diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index ae2513f..73af864 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -35,3 +35,30 @@ jobs:
 
       - name: Run tests
         run: pytest -q
+
+  lint:
+    name: "ruff"
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python 3.12
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Cache pip
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-ruff-${{ hashFiles('pyproject.toml') }}
+
+      - name: Install ruff
+        run: pip install ruff
+
+      - name: ruff check
+        run: ruff check .
+
+      - name: ruff format --check
+        run: ruff format --check .
diff --git a/pyproject.toml b/pyproject.toml
index 6708a58..2dbb47d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -36,3 +36,23 @@ packages = ["src/conclave"]
 asyncio_mode = "auto"
 testpaths = ["tests"]
 pythonpath = ["."]
+
+[tool.ruff]
+line-length = 100
+target-version = "py311"
+
+[tool.ruff.lint]
+select = [
+    "E",   # pycodestyle errors
+    "W",   # pycodestyle warnings
+    "F",   # pyflakes
+    "I",   # isort
+    "B",   # flake8-bugbear
+    "UP",  # pyupgrade
+]
+ignore = [
+    "E501",   # line too long — ruff format handles wrapping
+]
+
+[tool.ruff.lint.isort]
+known-first-party = ["conclave"]
diff --git a/src/conclave/adapters/__init__.py b/src/conclave/adapters/__init__.py
index d7d38b5..888f094 100644
--- a/src/conclave/adapters/__init__.py
+++ b/src/conclave/adapters/__init__.py
@@ -20,7 +20,8 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, Callable
+from collections.abc import Callable
+from typing import TYPE_CHECKING
 
 from ..registry import PROVIDER_ENV_VARS, provider_prefix
 from .anthropic import AnthropicAdapter
@@ -58,9 +59,7 @@ def _openai_compat_adapter(prefix: str) -> OpenAICompatAdapter:
     )
 
 
-def resolve_adapter(
-    model_id: str, config: "ConclaveConfig | None" = None
-) -> ProviderAdapter:
+def resolve_adapter(model_id: str, config: ConclaveConfig | None = None) -> ProviderAdapter:
     """Resolve a model id to the adapter that speaks its provider's wire format.
 
     Args:
diff --git a/src/conclave/adapters/anthropic.py b/src/conclave/adapters/anthropic.py
index 0c6080e..74df4e7 100644
--- a/src/conclave/adapters/anthropic.py
+++ b/src/conclave/adapters/anthropic.py
@@ -16,8 +16,6 @@
 
 from __future__ import annotations
 
-from typing import Optional
-
 from ..models import TokenUsage
 from ..registry import PROVIDER_ENV_VARS
 from .base import ProviderError
@@ -86,9 +84,7 @@ def build_request(
             body["system"] = "\n\n".join(system_parts)
         return self.completions_url, headers, body
 
-    def parse_response(
-        self, status: int, payload: object
-    ) -> tuple[str, Optional[TokenUsage]]:
+    def parse_response(self, status: int, payload: object) -> tuple[str, TokenUsage | None]:
         """Concatenate ``content[*].text`` and map usage.
 
         See :meth:`ProviderAdapter.parse_response`.
@@ -100,9 +96,7 @@ def parse_response(
 
         content = payload.get("content")
         if not isinstance(content, list):
-            raise ProviderError(
-                "anthropic: malformed response, missing content array"
-            )
+            raise ProviderError("anthropic: malformed response, missing content array")
         text = "".join(
             block.get("text", "")
             for block in content
@@ -115,7 +109,7 @@ def parse_response(
         return text, usage
 
 
-def _parse_usage(raw: object) -> Optional[TokenUsage]:
+def _parse_usage(raw: object) -> TokenUsage | None:
     """Map Anthropic ``input_tokens``/``output_tokens`` to :class:`TokenUsage`."""
     if not isinstance(raw, dict):
         return None
diff --git a/src/conclave/adapters/base.py b/src/conclave/adapters/base.py
index d13bf1e..b92bcd6 100644
--- a/src/conclave/adapters/base.py
+++ b/src/conclave/adapters/base.py
@@ -23,7 +23,7 @@
 
 import os
 import re
-from typing import Optional, Protocol, runtime_checkable
+from typing import Protocol, runtime_checkable
 
 from ..models import TokenUsage
 from ..registry import PROVIDER_ENV_VARS
@@ -33,9 +33,7 @@
 # Matches standalone provider-style keys: sk-..., xai-..., pplx-..., AIza... etc.
 _KEY_LIKE_RE = re.compile(r"\b(?:sk|xai|pplx|AIza)[A-Za-z0-9._\-]{8,}\b")
 # Matches an x-api-key / x-goog-api-key header echoed with its value.
-_HEADER_KEY_RE = re.compile(
-    r"(x-(?:goog-)?api-key)\s*[:=]\s*[A-Za-z0-9._\-]+", re.IGNORECASE
-)
+_HEADER_KEY_RE = re.compile(r"(x-(?:goog-)?api-key)\s*[:=]\s*[A-Za-z0-9._\-]+", re.IGNORECASE)
 
 _REDACTED = "[REDACTED]"
 
@@ -123,9 +121,7 @@ def build_request(
         """
         ...
 
-    def parse_response(
-        self, status: int, payload: object
-    ) -> tuple[str, Optional[TokenUsage]]:
+    def parse_response(self, status: int, payload: object) -> tuple[str, TokenUsage | None]:
         """Parse a provider response into ``(text, usage)``.
 
         Args:
diff --git a/src/conclave/adapters/gemini.py b/src/conclave/adapters/gemini.py
index dbab003..050f58b 100644
--- a/src/conclave/adapters/gemini.py
+++ b/src/conclave/adapters/gemini.py
@@ -18,8 +18,6 @@
 
 from __future__ import annotations
 
-from typing import Optional
-
 from ..models import TokenUsage
 from ..registry import PROVIDER_ENV_VARS
 from .base import ProviderError
@@ -87,14 +85,10 @@ def build_request(
             },
         }
         if system_parts:
-            body["systemInstruction"] = {
-                "parts": [{"text": "\n\n".join(system_parts)}]
-            }
+            body["systemInstruction"] = {"parts": [{"text": "\n\n".join(system_parts)}]}
         return url, headers, body
 
-    def parse_response(
-        self, status: int, payload: object
-    ) -> tuple[str, Optional[TokenUsage]]:
+    def parse_response(self, status: int, payload: object) -> tuple[str, TokenUsage | None]:
         """Concatenate the first candidate's text parts. See base protocol."""
         if status < 200 or status >= 300:
             raise ProviderError(_status_error(status, payload))
@@ -111,9 +105,7 @@ def parse_response(
             ) from exc
 
         text = "".join(
-            part.get("text", "")
-            for part in parts
-            if isinstance(part, dict) and "text" in part
+            part.get("text", "") for part in parts if isinstance(part, dict) and "text" in part
         )
         if not text:
             raise ProviderError("gemini: empty response (no text parts)")
@@ -122,7 +114,7 @@ def parse_response(
         return text, usage
 
 
-def _parse_usage(raw: object) -> Optional[TokenUsage]:
+def _parse_usage(raw: object) -> TokenUsage | None:
     """Map Gemini ``usageMetadata`` counts to :class:`TokenUsage`."""
     if not isinstance(raw, dict):
         return None
diff --git a/src/conclave/adapters/openai_compat.py b/src/conclave/adapters/openai_compat.py
index 0be033c..e1bdaca 100644
--- a/src/conclave/adapters/openai_compat.py
+++ b/src/conclave/adapters/openai_compat.py
@@ -14,8 +14,6 @@
 
 from __future__ import annotations
 
-from typing import Optional
-
 from ..models import TokenUsage
 from .base import ProviderError
 
@@ -45,7 +43,7 @@ def __init__(
         prefix: str,
         completions_url: str,
         env_vars: tuple[str, ...],
-        max_tokens: Optional[int] = None,
+        max_tokens: int | None = None,
     ) -> None:
         self.prefix = prefix
         self.completions_url = completions_url
@@ -82,9 +80,7 @@ def build_request(
             body["max_tokens"] = self.max_tokens
         return self.completions_url, headers, body
 
-    def parse_response(
-        self, status: int, payload: object
-    ) -> tuple[str, Optional[TokenUsage]]:
+    def parse_response(self, status: int, payload: object) -> tuple[str, TokenUsage | None]:
         """Parse ``choices[0].message.content`` + ``usage``.
 
         See :meth:`ProviderAdapter.parse_response`.
@@ -92,9 +88,7 @@ def parse_response(
         if status < 200 or status >= 300:
             raise ProviderError(_status_error(self.prefix, status, payload))
         if not isinstance(payload, dict):
-            raise ProviderError(
-                f"{self.prefix}: non-JSON response body (status {status})"
-            )
+            raise ProviderError(f"{self.prefix}: non-JSON response body (status {status})")
 
         try:
             choices = payload["choices"]
@@ -112,7 +106,7 @@ def parse_response(
         return content, usage
 
 
-def _parse_usage(raw: object) -> Optional[TokenUsage]:
+def _parse_usage(raw: object) -> TokenUsage | None:
     """Map an OpenAI-style ``usage`` block to :class:`TokenUsage`, or ``None``."""
     if not isinstance(raw, dict):
         return None
diff --git a/src/conclave/cli.py b/src/conclave/cli.py
index 4835680..aaca8e6 100644
--- a/src/conclave/cli.py
+++ b/src/conclave/cli.py
@@ -12,7 +12,6 @@
 from __future__ import annotations
 
 import json
-from typing import Optional
 
 import typer
 from rich.console import Console
@@ -60,9 +59,7 @@ def _answer_panel(ans, *, border: str = "cyan") -> Panel:
 def _print_skipped(result: CouncilResult) -> None:
     """Print the skipped-no-key warning line if any members were skipped."""
     if result.skipped:
-        err_console.print(
-            f"[yellow]Skipped (no key): {', '.join(result.skipped)}[/yellow]"
-        )
+        err_console.print(f"[yellow]Skipped (no key): {', '.join(result.skipped)}[/yellow]")
 
 
 def _print_synthesis(result: CouncilResult, title: str = "SYNTHESIS") -> None:
@@ -118,8 +115,7 @@ def _render_adversarial(result: CouncilResult) -> None:
         console.print(
             Panel(
                 adv.verdict,
-                title=f"[bold green]VERDICT[/bold green] "
-                f"({adv.judge} · {adv.judge_model_id})",
+                title=f"[bold green]VERDICT[/bold green] ({adv.judge} · {adv.judge_model_id})",
                 border_style="green",
             )
         )
@@ -154,13 +150,13 @@ def ask(
         "-m",
         help="Run mode: synthesize | raw | debate | adversarial.",
     ),
-    synthesizer: Optional[str] = typer.Option(
+    synthesizer: str | None = typer.Option(
         None, "--synthesizer", "-s", help="Override the synthesizer/judge model name."
     ),
     rounds: int = typer.Option(
         2, "--rounds", "-r", help="Number of debate rounds (debate mode only).", min=1
     ),
-    proposer: Optional[str] = typer.Option(
+    proposer: str | None = typer.Option(
         None,
         "--proposer",
         "-p",
@@ -174,8 +170,7 @@ def ask(
     mode_lower = mode.lower()
     if mode_lower not in _VALID_MODES:
         err_console.print(
-            f"[red]Unknown mode '{mode}'. Choose one of: "
-            f"{', '.join(sorted(_VALID_MODES))}.[/red]"
+            f"[red]Unknown mode '{mode}'. Choose one of: {', '.join(sorted(_VALID_MODES))}.[/red]"
         )
         raise typer.Exit(code=2)
 
@@ -199,8 +194,7 @@ def ask(
 
     if not result.answers:
         err_console.print(
-            "[red]No council members had keys available. "
-            "Run 'conclave providers' to check.[/red]"
+            "[red]No council members had keys available. Run 'conclave providers' to check.[/red]"
         )
         raise typer.Exit(code=1)
 
@@ -224,9 +218,7 @@ def providers() -> None:
         table.add_row(name, model_id, mark, source)
 
     console.print(table)
-    console.print(
-        f"[dim]synthesizer default: {cfg.synthesizer} · conclave {__version__}[/dim]"
-    )
+    console.print(f"[dim]synthesizer default: {cfg.synthesizer} · conclave {__version__}[/dim]")
 
 
 def _builtin_default_note() -> str:
diff --git a/src/conclave/config.py b/src/conclave/config.py
index 59be344..bd2a816 100644
--- a/src/conclave/config.py
+++ b/src/conclave/config.py
@@ -124,10 +124,7 @@ def load_config(path: Path | None = None) -> ConclaveConfig:
     merged_models = dict(DEFAULT_MODELS)
     merged_models.update(raw.get("models", {}) or {})
 
-    councils = {
-        name: list(members)
-        for name, members in (raw.get("councils", {}) or {}).items()
-    }
+    councils = {name: list(members) for name, members in (raw.get("councils", {}) or {}).items()}
     # Always provide a "default" council if none defined: all known providers.
     councils.setdefault("default", list(DEFAULT_MODELS.keys()))
 
diff --git a/src/conclave/council.py b/src/conclave/council.py
index 3f2695c..47af852 100644
--- a/src/conclave/council.py
+++ b/src/conclave/council.py
@@ -13,7 +13,7 @@
 from __future__ import annotations
 
 import asyncio
-from typing import Callable
+from collections.abc import Callable
 
 from .config import ConclaveConfig, load_config
 from .logging import get_logger
@@ -90,7 +90,7 @@ def _available_members(self) -> tuple[list[tuple[str, str]], list[str]]:
     async def fan_out(
         self,
         members: list[tuple[str, str]],
-        messages_for: "MessagesFor",
+        messages_for: MessagesFor,
     ) -> list[ModelAnswer]:
         """Fan a per-member message list out concurrently and collect results.
 
@@ -123,7 +123,7 @@ async def fan_out(
         # against any unexpected raise so one bad member can't abort the gather.
         gathered = await asyncio.gather(*tasks, return_exceptions=True)
         answers: list[ModelAnswer] = []
-        for (name, model_id), outcome in zip(members, gathered):
+        for (name, model_id), outcome in zip(members, gathered, strict=True):
             if isinstance(outcome, ModelAnswer):
                 answers.append(outcome)
             else:
@@ -161,9 +161,7 @@ async def ask(self, prompt: str, synthesize: bool = True) -> CouncilResult:
             return result
 
         base_messages = [{"role": "user", "content": prompt}]
-        result.answers = await self.fan_out(
-            members, lambda _name, _model_id: base_messages
-        )
+        result.answers = await self.fan_out(members, lambda _name, _model_id: base_messages)
 
         if synthesize:
             await self._synthesize(result)
@@ -189,9 +187,7 @@ async def _synthesize(self, result: CouncilResult) -> None:
             logger.warning(result.synthesis_error)
             return
 
-        blocks = "\n\n".join(
-            f"### Answer from {a.name} ({a.model_id})\n{a.answer}" for a in usable
-        )
+        blocks = "\n\n".join(f"### Answer from {a.name} ({a.model_id})\n{a.answer}" for a in usable)
         user_content = (
             f"Original prompt:\n{result.prompt}\n\n"
             f"Council answers:\n\n{blocks}\n\n"
@@ -203,9 +199,7 @@ async def _synthesize(self, result: CouncilResult) -> None:
         else:
             result.synthesis_error = answer.error
 
-    async def synthesize_blocks(
-        self, system_prompt: str, user_content: str
-    ) -> ModelAnswer:
+    async def synthesize_blocks(self, system_prompt: str, user_content: str) -> ModelAnswer:
         """Call the synthesizer model with an arbitrary system + user message.
 
         Shared by synthesize mode, debate's final consolidation, and the
@@ -244,9 +238,7 @@ async def debate(self, prompt: str, rounds: int = 2) -> CouncilResult:
 
         return await run_debate(self, prompt, rounds=rounds)
 
-    async def adversarial(
-        self, prompt: str, proposer: str | None = None
-    ) -> CouncilResult:
+    async def adversarial(self, prompt: str, proposer: str | None = None) -> CouncilResult:
         """Run propose -> refute -> verdict. See :func:`conclave.modes.run_adversarial`.
 
         ``proposer`` (friendly name) defaults to the first requested member.
@@ -256,15 +248,14 @@ async def adversarial(
         return await run_adversarial(self, prompt, proposer=proposer)
 
     @staticmethod
-    def _run_sync(coro_factory: Callable[[], "asyncio.Future | object"], label: str):
+    def _run_sync(coro_factory: Callable[[], asyncio.Future | object], label: str):
         """Run an async council method synchronously, guarding nested loops."""
         try:
             asyncio.get_running_loop()
         except RuntimeError:
             return asyncio.run(coro_factory())
         raise RuntimeError(
-            f"{label}() called from within a running event loop; "
-            "await the async method instead"
+            f"{label}() called from within a running event loop; await the async method instead"
         )
 
     def ask_sync(self, prompt: str, synthesize: bool = True) -> CouncilResult:
@@ -273,19 +264,13 @@ def ask_sync(self, prompt: str, synthesize: bool = True) -> CouncilResult:
         Safe to call from non-async code. Raises ``RuntimeError`` if invoked
         from inside a running event loop -- use :meth:`ask` there instead.
         """
-        return self._run_sync(
-            lambda: self.ask(prompt, synthesize=synthesize), "ask_sync"
-        )
+        return self._run_sync(lambda: self.ask(prompt, synthesize=synthesize), "ask_sync")
 
     def debate_sync(self, prompt: str, rounds: int = 2) -> CouncilResult:
         """Synchronous wrapper around :meth:`debate`."""
-        return self._run_sync(
-            lambda: self.debate(prompt, rounds=rounds), "debate_sync"
-        )
+        return self._run_sync(lambda: self.debate(prompt, rounds=rounds), "debate_sync")
 
-    def adversarial_sync(
-        self, prompt: str, proposer: str | None = None
-    ) -> CouncilResult:
+    def adversarial_sync(self, prompt: str, proposer: str | None = None) -> CouncilResult:
         """Synchronous wrapper around :meth:`adversarial`."""
         return self._run_sync(
             lambda: self.adversarial(prompt, proposer=proposer), "adversarial_sync"
diff --git a/src/conclave/logging.py b/src/conclave/logging.py
index 972293a..1f65c5e 100644
--- a/src/conclave/logging.py
+++ b/src/conclave/logging.py
@@ -28,9 +28,7 @@ def get_logger(name: str = "conclave") -> logging.Logger:
         level_name = os.environ.get("CONCLAVE_LOG_LEVEL", "WARNING").upper()
         level = getattr(logging, level_name, logging.WARNING)
         handler = logging.StreamHandler()
-        handler.setFormatter(
-            logging.Formatter("%(asctime)s %(name)s %(levelname)s %(message)s")
-        )
+        handler.setFormatter(logging.Formatter("%(asctime)s %(name)s %(levelname)s %(message)s"))
         root.addHandler(handler)
         root.setLevel(level)
         root.propagate = False
diff --git a/src/conclave/models.py b/src/conclave/models.py
index 04c17c2..25803b8 100644
--- a/src/conclave/models.py
+++ b/src/conclave/models.py
@@ -6,8 +6,6 @@
 
 from __future__ import annotations
 
-from typing import Optional
-
 from pydantic import BaseModel, Field
 
 
@@ -33,10 +31,10 @@ class ModelAnswer(BaseModel):
 
     name: str
     model_id: str
-    answer: Optional[str] = None
+    answer: str | None = None
     latency_s: float = 0.0
-    usage: Optional[TokenUsage] = None
-    error: Optional[str] = None
+    usage: TokenUsage | None = None
+    error: str | None = None
 
     @property
     def ok(self) -> bool:
@@ -81,10 +79,10 @@ class AdversarialResult(BaseModel):
     proposer: str
     proposal: ModelAnswer
     critiques: list[ModelAnswer] = Field(default_factory=list)
-    verdict: Optional[str] = None
-    verdict_error: Optional[str] = None
-    judge: Optional[str] = None
-    judge_model_id: Optional[str] = None
+    verdict: str | None = None
+    verdict_error: str | None = None
+    judge: str | None = None
+    judge_model_id: str | None = None
 
     @property
     def successful_critiques(self) -> list[ModelAnswer]:
@@ -117,13 +115,13 @@ class CouncilResult(BaseModel):
     prompt: str
     mode: str = "synthesize"
     answers: list[ModelAnswer] = Field(default_factory=list)
-    synthesizer: Optional[str] = None
-    synthesizer_model_id: Optional[str] = None
-    synthesis: Optional[str] = None
-    synthesis_error: Optional[str] = None
+    synthesizer: str | None = None
+    synthesizer_model_id: str | None = None
+    synthesis: str | None = None
+    synthesis_error: str | None = None
     skipped: list[str] = Field(default_factory=list)
     rounds: list[DebateRound] = Field(default_factory=list)
-    adversarial: Optional[AdversarialResult] = None
+    adversarial: AdversarialResult | None = None
 
     @property
     def successful_answers(self) -> list[ModelAnswer]:
diff --git a/src/conclave/modes.py b/src/conclave/modes.py
index 205b0e5..9f0541b 100644
--- a/src/conclave/modes.py
+++ b/src/conclave/modes.py
@@ -35,9 +35,7 @@
 logger = get_logger("modes")
 
 
-async def run_debate(
-    council: "Council", prompt: str, rounds: int = 2
-) -> CouncilResult:
+async def run_debate(council: Council, prompt: str, rounds: int = 2) -> CouncilResult:
     """Run a multi-round debate and return a structured :class:`CouncilResult`.
 
     Args:
@@ -62,8 +60,7 @@ async def run_debate(
 
     # Stable letter labels by initial position; survives drop-outs.
     letters = {
-        name: prompts.LETTERS[i % len(prompts.LETTERS)]
-        for i, (name, _) in enumerate(members)
+        name: prompts.LETTERS[i % len(prompts.LETTERS)] for i, (name, _) in enumerate(members)
     }
 
     survivors = list(members)  # (name, model_id) pairs still in the debate
@@ -74,9 +71,7 @@ async def run_debate(
             logger.warning("debate ended early at round %d: no survivors", round_no)
             break
 
-        messages_for = _debate_messages_for(
-            prompt, round_no, rounds, prior, letters
-        )
+        messages_for = _debate_messages_for(prompt, round_no, rounds, prior, letters)
         answers = await council.fan_out(survivors, messages_for)
         result.rounds.append(DebateRound(round_number=round_no, answers=answers))
 
@@ -119,23 +114,19 @@ def _debate_messages_for(
         return lambda _name, _model_id: base
 
     def messages_for(name: str, _model_id: str) -> list[dict[str, str]]:
-        peer_block = prompts.anonymized_peer_block(
-            name, letters[name], prior, letters
-        )
+        peer_block = prompts.anonymized_peer_block(name, letters[name], prior, letters)
         return [
             {"role": "system", "content": prompts.DEBATE_SYSTEM},
             {
                 "role": "user",
-                "content": prompts.debate_round_user(
-                    prompt, round_no, rounds, peer_block
-                ),
+                "content": prompts.debate_round_user(prompt, round_no, rounds, peer_block),
             },
         ]
 
     return messages_for
 
 
-async def _debate_synthesize(council: "Council", result: CouncilResult) -> None:
+async def _debate_synthesize(council: Council, result: CouncilResult) -> None:
     """Consolidate the final round's surviving answers via the synthesizer."""
     final = result.rounds[-1].successful_answers if result.rounds else []
     if not final:
@@ -166,7 +157,7 @@ async def _debate_synthesize(council: "Council", result: CouncilResult) -> None:
 
 
 async def run_adversarial(
-    council: "Council", prompt: str, proposer: str | None = None
+    council: Council, prompt: str, proposer: str | None = None
 ) -> CouncilResult:
     """Run a propose -> refute -> verdict pass and return a :class:`CouncilResult`.
 
@@ -239,9 +230,7 @@ def critic_messages(_name: str, _model_id: str) -> list[dict[str, str]]:
     return critic_messages
 
 
-def _pick_proposer(
-    members: list[tuple[str, str]], requested: str
-) -> tuple[str, str]:
+def _pick_proposer(members: list[tuple[str, str]], requested: str) -> tuple[str, str]:
     """Return the requested proposer member, or the first available as fallback."""
     for member in members:
         if member[0] == requested:
@@ -249,9 +238,7 @@ def _pick_proposer(
     return members[0]
 
 
-async def _adversarial_judge(
-    council: "Council", prompt: str, adv: AdversarialResult
-) -> None:
+async def _adversarial_judge(council: Council, prompt: str, adv: AdversarialResult) -> None:
     """Run the judge over the proposal + critiques, mutating ``adv``."""
     judge_id = council.config.resolve_model_id(council.synthesizer)
     adv.judge = council.synthesizer
@@ -259,8 +246,7 @@ async def _adversarial_judge(
 
     if not adv.proposal.ok:
         adv.verdict_error = (
-            f"proposal from '{adv.proposer}' failed ({adv.proposal.error}); "
-            "no verdict produced"
+            f"proposal from '{adv.proposer}' failed ({adv.proposal.error}); no verdict produced"
         )
         logger.warning(adv.verdict_error)
         return
@@ -275,8 +261,7 @@ async def _adversarial_judge(
     usable_critiques = adv.successful_critiques
     if usable_critiques:
         critique_blocks = "\n\n".join(
-            f"### Critique from {c.name} ({c.model_id})\n{c.answer}"
-            for c in usable_critiques
+            f"### Critique from {c.name} ({c.model_id})\n{c.answer}" for c in usable_critiques
         )
     else:
         critique_blocks = "(no usable critiques were produced)"
diff --git a/src/conclave/prompts.py b/src/conclave/prompts.py
index cb929f3..7ce5b38 100644
--- a/src/conclave/prompts.py
+++ b/src/conclave/prompts.py
@@ -70,9 +70,7 @@ def anonymized_peer_block(
     parts: list[str] = []
     own = prior.get(self_name)
     if own is not None and own.ok:
-        parts.append(
-            f"### Your previous answer (you are Model {self_letter})\n{own.answer}"
-        )
+        parts.append(f"### Your previous answer (you are Model {self_letter})\n{own.answer}")
     for name, ans in prior.items():
         if name == self_name or not ans.ok:
             continue
diff --git a/src/conclave/providers.py b/src/conclave/providers.py
index bf49787..6e84400 100644
--- a/src/conclave/providers.py
+++ b/src/conclave/providers.py
@@ -16,7 +16,6 @@
 
 import os
 import time
-from typing import Optional
 
 from . import transport
 from .adapters import ProviderError, resolve_adapter
@@ -29,7 +28,7 @@
 logger = get_logger("providers")
 
 
-def _resolve_key(adapter: ProviderAdapter) -> Optional[str]:
+def _resolve_key(adapter: ProviderAdapter) -> str | None:
     """Read the active key VALUE for an adapter from the environment, or None.
 
     Walks the adapter's candidate env var names in order and returns the first
@@ -77,9 +76,7 @@ async def call_model(
     except ProviderError as exc:
         latency = time.perf_counter() - started
         logger.warning("%s (%s) unresolved: %s", name, model_id, exc)
-        return ModelAnswer(
-            name=name, model_id=model_id, latency_s=latency, error=str(exc)
-        )
+        return ModelAnswer(name=name, model_id=model_id, latency_s=latency, error=str(exc))
 
     api_key = _resolve_key(adapter)
     if api_key is None:
@@ -87,9 +84,7 @@ async def call_model(
         names = " or ".join(adapter.env_vars) or "(none)"
         msg = f"no API key in environment (set {names})"
         logger.warning("%s (%s) %s", name, model_id, msg)
-        return ModelAnswer(
-            name=name, model_id=model_id, latency_s=latency, error=msg
-        )
+        return ModelAnswer(name=name, model_id=model_id, latency_s=latency, error=msg)
 
     try:
         url, headers, body = adapter.build_request(
@@ -112,13 +107,9 @@ async def call_model(
         # transport message and any composed string.
         message = redact(str(exc))
         logger.warning("%s (%s) failed: %s", name, model_id, message)
-        return ModelAnswer(
-            name=name, model_id=model_id, latency_s=latency, error=message
-        )
+        return ModelAnswer(name=name, model_id=model_id, latency_s=latency, error=message)
     except Exception as exc:  # noqa: BLE001 -- never let an unexpected raise kill the run
         latency = time.perf_counter() - started
         message = redact(f"{type(exc).__name__}: {exc}")
         logger.warning("%s (%s) unexpected error: %s", name, model_id, message)
-        return ModelAnswer(
-            name=name, model_id=model_id, latency_s=latency, error=message
-        )
+        return ModelAnswer(name=name, model_id=model_id, latency_s=latency, error=message)
diff --git a/src/conclave/transport.py b/src/conclave/transport.py
index 72a78e2..d056df3 100644
--- a/src/conclave/transport.py
+++ b/src/conclave/transport.py
@@ -13,8 +13,6 @@
 
 from __future__ import annotations
 
-from typing import Optional
-
 import httpx
 
 from .logging import get_logger
@@ -23,7 +21,7 @@
 
 # One shared, lazily-created client so connections are pooled across calls
 # within a process. httpx.AsyncClient is safe to share across concurrent tasks.
-_client: Optional[httpx.AsyncClient] = None
+_client: httpx.AsyncClient | None = None
 
 
 class TransportError(Exception):
@@ -69,9 +67,7 @@ async def post_json(
     """
     client = _get_client()
     try:
-        response = await client.post(
-            url, headers=headers, json=json_body, timeout=timeout
-        )
+        response = await client.post(url, headers=headers, json=json_body, timeout=timeout)
     except httpx.TimeoutException as exc:
         raise TransportError(f"request timed out after {timeout:.0f}s") from exc
     except httpx.HTTPError as exc:
diff --git a/tests/conftest.py b/tests/conftest.py
index b968ff1..904aa0e 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -19,8 +19,8 @@
 from __future__ import annotations
 
 import asyncio
+from collections.abc import Callable
 from dataclasses import dataclass
-from typing import Callable
 
 import pytest
 
@@ -61,9 +61,7 @@ def handler(model_id, messages, **kwargs):
     import conclave.council as council_mod
 
     def install(handler: Callable):
-        async def fake_call_model(
-            name, model_id, messages, *, temperature=0.7, timeout=120.0
-        ):
+        async def fake_call_model(name, model_id, messages, *, temperature=0.7, timeout=120.0):
             # A tiny await so concurrency is genuinely exercised by gather.
             await asyncio.sleep(0)
             try:
diff --git a/tests/test_adapters.py b/tests/test_adapters.py
index 442b000..e056b60 100644
--- a/tests/test_adapters.py
+++ b/tests/test_adapters.py
@@ -22,7 +22,6 @@
 from conclave.adapters.gemini import GeminiAdapter
 from conclave.adapters.openai_compat import OpenAICompatAdapter
 
-
 # --------------------------------------------------------------------------- #
 # OpenAI-compatible adapter (openai / xai / perplexity)
 # --------------------------------------------------------------------------- #
@@ -39,9 +38,7 @@ def _openai_adapter() -> OpenAICompatAdapter:
 def test_openai_compat_build_request():
     adapter = _openai_adapter()
     messages = [{"role": "user", "content": "hi"}]
-    url, headers, body = adapter.build_request(
-        "openai/gpt-4.1", messages, 0.7, 120.0, "sk-secret"
-    )
+    url, headers, body = adapter.build_request("openai/gpt-4.1", messages, 0.7, 120.0, "sk-secret")
     assert url == "https://api.openai.com/v1/chat/completions"
     assert headers["Authorization"] == "Bearer sk-secret"
     assert headers["Content-Type"] == "application/json"
@@ -210,8 +207,7 @@ def test_gemini_build_request_role_mapping_and_system_instruction():
     )
     # Model embedded in the URL path; gemini/ prefix stripped.
     assert url == (
-        "https://generativelanguage.googleapis.com/v1beta/models/"
-        "gemini-2.5-pro:generateContent"
+        "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-pro:generateContent"
     )
     # Auth header is x-goog-api-key (no Bearer).
     assert headers["x-goog-api-key"] == "AIza-secret"
@@ -243,9 +239,7 @@ def test_gemini_build_request_configurable_max_output_tokens_no_system():
 def test_gemini_parse_success():
     adapter = GeminiAdapter()
     payload = {
-        "candidates": [
-            {"content": {"parts": [{"text": "part one "}, {"text": "part two"}]}}
-        ],
+        "candidates": [{"content": {"parts": [{"text": "part one "}, {"text": "part two"}]}}],
         "usageMetadata": {
             "promptTokenCount": 8,
             "candidatesTokenCount": 6,
diff --git a/tests/test_council.py b/tests/test_council.py
index adc2798..c916a1c 100644
--- a/tests/test_council.py
+++ b/tests/test_council.py
@@ -72,21 +72,17 @@ async def test_concurrency_is_real(monkeypatch):
     """Members run concurrently: total time ~= slowest call, not the sum."""
     _all_keys(monkeypatch)
 
-    from conclave.models import ModelAnswer
     import conclave.council as council_mod
+    from conclave.models import ModelAnswer
 
     # Replace call_model with a coroutine that sleeps, to prove gather concurrency.
-    async def sleepy_call_model(
-        name, model_id, messages, *, temperature=0.7, timeout=120.0
-    ):
+    async def sleepy_call_model(name, model_id, messages, *, temperature=0.7, timeout=120.0):
         await asyncio.sleep(0.2)
         return ModelAnswer(name=name, model_id=model_id, answer=f"ok {model_id}")
 
     monkeypatch.setattr(council_mod, "call_model", sleepy_call_model)
 
-    council = Council(
-        models=["grok", "gemini", "perplexity"], config=_config()
-    )
+    council = Council(models=["grok", "gemini", "perplexity"], config=_config())
     start = asyncio.get_event_loop().time()
     result = await council.ask("hi", synthesize=False)
     elapsed = asyncio.get_event_loop().time() - start
@@ -160,9 +156,7 @@ def handler(model, messages, **kwargs):
 
     patch_call_model(handler)
 
-    council = Council(
-        models=["grok"], synthesizer="claude", config=_config()
-    )
+    council = Council(models=["grok"], synthesizer="claude", config=_config())
     result = await council.ask("q")
 
     assert len(result.successful_answers) == 1
@@ -173,6 +167,7 @@ def handler(model, messages, **kwargs):
 
 async def test_no_members_available(monkeypatch, patch_call_model, clear_keys):
     """Zero available members yields an empty result, not an exception."""
+
     def handler(model, messages, **kwargs):  # pragma: no cover - never called
         return make_response("unused")
 
@@ -195,9 +190,7 @@ def handler(model, messages, **kwargs):
 
     patch_call_model(handler)
 
-    council = Council(
-        models=["grok", "gemini"], synthesizer="claude", config=_config()
-    )
+    council = Council(models=["grok", "gemini"], synthesizer="claude", config=_config())
     result = await council.ask("q")
 
     assert len(result.failed_answers) == 2
diff --git a/tests/test_modes.py b/tests/test_modes.py
index 15f796e..9b8a68c 100644
--- a/tests/test_modes.py
+++ b/tests/test_modes.py
@@ -221,6 +221,7 @@ def handler(model, messages, **kwargs):
 
 async def test_debate_no_members_available(monkeypatch, patch_call_model, clear_keys):
     """Zero available members yields an empty debate result, not an exception."""
+
     def handler(model, messages, **kwargs):  # pragma: no cover - never called
         return make_response("unused")
 
@@ -372,9 +373,7 @@ def handler(model, messages, **kwargs):
 
     patch_call_model(handler)
 
-    council = Council(
-        models=["grok", "gemini"], synthesizer="claude", config=_config()
-    )
+    council = Council(models=["grok", "gemini"], synthesizer="claude", config=_config())
     result = await council.adversarial("q")
 
     adv = result.adversarial
@@ -386,9 +385,7 @@ def handler(model, messages, **kwargs):
     assert result.synthesis is None
 
 
-async def test_adversarial_proposer_no_key_falls_back(
-    monkeypatch, patch_call_model, clear_keys
-):
+async def test_adversarial_proposer_no_key_falls_back(monkeypatch, patch_call_model, clear_keys):
     """A requested proposer without a key falls back to the first available member."""
     # Only gemini + claude have keys; requested proposer grok does not.
     monkeypatch.setenv("GEMINI_API_KEY", "dummy")
@@ -432,9 +429,7 @@ def handler(model, messages, **kwargs):
 
     patch_call_model(handler)
 
-    council = Council(
-        models=["grok", "gemini"], synthesizer="claude", config=_config()
-    )
+    council = Council(models=["grok", "gemini"], synthesizer="claude", config=_config())
     result = await council.adversarial("q")
 
     adv = result.adversarial
@@ -444,10 +439,9 @@ def handler(model, messages, **kwargs):
     assert "no API key" in adv.verdict_error
 
 
-async def test_adversarial_no_members_available(
-    monkeypatch, patch_call_model, clear_keys
-):
+async def test_adversarial_no_members_available(monkeypatch, patch_call_model, clear_keys):
     """Zero available members yields an empty adversarial result, not an error."""
+
     def handler(model, messages, **kwargs):  # pragma: no cover - never called
         return make_response("unused")
 
@@ -478,9 +472,7 @@ def handler(model, messages, **kwargs):
 
     patch_call_model(handler)
 
-    council = Council(
-        models=["grok", "gemini"], synthesizer="claude", config=_config()
-    )
+    council = Council(models=["grok", "gemini"], synthesizer="claude", config=_config())
     result = council.adversarial_sync("hi")
 
     assert result.mode == "adversarial"
diff --git a/tests/test_providers.py b/tests/test_providers.py
index 0d97270..1d8beba 100644
--- a/tests/test_providers.py
+++ b/tests/test_providers.py
@@ -23,7 +23,6 @@
 from conclave.config import ConclaveConfig, CustomEndpoint
 from conclave.providers import call_model
 
-
 # --------------------------------------------------------------------------- #
 # Adapter registry
 # --------------------------------------------------------------------------- #
@@ -33,17 +32,12 @@ def test_resolve_adapter_built_in_prefixes():
     assert isinstance(resolve_adapter("openai/gpt-4.1"), OpenAICompatAdapter)
     assert isinstance(resolve_adapter("xai/grok-4.3"), OpenAICompatAdapter)
     assert isinstance(resolve_adapter("perplexity/sonar-pro"), OpenAICompatAdapter)
-    assert isinstance(
-        resolve_adapter("anthropic/claude-sonnet-4-6"), AnthropicAdapter
-    )
+    assert isinstance(resolve_adapter("anthropic/claude-sonnet-4-6"), AnthropicAdapter)
     assert isinstance(resolve_adapter("gemini/gemini-2.5-pro"), GeminiAdapter)
 
 
 def test_resolve_adapter_per_provider_urls():
-    assert (
-        resolve_adapter("xai/grok-4.3").completions_url
-        == "https://api.x.ai/v1/chat/completions"
-    )
+    assert resolve_adapter("xai/grok-4.3").completions_url == "https://api.x.ai/v1/chat/completions"
     # Perplexity has NO /v1 segment.
     assert (
         resolve_adapter("perplexity/sonar-pro").completions_url
@@ -125,9 +119,7 @@ async def boom(url, headers, json_body, timeout):
 
     monkeypatch.setattr("conclave.transport.post_json", boom)
 
-    answer = await call_model(
-        "openai", "openai/gpt-4.1", [{"role": "user", "content": "hi"}]
-    )
+    answer = await call_model("openai", "openai/gpt-4.1", [{"role": "user", "content": "hi"}])
     assert not answer.ok
     assert answer.answer is None
     assert "timed out" in answer.error
@@ -138,9 +130,7 @@ async def test_call_model_missing_key_is_error(monkeypatch):
     monkeypatch.delenv("OPENAI_API_KEY", raising=False)
     monkeypatch.setenv("CONCLAVE_CONFIG", "/nonexistent/conclave.yml")
 
-    answer = await call_model(
-        "openai", "openai/gpt-4.1", [{"role": "user", "content": "hi"}]
-    )
+    answer = await call_model("openai", "openai/gpt-4.1", [{"role": "user", "content": "hi"}])
     assert not answer.ok
     assert "OPENAI_API_KEY" in answer.error
 
@@ -149,9 +139,7 @@ async def test_call_model_unknown_provider_is_error(monkeypatch):
     """An unknown provider prefix surfaces as a helpful, non-raising error."""
     monkeypatch.setenv("CONCLAVE_CONFIG", "/nonexistent/conclave.yml")
 
-    answer = await call_model(
-        "mystery", "mystery/model", [{"role": "user", "content": "hi"}]
-    )
+    answer = await call_model("mystery", "mystery/model", [{"role": "user", "content": "hi"}])
     assert not answer.ok
     assert "unknown provider 'mystery'" in answer.error
 
diff --git a/tests/test_registry_config.py b/tests/test_registry_config.py
index d533879..8cc4436 100644
--- a/tests/test_registry_config.py
+++ b/tests/test_registry_config.py
@@ -2,8 +2,6 @@
 
 from __future__ import annotations
 
-from pathlib import Path
-
 from conclave.config import load_config
 from conclave.registry import (
     DEFAULT_MODELS,