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Daily Journal: 2026-06-30

Goal

Resume Milestone 0 by stabilizing the Nix development environment before implementing the first /health endpoint.

Progress

Today's work focused entirely on debugging the Nix development environment.

The original blocker was that native binaries installed inside the UV virtual environment (notably Ruff) could not execute under NixOS because of dynamically linked executables.

Rather than enabling nix-ld globally, I decided to investigate a project-local solution using a declarative flake.nix.

Findings

  • Created a minimal flake.nix providing the project development shell.
  • Learned how eachDefaultSystem exposes the shell for multiple architectures.
  • Confirmed the shell loads automatically through direnv.
  • Initially encountered a glibc symbol mismatch affecting Starship.
  • The issue disappeared after removing LD_LIBRARY_PATH from the shell and relying on the standard Nix environment.
  • Moved Ruff from the Python virtual environment into the Nix devShell.
  • Confirmed:
ruff check .

passes.

uv run ruff check

also passes.

Pyright and pytest continue working from the Python virtual environment.

Lessons Learned

  • Native tooling belongs in the Nix environment.
  • Python libraries belong in the virtual environment.
  • The first component reporting an error is not necessarily the component causing it.
  • Systematically testing hypotheses is more effective than searching for fixes.

Next Session

Resume the original milestone:

  • implement /health
  • run Docker
  • verify /docs
  • complete Milestone 0 acceptance tests.