# Market data > One instrument and series model owned by the chart, providers that translate upstream protocols, and a router that picks the source. Source: https://kcq.nebutra.com/docs/market-data KLineChartQuant reads every bar, intraday series and instrument through one model that the frontend defines. A feed never leaks its own wire format into the chart: a provider converts it first. That is what lets the same chart, the same comparison and the same Agent tool work over Tongdaxin, TradingView, MT5 or your own service. The model [#the-model] Three types carry almost everything. They are exported from `@363045841yyt/klinechart-core/market-data`. | Type | What it holds | | ---------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------- | | `InstrumentDescriptor` | Identity (`id`, `sourceId`, `symbol`, `name`, `assetClass`, `exchange`), optional `sessionId`, `currency`, `tickSize`, `lotSize`, and `capabilities` | | `BarSeries` | One page of K-lines: `instrumentId`, `period`, `adjustment`, `barAggregation`, `timezone`, optional `volumeUnit`, `data`, and `olderData` | | `TimeShareSeries` | One trading day of intraday points: `instrumentId`, `tradingDate`, `timezone`, `preClose`, optional `volumeUnit`, `data` | A few rules keep the model honest: * `id` is the only identity. Two descriptors with the same symbol on different exchanges are different instruments. * `providerRef` is private routing data. Only the provider that created it reads it; search, UI, comparison and the chart never do. * Period and adjustment menus come from `instrument.capabilities.bars`. Intraday mode needs `capabilities.timeShare === true` and a registered `sessionId`. * Volume is shown in the series' `volumeUnit` (`share`, `lot`, `contract` or `baseAsset`). No market is assumed to trade in lots. * `olderData` (`available`, `exhausted` or `unknown`) is declared by the backend, so the chart never guesses the end of history from an empty page. Providers and the registry [#providers-and-the-registry] A `MarketDataProvider` is composed from optional modules. A missing module means the source does not support that capability. ```ts interface MarketDataProvider { readonly source: DataSourceDescriptor probe(signal?: AbortSignal): Promise readonly catalog?: InstrumentCatalog readonly bars?: BarDataSource readonly tradingCalendar?: TradingCalendarDataSource readonly liveBars?: LiveBarsDataSource readonly timeShare?: TimeShareDataSource readonly timeShareRange?: TimeShareRangeDataSource readonly depth?: DepthDataSource } ``` Providers live in `marketDataProviderRegistry`. Each one has a runtime config of `enabled`, `priority` and an optional `baseUrl`. The registry keeps only the current session; persisting choices (for example to `localStorage`) is the host's job. ```ts import { marketDataProviderRegistry } from '@363045841yyt/klinechart-core/market-data' marketDataProviderRegistry.setConfig('gotdx', { baseUrl: 'http://127.0.0.1:8080' }) marketDataProviderRegistry.setConfig('mock', { enabled: false }) const enabled = marketDataProviderRegistry.getEnabled() ``` Importing `@363045841yyt/klinechart-core/market-data/sources` registers the built-in providers: `gotdx`, `baostock`, `finshare`, `tradingview`, `mock` and `mt5`. Registration order is the tie-breaker for sources with the same priority. See [Connectors](/docs/market-data/connectors) for what each one covers. Routing [#routing] The chart runtime never calls a provider directly. `ChartDataManager` asks `SourceRouter`, and the router decides which provider answers. * **An explicit `sourceId`** (`preferredSourceId`) means that source and nothing else. If it is disabled or lacks the capability, the request fails instead of silently switching. * **`auto`** builds a candidate list from enabled providers in priority order, filtered by declared source capabilities: the capability itself, `assetClass`, `period` and `adjustment`. Sources that have not declared capabilities are probed once first. * **Resolution** finds the instrument in each candidate's catalog by `symbol`, narrowed by `exchange` and `assetClass` when given. * **Fallthrough** happens only on deterministic rejections, `UNSUPPORTED_CAPABILITY` or `INSTRUMENT_NOT_FOUND`. A network failure or an abort stops the chain, so a flaky upstream is reported rather than masked by another source's data. When every candidate rejects, the router throws `SourceRoutingError` with the full list of attempts. When a symbol is ambiguous [#when-a-symbol-is-ambiguous] A code can name more than one instrument. `000012`, for example, can resolve to a stock and to a bond index. Nothing in the core picks one on the user's behalf. Agent tools such as `comparison_create` return `{ status: "ambiguous", candidates }` and add nothing; the Agent is then required to call `ask_user` with one option per candidate and retry with the chosen candidate's `source` and `exchange`. People and the Agent go through the same commands, so the rule holds for both. The cache [#the-cache] Each chart instance owns one `MarketDataCache`. The UI, the Agent and `ChartDataManager` all read through it, so scrolling and Agent queries reuse the same pages instead of fetching twice. It pages history with a `limit`/`before` cursor, retries failed requests, merges identical in-flight requests, and evicts least-recently-used entries once it reaches its size limit. The limit is the `marketDataCacheMaxMiB` setting: 50 MiB by default, from 5 to 512. It sits in the Data group of the settings panel and applies immediately. Lowering it evicts at once. ```ts controller.settingsCommands.applyValues({ marketDataCacheMaxMiB: 128 }) ``` Three ways to connect a feed [#three-ways-to-connect-a-feed] | Path | Use it when | Reference | | ------------------- | -------------------------------------------------------------------------------------------- | ---------------------------------------------- | | REST protocol | You run a service and can speak `market-data-v1`: probe, instrument search, bars, time share | [HTTP API](/docs/market-data/http-api) | | Live bars (SSE) | Your service can push forming and closed bars for a source | [Live bars](/docs/market-data/live-bars) | | In-process provider | The data is already in the browser, or you want to wrap a client SDK yourself | [Provider API](/docs/market-data/provider-api) | The REST path needs no provider code. `createMarketDataProvider` and `createHttpMarketDataTransport` assemble one from a base URL: ```ts import { createHttpMarketDataTransport, createMarketDataProvider, marketDataProviderRegistry, } from '@363045841yyt/klinechart-core/market-data' const provider = createMarketDataProvider({ source: { id: 'my-feed', displayName: 'My feed', defaultBaseUrl: 'http://127.0.0.1:9000' }, transport: createHttpMarketDataTransport({ baseUrl: () => marketDataProviderRegistry.getConfig('my-feed').baseUrl ?? 'http://127.0.0.1:9000', sourceLabel: 'my-feed', }), }) marketDataProviderRegistry.register(provider, { enabled: true }) ``` For a one-off dataset with no feed at all, the components still accept inline data (`customData`, or `setData` on the controller). Next [#next]