# Route C Timeline Pagination P017 restores Cinny's raw Matrix event pagination contract: ```text one raw Matrix event index = one virtual paginator index = one stable event-id position ``` ## Authority `RoomTimeline` obtains linked `EventTimeline` objects from the Matrix SDK. `getTimelinesEventsCount()` is the virtual paginator count. The paginator range, mounted item attributes, `getItems()`, event focus, and scroll targets all use raw absolute Matrix indexes. There is no Route C display index. Tool groups, placeholders, day dividers, and new-message dividers cannot become independent paginator items. A divider is rendered in the same fragment as its following Matrix event. Events Cinny normally hides retain their raw index and may render `null`. Reactions, edits, redactions, and unsupported events are not replaced with synthetic rows. ## Native Pagination The accepted Cinny `useVirtualPaginator` implementation owns local range expansion and anchor restoration. Backward and forward sentinels are observed with `IntersectionObserver`. When a local range changes, the paginator records a mounted raw event and its offset, renders the new range, then restores the same event offset. When the local range reaches a linked-timeline boundary, `RoomTimeline` asks the Matrix SDK to paginate backward or forward. Matrix pagination tokens and event IDs remain authoritative. Route C does not add one-scroll/one-page gates, suppressed retry timers, remote-end locks as viewport authority, or a second viewport ownership controller. ### Capacitor iOS remote restore transaction Capacitor iOS/WKWebView can overwrite Cinny's one-shot local offset restore while a touch or momentum scroll is still active. If the restore is lost, the new remote page head replaces the visible position and the still-visible sentinel can request more pages. P017 therefore permits one opt-in adapter only when both conditions are true: - the page is a clean Route C chat route; - the runtime is Capacitor iOS. Before a remote Matrix page fetch, the adapter records the mounted raw event nearest the viewport center as `{ event_id, viewport_offset }`. It does not store a display index or become range authority. The Matrix SDK fetch, native range recalibration, raw local expansion, event-id restore, and measured verification form one transaction. The adapter waits for touch release and layout frames before committing the remote range. It then measures the same event ID and reapplies only the missing scroll offset. A correction is accepted only after the anchor remains within two pixels for consecutive checks. Corrections are bounded; a failed verification leaves remote pagination blocked instead of allowing an unbounded sentinel loop. While the transaction is pending, neither remote direction may start another request. Local raw range expansion remains native and unrestricted. After a verified restore, another remote page is requested automatically only when the rendered content still cannot fill one viewport. Backward and forward use the same transaction; there is no direction-specific index, page quota, debounce, or bottom-follow writer. Generic Cinny rooms and non-iOS Route C clients keep the upstream paginator path with this adapter disabled. ## Focus And Live Behavior Search, pin, reply, hyperlink return-to, unread focus, and Host Owner navigation resolve an event ID through `getEventTimeline()` and `getEventIdAbsoluteIndex()`. Host Owner navigation chooses the mounted event nearest the current viewport as its anchor, not the previous button target. A focused historical timeline is not the live end. Provider arrivals cannot force Jump to Latest while the reader is away from bottom. Explicit Jump to Latest restores live-bottom behavior. A new local user send follows native Cinny `atBottom` behavior and does not force a historical viewport to latest. ### Live-bottom post-commit transaction When a live event arrives while the reader already owns the authoritative live bottom, Route C queues one revision-owned post-commit transaction. On the next animation frame, after the raw range and DOM commit, it verifies that the same live timeline is still linked and at its end, then positions the committed scroll container at its new legal bottom with `behavior: instant`. Live arrival never starts a smooth scroll. A newer event supersedes the pending revision, leaving the live timeline cancels it, and unmount cancels its frame. There is no delayed second correction, fixed timer, one-pixel nudge, user-agent CSS workaround, or independent range/index owner. This transaction does not change Cinny sentinels, Matrix pagination, local anchor restoration, or focused history behavior. The internal Fake provider command `P017_LIVE_TAIL_3S` emits 20 deterministic short, medium, and tall assistant rows at three-second intervals for this contract. Geometry diagnostics are disabled by default and require both `debug_host_artifact_writes_enabled` and `debug_routec_viewport_geometry_diagnostics_enabled`. When enabled, sanitized geometry-only records are written under the Host `operation_logs` folder; they contain event IDs and viewport measurements, not message bodies or secrets. ## Tool Events Every tool event that exists in Matrix is a normal raw event row. Stage 1 keeps all currently retained Matrix tool events as individual raw rows. Stage 2 changes new continuous runs to retain only the first event in Matrix; event 2+ belongs to the separate SQLite continuation store and never participates in timeline pagination. Existing P142 retained events remain individual raw rows. ## Verification Use the deterministic 20,000+ fixture for repeated PageUp/PageDown, wheel, direction reversal, focus, Owner navigation, live arrival, and Jump to Latest. The visible raw event must remain stable when either direction loads a page, and no permanent placeholder gap may appear.