diff --git a/src/build-args.test.ts b/src/build-args.test.ts
index 18628436..5a53c072 100644
--- a/src/build-args.test.ts
+++ b/src/build-args.test.ts
@@ -23,6 +23,24 @@ describe('buildCliArgs', () => {
     ).toStrictEqual(['build', 'game', '--targetPlatform=StandaloneLinux64']);
   });
 
+  it('omits --engineVersion when unityVersion is unset or "auto"', () => {
+    const noneSet = buildCliArgs(inputsOf({ targetPlatform: 'StandaloneLinux64' }));
+    const explicitAuto = buildCliArgs(
+      inputsOf({ targetPlatform: 'StandaloneLinux64', unityVersion: 'auto' }),
+    );
+
+    expect(noneSet.some((arg) => arg.startsWith('--engineVersion'))).toBe(false);
+    expect(explicitAuto.some((arg) => arg.startsWith('--engineVersion'))).toBe(false);
+  });
+
+  it('maps an explicit unityVersion to --engineVersion, overriding auto-detection', () => {
+    const args = buildCliArgs(
+      inputsOf({ targetPlatform: 'WebGL', unityVersion: '6000.0.36f1' }),
+    );
+
+    expect(args).toContain('--engineVersion=6000.0.36f1');
+  });
+
   it('throws for a non-local providerStrategy, matching the base action without @game-ci/orchestrator', () => {
     expect(() =>
       buildCliArgs(inputsOf({ targetPlatform: 'StandaloneLinux64', providerStrategy: 'aws' })),
diff --git a/src/build-args.ts b/src/build-args.ts
index 05a02941..665bbd7e 100644
--- a/src/build-args.ts
+++ b/src/build-args.ts
@@ -2,18 +2,20 @@
  * Translates unity-builder's action inputs into `game-ci build` (or, for
  * providerStrategy=local-system, `game-ci orchestrate`) CLI flags.
  *
- * Two deliberate omissions for the `build` path, both because there is
- * nothing to translate to:
- *  - `unityVersion` (except "auto"): the CLI always detects the Unity
- *    version from the checked-out project's ProjectSettings/ProjectVersion.txt
- *    and has no flag to override that today (game-ci/cli's engine-detection
- *    middleware unconditionally overwrites any passed value). Pinning a
- *    version other than "auto" is a known, real gap versus the original
- *    action - see the PR this shipped in.
+ * One deliberate omission for the `build` path, because there is nothing
+ * to translate to:
  *  - `providerStrategy` values other than "local"/"local-system": the base
  *    action (without the separately-installed @game-ci/orchestrator plugin)
  *    already throws for these today, so throwing here isn't a regression.
  *
+ * `unityVersion` (except "auto", which means "let the CLI auto-detect from
+ * ProjectSettings/ProjectVersion.txt", so it's never passed through as a
+ * literal flag value): mapped to `--engineVersion`, which game-ci/cli's
+ * engine-detection middleware now respects instead of unconditionally
+ * overwriting (game-ci/cli#154). Not carried into ORCHESTRATE_STRING_FLAGS -
+ * unverified whether `orchestrate`'s local-system path reads engineVersion
+ * the same way; scope this out until confirmed.
+ *
  * Boolean inputs use GitHub Actions' own truthy/falsy string convention
  * ('true'/'false', case-insensitive) - see actions/toolkit's getBooleanInput.
  */
@@ -236,6 +238,11 @@ export function buildCliArgs({ getInput }: BuildArgsOptions): string[] {
   }
   args.push(`--targetPlatform=${targetPlatform}`);
 
+  const unityVersion = getInput('unityVersion');
+  if (unityVersion && unityVersion !== 'auto') {
+    args.push(`--engineVersion=${unityVersion}`);
+  }
+
   pushStringFlags(args, getInput, STRING_FLAGS);
   pushBooleanFlags(args, getInput, BOOLEAN_FLAGS);
 
diff --git a/src/index.ts b/src/index.ts
index 1a27ff24..1bcf00c8 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -18,15 +18,6 @@ import { resolveProjectPath } from './resolve-project-path';
 
 export async function run() {
   try {
-    const unityVersion = core.getInput('unityVersion') || 'auto';
-    if (unityVersion !== 'auto') {
-      core.warning(
-        `unityVersion="${unityVersion}" is ignored: the underlying game-ci CLI always detects the Unity ` +
-          "version from the checked-out project's ProjectSettings/ProjectVersion.txt and has no flag to " +
-          'override it yet.',
-      );
-    }
-
     const cliVersion = core.getInput('cliVersion') || 'latest';
     const cliPath = await downloadCli(cliVersion);