feat: add custom prime template config option

cmd/check.go

@@ -5,10 +5,10 @@ import (
 	"fmt"
 	"os"
 
-	"github.com/spf13/cobra"
 	"github.com/hmans/beans/internal/beancore"
 	"github.com/hmans/beans/internal/config"
 	"github.com/hmans/beans/internal/ui"
+	"github.com/spf13/cobra"
 )
 
 var (
@@ -98,6 +98,18 @@ Note: Cycles cannot be auto-fixed and require manual intervention.`,
 			}
 		}
 
+		// 5. Check custom prime template exists (if configured)
+		if cfg.Templates.Prime != "" {
+			primePath := cfg.ResolvePrimeTemplatePath()
+			if _, err := os.Stat(primePath); os.IsNotExist(err) {
+				configErrors = append(configErrors, fmt.Sprintf("custom prime template not found: %s", primePath))
+			} else if err != nil {
+				configErrors = append(configErrors, fmt.Sprintf("cannot access custom prime template: %s: %v", primePath, err))
+			} else if !checkJSON {
+				fmt.Printf("  %s Custom prime template exists (%s)\n", ui.Success.Render("✓"), cfg.Templates.Prime)
+			}
+		}
+
 		// Print config errors in human-readable mode
 		if !checkJSON {
 			for _, e := range configErrors {

cmd/prime.go

@@ -1,12 +1,15 @@
 package cmd
 
 import (
+	"bytes"
 	_ "embed"
+	"fmt"
+	"io"
 	"os"
 	"text/template"
 
-	"github.com/spf13/cobra"
 	"github.com/hmans/beans/internal/config"
+	"github.com/spf13/cobra"
 )
 
 //go:embed prompt.tmpl
@@ -18,6 +21,62 @@ type promptData struct {
 	Types         []config.TypeConfig
 	Statuses      []config.StatusConfig
 	Priorities    []config.PriorityConfig
+	OriginalPrime string
+}
+
+// primeResult holds the output of renderPrime for inspection.
+type primeResult struct {
+	Output  string // The rendered prime output
+	Warning string // Non-empty if a fallback occurred
+}
+
+// renderPrime renders the prime output using the given config.
+// If a custom template is configured but cannot be loaded or parsed,
+// it falls back to the built-in template and sets a warning.
+func renderPrime(primeCfg *config.Config, data promptData) (*primeResult, error) {
+	builtinTmpl, err := template.New("prompt").Parse(agentPromptTemplate)
+	if err != nil {
+		return nil, err
+	}
+
+	primePath := primeCfg.ResolvePrimeTemplatePath()
+	if primePath == "" {
+		var buf bytes.Buffer
+		if err := builtinTmpl.Execute(&buf, data); err != nil {
+			return nil, err
+		}
+		return &primeResult{Output: buf.String()}, nil
+	}
+
+	// Custom template configured - render built-in to string first
+	var builtinBuf bytes.Buffer
+	if err := builtinTmpl.Execute(&builtinBuf, data); err != nil {
+		return nil, fmt.Errorf("rendering built-in prime template: %w", err)
+	}
+	data.OriginalPrime = builtinBuf.String()
+
+	// Read and parse the custom template
+	customTmplContent, err := os.ReadFile(primePath)
+	if err != nil {
+		return &primeResult{
+			Output:  builtinBuf.String(),
+			Warning: fmt.Sprintf("custom prime template not found: %s (falling back to built-in)", primePath),
+		}, nil
+	}
+
+	customTmpl, err := template.New("custom-prompt").Parse(string(customTmplContent))
+	if err != nil {
+		return &primeResult{
+			Output:  builtinBuf.String(),
+			Warning: fmt.Sprintf("parsing custom prime template: %v (falling back to built-in)", err),
+		}, nil
+	}
+
+	var customBuf bytes.Buffer
+	if err := customTmpl.Execute(&customBuf, data); err != nil {
+		return nil, fmt.Errorf("executing custom prime template: %w", err)
+	}
+	return &primeResult{Output: customBuf.String()}, nil
 }
 
 var primeCmd = &cobra.Command{
@@ -28,6 +87,7 @@ var primeCmd = &cobra.Command{
 	RunE: func(cmd *cobra.Command, args []string) error {
 		// If no explicit path given, check if a beans project exists by searching
 		// upward for a .beans.yml config file
+		var primeCfg *config.Config
 		if beansPath == "" && configPath == "" {
 			cwd, err := os.Getwd()
 			if err != nil {
@@ -38,11 +98,25 @@ var primeCmd = &cobra.Command{
 				// No config file found - silently exit
 				return nil
 			}
-		}
-
-		tmpl, err := template.New("prompt").Parse(agentPromptTemplate)
-		if err != nil {
-			return err
+			primeCfg, err = config.Load(configFile)
+			if err != nil {
+				return fmt.Errorf("loading config: %w", err)
+			}
+		} else if configPath != "" {
+			var err error
+			primeCfg, err = config.Load(configPath)
+			if err != nil {
+				return fmt.Errorf("loading config from %s: %w", configPath, err)
+			}
+		} else {
+			cwd, err := os.Getwd()
+			if err != nil {
+				return fmt.Errorf("getting current directory: %w", err)
+			}
+			primeCfg, err = config.LoadFromDirectory(cwd)
+			if err != nil {
+				return fmt.Errorf("loading config: %w", err)
+			}
 		}
 
 		data := promptData{
@@ -52,7 +126,17 @@ var primeCmd = &cobra.Command{
 			Priorities:    config.DefaultPriorities,
 		}
 
-		return tmpl.Execute(os.Stdout, data)
+		result, err := renderPrime(primeCfg, data)
+		if err != nil {
+			return err
+		}
+
+		if result.Warning != "" {
+			fmt.Fprintf(os.Stderr, "warning: %s\n", result.Warning)
+		}
+
+		_, err = io.WriteString(os.Stdout, result.Output)
+		return err
 	},
 }