feat(ai): add model caching, settings, and commands

- Introduce model caching with persistence to preferences
- Add provider default model and custom settings management
- Implement `/ai switch`, `/ai models`, and improve `/ai start`
- Add model name autocomplete for chat commands
- Update command definitions and help text
- Add unit tests for new functionality

src/ai/ai_client.c

@@ -32,6 +32,12 @@ static GHashTable* providers = NULL;
 static GHashTable* provider_keys = NULL;
 static Autocomplete providers_ac = NULL;
 
+/* ========================================================================
+ * Forward declarations
+ * ======================================================================== */
+static void _ai_load_models_for_provider(AIProvider* provider);
+static void _ai_save_models_for_provider(AIProvider* provider);
+
 /* ========================================================================
  * Curl helpers
  * ======================================================================== */
@@ -183,7 +189,10 @@ ai_provider_new(const gchar* name, const gchar* api_url, const gchar* org_id)
     provider->api_url = g_strdup(api_url ? api_url : "");
     provider->org_id = g_strdup(org_id);
     provider->project_id = NULL;
+    provider->default_model = NULL;
+    provider->settings = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, g_free);
     provider->models = NULL;
+    provider->models_fresh = FALSE;
     provider->ref_count = 1;
     return provider;
 }
@@ -211,6 +220,8 @@ ai_provider_unref(AIProvider* provider)
     g_free(provider->api_url);
     g_free(provider->org_id);
     g_free(provider->project_id);
+    g_free(provider->default_model);
+    g_hash_table_destroy(provider->settings);
 
     GList* curr = provider->models;
     while (curr) {
@@ -271,6 +282,16 @@ ai_client_init(void)
     /* Load saved API keys from config */
     ai_load_keys();
 
+    /* Load cached models for all providers */
+    GList* provider_list = ai_list_providers();
+    GList* curr = provider_list;
+    while (curr) {
+        AIProvider* provider = (AIProvider*)curr->data;
+        _ai_load_models_for_provider(provider);
+        curr = g_list_next(curr);
+    }
+    g_list_free(provider_list);
+
     log_info("AI client initialized with default providers: openai, perplexity");
 }
 
@@ -387,6 +408,37 @@ ai_providers_find(const char* const search_str, gboolean previous, void* context
     return autocomplete_complete(providers_ac, effective_search, FALSE, previous);
 }
 
+/* Stateful model name finder for autocomplete.
+ * Uses the current session's provider models for completion. */
+gchar*
+ai_models_find(const char* const search_str, gboolean previous, void* context)
+{
+    ProfAiWin* aiwin = (ProfAiWin*)context;
+    if (!aiwin || !aiwin->session) {
+        return NULL;
+    }
+
+    AIProvider* provider = aiwin->session->provider;
+    if (!provider || !provider->models) {
+        return NULL;
+    }
+
+    /* Create a temporary autocomplete for models */
+    Autocomplete models_ac = autocomplete_new();
+    GList* curr = provider->models;
+    while (curr) {
+        autocomplete_add(models_ac, curr->data);
+        curr = g_list_next(curr);
+    }
+
+    /* NULL search_str is treated as empty string for cycling */
+    const char* effective_search = (search_str != NULL) ? search_str : "";
+
+    gchar* result = autocomplete_complete(models_ac, effective_search, FALSE, previous);
+    autocomplete_free(models_ac);
+    return result;
+}
+
 gchar*
 ai_get_provider_key(const gchar* provider_name)
 {
@@ -419,6 +471,456 @@ ai_set_provider_key(const gchar* provider_name, const gchar* api_key)
     }
 }
 
+/* ========================================================================
+ * Provider default model and settings
+ * ======================================================================== */
+
+void
+ai_set_provider_default_model(const gchar* provider_name, const gchar* model)
+{
+    if (!provider_name || !model)
+        return;
+
+    AIProvider* provider = ai_get_provider(provider_name);
+    if (!provider) {
+        log_warning("Provider '%s' not found for default model setting", provider_name);
+        return;
+    }
+
+    g_free(provider->default_model);
+    provider->default_model = g_strdup(model);
+    log_info("Default model for provider '%s' set to: %s", provider_name, model);
+}
+
+const gchar*
+ai_get_provider_default_model(const gchar* provider_name)
+{
+    if (!provider_name)
+        return NULL;
+
+    AIProvider* provider = ai_get_provider(provider_name);
+    if (!provider)
+        return NULL;
+
+    return provider->default_model;
+}
+
+void
+ai_set_provider_setting(const gchar* provider_name, const gchar* setting, const gchar* value)
+{
+    if (!provider_name || !setting)
+        return;
+
+    AIProvider* provider = ai_get_provider(provider_name);
+    if (!provider) {
+        log_warning("Provider '%s' not found for setting '%s'", provider_name, setting);
+        return;
+    }
+
+    if (!provider->settings) {
+        provider->settings = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, g_free);
+    }
+
+    if (value) {
+        g_hash_table_insert(provider->settings, g_strdup(setting), g_strdup(value));
+        log_info("Setting '%s' for provider '%s' set to: %s", setting, provider_name, value);
+    } else {
+        g_hash_table_remove(provider->settings, setting);
+        log_info("Setting '%s' removed for provider '%s'", setting, provider_name);
+    }
+}
+
+gchar*
+ai_get_provider_setting(const gchar* provider_name, const gchar* setting)
+{
+    if (!provider_name || !setting)
+        return NULL;
+
+    AIProvider* provider = ai_get_provider(provider_name);
+    if (!provider || !provider->settings)
+        return NULL;
+
+    gchar* value = g_hash_table_lookup(provider->settings, setting);
+    return g_strdup(value);
+}
+
+/* ========================================================================
+ * Generic HTTP request handling
+ * ======================================================================== */
+
+typedef void (*ai_response_handler_t)(AIProvider* provider, const gchar* response, gpointer user_data);
+
+typedef struct
+{
+    gchar* provider_name;
+    gpointer user_data;
+    gchar* request_url;
+    ai_response_handler_t handler;
+} ai_request_t;
+
+/**
+ * Build curl headers with auth and optional org header.
+ * Returns headers list (caller must free with curl_slist_free_all).
+ */
+static struct curl_slist*
+_build_curl_headers(AIProvider* provider, const gchar* api_key)
+{
+    struct curl_slist* headers = NULL;
+    auto_gchar gchar* auth_header = g_strdup_printf("Authorization: Bearer %s", api_key);
+    headers = curl_slist_append(headers, "Content-Type: application/json");
+    headers = curl_slist_append(headers, auth_header);
+
+    if (provider && provider->org_id && strlen(provider->org_id) > 0) {
+        auto_gchar gchar* org_header = g_strdup_printf("OpenAI-Organization: %s", provider->org_id);
+        headers = curl_slist_append(headers, org_header);
+    }
+
+    return headers;
+}
+
+/**
+ * Execute a curl request and call handler on success.
+ * Returns CURLcode.
+ */
+static CURLcode
+_curl_exec_and_handle(CURL* curl, const gchar* url, struct curl_slist* headers,
+                      struct curl_response_t* response, ai_response_handler_t handler,
+                      AIProvider* provider, gpointer user_data)
+{
+    curl_easy_setopt(curl, CURLOPT_URL, url);
+    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, _write_callback);
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, response);
+    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 30L);
+
+    CURLcode res = curl_easy_perform(curl);
+    long http_code = 0;
+    curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &http_code);
+
+    if (res != CURLE_OK) {
+        auto_gchar gchar* error_msg = g_strdup(curl_easy_strerror(res));
+        log_error("Request failed for '%s': %s", provider->name, error_msg);
+        _aiwin_display_error(user_data, error_msg);
+    } else if (http_code >= 400) {
+        auto_gchar gchar* error_msg = g_strdup_printf("HTTP %ld: %s", http_code,
+                                                      response->data ? response->data : "Unknown error");
+        log_error("Request HTTP error for '%s': %s", provider->name, error_msg);
+        _aiwin_display_error(user_data, error_msg);
+    } else {
+        handler(provider, response->data, user_data);
+    }
+
+    return res;
+}
+
+static gpointer
+_ai_generic_request_thread(gpointer data)
+{
+    ai_request_t* req = (ai_request_t*)data;
+    AIProvider* provider = ai_get_provider(req->provider_name);
+    if (!provider) {
+        log_error("Provider '%s' not found for request", req->provider_name);
+        g_free(req->provider_name);
+        g_free(req->request_url);
+        g_free(req);
+        return NULL;
+    }
+
+    CURL* curl = curl_easy_init();
+    if (!curl) {
+        log_error("Failed to initialize curl for %s", req->provider_name);
+        g_free(req->provider_name);
+        g_free(req->request_url);
+        g_free(req);
+        return NULL;
+    }
+
+    auto_gchar gchar* api_key = ai_get_provider_key(req->provider_name);
+    if (!api_key || strlen(api_key) == 0) {
+        auto_gchar gchar* error_msg = g_strdup_printf("No API key set for provider '%s'.", req->provider_name);
+        _aiwin_display_error(req->user_data, error_msg);
+        curl_easy_cleanup(curl);
+        g_free(req->provider_name);
+        g_free(req->request_url);
+        g_free(req);
+        return NULL;
+    }
+
+    struct curl_slist* headers = _build_curl_headers(provider, api_key);
+    struct curl_response_t response;
+    response.data = g_new0(gchar, 1);
+    response.size = 0;
+
+    _curl_exec_and_handle(curl, req->request_url, headers, &response, req->handler, provider, req->user_data);
+
+    curl_slist_free_all(headers);
+    curl_easy_cleanup(curl);
+    g_free(response.data);
+    g_free(req->provider_name);
+    g_free(req->request_url);
+    g_free(req);
+    return NULL;
+}
+
+/* ========================================================================
+ * Model fetching
+ * ======================================================================== */
+
+gboolean
+ai_models_are_fresh(const gchar* provider_name)
+{
+    if (!provider_name)
+        return FALSE;
+
+    AIProvider* provider = ai_get_provider(provider_name);
+    if (!provider)
+        return FALSE;
+
+    return provider->models_fresh;
+}
+
+static gboolean
+_model_exists(AIProvider* provider, const gchar* model)
+{
+    GList* curr = provider->models;
+    while (curr) {
+        if (g_strcmp0(curr->data, model) == 0) {
+            return TRUE;
+        }
+        curr = g_list_next(curr);
+    }
+    return FALSE;
+}
+
+static void
+_add_model_if_new(AIProvider* provider, const gchar* model)
+{
+    if (!_model_exists(provider, model)) {
+        provider->models = g_list_append(provider->models, g_strdup(model));
+    }
+}
+
+/* ========================================================================
+ * Model cache persistence
+ * ======================================================================== */
+
+/**
+ * Load cached models for a provider from preferences.
+ */
+static void
+_ai_load_models_for_provider(AIProvider* provider)
+{
+    if (!provider)
+        return;
+
+    GList* models = prefs_ai_get_models(provider->name);
+    if (!models) {
+        log_info("No cached models for provider '%s'", provider->name);
+        return;
+    }
+
+    /* Add loaded models to provider */
+    GList* curr = models;
+    while (curr) {
+        _add_model_if_new(provider, curr->data);
+        curr = g_list_next(curr);
+    }
+
+    prefs_free_ai_models(models);
+
+    if (provider->models) {
+        provider->models_fresh = TRUE;
+        log_info("Loaded %d cached models for provider '%s'", g_list_length(provider->models), provider->name);
+    }
+}
+
+/**
+ * Save models for a provider to preferences.
+ */
+static void
+_ai_save_models_for_provider(AIProvider* provider)
+{
+    if (!provider || !provider->models)
+        return;
+
+    /* Build array of model strings */
+    gint count = g_list_length(provider->models);
+    gchar** models = g_new0(gchar*, count);
+    GList* curr = provider->models;
+    gint i = 0;
+    while (curr) {
+        models[i++] = curr->data;
+        curr = g_list_next(curr);
+    }
+
+    prefs_ai_set_models(provider->name, (const gchar* const*)models, count);
+    g_free(models);
+
+    log_debug("Saved %d models for provider '%s' to prefs", count, provider->name);
+}
+
+static const gchar*
+_find_json_field(const gchar* json, const gchar* field)
+{
+    auto_gchar gchar* key = g_strdup_printf("\"%s\":\"", field);
+    const gchar* pos = strstr(json, key);
+    if (!pos) {
+        return NULL;
+    }
+    return pos + strlen(key);
+}
+
+static void
+_parse_openai_models(AIProvider* provider, const gchar* json)
+{
+    /* Format: {"data": [{"id": "model1"}, {"id": "model2"}, ...]} */
+    const gchar* data_start = _find_json_field(json, "data");
+    if (!data_start) {
+        return;
+    }
+
+    const gchar* obj_start = strstr(data_start, "{\"id\":");
+    while (obj_start) {
+        const gchar* id_start = _find_json_field(obj_start, "id");
+        if (!id_start) {
+            break;
+        }
+
+        const gchar* id_end = strchr(id_start, '"');
+        if (!id_end) {
+            break;
+        }
+
+        auto_gchar gchar* model = g_strndup(id_start, id_end - id_start);
+        _add_model_if_new(provider, model);
+
+        obj_start = strstr(id_end, "{\"id\":");
+        if (obj_start) {
+            obj_start++;
+        }
+    }
+}
+
+static void
+_parse_array_models(AIProvider* provider, const gchar* json)
+{
+    /* Format: ["model1", "model2", ...] */
+    const gchar* arr_start = strchr(json, '[');
+    if (!arr_start) {
+        return;
+    }
+
+    const gchar* model_start = strchr(arr_start, '"');
+    while (model_start) {
+        const gchar* model_end = strchr(model_start + 1, '"');
+        if (!model_end) {
+            break;
+        }
+
+        auto_gchar gchar* model = g_strndup(model_start + 1, model_end - model_start - 1);
+        _add_model_if_new(provider, model);
+
+        model_start = strchr(model_end + 1, '"');
+    }
+}
+
+static void
+_parse_and_cache_models(AIProvider* provider, const gchar* response_json)
+{
+    if (!provider || !response_json) {
+        return;
+    }
+
+    /* Try OpenAI format first: {"data": [{"id": "model1"}, ...]} */
+    _parse_openai_models(provider, response_json);
+
+    /* If no models found, try simple array format: ["model1", ...] */
+    if (!provider->models) {
+        _parse_array_models(provider, response_json);
+    }
+
+    provider->models_fresh = TRUE;
+    log_info("Cached %d models for provider '%s'", g_list_length(provider->models), provider->name);
+
+    /* Persist models to preferences */
+    _ai_save_models_for_provider(provider);
+}
+
+static void
+_models_response_handler(AIProvider* provider, const gchar* response, gpointer user_data)
+{
+    _parse_and_cache_models(provider, response);
+
+    auto_gchar gchar* msg = g_strdup_printf("Cached %d models for provider '%s'. Use '/ai start <provider> <model>' to start a chat.",
+                                            g_list_length(provider->models), provider->name);
+    _aiwin_display_response(user_data, msg);
+}
+
+static gpointer
+_models_fetch_thread(gpointer data)
+{
+    ai_request_t* req = (ai_request_t*)data;
+    AIProvider* provider = ai_get_provider(req->provider_name);
+    if (!provider) {
+        g_free(req->provider_name);
+        g_free(req);
+        return NULL;
+    }
+
+    /* Build URL for listing models */
+    auto_gchar gchar* base_url = g_strdup_printf("%s%s", provider->api_url,
+                                                 g_str_has_suffix(provider->api_url, "/") ? "" : "/");
+    auto_gchar gchar* request_url = g_strdup_printf("%sv1/models", base_url);
+
+    req->request_url = g_strdup(request_url);
+    req->handler = _models_response_handler;
+
+    return _ai_generic_request_thread(req);
+}
+
+gboolean
+ai_fetch_models(const gchar* provider_name, gpointer user_data)
+{
+    if (!provider_name)
+        return FALSE;
+
+    AIProvider* provider = ai_get_provider(provider_name);
+    if (!provider) {
+        log_error("Provider '%s' not found for model fetch", provider_name);
+        return FALSE;
+    }
+
+    /* If models are fresh, just display them */
+    if (provider->models_fresh && provider->models) {
+        cons_show("Cached %d models for provider '%s':", g_list_length(provider->models), provider_name);
+        GList* curr = provider->models;
+        while (curr) {
+            cons_show("  %s", (gchar*)curr->data);
+            curr = g_list_next(curr);
+        }
+        cons_show("");
+        cons_show("Use '/ai models %s --refresh' to fetch fresh models from the API.", provider_name);
+        return TRUE;
+    }
+
+    /* Fetch models in a thread */
+    ai_request_t* req = g_new0(ai_request_t, 1);
+    req->provider_name = g_strdup(provider_name);
+    req->user_data = user_data;
+
+    GThread* thread = g_thread_new("ai_models_fetch", _models_fetch_thread, req);
+    if (!thread) {
+        g_free(req->provider_name);
+        g_free(req);
+        log_error("Failed to create thread for model fetch");
+        return FALSE;
+    }
+
+    g_thread_unref(thread);
+    cons_show("Fetching models for provider '%s'...", provider_name);
+    return TRUE;
+}
+
 /* ========================================================================
  * Session Management
  * ======================================================================== */
@@ -708,34 +1210,23 @@ _ai_request_thread(gpointer data)
     auto_gchar gchar* json_payload = _build_json_payload(session, prompt);
     log_debug("[AI-THREAD] JSON payload: %s", json_payload);
 
-    /* Set up headers */
-    struct curl_slist* headers = NULL;
-    auto_gchar gchar* auth_header = g_strdup_printf("Authorization: Bearer %s", session->api_key);
-    headers = curl_slist_append(headers, "Content-Type: application/json");
-    headers = curl_slist_append(headers, auth_header);
-
-    /* Add organization header if configured */
-    if (session->provider && session->provider->org_id && strlen(session->provider->org_id) > 0) {
-        auto_gchar gchar* org_header = g_strdup_printf("OpenAI-Organization: %s", session->provider->org_id);
-        headers = curl_slist_append(headers, org_header);
-    }
+    /* Build headers using shared helper */
+    struct curl_slist* headers = _build_curl_headers(session->provider, session->api_key);
 
     /* Response buffer */
     struct curl_response_t response;
     response.data = g_new0(gchar, 1);
     response.size = 0;
 
-    /* Configure request */
+    /* Build request URL */
     const gchar* api_url = session->provider ? session->provider->api_url : DEFAULT_OPENAI_URL;
     auto_gchar gchar* request_url = g_strdup_printf("%s%sv1/responses", api_url, g_str_has_suffix(api_url, "/") ? "" : "/");
     log_debug("[AI-THREAD] API URL: %s", api_url);
     log_debug("[AI-THREAD] API Request URL: %s", request_url);
     log_debug("[AI-THREAD] Model: %s", session->model);
-    curl_easy_setopt(curl, CURLOPT_URL, request_url);
-    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
+
+    /* Execute request with POST fields */
     curl_easy_setopt(curl, CURLOPT_POSTFIELDS, json_payload);
-    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, _write_callback);
-    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);
     curl_easy_setopt(curl, CURLOPT_TIMEOUT, 60L);
 
     CURLcode res = curl_easy_perform(curl);

src/ai/ai_client.h

@@ -17,12 +17,15 @@ typedef struct ai_message_t
  */
 typedef struct ai_provider_t
 {
-    gchar* name;       /* Provider name (e.g., "openai", "perplexity") */
-    gchar* api_url;    /* API endpoint URL */
-    gchar* org_id;     /* Optional organization ID */
-    gchar* project_id; /* Optional project ID (for some providers) */
-    GList* models;     /* List of available models (gchar*) */
-    gint32 ref_count;  /* Reference count (atomic) */
+    gchar* name;           /* Provider name (e.g., "openai", "perplexity") */
+    gchar* api_url;        /* API endpoint URL */
+    gchar* org_id;         /* Optional organization ID */
+    gchar* project_id;     /* Optional project ID (for some providers) */
+    gchar* default_model;  /* Default model for this provider */
+    GHashTable* settings;  /* Extensible per-provider settings (e.g., tools=enabled, search=disabled) */
+    GList* models;         /* Cached models (gchar*) */
+    gboolean models_fresh; /* Whether models cache is current */
+    gint32 ref_count;      /* Reference count (atomic) */
 } AIProvider;
 
 /**
@@ -97,6 +100,15 @@ GList* ai_list_providers(void);
  */
 gchar* ai_providers_find(const char* const search_str, gboolean previous, void* context);
 
+/**
+ * Find a model name for autocomplete.
+ * @param search_str The search string
+ * @param previous Whether to go to previous match
+ * @param context ProfAiWin* for the current session
+ * @return Model name, or NULL if not found
+ */
+gchar* ai_models_find(const char* const search_str, gboolean previous, void* context);
+
 /**
  * Get the API key for a provider.
  * @param provider_name The provider name
@@ -111,6 +123,51 @@ gchar* ai_get_provider_key(const gchar* provider_name);
  */
 void ai_set_provider_key(const gchar* provider_name, const gchar* api_key);
 
+/**
+ * Set the default model for a provider.
+ * @param provider_name The provider name
+ * @param model The default model name
+ */
+void ai_set_provider_default_model(const gchar* provider_name, const gchar* model);
+
+/**
+ * Get the default model for a provider.
+ * @param provider_name The provider name
+ * @return The default model name (caller must not free), or NULL if not set
+ */
+const gchar* ai_get_provider_default_model(const gchar* provider_name);
+
+/**
+ * Set a custom setting for a provider.
+ * @param provider_name The provider name
+ * @param setting The setting key (e.g., "tools", "search")
+ * @param value The setting value
+ */
+void ai_set_provider_setting(const gchar* provider_name, const gchar* setting, const gchar* value);
+
+/**
+ * Get a custom setting for a provider.
+ * @param provider_name The provider name
+ * @param setting The setting key
+ * @return The setting value (caller must free), or NULL if not set
+ */
+gchar* ai_get_provider_setting(const gchar* provider_name, const gchar* setting);
+
+/**
+ * Fetch available models from a provider's API.
+ * @param provider_name The provider name
+ * @param user_data User data (ProfAiWin* for UI display)
+ * @return TRUE if the request was successfully queued, FALSE otherwise
+ */
+gboolean ai_fetch_models(const gchar* provider_name, gpointer user_data);
+
+/**
+ * Check if models cache is fresh for a provider.
+ * @param provider_name The provider name
+ * @return TRUE if models are fresh, FALSE otherwise
+ */
+gboolean ai_models_are_fresh(const gchar* provider_name);
+
 /* ========================================================================
  * Session Management
  * ======================================================================== */