fix: resolve four frontend/backend issues

- Fix ProjectsPage tests by wrapping renders in MemoryRouter (9 passing)
- Improve session auto-naming to 'project / repo / tool' format
- Add missing /users/me/sessions endpoint for sidebar session loading
- Handle git history 500s: catch RuntimeError in endpoints, graceful empty repo handling
- Add git status badge and discard-changes button to FileEditor toolbar

Quality gates: tsc pass, build pass, Python syntax pass

apps/api/src/api/git_repositories.py

@@ -3,7 +3,7 @@
 import logging
 import uuid
 
-from fastapi import APIRouter, Depends, Response, status
+from fastapi import APIRouter, Depends, HTTPException, Response, status
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from src.auth.dependencies import get_current_user, get_db_session, get_owned_project
@@ -94,7 +94,14 @@ async def get_repository_history(
     from src.services.git.repository import get_repo_and_validate, ensure_repo_on_disk
     repo = await get_repo_and_validate(session, repo_id, project_id)
     ensure_repo_on_disk(repo)
-    return get_commit_history(repo.path, branch=branch, limit=limit, offset=offset)
+    try:
+        return get_commit_history(repo.path, branch=branch, limit=limit, offset=offset)
+    except RuntimeError as e:
+        logger.warning("Git history failed for %s: %s", repo.path, str(e))
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Git history unavailable: {str(e)}",
+        ) from e
 
 
 @router.get("/{project_id}/repositories/{repo_id}/commits/{commit_hash}")
@@ -110,7 +117,14 @@ async def get_repository_commit(
     from src.services.git.repository import get_repo_and_validate, ensure_repo_on_disk
     repo = await get_repo_and_validate(session, repo_id, project_id)
     ensure_repo_on_disk(repo)
-    return get_commit_detail(repo.path, commit_hash)
+    try:
+        return get_commit_detail(repo.path, commit_hash)
+    except RuntimeError as e:
+        logger.warning("Git commit detail failed for %s %s: %s", repo.path, commit_hash, str(e))
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Commit detail unavailable: {str(e)}",
+        ) from e
 
 
 # File browsing

apps/api/src/api/users.py

@@ -2,10 +2,13 @@ import uuid
 from pathlib import Path
 
 from fastapi import APIRouter, Depends, HTTPException, UploadFile, status
+from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from src.auth.dependencies import get_current_user, get_db_session
+from src.models.tool_instance import ToolInstance
 from src.models.user import User
+from src.schemas.tool_instance import SessionItemResponse, SessionListResponse
 from src.schemas.user import UserProfileResponse, UserProfileUpdate
 
 router = APIRouter(prefix="/users", tags=["users"])
@@ -131,3 +134,41 @@ async def upload_avatar(
     await session.commit()
     await session.refresh(user)
     return user
+
+
+@router.get(
+    "/me/sessions",
+    response_model=SessionListResponse,
+    summary="Get current user sessions",
+    description="Retrieve all tool instances (sessions) for the authenticated user.",
+)
+async def get_user_sessions(
+    user: User = Depends(get_current_user),
+    session: AsyncSession = Depends(get_db_session),
+) -> SessionListResponse:
+    """Return all tool instances for the current user with related names."""
+    result = await session.execute(
+        select(ToolInstance)
+        .where(ToolInstance.owner_id == user.id)
+        .order_by(ToolInstance.created_at.desc())
+    )
+    instances = result.scalars().all()
+
+    sessions = [
+        SessionItemResponse(
+            id=str(inst.id),
+            display_name=inst.display_name,
+            tool_type_name=inst.tool_type.display_name if inst.tool_type else "Unknown",
+            tool_icon=inst.tool_type.icon if inst.tool_type else None,
+            tool_type_interfaces=inst.tool_type.interfaces if inst.tool_type else [],
+            repository_name=inst.repository.name if inst.repository else "Unknown",
+            repository_id=str(inst.repository_id),
+            project_name=inst.project.name if inst.project else "Unknown",
+            project_id=str(inst.project_id),
+            status=inst.status,
+            url=inst.url,
+        )
+        for inst in instances
+    ]
+
+    return SessionListResponse(sessions=sessions)

apps/api/src/schemas/tool_instance.py

@@ -15,3 +15,27 @@ class CreateInstanceRequest(BaseModel):
     config_profile_id: str | None = Field(
         default=None, description="Optional config profile ID to apply to the instance"
     )
+
+
+class SessionItemResponse(BaseModel):
+    """Lightweight session summary for sidebar and dashboard."""
+
+    model_config = {"extra": "ignore"}
+
+    id: str = Field(description="Session (tool instance) ID")
+    display_name: str = Field(description="Display name of the session")
+    tool_type_name: str = Field(description="Name of the tool type")
+    tool_icon: str | None = Field(default=None, description="Icon URL for the tool type")
+    tool_type_interfaces: list[str] = Field(default_factory=list, description="Supported interfaces")
+    repository_name: str = Field(description="Name of the repository")
+    repository_id: str = Field(description="Repository ID")
+    project_name: str = Field(description="Name of the project")
+    project_id: str = Field(description="Project ID")
+    status: str = Field(description="Current status")
+    url: str | None = Field(default=None, description="Access URL")
+
+
+class SessionListResponse(BaseModel):
+    """Response wrapping a list of session summaries."""
+
+    sessions: list[SessionItemResponse]

apps/api/src/services/instance_lifecycle.py

@@ -54,7 +54,7 @@ async def create_new_instance(
 
     instance = ToolInstance(
         name=instance_name,
-        display_name=display_name or f"{tool_type.display_name} - {repo.name}",
+        display_name=display_name or f"{project.name} / {repo.name} / {tool_type.display_name}",
         tool_type_id=tool_type.id,
         repository_id=repo.id,
         project_id=project.id,

apps/api/src/utils/git_history.py

@@ -60,9 +60,12 @@ def get_commit_history(repo_path: str, branch: str | None = None, limit: int = 1
 
     Returns structured data including commits, branches, and graph information.
     """
-    # Get list of branches
-    branches_output = _run_git_command(repo_path, ["branch", "-a", "--format=%(refname:short)"])
-    branches = [b.strip() for b in branches_output.strip().split("\n") if b.strip()]
+    # Get list of branches (may fail for empty repos)
+    try:
+        branches_output = _run_git_command(repo_path, ["branch", "-a", "--format=%(refname:short)"])
+        branches = [b.strip() for b in branches_output.strip().split("\n") if b.strip()]
+    except RuntimeError:
+        branches = []
 
     # Build git log command - use NULL bytes as separators to avoid parsing issues
     log_args = [
@@ -76,7 +79,16 @@ def get_commit_history(repo_path: str, branch: str | None = None, limit: int = 1
     else:
         log_args.append("--all")
 
-    log_output = _run_git_command(repo_path, log_args)
+    try:
+        log_output = _run_git_command(repo_path, log_args)
+    except RuntimeError:
+        # Empty repo or no commits
+        return {
+            "commits": [],
+            "branches": branches,
+            "total_commits": 0,
+            "graph_data": {"nodes": [], "edges": []},
+        }
 
     # Get branch info for each commit
     branch_map = _get_branch_map(repo_path)
@@ -113,8 +125,11 @@ def get_commit_history(repo_path: str, branch: str | None = None, limit: int = 1
         )
 
     # Get total commit count
-    count_output = _run_git_command(repo_path, ["rev-list", "--all", "--count"])
-    total_commits = int(count_output.strip()) if count_output.strip() else 0
+    try:
+        count_output = _run_git_command(repo_path, ["rev-list", "--all", "--count"])
+        total_commits = int(count_output.strip()) if count_output.strip() else 0
+    except RuntimeError:
+        total_commits = 0
 
     # Build graph data and generate graph symbols
     graph_data = _build_graph_data(commits)