From f60cfef8a14b1206fecf65b4a9f779bef5633c57 Mon Sep 17 00:00:00 2001
From: Alex Castillo <alex.castillog33@gmail.com>
Date: Tue, 20 Oct 2026 09:29:05 -0400
Subject: [PATCH] Replace the retired gemini-2.0-flash PDF reading default

ReadPdfFn falls back to google-ai / gemini-2.0-flash when
FileHandler:Pdf:Reading has no provider and model, and the sample
appsettings.json configures the same model for PDF reading. Google shut
gemini-2.0-flash down on 2026-06-01, so reading a PDF with the default
settings returns an error from the Gemini API.

Use gemini-3.8-flash, the current stable Flash model, in the fallback and
in appsettings.json (the chat model entry and the FileHandler setting),
with its standard paid-tier prices per 1K tokens. The Google provider
sends a temperature (0.0 by default) that Gemini 3 accepts but recommends
leaving at its default.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
---
 .../Functions/ReadPdfFn.cs                    |  2 +-
 src/WebStarter/appsettings.json               | 10 +++----
 .../BotSharp.Core.UnitTests.csproj            |  2 ++
 .../Plugins/ReadPdfFnDefaultModelTests.cs     | 26 +++++++++++++++++++
 4 files changed, 34 insertions(+), 6 deletions(-)
 create mode 100644 tests/BotSharp.Core.UnitTests/Plugins/ReadPdfFnDefaultModelTests.cs

diff --git a/src/Plugins/BotSharp.Plugin.FileHandler/Functions/ReadPdfFn.cs b/src/Plugins/BotSharp.Plugin.FileHandler/Functions/ReadPdfFn.cs
index 198ed4e89..6a2557d48 100644
--- a/src/Plugins/BotSharp.Plugin.FileHandler/Functions/ReadPdfFn.cs
+++ b/src/Plugins/BotSharp.Plugin.FileHandler/Functions/ReadPdfFn.cs
@@ -146,7 +146,7 @@ private async Task<string> GetChatCompletion(Agent agent, List<RoleDialogModel>
         }
 
         provider = "google-ai";
-        model = "gemini-2.0-flash";
+        model = "gemini-3.8-flash";
 
         return (provider, model);
     }
diff --git a/src/WebStarter/appsettings.json b/src/WebStarter/appsettings.json
index 3e4bf12c9..d9a55c51c 100644
--- a/src/WebStarter/appsettings.json
+++ b/src/WebStarter/appsettings.json
@@ -1119,7 +1119,7 @@
       "Provider": "google-ai",
       "Models": [
         {
-          "Name": "gemini-2.0-flash",
+          "Name": "gemini-3.8-flash",
           "ApiKey": "",
           "Type": "chat",
           "MultiModal": true,
@@ -1129,11 +1129,11 @@
             "PdfReading"
           ],
           "Cost": {
-            "TextInputCost": 0.0015,
-            "CachedTextInputCost": 0,
+            "TextInputCost": 0.00075,
+            "CachedTextInputCost": 0.000075,
             "AudioInputCost": 0,
             "CachedAudioInputCost": 0,
-            "TextOutputCost": 0.002,
+            "TextOutputCost": 0.00375,
             "AudioOutputCost": 0
           }
         },
@@ -1368,7 +1368,7 @@
     "Pdf": {
       "Reading": {
         "Provider": "google-ai",
-        "Model": "gemini-2.0-flash",
+        "Model": "gemini-3.8-flash",
         "ConvertToImage": false,
         "ImageDetailLevel": "auto",
         "ImageConverter": {
diff --git a/tests/BotSharp.Core.UnitTests/BotSharp.Core.UnitTests.csproj b/tests/BotSharp.Core.UnitTests/BotSharp.Core.UnitTests.csproj
index 252d113e1..2e1475e43 100644
--- a/tests/BotSharp.Core.UnitTests/BotSharp.Core.UnitTests.csproj
+++ b/tests/BotSharp.Core.UnitTests/BotSharp.Core.UnitTests.csproj
@@ -44,6 +44,8 @@
     <ProjectReference Include="..\..\src\Infrastructure\BotSharp.OpenAPI\BotSharp.OpenAPI.csproj" />
     <!-- For StreamingToolCallReconstructionTests: the streamed tool-call reconstruction lives here. -->
     <ProjectReference Include="..\..\src\Plugins\BotSharp.Plugin.OpenAI\BotSharp.Plugin.OpenAI.csproj" />
+    <!-- For ReadPdfFnDefaultModelTests: the PDF reading fallback model lives here. -->
+    <ProjectReference Include="..\..\src\Plugins\BotSharp.Plugin.FileHandler\BotSharp.Plugin.FileHandler.csproj" />
   </ItemGroup>
 
 </Project>
diff --git a/tests/BotSharp.Core.UnitTests/Plugins/ReadPdfFnDefaultModelTests.cs b/tests/BotSharp.Core.UnitTests/Plugins/ReadPdfFnDefaultModelTests.cs
new file mode 100644
index 000000000..968a414a3
--- /dev/null
+++ b/tests/BotSharp.Core.UnitTests/Plugins/ReadPdfFnDefaultModelTests.cs
@@ -0,0 +1,26 @@
+using System.Reflection;
+using BotSharp.Plugin.FileHandler.Functions;
+using BotSharp.Plugin.FileHandler.Settings;
+using Microsoft.Extensions.Logging.Abstractions;
+using Xunit;
+
+namespace BotSharp.Core.UnitTests.Plugins;
+
+public class ReadPdfFnDefaultModelTests
+{
+    // Google shut down gemini-2.0-flash on 2026-06-01, so the model that ReadPdfFn
+    // falls back to when no FileHandler:Pdf:Reading provider and model are set
+    // must be one the Gemini API still serves.
+    [Fact]
+    public void Falls_back_to_a_gemini_model_that_is_still_served()
+    {
+        var fn = new ReadPdfFn(null!, NullLogger<ReadPdfFn>.Instance, new FileHandlerSettings());
+
+        var (provider, model) = ((string, string))typeof(ReadPdfFn)
+            .GetMethod("GetLlmProviderModel", BindingFlags.NonPublic | BindingFlags.Instance)!
+            .Invoke(fn, null)!;
+
+        Assert.Equal("google-ai", provider);
+        Assert.Equal("gemini-3.8-flash", model);
+    }
+}