config: support macros in peer apiKey and filters (#469)

* config: support environment variable macros in peer apiKeys

Add ${env.VAR_NAME} substitution for peer apiKey fields, consistent
with existing env macro support for model fields and global apiKeys.

- Add env macro substitution for peers.{name}.apiKey in LoadConfigFromReader
- Add tests for peer apiKey env substitution
- Update config.example.yaml to show env macro usage

* config: support macros in peer apiKey and filters

Extend macro substitution to peer configuration fields:
- peers.{name}.apiKey supports both global macros and env macros
- peers.{name}.filters.stripParams supports both macro types
- peers.{name}.filters.setParams supports both macro types

Also renamed validateMetadataForUnknownMacros to validateNestedForUnknownMacros
for reuse across model metadata and peer filters validation.

config.example.yaml

@@ -386,7 +386,8 @@ peers:
     # - optional, default: ""
     # - if blank, no key will be added to the request
     # - key will be injected into headers: Authorization: Bearer <key> and x-api-key: <key>
-    apiKey: sk-your-openrouter-key
+    # - can be a string or a macro
+    apiKey: ${env.OPENROUTER_API_KEY}
     models:
       - meta-llama/llama-3.1-8b-instruct
       - qwen/qwen3-235b-a22b-2507
@@ -413,4 +414,4 @@ peers:
         # Example: enforce zero-data-retention for OpenRouter
         provider:
           data_collection: "deny"
-          allow_fallbacks: false
+          zdr: true

proxy/config/config.go

@@ -427,7 +427,7 @@ func LoadConfigFromReader(r io.Reader) (Config, error) {
 
 		// Check for unknown macros in metadata
 		if len(modelConfig.Metadata) > 0 {
-			if err := validateMetadataForUnknownMacros(modelConfig.Metadata, modelId); err != nil {
+			if err := validateNestedForUnknownMacros(modelConfig.Metadata, fmt.Sprintf("model %s metadata", modelId)); err != nil {
 				return Config{}, err
 			}
 		}
@@ -502,6 +502,62 @@ func LoadConfigFromReader(r io.Reader) (Config, error) {
 		}
 	}
 
+	// substitute macros and env macros in peer fields
+	for peerName, peerConfig := range config.Peers {
+		// Substitute global macros first (LIFO order like models)
+		for i := len(config.Macros) - 1; i >= 0; i-- {
+			entry := config.Macros[i]
+			macroSlug := fmt.Sprintf("${%s}", entry.Name)
+			macroStr := fmt.Sprintf("%v", entry.Value)
+
+			peerConfig.ApiKey = strings.ReplaceAll(peerConfig.ApiKey, macroSlug, macroStr)
+			peerConfig.Filters.StripParams = strings.ReplaceAll(peerConfig.Filters.StripParams, macroSlug, macroStr)
+
+			// Substitute in setParams
+			if len(peerConfig.Filters.SetParams) > 0 {
+				result, err := substituteMacroInValue(peerConfig.Filters.SetParams, entry.Name, entry.Value)
+				if err != nil {
+					return Config{}, fmt.Errorf("peers.%s.filters.setParams: %w", peerName, err)
+				}
+				peerConfig.Filters.SetParams = result.(map[string]any)
+			}
+		}
+
+		// Substitute env macros
+		peerConfig.ApiKey, err = substituteEnvMacros(peerConfig.ApiKey)
+		if err != nil {
+			return Config{}, fmt.Errorf("peers.%s.apiKey: %w", peerName, err)
+		}
+
+		peerConfig.Filters.StripParams, err = substituteEnvMacros(peerConfig.Filters.StripParams)
+		if err != nil {
+			return Config{}, fmt.Errorf("peers.%s.filters.stripParams: %w", peerName, err)
+		}
+
+		if len(peerConfig.Filters.SetParams) > 0 {
+			result, err := substituteEnvMacrosInValue(peerConfig.Filters.SetParams)
+			if err != nil {
+				return Config{}, fmt.Errorf("peers.%s.filters.setParams: %w", peerName, err)
+			}
+			peerConfig.Filters.SetParams = result.(map[string]any)
+		}
+
+		// Validate no unknown macros remain
+		if matches := macroPatternRegex.FindAllStringSubmatch(peerConfig.ApiKey, -1); len(matches) > 0 {
+			return Config{}, fmt.Errorf("peers.%s.apiKey: unknown macro '${%s}'", peerName, matches[0][1])
+		}
+		if matches := macroPatternRegex.FindAllStringSubmatch(peerConfig.Filters.StripParams, -1); len(matches) > 0 {
+			return Config{}, fmt.Errorf("peers.%s.filters.stripParams: unknown macro '${%s}'", peerName, matches[0][1])
+		}
+		if len(peerConfig.Filters.SetParams) > 0 {
+			if err := validateNestedForUnknownMacros(peerConfig.Filters.SetParams, fmt.Sprintf("peers.%s.filters.setParams", peerName)); err != nil {
+				return Config{}, err
+			}
+		}
+
+		config.Peers[peerName] = peerConfig
+	}
+
 	return config, nil
 }
 
@@ -632,26 +688,26 @@ func validateMacro(name string, value any) error {
 	return nil
 }
 
-// validateMetadataForUnknownMacros recursively checks for any remaining macro references in metadata
+// validateNestedForUnknownMacros recursively checks for any remaining macro references in nested structures
-func validateMetadataForUnknownMacros(value any, modelId string) error {
+func validateNestedForUnknownMacros(value any, context string) error {
 	switch v := value.(type) {
 	case string:
 		matches := macroPatternRegex.FindAllStringSubmatch(v, -1)
 		for _, match := range matches {
 			macroName := match[1]
-			return fmt.Errorf("model %s metadata: unknown macro '${%s}'", modelId, macroName)
+			return fmt.Errorf("%s: unknown macro '${%s}'", context, macroName)
 		}
 		// Check for unsubstituted env macros
 		envMatches := envMacroRegex.FindAllStringSubmatch(v, -1)
 		for _, match := range envMatches {
 			varName := match[1]
-			return fmt.Errorf("model %s metadata: environment variable '%s' not set", modelId, varName)
+			return fmt.Errorf("%s: environment variable '%s' not set", context, varName)
 		}
 		return nil
 
 	case map[string]any:
 		for _, val := range v {
-			if err := validateMetadataForUnknownMacros(val, modelId); err != nil {
+			if err := validateNestedForUnknownMacros(val, context); err != nil {
 				return err
 			}
 		}
@@ -659,7 +715,7 @@ func validateMetadataForUnknownMacros(value any, modelId string) error {
 
 	case []any:
 		for _, val := range v {
-			if err := validateMetadataForUnknownMacros(val, modelId); err != nil {
+			if err := validateNestedForUnknownMacros(val, context); err != nil {
 				return err
 			}
 		}

proxy/config/config_test.go

@@ -1057,3 +1057,191 @@ models:
 		assert.Equal(t, "server --auth admin:secret", config.Models["test"].Cmd)
 	})
 }
+
+func TestConfig_PeerApiKey_EnvMacros(t *testing.T) {
+	t.Run("env substitution in peer apiKey", func(t *testing.T) {
+		t.Setenv("TEST_PEER_API_KEY", "sk-peer-secret-123")
+
+		content := `
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    apiKey: "${env.TEST_PEER_API_KEY}"
+    models:
+      - llama-3.1-8b
+`
+		config, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.NoError(t, err)
+		assert.Equal(t, "sk-peer-secret-123", config.Peers["openrouter"].ApiKey)
+	})
+
+	t.Run("missing env var in peer apiKey", func(t *testing.T) {
+		content := `
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    apiKey: "${env.NONEXISTENT_PEER_KEY}"
+    models:
+      - llama-3.1-8b
+`
+		_, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "peers.openrouter.apiKey")
+		assert.Contains(t, err.Error(), "NONEXISTENT_PEER_KEY")
+	})
+
+	t.Run("static apiKey unchanged", func(t *testing.T) {
+		content := `
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    apiKey: sk-static-key
+    models:
+      - llama-3.1-8b
+`
+		config, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.NoError(t, err)
+		assert.Equal(t, "sk-static-key", config.Peers["openrouter"].ApiKey)
+	})
+
+	t.Run("multiple peers with env apiKeys", func(t *testing.T) {
+		t.Setenv("TEST_PEER_KEY_1", "key-one")
+		t.Setenv("TEST_PEER_KEY_2", "key-two")
+
+		content := `
+peers:
+  peer1:
+    proxy: https://peer1.example.com
+    apiKey: "${env.TEST_PEER_KEY_1}"
+    models:
+      - model-a
+  peer2:
+    proxy: https://peer2.example.com
+    apiKey: "${env.TEST_PEER_KEY_2}"
+    models:
+      - model-b
+`
+		config, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.NoError(t, err)
+		assert.Equal(t, "key-one", config.Peers["peer1"].ApiKey)
+		assert.Equal(t, "key-two", config.Peers["peer2"].ApiKey)
+	})
+
+	t.Run("global macro substitution in peer apiKey", func(t *testing.T) {
+		content := `
+macros:
+  API_KEY: sk-from-global-macro
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    apiKey: "${API_KEY}"
+    models:
+      - llama-3.1-8b
+`
+		config, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.NoError(t, err)
+		assert.Equal(t, "sk-from-global-macro", config.Peers["openrouter"].ApiKey)
+	})
+
+	t.Run("global macro in peer filters.stripParams", func(t *testing.T) {
+		content := `
+macros:
+  STRIP_LIST: "temperature, top_p"
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    models:
+      - llama-3.1-8b
+    filters:
+      stripParams: "${STRIP_LIST}"
+`
+		config, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.NoError(t, err)
+		assert.Equal(t, "temperature, top_p", config.Peers["openrouter"].Filters.StripParams)
+	})
+
+	t.Run("global macro in peer filters.setParams", func(t *testing.T) {
+		content := `
+macros:
+  MAX_TOKENS: 4096
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    models:
+      - llama-3.1-8b
+    filters:
+      setParams:
+        max_tokens: "${MAX_TOKENS}"
+`
+		config, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.NoError(t, err)
+		assert.Equal(t, 4096, config.Peers["openrouter"].Filters.SetParams["max_tokens"])
+	})
+
+	t.Run("env macro in peer filters.setParams", func(t *testing.T) {
+		t.Setenv("TEST_RETENTION_POLICY", "deny")
+
+		content := `
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    models:
+      - llama-3.1-8b
+    filters:
+      setParams:
+        data_collection: "${env.TEST_RETENTION_POLICY}"
+`
+		config, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.NoError(t, err)
+		assert.Equal(t, "deny", config.Peers["openrouter"].Filters.SetParams["data_collection"])
+	})
+
+	t.Run("env macro in peer filters.stripParams", func(t *testing.T) {
+		t.Setenv("TEST_STRIP_PARAMS", "frequency_penalty, presence_penalty")
+
+		content := `
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    models:
+      - llama-3.1-8b
+    filters:
+      stripParams: "${env.TEST_STRIP_PARAMS}"
+`
+		config, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.NoError(t, err)
+		assert.Equal(t, "frequency_penalty, presence_penalty", config.Peers["openrouter"].Filters.StripParams)
+	})
+
+	t.Run("unknown macro in peer apiKey fails", func(t *testing.T) {
+		content := `
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    apiKey: "${UNDEFINED_MACRO}"
+    models:
+      - llama-3.1-8b
+`
+		_, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "peers.openrouter.apiKey")
+		assert.Contains(t, err.Error(), "unknown macro")
+	})
+
+	t.Run("unknown macro in peer filters.setParams fails", func(t *testing.T) {
+		content := `
+peers:
+  openrouter:
+    proxy: https://openrouter.ai/api
+    models:
+      - llama-3.1-8b
+    filters:
+      setParams:
+        value: "${UNDEFINED_MACRO}"
+`
+		_, err := LoadConfigFromReader(strings.NewReader(content))
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "peers.openrouter.filters.setParams")
+		assert.Contains(t, err.Error(), "unknown macro")
+	})
+}