diff --git a/apps/web/src/onboarding.ts b/apps/web/src/onboarding.ts
index c0029a63..22af8b30 100644
--- a/apps/web/src/onboarding.ts
+++ b/apps/web/src/onboarding.ts
@@ -430,13 +430,16 @@ async function postOnboarding(
   apiKey: string,
   baseURL?: string,
 ): Promise<{ readonly response: Response; readonly body: unknown }> {
+  // A key copied from a provider console often carries a trailing
+  // newline; sent verbatim the provider 401s a valid key (CL-6682).
+  const trimmedKey = apiKey.trim();
   const response = await fetch(`/api/onboarding/${path}`, {
     method: "POST",
     headers: { "content-type": "application/json" },
     body: JSON.stringify(
       baseURL !== undefined
-        ? { provider, apiKey, baseURL }
-        : { provider, apiKey },
+        ? { provider, apiKey: trimmedKey, baseURL }
+        : { provider, apiKey: trimmedKey },
     ),
   });
   const body: unknown = await response.json().catch(() => null);
diff --git a/apps/web/test/onboarding.test.tsx b/apps/web/test/onboarding.test.tsx
index 1749b9c8..41d99783 100644
--- a/apps/web/test/onboarding.test.tsx
+++ b/apps/web/test/onboarding.test.tsx
@@ -304,6 +304,27 @@ describe("submitCredential", () => {
     });
   });
 
+  // CL-6682: a key copied from a provider console often carries a
+  // trailing newline; sent verbatim the provider 401s a valid key.
+  test("strips leading/trailing whitespace from the pasted key", async () => {
+    let requestBody: unknown = null;
+    globalThis.fetch = (async (_url: string, init: RequestInit) => {
+      requestBody = JSON.parse((init as RequestInit).body as string);
+      return json({
+        kind: "ready",
+        tenantSlug: "ada-user1",
+        deployed: [],
+        pending: [],
+      });
+    }) as unknown as typeof fetch;
+
+    await submitCredential("anthropic", " sk-ant-good\n");
+    expect(requestBody).toEqual({
+      provider: "anthropic",
+      apiKey: "sk-ant-good",
+    });
+  });
+
   test("a bench whose agents are all live reports nothing pending", async () => {
     globalThis.fetch = (async () =>
       json({
diff --git a/packages/settings-ui/src/connections-api.ts b/packages/settings-ui/src/connections-api.ts
index 7762024e..b01a97e3 100644
--- a/packages/settings-ui/src/connections-api.ts
+++ b/packages/settings-ui/src/connections-api.ts
@@ -67,11 +67,13 @@ export function completeConnectorCredential(
   status: "active";
   modelGuidance?: string;
 }> {
+  // A key copied from a provider console often carries a trailing
+  // newline; sent verbatim the provider 401s a valid key (CL-6682).
   return request(
     `/api/tenants/${tenantId}/connections/${connectorId}/complete`,
     CompleteResult,
     "saving that connection",
-    { method: "POST", body: JSON.stringify({ apiKey }) },
+    { method: "POST", body: JSON.stringify({ apiKey: apiKey.trim() }) },
   );
 }
 
diff --git a/packages/settings-ui/test/connections-api.test.ts b/packages/settings-ui/test/connections-api.test.ts
index 7edfccda..db5772ab 100644
--- a/packages/settings-ui/test/connections-api.test.ts
+++ b/packages/settings-ui/test/connections-api.test.ts
@@ -94,6 +94,17 @@ describe("completeConnectorCredential", () => {
     expect(result).toEqual({ credentialId: "cred_1", status: "active" });
   });
 
+  // CL-6682: a key copied from a provider console often carries a
+  // trailing newline; sent verbatim it 401s a perfectly valid key.
+  test("strips leading/trailing whitespace from the pasted key", async () => {
+    const calls = stubFetch(() =>
+      json({ credentialId: "cred_1", status: "active" }, 200),
+    );
+    await completeConnectorCredential("tnt_1", "granola", " sk-good\n");
+    const body = JSON.parse(String(calls[0]?.init?.body));
+    expect(body).toEqual({ apiKey: "sk-good" });
+  });
+
   // CL-6377: connecting is the one round-trip — a rejected key throws
   // straight from this call, with no separate test step beforehand.
   test("throws ConnectionsApiError with the probe's own message on a 422", async () => {