diff --git a/packages/credentials/credentials/README.md b/packages/credentials/credentials/README.md
new file mode 100644
index 0000000000..48b7b0f952
--- /dev/null
+++ b/packages/credentials/credentials/README.md
@@ -0,0 +1,45 @@
+# dsh-credentials
+
+English | [中文](README.zh.md)
+
+Abstract credential seam (`ctx.credentials`). One doctrine, three consequences:
+
+**Configuration carries references to secrets, never the secrets.** A settings section or `cordis.yml` entry says `apiKeyEnv: DEEPSEEK_API_KEY`; the value behind that reference lives with a credential provider. So the settings document stays safe to sync and to render in a configuration UI, `describe()` can answer "is this configured, where from, can I write it" without ever holding a value, and rotating a secret touches no configuration file.
+
+**Consumers resolve per operation.** `resolve(ref)` is called at the start of each operation (the LLM adapters resolve once per model request) and never cached across operations — that read is what makes a changed credential reach the very next request without restarting any plugin.
+
+**An empty stored value is absent.** Everywhere: `resolve` skips it, `describe` reports it unconfigured. A blank can never masquerade as a configured secret.
+
+## Surface
+
+```ts
+import { credentialRef } from '@deepseek-ai/dsh-credentials'
+
+const ref = credentialRef('DEEPSEEK_API_KEY')            // POSIX shell identifier, branded
+const hit = await ctx.credentials.resolve(ref)           // { value, source } | undefined
+const info = await ctx.credentials.describe(ref)         // { configured, source?, writable } — never the value
+await ctx.credentials.set(ref, 'sk-…')                   // rejects while a read-only source shadows the ref
+await ctx.credentials.unset(ref)                         // no-op when absent; same shadowing rule
+```
+
+`credentials/updated (ref)` fires after a committed change to a provider-managed source — a `set`, an `unset`, or an external edit observed in storage. Ambient process-environment changes are not observable and never emit. Consumers do not need the event (they re-resolve per operation); it exists for configuration UIs refreshing a "configured" badge.
+
+The shadowing rule on `set`/`unset` is deliberate fail-loud: when a read-only source (the live process environment, in the local provider) currently supplies the reference, a write would appear to succeed while resolution keeps returning the shadowing value — the seam rejects instead, and `describe().writable` lets a UI render the reference read-only up front.
+
+## Providers
+
+[`dsh-credentials-local`](../credentials-local/README.md) layers the live process environment over a `$DSH_HOME/.env` file. The seam shape leaves room for keyring-, helper-command-, and KMS-backed providers; a remote settings provider never needs to carry secrets.
+
+## Model Experience
+
+Indirectly: a resolved value authorizes provider requests; the consuming adapter owns every model-visible surface.
+
+#### KV Cache effect
+
+No direct invalidation; credentials never enter a request prefix.
+
+## Known Limitations and Deferred Work
+
+- **No enumeration** — the seam answers questions about references it is given; configuration surfaces learn the references from settings schemas, so a `list()` has no current consumer.
+- **References are environment-variable-shaped** — one flat POSIX-identifier namespace until a provider needs richer addressing.
+- **Process-environment changes are invisible** — no event can fire for them; a UI only re-reads `describe()` on its own navigation.
diff --git a/packages/credentials/credentials/README.zh.md b/packages/credentials/credentials/README.zh.md
new file mode 100644
index 0000000000..ef9e32ebad
--- /dev/null
+++ b/packages/credentials/credentials/README.zh.md
@@ -0,0 +1,45 @@
+# dsh-credentials
+
+[English](README.md) | 中文
+
+抽象凭据 seam（`ctx.credentials`）。一条准则，三个推论：
+
+**配置只携带对秘密的引用，绝不携带秘密本身。** settings 分节或 `cordis.yml` 条目写 `apiKeyEnv: DEEPSEEK_API_KEY`，引用背后的值归凭据 provider 所有。于是设置文档可以放心同步、放心渲染进配置界面；`describe()` 无需持有值就能回答"配置了吗、来自哪层、能否写入"；轮换秘密不触碰任何配置文件。
+
+**消费方按操作解析。** `resolve(ref)` 在每个操作开始时调用（LLM adapter 每次模型请求解析一次），绝不跨操作缓存——正是这次读取让改过的凭据无需重启任何插件就作用于下一次请求。
+
+**空的存储值等于不存在。** 处处如此：`resolve` 跳过它，`describe` 报告未配置。空白永远不会伪装成已配置的秘密。
+
+## 接口面
+
+```ts
+import { credentialRef } from '@deepseek-ai/dsh-credentials'
+
+const ref = credentialRef('DEEPSEEK_API_KEY')            // POSIX shell 标识符，品牌类型
+const hit = await ctx.credentials.resolve(ref)           // { value, source } | undefined
+const info = await ctx.credentials.describe(ref)         // { configured, source?, writable } —— 绝不含值
+await ctx.credentials.set(ref, 'sk-…')                   // 被只读来源遮蔽时拒绝
+await ctx.credentials.unset(ref)                         // 不存在时为 no-op；同样的遮蔽规则
+```
+
+`credentials/updated (ref)` 在 provider 管理的来源发生已提交变更后触发——`set`、`unset` 或在存储中观察到的外部编辑。进程环境变量的变化不可观测，永不触发。消费方不需要该事件（它们按操作重新解析）；它服务于配置界面刷新"已配置"徽标。
+
+`set`/`unset` 的遮蔽规则是刻意的 fail-loud：当只读来源（本地 provider 中即活跃进程环境）正在提供该引用时，写入会表面成功而解析仍返回遮蔽值——seam 选择直接拒绝，并通过 `describe().writable` 让界面提前把该引用渲染为只读。
+
+## Providers
+
+[`dsh-credentials-local`](../credentials-local/README.md) 把活跃进程环境叠加在 `$DSH_HOME/.env` 文件之上。seam 形状为 keyring、辅助命令、KMS 后端的 provider 留好了位置；远端 settings provider 永远不必携带秘密。
+
+## Model Experience
+
+Indirectly: a resolved value authorizes provider requests; the consuming adapter owns every model-visible surface.
+
+#### KV Cache effect
+
+No direct invalidation; credentials never enter a request prefix.
+
+## Known Limitations and Deferred Work
+
+- **不提供枚举**——seam 只回答被问到的引用；配置界面从 settings schema 得知引用集合，`list()` 没有当前消费者。
+- **引用限定为环境变量形状**——在有 provider 需要更丰富寻址前，保持单一扁平的 POSIX 标识符命名空间。
+- **进程环境变化不可见**——不可能为其发事件；界面只能在自身导航时重新读取 `describe()`。
diff --git a/packages/credentials/credentials/package.json b/packages/credentials/credentials/package.json
new file mode 100644
index 0000000000..d907b0a1bb
--- /dev/null
+++ b/packages/credentials/credentials/package.json
@@ -0,0 +1,39 @@
+{
+  "name": "@deepseek-ai/dsh-credentials",
+  "description": "Abstract credential seam (ctx.credentials): settings carry references to secrets, providers own the values",
+  "version": "0.0.1",
+  "private": true,
+  "type": "module",
+  "main": "lib/index.js",
+  "types": "lib/types/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./lib/types/index.d.ts",
+      "default": "./lib/index.js"
+    },
+    "./invariant": {
+      "types": "./lib/types/invariant.d.ts",
+      "default": "./lib/invariant.js"
+    },
+    "./src/*": "./src/*",
+    "./package.json": "./package.json"
+  },
+  "files": [
+    "lib/index.js",
+    "lib/invariant.js",
+    "lib/types/**/*.d.ts",
+    "lib/types/**/*.d.ts.map",
+    "src"
+  ],
+  "license": "BSD-3-Clause",
+  "peerDependencies": {
+    "@deepseek-ai/dsh-brand": "^0.0.1",
+    "@deepseek-ai/dsh-invariants": "^0.0.1",
+    "cordis": "^4.0.0-rc.7"
+  },
+  "devDependencies": {
+    "@deepseek-ai/dsh-brand": "workspace:^",
+    "@deepseek-ai/dsh-invariants": "workspace:^",
+    "cordis": "^4.0.0-rc.7"
+  }
+}
diff --git a/packages/credentials/credentials/src/index.ts b/packages/credentials/credentials/src/index.ts
new file mode 100644
index 0000000000..2df89132ac
--- /dev/null
+++ b/packages/credentials/credentials/src/index.ts
@@ -0,0 +1,114 @@
+/**
+ * Credential seam (`ctx.credentials`). Settings and composition files carry
+ * *references* to secrets — environment-variable names — while providers own
+ * the actual values and their storage. Consumers resolve a reference once per
+ * operation, so a changed credential reaches the next operation without any
+ * plugin restart, and configuration surfaces describe a reference without
+ * ever seeing its value.
+ * @module @deepseek-ai/dsh-credentials
+ */
+
+import { Context, Service } from 'cordis'
+import type { Branded } from '@deepseek-ai/dsh-brand'
+
+/** Nominal reference to one credential: a POSIX-style environment-variable name. */
+export type CredentialRef = Branded<'CredentialRef'>
+
+const REF_PATTERN = /^[A-Za-z_][A-Za-z0-9_]*$/
+
+/**
+ * Brand a raw string as a {@link CredentialRef}.
+ * @param value - candidate reference; a POSIX shell identifier such as `DEEPSEEK_API_KEY`.
+ * @returns the branded reference.
+ */
+export function credentialRef(value: string): CredentialRef {
+  if (!REF_PATTERN.test(value)) {
+    throw new TypeError(`credential ref "${value}" must match ${String(REF_PATTERN)}`)
+  }
+  return value as CredentialRef
+}
+
+/** One resolved credential value and the source layer that supplied it. */
+export interface ResolvedCredential {
+  /** The non-empty secret value. */
+  value: string
+  /** Provider-defined source layer id (the local provider uses `env` and `file`). */
+  source: string
+}
+
+/** Source and writability facts for one reference, safe for configuration UIs — never the value. */
+export interface CredentialInfo {
+  /** Whether {@link Credentials.resolve} would currently return a value. */
+  configured: boolean
+  /** Source layer currently supplying the value; absent while unconfigured. */
+  source?: string
+  /** Whether {@link Credentials.set} would currently succeed for this reference. */
+  writable: boolean
+}
+
+declare module 'cordis' {
+  interface Context {
+    credentials: Credentials
+  }
+
+  interface Events {
+    /**
+     * Committed change to a provider-managed credential source: a `set`, an
+     * `unset`, or an external edit observed in storage. Ambient
+     * process-environment changes are not observable and never emit.
+     * @param ref - the reference whose stored value changed.
+     * @mode emit
+     */
+    'credentials/updated'(ref: CredentialRef): void
+  }
+}
+
+/**
+ * Abstract credential service. Providers implement the four operations over
+ * their source layers; one seam-wide rule binds them all: an empty stored
+ * value is absent everywhere — `resolve` skips it, `describe` reports it
+ * unconfigured — so a blank never masquerades as a configured secret.
+ */
+export abstract class Credentials extends Service {
+  constructor(ctx: Context) {
+    super(ctx, 'credentials')
+  }
+
+  /**
+   * Resolve one reference to its current value. Resolution is per call:
+   * consumers re-resolve at each operation and must not cache across
+   * operations — that per-operation read is what makes a changed credential
+   * reach the next operation without a restart.
+   * @param ref - the reference to resolve.
+   * @returns the value and its source, or `undefined` while unconfigured.
+   */
+  abstract resolve(ref: CredentialRef): Promise<ResolvedCredential | undefined>
+
+  /**
+   * Describe one reference for configuration surfaces without exposing the
+   * value.
+   * @param ref - the reference to describe.
+   * @returns configured state, supplying source, and writability.
+   */
+  abstract describe(ref: CredentialRef): Promise<CredentialInfo>
+
+  /**
+   * Durably store one value in the provider-managed writable source. Rejects
+   * while a read-only source shadows the reference — the write would appear
+   * to succeed while resolution keeps returning the shadowing value — and
+   * rejects an empty value (use {@link unset}).
+   * @param ref - the reference to store.
+   * @param value - the non-empty secret value.
+   */
+  abstract set(ref: CredentialRef, value: string): Promise<void>
+
+  /**
+   * Remove one reference from the provider-managed writable source; removing
+   * an absent reference is a no-op. Rejects while a read-only source shadows
+   * the reference, like {@link set}.
+   * @param ref - the reference to remove.
+   */
+  abstract unset(ref: CredentialRef): Promise<void>
+}
+
+export default Credentials
diff --git a/packages/credentials/credentials/src/invariant.ts b/packages/credentials/credentials/src/invariant.ts
new file mode 100644
index 0000000000..23c2dda45b
--- /dev/null
+++ b/packages/credentials/credentials/src/invariant.ts
@@ -0,0 +1,38 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-credentials`.
+ * @module @deepseek-ai/dsh-credentials/invariant
+ */
+
+import type { Context } from 'cordis'
+import type { InvariantFailure, InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-credentials'
+
+/** Cordis companion plugin name. */
+export const name = 'credentials-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * Install the commit-event lifecycle contract: `credentials/updated` names a
+ * committed provider-source change, so it can only fire while a credentials
+ * service is live — an emission after disposal means a provider leaked work
+ * past its teardown quiescence. The value relation itself (`describe`
+ * agreeing with `resolve`) is asynchronous provider I/O and stays pinned by
+ * each provider's own suite.
+ */
+const install: InvariantInstaller = (ctx: Context, fail: InvariantFailure) => {
+  ctx.on('credentials/updated', (ref) => {
+    if (ctx.get('credentials') === undefined) {
+      fail(`credentials/updated for "${ref}" emitted without a live credentials service`)
+    }
+  })
+}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
diff --git a/packages/credentials/credentials/tests/credentials.spec.ts b/packages/credentials/credentials/tests/credentials.spec.ts
new file mode 100644
index 0000000000..9b4cf7b1e8
--- /dev/null
+++ b/packages/credentials/credentials/tests/credentials.spec.ts
@@ -0,0 +1,71 @@
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import { credentialRef } from '../src/index.ts'
+import type { CredentialRef } from '../src/index.ts'
+import { MemoryCredentials } from './memory.ts'
+
+const REF = credentialRef('DEEPSEEK_API_KEY')
+
+async function boot(seed: Record<string, string> = {}): Promise<Context> {
+  const ctx = new Context()
+  await ctx.plugin(MemoryCredentials, seed)
+  return ctx
+}
+
+describe('credentialRef', () => {
+  it('brands POSIX shell identifiers', () => {
+    expect(credentialRef('DEEPSEEK_API_KEY')).toBe('DEEPSEEK_API_KEY')
+    expect(credentialRef('_private')).toBe('_private')
+    expect(credentialRef('lower_case9')).toBe('lower_case9')
+  })
+
+  it('rejects every other shape', () => {
+    for (const invalid of ['', '9LEADING', 'WITH-DASH', 'WITH SPACE', 'ns:key']) {
+      expect(() => credentialRef(invalid)).toThrow(TypeError)
+    }
+  })
+})
+
+describe('the credentials seam through the memory provider', () => {
+  it('mounts as ctx.credentials and resolves a seeded reference with its source', async () => {
+    const ctx = await boot({ DEEPSEEK_API_KEY: 'sk-seeded' })
+    expect(await ctx.credentials.resolve(REF)).toEqual({ value: 'sk-seeded', source: 'memory' })
+    expect(await ctx.credentials.describe(REF)).toEqual({ configured: true, source: 'memory', writable: true })
+  })
+
+  it('treats an empty stored value as absent everywhere', async () => {
+    const ctx = await boot({ DEEPSEEK_API_KEY: '' })
+    expect(await ctx.credentials.resolve(REF)).toBeUndefined()
+    expect(await ctx.credentials.describe(REF)).toEqual({ configured: false, writable: true })
+  })
+
+  it('stores through set, removes through unset, and emits the committed change', async () => {
+    const ctx = await boot()
+    const events: CredentialRef[] = []
+    ctx.on('credentials/updated', ref => void events.push(ref))
+
+    await ctx.credentials.set(REF, 'sk-live')
+    expect(await ctx.credentials.resolve(REF)).toEqual({ value: 'sk-live', source: 'memory' })
+    await ctx.credentials.unset(REF)
+    expect(await ctx.credentials.resolve(REF)).toBeUndefined()
+    expect(events).toEqual([REF, REF])
+  })
+
+  it('rejects an empty set and keeps an absent unset silent', async () => {
+    const ctx = await boot()
+    const events: CredentialRef[] = []
+    ctx.on('credentials/updated', ref => void events.push(ref))
+
+    await expect(ctx.credentials.set(REF, '')).rejects.toThrow(/empty value/)
+    await ctx.credentials.unset(REF)
+    expect(events).toEqual([])
+  })
+
+  it('removes the service with its fiber', async () => {
+    const ctx = new Context()
+    const fiber = await ctx.plugin(MemoryCredentials)
+    expect(ctx.get('credentials')).toBeDefined()
+    await fiber.dispose()
+    expect(ctx.get('credentials')).toBeUndefined()
+  })
+})
diff --git a/packages/credentials/credentials/tests/invariant.spec.ts b/packages/credentials/credentials/tests/invariant.spec.ts
new file mode 100644
index 0000000000..dccde4843f
--- /dev/null
+++ b/packages/credentials/credentials/tests/invariant.spec.ts
@@ -0,0 +1,37 @@
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import InvariantService from '@deepseek-ai/dsh-invariants'
+import { credentialRef } from '../src/index.ts'
+import * as CredentialsInvariant from '../src/invariant.ts'
+import { MemoryCredentials } from './memory.ts'
+
+const REF = credentialRef('DEEPSEEK_API_KEY')
+
+describe('credentials invariant companion', () => {
+  it('accepts a committed change emitted by a live service', async () => {
+    const ctx = new Context()
+    await ctx.plugin(InvariantService)
+    await ctx.plugin(CredentialsInvariant)
+    await ctx.plugin(MemoryCredentials)
+
+    await expect(ctx.credentials.set(REF, 'sk-live')).resolves.toBeUndefined()
+  })
+
+  it('fails an update event emitted without a live service', async () => {
+    const ctx = new Context()
+    await ctx.plugin(InvariantService)
+    await ctx.plugin(CredentialsInvariant)
+
+    expect(() => { ctx.emit('credentials/updated', REF) }).toThrow(/invariant violated by "@deepseek-ai\/dsh-credentials"/)
+  })
+
+  it('reserves the package name against duplicate registration', async () => {
+    const ctx = new Context()
+    await ctx.plugin(InvariantService)
+    await ctx.plugin(CredentialsInvariant)
+
+    expect(() => {
+      ctx.invariants.register('@deepseek-ai/dsh-credentials', () => {})
+    }).toThrow(/already registered/)
+  })
+})
diff --git a/packages/credentials/credentials/tests/memory.ts b/packages/credentials/credentials/tests/memory.ts
new file mode 100644
index 0000000000..c562d8ab0a
--- /dev/null
+++ b/packages/credentials/credentials/tests/memory.ts
@@ -0,0 +1,51 @@
+import type { Context } from 'cordis'
+import { Credentials } from '../src/index.ts'
+import type { CredentialInfo, CredentialRef, ResolvedCredential } from '../src/index.ts'
+
+/**
+ * In-memory credentials provider for interface and consumer tests: one
+ * always-writable `memory` source seeded from plugin config.
+ */
+export class MemoryCredentials extends Credentials {
+  private readonly store = new Map<string, string>()
+
+  constructor(ctx: Context, seed: Record<string, string> = {}) {
+    super(ctx)
+    for (const [key, value] of Object.entries(seed)) this.store.set(key, value)
+  }
+
+  override resolve(ref: CredentialRef): Promise<ResolvedCredential | undefined> {
+    const value = this.store.get(ref)
+    return Promise.resolve(value === undefined || value.length === 0
+      ? undefined
+      : { value, source: 'memory' })
+  }
+
+  override describe(ref: CredentialRef): Promise<CredentialInfo> {
+    const value = this.store.get(ref)
+    const configured = value !== undefined && value.length > 0
+    return Promise.resolve({
+      configured,
+      ...configured ? { source: 'memory' } : {},
+      writable: true,
+    })
+  }
+
+  override set(ref: CredentialRef, value: string): Promise<void> {
+    if (value.length === 0) {
+      return Promise.reject(new Error('memory credentials: an empty value cannot be stored; use unset'))
+    }
+    this.store.set(ref, value)
+    this.ctx.emit('credentials/updated', ref)
+    return Promise.resolve()
+  }
+
+  override unset(ref: CredentialRef): Promise<void> {
+    if (this.store.delete(ref)) {
+      this.ctx.emit('credentials/updated', ref)
+    }
+    return Promise.resolve()
+  }
+}
+
+export default MemoryCredentials
diff --git a/packages/credentials/credentials/tsconfig.json b/packages/credentials/credentials/tsconfig.json
new file mode 100644
index 0000000000..5bc7a9fcf5
--- /dev/null
+++ b/packages/credentials/credentials/tsconfig.json
@@ -0,0 +1,24 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "lib/types"
+  },
+  "include": [
+    "src"
+  ],
+  "references": [
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../util/brand"
+    },
+    {
+      "path": "../../support/invariants"
+    }
+  ]
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 2036f68aa6..31ff52fe9d 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2062,6 +2062,18 @@ importers:
         specifier: ^4.0.0-rc.7
         version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
 
+  packages/credentials/credentials:
+    devDependencies:
+      '@deepseek-ai/dsh-brand':
+        specifier: workspace:^
+        version: link:../../util/brand
+      '@deepseek-ai/dsh-invariants':
+        specifier: workspace:^
+        version: link:../../support/invariants
+      cordis:
+        specifier: ^4.0.0-rc.7
+        version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
+
   packages/examples/acp-demo:
     devDependencies:
       '@cordisjs/plugin-include':
diff --git a/tsconfig.base.json b/tsconfig.base.json
index a93c67b304..9ffb5618d7 100644
--- a/tsconfig.base.json
+++ b/tsconfig.base.json
@@ -88,6 +88,7 @@
         "./packages/session-projection/*/src/invariant.ts",
         "./packages/session-query/*/src/invariant.ts",
         "./packages/settings/*/src/invariant.ts",
+        "./packages/credentials/*/src/invariant.ts",
         "./packages/telemetry/*/src/invariant.ts",
         "./packages/acp/*/src/invariant.ts",
         "./packages/storage/*/src/invariant.ts",
@@ -173,6 +174,7 @@
         "./packages/session-query/*/src",
         "./packages/session-title/*/src",
         "./packages/settings/*/src",
+        "./packages/credentials/*/src",
         "./packages/telemetry/*/src",
         "./packages/acp/*/src",
         "./packages/storage/*/src",
diff --git a/tsconfig.host.json b/tsconfig.host.json
index 92eeea6a94..67e340e898 100644
--- a/tsconfig.host.json
+++ b/tsconfig.host.json
@@ -64,6 +64,7 @@
     { "path": "./packages/session-query/session-query-sqlite" },
     { "path": "./packages/settings/settings" },
     { "path": "./packages/settings/settings-local" },
+    { "path": "./packages/credentials/credentials" },
     { "path": "./packages/session-query/tool-session-query" },
     { "path": "./packages/storage/storage" },
     { "path": "./packages/storage/storage-json" },