chore: default OpenAI model to gpt-6-luna

.env.example

@@ -19,7 +19,7 @@ SENTRY_DSN=https://275ad5c45f7eb6454f31ae6a8c325f46@o4509941888122880.ingest.us.
 
 # OpenAI (default if no provider is forced)
 # OPENAI_API_KEY=your-openai-api-key
-# OPENAI_MODEL=gpt-5.4-nano
+# OPENAI_MODEL=gpt-6-luna
 
 # Anthropic (Claude)
 # ANTHROPIC_API_KEY=your-anthropic-api-key   # CLAUDE_API_KEY also accepted

AGENTS.md

@@ -38,7 +38,7 @@ go test ./internal/domain/categorizer/... -v   # single package
 Reads `config.yaml` or env vars:
 - `MONARCH_COOKIE` — required: a browser-copied Monarch session cookie (`sessionid=...; csrftoken=...`). The old `MONARCH_TOKEN` bearer token no longer works and is not read.
 - LLM categorizer — set **one** of:
-  - `OPENAI_API_KEY` (also `OPENAI_APIKEY`) with optional `OPENAI_MODEL` (default `gpt-5.6-luna`)
+  - `OPENAI_API_KEY` (also `OPENAI_APIKEY`) with optional `OPENAI_MODEL` (default `gpt-6-luna`)
   - `ANTHROPIC_API_KEY` (also `CLAUDE_API_KEY`) with optional `ANTHROPIC_MODEL` (default `claude-haiku-4-5`)
 - `CATEGORIZER_PROVIDER` — `openai` or `anthropic` to force a backend when both keys are set (auto-detected otherwise)
 - SQLite DB auto-created at `monarch_sync.db`

README.md

@@ -80,7 +80,7 @@ monarch:
 
 openai:
   api_key: "${OPENAI_API_KEY}"
-  model: "gpt-5.6-luna"
+  model: "gpt-6-luna"
 
 anthropic:
   api_key: "${ANTHROPIC_API_KEY}"

config.yaml

@@ -36,7 +36,7 @@ monarch:
 # OpenAI configuration
 openai:
   api_key: "${OPENAI_API_KEY}"
-  model: "gpt-5.6-luna"
+  model: "gpt-6-luna"
 
 # Anthropic (Claude) configuration — used when CATEGORIZER_PROVIDER=anthropic
 # or when ANTHROPIC_API_KEY is the only LLM key set.

docs/bug-fixes.md

@@ -12,6 +12,19 @@ Each bug fix entry should include:
 
 ## Bug Fixes
 
+### 2026-09-23: GPT-6 models would be sent `temperature` instead of `reasoning_effort`
+
+**Description:**
+The categorizer detected reasoning models with a `gpt-5` prefix check. Any `gpt-6-*` model (e.g. `OPENAI_MODEL=gpt-6-luna`) fell through to the non-reasoning path and was sent `temperature: 0.1` with no `reasoning_effort`.
+
+**Test Case:**
+`TestIsReasoningModel` in `internal/domain/categorizer/categorizer_test.go` — the `gpt-6-luna`, `gpt-6-sol`, and ` GPT-6-Luna ` cases failed against the old prefix check.
+
+**Fix Applied:**
+Replaced `isGPT5Model` with `isReasoningModel`, which parses the generation number after `gpt-` and treats generation 5 and later as reasoning models. The default OpenAI model moves to `gpt-6-luna` in the same change.
+
+**Commit:** Included in the pull request for this fix.
+
 ### 2026-08-23: CI and release builds used a vulnerable Go patch release
 
 **Description:**

internal/domain/categorizer/categorizer.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -96,7 +97,7 @@ func NewCategorizer(client ChatClient, cache Cache, model string) *Categorizer {
 	}
 }
 
-const DefaultModel = "gpt-5.6-luna"
+const DefaultModel = "gpt-6-luna"
 
 // CategorizeItems categorizes a list of items using available categories
 func (c *Categorizer) CategorizeItems(ctx context.Context, items []Item, categories []Category) (*CategorizationResult, error) {
@@ -233,7 +234,7 @@ func (c *Categorizer) callLLM(ctx context.Context, items []Item, categories []Ca
 			},
 		},
 	}
-	if isGPT5Model(c.Model) {
+	if isReasoningModel(c.Model) {
 		reasoningEffort := "low"
 		request.ReasoningEffort = &reasoningEffort
 	} else {
@@ -274,8 +275,19 @@ func (c *Categorizer) callLLM(ctx context.Context, items []Item, categories []Ca
 	return nil, fmt.Errorf("%w after %d attempts", lastErr, maxRetries)
 }
 
-func isGPT5Model(model string) bool {
-	return strings.HasPrefix(strings.ToLower(strings.TrimSpace(model)), "gpt-5")
+// isReasoningModel reports whether model is a GPT-5-or-later reasoning model,
+// which takes reasoning_effort and rejects a custom temperature.
+func isReasoningModel(model string) bool {
+	rest, ok := strings.CutPrefix(strings.ToLower(strings.TrimSpace(model)), "gpt-")
+	if !ok {
+		return false
+	}
+	end := strings.IndexFunc(rest, func(r rune) bool { return r < '0' || r > '9' })
+	if end == -1 {
+		end = len(rest)
+	}
+	generation, err := strconv.Atoi(rest[:end])
+	return err == nil && generation >= 5
 }
 
 // buildPrompt creates the prompt for OpenAI

internal/domain/categorizer/categorizer_test.go

@@ -425,3 +425,26 @@ func TestNewCategorizer_DefaultsModelWhenEmpty(t *testing.T) {
 
 	assert.Equal(t, DefaultModel, categorizer.Model)
 }
+
+func TestIsReasoningModel(t *testing.T) {
+	tests := []struct {
+		model string
+		want  bool
+	}{
+		{"gpt-5.4-nano", true},
+		{"gpt-5.6-luna", true},
+		{"gpt-6-luna", true},
+		{"gpt-6-sol", true},
+		{" GPT-6-Luna ", true},
+		{"gpt-4o-mini", false},
+		{"gpt-4.1", false},
+		{"claude-haiku-4-5", false},
+		{"", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.model, func(t *testing.T) {
+			assert.Equal(t, tt.want, isReasoningModel(tt.model))
+		})
+	}
+}

internal/infrastructure/config/config.go

@@ -188,7 +188,7 @@ func LoadFromEnv() *Config {
 		},
 		OpenAI: OpenAIConfig{
 			APIKey: os.Getenv("OPENAI_API_KEY"),
-			Model:  getEnv("OPENAI_MODEL", "gpt-5.6-luna"),
+			Model:  getEnv("OPENAI_MODEL", "gpt-6-luna"),
 		},
 		Anthropic: AnthropicConfig{
 			APIKey: firstNonEmpty(os.Getenv("ANTHROPIC_API_KEY"), os.Getenv("CLAUDE_API_KEY")),

internal/infrastructure/config/config_test.go

@@ -37,7 +37,7 @@ func TestLoadFromYAML(t *testing.T) {
 	require.NoError(t, err)
 	assert.NotNil(t, cfg)
 	assert.Equal(t, "monarch_sync.db", cfg.Storage.DatabasePath)
-	assert.Equal(t, "gpt-5.6-luna", cfg.OpenAI.Model)
+	assert.Equal(t, "gpt-6-luna", cfg.OpenAI.Model)
 }
 
 func TestLoadFromEnv(t *testing.T) {
@@ -66,7 +66,7 @@ func TestLoadFromEnv_Defaults(t *testing.T) {
 	cfg := LoadFromEnv()
 	assert.NotNil(t, cfg)
 	assert.Equal(t, "monarch_sync.db", cfg.Storage.DatabasePath)
-	assert.Equal(t, "gpt-5.6-luna", cfg.OpenAI.Model)
+	assert.Equal(t, "gpt-6-luna", cfg.OpenAI.Model)
 }
 
 func TestLoadOrEnv(t *testing.T) {