1 files changed, 242 insertions, 0 deletions
diff --git a/internal/appconfig/config_merge.go b/internal/appconfig/config_merge.go
new file mode 100644
index 0000000..d474fb7
--- /dev/null
+++ b/internal/appconfig/config_merge.go
@@ -0,0 +1,242 @@
+package appconfig
+
+import (
+	"slices"
+	"strings"
+)
+
+func (a *App) mergeWith(other *App) {
+	a.mergeBasics(other)
+	a.mergeProviderFields(other)
+	a.mergeSurfaceModels(other)
+	a.mergePrompts(other)
+	a.mergeTmuxEdit(other)
+}
+
+// mergeBasics merges general (non-provider) fields.
+func (a *App) mergeBasics(other *App) {
+	mergeBasicCore(a, other)
+	mergeBasicCompletion(a, other)
+	mergeBasicInteraction(a, other)
+	mergeBasicRuntime(a, other)
+}
+
+func mergeBasicCore(dst, src *App) {
+	if src.MaxTokens > 0 {
+		dst.MaxTokens = src.MaxTokens
+	}
+	if s := strings.TrimSpace(src.ContextMode); s != "" {
+		dst.ContextMode = s
+	}
+	if src.ContextWindowLines > 0 {
+		dst.ContextWindowLines = src.ContextWindowLines
+	}
+	if src.MaxContextTokens > 0 {
+		dst.MaxContextTokens = src.MaxContextTokens
+	}
+	if src.LogPreviewLimit >= 0 {
+		dst.LogPreviewLimit = src.LogPreviewLimit
+	}
+	if src.RequestTimeout > 0 {
+		dst.RequestTimeout = src.RequestTimeout
+	}
+	if src.CodingTemperature != nil { // allow explicit 0.0
+		dst.CodingTemperature = src.CodingTemperature
+	}
+}
+
+func mergeBasicCompletion(dst, src *App) {
+	if src.ManualInvokeMinPrefix >= 0 {
+		dst.ManualInvokeMinPrefix = src.ManualInvokeMinPrefix
+	}
+	if src.CompletionDebounceMs > 0 {
+		dst.CompletionDebounceMs = src.CompletionDebounceMs
+	}
+	if src.CompletionThrottleMs > 0 {
+		dst.CompletionThrottleMs = src.CompletionThrottleMs
+	}
+	if src.CompletionWaitAll != nil {
+		dst.CompletionWaitAll = src.CompletionWaitAll
+	}
+}
+
+func mergeBasicInteraction(dst, src *App) {
+	if len(src.TriggerCharacters) > 0 {
+		dst.TriggerCharacters = slices.Clone(src.TriggerCharacters)
+	}
+	if s := strings.TrimSpace(src.InlineOpen); s != "" {
+		dst.InlineOpen = s
+	}
+	if s := strings.TrimSpace(src.InlineClose); s != "" {
+		dst.InlineClose = s
+	}
+	if s := strings.TrimSpace(src.ChatSuffix); s != "" {
+		dst.ChatSuffix = s
+	}
+	if len(src.ChatPrefixes) > 0 {
+		dst.ChatPrefixes = slices.Clone(src.ChatPrefixes)
+	}
+	if s := strings.TrimSpace(src.Provider); s != "" {
+		dst.Provider = s
+	}
+}
+
+func mergeBasicRuntime(dst, src *App) {
+	if src.IgnoreGitignore != nil {
+		dst.IgnoreGitignore = src.IgnoreGitignore
+	}
+	if len(src.IgnoreExtraPatterns) > 0 {
+		dst.IgnoreExtraPatterns = slices.Clone(src.IgnoreExtraPatterns)
+	}
+	if src.IgnoreLSPNotify != nil {
+		dst.IgnoreLSPNotify = src.IgnoreLSPNotify
+	}
+	if s := strings.TrimSpace(src.MCPPromptsDir); s != "" {
+		dst.MCPPromptsDir = s
+	}
+	if src.MCPSlashCommandSync {
+		dst.MCPSlashCommandSync = src.MCPSlashCommandSync
+	}
+	if s := strings.TrimSpace(src.MCPSlashCommandDir); s != "" {
+		dst.MCPSlashCommandDir = s
+	}
+}
+
+// mergeProviderFields merges per-provider configuration.
+func (a *App) mergeProviderFields(other *App) {
+	if s := strings.TrimSpace(other.OpenAIBaseURL); s != "" {
+		a.OpenAIBaseURL = s
+	}
+	if s := strings.TrimSpace(other.OpenAIModel); s != "" {
+		a.OpenAIModel = s
+	}
+	if other.OpenAITemperature != nil { // allow explicit 0.0
+		a.OpenAITemperature = other.OpenAITemperature
+	}
+	if s := strings.TrimSpace(other.OpenRouterBaseURL); s != "" {
+		a.OpenRouterBaseURL = s
+	}
+	if s := strings.TrimSpace(other.OpenRouterModel); s != "" {
+		a.OpenRouterModel = s
+	}
+	if other.OpenRouterTemperature != nil { // allow explicit 0.0
+		a.OpenRouterTemperature = other.OpenRouterTemperature
+	}
+	if s := strings.TrimSpace(other.OllamaBaseURL); s != "" {
+		a.OllamaBaseURL = s
+	}
+	if s := strings.TrimSpace(other.OllamaModel); s != "" {
+		a.OllamaModel = s
+	}
+	if other.OllamaTemperature != nil { // allow explicit 0.0
+		a.OllamaTemperature = other.OllamaTemperature
+	}
+	if s := strings.TrimSpace(other.AnthropicBaseURL); s != "" {
+		a.AnthropicBaseURL = s
+	}
+	if s := strings.TrimSpace(other.AnthropicModel); s != "" {
+		a.AnthropicModel = s
+	}
+	if other.AnthropicTemperature != nil { // allow explicit 0.0
+		a.AnthropicTemperature = other.AnthropicTemperature
+	}
+}
+
+// mergeSurfaceModels copies per-surface model and temperature overrides.
+func (a *App) mergeSurfaceModels(other *App) {
+	if len(other.CompletionConfigs) > 0 {
+		a.CompletionConfigs = cloneSurfaceConfigs(other.CompletionConfigs)
+	}
+	if len(other.CodeActionConfigs) > 0 {
+		a.CodeActionConfigs = cloneSurfaceConfigs(other.CodeActionConfigs)
+	}
+	if len(other.ChatConfigs) > 0 {
+		a.ChatConfigs = cloneSurfaceConfigs(other.ChatConfigs)
+	}
+	if len(other.CLIConfigs) > 0 {
+		a.CLIConfigs = cloneSurfaceConfigs(other.CLIConfigs)
+	}
+}
+
+func cloneSurfaceConfigs(src []SurfaceConfig) []SurfaceConfig {
+	if len(src) == 0 {
+		return nil
+	}
+	out := make([]SurfaceConfig, len(src))
+	copy(out, src)
+	return out
+}
+
+// mergePrompts copies non-empty prompt templates from other.
+func (a *App) mergePrompts(other *App) {
+	mergeCompletionPrompts(a, other)
+	mergeProviderNativePrompt(a, other)
+	mergeChatPrompt(a, other)
+	mergeCodeActionPrompts(a, other)
+	mergeCLIPrompts(a, other)
+	mergeCustomActionPrompts(a, other)
+}
+
+func mergeCompletionPrompts(dst, src *App) {
+	mergeStringField(&dst.PromptCompletionSystemGeneral, src.PromptCompletionSystemGeneral)
+	mergeStringField(&dst.PromptCompletionSystemParams, src.PromptCompletionSystemParams)
+	mergeStringField(&dst.PromptCompletionSystemInline, src.PromptCompletionSystemInline)
+	mergeStringField(&dst.PromptCompletionUserGeneral, src.PromptCompletionUserGeneral)
+	mergeStringField(&dst.PromptCompletionUserParams, src.PromptCompletionUserParams)
+	mergeStringField(&dst.PromptCompletionExtraHeader, src.PromptCompletionExtraHeader)
+}
+
+func mergeProviderNativePrompt(dst, src *App) {
+	mergeStringField(&dst.PromptNativeCompletion, src.PromptNativeCompletion)
+}
+
+func mergeChatPrompt(dst, src *App) {
+	mergeStringField(&dst.PromptChatSystem, src.PromptChatSystem)
+}
+
+func mergeCodeActionPrompts(dst, src *App) {
+	mergeStringField(&dst.PromptCodeActionRewriteSystem, src.PromptCodeActionRewriteSystem)
+	mergeStringField(&dst.PromptCodeActionDiagnosticsSystem, src.PromptCodeActionDiagnosticsSystem)
+	mergeStringField(&dst.PromptCodeActionDocumentSystem, src.PromptCodeActionDocumentSystem)
+	mergeStringField(&dst.PromptCodeActionRewriteUser, src.PromptCodeActionRewriteUser)
+	mergeStringField(&dst.PromptCodeActionDiagnosticsUser, src.PromptCodeActionDiagnosticsUser)
+	mergeStringField(&dst.PromptCodeActionDocumentUser, src.PromptCodeActionDocumentUser)
+	mergeStringField(&dst.PromptCodeActionGoTestSystem, src.PromptCodeActionGoTestSystem)
+	mergeStringField(&dst.PromptCodeActionGoTestUser, src.PromptCodeActionGoTestUser)
+	mergeStringField(&dst.PromptCodeActionSimplifySystem, src.PromptCodeActionSimplifySystem)
+	mergeStringField(&dst.PromptCodeActionSimplifyUser, src.PromptCodeActionSimplifyUser)
+}
+
+func mergeCLIPrompts(dst, src *App) {
+	mergeStringField(&dst.PromptCLIDefaultSystem, src.PromptCLIDefaultSystem)
+	mergeStringField(&dst.PromptCLIExplainSystem, src.PromptCLIExplainSystem)
+}
+
+func mergeCustomActionPrompts(dst, src *App) {
+	if len(src.CustomActions) > 0 {
+		dst.CustomActions = append([]CustomAction{}, src.CustomActions...)
+	}
+	mergeStringField(&dst.TmuxCustomMenuHotkey, src.TmuxCustomMenuHotkey)
+}
+
+func mergeStringField(dst *string, src string) {
+	if strings.TrimSpace(src) != "" {
+		*dst = src
+	}
+}
+
+// mergeTmuxEdit copies non-empty tmux edit settings from other.
+func (a *App) mergeTmuxEdit(other *App) {
+	if s := strings.TrimSpace(other.TmuxEditPopupWidth); s != "" {
+		a.TmuxEditPopupWidth = s
+	}
+	if s := strings.TrimSpace(other.TmuxEditPopupHeight); s != "" {
+		a.TmuxEditPopupHeight = s
+	}
+	if s := strings.TrimSpace(other.TmuxEditDefaultAgent); s != "" {
+		a.TmuxEditDefaultAgent = s
+	}
+	if len(other.TmuxEditAgents) > 0 {
+		a.TmuxEditAgents = append([]TmuxEditAgentCfg{}, other.TmuxEditAgents...)
+	}
+}