diff --git a/scripts/build-plugins.cjs b/scripts/build-plugins.cjs
index 318c53294..1a585d11a 100644
--- a/scripts/build-plugins.cjs
+++ b/scripts/build-plugins.cjs
@@ -8,11 +8,12 @@
  *
  * For development, `--local <dir>` (or TERMIX_LOCAL_PLUGINS) points at a
  * folder of plugin repos like ../Termix-Plugins. A plugin there whose sources
- * changed since its last build is rebuilt first, then any built one (has
+ * changed since its last build is rebuilt first with this checkout's SDK, so
+ * SDK edits apply without publishing, then any built one (has
  * dist/) is copied in place of its pin, or added when it has no pin.
  */
 
-const { execSync } = require("node:child_process");
+const { execFileSync } = require("node:child_process");
 const fs = require("node:fs");
 const path = require("node:path");
 const {
@@ -21,6 +22,7 @@ const {
   extractArtifact,
   findLocalPluginBuilds,
   rebuildLocalPlugins,
+  localSdkBuildCommand,
   copyLocalBuild,
   buildBundledIndex,
 } = require("./lib/bundled-plugins.cjs");
@@ -34,9 +36,10 @@ async function main() {
   const localArg =
     flag !== -1 ? process.argv[flag + 1] : process.env.TERMIX_LOCAL_PLUGINS;
   const localDir = localArg ? path.resolve(root, localArg) : null;
+  const [node, buildArgs] = localSdkBuildCommand();
   rebuildLocalPlugins(localDir, null, (repo, id) => {
     console.log(`building ${id}`);
-    execSync("npm run build", { cwd: repo, stdio: "inherit" });
+    execFileSync(node, buildArgs, { cwd: repo, stdio: "inherit" });
   });
   const local = findLocalPluginBuilds(localDir);
 
diff --git a/scripts/bundled-plugins.test.ts b/scripts/bundled-plugins.test.ts
index 7ee32339a..2f77790c5 100644
--- a/scripts/bundled-plugins.test.ts
+++ b/scripts/bundled-plugins.test.ts
@@ -13,6 +13,7 @@ import {
   buildBundledIndex,
   findLocalPluginBuilds,
   isLocalBuildStale,
+  localSdkBuildCommand,
   rebuildLocalPlugins,
   copyLocalBuild,
 } from "./lib/bundled-plugins.cjs";
@@ -354,6 +355,40 @@ describe("rebuilding local plugins", () => {
     expect(isLocalBuildStale(root)).toBe(true);
   });
 
+  it("is stale when the SDK CLI changed after the build", () => {
+    const root = repo(tempDir(), "Plugin-A", "a");
+    const cli = path.join(tempDir(), "cli");
+    fs.mkdirSync(cli);
+    fs.writeFileSync(path.join(cli, "index.mjs"), "x");
+    fs.mkdirSync(path.join(root, "dist"));
+    fs.writeFileSync(path.join(root, "dist", "frontend.js"), "x");
+    touch(path.join(root, "manifest.json"), 60);
+    touch(path.join(root, "src", "index.ts"), 60);
+    touch(path.join(cli, "index.mjs"), 60);
+    expect(isLocalBuildStale(root, cli)).toBe(false);
+
+    touch(path.join(root, "dist", "frontend.js"), 30);
+    touch(path.join(cli, "index.mjs"), 0);
+    expect(isLocalBuildStale(root, cli)).toBe(true);
+    expect(isLocalBuildStale(root)).toBe(false);
+  });
+
+  it("builds with this checkout's SDK CLI, not the plugin's own", () => {
+    const [command, args] = localSdkBuildCommand();
+    expect(command).toBe(process.execPath);
+    expect(args).toEqual([
+      path.resolve(
+        __dirname,
+        "..",
+        "packages",
+        "plugin-sdk",
+        "cli",
+        "index.mjs",
+      ),
+      "build",
+    ]);
+  });
+
   it("builds only stale repos for bundled ids that have node_modules", () => {
     const dir = tempDir();
     repo(dir, "Plugin-A", "a");
diff --git a/scripts/dev.mjs b/scripts/dev.mjs
index 6d8ba5a8d..0b97b69d6 100644
--- a/scripts/dev.mjs
+++ b/scripts/dev.mjs
@@ -45,7 +45,10 @@ import {
 } from "./lib/dev-docker.mjs";
 
 const require = createRequire(import.meta.url);
-const { copyLocalBuild } = require("./lib/bundled-plugins.cjs");
+const {
+  copyLocalBuild,
+  localSdkBuildCommand,
+} = require("./lib/bundled-plugins.cjs");
 
 const root = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
 const BACKEND_ENTRY = path.join(
@@ -83,7 +86,9 @@ function run(command, args, cwd = root) {
     const child = spawn(command, args, {
       cwd,
       stdio: ["ignore", "inherit", "inherit"],
-      shell: process.platform === "win32",
+      // npm is a .cmd on Windows and needs the shell, but the shell splits
+      // arguments on spaces, so a path like "Personal Projects" gets cut.
+      shell: process.platform === "win32" && !path.isAbsolute(command),
     });
     child.on("error", reject);
     child.on("exit", (code) =>
@@ -541,7 +546,7 @@ function watchCoreForDocker() {
 async function rebuildPlugin({ id, repo }) {
   log(`building ${id}`);
   try {
-    await run("npm", ["run", "build"], repo);
+    await run(...localSdkBuildCommand(), repo);
   } catch (error) {
     warn(`${id} failed to build: ${error.message}`);
     return;
diff --git a/scripts/lib/bundled-plugins.cjs b/scripts/lib/bundled-plugins.cjs
index 940e1e02e..ddbbc034d 100644
--- a/scripts/lib/bundled-plugins.cjs
+++ b/scripts/lib/bundled-plugins.cjs
@@ -299,14 +299,37 @@ function newestMtime(target) {
 }
 
 /** True when a plugin repo has never been built or its sources changed since. */
-function isLocalBuildStale(repo) {
+/** The SDK CLI in this checkout, which dev builds local plugins with. */
+const LOCAL_SDK_CLI = path.join(
+  __dirname,
+  "..",
+  "..",
+  "packages",
+  "plugin-sdk",
+  "cli",
+);
+
+/**
+ * True when the build is missing, a source is newer than it, or the SDK CLI
+ * that builds it changed since (sdkCli, when given).
+ */
+function isLocalBuildStale(repo, sdkCli) {
   const built = newestMtime(path.join(repo, "dist"));
   if (!built) return true;
+  if (sdkCli && newestMtime(sdkCli) > built) return true;
   return BUILD_INPUTS.some(
     (entry) => newestMtime(path.join(repo, entry)) > built,
   );
 }
 
+/**
+ * The command that builds a plugin repo with this checkout's SDK instead of
+ * the published one in its node_modules, so SDK edits apply right away.
+ */
+function localSdkBuildCommand() {
+  return [process.execPath, [path.join(LOCAL_SDK_CLI, "index.mjs"), "build"]];
+}
+
 /**
  * Builds each plugin repo whose build is missing or out of date. ids limits
  * it to those plugins; null builds every one.
@@ -325,7 +348,8 @@ function rebuildLocalPlugins(dir, ids, run) {
     } catch {
       continue;
     }
-    if ((ids && !ids.has(id)) || !isLocalBuildStale(repo)) continue;
+    if ((ids && !ids.has(id)) || !isLocalBuildStale(repo, LOCAL_SDK_CLI))
+      continue;
     run(repo, id);
     rebuilt.push(id);
   }
@@ -346,6 +370,7 @@ function copyLocalBuild(repo, destination) {
 module.exports = {
   findLocalPluginBuilds,
   isLocalBuildStale,
+  localSdkBuildCommand,
   rebuildLocalPlugins,
   copyLocalBuild,
   parseBundledPlugins,