@@ -0,0 +1,24 @@
+---
+'@objectstack/spec': minor
+'@objectstack/service-automation': minor
+---
+
+feat(spec): `tencentcloud-tc3-hmac-sha256` joins the `signed` connector-instance auth schemes (ADR-0143 D2.3, #26710)
+
+Clause-②: yes (widening)
+Metadata-protocol: added
+
+<!-- adr-0087: not-required (no-migration-prescription) One member is added to the closed signing-scheme list and one shape to the `signed` union; the signer seam's `scheme` member is typed as that list instead of any string; that interface is in no release yet (it ships with the pending `26710-signed-connector-auth-aliyun` changeset), so no published surface narrows. Nothing an author wrote before is refused or re-shaped, so there is nothing for a migration to rewrite. -->
+
+A declarative connector instance can now declare Tencent Cloud's API 3.0 signature (v3) as its signing scheme. It joins Alibaba Cloud's V3 signature, which shipped with the `signed` kind.
+
+- **`@objectstack/spec`**
+  - `ConnectorSigningSchemeSchema` gains `tencentcloud-tc3-hmac-sha256`.
+  - The `signed` union gains its closed shape, `{ type: 'signed', scheme: 'tencentcloud-tc3-hmac-sha256', keyId, credentialRef }`. `keyId` is the SecretId. The SecretKey is only ever a `credentialRef`.
+  - The same publish refusals apply as for the first scheme: an inline key spelling by name, an authored `signature`, and `signed` on `provider: 'mcp'`. `secretId` is answered with `keyId`. An unknown scheme's refusal now lists both shipped schemes.
+  - `ConnectorRequestSigner.scheme` is typed as `ConnectorSigningScheme` rather than `string`. The interface ships for the first time in this release, together with the first scheme.
+- **`@objectstack/service-automation`**
+  - The signer registry binds a `tencentcloud-tc3-hmac-sha256` instance's key to its TC3-HMAC-SHA256 signer.
+  - Every attempt is signed with a fresh `X-TC-Timestamp`, over `content-type` and `host`. The scope's service is the first label of the endpoint host.
+  - A request without a content type is signed and sent as `application/x-www-form-urlencoded`.
+  - The key never leaves the host.
@@ -483,12 +483,21 @@ auth: {
   keyId: 'YourAccessKeyId',               // the AccessKey ID: public, stays in metadata
   credentialRef: 'ALIYUN_ACCESS_KEY_SECRET',
 }
+
+// Tencent Cloud API 3.0, signature v3 (TC3-HMAC-SHA256):
+auth: {
+  type: 'signed',
+  scheme: 'tencentcloud-tc3-hmac-sha256',
+  keyId: 'YourSecretId',                  // the SecretId: public, stays in metadata
+  credentialRef: 'TENCENT_SECRET_KEY',
+}
 ```
 
 What the platform does with it:
 
 - **Every request is signed, each attempt fresh.** A retry is signed again with
-  a new nonce and date, so a scheme that refuses a replayed nonce accepts it.
+  a new nonce and date, so a scheme that refuses a replayed nonce or a stale
+  timestamp accepts it.
 - **The key never reaches the provider.** The automation service binds the
   resolved key to the scheme's signer at materialization and hands the
   provider the signer only. A datasource cannot borrow a `signed` instance
@@ -501,6 +510,14 @@ What the platform does with it:
   `x-acs-content-sha256` and `Authorization`. The API's own action and version
   are yours to send, as `x-acs-action` / `x-acs-version` in `defaultHeaders`
   (rest) or in each call's headers.
+- **`tencentcloud-tc3-hmac-sha256`** signs `content-type` and `host`, and sets
+  `X-TC-Timestamp` and `Authorization`. The service in the signature's scope is
+  the first label of the endpoint host (`cvm.tencentcloudapi.com`, or a
+  regional `cvm.ap-guangzhou.tencentcloudapi.com`, is `cvm`), so point
+  `baseUrl` at the product's own endpoint. `X-TC-Action`, `X-TC-Version` and
+  `X-TC-Region` are yours to send and are not signed. A request without a body
+  is sent with `Content-Type: application/x-www-form-urlencoded`, the type it
+  is signed with.
 
 What the publish door refuses:
 
@@ -509,7 +526,8 @@ What the publish door refuses:
   signer and its test vectors, so a scheme the server cannot run is never
   accepted.
 - **An inline key**: `secret`, `privateKey`, `secretKey` or `accessKeySecret`
-  is refused by name, pointing at `credentialRef`. An authored `signature` is
+  is refused by name, pointing at `credentialRef`. The vendors' words for the
+  key id (`accessKeyId`, `secretId`) are answered with `keyId`. An authored `signature` is
   refused too: it is computed for every request.
 - **`provider: 'mcp'`**, at `auth.type`: an MCP server is not signed per
   request. Declare `provider: 'rest'` or `provider: 'openapi'`.
 
@@ -1,7 +1,7 @@
 ---
 title: Protocol reference — every schema by module
 navTitle: Protocol Reference
-description: Every schema published by @objectstack/spec — 1569 schemas across 14 protocol modules
+description: Every schema published by @objectstack/spec — 1570 schemas across 14 protocol modules
 ---
 
 {/* ⚠️  AUTO-GENERATED — DO NOT EDIT. Run build-docs.ts to regenerate. Hand-written docs live in the module folders under content/docs/. */}
@@ -25,7 +25,7 @@ counts are sums of the rows they head. Regenerate with
 | [Automation Protocol](/docs/references/automation) | 15 | 77 | Flows and their nodes, approvals, ETL pipelines, webhooks, state machines, execution records. |
 | [Data Protocol](/docs/references/data) | 31 | 174 | Objects, fields, queries, filters, datasources and drivers — the ObjectQL layer. |
 | [Identity Protocol](/docs/references/identity) | 5 | 27 | Users and accounts, organizations, positions, SCIM provisioning. |
-| [Integration Protocol](/docs/references/integration) | 1 | 21 | The single connector protocol (ADR-0097) — catalog descriptors and provider-bound instances. |
+| [Integration Protocol](/docs/references/integration) | 1 | 22 | The single connector protocol (ADR-0097) — catalog descriptors and provider-bound instances. |
 | [Kernel Protocol](/docs/references/kernel) | 29 | 151 | Plugin lifecycle and manifests, capabilities and security, metadata loading, service registry. |
 | [Marketplace Protocol](/docs/references/marketplace) | 4 | 30 | The package & marketplace format — package identity and versions, listing, publish, review, search, install, template manifests. |
 | [QA Protocol](/docs/references/qa) | 1 | 8 | Declarative test suites — scenarios, steps, actions and assertions. |
@@ -34,7 +34,7 @@ counts are sums of the rows they head. Regenerate with
 | [Studio Protocol](/docs/references/studio) | 3 | 35 | Studio designer metadata — the authoring surfaces for the protocols above. |
 | [System Protocol](/docs/references/system) | 37 | 287 | The runtime environment — logging, jobs, cache, metrics, notifications, i18n and compliance. |
 | [UI Protocol](/docs/references/ui) | 16 | 172 | Apps, pages, views, dashboards, reports, actions and themes — the ObjectUI layer. |
-| **Total** | **203** | **1569** | 14 protocol modules |
+| **Total** | **203** | **1570** | 14 protocol modules |
 
 ---
 
@@ -191,13 +191,13 @@ Users and accounts, organizations, positions, SCIM provisioning.
 
 ## Integration Protocol
 
-**Source:** `packages/spec/src/integration/` · **Import:** `@objectstack/spec/integration` · **1 page, 21 schemas**
+**Source:** `packages/spec/src/integration/` · **Import:** `@objectstack/spec/integration` · **1 page, 22 schemas**
 
 The single connector protocol (ADR-0097) — catalog descriptors and provider-bound instances.
 
 | File | Schemas |
 | :--- | :--- |
-| [`connector.zod.ts`](/docs/references/integration/connector) | `Connector`, `ConnectorAction`, `ConnectorActionEffect`, `ConnectorAppCredentialVendor`, `ConnectorInstanceAPIKeyAuth`, `ConnectorInstanceAppCredentialAuth`, `ConnectorInstanceAuth`, `ConnectorInstanceBasicAuth`, `ConnectorInstanceBearerAuth`, `ConnectorInstanceNoAuth`, `ConnectorInstanceOAuth2Auth`, `ConnectorInstanceOAuth2AuthorizationCodeAuth`, `ConnectorInstanceOAuth2ClientCredentialsAuth`, `ConnectorInstanceSignedAliyunAcs3Auth`, `ConnectorInstanceSignedAuth`, `ConnectorOAuth2Grant`, `ConnectorRetryStrategy`, `ConnectorSigningScheme`, `ConnectorType`, `DeclarativeConnectorEntry`, `RetryConfig` |
+| [`connector.zod.ts`](/docs/references/integration/connector) | `Connector`, `ConnectorAction`, `ConnectorActionEffect`, `ConnectorAppCredentialVendor`, `ConnectorInstanceAPIKeyAuth`, `ConnectorInstanceAppCredentialAuth`, `ConnectorInstanceAuth`, `ConnectorInstanceBasicAuth`, `ConnectorInstanceBearerAuth`, `ConnectorInstanceNoAuth`, `ConnectorInstanceOAuth2Auth`, `ConnectorInstanceOAuth2AuthorizationCodeAuth`, `ConnectorInstanceOAuth2ClientCredentialsAuth`, `ConnectorInstanceSignedAliyunAcs3Auth`, `ConnectorInstanceSignedAuth`, `ConnectorInstanceSignedTencentCloudTc3Auth`, `ConnectorOAuth2Grant`, `ConnectorRetryStrategy`, `ConnectorSigningScheme`, `ConnectorType`, `DeclarativeConnectorEntry`, `RetryConfig` |
 
 ---
 
 
@@ -165,8 +165,8 @@ an exception for itself.)
 ## TypeScript Usage
 
 ```typescript
-import { ConnectorSchema, ConnectorActionSchema, ConnectorActionEffectSchema, ConnectorAppCredentialVendorSchema, ConnectorInstanceAPIKeyAuthSchema, ConnectorInstanceAppCredentialAuthSchema, ConnectorInstanceAuthSchema, ConnectorInstanceBasicAuthSchema, ConnectorInstanceBearerAuthSchema, ConnectorInstanceNoAuthSchema, ConnectorInstanceOAuth2AuthSchema, ConnectorInstanceOAuth2AuthorizationCodeAuthSchema, ConnectorInstanceOAuth2ClientCredentialsAuthSchema, ConnectorInstanceSignedAliyunAcs3AuthSchema, ConnectorInstanceSignedAuthSchema, ConnectorOAuth2GrantSchema, ConnectorRetryStrategySchema, ConnectorSigningSchemeSchema, ConnectorTypeSchema, DeclarativeConnectorEntrySchema, RetryConfigSchema } from '@objectstack/spec/integration';
-import type { Connector, ConnectorAction, ConnectorActionEffect, ConnectorAppCredentialVendor, ConnectorInstanceAPIKeyAuth, ConnectorInstanceAppCredentialAuth, ConnectorInstanceAuth, ConnectorInstanceBasicAuth, ConnectorInstanceBearerAuth, ConnectorInstanceNoAuth, ConnectorInstanceOAuth2Auth, ConnectorInstanceOAuth2AuthorizationCodeAuth, ConnectorInstanceOAuth2ClientCredentialsAuth, ConnectorInstanceSignedAliyunAcs3Auth, ConnectorInstanceSignedAuth, ConnectorOAuth2Grant, ConnectorRetryStrategy, ConnectorSigningScheme, ConnectorType, DeclarativeConnectorEntry, RetryConfig } from '@objectstack/spec/integration';
+import { ConnectorSchema, ConnectorActionSchema, ConnectorActionEffectSchema, ConnectorAppCredentialVendorSchema, ConnectorInstanceAPIKeyAuthSchema, ConnectorInstanceAppCredentialAuthSchema, ConnectorInstanceAuthSchema, ConnectorInstanceBasicAuthSchema, ConnectorInstanceBearerAuthSchema, ConnectorInstanceNoAuthSchema, ConnectorInstanceOAuth2AuthSchema, ConnectorInstanceOAuth2AuthorizationCodeAuthSchema, ConnectorInstanceOAuth2ClientCredentialsAuthSchema, ConnectorInstanceSignedAliyunAcs3AuthSchema, ConnectorInstanceSignedAuthSchema, ConnectorInstanceSignedTencentCloudTc3AuthSchema, ConnectorOAuth2GrantSchema, ConnectorRetryStrategySchema, ConnectorSigningSchemeSchema, ConnectorTypeSchema, DeclarativeConnectorEntrySchema, RetryConfigSchema } from '@objectstack/spec/integration';
+import type { Connector, ConnectorAction, ConnectorActionEffect, ConnectorAppCredentialVendor, ConnectorInstanceAPIKeyAuth, ConnectorInstanceAppCredentialAuth, ConnectorInstanceAuth, ConnectorInstanceBasicAuth, ConnectorInstanceBearerAuth, ConnectorInstanceNoAuth, ConnectorInstanceOAuth2Auth, ConnectorInstanceOAuth2AuthorizationCodeAuth, ConnectorInstanceOAuth2ClientCredentialsAuth, ConnectorInstanceSignedAliyunAcs3Auth, ConnectorInstanceSignedAuth, ConnectorInstanceSignedTencentCloudTc3Auth, ConnectorOAuth2Grant, ConnectorRetryStrategy, ConnectorSigningScheme, ConnectorType, DeclarativeConnectorEntry, RetryConfig } from '@objectstack/spec/integration';
 
 // Validate data
 const result = ConnectorSchema.parse(data);
@@ -293,7 +293,7 @@ const result = ConnectorSchema.parse(data);
 | **appId** | `string` | ✅ | The vendor's app identifier (not a secret): Feishu `app_id`, DingTalk `appKey`, WeCom `corpid`. |
 | **credentialRef** | `string` | ✅ | Secrets-layer reference resolved to the app secret (WeCom: the application `corpsecret`). Never an inline secret. |
 
-### Nested Shape: `Connector.auth[option 7]`
+### Nested Shape: `Connector.auth[option 7][scheme='aliyun-acs3-hmac-sha256']`
 
 | Property | Type | Required | Description |
 | :--- | :--- | :--- | :--- |
@@ -302,6 +302,15 @@ const result = ConnectorSchema.parse(data);
 | **keyId** | `string` | ✅ | The AccessKey ID (not a secret); sent in the `Credential` of every signature. |
 | **credentialRef** | `string` | ✅ | Secrets-layer reference resolved to the AccessKey secret, the HMAC key every request is signed with. Never an inline secret. |
 
+### Nested Shape: `Connector.auth[option 7][scheme='tencentcloud-tc3-hmac-sha256']`
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| **type** | `'signed'` | ✅ |  |
+| **scheme** | `'tencentcloud-tc3-hmac-sha256'` | ✅ | Tencent Cloud API 3.0 signature v3 (TC3-HMAC-SHA256). |
+| **keyId** | `string` | ✅ | The SecretId (not a secret); sent in the `Credential` of every signature. |
+| **credentialRef** | `string` | ✅ | Secrets-layer reference resolved to the SecretKey every request's signing key is derived from. Never an inline secret. |
+
 ### Nested Shape: `Connector.actions[number]`
 
 | Property | Type | Required | Description |
@@ -481,7 +490,7 @@ Type: `{ type: 'oauth2'; tokenUrl?: string; scopes?: string[]; resource?: string
 
 #### Option 7
 
-Type: `{ type: 'signed'; scheme: 'aliyun-acs3-hmac-sha256'; keyId: string; credentialRef: string }`
+Type: `{ type: 'signed'; scheme: 'aliyun-acs3-hmac-sha256'; keyId: string; credentialRef: string } | { type: 'signed'; scheme: 'tencentcloud-tc3-hmac-sha256'; keyId: string; credentialRef: string }`
 
 ---
 
@@ -640,6 +649,35 @@ This schema accepts one of the following structures:
 
 ---
 
+#### Option 2
+
+**Type:** `signed`
+
+### Properties
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| **type** | `'signed'` | ✅ |  |
+| **scheme** | `'tencentcloud-tc3-hmac-sha256'` | ✅ | Tencent Cloud API 3.0 signature v3 (TC3-HMAC-SHA256). |
+| **keyId** | `string` | ✅ | The SecretId (not a secret); sent in the `Credential` of every signature. |
+| **credentialRef** | `string` | ✅ | Secrets-layer reference resolved to the SecretKey every request's signing key is derived from. Never an inline secret. |
+
+---
+
+
+---
+
+## ConnectorInstanceSignedTencentCloudTc3Auth
+
+### Properties
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| **type** | `'signed'` | ✅ |  |
+| **scheme** | `'tencentcloud-tc3-hmac-sha256'` | ✅ | Tencent Cloud API 3.0 signature v3 (TC3-HMAC-SHA256). |
+| **keyId** | `string` | ✅ | The SecretId (not a secret); sent in the `Credential` of every signature. |
+| **credentialRef** | `string` | ✅ | Secrets-layer reference resolved to the SecretKey every request's signing key is derived from. Never an inline secret. |
+
 
 ---
 
@@ -671,11 +709,12 @@ Retry strategy
 
 ## ConnectorSigningScheme
 
-Request-signing scheme: `aliyun-acs3-hmac-sha256` (Alibaba Cloud OpenAPI V3 signature).
+Request-signing scheme: `aliyun-acs3-hmac-sha256` (Alibaba Cloud OpenAPI V3 signature) or `tencentcloud-tc3-hmac-sha256` (Tencent Cloud API 3.0 signature v3).
 
 ### Allowed Values
 
 * `aliyun-acs3-hmac-sha256`
+* `tencentcloud-tc3-hmac-sha256`
 
 
 ---
@@ -815,7 +854,7 @@ Connector type
 | **appId** | `string` | ✅ | The vendor's app identifier (not a secret): Feishu `app_id`, DingTalk `appKey`, WeCom `corpid`. |
 | **credentialRef** | `string` | ✅ | Secrets-layer reference resolved to the app secret (WeCom: the application `corpsecret`). Never an inline secret. |
 
-### Nested Shape: `DeclarativeConnectorEntry.auth[option 7]`
+### Nested Shape: `DeclarativeConnectorEntry.auth[option 7][scheme='aliyun-acs3-hmac-sha256']`
 
 | Property | Type | Required | Description |
 | :--- | :--- | :--- | :--- |
@@ -824,6 +863,15 @@ Connector type
 | **keyId** | `string` | ✅ | The AccessKey ID (not a secret); sent in the `Credential` of every signature. |
 | **credentialRef** | `string` | ✅ | Secrets-layer reference resolved to the AccessKey secret, the HMAC key every request is signed with. Never an inline secret. |
 
+### Nested Shape: `DeclarativeConnectorEntry.auth[option 7][scheme='tencentcloud-tc3-hmac-sha256']`
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| **type** | `'signed'` | ✅ |  |
+| **scheme** | `'tencentcloud-tc3-hmac-sha256'` | ✅ | Tencent Cloud API 3.0 signature v3 (TC3-HMAC-SHA256). |
+| **keyId** | `string` | ✅ | The SecretId (not a secret); sent in the `Credential` of every signature. |
+| **credentialRef** | `string` | ✅ | Secrets-layer reference resolved to the SecretKey every request's signing key is derived from. Never an inline secret. |
+
 ### Nested Shape: `DeclarativeConnectorEntry.actions[number]`
 
 | Property | Type | Required | Description |
 
@@ -19,4 +19,4 @@ hand-patch a number here** — fix the code or the verdict and regenerate.
 
 | Dir | Sites |
 |---|---|
-| `shared/` | 24 |
+| `shared/` | 25 |
@@ -270,4 +270,55 @@ describe('ConnectorRestPlugin — a declarative `signed` instance (ADR-0143 D2.3
 
         await kernel.shutdown();
     });
+
+    it('signs a tencentcloud-tc3-hmac-sha256 instance the same way, with the service named by its host', async () => {
+        const KEY = 'dummy-tencent-secret-key-26710';
+        const calls: Array<{ url: string; headers: Record<string, string> }> = [];
+        const impl = (async (url: string, init: RequestInit) => {
+            calls.push({ url, headers: init.headers as Record<string, string> });
+            return new Response('{"Response":{"RequestId":"r-1"}}', { status: 200, headers: { 'content-type': 'application/json' } });
+        }) as unknown as typeof fetch;
+        const declared = [{
+            name: 'tencent_cvm',
+            label: 'Tencent CVM',
+            type: 'api',
+            provider: 'rest',
+            providerConfig: { baseUrl: 'https://cvm.tencentcloudapi.com', defaultHeaders: { 'X-TC-Version': '2017-03-12', 'X-TC-Region': 'ap-guangzhou' } },
+            auth: { type: 'signed', scheme: 'tencentcloud-tc3-hmac-sha256', keyId: 'test-secret-id', credentialRef: 'TENCENT_SECRET_26710' },
+        }];
+        const kernel = new LiteKernel();
+        kernel.use(new AutomationServicePlugin({ credentialResolver: (r) => (r === 'TENCENT_SECRET_26710' ? KEY : undefined) }));
+        kernel.use(new ConnectorRestPlugin({ fetchImpl: impl }));
+        kernel.use({
+            name: 'test.metadata',
+            type: 'standard',
+            version: '1.0.0',
+            dependencies: [],
+            async init(ctx: any) {
+                ctx.registerService('objectql', { registry: { listItems: (t: string) => (t === 'connector' ? declared : []) } });
+            },
+            async start() {},
+        } as never);
+        await kernel.bootstrap();
+        const engine = kernel.getService<AutomationEngine>('automation');
+        expect(engine.getConnectorDegradedReason('tencent_cvm')).toBeUndefined();
+
+        const request = engine.resolveConnectorAction('tencent_cvm', 'request')!;
+        const answered = await request({ method: 'POST', path: '/', body: { Limit: 1 }, headers: { 'X-TC-Action': 'DescribeInstances' } }, {} as never);
+        expect(answered).toEqual({ status: 200, ok: true, body: { Response: { RequestId: 'r-1' } } });
+
+        expect(calls).toHaveLength(1);
+        const headers = calls[0]!.headers;
+        expect(headers.authorization).toMatch(
+            /^TC3-HMAC-SHA256 Credential=test-secret-id\/\d{4}-\d{2}-\d{2}\/cvm\/tc3_request, SignedHeaders=content-type;host, Signature=[0-9a-f]{64}$/,
+        );
+        expect(headers['x-tc-timestamp']).toMatch(/^\d{10}$/);
+        expect(headers['content-type']).toBe('application/json');
+        expect(headers['x-tc-action']).toBe('DescribeInstances');
+
+        expect(JSON.stringify(calls)).not.toContain(KEY);
+        expect(JSON.stringify(engine.getConnectorDescriptors())).not.toContain(KEY);
+
+        await kernel.shutdown();
+    });
 });