diff --git a/src/@types/vscode.proposed.chatSessionsProvider.d.ts b/src/@types/vscode.proposed.chatSessionsProvider.d.ts
index 772fc387b9..2ec68c1731 100644
--- a/src/@types/vscode.proposed.chatSessionsProvider.d.ts
+++ b/src/@types/vscode.proposed.chatSessionsProvider.d.ts
@@ -49,26 +49,6 @@ declare module 'vscode' {
 		 */
 		readonly onDidCommitChatSessionItem: Event<{ original: ChatSessionItem /** untitled */; modified: ChatSessionItem /** newly created */ }>;
 
-		/**
-		 * DEPRECATED: Will be removed!
-		 * Creates a new chat session.
-		 *
-		 * @param options Options for the new session including an optional initial prompt and history
-		 * @param token A cancellation token
-		 * @returns Metadata for the chat session
-		 */
-		provideNewChatSessionItem?(options: {
-			/**
-			 * The chat request that initiated the session creation
-			 */
-			readonly request: ChatRequest;
-
-			/**
-			 * Additional metadata to use for session creation
-			 */
-			metadata?: any;
-		}, token: CancellationToken): ProviderResult<ChatSessionItem>;
-
 		// #endregion
 	}
 
@@ -241,6 +221,14 @@ declare module 'vscode' {
 		 */
 		readonly onDidChangeChatSessionOptions?: Event<ChatSessionOptionChangeEvent>;
 
+		/**
+		 * Event that the provider can fire to signal that the available provider options have changed.
+		 *
+		 * When fired, the editor will re-query {@link ChatSessionContentProvider.provideChatSessionProviderOptions}
+		 * and update the UI to reflect the new option groups.
+		 */
+		readonly onDidChangeChatSessionProviderOptions?: Event<void>;
+
 		/**
 		 * Provides the chat session content for a given uri.
 		 *
diff --git a/src/github/loggingOctokit.ts b/src/github/loggingOctokit.ts
index 09813b75ae..c6b83f0975 100644
--- a/src/github/loggingOctokit.ts
+++ b/src/github/loggingOctokit.ts
@@ -150,8 +150,8 @@ export class LoggingOctokit {
 	}
 }
 
-export async function compareCommits(remote: GitHubRemote, octokit: LoggingOctokit, base: GitHubRef, head: GitHubRef, compareWithBaseRef: string, prNumber: number, logId: string): Promise<{ mergeBaseSha: string; files: IRawFileChange[] }> {
-	Logger.debug(`Comparing commits for ${remote.owner}/${remote.repositoryName} with base ${base.repositoryCloneUrl.owner}:${compareWithBaseRef} and head ${head.repositoryCloneUrl.owner}:${head.sha}`, logId);
+export async function compareCommits(remote: GitHubRemote, octokit: LoggingOctokit, base: GitHubRef, head: GitHubRef, compareWithBaseRef: string, prNumber: number, logId: string, excludeMergeCommits: boolean = false): Promise<{ mergeBaseSha: string; files: IRawFileChange[] }> {
+	Logger.debug(`Comparing commits for ${remote.owner}/${remote.repositoryName} with base ${base.repositoryCloneUrl.owner}:${compareWithBaseRef} and head ${head.repositoryCloneUrl.owner}:${head.sha}${excludeMergeCommits ? ' (excluding merge commits)' : ''}`, logId);
 	let files: IRawFileChange[] | undefined;
 	let mergeBaseSha: string | undefined;
 
@@ -164,12 +164,27 @@ export async function compareCommits(remote: GitHubRemote, octokit: LoggingOctok
 	};
 
 	try {
-		const { data } = await octokit.call(octokit.api.repos.compareCommits, {
-			repo: remote.repositoryName,
-			owner: remote.owner,
-			base: `${base.repositoryCloneUrl.owner}:${compareWithBaseRef}`,
-			head: `${head.repositoryCloneUrl.owner}:${head.sha}`,
-		});
+		let data: any;
+		if (excludeMergeCommits) {
+			// Use three-dot syntax to show only changes unique to the head branch since it diverged from the base.
+			// This naturally excludes changes from merge commits.
+			const basehead = `${base.repositoryCloneUrl.owner}:${compareWithBaseRef}...${head.repositoryCloneUrl.owner}:${head.sha}`;
+			const response = await octokit.call(octokit.api.repos.compareCommitsWithBasehead, {
+				repo: remote.repositoryName,
+				owner: remote.owner,
+				basehead,
+			});
+			data = response.data;
+		} else {
+			// Use the default comparison (equivalent to two-dot) which shows all changes between base and head.
+			const response = await octokit.call(octokit.api.repos.compareCommits, {
+				repo: remote.repositoryName,
+				owner: remote.owner,
+				base: `${base.repositoryCloneUrl.owner}:${compareWithBaseRef}`,
+				head: `${head.repositoryCloneUrl.owner}:${head.sha}`,
+			});
+			data = response.data;
+		}
 		const MAX_FILE_CHANGES_IN_COMPARE_COMMITS = 100;
 
 		if (data.files && data.files.length >= MAX_FILE_CHANGES_IN_COMPARE_COMMITS) {
@@ -191,5 +206,5 @@ export async function compareCommits(remote: GitHubRemote, octokit: LoggingOctok
 			throw e;
 		}
 	}
-	return { mergeBaseSha, files };
+	return { mergeBaseSha: mergeBaseSha!, files: files! };
 }
diff --git a/src/github/pullRequestModel.ts b/src/github/pullRequestModel.ts
index d984d19b93..37ef4769a8 100644
--- a/src/github/pullRequestModel.ts
+++ b/src/github/pullRequestModel.ts
@@ -1793,7 +1793,7 @@ export class PullRequestModel extends IssueModel<PullRequest> implements IPullRe
 		}
 
 		Logger.debug(`Comparing commits for ${remote.owner}/${remote.repositoryName} with base ${this.base.repositoryCloneUrl.owner}:${compareWithBaseRef} and head ${this.head!.repositoryCloneUrl.owner}:${this.head!.sha}`, PullRequestModel.ID);
-		const { files, mergeBaseSha } = await compareCommits(remote, octokit, this.base, this.head!, compareWithBaseRef, this.number, PullRequestModel.ID);
+		const { files, mergeBaseSha } = await compareCommits(remote, octokit, this.base, this.head!, compareWithBaseRef, this.number, PullRequestModel.ID, this._showChangesSinceReview);
 		this.mergeBase = mergeBaseSha;
 
 		if (oldHasChangesSinceReview !== undefined && oldHasChangesSinceReview !== this.hasChangesSinceLastReview && this.hasChangesSinceLastReview && this._showChangesSinceReview) {