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Troubleshooting Authentication by tomevault-io

Name: Troubleshooting Authentication
Author: tomevault-io

Troubleshooting Authentication

Provides authentication troubleshooting for MSAL, JWT, and Entra ID. Use when debugging 401 errors, token issues, MSAL configuration problems, or credential failures in this repository.

tomevault-io 26d5fe6 2 files · 3.6 KB Updated Sep 17, 2026

File contents

Authentication Troubleshooting

Architecture

Browser → MSAL.js (PKCE flow) → JWT with Chat.ReadWrite scope
Frontend → Backend (JWT Bearer token)
Backend → Foundry Agent Service (ManagedIdentityCredential)

Common Issues

Issue	Cause	Fix
401 on `/api/*`	Token missing scope	Verify `Chat.ReadWrite` scope in token
`ManagedIdentityCredential` error locally	Wrong environment	Set `ASPNETCORE_ENVIRONMENT=Development`
Token popup blocked	Browser settings	Allow popups for localhost
Silent token fails	No cached token	Fallback to popup (handled by useAuth)

Backend: JWT Validation

Accepts both audience formats:

options.TokenValidationParameters.ValidAudiences = new[]
{
    builder.Configuration["AzureAd:ClientId"],
    $"api://{builder.Configuration["AzureAd:ClientId"]}"
};

Backend: Credential Strategy

TokenCredential credential = env.IsDevelopment()
    ? new ChainedTokenCredential(
        new AzureCliCredential(),
        new AzureDeveloperCliCredential())  // Supports 'azd auth login'
    : new ManagedIdentityCredential();

Local development: Requires az login or azd auth login to work.

Why ChainedTokenCredential: Avoids DefaultAzureCredential's unpredictable "fail fast" mode. Provides explicit, debuggable credential chain.

Frontend: MSAL Pattern

// Always try silent first
try {
  const { accessToken } = await instance.acquireTokenSilent({
    ...tokenRequest,
    account: accounts[0]
  });
  return accessToken;
} catch {
  // Fallback to popup
  const { accessToken } = await instance.acquireTokenPopup(tokenRequest);
  return accessToken;
}

Debugging Steps

Check token contents: https://jwt.ms
Verify scope: Token should have Chat.ReadWrite
Check audience: Should match client ID or api://{clientId}
Verify Entra app: Check redirect URIs in Azure Portal

Environment Variables

Frontend (.env.local):

VITE_ENTRA_SPA_CLIENT_ID=...
VITE_ENTRA_TENANT_ID=...

Backend (.env):

AzureAd__ClientId=...
AzureAd__TenantId=...

Regenerate: Run azd up to recreate Entra app and .env files.

Related Skills

writing-csharp-code - Backend JWT validation and credential patterns
writing-typescript-code - Frontend MSAL integration and useAuth hook
deploying-to-azure - Entra app provisioning and RBAC configuration

Source: microsoft-foundry/foundry-agent-webapp — distributed by TomeVault.

---name: troubleshooting-authenticationdescription: Provides authentication troubleshooting for MSAL, JWT, and Entra ID. Use when debugging 401 errors, token issues, MSAL configuration problems, or credential failures in this repository.---# Authentication Troubleshooting## Architecture1. Browser → MSAL.js (PKCE flow) → JWT with `Chat.ReadWrite` scope2. Frontend → Backend (JWT Bearer token)3. Backend → Foundry Agent Service (ManagedIdentityCredential)## Common Issues| Issue | Cause | Fix ||-------|-------|-----|| 401 on `/api/*` | Token missing scope | Verify `Chat.ReadWrite` scope in token || `ManagedIdentityCredential` error locally | Wrong environment | Set `ASPNETCORE_ENVIRONMENT=Development` || Token popup blocked | Browser settings | Allow popups for localhost || Silent token fails | No cached token | Fallback to popup (handled by useAuth) |## Backend: JWT ValidationAccepts both audience formats:```csharpoptions.TokenValidationParameters.ValidAudiences = new[]{ builder.Configuration["AzureAd:ClientId"], $"api://{builder.Configuration["AzureAd:ClientId"]}"};```## Backend: Credential Strategy```csharpTokenCredential credential = env.IsDevelopment() ? new ChainedTokenCredential( new AzureCliCredential(), new AzureDeveloperCliCredential()) // Supports 'azd auth login' : new ManagedIdentityCredential();```**Local development**: Requires `az login` or `azd auth login` to work.**Why ChainedTokenCredential**: Avoids `DefaultAzureCredential`'s unpredictable "fail fast" mode. Provides explicit, debuggable credential chain.## Frontend: MSAL Pattern```typescript// Always try silent firsttry { const { accessToken } = await instance.acquireTokenSilent({ ...tokenRequest, account: accounts[0] }); return accessToken;} catch { // Fallback to popup const { accessToken } = await instance.acquireTokenPopup(tokenRequest); return accessToken;}```## Debugging Steps1. **Check token contents**: https://jwt.ms2. **Verify scope**: Token should have `Chat.ReadWrite`3. **Check audience**: Should match client ID or `api://{clientId}`4. **Verify Entra app**: Check redirect URIs in Azure Portal## Environment Variables**Frontend** (`.env.local`):```iniVITE_ENTRA_SPA_CLIENT_ID=...VITE_ENTRA_TENANT_ID=...```**Backend** (`.env`):```iniAzureAd__ClientId=...AzureAd__TenantId=...```**Regenerate**: Run `azd up` to recreate Entra app and `.env` files.## Related Skills- **writing-csharp-code** - Backend JWT validation and credential patterns- **writing-typescript-code** - Frontend MSAL integration and useAuth hook- **deploying-to-azure** - Entra app provisioning and RBAC configuration---> Source: [microsoft-foundry/foundry-agent-webapp](https://github.com/microsoft-foundry/foundry-agent-webapp) — distributed by [TomeVault](https://tomevault.io).

Frequently asked questions