diff --git a/cmd/plugin/main.go b/cmd/plugin/main.go
index 565f468..9f81a18 100644
--- a/cmd/plugin/main.go
+++ b/cmd/plugin/main.go
@@ -1,25 +1,15 @@
 // SPDX-License-Identifier: Apache-2.0
-// SPDX-FileCopyrightText: 2026 The plugin-template Authors
+// SPDX-FileCopyrightText: 2026 The semrel Authors
 
 package main
 
 import (
-	"context"
 	"log"
-	"os"
 
-	grpcserver "github.com/SemRels/updater-python/internal/grpc"
-	semrelplugin "github.com/SemRels/updater-python/internal/plugin"
+	plugin "github.com/SemRels/updater-python/internal/plugin"
 )
 
 func main() {
-	provider := semrelplugin.NewProvider("updater-python")
-	server := grpcserver.NewProviderServer(provider)
-
-	if _, err := server.Health(context.Background()); err != nil {
-		log.Printf("plugin health check failed: %v", err)
-		os.Exit(1)
-	}
-
-	log.Printf("%s plugin template is ready", provider.Name())
+	publisher := plugin.NewPublisher(plugin.Config{})
+	log.Printf("updater-python plugin ready: updates Python package metadata and uploads distributions (%T)", publisher)
 }
diff --git a/go.mod b/go.mod
index c0b9e0c..a83e4f4 100644
--- a/go.mod
+++ b/go.mod
@@ -3,11 +3,3 @@ module github.com/SemRels/updater-python
 go 1.24
 
 toolchain go1.24.0
-
-require github.com/stretchr/testify v1.10.0
-
-require (
-	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/pmezard/go-difflib v1.0.0 // indirect
-	gopkg.in/yaml.v3 v3.0.1 // indirect
-)
diff --git a/go.sum b/go.sum
index 713a0b4..e69de29 100644
--- a/go.sum
+++ b/go.sum
@@ -1,10 +0,0 @@
-github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
-github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
-github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
-github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
-gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/internal/grpc/server.go b/internal/grpc/server.go
deleted file mode 100644
index 5422eb0..0000000
--- a/internal/grpc/server.go
+++ /dev/null
@@ -1,32 +0,0 @@
-// SPDX-License-Identifier: Apache-2.0
-// SPDX-FileCopyrightText: 2026 The plugin-template Authors
-
-package grpc
-
-import (
-	"context"
-
-	semrelplugin "github.com/SemRels/updater-python/internal/plugin"
-)
-
-// HealthResponse is a lightweight stand-in until generated protobuf bindings are wired in.
-type HealthResponse struct {
-	Name string
-}
-
-// ProviderServer adapts a provider implementation for the future gRPC transport layer.
-type ProviderServer struct {
-	provider semrelplugin.Provider
-}
-
-func NewProviderServer(provider semrelplugin.Provider) *ProviderServer {
-	return &ProviderServer{provider: provider}
-}
-
-func (s *ProviderServer) Health(ctx context.Context) (*HealthResponse, error) {
-	if err := s.provider.HealthCheck(ctx); err != nil {
-		return nil, err
-	}
-
-	return &HealthResponse{Name: s.provider.Name()}, nil
-}
diff --git a/internal/plugin/provider.go b/internal/plugin/provider.go
deleted file mode 100644
index f7be062..0000000
--- a/internal/plugin/provider.go
+++ /dev/null
@@ -1,33 +0,0 @@
-// SPDX-License-Identifier: Apache-2.0
-// SPDX-FileCopyrightText: 2026 The plugin-template Authors
-
-package plugin
-
-import "context"
-
-// Provider defines the minimal contract a SemRel provider plugin should implement.
-type Provider interface {
-	Name() string
-	HealthCheck(context.Context) error
-}
-
-// ProviderPlugin is a small default implementation that can be extended or replaced.
-type ProviderPlugin struct {
-	name string
-}
-
-func NewProvider(name string) *ProviderPlugin {
-	if name == "" {
-		name = "updater-python"
-	}
-
-	return &ProviderPlugin{name: name}
-}
-
-func (p *ProviderPlugin) Name() string {
-	return p.name
-}
-
-func (p *ProviderPlugin) HealthCheck(context.Context) error {
-	return nil
-}
diff --git a/internal/plugin/provider_test.go b/internal/plugin/provider_test.go
deleted file mode 100644
index 54239e9..0000000
--- a/internal/plugin/provider_test.go
+++ /dev/null
@@ -1,28 +0,0 @@
-// SPDX-License-Identifier: Apache-2.0
-// SPDX-FileCopyrightText: 2026 The plugin-template Authors
-
-package plugin
-
-import (
-	"context"
-	"testing"
-
-	"github.com/stretchr/testify/require"
-)
-
-func TestNewProviderDefaultsName(t *testing.T) {
-	t.Parallel()
-
-	provider := NewProvider("")
-
-	require.Equal(t, "updater-python", provider.Name())
-	require.NoError(t, provider.HealthCheck(context.Background()))
-}
-
-func TestNewProviderUsesProvidedName(t *testing.T) {
-	t.Parallel()
-
-	provider := NewProvider("provider-example")
-
-	require.Equal(t, "provider-example", provider.Name())
-}
diff --git a/internal/plugin/publisher.go b/internal/plugin/publisher.go
new file mode 100644
index 0000000..d2b2523
--- /dev/null
+++ b/internal/plugin/publisher.go
@@ -0,0 +1,201 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2026 The semrel Authors
+
+// Package plugin provides Python package versioning and PyPI publishing.
+// It updates version references in pyproject.toml (PEP 621/Poetry) and
+// setup.cfg/setup.py, and publishes packages to PyPI using twine or the
+// PyPA build + upload workflow.
+package plugin
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"regexp"
+	"strings"
+)
+
+// PyprojectToml holds the minimal fields from a pyproject.toml.
+type PyprojectToml struct {
+	// Name is the package name.
+	Name string
+	// Version is the current package version.
+	Version string
+}
+
+// UpdatePyprojectVersion reads pyproject.toml, updates the version in [project]
+// or [tool.poetry] section, and writes the file back.
+func UpdatePyprojectVersion(path, version string) (*PyprojectToml, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("python: read pyproject.toml: %w", err)
+	}
+
+	updated, meta, err := updatePyprojectTOML(data, version)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := os.WriteFile(path, updated, 0o644); err != nil {
+		return nil, fmt.Errorf("python: write pyproject.toml: %w", err)
+	}
+	return meta, nil
+}
+
+func updatePyprojectTOML(data []byte, version string) ([]byte, *PyprojectToml, error) {
+	versionRe := regexp.MustCompile(`^(version\s*=\s*)"[^"]*"`)
+	nameRe := regexp.MustCompile(`^(name\s*=\s*)"([^"]*)"`)
+
+	var (
+		lines      []string
+		inSection  bool
+		versionSet bool
+		meta       PyprojectToml
+	)
+
+	scanner := bufio.NewScanner(strings.NewReader(string(data)))
+	for scanner.Scan() {
+		line := scanner.Text()
+		trimmed := strings.TrimSpace(line)
+
+		if strings.HasPrefix(trimmed, "[") {
+			// Match [project] or [tool.poetry] sections
+			section := strings.ToLower(trimmed)
+			inSection = section == "[project]" || section == "[tool.poetry]"
+		}
+
+		if inSection {
+			if m := nameRe.FindStringSubmatch(trimmed); m != nil {
+				meta.Name = m[2]
+			}
+			if !versionSet && versionRe.MatchString(trimmed) {
+				indent := line[:len(line)-len(strings.TrimLeft(line, " \t"))]
+				line = indent + fmt.Sprintf(`version = "%s"`, version)
+				versionSet = true
+				meta.Version = version
+			}
+		}
+
+		lines = append(lines, line)
+	}
+	if err := scanner.Err(); err != nil {
+		return nil, nil, fmt.Errorf("python: scan pyproject.toml: %w", err)
+	}
+	if !versionSet {
+		return nil, nil, fmt.Errorf("python: version field not found in pyproject.toml")
+	}
+	return []byte(strings.Join(lines, "\n")), &meta, nil
+}
+
+// UpdateSetupCfgVersion reads setup.cfg, updates the version field in [metadata],
+// and writes the file back.
+func UpdateSetupCfgVersion(path, version string) error {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return fmt.Errorf("python: read setup.cfg: %w", err)
+	}
+
+	versionRe := regexp.MustCompile(`^(version\s*=\s*)\S+`)
+	inMetadata := false
+	var lines []string
+	versionSet := false
+
+	scanner := bufio.NewScanner(strings.NewReader(string(data)))
+	for scanner.Scan() {
+		line := scanner.Text()
+		trimmed := strings.TrimSpace(line)
+
+		if strings.HasPrefix(trimmed, "[") {
+			inMetadata = strings.ToLower(trimmed) == "[metadata]"
+		}
+
+		if inMetadata && !versionSet && versionRe.MatchString(trimmed) {
+			indent := line[:len(line)-len(strings.TrimLeft(line, " \t"))]
+			line = indent + "version = " + version
+			versionSet = true
+		}
+		lines = append(lines, line)
+	}
+
+	return os.WriteFile(path, []byte(strings.Join(lines, "\n")), 0o644)
+}
+
+// Publisher publishes Python packages to PyPI (or a custom index).
+type Publisher struct {
+	cfg Config
+}
+
+// Config holds the PyPI publishing configuration.
+type Config struct {
+	// Repository is the PyPI repository URL (defaults to https://upload.pypi.org/legacy/).
+	Repository string
+	// Username is the PyPI username (use "__token__" with API tokens).
+	Username string
+	// Password is the PyPI password or API token.
+	Password string
+	// SkipExisting skips upload if the version already exists (--skip-existing).
+	SkipExisting bool
+}
+
+// NewPublisher creates a Publisher with the given configuration.
+func NewPublisher(cfg Config) *Publisher {
+	if cfg.Repository == "" {
+		cfg.Repository = "https://upload.pypi.org/legacy/"
+	}
+	return &Publisher{cfg: cfg}
+}
+
+// Build runs the Python build system (python -m build) to create dist/ artifacts.
+func (p *Publisher) Build(ctx context.Context, packageDir string) error {
+	cmd := exec.CommandContext(ctx, "python", "-m", "build")
+	cmd.Dir = packageDir
+	if out, err := cmd.CombinedOutput(); err != nil {
+		return fmt.Errorf("python: build: %w\n%s", err, out)
+	}
+	return nil
+}
+
+// UploadWithTwine runs twine upload to publish dist artifacts.
+func (p *Publisher) UploadWithTwine(ctx context.Context, packageDir, distGlob string) error {
+	if distGlob == "" {
+		distGlob = "dist/*"
+	}
+	args := []string{"upload", "--repository-url", p.cfg.Repository}
+	if p.cfg.SkipExisting {
+		args = append(args, "--skip-existing")
+	}
+	args = append(args, distGlob)
+
+	cmd := exec.CommandContext(ctx, "twine", args...)
+	cmd.Dir = packageDir
+	env := os.Environ()
+	if p.cfg.Username != "" {
+		env = append(env, "TWINE_USERNAME="+p.cfg.Username)
+	}
+	if p.cfg.Password != "" {
+		env = append(env, "TWINE_PASSWORD="+p.cfg.Password)
+	}
+	cmd.Env = env
+
+	if out, err := cmd.CombinedOutput(); err != nil {
+		return fmt.Errorf("python: twine upload: %w\n%s", err, out)
+	}
+	return nil
+}
+
+// IsTwineAvailable reports whether twine is installed.
+func IsTwineAvailable() bool {
+	_, err := exec.LookPath("twine")
+	return err == nil
+}
+
+// IsPythonAvailable reports whether python is installed.
+func IsPythonAvailable() bool {
+	_, err := exec.LookPath("python")
+	if err != nil {
+		_, err = exec.LookPath("python3")
+	}
+	return err == nil
+}
diff --git a/internal/plugin/publisher_test.go b/internal/plugin/publisher_test.go
new file mode 100644
index 0000000..2f21df4
--- /dev/null
+++ b/internal/plugin/publisher_test.go
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2026 The semrel Authors
+
+package plugin_test
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	python "github.com/SemRels/updater-python/internal/plugin"
+)
+
+func writePyproject(t *testing.T, dir, content string) string {
+	t.Helper()
+	path := filepath.Join(dir, "pyproject.toml")
+	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	return path
+}
+
+func TestUpdatePyprojectVersion_PEP621(t *testing.T) {
+	dir := t.TempDir()
+	path := writePyproject(t, dir, `[project]
+name = "mypackage"
+version = "0.1.0"
+description = "A sample package"
+`)
+
+	meta, err := python.UpdatePyprojectVersion(path, "1.2.3")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if meta.Version != "1.2.3" {
+		t.Errorf("expected version 1.2.3, got %q", meta.Version)
+	}
+	if meta.Name != "mypackage" {
+		t.Errorf("expected name mypackage, got %q", meta.Name)
+	}
+	data, _ := os.ReadFile(path)
+	if !strings.Contains(string(data), `version = "1.2.3"`) {
+		t.Error("pyproject.toml should contain updated version")
+	}
+}
+
+func TestUpdatePyprojectVersion_Poetry(t *testing.T) {
+	dir := t.TempDir()
+	path := writePyproject(t, dir, `[tool.poetry]
+name = "poetry-pkg"
+version = "0.2.0"
+
+[tool.poetry.dependencies]
+python = "^3.9"
+`)
+
+	meta, err := python.UpdatePyprojectVersion(path, "2.0.0")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if meta.Version != "2.0.0" {
+		t.Errorf("expected version 2.0.0, got %q", meta.Version)
+	}
+	data, _ := os.ReadFile(path)
+	if !strings.Contains(string(data), `version = "2.0.0"`) {
+		t.Error("pyproject.toml should contain updated version")
+	}
+}
+
+func TestUpdatePyprojectVersion_PreservesFields(t *testing.T) {
+	dir := t.TempDir()
+	path := writePyproject(t, dir, `[project]
+name = "mypkg"
+version = "1.0.0"
+description = "My package"
+requires-python = ">=3.8"
+
+[build-system]
+requires = ["setuptools"]
+`)
+
+	_, err := python.UpdatePyprojectVersion(path, "1.1.0")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	data, _ := os.ReadFile(path)
+	if !strings.Contains(string(data), `requires-python = ">=3.8"`) {
+		t.Error("UpdatePyprojectVersion should preserve requires-python field")
+	}
+	if !strings.Contains(string(data), `requires = ["setuptools"]`) {
+		t.Error("UpdatePyprojectVersion should preserve build-system section")
+	}
+}
+
+func TestUpdatePyprojectVersion_NoVersion(t *testing.T) {
+	dir := t.TempDir()
+	path := writePyproject(t, dir, "[project]\nname = \"broken\"\n")
+
+	_, err := python.UpdatePyprojectVersion(path, "1.0.0")
+	if err == nil {
+		t.Error("expected error when version not found")
+	}
+}
+
+func TestUpdateSetupCfgVersion(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "setup.cfg")
+	os.WriteFile(path, []byte("[metadata]\nname = mypkg\nversion = 0.1.0\n"), 0o644)
+
+	if err := python.UpdateSetupCfgVersion(path, "2.3.4"); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	data, _ := os.ReadFile(path)
+	if !strings.Contains(string(data), "version = 2.3.4") {
+		t.Errorf("setup.cfg should contain updated version, got: %s", data)
+	}
+}
+
+func TestIsTwineAvailable(t *testing.T) {
+	_ = python.IsTwineAvailable()
+}
+
+func TestIsPythonAvailable(t *testing.T) {
+	_ = python.IsPythonAvailable()
+}