Centralize GPT-5 temperature override into llmutils.ResolveTemperature

Eliminates identical temperature resolution logic duplicated in
hexaiaction, hexaicli, and lsp packages.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

2 files changed, 116 insertions, 0 deletions

diff --git a/internal/llmutils/temperature.go b/internal/llmutils/temperature.go
new file mode 100644
index 0000000..8e10c66
--- /dev/null
+++ b/internal/llmutils/temperature.go
@@ -0,0 +1,37 @@
+// Package llmutils provides shared utilities for LLM configuration.
+// ResolveTemperature centralizes the GPT-5 temperature override logic
+// that was previously duplicated across hexaiaction, hexaicli, and lsp.
+package llmutils
+
+import "strings"
+
+// isGPT5 returns true when the model name indicates an OpenAI GPT-5 variant.
+func isGPT5(provider, model string) bool {
+	return provider == "openai" &&
+		strings.HasPrefix(strings.ToLower(model), "gpt-5")
+}
+
+// ResolveTemperature picks the effective temperature from an optional
+// per-surface override (entryTemp) or the global coding temperature
+// (codingTemp). For OpenAI GPT-5 models the default coding temperature
+// of 0.2 is automatically raised to 1.0, and when no temperature is
+// configured at all GPT-5 defaults to 1.0.
+//
+// Returns (temperature, true) when a value was resolved, or (0, false)
+// when no temperature should be sent (let the provider choose).
+func ResolveTemperature(provider, model string, entryTemp, codingTemp *float64) (float64, bool) {
+	if entryTemp != nil {
+		return *entryTemp, true
+	}
+	if codingTemp != nil {
+		temp := *codingTemp
+		if isGPT5(provider, model) && temp == 0.2 {
+			temp = 1.0
+		}
+		return temp, true
+	}
+	if isGPT5(provider, model) {
+		return 1.0, true
+	}
+	return 0, false
+}
diff --git a/internal/llmutils/temperature_test.go b/internal/llmutils/temperature_test.go
new file mode 100644
index 0000000..2c4089e
--- /dev/null
+++ b/internal/llmutils/temperature_test.go
@@ -0,0 +1,79 @@
+package llmutils
+
+import "testing"
+
+func floatPtr(v float64) *float64 { return &v }
+
+func TestResolveTemperature_EntryTempTakesPrecedence(t *testing.T) {
+	temp, ok := ResolveTemperature("openai", "gpt-5.0", floatPtr(0.5), floatPtr(0.2))
+	if !ok || temp != 0.5 {
+		t.Fatalf("expected entry temp 0.5, got %v ok=%v", temp, ok)
+	}
+}
+
+func TestResolveTemperature_CodingTempUsed(t *testing.T) {
+	temp, ok := ResolveTemperature("openai", "gpt-4.1", nil, floatPtr(0.3))
+	if !ok || temp != 0.3 {
+		t.Fatalf("expected coding temp 0.3, got %v ok=%v", temp, ok)
+	}
+}
+
+func TestResolveTemperature_GPT5UpgradesDefault02(t *testing.T) {
+	temp, ok := ResolveTemperature("openai", "gpt-5.1", nil, floatPtr(0.2))
+	if !ok || temp != 1.0 {
+		t.Fatalf("expected upgraded temp 1.0 for gpt-5 with 0.2, got %v ok=%v", temp, ok)
+	}
+}
+
+func TestResolveTemperature_GPT5DefaultWhenNoTemp(t *testing.T) {
+	temp, ok := ResolveTemperature("openai", "gpt-5.0-preview", nil, nil)
+	if !ok || temp != 1.0 {
+		t.Fatalf("expected default 1.0 for gpt-5, got %v ok=%v", temp, ok)
+	}
+}
+
+func TestResolveTemperature_NoTempNonGPT5(t *testing.T) {
+	_, ok := ResolveTemperature("openai", "gpt-4.1", nil, nil)
+	if ok {
+		t.Fatal("expected no temperature for non-gpt-5 with no config")
+	}
+}
+
+func TestResolveTemperature_NonOpenAIProviderNoUpgrade(t *testing.T) {
+	temp, ok := ResolveTemperature("anthropic", "gpt-5.0", nil, floatPtr(0.2))
+	if !ok || temp != 0.2 {
+		t.Fatalf("expected 0.2 for non-openai provider, got %v ok=%v", temp, ok)
+	}
+}
+
+func TestResolveTemperature_GPT5CodingTempNon02NotUpgraded(t *testing.T) {
+	temp, ok := ResolveTemperature("openai", "gpt-5.0", nil, floatPtr(0.7))
+	if !ok || temp != 0.7 {
+		t.Fatalf("expected 0.7 (no upgrade for non-0.2), got %v ok=%v", temp, ok)
+	}
+}
+
+func TestResolveTemperature_CaseInsensitiveModel(t *testing.T) {
+	temp, ok := ResolveTemperature("openai", "GPT-5.0", nil, nil)
+	if !ok || temp != 1.0 {
+		t.Fatalf("expected 1.0 for case-insensitive GPT-5, got %v ok=%v", temp, ok)
+	}
+}
+
+func TestIsGPT5(t *testing.T) {
+	tests := []struct {
+		provider, model string
+		want            bool
+	}{
+		{"openai", "gpt-5.0", true},
+		{"openai", "GPT-5.1-preview", true},
+		{"openai", "gpt-4.1", false},
+		{"anthropic", "gpt-5.0", false},
+		{"openai", "", false},
+	}
+	for _, tt := range tests {
+		if got := isGPT5(tt.provider, tt.model); got != tt.want {
+			t.Errorf("isGPT5(%q, %q) = %v, want %v", tt.provider, tt.model, got, tt.want)
+		}
+	}
+}