diff --git a/act/runner/job_executor.go b/act/runner/job_executor.go
index d4a3076b..7cc5fa9d 100644
--- a/act/runner/job_executor.go
+++ b/act/runner/job_executor.go
@@ -5,15 +5,46 @@
 package runner
 
 import (
+	"archive/tar"
+	"bytes"
 	"context"
+	"encoding/base64"
+	"encoding/json"
 	"fmt"
+	"io"
+	"net/http"
+	"path"
+	"slices"
 	"strconv"
+	"strings"
 	"time"
+	"unicode"
 
 	"gitea.com/gitea/runner/act/common"
+	"gitea.com/gitea/runner/act/container"
 	"gitea.com/gitea/runner/act/model"
 )
 
+const maxJobSummaryBytes = 1024 * 1024
+
+// jobSummaryTruncationMarker is appended to a summary that exceeded the size limit
+// so the rendered output makes the truncation visible instead of silently cutting off.
+const jobSummaryTruncationMarker = "\n\n---\n\n*Job summary truncated: it exceeded the maximum allowed size.*\n"
+
+var (
+	jobSummaryUploadRetryDelay = time.Second
+	// jobSummaryUploadRequestTimeout bounds a single step upload request. It is kept
+	// below jobSummaryUploadPhaseTimeout so one slow or unreachable request times out
+	// and lets the remaining steps still upload within the phase budget, instead of a
+	// single stuck request consuming the whole phase.
+	jobSummaryUploadRequestTimeout = 5 * time.Second
+	// jobSummaryUploadPhaseTimeout bounds the total time spent uploading all step
+	// summaries. The uploads run inside the job cleanup budget that is also used to
+	// stop and remove the container, so a slow or unreachable endpoint must not be
+	// allowed to consume it; this keeps the remaining budget available for teardown.
+	jobSummaryUploadPhaseTimeout = 15 * time.Second
+)
+
 type jobInfo interface {
 	matrix() map[string]any
 	steps() []*model.Step
@@ -80,8 +111,10 @@ func newJobExecutor(info jobInfo, sf stepFactory, rc *RunContext) common.Executo
 			return common.NewErrorExecutor(err)
 		}
 
+		stepIdx := stepModel.Number
 		preExec := step.pre()
 		preSteps = append(preSteps, useStepLogger(rc, stepModel, stepStagePre, func(ctx context.Context) error {
+			rc.CurrentStepIndex = stepIdx
 			preErr := preExec(ctx)
 			if preErr != nil {
 				reportStepError(ctx, preErr)
@@ -93,6 +126,7 @@ func newJobExecutor(info jobInfo, sf stepFactory, rc *RunContext) common.Executo
 
 		stepExec := step.main()
 		steps = append(steps, useStepLogger(rc, stepModel, stepStageMain, func(ctx context.Context) error {
+			rc.CurrentStepIndex = stepIdx
 			err := stepExec(ctx)
 			if err != nil {
 				reportStepError(ctx, err)
@@ -104,6 +138,7 @@ func newJobExecutor(info jobInfo, sf stepFactory, rc *RunContext) common.Executo
 
 		postFn := step.post()
 		postExec := useStepLogger(rc, stepModel, stepStagePost, func(ctx context.Context) error {
+			rc.CurrentStepIndex = stepIdx
 			err := postFn(ctx)
 			if err != nil {
 				reportStepError(ctx, err)
@@ -129,6 +164,7 @@ func newJobExecutor(info jobInfo, sf stepFactory, rc *RunContext) common.Executo
 			defer cancel()
 
 			logger := common.Logger(ctx)
+			tryUploadJobSummary(ctx, rc)
 			// For Gitea
 			// We don't need to call `stopServiceContainers` here since it will be called by following `info.stopContainer`
 			// logger.Infof("Cleaning up services for job %s", rc.JobName)
@@ -235,6 +271,180 @@ func setJobOutputs(ctx context.Context, rc *RunContext) {
 	}
 }
 
+func tryUploadJobSummary(ctx context.Context, rc *RunContext) {
+	if rc == nil || rc.JobContainer == nil || rc.Config == nil {
+		return
+	}
+	// Bound the whole upload phase so a slow or unreachable endpoint cannot consume
+	// the job cleanup budget reserved for stopping and removing the container.
+	ctx, cancel := context.WithTimeout(ctx, jobSummaryUploadPhaseTimeout)
+	defer cancel()
+	env := rc.GetEnv()
+	caps := strings.TrimSpace(env["GITEA_ACTIONS_CAPABILITIES"])
+	if !hasJobSummaryCapability(caps) {
+		// Server did not advertise support. Do not attempt upload.
+		return
+	}
+	runtimeURL := strings.TrimSpace(env["ACTIONS_RUNTIME_URL"])
+	runtimeToken := strings.TrimSpace(env["ACTIONS_RUNTIME_TOKEN"])
+	runID := strings.TrimSpace(env["GITEA_RUN_ID"])
+	if runtimeURL == "" || runtimeToken == "" || runID == "" {
+		return
+	}
+	if rc.Run == nil || rc.Run.Job() == nil {
+		return
+	}
+	// The numeric ActionRunJob ID is not exposed in the proto Task message or task context,
+	// but the server signs it into the ACTIONS_RUNTIME_TOKEN JWT claims. We decode the
+	// unverified claims to retrieve it; the server re-verifies the token on the request.
+	jobID := extractJobIDFromRuntimeToken(runtimeToken)
+	if jobID <= 0 {
+		return
+	}
+
+	base := strings.TrimRight(runtimeURL, "/") + "/_apis/pipelines/workflows/" + runID +
+		"/jobs/" + strconv.FormatInt(jobID, 10) + "/steps/"
+	actPath := rc.JobContainer.GetActPath()
+	// Reuse a single client across all step uploads so connections can be pooled.
+	client := &http.Client{Timeout: jobSummaryUploadRequestTimeout}
+	for i := range rc.Run.Job().Steps {
+		summaryPath := path.Join(actPath, "workflow", "step-summary-"+strconv.Itoa(i)+".md")
+		body, ok := readSingleFileFromContainerArchive(ctx, rc.JobContainer, summaryPath, maxJobSummaryBytes)
+		if !ok || len(body) == 0 {
+			continue
+		}
+		uploadJobSummary(ctx, client, base+strconv.Itoa(i)+"/summary", runtimeToken, body)
+	}
+}
+
+// extractJobIDFromRuntimeToken returns the JobID claim from an ACTIONS_RUNTIME_TOKEN JWT
+// without verifying its signature. Returns 0 if the token is unparseable or has no JobID.
+func extractJobIDFromRuntimeToken(token string) int64 {
+	parts := strings.Split(token, ".")
+	if len(parts) != 3 {
+		return 0
+	}
+	payload, err := base64.RawURLEncoding.DecodeString(parts[1])
+	if err != nil {
+		return 0
+	}
+	var claims struct {
+		JobID int64 `json:"JobID"`
+	}
+	if err := json.Unmarshal(payload, &claims); err != nil {
+		return 0
+	}
+	return claims.JobID
+}
+
+func hasJobSummaryCapability(caps string) bool {
+	return slices.Contains(strings.FieldsFunc(caps, func(r rune) bool {
+		return r == ',' || unicode.IsSpace(r)
+	}), "job-summary")
+}
+
+func uploadJobSummary(ctx context.Context, client *http.Client, url, runtimeToken string, body []byte) {
+	logger := common.Logger(ctx)
+
+	var lastStatus int
+	var lastErr error
+	for attempt := 0; attempt < 2; attempt++ {
+		status, err := putJobSummary(ctx, client, url, runtimeToken, body)
+		if err == nil && status/100 == 2 {
+			return
+		}
+		lastStatus = status
+		lastErr = err
+		if attempt == 1 || !isTransientJobSummaryUploadFailure(status, err) {
+			break
+		}
+		timer := time.NewTimer(jobSummaryUploadRetryDelay)
+		select {
+		case <-ctx.Done():
+			timer.Stop()
+			lastErr = ctx.Err()
+			attempt = 1
+		case <-timer.C:
+		}
+	}
+
+	// Best-effort only; do not fail job, but log because capability was advertised.
+	if lastErr != nil {
+		logger.WithError(lastErr).Warn("job summary upload failed")
+		return
+	}
+	logger.Warnf("job summary upload failed: status=%d", lastStatus)
+}
+
+func putJobSummary(ctx context.Context, client *http.Client, url, runtimeToken string, body []byte) (int, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodPut, url, bytes.NewReader(body))
+	if err != nil {
+		return 0, err
+	}
+	req.Header.Set("Authorization", "Bearer "+runtimeToken)
+	req.Header.Set("Content-Type", "text/markdown; charset=utf-8")
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return 0, err
+	}
+	defer resp.Body.Close()
+	_, _ = io.Copy(io.Discard, resp.Body)
+	return resp.StatusCode, nil
+}
+
+func isTransientJobSummaryUploadFailure(status int, err error) bool {
+	return err != nil || status == http.StatusRequestTimeout || status == http.StatusTooManyRequests || status/100 == 5
+}
+
+func readSingleFileFromContainerArchive(ctx context.Context, env container.ExecutionsEnvironment, p string, maxBytes int64) ([]byte, bool) {
+	rc, err := env.GetContainerArchive(ctx, p)
+	if err != nil {
+		return nil, false
+	}
+	defer rc.Close()
+
+	tr := tar.NewReader(rc)
+	for {
+		header, err := tr.Next()
+		if err == io.EOF {
+			return nil, false
+		}
+		if err != nil {
+			return nil, false
+		}
+		if header.Typeflag != tar.TypeReg {
+			continue
+		}
+		if !archiveEntryMatchesPath(header.Name, p) {
+			continue
+		}
+		// Summaries larger than the limit are truncated rather than dropped, so the
+		// user still gets the leading content (mirroring how GitHub caps oversized
+		// step summaries instead of discarding them). Read one extra byte so an
+		// over-limit file is detected from the actual stream rather than trusting
+		// header.Size, then cap the returned content at maxBytes.
+		b, err := io.ReadAll(io.LimitReader(tr, maxBytes+1))
+		if err != nil {
+			return nil, false
+		}
+		if int64(len(b)) > maxBytes {
+			// Reserve room for the marker so the marked-up result still fits in maxBytes.
+			marker := []byte(jobSummaryTruncationMarker)
+			keep := max(maxBytes-int64(len(marker)), 0)
+			b = append(b[:keep], marker...)
+			common.Logger(ctx).Warnf("job summary truncated: path=%s max=%d", p, maxBytes)
+		}
+		return b, true
+	}
+}
+
+func archiveEntryMatchesPath(entryName, requestedPath string) bool {
+	entryName = path.Clean(strings.TrimPrefix(entryName, "/"))
+	requestedPath = path.Clean(strings.TrimPrefix(requestedPath, "/"))
+	return entryName == requestedPath || entryName == path.Base(requestedPath)
+}
+
 func useStepLogger(rc *RunContext, stepModel *model.Step, stage stepStage, executor common.Executor) common.Executor {
 	return func(ctx context.Context) error {
 		ctx = withStepLogger(ctx, stepModel.Number, stepModel.ID, rc.ExprEval.Interpolate(ctx, stepModel.String()), stage.String())
diff --git a/act/runner/job_executor_test.go b/act/runner/job_executor_test.go
index a89ed0c7..55228e85 100644
--- a/act/runner/job_executor_test.go
+++ b/act/runner/job_executor_test.go
@@ -5,19 +5,29 @@
 package runner
 
 import (
+	"archive/tar"
+	"bytes"
 	"context"
+	"encoding/base64"
 	"errors"
 	"fmt"
 	"io"
+	"net/http"
+	"net/http/httptest"
 	"slices"
+	"strconv"
+	"strings"
 	"testing"
+	"time"
 
 	"gitea.com/gitea/runner/act/common"
 	"gitea.com/gitea/runner/act/container"
 	"gitea.com/gitea/runner/act/model"
 
+	logrustest "github.com/sirupsen/logrus/hooks/test"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/require"
 )
 
 func TestJobExecutor(t *testing.T) {
@@ -336,3 +346,331 @@ func TestNewJobExecutor(t *testing.T) {
 		})
 	}
 }
+
+func TestHasJobSummaryCapability(t *testing.T) {
+	assert.True(t, hasJobSummaryCapability("cache,job-summary artifacts"))
+	assert.True(t, hasJobSummaryCapability("cache,\njob-summary\tartifacts"))
+	assert.False(t, hasJobSummaryCapability("not-job-summary,job-summary-v2"))
+}
+
+// fakeRuntimeToken builds a JWT-shaped string whose middle (claims) segment encodes
+// the given JobID. The header and signature segments are filler — the runner does not
+// verify the signature; the server does.
+func fakeRuntimeToken(jobID int64) string {
+	header := base64.RawURLEncoding.EncodeToString([]byte(`{"alg":"HS256","typ":"JWT"}`))
+	claims := base64.RawURLEncoding.EncodeToString(fmt.Appendf(nil, `{"JobID":%d}`, jobID))
+	sig := base64.RawURLEncoding.EncodeToString([]byte("sig"))
+	return header + "." + claims + "." + sig
+}
+
+func newJobSummaryRC(env map[string]string, jobContainer container.ExecutionsEnvironment, stepCount int) *RunContext {
+	steps := make([]*model.Step, stepCount)
+	for i := range steps {
+		steps[i] = &model.Step{ID: strconv.Itoa(i)}
+	}
+	return &RunContext{
+		Config:       &Config{},
+		JobContainer: jobContainer,
+		Env:          env,
+		Run: &model.Run{
+			JobID: "test",
+			Workflow: &model.Workflow{
+				Jobs: map[string]*model.Job{
+					"test": {Steps: steps},
+				},
+			},
+		},
+	}
+}
+
+func TestTryUploadJobSummaryRetriesTransientFailure(t *testing.T) {
+	oldDelay := jobSummaryUploadRetryDelay
+	jobSummaryUploadRetryDelay = 0
+	defer func() {
+		jobSummaryUploadRetryDelay = oldDelay
+	}()
+
+	runtimeToken := fakeRuntimeToken(34)
+
+	requests := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requests++
+		assert.Equal(t, http.MethodPut, r.Method)
+		assert.Equal(t, "/_apis/pipelines/workflows/12/jobs/34/steps/0/summary", r.URL.Path)
+		assert.Equal(t, "Bearer "+runtimeToken, r.Header.Get("Authorization"))
+		assert.Equal(t, "text/markdown; charset=utf-8", r.Header.Get("Content-Type"))
+		body, err := io.ReadAll(r.Body)
+		assert.NoError(t, err)
+		assert.Equal(t, []byte("# summary"), body)
+		if requests == 1 {
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		w.WriteHeader(http.StatusNoContent)
+	}))
+	defer server.Close()
+
+	ctx := context.Background()
+	cm := &containerMock{}
+	cm.On("GetContainerArchive", mock.Anything, "/var/run/act/workflow/step-summary-0.md").Return(
+		io.NopCloser(bytes.NewReader(tarArchive(t, tarEntry{name: "step-summary-0.md", body: "# summary"}))),
+		nil,
+	).Once()
+
+	rc := newJobSummaryRC(map[string]string{
+		"GITEA_ACTIONS_CAPABILITIES": "cache, job-summary",
+		"ACTIONS_RUNTIME_URL":        server.URL,
+		"ACTIONS_RUNTIME_TOKEN":      runtimeToken,
+		"GITEA_RUN_ID":               "12",
+	}, cm, 1)
+
+	tryUploadJobSummary(ctx, rc)
+
+	assert.Equal(t, 2, requests)
+	cm.AssertExpectations(t)
+}
+
+func TestTryUploadJobSummaryStopsAtPhaseTimeout(t *testing.T) {
+	oldPhase := jobSummaryUploadPhaseTimeout
+	jobSummaryUploadPhaseTimeout = 100 * time.Millisecond
+	defer func() {
+		jobSummaryUploadPhaseTimeout = oldPhase
+	}()
+
+	runtimeToken := fakeRuntimeToken(34)
+
+	// The server blocks until either the request context is cancelled (the behaviour
+	// under test: the phase timeout aborts the in-flight upload) or the test tears it
+	// down. Without the phase timeout the upload would hang until the 30s client
+	// timeout instead of releasing the cleanup budget. The release channel guarantees
+	// the handler always returns so server.Close() cannot itself hang.
+	release := make(chan struct{})
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		select {
+		case <-r.Context().Done():
+		case <-release:
+		}
+	}))
+	defer server.Close()
+	defer close(release)
+
+	ctx := context.Background()
+	cm := &containerMock{}
+	cm.On("GetContainerArchive", mock.Anything, "/var/run/act/workflow/step-summary-0.md").Return(
+		io.NopCloser(bytes.NewReader(tarArchive(t, tarEntry{name: "step-summary-0.md", body: "# summary"}))),
+		nil,
+	).Once()
+
+	rc := newJobSummaryRC(map[string]string{
+		"GITEA_ACTIONS_CAPABILITIES": "job-summary",
+		"ACTIONS_RUNTIME_URL":        server.URL,
+		"ACTIONS_RUNTIME_TOKEN":      runtimeToken,
+		"GITEA_RUN_ID":               "12",
+	}, cm, 1)
+
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		tryUploadJobSummary(ctx, rc)
+	}()
+
+	select {
+	case <-done:
+	case <-time.After(5 * time.Second):
+		t.Fatal("tryUploadJobSummary did not honour the phase timeout")
+	}
+	cm.AssertExpectations(t)
+}
+
+func TestTryUploadJobSummaryUploadsEachStepIndependently(t *testing.T) {
+	runtimeToken := fakeRuntimeToken(34)
+
+	type upload struct {
+		path string
+		body string
+	}
+	var got []upload
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, err := io.ReadAll(r.Body)
+		assert.NoError(t, err)
+		got = append(got, upload{r.URL.Path, string(body)})
+		w.WriteHeader(http.StatusNoContent)
+	}))
+	defer server.Close()
+
+	ctx := context.Background()
+	cm := &containerMock{}
+	// Three steps: 0 has content, 1 has empty content (skipped), 2 has content.
+	cm.On("GetContainerArchive", mock.Anything, "/var/run/act/workflow/step-summary-0.md").Return(
+		io.NopCloser(bytes.NewReader(tarArchive(t, tarEntry{name: "step-summary-0.md", body: "first"}))),
+		nil,
+	).Once()
+	cm.On("GetContainerArchive", mock.Anything, "/var/run/act/workflow/step-summary-1.md").Return(
+		io.NopCloser(bytes.NewReader(tarArchive(t, tarEntry{name: "step-summary-1.md", body: ""}))),
+		nil,
+	).Once()
+	cm.On("GetContainerArchive", mock.Anything, "/var/run/act/workflow/step-summary-2.md").Return(
+		io.NopCloser(bytes.NewReader(tarArchive(t, tarEntry{name: "step-summary-2.md", body: "third"}))),
+		nil,
+	).Once()
+
+	rc := newJobSummaryRC(map[string]string{
+		"GITEA_ACTIONS_CAPABILITIES": "job-summary",
+		"ACTIONS_RUNTIME_URL":        server.URL,
+		"ACTIONS_RUNTIME_TOKEN":      runtimeToken,
+		"GITEA_RUN_ID":               "12",
+	}, cm, 3)
+
+	tryUploadJobSummary(ctx, rc)
+
+	assert.Equal(t, []upload{
+		{"/_apis/pipelines/workflows/12/jobs/34/steps/0/summary", "first"},
+		{"/_apis/pipelines/workflows/12/jobs/34/steps/2/summary", "third"},
+	}, got)
+	cm.AssertExpectations(t)
+}
+
+func TestTryUploadJobSummaryRequiresExactCapability(t *testing.T) {
+	requests := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requests++
+		w.WriteHeader(http.StatusNoContent)
+	}))
+	defer server.Close()
+
+	rc := newJobSummaryRC(map[string]string{
+		"GITEA_ACTIONS_CAPABILITIES": "not-job-summary,job-summary-v2",
+		"ACTIONS_RUNTIME_URL":        server.URL,
+		"ACTIONS_RUNTIME_TOKEN":      fakeRuntimeToken(34),
+		"GITEA_RUN_ID":               "12",
+	}, &containerMock{}, 1)
+
+	tryUploadJobSummary(context.Background(), rc)
+
+	assert.Equal(t, 0, requests)
+}
+
+func TestTryUploadJobSummarySkipsWhenJobIDMissingFromToken(t *testing.T) {
+	requests := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requests++
+		w.WriteHeader(http.StatusNoContent)
+	}))
+	defer server.Close()
+
+	rc := newJobSummaryRC(map[string]string{
+		"GITEA_ACTIONS_CAPABILITIES": "job-summary",
+		"ACTIONS_RUNTIME_URL":        server.URL,
+		"ACTIONS_RUNTIME_TOKEN":      "not-a-jwt",
+		"GITEA_RUN_ID":               "12",
+	}, &containerMock{}, 1)
+
+	tryUploadJobSummary(context.Background(), rc)
+
+	assert.Equal(t, 0, requests)
+}
+
+func TestExtractJobIDFromRuntimeToken(t *testing.T) {
+	assert.Equal(t, int64(42), extractJobIDFromRuntimeToken(fakeRuntimeToken(42)))
+	assert.Equal(t, int64(0), extractJobIDFromRuntimeToken("not-a-jwt"))
+	assert.Equal(t, int64(0), extractJobIDFromRuntimeToken("a.b.c"))
+	assert.Equal(t, int64(0), extractJobIDFromRuntimeToken(""))
+}
+
+func TestReadSingleFileFromContainerArchiveFindsMatchingRegularFile(t *testing.T) {
+	ctx := context.Background()
+	cm := &containerMock{}
+	cm.On("GetContainerArchive", ctx, "/var/run/act/workflow/SUMMARY.md").Return(
+		io.NopCloser(bytes.NewReader(tarArchive(t,
+			tarEntry{name: "workflow", typeflag: tar.TypeDir},
+			tarEntry{name: "other.md", body: "wrong"},
+			tarEntry{name: "SUMMARY.md", body: "right"},
+		))),
+		nil,
+	).Once()
+
+	body, ok := readSingleFileFromContainerArchive(ctx, cm, "/var/run/act/workflow/SUMMARY.md", 1024)
+
+	assert.True(t, ok)
+	assert.Equal(t, []byte("right"), body)
+	cm.AssertExpectations(t)
+}
+
+func TestReadSingleFileFromContainerArchiveTruncatesWhenTooLarge(t *testing.T) {
+	logger, hook := logrustest.NewNullLogger()
+	ctx := common.WithLogger(context.Background(), logger)
+	cm := &containerMock{}
+	content := strings.Repeat("a", 300)
+	cm.On("GetContainerArchive", ctx, "/var/run/act/workflow/SUMMARY.md").Return(
+		io.NopCloser(bytes.NewReader(tarArchive(t, tarEntry{name: "SUMMARY.md", body: content}))),
+		nil,
+	).Once()
+
+	const maxBytes = 200
+	body, ok := readSingleFileFromContainerArchive(ctx, cm, "/var/run/act/workflow/SUMMARY.md", maxBytes)
+
+	// Oversized summaries are truncated to the limit (reserving room for the marker)
+	// rather than dropped entirely, and the truncation marker is appended.
+	assert.True(t, ok)
+	assert.LessOrEqual(t, len(body), maxBytes)
+	keep := maxBytes - len(jobSummaryTruncationMarker)
+	assert.Equal(t, []byte(content[:keep]+jobSummaryTruncationMarker), body)
+	if assert.Len(t, hook.Entries, 1) {
+		assert.Contains(t, hook.Entries[0].Message, "job summary truncated")
+	}
+	cm.AssertExpectations(t)
+}
+
+func TestReadSingleFileFromContainerArchiveKeepsExactLimitWithoutWarning(t *testing.T) {
+	logger, hook := logrustest.NewNullLogger()
+	ctx := common.WithLogger(context.Background(), logger)
+	cm := &containerMock{}
+	cm.On("GetContainerArchive", ctx, "/var/run/act/workflow/SUMMARY.md").Return(
+		io.NopCloser(bytes.NewReader(tarArchive(t, tarEntry{name: "SUMMARY.md", body: "abc"}))),
+		nil,
+	).Once()
+
+	body, ok := readSingleFileFromContainerArchive(ctx, cm, "/var/run/act/workflow/SUMMARY.md", 3)
+
+	// A summary that is exactly at the limit is kept whole and not flagged as truncated.
+	assert.True(t, ok)
+	assert.Equal(t, []byte("abc"), body)
+	assert.Empty(t, hook.Entries)
+	cm.AssertExpectations(t)
+}
+
+type tarEntry struct {
+	name     string
+	body     string
+	typeflag byte
+}
+
+func tarArchive(t *testing.T, entries ...tarEntry) []byte {
+	t.Helper()
+
+	buf := &bytes.Buffer{}
+	tw := tar.NewWriter(buf)
+	for _, entry := range entries {
+		typeflag := entry.typeflag
+		if typeflag == 0 {
+			typeflag = tar.TypeReg
+		}
+		header := &tar.Header{
+			Name:     entry.name,
+			Typeflag: typeflag,
+			Mode:     0o644,
+			Size:     int64(len(entry.body)),
+		}
+		if typeflag == tar.TypeDir {
+			header.Mode = 0o755
+			header.Size = 0
+		}
+		require.NoError(t, tw.WriteHeader(header))
+		if typeflag == tar.TypeReg {
+			_, err := tw.Write([]byte(entry.body))
+			require.NoError(t, err)
+		}
+	}
+	require.NoError(t, tw.Close())
+	return buf.Bytes()
+}
diff --git a/act/runner/run_context.go b/act/runner/run_context.go
index a7f98ec9..0ff660bd 100644
--- a/act/runner/run_context.go
+++ b/act/runner/run_context.go
@@ -36,15 +36,19 @@ import (
 
 // RunContext contains info about current job
 type RunContext struct {
-	Name                string
-	Config              *Config
-	Matrix              map[string]any
-	Run                 *model.Run
-	EventJSON           string
-	Env                 map[string]string
-	GlobalEnv           map[string]string // to pass env changes of GITHUB_ENV and set-env correctly, due to dirty Env field
-	ExtraPath           []string
-	CurrentStep         string
+	Name        string
+	Config      *Config
+	Matrix      map[string]any
+	Run         *model.Run
+	EventJSON   string
+	Env         map[string]string
+	GlobalEnv   map[string]string // to pass env changes of GITHUB_ENV and set-env correctly, due to dirty Env field
+	ExtraPath   []string
+	CurrentStep string
+	// CurrentStepIndex is the index of the top-level job step currently executing
+	// (model.Step.Number). Composite sub-steps inherit the outer step's index by
+	// walking the Parent chain; see topLevelRunContext.
+	CurrentStepIndex    int
 	StepResults         map[string]*model.StepResult
 	IntraActionState    map[string]map[string]string
 	ExprEval            ExpressionEvaluator
@@ -57,6 +61,14 @@ type RunContext struct {
 	Masks               []string
 	cleanUpJobContainer common.Executor
 	caller              *caller // job calling this RunContext (reusable workflows)
+	// summaryFileInitialized tracks which per-step summary files (workflow/step-summary-N.md)
+	// have already been created on the JobContainer. The runner sets up file-command files
+	// via JobContainer.Copy at the start of every phase, which truncates them — fine for
+	// GITHUB_ENV/OUTPUT/STATE/PATH (consumed per phase) but wrong for GITHUB_STEP_SUMMARY,
+	// which has accumulating semantics. We initialize each step's summary file exactly once
+	// so writes from later phases and from composite sub-steps append to the same file.
+	// Only populated on the top-level RunContext; child RCs walk Parent via topLevelRunContext.
+	summaryFileInitialized map[int]bool
 	// outputTemplate is this combination's pristine snapshot of the job's output expressions,
 	// captured before execution so each matrix combo interpolates from the originals rather
 	// than from a sibling's already-resolved values written into the shared Job.Outputs.
@@ -704,6 +716,17 @@ func (rc *RunContext) steps() []*model.Step {
 	return steps
 }
 
+// topLevelRunContext walks the Parent chain to the outermost RunContext. Composite
+// actions create child RunContexts whose sub-steps need to share the outer job step's
+// summary file path so that nested writes accumulate under the right step_index.
+func (rc *RunContext) topLevelRunContext() *RunContext {
+	top := rc
+	for top.Parent != nil {
+		top = top.Parent
+	}
+	return top
+}
+
 // Executor returns a pipeline executor for all the steps in the job
 func (rc *RunContext) Executor() (common.Executor, error) {
 	var executor common.Executor
diff --git a/act/runner/step.go b/act/runner/step.go
index 8a241acf..c67f5ba7 100644
--- a/act/runner/step.go
+++ b/act/runner/step.go
@@ -124,7 +124,12 @@ func runStepExecutor(step step, stage stepStage, executor common.Executor) commo
 		envFileCommand := path.Join("workflow", "envs.txt")
 		(*step.getEnv())["GITHUB_ENV"] = path.Join(actPath, envFileCommand)
 
-		summaryFileCommand := path.Join("workflow", "SUMMARY.md")
+		// Per-step summary file. Composite sub-steps share the outer job step's index
+		// via the Parent chain so all writes from within a composite action accumulate
+		// in the same file and upload under the outer step_index.
+		topRC := rc.topLevelRunContext()
+		stepSummaryIndex := topRC.CurrentStepIndex
+		summaryFileCommand := path.Join("workflow", "step-summary-"+strconv.Itoa(stepSummaryIndex)+".md")
 		(*step.getEnv())["GITHUB_STEP_SUMMARY"] = path.Join(actPath, summaryFileCommand)
 
 		{
@@ -136,22 +141,23 @@ func runStepExecutor(step step, stage stepStage, executor common.Executor) commo
 			(*step.getEnv())["GITEA_STEP_SUMMARY"] = (*step.getEnv())["GITHUB_STEP_SUMMARY"]
 		}
 
-		_ = rc.JobContainer.Copy(actPath, &container.FileEntry{
-			Name: outputFileCommand,
-			Mode: 0o666,
-		}, &container.FileEntry{
-			Name: stateFileCommand,
-			Mode: 0o666,
-		}, &container.FileEntry{
-			Name: pathFileCommand,
-			Mode: 0o666,
-		}, &container.FileEntry{
-			Name: envFileCommand,
-			Mode: 0o666,
-		}, &container.FileEntry{
-			Name: summaryFileCommand,
-			Mode: 0o666,
-		})(ctx)
+		// Reset the per-phase file-command files. GITHUB_STEP_SUMMARY is intentionally
+		// excluded here and initialized below at most once per step so writes from later
+		// phases and from composite sub-steps accumulate instead of being truncated.
+		files := []*container.FileEntry{
+			{Name: outputFileCommand, Mode: 0o666},
+			{Name: stateFileCommand, Mode: 0o666},
+			{Name: pathFileCommand, Mode: 0o666},
+			{Name: envFileCommand, Mode: 0o666},
+		}
+		if topRC.summaryFileInitialized == nil {
+			topRC.summaryFileInitialized = map[int]bool{}
+		}
+		if !topRC.summaryFileInitialized[stepSummaryIndex] {
+			files = append(files, &container.FileEntry{Name: summaryFileCommand, Mode: 0o666})
+			topRC.summaryFileInitialized[stepSummaryIndex] = true
+		}
+		_ = rc.JobContainer.Copy(actPath, files...)(ctx)
 
 		timeoutctx, cancelTimeOut := evaluateStepTimeout(ctx, rc.ExprEval, stepModel)
 		defer cancelTimeOut()
diff --git a/internal/app/cmd/daemon.go b/internal/app/cmd/daemon.go
index 247d77f0..f533b017 100644
--- a/internal/app/cmd/daemon.go
+++ b/internal/app/cmd/daemon.go
@@ -148,6 +148,7 @@ func runDaemon(ctx context.Context, daemArgs *daemonArgs, configFile *string) fu
 			log.Infof("runner: %s, with version: %s, with labels: %v, declare successfully",
 				resp.Msg.Runner.Name, resp.Msg.Runner.Version, resp.Msg.Runner.Labels)
 		}
+		runner.SetCapabilitiesFromDeclare(resp)
 
 		if cfg.Metrics.Enabled {
 			metrics.Init()
diff --git a/internal/app/run/runner.go b/internal/app/run/runner.go
index d3d787c7..9bcb9f4a 100644
--- a/internal/app/run/runner.go
+++ b/internal/app/run/runner.go
@@ -47,6 +47,7 @@ type Runner struct {
 	labels       labels.Labels
 	envs         map[string]string
 	cacheHandler *artifactcache.Handler
+	capabilities string
 
 	runningTasks            sync.Map
 	runningCount            atomic.Int64
@@ -185,6 +186,14 @@ func (r *Runner) cleanupStaleTaskDirs(ctx context.Context, workdirRoot string) {
 	}
 }
 
+func (r *Runner) SetCapabilitiesFromDeclare(resp *connect.Response[runnerv1.DeclareResponse]) {
+	if resp == nil {
+		return
+	}
+	// Capability negotiation is done via response headers to avoid a hard proto bump.
+	r.capabilities = strings.TrimSpace(resp.Header().Get("X-Gitea-Actions-Capabilities"))
+}
+
 func (r *Runner) Run(ctx context.Context, task *runnerv1.Task) error {
 	if _, ok := r.runningTasks.Load(task.Id); ok {
 		return fmt.Errorf("task %d is already running", task.Id)
@@ -219,9 +228,10 @@ func (r *Runner) Run(ctx context.Context, task *runnerv1.Task) error {
 }
 
 func (r *Runner) cloneEnvs() map[string]string {
-	// +3 reserves space for the per-task keys injected by run():
-	// ACTIONS_ID_TOKEN_REQUEST_URL, ACTIONS_ID_TOKEN_REQUEST_TOKEN, ACTIONS_RUNTIME_TOKEN.
-	envs := make(map[string]string, len(r.envs)+3)
+	// Reserve space for the per-task keys injected by run():
+	// ACTIONS_ID_TOKEN_REQUEST_URL, ACTIONS_ID_TOKEN_REQUEST_TOKEN, ACTIONS_RUNTIME_TOKEN,
+	// GITEA_ACTIONS_CAPABILITIES, GITEA_RUN_ID.
+	envs := make(map[string]string, len(r.envs)+5)
 	maps.Copy(envs, r.envs)
 	return envs
 }
@@ -261,6 +271,13 @@ func (r *Runner) run(ctx context.Context, task *runnerv1.Task, reporter *report.
 	taskContext := task.Context.Fields
 	envs := r.cloneEnvs()
 
+	if r.capabilities != "" {
+		envs["GITEA_ACTIONS_CAPABILITIES"] = r.capabilities
+	}
+	if v := taskContext["run_id"].GetStringValue(); v != "" {
+		envs["GITEA_RUN_ID"] = v
+	}
+
 	log.Infof("task %v repo is %v %v %v", task.Id, taskContext["repository"].GetStringValue(),
 		r.getDefaultActionsURL(task),
 		r.client.Address())