Node: Add post user prompt hook

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

Author: SteveSandersonMS

nodejs/src/index.ts

@@ -97,6 +97,9 @@ export type {
     PermissionHandler,
     PermissionRequest,
     PermissionRequestResult,
+    PostUserPromptSubmittedHandler,
+    PostUserPromptSubmittedHookInput,
+    PostUserPromptSubmittedHookOutput,
     ProviderConfig,
     ProviderModelConfig,
     RemoteSessionMode,

nodejs/src/session.ts

@@ -1140,6 +1140,9 @@ export class CopilotSession {
             postToolUse: this.hooks.onPostToolUse as GenericHandler | undefined,
             postToolUseFailure: this.hooks.onPostToolUseFailure as GenericHandler | undefined,
             userPromptSubmitted: this.hooks.onUserPromptSubmitted as GenericHandler | undefined,
+            postUserPromptSubmitted: this.hooks.onPostUserPromptSubmitted as
+                | GenericHandler
+                | undefined,
             sessionStart: this.hooks.onSessionStart as GenericHandler | undefined,
             sessionEnd: this.hooks.onSessionEnd as GenericHandler | undefined,
             errorOccurred: this.hooks.onErrorOccurred as GenericHandler | undefined,

nodejs/src/types.ts

@@ -1272,6 +1272,34 @@ export type UserPromptSubmittedHandler = (
     invocation: { sessionId: string }
 ) => Promise<UserPromptSubmittedHookOutput | void> | UserPromptSubmittedHookOutput | void;
 
+/**
+ * Input for post-user-prompt-submitted hook.
+ *
+ * This hook runs after the runtime has transformed the submitted prompt with
+ * generated context such as `<current_datetime>`, but before the transformed
+ * prompt is persisted to session history or sent to the model.
+ */
+export interface PostUserPromptSubmittedHookInput extends BaseHookInput {
+    prompt: string;
+    transformedPrompt: string;
+}
+
+/**
+ * Output for post-user-prompt-submitted hook.
+ */
+export interface PostUserPromptSubmittedHookOutput {
+    modifiedTransformedPrompt?: string;
+    suppressOutput?: boolean;
+}
+
+/**
+ * Handler for post-user-prompt-submitted hook.
+ */
+export type PostUserPromptSubmittedHandler = (
+    input: PostUserPromptSubmittedHookInput,
+    invocation: { sessionId: string }
+) => Promise<PostUserPromptSubmittedHookOutput | void> | PostUserPromptSubmittedHookOutput | void;
+
 /**
  * Input for session-start hook
  */
@@ -1385,6 +1413,11 @@ export interface SessionHooks {
      */
     onUserPromptSubmitted?: UserPromptSubmittedHandler;
 
+    /**
+     * Called after the runtime transforms a submitted prompt and before it is stored.
+     */
+    onPostUserPromptSubmitted?: PostUserPromptSubmittedHandler;
+
     /**
      * Called when a session starts
      */

nodejs/test/e2e/hooks_extended.e2e.test.ts

@@ -7,6 +7,7 @@ import { z } from "zod";
 import { approveAll, defineTool } from "../../src/index.js";
 import type {
     ErrorOccurredHookInput,
+    PostUserPromptSubmittedHookInput,
     PostToolUseFailureHookInput,
     PostToolUseHookInput,
     PreToolUseHookInput,
@@ -149,6 +150,42 @@ describe("Extended session hooks", async () => {
         await session.disconnect();
     });
 
+    it("should invoke postUserPromptSubmitted hook and modify transformed prompt", async () => {
+        const inputs: PostUserPromptSubmittedHookInput[] = [];
+        const session = await client.createSession({
+            onPermissionRequest: approveAll,
+            hooks: {
+                onPostUserPromptSubmitted: async (input, invocation) => {
+                    inputs.push(input);
+                    expect(invocation.sessionId).toBeTruthy();
+                    expect(input.prompt).toContain("Say something after prompt transformation");
+                    expect(input.transformedPrompt).toContain(
+                        "Say something after prompt transformation"
+                    );
+                    expect(input.transformedPrompt).toContain("<current_datetime>");
+
+                    return {
+                        modifiedTransformedPrompt: input.transformedPrompt.replace(
+                            /<current_datetime>.*?<\/current_datetime>\n*/s,
+                            "POST_USER_PROMPT_SUBMITTED_HOOK\n"
+                        ),
+                    };
+                },
+            },
+        });
+
+        const response = await session.sendAndWait({
+            prompt: "Say something after prompt transformation",
+        });
+
+        expect(inputs.length).toBeGreaterThan(0);
+        expect(inputs[0].timestamp).toBeInstanceOf(Date);
+        expect(inputs[0].workingDirectory).toBeDefined();
+        expect(response?.data.content ?? "").toContain("POST_USER_PROMPT_SUBMITTED_HOOK");
+
+        await session.disconnect();
+    });
+
     it("should invoke sessionStart hook", async () => {
         const inputs: SessionStartHookInput[] = [];
         const session = await client.createSession({

test/snapshots/hooks_extended/should_invoke_postuserpromptsubmitted_hook_and_modify_transformed_prompt.yaml

@@ -0,0 +1,12 @@
+models:
+  - claude-sonnet-4.5
+conversations:
+  - messages:
+      - role: system
+        content: ${system}
+      - role: user
+        content: |-
+          POST_USER_PROMPT_SUBMITTED_HOOK
+          Say something after prompt transformation
+      - role: assistant
+        content: POST_USER_PROMPT_SUBMITTED_HOOK