diff --git a/.changeset/five-rats-compare.md b/.changeset/five-rats-compare.md
new file mode 100644
index 00000000..4c57eec3
--- /dev/null
+++ b/.changeset/five-rats-compare.md
@@ -0,0 +1,5 @@
+---
+'@srcbook/api': patch
+---
+
+Add typing support and errors for environment variables
diff --git a/packages/api/server/http.mts b/packages/api/server/http.mts
index 3c8c469d..d40e528d 100644
--- a/packages/api/server/http.mts
+++ b/packages/api/server/http.mts
@@ -29,6 +29,7 @@ import {
   importSrcbookFromSrcmdFile,
   importSrcbookFromSrcmdText,
   importSrcbookFromSrcmdUrl,
+  updateSessionEnvTypeDeclarations,
 } from '../srcbook/index.mjs';
 import { readdir } from '../fs-utils.mjs';
 import { EXAMPLE_SRCBOOKS } from '../srcbook/examples.mjs';
@@ -276,12 +277,14 @@ router.options('/sessions/:id/secrets/:name', cors());
 router.put('/sessions/:id/secrets/:name', cors(), async (req, res) => {
   const { id, name } = req.params;
   await associateSecretWithSession(name, id);
+  await updateSessionEnvTypeDeclarations(id);
   return res.status(204).end();
 });
 
 router.delete('/sessions/:id/secrets/:name', cors(), async (req, res) => {
   const { id, name } = req.params;
   await disassociateSecretWithSession(name, id);
+  await updateSessionEnvTypeDeclarations(id);
   return res.status(204).end();
 });
 
diff --git a/packages/api/srcbook/config.mts b/packages/api/srcbook/config.mts
index 5ad9d778..532f4a60 100644
--- a/packages/api/srcbook/config.mts
+++ b/packages/api/srcbook/config.mts
@@ -32,14 +32,17 @@ export function buildTSPackageJson() {
 export function buildTsconfigJson() {
   return {
     compilerOptions: {
+      types: [],
+      strict: true,
       module: 'nodenext',
       moduleResolution: 'nodenext',
       target: 'es2022',
       resolveJsonModule: true,
       noEmit: true,
       allowImportingTsExtensions: true,
+      noPropertyAccessFromIndexSignature: true,
     },
-    include: ['src/**/*'],
+    include: ['src/**/*', 'env.d.ts'],
     exclude: ['node_modules'],
   };
 }
diff --git a/packages/api/srcbook/index.mts b/packages/api/srcbook/index.mts
index 3f9db7b9..0d53131f 100644
--- a/packages/api/srcbook/index.mts
+++ b/packages/api/srcbook/index.mts
@@ -12,9 +12,16 @@ import { toFormattedJSON } from '../utils.mjs';
 import { readdir } from '../fs-utils.mjs';
 import { SRCBOOKS_DIR } from '../constants.mjs';
 import { EXAMPLE_SRCBOOKS } from '../srcbook/examples.mjs';
-import { pathToCodeFile, pathToPackageJson, pathToReadme, pathToTsconfigJson } from './path.mjs';
+import {
+  pathToCodeFile,
+  pathToPackageJson,
+  pathToReadme,
+  pathToSrcbook,
+  pathToTsconfigJson,
+} from './path.mjs';
 import { buildJSPackageJson, buildTSPackageJson, buildTsconfigJson } from './config.mjs';
 import type { SessionType } from '../types.mjs';
+import { getSecretsAssociatedWithSession } from '../config.mjs';
 
 function writeCellOnlyToDisk(srcbookDir: string, cell: PackageJsonCellType | CodeCellType) {
   const path =
@@ -203,6 +210,10 @@ async function createSrcbookDir(basename: string = randomid()) {
   const srcPath = Path.join(srcbookDirectoryPath, 'src');
   await fs.mkdir(srcPath);
 
+  const envTypeDeclarationPath = Path.join(srcbookDirectoryPath, 'env.d.ts');
+  const envTypeDeclarationFileContent = generateEnvTypesFile({});
+  await fs.writeFile(envTypeDeclarationPath, envTypeDeclarationFileContent);
+
   return srcbookDirectoryPath;
 }
 
@@ -217,3 +228,33 @@ export function removeSrcbook(srcbookDir: string) {
 export function removeCodeCellFromDisk(srcbookDir: string, filename: string) {
   return fs.rm(pathToCodeFile(srcbookDir, filename));
 }
+
+export async function updateSessionEnvTypeDeclarations(sessionId: string) {
+  const sessionSecrets = await getSecretsAssociatedWithSession(sessionId);
+  if (!Object.entries(sessionSecrets).length) return;
+  const envTypeDeclarationFileContent = generateEnvTypesFile(sessionSecrets);
+  const srcbookDir = pathToSrcbook(sessionId);
+  const envDtsPath = Path.join(srcbookDir, 'env.d.ts');
+  await fs.writeFile(envDtsPath, envTypeDeclarationFileContent);
+}
+
+export function generateEnvTypesFile(secrets: Record<string, string>) {
+  const envTypes = Object.entries(secrets).length
+    ? Object.keys(secrets)
+        .map((key) => `readonly ${key}: string;`)
+        .join('\n')
+    : '';
+
+  return `
+  declare namespace NodeJS {
+  interface ProcessEnv {
+    ${envTypes}
+  }
+}
+
+declare var process: {
+  env: NodeJS.ProcessEnv;
+};
+
+  `;
+}
diff --git a/packages/web/src/routes/session.tsx b/packages/web/src/routes/session.tsx
index c40a95a9..2d6aa39f 100644
--- a/packages/web/src/routes/session.tsx
+++ b/packages/web/src/routes/session.tsx
@@ -37,7 +37,6 @@ async function loader({ params }: LoaderFunctionArgs) {
     loadSessions(),
     loadSession({ id: params.id! }),
   ]);
-
   return { config, srcbooks, session };
 }