Document bin padding and pin the print_summary wiring

esphome/espidf/size_summary.py

@@ -11,7 +11,10 @@ byte-identical to PlatformIO's output:
 The format matches ``script/ci_memory_impact_extract.py`` so CI memory
 analysis works unchanged on native ESP-IDF builds. RAM usage comes from
 the DRAM (or unified DIRAM) region of the linker map; Flash used is the
-size of the app ``.bin`` on disk, and Flash total is taken from
+size of the app ``.bin`` on disk, which includes esptool's 16-byte
+image padding and appended SHA-256, so it reads slightly above the
+map-derived ``Total image size`` line and moves in 16-byte steps.
+Flash total is taken from
 ``partitions.csv`` using PlatformIO's rule (first app partition whose
 subtype is ``factory`` or ``ota_0``; see
 ``platform-espressif32/builder/main.py::_update_max_upload_size``).

tests/unit_tests/test_espidf_toolchain.py

@@ -638,6 +638,27 @@ def test_run_compile_passes_compile_process_limit(setup_core: Path) -> None:
     mock_run.assert_called_once_with("build", "size", jobs=1)
 
 
+def test_run_compile_passes_size_summary_paths(setup_core: Path) -> None:
+    """print_summary receives the size json, partitions.csv, and the firmware
+    bin from get_firmware_path, which must stay in lockstep with the
+    project() name in the generated CMakeLists."""
+    _setup_build(setup_core)
+    config = {CONF_ESPHOME: {}}
+
+    with (
+        patch.object(toolchain, "need_reconfigure", return_value=False),
+        patch.object(toolchain, "run_idf_py", return_value=0),
+        patch.object(toolchain, "print_summary") as mock_summary,
+    ):
+        assert toolchain.run_compile(config, verbose=False) == 0
+
+    mock_summary.assert_called_once_with(
+        CORE.relative_build_path("build", "esp_idf_size.json"),
+        CORE.relative_build_path("partitions.csv"),
+        toolchain.get_firmware_path(),
+    )
+
+
 def test_run_compile_without_compile_process_limit(setup_core: Path) -> None:
     """When no compile_process_limit is set, no job limit is passed to idf.py."""
     _setup_build(setup_core)