feat(gateway): adapt Claude Haiku 5.5

Closes #7919. Wire claude-haiku-5-5 (released 2026-10-07) across model
registry, effort catalog, pricing, billing, validation and Codex
descriptors, following the opus-5-5/sonnet-5-5 template and the official
migration guide + overview specs.

- registry: DefaultModels entry (fixed ID, no date suffix per guide)
- effort: full low/medium/high/xhigh/max family + IsHaiku55 +
  claude-haiku-5.5 dotted normalization (official default: medium)
- pricing catalog: 1M/128k limits, base (<=100k) prices and
  *_above_100k_tokens absolute prices; the existing ladder derivation
  yields threshold=100000 with uniform 5x multipliers, matching the
  official two-tier table exactly (cache tiers follow input x5)
- billing/pricing fallbacks carry the same tier so a missing catalog
  entry can never silently bill >100k prompts at base rate
- validation: adaptive-only thinking (enabled always 400; disabled 400
  at xhigh/max), sonnet-style sampling locks, temp+top_p combo rejected,
  forced tool_choice explicitly allowed (differs from opus/sonnet)
- oauth mimicry: skip temperature:1 top-up when top_p is present on
  sampling-locked models (sonnet-5-5 included), otherwise the gateway
  manufactures the temp+top_p 400 itself
- toolset beta filter + Codex 1M context cover haiku-5-5
- Bedrock/Antigravity mappings intentionally left out (no 5.5 entries
  exist there at all, same as opus-5-5); Vertex passes the fixed ID
  through untouched

backend/internal/pkg/claude/constants.go

@@ -223,6 +223,12 @@ var DefaultModels = []Model{
 		DisplayName: "Claude Haiku 4.5",
 		CreatedAt:   "2025-10-01T00:00:00Z",
 	},
+	{
+		ID:          "claude-haiku-5-5",
+		Type:        "model",
+		DisplayName: "Claude Haiku 5.5",
+		CreatedAt:   "2026-10-07T00:00:00Z",
+	},
 }
 
 // DefaultModelIDs 返回默认模型的 ID 列表

backend/internal/pkg/claude/constants_model_test.go

@@ -43,3 +43,16 @@ func TestDefaultModelsContainsSonnet55(t *testing.T) {
 	}
 	t.Fatal("claude-sonnet-5-5 missing from DefaultModels")
 }
+
+func TestDefaultModelsContainsHaiku55(t *testing.T) {
+	t.Parallel()
+
+	for _, model := range DefaultModels {
+		if model.ID == "claude-haiku-5-5" {
+			require.Equal(t, "Claude Haiku 5.5", model.DisplayName)
+			require.Equal(t, "2026-10-07T00:00:00Z", model.CreatedAt)
+			return
+		}
+	}
+	t.Fatal("claude-haiku-5-5 missing from DefaultModels")
+}

backend/internal/pkg/claude/effort_catalog.go

@@ -27,6 +27,7 @@ var effortFamilies = []struct {
 	{family: "claude-opus-4-5", levels: effortLowMediumHigh},
 	{family: "claude-opus-5-5", levels: effortLowMediumHighXHighMax},
 	{family: "claude-opus-5", levels: effortLowMediumHighXHighMax},
+	{family: "claude-haiku-5-5", levels: effortLowMediumHighXHighMax},
 }
 
 // EffortLevelsForModel returns the output_config.effort values accepted by a
@@ -51,6 +52,11 @@ func IsSonnet55(model string) bool {
 	return normalizeEffortModelID(model) == "claude-sonnet-5-5"
 }
 
+// IsHaiku55 identifies the fixed Haiku 5.5 ID after provider/local suffix normalization.
+func IsHaiku55(model string) bool {
+	return normalizeEffortModelID(model) == "claude-haiku-5-5"
+}
+
 func normalizeEffortModelID(model string) string {
 	id := strings.ToLower(strings.TrimSpace(model))
 	id = strings.TrimPrefix(id, "models/")
@@ -70,6 +76,9 @@ func normalizeEffortModelID(model string) string {
 	if id == "claude-sonnet-5.5" {
 		id = "claude-sonnet-5-5"
 	}
+	if id == "claude-haiku-5.5" {
+		id = "claude-haiku-5-5"
+	}
 	if mapped, ok := ModelIDReverseOverrides[id]; ok {
 		id = mapped
 	}

backend/internal/pkg/claude/effort_catalog_test.go

@@ -18,6 +18,9 @@ func TestEffortLevelsForModel(t *testing.T) {
 		{model: "claude-opus-5", want: []string{"low", "medium", "high", "xhigh", "max"}},
 		{model: "anthropic/claude-opus-5.5", want: []string{"low", "medium", "high", "xhigh", "max"}},
 		{model: "claude-sonnet-5-5", want: []string{"low", "medium", "high", "xhigh", "max"}},
+		{model: "claude-haiku-5-5", want: []string{"low", "medium", "high", "xhigh", "max"}},
+		{model: "anthropic/claude-haiku-5.5", want: []string{"low", "medium", "high", "xhigh", "max"}},
+		{model: "us.anthropic.claude-haiku-5-5", want: []string{"low", "medium", "high", "xhigh", "max"}},
 		{model: "us.anthropic.claude-sonnet-5-5", want: []string{"low", "medium", "high", "xhigh", "max"}},
 		{model: "claude-opus-4-5-20251101", want: []string{"low", "medium", "high"}},
 		{model: "claude-haiku-4-5-20251001", want: nil},
@@ -57,3 +60,19 @@ func TestIsSonnet55(t *testing.T) {
 		require.False(t, IsSonnet55(model), model)
 	}
 }
+
+func TestIsHaiku55(t *testing.T) {
+	t.Parallel()
+	for _, model := range []string{
+		"claude-haiku-5-5",
+		"anthropic/claude-haiku-5.5",
+		"anthropic.claude-haiku-5-5",
+		"us.anthropic.claude-haiku-5-5",
+		"global.anthropic.claude-haiku-5-5-thinking",
+	} {
+		require.True(t, IsHaiku55(model), model)
+	}
+	for _, model := range []string{"claude-haiku-5", "claude-haiku-4-5", "claude-haiku-4-5-20251001", "claude-sonnet-5-5", "claude-opus-5-5"} {
+		require.False(t, IsHaiku55(model), model)
+	}
+}