refactor: decouple claude max cache policy and add tokenizer

backend/internal/service/claude_max_simulation_test.go

@@ -1,6 +1,9 @@
 package service
 
-import "testing"
+import (
+	"strings"
+	"testing"
+)
 
 func TestProjectUsageToClaudeMax1H_Conservation(t *testing.T) {
 	usage := &ClaudeUsage{
@@ -13,8 +16,18 @@ func TestProjectUsageToClaudeMax1H_Conservation(t *testing.T) {
 		Model: "claude-sonnet-4-5",
 		Messages: []any{
 			map[string]any{
-				"role":    "user",
-				"content": "请帮我总结这段代码并给出优化建议",
+				"role": "user",
+				"content": []any{
+					map[string]any{
+						"type":          "text",
+						"text":          strings.Repeat("cached context ", 200),
+						"cache_control": map[string]any{"type": "ephemeral"},
+					},
+					map[string]any{
+						"type": "text",
+						"text": "summarize quickly",
+					},
+				},
 			},
 		},
 	}
@@ -34,6 +47,9 @@ func TestProjectUsageToClaudeMax1H_Conservation(t *testing.T) {
 	if usage.InputTokens <= 0 || usage.InputTokens >= 1200 {
 		t.Fatalf("simulated input out of range, got=%d", usage.InputTokens)
 	}
+	if usage.InputTokens > 100 {
+		t.Fatalf("simulated input should stay near cache breakpoint tail, got=%d", usage.InputTokens)
+	}
 	if usage.CacheCreation1hTokens <= 0 {
 		t.Fatalf("cache_creation_1h should be > 0, got=%d", usage.CacheCreation1hTokens)
 	}
@@ -42,22 +58,29 @@ func TestProjectUsageToClaudeMax1H_Conservation(t *testing.T) {
 	}
 }
 
-func TestComputeClaudeMaxSimulatedInputTokens_Deterministic(t *testing.T) {
+func TestComputeClaudeMaxProjectedInputTokens_Deterministic(t *testing.T) {
 	parsed := &ParsedRequest{
 		Model: "claude-opus-4-5",
 		Messages: []any{
 			map[string]any{
 				"role": "user",
 				"content": []any{
-					map[string]any{"type": "text", "text": "请整理以下日志并定位错误根因"},
-					map[string]any{"type": "tool_use", "name": "grep_logs"},
+					map[string]any{
+						"type":          "text",
+						"text":          "build context",
+						"cache_control": map[string]any{"type": "ephemeral"},
+					},
+					map[string]any{
+						"type": "text",
+						"text": "what is failing now",
+					},
 				},
 			},
 		},
 	}
 
-	got1 := computeClaudeMaxSimulatedInputTokens(4096, parsed)
-	got2 := computeClaudeMaxSimulatedInputTokens(4096, parsed)
+	got1 := computeClaudeMaxProjectedInputTokens(4096, parsed)
+	got2 := computeClaudeMaxProjectedInputTokens(4096, parsed)
 	if got1 != got2 {
 		t.Fatalf("non-deterministic input tokens: %d != %d", got1, got2)
 	}
@@ -78,13 +101,54 @@ func TestShouldSimulateClaudeMaxUsage(t *testing.T) {
 				CacheCreation1hTokens:    0,
 			},
 		},
+		ParsedRequest: &ParsedRequest{
+			Messages: []any{
+				map[string]any{
+					"role": "user",
+					"content": []any{
+						map[string]any{
+							"type":          "text",
+							"text":          "cached",
+							"cache_control": map[string]any{"type": "ephemeral"},
+						},
+						map[string]any{
+							"type": "text",
+							"text": "tail",
+						},
+					},
+				},
+			},
+		},
 		APIKey: &APIKey{Group: group},
 	}
 
 	if !shouldSimulateClaudeMaxUsage(input) {
-		t.Fatalf("expected simulate=true for claude group without cache creation")
+		t.Fatalf("expected simulate=true for claude group with cache signal")
 	}
 
+	input.ParsedRequest = &ParsedRequest{
+		Messages: []any{
+			map[string]any{"role": "user", "content": "no cache signal"},
+		},
+	}
+	if shouldSimulateClaudeMaxUsage(input) {
+		t.Fatalf("expected simulate=false when request has no cache signal")
+	}
+
+	input.ParsedRequest = &ParsedRequest{
+		Messages: []any{
+			map[string]any{
+				"role": "user",
+				"content": []any{
+					map[string]any{
+						"type":          "text",
+						"text":          "cached",
+						"cache_control": map[string]any{"type": "ephemeral"},
+					},
+				},
+			},
+		},
+	}
 	input.Result.Usage.CacheCreationInputTokens = 100
 	if shouldSimulateClaudeMaxUsage(input) {
 		t.Fatalf("expected simulate=false when cache creation already exists")