# Which Problems Are Solved
- IDP intent authorization redirects used by Login v2 ignored the
configured `UsePKCE` setting for Generic OAuth providers
- This caused providers such as X/Twitter OAuth2 to receive
authorization requests without `code_challenge` and
`code_challenge_method`
- OIDC provider construction had the same gap, even though PKCE is
already part of the provider configuration model
- Existing IDP intent redirect tests expected non-PKCE OAuth URLs and
failed once PKCE was applied correctly
# How the Problems Are Solved
- Updated `OAuthIDPWriteModel.ToProvider` in
internal/command/idp_model.go to pass `rp.WithPKCE(nil)` when `UsePKCE`
is enabled
- Updated `OIDCIDPWriteModel.ToProvider` to apply the same PKCE
relying-party option for OIDC providers
# Additional Changes
- Added focused provider-construction tests covering:
- OAuth provider redirects include code_challenge
- OIDC provider redirects include code_challenge
- both providers use code_challenge_method=S256
- both persist the generated codeVerifier for token exchange
- Updated `TestCommands_AuthFromProvider` in
internal/command/idp_intent_test.go so OAuth redirect assertions verify
PKCE structurally instead of hard-coding the generated challenge value
# Additional Context
- Reproduced with X/Twitter OAuth2 where the generated authorization URL
was missing PKCE parameters despite `usePkce: true`
- Verified both the focused PKCE tests and the full unit test suite run
successfully with the fix
- Closes#12036
- Closes/supersedes #12054:
- Tests are included
- No slice re-allocation on `opts` append
# Result
### Before
`authUrl` in `StartIdentityProviderIntent` response is missing
`code_challenge` and `code_challenge_method` for Generic OAuth IDP with
PKCE enabled:
```json
{
"details": {
"sequence": "1",
"changeDate": "2026-06-07T18:48:16.921317Z",
"resourceOwner": "376298239768395779"
},
"authUrl": "https://x.com/i/oauth2/authorize?client_id=<REDACTED>&prompt=select_account&redirect_uri=http%3A%2F%2Flocalhost%3A8080%2Fidps%2Fcallback&response_type=code&scope=tweet.read+users.email+users.read+offline.access&state=376417136207200259"
}
```
### After
`code_challenge` and `code_challenge_method` are correctly included into
`authUrl`:
```json
{
"details": {
"sequence": "1",
"changeDate": "2026-06-07T18:49:39.488941Z",
"resourceOwner": "376298239768395779"
},
"authUrl": "https://x.com/i/oauth2/authorize?client_id=<REDACTED>&code_challenge=8G4vN8QNgSsbvGSHKwYPEc2qUYU2BK5L0fsr992duTA&code_challenge_method=S256&prompt=select_account&redirect_uri=http%3A%2F%2Flocalhost%3A8080%2Fidps%2Fcallback&response_type=code&scope=tweet.read+users.email+users.read+offline.access&state=376417274736672771"
}
```
