diff --git a/HISTORY.rst b/HISTORY.rst
index 2aa67744..8ec95eb4 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -15,6 +15,12 @@ PlatformIO Core 6
 
 **A professional collaborative platform for declarative, safety-critical, and test-driven embedded development.**
 
+6.1.9 (2023-07-06)
+~~~~~~~~~~~~~~~~~~
+
+* Rectified a regression bug that occurred when the ``-include`` flag was passed via the `build_flags <https://docs.platformio.org/en/latest/projectconf/sections/env/options/build/build_flags.html>`__ option as a relative path and subsequently expanded (`issue #4683 <https://github.com/platformio/platformio-core/issues/4683>`_)
+* Resolved an issue that resulted in unresolved absolute toolchain paths when generating the `Compilation database "compile_commands.json" <https://docs.platformio.org/en/latest/integration/compile_commands.html>`__ (`issue #4684 <https://github.com/platformio/platformio-core/issues/4684>`_)
+
 6.1.8 (2023-07-05)
 ~~~~~~~~~~~~~~~~~~
 
diff --git a/docs b/docs
index 3f462c9a..f8dbf012 160000
--- a/docs
+++ b/docs
@@ -1 +1 @@
-Subproject commit 3f462c9ae63623710d48c85e16241bbb0a2b6553
+Subproject commit f8dbf012e4a7ddbe79279540e95c08a2d108c725
diff --git a/platformio/__init__.py b/platformio/__init__.py
index 75b51791..c720d005 100644
--- a/platformio/__init__.py
+++ b/platformio/__init__.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-VERSION = (6, 1, 8)
+VERSION = (6, 1, 9)
 __version__ = ".".join([str(s) for s in VERSION])
 
 __title__ = "platformio"
diff --git a/platformio/builder/main.py b/platformio/builder/main.py
index 3aa460cd..2ca41f38 100644
--- a/platformio/builder/main.py
+++ b/platformio/builder/main.py
@@ -30,7 +30,7 @@ from SCons.Script import Variables  # pylint: disable=import-error
 
 from platformio import app, fs
 from platformio.platform.base import PlatformBase
-from platformio.proc import get_pythonexe_path, where_is_program
+from platformio.proc import get_pythonexe_path
 from platformio.project.helpers import get_project_dir
 
 AllowSubstExceptions(NameError)
@@ -195,13 +195,6 @@ if env.get("SIZETOOL") and not (
     Default("checkprogsize")
 
 if "compiledb" in COMMAND_LINE_TARGETS:
-    # Resolve absolute path of toolchain
-    for cmd in ("CC", "CXX", "AS"):
-        if cmd not in env:
-            continue
-        if os.path.isabs(env[cmd]):
-            continue
-        env[cmd] = where_is_program(env.subst("$%s" % cmd), env.subst("${ENV['PATH']}"))
     env.Alias("compiledb", env.CompilationDatabase("$COMPILATIONDB_PATH"))
 
 # Print configured protocols
diff --git a/platformio/builder/tools/piobuild.py b/platformio/builder/tools/piobuild.py
index 1646dc95..74725a02 100644
--- a/platformio/builder/tools/piobuild.py
+++ b/platformio/builder/tools/piobuild.py
@@ -26,6 +26,7 @@ from SCons.Script import SConscript  # pylint: disable=import-error
 from platformio import __version__, fs
 from platformio.compat import IS_MACOS, string_types
 from platformio.package.version import pepver_to_semver
+from platformio.proc import where_is_program
 
 SRC_HEADER_EXT = ["h", "hpp"]
 SRC_ASM_EXT = ["S", "spp", "SPP", "sx", "s", "asm", "ASM"]
@@ -125,12 +126,21 @@ def ProcessProgramDeps(env):
     # remove specified flags
     env.ProcessUnFlags(env.get("BUILD_UNFLAGS"))
 
-    if "compiledb" in COMMAND_LINE_TARGETS and env.get(
-        "COMPILATIONDB_INCLUDE_TOOLCHAIN"
-    ):
-        for scope, includes in env.DumpIntegrationIncludes().items():
-            if scope in ("toolchain",):
-                env.Append(CPPPATH=includes)
+    if "compiledb" in COMMAND_LINE_TARGETS:
+        # Resolve absolute path of toolchain
+        for cmd in ("CC", "CXX", "AS"):
+            if cmd not in env:
+                continue
+            if os.path.isabs(env[cmd]):
+                continue
+            env[cmd] = where_is_program(
+                env.subst("$%s" % cmd), env.subst("${ENV['PATH']}")
+            )
+
+        if env.get("COMPILATIONDB_INCLUDE_TOOLCHAIN"):
+            for scope, includes in env.DumpIntegrationIncludes().items():
+                if scope in ("toolchain",):
+                    env.Append(CPPPATH=includes)
 
 
 def ProcessProjectDeps(env):
@@ -207,9 +217,7 @@ def ParseFlagsExtended(env, flags):  # pylint: disable=too-many-branches
     # fix relative path for "-include"
     for i, f in enumerate(result.get("CCFLAGS", [])):
         if isinstance(f, tuple) and f[0] == "-include":
-            p = env.subst(f[1].get_path())
-            if os.path.exists(p):
-                result["CCFLAGS"][i] = (f[0], os.path.abspath(p))
+            result["CCFLAGS"][i] = (f[0], env.subst(f[1].get_path()))
 
     return result
 
diff --git a/tests/commands/test_run.py b/tests/commands/test_run.py
index de13a5a8..820de44f 100644
--- a/tests/commands/test_run.py
+++ b/tests/commands/test_run.py
@@ -22,7 +22,10 @@ def test_generic_build(clirunner, validate_cliresult, tmpdir):
         ("-D TEST_INT=13", "-DTEST_INT=13"),
         ("-DTEST_SINGLE_MACRO", "-DTEST_SINGLE_MACRO"),
         ('-DTEST_STR_SPACE="Andrew Smith"', '"-DTEST_STR_SPACE=Andrew Smith"'),
+        ("-Iinclude", "-Iinclude"),
+        ("-include cpppath-include.h", "cpppath-include.h"),
         ("-Iextra_inc", "-Iextra_inc"),
+        ("-Inon-existing-dir", "non-existing-dir"),
         (
             "-include $PROJECT_DIR/lib/component/component-forced-include.h",
             "component-forced-include.h",
@@ -103,12 +106,22 @@ projenv.Append(CPPDEFINES="POST_SCRIPT_MACRO")
 #error "I_AM_FORCED_COMPONENT_INCLUDE"
 #endif
 
+#ifndef I_AM_FORCED_CPPPATH_INCLUDE
+#error "I_AM_FORCED_CPPPATH_INCLUDE"
+#endif
+
 #ifdef COMMENTED_MACRO
 #error "COMMENTED_MACRO"
 #endif
 
 int main() {
 }
+"""
+    )
+
+    tmpdir.mkdir("include").join("cpppath-include.h").write(
+        """
+#define I_AM_FORCED_CPPPATH_INCLUDE
 """
     )
     component_dir = tmpdir.mkdir("lib").mkdir("component")