diff --git a/README.md b/README.md
index 8b57d856..7735ef43 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,8 @@ Or as a Claude Code plugin:
 > [!NOTE]
 > The plugin ships the skills only. Run `/super-board:super-board onboard` and its 🔍 Checks step adds the guard hooks, scripts and workflows. Needs Claude Code, `gh`, `jq`, bash 3.2+ and Python 3.9+; the installer checks.
 
+Running from Codex or OpenCode? See [supported hosts](docs/hosts.md) for tested versions, sign-in and gaps.
+
 Optional post-run learning can delegate an already installed `calibrate` skill after
 verified selected work completes. It applies only to explicitly permitted existing
 canonical skill files; the package bundles no private skill. See
diff --git a/docs/hosts.md b/docs/hosts.md
new file mode 100644
index 00000000..57ba5403
--- /dev/null
+++ b/docs/hosts.md
@@ -0,0 +1,37 @@
+# Agent hosts
+
+super-board runs inside an agent host: the CLI whose session types `/super-board run`.
+`scripts/super-board-host.sh` (installed as `.claude/bin/super-board-host.sh`) names it.
+
+| Host value | Tested version | Start a run | Sign-in | Gaps |
+|---|---|---|---|---|
+| `claude` | Claude Code 2.1.302 | `/super-board run` (Workflow backend) | `claude` then `/login`; `gh auth login` | None. The reference host. |
+| `codex` | codex-cli 0.160.0 | `/super-board run` inside Codex runs as `--codex`; from Claude, `/super-board run --codex` | `codex login`; `gh auth login` | No Workflow tool, so every lane is headless `codex exec`. Review runs only with explicit `--codex` (a host-switched plain `run` counts). No Claude usage guard. |
+| `opencode` | OpenCode v2.0.22 | Not supported yet: the run halts with a host-selection request | `opencode auth login`; `gh auth login` | No OpenCode lane backend yet. `permission.external_directory: deny` is not enforced in v2.0.22 (`patch` still writes outside the repo), so OpenCode runs stay attended-only once a backend lands. |
+
+Every host also needs `gh`, `jq`, bash 3.2+ and Python 3.9+.
+
+## How the host is picked
+
+`super-board-host.sh [--config <config.json>]` prints one value. First match wins:
+
+1. `SUPER_BOARD_HOST=claude|codex|opencode`, the manual override. Any other value exits 64.
+2. `CODEX_THREAD_ID` or `CODEX_SESSION_ID` → `codex`.
+3. `OPENCODE=1` → `opencode`. Checked before `CLAUDECODE`, which leaks into an OpenCode
+   session started from Claude Code. `AGENT=1` is ignored: other tools set it too.
+4. `CLAUDECODE` → `claude`.
+5. The board config's top-level `host` key, when `--config` is given.
+6. Nothing matched: empty stdout, a hint on stderr, exit 65. The run halts and asks for a
+   host. It never guesses Claude.
+
+A live env sign beats the saved config, so a Codex lane started from a Claude-configured
+board still answers `codex`.
+
+Onboard always writes `host` into `.claude/super-board/configs/<slug>.json`.
+`super-board-setup.py fix` adds a missing one from `--host`; `check` flags any other value.
+
+## Evidence
+
+- Codex: env of `codex exec -s read-only`, 2026-10-04 (recorded in the script header).
+- OpenCode: env diff of an `opencode run` shell, 2026-10-19: `OPENCODE=1`,
+  `OPENCODE_SESSION_ID`, `OPENCODE_TERMINAL=1`, `AGENT=1`.
diff --git a/scripts/super-board-host.sh b/scripts/super-board-host.sh
index 41c21d35..87900a7a 100755
--- a/scripts/super-board-host.sh
+++ b/scripts/super-board-host.sh
@@ -1,29 +1,60 @@
 #!/usr/bin/env bash
-# super-board-host.sh — which agent host is this shell inside: `claude` or `codex`.
+# super-board-host.sh — which agent host is this shell inside: `claude`, `codex` or `opencode`.
 #
 # WHY. `/super-board run` launched from a Codex CLI session has no Claude Workflow tool, so the
 # workflow backend cannot start. The orchestrator checks its own tool list first; this is the
-# check a script can make, and the tie-breaker when the tool list is unclear.
+# check a script can make, and the tie-breaker when the tool list is unclear. A shell with no
+# known sign gets no answer (exit 65): guessing Claude there starts the wrong backend.
 #
-# THE SIGNAL. Codex CLI sets CODEX_THREAD_ID (and CODEX_SESSION_ID, the same value) in every
-# shell it runs. Observed 2026-10-04 on codex-cli 0.160.0 with `codex exec -s read-only`:
-# CODEX_THREAD_ID, CODEX_SESSION_ID, CODEX_VERSION, CODEX_SANDBOX=seatbelt, CODEX_CI=1.
-# Not used: CODEX_HOME (people export it in their own profile), CODEX_SANDBOX (absent when
-# the sandbox is off). A Codex lane started from a Claude session also carries CLAUDECODE; the
-# Codex ids still win there, because the innermost host is the one running this shell.
+# THE SIGNALS.
+# - Codex CLI sets CODEX_THREAD_ID (and CODEX_SESSION_ID, the same value) in every shell it
+#   runs. Observed 2026-10-04 on codex-cli 0.160.0 with `codex exec -s read-only`:
+#   CODEX_THREAD_ID, CODEX_SESSION_ID, CODEX_VERSION, CODEX_SANDBOX=seatbelt, CODEX_CI=1.
+#   Not used: CODEX_HOME (people export it in their own profile), CODEX_SANDBOX (absent when
+#   the sandbox is off). A Codex lane started from a Claude session also carries CLAUDECODE;
+#   the Codex ids still win there, because the innermost host is the one running this shell.
+# - OpenCode sets OPENCODE=1 (plus OPENCODE_SESSION_ID, OPENCODE_TERMINAL=1, AGENT=1) in the
+#   shells it runs. Observed 2026-10-19 on opencode v2.0.22 (env diff of a `run` shell).
+#   Checked before CLAUDECODE, which leaks into OpenCode started from a Claude session.
+#   Not used: AGENT=1 (a generic name other tools set too).
+# - Claude Code sets CLAUDECODE=1.
 #
-# Usage: super-board-host.sh          prints `claude` or `codex`, exit 0
-# SUPER_BOARD_HOST=claude|codex forces the answer (tests, or a host the check misreads).
+# ORDER. SUPER_BOARD_HOST, Codex ids, OPENCODE, CLAUDECODE, then the config's top-level
+# `host` key (--config <file>), else exit 65. A live env sign beats the saved config.
+#
+# Usage: super-board-host.sh [--config <config.json>]
+#        prints `claude`, `codex` or `opencode`, exit 0
+#        exit 65   no sign: nothing on stdout, how to choose on stderr
+#        exit 64   SUPER_BOARD_HOST or config `host` is not one of the three
+# SUPER_BOARD_HOST=claude|codex|opencode forces the answer (tests, or a host the check
+# misreads).
 set -euo pipefail
 
+config=
+case "${1:-}" in
+  --config) config=${2:-} ;;
+  '') ;;
+  *) echo "usage: super-board-host.sh [--config <config.json>]" >&2; exit 64 ;;
+esac
+
 case "${SUPER_BOARD_HOST:-}" in
-  claude|codex) echo "$SUPER_BOARD_HOST"; exit 0 ;;
+  claude|codex|opencode) echo "$SUPER_BOARD_HOST"; exit 0 ;;
   '') ;;
-  *) echo "super-board-host.sh: SUPER_BOARD_HOST must be claude or codex" >&2; exit 64 ;;
+  *) echo "super-board-host.sh: SUPER_BOARD_HOST must be claude, codex or opencode" >&2; exit 64 ;;
 esac
 
 if [ -n "${CODEX_THREAD_ID:-}" ] || [ -n "${CODEX_SESSION_ID:-}" ]; then
   echo codex
-else
+elif [ -n "${OPENCODE:-}" ]; then
+  echo opencode
+elif [ -n "${CLAUDECODE:-}" ]; then
   echo claude
+elif saved=$( [ -f "$config" ] && jq -r '.host // empty' "$config" 2>/dev/null ) && [ -n "$saved" ]; then
+  case "$saved" in
+    claude|codex|opencode) echo "$saved" ;;
+    *) echo "super-board-host.sh: config host must be claude, codex or opencode, got '$saved'" >&2; exit 64 ;;
+  esac
+else
+  echo "super-board-host.sh: unknown agent host. Pick one: SUPER_BOARD_HOST=claude|codex|opencode, or set \"host\" in the board config" >&2
+  exit 65
 fi
diff --git a/scripts/super-board-setup.py b/scripts/super-board-setup.py
index acfab70f..1e494250 100755
--- a/scripts/super-board-setup.py
+++ b/scripts/super-board-setup.py
@@ -22,7 +22,8 @@
   - installs or refreshes skills, .claude/bin scripts, workflows, guard hooks and their
     settings.json entries (runs the pack's install.sh) when any is missing or older
   - removes the folders of skills that no longer exist: super-refine, cleanup-wt, arch-loop
-  - migrates every .claude/super-board/configs/*.json to the v3 keys (migrate-config)
+  - migrates every .claude/super-board/configs/*.json to the v3 keys (migrate-config), and
+    writes a missing top-level `host` from --host (check flags a host outside claude/codex/opencode)
   - `git init` when the folder is not a repo
   - adds Matt Pocock's helper skills with npx when Node is present and they are missing
 It never installs a system tool or signs in: those come back in `needs` with the exact
@@ -58,6 +59,7 @@
 import sys
 
 COLUMNS = ["Backlog", "Ready", "Building", "QA", "Review", "Blocked", "Done"]
+HOSTS = ("claude", "codex", "opencode")  # config `host`; super-board-host.sh accepts the same
 LABELS = {
     "qa": ("0e8a16", "Test what exists; skips Building (super-board)"),
     "bug": ("d73a4a", "Something is broken; built, tested, reviewed (super-board)"),
@@ -215,9 +217,10 @@ def machine_tz():
     return "UTC"
 
 
-def migrate_config(cfg):
+def migrate_config(cfg, host=None):
     """Return (new config, [human-readable change lines]). Pure; never drops a project setting
-    that still means something."""
+    that still means something. `host` (the actual worker host) fills a missing top-level
+    `host` key; a set one is never replaced."""
     c = json.loads(json.dumps(cfg))
     changes = []
     variant = c.pop("variant", None)
@@ -268,6 +271,9 @@ def migrate_config(cfg):
     if not c.get("worker_backend"):
         c["worker_backend"] = "workflow"
         changes.append("worker_backend \"workflow\" added")
+    if host and "host" not in c:
+        c["host"] = host
+        changes.append(f"host \"{host}\" added")
     return c, changes
 
 
@@ -295,6 +301,7 @@ def check(root, pack, host="claude", home=None, catalog=None):
     old_dirs = [d for d in OLD_SKILL_DIRS if os.path.isdir(os.path.join(claude, "skills", d))]
     configs = {}
     verification = {}
+    host_errors = {}
     for p in sorted(glob.glob(os.path.join(claude, "super-board", "configs", "*.json"))):
         cfg = load_json(p)
         ready = subprocess.run([sys.executable, os.path.join(os.path.dirname(__file__),
@@ -303,7 +310,10 @@ def check(root, pack, host="claude", home=None, catalog=None):
         if ready.returncode:
             verification[os.path.relpath(p, root)] = ready.stderr.strip()
         if isinstance(cfg, dict):
-            _, ch = migrate_config(cfg)
+            if "host" in cfg and cfg["host"] not in HOSTS:
+                host_errors[os.path.relpath(p, root)] = (
+                    f"host \"{cfg['host']}\" must be one of {', '.join(HOSTS)}")
+            _, ch = migrate_config(cfg, host)
             if ch:
                 configs[os.path.relpath(p, root)] = ch
     older = bool(upgrade_rec.get("from")) or bool(old_dirs) or any(
@@ -332,12 +342,13 @@ def check(root, pack, host="claude", home=None, catalog=None):
         ok.append("git repo found")
     if helpers:
         ok.append("required worker skills resolved for " + host)
-    red = bool(missing or old_dirs or configs or verification or not git or needs or not helpers)
+    red = bool(missing or old_dirs or configs or verification or host_errors or not git or needs or not helpers)
     return {
         "root": root, "pack": pack, "pack_version": pack_version, "installed_version": have_v,
         "upgrade": older, "from": from_v or ("older" if older else None),
         "added_skills": upgrade_rec.get("added_skills", []),
-        "missing": missing, "old_dirs": old_dirs, "configs": configs, "verification": verification, "git": git,
+        "missing": missing, "old_dirs": old_dirs, "configs": configs, "verification": verification,
+        "host_errors": host_errors, "git": git,
         "helper_skills": helpers, "helper_readiness": readiness, "needs": needs, "os": fam, "ok": ok, "green": not red,
     }
 
@@ -397,7 +408,7 @@ def fix(root, pack, helpers=True, dry=False, host="claude", home=None, catalog=N
 
     for rel, ch in before["configs"].items():
         p = os.path.join(root, rel)
-        new, _ = migrate_config(load_json(p))
+        new, _ = migrate_config(load_json(p), host)
         if not dry:
             write_json(p, new)
         if before["upgrade"]:
@@ -455,7 +466,7 @@ def text_report(res):
             lines.append(f"  ✗ missing {entry['name']} for {res['helper_readiness']['host']}; install it in that host and restart")
     if res.get("helper_readiness", {}).get("error"):
         lines.append("  ✗ " + res["helper_readiness"]["error"])
-    for path, error in res.get("verification", {}).items():
+    for path, error in {**res.get("verification", {}), **res.get("host_errors", {})}.items():
         lines.append(f"  ✗ {path}: {error}")
     for n in res.get("needs", []):
         lines.append(f"  Needs your machine: {n['name']} isn't installed. It's needed for {n['why']}.")
diff --git a/skills/super-board/references/config-schema.json b/skills/super-board/references/config-schema.json
index c9d3be07..e4bd4bbb 100644
--- a/skills/super-board/references/config-schema.json
+++ b/skills/super-board/references/config-schema.json
@@ -31,6 +31,13 @@
   // only; the dispatcher refuses to run (exit 78) unless set here.
   "worker_backend": "workflow",
 
+  // Agent host this project runs on: "claude" | "codex" | "opencode". Separate from
+  // worker_backend. Onboard and setup's fix ALWAYS write it (setup fills a missing key
+  // from --host and never replaces a set one); setup's check flags any other value.
+  // `super-board-host.sh --config <this file>` uses it only when SUPER_BOARD_HOST and
+  // every env sign (Codex ids, OPENCODE, CLAUDECODE) are absent. See docs/hosts.md.
+  "host": "claude",
+
   // Optional post-completion adapter; never bundles or installs the external skill.
   // Runs only after selected work is verified merged and no work/approvals remain.
   // The supervising host checks the resulting diff; the helper itself is read-only.
diff --git a/skills/super-board/references/onboard.md b/skills/super-board/references/onboard.md
index 1d55e58e..c91e9022 100644
--- a/skills/super-board/references/onboard.md
+++ b/skills/super-board/references/onboard.md
@@ -360,7 +360,8 @@ Write it atomically (temp file + rename) after every answer. A halt never loses
    │    ├─ .claude/super-board/configs/<slug>.json (committed): description, project, target
    │    │    {type: repo | repo+url}, repo, base_branch, timezone, columns (the seven), labels,
    │    │    paths, merge_policy, migrations, collect (incl. custom), notifications {channel:
-   │    │    "session", bot_identity}, worker_backend "workflow", verify_commands (non-blank project checks). No `variant`.
+   │    │    "session", bot_identity}, worker_backend "workflow", host (always: `bash $SB/super-board-host.sh`;
+   │    │    on exit 65 ask claude/codex/opencode), verify_commands (non-blank project checks). No `variant`.
    │    ├─ .claude/super-board/active ← <slug>
    │    ├─ .gitignore += .claude/super-board/active, onboard-answers.json, onboard-staged/,
    │    │    backup/, inflight/, migrations/, upgrade.json (all under .claude/super-board/)
diff --git a/skills/super-board/references/run-workflow.md b/skills/super-board/references/run-workflow.md
index 0bf73526..c63f5f08 100644
--- a/skills/super-board/references/run-workflow.md
+++ b/skills/super-board/references/run-workflow.md
@@ -21,10 +21,14 @@ pins one model for every card and skips the router.
 Keep this run choice in each wave and resume command; skip only the Claude usage guard.
 
 **Inside Codex, plain `run` is `--codex`.** Your tool list has no Workflow tool, or
-`bash .claude/bin/super-board-host.sh` prints `codex` → run as `--codex` (tier flags and
+`bash .claude/bin/super-board-host.sh --config <config-path>` prints `codex` → run as `--codex` (tier flags and
 `--codex=<model>` still apply); it counts as explicit `--codex`, Review included.
 Say so once, in the first wave report: `🔁 codex host — running as --codex`. Never improvise a Claude workflow wave in Codex.
 
+**Unknown host halts.** Run the host check before preconditions. Exit 65 (no host sign) or
+`opencode` (no OpenCode backend yet) halts before any claim, even with no Workflow tool, with one line:
+`⛔ unknown host — set SUPER_BOARD_HOST=claude|codex and re-run`. Never guess a backend.
+
 After the same plan and claim steps, launch this command as a background task:
 `bash .claude/bin/super-board-codex-wave.sh --config <config-path> --cards <claimed-cards.json> --codex[=<model>] --tier <low|medium|high> --output <wave-result.json>`.
 The helper starts one `super-board-codex-lane.sh` per card/lane, cards in parallel,
@@ -242,7 +246,8 @@ Repeat until a done condition or halt gate fires:
    there is no cross-session claim at all, so never run two orchestrators
    (or /loop re-entries) against the same board without bot_identity.
 4. **Launch** — With `--codex`, or no Workflow tool, or the host check printing `codex`, use
-   "Codex runs" above; otherwise Workflow tool with
+   "Codex runs" above. The host check printing `claude` uses the Workflow tool; exit 65 or
+   `opencode` never reaches Launch (see "Unknown host halts"). Workflow tool with
    `scriptPath: .claude/workflows/super-board-wave.js` and
    `args: { configPath, cards, humanApprovesMerge, tier }` (`cards` hydrated after the planner: each
    carries `lane` and `labels`, and a `qa` card skips the Builder). Runs in the background; the
diff --git a/tests/test-host.sh b/tests/test-host.sh
index 02f669a4..fb323715 100644
--- a/tests/test-host.sh
+++ b/tests/test-host.sh
@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
-# Tests super-board-host.sh — the Codex-host check that turns a plain `run` into `--codex`.
+# Tests super-board-host.sh — which agent host runs this shell, else exit 65 so the run
+# asks for a host instead of guessing.
 set -euo pipefail
 KIT=$(cd "$(dirname "$0")/.." && pwd)
 S="$KIT/scripts/super-board-host.sh"
@@ -7,14 +8,50 @@ fail() { echo "FAIL: $1" >&2; exit 1; }
 # A clean env, so the test answers the same inside Claude Code, Codex or CI.
 host() { env -i PATH="$PATH" "$@" bash "$S"; }
 
-[ "$(host)" = claude ] || fail 'no Codex ids means claude'
+[ "$(host CLAUDECODE=1)" = claude ] || fail 'CLAUDECODE means claude'
 [ "$(host CODEX_THREAD_ID=01a1)" = codex ] || fail 'CODEX_THREAD_ID means codex'
 [ "$(host CODEX_SESSION_ID=01a1)" = codex ] || fail 'CODEX_SESSION_ID means codex'
 [ "$(host CODEX_THREAD_ID=01a1 CLAUDECODE=1)" = codex ] || fail 'a Codex lane under Claude is codex'
-[ "$(host CODEX_HOME=/x CODEX_SANDBOX=seatbelt)" = claude ] || fail 'CODEX_HOME/CODEX_SANDBOX alone are not a host'
-[ "$(host CODEX_THREAD_ID=)" = claude ] || fail 'an empty id is not a host'
 [ "$(host SUPER_BOARD_HOST=codex)" = codex ] || fail 'override forces codex'
 [ "$(host SUPER_BOARD_HOST=claude CODEX_THREAD_ID=01a1)" = claude ] || fail 'override beats the env'
+[ "$(host SUPER_BOARD_HOST=opencode)" = opencode ] || fail 'override accepts opencode'
 rc=0; host SUPER_BOARD_HOST=gemini >/dev/null 2>&1 || rc=$?
 [ "$rc" = 64 ] || fail "bad override exits 64, got $rc"
+
+# No sign and no override: empty stdout, a hint on stderr, exit 65 — never a guessed claude.
+ERR=$(mktemp); trap 'rm -f "$ERR"' EXIT
+nohost() {
+  local rc=0 out
+  out=$(host "$@" 2>"$ERR") || rc=$?
+  [ "$rc" = 65 ] || fail "'$*' should exit 65, got $rc"
+  [ -z "$out" ] || fail "'$*' should print nothing to stdout, got '$out'"
+  grep -q SUPER_BOARD_HOST "$ERR" || fail "'$*' should explain SUPER_BOARD_HOST on stderr"
+}
+nohost
+nohost CODEX_HOME=/x CODEX_SANDBOX=seatbelt   # not host signs
+nohost CODEX_THREAD_ID= CLAUDECODE=            # empty values are not signs
+nohost AGENT=1                                 # OpenCode sets it, but so do other tools
+
+# OpenCode v2.0.22 exports OPENCODE=1. It wins over a CLAUDECODE leaked from a parent Claude
+# session; the override and a Codex id still win over it.
+[ "$(host OPENCODE=1)" = opencode ] || fail 'OPENCODE=1 means opencode'
+[ "$(host OPENCODE=1 CLAUDECODE=1)" = opencode ] || fail 'OpenCode under a Claude parent is opencode'
+[ "$(host SUPER_BOARD_HOST=claude OPENCODE=1)" = claude ] || fail 'override beats the OpenCode sign'
+[ "$(host CODEX_THREAD_ID=01a1 OPENCODE=1)" = codex ] || fail 'a Codex id beats the OpenCode sign'
+
+# Config `host` (top-level key): used only when no override and no env sign is present.
+T=$(mktemp -d); trap 'rm -f "$ERR"; rm -rf "$T"' EXIT
+printf '{"host":"codex"}' > "$T/codex.json"
+printf '{"worker_backend":"workflow"}' > "$T/none.json"
+printf '{"host":"gemini"}' > "$T/bad.json"
+cfg() { local f=$1; shift; env -i PATH="$PATH" "$@" bash "$S" --config "$f"; }
+[ "$(cfg "$T/codex.json")" = codex ] || fail 'config host codex prints codex'
+[ "$(cfg "$T/codex.json" CLAUDECODE=1)" = claude ] || fail 'an env sign beats config host'
+[ "$(cfg "$T/codex.json" SUPER_BOARD_HOST=opencode)" = opencode ] || fail 'override beats config host'
+for f in none missing; do
+  rc=0; out=$(cfg "$T/$f.json" 2>/dev/null) || rc=$?
+  [ "$rc" = 65 ] && [ -z "$out" ] || fail "config $f without host should exit 65, got $rc '$out'"
+done
+rc=0; cfg "$T/bad.json" >/dev/null 2>&1 || rc=$?
+[ "$rc" = 64 ] || fail "a bad config host exits 64, got $rc"
 echo "PASS: super-board-host"
diff --git a/tests/test-hosts-doc.sh b/tests/test-hosts-doc.sh
new file mode 100644
index 00000000..1ad2f1ea
--- /dev/null
+++ b/tests/test-hosts-doc.sh
@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# Tests docs/hosts.md — every host value super-board-host.sh accepts in its SUPER_BOARD_HOST
+# case has a table row, and README's Install section links the page.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+fail() { echo "FAIL: $1" >&2; exit 1; }
+DOC=docs/hosts.md
+[ -f "$DOC" ] || fail "$DOC is missing"
+
+# The accepted values: the first case arm after `case "${SUPER_BOARD_HOST:-}" in`.
+values=$(awk '/case "\$\{SUPER_BOARD_HOST:-\}" in/{getline; sub(/^[ \t]*/, ""); sub(/\).*/, ""); print; exit}' \
+  scripts/super-board-host.sh | tr '|' ' ')
+[ -n "$values" ] || fail "no SUPER_BOARD_HOST values found in super-board-host.sh"
+n=0
+for v in $values; do
+  grep -q "^| \`$v\` |" "$DOC" || fail "host \`$v\` has no row in $DOC"
+  n=$((n + 1))
+done
+[ "$n" -ge 3 ] || fail "expected at least claude, codex and opencode, got: $values"
+
+# README links the page from the Install section (between ## Install and the next ## heading).
+awk '/^## Install/{on=1; next} /^## /{on=0} on' README.md | grep -q '(docs/hosts.md)' \
+  || fail "README Install section must link docs/hosts.md"
+echo "PASS: test-hosts-doc.sh ($n hosts)"
diff --git a/tests/test-setup.sh b/tests/test-setup.sh
index fd90b397..1aa485f3 100644
--- a/tests/test-setup.sh
+++ b/tests/test-setup.sh
@@ -74,6 +74,7 @@ q '.columns == ["Backlog","Ready","Building","QA","Review","Blocked","Done"]' "$
 q '.collect.sources == ["sentry","github","prs","architecture"] and (.collect | has("lookback_runs") | not)' "$C" || fail "collect keys not migrated"
 q '.merge_policy.default == "human" and .notifications.channel == "session" and (.refine | has("qa_hook_rounds") | not)' "$C" \
   || fail "merge rule / notifications / refine not migrated: $(cat "$C")"
+q '.host == "claude"' "$C" || fail "fix must always write the top-level host (from --host): $(cat "$C")"
 [ ! -e "$T/.claude/super-board/upgrade.json" ] || fail "upgrade.json should be cleared once the upgrade is done"
 TXT=$(python3 "$SETUP" check --root "$T" --text || true)
 echo "$TXT" | grep -q "Upgraded for you" && fail "a finished upgrade must not be reported again"
@@ -301,4 +302,22 @@ cmp -s "$GH_STATE" "$WORK/before.json" || fail "dry-run changed board state: $(c
 [ ! -e "$WORK/dry/.claude" ] || fail "dry-run must not write a backup file"
 echo "$OUT" | q '.status_backup == null and .restored == 0 and .added_columns != []' || fail "dry-run report wrong: $OUT"
 
-echo "PASS: test-setup.sh (12 scenarios)"
+# 13 — config `host`: check accepts claude / codex / opencode, flags anything else, and
+#      fix never overwrites a host that is already set.
+H="$WORK/bare/.claude/super-board/configs"; mkdir -p "$H"
+for h in claude codex opencode; do
+  printf '{"host":"%s"}' "$h" > "$H/b.json"
+  OUT=$(python3 "$SETUP" check --root "$WORK/bare" || true)
+  echo "$OUT" | q '.host_errors == {}' || fail "host $h must be accepted: $OUT"
+done
+printf '{"host":"gemini"}' > "$H/b.json"
+OUT=$(python3 "$SETUP" check --root "$WORK/bare" || true)
+echo "$OUT" | q '.green == false and (.host_errors | to_entries | .[0].value | test("gemini"))' \
+  || fail "host gemini must be flagged: $OUT"
+TXT=$(python3 "$SETUP" check --root "$WORK/bare" --text || true)
+echo "$TXT" | grep -q "✗ .*b.json.*gemini" || fail "text report must name the bad host: $TXT"
+python3 "$SETUP" fix --root "$WORK/bare" --no-helpers >/dev/null || true
+q '.host == "gemini"' "$H/b.json" || fail "fix must not guess over a set host: $(cat "$H/b.json")"
+rm "$H/b.json"
+
+echo "PASS: test-setup.sh (13 scenarios)"