[BUG] "Compacted (ctrl+o to see full summary)" — Ctrl+O never renders the compact summary, though it is stored in the JSONL with isVisibleInTranscriptOnly: true

Summary

After compaction the TUI prints:

⎿ Compacted (ctrl+o to see full summary)

Pressing Ctrl+O switches to Showing detailed transcript, but the compact summary is never rendered. The line stays collapsed exactly as before — no Compact summary block, no summary body, nothing. The affordance the UI advertises does not exist.

This is a rendering bug only: the summary text is persisted correctly in the session JSONL, and the record is even explicitly flagged for transcript display. The TUI just doesn't show it.

Environment

• Version: 2.1.220 (Claude Code CLI)
• OS: macOS 26.6 (Darwin 25.6.0)
• Terminal: iTerm2

Steps to reproduce

1. Run a long session, then run /compact (manual trigger; auto-compaction behaves the same).
2. After compaction, observe the collapsed line: Compacted (ctrl+o to see full summary).
3. Press Ctrl+O.
4. Footer changes to Showing detailed transcript · ctrl+o to toggle · ↑↓ scroll · v to open in code.
5. Scroll to the compaction point.

Expected

The full compact summary is displayed (as it used to be, rendered as a Compact summary block).

Actual

Only the same collapsed one-liner plus the post-compaction tool lines (Read …, Referenced file …, Skills restored …). The summary body is nowhere in the transcript view. Ctrl+O toggling has zero effect on that line.

Evidence that the data is present

From the session JSONL, the message immediately after the compact_boundary system record:

{
  "parentUuid": "90523a41-bb8b-4225-81fb-20444328ae75",
  "type": "user",
  "isVisibleInTranscriptOnly": true,
  "isCompactSummary": true,
  "uuid": "9bd2cd48-effd-4903-b247-cb1b2fad50cc",
  "timestamp": "2026-07-30T07:56:53.689Z",
  "sessionId": "d72da877-…",
  "version": "2.1.220",
  "message": {
    "role": "user",
    "content": "This session is being continued from a previous conversation that ran out of context. The summary below covers the earlier portion of the conversation.\n\nSummary:\n## 1. …"
  }
}

• message.content length: 12030 chars — the summary is complete.
• The preceding record is {"type":"system","subtype":"compact_boundary","compactMetadata":{"trigger":"manual","preTokens":897264,"postTokens":14684,…}}.
• Note "isVisibleInTranscriptOnly": true — this record is explicitly marked as the thing transcript mode should render, yet transcript mode skips it. That flag looks like the most likely place the regression lives: the transcript renderer appears to filter out isCompactSummary messages (or drops isVisibleInTranscriptOnly records) instead of rendering them.

Reproduced across two separate compactions in the same session (boundaries at 2026-07-26T18:39:58Z and 2026-07-30T07:56:54Z); both stored a valid summary (16081 and 12030 chars), neither is viewable via Ctrl+O.

Impact

The compact summary is the only remaining representation of everything that was dropped from context (here: 897k → 15k tokens, 1.7M cumulative dropped tokens). Being unable to read it means there is no in-TUI way to check what the model actually kept — which matters a lot when using /compact with custom instructions, since you can't verify the instructions were honored. The only workaround is jq-ing the raw JSONL.

Regression note

Older reports (e.g. #27242) show a ⏺ Compact summary block was rendered in transcript mode on ~2.1.47–2.1.52, with the complaint being about pre-compaction history. On 2.1.220 even the summary itself is gone, and the label changed to the more explicit "ctrl+o to see full summary" — so the promise got stronger while the behavior got worse.

Related but distinct: #27242 (no access to pre-compaction history — that's about the dropped messages; this is about the summary that replaced them).

Suggested fix

Render isCompactSummary: true / isVisibleInTranscriptOnly: true user messages in transcript mode (Ctrl+O), or — if they are intentionally hidden — change the label so it stops advertising an action that does nothing.