diff --git a/pw_bloat/bloat.gni b/pw_bloat/bloat.gni
index 9acfd05..a22f0b2 100644
--- a/pw_bloat/bloat.gni
+++ b/pw_bloat/bloat.gni
@@ -161,6 +161,7 @@
           pw_doc_sources = rebase_path([ _doc_rst_output ], root_build_dir)
         }
         script = "$dir_pw_bloat/py/pw_bloat/no_bloaty.py"
+        python_deps = [ "$dir_pw_bloat/py" ]
         args = [ rebase_path(_doc_rst_output) ]
         outputs = [ _doc_rst_output ]
       }
@@ -176,6 +177,7 @@
           pw_doc_sources = rebase_path([ _doc_rst_output ], root_build_dir)
         }
         script = "$dir_pw_bloat/py/pw_bloat/bloat.py"
+        python_deps = [ "$dir_pw_bloat/py" ]
         inputs = _bloaty_configs
         outputs = [
           "$target_gen_dir/${target_name}.txt",
@@ -321,6 +323,7 @@
         pw_doc_sources = rebase_path([ _doc_rst_output ], root_build_dir)
       }
       script = "$dir_pw_bloat/py/pw_bloat/no_toolchains.py"
+      python_deps = [ "$dir_pw_bloat/py" ]
       args = [ rebase_path(_doc_rst_output) ]
       outputs = [ _doc_rst_output ]
     }
diff --git a/pw_bloat/py/BUILD.gn b/pw_bloat/py/BUILD.gn
index 53198ae..c6d5ea3 100644
--- a/pw_bloat/py/BUILD.gn
+++ b/pw_bloat/py/BUILD.gn
@@ -27,4 +27,5 @@
     "pw_bloat/no_toolchains.py",
   ]
   pylintrc = "$dir_pigweed/.pylintrc"
+  python_deps = [ "$dir_pw_cli/py" ]
 }
diff --git a/pw_bloat/py/setup.py b/pw_bloat/py/setup.py
index 73410da..73c2a7e 100644
--- a/pw_bloat/py/setup.py
+++ b/pw_bloat/py/setup.py
@@ -24,4 +24,5 @@
     packages=setuptools.find_packages(),
     package_data={'pw_bloat': ['py.typed']},
     zip_safe=False,
+    install_requires=['pw_cli'],
 )
diff --git a/pw_build/py/BUILD.gn b/pw_build/py/BUILD.gn
index fde1846..7f941d2 100644
--- a/pw_build/py/BUILD.gn
+++ b/pw_build/py/BUILD.gn
@@ -33,5 +33,9 @@
     "pw_build/zip_test.py",
   ]
   tests = [ "python_runner_test.py" ]
+  python_deps = [
+    "$dir_pw_cli/py",
+    "$dir_pw_presubmit/py",
+  ]
   pylintrc = "$dir_pigweed/.pylintrc"
 }
diff --git a/pw_build/py/setup.py b/pw_build/py/setup.py
index c8fc23e..2a5a746 100644
--- a/pw_build/py/setup.py
+++ b/pw_build/py/setup.py
@@ -26,5 +26,7 @@
     zip_safe=False,
     install_requires=[
         'wheel',
+        'pw_cli',
+        'pw_presubmit',
     ],
 )
diff --git a/pw_build/python.gni b/pw_build/python.gni
index 7c5a58a..5af65c7 100644
--- a/pw_build/python.gni
+++ b/pw_build/python.gni
@@ -17,6 +17,16 @@
 import("$dir_pw_build/input_group.gni")
 import("$dir_pw_build/python_action.gni")
 
+# Python packages provide the following targets as $target_name.$subtarget.
+_python_subtargets = [
+  "tests",
+  "lint",
+  "lint.mypy",
+  "lint.pylint",
+  "install",
+  "wheel",
+]
+
 # Defines a Python package. GN Python packages contain several GN targets:
 #
 #   - $name - Provides the Python files in the build, but does not take any
@@ -29,6 +39,9 @@
 #   - $name.install - Installs the package in a venv.
 #   - $name.wheel - Builds a Python wheel for the package. (Not implemented.)
 #
+# All Python packages are instantiated with the default toolchain, regardless of
+# the current toolchain.
+#
 # TODO(pwbug/239): Implement wheel building.
 #
 # Args:
@@ -115,10 +128,28 @@
     }
   }
 
+  _internal_target = "$target_name._internal"
+
+  # Create groups with the public target names ($target_name, $target_name.lint,
+  # $target_name.install, etc.). These are actually wrappers around internal
+  # Python actions instantiated with the default toolchain. This ensures there
+  # is only a single copy of each Python action in the build.
+  #
+  # The $target_name.tests group is created separately below.
+  foreach(subtarget, _python_subtargets - [ "tests" ]) {
+    group("$target_name.$subtarget") {
+      deps = [ ":$_internal_target.$subtarget($default_toolchain)" ]
+    }
+  }
+
+  group("$target_name") {
+    deps = [ ":$_internal_target($default_toolchain)" ]
+  }
+
   # Declare the main Python package group. This represents the Python files, but
   # does not take any actions. GN targets can depend on the package name to run
   # when any files in the package change.
-  pw_input_group(target_name) {
+  pw_input_group("$_internal_target") {
     inputs = _all_py_files
     if (defined(invoker.inputs)) {
       inputs += invoker.inputs
@@ -131,12 +162,10 @@
     }
   }
 
-  _package_target = ":$target_name"
-
   if (_is_package) {
     # Install this Python package and its dependencies in the current Python
     # environment.
-    pw_python_action("$target_name.install") {
+    pw_python_action("$_internal_target.install") {
       module = "pip"
       args = [ "install" ]
 
@@ -152,7 +181,7 @@
       # Parallel pip installations don't work, so serialize pip invocations.
       pool = "$dir_pw_build:pip_pool"
 
-      deps = [ _package_target ]
+      deps = [ ":$_internal_target" ]
       foreach(dep, _python_deps) {
         deps += [ "$dep.install" ]
       }
@@ -160,7 +189,7 @@
 
     # TODO(pwbug/239): Add support for building groups of wheels. The code below
     #     is incomplete and untested.
-    pw_python_action("$target_name.wheel") {
+    pw_python_action("$_internal_target.wheel") {
       script = "$dir_pw_build/py/pw_build/python_wheels.py"
 
       args = [
@@ -169,18 +198,18 @@
       ]
       args += rebase_path(_all_py_files)
 
-      deps = [ _package_target ]
+      deps = [ ":$_internal_target.install" ]
       stamp = true
     }
   } else {
     # If this is not a package, install or build wheels for its deps only.
-    group("$target_name.install") {
+    group("$_internal_target.install") {
       deps = []
       foreach(dep, _python_deps) {
         deps += [ "$dep.install" ]
       }
     }
-    group("$target_name.wheel") {
+    group("$_internal_target.wheel") {
       deps = []
       foreach(dep, _python_deps) {
         deps += [ "$dep.wheel" ]
@@ -189,10 +218,10 @@
   }
 
   # Define the static analysis targets for this package.
-  group("$target_name.lint") {
+  group("$_internal_target.lint") {
     deps = [
-      "$_package_target.lint.mypy",
-      "$_package_target.lint.pylint",
+      ":$_internal_target.lint.mypy",
+      ":$_internal_target.lint.pylint",
     ]
   }
 
@@ -208,7 +237,7 @@
       _lint_directory = rebase_path(".")
     }
 
-    pw_python_action("$target_name.lint.mypy") {
+    pw_python_action("$_internal_target.lint.mypy") {
       module = "mypy"
       args = [
         "--pretty",
@@ -233,7 +262,7 @@
       directory = _lint_directory
       stamp = true
 
-      deps = [ _package_target ]
+      deps = [ ":$_internal_target.install" ]
       foreach(dep, _python_deps) {
         deps += [ "$dep.lint.mypy" ]
       }
@@ -241,7 +270,7 @@
 
     # Create a target to run pylint on each of the Python files in this
     # package and its dependencies.
-    pw_python_action_foreach("$target_name.lint.pylint") {
+    pw_python_action_foreach("$_internal_target.lint.pylint") {
       module = "pylint"
       args = [
         rebase_path(".") + "/{{source_target_relative}}",
@@ -264,18 +293,18 @@
       directory = _lint_directory
       stamp = "$target_gen_dir/{{source_target_relative}}.pylint.passed"
 
-      deps = [ _package_target ]
+      deps = [ ":$_internal_target.install" ]
       foreach(dep, _python_deps) {
         deps += [ "$dep.lint.pylint" ]
       }
     }
   } else {
-    pw_input_group("$target_name.lint.mypy") {
+    pw_input_group("$_internal_target.lint.mypy") {
       if (defined(invoker.pylintrc)) {
         inputs = [ invoker.pylintrc ]
       }
     }
-    pw_input_group("$target_name.lint.pylint") {
+    pw_input_group("$_internal_target.lint.pylint") {
       if (defined(invoker.mypy_ini)) {
         inputs = [ invoker.mypy_ini ]
       }
@@ -287,19 +316,25 @@
 
   foreach(test, _test_sources) {
     _test_name = string_replace(test, "/", "_")
-    _test_target = "$target_name.tests.$_test_name"
+    _internal_test_target = "$_internal_target.tests.$_test_name"
 
-    pw_python_action(_test_target) {
+    pw_python_action(_internal_test_target) {
       script = test
       stamp = true
 
-      deps = [ _package_target ]
+      deps = [ ":$_internal_target.install" ]
       foreach(dep, _python_deps) {
         deps += [ "$dep.tests" ]
       }
     }
 
-    _test_targets += [ ":$_test_target" ]
+    # Create a public version of each test target, so tests can be executed as
+    # //path/to:package.tests.foo.py.
+    group("$target_name.tests.$_test_name") {
+      deps = [ ":$_internal_test_target" ]
+    }
+
+    _test_targets += [ ":$target_name.tests.$_test_name" ]
   }
 
   group("$target_name.tests") {
@@ -307,15 +342,6 @@
   }
 }
 
-_python_subtargets = [
-  "tests",
-  "lint",
-  "lint.mypy",
-  "lint.pylint",
-  "install",
-  "wheel",
-]
-
 # Declares a group of Python packages or other Python groups. pw_python_groups
 # expose the same set of subtargets as pw_python_package (e.g.
 # "$group_name.lint" and "$group_name.tests"), but these apply to all packages
diff --git a/pw_build/python_action.gni b/pw_build/python_action.gni
index a420fce..87f4bc2 100644
--- a/pw_build/python_action.gni
+++ b/pw_build/python_action.gni
@@ -50,6 +50,8 @@
 #                     <TARGET_OBJECTS(//some/label:here)> - expands to the
 #                         object files produced by the provided GN target
 #
+#   python_deps     Dependencies on pw_python_package or related Python targets.
+#
 template("pw_python_action") {
   _script_args = [
     # GN root directory relative to the build directory (in which the runner
@@ -142,10 +144,23 @@
     _action_type = "action"
   }
 
+  if (defined(invoker.deps)) {
+    _deps = invoker.deps
+  } else {
+    _deps = []
+  }
+
+  if (defined(invoker.python_deps)) {
+    foreach(dep, invoker.python_deps) {
+      _deps += [ get_label_info(dep, "label_no_toolchain") + ".install" ]
+    }
+  }
+
   target(_action_type, target_name) {
     _ignore_vars = [
       "script",
       "args",
+      "deps",
       "inputs",
       "outputs",
     ]
@@ -155,6 +170,7 @@
     args = _script_args
     inputs = _inputs
     outputs = _outputs
+    deps = _deps
   }
 }
 
diff --git a/pw_cpu_exception_cortex_m/py/BUILD.gn b/pw_cpu_exception_cortex_m/py/BUILD.gn
index 8af1eb2..df5dc96 100644
--- a/pw_cpu_exception_cortex_m/py/BUILD.gn
+++ b/pw_cpu_exception_cortex_m/py/BUILD.gn
@@ -24,5 +24,9 @@
     "pw_cpu_exception_cortex_m/exception_analyzer.py",
   ]
   tests = [ "exception_analyzer_test.py" ]
+  python_deps = [
+    "$dir_pw_cli/py",
+    "$dir_pw_protobuf_compiler/py",
+  ]
   pylintrc = "$dir_pigweed/.pylintrc"
 }
diff --git a/pw_cpu_exception_cortex_m/py/setup.py b/pw_cpu_exception_cortex_m/py/setup.py
index e476dee..9cc3e8e 100644
--- a/pw_cpu_exception_cortex_m/py/setup.py
+++ b/pw_cpu_exception_cortex_m/py/setup.py
@@ -24,5 +24,9 @@
     packages=setuptools.find_packages(),
     package_data={'pw_cpu_exception_cortex_m': ['py.typed']},
     zip_safe=False,
-    install_requires=['protobuf'],
+    install_requires=[
+        'protobuf',
+        'pw_cli',
+        'pw_protobuf_compiler',
+    ],
 )
diff --git a/pw_hdlc/py/BUILD.gn b/pw_hdlc/py/BUILD.gn
index 5532c3e..255c10b 100644
--- a/pw_hdlc/py/BUILD.gn
+++ b/pw_hdlc/py/BUILD.gn
@@ -31,6 +31,7 @@
     "encode_test.py",
   ]
   python_deps = [
+    "$dir_pw_build/py",
     "$dir_pw_protobuf_compiler/py",
     "$dir_pw_rpc/py",
   ]
diff --git a/pw_hdlc/py/setup.py b/pw_hdlc/py/setup.py
index a62ce75..88db976 100644
--- a/pw_hdlc/py/setup.py
+++ b/pw_hdlc/py/setup.py
@@ -24,6 +24,10 @@
     packages=setuptools.find_packages(),
     package_data={'pw_hdlc': ['py.typed']},
     zip_safe=False,
-    install_requires=['ipython'],
+    install_requires=[
+        'ipython',
+        'pw_protobuf_compiler',
+        'pw_rpc',
+    ],
     tests_require=['pw_build'],
 )
diff --git a/pw_presubmit/py/setup.py b/pw_presubmit/py/setup.py
index a738a74..9832e9c 100644
--- a/pw_presubmit/py/setup.py
+++ b/pw_presubmit/py/setup.py
@@ -25,6 +25,7 @@
         'mypy==0.790',
         'pylint==2.6.0',
         'yapf==0.30.0',
+        'pw_cli',
         'pw_package',
     ],
     packages=setuptools.find_packages(),
diff --git a/pw_protobuf/py/BUILD.gn b/pw_protobuf/py/BUILD.gn
index e977f5d..6d42440 100644
--- a/pw_protobuf/py/BUILD.gn
+++ b/pw_protobuf/py/BUILD.gn
@@ -25,5 +25,9 @@
     "pw_protobuf/plugin.py",
     "pw_protobuf/proto_tree.py",
   ]
+  python_deps = [
+    "$dir_pw_cli/py",
+    "$dir_pw_protobuf_compiler/py",
+  ]
   pylintrc = "$dir_pigweed/.pylintrc"
 }
diff --git a/pw_protobuf/py/setup.py b/pw_protobuf/py/setup.py
index 96a8209..2c8c692 100644
--- a/pw_protobuf/py/setup.py
+++ b/pw_protobuf/py/setup.py
@@ -29,5 +29,7 @@
     },
     install_requires=[
         'protobuf',
+        'pw_cli',
     ],
+    tests_require=['pw_protobuf_compiler'],
 )
diff --git a/pw_protobuf_compiler/proto.gni b/pw_protobuf_compiler/proto.gni
index 527e25b..94d0c6c 100644
--- a/pw_protobuf_compiler/proto.gni
+++ b/pw_protobuf_compiler/proto.gni
@@ -41,6 +41,11 @@
     script =
         "$dir_pw_protobuf_compiler/py/pw_protobuf_compiler/generate_protos.py"
 
+    python_deps = [ "$dir_pw_protobuf_compiler/py" ]
+    if (defined(invoker.python_deps)) {
+      python_deps += invoker.python_deps
+    }
+
     deps = [
              ":${invoker.base_target}._metadata",
              ":${invoker.base_target}._inputs",
@@ -96,7 +101,7 @@
     forward_variables_from(invoker, "*", _forwarded_vars)
     language = "pwpb"
     plugin = "$dir_pw_protobuf/py/pw_protobuf/plugin.py"
-    deps += [ "$dir_pw_protobuf/py" ]
+    python_deps = [ "$dir_pw_protobuf/py" ]
     output_extensions = [ ".pwpb.h" ]
   }
 
@@ -121,7 +126,7 @@
     forward_variables_from(invoker, "*", _forwarded_vars)
     language = "nanopb_rpc"
     plugin = "$dir_pw_rpc/py/pw_rpc/plugin_nanopb.py"
-    deps += [ "$dir_pw_rpc/py" ]
+    python_deps = [ "$dir_pw_rpc/py" ]
     include_paths = [ "$dir_pw_third_party_nanopb/generator/proto" ]
     output_extensions = [ ".rpc.pb.h" ]
   }
@@ -179,7 +184,7 @@
     forward_variables_from(invoker, "*", _forwarded_vars)
     language = "raw_rpc"
     plugin = "$dir_pw_rpc/py/pw_rpc/plugin_raw.py"
-    deps += [ "$dir_pw_rpc/py" ]
+    python_deps = [ "$dir_pw_rpc/py" ]
     output_extensions = [ ".raw_rpc.pb.h" ]
   }
 
diff --git a/pw_rpc/BUILD.gn b/pw_rpc/BUILD.gn
index 3569aeb..3e34b38 100644
--- a/pw_rpc/BUILD.gn
+++ b/pw_rpc/BUILD.gn
@@ -16,6 +16,7 @@
 
 import("$dir_pw_bloat/bloat.gni")
 import("$dir_pw_build/module_config.gni")
+import("$dir_pw_build/python_action.gni")
 import("$dir_pw_build/target_types.gni")
 import("$dir_pw_docgen/docs.gni")
 import("$dir_pw_protobuf_compiler/proto.gni")
@@ -210,11 +211,14 @@
   sources = [ "channel_test.cc" ]
 }
 
-action("generate_ids_test") {
+pw_python_action("generate_ids_test") {
   outputs = [ "$target_gen_dir/generated_ids_test.cc" ]
   script = "py/ids_test.py"
   args = [ "--generate-cc-test" ] + rebase_path(outputs)
-  deps = [ "$dir_pw_build/py" ]
+  python_deps = [
+    "$dir_pw_build/py",
+    "py",
+  ]
 }
 
 pw_test("ids_test") {
diff --git a/pw_rpc/py/BUILD.gn b/pw_rpc/py/BUILD.gn
index 6f0baa6..802efd2 100644
--- a/pw_rpc/py/BUILD.gn
+++ b/pw_rpc/py/BUILD.gn
@@ -41,6 +41,7 @@
     "packets_test.py",
   ]
   python_deps = [
+    "$dir_pw_build/py",
     "$dir_pw_protobuf_compiler/py",
     "$dir_pw_status/py",
   ]
diff --git a/pw_trace_tokenized/py/BUILD.gn b/pw_trace_tokenized/py/BUILD.gn
index 2116cc5..00b85f8 100644
--- a/pw_trace_tokenized/py/BUILD.gn
+++ b/pw_trace_tokenized/py/BUILD.gn
@@ -22,5 +22,6 @@
     "pw_trace_tokenized/__init__.py",
     "pw_trace_tokenized/trace_tokenized.py",
   ]
+  python_deps = [ "$dir_pw_tokenizer/py" ]
   pylintrc = "$dir_pigweed/.pylintrc"
 }
diff --git a/pw_trace_tokenized/py/setup.py b/pw_trace_tokenized/py/setup.py
index cea2439..c20e9cf 100644
--- a/pw_trace_tokenized/py/setup.py
+++ b/pw_trace_tokenized/py/setup.py
@@ -24,4 +24,5 @@
     packages=setuptools.find_packages(),
     package_data={'pw_trace_tokenized': ['py.typed']},
     zip_safe=False,
+    install_requires=['pw_tokenizer'],
 )
diff --git a/pw_unit_test/py/setup.py b/pw_unit_test/py/setup.py
index ea467d5..0a7db0b 100644
--- a/pw_unit_test/py/setup.py
+++ b/pw_unit_test/py/setup.py
@@ -26,5 +26,6 @@
     zip_safe=False,
     install_requires=[
         'pw_cli',
+        'pw_rpc',
     ],
 )
diff --git a/pw_unit_test/test.gni b/pw_unit_test/test.gni
index 50d107b..1fdb428 100644
--- a/pw_unit_test/test.gni
+++ b/pw_unit_test/test.gni
@@ -182,6 +182,7 @@
       deps = [ ":$_test_target_name" ]
       inputs = [ pw_unit_test_AUTOMATIC_RUNNER ]
       script = "$dir_pw_unit_test/py/pw_unit_test/test_runner.py"
+      python_deps = [ "$dir_pw_cli/py" ]
       args = [
         "--runner",
         rebase_path(pw_unit_test_AUTOMATIC_RUNNER),
diff --git a/pw_watch/py/BUILD.gn b/pw_watch/py/BUILD.gn
index b6c76f8..a4d4c0e 100644
--- a/pw_watch/py/BUILD.gn
+++ b/pw_watch/py/BUILD.gn
@@ -25,4 +25,5 @@
     "pw_watch/watch_test.py",
   ]
   pylintrc = "$dir_pigweed/.pylintrc"
+  python_deps = [ "$dir_pw_cli/py" ]
 }
diff --git a/pw_watch/py/setup.py b/pw_watch/py/setup.py
index 7958eab..086747d 100644
--- a/pw_watch/py/setup.py
+++ b/pw_watch/py/setup.py
@@ -25,6 +25,7 @@
     package_data={'pw_watch': ['py.typed']},
     zip_safe=False,
     install_requires=[
+        'pw_cli',
         'watchdog',
     ],
 )
diff --git a/targets/stm32f429i-disc1/py/BUILD.gn b/targets/stm32f429i-disc1/py/BUILD.gn
index d4b229e..85dd255 100644
--- a/targets/stm32f429i-disc1/py/BUILD.gn
+++ b/targets/stm32f429i-disc1/py/BUILD.gn
@@ -26,4 +26,5 @@
     "stm32f429i_disc1_utils/unit_test_server.py",
   ]
   pylintrc = "$dir_pigweed/.pylintrc"
+  python_deps = [ "$dir_pw_cli/py" ]
 }
diff --git a/targets/stm32f429i-disc1/py/setup.py b/targets/stm32f429i-disc1/py/setup.py
index 309ff7e..28372f2 100644
--- a/targets/stm32f429i-disc1/py/setup.py
+++ b/targets/stm32f429i-disc1/py/setup.py
@@ -37,5 +37,9 @@
             '    stm32f429i_disc1_utils.unit_test_client:main',
         ]
     },
-    install_requires=['pyserial', 'coloredlogs'],
+    install_requires=[
+        'pyserial',
+        'coloredlogs',
+        'pw_cli',
+    ],
 )