diff --git a/CHANGELOG.md b/CHANGELOG.md
index da9a675..6a8294c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,23 @@
 
 All notable changes to TagLock will be documented here.
 
+## Unreleased
+
+No unreleased changes yet.
+
+## 0.4.0 - 2026-08-14
+
+### Added
+
+- `taglock check --format github` emits GitHub Actions workflow commands (`::error`, `::warning`, `::notice`) so pull-request files are annotated without a SARIF upload.
+- `output.GitHub` for embedders that want the same annotation stream.
+
+### Compatibility
+
+- Existing analyzer, CLI, snapshot, schema, verification, and evolution APIs are unchanged.
+- `text`, `json`, and `sarif` formats remain the default and previous options.
+- The release is additive and requires no configuration migration.
+
 ## 0.3.0 - 2026-08-11
 
 ### Added
diff --git a/README.md b/README.md
index ad298c4..9229543 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,7 @@ go install github.com/theworker02/taglock/cmd/taglock@latest
 taglock check ./...
 taglock check --format json --fail-on error ./...
 taglock check --format sarif ./... > taglock.sarif
+taglock check --format github ./...
 taglock check --json-semantics v2 ./...
 ```
 
diff --git a/docs/releases/v0.4.0.md b/docs/releases/v0.4.0.md
new file mode 100644
index 0000000..11f9e95
--- /dev/null
+++ b/docs/releases/v0.4.0.md
@@ -0,0 +1,26 @@
+# TagLock v0.4.0 — GitHub Actions annotations
+
+TagLock v0.4.0 adds a GitHub Actions workflow-command report format so `taglock check` can annotate pull-request files without uploading SARIF.
+
+## Added
+
+- `taglock check --format github` emits `::error`, `::warning`, and `::notice` commands with file, line, column, and rule title.
+- `output.GitHub` for library embedders.
+
+## Compatibility
+
+- Existing analyzer, CLI, snapshot, schema, verification, and evolution APIs are unchanged.
+- `text`, `json`, and `sarif` remain supported. The default check format is still `text`.
+- Go 1.24 remains the minimum supported toolchain.
+
+## Upgrade
+
+```bash
+go get github.com/theworker02/taglock@v0.4.0
+```
+
+## Example
+
+```bash
+taglock check --format github --fail-on error ./...
+```
diff --git a/internal/cli/run.go b/internal/cli/run.go
index 8eaeebf..7fb3dbe 100644
--- a/internal/cli/run.go
+++ b/internal/cli/run.go
@@ -102,7 +102,7 @@ func Run(arguments []string, stdout, stderr io.Writer) int {
 
 func runCheck(arguments []string, stdout, stderr io.Writer) int {
 	set := newFlagSet("check", stderr)
-	format := set.String("format", "text", "output format: text, json, or sarif")
+	format := set.String("format", "text", "output format: text, json, sarif, or github")
 	failOn := set.String("fail-on", "warning", "minimum severity that fails")
 	configPath := set.String("config", "", "configuration path")
 	baselinePath := set.String("baseline", "", "baseline file")
@@ -115,7 +115,7 @@ func runCheck(arguments []string, stdout, stderr io.Writer) int {
 		fmt.Fprintln(stderr, "taglock:", err)
 		return ExitUsage
 	}
-	if *format != "text" && *format != "json" && *format != "sarif" {
+	if *format != "text" && *format != "json" && *format != "sarif" && *format != "github" {
 		fmt.Fprintf(stderr, "taglock: invalid format %q\n", *format)
 		return ExitUsage
 	}
@@ -170,6 +170,8 @@ func runCheck(arguments []string, stdout, stderr io.Writer) int {
 		err = output.JSON(stdout, result.FileSet, diagnostics)
 	case "sarif":
 		err = output.SARIF(stdout, result.FileSet, diagnostics)
+	case "github":
+		err = output.GitHub(stdout, result.FileSet, diagnostics)
 	}
 	if err != nil {
 		fmt.Fprintln(stderr, "taglock: write output:", err)
diff --git a/internal/cli/run_test.go b/internal/cli/run_test.go
index 5f5b2fe..cb12eca 100644
--- a/internal/cli/run_test.go
+++ b/internal/cli/run_test.go
@@ -60,6 +60,17 @@ func TestRulesAndExplainShareCatalog(t *testing.T) {
 	}
 }
 
+func TestGitHubCheckFormat(t *testing.T) {
+	var out, errOut bytes.Buffer
+	code := cli.Run([]string{"check", "--format", "github", "./testdata/violation"}, &out, &errOut)
+	if code != cli.ExitViolations {
+		t.Fatalf("check github code=%d out=%s err=%s", code, out.String(), errOut.String())
+	}
+	if !strings.Contains(out.String(), "::error ") || !strings.Contains(out.String(), "title=") {
+		t.Fatalf("expected GitHub workflow commands, got %s", out.String())
+	}
+}
+
 func TestVersionCommand(t *testing.T) {
 	var out, errOut bytes.Buffer
 	if code := cli.Run([]string{"version"}, &out, &errOut); code != cli.ExitOK {
diff --git a/output/output.go b/output/output.go
index e0bbfb1..edad8b8 100644
--- a/output/output.go
+++ b/output/output.go
@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"github.com/theworker02/taglock/baseline"
+	"github.com/theworker02/taglock/rule"
 	"github.com/theworker02/taglock/rules"
 )
 
@@ -85,6 +86,47 @@ func JSON(writer io.Writer, fileSet *token.FileSet, diagnostics []rules.Diagnost
 	return encoder.Encode(JSONDocument{SchemaVersion: JSONSchemaVersion, Findings: Flatten(fileSet, diagnostics)})
 }
 
+// GitHub writes GitHub Actions workflow commands so `check --format github`
+// annotates pull-request files without a SARIF upload step.
+func GitHub(writer io.Writer, fileSet *token.FileSet, diagnostics []rules.Diagnostic) error {
+	for _, diagnostic := range diagnostics {
+		position := fileSet.Position(diagnostic.Pos)
+		command := githubCommand(diagnostic.Severity)
+		title := githubEscapeProperty(diagnostic.Rule.ID)
+		file := githubEscapeProperty(position.Filename)
+		message := githubEscapeMessage(diagnostic.Rule.ID + " " + diagnostic.Message)
+		if _, err := fmt.Fprintf(writer, "::%s file=%s,line=%d,col=%d,title=%s::%s\n", command, file, position.Line, position.Column, title, message); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func githubCommand(severity rule.Severity) string {
+	switch severity {
+	case rule.SeverityError:
+		return "error"
+	case rule.SeverityWarning:
+		return "warning"
+	default:
+		return "notice"
+	}
+}
+
+func githubEscapeMessage(value string) string {
+	value = strings.ReplaceAll(value, "%", "%25")
+	value = strings.ReplaceAll(value, "\r", "%0D")
+	value = strings.ReplaceAll(value, "\n", "%0A")
+	return value
+}
+
+func githubEscapeProperty(value string) string {
+	value = githubEscapeMessage(value)
+	value = strings.ReplaceAll(value, ":", "%3A")
+	value = strings.ReplaceAll(value, ",", "%2C")
+	return value
+}
+
 type sarifLog struct {
 	Version string     `json:"version"`
 	Schema  string     `json:"$schema"`
diff --git a/output/output_test.go b/output/output_test.go
index c4e4f93..f965d13 100644
--- a/output/output_test.go
+++ b/output/output_test.go
@@ -46,3 +46,17 @@ func TestSARIFContainsRuleAndLocation(t *testing.T) {
 		}
 	}
 }
+
+func TestGitHubWorkflowCommands(t *testing.T) {
+	set, diagnostics := testDiagnostic()
+	var buffer bytes.Buffer
+	if err := output.GitHub(&buffer, set, diagnostics); err != nil {
+		t.Fatal(err)
+	}
+	value := buffer.String()
+	for _, expected := range []string{"::error file=model.go,line=2,col=", "title=TAG104::", "TAG104 duplicate json name"} {
+		if !strings.Contains(value, expected) {
+			t.Fatalf("missing %s in %s", expected, value)
+		}
+	}
+}