improvement: add file limit, warning, and more performant file detection

[mscolnick]

Fixes #7317

• add file limit when displaying the workspace (1000 files)
• show a warning when we go over the limit
• more performant file detection by only reading the first 500b header

[vercel]

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Project	Deployment	Preview	Comments	Updated (UTC)
marimo-docs	Ready	Preview	Comment	Dec 1, 2025 9:44pm

[github-actions]

Breaking changes detected in the OpenAPI specification!

[Copilot]

Pull request overview

This pull request enhances workspace file scanning with performance optimizations and user experience improvements. It addresses issue #7317 by implementing a file limit (1000 files), displaying a warning when the limit is exceeded, and optimizing file detection to read only the first 512 bytes of files for faster scanning.

Key Changes

• Added MAX_FILES constant (1000) to limit workspace file scanning and prevent performance degradation in large workspaces
• Implemented header-based file detection that reads only the first 512 bytes for most files, with full file reading only for Python files containing PEP 723 script headers
• Added hasMore and fileCount fields to WorkspaceFilesResponse to communicate limit status to the frontend
• Introduced async file scanning using asyncio.to_thread() to prevent blocking the server during workspace scans

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
marimo/_server/file_router.py	Core changes: extracted is_marimo_app() function with optimized header-based detection, added count_files() helper, implemented MAX_FILES limit enforcement with file counting and early termination, expanded skip_dirs set with additional common directories
marimo/_server/models/home.py	Added has_more and file_count fields to WorkspaceFilesResponse model with default values
marimo/_server/api/endpoints/home.py	Updated workspace_files endpoint to use async file scanning, calculate file count, and populate new response fields
marimo/_utils/marimo_path.py	Added read_bytes() method to MarimoPath for binary file reading
frontend/src/components/pages/home-page.tsx	Added warning banner that displays when file limit is reached
packages/openapi/api.yaml	Updated WorkspaceFilesResponse schema with new fileCount and hasMore fields
packages/openapi/src/api.ts	Updated TypeScript interfaces to reflect API schema changes
tests/_utils/test_marimo_path.py	Added test coverage for new read_bytes() method
tests/_server/test_file_router.py	Added comprehensive tests for is_marimo_app() function, MAX_FILES enforcement, skip_dirs behavior, and count_files() helper
tests/_server/api/endpoints/test_home.py	Added assertions to verify new response fields are present and correct
pixi.lock	Version bump from 0.18.0 to 0.18.1

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