diff --git a/src/cli.ts b/src/cli.ts
index ae37e4d..82d9d69 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -1129,13 +1129,25 @@ function nativeProofConfigFromModule(loaded: unknown): NativeProofConfig | undef
   return isNativeProofConfig(current) ? current : undefined;
 }
 
+/**
+ * The selection the preflight resolves the project with: CLI flags first, then the same
+ * env vars the runner itself reads (PLATFORM / NATIVEPROOF_PROJECT). Without the env
+ * fallback, `PLATFORM=ios nativeproof` preflighted the android project (wrong Appium
+ * driver ensured, macOS guard skipped) and then ran the ios one.
+ */
+export function runSelection(args: CliArgs, env: NodeJS.ProcessEnv = process.env): RunnerEnv {
+  const selection: RunnerEnv = {};
+  const platform = args.platform ?? env.PLATFORM;
+  const project = args.project ?? env.NATIVEPROOF_PROJECT;
+  if (platform) selection.platform = platform;
+  if (project) selection.project = project;
+  return selection;
+}
+
 async function runTests(args: CliArgs): Promise<number> {
   const { wdioConfig, configPath, extraEnv } = resolveRunner(args);
   const userConfig = await loadNativeProofConfig(configPath);
-  const selection: RunnerEnv = {};
-  if (args.platform) selection.platform = args.platform;
-  if (args.project) selection.project = args.project;
-  const project = resolveProject(userConfig, selection);
+  const project = resolveProject(userConfig, runSelection(args));
   const appium = await ensureAppium(userConfig.appium, args.startAppium, project.platform);
   try {
     return await new Promise<number>((resolve, reject) => {
diff --git a/src/config.ts b/src/config.ts
index a08a582..06001b7 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -181,7 +181,7 @@ export interface RunnerEnv {
   spec?: string;
 }
 
-/** Pick the project by explicit name, else by platform, else the first one. */
+/** Pick the project by explicit name, else by platform (loudly failing on no match), else the first one. */
 export function resolveProject(config: RunnerConfig, env: RunnerEnv = {}): DeviceProject {
   if (env.project) {
     const named = config.projects.find((project) => project.name === env.project);
@@ -191,6 +191,12 @@ export function resolveProject(config: RunnerConfig, env: RunnerEnv = {}): Devic
   if (env.platform) {
     const byPlatform = config.projects.find((project) => project.platform === env.platform);
     if (byPlatform) return byPlatform;
+    // Falling back to projects[0] here silently ran the WRONG platform: `--ios` with an
+    // android-only config did an android run with android evidence and zero warning.
+    const available = config.projects.map((project) => `${project.name} (${project.platform})`).join(", ");
+    throw new Error(
+      `nativeproof: no ${env.platform} project in nativeproof.config.ts — available: ${available}`,
+    );
   }
   const first = config.projects[0];
   if (!first) throw new Error("nativeproof: config has no `projects`");
diff --git a/test/cli.test.ts b/test/cli.test.ts
index 09dd724..9430c36 100644
--- a/test/cli.test.ts
+++ b/test/cli.test.ts
@@ -17,6 +17,7 @@ import {
   onboardCommand,
   parseArgs,
   resolveRunner,
+  runSelection,
   type ScaffoldIo,
   scaffold,
   scaffoldFiles,
@@ -649,3 +650,12 @@ test("updateConfigAppPath survives comments containing apostrophes and braces",
   assert.match(updated.slice(androidAt), /"appium:app": "\.\/old\.apk"/); // android untouched
   assert.doesNotMatch(updated.slice(androidAt), /New\.app/);
 });
+
+test("runSelection falls back to the env vars the runner itself reads", () => {
+  const args = parseArgs([]);
+  // Flags win; without them, PLATFORM/NATIVEPROOF_PROJECT steer the preflight exactly
+  // like they steer the runner — previously the CLI preflighted projects[0] instead.
+  assert.deepEqual(runSelection(args, { PLATFORM: "ios" }), { platform: "ios" });
+  assert.deepEqual(runSelection(args, { NATIVEPROOF_PROJECT: "beta" }), { project: "beta" });
+  assert.deepEqual(runSelection(parseArgs(["--android"]), { PLATFORM: "ios" }), { platform: "android" });
+});
diff --git a/test/config.test.ts b/test/config.test.ts
index 99c90d9..e09a68b 100644
--- a/test/config.test.ts
+++ b/test/config.test.ts
@@ -214,3 +214,11 @@ test("findConfigFile locates nativeproof.config.* via the injected exists check"
     null,
   );
 });
+
+test("resolveProject errors when an explicit platform has no matching project", () => {
+  // Falling back to projects[0] silently ran the wrong platform for `--ios`.
+  assert.throws(
+    () => resolveProject({ projects }, { platform: "ios2" }),
+    /no ios2 project in nativeproof\.config\.ts — available: .*android/,
+  );
+});