Improve chat session switching and history pagination, with most of the aggressive limits scoped to the VS Code webview where the freezes were observed.
Session history loading and pagination:
- Reduce the VS Code message page size to 30 records so switching sessions does not immediately hydrate large histories into the webview.
- Keep manual Load older messages in VS Code fixed at 30 records per request instead of growing the request size over time.
- Add a bounded VS Code initial-tail expansion path from 30 to 50, 80, and 120 records only when the initial page has no user-message turn boundary, preventing large final turns from rendering as an empty chat.
- Lower the normal web message page size from 200 to 150 for a mild shared optimization without adopting the aggressive VS Code limits.
- Make session pagination metadata reactive per session so ChatContainer receives cursor updates from materialization and reconnect paths without requiring a switch away and back.
- Write pagination metadata before publishing newly materialized messages so the first render sees the correct has-more state.
- Store cursor information from direct materialization and reconnect message fetches in the shared session prefetch metadata cache.
VS Code cache and memory pressure reductions:
- Use a shared per-directory session recency map so cache eviction is based on app-level recency instead of whichever useSync instance happened to run.
- Limit VS Code warm session cache retention to 4 sessions and evict heavy inactive message caches after switching away from a large session.
- Disable sidebar session prefetch in VS Code because warming extra sessions was increasing webview memory and GC pressure during navigation.
- Remove dropdown background message prefetch so opening the switcher does not start additional session materialization work.
- Drop cached session-message-record snapshots when evicting session data so stale derived records do not remain after the raw session cache is cleared.
- Add bounded LRU caching for session message record snapshots, with much smaller VS Code limits and a VS Code cap that avoids caching snapshots above 30 messages.
- Bound the turn-window model cache in VS Code and avoid caching turn models for sessions above the VS Code message-page size.
Chat render-path reductions:
- Reuse ChatContainer's already-materialized message records in plan detection instead of adding a second active-session message subscription.
- Add a no-op guard when marking session plan availability so repeated detections do not create new Map references and fan out renders.
- Add no-op guards for session switcher and dropdown open state updates to avoid unnecessary store updates and renders.
- Convert several session-specific hooks to useSyncExternalStore with empty-session no-subscribe behavior so empty IDs do not subscribe to broad store updates.
- Remount the chat viewport when the current session changes, isolating per-session viewport and list state.
- Change the virtualized message-list fallback to render only a tail window when the virtualizer has not produced rows yet, instead of rendering an entire large history.
VS Code layout and header improvements:
- Remove the broad useSessions subscription from the VS Code layout header path and subscribe only to the active session title and initial-session existence.
- Unmount the compact VS Code session sidebar when the user is in chat view instead of keeping the hidden session list mounted and subscribed.
- Compute the latest assistant model and latest context-token usage in a single reverse scan of current-session messages instead of scanning the same list twice.
- Remove switcher git-status warmup work so the switcher reads already-loaded branch labels without starting extra background git status requests.
Markdown and file-reference safeguards:
- Skip expensive syntax highlighting for very large code blocks, with a 200-line cap in VS Code and a softer 1200-line cap in web.
- Add an LRU cap to file-reference stat lookups so the cache cannot grow without bound across many rendered messages.
- Limit the number of file references annotated per render to 40 in VS Code and 200 in web to prevent large assistant outputs from spawning too many stat checks.
- Clear file-link annotations when file-reference mode is disabled so stale attributes and handlers do not remain on previously annotated nodes.
Assistant-message action and preview reductions:
- Skip preview URL scanning on VS Code, mobile, and mini-chat surfaces so assistant text and tool output are not scanned where the preview action is unavailable.
- Skip Save-as-Plan project lookup on VS Code, mini-chat, and mobile surfaces.
- Hide Save-as-Plan and Start MultiRun assistant-message actions on VS Code, mini-chat, and mobile surfaces.
- Resolve the current session directory on demand for assistant actions instead of subscribing each assistant message to the full session list.
Tool and task rendering optimizations:
- Prefer finalized task metadata summaries without fetching child-session messages when the summary is already present.
- Avoid polling or final-fetching task child sessions once a final metadata summary is available.
- Use VS Code-specific task child fetch limits of 30 records for initial, active, and idle fetches.
- Parse diff stats by scanning patch text line-by-line instead of splitting large patches into arrays.
- Count write-tool lines by scanning content instead of allocating a split array for large files.
- Avoid trimming large patch strings just to test whether they contain content.
- Memoize diff and write statistics so unchanged tool parts do not recalculate them on every render.
VS Code bridge improvements:
- Return JSON and text proxy responses through the VS Code bridge as bodyText instead of base64 so the webview avoids synchronous base64 decoding for common API responses.
- Keep binary responses on the base64 path while making bodyBase64 optional in the bridge contract.
- Strip content-length, content-encoding, and transfer-encoding headers from proxied responses because the bridge reconstructs the Response body.
Validation:
- bun run type-check
- bun run lint
- bun run vscode:build
Bohdan Triapitsyn
51c8d52ab5