diff --git a/CHANGELOG_AUTOMATION_CONTRACT.md b/CHANGELOG_AUTOMATION_CONTRACT.md
new file mode 100644
index 0000000..497f2aa
--- /dev/null
+++ b/CHANGELOG_AUTOMATION_CONTRACT.md
@@ -0,0 +1,104 @@
+# Changelog Automation Contract
+
+## Scope
+
+This contract governs release changelog generation across:
+
+- `toolkit/` as the implementation owner
+- `module/` as a changelog-producing consumer
+- `assets/` as a changelog-producing consumer
+
+The immediate goal is to produce stable per-repo `CHANGELOG.md` release artifacts
+that can later be merged by a NodeBB bot into one combined release post.
+
+## Ownership Split
+
+- `toolkit/`
+  - owns the shared changelog generator implementation
+  - owns the CLI contract exposed through `sow-toolkit`
+  - owns the config schema used by consumer repos
+- `module/`
+  - owns its changelog section mapping under `scripts/changelog.json`
+  - owns invoking changelog generation during its tag release flow
+- `assets/`
+  - owns its changelog section mapping under `scripts/changelog.json`
+  - owns invoking changelog generation during its tag release flow
+
+## Shared CLI Contract
+
+The canonical generator entrypoint is:
+
+```bash
+sow-toolkit build-changelog
+```
+
+Supported flags:
+
+- `--config <path>`: repo-local JSON section config
+- `--output <path>`: write rendered Markdown to a file; otherwise stdout
+- `--current-tag <tag>`: optional explicit current tag
+- `--previous-tag <tag>`: optional explicit previous tag
+- `--api-base-url <url>`: optional explicit Gitea API base URL
+- `--token <token>`: optional explicit Gitea API token
+
+If `--current-tag` is omitted, the generator must resolve the exact tag at
+`HEAD`. If `--previous-tag` is omitted, it must select the next older tag by
+`creatordate`.
+
+## Config Contract
+
+Each consumer repo provides `scripts/changelog.json` with:
+
+- `repo_url`: canonical web URL for pull request links
+- `categories[]`
+- `categories[].title`
+- `categories[].sections[]`
+- `categories[].sections[].title`
+- `categories[].sections[].paths[]`
+
+Paths are repo-relative path filters passed through to `git log`.
+
+## Author Contract
+
+Rendered changelog entries must resolve pull request author names from the
+Gitea pull request API rather than trusting the merge commit author field.
+
+Expected endpoint shape:
+
+- `GET /api/v1/repos/{owner}/{repo}/pulls/{index}`
+- prefer `user.full_name`
+- fall back to `user.login` only if `full_name` is empty
+
+## Release Contract
+
+For each version-tagged release workflow:
+
+1. generate `build/CHANGELOG.md` for the current tag;
+2. upload `CHANGELOG.md` as a release asset on the versioned release;
+3. keep the file name stable across repos so later automation can fetch it
+   without repo-specific asset naming logic.
+
+The changelog is a staged build artifact, not a committed source-controlled file.
+This avoids detached-tag push complexity while preserving a stable artifact for
+later aggregation.
+
+## Output Contract
+
+The Markdown output must remain simple and merge-friendly:
+
+- title line with current tag and publish date
+- comparison line naming the previous tag when one exists
+- category headings
+- section headings
+- bullet entries in the form:
+
+```text
+- Title ([#123](.../pulls/123)) - From Author Name
+```
+
+## Deferred Work
+
+- add a dedicated bot that fetches `CHANGELOG.md` assets from module and assets
+  releases, merges them, and publishes a single NodeBB release post
+- decide whether changelog generation should later move from shell wrappers into
+  first-class repo-root user commands
diff --git a/internal/app/app.go b/internal/app/app.go
index bc757ff..5183fb3 100644
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -11,6 +11,7 @@ import (
 	"sync"
 	"time"
 
+	"gitea.westgate.pw/ShadowsOverWestgate/sow-tools/internal/changelog"
 	"gitea.westgate.pw/ShadowsOverWestgate/sow-tools/internal/pipeline"
 	"gitea.westgate.pw/ShadowsOverWestgate/sow-tools/internal/project"
 	"gitea.westgate.pw/ShadowsOverWestgate/sow-tools/internal/topdata"
@@ -158,6 +159,11 @@ var commands = []command{
 		description: "Deploy generated wiki pages to NodeBB.",
 		run:         runDeployWiki,
 	},
+	{
+		name:        "build-changelog",
+		description: "Build a release changelog from tagged pull requests and write it to stdout or a file.",
+		run:         runBuildChangelog,
+	},
 }
 
 func Run(args []string) (int, error) {
@@ -830,6 +836,86 @@ func parseDeployWikiArgs(commandName string, args []string) (topdata.DeployWikiO
 	return opts, nil
 }
 
+type buildChangelogOptions struct {
+	configPath  string
+	outputPath  string
+	currentTag  string
+	previousTag string
+	apiBaseURL  string
+	token       string
+}
+
+func runBuildChangelog(ctx context) error {
+	opts, err := parseBuildChangelogArgs("build-changelog", ctx.args[1:])
+	if err != nil {
+		return err
+	}
+
+	return changelog.Generate(changelog.Options{
+		RepoRoot:    ctx.cwd,
+		ConfigPath:  opts.configPath,
+		OutputPath:  opts.outputPath,
+		CurrentTag:  opts.currentTag,
+		PreviousTag: opts.previousTag,
+		APIBaseURL:  opts.apiBaseURL,
+		Token:       opts.token,
+		Stdout:      ctx.stdout,
+	})
+}
+
+func parseBuildChangelogArgs(commandName string, args []string) (buildChangelogOptions, error) {
+	opts := buildChangelogOptions{}
+	usage := fmt.Errorf("usage: %s [--config <path>] [--output <path>] [--current-tag <tag>] [--previous-tag <tag>] [--api-base-url <url>] [--token <token>]", commandName)
+
+	for i := 0; i < len(args); i++ {
+		arg := args[i]
+		switch arg {
+		case "--config":
+			i++
+			if i >= len(args) || strings.TrimSpace(args[i]) == "" {
+				return opts, usage
+			}
+			opts.configPath = args[i]
+		case "--output":
+			i++
+			if i >= len(args) || strings.TrimSpace(args[i]) == "" {
+				return opts, usage
+			}
+			opts.outputPath = args[i]
+		case "--current-tag":
+			i++
+			if i >= len(args) || strings.TrimSpace(args[i]) == "" {
+				return opts, usage
+			}
+			opts.currentTag = args[i]
+		case "--previous-tag":
+			i++
+			if i >= len(args) || strings.TrimSpace(args[i]) == "" {
+				return opts, usage
+			}
+			opts.previousTag = args[i]
+		case "--api-base-url":
+			i++
+			if i >= len(args) || strings.TrimSpace(args[i]) == "" {
+				return opts, usage
+			}
+			opts.apiBaseURL = args[i]
+		case "--token":
+			i++
+			if i >= len(args) || strings.TrimSpace(args[i]) == "" {
+				return opts, usage
+			}
+			opts.token = args[i]
+		case "-h", "--help":
+			return opts, usage
+		default:
+			return opts, fmt.Errorf("unknown %s argument %q", commandName, arg)
+		}
+	}
+
+	return opts, nil
+}
+
 func parseWikiCategoryList(raw string, target map[string]int) error {
 	for _, part := range strings.Split(raw, ",") {
 		part = strings.TrimSpace(part)
diff --git a/internal/changelog/changelog.go b/internal/changelog/changelog.go
new file mode 100644
index 0000000..81ee71c
--- /dev/null
+++ b/internal/changelog/changelog.go
@@ -0,0 +1,429 @@
+package changelog
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+)
+
+type Config struct {
+	RepoURL    string     `json:"repo_url"`
+	Categories []Category `json:"categories"`
+}
+
+type Category struct {
+	Title    string    `json:"title"`
+	Sections []Section `json:"sections"`
+}
+
+type Section struct {
+	Title string   `json:"title"`
+	Paths []string `json:"paths"`
+}
+
+type Options struct {
+	RepoRoot    string
+	ConfigPath  string
+	OutputPath  string
+	CurrentTag  string
+	PreviousTag string
+	APIBaseURL  string
+	Token       string
+	Stdout      io.Writer
+}
+
+type pullInfo struct {
+	AuthorName string
+}
+
+type generator struct {
+	repoRoot    string
+	config      Config
+	currentTag  string
+	previousTag string
+	apiBaseURL  string
+	repoURL     string
+	owner       string
+	name        string
+	token       string
+	httpClient  *http.Client
+	pullCache   map[string]pullInfo
+}
+
+type changelogEntry struct {
+	Title      string
+	PullNumber string
+	AuthorName string
+}
+
+var pullNumberPattern = regexp.MustCompile(`\(#([0-9]+)\)`)
+
+func Generate(opts Options) error {
+	repoRoot := strings.TrimSpace(opts.RepoRoot)
+	if repoRoot == "" {
+		detectedRepoRoot, err := gitOutput("", "rev-parse", "--show-toplevel")
+		if err != nil {
+			return fmt.Errorf("detect repo root: %w", err)
+		}
+		repoRoot = strings.TrimSpace(detectedRepoRoot)
+	}
+
+	configPath := opts.ConfigPath
+	if configPath == "" {
+		configPath = filepath.Join(repoRoot, "scripts", "changelog.json")
+	}
+	config, err := loadConfig(configPath)
+	if err != nil {
+		return err
+	}
+
+	currentTag := strings.TrimSpace(opts.CurrentTag)
+	if currentTag == "" {
+		currentTag, err = gitOutput(repoRoot, "describe", "--tags", "--exact-match")
+		if err != nil {
+			return fmt.Errorf("detect current tag: %w", err)
+		}
+		currentTag = strings.TrimSpace(currentTag)
+	}
+	if currentTag == "" {
+		return fmt.Errorf("could not determine current tag")
+	}
+
+	previousTag := strings.TrimSpace(opts.PreviousTag)
+	if previousTag == "" {
+		previousTag, err = previousTagFor(repoRoot, currentTag)
+		if err != nil {
+			return err
+		}
+	}
+
+	repoURL := strings.TrimSpace(config.RepoURL)
+	if repoURL == "" {
+		return fmt.Errorf("config %s is missing repo_url", configPath)
+	}
+	apiBaseURL := strings.TrimSpace(opts.APIBaseURL)
+	if apiBaseURL == "" {
+		if apiBaseURL = strings.TrimSpace(os.Getenv("GITEA_SERVER_URL")); apiBaseURL == "" {
+			apiBaseURL = deriveAPIBaseURL(repoURL)
+		}
+	}
+	apiBaseURL = normalizeAPIBaseURL(apiBaseURL)
+	if apiBaseURL == "" {
+		return fmt.Errorf("could not determine Gitea API base URL")
+	}
+
+	owner, name, err := ownerAndRepoFromURL(repoURL)
+	if err != nil {
+		return err
+	}
+
+	g := generator{
+		repoRoot:    repoRoot,
+		config:      config,
+		currentTag:  currentTag,
+		previousTag: previousTag,
+		apiBaseURL:  strings.TrimRight(apiBaseURL, "/"),
+		repoURL:     strings.TrimRight(repoURL, "/"),
+		owner:       owner,
+		name:        name,
+		token:       firstNonEmpty(opts.Token, os.Getenv("GITEA_API_TOKEN"), os.Getenv("GITEA_TOKEN"), os.Getenv("SOW_TOOLS_TOKEN")),
+		httpClient:  http.DefaultClient,
+		pullCache:   map[string]pullInfo{},
+	}
+
+	rendered, err := g.render()
+	if err != nil {
+		return err
+	}
+
+	if opts.OutputPath != "" {
+		if err := os.MkdirAll(filepath.Dir(opts.OutputPath), 0o755); err != nil {
+			return fmt.Errorf("create output directory: %w", err)
+		}
+		if err := os.WriteFile(opts.OutputPath, rendered, 0o644); err != nil {
+			return fmt.Errorf("write changelog: %w", err)
+		}
+		return nil
+	}
+
+	stdout := opts.Stdout
+	if stdout == nil {
+		stdout = os.Stdout
+	}
+	_, err = stdout.Write(rendered)
+	return err
+}
+
+func loadConfig(path string) (Config, error) {
+	var config Config
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return Config{}, fmt.Errorf("read changelog config %s: %w", path, err)
+	}
+	if err := json.Unmarshal(data, &config); err != nil {
+		return Config{}, fmt.Errorf("parse changelog config %s: %w", path, err)
+	}
+	if len(config.Categories) == 0 {
+		return Config{}, fmt.Errorf("changelog config %s does not define any categories", path)
+	}
+	return config, nil
+}
+
+func previousTagFor(repoRoot string, currentTag string) (string, error) {
+	output, err := gitOutput(repoRoot, "for-each-ref", "--sort=-creatordate", "--format=%(refname:strip=2)", "refs/tags")
+	if err != nil {
+		return "", fmt.Errorf("list tags: %w", err)
+	}
+
+	tags := strings.Fields(output)
+	for idx, tag := range tags {
+		if tag != currentTag {
+			continue
+		}
+		if idx+1 < len(tags) {
+			return tags[idx+1], nil
+		}
+		return "", nil
+	}
+
+	return "", fmt.Errorf("current tag %s was not found in repository tag list", currentTag)
+}
+
+func deriveAPIBaseURL(repoURL string) string {
+	parsed, err := url.Parse(repoURL)
+	if err != nil || parsed.Scheme == "" || parsed.Host == "" {
+		return ""
+	}
+	return fmt.Sprintf("%s://%s/api/v1", parsed.Scheme, parsed.Host)
+}
+
+func normalizeAPIBaseURL(raw string) string {
+	raw = strings.TrimRight(strings.TrimSpace(raw), "/")
+	if raw == "" {
+		return ""
+	}
+	if strings.HasSuffix(raw, "/api/v1") {
+		return raw
+	}
+	return raw + "/api/v1"
+}
+
+func ownerAndRepoFromURL(repoURL string) (string, string, error) {
+	parsed, err := url.Parse(repoURL)
+	if err != nil {
+		return "", "", fmt.Errorf("parse repo_url %s: %w", repoURL, err)
+	}
+
+	parts := strings.Split(strings.Trim(parsed.Path, "/"), "/")
+	if len(parts) < 2 {
+		return "", "", fmt.Errorf("repo_url %s does not include owner/repo", repoURL)
+	}
+
+	owner := strings.TrimSpace(parts[0])
+	name := strings.TrimSuffix(strings.TrimSpace(parts[1]), ".git")
+	if owner == "" || name == "" {
+		return "", "", fmt.Errorf("repo_url %s does not include owner/repo", repoURL)
+	}
+	return owner, name, nil
+}
+
+func (g generator) render() ([]byte, error) {
+	publishDate, err := gitOutput(g.repoRoot, "log", "-1", "--format=%cs", g.currentTag)
+	if err != nil {
+		return nil, fmt.Errorf("resolve publish date: %w", err)
+	}
+	publishDate = strings.TrimSpace(publishDate)
+
+	var buf bytes.Buffer
+	fmt.Fprintf(&buf, "# %s - %s\n\n", g.currentTag, publishDate)
+	if g.previousTag != "" {
+		fmt.Fprintf(&buf, "_Compared against %s_\n\n", g.previousTag)
+	} else {
+		buf.WriteString("_Initial tagged release_\n\n")
+	}
+
+	for _, category := range g.config.Categories {
+		categoryText, err := g.renderCategory(category)
+		if err != nil {
+			return nil, err
+		}
+		if categoryText == "" {
+			continue
+		}
+		fmt.Fprintf(&buf, "## %s\n\n", category.Title)
+		buf.WriteString(categoryText)
+	}
+
+	return buf.Bytes(), nil
+}
+
+func (g generator) renderCategory(category Category) (string, error) {
+	var buf bytes.Buffer
+	for _, section := range category.Sections {
+		entries, err := g.sectionEntries(section)
+		if err != nil {
+			return "", err
+		}
+		if len(entries) == 0 {
+			continue
+		}
+		fmt.Fprintf(&buf, "### %s\n", section.Title)
+		for _, entry := range entries {
+			fmt.Fprintf(&buf, "- %s ([#%s](%s/pulls/%s)) - From %s\n", entry.Title, entry.PullNumber, g.repoURL, entry.PullNumber, entry.AuthorName)
+		}
+		buf.WriteString("\n")
+	}
+	return buf.String(), nil
+}
+
+func (g generator) sectionEntries(section Section) ([]changelogEntry, error) {
+	if len(section.Paths) == 0 {
+		return nil, nil
+	}
+
+	args := []string{"log", "--pretty=format:%s%x1f%an"}
+	if g.previousTag != "" {
+		args = append(args, fmt.Sprintf("%s..%s", g.previousTag, g.currentTag))
+	} else {
+		args = append(args, g.currentTag)
+	}
+	args = append(args, "--")
+	args = append(args, section.Paths...)
+
+	output, err := gitOutput(g.repoRoot, args...)
+	if err != nil {
+		return nil, fmt.Errorf("list git log for section %s: %w", section.Title, err)
+	}
+
+	seen := map[string]struct{}{}
+	var entries []changelogEntry
+	for _, line := range strings.Split(output, "\n") {
+		if strings.TrimSpace(line) == "" {
+			continue
+		}
+		parts := strings.SplitN(line, "\x1f", 2)
+		subject := strings.TrimSpace(parts[0])
+		fallbackAuthor := ""
+		if len(parts) > 1 {
+			fallbackAuthor = strings.TrimSpace(parts[1])
+		}
+		matches := pullNumberPattern.FindStringSubmatch(subject)
+		if len(matches) != 2 {
+			continue
+		}
+		pullNumber := matches[1]
+		if _, exists := seen[pullNumber]; exists {
+			continue
+		}
+		seen[pullNumber] = struct{}{}
+
+		pullInfo, err := g.pullDetails(pullNumber)
+		if err != nil {
+			return nil, err
+		}
+		authorName := strings.TrimSpace(pullInfo.AuthorName)
+		if authorName == "" {
+			authorName = fallbackAuthor
+		}
+
+		entries = append(entries, changelogEntry{
+			Title:      sanitizeSubject(subject),
+			PullNumber: pullNumber,
+			AuthorName: authorName,
+		})
+	}
+
+	sort.Slice(entries, func(i, j int) bool {
+		if entries[i].Title == entries[j].Title {
+			return entries[i].PullNumber < entries[j].PullNumber
+		}
+		return entries[i].Title < entries[j].Title
+	})
+
+	return entries, nil
+}
+
+func sanitizeSubject(subject string) string {
+	title := strings.TrimSpace(subject)
+	title = pullNumberPattern.ReplaceAllString(title, "")
+	title = strings.TrimSpace(title)
+	title = strings.TrimPrefix(title, "Merge pull request")
+	title = strings.TrimSpace(title)
+	title = strings.Trim(title, `"'`)
+	title = strings.TrimSpace(title)
+	if title == "" {
+		return strings.TrimSpace(subject)
+	}
+	return title
+}
+
+func (g generator) pullDetails(pullNumber string) (pullInfo, error) {
+	if cached, ok := g.pullCache[pullNumber]; ok {
+		return cached, nil
+	}
+
+	endpoint := fmt.Sprintf("%s/repos/%s/%s/pulls/%s", g.apiBaseURL, url.PathEscape(g.owner), url.PathEscape(g.name), url.PathEscape(pullNumber))
+	req, err := http.NewRequest(http.MethodGet, endpoint, nil)
+	if err != nil {
+		return pullInfo{}, fmt.Errorf("build Gitea request for pull #%s: %w", pullNumber, err)
+	}
+	req.Header.Set("Accept", "application/json")
+	if g.token != "" {
+		req.Header.Set("Authorization", "token "+g.token)
+	}
+
+	resp, err := g.httpClient.Do(req)
+	if err != nil {
+		return pullInfo{}, fmt.Errorf("request Gitea pull #%s: %w", pullNumber, err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		body, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
+		return pullInfo{}, fmt.Errorf("request Gitea pull #%s: unexpected HTTP %d: %s", pullNumber, resp.StatusCode, strings.TrimSpace(string(body)))
+	}
+
+	var payload struct {
+		User struct {
+			FullName string `json:"full_name"`
+			Login    string `json:"login"`
+		} `json:"user"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
+		return pullInfo{}, fmt.Errorf("decode Gitea pull #%s: %w", pullNumber, err)
+	}
+
+	info := pullInfo{AuthorName: firstNonEmpty(strings.TrimSpace(payload.User.FullName), strings.TrimSpace(payload.User.Login))}
+	g.pullCache[pullNumber] = info
+	return info, nil
+}
+
+func gitOutput(repoRoot string, args ...string) (string, error) {
+	cmd := exec.Command("git", args...)
+	if repoRoot != "" {
+		cmd.Dir = repoRoot
+	}
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		return "", fmt.Errorf("%s: %s", strings.Join(cmd.Args, " "), strings.TrimSpace(string(output)))
+	}
+	return string(output), nil
+}
+
+func firstNonEmpty(values ...string) string {
+	for _, value := range values {
+		if strings.TrimSpace(value) != "" {
+			return value
+		}
+	}
+	return ""
+}
diff --git a/internal/changelog/changelog_test.go b/internal/changelog/changelog_test.go
new file mode 100644
index 0000000..4addf37
--- /dev/null
+++ b/internal/changelog/changelog_test.go
@@ -0,0 +1,79 @@
+package changelog
+
+import "testing"
+
+func TestSanitizeSubject(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		subject string
+		want    string
+	}{
+		{
+			name:    "merge prefix with quotes",
+			subject: "Merge pull request 'Add classes overhaul (#123)'",
+			want:    "Add classes overhaul",
+		},
+		{
+			name:    "plain subject",
+			subject: "Add classes overhaul (#123)",
+			want:    "Add classes overhaul",
+		},
+		{
+			name:    "double quotes",
+			subject: `Merge pull request "Add classes overhaul (#123)"`,
+			want:    "Add classes overhaul",
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			if got := sanitizeSubject(tt.subject); got != tt.want {
+				t.Fatalf("sanitizeSubject(%q) = %q, want %q", tt.subject, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestOwnerAndRepoFromURL(t *testing.T) {
+	t.Parallel()
+
+	owner, repo, err := ownerAndRepoFromURL("https://gitea.example.test/org/repo.git")
+	if err != nil {
+		t.Fatalf("ownerAndRepoFromURL returned error: %v", err)
+	}
+	if owner != "org" || repo != "repo" {
+		t.Fatalf("ownerAndRepoFromURL returned %q/%q", owner, repo)
+	}
+}
+
+func TestDeriveAPIBaseURL(t *testing.T) {
+	t.Parallel()
+
+	got := deriveAPIBaseURL("https://gitea.example.test/org/repo")
+	want := "https://gitea.example.test/api/v1"
+	if got != want {
+		t.Fatalf("deriveAPIBaseURL() = %q, want %q", got, want)
+	}
+}
+
+func TestNormalizeAPIBaseURL(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		input string
+		want  string
+	}{
+		{input: "https://gitea.example.test", want: "https://gitea.example.test/api/v1"},
+		{input: "https://gitea.example.test/api/v1", want: "https://gitea.example.test/api/v1"},
+	}
+
+	for _, tt := range tests {
+		if got := normalizeAPIBaseURL(tt.input); got != tt.want {
+			t.Fatalf("normalizeAPIBaseURL(%q) = %q, want %q", tt.input, got, tt.want)
+		}
+	}
+}