity()}
+                data-testid="hosted-connect-identity"
               >
                 {busy ? (
                   <LoaderCircle className="h-4 w-4 animate-spin" />
@@ -539,8 +550,10 @@ export function HostedCommunityOnboarding({
                 This account uses a different Buzz identity
               </DialogTitle>
               <DialogDescription className="mt-2 text-sm leading-6 text-foreground">
-                This account is connected to another Buzz identity. Reconnect
-                this device, or sign out to use a different email.
+                This Builderlab account is already linked to a different Buzz
+                identity. Use this device&apos;s key (rebinds the account), sign
+                in with a different email, or switch the local Buzz identity
+                under Settings → Account before reconnecting.
               </DialogDescription>
               <p className="mt-4 w-full break-all rounded-xl bg-[rgb(var(--buzz-hosted-community-identity-bg)/0.5)] px-4 py-3 text-left font-mono text-xs text-foreground">
                 Account: {identity.npub ?? boundPubkey}
diff --git a/desktop/src/features/settings/ui/HostedCommunitiesSettingsCard.tsx b/desktop/src/features/settings/ui/HostedCommunitiesSettingsCard.tsx
index 4eebddaea9..fa031a96f1 100644
--- a/desktop/src/features/settings/ui/HostedCommunitiesSettingsCard.tsx
+++ b/desktop/src/features/settings/ui/HostedCommunitiesSettingsCard.tsx
@@ -482,7 +482,9 @@ export function HostedCommunitiesSettingsCard() {
                 This Builderlab account isn&apos;t linked to a Buzz identity
                 yet. Connect this device&apos;s key to create and own
                 communities under it — Buzz signs a one-time challenge locally,
-                so your private key never leaves Desktop.
+                so your private key never leaves Desktop. To link a different
+                nsec, switch identities under Account (sign out, then import or
+                create) before connecting.
               </p>
               <Button
                 className="mt-4"
diff --git a/desktop/tests/e2e/onboarding.spec.ts b/desktop/tests/e2e/onboarding.spec.ts
index e5217da3d3..66d90121e2 100644
--- a/desktop/tests/e2e/onboarding.spec.ts
+++ b/desktop/tests/e2e/onboarding.spec.ts
@@ -1232,7 +1232,10 @@ test("first-community owner can create and connect a hosted community", async ({
   await expect(
     page.getByRole("heading", { name: "Finish connecting Buzz" }),
   ).toBeVisible();
-  await page.getByRole("button", { name: "Connect and continue" }).click();
+  await expect(page.getByTestId("hosted-connect-identity-hint")).toContainText(
+    "different Buzz private key",
+  );
+  await page.getByTestId("hosted-connect-identity").click();
   const createSurface = page.getByTestId("hosted-community-create-surface");
   const surfaceBoxBeforeFeedback = await createSurface.boundingBox();
   const communityNameInput = page.getByTestId("hosted-community-address-input");
diff --git a/docs/hosted-community-identity.md b/docs/hosted-community-identity.md
new file mode 100644
index 0000000000..9957fac863
--- /dev/null
+++ b/docs/hosted-community-identity.md
@@ -0,0 +1,34 @@
+# Hosted communities and Buzz identity
+
+Builderlab (hosted community) accounts are **email logins**. Buzz identities
+are **Nostr keypairs** stored in the OS keyring on each device. Connecting
+binds the current device key to that Builderlab account — it does **not**
+generate a second identity for the email.
+
+## Common confusion (#3880)
+
+Symptom: after signing into Builderlab with a work email, the app asks to
+"Finish connecting Buzz" / "Connect this device's Buzz identity," and there
+is no "create a new private key" button on that screen.
+
+That is intentional. The bind step always uses the key already on the device.
+
+### Want a different key for this Builderlab email?
+
+1. Back up the current nsec (Settings → Account → private key backup).
+2. Sign out of the Buzz identity (Settings → Account → Sign out).
+3. Import an nsec or create a fresh identity during onboarding.
+4. Return to hosted community setup and connect again.
+
+### Want the same Buzz identity on another machine?
+
+Import the same nsec on that machine (do not generate a new key), then connect
+the Builderlab account. Binding a different local key to an account that is
+already linked shows the mismatch dialog ("This account uses a different Buzz
+identity").
+
+### Want a different Builderlab email with the same key?
+
+Sign out of Builderlab (hosted community flow / settings), sign in with the
+other email, then connect — the local Buzz key can be linked to multiple
+Builderlab accounts over time, but each account stores one linked npub.