diff --git a/agent/compaction.go b/agent/compaction.go
index 06a8654..7149e88 100644
--- a/agent/compaction.go
+++ b/agent/compaction.go
@@ -2,21 +2,13 @@ package agent
 
 import "os"
 
-// defaultCompactionModels maps backend names to cheap models suitable for compaction.
-var defaultCompactionModels = map[string]string{
-	"anthropic":  "claude-3-5-haiku-latest",
-	"openai":     "gpt-4o-mini",
-	"openrouter": "deepseek-v4-flash",
-	"gemini":     "gemini-2.0-flash",
-}
-
-// backendNamer is the subset of backend.Backend needed for compaction model resolution.
+// backendNamer is the subset of backend.Backend needed for model resolution.
 type backendNamer interface {
 	Name() string
 }
 
 // resolveCompactionModel returns the model to use for compaction.
-// Priority: agent config > OLLIE_COMPACTION_MODEL env > per-backend default.
+// Priority: agent config > OLLIE_COMPACTION_MODEL env > per-backend default from models.yaml > session's current model.
 // Returns "" if no override is configured (use the session's current model).
 func resolveCompactionModel(cfgModel string, b backendNamer) string {
 	if cfgModel != "" {
@@ -25,8 +17,11 @@ func resolveCompactionModel(cfgModel string, b backendNamer) string {
 	if env := os.Getenv("OLLIE_COMPACTION_MODEL"); env != "" {
 		return env
 	}
+	cfg := loadModelsConfig()
 	if b != nil {
-		return defaultCompactionModels[b.Name()]
+		if m, ok := cfg.Compaction[b.Name()]; ok {
+			return m
+		}
 	}
 	return ""
 }
diff --git a/agent/complete.go b/agent/complete.go
index 3199ece..b79e636 100644
--- a/agent/complete.go
+++ b/agent/complete.go
@@ -24,7 +24,16 @@ func Complete(cwd, filePath, prefix, suffix, extraContext string) (string, error
 	model := os.Getenv("OLLIE_COMPLETE_MODEL")
 	backendName := os.Getenv("OLLIE_COMPLETE_BACKEND")
 	if model == "" || backendName == "" {
-		return "", fmt.Errorf("OLLIE_COMPLETE_MODEL and OLLIE_COMPLETE_BACKEND must be set")
+		cfg := loadModelsConfig()
+		if model == "" && cfg.Completion.Model != "" {
+			model = cfg.Completion.Model
+		}
+		if backendName == "" && cfg.Completion.Backend != "" {
+			backendName = cfg.Completion.Backend
+		}
+	}
+	if model == "" || backendName == "" {
+		return "", fmt.Errorf("OLLIE_COMPLETE_MODEL and OLLIE_COMPLETE_BACKEND must be set (or configured in models.yaml)")
 	}
 
 	const prefixMax = 12000
diff --git a/agent/models.go b/agent/models.go
new file mode 100644
index 0000000..148059a
--- /dev/null
+++ b/agent/models.go
@@ -0,0 +1,41 @@
+package agent
+
+import (
+	"os"
+	"path/filepath"
+
+	"gopkg.in/yaml.v3"
+)
+
+// modelsConfig holds the parsed contents of ~/.config/ollie/models.yaml.
+type modelsConfig struct {
+	Compaction map[string]string `yaml:"compaction"`
+	Completion struct {
+		Model   string `yaml:"model"`
+		Backend string `yaml:"backend"`
+	} `yaml:"completion"`
+}
+
+// loadModelsConfig reads and parses the models config file.
+// Returns zero value if the file doesn't exist or is invalid.
+func loadModelsConfig() modelsConfig {
+	path := filepath.Join(cfgDir(), "models.yaml")
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return modelsConfig{}
+	}
+	var cfg modelsConfig
+	if err := yaml.Unmarshal(data, &cfg); err != nil {
+		return modelsConfig{}
+	}
+	return cfg
+}
+
+// cfgDir returns the ollie config directory, respecting XDG_CONFIG_HOME.
+func cfgDir() string {
+	if xdg := os.Getenv("XDG_CONFIG_HOME"); xdg != "" {
+		return filepath.Join(xdg, "ollie")
+	}
+	home, _ := os.UserHomeDir()
+	return filepath.Join(home, ".config", "ollie")
+}