From ec8b9810b4231cd6a5c69ccd930b6c50999fc997 Mon Sep 17 00:00:00 2001
From: Adam <2363879+adamdotdevin@users.noreply.github.com>
Date: Tue, 7 Apr 2026 11:06:23 -0500
Subject: feat(app): better subagent experience (#20708)

---
 packages/ui/src/components/basic-tool.css   |  92 +++++++++++++++++
 packages/ui/src/components/basic-tool.tsx   | 142 +++++++++++++++-----------
 packages/ui/src/components/collapsible.css  |   5 +
 packages/ui/src/components/message-part.tsx | 150 ++++++++++++++++++++++------
 packages/ui/src/context/data.tsx            |   4 +
 5 files changed, 307 insertions(+), 86 deletions(-)

(limited to 'packages/ui/src')

diff --git a/packages/ui/src/components/basic-tool.css b/packages/ui/src/components/basic-tool.css
index f52a5e576..198412dcb 100644
--- a/packages/ui/src/components/basic-tool.css
+++ b/packages/ui/src/components/basic-tool.css
@@ -7,6 +7,21 @@
   gap: 0px;
   justify-content: flex-start;
 
+  &[data-clickable="true"] {
+    cursor: pointer;
+  }
+
+  &[data-hide-details="true"] {
+    [data-slot="basic-tool-tool-trigger-content"] {
+      flex: 1 1 auto;
+      max-width: 100%;
+    }
+
+    [data-slot="basic-tool-tool-info"] {
+      flex: 1 1 auto;
+    }
+  }
+
   [data-slot="basic-tool-tool-trigger-content"] {
     flex: 0 1 auto;
     width: auto;
@@ -165,3 +180,80 @@
     flex-shrink: 0;
   }
 }
+
+[data-component="task-tool-card"] {
+  width: 100%;
+  min-width: 0;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 8px 12px;
+  border-radius: 6px;
+  border: 1px solid var(--border-weak-base, rgba(255, 255, 255, 0.08));
+  background: color-mix(in srgb, var(--background-base) 92%, transparent);
+  transition:
+    border-color 0.15s ease,
+    background-color 0.15s ease,
+    color 0.15s ease;
+
+  [data-slot="basic-tool-tool-info-structured"] {
+    flex: 1 1 auto;
+    min-width: 0;
+  }
+
+  [data-slot="basic-tool-tool-info-main"] {
+    flex: 1 1 auto;
+    min-width: 0;
+    align-items: center;
+  }
+
+  [data-component="task-tool-spinner"] {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    flex-shrink: 0;
+
+    [data-component="spinner"] {
+      width: 16px;
+      height: 16px;
+    }
+  }
+
+  [data-component="task-tool-action"] {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    flex-shrink: 0;
+    color: var(--icon-weak);
+    margin-left: auto;
+    opacity: 0;
+    transition:
+      opacity 0.15s ease,
+      color 0.15s ease;
+  }
+
+  [data-component="task-tool-title"] {
+    flex-shrink: 0;
+    font-family: var(--font-family-sans);
+    font-size: 14px;
+    font-style: normal;
+    font-weight: var(--font-weight-medium);
+    line-height: var(--line-height-large);
+    letter-spacing: var(--letter-spacing-normal);
+    text-transform: capitalize;
+  }
+
+  [data-slot="basic-tool-tool-subtitle"] {
+    color: var(--text-strong);
+  }
+
+  &:hover,
+  &:focus-visible {
+    border-color: var(--border-weak-base, rgba(255, 255, 255, 0.08));
+    background: color-mix(in srgb, var(--background-stronger) 88%, transparent);
+
+    [data-component="task-tool-action"] {
+      opacity: 1;
+    }
+  }
+}
diff --git a/packages/ui/src/components/basic-tool.tsx b/packages/ui/src/components/basic-tool.tsx
index a02fe941b..7d18dfacd 100644
--- a/packages/ui/src/components/basic-tool.tsx
+++ b/packages/ui/src/components/basic-tool.tsx
@@ -34,6 +34,9 @@ export interface BasicToolProps {
   locked?: boolean
   animated?: boolean
   onSubtitleClick?: () => void
+  onTriggerClick?: JSX.EventHandlerUnion<HTMLElement, MouseEvent>
+  triggerHref?: string
+  clickable?: boolean
 }
 
 const SPRING = { type: "spring" as const, visualDuration: 0.35, bounce: 0 }
@@ -121,74 +124,101 @@ export function BasicTool(props: BasicToolProps) {
     setState("open", value)
   }
 
-  return (
-    <Collapsible open={open()} onOpenChange={handleOpenChange} class="tool-collapsible">
-      <Collapsible.Trigger>
-        <div data-component="tool-trigger">
-          <div data-slot="basic-tool-tool-trigger-content">
-            <div data-slot="basic-tool-tool-info">
-              <Switch>
-                <Match when={isTriggerTitle(props.trigger) && props.trigger}>
-                  {(trigger) => (
-                    <div data-slot="basic-tool-tool-info-structured">
-                      <div data-slot="basic-tool-tool-info-main">
+  const trigger = () => (
+    <div
+      data-component="tool-trigger"
+      data-clickable={props.clickable ? "true" : undefined}
+      data-hide-details={props.hideDetails ? "true" : undefined}
+    >
+      <div data-slot="basic-tool-tool-trigger-content">
+        <div data-slot="basic-tool-tool-info">
+          <Switch>
+            <Match when={isTriggerTitle(props.trigger) && props.trigger}>
+              {(title) => (
+                <div data-slot="basic-tool-tool-info-structured">
+                  <div data-slot="basic-tool-tool-info-main">
+                    <span
+                      data-slot="basic-tool-tool-title"
+                      classList={{
+                        [title().titleClass ?? ""]: !!title().titleClass,
+                      }}
+                    >
+                      <TextShimmer text={title().title} active={pending()} />
+                    </span>
+                    <Show when={!pending()}>
+                      <Show when={title().subtitle}>
                         <span
-                          data-slot="basic-tool-tool-title"
+                          data-slot="basic-tool-tool-subtitle"
                           classList={{
-                            [trigger().titleClass ?? ""]: !!trigger().titleClass,
+                            [title().subtitleClass ?? ""]: !!title().subtitleClass,
+                            clickable: !!props.onSubtitleClick,
+                          }}
+                          onClick={(e) => {
+                            if (props.onSubtitleClick) {
+                              e.stopPropagation()
+                              props.onSubtitleClick()
+                            }
                           }}
                         >
-                          <TextShimmer text={trigger().title} active={pending()} />
+                          {title().subtitle}
                         </span>
-                        <Show when={!pending()}>
-                          <Show when={trigger().subtitle}>
+                      </Show>
+                      <Show when={title().args?.length}>
+                        <For each={title().args}>
+                          {(arg) => (
                             <span
-                              data-slot="basic-tool-tool-subtitle"
+                              data-slot="basic-tool-tool-arg"
                               classList={{
-                                [trigger().subtitleClass ?? ""]: !!trigger().subtitleClass,
-                                clickable: !!props.onSubtitleClick,
-                              }}
-                              onClick={(e) => {
-                                if (props.onSubtitleClick) {
-                                  e.stopPropagation()
-                                  props.onSubtitleClick()
-                                }
+                                [title().argsClass ?? ""]: !!title().argsClass,
                               }}
                             >
-                              {trigger().subtitle}
+                              {arg}
                             </span>
-                          </Show>
-                          <Show when={trigger().args?.length}>
-                            <For each={trigger().args}>
-                              {(arg) => (
-                                <span
-                                  data-slot="basic-tool-tool-arg"
-                                  classList={{
-                                    [trigger().argsClass ?? ""]: !!trigger().argsClass,
-                                  }}
-                                >
-                                  {arg}
-                                </span>
-                              )}
-                            </For>
-                          </Show>
-                        </Show>
-                      </div>
-                      <Show when={!pending() && trigger().action}>
-                        <span data-slot="basic-tool-tool-action">{trigger().action}</span>
+                          )}
+                        </For>
                       </Show>
-                    </div>
-                  )}
-                </Match>
-                <Match when={true}>{props.trigger as JSX.Element}</Match>
-              </Switch>
-            </div>
-          </div>
-          <Show when={props.children && !props.hideDetails && !props.locked && !pending()}>
-            <Collapsible.Arrow />
-          </Show>
+                    </Show>
+                  </div>
+                  <Show when={!pending() && title().action}>
+                    <span data-slot="basic-tool-tool-action">{title().action}</span>
+                  </Show>
+                </div>
+              )}
+            </Match>
+            <Match when={true}>{props.trigger as JSX.Element}</Match>
+          </Switch>
         </div>
-      </Collapsible.Trigger>
+      </div>
+      <Show when={props.children && !props.hideDetails && !props.locked && !pending()}>
+        <Collapsible.Arrow />
+      </Show>
+    </div>
+  )
+
+  return (
+    <Collapsible open={open()} onOpenChange={handleOpenChange} class="tool-collapsible">
+      <Show
+        when={props.triggerHref}
+        fallback={
+          <Collapsible.Trigger
+            data-hide-details={props.hideDetails ? "true" : undefined}
+            onClick={props.onTriggerClick}
+          >
+            {trigger()}
+          </Collapsible.Trigger>
+        }
+      >
+        {(href) => (
+          <Collapsible.Trigger
+            as="a"
+            href={href()}
+            data-hide-details={props.hideDetails ? "true" : undefined}
+            onClick={props.onTriggerClick}
+          >
+            {trigger()}
+          </Collapsible.Trigger>
+        )}
+      </Show>
       <Show when={props.animated && props.children && !props.hideDetails}>
         <div
           ref={contentRef}
diff --git a/packages/ui/src/components/collapsible.css b/packages/ui/src/components/collapsible.css
index a999f6298..608ca6e0e 100644
--- a/packages/ui/src/components/collapsible.css
+++ b/packages/ui/src/components/collapsible.css
@@ -62,6 +62,11 @@
       cursor: not-allowed;
     }
 
+    &[data-hide-details="true"] {
+      height: auto;
+      align-items: stretch;
+    }
+
     [data-slot="collapsible-arrow"] {
       flex-shrink: 0;
       width: 24px;
diff --git a/packages/ui/src/components/message-part.tsx b/packages/ui/src/components/message-part.tsx
index 03477e5a7..3627eca40 100644
--- a/packages/ui/src/components/message-part.tsx
+++ b/packages/ui/src/components/message-part.tsx
@@ -22,6 +22,7 @@ import {
   Message as MessageType,
   Part as PartType,
   ReasoningPart,
+  Session,
   TextPart,
   ToolPart,
   UserMessage,
@@ -49,6 +50,7 @@ import { getDirectory as _getDirectory, getFilename } from "@opencode-ai/util/pa
 import { checksum } from "@opencode-ai/util/encode"
 import { Tooltip } from "./tooltip"
 import { IconButton } from "./icon-button"
+import { Spinner } from "./spinner"
 import { TextShimmer } from "./text-shimmer"
 import { AnimatedCountList } from "./tool-count-summary"
 import { ToolStatusTitle } from "./tool-status-title"
@@ -274,6 +276,47 @@ function agentTitle(i18n: UiI18n, type?: string) {
   return i18n.t("ui.tool.agent", { type })
 }
 
+const agentTones: Record<string, string> = {
+  ask: "var(--icon-agent-ask-base)",
+  build: "var(--icon-agent-build-base)",
+  docs: "var(--icon-agent-docs-base)",
+  plan: "var(--icon-agent-plan-base)",
+}
+
+const agentPalette = [
+  "var(--icon-agent-ask-base)",
+  "var(--icon-agent-build-base)",
+  "var(--icon-agent-docs-base)",
+  "var(--icon-agent-plan-base)",
+  "var(--syntax-info)",
+  "var(--syntax-success)",
+  "var(--syntax-warning)",
+  "var(--syntax-property)",
+  "var(--syntax-constant)",
+  "var(--text-diff-add-base)",
+  "var(--text-diff-delete-base)",
+  "var(--icon-warning-base)",
+]
+
+function tone(name: string) {
+  let hash = 0
+  for (const char of name) hash = (hash * 31 + char.charCodeAt(0)) >>> 0
+  return agentPalette[hash % agentPalette.length]
+}
+
+function taskAgent(
+  raw: unknown,
+  list?: readonly { name: string; color?: string }[],
+): { name?: string; color?: string } {
+  if (typeof raw !== "string" || !raw) return {}
+  const key = raw.toLowerCase()
+  const item = list?.find((entry) => entry.name === raw || entry.name.toLowerCase() === key)
+  return {
+    name: item?.name ?? `${raw[0]!.toUpperCase()}${raw.slice(1)}`,
+    color: item?.color ?? agentTones[key] ?? tone(key),
+  }
+}
+
 export function getToolInfo(tool: string, input: any = {}): ToolInfo {
   const i18n = useI18n()
   switch (tool) {
@@ -402,6 +445,27 @@ function sessionLink(id: string | undefined, path: string, href?: (id: string) =
   return `${path.slice(0, idx)}/session/${id}`
 }
 
+function currentSession(path: string) {
+  return path.match(/\/session\/([^/?#]+)/)?.[1]
+}
+
+function taskSession(
+  input: Record<string, any>,
+  path: string,
+  sessions: Session[] | undefined,
+  agents?: readonly { name: string; color?: string }[],
+) {
+  const parentID = currentSession(path)
+  if (!parentID) return
+  const description = typeof input.description === "string" ? input.description : ""
+  const agent = taskAgent(input.subagent_type, agents).name
+  return (sessions ?? [])
+    .filter((session) => session.parentID === parentID && !session.time?.archived)
+    .filter((session) => (description ? session.title.startsWith(description) : true))
+    .filter((session) => (agent ? session.title.includes(`@${agent}`) : true))
+    .sort((a, b) => (b.time.created ?? 0) - (a.time.created ?? 0))[0]?.id
+}
+
 const CONTEXT_GROUP_TOOLS = new Set(["read", "glob", "grep", "list"])
 const HIDDEN_TOOLS = new Set(["todowrite"])
 
@@ -1678,13 +1742,14 @@ ToolRegistry.register({
     const data = useData()
     const i18n = useI18n()
     const location = useLocation()
-    const childSessionId = () => props.metadata.sessionId as string | undefined
-    const type = createMemo(() => {
-      const raw = props.input.subagent_type
-      if (typeof raw !== "string" || !raw) return undefined
-      return raw[0]!.toUpperCase() + raw.slice(1)
+    const childSessionId = createMemo(() => {
+      const value = props.metadata.sessionId
+      if (typeof value === "string" && value) return value
+      return taskSession(props.input, location.pathname, data.store.session, data.store.agent)
     })
-    const title = createMemo(() => agentTitle(i18n, type()))
+    const agent = createMemo(() => taskAgent(props.input.subagent_type, data.store.agent))
+    const title = createMemo(() => agent().name ?? i18n.t("ui.tool.agent.default"))
+    const tone = createMemo(() => agent().color)
     const subtitle = createMemo(() => {
       const value = props.input.description
       if (typeof value === "string" && value) return value
@@ -1693,37 +1758,62 @@ ToolRegistry.register({
     const running = createMemo(() => props.status === "pending" || props.status === "running")
 
     const href = createMemo(() => sessionLink(childSessionId(), location.pathname, data.sessionHref))
+    const clickable = createMemo(() => !!(childSessionId() && (data.navigateToSession || href())))
+
+    const open = () => {
+      const id = childSessionId()
+      if (!id) return
+      if (data.navigateToSession) {
+        data.navigateToSession(id)
+        return
+      }
+      const value = href()
+      if (value) window.location.assign(value)
+    }
 
-    const titleContent = () => <TextShimmer text={title()} active={running()} />
+    const navigate = (event: MouseEvent) => {
+      if (!data.navigateToSession) return
+      if (event.button !== 0 || event.altKey || event.ctrlKey || event.metaKey || event.shiftKey) return
+      event.preventDefault()
+      open()
+    }
 
     const trigger = () => (
-      <div data-slot="basic-tool-tool-info-structured">
-        <div data-slot="basic-tool-tool-info-main">
-          <span data-slot="basic-tool-tool-title" class="capitalize agent-title">
-            {titleContent()}
-          </span>
-          <Show when={subtitle()}>
-            <Switch>
-              <Match when={href()}>
-                <a
-                  data-slot="basic-tool-tool-subtitle"
-                  class="clickable subagent-link"
-                  href={href()!}
-                  onClick={(e) => e.stopPropagation()}
-                >
-                  {subtitle()}
-                </a>
-              </Match>
-              <Match when={true}>
-                <span data-slot="basic-tool-tool-subtitle">{subtitle()}</span>
-              </Match>
-            </Switch>
-          </Show>
+      <div data-component="task-tool-card">
+        <div data-slot="basic-tool-tool-info-structured">
+          <div data-slot="basic-tool-tool-info-main">
+            <Show when={running()}>
+              <span data-component="task-tool-spinner" style={{ color: tone() ?? "var(--icon-interactive-base)" }}>
+                <Spinner />
+              </span>
+            </Show>
+            <span data-component="task-tool-title" style={{ color: tone() ?? "var(--text-strong)" }}>
+              {title()}
+            </span>
+            <Show when={subtitle()}>
+              <span data-slot="basic-tool-tool-subtitle">{subtitle()}</span>
+            </Show>
+          </div>
         </div>
+        <Show when={clickable()}>
+          <div data-component="task-tool-action">
+            <Icon name="square-arrow-top-right" size="small" />
+          </div>
+        </Show>
       </div>
     )
 
-    return <BasicTool icon="task" status={props.status} trigger={trigger()} hideDetails />
+    return (
+      <BasicTool
+        icon="task"
+        status={props.status}
+        trigger={trigger()}
+        hideDetails
+        triggerHref={href()}
+        clickable={clickable()}
+        onTriggerClick={navigate}
+      />
+    )
   },
 })
 
diff --git a/packages/ui/src/context/data.tsx b/packages/ui/src/context/data.tsx
index e116199eb..93368c2a0 100644
--- a/packages/ui/src/context/data.tsx
+++ b/packages/ui/src/context/data.tsx
@@ -3,6 +3,10 @@ import { createSimpleContext } from "./helper"
 import { PreloadMultiFileDiffResult } from "@pierre/diffs/ssr"
 
 type Data = {
+  agent?: {
+    name: string
+    color?: string
+  }[]
   provider?: ProviderListResponse
   session: Session[]
   session_status: {
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