diff --git a/.gitignore b/.gitignore
index 8f538f09..0712e779 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@ yarn-error.log
 .vscode
 todo.txt
 result
+shell.nix
diff --git a/packages/components/package.json b/packages/components/package.json
index e0a1abd2..6e0cba3f 100644
--- a/packages/components/package.json
+++ b/packages/components/package.json
@@ -10,6 +10,7 @@
     "@hookform/resolvers": "^2.9.8",
     "@quri/squiggle-lang": "^0.5.0",
     "@react-hook/size": "^2.1.2",
+    "@types/uuid": "^8.3.4",
     "clsx": "^1.2.1",
     "framer-motion": "^7.5.1",
     "lodash": "^4.17.21",
@@ -18,6 +19,7 @@
     "react-hook-form": "^7.36.1",
     "react-use": "^17.4.0",
     "react-vega": "^7.6.0",
+    "uuid": "^9.0.0",
     "vega": "^5.22.1",
     "vega-embed": "^6.21.0",
     "vega-lite": "^5.5.0",
@@ -42,6 +44,7 @@
     "@types/node": "^18.8.0",
     "@types/react": "^18.0.21",
     "@types/styled-components": "^5.1.26",
+    "@types/uuid": "^8.3.4",
     "@types/webpack": "^5.28.0",
     "canvas": "^2.10.1",
     "cross-env": "^7.0.3",
@@ -82,7 +85,8 @@
     "format": "prettier --write .",
     "prepack": "yarn run build:cjs && yarn run bundle",
     "test": "jest",
-    "test:debug": "node --inspect-brk node_modules/.bin/jest --runInBand"
+    "test:debug": "node --inspect-brk node_modules/.bin/jest --runInBand",
+    "test:profile": "node --cpu-prof node_modules/.bin/jest --runInBand"
   },
   "eslintConfig": {
     "extends": [
diff --git a/packages/components/src/components/SquiggleChart.tsx b/packages/components/src/components/SquiggleChart.tsx
index 2e126d4c..215031a7 100644
--- a/packages/components/src/components/SquiggleChart.tsx
+++ b/packages/components/src/components/SquiggleChart.tsx
@@ -1,25 +1,17 @@
 import * as React from "react";
-import {
-  SqValue,
-  environment,
-  defaultEnvironment,
-  resultMap,
-  SqValueTag,
-} from "@quri/squiggle-lang";
+import { SqValue, environment, SqProject } from "@quri/squiggle-lang";
 import { useSquiggle } from "../lib/hooks";
 import { SquiggleViewer } from "./SquiggleViewer";
 import { JsImports } from "../lib/jsImports";
 import { getValueToRender } from "../lib/utility";
 
-export interface SquiggleChartProps {
+export type SquiggleChartProps = {
   /** The input string for squiggle */
-  code?: string;
+  code: string;
   /** Allows to re-run the code if code hasn't changed */
   executionId?: number;
   /** If the output requires monte carlo sampling, the amount of samples */
   sampleCount?: number;
-  /** The amount of points returned to draw the distribution */
-  environment?: environment;
   /** If the result is a function, where the function domain starts */
   diagramStart?: number;
   /** If the result is a function, where the function domain ends */
@@ -27,7 +19,7 @@ export interface SquiggleChartProps {
   /** If the result is a function, the amount of stops sampled */
   diagramCount?: number;
   /** When the squiggle code gets reevaluated */
-  onChange?(expr: SqValue | undefined): void;
+  onChange?(expr: SqValue | undefined, sourceName: string): void;
   /** CSS width of the element */
   width?: number;
   height?: number;
@@ -54,10 +46,27 @@ export interface SquiggleChartProps {
   /** Whether to show vega actions to the user, so they can copy the chart spec */
   distributionChartActions?: boolean;
   enableLocalSettings?: boolean;
-}
+} & (StandaloneExecutionProps | ProjectExecutionProps);
 
+// Props needed for a standalone execution
+type StandaloneExecutionProps = {
+  project?: undefined;
+  continues?: undefined;
+  /** The amount of points returned to draw the distribution, not needed if using a project */
+  environment?: environment;
+};
+
+// Props needed when executing inside a project.
+type ProjectExecutionProps = {
+  environment?: undefined;
+  /** The project that this execution is part of */
+  project: SqProject;
+  /** What other squiggle sources from the project to continue. Default [] */
+  continues?: string[];
+};
 const defaultOnChange = () => {};
 const defaultImports: JsImports = {};
+const defaultContinues: string[] = [];
 
 export const splitSquiggleChartSettings = (props: SquiggleChartProps) => {
   const {
@@ -104,19 +113,32 @@ export const SquiggleChart: React.FC<SquiggleChartProps> = React.memo(
       splitSquiggleChartSettings(props);
 
     const {
-      code = "",
-      environment,
+      code,
       jsImports = defaultImports,
       onChange = defaultOnChange, // defaultOnChange must be constant, don't move its definition here
       executionId = 0,
       width,
       height = 200,
       enableLocalSettings = false,
+      continues = defaultContinues,
     } = props;
 
+    const p = React.useMemo(() => {
+      if (props.project) {
+        return props.project;
+      } else {
+        const p = SqProject.create();
+        if (props.environment) {
+          p.setEnvironment(props.environment);
+        }
+        return p;
+      }
+    }, [props.project, props.environment]);
+
     const resultAndBindings = useSquiggle({
+      continues,
+      project: p,
       code,
-      environment,
       jsImports,
       onChange,
       executionId,
@@ -131,7 +153,7 @@ export const SquiggleChart: React.FC<SquiggleChartProps> = React.memo(
         height={height}
         distributionPlotSettings={distributionPlotSettings}
         chartSettings={chartSettings}
-        environment={environment ?? defaultEnvironment}
+        environment={p.getEnvironment()}
         enableLocalSettings={enableLocalSettings}
       />
     );
diff --git a/packages/components/src/components/SquiggleEditor.tsx b/packages/components/src/components/SquiggleEditor.tsx
index 731b5d0c..23765f38 100644
--- a/packages/components/src/components/SquiggleEditor.tsx
+++ b/packages/components/src/components/SquiggleEditor.tsx
@@ -7,7 +7,7 @@ import {
 } from "./SquiggleChart";
 import { useMaybeControlledValue, useSquiggle } from "../lib/hooks";
 import { JsImports } from "../lib/jsImports";
-import { defaultEnvironment, SqLocation } from "@quri/squiggle-lang";
+import { defaultEnvironment, SqLocation, SqProject } from "@quri/squiggle-lang";
 import { SquiggleViewer } from "./SquiggleViewer";
 import { getErrorLocations, getValueToRender } from "../lib/utility";
 
@@ -56,9 +56,17 @@ export const SquiggleEditor: React.FC<SquiggleEditorProps> = (props) => {
     enableLocalSettings = false,
   } = props;
 
+  const project = React.useMemo(() => {
+    const p = SqProject.create();
+    if (environment) {
+      p.setEnvironment(environment);
+    }
+    return p;
+  }, [environment]);
+
   const resultAndBindings = useSquiggle({
     code,
-    environment,
+    project,
     jsImports,
     onChange,
     executionId,
diff --git a/packages/components/src/components/SquigglePlayground.tsx b/packages/components/src/components/SquigglePlayground.tsx
index de467918..59898d6b 100644
--- a/packages/components/src/components/SquigglePlayground.tsx
+++ b/packages/components/src/components/SquigglePlayground.tsx
@@ -28,7 +28,7 @@ import {
 } from "@heroicons/react/solid";
 import clsx from "clsx";
 
-import { environment } from "@quri/squiggle-lang";
+import { environment, SqProject } from "@quri/squiggle-lang";
 
 import { SquiggleChartProps } from "./SquiggleChart";
 import { CodeEditor } from "./CodeEditor";
@@ -305,9 +305,17 @@ export const SquigglePlayground: FC<PlaygroundProps> = ({
     executionId,
   } = useRunnerState(code);
 
+  const project = React.useMemo(() => {
+    const p = SqProject.create();
+    if (environment) {
+      p.setEnvironment(environment);
+    }
+    return p;
+  }, [environment]);
+
   const resultAndBindings = useSquiggle({
     code,
-    environment,
+    project,
     jsImports: imports,
     executionId,
   });
diff --git a/packages/components/src/components/SquiggleViewer/ExpressionViewer.tsx b/packages/components/src/components/SquiggleViewer/ExpressionViewer.tsx
index cb40c509..1c041dbf 100644
--- a/packages/components/src/components/SquiggleViewer/ExpressionViewer.tsx
+++ b/packages/components/src/components/SquiggleViewer/ExpressionViewer.tsx
@@ -2,7 +2,7 @@ import React, { useContext } from "react";
 import { SqDistributionTag, SqValue, SqValueTag } from "@quri/squiggle-lang";
 import { NumberShower } from "../NumberShower";
 import { DistributionChart, defaultPlot, makePlot } from "../DistributionChart";
-import { FunctionChart, FunctionChartSettings } from "../FunctionChart";
+import { FunctionChart } from "../FunctionChart";
 import clsx from "clsx";
 import { VariableBox } from "./VariableBox";
 import { ItemSettingsMenu } from "./ItemSettingsMenu";
diff --git a/packages/components/src/index.ts b/packages/components/src/index.ts
index bbd0d178..b8a6e385 100644
--- a/packages/components/src/index.ts
+++ b/packages/components/src/index.ts
@@ -1,3 +1,4 @@
+export { SqProject } from "@quri/squiggle-lang/";
 export { SquiggleChart } from "./components/SquiggleChart";
 export { SquiggleEditor } from "./components/SquiggleEditor";
 export { SquigglePlayground } from "./components/SquigglePlayground";
diff --git a/packages/components/src/lib/hooks/useSquiggle.ts b/packages/components/src/lib/hooks/useSquiggle.ts
index b2812d6f..63fa3839 100644
--- a/packages/components/src/lib/hooks/useSquiggle.ts
+++ b/packages/components/src/lib/hooks/useSquiggle.ts
@@ -1,5 +1,4 @@
 import {
-  environment,
   result,
   SqError,
   SqProject,
@@ -8,13 +7,15 @@ import {
 } from "@quri/squiggle-lang";
 import { useEffect, useMemo } from "react";
 import { JsImports, jsImportsToSquiggleCode } from "../jsImports";
+import * as uuid from "uuid";
 
 type SquiggleArgs = {
   code: string;
   executionId?: number;
   jsImports?: JsImports;
-  environment?: environment;
-  onChange?: (expr: SqValue | undefined) => void;
+  project: SqProject;
+  continues?: string[];
+  onChange?: (expr: SqValue | undefined, sourceName: string) => void;
 };
 
 export type ResultAndBindings = {
@@ -22,33 +23,63 @@ export type ResultAndBindings = {
   bindings: SqRecord;
 };
 
+const importSourceName = (sourceName: string) => "imports-" + sourceName;
+const defaultContinues = [];
+
 export const useSquiggle = (args: SquiggleArgs): ResultAndBindings => {
+  const sourceName = useMemo(() => uuid.v4(), []);
+
+  const env = args.project.getEnvironment();
+  const continues = args.continues || defaultContinues;
+
   const result = useMemo(
     () => {
-      const project = SqProject.create();
-      project.setSource("main", args.code);
-      if (args.environment) {
-        project.setEnvironment(args.environment);
-      }
+      const project = args.project;
+
+      project.setSource(sourceName, args.code);
+      let fullContinues = continues;
       if (args.jsImports && Object.keys(args.jsImports).length) {
         const importsSource = jsImportsToSquiggleCode(args.jsImports);
-        project.setSource("imports", importsSource);
-        project.setContinues("main", ["imports"]);
+        project.setSource(importSourceName(sourceName), importsSource);
+        fullContinues = continues.concat(importSourceName(sourceName));
       }
-      project.run("main");
-      const result = project.getResult("main");
-      const bindings = project.getBindings("main");
+      project.setContinues(sourceName, fullContinues);
+      project.run(sourceName);
+      const result = project.getResult(sourceName);
+      const bindings = project.getBindings(sourceName);
       return { result, bindings };
     },
+    // This complains about executionId not being used inside the function body.
+    // This is on purpose, as executionId simply allows you to run the squiggle
+    // code again
     // eslint-disable-next-line react-hooks/exhaustive-deps
-    [args.code, args.environment, args.jsImports, args.executionId]
+    [
+      args.code,
+      args.jsImports,
+      args.executionId,
+      sourceName,
+      continues,
+      args.project,
+      env,
+    ]
   );
 
   const { onChange } = args;
 
   useEffect(() => {
-    onChange?.(result.result.tag === "Ok" ? result.result.value : undefined);
-  }, [result, onChange]);
+    onChange?.(
+      result.result.tag === "Ok" ? result.result.value : undefined,
+      sourceName
+    );
+  }, [result, onChange, sourceName]);
+
+  useEffect(() => {
+    return () => {
+      args.project.removeSource(sourceName);
+      if (args.project.getSource(importSourceName(sourceName)))
+        args.project.removeSource(importSourceName(sourceName));
+    };
+  }, [args.project, sourceName]);
 
   return result;
 };
diff --git a/packages/components/test/basic.test.tsx b/packages/components/test/basic.test.tsx
index 9eb4973a..e77f104b 100644
--- a/packages/components/test/basic.test.tsx
+++ b/packages/components/test/basic.test.tsx
@@ -3,11 +3,11 @@ import React from "react";
 import "@testing-library/jest-dom";
 import { SquiggleChart } from "../src/index";
 
-test("Logs no warnings or errors", async () => {
-  debugger;
+test("Logs nothing on render", async () => {
   const { unmount } = render(<SquiggleChart code={"normal(0, 1)"} />);
   unmount();
 
+  expect(console.log).not.toBeCalled();
   expect(console.warn).not.toBeCalled();
   expect(console.error).not.toBeCalled();
 });
diff --git a/packages/components/test/cleanup.test.tsx b/packages/components/test/cleanup.test.tsx
new file mode 100644
index 00000000..d2be427a
--- /dev/null
+++ b/packages/components/test/cleanup.test.tsx
@@ -0,0 +1,39 @@
+import { render } from "@testing-library/react";
+import React from "react";
+import "@testing-library/jest-dom";
+import { SquiggleChart } from "../src/index";
+import { SqProject } from "@quri/squiggle-lang";
+
+test("Creates and cleans up source", async () => {
+  const project = SqProject.create();
+
+  const { unmount } = render(
+    <SquiggleChart code={"normal(0, 1)"} project={project} />
+  );
+
+  expect(project.getSourceIds().length).toBe(1);
+
+  const sourceId = project.getSourceIds()[0];
+  expect(project.getSource(sourceId)).toBe("normal(0, 1)");
+
+  unmount();
+  expect(project.getSourceIds().length).toBe(0);
+  expect(project.getSource(sourceId)).toBe(undefined);
+});
+
+test("Creates and cleans up source and imports", async () => {
+  const project = SqProject.create();
+
+  const { unmount } = render(
+    <SquiggleChart
+      code={"normal($x, 1)"}
+      project={project}
+      jsImports={{ x: 3 }}
+    />
+  );
+
+  expect(project.getSourceIds().length).toBe(2);
+
+  unmount();
+  expect(project.getSourceIds()).toStrictEqual([]);
+});
diff --git a/yarn.lock b/yarn.lock
index 9e4d2db1..2292e288 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -5186,6 +5186,11 @@
   resolved "https://registry.yarnpkg.com/@types/unist/-/unist-2.0.6.tgz#250a7b16c3b91f672a24552ec64678eeb1d3a08d"
   integrity sha512-PBjIUxZHOuj0R15/xuwJYjFi+KZdNFrehocChv4g5hu6aFroHue8m0lBP0POdK2nKzbw0cgV1mws8+V/JAcEkQ==
 
+"@types/uuid@^8.3.4":
+  version "8.3.4"
+  resolved "https://registry.yarnpkg.com/@types/uuid/-/uuid-8.3.4.tgz#bd86a43617df0594787d38b735f55c805becf1bc"
+  integrity sha512-c/I8ZRb51j+pYGAu5CrFMRxqZ2ke4y2grEBO5AUjgSkSk+qT2Ea+OdWElz/OiMf5MNpn2b17kuVBwZLQJXzihw==
+
 "@types/vscode@^1.70.0":
   version "1.71.0"
   resolved "https://registry.yarnpkg.com/@types/vscode/-/vscode-1.71.0.tgz#a8d9bb7aca49b0455060e6eb978711b510bdd2e2"
@@ -18723,6 +18728,11 @@ uuid@^8.0.0, uuid@^8.3.2:
   resolved "https://registry.yarnpkg.com/uuid/-/uuid-8.3.2.tgz#80d5b5ced271bb9af6c445f21a1a04c606cefbe2"
   integrity sha512-+NYs2QeMWy+GWFOEm9xnn6HCDp0l7QBD7ml8zLUmJ+93Q5NF0NocErnwkTkXVFNiX3/fpC6afS8Dhb/gz7R7eg==
 
+uuid@^9.0.0:
+  version "9.0.0"
+  resolved "https://registry.yarnpkg.com/uuid/-/uuid-9.0.0.tgz#592f550650024a38ceb0c562f2f6aa435761efb5"
+  integrity sha512-MXcSTerfPa4uqyzStbRoTgt5XIe3x5+42+q1sDuy3R5MDk66URdLMOZe5aPX/SQd+kuYAh0FdP/pO28IkQyTeg==
+
 v8-compile-cache-lib@^3.0.1:
   version "3.0.1"
   resolved "https://registry.yarnpkg.com/v8-compile-cache-lib/-/v8-compile-cache-lib-3.0.1.tgz#6336e8d71965cb3d35a1bbb7868445a7c05264bf"