diff --git a/codex-rs/app-server/tests/suite/v2/turn_start.rs b/codex-rs/app-server/tests/suite/v2/turn_start.rs
index 66f704f83..236d57a0e 100644
--- a/codex-rs/app-server/tests/suite/v2/turn_start.rs
+++ b/codex-rs/app-server/tests/suite/v2/turn_start.rs
@@ -1004,10 +1004,14 @@ async fn turn_start_rejects_invalid_permission_selection_before_starting_turn()
     assert!(
         err.error
             .message
-            .contains("invalid thread settings override")
+            .contains("`approval_policy = \"never\"` cannot be used"),
+        "unexpected error message: {}",
+        err.error.message
     );
     assert!(
-        err.error.message.contains("allowed set [ReadOnly]"),
+        err.error
+            .message
+            .contains("requirements do not allow `sandbox_mode = \"danger-full-access\"`"),
         "unexpected error message: {}",
         err.error.message
     );
diff --git a/codex-rs/core/src/config/config_tests.rs b/codex-rs/core/src/config/config_tests.rs
index 5fa284ad3..ccde74afe 100644
--- a/codex-rs/core/src/config/config_tests.rs
+++ b/codex-rs/core/src/config/config_tests.rs
@@ -9906,6 +9906,73 @@ async fn explicit_sandbox_mode_falls_back_when_disallowed_by_requirements() -> s
     Ok(())
 }
 
+#[tokio::test]
+async fn danger_full_access_with_never_is_rejected_when_requirements_force_read_only()
+-> std::io::Result<()> {
+    let codex_home = TempDir::new()?;
+    std::fs::write(
+        codex_home.path().join(CONFIG_TOML_FILE),
+        r#"approval_policy = "never"
+sandbox_mode = "danger-full-access"
+"#,
+    )?;
+
+    let err = ConfigBuilder::without_managed_config_for_tests()
+        .codex_home(codex_home.path().to_path_buf())
+        .fallback_cwd(Some(codex_home.path().to_path_buf()))
+        .cloud_requirements(CloudRequirementsLoader::new(async {
+            Ok(Some(codex_config::ConfigRequirementsToml {
+                allowed_sandbox_modes: Some(vec![codex_config::SandboxModeRequirement::ReadOnly]),
+                ..Default::default()
+            }))
+        }))
+        .build()
+        .await
+        .expect_err("requirements-constrained yolo should require sandbox approval");
+
+    assert_eq!(err.kind(), std::io::ErrorKind::InvalidInput);
+    assert_eq!(
+        err.to_string(),
+        "`approval_policy = \"never\"` cannot be used because requirements do not allow `sandbox_mode = \"danger-full-access\"`; Codex would fall back to read-only permissions with approvals disabled. Choose an `approval_policy` based on what you need, such as `on-request`, or choose an allowed sandbox mode."
+    );
+    Ok(())
+}
+
+#[tokio::test]
+async fn named_full_access_profile_with_never_is_rejected_when_requirements_force_read_only()
+-> std::io::Result<()> {
+    let codex_home = TempDir::new()?;
+    std::fs::write(
+        codex_home.path().join(CONFIG_TOML_FILE),
+        r#"approval_policy = "never"
+default_permissions = "dev"
+
+[permissions.dev.filesystem]
+":root" = "write"
+"#,
+    )?;
+
+    let err = ConfigBuilder::without_managed_config_for_tests()
+        .codex_home(codex_home.path().to_path_buf())
+        .fallback_cwd(Some(codex_home.path().to_path_buf()))
+        .cloud_requirements(CloudRequirementsLoader::new(async {
+            Ok(Some(codex_config::ConfigRequirementsToml {
+                allowed_sandbox_modes: Some(vec![codex_config::SandboxModeRequirement::ReadOnly]),
+                ..Default::default()
+            }))
+        }))
+        .build()
+        .await
+        .expect_err("requirements-constrained full-access profile should require sandbox approval");
+
+    assert_eq!(err.kind(), std::io::ErrorKind::InvalidInput);
+    assert_eq!(
+        err.to_string(),
+        "`approval_policy = \"never\"` cannot be used because requirements do not allow `sandbox_mode = \"danger-full-access\"`; Codex would fall back to read-only permissions with approvals disabled. Choose an `approval_policy` based on what you need, such as `on-request`, or choose an allowed sandbox mode."
+    );
+    Ok(())
+}
+
 #[tokio::test]
 async fn permission_profile_override_falls_back_when_disallowed_by_requirements()
 -> std::io::Result<()> {
diff --git a/codex-rs/core/src/config/mod.rs b/codex-rs/core/src/config/mod.rs
index 305ae3b75..9ff9434fb 100644
--- a/codex-rs/core/src/config/mod.rs
+++ b/codex-rs/core/src/config/mod.rs
@@ -3334,6 +3334,17 @@ impl Config {
             &mut constrained_permission_profile,
             &mut startup_warnings,
         )?;
+        if permission_profile_was_constrained
+            && sandbox_mode_requirement_for_permission_profile(&original_permission_profile)
+                == SandboxModeRequirement::DangerFullAccess
+            && constrained_permission_profile.get() == &PermissionProfile::read_only()
+            && constrained_approval_policy.value() == AskForApproval::Never
+        {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                "`approval_policy = \"never\"` cannot be used because requirements do not allow `sandbox_mode = \"danger-full-access\"`; Codex would fall back to read-only permissions with approvals disabled. Choose an `approval_policy` based on what you need, such as `on-request`, or choose an allowed sandbox mode.",
+            ));
+        }
         if permission_profile_was_constrained {
             // The selected profile no longer describes the effective
             // permissions after requirements forced a fallback.