feat(devserver): Tee console output to a local dev log file

The devserver now mirrors all honcho-routed console output to a log file
(truncated each run) so it can be inspected after the fact — for example by
AI agents reading the dev logs. ANSI color codes are stripped from the file
copy while the interactive console keeps its coloring (the tee delegates
isatty()).

The path defaults to <repo>/.artifacts/dev.log and is configurable via the
SENTRY_DEV_LOG_FILE environment variable. Both .artifacts/ and *.log are
already gitignored.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: trevor-e

AGENTS.md

@@ -51,6 +51,8 @@ That is all that is required to run `pytest`.
 
 `devservices serve` starts the development server.
 
+When the devserver is running, its full console output (all honcho-managed processes — `server`, `taskworker`, kafka consumers, webpack/watchers, etc.) is teed to `.artifacts/dev.log`, ANSI-stripped and gitignored. Agents can't see the devserver terminal, so `tail`/`grep` this file to inspect what's happening (startup, reloads, request logs, tracebacks). The file is truncated on each devserver process start (in-process granian reloads keep appending); override its path with `SENTRY_DEV_LOG_FILE`. Dev-only — this teeing lives in `sentry devserver` and is not used in production.
+
 #### Linting
 
 prek is the single entrypoint for all lint, format, and type-checking tools.

src/sentry/runner/commands/devserver.py

@@ -3,6 +3,7 @@
 import os
 import threading
 from collections.abc import MutableSequence, Sequence
+from pathlib import Path
 from typing import NoReturn
 
 import click
@@ -461,9 +462,20 @@ def devserver(
 
         cwd = os.path.realpath(os.path.join(settings.PROJECT_ROOT, os.pardir, os.pardir))
 
-        from sentry.runner.formatting import get_honcho_printer
+        # Tee console output to a log file (truncated each run) so it can be
+        # inspected after the fact (e.g. by AI agents reading the dev logs).
+        # Path is configurable; defaults to <repo>/.artifacts/dev.log.
+        from sentry.runner.formatting import TeeStream, get_honcho_printer
 
-        honcho_printer = get_honcho_printer(prefix=prefix, pretty=pretty)
+        log_path = Path(
+            os.environ.get("SENTRY_DEV_LOG_FILE", os.path.join(cwd, ".artifacts", "dev.log"))
+        )
+        log_path.parent.mkdir(parents=True, exist_ok=True)
+        log_file = open(log_path, "w", encoding="utf-8")
+
+        honcho_printer = get_honcho_printer(
+            prefix=prefix, pretty=pretty, output=TeeStream(sys.stdout, log_file)
+        )
 
         manager = Manager(honcho_printer)
         for name, cmd in daemons:

src/sentry/runner/formatting.py

@@ -1,11 +1,37 @@
 from __future__ import annotations
 
 import re
-from typing import TYPE_CHECKING
+import sys
+from typing import IO, TYPE_CHECKING, cast
 
 if TYPE_CHECKING:
     import honcho.printer
 
+_ANSI_RE = re.compile(r"\x1b\[[0-9;]*m")
+
+
+class TeeStream:
+    """Mirror writes to a console stream verbatim and a log file with ANSI stripped."""
+
+    def __init__(self, console: IO[str], log_file: IO[str]) -> None:
+        self._console = console
+        self._log_file = log_file
+
+    def write(self, s: str) -> int:
+        self._console.write(s)
+        self._log_file.write(_ANSI_RE.sub("", s))
+        self._log_file.flush()
+        return len(s)
+
+    def flush(self) -> None:
+        self._console.flush()
+        self._log_file.flush()
+
+    def isatty(self) -> bool:
+        # Delegate so honcho keeps coloring the console; the file copy is stripped above.
+        return self._console.isatty()
+
+
 # Sentry colors taken from our design system. Might not look good on all
 # terminal themes tbh
 COLORS = {
@@ -75,7 +101,9 @@ def colorize_traceback(pattern: re.Match[str]) -> str:
     )
 
 
-def get_honcho_printer(*, prefix: bool, pretty: bool) -> honcho.printer.Printer:
+def get_honcho_printer(
+    *, prefix: bool, pretty: bool, output: IO[str] | TeeStream | None = None
+) -> honcho.printer.Printer:
     import honcho.printer
 
     class SentryPrinter(honcho.printer.Printer):
@@ -117,4 +145,6 @@ def write(self, message: honcho.printer.Message) -> None:
             for line in string.splitlines():
                 self.output.write(f"{prefix}{line}\n")
 
-    return SentryPrinter(prefix=prefix)
+    return SentryPrinter(
+        prefix=prefix, output=cast("IO[str]", output) if output is not None else sys.stdout
+    )