diff --git a/src/cli/system-credential-store.ts b/src/cli/system-credential-store.ts
index d0ea8063..364fac79 100644
--- a/src/cli/system-credential-store.ts
+++ b/src/cli/system-credential-store.ts
@@ -167,24 +167,41 @@ function macOsCredentialStore(
         label: "artifact-server-cli-profile",
       })),
     ),
+    // `security` takes the `-w` value only from argv or a terminal prompt,
+    // never from stdin, so the piped secret was stored as an empty password
+    // and every later read came back blank. `security -i` reads whole
+    // commands from stdin, which keeps the secret out of argv.
     write: (account, secret) => runCredentialProcess({
-      arguments: [
+      arguments: ["-i"],
+      environment,
+      executable: "/usr/bin/security",
+      input: [
         "add-generic-password",
         "-a",
-        account,
+        quoteForSecurity(account),
         "-s",
-        credentialService,
+        quoteForSecurity(credentialService),
         "-U",
         "-w",
-      ],
-      environment,
-      executable: "/usr/bin/security",
-      input: `${Redacted.value(secret)}\n`,
+        quoteForSecurity(Redacted.value(secret)),
+      ].join(" ") + "\n",
       operation: "write",
     }).pipe(Effect.asVoid),
   };
 }
 
+/**
+ * Quote one argument for `security -i`. Stored values are JSON of base64url
+ * or hex tokens and UUID accounts, so a single quote or newline never occurs;
+ * refuse rather than guess at the interactive tokenizer's escaping.
+ */
+function quoteForSecurity(value: string): string {
+  if (value.includes("'") || value.includes("\n")) {
+    throw new Error("A credential value cannot contain a single quote or newline.");
+  }
+  return `'${value}'`;
+}
+
 function linuxCredentialStore(
   environment: NodeJS.ProcessEnv,
 ): CliCredentialStoreOperations {