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fix(cli): scope exchanges to the session agent #47

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Merged
michiosw merged 2 commits into from
Apr 9, 2026
Merged

fix(cli): scope exchanges to the session agent #47

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8a9db2e
fix(cli): scope exchanges to the session agent
michiosw Apr 9, 2026
4f16a7f
fix: handle missing session agent id
michiosw Apr 9, 2026
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85 changes: 65 additions & 20 deletions internal/run/run.go
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Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,7 @@ func Start(ctx context.Context, opts Options) error {
}

sessionID := createResp.SessionId
credentialClientID := resolveCredentialClientID(createResp.AgentId, opts.ClientID)
fmt.Fprintf(os.Stderr, "✓ Session: %s (%s)\n", createResp.SessionName, truncateID(sessionID))

// 4. Resolve credentials (before sidecar starts — no background goroutines yet,
Expand All @@ -91,7 +92,7 @@ func Start(ctx context.Context, opts Options) error {
return fmt.Errorf("parse template: %w", err)
}
if len(entries) > 0 {
resolved, err = resolveCredentials(ctx, session, entries, opts.ClientID)
resolved, err = resolveCredentials(ctx, session, entries, credentialClientID)
if err != nil {
return err
}
Expand Down Expand Up @@ -175,7 +176,7 @@ func resolveCredentials(ctx context.Context, session *auth.Session, entries []cr
if err != nil {
if isNotConnectedError(err) {
fmt.Fprintln(os.Stderr, "not connected")
connectURL, connectErr := fetchConnectURL(ctx, session)
connectURL, connectErr := fetchConnectURL(ctx, session, clientID)
if connectErr != nil {
err = fmt.Errorf("create connect session: %w", connectErr)
} else {
Expand All @@ -200,15 +201,20 @@ func resolveCredentials(ctx context.Context, session *auth.Session, entries []cr
return resolved, nil
}

func fetchConnectURL(ctx context.Context, session *auth.Session) (string, error) {
func fetchConnectURL(ctx context.Context, session *auth.Session, clientID string) (string, error) {
gatewayToken, err := exchangeGatewayToken(ctx, session, clientID)
if err != nil {
return "", err
}

connectSessionURL := strings.TrimRight(session.IssuerURL, "/") + "/mcp/connect-session"

req, err := http.NewRequestWithContext(ctx, "POST", connectSessionURL, strings.NewReader("{}"))
if err != nil {
return "", fmt.Errorf("build request: %w", err)
}
req.Header.Set("Content-Type", "application/json")
req.Header.Set("Authorization", "Bearer "+session.AccessToken)
req.Header.Set("Authorization", "Bearer "+gatewayToken)

resp, err := http.DefaultClient.Do(req)
if err != nil {
Expand Down Expand Up @@ -242,47 +248,86 @@ func fetchConnectURL(ctx context.Context, session *auth.Session) (string, error)
return result.ConnectURL, nil
}

// exchangeCredential calls POST /oauth2/token with RFC 8693 token exchange
// to resolve a provider credential. The user's access token serves as both
// the subject_token and the Bearer auth — no client secret needed.
func exchangeCredential(ctx context.Context, session *auth.Session, entry credential.Entry, clientID string) (string, error) {
func agentOAuthClientID(agentID string) string {
return "app_" + agentID
}

func resolveCredentialClientID(agentID, fallback string) string {
if strings.TrimSpace(agentID) == "" {
return fallback
}
return agentOAuthClientID(agentID)
}

type tokenExchangeResponse struct {
AccessToken string `json:"access_token"`
TokenType string `json:"token_type"`
ProviderKind string `json:"provider_kind"`
Error string `json:"error"`
ErrorDesc string `json:"error_description"`
}

func exchangeToken(ctx context.Context, session *auth.Session, clientID, resource string, scopes ...string) (*tokenExchangeResponse, error) {
meta, err := auth.DiscoverEndpoints(ctx, session.IssuerURL)
if err != nil {
return "", fmt.Errorf("oauth discovery: %w", err)
return nil, fmt.Errorf("oauth discovery: %w", err)
}

form := url.Values{
"grant_type": {"urn:ietf:params:oauth:grant-type:token-exchange"},
"client_id": {clientID},
"subject_token": {session.AccessToken},
"subject_token_type": {"urn:ietf:params:oauth:token-type:access_token"},
"resource": {entry.Target()},
"resource": {resource},
}
if len(scopes) > 0 {
form.Set("scope", strings.Join(scopes, " "))
}

req, err := http.NewRequestWithContext(ctx, "POST", meta.TokenEndpoint, strings.NewReader(form.Encode()))
if err != nil {
return "", fmt.Errorf("build request: %w", err)
return nil, fmt.Errorf("build request: %w", err)
}
req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
req.Header.Set("Authorization", "Bearer "+session.AccessToken)

resp, err := http.DefaultClient.Do(req)
if err != nil {
return "", fmt.Errorf("token exchange request: %w", err)
return nil, fmt.Errorf("token exchange request: %w", err)
}
defer resp.Body.Close()

var result struct {
AccessToken string `json:"access_token"`
TokenType string `json:"token_type"`
ProviderKind string `json:"provider_kind"`
Error string `json:"error"`
ErrorDesc string `json:"error_description"`
}
var result tokenExchangeResponse
if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
return "", fmt.Errorf("decode token exchange response: %w", err)
return nil, fmt.Errorf("decode token exchange response: %w", err)
}

return &result, nil
}

func exchangeGatewayToken(ctx context.Context, session *auth.Session, clientID string) (string, error) {
result, err := exchangeToken(ctx, session, clientID, "mcp-gateway", "gateway:access")
if err != nil {
return "", err
}
if result.Error != "" {
return "", fmt.Errorf("gateway token exchange failed: %s: %s", result.Error, result.ErrorDesc)
}
if result.AccessToken == "" {
return "", fmt.Errorf("gateway token exchange returned empty access_token")
}

return result.AccessToken, nil
}

// exchangeCredential calls POST /oauth2/token with RFC 8693 token exchange
// to resolve a provider credential. The user's access token serves as both
// the subject_token and the Bearer auth — no client secret needed.
func exchangeCredential(ctx context.Context, session *auth.Session, entry credential.Entry, clientID string) (string, error) {
result, err := exchangeToken(ctx, session, clientID, entry.Target())
if err != nil {
return "", err
}
if result.Error != "" {
if result.Error == "invalid_target" && strings.Contains(result.ErrorDesc, "not allowed") {
return "", fmt.Errorf("provider not connected: %s", entry.Provider)
Expand Down
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