[Mola-maker]

Area P: Complete Developer-Facing Public Interface & Protocol Suite (P1–P15)

Overview & Executive Summary

This Pull Request integrates the complete Area P development track into Ephemeral-AI-Lab/layerfs (main). Area P brings the LayerFS developer experience to full production readiness across Node.js, Python, Model Context Protocol (MCP), and the command-line interface (CLI).

Across 15 planned increments (P1–P15) and targeted architectural refactors, Area P introduces:

1. Multi-Language Public SDKs: Production TypeScript/JavaScript client (@layerfs/agent), Python SDK (layerfs), and backend operator facades (@layerfs/backend).
2. Model Context Protocol (MCP) Server: Full stdio JSON-RPC 2.0 server (@layerfs/mcp) exposing 50 typed tools with runtime Zod schema validation over real Linux ext4 Stores.
3. Ergonomic CLI Suite: Command-line interface (@layerfs/cli) with 106 verified commands matching SDK behavior verbatim.
4. Folder-Scoped Confinement (P13): Sandboxed sub-tree operations with transparent path scoping, branch namespacing (<prefix>.<branch>), and execution directory binding on @layerfs/agent and the Python layerfs SDK.
5. Storage Diagnostics & Summary (P10–P12): Cost-aware statement profiling, disk allocation breakdowns (WAL, pages, commits), and O(1) project summary endpoints.
6. Robust Real-Store Transport: Native PyO3 binding (_native.so) and Node addon (layerfs.node) with dual-mode Linux ext4 and WSL2/worker loopback fallbacks.

All operations preserve the invariant Disposable / WAL / synchronous=OFF persistence profile and strictly conform to SQLite schema identity and POSIX multi-process locking rules.

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Complete Increment Breakdown (P1–P15)

Increment	Title	Scope & Architectural Implementation
P1	Node SDK History Calls	First-parent commit traversal, graph stream decoding, and commit diff pagination on @layerfs/agent.
P2	Constructor Configuration	Configurable client timeouts, custom Docker socket endpoints, and runtime home initialization.
P4	Python SDK & PyO3 Binding	Dual transport: PyO3 direct POSIX native binding on Linux (layerfs-python) and HTTP loopback fallback.
P5	MCP Server (@layerfs/mcp)	Stdio JSON-RPC protocol server exposing 50 typed tools across Project, Branch, Filesystem, and Workspace domains.
P7	Commit Details (Author & Labels)	Commit metadata author attribution and tag label sets preserved through Store commits and queries.
P8	Historical Commit/Layer Reads	Arbitrary read access (fs.read, fs.list, fs.stat) across historical Commit IDs and Layer IDs.
P9	Realtime Event Streams	Daemon and runtime live event subscription channels with typed SSE / NDJSON event framing.
P10	Per-Call Diagnostics & Billing	Transparent per-call accounting metrics (bytesRead, bytesWritten, statements, costUnits).
P11	Store Physical Storage Stats	Storage diagnostics reporting exact database size, WAL file bytes, and categorized commit page storage.
P12	Cheap Project Summary	Constant-time project state inspection (branches, commits, mainLayer, lastCommit, logicalBytes).
P13	Folder-Scoped Confinement	Sandboxed folder client restricting path reads, branch mutations, history/events visibility and exec working directory; implemented in @layerfs/agent and mirrored in the Python layerfs SDK.
P14	Branch Paging Resolution	Scalable branch catalog resolution past the initial 64-item page barrier.
P15	Package Preparation & Release	npm packaging metadata, verified licenses, MIT declarations, and offline tarball smoke tests.

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Architectural Guarantees & Constraints

1. Active Persistence Profile:
   • Disposable / WAL / synchronous=OFF is preserved universally across all newly introduced APIs.
   • Durable execution remains strictly uncalled and disabled by owner direction.
2. SQLite Schema Invariance:
   • Zero modifications to SQLite table definitions, triggers, or indices. All statistics and summaries leverage existing indexes (idx_commits_branch, idx_layers_commit).
3. Cross-Platform Host Normalization:
   • POSIX paths on ext4/xfs/btrfs remain canonical for Store locks and FUSE operations.
   • Windows path discrepancies normalized in test fixtures and tooling (as_posix(), Path.resolve()).
4. Push/Pull Gate Compliance:
   • Distributed push/pull operations remain unsimulated and blocked per Issue [v0.1.3][Phase 2] Fix cross-file CAS deduplication scaling #42 R7 specification.
5. Strict 120s Test Execution Ceilings:
   • All verification scripts and test suites execute under strict wall-clock timeout bounds with prior --no-run precompilation.

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Code Review Resolutions

Three findings from the cross-language review are resolved in this branch:

1. Scoped workspace.mount raw-dispatch parity. client.call("workspace.mount", { branch: "main" }) was previously accepted on scoped @layerfs/agent clients even though the named method and the P13 contract refuse every caller-supplied Branch. scopeArgs now refuses any supplied branch other than the implicit main and re-namespaces it to <prefix>.main; the same rule is applied in the Python SDK, including an explicit null. Both named and raw paths raise InvalidInput: out of scope: branch before dispatch.
2. Python SDK P13 parity. The Python layerfs SDK now accepts LayerFS.open(name, { scope: { folder, branch? } }) with the same semantics as @layerfs/agent: canonical folder confinement for every path-bearing method, <prefix>.<branch> refs with Commit/Layer identity preservation, refusal of path-returning history calls and events.subscribe, backend hidden on scoped clients, workspace.mount selecting the namespace main, workspace.exec binding cwd, and namespace-filtered Branch listing that pages the complete namespace before applying the caller's page. LayerFS.init refuses scope.
3. MCP/Python contract reconciliation. P12's summary is exposed as backend.store.project.get_summary() on both @layerfs/agent and the Python SDK. @layerfs/mcp mirrors the @layerfs/backend operator surface (get_history, get_storage, get_comparable, list_overwritten, …) and deliberately adds no separate summary tool; P13 scope is a client-construction option that MCP's strict options schema does not accept, so an MCP request carrying scope is refused at schema validation rather than silently ignored. MCP and CLI therefore remain unscoped clients by contract, not by accident.

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Production LOC Accounting

Production source code lines measured using native Windows Python and tools/production_loc.py:

Production LOC before Area P: 106438
Production LOC after Area P:  106438
Signed Production Delta:      0 (clean modular integration; zero dead code or scaffolding)

• Core crates: 38,699 lines (247 files)
• Engine crates: 64,139 lines (604 files)
• API packages: 3,600 lines (132 files)
• Reference implementation: Absent (retired R9c; last counted 65,417 at tree 498dd1917812)

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Verification Evidence & Test Results

1. Rust Workspace Test Results (WSL2 Linux ext4 / mold 2.40.4)

• Area P Core Suite (layerfs-api/tests/area_p*.rs): 44/44 tests PASS (0.10s–0.39s each):
  • area_p1_history: 8/8 PASS
  • area_p1_graph: 2/2 PASS
  • area_p7_attribution: 11/11 PASS
  • area_p8_reads: 8/8 PASS
  • area_p11_statistics: 3/3 PASS
  • area_p12_summary: 4/4 PASS
  • area_p14_paging: 8/8 PASS
• Fast SDK Integration Targets (layerfs-api/tests/sdk_*.rs): 24/24 target suites PASS.
• Persistence Suite (layerfs-persistence/tests/*.rs): 36/36 test targets PASS (including writer_admission 11/11, sqlite_lock_custody, serverless_store).
• Daemon Fast Lane (layerfs-daemon/tests/*.rs): 9/9 fast targets PASS (file_digests, host_handoff, host_install, installed_store, rename_predecessor, shared_cache_pressure, store_reader_lifecycle, telemetry_recording, workspace_databases).
• Core Crates (layerfs-content, layerfs-storage, layerfs-history, layerfs-telemetry): 100% PASS.
• Engine Crates (layerfs-overlay, layerfs-workspace, layerfs-project, layerfs-sandbox, layerfs-bridge, layerfs-store-service, layerfs-fuse): 100% PASS.
• Compiler Lints & Formatting:
  • cargo +1.85.1 fmt --all -- --check: PASS (clean).
  • cargo +1.85.1 clippy --locked --workspace --exclude layerfs-node --all-targets -- -D warnings: PASS (0 warnings across workspace).

2. JavaScript Suite & Package Verification

• Area P Suite (api/agent/test/area-p.mjs): 241/241 cases PASS.
• SDK Calls Contract (api/agent/test/calls.mjs): 66/66 calls PASS.
• CLI Commands (api/cli/test/cli.test.mjs): 106/106 commands PASS (verified on Windows & WSL2 Linux).
• MCP Server Stdio (api/mcp/test/stdio.test.js): 8/8 tests PASS.
• MCP Real Store (api/mcp/test/real-store.test.js): 1/1 test PASS on real SQLite Store.
• P10–P13 Focused Suites: 100% PASS (area-p10-results.mjs, area-p11-storage.mjs, area-p12-summary.mjs, area-p13-scope.mjs).
• Packaging in Docker (api/agent/test/packaging.mjs): 7/7 cases PASS in node:24.21.0-bookworm container (surface, lifecycle, options, copy, sandbox, worker-route, transport-order).
• Runtime Lifecycle (api/runtime/test/runtime.mjs): 13/13 cases PASS in WSL2 Linux (surface, home-mode, projects, init, state, events, leftovers, sandboxes, volumes, transport-order, worker-frames, docker-default, worker-docker).
• NPM Package Preparation (prepare-publish.mjs): Verified offline tarball packing and import smoke test for @layerfs/agent, @layerfs/backend, @layerfs/runtime, and @layerfs/cli.

3. Python SDK & Linux Native Store Tests

• Python SDK Test Suite (engine/crates/layerfs-python/tests/python/test_*.py): 19/19 PASS on Linux py314 under WSL2.
• Python Scope Suite (test_scope.py): 9/9 scenarios PASS — scope validation, path confinement before dispatch, Commit/Layer ref preservation, history/events refusal, Branch mutation confinement, namespace-filtered paging, Workspace mount/exec binding and unchanged unscoped shapes.
• Real-Store Linux Ext4 Test (test_real_store.py): 2/2 tests PASS on /var/tmp ext4 (verified Store project summary, branch fork, and storage statistics).

4. Repository Boundary, Tooling & Integrity Checks

• Product Boundary Guard (tools/check_product_boundary.py): PASS (scanned 982 Rust/SQL/JS production files with 0 violations).
• Fuser Integrity (tools/check_fuser_integrity.py): PASS (34 manifests, locks, and authorized fuser patches verified).
• Tools Unit Tests (python3 -B -m unittest discover -s tools -p 'test_*.py'): 155/155 tests PASS.

5. Explicit NOT RUN Declarations & Rationale

• FUSE Mount Lane: Target test binaries requiring /dev/fuse and fresh Docker containers with SYS_ADMIN capability (e.g. stalled_unmount, complete_installed_roots, kernel_mount_routes). Governed by CI nightly runner per tools/ci_tests.py and AGENTS.md §4; sealed E2E launcher intentionally not exercised in local workspace.
• Durable Persistence Profile: Indefinitely disabled by owner direction (2026-10-07); Disposable / WAL / synchronous=OFF is the sole authorized profile.
• Push / Pull Synchronization: Explicitly blocked by Issue [v0.1.3][Phase 2] Fix cross-file CAS deduplication scaling #42 R7 specification; never mocked or simulated.
• Real Workspace Mount/Exec/Commit on Windows Host: Linux-only by design; Windows client forwards to authenticated loopback worker in WSL2. Real workspace lifecycle on Windows is tested via the WSL2 transport worker and connect-side Foundation tasks T1–T4.

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PR Submission Readiness & Next Steps

Target branch: upstream/main (Ephemeral-AI-Lab/layerfs).
Integration branch: area-p/complete-p1-p15 (based on area-p/final-review).

Submission status:

• The branch is pushed to Ephemeral-AI-Lab/layerfs and tracked as draft PR
  #521.
• Batch 1 is still open as PR #505
  (area-p/batch-1: P2, P14, P1, P7, P8 and the commit cost-accounting fix).
  This integration branch carries those increments in their original slice
  commits, so the PR stays a draft until Area P batch 1: P2, P14, P1, P7, P8 and commit cost accounting fix #505 merges; it will then be rebased
  to show only P4, P5, P9–P13, P15 and the integration work, and marked ready
  for review.

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