fix(auth): preserve Codex id_token during OAuth exchange

crates/forge_infra/src/auth/http/standard.rs

@@ -1,8 +1,6 @@
 use forge_app::OAuthHttpProvider;
 use forge_domain::{AuthCodeParams, OAuthConfig, OAuthTokenResponse};
-use oauth2::{
-    AuthorizationCode as OAuth2AuthCode, CsrfToken, PkceCodeChallenge, PkceCodeVerifier, Scope,
-};
+use oauth2::{CsrfToken, PkceCodeChallenge, Scope};
 
 use crate::auth::util::*;
 
@@ -58,27 +56,39 @@ impl OAuthHttpProvider for StandardHttpProvider {
         code: &str,
         verifier: Option<&str>,
     ) -> anyhow::Result<OAuthTokenResponse> {
-        use oauth2::{AuthUrl, ClientId, TokenUrl};
-
-        let mut client =
-            oauth2::basic::BasicClient::new(ClientId::new(config.client_id.to_string()))
-                .set_auth_uri(AuthUrl::new(config.auth_url.to_string())?)
-                .set_token_uri(TokenUrl::new(config.token_url.to_string())?);
+        let http_client = self.build_http_client(config)?;
+        let mut params = vec![
+            ("grant_type".to_string(), "authorization_code".to_string()),
+            ("code".to_string(), code.to_string()),
+            ("client_id".to_string(), config.client_id.to_string()),
+        ];
 
         if let Some(redirect_uri) = &config.redirect_uri {
-            client = client.set_redirect_uri(oauth2::RedirectUrl::new(redirect_uri.clone())?);
+            params.push(("redirect_uri".to_string(), redirect_uri.clone()));
         }
 
-        let http_client = self.build_http_client(config)?;
+        if let Some(verifier) = verifier {
+            params.push(("code_verifier".to_string(), verifier.to_string()));
+        }
+
+        let response = http_client
+            .post(config.token_url.as_str())
+            .header("Content-Type", "application/x-www-form-urlencoded")
+            .header("Accept", "application/json")
+            .body(serde_urlencoded::to_string(params)?)
+            .send()
+            .await?;
 
-        let mut request = client.exchange_code(OAuth2AuthCode::new(code.to_string()));
+        let status = response.status();
+        let body = response.text().await?;
 
-        if let Some(v) = verifier {
-            request = request.set_pkce_verifier(PkceCodeVerifier::new(v.to_string()));
+        if !status.is_success() {
+            anyhow::bail!("OAuth token exchange failed ({status}): {body}");
         }
 
-        let token_result = request.request_async(&http_client).await?;
-        Ok(into_domain(token_result))
+        // Parse the raw token payload so provider-specific fields like
+        // `id_token` are preserved instead of being dropped by generic helpers.
+        Ok(parse_token_response(&body)?)
     }
 
     /// Create HTTP client with provider-specific headers/behavior

crates/forge_infra/src/auth/strategy.rs

@@ -772,23 +772,12 @@ async fn poll_for_tokens(
             }
 
             // No error field - parse as success
-            let (access_token, refresh_token, expires_in) = parse_token_response(&body_text)?;
-
-            return Ok(build_token_response(
-                access_token,
-                refresh_token,
-                expires_in,
-            ));
+            return Ok(parse_token_response(&body_text)?);
         }
 
         // Standard OAuth: HTTP success means tokens
         if !github_compatible && status.is_success() {
-            let (access_token, refresh_token, expires_in) = parse_token_response(&body_text)?;
-            return Ok(build_token_response(
-                access_token,
-                refresh_token,
-                expires_in,
-            ));
+            return Ok(parse_token_response(&body_text)?);
         }
 
         // Handle error responses (non-200 status for standard OAuth)
@@ -911,16 +900,11 @@ async fn codex_poll_for_tokens(
                 .into());
             }
 
-            let (access_token, refresh_token, expires_in) =
-                parse_token_response(&token_response.text().await.map_err(|e| {
+            return Ok(parse_token_response(
+                &token_response.text().await.map_err(|e| {
                     AuthError::PollFailed(format!("Failed to read token response: {e}"))
-                })?)?;
-
-            return Ok(build_token_response(
-                access_token,
-                refresh_token,
-                expires_in,
-            ));
+                })?,
+            )?);
         }
 
         // 403/404 means authorization pending (user hasn't entered code yet)
@@ -1323,6 +1307,49 @@ mod tests {
         assert_eq!(actual, None);
     }
 
+    #[test]
+    fn test_enrich_codex_oauth_credential_uses_id_token_claims() {
+        let fixture_id_token = build_jwt(&serde_json::json!({
+            "chatgpt_account_id": "acct_from_id_token"
+        }));
+        let fixture_access_token = "not-a-jwt";
+        let mut actual = AuthCredential::new_oauth(
+            ProviderId::CODEX,
+            OAuthTokens::new(
+                fixture_access_token,
+                None::<String>,
+                chrono::Utc::now() + chrono::Duration::hours(1),
+            ),
+            OAuthConfig {
+                client_id: "test".to_string().into(),
+                auth_url: Url::parse("https://example.com/auth").unwrap(),
+                token_url: Url::parse("https://example.com/token").unwrap(),
+                scopes: vec![],
+                redirect_uri: Some("http://localhost:1455/auth/callback".to_string()),
+                use_pkce: true,
+                token_refresh_url: None,
+                extra_auth_params: None,
+                custom_headers: None,
+            },
+        );
+
+        enrich_codex_oauth_credential(
+            &ProviderId::CODEX,
+            &mut actual,
+            Some(&fixture_id_token),
+            fixture_access_token,
+        );
+
+        let actual = actual
+            .url_params
+            .get(&URLParam::from("chatgpt_account_id".to_string()));
+        let expected = Some(&forge_domain::URLParamValue::from(
+            "acct_from_id_token".to_string(),
+        ));
+
+        assert_eq!(actual, expected);
+    }
+
     #[tokio::test]
     async fn test_refresh_oauth_credential_preserves_url_params() {
         let fixture_config = OAuthConfig {

crates/forge_infra/src/auth/util.rs

@@ -86,23 +86,6 @@ pub(crate) fn build_oauth_credential(
     ))
 }
 
-/// Build OAuthTokenResponse with standard defaults
-pub(crate) fn build_token_response(
-    access_token: String,
-    refresh_token: Option<String>,
-    expires_in: Option<u64>,
-) -> OAuthTokenResponse {
-    OAuthTokenResponse {
-        access_token,
-        refresh_token,
-        expires_in,
-        expires_at: None,
-        token_type: "Bearer".to_string(),
-        scope: None,
-        id_token: None,
-    }
-}
-
 /// Extract OAuth tokens from any credential type
 pub(crate) fn extract_oauth_tokens(credential: &AuthCredential) -> anyhow::Result<&OAuthTokens> {
     match &credential.auth_details {
@@ -217,25 +200,18 @@ pub(crate) fn handle_oauth_error(error_code: &str) -> Result<(), Error> {
     }
 }
 
-/// Parse token response from JSON
-pub(crate) fn parse_token_response(
-    body: &str,
-) -> Result<(String, Option<String>, Option<u64>), Error> {
-    let token_response: serde_json::Value = serde_json::from_str(body)
+/// Parse token response from JSON.
+pub(crate) fn parse_token_response(body: &str) -> Result<OAuthTokenResponse, Error> {
+    let token_response: OAuthTokenResponse = serde_json::from_str(body)
         .map_err(|e| Error::PollFailed(format!("Failed to parse token response: {e}")))?;
 
-    let access_token = token_response["access_token"]
-        .as_str()
-        .ok_or_else(|| Error::PollFailed("Missing access_token in response".to_string()))?
-        .to_string();
-
-    let refresh_token = token_response["refresh_token"]
-        .as_str()
-        .map(|s| s.to_string());
-
-    let expires_in = token_response["expires_in"].as_u64();
+    if token_response.access_token.trim().is_empty() {
+        return Err(Error::PollFailed(
+            "Missing access_token in response".to_string(),
+        ));
+    }
 
-    Ok((access_token, refresh_token, expires_in))
+    Ok(token_response)
 }
 
 #[cfg(test)]
@@ -265,17 +241,20 @@ mod tests {
     }
 
     #[test]
-    fn test_build_token_response() {
-        let response = build_token_response(
-            "test_token".to_string(),
-            Some("refresh_token".to_string()),
-            Some(3600),
-        );
-
-        assert_eq!(response.access_token, "test_token");
-        assert_eq!(response.refresh_token, Some("refresh_token".to_string()));
-        assert_eq!(response.expires_in, Some(3600));
-        assert_eq!(response.token_type, "Bearer");
+    fn test_parse_token_response_preserves_id_token() {
+        let fixture = r#"{
+            "access_token": "test_token",
+            "refresh_token": "refresh_token",
+            "expires_in": 3600,
+            "id_token": "test_id_token"
+        }"#;
+
+        let actual = parse_token_response(fixture).unwrap();
+
+        assert_eq!(actual.access_token, "test_token");
+        assert_eq!(actual.refresh_token, Some("refresh_token".to_string()));
+        assert_eq!(actual.expires_in, Some(3600));
+        assert_eq!(actual.id_token, Some("test_id_token".to_string()));
     }
 
     #[test]