diff --git a/esphome/build_gen/espidf.py b/esphome/build_gen/espidf.py
index 65ed710ad7..7f0cd6fee8 100644
--- a/esphome/build_gen/espidf.py
+++ b/esphome/build_gen/espidf.py
@@ -92,7 +92,9 @@ def get_project_cmakelists(
 
     # esp_idf_size 2.x (bundled with IDF >=6.0) made NG the default and
     # removed the --ng flag; on 1.x (IDF 5.5) --ng is required to get
-    # --format=json2 because the legacy mode doesn't support it.
+    # --format=json2 because the legacy mode doesn't support it. 1.x json2
+    # also lacks total_size, which is why espidf/size_summary.py carries an
+    # ELF fallback; both go away together when 1.x support is dropped.
     size_ng_flag = "--ng" if idf_version() < cv.Version(6, 0, 0) else ""
 
     # Project-wide compile options: -D defines and -W warning flags (skip
diff --git a/esphome/espidf/size_summary.py b/esphome/espidf/size_summary.py
index 6aa667b023..e52e1f04c6 100644
--- a/esphome/espidf/size_summary.py
+++ b/esphome/espidf/size_summary.py
@@ -11,11 +11,9 @@ 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
-exact image size matching the ``Total image size`` line: the json2
-``total_size`` field when present (esp-idf-size >= 2.1); older 1.x
-json2 lacks it, so we derive the same figure from the ELF by summing
-loadable PROGBITS sections, the rule esp_idf_size itself uses.
-Flash total is taken from
+exact image size matching the ``Total image size`` line: json2
+``total_size`` when present, otherwise derived from the ELF (see
+``_image_size_from_elf``). 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``).
@@ -82,20 +80,29 @@ def _image_size_from_elf(elf: Path) -> int:
 
     This is the rule ``esp_idf_size.ng.memorymap._get_image_size`` uses for
     its image size figure, so the result is byte-identical to the tool's.
-    Raises ``ValueError`` if the file is not a 32-bit little-endian ELF.
+    esptool's ``ELFFile`` is deliberately not reused: its section filter
+    differs (counts INIT/FINI arrays, skips lma==0 sections) and would
+    report a different number. Reads only the header and section table,
+    not the multi-MB debug payload. Raises ``ValueError`` for anything
+    that is not a well-formed 32-bit little-endian ELF.
     """
-    data = elf.read_bytes()
-    if len(data) < 52 or data[:4] != b"\x7fELF" or data[4] != 1 or data[5] != 1:
-        raise ValueError(f"{elf} is not a 32-bit little-endian ELF")
-    (e_shoff,) = struct.unpack_from("<I", data, 0x20)
-    e_shentsize, e_shnum = struct.unpack_from("<HH", data, 0x2E)
+    with elf.open("rb") as f:
+        header = f.read(52)  # ELF32 header
+        if len(header) < 52 or header[:6] != b"\x7fELF\x01\x01":
+            raise ValueError(f"{elf} is not a 32-bit little-endian ELF")
+        (e_shoff,) = struct.unpack_from("<I", header, 0x20)  # e_shoff
+        e_shentsize, e_shnum = struct.unpack_from("<HH", header, 0x2E)
+        if e_shentsize < 40:  # sizeof(Elf32_Shdr)
+            raise ValueError(f"{elf} has an invalid section header size")
+        f.seek(e_shoff)
+        table = f.read(e_shnum * e_shentsize)
+    if len(table) < e_shnum * e_shentsize:
+        raise ValueError(f"{elf} has a truncated section header table")
     total = 0
-    for i in range(e_shnum):
-        off = e_shoff + i * e_shentsize
-        sh_type, sh_flags = struct.unpack_from("<II", data, off + 4)
-        (sh_size,) = struct.unpack_from("<I", data, off + 20)
-        # SHT_PROGBITS with SHF_ALLOC: sections with data that occupy memory
-        if sh_size and sh_type == 1 and sh_flags & 0x2:
+    for off in range(0, e_shnum * e_shentsize, e_shentsize):
+        sh_type, sh_flags = struct.unpack_from("<II", table, off + 4)
+        (sh_size,) = struct.unpack_from("<I", table, off + 20)
+        if sh_type == 1 and sh_flags & 0x2:  # SHT_PROGBITS with SHF_ALLOC
             total += sh_size
     return total
 
@@ -125,6 +132,8 @@ def print_summary(size_json: Path, partitions_csv: Path, firmware_elf: Path) ->
     ram_total = ram_region.get("total")
     if ram_total and ram_used is not None:
         print_size_line("RAM", ram_used, ram_total)
+    else:
+        _LOGGER.debug("Skipping RAM summary: no DRAM/DIRAM region in %s", 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.
@@ -133,7 +142,12 @@ def print_summary(size_json: Path, partitions_csv: Path, firmware_elf: Path) ->
         if flash_used is None:
             flash_used = _image_size_from_elf(firmware_elf)
         app_size = _find_app_partition_size(partitions_csv)
-    except (OSError, ValueError, struct.error) as e:
+    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:
         _LOGGER.debug("Skipping Flash summary: %s", e)
         return
     print_size_line("Flash", flash_used, app_size)
diff --git a/tests/unit_tests/test_espidf_toolchain.py b/tests/unit_tests/test_espidf_toolchain.py
index a26952aa8d..bb2aab17a2 100644
--- a/tests/unit_tests/test_espidf_toolchain.py
+++ b/tests/unit_tests/test_espidf_toolchain.py
@@ -655,7 +655,7 @@ def test_run_compile_passes_size_summary_paths(setup_core: Path) -> None:
     mock_summary.assert_called_once_with(
         CORE.relative_build_path("build", "esp_idf_size.json"),
         CORE.relative_build_path("partitions.csv"),
-        toolchain.get_built_elf_path(),
+        CORE.relative_build_path("build", f"{CORE.name}.elf"),
     )
 
 
diff --git a/tests/unit_tests/test_size_summary.py b/tests/unit_tests/test_size_summary.py
index d84be67af8..dc871fe3a2 100644
--- a/tests/unit_tests/test_size_summary.py
+++ b/tests/unit_tests/test_size_summary.py
@@ -28,22 +28,26 @@ def _write_partitions(tmp_path: Path) -> Path:
     return out
 
 
-def _write_elf(tmp_path: Path, sections: list[tuple[int, int, int]]) -> Path:
+def _write_elf(
+    tmp_path: Path,
+    sections: list[tuple[int, int, int]],
+    shentsize: int = 40,
+    truncate: int | None = None,
+) -> Path:
     """Write a minimal ELF32 LE whose section headers carry the given
     (sh_type, sh_flags, sh_size) triples."""
-    header = bytearray(52)
-    header[0:4] = b"\x7fELF"
-    header[4] = header[5] = 1  # 32-bit, little-endian
-    struct.pack_into("<I", header, 0x20, 52)  # e_shoff
-    struct.pack_into("<HH", header, 0x2E, 40, len(sections))
-    out = bytearray(header)
+    out = bytearray(52)
+    out[0:4] = b"\x7fELF"
+    out[4] = out[5] = 1  # 32-bit, little-endian
+    struct.pack_into("<I", out, 0x20, 52)  # e_shoff
+    struct.pack_into("<HH", out, 0x2E, shentsize, len(sections))
     for sh_type, sh_flags, sh_size in sections:
         shdr = bytearray(40)
         struct.pack_into("<II", shdr, 4, sh_type, sh_flags)
         struct.pack_into("<I", shdr, 20, sh_size)
         out += shdr
     elf = tmp_path / "firmware.elf"
-    elf.write_bytes(bytes(out))
+    elf.write_bytes(out if truncate is None else out[:truncate])
     return elf
 
 
@@ -111,8 +115,8 @@ def _s3_size_data() -> dict:
 
 
 def _print_summary_ram_only(tmp_path: Path, size_json: Path) -> None:
-    """Call print_summary with no partitions.csv or firmware bin on disk."""
-    print_summary(size_json, tmp_path / "partitions.csv", tmp_path / "firmware.bin")
+    """Call print_summary with no partitions.csv or ELF on disk."""
+    print_summary(size_json, tmp_path / "partitions.csv", tmp_path / "firmware.elf")
 
 
 def test_print_summary_esp32_uses_dram(
@@ -203,19 +207,32 @@ def test_print_summary_flash_line_derives_from_elf(
     assert "(used 724215 bytes from 1835008 bytes)" in out
 
 
-@pytest.mark.parametrize("problem", ["missing_elf", "not_an_elf", "missing_partitions"])
+@pytest.mark.parametrize(
+    "problem",
+    [
+        "missing_elf",
+        "not_an_elf",
+        "bad_shentsize",
+        "truncated_table",
+        "missing_partitions",
+    ],
+)
 def test_print_summary_skips_flash_on_bad_input(
     problem: str, tmp_path: Path, capsys: pytest.CaptureFixture[str]
 ) -> 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())
     firmware_elf = tmp_path / "firmware.elf"
-    if problem == "missing_partitions":
-        _write_elf(tmp_path, [(1, 0x2, 1024)])
-    else:
+    if problem != "missing_partitions":
         _write_partitions(tmp_path)
-        if problem == "not_an_elf":
-            firmware_elf.write_bytes(b"junk")
+    if problem == "not_an_elf":
+        firmware_elf.write_bytes(b"junk")
+    elif problem == "bad_shentsize":
+        _write_elf(tmp_path, [(1, 0x2, 1024)], shentsize=0)
+    elif problem == "truncated_table":
+        _write_elf(tmp_path, [(1, 0x2, 1024)], truncate=60)
+    elif problem == "missing_partitions":
+        _write_elf(tmp_path, [(1, 0x2, 1024)])
     print_summary(size_json, tmp_path / "partitions.csv", firmware_elf)
     out = capsys.readouterr().out
     assert "RAM:" in out