forge-host

WHICH forge a repo talks to is a repo fact, not a constant — resolveForgeHost() derives the host from the origin remote (github.com → github, gitlab/self-hosted forms → gitlab), an explicit forge.host config overrides, and a resolved host with no registered driver degrades to an empty slice, never a wrong-host call.

The host-selection seam of spec-forge. The port made the driver shape host-agnostic, but every consumer still chose the host as a constant — the resident cache hardwired the github driver, the board/issues slices said host: 'github' literally — so a repo whose remote is not GitHub (z-code's self-hosted GitLab) rendered a permanently empty Issues surface with no path to a different answer. This node makes the choice a derived repo fact: resolveForgeHost() reads it from the repo itself, and every "this repo's forge" consumer — the resident cache, the board/issues fold, promotion, the spex issues live pull, spex forge's default — asks the seam instead of naming a vendor.

Resolution ladder, most explicit first:

• forge.host in spexcode.json / spexcode.local.json (local wins, same layering as every other setting; documented in spex guide settings). The escape hatch for a domain the heuristic misreads.
• the origin remote's hostname (git remote get-url origin, both URL and scp-like shapes): a github domain → github, bitbucket → bitbucket, and any other resolvable host → gitlab — the common self-hosted forge shape (e.g. dev.aminer.cn), deliberately a guess because a wrong guess costs only an empty slice (next clause) while "unknown means github" was simply wrong.
• no repo / no origin → DEFAULT_FORGE_HOST (github), the pre-seam behaviour.

The degrade contract — resolved host without a registered driver. The registry (FORGE_DRIVERS / forgeDriverFor) stays the single meeting point: a new host lands by adding one driver entry, nothing here changes. Until that driver exists, a resolved-but-driverless host (gitlab today) must degrade to an empty forge slice — the resident cache skips the cycle without spawning anything, the store list offers no forge store (scoped to the resolved host, so a gitlab repo never sees a github New-issue target), and the board/issues surfaces carry the local slice alone, no error. This is what lets a gitlab driver be built and verified independently: the seam routes to it the moment it registers. Write verbs differ deliberately: an explicit write (promote, --store <host>) against a driverless host fails loud naming the resolved host — a silent no-op write would fake closure.

The seam lives in spec-forge and reads git/config itself (env-stripped like spec-cli's git() helper, so hook-context calls still discover the repo), because its callers include spec-forge-internal code (the resident cache) that must not depend back on spec-cli. Resolution is memoized briefly; a config edit takes effect within seconds, not process lifetime.

Read-only throughout: resolving a host reads a remote URL and two config files — git/.spec stays the single source of truth, and nothing here touches the network or a node's git-derived status.

Out of scope: the gitlab driver itself (a sibling node adds the registry entry), per-repo multi-forge (one repo, one resolved host), and moving platform normalization — that stays at the drivers (port).