> ## Documentation Index
> Fetch the complete documentation index at: https://smithers-feat-claude-workflow-mirror.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# <Sidecar>

> Run a cheap shadow agent beside a primary task and compare their scorer results.

```ts theme={null}
// Props
import { Sidecar, computeSidecarDelta } from "smithers-orchestrator";

type SidecarProps = {
  id?: string;                         // default: "sidecar"
  agent: AgentLike;                    // primary agent
  sidecar: AgentLike;                  // cheap shadow agent
  output: OutputTarget;                // primary output target
  sidecarOutput?: OutputTarget;        // default: output
  scorers?: ScorersMap;                // attached to both tasks
  prompt?: string | ReactNode;
  input?: string | ReactNode;
  maxConcurrency?: number;
  groundTruth?: unknown;
  context?: unknown;
  primaryLabel?: string;
  sidecarLabel?: string;
  skipIf?: boolean;
  children?: string | ReactNode;
};

type SidecarDelta = {
  primaryScore: number | null;
  sidecarScore: number | null;
  delta: number | null;
  cheaperWins: boolean;
};
```

```tsx theme={null}
<Workflow name="cheap-model-shadow">
  <Sidecar
    id="answer"
    agent={primaryAgent}
    sidecar={cheapAgent}
    output={outputs.answer}
    scorers={scorers}
  >
    Answer the customer question with the most accurate response.
  </Sidecar>
</Workflow>
```

## Behavior

`<Sidecar>` renders a `<Parallel>` with two `<Task>` children. The primary task uses the component `id`, writes to `output`, and is the node downstream workflow code should consume. The sidecar task uses `${id}-sidecar`, receives the same prompt, gets `continueOnFail: true`, and writes to `sidecarOutput` when supplied or to `output` by default.

Both tasks receive the same `scorers` prop. Smithers records live scorer results in `_smithers_scorers` once per task node id, so `bunx smithers-orchestrator scores RUN_ID` can show the primary row and the sidecar row separately.

Use `computeSidecarDelta(rows, { primaryNodeId, sidecarNodeId, scorerId })` after reading persisted scorer rows. It derives `primaryScore`, `sidecarScore`, `delta`, and `cheaperWins` from those rows only.

## Notes

* The sidecar can fail without failing the workflow.
* The sidecar result does not replace the primary result.
* `delta` is `primaryScore - sidecarScore`.
* `cheaperWins` is true when the sidecar score is greater than or equal to the primary score.

## Source

The `<Sidecar>` implementation and the files it imports, straight from the package source. This section is generated; edit the source, not this block.

<CodeGroup>
  ```js Sidecar.js theme={null}
  // @smithers-type-exports-begin
  /** @typedef {import("./SidecarProps.ts").SidecarProps} SidecarProps */
  // @smithers-type-exports-end

  import React from "react";
  import { Parallel } from "./Parallel.js";
  import { Task } from "./Task.js";

  /**
   * Runs a primary task and a cheap shadow task over the same prompt.
   *
   * The primary task keeps the component id so downstream `needs` can consume it.
   * The sidecar task is continue-on-fail and writes its own scorer rows.
   *
   * @param {SidecarProps} props
   */
  export function Sidecar(props) {
  	if (props.skipIf) return null;
  	const {
  		id = "sidecar",
  		agent,
  		sidecar,
  		output,
  		sidecarOutput,
  		scorers,
  		prompt,
  		input,
  		maxConcurrency,
  		groundTruth,
  		context,
  		primaryLabel,
  		sidecarLabel,
  		children,
  	} = props;
  	const promptNode = prompt ?? input ?? children;
  	const shadowId = `${id}-sidecar`;
  	return React.createElement(
  		Parallel,
  		{ id: `${id}-parallel`, maxConcurrency },
  		React.createElement(
  			Task,
  			{
  				id,
  				output,
  				agent,
  				scorers,
  				groundTruth,
  				context,
  				label: primaryLabel,
  			},
  			promptNode,
  		),
  		React.createElement(
  			Task,
  			{
  				id: shadowId,
  				output: sidecarOutput ?? output,
  				agent: sidecar,
  				continueOnFail: true,
  				scorers,
  				groundTruth,
  				context,
  				label: sidecarLabel,
  			},
  			promptNode,
  		),
  	);
  }
  ```

  ```js Parallel.js theme={null}
  import React from "react";
  /** @typedef {import("./ParallelProps.ts").ParallelProps} ParallelProps */

  /**
   * @param {ParallelProps} props
   */
  export function Parallel(props) {
      if (props.skipIf)
          return null;
      // Align prop sanitization with other structural components
      const next = {
          maxConcurrency: props.maxConcurrency,
          id: props.id,
      };
      return React.createElement("smithers:parallel", next, props.children);
  }
  ```

  ```js Task.js theme={null}
  // @smithers-type-exports-begin
  /**
   * @template D
   * @typedef {import("./InferDeps.ts").InferDeps<D>} InferDeps
   */
  /** @typedef {import("./OutputTarget.ts").OutputTarget} OutputTarget */
  // @smithers-type-exports-end

  import React from "react";
  import { renderToStaticMarkup } from "react-dom/server";
  import { markdownComponents } from "../markdownComponents.js";
  import { zodSchemaToJsonExample } from "../zod-to-example.js";
  import { SmithersError } from "@smithers-orchestrator/errors/SmithersError";
  import { SmithersContext } from "@smithers-orchestrator/react-reconciler/context";
  import { AspectContext } from "../aspects/AspectContext.js";
  import { AntigravityAgent } from "@smithers-orchestrator/agents/AntigravityAgent";
  import { ClaudeCodeAgent } from "@smithers-orchestrator/agents/ClaudeCodeAgent";
  import { GeminiAgent } from "@smithers-orchestrator/agents/GeminiAgent";
  import { PiAgent } from "@smithers-orchestrator/agents/PiAgent";
  /** @typedef {import("@smithers-orchestrator/agents/AgentLike").AgentLike} AgentLike */
  /** @typedef {import("./DepsSpec.ts").DepsSpec} DepsSpec */
  /**
   * @template Row, Output, D
   * @typedef {import("./TaskProps.ts").TaskProps<Row, Output, D>} TaskProps
   */

  /**
   * Render a prompt React node to plain markdown text.
   *
   * If the prompt is a React element (e.g. a compiled MDX component), we inject
   * `markdownComponents` via the standard MDX `components` prop so that
   * renderToStaticMarkup outputs clean markdown instead of HTML.
   * No HTML tag stripping or entity decoding needed.
   * @param {unknown} prompt
   * @returns {string}
   */
  export function renderPromptToText(prompt) {
      if (prompt == null)
          return "";
      if (typeof prompt === "string")
          return prompt;
      if (typeof prompt === "number")
          return String(prompt);
      try {
          let element;
          if (React.isValidElement(prompt)) {
              // Inject markdown components into the element so MDX components
              // render fragments instead of HTML tags.
              element = React.cloneElement(prompt, {
                  components: markdownComponents,
              });
          }
          else {
              element = React.createElement(React.Fragment, null, prompt);
          }
          return renderToStaticMarkup(element)
              .replace(/\n{3,}/g, "\n\n")
              .trim();
      }
      catch (err) {
          const result = String(prompt ?? "");
          if (result === "[object Object]") {
              throw new SmithersError("MDX_PRELOAD_INACTIVE", `MDX prompt could not be rendered — the prompt resolved to [object Object] instead of a React component.\n\n` +
                  `This usually means the MDX preload is not active. Common causes:\n` +
                  `  • bunfig.toml uses [run] preload instead of top-level preload (the [run] section doesn't apply to dynamic imports)\n` +
                  `  • bunfig.toml is not in the current working directory\n` +
                  `  • mdxPlugin() is not registered in the preload script\n` +
                  `  • The MDX file is imported without a default import (use: import MyPrompt from "./prompt.mdx")\n\n` +
                  `Original error: ${err instanceof Error ? err.message : String(err)}`);
          }
          return result;
      }
  }
  /**
   * @param {unknown} value
   * @returns {value is import("zod").ZodObject<import("zod").ZodRawShape>}
   */
  function isZodObject(value) {
      return Boolean(value && typeof value === "object" && "shape" in value);
  }
  /**
   * @param {DepsSpec | undefined} deps
   * @param {Record<string, string> | undefined} needs
   * @returns {string[] | undefined}
   */
  function deriveDepNodeIds(deps, needs) {
      if (!deps)
          return undefined;
      const ids = new Set();
      for (const key of Object.keys(deps)) {
          const nodeId = needs?.[key] ?? key;
          if (nodeId)
              ids.add(nodeId);
      }
      return ids.size > 0 ? [...ids] : undefined;
  }
  /**
   * @param {string[] | undefined} dependsOn
   * @param {string[] | undefined} depNodeIds
   * @returns {string[] | undefined}
   */
  function mergeDependsOn(dependsOn, depNodeIds) {
      const merged = new Set();
      for (const id of dependsOn ?? [])
          merged.add(id);
      for (const id of depNodeIds ?? [])
          merged.add(id);
      return merged.size > 0 ? [...merged] : undefined;
  }
  /**
   * @param {any} ctx
   * @param {DepsSpec | undefined} deps
   * @param {Record<string, string> | undefined} needs
   * @returns {Record<string, unknown> | null}
   */
  function resolveDeps(ctx, deps, needs) {
      if (!deps)
          return Object.create(null);
      const keys = Object.keys(deps);
      if (keys.length === 0)
          return Object.create(null);
      const resolved = Object.create(null);
      for (const key of keys) {
          const target = deps[key];
          const nodeId = needs?.[key] ?? key;
          const value = ctx.outputMaybe(target, { nodeId });
          if (value === undefined)
              return null;
          resolved[key] = value;
      }
      return resolved;
  }
  /**
   * @param {AgentLike} agent
   * @param {string[] | undefined} allowTools
   * @returns {AgentLike}
   */
  function applyCliToolAllowlist(agent, allowTools) {
      if (!allowTools) {
          return agent;
      }
      if (agent instanceof ClaudeCodeAgent) {
          const opts = { ...agent.opts };
          if (allowTools.length === 0) {
              return new ClaudeCodeAgent({
                  ...opts,
                  allowedTools: [],
                  tools: "",
              });
          }
          return new ClaudeCodeAgent({
              ...opts,
              allowedTools: [...allowTools],
          });
      }
      if (agent instanceof PiAgent) {
          const opts = { ...agent.opts };
          if (allowTools.length === 0) {
              return new PiAgent({
                  ...opts,
                  tools: [],
                  noTools: true,
              });
          }
          return new PiAgent({
              ...opts,
              tools: [...allowTools],
              noTools: false,
          });
      }
      if (agent instanceof GeminiAgent) {
          const opts = { ...agent.opts };
          return new GeminiAgent({
              ...opts,
              allowedTools: [...allowTools],
          });
      }
      if (agent instanceof AntigravityAgent) {
          const opts = { ...agent.opts };
          return new AntigravityAgent({
              ...opts,
              allowedTools: [...allowTools],
          });
      }
      return agent;
  }
  /**
   * @param {unknown} ctx
   * @param {string[] | undefined} allowTools
   * @returns {string[] | undefined}
   */
  function resolveCliToolAllowlist(ctx, allowTools) {
      if (allowTools !== undefined) {
          return allowTools;
      }
      const cliAgentToolsDefault = ctx && typeof ctx === "object"
          ? ctx.__smithersRuntime?.cliAgentToolsDefault
          : undefined;
      return cliAgentToolsDefault === "explicit-only" ? [] : undefined;
  }
  /**
   * @template Row, Output, D
   * @param {TaskProps<Row, Output, D>} props
   * @returns {React.ReactElement | null}
   */
  export function Task(props) {
      const { children, agent, fallbackAgent, deps, ...rest } = props;
      const taskContext = props.smithersContext ?? SmithersContext;
      const ctx = React.useContext(taskContext);
      const aspectCtx = React.useContext(AspectContext);
      const depNodeIds = deriveDepNodeIds(deps, rest.needs);
      if (deps && !ctx) {
          throw new SmithersError("CONTEXT_OUTSIDE_WORKFLOW", "Task deps require a workflow context. Build the workflow with createSmithers().");
      }
      const resolvedDeps = deps ? resolveDeps(ctx, deps, rest.needs) : undefined;
      if (deps && resolvedDeps == null) {
          // Deps not yet available — component defers until upstream tasks complete.
          // This is normal reactive behavior; the task will re-render once deps are
          // ready. Record the deferral so the engine can distinguish a transient wait
          // from a permanent one: a deferral that survives to quiescence means a
          // dependency that can never resolve (e.g. a deps key that maps to a node id
          // no task produces), which would otherwise be a silent skip.
          ctx?.recordDeferredDep?.(props.id, depNodeIds ?? []);
          return null;
      }
      // Build aspect metadata to attach to the task element so the engine can
      // enforce budgets and track metrics at execution time.
      const aspectMeta = aspectCtx ? buildAspectMeta(aspectCtx) : undefined;
      const agentChain = Array.isArray(agent)
          ? fallbackAgent
              ? [...agent, fallbackAgent]
              : agent
          : agent && fallbackAgent
              ? [agent, fallbackAgent]
              : agent;
      const effectiveAllowTools = resolveCliToolAllowlist(ctx, rest.allowTools);
      const restrictedAgentChain = Array.isArray(agentChain)
          ? agentChain.map((entry) => applyCliToolAllowlist(entry, effectiveAllowTools))
          : agentChain
              ? applyCliToolAllowlist(agentChain, effectiveAllowTools)
              : agentChain;
      const nextDependsOn = mergeDependsOn(rest.dependsOn, depNodeIds);
      const childValue = typeof children === "function" && (agent || deps)
          ? children(resolvedDeps ?? Object.create(null))
          : children;
      if (agent) {
          // Auto-inject `schema` prop into React element children when output is a ZodObject
          let childElement = childValue;
          const schemaForInjection = props.outputSchema ??
              (isZodObject(props.output) ? props.output : undefined);
          if (React.isValidElement(childValue) && schemaForInjection) {
              childElement = React.cloneElement(childValue, {
                  schema: zodSchemaToJsonExample(schemaForInjection),
              });
          }
          const prompt = renderPromptToText(childElement);
          return React.createElement("smithers:task", {
              ...rest,
              dependsOn: nextDependsOn,
              waitAsync: rest.async === true,
              agent: restrictedAgentChain,
              __smithersKind: "agent",
              ...aspectMeta,
          }, prompt);
      }
      if (typeof children === "function" && !deps) {
          const nextProps = {
              ...rest,
              dependsOn: nextDependsOn,
              waitAsync: rest.async === true,
              __smithersKind: "compute",
              __smithersComputeFn: children,
              ...aspectMeta,
          };
          return React.createElement("smithers:task", nextProps, null);
      }
      const nextProps = {
          ...rest,
          dependsOn: nextDependsOn,
          waitAsync: rest.async === true,
          __smithersKind: "static",
          __smithersPayload: childValue,
          __payload: childValue,
          ...aspectMeta,
      };
      return React.createElement("smithers:task", nextProps, null);
  }
  /**
   * Build the __aspects metadata object from the current AspectContext.
   * This is attached to the smithers:task element props so the engine can read
   * budgets and tracking config at execution time.
   * @param {{
   *     tokenBudget?: unknown;
   *     latencySlo?: unknown;
   *     tracking?: unknown;
   *     accumulator?: unknown;
   * }} aspectCtx
   * @returns {{ __aspects: Record<string, unknown> }}
   */
  function buildAspectMeta(aspectCtx) {
      return {
          __aspects: {
              tokenBudget: aspectCtx.tokenBudget,
              latencySlo: aspectCtx.latencySlo,
              tracking: aspectCtx.tracking,
              accumulator: aspectCtx.accumulator,
          },
      };
  }
  ```

  ```ts SidecarProps.ts theme={null}
  import type React from "react";
  import type { AgentLike } from "@smithers-orchestrator/agents/AgentLike";
  import type { ScorersMap } from "@smithers-orchestrator/graph/types";
  import type { OutputTarget } from "./OutputTarget.ts";

  export type SidecarProps = {
  	id?: string;
  	agent: AgentLike;
  	sidecar: AgentLike;
  	output: OutputTarget;
  	sidecarOutput?: OutputTarget;
  	scorers?: ScorersMap;
  	prompt?: string | React.ReactNode;
  	input?: string | React.ReactNode;
  	maxConcurrency?: number;
  	groundTruth?: unknown;
  	context?: unknown;
  	primaryLabel?: string;
  	sidecarLabel?: string;
  	skipIf?: boolean;
  	children?: string | React.ReactNode;
  };
  ```
</CodeGroup>