From bd36dcc172b3ea9cdd46ba771366be2265da254f Mon Sep 17 00:00:00 2001
From: Dax Raad <d@ironbay.co>
Date: Sun, 18 Oct 2026 16:12:21 -0400
Subject: [PATCH] feat(session-ui): show subagents ungrouped by default

---
 packages/session-ui/src/timeline/detail.ts    |  4 +-
 .../timeline/research-and-agents.stories.tsx  | 46 +++++++++++++++++++
 .../src/timeline/rows-current.test.ts         | 41 +++++++++++++++++
 3 files changed, 89 insertions(+), 2 deletions(-)

diff --git a/packages/session-ui/src/timeline/detail.ts b/packages/session-ui/src/timeline/detail.ts
index 3716935a55c..668a699fcd4 100644
--- a/packages/session-ui/src/timeline/detail.ts
+++ b/packages/session-ui/src/timeline/detail.ts
@@ -50,7 +50,7 @@ export const timelinePresets = [
       shell: { placement: "grouped", details: "collapsed" },
       edit: { placement: "grouped", details: "collapsed" },
       thinking: { placement: "grouped", details: "collapsed" },
-      subagents: { placement: "grouped" },
+      subagents: { placement: "separate" },
       notices: { placement: "grouped" },
       tools: { placement: "grouped" },
       commentary: { placement: "separate" },
@@ -62,7 +62,7 @@ export const timelinePresets = [
       shell: { placement: "hidden", details: "collapsed" },
       edit: { placement: "grouped", details: "collapsed" },
       thinking: { placement: "hidden", details: "collapsed" },
-      subagents: { placement: "grouped" },
+      subagents: { placement: "separate" },
       notices: { placement: "hidden" },
       tools: { placement: "hidden" },
       commentary: { placement: "separate" },
diff --git a/packages/session-ui/src/timeline/research-and-agents.stories.tsx b/packages/session-ui/src/timeline/research-and-agents.stories.tsx
index 43c98a60b0b..29d51b374e0 100644
--- a/packages/session-ui/src/timeline/research-and-agents.stories.tsx
+++ b/packages/session-ui/src/timeline/research-and-agents.stories.tsx
@@ -14,6 +14,7 @@ import {
   webResearchDocument,
 } from "../storybook/current-session-fixtures"
 import { storyDocument, storyPatchFile, storyTool } from "../storybook/current-session-scenarios"
+import { timelinePresets } from "./detail"
 import { SessionTimeline } from "./session-timeline"
 
 export default {
@@ -75,6 +76,51 @@ export const DelegateFocusedTasks = {
   ),
 }
 
+const delegationDocument = storyDocument([
+  storyTool("tool_delegation_glob", "glob", "completed", { pattern: "src/timeline/**/*.ts" }),
+  storyTool("tool_delegation_grep", "grep", "completed", { pattern: "timelineDetail" }),
+  storyTool("tool_delegation_read", "read", "completed", { path: "src/timeline/projection.ts" }),
+  storyTool(
+    "tool_delegation_explore",
+    "subagent",
+    "completed",
+    { agent: "explore", description: "Map the timeline grouping rules", prompt: "Find where tool rows are grouped." },
+    { output: "Grouping lives in the timeline projection.", metadata: { sessionID: "session_child_explore" } },
+  ),
+  storyTool(
+    "tool_delegation_review",
+    "subagent",
+    "completed",
+    { agent: "review", description: "Review the detail presets", prompt: "Check each timeline preset." },
+    { output: "Every preset is consistent.", metadata: { sessionID: "session_child_review" } },
+  ),
+  storyTool("tool_delegation_read_tests", "read", "completed", { path: "src/timeline/rows-current.test.ts" }),
+  storyTool("tool_delegation_grep_tests", "grep", "completed", { pattern: "subagent" }),
+  storyTool(
+    "tool_delegation_general",
+    "subagent",
+    "completed",
+    { agent: "general", description: "Run the focused timeline tests", prompt: "Run the timeline tests." },
+    { output: "All timeline tests pass.", metadata: { sessionID: "session_child_general" } },
+  ),
+  { type: "text", text: "Each delegated task keeps its own row while the reads and searches between them stay grouped." },
+])
+
+export const DelegateBetweenTools = {
+  args: { subagents: "separate" },
+  argTypes: { subagents: { control: { type: "inline-radio" }, options: ["separate", "grouped"] } },
+  render: (args: { subagents: "separate" | "grouped" }) => (
+    <section class="mx-auto min-h-screen w-full max-w-[720px] bg-v2-background-bg-base p-6">
+      <CurrentSessionProviders document={delegationDocument}>
+        <SessionTimeline
+          document={delegationDocument}
+          timelineDetail={{ ...timelinePresets[2].value, subagents: { placement: args.subagents } }}
+        />
+      </CurrentSessionProviders>
+    </section>
+  ),
+}
+
 function CodebaseExplorationStory() {
   const [state, setState] = createStore({ read: false, glob: false })
 
diff --git a/packages/session-ui/src/timeline/rows-current.test.ts b/packages/session-ui/src/timeline/rows-current.test.ts
index 9eb93268b3e..7192179193c 100644
--- a/packages/session-ui/src/timeline/rows-current.test.ts
+++ b/packages/session-ui/src/timeline/rows-current.test.ts
@@ -1104,6 +1104,47 @@ describe("current session timeline rows", () => {
     ])
   })
 
+  test.each([
+    {
+      name: "default",
+      grouped: false,
+      groups: [["context", "read", "grep"], ["part", "agent_1"], ["part", "agent_2"], ["context", "glob", "read_2"]],
+    },
+    { name: "opted in", grouped: true, groups: [["context", "read", "grep", "agent_1", "agent_2", "glob", "read_2"]] },
+  ])("gives each subagent its own row unless subagent grouping is enabled ($name)", (input) => {
+    const compact = timelinePresets.find((preset) => preset.id === "compact")!.value
+    const rows = Timeline.constructSessionMessageRows(
+      storyDocument([
+        storyTool("read", "read", "completed", { path: "src/a.ts" }),
+        storyTool("grep", "grep", "completed", { pattern: "agent" }),
+        storyTool("agent_1", "subagent", "completed", { agent: "explore", description: "Map the code" }),
+        storyTool("agent_2", "subagent", "completed", { agent: "general", description: "Check the tests" }),
+        storyTool("glob", "glob", "completed", { pattern: "*.ts" }),
+        storyTool("read_2", "read", "completed", { path: "src/b.ts" }),
+      ]).messages,
+      true,
+      { type: "idle" },
+      undefined,
+      false,
+      false,
+      undefined,
+      input.grouped ? { ...compact, subagents: { placement: "grouped" } } : compact,
+    ).rows
+
+    expect(
+      rows.flatMap((row) =>
+        !Predicate.isTagged(row, "AssistantPart")
+          ? []
+          : [
+              [
+                row.group.type,
+                ...(row.group.type === "part" ? [row.group.ref] : row.group.refs).map((ref) => ref.partID),
+              ],
+            ],
+      ),
+    ).toEqual(input.groups.map((group) => [...group]))
+  })
+
   test("merges adjacent separate reads into one read row split by other parts", () => {
     const rows = Timeline.constructSessionMessageRows(
       storyDocument([