fix(agents): carry the backend provider into persona templates

Corrects an earlier call to omit provider from the save-as-persona-template
port. On main the provider is NOT a top-level ManagedAgent field, but it is
NOT absent either — it lives in the backend union: a `{ type: "provider",
id }` backend carries the provider id, while a `{ type: "local" }` backend
has none.

- saveAsPersonaTemplateDialogState now derives provider from agent.backend
  (providerForAgentBackend): a provider backend carries backend.id; a local
  backend leaves it unset. A databricks agent promotes with its provider
  instead of losing it.
- CreateAgentDialog's opt-in template mint mirrors this: it carries the
  selected backend provider (runOn) when the agent runs on a provider.

Tests updated: provider carries from a provider backend; stays unset for a
local backend.

Co-authored-by: Taylor Ho <taylorkmho@gmail.com>
Signed-off-by: Taylor Ho <taylorkmho@gmail.com>

desktop/src/features/agents/ui/CreateAgentDialog.tsx

@@ -443,6 +443,10 @@ export function CreateAgentDialog({
           runtime:
             selectedRuntimeId !== "custom" ? selectedRuntimeId : undefined,
           model: useMesh ? meshModelId.trim() || undefined : undefined,
+          // Carry the backend provider when the agent runs on one ("Run on" is
+          // a provider, not local). Mirrors what the agent input persists in
+          // `backend.id`; local agents leave it unset.
+          provider: isProviderMode ? runOn : undefined,
           envVars,
         };
         try {

desktop/src/features/agents/ui/personaDialogState.test.mjs

@@ -259,6 +259,7 @@ function makeAgent(overrides = {}) {
     lastStoppedAt: null,
     lastExitCode: null,
     lastError: null,
+    backend: { type: "local" },
     ...overrides,
   };
 }
@@ -316,12 +317,26 @@ test("saveAsPersonaTemplateDialogState carries name, prompt, model, and envVars"
   assert.deepEqual(state.initialValues.namePool, []);
 });
 
-test("saveAsPersonaTemplateDialogState omits provider (no top-level field on ManagedAgent)", () => {
-  // A ManagedAgent has no top-level provider, so there is nothing lossless to
-  // carry — the builder must not invent one.
-  const state = saveAsPersonaTemplateDialogState(makeAgent(), []);
+test("saveAsPersonaTemplateDialogState carries the provider id from a provider backend", () => {
+  // A databricks/anthropic agent must promote with its provider, not lose it.
+  // ManagedAgent has no top-level provider on main; it lives in backend.id.
+  const state = saveAsPersonaTemplateDialogState(
+    makeAgent({ backend: { type: "provider", id: "databricks", config: {} } }),
+    [],
+  );
 
-  assert.equal("provider" in state.initialValues, false);
+  assert.equal(state.initialValues.provider, "databricks");
+});
+
+test("saveAsPersonaTemplateDialogState leaves provider unset for a local backend", () => {
+  // A local backend has no provider; the persona's provider is optional, so it
+  // carries as undefined (auto-detect / provider-locked runtime).
+  const state = saveAsPersonaTemplateDialogState(
+    makeAgent({ backend: { type: "local" } }),
+    [],
+  );
+
+  assert.equal(state.initialValues.provider, undefined);
 });
 
 test("saveAsPersonaTemplateDialogState tolerates null systemPrompt and model", () => {

desktop/src/features/agents/ui/personaDialogState.ts

@@ -76,21 +76,34 @@ function runtimeIdForAgentCommand(
   return match?.id;
 }
 
+/**
+ * Extract the LLM provider id from a managed agent's backend so it can carry
+ * into the persona template (a databricks/anthropic agent should promote with
+ * its provider, not lose it). On `main` the provider is NOT a top-level field
+ * on `ManagedAgent`; it lives in the backend union: a `"provider"` backend
+ * carries the provider id, while a `"local"` backend has none. Returns
+ * `undefined` for local backends — the persona's `provider` is optional, so an
+ * absent provider just carries as unset (auto-detect / provider-locked runtime).
+ */
+function providerForAgentBackend(
+  backend: ManagedAgent["backend"],
+): string | undefined {
+  return backend.type === "provider" ? backend.id : undefined;
+}
+
 /**
  * Dialog state for the opt-in "Save as persona template" action on an existing
  * agent. Prefills the persona editor from the agent so the user reviews and
  * confirms before a persona template is created — nothing is minted silently.
  *
  * Near-lossless promote: name, system prompt, model, and env vars copy
- * straight across; the harness command reverse-maps to a runtime ID.
- * `namePool` is persona-only and starts empty — the user can fill it in the
- * same dialog (it's how a template bulk-adds bots later).
+ * straight across; the harness command reverse-maps to a runtime ID and the
+ * backend provider id carries into the persona's provider. `namePool` is
+ * persona-only and starts empty — the user can fill it in the same dialog
+ * (it's how a template bulk-adds bots later).
  *
  * Note: "persona template" is the UI name for what the backend calls a
  * `persona` (kind:30175). This builder produces a backend `CreatePersonaInput`.
- * `provider` is intentionally not carried: a `ManagedAgent` does not expose a
- * top-level provider field (it lives in backend/provider config), so there is
- * nothing lossless to copy here.
  */
 export function saveAsPersonaTemplateDialogState(
   agent: ManagedAgent,
@@ -106,6 +119,9 @@ export function saveAsPersonaTemplateDialogState(
       systemPrompt: agent.systemPrompt ?? "",
       runtime: runtimeIdForAgentCommand(agent.agentCommand, runtimes),
       model: agent.model ?? undefined,
+      // Carry the provider from a `"provider"` backend; `"local"` backends
+      // have none and leave it unset (see providerForAgentBackend).
+      provider: providerForAgentBackend(agent.backend),
       // namePool is persona-only; start empty so the user fills it here.
       namePool: [],
       envVars: agent.envVars ?? {},