diff --git a/ai-plans/issue-336-macro-in-macro.md b/ai-plans/issue-336-macro-in-macro.md
new file mode 100644
index 0000000..4f0bca8
--- /dev/null
+++ b/ai-plans/issue-336-macro-in-macro.md
@@ -0,0 +1,397 @@
+# Improve macro-in-macro support
+
+**Status: COMPLETED ✅**
+
+## Title
+
+Fix macro substitution ordering by preserving definition order using ordered YAML parsing
+
+## Overview
+
+The current macro implementation uses `map[string]any` which does not preserve insertion order. This causes issues when macros reference other macros - if macro `B` contains `${A}` but `B` is processed before `A`, the reference won't be substituted, leading to "unknown macro" errors.
+
+**Goal:** Ensure macros are substituted in definition order (LIFO - last in, first out) to allow macros to reliably reference previously-defined macros.
+
+**Outcomes:**
+- Macros can reference other macros defined earlier in the config
+- Macro substitution is deterministic and order-dependent
+- Single-pass substitution prevents circular dependencies
+- Use `yaml.Node` from `gopkg.in/yaml.v3` to preserve macro definition order
+- All existing tests pass
+- New tests validate substitution order and self-reference detection
+
+## Design Requirements
+
+### 1. YAML Parsing Strategy
+- **Continue using:** `gopkg.in/yaml.v3` (current library)
+- **Use:** `yaml.Node` for ordered parsing of macros
+- **Reason:** `yaml.Node` preserves document structure and order, avoiding need for migration
+
+### 2. Data Structure Changes
+
+#### Current Implementation (config.go:19)
+```go
+type MacroList map[string]any
+```
+
+#### New Implementation
+```go
+type MacroList []MacroEntry
+
+type MacroEntry struct {
+    Name  string
+    Value any
+}
+```
+
+**Implementation Note:** Parse macros using `yaml.Node` to extract key-value pairs in document order, then construct the ordered `MacroList`.
+
+### 3. Macro Substitution Order Rules
+
+The substitution must follow this hierarchy (from most specific to least):
+
+1. **Reserved macros** (last): `PORT`, `MODEL_ID` - substituted last, highest priority
+2. **Model-level macros** (middle): Defined in specific model config, overrides global
+3. **Global macros** (first): Defined at config root level
+
+Within each level, macros are substituted in **reverse definition order** (LIFO):
+- The last macro defined is substituted first
+- This allows later macros to reference earlier ones
+- Single-pass substitution prevents circular dependencies
+
+### 4. Macro Reference Rules
+
+**Allowed:**
+- Macro can reference any macro defined **before** it (earlier in the file)
+- Model macros can reference global macros
+- Macros can reference reserved macros (`${PORT}`, `${MODEL_ID}`)
+
+**Prohibited:**
+- Macro cannot reference itself (e.g., `foo: "value ${foo}"`)
+- Macro cannot reference macros defined **after** it
+- No circular references (prevented by single-pass, ordered substitution)
+
+### 5. Validation Requirements
+
+Add validation to detect:
+- **Self-references:** Macro value contains reference to its own name
+- **Unknown macros:** After substitution, any remaining `${...}` references
+
+Error messages should be clear:
+```
+macro 'foo' contains self-reference
+unknown macro '${bar}' in model.cmd
+```
+
+### 6. Implementation Changes
+
+#### Files to Modify
+
+1. **[proxy/config/config.go](proxy/config/config.go)**
+   - Line 19: Change `MacroList` type definition
+   - Line 69: Update `Macros MacroList` field
+   - Line 153-157: Update macro validation loop to work with ordered structure
+   - Line 175-188: Update model-level macro validation
+   - Line 181-188: **NEW** Implement proper macro merging respecting order
+   - Line 193-202: **NEW** Implement ordered macro substitution in LIFO order
+   - Line 389-415: Update `validateMacro` to detect self-references
+   - Line 420-475: Update `substituteMetadataMacros` to accept ordered MacroList
+
+2. **[proxy/config/model_config.go](proxy/config/model_config.go)**
+   - Line 33: Update `Macros MacroList` field type
+
+3. **All test files**
+   - Update test fixtures to use ordered macro definitions
+   - Ensure tests specify macro order explicitly
+
+#### Core Algorithm
+
+Replace the macro substitution logic in [config.go:181-252](proxy/config/config.go#L181-L252) with:
+
+```go
+// Merge global config and model macros. Model macros take precedence
+mergedMacros := make(MacroList, 0, len(config.Macros)+len(modelConfig.Macros)+2)
+
+// Add global macros first
+for _, entry := range config.Macros {
+	mergedMacros = append(mergedMacros, entry)
+}
+
+// Add model macros (can override global)
+for _, entry := range modelConfig.Macros {
+	// Remove any existing global macro with same name
+	found := false
+	for i, existing := range mergedMacros {
+		if existing.Name == entry.Name {
+			mergedMacros[i] = entry // Override
+			found = true
+			break
+		}
+	}
+	if !found {
+		mergedMacros = append(mergedMacros, entry)
+	}
+}
+
+// Add reserved MODEL_ID macro at the end
+mergedMacros = append(mergedMacros, MacroEntry{Name: "MODEL_ID", Value: modelId})
+
+// Check if PORT macro is needed
+if strings.Contains(modelConfig.Cmd, "${PORT}") || strings.Contains(modelConfig.Proxy, "${PORT}") || strings.Contains(modelConfig.CmdStop, "${PORT}") {
+	// enforce ${PORT} used in both cmd and proxy
+	if !strings.Contains(modelConfig.Cmd, "${PORT}") && strings.Contains(modelConfig.Proxy, "${PORT}") {
+		return Config{}, fmt.Errorf("model %s: proxy uses ${PORT} but cmd does not - ${PORT} is only available when used in cmd", modelId)
+	}
+
+	// Add PORT macro to the end (highest priority)
+	mergedMacros = append(mergedMacros, MacroEntry{Name: "PORT", Value: nextPort})
+	nextPort++
+}
+
+// Single-pass substitution: Substitute all macros in LIFO order (last defined first)
+// This allows later macros to reference earlier ones
+for i := len(mergedMacros) - 1; i >= 0; i-- {
+	entry := mergedMacros[i]
+	macroSlug := fmt.Sprintf("${%s}", entry.Name)
+	macroStr := fmt.Sprintf("%v", entry.Value)
+
+	// Substitute in command fields
+	modelConfig.Cmd = strings.ReplaceAll(modelConfig.Cmd, macroSlug, macroStr)
+	modelConfig.CmdStop = strings.ReplaceAll(modelConfig.CmdStop, macroSlug, macroStr)
+	modelConfig.Proxy = strings.ReplaceAll(modelConfig.Proxy, macroSlug, macroStr)
+	modelConfig.CheckEndpoint = strings.ReplaceAll(modelConfig.CheckEndpoint, macroSlug, macroStr)
+	modelConfig.Filters.StripParams = strings.ReplaceAll(modelConfig.Filters.StripParams, macroSlug, macroStr)
+
+	// Substitute in metadata (recursive)
+	if len(modelConfig.Metadata) > 0 {
+		var err error
+		modelConfig.Metadata, err = substituteMacroInValue(modelConfig.Metadata, entry.Name, entry.Value)
+		if err != nil {
+			return Config{}, fmt.Errorf("model %s metadata: %s", modelId, err.Error())
+		}
+	}
+}
+```
+
+Add this new helper function to replace `substituteMetadataMacros`:
+
+```go
+// substituteMacroInValue recursively substitutes a single macro in a value structure
+// This is called once per macro, allowing LIFO substitution order
+func substituteMacroInValue(value any, macroName string, macroValue any) (any, error) {
+	macroSlug := fmt.Sprintf("${%s}", macroName)
+	macroStr := fmt.Sprintf("%v", macroValue)
+
+	switch v := value.(type) {
+	case string:
+		// Check if this is a direct macro substitution
+		if v == macroSlug {
+			return macroValue, nil
+		}
+		// Handle string interpolation
+		if strings.Contains(v, macroSlug) {
+			return strings.ReplaceAll(v, macroSlug, macroStr), nil
+		}
+		return v, nil
+
+	case map[string]any:
+		// Recursively process map values
+		newMap := make(map[string]any)
+		for key, val := range v {
+			newVal, err := substituteMacroInValue(val, macroName, macroValue)
+			if err != nil {
+				return nil, err
+			}
+			newMap[key] = newVal
+		}
+		return newMap, nil
+
+	case []any:
+		// Recursively process slice elements
+		newSlice := make([]any, len(v))
+		for i, val := range v {
+			newVal, err := substituteMacroInValue(val, macroName, macroValue)
+			if err != nil {
+				return nil, err
+			}
+			newSlice[i] = newVal
+		}
+		return newSlice, nil
+
+	default:
+		// Return scalar types as-is
+		return value, nil
+	}
+}
+```
+
+### 7. Self-Reference Detection
+
+Add to `validateMacro` function:
+
+```go
+func validateMacro(name string, value any) error {
+    // ... existing validation ...
+
+    // Check for self-reference
+    if str, ok := value.(string); ok {
+        macroSlug := fmt.Sprintf("${%s}", name)
+        if strings.Contains(str, macroSlug) {
+            return fmt.Errorf("macro '%s' contains self-reference", name)
+        }
+    }
+
+    return nil
+}
+```
+
+## Testing Plan
+
+### 1. Migration Tests
+- **Test:** All existing macro tests still pass after YAML library migration
+- **Files:** All `*_test.go` files with macro tests
+
+### 2. Macro Order Tests
+
+#### Test: Macro-in-macro substitution order
+```yaml
+macros:
+  "A": "value-A"
+  "B": "prefix-${A}-suffix"
+
+models:
+  test:
+    cmd: "echo ${B}"
+```
+**Expected:** `cmd` becomes `"echo prefix-value-A-suffix"`
+
+#### Test: LIFO substitution order
+```yaml
+macros:
+  "base": "/models"
+  "path": "${base}/llama"
+  "full": "${path}/model.gguf"
+
+models:
+  test:
+    cmd: "load ${full}"
+```
+**Expected:** `cmd` becomes `"load /models/llama/model.gguf"`
+
+#### Test: Model macro overrides global
+```yaml
+macros:
+  "tag": "global"
+  "msg": "value-${tag}"
+
+models:
+  test:
+    macros:
+      "tag": "model-level"
+    cmd: "echo ${msg}"
+```
+**Expected:** `cmd` becomes `"echo value-model-level"` (model macro overrides global)
+
+### 3. Reserved Macro Tests
+
+#### Test: MODEL_ID substituted in macro
+```yaml
+macros:
+  "podman-llama": "podman run --name ${MODEL_ID} ghcr.io/ggml-org/llama.cpp:server-cuda"
+
+models:
+  my-model:
+    cmd: "${podman-llama} -m model.gguf"
+```
+**Expected:** `cmd` becomes `"podman run --name my-model ghcr.io/ggml-org/llama.cpp:server-cuda -m model.gguf"`
+
+### 4. Error Detection Tests
+
+#### Test: Self-reference detection
+```yaml
+macros:
+  "recursive": "value-${recursive}"
+```
+**Expected:** Error: `macro 'recursive' contains self-reference`
+
+#### Test: Undefined macro reference
+```yaml
+macros:
+  "A": "value-${UNDEFINED}"
+```
+**Expected:** Error: `unknown macro '${UNDEFINED}' found in macros.A` (or similar)
+
+### 5. Regression Tests
+- Run all existing macro tests: `TestConfig_MacroReplacement`, `TestConfig_MacroReservedNames`, etc.
+- Ensure all pass without modification (except test fixtures if needed)
+
+## Checklist
+
+### Phase 1: Data Structure Changes
+- [ ] Implement custom `UnmarshalYAML` method for `MacroList` that uses `yaml.Node`
+- [ ] Define new ordered `MacroList` type as `[]MacroEntry`
+- [ ] Update `MacroList` type definition in [config.go](proxy/config/config.go#L19)
+- [ ] Update `Config.Macros` field type in [config.go](proxy/config/config.go#L69)
+- [ ] Update `ModelConfig.Macros` field type in [model_config.go](proxy/config/model_config.go#L33)
+- [ ] Implement helper functions:
+  - [ ] `func (ml MacroList) Get(name string) (any, bool)` - lookup by name
+  - [ ] `func (ml MacroList) Set(name string, value any) MacroList` - add/override entry
+  - [ ] `func (ml MacroList) ToMap() map[string]any` - convert to map if needed
+
+### Phase 2: Macro Validation Updates
+- [ ] Update macro validation loop at [config.go:153-157](proxy/config/config.go#L153-L157)
+- [ ] Update model macro validation at [config.go:175-179](proxy/config/config.go#L175-L179)
+- [ ] Add self-reference detection to `validateMacro` function [config.go:389](proxy/config/config.go#L389)
+- [ ] Test self-reference detection with new test case
+
+### Phase 3: Macro Substitution Algorithm
+- [ ] Implement ordered macro merging (global → model → reserved) at [config.go:181-188](proxy/config/config.go#L181-L188)
+- [ ] Implement single-pass LIFO substitution loop (reverse iteration) at [config.go:193-202](proxy/config/config.go#L193-L202)
+  - [ ] Substitute in all string fields (cmd, cmdStop, proxy, checkEndpoint, stripParams)
+  - [ ] Substitute in metadata within same loop
+- [ ] Ensure `MODEL_ID` is added to merged macros before substitution
+- [ ] Ensure `PORT` is added after port assignment (if needed)
+- [ ] Replace `substituteMetadataMacros` with new `substituteMacroInValue` function that processes one macro at a time [config.go:420](proxy/config/config.go#L420)
+- [ ] Remove old metadata substitution code that was separate from main loop [config.go:245-251](proxy/config/config.go#L245-L251)
+
+### Phase 4: Testing
+- [ ] Run `make test-dev` - fix any static checking errors
+- [ ] Add test: macro-in-macro basic substitution
+- [ ] Add test: LIFO substitution order with 3+ macro levels
+- [ ] Add test: MODEL_ID in global macro used by model
+- [ ] Add test: PORT in global macro used by model
+- [ ] Add test: model macro overrides global macro in substitution
+- [ ] Add test: self-reference detection error
+- [ ] Add test: undefined macro reference error
+- [ ] Verify all existing macro tests pass: `TestConfig_Macro*`
+- [ ] Run `make test-all` - ensure all tests including concurrency tests pass
+
+### Phase 5: Documentation
+- [ ] Update plan status in this file (mark completed)
+- [ ] Update CLAUDE.md if macro behavior needs documentation
+- [ ] Verify no new error messages need user documentation
+
+## Bug Example (Original Issue)
+
+```yaml
+macros:
+  "podman-llama": >
+    podman run --name ${MODEL_ID}
+    --init --rm -p ${PORT}:8080 -v /home/alex/ai/models:/models:z --gpus=all
+    ghcr.io/ggml-org/llama.cpp:server-cuda
+
+  "standard-options": >
+    --no-mmap --jinja
+
+  "kv8": >
+    -fa on -ctk q8_0 -ctv q8_0
+```
+
+**Current Bug:**
+- During macro substitution, if `${MODEL_ID}` is processed before `${podman-llama}`, the `${MODEL_ID}` reference inside `podman-llama` remains unsubstituted
+- Results in error: `unknown macro '${MODEL_ID}' found in model.cmd`
+
+**After Fix:**
+- Macros substituted in LIFO order: `kv8` → `standard-options` → `podman-llama`
+- `MODEL_ID` is a reserved macro, substituted last (after all user macros)
+- `${MODEL_ID}` inside `podman-llama` is correctly replaced with the model name
diff --git a/config.example.yaml b/config.example.yaml
index 711e427..189352b 100644
--- a/config.example.yaml
+++ b/config.example.yaml
@@ -43,14 +43,19 @@ startPort: 10001
 # - macro names are strings and must be less than 64 characters
 # - macro names must match the regex ^[a-zA-Z0-9_-]+$
 # - macro names must not be a reserved name: PORT or MODEL_ID
-# - macro values must be less than 1024 characters
-#
-# Important: do not nest macros inside other macros; expansion is single-pass
+# - macro values can be numbers, bools, or strings
+# - macros can contain other macros, but they must be defined before they are used
 macros:
+  # Example of a multi-line macro
   "latest-llama": >
     /path/to/llama-server/llama-server-ec9e0301
     --port ${PORT}
-  "default_ctx": "4096"
+
+  "default_ctx": 4096
+
+  # Example of macro-in-macro usage. macros can contain other macros
+  # but they must be previously declared.
+  "default_args": "--ctx-size ${default_ctx}"
 
 # models: a dictionary of model configurations
 # - required
diff --git a/proxy/config/config.go b/proxy/config/config.go
index 2bf4067..97cb56b 100644
--- a/proxy/config/config.go
+++ b/proxy/config/config.go
@@ -7,7 +7,6 @@ import (
 	"regexp"
 	"runtime"
 	"sort"
-	"strconv"
 	"strings"
 
 	"github.com/billziss-gh/golib/shlex"
@@ -16,7 +15,60 @@ import (
 
 const DEFAULT_GROUP_ID = "(default)"
 
-type MacroList map[string]any
+type MacroEntry struct {
+	Name  string
+	Value any
+}
+
+type MacroList []MacroEntry
+
+// UnmarshalYAML implements custom YAML unmarshaling that preserves macro definition order
+func (ml *MacroList) UnmarshalYAML(value *yaml.Node) error {
+	if value.Kind != yaml.MappingNode {
+		return fmt.Errorf("macros must be a mapping")
+	}
+
+	// yaml.Node.Content for a mapping contains alternating key/value nodes
+	entries := make([]MacroEntry, 0, len(value.Content)/2)
+	for i := 0; i < len(value.Content); i += 2 {
+		keyNode := value.Content[i]
+		valueNode := value.Content[i+1]
+
+		var name string
+		if err := keyNode.Decode(&name); err != nil {
+			return fmt.Errorf("failed to decode macro name: %w", err)
+		}
+
+		var val any
+		if err := valueNode.Decode(&val); err != nil {
+			return fmt.Errorf("failed to decode macro value for '%s': %w", name, err)
+		}
+
+		entries = append(entries, MacroEntry{Name: name, Value: val})
+	}
+
+	*ml = entries
+	return nil
+}
+
+// Get retrieves a macro value by name
+func (ml MacroList) Get(name string) (any, bool) {
+	for _, entry := range ml {
+		if entry.Name == name {
+			return entry.Value, true
+		}
+	}
+	return nil, false
+}
+
+// ToMap converts MacroList to a map (for backward compatibility if needed)
+func (ml MacroList) ToMap() map[string]any {
+	result := make(map[string]any, len(ml))
+	for _, entry := range ml {
+		result[entry.Name] = entry.Value
+	}
+	return result
+}
 
 type GroupConfig struct {
 	Swap       bool     `yaml:"swap"`
@@ -150,8 +202,8 @@ func LoadConfigFromReader(r io.Reader) (Config, error) {
 	- name can not be any reserved macros: PORT, MODEL_ID
 	- macro values must be less than 1024 characters
 	*/
-	for macroName, macroValue := range config.Macros {
-		if err = validateMacro(macroName, macroValue); err != nil {
+	for _, macro := range config.Macros {
+		if err = validateMacro(macro.Name, macro.Value); err != nil {
 			return Config{}, err
 		}
 	}
@@ -172,49 +224,88 @@ func LoadConfigFromReader(r io.Reader) (Config, error) {
 		modelConfig.CmdStop = StripComments(modelConfig.CmdStop)
 
 		// validate model macros
-		for macroName, macroValue := range modelConfig.Macros {
-			if err = validateMacro(macroName, macroValue); err != nil {
+		for _, macro := range modelConfig.Macros {
+			if err = validateMacro(macro.Name, macro.Value); err != nil {
 				return Config{}, fmt.Errorf("model %s: %s", modelId, err.Error())
 			}
 		}
 
 		// Merge global config and model macros. Model macros take precedence
-		mergedMacros := make(MacroList)
-		for k, v := range config.Macros {
-			mergedMacros[k] = v
-		}
-		for k, v := range modelConfig.Macros {
-			mergedMacros[k] = v
+		mergedMacros := make(MacroList, 0, len(config.Macros)+len(modelConfig.Macros))
+		mergedMacros = append(mergedMacros, MacroEntry{Name: "MODEL_ID", Value: modelId})
+
+		// Add global macros first
+		mergedMacros = append(mergedMacros, config.Macros...)
+
+		// Add model macros (can override global)
+		for _, entry := range modelConfig.Macros {
+			// Remove any existing global macro with same name
+			found := false
+			for i, existing := range mergedMacros {
+				if existing.Name == entry.Name {
+					mergedMacros[i] = entry // Override
+					found = true
+					break
+				}
+			}
+			if !found {
+				mergedMacros = append(mergedMacros, entry)
+			}
 		}
 
-		mergedMacros["MODEL_ID"] = modelId
+		// First pass: Substitute user-defined macros in reverse order (LIFO - last defined first)
+		// This allows later macros to reference earlier ones
+		for i := len(mergedMacros) - 1; i >= 0; i-- {
+			entry := mergedMacros[i]
+			macroSlug := fmt.Sprintf("${%s}", entry.Name)
+			macroStr := fmt.Sprintf("%v", entry.Value)
 
-		// go through model config fields: cmd, cmdStop, proxy, checkEndPoint and replace macros with macro values
-		for macroName, macroValue := range mergedMacros {
-			macroSlug := fmt.Sprintf("${%s}", macroName)
-			// Convert macro value to string for command/string field substitution
-			macroStr := fmt.Sprintf("%v", macroValue)
+			// Substitute in command fields
 			modelConfig.Cmd = strings.ReplaceAll(modelConfig.Cmd, macroSlug, macroStr)
 			modelConfig.CmdStop = strings.ReplaceAll(modelConfig.CmdStop, macroSlug, macroStr)
 			modelConfig.Proxy = strings.ReplaceAll(modelConfig.Proxy, macroSlug, macroStr)
 			modelConfig.CheckEndpoint = strings.ReplaceAll(modelConfig.CheckEndpoint, macroSlug, macroStr)
 			modelConfig.Filters.StripParams = strings.ReplaceAll(modelConfig.Filters.StripParams, macroSlug, macroStr)
+
+			// Substitute in metadata (recursive)
+			if len(modelConfig.Metadata) > 0 {
+				var err error
+				result, err := substituteMacroInValue(modelConfig.Metadata, entry.Name, entry.Value)
+				if err != nil {
+					return Config{}, fmt.Errorf("model %s metadata: %s", modelId, err.Error())
+				}
+				modelConfig.Metadata = result.(map[string]any)
+			}
 		}
 
-		// enforce ${PORT} used in both cmd and proxy
-		if !strings.Contains(modelConfig.Cmd, "${PORT}") && strings.Contains(modelConfig.Proxy, "${PORT}") {
-			return Config{}, fmt.Errorf("model %s: proxy uses ${PORT} but cmd does not - ${PORT} is only available when used in cmd", modelId)
-		}
+		// Final pass: check if PORT macro is needed after macro expansion
+		// ${PORT} is a resource on the local machine so a new port is only allocated
+		// if it is required in either cmd or proxy keys
+		cmdHasPort := strings.Contains(modelConfig.Cmd, "${PORT}")
+		proxyHasPort := strings.Contains(modelConfig.Proxy, "${PORT}")
+		if cmdHasPort || proxyHasPort { // either has it
+			if !cmdHasPort && proxyHasPort { // but both don't have it
+				return Config{}, fmt.Errorf("model %s: proxy uses ${PORT} but cmd does not - ${PORT} is only available when used in cmd", modelId)
+			}
 
-		// only iterate over models that use ${PORT} to keep port numbers from increasing unnecessarily
-		if strings.Contains(modelConfig.Cmd, "${PORT}") || strings.Contains(modelConfig.Proxy, "${PORT}") || strings.Contains(modelConfig.CmdStop, "${PORT}") {
-			nextPortStr := strconv.Itoa(nextPort)
-			modelConfig.Cmd = strings.ReplaceAll(modelConfig.Cmd, "${PORT}", nextPortStr)
-			modelConfig.CmdStop = strings.ReplaceAll(modelConfig.CmdStop, "${PORT}", nextPortStr)
-			modelConfig.Proxy = strings.ReplaceAll(modelConfig.Proxy, "${PORT}", nextPortStr)
+			// Add PORT macro and substitute it
+			portEntry := MacroEntry{Name: "PORT", Value: nextPort}
+			macroSlug := "${PORT}"
+			macroStr := fmt.Sprintf("%v", nextPort)
 
-			// add port to merged macros so it can be used in metadata
-			mergedMacros["PORT"] = nextPort
+			modelConfig.Cmd = strings.ReplaceAll(modelConfig.Cmd, macroSlug, macroStr)
+			modelConfig.CmdStop = strings.ReplaceAll(modelConfig.CmdStop, macroSlug, macroStr)
+			modelConfig.Proxy = strings.ReplaceAll(modelConfig.Proxy, macroSlug, macroStr)
+
+			// Substitute PORT in metadata
+			if len(modelConfig.Metadata) > 0 {
+				var err error
+				result, err := substituteMacroInValue(modelConfig.Metadata, portEntry.Name, portEntry.Value)
+				if err != nil {
+					return Config{}, fmt.Errorf("model %s metadata: %s", modelId, err.Error())
+				}
+				modelConfig.Metadata = result.(map[string]any)
+			}
 
 			nextPort++
 		}
@@ -235,19 +326,20 @@ func LoadConfigFromReader(r io.Reader) (Config, error) {
 				if macroName == "PID" && fieldName == "cmdStop" {
 					continue // this is ok, has to be replaced by process later
 				}
-				if _, exists := config.Macros[macroName]; !exists {
-					return Config{}, fmt.Errorf("unknown macro '${%s}' found in %s.%s", macroName, modelId, fieldName)
+				// Reserved macros are always valid (they should have been substituted already)
+				if macroName == "PORT" || macroName == "MODEL_ID" {
+					return Config{}, fmt.Errorf("macro '${%s}' should have been substituted in %s.%s", macroName, modelId, fieldName)
 				}
+				// Any other macro is unknown
+				return Config{}, fmt.Errorf("unknown macro '${%s}' found in %s.%s", macroName, modelId, fieldName)
 			}
 		}
 
-		// Apply macro substitution to metadata
+		// Check for unknown macros in metadata
 		if len(modelConfig.Metadata) > 0 {
-			substitutedMetadata, err := substituteMetadataMacros(modelConfig.Metadata, mergedMacros)
-			if err != nil {
-				return Config{}, fmt.Errorf("model %s metadata: %s", modelId, err.Error())
+			if err := validateMetadataForUnknownMacros(modelConfig.Metadata, modelId); err != nil {
+				return Config{}, err
 			}
-			modelConfig.Metadata = substitutedMetadata.(map[string]any)
 		}
 
 		config.Models[modelId] = modelConfig
@@ -400,6 +492,11 @@ func validateMacro(name string, value any) error {
 		if len(v) >= 1024 {
 			return fmt.Errorf("macro value for '%s' exceeds maximum length of 1024 characters", name)
 		}
+		// Check for self-reference
+		macroSlug := fmt.Sprintf("${%s}", name)
+		if strings.Contains(v, macroSlug) {
+			return fmt.Errorf("macro '%s' contains self-reference", name)
+		}
 	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64, float32, float64, bool:
 		// These types are allowed
 	default:
@@ -414,41 +511,62 @@ func validateMacro(name string, value any) error {
 	return nil
 }
 
-// substituteMetadataMacros recursively substitutes macros in metadata structures
-// Direct substitution (key: ${macro}) preserves the macro's type
-// Interpolated substitution (key: "text ${macro}") converts to string
-func substituteMetadataMacros(value any, macros MacroList) (any, error) {
+// validateMetadataForUnknownMacros recursively checks for any remaining macro references in metadata
+func validateMetadataForUnknownMacros(value any, modelId string) error {
+	switch v := value.(type) {
+	case string:
+		matches := macroPatternRegex.FindAllStringSubmatch(v, -1)
+		for _, match := range matches {
+			macroName := match[1]
+			return fmt.Errorf("model %s metadata: unknown macro '${%s}'", modelId, macroName)
+		}
+		return nil
+
+	case map[string]any:
+		for _, val := range v {
+			if err := validateMetadataForUnknownMacros(val, modelId); err != nil {
+				return err
+			}
+		}
+		return nil
+
+	case []any:
+		for _, val := range v {
+			if err := validateMetadataForUnknownMacros(val, modelId); err != nil {
+				return err
+			}
+		}
+		return nil
+
+	default:
+		// Scalar types don't contain macros
+		return nil
+	}
+}
+
+// substituteMacroInValue recursively substitutes a single macro in a value structure
+// This is called once per macro, allowing LIFO substitution order
+func substituteMacroInValue(value any, macroName string, macroValue any) (any, error) {
+	macroSlug := fmt.Sprintf("${%s}", macroName)
+	macroStr := fmt.Sprintf("%v", macroValue)
+
 	switch v := value.(type) {
 	case string:
 		// Check if this is a direct macro substitution
-		if strings.HasPrefix(v, "${") && strings.HasSuffix(v, "}") && strings.Count(v, "${") == 1 {
-			macroName := v[2 : len(v)-1]
-			if macroValue, exists := macros[macroName]; exists {
-				return macroValue, nil
-			}
-			return nil, fmt.Errorf("unknown macro '${%s}' in metadata", macroName)
+		if v == macroSlug {
+			return macroValue, nil
 		}
-
 		// Handle string interpolation
-		matches := macroPatternRegex.FindAllStringSubmatch(v, -1)
-		result := v
-		for _, match := range matches {
-			macroName := match[1]
-			macroValue, exists := macros[macroName]
-			if !exists {
-				return nil, fmt.Errorf("unknown macro '${%s}' in metadata", macroName)
-			}
-			// Convert macro value to string for interpolation
-			macroStr := fmt.Sprintf("%v", macroValue)
-			result = strings.ReplaceAll(result, match[0], macroStr)
+		if strings.Contains(v, macroSlug) {
+			return strings.ReplaceAll(v, macroSlug, macroStr), nil
 		}
-		return result, nil
+		return v, nil
 
 	case map[string]any:
 		// Recursively process map values
 		newMap := make(map[string]any)
 		for key, val := range v {
-			newVal, err := substituteMetadataMacros(val, macros)
+			newVal, err := substituteMacroInValue(val, macroName, macroValue)
 			if err != nil {
 				return nil, err
 			}
@@ -460,7 +578,7 @@ func substituteMetadataMacros(value any, macros MacroList) (any, error) {
 		// Recursively process slice elements
 		newSlice := make([]any, len(v))
 		for i, val := range v {
-			newVal, err := substituteMetadataMacros(val, macros)
+			newVal, err := substituteMacroInValue(val, macroName, macroValue)
 			if err != nil {
 				return nil, err
 			}
diff --git a/proxy/config/config_posix_test.go b/proxy/config/config_posix_test.go
index 036c92f..abf0ea7 100644
--- a/proxy/config/config_posix_test.go
+++ b/proxy/config/config_posix_test.go
@@ -164,7 +164,7 @@ groups:
 		LogLevel:  "info",
 		StartPort: 5800,
 		Macros: MacroList{
-			"svr-path": "path/to/server",
+			{"svr-path", "path/to/server"},
 		},
 		Hooks: HooksConfig{
 			OnStartup: HookOnStartup{
diff --git a/proxy/config/config_test.go b/proxy/config/config_test.go
index ec2aa05..e624a8c 100644
--- a/proxy/config/config_test.go
+++ b/proxy/config/config_test.go
@@ -213,7 +213,9 @@ models:
 `
 
 	config, err := LoadConfigFromReader(strings.NewReader(content))
-	assert.NoError(t, err)
+	if !assert.NoError(t, err) {
+		t.FailNow()
+	}
 	sanitizedCmd, err := SanitizeCommand(config.Models["model1"].Cmd)
 	assert.NoError(t, err)
 	assert.Equal(t, "path/to/server --arg2 --port 9990 --arg1 --arg3 three --overridden success", strings.Join(sanitizedCmd, " "))
@@ -321,7 +323,7 @@ macros:
 models:
   model1:
     cmd: "${svr-path} --port ${PORT}"
-    proxy: "http://localhost:${unknownMacro}"
+    proxy: "http://${unknownMacro}:${PORT}"
 `,
 		},
 		{
@@ -503,7 +505,9 @@ models:
 	assert.NoError(t, err)
 	assert.Equal(t, "/path/to/server -p 9001 -hf model1", strings.Join(sanitizedCmd, " "))
 
-	assert.Equal(t, "docker stop ${MODEL_ID}", config.Macros["docker-stop"])
+	dockerStopMacro, found := config.Macros.Get("docker-stop")
+	assert.True(t, found)
+	assert.Equal(t, "docker stop ${MODEL_ID}", dockerStopMacro)
 
 	sanitizedCmd2, err := SanitizeCommand(config.Models["model2"].Cmd)
 	assert.NoError(t, err)
diff --git a/proxy/config/config_windows_test.go b/proxy/config/config_windows_test.go
index 293f41a..20ff692 100644
--- a/proxy/config/config_windows_test.go
+++ b/proxy/config/config_windows_test.go
@@ -156,7 +156,7 @@ groups:
 		LogLevel:  "info",
 		StartPort: 5800,
 		Macros: MacroList{
-			"svr-path": "path/to/server",
+			{"svr-path", "path/to/server"},
 		},
 		Models: map[string]ModelConfig{
 			"model1": {
diff --git a/proxy/config/macro_in_macro_test.go b/proxy/config/macro_in_macro_test.go
new file mode 100644
index 0000000..e110ed2
--- /dev/null
+++ b/proxy/config/macro_in_macro_test.go
@@ -0,0 +1,123 @@
+package config
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// Test macro-in-macro basic substitution
+func TestConfig_MacroInMacroBasic(t *testing.T) {
+	content := `
+startPort: 10000
+macros:
+  "A": "value-A"
+  "B": "prefix-${A}-suffix"
+
+models:
+  test:
+    cmd: echo ${B}
+    proxy: http://localhost:8080
+`
+
+	config, err := LoadConfigFromReader(strings.NewReader(content))
+	assert.NoError(t, err)
+	assert.Equal(t, "echo prefix-value-A-suffix", config.Models["test"].Cmd)
+}
+
+// Test LIFO substitution order with 3+ macro levels
+func TestConfig_MacroInMacroLIFOOrder(t *testing.T) {
+	content := `
+startPort: 10000
+macros:
+  "base": "/models"
+  "path": "${base}/llama"
+  "full": "${path}/model.gguf"
+
+models:
+  test:
+    cmd: load ${full}
+    proxy: http://localhost:8080
+`
+
+	config, err := LoadConfigFromReader(strings.NewReader(content))
+	assert.NoError(t, err)
+	assert.Equal(t, "load /models/llama/model.gguf", config.Models["test"].Cmd)
+}
+
+// Test MODEL_ID in global macro used by model
+func TestConfig_ModelIdInGlobalMacro(t *testing.T) {
+	content := `
+startPort: 10000
+macros:
+  "podman-llama": "podman run --name ${MODEL_ID} ghcr.io/ggml-org/llama.cpp:server-cuda"
+
+models:
+  my-model:
+    cmd: ${podman-llama} -m model.gguf
+    proxy: http://localhost:8080
+`
+
+	config, err := LoadConfigFromReader(strings.NewReader(content))
+	assert.NoError(t, err)
+	assert.Equal(t, "podman run --name my-model ghcr.io/ggml-org/llama.cpp:server-cuda -m model.gguf", config.Models["my-model"].Cmd)
+}
+
+// Test model macro overrides global macro in substitution
+func TestConfig_ModelMacroOverridesGlobal(t *testing.T) {
+	content := `
+startPort: 10000
+macros:
+  "tag": "global"
+  "msg": "value-${tag}"
+
+models:
+  test:
+    macros:
+      "tag": "model-level"
+    cmd: echo ${msg}
+    proxy: http://localhost:8080
+`
+
+	config, err := LoadConfigFromReader(strings.NewReader(content))
+	assert.NoError(t, err)
+	assert.Equal(t, "echo value-model-level", config.Models["test"].Cmd)
+}
+
+// Test self-reference detection error
+func TestConfig_SelfReferenceDetection(t *testing.T) {
+	content := `
+startPort: 10000
+macros:
+  "recursive": "value-${recursive}"
+
+models:
+  test:
+    cmd: echo ${recursive}
+    proxy: http://localhost:8080
+`
+
+	_, err := LoadConfigFromReader(strings.NewReader(content))
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "recursive")
+	assert.Contains(t, err.Error(), "self-reference")
+}
+
+// Test undefined macro reference error
+func TestConfig_UndefinedMacroReference(t *testing.T) {
+	content := `
+startPort: 10000
+macros:
+  "A": "value-${UNDEFINED}"
+
+models:
+  test:
+    cmd: echo ${A}
+    proxy: http://localhost:8080
+`
+
+	_, err := LoadConfigFromReader(strings.NewReader(content))
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "UNDEFINED")
+}