style: fix ruff lint/format and mypy errors for CI 3.12 pass

- Remove 101 trailing whitespace violations (W293), 2 unused imports
  (F401), 1 import sort issue (I001) in anthropic handler and test file
- Apply ruff format to anthropic handler and oauth routing test
- Fix mypy no-any-return in jitter_delay_ms by adding explicit type
- Fix mypy attr-defined for signal.SIGKILL on Windows using getattr

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

headroom/cli/wrap.py

@@ -612,9 +612,10 @@ def _kill_proxy_by_pid(pid: int, port: int) -> bool:
         if not _check_proxy(port):
             return True
 
-    # SIGTERM didn't work — escalate to SIGKILL
+    # SIGTERM didn't work — escalate to SIGKILL (Unix) or terminate (Windows)
     try:
-        os.kill(pid, signal.SIGKILL)
+        _kill_signal = getattr(signal, "SIGKILL", signal.SIGTERM)
+        os.kill(pid, _kill_signal)
     except (ProcessLookupError, PermissionError):
         pass
 

headroom/proxy/handlers/anthropic.py

@@ -1082,7 +1082,10 @@ class AnthropicHandlerMixin:
                         # Non-stream: first-byte and connect are effectively
                         # the same horizon — ``send_message`` awaits until
                         # the response body is fully buffered.
-                        if "upstream_first_byte" not in stage_timer and "upstream_connect" in stage_timer:
+                        if (
+                            "upstream_first_byte" not in stage_timer
+                            and "upstream_connect" in stage_timer
+                        ):
                             stage_timer.record(
                                 "upstream_first_byte",
                                 stage_timer.summary()["upstream_connect"],
@@ -1186,7 +1189,10 @@ class AnthropicHandlerMixin:
                 else:
                     async with stage_timer.measure("upstream_connect"):
                         response = await self._retry_request("POST", url, headers, body)
-                    if "upstream_first_byte" not in stage_timer and "upstream_connect" in stage_timer:
+                    if (
+                        "upstream_first_byte" not in stage_timer
+                        and "upstream_connect" in stage_timer
+                    ):
                         stage_timer.record(
                             "upstream_first_byte",
                             stage_timer.summary()["upstream_connect"],
@@ -1319,7 +1325,9 @@ class AnthropicHandlerMixin:
                             }
 
                             # Reuse main client for CCR continuations (connection pooling)
-                            logger.info(f"CCR: Making continuation request with {len(msgs)} messages")
+                            logger.info(
+                                f"CCR: Making continuation request with {len(msgs)} messages"
+                            )
                             assert self.http_client is not None, "HTTP client not initialized"
                             try:
                                 cont_response = await self.http_client.post(
@@ -1453,7 +1461,9 @@ class AnthropicHandlerMixin:
                         output_tokens = usage.get("output_tokens", 0)
                         cr_tokens = usage.get("cache_read_input_tokens", 0)
                         cw_tokens = usage.get("cache_creation_input_tokens", 0)
-                        cw_5m_tokens, cw_1h_tokens = self._extract_anthropic_cache_ttl_metrics(usage)
+                        cw_5m_tokens, cw_1h_tokens = self._extract_anthropic_cache_ttl_metrics(
+                            usage
+                        )
                         uncached_input_tokens = usage.get("input_tokens", 0)
 
                     # Track cache bust: tokens that lost their cache discount due to compression.
@@ -1562,7 +1572,9 @@ class AnthropicHandlerMixin:
                                 cache_hit=cache_hit,
                                 transforms_applied=transforms_applied,
                                 waste_signals=waste_signals_dict,
-                                request_messages=messages if self.config.log_full_messages else None,
+                                request_messages=messages
+                                if self.config.log_full_messages
+                                else None,
                             )
                         )
 
@@ -1673,6 +1685,7 @@ class AnthropicHandlerMixin:
             # deep-copy) would otherwise leak the pre-upstream semaphore
             # permanently. The emit function is idempotent.
             await _finalize_pre_upstream()
+
     async def handle_anthropic_batch_create(
         self,
         request: Request,

headroom/proxy/helpers.py

@@ -44,7 +44,8 @@ def jitter_delay_ms(base_ms: int, max_ms: int, attempt: int) -> float:
     canonical formula used across proxy retry loops. Extracted so every
     retry site shares one implementation.
     """
-    return min(base_ms * (2**attempt), max_ms) * (0.5 + random.random())
+    capped: float = min(base_ms * (2**attempt), max_ms)
+    return capped * (0.5 + random.random())
 
 
 # Image compression (lazy-loaded to avoid heavy dependencies at startup)

tests/test_oauth_bearer_routing.py

@@ -1,12 +1,10 @@
 """Tests for OAuth Bearer token routing and auth detection."""
 
 import httpx
-import pytest
 from fastapi.testclient import TestClient
 
 from headroom.proxy.helpers import is_anthropic_auth
-from headroom.proxy.server import HeadroomProxy, ProxyConfig, create_app
-
+from headroom.proxy.server import ProxyConfig, create_app
 
 # ---------------------------------------------------------------------------
 # Unit tests: is_anthropic_auth
@@ -39,10 +37,15 @@ class TestIsAnthropicAuth:
 
     def test_anthropic_version_plus_bearer(self):
         """Claude Code sends both anthropic-version and Bearer token."""
-        assert is_anthropic_auth({
-            "anthropic-version": "2023-06-01",
-            "authorization": "Bearer 1a18a113-ab50-43c8",
-        }) is True
+        assert (
+            is_anthropic_auth(
+                {
+                    "anthropic-version": "2023-06-01",
+                    "authorization": "Bearer 1a18a113-ab50-43c8",
+                }
+            )
+            is True
+        )
 
     def test_empty_authorization(self):
         assert is_anthropic_auth({"authorization": ""}) is False