feat(storage): storage hub with named backend registry and data-form mounts

ctx.storage is a pure registration hub: multiple named backends stay
mounted side by side, data forms (domain first) mount via the
merge-extensible StorageForms map. src/backend.ts is the normative
KV-facet contract; tests/contract.ts is the shared conformance suite
every backend runs. Backends expose data-shape facets (kv now, an
append-log facet reserved for the future session-backend migration).

packages/storage/storage/README.md

@@ -0,0 +1,18 @@
+# @deepseek-ai/dsh-storage
+
+Storage hub (`ctx.storage`) for non-session data: a named backend registry plus mounted data-form facilities. The hub performs no IO itself — backends own media, data forms own semantics. Design and trade-offs: [domain KV storage Agent Note](../../../.agents/notes/proposed/architecture/2026-07-24-domain-kv-storage-and-workspace.zh.md).
+
+## Shape
+
+- `ctx.storage.backend` — name → backend table. Multiple backends stay mounted side by side (`json`, `sqlite`); which backend serves a consumer is that consumer's configuration (the domain layer's route table), never a hub-global choice. `register()` returns the disposer; duplicate names and unknown lookups fail loud.
+- `ctx.storage.mount(form, facility)` / `ctx.storage.form(form)` — data-form mounting. `StorageForms` is merge-extensible; the domain layer merges `domain` and is reached as `ctx.storage.domain`.
+- A backend owns one medium (file-tree root, database file) and exposes optional data-shape **facets** — `kv` today; an append-log facet is reserved for the future session-backend migration. `src/backend.ts` is the normative contract text; `tests/contract.ts` exports the shared conformance suite every backend runs.
+
+## Packages in this group
+
+| Package | Role |
+| --- | --- |
+| `dsh-storage` | The hub service + backend vocabulary + shared conformance suite |
+| `dsh-storage-json` | JSON backend: one unit per human-readable file, atomic whole-file rewrite |
+| `dsh-storage-sqlite` | SQLite backend: one database hosting all routed units, document-per-row |
+| `dsh-domain` | Domain data form (`ctx.storage.domain`): typed schemas, write chain, change events |

packages/storage/storage/package.json

@@ -0,0 +1,37 @@
+{
+  "name": "@deepseek-ai/dsh-storage",
+  "description": "Storage hub (ctx.storage): named backend registry plus mounted data-form facilities for the DeepSeek Harness",
+  "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-invariants": "^0.0.1",
+    "cordis": "^4.0.0-rc.7"
+  },
+  "devDependencies": {
+    "@deepseek-ai/dsh-invariants": "workspace:^",
+    "cordis": "^4.0.0-rc.7"
+  }
+}

packages/storage/storage/src/backend.ts

@@ -0,0 +1,104 @@
+/**
+ * Backend-facing vocabulary of the storage hub: a backend owns one medium
+ * (a file-tree root, a database file) and exposes data-shape facets over it.
+ * This module is the normative contract text for backend implementers; the
+ * shared conformance suite in `tests/contract.ts` asserts every clause.
+ * @module @deepseek-ai/dsh-storage/src/backend
+ */
+
+/** Allowed shape for unit and table names: safe as a file name and as a SQL identifier segment without escaping. */
+export const UNIT_NAME_RE = /^[a-z][a-z0-9_]*$/
+
+/**
+ * One registered backend. A backend owns exactly one medium and shares its
+ * lifecycle across all facets; facets are optional members — a backend that
+ * cannot serve a shape simply omits it, and resolution fails loud instead.
+ */
+export interface StorageBackend {
+  /** Key-value data shape; absent when this backend cannot serve it. */
+  readonly kv?: KvFacet
+
+  /**
+   * Drain in-flight writes across all open units and release the medium.
+   * Idempotent; concurrent and repeated calls resolve once teardown finishes.
+   * @returns resolution after the medium is released.
+   */
+  close(): Promise<void>
+}
+
+/** The key-value data shape: whole-unit snapshots plus per-record durable writes. */
+export interface KvFacet {
+  /**
+   * Open one unit, creating it when the medium holds no trace of it yet
+   * (materialization may defer to the first write, but {@link KvUnit.loadAll}
+   * must immediately serve the empty shape). A version already stamped on the
+   * medium that differs from `descriptor.version` rejects with
+   * `version-mismatch`; a medium that cannot be parsed as this unit rejects
+   * with `malformed-medium`. Opening the same unit name twice without closing
+   * is a caller bug and rejects.
+   * @param descriptor - Static identity and shape of the unit to open.
+   * @returns the opened unit.
+   */
+  open(descriptor: KvUnitDescriptor): Promise<KvUnit>
+}
+
+/** Static identity and shape of one KV unit, projected from its owner's spec. */
+export interface KvUnitDescriptor {
+  /** Unit name; must match {@link UNIT_NAME_RE}. Also the file-name / SQL-identifier segment. */
+  readonly name: string
+  /** Unit format version; a non-negative integer stamped on the medium at first materialization. */
+  readonly version: number
+  /** Table names; each must match {@link UNIT_NAME_RE}. */
+  readonly tables: readonly string[]
+  /** Whether this unit carries the global singleton slot. */
+  readonly hasGlobal: boolean
+}
+
+/**
+ * One opened unit. Values are opaque JSON to this layer: no schema, no
+ * events, no domain meaning. The unit does NOT serialize concurrent writes —
+ * write ordering is the caller's responsibility (the domain layer runs one
+ * write chain per unit); the unit only guarantees that each single call is
+ * atomic on the medium and durable once resolved (a crash after resolution
+ * followed by a re-open observes the write). Any call after {@link close}
+ * rejects with `closed`.
+ */
+export interface KvUnit {
+  /**
+   * Read the full current snapshot.
+   * @returns every table's records keyed by table name, plus the global
+   * singleton (`null` when never written or not declared).
+   */
+  loadAll(): Promise<{ tables: Record<string, Record<string, unknown>>; global: unknown | null }>
+
+  /**
+   * Upsert one record durably. Overwrite semantics: an existing key is replaced.
+   * @param table - Declared table name.
+   * @param key - Record key; any string is safe (keys never reach file paths).
+   * @param value - Opaque JSON-serializable record.
+   * @returns resolution after durability.
+   */
+  putRecord(table: string, key: string, value: unknown): Promise<void>
+
+  /**
+   * Delete one record durably. Idempotent: a missing key is a no-op.
+   * @param table - Declared table name.
+   * @param key - Record key.
+   * @returns resolution after durability.
+   */
+  deleteRecord(table: string, key: string): Promise<void>
+
+  /**
+   * Write the global singleton durably. Only valid when the descriptor
+   * declared `hasGlobal`.
+   * @param value - Opaque JSON-serializable value.
+   * @returns resolution after durability.
+   */
+  setGlobal(value: unknown): Promise<void>
+
+  /**
+   * Drain this unit's in-flight writes and release it. Idempotent.
+   * @returns resolution after the unit is released.
+   */
+  close(): Promise<void>
+}

packages/storage/storage/src/error.ts

@@ -0,0 +1,35 @@
+/**
+ * Error vocabulary for the storage hub and its backends.
+ * @module @deepseek-ai/dsh-storage/src/error
+ */
+
+/** Discriminant codes carried by every {@link StorageError}. */
+export type StorageErrorCode =
+  | 'backend-not-found'
+  | 'form-not-mounted'
+  | 'duplicate-backend'
+  | 'duplicate-mount'
+  | 'version-mismatch'
+  | 'malformed-medium'
+  | 'closed'
+
+/**
+ * Error thrown by the hub and by backend implementations. The `code` is the
+ * stable contract consumers may switch on; `message` is diagnostic prose.
+ */
+export class StorageError extends Error {
+  override readonly name = 'StorageError'
+
+  /**
+   * @param code - Stable discriminant for the failure class.
+   * @param message - Human-readable diagnostic detail.
+   * @param options - Standard error options (`cause`).
+   */
+  constructor(
+    readonly code: StorageErrorCode,
+    message: string,
+    options?: ErrorOptions,
+  ) {
+    super(message, options)
+  }
+}

packages/storage/storage/src/index.ts

@@ -0,0 +1,86 @@
+/**
+ * Storage hub (`ctx.storage`): a named backend registry plus mounted
+ * data-form facilities. The hub itself performs no IO — backends own media,
+ * data forms (the domain layer first) own semantics.
+ * @module @deepseek-ai/dsh-storage
+ */
+
+import { Context, Service } from 'cordis'
+import { StorageError } from './error.ts'
+import { BackendRegistry } from './registry.ts'
+
+export { BackendRegistry } from './registry.ts'
+export { StorageError } from './error.ts'
+export type { StorageErrorCode } from './error.ts'
+export { UNIT_NAME_RE } from './backend.ts'
+export type { StorageBackend, KvFacet, KvUnit, KvUnitDescriptor } from './backend.ts'
+
+declare module 'cordis' {
+  interface Context {
+    storage: Storage
+  }
+}
+
+/**
+ * Data forms mountable on the hub, keyed by form name. Form owners extend
+ * this map via declaration merging (the domain layer merges
+ * `domain: DomainFacility`) and mount the facility in their `apply`.
+ */
+export interface StorageForms {}
+
+/**
+ * The storage hub service. Backends register under `backend`; data forms
+ * mount under their `StorageForms` key and are reached as `ctx.storage.<form>`.
+ */
+export class Storage extends Service {
+  /** Named backend table; multiple backends stay mounted side by side. */
+  readonly backend = new BackendRegistry()
+
+  private readonly forms = new Map<keyof StorageForms, unknown>()
+
+  constructor(ctx: Context) {
+    super(ctx, 'storage')
+  }
+
+  /**
+   * Mount a data-form facility on the hub. Mounting is an effect: the
+   * returned disposer unmounts the form.
+   * @param form - Form key declared in {@link StorageForms}.
+   * @param facility - The facility instance to expose.
+   * @returns the disposer that unmounts the form.
+   */
+  mount<K extends keyof StorageForms>(form: K, facility: StorageForms[K]): () => void {
+    if (this.forms.has(form)) {
+      throw new StorageError('duplicate-mount', `storage form '${String(form)}' is already mounted`)
+    }
+    this.forms.set(form, facility)
+    return () => {
+      this.forms.delete(form)
+    }
+  }
+
+  /**
+   * Resolve a mounted data form.
+   * @param form - Form key declared in {@link StorageForms}.
+   * @returns the mounted facility.
+   */
+  form<K extends keyof StorageForms>(form: K): StorageForms[K] {
+    if (!this.forms.has(form)) {
+      throw new StorageError('form-not-mounted', `storage form '${String(form)}' is not mounted`)
+    }
+    return this.forms.get(form) as StorageForms[K]
+  }
+
+  /** Domain data form; present once the domain layer plugin is loaded. */
+  get domain(): StorageForms extends { domain: infer D } ? D : never {
+    return this.form('domain' as keyof StorageForms) as StorageForms extends { domain: infer D } ? D : never
+  }
+}
+
+/**
+ * Mount the storage hub service.
+ * @param ctx - Plugin context.
+ */
+export function apply(ctx: Context) {
+  ctx.plugin(Storage)
+}

packages/storage/storage/src/invariant.ts

@@ -0,0 +1,32 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-storage`.
+ * @module @deepseek-ai/dsh-storage/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-storage'
+
+/** Cordis companion plugin name. */
+export const name = 'storage-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: the hub is a pure registration table (names →
+ * backends, forms → facilities) whose consistency is fully enforced at the
+ * call sites (duplicate/missing entries fail loud synchronously); it owns no
+ * event stream or mutable medium to cross-check.
+ */
+const install: InvariantInstaller = () => {}
+
+/**
+ * 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))
+/* jscpd:ignore-end */

packages/storage/storage/src/registry.ts

@@ -0,0 +1,58 @@
+/**
+ * Named backend registry of the storage hub.
+ * @module @deepseek-ai/dsh-storage/src/registry
+ */
+
+import type { StorageBackend } from './backend.ts'
+import { StorageError } from './error.ts'
+
+/**
+ * Mutable name → backend table. Multiple backends stay mounted side by side;
+ * which backend serves which consumer is the consumer's configuration
+ * (e.g. the domain layer's route table), never a hub-global choice.
+ */
+export class BackendRegistry {
+  private readonly backends = new Map<string, StorageBackend>()
+
+  /**
+   * Register a named backend. Registration is an effect: the returned
+   * disposer removes the name. Disposal does NOT close the backend — the
+   * owning plugin closes it after unregistering.
+   * @param name - Backend name, e.g. `json` or `sqlite`.
+   * @param backend - The backend instance.
+   * @returns the disposer that unregisters the name.
+   */
+  register(name: string, backend: StorageBackend): () => void {
+    if (this.backends.has(name)) {
+      throw new StorageError('duplicate-backend', `storage backend '${name}' is already registered`)
+    }
+    this.backends.set(name, backend)
+    return () => {
+      this.backends.delete(name)
+    }
+  }
+
+  /**
+   * Resolve a backend by name.
+   * @param name - Registered backend name.
+   * @returns the backend.
+   */
+  get(name: string): StorageBackend {
+    const backend = this.backends.get(name)
+    if (!backend) {
+      throw new StorageError(
+        'backend-not-found',
+        `storage backend '${name}' is not registered (registered: ${[...this.backends.keys()].join(', ') || 'none'})`,
+      )
+    }
+    return backend
+  }
+
+  /**
+   * Registered backend names, for diagnostics.
+   * @returns a snapshot array of names.
+   */
+  names(): string[] {
+    return [...this.backends.keys()]
+  }
+}

packages/storage/storage/tests/contract.ts

@@ -0,0 +1,102 @@
+/**
+ * Shared KV-backend conformance suite. Each backend's spec file calls
+ * {@link runKvBackendContract} with a factory bound to its own medium; the
+ * suite asserts every clause of the `src/backend.ts` contract so both
+ * backends are held to identical semantics.
+ * @module
+ */
+
+import { describe, expect, it } from 'vitest'
+import type { KvUnitDescriptor, StorageBackend } from '../src/backend.ts'
+
+/** One conformance run: a fresh backend plus a way to reopen the same medium (crash simulation). */
+export interface KvBackendContractHarness {
+  /** The backend under test, freshly created over an empty medium. */
+  backend: StorageBackend
+  /** Open a NEW backend instance over the SAME medium, as after a process restart. */
+  reopen(): Promise<StorageBackend>
+}
+
+const DESCRIPTOR: KvUnitDescriptor = {
+  name: 'contract_unit',
+  version: 3,
+  tables: ['alpha', 'beta'],
+  hasGlobal: true,
+}
+
+/**
+ * Run the shared conformance suite against one backend implementation.
+ * @param label - Suite label, e.g. `json` / `sqlite`.
+ * @param create - Factory producing a fresh harness per test.
+ */
+export function runKvBackendContract(label: string, create: () => Promise<KvBackendContractHarness>) {
+  describe(`kv backend contract: ${label}`, () => {
+    it('opens a missing unit as empty and serves loadAll immediately', async () => {
+      const { backend } = await create()
+      const unit = await backend.kv!.open(DESCRIPTOR)
+      const snapshot = await unit.loadAll()
+      expect(snapshot.tables).toEqual({ alpha: {}, beta: {} })
+      expect(snapshot.global).toBeNull()
+      await backend.close()
+    })
+
+    it('round-trips records and global durably across reopen', async () => {
+      const harness = await create()
+      const unit = await harness.backend.kv!.open(DESCRIPTOR)
+      await unit.putRecord('alpha', 'k1', { n: 1 })
+      await unit.putRecord('alpha', 'k2', { n: 2 })
+      await unit.putRecord('beta', 'weird key / with:stuff', { ok: true })
+      await unit.setGlobal({ counter: 7 })
+      await harness.backend.close()
+
+      const reopened = await harness.reopen()
+      const unit2 = await reopened.kv!.open(DESCRIPTOR)
+      const snapshot = await unit2.loadAll()
+      expect(snapshot.tables['alpha']).toEqual({ k1: { n: 1 }, k2: { n: 2 } })
+      expect(snapshot.tables['beta']).toEqual({ 'weird key / with:stuff': { ok: true } })
+      expect(snapshot.global).toEqual({ counter: 7 })
+      await reopened.close()
+    })
+
+    it('putRecord overwrites and deleteRecord is idempotent', async () => {
+      const { backend } = await create()
+      const unit = await backend.kv!.open(DESCRIPTOR)
+      await unit.putRecord('alpha', 'k', { v: 'old' })
+      await unit.putRecord('alpha', 'k', { v: 'new' })
+      await unit.deleteRecord('alpha', 'k')
+      await unit.deleteRecord('alpha', 'k')
+      await unit.deleteRecord('alpha', 'never-existed')
+      const snapshot = await unit.loadAll()
+      expect(snapshot.tables['alpha']).toEqual({})
+      await backend.close()
+    })
+
+    it('rejects a version mismatch on reopen without touching the data', async () => {
+      const harness = await create()
+      const unit = await harness.backend.kv!.open(DESCRIPTOR)
+      await unit.putRecord('alpha', 'k', { v: 1 })
+      await harness.backend.close()
+
+      const reopened = await harness.reopen()
+      await expect(reopened.kv!.open({ ...DESCRIPTOR, version: 4 })).rejects.toMatchObject({
+        name: 'StorageError',
+        code: 'version-mismatch',
+      })
+      // Original version still opens and still holds the data.
+      const unit2 = await reopened.kv!.open(DESCRIPTOR)
+      expect((await unit2.loadAll()).tables['alpha']).toEqual({ k: { v: 1 } })
+      await reopened.close()
+    })
+
+    it('rejects operations after unit close, and close is idempotent', async () => {
+      const { backend } = await create()
+      const unit = await backend.kv!.open(DESCRIPTOR)
+      await unit.close()
+      await unit.close()
+      await expect(unit.putRecord('alpha', 'k', {})).rejects.toMatchObject({ code: 'closed' })
+      await expect(unit.loadAll()).rejects.toMatchObject({ code: 'closed' })
+      await backend.close()
+      await backend.close()
+    })
+  })
+}

packages/storage/storage/tests/registry.spec.ts

@@ -0,0 +1,62 @@
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import { BackendRegistry, Storage, apply } from '../src/index.ts'
+import type { StorageBackend } from '../src/index.ts'
+
+const fakeBackend = (): StorageBackend => ({ close: async () => {} })
+
+describe('BackendRegistry', () => {
+  it('registers, resolves, and disposes names', () => {
+    const registry = new BackendRegistry()
+    const backend = fakeBackend()
+    const dispose = registry.register('json', backend)
+    expect(registry.get('json')).toBe(backend)
+    expect(registry.names()).toEqual(['json'])
+    dispose()
+    expect(registry.names()).toEqual([])
+    expect(() => registry.get('json')).toThrowMatchingObject({ code: 'backend-not-found' })
+  })
+
+  it('rejects duplicate names', () => {
+    const registry = new BackendRegistry()
+    registry.register('json', fakeBackend())
+    expect(() => registry.register('json', fakeBackend())).toThrowMatchingObject({ code: 'duplicate-backend' })
+  })
+})
+
+describe('Storage service', () => {
+  it('mounts on the context and exposes registry plus form mounting', async () => {
+    const ctx = new Context()
+    await ctx.plugin({ apply })
+    expect(ctx.storage).toBeInstanceOf(Storage)
+
+    const facility = { marker: true }
+    const dispose = ctx.storage.mount('domain' as never, facility as never)
+    expect(ctx.storage.form('domain' as never)).toBe(facility)
+    expect(() => ctx.storage.mount('domain' as never, facility as never)).toThrowMatchingObject({
+      code: 'duplicate-mount',
+    })
+    dispose()
+    expect(() => ctx.storage.form('domain' as never)).toThrowMatchingObject({ code: 'form-not-mounted' })
+  })
+})
+
+expect.extend({
+  toThrowMatchingObject(received: () => unknown, expected: object) {
+    try {
+      received()
+    } catch (error) {
+      const pass = Object.entries(expected).every(
+        (entry) => (error as Record<string, unknown>)[entry[0]] === entry[1],
+      )
+      return { pass, message: () => `expected thrown error to match ${JSON.stringify(expected)}, got ${String(error)}` }
+    }
+    return { pass: false, message: () => 'expected function to throw' }
+  },
+})
+
+declare module 'vitest' {
+  interface Assertion<T> {
+    toThrowMatchingObject(expected: object): T
+  }
+}

packages/storage/storage/tsconfig.json

@@ -0,0 +1,21 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "lib/types"
+  },
+  "include": [
+    "src"
+  ],
+  "references": [
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../support/invariants"
+    }
+  ]
+}

tsconfig.base.json

@@ -74,6 +74,8 @@
         "./packages/hooks/*/src/invariant.ts",
         "./packages/session-persistence/*/src/invariant.ts",
         "./packages/session-query/*/src/invariant.ts",
+        "./packages/storage/*/src/invariant.ts",
+        "./packages/workspace/*/src/invariant.ts",
         "./packages/sdk/*/src/invariant.ts",
         "./packages/ui/*/src/invariant.ts",
         "./packages/examples/*/src/invariant.ts",
@@ -142,6 +144,8 @@
         "./packages/session-persistence/*/src",
         "./packages/session-query/*/src",
         "./packages/session-title/*/src",
+        "./packages/storage/*/src",
+        "./packages/workspace/*/src",
         "./packages/sdk/*/src",
         "./packages/ui/*/src",
         "./packages/examples/*/src",

tsconfig.host.json

@@ -44,6 +44,11 @@
     { "path": "./packages/session-persistence/session-persistence-sqlite" },
     { "path": "./packages/session-query/session-query" },
     { "path": "./packages/session-query/session-query-sqlite" },
+    { "path": "./packages/storage/storage" },
+    { "path": "./packages/storage/storage-json" },
+    { "path": "./packages/storage/storage-sqlite" },
+    { "path": "./packages/storage/domain" },
+    { "path": "./packages/workspace/workspace" },
     { "path": "./packages/session-title/session-title" },
     { "path": "./packages/session-title/session-title-llm" },
     { "path": "./packages/session-title/session-title-first-message-llm" },