Standalone launch failing with invalid_request

[Dylan Klomparens]

I'm attempting to perform SMART App Launch against the SMART Launcher.

Everything works great when I perform an EHR launch. The auth flow completes successfully. But Standalone launch is failing upon trying to acquire an authorization code, and I don't understand why. Does anyone have insight into why Standalone launch is failing?

Here are the redirect URLs I'm prompting the browser to use to obtain an authorization code:

EHR launch, works successfully:

https://launch.smarthealthit.org/v/r4/auth/authorize?response_type=code&scope=launch+openid+fhirUser+online_access+user%2F%2A.cruds+smart_style_url&client_id=11111111-2222-3333-4444-555555555555&redirect_uri=http%3A%2F%2Flocalhost%3A8000%2Fcallback&state=L3HXBALxvQJLp54VRYzs8Fbc6cyxT4lm&aud=https%3A%2F%2Flaunch.smarthealthit.org%2Fv%2Fr4%2Ffhir&code_challenge=yQoEOKt2I_CiSg3tIT2h8T5HswlFotdDsYe01EmaNUM&code_challenge_method=S256&launch=WzAsIiIsIiIsIkFVVE8iLDAsMCwwLCIiLCIiLCIiLCIiLCIiLCIiLCIiLDEsMSwiIl0

Standalone launch, fails:

https://launch.smarthealthit.org/v/r4/auth/authorize?response_type=code&scope=launch+openid+fhirUser+online_access+user%2F%2A.cruds+smart_style_url&client_id=11111111-2222-3333-4444-555555555555&redirect_uri=http%3A%2F%2Flocalhost%3A8000%2Fcallback&state=PBlqnfzhtdlV5y72OxIT1IAaDl3W2uai&aud=https%3A%2F%2Flaunch.smarthealthit.org%2Fv%2Fr4%2Ffhir&code_challenge=cTx46byqQHcJLhpxoAEm3Ikx4hVdtBw7t4adLrx7BOM&code_challenge_method=S256

Error: invalid_request
Description: Invalid launch options: SyntaxError: Unexpected end of JSON input

The redirects to obtain the authorization code are nearly identical. I'm perplexed why standalone launch is failing. Any guidance is greatly appreciated.