fix(pricing): ship claude-opus-4-8 fallback rates

Opus 4.8 launched at the same rates as Opus 4.6/4.7 ($5/$25 in/out,
$6.25/$0.50 cache create/read) but is not yet in the LiteLLM catalog,
so the exact-match pricing lookup returned zero rates and usage showed
$0 in `usage daily`.

Add a claude-opus-4-8 fallback entry and bump FallbackVersion so the
startup seeder re-upserts it. The async LiteLLM refresh leaves the row
untouched since the upstream catalog has no opus-4-8 key yet.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: wesm

internal/pricing/fallback.go

@@ -2,11 +2,11 @@ package pricing
 
 // FallbackVersion must be bumped whenever FallbackPricing
 // rates change so the startup seeder knows to re-upsert.
-const FallbackVersion = "2026-04-13"
+const FallbackVersion = "2026-05-28"
 
 // FallbackPricing returns hardcoded pricing for key Claude
 // models. Used when the LiteLLM fetch fails.
-// Prices in USD per million tokens, current as of 2026-04.
+// Prices in USD per million tokens, current as of 2026-05.
 func FallbackPricing() []ModelPricing {
 	return []ModelPricing{
 		// Current model names (used by Claude Code / Codex)
@@ -24,6 +24,16 @@ func FallbackPricing() []ModelPricing {
 			CacheCreationPerMTok: 6.25,
 			CacheReadPerMTok:     0.50,
 		},
+		{
+			// Opus 4.8 launched at the Opus 4.6/4.7 rates and is
+			// not yet in the LiteLLM catalog, so it ships here so
+			// usage is priced until LiteLLM adds it.
+			ModelPattern:         "claude-opus-4-8",
+			InputPerMTok:         5.0,
+			OutputPerMTok:        25.0,
+			CacheCreationPerMTok: 6.25,
+			CacheReadPerMTok:     0.50,
+		},
 		{
 			ModelPattern:         "claude-haiku-4-5-20251001",
 			InputPerMTok:         1.0,

internal/pricing/fallback_test.go

@@ -28,3 +28,27 @@ func TestFallbackPricing_Opus46Rates(t *testing.T) {
 	}
 	assert.Equal(t, want, *got)
 }
+
+func TestFallbackPricing_Opus48Rates(t *testing.T) {
+	prices := FallbackPricing()
+	var got *ModelPricing
+	for i := range prices {
+		if prices[i].ModelPattern == "claude-opus-4-8" {
+			got = &prices[i]
+			break
+		}
+	}
+	require.NotNil(t, got, "claude-opus-4-8 entry missing from FallbackPricing")
+
+	// Opus 4.8 launched at the same rates as Opus 4.6/4.7 and is
+	// not yet in the LiteLLM catalog, so the shipped fallback must
+	// price it at the current Opus tier.
+	want := ModelPricing{
+		ModelPattern:         "claude-opus-4-8",
+		InputPerMTok:         5.0,
+		OutputPerMTok:        25.0,
+		CacheCreationPerMTok: 6.25,
+		CacheReadPerMTok:     0.50,
+	}
+	assert.Equal(t, want, *got)
+}

internal/pricing/litellm_test.go

@@ -97,6 +97,7 @@ func TestFallbackPricing(t *testing.T) {
 	required := map[string]bool{
 		"claude-sonnet-4-6":         false,
 		"claude-opus-4-6":           false,
+		"claude-opus-4-8":           false,
 		"claude-haiku-4-5-20251001": false,
 		"claude-sonnet-4-20250514":  false,
 		"claude-opus-4-20250514":    false,