Fields

Logger and call-site fields are property lists:

(make-logger :fields '(:service "api" :attempt 1))
(log-info logger "connected" :host "db.example" :tls t)

Keys and duplicates

Keys must be symbols or strings. Property lists must be finite, proper, and contain an even number of elements — a circular or dotted list signals invalid-log-fields in bounded time rather than looping or erroring obscurely. Length is bounded too: a plist of more than 16,384 pairs signals log-resource-limit-exceeded (see Resource limits), not invalid-log-fields.

Field names are canonicalized case-insensitively (a symbol's symbol-name, or a string as-is, downcased) before comparison. Duplicate keys after canonicalization — for example :PORT and "port" in the same plist — signal invalid-log-fields.

Snapshotting

Records and loggers recursively snapshot strings, conses, arrays, hash tables, and the explicit JSON containers (json-object, json-array) described in Handlers. Every public accessor (log-record-fields, logger-fields, json-object-members, json-array-elements, …) returns a fresh copy, so a caller that later mutates a value it passed in — or a value it read back out — can never change what a record or logger holds. Cyclic values signal invalid-log-fields instead of recursing indefinitely: the snapshot walk marks each container it is currently copying in an eq table, so a value that reaches itself is rejected rather than followed. The list-shape checks that run before the walk — plist properness, JSON object member and array element lists — use Floyd's tortoise-and-hare instead, so a circular list is rejected in bounded time without being traversed.

Condition details

Field-related conditions expose their details through readers rather than requiring callers to parse report strings:

• invalid-log-fields-value / invalid-log-fields-reason
• unsupported-json-value-value / unsupported-json-value-reason
• log-resource-limit-resource / log-resource-limit-limit / log-resource-limit-actual

Resource limits

Recursive snapshots enforce fixed safety limits so a hostile or accidentally huge field value cannot exhaust memory or overflow the stack:

Limit	Value
Nesting depth	64
Visited nodes	65,536
Characters per string	1,048,576
Array elements / object members / hash-table entries	16,384

Exceeding any of these signals log-resource-limit-exceeded. Its log-resource-limit-resource reader identifies which bound failed — :depth, :nodes, :string-length, :array-elements, :hash-table-entries, or, for log-condition's own output bounds, :condition-message-length / :condition-backtrace-length (see Logging Conditions). log-resource-limit-limit and log-resource-limit-actual report the configured bound and the observed value.