v0.35.2 lwconf, doc and deploy update

2026-10-13 14:23:37 -04:00
1 parent 0b8701ec13
commit de87b9a008
@@ -31,8 +31,9 @@ function script(src, integrity) {
 }

 // Engine's calls take objects or JSON text and return the engine's answer,
-// {value} or {error, path?, pipeline?, node?, key?}; dirs answers whether a
-// preset path is a directory, {"/var/log/app.log": false}
+// {value} or {error, path?, pipeline?, node?, key?, ask?}; ask is the path a
+// preset names whose kind dirs must answer: pass dirs {[ask]: true for a
+// directory, false for a file} and call again
 export class Engine {
  #api;
  constructor(api) { this.#api = api; }
@@ -72,10 +72,22 @@ test("load takes an engine a server sends as plain bytes", async () => {
  }
 });

+// A path neither ending in '/' nor holding a glob is a question, in a preset
+// or a pasted one, whose ask dirs answers
+test("a preset path of unknown kind is asked, and dirs answers it", () => {
+  const path = { path: "/var/log/app.log" }, dirs = { "/var/log/app.log": false };
+  const asked = engine.preset("tail", path);
+  assert.deepEqual([asked.path, asked.ask, asked.value], ["path", "/var/log/app.log", undefined]);
+  assert.match(asked.error, /^path: "\/var\/log\/app\.log": a directory or a file\? end a directory with \//);
+  const pasted = engine.parse("lw -p tail:path=/var/log/app.log", "command");
+  assert.deepEqual([pasted.path, pasted.ask], ["path", "/var/log/app.log"]);
+  const { value: pipelines } = engine.preset("tail", path, dirs);
+  assert.deepEqual(value(pipelines, 0, { role: "source", id: "file" }), { directory: "/var/log", pattern: "app.log", from: "end" });
+});
+
 // The environment holds one pipeline, which a preset makes
 test("a preset's pipeline, a single file answered by dirs, reads back from every form", () => {
  const path = { path: "/var/log/app.log" }, dirs = { "/var/log/app.log": false };
-  assert.deepEqual(engine.preset("tail", path), { error: "path: a directory or a file pattern?", path: "path" });
  const { value: pipelines } = engine.preset("serve", { ...path, allow: ["192.0.2.0/24", "198.51.100.7"] }, dirs);
  assert.deepEqual(value(pipelines, 0, { role: "source", id: "file" }), { directory: "/var/log", pattern: "app.log", from: "end" });
  assert.deepEqual(value(pipelines, 0, { role: "sink", id: "http" }, "acl.allow"), ["192.0.2.0/24", "198.51.100.7"]);
@@ -166,7 +178,7 @@ test("a refused call answers why and where, and the engine keeps answering", ()
    [["edit", JSON.stringify([{ name: "p", plugin_sinks: [{ type: "tcp" }] }]),
      JSON.stringify({ op: "set", pipeline: 0, node: { role: "sink", id: "tcp" }, key: "port", values: ["x"] })],
      { error: /port: not an integer$/, path: "pipelines[0].plugin_sinks[tcp].config.port", pipeline: 0, key: "port" }],
-    [["emit", JSON.stringify([{ name: "p" }]), "command"], { error: /no sources defined/, path: "pipelines[0].plugin_sources" }],
+    [["emit", JSON.stringify([{ name: "p" }]), "command"], { error: /plugin_sources: add a source; a pipeline needs at least one\n/, path: "pipelines[0].plugin_sources" }],
    [["emit", "[]", "yaml"], { error: /no form "yaml"/ }],
    [["edit", "[]", JSON.stringify({ op: "add_pipeline", nmae: "p" })], { error: /unknown field "nmae"/ }],
    [["edit", "[]", JSON.stringify({ op: "rename" })], { error: /^no op "rename" \(valid: add, add_pipeline/ }],
@@ -4,7 +4,7 @@
 // globalThis.lwconf for lwconf.js, calls taking strings and returning JSON,
 // {"value"} or {"error"} with its path, one in a pipeline placed on its node
 // and key, any other a preset's or flag's key. Pipelines are compose's JSON
-// form; dirs answers config.IsDir by path, {} leaving '/' and globs to tell.
+// form; dirs answers config.IsDir by path; an error's ask is a path to answer.
 package main

 import (
@@ -146,7 +146,8 @@ var edits = map[string]func(*compose.Composition, op) (compose.Node, error){
 }

 // problem is where a problem, or a call's refusal, lies as far as the engine
-// knows: its path, and the pipeline, node and key Locate reads from it
+// knows: its path, and the pipeline, node and key Locate reads from it; ask
+// is a preset's path whose kind dirs must answer
 type problem struct {
 	Error    string        `json:"error,omitempty"`
 	Path     string        `json:"path,omitempty"`
@@ -154,6 +155,7 @@ type problem struct {
 	Node     *compose.Node `json:"node,omitempty"`
 	Key      string        `json:"key,omitempty"`
 	Text     string        `json:"text,omitempty"`
+	Ask      string        `json:"ask,omitempty"`
 }

 func place(err error) problem {
@@ -161,6 +163,9 @@ func place(err error) problem {
 	if ke, ok := errors.AsType[*config.KeyError](err); ok {
 		p.Path = ke.Key
 	}
+	if pk, ok := errors.AsType[*config.PathKindError](err); ok {
+		p.Ask = pk.Path
+	}
 	if pi, n, key, text, ok := compose.Locate(err); ok {
 		p.Pipeline, p.Key, p.Text = &pi, key, text
 		if n.Role != "" {
@@ -93,7 +93,7 @@
 # interval_ms = 1000                    # At least 100
 # include_timestamp = false             # false: level only; the raw format shows neither
 # include_stats = false                 # Adds type, beat_count and, from the second beat, interval_ms
-# format = "txt"                        # txt|json|raw; no effect: heartbeats use the flow's format
+# format = "txt"                        # txt|json|raw; kept for older files: heartbeats use the flow's format

 ###============================================================================
 ### TLS (a [...tls] table on every network source and sink)
@@ -235,7 +235,7 @@
 # id = "chain_in"
 # type = "tcp_chain"
 # [pipelines.plugin_sources.config]
-# host = "0.0.0.0"                      # IPv4 only; "::" for IPv6 only
+# host = "0.0.0.0"                      # IPv4 only; "::" IPv6 only; 127.0.0.1 or ::1 this machine only
 # port = 9440                           # Required (example)
 # buffer_size = 1000
 # max_connections = 0                   # 0 = unlimited
@@ -274,7 +274,7 @@
 # id = "hchain_in"
 # type = "http_chain"
 # [pipelines.plugin_sources.config]
-# host = "0.0.0.0"                      # IPv4 only; "::" for IPv6 only
+# host = "0.0.0.0"                      # IPv4 only; "::" IPv6 only; 127.0.0.1 or ::1 this machine only
 # port = 9441                           # Required (example)
 # ingest_path = "/ingest"               # Must start with "/"; not "/auth"
 # buffer_size = 1000
@@ -353,7 +353,7 @@
 # id = "http_out"
 # type = "http"
 # [pipelines.plugin_sinks.config]
-# host = "0.0.0.0"                      # IPv4 only; "::" for IPv6 only
+# host = "0.0.0.0"                      # IPv4 only; "::" IPv6 only; 127.0.0.1 or ::1 this machine only
 # port = 8081                           # Required (example)
 # stream_path = "/stream"               # Exact; starts with "/", clean (one trailing "/" allowed), none of { } % ? #; not /auth or under it
 # status_path = "/status"               # Same rules; differs from stream_path
@@ -399,7 +399,7 @@
 # id = "tcp_out"
 # type = "tcp"
 # [pipelines.plugin_sinks.config]
-# host = "0.0.0.0"                      # IPv4 only; "::" for IPv6 only
+# host = "0.0.0.0"                      # IPv4 only; "::" IPv6 only; 127.0.0.1 or ::1 this machine only
 # port = 9090                           # Required (example)
 # buffer_size = 1000
 # client_buffer_size = 256
@@ -94,31 +94,31 @@ preset:*)
 	(( CURRENT -= 2 ))
 	case ${words[1]} in
 	pipe) _arguments -S \
-		'--format=[raw|txt|json: entry format]:value:_default' \
+		'--format=[raw|txt|json: raw writes each message as it came, txt a line with time and level, json one object an entry]:value:_default' \
 		'(-h --help)'{-h,--help}'[print the flags]' ;;
 	tail) _arguments -S \
-		'--format=[raw|txt|json: entry format]:value:_default' \
+		'--format=[raw|txt|json: raw writes each message as it came, txt a line with time and level, json one object an entry]:value:_default' \
 		'--from=[start|end: where reading a file starts]:value:_default' \
-		'--path=[file, directory (its files) or glob to follow]:value:_default' \
+		'--path=[a file, a directory (its files) or a glob such as /var/log/*.log, to follow]:value:_default' \
 		'(-h --help)'{-h,--help}'[print the flags]' ;;
 	serve) _arguments -S \
 		'--allow=[addresses or CIDRs that may connect, of listen'\''s family (either behind proxy=); default: all; '\'','\'' between them]:value:_default' \
 		'--cert=[certificate file, for tls=files]:value:_default' \
 		'--deny=[addresses or CIDRs refused, allow or not; '\'','\'' between them]:value:_default' \
-		'--format=[raw|txt|json: entry format]:value:_default' \
+		'--format=[raw|txt|json: raw writes each message as it came, txt a line with time and level, json one object an entry]:value:_default' \
 		'--from=[start|end: where reading a file starts]:value:_default' \
 		'--hosts=[names and addresses, beyond this host'\''s, of a self or issuer certificate; '\'','\'' between them]:value:_default' \
 		'--issuer_cert=[CA certificate file (lw tls ca), for tls=issuer]:value:_default' \
 		'--issuer_key=[CA key file, for tls=issuer]:value:_default' \
 		'--key=[key file, for tls=files]:value:_default' \
-		'--listen=[HOST:PORT; [IPV6\]:PORT]:value:_default' \
+		'--listen=[HOST:PORT to listen on: 127.0.0.1:8080 this machine only, 0.0.0.0:8080 every IPv4 interface, [::\]:8080 every IPv6 interface]:value:_default' \
 		'--password_file=[file holding user'\''s password; /dev/fd/N or a pipe is read once; default: /dev/tty, which asks]:value:_default' \
-		'--path=[file, directory (its files) or glob to follow; default: standard input]:value:_default' \
+		'--path=[a file, a directory (its files) or a glob such as /var/log/*.log, to follow; default: standard input]:value:_default' \
 		'--proxy=[addresses or CIDRs of the TLS-terminating proxies browsers come through; '\'','\'' between them]:value:_default' \
 		'--tls=[off|self|issuer|files: plain text, a certificate made at startup (self-signed, or from issuer_*), or files]:value:_default' \
-		'(-u --user)'{-u=,--user=}'[SCRAM user: an edge'\''s login, or a listener'\''s only user in place of users]:value:_default' \
+		'(-u --user)'{-u=,--user=}'[the one SCRAM user readers log in as, in place of users]:value:_default' \
 		'--users=[credentials file (lw auth add-user): readers log in with SCRAM]:value:_default' \
-		'--viewer=[true|false: the login page and viewer, behind proxy; without user or users the viewer is always on]:value:_default' \
+		'--viewer=[true|false: a login page, then the viewer, for browsers behind proxy; without user or users the viewer is on anyway]:value:_default' \
 		'(-h --help)'{-h,--help}'[print the flags]' ;;
 	edge) _arguments -S \
 		'--ca=[CA file that verifies the aggregator; default: system roots]:value:_default' \
@@ -127,29 +127,29 @@ preset:*)
 		'--key=[client key file]:value:_default' \
 		'--node=[origin label; default: this host'\''s name]:value:_default' \
 		'--password_file=[file holding user'\''s password; /dev/fd/N or a pipe is read once; default: /dev/tty, which asks]:value:_default' \
-		'--path=[file, directory (its files) or glob to follow; default: standard input]:value:_default' \
+		'--path=[a file, a directory (its files) or a glob such as /var/log/*.log, to follow; default: standard input]:value:_default' \
 		'--pin=[sha256//BASE64 of the aggregator'\''s key, which it logs with tls=self]:value:_default' \
 		'--server_name=[name the aggregator'\''s certificate carries; default: to'\''s host]:value:_default' \
-		'--to=[the aggregator'\''s HOST:PORT; [IPV6\]:PORT]:value:_default' \
-		'--transport=[tcp|http: tcp_chain or http_chain]:value:_default' \
-		'(-u --user)'{-u=,--user=}'[SCRAM user: an edge'\''s login, or a listener'\''s only user in place of users]:value:_default' \
+		'--to=[the aggregator'\''s HOST:PORT, an IPv6 address in brackets: logs.example.net:9000, [2001:db8::1\]:9000]:value:_default' \
+		'--transport=[tcp|http: tcp sends over one lasting connection (tcp_chain), http posts batches (http_chain)]:value:_default' \
+		'(-u --user)'{-u=,--user=}'[SCRAM user this edge logs in to the aggregator as]:value:_default' \
 		'(-h --help)'{-h,--help}'[print the flags]' ;;
 	aggregator) _arguments -S \
 		'--allow=[addresses or CIDRs that may connect, of listen'\''s family (either behind proxy=); default: all; '\'','\'' between them]:value:_default' \
 		'--cert=[certificate file, for tls=files]:value:_default' \
 		'--client_ca=[CA file that verifies edge certificates (mTLS)]:value:_default' \
 		'--deny=[addresses or CIDRs refused, allow or not; '\'','\'' between them]:value:_default' \
-		'--format=[raw|txt|json: entry format]:value:_default' \
+		'--format=[raw|txt|json: raw writes each message as it came, txt a line with time and level, json one object an entry]:value:_default' \
 		'--hosts=[names and addresses, beyond this host'\''s, of a self or issuer certificate; '\'','\'' between them]:value:_default' \
 		'--issuer_cert=[CA certificate file (lw tls ca), for tls=issuer]:value:_default' \
 		'--issuer_key=[CA key file, for tls=issuer]:value:_default' \
 		'--key=[key file, for tls=files]:value:_default' \
-		'--listen=[HOST:PORT; [IPV6\]:PORT; [::\] for IPv6 only]:value:_default' \
+		'--listen=[HOST:PORT to listen on: 0.0.0.0:9000 every IPv4 interface, [::\]:9000 every IPv6 interface, 127.0.0.1:9000 this machine only]:value:_default' \
 		'--out=[directory for the received entries; default: standard output]:value:_default' \
 		'--password_file=[file holding user'\''s password; /dev/fd/N or a pipe is read once; default: /dev/tty, which asks]:value:_default' \
 		'--tls=[self|issuer|files: a certificate made at startup (self-signed, or from issuer_*), or files]:value:_default' \
-		'--transport=[tcp|http: tcp_chain or http_chain]:value:_default' \
-		'(-u --user)'{-u=,--user=}'[SCRAM user: an edge'\''s login, or a listener'\''s only user in place of users]:value:_default' \
+		'--transport=[tcp|http: tcp sends over one lasting connection (tcp_chain), http posts batches (http_chain)]:value:_default' \
+		'(-u --user)'{-u=,--user=}'[the one SCRAM user edges log in as, in place of users]:value:_default' \
 		'--users=[credentials file (lw auth add-user): edges log in with SCRAM]:value:_default' \
 		'(-h --help)'{-h,--help}'[print the flags]' ;;
 	esac
@@ -96,29 +96,29 @@ complete -c lw -n '__lw_in preset; and test (count (commandline -opc)) -eq 2' -a
 complete -c lw -n '__lw_in preset; and test (count (commandline -opc)) -eq 2' -a serve -d 'Serve files or standard input live: a browser viewer at /, SSE at /stream'
 complete -c lw -n '__lw_in preset; and test (count (commandline -opc)) -eq 2' -a edge -d 'Forward files or standard input to an aggregator over TLS, authenticated'
 complete -c lw -n '__lw_in preset; and test (count (commandline -opc)) -eq 2' -a aggregator -d 'Receive from edges over TLS, authenticated, to files or standard output'
-complete -c lw -n '__lw_in preset pipe' -l format -r -F -d 'raw|txt|json: entry format'
+complete -c lw -n '__lw_in preset pipe' -l format -r -F -d 'raw|txt|json: raw writes each message as it came, txt a line with time and level, json one object an entry'
 complete -c lw -n '__lw_in preset pipe' -l help -o h -d 'print the flags'
-complete -c lw -n '__lw_in preset tail' -l format -r -F -d 'raw|txt|json: entry format'
+complete -c lw -n '__lw_in preset tail' -l format -r -F -d 'raw|txt|json: raw writes each message as it came, txt a line with time and level, json one object an entry'
 complete -c lw -n '__lw_in preset tail' -l from -r -F -d 'start|end: where reading a file starts'
-complete -c lw -n '__lw_in preset tail' -l path -r -F -d 'file, directory (its files) or glob to follow'
+complete -c lw -n '__lw_in preset tail' -l path -r -F -d 'a file, a directory (its files) or a glob such as /var/log/*.log, to follow'
 complete -c lw -n '__lw_in preset tail' -l help -o h -d 'print the flags'
 complete -c lw -n '__lw_in preset serve' -l allow -r -F -d 'addresses or CIDRs that may connect, of listen\'s family (either behind proxy=); default: all; \',\' between them'
 complete -c lw -n '__lw_in preset serve' -l cert -r -F -d 'certificate file, for tls=files'
 complete -c lw -n '__lw_in preset serve' -l deny -r -F -d 'addresses or CIDRs refused, allow or not; \',\' between them'
-complete -c lw -n '__lw_in preset serve' -l format -r -F -d 'raw|txt|json: entry format'
+complete -c lw -n '__lw_in preset serve' -l format -r -F -d 'raw|txt|json: raw writes each message as it came, txt a line with time and level, json one object an entry'
 complete -c lw -n '__lw_in preset serve' -l from -r -F -d 'start|end: where reading a file starts'
 complete -c lw -n '__lw_in preset serve' -l hosts -r -F -d 'names and addresses, beyond this host\'s, of a self or issuer certificate; \',\' between them'
 complete -c lw -n '__lw_in preset serve' -l issuer_cert -r -F -d 'CA certificate file (lw tls ca), for tls=issuer'
 complete -c lw -n '__lw_in preset serve' -l issuer_key -r -F -d 'CA key file, for tls=issuer'
 complete -c lw -n '__lw_in preset serve' -l key -r -F -d 'key file, for tls=files'
-complete -c lw -n '__lw_in preset serve' -l listen -r -F -d 'HOST:PORT; [IPV6]:PORT'
+complete -c lw -n '__lw_in preset serve' -l listen -r -F -d 'HOST:PORT to listen on: 127.0.0.1:8080 this machine only, 0.0.0.0:8080 every IPv4 interface, [::]:8080 every IPv6 interface'
 complete -c lw -n '__lw_in preset serve' -l password_file -r -F -d 'file holding user\'s password; /dev/fd/N or a pipe is read once; default: /dev/tty, which asks'
-complete -c lw -n '__lw_in preset serve' -l path -r -F -d 'file, directory (its files) or glob to follow; default: standard input'
+complete -c lw -n '__lw_in preset serve' -l path -r -F -d 'a file, a directory (its files) or a glob such as /var/log/*.log, to follow; default: standard input'
 complete -c lw -n '__lw_in preset serve' -l proxy -r -F -d 'addresses or CIDRs of the TLS-terminating proxies browsers come through; \',\' between them'
 complete -c lw -n '__lw_in preset serve' -l tls -r -F -d 'off|self|issuer|files: plain text, a certificate made at startup (self-signed, or from issuer_*), or files'
-complete -c lw -n '__lw_in preset serve' -l user -o u -r -F -d 'SCRAM user: an edge\'s login, or a listener\'s only user in place of users'
+complete -c lw -n '__lw_in preset serve' -l user -o u -r -F -d 'the one SCRAM user readers log in as, in place of users'
 complete -c lw -n '__lw_in preset serve' -l users -r -F -d 'credentials file (lw auth add-user): readers log in with SCRAM'
-complete -c lw -n '__lw_in preset serve' -l viewer -r -F -d 'true|false: the login page and viewer, behind proxy; without user or users the viewer is always on'
+complete -c lw -n '__lw_in preset serve' -l viewer -r -F -d 'true|false: a login page, then the viewer, for browsers behind proxy; without user or users the viewer is on anyway'
 complete -c lw -n '__lw_in preset serve' -l help -o h -d 'print the flags'
 complete -c lw -n '__lw_in preset edge' -l ca -r -F -d 'CA file that verifies the aggregator; default: system roots'
 complete -c lw -n '__lw_in preset edge' -l cert -r -F -d 'client certificate file, for an aggregator with client_ca'
@@ -126,28 +126,28 @@ complete -c lw -n '__lw_in preset edge' -l from -r -F -d 'start|end: where readi
 complete -c lw -n '__lw_in preset edge' -l key -r -F -d 'client key file'
 complete -c lw -n '__lw_in preset edge' -l node -r -F -d 'origin label; default: this host\'s name'
 complete -c lw -n '__lw_in preset edge' -l password_file -r -F -d 'file holding user\'s password; /dev/fd/N or a pipe is read once; default: /dev/tty, which asks'
-complete -c lw -n '__lw_in preset edge' -l path -r -F -d 'file, directory (its files) or glob to follow; default: standard input'
+complete -c lw -n '__lw_in preset edge' -l path -r -F -d 'a file, a directory (its files) or a glob such as /var/log/*.log, to follow; default: standard input'
 complete -c lw -n '__lw_in preset edge' -l pin -r -F -d 'sha256//BASE64 of the aggregator\'s key, which it logs with tls=self'
 complete -c lw -n '__lw_in preset edge' -l server_name -r -F -d 'name the aggregator\'s certificate carries; default: to\'s host'
-complete -c lw -n '__lw_in preset edge' -l to -r -F -d 'the aggregator\'s HOST:PORT; [IPV6]:PORT'
-complete -c lw -n '__lw_in preset edge' -l transport -r -F -d 'tcp|http: tcp_chain or http_chain'
-complete -c lw -n '__lw_in preset edge' -l user -o u -r -F -d 'SCRAM user: an edge\'s login, or a listener\'s only user in place of users'
+complete -c lw -n '__lw_in preset edge' -l to -r -F -d 'the aggregator\'s HOST:PORT, an IPv6 address in brackets: logs.example.net:9000, [2001:db8::1]:9000'
+complete -c lw -n '__lw_in preset edge' -l transport -r -F -d 'tcp|http: tcp sends over one lasting connection (tcp_chain), http posts batches (http_chain)'
+complete -c lw -n '__lw_in preset edge' -l user -o u -r -F -d 'SCRAM user this edge logs in to the aggregator as'
 complete -c lw -n '__lw_in preset edge' -l help -o h -d 'print the flags'
 complete -c lw -n '__lw_in preset aggregator' -l allow -r -F -d 'addresses or CIDRs that may connect, of listen\'s family (either behind proxy=); default: all; \',\' between them'
 complete -c lw -n '__lw_in preset aggregator' -l cert -r -F -d 'certificate file, for tls=files'
 complete -c lw -n '__lw_in preset aggregator' -l client_ca -r -F -d 'CA file that verifies edge certificates (mTLS)'
 complete -c lw -n '__lw_in preset aggregator' -l deny -r -F -d 'addresses or CIDRs refused, allow or not; \',\' between them'
-complete -c lw -n '__lw_in preset aggregator' -l format -r -F -d 'raw|txt|json: entry format'
+complete -c lw -n '__lw_in preset aggregator' -l format -r -F -d 'raw|txt|json: raw writes each message as it came, txt a line with time and level, json one object an entry'
 complete -c lw -n '__lw_in preset aggregator' -l hosts -r -F -d 'names and addresses, beyond this host\'s, of a self or issuer certificate; \',\' between them'
 complete -c lw -n '__lw_in preset aggregator' -l issuer_cert -r -F -d 'CA certificate file (lw tls ca), for tls=issuer'
 complete -c lw -n '__lw_in preset aggregator' -l issuer_key -r -F -d 'CA key file, for tls=issuer'
 complete -c lw -n '__lw_in preset aggregator' -l key -r -F -d 'key file, for tls=files'
-complete -c lw -n '__lw_in preset aggregator' -l listen -r -F -d 'HOST:PORT; [IPV6]:PORT; [::] for IPv6 only'
+complete -c lw -n '__lw_in preset aggregator' -l listen -r -F -d 'HOST:PORT to listen on: 0.0.0.0:9000 every IPv4 interface, [::]:9000 every IPv6 interface, 127.0.0.1:9000 this machine only'
 complete -c lw -n '__lw_in preset aggregator' -l out -r -F -d 'directory for the received entries; default: standard output'
 complete -c lw -n '__lw_in preset aggregator' -l password_file -r -F -d 'file holding user\'s password; /dev/fd/N or a pipe is read once; default: /dev/tty, which asks'
 complete -c lw -n '__lw_in preset aggregator' -l tls -r -F -d 'self|issuer|files: a certificate made at startup (self-signed, or from issuer_*), or files'
-complete -c lw -n '__lw_in preset aggregator' -l transport -r -F -d 'tcp|http: tcp_chain or http_chain'
-complete -c lw -n '__lw_in preset aggregator' -l user -o u -r -F -d 'SCRAM user: an edge\'s login, or a listener\'s only user in place of users'
+complete -c lw -n '__lw_in preset aggregator' -l transport -r -F -d 'tcp|http: tcp sends over one lasting connection (tcp_chain), http posts batches (http_chain)'
+complete -c lw -n '__lw_in preset aggregator' -l user -o u -r -F -d 'the one SCRAM user edges log in as, in place of users'
 complete -c lw -n '__lw_in preset aggregator' -l users -r -F -d 'credentials file (lw auth add-user): edges log in with SCRAM'
 complete -c lw -n '__lw_in preset aggregator' -l help -o h -d 'print the flags'

@@ -254,8 +254,8 @@ never a key:
 - `value`, `at` and `group` read a node's value and sort problems by node.

 The engine's calls take strings (`lwconf.js` writes objects as JSON) and
-answer `{"value": ...}` or `{"error", "path", "pipeline", "node", "key"}`, as
-far as the engine places the refusal:
+answer `{"value": ...}` or `{"error", "path", "pipeline", "node", "key",
+"ask"}`, as far as the engine places the refusal:

 - `schema()`: what `lw --schema` prints.
 - `preset(name, values, dirs)`: a preset's pipelines; `values` maps a key to
@@ -273,7 +273,8 @@ far as the engine places the refusal:
  - `set` (`node`, `key`, `values`), `unset` (`node`, `key`)
 - `dirs` answers whether a path a preset names is a directory,
  `{"/var/log/app.log": false}`; unanswered, a path ending in `/` is one, one
-  with a glob a pattern, and any other is refused at `path`.
+  with a glob a pattern, and any other is refused at `path` with `ask` naming
+  it: answer it in `dirs` and call again.
 - Pipelines are a JSON list in the file's shape (`name`, `flow`,
  `plugin_sources`, `plugin_sinks`); a misspelled key is refused. A node is
  `{role, id, index}`: a source's or sink's id, a filter's index.
@@ -457,8 +457,9 @@ WebAssembly; `t` runs them under the screen and shows what flows.

 - Start: the pipelines `lw` would run with the same options (`-c FILE`,
  pipeline flags, `LOGWISP_SOURCE`, a discovered file); with none but the
-  built-in pipe, the preset menu (or `empty`). A pasted `lw` command line
-  replaces the pipelines, in the preset menu too.
+  built-in pipe, the preset menu (or `empty`). A pasted `lw` command line of
+  pipeline flags, or the `lw` part of `... | lw ...`, replaces the
+  pipelines, in the preset menu too.
 - Screen: the pipeline bar on top; SOURCES, FLOW and SINKS side by side
  from 64 columns, stacked below; each source and sink a tinted bar with its
  type, whether it listens or dials, and a summary; the four flow stages in
@@ -172,8 +172,8 @@ Options, each as type and default:
  timestamp; the `raw` format shows neither.
 - `include_stats` (bool, `false`): add `type = "heartbeat"`, `beat_count` and,
  from the second beat, the measured `interval_ms` as fields.
- `format` (string, `txt`): `txt`, `json` or `raw`; no effect: heartbeats go
-  through the flow's `format`.
+- `format` (string, `txt`): `txt`, `json` or `raw`, kept for older files:
+  heartbeats go through the flow's `format`.

 Heartbeats are ordinary entries with source `heartbeat` and level `INFO`. They
 are generated after the flow's filter and rate-limit stages, so filters do not
@@ -209,8 +209,8 @@ preamble, headers, and entry encoding.
  - `PROXY header: …` — malformed, too long, or incomplete after 10 s.
  - `PROXY header from a peer outside proxy_from` — at the first read, after
    the connection opened: list the proxy in `proxy_from`.
- `acl: allow entry "...": not of the listener's family` at startup — an IPv4
-  entry on an IPv6 `host`, or the reverse: each family's listener takes its own.
+- `acl: allow entry "...": IPv4, and the listener's host is IPv6` at startup,
+  or the reverse: each family's listener takes its own.
  Behind `proxy_from` or `trusted_proxies`, `allow` and `deny` take both;
  `proxy_from` its own.

@@ -156,7 +156,7 @@ func TestNewValidation(t *testing.T) {
 		{"trusted proxies on a chain source", listener(config.AuthOptions{TrustedProxies: proxies}), nil, config.ChainListener, HTTP, "only to the http sink"},
 		{"trusted proxies on tcp", listener(config.AuthOptions{TrustedProxies: proxies}), nil, config.Listener, TCP, "only to HTTP listeners"},
 		{"trusted proxies with certificate binding", listener(config.AuthOptions{TrustedProxies: proxies, Identity: "cn"}), f.serverTLS, config.Listener, HTTP, "TLS-terminating proxy"},
-		{"malformed trusted proxy", listener(config.AuthOptions{TrustedProxies: []string{"localhost"}}), nil, config.Listener, HTTP, "neither an address"},
+		{"malformed trusted proxy", listener(config.AuthOptions{TrustedProxies: []string{"localhost"}}), nil, config.Listener, HTTP, "host names and IPv6 zones are not accepted"},
 		{"trusted proxies on a dialer", dialer(config.AuthOptions{TrustedProxies: proxies}), &tls.Config{}, config.Dialer, HTTP, "only to listeners"},
 	}
 	for _, tc := range tests {
@@ -61,13 +61,21 @@ func FromPreset(name string, values map[string]string, isDir config.IsDir) (*Com

 // FromCommandLine starts from a pasted lw command line, quoted as a POSIX
 // shell reads it; it takes pipeline flags only, at least one, as a composition
-// holds no settings
+// holds no settings. Of a line piped into lw it reads lw's part, whose
+// pipelines read standard input.
 func FromCommandLine(line string, isDir config.IsDir) (*Composition, error) {
 	words, err := split(strings.NewReplacer("\r\n", "\n", "\r", "\n").Replace(line)) // pasted line ends
 	if err != nil {
 		return nil, err
 	}
-	if len(words) > 0 && (words[0] == "lw" || strings.HasSuffix(words[0], "/lw")) {
+	lw := func(word string) bool { return word == "lw" || strings.HasSuffix(word, "/lw") }
+	for i := len(words) - 2; i >= 0; i-- {
+		if words[i] == "|" && lw(words[i+1]) {
+			words = words[i+1:]
+			break
+		}
+	}
+	if len(words) > 0 && lw(words[0]) {
 		words = words[1:]
 	}
 	var specs []config.Spec
@@ -77,8 +85,12 @@ func FromCommandLine(line string, isDir config.IsDir) (*Composition, error) {
 			name = "--preset"
 		}
 		flag, long := strings.CutPrefix(name, "--")
-		if !long || !slices.ContainsFunc(config.SpecFlags(), func(f config.SpecFlag) bool { return f.Flag == flag }) {
-			return nil, fmt.Errorf("%s: not a pipeline flag", words[i])
+		if flags := config.SpecFlags(); !long || !slices.ContainsFunc(flags, func(f config.SpecFlag) bool { return f.Flag == flag }) {
+			var names []string
+			for _, f := range flags {
+				names = append(names, "--"+f.Flag)
+			}
+			return nil, fmt.Errorf("%s: not a pipeline flag; paste lw's %s only", words[i], strings.Join(names, ", "))
 		}
 		if !inline {
 			if i++; i == len(words) || strings.HasPrefix(words[i], "-") {
@@ -205,8 +217,11 @@ func (c *Composition) RenamePipeline(i int, name string) error {

 // free refuses a name that is empty or held by a pipeline other than i
 func (c *Composition) free(name string, i int) error {
-	if j := slices.IndexFunc(c.Pipelines, func(p config.PipelineConfig) bool { return p.Name == name }); name == "" || j >= 0 && j != i {
-		return fmt.Errorf("pipeline %q: a name no other pipeline has", name)
+	switch j := slices.IndexFunc(c.Pipelines, func(p config.PipelineConfig) bool { return p.Name == name }); {
+	case name == "":
+		return errors.New("a pipeline needs a name; give it one")
+	case j >= 0 && j != i:
+		return fmt.Errorf("another pipeline is named %q; choose another name", name)
 	}
 	return nil
 }
@@ -574,7 +589,7 @@ func (c *Composition) CommandLine() (string, error) {
 // line as an environment file holds them; the environment holds one pipeline
 func (c *Composition) Environment() (string, error) {
 	if len(c.Pipelines) != 1 {
-		return "", fmt.Errorf("the environment holds one pipeline, not %d", len(c.Pipelines))
+		return "", fmt.Errorf("the environment holds one pipeline, not %d; choose the command or file form, or remove pipelines down to one", len(c.Pipelines))
 	}
 	specs, err := c.shellSpecs()
 	if err != nil {
@@ -632,9 +647,9 @@ type Form struct {
 }

 var forms = []Form{
-	{"command", "lw's flags", (*Composition).CommandLine, FromCommandLine},
-	{"environment", "LOGWISP_ variables: one pipeline", (*Composition).Environment, FromEnvironment},
-	{"file", "a configuration file's pipelines", func(c *Composition) (string, error) {
+	{"command", "an lw command line", (*Composition).CommandLine, FromCommandLine},
+	{"environment", "LOGWISP_ variables for one pipeline", (*Composition).Environment, FromEnvironment},
+	{"file", "the pipelines of a configuration file", func(c *Composition) (string, error) {
 		data, err := c.File()
 		return string(data), err
 	}, func(text string, _ config.IsDir) (*Composition, error) { return FromFile([]byte(text)) }},
@@ -115,6 +115,18 @@ func TestPastedEnvironmentReadsAsAShellRunsIt(t *testing.T) {
 	}
 }

+// Of a line piped into lw, lw's part is read, its pipeline reading standard
+// input; a word that is no pipeline flag is refused, naming those to paste
+func TestPastedCommandLineIsLwsPart(t *testing.T) {
+	c, err := FromCommandLine("tail -F app.log | lw --filter include:patterns=ERROR", nil)
+	if err != nil || c.Pipelines[0].PluginSources[0].Type != "console" || len(c.Pipelines[0].Flow.Filters) != 1 {
+		t.Fatalf("%v %v", c, err)
+	}
+	if _, err := FromCommandLine("lw -c lw.toml --sink null", nil); err == nil || !strings.HasPrefix(err.Error(), "-c: not a pipeline flag; paste lw's --pipeline, --preset, ") {
+		t.Fatalf("-c: %v", err)
+	}
+}
+
 // Locate places a problem by its path: a plugin's key, a key of its table, a
 // rule between its table's keys, a list entry, the plugin itself under an id
 // holding ']', a filter's list entry, a stage and the pipeline; and nothing
@@ -192,8 +204,9 @@ func TestShellFormsRefuseControlCharacters(t *testing.T) {
 	}
 }

-// Set refuses a value of the wrong kind and leaves the key as it was; Unset
-// returns a key to its default, dropping a table it leaves empty
+// Set refuses a value of the wrong kind, a plugin's and a stage's alike, and
+// leaves the key as it was; Unset returns a key to its default, dropping a
+// table it leaves empty
 func TestSetKeepsAKeyItCannotTake(t *testing.T) {
 	c := &Composition{}
 	if err := c.AddPipeline("p"); err != nil {
@@ -207,8 +220,11 @@ func TestSetKeepsAKeyItCannotTake(t *testing.T) {
 			t.Fatal(err)
 		}
 	}
-	if err := c.Set(0, n, "port", "http"); err == nil || !strings.HasPrefix(err.Error(), "port: ") {
-		t.Fatalf("port http: %v", err)
+	for want, err := range map[string]error{"port: not an integer": c.Set(0, n, "port", "http"),
+		"interval_ms: not an integer": c.Set(0, beat, "interval_ms", "soon")} {
+		if err == nil || err.Error() != want {
+			t.Errorf("%v, want %s", err, want)
+		}
 	}
 	if m, beat := c.Pipelines[0].PluginSinks[0].Config, c.Pipelines[0].Flow.Heartbeat; !reflect.DeepEqual(m, map[string]any{"port": int64(8080)}) ||
 		beat.IntervalMS != 1000 {
@@ -75,18 +75,18 @@ type FlowConfig struct {

 // HeartbeatConfig defines settings for periodic keep-alive or status messages
 type HeartbeatConfig struct {
-	Enabled          bool   `toml:"enabled" help:"send heartbeats"`
+	Enabled          bool   `toml:"enabled" help:"send heartbeats; false keeps these settings and sends none"`
 	IntervalMS       int64  `toml:"interval_ms" default:"1000" lw:"min=100" help:"milliseconds between heartbeats"`
 	IncludeTimestamp bool   `toml:"include_timestamp" help:"stamp each heartbeat with its time"`
 	IncludeStats     bool   `toml:"include_stats" help:"add type, beat_count and, from the second beat, the measured interval_ms"`
-	Format           string `toml:"format" default:"txt" lw:"enum=txt|json|raw" help:"no effect: heartbeats use the flow's format"`
+	Format           string `toml:"format" default:"txt" lw:"enum=txt|json|raw" help:"kept for older files; heartbeats are written in the flow's format"`
 }

 // FormatConfig is how a pipeline writes its entries
 type FormatConfig struct {
-	Type            string `toml:"type" default:"raw" lw:"enum=raw|txt|json" help:"entry format"`
-	Flags           int64  `toml:"flags,omitempty" lw:"zero=by type" help:"formatter flags"`
-	TimestampFormat string `toml:"timestamp_format,omitempty" lw:"zero=RFC 3339 with nanoseconds" help:"Go time layout of timestamps"`
+	Type            string `toml:"type" default:"raw" lw:"enum=raw|txt|json" help:"raw writes each message as it came, txt a line with time and level, json one object an entry"`
+	Flags           int64  `toml:"flags,omitempty" lw:"zero=by type" help:"for experts, a sum of bits over the type's choice: 1 writes messages verbatim, 16 drops the time, 32 the level"`
+	TimestampFormat string `toml:"timestamp_format,omitempty" lw:"zero=RFC 3339 with nanoseconds" help:"timestamp layout: the reference time 2006-01-02 15:04:05 written as timestamps should look, such as 02 Jan 15:04"`
 	SanitizerPolicy string `toml:"sanitizer_policy,omitempty" lw:"enum=raw|json|txt|shell,zero=by type" help:"how control characters are escaped"`
 }

@@ -102,10 +102,10 @@ const (

 // RateLimitConfig defines the configuration for pipeline-level rate limiting
 type RateLimitConfig struct {
-	EntriesPerSecond  float64 `toml:"entries_per_second" lw:"min=0,zero=off" help:"entries a second the limit lets through"`
-	BurstEntries      float64 `toml:"burst_entries" lw:"min=0,zero=one second's worth" help:"entries let through at once before the rate applies"`
-	Policy            string  `toml:"policy" default:"pass" lw:"enum=pass|drop" help:"drop entries over the rate, or pass them"`
-	MaxEntrySizeBytes int64   `toml:"max_entry_size_bytes" lw:"min=0,zero=unlimited" help:"drop larger entries"`
+	EntriesPerSecond  float64 `toml:"entries_per_second" lw:"min=0,zero=off" help:"entries a second let through; unset, the stage limits nothing, sizes included"`
+	BurstEntries      float64 `toml:"burst_entries" lw:"min=0,zero=one second's worth" help:"entries that may pass in a burst before entries_per_second holds them back"`
+	Policy            string  `toml:"policy" default:"pass" lw:"enum=pass|drop" help:"drop enforces entries_per_second and max_entry_size_bytes; pass lets every entry through"`
+	MaxEntrySizeBytes int64   `toml:"max_entry_size_bytes" lw:"min=0,zero=unlimited" help:"drop larger entries; needs entries_per_second and policy drop"`
 }

 // FilterType represents the filter's behavior (include or exclude)
@@ -174,31 +174,31 @@ type ConsoleSourceOptions struct {
 // TCPChainSourceOptions defines settings for a stdlib TCP listener ingesting
 // NDJSON entries from upstream logwisp tcp_chain sinks
 type TCPChainSourceOptions struct {
-	TLS            *TLSOptions  `toml:"tls"`
-	Host           string       `toml:"host" default:"0.0.0.0" lw:"hint=host" help:"address to listen on; :: for IPv6"`
+	TLS            *TLSOptions  `toml:"tls" help:"TLS for the connections it accepts"`
+	Host           string       `toml:"host" default:"0.0.0.0" lw:"hint=host" help:"address to listen on, one family per listener: 0.0.0.0 every IPv4 interface, :: every IPv6 interface, 127.0.0.1 or ::1 this machine only"`
 	Port           int64        `toml:"port" lw:"required,min=1,max=65535" help:"port to listen on"`
 	BufferSize     int64        `toml:"buffer_size" default:"1000" lw:"min=1" help:"entries queued"`
 	MaxConnections int64        `toml:"max_connections" lw:"min=0,zero=unlimited" help:"connections at once"`
 	ReadTimeoutMS  int64        `toml:"read_timeout_ms" lw:"min=0,zero=none" help:"milliseconds a connection may idle"`
 	HelloTimeoutMS int64        `toml:"hello_timeout_ms" default:"10000" lw:"min=1" help:"milliseconds for a peer's hello"`
 	TrustNode      bool         `toml:"trust_node" default:"true" help:"keep the node label a peer declares; off, the label is its address"`
-	Auth           *AuthOptions `toml:"auth"`
-	ACL            *ACLOptions  `toml:"acl"`
+	Auth           *AuthOptions `toml:"auth" help:"how peers authenticate: mtls by client certificate, scram by user and password"`
+	ACL            *ACLOptions  `toml:"acl" help:"client addresses admitted or refused, and per-client limits"`
 }

 // HTTPChainSourceOptions defines settings for a stdlib HTTP listener ingesting
 // NDJSON batches from upstream logwisp http_chain sinks
 type HTTPChainSourceOptions struct {
-	TLS           *TLSOptions  `toml:"tls"`
-	Host          string       `toml:"host" default:"0.0.0.0" lw:"hint=host" help:"address to listen on; :: for IPv6"`
+	TLS           *TLSOptions  `toml:"tls" help:"TLS for the connections it accepts"`
+	Host          string       `toml:"host" default:"0.0.0.0" lw:"hint=host" help:"address to listen on, one family per listener: 0.0.0.0 every IPv4 interface, :: every IPv6 interface, 127.0.0.1 or ::1 this machine only"`
 	Port          int64        `toml:"port" lw:"required,min=1,max=65535" help:"port to listen on"`
 	IngestPath    string       `toml:"ingest_path" default:"/ingest" lw:"hint=path" help:"path batches are posted to"`
 	BufferSize    int64        `toml:"buffer_size" default:"1000" lw:"min=1" help:"entries queued"`
 	MaxBodyBytes  int64        `toml:"max_body_bytes" default:"8388608" lw:"min=1" help:"largest batch accepted"`
 	ReadTimeoutMS int64        `toml:"read_timeout_ms" default:"30000" lw:"min=1" help:"milliseconds to read a request"`
 	TrustNode     bool         `toml:"trust_node" default:"true" help:"keep the node label a peer declares; off, the label is its address"`
-	Auth          *AuthOptions `toml:"auth"`
-	ACL           *ACLOptions  `toml:"acl"`
+	Auth          *AuthOptions `toml:"auth" help:"how peers authenticate: mtls by client certificate, scram by user and password"`
+	ACL           *ACLOptions  `toml:"acl" help:"client addresses admitted or refused, and per-client limits"`
 }

 // --- Sinks ---
@@ -228,7 +228,7 @@ type FileSinkOptions struct {
 	Name            string  `toml:"name" lw:"required" help:"base name of the files"`
 	MaxSizeMB       int64   `toml:"max_size_mb" default:"100" lw:"min=1" help:"size at which a file rotates"`
 	MaxTotalSizeMB  int64   `toml:"max_total_size_mb" default:"1000" lw:"min=1" help:"size of all files, beyond which the oldest go"`
-	MinDiskFreeMB   int64   `toml:"min_disk_free_mb" lw:"zero=none" help:"free space kept on the disk; negative means 100"`
+	MinDiskFreeMB   int64   `toml:"min_disk_free_mb" lw:"zero=none" help:"megabytes kept free on the disk, the oldest .log files deleted for it; a negative value means 100"`
 	RetentionHours  float64 `toml:"retention_hours" default:"168" lw:"min=0,zero=kept" help:"hours a .log file is kept; 0 keeps them"`
 	BufferSize      int64   `toml:"buffer_size" default:"1000" lw:"min=1" help:"entries queued"`
 	FlushIntervalMs int64   `toml:"flush_interval_ms" default:"100" lw:"min=1" help:"milliseconds between flushes"`
@@ -236,8 +236,8 @@ type FileSinkOptions struct {

 // TCPSinkOptions defines settings for a TCP server sink
 type TCPSinkOptions struct {
-	TLS               *TLSOptions  `toml:"tls"`
-	Host              string       `toml:"host" default:"0.0.0.0" lw:"hint=host" help:"address to listen on; :: for IPv6"`
+	TLS               *TLSOptions  `toml:"tls" help:"TLS for the connections it accepts"`
+	Host              string       `toml:"host" default:"0.0.0.0" lw:"hint=host" help:"address to listen on, one family per listener: 0.0.0.0 every IPv4 interface, :: every IPv6 interface, 127.0.0.1 or ::1 this machine only"`
 	Port              int64        `toml:"port" lw:"required,min=1,max=65535" help:"port to listen on"`
 	BufferSize        int64        `toml:"buffer_size" default:"1000" lw:"min=1" help:"entries queued for all clients"`
 	ClientBufferSize  int64        `toml:"client_buffer_size" default:"256" lw:"min=1" help:"entries queued per client"`
@@ -245,14 +245,14 @@ type TCPSinkOptions struct {
 	KeepAlive         bool         `toml:"keep_alive" default:"true" help:"TCP keep-alive"`
 	KeepAlivePeriodMS int64        `toml:"keep_alive_period_ms" default:"30000" lw:"min=1" help:"milliseconds idle before a keep-alive probe"`
 	MaxConnections    int64        `toml:"max_connections" lw:"min=0,zero=unlimited" help:"clients at once"`
-	Auth              *AuthOptions `toml:"auth"`
-	ACL               *ACLOptions  `toml:"acl"`
+	Auth              *AuthOptions `toml:"auth" help:"how peers authenticate: mtls by client certificate, scram by user and password"`
+	ACL               *ACLOptions  `toml:"acl" help:"client addresses admitted or refused, and per-client limits"`
 }

 // HTTPSinkOptions defines settings for an HTTP SSE server sink
 type HTTPSinkOptions struct {
-	TLS              *TLSOptions  `toml:"tls"`
-	Host             string       `toml:"host" default:"0.0.0.0" lw:"hint=host" help:"address to listen on; :: for IPv6"`
+	TLS              *TLSOptions  `toml:"tls" help:"TLS for the connections it accepts"`
+	Host             string       `toml:"host" default:"0.0.0.0" lw:"hint=host" help:"address to listen on, one family per listener: 0.0.0.0 every IPv4 interface, :: every IPv6 interface, 127.0.0.1 or ::1 this machine only"`
 	Port             int64        `toml:"port" lw:"required,min=1,max=65535" help:"port to listen on"`
 	StreamPath       string       `toml:"stream_path" default:"/stream" lw:"hint=path" help:"path of the event stream"`
 	StatusPath       string       `toml:"status_path" default:"/status" lw:"hint=path" help:"path of the status document"`
@@ -263,14 +263,14 @@ type HTTPSinkOptions struct {
 	ReplayLines      int64        `toml:"replay_lines" lw:"min=0,zero=none" help:"recent entries a new stream gets first"`
 	LoginPage        bool         `toml:"login_page" help:"scram behind auth.trusted_proxies only: a login page at /auth/login"`
 	ViewerPage       bool         `toml:"viewer_page" help:"scram behind auth.trusted_proxies only: the viewer after a login; without scram it is always at /"`
-	Auth             *AuthOptions `toml:"auth"`
-	ACL              *ACLOptions  `toml:"acl"`
+	Auth             *AuthOptions `toml:"auth" help:"how peers authenticate: mtls by client certificate, scram by user and password"`
+	ACL              *ACLOptions  `toml:"acl" help:"client addresses admitted or refused, and per-client limits"`
 }

 // TCPChainSinkOptions defines settings for a stdlib TCP client forwarding
 // entries to a downstream logwisp tcp_chain source
 type TCPChainSinkOptions struct {
-	TLS               *TLSOptions  `toml:"tls"`
+	TLS               *TLSOptions  `toml:"tls" help:"TLS to the source it connects to"`
 	Node              string       `toml:"node" lw:"zero=the host name" help:"origin label of the entries"`
 	Host              string       `toml:"host" lw:"required,hint=host" help:"host of the tcp_chain source"`
 	Port              int64        `toml:"port" lw:"required,min=1,max=65535" help:"port of the tcp_chain source"`
@@ -281,13 +281,13 @@ type TCPChainSinkOptions struct {
 	BackoffMaxMS      int64        `toml:"backoff_max_ms" default:"30000" lw:"min=1" help:"longest wait before reconnecting; below the first, the default"`
 	KeepAlivePeriodMS int64        `toml:"keep_alive_period_ms" default:"30000" lw:"min=1" help:"milliseconds idle before a keep-alive probe"`
 	KeepAlive         bool         `toml:"keep_alive" default:"true" help:"TCP keep-alive"`
-	Auth              *AuthOptions `toml:"auth"`
+	Auth              *AuthOptions `toml:"auth" help:"how it authenticates with the source: scram logs in, mtls checks the source's identity"`
 }

 // HTTPChainSinkOptions defines settings for a stdlib HTTP client posting
 // NDJSON batches to a downstream logwisp http_chain source
 type HTTPChainSinkOptions struct {
-	TLS              *TLSOptions  `toml:"tls"`
+	TLS              *TLSOptions  `toml:"tls" help:"TLS to the source it connects to"`
 	Node             string       `toml:"node" lw:"zero=the host name" help:"origin label of the entries"`
 	Host             string       `toml:"host" lw:"required,hint=host" help:"host of the http_chain source"`
 	Port             int64        `toml:"port" lw:"required,min=1,max=65535" help:"port of the http_chain source"`
@@ -299,7 +299,7 @@ type HTTPChainSinkOptions struct {
 	RequestTimeoutMS int64        `toml:"request_timeout_ms" default:"10000" lw:"min=1" help:"milliseconds for a request: dial, write and response"`
 	BackoffMinMS     int64        `toml:"backoff_min_ms" default:"500" lw:"min=1" help:"first wait before retrying"`
 	BackoffMaxMS     int64        `toml:"backoff_max_ms" default:"30000" lw:"min=1" help:"longest wait before retrying; below the first, the default"`
-	Auth             *AuthOptions `toml:"auth"`
+	Auth             *AuthOptions `toml:"auth" help:"how it authenticates with the source: scram logs in, mtls checks the source's identity"`
 }

 // --- Auth Options ---
@@ -312,14 +312,14 @@ type HTTPChainSinkOptions struct {
 type AuthOptions struct {
 	Type            string   `toml:"type" default:"none" lw:"enum=none|mtls|scram" help:"how peers authenticate"`
 	Identity        string   `toml:"identity" lw:"enum=cn|san_dns|san_uri|san_email,zero=cn under mtls; no binding under scram" help:"certificate field naming the peer; under scram it must equal the user"`
-	Allow           []string `toml:"allow" help:"mtls: identities admitted; with allow_patterns empty, any the CA issued"`
+	Allow           []string `toml:"allow" help:"mtls: identities admitted; with neither this nor allow_patterns set, any the CA issued"`
 	AllowPatterns   []string `toml:"allow_patterns" lw:"hint=regex" help:"mtls: RE2 patterns of identities admitted; anchor them"`
-	NodeBinding     string   `toml:"node_binding" lw:"listener,enum=none|assert|force,zero=force" help:"chain sources: how a peer's identity binds its node label; overrides trust_node"`
-	CredentialsFile string   `toml:"credentials_file" lw:"listener,hint=file" help:"scram: verifiers, from lw auth add-user"`
+	NodeBinding     string   `toml:"node_binding" lw:"chain_listener,enum=none|assert|force,zero=force" help:"chain sources: force labels every entry with the peer's identity, assert refuses a peer declaring another node, none leaves it to trust_node"`
+	CredentialsFile string   `toml:"credentials_file" lw:"listener,hint=file" help:"scram: file of the users who may log in, made by lw auth add-user"`
 	// exp has whole seconds, a sub-second expires_in reads as unknown, and 10 s
 	// leaves room for renewal ahead of expiry
 	TokenLifetimeMS int64    `toml:"token_lifetime_ms" lw:"listener,http,min=10000,max=86400000,zero=15 minutes" help:"scram on HTTP: bearer token lifetime"`
-	TrustedProxies  []string `toml:"trusted_proxies" lw:"listener,http,hint=cidr" help:"scram on the http sink: proxies ending the browsers' TLS; logins are then unbound"`
+	TrustedProxies  []string `toml:"trusted_proxies" lw:"listener,http,hint=cidr" help:"scram on the http sink: addresses or CIDRs of the proxies that end browsers' TLS, through which browsers then log in"`
 	Username        string   `toml:"username" help:"scram: the user a dialer logs in as, or a listener's one user"`
 	PasswordFile    string   `toml:"password_file" lw:"hint=file" help:"scram: file holding the password; /dev/fd/N or a pipe is read once, /dev/tty asks"`
 }
@@ -329,8 +329,8 @@ type AuthOptions struct {
 // the L4 proxies whose PROXY header names the client the rules then see; the
 // per-client limits count that client. ACLOptions.Check holds the rules.
 type ACLOptions struct {
-	Allow                      []string `toml:"allow" lw:"hint=cidr" help:"addresses admitted; empty, all deny does not list"`
-	Deny                       []string `toml:"deny" lw:"hint=cidr" help:"addresses refused"`
+	Allow                      []string `toml:"allow" lw:"hint=cidr" help:"addresses or CIDRs that may connect; unset, any that deny does not refuse"`
+	Deny                       []string `toml:"deny" lw:"hint=cidr" help:"addresses or CIDRs refused, even when allow lists them"`
 	ProxyProtocol              string   `toml:"proxy_protocol" default:"off" lw:"enum=off|optional|required" help:"read a PROXY header from proxy_from"`
 	ProxyFrom                  []string `toml:"proxy_from" lw:"hint=cidr" help:"proxies that may send a PROXY header"`
 	MaxConnectionsPerClient    int64    `toml:"max_connections_per_client" lw:"min=0,zero=unlimited" help:"connections a client may hold"`
@@ -346,12 +346,12 @@ type ACLOptions struct {
 // may present cert_file and key_file.
 type TLSOptions struct {
 	Enabled            bool     `toml:"enabled" help:"use TLS"`
-	CertFile           string   `toml:"cert_file" lw:"hint=file" help:"certificate presented; a dialer's for mTLS"`
+	CertFile           string   `toml:"cert_file" lw:"hint=file" help:"certificate file this end presents; a dialer's, for a listener with client_auth"`
 	KeyFile            string   `toml:"key_file" lw:"hint=file" help:"key of cert_file"`
 	SelfSigned         bool     `toml:"self_signed" lw:"listener" help:"a self-signed certificate on a key made at startup"`
-	IssuerCertFile     string   `toml:"issuer_cert_file" lw:"listener,hint=file" help:"CA certificate (lw tls ca) that issues the listener's at startup"`
+	IssuerCertFile     string   `toml:"issuer_cert_file" lw:"listener,hint=file" help:"CA certificate file (lw tls ca) that signs a certificate made at startup"`
 	IssuerKeyFile      string   `toml:"issuer_key_file" lw:"listener,hint=file" help:"key of issuer_cert_file"`
-	Hosts              []string `toml:"hosts" lw:"listener" help:"names and addresses a made certificate carries beyond host, this machine's and loopback"`
+	Hosts              []string `toml:"hosts" lw:"listener" help:"more names and addresses for a certificate made at startup, which always carries host, this machine's name and localhost"`
 	ClientAuth         bool     `toml:"client_auth" lw:"listener" help:"require and verify client certificates"`
 	ClientCAFile       string   `toml:"client_ca_file" lw:"listener,hint=file" help:"CA bundle verifying client certificates"`
 	CAFile             string   `toml:"ca_file" lw:"dialer,hint=file,zero=the system roots" help:"CA bundle verifying the server"`
@@ -63,10 +63,19 @@ func mirror[T any](p PresetParam, key string) PresetParam {
 // IsDir tells whether a preset's path is a directory, whose files it follows,
 // or a file pattern; a path ending in '/' is a directory without asking. Off
 // the target host it is the user's Answers, or nil: a path with a glob is then
-// a pattern, and any other fails with ErrPathKind.
+// a pattern, and any other fails at key path with a PathKindError.
 type IsDir func(path string) (bool, error)

-var ErrPathKind error = &KeyError{"path", errors.New("a directory or a file pattern?")}
+// ErrPathKind is what every PathKindError unwraps to
+var ErrPathKind = errors.New("a directory or a file?")
+
+// PathKindError asks whether Path, which a preset names, is a directory
+type PathKindError struct{ Path string }
+
+func (e *PathKindError) Error() string {
+	return fmt.Sprintf("%q: %v end a directory with / to follow its files", e.Path, ErrPathKind)
+}
+func (e *PathKindError) Unwrap() error { return ErrPathKind }

 // HostIsDir asks this host, a leading ~ being the home directory: a path that
 // does not exist is a pattern
@@ -85,16 +94,16 @@ func Answers(dirs map[string]bool) IsDir {
 		if strings.ContainsAny(path, `*?[\`) {
 			return false, nil
 		}
-		return false, ErrPathKind
+		return false, &KeyError{"path", &PathKindError{path}}
 	}
 }

 // Keys several presets share
 var (
-	pathParam   = PresetParam{Name: "path", Help: "file, directory (its files) or glob to follow; default: standard input"}
+	pathParam   = PresetParam{Name: "path", Help: "a file, a directory (its files) or a glob such as /var/log/*.log, to follow; default: standard input"}
 	fromParam   = mirror[FileSourceOptions](PresetParam{Name: "from", Default: "end", Help: "where reading a file starts"}, "from")
 	formatParam = func(def string) PresetParam {
-		return mirror[FormatConfig](PresetParam{Name: "format", Default: def, Help: "entry format"}, "type")
+		return mirror[FormatConfig](PresetParam{Name: "format", Default: def, Help: "raw writes each message as it came, txt a line with time and level, json one object an entry"}, "type")
 	}
 	tlsParams = []PresetParam{
 		mirror[TLSOptions](PresetParam{Name: "cert", Help: "certificate file, for tls=files"}, "cert_file"),
@@ -107,13 +116,13 @@ var (
 		mirror[ACLOptions](PresetParam{Name: "allow", List: true, Help: "addresses or CIDRs that may connect, of listen's family (either behind proxy=); default: all; ',' between them"}, "allow"),
 		mirror[ACLOptions](PresetParam{Name: "deny", List: true, Help: "addresses or CIDRs refused, allow or not; ',' between them"}, "deny"),
 	}
-	transportParam = PresetParam{Name: "transport", Default: "tcp", Help: "tcp_chain or http_chain", Enum: transports()}
+	transportParam = PresetParam{Name: "transport", Default: "tcp", Help: "tcp sends over one lasting connection (tcp_chain), http posts batches (http_chain)", Enum: transports()}
 	usersParam     = func(who string) PresetParam {
 		return mirror[AuthOptions](PresetParam{Name: "users", Help: "credentials file (lw auth add-user): " + who + " log in with SCRAM"}, "credentials_file")
 	}
-	userParams = []PresetParam{
-		{Name: "user", Help: "SCRAM user: an edge's login, or a listener's only user in place of users"},
-		mirror[AuthOptions](PresetParam{Name: "password_file", Help: "file holding user's password; /dev/fd/N or a pipe is read once; default: /dev/tty, which asks"}, "password_file"),
+	userParams = func(help string) []PresetParam {
+		return []PresetParam{{Name: "user", Help: help},
+			mirror[AuthOptions](PresetParam{Name: "password_file", Help: "file holding user's password; /dev/fd/N or a pipe is read once; default: /dev/tty, which asks"}, "password_file")}
 	}
 )

@@ -146,7 +155,7 @@ var presets = []Preset{
 			return nil
 		}},
 	{"tail", "Follow files to standard output, like tail -F",
-		[]PresetParam{{Name: "path", Required: true, Help: "file, directory (its files) or glob to follow"}, fromParam, formatParam("raw")},
+		[]PresetParam{{Name: "path", Required: true, Help: "a file, a directory (its files) or a glob such as /var/log/*.log, to follow"}, fromParam, formatParam("raw")},
 		func(p *PipelineConfig, v map[string]string, isDir IsDir) error {
 			sources, err := pathOrStdin(v, isDir)
 			p.PluginSources, p.PluginSinks = sources, pipeDefault("").PluginSinks
@@ -155,12 +164,12 @@ var presets = []Preset{
 		}},
 	{"serve", "Serve files or standard input live: a browser viewer at /, SSE at /stream",
 		slices.Concat([]PresetParam{pathParam, fromParam, formatParam("json"),
-			{Name: "listen", Default: "127.0.0.1:8080", Help: "HOST:PORT; [IPV6]:PORT"},
+			{Name: "listen", Default: "127.0.0.1:8080", Help: "HOST:PORT to listen on: 127.0.0.1:8080 this machine only, 0.0.0.0:8080 every IPv4 interface, [::]:8080 every IPv6 interface"},
 			serveTLS,
 			usersParam("readers"),
-		}, userParams, []PresetParam{
+		}, userParams("the one SCRAM user readers log in as, in place of users"), []PresetParam{
 			mirror[AuthOptions](PresetParam{Name: "proxy", List: true, Help: "addresses or CIDRs of the TLS-terminating proxies browsers come through; ',' between them"}, "trusted_proxies"),
-			mirror[HTTPSinkOptions](PresetParam{Name: "viewer", Default: "false", Help: "the login page and viewer, behind proxy; without user or users the viewer is always on"}, "viewer_page"),
+			mirror[HTTPSinkOptions](PresetParam{Name: "viewer", Default: "false", Help: "a login page, then the viewer, for browsers behind proxy; without user or users the viewer is on anyway"}, "viewer_page"),
 		}, aclParams, tlsParams),
 		func(p *PipelineConfig, v map[string]string, isDir IsDir) error {
 			sources, err := pathOrStdin(v, isDir)
@@ -177,11 +186,11 @@ var presets = []Preset{
 			case err != nil:
 				return err
 			case auth != nil && v["tls"] == "off" && v["proxy"] == "":
-				return fmt.Errorf("user and users need tls (self, issuer or files), or proxy")
+				return &KeyError{"tls", errors.New("user and users need self, issuer or files, or proxy")}
 			case auth != nil:
 				sink["auth"] = auth
 			case v["proxy"] != "":
-				return fmt.Errorf("proxy needs user or users: browsers log in with SCRAM")
+				return &KeyError{"proxy", errors.New("needs user or users: browsers log in with SCRAM")}
 			}
 			if v["proxy"] != "" {
 				auth["trusted_proxies"] = list(v["proxy"])
@@ -189,12 +198,12 @@ var presets = []Preset{
 			switch v["viewer"] {
 			case "true":
 				if v["proxy"] == "" {
-					return fmt.Errorf("viewer=true needs proxy, behind which browsers log in; without users the viewer is always on")
+					return &KeyError{"viewer", errors.New("true needs proxy, behind which browsers log in; without users the viewer is always on")}
 				}
 				sink["login_page"], sink["viewer_page"] = true, true
 			case "false":
 			default:
-				return fmt.Errorf("viewer %q (valid: true, false)", v["viewer"])
+				return &KeyError{"viewer", fmt.Errorf("must be true or false, got %q", v["viewer"])}
 			}
 			sink["replay_lines"] = int64(1000) // a browser opened late sees the recent entries
 			p.Flow.Format = &FormatConfig{Type: v["format"]}
@@ -203,12 +212,12 @@ var presets = []Preset{
 		}},
 	{"edge", "Forward files or standard input to an aggregator over TLS, authenticated",
 		slices.Concat([]PresetParam{pathParam, fromParam,
-			{Name: "to", Required: true, Help: "the aggregator's HOST:PORT; [IPV6]:PORT"},
+			{Name: "to", Required: true, Help: "the aggregator's HOST:PORT, an IPv6 address in brackets: logs.example.net:9000, [2001:db8::1]:9000"},
 			transportParam,
 			mirror[TLSOptions](PresetParam{Name: "ca", Help: "CA file that verifies the aggregator; default: system roots"}, "ca_file"),
 			{Name: "pin", Help: "sha256//BASE64 of the aggregator's key, which it logs with tls=self"},
 			{Name: "server_name", Help: "name the aggregator's certificate carries; default: to's host"},
-		}, userParams, []PresetParam{
+		}, userParams("SCRAM user this edge logs in to the aggregator as"), []PresetParam{
 			mirror[TLSOptions](PresetParam{Name: "cert", Help: "client certificate file, for an aggregator with client_ca"}, "cert_file"),
 			mirror[TLSOptions](PresetParam{Name: "key", Help: "client key file"}, "key_file"),
 			{Name: "node", Help: "origin label; default: this host's name"},
@@ -241,7 +250,7 @@ var presets = []Preset{
 			case v["cert"] != "" && v["key"] != "":
 				auth = map[string]any{"type": "mtls"}
 			default:
-				return fmt.Errorf("edge needs user, or cert and key: it never sends unauthenticated")
+				return &KeyError{"user", errors.New("required unless cert and key are set; an edge never sends unauthenticated")}
 			}
 			sink := map[string]any{"host": host, "port": port, "tls": tls, "auth": auth}
 			if v["node"] != "" {
@@ -252,11 +261,11 @@ var presets = []Preset{
 		}},
 	{"aggregator", "Receive from edges over TLS, authenticated, to files or standard output",
 		slices.Concat([]PresetParam{
-			{Name: "listen", Default: "0.0.0.0:9000", Help: "HOST:PORT; [IPV6]:PORT; [::] for IPv6 only"},
+			{Name: "listen", Default: "0.0.0.0:9000", Help: "HOST:PORT to listen on: 0.0.0.0:9000 every IPv4 interface, [::]:9000 every IPv6 interface, 127.0.0.1:9000 this machine only"},
 			transportParam,
 			aggregatorTLS,
 			usersParam("edges"),
-		}, userParams, []PresetParam{
+		}, userParams("the one SCRAM user edges log in as, in place of users"), []PresetParam{
 			mirror[TLSOptions](PresetParam{Name: "client_ca", Help: "CA file that verifies edge certificates (mTLS)"}, "client_ca_file"),
 			mirror[FileSinkOptions](PresetParam{Name: "out", Help: "directory for the received entries; default: standard output"}, "directory"),
 			formatParam("json"),
@@ -283,7 +292,7 @@ var presets = []Preset{
 			case v["client_ca"] != "":
 				src["auth"] = map[string]any{"type": "mtls"}
 			default:
-				return fmt.Errorf("aggregator needs user, users or client_ca: it never receives unauthenticated")
+				return &KeyError{"users", errors.New("required unless user or client_ca is set; an aggregator never receives unauthenticated")}
 			}
 			p.PluginSources = append(p.PluginSources, PluginSourceConfig{ID: "edges", Type: typ, Config: src})
 			p.PluginSinks = pipeDefault("").PluginSinks
@@ -331,13 +340,13 @@ func applyPreset(p *PipelineConfig, name string, values map[string][]string, isD
 		case j < 0:
 			return fmt.Errorf("preset %s has no key %q (valid: %s)", name, k, strings.Join(keys, ", "))
 		case len(each) > 1 && !r.Params[j].List:
-			return fmt.Errorf("preset %s key %q takes one value", name, k)
+			return &KeyError{k, errors.New("takes one value")}
 		}
 		v[k] = cmp.Or(strings.Join(each, ","), v[k])
 	}
 	for _, k := range r.Params {
 		if k.Required && v[k.Name] == "" {
-			return fmt.Errorf("preset %s needs %s", name, k.Name)
+			return &KeyError{k.Name, errors.New("must be set")}
 		}
 	}
 	p.Name = cmp.Or(p.Name, name)
@@ -404,20 +413,20 @@ func listener(v map[string]string, key PresetParam) (map[string]any, error) {
 	mode := cmp.Or(v["tls"], key.Default)
 	i := slices.IndexFunc(tlsModes, func(m tlsMode) bool { return m.name == mode })
 	if i < 0 || !slices.Contains(key.Enum, mode) {
-		return nil, fmt.Errorf("tls %q (valid: %s)", mode, strings.Join(key.Enum, ", "))
+		return nil, &KeyError{"tls", fmt.Errorf("must be one of %s, got %q", strings.Join(key.Enum, ", "), mode)}
 	}
 	m := tlsModes[i]
 	for _, other := range tlsModes {
 		for k := range other.needs {
 			if _, needed := m.needs[k]; needed && v[k] == "" {
-				return nil, fmt.Errorf("tls=%s needs %s", mode, k)
+				return nil, &KeyError{k, fmt.Errorf("must be set for tls=%s", mode)}
 			} else if !needed && v[k] != "" {
-				return nil, fmt.Errorf("%s does not apply to tls=%s", k, mode)
+				return nil, &KeyError{k, fmt.Errorf("does not apply to tls=%s", mode)}
 			}
 		}
 	}
 	if v["hosts"] != "" && !m.made {
-		return nil, fmt.Errorf("hosts does not apply to tls=%s", mode)
+		return nil, &KeyError{"hosts", fmt.Errorf("does not apply to tls=%s", mode)}
 	}
 	if mode == "off" {
 		return opts, nil
@@ -439,11 +448,11 @@ func listener(v map[string]string, key PresetParam) (map[string]any, error) {
 func scramAuth(v map[string]string) (map[string]any, error) {
 	switch {
 	case v["user"] != "" && v["users"] != "":
-		return nil, fmt.Errorf("user or users, not both")
+		return nil, &KeyError{"user", errors.New("set user or users, not both")}
 	case v["user"] != "":
 		return map[string]any{"type": "scram", "username": v["user"], "password_file": cmp.Or(v["password_file"], "/dev/tty")}, nil
 	case v["password_file"] != "":
-		return nil, fmt.Errorf("password_file needs user")
+		return nil, &KeyError{"password_file", errors.New("needs user")}
 	case v["users"] != "":
 		return map[string]any{"type": "scram", "credentials_file": v["users"]}, nil
 	}
@@ -454,7 +463,7 @@ func splitAddr(key, addr string) (string, int64, error) {
 	host, p, err := net.SplitHostPort(addr)
 	port, perr := strconv.ParseUint(p, 10, 16)
 	if err != nil || perr != nil || port == 0 {
-		return "", 0, fmt.Errorf("%s %q: want HOST:PORT, an IPv6 address in brackets", key, addr)
+		return "", 0, &KeyError{key, fmt.Errorf("must be HOST:PORT, an IPv6 address in brackets as in [::1]:9000, got %q", addr)}
 	}
 	return host, int64(port), nil
 }
@@ -462,7 +471,7 @@ func splitAddr(key, addr string) (string, int64, error) {
 // chainType is a transport's chain plugin type, both a source and a sink
 func chainType(transport string) (string, error) {
 	if !slices.Contains(transports(), transport) {
-		return "", fmt.Errorf("transport %q (valid: %s)", transport, strings.Join(transports(), ", "))
+		return "", &KeyError{"transport", fmt.Errorf("must be one of %s, got %q", strings.Join(transports(), ", "), transport)}
 	}
 	return transport + "_chain", nil
 }
@@ -39,34 +39,39 @@ func TestPresetStartsAndNamesItsPipeline(t *testing.T) {
 }

 // Keys are checked against the preset's own, required ones enforced, and
-// the edge and aggregator refuse to run without authentication.
+// the edge and aggregator refuse to run without authentication; a refusal of
+// one key is a KeyError at it, the others name the preset.
 func TestPresetKeysAreChecked(t *testing.T) {
 	isolateConfig(t)
 	for spec, want := range map[string]string{
 		"nope":                             `no preset "nope" (valid: pipe, tail, serve, edge, aggregator)`,
 		"tail:path=x,colour=1":             `preset tail has no key "colour" (valid: path, from, format)`,
-		"tail":                             "preset tail needs path",
+		"tail":                             "path: must be set",
 		"tail:path=x,format.type=json":     "preset keys do not nest",
-		"tail:path=x,path=y":               `key "path" takes one value`,
-		"serve:listen=8080":                `listen "8080": want HOST:PORT`,
-		"serve:tls=self,cert=c":            "cert does not apply to tls=self",
-		"serve:tls=files,cert=c":           "tls=files needs key",
-		"serve:viewer=yes":                 `viewer "yes"`,
-		"serve:proxy=127.0.0.1":            "proxy needs user or users",
-		"serve:viewer=true":                "viewer=true needs proxy",
-		"serve:user=u":                     "user and users need tls (self, issuer or files), or proxy",
-		"serve:tls=self,user=u,users=f":    "user or users, not both",
-		"edge:to=agg:9000":                 "it never sends unauthenticated",
-		"edge:to=agg:9000,password_file=p": "password_file needs user",
-		"edge:to=agg:9000,user=u,password_file=p,transport=udp": `transport "udp"`,
-		"aggregator:users=u,tls=off":                            `tls "off" (valid: `,
-		"aggregator:user=u,users=f":                             "user or users, not both",
-		"aggregator":                                            "it never receives unauthenticated",
+		"tail:path=x,path=y":               "path: takes one value",
+		"serve:listen=8080":                `listen: must be HOST:PORT, an IPv6 address in brackets as in [::1]:9000, got "8080"`,
+		"serve:tls=self,cert=c":            "cert: does not apply to tls=self",
+		"serve:tls=files,cert=c":           "key: must be set for tls=files",
+		"serve:viewer=yes":                 `viewer: must be true or false, got "yes"`,
+		"serve:proxy=127.0.0.1":            "proxy: needs user or users",
+		"serve:viewer=true":                "viewer: true needs proxy",
+		"serve:user=u":                     "tls: user and users need self, issuer or files, or proxy",
+		"serve:tls=self,user=u,users=f":    "user: set user or users, not both",
+		"edge:to=agg:9000":                 "user: required unless cert and key are set; an edge never sends unauthenticated",
+		"edge:to=agg:9000,password_file=p": "password_file: needs user",
+		"edge:to=agg:9000,user=u,password_file=p,transport=udp": `transport: must be one of tcp, http, got "udp"`,
+		"aggregator:users=u,tls=off":                            `tls: must be one of self, issuer, files, got "off"`,
+		"aggregator:user=u,users=f":                             "user: set user or users, not both",
+		"aggregator":                                            "users: required unless user or client_ca is set; an aggregator never receives unauthenticated",
 	} {
 		_, err := Load(Args{Specs: specs("preset", spec)})
 		if err == nil || !strings.Contains(err.Error(), want) {
 			t.Errorf("%s: err = %v, want %s", spec, err, want)
 		}
+		ke, keyed := errors.AsType[*KeyError](err)
+		if keyed == strings.Contains(want, "preset") || keyed && !strings.HasPrefix(want, ke.Key+": ") {
+			t.Errorf("%s: %v placed at %v", spec, err, ke)
+		}
 	}
 }

@@ -127,7 +132,7 @@ func TestPresetUserWithoutPasswordFileAsks(t *testing.T) {
 // A preset path ending in '/' is a directory, there yet or not; any other is
 // what isDir answers, a directory named with brackets too: this host's,
 // reading ~ as home, or off it the user's answer, a single file too; without
-// one it is a pattern when it holds a glob, and otherwise ErrPathKind asks
+// one it is a pattern when it holds a glob, and otherwise PathKindError asks
 func TestPresetPathKind(t *testing.T) {
 	home := t.TempDir()
 	t.Setenv("HOME", home)
@@ -145,8 +150,8 @@ func TestPresetPathKind(t *testing.T) {
 		{"~/logs", HostIsDir, "~/logs *"}, {home + "/later/", HostIsDir, home + "/later/ *"}} {
 		p, err := ExpandPreset("tail", map[string]string{"path": c.path}, c.isDir)
 		if c.want == "" {
-			if !errors.Is(err, ErrPathKind) {
-				t.Errorf("%s: %v, want ErrPathKind", c.path, err)
+			if pk, ok := errors.AsType[*PathKindError](err); !errors.Is(err, ErrPathKind) || !ok || pk.Path != c.path {
+				t.Errorf("%s: %v, want ErrPathKind asking about it", c.path, err)
 			}
 			continue
 		}
@@ -35,7 +35,7 @@ type Plugin struct {
 	Type    string `json:"type"`
 	Side    Side   `json:"side"`
 	HTTP    bool   `json:"http"`   // speaks HTTP: takes bearer tokens and request limits
-	Single  bool   `json:"single"` // one instance per process
+	Single  bool   `json:"single"` // one instance per process, as standard input is one
 	Summary string `json:"summary"`
 	options reflect.Type
 }
@@ -45,15 +45,15 @@ var plugins = []Plugin{
 	{"source", "file", Local, false, false, "Follow the files of a directory that match a pattern", reflect.TypeFor[FileSourceOptions]()},
 	{"source", "random", Local, false, false, "Generated entries, to check a deployment before real logs", reflect.TypeFor[RandomSourceOptions]()},
 	{"source", "null", Local, false, false, "Nothing; holds a source's place until one is chosen", reflect.TypeFor[NullSourceOptions]()},
-	{"source", "tcp_chain", ChainListener, false, false, "Entries from tcp_chain sinks of other instances", reflect.TypeFor[TCPChainSourceOptions]()},
-	{"source", "http_chain", ChainListener, true, false, "Entry batches from http_chain sinks of other instances", reflect.TypeFor[HTTPChainSourceOptions]()},
+	{"source", "tcp_chain", ChainListener, false, false, "Receive entries from other nodes' tcp_chain sinks, each over one lasting TCP connection", reflect.TypeFor[TCPChainSourceOptions]()},
+	{"source", "http_chain", ChainListener, true, false, "Receive entries from other nodes' http_chain sinks, as batches each posts over HTTP", reflect.TypeFor[HTTPChainSourceOptions]()},
 	{"sink", "console", Local, false, false, "Standard output or standard error", reflect.TypeFor[ConsoleSinkOptions]()},
 	{"sink", "file", Local, false, false, "Rotating files", reflect.TypeFor[FileSinkOptions]()},
 	{"sink", "null", Local, false, false, "Discards; holds a sink's place until one is chosen", reflect.TypeFor[NullSinkOptions]()},
 	{"sink", "tcp", Listener, false, false, "Serve entries to TCP clients, one per line", reflect.TypeFor[TCPSinkOptions]()},
 	{"sink", "http", Listener, true, false, "Serve entries as server-sent events, with a browser viewer", reflect.TypeFor[HTTPSinkOptions]()},
-	{"sink", "tcp_chain", Dialer, false, false, "Forward entries to a tcp_chain source", reflect.TypeFor[TCPChainSinkOptions]()},
-	{"sink", "http_chain", Dialer, true, false, "Post entry batches to an http_chain source", reflect.TypeFor[HTTPChainSinkOptions]()},
+	{"sink", "tcp_chain", Dialer, false, false, "Forward entries to another node's tcp_chain source over one lasting TCP connection", reflect.TypeFor[TCPChainSinkOptions]()},
+	{"sink", "http_chain", Dialer, true, false, "Forward entries to another node's http_chain source in batches, an HTTP POST each", reflect.TypeFor[HTTPChainSinkOptions]()},
 }

 // Plugins lists the catalogue
@@ -64,12 +64,9 @@ func Plugins() []Plugin { return slices.Clone(plugins) }
 func (p Plugin) Keys() []Key { return p.applying(keys(p.options)) }

 func (p Plugin) applying(all []Key) []Key {
-	side, out := "listener", []Key{}
-	if p.Side == Dialer {
-		side = "dialer"
-	}
+	out := []Key{}
 	for _, k := range all {
-		if (k.Side == "" || k.Side == side) && (!k.HTTP || p.HTTP) {
+		if (k.Side == "" || k.Side == sideNames[p.Side] || k.Side == "listener" && p.Side == ChainListener) && (!k.HTTP || p.HTTP) {
 			if k.Keys != nil {
 				k.Keys = p.applying(k.Keys)
 			}
@@ -99,10 +96,10 @@ func (e *KeyError) Error() string { return e.Key + ": " + e.Err.Error() }
 func (e *KeyError) Unwrap() error { return e.Err }

 // option is one key of an options table, from its field's tags: toml names
-// it, default: holds the default as typed on a command line, help: says what
-// it does, and lw: lists its rules: required, enum=a|b, min=N, max=N,
-// zero=MEANING (zero is a value, not the default), hint=KIND, listener or
-// dialer, and http (only plugins that speak HTTP take it).
+// it, default: holds the default as a command line types it, help: says what
+// it does, lw: lists its rules: required, enum=a|b, min=N, max=N, zero=MEANING
+// (a value, not the default), hint=KIND, a side (listener, a chain source's
+// too; chain_listener; dialer), and http (only plugins that speak HTTP take it).
 type option struct {
 	Key
 	index int
@@ -125,7 +122,7 @@ func options(t reflect.Type) []option {
 			case "":
 			case "required":
 				o.Required = true
-			case "listener", "dialer":
+			case "listener", "chain_listener", "dialer":
 				o.Side = name
 			case "http":
 				o.HTTP = true
@@ -173,7 +173,8 @@ func TestLoadReportsEveryProblemALine(t *testing.T) {
 }

 // A plugin lists the table keys that apply to it: those of its side, a chain
-// source's being a listener's, and the HTTP ones only when it speaks HTTP
+// source's being a listener's and its own, and the HTTP ones only when it
+// speaks HTTP
 func TestTableKeysFollowThePlugin(t *testing.T) {
 	has := func(role, typ, path string) bool {
 		p, _ := LookupPlugin(role, typ)
@@ -190,7 +191,7 @@ func TestTableKeysFollowThePlugin(t *testing.T) {
 	for path, want := range map[string]bool{
 		"sink tcp_chain tls.pin_sha256": true, "sink tcp_chain tls.self_signed": false,
 		"source tcp_chain tls.self_signed": true, "source tcp_chain tls.pin_sha256": false,
-		"source tcp_chain auth.node_binding": true, "sink tcp_chain auth.credentials_file": false,
+		"source tcp_chain auth.node_binding": true, "sink http auth.node_binding": false, "sink tcp_chain auth.credentials_file": false,
 		"sink tcp acl.requests_per_second_per_client": false, "sink tcp auth.token_lifetime_ms": false,
 		"sink http acl.requests_per_second_per_client": true, "sink http auth.trusted_proxies": true,
 	} {
@@ -59,10 +59,10 @@ func ValidatePipelines(pipelines []PipelineConfig) error {
 		}
 		names[p.Name] = true
 		if len(p.PluginSources) == 0 {
-			at(path+".plugin_sources", errors.New("no sources defined"))
+			at(path+".plugin_sources", errors.New("add a source; a pipeline needs at least one"))
 		}
 		if len(p.PluginSinks) == 0 {
-			at(path+".plugin_sinks", errors.New("no sinks defined"))
+			at(path+".plugin_sinks", errors.New("add a sink; a pipeline needs at least one"))
 		}
 		if err := checkFlow(p.Flow, path+".flow"); err != nil {
 			errs = append(errs, err)
@@ -77,7 +77,7 @@ func ValidatePipelines(pipelines []PipelineConfig) error {
 			case !ok:
 				at(path+".type", fmt.Errorf("unknown %s type %q", role, typ))
 			case plugin.Single && single[role+typ] != "":
-				at(path, fmt.Errorf("one %s %s may run, and pipeline %q has it", typ, role, single[role+typ]))
+				at(path, fmt.Errorf("one %s %s may run, and pipeline %q has it, as lw has one standard input; give this pipeline another %s", typ, role, single[role+typ], role))
 			default:
 				ids[list+id] = true
 				if plugin.Single {
@@ -414,15 +414,17 @@ func ParsePrefix(entry, network string) (netip.Prefix, error) {
 	if err != nil {
 		addr, aerr := netip.ParseAddr(entry)
 		if aerr != nil || addr.Zone() != "" {
-			return netip.Prefix{}, fmt.Errorf("neither an address nor a CIDR (and no zone)")
+			return netip.Prefix{}, errors.New("not an IP address or CIDR; host names and IPv6 zones are not accepted")
 		}
 		prefix = netip.PrefixFrom(addr, addr.BitLen())
 	}
 	switch a := prefix.Addr(); {
 	case a.Is4In6():
 		return netip.Prefix{}, fmt.Errorf("IPv4-mapped; write it as IPv4")
-	case network == "tcp4" && !a.Is4(), network == "tcp6" && a.Is4():
-		return netip.Prefix{}, fmt.Errorf("not of the listener's family (%s)", network)
+	case network == "tcp4" && !a.Is4():
+		return netip.Prefix{}, errors.New("IPv6, and the listener's host is IPv4; write an IPv4 address or CIDR")
+	case network == "tcp6" && a.Is4():
+		return netip.Prefix{}, errors.New("IPv4, and the listener's host is IPv6; write an IPv6 address or CIDR")
 	}
 	return prefix, nil
 }
@@ -520,11 +522,15 @@ func (c *FilterConfig) Check() error {
 }

 // Scan decodes a flow stage's command-line map into target, rejecting keys
-// target does not declare: a misspelled key must fail, not be dropped.
+// target does not declare: a misspelled key must fail, not be dropped. Its
+// values take their kinds as a plugin's do, a wrong one refused at its key.
 func Scan(configMap map[string]any, target any) error {
 	if err := checkKeys(configMap, reflect.TypeOf(target), ""); err != nil {
 		return err
 	}
+	if err := coerce(reflect.TypeOf(target).Elem(), configMap, ""); err != nil {
+		return err
+	}
 	return lconfig.ScanMap(configMap, target)
 }

@@ -811,7 +811,8 @@ func TestPresetFormShowsTheChoices(t *testing.T) {
 	ps := config.Presets()
 	tail := ps[slices.IndexFunc(ps, func(p config.Preset) bool { return p.Name == "tail" })].Params
 	format := tail[slices.IndexFunc(tail, func(p config.PresetParam) bool { return p.Name == "format" })]
-	if screen := strings.Join(text(render(a, 80, 24), 80), "\n"); !strings.Contains(screen, format.Usage()) || len(format.Enum) == 0 {
+	note := strings.Join(format.Enum, "|") + ": " + strings.Fields(format.Help)[0] // the help wraps
+	if screen := strings.Join(text(render(a, 80, 24), 80), "\n"); !strings.Contains(screen, note) || len(format.Enum) == 0 {
 		t.Fatalf("format's choices not shown:\n%s", screen)
 	}
 }
@@ -96,7 +96,7 @@ section "Rules"
 rejects() { ! lw --check --source null --sink "$1" >/dev/null 2>"$LOG/check.err" && grep -q -- "$2" "$LOG/check.err" && echo 1 || echo 0; }
 # warns SINK PATTERN: lw --check builds SINK and WARNs PATTERN
 warns() { lw --check --source null --sink "$1" 2>&1 >/dev/null | grep ' WARN ' | grep -q -- "$2" && echo 1 || echo 0; }
-check "an IPv4 entry on an IPv6 listener is refused" "$(rejects 'tcp:host=::1,port=15881,acl.allow=10.0.0.0/8' "not of the listener's family")"
+check "an IPv4 entry on an IPv6 listener is refused" "$(rejects 'tcp:host=::1,port=15881,acl.allow=10.0.0.0/8' "IPv4, and the listener's host is IPv6")"
 check "an acl on a dialer is refused" "$(rejects 'tcp_chain:host=127.0.0.1,port=15881,acl.deny=10.0.0.1' 'unknown key "acl"')"
 check "a CIDR with host bits warns, naming the network it matches" "$(warns 'tcp:host=127.0.0.1,port=15881,acl.allow=10.0.0.1/8' 'network 10.0.0.0/8')"
 check "a deny list alone on a wildcard listener warns" "$(warns 'tcp:port=15881,acl.deny=10.0.0.1' 'admits all that acl.deny does not list')"