diff --git a/.changes/next-release/bugfix-core-ki36vzwj.json b/.changes/next-release/bugfix-core-ki36vzwj.json
new file mode 100644
index 0000000..608b1f3
--- /dev/null
+++ b/.changes/next-release/bugfix-core-ki36vzwj.json
@@ -0,0 +1,5 @@
+{
+  "type": "bugfix",
+  "category": "core",
+  "description": "Redact credential fields (embedded kubeconfig, tokens, client certs/keys, secrets) in --debug request/response logging so 'update-kubeconfig --debug' and similar no longer print long-lived credentials to stderr (SEC-07)"
+}
diff --git a/go/internal/client/client.go b/go/internal/client/client.go
index 6c209fb..939c1e8 100644
--- a/go/internal/client/client.go
+++ b/go/internal/client/client.go
@@ -209,7 +209,7 @@ func (c *GreenodeClient) requestRaw(method, path string, params map[string]strin
 		if c.debug {
 			fmt.Fprintf(os.Stderr, "[debug] %s %s\n", method, fullURL)
 			if jsonBody != nil {
-				fmt.Fprintf(os.Stderr, "[debug] request body: %s\n", string(jsonBody))
+				fmt.Fprintf(os.Stderr, "[debug] request body: %s\n", redactDebugBody(string(jsonBody)))
 			}
 		}
 
@@ -228,7 +228,7 @@ func (c *GreenodeClient) requestRaw(method, path string, params map[string]strin
 		resp.Body.Close()
 
 		if c.debug {
-			fmt.Fprintf(os.Stderr, "[debug] response %d: %s\n", resp.StatusCode, string(respBody))
+			fmt.Fprintf(os.Stderr, "[debug] response %d: %s\n", resp.StatusCode, redactDebugBody(string(respBody)))
 		}
 
 		// 401 — refresh token and retry once
diff --git a/go/internal/client/redact.go b/go/internal/client/redact.go
new file mode 100644
index 0000000..b121d3a
--- /dev/null
+++ b/go/internal/client/redact.go
@@ -0,0 +1,60 @@
+package client
+
+import (
+	"encoding/json"
+	"strings"
+)
+
+// redactDebugBody returns a copy of a JSON request/response body safe to print
+// in --debug output: values of credential-bearing fields (e.g. the embedded
+// kubeconfig, tokens, client certs/keys, secrets) are replaced with
+// "[REDACTED]". Only used for debug logging — the real body is never modified.
+// Non-JSON bodies are returned unchanged (VKS/vServer bodies are JSON).
+func redactDebugBody(raw string) string {
+	trimmed := strings.TrimSpace(raw)
+	if trimmed == "" {
+		return raw
+	}
+	var v interface{}
+	if err := json.Unmarshal([]byte(trimmed), &v); err != nil {
+		return raw
+	}
+	redactValue(v)
+	out, err := json.Marshal(v)
+	if err != nil {
+		return raw
+	}
+	return string(out)
+}
+
+func redactValue(v interface{}) {
+	switch t := v.(type) {
+	case map[string]interface{}:
+		for k, val := range t {
+			if isSensitiveKey(k) {
+				t[k] = "[REDACTED]"
+				continue
+			}
+			redactValue(val)
+		}
+	case []interface{}:
+		for _, item := range t {
+			redactValue(item)
+		}
+	}
+}
+
+// isSensitiveKey reports whether a JSON key's value should be redacted in debug
+// output. Matches known credential fields plus common secret-ish key patterns.
+func isSensitiveKey(k string) bool {
+	lk := strings.ToLower(k)
+	switch lk {
+	case "kubeconfig", "token", "client-certificate-data", "client-key-data",
+		"client_secret", "clientsecret", "password":
+		return true
+	}
+	return strings.Contains(lk, "secret") ||
+		strings.Contains(lk, "password") ||
+		strings.HasSuffix(lk, "token") ||
+		strings.HasSuffix(lk, "key-data")
+}
diff --git a/go/internal/client/redact_test.go b/go/internal/client/redact_test.go
new file mode 100644
index 0000000..b0fdcf5
--- /dev/null
+++ b/go/internal/client/redact_test.go
@@ -0,0 +1,53 @@
+package client
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestRedactDebugBodyMasksKubeconfig(t *testing.T) {
+	in := `{"status":"ACTIVE","kubeConfig":"apiVersion: v1\nclient-key-data: SUPERSECRETKEY","renewalWarning":false}`
+	out := redactDebugBody(in)
+	if strings.Contains(out, "SUPERSECRETKEY") {
+		t.Errorf("kubeConfig value not redacted: %s", out)
+	}
+	if !strings.Contains(out, "[REDACTED]") {
+		t.Errorf("expected [REDACTED] marker: %s", out)
+	}
+	if !strings.Contains(out, "ACTIVE") {
+		t.Errorf("non-sensitive field lost: %s", out)
+	}
+}
+
+func TestRedactDebugBodyNestedAndTokens(t *testing.T) {
+	in := `{"data":{"token":"abc123","name":"ok"},"clientSecret":"shh","items":[{"bearerToken":"xyz"}]}`
+	out := redactDebugBody(in)
+	for _, leaked := range []string{"abc123", "shh", "xyz"} {
+		if strings.Contains(out, leaked) {
+			t.Errorf("secret %q leaked: %s", leaked, out)
+		}
+	}
+	if !strings.Contains(out, "ok") {
+		t.Errorf("non-sensitive value lost: %s", out)
+	}
+}
+
+func TestRedactDebugBodyKeepsNonSensitive(t *testing.T) {
+	in := `{"id":"cls-1","numNodes":3,"status":"CREATING"}`
+	out := redactDebugBody(in)
+	for _, keep := range []string{"cls-1", "3", "CREATING"} {
+		if !strings.Contains(out, keep) {
+			t.Errorf("non-sensitive %q should be kept: %s", keep, out)
+		}
+	}
+	if strings.Contains(out, "[REDACTED]") {
+		t.Errorf("nothing should be redacted here: %s", out)
+	}
+}
+
+func TestRedactDebugBodyNonJSONPassthrough(t *testing.T) {
+	in := "not json"
+	if got := redactDebugBody(in); got != in {
+		t.Errorf("non-JSON should pass through unchanged, got %q", got)
+	}
+}