feat: /healthz reports JWT validator status (refs #6)

/healthz now returns JSON with three-state JWT status: disabled
(DEX_ISSUER_URL unset), enabled (validator initialized), or
degraded (configured but init failed — only static-token auth
currently accepted). last_error surfaces the init failure so ops
can correlate with Dex outage windows.

Partial fix for #6. The cited internal/auth/jwt.go moved out
of this repo in 658f4ba (mcp-chassis migration); per-attempt
logging and 503 + WWW-Authenticate temporarily_unavailable
require chassis-side changes and a coordinated v0.1.1 bump
across all MCP consumers — tracked separately.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/gitea-mcp/healthz.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+type healthStatus struct {
+	OK  bool      `json:"ok"`
+	JWT jwtStatus `json:"jwt"`
+}
+
+// jwtStatus surfaces the runtime state of the Dex JWT validator so ops
+// can distinguish "Dex unreachable at startup" from "JWT auth not
+// configured" — both previously degraded silently to static-token-only
+// (refs hyperguild/gitea-mcp#6).
+type jwtStatus struct {
+	// Status is one of: "disabled" (DEX_ISSUER_URL not set),
+	// "enabled" (validator initialized), "degraded" (configured but
+	// init failed; only static-token auth currently accepted).
+	Status    string `json:"status"`
+	LastError string `json:"last_error,omitempty"`
+}
+
+func newHealthzHandler(dexConfigured, validatorReady bool, initErr error) http.HandlerFunc {
+	status := healthStatus{OK: true, JWT: jwtStatus{Status: jwtStatusFor(dexConfigured, validatorReady)}}
+	if initErr != nil {
+		status.JWT.LastError = initErr.Error()
+	}
+	body, _ := json.Marshal(status)
+	return func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write(body)
+	}
+}
+
+func jwtStatusFor(dexConfigured, validatorReady bool) string {
+	switch {
+	case !dexConfigured:
+		return "disabled"
+	case validatorReady:
+		return "enabled"
+	default:
+		return "degraded"
+	}
+}

cmd/gitea-mcp/healthz_test.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHealthzHandler(t *testing.T) {
+	tests := []struct {
+		name           string
+		dexConfigured  bool
+		validatorReady bool
+		initErr        error
+		wantStatus     string
+		wantLastError  string
+	}{
+		{
+			name:          "disabled when DEX_ISSUER_URL unset",
+			wantStatus:    "disabled",
+			wantLastError: "",
+		},
+		{
+			name:           "enabled when validator initialized",
+			dexConfigured:  true,
+			validatorReady: true,
+			wantStatus:     "enabled",
+			wantLastError:  "",
+		},
+		{
+			name:          "degraded when Dex configured but init failed",
+			dexConfigured: true,
+			initErr:       errors.New("fetch oidc discovery: dial tcp: connection refused"),
+			wantStatus:    "degraded",
+			wantLastError: "fetch oidc discovery: dial tcp: connection refused",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			h := newHealthzHandler(tc.dexConfigured, tc.validatorReady, tc.initErr)
+			rec := httptest.NewRecorder()
+			h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/healthz", nil))
+
+			require.Equal(t, http.StatusOK, rec.Code)
+			assert.Equal(t, "application/json", rec.Header().Get("Content-Type"))
+
+			var got healthStatus
+			require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &got))
+			assert.True(t, got.OK)
+			assert.Equal(t, tc.wantStatus, got.JWT.Status)
+			assert.Equal(t, tc.wantLastError, got.JWT.LastError)
+		})
+	}
+}

cmd/gitea-mcp/main.go

@@ -29,9 +29,9 @@ func main() {
 
 	ctx := context.Background()
 
-	jwtValidator, err := chassisauth.NewJWTValidator(ctx, cfg.DexIssuerURL, cfg.MCPAudience)
-	if err != nil {
-		logger.Warn("jwt validator init failed; JWT auth disabled", "err", err)
+	jwtValidator, jwtInitErr := chassisauth.NewJWTValidator(ctx, cfg.DexIssuerURL, cfg.MCPAudience)
+	if jwtInitErr != nil {
+		logger.Warn("jwt validator init failed; JWT auth degraded", "err", jwtInitErr)
 	}
 
 	giteaClient := gitea.NewClient(cfg.GiteaBaseURL, cfg.DefaultToken)
@@ -95,10 +95,7 @@ func main() {
 			auth.CallerMiddleware(mcpSrv),
 		),
 	))
-	mux.HandleFunc("/healthz", func(w http.ResponseWriter, _ *http.Request) {
-		w.WriteHeader(http.StatusOK)
-		_, _ = w.Write([]byte("ok"))
-	})
+	mux.Handle("/healthz", newHealthzHandler(cfg.DexIssuerURL != "", jwtValidator != nil, jwtInitErr))
 	if cfg.DexIssuerURL != "" {
 		mux.HandleFunc("GET /.well-known/oauth-protected-resource",
 			chassisauth.ProtectedResourceHandler(cfg.MCPResourceURL, cfg.DexIssuerURL))