Document how chat templates carry tools and data sources

app/MindWork AI Studio/Plugins/assistants/README.md

@@ -147,10 +147,13 @@ ASSISTANT = {
 - `OPEN_TEMPORARY_CHAT` must not carry a `WorkspaceName`. A name next to it stops the plugin from loading rather than being ignored, so a leftover or mistyped name cannot silently turn a workspace launcher into a disappearing one.
 - Omitted optional IDs use the chat defaults active when the tile is opened. An explicit empty GUID selects no profile or no chat template; an empty provider or data-source GUID is invalid.
 - `ProviderId` overrides both the chat-specific and app-wide default provider. It must name a provider that is permitted for chats at the required confidence level.
-- Explicit data sources are enabled and manually preselected, automatic source selection is disabled, and the normal automatic-validation setting is retained. Every referenced source must currently be available and permitted for the effective provider.
+- Explicit data sources are enabled and manually preselected, automatic source selection is disabled, and the normal automatic-validation setting is retained. Every referenced source must currently be available and permitted for the effective provider. This describes a launcher whose chat template brings no data source options of its own; see the rule below for the case where it does.
 - Invalid or unavailable references stop the launch with an error before a workspace or chat is created.
 - A selected chat template supplies the chat system prompt, profile allowance, predefined user prompt, attachments, and cloned example conversation. A launcher `SystemPrompt`, if retained in an older plugin, is ignored, so there is never a second competing system prompt.
 - When the selected chat template does not allow profiles, the template wins: the launcher `ProfileId` is dropped and the chat starts without a profile. This matches the disabled profile selection such a template produces in the chat.
+- A chat template may preselect tools and data sources as well. When it does, it decides them alone: the launcher `ToolIds` and `DataSourceIds` are dropped, and AI Studio writes a warning into the log naming both sides. The rule is the same for tools and for data sources, so there is only one to remember.
+- The reason the template wins as a whole rather than field by field is a difference in what the two can express. A launcher can only ever say "these sources, picked by hand", while a chat template carries the whole data source options and can also say "let an agent pick the sources for each message". A mix of both would be something neither of them asked for.
+- The data sources of a chat template are checked exactly like the ones of a launcher: a source which no longer exists, or which is not permitted for the effective provider, stops the launch before a workspace or chat is created. The message then names the chat template as the cause, not the launcher. A template which leaves the choice to an agent names no source and is therefore not checked here; that decision is made per message in the chat.
 - The predefined user prompt and the attachments of the selected chat template are placed into the chat input, unless the user already has an unsent draft there.
 
 ### Editing a launcher in AI Studio

app/MindWork AI Studio/Plugins/assistants/plugin.lua

@@ -454,12 +454,18 @@ ASSISTANT = {
     ["ProviderId"] = "<optional provider GUID; omit to use the chat default>",
     ["ProfileId"] = "<optional profile GUID; use the empty GUID for no profile>",
     ["ChatTemplateId"] = "<optional chat template GUID; use the empty GUID for no template>",
+    -- Optional: the data sources the chat starts with. A chat template chosen above may bring
+    -- data source options of its own. It then decides them alone, the IDs named here are dropped,
+    -- and AI Studio writes a warning into the log. Only a chat template can also say that the AI
+    -- picks the sources for each message, which is why it wins as a whole instead of field by
+    -- field.
     ["DataSourceIds"] = {
         "<optional data source GUID>",
     },
     -- Optional: the tools preselected when the chat opens. Users may change the selection
     -- in the chat afterwards, and every tool has to meet the confidence requirements of the
-    -- provider in use. A tool ID unknown to the installation is ignored.
+    -- provider in use. A tool ID unknown to the installation is ignored. The same rule as for the
+    -- data sources applies here: a chat template which names tools of its own wins over this list.
     -- Tool IDs include: web_search, read_web_page
     ["ToolIds"] = {
         "<optional tool ID>",