backend/Dockerfile

@@ -49,9 +49,14 @@ COPY --from=build /out/backend /usr/local/bin/backend
 # Own the seed dictionary as the nonroot runtime user (UID 65532): a named volume
 # mounted at /opt/dawg inherits this ownership on first use, so the admin console
 # can write new version subdirectories at runtime. The volume preserves uploaded
-# versions across deploys and, once seeded, is not re-seeded — so after bootstrap
-# every dictionary change goes through the console, not a rebuild (ARCHITECTURE.md §5).
+# versions across deploys and, once seeded, is not re-seeded (ARCHITECTURE.md §5).
 COPY --from=dawg --chown=65532:65532 /dawg /opt/dawg
+# A second, UNSHADOWED copy of the build's DAWGs: the /opt/dawg volume mount hides the
+# image's copy there, so this is where engine.DeliverVersion reads the build version from
+# to add it (add-only) to the volume on boot — the deploy-delivers path that lets a bumped
+# BACKEND_DICT_VERSION go live for new games without an admin upload (ARCHITECTURE.md §5).
+COPY --from=dawg --chown=65532:65532 /dawg /opt/dawg-seed
 ENV BACKEND_DICT_DIR=/opt/dawg
+ENV BACKEND_DICT_SEED_DIR=/opt/dawg-seed
 ENV BACKEND_DICT_VERSION=${DICT_VERSION}
 ENTRYPOINT ["/usr/local/bin/backend"]

backend/cmd/backend/main.go

@@ -111,6 +111,12 @@ func run(ctx context.Context, cfg config.Config, logger *zap.Logger) error {
 	}
 	logger.Info("database migrations applied")
 
+	// Deliver the build's dictionary version onto the persistent volume if a redeploy
+	// bumped it (add-only; old versions in-flight games pin are untouched), so the new
+	// dictionary is resident and can be activated below without an admin upload.
+	if err := engine.DeliverVersion(cfg.Game.DictDir, cfg.Game.DictSeedDir, cfg.Game.DictVersion); err != nil {
+		return fmt.Errorf("deliver dictionary version: %w", err)
+	}
 	registry, err := engine.OpenWithVersions(cfg.Game.DictDir, cfg.Game.DictVersion)
 	if err != nil {
 		return fmt.Errorf("load dictionaries: %w", err)
@@ -118,6 +124,7 @@ func run(ctx context.Context, cfg config.Config, logger *zap.Logger) error {
 	defer func() { _ = registry.Close() }()
 	logger.Info("dictionaries loaded",
 		zap.String("dir", cfg.Game.DictDir),
+		zap.String("seed_dir", cfg.Game.DictSeedDir),
 		zap.String("version", cfg.Game.DictVersion))
 
 	// Admin console: an optional backend client to the Telegram connector
@@ -147,10 +154,10 @@ func run(ctx context.Context, cfg config.Config, logger *zap.Logger) error {
 	accounts := account.NewStore(db)
 	accounts.SetMetrics(tel.MeterProvider().Meter("scrabble/backend/account"))
 	games := game.NewService(game.NewStore(db), accounts, registry, cfg.Game, logger)
-	// Reconcile the persisted active dictionary version with the registry: a
-	// version activated through the admin console (and written to the dictionary
-	// volume) is adopted again after a restart; otherwise the configured seed
-	// version is kept and persisted (docs/ARCHITECTURE.md §5).
+	// Reconcile the active dictionary version with the registry: the build version
+	// (delivered above) becomes active so a redeploy that bumped it goes live for new
+	// games, except a newer version installed out-of-band through the admin console,
+	// which is not downgraded by a restart (docs/ARCHITECTURE.md §5).
 	if err := games.InitActiveVersion(ctx); err != nil {
 		return fmt.Errorf("init active dictionary version: %w", err)
 	}

backend/internal/config/config.go

@@ -106,6 +106,7 @@ func Load() (Config, error) {
 	gm := game.DefaultConfig()
 	gm.DictDir = envOr("BACKEND_DICT_DIR", gm.DictDir)
 	gm.DictVersion = envOr("BACKEND_DICT_VERSION", gm.DictVersion)
+	gm.DictSeedDir = envOr("BACKEND_DICT_SEED_DIR", gm.DictSeedDir)
 	if gm.TimeoutSweepInterval, err = envDuration("BACKEND_GAME_TIMEOUT_SWEEP_INTERVAL", gm.TimeoutSweepInterval); err != nil {
 		return Config{}, err
 	}

backend/internal/engine/deliver.go

@@ -0,0 +1,92 @@
+package engine
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+// DeliverVersion makes the build's dictionary version resident on the persistent
+// dictionary volume without disturbing the versions in-flight games already pin.
+//
+// The volume is seeded from the image once and never re-seeded, and the image's
+// /opt/dawg is shadowed by that volume mount, so a redeploy that bumped
+// BACKEND_DICT_VERSION cannot otherwise make the new DAWGs reachable at runtime.
+// The image therefore keeps an unshadowed read-only copy at seedDir, and this
+// copies it into dictDir/<version>/ when the version is not already present —
+// neither the flat seed's own recorded label nor an existing version
+// subdirectory. It is add-only and idempotent: the flat seed and any prior admin
+// uploads are never touched, so old games keep the version they pin while the new
+// one becomes resident and activatable (see game.Service.InitActiveVersion). A
+// blank seedDir disables delivery (the pre-existing seed-only behaviour).
+func DeliverVersion(dictDir, seedDir, version string) error {
+	if seedDir == "" || version == "" {
+		return nil
+	}
+	target := filepath.Join(dictDir, version)
+	if _, err := os.Stat(target); err == nil {
+		return nil // already delivered on a prior boot
+	} else if !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("engine: stat delivered dictionary %s: %w", target, err)
+	}
+	// A fresh volume is populated from the image and recorded as this version by the
+	// marker: it is the flat dir, so there is nothing to deliver. resolveSeedVersion
+	// records the label on first use, matching OpenWithVersions.
+	seed, err := resolveSeedVersion(dictDir, version)
+	if err != nil {
+		return err
+	}
+	if seed == version {
+		return nil
+	}
+	// Stage into a dot-prefixed directory (skipped by OpenWithVersions' version scan)
+	// then rename, so a crash mid-copy never leaves a half-populated version subdir.
+	staging := filepath.Join(dictDir, ".staging-deliver-"+version)
+	if err := os.RemoveAll(staging); err != nil {
+		return fmt.Errorf("engine: clear deliver staging %s: %w", staging, err)
+	}
+	if err := os.MkdirAll(staging, 0o755); err != nil {
+		return fmt.Errorf("engine: create deliver staging %s: %w", staging, err)
+	}
+	for _, file := range dictFiles {
+		src := filepath.Join(seedDir, file)
+		if _, err := os.Stat(src); errors.Is(err, os.ErrNotExist) {
+			continue // a variant absent from the seed is simply absent under this version
+		} else if err != nil {
+			_ = os.RemoveAll(staging)
+			return fmt.Errorf("engine: stat seed dawg %s: %w", src, err)
+		}
+		if err := copyFile(src, filepath.Join(staging, file)); err != nil {
+			_ = os.RemoveAll(staging)
+			return err
+		}
+	}
+	if err := os.Rename(staging, target); err != nil {
+		_ = os.RemoveAll(staging)
+		return fmt.Errorf("engine: publish delivered dictionary %s: %w", target, err)
+	}
+	return nil
+}
+
+// copyFile copies a single file, truncating the destination.
+func copyFile(src, dst string) error {
+	in, err := os.Open(src)
+	if err != nil {
+		return fmt.Errorf("engine: open %s: %w", src, err)
+	}
+	defer func() { _ = in.Close() }()
+	out, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o644)
+	if err != nil {
+		return fmt.Errorf("engine: create %s: %w", dst, err)
+	}
+	if _, err := io.Copy(out, in); err != nil {
+		_ = out.Close()
+		return fmt.Errorf("engine: copy %s -> %s: %w", src, dst, err)
+	}
+	if err := out.Close(); err != nil {
+		return fmt.Errorf("engine: finalise %s: %w", dst, err)
+	}
+	return nil
+}

backend/internal/engine/deliver_test.go

@@ -0,0 +1,68 @@
+package engine
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestDeliverVersion(t *testing.T) {
+	// A blank seed directory disables delivery (the pre-existing seed-only behaviour).
+	if err := DeliverVersion(t.TempDir(), "", "v1.3.1"); err != nil {
+		t.Fatalf("blank seedDir: %v", err)
+	}
+
+	// An existing volume flat-seeded as v1.3.0 gets v1.3.1 delivered as a subdirectory,
+	// add-only: the flat seed's marker is left intact and the new version's DAWGs land.
+	dict := t.TempDir()
+	seed := t.TempDir()
+	if err := os.WriteFile(filepath.Join(dict, seedMarkerFile), []byte("v1.3.0\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	for _, f := range dictFiles {
+		if err := os.WriteFile(filepath.Join(seed, f), []byte("dawg:"+f), 0o644); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := DeliverVersion(dict, seed, "v1.3.1"); err != nil {
+		t.Fatalf("deliver v1.3.1: %v", err)
+	}
+	for _, f := range dictFiles {
+		got, err := os.ReadFile(filepath.Join(dict, "v1.3.1", f))
+		if err != nil {
+			t.Fatalf("delivered %s: %v", f, err)
+		}
+		if string(got) != "dawg:"+f {
+			t.Errorf("delivered %s = %q, want the seed bytes", f, got)
+		}
+	}
+	if m, _ := os.ReadFile(filepath.Join(dict, seedMarkerFile)); string(m) != "v1.3.0\n" {
+		t.Errorf("flat seed marker relabelled to %q (delivery must be add-only)", m)
+	}
+	// Idempotent: a second call is a no-op and leaves no staging directory behind.
+	if err := DeliverVersion(dict, seed, "v1.3.1"); err != nil {
+		t.Fatalf("re-deliver v1.3.1: %v", err)
+	}
+	if entries, _ := os.ReadDir(dict); hasStaging(entries) {
+		t.Errorf("a staging directory survived delivery")
+	}
+
+	// On a fresh directory the build version becomes the flat seed, so nothing is delivered
+	// as a redundant subdirectory.
+	fresh := t.TempDir()
+	if err := DeliverVersion(fresh, seed, "v1.3.1"); err != nil {
+		t.Fatalf("fresh deliver: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(fresh, "v1.3.1")); !os.IsNotExist(err) {
+		t.Errorf("fresh volume got a redundant v1.3.1 subdir; it should be the flat seed")
+	}
+}
+
+func hasStaging(entries []os.DirEntry) bool {
+	for _, e := range entries {
+		if len(e.Name()) >= len(".staging") && e.Name()[:len(".staging")] == ".staging" {
+			return true
+		}
+	}
+	return false
+}

backend/internal/engine/seedmarker.go

@@ -25,11 +25,11 @@ const seedMarkerFile = ".seed_version"
 //     BACKEND_DICT_VERSION) and return it — the seed of a fresh volume;
 //   - already-seeded directory: return the recorded marker and ignore bootVersion.
 //
-// So bumping the build seed on a live volume is a harmless no-op (it only takes
-// effect on a future fresh volume) instead of relabelling the already-seeded bytes —
-// which would void games pinned to the prior label and mis-serve new ones. New games
-// still pin the active version (DB-persisted, set by the admin console), which is the
-// real way a running contour moves to a new release.
+// So a later build seed never relabels the already-seeded flat bytes — which would void
+// games pinned to the prior label and mis-serve new ones. The new build version is instead
+// delivered as a NEW subdirectory (DeliverVersion) and made active (Service.InitActiveVersion),
+// so a redeploy still moves new games to it while old games keep the flat label. New games
+// pin the active version (DB-persisted); a console upload can also set it out-of-band.
 //
 // A directory that cannot be written makes the first record fail; that also breaks
 // the admin console (which writes version subdirectories here), so the error is

backend/internal/game/config.go

@@ -18,6 +18,13 @@ type Config struct {
 	// DictVersion labels the dictionary version new games pin. Sourced from
 	// BACKEND_DICT_VERSION.
 	DictVersion string
+	// DictSeedDir holds the image's read-only copy of the build's DictVersion DAWGs,
+	// on a path the persistent DictDir volume does NOT shadow. On boot the backend
+	// delivers this version into DictDir/<DictVersion>/ if absent (add-only), so a
+	// redeploy that bumped DICT_VERSION makes the new dictionary resident and activatable
+	// without disturbing the versions in-flight games already pin. Sourced from
+	// BACKEND_DICT_SEED_DIR; empty disables delivery (the pre-existing seed-only behaviour).
+	DictSeedDir string
 	// TimeoutSweepInterval is how often the sweeper scans for overdue turns.
 	// Sourced from BACKEND_GAME_TIMEOUT_SWEEP_INTERVAL.
 	TimeoutSweepInterval time.Duration

backend/internal/game/service.go

@@ -232,21 +232,31 @@ func (svc *Service) ActiveVersion() string {
 }
 
 // InitActiveVersion reconciles the persisted active dictionary version with the
-// registry at startup. If a version was persisted and is resident, it becomes the
-// active version; otherwise the configured seed version is kept and persisted as
-// the initial active version. Call once during wiring, before serving traffic.
+// registry at startup and makes the build's version (BACKEND_DICT_VERSION, delivered
+// resident by engine.DeliverVersion) authoritative: a redeploy that bumped the build
+// version thus activates it for new games without any admin step, while old games keep
+// the version they pin. The one exception is a version installed out-of-band through
+// the admin console that is NEWER than the build version and still resident — it is
+// kept, so a restart on an older image never downgrades a hotfix. A build version that
+// is not resident (delivery disabled or a partial state) falls back to a resident
+// persisted version. The chosen version is persisted so the admin console reflects it.
+// Call once during wiring, before serving traffic.
 func (svc *Service) InitActiveVersion(ctx context.Context) error {
 	persisted, ok, err := svc.store.GetActiveDictVersion(ctx)
 	if err != nil {
 		return err
 	}
-	if ok && svc.versionResident(persisted) {
-		svc.verMu.Lock()
-		svc.version = persisted
-		svc.verMu.Unlock()
-		return nil
+	target := svc.activeVersion() // the build seed version (config.DictVersion)
+	if ok && svc.versionResident(persisted) && compareDictVersions(persisted, target) > 0 {
+		target = persisted // a newer out-of-band install wins over the build version
 	}
-	return svc.store.SetActiveDictVersion(ctx, svc.activeVersion())
+	if !svc.versionResident(target) && ok && svc.versionResident(persisted) {
+		target = persisted // the build version is unloadable — keep a resident one
+	}
+	svc.verMu.Lock()
+	svc.version = target
+	svc.verMu.Unlock()
+	return svc.store.SetActiveDictVersion(ctx, target)
 }
 
 // SetActiveVersion records version as the active dictionary version, persisting it

backend/internal/game/version.go

@@ -0,0 +1,45 @@
+package game
+
+import (
+	"strconv"
+	"strings"
+)
+
+// compareDictVersions orders two dictionary version labels of the shape "vMAJOR.MINOR.PATCH"
+// numerically, returning -1, 0 or +1 as a is less than, equal to or greater than b. Labels
+// that do not parse fall back to a byte comparison, so the ordering is always total (a mixed
+// or malformed pair never crashes the boot-time active-version reconcile).
+func compareDictVersions(a, b string) int {
+	pa, oka := parseDictVersion(a)
+	pb, okb := parseDictVersion(b)
+	if !oka || !okb {
+		return strings.Compare(a, b)
+	}
+	for i := range pa {
+		if pa[i] != pb[i] {
+			if pa[i] < pb[i] {
+				return -1
+			}
+			return 1
+		}
+	}
+	return 0
+}
+
+// parseDictVersion parses a "vMAJOR.MINOR.PATCH" label into its three numeric parts, reporting
+// whether it matched that shape.
+func parseDictVersion(v string) ([3]int, bool) {
+	parts := strings.Split(strings.TrimPrefix(v, "v"), ".")
+	if len(parts) != 3 {
+		return [3]int{}, false
+	}
+	var out [3]int
+	for i, p := range parts {
+		n, err := strconv.Atoi(p)
+		if err != nil {
+			return [3]int{}, false
+		}
+		out[i] = n
+	}
+	return out, true
+}

backend/internal/game/version_test.go

@@ -0,0 +1,37 @@
+package game
+
+import "testing"
+
+func TestCompareDictVersions(t *testing.T) {
+	cases := []struct {
+		a, b string
+		want int
+	}{
+		{"v1.3.0", "v1.3.1", -1},
+		{"v1.3.1", "v1.3.0", 1},
+		{"v1.3.1", "v1.3.1", 0},
+		{"v1.3.9", "v1.3.10", -1}, // numeric, not lexical
+		{"v1.10.0", "v1.9.0", 1},
+		{"v2.0.0", "v1.9.9", 1},
+		{"1.3.1", "v1.3.1", 0}, // the leading v is optional
+		// Non-semver falls back to a byte comparison, keeping the ordering total.
+		{"weird", "weird", 0},
+		{"a", "b", -1},
+	}
+	for _, c := range cases {
+		if got := compareDictVersions(c.a, c.b); sign(got) != c.want {
+			t.Errorf("compareDictVersions(%q, %q) = %d, want sign %d", c.a, c.b, got, c.want)
+		}
+	}
+}
+
+func sign(n int) int {
+	switch {
+	case n < 0:
+		return -1
+	case n > 0:
+		return 1
+	default:
+		return 0
+	}
+}

backend/internal/inttest/dictionary_update_test.go

@@ -103,14 +103,31 @@ func TestDictionaryUpdateFlow(t *testing.T) {
 		t.Errorf("installed dawg missing on disk: %v", err)
 	}
 
-	// The choice survives a restart: a fresh service over the same DB and registry
-	// re-adopts the persisted active version.
+	// The choice survives a restart on the SAME build: an out-of-band admin install newer
+	// than the build version is not downgraded (a restart on an older image keeps the hotfix).
 	restarted := newGameServiceOn(dir, "v1.0.0", reg)
 	if err := restarted.InitActiveVersion(ctx); err != nil {
 		t.Fatalf("restart init: %v", err)
 	}
 	if got := restarted.ActiveVersion(); got != "v9.9.9" {
-		t.Errorf("restarted active version = %q, want v9.9.9 (persisted)", got)
+		t.Errorf("restarted active version = %q, want v9.9.9 (a newer out-of-band install is kept)", got)
+	}
+
+	// A redeploy that delivered a build version NEWER than the out-of-band one activates it
+	// for new games without any admin step (the deploy-delivers path — docs/ARCHITECTURE.md §5).
+	if _, err := reg.LoadAvailable(dir, "v10.0.0"); err != nil {
+		t.Fatalf("make v10.0.0 resident: %v", err)
+	}
+	deployed := newGameServiceOn(dir, "v10.0.0", reg)
+	if err := deployed.InitActiveVersion(ctx); err != nil {
+		t.Fatalf("deploy init: %v", err)
+	}
+	if got := deployed.ActiveVersion(); got != "v10.0.0" {
+		t.Errorf("deployed active version = %q, want v10.0.0 (a newer build version wins)", got)
+	}
+	// Restore the out-of-band active version so the assertions below still read v9.9.9.
+	if err := restarted.SetActiveVersion(ctx, "v9.9.9"); err != nil {
+		t.Fatalf("restore active: %v", err)
 	}
 
 	// New games pin the new version; the in-progress game keeps its own, still resident.

deploy/README.md

@@ -98,7 +98,7 @@ without it Docker's resolver handles `otelcol`, `gateway` and `api.telegram.org`
 | --- | --- | --- | --- |
 | `POSTGRES_DB` | variable | `scrabble` | Database name. |
 | `POSTGRES_USER` | variable | `scrabble` | Database user. |
-| `DICT_VERSION` | variable (shared) | `v1.3.1` | `scrabble-dictionary` release tag baked into the backend image as the **seed for a fresh volume** (build-arg). A live contour changes dictionary through the admin console, not this; on a seeded volume a changed value is ignored (the recorded `.seed_version` marker wins — the seed-drift guard, ARCHITECTURE.md §5). One shared unprefixed Gitea variable seeds both contours and pins the CI test suite. |
+| `DICT_VERSION` | variable (shared) | `v1.3.1` | `scrabble-dictionary` release tag baked into the backend image (build-arg). **Deploy-authoritative**: a redeploy that bumped it **delivers** the version onto the volume (add-only) and **activates** it for new games — old games keep the version they pin, and a newer out-of-band console upload is never downgraded (ARCHITECTURE.md §5). The `.seed_version` marker still guards the flat seed's label (a bump is delivered as a new subdirectory, never a relabel). One shared unprefixed Gitea variable seeds both contours and pins the CI test suite. |
 | `LOG_LEVEL` | variable | `info` | Shared log level for backend / gateway / validator / bot (`debug\|info\|warn\|error`). |
 | `CADDY_SITE_ADDRESS` | variable | `:80` | Caddy site address. Test: `:80` (host caddy terminates TLS). Prod: a domain, so caddy does its own ACME. |
 | `GM_BASICAUTH_USER` | variable | `gm` | Username for the `/_gm` Basic-Auth. |
@@ -176,10 +176,14 @@ For local builds set `DICT_VERSION` in `deploy/.env` (template: `.env.example`);
 `docker build` needs `--build-arg DICT_VERSION=vX.Y.Z`. The Dockerfiles and `compose` carry no
 default — a missing value fails loudly instead of baking a stale tag.
 
-Bumping the seed is a **no-op on a live volume** (the `.seed_version` marker wins — the
-seed-drift guard). A running contour/prod moves to a new release **through the admin console**
-`/_gm/dictionary` (upload the tarball, preview the per-variant diff, confirm); in-flight games
-keep their pinned version, new games use the new one (ARCHITECTURE.md §5).
+Bumping `DICT_VERSION` and **redeploying** takes a live contour/prod to the new dictionary:
+on boot the backend **delivers** the build's version onto the volume (add-only, into
+`BACKEND_DICT_DIR/<version>/` from the unshadowed `BACKEND_DICT_SEED_DIR`) and **activates** it,
+so new games pin it while in-flight games keep the version they started on. The `.seed_version`
+marker still guards the flat seed's label (the delivery is a new subdirectory, never a relabel).
+The admin console `/_gm/dictionary` (upload the tarball, preview the per-variant diff, confirm)
+remains for an **out-of-band** update without a redeploy; a console version newer than the build
+survives a later restart on an older image (ARCHITECTURE.md §5).
 
 ## Production rollout
 

docs/ARCHITECTURE.md

@@ -446,22 +446,27 @@ Key points:
   version while new games use the new one. A restart re-loads every resident
   version via `engine.OpenWithVersions` (the flat seed plus each subdirectory,
   skipping the `.staging/` upload area) and restores the active pointer from
-  `dictionary_state`. The volume preserves uploaded versions across redeploys;
-  once seeded it is not re-seeded, so after bootstrap dictionary changes go through
-  the console rather than a rebuild. Because the flat DAWGs carry no embedded
-  version, `OpenWithVersions` records the version the flat directory was first seeded
-  at in a `.seed_version` marker on the volume and treats that marker as
-  **authoritative** (the **seed-drift guard**): on an already-seeded volume a later
-  `BACKEND_DICT_VERSION` is ignored, so a bumped build seed cannot relabel the
-  already-seeded bytes — which would otherwise silently serve the wrong dictionary
-  and void games pinned to the prior label. A running contour therefore moves to a
-  new release **through the console** (the prior version stays resident, so its games
-  keep replaying), and `DICT_VERSION` is the seed for a **fresh** volume only:
-  bumping it on a live contour is a harmless no-op that takes effect on the next
-  fresh volume. Set it per contour from the deploy's `TEST_`/`PROD_DICT_VERSION`.
-  (The dictionaries ship as a versioned **release artifact** from the
-  `scrabble-dictionary` repo; the build's `DICT_VERSION` selects
-  only the seed.)
+  `dictionary_state`. The volume preserves uploaded versions across redeploys, so
+  in-flight games keep replaying on the version they pin. The build's
+  `BACKEND_DICT_VERSION` is **deploy-authoritative**: on boot `engine.DeliverVersion`
+  copies the image's DAWGs — kept unshadowed at `BACKEND_DICT_SEED_DIR`, since the
+  volume mount hides the image's `BACKEND_DICT_DIR` copy — into
+  `BACKEND_DICT_DIR/<version>/` when that version is not already resident (**add-only**:
+  the flat seed and prior uploads are never touched), and `InitActiveVersion` makes it
+  the active version. So a redeploy that bumped `DICT_VERSION` moves new games to the
+  new dictionary automatically, while old games stay on theirs — no console step. The
+  one exception: a version installed out-of-band through the console that is **newer**
+  than the build version and still resident is kept, so a restart on an older image never
+  downgrades a hotfix (versions compare numerically). Because the flat DAWGs carry no
+  embedded version, `OpenWithVersions` records the version the flat directory was first
+  seeded at in a `.seed_version` marker and treats it as authoritative for **that flat
+  directory** (the **seed-drift guard**): a later `BACKEND_DICT_VERSION` never relabels
+  the already-seeded flat bytes — it is delivered as a **new subdirectory** instead — so
+  the guard still prevents mis-serving a game pinned to the flat label. The console
+  remains the way to update a dictionary **without** a redeploy (an out-of-band upload).
+  Set `DICT_VERSION` per contour from the deploy's `TEST_`/`PROD_DICT_VERSION`. (The
+  dictionaries ship as a versioned **release artifact** from the `scrabble-dictionary`
+  repo.)
 - Move generation/validation/scoring use `Solver.GenerateMoves` (ranked),
   `Solver.ValidatePlay` and `Solver.ScorePlay`; board mutation uses
   `scrabble.Apply`. The engine adds its own deterministic, seeded tile **bag**