src/ai/ai_client.c

@@ -186,6 +186,22 @@ ai_json_escape(const gchar* str)
     return g_string_free(result, FALSE);
 }
 
+/* Keys emitted as fixed payload fields; custom settings must not duplicate them */
+static gboolean
+_is_reserved_payload_key(const gchar* key)
+{
+    return g_strcmp0(key, "model") == 0 || g_strcmp0(key, "messages") == 0 || g_strcmp0(key, "stream") == 0;
+}
+
+/* RFC 8259 scalars (number/true/false/null) may be emitted bare in a JSON payload */
+static gboolean
+_is_json_bare_token(const gchar* value)
+{
+    if (g_strcmp0(value, "true") == 0 || g_strcmp0(value, "false") == 0 || g_strcmp0(value, "null") == 0)
+        return TRUE;
+    return g_regex_match_simple("^-?(0|[1-9][0-9]*)(\\.[0-9]+)?([eE][+-]?[0-9]+)?$", value, 0, 0);
+}
+
 /**
  * Convert a 4-hex-digit sequence at @p to a 16-bit code point.
  * Returns -1 on invalid hex.
@@ -392,6 +408,7 @@ ai_provider_new(const gchar* name, const gchar* api_url)
     provider->models = NULL;
     provider->models_fresh = FALSE;
     provider->ref_count = 1;
+    pthread_mutex_init(&provider->settings_lock, NULL);
     return provider;
 }
 
@@ -419,6 +436,7 @@ ai_provider_unref(AIProvider* provider)
     g_free(provider->project_id);
     g_free(provider->default_model);
     g_hash_table_destroy(provider->settings);
+    pthread_mutex_destroy(&provider->settings_lock);
 
     GList* curr = provider->models;
     while (curr) {
@@ -729,31 +747,44 @@ ai_get_provider_default_model(const gchar* provider_name)
     return provider->default_model;
 }
 
-void
+gboolean
 ai_set_provider_setting(const gchar* provider_name, const gchar* setting, const gchar* value)
 {
     if (!provider_name || !setting)
-        return;
+        return FALSE;
+
+    if (_is_reserved_payload_key(setting)) {
+        log_warning("Setting '%s' for provider '%s' rejected: reserved payload key", setting, provider_name);
+        return FALSE;
+    }
 
     AIProvider* provider = ai_get_provider(provider_name);
     if (!provider) {
         log_warning("Provider '%s' not found for setting '%s'", provider_name, setting);
-        return;
+        return FALSE;
     }
 
+    /* settings is iterated by the request thread; mutate under settings_lock */
+    pthread_mutex_lock(&provider->settings_lock);
     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));
+    } else {
+        g_hash_table_remove(provider->settings, setting);
+    }
+    pthread_mutex_unlock(&provider->settings_lock);
+
+    if (value) {
         prefs_ai_set_setting(provider_name, setting, value);
         log_info("Setting '%s' for provider '%s' set to: %s", setting, provider_name, value);
     } else {
-        g_hash_table_remove(provider->settings, setting);
         prefs_ai_remove_setting(provider_name, setting);
         log_info("Setting '%s' removed for provider '%s'", setting, provider_name);
     }
+    return TRUE;
 }
 
 gchar*
@@ -766,8 +797,10 @@ ai_get_provider_setting(const gchar* provider_name, const gchar* setting)
     if (!provider || !provider->settings)
         return NULL;
 
-    gchar* value = g_hash_table_lookup(provider->settings, setting);
-    return g_strdup(value);
+    pthread_mutex_lock(&provider->settings_lock);
+    gchar* value = g_strdup(g_hash_table_lookup(provider->settings, setting));
+    pthread_mutex_unlock(&provider->settings_lock);
+    return value;
 }
 
 /* ========================================================================
@@ -1436,7 +1469,9 @@ ai_session_switch(AISession* session, const gchar* provider_name,
  * the session lock while calling it.
  *
  * Custom provider settings are merged into the payload as additional JSON
- * key-value pairs alongside "model" and "input".
+ * key-value pairs alongside "model" and "messages": scalar values
+ * (number/true/false/null) are emitted bare, anything else as a JSON string;
+ * reserved keys (model/messages/stream) are skipped.
  *
  * @param provider The AI provider (for custom settings)
  * @param model The model identifier
@@ -1473,20 +1508,33 @@ _build_json_payload_from_list(AIProvider* provider, const gchar* model, GList* h
 
     auto_gchar gchar* escaped_model = ai_json_escape(model);
 
-    /* Build custom settings JSON fragment */
+    /* Build custom settings JSON fragment; settings is mutated on the main
+     * thread (/ai set custom), so iterate under settings_lock */
     GString* custom_json = g_string_new("");
-    if (provider && provider->settings) {
-        GHashTableIter iter;
-        gpointer key, value;
-        g_hash_table_iter_init(&iter, provider->settings);
-        while (g_hash_table_iter_next(&iter, &key, &value)) {
-            auto_gchar gchar* escaped_key = ai_json_escape((gchar*)key);
-            auto_gchar gchar* escaped_val = ai_json_escape((gchar*)value);
-            if (custom_json->len > 0) {
-                g_string_append_c(custom_json, ',');
+    if (provider) {
+        pthread_mutex_lock(&provider->settings_lock);
+        if (provider->settings) {
+            GHashTableIter iter;
+            gpointer key, value;
+            g_hash_table_iter_init(&iter, provider->settings);
+            while (g_hash_table_iter_next(&iter, &key, &value)) {
+                if (_is_reserved_payload_key((gchar*)key)) {
+                    continue; /* fixed payload fields stay authoritative */
+                }
+                auto_gchar gchar* escaped_key = ai_json_escape((gchar*)key);
+                if (custom_json->len > 0) {
+                    g_string_append_c(custom_json, ',');
+                }
+                if (_is_json_bare_token((gchar*)value)) {
+                    g_string_append_printf(custom_json, "\"%s\": %s", escaped_key, (gchar*)value);
+                } else {
+                    /* non-scalar values must be quoted, else the payload is invalid JSON */
+                    auto_gchar gchar* escaped_val = ai_json_escape((gchar*)value);
+                    g_string_append_printf(custom_json, "\"%s\": \"%s\"", escaped_key, escaped_val);
+                }
             }
-            g_string_append_printf(custom_json, "\"%s\": %s", escaped_key, escaped_val);
         }
+        pthread_mutex_unlock(&provider->settings_lock);
     }
 
     /* Assemble final payload: model, messages, custom settings, then fixed keys */

src/ai/ai_client.h

@@ -17,14 +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* 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) */
+    gchar* name;                   /* Provider name (e.g., "openai", "perplexity") */
+    gchar* api_url;                /* API endpoint URL */
+    gchar* project_id;             /* Optional project ID (for some providers) */
+    gchar* default_model;          /* Default model for this provider */
+    pthread_mutex_t settings_lock; /* Protects settings (iterated by the request thread) */
+    GHashTable* settings;          /* Extensible per-provider settings (e.g., temperature=0.7) */
+    GList* models;                 /* Cached models (gchar*) */
+    gboolean models_fresh;         /* Whether models cache is current */
+    gint32 ref_count;              /* Reference count (atomic) */
 } AIProvider;
 
 /**
@@ -142,11 +143,13 @@ const gchar* ai_get_provider_default_model(const gchar* provider_name);
 
 /**
  * Set a custom setting for a provider.
+ * Reserved payload keys (model, messages, stream) are rejected.
  * @param provider_name The provider name
- * @param setting The setting key (e.g., "tools", "search")
- * @param value The setting value
+ * @param setting The setting key (e.g., "temperature")
+ * @param value The setting value, or NULL to remove
+ * @return TRUE on success, FALSE on unknown provider or reserved key
  */
-void ai_set_provider_setting(const gchar* provider_name, const gchar* setting, const gchar* value);
+gboolean ai_set_provider_setting(const gchar* provider_name, const gchar* setting, const gchar* value);
 
 /**
  * Get a custom setting for a provider.
@@ -184,9 +187,9 @@ gboolean ai_models_are_fresh(const gchar* provider_name);
 void ai_parse_models_from_json(AIProvider* provider, const gchar* json);
 
 /**
- * Extract assistant content from an LLM response body. Tries Perplexity
- * /v1/responses "text" first, falls back to OpenAI "content". Decodes
- * the \" and \n escape sequences only.
+ * Extract assistant content from an OpenAI chat-completions response body
+ * ({"choices":[{"message":{"content":"..."}}]}). Decodes the \" and \n
+ * escape sequences only.
  * @param response_json The JSON body from the provider
  * @return Newly allocated content string, or NULL if not found (caller frees)
  */

src/command/cmd_defs.c

@@ -2833,7 +2833,7 @@ static const struct cmd_t command_defs[] = {
               { "set provider <name> <url>", "Add or update a provider with custom API endpoint" },
               { "set token <provider> <token>", "Set API token for a provider (e.g., openai, perplexity)" },
               { "set default-model <provider> <model>", "Set default model for a provider" },
-              { "set custom <provider> <setting> <value>", "Set provider-level setting (e.g., tools, search)" },
+              { "set custom <provider> <setting> <value>", "Set provider-level setting (e.g., temperature, max_tokens)" },
               { "remove provider <name>", "Remove a custom provider" },
               { "providers", "List configured providers with full details" },
               { "start <provider> [<model>]", "Start new AI chat (space-separated, uses defaults if omitted)" },
@@ -2846,7 +2846,7 @@ static const struct cmd_t command_defs[] = {
               "/ai set token perplexity pplx-xxx",
               "/ai set provider custom https://my-api.com/v1/chat/completions",
               "/ai set default-model perplexity sonar",
-              "/ai set custom perplexity tools enabled",
+              "/ai set custom perplexity temperature 0.7",
               "/ai remove provider custom",
               "/ai start",
               "/ai start perplexity",

src/command/cmd_funcs.c

@@ -10787,8 +10787,11 @@ cmd_ai_set(ProfWin* window, const char* const command, gchar** args)
             cons_bad_cmd_usage(command);
             return TRUE;
         }
-        ai_set_provider_setting(args[2], args[3], args[4]);
-        cons_show("Setting '%s' for provider '%s' set to: %s", args[3], args[2], args[4]);
+        if (ai_set_provider_setting(args[2], args[3], args[4])) {
+            cons_show("Setting '%s' for provider '%s' set to: %s", args[3], args[2], args[4]);
+        } else {
+            cons_show_error("Cannot set '%s' for provider '%s': unknown provider or reserved key (model, messages, stream).", args[3], args[2]);
+        }
         cons_show("");
         return TRUE;
     }

tests/unittests/test_ai_client.c

@@ -614,6 +614,24 @@ test_ai_set_provider_setting(void** state)
     assert_null(ai_get_provider_setting("p_set_settings", "nonexistent_setting"));
 }
 
+void
+test_ai_set_provider_setting_reserved_key(void** state)
+{
+    ai_add_provider("p_reserved_keys", "https://example.test/rk/");
+
+    /* Reserved payload keys are rejected (would duplicate fixed fields) */
+    assert_false(ai_set_provider_setting("p_reserved_keys", "model", "x"));
+    assert_false(ai_set_provider_setting("p_reserved_keys", "messages", "[]"));
+    assert_false(ai_set_provider_setting("p_reserved_keys", "stream", "true"));
+    assert_null(ai_get_provider_setting("p_reserved_keys", "model"));
+
+    /* Ordinary keys still work */
+    assert_true(ai_set_provider_setting("p_reserved_keys", "temperature", "0.7"));
+    auto_gchar gchar* temp = ai_get_provider_setting("p_reserved_keys", "temperature");
+    assert_non_null(temp);
+    assert_string_equal("0.7", temp);
+}
+
 void
 test_ai_get_provider_setting(void** state)
 {
@@ -919,22 +937,22 @@ test_ai_parse_response_openai_content(void** state)
 }
 
 void
-test_ai_parse_response_perplexity_text(void** state)
+test_ai_parse_response_legacy_text_format_unsupported(void** state)
 {
+    /* Legacy Perplexity /v1/agent format: "content" is an array, not a string.
+     * Dropped with the chat-completions alignment, so parsing yields NULL. */
     const gchar* json = "{\"output\":[{\"content\":[{\"text\":\"Search result\",\"type\":\"output_text\"}]}]}";
-    auto_gchar gchar* out = ai_parse_response(json);
-    assert_non_null(out);
-    assert_string_equal("Search result", out);
+    assert_null(ai_parse_response(json));
 }
 
 void
-test_ai_parse_response_text_preferred_over_content(void** state)
+test_ai_parse_response_content_preferred_over_text(void** state)
 {
-    /* When both formats are present, "text" wins (Perplexity path tried first). */
+    /* Chat-completions "content" is extracted; a stray "text" field is ignored. */
     const gchar* json = "{\"text\":\"from text field\",\"content\":\"from content field\"}";
     auto_gchar gchar* out = ai_parse_response(json);
     assert_non_null(out);
-    assert_string_equal("from text field", out);
+    assert_string_equal("from content field", out);
 }
 
 void

tests/unittests/test_ai_client.h

@@ -43,6 +43,7 @@ void test_ai_providers_find_case_insensitive(void** state);
 void test_ai_set_provider_default_model(void** state);
 void test_ai_get_provider_default_model(void** state);
 void test_ai_set_provider_setting(void** state);
+void test_ai_set_provider_setting_reserved_key(void** state);
 void test_ai_get_provider_setting(void** state);
 /* Model caching tests */
 void test_ai_models_are_fresh_initial(void** state);
@@ -64,8 +65,8 @@ int ai_client_teardown_with_prefs(void** state);
 
 /* Chat response parser tests (ai_parse_response) */
 void test_ai_parse_response_openai_content(void** state);
-void test_ai_parse_response_perplexity_text(void** state);
-void test_ai_parse_response_text_preferred_over_content(void** state);
+void test_ai_parse_response_legacy_text_format_unsupported(void** state);
+void test_ai_parse_response_content_preferred_over_text(void** state);
 void test_ai_parse_response_escaped_quote(void** state);
 void test_ai_parse_response_newline_escape(void** state);
 void test_ai_parse_response_empty_content(void** state);

tests/unittests/unittests.c

@@ -752,6 +752,7 @@ main(int argc, char* argv[])
         cmocka_unit_test_setup_teardown(test_ai_set_provider_default_model, ai_client_setup, ai_client_teardown),
         cmocka_unit_test_setup_teardown(test_ai_get_provider_default_model, ai_client_setup, ai_client_teardown),
         cmocka_unit_test_setup_teardown(test_ai_set_provider_setting, ai_client_setup, ai_client_teardown),
+        cmocka_unit_test_setup_teardown(test_ai_set_provider_setting_reserved_key, ai_client_setup, ai_client_teardown),
         cmocka_unit_test_setup_teardown(test_ai_get_provider_setting, ai_client_setup, ai_client_teardown),
         /* Model caching tests */
         cmocka_unit_test_setup_teardown(test_ai_models_are_fresh_initial, ai_client_setup, ai_client_teardown),
@@ -774,8 +775,8 @@ main(int argc, char* argv[])
         cmocka_unit_test(test_ai_json_escape_backslash_quote),
         /* Chat response parser */
         cmocka_unit_test(test_ai_parse_response_openai_content),
-        cmocka_unit_test(test_ai_parse_response_perplexity_text),
-        cmocka_unit_test(test_ai_parse_response_text_preferred_over_content),
+        cmocka_unit_test(test_ai_parse_response_legacy_text_format_unsupported),
+        cmocka_unit_test(test_ai_parse_response_content_preferred_over_text),
         cmocka_unit_test(test_ai_parse_response_escaped_quote),
         cmocka_unit_test(test_ai_parse_response_newline_escape),
         cmocka_unit_test(test_ai_parse_response_empty_content),