Hardcode toolFilterMode=denyPrecedence on SDK; drop public toggle

The SDK no longer exposes 'toolFilterMode'. Every session.create / session.resume request now sends toolFilterMode: 'denyPrecedence' unconditionally, so SDK callers always get composable include+exclude semantics (a tool is enabled when it matches availableTools — or availableTools is unset — AND it does not match excludedTools).

Allowlist-precedence remains available on the runtime side as a CLI-only concession to legacy behavior; SDK consumers don't need it and the toggle was just extra surface area.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 2 people

nodejs/src/client.ts

@@ -880,19 +880,23 @@ export class CopilotClient {
     /**
      * Normalizes session-level tool filter options. Converts {@link ToolSet}
      * instances to plain string arrays, rejects misuse (bare `"*"`) and the
-     * missing-availableTools case in `mode = "empty"`, and applies the
-     * mode-aware default for `toolFilterMode`.
+     * missing-availableTools case in `mode = "empty"`.
+     *
+     * The SDK always sends `toolFilterMode: "denyPrecedence"` so callers can
+     * compose include + exclude lists naturally (e.g. "everything matching X
+     * except Y") regardless of mode. Allowlist-precedence is intentionally not
+     * exposed — it's available on the runtime side as a CLI-only concession to
+     * legacy behavior, but SDK consumers always get the composable semantics.
      *
      * @internal
      */
     private resolveToolFilterOptions(config: {
         availableTools?: string[] | ToolSet;
         excludedTools?: string[] | ToolSet;
-        toolFilterMode?: "allowPrecedence" | "denyPrecedence";
     }): {
         availableTools: string[] | undefined;
         excludedTools: string[] | undefined;
-        toolFilterMode: "allowPrecedence" | "denyPrecedence" | undefined;
+        toolFilterMode: "denyPrecedence";
     } {
         const availableTools = toolFilterListToArray(config.availableTools);
         const excludedTools = toolFilterListToArray(config.excludedTools);
@@ -910,13 +914,7 @@ export class CopilotClient {
             }
         }
 
-        // Empty mode flips the default to deny-precedence so apps can compose
-        // include + exclude lists naturally (e.g. "everything matching X
-        // except Y"). Callers can still override this explicitly.
-        const toolFilterMode =
-            config.toolFilterMode ?? (this.options.mode === "empty" ? "denyPrecedence" : undefined);
-
-        return { availableTools, excludedTools, toolFilterMode };
+        return { availableTools, excludedTools, toolFilterMode: "denyPrecedence" };
     }
 
     async createSession(config: SessionConfig): Promise<CopilotSession> {

nodejs/src/types.ts

@@ -1558,36 +1558,21 @@ export interface SessionConfigBase {
      * name form (exact match across any source). Build this list with
      * {@link ToolSet} for type safety and readable intent.
      *
-     * Interacts with {@link excludedTools} per
-     * {@link SessionConfigBase.toolFilterMode}.
+     * Composes with {@link excludedTools}: a tool is enabled when it matches
+     * `availableTools` (or `availableTools` is unset) AND it does not match
+     * `excludedTools`. This lets you express "everything matching X except Y".
      */
     availableTools?: string[] | ToolSet;
 
     /**
      * List of tool names to disable. Supports the same pattern syntax as
      * {@link availableTools}.
      *
-     * Interacts with {@link availableTools} per
-     * {@link SessionConfigBase.toolFilterMode}: by default (`"allowPrecedence"`),
-     * `excludedTools` is ignored whenever `availableTools` is set; under
-     * `"denyPrecedence"` it always takes effect.
+     * Always takes precedence over {@link availableTools}: a tool listed here
+     * is disabled even if it also matches `availableTools`.
      */
     excludedTools?: string[] | ToolSet;
 
-    /**
-     * Controls how {@link availableTools} and {@link excludedTools} combine
-     * when both are set.
-     *
-     * - `"allowPrecedence"` (default): If `availableTools` is set, `excludedTools`
-     *   is ignored. Preserves the historical CLI behavior.
-     * - `"denyPrecedence"`: `excludedTools` always wins. Enables "everything
-     *   matching X, except Y" patterns.
-     *
-     * When the client is in `Mode = "empty"`, the SDK defaults this to
-     * `"denyPrecedence"` so apps can subtract from `BuiltInTools.Isolated` etc.
-     */
-    toolFilterMode?: "allowPrecedence" | "denyPrecedence";
-
     /**
      * Custom provider configuration (BYOK - Bring Your Own Key).
      * When specified, uses the provided API endpoint instead of the Copilot API.

nodejs/test/toolSet.test.ts

@@ -174,29 +174,17 @@ describe("Tool filter wiring", () => {
         ).rejects.toThrowError(/bare wildcard/);
     });
 
-    it("forwards toolFilterMode unchanged when set explicitly", async () => {
-        const { client, spy } = await setupClient();
-        await client.createSession({
-            onPermissionRequest: approveAll,
-            availableTools: ["builtin:bash"],
-            excludedTools: ["builtin:bash"],
-            toolFilterMode: "denyPrecedence",
-        });
-        const payload = spy.mock.calls.find(([m]) => m === "session.create")![1] as any;
-        expect(payload.toolFilterMode).toBe("denyPrecedence");
-    });
-
-    it("does not default toolFilterMode in copilot-cli mode", async () => {
+    it("always sends toolFilterMode: denyPrecedence in copilot-cli mode", async () => {
         const { client, spy } = await setupClient("copilot-cli");
         await client.createSession({
             onPermissionRequest: approveAll,
             availableTools: ["builtin:bash"],
         });
         const payload = spy.mock.calls.find(([m]) => m === "session.create")![1] as any;
-        expect(payload.toolFilterMode).toBeUndefined();
+        expect(payload.toolFilterMode).toBe("denyPrecedence");
     });
 
-    it("defaults toolFilterMode to denyPrecedence in empty mode", async () => {
+    it("always sends toolFilterMode: denyPrecedence in empty mode", async () => {
         const { client, spy } = await setupClient("empty");
         await client.createSession({
             onPermissionRequest: approveAll,
@@ -206,17 +194,6 @@ describe("Tool filter wiring", () => {
         expect(payload.toolFilterMode).toBe("denyPrecedence");
     });
 
-    it("empty-mode default can be overridden to allowPrecedence", async () => {
-        const { client, spy } = await setupClient("empty");
-        await client.createSession({
-            onPermissionRequest: approveAll,
-            availableTools: ["builtin:bash"],
-            toolFilterMode: "allowPrecedence",
-        });
-        const payload = spy.mock.calls.find(([m]) => m === "session.create")![1] as any;
-        expect(payload.toolFilterMode).toBe("allowPrecedence");
-    });
-
     it("applies the same filter normalization on session.resume", async () => {
         const { client, spy } = await setupClient("empty");
         const session = await client.createSession({