diff --git a/src/together/lib/cli/api/beta/jig/jig.py b/src/together/lib/cli/api/beta/jig/jig.py
index 11d3a951..2e9bd683 100644
--- a/src/together/lib/cli/api/beta/jig/jig.py
+++ b/src/together/lib/cli/api/beta/jig/jig.py
@@ -592,6 +592,11 @@ def delete_secret(self, name: str) -> None:
     # == Build / Push / Deploy / Track ==
 
     def build(self, tag: str = "latest", warmup: bool = False, docker_args: str | None = None) -> None:
+        if self.config.deploy.image:
+            raise JigError(
+                f"Invalid command: deploy.image is set to '{self.config.deploy.image}'. "
+                "Use 'jig deploy' to deploy the configured image, or remove deploy.image to build from source."
+            )
         image = self.image(tag)
 
         if not _dockerfile(self.config):
diff --git a/tests/cli/test_beta_jig.py b/tests/cli/test_beta_jig.py
index dd9bd3ae..fc443398 100644
--- a/tests/cli/test_beta_jig.py
+++ b/tests/cli/test_beta_jig.py
@@ -228,6 +228,28 @@ def test_unset_missing_secret_message(self, tmp_path: Path) -> None:
         assert "Secret nope is not set" in result.output
 
 
+class TestBetaJigBuild:
+    def test_build_blocked_when_deploy_image_set(self, tmp_path: Path) -> None:
+        with patch.object(_jig_mod.Config, "__post_init__", _noop_config_post_init):
+            cfg = _jig_mod.Config(
+                model_name=_DEPLOY_NAME,
+                image=_jig_mod.ImageConfig(),
+                deploy=_jig_mod.DeployConfig(image="ghcr.io/org/prebuilt:latest"),
+                _path=tmp_path / "pyproject.toml",
+                _unique_name_hint="h",
+            )
+
+            def _find(*_args: Any):
+                return cfg
+
+            with patch.object(_jig_mod.Config, "find", classmethod(_find)):
+                runner = CliRunner(env=_ENV)
+                with _chdir(tmp_path):
+                    result = runner.invoke(main, ["beta", "jig", "build"])
+        assert result.exit_code == 1
+        assert "deploy.image is set" in result.output
+
+
 class TestBetaJigVolumes:
     @pytest.mark.respx(base_url=base_url)
     def test_delete(self, respx_mock: MockRouter, tmp_path: Path) -> None: