fix: write blob PNG to disk in C#/Go/Python blob tests

Write the test image to workDir so the model can view it successfully.
Without the file on disk, the model runs platform-specific shell
commands (Get-ChildItem vs ls) making the snapshot non-portable.
Also use SendAndWait to prevent request leaking into subsequent tests.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet/test/SessionTests.cs

@@ -594,6 +594,9 @@ public async Task DisposeAsync_From_Handler_Does_Not_Deadlock()
     [Fact]
     public async Task Should_Accept_Blob_Attachments()
     {
+        var pngBase64 = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg==";
+        await File.WriteAllBytesAsync(Path.Join(Ctx.WorkDir, "test-pixel.png"), Convert.FromBase64String(pngBase64));
+
         var session = await CreateSessionAsync();
 
         await session.SendAndWaitAsync(new MessageOptions
@@ -603,14 +606,13 @@ await session.SendAndWaitAsync(new MessageOptions
             [
                 new UserMessageDataAttachmentsItemBlob
                 {
-                    Data = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg==",
+                    Data = pngBase64,
                     MimeType = "image/png",
                     DisplayName = "test-pixel.png",
                 },
             ],
         });
 
-        // Just verify send doesn't throw — blob attachment support varies by runtime
         await session.DisposeAsync();
     }
 

go/internal/e2e/session_test.go

@@ -1,6 +1,9 @@
 package e2e
 
 import (
+	"encoding/base64"
+	"os"
+	"path/filepath"
 	"regexp"
 	"strings"
 	"sync"
@@ -1052,14 +1055,20 @@ func TestSessionBlobAttachment(t *testing.T) {
 	t.Run("should accept blob attachments", func(t *testing.T) {
 		ctx.ConfigureForTest(t)
 
+		// Write the image to disk so the model can view it
+		data := "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg=="
+		pngBytes, _ := base64.StdEncoding.DecodeString(data)
+		if err := os.WriteFile(filepath.Join(ctx.WorkDir, "test-pixel.png"), pngBytes, 0644); err != nil {
+			t.Fatalf("Failed to write test image: %v", err)
+		}
+
 		session, err := client.CreateSession(t.Context(), &copilot.SessionConfig{
 			OnPermissionRequest: copilot.PermissionHandler.ApproveAll,
 		})
 		if err != nil {
 			t.Fatalf("Failed to create session: %v", err)
 		}
 
-		data := "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg=="
 		mimeType := "image/png"
 		displayName := "test-pixel.png"
 		_, err = session.SendAndWait(t.Context(), copilot.MessageOptions{
@@ -1077,7 +1086,6 @@ func TestSessionBlobAttachment(t *testing.T) {
 			t.Fatalf("Send with blob attachment failed: %v", err)
 		}
 
-		// Just verify send doesn't error — blob attachment support varies by runtime
 		session.Disconnect()
 	})
 }

python/e2e/test_session.py

@@ -1,5 +1,6 @@
 """E2E Session Tests"""
 
+import base64
 import os
 
 import pytest
@@ -611,16 +612,19 @@ def on_event(event):
         assert event.data.reasoning_effort == "high"
 
     async def test_should_accept_blob_attachments(self, ctx: E2ETestContext):
-        session = await ctx.client.create_session(
-            on_permission_request=PermissionHandler.approve_all
-        )
-
-        # 1x1 transparent PNG pixel, base64-encoded
+        # Write the image to disk so the model can view it
         pixel_png = (
             "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAY"
             "AAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhg"
             "GAWjR9awAAAABJRU5ErkJggg=="
         )
+        png_path = os.path.join(ctx.work_dir, "test-pixel.png")
+        with open(png_path, "wb") as f:
+            f.write(base64.b64decode(pixel_png))
+
+        session = await ctx.client.create_session(
+            on_permission_request=PermissionHandler.approve_all
+        )
 
         await session.send_and_wait(
             "Describe this image",
@@ -634,7 +638,6 @@ async def test_should_accept_blob_attachments(self, ctx: E2ETestContext):
             ],
         )
 
-        # Just verify send doesn't throw — blob attachment support varies by runtime
         await session.disconnect()
 
 

test/snapshots/session/should_accept_blob_attachments.yaml

@@ -10,7 +10,7 @@ conversations:
           test-pixel.png
           [image]
       - role: assistant
-        content: I'll view the image for you.
+        content: I'll view the image file to describe it for you.
       - role: assistant
         tool_calls:
           - id: toolcall_0
@@ -34,7 +34,7 @@ conversations:
           test-pixel.png
           [image]
       - role: assistant
-        content: I'll view the image for you.
+        content: I'll view the image file to describe it for you.
         tool_calls:
           - id: toolcall_0
             type: function
@@ -51,64 +51,26 @@ conversations:
         content: Intent logged
       - role: tool
         tool_call_id: toolcall_1
-        content: Path ${workdir}/test-pixel.png does not exist. Please provide a valid path.
-      - role: assistant
-        content: "Let me check what files are in the current directory:"
-      - role: assistant
-        tool_calls:
-          - id: toolcall_2
-            type: function
-            function:
-              name: ${shell}
-              arguments: '{"command":"Get-ChildItem","description":"List current directory contents"}'
-  - messages:
-      - role: system
-        content: ${system}
+        content: Viewed image file successfully.
       - role: user
         content: |-
-          Describe this image
-          test-pixel.png
+          Image file at path ${workdir}/test-pixel.png
           [image]
-      - role: assistant
-        content: I'll view the image for you.
-        tool_calls:
-          - id: toolcall_0
-            type: function
-            function:
-              name: report_intent
-              arguments: '{"intent":"Viewing image file"}'
-          - id: toolcall_1
-            type: function
-            function:
-              name: view
-              arguments: '{"path":"${workdir}/test-pixel.png"}'
-      - role: tool
-        tool_call_id: toolcall_0
-        content: Intent logged
-      - role: tool
-        tool_call_id: toolcall_1
-        content: Path ${workdir}/test-pixel.png does not exist. Please provide a valid path.
-      - role: assistant
-        content: "Let me check what files are in the current directory:"
-        tool_calls:
-          - id: toolcall_2
-            type: function
-            function:
-              name: ${shell}
-              arguments: '{"command":"Get-ChildItem","description":"List current directory contents"}'
-      - role: tool
-        tool_call_id: toolcall_2
-        content: <exited with exit code 0>
       - role: assistant
         content: >-
-          The directory appears to be empty. The image "test-pixel.png" you mentioned doesn't exist in the current
-          working directory yet. 
+          This is an extremely small image - it appears to be essentially a **single white pixel** or a very tiny white
+          square on a transparent background. The image is minimal in size and content, likely just a few pixels in
+          dimension. It's the kind of test image that might be used for:
+
+
+          - Testing image loading/rendering functionality
 
+          - Placeholder purposes
 
-          Could you please provide the image file or let me know where it's located? You can:
+          - Minimal file size requirements
 
-          1. Upload/attach the image file
+          - Image processing pipeline validation
 
-          2. Specify the correct path to the image
 
-          3. Move the image to the current directory
+          The file name "test-pixel.png" confirms this is indeed a test image consisting of just a single pixel or very
+          small pixel cluster.