# Decisions

Spec-silent choices, recorded as required by the build instructions.

## Phase 1

- **Go toolchain 1.26.4** (latest stable; spec requires ≥ 1.22). Installed at
  `/usr/local/go`.
- **Module name `bountyboard`** — no remote repository exists; a single-word
  module keeps import paths short (`bountyboard/internal/...`).
- **Package in `internal/http` is named `httpx`** to avoid clashing with
  stdlib `net/http` inside its own files. The directory stays `internal/http`
  per spec §14; importers alias it (`httpx "bountyboard/internal/http"`).
- **`/readyz` uses a pluggable checker registry** (`AddReadinessCheck`):
  required checks (Mongo, Phase 2) gate readiness with 503; optional checks
  (atomizer / work performer, Phase 11) are reported as `degraded` but stay
  200, matching §6's "non-fatal, reported".
- **Runtime image is `alpine:3.21`, not distroless** — busybox `wget` enables
  the compose healthcheck without adding tooling, and `ca-certificates` is
  needed for outbound HTTPS to Jira/ADO/YouTrack. Non-root user.
- **Config validation is strict and fail-fast**: `CREDENTIALS_ENC_KEY` is
  mandatory at startup (base64, exactly 32 bytes) and `SESSION_SECRET` must be
  ≥ 16 chars, even before the features using them land — a misconfigured
  deployment should die at boot, not at first use. All validation errors are
  reported together via `errors.Join`.
- **Trusted-proxy resolution walks X-Forwarded-For right-to-left**, skipping
  addresses inside `TRUSTED_PROXY_CIDRS`; the first untrusted address is the
  client. A malformed entry stops the walk (everything left of it is
  attacker-controllable). If the whole chain is trusted, the leftmost entry is
  used. Headers are ignored entirely when the direct peer is untrusted.
- **ULID**: canonical 48-bit ms timestamp + 80-bit crypto randomness, no
  intra-millisecond monotonicity (spec only needs sortability at ms
  resolution; randomness makes collisions negligible).
- **`.env` loader semantics**: real environment variables win over `.env`
  values; unquoted values support trailing ` # comment`; missing `.env` file
  is not an error (containers receive env via compose `env_file`).
- **Makefile `seed`/`backup`/`restore` are failing stubs until Phase 12** so
  the targets exist but cannot be mistaken for working.

## Phase 2

- **Integration tests reach Mongo via `docker-compose.test.yml`**, an explicit
  test-only overlay publishing Mongo on `127.0.0.1:27017`. The normal compose
  file still never publishes Mongo (§12); the spec's integration-test
  requirement (§2.1) needs host access, and a loopback-only opt-in overlay is
  the smallest hole. Each run uses a `bountyboard_test_<ulid>` database and
  drops it on cleanup.
- **`UpdateVersioned` rejects updates that touch `version`** and merges
  `updatedAt`/`$inc version` into the caller's operators; it distinguishes
  `ErrNotFound` from `ErrVersionConflict` with a follow-up existence check.
- **File MIME type = sniffed (`http.DetectContentType`) unless inconclusive**
  (`application/octet-stream`), in which case the client-declared type is
  kept. A confident sniff overrides a lying declaration.
- **sha256 of uploads is recorded post-upload** via an update on `fs.files`
  metadata (GridFS metadata must be supplied before streaming; the hash is
  only known after).
- **Signed file tokens** are `base64url(exp || hmac-sha256(fileID|exp))` with
  a key derived as `sha256("bountyboard/file-url/v1" + SESSION_SECRET)` so
  file tokens can never collide with other uses of the session secret.

## Phase 3

- **OIDC linking requires `email_verified=true`.** An unverified IdP email
  matching an existing local account is rejected (`oidc_email_unverified`)
  instead of linking or creating a duplicate — linking on unverified email
  would allow account takeover via a rogue IdP account.
- **OIDC provider discovery is lazy** (first login attempt, retried on
  failure) so an unreachable IdP cannot block app startup.
- **CSRF protection applies to authenticated mutations only**; login and
  register are pre-session and protected by rate limiting + SameSite=Lax.
  The CSRF cookie is intentionally JS-readable (double-submit pattern).
- **Password change revokes all other sessions** of the user (recovery
  semantics) but keeps the current one. `SetPassword` is deliberately not
  version-checked: a password change must never lose an optimistic-locking
  race against a profile edit.
- **Forced password change (`mustChange`)** is enforced in `requireAuth` via
  a path allowlist (`me`, `logout`, `logout-all`, `change-password`).
- **Sessions slide at most once per hour** (refreshedAt watermark) instead of
  updating expiry on every request.
- **Login rate-limit key is `clientIP|email`** (and `register|clientIP` for
  registration), using the trusted-proxy-resolved IP.
- **Mongo runs with `--wiredTigerCacheSizeGB 0.5`** in compose — the target
  host has 4 GB RAM; default cache (≈50% of RAM) caused a restart under the
  integration-test load.

## Phase 4

- **CSP has no `unsafe-inline` for scripts from day one** (§12), so all JS is
  external ES modules (`theme.js` loads synchronously in `<head>` to avoid a
  theme flash; everything else is `type=module`). Inline event handlers are
  never used.
- **`PATCH /api/v1/profile` is a partial update**: only fields present in the
  body change. `version` is optional — when present the update is
  version-checked (409 + reload toast on conflict); the nav theme toggle
  omits it so flipping themes can't conflict with a profile edit.
- **Avatar uploads must sniff as `image/*`**; the rejected/replaced GridFS
  files are deleted eagerly. Replacing an avatar removes the previous file.
- **File serving (`GET /files/{id}`)**: valid signed token (?st=) OR session.
  With a session: avatars are visible to any logged-in user; other scopes
  (chat/task) currently allow owner/admin/consultant and will be tightened as
  those features land.
- **Pages that need login redirect to `/login?next=…`** (HTML UX), while API
  routes return 401 JSON. Forced password change redirects all pages to
  /change-password.
- **Pages for later phases render an "under construction" placeholder** so
  role-based navigation is complete and clickable now.