fix: stop polling llama-servers during external-model sessions

selectSessionUrls fell back to all discovered servers when the current
session's provider matched no candidate, so external sessions kept
polling local servers: one answered /slots with idle slots (showing
'- tps (TG)') while another rejected unknown models with HTTP 400
(flickering 'n/a'). Narrow to zero URLs instead and surface n/a.

src/stats.ts

@@ -284,7 +284,7 @@ export function selectSessionUrls(
 ): string[] {
   if (typeof providerID !== "string" || providerID.trim() === "" || candidates.length === 0)
     return candidates
-  if (!Array.isArray(providers)) return candidates
+  if (!Array.isArray(providers) || providers.length === 0) return candidates
   for (const entry of providers) {
     if (!entry || typeof entry !== "object") continue
     const provider = entry as Record<string, unknown>
@@ -298,7 +298,7 @@ export function selectSessionUrls(
         if (candidates.includes(normalized)) return [normalized]
       }
     }
-    break
+    return []
   }
-  return candidates
+  return []
 }

test-backoff.ts

@@ -178,10 +178,10 @@ test("selectSessionUrls returns candidates unchanged when provider not found", (
   assert.deepEqual(selectSessionUrls(candidates, [], "nope"), ["http://a:1"])
 })
 
-test("selectSessionUrls returns candidates unchanged when matched provider URL is not a candidate", () => {
+test("selectSessionUrls excludes polling when matched provider URL is not a candidate", () => {
   const candidates = ["http://a:1"]
   const providers = [{ id: "ollama", name: "Ollama", options: { baseURL: "http://d:4" } }]
-  assert.deepEqual(selectSessionUrls(candidates, providers, "ollama"), ["http://a:1"])
+  assert.deepEqual(selectSessionUrls(candidates, providers, "ollama"), [])
 })
 
 test("selectSessionUrls returns candidates unchanged for missing or empty providerID", () => {
@@ -191,20 +191,36 @@ test("selectSessionUrls returns candidates unchanged for missing or empty provid
   assert.deepEqual(selectSessionUrls(["http://a:1"], [], 42), ["http://a:1"])
 })
 
-test("selectSessionUrls ignores non-string baseURL on matched provider", () => {
+test("selectSessionUrls excludes polling when matched provider has no usable baseURL", () => {
   const candidates = ["http://a:1"]
   const providers = [{ id: "p", name: "P", options: { baseURL: 42 } }]
-  assert.deepEqual(selectSessionUrls(candidates, providers, "p"), ["http://a:1"])
+  assert.deepEqual(selectSessionUrls(candidates, providers, "p"), [])
 })
 
 test("selectSessionUrls returns empty candidates unchanged", () => {
   assert.deepEqual(selectSessionUrls([], [], "p"), [])
 })
 
-test("selectSessionUrls tolerates non-array and malformed providers", () => {
+test("selectSessionUrls tolerates non-array providers", () => {
   const c = ["http://a:1"]
   assert.deepEqual(selectSessionUrls(c, undefined, "p"), c)
-  assert.deepEqual(selectSessionUrls(c, [null, 42, {}, { id: "p" }], "p"), c)
+})
+
+test("selectSessionUrls excludes polling when id is absent from a non-empty provider list", () => {
+  assert.deepEqual(selectSessionUrls(["http://a:1"], [null, 42, {}], "p"), [])
+  assert.deepEqual(selectSessionUrls(["http://a:1"], [{ id: "other", options: { baseURL: "http://a:1" } }], "p"), [])
+})
+
+test("selectSessionUrls excludes polling during external-model sessions", () => {
+  // Mirrors the reported regression: local router + single-model server discovered,
+  // while the session runs on an unrelated external provider.
+  const candidates = ["http://localhost:8080", "http://127.0.0.1:40909"]
+  const providers = [
+    { id: "llamacpp-router", name: "llama.cpp router", options: { baseURL: "http://localhost:8080/v1" } },
+    { id: "ornith", name: "Ornith", options: { baseURL: "http://127.0.0.1:40909/v1" } },
+    { id: "opencode", name: "OpenCode", options: { baseURL: "https://api.example.internal/v1" } },
+  ]
+  assert.deepEqual(selectSessionUrls(candidates, providers, "opencode"), [])
 })
 
 test("selectSessionUrls first match wins for duplicate ids", () => {

tui.tsx

@@ -197,7 +197,11 @@ const tui: TuiPlugin = async (api, options) => {
     }
 
     const activeUrls = selectSessionUrls(llamaServerUrls, api.state.provider, sessionProviderId)
-    if (!activeUrls.length) return
+    if (!activeUrls.length) {
+      tracker.failure = "n/a"
+      bump()
+      return
+    }
     for (const baseUrl of activeUrls) {
       const now = Date.now()
       const backoff = backoffByUrl.get(baseUrl)