fix(desktop): clarify inherited agent parallelism (#4010)

## Summary

- show an unambiguous `App default (10)` inherited state for parallelism
in create and edit forms
- explain that blank inherits the app default and suppress create-form
number steppers that could silently set `1`
- align the E2E mint fallback with production while preserving explicit
input → definition → app-default precedence

## Why

The forms displayed `1` even though an untouched field is omitted and
desktop minting materializes `10`. The create-form spinner could also
turn blank/inherited into an explicit `1` with one click while leaving
the field looking nearly unchanged.

## Testing

- `pnpm test` (desktop: 3,886 passed)
- `pnpm typecheck` (desktop)
- `pnpm check` (desktop)
- pre-push `desktop-check` and `desktop-test`

---------

Signed-off-by: Wes <wesbillman@users.noreply.github.com>
Co-authored-by: Carl <c7ebe626f000404285d3686e1dc74cc07cc60a9754a150041ba132e14bd3e2ec@buzz.block.builderlab.xyz>

desktop/src-tauri/src/key_backup_tests.rs

@@ -250,12 +250,16 @@ fn generated_passphrase_respects_word_count_and_separator() {
 
 #[test]
 fn generated_passphrase_clamps_word_count() {
+    // Use a separator that cannot appear in the EFF wordlist so a generated
+    // word such as "yo-yo" cannot be mistaken for two words.
+    const SEPARATOR: &str = "|";
+
     // Below the floor: clamped up to MIN_PASSPHRASE_WORDS, never shorter.
-    let phrase = generate_passphrase(1, "-").unwrap();
-    assert_eq!(phrase.split('-').count(), MIN_PASSPHRASE_WORDS);
+    let phrase = generate_passphrase(1, SEPARATOR).unwrap();
+    assert_eq!(phrase.split(SEPARATOR).count(), MIN_PASSPHRASE_WORDS);
     // Above the ceiling: clamped down to MAX_PASSPHRASE_WORDS.
-    let phrase = generate_passphrase(50, "-").unwrap();
-    assert_eq!(phrase.split('-').count(), MAX_PASSPHRASE_WORDS);
+    let phrase = generate_passphrase(50, SEPARATOR).unwrap();
+    assert_eq!(phrase.split(SEPARATOR).count(), MAX_PASSPHRASE_WORDS);
 }
 
 #[test]

desktop/src/features/agents/lib/agentParallelism.test.mjs

@@ -0,0 +1,20 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  DEFAULT_AGENT_PARALLELISM,
+  resolveAgentParallelism,
+} from "./agentParallelism.ts";
+
+test("parallelism uses the app default only when input and definition omit it", () => {
+  assert.equal(
+    resolveAgentParallelism(undefined, undefined),
+    DEFAULT_AGENT_PARALLELISM,
+  );
+  assert.equal(
+    resolveAgentParallelism(undefined, null),
+    DEFAULT_AGENT_PARALLELISM,
+  );
+  assert.equal(resolveAgentParallelism(undefined, 4), 4);
+  assert.equal(resolveAgentParallelism(2, 4), 2);
+});

desktop/src/features/agents/lib/agentParallelism.ts

@@ -0,0 +1,18 @@
+/**
+ * Desktop-managed agents materialize this value when neither the create input
+ * nor the linked definition sets parallelism. Keep in sync with
+ * `managed_agents::DEFAULT_AGENT_PARALLELISM` in the Tauri backend.
+ */
+export const DEFAULT_AGENT_PARALLELISM = 10;
+
+export const AGENT_PARALLELISM_PLACEHOLDER = `App default (${DEFAULT_AGENT_PARALLELISM})`;
+export const AGENT_PARALLELISM_HELP = `Leave blank to use the app default (currently ${DEFAULT_AGENT_PARALLELISM}). Custom values may be 1–32.`;
+export const EDIT_AGENT_PARALLELISM_HELP =
+  "Current value for this agent. Custom values may be 1–32.";
+
+export function resolveAgentParallelism(
+  input: number | undefined,
+  definition: number | null | undefined,
+): number {
+  return input ?? definition ?? DEFAULT_AGENT_PARALLELISM;
+}

desktop/src/features/agents/ui/EditAgentAdvancedFields.tsx

@@ -11,6 +11,7 @@ import {
 import type { AgentPersona } from "@/shared/api/types";
 import { BuzzAgentModelTuningFields } from "./buzzAgentModelTuningFields";
 import { isBuzzAgentRuntime } from "./buzzAgentConfig";
+import { EDIT_AGENT_PARALLELISM_HELP } from "../lib/agentParallelism";
 
 export function EditAgentAdvancedFields({
   acpCommand,
@@ -173,10 +174,14 @@ export function EditAgentAdvancedFields({
             id="edit-agent-parallelism"
             inputMode="numeric"
             onChange={(event) => onParallelismChange(event.target.value)}
-            placeholder="1"
+            placeholder="Current value"
+            type="text"
             value={parallelism}
           />
         </div>
+        <p className="text-xs text-muted-foreground">
+          {EDIT_AGENT_PARALLELISM_HELP}
+        </p>
       </div>
 
       {/* Relay URL: intentionally no editor. The legacy per-record relay pin

desktop/src/features/agents/ui/PersonaAdvancedFields.tsx

@@ -4,6 +4,10 @@ import { EnvVarsEditor, type EnvVarsValue } from "./EnvVarsEditor";
 import { CreateAgentRespondToField } from "./RespondToField";
 import type { PersonaBehaviorDraft } from "./personaBehaviorDraft";
 import { isBuzzAgentRuntime } from "./buzzAgentConfig";
+import {
+  AGENT_PARALLELISM_HELP,
+  AGENT_PARALLELISM_PLACEHOLDER,
+} from "../lib/agentParallelism";
 import { BuzzAgentModelTuningFields } from "./buzzAgentModelTuningFields";
 import {
   CARD_MINT_KEY_ANNOTATIONS,
@@ -83,7 +87,7 @@ export function PersonaAdvancedFields({
           >
             <Input
               className={cn(
-                "h-8 px-0 py-0 leading-6",
+                "h-8 px-0 py-0 leading-6 [appearance:textfield] [&::-webkit-inner-spin-button]:appearance-none [&::-webkit-outer-spin-button]:appearance-none",
                 PERSONA_FIELD_CONTROL_CLASS,
               )}
               disabled={disabled}
@@ -97,13 +101,13 @@ export function PersonaAdvancedFields({
                   parallelism: event.target.value,
                 })
               }
-              placeholder="1"
+              placeholder={AGENT_PARALLELISM_PLACEHOLDER}
               type="number"
               value={behaviorDraft.parallelism}
             />
           </div>
           <p className="text-xs text-muted-foreground">
-            How many conversations each running instance handles at once (1–32).
+            {AGENT_PARALLELISM_HELP}
           </p>
         </div>
       </div>

desktop/src/testing/e2eBridge.ts

@@ -12,6 +12,7 @@ import {
 
 import { relayClient } from "@/shared/api/relayClient";
 import { activateRateLimit } from "@/shared/api/relayRateLimitGate";
+import { resolveAgentParallelism } from "@/features/agents/lib/agentParallelism";
 import type { ConnectionState } from "@/shared/api/relayClientShared";
 import type { ChannelTemplate, RelayEvent } from "@/shared/api/types";
 import { getMarkdownParseCount } from "@/shared/ui/markdown/nodeCache";
@@ -8075,8 +8076,10 @@ async function handleCreateManagedAgent(
     args.input.respondTo !== undefined
       ? (args.input.respondToAllowlist ?? [])
       : (linkedPersona?.respond_to_allowlist ?? []);
-  const mintParallelism =
-    args.input.parallelism ?? linkedPersona?.parallelism ?? 1;
+  const mintParallelism = resolveAgentParallelism(
+    args.input.parallelism,
+    linkedPersona?.parallelism,
+  );
   const personaAvatarUrl =
     args.input.personaId === undefined
       ? null