fix(providers): omit temperature for Claude Opus/Sonnet 4.6+

internal/providers/adapter_anthropic_test.go

@@ -150,6 +150,48 @@ func TestAnthropicAdapterToRequest_Thinking(t *testing.T) {
 	}
 }
 
+func TestAnthropicAdapterToRequest_SkipsTemperatureForClaude46(t *testing.T) {
+	adapter, _ := NewAnthropicAdapter(ProviderConfig{APIKey: "sk-test"})
+
+	for _, model := range []string{"claude-opus-4-6", "claude-sonnet-4-6", "claude-opus-4-7-20260501"} {
+		t.Run(model, func(t *testing.T) {
+			req := ChatRequest{
+				Model:    model,
+				Messages: []Message{{Role: "user", Content: "hi"}},
+				Options:  map[string]any{OptTemperature: 0.7},
+			}
+			data, _, err := adapter.ToRequest(req)
+			if err != nil {
+				t.Fatal(err)
+			}
+			var body map[string]any
+			if err := json.Unmarshal(data, &body); err != nil {
+				t.Fatal(err)
+			}
+			if _, hasTemp := body["temperature"]; hasTemp {
+				t.Errorf("model %q: temperature should be omitted", model)
+			}
+		})
+	}
+
+	req := ChatRequest{
+		Model:    "claude-sonnet-4-5-20250929",
+		Messages: []Message{{Role: "user", Content: "hi"}},
+		Options:  map[string]any{OptTemperature: 0.7},
+	}
+	data, _, err := adapter.ToRequest(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var body map[string]any
+	if err := json.Unmarshal(data, &body); err != nil {
+		t.Fatal(err)
+	}
+	if body["temperature"] != 0.7 {
+		t.Errorf("sonnet 4.5 should keep temperature, got %v", body["temperature"])
+	}
+}
+
 func TestAnthropicAdapterFromResponse_ToolCalls(t *testing.T) {
 	adapter, _ := NewAnthropicAdapter(ProviderConfig{APIKey: "sk-test"})
 

internal/providers/anthropic_request.go

@@ -213,7 +213,9 @@ func (p *AnthropicProvider) buildRequestBody(model string, req ChatRequest, stre
 		body["max_tokens"] = v
 	}
 	if v, ok := req.Options[OptTemperature]; ok {
-		body["temperature"] = v
+		if !anthropicSkipsTemperature(model) {
+			body["temperature"] = v
+		}
 	}
 
 	// Enable extended thinking if thinking_level is set
@@ -234,6 +236,30 @@ func (p *AnthropicProvider) buildRequestBody(model string, req ChatRequest, stre
 	return body
 }
 
+// anthropicSkipsTemperature reports whether the Messages API rejects sampling
+// parameters for this model. Claude Opus/Sonnet 4.6+ and Opus 4.7+ return HTTP
+// 400 when temperature (and top_p/top_k) are included; omit them entirely.
+func anthropicSkipsTemperature(model string) bool {
+	m := strings.ToLower(model)
+	for _, family := range []string{"claude-opus-4-", "claude-sonnet-4-"} {
+		after, ok := strings.CutPrefix(m, family)
+		if !ok {
+			continue
+		}
+		minor := 0
+		for _, c := range after {
+			if c < '0' || c > '9' {
+				break
+			}
+			minor = minor*10 + int(c-'0')
+		}
+		if minor >= 6 {
+			return true
+		}
+	}
+	return false
+}
+
 // anthropicThinkingBudget maps a thinking level to a token budget.
 func anthropicThinkingBudget(level string) int {
 	switch level {