diff --git a/README.md b/README.md
index 5268bc1..0973975 100644
--- a/README.md
+++ b/README.md
@@ -310,6 +310,7 @@ path under `/v1/` answers 200, in maintenance mode too.
     - 403 when the upstream host, or a host it redirects to, has an address in a
       blocked network (see `blocked_networks`).
     - 429 over `image_requests_per_minute` (below).
+    - 499 when the client goes away before the image is ready.
     - 415 when the upstream answers with a `Content-Type` that is not one of the
       source formats (below).
     - 415 when the upstream sends a body whose first bytes are not those of the
@@ -341,6 +342,7 @@ path under `/v1/` answers 200, in maintenance mode too.
         - 403
         - 415
         - 429
+        - 499
         - 502
         - 503
         - 504
diff --git a/TODO.md b/TODO.md
index 92228e4..b12e97b 100644
--- a/TODO.md
+++ b/TODO.md
@@ -30,6 +30,16 @@ P2: security: per-origin rate limiting
 
 # Completed Steps
 
+- 2026-10-26 on both image routes, a request whose client went away before its
+  image was ready is answered 499 and logged at info level (closes #339). It was
+  answered 500 and logged at error level, as pixa's own failure.
+    - The line is "client went away before the image was ready". It carries the
+      `request_id`, the host and the path.
+    - The 499 has no body, since nobody reads it.
+    - `serveImage` answers it before calling `respondImageError`, which cannot
+      see the request's context.
+    - An error wrapping `context.Canceled` while the request's context is live
+      is still answered 500 and logged at error level.
 - 2026-10-26 `README.md`'s Design section starts with a Concepts list (closes
   #321). Each concept gets one sentence, under the name the code gives it.
     - Storage calls the transformed images variants, in shorter sentences.
diff --git a/internal/handlers/client_gone_internal_test.go b/internal/handlers/client_gone_internal_test.go
new file mode 100644
index 0000000..554beff
--- /dev/null
+++ b/internal/handlers/client_gone_internal_test.go
@@ -0,0 +1,173 @@
+package handlers
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"slices"
+	"testing"
+
+	"github.com/go-chi/chi/v5/middleware"
+	"sneak.berlin/go/pixa/internal/httpfetcher"
+	"sneak.berlin/go/pixa/internal/imagerequest"
+)
+
+// heldFetcher sends on started when a fetch begins, and holds the fetch until
+// release is closed. It then fails the fetch as an upstream error.
+type heldFetcher struct {
+	started chan struct{}
+	release chan struct{}
+}
+
+// Fetch sends on f.started, waits for f.release to be closed, and returns
+// httpfetcher.ErrUpstreamError.
+func (f heldFetcher) Fetch(
+	context.Context, imagerequest.Source,
+) (*httpfetcher.FetchResult, error) {
+	f.started <- struct{}{}
+
+	<-f.release
+
+	return nil, httpfetcher.ErrUpstreamError
+}
+
+// readLogLines decodes the JSON log lines in logs.
+func readLogLines(t *testing.T, logs *bytes.Buffer) []map[string]any {
+	t.Helper()
+
+	t.Logf("logged:\n%s", logs.String())
+
+	var lines []map[string]any
+
+	dec := json.NewDecoder(logs)
+	for dec.More() {
+		var line map[string]any
+
+		err := dec.Decode(&line)
+		if err != nil {
+			t.Fatalf("decoding log line: %v", err)
+		}
+
+		lines = append(lines, line)
+	}
+
+	return lines
+}
+
+// TestImageRoutes_ClientGoneAnswers499 checks that both image routes answer
+// 499 to a request whose client goes away while its image is being made. A
+// first request's fetch is held, so the image is being made, and a second
+// request for the same image waits for it until its client goes away. The
+// second request must be logged once at info level with its request ID and
+// the source host and path. Nothing may be logged at error level.
+func TestImageRoutes_ClientGoneAnswers499(t *testing.T) {
+	t.Parallel()
+
+	const requestID = "test-request-id"
+
+	for route, imageURL := range photoURLsByRoute() {
+		t.Run(route, func(t *testing.T) {
+			t.Parallel()
+
+			var logs bytes.Buffer
+
+			fetcher := heldFetcher{started: make(chan struct{}), release: make(chan struct{})}
+			h, routes := newRoutesFetchingThrough(t, fetcher,
+				slog.New(slog.NewJSONHandler(&logs, nil)))
+			target := imageURL(t, h)
+
+			firstDone := make(chan struct{})
+
+			go func() {
+				defer close(firstDone)
+
+				sendGet(t, routes, target)
+			}()
+
+			<-fetcher.started
+
+			ctx, cancel := context.WithCancel(context.WithValue(t.Context(),
+				middleware.RequestIDKey, requestID))
+			rec := httptest.NewRecorder()
+			secondDone := make(chan struct{})
+
+			go func() {
+				defer close(secondDone)
+
+				routes.ServeHTTP(rec, httptest.NewRequestWithContext(
+					ctx, http.MethodGet, target, nil))
+			}()
+
+			// The fetch is still held, so the second request can end only
+			// because its client went away
+			cancel()
+			<-secondDone
+
+			close(fetcher.release)
+			<-firstDone
+
+			if rec.Code != statusClientClosedRequest {
+				t.Errorf("status = %d, want %d", rec.Code, statusClientClosedRequest)
+			}
+
+			var clientGoneLines int
+
+			for _, line := range readLogLines(t, &logs) {
+				if line["level"] == slog.LevelError.String() {
+					t.Errorf("logged at error level: %v", line["msg"])
+				}
+
+				if line["level"] == slog.LevelInfo.String() &&
+					line["msg"] == "client went away before the image was ready" &&
+					line["request_id"] == requestID &&
+					line["host"] == signedHost &&
+					line["path"] == photoPath {
+					clientGoneLines++
+				}
+			}
+
+			if clientGoneLines != 1 {
+				t.Errorf("info line naming the request logged %d times, want 1",
+					clientGoneLines)
+			}
+		})
+	}
+}
+
+// TestImageRoutes_CanceledWithLiveRequestAnswers500 checks that both image
+// routes answer 500, logged as "failed to get image" at error level, for an
+// image service error that wraps context.Canceled while the request's own
+// context is live. Its client has not gone away, so the cancellation is
+// pixa's own failure.
+func TestImageRoutes_CanceledWithLiveRequestAnswers500(t *testing.T) {
+	t.Parallel()
+
+	for route, imageURL := range photoURLsByRoute() {
+		t.Run(route, func(t *testing.T) {
+			t.Parallel()
+
+			var logs bytes.Buffer
+
+			h, routes := newRoutesFetchingThrough(t,
+				failingFetcher{err: context.Canceled},
+				slog.New(slog.NewJSONHandler(&logs, nil)))
+
+			rec := sendGet(t, routes, imageURL(t, h))
+			if rec.Code != http.StatusInternalServerError {
+				t.Errorf("status = %d, want %d",
+					rec.Code, http.StatusInternalServerError)
+			}
+
+			if !slices.ContainsFunc(readLogLines(t, &logs),
+				func(line map[string]any) bool {
+					return line["level"] == slog.LevelError.String() &&
+						line["msg"] == "failed to get image"
+				}) {
+				t.Error(`no "failed to get image" line logged at error level`)
+			}
+		})
+	}
+}
diff --git a/internal/handlers/image.go b/internal/handlers/image.go
index 68c2fee..7c1c468 100644
--- a/internal/handlers/image.go
+++ b/internal/handlers/image.go
@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -19,6 +20,11 @@ import (
 	"sneak.berlin/go/pixa/internal/magic"
 )
 
+// statusClientClosedRequest is the status nginx calls "client closed
+// request". The image routes answer it to a request whose client went away
+// before its image was ready. Nobody reads it; it is for logs and metrics.
+const statusClientClosedRequest = 499
+
 // HandleImage handles the main image proxy route:
 // /v1/image/<host>/<path>/<width>x<height>.<format>, or with no format
 // /v1/image/<host>/<path>/<width>x<height>
@@ -345,8 +351,9 @@ func notModified(w http.ResponseWriter, r *http.Request, etag string) bool {
 // serveImage serves the image that req asks for. Both image routes call it
 // once they have the request and its URL's expiry, which ends the
 // Cache-Control max-age. It chooses the format for the format auto, answers
-// If-None-Match with 304 and HEAD with the headers only, and answers an error
-// of the image service with respondImageError.
+// If-None-Match with 304 and HEAD with the headers only. It answers 499 when
+// the client went away before the image was ready, and any other error of
+// the image service with respondImageError.
 func (s *Handlers) serveImage(
 	w http.ResponseWriter, r *http.Request,
 	req *imagerequest.Request, expires time.Time,
@@ -362,6 +369,21 @@ func (s *Handlers) serveImage(
 	startTime := time.Now()
 
 	resp, err := s.imgSvc.Get(r.Context(), req)
+
+	// The client went away before its image was ready, which is not pixa's
+	// failure. A cancellation while the request's context is live is pixa's,
+	// and respondImageError answers it 500.
+	if errors.Is(err, context.Canceled) && r.Context().Err() != nil {
+		s.log.Info("client went away before the image was ready",
+			"request_id", middleware.GetReqID(r.Context()),
+			"host", req.Source.Host,
+			"path", req.Source.Path,
+		)
+		w.WriteHeader(statusClientClosedRequest)
+
+		return
+	}
+
 	if err != nil {
 		s.respondImageError(w, req, err)