Strip the sub-agent report envelope from expanded task details

A task tool result wraps a sub-agent's reply as `Sub-agent "desc"
reported:` followed by raw `## Summary` / `## Findings` markdown
headings. The collapsed one-line preview already stripped this
envelope, but the expanded detail behind the arrow rendered the
result text as plain lines, so the raw prefix and literal `##`
markers leaked straight into the transcript.

Give "task" results the same always-curated treatment tool_search
catalogues already get in resultSummary, and strip the envelope and
heading markers from the text that becomes the expanded body.

Author: TheGreatAxios

src/tui-opentui/mcp-view.test.ts

@@ -214,6 +214,36 @@ describe("collapsed tool results", () => {
     expect(row.summary).toBe("Read Linear project Alpha")
   })
 
+  test("a sub-agent report collapses to its summary line, envelope and headings stripped from the detail", () => {
+    const row = toolResultRow({
+      name: "task",
+      content:
+        'Sub-agent "explore callers" reported:\n\n## Summary\nFound 3 call sites in src/tui-opentui.\n\n## Findings\n- shell.ts line 40\n- diff.ts line 12',
+    })
+    expect(row.summary).toBe("Found 3 call sites in src/tui-opentui.")
+    expect(isCollapsibleRow(row)).toBe(true)
+    const detailText = (row.detail ?? [])
+      .map((line) => line.map((seg) => seg.text).join(""))
+      .join("\n")
+    expect(detailText).not.toContain("Sub-agent")
+    expect(detailText).not.toContain("## ")
+    expect(detailText).toContain("Found 3 call sites in src/tui-opentui.")
+    expect(detailText).toContain("Findings")
+  })
+
+  test("a short sub-agent report is still curated, not left as raw envelope", () => {
+    const row = toolResultRow({
+      name: "task",
+      content: 'Sub-agent "quick check" reported:\n\n## Summary\nAll clear.',
+    })
+    expect(row.summary).toBe("All clear.")
+    const detailText = (row.detail ?? [])
+      .map((line) => line.map((seg) => seg.text).join(""))
+      .join("\n")
+    expect(detailText).not.toContain("Sub-agent")
+    expect(detailText).not.toContain("## ")
+  })
+
   test("an error result is neither summarised nor collapsed", () => {
     const row = toolResultRow({
       name: "mcp__linear__list_projects",

src/tui-opentui/mcp-view.ts

@@ -26,7 +26,7 @@ import {
   recordScalar,
   type McpRecords,
 } from "../tui/mcp-result-format.js"
-import { summarizeToolResult } from "../tui/tool-formatter.js"
+import { stripTaskReportEnvelope, summarizeToolResult } from "../tui/tool-formatter.js"
 import type { StreamRow, StyledBodyLine } from "./stream.js"
 
 export type McpTone =
@@ -280,6 +280,9 @@ const DETAIL_TEXT_MAX = 72
 /** The tool a capability search arrives through; its result is a catalogue. */
 const TOOL_SEARCH_TOOL = "tool_search"
 
+/** The tool a sub-agent dispatch arrives through; its result is a report. */
+const TASK_TOOL = "task"
+
 function titleCase(word: string): string {
   return word.length === 0 ? word : `${word[0]!.toUpperCase()}${word.slice(1)}`
 }
@@ -448,6 +451,13 @@ function recordSummary(
  */
 function resultSummary(input: ToolResultRowInput): ResultSummary | null {
   const content = input.content
+  if (input.name === TASK_TOOL) {
+    // A worker's reply wraps a "Sub-agent ... reported:" / "## Summary"
+    // envelope. The one-line preview already strips it; the expanded detail
+    // must too, or the raw envelope and heading markers leak as plain text.
+    const { preview } = summarizeToolResult(input.name, content)
+    return { summary: preview, detail: bodyLines(stripTaskReportEnvelope(content)) }
+  }
   if (input.name === TOOL_SEARCH_TOOL) {
     const catalogue = toolCatalogueSummary(content)
     if (catalogue !== null) return catalogue

src/tui/tool-formatter.ts

@@ -424,6 +424,22 @@ function pathFromResult(toolName: string, content: string): string | null {
   return null;
 }
 
+/**
+ * Task tool results wrap a sub-agent's reply in `Sub-agent "desc" reported:`
+ * plus raw `## ` markdown headings. The transcript's expanded detail view
+ * renders plain text, so an unstripped heading would show its literal `##` —
+ * drop the envelope and heading markers, keeping the report's own words.
+ */
+export function stripTaskReportEnvelope(content: string): string {
+  const trimmed = content.trim();
+  const reported = trimmed.match(/^Sub-agent "([^"]*)" reported:\s*([\s\S]*)$/i);
+  const body = (reported?.[2] ?? trimmed).trim();
+  return body
+    .split("\n")
+    .map((line) => line.replace(/^##\s+/, ""))
+    .join("\n");
+}
+
 // Task tool results are either "Sub-agent \"desc\" reported:\n\n## Summary\n..."
 // or a cancel notice. Pull a one-line human preview without leaking markdown headers.
 function summarizeTaskResultPreview(content: string): string {