diff --git a/esphome/espidf/size_summary.py b/esphome/espidf/size_summary.py
index cab632defe..d5d345b7e6 100644
--- a/esphome/espidf/size_summary.py
+++ b/esphome/espidf/size_summary.py
@@ -124,32 +124,36 @@ def print_summary(size_json: Path, partitions_csv: Path, firmware_elf: Path) ->
         for entry in data.get("layout", [])
         if isinstance(entry, dict)
     }
-    ram_region = regions.get("DRAM") or regions.get("DIRAM") or {}
-    ram_used = ram_region.get("used")
-    ram_total = ram_region.get("total")
-    if ram_total and ram_used is not None:
+    # Every chip has a DRAM or DIRAM region, so a warning here usually
+    # means the esp_idf_size json schema changed
+    ram_region = regions.get("DRAM") or regions.get("DIRAM")
+    if ram_region is None:
+        _LOGGER.warning("Skipping RAM summary: no DRAM/DIRAM region in %s", size_json)
+    elif (
+        isinstance(ram_total := ram_region.get("total"), int)
+        and ram_total > 0
+        and isinstance(ram_used := ram_region.get("used"), int)
+    ):
         print_size_line("RAM", ram_used, ram_total)
     else:
-        # Every chip has a DRAM or DIRAM region, so this firing usually
-        # means the esp_idf_size json schema changed
-        _LOGGER.warning("Skipping RAM summary: no DRAM/DIRAM region in %s", size_json)
+        _LOGGER.warning(
+            "Skipping RAM summary: unusable region %s in %s", ram_region, size_json
+        )
 
     # esp-idf-size >= 2.1 (IDF >= 6.0) reports the exact image size in
     # json2; older 1.x omits it, so derive the same figure from the ELF.
     flash_used = data.get("total_size")
-    try:
-        if flash_used is None:
-            _LOGGER.debug(
-                "No total_size in %s, deriving from %s", size_json, firmware_elf
-            )
+    if not (isinstance(flash_used, int) and flash_used > 0):
+        _LOGGER.debug("No total_size in %s, deriving from %s", size_json, firmware_elf)
+        try:
             flash_used = _image_size_from_elf(firmware_elf)
+        except (OSError, ValueError) as e:
+            # The ELF must be present and well formed after a successful build
+            _LOGGER.warning("Skipping Flash summary: %s", e)
+            return
+    try:
         app_size = _find_app_partition_size(partitions_csv)
-    except FileNotFoundError as e:
-        # The ELF must exist after a successful build; a missing
-        # partitions.csv raises ValueError and stays at debug level.
-        _LOGGER.warning("Skipping Flash summary: %s", e)
-        return
-    except (OSError, ValueError) as e:
+    except ValueError as e:
         _LOGGER.debug("Skipping Flash summary: %s", e)
         return
     print_size_line("Flash", flash_used, app_size)
diff --git a/tests/unit_tests/test_size_summary.py b/tests/unit_tests/test_size_summary.py
index cebf16eca5..be4b96f1ba 100644
--- a/tests/unit_tests/test_size_summary.py
+++ b/tests/unit_tests/test_size_summary.py
@@ -134,7 +134,9 @@ def test_print_summary_s3_falls_back_to_diram(
 
 
 def test_print_summary_skips_when_diram_total_collapses(
-    tmp_path: Path, capsys: pytest.CaptureFixture[str]
+    tmp_path: Path,
+    capsys: pytest.CaptureFixture[str],
+    caplog: pytest.LogCaptureFixture,
 ) -> None:
     """A zero-size region drops the RAM line rather than divide by zero."""
     size_json = _write_size_json(
@@ -147,6 +149,7 @@ def test_print_summary_skips_when_diram_total_collapses(
     _print_summary_ram_only(tmp_path, size_json)
     out = capsys.readouterr().out
     assert "RAM:" not in out
+    assert "unusable region" in caplog.text
 
 
 def test_print_summary_handles_missing_json(
@@ -158,12 +161,18 @@ def test_print_summary_handles_missing_json(
 
 
 def test_print_summary_handles_no_layout(
-    tmp_path: Path, capsys: pytest.CaptureFixture[str]
+    tmp_path: Path,
+    capsys: pytest.CaptureFixture[str],
+    caplog: pytest.LogCaptureFixture,
 ) -> None:
-    """A size json without ``layout`` still doesn't crash."""
+    """A size json without ``layout`` warns so schema drift is visible."""
     size_json = _write_size_json(tmp_path, {"version": "1.1"})
     _print_summary_ram_only(tmp_path, size_json)
     assert capsys.readouterr().out == ""
+    assert any(
+        r.levelname == "WARNING" and "no DRAM/DIRAM region" in r.message
+        for r in caplog.records
+    )
 
 
 def test_print_summary_flash_line_prefers_total_size(
@@ -202,6 +211,22 @@ def test_print_summary_flash_line_derives_from_elf(
     assert "(used 724215 bytes from 1835008 bytes)" in out
 
 
+def test_print_summary_flash_falls_back_on_bad_total_size(
+    tmp_path: Path, capsys: pytest.CaptureFixture[str]
+) -> None:
+    """A zero or non-int total_size falls back to the ELF instead of
+    printing a used-0-bytes line CI would read as a real measurement."""
+    data = _s3_size_data()
+    data["total_size"] = 0
+    size_json = _write_size_json(tmp_path, data)
+    partitions = _write_partitions(tmp_path)
+    firmware_elf = tmp_path / "firmware.elf"
+    firmware_elf.write_bytes(_elf_bytes([(1, 0x2, 4096)]))
+    print_summary(size_json, partitions, firmware_elf)
+    out = capsys.readouterr().out
+    assert "(used 4096 bytes from 1835008 bytes)" in out
+
+
 _GOOD_ELF = _elf_bytes([(1, 0x2, 1024)])
 
 
@@ -224,6 +249,7 @@ def test_print_summary_skips_flash_on_bad_input(
     with_partitions: bool,
     tmp_path: Path,
     capsys: pytest.CaptureFixture[str],
+    caplog: pytest.LogCaptureFixture,
 ) -> None:
     """An unusable ELF or missing partitions.csv skips the Flash line, not the RAM line."""
     size_json = _write_size_json(tmp_path, _s3_size_data())
@@ -236,3 +262,10 @@ def test_print_summary_skips_flash_on_bad_input(
     out = capsys.readouterr().out
     assert "RAM:" in out
     assert "Flash:" not in out
+    # ELF problems warn (anomaly after a successful build); a missing
+    # partitions.csv stays at debug
+    warned = any(
+        r.levelname == "WARNING" and "Skipping Flash summary" in r.message
+        for r in caplog.records
+    )
+    assert warned == with_partitions