Allow omitting MCP tool prefixes per server (#34991)

## What changed

- Accept a table form of `features.non_prefixed_mcp_tool_names` with an
  optional `server_names` list while preserving the existing boolean form.
- Omit the legacy `mcp__` namespace prefix only for tools from selected MCP
  servers. When no server list is provided, the enabled feature continues to
  omit the prefix for every server.
- Cover configuration resolution, tool normalization, and an MCP stdio
  round trip with selected servers.

GitOrigin-RevId: bdfb7ac54226de5051f06610e2c6b78b23912ef0

codex-rs/codex-mcp/src/connection_manager.rs

@@ -149,6 +149,7 @@ pub(crate) struct McpConnectionSet {
     codex_apps_refresh_lock: Mutex<()>,
     tool_plugin_provenance: Arc<ToolPluginProvenance>,
     prefix_mcp_tool_names: bool,
+    non_prefixed_mcp_tool_servers: Vec<String>,
     elicitation_requests: ElicitationRequestManager,
 }
 
@@ -185,6 +186,7 @@ impl McpConnectionSet {
         let initial_permission_profile = config.permission_profile.clone();
         let codex_home = config.codex_home.clone();
         let prefix_mcp_tool_names = config.prefix_mcp_tool_names;
+        let non_prefixed_mcp_tool_servers = config.non_prefixed_mcp_tool_servers.clone();
         let client_elicitation_capability = config.client_elicitation_capability.clone();
         let tool_plugin_provenance = crate::mcp::tool_plugin_provenance(&config);
         let auth = auth.as_ref();
@@ -461,6 +463,7 @@ impl McpConnectionSet {
             codex_apps_refresh_lock: Mutex::new(()),
             tool_plugin_provenance,
             prefix_mcp_tool_names,
+            non_prefixed_mcp_tool_servers,
             elicitation_requests: elicitation_requests.clone(),
         };
         let summary_publication_gate = publication_gate;
@@ -517,6 +520,7 @@ impl McpConnectionSet {
             codex_apps_refresh_lock: Mutex::new(()),
             tool_plugin_provenance: Arc::new(ToolPluginProvenance::default()),
             prefix_mcp_tool_names,
+            non_prefixed_mcp_tool_servers: Vec::new(),
             elicitation_requests: ElicitationRequestManager::new(
                 AskForApproval::Never,
                 PermissionProfile::default(),

codex-rs/codex-mcp/src/connection_manager/tool_catalog.rs

@@ -110,7 +110,11 @@ impl McpConnectionSet {
                     .map(|tool| Self::with_server_metadata(tool, &view.metadata)),
             );
         }
-        let tools = normalize_tools_for_model_with_prefix(tools, self.prefix_mcp_tool_names);
+        let tools = normalize_tools_for_model_with_prefix(
+            tools,
+            self.prefix_mcp_tool_names,
+            &self.non_prefixed_mcp_tool_servers,
+        );
         trace!(
             available_server_count,
             unavailable_server_count,
@@ -170,8 +174,11 @@ impl McpConnectionSet {
             );
         }
         let clients = Arc::new(McpBindingClients::new(clients));
-        let listed_tools =
-            normalize_tools_for_model_with_prefix(listed_tools, self.prefix_mcp_tool_names);
+        let listed_tools = normalize_tools_for_model_with_prefix(
+            listed_tools,
+            self.prefix_mcp_tool_names,
+            &self.non_prefixed_mcp_tool_servers,
+        );
         let mut tools = Vec::with_capacity(listed_tools.len());
         let mut calls = std::collections::HashMap::with_capacity(listed_tools.len());
         for tool_info in listed_tools {
@@ -298,7 +305,11 @@ impl McpConnectionSet {
         )
         .into_iter()
         .map(|tool| Self::with_server_metadata(tool, &view.metadata));
-        let tools = normalize_tools_for_model_with_prefix(tools, self.prefix_mcp_tool_names);
+        let tools = normalize_tools_for_model_with_prefix(
+            tools,
+            self.prefix_mcp_tool_names,
+            &self.non_prefixed_mcp_tool_servers,
+        );
         emit_duration(
             CODEX_APPS_REFRESH_DURATION_METRIC,
             refresh_start.elapsed(),

codex-rs/codex-mcp/src/connection_manager_tests.rs

@@ -91,6 +91,7 @@ impl McpConnectionSet {
             codex_apps_refresh_lock: Mutex::new(()),
             tool_plugin_provenance: Arc::new(ToolPluginProvenance::default()),
             prefix_mcp_tool_names,
+            non_prefixed_mcp_tool_servers: Vec::new(),
             elicitation_requests: ElicitationRequestManager::new(
                 approval_policy.value(),
                 permission_profile.get().clone(),
@@ -806,7 +807,7 @@ fn test_normalize_tools_short_non_duplicated_names() {
     ];
 
     let model_tools =
-        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true);
+        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true, &[]);
 
     assert_eq!(
         model_tool_names(&model_tools),
@@ -817,6 +818,69 @@ fn test_normalize_tools_short_non_duplicated_names() {
     );
 }
 
+#[test]
+fn test_normalize_tools_omits_prefix_only_for_selected_servers() {
+    let tools = vec![
+        create_test_tool("history", "search"),
+        create_test_tool("notes", "read"),
+        create_test_tool("calendar", "list"),
+    ];
+
+    let model_tools = normalize_tools_for_model_with_prefix(
+        tools,
+        /*prefix_mcp_tool_names*/ true,
+        &["history".to_string(), "notes".to_string()],
+    );
+
+    assert_eq!(
+        model_tool_names(&model_tools),
+        HashSet::from([
+            ToolName::namespaced("history", "search"),
+            ToolName::namespaced("notes", "read"),
+            ToolName::namespaced("mcp__calendar", "list"),
+        ])
+    );
+}
+
+#[test]
+fn test_normalize_tools_selects_raw_server_name() {
+    let mut tool = create_test_tool("codex_apps", "search");
+    tool.callable_namespace = "codex_apps__calendar".to_string();
+
+    let model_tools = normalize_tools_for_model_with_prefix(
+        vec![tool],
+        /*prefix_mcp_tool_names*/ true,
+        &["codex_apps".to_string()],
+    );
+
+    assert_eq!(
+        model_tool_names(&model_tools),
+        HashSet::from([ToolName::namespaced("codex_apps__calendar", "search")])
+    );
+}
+
+#[test]
+fn test_normalize_tools_global_feature_omits_prefix_for_every_server() {
+    let tools = vec![
+        create_test_tool("history", "search"),
+        create_test_tool("calendar", "list"),
+    ];
+
+    let model_tools = normalize_tools_for_model_with_prefix(
+        tools,
+        /*prefix_mcp_tool_names*/ false,
+        &["history".to_string()],
+    );
+
+    assert_eq!(
+        model_tool_names(&model_tools),
+        HashSet::from([
+            ToolName::namespaced("history", "search"),
+            ToolName::namespaced("calendar", "list"),
+        ])
+    );
+}
+
 #[test]
 fn test_normalize_tools_duplicated_names_skipped() {
     let tools = vec![
@@ -825,7 +889,7 @@ fn test_normalize_tools_duplicated_names_skipped() {
     ];
 
     let model_tools =
-        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true);
+        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true, &[]);
 
     // Only the first tool should remain, the second is skipped
     assert_eq!(
@@ -850,7 +914,7 @@ fn test_normalize_tools_long_names_same_server() {
     ];
 
     let model_tools =
-        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true);
+        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true, &[]);
 
     assert_eq!(model_tools.len(), 2);
 
@@ -873,7 +937,7 @@ fn test_normalize_tools_sanitizes_invalid_characters() {
     let tools = vec![create_test_tool("server.one", "tool.two-three")];
 
     let model_tools =
-        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true);
+        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true, &[]);
 
     assert_eq!(model_tools.len(), 1);
     let tool = model_tools.into_iter().next().expect("one tool");
@@ -904,7 +968,7 @@ fn test_normalize_tools_keeps_hyphenated_mcp_tools_callable() {
     let tools = vec![create_test_tool("music-studio", "get-strudel-guide")];
 
     let model_tools =
-        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true);
+        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true, &[]);
 
     assert_eq!(model_tools.len(), 1);
     let tool = model_tools.into_iter().next().expect("one tool");
@@ -925,7 +989,7 @@ fn test_normalize_tools_disambiguates_sanitized_namespace_collisions() {
     ];
 
     let model_tools =
-        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true);
+        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true, &[]);
 
     assert_eq!(model_tools.len(), 2);
     let mut namespaces = model_tools
@@ -956,7 +1020,7 @@ fn test_normalize_tools_disambiguates_sanitized_tool_name_collisions() {
     ];
 
     let model_tools =
-        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true);
+        normalize_tools_for_model_with_prefix(tools, /*prefix_mcp_tool_names*/ true, &[]);
 
     assert_eq!(model_tools.len(), 2);
     let raw_tool_names = model_tools

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

@@ -155,6 +155,8 @@ pub struct McpConfig {
     /// Whether model-visible MCP tool namespaces should keep the legacy
     /// `mcp__` prefix.
     pub prefix_mcp_tool_names: bool,
+    /// MCP servers whose model-visible tool namespaces omit the `mcp__` prefix.
+    pub non_prefixed_mcp_tool_servers: Vec<String>,
     /// Client-side elicitation capabilities advertised during MCP initialization.
     pub client_elicitation_capability: ElicitationCapability,
     /// Resolved MCP registrations keyed by logical server name.

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

@@ -36,6 +36,7 @@ pub(crate) fn test_mcp_config(codex_home: PathBuf) -> McpConfig {
         use_legacy_landlock: false,
         apps_enabled: false,
         prefix_mcp_tool_names: true,
+        non_prefixed_mcp_tool_servers: Vec::new(),
         client_elicitation_capability: ElicitationCapability::default(),
         mcp_server_catalog: ResolvedMcpCatalog::default(),
         connector_snapshot: codex_connectors::ConnectorSnapshot::default(),

codex-rs/codex-mcp/src/tools.rs

@@ -109,10 +109,11 @@ pub(crate) fn filter_tools(tools: Vec<ToolInfo>, filter: &ToolFilter) -> Vec<Too
 /// every model-visible name is unique and <= 64 bytes.
 ///
 /// When `prefix_mcp_tool_names` is true, the historical `mcp__` namespace
-/// prefix is added without restoring the old trailing `__` namespace suffix.
+/// prefix is added except for tools from `non_prefixed_mcp_tool_servers`.
 pub(crate) fn normalize_tools_for_model_with_prefix<I>(
     tools: I,
     prefix_mcp_tool_names: bool,
+    non_prefixed_mcp_tool_servers: &[String],
 ) -> Vec<ToolInfo>
 where
     I: IntoIterator<Item = ToolInfo>,
@@ -137,7 +138,7 @@ where
 
         let callable_namespace = callable_namespace_with_prefix(
             &sanitize_responses_api_tool_name(&tool.callable_namespace),
-            prefix_mcp_tool_names,
+            prefix_mcp_tool_names && !non_prefixed_mcp_tool_servers.contains(&tool.server_name),
         );
 
         candidates.push(CallableToolCandidate {

codex-rs/config/src/schema.rs

@@ -35,6 +35,15 @@ pub fn features_schema(schema_gen: &mut SchemaGenerator) -> Schema {
             );
             continue;
         }
+        if feature.id == codex_features::Feature::NonPrefixedMcpToolNames {
+            validation.properties.insert(
+                feature.key.to_string(),
+                schema_gen.subschema_for::<codex_features::FeatureToml<
+                    codex_features::NonPrefixedMcpToolNamesConfigToml,
+                >>(),
+            );
+            continue;
+        }
         if feature.id == codex_features::Feature::MultiAgentV2 {
             validation.properties.insert(
                 feature.key.to_string(),

codex-rs/core/config.schema.json

@@ -591,7 +591,7 @@
               "$ref": "#/definitions/FeatureToml_for_NetworkProxyConfigToml"
             },
             "non_prefixed_mcp_tool_names": {
-              "type": "boolean"
+              "$ref": "#/definitions/FeatureToml_for_NonPrefixedMcpToolNamesConfigToml"
             },
             "personality": {
               "type": "boolean"
@@ -1007,6 +1007,16 @@
         }
       ]
     },
+    "FeatureToml_for_NonPrefixedMcpToolNamesConfigToml": {
+      "anyOf": [
+        {
+          "type": "boolean"
+        },
+        {
+          "$ref": "#/definitions/NonPrefixedMcpToolNamesConfigToml"
+        }
+      ]
+    },
     "FeatureToml_for_RolloutBudgetConfigToml": {
       "anyOf": [
         {
@@ -2085,6 +2095,22 @@
     "NetworkUnixSocketPermissionsToml": {
       "type": "object"
     },
+    "NonPrefixedMcpToolNamesConfigToml": {
+      "additionalProperties": false,
+      "properties": {
+        "enabled": {
+          "type": "boolean"
+        },
+        "server_names": {
+          "description": "MCP servers whose tools should omit the legacy `mcp__` namespace prefix.",
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        }
+      },
+      "type": "object"
+    },
     "Notice": {
       "additionalProperties": false,
       "properties": {
@@ -5076,7 +5102,7 @@
           "$ref": "#/definitions/FeatureToml_for_NetworkProxyConfigToml"
         },
         "non_prefixed_mcp_tool_names": {
-          "type": "boolean"
+          "$ref": "#/definitions/FeatureToml_for_NonPrefixedMcpToolNamesConfigToml"
         },
         "personality": {
           "type": "boolean"

codex-rs/core/src/config/config_tests.rs

@@ -443,6 +443,65 @@ async fn load_config_resolves_experimental_request_user_input_enabled() -> std::
     Ok(())
 }
 
+#[tokio::test]
+async fn load_config_resolves_non_prefixed_mcp_tool_servers() -> std::io::Result<()> {
+    let cases = [
+        (
+            "[features]\nnon_prefixed_mcp_tool_names = false\n",
+            None,
+            true,
+        ),
+        (
+            "[features]\nnon_prefixed_mcp_tool_names = true\n",
+            None,
+            false,
+        ),
+        (
+            "[features.non_prefixed_mcp_tool_names]\nenabled = true\n",
+            None,
+            false,
+        ),
+        (
+            "[features.non_prefixed_mcp_tool_names]\nenabled = true\nserver_names = [\"history\", \"notes\"]\n",
+            Some(vec!["history".to_string(), "notes".to_string()]),
+            true,
+        ),
+        (
+            "[features.non_prefixed_mcp_tool_names]\nenabled = true\nserver_names = []\n",
+            Some(Vec::new()),
+            true,
+        ),
+        (
+            "[features.non_prefixed_mcp_tool_names]\nenabled = false\nserver_names = [\"history\"]\n",
+            None,
+            true,
+        ),
+    ];
+
+    for (config_contents, expected_servers, expected_prefix) in cases {
+        let codex_home = tempdir()?;
+        let config_toml = toml::from_str::<ConfigToml>(config_contents)
+            .expect("TOML deserialization should succeed");
+        let config = Config::load_from_base_config_with_overrides(
+            config_toml,
+            ConfigOverrides::default(),
+            codex_home.abs(),
+        )
+        .await?;
+
+        assert_eq!(config.non_prefixed_mcp_tool_servers, expected_servers);
+        assert_eq!(config.prefix_mcp_tool_names(), expected_prefix);
+        let plugins_manager = PluginsManager::new(codex_home.path().to_path_buf());
+        let mcp_config = config.to_mcp_config(&plugins_manager).await;
+        assert_eq!(mcp_config.prefix_mcp_tool_names, expected_prefix);
+        assert_eq!(
+            mcp_config.non_prefixed_mcp_tool_servers,
+            expected_servers.unwrap_or_default()
+        );
+    }
+    Ok(())
+}
+
 #[tokio::test]
 async fn load_config_resolves_code_mode_config() -> std::io::Result<()> {
     let codex_home = tempdir()?;
@@ -6225,10 +6284,25 @@ async fn to_mcp_config_flows_mcp_tool_prefix_from_feature() -> std::io::Result<(
 
     let mcp_config = config.to_mcp_config(&plugins_manager).await;
     assert!(mcp_config.prefix_mcp_tool_names);
+    assert!(mcp_config.non_prefixed_mcp_tool_servers.is_empty());
 
     let _ = config.features.enable(Feature::NonPrefixedMcpToolNames);
     let mcp_config = config.to_mcp_config(&plugins_manager).await;
     assert!(!mcp_config.prefix_mcp_tool_names);
+    assert!(mcp_config.non_prefixed_mcp_tool_servers.is_empty());
+
+    config.non_prefixed_mcp_tool_servers = Some(vec!["history".to_string(), "notes".to_string()]);
+    let mcp_config = config.to_mcp_config(&plugins_manager).await;
+    assert!(mcp_config.prefix_mcp_tool_names);
+    assert_eq!(
+        mcp_config.non_prefixed_mcp_tool_servers,
+        vec!["history".to_string(), "notes".to_string()]
+    );
+
+    let _ = config.features.disable(Feature::NonPrefixedMcpToolNames);
+    let mcp_config = config.to_mcp_config(&plugins_manager).await;
+    assert!(mcp_config.prefix_mcp_tool_names);
+    assert!(mcp_config.non_prefixed_mcp_tool_servers.is_empty());
 
     Ok(())
 }

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

@@ -829,6 +829,9 @@ pub struct Config {
     /// Definition for MCP servers that Codex can reach out to for tool calls.
     pub mcp_servers: Constrained<HashMap<String, McpServerConfig>>,
 
+    /// When present, only these MCP servers omit the legacy `mcp__` namespace prefix.
+    pub non_prefixed_mcp_tool_servers: Option<Vec<String>>,
+
     /// Preferred store for MCP OAuth credentials.
     /// keyring: Use an OS-specific keyring service.
     ///          Credentials stored in the keyring will only be readable by Codex unless the user explicitly grants access via OS-level keyring access.
@@ -1641,6 +1644,16 @@ impl Config {
             use_legacy_landlock: self.features.use_legacy_landlock(),
             apps_enabled: self.features.enabled(Feature::Apps),
             prefix_mcp_tool_names: self.prefix_mcp_tool_names(),
+            non_prefixed_mcp_tool_servers: if self
+                .features
+                .enabled(Feature::NonPrefixedMcpToolNames)
+            {
+                self.non_prefixed_mcp_tool_servers
+                    .clone()
+                    .unwrap_or_default()
+            } else {
+                Vec::new()
+            },
             client_elicitation_capability: if self.features.enabled(Feature::AuthElicitation) {
                 ElicitationCapability {
                     form: Some(FormElicitationCapability::default()),
@@ -1661,6 +1674,7 @@ impl Config {
 
     pub(crate) fn prefix_mcp_tool_names(&self) -> bool {
         !self.features.enabled(Feature::NonPrefixedMcpToolNames)
+            || self.non_prefixed_mcp_tool_servers.is_some()
     }
 
     pub async fn rebuild_preserving_session_layers(
@@ -3203,6 +3217,17 @@ impl Config {
             feature_requirements,
             &mut startup_warnings,
         )?;
+        let non_prefixed_mcp_tool_servers = if features.enabled(Feature::NonPrefixedMcpToolNames) {
+            cfg.features
+                .as_ref()
+                .and_then(|features| features.non_prefixed_mcp_tool_names.as_ref())
+                .and_then(|feature| match feature {
+                    FeatureToml::Enabled(_) => None,
+                    FeatureToml::Config(config) => config.server_names.clone(),
+                })
+        } else {
+            None
+        };
         let respect_system_proxy = features.enabled(Feature::RespectSystemProxy);
         let enable_network_proxy = features.enabled(Feature::NetworkProxy);
         let configured_windows_sandbox_mode = resolve_windows_sandbox_mode(&cfg);
@@ -3960,6 +3985,7 @@ impl Config {
                 env!("CARGO_PKG_VERSION"),
             ),
             mcp_servers,
+            non_prefixed_mcp_tool_servers,
             // The config.toml omits "_mode" because it's a config file. However, "_mode"
             // is important in code to differentiate the mode from the store implementation.
             mcp_oauth_credentials_store_mode: resolve_mcp_oauth_credentials_store_mode(

codex-rs/core/tests/suite/rmcp_client.rs

@@ -695,6 +695,119 @@ async fn stdio_server_round_trip() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn stdio_mcp_tool_names_respect_selected_servers() -> anyhow::Result<()> {
+    skip_if_wine_exec!(
+        Ok(()),
+        "requires a Windows test_stdio_server in the Wine-exec environment"
+    );
+    skip_if_no_network!(Ok(()));
+
+    let server = responses::start_mock_server().await;
+    let call_id = "history-echo";
+    let search_call_id = "search-mcp-echo";
+    mount_sse_once(
+        &server,
+        responses::sse(vec![
+            responses::ev_response_created("resp-1"),
+            responses::ev_tool_search_call(
+                search_call_id,
+                &json!({"query": "echo message and environment data"}),
+            ),
+            responses::ev_completed("resp-1"),
+        ]),
+    )
+    .await;
+    let call_mock = mount_sse_once(
+        &server,
+        responses::sse(vec![
+            responses::ev_response_created("resp-2"),
+            responses::ev_function_call_with_namespace(
+                call_id,
+                "history",
+                "echo",
+                r#"{"message":"ping"}"#,
+            ),
+            responses::ev_completed("resp-2"),
+        ]),
+    )
+    .await;
+    let final_mock = mount_sse_once(
+        &server,
+        responses::sse(vec![
+            responses::ev_assistant_message("msg-1", "history echo completed successfully."),
+            responses::ev_completed("resp-3"),
+        ]),
+    )
+    .await;
+
+    let command = remote_aware_stdio_server_bin()?;
+    let fixture = test_codex()
+        .with_pre_build_hook(move |codex_home| {
+            fs::write(
+                codex_home.join("config.toml"),
+                r#"
+[features.non_prefixed_mcp_tool_names]
+enabled = true
+server_names = ["history", "notes"]
+"#,
+            )
+            .expect("write MCP namespace configuration");
+        })
+        .with_config(move |config| {
+            for server_name in ["history", "notes", "other"] {
+                insert_mcp_server(
+                    config,
+                    server_name,
+                    stdio_transport(command.clone(), /*env*/ None, Vec::new()),
+                    TestMcpServerOptions {
+                        environment_id: remote_aware_environment_id(),
+                        ..Default::default()
+                    },
+                );
+            }
+        })
+        .build_with_auto_env(&server)
+        .await?;
+    wait_for_mcp_server(&fixture.codex, "history").await?;
+
+    fixture
+        .submit_turn_with_permission_profile(
+            "call the history echo tool",
+            PermissionProfile::read_only(),
+        )
+        .await?;
+
+    let search_output = call_mock
+        .single_request()
+        .tool_search_output(search_call_id);
+    let mut actual_namespaces = [
+        "history",
+        "notes",
+        "other",
+        "mcp__history",
+        "mcp__notes",
+        "mcp__other",
+    ]
+    .into_iter()
+    .filter(|namespace| {
+        responses::namespace_child_tool(&search_output, namespace, "echo").is_some()
+    })
+    .collect::<Vec<_>>();
+    actual_namespaces.sort_unstable();
+    assert_eq!(actual_namespaces, ["history", "mcp__other", "notes"]);
+
+    let output = final_mock.single_request().function_call_output(call_id);
+    let output_text = output["output"]
+        .as_str()
+        .expect("MCP function-call output should be a string");
+    let output_json: Value = serde_json::from_str(split_wall_time_wrapped_output(output_text))?;
+    assert_eq!(output_json["echo"], "ECHOING: ping");
+
+    server.verify().await;
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn shutdown_cancels_startup_prewarm_waiting_for_mcp_startup() -> anyhow::Result<()> {
     skip_if_no_network!(Ok(()));

codex-rs/features/src/feature_configs.rs

@@ -29,6 +29,26 @@ impl FeatureConfig for CodeModeConfigToml {
     }
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq, Eq, JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub struct NonPrefixedMcpToolNamesConfigToml {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub enabled: Option<bool>,
+    /// MCP servers whose tools should omit the legacy `mcp__` namespace prefix.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub server_names: Option<Vec<String>>,
+}
+
+impl FeatureConfig for NonPrefixedMcpToolNamesConfigToml {
+    fn enabled(&self) -> Option<bool> {
+        self.enabled
+    }
+
+    fn set_enabled(&mut self, enabled: bool) {
+        self.enabled = Some(enabled);
+    }
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq, Eq, JsonSchema)]
 #[serde(deny_unknown_fields)]
 pub struct MultiAgentV2ConfigToml {

codex-rs/features/src/lib.rs

@@ -25,6 +25,7 @@ pub use feature_configs::NetworkProxyConfigToml;
 pub use feature_configs::NetworkProxyDomainPermissionToml;
 pub use feature_configs::NetworkProxyModeToml;
 pub use feature_configs::NetworkProxyUnixSocketPermissionToml;
+pub use feature_configs::NonPrefixedMcpToolNamesConfigToml;
 use feature_configs::RemovedAppsMcpPathOverrideConfigToml;
 pub use feature_configs::RolloutBudgetConfigToml;
 pub use feature_configs::TokenBudgetConfigToml;
@@ -647,6 +648,8 @@ pub struct FeaturesToml {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub code_mode: Option<FeatureToml<CodeModeConfigToml>>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub non_prefixed_mcp_tool_names: Option<FeatureToml<NonPrefixedMcpToolNamesConfigToml>>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
     pub multi_agent_v2: Option<FeatureToml<MultiAgentV2ConfigToml>>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub token_budget: Option<FeatureToml<TokenBudgetConfigToml>>,
@@ -683,6 +686,13 @@ impl FeaturesToml {
         if let Some(enabled) = self.code_mode.as_ref().and_then(FeatureToml::enabled) {
             entries.insert(Feature::CodeMode.key().to_string(), enabled);
         }
+        if let Some(enabled) = self
+            .non_prefixed_mcp_tool_names
+            .as_ref()
+            .and_then(FeatureToml::enabled)
+        {
+            entries.insert(Feature::NonPrefixedMcpToolNames.key().to_string(), enabled);
+        }
         if let Some(enabled) = self.multi_agent_v2.as_ref().and_then(FeatureToml::enabled) {
             entries.insert(Feature::MultiAgentV2.key().to_string(), enabled);
         }
@@ -709,6 +719,7 @@ impl FeaturesToml {
         self.clear_removed_compatibility_entries();
         let Self {
             code_mode,
+            non_prefixed_mcp_tool_names,
             multi_agent_v2,
             token_budget,
             rollout_budget,
@@ -724,6 +735,8 @@ impl FeaturesToml {
             let enabled = features.enabled(spec.id);
             if spec.id == Feature::CodeMode {
                 materialize_resolved_feature_enabled(code_mode, enabled);
+            } else if spec.id == Feature::NonPrefixedMcpToolNames {
+                materialize_resolved_feature_enabled(non_prefixed_mcp_tool_names, enabled);
             } else if spec.id == Feature::MultiAgentV2 {
                 materialize_resolved_feature_enabled(multi_agent_v2, enabled);
             } else if spec.id == Feature::TokenBudget {

codex-rs/features/src/tests.rs

@@ -444,12 +444,54 @@ non_code_mode_only = true
     );
 }
 
+#[test]
+fn non_prefixed_mcp_tool_names_feature_config_deserializes_boolean_toggle() {
+    let features: FeaturesToml = toml::from_str("non_prefixed_mcp_tool_names = true")
+        .expect("features table should deserialize");
+
+    assert_eq!(
+        features.entries(),
+        BTreeMap::from([("non_prefixed_mcp_tool_names".to_string(), true)])
+    );
+    assert_eq!(
+        features.non_prefixed_mcp_tool_names,
+        Some(FeatureToml::Enabled(true))
+    );
+}
+
+#[test]
+fn non_prefixed_mcp_tool_names_feature_config_deserializes_table() {
+    let features: FeaturesToml = toml::from_str(
+        r#"
+[non_prefixed_mcp_tool_names]
+enabled = true
+server_names = ["history", "notes"]
+"#,
+    )
+    .expect("features table should deserialize");
+
+    assert_eq!(
+        features.entries(),
+        BTreeMap::from([("non_prefixed_mcp_tool_names".to_string(), true)])
+    );
+    assert_eq!(
+        features.non_prefixed_mcp_tool_names,
+        Some(FeatureToml::Config(
+            crate::NonPrefixedMcpToolNamesConfigToml {
+                enabled: Some(true),
+                server_names: Some(vec!["history".to_string(), "notes".to_string()]),
+            }
+        ))
+    );
+}
+
 #[test]
 fn materialize_resolved_enabled_writes_all_features_and_preserves_custom_config() {
     let mut features = Features::with_defaults();
     features.enable(Feature::CodeMode);
     features.enable(Feature::MultiAgentV2);
     features.enable(Feature::NetworkProxy);
+    features.enable(Feature::NonPrefixedMcpToolNames);
     features.enable(Feature::RespectSystemProxy);
 
     let mut features_toml = FeaturesToml {
@@ -463,6 +505,12 @@ fn materialize_resolved_enabled_writes_all_features_and_preserves_custom_config(
             proxy_url: Some("http://127.0.0.1:43128".to_string()),
             ..Default::default()
         })),
+        non_prefixed_mcp_tool_names: Some(FeatureToml::Config(
+            crate::NonPrefixedMcpToolNamesConfigToml {
+                enabled: Some(false),
+                server_names: Some(vec!["history".to_string(), "notes".to_string()]),
+            },
+        )),
         entries: BTreeMap::new(),
         ..Default::default()
     };
@@ -494,6 +542,15 @@ fn materialize_resolved_enabled_writes_all_features_and_preserves_custom_config(
             ..Default::default()
         }))
     );
+    assert_eq!(
+        features_toml.non_prefixed_mcp_tool_names,
+        Some(FeatureToml::Config(
+            crate::NonPrefixedMcpToolNamesConfigToml {
+                enabled: Some(true),
+                server_names: Some(vec!["history".to_string(), "notes".to_string()]),
+            }
+        ))
+    );
     let replayed = Features::from_sources(
         FeatureConfigSource {
             features: Some(&features_toml),

codex-rs/thread-manager-sample/src/main.rs

@@ -235,6 +235,7 @@ fn new_config(model: Option<String>, arg0_paths: Arg0DispatchPaths) -> anyhow::R
         workspace_roots_explicit: false,
         cli_auth_credentials_store_mode: AuthCredentialsStoreMode::File,
         mcp_servers: Constrained::allow_any(HashMap::new()),
+        non_prefixed_mcp_tool_servers: None,
         mcp_oauth_credentials_store_mode: OAuthCredentialsStoreMode::File,
         mcp_oauth_callback_port: None,
         mcp_oauth_callback_url: None,