Add ephemeral side conversations

Author: etraut-openai

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

@@ -2784,6 +2784,16 @@
         },
         "threadId": {
           "type": "string"
+        },
+        "toolAccessPolicy": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/ToolAccessPolicy"
+            },
+            {
+              "type": "null"
+            }
+          ]
         }
       },
       "required": [
@@ -3383,6 +3393,13 @@
       ],
       "type": "object"
     },
+    "ToolAccessPolicy": {
+      "enum": [
+        "default",
+        "noExternalTools"
+      ],
+      "type": "string"
+    },
     "TurnInterruptParams": {
       "properties": {
         "threadId": {

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

@@ -12964,6 +12964,16 @@
           },
           "threadId": {
             "type": "string"
+          },
+          "toolAccessPolicy": {
+            "anyOf": [
+              {
+                "$ref": "#/definitions/v2/ToolAccessPolicy"
+              },
+              {
+                "type": "null"
+              }
+            ]
           }
         },
         "required": [
@@ -15003,6 +15013,13 @@
         ],
         "type": "object"
       },
+      "ToolAccessPolicy": {
+        "enum": [
+          "default",
+          "noExternalTools"
+        ],
+        "type": "string"
+      },
       "ToolsV2": {
         "properties": {
           "view_image": {

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

@@ -10808,6 +10808,16 @@
         },
         "threadId": {
           "type": "string"
+        },
+        "toolAccessPolicy": {
+          "anyOf": [
+            {
+              "$ref": "#/definitions/ToolAccessPolicy"
+            },
+            {
+              "type": "null"
+            }
+          ]
         }
       },
       "required": [
@@ -12847,6 +12857,13 @@
       ],
       "type": "object"
     },
+    "ToolAccessPolicy": {
+      "enum": [
+        "default",
+        "noExternalTools"
+      ],
+      "type": "string"
+    },
     "ToolsV2": {
       "properties": {
         "view_image": {

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

@@ -73,6 +73,13 @@
         "flex"
       ],
       "type": "string"
+    },
+    "ToolAccessPolicy": {
+      "enum": [
+        "default",
+        "noExternalTools"
+      ],
+      "type": "string"
     }
   },
   "description": "There are two ways to fork a thread: 1. By thread_id: load the thread from disk by thread_id and fork it into a new thread. 2. By path: load the thread from disk by path and fork it into a new thread.\n\nIf using path, the thread_id param will be ignored.\n\nPrefer using thread_id whenever possible.",
@@ -168,6 +175,16 @@
     },
     "threadId": {
       "type": "string"
+    },
+    "toolAccessPolicy": {
+      "anyOf": [
+        {
+          "$ref": "#/definitions/ToolAccessPolicy"
+        },
+        {
+          "type": "null"
+        }
+      ]
     }
   },
   "required": [

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

@@ -6,6 +6,7 @@ import type { JsonValue } from "../serde_json/JsonValue";
 import type { ApprovalsReviewer } from "./ApprovalsReviewer";
 import type { AskForApproval } from "./AskForApproval";
 import type { SandboxMode } from "./SandboxMode";
+import type { ToolAccessPolicy } from "./ToolAccessPolicy";
 
 /**
  * There are two ways to fork a thread:
@@ -27,7 +28,7 @@ model?: string | null, modelProvider?: string | null, serviceTier?: ServiceTier
  * Override where approval requests are routed for review on this thread
  * and subsequent turns.
  */
-approvalsReviewer?: ApprovalsReviewer | null, sandbox?: SandboxMode | null, config?: { [key in string]?: JsonValue } | null, baseInstructions?: string | null, developerInstructions?: string | null, ephemeral?: boolean, /**
+approvalsReviewer?: ApprovalsReviewer | null, sandbox?: SandboxMode | null, config?: { [key in string]?: JsonValue } | null, baseInstructions?: string | null, developerInstructions?: string | null, toolAccessPolicy?: ToolAccessPolicy | null, ephemeral?: boolean, /**
  * If true, persist additional rollout EventMsg variants required to
  * reconstruct a richer thread history on subsequent resume/fork/read.
  */

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

@@ -0,0 +1,5 @@
+// GENERATED CODE! DO NOT MODIFY BY HAND!
+
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+
+export type ToolAccessPolicy = "default" | "noExternalTools";

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

@@ -334,6 +334,7 @@ export type { ThreadUnsubscribeParams } from "./ThreadUnsubscribeParams";
 export type { ThreadUnsubscribeResponse } from "./ThreadUnsubscribeResponse";
 export type { ThreadUnsubscribeStatus } from "./ThreadUnsubscribeStatus";
 export type { TokenUsageBreakdown } from "./TokenUsageBreakdown";
+export type { ToolAccessPolicy } from "./ToolAccessPolicy";
 export type { ToolRequestUserInputAnswer } from "./ToolRequestUserInputAnswer";
 export type { ToolRequestUserInputOption } from "./ToolRequestUserInputOption";
 export type { ToolRequestUserInputParams } from "./ToolRequestUserInputParams";

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

@@ -24,6 +24,7 @@ use codex_protocol::config_types::Personality;
 use codex_protocol::config_types::ReasoningSummary;
 use codex_protocol::config_types::SandboxMode as CoreSandboxMode;
 use codex_protocol::config_types::ServiceTier;
+use codex_protocol::config_types::ToolAccessPolicy as CoreToolAccessPolicy;
 use codex_protocol::config_types::Verbosity;
 use codex_protocol::config_types::WebSearchMode;
 use codex_protocol::config_types::WebSearchToolConfig;
@@ -357,6 +358,13 @@ impl From<CoreSandboxMode> for SandboxMode {
     }
 }
 
+v2_enum_from_core!(
+    pub enum ToolAccessPolicy from CoreToolAccessPolicy {
+        Default,
+        NoExternalTools
+    }
+);
+
 v2_enum_from_core!(
     pub enum ReviewDelivery from codex_protocol::protocol::ReviewDelivery {
         Inline, Detached
@@ -2898,6 +2906,8 @@ pub struct ThreadForkParams {
     pub base_instructions: Option<String>,
     #[ts(optional = nullable)]
     pub developer_instructions: Option<String>,
+    #[ts(optional = nullable)]
+    pub tool_access_policy: Option<ToolAccessPolicy>,
     #[serde(default, skip_serializing_if = "std::ops::Not::not")]
     pub ephemeral: bool,
     /// If true, persist additional rollout EventMsg variants required to
@@ -8693,6 +8703,26 @@ mod tests {
         assert_eq!(serialized_without_override.get("serviceTier"), None);
     }
 
+    #[test]
+    fn thread_fork_params_round_trip_tool_access_policy() {
+        let params: ThreadForkParams = serde_json::from_value(json!({
+            "threadId": "thr_123",
+            "ephemeral": true,
+            "toolAccessPolicy": "noExternalTools"
+        }))
+        .expect("params should deserialize");
+
+        assert_eq!(
+            params.tool_access_policy,
+            Some(ToolAccessPolicy::NoExternalTools)
+        );
+        let serialized = serde_json::to_value(&params).expect("params should serialize");
+        assert_eq!(
+            serialized.get("toolAccessPolicy"),
+            Some(&json!("noExternalTools"))
+        );
+    }
+
     #[test]
     fn thread_lifecycle_responses_default_missing_instruction_sources() {
         let response = json!({

codex-rs/app-server/README.md

@@ -272,6 +272,8 @@ To branch from a stored session, call `thread/fork` with the `thread.id`. This c
 { "method": "thread/started", "params": { "thread": { … } } }
 ```
 
+Ephemeral forks can also pass `toolAccessPolicy: "noExternalTools"` to disable MCP servers, app connector tools, and dynamic external tools for the fork while leaving built-in Codex tools available. This policy is rejected for non-ephemeral forks.
+
 Experimental API: `thread/start`, `thread/resume`, and `thread/fork` accept `persistExtendedHistory: true` to persist a richer subset of ThreadItems for non-lossy history when calling `thread/read`, `thread/resume`, and `thread/fork` later. This does not backfill events that were not persisted previously.
 
 ### Example: List threads (with pagination & filters)

codex-rs/app-server/src/codex_message_processor.rs

@@ -183,6 +183,7 @@ use codex_app_server_protocol::ThreadUnarchivedNotification;
 use codex_app_server_protocol::ThreadUnsubscribeParams;
 use codex_app_server_protocol::ThreadUnsubscribeResponse;
 use codex_app_server_protocol::ThreadUnsubscribeStatus;
+use codex_app_server_protocol::ToolAccessPolicy;
 use codex_app_server_protocol::Turn;
 use codex_app_server_protocol::TurnError;
 use codex_app_server_protocol::TurnInterruptParams;
@@ -4540,10 +4541,21 @@ impl CodexMessageProcessor {
             config: cli_overrides,
             base_instructions,
             developer_instructions,
+            tool_access_policy,
             ephemeral,
             persist_extended_history,
         } = params;
 
+        if matches!(tool_access_policy, Some(ToolAccessPolicy::NoExternalTools)) && !ephemeral {
+            self.send_invalid_request_error(
+                request_id,
+                "toolAccessPolicy=noExternalTools is only supported for ephemeral forks"
+                    .to_string(),
+            )
+            .await;
+            return;
+        }
+
         let (rollout_path, source_thread_id) = if let Some(path) = path {
             (path, None)
         } else {
@@ -4663,6 +4675,9 @@ impl CodexMessageProcessor {
                 config,
                 rollout_path.clone(),
                 persist_extended_history,
+                tool_access_policy
+                    .map(ToolAccessPolicy::to_core)
+                    .unwrap_or_default(),
                 self.request_trace_context(&request_id).await,
             )
             .await
@@ -7383,6 +7398,7 @@ impl CodexMessageProcessor {
                 config,
                 rollout_path,
                 /*persist_extended_history*/ false,
+                /*tool_access_policy*/ Default::default(),
                 self.request_trace_context(request_id).await,
             )
             .await