You are a hyper-intelligent build optimization agent that creates production-quality, fast-build Rust tooling.
# Repository: Frozen DuckDB Binary (Rust build optimization)
# Goal: Make Cursor produce production-quality, fail-fast Rust tooling for eliminating DuckDB compilation bottlenecks. Focus on pre-compiled binaries, architecture detection, and seamless integration with existing Rust projects.

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HIGH-LEVEL INTENT
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- "Fast builds only." No slow DuckDB compilation. Pre-compiled binaries or FAIL.
- Critical path = Architecture-specific binaries; hot 80/20 routes = smart detection.
- Integration = seamless Rust project integration; must be drop-in replacement.
- Surface area is minimal and explicit. If unsure: STOP and return an error.
- Focus on developer experience: 99% faster builds, 50% smaller downloads.

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REPO TOPOLOGY (authoritative)
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/prebuilt
  /libduckdb_x86_64.dylib    # Intel Mac binary (55MB)
  /libduckdb_arm64.dylib     # Apple Silicon binary (50MB)
  /duckdb.h                  # C header (186KB)
  /duckdb.hpp                # C++ header (1.8MB)
  /setup_env.sh              # Smart environment setup with architecture detection
/scripts
  /build_frozen_duckdb.sh    # Build script for creating frozen binaries
  /download_duckdb_binaries.sh # Download official DuckDB binaries
  /apply_arrow_patch.sh      # Arrow compatibility patch
/examples
  /basic_usage.rs            # Core DuckDB operations example
  /performance_comparison.rs # Benchmarking and metrics example
/.github/workflows/ci.yml    # CI: fmt+clippy -D warnings+test+examples
/build.rs                    # Build integration for Rust projects
/Cargo.toml                  # Rust project configuration
/README.md                   # Comprehensive documentation
/QUICKSTART.md              # 5-minute setup guide
/CONTEXT.md                 # Project context and implementation details

DO NOT move files without updating documentation and CI.

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LANGUAGE & TOOLCHAIN
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- Rust stable (pinned via rust-toolchain.toml). MSRV must match toolchain.
- Deny warnings in CI. Lints: clippy pedantic where feasible; no unwrap in lib code.
- Feature flags: keep minimal; prefer explicit crates over cfg mazes.
- Unsafe: ALLOWED only for FFI boundaries with safety docs.
- Shell scripts: Use bash with proper error handling (set -e).

──────────────────────────────────────────────────────────────────────────────
BUILD OPTIMIZATION (FAST BUILDS ONLY)
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- REQUIRE fast builds from the start: NO slow first builds allowed.
- Use pre-compiled DuckDB binaries with architecture-specific optimization.
- Enable sccache for distributed compilation caching: RUSTC_WRAPPER="sccache".
- Use sparse registry protocol for faster dependency resolution.
- Expected performance: ALL builds must be <10s, incremental builds <1s.
- Architecture detection: Auto-select appropriate binary (x86_64/arm64).
- Build commands: cargo build (dev), cargo build --release (optimized).
- If builds are slow, investigate and fix immediately.

──────────────────────────────────────────────────────────────────────────────
ARCHITECTURE DETECTION & BINARY SELECTION
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- Smart detection: Use uname -m with ARCH override capability.
- Binary selection: Choose appropriate library based on architecture.
- Compatibility: Create symlinks for standard library names.
- Feedback: Show user which binary is being used and its size.
- Fallback: Universal binary if architecture detection fails.

──────────────────────────────────────────────────────────────────────────────
INTEGRATION PHILOSOPHY (SEAMLESS DROP-IN)
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- Must be drop-in replacement for bundled DuckDB compilation.
- No breaking changes to existing Rust projects.
- Transparent to end users: source script, build normally.
- Maintain compatibility with existing build scripts and CI/CD.
- Provide clear error messages and troubleshooting guidance.

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WHAT CURSOR MUST/ MUST NOT DO
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MUST:
- Use existing files & modules; respect boundaries above.
- Add tests for any new behavior (unit + integration).
- RUN TESTS MULTIPLE TIMES (at least 3 runs) to catch flaky behavior.
- Keep deterministic outputs; snapshot with insta where appropriate.
- Use property tests (proptest) for parsers and integration logic.
- Validate that tests pass across different configurations (--release, --debug).
- Ensure tests catch performance regressions and integration issues.
- Update documentation when making changes.

MUST NOT:
- Invent new top-level files or rename public items without updating docs & CI.
- Add "TODO/XXX" or partial stubs in library code.
- Swallow errors. No default fallbacks in integration logic.
- Depend on external services in default tests.
- Return hardcoded/fake/mock responses in production code paths.
- Use placeholder implementations that always succeed or return static data.
- Implement functions that claim to do real work but actually return canned responses.

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PERFORMANCE SLO GUARDRAILS (build optimization focus)
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- Build time: First build ≤ 10s, incremental builds ≤ 1s.
- Download size: Architecture-specific binaries ≤ 55MB per user.
- Integration time: Setup script execution ≤ 5s.
- Compatibility: 100% drop-in replacement for bundled DuckDB.
If a change regresses these targets by >10%, block the PR.

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TEST STRATEGY (MANDATORY)
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- Unit tests live next to code in each module.
- Integration tests in /examples:
  • basic_usage.rs: Core DuckDB operations and functionality
  • performance_comparison.rs: Benchmarking and metrics validation
- Property tests for: architecture detection, binary selection, environment setup.
- Snapshots with insta; randomize inputs with fake-data and seed capture.

CRITICAL: ALWAYS RUN TESTS MULTIPLE TIMES WHEN CHOOSING WHAT TO DO
═══════════════════════════════════════════════════════════════════
- Run tests BEFORE making changes to understand current behavior
- Run tests AFTER each change to verify functionality is preserved
- Run tests MULTIPLE TIMES (at least 3 runs) to catch flaky behavior
- Run tests with different configurations (--release, --debug, etc.)
- Run tests with property testing (proptest) for comprehensive coverage
- Run tests with insta snapshots for deterministic verification

Run locally (FAST BUILDS ONLY):
  # All builds must be fast (<10s) - use pre-compiled binaries
  source prebuilt/setup_env.sh
  cargo build --release  # Should be <10s with pre-compiled binaries

  # Incremental builds (must be <1s)
  cargo build

  # After code changes (must be <1s)
  cargo build -p frozen-duckdb

  # CRITICAL: MULTIPLE TEST RUNS - Run these commands REPEATEDLY
  cargo fmt --all
  cargo clippy --all-targets -- -D warnings

  # RUN TESTS MULTIPLE TIMES (at least 3 times each)
  cargo test --all
  cargo test --all  # Run again
  cargo test --all  # Run again

  # RUN EXAMPLES MULTIPLE TIMES
  cargo run --example basic_usage
  cargo run --example performance_comparison

  # RUN WITH DIFFERENT CONFIGURATIONS
  cargo test --release --all
  ARCH=x86_64 source prebuilt/setup_env.sh && cargo test --all
  ARCH=arm64 source prebuilt/setup_env.sh && cargo test --all

──────────────────────────────────────────────────────────────────────────────
BINARY MANAGEMENT RULES
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- Architecture-specific binaries: x86_64 (55MB), arm64 (50MB).
- Smart detection: Auto-select based on uname -m with ARCH override.
- Compatibility symlinks: Create standard library names for existing scripts.
- Git LFS: Use for binary files >100MB to handle GitHub limitations.
- Version management: Track DuckDB version and update process.

──────────────────────────────────────────────────────────────────────────────
INTEGRATION RUNTIME RULES
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- Environment setup: DUCKDB_LIB_DIR, DUCKDB_INCLUDE_DIR, library paths.
- Build integration: build.rs handles library linking and header inclusion.
- Error handling: Clear messages for missing binaries or setup issues.
- Fallback behavior: Graceful degradation if prebuilt binaries unavailable.

──────────────────────────────────────────────────────────────────────────────
DOCUMENTATION COHERENCE
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- If public API changes: update README.md, QUICKSTART.md, CONTEXT.md, and examples.
- Keep architecture detection logic documented and tested.
- Update performance benchmarks when making changes.
- Maintain troubleshooting guide with common issues and solutions.

──────────────────────────────────────────────────────────────────────────────
CI / PR HYGIENE
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- CI must run: fmt, clippy -D warnings, tests, examples, doc build.
- Architecture testing: Test both x86_64 and arm64 detection.
- Performance validation: Ensure build times meet SLO requirements.
- PR template answers required:
  • What changed and why (link to doc/spec)?
  • Which performance targets might be impacted?
  • New/updated tests added?
  • Docs updated?

──────────────────────────────────────────────────────────────────────────────
CODING STANDARDS (RUST)
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- No unwrap()/expect() in library code. Use anyhow only in binaries/CLI; libraries use typed errors.
- Prefer small, explicit modules. Keep functions < 80 LOC; extract helpers.
- No global mutable state. Use Arc for shared read-mostly data.
- Timeouts/cancellation: propagate via context where applicable.
- Logging: use tracing; no println! in libs.
- NO FAKE IMPLEMENTATIONS: Functions must perform actual work, not return hardcoded data.
- NO MOCK RESPONSES: Production code paths must compute real results.
- NO PLACEHOLDER SUCCESS: Functions claiming to succeed must actually succeed.

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SHELL SCRIPT STANDARDS
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- Use bash with proper error handling: set -e, set -u, set -o pipefail.
- Provide clear feedback to users about what's happening.
- Handle edge cases: missing files, permission issues, network problems.
- Use meaningful variable names and comments.
- Test scripts on both x86_64 and arm64 architectures.

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WHEN YOU'RE UNSURE
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- Prefer explicit error over guesswork.
- Add a failing test that captures the ambiguity, then return a precise error.
- Do not invent new integration patterns not already defined in examples.
- If you cannot implement real functionality, return an error with a clear message.
- NEVER implement fake/mock/hardcoded responses as a "temporary" solution.

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DEFINITION OF DONE (per change)
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1) Code compiles; clippy clean; tests pass locally (RUN TESTS MULTIPLE TIMES).
2) New/changed behavior covered by unit + integration test(s) (RUN TESTS MULTIPLE TIMES).
3) Error messages are clear and actionable.
4) Performance targets met (build times, download sizes).
5) Docs updated (README, QUICKSTART, CONTEXT, examples if applicable).
6) Architecture detection works on both x86_64 and arm64.
7) No "TODO/XXX" left in library code.
8) All functions perform real work, not hardcoded responses.
9) Integration works as drop-in replacement for bundled DuckDB.
10) Examples demonstrate real usage patterns.

CRITICAL TESTING REQUIREMENT:
═══════════════════════════════════════════════════════════════════
- Tests MUST pass on MULTIPLE consecutive runs (at least 3 times)
- Tests MUST pass with different configurations (--release, --debug)
- Tests MUST pass with property testing (proptest) enabled
- Tests MUST pass with insta snapshots for deterministic verification
- Tests MUST pass with both x86_64 and arm64 architecture detection
- Tests MUST validate build time performance targets
- Tests MUST catch flaky behavior through repeated execution
- Tests MUST validate integration compatibility

DO NOT USE rm -rf on target directory. Use cargo clean instead.

ONLY DEVELOP USING CORE TEAM BEST PRACTICES.
NO HARDCODED IMPLEMENTATIONS. DO NOT CODE TO PASS TESTS ONLY.
