perf(panel): speed up file browsing and preserve loading forms

internal/fileedit/browser.go

@@ -0,0 +1,266 @@
+package fileedit
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"crypto/subtle"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+)
+
+// Browse runs inside the read-only Job and reuses Execute for every command.
+// Refuse write commands even if the other end violates the protocol.
+func Browse(ctx context.Context, worldRoot, url, token string) error {
+	if token == "" {
+		return fmt.Errorf("fileedit: browser token is required")
+	}
+	client := &http.Client{Timeout: browserIdle + 30*time.Second,
+		CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}
+	answer := BrowseAnswer{}
+	for {
+		body, err := json.Marshal(answer)
+		if err != nil {
+			return err
+		}
+		req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
+		if err != nil {
+			return err
+		}
+		req.Header.Set("Authorization", "Bearer "+token)
+		req.Header.Set("Content-Type", "application/json")
+		resp, err := client.Do(req)
+		if err != nil {
+			return err
+		}
+		if resp.StatusCode == http.StatusNoContent {
+			resp.Body.Close()
+			return nil
+		}
+		if resp.StatusCode != http.StatusOK {
+			resp.Body.Close()
+			return fmt.Errorf("fileedit: browser exchange returned %s", resp.Status)
+		}
+		var command BrowseCommand
+		err = json.NewDecoder(io.LimitReader(resp.Body, 64<<10)).Decode(&command)
+		resp.Body.Close()
+		if err != nil {
+			return err
+		}
+		if command.Op != OpList && command.Op != OpRead {
+			return fmt.Errorf("fileedit: browser refused operation %q", command.Op)
+		}
+		res, err := Execute(worldRoot, Request{Op: command.Op, Path: command.Path})
+		answer = BrowseAnswer{ID: command.ID}
+		if err != nil {
+			answer.Error = err.Error()
+			continue
+		}
+		answer.Result, err = json.Marshal(res)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+const (
+	BrowserTokenEnv = "FELIS_FILE_BROWSER_TOKEN"
+	BrowserRoute    = "/api/v1/internal/file-browser/"
+	browserIdle     = 45 * time.Second
+	browserLifetime = 4 * time.Minute
+	maxBrowsers     = 4
+)
+
+var errBrowserFull = errors.New("fileedit: browser capacity reached")
+
+// Browser reuses a short-lived, read-only Job per world. Jobs pull commands from
+// the existing internal API face: no inbound Pod port or new RBAC is needed.
+// Every browser request is still authorized by the normal file API handlers.
+type Browser struct {
+	BaseURL  string
+	mu       sync.Mutex
+	sessions map[string]*browseSession
+}
+
+type BrowseCommand struct {
+	ID   string `json:"id"`
+	Op   string `json:"op"`
+	Path string `json:"path"`
+}
+
+type BrowseAnswer struct {
+	ID     string          `json:"id"`
+	Result json.RawMessage `json:"result,omitempty"`
+	Error  string          `json:"error,omitempty"`
+}
+
+type browseSession struct {
+	id, key   string
+	tokenHash [sha256.Size]byte
+	commands  chan BrowseCommand
+	answers   chan BrowseAnswer
+	serial    chan struct{}
+	done      chan struct{}
+	once      sync.Once
+	timer     *time.Timer
+	mu        sync.Mutex
+	connected bool
+	pending   string
+}
+
+func (b *Browser) close(s *browseSession) {
+	b.mu.Lock()
+	if b.sessions[s.key] == s {
+		delete(b.sessions, s.key)
+	}
+	b.mu.Unlock()
+	s.once.Do(func() {
+		if s.timer != nil {
+			s.timer.Stop()
+		}
+		close(s.done)
+	})
+}
+
+func (b *Browser) session(ctx context.Context, p JobParams, start func(context.Context, JobParams) error) (*browseSession, error) {
+	key := strings.Join([]string{p.Namespace, p.Server, p.WorldPVC, p.NodeName, p.Image}, "\x00")
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if s := b.sessions[key]; s != nil {
+		return s, nil
+	}
+	if len(b.sessions) >= maxBrowsers {
+		return nil, errBrowserFull
+	}
+	token, err := randomHex(32)
+	if err != nil {
+		return nil, err
+	}
+	s := &browseSession{id: p.OpID, key: key, tokenHash: sha256.Sum256([]byte(token)),
+		commands: make(chan BrowseCommand, 1), answers: make(chan BrowseAnswer, 1), serial: make(chan struct{}, 1), done: make(chan struct{})}
+	if b.sessions == nil {
+		b.sessions = make(map[string]*browseSession)
+	}
+	b.sessions[key] = s
+	p.BrowserURL, p.BrowserToken = strings.TrimRight(b.BaseURL, "/")+BrowserRoute+s.id, token
+	p.Deadline = browserLifetime
+	if err := start(ctx, p); err != nil {
+		delete(b.sessions, key)
+		return nil, err
+	}
+	if err := ctx.Err(); err != nil {
+		delete(b.sessions, key)
+		return nil, err
+	}
+	s.timer = time.AfterFunc(browserLifetime, func() { b.close(s) })
+	return s, nil
+}
+
+func (b *Browser) Run(ctx context.Context, p JobParams, start func(context.Context, JobParams) error) ([]byte, error) {
+	s, err := b.session(ctx, p, start)
+	if err != nil {
+		return nil, err
+	}
+	select {
+	case s.serial <- struct{}{}:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	case <-s.done:
+		return nil, fmt.Errorf("fileedit: browser closed")
+	}
+	defer func() { <-s.serial }()
+	s.mu.Lock()
+	s.pending = p.OpID
+	s.mu.Unlock()
+	select {
+	case s.commands <- BrowseCommand{ID: p.OpID, Op: p.Op, Path: p.Path}:
+	case <-ctx.Done():
+		b.close(s)
+		return nil, ctx.Err()
+	case <-s.done:
+		return nil, fmt.Errorf("fileedit: browser closed")
+	}
+	select {
+	case answer := <-s.answers:
+		if answer.Error != "" {
+			return nil, fmt.Errorf("fileedit: browser read: %s", answer.Error)
+		}
+		return answer.Result, nil
+	case <-ctx.Done():
+		b.close(s)
+		return nil, ctx.Err()
+	case <-s.done:
+		return nil, fmt.Errorf("fileedit: browser closed before returning a result")
+	}
+}
+
+// ServeHTTP accepts one worker's result and long-polls its next command. The
+// random token opens only this world/session, and lives only in the Job's env.
+func (b *Browser) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	id := strings.TrimPrefix(r.URL.Path, BrowserRoute)
+	b.mu.Lock()
+	var s *browseSession
+	for _, candidate := range b.sessions {
+		if candidate.id == id {
+			s = candidate
+			break
+		}
+	}
+	b.mu.Unlock()
+	token, bearer := strings.CutPrefix(r.Header.Get("Authorization"), "Bearer ")
+	sum := sha256.Sum256([]byte(token))
+	if s == nil || !bearer || subtle.ConstantTimeCompare(sum[:], s.tokenHash[:]) != 1 {
+		http.Error(w, "unknown browser", http.StatusNotFound)
+		return
+	}
+	var answer BrowseAnswer
+	decoder := json.NewDecoder(http.MaxBytesReader(w, r.Body, maxLogBytes))
+	decoder.DisallowUnknownFields()
+	if err := decoder.Decode(&answer); err != nil {
+		http.Error(w, "invalid result", http.StatusBadRequest)
+		return
+	}
+	s.mu.Lock()
+	valid := !s.connected && answer.ID == "" || s.connected && answer.ID != "" && answer.ID == s.pending
+	if valid {
+		s.connected = true
+		if answer.ID != "" {
+			s.pending = ""
+		}
+	}
+	s.mu.Unlock()
+	if !valid {
+		http.Error(w, "unexpected result", http.StatusConflict)
+		return
+	}
+	if answer.ID != "" {
+		select {
+		case s.answers <- answer:
+		case <-s.done:
+			w.WriteHeader(http.StatusGone)
+			return
+		}
+	}
+	timer := time.NewTimer(browserIdle)
+	defer timer.Stop()
+	select {
+	case command := <-s.commands:
+		w.Header().Set("Content-Type", "application/json")
+		if err := json.NewEncoder(w).Encode(command); err != nil {
+			b.close(s)
+		}
+	case <-timer.C:
+		b.close(s)
+		w.WriteHeader(http.StatusNoContent)
+	case <-s.done:
+		w.WriteHeader(http.StatusNoContent)
+	case <-r.Context().Done():
+		b.close(s)
+	}
+}

internal/fileedit/browser_test.go

@@ -0,0 +1,199 @@
+package fileedit
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestBrowserReusesWorkerAndReadsCurrentBytes(t *testing.T) {
+	root := t.TempDir()
+	if err := os.WriteFile(filepath.Join(root, "config.yml"), []byte("enabled: true\n"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	b := &Browser{}
+	srv := httptest.NewServer(b)
+	b.BaseURL = srv.URL
+	defer srv.Close()
+	defer cancel()
+	var workers atomic.Int32
+	start := func(_ context.Context, p JobParams) error {
+		workers.Add(1)
+		job, err := FilesJob(p)
+		if err != nil {
+			return err
+		}
+		pod := job.Spec.Template.Spec
+		if pod.AutomountServiceAccountToken == nil || *pod.AutomountServiceAccountToken || len(pod.Volumes) != 1 || !pod.Containers[0].VolumeMounts[0].ReadOnly {
+			t.Error("browser weakened the file Job's isolation")
+		}
+		go func() {
+			if err := Browse(ctx, root, p.BrowserURL, p.BrowserToken); err != nil && ctx.Err() == nil {
+				t.Errorf("worker: %v", err)
+			}
+		}()
+		return nil
+	}
+	read := func(op, path string) Result {
+		p := testParams(op)
+		p.Path = path
+		p.OpID, _ = newOpID()
+		payload, err := b.Run(ctx, p, start)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var result Result
+		if err := json.Unmarshal(payload, &result); err != nil {
+			t.Fatal(err)
+		}
+		return result
+	}
+	if got := read(OpRead, "config.yml"); string(got.Content) != "enabled: true\n" {
+		t.Fatalf("first read: %+v", got)
+	}
+	if err := os.WriteFile(filepath.Join(root, "config.yml"), []byte("enabled: false\n"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	if got := read(OpRead, "config.yml"); string(got.Content) != "enabled: false\n" {
+		t.Fatalf("stale read: %+v", got)
+	}
+	if got := read(OpList, ""); len(got.Entries) != 1 {
+		t.Fatalf("listing: %+v", got)
+	}
+	if got := read(OpRead, "../outside"); got.Code != CodeBadPath {
+		t.Fatalf("containment: %+v", got)
+	}
+	if workers.Load() != 1 {
+		t.Fatalf("started %d workers for repeated reads", workers.Load())
+	}
+
+	// Simultaneous readers still receive their own result, never the other path's.
+	var wg sync.WaitGroup
+	for _, path := range []string{"config.yml", "missing.yml"} {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			p := testParams(OpRead)
+			p.Path = path
+			p.OpID, _ = newOpID()
+			payload, err := b.Run(ctx, p, start)
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			var got Result
+			json.Unmarshal(payload, &got)
+			if path == "missing.yml" && got.Code != CodeNotFound || path == "config.yml" && string(got.Content) != "enabled: false\n" {
+				t.Errorf("%s: %+v", path, got)
+			}
+		}()
+	}
+	wg.Wait()
+}
+
+func TestBrowserCancellationRevokesToken(t *testing.T) {
+	b := &Browser{BaseURL: "http://internal"}
+	var started JobParams
+	ctx, cancel := context.WithCancel(context.Background())
+	p := testParams(OpRead)
+	_, err := b.Run(ctx, p, func(_ context.Context, p JobParams) error { started = p; cancel(); return nil })
+	if err == nil {
+		t.Fatal("cancelled read succeeded")
+	}
+	r := httptest.NewRequest(http.MethodPost, started.BrowserURL, strings.NewReader(`{}`))
+	r.Header.Set("Authorization", "Bearer "+started.BrowserToken)
+	w := httptest.NewRecorder()
+	b.ServeHTTP(w, r)
+	if w.Code != http.StatusNotFound {
+		t.Fatalf("cancelled token returned %d", w.Code)
+	}
+}
+
+func TestBrowserRejectsWrongTokenAndStaleResult(t *testing.T) {
+	b := &Browser{BaseURL: "http://internal"}
+	p := testParams(OpRead)
+	var started JobParams
+	s, err := b.session(context.Background(), p, func(_ context.Context, p JobParams) error { started = p; return nil })
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer b.close(s)
+	for _, header := range []string{"", "Bearer wrong", started.BrowserToken} {
+		r := httptest.NewRequest(http.MethodPost, started.BrowserURL, strings.NewReader(`{}`))
+		r.Header.Set("Authorization", header)
+		w := httptest.NewRecorder()
+		b.ServeHTTP(w, r)
+		if w.Code != http.StatusNotFound {
+			t.Fatalf("wrong token returned %d", w.Code)
+		}
+	}
+	r := httptest.NewRequest(http.MethodPost, started.BrowserURL, strings.NewReader(`{"id":"another-read","result":{}}`))
+	r.Header.Set("Authorization", "Bearer "+started.BrowserToken)
+	w := httptest.NewRecorder()
+	b.ServeHTTP(w, r)
+	if w.Code != http.StatusConflict {
+		t.Fatalf("stale result returned %d", w.Code)
+	}
+}
+
+func TestBrowserCapacityReleasedAfterClosingSession(t *testing.T) {
+	b := &Browser{BaseURL: "http://internal"}
+	defer func() {
+		for _, s := range b.sessions {
+			b.close(s)
+		}
+	}()
+	started := 0
+	start := func(context.Context, JobParams) error { started++; return nil }
+	for i := 0; i < maxBrowsers; i++ {
+		p := testParams(OpList)
+		p.Server = string(rune('a' + i))
+		p.OpID = p.Server
+		if _, err := b.session(context.Background(), p, start); err != nil {
+			t.Fatal(err)
+		}
+	}
+	p := testParams(OpRead)
+	if _, err := b.session(context.Background(), p, start); err != errBrowserFull || started != maxBrowsers {
+		t.Fatalf("capacity: err=%v, started=%d", err, started)
+	}
+	for _, s := range b.sessions {
+		b.close(s)
+		break
+	}
+	if _, err := b.session(context.Background(), p, start); err != nil || started != maxBrowsers+1 {
+		t.Fatalf("reopen: err=%v, started=%d", err, started)
+	}
+}
+
+func TestBrowseRefusesMutation(t *testing.T) {
+	root := t.TempDir()
+	path := filepath.Join(root, "keep.txt")
+	os.WriteFile(path, []byte("keep"), 0600)
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewEncoder(w).Encode(BrowseCommand{ID: "x", Op: OpDelete, Path: "keep.txt"})
+	}))
+	defer srv.Close()
+	if err := Browse(context.Background(), root, srv.URL, "token"); err == nil {
+		t.Fatal("worker accepted a write command")
+	}
+	got, err := os.ReadFile(path)
+	if err != nil || string(got) != "keep" {
+		t.Fatalf("file changed: %q, %v", got, err)
+	}
+	p := testParams(OpWrite)
+	p.BrowserURL = srv.URL
+	p.BrowserToken = "token"
+	if _, err := FilesJob(p); err == nil {
+		t.Fatal("writable browser Job was allowed")
+	}
+}

internal/fileedit/editor.go

@@ -32,14 +32,14 @@
 // upload fetched by the Job from felis-api's internal face (see Stage), because a
 // 64 MiB jar fits in neither a Job spec nor an environment.
 //
-// The price is latency: every operation is a Pod schedule + image pull, so a
-// listing takes seconds rather than milliseconds. That is inherent to RWO plus a
-// stopped server, not a property of this transport: the file manager works on a
-// stopped server, one operation per Job.
+// Interactive reads reuse a bounded, short-lived, read-only Job through Browser.
+// Its command channel uses the existing internal API face. At capacity, reads
+// use one-shot Jobs and stream results before the Pod's terminal phase. Changes
+// still wait for termination to preserve the world lock's ordering.
 //
 // The Editor depends on the Runner interface, so the orchestration and the error
-// mapping are unit-tested against an in-memory fake; the client-go implementation
-// (k8sjobs.go) compiles here but is exercised only against a live cluster.
+// mapping are unit-tested against an in-memory fake; the client-go transport
+// (k8sjobs.go) is tested against the Kubernetes HTTP API shape.
 package fileedit
 
 import (

internal/fileedit/jobspec.go

@@ -69,8 +69,10 @@ type JobParams struct {
 	// Async marks a Job felis-api does not wait on: it carries LabelAsync and
 	// AnnotationPath, which Ops reads it back by. Only an upload or an unzip
 	// runs so.
-	Async    bool
-	WorldPVC string
+	Async        bool
+	WorldPVC     string
+	BrowserURL   string
+	BrowserToken string
 
 	Namespace      string
 	ServiceAccount string
@@ -128,7 +130,7 @@ func filesLabels(p JobParams) map[string]string {
 //   - mounts EXACTLY ONE volume — the world PVC — and NO Secret, NO ConfigMap, and
 //     NO backup PVC. It is therefore strictly blinder than the backup Pod, which
 //     mounts the config Secret to self-record its row: a file-editor Pod has nothing
-//     to record, so it is handed no database URL and no credential of any kind (the
+//     to record, so it is handed no database URL or platform credential (the
 //     four-power red line, spec §22);
 //   - mounts that one volume READ-ONLY for list and read (see mutates), so the
 //     two operations that only look physically cannot change anything — the
@@ -147,8 +149,12 @@ func filesLabels(p JobParams) map[string]string {
 //
 // The container runs `/usr/local/bin/felis files` (cmd/felis), which performs the
 // operation under os.Root containment and prints the marked JSON Result line that
-// felis-api reads back through pods/log.
+// felis-api reads back through pods/log. A browser instead pulls read commands
+// from the internal API and posts each result there using a scoped token.
 func FilesJob(p JobParams) (*batchv1.Job, error) {
+	if p.BrowserURL != "" && (mutates(p.Op) || p.BrowserToken == "" || p.Async) {
+		return nil, fmt.Errorf("fileedit: a browser must be read-only and have a token")
+	}
 	if p.Image == "" {
 		return nil, fmt.Errorf("fileedit: image is empty")
 	}
@@ -246,7 +252,7 @@ func FilesJob(p JobParams) (*batchv1.Job, error) {
 	// so the spec is the sole channel into the Pod; base64 keeps arbitrary bytes —
 	// CRLF line endings, a UTF-8 BOM, a binary blob — intact through a field that
 	// must be a valid string. Content is set ONLY for a write and the token ONLY
-	// for an upload, so no other Job spec carries either.
+	// for an upload or read-only browser, so no other Job spec carries either.
 	switch p.Op {
 	case OpWrite:
 		parts := splitContent(p.Content)
@@ -257,6 +263,11 @@ func FilesJob(p JobParams) (*batchv1.Job, error) {
 	case OpUpload:
 		container.Env = []corev1.EnvVar{{Name: UploadTokenEnv, Value: p.UploadToken}}
 	}
+	if p.BrowserURL != "" {
+		container.Args = []string{"--browse-url", p.BrowserURL, "--worlds-root", p.WorldsRoot}
+		container.Env = []corev1.EnvVar{{Name: BrowserTokenEnv, Value: p.BrowserToken}}
+		container.Resources.Requests = corev1.ResourceList{corev1.ResourceCPU: resource.MustParse("10m"), corev1.ResourceMemory: resource.MustParse("32Mi")}
+	}
 
 	job := &batchv1.Job{
 		ObjectMeta: metav1.ObjectMeta{

internal/fileedit/k8sjobs.go

@@ -18,12 +18,10 @@ import (
 )
 
 // pollInterval is how often the runner re-Lists Pods while waiting for the file
-// Job to finish. It is a POLL rather than a Watch because felis-api holds
+// container to start. It is a POLL rather than a Watch because felis-api holds
 // pods:list and NOT pods:watch (internal/platform.APIMinecraftRole) — establishing
-// a watch would need a permission this design exists to avoid. Half a second is
-// well inside the human-perceptible floor for an operation already dominated by
-// Pod scheduling, while keeping the request count on a slow image pull modest.
-const pollInterval = 500 * time.Millisecond
+// a watch would need a permission this design exists to avoid.
+const pollInterval = 150 * time.Millisecond
 
 // maxLogBytes bounds what the runner will buffer from a Pod's log. The payload is
 // at most a base64-encoded MaxReadBytes (≈4/3 of 1 MiB) plus the JSON envelope, so
@@ -45,12 +43,11 @@ const maxLogBytes = 4 << 20
 // the Job create is available on both — so one client covers all three calls
 // instead of the binding carrying two.
 //
-// INTEGRATION-ONLY: like K8sLogStreamer and K8sCluster this needs a live cluster;
-// it compiles here but is exercised only against one, never by the hermetic test
-// suite. The Oracle verifies the layer above it (Editor orchestration and error
-// mapping) against a fake Runner, and the Job shape via the pure jobspec.
+// The transport is tested against the Kubernetes HTTP API shape; the Editor
+// tests separately verify orchestration and error mapping against a fake Runner.
 type K8sRunner struct {
-	cs kubernetes.Interface
+	cs      kubernetes.Interface
+	Browser *Browser
 }
 
 // NewK8sRunner builds a Runner over cs. Every per-operation parameter — the
@@ -60,14 +57,23 @@ func NewK8sRunner(cs kubernetes.Interface) *K8sRunner {
 	return &K8sRunner{cs: cs}
 }
 
-// Run creates the file Job, waits for its Pod to reach a terminal phase, and
-// returns the JSON payload from the ResultPrefix line of that Pod's log.
+// Run streams read results as soon as they are printed. Mutations still wait
+// for termination so returning success does not leave the next write racing
+// the cluster-side world lock.
 //
 // The Job name carries a fresh random OpID (FilesJobName), so a create collision is
 // not an expected condition the way it is for restore — an AlreadyExists here means
 // a 64-bit collision inside one TTL window and is reported rather than absorbed,
 // because absorbing it would mean returning ANOTHER operation's output.
 func (k *K8sRunner) Run(ctx context.Context, p JobParams) ([]byte, error) {
+	if k.Browser != nil && !mutates(p.Op) {
+		payload, err := k.Browser.Run(ctx, p, k.Start)
+		// At capacity, retain the bounded one-shot path instead of starting
+		// more idle workers. All reads still use the same containment checks.
+		if !errors.Is(err, errBrowserFull) {
+			return payload, err
+		}
+	}
 	job, err := FilesJob(p)
 	if err != nil {
 		return nil, err
@@ -81,24 +87,30 @@ func (k *K8sRunner) Run(ctx context.Context, p JobParams) ([]byte, error) {
 		return nil, err
 	}
 
-	log, err := k.podLog(ctx, p.Namespace, pod.Name)
+	stream, err := k.cs.CoreV1().Pods(p.Namespace).GetLogs(pod.Name, &corev1.PodLogOptions{
+		Container: containerName, Follow: true,
+	}).Stream(ctx)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("fileedit: read file job log: %w", err)
 	}
-
-	payload, ok := extractResult(log)
-	if !ok {
-		// No marked line: the entrypoint died before printing (an unmountable volume,
-		// an OOM kill, a deadline). The log tail travels in the error for the operator's
-		// benefit — this error reaches felis-api's logs, while the caller gets the
-		// generic 500 writeError produces, so no node detail leaks to the browser.
-		return nil, fmt.Errorf("fileedit: file job %s produced no result (phase %s): %s",
-			job.Name, pod.Status.Phase, tail(log))
+	defer stream.Close()
+	sc := bufio.NewScanner(io.LimitReader(stream, maxLogBytes))
+	sc.Buffer(make([]byte, 0, 64*1024), maxLogBytes)
+	var last string
+	for sc.Scan() {
+		if payload, ok := strings.CutPrefix(sc.Text(), ResultPrefix); ok {
+			return []byte(payload), nil
+		}
+		last = sc.Text()
 	}
-	return payload, nil
+	if err := sc.Err(); err != nil {
+		return nil, fmt.Errorf("fileedit: read file job result: %w", err)
+	}
+	return nil, fmt.Errorf("fileedit: file job %s produced no result (phase %s): %s",
+		job.Name, pod.Status.Phase, tail(last))
 }
 
-// awaitPod polls until the operation's Pod reaches a terminal phase. It selects by
+// awaitPod polls until the file container has started (or failed). It selects by
 // the per-invocation LabelOpID, so it can never observe a different operation's Pod
 // — the reason that label exists.
 //
@@ -107,7 +119,7 @@ func (k *K8sRunner) Run(ctx context.Context, p JobParams) ([]byte, error) {
 // is too large) is printed and then exited on cleanly, and even a genuinely failed
 // Pod may have printed a diagnosable result first. Deciding what the outcome MEANS
 // is the caller's job (Run reads the printed result); this function only decides
-// when there is nothing left to wait for.
+// when its log can be opened without a ContainerCreating refusal.
 func (k *K8sRunner) awaitPod(ctx context.Context, p JobParams) (*corev1.Pod, error) {
 	ticker := time.NewTicker(pollInterval)
 	defer ticker.Stop()
@@ -120,9 +132,17 @@ func (k *K8sRunner) awaitPod(ctx context.Context, p JobParams) (*corev1.Pod, err
 			return nil, fmt.Errorf("fileedit: find file job pod: %w", err)
 		}
 		for i := range pods.Items {
-			switch pods.Items[i].Status.Phase {
+			pod := &pods.Items[i]
+			if !mutates(p.Op) {
+				for _, c := range pod.Status.ContainerStatuses {
+					if c.Name == containerName && (c.State.Running != nil || c.State.Terminated != nil) {
+						return pod, nil
+					}
+				}
+			}
+			switch pod.Status.Phase {
 			case corev1.PodSucceeded, corev1.PodFailed:
-				return &pods.Items[i], nil
+				return pod, nil
 			}
 		}
 

internal/fileedit/k8sjobs_test.go

@@ -3,6 +3,10 @@ package fileedit
 import (
 	"context"
 	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
 	"testing"
 	"time"
 
@@ -10,10 +14,73 @@ import (
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/kubernetes/fake"
+	"k8s.io/client-go/rest"
 	k8stesting "k8s.io/client-go/testing"
 )
 
+func TestRunReadsResultBeforePodTermination(t *testing.T) {
+	for _, op := range []string{OpList, OpRead} {
+		t.Run(op, func(t *testing.T) {
+			closed := make(chan struct{})
+			srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				switch {
+				case r.Method == http.MethodPost && strings.HasSuffix(r.URL.Path, "/jobs"):
+					w.Header().Set("Content-Type", "application/json")
+					io.WriteString(w, `{"apiVersion":"batch/v1","kind":"Job","metadata":{"name":"files-test"}}`)
+				case strings.HasSuffix(r.URL.Path, "/pods"):
+					if !strings.Contains(r.URL.Query().Get("labelSelector"), LabelOpID+"=") {
+						t.Error("pod lookup did not select this operation")
+					}
+					w.Header().Set("Content-Type", "application/json")
+					io.WriteString(w, `{"apiVersion":"v1","kind":"PodList","items":[{"metadata":{"name":"file-pod"},"status":{"phase":"Running","containerStatuses":[{"name":"files","state":{"running":{}}}]}}]}`)
+				case strings.HasSuffix(r.URL.Path, "/log"):
+					if r.URL.Query().Get("follow") != "true" {
+						t.Error("result log was not streamed")
+					}
+					io.WriteString(w, "diagnostic line\n"+ResultPrefix+`{"entries":[]}`+"\n")
+					w.(http.Flusher).Flush()
+					// The log stays open and the Pod stays Running. Run must return
+					// on the result line and close the stream, not await either EOF.
+					<-r.Context().Done()
+					close(closed)
+				default:
+					t.Errorf("unexpected cluster call: %s %s", r.Method, r.URL)
+					w.WriteHeader(http.StatusNotFound)
+				}
+			}))
+			defer srv.Close()
+			cs, err := kubernetes.NewForConfig(&rest.Config{Host: srv.URL})
+			if err != nil {
+				t.Fatal(err)
+			}
+			ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+			defer cancel()
+			got, err := NewK8sRunner(cs).Run(ctx, testParams(op))
+			if err != nil || string(got) != `{"entries":[]}` {
+				t.Fatalf("Run = %s, %v", got, err)
+			}
+			select {
+			case <-closed:
+			case <-ctx.Done():
+				t.Fatal("result stream was not closed")
+			}
+		})
+	}
+}
+
+func TestAwaitPodKeepsWritesWaitingForTermination(t *testing.T) {
+	p := testParams(OpWrite)
+	pod := &corev1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "file-pod", Namespace: p.Namespace, Labels: filesLabels(p)},
+		Status: corev1.PodStatus{Phase: corev1.PodRunning, ContainerStatuses: []corev1.ContainerStatus{{Name: containerName, State: corev1.ContainerState{Running: &corev1.ContainerStateRunning{}}}}}}
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Millisecond)
+	defer cancel()
+	if got, err := NewK8sRunner(fake.NewSimpleClientset(pod)).awaitPod(ctx, p); err == nil || got != nil {
+		t.Fatalf("a running writer was treated as finished: %v, %v", got, err)
+	}
+}
+
 var (
 	opCreated = time.Date(2026, 9, 28, 10, 0, 0, 0, time.UTC)
 	opEnded   = opCreated.Add(3 * time.Minute)