fix(check): tolerate an unverifiable check instead of dying on it

bin/check-mcp-env exits 2 for "could not run" -- no jq, or no env-file --
and the gate was written to report that as a NOTE rather than fail:

    "$DIR/check-mcp-env" "$DIR/.mcp.json" "$HOME/.op-env"
    case $? in 0) ;; 2) echo "NOTE: ..." ;; *) fail=1 ;; esac

That tolerance never executed. Task runs each cmds block under `sh -e`, so
a bare command exiting non-zero aborts the shell before `case $?` is
reached. main went red on the very commit that added the check (run #57),
with `task: Failed to run task "check": exit status 2`.

It passed locally because this host has both jq and ~/.op-env, so the
check exited 0 and the untested branch never ran. CI has neither. A
tolerated exit code that is only tolerated where it never fires is not
tolerated at all.

`|| rc=$?` puts the invocation in a compound command, which `set -e`
exempts, so `case` is reached. Both exit-2 paths verified: no env-file
(the new test's precondition) and no jq (PATH sandbox, same SKIP message
CI printed).

The test pins the tolerance itself rather than the checker: it points HOME
at an empty directory, which is exactly CI's condition, and asserts `task
check` exits 0 AND still says it could not verify -- silence would mean
skipped rather than tolerated.

Bump-Type: patch

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "skills",
   "description": "Mathias's engineering skills library, plus the hooks and MCP servers that make it enforceable: TDD, clean code, debugging, specs, discovery, CI, and secret hygiene.",
-  "version": "0.18.0",
+  "version": "0.19.1",
   "author": {
     "name": "Mathias",
     "url": "https://git.d-ma.be/mathias"

.mcp.json

@@ -1,5 +1,5 @@
 {
-  "_comment": "Tailscale Serve on koala, not the public d-ma.be hostnames. The public path exits to Cloudflare and NPM to reach a k3s service on the same machine most sessions run on, which imposes rate limits and message-size caps on tool results. Serve terminates TLS with a real Tailscale cert and proxies to the NodePort over loopback, so traffic reaches the service from koala itself and satisfies the default-deny-ingress NetworkPolicy with no cluster change. Clients need 'tailscale set --accept-dns=true' for the MagicDNS name to resolve; see mathias/skills#24.",
+  "_comment": "Tailscale Serve on koala, not the public d-ma.be hostnames. The public path exits to Cloudflare and NPM to reach a k3s service on the same machine most sessions run on, which imposes rate limits and message-size caps on tool results. Serve terminates TLS with a real Tailscale cert and proxies to the NodePort over loopback, so traffic reaches the service from koala itself and satisfies the default-deny-ingress NetworkPolicy with no cluster change. Clients need 'tailscale set --accept-dns=true' for the MagicDNS name to resolve; see mathias/skills#24. Every ${VAR} below must be one ~/.op-env defines -- bin/check-mcp-env enforces that, because an undefined one sends an empty Authorization header and reports as 'requires authentication', which is indistinguishable from a revoked credential.",
   "mcpServers": {
     "brain": {
       "type": "http",
@@ -11,23 +11,24 @@
     "infra": {
       "type": "http",
       "url": "https://koala.tail30472e.ts.net:8444/mcp"
+    },
+    "gitea": {
+      "_comment": "gitea-mcp authenticates by PASS-THROUGH: the bearer is a Gitea PAT, which the server validates against Gitea and then acts as. So no dedicated MCP token is needed, and the AgentSecrets blocker that parked this entry (skills#32, #33) never applied to it -- DMABE_GITEA_API_TOKEN is op://HomeLab and already in the session environment. Verified 2026-09-07: initialize 200 (serverInfo gitea-mcp) and tools/list returns 41 tools. Two DIFFERENT PATs both authenticate while GITEA_MCP_TOKEN 401s, which is what proves this is pass-through validation and not a static-token comparison.",
+      "type": "http",
+      "url": "https://koala.tail30472e.ts.net:8446/mcp",
+      "headers": {
+        "Authorization": "Bearer ${DMABE_GITEA_API_TOKEN}"
+      }
     }
   },
   "_parked": {
-    "_reason": "cad and gitea-mcp are proxied, reachable and AUTHENTICATING: tailscale serve 8445 -> 127.0.0.1:31877 and 8446 -> 127.0.0.1:30340; an MCP initialize with the correct bearer returns 200 from both (serverInfo gitea-mcp 0.1.0, cad aed2aaf). They stay parked only because nothing puts those two tokens into the session environment. Both live in the 1Password AgentSecrets vault, and by deliberate design (infra#224, closed) no single identity on koala reads both vaults: koala-homelab is HomeLab-only and resolves ~/.op-env, koala-agentsecrets-write is AgentSecrets-only and lives in ~/.op-agent-write.env. Adding an AgentSecrets reference to ~/.op-env does NOT degrade gracefully -- `op run` fails wholesale and every other token, BRAIN_MCP_TOKEN included, goes unresolved with it. Enabling needs a read-scoped AgentSecrets identity in the session-env path; see mathias/skills#32, #33.",
+    "_reason": "cad is proxied, reachable and AUTHENTICATING: tailscale serve 8445 -> 127.0.0.1:31877, and an MCP initialize with the correct bearer returns 200 (serverInfo cad aed2aaf). It stays parked only because nothing puts CAD_MCP_TOKEN into the session environment. It lives in the 1Password AgentSecrets vault, and by deliberate design (infra#224, closed) no single identity on koala reads both vaults: koala-homelab is HomeLab-only and resolves ~/.op-env, koala-agentsecrets-write is AgentSecrets-only and lives in ~/.op-agent-write.env. Adding an AgentSecrets reference to ~/.op-env does NOT degrade gracefully -- `op run` fails wholesale and every other token, BRAIN_MCP_TOKEN included, goes unresolved with it. Enabling needs a read-scoped AgentSecrets identity in the session-env path; see mathias/skills#32, #33. gitea was parked here for the same stated reason and has been unparked: it needs no AgentSecrets token at all, because gitea-mcp is pass-through-authenticated.",
     "cad": {
       "type": "http",
       "url": "https://koala.tail30472e.ts.net:8445/mcp",
       "headers": {
         "Authorization": "Bearer ${CAD_MCP_TOKEN}"
       }
-    },
-    "gitea": {
-      "type": "http",
-      "url": "https://koala.tail30472e.ts.net:8446/mcp",
-      "headers": {
-        "Authorization": "Bearer ${GITEA_MCP_STATIC_TOKEN}"
-      }
     }
   }
 }

Taskfile.yml

@@ -138,6 +138,26 @@ tasks:
           echo "ERROR: missing .claude-plugin/plugin.json" >&2; fail=1
         fi
 
+        # Every ${VAR} a live .mcp.json server interpolates must be one the
+        # session env-file defines. An undefined one is silent: the header
+        # goes out empty and the server reports "requires authentication",
+        # which reads as a revoked credential. Exit 2 means the check could
+        # not run (no jq, or no env-file — CI has neither); that is reported
+        # and not fatal, but it is never treated as a pass.
+        if [ -x "{{.TASKFILE_DIR}}/bin/check-mcp-env" ]; then
+          # `|| rc=$?` is load-bearing, not style. Task runs this block under
+          # `sh -e`, so a bare invocation exiting non-zero kills the shell
+          # before `case` is reached -- the tolerance below never ran, and the
+          # gate died with `exit status 2` on the commit that added it.
+          rc=0
+          "{{.TASKFILE_DIR}}/bin/check-mcp-env" "{{.TASKFILE_DIR}}/.mcp.json" "$HOME/.op-env" || rc=$?
+          case $rc in
+            0) ;;
+            2) echo "NOTE: MCP env wiring unverified on this host" >&2 ;;
+            *) fail=1 ;;
+          esac
+        fi
+
         if [ $fail -ne 0 ]; then
           echo "check FAILED" >&2; exit 1
         fi

bin/check-mcp-env

@@ -0,0 +1,89 @@
+#!/bin/sh
+# check-mcp-env — assert every variable a live MCP server interpolates is one
+# the session env-file actually defines.
+#
+# Why this is a gate and not a comment: the failure is silent. A header of
+# "Bearer ${FOO}" where FOO is undefined does not error -- it goes out empty,
+# the server answers 401, and Claude Code reports "requires authentication",
+# which reads exactly like a revoked credential. On 2026-09-07 that cost a
+# full investigation on koala before the credential turned out to be fine.
+#
+# Servers under `_parked` are exempt by design. Parked means "reachable, but
+# nothing puts its token in the environment yet" -- flagging those would
+# report the intended state as a fault.
+#
+# Usage:  check-mcp-env <mcp.json> <env-file>
+#
+# Exit 0  every live server's variables are defined
+#      1  at least one is not, named on stderr
+#      2  could not verify (bad usage, unreadable input, jq absent).
+#         Deliberately distinct from 0: an unverified config is not a clean
+#         one, and a gate that cannot run should say so rather than pass.
+
+set -u
+
+CONFIG=${1:-}
+ENVFILE=${2:-}
+
+if [ -z "$CONFIG" ] || [ -z "$ENVFILE" ]; then
+  echo "usage: check-mcp-env <mcp.json> <env-file>" >&2
+  exit 2
+fi
+
+if ! command -v jq >/dev/null 2>&1; then
+  echo "SKIP: jq not installed -- MCP env wiring unverified" >&2
+  exit 2
+fi
+
+if [ ! -f "$CONFIG" ]; then
+  echo "ERROR: no such config: $CONFIG" >&2
+  exit 2
+fi
+
+if [ ! -f "$ENVFILE" ]; then
+  echo "ERROR: no such env-file: $ENVFILE -- cannot verify MCP variables" >&2
+  exit 2
+fi
+
+# Every "<server>\t<VAR>" pair a live server interpolates. `..` walks the whole
+# value, so a variable is found wherever it is placed, not only under headers.
+refs=$(jq -r '
+  .mcpServers // {}
+  | to_entries[]
+  | .key as $server
+  | (.value | .. | strings)
+  | select(test("\\$\\{"))
+  | [ scan("\\$\\{([A-Za-z_][A-Za-z0-9_]*)\\}")[] ]
+  | .[]
+  | "\($server)\t\(.)"
+' "$CONFIG" 2>/dev/null) || {
+  echo "ERROR: $CONFIG is not valid JSON -- MCP env wiring unverified" >&2
+  exit 2
+}
+
+if [ -z "$refs" ]; then
+  echo "check-mcp-env: no interpolated variables in live servers"
+  exit 0
+fi
+
+fail=0
+checked=0
+for pair in $(printf '%s\n' "$refs" | tr '\t' ':'); do
+  server=${pair%%:*}
+  var=${pair#*:}
+  checked=$((checked + 1))
+  if grep -qE "^[[:space:]]*(export[[:space:]]+)?$var=" "$ENVFILE"; then
+    continue
+  fi
+  printf 'ERROR: MCP server %s interpolates %s, which %s does not define.\n' \
+    "$server" "$var" "$ENVFILE" >&2
+  printf '       It will send an empty Authorization header and report as "requires authentication".\n' >&2
+  fail=1
+done
+
+if [ "$fail" -ne 0 ]; then
+  exit 1
+fi
+
+printf 'check-mcp-env: %d interpolated variable(s) across live MCP servers, all defined in %s\n' \
+  "$checked" "$ENVFILE"

skills/adr/SKILL.md

@@ -58,8 +58,8 @@ adr:           0004
 title:         <the decision, as a sentence — not "database choice">
 status:        proposed | accepted | superseded | amended
 date:          2026-08-29
-deciders:      <who accepted it, by name — or "pending: <name>" while proposed>
+deciders:      <who accepted it, by name — or "pending: <name>" (QUOTED) while proposed>
-supersedes:    <adr number, or ->
+supersedes:    <adr number, or null>
 ---
 
 # ADR-0004 — <same title>
@@ -97,6 +97,25 @@ the condition that fires a revisit. An ADR with no validation section is a prefe
 with a template around it.
 ```
 
+### The frontmatter must actually parse
+
+It exists to be machine-read, so a block that does not load is worse than no block at
+all: it drops that ADR silently out of every "what is still open?" query, while looking
+correct. Two shapes this template used to suggest are invalid YAML, and both were found
+live in the estate on 2026-09-05 — `openbanking-api` ADR-0001 and `infra` ADR-0019, each
+copied verbatim from here:
+
+| Wrong | Why | Right |
+|---|---|---|
+| `supersedes:    -` | a bare dash is a YAML *sequence entry*, not a string | `supersedes:    null` |
+| `deciders:      pending: Mathias` | the second, unquoted colon reads as a nested mapping | `deciders:      "pending: Mathias"` |
+
+Check before committing:
+
+```sh
+python3 -c "import yaml,sys;yaml.safe_load(open(sys.argv[1]).read().split('---')[1]);print('ok')" docs/adr/0004-*.md
+```
+
 ## Preserving a productive tension
 
 Some tradeoffs are not unresolved because nobody thought hard enough. They are

tests/check_tolerates_unverifiable_test.sh

@@ -0,0 +1,70 @@
+#!/bin/sh
+# `task check` must survive a check that reports "could not verify".
+#
+# The regression these exist for: bin/check-mcp-env exits 2 to mean "I could
+# not run — no jq, or no env-file", which the gate deliberately treats as a
+# reported NOTE rather than a failure. The Taskfile said exactly that:
+#
+#   "$DIR/check-mcp-env" "$DIR/.mcp.json" "$HOME/.op-env"
+#   case $? in 0) ;; 2) echo "NOTE: ..." ;; *) fail=1 ;; esac
+#
+# and it did not work. Task runs each cmds block under `sh -e`, so a bare
+# command exiting non-zero aborts the shell *before* `case $?` is ever
+# reached. The whole gate died with `exit status 2`. Locally the check found
+# jq and exited 0, so it went green; CI has neither jq nor ~/.op-env, so main
+# went red on the very commit that added it (skills run #57, 2026-09-07).
+#
+# A tolerated exit code that is only tolerated on the host where it never
+# fires is not tolerated at all. This pins the tolerance itself.
+#
+# No mocking: pointing HOME at an empty directory removes ~/.op-env, which is
+# exactly the condition CI runs under, so check-mcp-env genuinely exits 2.
+
+set -u
+
+ROOT=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+
+pass=0
+fail=0
+
+ok() { pass=$((pass + 1)); printf '  ok   %s\n' "$1"; }
+no() { fail=$((fail + 1)); printf '  FAIL %s\n' "$1"; }
+
+if ! command -v task >/dev/null 2>&1; then
+  printf '  SKIP: task not installed -- cannot exercise the gate\n'
+  exit 0
+fi
+
+TMP=$(mktemp -d)
+trap 'rm -rf "$TMP"' EXIT
+
+# Sanity: the precondition must actually hold, or the test proves nothing.
+# An empty HOME means no ~/.op-env, so check-mcp-env cannot verify anything.
+"$ROOT/bin/check-mcp-env" "$ROOT/.mcp.json" "$TMP/.op-env" >/dev/null 2>&1
+rc=$?
+if [ "$rc" -eq 2 ]; then
+  ok 'precondition: check-mcp-env exits 2 when the env-file is absent'
+else
+  no "precondition: expected check-mcp-env to exit 2, got $rc"
+fi
+
+# The assertion. `task check` must still pass, and must say why it could not
+# verify -- silence would mean the check was skipped rather than tolerated.
+out=$(HOME="$TMP" task --dir "$ROOT" check 2>&1)
+rc=$?
+
+if [ "$rc" -eq 0 ]; then
+  ok 'task check passes when MCP env wiring cannot be verified'
+else
+  no "task check exited $rc when check-mcp-env reported unverifiable"
+  printf '%s\n' "$out" | sed 's/^/       | /' | tail -8
+fi
+
+if printf '%s' "$out" | grep -q 'unverified'; then
+  ok 'the unverifiable check is reported, not silently skipped'
+else
+  no 'no NOTE reported -- an unverifiable check must never look like a pass'
+fi
+
+printf '  %d passed, %d failed\n' "$pass" "$fail"
+[ "$fail" -eq 0 ]

tests/mcp_config_test.sh

@@ -0,0 +1,118 @@
+#!/bin/sh
+# Tests for bin/check-mcp-env.
+#
+# The fault this gate exists for is silent, which is why it needs a gate at
+# all. An `.mcp.json` server whose Authorization header interpolates a
+# variable nothing in the session environment defines does not error: the
+# header goes out empty, the server answers 401, and Claude Code reports
+# "requires authentication". That is indistinguishable from a revoked or
+# expired credential, and on 2026-09-07 it cost a full investigation on koala
+# to establish that the credential was fine and the variable was simply never
+# set.
+#
+# So the property is: every ${VAR} a LIVE server interpolates must be a
+# variable the session env-file actually defines.
+#
+# The `_parked` block is deliberately exempt. Parked servers reference
+# variables nothing provides on purpose -- that is what parked means -- and a
+# gate that flagged them would be reporting the intended state as a fault.
+#
+# Fixtures drive the checker through argv, so no test touches the real host.
+
+set -u
+
+ROOT=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+CHECK="$ROOT/bin/check-mcp-env"
+
+pass=0
+fail=0
+WORK=${TMPDIR:-/tmp}/mcp_config_test.$$
+
+if [ ! -f "$CHECK" ]; then
+  printf 'FAIL: %s does not exist\n' "$CHECK"
+  exit 1
+fi
+
+cleanup() { rm -rf "$WORK"; }
+trap cleanup EXIT INT TERM
+mkdir -p "$WORK"
+
+if ! command -v jq >/dev/null 2>&1; then
+  printf 'SKIP: jq not installed -- bin/check-mcp-env cannot be exercised\n'
+  exit 0
+fi
+
+# ok <name> / bad <name> <detail>
+ok()  { pass=$((pass+1)); printf '  ok   %s\n' "$1"; }
+bad() { fail=$((fail+1)); printf '  FAIL %s  %s\n' "$1" "${2:-}"; }
+
+# run <mcp-json> <env-file> -> sets $rc and $out
+run() {
+  out=$("$CHECK" "$1" "$2" 2>&1); rc=$?
+}
+
+ENVFILE="$WORK/op-env"
+cat > "$ENVFILE" <<'ENVEOF'
+BRAIN_MCP_TOKEN=op://HomeLab/brain/token
+DMABE_GITEA_API_TOKEN=op://HomeLab/gitea/token
+ENVEOF
+
+# --- a live server whose variable IS defined ---------------------------------
+cat > "$WORK/good.json" <<'JSONEOF'
+{"mcpServers":{"brain":{"type":"http","url":"https://x/mcp",
+ "headers":{"Authorization":"Bearer ${BRAIN_MCP_TOKEN}"}}}}
+JSONEOF
+run "$WORK/good.json" "$ENVFILE"
+[ "$rc" -eq 0 ] && ok "defined variable passes" || bad "defined variable passes" "rc=$rc $out"
+
+# --- a live server whose variable is NOT defined ------------------------------
+# The exact shape that broke: the server looks correct and fails at runtime.
+cat > "$WORK/missing.json" <<'JSONEOF'
+{"mcpServers":{"gitea":{"type":"http","url":"https://x/mcp",
+ "headers":{"Authorization":"Bearer ${GITEA_MCP_STATIC_TOKEN}"}}}}
+JSONEOF
+run "$WORK/missing.json" "$ENVFILE"
+if [ "$rc" -ne 0 ]; then
+  case "$out" in
+    *gitea*GITEA_MCP_STATIC_TOKEN*) ok "undefined variable is flagged, naming server and variable" ;;
+    *) bad "undefined variable is flagged, naming server and variable" "report did not name both: $out" ;;
+  esac
+else
+  bad "undefined variable is flagged, naming server and variable" "rc=0"
+fi
+
+# --- a server with no headers at all (the `infra` shape) ----------------------
+# Unauthenticated by design. Nothing to resolve, so nothing to flag.
+cat > "$WORK/noauth.json" <<'JSONEOF'
+{"mcpServers":{"infra":{"type":"http","url":"https://x/mcp"}}}
+JSONEOF
+run "$WORK/noauth.json" "$ENVFILE"
+[ "$rc" -eq 0 ] && ok "header-less server is not flagged" || bad "header-less server is not flagged" "rc=$rc $out"
+
+# --- parked servers are exempt ------------------------------------------------
+cat > "$WORK/parked.json" <<'JSONEOF'
+{"mcpServers":{"brain":{"type":"http","url":"https://x/mcp",
+  "headers":{"Authorization":"Bearer ${BRAIN_MCP_TOKEN}"}}},
+ "_parked":{"_reason":"no identity provides these yet",
+  "cad":{"type":"http","url":"https://x/mcp",
+   "headers":{"Authorization":"Bearer ${CAD_MCP_TOKEN}"}}}}
+JSONEOF
+run "$WORK/parked.json" "$ENVFILE"
+if [ "$rc" -eq 0 ]; then
+  ok "parked server is exempt"
+else
+  bad "parked server is exempt" "rc=$rc $out"
+fi
+
+# --- malformed JSON must not pass silently ------------------------------------
+# A config the checker cannot read is an unverified config, not a clean one.
+printf '{"mcpServers":{' > "$WORK/broken.json"
+run "$WORK/broken.json" "$ENVFILE"
+[ "$rc" -ne 0 ] && ok "unparseable config does not report success" || bad "unparseable config does not report success" "rc=0"
+
+# --- a missing env-file is unverifiable, not clean ----------------------------
+run "$WORK/good.json" "$WORK/no-such-env"
+[ "$rc" -ne 0 ] && ok "missing env-file does not report success" || bad "missing env-file does not report success" "rc=0"
+
+printf '\n%s: %d passed, %d failed\n' "$(basename "$0")" "$pass" "$fail"
+[ "$fail" -eq 0 ]