use TOML not JSON for configuration

13 files changed, 7486 insertions, 7304 deletions

diff --git a/AGENTS.md b/AGENTS.md
index 629c5de..8758804 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -10,7 +10,7 @@
 
 - If possible, construct individual methods so that they can be unit tested. But only if it doesn't add too much boilerplate to the code base.
 - Aim for at least 85% unit test coverage of all source code.
-- Ensure that all unit tests pass before merging any changes.
+- Ensure that all unit tests pass before commiting any changes.
 - Always run the gofumpt code reformatter on all go files modified.
 - There should be no source code file larger than 1000 lines. If so, split it up into multiple.
 - There should be no function larger then 50 lines. If so, refactor or split up into multiple smaller functions.
diff --git a/PROJECTSTATUS.md b/PROJECTSTATUS.md
index cc87928..4114df6 100644
--- a/PROJECTSTATUS.md
+++ b/PROJECTSTATUS.md
@@ -4,26 +4,22 @@
 
 ### New features
 
-* [X] Create "generate unit test" code action for selected code block => write test to FILE_test.go file
+* [ ] Have all text LLM prompts be configurable. With defaults as of now.
 * [ ] implement a code action for selected code block the way via a unix pipe as faster access in helix
+  - pipe selected code to external command and replace selection with output
+  - the external command should open a menu to select an action (e.g. "format", "refactor", "explain", "test", etc.) and then apply it to the selected code
+  - the external menu can be opened in a separate tmux pane
+* [ ] Fish and zsh and bash shell integration for command completion? Have access to the current shell history (N last commands), current directory content, and current directory name.
+* [X] Create "generate unit test" code action for selected code block => write test to FILE_test.go file
 * [X] Use hexai as a gh copilot... CLI replacemant for command line questions
 * [X] Resolve diagnostics code action feature
 * [X] LSP server to be used with the Helix text editor
 * [X] Code completion using LLMs
-* [ ] Have all text LLM prompts be configurable. With defaults as of now.
 * [X] Text completion in general
 * [/] Be a replacement for 'github copilot cli'
 * [X] Be able to perform inline chats (keeping history in the document)
-* [ ] Be able to switch the underlying model via a prompt
 * [X] Fine tune when Large Language Model (LLM) completions trigger, as it seems that there are some cases where the Large Language Model (LLM) receives a request but Helix isn't suggesting any completions. There seems to be something odd with the in logic. Investigate the TriggerChar logic and make sure it matches Helix's expectations.
 * [X] Can anything else can be done with LSP?
-* [ ] Fish and zsh and bash shell integration for command completion? Have access to the current shell history (N last commands), current directory content, and current directory name.
-
-Be able to select code blocks and perform code actions on them
-
-* [X] Commenting exiting code
-* [X] Add unit test (for Go)
-* [X] Code refactoring (via comment instruction)
 
 Be able to switch LLMs. 
 
diff --git a/config.json.example b/config.json.example
deleted file mode 100644
index 7a4298c..0000000
--- a/config.json.example
+++ /dev/null
@@ -1,30 +0,0 @@
-{
-  "max_tokens": 4000,
-  "context_mode": "file-on-new-func",
-  "context_window_lines": 120,
-  "max_context_tokens": 4000,
-  "log_preview_limit": 100,
-  "completion_debounce_ms": 200,
-  "completion_throttle_ms": 0,
-  "no_disk_io": true,
-  "trigger_characters": [".", ":", "/", "_", " "],
-  "inline_open": ">",
-  "inline_close": ">",
-  "chat_suffix": ">",
-  "chat_prefixes": ["?", "!", ":", ";"],
-  "coding_temperature": 0.2,
-
-  "provider": "openai",
-
-  "openai_model": "gpt-4.1",
-  "openai_base_url": "https://api.openai.com/v1",
-  "openai_temperature": 0.2,
-
-  "ollama_model": "qwen3-coder:30b-a3b-q4_K_M",
-  "ollama_base_url": "http://localhost:11434",
-  "ollama_temperature": 0.2,
-
-  "copilot_model": "gpt-4o-mini",
-  "copilot_base_url": "https://api.githubcopilot.com",
-  "copilot_temperature": 0.2
-}
diff --git a/config.toml.example b/config.toml.example
new file mode 100644
index 0000000..70b4442
--- /dev/null
+++ b/config.toml.example
@@ -0,0 +1,34 @@
+max_tokens = 4000
+context_mode = "file-on-new-func"
+context_window_lines = 120
+max_context_tokens = 4000
+log_preview_limit = 100
+completion_debounce_ms = 200
+completion_throttle_ms = 0
+# Optional: disable disk IO while building context (reserved)
+# no_disk_io = true
+trigger_characters = [".", ":", "/", "_", " "]
+inline_open = ">"
+inline_close = ">"
+chat_suffix = ">"
+chat_prefixes = ["?", "!", ":", ";"]
+coding_temperature = 0.2
+
+# Provider: openai | copilot | ollama
+provider = "openai"
+
+# OpenAI
+openai_model = "gpt-4.1"
+openai_base_url = "https://api.openai.com/v1"
+openai_temperature = 0.2
+
+# Ollama
+ollama_model = "qwen3-coder:30b-a3b-q4_K_M"
+ollama_base_url = "http://localhost:11434"
+ollama_temperature = 0.2
+
+# GitHub Copilot
+copilot_model = "gpt-4o-mini"
+copilot_base_url = "https://api.githubcopilot.com"
+copilot_temperature = 0.2
+
diff --git a/docs/configuration.md b/docs/configuration.md
index 3b862af..d52323c 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -7,36 +7,39 @@ environment overrides, provider selection, and temperature behavior.
 
 The config file is optional. 
 
-- Location: `$XDG_CONFIG_HOME/hexai/config.json` (usually `~/.config/hexai/config.json`).
+- Location: `$XDG_CONFIG_HOME/hexai/config.toml` (usually `~/.config/hexai/config.toml`).
 - Example:
 
-```json
-{
-  "max_tokens": 4000,
-  "context_mode": "always-full",
-  "context_window_lines": 120,
-  "max_context_tokens": 4000,
-  "log_preview_limit": 100,
-  "completion_debounce_ms": 200,
-  "completion_throttle_ms": 0,
-  "no_disk_io": true,
-  "trigger_characters": [".", ":", "/", "_", " " ],
-  "inline_open": ">",
-  "inline_close": ">",
-  "chat_suffix": ">",
-  "chat_prefixes": ["?", "!", ":", ";"],
-  "coding_temperature": 0.2,
-  "provider": "ollama",
-  "copilot_model": "gpt-4o-mini",
-  "copilot_base_url": "https://api.githubcopilot.com",
-  "copilot_temperature": 0.2,
-  "openai_model": "gpt-4.1",
-  "openai_base_url": "https://api.openai.com/v1",
-  "openai_temperature": 0.2,
-  "ollama_model": "qwen3-coder:30b-a3b-q4_K_M",
-  "ollama_base_url": "http://localhost:11434",
-  "ollama_temperature": 0.2
-}
+```toml
+max_tokens = 4000
+context_mode = "always-full"
+context_window_lines = 120
+max_context_tokens = 4000
+log_preview_limit = 100
+completion_debounce_ms = 200
+completion_throttle_ms = 0
+# no_disk_io is reserved for future use
+trigger_characters = [".", ":", "/", "_", " "]
+inline_open = ">"
+inline_close = ">"
+chat_suffix = ">"
+chat_prefixes = ["?", "!", ":", ";"]
+coding_temperature = 0.2
+
+# choose one provider: openai | copilot | ollama
+provider = "ollama"
+
+copilot_model = "gpt-4o-mini"
+copilot_base_url = "https://api.githubcopilot.com"
+copilot_temperature = 0.2
+
+openai_model = "gpt-4.1"
+openai_base_url = "https://api.openai.com/v1"
+openai_temperature = 0.2
+
+ollama_model = "qwen3-coder:30b-a3b-q4_K_M"
+ollama_base_url = "http://localhost:11434"
+ollama_temperature = 0.2
 ```
 
 Key fields:
@@ -60,14 +63,12 @@ Key fields:
 
 Defaults use `>` for inline prompts and chat suffix. You can change them, e.g.:
 
-```json
-{
-  "inline_open": "<",
-  "inline_close": ">",
-  "chat_suffix": "/",
-  "chat_prefixes": ["?", "!"],
-  "trigger_characters": [".", ":", "/", "_", " "]
-}
+```toml
+inline_open = "<"
+inline_close = ">"
+chat_suffix = "/"
+chat_prefixes = ["?", "!"]
+trigger_characters = [".", ":", "/", "_", " "]
 ```
 
 Notes:
@@ -77,7 +78,7 @@ Notes:
 ## Environment overrides
 
 - All config-file options can be overridden by environment variables prefixed with `HEXAI_`.
-- Env values take precedence over `config.json`.
+- Env values take precedence over `config.toml`.
 - Examples:
   - `HEXAI_PROVIDER`, `HEXAI_MAX_TOKENS`, `HEXAI_CONTEXT_MODE`, `HEXAI_CONTEXT_WINDOW_LINES`, `HEXAI_MAX_CONTEXT_TOKENS`, `HEXAI_LOG_PREVIEW_LIMIT`
   - `HEXAI_CODING_TEMPERATURE`
diff --git a/docs/coverage.html b/docs/coverage.html
index d940029..49b89df 100644
--- a/docs/coverage.html
+++ b/docs/coverage.html
@@ -59,7 +59,7 @@
 				
 				<option value="file1">codeberg.org/snonux/hexai/cmd/hexai/main.go (0.0%)</option>
 				
-				<option value="file2">codeberg.org/snonux/hexai/internal/appconfig/config.go (86.9%)</option>
+				<option value="file2">codeberg.org/snonux/hexai/internal/appconfig/config.go (87.0%)</option>
 				
 				<option value="file3">codeberg.org/snonux/hexai/internal/hexaicli/run.go (91.4%)</option>
 				
@@ -83,19 +83,19 @@
 				
 				<option value="file13">codeberg.org/snonux/hexai/internal/lsp/document.go (90.1%)</option>
 				
-				<option value="file14">codeberg.org/snonux/hexai/internal/lsp/handlers.go (90.5%)</option>
+				<option value="file14">codeberg.org/snonux/hexai/internal/lsp/handlers.go (92.1%)</option>
 				
 				<option value="file15">codeberg.org/snonux/hexai/internal/lsp/handlers_codeaction.go (81.2%)</option>
 				
-				<option value="file16">codeberg.org/snonux/hexai/internal/lsp/handlers_completion.go (86.1%)</option>
+				<option value="file16">codeberg.org/snonux/hexai/internal/lsp/handlers_completion.go (87.5%)</option>
 				
-				<option value="file17">codeberg.org/snonux/hexai/internal/lsp/handlers_document.go (87.4%)</option>
+				<option value="file17">codeberg.org/snonux/hexai/internal/lsp/handlers_document.go (88.9%)</option>
 				
 				<option value="file18">codeberg.org/snonux/hexai/internal/lsp/handlers_execute.go (75.0%)</option>
 				
 				<option value="file19">codeberg.org/snonux/hexai/internal/lsp/handlers_init.go (55.6%)</option>
 				
-				<option value="file20">codeberg.org/snonux/hexai/internal/lsp/handlers_utils.go (88.2%)</option>
+				<option value="file20">codeberg.org/snonux/hexai/internal/lsp/handlers_utils.go (88.5%)</option>
 				
 				<option value="file21">codeberg.org/snonux/hexai/internal/lsp/server.go (77.9%)</option>
 				
@@ -178,117 +178,118 @@ func main() <span class="cov0" title="0">{
 }
 </pre>
 		
-		<pre class="file" id="file2" style="display: none">// Summary: Application configuration model and loader; reads ~/.config/hexai/config.json and merges defaults.
+		<pre class="file" id="file2" style="display: none">// Summary: Application configuration model and loader; reads ~/.config/hexai/config.toml and merges defaults.
 package appconfig
 
 import (
-    "encoding/json"
-    "fmt"
-    "log"
-    "os"
-    "path/filepath"
-    "slices"
-    "strconv"
-    "strings"
+        "fmt"
+        "log"
+        "os"
+        "path/filepath"
+        "slices"
+        "strconv"
+        "strings"
+
+        "github.com/pelletier/go-toml/v2"
 )
 
-// App holds user-configurable settings read from ~/.config/hexai/config.json.
+// App holds user-configurable settings read from ~/.config/hexai/config.toml.
 type App struct {
-        MaxTokens          int    `json:"max_tokens"`
-        ContextMode        string `json:"context_mode"`
-        ContextWindowLines int    `json:"context_window_lines"`
-        MaxContextTokens   int    `json:"max_context_tokens"`
-        LogPreviewLimit    int    `json:"log_preview_limit"`
+        MaxTokens          int    `json:"max_tokens" toml:"max_tokens"`
+        ContextMode        string `json:"context_mode" toml:"context_mode"`
+        ContextWindowLines int    `json:"context_window_lines" toml:"context_window_lines"`
+        MaxContextTokens   int    `json:"max_context_tokens" toml:"max_context_tokens"`
+        LogPreviewLimit    int    `json:"log_preview_limit" toml:"log_preview_limit"`
         // Single knob for LSP requests; if set, overrides hardcoded temps in LSP.
-    CodingTemperature *float64 `json:"coding_temperature"`
-    // Minimum identifier characters required for manual (TriggerKind=1) invoke
-    // to proceed without structural triggers. 0 means always allow.
-    ManualInvokeMinPrefix int `json:"manual_invoke_min_prefix"`
-
-    // Completion debounce in milliseconds. When &gt; 0, the server waits until
-    // there has been no text change for at least this duration before sending
-    // an LLM completion request.
-    CompletionDebounceMs int `json:"completion_debounce_ms"`
-    // Completion throttle in milliseconds. When &gt; 0, caps the minimum spacing
-    // between LLM requests (both chat and code-completer paths).
-    CompletionThrottleMs int `json:"completion_throttle_ms"`
-
-        TriggerCharacters []string `json:"trigger_characters"`
-        Provider          string   `json:"provider"`
+        CodingTemperature *float64 `json:"coding_temperature" toml:"coding_temperature"`
+        // Minimum identifier characters required for manual (TriggerKind=1) invoke
+        // to proceed without structural triggers. 0 means always allow.
+        ManualInvokeMinPrefix int `json:"manual_invoke_min_prefix" toml:"manual_invoke_min_prefix"`
+
+        // Completion debounce in milliseconds. When &gt; 0, the server waits until
+        // there has been no text change for at least this duration before sending
+        // an LLM completion request.
+        CompletionDebounceMs int `json:"completion_debounce_ms" toml:"completion_debounce_ms"`
+        // Completion throttle in milliseconds. When &gt; 0, caps the minimum spacing
+        // between LLM requests (both chat and code-completer paths).
+        CompletionThrottleMs int `json:"completion_throttle_ms" toml:"completion_throttle_ms"`
+
+        TriggerCharacters []string `json:"trigger_characters" toml:"trigger_characters"`
+        Provider          string   `json:"provider" toml:"provider"`
 
         // Inline prompt trigger characters (default: &gt;text&gt; and &gt;&gt;text&gt;)
-        InlineOpen  string   `json:"inline_open"`
-        InlineClose string   `json:"inline_close"`
+        InlineOpen  string `json:"inline_open" toml:"inline_open"`
+        InlineClose string `json:"inline_close" toml:"inline_close"`
         // In-editor chat triggers (default: suffix "&gt;" after one of [?, !, :, ;])
-        ChatSuffix   string   `json:"chat_suffix"`
-        ChatPrefixes []string `json:"chat_prefixes"`
+        ChatSuffix   string   `json:"chat_suffix" toml:"chat_suffix"`
+        ChatPrefixes []string `json:"chat_prefixes" toml:"chat_prefixes"`
 
         // Provider-specific options
-        OpenAIBaseURL string `json:"openai_base_url"`
-        OpenAIModel   string `json:"openai_model"`
+        OpenAIBaseURL string `json:"openai_base_url" toml:"openai_base_url"`
+        OpenAIModel   string `json:"openai_model" toml:"openai_model"`
         // Default temperature for OpenAI requests (nil means use provider default)
-        OpenAITemperature *float64 `json:"openai_temperature"`
-        OllamaBaseURL     string   `json:"ollama_base_url"`
-        OllamaModel       string   `json:"ollama_model"`
+        OpenAITemperature *float64 `json:"openai_temperature" toml:"openai_temperature"`
+        OllamaBaseURL     string   `json:"ollama_base_url" toml:"ollama_base_url"`
+        OllamaModel       string   `json:"ollama_model" toml:"ollama_model"`
         // Default temperature for Ollama requests (nil means use provider default)
-        OllamaTemperature *float64 `json:"ollama_temperature"`
-        CopilotBaseURL    string   `json:"copilot_base_url"`
-        CopilotModel      string   `json:"copilot_model"`
+        OllamaTemperature *float64 `json:"ollama_temperature" toml:"ollama_temperature"`
+        CopilotBaseURL    string   `json:"copilot_base_url" toml:"copilot_base_url"`
+        CopilotModel      string   `json:"copilot_model" toml:"copilot_model"`
         // Default temperature for Copilot requests (nil means use provider default)
-        CopilotTemperature *float64 `json:"copilot_temperature"`
+        CopilotTemperature *float64 `json:"copilot_temperature" toml:"copilot_temperature"`
 }
 
 // Constructor: defaults for App (kept first among functions)
 func newDefaultConfig() App <span class="cov5" title="9">{
         // Coding-friendly default temperature across providers
-        // Users can override per provider in config.json (including 0.0).
+        // Users can override per provider in config.toml (including 0.0).
         t := 0.2
         return App{
-                MaxTokens:          4000,
-                ContextMode:        "always-full",
-                ContextWindowLines: 120,
-                MaxContextTokens:   4000,
-                LogPreviewLimit:    100,
-                CodingTemperature:  &amp;t,
-                OpenAITemperature:  &amp;t,
-                OllamaTemperature:  &amp;t,
-        CopilotTemperature: &amp;t,
-        ManualInvokeMinPrefix: 0,
-        CompletionDebounceMs: 200,
-        CompletionThrottleMs: 0,
-        // Inline/chat trigger defaults
-        InlineOpen:  "&gt;",
-        InlineClose: "&gt;",
-        ChatSuffix:  "&gt;",
-        ChatPrefixes: []string{"?", "!", ":", ";"},
-    }
+                MaxTokens:             4000,
+                ContextMode:           "always-full",
+                ContextWindowLines:    120,
+                MaxContextTokens:      4000,
+                LogPreviewLimit:       100,
+                CodingTemperature:     &amp;t,
+                OpenAITemperature:     &amp;t,
+                OllamaTemperature:     &amp;t,
+                CopilotTemperature:    &amp;t,
+                ManualInvokeMinPrefix: 0,
+                CompletionDebounceMs:  200,
+                CompletionThrottleMs:  0,
+                // Inline/chat trigger defaults
+                InlineOpen:   "&gt;",
+                InlineClose:  "&gt;",
+                ChatSuffix:   "&gt;",
+                ChatPrefixes: []string{"?", "!", ":", ";"},
+        }
 }</span>
 
 // Load reads configuration from a file and merges with defaults.
 // It respects the XDG Base Directory Specification.
 func Load(logger *log.Logger) App <span class="cov4" title="8">{
-    cfg := newDefaultConfig()
-    if logger == nil </span><span class="cov3" title="3">{
-        return cfg // Return defaults if no logger is provided (e.g. in tests)
-    }</span>
-
-    <span class="cov4" title="5">configPath, err := getConfigPath()
-    if err != nil </span><span class="cov0" title="0">{
-        logger.Printf("%v", err)
-        // Even if config path cannot be resolved, still allow env overrides below.
-    }</span> else<span class="cov4" title="5"> {
-        if fileCfg, err := loadFromFile(configPath, logger); err == nil &amp;&amp; fileCfg != nil </span><span class="cov3" title="3">{
-            cfg.mergeWith(fileCfg)
-        }</span>
-        // When the config file is missing or invalid, we keep defaults and still
-        // apply any environment overrides below.
-    }
-
-    // Environment overrides (take precedence over file)
-    <span class="cov4" title="5">if envCfg := loadFromEnv(logger); envCfg != nil </span><span class="cov1" title="1">{
-        cfg.mergeWith(envCfg)
-    }</span>
-    <span class="cov4" title="5">return cfg</span>
+        cfg := newDefaultConfig()
+        if logger == nil </span><span class="cov3" title="3">{
+                return cfg // Return defaults if no logger is provided (e.g. in tests)
+        }</span>
+
+        <span class="cov4" title="5">configPath, err := getConfigPath()
+        if err != nil </span><span class="cov0" title="0">{
+                logger.Printf("%v", err)
+                // Even if config path cannot be resolved, still allow env overrides below.
+        }</span> else<span class="cov4" title="5"> {
+                if fileCfg, err := loadFromFile(configPath, logger); err == nil &amp;&amp; fileCfg != nil </span><span class="cov3" title="3">{
+                        cfg.mergeWith(fileCfg)
+                }</span>
+                // When the config file is missing or invalid, we keep defaults and still
+                // apply any environment overrides below.
+        }
+
+        // Environment overrides (take precedence over file)
+        <span class="cov4" title="5">if envCfg := loadFromEnv(logger); envCfg != nil </span><span class="cov1" title="1">{
+                cfg.mergeWith(envCfg)
+        }</span>
+        <span class="cov4" title="5">return cfg</span>
 }
 
 // Private helpers
@@ -296,26 +297,29 @@ func loadFromFile(path string, logger *log.Logger) (*App, error) <span class="co
         f, err := os.Open(path)
         if err != nil </span><span class="cov2" title="2">{
                 if !os.IsNotExist(err) &amp;&amp; logger != nil </span><span class="cov0" title="0">{
-                        logger.Printf("cannot open config file %s: %v", path, err)
+                        logger.Printf("cannot open TOML config file %s: %v", path, err)
                 }</span>
                 <span class="cov2" title="2">return nil, err</span>
         }
         <span class="cov3" title="4">defer f.Close()
 
-        dec := json.NewDecoder(f)
+        dec := toml.NewDecoder(f)
         var fileCfg App
         if err := dec.Decode(&amp;fileCfg); err != nil </span><span class="cov1" title="1">{
                 if logger != nil </span><span class="cov1" title="1">{
-                        logger.Printf("invalid config file %s: %v", path, err)
+                        logger.Printf("invalid TOML config file %s: %v", path, err)
                 }</span>
                 <span class="cov1" title="1">return nil, err</span>
         }
+        <span class="cov3" title="3">if logger != nil </span><span class="cov3" title="3">{
+                logger.Printf("loaded configuration from %s (TOML)", path)
+        }</span>
         <span class="cov3" title="3">return &amp;fileCfg, nil</span>
 }
 
 func (a *App) mergeWith(other *App) <span class="cov3" title="4">{
-    a.mergeBasics(other)
-    a.mergeProviderFields(other)
+        a.mergeBasics(other)
+        a.mergeProviderFields(other)
 }</span>
 
 // mergeBasics merges general (non-provider) fields.
@@ -335,32 +339,36 @@ func (a *App) mergeBasics(other *App) <span class="cov3" title="4">{
         <span class="cov3" title="4">if other.LogPreviewLimit &gt;= 0 </span><span class="cov3" title="4">{
                 a.LogPreviewLimit = other.LogPreviewLimit
         }</span>
-    <span class="cov3" title="4">if other.CodingTemperature != nil </span><span class="cov3" title="3">{ // allow explicit 0.0
-        a.CodingTemperature = other.CodingTemperature
-    }</span>
-    <span class="cov3" title="4">if other.ManualInvokeMinPrefix &gt;= 0 </span><span class="cov3" title="4">{
-        a.ManualInvokeMinPrefix = other.ManualInvokeMinPrefix
-    }</span>
-    <span class="cov3" title="4">if other.CompletionDebounceMs &gt; 0 </span><span class="cov3" title="3">{ a.CompletionDebounceMs = other.CompletionDebounceMs }</span>
-    <span class="cov3" title="4">if other.CompletionThrottleMs &gt; 0 </span><span class="cov3" title="3">{ a.CompletionThrottleMs = other.CompletionThrottleMs }</span>
-    <span class="cov3" title="4">if len(other.TriggerCharacters) &gt; 0 </span><span class="cov3" title="3">{
-        a.TriggerCharacters = slices.Clone(other.TriggerCharacters)
-    }</span>
-    <span class="cov3" title="4">if s := strings.TrimSpace(other.InlineOpen); s != "" </span><span class="cov0" title="0">{
-        a.InlineOpen = s
-    }</span>
-    <span class="cov3" title="4">if s := strings.TrimSpace(other.InlineClose); s != "" </span><span class="cov0" title="0">{
-        a.InlineClose = s
-    }</span>
-    <span class="cov3" title="4">if s := strings.TrimSpace(other.ChatSuffix); s != "" </span><span class="cov0" title="0">{
-        a.ChatSuffix = s
-    }</span>
-    <span class="cov3" title="4">if len(other.ChatPrefixes) &gt; 0 </span><span class="cov0" title="0">{
-        a.ChatPrefixes = slices.Clone(other.ChatPrefixes)
-    }</span>
-    <span class="cov3" title="4">if s := strings.TrimSpace(other.Provider); s != "" </span><span class="cov3" title="4">{
-        a.Provider = s
-    }</span>
+        <span class="cov3" title="4">if other.CodingTemperature != nil </span><span class="cov3" title="3">{ // allow explicit 0.0
+                a.CodingTemperature = other.CodingTemperature
+        }</span>
+        <span class="cov3" title="4">if other.ManualInvokeMinPrefix &gt;= 0 </span><span class="cov3" title="4">{
+                a.ManualInvokeMinPrefix = other.ManualInvokeMinPrefix
+        }</span>
+        <span class="cov3" title="4">if other.CompletionDebounceMs &gt; 0 </span><span class="cov3" title="3">{
+                a.CompletionDebounceMs = other.CompletionDebounceMs
+        }</span>
+        <span class="cov3" title="4">if other.CompletionThrottleMs &gt; 0 </span><span class="cov3" title="3">{
+                a.CompletionThrottleMs = other.CompletionThrottleMs
+        }</span>
+        <span class="cov3" title="4">if len(other.TriggerCharacters) &gt; 0 </span><span class="cov3" title="3">{
+                a.TriggerCharacters = slices.Clone(other.TriggerCharacters)
+        }</span>
+        <span class="cov3" title="4">if s := strings.TrimSpace(other.InlineOpen); s != "" </span><span class="cov0" title="0">{
+                a.InlineOpen = s
+        }</span>
+        <span class="cov3" title="4">if s := strings.TrimSpace(other.InlineClose); s != "" </span><span class="cov0" title="0">{
+                a.InlineClose = s
+        }</span>
+        <span class="cov3" title="4">if s := strings.TrimSpace(other.ChatSuffix); s != "" </span><span class="cov0" title="0">{
+                a.ChatSuffix = s
+        }</span>
+        <span class="cov3" title="4">if len(other.ChatPrefixes) &gt; 0 </span><span class="cov0" title="0">{
+                a.ChatPrefixes = slices.Clone(other.ChatPrefixes)
+        }</span>
+        <span class="cov3" title="4">if s := strings.TrimSpace(other.Provider); s != "" </span><span class="cov3" title="4">{
+                a.Provider = s
+        }</span>
 }
 
 // mergeProviderFields merges per-provider configuration.
@@ -397,15 +405,15 @@ func (a *App) mergeProviderFields(other *App) <span class="cov3" title="4">{
 func getConfigPath() (string, error) <span class="cov4" title="6">{
         var configPath string
         if xdgConfigHome := os.Getenv("XDG_CONFIG_HOME"); xdgConfigHome != "" </span><span class="cov4" title="5">{
-                configPath = filepath.Join(xdgConfigHome, "hexai", "config.json")
+                configPath = filepath.Join(xdgConfigHome, "hexai", "config.toml")
         }</span> else<span class="cov1" title="1"> {
                 home, err := os.UserHomeDir()
                 if err != nil </span><span class="cov0" title="0">{
                         return "", fmt.Errorf("cannot find user home directory: %v", err)
                 }</span>
-                <span class="cov1" title="1">configPath = filepath.Join(home, ".config", "hexai", "config.json")</span>
+                <span class="cov1" title="1">configPath = filepath.Join(home, ".config", "hexai", "config.toml")</span>
         }
-    <span class="cov4" title="6">return configPath, nil</span>
+        <span class="cov4" title="6">return configPath, nil</span>
 }
 
 // --- Environment overrides ---
@@ -413,100 +421,157 @@ func getConfigPath() (string, error) <span class="cov4" title="6">{
 // loadFromEnv constructs an App containing only fields set via HEXAI_* env vars.
 // These values should take precedence over file config when merged.
 func loadFromEnv(logger *log.Logger) *App <span class="cov4" title="5">{
-    var out App
-    var any bool
-
-    // helpers
-    getenv := func(k string) string </span><span class="cov10" title="120">{ return strings.TrimSpace(os.Getenv(k)) }</span>
-    <span class="cov4" title="5">parseInt := func(k string) (int, bool) </span><span class="cov7" title="35">{
-        v := getenv(k)
-        if v == "" </span><span class="cov7" title="28">{ return 0, false }</span>
-        <span class="cov4" title="7">n, err := strconv.Atoi(v)
-        if err != nil </span><span class="cov0" title="0">{ if logger != nil </span><span class="cov0" title="0">{ logger.Printf("invalid %s: %v", k, err) }</span> ; <span class="cov0" title="0">return 0, false</span> }
-        <span class="cov4" title="7">return n, true</span>
-    }
-    <span class="cov4" title="5">parseFloatPtr := func(k string) (*float64, bool) </span><span class="cov6" title="20">{
-        v := getenv(k)
-        if v == "" </span><span class="cov6" title="16">{ return nil, false }</span>
-        <span class="cov3" title="4">f, err := strconv.ParseFloat(v, 64)
-        if err != nil </span><span class="cov0" title="0">{
-            if logger != nil </span><span class="cov0" title="0">{ logger.Printf("invalid %s: %v", k, err) }</span>
-            <span class="cov0" title="0">return nil, false</span>
+        var out App
+        var any bool
+
+        // helpers
+        getenv := func(k string) string </span><span class="cov10" title="120">{ return strings.TrimSpace(os.Getenv(k)) }</span>
+        <span class="cov4" title="5">parseInt := func(k string) (int, bool) </span><span class="cov7" title="35">{
+                v := getenv(k)
+                if v == "" </span><span class="cov7" title="28">{
+                        return 0, false
+                }</span>
+                <span class="cov4" title="7">n, err := strconv.Atoi(v)
+                if err != nil </span><span class="cov0" title="0">{
+                        if logger != nil </span><span class="cov0" title="0">{
+                                logger.Printf("invalid %s: %v", k, err)
+                        }</span>
+                        <span class="cov0" title="0">return 0, false</span>
+                }
+                <span class="cov4" title="7">return n, true</span>
         }
-        <span class="cov3" title="4">return &amp;f, true</span>
-    }
-
-    <span class="cov4" title="5">if n, ok := parseInt("HEXAI_MAX_TOKENS"); ok </span><span class="cov1" title="1">{
-        out.MaxTokens = n; any = true
-    }</span>
-    <span class="cov4" title="5">if s := getenv("HEXAI_CONTEXT_MODE"); s != "" </span><span class="cov1" title="1">{
-        out.ContextMode = s; any = true
-    }</span>
-    <span class="cov4" title="5">if n, ok := parseInt("HEXAI_CONTEXT_WINDOW_LINES"); ok </span><span class="cov1" title="1">{
-        out.ContextWindowLines = n; any = true
-    }</span>
-    <span class="cov4" title="5">if n, ok := parseInt("HEXAI_MAX_CONTEXT_TOKENS"); ok </span><span class="cov1" title="1">{
-        out.MaxContextTokens = n; any = true
-    }</span>
-    <span class="cov4" title="5">if n, ok := parseInt("HEXAI_LOG_PREVIEW_LIMIT"); ok </span><span class="cov1" title="1">{
-        out.LogPreviewLimit = n; any = true
-    }</span>
-    <span class="cov4" title="5">if n, ok := parseInt("HEXAI_MANUAL_INVOKE_MIN_PREFIX"); ok </span><span class="cov1" title="1">{
-        out.ManualInvokeMinPrefix = n; any = true
-    }</span>
-    <span class="cov4" title="5">if n, ok := parseInt("HEXAI_COMPLETION_DEBOUNCE_MS"); ok </span><span class="cov1" title="1">{
-        out.CompletionDebounceMs = n; any = true
-    }</span>
-    <span class="cov4" title="5">if n, ok := parseInt("HEXAI_COMPLETION_THROTTLE_MS"); ok </span><span class="cov1" title="1">{
-        out.CompletionThrottleMs = n; any = true
-    }</span>
-    <span class="cov4" title="5">if f, ok := parseFloatPtr("HEXAI_CODING_TEMPERATURE"); ok </span><span class="cov1" title="1">{
-        out.CodingTemperature = f; any = true
-    }</span>
-    <span class="cov4" title="5">if s := getenv("HEXAI_TRIGGER_CHARACTERS"); s != "" </span><span class="cov1" title="1">{
-        parts := strings.Split(s, ",")
-        out.TriggerCharacters = nil
-        for _, p := range parts </span><span class="cov3" title="3">{
-            if t := strings.TrimSpace(p); t != "" </span><span class="cov3" title="3">{
-                out.TriggerCharacters = append(out.TriggerCharacters, t)
-            }</span>
+        <span class="cov4" title="5">parseFloatPtr := func(k string) (*float64, bool) </span><span class="cov6" title="20">{
+                v := getenv(k)
+                if v == "" </span><span class="cov6" title="16">{
+                        return nil, false
+                }</span>
+                <span class="cov3" title="4">f, err := strconv.ParseFloat(v, 64)
+                if err != nil </span><span class="cov0" title="0">{
+                        if logger != nil </span><span class="cov0" title="0">{
+                                logger.Printf("invalid %s: %v", k, err)
+                        }</span>
+                        <span class="cov0" title="0">return nil, false</span>
+                }
+                <span class="cov3" title="4">return &amp;f, true</span>
+        }
+
+        <span class="cov4" title="5">if n, ok := parseInt("HEXAI_MAX_TOKENS"); ok </span><span class="cov1" title="1">{
+                out.MaxTokens = n
+                any = true
+        }</span>
+        <span class="cov4" title="5">if s := getenv("HEXAI_CONTEXT_MODE"); s != "" </span><span class="cov1" title="1">{
+                out.ContextMode = s
+                any = true
+        }</span>
+        <span class="cov4" title="5">if n, ok := parseInt("HEXAI_CONTEXT_WINDOW_LINES"); ok </span><span class="cov1" title="1">{
+                out.ContextWindowLines = n
+                any = true
+        }</span>
+        <span class="cov4" title="5">if n, ok := parseInt("HEXAI_MAX_CONTEXT_TOKENS"); ok </span><span class="cov1" title="1">{
+                out.MaxContextTokens = n
+                any = true
+        }</span>
+        <span class="cov4" title="5">if n, ok := parseInt("HEXAI_LOG_PREVIEW_LIMIT"); ok </span><span class="cov1" title="1">{
+                out.LogPreviewLimit = n
+                any = true
+        }</span>
+        <span class="cov4" title="5">if n, ok := parseInt("HEXAI_MANUAL_INVOKE_MIN_PREFIX"); ok </span><span class="cov1" title="1">{
+                out.ManualInvokeMinPrefix = n
+                any = true
+        }</span>
+        <span class="cov4" title="5">if n, ok := parseInt("HEXAI_COMPLETION_DEBOUNCE_MS"); ok </span><span class="cov1" title="1">{
+                out.CompletionDebounceMs = n
+                any = true
+        }</span>
+        <span class="cov4" title="5">if n, ok := parseInt("HEXAI_COMPLETION_THROTTLE_MS"); ok </span><span class="cov1" title="1">{
+                out.CompletionThrottleMs = n
+                any = true
+        }</span>
+        <span class="cov4" title="5">if f, ok := parseFloatPtr("HEXAI_CODING_TEMPERATURE"); ok </span><span class="cov1" title="1">{
+                out.CodingTemperature = f
+                any = true
+        }</span>
+        <span class="cov4" title="5">if s := getenv("HEXAI_TRIGGER_CHARACTERS"); s != "" </span><span class="cov1" title="1">{
+                parts := strings.Split(s, ",")
+                out.TriggerCharacters = nil
+                for _, p := range parts </span><span class="cov3" title="3">{
+                        if t := strings.TrimSpace(p); t != "" </span><span class="cov3" title="3">{
+                                out.TriggerCharacters = append(out.TriggerCharacters, t)
+                        }</span>
+                }
+                <span class="cov1" title="1">any = true</span>
         }
-        <span class="cov1" title="1">any = true</span>
-    }
-    <span class="cov4" title="5">if s := getenv("HEXAI_INLINE_OPEN"); s != "" </span><span class="cov0" title="0">{ out.InlineOpen = s; any = true }</span>
-    <span class="cov4" title=