Bypass review for always-allow MCP tools in auto-review (#20069)

## Why

When an MCP or app tool is configured with approval mode `approve`
(always allow), users expect that decision to be authoritative. In
guardian auto-review mode, ARC could still return `ask-user`, which then
routed the approval question into guardian with the ARC reason as
context. That meant a tool explicitly configured as always allowed still
went through both safety monitors before running.

This change keeps the existing ARC behavior for non-auto-review
sessions, but avoids the ARC-to-guardian sequence when
`approvals_reviewer = auto_review` and the tool approval mode is
`approve`.

## What changed

- Short-circuit MCP tool approval handling when `approval_mode ==
approve` and `approvals_reviewer == auto_review`.
- Updated the MCP approval regression test so the auto-review case
asserts neither ARC nor guardian is called.
- Preserved existing tests that verify ARC can still block always-allow
MCP tools outside guardian auto-review mode.

## Verification

- `cargo test -p codex-core --lib mcp_tool_call`

codex-rs/codex-mcp/src/mcp/mod.rs

@@ -20,6 +20,8 @@ use async_channel::unbounded;
 use codex_config::Constrained;
 use codex_config::McpServerConfig;
 use codex_config::McpServerTransportConfig;
+use codex_config::types::AppToolApproval;
+use codex_config::types::ApprovalsReviewer;
 use codex_config::types::OAuthCredentialsStoreMode;
 use codex_login::CodexAuth;
 use codex_plugin::PluginCapabilitySummary;
@@ -67,7 +69,17 @@ pub fn qualified_mcp_tool_name_prefix(server_name: &str) -> String {
 pub fn mcp_permission_prompt_is_auto_approved(
     approval_policy: AskForApproval,
     permission_profile: &PermissionProfile,
+    context: McpPermissionPromptAutoApproveContext,
 ) -> bool {
+    if matches!(
+        approval_policy,
+        AskForApproval::OnRequest | AskForApproval::Granular(_)
+    ) && context.approvals_reviewer == Some(ApprovalsReviewer::AutoReview)
+        && context.tool_approval_mode == Some(AppToolApproval::Approve)
+    {
+        return true;
+    }
+
     if approval_policy != AskForApproval::Never {
         return false;
     }
@@ -80,6 +92,12 @@ pub fn mcp_permission_prompt_is_auto_approved(
     }
 }
 
+#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
+pub struct McpPermissionPromptAutoApproveContext {
+    pub approvals_reviewer: Option<ApprovalsReviewer>,
+    pub tool_approval_mode: Option<AppToolApproval>,
+}
+
 /// MCP runtime settings derived from `codex_core::config::Config`.
 ///
 /// This struct should contain only long-lived configuration values that the

codex-rs/codex-mcp/src/mcp/mod_tests.rs

@@ -1,5 +1,7 @@
 use super::*;
 use codex_config::Constrained;
+use codex_config::types::AppToolApproval;
+use codex_config::types::ApprovalsReviewer;
 use codex_login::CodexAuth;
 use codex_plugin::AppConnectorId;
 use codex_plugin::PluginCapabilitySummary;
@@ -7,6 +9,7 @@ use codex_protocol::models::ManagedFileSystemPermissions;
 use codex_protocol::models::PermissionProfile;
 use codex_protocol::permissions::NetworkSandboxPolicy;
 use codex_protocol::protocol::AskForApproval;
+use codex_protocol::protocol::GranularApprovalConfig;
 use pretty_assertions::assert_eq;
 use std::collections::HashMap;
 use std::path::PathBuf;
@@ -45,6 +48,7 @@ fn mcp_prompt_auto_approval_honors_unrestricted_managed_profiles() {
             file_system: ManagedFileSystemPermissions::Unrestricted,
             network: NetworkSandboxPolicy::Enabled,
         },
+        McpPermissionPromptAutoApproveContext::default(),
     ));
     assert!(mcp_permission_prompt_is_auto_approved(
         AskForApproval::Never,
@@ -52,10 +56,12 @@ fn mcp_prompt_auto_approval_honors_unrestricted_managed_profiles() {
             file_system: ManagedFileSystemPermissions::Unrestricted,
             network: NetworkSandboxPolicy::Restricted,
         },
+        McpPermissionPromptAutoApproveContext::default(),
     ));
     assert!(!mcp_permission_prompt_is_auto_approved(
         AskForApproval::Never,
         &PermissionProfile::read_only(),
+        McpPermissionPromptAutoApproveContext::default(),
     ));
     assert!(!mcp_permission_prompt_is_auto_approved(
         AskForApproval::OnRequest,
@@ -63,6 +69,57 @@ fn mcp_prompt_auto_approval_honors_unrestricted_managed_profiles() {
             file_system: ManagedFileSystemPermissions::Unrestricted,
             network: NetworkSandboxPolicy::Enabled,
         },
+        McpPermissionPromptAutoApproveContext::default(),
+    ));
+}
+
+#[test]
+fn mcp_prompt_auto_approval_honors_auto_review_approved_tools() {
+    assert!(mcp_permission_prompt_is_auto_approved(
+        AskForApproval::OnRequest,
+        &PermissionProfile::read_only(),
+        McpPermissionPromptAutoApproveContext {
+            approvals_reviewer: Some(ApprovalsReviewer::AutoReview),
+            tool_approval_mode: Some(AppToolApproval::Approve),
+        },
+    ));
+    assert!(mcp_permission_prompt_is_auto_approved(
+        AskForApproval::Granular(GranularApprovalConfig {
+            sandbox_approval: true,
+            rules: true,
+            skill_approval: true,
+            request_permissions: true,
+            mcp_elicitations: true,
+        }),
+        &PermissionProfile::read_only(),
+        McpPermissionPromptAutoApproveContext {
+            approvals_reviewer: Some(ApprovalsReviewer::AutoReview),
+            tool_approval_mode: Some(AppToolApproval::Approve),
+        },
+    ));
+    assert!(!mcp_permission_prompt_is_auto_approved(
+        AskForApproval::OnRequest,
+        &PermissionProfile::read_only(),
+        McpPermissionPromptAutoApproveContext {
+            approvals_reviewer: Some(ApprovalsReviewer::User),
+            tool_approval_mode: Some(AppToolApproval::Approve),
+        },
+    ));
+    assert!(!mcp_permission_prompt_is_auto_approved(
+        AskForApproval::OnFailure,
+        &PermissionProfile::read_only(),
+        McpPermissionPromptAutoApproveContext {
+            approvals_reviewer: Some(ApprovalsReviewer::AutoReview),
+            tool_approval_mode: Some(AppToolApproval::Approve),
+        },
+    ));
+    assert!(!mcp_permission_prompt_is_auto_approved(
+        AskForApproval::UnlessTrusted,
+        &PermissionProfile::read_only(),
+        McpPermissionPromptAutoApproveContext {
+            approvals_reviewer: Some(ApprovalsReviewer::AutoReview),
+            tool_approval_mode: Some(AppToolApproval::Approve),
+        },
     ));
 }