fix: preserve full Error for unknown decrypt failures + improve dedup comment

Addresses 3 distinct PR #391 review findings (Copilot Major + Codex P2 + Copilot
nitpick — all valid):

#2 Copilot Major + #4 Codex P2 (same root, MAJOR):
   The previous slim of `errorContext.err` to `{name, message, type}` was applied
   uniformly to all three decrypt-failure branches. The unknown-error branch
   (lines 481-491 — "Unknown/unexpected errors (protobuf, parsing, etc.)") is
   exactly where stack traces matter MOST: there's no recovery path for those,
   so production root-cause analysis depends on having the stack.

   FIX: condition `errorContext.err` on category. Only slim for known-recoverable
   categories (corrupted-session / session-record). Unknown errors keep the full
   originalError so logger.error pino still emits the stack. Adds the
   `isRecoverableCategory` flag to make the intent obvious to future readers.

#3 Copilot (related to #2):
   The previous comment claimed "Full stack is still available via originalError
   if needed in custom handlers" — but originalError wasn't actually exposed
   anywhere downstream and the error wasn't re-thrown. Updated the comment to
   reflect the new conditional behavior (slim only for recoverable cases) so
   future maintainers don't misread the intent.

#1 Copilot (dedup window comment, MINOR):
   The 5000ms dedup window in src/index.ts can suppress genuinely-different
   errors for the same JID within the window. Kept the 5s value (it's the right
   trade-off for noisy production streams) but expanded the comment to spell
   out the trade-off and how to bypass it (BAILEYS_LOG_LEVEL=debug).

Skipped: nothing — all reviewer points addressed.

Tests: 35/35 suites, 824/824 still passing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Utils/decode-wa-message.ts

@@ -427,8 +427,12 @@ export const decryptMessageNode = (
 
 						// Slim error projection — keep name/message/type for diagnosis,
 						// drop `stack` which adds 4-5 lines of node_modules paths per log
-						// for known-recoverable libsignal errors. Full stack is still
-						// available via originalError if needed in custom handlers.
+						// for known-recoverable libsignal errors.
+						//
+						// CRITICAL: only slim for KNOWN-RECOVERABLE categories (corrupted /
+						// session-record). The unknown-error branch keeps the full Error so
+						// protobuf/parsing/runtime bugs still emit a stack trace where it
+						// matters most. Catches Copilot/Codex P2 review on PR #391.
 						const slimErr = originalError
 							? {
 									name: (originalError as { name?: string }).name,
@@ -436,10 +440,11 @@ export const decryptMessageNode = (
 									type: (originalError as { type?: string }).type
 								}
 							: undefined
+						const isRecoverableCategory = isCorrupted || isSessionRecord
 
 						const errorContext = {
 							key: fullMessage.key,
-							err: slimErr,
+							err: isRecoverableCategory ? slimErr : originalError,
 							messageType: tag === 'plaintext' ? 'plaintext' : attrs.type,
 							sender,
 							author,

src/index.ts

@@ -30,8 +30,13 @@ console.info = function (...args: unknown[]) {
 const _errorTimestamps = new Map<string, number>()
 // Dedup window for repeated decrypt-error console lines (Bad MAC / Counter / etc).
 // Was 150ms, but retry attempts of the SAME message are typically ~300-1000ms apart,
-// so the second attempt fell outside the window and double-printed. 5s comfortably
-// covers a retry pair without suppressing genuinely new errors for the same JID.
+// so the second attempt fell outside the window and double-printed.
+//
+// TRADE-OFF: dedup key is `errorType + JID` (no message-id). With 5s, a burst of
+// errors for the SAME JID — even of slightly different categories or different
+// messages — collapses to one log line every 5s. This is intentional for a noisy
+// production stream; if you need per-message visibility, set BAILEYS_LOG_LEVEL=debug
+// to bypass this console-side dedup and see the structured pino logs in full.
 const DEDUP_WINDOW_MS = 5000
 
 console.error = function (...args: unknown[]) {