From be20eebc21692ac9e1113a0104af8e2ad70cbeae Mon Sep 17 00:00:00 2001
From: HCL <chenglunhu@gmail.com>
Date: Tue, 24 Mar 2026 07:05:11 +0800
Subject: [PATCH] fix(ui): resolve model provider from catalog instead of stale
 session default
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When the server returns a bare model name (e.g. "deepseek-chat") with
a session-level modelProvider (e.g. "zai"), the UI blindly prepends
the provider — producing "zai/deepseek-chat" instead of the correct
"deepseek/deepseek-chat". This causes "model not allowed" errors
when switching between models from different providers.

Root cause: resolveModelOverrideValue() and resolveDefaultModelValue()
in app-render.helpers.ts, plus the /model slash command handler in
slash-command-executor.ts, all call resolveServerChatModelValue()
which trusts the session's default provider. The session provider
reflects the PREVIOUS model, not the newly selected one.

Fix: for bare model names, create a raw ChatModelOverride and resolve
through normalizeChatModelOverrideValue() which looks up the correct
provider from the model catalog. Falls back to server-provided provider
only if the catalog lookup fails. All 3 call sites are fixed.

Closes #53031

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: HCL <chenglunhu@gmail.com>
---
 ui/src/ui/app-render.helpers.ts          | 25 ++++++++++++++++++++++--
 ui/src/ui/chat/slash-command-executor.ts | 12 +++++++-----
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/ui/src/ui/app-render.helpers.ts b/ui/src/ui/app-render.helpers.ts
index 2f41a25fa8d..e69658a0e20 100644
--- a/ui/src/ui/app-render.helpers.ts
+++ b/ui/src/ui/app-render.helpers.ts
@@ -536,9 +536,19 @@ function resolveModelOverrideValue(state: AppViewState): string {
     return "";
   }
   // No local override recorded yet — fall back to server data.
-  // Include provider prefix so the value matches option keys (provider/model).
+  // Use the bare model name and resolve provider from the catalog rather than
+  // trusting the session's modelProvider, which may be the session default and
+  // not the model's actual provider (e.g. "zai" for a "deepseek-chat" model).
   const activeRow = resolveActiveSessionRow(state);
   if (activeRow && typeof activeRow.model === "string" && activeRow.model.trim()) {
+    const rawOverride = createChatModelOverride(activeRow.model.trim());
+    if (rawOverride) {
+      const normalized = normalizeChatModelOverrideValue(rawOverride, state.chatModelCatalog ?? []);
+      if (normalized) {
+        return normalized;
+      }
+    }
+    // Fallback: use server-provided provider if catalog lookup fails.
     return resolveServerChatModelValue(activeRow.model, activeRow.modelProvider);
   }
   return "";
@@ -546,7 +556,18 @@ function resolveModelOverrideValue(state: AppViewState): string {
 
 function resolveDefaultModelValue(state: AppViewState): string {
   const defaults = state.sessionsResult?.defaults;
-  return resolveServerChatModelValue(defaults?.model, defaults?.modelProvider);
+  const model = defaults?.model;
+  if (typeof model !== "string" || !model.trim()) {
+    return "";
+  }
+  const rawOverride = createChatModelOverride(model.trim());
+  if (rawOverride) {
+    const normalized = normalizeChatModelOverrideValue(rawOverride, state.chatModelCatalog ?? []);
+    if (normalized) {
+      return normalized;
+    }
+  }
+  return resolveServerChatModelValue(model, defaults?.modelProvider);
 }
 
 function buildChatModelOptions(
diff --git a/ui/src/ui/chat/slash-command-executor.ts b/ui/src/ui/chat/slash-command-executor.ts
index b1d06d5e2b2..55e8b4b3182 100644
--- a/ui/src/ui/chat/slash-command-executor.ts
+++ b/ui/src/ui/chat/slash-command-executor.ts
@@ -16,7 +16,7 @@ import {
   isSubagentSessionKey,
   parseAgentSessionKey,
 } from "../../../../src/routing/session-key.js";
-import { createChatModelOverride, resolveServerChatModelValue } from "../chat-model-ref.ts";
+import { createChatModelOverride, normalizeChatModelOverrideValue, resolveServerChatModelValue } from "../chat-model-ref.ts";
 import type { GatewayBrowserClient } from "../gateway.ts";
 import type {
   AgentsListResult,
@@ -155,10 +155,12 @@ async function executeModel(
       key: sessionKey,
       model: args.trim(),
     });
-    const resolvedValue = resolveServerChatModelValue(
-      patched.resolved?.model ?? args.trim(),
-      patched.resolved?.modelProvider,
-    );
+    const patchedModel = patched.resolved?.model ?? args.trim();
+    const rawOverride = createChatModelOverride(patchedModel.trim());
+    const resolvedValue = rawOverride
+      ? (normalizeChatModelOverrideValue(rawOverride, state.chatModelCatalog ?? []) ||
+         resolveServerChatModelValue(patchedModel, patched.resolved?.modelProvider))
+      : resolveServerChatModelValue(patchedModel, patched.resolved?.modelProvider);
     return {
       content: `Model set to \`${args.trim()}\`.`,
       action: "refresh",