From 987da8f5c4c19cfc095b55cbcca1efd288824748 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Wed, 26 Aug 2026 08:40:35 -0500
Subject: [PATCH] Treat resource exhaustion as transient in the generic pch
 flow too

---
 esphome/build_helpers/pch.py              |  6 ++++++
 tests/unit_tests/build_gen/test_espidf.py | 26 +++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/esphome/build_helpers/pch.py b/esphome/build_helpers/pch.py
index fe414a94ca..aff553a087 100644
--- a/esphome/build_helpers/pch.py
+++ b/esphome/build_helpers/pch.py
@@ -71,6 +71,9 @@ _CCACHE_PCH_ENV = {
 
 # Both include forms: an angle include resolving under src/ must enter the
 # digest too; ones that do not resolve simply end the walk
+# Compiler failures that clear on their own must not latch the .failed marker
+_TRANSIENT_ERRORS = ("No space left", "Cannot allocate", "Resource temporarily")
+
 _INCLUDE_RE = re.compile(rb'^\s*#\s*include\s+["<]([^">]+)[">]', re.MULTILINE)
 
 
@@ -379,6 +382,9 @@ def prepare_pch(
         # This path latches, so keep the full compiler output recoverable
         _LOGGER.debug("Full pch compile output: %s", error)
         discard_pch(build_dir)
+        if any(m in error for m in _TRANSIENT_ERRORS):
+            # Resource exhaustion clears on its own; retry next build
+            return
         # Skip retries until a header/flag/backend-identity/command change
         failed_marker.write_text(checksum + "\n", encoding="utf-8")
         os.utime(header)
diff --git a/tests/unit_tests/build_gen/test_espidf.py b/tests/unit_tests/build_gen/test_espidf.py
index a01c35c18c..dca97c5fde 100644
--- a/tests/unit_tests/build_gen/test_espidf.py
+++ b/tests/unit_tests/build_gen/test_espidf.py
@@ -1052,3 +1052,29 @@ def test_prepare_pch_identity_unknown_discards(tmp_path: Path) -> None:
         prepare_pch()
     assert not stale.exists()
     assert not (dev / "build" / "esphome_pch.h.gch.sum").exists()
+
+
+def test_prepare_pch_transient_compiler_failure_does_not_latch(
+    tmp_path: Path,
+) -> None:
+    """ENOSPC-style failures clear on their own; no .failed marker."""
+    from esphome.build_gen.espidf import prepare_pch
+
+    dev = _make_pch_device(tmp_path, "dev_e")
+    CORE.build_path = dev
+    calls = []
+
+    def enospc(cmd, **kwargs):
+        calls.append(cmd)
+        return subprocess.CompletedProcess(
+            cmd, 1, "", "fatal error: No space left on device"
+        )
+
+    with (
+        patch.object(CORE, "name", "test"),
+        patch("esphome.build_helpers.pch.subprocess.run", side_effect=enospc),
+    ):
+        prepare_pch()
+        prepare_pch()
+    assert not (dev / "build" / "esphome_pch.h.gch.failed").exists()
+    assert len(calls) == 2