Delegate sub-agent enablement to language server

CONTEXT.md

@@ -0,0 +1,29 @@
+# Context & Glossary
+
+This file is a glossary of the ubiquitous language used in this codebase. It is
+intentionally free of implementation detail — it defines *what words mean*, not
+*how things are built*.
+
+## Terms
+
+### Sub-agent
+A delegated agent that the main agent spawns to carry out a scoped sub-task on
+its behalf. The main agent invokes it through the `run_subagent` tool and
+receives the sub-agent's result back as part of its own turn.
+
+### Sub-agent policy
+Organization-level governance that decides whether sub-agents are permitted for
+a user. It is authoritative and is **enforced by the language server**, not by
+the editor client: when the policy forbids sub-agents, the server refuses to
+offer the `run_subagent` tool regardless of what the client advertises.
+
+### Capability
+A feature the editor client declares support for when it initializes its
+connection to the language server. A capability is an *offer of support*, not a
+*grant of permission* — the server may still withhold the corresponding feature
+(for example, because the sub-agent policy forbids it).
+
+### Client preview feature
+A gate that exposes in-development features to a subset of users. It is distinct
+from the sub-agent policy: after this change, the availability of sub-agents no
+longer depends on the client preview feature.

com.microsoft.copilot.eclipse.core/src/com/microsoft/copilot/eclipse/core/Constants.java

@@ -26,7 +26,6 @@ private Constants() {
   public static final String PROXY_KERBEROS_SP = "proxyKerberosSp";
   public static final String GITHUB_ENTERPRISE = "githubEnterprise";
   public static final String WORKSPACE_CONTEXT_ENABLED = "workspaceContextEnabled";
-  public static final String SUB_AGENT_ENABLED = "subAgentEnabled";
   public static final String AGENT_MAX_REQUESTS = "agentMaxRequests";
   public static final String ENABLE_SKILLS = "enableSkills";
   public static final String TRANSCRIPT_SUBDIR = ".copilot/eclipse";

com.microsoft.copilot.eclipse.core/src/com/microsoft/copilot/eclipse/core/FeatureFlags.java

@@ -5,7 +5,6 @@
 
 import org.eclipse.core.runtime.preferences.IEclipsePreferences;
 import org.eclipse.core.runtime.preferences.InstanceScope;
-import org.osgi.service.prefs.BackingStoreException;
 
 /**
  * Class to manage feature flags for the Copilot plugin. This class allows enabling or disabling features.
@@ -21,8 +20,6 @@ public class FeatureFlags {
 
   private boolean mcpContributionPointEnabled = false;
 
-  private boolean subAgentPolicyEnabled = true;
-
   private boolean customAgentPolicyEnabled = true;
 
   private boolean autoApprovalTokenEnabled = true;
@@ -61,25 +58,6 @@ public void setMcpContributionPointEnabled(boolean mcpContributionPointEnabled)
     this.mcpContributionPointEnabled = mcpContributionPointEnabled;
   }
 
-  public boolean isSubAgentPolicyEnabled() {
-    return subAgentPolicyEnabled;
-  }
-
-  /**
-   * Sets whether the sub-agent policy is enabled.
-   * When the policy is disabled, it also disables the user preference for sub-agent.
-   *
-   * @param subAgentPolicyEnabled true to enable the sub-agent policy, false to disable it
-   */
-  public void setSubAgentPolicyEnabled(boolean subAgentPolicyEnabled) {
-    this.subAgentPolicyEnabled = subAgentPolicyEnabled;
-
-    // When policy disables subagent, also disable the user preference
-    if (!subAgentPolicyEnabled) {
-      disableSubAgentPreference();
-    }
-  }
-
   public boolean isCustomAgentPolicyEnabled() {
     return customAgentPolicyEnabled;
   }
@@ -113,17 +91,11 @@ public boolean isClientPreviewFeatureEnabled() {
 
   /**
    * Sets whether the client preview feature is enabled.
-   * When the feature is disabled, it also disables the user preference for sub-agent.
    *
    * @param clientPreviewFeatureEnabled true to enable the client preview feature, false to disable it
    */
   public void setClientPreviewFeatureEnabled(boolean clientPreviewFeatureEnabled) {
     this.clientPreviewFeatureEnabled = clientPreviewFeatureEnabled;
-
-    // When client preview feature is disabled, also disable the user preference for subagent
-    if (!clientPreviewFeatureEnabled) {
-      disableSubAgentPreference();
-    }
   }
 
   /**
@@ -143,46 +115,6 @@ public static boolean isWorkspaceContextEnabled() {
     return false;
   }
 
-  /**
-   * Disables the user preference for sub-agent.
-   * This method accesses the UI plugin's preference store to set the sub-agent preference to false.
-   *
-   * <p>Note: The sub-agent preference is used to initialize capabilities which happens before policies
-   * are sent to us. Therefore, we need to flush the preference immediately when policy changes occur
-   * to ensure the next capability initialization reflects the updated policy state.
-   */
-  private void disableSubAgentPreference() {
-    // The preference is stored in the UI plugin's preference store, which uses InstanceScope internally
-    IEclipsePreferences prefs = InstanceScope.INSTANCE.getNode("com.microsoft.copilot.eclipse.ui");
-    if (prefs != null) {
-      // Only update and flush if the current setting is true
-      boolean currentValue = prefs.getBoolean(Constants.SUB_AGENT_ENABLED, false);
-      if (currentValue) {
-        prefs.putBoolean(Constants.SUB_AGENT_ENABLED, false);
-        try {
-          prefs.flush();
-        } catch (BackingStoreException e) {
-          CopilotCore.LOGGER.error("Failed to save subagent preference when disabled by policy", e);
-        }
-      }
-    }
-  }
-
-  /**
-   * Checks if the sub-agent is enabled.
-   * Sub-agent is enabled only if both the user preference is enabled AND the organization policy allows it.
-   *
-   * @return true if the sub-agent is enabled, false otherwise.
-   */
-  public static boolean isSubAgentEnabled() {
-    IEclipsePreferences uiPrefs = InstanceScope.INSTANCE.getNode("com.microsoft.copilot.eclipse.ui");
-    if (uiPrefs != null) {
-      return uiPrefs.getBoolean(Constants.SUB_AGENT_ENABLED, false);
-    }
-
-    return false;
-  }
-
   /**
    * Checks if the custom agent is enabled.
    * Custom agent is enabled only if the organization policy allows it.

com.microsoft.copilot.eclipse.core/src/com/microsoft/copilot/eclipse/core/events/CopilotEventConstants.java

@@ -86,11 +86,6 @@ public class CopilotEventConstants {
   public static final String TOPIC_DID_CHANGE_MCP_CONTRIBUTION_POINT_POLICY = TOPIC_POLICY
       + "MCP_CONTRIBUTION_POINT_ENABLED";
 
-  /**
-   * Event when the sub-agent policy flag is updated.
-   */
-  public static final String TOPIC_DID_CHANGE_SUB_AGENT_POLICY = TOPIC_POLICY + "SUB_AGENT_ENABLED";
-
   /**
    * Event when the custom agent policy flag is updated.
    */

com.microsoft.copilot.eclipse.core/src/com/microsoft/copilot/eclipse/core/lsp/CopilotLanguageClient.java

@@ -351,10 +351,6 @@ public void onDidChangePolicy(DidChangePolicyParams params) {
         eventBroker.post(CopilotEventConstants.TOPIC_DID_CHANGE_MCP_CONTRIBUTION_POINT_POLICY,
             params.isMcpContributionPointEnabled());
       }
-      if (flags.isSubAgentPolicyEnabled() != params.isSubAgentEnabled()) {
-        flags.setSubAgentPolicyEnabled(params.isSubAgentEnabled());
-        eventBroker.post(CopilotEventConstants.TOPIC_DID_CHANGE_SUB_AGENT_POLICY, params.isSubAgentEnabled());
-      }
       if (flags.isCustomAgentPolicyEnabled() != params.isCustomAgentEnabled()) {
         flags.setCustomAgentPolicyEnabled(params.isCustomAgentEnabled());
         eventBroker.post(CopilotEventConstants.TOPIC_DID_CHANGE_CUSTOM_AGENT_POLICY, params.isCustomAgentEnabled());

com.microsoft.copilot.eclipse.core/src/com/microsoft/copilot/eclipse/core/lsp/LsStreamConnectionProvider.java

@@ -55,7 +55,7 @@ public Object getInitializationOptions(@Nullable URI rootUri) {
     NameAndVersion editorPluginInfo = new NameAndVersion(EDITOR_PLUGIN_NAME, bundleVersion);
     List<String> supportedUriSchemes = PlatformUtils.getSupportedUriSchemes();
     CopilotCapabilities capabilities = new CopilotCapabilities(false, FeatureFlags.isWorkspaceContextEnabled(),
-        FeatureFlags.isSubAgentEnabled(), supportedUriSchemes);
+        true /*isSubAgentEnabled*/, supportedUriSchemes);
     return new InitializationOptions(editorInfo, editorPluginInfo, capabilities);
   }
 

com.microsoft.copilot.eclipse.core/src/com/microsoft/copilot/eclipse/core/lsp/protocol/policy/DidChangePolicyParams.java

@@ -16,9 +16,6 @@ public class DidChangePolicyParams {
   @SerializedName("mcp.contributionPoint.enabled")
   private boolean mcpContributionPointEnabled;
 
-  @SerializedName("subAgent.enabled")
-  private boolean subAgentEnabled = true;
-
   @SerializedName("customAgent.enabled")
   private boolean customAgentEnabled = true;
 
@@ -33,14 +30,6 @@ public void setMcpContributionPointEnabled(boolean mcpContributionPointEnabled)
     this.mcpContributionPointEnabled = mcpContributionPointEnabled;
   }
 
-  public boolean isSubAgentEnabled() {
-    return subAgentEnabled;
-  }
-
-  public void setSubAgentEnabled(boolean subAgentEnabled) {
-    this.subAgentEnabled = subAgentEnabled;
-  }
-
   public boolean isCustomAgentEnabled() {
     return customAgentEnabled;
   }
@@ -59,7 +48,7 @@ public void setAutoApprovalPolicyEnabled(boolean autoApprovalPolicyEnabled) {
 
   @Override
   public int hashCode() {
-    return Objects.hash(mcpContributionPointEnabled, subAgentEnabled, customAgentEnabled,
+    return Objects.hash(mcpContributionPointEnabled, customAgentEnabled,
         autoApprovalPolicyEnabled);
   }
 
@@ -76,7 +65,6 @@ public boolean equals(Object obj) {
     }
     DidChangePolicyParams other = (DidChangePolicyParams) obj;
     return mcpContributionPointEnabled == other.mcpContributionPointEnabled
-        && subAgentEnabled == other.subAgentEnabled
         && customAgentEnabled == other.customAgentEnabled
         && autoApprovalPolicyEnabled == other.autoApprovalPolicyEnabled;
   }
@@ -85,7 +73,6 @@ public boolean equals(Object obj) {
   public String toString() {
     ToStringBuilder builder = new ToStringBuilder(this);
     builder.append("mcpContributionPointEnabled", mcpContributionPointEnabled);
-    builder.append("subAgentEnabled", subAgentEnabled);
     builder.append("customAgentEnabled", customAgentEnabled);
     builder.append("autoApprovalPolicyEnabled", autoApprovalPolicyEnabled);
     return builder.toString();

com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/preferences/ChatPreferencesPage.java

@@ -3,12 +3,6 @@
 
 package com.microsoft.copilot.eclipse.ui.preferences;
 
-import java.lang.reflect.Type;
-import java.util.HashMap;
-import java.util.Map;
-
-import com.google.gson.Gson;
-import com.google.gson.reflect.TypeToken;
 import org.eclipse.core.runtime.preferences.InstanceScope;
 import org.eclipse.jface.dialogs.MessageDialog;
 import org.eclipse.jface.layout.GridDataFactory;
@@ -60,29 +54,6 @@ public void createFieldEditors() {
     addNote(parent, Messages.preferences_page_watched_files_note_content);
     addSeparator(parent);
 
-    // Add sub-agent toggle
-    Composite subAgentComposite = createSectionComposite(parent, gdf);
-    boolean policyAllowsSubAgent = isPolicyAllowsSubAgent();
-    if (!policyAllowsSubAgent) {
-      Composite disabledComposite = new Composite(subAgentComposite, SWT.NONE);
-      GridLayout disabledCompositeLayout = new GridLayout(1, false);
-      disabledCompositeLayout.marginWidth = 0;
-      disabledCompositeLayout.marginHeight = 0;
-      disabledComposite.setLayout(disabledCompositeLayout);
-      disabledComposite.setLayoutData(new GridData(SWT.FILL, SWT.TOP, true, false));
-      WrappableIconLink.createWithCustomizedImage(disabledComposite, "/icons/information.png",
-          Messages.setting_managed_by_organization);
-    }
-
-    BooleanFieldEditor subAgentField = new BooleanFieldEditor(Constants.SUB_AGENT_ENABLED,
-        Messages.preferences_page_sub_agent, SWT.WRAP, subAgentComposite);
-    subAgentField.setEnabled(policyAllowsSubAgent, subAgentComposite);
-    applyFieldWidthHint(subAgentField, subAgentComposite);
-    addField(subAgentField);
-
-    addNote(parent, Messages.preferences_page_sub_agent_note_content);
-    addSeparator(parent);
-
     if (isClientPreviewFeatureEnabled()) {
       // Add Enable Skills toggle
       Composite skillsComposite = createSectionComposite(parent, gdf);
@@ -111,51 +82,23 @@ public void createFieldEditors() {
   @Override
   public void init(IWorkbench workbench) {
     setPreferenceStore(CopilotUi.getPlugin().getPreferenceStore());
-
-    // Ensure run_subagent tool configuration is consistent with sub-agent preference
-    // Only check if sub-agent is policy-enabled
-    if (isPolicyAllowsSubAgent()) {
-      boolean subAgentEnabled = getPreferenceStore().getBoolean(Constants.SUB_AGENT_ENABLED);
-      updateSubAgentToolConfiguration(subAgentEnabled);
-    }
   }
 
   @Override
   public boolean performOk() {
     final boolean oldWorkspaceContextValue = getPreferenceStore().getBoolean(Constants.WORKSPACE_CONTEXT_ENABLED);
 
-    // Check if sub-agent is policy-enabled before handling sub-agent preferences
-    boolean policyAllowsSubAgent = isPolicyAllowsSubAgent();
-
-    boolean oldSubAgentValue = false;
-    if (policyAllowsSubAgent) {
-      oldSubAgentValue = getPreferenceStore().getBoolean(Constants.SUB_AGENT_ENABLED);
-    }
-
     final boolean result = super.performOk();
     boolean newWorkspaceContextValue = getPreferenceStore().getBoolean(Constants.WORKSPACE_CONTEXT_ENABLED);
 
-    boolean newSubAgentValue = false;
-    if (policyAllowsSubAgent) {
-      newSubAgentValue = getPreferenceStore().getBoolean(Constants.SUB_AGENT_ENABLED);
-    }
-
-    // Handle sub-agent preference change
-    boolean isSubAgentChanged = policyAllowsSubAgent && (oldSubAgentValue ^ newSubAgentValue);
-    if (isSubAgentChanged) {
-      updateSubAgentToolConfiguration(newSubAgentValue);
-    }
-
     boolean isWorkspaceContextChanged = oldWorkspaceContextValue ^ newWorkspaceContextValue;
     if (isWorkspaceContextChanged) {
       try {
         InstanceScope.INSTANCE.getNode(CopilotUi.getPlugin().getBundle().getSymbolicName()).flush();
       } catch (BackingStoreException e) {
         CopilotCore.LOGGER.error("Failed to save preference 'Enable workspace context'", e);
       }
-    }
 
-    if (isSubAgentChanged || isWorkspaceContextChanged) {
       boolean restart = MessageDialog.openQuestion(getShell(), Messages.preferences_page_restart_required,
           Messages.preferences_page_restart_question);
 
@@ -196,63 +139,8 @@ private void addSeparator(Composite parent) {
     separator.setLayoutData(gridData);
   }
 
-  private boolean isPolicyAllowsSubAgent() {
-    FeatureFlags flags = CopilotCore.getPlugin().getFeatureFlags();
-    return isClientPreviewFeatureEnabled() && flags != null && flags.isSubAgentPolicyEnabled();
-  }
-
   private boolean isClientPreviewFeatureEnabled() {
     FeatureFlags flags = CopilotCore.getPlugin().getFeatureFlags();
     return flags != null && flags.isClientPreviewFeatureEnabled();
   }
-
-  /**
-   * Updates the MCP tool configuration to include or exclude the run_subagent tool for agent mode based on the
-   * sub-agent preference setting.
-   *
-   * @param subAgentEnabled true if sub-agent is enabled, false otherwise
-   */
-  private void updateSubAgentToolConfiguration(boolean subAgentEnabled) {
-    try {
-      // Load existing MCP tools mode status
-      String existingJson = getPreferenceStore().getString(Constants.MCP_TOOLS_MODE_STATUS);
-
-      // Parse existing configuration or create new one
-      Map<String, Map<String, Map<String, Boolean>>> modeToolStatus;
-      if (existingJson != null && !existingJson.trim().isEmpty()) {
-        Type type = new TypeToken<Map<String, Map<String, Map<String, Boolean>>>>() {
-        }.getType();
-        modeToolStatus = new Gson().fromJson(existingJson, type);
-      } else {
-        modeToolStatus = new HashMap<>();
-      }
-
-      // Ensure agent-mode map exists
-      if (!modeToolStatus.containsKey("agent-mode")) {
-        modeToolStatus.put("agent-mode", new HashMap<>());
-      }
-
-      // Get or create the Built-in Tools server map
-      Map<String, Map<String, Boolean>> agentModeTools = modeToolStatus.get("agent-mode");
-      String builtInToolsKey = Messages.preferences_page_mcp_tools_builtin;
-      if (!agentModeTools.containsKey(builtInToolsKey)) {
-        agentModeTools.put(builtInToolsKey, new HashMap<>());
-      }
-
-      // Update the run_subagent tool status
-      Map<String, Boolean> builtInTools = agentModeTools.get(builtInToolsKey);
-      if (subAgentEnabled) {
-        builtInTools.put("run_subagent", true);
-      } else {
-        builtInTools.remove("run_subagent");
-      }
-
-      // Save back to preferences
-      String updatedJson = new Gson().toJson(modeToolStatus);
-      getPreferenceStore().setValue(Constants.MCP_TOOLS_MODE_STATUS, updatedJson);
-
-    } catch (Exception e) {
-      CopilotCore.LOGGER.error("Failed to update sub-agent tool configuration", e);
-    }
-  }
 }

com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/preferences/CopilotPreferenceInitializer.java

@@ -31,7 +31,6 @@ public void initializeDefaultPreferences() {
     pref.setDefault(Constants.PROXY_KERBEROS_SP, "");
     pref.setDefault(Constants.GITHUB_ENTERPRISE, "");
     pref.setDefault(Constants.WORKSPACE_CONTEXT_ENABLED, false);
-    pref.setDefault(Constants.SUB_AGENT_ENABLED, true);
     pref.setDefault(Constants.AGENT_MAX_REQUESTS, 25);
     pref.setDefault(Constants.ENABLE_SKILLS, true);
     pref.setDefault(Constants.CUSTOM_INSTRUCTIONS_WORKSPACE_ENABLED, false);