Summary

Fixes #76415 by making compaction boundaries explicit in Control UI/WebChat history instead of letting refreshes look like earlier turns silently disappeared.

The narrow product choice here is to preserve the current bounded active-transcript chat.history behavior and add a chat-level recovery affordance:

• render compaction transcript entries as Compacted history dividers instead of a generic Compaction label
• explain that earlier turns are preserved in a compaction checkpoint
• add an Open checkpoints action that switches to the Sessions view, expands the active session's checkpoint panel, and refreshes checkpoint metadata
• keep checkpoint branch/restore permissions enforced by the existing Sessions APIs
• document the behavior in WebChat docs and add a user-facing changelog entry

Bug / Current Behavior

Issue #76415 reports that after automatic compaction, a long Control UI/WebChat session reloads from the compacted successor transcript. The old full turn-by-turn transcript is retained in checkpoint/reset files, but normal chat history can make earlier messages look lost after refresh.

I verified the issue is still open and not already closed by a linked PR. closedByPullRequestsReferences is empty.

Related PR Review

I checked related live PRs before opening this one:

• fix(gateway): preserve chat history across compaction checkpoint chains #68765 directly attempts checkpoint-chain transcript stitching, but ClawSweeper found P1/security blockers around active-branch reads, reset/restore epoch replay, untrimmed compaction tails, and uncontained checkpoint paths.
• feat(session): add includeArchived to chat.history and sessions_history #73883 and fix(session): fall back to reset archive in chat.history when primary transcript is missing #60409 address reset/archive opt-in or fallback behavior, not this default visible compaction-boundary UX.
• Filter internal compaction artifacts from chat history #70348 filters internal compaction artifacts, which is adjacent but does not explain or recover pre-compaction history.
• Harden main webchat reliability #75776 is broader WebChat reliability work and is not a focused checkpoint-boundary fix.

gitcrawl was stale for #76415 (local store last updated before the issue existed), so I fell back to live GitHub search. prtags was installed and authenticated, but the prtags API returned 502 for list/search/write attempts, so duplicate-group writes could not be completed in this run.

Security / Privacy

This PR intentionally does not read, stitch, replay, or expose archived/checkpoint transcript bytes through chat.history.

Security-relevant boundaries preserved:

• no new filesystem reads
• no checkpoint-path trust changes
• no reset/restore epoch replay by default
• no dependency, workflow, lockfile, or secret-handling changes
• branch/restore remains behind the existing sessions.compaction.* methods and server-side permissions

Tests

RED proof first:

• pnpm test ui/src/ui/chat/build-chat-items.test.ts ui/src/ui/views/chat.test.ts failed before implementation because the builder emitted only Compaction and the view rendered no explanation/action.

Passing proof:

• pnpm test ui/src/ui/chat/build-chat-items.test.ts ui/src/ui/views/chat.test.ts — 27 tests passed
• pnpm exec oxfmt --check --threads=1 CHANGELOG.md docs/web/webchat.md ui/src/styles/chat/grouped.css ui/src/ui/app-render.ts ui/src/ui/types/chat-types.ts ui/src/ui/chat/build-chat-items.ts ui/src/ui/chat/build-chat-items.test.ts ui/src/ui/views/chat.ts ui/src/ui/views/chat.test.ts — passed
• git diff --check — passed
• Blacksmith Testbox tbx_01kqp0e8zndm2cng8ky8d9jpan: OPENCLAW_TESTBOX=1 pnpm check:changed — passed (core, coreTests, docs lanes)

Docs

Updated WebChat docs: https://docs.openclaw.ai/web/webchat