Pass location names to recognizer initial prompt

Adds a WithLocations functional option to NewWhisperRecognizer and the
OpenAI recognizers. When set, location names are appended to the initial
prompt so Whisper biases transcription towards known place names (e.g.
"Incirlik" instead of "INSULIC").

The application wires this up automatically from config.Locations.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: dharmab

internal/application/app.go

@@ -153,26 +153,28 @@ func NewApplication(config conf.Configuration) (*Application, error) {
 		)
 	}
 
+	locationNames := make([]string, 0)
+	for _, loc := range config.Locations {
+		locationNames = append(locationNames, loc.Names...)
+	}
+
+	recognizerOpts := []recognizer.Option{recognizer.WithLocations(locationNames)}
+
 	log.Info().Msg("constructing speech-to-text recognizer")
 	var speechRecognizer recognizer.Recognizer
 	switch config.Recognizer {
 	case conf.WhisperLocal:
-		speechRecognizer = recognizer.NewWhisperRecognizer(config.WhisperModel, config.Callsign)
+		speechRecognizer = recognizer.NewWhisperRecognizer(config.WhisperModel, config.Callsign, recognizerOpts...)
 	case conf.WhisperAPI:
-		speechRecognizer = recognizer.NewWhisperAPIRecognizer(config.OpenAIAPIKey, config.Callsign)
+		speechRecognizer = recognizer.NewWhisperAPIRecognizer(config.OpenAIAPIKey, config.Callsign, recognizerOpts...)
 	case conf.GPT4o:
-		speechRecognizer = recognizer.NewGPT4oRecognizer(config.OpenAIAPIKey, config.Callsign)
+		speechRecognizer = recognizer.NewGPT4oRecognizer(config.OpenAIAPIKey, config.Callsign, recognizerOpts...)
 	case conf.GPT4oMini:
-		speechRecognizer = recognizer.NewGPT4oMiniRecognizer(config.OpenAIAPIKey, config.Callsign)
+		speechRecognizer = recognizer.NewGPT4oMiniRecognizer(config.OpenAIAPIKey, config.Callsign, recognizerOpts...)
 	default:
 		return nil, fmt.Errorf("failed to construct application: unrecognized recognizer %q", config.Recognizer)
 	}
 
-	locationNames := make([]string, 0)
-	for _, loc := range config.Locations {
-		locationNames = append(locationNames, loc.Names...)
-	}
-
 	log.Info().Msg("constructing request parser")
 	requestParser := parser.New(config.Callsign, locationNames, config.EnableTranscriptionLogging)
 

pkg/recognizer/openai.go

@@ -18,39 +18,44 @@ type openAIRecognizer struct {
 	callsign string
 	client   *openai.Client
 	model    string
+	recognizerOptions
 }
 
 var _ Recognizer = &openAIRecognizer{}
 
-func newOpenAIRecognizer(apiKey, model, callsign string) Recognizer {
-	return &openAIRecognizer{
+func newOpenAIRecognizer(apiKey, model, callsign string, opts ...Option) Recognizer {
+	r := &openAIRecognizer{
 		callsign: callsign,
 		client: openai.NewClient(
 			option.WithAPIKey(apiKey),
 		),
 		model: model,
 	}
+	for _, opt := range opts {
+		opt(&r.recognizerOptions)
+	}
+	return r
 }
 
-func NewWhisperAPIRecognizer(apiKey, callsign string) Recognizer {
-	return newOpenAIRecognizer(apiKey, "whisper-1", callsign)
+func NewWhisperAPIRecognizer(apiKey, callsign string, opts ...Option) Recognizer {
+	return newOpenAIRecognizer(apiKey, "whisper-1", callsign, opts...)
 }
 
 // NewGPT4oRecognizer creates a new recognizer using OpenAI Platform's GPT-4o model.
-func NewGPT4oRecognizer(apiKey, callsign string) Recognizer {
-	return newOpenAIRecognizer(apiKey, "gpt-4o-transcribe", callsign)
+func NewGPT4oRecognizer(apiKey, callsign string, opts ...Option) Recognizer {
+	return newOpenAIRecognizer(apiKey, "gpt-4o-transcribe", callsign, opts...)
 }
 
 // NewGPT4oMiniRecognizer creates a new recognizer using OpenAI Platform's GPT-4o Mini model.
-func NewGPT4oMiniRecognizer(apiKey, callsign string) Recognizer {
-	return newOpenAIRecognizer(apiKey, "gpt-4o-mini-transcribe", callsign)
+func NewGPT4oMiniRecognizer(apiKey, callsign string, opts ...Option) Recognizer {
+	return newOpenAIRecognizer(apiKey, "gpt-4o-mini-transcribe", callsign, opts...)
 }
 
 // NewOpenAIRecognizer creates a new recognizer using OpenAI Platform.
 //
 // Deprecated: Use NewWhisperAPIRecognizer, NewGPT4oRecognizer, or NewGPT4oMiniRecognizer instead.
-func NewOpenAIRecognizer(apiKey, callsign string) Recognizer { // nolint: revive // Ignore deprecated function
-	return NewWhisperAPIRecognizer(apiKey, callsign)
+func NewOpenAIRecognizer(apiKey, callsign string, opts ...Option) Recognizer { // nolint: revive // Ignore deprecated function
+	return NewWhisperAPIRecognizer(apiKey, callsign, opts...)
 }
 
 // Recognize implements [Recognizer.Recognize] using OpenAI Platform's hosted GPT4 transcription model.
@@ -65,7 +70,7 @@ func (r *openAIRecognizer) Recognize(ctx context.Context, sample []float32, _ bo
 		File:     openai.FileParam(buf, "audio.wav", "audio/wav"),
 		Model:    openai.String(r.model),
 		Language: openai.String("en"),
-		Prompt:   openai.String(prompt(r.callsign)),
+		Prompt:   openai.String(prompt(r.callsign, r.locations)),
 	}
 
 	log.Info().Str("model", r.model).Msg("calling OpenAI Audio Transcriptions API")

pkg/recognizer/options.go

@@ -0,0 +1,16 @@
+package recognizer
+
+type recognizerOptions struct {
+	locations []string
+}
+
+// Option configures a recognizer.
+type Option func(*recognizerOptions)
+
+// WithLocations adds location names to the recognizer's initial prompt,
+// improving transcription accuracy for place names.
+func WithLocations(locations []string) Option {
+	return func(o *recognizerOptions) {
+		o.locations = locations
+	}
+}

pkg/recognizer/prompt.go

@@ -1,8 +1,15 @@
 package recognizer
 
-import "fmt"
+import (
+	"fmt"
+	"strings"
+)
 
 // prompt constructs a prompt for OpenAI's audio transcription models. See https://platform.openai.com/docs/guides/speech-to-text#prompting
-func prompt(callsign string) string {
-	return fmt.Sprintf("Either ANYFACE or %s, PILOT CALLSIGN, DIGITS, one of 'RADIO' 'ALPHA' 'BOGEY' 'PICTURE' 'DECLARE' 'SNAPLOCK' 'SPIKED', ARGUMENTS such as BULLSEYE, BRAA, numbers or digits.", callsign)
+func prompt(callsign string, locations []string) string {
+	s := fmt.Sprintf("Either ANYFACE or %s, PILOT CALLSIGN, DIGITS, one of 'RADIO' 'ALPHA' 'BOGEY' 'PICTURE' 'DECLARE' 'SNAPLOCK' 'SPIKED', ARGUMENTS such as BULLSEYE, BRAA, numbers or digits.", callsign)
+	if len(locations) > 0 {
+		s += " Locations: " + strings.Join(locations, ", ") + "."
+	}
+	return s
 }

pkg/recognizer/whisper.go

@@ -14,16 +14,21 @@ import (
 type whisperRecognizer struct {
 	model    whisper.Model
 	callsign string
+	recognizerOptions
 }
 
 var _ Recognizer = &whisperRecognizer{}
 
 // NewWhisperRecognizer creates a new recognizer using OpenAI Whisper.
-func NewWhisperRecognizer(model *whisper.Model, callsign string) Recognizer {
-	return &whisperRecognizer{
+func NewWhisperRecognizer(model *whisper.Model, callsign string, opts ...Option) Recognizer {
+	r := &whisperRecognizer{
 		model:    *model,
 		callsign: callsign,
 	}
+	for _, opt := range opts {
+		opt(&r.recognizerOptions)
+	}
+	return r
 }
 
 const maxSize = 256 * 1024
@@ -40,7 +45,7 @@ func (r *whisperRecognizer) Recognize(ctx context.Context, sample []float32, ena
 		return "", fmt.Errorf("error creating whisper context: %w", err)
 	}
 
-	wCtx.SetInitialPrompt(prompt(r.callsign))
+	wCtx.SetInitialPrompt(prompt(r.callsign, r.locations))
 
 	if wCtx.IsMultilingual() {
 		_ = wCtx.SetLanguage("en")