feat(sub): add read-only HWID device-slot status endpoint (#6380)

* feat(sub): add read-only HWID device-slot status endpoint

Closes #6357

A client with an HWID limit had no way to tell a subscriber how many device
slots were left: /{subPath}/{subId} only exposes the gate as a boolean through
X-Hwid-* headers on a 404, and ?format=info carries no limitHwid or registered
count. Every "why can't I connect on my new phone" case therefore had to be
answered by the operator by hand.

GET /{subPath}/{subId}/hwid-status now returns the aggregate counters:

  {"active":true,"limit":2,"registered":1,"remaining":1,"full":false}

- SELECT-only. It never registers an hwid, never touches last_seen and never
  calls the enforcement path, so asking about a slot cannot spend one.
- Counters only: no hwid value or hash, no email, no device metadata, no IP,
  no User-Agent, and none of the X-Hwid-* gate headers.
- The subscription id is already the bearer secret for /{subPath}/{subId}, so
  no admin token and no new auth mechanism.
- Unknown and disabled subscriptions both answer a bare 404, with identical
  status, headers and body, so the route cannot be used to probe which
  subscription ids exist.
- No HWID limit configured returns {"active":false,"limit":0,...}.
- No schema change and no migration.

Scoped to enabled clients exactly like effectiveHwidLimitForSubID, so the
reported limit is always the limit the gate enforces on a shared sub_id, and
remaining clamps at zero when the effective limit drops below the number of
registered devices. A separate route leaves /{subPath}/{subId}, ?format=info
and the JSON/Clash routes byte-for-byte unchanged.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

* fix(sub): document hwid-status as the bare object it returns

The OpenAPI operation for GET /{subPath}/{subId}/hwid-status inherited the
{success,msg,obj} panel envelope from build-openapi.mjs's default 200
response, while the handler writes the HwidSlotStatus struct bare. A client
generated from the spec would read `obj` and never find the counters, and
the description prose contradicted the schema with a hand-written example.

HwidSlotStatus now sits in openapigen's StructAllow with example: tags, the
entry references the generated schema through a `responses` block, and
build-openapi.mjs attaches the generated example to any `responses` entry
that $refs a generated schema, so no example is hand-written. The HEAD
variant the controller registers is documented like its siblings, and the
summary follows the "path prefix is configured by subPath" wording now that
fresh panels randomise the prefix.

Regenerated frontend/public/openapi.json, docs/public/openapi.json and the
subscription-server MDX. openapi-runtime-contracts.test.ts pins the bare
schema, the generated example and the HEAD operation.

---------

Co-authored-by: Claude Opus 5 (1M context) <[email protected]>
Co-authored-by: Sanaei <[email protected]>

docs/content/docs/en/reference/api/subscription-server.mdx

@@ -23,6 +23,17 @@ _openapi:
       title: Return the same status and subscription metadata headers as GET without a
         response body.
       url: '#return-the-same-status-and-subscription-metadata-headers-as-get-without-a-response-body'
+    - depth: 2
+      title: 'Return aggregate HWID device-slot usage for the subscription: whether an
+        HWID limit is active, the limit, how many devices are registered and how
+        many slots remain. Read-only — it never registers a device, so asking
+        does not consume a slot. Counters only: no HWID value, email or device
+        metadata. The path prefix is configured by subPath.'
+      url: '#return-aggregate-hwid-device-slot-usage-for-the-subscription-whether-an-hwid-limit-is-active-the-limit-how-many-devices-are-registered-and-how-many-slots-remain-read-only--it-never-registers-a-device-so-asking-does-not-consume-a-slot-counters-only-no-hwid-value-email-or-device-metadata-the-path-prefix-is-configured-by-subpath'
+    - depth: 2
+      title: Return the HWID device-slot status code and headers as GET without a
+        response body.
+      url: '#return-the-hwid-device-slot-status-code-and-headers-as-get-without-a-response-body'
     - depth: 2
       title: Return subscription as a JSON array of proxy configs (one per enabled
         client). Only when JSON subscription is enabled in settings. The path
@@ -53,6 +64,15 @@ _openapi:
       - content: Return the same status and subscription metadata headers as GET without
           a response body.
         id: return-the-same-status-and-subscription-metadata-headers-as-get-without-a-response-body
+      - content: 'Return aggregate HWID device-slot usage for the subscription: whether
+          an HWID limit is active, the limit, how many devices are registered
+          and how many slots remain. Read-only — it never registers a device, so
+          asking does not consume a slot. Counters only: no HWID value, email or
+          device metadata. The path prefix is configured by subPath.'
+        id: return-aggregate-hwid-device-slot-usage-for-the-subscription-whether-an-hwid-limit-is-active-the-limit-how-many-devices-are-registered-and-how-many-slots-remain-read-only--it-never-registers-a-device-so-asking-does-not-consume-a-slot-counters-only-no-hwid-value-email-or-device-metadata-the-path-prefix-is-configured-by-subpath
+      - content: Return the HWID device-slot status code and headers as GET without a
+          response body.
+        id: return-the-hwid-device-slot-status-code-and-headers-as-get-without-a-response-body
       - content: Return subscription as a JSON array of proxy configs (one per enabled
           client). Only when JSON subscription is enabled in settings. The path
           prefix is configured by subJsonPath.
@@ -67,7 +87,12 @@ _openapi:
       - content: Return the Clash subscription status and metadata headers without a
           body. Registered only when Clash subscriptions are enabled.
         id: return-the-clash-subscription-status-and-metadata-headers-without-a-body-registered-only-when-clash-subscriptions-are-enabled
-    contents: []
+    contents:
+      - content: Responds with the bare HwidSlotStatus object, not the
+          <code>{success,msg,obj}</code> panel envelope, like the other
+          subscription-server routes. With no HWID limit configured,
+          <code>active</code> is false and every counter is 0.
+        heading: return-aggregate-hwid-device-slot-usage-for-the-subscription-whether-an-hwid-limit-is-active-the-limit-how-many-devices-are-registered-and-how-many-slots-remain-read-only--it-never-registers-a-device-so-asking-does-not-consume-a-slot-counters-only-no-hwid-value-email-or-device-metadata-the-path-prefix-is-configured-by-subpath
 ---
 
 {/* This file was generated by Fumadocs. Do not edit this file directly. Any changes should be made by running the generation command again. */}
@@ -79,7 +104,7 @@ export default function Layout(props) {
   return (
     <>
       {props.children}
-      <Comp document="./public/openapi.json" webhooks={[]} operations={[{"path":"/{subPath}{subid}","method":"get"},{"path":"/{subPath}{subid}","method":"head"},{"path":"/{jsonPath}{subid}","method":"get"},{"path":"/{jsonPath}{subid}","method":"head"},{"path":"/{clashPath}{subid}","method":"get"},{"path":"/{clashPath}{subid}","method":"head"}]} showTitle />
+      <Comp document="./public/openapi.json" webhooks={[]} operations={[{"path":"/{subPath}{subid}","method":"get"},{"path":"/{subPath}{subid}","method":"head"},{"path":"/{subPath}{subid}/hwid-status","method":"get"},{"path":"/{subPath}{subid}/hwid-status","method":"head"},{"path":"/{jsonPath}{subid}","method":"get"},{"path":"/{jsonPath}{subid}","method":"head"},{"path":"/{clashPath}{subid}","method":"get"},{"path":"/{clashPath}{subid}","method":"head"}]} showTitle />
     </>
   );
 }

docs/public/openapi.json

@@ -2492,6 +2492,39 @@
         ],
         "type": "object"
       },
+      "HwidSlotStatus": {
+        "description": "HwidSlotStatus is the aggregate device-slot view exposed to subscribers:\ncounters only, no hwid value or hash, no email, no device metadata.",
+        "properties": {
+          "active": {
+            "example": true,
+            "type": "boolean"
+          },
+          "full": {
+            "example": false,
+            "type": "boolean"
+          },
+          "limit": {
+            "example": 2,
+            "type": "integer"
+          },
+          "registered": {
+            "example": 1,
+            "type": "integer"
+          },
+          "remaining": {
+            "example": 1,
+            "type": "integer"
+          }
+        },
+        "required": [
+          "active",
+          "full",
+          "limit",
+          "registered",
+          "remaining"
+        ],
+        "type": "object"
+      },
       "Inbound": {
         "description": "Inbound represents an Xray inbound configuration with traffic statistics and settings.",
         "properties": {
@@ -14404,6 +14437,99 @@
         }
       }
     },
+    "/{subPath}{subid}/hwid-status": {
+      "get": {
+        "tags": [
+          "Subscription Server"
+        ],
+        "summary": "Return aggregate HWID device-slot usage for the subscription: whether an HWID limit is active, the limit, how many devices are registered and how many slots remain. Read-only — it never registers a device, so asking does not consume a slot. Counters only: no HWID value, email or device metadata. The path prefix is configured by subPath.",
+        "operationId": "get_subPath_subid_hwid_status",
+        "description": "Responds with the bare HwidSlotStatus object, not the <code>{success,msg,obj}</code> panel envelope, like the other subscription-server routes. With no HWID limit configured, <code>active</code> is false and every counter is 0.",
+        "parameters": [
+          {
+            "name": "subid",
+            "in": "path",
+            "required": true,
+            "description": "Client subscription ID.",
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "subPath",
+            "in": "path",
+            "required": true,
+            "description": "",
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Device-slot counters for the subscription.",
+            "content": {
+              "application/json": {
+                "example": {
+                  "active": true,
+                  "full": false,
+                  "limit": 2,
+                  "registered": 1,
+                  "remaining": 1
+                },
+                "schema": {
+                  "$ref": "#/components/schemas/HwidSlotStatus"
+                }
+              }
+            }
+          },
+          "404": {
+            "description": "No enabled client matches the subscription ID. Empty body."
+          },
+          "500": {
+            "description": "Database lookup failed. Empty body."
+          }
+        }
+      },
+      "head": {
+        "tags": [
+          "Subscription Server"
+        ],
+        "summary": "Return the HWID device-slot status code and headers as GET without a response body.",
+        "operationId": "head_subPath_subid_hwid_status",
+        "parameters": [
+          {
+            "name": "subid",
+            "in": "path",
+            "required": true,
+            "description": "Client subscription ID.",
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "subPath",
+            "in": "path",
+            "required": true,
+            "description": "",
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Headers match GET; no response body."
+          },
+          "404": {
+            "description": "No enabled client matches the subscription ID. Empty body."
+          },
+          "500": {
+            "description": "Database lookup failed. Empty body."
+          }
+        }
+      }
+    },
     "/{jsonPath}{subid}": {
       "get": {
         "tags": [

frontend/public/openapi.json

@@ -2492,6 +2492,39 @@
         ],
         "type": "object"
       },
+      "HwidSlotStatus": {
+        "description": "HwidSlotStatus is the aggregate device-slot view exposed to subscribers:\ncounters only, no hwid value or hash, no email, no device metadata.",
+        "properties": {
+          "active": {
+            "example": true,
+            "type": "boolean"
+          },
+          "full": {
+            "example": false,
+            "type": "boolean"
+          },
+          "limit": {
+            "example": 2,
+            "type": "integer"
+          },
+          "registered": {
+            "example": 1,
+            "type": "integer"
+          },
+          "remaining": {
+            "example": 1,
+            "type": "integer"
+          }
+        },
+        "required": [
+          "active",
+          "full",
+          "limit",
+          "registered",
+          "remaining"
+        ],
+        "type": "object"
+      },
       "Inbound": {
         "description": "Inbound represents an Xray inbound configuration with traffic statistics and settings.",
         "properties": {
@@ -14404,6 +14437,99 @@
         }
       }
     },
+    "/{subPath}{subid}/hwid-status": {
+      "get": {
+        "tags": [
+          "Subscription Server"
+        ],
+        "summary": "Return aggregate HWID device-slot usage for the subscription: whether an HWID limit is active, the limit, how many devices are registered and how many slots remain. Read-only — it never registers a device, so asking does not consume a slot. Counters only: no HWID value, email or device metadata. The path prefix is configured by subPath.",
+        "operationId": "get_subPath_subid_hwid_status",
+        "description": "Responds with the bare HwidSlotStatus object, not the <code>{success,msg,obj}</code> panel envelope, like the other subscription-server routes. With no HWID limit configured, <code>active</code> is false and every counter is 0.",
+        "parameters": [
+          {
+            "name": "subid",
+            "in": "path",
+            "required": true,
+            "description": "Client subscription ID.",
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "subPath",
+            "in": "path",
+            "required": true,
+            "description": "",
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Device-slot counters for the subscription.",
+            "content": {
+              "application/json": {
+                "example": {
+                  "active": true,
+                  "full": false,
+                  "limit": 2,
+                  "registered": 1,
+                  "remaining": 1
+                },
+                "schema": {
+                  "$ref": "#/components/schemas/HwidSlotStatus"
+                }
+              }
+            }
+          },
+          "404": {
+            "description": "No enabled client matches the subscription ID. Empty body."
+          },
+          "500": {
+            "description": "Database lookup failed. Empty body."
+          }
+        }
+      },
+      "head": {
+        "tags": [
+          "Subscription Server"
+        ],
+        "summary": "Return the HWID device-slot status code and headers as GET without a response body.",
+        "operationId": "head_subPath_subid_hwid_status",
+        "parameters": [
+          {
+            "name": "subid",
+            "in": "path",
+            "required": true,
+            "description": "Client subscription ID.",
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "subPath",
+            "in": "path",
+            "required": true,
+            "description": "",
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Headers match GET; no response body."
+          },
+          "404": {
+            "description": "No enabled client matches the subscription ID. Empty body."
+          },
+          "500": {
+            "description": "Database lookup failed. Empty body."
+          }
+        }
+      }
+    },
     "/{jsonPath}{subid}": {
       "get": {
         "tags": [

frontend/scripts/build-openapi.mjs

@@ -112,6 +112,21 @@ function paramToOpenApi(p) {
   return out;
 }
 
+// A `responses` entry that $refs a generated schema takes its example from the
+// Go `example:` tags, the same source responseSchema uses — never hand-written.
+function withGeneratedExample(ep, code, res) {
+  const json = res.content?.['application/json'];
+  const name = json?.schema?.$ref?.replace('#/components/schemas/', '');
+  if (!name) return res;
+  if (SCHEMAS[name] === undefined || EXAMPLES[name] === undefined) {
+    throw new Error(`${ep.method} ${ep.path}: ${code} response schema "${name}" is not generated`);
+  }
+  return {
+    ...res,
+    content: { ...res.content, 'application/json': { example: EXAMPLES[name], ...json } },
+  };
+}
+
 function buildOperation(ep, tag) {
   const op = {
     tags: [tag],
@@ -257,7 +272,9 @@ function buildOperation(ep, tag) {
     }
   }
   if (ep.responses) {
-    Object.assign(responses, ep.responses);
+    for (const [code, res] of Object.entries(ep.responses)) {
+      responses[code] = withGeneratedExample(ep, code, res);
+    }
   } else {
     responses['200'] = {
       description: 'Successful response',

frontend/src/generated/examples.ts

@@ -644,6 +644,13 @@ export const EXAMPLES: Record<string, unknown> = {
     "verifyPeerCertByName": "",
     "vlessRoute": ""
   },
+  "HwidSlotStatus": {
+    "active": true,
+    "full": false,
+    "limit": 2,
+    "registered": 1,
+    "remaining": 1
+  },
   "Inbound": {
     "clientStats": [
       {

frontend/src/generated/schemas.ts

@@ -2466,6 +2466,39 @@ export const SCHEMAS: Record<string, unknown> = {
     ],
     "type": "object"
   },
+  "HwidSlotStatus": {
+    "description": "HwidSlotStatus is the aggregate device-slot view exposed to subscribers:\ncounters only, no hwid value or hash, no email, no device metadata.",
+    "properties": {
+      "active": {
+        "example": true,
+        "type": "boolean"
+      },
+      "full": {
+        "example": false,
+        "type": "boolean"
+      },
+      "limit": {
+        "example": 2,
+        "type": "integer"
+      },
+      "registered": {
+        "example": 1,
+        "type": "integer"
+      },
+      "remaining": {
+        "example": 1,
+        "type": "integer"
+      }
+    },
+    "required": [
+      "active",
+      "full",
+      "limit",
+      "registered",
+      "remaining"
+    ],
+    "type": "object"
+  },
   "Inbound": {
     "description": "Inbound represents an Xray inbound configuration with traffic statistics and settings.",
     "properties": {

frontend/src/generated/types.ts

@@ -570,6 +570,14 @@ export interface HostGroup {
   vlessRoute: string;
 }
 
+export interface HwidSlotStatus {
+  active: boolean;
+  full: boolean;
+  limit: number;
+  registered: number;
+  remaining: number;
+}
+
 export interface Inbound {
   clientStats: ClientTraffic[];
   disableFlow: boolean;

frontend/src/generated/zod.ts

@@ -609,6 +609,15 @@ export const HostGroupSchema = z.object({
 });
 export type HostGroup = z.infer<typeof HostGroupSchema>;
 
+export const HwidSlotStatusSchema = z.object({
+  active: z.boolean(),
+  full: z.boolean(),
+  limit: z.number().int(),
+  registered: z.number().int(),
+  remaining: z.number().int(),
+});
+export type HwidSlotStatus = z.infer<typeof HwidSlotStatusSchema>;
+
 export const InboundSchema = z.object({
   clientStats: z.array(z.lazy(() => ClientTrafficSchema)),
   disableFlow: z.boolean(),

frontend/src/pages/api-docs/endpoints.ts

@@ -183,6 +183,11 @@ const subscriptionHeadResponses = {
   '500': { description: 'Subscription generation failed.' },
 };
 
+const hwidStatusErrorResponses = {
+  '404': { description: 'No enabled client matches the subscription ID. Empty body.' },
+  '500': { description: 'Database lookup failed. Empty body.' },
+};
+
 export const sections: readonly Section[] = [
   {
     id: 'authentication',
@@ -2618,6 +2623,35 @@ export const sections: readonly Section[] = [
         params: [{ name: 'subid', in: 'path', type: 'string', desc: 'Client subscription ID.' }],
         responses: subscriptionHeadResponses,
       },
+      {
+        method: 'GET',
+        path: '/{subPath}:subid/hwid-status',
+        summary:
+          'Return aggregate HWID device-slot usage for the subscription: whether an HWID limit is active, the limit, how many devices are registered and how many slots remain. Read-only — it never registers a device, so asking does not consume a slot. Counters only: no HWID value, email or device metadata. The path prefix is configured by subPath.',
+        description:
+          'Responds with the bare HwidSlotStatus object, not the <code>{success,msg,obj}</code> panel envelope, like the other subscription-server routes. With no HWID limit configured, <code>active</code> is false and every counter is 0.',
+        params: [{ name: 'subid', in: 'path', type: 'string', desc: 'Client subscription ID.' }],
+        responses: {
+          '200': {
+            description: 'Device-slot counters for the subscription.',
+            content: {
+              'application/json': { schema: { $ref: '#/components/schemas/HwidSlotStatus' } },
+            },
+          },
+          ...hwidStatusErrorResponses,
+        },
+      },
+      {
+        method: 'HEAD',
+        path: '/{subPath}:subid/hwid-status',
+        summary:
+          'Return the HWID device-slot status code and headers as GET without a response body.',
+        params: [{ name: 'subid', in: 'path', type: 'string', desc: 'Client subscription ID.' }],
+        responses: {
+          '200': { description: 'Headers match GET; no response body.' },
+          ...hwidStatusErrorResponses,
+        },
+      },
       {
         method: 'GET',
         path: '/{jsonPath}:subid',

frontend/src/test/openapi-runtime-contracts.test.ts

@@ -241,4 +241,19 @@ describe('generated OpenAPI runtime contracts', () => {
     expect(operation('/{jsonPath}{subid}', 'head')).toBeDefined();
     expect(operation('/{clashPath}{subid}', 'head')).toBeDefined();
   });
+
+  it('documents the HWID slot status as a bare generated object, not the panel envelope', () => {
+    const path = '/{subPath}{subid}/hwid-status';
+    const json = operation(path, 'get').responses['200'].content?.['application/json'];
+    expect(json?.schema).toEqual({ $ref: '#/components/schemas/HwidSlotStatus' });
+    expect(json?.example).toEqual(EXAMPLES.HwidSlotStatus);
+    expect(spec.components.schemas.HwidSlotStatus.required).toEqual([
+      'active',
+      'full',
+      'limit',
+      'registered',
+      'remaining',
+    ]);
+    expect(operation(path, 'head')).toBeDefined();
+  });
 });

internal/sub/controller.go

@@ -311,6 +311,8 @@ func (a *SUBController) initRouter(g *gin.RouterGroup) {
 	gLink := g.Group(a.subPath)
 	gLink.GET(":subid", a.subs)
 	gLink.HEAD(":subid", a.subs)
+	gLink.GET(":subid/hwid-status", a.hwidStatus)
+	gLink.HEAD(":subid/hwid-status", a.hwidStatus)
 	if a.jsonEnabled {
 		gJson := g.Group(a.subJsonPath)
 		gJson.GET(":subid", a.subJsons)
@@ -707,6 +709,18 @@ func applyHwidHeaders(c *gin.Context, result service.HwidGateResult) {
 	}
 }
 
+// hwidStatus serves read-only device-slot counters for a subscription. It
+// deliberately skips enforceHwid: asking about slots must not consume one.
+func (a *SUBController) hwidStatus(c *gin.Context) {
+	status, found, err := a.clientService.HwidSlotStatusForSubID(c.Param("subid"))
+	if err != nil || !found {
+		writeSubError(c, err)
+		return
+	}
+	setNoCacheHeaders(c)
+	c.JSON(http.StatusOK, status)
+}
+
 // setNoCacheHeaders marks a subscription page response as non-cacheable so VPN
 // clients and browsers always fetch fresh traffic/expiry data.
 func setNoCacheHeaders(c *gin.Context) {

internal/sub/hwid_controller_test.go

@@ -1,10 +1,12 @@
 package sub
 
 import (
+	"encoding/json"
 	"net/http"
 	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"reflect"
 	"testing"
 
 	"github.com/gin-gonic/gin"
@@ -144,3 +146,113 @@ func TestSubscriptionHwidGateSkipsHtmlInfoPage(t *testing.T) {
 		t.Fatalf("HTML sub page should not be HWID-gated: %#v", rec.Header())
 	}
 }
+
+// Decoding into a map rather than the service struct keeps the exact field set
+// asserted, so an extra field leaking into the response fails the test.
+func assertHwidStatus(t *testing.T, rec *httptest.ResponseRecorder, active bool, limit, registered, remaining int, full bool) {
+	t.Helper()
+	if rec.Code != http.StatusOK {
+		t.Fatalf("hwid-status status = %d, body=%q", rec.Code, rec.Body.String())
+	}
+	var got map[string]any
+	if err := json.Unmarshal(rec.Body.Bytes(), &got); err != nil {
+		t.Fatalf("decode hwid-status body %q: %v", rec.Body.String(), err)
+	}
+	want := map[string]any{
+		"active":     active,
+		"limit":      float64(limit),
+		"registered": float64(registered),
+		"remaining":  float64(remaining),
+		"full":       full,
+	}
+	if len(got) != len(want) {
+		t.Fatalf("hwid-status fields = %#v, want exactly %#v", got, want)
+	}
+	for key, value := range want {
+		if got[key] != value {
+			t.Fatalf("hwid-status[%q] = %#v, want %#v (body %#v)", key, got[key], value, got)
+		}
+	}
+}
+
+func TestSubscriptionHwidStatusCountsRegisteredDevices(t *testing.T) {
+	router, subID := initHwidSubRouter(t, 2)
+	statusPath := "/sub/" + subID + "/hwid-status"
+
+	assertHwidStatus(t, requestSub(t, router, http.MethodGet, statusPath, "", ""), true, 2, 0, 2, false)
+
+	for i, hwid := range []string{"device-one", "device-two"} {
+		if rec := requestSub(t, router, http.MethodGet, "/sub/"+subID, hwid, ""); rec.Code != http.StatusOK {
+			t.Fatalf("register %s = %d, want 200", hwid, rec.Code)
+		}
+		registered := i + 1
+		rec := requestSub(t, router, http.MethodGet, statusPath, "", "")
+		assertHwidStatus(t, rec, true, 2, registered, 2-registered, registered == 2)
+	}
+
+	if rec := requestSub(t, router, http.MethodHead, statusPath, "", ""); rec.Code != http.StatusOK {
+		t.Fatalf("HEAD hwid-status = %d, want 200", rec.Code)
+	}
+}
+
+// The endpoint must stay SELECT-only: asking about slots while carrying an
+// X-HWID header must not spend the slot the caller is asking about.
+func TestSubscriptionHwidStatusDoesNotRegisterDevice(t *testing.T) {
+	router, subID := initHwidSubRouter(t, 1)
+
+	rec := requestSub(t, router, http.MethodGet, "/sub/"+subID+"/hwid-status", "device-probe", "")
+	assertHwidStatus(t, rec, true, 1, 0, 1, false)
+	for _, header := range []string{"X-Hwid-Active", "X-Hwid-Limit", "X-Hwid-Not-Supported", "X-Hwid-Max-Devices-Reached"} {
+		if value := rec.Header().Get(header); value != "" {
+			t.Fatalf("hwid-status leaked gate header %s = %q", header, value)
+		}
+	}
+
+	var count int64
+	if err := database.GetDB().Model(&model.ClientHwid{}).Where("sub_id = ?", subID).Count(&count).Error; err != nil {
+		t.Fatalf("count hwids: %v", err)
+	}
+	if count != 0 {
+		t.Fatalf("client_hwids rows after status probe = %d, want 0", count)
+	}
+	if rec := requestSub(t, router, http.MethodGet, "/sub/"+subID, "device-probe", ""); rec.Code != http.StatusOK {
+		t.Fatalf("subscription fetch after probe = %d, want 200", rec.Code)
+	}
+}
+
+func TestSubscriptionHwidStatusWithoutLimit(t *testing.T) {
+	router, subID := initHwidSubRouter(t, 0)
+
+	assertHwidStatus(t, requestSub(t, router, http.MethodGet, "/sub/"+subID+"/hwid-status", "", ""), false, 0, 0, 0, false)
+}
+
+// An unknown and a disabled subscription must be indistinguishable, so a
+// caller cannot probe which subscription ids exist.
+func TestSubscriptionHwidStatusHidesUnknownVersusDisabled(t *testing.T) {
+	router, subID := initHwidSubRouter(t, 1)
+
+	unknown := requestSub(t, router, http.MethodGet, "/sub/does-not-exist/hwid-status", "", "")
+	if unknown.Code != http.StatusNotFound {
+		t.Fatalf("unknown subId status = %d, want 404", unknown.Code)
+	}
+
+	if err := database.GetDB().Model(&model.ClientRecord{}).
+		Where("sub_id = ?", subID).
+		UpdateColumn("enable", false).Error; err != nil {
+		t.Fatalf("disable client: %v", err)
+	}
+	disabled := requestSub(t, router, http.MethodGet, "/sub/"+subID+"/hwid-status", "", "")
+
+	if disabled.Code != unknown.Code {
+		t.Fatalf("disabled status = %d, unknown status = %d, want identical", disabled.Code, unknown.Code)
+	}
+	if disabled.Body.String() != unknown.Body.String() {
+		t.Fatalf("disabled body = %q, unknown body = %q, want identical", disabled.Body.String(), unknown.Body.String())
+	}
+	if !reflect.DeepEqual(disabled.Header(), unknown.Header()) {
+		t.Fatalf("disabled headers = %#v, unknown headers = %#v, want identical", disabled.Header(), unknown.Header())
+	}
+	if disabled.Body.Len() != 0 {
+		t.Fatalf("404 body = %q, want empty", disabled.Body.String())
+	}
+}

internal/web/service/client_hwid.go

@@ -31,6 +31,16 @@ type HwidGateResult struct {
 	Registered        int
 }
 
+// HwidSlotStatus is the aggregate device-slot view exposed to subscribers:
+// counters only, no hwid value or hash, no email, no device metadata.
+type HwidSlotStatus struct {
+	Active     bool `json:"active" example:"true"`
+	Limit      int  `json:"limit" example:"2"`
+	Registered int  `json:"registered" example:"1"`
+	Remaining  int  `json:"remaining" example:"1"`
+	Full       bool `json:"full" example:"false"`
+}
+
 const minHwidLength = 6
 
 type ClientHwidInfo struct {
@@ -156,6 +166,45 @@ func (s *ClientService) EnforceHwidForSubID(subID string, req HwidRequest) (Hwid
 	return res, err
 }
 
+// HwidSlotStatusForSubID is SELECT-only: it must never write client_hwids or
+// last_seen. Enabled-clients scope mirrors the gate, so limit == limit enforced.
+func (s *ClientService) HwidSlotStatusForSubID(subID string) (status HwidSlotStatus, found bool, err error) {
+	subID = strings.TrimSpace(subID)
+	if subID == "" {
+		return status, false, nil
+	}
+
+	db := database.GetDB()
+	var enabled int64
+	if err := db.Model(&model.ClientRecord{}).
+		Where("sub_id = ? AND enable = ?", subID, true).
+		Count(&enabled).Error; err != nil {
+		return status, false, err
+	}
+	if enabled == 0 {
+		return status, false, nil
+	}
+
+	limit, err := effectiveHwidLimitForSubID(db, subID)
+	if err != nil {
+		return status, false, err
+	}
+	if limit <= 0 {
+		return status, true, nil
+	}
+
+	var registered int64
+	if err := db.Model(&model.ClientHwid{}).Where("sub_id = ?", subID).Count(&registered).Error; err != nil {
+		return status, false, err
+	}
+	status.Active = true
+	status.Limit = limit
+	status.Registered = int(registered)
+	status.Remaining = max(limit-status.Registered, 0)
+	status.Full = status.Registered >= limit
+	return status, true, nil
+}
+
 func (s *ClientService) ListClientHwids(email string) ([]ClientHwidInfo, error) {
 	rec, err := s.GetRecordByEmail(nil, email)
 	if err != nil {

internal/web/service/client_hwid_test.go

@@ -217,3 +217,61 @@ func TestClientHwidGateSharedSubIdUsesMaxLimit(t *testing.T) {
 		t.Fatalf("missing HWID should be denied: %+v", res)
 	}
 }
+
+func TestClientHwidSlotStatus(t *testing.T) {
+	initClientHwidTestDB(t)
+	svc := &ClientService{}
+	db := database.GetDB()
+	rec := seedHwidClient(t, 1)
+
+	status, found, err := svc.HwidSlotStatusForSubID("no-such-sub")
+	if err != nil || found || status != (HwidSlotStatus{}) {
+		t.Fatalf("unknown subId = (%+v, %v, %v), want zero status and found=false", status, found, err)
+	}
+
+	status, found, err = svc.HwidSlotStatusForSubID(" " + rec.SubID + " ")
+	if err != nil || !found {
+		t.Fatalf("padded subId = (%+v, %v, %v), want found=true", status, found, err)
+	}
+	if want := (HwidSlotStatus{Active: true, Limit: 1, Remaining: 1}); status != want {
+		t.Fatalf("empty slots = %+v, want %+v", status, want)
+	}
+
+	// A shared sub_id takes the highest limit, matching the enforcement gate.
+	if err := db.Create(&model.ClientRecord{Email: "[email protected]", SubID: rec.SubID, UUID: "22222222-2222-4333-8444-555555555555", Enable: true, LimitHwid: 3}).Error; err != nil {
+		t.Fatalf("seed second client: %v", err)
+	}
+	for _, hwid := range []string{"device-one", "device-two", "device-three"} {
+		if _, err := svc.EnforceHwidForSubID(rec.SubID, HwidRequest{Hwid: hwid}); err != nil {
+			t.Fatalf("register %s: %v", hwid, err)
+		}
+	}
+	status, found, err = svc.HwidSlotStatusForSubID(rec.SubID)
+	if err != nil || !found {
+		t.Fatalf("shared subId = (%+v, %v, %v), want found=true", status, found, err)
+	}
+	if want := (HwidSlotStatus{Active: true, Limit: 3, Registered: 3, Full: true}); status != want {
+		t.Fatalf("full slots = %+v, want %+v", status, want)
+	}
+
+	// Deleting the highest-limit client drops the effective limit below the
+	// registered count, and remaining must clamp at zero instead of going negative.
+	if err := db.Where("email = ?", "[email protected]").Delete(&model.ClientRecord{}).Error; err != nil {
+		t.Fatalf("delete second client: %v", err)
+	}
+	status, _, err = svc.HwidSlotStatusForSubID(rec.SubID)
+	if err != nil {
+		t.Fatalf("lowered limit: %v", err)
+	}
+	if want := (HwidSlotStatus{Active: true, Limit: 1, Registered: 3, Remaining: 0, Full: true}); status != want {
+		t.Fatalf("over-limit slots = %+v, want %+v", status, want)
+	}
+
+	if err := db.Model(&model.ClientRecord{}).Where("sub_id = ?", rec.SubID).UpdateColumn("enable", false).Error; err != nil {
+		t.Fatalf("disable clients: %v", err)
+	}
+	status, found, err = svc.HwidSlotStatusForSubID(rec.SubID)
+	if err != nil || found || status != (HwidSlotStatus{}) {
+		t.Fatalf("disabled subId = (%+v, %v, %v), want zero status and found=false", status, found, err)
+	}
+}

tools/openapigen/main.go

@@ -106,6 +106,7 @@ func run(root, outDir string) error {
 				"GeodataTokenIssue",
 				"AmneziaWGLogs",
 				"PeerActivity",
+				"HwidSlotStatus",
 			),
 		},
 		{