Fix per-agent default models to use valid upstream ids

Gemini CLI 0.37.x only registers `gemini-3-flash-base` (and friends);
the previous examples pointed users at `gemini3-flash`, which 404s as
ModelNotFoundError. Introduce DefaultAgentModels so `sah run` picks
`codex=gpt-5.4-mini`, `gemini=gemini-3-flash-base`, `claude=sonnet`
when neither --model nor --models is supplied, and align every help
string and example accordingly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: akcorca

cmd/sah/main.go

@@ -72,7 +72,7 @@ Commands:
 Examples:
   sah auth login
   sah run --rotate-installed
-  sah run --agents codex,gemini,claude --models codex=gpt-5.4-mini,gemini=gemini3-flash,claude=sonnet
+  sah run --agents codex,gemini,claude --models codex=gpt-5.4-mini,gemini=gemini-3-flash-base,claude=sonnet
   sah daemon install --agents codex,claude --interval 30m
   sah me
 `)
@@ -173,7 +173,7 @@ func runCmd(args []string) error {
 	agents := fs.String("agents", "", "Comma-separated round-robin agent order, e.g. codex,gemini,claude")
 	rotateInstalled := fs.Bool("rotate-installed", false, "Rotate through every supported agent CLI installed on this Mac")
 	model := fs.String("model", "", "Optional model override passed to the agent CLI")
-	models := fs.String("models", "", "Per-agent model overrides, e.g. codex=gpt-5.4-mini,gemini=gemini3-flash,claude=sonnet")
+	models := fs.String("models", "", "Per-agent model overrides, e.g. codex=gpt-5.4-mini,gemini=gemini-3-flash-base,claude=sonnet")
 	interval := fs.String("interval", "", "Polling interval")
 	timeout := fs.String("timeout", "", "Per-assignment agent timeout")
 	taskType := fs.String("task-type", "", "Optional task type filter")
@@ -351,7 +351,7 @@ func parseDaemonInstallOptions(args []string) (daemonInstallOptions, error) {
 	fs.StringVar(&options.agents, "agents", "", "Comma-separated round-robin agent order for the daemon")
 	fs.BoolVar(&options.rotateInstalled, "rotate-installed", false, "Rotate through every installed supported agent CLI")
 	fs.StringVar(&options.model, "model", "", "Default model override")
-	fs.StringVar(&options.models, "models", "", "Per-agent model overrides, e.g. codex=gpt-5.4-mini,gemini=gemini3-flash,claude=sonnet")
+	fs.StringVar(&options.models, "models", "", "Per-agent model overrides, e.g. codex=gpt-5.4-mini,gemini=gemini-3-flash-base,claude=sonnet")
 	fs.StringVar(&options.interval, "interval", "", "Default polling interval")
 	fs.StringVar(&options.timeout, "timeout", "", "Default per-assignment timeout")
 	fs.StringVar(&options.baseURL, "base-url", "", "SCIENCE@home base URL")

internal/sah/agent_selection.go

@@ -140,11 +140,29 @@ func MergeAgentModels(base map[string]string, overrides map[string]string) map[s
 	return merged
 }
 
+// DefaultAgentModels is the per-agent model used when neither --models nor
+// --model is supplied. Keep these in sync with what each upstream CLI actually
+// accepts today: Gemini CLI 0.37.x only exposes `gemini-3-flash-base` (and
+// friends) -- `gemini3-flash` / `gemini-3-flash` are NOT valid ids and cause
+// ModelNotFoundError.
+var DefaultAgentModels = map[string]string{
+	"codex":  "gpt-5.4-mini",
+	"gemini": "gemini-3-flash-base",
+	"claude": "sonnet",
+}
+
 func ModelForAgent(agentName string, fallback string, overrides map[string]string) string {
-	if model, ok := normalizeAgentModels(overrides)[normalizeAgentName(agentName)]; ok {
+	name := normalizeAgentName(agentName)
+	if model, ok := normalizeAgentModels(overrides)[name]; ok {
+		return model
+	}
+	if trimmed := strings.TrimSpace(fallback); trimmed != "" {
+		return trimmed
+	}
+	if model, ok := DefaultAgentModels[name]; ok {
 		return model
 	}
-	return strings.TrimSpace(fallback)
+	return ""
 }
 
 func DescribeAgentMode(config Config, options WorkerOptions) string {

internal/sah/agent_selection_test.go

@@ -10,11 +10,11 @@ func TestParseAgentList(t *testing.T) {
 }
 
 func TestParseAgentModels(t *testing.T) {
-	models, err := ParseAgentModels("codex=gpt-5.4-mini, gemini=gemini3-flash, claude=sonnet")
+	models, err := ParseAgentModels("codex=gpt-5.4-mini, gemini=gemini-3-flash-base, claude=sonnet")
 	if err != nil {
 		t.Fatalf("ParseAgentModels returned error: %v", err)
 	}
-	if models["codex"] != "gpt-5.4-mini" || models["gemini"] != "gemini3-flash" || models["claude"] != "sonnet" {
+	if models["codex"] != "gpt-5.4-mini" || models["gemini"] != "gemini-3-flash-base" || models["claude"] != "sonnet" {
 		t.Fatalf("unexpected models: %#v", models)
 	}
 }
@@ -25,3 +25,23 @@ func TestModelForAgentPrefersOverride(t *testing.T) {
 		t.Fatalf("unexpected model: %q", model)
 	}
 }
+
+func TestModelForAgentFallsBackToGlobal(t *testing.T) {
+	model := ModelForAgent("gemini", "some-global", nil)
+	if model != "some-global" {
+		t.Fatalf("expected global fallback, got %q", model)
+	}
+}
+
+func TestModelForAgentUsesBuiltinDefaults(t *testing.T) {
+	cases := map[string]string{
+		"codex":  "gpt-5.4-mini",
+		"gemini": "gemini-3-flash-base",
+		"claude": "sonnet",
+	}
+	for agent, want := range cases {
+		if got := ModelForAgent(agent, "", nil); got != want {
+			t.Fatalf("%s: expected %q, got %q", agent, want, got)
+		}
+	}
+}