feat(thinking): add adaptive thinking support for Claude models

Add support for Claude's "adaptive" and "auto" thinking modes using `output_config.effort`. Introduce support for new effort level "max" in adaptive thinking. Update thinking logic, validate model capabilities, and extend converters and handling to ensure compatibility with adaptive modes. Adjust static model data with supported levels and refine handling across translators and executors.

internal/registry/model_definitions_static_data.go

@@ -37,7 +37,7 @@ func GetClaudeModels() []*ModelInfo {
 			DisplayName:         "Claude 4.6 Sonnet",
 			ContextLength:       200000,
 			MaxCompletionTokens: 64000,
-			Thinking:            &ThinkingSupport{Min: 1024, Max: 128000, ZeroAllowed: true, DynamicAllowed: false},
+			Thinking:            &ThinkingSupport{Min: 1024, Max: 128000, ZeroAllowed: true, DynamicAllowed: false, Levels: []string{"low", "medium", "high"}},
 		},
 		{
 			ID:                  "claude-opus-4-6",
@@ -49,7 +49,7 @@ func GetClaudeModels() []*ModelInfo {
 			Description:         "Premium model combining maximum intelligence with practical performance",
 			ContextLength:       1000000,
 			MaxCompletionTokens: 128000,
-			Thinking:            &ThinkingSupport{Min: 1024, Max: 128000, ZeroAllowed: true, DynamicAllowed: false},
+			Thinking:            &ThinkingSupport{Min: 1024, Max: 128000, ZeroAllowed: true, DynamicAllowed: false, Levels: []string{"low", "medium", "high", "max"}},
 		},
 		{
 			ID:                  "claude-opus-4-5-20251101",

internal/runtime/executor/claude_executor.go

@@ -634,6 +634,12 @@ func disableThinkingIfToolChoiceForced(body []byte) []byte {
 	if toolChoiceType == "any" || toolChoiceType == "tool" {
 		// Remove thinking configuration entirely to avoid API error
 		body, _ = sjson.DeleteBytes(body, "thinking")
+		// Adaptive thinking may also set output_config.effort; remove it to avoid
+		// leaking thinking controls when tool_choice forces tool use.
+		body, _ = sjson.DeleteBytes(body, "output_config.effort")
+		if oc := gjson.GetBytes(body, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+			body, _ = sjson.DeleteBytes(body, "output_config")
+		}
 	}
 	return body
 }

internal/thinking/apply.go

@@ -353,6 +353,26 @@ func extractClaudeConfig(body []byte) ThinkingConfig {
 	if thinkingType == "disabled" {
 		return ThinkingConfig{Mode: ModeNone, Budget: 0}
 	}
+	if thinkingType == "adaptive" || thinkingType == "auto" {
+		// Claude adaptive thinking uses output_config.effort (low/medium/high/max).
+		// We only treat it as a thinking config when effort is explicitly present;
+		// otherwise we passthrough and let upstream defaults apply.
+		if effort := gjson.GetBytes(body, "output_config.effort"); effort.Exists() && effort.Type == gjson.String {
+			value := strings.ToLower(strings.TrimSpace(effort.String()))
+			if value == "" {
+				return ThinkingConfig{}
+			}
+			switch value {
+			case "none":
+				return ThinkingConfig{Mode: ModeNone, Budget: 0}
+			case "auto":
+				return ThinkingConfig{Mode: ModeAuto, Budget: -1}
+			default:
+				return ThinkingConfig{Mode: ModeLevel, Level: ThinkingLevel(value)}
+			}
+		}
+		return ThinkingConfig{}
+	}
 
 	// Check budget_tokens
 	if budget := gjson.GetBytes(body, "thinking.budget_tokens"); budget.Exists() {

internal/thinking/convert.go

@@ -16,6 +16,9 @@ var levelToBudgetMap = map[string]int{
 	"medium":  8192,
 	"high":    24576,
 	"xhigh":   32768,
+	// "max" is used by Claude adaptive thinking effort. We map it to a large budget
+	// and rely on per-model clamping when converting to budget-only providers.
+	"max": 128000,
 }
 
 // ConvertLevelToBudget converts a thinking level to a budget value.
@@ -31,6 +34,7 @@ var levelToBudgetMap = map[string]int{
 //   - medium  → 8192
 //   - high    → 24576
 //   - xhigh   → 32768
+//   - max     → 128000
 //
 // Returns:
 //   - budget: The converted budget value

internal/thinking/provider/claude/apply.go

@@ -1,8 +1,10 @@
 // Package claude implements thinking configuration scaffolding for Claude models.
 //
-// Claude models use the thinking.budget_tokens format with values in the range
-// 1024-128000. Some Claude models support ZeroAllowed (sonnet-4-5, opus-4-5),
-// while older models do not.
+// Claude models support two thinking control styles:
+//   - Manual thinking: thinking.type="enabled" with thinking.budget_tokens (token budget)
+//   - Adaptive thinking (Claude 4.6): thinking.type="adaptive" with output_config.effort (low/medium/high/max)
+//
+// Some Claude models support ZeroAllowed (sonnet-4-5, opus-4-5), while older models do not.
 // See: _bmad-output/planning-artifacts/architecture.md#Epic-6
 package claude
 
@@ -34,7 +36,11 @@ func init() {
 //   - Budget clamping to model range
 //   - ZeroAllowed constraint enforcement
 //
-// Apply only processes ModeBudget and ModeNone; other modes are passed through unchanged.
+// Apply processes:
+//   - ModeBudget: manual thinking budget_tokens
+//   - ModeLevel: adaptive thinking effort (Claude 4.6)
+//   - ModeAuto: provider default adaptive/manual behavior
+//   - ModeNone: disabled
 //
 // Expected output format when enabled:
 //
@@ -45,6 +51,17 @@ func init() {
 //	  }
 //	}
 //
+// Expected output format for adaptive:
+//
+//	{
+//	  "thinking": {
+//	    "type": "adaptive"
+//	  },
+//	  "output_config": {
+//	    "effort": "high"
+//	  }
+//	}
+//
 // Expected output format when disabled:
 //
 //	{
@@ -60,30 +77,91 @@ func (a *Applier) Apply(body []byte, config thinking.ThinkingConfig, modelInfo *
 		return body, nil
 	}
 
-	// Only process ModeBudget and ModeNone; other modes pass through
-	// (caller should use ValidateConfig first to normalize modes)
-	if config.Mode != thinking.ModeBudget && config.Mode != thinking.ModeNone {
-		return body, nil
-	}
-
 	if len(body) == 0 || !gjson.ValidBytes(body) {
 		body = []byte(`{}`)
 	}
 
-	// Budget is expected to be pre-validated by ValidateConfig (clamped, ZeroAllowed enforced)
-	// Decide enabled/disabled based on budget value
-	if config.Budget == 0 {
+	supportsAdaptive := modelInfo != nil && modelInfo.Thinking != nil && len(modelInfo.Thinking.Levels) > 0
+
+	switch config.Mode {
+	case thinking.ModeNone:
 		result, _ := sjson.SetBytes(body, "thinking.type", "disabled")
 		result, _ = sjson.DeleteBytes(result, "thinking.budget_tokens")
+		result, _ = sjson.DeleteBytes(result, "output_config.effort")
+		if oc := gjson.GetBytes(result, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+			result, _ = sjson.DeleteBytes(result, "output_config")
+		}
 		return result, nil
+
+	case thinking.ModeLevel:
+		// Adaptive thinking effort is only valid when the model advertises discrete levels.
+		// (Claude 4.6 uses output_config.effort.)
+		if supportsAdaptive && config.Level != "" {
+			result, _ := sjson.SetBytes(body, "thinking.type", "adaptive")
+			result, _ = sjson.DeleteBytes(result, "thinking.budget_tokens")
+			result, _ = sjson.SetBytes(result, "output_config.effort", string(config.Level))
+			return result, nil
+		}
+
+		// Fallback for non-adaptive Claude models: convert level to budget_tokens.
+		if budget, ok := thinking.ConvertLevelToBudget(string(config.Level)); ok {
+			config.Mode = thinking.ModeBudget
+			config.Budget = budget
+			config.Level = ""
+		} else {
+			return body, nil
+		}
+		fallthrough
+
+	case thinking.ModeBudget:
+		// Budget is expected to be pre-validated by ValidateConfig (clamped, ZeroAllowed enforced).
+		// Decide enabled/disabled based on budget value.
+		if config.Budget == 0 {
+			result, _ := sjson.SetBytes(body, "thinking.type", "disabled")
+			result, _ = sjson.DeleteBytes(result, "thinking.budget_tokens")
+			result, _ = sjson.DeleteBytes(result, "output_config.effort")
+			if oc := gjson.GetBytes(result, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+				result, _ = sjson.DeleteBytes(result, "output_config")
+			}
+			return result, nil
+		}
+
+		result, _ := sjson.SetBytes(body, "thinking.type", "enabled")
+		result, _ = sjson.SetBytes(result, "thinking.budget_tokens", config.Budget)
+		result, _ = sjson.DeleteBytes(result, "output_config.effort")
+		if oc := gjson.GetBytes(result, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+			result, _ = sjson.DeleteBytes(result, "output_config")
+		}
+
+		// Ensure max_tokens > thinking.budget_tokens (Anthropic API constraint).
+		result = a.normalizeClaudeBudget(result, config.Budget, modelInfo)
+		return result, nil
+
+	case thinking.ModeAuto:
+		// For Claude 4.6 models, auto maps to adaptive thinking with upstream defaults.
+		if supportsAdaptive {
+			result, _ := sjson.SetBytes(body, "thinking.type", "adaptive")
+			result, _ = sjson.DeleteBytes(result, "thinking.budget_tokens")
+			// Explicit effort is optional for adaptive thinking; omit it to allow upstream default.
+			result, _ = sjson.DeleteBytes(result, "output_config.effort")
+			if oc := gjson.GetBytes(result, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+				result, _ = sjson.DeleteBytes(result, "output_config")
+			}
+			return result, nil
+		}
+
+		// Legacy fallback: enable thinking without specifying budget_tokens.
+		result, _ := sjson.SetBytes(body, "thinking.type", "enabled")
+		result, _ = sjson.DeleteBytes(result, "thinking.budget_tokens")
+		result, _ = sjson.DeleteBytes(result, "output_config.effort")
+		if oc := gjson.GetBytes(result, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+			result, _ = sjson.DeleteBytes(result, "output_config")
+		}
+		return result, nil
+
+	default:
+		return body, nil
 	}
-
-	result, _ := sjson.SetBytes(body, "thinking.type", "enabled")
-	result, _ = sjson.SetBytes(result, "thinking.budget_tokens", config.Budget)
-
-	// Ensure max_tokens > thinking.budget_tokens (Anthropic API constraint)
-	result = a.normalizeClaudeBudget(result, config.Budget, modelInfo)
-	return result, nil
 }
 
 // normalizeClaudeBudget applies Claude-specific constraints to ensure max_tokens > budget_tokens.
@@ -141,7 +219,7 @@ func (a *Applier) effectiveMaxTokens(body []byte, modelInfo *registry.ModelInfo)
 }
 
 func applyCompatibleClaude(body []byte, config thinking.ThinkingConfig) ([]byte, error) {
-	if config.Mode != thinking.ModeBudget && config.Mode != thinking.ModeNone && config.Mode != thinking.ModeAuto {
+	if config.Mode != thinking.ModeBudget && config.Mode != thinking.ModeNone && config.Mode != thinking.ModeAuto && config.Mode != thinking.ModeLevel {
 		return body, nil
 	}
 
@@ -153,14 +231,36 @@ func applyCompatibleClaude(body []byte, config thinking.ThinkingConfig) ([]byte,
 	case thinking.ModeNone:
 		result, _ := sjson.SetBytes(body, "thinking.type", "disabled")
 		result, _ = sjson.DeleteBytes(result, "thinking.budget_tokens")
+		result, _ = sjson.DeleteBytes(result, "output_config.effort")
+		if oc := gjson.GetBytes(result, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+			result, _ = sjson.DeleteBytes(result, "output_config")
+		}
 		return result, nil
 	case thinking.ModeAuto:
 		result, _ := sjson.SetBytes(body, "thinking.type", "enabled")
 		result, _ = sjson.DeleteBytes(result, "thinking.budget_tokens")
+		result, _ = sjson.DeleteBytes(result, "output_config.effort")
+		if oc := gjson.GetBytes(result, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+			result, _ = sjson.DeleteBytes(result, "output_config")
+		}
+		return result, nil
+	case thinking.ModeLevel:
+		// For user-defined models, interpret ModeLevel as Claude adaptive thinking effort.
+		// Upstream is responsible for validating whether the target model supports it.
+		if config.Level == "" {
+			return body, nil
+		}
+		result, _ := sjson.SetBytes(body, "thinking.type", "adaptive")
+		result, _ = sjson.DeleteBytes(result, "thinking.budget_tokens")
+		result, _ = sjson.SetBytes(result, "output_config.effort", string(config.Level))
 		return result, nil
 	default:
 		result, _ := sjson.SetBytes(body, "thinking.type", "enabled")
 		result, _ = sjson.SetBytes(result, "thinking.budget_tokens", config.Budget)
+		result, _ = sjson.DeleteBytes(result, "output_config.effort")
+		if oc := gjson.GetBytes(result, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+			result, _ = sjson.DeleteBytes(result, "output_config")
+		}
 		return result, nil
 	}
 }

internal/thinking/strip.go

@@ -30,7 +30,7 @@ func StripThinkingConfig(body []byte, provider string) []byte {
 	var paths []string
 	switch provider {
 	case "claude":
-		paths = []string{"thinking"}
+		paths = []string{"thinking", "output_config.effort"}
 	case "gemini":
 		paths = []string{"generationConfig.thinkingConfig"}
 	case "gemini-cli", "antigravity":
@@ -59,5 +59,12 @@ func StripThinkingConfig(body []byte, provider string) []byte {
 	for _, path := range paths {
 		result, _ = sjson.DeleteBytes(result, path)
 	}
+
+	// Avoid leaving an empty output_config object for Claude when effort was the only field.
+	if provider == "claude" {
+		if oc := gjson.GetBytes(result, "output_config"); oc.Exists() && oc.IsObject() && len(oc.Map()) == 0 {
+			result, _ = sjson.DeleteBytes(result, "output_config")
+		}
+	}
 	return result
 }

internal/thinking/suffix.go

@@ -109,7 +109,7 @@ func ParseSpecialSuffix(rawSuffix string) (mode ThinkingMode, ok bool) {
 // ParseLevelSuffix attempts to parse a raw suffix as a discrete thinking level.
 //
 // This function parses the raw suffix content (from ParseSuffix.RawSuffix) as a level.
-// Only discrete effort levels are valid: minimal, low, medium, high, xhigh.
+// Only discrete effort levels are valid: minimal, low, medium, high, xhigh, max.
 // Level matching is case-insensitive.
 //
 // Special values (none, auto) are NOT handled by this function; use ParseSpecialSuffix
@@ -140,6 +140,8 @@ func ParseLevelSuffix(rawSuffix string) (level ThinkingLevel, ok bool) {
 		return LevelHigh, true
 	case "xhigh":
 		return LevelXHigh, true
+	case "max":
+		return LevelMax, true
 	default:
 		return "", false
 	}

internal/thinking/types.go

@@ -54,6 +54,9 @@ const (
 	LevelHigh ThinkingLevel = "high"
 	// LevelXHigh sets extra-high thinking effort
 	LevelXHigh ThinkingLevel = "xhigh"
+	// LevelMax sets maximum thinking effort.
+	// This is currently used by Claude 4.6 adaptive thinking (opus supports "max").
+	LevelMax ThinkingLevel = "max"
 )
 
 // ThinkingConfig represents a unified thinking configuration.

internal/thinking/validate.go

@@ -201,7 +201,7 @@ func convertAutoToMidRange(config ThinkingConfig, support *registry.ThinkingSupp
 }
 
 // standardLevelOrder defines the canonical ordering of thinking levels from lowest to highest.
-var standardLevelOrder = []ThinkingLevel{LevelMinimal, LevelLow, LevelMedium, LevelHigh, LevelXHigh}
+var standardLevelOrder = []ThinkingLevel{LevelMinimal, LevelLow, LevelMedium, LevelHigh, LevelXHigh, LevelMax}
 
 // clampLevel clamps the given level to the nearest supported level.
 // On tie, prefers the lower level.

internal/translator/claude/openai/chat-completions/claude_openai_request.go

@@ -14,6 +14,7 @@ import (
 	"strings"
 
 	"github.com/google/uuid"
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/registry"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/thinking"
 	"github.com/tidwall/gjson"
 	"github.com/tidwall/sjson"
@@ -68,17 +69,63 @@ func ConvertOpenAIRequestToClaude(modelName string, inputRawJSON []byte, stream
 	if v := root.Get("reasoning_effort"); v.Exists() {
 		effort := strings.ToLower(strings.TrimSpace(v.String()))
 		if effort != "" {
-			budget, ok := thinking.ConvertLevelToBudget(effort)
-			if ok {
-				switch budget {
-				case 0:
+			hasLevel := func(levels []string, target string) bool {
+				for _, level := range levels {
+					if strings.EqualFold(strings.TrimSpace(level), target) {
+						return true
+					}
+				}
+				return false
+			}
+			mi := registry.LookupModelInfo(modelName, "claude")
+			supportsAdaptive := mi != nil && mi.Thinking != nil && len(mi.Thinking.Levels) > 0
+			supportsMax := supportsAdaptive && hasLevel(mi.Thinking.Levels, "max")
+
+			// Claude 4.6 supports adaptive thinking with output_config.effort.
+			if supportsAdaptive {
+				switch effort {
+				case "none":
 					out, _ = sjson.Set(out, "thinking.type", "disabled")
-				case -1:
-					out, _ = sjson.Set(out, "thinking.type", "enabled")
+					out, _ = sjson.Delete(out, "thinking.budget_tokens")
+					out, _ = sjson.Delete(out, "output_config.effort")
+				case "auto":
+					out, _ = sjson.Set(out, "thinking.type", "adaptive")
+					out, _ = sjson.Delete(out, "thinking.budget_tokens")
+					out, _ = sjson.Delete(out, "output_config.effort")
 				default:
-					if budget > 0 {
+					// Map non-Claude effort levels into Claude 4.6 effort vocabulary.
+					switch effort {
+					case "minimal":
+						effort = "low"
+					case "xhigh":
+						if supportsMax {
+							effort = "max"
+						} else {
+							effort = "high"
+						}
+					case "max":
+						if !supportsMax {
+							effort = "high"
+						}
+					}
+					out, _ = sjson.Set(out, "thinking.type", "adaptive")
+					out, _ = sjson.Delete(out, "thinking.budget_tokens")
+					out, _ = sjson.Set(out, "output_config.effort", effort)
+				}
+			} else {
+				// Legacy/manual thinking (budget_tokens).
+				budget, ok := thinking.ConvertLevelToBudget(effort)
+				if ok {
+					switch budget {
+					case 0:
+						out, _ = sjson.Set(out, "thinking.type", "disabled")
+					case -1:
 						out, _ = sjson.Set(out, "thinking.type", "enabled")
-						out, _ = sjson.Set(out, "thinking.budget_tokens", budget)
+					default:
+						if budget > 0 {
+							out, _ = sjson.Set(out, "thinking.type", "enabled")
+							out, _ = sjson.Set(out, "thinking.budget_tokens", budget)
+						}
 					}
 				}
 			}

internal/translator/claude/openai/responses/claude_openai-responses_request.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"github.com/google/uuid"
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/registry"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/thinking"
 	"github.com/tidwall/gjson"
 	"github.com/tidwall/sjson"
@@ -56,17 +57,63 @@ func ConvertOpenAIResponsesRequestToClaude(modelName string, inputRawJSON []byte
 	if v := root.Get("reasoning.effort"); v.Exists() {
 		effort := strings.ToLower(strings.TrimSpace(v.String()))
 		if effort != "" {
-			budget, ok := thinking.ConvertLevelToBudget(effort)
-			if ok {
-				switch budget {
-				case 0:
+			hasLevel := func(levels []string, target string) bool {
+				for _, level := range levels {
+					if strings.EqualFold(strings.TrimSpace(level), target) {
+						return true
+					}
+				}
+				return false
+			}
+			mi := registry.LookupModelInfo(modelName, "claude")
+			supportsAdaptive := mi != nil && mi.Thinking != nil && len(mi.Thinking.Levels) > 0
+			supportsMax := supportsAdaptive && hasLevel(mi.Thinking.Levels, "max")
+
+			// Claude 4.6 supports adaptive thinking with output_config.effort.
+			if supportsAdaptive {
+				switch effort {
+				case "none":
 					out, _ = sjson.Set(out, "thinking.type", "disabled")
-				case -1:
-					out, _ = sjson.Set(out, "thinking.type", "enabled")
+					out, _ = sjson.Delete(out, "thinking.budget_tokens")
+					out, _ = sjson.Delete(out, "output_config.effort")
+				case "auto":
+					out, _ = sjson.Set(out, "thinking.type", "adaptive")
+					out, _ = sjson.Delete(out, "thinking.budget_tokens")
+					out, _ = sjson.Delete(out, "output_config.effort")
 				default:
-					if budget > 0 {
+					// Map non-Claude effort levels into Claude 4.6 effort vocabulary.
+					switch effort {
+					case "minimal":
+						effort = "low"
+					case "xhigh":
+						if supportsMax {
+							effort = "max"
+						} else {
+							effort = "high"
+						}
+					case "max":
+						if !supportsMax {
+							effort = "high"
+						}
+					}
+					out, _ = sjson.Set(out, "thinking.type", "adaptive")
+					out, _ = sjson.Delete(out, "thinking.budget_tokens")
+					out, _ = sjson.Set(out, "output_config.effort", effort)
+				}
+			} else {
+				// Legacy/manual thinking (budget_tokens).
+				budget, ok := thinking.ConvertLevelToBudget(effort)
+				if ok {
+					switch budget {
+					case 0:
+						out, _ = sjson.Set(out, "thinking.type", "disabled")
+					case -1:
 						out, _ = sjson.Set(out, "thinking.type", "enabled")
-						out, _ = sjson.Set(out, "thinking.budget_tokens", budget)
+					default:
+						if budget > 0 {
+							out, _ = sjson.Set(out, "thinking.type", "enabled")
+							out, _ = sjson.Set(out, "thinking.budget_tokens", budget)
+						}
 					}
 				}
 			}

internal/translator/codex/claude/codex_claude_request.go

@@ -231,9 +231,22 @@ func ConvertClaudeRequestToCodex(modelName string, inputRawJSON []byte, _ bool)
 				}
 			}
 		case "adaptive", "auto":
-			// Claude adaptive/auto means "enable with max capacity"; keep it as highest level
-			// and let ApplyThinking normalize per target model capability.
-			reasoningEffort = string(thinking.LevelXHigh)
+			// Adaptive thinking can carry an explicit effort in output_config.effort (Claude 4.6).
+			// Preserve it when present; otherwise keep the previous "max capacity" sentinel.
+			effort := ""
+			if v := rootResult.Get("output_config.effort"); v.Exists() && v.Type == gjson.String {
+				effort = strings.ToLower(strings.TrimSpace(v.String()))
+			}
+			switch effort {
+			case "low", "medium", "high":
+				reasoningEffort = effort
+			case "max":
+				reasoningEffort = string(thinking.LevelXHigh)
+			default:
+				// Keep adaptive/auto as a high level sentinel; ApplyThinking resolves it
+				// to model-specific max capability.
+				reasoningEffort = string(thinking.LevelXHigh)
+			}
 		case "disabled":
 			if effort, ok := thinking.ConvertBudgetToLevel(0); ok && effort != "" {
 				reasoningEffort = effort

internal/translator/openai/claude/openai_claude_request.go

@@ -76,9 +76,22 @@ func ConvertClaudeRequestToOpenAI(modelName string, inputRawJSON []byte, stream
 					}
 				}
 			case "adaptive", "auto":
-				// Claude adaptive/auto means "enable with max capacity"; keep it as highest level
-				// and let ApplyThinking normalize per target model capability.
-				out, _ = sjson.Set(out, "reasoning_effort", string(thinking.LevelXHigh))
+				// Adaptive thinking can carry an explicit effort in output_config.effort (Claude 4.6).
+				// Preserve it when present; otherwise keep the previous "max capacity" sentinel.
+				effort := ""
+				if v := root.Get("output_config.effort"); v.Exists() && v.Type == gjson.String {
+					effort = strings.ToLower(strings.TrimSpace(v.String()))
+				}
+				switch effort {
+				case "low", "medium", "high":
+					out, _ = sjson.Set(out, "reasoning_effort", effort)
+				case "max":
+					out, _ = sjson.Set(out, "reasoning_effort", string(thinking.LevelXHigh))
+				default:
+					// Keep adaptive/auto as a high level sentinel; ApplyThinking resolves it
+					// to model-specific max capability.
+					out, _ = sjson.Set(out, "reasoning_effort", string(thinking.LevelXHigh))
+				}
 			case "disabled":
 				if effort, ok := thinking.ConvertBudgetToLevel(0); ok && effort != "" {
 					out, _ = sjson.Set(out, "reasoning_effort", effort)