diff --git a/CHANGELOG.md b/CHANGELOG.md
index cc80cc6..6923726 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,39 @@ on the way to cutting its first release, and this file starts there.
 
 ## Unreleased
 
+### Added
+
+- **`rig platform` — what is this machine, calculated at run time, stored
+  nowhere** (#64) — rig read no hardware at all; the single exception was
+  `uname -m` in `runner-install.sh`, used to pick a tarball and then
+  discarded. So "is this the 32GB one, or the M900?" was answered by logging
+  in and running `free -h`, `nproc`, `df -h` and `uname -r` by hand, four
+  commands deep, on a machine you were already unsure about. `rig platform`
+  prints hostname, OS, kernel, CPU, memory, disk and virtualization, then a
+  provenance block (which rig, when, and the role marker's traits). It
+  **computes rather than stores**: specs change without rig doing anything —
+  RAM added, root disk resized, the unattended-upgrades bootstrap itself
+  enables patching the kernel — so a stored spec is stale the moment the
+  machine changes, and refreshing one per run would collide with bootstrap's
+  "a second run changes nothing" contract. Nothing is written, so nothing can
+  go stale. The corollary is deliberate: reading only `/proc`, `uname`,
+  `/etc/os-release`, `df` and `systemd-detect-virt` means it needs no root,
+  makes no network call, and **runs on a pristine Debian box rig has never
+  bootstrapped** — useful for deciding what to converge a machine into, not
+  only for auditing it afterwards. That also makes it the rare rig command
+  the harness can RUN for real instead of grepping: the tests assert the
+  actual answer describes the actual test machine. Provenance is read, never
+  written, and degrades per-file — `/etc/rig/manifest` is #61 and does not
+  exist yet, so that line reads `not bootstrapped` on every machine today and
+  nothing else depends on it. Named `platform` and not `status` on purpose:
+  `users status` and `runner status` cross-check recorded against live state
+  and print `DRIFT`, and a command that records nothing cannot drift — which
+  also leaves `rig status` free for the machine-wide roll-up. Known
+  limitation, stated rather than guessed at: `CPU`/`MEMORY` are read from
+  `/proc` with no cgroup awareness, and whether an `lxc` guest sees its own
+  limits or the host's totals depends on whether `lxcfs` is in play — it is
+  unverified, so those two lines are unreliable there.
+
 ### Changed
 
 - **BREAKING: `--class human|server` is now `--root-door closed|open`** (#77) —
diff --git a/README.md b/README.md
index 806c0ab..9743bda 100644
--- a/README.md
+++ b/README.md
@@ -719,6 +719,83 @@ default, dumps it, restores into a second container whose superuser differs, and
 asserts the rows and an ordered checksum survived — the same proof, done against
 throwaway containers on every push.
 
+### `rig platform`
+
+```sh
+rig platform
+```
+
+What is this machine — computed at run time, **stored nowhere**:
+
+```
+PLATFORM
+HOSTNAME   hetzner-cp-1
+OS         Debian GNU/Linux 13 (trixie)
+KERNEL     6.12.95+deb13-amd64 (x86_64)
+CPU        AMD Ryzen 7 3700X 8-Core Processor (16 cores)
+MEMORY     31Gi total, 24Gi available
+DISK       456Gi total, 201Gi free on /
+VIRT       kvm
+
+PROVENANCE
+RIG        0.4.0, bootstrapped 2026-07-19T14:24:51Z
+ROLE       dev (class=human host=yes join=authkey)
+```
+
+"Is this the 32GB one, or the M900?" was previously a question you answered by
+logging in and running `free -h`, `nproc`, `df -h` and `uname -r` by hand —
+four commands deep, on a machine you were already unsure about.
+
+**Why this computes instead of storing.** It would be easy to write the specs
+into a file at bootstrap. That is the wrong shape: specs change without rig
+doing anything — someone adds RAM, resizes the root disk, or the
+unattended-upgrades that bootstrap itself enables patches the kernel. A stored
+spec is stale the moment the machine changes, and refreshing it on every run
+would collide with bootstrap's contract that a second run changes nothing.
+Computing at run time removes the problem instead of managing it: the answer
+is correct by construction because there is nothing to go stale.
+
+The corollary is deliberate: **`rig platform` works on a machine rig has never
+converged.** It reads only `/proc`, `uname`, `/etc/os-release`, `df` and
+`systemd-detect-virt`, so it runs on bare Debian before bootstrap — useful for
+deciding *what to converge this into*, not just for auditing afterwards. It
+needs no root, makes no network call, and writes nothing, ever.
+
+The `PROVENANCE` block is the complementary half — which rig, and when, which
+is *decided* rather than observed, so it is stored. It is **read, never
+written**: `RIG` comes from `/etc/rig/manifest` and `ROLE` from
+`/etc/rig/role`. Neither file is required — a machine missing one reads `not
+bootstrapped` for that line, which is itself the useful answer. The manifest
+is #61 and is not implemented yet, so today that line reads `not bootstrapped`
+on every machine; nothing else in the command depends on it.
+
+**Known limitation — `CPU` and `MEMORY` inside a container-style guest are
+unverified.** `CPU` and `MEMORY` are read straight from `/proc/cpuinfo` and
+`/proc/meminfo`, with no cgroup awareness. Inside a box-minted guest (`VIRT`
+says `lxc`) it is **not currently established** whether those files report the
+instance's configured limits or the host's totals: neither file is namespaced
+by the kernel, but `lxcfs` — when the guest has it — overmounts both with
+limit-aware versions, so the answer depends on the guest's setup rather than
+on anything rig controls. Until someone confirms it against a real guest,
+treat those two lines as unreliable on `lxc` machines and check the instance
+config if the number matters. Everything else (OS, kernel, disk, virt,
+provenance) is the guest's own either way.
+
+Deliberately not guessed at: cgroup-aware limit detection would be the fix if
+the numbers do turn out to be the host's, but writing it against a *reasoned*
+answer rather than an *observed* one risks correcting a bug that isn't there
+and papering over one that is.
+
+Deliberately **not** here: NIC names, MAC addresses, PCI inventory, mount
+tables, sensors — this is a cheatsheet, not `inxi`, and the bar is "what would
+I want to know before I SSH in". Nor any health judgement ("disk nearly
+full"): that needs thresholds this command has no business owning. It is
+called `platform` and not `status` on purpose — `rig users status` and `rig
+runner status` cross-check recorded state against live state and print
+`DRIFT`, and this command records nothing, so it cannot drift and must not
+borrow a promise it structurally cannot make. That leaves `rig status` free
+for the machine-wide roll-up it will eventually want to be.
+
 ### `rig runner install --repo <owner/repo>`
 
 Runner box only, run after `rig bootstrap runner-server` (the same two-step rhythm
diff --git a/bin/rig b/bin/rig
index c352918..a077496 100755
--- a/bin/rig
+++ b/bin/rig
@@ -54,6 +54,15 @@ commands:
       writes a gzipped SQL artifact (--no-owner --no-acl, so it restores
       onto a different instance); `restore` loads one back, connecting as
       the container's own superuser, behind a confirm gate. Run as root.
+  platform
+      What is this machine: hostname, OS, kernel, CPU, memory, disk and
+      virtualization, then rig's own provenance (which rig, when, and the
+      role marker bootstrap wrote). Computed at run time from /proc, uname,
+      /etc/os-release, df and systemd-detect-virt and stored NOWHERE — a
+      spec goes stale the moment someone adds RAM, so there is nothing to
+      go stale here. Writes nothing, needs no root, makes no network call,
+      and therefore also runs on a pristine Debian box rig has never
+      bootstrapped, where the provenance block reads 'not bootstrapped'.
   runner install --repo <owner/repo> [options]
       GitHub Actions runner as a systemd service under an unprivileged
       user — outbound-only, no Docker. Prompts for the short-lived
@@ -383,6 +392,10 @@ case "$cmd" in
         ;;
     esac
     ;;
+  platform)
+    shift
+    exec "$ROOT/commands/platform.sh" "$@"
+    ;;
   runner)
     shift
     sub="${1:-}"
diff --git a/commands/platform.sh b/commands/platform.sh
new file mode 100755
index 0000000..12ccdaa
--- /dev/null
+++ b/commands/platform.sh
@@ -0,0 +1,173 @@
+#!/usr/bin/env bash
+# rig platform — what is this machine? Calculated at run time, stored nowhere.
+#
+# Read-only in the strongest sense rig has: it reads /proc, uname,
+# /etc/os-release, df and systemd-detect-virt, and writes NOTHING, ever. That
+# is the design, not an implementation detail — specs change without rig doing
+# anything (RAM added, root disk resized, unattended-upgrades patching the
+# kernel), so a stored spec is stale the moment the machine changes, and
+# refreshing one on every run would collide with bootstrap's convergence
+# contract ("safe to re-run; a second run changes nothing").
+#
+# The corollary is worth having deliberately: this runs on a machine rig has
+# never converged, and needs no root. It answers "what should I converge this
+# into?", not only "what did I converge this into?".
+set -euo pipefail
+
+HERE="$(cd "$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")" && pwd)"
+# shellcheck source=SCRIPTDIR/lib/users-config.sh
+. "$HERE/lib/users-config.sh"   # read_role_marker — one reader of /etc/rig/role
+
+die() { printf 'rig-platform: ERROR: %s\n' "$1" >&2; exit "${2:-1}"; }
+
+usage() {
+  cat <<'EOF'
+usage: rig platform
+
+Describes the machine you are on: hostname, OS, kernel, CPU, memory, disk
+and virtualization, then rig's own provenance (which rig, when, and the role
+marker bootstrap wrote).
+
+Computed at run time from /proc, uname, /etc/os-release, df and
+systemd-detect-virt. Writes nothing, needs no root, makes no network call —
+so it also works on a pristine Debian box rig has never bootstrapped, where
+the provenance block reads 'not bootstrapped'.
+EOF
+}
+
+# --- args ------------------------------------------------------------------
+while [ $# -gt 0 ]; do
+  case "$1" in
+    -h|--help) usage; exit 0 ;;
+    *) die "unknown flag: $1" 2 ;;
+  esac
+done
+
+# One aligned column for every line, so the output diffs cleanly across a
+# fleet and reads as one table rather than a log.
+field() { printf '%-10s %s\n' "$1" "$2"; }
+
+# --- hostname ---------------------------------------------------------------
+# uname -n is the coreutils fallback: `hostname` lives in its own package and a
+# minimal image may not carry it, and this command's whole point is running
+# before anything has been installed.
+HOSTNAME_V="$(hostname 2>/dev/null || uname -n)"
+
+# --- OS ---------------------------------------------------------------------
+# THE os-release TRAP: /etc/os-release defines VERSION, NAME and ID, so
+# sourcing it in the MAIN shell silently clobbers same-named script variables.
+# Every site in this tree sources it in a SUBSHELL instead (bootstrap.sh:305,
+# bootstrap-tenant.sh:126, runner-install.sh:88, db.sh:52,
+# coolify-backup-install.sh:88), and test/cli.sh greps commands/ to keep it
+# that way. Follow the form verbatim.
+if [ -r /etc/os-release ]; then
+  OS="$(. /etc/os-release && printf '%s %s' "${NAME:-}" "${VERSION:-${VERSION_ID:-}}")"
+else
+  OS=""
+fi
+
+# --- kernel -----------------------------------------------------------------
+KERNEL="$(uname -r) ($(uname -m))"
+
+# --- CPU --------------------------------------------------------------------
+# 'model name' is x86's spelling; arm64 /proc/cpuinfo has no such field, so an
+# unnamed CPU still reports its core count rather than nothing at all.
+CPU_MODEL="$(awk -F': ' '/^model name/ {print $2; exit}' /proc/cpuinfo 2>/dev/null || true)"
+CORES="$(nproc 2>/dev/null || true)"
+
+# --- memory -----------------------------------------------------------------
+# /proc/meminfo is in kB. MemAvailable is the kernel's own estimate of what a
+# new workload could claim (MemFree undercounts badly, reclaimable cache being
+# most of a busy box's RAM); it predates every kernel rig targets, but degrade
+# rather than print a wrong number if it is missing.
+mem_kb() { awk -v k="$1" '$1 == k":" {print $2; exit}' /proc/meminfo 2>/dev/null || true; }
+MEM_TOTAL_KB="$(mem_kb MemTotal)"
+MEM_AVAIL_KB="$(mem_kb MemAvailable)"
+human_kb() {   # kB -> IEC, matching df's units below
+  [ -n "${1:-}" ] || { printf 'unknown'; return 0; }
+  numfmt --to=iec-i "$(( $1 * 1024 ))" 2>/dev/null || printf '%s kB' "$1"
+}
+
+# --- disk -------------------------------------------------------------------
+# -P is the one-line-per-filesystem guarantee (a long device name otherwise
+# wraps and breaks field positions); -B1 gives bytes, so numfmt renders the
+# same IEC units as memory above instead of df's own bare 'G'.
+DISK_TOTAL="" DISK_FREE=""
+if DF="$(df -PB1 / 2>/dev/null)"; then
+  DISK_TOTAL="$(printf '%s\n' "$DF" | awk 'NR==2 {print $2}')"
+  DISK_FREE="$(printf '%s\n' "$DF" | awk 'NR==2 {print $4}')"
+fi
+human_b() { [ -n "${1:-}" ] && numfmt --to=iec-i "$1" 2>/dev/null || printf 'unknown'; }
+
+# --- virtualization ---------------------------------------------------------
+# THE set -e TRAP: systemd-detect-virt exits NON-ZERO on bare metal while
+# printing 'none'. That is a normal, correct answer — without the `|| true` a
+# bare-metal machine would turn this whole command into a failed run. The
+# substitution also swallows the binary being absent entirely (a non-systemd
+# box), which lands as 'unknown'.
+VIRT="$(systemd-detect-virt 2>/dev/null || true)"
+
+printf '%s\n' "PLATFORM"
+field HOSTNAME "$HOSTNAME_V"
+field OS       "${OS:-unknown}"
+field KERNEL   "$KERNEL"
+field CPU      "${CPU_MODEL:-unknown}${CORES:+ ($CORES cores)}"
+field MEMORY   "$(human_kb "$MEM_TOTAL_KB") total, $(human_kb "$MEM_AVAIL_KB") available"
+field DISK     "$(human_b "$DISK_TOTAL") total, $(human_b "$DISK_FREE") free on /"
+field VIRT     "${VIRT:-unknown}"
+echo
+
+# --- provenance: READ, never written ----------------------------------------
+# The complementary half of the answer — which rig, and when — is decided
+# rather than observed, so unlike everything above it IS stored. rig writes it
+# during bootstrap; this command only ever reads it.
+#
+# /etc/rig/manifest is #61 and is NOT implemented yet, so on every machine in
+# existence today this block reads 'not bootstrapped'. That degradation is the
+# point: the two features are independent and neither blocks the other. The
+# parse is the flat key=value shape the manifest is specified to use — the
+# same jq-free shape /etc/rig/users and /etc/rig/role already use, parseable
+# with `read` on a box that has no YAML parser.
+#
+# RIG_MANIFEST / RIG_ROLE_MARKER override the paths so the harness can drive
+# both the present and the absent case against fixtures, non-root, without a
+# real marker on the machine running the tests (repo precedent: the
+# RIG_ROLE_MARKER gate in bin/rig, install.sh and users-close-root.sh).
+MANIFEST="${RIG_MANIFEST:-/etc/rig/manifest}"
+MARKER="${RIG_ROLE_MARKER:-/etc/rig/role}"
+
+manifest_field() {   # $1 = key — empty when absent, unreadable or unset
+  local k v
+  [ -r "$MANIFEST" ] || return 0
+  while IFS='=' read -r k v; do
+    [ "$k" = "$1" ] || continue
+    printf '%s\n' "$v"
+    return 0
+  done < "$MANIFEST"
+  return 0
+}
+
+printf '%s\n' "PROVENANCE"
+if [ -r "$MANIFEST" ]; then
+  RIG_VER="$(manifest_field version)"
+  RIG_WHEN="$(manifest_field bootstrapped)"
+  field RIG "${RIG_VER:-unknown}${RIG_WHEN:+, bootstrapped $RIG_WHEN}"
+else
+  field RIG "not bootstrapped (no $MANIFEST)"
+fi
+
+# The role marker is bootstrap's own line — 'role=dev class=human host=yes
+# join=authkey' — printed as the role plus its traits.
+MARKER_LINE="$(read_role_marker "$MARKER")"
+if [ -n "$MARKER_LINE" ]; then
+  ROLE_NAME="" ROLE_TRAITS=""
+  for kv in $MARKER_LINE; do
+    case "$kv" in
+      role=*) ROLE_NAME="${kv#role=}" ;;
+      *)      ROLE_TRAITS="${ROLE_TRAITS:+$ROLE_TRAITS }$kv" ;;
+    esac
+  done
+  field ROLE "${ROLE_NAME:-unknown}${ROLE_TRAITS:+ ($ROLE_TRAITS)}"
+else
+  field ROLE "not bootstrapped (no $MARKER)"
+fi
diff --git a/test/cli.sh b/test/cli.sh
index ec6c0f3..a05ecfb 100644
--- a/test/cli.sh
+++ b/test/cli.sh
@@ -977,6 +977,56 @@ else
   echo "skip: runner status/remove/repoint non-root refusals (running as root)"
 fi
 
+# ---------------------------------------------------------------------------
+# rig platform (#64). Unusually testable for this repo: it needs no root, no
+# network and no fixtures, and it WRITES NOTHING — so unlike every other
+# command here the harness can RUN it for real on the machine running the
+# tests and assert on the actual answer, instead of proving arg-parse
+# refusals and grepping the rest.
+# ---------------------------------------------------------------------------
+check "platform: --help exits 0"           0 "usage:"      "$ROOT/commands/platform.sh" --help
+check "platform: unknown flag exits 2"     2 "unknown flag" "$ROOT/commands/platform.sh" --nope
+check "platform: dispatches through bin/rig" 0 "PLATFORM"  "$ROOT/bin/rig" platform
+
+# The real run: exit 0 and every field present, as the running user.
+check "platform: runs as this user, exit 0" 0 "PLATFORM" "$ROOT/bin/rig" platform
+for f in HOSTNAME OS KERNEL CPU MEMORY DISK VIRT; do
+  check "platform: reports $f" 0 "$f" "$ROOT/bin/rig" platform
+done
+# Not just the labels — the VALUES have to describe THIS machine. uname -r and
+# the hostname are the two the harness can independently compute and compare,
+# which is what separates "it printed a table" from "it read the machine".
+check "platform: KERNEL is this kernel"   0 "$(uname -r)" "$ROOT/bin/rig" platform
+check "platform: HOSTNAME is this host"   0 "$(uname -n)" "$ROOT/bin/rig" platform
+# MemAvailable/df rendered, not left as the 'unknown' fallback: a numfmt or
+# /proc parse that silently broke would still print the labels above.
+check "platform: MEMORY carries real numbers" 0 "total," "$ROOT/bin/rig" platform
+
+# Provenance degrades on a machine rig never converged — #61's manifest does
+# not exist yet, so 'not bootstrapped' is the state of the world today and the
+# command must ship complete without it. Both paths driven against fixtures.
+PLATWORK="$(mktemp -d)"
+printf 'version=9.9.9\nbootstrapped=2026-07-19T14:24:51Z\n' > "$PLATWORK/manifest"
+check "platform: no manifest reads 'not bootstrapped'" 0 "RIG        not bootstrapped" \
+  env RIG_MANIFEST="$PLATWORK/absent" RIG_ROLE_MARKER="$PLATWORK/absent" "$ROOT/bin/rig" platform
+check "platform: no role marker reads 'not bootstrapped'" 0 "ROLE       not bootstrapped" \
+  env RIG_MANIFEST="$PLATWORK/absent" RIG_ROLE_MARKER="$PLATWORK/absent" "$ROOT/bin/rig" platform
+# A manifest that DOES exist is read, never written — the forward-compatible
+# half, so #61 landing needs no change here.
+check "platform: reads the manifest version" 0 "9.9.9" \
+  env RIG_MANIFEST="$PLATWORK/manifest" RIG_ROLE_MARKER="$PLATWORK/absent" "$ROOT/bin/rig" platform
+check "platform: reads the manifest timestamp" 0 "bootstrapped 2026-07-19T14:24:51Z" \
+  env RIG_MANIFEST="$PLATWORK/manifest" RIG_ROLE_MARKER="$PLATWORK/absent" "$ROOT/bin/rig" platform
+printf 'role=dev class=human host=yes join=authkey\n' > "$PLATWORK/role"
+check "platform: renders the role marker's traits" 0 "dev (class=human host=yes join=authkey)" \
+  env RIG_MANIFEST="$PLATWORK/absent" RIG_ROLE_MARKER="$PLATWORK/role" "$ROOT/bin/rig" platform
+# The defining property: it writes NOTHING. Not the manifest it just reported
+# missing, not the marker, not anything else in the fixture directory — the
+# whole design rests on this, so assert it rather than trust it.
+env RIG_MANIFEST="$PLATWORK/absent" RIG_ROLE_MARKER="$PLATWORK/absent" "$ROOT/bin/rig" platform >/dev/null 2>&1
+check "platform: writes nothing (no manifest created)" 1 "" test -e "$PLATWORK/absent"
+rm -rf "$PLATWORK"
+
 check "bare users shows usage, exit 2"    2 "usage:"        "$ROOT/bin/rig" users
 check "users: bad subcommand exits 2"     2 "usage:"        "$ROOT/bin/rig" users frobnicate