diff --git a/CHANGELOG.md b/CHANGELOG.md
index 11985b62..4143e5ef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Grafana dashboard for adapter metrics (`charts/dashboards/hyperfleet-adapter.json`) — covers events processed, processing duration, errors by type, resource deletions, and adapter health ([HYPERFLEET-1360](https://issues.redhat.com/browse/HYPERFLEET-1360))
+- `clients.hyperfleet_api.auth.scheme` (Helm: `adapterConfig.hyperfleetApi.auth.scheme`) configures the Authorization header scheme sent with the service account token; defaults to `Bearer` for backwards compatibility, set to `ServiceAccount` when fronted by a gateway that differentiates human-jwt callers from machine callers ([HYPERFLEET-1480](https://issues.redhat.com/browse/HYPERFLEET-1480))
 
 ### Fixed
 
diff --git a/charts/README.md b/charts/README.md
index e3f3b061..09e08a85 100644
--- a/charts/README.md
+++ b/charts/README.md
@@ -27,16 +27,17 @@ helm install hyperfleet-adapter oci://REGISTRY/hyperfleet-adapter \
 
 | Key | Type | Default | Description |
 |-----|------|---------|-------------|
-| adapterConfig | object | `{"create":true,"hyperfleetApi":{"auth":{"audience":"hyperfleet-api","enabled":false,"expirationSeconds":3600,"tokenCacheTtl":"30s","tokenPath":"/var/run/secrets/hyperfleet/token"},"baseUrl":"http://hyperfleet-api:8000","version":"v1"},"log":{"level":"info"}}` | Adapter deployment configuration. Controls how the adapter-config ConfigMap is created. Use `adapterConfig.yaml` for inline YAML, `adapterConfig.files` for chart-packaged files, or set `create: false` and provide `configMapName` to reference an existing ConfigMap. |
+| adapterConfig | object | `{"create":true,"hyperfleetApi":{"auth":{"audience":"hyperfleet-api","enabled":false,"expirationSeconds":3600,"scheme":"Bearer","tokenCacheTtl":"30s","tokenPath":"/var/run/secrets/hyperfleet/token"},"baseUrl":"http://hyperfleet-api:8000","version":"v1"},"log":{"level":"info"}}` | Adapter deployment configuration. Controls how the adapter-config ConfigMap is created. Use `adapterConfig.yaml` for inline YAML, `adapterConfig.files` for chart-packaged files, or set `create: false` and provide `configMapName` to reference an existing ConfigMap. |
 | adapterConfig.create | bool | `true` | Create the adapter-config ConfigMap |
-| adapterConfig.hyperfleetApi | object | `{"auth":{"audience":"hyperfleet-api","enabled":false,"expirationSeconds":3600,"tokenCacheTtl":"30s","tokenPath":"/var/run/secrets/hyperfleet/token"},"baseUrl":"http://hyperfleet-api:8000","version":"v1"}` | HyperFleet API connection settings injected as environment variables |
+| adapterConfig.hyperfleetApi | object | `{"auth":{"audience":"hyperfleet-api","enabled":false,"expirationSeconds":3600,"scheme":"Bearer","tokenCacheTtl":"30s","tokenPath":"/var/run/secrets/hyperfleet/token"},"baseUrl":"http://hyperfleet-api:8000","version":"v1"}` | HyperFleet API connection settings injected as environment variables |
 | adapterConfig.hyperfleetApi.baseUrl | string | `"http://hyperfleet-api:8000"` | API base URL (`HYPERFLEET_API_BASE_URL`) |
 | adapterConfig.hyperfleetApi.version | string | `"v1"` | API version (`HYPERFLEET_API_VERSION`) |
-| adapterConfig.hyperfleetApi.auth | object | `{"audience":"hyperfleet-api","enabled":false,"expirationSeconds":3600,"tokenCacheTtl":"30s","tokenPath":"/var/run/secrets/hyperfleet/token"}` | JWT bearer token authentication via Kubernetes projected ServiceAccount token |
-| adapterConfig.hyperfleetApi.auth.enabled | bool | `false` | Enable bearer token auth (`HYPERFLEET_API_AUTH_TOKEN_PATH`) |
-| adapterConfig.hyperfleetApi.auth.audience | string | `"hyperfleet-api"` | ServiceAccount token audience (used for the projected volume) |
+| adapterConfig.hyperfleetApi.auth | object | `{"audience":"hyperfleet-api","enabled":false,"expirationSeconds":3600,"scheme":"Bearer","tokenCacheTtl":"30s","tokenPath":"/var/run/secrets/hyperfleet/token"}` | Token-based authentication via a Kubernetes projected service account token |
+| adapterConfig.hyperfleetApi.auth.enabled | bool | `false` | Enable token auth (`HYPERFLEET_API_AUTH_TOKEN_PATH`) |
+| adapterConfig.hyperfleetApi.auth.audience | string | `"hyperfleet-api"` | Service account token audience (used for the projected volume) |
 | adapterConfig.hyperfleetApi.auth.tokenPath | string | `"/var/run/secrets/hyperfleet/token"` | Absolute path where the token file is mounted |
-| adapterConfig.hyperfleetApi.auth.expirationSeconds | int | `3600` | Token lifetime in seconds for the projected ServiceAccount token |
+| adapterConfig.hyperfleetApi.auth.scheme | string | `"Bearer"` | Authorization header scheme used when sending the token (`HYPERFLEET_API_AUTH_SCHEME`). Defaults to `Bearer`; set to `ServiceAccount` when fronted by a gateway that differentiates machine callers from human-jwt callers. |
+| adapterConfig.hyperfleetApi.auth.expirationSeconds | int | `3600` | Token lifetime in seconds for the projected service account token |
 | adapterConfig.hyperfleetApi.auth.tokenCacheTtl | string | `"30s"` | How long the token is cached in memory (`HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL`). Zero means re-read on every request. |
 | adapterConfig.log | object | `{"level":"info"}` | Log level for the adapter |
 | adapterConfig.log.level | string | `"info"` | Log level (`debug`, `info`, `warn`, `error`) |
diff --git a/charts/templates/deployment.yaml b/charts/templates/deployment.yaml
index 15f47994..e1871382 100644
--- a/charts/templates/deployment.yaml
+++ b/charts/templates/deployment.yaml
@@ -92,6 +92,8 @@ spec:
             {{- if .Values.adapterConfig.hyperfleetApi.auth.enabled }}
             - name: HYPERFLEET_API_AUTH_TOKEN_PATH
               value: {{ .Values.adapterConfig.hyperfleetApi.auth.tokenPath | quote }}
+            - name: HYPERFLEET_API_AUTH_SCHEME
+              value: {{ .Values.adapterConfig.hyperfleetApi.auth.scheme | quote }}
             - name: HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL
               value: {{ .Values.adapterConfig.hyperfleetApi.auth.tokenCacheTtl | quote }}
             {{- end }}
diff --git a/charts/values.yaml b/charts/values.yaml
index 87660efb..09cb8129 100644
--- a/charts/values.yaml
+++ b/charts/values.yaml
@@ -27,15 +27,20 @@ adapterConfig:
     baseUrl: http://hyperfleet-api:8000
     # -- API version (`HYPERFLEET_API_VERSION`)
     version: v1
-    # -- JWT bearer token authentication via Kubernetes projected ServiceAccount token
+    # -- Token-based authentication via a Kubernetes projected service account token
     auth:
-      # -- Enable bearer token auth (`HYPERFLEET_API_AUTH_TOKEN_PATH`)
+      # -- Enable token auth (`HYPERFLEET_API_AUTH_TOKEN_PATH`)
       enabled: false
-      # -- ServiceAccount token audience (used for the projected volume)
+      # -- Service account token audience (used for the projected volume)
       audience: hyperfleet-api
       # -- Absolute path where the token file is mounted
       tokenPath: /var/run/secrets/hyperfleet/token
-      # -- Token lifetime in seconds for the projected ServiceAccount token
+      # -- Authorization header scheme used when sending the token
+      # (`HYPERFLEET_API_AUTH_SCHEME`). Defaults to `Bearer`; set to
+      # `ServiceAccount` when fronted by a gateway that differentiates
+      # machine callers from human-jwt callers.
+      scheme: Bearer
+      # -- Token lifetime in seconds for the projected service account token
       expirationSeconds: 3600
       # -- How long the token is cached in memory (`HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL`).
       # Zero means re-read on every request.
diff --git a/cmd/adapter/main.go b/cmd/adapter/main.go
index c35319bf..ad184d70 100644
--- a/cmd/adapter/main.go
+++ b/cmd/adapter/main.go
@@ -327,7 +327,7 @@ func createAPIClient(apiConfig configloader.HyperfleetAPIConfig) (hyperfleetapi.
 		opts = append(opts, hyperfleetapi.WithDefaultHeader(key, value))
 	}
 
-	// Configure bearer token auth if set
+	// Configure token-based auth if set
 	if apiConfig.Auth != nil {
 		opts = append(opts, hyperfleetapi.WithAuth(apiConfig.Auth))
 	}
diff --git a/configs/adapter-config-template.yaml b/configs/adapter-config-template.yaml
index b84f5840..9befbfd2 100644
--- a/configs/adapter-config-template.yaml
+++ b/configs/adapter-config-template.yaml
@@ -114,12 +114,14 @@ clients:
     timeout: 2s
     retry_attempts: 3
     retry_backoff: exponential
-    # Optional JWT bearer token authentication via a file (e.g. Kubernetes projected ServiceAccount token).
-    # When configured, the token is read from token_path and attached as Authorization: Bearer <token>.
-    # token_path must be an absolute path.
-    # Environment variables: HYPERFLEET_API_AUTH_TOKEN_PATH, HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL
+    # Optional token-based authentication via a token file (e.g. Kubernetes projected service account token).
+    # When configured, the token is read from token_path and attached as Authorization: <scheme> <token>.
+    # scheme defaults to Bearer; set to ServiceAccount when fronted by a gateway that
+    # differentiates human-jwt callers from machine callers. token_path must be an absolute path.
+    # Environment variables: HYPERFLEET_API_AUTH_TOKEN_PATH, HYPERFLEET_API_AUTH_SCHEME, HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL
     # auth:
     #   token_path: "/var/run/secrets/hyperfleet/token"
+    #   scheme: Bearer
     #   token_cache_ttl: "30s"  # 0 = re-read on every request
 
   # Broker consumer configuration (adapter-level)
diff --git a/docs/configuration.md b/docs/configuration.md
index 90490858..746774e4 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -64,6 +64,7 @@ clients:
       X-Example: "value"
     auth:
       token_path: "/var/run/secrets/hyperfleet/token"
+      scheme: "Bearer"
       token_cache_ttl: "30s"
   broker:
     subscription_id: "example-subscription"
@@ -115,7 +116,8 @@ clients:
 - `base_delay` (duration string): Initial retry delay. Default: `1s`.
 - `max_delay` (duration string): Maximum retry delay. Default: `30s`.
 - `default_headers` (map[string]string): Headers added to all API requests.
-- `auth.token_path` (string): Absolute path to a file containing a JWT bearer token. When set, the token is read from this file and attached as `Authorization: Bearer <token>` on every request. Typically a Kubernetes projected ServiceAccount token. Must be an absolute path.
+- `auth.token_path` (string): Absolute path to a file containing a service account token. When set, the token is read from this file and attached as `Authorization: <scheme> <token>` on every request. Typically a Kubernetes projected service account token. Must be an absolute path.
+- `auth.scheme` (string): Authorization header scheme used when sending the token. Defaults to `Bearer`. Set to `ServiceAccount` when fronted by a gateway that differentiates human-jwt callers from machine callers.
 - `auth.token_cache_ttl` (duration string): How long the token is cached in memory before re-reading the file. Zero (default) means re-read on every request.
 
 ### Broker (`clients.broker`)
@@ -293,6 +295,7 @@ All deployment overrides use the `HYPERFLEET_` prefix unless noted.
 - `HYPERFLEET_API_BASE_DELAY` -> `clients.hyperfleet_api.base_delay`
 - `HYPERFLEET_API_MAX_DELAY` -> `clients.hyperfleet_api.max_delay`
 - `HYPERFLEET_API_AUTH_TOKEN_PATH` -> `clients.hyperfleet_api.auth.token_path`
+- `HYPERFLEET_API_AUTH_SCHEME` -> `clients.hyperfleet_api.auth.scheme`
 - `HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL` -> `clients.hyperfleet_api.auth.token_cache_ttl`
 
 **Broker**
diff --git a/docs/deployment.md b/docs/deployment.md
index 6ca3bc55..e9b8bed3 100644
--- a/docs/deployment.md
+++ b/docs/deployment.md
@@ -84,11 +84,12 @@ These fields have first-class Helm values that the chart injects as environment
 | `adapterConfig.log.level` | Log level (`debug`, `info`, `warn`, `error`) | `LOG_LEVEL` | `info` |
 | `adapterConfig.hyperfleetApi.baseUrl` | HyperFleet API base URL | `HYPERFLEET_API_BASE_URL` | `http://hyperfleet-api:8000` |
 | `adapterConfig.hyperfleetApi.version` | API version | `HYPERFLEET_API_VERSION` | `v1` |
-| `adapterConfig.hyperfleetApi.auth.enabled` | Enable JWT bearer token auth | — (controls volume + env vars) | `false` |
+| `adapterConfig.hyperfleetApi.auth.enabled` | Enable token auth | — (controls volume + env vars) | `false` |
 | `adapterConfig.hyperfleetApi.auth.tokenPath` | Absolute path to the token file | `HYPERFLEET_API_AUTH_TOKEN_PATH` | `/var/run/secrets/hyperfleet/token` |
+| `adapterConfig.hyperfleetApi.auth.scheme` | Authorization header scheme sent with the token | `HYPERFLEET_API_AUTH_SCHEME` | `Bearer` |
 | `adapterConfig.hyperfleetApi.auth.tokenCacheTtl` | In-memory token cache TTL | `HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL` | `30s` |
-| `adapterConfig.hyperfleetApi.auth.audience` | ServiceAccount token audience | — (used in projected volume) | `hyperfleet-api` |
-| `adapterConfig.hyperfleetApi.auth.expirationSeconds` | ServiceAccount token lifetime (seconds) | — (used in projected volume) | `3600` |
+| `adapterConfig.hyperfleetApi.auth.audience` | Service account token audience | — (used in projected volume) | `hyperfleet-api` |
+| `adapterConfig.hyperfleetApi.auth.expirationSeconds` | Service account token lifetime (seconds) | — (used in projected volume) | `3600` |
 
 ### Fields settable via the `env` list
 
@@ -147,12 +148,12 @@ When using individual properties, `broker.type` must be set to `googlepubsub` or
 
 ## HyperFleet API Authentication
 
-The adapter can authenticate to the HyperFleet API using a Kubernetes projected ServiceAccount token (JWT bearer token). Authentication is **disabled by default** — existing deployments are unaffected.
+The adapter can authenticate to the HyperFleet API using a Kubernetes projected service account token. Authentication is **disabled by default** — existing deployments are unaffected.
 
 When enabled, the Helm chart:
 1. Mounts a projected `serviceAccountToken` volume at the configured `tokenPath` directory.
-2. Sets `HYPERFLEET_API_AUTH_TOKEN_PATH` and `HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL` env vars.
-3. The adapter reads the token file and attaches `Authorization: Bearer <token>` to every HyperFleet API request.
+2. Sets `HYPERFLEET_API_AUTH_TOKEN_PATH`, `HYPERFLEET_API_AUTH_SCHEME`, and `HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL` env vars.
+3. The adapter reads the token file and attaches `Authorization: <scheme> <token>` to every HyperFleet API request. `scheme` defaults to `Bearer`; set it to `ServiceAccount` when fronted by a gateway that differentiates human-jwt callers from machine callers.
 
 ```yaml
 adapterConfig:
@@ -161,6 +162,7 @@ adapterConfig:
       enabled: true
       audience: hyperfleet-api        # token audience claimed by the API server
       tokenPath: /var/run/secrets/hyperfleet/token
+      scheme: Bearer                  # defaults to Bearer; use ServiceAccount behind a gateway that expects it
       expirationSeconds: 3600         # kubelet rotates the token before expiry
       tokenCacheTtl: 30s              # re-read file every 30s; 0 = re-read per request
 ```
@@ -191,6 +193,7 @@ The chart automatically sets these environment variables from Helm values:
 | `HYPERFLEET_API_BASE_URL` | `adapterConfig.hyperfleetApi.baseUrl` | Always |
 | `HYPERFLEET_API_VERSION` | `adapterConfig.hyperfleetApi.version` | Always |
 | `HYPERFLEET_API_AUTH_TOKEN_PATH` | `adapterConfig.hyperfleetApi.auth.tokenPath` | When `auth.enabled` is `true` |
+| `HYPERFLEET_API_AUTH_SCHEME` | `adapterConfig.hyperfleetApi.auth.scheme` | When `auth.enabled` is `true` |
 | `HYPERFLEET_API_AUTH_TOKEN_CACHE_TTL` | `adapterConfig.hyperfleetApi.auth.tokenCacheTtl` | When `auth.enabled` is `true` |
 | `BROKER_CONFIG_FILE` | Hardcoded `/etc/broker/broker.yaml` | Always |
 | `HYPERFLEET_BROKER_SUBSCRIPTION_ID` | `broker.googlepubsub.subscriptionId` | When broker type is `googlepubsub` |
diff --git a/internal/configloader/viper_loader.go b/internal/configloader/viper_loader.go
index 15b25566..d356779a 100644
--- a/internal/configloader/viper_loader.go
+++ b/internal/configloader/viper_loader.go
@@ -43,6 +43,7 @@ var viperKeyMappings = map[string]string{
 	"clients::hyperfleet_api::base_delay":              "API_BASE_DELAY",
 	"clients::hyperfleet_api::max_delay":               "API_MAX_DELAY",
 	"clients::hyperfleet_api::auth::token_path":        "API_AUTH_TOKEN_PATH",
+	"clients::hyperfleet_api::auth::scheme":            "API_AUTH_SCHEME",
 	"clients::hyperfleet_api::auth::token_cache_ttl":   "API_AUTH_TOKEN_CACHE_TTL",
 	"clients::broker::subscription_id":                 "BROKER_SUBSCRIPTION_ID",
 	"clients::broker::topic":                           "BROKER_TOPIC",
diff --git a/internal/hyperfleetapi/client.go b/internal/hyperfleetapi/client.go
index 2a330b45..c2a8d84b 100644
--- a/internal/hyperfleetapi/client.go
+++ b/internal/hyperfleetapi/client.go
@@ -38,6 +38,7 @@ type httpClient struct {
 	client      *http.Client
 	config      *ClientConfig
 	tokenSource *fileTokenSource
+	authScheme  string
 }
 
 // ClientOption is a functional option for configuring the client
@@ -111,7 +112,7 @@ func WithBaseURL(baseURL string) ClientOption {
 	}
 }
 
-// WithAuth configures JWT bearer token authentication from a file.
+// WithAuth configures token-based authentication from a token file.
 func WithAuth(auth *AuthConfig) ClientOption {
 	return func(c *httpClient) {
 		c.config.Auth = auth
@@ -157,9 +158,13 @@ func NewClient(opts ...ClientOption) (Client, error) {
 		}
 	}
 
-	// Initialize token source for bearer token auth if configured
+	// Initialize the token source if auth is configured
 	if c.config.Auth != nil && c.config.Auth.TokenPath != "" {
 		c.tokenSource = newFileTokenSource(c.config.Auth.TokenPath, c.config.Auth.TokenCacheTTL)
+		c.authScheme = c.config.Auth.Scheme
+		if c.authScheme == "" {
+			c.authScheme = DefaultAuthScheme
+		}
 	}
 
 	return c, nil
@@ -334,13 +339,13 @@ func (c *httpClient) doRequest(ctx context.Context, req *Request) (*Response, er
 		httpReq.Header.Set(k, v)
 	}
 
-	// Inject bearer token auth header
+	// Inject the auth header
 	if c.tokenSource != nil {
 		tok, authErr := c.tokenSource.get()
 		if authErr != nil {
 			return nil, fmt.Errorf("getting auth token: %w", authErr)
 		}
-		httpReq.Header.Set("Authorization", "Bearer "+tok)
+		httpReq.Header.Set("Authorization", c.authScheme+" "+tok)
 	}
 
 	// Set default Content-Type for requests with body
diff --git a/internal/hyperfleetapi/client_test.go b/internal/hyperfleetapi/client_test.go
index 9f072101..e7e055d3 100644
--- a/internal/hyperfleetapi/client_test.go
+++ b/internal/hyperfleetapi/client_test.go
@@ -208,7 +208,7 @@ func TestClientWithHeaders(t *testing.T) {
 	defer server.Close()
 
 	client, err := NewClient(WithBaseURL(server.URL),
-		WithDefaultHeader("Authorization", "Bearer default-token"))
+		WithDefaultHeader("Authorization", "ServiceAccount default-token"))
 	require.NoError(t, err, "failed to create client")
 	ctx := context.Background()
 
@@ -218,8 +218,8 @@ func TestClientWithHeaders(t *testing.T) {
 	)
 	require.NoError(t, err, "unexpected error")
 
-	if receivedAuth != "Bearer default-token" {
-		t.Errorf("expected Authorization header 'Bearer default-token', got %q", receivedAuth)
+	if receivedAuth != "ServiceAccount default-token" {
+		t.Errorf("expected Authorization header 'ServiceAccount default-token', got %q", receivedAuth)
 	}
 
 	if receivedCustom != "custom-value" {
@@ -667,10 +667,10 @@ func TestAPIErrorInRetryExhausted(t *testing.T) {
 	}
 }
 
-func TestClientBearerTokenAuth(t *testing.T) {
+func TestClientDefaultBearerScheme(t *testing.T) {
 	dir := t.TempDir()
 	tokenFile := filepath.Join(dir, "token")
-	if err := os.WriteFile(tokenFile, []byte("test-jwt-token"), 0600); err != nil {
+	if err := os.WriteFile(tokenFile, []byte("test-token"), 0600); err != nil {
 		t.Fatal(err)
 	}
 
@@ -690,8 +690,36 @@ func TestClientBearerTokenAuth(t *testing.T) {
 	_, err = client.Get(context.Background(), "/test")
 	require.NoError(t, err)
 
-	if receivedAuth != "Bearer test-jwt-token" {
-		t.Errorf("Authorization = %q, want %q", receivedAuth, "Bearer test-jwt-token")
+	if receivedAuth != "Bearer test-token" {
+		t.Errorf("Authorization = %q, want %q", receivedAuth, "Bearer test-token")
+	}
+}
+
+func TestClientConfiguredServiceAccountScheme(t *testing.T) {
+	dir := t.TempDir()
+	tokenFile := filepath.Join(dir, "token")
+	if err := os.WriteFile(tokenFile, []byte("test-token"), 0600); err != nil {
+		t.Fatal(err)
+	}
+
+	var receivedAuth string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		receivedAuth = r.Header.Get("Authorization")
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer server.Close()
+
+	client, err := NewClient(
+		WithBaseURL(server.URL),
+		WithAuth(&AuthConfig{TokenPath: tokenFile, Scheme: "ServiceAccount", TokenCacheTTL: 0}),
+	)
+	require.NoError(t, err)
+
+	_, err = client.Get(context.Background(), "/test")
+	require.NoError(t, err)
+
+	if receivedAuth != "ServiceAccount test-token" {
+		t.Errorf("Authorization = %q, want %q", receivedAuth, "ServiceAccount test-token")
 	}
 }
 
diff --git a/internal/hyperfleetapi/token.go b/internal/hyperfleetapi/token.go
index d2282421..257a6f20 100644
--- a/internal/hyperfleetapi/token.go
+++ b/internal/hyperfleetapi/token.go
@@ -8,7 +8,7 @@ import (
 	"time"
 )
 
-// fileTokenSource reads a bearer token from disk on every call, or caches it
+// fileTokenSource reads a token from disk on every call, or caches it
 // for cacheTTL when cacheTTL > 0. A zero cacheTTL disables caching and causes
 // the file to be re-read on every request. It is safe for concurrent use.
 type fileTokenSource struct {
diff --git a/internal/hyperfleetapi/types.go b/internal/hyperfleetapi/types.go
index 1acd0f22..f1a80267 100644
--- a/internal/hyperfleetapi/types.go
+++ b/internal/hyperfleetapi/types.go
@@ -34,12 +34,20 @@ const (
 // Client Configuration
 // -----------------------------------------------------------------------------
 
-// AuthConfig holds optional JWT bearer token authentication configuration.
-// When set, a bearer token is read from TokenPath and injected as an
-// Authorization header on every outbound request.
+// DefaultAuthScheme is the Authorization header scheme used when AuthConfig.Scheme
+// is not set, matching the "Bearer"-only validation in hyperfleet-api's JWT handler.
+const DefaultAuthScheme = "Bearer"
+
+// AuthConfig holds optional token-based authentication configuration.
+// When set, a token is read from TokenPath and injected using Scheme
+// (defaults to "Bearer") on every outbound request.
 type AuthConfig struct {
-	// TokenPath is the absolute path to a file containing the bearer token.
+	// TokenPath is the absolute path to a file containing the service account token.
 	TokenPath string `yaml:"token_path,omitempty" mapstructure:"token_path"`
+	// Scheme is the Authorization header scheme used when sending the token.
+	// Defaults to "Bearer" when empty; set to "ServiceAccount" when fronted by
+	// a gateway that differentiates human-jwt callers from machine callers.
+	Scheme string `yaml:"scheme,omitempty" mapstructure:"scheme"`
 	// TokenCacheTTL controls how long the token is cached in memory.
 	// Zero means the file is re-read on every request.
 	TokenCacheTTL time.Duration `yaml:"token_cache_ttl,omitempty" mapstructure:"token_cache_ttl"`
@@ -49,7 +57,7 @@ type AuthConfig struct {
 type ClientConfig struct {
 	// DefaultHeaders are headers added to all requests
 	DefaultHeaders map[string]string `yaml:"default_headers,omitempty" mapstructure:"default_headers"`
-	// Auth configures optional JWT bearer token authentication.
+	// Auth configures optional token-based authentication.
 	// When nil, requests are sent without an Authorization header.
 	Auth *AuthConfig `yaml:"auth,omitempty" mapstructure:"auth"`
 	// BaseURL is the base URL for all API requests (must be set by caller)