feat(builder): SteamCMD first for Linux servers, and fall back to the next image

A draft built on a ready-made image whose files all live outside /server
(nodes keep only /server and /data) went round three times and ended as
WIP, although research had also verified the game's Steam app, which
SteamCMD installs straight into /server. The builder never tried it.

- research reads each Steam app's OS list. When it ships a Linux server,
  cm2network/steamcmd goes first in the variant's images and that variant
  is recommended. Windows-only servers keep images with Proton or Wine
  first. The research prompt says the same.
- build tries the variant's images in order: when no draft passes with one,
  the next image gets a fresh start. The first draft that boots wins; if
  none does, the PR gets the draft that got furthest, and its summary lists
  each image tried and how it went.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/gbrgames/build.go

@@ -27,6 +27,7 @@ type buildResult struct {
 	Verified []string `json:"verified"`
 	Problems []string `json:"problems"`
 	Summary  string   `json:"summary"`
+	Tried    []string `json:"tried,omitempty"` // each image tried, and how it went
 }
 
 const defaultAgentImage = "www.gitea.gbreed.com/gbreed-public/gbr-node-agent:latest"
@@ -93,21 +94,67 @@ type buildOptions struct {
 	agentImage                    string
 }
 
-// build drafts the template for exactly the option the admin chose: one image (research lists each way to
+// build tries the variant's images in order (research puts SteamCMD first when the game ships a Linux
-// run a game as its own option). It never switches to another image; if the chosen one can't be made to
+// server) and keeps the first draft that boots. A draft that can't be made to work with one image is set
-// work, the result says so and the admin can pick a different option.
+// aside and the next image gets a fresh start; if none works, the draft that got furthest is returned.
 func build(o buildOptions) (*buildResult, error) {
+	var candidates []string
 	for _, image := range o.variant.Images {
 		if isSteamCMDImage(image) && o.variant.SteamAppID == "" {
 			continue // the SteamCMD image alone runs nothing
 		}
-		res, err := buildWithImage(o, image)
+		candidates = append(candidates, image)
-		if res != nil {
-			res.Summary = buildSummary(o, res)
 	}
+	if len(candidates) == 0 {
+		return nil, errors.New("the variant has no image to build from")
+	}
+	dir := filepath.Join(o.gamesDir, o.id)
+	setAside := filepath.Join("firstboot-out", o.id+"-best-draft")
+	var best *buildResult
+	var tried []string
+	for i, image := range candidates {
+		if i > 0 {
+			fmt.Printf("[build] trying the next image: %s\n", image)
+		}
+		res, err := buildWithImage(o, image)
+		if err != nil {
 			return res, err
 		}
-	return nil, errors.New("the variant has no image to build from")
+		tried = append(tried, attemptNote(res))
+		if res.Passed {
+			res.Tried = tried
+			res.Summary = buildSummary(o, res)
+			return res, nil
+		}
+		if _, err := os.Stat(filepath.Join(dir, "game.yaml")); err == nil {
+			// This one got a draft written: keep it in case no later image does better
+			os.RemoveAll(setAside)
+			if err := os.Rename(dir, setAside); err != nil {
+				return res, err
+			}
+			best = res
+		}
+	}
+	if best == nil {
+		return &buildResult{GameID: o.id, Dir: dir, Tried: tried, Problems: []string{"no image of this variant could be drafted"}},
+			errors.New("no image of this variant could be drafted: " + strings.Join(tried, "; "))
+	}
+	if err := os.Rename(setAside, dir); err != nil {
+		return best, err
+	}
+	best.Tried = tried
+	best.Summary = buildSummary(o, best)
+	return best, nil
+}
+
+func attemptNote(res *buildResult) string {
+	switch {
+	case res.Passed:
+		return res.Image + ": booted"
+	case len(res.Problems) > 0:
+		return res.Image + ": " + firstLine(res.Problems[0])
+	}
+	return res.Image + ": did not boot"
 }
 
 // buildWithImage drafts the template for one image: first boot, draft, then boots of the draft with
@@ -414,6 +461,12 @@ func buildSummary(o buildOptions, res *buildResult) string {
 		fmt.Fprintf(&b, ", Steam app %s", o.variant.SteamAppID)
 	}
 	fmt.Fprintf(&b, "\n- Model rounds: %d\n", res.Rounds)
+	if len(res.Tried) > 1 {
+		b.WriteString("\n**Images tried, in order**\n")
+		for _, t := range res.Tried {
+			fmt.Fprintf(&b, "- %s\n", firstLine(t))
+		}
+	}
 	if len(res.Verified) > 0 {
 		b.WriteString("\n**Checked for real**\n")
 		for _, v := range res.Verified {

cmd/gbrgames/research.go

@@ -329,7 +329,7 @@ func verifyVariants(res *researchResult) {
 				v.Verified = append(v.Verified, fmt.Sprintf("Steam app %s is %q", v.SteamAppID, app.name))
 				v.Images = withSteamCMD(v.Images, app.linux)
 				if app.linux {
-					v.Verified = append(v.Verified, "it ships a Linux server, so the SteamCMD option (installing it into /server) is recommended")
+					v.Verified = append(v.Verified, "it ships a Linux server, so SteamCMD (installing it into /server) is tried first")
 				}
 			} else {
 				v.Problems = append(v.Problems, "Steam app "+v.SteamAppID+" not found for anonymous SteamCMD")
@@ -348,7 +348,6 @@ func verifyVariants(res *researchResult) {
 		res.Reason = "unknown"
 		res.Message = "No variant has a Docker image or Steam app that could be confirmed. " + res.Message
 	}
-	res.Variants = oneOptionPerImage(res.Variants)
 	recommend(res.Variants)
 }
 
@@ -432,37 +431,3 @@ func withSteamCMD(images []string, linux bool) []string {
 	}
 	return append(others, "cm2network/steamcmd")
 }
-
-// oneOptionPerImage turns a variant that can run on several images into one choice per image, so the
-// admin picks exactly how the server runs and the build uses that and nothing else.
-func oneOptionPerImage(variants []variant) []variant {
-	var out []variant
-	for _, v := range variants {
-		if len(v.Images) <= 1 {
-			out = append(out, v)
-			continue
-		}
-		for _, img := range v.Images {
-			o := v
-			o.Images = []string{img}
-			o.Verified = nil
-			for _, line := range v.Verified {
-				if !strings.HasPrefix(line, "image ") || line == "image "+img+" exists" {
-					o.Verified = append(o.Verified, line)
-				}
-			}
-			if isSteamCMDImage(img) {
-				o.ID = v.ID + "-steamcmd"
-				o.Title = v.Title + " (SteamCMD)"
-				o.Description = strings.TrimSpace(v.Description + " Installed with SteamCMD into the server volume.")
-			} else {
-				o.ID = v.ID + "-" + gameID(img)
-				o.Title = v.Title + " (image " + img + ")"
-				o.Description = strings.TrimSpace(v.Description + " Runs in the ready-made image " + img + ".")
-				o.SteamAppID = ""
-			}
-			out = append(out, o)
-		}
-	}
-	return out
-}

cmd/gbrgames/research_test.go

@@ -88,27 +88,3 @@ func TestRecommendPrefersTheSteamCMDVariant(t *testing.T) {
 		t.Errorf("got %+v", v)
 	}
 }
-
-func TestOneOptionPerImageThenSteamCMDRecommended(t *testing.T) {
-	v := oneOptionPerImage([]variant{{
-		ID: "dedicated", Title: "Example Dedicated Server", Recommended: true, SteamAppID: "1000000",
-		Images:   withSteamCMD([]string{"someone/example-server"}, true),
-		Verified: []string{"image someone/example-server exists", "Steam app 1000000 is \"Example Dedicated Server\""},
-	}})
-	recommend(v)
-	if len(v) != 2 {
-		t.Fatalf("want one option per image, got %+v", v)
-	}
-	steam, image := v[0], v[1]
-	if steam.Title != "Example Dedicated Server (SteamCMD)" || !steam.Recommended || steam.SteamAppID != "1000000" || len(steam.Images) != 1 {
-		t.Errorf("SteamCMD option: %+v", steam)
-	}
-	if image.Title != "Example Dedicated Server (image someone/example-server)" || image.Recommended || image.SteamAppID != "" {
-		t.Errorf("image option: %+v", image)
-	}
-	for _, line := range steam.Verified {
-		if line == "image someone/example-server exists" {
-			t.Error("SteamCMD option lists the other option's image check")
-		}
-	}
-}