Blog Post 27 — PR #69: synlynk doctor Health Command (v0.9.8)

Series: Building synlynk — The Coordination OS for Multi-Agent Development
PR: #69 — feat/v0.9.8-doctor
Date: 2026-06-27

Where We Were After PR #68

PR #68 shipped pyproject.toml + synlynk/__main__.py — standard packaging so pipx install git+... works as the primary install path. The v0.10.0 Developer Preview checklist now has packaging checked off. The next prerequisite before the public launch was synlynk doctor: a health-check command that gives a new developer (or an existing one debugging a broken setup) a single command to verify their installation.

What This PR Ships

HealthCheck dataclass — four fields: name, status ("ok" | "warn" | "fail"), message, and fix (empty by default). Deliberately minimal — one clear data unit, no inheritance, no base class.

HEALTH_CHECKS registry — an ordered list of seven check functions. Ordered from most fundamental to least: a failing Python version check is more load-bearing than a missing agent profile warning. Each function returns one HealthCheck.

cmd_doctor(checks=None) — runs the registry, prints a formatted report, returns exit code 0 (ok/warn) or 1 (any fail). The checks param accepts a custom list for testing without hitting real filesystem or network.

Output design — matches the brew doctor / cargo doctor idiom: green ✓ / yellow ⚠ / red ✗ icons, name+message on one line, fix suggestion indented below on mismatch:

synlynk doctor

  ✓  python_version: Python 3.14.4
  ✗  project_init: Project not initialized — .synlynk/config.json missing
     → Run: synlynk init
  ✓  docs_dir: project-docs complete (project-docs)
  ✓  identity_key: Ed25519 identity key present
  ⚠  agent_profiles: Missing .agents/ profiles: claude, agy, codex
     → Run: synlynk agent configure <name>
  ⚠  instruction_files: Missing instruction files: AGENTS.md
     → Run: synlynk init
  ✓  version_current: synlynk 0.9.7 is up to date

  1 check(s) failed — fix these before running synlynk.

19 new tests — one per check (ok + fail/warn variants), plus dataclass defaults and cmd_doctor() aggregation behavior. 510 tests total, all passing.

One Note on Version Check Testability

The version check makes a real HTTP call. The tests monkeypatch urllib.request.urlopen rather than reaching the network — a FakeResp context manager that returns a preset {"tag_name": "..."} JSON body. Offline degradation (returns warn with "offline or timeout" message) is tested by patching urlopen to throw urllib.error.URLError.

Progress Toward Developer Preview

New Goalpost

synlynk doctor closes the last code prereq for v0.10.0. What remains is documentation and narrative: the README overhaul, three brainstorm sessions (BS-5 website, BS-6 OKF+viz, BS-7 skill pack interop), and the HN launch draft. The v0.10.0 Named Release will cut when those are done.