The chat surface now relies on the current-turn changes card for file rollback, so the older per-message hover rewind affordance was removed to avoid two competing rollback models.
Constraint: Current-turn undo still depends on the existing checkpoint rewind API.
Rejected: Keep both rewind entry points | duplicate rollback affordances make the product harder to explain and test.
Confidence: high
Scope-risk: moderate
Directive: Prefer adding rollback behavior through the current-turn change card instead of restoring per-message hover rewind.
Tested: bun test src/server/__tests__/sessions.test.ts
Tested: cd desktop && bun run test
Tested: cd desktop && bun run lint
Tested: cd desktop && bun run build
Not-tested: Browser E2E scripts were updated but not executed in this commit.
Desktop rewind previously used the visible user-message index as the primary selector. That can drift from the persisted active chain when hidden or non-rendered user messages exist, so the API now prefers a stable user message id and checks the selected prompt text before mutating transcript or files.
Constraint: Desktop UI can hide transcript entries that still exist in the persisted session chain
Rejected: Keep index-only rewind | can target an earlier user message after UI/server chain drift
Confidence: high
Scope-risk: moderate
Directive: Do not remove targetUserMessageId or expectedContent guards without reproducing shifted visible-index sessions
Tested: bun test src/server/__tests__/sessions.test.ts --timeout 20000
Tested: cd desktop && bun run test MessageList.test.tsx chatStore.test.ts -- --run
Tested: desktop/scripts/e2e-rewind-agent-browser.sh
Tested: desktop/scripts/e2e-rewind-complex-agent-browser.sh
Not-tested: Full desktop Vitest suite still has unrelated locale-sensitive failures
The desktop client already had a conversation-level rewind UI concept on the
CLI side, but the web/desktop surface lacked the protocol, session trimming,
and file checkpoint restore path needed to make rewind trustworthy. This change
adds a desktop-specific rewind API, wires the message-level UI affordance and
confirmation modal, enables SDK file checkpointing for desktop sessions, and
covers the restore path with service tests plus a real agent-browser workflow.
Constraint: Desktop sessions run the CLI in SDK/print mode, so file checkpointing had to be enabled explicitly for that path
Constraint: main branch is checked out in a separate worktree, so merge-back must happen from the primary worktree after commit
Rejected: UI-only rewind that only trims local state | would leave persisted transcript and disk state inconsistent after refresh
Rejected: Reuse getLastSessionLog as the sole snapshot source | active rewind must read file-history metadata directly from the session file
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Keep desktop rewind keyed to persisted user-message order unless the UI model starts carrying stable transcript UUIDs end-to-end
Tested: bun test src/server/__tests__/conversation-service.test.ts src/server/__tests__/sessions.test.ts; desktop MessageList vitest; desktop tsc no-emit; live agent-browser E2E on isolated ports with file edit then rewind
Not-tested: Browser E2E matrix for multi-file and second-edit scenarios is still covered at service-test level rather than full UI level
