diff --git a/esphome/arduino8266/toolchain.py b/esphome/arduino8266/toolchain.py
index 6513bbe866..f671a68ba7 100644
--- a/esphome/arduino8266/toolchain.py
+++ b/esphome/arduino8266/toolchain.py
@@ -107,6 +107,10 @@ def run_compile(config: ConfigType, verbose: bool) -> int:
         check=False,
         close_fds=False,
     )
+    if probe.stderr.strip():
+        # A load-time diagnostic (e.g. "multiple rules generate X") flags a
+        # generator bug; the skip branch would otherwise swallow it forever
+        _LOGGER.warning("ninja: %s", probe.stderr.strip())
     if probe.returncode == 0 and "no work to do" in probe.stdout:
         _LOGGER.debug("ninja: nothing to rebuild")
     else:
@@ -117,6 +121,14 @@ def run_compile(config: ConfigType, verbose: bool) -> int:
         if rc != 0:
             return rc
 
+    # A generator defect emitting no default targets must not turn into a
+    # green build with no firmware (size summary and idedata only warn)
+    build_dir_artifacts = (get_elf_path(), get_build_dir() / "firmware.bin")
+    for artifact in build_dir_artifacts:
+        if not artifact.is_file():
+            _LOGGER.error("Build produced no %s", artifact)
+            return 1
+
     _print_size_summary(build_dir, paths)
     try:
         idedata = get_idedata(ccache)
diff --git a/script/test_build_components.py b/script/test_build_components.py
index ddd8a6a67d..0e3281fd8c 100755
--- a/script/test_build_components.py
+++ b/script/test_build_components.py
@@ -1178,6 +1178,12 @@ def test_components(
                         toolchain=toolchain,
                     )
 
+    if not test_results:
+        # A green run that compiled nothing (renamed/removed test fixture,
+        # bad platform filter) must not pass CI
+        print("No tests matched the requested components/platform")
+        return 1
+
     # Separate results into passed and failed
     passed_results = [r for r in test_results if r.success]
     failed_results = [r for r in test_results if not r.success]
diff --git a/tests/script/test_test_build_components.py b/tests/script/test_test_build_components.py
index 74e150380c..502d888c12 100644
--- a/tests/script/test_test_build_components.py
+++ b/tests/script/test_test_build_components.py
@@ -236,3 +236,12 @@ def test_run_grouped_test_closes_group_when_subprocess_raises(
         )
 
     assert "::endgroup::" in capsys.readouterr().out
+
+
+def test_components_empty_match_fails(capsys: pytest.CaptureFixture[str]) -> None:
+    """A real component filtered to a platform with no matching test file
+    must not pass CI as a green zero-component compile. (An unknown
+    component name instead builds the reference baseline.)"""
+    rc = tbc.test_components(["logger"], "zz-none", "compile", False)
+    assert rc == 1
+    assert "No tests matched" in capsys.readouterr().out
diff --git a/tests/unit_tests/test_arduino8266_toolchain.py b/tests/unit_tests/test_arduino8266_toolchain.py
index 49363fcff4..ec760887ae 100644
--- a/tests/unit_tests/test_arduino8266_toolchain.py
+++ b/tests/unit_tests/test_arduino8266_toolchain.py
@@ -38,6 +38,12 @@ def _setup_core(tmp_path: Path) -> None:
     CORE.config_path = tmp_path / "test8266.yaml"
     CORE.build_path = tmp_path
     CORE.data[KEY_CORE] = {KEY_FRAMEWORK_VERSION: cv.Version(3, 1, 2)}
+    # run_compile verifies the produced artifacts; give every test a build
+    # that "produced" them (tests for the guard delete them again)
+    build_dir = CORE.relative_pioenvs_path("test8266")
+    build_dir.mkdir(parents=True, exist_ok=True)
+    (build_dir / "firmware.elf").write_bytes(b"")
+    (build_dir / "firmware.bin").write_bytes(b"")
 
 
 def _paths(tmp_path: Path) -> framework.InstalledPaths:
@@ -82,7 +88,9 @@ def test_run_compile_success(tmp_path: Path) -> None:
         patch.object(framework, "get_build_env", return_value={}),
         patch("esphome.build_gen.arduino8266.write_project"),
         patch.object(
-            toolchain.subprocess, "run", return_value=MagicMock(returncode=0)
+            toolchain.subprocess,
+            "run",
+            return_value=MagicMock(returncode=0, stdout="", stderr=""),
         ) as mock_run,
         patch.object(toolchain, "_write_compile_commands") as mock_compdb,
         patch.object(toolchain, "_print_size_summary") as mock_size,
@@ -114,7 +122,9 @@ def test_run_compile_noop_skips_the_build_spawn(tmp_path: Path) -> None:
         patch.object(
             toolchain.subprocess,
             "run",
-            return_value=MagicMock(returncode=0, stdout="ninja: no work to do.\n"),
+            return_value=MagicMock(
+                returncode=0, stdout="ninja: no work to do.\n", stderr=""
+            ),
         ) as mock_run,
         patch.object(toolchain, "_write_compile_commands"),
         patch.object(toolchain, "_print_size_summary"),
@@ -127,6 +137,58 @@ def test_run_compile_noop_skips_the_build_spawn(tmp_path: Path) -> None:
     assert ninja_calls[0][0][0][-1] == "-n"
 
 
+def test_run_compile_surfaces_probe_diagnostics(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    """A load-time ninja diagnostic (a generator bug signal) reaches the
+    user even when the no-work branch skips the real spawn."""
+    with (
+        patch.object(framework, "check_and_install", return_value=_paths(tmp_path)),
+        patch.object(framework, "get_build_env", return_value={}),
+        patch("esphome.build_gen.arduino8266.write_project"),
+        patch.object(
+            toolchain.subprocess,
+            "run",
+            return_value=MagicMock(
+                returncode=0,
+                stdout="ninja: no work to do.\n",
+                stderr="ninja: warning: multiple rules generate x\n",
+            ),
+        ),
+        patch.object(toolchain, "_write_compile_commands"),
+        patch.object(toolchain, "_print_size_summary"),
+        patch.object(toolchain, "get_idedata"),
+    ):
+        rc = toolchain.run_compile({CONF_ESPHOME: {}}, verbose=False)
+    assert rc == 0
+    assert "multiple rules generate x" in caplog.text
+
+
+def test_run_compile_missing_artifact_fails(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    """A zero ninja exit that produced no firmware must not be a green
+    build (size summary and idedata only warn)."""
+    (toolchain.get_build_dir() / "firmware.elf").unlink()
+    with (
+        patch.object(framework, "check_and_install", return_value=_paths(tmp_path)),
+        patch.object(framework, "get_build_env", return_value={}),
+        patch("esphome.build_gen.arduino8266.write_project"),
+        patch.object(
+            toolchain.subprocess,
+            "run",
+            return_value=MagicMock(returncode=0, stdout="", stderr=""),
+        ),
+        patch.object(toolchain, "_write_compile_commands"),
+        patch.object(toolchain, "_print_size_summary") as mock_size,
+        patch.object(toolchain, "get_idedata"),
+    ):
+        rc = toolchain.run_compile({CONF_ESPHOME: {}}, verbose=False)
+    assert rc == 1
+    assert "Build produced no" in caplog.text
+    mock_size.assert_not_called()
+
+
 def test_run_compile_warns_when_idedata_fails(
     tmp_path: Path, caplog: pytest.LogCaptureFixture
 ) -> None:
@@ -136,7 +198,11 @@ def test_run_compile_warns_when_idedata_fails(
         patch.object(framework, "check_and_install", return_value=_paths(tmp_path)),
         patch.object(framework, "get_build_env", return_value={}),
         patch("esphome.build_gen.arduino8266.write_project"),
-        patch.object(toolchain.subprocess, "run", return_value=MagicMock(returncode=0)),
+        patch.object(
+            toolchain.subprocess,
+            "run",
+            return_value=MagicMock(returncode=0, stdout="", stderr=""),
+        ),
         patch.object(toolchain, "_write_compile_commands"),
         patch.object(toolchain, "_print_size_summary"),
         patch.object(toolchain, "get_idedata", return_value=None),
@@ -316,7 +382,7 @@ def test_get_idedata_no_ccache(tmp_path: Path) -> None:
 def test_run_compile_skips_compdb_when_ninja_unchanged(tmp_path: Path) -> None:
     """An unchanged build.ninja means the compile DB is already current."""
     build_dir = toolchain.get_build_dir()
-    build_dir.mkdir(parents=True)
+    build_dir.mkdir(parents=True, exist_ok=True)
 
     def run(regenerate_expected: bool) -> None:
         with (
@@ -324,7 +390,9 @@ def test_run_compile_skips_compdb_when_ninja_unchanged(tmp_path: Path) -> None:
             patch.object(framework, "get_build_env", return_value={}),
             patch("esphome.build_gen.arduino8266.write_project", return_value=False),
             patch.object(
-                toolchain.subprocess, "run", return_value=MagicMock(returncode=0)
+                toolchain.subprocess,
+                "run",
+                return_value=MagicMock(returncode=0, stdout="", stderr=""),
             ),
             patch.object(toolchain, "_write_compile_commands") as mock_compdb,
             patch.object(toolchain, "_print_size_summary"),
@@ -420,7 +488,11 @@ def test_run_compile_idedata_error_does_not_fail_build(
         patch.object(framework, "check_and_install", return_value=_paths(tmp_path)),
         patch.object(framework, "get_build_env", return_value={}),
         patch("esphome.build_gen.arduino8266.write_project"),
-        patch.object(toolchain.subprocess, "run", return_value=MagicMock(returncode=0)),
+        patch.object(
+            toolchain.subprocess,
+            "run",
+            return_value=MagicMock(returncode=0, stdout="", stderr=""),
+        ),
         patch.object(toolchain, "_write_compile_commands"),
         patch.object(toolchain, "_print_size_summary"),
         patch.object(