From e2d6c4bd4a2547797f0be993434eb20393d827c0 Mon Sep 17 00:00:00 2001
From: Luke Parker <10430890+Hona@users.noreply.github.com>
Date: Thu, 27 Aug 2026 14:36:27 +1000
Subject: [PATCH] fix(app): merge adjacent patches inside used groups (#45477)

---
 ...ession-timeline-reducer-projection.spec.ts | 56 +++++++++++++
 .../component-tests/patch-group.spec.ts       | 34 ++++++++
 .../src/tools/tool-group.stories.tsx          | 78 ++++++++++++++++++-
 .../session-ui/src/tools/tool-renderer.tsx    | 46 +++++++----
 4 files changed, 198 insertions(+), 16 deletions(-)
 create mode 100644 packages/session-ui/component-tests/patch-group.spec.ts

diff --git a/packages/app/e2e/regression/session-timeline-reducer-projection.spec.ts b/packages/app/e2e/regression/session-timeline-reducer-projection.spec.ts
index e90c218dc51..189ff9ea2b5 100644
--- a/packages/app/e2e/regression/session-timeline-reducer-projection.spec.ts
+++ b/packages/app/e2e/regression/session-timeline-reducer-projection.spec.ts
@@ -1,4 +1,5 @@
 import { expect, test } from "@playwright/test"
+import { createTwoFilesPatch } from "diff"
 import {
   assistantMessage,
   completedAssistantInfo,
@@ -78,6 +79,61 @@ test("leaves tools expanded by settings outside the collapsed stack", async ({ p
   await expect(page.locator('[data-timeline-spacing="tool"]')).toHaveCSS("padding-top", "8px")
 })
 
+test("combines follow-up patches into one three-file stack inside Used", async ({ page }) => {
+  const file = (path: string, before: number, after: number) => ({
+    file: path,
+    status: "modified",
+    additions: 1,
+    deletions: 1,
+    patch: createTwoFilesPatch(
+      path,
+      path,
+      `export const value = ${before}\n`,
+      `export const value = ${after}\n`,
+      "",
+      "",
+      { context: Infinity },
+    ),
+  })
+  const timeline = await setupTimeline(page, {
+    messages: [
+      userMessage(),
+      assistantMessage([
+        shell("patch_shell", "completed"),
+        toolPart(
+          "patch_first",
+          "patch",
+          "completed",
+          {},
+          {
+            metadata: { files: [file("src/a.ts", 0, 1), file("src/b.ts", 0, 1)] },
+          },
+        ),
+      ]),
+    ],
+  })
+  const group = page.locator('[data-component="collapsed-tool-group"]')
+  await group.getByRole("button", { name: "Used Shell, Patch", exact: true }).click()
+  await expect(group.getByText("2 files", { exact: true })).toBeVisible()
+  await timeline.send(
+    partUpdated(
+      toolPart(
+        "patch_next",
+        "patch",
+        "completed",
+        {},
+        {
+          metadata: { files: [file("src/a.ts", 1, 2), file("src/c.ts", 0, 1)] },
+        },
+      ),
+    ),
+  )
+  await expect(group.locator('[data-component="tag"]')).toHaveText("3")
+  await expect(group.locator('[data-component="apply-patch-tool"]')).toHaveCount(1)
+  await expect(group.getByText("3 files", { exact: true })).toBeVisible()
+  await expect(group.locator('[data-slot="apply-patch-filename"]')).toHaveText(["a.ts", "b.ts", "c.ts"])
+})
+
 test("keeps failed search calls and their error cards inside the collapsed stack", async ({ page }) => {
   const parts = [
     toolPart(
diff --git a/packages/session-ui/component-tests/patch-group.spec.ts b/packages/session-ui/component-tests/patch-group.spec.ts
new file mode 100644
index 00000000000..9abc2667d6a
--- /dev/null
+++ b/packages/session-ui/component-tests/patch-group.spec.ts
@@ -0,0 +1,34 @@
+import { expect, story } from "../../storybook/playwright/story"
+
+story("merges follow-up patches into one stack with a distinct file count", async ({ mount }, info) => {
+  const root = await mount("current-tool-group--patch-follow-ups")
+  const group = root.locator('[data-component="collapsed-tool-group"]')
+  const patches = group.locator('[data-component="apply-patch-tool"]')
+  await expect(patches).toHaveCount(1)
+  await expect(patches.getByText("2 files", { exact: true })).toBeVisible()
+  const first = patches.locator('[data-scope="apply-patch"] button').filter({ hasText: "a.ts" })
+  await first.click()
+  await expect(first).toHaveAttribute("aria-expanded", "true")
+  await root.getByRole("button", { name: "Start follow-up patch" }).click()
+  await expect(group.locator('[data-component="tag"]')).toHaveText("3")
+  await expect(patches).toHaveCount(1)
+  await expect(patches.getByText("2 files", { exact: true })).toBeVisible()
+  await root.getByRole("button", { name: "Finish follow-up patch" }).click()
+  await expect(patches).toHaveCount(1)
+  await expect(patches.getByText("3 files", { exact: true })).toBeVisible()
+  await expect(patches.locator('[data-slot="apply-patch-filename"]')).toHaveText(["a.ts", "b.ts", "c.ts"])
+  await expect(first).toHaveAttribute("aria-expanded", "true")
+  await expect(patches.locator('[data-component="file"]')).toBeVisible()
+  await group.screenshot({ path: info.outputPath("merged.png") })
+})
+
+for (const separator of ["shell", "error"]) {
+  story(`does not merge patches across an intervening ${separator}`, async ({ mount }) => {
+    const root = await mount("current-tool-group--patch-follow-ups", { args: { separator } })
+    await root.getByRole("button", { name: "Finish follow-up patch" }).click()
+    const group = root.locator('[data-component="collapsed-tool-group"]')
+    await expect(group.locator('[data-component="apply-patch-tool"]')).toHaveCount(2)
+    await expect(group.locator('[data-slot="apply-patch-filename"]')).toHaveText(["a.ts", "b.ts", "a.ts", "c.ts"])
+    if (separator === "error") await expect(group.locator('[data-kind="tool-error-card"]')).toBeVisible()
+  })
+}
diff --git a/packages/session-ui/src/tools/tool-group.stories.tsx b/packages/session-ui/src/tools/tool-group.stories.tsx
index 711aeaa175c..6424aecac31 100644
--- a/packages/session-ui/src/tools/tool-group.stories.tsx
+++ b/packages/session-ui/src/tools/tool-group.stories.tsx
@@ -1,4 +1,6 @@
-import { createSignal } from "solid-js"
+import { createMemo, createSignal } from "solid-js"
+import { createStore } from "solid-js/store"
+import { createTwoFilesPatch } from "diff"
 import { CurrentSessionProviders } from "../storybook/current-session-story"
 import { storyDocument, storyTool } from "../storybook/current-session-scenarios"
 import { CurrentContextToolGroup } from "./tool-renderer"
@@ -33,3 +35,77 @@ export const MixedTools = {
     )
   },
 }
+
+export const PatchFollowUps = {
+  args: { separator: "none" },
+  argTypes: { separator: { control: "select", options: ["none", "shell", "error"] } },
+  render: (args: { separator: string }) => {
+    const [state, setState] = createStore({ phase: "initial", open: true })
+    const file = (path: string, before: number, after: number) => ({
+      file: path,
+      status: "modified",
+      additions: 1,
+      deletions: 1,
+      patch: createTwoFilesPatch(
+        path,
+        path,
+        `export const value = ${before}\n`,
+        `export const value = ${after}\n`,
+        "",
+        "",
+        { context: Infinity },
+      ),
+    })
+    const tools = createMemo(() => [
+      storyTool("patch_shell", "shell", "completed", { command: "printf checked" }, { output: "checked" }),
+      storyTool(
+        "patch_first",
+        "patch",
+        "completed",
+        {},
+        {
+          metadata: { files: [file("src/a.ts", 0, 1), file("src/b.ts", 0, 1)] },
+        },
+      ),
+      ...(state.phase === "initial"
+        ? []
+        : [
+            ...(args.separator === "shell"
+              ? [storyTool("patch_separator", "shell", "completed", { command: "printf checked" })]
+              : []),
+            ...(args.separator === "error"
+              ? [storyTool("patch_error", "patch", "error", {}, { error: "Patch failed" })]
+              : []),
+            storyTool(
+              "patch_next",
+              "patch",
+              state.phase === "running" ? "running" : "completed",
+              {},
+              {
+                metadata: state.phase === "running" ? {} : { files: [file("src/a.ts", 1, 2), file("src/c.ts", 0, 1)] },
+              },
+            ),
+          ]),
+    ])
+    return (
+      <section class="mx-auto flex w-full max-w-[860px] flex-col gap-4 p-6">
+        <div class="flex flex-wrap gap-3">
+          <button type="button" onClick={() => setState("phase", "running")}>
+            Start follow-up patch
+          </button>
+          <button type="button" onClick={() => setState("phase", "completed")}>
+            Finish follow-up patch
+          </button>
+        </div>
+        <CurrentSessionProviders document={storyDocument(tools())}>
+          <CurrentContextToolGroup
+            tools={tools()}
+            busy={state.phase === "running"}
+            open={state.open}
+            onOpenChange={(open) => setState("open", open)}
+          />
+        </CurrentSessionProviders>
+      </section>
+    )
+  },
+}
diff --git a/packages/session-ui/src/tools/tool-renderer.tsx b/packages/session-ui/src/tools/tool-renderer.tsx
index db08b99ad69..a84d2a4ce2d 100644
--- a/packages/session-ui/src/tools/tool-renderer.tsx
+++ b/packages/session-ui/src/tools/tool-renderer.tsx
@@ -502,6 +502,15 @@ export function CurrentContextToolGroup(props: {
   const items = createMemo(() =>
     props.tools.reduce<SessionMessageAssistantTool[][]>((groups, tool) => {
       const previous = groups.at(-1)
+      if (
+        tool.name === "patch" &&
+        tool.state.status !== "error" &&
+        previous?.[0]?.name === "patch" &&
+        previous[0].state.status !== "error"
+      ) {
+        previous.push(tool)
+        return groups
+      }
       if (
         tool.name === "skill" &&
         tool.state.status !== "error" &&
@@ -567,19 +576,26 @@ export function CurrentContextToolGroup(props: {
                       <Show
                         when={tool().name === "skill" && group().length > 1 && skills().length === group().length}
                         fallback={
-                          <ToolDisplay
-                            id={tool().id}
-                            tool={tool().name}
-                            input={currentToolInput(tool())}
-                            metadata={currentToolMetadata(tool())}
-                            output={currentToolOutput(tool())}
-                            error={currentToolError(tool())}
-                            status={tool().state.status}
-                            defaultOpen={false}
-                            deferContent
-                            virtualizeDiff={false}
-                            onContentRendered={props.onSizeChange}
-                          />
+                          <Show
+                            when={tool().name === "patch" && tool().state.status !== "error"}
+                            fallback={
+                              <ToolDisplay
+                                id={tool().id}
+                                tool={tool().name}
+                                input={currentToolInput(tool())}
+                                metadata={currentToolMetadata(tool())}
+                                output={currentToolOutput(tool())}
+                                error={currentToolError(tool())}
+                                status={tool().state.status}
+                                defaultOpen={false}
+                                deferContent
+                                virtualizeDiff={false}
+                                onContentRendered={props.onSizeChange}
+                              />
+                            }
+                          >
+                            <CurrentFileToolGroup tools={group()} onSizeChange={props.onSizeChange} />
+                          </Show>
                         }
                       >
                         <div
@@ -662,8 +678,8 @@ export function CurrentContextToolGroup(props: {
 
 export function CurrentFileToolGroup(props: {
   tools: SessionMessageAssistantTool[]
-  fileOpen: (path: string) => boolean | undefined
-  onFileOpenChange: (path: string, open: boolean) => void
+  fileOpen?: (path: string) => boolean | undefined
+  onFileOpenChange?: (path: string, open: boolean) => void
   onSizeChange?: () => void
 }) {
   const files = createMemo((previous: { key: string; value: unknown }[]) => {