fix(gui): harden multimodal image attachments

packages/client/runtime/README.md

@@ -1,6 +1,6 @@
 # @deepseek-ai/dsh-client-runtime
 
-Client cordis boot + core services: SlotsService (Service wrapper over SlotCore + 'slots/changed' bridge), SessionsService (list store projection, scope tree, bindings, ancestry), the Session object layer (exported as a type; instances are owned and handed out by SessionsService — the manager/paging internals stay package-internal, tests reach them via src), ClientLoader (`./loader` subpath, statically held by the shell). Contract: api-contracts v3 §4.
+Client cordis boot + core services: SlotsService (Service wrapper over SlotCore + 'slots/changed' bridge), SessionsService (list store projection, scope tree, bindings, ancestry, and the latest successful host capability description), the Session object layer (exported as a type; instances are owned and handed out by SessionsService — the manager/paging internals stay package-internal, tests reach them via src), ClientLoader (`./loader` subpath, statically held by the shell). Contract: api-contracts v3 §4.
 
 ## Model Experience
 

packages/client/runtime/src/client/index.ts

@@ -148,6 +148,7 @@ export function apply(ctx: Context): void {
   const loop = connection.start({
     onMuxEnvelope: (envelope) => { sessions.manager.handleMuxEnvelope(envelope) },
     onHostEnvelope: (envelope) => { sessions.manager.handleHostEnvelope(envelope) },
+    onDescription: (description) => { sessions.handleDescription(description) },
     onConnected: () => { sessions.manager.handleConnected() },
   })
   ctx.effect(() => () => { loop.stop() }, 'runtime: connection stream loop')

packages/client/runtime/src/client/sessions/service.ts

@@ -14,7 +14,7 @@
  * read-only view).
  */
 import type { Context, Fiber } from 'cordis'
-import type { IApiClient, SessionId } from '@deepseek-ai/dsh-client-connection/client'
+import type { HostDescription, IApiClient, SessionId } from '@deepseek-ai/dsh-client-connection/client'
 import type { SessionCell } from '@deepseek-ai/dsh-client-ui-slots'
 import type { SnapshotStore } from '../contract/store.ts'
 import { createSnapshotStore } from '../contract/store.ts'
@@ -101,6 +101,7 @@ export class SessionsService {
   private watched: SessionId | undefined
   /** Removed-while-watched sessions whose teardown waits for the watch to move away. */
   private readonly deferredRemovals = new Set<SessionId>()
+  private description: HostDescription | undefined
 
   /**
    * @param ctx - client root context (scope fibers mount under it).
@@ -118,6 +119,22 @@ export class SessionsService {
     rootCtx.reflect.provide('sessions', this, undefined)
   }
 
+  /**
+   * Store the latest successful connection-generation host description.
+   * @param description - capability and deployment snapshot from `host.describe`.
+   */
+  handleDescription(description: HostDescription): void {
+    this.description = description
+  }
+
+  /**
+   * Read the latest host capability snapshot.
+   * @returns the last successful description, or undefined before connection.
+   */
+  hostDescription(): HostDescription | undefined {
+    return this.description
+  }
+
   /**
    * Select a session as current. Unknown ids fail loud instead of navigating
    * nowhere (the sole selection write path).

packages/client/runtime/tests/client-apply.spec.ts

@@ -53,6 +53,8 @@ describe('runtime client apply', () => {
     expect((sessions as { list: { getSnapshot(): { ids: string[] } } }).list.getSnapshot().ids).toContain('s-new')
     // Mux sink and onConnected route without throwing (manager semantics own the behavior).
     bench.sinks?.onMuxEnvelope?.({ rpcId: 'r2' as never, payload: { type: 'stream/error', message: 'x' } as never })
+    bench.sinks?.onDescription?.({ version: '0', cwd: '/f', attachedSessions: 0 })
+    expect(sessions?.hostDescription()).toEqual({ version: '0', cwd: '/f', attachedSessions: 0 })
     bench.sinks?.onConnected?.()
   })