fix(cli): <plugin> config set writes the value instead of printing

CHANGELOG.md

@@ -64,6 +64,32 @@ number. Their individual histories are preserved under
   and signposts the config layer, which was useful with zero gates installed and started
   at line 340 of 878.
 
+## [Unreleased]
+
+### Fixed
+
+- **`<plugin> config set` printed the config and changed nothing.** The plugin shim's
+  `config` case forwarded everything to `cmd_config show` as trailing arguments, which
+  ignores them — so `temper config set auto_nudge_lines 300` exited 0 having set
+  nothing, and `cairn config reset local` did the same. That is the *reports success,
+  did nothing* failure mode, in the CLI of a tool built to catch it.
+
+  The shim now forwards the subcommand and resolves the key's section from the manifest
+  schema, which is the point of having a shim at all:
+
+  ```bash
+  temper config set auto_nudge_lines 300   # → [temper] auto_nudge_lines
+  cairn  config set trailers Signed-off-by # → [git] trailers — cairn declares it there
+  cairn  config set pr.base develop        # → [cairn] pr.base, dots intact
+  ```
+
+  `get`, `unset` and `explain` are namespaced the same way; `doctor`, `path` and `edit`
+  pass through unchanged; an already-qualified key is not prefixed twice; and an
+  unrecognised subcommand now exits 1 naming the real ones instead of silently showing.
+
+- The `trailers` doc string suggested `Co-Authored-By`, and that text is written into
+  every config file the tool generates. It now suggests `Signed-off-by`.
+
 ## [1.5.0] — 2026-07-31
 
 ### Changed

README.md

@@ -719,6 +719,15 @@ Every plugin answers to its own name — `aether cairn status` — and the `cair
 `temper`, `whetstone` and `bonsai` binaries are 24-line shims that exec exactly
 that, so there is one implementation.
 
+A plugin's `config` subcommand takes the same verbs as `aether config` and resolves the
+section from the schema, so you do not have to know which one a key lives in — including
+the keys cairn declares under `[git]`:
+
+```
+cairn config set trailers Signed-off-by     ≡  aether config set git.trailers Signed-off-by
+temper config set auto_nudge_lines 300      ≡  aether config set temper.auto_nudge_lines 300
+```
+
 `enable`/`disable` writes `enabled: false` for the gate to read; `hook
 enable`/`disable` stops the gate being loaded. The soft mute is usually what you
 want.

bin/aether

@@ -1435,6 +1435,30 @@ _cfg_origin() {
   printf 'default||'
 }
 
+# _plugin_section_for <plugin> <key> -> the [section] that plugin declares <key> under
+#
+# Not always the plugin's own section: cairn declares `trailers` under [git], because a
+# house rule about commit text is not a cairn setting. The schema already records that
+# (`config.<key>.section:`), so this is a lookup rather than a second place to encode it.
+_plugin_section_for() {
+  # No `exit` in the awk — see the note under _schema_plugin_for. Exiting early closes
+  # the pipe while _schema_all is still writing, and bash on Linux reports the EPIPE as
+  # `printf: write error: Broken pipe` into whatever the caller captured.
+  local s
+  s=$(_schema_all | awk -F'|' -v p="$1" -v k="$2" '$3 == p && $2 == k && !f { print $1; f = 1 }')
+  [ -n "$s" ] && { printf '%s' "$s"; return 0; }
+  # Unknown key: fall back to the plugin's own section so `cmd_config set` reaches its
+  # "no plugin declares this" warning instead of us inventing a section here.
+  s=$(_mf "$1" config_section); printf '%s' "${s:-$1}"
+}
+
+# _is_known_section <name> -> 0 when some manifest declares keys under it
+# The `exit` here is in END, after all input is read, so it cannot close the pipe early.
+_is_known_section() {
+  [ -n "$1" ] || return 1
+  _schema_all | awk -F'|' -v s="$1" '$1 == s { found = 1 } END { exit !found }'
+}
+
 _split_key() {           # temper.auto_nudge_lines -> "temper auto_nudge_lines"
   case "$1" in
     *.*) printf '%s %s' "${1%%.*}" "${1#*.}" ;;
@@ -2976,7 +3000,41 @@ case "$COMMAND" in
         # `aether uninstall` and the three plugin updates before it.
         update)    cmd_install "$_PLUGIN" "$(_manifest_get scope)" "$@" ;;
         hook)      cmd_hook "$@" "$_PLUGIN" ;;
-        config)    cmd_config show "$(_mf "$_PLUGIN" config_section || printf '%s' "$_PLUGIN")" "$@" ;;
+        # `temper config set auto_nudge_lines 300` used to reach `cmd_config show` with
+        # the rest as trailing arguments, which ignores them — so it printed the config
+        # and exited 0 having changed nothing. Forward the subcommand instead, and
+        # namespace the key, since the shim exists precisely so you do not have to know
+        # which section a key lives in.
+        config)
+          _csub="${1:-show}"
+          case "$_csub" in
+            show|'')
+              shift 2>/dev/null || true
+              cmd_config show "$(_mf "$_PLUGIN" config_section || printf '%s' "$_PLUGIN")" "$@" ;;
+            doctor|path|edit)
+              # Not section-scoped — these answer for the whole config file.
+              shift; cmd_config "$_csub" "$@" ;;
+            get|explain|set|unset)
+              shift
+              _ckey="${1:-}"
+              if [ -z "$_ckey" ]; then
+                printf 'Usage: %s config %s <key> %s\n' "$_PLUGIN" "$_csub" \
+                  "$([ "$_csub" = set ] && printf '<value> ' )[global]"
+                exit 1
+              fi
+              shift
+              # A key given fully qualified is passed through: prefixing again would
+              # write temper.temper.auto_nudge_lines.
+              if _is_known_section "$(_split_key "$_ckey" | cut -d' ' -f1)"; then
+                cmd_config "$_csub" "$_ckey" "$@"
+              else
+                cmd_config "$_csub" "$(_plugin_section_for "$_PLUGIN" "$_ckey").$_ckey" "$@"
+              fi ;;
+            *)
+              printf 'Unknown %s config subcommand: %s\n\n' "$_PLUGIN" "$_csub"
+              printf 'Try: show, get, set, unset, explain, doctor, path, edit\n'
+              exit 1 ;;
+          esac ;;
         help|--help|-h) usage ;;
         *) printf 'Unknown %s subcommand: %s\n' "$_PLUGIN" "$sub"; exit 1 ;;
       esac

plugins/cairn/README.md

@@ -306,6 +306,8 @@ A global install also provides a `cairn` command for managing your setup:
 ```bash
 cairn status                       # install state + resolved config
 cairn config                       # show the resolved [cairn] section, with sources
+cairn config set style plain       # set a key, section resolved for you
+cairn config get|unset style       # read or remove one
 
 cairn disable local                # silence /draft-commit for this project
 cairn disable global               # silence everywhere
@@ -315,15 +317,18 @@ cairn update                       # reinstall cairn from the clone
 cairn uninstall global --claude-md # full removal
 ```
 
-`cairn` is a shim that execs `aether cairn …`. **Changing a value is `aether config set
-<section>.<key> <value>`** — namespaced, space-separated, no `=`. The plugin shim's
-`config` only shows:
+`cairn` is a shim that execs `aether cairn …`. Values are space-separated, never `=`.
+`cairn config set` resolves the section from the schema — including the `[git]` keys,
+which are cairn's to declare but do not live in `[cairn]`:
 
 ```bash
-aether config set cairn.style plain
-aether config set cairn.pr.base develop
+cairn config set style plain            # → [cairn] style
+cairn config set trailers Signed-off-by # → [git] trailers  (resolved from the schema)
+cairn config set pr.base develop        # → [cairn] pr.base
+cairn config unset summary.window
+
+aether config set cairn.style plain     # the explicit form, always available
 aether config set git.ticket 'TK-[0-9]+'
-aether config unset cairn.summary.window
 ```
 
 Run `aether help` for the full reference.

plugins/cairn/aether.plugin

@@ -118,7 +118,7 @@ config.ticket.used_by: /draft-commit /draft-pr /critique-pr
 
 config.trailers.section: git
 config.trailers.default:
-config.trailers.doc: Trailers every commit message must carry, e.g. Co-Authored-By
+config.trailers.doc: Trailers every commit message must carry, e.g. Signed-off-by
 config.trailers.used_by: /draft-commit
 
 config.base.section: git

plugins/temper/README.md

@@ -189,13 +189,21 @@ temper status                     Install state and resolved config
 temper enable  [local|global]     Enable temper
 temper disable [local|global]     Disable temper
 temper config                     Show the resolved [temper] section
+temper config set <key> <value>   Set a key, without naming the section
+temper config get|unset <key>     Read or remove one
 temper update                     Reinstall temper from the clone
 temper uninstall [global] [--claude-md]
 ```
 
 `temper` is a shim that execs `aether temper …`, so `aether temper status` is the same
-command. **Changing a value is `aether config set`**, not `temper config set` — the
-plugin shim's `config` only shows.
+command. `temper config set` resolves the section for you from the schema, which is the
+point of the shim:
+
+```bash
+temper config set auto_nudge_lines 300          # → [temper] auto_nudge_lines
+temper config set auto_nudge_lines 300 global   # → ~/.aether/config
+aether config set temper.auto_nudge_lines 300   # the explicit form, always available
+```
 
 ---
 

plugins/whetstone/README.md

@@ -209,6 +209,8 @@ A global install also provides a `whetstone` command for managing your setup:
 ```bash
 whetstone status                          # install state + resolved config
 whetstone config                          # show the resolved [whetstone] section
+whetstone config set severity red         # set a key, section resolved for you
+whetstone config get|unset severity       # read or remove one
 
 whetstone disable local                   # silence for this project
 whetstone disable global                  # silence everywhere
@@ -218,8 +220,9 @@ whetstone update                          # reinstall whetstone from the clone
 whetstone uninstall global --claude-md    # full removal
 ```
 
-`whetstone` is a shim that execs `aether whetstone …`. **Changing a value is `aether
-config set <key> <value>`** — the plugin shim's `config` only shows.
+`whetstone` is a shim that execs `aether whetstone …`. `whetstone config set` resolves
+the section from the schema; `aether config set whetstone.<key> <value>` is the explicit
+form and always works. Append `global` to either to write `~/.aether/config`.
 
 Run `aether help` for the full reference.
 

tests/test_cli.sh

@@ -29,6 +29,84 @@ assert_contains "$out" "aether version" "help documents version"
 out=$(bash "$CLI" nonsense 2>&1); e=$?
 assert_exit 1 "$e" "unknown subcommand exits 1"
 
+# ── plugin config subcommands ────────────────────────────────────────────────
+# `temper config set auto_nudge_lines 300` used to reach `cmd_config show` with the rest
+# as trailing arguments, which ignores them: it printed the config and exited 0 having
+# changed nothing. The regression assertion is the first one, because a silent success is
+# the failure mode this project exists to catch, and it was in its own CLI.
+suite "plugin config subcommands"
+
+PC_HOME=$(new_home)
+PC_DIR=$(mktemp -d); FAKE_HOMES+=("$PC_DIR")
+( cd "$PC_DIR" && git init -q . && mkdir -p .aether )
+
+pc() { ( cd "$PC_DIR" && env HOME="$PC_HOME" AETHER_REPO="$REPO" bash "$CLI" "$@" 2>&1 ); }
+pc_cfg() { cat "$PC_DIR/.aether/config" 2>/dev/null; }
+
+out=$(pc temper config set auto_nudge_lines 300); e=$?
+assert_exit 0 "$e" "temper config set exits 0"
+assert_contains "$(pc_cfg)" "auto_nudge_lines: 300" "…and actually writes the value"
+assert_contains "$out" "temper.auto_nudge_lines" "…naming the resolved section.key"
+
+# cairn declares `trailers` under [git], not [cairn] — the shim has to read the schema
+# rather than assume the plugin's own section.
+pc cairn config set trailers Signed-off-by >/dev/null
+assert_contains "$(pc_cfg)" "[git]" "a key declared under [git] lands in [git]"
+
+# `_split_key` splits on the first dot, so a bare `pr.base` would resolve to section
+# `pr`. Prefixing is what makes dotted keys work.
+pc cairn config set pr.base develop >/dev/null
+assert_contains "$(pc_cfg)" "pr.base: develop" "a dotted key keeps its dots"
+case "$(pc_cfg)" in
+  *"[pr]"*) fail "a dotted key does not invent a [pr] section" "found [pr]" ;;
+  *) pass "a dotted key does not invent a [pr] section" ;;
+esac
+
+# Already qualified: prefixing again would write temper.temper.auto_nudge_lines.
+pc temper config set temper.auto_nudge_lines 400 >/dev/null
+case "$(pc_cfg)" in
+  *temper.temper*) fail "an already-qualified key is not prefixed twice" "found temper.temper" ;;
+  *) pass "an already-qualified key is not prefixed twice" ;;
+esac
+assert_eq "400" "$(pc temper config get auto_nudge_lines)" "get reads the value back"
+
+pc temper config unset auto_nudge_lines >/dev/null
+case "$(pc_cfg)" in
+  *auto_nudge_lines*) fail "unset removes the key" "still present" ;;
+  *) pass "unset removes the key" ;;
+esac
+
+# Scope still resolves through cmd_config, which the shim now actually reaches.
+pc temper config set auto_nudge_lines 500 global >/dev/null
+assert_contains "$(cat "$PC_HOME/.aether/config" 2>/dev/null)" "auto_nudge_lines: 500" \
+  "the global scope argument still works"
+
+out=$(pc temper config); e=$?
+assert_exit 0 "$e" 'bare temper config still shows'
+assert_contains "$out" "[temper]" "…the plugin's own section"
+
+out=$(pc temper config bogus); e=$?
+assert_exit 1 "$e" "an unknown config subcommand exits 1"
+assert_contains "$out" "Try: show" "…and names the real ones"
+
+out=$(pc temper config set); e=$?
+assert_exit 1 "$e" "set with no key exits 1"
+assert_contains "$out" "Usage" "…with a usage line"
+
+# The shim's section lookup pipes _schema_all into awk, which is the shape that
+# produced `printf: write error: Broken pipe` once before: an `exit` in the awk closes
+# the pipe mid-write and bash on Linux reports the EPIPE into whatever the caller
+# captured. macOS dies from SIGPIPE silently, so this must be asserted directly rather
+# than left for a value comparison to notice — it passed locally and failed in CI.
+for c in "temper config set auto_nudge_lines 300" "temper config get auto_nudge_lines" \
+         "temper config unset auto_nudge_lines" "cairn config set trailers Signed-off-by" \
+         "cairn config explain pr.base" "temper config"; do
+  # shellcheck disable=SC2086
+  err=$( cd "$PC_DIR" && env HOME="$PC_HOME" AETHER_REPO="$REPO" bash "$CLI" $c 2>&1 >/dev/null )
+  if [ -z "$err" ]; then pass "no stderr from: $c"
+  else fail "no stderr from: $c" "${err%%$'\n'*}"; fi
+done
+
 # ── status against a real install ────────────────────────────────────────────
 suite "status"
 H=$(new_home)