diff --git a/apps/web/tests/chat-continuous-conversation.e2e.ts b/apps/web/tests/chat-continuous-conversation.e2e.ts
index a7b659dab2..cd15f2e054 100644
--- a/apps/web/tests/chat-continuous-conversation.e2e.ts
+++ b/apps/web/tests/chat-continuous-conversation.e2e.ts
@@ -12,14 +12,13 @@ import { afterAll, beforeAll, describe, expect, it, onTestFailed } from 'vitest'
 import { CallId, type StreamChunk } from '@deepseek-ai/dsh-llm'
 import type { ReplayEntry, ReplayOverrideDoc } from '@deepseek-ai/dsh-llm-replay'
 import type { SessionEvent, SessionId } from '@deepseek-ai/dsh-session'
-import { conversationContextKey } from '@deepseek-ai/dsh-client-runtime/client'
 import {
   launchWebScaffold,
   watchConsole,
   webSnapshotMode,
   type WebScaffold,
 } from './scaffold.ts'
-import { connectFreshWorkspace, newEnglishPage, saveFailureShot } from './support.ts'
+import { connectFreshWorkspace, conversationContextKey, newEnglishPage, saveFailureShot } from './support.ts'
 
 const MODE = webSnapshotMode()
 const TURN_COUNT = 12
diff --git a/apps/web/tests/chat-long-interactions.e2e.ts b/apps/web/tests/chat-long-interactions.e2e.ts
index aca85146b5..58d97e5e3e 100644
--- a/apps/web/tests/chat-long-interactions.e2e.ts
+++ b/apps/web/tests/chat-long-interactions.e2e.ts
@@ -11,7 +11,6 @@ import { afterAll, beforeAll, describe, expect, it, onTestFailed } from 'vitest'
 import type { StreamChunk } from '@deepseek-ai/dsh-llm'
 import type { ReplayEntry, ReplayOverrideDoc } from '@deepseek-ai/dsh-llm-replay'
 import { SessionId, type SessionEvent } from '@deepseek-ai/dsh-session'
-import { conversationContextKey } from '@deepseek-ai/dsh-client-runtime/client'
 import { createChatScrollFixture } from './chat-scroll-fixture.ts'
 import {
   launchWebScaffold,
@@ -20,7 +19,7 @@ import {
   webSnapshotMode,
   type WebScaffold,
 } from './scaffold.ts'
-import { newEnglishPage, saveFailureShot } from './support.ts'
+import { conversationContextKey, newEnglishPage, saveFailureShot } from './support.ts'
 
 const MODE = webSnapshotMode()
 const SESSION_ID = 'chat-long-interactions-e2e'
diff --git a/apps/web/tests/support.ts b/apps/web/tests/support.ts
index ee2a1a1a62..38d0849784 100644
--- a/apps/web/tests/support.ts
+++ b/apps/web/tests/support.ts
@@ -119,3 +119,17 @@ export async function saveFailureShot(page: Page, name: string): Promise<void> {
     // Best-effort evidence: a dead page/browser at failure time must not mask the real assertion error.
   }
 }
+
+/**
+ * The conversation engine's Context key format, restated here rather than
+ * imported: these specs live in the Host compiler aggregate, which must not
+ * reach the Client plane. The engine's own copy is
+ * `conversationContextKey` in dsh-client-runtime; a drift between them makes
+ * the key miss its rendered node, so the assertion fails loudly.
+ * @param kind - Definition kind.
+ * @param id - Definition-local business identity.
+ * @returns the engine-owned Context key.
+ */
+export function conversationContextKey(kind: string, id: string): string {
+  return `${kind.length}:${kind}${id}`
+}
diff --git a/packages/api/gateway/tsconfig.client.json b/packages/api/gateway/tsconfig.client.json
new file mode 100644
index 0000000000..de257c951a
--- /dev/null
+++ b/packages/api/gateway/tsconfig.client.json
@@ -0,0 +1,22 @@
+{
+  "extends": "../../../tsconfig.base.client.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "lib/types",
+    "tsBuildInfoFile": "lib/tsconfig.client.tsbuildinfo"
+  },
+  "files": [
+    "src/client/index.ts"
+  ],
+  "references": [
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../client/connection/tsconfig.client.json"
+    },
+    {
+      "path": "../../typert/type-meta"
+    }
+  ]
+}
diff --git a/packages/api/gateway/tsconfig.host.json b/packages/api/gateway/tsconfig.host.json
new file mode 100644
index 0000000000..5c12e43cc2
--- /dev/null
+++ b/packages/api/gateway/tsconfig.host.json
@@ -0,0 +1,30 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "lib/types",
+    "tsBuildInfoFile": "lib/tsconfig.host.tsbuildinfo"
+  },
+  "files": [
+    "src/index.ts",
+    "src/invariant.ts",
+    "src/types.ts"
+  ],
+  "references": [
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../support/invariants"
+    },
+    {
+      "path": "../../client/connection/tsconfig.host.json"
+    },
+    {
+      "path": "../../typert/type-meta"
+    }
+  ]
+}
diff --git a/packages/api/gateway/tsconfig.json b/packages/api/gateway/tsconfig.json
index fea39663f7..2eca820546 100644
--- a/packages/api/gateway/tsconfig.json
+++ b/packages/api/gateway/tsconfig.json
@@ -1,27 +1,11 @@
 {
-  "extends": "../../../tsconfig.base.json",
-  "compilerOptions": {
-    "rootDir": "src",
-    "outDir": "lib/types"
-  },
-  "include": [
-    "src"
-  ],
+  "files": [],
   "references": [
     {
-      "path": "../../../vendor/cosmokit"
+      "path": "./tsconfig.host.json"
     },
     {
-      "path": "../../../vendor/cordis"
-    },
-    {
-      "path": "../../support/invariants"
-    },
-    {
-      "path": "../../client/connection"
-    },
-    {
-      "path": "../../typert/type-meta"
+      "path": "./tsconfig.client.json"
     }
   ]
 }
diff --git a/packages/api/remotes/tsconfig.client.json b/packages/api/remotes/tsconfig.client.json
index 256258c668..8f28b83a6e 100644
--- a/packages/api/remotes/tsconfig.client.json
+++ b/packages/api/remotes/tsconfig.client.json
@@ -15,7 +15,10 @@
       "path": "../../../vendor/cordis"
     },
     {
-      "path": "../gateway"
+      "path": "../gateway/tsconfig.client.json"
+    },
+    {
+      "path": "../../client/connection/tsconfig.client.json"
     },
     {
       "path": "../../credentials/credentials"
diff --git a/packages/client/connection/tsconfig.client.json b/packages/client/connection/tsconfig.client.json
new file mode 100644
index 0000000000..91ec8b42c7
--- /dev/null
+++ b/packages/client/connection/tsconfig.client.json
@@ -0,0 +1,49 @@
+{
+  "extends": "../../../tsconfig.base.client.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "lib/types",
+    "tsBuildInfoFile": "lib/tsconfig.client.tsbuildinfo"
+  },
+  "files": [
+    "src/api-path.ts",
+    "src/client/api.ts",
+    "src/client/connection.ts",
+    "src/client/fixture.ts",
+    "src/client/index.ts",
+    "src/client/random-uuid.ts",
+    "src/client/rpc.ts",
+    "src/client/web-api-client.ts",
+    "src/loopback-hostname.ts",
+    "src/rpc.ts"
+  ],
+  "references": [
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../attachment/attachment"
+    },
+    {
+      "path": "../../core/session"
+    },
+    {
+      "path": "../../core/tools"
+    },
+    {
+      "path": "../../host/apiproxy"
+    },
+    {
+      "path": "../../interaction/commands"
+    },
+    {
+      "path": "../../llm/llm"
+    },
+    {
+      "path": "../../support/invariants"
+    },
+    {
+      "path": "../../util/brand"
+    }
+  ]
+}
diff --git a/packages/client/connection/tsconfig.host.json b/packages/client/connection/tsconfig.host.json
new file mode 100644
index 0000000000..dca9b1a1b2
--- /dev/null
+++ b/packages/client/connection/tsconfig.host.json
@@ -0,0 +1,33 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "lib/types",
+    "tsBuildInfoFile": "lib/tsconfig.host.tsbuildinfo"
+  },
+  "files": [
+    "src/api-path.ts",
+    "src/api-request-trust.ts",
+    "src/http-bridge.ts",
+    "src/index.ts",
+    "src/invariant.ts",
+    "src/loopback-hostname.ts",
+    "src/rpc-host.ts",
+    "src/rpc.ts",
+    "src/websocket-downlink.ts"
+  ],
+  "references": [
+    {
+      "path": "../../attachment/attachment"
+    },
+    {
+      "path": "../../host/apiproxy"
+    },
+    {
+      "path": "../../host/webserver"
+    },
+    {
+      "path": "../../support/invariants"
+    }
+  ]
+}
diff --git a/packages/client/connection/tsconfig.json b/packages/client/connection/tsconfig.json
index 7bf86ffefe..2eca820546 100644
--- a/packages/client/connection/tsconfig.json
+++ b/packages/client/connection/tsconfig.json
@@ -1,46 +1,11 @@
 {
-  "extends": "../../../tsconfig.base.client.json",
-  "compilerOptions": {
-    "rootDir": "src",
-    "outDir": "lib/types",
-    "types": ["node"]
-  },
-  "include": [
-    "src"
-  ],
+  "files": [],
   "references": [
     {
-      "path": "../../attachment/attachment"
+      "path": "./tsconfig.host.json"
     },
     {
-      "path": "../../llm/llm"
-    },
-    {
-      "path": "../../core/session"
-    },
-    {
-      "path": "../../interaction/commands"
-    },
-    {
-      "path": "../../util/brand"
-    },
-    {
-      "path": "../../host/apiproxy"
-    },
-    {
-      "path": "../../host/webserver"
-    },
-    {
-      "path": "../../interaction/user-approval"
-    },
-    {
-      "path": "../../interaction/user-interaction"
-    },
-    {
-      "path": "../../support/invariants"
+      "path": "./tsconfig.client.json"
     }
-  ],
-  "exclude": [
-    "**/*.legacy.*"
   ]
 }
diff --git a/tsconfig.client.json b/tsconfig.client.json
index a054cb8751..9e2a7778d7 100644
--- a/tsconfig.client.json
+++ b/tsconfig.client.json
@@ -19,10 +19,7 @@
     "packages/client/*/src/css-modules.d.ts",
     "packages/client/*/tests/**/*.ts",
     "packages/client/*/tests/**/*.tsx",
-    "packages/host/directory-picker-browse/tests/**/*.ts",
-    "packages/host/directory-picker-browse/tests/**/*.tsx",
-    "packages/host/directory-picker-native/tests/**/*.ts",
-    "packages/host/directory-picker-native/tests/**/*.tsx",
+    "packages/api/gateway/tests/client.spec.ts",
     "packages/client/tsdown.client.ts",
     "scripts/client-bundle-css.spec.ts",
     "scripts/client-bundle-purity.spec.ts"
@@ -32,11 +29,6 @@
     // smoke policy). webserver has zero workspace deps and no cordis merge,
     // so it cannot drag host-side Context augmentation into this program.
     { "path": "./packages/host/webserver" },
-    // Dual-face host leaf: the node half is the native picking backend, the
-    // browser half registers the picking flow into ui-workspace's slot —
-    // client-side Context merges keep it out of the host program.
-    { "path": "./packages/host/directory-picker-native" },
-    { "path": "./packages/host/directory-picker-browse" },
     // Compaction seam: the client-runtime pin test value-imports the canonical
     // checkpoint const from the cordis-free dsh-compact/checkpoint leaf and
     // deliberately never loads the dsh-compact package root or the host-side
@@ -51,9 +43,12 @@
     { "path": "./packages/client/web-react" },
     { "path": "./packages/client/modules" },
     { "path": "./packages/client/hmr" },
-    { "path": "./packages/client/connection" },
+    { "path": "./packages/client/connection/tsconfig.client.json" },
+    // The carrier's node-half spec rides this aggregate's package test glob, so
+    // its Host face is referenced here too — the mirror of the webserver leaf.
+    { "path": "./packages/client/connection/tsconfig.host.json" },
     { "path": "./packages/typert/registry" },
-    { "path": "./packages/api/gateway" },
+    { "path": "./packages/api/gateway/tsconfig.client.json" },
     { "path": "./packages/api/remotes/tsconfig.client.json" },
     { "path": "./packages/client/runtime" },
     { "path": "./packages/client/test-runtime" },
@@ -69,6 +64,8 @@
     { "path": "./packages/client/ui-skill" },
     { "path": "./packages/client/ui-subagent" },
     { "path": "./packages/client/ui-task" },
+    { "path": "./packages/client/ui-directory-picker" },
+    { "path": "./packages/client/ui-directory-picker-native" },
     { "path": "./packages/client/ui-goal" },
     { "path": "./packages/client/ui-model" },
     { "path": "./packages/client/ui-agent-preset" },
diff --git a/tsconfig.host.json b/tsconfig.host.json
index 90a254f72a..ef02fc557f 100644
--- a/tsconfig.host.json
+++ b/tsconfig.host.json
@@ -89,8 +89,7 @@
   ],
   "exclude": [
     "packages/client/**",
-    "packages/host/directory-picker-browse/**",
-    "packages/host/directory-picker-native/**",
+    "packages/api/gateway/tests/client.spec.ts",
     "scripts/client-bundle-css.spec.ts",
     "packages/typert/generator/tests/fixtures/**",
     "scripts/client-bundle-purity.spec.ts"
@@ -120,7 +119,7 @@
     { "path": "./packages/core/scope" },
     { "path": "./packages/typert/type-meta" },
     { "path": "./packages/typert/registry" },
-    { "path": "./packages/api/gateway" },
+    { "path": "./packages/api/gateway/tsconfig.host.json" },
     { "path": "./packages/api/remotes/tsconfig.host.json" },
     { "path": "./packages/typert/loader" },
     { "path": "./packages/session/session-persistence" },
@@ -270,11 +269,6 @@
     { "path": "./packages/host/apiproxy" },
     { "path": "./packages/host/directory-picker" },
     { "path": "./packages/host/directory-picker-auto" },
-    // Dual-face backend leaves stay client-registered (their tests and client
-    // halves are excluded above); these references only let the adaptive
-    // chooser's composition test import each backend's NODE entry, whose
-    // declarations carry no client-side Context merge — the mirror of the
-    // client aggregate's webserver reference.
     { "path": "./packages/host/directory-picker-browse" },
     { "path": "./packages/host/directory-picker-native" },
     { "path": "./packages/host/frontend-static" },