release: 1.0.0

first stable release. pre-1.0.0 verification complete: all surviving MED regressions and
gaps resolved and independently re-fired, tree audited clean across the suite.

Signed-off-by: disqualifier <dev@disqualifier.me>

README.md

@@ -13,12 +13,12 @@ and emit; their records flow into the handlers `log_setup` wired.
 ## Install
 
 ```
-log_setup @ git+ssh://git@git.rethinkstudios.io/rethink-public/log_setup.git@v0.5.0
+log_setup @ git+ssh://git@git.rethinkstudios.io/rethink-public/log_setup.git@v1.0.0
 ```
 
 No dependencies — stdlib only.
 
-Drop the `@v0.5.0` suffix from the line above to install the latest unpinned.
+Drop the `@v1.0.0` suffix from the line above to install the latest unpinned.
 
 ## Quick start
 
@@ -44,7 +44,10 @@ emits; the records land in the configured root.
   `getLogger` name each module used, so you see which lib/module logged.
 - **Rotation** (`rotate=`):
   - `"daily"` (default) — rolls at midnight into `log_dir`, keeps `backup_count` days.
-  - `"size"` — rolls at `max_bytes` into `log_dir`, keeps `backup_count`.
+  - `"size"` — rolls at `max_bytes` into `log_dir`, keeps `backup_count`. `backup_count=0`
+    means **keep no rolled history**: the live file still rolls at `max_bytes` (size is
+    always bounded), each rolled file is deleted immediately after landing — it does not
+    disable rotation (see **Retention** below).
   - `"on_start"` — on startup, moves an existing live file into `log_dir` and starts fresh;
     prunes to `backup_count`.
   - `None` — single file, no rotation.
@@ -52,7 +55,8 @@ emits; the records land in the configured root.
   `<project>.<timestamp>.log[.gz]`; the live file keeps its own name.
 - **compress=True** (default) gzips each rolled file.
 - **Retention** = `backup_count` (default 14) for every mode — unless tiered retention is
-  enabled (below).
+  enabled (below). For `rotate="size"`, `backup_count=0` is "keep none" (not "disable
+  rotation") — see the `size` bullet above and the note at the bottom of this section.
 - **console=True** (off by default) also logs to stdout in the same format — opt in when
   you want live terminal output alongside the file.
 
@@ -88,6 +92,7 @@ are deleted past the count. If instead you want the recent logs **uncompressed**
 without `zcat`) and older ones **gzipped**, pass the two tier knobs:
 
 ```python
+# app run from  bestbuy/run.py , with name="latest":
 setup_logging(
     name="latest",
     rotate="on_start",        # works for on_start, daily, and size
@@ -96,13 +101,15 @@ setup_logging(
 )
 ```
 
-Result in `log_dir` (newest → oldest):
+Result — the live file stays at its stable path in cwd; `log_dir` (default `logs/`) holds
+the tiered historic files, named off the project stem (newest → oldest):
 
 ```
-latest.log                       <- live "latest" (stable, tail -f)
-latest.<t1>.log   latest.<t2>.log   latest.<t3>.log       <- 3 newest: plain
-latest.<t4>.log.gz ... latest.<t10>.log.gz                 <- next 7: gzipped
-(anything past 10 deleted)
+./latest.log                                              <- live (stable, tail -f, in cwd)
+logs/
+    bestbuy.<t1>.log  bestbuy.<t2>.log  bestbuy.<t3>.log   <- 3 newest: plain
+    bestbuy.<t4>.log.gz ... bestbuy.<t10>.log.gz           <- next 7: gzipped
+    (anything past 10 deleted)
 ```
 
 - Each restart (`on_start`) or roll (`daily`/`size`) moves the live file into `log_dir`,
@@ -132,17 +139,22 @@ Promtail glob, bind-mount path, or your `tail` command.
 ```python
 setup_logging(name="run", output="json")
 logging.getLogger("bot.core").info("ready", extra={"monitor": "heartbeat"})
-# -> {"time": "2026-06-28T14:03:11Z", "level": "INFO", "module": "bot.core",
-#     "message": "ready", "monitor": "heartbeat"}
+# -> {"time": "2026-06-28T14:03:11Z", "ts": 1782151391, "level": "INFO",
+#     "module": "bot.core", "message": "ready", "monitor": "heartbeat"}
 ```
 
-- **Fields:** `time`, `level`, `module`, `message` always; any `extra={...}` keys land
-  as **top-level** fields (stamp `monitor`/`service`/request-id for Loki labels — the lib
-  stays domain-agnostic); error records carry the traceback in `exc_info` (never dropped).
+- **Fields:** `time`, `ts`, `level`, `module`, `message` always; any `extra={...}` keys
+  land as **top-level** fields (stamp `monitor`/`service`/request-id for Loki labels —
+  the lib stays domain-agnostic); error records carry the traceback in `exc_info` (never
+  dropped).
 - **Time is UTC ISO-8601 with a `Z`** (`2026-06-28T14:03:11Z`), not local. json is the
   aggregation path — logs from many servers/containers sort unambiguously only in UTC;
   Grafana converts to local for display. (Text mode stays local — that's a human on one
   box.)
+- **`ts` (added v0.6.0)** is the same instant as a unix epoch integer
+  (`int(record.created)`, second resolution) alongside `time` — for a consumer that wants
+  a sortable number instead of parsing the ISO string. Additive: existing `time` is
+  unchanged, and a consumer that ignores unknown JSON keys is unaffected.
 - Both file and console use the chosen format. `fmt`/`datefmt` apply to text only (json
   builds fields, not a format string). An unknown `output` falls back to text + warns,
   never crashes. **Zero new deps** — stdlib `json` only.
@@ -228,6 +240,42 @@ setup_logging(name="run", queue=True)
   duplicate lines) and leaves handlers your app added itself alone.
 - **Never crashes the app over logging:** if `log_dir` isn't writable, it falls back to
   console-only with a warning instead of raising.
+- **`rotate="size"` always bounds the live file (v0.5.1+).** Previously, `backup_count=0`
+  with `rotate="size"` silently disabled rotation entirely (the live file grew forever,
+  ignoring `max_bytes`). As of v0.5.1, the live file always rolls at `max_bytes`
+  regardless of `backup_count`; `backup_count=0` means "keep zero rolled files" (each roll
+  is deleted right after it lands) rather than "never roll." `backup_count>=1` behaves as
+  documented (keeps that many rolled files). This does not change `"daily"`/`"on_start"`,
+  where `backup_count=0` still means "roll, but don't prune the rolled files" (unbounded
+  `log_dir` growth) — that is a separate, pre-existing knob, not this fix's scope.
+- **`console=True` writes to stdout (v0.6.3).** the console handler now binds `sys.stdout`
+  explicitly instead of the stdlib `StreamHandler` default of `sys.stderr`, so a supervisor
+  capturing stdout sees console log lines. `console` stays off by default — the file is the
+  primary sink.
+- **`"daily"` regression fixed (v0.6.2).** v0.5.1's `rotate="size"` fix above shared its
+  rotator with `"daily"`, so a `rotate="daily", backup_count=0` roll was incorrectly
+  deleted at every midnight rollover instead of just landing unpruned. The rotator is now
+  rotate-mode aware: the zero-retention delete only ever fires for `"size"`, matching the
+  contract in the bullet above — `"daily"`/`"on_start"` with `backup_count=0` were always
+  meant to roll without pruning and now do again.
+- **Gzip is atomic compress-or-skip (v0.5.1+).** `_gzip_file` writes to a `.tmp` sibling,
+  verifies it decompresses cleanly, and only then `os.replace`s it onto the final `.gz` and
+  removes the plain source — a crash/OOM/interrupt at any point leaves the plain `.log`
+  intact with no `.gz` (or the `.tmp` cleaned up), so this code never produces a truncated
+  `.gz` at the path retention trusts. Because a corrupt `.gz` can't arise from this path, the
+  tiered retention dedupe drops a plain twin unconditionally when its `.gz` exists (no
+  runtime `_gz_intact` reconciliation — that was removed once compression became atomic).
+- **Setup-time warnings reach the log file (v0.6.0+).** Previously, a warning raised
+  during `setup_logging` itself (an invalid `module_levels` entry, a handler failing to
+  close on re-setup, an unknown `rotate` value) was emitted *before* any handler was
+  attached, so it only reached stderr via logging's `lastResort` fallback and never
+  `run.log`. As of v0.6.0 these are buffered and flushed once the handlers are attached,
+  so they land in the configured log like any other record.
+- **JSON output gained a `ts` field (v0.6.0, additive).** Alongside the existing `time`
+  (UTC ISO-8601, unchanged), each JSON line now also carries `ts`: the same instant as a
+  unix epoch integer (`int(record.created)`, second resolution) — for a consumer that
+  wants a sortable number instead of parsing the ISO string. Purely additive: `time` is
+  byte-for-byte unchanged, and a consumer that ignores unknown JSON keys is unaffected.
 
 ## Scope — what this is NOT
 

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "log_setup"
-version = "0.5.0"
+version = "1.0.0"
 description = "stdlib app-entry-point logging setup: live run.log, rotation, gzip, retention, consistent format"
 requires-python = ">=3.10"
 dependencies = []

src/log_setup/__init__.py

@@ -1,22 +1,21 @@
-"""log_setup — app-entry-point logging configuration (sync, stdlib only).
-
-call once at an application's entry point to configure the whole process: a live
-run.log, rotation (daily/size/on_start), gzip of rolled files, retention, console
-output, and a consistent `time | module | level | message` format.
+"""log_setup - app-entry-point logging configuration (sync, stdlib only). see README.
 
     from log_setup import setup_logging
 
     setup_logging(name="run", level="INFO")        # daily rotation, logs/ dir, gzip
     log = logging.getLogger(__name__)
-    log.info("up")                                  # -> run.log + console
+    log.info("up")                                  # -> run.log (add console=True for stdout too)
 
-reusable libraries do NOT call this — they only `logging.getLogger(__name__)` and
-emit; the application owns this setup. shipping logs to a backend is out of scope
-(that's Promtail's job against the produced files).
+reusable libraries do NOT call this; the application owns setup, libraries only emit.
 """
 
+from importlib.metadata import PackageNotFoundError, version
+
 from .setup import setup_logging
 
 __all__ = ["setup_logging"]
 
-__version__ = "0.5.0"
+try:
+    __version__ = version("log_setup")
+except PackageNotFoundError:
+    __version__ = "0.0.0+unknown"

src/log_setup/formats.py

@@ -1,10 +1,8 @@
 """log formats for the app-wide setup: human-readable text + structured JSON lines.
 
-two output formats, two proven needs. `text` (default) is the human `tail -f` format
-(`time | module | level | message`, local time). `json` is the Grafana/Loki path —
-one JSON object per line (JSON Lines), fields parsed into labels natively, UTC
-timestamps so logs aggregated from many machines/containers sort unambiguously.
-`%(name)s` is the getLogger name the emitting module used, so each module shows.
+`text` (default) is the human `tail -f` format (`time | module | level | message`,
+local time). `json` is the Grafana/Loki path - one JSON object per line, UTC
+timestamps so logs aggregated from many machines sort unambiguously. see README.
 """
 
 import datetime
@@ -15,29 +13,28 @@ DEFAULT_FORMAT = "%(asctime)s | %(name)s | %(levelname)s | %(message)s"
 DEFAULT_DATEFMT = "%Y-%m-%d %H:%M:%S"
 
 _RESERVED = frozenset(vars(logging.makeLogRecord({})).keys()) | {"message", "asctime"}
-# this formatter's own canonical output keys — stdlib's LogRecord rejects `extra` keys
-# colliding with real attribute names (e.g. `module`), but `time`/`level` are NOT
-# LogRecord attrs, so a caller's extra={"time":...}/{"level":...} would otherwise
-# overwrite the UTC timestamp / levelname. guard them explicitly
-_OUTPUT_KEYS = frozenset({"time", "level", "module", "message"})
+# this formatter's own canonical output keys - stdlib's LogRecord rejects `extra` keys
+# colliding with real attribute names (e.g. `module`), but `time`/`level`/`ts` are NOT
+# LogRecord attrs, so a caller's extra={"time":...}/{"ts":...} would otherwise overwrite
+# the UTC timestamp / epoch. guard them explicitly
+_OUTPUT_KEYS = frozenset({"time", "ts", "level", "module", "message"})
 
 
 class JsonLinesFormatter(logging.Formatter):
     """format each record as a single-line JSON object (JSON Lines / .jsonl)
 
-    emits at minimum time/level/module/message. time is UTC ISO-8601 with a `Z`
-    suffix (e.g. 2026-06-28T14:03:11Z) so logs aggregated across machines and
-    containers sort unambiguously — Grafana converts to local for display. any
-    field passed via logging `extra={...}` lands as a top-level JSON field, which
-    is how a caller stamps monitor/service/request-id for Loki labels without the
-    lib knowing those domain concepts. a traceback (exc_info) is rendered into an
-    `exc_info` string field rather than dropped.
+    emits at minimum time/ts/level/module/message. `time` is UTC ISO-8601 with a `Z`
+    suffix; `ts` is the same instant as a unix epoch int, both sortable across
+    machines/containers. any field passed via logging `extra={...}` lands as a
+    top-level JSON field. a traceback (exc_info) is rendered into an `exc_info`
+    string field rather than dropped.
     """
 
     def format(self, record: logging.LogRecord) -> str:
         when = datetime.datetime.fromtimestamp(record.created, datetime.timezone.utc)
         payload = {
             "time": when.strftime("%Y-%m-%dT%H:%M:%SZ"),
+            "ts": int(record.created),
             "level": record.levelname,
             "module": record.name,
             "message": record.getMessage(),
@@ -46,8 +43,7 @@ class JsonLinesFormatter(logging.Formatter):
             if key not in _RESERVED and key not in _OUTPUT_KEYS and not key.startswith("_"):
                 payload[key] = value
         if record.exc_info:
-            # cache the rendered traceback on the record (as stdlib Formatter does) so a
-            # second handler/format() of the same record doesn't re-render it
+            # cache the rendered traceback on the record, like stdlib Formatter does
             if not record.exc_text:
                 record.exc_text = self.formatException(record.exc_info)
             payload["exc_info"] = record.exc_text
@@ -58,19 +54,27 @@ class JsonLinesFormatter(logging.Formatter):
         return json.dumps(payload, default=str)
 
 
-def build_formatter(output: str = "text", fmt=None, datefmt=None) -> logging.Formatter:
+def build_formatter(output: str = "text", fmt=None, datefmt=None, warnings: list = None) -> logging.Formatter:
     """build the formatter for the chosen output format
 
     `output="text"` (default) returns the human-readable text formatter, honoring
     the raw `fmt`/`datefmt` format-string overrides. `output="json"` returns the
-    structured `JsonLinesFormatter` (which ignores `fmt`/`datefmt` — it builds
+    structured `JsonLinesFormatter` (which ignores `fmt`/`datefmt` - it builds
     fields, not a format string). an unrecognized `output` falls back to text and
-    warns, never raising — a bad format arg must not take the app down.
+    warns, never raising - a bad format arg must not take the app down.
+
+    `warnings` is the setup-time buffer (see `setup_logging`): passing it appends
+    the unknown-output warning there instead of emitting immediately, so it lands
+    in the configured log like the other setup-time warnings rather than only
+    stderr. `None` (default) preserves the old immediate-emit behavior for direct
+    callers outside `setup_logging`.
     """
     if output == "json":
         return JsonLinesFormatter()
     if output != "text":
-        logging.getLogger(__name__).warning(
-            "log_setup: unknown output %r; falling back to 'text'", output
-        )
+        message = "log_setup: unknown output %r; falling back to 'text'"
+        if warnings is None:
+            logging.getLogger(__name__).warning(message, output)
+        else:
+            warnings.append((message, output))
     return logging.Formatter(fmt or DEFAULT_FORMAT, datefmt or DEFAULT_DATEFMT)

src/log_setup/rotation.py

@@ -1,13 +1,20 @@
 """custom namer/rotator + on-start rotation + retention pruning (stdlib only).
 
-the stdlib rotating handlers roll a file next to the live file; these helpers
-override the namer/rotator so rolled files land in `log_dir` and are gzipped when
-asked, keep the live file at its stable path, and handle the on-start and prune
-paths the handlers don't manage themselves.
+the stdlib rotating handlers roll a file next to the live file; these helpers override
+the namer/rotator so rolled files land in `log_dir` and are gzipped when asked, keep
+the live file at its stable path, and handle the on-start and prune paths the handlers
+don't manage themselves.
+
+FOOTGUN: compression is atomic - `_gzip_file` writes to a `.tmp` sibling, verifies it
+decompresses, and only then `os.replace`s it onto the final `.gz` and removes the plain.
+a crash/OOM/power-loss or failed verify at any point leaves the plain `.log` intact and
+no `.gz`, so a corrupt/partial `.gz` is never produced and retention never has to choose
+between an intact plain and a corrupt archive.
 """
 
 import gzip
 import os
+import re
 import shutil
 import time
 from typing import Callable, Optional, Tuple
@@ -16,15 +23,10 @@ from typing import Callable, Optional, Tuple
 def _move(source: str, dest: str) -> None:
     """rename source to dest, falling back to copy+unlink across filesystems
 
-    os.replace is atomic but raises OSError(EXDEV) when source and dest are on
-    different filesystems — exactly the container bind-mount / separate-logs-volume
-    case this lib targets. fall back to shutil.move (copy+unlink) so the roll still
-    lands instead of failing every rotation via the handler's silent handleError.
-
-    precondition: `dest` is a free, non-directory path (all call sites generate a unique
-    timestamped/dated dest). os.replace and shutil.move differ on a dest that already
-    exists as a directory, so this helper is not safe for arbitrary dests — only the
-    rotation paths that guarantee a fresh file dest.
+    FOOTGUN: os.replace is atomic but raises OSError(EXDEV) across filesystems (the
+    container bind-mount / separate-logs-volume case) - falls back to shutil.move so
+    the roll still lands instead of failing rotation silently. precondition: `dest` is
+    a free, non-directory path.
     """
     try:
         os.replace(source, dest)
@@ -35,10 +37,8 @@ def _move(source: str, dest: str) -> None:
 def _free_dest(dest: str) -> str:
     """return `dest`, or a `.N`-suffixed variant if it (or its .gz twin) already exists
 
-    used by the tiered rotator so a second roll landing on the same dated/stamped name
-    (e.g. two daily rolls in one day) doesn't clobber the earlier file. the suffix goes
-    before nothing here (dest is already the plain path) — checks both the plain and .gz
-    forms of each candidate.
+    used by the tiered rotator so a second same-stamp roll doesn't clobber the earlier
+    file; checks both the plain and .gz forms of each candidate.
     """
     if not os.path.exists(dest) and not os.path.exists(dest + ".gz"):
         return dest
@@ -51,15 +51,32 @@ def _free_dest(dest: str) -> str:
 
 
 def _gzip_file(source: str, dest: str) -> None:
-    """gzip source into dest then remove source (the rolled-file compression idiom)
+    """atomically gzip source into dest, then remove source - or leave source untouched
 
-    the source mtime is carried onto dest so a file keeps its position when it crosses
-    the plain->gz tier boundary — retier ranks by mtime, and a fresh write would
-    otherwise make a just-compressed file look like the newest one and reshuffle tiers.
+    compression is all-or-nothing: writes to `dest + ".tmp"`, verifies that tmp
+    decompresses cleanly, and only then `os.replace`s it onto `dest` and removes source.
+    a crash/OOM/power-loss or a failed verify at ANY point removes the tmp and raises with
+    source intact and no `.gz` at `dest` - so a corrupt/partial `.gz` is never produced and
+    nothing downstream ever has to choose between an intact plain and a corrupt archive.
+
+    the source mtime is carried onto dest so a file keeps its tier position when it
+    crosses the plain->gz boundary - a fresh write would otherwise make a
+    just-compressed file look newest and reshuffle tiers.
     """
     mtime = _safe_mtime(source)
-    with open(source, "rb") as src, gzip.open(dest, "wb") as dst:
+    tmp_dest = dest + ".tmp"
+    try:
+        with open(source, "rb") as src, gzip.open(tmp_dest, "wb") as dst:
             shutil.copyfileobj(src, dst)
+        if not _gz_intact(tmp_dest):
+            raise OSError(f"gzip of {source!r} did not verify")
+    except BaseException:
+        try:
+            os.remove(tmp_dest)
+        except OSError:
+            pass
+        raise
+    os.replace(tmp_dest, dest)
     os.remove(source)
     try:
         os.utime(dest, (mtime, mtime))
@@ -67,17 +84,19 @@ def _gzip_file(source: str, dest: str) -> None:
         pass
 
 
-def make_namer(log_dir: str, compress: bool) -> Callable[[str], str]:
-    """namer: redirect a rolled filename into log_dir, adding .gz when compressing
+def _gz_intact(path: str) -> bool:
+    """return True if the gzip file at path decompresses cleanly end to end
 
-    the handler hands us the default rolled path (next to the live file); we keep its
-    basename but place it under log_dir, and append .gz so the gzipped name matches.
+    used by `_gzip_file` to verify a freshly-written `.gz` before it replaces the plain
+    source; reads the whole stream, any failure means "not intact".
     """
-    def namer(default_name: str) -> str:
-        base = os.path.basename(default_name)
-        target = os.path.join(log_dir, base)
-        return target + ".gz" if compress else target
-    return namer
+    try:
+        with gzip.open(path, "rb") as handle:
+            while handle.read(1 << 20):
+                pass
+        return True
+    except Exception:
+        return False
 
 
 def make_history_namer(
@@ -87,14 +106,14 @@ def make_history_namer(
     """namer minting historic rolled files `<stem>.<Y-m-d_H-M-S>.log[.gz]` in log_dir
 
     used by size and daily (and their tiered variants). `stem` is the HISTORY stem (the
-    project namespace), independent of the live file's name — the returned rolled files
-    are keyed off it, and prune/retier glob the same stem.
+    project namespace), independent of the live file's name. FOOTGUN: prune/retier's
+    `stem` must match this one or nothing matches and retention silently never fires.
 
-    the stdlib handler's own rolled name (`.N` for size, `.log.<date>` for daily) is
-    ignored — we mint our own uniform timestamped name so all modes converge on one shape
-    and retier can rank/tier them. `plain=True` (tiered mode) always lands `.log` and lets
-    retier decide compression; otherwise `.gz` is appended when `compress`. same-second
-    collisions are disambiguated with a counter, checking both .log and .log.gz forms.
+    ignores the stdlib handler's own rolled name (`.N` for size, `.log.<date>` for
+    daily) in favor of a uniform timestamped name so all modes converge on one shape
+    retier can rank/tier. `plain=True` (tiered mode) always lands `.log`, letting retier
+    decide compression; same-second collisions disambiguate with a counter, checking
+    both .log and .log.gz forms.
     """
     def namer(default_name: str) -> str:
         stamp = time.strftime("%Y-%m-%d_%H-%M-%S", clock())
@@ -113,19 +132,24 @@ def make_rotator(
     compress: bool, log_dir: Optional[str] = None,
     prune_stem: Optional[str] = None, backup_count: int = 0,
     keep_uncompressed: Optional[int] = None, keep_compressed: Optional[int] = None,
+    rotate_mode: Optional[str] = None, live_stem: Optional[str] = None,
 ) -> Callable[[str, str], None]:
     """rotator: move (or gzip) the source live file to the destination rolled path
 
     legacy mode (default): gzip on roll when `compress`, then prune `log_dir` to
-    `backup_count` newest rolled files. the stdlib handler's own retention
-    (`getFilesToDelete`) only scans the live file's directory, so it never sees the
-    rolled files we redirect into `log_dir` — pruning here is what bounds retention for
-    the daily and size rolling modes.
+    `backup_count` newest rolled files - the stdlib handler's own retention only scans
+    the live file's directory, so it never sees files redirected into `log_dir`; pruning
+    here is what bounds retention for daily/size. FOOTGUN: for `rotate_mode="size"`,
+    `backup_count <= 0` means "keep no rolled history", but `prune()` itself no-ops at
+    `<= 0` (its own sentinel for "don't touch history") - so a zero-retention roll is
+    deleted by the rotator directly right after landing, rather than relying on prune to
+    do it. `rotate_mode` gates this delete-on-land branch to `"size"` only - `"daily"`
+    (and any other non-size mode) with `backup_count <= 0` still rolls without pruning,
+    matching the documented contract that only `size` always bounds the live file.
 
     tiered mode (when `keep_uncompressed`/`keep_compressed` are given): land the rolled
-    file PLAIN and re-tier `log_dir` — newest `keep_uncompressed` stay uncompressed, the
-    next `keep_compressed` are gzipped, the rest deleted. `compress`/`backup_count` are
-    ignored in this mode (the tier counts bound retention instead).
+    file PLAIN and re-tier `log_dir` - newest `keep_uncompressed` stay uncompressed, next
+    `keep_compressed` gzipped, rest deleted. `compress`/`backup_count` are ignored.
     """
     tiered = keep_uncompressed is not None or keep_compressed is not None
 
@@ -133,22 +157,25 @@ def make_rotator(
         if not os.path.exists(source):
             return
         if tiered:
-            # dest carries the namer's .gz suffix in compress mode; strip it so the
-            # freshly-rolled file lands plain and retier decides its tier. disambiguate a
-            # dest that already exists (a second same-interval daily roll reuses the same
-            # dated name) with a counter, checking both .log and .log.gz forms, so the
-            # earlier roll isn't clobbered.
+            # strip the namer's .gz suffix so the roll lands plain and retier decides
+            # its tier; disambiguate a same-interval collision via _free_dest
             plain_dest = _free_dest(dest[:-3] if dest.endswith(".gz") else dest)
             _move(source, plain_dest)
             if log_dir is not None and prune_stem is not None:
-                retier(log_dir, prune_stem, keep_uncompressed or 0, keep_compressed or 0)
+                retier(log_dir, prune_stem, keep_uncompressed or 0, keep_compressed or 0, live_stem)
             return
         if compress:
             _gzip_file(source, dest)
         else:
             _move(source, dest)
-        if log_dir is not None and prune_stem is not None:
-            prune(log_dir, prune_stem, backup_count)
+        if backup_count <= 0:
+            if rotate_mode == "size":
+                try:
+                    os.remove(dest)
+                except OSError:
+                    pass
+        elif log_dir is not None and prune_stem is not None:
+            prune(log_dir, prune_stem, backup_count, live_stem)
     return rotator
 
 
@@ -159,17 +186,16 @@ def rotate_on_start(
 ) -> None:
     """move an existing live file into log_dir with a timestamp, gzipped if asked
 
-    the rolled file is named off `history_stem` (the project namespace) when given, so
-    historic files carry the project name independent of the live file's stem; falls back
-    to the live file's own stem when history_stem is None/empty.
+    named off `history_stem` (the project namespace) when given, so historic files
+    carry the project name independent of the live file's stem; falls back to the live
+    file's own stem when history_stem is None/empty.
 
     no-op if the live file doesn't exist. used by rotate="on_start" before the fresh
-    handler opens a new live file. the timestamp form is run.<%Y-%m-%d_%H-%M-%S>.log.
+    handler opens a new live file. timestamp form is run.<%Y-%m-%d_%H-%M-%S>.log.
 
-    tiered mode (when `keep_uncompressed`/`keep_compressed` are given): the rolled file
-    always lands PLAIN (so it can occupy the newest uncompressed tier) and `retier`
-    decides compression/deletion across the whole stem — `compress` is ignored for the
-    just-rolled file.
+    tiered mode (`keep_uncompressed`/`keep_compressed` given): the rolled file always
+    lands PLAIN (so it can occupy the newest uncompressed tier) and `retier` decides
+    compression/deletion across the whole stem - `compress` is ignored here.
     """
     if not os.path.exists(live_path):
         return
@@ -178,13 +204,10 @@ def rotate_on_start(
     stem = os.path.basename(history_stem) if history_stem else live_stem
     stamp = time.strftime("%Y-%m-%d_%H-%M-%S", clock())
     suffix = ".log.gz" if (compress and not tiered) else ".log"
-    # the stamp is 1-second resolution; two starts in the same second would collide
-    # and the second clobber the first. disambiguate with a numeric counter so a rapid
-    # crash-restart loop doesn't lose the earlier rolled file. check BOTH the .log and
-    # .log.gz forms of each candidate: in tiered mode an earlier same-stamp roll may have
-    # already been compressed to .log.gz, and reusing its bare stem would create a second
-    # file for the same logical roll and break the tier counts
 
+    # a 1-second stamp collision (rapid crash-restart) is disambiguated with a
+    # counter; check BOTH .log and .log.gz since a tiered same-stamp roll may
+    # already be compressed
     def _taken(path: str) -> bool:
         base = path[:-3] if path.endswith(".gz") else path
         return os.path.exists(base) or os.path.exists(base + ".gz")
@@ -199,52 +222,58 @@ def rotate_on_start(
     else:
         _move(live_path, dest)
     if tiered:
-        retier(log_dir, stem, keep_uncompressed or 0, keep_compressed or 0)
+        retier(log_dir, stem, keep_uncompressed or 0, keep_compressed or 0, live_stem)
 
 
-def retier(log_dir: str, stem: str, keep_uncompressed: int, keep_compressed: int) -> None:
+def retier(log_dir: str, stem: str, keep_uncompressed: int, keep_compressed: int,
+           live_stem: Optional[str] = None) -> None:
     """re-tier rolled files for stem: newest plain, next gzipped, rest deleted
 
     newest-first by mtime: the first `keep_uncompressed` stay uncompressed, the next
-    `keep_compressed` are gzipped in place (a still-plain file in that band is compressed
-    to <name>.gz and the plain source removed), and everything beyond
+    `keep_compressed` are gzipped in place, everything beyond
     keep_uncompressed+keep_compressed is deleted. the live <stem>.log is never touched.
     fail-soft per file (skip on OSError) so retention never crashes setup.
 
-    `stem` is reduced to its basename: rolled files land in log_dir under the basename
-    (the namer/rotate_on_start basename them), so a `name` containing a directory (e.g.
-    "sub/run") must be matched by "run." here or nothing matches and retention silently
-    never fires (unbounded pileup).
+    FOOTGUN: `stem` is reduced to its basename to match how rolled files land in
+    log_dir (namer/rotate_on_start basename them) - a `name` containing a directory
+    (e.g. "sub/run") must be matched by "run." here or nothing matches and retention
+    silently never fires (unbounded pileup).
 
-    ordering is by mtime, then by the roll counter parsed from the name so a same-second
-    burst (tied mtimes, counter-disambiguated stamps like run.<t>.log / run.<t>.1.log)
-    still tiers newest-first correctly rather than falling back to arbitrary listdir order.
+    ordering is by mtime, then by the roll counter parsed from the name, so a
+    same-second burst (tied mtimes, counter-disambiguated stamps like run.<t>.log /
+    run.<t>.1.log) still tiers newest-first rather than falling back to listdir order.
+
+    candidates are also checked against this lib's own rolled-file shape
+    (`<stem>.<stamp>[.N].log[.gz]`, see `_is_rolled_name`) - a foreign file that only
+    shares the `<stem>.` prefix (e.g. a project's own `<stem>.audit.log` dropped into
+    the same log_dir) is left alone rather than tiered/gzipped/deleted.
     """
     stem = os.path.basename(stem)
+    live_stem = os.path.basename(live_stem) if live_stem else None
     try:
         names = [
             name for name in os.listdir(log_dir)
-            if name.startswith(f"{stem}.") and name != f"{stem}.log"
+            if name != f"{stem}.log" and _is_rolled_name(stem, name, live_stem)
         ]
     except OSError:
         return
     entries = [os.path.join(log_dir, name) for name in names]
-    # dedupe plain/gz twins FIRST (a crash between _gzip_file's write and its os.remove can
-    # leave <x>.log beside <x>.log.gz). drop the redundant plain copy up front so the
-    # phantom twin never occupies a retention slot and evicts a distinct older roll.
+    # dedupe plain/gz twins FIRST: a crash between _gzip_file's os.replace and its
+    # os.remove(source) can leave <x>.log beside <x>.log.gz. the .gz is guaranteed intact
+    # (_gzip_file verifies before it replaces, and never produces a partial .gz), so the
+    # plain twin is redundant and dropped unconditionally.
     present = set(entries)
     kept = []
     for p in entries:
         if not p.endswith(".gz") and (p + ".gz") in present:
             try:
                 os.remove(p)
-            except OSError:
-                kept.append(p)  # couldn't remove — keep it in the accounting
                 continue
+            except OSError:
+                pass  # couldn't remove - keep it in the accounting
         kept.append(p)
     files = [(p, _safe_mtime(p), _roll_counter(p)) for p in kept if os.path.isfile(p)]
-    # newest-first: higher mtime first, and within a tied second the higher roll counter
-    # (a later same-second roll) is newer
+    # newest-first: higher mtime first, ties broken by higher (later) roll counter
     files.sort(key=lambda t: (t[1], t[2]), reverse=True)
 
     keep = keep_uncompressed + keep_compressed
@@ -257,10 +286,8 @@ def retier(log_dir: str, stem: str, keep_uncompressed: int, keep_compressed: int
         elif index >= keep_uncompressed and not path.endswith(".gz"):
             dest = path + ".gz"
             if os.path.exists(dest):
-                # a crash/power-loss between _gzip_file's write and its os.remove can leave
-                # a plain source beside a fresh .gz. don't keep both (they'd double-count
-                # toward retention and evict a distinct older roll) — drop the redundant
-                # plain twin, keeping the compressed copy.
+                # a verified .gz twin already exists (a prior crashed roll) - drop the
+                # redundant plain rather than re-gzip over it
                 try:
                     os.remove(path)
                 except OSError:
@@ -272,16 +299,39 @@ def retier(log_dir: str, stem: str, keep_uncompressed: int, keep_compressed: int
                 pass
 
 
+def _rolled_name_pattern(stem: str, live_stem: Optional[str] = None) -> "re.Pattern":
+    """compiled regex matching this lib's own rolled-file shapes for stem
+
+    all forms are date-bearing so a foreign same-stem file (e.g. `proj.audit.log`) is
+    never mistaken for a roll and pruned/retiered/deleted:
+    - current uniform namer: `<stem>.<Y-m-d_H-M-S>[.N].log[.gz]`
+      (make_history_namer/rotate_on_start, see attach_rolling)
+    - legacy pre-v0.5.0 daily: `<stem>.log.<Y-m-d>[.gz]` (the stdlib TimedRotatingFileHandler
+      shape) - matched so an upgraded deployment's existing history is still pruned/retired
+      instead of piling up forever. legacy rolls were named off the LIVE file's name, not the
+      history stem, so when `live_stem` is given (and differs) its legacy shape is matched too
+    """
+    stems = [stem] if live_stem is None or live_stem == stem else [stem, live_stem]
+    forms = []
+    for s in stems:
+        esc = re.escape(s)
+        forms.append(rf"{esc}\.\d{{4}}-\d{{2}}-\d{{2}}_\d{{2}}-\d{{2}}-\d{{2}}(?:\.\d+)?\.log(?:\.gz)?")
+        forms.append(rf"{esc}\.log\.\d{{4}}-\d{{2}}-\d{{2}}(?:\.gz)?")
+    return re.compile(rf"^(?:{'|'.join(forms)})$")
+
+
+def _is_rolled_name(stem: str, name: str, live_stem: Optional[str] = None) -> bool:
+    """return whether name has this lib's own rolled-log shape for stem (or the live stem)"""
+    return _rolled_name_pattern(stem, live_stem).match(name) is not None
+
+
 def _roll_counter(path: str) -> int:
     """parse the same-second disambiguation counter out of a rolled filename
 
     only the on_start / size-namer shape carries a counter: `<stem>.<stamp>[.<counter>].log`
-    (optionally `.gz`), where a colliding same-second roll gets `.1`, `.2`, ... and a higher
-    counter is the later (newer) roll. the first roll of a second has no counter (0).
-
-    daily's dated names (`<stem>.log.<Y-m-d>`) do NOT end in `.log` and are second+-granular
-    (distinct mtimes), so they never need the counter tie-break — return 0 for them rather
-    than misparsing the trailing date component as a counter.
+    (optionally `.gz`); a higher counter is the later roll, first roll of a second is 0.
+    daily's dated names (`<stem>.log.<Y-m-d>`) don't end in `.log`, so they never need
+    the tie-break - return 0 rather than misparsing the trailing date as a counter.
     """
     base = path[:-3] if path.endswith(".gz") else path
     if not base.endswith(".log"):
@@ -291,30 +341,37 @@ def _roll_counter(path: str) -> int:
     return int(tail) if tail.isdigit() else 0
 
 
-def prune(log_dir: str, stem: str, backup_count: int) -> None:
+def prune(log_dir: str, stem: str, backup_count: int, live_stem: Optional[str] = None) -> None:
     """keep only the newest `backup_count` rolled files for a given stem in log_dir
 
-    matches files beginning with `<stem>.` (e.g. run.*), sorted by mtime, deleting the
+    matches files beginning with `<stem>.` (e.g. run.*), sorted newest-first by mtime
+    then roll counter (mirrors retier's ordering, see _roll_counter), deleting the
     oldest beyond the count. used for on_start, which the handlers don't auto-prune.
 
-    `stem` is reduced to its basename so a `name` containing a directory (e.g. "sub/run")
-    still matches the basenamed rolled files in log_dir (else nothing matches and old
-    files pile up forever).
+    FOOTGUN: `stem` is reduced to its basename so a `name` containing a directory (e.g.
+    "sub/run") still matches the basenamed rolled files in log_dir - else nothing
+    matches and old files pile up forever.
+
+    candidates are also checked against this lib's own rolled-file shape
+    (`<stem>.<stamp>[.N].log[.gz]`, see `_is_rolled_name`) - a foreign file that only
+    shares the `<stem>.` prefix (e.g. a project's own `<stem>.audit.log` dropped into
+    the same log_dir) is left alone rather than counted and deleted as a roll.
     """
     if backup_count <= 0:
         return
     stem = os.path.basename(stem)
+    live_stem = os.path.basename(live_stem) if live_stem else None
     try:
         entries = [
             os.path.join(log_dir, name)
             for name in os.listdir(log_dir)
-            if name.startswith(f"{stem}.") and name != f"{stem}.log"
+            if name != f"{stem}.log" and _is_rolled_name(stem, name, live_stem)
         ]
     except OSError:
         return
-    files = [(p, _safe_mtime(p)) for p in entries if os.path.isfile(p)]
-    files.sort(key=lambda pair: pair[1], reverse=True)
-    for path, _ in files[backup_count:]:
+    files = [(p, _safe_mtime(p), _roll_counter(p)) for p in entries if os.path.isfile(p)]
+    files.sort(key=lambda t: (t[1], t[2]), reverse=True)
+    for path, _, _ in files[backup_count:]:
         try:
             os.remove(path)
         except OSError:
@@ -333,26 +390,33 @@ def attach_rolling(
     handler, log_dir: str, compress: bool,
     prune_stem: Optional[str] = None, backup_count: int = 0,
     keep_uncompressed: Optional[int] = None, keep_compressed: Optional[int] = None,
-    tiered: bool = False,
+    tiered: bool = False, rotate_mode: Optional[str] = None,
 ) -> Tuple[Callable, Callable]:
     """wire the custom namer + rotator onto a rotating handler; return them
 
-    rolled files are named off `prune_stem` (the HISTORY stem — the project namespace),
+    rolled files are named off `prune_stem` (the HISTORY stem - the project namespace),
     independent of the live file name, via make_history_namer: `<stem>.<stamp>.log[.gz]`
-    uniform across size and daily. this replaces the stdlib handler's own rolled-name
-    scheme (`.N` for size, `.log.<date>` for daily), which can't inject a project stem and
-    (for size) can't be managed once files are redirected into log_dir.
+    uniform across size and daily - replacing the stdlib handler's own rolled-name
+    scheme (`.N` for size, `.log.<date>` for daily), which can't inject a project stem
+    and (for size) can't be managed once files are redirected into log_dir.
 
-    pass `prune_stem`/`backup_count` so the rotator prunes `log_dir` after each roll (the
-    handler's own retention can't see the redirected rolled files). pass
-    `keep_uncompressed`/`keep_compressed` for tiered retention (newest plain, next gzipped,
-    rest deleted) — see make_rotator. `tiered=True` lands rolls plain (retier compresses).
+    pass `prune_stem`/`backup_count` so the rotator prunes `log_dir` after each roll
+    (the handler's own retention can't see the redirected files). pass
+    `keep_uncompressed`/`keep_compressed` for tiered retention instead (see
+    make_rotator); `tiered=True` lands rolls plain (retier compresses). `rotate_mode`
+    ("size"/"daily") is forwarded to `make_rotator` so the zero-retention delete-on-land
+    branch only ever fires for `"size"`.
     """
     namer = make_history_namer(
         os.path.basename(prune_stem or ""), log_dir, compress, plain=tiered,
     )
+    # the live file name (stem of the handler's baseFilename, minus one .log) - so retention
+    # also recognizes pre-v0.5.0 legacy rolls, which were named off the LIVE name not the stem
+    live_base = os.path.basename(getattr(handler, "baseFilename", "") or "")
+    live_stem = live_base[:-4] if live_base.endswith(".log") else live_base
     rotator = make_rotator(
         compress, log_dir, prune_stem, backup_count, keep_uncompressed, keep_compressed,
+        rotate_mode=rotate_mode, live_stem=live_stem or None,
     )
     handler.namer = namer
     handler.rotator = rotator

src/log_setup/setup.py

@@ -1,11 +1,13 @@
-"""app-entry-point logging setup (sync, stdlib only).
+"""app-entry-point logging setup (sync, stdlib only). see README.
 
-`setup_logging` configures the root logger once for the whole process: a live
-run.log at a stable path, rotation (daily/size/on_start/none) into a logs/ dir, gzip
-of rolled files, retention, console output, and a consistent format. it is called by
-the APPLICATION, not by reusable libraries (those stay emit-only). it is idempotent
-(no duplicate handlers on repeat calls), never crashes the app over logging, and can
-route through a background queue so an async event loop doesn't block on file I/O.
+`setup_logging` configures the root logger once for the whole process. called by the
+APPLICATION, not by reusable libraries (those stay emit-only). idempotent, never
+crashes the app over logging, and can route through a background queue so an async
+event loop doesn't block on file I/O.
+
+`rotate="size"` always bounds the live file: the roll fires at `max_bytes` regardless
+of `backup_count`, including `backup_count=0` (means "keep zero rolled files", not
+"never roll" - each roll is deleted right after landing).
 """
 
 import atexit
@@ -13,6 +15,8 @@ import logging
 import logging.handlers
 import os
 import queue as _queue
+import sys
+import traceback
 from typing import Dict, Optional, Union
 
 from .formats import build_formatter
@@ -25,29 +29,49 @@ _listener = None
 _atexit_registered = False
 
 
+class _PreservingQueueHandler(logging.handlers.QueueHandler):
+    """QueueHandler that hands the record to the listener untouched
+
+    stdlib's QueueHandler.prepare() calls self.format(record) with the queue
+    handler's OWN (default) formatter, then nulls exc_info/exc_text/stack_info -
+    losing structured fields (e.g. JsonLinesFormatter's exc_info key) before the
+    listener's real formatter ever sees the record. that behavior exists to keep a
+    record picklable across a multiprocessing.Queue; this lib only ever uses an
+    in-process queue.Queue, so there is nothing to pickle and nothing to strip -
+    the listener's handler formats the untouched record exactly once.
+    """
+
+    def prepare(self, record: logging.LogRecord) -> logging.LogRecord:
+        return record
+
+
+def _exc_text() -> str:
+    """render sys.exc_info() as text, for capturing a traceback into a buffered warning"""
+    return "".join(traceback.format_exception(*sys.exc_info())).strip()
+
+
+def _flush_warnings(warnings: list) -> None:
+    """emit buffered setup-time warnings now that handlers are attached"""
+    for message, *args in warnings:
+        log.warning(message, *args)
+
+
 def _level_value(level: Union[int, str]) -> int:
     """coerce a level name or int to a logging level int (defaults to INFO)"""
     if isinstance(level, bool):
-        # bool is an int subclass (True==1, below DEBUG) but is never a real level —
-        # reject it consistently with the per-module path rather than set level 1
+        # bool is an int subclass (True==1, below DEBUG) but never a real level
         return logging.INFO
     if isinstance(level, int):
         return level
     if not isinstance(level, str):
         return logging.INFO
     resolved = logging.getLevelName(level.upper())
-    # getLevelName returns the string "Level XXX" for an unknown name, which
-    # setLevel then rejects — never crash the app over a bad level, fall back to INFO
+    # getLevelName returns "Level XXX" for an unknown name; fall back to INFO
     return resolved if isinstance(resolved, int) else logging.INFO
 
 
 def _strict_level_value(level: Union[int, str]) -> Optional[int]:
-    """coerce a level name or int to a logging level int, or None if invalid
-
-    unlike `_level_value` (which falls back to INFO for the root `level`), this reports
-    an invalid value as None so the per-module path can skip + warn rather than silently
-    apply INFO to a logger the caller named with a typo'd level
-    """
+    """like _level_value but reports invalid as None so the caller can skip + warn"""
     if isinstance(level, bool):
         return None
     if isinstance(level, int):
@@ -58,37 +82,30 @@ def _strict_level_value(level: Union[int, str]) -> Optional[int]:
     return resolved if isinstance(resolved, int) else None
 
 
-def _apply_module_levels(module_levels: Optional[Dict[str, Union[int, str]]]) -> None:
-    """set per-logger level overrides by exact logger name, never crashing
-
-    each name->level entry calls `logging.getLogger(name).setLevel(<level>)`. names are
-    matched exactly (no discovery); stdlib hierarchy still applies, so a parent name
-    quiets its whole subtree. a bad level for one entry is skipped with a warning so the
-    other entries and the rest of setup still proceed.
-    """
+def _apply_module_levels(module_levels: Optional[Dict[str, Union[int, str]]], warnings: list) -> None:
+    """set per-logger level overrides by exact logger name, never crashing"""
     if not module_levels:
         return
     for mod_name, raw_level in module_levels.items():
         value = _strict_level_value(raw_level)
         if value is None:
-            log.warning("log_setup: invalid level %r for logger %r; skipping", raw_level, mod_name)
+            warnings.append(("log_setup: invalid level %r for logger %r; skipping", raw_level, mod_name))
             continue
         logging.getLogger(mod_name).setLevel(value)
 
 
-def _clear_owned(root: logging.Logger) -> None:
+def _clear_owned(root: logging.Logger, warnings: list) -> None:
     """remove only the handlers this lib previously added; leave app handlers alone"""
     global _listener
     if _listener is not None:
         _listener.stop()
-        # the listener owns the real file/console handlers (only the QueueHandler is
-        # root-attached + marked); stopping it doesn't close them, so close them here
-        # to avoid relying on GC finalizers across a re-setup
+        # listener owns the real file/console handlers; stopping it doesn't close
+        # them, so close here rather than rely on GC finalizers across a re-setup
         for wrapped in getattr(_listener, "handlers", ()):
             try:
                 wrapped.close()
             except Exception:
-                log.warning("log_setup: failed to close queued handler %r", wrapped, exc_info=True)
+                warnings.append(("log_setup: failed to close queued handler %r: %s", wrapped, _exc_text()))
         _listener = None
     for handler in list(root.handlers):
         if getattr(handler, _MARKER, False):
@@ -96,9 +113,9 @@ def _clear_owned(root: logging.Logger) -> None:
             try:
                 handler.close()
             except Exception:
-                # a handler failing to close must not abort re-setup, but log it
-                # rather than swallow silently (consistent with the lib's warn pattern)
-                log.warning("log_setup: failed to close handler %r during re-setup", handler, exc_info=True)
+                warnings.append(
+                    ("log_setup: failed to close handler %r during re-setup: %s", handler, _exc_text())
+                )
 
 
 def _tag(handler: logging.Handler) -> logging.Handler:
@@ -110,10 +127,8 @@ def _tag(handler: logging.Handler) -> logging.Handler:
 def _normalize_name(name: str) -> str:
     """strip one trailing '.log' (case-insensitive) so the stem is extension-free
 
-    `name` is allowed to be passed with or without the extension — "latest" and
-    "latest.log" both yield stem "latest" (live file latest.log), never latest.log.log.
-    only one level is stripped: "app.log.log" -> "app.log" so a legit ".log" inside a
-    name survives.
+    "latest" and "latest.log" both yield stem "latest" (never latest.log.log); only
+    one level is stripped, so "app.log.log" -> "app.log".
     """
     if name.lower().endswith(".log"):
         return name[:-4]
@@ -121,12 +136,7 @@ def _normalize_name(name: str) -> str:
 
 
 def _history_stem() -> str:
-    """the project namespace for historic files: the cwd basename
-
-    a service run from bestbuy/ gives historic files bestbuy.<stamp>.log[.gz]. falls back
-    to an empty string only for a degenerate cwd (e.g. "/"), which the caller resolves to
-    the live stem.
-    """
+    """the project namespace for historic files: the cwd basename, "" for a degenerate cwd"""
     try:
         return os.path.basename(os.getcwd().rstrip(os.sep))
     except OSError:
@@ -134,30 +144,28 @@ def _history_stem() -> str:
 
 
 def _file_handler(
-    name: str, history_stem: str, live_path: str, log_dir: str, rotate: Optional[str],
+    history_stem: str, live_path: str, log_dir: str, rotate: Optional[str],
     backup_count: int, max_bytes: int, compress: bool,
-    keep_uncompressed: Optional[int], keep_compressed: Optional[int],
+    keep_uncompressed: Optional[int], keep_compressed: Optional[int], warnings: list,
 ) -> logging.Handler:
     """build the configured file handler with custom rolling into log_dir
 
-    `name` is the LIVE stem (drives live_path); `history_stem` is the PROJECT stem that
-    rolled/historic files are named off + the retention glob keys on. they are decoupled:
-    the live file keeps its defined name, historic files carry the project namespace.
+    `history_stem` is the PROJECT stem that rolled/historic files are named off,
+    decoupled from the live file's own name (`live_path`).
     """
     tiered = keep_uncompressed is not None or keep_compressed is not None
     if rotate == "size":
-        # stdlib doRollover is a no-op when backupCount == 0, and its numbered .1/.2 shift
-        # can't manage files redirected into log_dir. force a nonzero backupCount so the
-        # roll always fires, and let attach_rolling's history namer name + retier/prune
-        # bound retention (keyed to history_stem).
-        size_backup = backup_count if not tiered else max(backup_count, 1)
+        # stdlib doRollover no-ops at backupCount==0 - force nonzero so the roll
+        # always fires; the REAL backup_count still flows to attach_rolling, whose
+        # make_rotator treats <=0 as "keep no rolled history" and deletes each roll
+        size_backup = max(backup_count, 1)
         handler = logging.handlers.RotatingFileHandler(
             live_path, maxBytes=max_bytes, backupCount=size_backup, encoding="utf-8",
         )
         attach_rolling(
             handler, log_dir, compress, prune_stem=history_stem, backup_count=backup_count,
             keep_uncompressed=keep_uncompressed, keep_compressed=keep_compressed,
-            tiered=tiered,
+            tiered=tiered, rotate_mode=rotate,
         )
     elif rotate == "daily":
         handler = logging.handlers.TimedRotatingFileHandler(
@@ -166,7 +174,7 @@ def _file_handler(
         attach_rolling(
             handler, log_dir, compress, prune_stem=history_stem, backup_count=backup_count,
             keep_uncompressed=keep_uncompressed, keep_compressed=keep_compressed,
-            tiered=tiered,
+            tiered=tiered, rotate_mode=rotate,
         )
     else:
         if rotate == "on_start":
@@ -177,15 +185,16 @@ def _file_handler(
                 )
             else:
                 rotate_on_start(live_path, log_dir, compress, history_stem=history_stem)
-                prune(log_dir, history_stem, backup_count)
+                live_base = os.path.basename(live_path)
+                live_stem = live_base[:-4] if live_base.endswith(".log") else live_base
+                prune(log_dir, history_stem, backup_count, live_stem or None)
         elif rotate is not None:
-            # a typo'd rotate value (e.g. "hourly") would otherwise silently fall through
-            # to a non-rotating FileHandler and grow forever — warn, matching the
-            # unknown-`output` convention, rather than degrade silently
-            log.warning(
-                "log_setup: unknown rotate %r; expected 'daily'/'size'/'on_start'/None — "
+            # a typo'd value would otherwise silently fall through to a non-rotating
+            # FileHandler and grow forever - warn instead of degrade silently
+            warnings.append((
+                "log_setup: unknown rotate %r; expected 'daily'/'size'/'on_start'/None - "
                 "no rotation applied (single growing file)", rotate,
-            )
+            ))
         handler = logging.FileHandler(live_path, encoding="utf-8")
     return handler
 
@@ -211,54 +220,59 @@ def setup_logging(
     """configure the root logger for the whole process and return it
 
     `name` -> <name>.log live file at cwd; rolled/compressed copies go to `log_dir`. a
-    trailing ".log" in `name` is stripped so "latest" and "latest.log" both produce the
-    live file latest.log (never latest.log.log).
+    trailing ".log" in `name` is stripped so "latest" and "latest.log" both produce
+    latest.log (never latest.log.log).
+
     `history_name` names the rolled/historic files (`<history_name>.<timestamp>.log[.gz]`),
-    independent of the live file: it defaults to the PROJECT namespace = the cwd basename
-    (run from bestbuy/ -> historic files bestbuy.<stamp>...), and can be set explicitly. the
-    live file always keeps `name`; only the historic files carry the project name.
+    independent of the live file: defaults to the PROJECT namespace = the cwd basename
+    (run from bestbuy/ -> historic files bestbuy.<stamp>...). the live file always keeps
+    `name`; only historic files carry the project name.
+
     `keep_uncompressed`/`keep_compressed` (default None) enable TIERED retention: when
     either is given, rolled files are kept as the newest `keep_uncompressed` uncompressed
-    + the next `keep_compressed` gzipped, and the rest are deleted (total retained =
-    sum). this applies to "on_start", "daily", and "size". `backup_count` and the
-    gzip-on-roll behavior of `compress` are IGNORED in tiered mode (the tier counts bound
-    retention). pass NEITHER knob and rotation behaves exactly as before (backup_count +
-    compress) — existing callers are unaffected.
+    + the next `keep_compressed` gzipped, rest deleted (total retained = sum). applies to
+    "on_start", "daily", and "size". `backup_count` and gzip-on-roll `compress` are
+    IGNORED in tiered mode. pass NEITHER knob and rotation behaves exactly as before.
+
     `level` is the root default every logger inherits. `module_levels` is an optional
     map of exact logger name -> level applied after the root is set, the ergonomic way
-    to quiet noisy dependencies (e.g. {"motor": "WARNING", "aiohttp": "WARNING"}) from
-    the one setup call instead of scattering `getLogger(...).setLevel(...)` afterwards —
-    it's stdlib hierarchy under the hood, not new capability. names match EXACTLY (no
-    discovery: a typo'd name silently configures an unused logger), but stdlib hierarchy
-    applies, so naming a parent ("aiohttp") quiets its whole subtree (aiohttp.client,
-    aiohttp.access, ...). each entry accepts a str or int level; a bad value for one
-    entry is skipped with a warning and never aborts the others or the setup.
-    `rotate` is "daily" (default), "size", "on_start", or None. `console=True` adds a
-    stdout handler (off by default — the file is the output). `queue=True` routes records
-    through a background QueueListener so file I/O never blocks the caller (the listener
-    is stopped at exit). `output` is "text" (default, human `time | module | level |
-    message`, local time) or "json" (structured one-JSON-object-per-line for the
-    Grafana/Loki path, UTC timestamps, `extra=` fields surfaced as top-level keys); both
-    file and console use the chosen format and the live-file name is the same regardless.
-    the raw `fmt`/`datefmt` overrides apply to text output only. idempotent: a repeat call
-    clears only the handlers this function added. never raises over logging — an
-    unwritable `log_dir` falls back to console-only with a warning even when `console` is
-    off, so output is never silently lost; an unknown `output` falls back to text.
+    to quiet noisy dependencies (e.g. {"motor": "WARNING"}) from one call instead of
+    scattering `getLogger(...).setLevel(...)` calls. names match EXACTLY (no discovery:
+    a typo'd name silently configures an unused logger), but hierarchy applies, so
+    naming a parent ("aiohttp") quiets its whole subtree. str or int per entry; a bad
+    value is skipped with a warning and never aborts the others or the setup.
+
+    `rotate` is "daily" (default), "size", "on_start", or None. for `rotate="size"`, the
+    live file always rolls at `max_bytes` regardless of `backup_count`: `backup_count=0`
+    means "keep zero rolled files" (each roll lands then is deleted immediately), NOT
+    "disable rotation". `backup_count>=1` keeps that many rolled files as before.
+
+    `console=True` adds a stdout handler (off by default - the file is the output).
+    `queue=True` routes records through a background QueueListener so file I/O never
+    blocks the caller (stopped at exit). `output` is "text" (default, human `time |
+    module | level | message`, local time) or "json" (structured JSON Lines, UTC
+    timestamps + a unix-epoch `ts`, `extra=` fields surfaced as top-level keys); file
+    and console use the same format, live-file name unaffected. `fmt`/`datefmt` apply
+    to text output only.
+
+    idempotent: a repeat call clears only the handlers this function added. never
+    raises over logging - an unwritable `log_dir` falls back to console-only with a
+    warning even when `console` is off; an unknown `output` falls back to text.
     """
     global _listener, _atexit_registered
 
+    warnings: list = []
+
     root = logging.getLogger()
     root.setLevel(_level_value(level))
-    _apply_module_levels(module_levels)
-    _clear_owned(root)
+    _apply_module_levels(module_levels, warnings)
+    _clear_owned(root, warnings)
 
-    formatter = build_formatter(output, fmt, datefmt)
+    formatter = build_formatter(output, fmt, datefmt, warnings)
     stem = _normalize_name(name)
     live_path = f"{stem}.log"
-    # historic/rolled files are named off the project namespace, independent of the live
-    # file: history_name if given, else the cwd basename (e.g. run from bestbuy/ -> historic
-    # files bestbuy.<stamp>.log[.gz]). normalized + basenamed like `name`; falls back to the
-    # live stem for a degenerate cwd so naming/retention never break.
+    # history_name if given, else the cwd basename; falls back to the live stem for a
+    # degenerate cwd so naming/retention never break
     history_source = history_name if history_name is not None else _history_stem()
     history_stem = os.path.basename(_normalize_name(history_source)) or stem
 
@@ -273,8 +287,8 @@ def setup_logging(
     if file_ok:
         try:
             fh = _file_handler(
-                stem, history_stem, live_path, log_dir, rotate, backup_count, max_bytes, compress,
-                keep_uncompressed, keep_compressed,
+                history_stem, live_path, log_dir, rotate, backup_count, max_bytes, compress,
+                keep_uncompressed, keep_compressed, warnings,
             )
             fh.setFormatter(formatter)
             handlers.append(fh)
@@ -282,19 +296,18 @@ def setup_logging(
             file_ok = False
 
     if console or not file_ok:
-        sh = logging.StreamHandler()
+        sh = logging.StreamHandler(sys.stdout)
         sh.setFormatter(formatter)
         handlers.append(sh)
 
     if queue:
         record_queue: "_queue.Queue" = _make_queue()
-        qh = _tag(logging.handlers.QueueHandler(record_queue))
+        qh = _tag(_PreservingQueueHandler(record_queue))
         root.addHandler(qh)
         _listener = logging.handlers.QueueListener(record_queue, *handlers, respect_handler_level=True)
         _listener.start()
         if not _atexit_registered:
-            # register once — atexit doesn't dedupe, so repeated queue re-setups would
-            # otherwise stack identical callbacks (harmless but unbounded)
+            # register once - atexit doesn't dedupe, repeated re-setups would stack
             atexit.register(_stop_listener)
             _atexit_registered = True
     else:
@@ -302,7 +315,10 @@ def setup_logging(
             root.addHandler(_tag(handler))
 
     if not file_ok:
-        log.warning("log_setup: log_dir %r not writable; logging to console only", log_dir)
+        warnings.append(("log_setup: log_dir %r not writable; logging to console only", log_dir))
+
+    # flush now that handlers are attached, so warnings land in the configured log
+    _flush_warnings(warnings)
 
     return root