Rebrand approvals reviewer config to auto-review (#18504)

### Why

Auto-review is the user-facing name for the approvals reviewer, but the
config/API value still exposed the old `guardian_subagent` name. That
made new configs and generated schemas point users at Guardian
terminology even though the intended product surface is Auto-review.

This PR updates the external `approvals_reviewer` value while preserving
compatibility for existing configs and clients.

### What changed

- Makes `auto_review` the canonical serialized value for
`approvals_reviewer`.
- Keeps `guardian_subagent` accepted as a legacy alias.
- Keeps `user` accepted and serialized as `user`.
- Updates generated config and app-server schemas so
`approvals_reviewer` includes:
  - `user`
  - `auto_review`
  - `guardian_subagent`
- Updates app-server README docs for the reviewer value.
- Updates analytics and config requirements tests for the canonical
auto_review value.


### Compatibility

Existing configs and API payloads using:

```toml
approvals_reviewer = "guardian_subagent"
```

continue to load and map to the Auto-review reviewer behavior. 

New serialization emits: 
```toml
approvals_reviewer = "auto_review" 
```

This PR intentionally does not rename the [features].guardian_approval
key or broad internal Guardian symbols. Those are split out for a
follow-up PR to keep this migration small and avoid touching large
TUI/internal surfaces.

**Verification**
cargo test -p codex-protocol
approvals_reviewer_serializes_auto_review_and_accepts_legacy_guardian_subagent
cargo test -p codex-app-server-protocol
approvals_reviewer_serializes_auto_review_and_accepts_legacy_guardian_subagent

codex-rs/analytics/src/analytics_client_tests.rs

@@ -1334,7 +1334,7 @@ fn subagent_thread_started_other_serializes_explicit_parent_thread_id() {
         },
     ));
 
-    let payload = serde_json::to_value(&event).expect("serialize guardian subagent event");
+    let payload = serde_json::to_value(&event).expect("serialize auto-review subagent event");
     assert_eq!(payload["event_params"]["subagent_source"], "guardian");
     assert_eq!(
         payload["event_params"]["parent_thread_id"],
@@ -1758,7 +1758,7 @@ fn turn_event_serializes_expected_shape() {
             reasoning_summary: Some("detailed".to_string()),
             service_tier: "flex".to_string(),
             approval_policy: "on-request".to_string(),
-            approvals_reviewer: "guardian_subagent".to_string(),
+            approvals_reviewer: "auto_review".to_string(),
             sandbox_network_access: true,
             collaboration_mode: Some("plan"),
             personality: Some("pragmatic".to_string()),
@@ -1819,7 +1819,7 @@ fn turn_event_serializes_expected_shape() {
                 "reasoning_summary": "detailed",
                 "service_tier": "flex",
                 "approval_policy": "on-request",
-                "approvals_reviewer": "guardian_subagent",
+                "approvals_reviewer": "auto_review",
                 "sandbox_network_access": true,
                 "collaboration_mode": "plan",
                 "personality": "pragmatic",

codex-rs/app-server-protocol/schema/json/ClientRequest.json

@@ -13,9 +13,10 @@
       "type": "string"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -5728,9 +5728,10 @@
         "type": "object"
       },
       "ApprovalsReviewer": {
-        "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+        "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
         "enum": [
           "user",
+          "auto_review",
           "guardian_subagent"
         ],
         "type": "string"

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json

@@ -605,9 +605,10 @@
       "type": "object"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/v2/ConfigReadResponse.json

@@ -97,9 +97,10 @@
       "type": "object"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/v2/ConfigRequirementsReadResponse.json

@@ -2,9 +2,10 @@
   "$schema": "http://json-schema.org/draft-07/schema#",
   "definitions": {
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/v2/ThreadForkParams.json

@@ -6,9 +6,10 @@
       "type": "string"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/v2/ThreadForkResponse.json

@@ -9,9 +9,10 @@
       "type": "string"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json

@@ -6,9 +6,10 @@
       "type": "string"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/v2/ThreadResumeResponse.json

@@ -9,9 +9,10 @@
       "type": "string"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/v2/ThreadStartParams.json

@@ -6,9 +6,10 @@
       "type": "string"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/v2/ThreadStartResponse.json

@@ -9,9 +9,10 @@
       "type": "string"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/json/v2/TurnStartParams.json

@@ -6,9 +6,10 @@
       "type": "string"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/app-server-protocol/schema/typescript/v2/ApprovalsReviewer.ts

@@ -5,8 +5,8 @@
 /**
  * Configures who approval requests are routed to for review. Examples
  * include sandbox escapes, blocked network access, MCP approval prompts, and
- * ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully
+ * ARC escalations. Defaults to `user`. `auto_review` uses a carefully
  * prompted subagent to gather relevant context and apply a risk-based
  * decision framework before approving or denying the request.
  */
-export type ApprovalsReviewer = "user" | "guardian_subagent";
+export type ApprovalsReviewer = "user" | "auto_review" | "guardian_subagent";

codex-rs/app-server-protocol/src/protocol/v2.rs

@@ -101,6 +101,11 @@ use codex_protocol::user_input::TextElement as CoreTextElement;
 use codex_protocol::user_input::UserInput as CoreUserInput;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use schemars::JsonSchema;
+use schemars::r#gen::SchemaGenerator;
+use schemars::schema::InstanceType;
+use schemars::schema::Metadata;
+use schemars::schema::Schema;
+use schemars::schema::SchemaObject;
 use serde::Deserialize;
 use serde::Serialize;
 use serde_json::Value as JsonValue;
@@ -304,19 +309,54 @@ impl From<CoreAskForApproval> for AskForApproval {
     }
 }
 
-#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, JsonSchema, TS)]
-#[serde(rename_all = "snake_case")]
-#[ts(rename_all = "snake_case", export_to = "v2/")]
+#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, TS)]
+#[ts(
+    type = r#""user" | "auto_review" | "guardian_subagent""#,
+    export_to = "v2/"
+)]
 /// Configures who approval requests are routed to for review. Examples
 /// include sandbox escapes, blocked network access, MCP approval prompts, and
-/// ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully
+/// ARC escalations. Defaults to `user`. `auto_review` uses a carefully
 /// prompted subagent to gather relevant context and apply a risk-based
 /// decision framework before approving or denying the request.
 pub enum ApprovalsReviewer {
+    #[serde(rename = "user")]
     User,
+    #[serde(rename = "auto_review", alias = "guardian_subagent")]
     GuardianSubagent,
 }
 
+impl JsonSchema for ApprovalsReviewer {
+    fn schema_name() -> String {
+        "ApprovalsReviewer".to_string()
+    }
+
+    fn json_schema(_generator: &mut SchemaGenerator) -> Schema {
+        string_enum_schema_with_description(
+            &["user", "auto_review", "guardian_subagent"],
+            "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
+        )
+    }
+}
+
+fn string_enum_schema_with_description(values: &[&str], description: &str) -> Schema {
+    let mut schema = SchemaObject {
+        instance_type: Some(InstanceType::String.into()),
+        metadata: Some(Box::new(Metadata {
+            description: Some(description.to_string()),
+            ..Default::default()
+        })),
+        ..Default::default()
+    };
+    schema.enum_values = Some(
+        values
+            .iter()
+            .map(|value| JsonValue::String((*value).to_string()))
+            .collect(),
+    );
+    Schema::Object(schema)
+}
+
 impl ApprovalsReviewer {
     pub fn to_core(self) -> CoreApprovalsReviewer {
         match self {
@@ -7346,6 +7386,31 @@ mod tests {
         absolute_path("readable")
     }
 
+    #[test]
+    fn approvals_reviewer_serializes_auto_review_and_accepts_legacy_guardian_subagent() {
+        assert_eq!(
+            serde_json::to_string(&ApprovalsReviewer::User).expect("serialize reviewer"),
+            "\"user\""
+        );
+        assert_eq!(
+            serde_json::to_string(&ApprovalsReviewer::GuardianSubagent)
+                .expect("serialize reviewer"),
+            "\"auto_review\""
+        );
+
+        for value in ["user", "auto_review", "guardian_subagent"] {
+            let json = format!("\"{value}\"");
+            let reviewer: ApprovalsReviewer =
+                serde_json::from_str(&json).expect("deserialize reviewer");
+            let expected = if value == "user" {
+                ApprovalsReviewer::User
+            } else {
+                ApprovalsReviewer::GuardianSubagent
+            };
+            assert_eq!(expected, reviewer);
+        }
+    }
+
     #[test]
     fn thread_list_params_accepts_single_cwd() {
         let params = serde_json::from_value::<ThreadListParams>(json!({

codex-rs/app-server/README.md

@@ -529,7 +529,7 @@ You can optionally specify config overrides on the new turn. If specified, these
 `approvalsReviewer` accepts:
 
 - `"user"` — default. Review approval requests directly in the client.
-- `"guardian_subagent"` — route approval requests to a carefully prompted subagent, which gathers relevant context and applies a risk-based decision framework before approving or denying the request.
+- `"auto_review"` — route approval requests to a carefully prompted subagent, which gathers relevant context and applies a risk-based decision framework before approving or denying the request. The legacy value `"guardian_subagent"` is still accepted for compatibility.
 
 ```json
 { "method": "turn/start", "id": 30, "params": {

codex-rs/config/src/config_requirements.rs

@@ -1649,7 +1649,7 @@ allowed_approvals_reviewers = ["user"]
         let source: ConfigRequirementsToml = from_str(
             r#"
                 allowed_approval_policies = ["on-request"]
-                allowed_approvals_reviewers = ["guardian_subagent"]
+                allowed_approvals_reviewers = ["auto_review"]
                 allowed_sandbox_modes = ["read-only"]
             "#,
         )?;
@@ -1730,7 +1730,7 @@ allowed_approvals_reviewers = ["user"]
         let source: ConfigRequirementsToml = from_str(
             r#"
                 allowed_approval_policies = ["on-request"]
-                allowed_approvals_reviewers = ["guardian_subagent"]
+                allowed_approvals_reviewers = ["auto_review"]
                 allowed_sandbox_modes = ["read-only"]
                 allowed_web_search_modes = ["cached"]
                 enforce_residency = "us"
@@ -1830,7 +1830,7 @@ allowed_approvals_reviewers = ["user"]
     #[test]
     fn deserialize_allowed_approvals_reviewers() -> Result<()> {
         let toml_str = r#"
-            allowed_approvals_reviewers = ["guardian_subagent", "user"]
+            allowed_approvals_reviewers = ["auto_review", "user"]
         "#;
         let config: ConfigRequirementsToml = from_str(toml_str)?;
         let requirements: ConfigRequirements = with_unknown_source(config).try_into()?;
@@ -1856,6 +1856,22 @@ allowed_approvals_reviewers = ["user"]
         Ok(())
     }
 
+    #[test]
+    fn deserialize_legacy_allowed_approvals_reviewer() -> Result<()> {
+        let toml_str = r#"
+            allowed_approvals_reviewers = ["guardian_subagent", "user"]
+        "#;
+        let config: ConfigRequirementsToml = from_str(toml_str)?;
+        let requirements: ConfigRequirements = with_unknown_source(config).try_into()?;
+
+        assert_eq!(
+            requirements.approvals_reviewer.value(),
+            ApprovalsReviewer::GuardianSubagent
+        );
+
+        Ok(())
+    }
+
     #[test]
     fn empty_allowed_approvals_reviewers_is_rejected() -> Result<()> {
         let toml_str = r#"

codex-rs/core/config.schema.json

@@ -169,9 +169,10 @@
       "type": "object"
     },
     "ApprovalsReviewer": {
-      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request.",
+      "description": "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
       "enum": [
         "user",
+        "auto_review",
         "guardian_subagent"
       ],
       "type": "string"

codex-rs/core/src/config_loader/mod.rs

@@ -1025,8 +1025,8 @@ async fn load_project_layers(
 ///
 /// If present, re-interpret `managed_config.toml` as a `requirements.toml`
 /// where each specified field is treated as a constraint. Most fields allow
-/// only the specified value. `approvals_reviewer = "guardian_subagent"` also
-/// allows `user` so people can opt out of the guardian reviewer.
+/// only the specified value. `approvals_reviewer = "auto_review"` also allows
+/// `user` so people can opt out of the auto-reviewer.
 #[derive(Deserialize, Debug, Clone, Default, PartialEq)]
 struct LegacyManagedConfigToml {
     approval_policy: Option<AskForApproval>,
@@ -1145,7 +1145,7 @@ foo = "xyzzy"
             requirements.allowed_approvals_reviewers,
             Some(vec![
                 ApprovalsReviewer::GuardianSubagent,
-                ApprovalsReviewer::User
+                ApprovalsReviewer::User,
             ])
         );
     }

codex-rs/protocol/src/config_types.rs

@@ -1,7 +1,13 @@
 use codex_utils_absolute_path::AbsolutePathBuf;
 use schemars::JsonSchema;
+use schemars::r#gen::SchemaGenerator;
+use schemars::schema::InstanceType;
+use schemars::schema::Metadata;
+use schemars::schema::Schema;
+use schemars::schema::SchemaObject;
 use serde::Deserialize;
 use serde::Serialize;
+use serde_json::Value;
 use std::num::NonZeroU64;
 use std::time::Duration;
 use strum_macros::Display;
@@ -69,22 +75,54 @@ pub enum SandboxMode {
     DangerFullAccess,
 }
 
-#[derive(
-    Deserialize, Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Display, JsonSchema, TS,
-)]
-#[serde(rename_all = "snake_case")]
+#[derive(Deserialize, Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Display, TS)]
 #[strum(serialize_all = "snake_case")]
+#[ts(type = r#""user" | "auto_review" | "guardian_subagent""#)]
 /// Configures who approval requests are routed to for review. Examples
 /// include sandbox escapes, blocked network access, MCP approval prompts, and
-/// ARC escalations. Defaults to `user`. `guardian_subagent` uses a carefully
+/// ARC escalations. Defaults to `user`. `auto_review` uses a carefully
 /// prompted subagent to gather relevant context and apply a risk-based
 /// decision framework before approving or denying the request.
 pub enum ApprovalsReviewer {
     #[default]
+    #[serde(rename = "user")]
     User,
+    #[serde(rename = "auto_review", alias = "guardian_subagent")]
+    #[strum(serialize = "auto_review")]
     GuardianSubagent,
 }
 
+impl JsonSchema for ApprovalsReviewer {
+    fn schema_name() -> String {
+        "ApprovalsReviewer".to_string()
+    }
+
+    fn json_schema(_generator: &mut SchemaGenerator) -> Schema {
+        string_enum_schema_with_description(
+            &["user", "auto_review", "guardian_subagent"],
+            "Configures who approval requests are routed to for review. Examples include sandbox escapes, blocked network access, MCP approval prompts, and ARC escalations. Defaults to `user`. `auto_review` uses a carefully prompted subagent to gather relevant context and apply a risk-based decision framework before approving or denying the request. The legacy value `guardian_subagent` is accepted for compatibility.",
+        )
+    }
+}
+
+fn string_enum_schema_with_description(values: &[&str], description: &str) -> Schema {
+    let mut schema = SchemaObject {
+        instance_type: Some(InstanceType::String.into()),
+        metadata: Some(Box::new(Metadata {
+            description: Some(description.to_string()),
+            ..Default::default()
+        })),
+        ..Default::default()
+    };
+    schema.enum_values = Some(
+        values
+            .iter()
+            .map(|value| Value::String((*value).to_string()))
+            .collect(),
+    );
+    Schema::Object(schema)
+}
+
 #[derive(
     Deserialize, Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Display, JsonSchema, TS,
 )]
@@ -562,6 +600,32 @@ mod tests {
         }
     }
 
+    #[test]
+    fn approvals_reviewer_serializes_auto_review_and_accepts_legacy_guardian_subagent() {
+        assert_eq!(ApprovalsReviewer::User.to_string(), "user");
+        assert_eq!(
+            serde_json::to_string(&ApprovalsReviewer::User).expect("serialize reviewer"),
+            "\"user\""
+        );
+        assert_eq!(
+            serde_json::to_string(&ApprovalsReviewer::GuardianSubagent)
+                .expect("serialize reviewer"),
+            "\"auto_review\""
+        );
+
+        for value in ["user", "auto_review", "guardian_subagent"] {
+            let json = format!("\"{value}\"");
+            let reviewer: ApprovalsReviewer =
+                serde_json::from_str(&json).expect("deserialize reviewer");
+            let expected = if value == "user" {
+                ApprovalsReviewer::User
+            } else {
+                ApprovalsReviewer::GuardianSubagent
+            };
+            assert_eq!(expected, reviewer);
+        }
+    }
+
     #[test]
     fn tui_visible_collaboration_modes_match_mode_kind_visibility() {
         let expected = [ModeKind::Default, ModeKind::Plan];

codex-rs/tui/src/app/tests.rs

@@ -1675,7 +1675,7 @@ async fn update_feature_flags_enabling_guardian_selects_guardian_approvals() ->
 
     let config = std::fs::read_to_string(codex_home.path().join("config.toml"))?;
     assert!(config.contains("guardian_approval = true"));
-    assert!(config.contains("approvals_reviewer = \"guardian_subagent\""));
+    assert!(config.contains("approvals_reviewer = \"auto_review\""));
     assert!(config.contains("approval_policy = \"on-request\""));
     assert!(config.contains("sandbox_mode = \"workspace-write\""));
     Ok(())
@@ -1835,7 +1835,7 @@ async fn update_feature_flags_enabling_guardian_overrides_explicit_manual_review
     );
 
     let config = std::fs::read_to_string(codex_home.path().join("config.toml"))?;
-    assert!(config.contains("approvals_reviewer = \"guardian_subagent\""));
+    assert!(config.contains("approvals_reviewer = \"auto_review\""));
     assert!(config.contains("guardian_approval = true"));
     assert!(config.contains("approval_policy = \"on-request\""));
     assert!(config.contains("sandbox_mode = \"workspace-write\""));
@@ -1969,7 +1969,7 @@ async fn update_feature_flags_enabling_guardian_in_profile_sets_profile_auto_rev
     );
     assert_eq!(
         profile_config.get("approvals_reviewer"),
-        Some(&TomlValue::String("guardian_subagent".to_string()))
+        Some(&TomlValue::String("auto_review".to_string()))
     );
     Ok(())
 }

codex-rs/tui/src/debug_config.rs

@@ -690,7 +690,7 @@ mod tests {
             rendered.contains("allowed_approval_policies: on-request (source: cloud requirements)")
         );
         assert!(rendered.contains(
-            "allowed_approvals_reviewers: guardian_subagent (source: MDM managed_config.toml (legacy))"
+            "allowed_approvals_reviewers: auto_review (source: MDM managed_config.toml (legacy))"
         ));
         assert!(
             rendered.contains(
@@ -745,7 +745,7 @@ mod tests {
 
         let rendered = render_to_text(&render_debug_config_lines(&stack));
         assert!(rendered.contains(
-            "allowed_approvals_reviewers: guardian_subagent (source: MDM managed_config.toml (legacy))"
+            "allowed_approvals_reviewers: auto_review (source: MDM managed_config.toml (legacy))"
         ));
         assert!(!rendered.contains("Requirements:\n  <none>"));
     }