diff --git a/strix/interface/scan_setup.py b/strix/interface/scan_setup.py
index 7b22250a..838a1d1e 100644
--- a/strix/interface/scan_setup.py
+++ b/strix/interface/scan_setup.py
@@ -66,14 +66,26 @@ def _first_non_ascii(value: str) -> tuple[int, str] | None:
     return None
 
 
+def _header_candidates(
+    prefix: str, api_key: str | None, extra_headers: dict[str, str] | None
+) -> list[tuple[str, str]]:
+    candidates: list[tuple[str, str]] = []
+    if api_key:
+        candidates.append((f"{prefix}LLM_API_KEY", api_key))
+    for header, value in (extra_headers or {}).items():
+        candidates.append((f"{prefix}LLM_EXTRA_HEADERS header name {header!r}", header))
+        candidates.append((f"{prefix}LLM_EXTRA_HEADERS value for {header!r}", value))
+    return candidates
+
+
 def check_header_safe_credentials(settings: Settings) -> None:
     llm = settings.llm
+    dedupe = settings.dedupe
     candidates: list[tuple[str, str]] = []
-    if llm.api_key:
-        candidates.append(("LLM_API_KEY", llm.api_key))
-    for header, value in (llm.extra_headers or {}).items():
-        candidates.append((f"LLM_EXTRA_HEADERS header name {header!r}", header))
-        candidates.append((f"LLM_EXTRA_HEADERS value for {header!r}", value))
+    if not codex.subscription_model(llm.model):
+        candidates += _header_candidates("", llm.api_key, llm.extra_headers)
+    if dedupe.model and not codex.subscription_model(dedupe.model):
+        candidates += _header_candidates("DEDUPE_", dedupe.api_key, dedupe.extra_headers)
     for setting, value in candidates:
         found = _first_non_ascii(value)
         if found is None:
diff --git a/tests/test_preflight_header_values.py b/tests/test_preflight_header_values.py
index 4e99a993..21c0c531 100644
--- a/tests/test_preflight_header_values.py
+++ b/tests/test_preflight_header_values.py
@@ -8,7 +8,16 @@ from strix.config import Settings
 from strix.interface.scan_setup import check_header_safe_credentials, preflight_model_connection
 
 
-_ENV_KEYS = ("LLM_API_KEY", "OPENAI_API_KEY", "LLM_EXTRA_HEADERS", "LLM_API_BASE", "STRIX_LLM")
+_ENV_KEYS = (
+    "LLM_API_KEY",
+    "OPENAI_API_KEY",
+    "LLM_EXTRA_HEADERS",
+    "LLM_API_BASE",
+    "STRIX_LLM",
+    "STRIX_DEDUPE_MODEL",
+    "DEDUPE_LLM_API_KEY",
+    "DEDUPE_LLM_EXTRA_HEADERS",
+)
 
 
 @pytest.fixture(autouse=True)
@@ -67,6 +76,32 @@ def test_extra_header_value_is_checked(monkeypatch: pytest.MonkeyPatch) -> None:
         check_header_safe_credentials(settings)
 
 
+def test_subscription_model_ignores_an_unused_main_key(monkeypatch: pytest.MonkeyPatch) -> None:
+    settings = _settings(monkeypatch, STRIX_LLM="chatgpt/gpt-5", LLM_API_KEY="sk-abc\u201d")
+
+    check_header_safe_credentials(settings)
+
+
+def test_dedupe_key_is_checked_when_a_dedupe_model_is_set(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    settings = _settings(
+        monkeypatch,
+        LLM_API_KEY="sk-plain",
+        STRIX_DEDUPE_MODEL="openai/gpt-4o-mini",
+        DEDUPE_LLM_API_KEY="sk-dedupe\u00a0",
+    )
+
+    with pytest.raises(ValueError, match=r"DEDUPE_LLM_API_KEY.*U\+00A0"):
+        check_header_safe_credentials(settings)
+
+
+def test_dedupe_key_is_ignored_without_a_dedupe_model(monkeypatch: pytest.MonkeyPatch) -> None:
+    settings = _settings(monkeypatch, LLM_API_KEY="sk-plain", DEDUPE_LLM_API_KEY="sk-dedupe\u00a0")
+
+    check_header_safe_credentials(settings)
+
+
 def test_preflight_rejects_the_key_before_any_request(monkeypatch: pytest.MonkeyPatch) -> None:
     settings = _settings(
         monkeypatch,