diff --git a/pkg/nuclide-rust/lib/BuckIntegration.js b/pkg/nuclide-rust/lib/BuckIntegration.js
new file mode 100644
index 00000000000..6c91bb892c9
--- /dev/null
+++ b/pkg/nuclide-rust/lib/BuckIntegration.js
@@ -0,0 +1,85 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the license found in the LICENSE file in
+ * the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TaskInfo} from '../../nuclide-buck/lib/types';
+import type {
+  AtomLanguageService,
+  LanguageService,
+} from '../../nuclide-language-service';
+
+import invariant from 'invariant';
+import {getLogger} from 'log4js';
+import fsPromise from 'nuclide-commons/fsPromise';
+import nuclideUri from 'nuclide-commons/nuclideUri';
+import {getRustInputs, getSaveAnalysisTargets, normalizeNameForBuckQuery} from './BuckUtils';
+
+import * as BuckService from '../../nuclide-buck-rpc';
+
+const logger = getLogger('nuclide-rust');
+
+export async function updateRlsBuildForTask(
+  task: TaskInfo,
+  service: AtomLanguageService<LanguageService>,
+) {
+  const buildTarget = normalizeNameForBuckQuery(task.buildTarget);
+
+  const files = await getRustInputs(task.buckRoot, buildTarget);
+  // Probably not a Rust build target, ignore
+  if (files.length == 0)
+    return;
+  // We need only to pick a representative file to get a related lang service
+  const fileUri = task.buckRoot + '/' + files[0];
+  atom.notifications.addInfo(`fileUri: ${fileUri}`);
+
+  const langService = await service.getLanguageServiceForUri(fileUri);
+  invariant(langService != null);
+
+  // Since `buck` execution is not trivial - the command may be overriden, needs
+  // to inherit the environment, passes internal FB USER to env etc. the RLS
+  // can't just invoke that.
+  // Instead, we build now, copy paths to resulting .json analysis artifacts to
+  // a temp file and just use `cat $TMPFILE` as a dummy build command.
+  const analysisTargets = await getSaveAnalysisTargets(task.buckRoot, buildTarget);
+  logger.debug(`analysisTargets: ${analysisTargets.join('\n')}`);
+  let artifacts: Array<string> = [];
+
+  const buildReport = await BuckService.build(task.buckRoot, analysisTargets);
+  if (buildReport.success === false) {
+    atom.notifications.addError("save-analysis build failed");
+    return;
+  }
+
+  Object.values(buildReport.results)
+    // TODO: https://buckbuild.com/command/build.html specifies that for
+    // FETCHED_FROM_CACHE we might not get an output file - can we force it
+    // somehow? Or we always locally produce a save-analysis .json file?
+    .forEach((targetReport: any) => artifacts.push(targetReport.output));
+
+  const tempfile = await fsPromise.tempfile();
+  await fsPromise.writeFile(tempfile, artifacts.join('\n'));
+
+  // TODO: Windows?
+  const buildCommand = `cat ${tempfile}`;
+
+  logger.debug(`Built SA artifacts: ${artifacts.join('\n')}`);
+  logger.debug(`buildCommand: ${buildCommand}`);
+
+  langService.sendLspNotification(fileUri, 'workspace/didChangeConfiguration',
+    {
+      settings: {
+        rust: {
+          unstable_features: true, // Required for build_command
+          build_on_save: true,
+          build_command: buildCommand, // TODO: Only in RLS branch: https://github.com/Xanewok/rls/tree/external-build
+        }
+      }
+    });
+}
diff --git a/pkg/nuclide-rust/lib/BuckUtils.js b/pkg/nuclide-rust/lib/BuckUtils.js
new file mode 100644
index 00000000000..c0440c125a2
--- /dev/null
+++ b/pkg/nuclide-rust/lib/BuckUtils.js
@@ -0,0 +1,50 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the license found in the LICENSE file in
+ * the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {TaskInfo} from '../../nuclide-buck/lib/types';
+
+import * as BuckService from '../../nuclide-buck-rpc';
+
+export function getRustInputs(buckRoot: string, buildTarget: BuildTarget): Promise<Array<string>> {
+  return BuckService.
+    query(buckRoot, `filter('.*\\.rs$', inputs('${buildTarget}'))`, []);
+}
+
+export function getSaveAnalysisTargets(buckRoot: string, buildTarget: BuildTarget): Promise<Array<string>> {
+  // Save-analysis build flavor is only supported by rust_{binary, library}
+  // kinds (so exclude prebuilt_rust_library kind)
+  const query: string = `kind('^rust_.*', deps(${buildTarget}))`;
+
+  return BuckService.query(buckRoot, query, []).then(deps =>
+    deps.map(dep => dep + '#save-analysis'),
+  );
+}
+
+export type BuildTarget = string;
+
+// FIXME: Copied from nuclide-buck-rpc
+// Buck query doesn't allow omitting // or adding # for flavors, this needs to be fixed in buck.
+export function normalizeNameForBuckQuery(aliasOrTarget: string): BuildTarget {
+  let canonicalName = aliasOrTarget;
+  // Don't prepend // for aliases (aliases will not have colons or .)
+  if (
+    (canonicalName.indexOf(':') !== -1 || canonicalName.indexOf('.') !== -1) &&
+    canonicalName.indexOf('//') === -1
+  ) {
+    canonicalName = '//' + canonicalName;
+  }
+  // Strip flavor string
+  const flavorIndex = canonicalName.indexOf('#');
+  if (flavorIndex !== -1) {
+    canonicalName = canonicalName.substr(0, flavorIndex);
+  }
+  return canonicalName;
+}
diff --git a/pkg/nuclide-rust/lib/RustLanguage.js b/pkg/nuclide-rust/lib/RustLanguage.js
index abdc42f0ce4..05978ecbd67 100644
--- a/pkg/nuclide-rust/lib/RustLanguage.js
+++ b/pkg/nuclide-rust/lib/RustLanguage.js
@@ -49,6 +49,11 @@ async function connectionToRustService(
       useOriginalEnvironment: true,
       additionalLogFilesRetentionPeriod: 5 * 60 * 1000, // 5 minutes
       waitForDiagnostics: true,
+      initializationOptions: {
+        // Don't let RLS eagerly build (and fail crashing while finding a
+        // Cargo.toml if the project uses Buck) for now.
+        omitInitBuild: true,
+      },
     },
   );
 
diff --git a/pkg/nuclide-rust/lib/main.js b/pkg/nuclide-rust/lib/main.js
index a853cfb607e..441b2a051c1 100644
--- a/pkg/nuclide-rust/lib/main.js
+++ b/pkg/nuclide-rust/lib/main.js
@@ -19,6 +19,8 @@ import createPackage from 'nuclide-commons-atom/createPackage';
 import UniversalDisposable from 'nuclide-commons/UniversalDisposable';
 import {createRustLanguageService} from './RustLanguage';
 
+import {updateRlsBuildForTask} from './BuckIntegration';
+
 class Activation {
   _rustLanguageService: AtomLanguageService<LanguageService>;
   _buckTaskRunnerService: ?BuckTaskRunnerService;
@@ -32,6 +34,8 @@ class Activation {
   }
 
   consumeBuckTaskRunner(service: BuckTaskRunnerService): IDisposable {
+    service.onDidCompleteTask(task => updateRlsBuildForTask(task, this._rustLanguageService));
+
     this._buckTaskRunnerService = service;
     return new UniversalDisposable(() => {
       this._buckTaskRunnerService = null;