diff --git a/packages/pyright-internal/jest.config.js b/packages/pyright-internal/jest.config.js
index 9fd7c0fd9..a88202d8c 100644
--- a/packages/pyright-internal/jest.config.js
+++ b/packages/pyright-internal/jest.config.js
@@ -4,7 +4,8 @@
  * Configuration for jest tests.
  */
 
-module.exports = {
+/** @type {import('ts-jest/dist/types').JestConfigWithTsJest} */
+const config = {
     testEnvironment: 'node',
     roots: ['<rootDir>/src/tests'],
     transform: {
@@ -19,3 +20,5 @@ module.exports = {
     moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx'],
     setupFiles: ['./src/tests/setupTests.ts'],
 };
+
+module.exports = config;
diff --git a/packages/pyright-internal/src/baseline.ts b/packages/pyright-internal/src/baseline.ts
index 2c73056aa..b69191b1d 100644
--- a/packages/pyright-internal/src/baseline.ts
+++ b/packages/pyright-internal/src/baseline.ts
@@ -12,7 +12,7 @@ export interface BaselinedDiagnostic {
     range: { startColumn: number; endColumn: number };
 }
 
-interface BaselineFile {
+export interface BaselineFile {
     files: {
         [filePath: string]: BaselinedDiagnostic[];
     };
diff --git a/packages/pyright-internal/src/tests/languageServer.test.ts b/packages/pyright-internal/src/tests/languageServer.test.ts
index 5f535651e..ea24b722d 100644
--- a/packages/pyright-internal/src/tests/languageServer.test.ts
+++ b/packages/pyright-internal/src/tests/languageServer.test.ts
@@ -34,6 +34,8 @@ import {
     runPyrightServer,
     waitForDiagnostics,
 } from './lsp/languageServerTestUtils';
+import { BaselineFile } from '../baseline';
+import { DiagnosticRule } from '../common/diagnosticRules';
 
 /** objects from `sendRequest` don't work with assertions and i cant figure out why */
 const assertEqual = <T>(actual: T, expected: T) => expect(JSON.parse(JSON.stringify(actual))).toStrictEqual(expected);
@@ -962,4 +964,70 @@ describe(`Basic language server tests`, () => {
                 'invalid diagnosticMode: "asdf". valid options are "workspace" or "openFilesOnly"'
         );
     });
+    describe('baseline', () => {
+        test('baselined error not shown', async () => {
+            const baseline: BaselineFile = {
+                files: {
+                    './foo.py': [
+                        {
+                            code: DiagnosticRule.reportAssignmentType,
+                            range: {
+                                startColumn: 11,
+                                endColumn: 13,
+                            },
+                        },
+                    ],
+                },
+            };
+            const code = `
+// @filename: .basedpyright/baseline.json
+//// ${JSON.stringify(baseline)}
+//// 
+// @filename: foo.py
+//// foo: int = ""
+//// asdf
+//// [|/*marker*/|]
+`;
+            const settings = [
+                {
+                    item: {
+                        scopeUri: `file://${normalizeSlashes(DEFAULT_WORKSPACE_ROOT, '/')}`,
+                        section: 'basedpyright.analysis',
+                    },
+                    value: {
+                        diagnosticSeverityOverrides: {
+                            reportAssignmentType: 'error',
+                            reportUndefinedVariable: 'error',
+                        },
+                    },
+                },
+            ];
+
+            const info = await runLanguageServer(
+                DEFAULT_WORKSPACE_ROOT,
+                code,
+                /* callInitialize */ true,
+                settings,
+                undefined,
+                /* supportsBackgroundThread */ false
+            );
+
+            // get the file containing the marker that also contains our task list comments
+            await openFile(info, 'marker');
+
+            // Wait for the diagnostics to publish
+            const diagnostics = await waitForDiagnostics(info);
+            const file = diagnostics.find((d) => d.uri.includes('test.py'));
+            assert(file);
+
+            // Make sure the error has a special rule
+            assert.equal(file.diagnostics[0].code, 'reportUnknownParameterType');
+
+            // make sure additional diagnostic severities work
+            assert.equal(
+                file.diagnostics.find((diagnostic) => diagnostic.code === 'reportUnusedFunction')?.severity,
+                DiagnosticSeverity.Hint // TODO: hint? how do we differentiate between unused/unreachable/deprecated?
+            );
+        });
+    });
 });
diff --git a/packages/pyright-internal/src/tests/testUtils.ts b/packages/pyright-internal/src/tests/testUtils.ts
index 56034c2bd..f852dbe44 100644
--- a/packages/pyright-internal/src/tests/testUtils.ts
+++ b/packages/pyright-internal/src/tests/testUtils.ts
@@ -32,6 +32,7 @@ import { SemanticTokenItem, SemanticTokensWalker } from '../analyzer/semanticTok
 import { TypeInlayHintsItemType, TypeInlayHintsWalker } from '../analyzer/typeInlayHintsWalker';
 import { Range } from 'vscode-languageserver-types';
 import { ServiceProvider } from '../common/serviceProvider';
+import { BaselineDiff, BaselineHandler } from '../baseline';
 
 // This is a bit gross, but it's necessary to allow the fallback typeshed
 // directory to be located when running within the jest environment. This
@@ -48,6 +49,7 @@ export interface FileAnalysisResult {
     unusedCodes: Diagnostic[];
     unreachableCodes: Diagnostic[];
     deprecateds: Diagnostic[];
+    baselineDiff: BaselineDiff<boolean> | undefined;
 }
 
 export function resolveSampleFilePath(fileName: string): string {
@@ -171,6 +173,7 @@ export function getAnalysisResults(
     }
 
     const sourceFiles = fileUris.map((filePath) => program.getSourceFile(filePath));
+    const baseline = new BaselineHandler(program.fileSystem, program.rootPath);
     return sourceFiles.map((sourceFile, index) => {
         if (sourceFile) {
             const diagnostics = sourceFile.getDiagnostics(configOptions) || [];
@@ -183,6 +186,9 @@ export function getAnalysisResults(
                 unusedCodes: diagnostics.filter((diag) => diag.category === DiagnosticCategory.UnusedCode),
                 unreachableCodes: diagnostics.filter((diag) => diag.category === DiagnosticCategory.UnreachableCode),
                 deprecateds: diagnostics.filter((diag) => diag.category === DiagnosticCategory.Deprecated),
+                baselineDiff: baseline.write(false, true, [
+                    { diagnostics, fileUri: sourceFile.getUri(), version: 1, reason: 'analysis' },
+                ]),
             };
             return analysisResult;
         } else {
@@ -197,6 +203,7 @@ export function getAnalysisResults(
                 unusedCodes: [],
                 unreachableCodes: [],
                 deprecateds: [],
+                baselineDiff: undefined,
             };
             return analysisResult;
         }
@@ -265,7 +272,7 @@ export const validateResultsButBased = (allResults: FileAnalysisResult[], expect
     assert.strictEqual(allResults.length, 1);
     const result = allResults[0];
     for (const [diagnosticType] of entries(result)) {
-        if (diagnosticType === 'fileUri' || diagnosticType === 'parseResults') {
+        if (diagnosticType === 'fileUri' || diagnosticType === 'parseResults' || diagnosticType === 'baselineDiff') {
             continue;
         }
         const actualResult = result[diagnosticType].map(