diff --git a/changelog.md b/changelog.md
index bf51cc9..4a06f0f 100644
--- a/changelog.md
+++ b/changelog.md
@@ -2,6 +2,9 @@
 
 ## unreleased
 
+- add auto-router runner selection with configurable default engine
+- add `/cancel` + `/{engine}` command menu sync on startup
+
 ## v0.3.0 (2026-01-01)
 
 ### changes
diff --git a/docs/developing.md b/docs/developing.md
index fd92456..c7ba50f 100644
--- a/docs/developing.md
+++ b/docs/developing.md
@@ -26,6 +26,9 @@ uv run ty check .
 make check
 ```
 
+Takopi runs in **auto-router** mode by default. `default_engine` in `takopi.toml` selects
+the engine for new threads; engine subcommands override that default for the process.
+
 ## Module Responsibilities
 
 ### `bridge.py` - Telegram bridge loop
@@ -44,9 +47,11 @@ The orchestrator module containing:
 **Key patterns:**
 - Bridge schedules runs FIFO per thread to avoid concurrent progress messages; runner locks enforce per-thread serialization
 - `/cancel` routes by reply-to progress message id (accepts extra text)
-- Progress edits are throttled to ~1s intervals and only run when new events arrive
+- `/{engine}` on the first line selects the engine for new threads
+- Progress edits are throttled to 2s intervals and only run when new events arrive
 - Resume tokens are runner-formatted command lines (e.g., `` `codex resume <token>` ``)
-- Resume parsing is delegated to the active runner (no cross-engine fallback)
+- Resume parsing polls all runners via `AutoRouter.resolve_resume()` and routes to the first match
+- Bot command menu is synced on startup (`cancel` + engine commands)
 
 ### `cli.py` - CLI entry point
 
@@ -164,12 +169,16 @@ poll_updates() drains backlog, long-polls, filters chat_id == from_id == cfg.cha
     ↓
 run_main_loop() spawns tasks in TaskGroup
     ↓
-handle_message() spawned as task
+router.resolve_resume(text, reply_text) → ResumeToken | None
+    ↓
+router.runner_for(resume_token) → selects runner (default engine if None)
+    ↓
+handle_message() spawned as task with selected runner
     ↓
 Send initial progress message (silent)
     ↓
-CodexRunner.run()
-    ├── Spawns: codex exec --json ... -
+runner.run(prompt, resume_token)
+    ├── Spawns engine subprocess (e.g., codex exec --json)
     ├── Streams JSONL from stdout
     ├── Normalizes JSONL -> takopi events
     ├── Yields Takopi events (async iterator)
@@ -186,10 +195,10 @@ Send/edit final message
 
 ### Resume Flow
 
-Same as above, but:
-- Runners parse resume lines (e.g. `` `codex resume <token>` ``)
-- Command becomes: `codex exec --json resume <token> -`
-- Per-token lock serializes concurrent resumes
+Same as above; auto-router polls all runners to extract resume tokens:
+- Router returns first matching token (e.g. `` `claude --resume <id>` `` routes to Claude)
+- Selected runner spawns with resume (e.g. `codex exec --json resume <token> -`)
+- Per-token lock serializes concurrent resumes on the same thread
 
 ## Error Handling
 
diff --git a/docs/specification.md b/docs/specification.md
index 373687a..d7de39b 100644
--- a/docs/specification.md
+++ b/docs/specification.md
@@ -1,10 +1,10 @@
-# Takopi Specification v0.2.0 (minimal) [2025-12-31]
+# Takopi Specification v0.4.0 [2026-01-01]
 
 This document is **normative**. The words **MUST**, **SHOULD**, and **MAY** express requirements.
 
 ## 1. Scope
 
-Takopi v0.2.0 specifies:
+Takopi v0.4.0 specifies:
 
 - A **Telegram** bot bridge that runs an agent **Runner** and posts:
   - a throttled, edited **progress message**
@@ -12,12 +12,12 @@ Takopi v0.2.0 specifies:
 - **Thread continuation** via a **resume command** embedded in chat messages
 - **Parallel runs across different threads**
 - **Serialization within a thread** (no concurrent runs on the same thread)
+- **Automatic runner selection** among multiple engines based on ResumeLine (with a configurable default for new threads)
 - A Takopi-owned **normalized event model** produced by runners and consumed by renderers/bridge
 
-Out of scope for v0.2.0:
+Out of scope for v0.4.0:
 
 - Non-Telegram clients (Slack/Discord/etc.)
-- Auto-selecting among multiple runners
 - Token-by-token streaming of the assistant’s final answer
 - Engines/runners that cannot provide **stable action IDs** within a run
 
@@ -71,11 +71,13 @@ Constraints:
 
 ### 3.4 Bridge resume resolution (MUST)
 
-Given `text` (user message) and optional `reply_text` (the message being replied to):
+Given `text` (user message), optional `reply_text` (the message being replied to), and an ordered list of available runners `runners`:
 
-1. The bridge MUST attempt `runner.extract_resume(text)`.
-2. If not found, it MUST attempt `runner.extract_resume(reply_text)` if present.
-3. If still not found, the run MUST start with `resume=None` (new thread).
+1. The bridge MUST attempt to extract a resume token by polling all runners in order:
+   1. for each `r` in `runners`, attempt `r.extract_resume(text)`
+   2. choose the **first** runner that returns a non-`None` token and stop
+2. If not found, it MUST repeat step (1) for `reply_text` if present.
+3. If still not found, the run MUST start with `resume=None` (new thread) on the default runner (per §8, including chat-level overrides).
 
 ## 4. Normalized event model
 
@@ -335,12 +337,30 @@ Action update collapsing:
 
 ## 8. Configuration and engine selection
 
-Decision (v0.2.0):
+Decision (v0.4.0):
 
-* Exactly one runner is selected at startup via a CLI subcommand (no default).
-* If no engine subcommand is provided, Takopi prints an engine chooser panel and exits.
-* Resume extraction uses only the selected runner.
-* If a user provides a resume line for a different engine, extraction fails and the bridge treats the message as a new thread (`resume=None`).
+* Takopi MUST support configuring a **default engine** used to start new threads (`resume=None`).
+  * If not configured, the default engine is implementation-defined (non-normative: the reference implementation defaults to `codex`).
+* If no engine subcommand is provided, Takopi MUST run in **auto-router** mode:
+  * new threads use the configured default engine
+  * resumed threads are routed based on ResumeLine extraction (per §3.4)
+* If an engine subcommand is provided, Takopi MUST still use the auto-router, but it overrides the configured default engine for new threads.
+* Resume extraction MUST poll **all** available runners (per §3.4) and route to the first matching runner.
+* New thread engine override (chat-level):
+  * Users MAY prefix the first non-empty line with `/{engine}` (e.g. `/claude` or `/codex`) to select the engine for a **new** thread.
+  * The bridge MUST strip that directive from the prompt before invoking the runner.
+  * If a ResumeToken is resolved from the message or reply, it MUST take precedence and the `/{engine}` directive MUST be ignored.
+
+### 8.1 Command menu (Telegram)
+
+Takopi SHOULD keep the bot’s slash-command menu in sync at startup by calling
+`setMyCommands` with the canonical list of supported commands.
+
+* The command list MUST include:
+  * `cancel` — cancel the current run
+  * one entry per configured engine
+* The command list MUST NOT include commands the bot does not support.
+* Command descriptions SHOULD be terse and lowercase.
 
 ## 9. Testing requirements (MUST)
 
@@ -373,5 +393,23 @@ Tests MUST cover:
 
    * completed-only actions render correctly
    * repeated events for same Action.id collapse as intended
+7. **Auto-router engine selection**
+
+   * resume lines for non-default engines are detected and routed correctly (poll all runners)
+   * new threads use the configured default engine, with CLI subcommand overriding it
 
 Test tooling SHOULD include event factories, deterministic/fake time, and a script/mock runner.
+
+## 10. Changelog
+
+### v0.4.0 (2026-01-01)
+
+- Add auto-router engine selection by polling all runners to decode resume lines; add configurable default engine for new threads (subcommand overrides default).
+
+### v0.3.0 (2026-01-01)
+
+- Require runners to implement explicit resume formatting/extraction/detection and treat runners as authoritative for resume tokens/lines.
+
+### v0.2.0 (2025-12-31)
+
+- Initial minimal Takopi specification (Telegram bridge + runner protocol + normalized events + resume support).
diff --git a/readme.md b/readme.md
index a29cb14..302ffc7 100644
--- a/readme.md
+++ b/readme.md
@@ -2,7 +2,7 @@
 
 🐙 *he just wants to help-pi*
 
-telegram bridge for codex and claude code. runs the agent cli, streams progress, and supports resumable sessions.
+telegram bridge for codex, claude code, and [other agents](docs/adding-a-runner.md). runs the agent cli, streams progress, and supports resumable sessions.
 
 ## features
 
@@ -40,6 +40,8 @@ parallel runs across threads, per thread queue support.
 global config `~/.takopi/takopi.toml`, repo-level config `.takopi/takopi.toml`
 
 ```toml
+default_engine = "codex"
+
 bot_token = "123456789:ABCdefGHIjklMNOpqrsTUVwxyz"
 chat_id = 123456789
 
@@ -61,13 +63,17 @@ start takopi in the repo you want to work on:
 
 ```sh
 cd ~/dev/your-repo
-takopi codex
-# or
+takopi
+# or override the default engine for new threads:
 takopi claude
 ```
 
+resume lines always route to the matching engine; subcommands only override the default for new threads.
+
 send a message to the bot.
 
+start a new thread with a specific engine by prefixing your message with `/codex` or `/claude`.
+
 to continue a thread, reply to a bot message containing a resume line.
 you can also copy it to resume an interactive session in your terminal.
 
diff --git a/src/takopi/bridge.py b/src/takopi/bridge.py
index f5d3d9f..fc4d541 100644
--- a/src/takopi/bridge.py
+++ b/src/takopi/bridge.py
@@ -1,4 +1,4 @@
-"""Telegram bridge orchestration for running a single runner and streaming progress."""
+"""Telegram bridge orchestration for running runners and streaming progress."""
 
 from __future__ import annotations
 
@@ -12,8 +12,9 @@ from typing import Any
 import anyio
 
 from .markdown import TELEGRAM_MARKDOWN_LIMIT, prepare_telegram
-from .model import CompletedEvent, ResumeToken, StartedEvent, TakopiEvent
+from .model import CompletedEvent, EngineId, ResumeToken, StartedEvent, TakopiEvent
 from .render import ExecProgressRenderer, render_event_cli
+from .router import AutoRouter, RunnerUnavailableError
 from .runner import Runner
 from .telegram import BotClient
 
@@ -21,12 +22,6 @@ from .telegram import BotClient
 logger = logging.getLogger(__name__)
 
 
-def _resolve_resume(
-    runner: Runner, text: str | None, reply_text: str | None
-) -> ResumeToken | None:
-    return runner.extract_resume(text) or runner.extract_resume(reply_text)
-
-
 def _log_runner_event(evt: TakopiEvent) -> None:
     for line in render_event_cli(evt):
         logger.info("[runner] %s", line)
@@ -45,6 +40,73 @@ def _is_cancel_command(text: str) -> bool:
     return command == "/cancel" or command.startswith("/cancel@")
 
 
+def _strip_engine_command(
+    text: str, *, engine_ids: tuple[EngineId, ...]
+) -> tuple[str, EngineId | None]:
+    if not text:
+        return text, None
+
+    if not engine_ids:
+        return text, None
+
+    engine_map = {engine.lower(): engine for engine in engine_ids}
+    lines = text.splitlines()
+    idx = next((i for i, line in enumerate(lines) if line.strip()), None)
+    if idx is None:
+        return text, None
+
+    line = lines[idx].lstrip()
+    if not line.startswith("/"):
+        return text, None
+
+    parts = line.split(maxsplit=1)
+    command = parts[0][1:]
+    if "@" in command:
+        command = command.split("@", 1)[0]
+    engine = engine_map.get(command.lower())
+    if engine is None:
+        return text, None
+
+    remainder = parts[1] if len(parts) > 1 else ""
+    if remainder:
+        lines[idx] = remainder
+    else:
+        lines.pop(idx)
+    return "\n".join(lines).strip(), engine
+
+
+def _build_bot_commands(router: AutoRouter) -> list[dict[str, str]]:
+    commands: list[dict[str, str]] = [
+        {"command": "cancel", "description": "cancel run"}
+    ]
+    seen = {"cancel"}
+    for engine in router.engine_ids:
+        cmd = engine.lower()
+        if cmd in seen:
+            continue
+        commands.append({"command": cmd, "description": f"start {cmd}"})
+        seen.add(cmd)
+    return commands
+
+
+async def _set_command_menu(cfg: BridgeConfig) -> None:
+    commands = _build_bot_commands(cfg.router)
+    if not commands:
+        return
+    try:
+        ok = await cfg.bot.set_my_commands(commands)
+    except Exception as exc:
+        logger.info("[startup] command menu update failed: %s", exc)
+        return
+    if not ok:
+        logger.info("[startup] command menu update rejected")
+        return
+    logger.info(
+        "[startup] command menu updated commands=%s",
+        ", ".join(cmd["command"] for cmd in commands),
+    )
+
+
 def _strip_resume_lines(text: str, *, is_resume_line: Callable[[str], bool]) -> str:
     stripped_lines: list[str] = []
     for line in text.splitlines():
@@ -55,6 +117,34 @@ def _strip_resume_lines(text: str, *, is_resume_line: Callable[[str], bool]) ->
     return prompt or "continue"
 
 
+def _flatten_exception_group(error: BaseException) -> list[BaseException]:
+    if isinstance(error, BaseExceptionGroup):
+        flattened: list[BaseException] = []
+        for exc in error.exceptions:
+            flattened.extend(_flatten_exception_group(exc))
+        return flattened
+    return [error]
+
+
+def _format_error(error: Exception) -> str:
+    cancel_exc = anyio.get_cancelled_exc_class()
+    flattened = [
+        exc
+        for exc in _flatten_exception_group(error)
+        if not isinstance(exc, cancel_exc)
+    ]
+    if len(flattened) == 1:
+        return str(flattened[0]) or flattened[0].__class__.__name__
+    if not flattened:
+        return str(error) or error.__class__.__name__
+    messages = [str(exc) for exc in flattened if str(exc)]
+    if not messages:
+        return str(error) or error.__class__.__name__
+    if len(messages) == 1:
+        return messages[0]
+    return "\n".join(messages)
+
+
 PROGRESS_EDIT_EVERY_S = 2.0
 
 
@@ -187,7 +277,7 @@ class ProgressEdits:
 @dataclass(frozen=True)
 class BridgeConfig:
     bot: BotClient
-    runner: Runner
+    router: AutoRouter
     chat_id: int
     final_notify: bool
     startup_msg: str
@@ -376,10 +466,12 @@ async def send_result_message(
 async def handle_message(
     cfg: BridgeConfig,
     *,
+    runner: Runner,
     chat_id: int,
     user_msg_id: int,
     text: str,
     resume_token: ResumeToken | None,
+    strip_resume_line: Callable[[str], bool] | None = None,
     running_tasks: dict[int, RunningTask] | None = None,
     on_thread_known: Callable[[ResumeToken, anyio.Event], Awaitable[None]]
     | None = None,
@@ -395,9 +487,9 @@ async def handle_message(
         text,
     )
     started_at = clock()
-    runner = cfg.runner
     is_resume_line = runner.is_resume_line
-    runner_text = _strip_resume_lines(text, is_resume_line=is_resume_line)
+    resume_strip = strip_resume_line or is_resume_line
+    runner_text = _strip_resume_lines(text, is_resume_line=resume_strip)
 
     progress_renderer = ExecProgressRenderer(
         max_actions=5, resume_formatter=runner.format_resume
@@ -464,6 +556,7 @@ async def handle_message(
             )
         except Exception as e:
             error = e
+            logger.exception("[handle] runner failed")
         finally:
             if (
                 running_task is not None
@@ -481,7 +574,7 @@ async def handle_message(
 
     if error is not None:
         sync_resume_token(progress_renderer, outcome.resume)
-        err_body = str(error)
+        err_body = _format_error(error)
         final_md = progress_renderer.render_final(elapsed, err_body, status="error")
         logger.debug("[error] markdown: %s", final_md)
         await send_result_message(
@@ -681,6 +774,32 @@ async def _send_with_resume(
     await enqueue(chat_id, user_msg_id, text, resume)
 
 
+async def _send_runner_unavailable(
+    cfg: BridgeConfig,
+    *,
+    chat_id: int,
+    user_msg_id: int,
+    resume_token: ResumeToken | None,
+    runner: Runner,
+    reason: str,
+) -> None:
+    progress_renderer = ExecProgressRenderer(
+        max_actions=0, resume_formatter=runner.format_resume
+    )
+    if resume_token is not None:
+        progress_renderer.resume_token = resume_token
+    final_md = progress_renderer.render_final(0.0, f"Error:\n{reason}", status="error")
+    await _send_or_edit_markdown(
+        cfg.bot,
+        chat_id=chat_id,
+        text=final_md,
+        reply_to_message_id=user_msg_id,
+        disable_notification=False,
+        limit=TELEGRAM_MARKDOWN_LIMIT,
+        is_resume_line=runner.is_resume_line,
+    )
+
+
 async def run_main_loop(
     cfg: BridgeConfig,
     poller: Callable[[BridgeConfig], AsyncIterator[dict[str, Any]]] = poll_updates,
@@ -688,6 +807,7 @@ async def run_main_loop(
     running_tasks: dict[int, RunningTask] = {}
 
     try:
+        await _set_command_menu(cfg)
         async with anyio.create_task_group() as tg:
             scheduler_lock = anyio.Lock()
 
@@ -726,14 +846,44 @@ async def run_main_loop(
                 resume_token: ResumeToken | None,
                 on_thread_known: Callable[[ResumeToken, anyio.Event], Awaitable[None]]
                 | None = None,
+                engine_override: EngineId | None = None,
             ) -> None:
                 try:
+                    try:
+                        entry = (
+                            cfg.router.entry_for_engine(engine_override)
+                            if resume_token is None
+                            else cfg.router.entry_for(resume_token)
+                        )
+                    except RunnerUnavailableError as exc:
+                        await _send_or_edit_markdown(
+                            cfg.bot,
+                            chat_id=chat_id,
+                            text=f"Error:\n{exc}",
+                            reply_to_message_id=user_msg_id,
+                            disable_notification=False,
+                            limit=TELEGRAM_MARKDOWN_LIMIT,
+                        )
+                        return
+                    if not entry.available:
+                        reason = entry.issue or "engine unavailable"
+                        await _send_runner_unavailable(
+                            cfg,
+                            chat_id=chat_id,
+                            user_msg_id=user_msg_id,
+                            resume_token=resume_token,
+                            runner=entry.runner,
+                            reason=reason,
+                        )
+                        return
                     await handle_message(
                         cfg,
+                        runner=entry.runner,
                         chat_id=chat_id,
                         user_msg_id=user_msg_id,
                         text=text,
                         resume_token=resume_token,
+                        strip_resume_line=cfg.router.is_resume_line,
                         running_tasks=running_tasks,
                         on_thread_known=on_thread_known,
                         progress_edit_every=cfg.progress_edit_every,
@@ -799,8 +949,12 @@ async def run_main_loop(
                     tg.start_soon(_handle_cancel, cfg, msg, running_tasks)
                     continue
 
+                text, engine_override = _strip_engine_command(
+                    text, engine_ids=cfg.router.engine_ids
+                )
+
                 r = msg.get("reply_to_message") or {}
-                resume_token = _resolve_resume(cfg.runner, text, r.get("text"))
+                resume_token = cfg.router.resolve_resume(text, r.get("text"))
                 reply_id = r.get("message_id")
                 if resume_token is None and reply_id is not None:
                     running_task = running_tasks.get(int(reply_id))
@@ -824,6 +978,7 @@ async def run_main_loop(
                         text,
                         None,
                         note_thread_known,
+                        engine_override,
                     )
                 else:
                     await enqueue(msg["chat"]["id"], user_msg_id, text, resume_token)
diff --git a/src/takopi/cli.py b/src/takopi/cli.py
index 48511b7..6bc8f1b 100644
--- a/src/takopi/cli.py
+++ b/src/takopi/cli.py
@@ -1,7 +1,10 @@
 from __future__ import annotations
 
+import logging
 import os
+import shutil
 from collections.abc import Callable
+from pathlib import Path
 
 import anyio
 import typer
@@ -12,9 +15,12 @@ from .bridge import BridgeConfig, run_main_loop
 from .config import ConfigError, load_telegram_config
 from .engines import get_backend, get_engine_config, list_backends
 from .logging import setup_logging
-from .onboarding import check_setup, render_engine_choice, render_setup_guide
+from .onboarding import check_setup, render_setup_guide
+from .router import AutoRouter, RunnerEntry
 from .telegram import TelegramClient
 
+logger = logging.getLogger(__name__)
+
 
 def _print_version_and_exit() -> None:
     typer.echo(__version__)
@@ -26,10 +32,113 @@ def _version_callback(value: bool) -> None:
         _print_version_and_exit()
 
 
+def _default_engine_for_setup(override: str | None) -> str:
+    if override:
+        return override
+    try:
+        config, config_path = load_telegram_config()
+    except ConfigError:
+        return "codex"
+    value = config.get("default_engine")
+    if value is None:
+        return "codex"
+    if not isinstance(value, str) or not value.strip():
+        raise ConfigError(
+            f"Invalid `default_engine` in {config_path}; expected a non-empty string."
+        )
+    return value.strip()
+
+
+def _resolve_default_engine(
+    *,
+    override: str | None,
+    config: dict,
+    config_path: Path,
+    backends: list[EngineBackend],
+) -> str:
+    default_engine = override or config.get("default_engine") or "codex"
+    if not isinstance(default_engine, str) or not default_engine.strip():
+        raise ConfigError(
+            f"Invalid `default_engine` in {config_path}; expected a non-empty string."
+        )
+    default_engine = default_engine.strip()
+    backend_ids = {backend.id for backend in backends}
+    if default_engine not in backend_ids:
+        available = ", ".join(sorted(backend_ids))
+        raise ConfigError(
+            f"Unknown default engine {default_engine!r}. Available: {available}."
+        )
+    return default_engine
+
+
+def _build_router(
+    *,
+    config: dict,
+    config_path: Path,
+    backends: list[EngineBackend],
+    default_engine: str,
+) -> AutoRouter:
+    entries: list[RunnerEntry] = []
+    warnings: list[str] = []
+
+    for backend in backends:
+        engine_id = backend.id
+        issue: str | None = None
+        engine_cfg: dict
+        try:
+            engine_cfg = get_engine_config(config, engine_id, config_path)
+        except ConfigError as exc:
+            if engine_id == default_engine:
+                raise
+            issue = str(exc)
+            engine_cfg = {}
+
+        try:
+            runner = backend.build_runner(engine_cfg, config_path)
+        except Exception as exc:
+            if engine_id == default_engine:
+                raise
+            issue = issue or str(exc)
+            if engine_cfg:
+                try:
+                    runner = backend.build_runner({}, config_path)
+                except Exception as fallback_exc:
+                    warnings.append(f"{engine_id}: {issue or str(fallback_exc)}")
+                    continue
+            else:
+                warnings.append(f"{engine_id}: {issue}")
+                continue
+
+        cmd = backend.cli_cmd or backend.id
+        if shutil.which(cmd) is None:
+            issue = issue or f"{cmd} not found on PATH"
+
+        if issue and engine_id == default_engine:
+            raise ConfigError(f"Default engine {engine_id!r} unavailable: {issue}")
+
+        available = issue is None
+        if issue and engine_id != default_engine:
+            warnings.append(f"{engine_id}: {issue}")
+
+        entries.append(
+            RunnerEntry(
+                engine=engine_id,
+                runner=runner,
+                available=available,
+                issue=issue,
+            )
+        )
+
+    for warning in warnings:
+        logger.warning("[setup] %s", warning)
+
+    return AutoRouter(entries=entries, default_engine=default_engine)
+
+
 def _parse_bridge_config(
     *,
     final_notify: bool,
-    backend: EngineBackend,
+    default_engine_override: str | None,
 ) -> BridgeConfig:
     startup_pwd = os.getcwd()
 
@@ -52,29 +161,46 @@ def _parse_bridge_config(
         ) from None
     chat_id = chat_id_value
 
-    engine_cfg = get_engine_config(config, backend.id, config_path)
+    backends = list_backends()
+    default_engine = _resolve_default_engine(
+        override=default_engine_override,
+        config=config,
+        config_path=config_path,
+        backends=backends,
+    )
+    router = _build_router(
+        config=config,
+        config_path=config_path,
+        backends=backends,
+        default_engine=default_engine,
+    )
+    engine_list = ", ".join(router.engine_ids)
     startup_msg = (
         f"\N{OCTOPUS} **takopi is ready**\n\n"
-        f"agent: `{backend.id}`  \n"
+        f"mode: `auto-router`  \n"
+        f"default: `{router.default_engine}`  \n"
+        f"engines: `{engine_list}`  \n"
         f"working in: `{startup_pwd}`"
     )
 
     bot = TelegramClient(token)
-    runner = backend.build_runner(engine_cfg, config_path)
 
     return BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=router,
         chat_id=chat_id,
         final_notify=final_notify,
         startup_msg=startup_msg,
     )
 
 
-def _run_engine(*, engine: str, final_notify: bool, debug: bool) -> None:
+def _run_auto_router(
+    *, default_engine_override: str | None, final_notify: bool, debug: bool
+) -> None:
     setup_logging(debug=debug)
     try:
-        backend = get_backend(engine)
+        default_engine = _default_engine_for_setup(default_engine_override)
+        backend = get_backend(default_engine)
     except ConfigError as e:
         typer.echo(str(e), err=True)
         raise typer.Exit(code=1)
@@ -85,7 +211,7 @@ def _run_engine(*, engine: str, final_notify: bool, debug: bool) -> None:
     try:
         cfg = _parse_bridge_config(
             final_notify=final_notify,
-            backend=backend,
+            default_engine_override=default_engine_override,
         )
     except ConfigError as e:
         typer.echo(str(e), err=True)
@@ -96,7 +222,7 @@ def _run_engine(*, engine: str, final_notify: bool, debug: bool) -> None:
 app = typer.Typer(
     add_completion=False,
     invoke_without_command=True,
-    help="Run takopi with an explicit engine subcommand.",
+    help="Run takopi with auto-router (subcommands override the default engine).",
 )
 
 
@@ -110,11 +236,25 @@ def app_main(
         callback=_version_callback,
         is_eager=True,
     ),
+    final_notify: bool = typer.Option(
+        True,
+        "--final-notify/--no-final-notify",
+        help="Send the final response as a new message (not an edit).",
+    ),
+    debug: bool = typer.Option(
+        False,
+        "--debug/--no-debug",
+        help="Log engine JSONL, Telegram requests, and rendered messages.",
+    ),
 ) -> None:
     """Takopi CLI."""
     if ctx.invoked_subcommand is None:
-        render_engine_choice(list_backends())
-        raise typer.Exit(code=1)
+        _run_auto_router(
+            default_engine_override=None,
+            final_notify=final_notify,
+            debug=debug,
+        )
+        raise typer.Exit()
 
 
 def make_engine_cmd(engine_id: str) -> Callable[..., None]:
@@ -130,7 +270,11 @@ def make_engine_cmd(engine_id: str) -> Callable[..., None]:
             help="Log engine JSONL, Telegram requests, and rendered messages.",
         ),
     ) -> None:
-        _run_engine(engine=engine_id, final_notify=final_notify, debug=debug)
+        _run_auto_router(
+            default_engine_override=engine_id,
+            final_notify=final_notify,
+            debug=debug,
+        )
 
     _cmd.__name__ = f"run_{engine_id}"
     return _cmd
diff --git a/src/takopi/router.py b/src/takopi/router.py
new file mode 100644
index 0000000..dc8a67b
--- /dev/null
+++ b/src/takopi/router.py
@@ -0,0 +1,99 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Iterable
+
+from .model import EngineId, ResumeToken
+from .runner import Runner
+
+
+class RunnerUnavailableError(RuntimeError):
+    def __init__(self, engine: EngineId, issue: str | None = None) -> None:
+        message = f"engine {engine!r} is unavailable"
+        if issue:
+            message = f"{message}: {issue}"
+        super().__init__(message)
+        self.engine = engine
+        self.issue = issue
+
+
+@dataclass(frozen=True, slots=True)
+class RunnerEntry:
+    engine: EngineId
+    runner: Runner
+    available: bool = True
+    issue: str | None = None
+
+
+class AutoRouter:
+    def __init__(
+        self, entries: Iterable[RunnerEntry], default_engine: EngineId
+    ) -> None:
+        self._entries = tuple(entries)
+        if not self._entries:
+            raise ValueError("AutoRouter requires at least one runner.")
+        by_engine: dict[EngineId, RunnerEntry] = {}
+        for entry in self._entries:
+            if entry.engine in by_engine:
+                raise ValueError(f"duplicate runner engine: {entry.engine}")
+            by_engine[entry.engine] = entry
+        if default_engine not in by_engine:
+            raise ValueError(f"default engine {default_engine!r} is not configured")
+        self._by_engine = by_engine
+        self.default_engine = default_engine
+
+    @property
+    def entries(self) -> tuple[RunnerEntry, ...]:
+        return self._entries
+
+    @property
+    def engine_ids(self) -> tuple[EngineId, ...]:
+        return tuple(entry.engine for entry in self._entries)
+
+    @property
+    def default_entry(self) -> RunnerEntry:
+        return self._by_engine[self.default_engine]
+
+    def entry_for_engine(self, engine: EngineId | None) -> RunnerEntry:
+        engine = self.default_engine if engine is None else engine
+        entry = self._by_engine.get(engine)
+        if entry is None:
+            raise RunnerUnavailableError(engine, "engine not configured")
+        return entry
+
+    def entry_for(self, resume: ResumeToken | None) -> RunnerEntry:
+        if resume is None:
+            return self.entry_for_engine(None)
+        return self.entry_for_engine(resume.engine)
+
+    def runner_for(self, resume: ResumeToken | None) -> Runner:
+        entry = self.entry_for(resume)
+        if not entry.available:
+            raise RunnerUnavailableError(entry.engine, entry.issue)
+        return entry.runner
+
+    def format_resume(self, token: ResumeToken) -> str:
+        entry = self.entry_for(token)
+        return entry.runner.format_resume(token)
+
+    def extract_resume(self, text: str | None) -> ResumeToken | None:
+        if not text:
+            return None
+        for entry in self._entries:
+            token = entry.runner.extract_resume(text)
+            if token is not None:
+                return token
+        return None
+
+    def resolve_resume(
+        self, text: str | None, reply_text: str | None
+    ) -> ResumeToken | None:
+        token = self.extract_resume(text)
+        if token is not None:
+            return token
+        if reply_text is None:
+            return None
+        return self.extract_resume(reply_text)
+
+    def is_resume_line(self, line: str) -> bool:
+        return any(entry.runner.is_resume_line(line) for entry in self._entries)
diff --git a/src/takopi/runner.py b/src/takopi/runner.py
index 0691e02..ed8a8cd 100644
--- a/src/takopi/runner.py
+++ b/src/takopi/runner.py
@@ -283,14 +283,22 @@ class JsonlSubprocessRunner(BaseRunner):
         found_session: ResumeToken | None,
     ) -> tuple[ResumeToken | None, bool]:
         if event.engine != self.engine:
-            raise RuntimeError(f"{self.tag()} emitted session token for wrong engine")
+            raise RuntimeError(
+                f"{self.tag()} emitted session token for engine {event.engine!r}"
+            )
         if expected_session is not None and event.resume != expected_session:
-            message = f"{self.tag()} emitted a different session id than expected"
+            message = (
+                f"{self.tag()} emitted session id {event.resume.value} "
+                f"but expected {expected_session.value}"
+            )
             raise RuntimeError(message)
         if found_session is None:
             return event.resume, True
         if event.resume != found_session:
-            message = f"{self.tag()} emitted a different session id than expected"
+            message = (
+                f"{self.tag()} emitted session id {event.resume.value} "
+                f"but expected {found_session.value}"
+            )
             raise RuntimeError(message)
         return found_session, False
 
diff --git a/src/takopi/runners/codex.py b/src/takopi/runners/codex.py
index 073aafd..bb37719 100644
--- a/src/takopi/runners/codex.py
+++ b/src/takopi/runners/codex.py
@@ -472,12 +472,18 @@ class CodexRunner(ResumeTokenMixin, JsonlSubprocessRunner):
                 f"codex emitted session token for engine {event.engine!r}"
             )
         if expected_session is not None and event.resume != expected_session:
-            message = "codex emitted a different session id than expected"
+            message = (
+                f"codex emitted session id {event.resume.value} "
+                f"but expected {expected_session.value}"
+            )
             raise RuntimeError(message)
         if found_session is None:
             return event.resume, True
         if event.resume != found_session:
-            message = "codex emitted a different session id than expected"
+            message = (
+                f"codex emitted session id {event.resume.value} "
+                f"but expected {found_session.value}"
+            )
             raise RuntimeError(message)
         return found_session, False
 
diff --git a/src/takopi/telegram.py b/src/takopi/telegram.py
index 45c274e..c399275 100644
--- a/src/takopi/telegram.py
+++ b/src/takopi/telegram.py
@@ -42,6 +42,14 @@ class BotClient(Protocol):
 
     async def delete_message(self, chat_id: int, message_id: int) -> bool: ...
 
+    async def set_my_commands(
+        self,
+        commands: list[dict[str, Any]],
+        *,
+        scope: dict[str, Any] | None = None,
+        language_code: str | None = None,
+    ) -> bool: ...
+
 
 class TelegramClient:
     def __init__(
@@ -184,3 +192,18 @@ class TelegramClient:
             },
         )
         return bool(res)
+
+    async def set_my_commands(
+        self,
+        commands: list[dict[str, Any]],
+        *,
+        scope: dict[str, Any] | None = None,
+        language_code: str | None = None,
+    ) -> bool:
+        params: dict[str, Any] = {"commands": commands}
+        if scope is not None:
+            params["scope"] = scope
+        if language_code is not None:
+            params["language_code"] = language_code
+        res = await self._post("setMyCommands", params)
+        return bool(res)
diff --git a/tests/test_auto_router.py b/tests/test_auto_router.py
new file mode 100644
index 0000000..0828ebb
--- /dev/null
+++ b/tests/test_auto_router.py
@@ -0,0 +1,48 @@
+from takopi.model import ResumeToken
+from takopi.router import AutoRouter, RunnerEntry
+from takopi.runners.claude import ClaudeRunner
+from takopi.runners.codex import CodexRunner
+
+
+def _router() -> tuple[AutoRouter, ClaudeRunner, CodexRunner]:
+    codex = CodexRunner(codex_cmd="codex", extra_args=[])
+    claude = ClaudeRunner(claude_cmd="claude")
+    router = AutoRouter(
+        entries=[
+            RunnerEntry(engine=claude.engine, runner=claude),
+            RunnerEntry(engine=codex.engine, runner=codex),
+        ],
+        default_engine=codex.engine,
+    )
+    return router, claude, codex
+
+
+def test_router_resolves_text_before_reply() -> None:
+    router, _claude, _codex = _router()
+    token = router.resolve_resume("`codex resume abc`", "`claude --resume def`")
+
+    assert token == ResumeToken(engine="codex", value="abc")
+
+
+def test_router_poll_order_selects_first_matching_runner() -> None:
+    router, _claude, _codex = _router()
+    text = "`codex resume abc`\n`claude --resume def`"
+
+    token = router.resolve_resume(text, None)
+
+    assert token == ResumeToken(engine="claude", value="def")
+
+
+def test_router_resolves_reply_text_when_text_missing() -> None:
+    router, _claude, _codex = _router()
+
+    token = router.resolve_resume(None, "`codex resume xyz`")
+
+    assert token == ResumeToken(engine="codex", value="xyz")
+
+
+def test_router_is_resume_line_union() -> None:
+    router, _claude, _codex = _router()
+
+    assert router.is_resume_line("`codex resume abc`")
+    assert router.is_resume_line("claude --resume def")
diff --git a/tests/test_exec_bridge.py b/tests/test_exec_bridge.py
index 4546690..381e7af 100644
--- a/tests/test_exec_bridge.py
+++ b/tests/test_exec_bridge.py
@@ -3,9 +3,10 @@ import uuid
 import anyio
 import pytest
 
-from takopi import engines
+from takopi.bridge import _build_bot_commands, _strip_engine_command
 from takopi.markdown import prepare_telegram, truncate_for_telegram
 from takopi.model import EngineId, ResumeToken, TakopiEvent
+from takopi.router import AutoRouter, RunnerEntry
 from takopi.runners.codex import CodexRunner
 from takopi.runners.mock import Advance, Emit, Raise, Return, ScriptRunner, Sleep, Wait
 from tests.factories import action_completed, action_started
@@ -13,6 +14,13 @@ from tests.factories import action_completed, action_started
 CODEX_ENGINE = EngineId("codex")
 
 
+def _make_router(runner) -> AutoRouter:
+    return AutoRouter(
+        entries=[RunnerEntry(engine=runner.engine, runner=runner)],
+        default_engine=runner.engine,
+    )
+
+
 def _patch_config(monkeypatch, config):
     from pathlib import Path
 
@@ -33,7 +41,7 @@ def test_parse_bridge_config_rejects_empty_token(monkeypatch) -> None:
     with pytest.raises(cli.ConfigError, match="bot_token"):
         cli._parse_bridge_config(
             final_notify=True,
-            backend=engines.get_backend("codex"),
+            default_engine_override=None,
         )
 
 
@@ -45,7 +53,7 @@ def test_parse_bridge_config_rejects_string_chat_id(monkeypatch) -> None:
     with pytest.raises(cli.ConfigError, match="chat_id"):
         cli._parse_bridge_config(
             final_notify=True,
-            backend=engines.get_backend("codex"),
+            default_engine_override=None,
         )
 
 
@@ -114,6 +122,55 @@ def test_truncate_for_telegram_keeps_last_non_empty_line() -> None:
     assert out.rstrip().endswith("last line")
 
 
+def test_strip_engine_command_inline() -> None:
+    text, engine = _strip_engine_command(
+        "/claude do it", engine_ids=("codex", "claude")
+    )
+    assert engine == "claude"
+    assert text == "do it"
+
+
+def test_strip_engine_command_newline() -> None:
+    text, engine = _strip_engine_command(
+        "/codex\nhello", engine_ids=("codex", "claude")
+    )
+    assert engine == "codex"
+    assert text == "hello"
+
+
+def test_strip_engine_command_ignores_unknown() -> None:
+    text, engine = _strip_engine_command("/unknown hi", engine_ids=("codex", "claude"))
+    assert engine is None
+    assert text == "/unknown hi"
+
+
+def test_strip_engine_command_bot_suffix() -> None:
+    text, engine = _strip_engine_command(
+        "/claude@bunny_agent_bot hi", engine_ids=("claude",)
+    )
+    assert engine == "claude"
+    assert text == "hi"
+
+
+def test_strip_engine_command_only_first_non_empty_line() -> None:
+    text, engine = _strip_engine_command(
+        "hello\n/claude hi", engine_ids=("codex", "claude")
+    )
+    assert engine is None
+    assert text == "hello\n/claude hi"
+
+
+def test_build_bot_commands_includes_cancel_and_engine() -> None:
+    runner = ScriptRunner(
+        [Return(answer="ok")], engine=CODEX_ENGINE, resume_value="sid"
+    )
+    router = _make_router(runner)
+    commands = _build_bot_commands(router)
+
+    assert {"command": "cancel", "description": "cancel run"} in commands
+    assert any(cmd["command"] == "codex" for cmd in commands)
+
+
 def test_prepare_telegram_drops_entities_on_truncate() -> None:
     md = ("**bold** " * 200).strip()
 
@@ -126,6 +183,7 @@ def test_prepare_telegram_drops_entities_on_truncate() -> None:
 class _FakeBot:
     def __init__(self) -> None:
         self._next_id = 1
+        self.command_calls: list[dict] = []
         self.send_calls: list[dict] = []
         self.edit_calls: list[dict] = []
         self.delete_calls: list[dict] = []
@@ -176,6 +234,22 @@ class _FakeBot:
         self.delete_calls.append({"chat_id": chat_id, "message_id": message_id})
         return True
 
+    async def set_my_commands(
+        self,
+        commands: list[dict],
+        *,
+        scope: dict | None = None,
+        language_code: str | None = None,
+    ) -> bool:
+        self.command_calls.append(
+            {
+                "commands": commands,
+                "scope": scope,
+                "language_code": language_code,
+            }
+        )
+        return True
+
     async def get_updates(
         self,
         offset: int | None,
@@ -238,7 +312,7 @@ async def test_final_notify_sends_loud_final_message() -> None:
     runner = _return_runner(answer="ok")
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -246,6 +320,7 @@ async def test_final_notify_sends_loud_final_message() -> None:
 
     await handle_message(
         cfg,
+        runner=runner,
         chat_id=123,
         user_msg_id=10,
         text="hi",
@@ -265,7 +340,7 @@ async def test_handle_message_strips_resume_line_from_prompt() -> None:
     runner = ScriptRunner([Return(answer="ok")], engine=CODEX_ENGINE)
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -275,6 +350,7 @@ async def test_handle_message_strips_resume_line_from_prompt() -> None:
 
     await handle_message(
         cfg,
+        runner=runner,
         chat_id=123,
         user_msg_id=10,
         text=text,
@@ -295,7 +371,7 @@ async def test_new_final_message_forces_notification_when_too_long_to_edit() ->
     runner = _return_runner(answer="x" * 10_000)
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=False,
         startup_msg="",
@@ -303,6 +379,7 @@ async def test_new_final_message_forces_notification_when_too_long_to_edit() ->
 
     await handle_message(
         cfg,
+        runner=runner,
         chat_id=123,
         user_msg_id=10,
         text="hi",
@@ -336,7 +413,7 @@ async def test_progress_edits_are_rate_limited() -> None:
     )
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -344,6 +421,7 @@ async def test_progress_edits_are_rate_limited() -> None:
 
     await handle_message(
         cfg,
+        runner=runner,
         chat_id=123,
         user_msg_id=10,
         text="hi",
@@ -380,7 +458,7 @@ async def test_progress_edits_do_not_sleep_again_without_new_events() -> None:
     )
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -389,6 +467,7 @@ async def test_progress_edits_do_not_sleep_again_without_new_events() -> None:
     async def run_handle_message() -> None:
         await handle_message(
             cfg,
+            runner=runner,
             chat_id=123,
             user_msg_id=10,
             text="hi",
@@ -455,7 +534,7 @@ async def test_bridge_flow_sends_progress_edits_and_final_resume() -> None:
     )
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -463,6 +542,7 @@ async def test_bridge_flow_sends_progress_edits_and_final_resume() -> None:
 
     await handle_message(
         cfg,
+        runner=runner,
         chat_id=123,
         user_msg_id=42,
         text="do it",
@@ -488,7 +568,7 @@ async def test_handle_cancel_without_reply_prompts_user() -> None:
     runner = _return_runner(answer="ok")
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -510,7 +590,7 @@ async def test_handle_cancel_with_no_progress_message_says_nothing_running() ->
     runner = _return_runner(answer="ok")
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -536,7 +616,7 @@ async def test_handle_cancel_with_finished_task_says_nothing_running() -> None:
     runner = _return_runner(answer="ok")
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -563,7 +643,7 @@ async def test_handle_cancel_cancels_running_task() -> None:
     runner = _return_runner(answer="ok")
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -593,7 +673,7 @@ async def test_handle_cancel_only_cancels_matching_progress_message() -> None:
     runner = _return_runner(answer="ok")
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -638,7 +718,7 @@ async def test_handle_message_cancelled_renders_cancelled_state() -> None:
     )
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -648,6 +728,7 @@ async def test_handle_message_cancelled_renders_cancelled_state() -> None:
     async def run_handle_message() -> None:
         await handle_message(
             cfg,
+            runner=runner,
             chat_id=123,
             user_msg_id=10,
             text="do something",
@@ -687,7 +768,7 @@ async def test_handle_message_error_preserves_resume_token() -> None:
     )
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",
@@ -695,6 +776,7 @@ async def test_handle_message_error_preserves_resume_token() -> None:
 
     await handle_message(
         cfg,
+        runner=runner,
         chat_id=123,
         user_msg_id=10,
         text="do something",
@@ -817,7 +899,7 @@ async def test_run_main_loop_routes_reply_to_running_resume() -> None:
     )
     cfg = BridgeConfig(
         bot=bot,
-        runner=runner,
+        router=_make_router(runner),
         chat_id=123,
         final_notify=True,
         startup_msg="",