Keep MCP resource helpers available in code mode (#50546)

## Why

In `CodeModeOnly`, MCP resource helper definitions changed when the first server was added or the last server was removed.

## What changed

Always register `list_mcp_resources`, `list_mcp_resource_templates`, and `read_mcp_resource` in `CodeModeOnly`, even without configured MCP servers. This keeps their definitions stable across server configuration changes.

## Testing

Add a regression scenario that calls all three helpers before adding a server, with a server registered, and after removing it. Assert identical tool definitions across requests, empty resource and template lists, and the expected error when reading from an unknown server.

GitOrigin-RevId: c5777efac250b83dd4bb1c9100a6b6169470556f

codex-rs/core/src/tools/spec_plan.rs

@@ -1113,7 +1113,9 @@ fn unified_exec_should_include_shell_parameter(
 
 #[instrument(level = "trace", skip_all)]
 fn add_mcp_resource_tools(context: &CoreToolPlanContext<'_>, registry: &mut ToolRegistry) {
-    if context.mcp.has_servers() {
+    if context.mcp.has_servers()
+        || effective_tool_mode(context.turn_context, context.model_info) == ToolMode::CodeModeOnly
+    {
         let messages = ResolvedModelMessages::from_model(context.model_info).mcp_resources();
         registry.add(ListMcpResourcesHandler::new(
             messages.and_then(|messages| messages.list_mcp_resources.as_ref()),

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

@@ -3,18 +3,25 @@
 use super::super::rmcp_client::remote_aware_environment_id;
 use super::super::rmcp_client::remote_aware_stdio_server_bin;
 use anyhow::Result;
+use codex_core::ConfigRefreshOutcome;
 use codex_features::Feature;
 use codex_protocol::openai_models::ToolMode;
+use codex_protocol::protocol::EventMsg;
+use codex_protocol::protocol::McpStartupStatus;
+use core_test_support::apps_test_server::AppsTestServer;
 use core_test_support::context_snapshot;
 use core_test_support::context_snapshot::ContextSnapshotOptions;
 use core_test_support::responses;
 use core_test_support::skip_if_no_network;
 use core_test_support::skip_if_wine_exec;
 use core_test_support::test_codex::test_codex;
+use core_test_support::wait_for_event_match;
 use core_test_support::wait_for_mcp_server;
 use pretty_assertions::assert_eq;
 use serde_json::json;
 use std::collections::HashMap;
+use std::sync::Arc;
+use std::sync::Mutex;
 use test_case::test_case;
 
 #[test_case(ToolMode::Direct; "direct")]
@@ -160,3 +167,98 @@ async fn mcp_resource_messages(tool_mode: ToolMode) -> Result<()> {
     }
     Ok(())
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn resource_helpers_across_server_changes() -> Result<()> {
+    let server = responses::start_mock_server().await;
+    let mcp = responses::start_mock_server().await;
+    // Empty tools isolate the resource helper definitions from the separate
+    // deferred and MCP type guidance when the first server comes and goes.
+    let empty_server =
+        AppsTestServer::mount_with_tools(&mcp, Arc::new(Mutex::new(Vec::new()))).await?;
+    let test = test_codex()
+        .with_config(move |config| {
+            super::configure_scenario_catalog(config);
+            config.code_mode.disable_in_process_fallback = true;
+            config.features.enable(Feature::CodeModeHost).unwrap();
+        })
+        .with_model_info_override("gpt-6-astra", |model| {
+            model.tool_mode = Some(ToolMode::CodeModeOnly);
+            model.use_responses_lite = false;
+        })
+        .build_with_auto_env(&server)
+        .await?;
+    let script = r#"text(await tools.list_mcp_resources({}));
+    text(await tools.list_mcp_resource_templates({}));
+    try {
+      await tools.read_mcp_resource({ server: "missing", uri: "memo://missing" });
+    } catch (error) {
+      text(String(error));
+    }"#;
+    let mut events = Vec::new();
+    for phase in ["before", "registered", "removed"] {
+        events.push(responses::sse(vec![
+            responses::ev_custom_tool_call(phase, "exec", script),
+            responses::ev_completed(phase),
+        ]));
+        events.push(responses::sse_completed(&format!("{phase}-done")));
+    }
+    let mock = responses::mount_sse_sequence(&server, events).await;
+    test.submit_turn("Inspect resources without any configured server.")
+        .await?;
+    let current = test.codex.config().await;
+    let mut next = current.as_ref().clone();
+    next.mcp_servers.set(HashMap::from([(
+        "resources".to_string(),
+        serde_json::from_value(json!({
+            "url": format!("{}/api/codex/ps/mcp", empty_server.chatgpt_base_url),
+        }))?,
+    )]))?;
+    assert_eq!(
+        test.codex.refresh_mcp_config(current, next).await,
+        ConfigRefreshOutcome::Published,
+    );
+    let startup = wait_for_event_match(&test.codex, |event| match event {
+        EventMsg::McpStartupUpdate(update)
+            if update.server == "resources"
+                && !matches!(update.status, McpStartupStatus::Starting) =>
+        {
+            Some(update.status.clone())
+        }
+        _ => None,
+    })
+    .await;
+    assert!(matches!(startup, McpStartupStatus::Ready), "{startup:?}");
+    test.submit_turn("Inspect resources with one server.")
+        .await?;
+    let current = test.codex.config().await;
+    let mut next = current.as_ref().clone();
+    next.mcp_servers.set(HashMap::new())?;
+    assert_eq!(
+        test.codex.refresh_mcp_config(current, next).await,
+        ConfigRefreshOutcome::Published,
+    );
+    test.submit_turn("Inspect resources after removing the last server.")
+        .await?;
+    let requests = mock.requests();
+    let tools = requests
+        .iter()
+        .map(|request| request.body_json()["tools"].clone())
+        .collect::<Vec<_>>();
+    assert_eq!(requests.len(), 6);
+    assert_eq!(tools, vec![tools[0].clone(); requests.len()]);
+    for (request, phase) in
+        requests
+            .iter()
+            .skip(1)
+            .step_by(2)
+            .zip(["before", "registered", "removed"])
+    {
+        let output = request.custom_tool_call_output(phase).to_string();
+        assert!(output.contains(r#"{\"resources\":[]}"#), "{output}");
+        assert!(output.contains(r#"{\"resourceTemplates\":[]}"#), "{output}");
+        assert!(output.contains("unknown MCP server 'missing'"), "{output}");
+    }
+    test.codex.shutdown_and_wait().await?;
+    Ok(())
+}

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__astra_active_environment_selection.snap

@@ -6,8 +6,8 @@ Scenario: Astra starts in one workspace, switches for the next step of the activ
 
 ## Window 1
 -- request 1 (turn) --
-00:additional_tools/developer (3; hash=5c3ec9cbf2000b64):
-        - namespace/functions; hash=e6c4aaa15e6d6f30
+00:additional_tools/developer (3; hash=34dffd584d55c8e8):
+        - namespace/functions; hash=93657a45ae4a5a60
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__astra_async_question_and_answer.snap

@@ -7,8 +7,8 @@ Scenario: Astra uses the catalog question schema to ask who a launch update is f
 
 ## Window 1
 -- request 1 (request) --
-00:additional_tools/developer (3; hash=f19fc129e930a86e):
-        - namespace/functions; hash=b5c27b6b8551a052
+00:additional_tools/developer (3; hash=2351b38cd1e61302):
+        - namespace/functions; hash=27bd0dde5ddb5182
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__astra_code_mode_call_timing.snap

@@ -6,8 +6,8 @@ Scenario: Astra receives host and handler timings on completed and failed code-m
 
 ## Window 1
 -- request 1 (turn) --
-00:additional_tools/developer (3; hash=10256ca2e2118704):
-        - namespace/functions; hash=f01b11ec77d41982
+00:additional_tools/developer (3; hash=fe0dd2d6b97e53b8):
+        - namespace/functions; hash=3a795ca1f0e0f332
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__astra_disabled_executor_skills.snap

@@ -16,8 +16,8 @@ Settings:
   text: {"verbosity":"low"}
   tool_choice: "auto"
 -- request 1 (request) --
-00:additional_tools/developer (3; hash=1b07ea833720903d):
-        - namespace/functions; hash=986d556577441f79
+00:additional_tools/developer (3; hash=e22abab074c3c061):
+        - namespace/functions; hash=fd198a707305c309
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__astra_input_interrupts_response.snap

@@ -6,8 +6,8 @@ Scenario: Astra receives new user input after its unfinished response is interru
 
 ## Window 1
 -- request 1 (request) --
-00:additional_tools/developer (3; hash=10256ca2e2118704):
-        - namespace/functions; hash=f01b11ec77d41982
+00:additional_tools/developer (3; hash=fe0dd2d6b97e53b8):
+        - namespace/functions; hash=3a795ca1f0e0f332
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__astra_input_yields_code_mode_cell.snap

@@ -6,8 +6,8 @@ Scenario: Astra continues after new user input yields a running code cell, then
 
 ## Window 1
 -- request 1 (turn) --
-00:additional_tools/developer (3; hash=7125a91d9e3d997f):
-        - namespace/functions; hash=5cf23dadab8c4adb
+00:additional_tools/developer (3; hash=c42aa1aa511db58f):
+        - namespace/functions; hash=b655cdad519813cb
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__astra_kickoff_remote_compaction_windows.snap

@@ -16,8 +16,8 @@ Settings:
   text: {"verbosity":"low"}
   tool_choice: "auto"
 -- request 1 (turn) --
-00:additional_tools/developer (3; hash=10256ca2e2118704):
-        - namespace/functions; hash=f01b11ec77d41982
+00:additional_tools/developer (3; hash=fe0dd2d6b97e53b8):
+        - namespace/functions; hash=3a795ca1f0e0f332
           - custom/exec
           - function/wait
           - function/request_user_input
@@ -187,8 +187,8 @@ Settings:
 ## Window 2 (after request 3: input diverged at item 02)
 Settings: same as window 1
 -- request 4 (turn) --
-00:additional_tools/developer (3; hash=10256ca2e2118704):
-        - namespace/functions; hash=f01b11ec77d41982
+00:additional_tools/developer (3; hash=fe0dd2d6b97e53b8):
+        - namespace/functions; hash=3a795ca1f0e0f332
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__astra_plugin_refresh.snap

@@ -16,8 +16,8 @@ Settings:
   text: {"verbosity":"low"}
   tool_choice: "auto"
 -- request 1 (turn) --
-00:additional_tools/developer (3; hash=10256ca2e2118704):
-        - namespace/functions; hash=f01b11ec77d41982
+00:additional_tools/developer (3; hash=fe0dd2d6b97e53b8):
+        - namespace/functions; hash=3a795ca1f0e0f332
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__compaction__remote_slash_compact.snap

@@ -16,8 +16,8 @@ Settings:
   text: {"verbosity":"low"}
   tool_choice: "auto"
 -- request 1 (turn; Before /compact) --
-00:additional_tools/developer (3; hash=10256ca2e2118704):
-        - namespace/functions; hash=f01b11ec77d41982
+00:additional_tools/developer (3; hash=fe0dd2d6b97e53b8):
+        - namespace/functions; hash=3a795ca1f0e0f332
           - custom/exec
           - function/wait
           - function/request_user_input
@@ -115,8 +115,8 @@ Settings: unavailable (items only)
 ## Window 3 (after request 3: input diverged at item 00)
 Settings: same as window 1
 -- request 4 (turn; First turn after /compact) --
-00:additional_tools/developer (3; hash=10256ca2e2118704):
-        - namespace/functions; hash=f01b11ec77d41982
+00:additional_tools/developer (3; hash=fe0dd2d6b97e53b8):
+        - namespace/functions; hash=3a795ca1f0e0f332
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__guardian_checkpoint_migration.snap

@@ -50,8 +50,8 @@ Settings: relative to window 1
   reasoning: {"context":"all_turns","effort":"medium"}
   tools: <removed>
 -- request 4 (turn) --
-00:additional_tools/developer (1; hash=803cb4ba2a73d531):
-        - namespace/functions; hash=4b4ed79c9bae9f27
+00:additional_tools/developer (1; hash=77ff9904ddb4aedd):
+        - namespace/functions; hash=99a6a9ccd0de2a13
           - custom/exec
           - function/wait
           - function/request_user_input
@@ -187,8 +187,8 @@ Settings: relative to window 2
 ## Window 4 (after request 6: input diverged at item 00)
 Settings: same as window 2
 -- request 7 (turn) --
-00:additional_tools/developer (1; hash=803cb4ba2a73d531):
-        - namespace/functions; hash=4b4ed79c9bae9f27
+00:additional_tools/developer (1; hash=77ff9904ddb4aedd):
+        - namespace/functions; hash=99a6a9ccd0de2a13
           - custom/exec
           - function/wait
           - function/request_user_input
@@ -216,8 +216,8 @@ Settings: same as window 2
 ## Window 5 (after request 8: input diverged at item 04)
 Settings: same as window 2
 -- request 9 (turn) --
-00:additional_tools/developer (1; hash=803cb4ba2a73d531):
-        - namespace/functions; hash=4b4ed79c9bae9f27
+00:additional_tools/developer (1; hash=77ff9904ddb4aedd):
+        - namespace/functions; hash=99a6a9ccd0de2a13
           - custom/exec
           - function/wait
           - function/request_user_input
@@ -340,8 +340,8 @@ Settings: same as window 3
 ## Window 7 (after request 10: input diverged at item 00)
 Settings: same as window 2
 -- request 11 (turn) --
-00:additional_tools/developer (1; hash=803cb4ba2a73d531):
-        - namespace/functions; hash=4b4ed79c9bae9f27
+00:additional_tools/developer (1; hash=77ff9904ddb4aedd):
+        - namespace/functions; hash=99a6a9ccd0de2a13
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__multi_agent_catalog_parameters.snap

@@ -16,8 +16,8 @@ Settings:
   text: {"verbosity":"low"}
   tool_choice: "auto"
 -- request 1 (turn) --
-00:additional_tools/developer (3; hash=954d592d9c1e75d8):
-        - namespace/functions; hash=f01b11ec77d41982
+00:additional_tools/developer (3; hash=2c396104084747ac):
+        - namespace/functions; hash=3a795ca1f0e0f332
           - custom/exec
           - function/wait
           - function/request_user_input

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__skill_catalog_dedup__dedup_before_budgeting.snap

@@ -16,8 +16,8 @@ Settings:
   text: {"verbosity":"low"}
   tool_choice: "auto"
 -- request 1 (turn) --
-00:additional_tools/developer (3; hash=a1c4ca6659851eb8):
-        - namespace/functions; hash=8741ef7a7ba4ed8c
+00:additional_tools/developer (3; hash=5551438133509eec):
+        - namespace/functions; hash=c60996290e7ef438
           - custom/exec
           - function/wait
           - function/request_user_input