fix(claude): 🐛 补齐 thinking block binding beta

Co-authored-by: Wine Fox <fox@ling.plus>

backend/internal/pkg/claude/constants.go

@@ -20,11 +20,12 @@ const (
 	BetaFastMode                 = "fast-mode-2026-02-01"
 
 	// 新增（对齐官方 CLI 2.1.9x 以来的流量）
-	BetaPromptCachingScope = "prompt-caching-scope-2026-01-05"
-	BetaEffort             = "effort-2025-11-24"
-	BetaRedactThinking     = "redact-thinking-2026-02-12"
-	BetaContextManagement  = "context-management-2025-06-27"
-	BetaExtendedCacheTTL   = "extended-cache-ttl-2025-04-11"
+	BetaPromptCachingScope      = "prompt-caching-scope-2026-01-05"
+	BetaEffort                  = "effort-2025-11-24"
+	BetaRedactThinking          = "redact-thinking-2026-02-12"
+	BetaContextManagement       = "context-management-2025-06-27"
+	BetaThinkingBindingControls = "thinking-binding-controls-2026-08-01"
+	BetaExtendedCacheTTL        = "extended-cache-ttl-2025-04-11"
 
 	// server-side refusal fallback beta 字段族（beta Messages API 专有）。
 	// 客户端（Claude Code / SDK / OpenCode 等）会默认透传 body.fallbacks /
@@ -99,6 +100,7 @@ func FullClaudeCodeMimicryBetas() []string {
 		BetaPromptCachingScope,
 		BetaEffort,
 		BetaContextManagement,
+		BetaThinkingBindingControls,
 		BetaExtendedCacheTTL,
 	}
 }

backend/internal/service/gateway_context_management_test.go

@@ -114,6 +114,23 @@ func TestSanitizeAnthropicBodyForBetaTokens_EmptyBody(t *testing.T) {
 	require.Empty(t, out)
 }
 
+func TestSanitizeAnthropicBodyForBetaTokens_ThinkingBlockBindingKeptWhenBetaPresent(t *testing.T) {
+	body := []byte(`{"model":"claude-fable-5-1","thinking":{"type":"adaptive","display":"summarized","block_binding":{"prefix_mismatch_behavior":"drop_block"}},"messages":[]}`)
+	out, changed := sanitizeAnthropicBodyForBetaTokens(body, claude.BetaThinkingBindingControls)
+	require.False(t, changed)
+	require.Equal(t, "drop_block",
+		gjson.GetBytes(out, "thinking.block_binding.prefix_mismatch_behavior").String())
+}
+
+func TestSanitizeAnthropicBodyForBetaTokens_ThinkingBlockBindingStrippedWhenBetaMissing(t *testing.T) {
+	body := []byte(`{"model":"claude-fable-5-1","thinking":{"type":"adaptive","display":"summarized","block_binding":{"prefix_mismatch_behavior":"drop_block"}},"messages":[]}`)
+	out, changed := sanitizeAnthropicBodyForBetaTokens(body, claude.BetaContextManagement)
+	require.True(t, changed)
+	require.False(t, gjson.GetBytes(out, "thinking.block_binding").Exists())
+	require.Equal(t, "adaptive", gjson.GetBytes(out, "thinking.type").String())
+	require.Equal(t, "summarized", gjson.GetBytes(out, "thinking.display").String())
+}
+
 // ★ 关键回归断言：能力维度 sanitize 解决了 "真 CC + haiku" 路径的过度删除问题。
 // 真实 Claude Code CLI 2.1.87+ 客户端 header 含 context-management beta；
 // 即使 model 是 haiku，sanitize 也不应剥离功能字段。
@@ -145,6 +162,8 @@ func TestComputeFinalAnthropicBeta_OAuthMimic_NonHaiku_IncludesContextManagement
 		"OAuth mimic non-haiku 必须注入完整 CC mimicry beta，含 context-management-2025-06-27")
 	require.True(t, anthropicBetaTokensContains(final, claude.BetaOAuth))
 	require.True(t, anthropicBetaTokensContains(final, claude.BetaClaudeCode))
+	require.True(t, anthropicBetaTokensContains(final, claude.BetaThinkingBindingControls),
+		"OAuth mimic 必须注入 thinking block binding 所需的 beta")
 }
 
 func TestComputeFinalAnthropicBeta_OAuthMimic_Haiku_IncludesFullClaudeCodeBetas(t *testing.T) {

backend/internal/service/gateway_request.go

@@ -912,6 +912,12 @@ const anthropicBetaContextManagementToken = "context-management-2025-06-27"
 //     FullClaudeCodeMimicryBetas 覆盖客户端 beta（该列表不含 fallback beta），
 //     若不 strip，body 字段与 header 不对称 → 所有模型 400
 //
+// thinking.block_binding 场景：
+//   - Claude Fable 5.1 的会话前缀绑定控制受
+//     `thinking-binding-controls-2026-08-01` beta 保护
+//   - 缺 token 时上游拒收：
+//     "thinking.adaptive.block_binding: Extra inputs are not permitted"
+//
 // 本函数按最终发送的 anthropic-beta header 决定是否保留 body 中的上述字段：
 // 缺对应 beta token → strip；客户端 header 已带对应 beta → 保留（不过度删除）。
 // 这将限制完全建立在 "能力维度" 上，与 model 名 / token type / mimicry 子路径无关。
@@ -935,6 +941,13 @@ func sanitizeAnthropicBodyForBetaTokens(body []byte, anthropicBetaHeader string)
 		body, changed = b, true
 	}
 
+	// thinking.block_binding：需要 thinking-binding-controls beta。
+	if b, deleted := stripAnthropicBodyFieldUnlessBeta(
+		body, "thinking.block_binding", anthropicBetaHeader, claude.BetaThinkingBindingControls,
+	); deleted {
+		body, changed = b, true
+	}
+
 	// fallbacks：server-side refusal fallback，仅接受 server-side-fallback beta。
 	if b, deleted := stripAnthropicBodyFieldUnlessBeta(
 		body, "fallbacks", anthropicBetaHeader, claude.BetaServerSideFallback,