fix: preserve Hermes sessions across transport changes

desktop/src/agents/cli/cli-invocations.cjs

@@ -73,9 +73,10 @@ function invocation(kind, executable, workdir, sessionRef = '', options = {}) {
     }
   }
   if (kind === 'hermes') {
-    const legacySessionRef = options.sessionTransport === 'acp' ? '' : sessionRef
+    // Hermes uses the same native conversation identifier across its ACP and
+    // legacy transports. Keep it when an attachment requires the legacy path.
+    const legacySessionRef = sessionRef
     const useAcp = options.invocationTransport !== 'legacy'
-      && !attachments.length
       && options.hermesAcpAvailable !== false
       && (!sessionRef || options.sessionTransport === 'acp')
     if (useAcp) {
@@ -187,7 +188,7 @@ function invocation(kind, executable, workdir, sessionRef = '', options = {}) {
     }
   }
   if (kind === 'mimo') {
-    if (options.invocationTransport !== 'json') {
+    if (!attachments.length && options.invocationTransport !== 'json') {
       return {
         command: executable,
         args: ['acp', '--pure', '--cwd', workdir],

desktop/src/workspace/local-workspace-agent-invocation.cjs

@@ -770,7 +770,7 @@ class LocalWorkspaceAgentInvocation {
     const hermesNeedsLegacy = kind === 'hermes' && sessionTransport === 'acp'
       && (!HERMES_WORKSPACE_ACP_ENABLED
         || agent.acpAvailable === false
-        || (context.attachments || []).length > 0)
+      )
     if (resumedPermission && hermesNeedsLegacy) {
       throw new Error('LOCAL_RUN_PERMISSION_RESUME_UNAVAILABLE')
     }