> ## Documentation Index
> Fetch the complete documentation index at: https://prefab.prefect.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Update MCP Context

> Silently update the model's context from a UI interaction.

export const ComponentPreview = ({json, height, resizable, bare, hideJson, playground, children}) => {
  const hostRef = React.useRef(null);
  const handleRef = React.useRef(null);
  const cardRef = React.useRef(null);
  const containerRef = React.useRef(null);
  const [previewWidth, setPreviewWidth] = React.useState(null);
  const [isDragging, setIsDragging] = React.useState(false);
  const [playgroundHref, setPlaygroundHref] = React.useState(null);
  React.useEffect(function () {
    if (!playground) return;
    var isLocal = location.hostname === "localhost" || location.hostname === "127.0.0.1";
    var path = isLocal ? "/playground" : "/docs/playground";
    var url = new URL(path, window.location.href);
    url.hash = "code=" + playground;
    setPlaygroundHref(url.href);
  }, [playground]);
  var jsonStr = typeof json === "string" ? json : JSON.stringify(json, null, 2);
  React.useEffect(function () {
    if (cardRef.current) {
      var card = cardRef.current.closest(".group");
      if (card) card.classList.remove("group");
    }
    var host = hostRef.current;
    if (!host || !json) return;
    function mount() {
      if (!window.__prefab || !host) return;
      var dark = document.documentElement.classList.contains("dark");
      handleRef.current = window.__prefab.mountPreview(host, jsonStr, {
        dark: dark
      });
      if (bare && host.shadowRoot) {
        var m = host.shadowRoot.querySelector("[data-prefab-mount]");
        if (m) m.style.background = "transparent";
      }
    }
    if (window.__prefab) {
      mount();
    } else {
      if (!window.__prefabLoading) {
        if (!window.__prefabReady) {
          var s = document.createElement("script");
          s.src = "/renderer.js";
          document.head.appendChild(s);
        }
        window.__prefabLoading = new Promise(function (resolve) {
          function check() {
            if (window.__prefabReady) {
              window.__prefabReady.then(resolve);
            } else {
              setTimeout(check, 10);
            }
          }
          check();
        });
      }
      window.__prefabLoading.then(mount);
    }
    var observer = new MutationObserver(function () {
      var dark = document.documentElement.classList.contains("dark");
      if (handleRef.current) handleRef.current.setDark(dark);
    });
    observer.observe(document.documentElement, {
      attributes: true,
      attributeFilter: ["class"]
    });
    return function () {
      observer.disconnect();
      if (handleRef.current) {
        handleRef.current.unmount();
        handleRef.current = null;
      }
    };
  }, [json]);
  function startResize(e) {
    e.preventDefault();
    var startX = e.clientX;
    var startW = hostRef.current ? hostRef.current.offsetWidth : 0;
    var maxW = containerRef.current ? containerRef.current.offsetWidth - 10 : startW;
    setIsDragging(true);
    function onMove(ev) {
      var w = Math.max(260, Math.min(startW + (ev.clientX - startX), maxW));
      setPreviewWidth(w);
    }
    function onUp() {
      document.removeEventListener("mousemove", onMove);
      document.removeEventListener("mouseup", onUp);
      setIsDragging(false);
    }
    document.addEventListener("mousemove", onMove);
    document.addEventListener("mouseup", onUp);
  }
  if (bare) {
    return <div ref={hostRef} />;
  }
  if (resizable) {
    return <Card>
        <div ref={cardRef} />
        <div ref={containerRef} style={{
      display: "flex",
      position: "relative",
      overflow: "hidden"
    }}>
          <div ref={hostRef} style={{
      flex: previewWidth ? "none" : 1,
      width: previewWidth ? previewWidth + "px" : undefined,
      minWidth: 0
    }} />
          <div onMouseDown={startResize} style={{
      width: "14px",
      flexShrink: 0,
      cursor: "col-resize",
      background: isDragging ? "var(--border, #e5e7eb)" : "color-mix(in srgb, var(--border, #e5e7eb) 40%, transparent)",
      display: "flex",
      alignItems: "center",
      justifyContent: "center",
      transition: "background 0.15s",
      userSelect: "none"
    }}>
            <svg width="6" height="24" style={{
      opacity: 0.5
    }}>
              <circle cx="2" cy="4" r="1.2" fill="currentColor" />
              <circle cx="2" cy="9" r="1.2" fill="currentColor" />
              <circle cx="2" cy="14" r="1.2" fill="currentColor" />
              <circle cx="2" cy="19" r="1.2" fill="currentColor" />
              <circle cx="5" cy="4" r="1.2" fill="currentColor" />
              <circle cx="5" cy="9" r="1.2" fill="currentColor" />
              <circle cx="5" cy="14" r="1.2" fill="currentColor" />
              <circle cx="5" cy="19" r="1.2" fill="currentColor" />
            </svg>
          </div>
          <div style={{
      flex: previewWidth ? 1 : "0 0 24px",
      minWidth: "24px",
      background: "repeating-linear-gradient(-45deg, transparent, transparent 3px, var(--border, #e5e7eb) 3px, var(--border, #e5e7eb) 4px)",
      opacity: 0.4
    }} />
          {previewWidth && <div style={{
      position: "absolute",
      bottom: "8px",
      right: "8px",
      background: "var(--background, white)",
      border: "1px solid var(--border, #e5e7eb)",
      borderRadius: "4px",
      padding: "1px 6px",
      fontSize: "11px",
      fontFamily: "monospace",
      color: "var(--muted-foreground, #6b7280)",
      pointerEvents: "none"
    }}>
              {previewWidth}px
            </div>}
        </div>
        {playgroundHref && <div style={{
      display: "flex",
      justifyContent: "flex-end",
      padding: "4px 0 8px"
    }}>
            <a href={playgroundHref} target="_blank" rel="noopener noreferrer" style={{
      fontSize: "11px",
      opacity: 0.4,
      textDecoration: "none",
      textDecorationLine: "none",
      borderBottom: "none",
      boxShadow: "none",
      display: "inline-flex",
      alignItems: "center",
      gap: "3px",
      transition: "opacity 0.15s",
      fontWeight: 400
    }} onMouseOver={function (e) {
      e.currentTarget.style.opacity = "0.6";
    }} onMouseOut={function (e) {
      e.currentTarget.style.opacity = "0.4";
    }}>
              Edit in Playground
              <svg xmlns="http://www.w3.org/2000/svg" width="11" height="11" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><path d="M15 3h6v6" /><path d="M10 14 21 3" /><path d="M18 13v6a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V8a2 2 0 0 1 2-2h6" /></svg>
            </a>
          </div>}
        <div style={{
      marginBottom: "-2rem"
    }}>{children}</div>
      </Card>;
  }
  return <Card>
      <div ref={cardRef} />
      <div ref={hostRef} />
      {playgroundHref && <div style={{
    display: "flex",
    justifyContent: "flex-end",
    padding: "4px 0 8px"
  }}>
          <a href={playgroundHref} target="_blank" rel="noopener noreferrer" style={{
    fontSize: "11px",
    opacity: 0.4,
    textDecoration: "none",
    textDecorationLine: "none",
    borderBottom: "none",
    boxShadow: "none",
    display: "inline-flex",
    alignItems: "center",
    gap: "3px",
    transition: "opacity 0.15s",
    fontWeight: 400
  }} onMouseOver={function (e) {
    e.currentTarget.style.opacity = "0.6";
  }} onMouseOut={function (e) {
    e.currentTarget.style.opacity = "0.4";
  }}>
            Edit in Playground
            <svg xmlns="http://www.w3.org/2000/svg" width="11" height="11" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><path d="M15 3h6v6" /><path d="M10 14 21 3" /><path d="M18 13v6a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V8a2 2 0 0 1 2-2h6" /></svg>
          </a>
        </div>}
      <div style={{
    marginBottom: "-2rem"
  }}>{children}</div>
    </Card>;
};

`UpdateContext` feeds information into the conversation without triggering a visible response. Where `SendMessage` creates a chat message the user sees, `UpdateContext` works behind the scenes — it updates what the model knows without interrupting the flow.

<ComponentPreview json={{"view":{"type":"Button","label":"Use Advanced Mode","variant":"default","size":"default","disabled":false,"onClick":{"action":"updateContext","content":"User has selected advanced mode. Provide detailed technical responses."}}}} playground="ZnJvbSBwcmVmYWJfdWkuY29tcG9uZW50cyBpbXBvcnQgQnV0dG9uCmZyb20gcHJlZmFiX3VpLmFjdGlvbnMubWNwIGltcG9ydCBVcGRhdGVDb250ZXh0CgpCdXR0b24oCiAgICAiVXNlIEFkdmFuY2VkIE1vZGUiLAogICAgb25fY2xpY2s9VXBkYXRlQ29udGV4dCgKICAgICAgICBjb250ZW50PSJVc2VyIGhhcyBzZWxlY3RlZCBhZHZhbmNlZCBtb2RlLiBQcm92aWRlIGRldGFpbGVkIHRlY2huaWNhbCByZXNwb25zZXMuIgogICAgKSwKKQo">
  <CodeGroup>
    ```python Python icon="python" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
    from prefab_ui.components import Button
    from prefab_ui.actions.mcp import UpdateContext

    Button(
        "Use Advanced Mode",
        on_click=UpdateContext(
            content="User has selected advanced mode. Provide detailed technical responses."
        ),
    )
    ```

    ```json Protocol icon="brackets-curly" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
    {
      "view": {
        "type": "Button",
        "label": "Use Advanced Mode",
        "variant": "default",
        "size": "default",
        "disabled": false,
        "onClick": {
          "action": "updateContext",
          "content": "User has selected advanced mode. Provide detailed technical responses."
        }
      }
    }
    ```
  </CodeGroup>
</ComponentPreview>

## When to Use It

`UpdateContext` is for situations where the UI interaction should inform the model's future behavior without generating an immediate response:

* User selects a preference or mode that should influence subsequent answers
* A form submission captures structured data the model should reference later
* Background state changes that provide context for the next conversation turn

## Structured Content

For richer data, pass a dict instead of plain text:

<ComponentPreview json={{"view":{"cssClass":"gap-3","type":"Column","children":[{"name":"thinking","type":"Select","placeholder":"Thinking level...","size":"default","disabled":false,"required":false,"invalid":false,"children":[{"type":"SelectOption","value":"low","label":"Low","selected":false,"disabled":false},{"type":"SelectOption","value":"medium","label":"Medium","selected":false,"disabled":false},{"type":"SelectOption","value":"high","label":"High","selected":false,"disabled":false}]},{"type":"Button","label":"Set Preference","variant":"default","size":"default","disabled":false,"onClick":{"action":"updateContext","structuredContent":{"preference":{"thinking":"{{ thinking }}"}}}}]}}} playground="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">
  <CodeGroup>
    ```python Python icon="python" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
    from prefab_ui.components import Button, Select, SelectOption, Column
    from prefab_ui.actions.mcp import UpdateContext

    with Column(gap=3):
        with Select(name="thinking", placeholder="Thinking level...") as thinking:
            SelectOption(value="low", label="Low")
            SelectOption(value="medium", label="Medium")
            SelectOption(value="high", label="High")
        Button(
            "Set Preference",
            on_click=UpdateContext(
                structured_content={"preference": {"thinking": thinking.rx}},
            ),
        )
    ```

    ```json Protocol icon="brackets-curly" theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
    {
      "view": {
        "cssClass": "gap-3",
        "type": "Column",
        "children": [
          {
            "name": "thinking",
            "type": "Select",
            "placeholder": "Thinking level...",
            "size": "default",
            "disabled": false,
            "required": false,
            "invalid": false,
            "children": [
              {
                "type": "SelectOption",
                "value": "low",
                "label": "Low",
                "selected": false,
                "disabled": false
              },
              {
                "type": "SelectOption",
                "value": "medium",
                "label": "Medium",
                "selected": false,
                "disabled": false
              },
              {
                "type": "SelectOption",
                "value": "high",
                "label": "High",
                "selected": false,
                "disabled": false
              }
            ]
          },
          {
            "type": "Button",
            "label": "Set Preference",
            "variant": "default",
            "size": "default",
            "disabled": false,
            "onClick": {
              "action": "updateContext",
              "structuredContent": {"preference": {"thinking": "{{ thinking }}"}}
            }
          }
        ]
      }
    }
    ```
  </CodeGroup>
</ComponentPreview>

## API Reference

<Card icon="code" title="UpdateContext Parameters">
  <ParamField body="content" type="str | None" default="None">
    Text content to add to the model's context. Can be passed as a positional argument.
  </ParamField>

  <ParamField body="structured_content" type="dict[str, Any] | None" default="None">
    Structured data to add to the model's context.
  </ParamField>
</Card>

## Protocol Reference

```json UpdateContext theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
{
  "action": "updateContext",
  "content?": "string",
  "structuredContent?": "object"
}
```

For the complete protocol schema, see [UpdateContext](/protocol/update-context).