diff --git a/.claude/worktrees/provider-file-ids b/.claude/worktrees/provider-file-ids
new file mode 160000
index 0000000000..7069d37059
--- /dev/null
+++ b/.claude/worktrees/provider-file-ids
@@ -0,0 +1 @@
+Subproject commit 7069d37059db3a48dec1ef748bb71ada9a85d5d4
diff --git a/docs/module-graph.md b/docs/module-graph.md
index 212fd723a7..b77129f8b3 100644
--- a/docs/module-graph.md
+++ b/docs/module-graph.md
@@ -131,6 +131,10 @@ flowchart TD
     pkg_user_approval["user-approval"]
     pkg_user_interaction["user-interaction"]
   end
+  subgraph group_attachment["packages/attachment"]
+    pkg_attachment["attachment"]
+    pkg_attachment_local["attachment-local"]
+  end
   subgraph group_client["packages/client"]
     pkg_client_connection["client-connection"]
     pkg_client_hmr["client-hmr"]
@@ -230,14 +234,10 @@ flowchart TD
   pkg_host_apiproxy --> pkg_invariants
   pkg_host_runtime --> pkg_invariants
   pkg_host_webserver --> pkg_invariants
-  pkg_llm --> pkg_brand
-  pkg_llm --> pkg_invariants
+  pkg_attachment --> pkg_brand
+  pkg_attachment --> pkg_invariants
   pkg_client_hmr --> pkg_client_modules
   pkg_client_hmr --> pkg_invariants
-  pkg_client_ui_conversation --> pkg_client_runtime
-  pkg_client_ui_conversation --> pkg_client_ui_primitives
-  pkg_client_ui_conversation --> pkg_client_ui_slots
-  pkg_client_ui_conversation --> pkg_invariants
   pkg_client_ui_layout --> pkg_client_runtime
   pkg_client_ui_layout --> pkg_client_ui_slots
   pkg_client_ui_layout --> pkg_invariants
@@ -250,9 +250,21 @@ flowchart TD
   pkg_telemetry --> pkg_brand
   pkg_telemetry --> pkg_invariants
   pkg_telemetry --> pkg_paths
+  pkg_llm --> pkg_attachment
+  pkg_llm --> pkg_brand
+  pkg_llm --> pkg_invariants
+  pkg_attachment_local --> pkg_attachment
+  pkg_attachment_local --> pkg_invariants
+  pkg_attachment_local --> pkg_paths
+  pkg_client_ui_conversation --> pkg_attachment
+  pkg_client_ui_conversation --> pkg_client_runtime
+  pkg_client_ui_conversation --> pkg_client_ui_primitives
+  pkg_client_ui_conversation --> pkg_client_ui_slots
+  pkg_client_ui_conversation --> pkg_invariants
   pkg_llm_deepseek --> pkg_invariants
   pkg_llm_deepseek --> pkg_llm
   pkg_llm_deepseek --> pkg_timeout
+  pkg_llm_pi_ai --> pkg_attachment
   pkg_llm_pi_ai --> pkg_invariants
   pkg_llm_pi_ai --> pkg_llm
   pkg_llm_pi_ai --> pkg_timeout
@@ -805,15 +817,17 @@ flowchart TD
 | [`host-apiproxy`](../packages/host/apiproxy) | `host` | [`invariants`](../packages/support/invariants) |
 | [`host-runtime`](../packages/host/runtime) | `host` | [`invariants`](../packages/support/invariants) |
 | [`host-webserver`](../packages/host/webserver) | `host` | [`invariants`](../packages/support/invariants) |
-| [`llm`](../packages/llm/llm) | `llm` | [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants) |
+| [`attachment`](../packages/attachment/attachment) | `attachment` | [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants) |
 | [`client-hmr`](../packages/client/hmr) | `client` | [`client-modules`](../packages/client/modules), [`invariants`](../packages/support/invariants) |
-| [`client-ui-conversation`](../packages/client/ui-conversation) | `client` | [`client-runtime`](../packages/client/runtime), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-slots`](../packages/client/ui-slots), [`invariants`](../packages/support/invariants) |
 | [`client-ui-layout`](../packages/client/ui-layout) | `client` | [`client-runtime`](../packages/client/runtime), [`client-ui-slots`](../packages/client/ui-slots), [`invariants`](../packages/support/invariants) |
 | [`client-ui-sidebar`](../packages/client/ui-sidebar) | `client` | [`client-runtime`](../packages/client/runtime), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-slots`](../packages/client/ui-slots), [`invariants`](../packages/support/invariants) |
 | [`helper`](../packages/sdk/helper) | `sdk` | [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants) |
 | [`telemetry`](../packages/sdk/telemetry) | `sdk` | [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants), [`paths`](../packages/util/paths) |
+| [`llm`](../packages/llm/llm) | `llm` | [`attachment`](../packages/attachment/attachment), [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants) |
+| [`attachment-local`](../packages/attachment/attachment-local) | `attachment` | [`attachment`](../packages/attachment/attachment), [`invariants`](../packages/support/invariants), [`paths`](../packages/util/paths) |
+| [`client-ui-conversation`](../packages/client/ui-conversation) | `client` | [`attachment`](../packages/attachment/attachment), [`client-runtime`](../packages/client/runtime), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-slots`](../packages/client/ui-slots), [`invariants`](../packages/support/invariants) |
 | [`llm-deepseek`](../packages/llm/llm-deepseek) | `llm` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`timeout`](../packages/util/timeout) |
-| [`llm-pi-ai`](../packages/llm/llm-pi-ai) | `llm` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`timeout`](../packages/util/timeout) |
+| [`llm-pi-ai`](../packages/llm/llm-pi-ai) | `llm` | [`attachment`](../packages/attachment/attachment), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`timeout`](../packages/util/timeout) |
 | [`session`](../packages/core/session) | `core` | [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`scope`](../packages/core/scope) |
 | [`system-prompt`](../packages/core/system-prompt) | `core` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`scope`](../packages/core/scope) |
 | [`web`](../packages/web/web) | `web` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm) |
diff --git a/packages/llm/llm-pi-ai/tests/provider-apis.e2e.ts b/packages/llm/llm-pi-ai/tests/provider-apis.e2e.ts
index 6bee0aa0d0..85dcbd5706 100644
--- a/packages/llm/llm-pi-ai/tests/provider-apis.e2e.ts
+++ b/packages/llm/llm-pi-ai/tests/provider-apis.e2e.ts
@@ -25,8 +25,10 @@ interface ProviderCase {
 
 const openAIBaseURL = process.env.DSH_PI_AI_OPENAI_BASE_URL
 const azureOpenAIKey = process.env.AZURE_OPENAI_API_KEY
-const anthropicApiKey = process.env.ANTHROPIC_API_KEY ?? process.env.DEEPSEEK_API_KEY
-const anthropicBaseURL = process.env.DSH_PI_AI_ANTHROPIC_BASE_URL ?? process.env.DEEPSEEK_BASE_URL
+// Strictly ANTHROPIC_*: the DeepSeek endpoint does not serve the anthropic-messages
+// protocol, so falling back to DEEPSEEK_API_KEY turns the keyless skip into a 404.
+const anthropicApiKey = process.env.ANTHROPIC_API_KEY
+const anthropicBaseURL = process.env.DSH_PI_AI_ANTHROPIC_BASE_URL
 
 const providerCases: ProviderCase[] = [
   {
diff --git a/packages/sandbox/sandbox-local/tests/packed-install.e2e.ts b/packages/sandbox/sandbox-local/tests/packed-install.e2e.ts
index 9fcfe23de8..e453aad6a4 100644
--- a/packages/sandbox/sandbox-local/tests/packed-install.e2e.ts
+++ b/packages/sandbox/sandbox-local/tests/packed-install.e2e.ts
@@ -25,6 +25,7 @@ const WORKSPACE_CLOSURE = [
   'packages/sandbox/sandbox-local',
   'packages/sandbox/sandbox',
   'packages/llm/llm',
+  'packages/attachment/attachment',
   'packages/util/brand',
   'packages/support/invariants',
 ]