Extract chat session routing heuristics (#329522)

* Extract chat session routing heuristics

* Export routing enrichment limit

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

src/vs/workbench/contrib/chat/browser/sessionRouter/chatSessionRoutingHelpers.ts

@@ -0,0 +1,159 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { URI } from '../../../../../base/common/uri.js';
+import { IWorkspaceFolder } from '../../../../../platform/workspace/common/workspace.js';
+import { IRoutableSession, isHighConfidenceSessionRoute, ISessionRouteResult } from '../../common/sessionRouter.js';
+
+/** Number of top-ranked candidates whose conversation content should be resolved. */
+export const ROUTE_ENRICH_MAX_CANDIDATES = 12;
+const RELATED_SESSION_FOLDER_CONFIDENCE = 0.35;
+
+/**
+ * Extracts the task from an explicit request to start a new session.
+ * Requests that merely mention creating another resource are deliberately ignored.
+ */
+export function parseExplicitNewSessionRequest(utterance: string): string | undefined {
+	const match = /^(?:please\s+)?(?:create|start|open)\s+(?:a\s+)?new\s+(?:chat\s+)?session(?:\s+(?:to|for|and)\s+|\s*[:,-]\s*)(.+)$/i.exec(utterance.trim());
+	const task = match?.[1]?.trim();
+	return task || undefined;
+}
+
+/**
+ * Chooses the workspace folder for a newly routed session. Explicit folder
+ * mentions win, followed by a sufficiently related session's folder and then
+ * the caller's default.
+ */
+export function resolveNewSessionWorkspaceFolder(
+	utterance: string,
+	folders: readonly IWorkspaceFolder[],
+	results: readonly ISessionRouteResult[],
+	candidates: readonly IRoutableSession[],
+	defaultFolder: URI | undefined,
+): URI | undefined {
+	return folderMentionedInUtterance(utterance, folders)
+		?? folderFromRelatedSession(results, candidates, folders)
+		?? defaultFolder
+		?? folders[0]?.uri;
+}
+
+/**
+ * Bounds transcript enrichment while preserving the model's preliminary order.
+ * Any remaining slots favor active and recently updated sessions.
+ */
+export function selectRouterShortlist(
+	candidates: readonly IRoutableSession[],
+	preliminaryResults: readonly ISessionRouteResult[],
+	limit: number = ROUTE_ENRICH_MAX_CANDIDATES,
+): IRoutableSession[] {
+	if (candidates.length <= limit) {
+		return [...candidates];
+	}
+
+	const candidatesById = new Map(candidates.map(candidate => [candidate.sessionId, candidate]));
+	const selectedIds = new Set<string>();
+	const shortlist: IRoutableSession[] = [];
+	for (const result of preliminaryResults) {
+		const candidate = candidatesById.get(result.sessionId);
+		if (candidate && !selectedIds.has(candidate.sessionId)) {
+			selectedIds.add(candidate.sessionId);
+			shortlist.push(candidate);
+			if (shortlist.length === limit) {
+				return shortlist;
+			}
+		}
+	}
+
+	const fallback = candidates
+		.filter(candidate => !selectedIds.has(candidate.sessionId))
+		.sort((a, b) =>
+			sessionStatusPriority(b.status) - sessionStatusPriority(a.status)
+			|| (b.lastActivity ?? 0) - (a.lastActivity ?? 0)
+			|| a.label.localeCompare(b.label)
+			|| a.sessionId.localeCompare(b.sessionId));
+	shortlist.push(...fallback.slice(0, limit - shortlist.length));
+	return shortlist;
+}
+
+/** Selects the top result only when it clears the shared confidence threshold. */
+export function selectBestSessionRoute(results: readonly ISessionRouteResult[]): ISessionRouteResult | undefined {
+	const top = results[0];
+	return top && isHighConfidenceSessionRoute(top) ? top : undefined;
+}
+
+function sessionStatusPriority(status: string | undefined): number {
+	return status === 'working' ? 2 : status === 'idle' ? 1 : 0;
+}
+
+function folderMentionedInUtterance(utterance: string, folders: readonly IWorkspaceFolder[]): URI | undefined {
+	const normalizedUtterance = utterance.toLocaleLowerCase();
+	let best: { folder: IWorkspaceFolder; length: number } | undefined;
+	for (const folder of folders) {
+		const names = new Set([folder.name, folder.uri.path.split('/').filter(Boolean).at(-1)]);
+		for (const name of names) {
+			if (!name || name.length < 3) {
+				continue;
+			}
+			const normalizedName = name.toLocaleLowerCase();
+			let start = normalizedUtterance.indexOf(normalizedName);
+			while (start >= 0) {
+				if (isWordBoundary(normalizedUtterance[start - 1])
+					&& isWordBoundary(normalizedUtterance[start + normalizedName.length])) {
+					if (!best || normalizedName.length > best.length) {
+						best = { folder, length: normalizedName.length };
+					}
+					break;
+				}
+				start = normalizedUtterance.indexOf(normalizedName, start + normalizedName.length);
+			}
+		}
+	}
+	return best?.folder.uri;
+}
+
+function folderFromRelatedSession(
+	results: readonly ISessionRouteResult[],
+	candidates: readonly IRoutableSession[],
+	folders: readonly IWorkspaceFolder[],
+): URI | undefined {
+	const candidateById = new Map(candidates.map(candidate => [candidate.sessionId, candidate]));
+	for (const result of results) {
+		if (result.confidence < RELATED_SESSION_FOLDER_CONFIDENCE) {
+			continue;
+		}
+		const candidate = candidateById.get(result.sessionId);
+		const folder = candidate && folderForSessionMetadata(candidate, folders);
+		if (folder) {
+			return folder.uri;
+		}
+	}
+	return undefined;
+}
+
+function folderForSessionMetadata(candidate: IRoutableSession, folders: readonly IWorkspaceFolder[]): IWorkspaceFolder | undefined {
+	for (const path of [candidate.cwd, candidate.repo]) {
+		if (!path) {
+			continue;
+		}
+		const normalizedPath = path.replaceAll('\\', '/').replace(/\/+$/, '').replace(/^([a-zA-Z]:\/)/, '/$1').toLocaleLowerCase();
+		const match = folders
+			.filter(folder => {
+				const folderPath = folder.uri.path.replace(/\/+$/, '').toLocaleLowerCase();
+				return normalizedPath === folderPath
+					|| normalizedPath.startsWith(`${folderPath}/`)
+					|| normalizedPath.endsWith(`/${folder.name.toLocaleLowerCase()}`)
+					|| normalizedPath.endsWith(`/${folder.name.toLocaleLowerCase()}.git`);
+			})
+			.sort((a, b) => b.uri.path.length - a.uri.path.length)[0];
+		if (match) {
+			return match;
+		}
+	}
+	return undefined;
+}
+
+function isWordBoundary(value: string | undefined): boolean {
+	return value === undefined || !/[\p{L}\p{N}_-]/u.test(value);
+}

src/vs/workbench/contrib/chat/test/browser/sessionRouter/chatSessionRoutingHelpers.test.ts

@@ -0,0 +1,113 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import assert from 'assert';
+import { URI } from '../../../../../../base/common/uri.js';
+import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../../../base/test/common/utils.js';
+import { IWorkspaceFolder } from '../../../../../../platform/workspace/common/workspace.js';
+import { parseExplicitNewSessionRequest, resolveNewSessionWorkspaceFolder, selectBestSessionRoute, selectRouterShortlist } from '../../../browser/sessionRouter/chatSessionRoutingHelpers.js';
+
+suite('Chat session routing helpers', () => {
+
+	ensureNoDisposablesAreLeakedInTestSuite();
+
+	const vscode = folder('vscode', '/work/vscode', 0);
+	const docs = folder('vscode-docs', '/work/vscode-docs', 1);
+
+	test('chooses an explicitly mentioned workspace folder', () => {
+		const result = resolveNewSessionWorkspaceFolder(
+			'update the vscode-docs API reference',
+			[vscode, docs],
+			[],
+			[],
+			vscode.uri,
+		);
+
+		assert.strictEqual(result?.toString(), docs.uri.toString());
+	});
+
+	test('uses a related session working directory when starting a new session', () => {
+		const result = resolveNewSessionWorkspaceFolder(
+			'continue the authentication cleanup',
+			[vscode, docs],
+			[{ sessionId: 'related', confidence: 0.5 }],
+			[{ sessionId: 'related', label: 'Authentication cleanup', cwd: '/work/vscode-docs/src' }],
+			vscode.uri,
+		);
+
+		assert.strictEqual(result?.toString(), docs.uri.toString());
+	});
+
+	test('explicit folder mention overrides a related session in another folder', () => {
+		const result = resolveNewSessionWorkspaceFolder(
+			'update the vscode-docs API reference',
+			[vscode, docs],
+			[{ sessionId: 'related', confidence: 0.9 }],
+			[{ sessionId: 'related', label: 'Related work', cwd: '/work/vscode/src' }],
+			vscode.uri,
+		);
+
+		assert.strictEqual(result?.toString(), docs.uri.toString());
+	});
+
+	test('bounds transcript enrichment after every candidate receives model scoring', () => {
+		const candidates = Array.from({ length: 13 }, (_, index) => ({
+			sessionId: `s${index}`,
+			label: `Session ${index}`,
+			status: index === 12 ? 'working' : 'idle',
+			lastActivity: index,
+		}));
+		const shortlist = selectRouterShortlist(candidates, [
+			{ sessionId: 's0', confidence: 0.9 },
+			{ sessionId: 's3', confidence: 0.8 },
+		]);
+
+		assert.deepStrictEqual({
+			length: shortlist.length,
+			first: shortlist[0].sessionId,
+			second: shortlist[1].sessionId,
+			third: shortlist[2].sessionId,
+			excluded: candidates.filter(candidate => !shortlist.includes(candidate)).map(candidate => candidate.sessionId),
+		}, {
+			length: 12,
+			first: 's0',
+			second: 's3',
+			third: 's12',
+			excluded: ['s1'],
+		});
+	});
+
+	test('selects only a high-confidence route', () => {
+		assert.deepStrictEqual(selectBestSessionRoute([
+			{ sessionId: 'best', confidence: 0.9 },
+			{ sessionId: 'previous', confidence: 0.86 },
+		]), { sessionId: 'best', confidence: 0.9 });
+		assert.strictEqual(selectBestSessionRoute([{ sessionId: 'weak', confidence: 0.8 }]), undefined);
+	});
+
+	test('keeps the default folder for a weak related-session match', () => {
+		const result = resolveNewSessionWorkspaceFolder(
+			'start something new',
+			[vscode, docs],
+			[{ sessionId: 'weak', confidence: 0.1 }],
+			[{ sessionId: 'weak', label: 'Unrelated docs work', cwd: '/work/vscode-docs' }],
+			vscode.uri,
+		);
+
+		assert.strictEqual(result?.toString(), vscode.uri.toString());
+	});
+
+	test('extracts only explicit new-session tasks', () => {
+		assert.strictEqual(parseExplicitNewSessionRequest('Create a new session to update the chocolate file'), 'update the chocolate file');
+		assert.strictEqual(parseExplicitNewSessionRequest('Please start a new chat session for fixing tests'), 'fixing tests');
+		assert.strictEqual(parseExplicitNewSessionRequest('Create a new session'), undefined);
+		assert.strictEqual(parseExplicitNewSessionRequest('Create a file in the current session'), undefined);
+	});
+});
+
+function folder(name: string, path: string, index: number): IWorkspaceFolder {
+	const uri = URI.file(path);
+	return { uri, name, index, toResource: relativePath => URI.joinPath(uri, relativePath) };
+}