fix(electrobun): session resume uses pending mode — user types prompt first, no empty string to SDK

ui-electrobun/src/mainview/AgentPane.svelte

@@ -3,6 +3,7 @@
   import ChatInput from "./ChatInput.svelte";
   import SessionPicker from "./SessionPicker.svelte";
   import type { AgentMessage, AgentStatus } from "./agent-store.svelte.ts";
+  import { getPendingResume } from "./agent-store.svelte.ts";
   import { t } from "./i18n.svelte.ts";
 
   interface Props {
@@ -55,6 +56,8 @@
     return () => observer.disconnect();
   });
 
+  function getPendingResumeForProject() { return projectId ? getPendingResume(projectId) : undefined; }
+
   function handleSend() {
     const text = promptText.trim();
     if (!text) return;
@@ -236,7 +239,7 @@
       {model}
       {provider}
       {contextPct}
-      placeholder={t("agent.prompt.placeholder")}
+      placeholder={getPendingResumeForProject() ? 'Type to resume session...' : t("agent.prompt.placeholder")}
       onSend={handleSend}
       onInput={(v) => (promptText = v)}
     />

ui-electrobun/src/mainview/SessionPicker.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
   import { onMount } from 'svelte';
   import type { ClaudeSessionInfo } from './agent-store.svelte.ts';
-  import { listProjectSessions, resumeSession, continueLastSession, startAgent } from './agent-store.svelte.ts';
+  import { listProjectSessions, setPendingResume, getPendingResume, clearPendingResume } from './agent-store.svelte.ts';
   import { t } from './i18n.svelte.ts';
 
   interface Props {
@@ -72,18 +72,21 @@
     return s.length > max ? s.slice(0, max - 3) + '...' : s;
   }
 
-  async function handleContinue() {
+  function handleContinue() {
     open = false;
-    await continueLastSession(projectId, provider, '', cwd);
+    setPendingResume(projectId, 'continue');
+    // User types their next prompt and hits Send — startAgent reads the pending resume
   }
 
-  async function handleResume(sdkSessionId: string) {
+  function handleResume(sdkSessionId: string) {
     open = false;
-    await resumeSession(projectId, provider, sdkSessionId, '', cwd);
+    setPendingResume(projectId, 'resume', sdkSessionId);
+    // User types their next prompt and hits Send — startAgent reads the pending resume
   }
 
   function handleNew() {
     open = false;
+    clearPendingResume(projectId);
     onNewSession?.('');
   }
 </script>

ui-electrobun/src/mainview/agent-store.svelte.ts

@@ -127,6 +127,33 @@ function validateExtraEnv(env: Record<string, string> | undefined): Record<strin
 // Map projectId -> sessionId for lookup
 const projectSessionMap = new Map<string, string>();
 
+// Pending resume: when the user selects a session to resume, we store the
+// resume options here. The next startAgent() call reads and clears them.
+// This avoids sending an empty prompt — the user types their message first.
+interface PendingResume {
+  mode: 'continue' | 'resume';
+  sdkSessionId?: string;
+}
+const pendingResumes = new Map<string, PendingResume>();
+
+/** Set a pending resume for a project — next startAgent will use these options. */
+export function setPendingResume(projectId: string, mode: 'continue' | 'resume', sdkSessionId?: string): void {
+  pendingResumes.set(projectId, { mode, sdkSessionId });
+  bump();
+}
+
+/** Check if a project has a pending resume. */
+export function getPendingResume(projectId: string): PendingResume | undefined {
+  void _v;
+  return pendingResumes.get(projectId);
+}
+
+/** Clear pending resume (called after startAgent consumes it). */
+export function clearPendingResume(projectId: string): void {
+  pendingResumes.delete(projectId);
+  bump();
+}
+
 // Map sessionId -> reactive session state
 let sessions = $state<Record<string, AgentSession>>({});
 
@@ -522,6 +549,16 @@ async function _startAgentInner(
   // If there's an existing done/error session for this project, clear it first
   clearSession(projectId);
 
+  // Check for pending resume (user selected a session in the picker)
+  const pending = pendingResumes.get(projectId);
+  if (pending) {
+    pendingResumes.delete(projectId);
+    if (!options.resumeMode) {
+      options.resumeMode = pending.mode;
+      options.resumeSessionId = pending.sdkSessionId;
+    }
+  }
+
   const sessionId = `${projectId}-${Date.now()}`;
 
   // Read settings defaults if not explicitly provided (Fix #5)