feat: add image generation tool and WebUI mode

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/utils/test_artifacts.py

@@ -0,0 +1,84 @@
+from __future__ import annotations
+
+import json
+from datetime import datetime, timezone
+from pathlib import Path
+
+import pytest
+
+from nanobot.config.loader import set_config_path
+from nanobot.utils.artifacts import (
+    ArtifactError,
+    decode_image_data_url,
+    generated_image_paths_from_messages,
+    generated_image_tool_result,
+    store_generated_image_artifact,
+)
+
+PNG_DATA_URL = (
+    "data:image/png;base64,"
+    "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8/x8AAwMCAO+/p9sAAAAASUVORK5CYII="
+)
+
+
+def test_decode_image_data_url_validates_image_payload() -> None:
+    raw, mime = decode_image_data_url(PNG_DATA_URL)
+
+    assert raw.startswith(b"\x89PNG")
+    assert mime == "image/png"
+
+    with pytest.raises(ArtifactError):
+        decode_image_data_url("data:image/png;base64,not-base64")
+
+
+def test_store_generated_image_artifact_writes_image_and_sidecar(tmp_path: Path) -> None:
+    set_config_path(tmp_path / "config.json")
+    created_at = datetime(2026, 5, 8, 12, 0, tzinfo=timezone.utc)
+
+    artifact = store_generated_image_artifact(
+        PNG_DATA_URL,
+        prompt="draw a tiny pixel",
+        model="openai/gpt-5.4-image-2",
+        source_images=["/tmp/ref.png"],
+        save_dir="generated",
+        created_at=created_at,
+    )
+
+    image_path = Path(artifact["path"])
+    assert image_path.is_file()
+    assert image_path.parent == tmp_path / "media" / "generated" / "2026-05-08"
+    assert artifact["id"].startswith("img_")
+    assert artifact["mime"] == "image/png"
+
+    sidecar = image_path.with_suffix(".json")
+    metadata = json.loads(sidecar.read_text(encoding="utf-8"))
+    assert metadata["path"] == str(image_path)
+    assert metadata["source_images"] == ["/tmp/ref.png"]
+
+
+def test_store_generated_image_artifact_rejects_unsafe_save_dir(tmp_path: Path) -> None:
+    set_config_path(tmp_path / "config.json")
+
+    with pytest.raises(ArtifactError):
+        store_generated_image_artifact(
+            PNG_DATA_URL,
+            prompt="x",
+            model="m",
+            save_dir="../outside",
+        )
+
+
+def test_generated_image_paths_from_tool_results() -> None:
+    result = generated_image_tool_result(
+        [
+            {"id": "img_1", "path": "/tmp/one.png"},
+            {"id": "img_2", "path": "/tmp/two.png"},
+        ]
+    )
+
+    assert generated_image_paths_from_messages(
+        [
+            {"role": "tool", "name": "generate_image", "content": result},
+            {"role": "tool", "name": "other", "content": result},
+        ]
+    ) == ["/tmp/one.png", "/tmp/two.png"]