<!-- CURSOR_SUMMARY -->
> [!NOTE]
> Refactors code highlighting to use react-shiki/core with a singleton
highlighter and preloaded langs/themes, adds a fallback renderer, bumps
react-shiki, and adds tests for message summarization.
>
> - **Frontend**
> - **CodeHighlight** (`src/components/chat/CodeHighlight.tsx`): Replace
`useShikiHighlighter` with `ShikiHighlighter` from `react-shiki/core`
using a singleton `createHighlighterCore` and JS regex engine; preload
common languages and GitHub light/dark themes; add `<pre><code>`
fallback while loading.
> - **Tests**
> - Add/expand Vitest suite for `formatMessagesForSummary`
(`src/__tests__/formatMessagesForSummary.test.ts`): covers truncation,
ordering, special chars, undefined content, and edge cases.
> - **Dependencies**
> - Upgrade `react-shiki` to `^0.9.0` in `package.json`.
>
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
b32d224cd21d3c76e77799f2995905e523406bf9. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->
<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Preloaded a specific set of Shiki languages and themes using react-shiki
core, and updated CodeHighlight to use a singleton highlighter. This
reduces bundle size and stabilizes code rendering with a simple fallback
while loading.
- **Refactors**
- Switched to react-shiki/core with ShikiHighlighter and a singleton
highlighter.
- Preloaded common languages
(js/ts/jsx/tsx/html/css/json/markdown/python/etc.) and GitHub light/dark
themes.
- Used the JavaScript regex engine and added a plain <pre><code>
fallback until the highlighter is ready.
- **Dependencies**
- Upgraded react-shiki to ^0.9.0.
<sup>Written for commit b32d224cd21d3c76e77799f2995905e523406bf9.
Summary will update automatically on new commits.</sup>
<!-- End of auto-generated description by cubic. -->
<!-- CURSOR_SUMMARY -->
> [!NOTE]
> Adds a context-limit banner with one-click “summarize into new chat,”
refactors token counting with react-query, and persists per-message max
token usage.
>
> - **Chat UX**
> - **Context limit banner** (`ContextLimitBanner.tsx`,
`MessagesList.tsx`): shows when within 40k tokens of `contextWindow`,
with tooltip and action to summarize into a new chat.
> - **Summarize flow**: extracted to `useSummarizeInNewChat` and used in
chat input and banner; new summarize system prompt
(`summarize_chat_system_prompt.ts`).
> - **Token usage & counting**
> - **Persist max tokens used per assistant message**: DB migration
(`messages.max_tokens_used`), schema updates, and saving usage during
streaming (`chat_stream_handlers.ts`).
> - **Token counting refactor** (`useCountTokens.ts`): react-query with
debounce; returns `estimatedTotalTokens` and `actualMaxTokens`;
invalidated on model change and stream end; `TokenBar` updated.
> - **Surfacing usage**: tooltip on latest assistant message shows total
tokens (`ChatMessage.tsx`).
> - **Model/config tweaks**
> - Set `auto` model `contextWindow` to `200_000`
(`language_model_constants.ts`).
> - Improve chat auto-scroll dependency (`ChatPanel.tsx`).
> - Fix app path validation regex (`app_handlers.ts`).
> - **Testing & dev server**
> - E2E tests for banner and summarize
(`e2e-tests/context_limit_banner.spec.ts` + fixtures/snapshot).
> - Fake LLM server streams usage to simulate high token scenarios
(`testing/fake-llm-server/*`).
>
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
2ae16a14d50699cc772407426419192c2fdf2ec3. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->
<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Adds a “Summarize into new chat” trigger and a context limit banner to
help keep conversations focused and avoid hitting model limits. Also
tracks and surfaces actual token usage per assistant message, with a
token counting refactor for reliability.
- **New Features**
- Summarize into new chat from the input or banner; improved system
prompt with clear output format.
- Context limit banner shows when within 40k tokens of the model’s
context window and offers a one-click summarize action.
- Tooltip on the latest assistant message shows total tokens used.
- **Refactors**
- Token counting now uses react-query and returns estimatedTotalTokens
and actualMaxTokens; counts are invalidated on model change and when
streaming settles.
- Persist per-message max_tokens_used in the messages table; backend
aggregates model usage during streaming and saves it.
- Adjusted default “Auto” model contextWindow to 200k for more realistic
limits.
- Improved chat scrolling while streaming; fixed app path validation
regex.
<sup>Written for commit 2ae16a14d50699cc772407426419192c2fdf2ec3.
Summary will update automatically on new commits.</sup>
<!-- End of auto-generated description by cubic. -->
