gstack/docs/capy-install.md

Installing gstack on a Capy cloud machine

Three layers, each owned by gstack:

Layer	Where	Job
Bootstrapper	capy/skill/gstack/scripts/install.sh (copied once into the owner's Drive skill folder; frozen)	clone when absent; fetch origin's default branch and read the supported minimum from FETCH_HEAD:capy/support.env; in install mode fast-forward a clean, unpinned checkout below it; exec the full wrapper
Full wrapper	bin/gstack-capy-session (moves with the checkout)	map the session start onto the installer: --check certifies (and reports a checkout behind origin), otherwise fast-forward a checkout behind origin (bin/gstack-upgrade --ff-only-no-reinstall), then install or repair
Installer	bin/gstack-capy-install	Bun, both host profiles, the doctor, the install verdict, the launch line, the trailer

The vendored skill (capy/skill/gstack/SKILL.md) tells a Capy agent how to use them. The Drive folder is a mirror: the owner copies capy/skill/gstack/ there when asked; nothing writes the Drive automatically.

Direct use, without the skill:

git clone --single-branch --depth 1 https://github.com/garrytan/gstack.git ~/.local/share/gstack
~/.local/share/gstack/bin/gstack-capy-install --for autoplan

Session start

1. bash <skill>/scripts/install.sh --check --for <skill> (under a second when a checkout exists). It fetches refs only and never moves the checkout. With no checkout it prints gstack: fail not-installed — ... and the session records that line and continues when it runs no gstack workflow; install right before the first workflow.
2. When the trailer is gstack: fail revision ... or gstack: fail runtime ... and a checkout exists, run the same command without --check. Below the supported minimum, a clean checkout on the remote default branch is fast-forwarded (gstack-capy-skill: upgraded <old> -> <new>), reinstalled and rechecked as one transaction under .gstack-capy-install.lock (the bootstrapper holds it and hands it over with GSTACK_CAPY_LOCK_HELD=1). A pinned (--revision, detached HEAD, another branch), dirty or diverged checkout is never moved; the trailer names the cause and the exact commands (REVISION_BELOW_MINIMUM). GSTACK_CAPY_AUTO_UPGRADE=0 disables the fast-forward.
3. The minimum is the floor, not the trigger. Above it, a checkout behind origin's default branch still moves at install-mode session start: the full wrapper runs bin/gstack-upgrade --ff-only-no-reinstall (every refusal of gstack-upgrade applies), prints SELF_UPGRADE: done <old> -> <new> and re-execs the new checkout's wrapper, which installs from the new revision (GSTACK_CAPY_UPGRADED_FROM set, so setup is never skipped). A refusal prints SELF_UPGRADE: skipped (<reason>) and the session continues on the installed revision; the trailer stays the doctor's. SELF_UPGRADE: none (current) when nothing is ahead; GSTACK_CAPY_SELF_UPGRADE=off (or GSTACK_CAPY_AUTO_UPGRADE=0) prints SELF_UPGRADE: disabled (<variable>). --check never moves the checkout; behind origin it prints gstack-capy-session: behind origin/<branch>: <installed> -> <remote> (<n> commits); fix: bash <skill>/scripts/install.sh [--for <skill>] (fast-forwards) and the agent runs that fix.
4. When the fetch fails (offline), the bootstrapper says remote minimum unknown (fetch failed) and checks the local install only; it never claims the minimum, and nothing is fast-forwarded.

The upgrade target is always the tip of the default branch: every commit there is a stamped release that passed CI. Recovery runs forward, never back: an install interrupted after a fast-forward leaves the trailer fail, and the next install or bin/gstack-upgrade run completes the pending install stages (setup is never skipped after a fast-forward) or refuses and names the cause. Checking out an older commit is not a supported rollback; it does not undo setup migrations that already ran.

Between minimums, bin/gstack-upgrade --check says current <v> or behind <installed> -> <remote> (<n> commits), and bin/gstack-upgrade fast-forwards and reinstalls (bin/gstack-capy-install on a Capy install, else ./setup --refresh-registered). It refuses a dirty, diverged or pinned checkout with UPGRADE_REFUSED and never stashes or resets.

Several agents sharing one checkout (eight Capy subagents on a machine) hold workflow leases on it: every bin/gstack-skill-start touches <git dir>/gstack-leases/<harness pid> (bin/gstack-lease touch; pruned after 120 minutes). bin/gstack-upgrade, and so the session-start self-upgrade, refuses with UPGRADE_BUSY while a lease whose pid is alive and outside its own process chain exists; bin/gstack-lease list shows them and GSTACK_UPGRADE_FORCE=1 overrides.

What the installer does

1. Reuses the checkout it lives in (or clones into --root <dir>), under the lock. It never resets or pulls; --revision <ref> pins a fresh clone, and an existing checkout at another revision is reused with the trailer note requested: <ref> (run <checkout>/bin/gstack-upgrade to move). A fresh clone prints cloned <repo> at <sha12> (<version>) (the bootstrapper's clone too, through GSTACK_CAPY_CLONED).
2. Preflight: git, curl, node, jq, then Bun. The project's pins (--project <path>, default the git toplevel of the current directory) are read with the doctor's own parser (bin/gstack-runtime-pins.ts: engines, packageManager, .tool-versions, .bun-version and CI bun-version: lanes for this platform). CI exact pins for this platform are alternatives: a repository may test several Bun versions (gstack's own CI pins 1.4.2 and runs one job on 1.4.3), so a Bun equal to any one of them satisfies CI; CI ranges and every non-CI pin stay required. One resolver picks the Bun (gstack_bun_resolve in bin/gstack-bun-version.sh; resolveBun in lib/pregate/runtime.ts is its TypeScript twin), and the installer, --check, the doctor, the bun shim and install admission all use it. Candidates, first eligible wins: the store copy of the project's exact pin (rule pin), the store copy of the install default (default), $BUN_INSTALL/bin/bun, ~/.bun/bin/bun (home), then every bun on PATH. Eligible means it runs, reports a version at or above the supported minimum (1.4.2) and satisfies the project's pins. When nothing qualifies, the installer downloads one exact release archive, verifies its SHA-256 against bin/gstack-bun-version.sh and unpacks it into the versioned store <state root>/runtimes/bun/<version>/bun, under ~/.gstack-runtime.lock. Each version directory also holds bunx -> bun. A broken entry is repaired without a window (its files are renamed over their predecessors), and ~/.bun/bin is never written. The archive is the project's non-CI exact pin when gstack carries a verified archive for it (GSTACK_BUN_VERIFIED: 1.4.2, 1.4.3); with only CI exact pins, the install default when it is one of them, else the highest verified one; else the install default GSTACK_BUN_DEFAULT (1.4.3, above the 1.4.2 minimum; one CI job runs the quick free tier on it). GSTACK_BUN_INSTALL_VERSION=<v> overrides the default; a version without a verified archive or below the minimum stops the install (BUN_INSTALL_VERSION_INVALID). With a non-CI exact pin, only that version satisfies it. Any other exact pin (below the minimum, two different non-CI ones, or one without a verified archive), or a range gstack's minimum does not satisfy, stops with both constraints (RUNTIME_PIN_CONFLICT, exit 3) before ./setup. With no Bun at or above the security floor, the default is installed first so the pins can be read.
3. ./setup --host claude --no-prefix, then ./setup --host codex --model gpt-6-astra, both with --no-browser. Skipped when this exact HEAD was set up with the same hosts, model and browser flag (recorded in the git dir after a successful setup) and gstack-doctor --check passes; a warm rerun takes about a second. Each setup ends with its own gstack ready (<host>); the installer then prints gstack ready (claude, codex).
4. gstack-doctor --check for the requested workflow (--for <skill>, --only <skill>, or --require <id,id>; default claude,codex,patch), run with the launch PATH, so the trailer certifies the Bun workflows run.
5. The install verdict (schema 2), written atomically to <state root>/install-verdicts/<sha256 of the checkout realpath>/<sha256 of the project realpath, or "none">.json: checkout, project, HEAD, the workflow and required components it certified, whether pins were skipped as planning-only, the pin it honoured, the resolved Bun (bun_path, bun_version, bun_rule, and bun_install when this run downloaded it), the trailer, the remote minimum, the launch PATH and the time. Admission refuses a workflow whose running Bun is not the one the verdict recorded (BUN_RESOLUTION_DRIFT), and so do the pregate's lanes and guards, which also refuse an invalid verdict (INSTALL_UNVERIFIED) under GSTACK_CAPY=1 or whenever a verdict exists. --check keeps the recorded Bun while it exists, reports the recorded version and satisfies the pins; a candidate that would now resolve first is a note: line, and only a recorded Bun that is gone, changed or no longer satisfies the pins fails the doctor's runtime row. A schema 1 verdict (keyed by checkout only) is still read.
6. On a Capy machine (CAPY_MACHINE_CONFIG set or ~/.capy/system present), install mode writes the bun shims described below.

--check runs only steps 4 and 5 (no clone, Bun install, setup or shim).

The bun shim

A fresh shell on Capy finds the image's /usr/local/bin/bun (1.3.14) first, so a bun test typed without the GSTACK_LAUNCH prefix used to run the wrong Bun. Install mode therefore writes ~/.local/bin/bun and ~/.local/bin/bunx (~/.local/bin precedes /usr/local/bin on the Capy image's PATH). Each is a small POSIX script whose second line is the marker # gstack-bun-shim: gstack-owned; delete this file to remove it. At every call the bun shim finds the git toplevel around the working directory and runs, in order: the Bun that project's install verdict recorded (the none verdict outside any project and inside the gstack checkout), the store copy of the project's exact pin, the store copy of the install default, then $BUN_INSTALL/bin/bun, ~/.bun/bin/bun and every non-shim bun on PATH, first at or above the supported minimum, then at or above the security floor. A pin is used only when it is x.y.z and its store entry is a real binary inside the store (no .., symlink escape or shim-marked file). A project pinning a Bun the store lacks prints gstack bun shim: <root> pins bun <v>, which is not in gstack's runtime store; run ... --check here; an unrecorded, unpinned repo falls through quietly. bunx runs bun x through the bun shim beside it.

• GSTACK_BUN_SHIM_EXPLAIN=1 bun --version prints gstack bun shim: project=<root> record=<file> chose=<bun> rule=<rule> (and names a missing record).
• GSTACK_BUN_SHIM=0 at install time writes no shim.
• Removing it: delete ~/.local/bin/bun and ~/.local/bin/bunx. gstack replaces only a missing file or a file carrying the marker; a foreign file or a dangling link there is left untouched with a note, and the GSTACK_LAUNCH prefix stays the way to reach the certified Bun.
• The doctor's runtime row notes the shim; the resolver never treats a shim-marked file as a Bun candidate.

The one line to grep

The last line is the trailer:

gstack: ok 1.91.96.0 for=autoplan
gstack: ok 1.91.96.0 for=review (requested: v1.91.90.0 (run <checkout>/bin/gstack-upgrade to move); latest: 1.91.101.0 available)
gstack: ok 1.91.96.0 for=autoplan (pins: skipped (planning-only))
gstack: fail runtime,pins

An ok trailer carries at most one parenthesised note group, ; -separated, in this order: requested: … (an existing checkout at another revision than --revision), pins: skipped (planning-only|no project), and latest: <ver> available (origin's default branch has a newer VERSION; the bootstrapper exports it as GSTACK_CAPY_REMOTE_VERSION only after a fetch that succeeded in this run). A fail trailer never carries notes. Match ^gstack: ok or ^gstack: fail ; never parse past the first space after the version.

Exit 0 only with gstack: ok. Read the exit status and the trailer directly:

out=$(bash <skill>/scripts/install.sh --check --for autoplan 2>&1); rc=$?
printf '%s\n' "$out" | grep '^gstack: '
[ "$rc" -eq 0 ]

Never pipe --check (or the installer) through tail, head or grep alone: the pipe's exit status replaces the doctor's, and a silent failure is the incident this installer exists to end. Every FAIL <id> row carries a fix: clause and a reason code with its troubleshooting anchor. A parent agent confirms each subagent machine with this grep; one machine's install never covers another, and a subagent's first report carries its own gstack: line.

SKIP pins (planning-only; repo pins differ: ..., launch bun <v>) (trailer note pins: skipped (planning-only)) is not a failure: planning workflows (--for autoplan, the plan reviews, office-hours) never run the target repo's tests. Workflows that do (review, ship, qa) and --require keep pins required.

When a lane reports to another thread (a handoff, a gstack-lane-check result, a coordinator contract), store and use the full thread id (jam_…) in the message, never the short display code: the code is a label the app renders, the id is what another agent can address and what the evidence bundle records. UBI_OWNER and lane ownership records take the same full id.

Browser

The default install prints SKIP browser (lazy; gstack-browser-ensure installs on first use) and downloads nothing. The first browser skill run (/browse, /qa, /design-review, ...) calls bin/gstack-browser-ensure from its preflight, which installs Chromium (~115 MiB, about 86 s on a Capy machine) under setup's lock and prints BROWSER_OK or BROWSER_UNAVAILABLE <reason>. --with-browser installs it during the install instead, and the installer then prints the planning-only install time and the browser bootstrap time separately.

The launch line

Every successful run, --check included, prints before the trailer:

GSTACK_LAUNCH: PATH=<dir>:$PATH GSTACK_SESSION_KIND=unattended GSTACK_STATE_ROOT=<path> GSTACK_EPHEMERAL=1 GSTACK_CAPY=1 GSTACK_INSTALL_VERDICT=<file>
GSTACK_LAUNCH_PATH: <dir>

PATH=<dir>:$PATH and GSTACK_LAUNCH_PATH appear only when the certified Bun is not first on PATH (the Capy image's /usr/local/bin/bun is 1.3.14; 57 gstack commands start with #!/usr/bin/env bun). A child shell's export cannot configure the parent's later commands, so the parent supplies these assignments to every gstack command it launches (prefix the command, or export them once in the shell that runs it). A fresh shell without them keeps reporting the Bun it would really run: FAIL runtime — bun 1.3.14 at /usr/local/bin/bun ...; verified bun 1.4.2 found at ~/.bun/bin (not on PATH); fix: export PATH="$HOME/.bun/bin:$PATH" or prefix commands with the GSTACK_LAUNCH line.

GSTACK_EPHEMERAL=1 tells gstack the disk vanishes with the machine, so the doctor's state root row reads durable=no and unattended runs say learnings: skipped instead of writing silently. A durable root is opt-in: set GSTACK_STATE_ROOT to a directory that outlives the machine. The installer never writes to the Capy drive. See docs/state-root.md.

GSTACK_CAPY=1 turns on install admission. An unattended session (any host) refuses to start a workflow on a Bun below the supported minimum; with GSTACK_CAPY=1, an unattended or GSTACK_SESSION_KIND=spawned session also needs a passing verdict for this checkout, its current HEAD and a workflow at least as wide as the one starting. A refusal prints INSTALL: fail ... and GSTACK_RESULT: skill=<s> status=refused run=- and exits 3 (INSTALL_UNVERIFIED). Ambient spawned sessions (OpenClaw) only warn. GSTACK_ALLOW_UNSUPPORTED_RUNTIME=1 admits anyway and says so.

Bake into a Capy snapshot

Machines that never run a workflow should not pay the install (about 30 s cold). A project that runs gstack on most machines can bake it instead: the project Setup's initialize step runs

git clone --single-branch --depth 1 https://github.com/garrytan/gstack.git ~/.local/share/gstack
~/.local/share/gstack/bin/gstack-capy-install --require claude,codex,patch

and snapshots capture $HOME (the checkout, ~/.bun/bin, both host profiles). Each session then pays only the --check. A baked revision still moves forward at install-mode session start whenever it is behind origin, and the baked ~/.bun/bin reaches workflows through the GSTACK_LAUNCH line. The project Setup is shared by every thread in the project, so changing it is the project's decision.

Raising the supported minimum

capy/support.env holds GSTACK_MIN_REVISION and GSTACK_CAPY_MIN_WRAPPER. Raise GSTACK_MIN_REVISION only for install-honesty or security fixes, at stamp time, to the VERSION being released: it is the floor below which the trailer fails and the bootstrapper itself fast-forwards (a checkout above it that is behind origin is fast-forwarded by the checkout's own wrapper, so the floor is not what keeps machines current). It never exceeds VERSION (test/capy-skill-wrapper.test.ts). Raise GSTACK_CAPY_MIN_WRAPPER together with GSTACK_CAPY_WRAPPER in the bootstrapper when the bootstrapper itself changes in a way older copies cannot work with; older Drive copies keep working and print an owner action (CAPY_WRAPPER_STALE), and the doctor's wrapper row warns (an active copy below the minimum is a WARN, never a FAIL; bin/gstack-upgrade never leaves a pending reinstall for it). Wrapper 2 only adds optional exports (the trailer's latest: note and the cloned line), so the minimum stays 1.

Exit codes

Exit	Meaning
0	gstack: ok — every required component passed
1	gstack: fail <ids> — a required component failed; each row has a fix
2	usage error
3	preflight stopped before ./setup (INSTALL_PREFLIGHT_FAILED, RUNTIME_PIN_CONFLICT); nothing was installed