diff --git a/agent/auxiliary_client.py b/agent/auxiliary_client.py
index 980813f123584..22bf9c165cf04 100644
--- a/agent/auxiliary_client.py
+++ b/agent/auxiliary_client.py
@@ -1133,6 +1133,29 @@ def _nous_min_key_ttl_seconds() -> int:
         return 1800
 
 
+def _scoped_key_env(name: str) -> str:
+    """Read a provider API key env var through the profile secret scope.
+
+    Auxiliary-client resolution runs both inside agent turns (secret scope
+    installed — its verdict is authoritative under multiplex, so a scoped
+    miss must NOT borrow another profile's process-env key) and on unscoped
+    startup/CLI probe paths, which keep the legacy ``os.environ`` read via
+    the ``UnscopedSecretError`` fallback (Slack pattern, #59739).
+    """
+    if not name:
+        return ""
+    try:
+        from agent.secret_scope import UnscopedSecretError, get_secret
+
+        try:
+            return (get_secret(name) or "").strip()
+        except UnscopedSecretError:
+            pass
+    except Exception:
+        pass
+    return (os.getenv(name) or "").strip()
+
+
 # ── Codex Responses → chat.completions adapter ─────────────────────────────
 # All auxiliary consumers call client.chat.completions.create(**kwargs) and
 # read response.choices[0].message.content. This adapter translates those
@@ -2470,7 +2493,7 @@ def _try_openrouter(explicit_api_key: str = None, model: str = None) -> Tuple[Op
         # the OPENROUTER_API_KEY env-var path rather than failing outright.
         logger.debug("Auxiliary client: OpenRouter pool exhausted, trying OPENROUTER_API_KEY")
 
-    or_key = explicit_api_key or os.getenv("OPENROUTER_API_KEY")
+    or_key = explicit_api_key or _scoped_key_env("OPENROUTER_API_KEY")
     if not or_key:
         _mark_provider_unhealthy("openrouter", ttl=60)
         return None, None
@@ -2487,7 +2510,7 @@ def _describe_openrouter_unavailable() -> str:
             return "OpenRouter credential pool has no usable entries (credentials may be exhausted)"
         if not _pool_runtime_api_key(entry):
             return "OpenRouter credential pool entry is missing a runtime API key"
-    if not str(os.getenv("OPENROUTER_API_KEY") or "").strip():
+    if not _scoped_key_env("OPENROUTER_API_KEY"):
         return "OPENROUTER_API_KEY not set"
     return "no usable OpenRouter credentials found"
 
@@ -3119,7 +3142,7 @@ def _resolve_custom_runtime() -> Tuple[Optional[str], Optional[str], Optional[st
 
     if not isinstance(runtime, dict):
         openai_base = os.getenv("OPENAI_BASE_URL", "").strip().rstrip("/")
-        openai_key = os.getenv("OPENAI_API_KEY", "").strip()
+        openai_key = _scoped_key_env("OPENAI_API_KEY")
         if not openai_base:
             return None, None, None
         runtime = {
@@ -5925,7 +5948,7 @@ def resolve_provider_client(
             custom_base = _to_openai_base_url(explicit_base_url).strip()
             custom_key = (
                 (explicit_api_key or "").strip()
-                or os.getenv("OPENAI_API_KEY", "").strip()
+                or _scoped_key_env("OPENAI_API_KEY")
                 or _read_main_api_key_if_same_host(custom_base)
                 or "no-key-required"  # local servers don't need auth
             )
@@ -6021,7 +6044,7 @@ def resolve_provider_client(
             custom_key = (custom_entry.get("api_key") or "").strip()
             custom_key_env = (custom_entry.get("key_env") or custom_entry.get("api_key_env") or "").strip()
             if not custom_key and custom_key_env:
-                custom_key = os.getenv(custom_key_env, "").strip()
+                custom_key = _scoped_key_env(custom_key_env)
             custom_key = custom_key or "no-key-required"
             if custom_key == "no-key-required":
                 logger.warning(
@@ -6843,7 +6866,7 @@ def auxiliary_max_tokens_param(value: int, *, model: Optional[str] = None) -> di
     misses the case where a custom base URL serves e.g. ``gpt-5.4``.
     """
     custom_base = _current_custom_base_url()
-    or_key = os.getenv("OPENROUTER_API_KEY")
+    or_key = _scoped_key_env("OPENROUTER_API_KEY")
     # Use max_completion_tokens for direct OpenAI-compatible providers that reject
     # max_tokens on newer GPT-4o/o-series/GPT-5-style models.
     _custom_host = base_url_hostname(custom_base) or ""
@@ -7304,7 +7327,7 @@ def _resolve_task_provider_model(
                 task_config.get("key_env") or task_config.get("api_key_env") or ""
             ).strip()
             if cfg_key_env:
-                cfg_api_key = os.getenv(cfg_key_env, "").strip() or None
+                cfg_api_key = _scoped_key_env(cfg_key_env) or None
         cfg_api_mode = str(task_config.get("api_mode", "")).strip() or None
 
     # 'auto' is a sentinel meaning "inherit from main runtime / auto-detect", not