diff --git a/acp_adapter/session.py b/acp_adapter/session.py
index 8590a62e4..0f5b2428e 100644
--- a/acp_adapter/session.py
+++ b/acp_adapter/session.py
@@ -194,6 +194,8 @@ class SessionManager:
                     "api_mode": runtime.get("api_mode"),
                     "base_url": runtime.get("base_url"),
                     "api_key": runtime.get("api_key"),
+                    "command": runtime.get("command"),
+                    "args": list(runtime.get("args") or []),
                 }
             )
         except Exception:
diff --git a/agent/auxiliary_client.py b/agent/auxiliary_client.py
index 94be9d6fe..22b967fd2 100644
--- a/agent/auxiliary_client.py
+++ b/agent/auxiliary_client.py
@@ -480,11 +480,11 @@ def _read_codex_access_token() -> Optional[str]:
 def _resolve_api_key_provider() -> Tuple[Optional[OpenAI], Optional[str]]:
     """Try each API-key provider in PROVIDER_REGISTRY order.
 
-    Returns (client, model) for the first provider whose env var is set,
-    or (None, None) if none are configured.
+    Returns (client, model) for the first provider with usable runtime
+    credentials, or (None, None) if none are configured.
     """
     try:
-        from hermes_cli.auth import PROVIDER_REGISTRY
+        from hermes_cli.auth import PROVIDER_REGISTRY, resolve_api_key_provider_credentials
     except ImportError:
         logger.debug("Could not import PROVIDER_REGISTRY for API-key fallback")
         return None, None
@@ -492,34 +492,24 @@ def _resolve_api_key_provider() -> Tuple[Optional[OpenAI], Optional[str]]:
     for provider_id, pconfig in PROVIDER_REGISTRY.items():
         if pconfig.auth_type != "api_key":
             continue
-        # Check if any of the provider's env vars are set
-        api_key = ""
-        for env_var in pconfig.api_key_env_vars:
-            val = os.getenv(env_var, "").strip()
-            if val:
-                api_key = val
-                break
-        if not api_key:
-            continue
         if provider_id == "anthropic":
             return _try_anthropic()
 
-        # Resolve base URL (with optional env-var override)
-        # Kimi Code keys (sk-kimi-) need api.kimi.com/coding/v1
-        env_url = ""
-        if pconfig.base_url_env_var:
-            env_url = os.getenv(pconfig.base_url_env_var, "").strip()
-        if env_url:
-            base_url = env_url.rstrip("/")
-        elif provider_id == "kimi-coding" and api_key.startswith("sk-kimi-"):
-            base_url = "https://api.kimi.com/coding/v1"
-        else:
-            base_url = pconfig.inference_base_url
+        creds = resolve_api_key_provider_credentials(provider_id)
+        api_key = str(creds.get("api_key", "")).strip()
+        if not api_key:
+            continue
+
+        base_url = str(creds.get("base_url", "")).strip().rstrip("/") or pconfig.inference_base_url
         model = _API_KEY_PROVIDER_AUX_MODELS.get(provider_id, "default")
         logger.debug("Auxiliary text client: %s (%s)", pconfig.name, model)
         extra = {}
         if "api.kimi.com" in base_url.lower():
             extra["default_headers"] = {"User-Agent": "KimiCLI/1.0"}
+        elif "api.githubcopilot.com" in base_url.lower():
+            from hermes_cli.models import copilot_default_headers
+
+            extra["default_headers"] = copilot_default_headers()
         return OpenAI(api_key=api_key, base_url=base_url, **extra), model
 
     return None, None
@@ -744,6 +734,10 @@ def _to_async_client(sync_client, model: str):
     base_lower = str(sync_client.base_url).lower()
     if "openrouter" in base_lower:
         async_kwargs["default_headers"] = dict(_OR_HEADERS)
+    elif "api.githubcopilot.com" in base_lower:
+        from hermes_cli.models import copilot_default_headers
+
+        async_kwargs["default_headers"] = copilot_default_headers()
     elif "api.kimi.com" in base_lower:
         async_kwargs["default_headers"] = {"User-Agent": "KimiCLI/1.0"}
     return AsyncOpenAI(**async_kwargs), model
@@ -885,7 +879,7 @@ def resolve_provider_client(
 
     # ── API-key providers from PROVIDER_REGISTRY ─────────────────────
     try:
-        from hermes_cli.auth import PROVIDER_REGISTRY, _resolve_kimi_base_url
+        from hermes_cli.auth import PROVIDER_REGISTRY, resolve_api_key_provider_credentials
     except ImportError:
         logger.debug("hermes_cli.auth not available for provider %s", provider)
         return None, None
@@ -904,26 +898,18 @@ def resolve_provider_client(
             final_model = model or default_model
             return (_to_async_client(client, final_model) if async_mode else (client, final_model))
 
-        # Find the first configured API key
-        api_key = ""
-        for env_var in pconfig.api_key_env_vars:
-            api_key = os.getenv(env_var, "").strip()
-            if api_key:
-                break
+        creds = resolve_api_key_provider_credentials(provider)
+        api_key = str(creds.get("api_key", "")).strip()
         if not api_key:
+            tried_sources = list(pconfig.api_key_env_vars)
+            if provider == "copilot":
+                tried_sources.append("gh auth token")
             logger.warning("resolve_provider_client: provider %s has no API "
                            "key configured (tried: %s)",
-                           provider, ", ".join(pconfig.api_key_env_vars))
+                           provider, ", ".join(tried_sources))
             return None, None
 
-        # Resolve base URL (env override → provider-specific logic → default)
-        base_url_override = os.getenv(pconfig.base_url_env_var, "").strip() if pconfig.base_url_env_var else ""
-        if provider == "kimi-coding":
-            base_url = _resolve_kimi_base_url(api_key, pconfig.inference_base_url, base_url_override)
-        elif base_url_override:
-            base_url = base_url_override
-        else:
-            base_url = pconfig.inference_base_url
+        base_url = str(creds.get("base_url", "")).strip().rstrip("/") or pconfig.inference_base_url
 
         default_model = _API_KEY_PROVIDER_AUX_MODELS.get(provider, "")
         final_model = model or default_model
@@ -932,6 +918,10 @@ def resolve_provider_client(
         headers = {}
         if "api.kimi.com" in base_url.lower():
             headers["User-Agent"] = "KimiCLI/1.0"
+        elif "api.githubcopilot.com" in base_url.lower():
+            from hermes_cli.models import copilot_default_headers
+
+            headers.update(copilot_default_headers())
 
         client = OpenAI(api_key=api_key, base_url=base_url,
                         **({"default_headers": headers} if headers else {}))
diff --git a/agent/copilot_acp_client.py b/agent/copilot_acp_client.py
new file mode 100644
index 000000000..7b8f45d9c
--- /dev/null
+++ b/agent/copilot_acp_client.py
@@ -0,0 +1,447 @@
+"""OpenAI-compatible shim that forwards Hermes requests to `copilot --acp`.
+
+This adapter lets Hermes treat the GitHub Copilot ACP server as a chat-style
+backend. Each request starts a short-lived ACP session, sends the formatted
+conversation as a single prompt, collects text chunks, and converts the result
+back into the minimal shape Hermes expects from an OpenAI client.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import queue
+import shlex
+import subprocess
+import threading
+import time
+from collections import deque
+from pathlib import Path
+from types import SimpleNamespace
+from typing import Any
+
+ACP_MARKER_BASE_URL = "acp://copilot"
+_DEFAULT_TIMEOUT_SECONDS = 900.0
+
+
+def _resolve_command() -> str:
+    return (
+        os.getenv("HERMES_COPILOT_ACP_COMMAND", "").strip()
+        or os.getenv("COPILOT_CLI_PATH", "").strip()
+        or "copilot"
+    )
+
+
+def _resolve_args() -> list[str]:
+    raw = os.getenv("HERMES_COPILOT_ACP_ARGS", "").strip()
+    if not raw:
+        return ["--acp", "--stdio"]
+    return shlex.split(raw)
+
+
+def _jsonrpc_error(message_id: Any, code: int, message: str) -> dict[str, Any]:
+    return {
+        "jsonrpc": "2.0",
+        "id": message_id,
+        "error": {
+            "code": code,
+            "message": message,
+        },
+    }
+
+
+def _format_messages_as_prompt(messages: list[dict[str, Any]], model: str | None = None) -> str:
+    sections: list[str] = [
+        "You are being used as the active ACP agent backend for Hermes.",
+        "Use your own ACP capabilities and respond directly in natural language.",
+        "Do not emit OpenAI tool-call JSON.",
+    ]
+    if model:
+        sections.append(f"Hermes requested model hint: {model}")
+
+    transcript: list[str] = []
+    for message in messages:
+        if not isinstance(message, dict):
+            continue
+        role = str(message.get("role") or "unknown").strip().lower()
+        if role == "tool":
+            role = "tool"
+        elif role not in {"system", "user", "assistant"}:
+            role = "context"
+
+        content = message.get("content")
+        rendered = _render_message_content(content)
+        if not rendered:
+            continue
+
+        label = {
+            "system": "System",
+            "user": "User",
+            "assistant": "Assistant",
+            "tool": "Tool",
+            "context": "Context",
+        }.get(role, role.title())
+        transcript.append(f"{label}:\n{rendered}")
+
+    if transcript:
+        sections.append("Conversation transcript:\n\n" + "\n\n".join(transcript))
+
+    sections.append("Continue the conversation from the latest user request.")
+    return "\n\n".join(section.strip() for section in sections if section and section.strip())
+
+
+def _render_message_content(content: Any) -> str:
+    if content is None:
+        return ""
+    if isinstance(content, str):
+        return content.strip()
+    if isinstance(content, dict):
+        if "text" in content:
+            return str(content.get("text") or "").strip()
+        if "content" in content and isinstance(content.get("content"), str):
+            return str(content.get("content") or "").strip()
+        return json.dumps(content, ensure_ascii=True)
+    if isinstance(content, list):
+        parts: list[str] = []
+        for item in content:
+            if isinstance(item, str):
+                parts.append(item)
+            elif isinstance(item, dict):
+                text = item.get("text")
+                if isinstance(text, str) and text.strip():
+                    parts.append(text.strip())
+        return "\n".join(parts).strip()
+    return str(content).strip()
+
+
+def _ensure_path_within_cwd(path_text: str, cwd: str) -> Path:
+    candidate = Path(path_text)
+    if not candidate.is_absolute():
+        raise PermissionError("ACP file-system paths must be absolute.")
+    resolved = candidate.resolve()
+    root = Path(cwd).resolve()
+    try:
+        resolved.relative_to(root)
+    except ValueError as exc:
+        raise PermissionError(f"Path '{resolved}' is outside the session cwd '{root}'.") from exc
+    return resolved
+
+
+class _ACPChatCompletions:
+    def __init__(self, client: "CopilotACPClient"):
+        self._client = client
+
+    def create(self, **kwargs: Any) -> Any:
+        return self._client._create_chat_completion(**kwargs)
+
+
+class _ACPChatNamespace:
+    def __init__(self, client: "CopilotACPClient"):
+        self.completions = _ACPChatCompletions(client)
+
+
+class CopilotACPClient:
+    """Minimal OpenAI-client-compatible facade for Copilot ACP."""
+
+    def __init__(
+        self,
+        *,
+        api_key: str | None = None,
+        base_url: str | None = None,
+        default_headers: dict[str, str] | None = None,
+        acp_command: str | None = None,
+        acp_args: list[str] | None = None,
+        acp_cwd: str | None = None,
+        command: str | None = None,
+        args: list[str] | None = None,
+        **_: Any,
+    ):
+        self.api_key = api_key or "copilot-acp"
+        self.base_url = base_url or ACP_MARKER_BASE_URL
+        self._default_headers = dict(default_headers or {})
+        self._acp_command = acp_command or command or _resolve_command()
+        self._acp_args = list(acp_args or args or _resolve_args())
+        self._acp_cwd = str(Path(acp_cwd or os.getcwd()).resolve())
+        self.chat = _ACPChatNamespace(self)
+        self.is_closed = False
+        self._active_process: subprocess.Popen[str] | None = None
+        self._active_process_lock = threading.Lock()
+
+    def close(self) -> None:
+        proc: subprocess.Popen[str] | None
+        with self._active_process_lock:
+            proc = self._active_process
+            self._active_process = None
+        self.is_closed = True
+        if proc is None:
+            return
+        try:
+            proc.terminate()
+            proc.wait(timeout=2)
+        except Exception:
+            try:
+                proc.kill()
+            except Exception:
+                pass
+
+    def _create_chat_completion(
+        self,
+        *,
+        model: str | None = None,
+        messages: list[dict[str, Any]] | None = None,
+        timeout: float | None = None,
+        **_: Any,
+    ) -> Any:
+        prompt_text = _format_messages_as_prompt(messages or [], model=model)
+        response_text, reasoning_text = self._run_prompt(
+            prompt_text,
+            timeout_seconds=float(timeout or _DEFAULT_TIMEOUT_SECONDS),
+        )
+
+        usage = SimpleNamespace(
+            prompt_tokens=0,
+            completion_tokens=0,
+            total_tokens=0,
+            prompt_tokens_details=SimpleNamespace(cached_tokens=0),
+        )
+        assistant_message = SimpleNamespace(
+            content=response_text,
+            tool_calls=[],
+            reasoning=reasoning_text or None,
+            reasoning_content=reasoning_text or None,
+            reasoning_details=None,
+        )
+        choice = SimpleNamespace(message=assistant_message, finish_reason="stop")
+        return SimpleNamespace(
+            choices=[choice],
+            usage=usage,
+            model=model or "copilot-acp",
+        )
+
+    def _run_prompt(self, prompt_text: str, *, timeout_seconds: float) -> tuple[str, str]:
+        try:
+            proc = subprocess.Popen(
+                [self._acp_command] + self._acp_args,
+                stdin=subprocess.PIPE,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                text=True,
+                bufsize=1,
+                cwd=self._acp_cwd,
+            )
+        except FileNotFoundError as exc:
+            raise RuntimeError(
+                f"Could not start Copilot ACP command '{self._acp_command}'. "
+                "Install GitHub Copilot CLI or set HERMES_COPILOT_ACP_COMMAND/COPILOT_CLI_PATH."
+            ) from exc
+
+        if proc.stdin is None or proc.stdout is None:
+            proc.kill()
+            raise RuntimeError("Copilot ACP process did not expose stdin/stdout pipes.")
+
+        self.is_closed = False
+        with self._active_process_lock:
+            self._active_process = proc
+
+        inbox: queue.Queue[dict[str, Any]] = queue.Queue()
+        stderr_tail: deque[str] = deque(maxlen=40)
+
+        def _stdout_reader() -> None:
+            for line in proc.stdout:
+                try:
+                    inbox.put(json.loads(line))
+                except Exception:
+                    inbox.put({"raw": line.rstrip("\n")})
+
+        def _stderr_reader() -> None:
+            if proc.stderr is None:
+                return
+            for line in proc.stderr:
+                stderr_tail.append(line.rstrip("\n"))
+
+        out_thread = threading.Thread(target=_stdout_reader, daemon=True)
+        err_thread = threading.Thread(target=_stderr_reader, daemon=True)
+        out_thread.start()
+        err_thread.start()
+
+        next_id = 0
+
+        def _request(method: str, params: dict[str, Any], *, text_parts: list[str] | None = None, reasoning_parts: list[str] | None = None) -> Any:
+            nonlocal next_id
+            next_id += 1
+            request_id = next_id
+            payload = {
+                "jsonrpc": "2.0",
+                "id": request_id,
+                "method": method,
+                "params": params,
+            }
+            proc.stdin.write(json.dumps(payload) + "\n")
+            proc.stdin.flush()
+
+            deadline = time.time() + timeout_seconds
+            while time.time() < deadline:
+                if proc.poll() is not None:
+                    break
+                try:
+                    msg = inbox.get(timeout=0.1)
+                except queue.Empty:
+                    continue
+
+                if self._handle_server_message(
+                    msg,
+                    process=proc,
+                    cwd=self._acp_cwd,
+                    text_parts=text_parts,
+                    reasoning_parts=reasoning_parts,
+                ):
+                    continue
+
+                if msg.get("id") != request_id:
+                    continue
+                if "error" in msg:
+                    err = msg.get("error") or {}
+                    raise RuntimeError(
+                        f"Copilot ACP {method} failed: {err.get('message') or err}"
+                    )
+                return msg.get("result")
+
+            stderr_text = "\n".join(stderr_tail).strip()
+            if proc.poll() is not None and stderr_text:
+                raise RuntimeError(f"Copilot ACP process exited early: {stderr_text}")
+            raise TimeoutError(f"Timed out waiting for Copilot ACP response to {method}.")
+
+        try:
+            _request(
+                "initialize",
+                {
+                    "protocolVersion": 1,
+                    "clientCapabilities": {
+                        "fs": {
+                            "readTextFile": True,
+                            "writeTextFile": True,
+                        }
+                    },
+                    "clientInfo": {
+                        "name": "hermes-agent",
+                        "title": "Hermes Agent",
+                        "version": "0.0.0",
+                    },
+                },
+            )
+            session = _request(
+                "session/new",
+                {
+                    "cwd": self._acp_cwd,
+                    "mcpServers": [],
+                },
+            ) or {}
+            session_id = str(session.get("sessionId") or "").strip()
+            if not session_id:
+                raise RuntimeError("Copilot ACP did not return a sessionId.")
+
+            text_parts: list[str] = []
+            reasoning_parts: list[str] = []
+            _request(
+                "session/prompt",
+                {
+                    "sessionId": session_id,
+                    "prompt": [
+                        {
+                            "type": "text",
+                            "text": prompt_text,
+                        }
+                    ],
+                },
+                text_parts=text_parts,
+                reasoning_parts=reasoning_parts,
+            )
+            return "".join(text_parts).strip(), "".join(reasoning_parts).strip()
+        finally:
+            self.close()
+
+    def _handle_server_message(
+        self,
+        msg: dict[str, Any],
+        *,
+        process: subprocess.Popen[str],
+        cwd: str,
+        text_parts: list[str] | None,
+        reasoning_parts: list[str] | None,
+    ) -> bool:
+        method = msg.get("method")
+        if not isinstance(method, str):
+            return False
+
+        if method == "session/update":
+            params = msg.get("params") or {}
+            update = params.get("update") or {}
+            kind = str(update.get("sessionUpdate") or "").strip()
+            content = update.get("content") or {}
+            chunk_text = ""
+            if isinstance(content, dict):
+                chunk_text = str(content.get("text") or "").strip()
+            if kind == "agent_message_chunk" and chunk_text and text_parts is not None:
+                text_parts.append(chunk_text)
+            elif kind == "agent_thought_chunk" and chunk_text and reasoning_parts is not None:
+                reasoning_parts.append(chunk_text)
+            return True
+
+        if process.stdin is None:
+            return True
+
+        message_id = msg.get("id")
+        params = msg.get("params") or {}
+
+        if method == "session/request_permission":
+            response = {
+                "jsonrpc": "2.0",
+                "id": message_id,
+                "result": {
+                    "outcome": {
+                        "outcome": "allow_once",
+                    }
+                },
+            }
+        elif method == "fs/read_text_file":
+            try:
+                path = _ensure_path_within_cwd(str(params.get("path") or ""), cwd)
+                content = path.read_text() if path.exists() else ""
+                line = params.get("line")
+                limit = params.get("limit")
+                if isinstance(line, int) and line > 1:
+                    lines = content.splitlines(keepends=True)
+                    start = line - 1
+                    end = start + limit if isinstance(limit, int) and limit > 0 else None
+                    content = "".join(lines[start:end])
+                response = {
+                    "jsonrpc": "2.0",
+                    "id": message_id,
+                    "result": {
+                        "content": content,
+                    },
+                }
+            except Exception as exc:
+                response = _jsonrpc_error(message_id, -32602, str(exc))
+        elif method == "fs/write_text_file":
+            try:
+                path = _ensure_path_within_cwd(str(params.get("path") or ""), cwd)
+                path.parent.mkdir(parents=True, exist_ok=True)
+                path.write_text(str(params.get("content") or ""))
+                response = {
+                    "jsonrpc": "2.0",
+                    "id": message_id,
+                    "result": None,
+                }
+            except Exception as exc:
+                response = _jsonrpc_error(message_id, -32602, str(exc))
+        else:
+            response = _jsonrpc_error(
+                message_id,
+                -32601,
+                f"ACP client method '{method}' is not supported by Hermes yet.",
+            )
+
+        process.stdin.write(json.dumps(response) + "\n")
+        process.stdin.flush()
+        return True
diff --git a/agent/smart_model_routing.py b/agent/smart_model_routing.py
index 249548701..d57cd1b83 100644
--- a/agent/smart_model_routing.py
+++ b/agent/smart_model_routing.py
@@ -125,6 +125,8 @@ def resolve_turn_route(user_message: str, routing_config: Optional[Dict[str, Any
                 "base_url": primary.get("base_url"),
                 "provider": primary.get("provider"),
                 "api_mode": primary.get("api_mode"),
+                "command": primary.get("command"),
+                "args": list(primary.get("args") or []),
             },
             "label": None,
             "signature": (
@@ -132,6 +134,8 @@ def resolve_turn_route(user_message: str, routing_config: Optional[Dict[str, Any
                 primary.get("provider"),
                 primary.get("base_url"),
                 primary.get("api_mode"),
+                primary.get("command"),
+                tuple(primary.get("args") or ()),
             ),
         }
 
@@ -156,6 +160,8 @@ def resolve_turn_route(user_message: str, routing_config: Optional[Dict[str, Any
                 "base_url": primary.get("base_url"),
                 "provider": primary.get("provider"),
                 "api_mode": primary.get("api_mode"),
+                "command": primary.get("command"),
+                "args": list(primary.get("args") or []),
             },
             "label": None,
             "signature": (
@@ -163,6 +169,8 @@ def resolve_turn_route(user_message: str, routing_config: Optional[Dict[str, Any
                 primary.get("provider"),
                 primary.get("base_url"),
                 primary.get("api_mode"),
+                primary.get("command"),
+                tuple(primary.get("args") or ()),
             ),
         }
 
@@ -173,6 +181,8 @@ def resolve_turn_route(user_message: str, routing_config: Optional[Dict[str, Any
             "base_url": runtime.get("base_url"),
             "provider": runtime.get("provider"),
             "api_mode": runtime.get("api_mode"),
+            "command": runtime.get("command"),
+            "args": list(runtime.get("args") or []),
         },
         "label": f"smart route → {route.get('model')} ({runtime.get('provider')})",
         "signature": (
@@ -180,5 +190,7 @@ def resolve_turn_route(user_message: str, routing_config: Optional[Dict[str, Any
             runtime.get("provider"),
             runtime.get("base_url"),
             runtime.get("api_mode"),
+            runtime.get("command"),
+            tuple(runtime.get("args") or ()),
         ),
     }
diff --git a/cli.py b/cli.py
index 19a0c972f..7df55a92c 100755
--- a/cli.py
+++ b/cli.py
@@ -1063,6 +1063,8 @@ class HermesCLI:
         self._provider_source: Optional[str] = None
         self.provider = self.requested_provider
         self.api_mode = "chat_completions"
+        self.acp_command: Optional[str] = None
+        self.acp_args: list[str] = []
         self.base_url = (
             base_url
             or os.getenv("OPENAI_BASE_URL")
@@ -1374,27 +1376,35 @@ class HermesCLI:
             return [("class:status-bar", f" {self._build_status_bar_text()} ")]
 
     def _normalize_model_for_provider(self, resolved_provider: str) -> bool:
-        """Strip provider prefixes and swap the default model for Codex.
-
-        When the resolved provider is ``openai-codex``:
-
-        1. Strip any ``provider/`` prefix (the Codex Responses API only
-           accepts bare model slugs like ``gpt-5.4``, not ``openai/gpt-5.4``).
-        2. If the active model is still the *untouched default* (user never
-           explicitly chose a model), replace it with a Codex-compatible
-           default so the first session doesn't immediately error.
-
-        If the user explicitly chose a model — *any* model — we trust them
-        and let the API be the judge.  No allowlists, no slug checks.
-
-        Returns True when the active model was changed.
-        """
-        if resolved_provider != "openai-codex":
-            return False
-
+        """Normalize provider-specific model IDs and routing."""
         current_model = (self.model or "").strip()
         changed = False
 
+        if resolved_provider == "copilot":
+            try:
+                from hermes_cli.models import copilot_model_api_mode, normalize_copilot_model_id
+
+                canonical = normalize_copilot_model_id(current_model, api_key=self.api_key)
+                if canonical and canonical != current_model:
+                    if not self._model_is_default:
+                        self.console.print(
+                            f"[yellow]⚠️  Normalized Copilot model '{current_model}' to '{canonical}'.[/]"
+                        )
+                    self.model = canonical
+                    current_model = canonical
+                    changed = True
+
+                resolved_mode = copilot_model_api_mode(current_model, api_key=self.api_key)
+                if resolved_mode != self.api_mode:
+                    self.api_mode = resolved_mode
+                    changed = True
+            except Exception:
+                pass
+            return changed
+
+        if resolved_provider != "openai-codex":
+            return False
+
         # 1. Strip provider prefix ("openai/gpt-5.4" → "gpt-5.4")
         if "/" in current_model:
             slug = current_model.split("/", 1)[1]
@@ -1670,6 +1680,8 @@ class HermesCLI:
         base_url = runtime.get("base_url")
         resolved_provider = runtime.get("provider", "openrouter")
         resolved_api_mode = runtime.get("api_mode", self.api_mode)
+        resolved_acp_command = runtime.get("command")
+        resolved_acp_args = list(runtime.get("args") or [])
         if not isinstance(api_key, str) or not api_key:
             self.console.print("[bold red]Provider resolver returned an empty API key.[/]")
             return False
@@ -1681,9 +1693,13 @@ class HermesCLI:
         routing_changed = (
             resolved_provider != self.provider
             or resolved_api_mode != self.api_mode
+            or resolved_acp_command != self.acp_command
+            or resolved_acp_args != self.acp_args
         )
         self.provider = resolved_provider
         self.api_mode = resolved_api_mode
+        self.acp_command = resolved_acp_command
+        self.acp_args = resolved_acp_args
         self._provider_source = runtime.get("source")
         self.api_key = api_key
         self.base_url = base_url
@@ -1713,6 +1729,8 @@ class HermesCLI:
                 "base_url": self.base_url,
                 "provider": self.provider,
                 "api_mode": self.api_mode,
+                "command": self.acp_command,
+                "args": list(self.acp_args or []),
             },
         )
 
@@ -1781,6 +1799,8 @@ class HermesCLI:
                 "base_url": self.base_url,
                 "provider": self.provider,
                 "api_mode": self.api_mode,
+                "command": self.acp_command,
+                "args": list(self.acp_args or []),
             }
             effective_model = model_override or self.model
             self.agent = AIAgent(
@@ -1789,6 +1809,8 @@ class HermesCLI:
                 base_url=runtime.get("base_url"),
                 provider=runtime.get("provider"),
                 api_mode=runtime.get("api_mode"),
+                acp_command=runtime.get("command"),
+                acp_args=runtime.get("args"),
                 max_iterations=self.max_turns,
                 enabled_toolsets=self.enabled_toolsets,
                 verbose_logging=self.verbose,
@@ -1825,6 +1847,8 @@ class HermesCLI:
                 runtime.get("provider"),
                 runtime.get("base_url"),
                 runtime.get("api_mode"),
+                runtime.get("command"),
+                tuple(runtime.get("args") or ()),
             )
 
             if self._pending_title and self._session_db:
@@ -3750,6 +3774,8 @@ class HermesCLI:
                     base_url=turn_route["runtime"].get("base_url"),
                     provider=turn_route["runtime"].get("provider"),
                     api_mode=turn_route["runtime"].get("api_mode"),
+                    acp_command=turn_route["runtime"].get("command"),
+                    acp_args=turn_route["runtime"].get("args"),
                     max_iterations=self.max_turns,
                     enabled_toolsets=self.enabled_toolsets,
                     quiet_mode=True,
diff --git a/cron/scheduler.py b/cron/scheduler.py
index 2060bf2fb..ea7ff0e9b 100644
--- a/cron/scheduler.py
+++ b/cron/scheduler.py
@@ -359,6 +359,8 @@ def run_job(job: dict) -> tuple[bool, str, str, Optional[str]]:
                 "base_url": runtime.get("base_url"),
                 "provider": runtime.get("provider"),
                 "api_mode": runtime.get("api_mode"),
+                "command": runtime.get("command"),
+                "args": list(runtime.get("args") or []),
             },
         )
 
@@ -368,6 +370,8 @@ def run_job(job: dict) -> tuple[bool, str, str, Optional[str]]:
             base_url=turn_route["runtime"].get("base_url"),
             provider=turn_route["runtime"].get("provider"),
             api_mode=turn_route["runtime"].get("api_mode"),
+            acp_command=turn_route["runtime"].get("command"),
+            acp_args=turn_route["runtime"].get("args"),
             max_iterations=max_iterations,
             reasoning_config=reasoning_config,
             prefill_messages=prefill_messages,
diff --git a/gateway/run.py b/gateway/run.py
index ea9f2a283..4e9666a90 100644
--- a/gateway/run.py
+++ b/gateway/run.py
@@ -242,6 +242,8 @@ def _resolve_runtime_agent_kwargs() -> dict:
         "base_url": runtime.get("base_url"),
         "provider": runtime.get("provider"),
         "api_mode": runtime.get("api_mode"),
+        "command": runtime.get("command"),
+        "args": list(runtime.get("args") or []),
     }
 
 
@@ -601,6 +603,8 @@ class GatewayRunner:
             "base_url": runtime_kwargs.get("base_url"),
             "provider": runtime_kwargs.get("provider"),
             "api_mode": runtime_kwargs.get("api_mode"),
+            "command": runtime_kwargs.get("command"),
+            "args": list(runtime_kwargs.get("args") or []),
         }
         return resolve_turn_route(user_message, getattr(self, "_smart_model_routing", {}), primary)
 
diff --git a/hermes_cli/__init__.py b/hermes_cli/__init__.py
index 90f082720..eea32d6db 100644
--- a/hermes_cli/__init__.py
+++ b/hermes_cli/__init__.py
@@ -11,5 +11,5 @@ Provides subcommands for:
 - hermes cron          - Manage cron jobs
 """
 
-__version__ = "0.3.0"
-__release_date__ = "2026.3.17"
+__version__ = "0.4.0"
+__release_date__ = "2026.3.18"
diff --git a/hermes_cli/auth.py b/hermes_cli/auth.py
index 54573acf1..f73506371 100644
--- a/hermes_cli/auth.py
+++ b/hermes_cli/auth.py
@@ -19,6 +19,7 @@ import json
 import logging
 import os
 import shutil
+import shlex
 import stat
 import base64
 import hashlib
@@ -66,6 +67,8 @@ DEFAULT_AGENT_KEY_MIN_TTL_SECONDS = 30 * 60  # 30 minutes
 ACCESS_TOKEN_REFRESH_SKEW_SECONDS = 120       # refresh 2 min before expiry
 DEVICE_AUTH_POLL_INTERVAL_CAP_SECONDS = 1     # poll at most every 1s
 DEFAULT_CODEX_BASE_URL = "https://chatgpt.com/backend-api/codex"
+DEFAULT_GITHUB_MODELS_BASE_URL = "https://api.githubcopilot.com"
+DEFAULT_COPILOT_ACP_BASE_URL = "acp://copilot"
 CODEX_OAUTH_CLIENT_ID = "app_EMoamEEZ73f0CkXaXp7hrann"
 CODEX_OAUTH_TOKEN_URL = "https://auth.openai.com/oauth/token"
 CODEX_ACCESS_TOKEN_REFRESH_SKEW_SECONDS = 120
@@ -108,6 +111,20 @@ PROVIDER_REGISTRY: Dict[str, ProviderConfig] = {
         auth_type="oauth_external",
         inference_base_url=DEFAULT_CODEX_BASE_URL,
     ),
+    "copilot": ProviderConfig(
+        id="copilot",
+        name="GitHub Copilot",
+        auth_type="api_key",
+        inference_base_url=DEFAULT_GITHUB_MODELS_BASE_URL,
+        api_key_env_vars=("GITHUB_TOKEN", "GH_TOKEN"),
+    ),
+    "copilot-acp": ProviderConfig(
+        id="copilot-acp",
+        name="GitHub Copilot ACP",
+        auth_type="external_process",
+        inference_base_url=DEFAULT_COPILOT_ACP_BASE_URL,
+        base_url_env_var="COPILOT_ACP_BASE_URL",
+    ),
     "zai": ProviderConfig(
         id="zai",
         name="Z.AI / GLM",
@@ -222,6 +239,62 @@ def _resolve_kimi_base_url(api_key: str, default_url: str, env_override: str) ->
     return default_url
 
 
+def _gh_cli_candidates() -> list[str]:
+    """Return candidate ``gh`` binary paths, including common Homebrew installs."""
+    candidates: list[str] = []
+
+    resolved = shutil.which("gh")
+    if resolved:
+        candidates.append(resolved)
+
+    for candidate in (
+        "/opt/homebrew/bin/gh",
+        "/usr/local/bin/gh",
+        str(Path.home() / ".local" / "bin" / "gh"),
+    ):
+        if candidate in candidates:
+            continue
+        if os.path.isfile(candidate) and os.access(candidate, os.X_OK):
+            candidates.append(candidate)
+
+    return candidates
+
+
+def _try_gh_cli_token() -> Optional[str]:
+    """Return a token from ``gh auth token`` when the GitHub CLI is available."""
+    for gh_path in _gh_cli_candidates():
+        try:
+            result = subprocess.run(
+                [gh_path, "auth", "token"],
+                capture_output=True,
+                text=True,
+                timeout=5,
+            )
+        except (FileNotFoundError, subprocess.TimeoutExpired) as exc:
+            logger.debug("gh CLI token lookup failed (%s): %s", gh_path, exc)
+            continue
+        if result.returncode == 0 and result.stdout.strip():
+            return result.stdout.strip()
+    return None
+
+
+def _resolve_api_key_provider_secret(
+    provider_id: str, pconfig: ProviderConfig
+) -> tuple[str, str]:
+    """Resolve an API-key provider's token and indicate where it came from."""
+    for env_var in pconfig.api_key_env_vars:
+        val = os.getenv(env_var, "").strip()
+        if val:
+            return val, env_var
+
+    if provider_id == "copilot":
+        token = _try_gh_cli_token()
+        if token:
+            return token, "gh auth token"
+
+    return "", ""
+
+
 # =============================================================================
 # Z.AI Endpoint Detection
 # =============================================================================
@@ -572,6 +645,9 @@ def resolve_provider(
         "kimi": "kimi-coding", "moonshot": "kimi-coding",
         "minimax-china": "minimax-cn", "minimax_cn": "minimax-cn",
         "claude": "anthropic", "claude-code": "anthropic",
+        "github": "copilot", "github-copilot": "copilot",
+        "github-models": "copilot", "github-model": "copilot",
+        "github-copilot-acp": "copilot-acp", "copilot-acp-agent": "copilot-acp",
         "aigateway": "ai-gateway", "vercel": "ai-gateway", "vercel-ai-gateway": "ai-gateway",
         "opencode": "opencode-zen", "zen": "opencode-zen",
         "go": "opencode-go", "opencode-go-sub": "opencode-go",
@@ -611,6 +687,11 @@ def resolve_provider(
     for pid, pconfig in PROVIDER_REGISTRY.items():
         if pconfig.auth_type != "api_key":
             continue
+        # GitHub tokens are commonly present for repo/tool access but should not
+        # hijack inference auto-selection unless the user explicitly chooses
+        # Copilot/GitHub Models as the provider.
+        if pid == "copilot":
+            continue
         for env_var in pconfig.api_key_env_vars:
             if os.getenv(env_var, "").strip():
                 return pid
@@ -1479,12 +1560,7 @@ def get_api_key_provider_status(provider_id: str) -> Dict[str, Any]:
 
     api_key = ""
     key_source = ""
-    for env_var in pconfig.api_key_env_vars:
-        val = os.getenv(env_var, "").strip()
-        if val:
-            api_key = val
-            key_source = env_var
-            break
+    api_key, key_source = _resolve_api_key_provider_secret(provider_id, pconfig)
 
     env_url = ""
     if pconfig.base_url_env_var:
@@ -1507,6 +1583,36 @@ def get_api_key_provider_status(provider_id: str) -> Dict[str, Any]:
     }
 
 
+def get_external_process_provider_status(provider_id: str) -> Dict[str, Any]:
+    """Status snapshot for providers that run a local subprocess."""
+    pconfig = PROVIDER_REGISTRY.get(provider_id)
+    if not pconfig or pconfig.auth_type != "external_process":
+        return {"configured": False}
+
+    command = (
+        os.getenv("HERMES_COPILOT_ACP_COMMAND", "").strip()
+        or os.getenv("COPILOT_CLI_PATH", "").strip()
+        or "copilot"
+    )
+    raw_args = os.getenv("HERMES_COPILOT_ACP_ARGS", "").strip()
+    args = shlex.split(raw_args) if raw_args else ["--acp", "--stdio"]
+    base_url = os.getenv(pconfig.base_url_env_var, "").strip() if pconfig.base_url_env_var else ""
+    if not base_url:
+        base_url = pconfig.inference_base_url
+
+    resolved_command = shutil.which(command) if command else None
+    return {
+        "configured": bool(resolved_command or base_url.startswith("acp+tcp://")),
+        "provider": provider_id,
+        "name": pconfig.name,
+        "command": command,
+        "args": args,
+        "resolved_command": resolved_command,
+        "base_url": base_url,
+        "logged_in": bool(resolved_command or base_url.startswith("acp+tcp://")),
+    }
+
+
 def get_auth_status(provider_id: Optional[str] = None) -> Dict[str, Any]:
     """Generic auth status dispatcher."""
     target = provider_id or get_active_provider()
@@ -1514,6 +1620,8 @@ def get_auth_status(provider_id: Optional[str] = None) -> Dict[str, Any]:
         return get_nous_auth_status()
     if target == "openai-codex":
         return get_codex_auth_status()
+    if target == "copilot-acp":
+        return get_external_process_provider_status(target)
     # API-key providers
     pconfig = PROVIDER_REGISTRY.get(target)
     if pconfig and pconfig.auth_type == "api_key":
@@ -1536,12 +1644,7 @@ def resolve_api_key_provider_credentials(provider_id: str) -> Dict[str, Any]:
 
     api_key = ""
     key_source = ""
-    for env_var in pconfig.api_key_env_vars:
-        val = os.getenv(env_var, "").strip()
-        if val:
-            api_key = val
-            key_source = env_var
-            break
+    api_key, key_source = _resolve_api_key_provider_secret(provider_id, pconfig)
 
     env_url = ""
     if pconfig.base_url_env_var:
@@ -1562,6 +1665,46 @@ def resolve_api_key_provider_credentials(provider_id: str) -> Dict[str, Any]:
     }
 
 
+def resolve_external_process_provider_credentials(provider_id: str) -> Dict[str, Any]:
+    """Resolve runtime details for local subprocess-backed providers."""
+    pconfig = PROVIDER_REGISTRY.get(provider_id)
+    if not pconfig or pconfig.auth_type != "external_process":
+        raise AuthError(
+            f"Provider '{provider_id}' is not an external-process provider.",
+            provider=provider_id,
+            code="invalid_provider",
+        )
+
+    base_url = os.getenv(pconfig.base_url_env_var, "").strip() if pconfig.base_url_env_var else ""
+    if not base_url:
+        base_url = pconfig.inference_base_url
+
+    command = (
+        os.getenv("HERMES_COPILOT_ACP_COMMAND", "").strip()
+        or os.getenv("COPILOT_CLI_PATH", "").strip()
+        or "copilot"
+    )
+    raw_args = os.getenv("HERMES_COPILOT_ACP_ARGS", "").strip()
+    args = shlex.split(raw_args) if raw_args else ["--acp", "--stdio"]
+    resolved_command = shutil.which(command) if command else None
+    if not resolved_command and not base_url.startswith("acp+tcp://"):
+        raise AuthError(
+            f"Could not find the Copilot CLI command '{command}'. "
+            "Install GitHub Copilot CLI or set HERMES_COPILOT_ACP_COMMAND/COPILOT_CLI_PATH.",
+            provider=provider_id,
+            code="missing_copilot_cli",
+        )
+
+    return {
+        "provider": provider_id,
+        "api_key": "copilot-acp",
+        "base_url": base_url.rstrip("/"),
+        "command": resolved_command or command,
+        "args": args,
+        "source": "process",
+    }
+
+
 # =============================================================================
 # External credential detection
 # =============================================================================
diff --git a/hermes_cli/main.py b/hermes_cli/main.py
index d5d4885a7..a578c4d7d 100644
--- a/hermes_cli/main.py
+++ b/hermes_cli/main.py
@@ -125,6 +125,17 @@ def _has_any_provider_configured() -> bool:
         except Exception:
             pass
 
+    # Check provider-specific auth fallbacks (for example, Copilot via gh auth).
+    try:
+        for provider_id, pconfig in PROVIDER_REGISTRY.items():
+            if pconfig.auth_type != "api_key":
+                continue
+            status = get_auth_status(provider_id)
+            if status.get("logged_in"):
+                return True
+    except Exception:
+        pass
+
     # Check for Nous Portal OAuth credentials
     auth_file = get_hermes_home() / "auth.json"
     if auth_file.exists():
@@ -775,6 +786,8 @@ def cmd_model(args):
         "openrouter": "OpenRouter",
         "nous": "Nous Portal",
         "openai-codex": "OpenAI Codex",
+        "copilot-acp": "GitHub Copilot ACP",
+        "copilot": "GitHub Copilot",
         "anthropic": "Anthropic",
         "zai": "Z.AI / GLM",
         "kimi-coding": "Kimi / Moonshot",
@@ -799,6 +812,8 @@ def cmd_model(args):
         ("openrouter", "OpenRouter (100+ models, pay-per-use)"),
         ("nous", "Nous Portal (Nous Research subscription)"),
         ("openai-codex", "OpenAI Codex"),
+        ("copilot-acp", "GitHub Copilot ACP (spawns `copilot --acp --stdio`)"),
+        ("copilot", "GitHub Copilot (uses GITHUB_TOKEN or gh auth token)"),
         ("anthropic", "Anthropic (Claude models — API key or Claude Code)"),
         ("zai", "Z.AI / GLM (Zhipu AI direct API)"),
         ("kimi-coding", "Kimi / Moonshot (Moonshot AI direct API)"),
@@ -867,6 +882,10 @@ def cmd_model(args):
         _model_flow_nous(config, current_model)
     elif selected_provider == "openai-codex":
         _model_flow_openai_codex(config, current_model)
+    elif selected_provider == "copilot-acp":
+        _model_flow_copilot_acp(config, current_model)
+    elif selected_provider == "copilot":
+        _model_flow_copilot(config, current_model)
     elif selected_provider == "custom":
         _model_flow_custom(config)
     elif selected_provider.startswith("custom:") and selected_provider in _custom_provider_map:
@@ -1407,6 +1426,25 @@ def _model_flow_named_custom(config, provider_info):
 
 # Curated model lists for direct API-key providers
 _PROVIDER_MODELS = {
+    "copilot-acp": [
+        "copilot-acp",
+    ],
+    "copilot": [
+        "gpt-5.4",
+        "gpt-5.4-mini",
+        "gpt-5-mini",
+        "gpt-5.3-codex",
+        "gpt-5.2-codex",
+        "gpt-4.1",
+        "gpt-4o",
+        "gpt-4o-mini",
+        "claude-opus-4.6",
+        "claude-sonnet-4.6",
+        "claude-sonnet-4.5",
+        "claude-haiku-4.5",
+        "gemini-2.5-pro",
+        "grok-code-fast-1",
+    ],
     "zai": [
         "glm-5",
         "glm-4.7",
@@ -1447,6 +1485,331 @@ _PROVIDER_MODELS = {
 }
 
 
+def _current_reasoning_effort(config) -> str:
+    agent_cfg = config.get("agent")
+    if isinstance(agent_cfg, dict):
+        return str(agent_cfg.get("reasoning_effort") or "").strip().lower()
+    return ""
+
+
+def _set_reasoning_effort(config, effort: str) -> None:
+    agent_cfg = config.get("agent")
+    if not isinstance(agent_cfg, dict):
+        agent_cfg = {}
+        config["agent"] = agent_cfg
+    agent_cfg["reasoning_effort"] = effort
+
+
+def _prompt_reasoning_effort_selection(efforts, current_effort=""):
+    """Prompt for a reasoning effort. Returns effort, 'none', or None to keep current."""
+    ordered = list(dict.fromkeys(str(effort).strip().lower() for effort in efforts if str(effort).strip()))
+    if not ordered:
+        return None
+
+    def _label(effort):
+        if effort == current_effort:
+            return f"{effort}  ← currently in use"
+        return effort
+
+    disable_label = "Disable reasoning"
+    skip_label = "Skip (keep current)"
+
+    if current_effort == "none":
+        default_idx = len(ordered)
+    elif current_effort in ordered:
+        default_idx = ordered.index(current_effort)
+    elif "medium" in ordered:
+        default_idx = ordered.index("medium")
+    else:
+        default_idx = 0
+
+    try:
+        from simple_term_menu import TerminalMenu
+
+        choices = [f"  {_label(effort)}" for effort in ordered]
+        choices.append(f"  {disable_label}")
+        choices.append(f"  {skip_label}")
+        menu = TerminalMenu(
+            choices,
+            cursor_index=default_idx,
+            menu_cursor="-> ",
+            menu_cursor_style=("fg_green", "bold"),
+            menu_highlight_style=("fg_green",),
+            cycle_cursor=True,
+            clear_screen=False,
+            title="Select reasoning effort:",
+        )
+        idx = menu.show()
+        if idx is None:
+            return None
+        print()
+        if idx < len(ordered):
+            return ordered[idx]
+        if idx == len(ordered):
+            return "none"
+        return None
+    except (ImportError, NotImplementedError):
+        pass
+
+    print("Select reasoning effort:")
+    for i, effort in enumerate(ordered, 1):
+        print(f"  {i}. {_label(effort)}")
+    n = len(ordered)
+    print(f"  {n + 1}. {disable_label}")
+    print(f"  {n + 2}. {skip_label}")
+    print()
+
+    while True:
+        try:
+            choice = input(f"Choice [1-{n + 2}] (default: keep current): ").strip()
+            if not choice:
+                return None
+            idx = int(choice)
+            if 1 <= idx <= n:
+                return ordered[idx - 1]
+            if idx == n + 1:
+                return "none"
+            if idx == n + 2:
+                return None
+            print(f"Please enter 1-{n + 2}")
+        except ValueError:
+            print("Please enter a number")
+        except (KeyboardInterrupt, EOFError):
+            return None
+
+
+def _model_flow_copilot(config, current_model=""):
+    """GitHub Copilot flow using env vars or ``gh auth token``."""
+    from hermes_cli.auth import (
+        PROVIDER_REGISTRY,
+        _prompt_model_selection,
+        _save_model_choice,
+        deactivate_provider,
+        resolve_api_key_provider_credentials,
+    )
+    from hermes_cli.config import get_env_value, save_env_value, load_config, save_config
+    from hermes_cli.models import (
+        fetch_api_models,
+        fetch_github_model_catalog,
+        github_model_reasoning_efforts,
+        copilot_model_api_mode,
+        normalize_copilot_model_id,
+    )
+
+    provider_id = "copilot"
+    pconfig = PROVIDER_REGISTRY[provider_id]
+
+    creds = resolve_api_key_provider_credentials(provider_id)
+    api_key = creds.get("api_key", "")
+    source = creds.get("source", "")
+
+    if not api_key:
+        print("No GitHub token configured for GitHub Copilot.")
+        print("  Hermes can use GITHUB_TOKEN, GH_TOKEN, or your gh CLI login.")
+        try:
+            new_key = input("GITHUB_TOKEN (or Enter to cancel): ").strip()
+        except (KeyboardInterrupt, EOFError):
+            print()
+            return
+        if not new_key:
+            print("Cancelled.")
+            return
+        save_env_value("GITHUB_TOKEN", new_key)
+        print("GitHub token saved.")
+        print()
+        creds = resolve_api_key_provider_credentials(provider_id)
+        api_key = creds.get("api_key", "")
+        source = creds.get("source", "")
+    else:
+        if source in ("GITHUB_TOKEN", "GH_TOKEN"):
+            print(f"  GitHub token: {api_key[:8]}... ✓ ({source})")
+        elif source == "gh auth token":
+            print("  GitHub token: ✓ (from `gh auth token`)")
+        else:
+            print("  GitHub token: ✓")
+        print()
+
+    effective_base = pconfig.inference_base_url
+
+    catalog = fetch_github_model_catalog(api_key)
+    live_models = [item.get("id", "") for item in catalog if item.get("id")] if catalog else fetch_api_models(api_key, effective_base)
+    normalized_current_model = normalize_copilot_model_id(
+        current_model,
+        catalog=catalog,
+        api_key=api_key,
+    ) or current_model
+    if live_models:
+        model_list = [model_id for model_id in live_models if model_id]
+        print(f"  Found {len(model_list)} model(s) from GitHub Copilot")
+    else:
+        model_list = _PROVIDER_MODELS.get(provider_id, [])
+        if model_list:
+            print("  ⚠ Could not auto-detect models from GitHub Copilot — showing defaults.")
+            print('    Use "Enter custom model name" if you do not see your model.')
+
+    if model_list:
+        selected = _prompt_model_selection(model_list, current_model=normalized_current_model)
+    else:
+        try:
+            selected = input("Model name: ").strip()
+        except (KeyboardInterrupt, EOFError):
+            selected = None
+
+    if selected:
+        selected = normalize_copilot_model_id(
+            selected,
+            catalog=catalog,
+            api_key=api_key,
+        ) or selected
+        # Clear stale custom-endpoint overrides so the Copilot provider wins cleanly.
+        if get_env_value("OPENAI_BASE_URL"):
+            save_env_value("OPENAI_BASE_URL", "")
+            save_env_value("OPENAI_API_KEY", "")
+
+        initial_cfg = load_config()
+        current_effort = _current_reasoning_effort(initial_cfg)
+        reasoning_efforts = github_model_reasoning_efforts(
+            selected,
+            catalog=catalog,
+            api_key=api_key,
+        )
+        selected_effort = None
+        if reasoning_efforts:
+            print(f"  {selected} supports reasoning controls.")
+            selected_effort = _prompt_reasoning_effort_selection(
+                reasoning_efforts, current_effort=current_effort
+            )
+
+        _save_model_choice(selected)
+
+        cfg = load_config()
+        model = cfg.get("model")
+        if not isinstance(model, dict):
+            model = {"default": model} if model else {}
+            cfg["model"] = model
+        model["provider"] = provider_id
+        model["base_url"] = effective_base
+        model["api_mode"] = copilot_model_api_mode(
+            selected,
+            catalog=catalog,
+            api_key=api_key,
+        )
+        if selected_effort is not None:
+            _set_reasoning_effort(cfg, selected_effort)
+        save_config(cfg)
+        deactivate_provider()
+
+        print(f"Default model set to: {selected} (via {pconfig.name})")
+        if reasoning_efforts:
+            if selected_effort == "none":
+                print("Reasoning disabled for this model.")
+            elif selected_effort:
+                print(f"Reasoning effort set to: {selected_effort}")
+    else:
+        print("No change.")
+
+
+def _model_flow_copilot_acp(config, current_model=""):
+    """GitHub Copilot ACP flow using the local Copilot CLI."""
+    from hermes_cli.auth import (
+        PROVIDER_REGISTRY,
+        _prompt_model_selection,
+        _save_model_choice,
+        deactivate_provider,
+        get_external_process_provider_status,
+        resolve_api_key_provider_credentials,
+        resolve_external_process_provider_credentials,
+    )
+    from hermes_cli.models import (
+        fetch_github_model_catalog,
+        normalize_copilot_model_id,
+    )
+    from hermes_cli.config import load_config, save_config
+
+    del config
+
+    provider_id = "copilot-acp"
+    pconfig = PROVIDER_REGISTRY[provider_id]
+
+    status = get_external_process_provider_status(provider_id)
+    resolved_command = status.get("resolved_command") or status.get("command") or "copilot"
+    effective_base = status.get("base_url") or pconfig.inference_base_url
+
+    print("  GitHub Copilot ACP delegates Hermes turns to `copilot --acp`.")
+    print("  Hermes currently starts its own ACP subprocess for each request.")
+    print("  Hermes uses your selected model as a hint for the Copilot ACP session.")
+    print(f"  Command: {resolved_command}")
+    print(f"  Backend marker: {effective_base}")
+    print()
+
+    try:
+        creds = resolve_external_process_provider_credentials(provider_id)
+    except Exception as exc:
+        print(f"  ⚠ {exc}")
+        print("  Set HERMES_COPILOT_ACP_COMMAND or COPILOT_CLI_PATH if Copilot CLI is installed elsewhere.")
+        return
+
+    effective_base = creds.get("base_url") or effective_base
+
+    catalog_api_key = ""
+    try:
+        catalog_creds = resolve_api_key_provider_credentials("copilot")
+        catalog_api_key = catalog_creds.get("api_key", "")
+    except Exception:
+        pass
+
+    catalog = fetch_github_model_catalog(catalog_api_key)
+    normalized_current_model = normalize_copilot_model_id(
+        current_model,
+        catalog=catalog,
+        api_key=catalog_api_key,
+    ) or current_model
+
+    if catalog:
+        model_list = [item.get("id", "") for item in catalog if item.get("id")]
+        print(f"  Found {len(model_list)} model(s) from GitHub Copilot")
+    else:
+        model_list = _PROVIDER_MODELS.get("copilot", [])
+        if model_list:
+            print("  ⚠ Could not auto-detect models from GitHub Copilot — showing defaults.")
+            print('    Use "Enter custom model name" if you do not see your model.')
+
+    if model_list:
+        selected = _prompt_model_selection(
+            model_list,
+            current_model=normalized_current_model,
+        )
+    else:
+        try:
+            selected = input("Model name: ").strip()
+        except (KeyboardInterrupt, EOFError):
+            selected = None
+
+    if not selected:
+        print("No change.")
+        return
+
+    selected = normalize_copilot_model_id(
+        selected,
+        catalog=catalog,
+        api_key=catalog_api_key,
+    ) or selected
+    _save_model_choice(selected)
+
+    cfg = load_config()
+    model = cfg.get("model")
+    if not isinstance(model, dict):
+        model = {"default": model} if model else {}
+        cfg["model"] = model
+    model["provider"] = provider_id
+    model["base_url"] = effective_base
+    model["api_mode"] = "chat_completions"
+    save_config(cfg)
+    deactivate_provider()
+
+    print(f"Default model set to: {selected} (via {pconfig.name})")
+
+
 def _model_flow_kimi(config, current_model=""):
     """Kimi / Moonshot model selection with automatic endpoint routing.
 
@@ -2642,7 +3005,7 @@ For more help on a command:
     )
     chat_parser.add_argument(
         "--provider",
-        choices=["auto", "openrouter", "nous", "openai-codex", "anthropic", "zai", "kimi-coding", "minimax", "minimax-cn", "kilocode"],
+        choices=["auto", "openrouter", "nous", "openai-codex", "copilot-acp", "copilot", "anthropic", "zai", "kimi-coding", "minimax", "minimax-cn", "kilocode"],
         default=None,
         help="Inference provider (default: auto)"
     )
diff --git a/hermes_cli/models.py b/hermes_cli/models.py
index 174aa9475..e6f4bc5d5 100644
--- a/hermes_cli/models.py
+++ b/hermes_cli/models.py
@@ -14,6 +14,16 @@ import urllib.error
 from difflib import get_close_matches
 from typing import Any, Optional
 
+COPILOT_BASE_URL = "https://api.githubcopilot.com"
+COPILOT_MODELS_URL = f"{COPILOT_BASE_URL}/models"
+COPILOT_EDITOR_VERSION = "vscode/1.104.1"
+COPILOT_REASONING_EFFORTS_GPT5 = ["minimal", "low", "medium", "high"]
+COPILOT_REASONING_EFFORTS_O_SERIES = ["low", "medium", "high"]
+
+# Backward-compatible aliases for the earlier GitHub Models-backed Copilot work.
+GITHUB_MODELS_BASE_URL = COPILOT_BASE_URL
+GITHUB_MODELS_CATALOG_URL = COPILOT_MODELS_URL
+
 # (model_id, display description shown in menus)
 OPENROUTER_MODELS: list[tuple[str, str]] = [
     ("anthropic/claude-opus-4.6",       "recommended"),
@@ -46,6 +56,25 @@ _PROVIDER_MODELS: dict[str, list[str]] = {
         "gpt-5.1-codex-mini",
         "gpt-5.1-codex-max",
     ],
+    "copilot-acp": [
+        "copilot-acp",
+    ],
+    "copilot": [
+        "gpt-5.4",
+        "gpt-5.4-mini",
+        "gpt-5-mini",
+        "gpt-5.3-codex",
+        "gpt-5.2-codex",
+        "gpt-4.1",
+        "gpt-4o",
+        "gpt-4o-mini",
+        "claude-opus-4.6",
+        "claude-sonnet-4.6",
+        "claude-sonnet-4.5",
+        "claude-haiku-4.5",
+        "gemini-2.5-pro",
+        "grok-code-fast-1",
+    ],
     "zai": [
         "glm-5",
         "glm-4.7",
@@ -160,7 +189,9 @@ _PROVIDER_MODELS: dict[str, list[str]] = {
 _PROVIDER_LABELS = {
     "openrouter": "OpenRouter",
     "openai-codex": "OpenAI Codex",
+    "copilot-acp": "GitHub Copilot ACP",
     "nous": "Nous Portal",
+    "copilot": "GitHub Copilot",
     "zai": "Z.AI / GLM",
     "kimi-coding": "Kimi / Moonshot",
     "minimax": "MiniMax",
@@ -180,6 +211,12 @@ _PROVIDER_ALIASES = {
     "z-ai": "zai",
     "z.ai": "zai",
     "zhipu": "zai",
+    "github": "copilot",
+    "github-copilot": "copilot",
+    "github-models": "copilot",
+    "github-model": "copilot",
+    "github-copilot-acp": "copilot-acp",
+    "copilot-acp-agent": "copilot-acp",
     "kimi": "kimi-coding",
     "moonshot": "kimi-coding",
     "minimax-china": "minimax-cn",
@@ -233,7 +270,7 @@ def list_available_providers() -> list[dict[str, str]]:
     """
     # Canonical providers in display order
     _PROVIDER_ORDER = [
-        "openrouter", "nous", "openai-codex",
+        "openrouter", "nous", "openai-codex", "copilot", "copilot-acp",
         "zai", "kimi-coding", "minimax", "minimax-cn", "kilocode", "anthropic", "alibaba",
         "opencode-zen", "opencode-go",
         "ai-gateway", "deepseek", "custom",
@@ -454,6 +491,17 @@ def provider_label(provider: Optional[str]) -> str:
     return _PROVIDER_LABELS.get(normalized, original or "OpenRouter")
 
 
+def _resolve_copilot_catalog_api_key() -> str:
+    """Best-effort GitHub token for fetching the Copilot model catalog."""
+    try:
+        from hermes_cli.auth import resolve_api_key_provider_credentials
+
+        creds = resolve_api_key_provider_credentials("copilot")
+        return str(creds.get("api_key") or "").strip()
+    except Exception:
+        return ""
+
+
 def provider_model_ids(provider: Optional[str]) -> list[str]:
     """Return the best known model catalog for a provider.
 
@@ -467,6 +515,15 @@ def provider_model_ids(provider: Optional[str]) -> list[str]:
         from hermes_cli.codex_models import get_codex_model_ids
 
         return get_codex_model_ids()
+    if normalized in {"copilot", "copilot-acp"}:
+        try:
+            live = _fetch_github_models(_resolve_copilot_catalog_api_key())
+            if live:
+                return live
+        except Exception:
+            pass
+        if normalized == "copilot-acp":
+            return list(_PROVIDER_MODELS.get("copilot", []))
     if normalized == "nous":
         # Try live Nous Portal /models endpoint
         try:
@@ -545,6 +602,274 @@ def _fetch_anthropic_models(timeout: float = 5.0) -> Optional[list[str]]:
         return None
 
 
+def _payload_items(payload: Any) -> list[dict[str, Any]]:
+    if isinstance(payload, list):
+        return [item for item in payload if isinstance(item, dict)]
+    if isinstance(payload, dict):
+        data = payload.get("data", [])
+        if isinstance(data, list):
+            return [item for item in data if isinstance(item, dict)]
+    return []
+
+
+def _extract_model_ids(payload: Any) -> list[str]:
+    return [item.get("id", "") for item in _payload_items(payload) if item.get("id")]
+
+
+def copilot_default_headers() -> dict[str, str]:
+    return {
+        "Editor-Version": COPILOT_EDITOR_VERSION,
+        "User-Agent": "HermesAgent/1.0",
+    }
+
+
+def _copilot_catalog_item_is_text_model(item: dict[str, Any]) -> bool:
+    model_id = str(item.get("id") or "").strip()
+    if not model_id:
+        return False
+
+    if item.get("model_picker_enabled") is False:
+        return False
+
+    capabilities = item.get("capabilities")
+    if isinstance(capabilities, dict):
+        model_type = str(capabilities.get("type") or "").strip().lower()
+        if model_type and model_type != "chat":
+            return False
+
+    supported_endpoints = item.get("supported_endpoints")
+    if isinstance(supported_endpoints, list):
+        normalized_endpoints = {
+            str(endpoint).strip()
+            for endpoint in supported_endpoints
+            if str(endpoint).strip()
+        }
+        if normalized_endpoints and not normalized_endpoints.intersection(
+            {"/chat/completions", "/responses", "/v1/messages"}
+        ):
+            return False
+
+    return True
+
+
+def fetch_github_model_catalog(
+    api_key: Optional[str] = None, timeout: float = 5.0
+) -> Optional[list[dict[str, Any]]]:
+    """Fetch the live GitHub Copilot model catalog for this account."""
+    attempts: list[dict[str, str]] = []
+    if api_key:
+        attempts.append({
+            **copilot_default_headers(),
+            "Authorization": f"Bearer {api_key}",
+        })
+    attempts.append(copilot_default_headers())
+
+    for headers in attempts:
+        req = urllib.request.Request(COPILOT_MODELS_URL, headers=headers)
+        try:
+            with urllib.request.urlopen(req, timeout=timeout) as resp:
+                data = json.loads(resp.read().decode())
+                items = _payload_items(data)
+                models: list[dict[str, Any]] = []
+                seen_ids: set[str] = set()
+                for item in items:
+                    if not _copilot_catalog_item_is_text_model(item):
+                        continue
+                    model_id = str(item.get("id") or "").strip()
+                    if not model_id or model_id in seen_ids:
+                        continue
+                    seen_ids.add(model_id)
+                    models.append(item)
+                if models:
+                    return models
+        except Exception:
+            continue
+    return None
+
+
+def _is_github_models_base_url(base_url: Optional[str]) -> bool:
+    normalized = (base_url or "").strip().rstrip("/").lower()
+    return (
+        normalized.startswith(COPILOT_BASE_URL)
+        or normalized.startswith("https://models.github.ai/inference")
+    )
+
+
+def _fetch_github_models(api_key: Optional[str] = None, timeout: float = 5.0) -> Optional[list[str]]:
+    catalog = fetch_github_model_catalog(api_key=api_key, timeout=timeout)
+    if not catalog:
+        return None
+    return [item.get("id", "") for item in catalog if item.get("id")]
+
+
+_COPILOT_MODEL_ALIASES = {
+    "openai/gpt-5": "gpt-5-mini",
+    "openai/gpt-5-chat": "gpt-5-mini",
+    "openai/gpt-5-mini": "gpt-5-mini",
+    "openai/gpt-5-nano": "gpt-5-mini",
+    "openai/gpt-4.1": "gpt-4.1",
+    "openai/gpt-4.1-mini": "gpt-4.1",
+    "openai/gpt-4.1-nano": "gpt-4.1",
+    "openai/gpt-4o": "gpt-4o",
+    "openai/gpt-4o-mini": "gpt-4o-mini",
+    "openai/o1": "gpt-5.2",
+    "openai/o1-mini": "gpt-5-mini",
+    "openai/o1-preview": "gpt-5.2",
+    "openai/o3": "gpt-5.3-codex",
+    "openai/o3-mini": "gpt-5-mini",
+    "openai/o4-mini": "gpt-5-mini",
+    "anthropic/claude-opus-4.6": "claude-opus-4.6",
+    "anthropic/claude-sonnet-4.6": "claude-sonnet-4.6",
+    "anthropic/claude-sonnet-4.5": "claude-sonnet-4.5",
+    "anthropic/claude-haiku-4.5": "claude-haiku-4.5",
+}
+
+
+def _copilot_catalog_ids(
+    catalog: Optional[list[dict[str, Any]]] = None,
+    api_key: Optional[str] = None,
+) -> set[str]:
+    if catalog is None and api_key:
+        catalog = fetch_github_model_catalog(api_key=api_key)
+    if not catalog:
+        return set()
+    return {
+        str(item.get("id") or "").strip()
+        for item in catalog
+        if str(item.get("id") or "").strip()
+    }
+
+
+def normalize_copilot_model_id(
+    model_id: Optional[str],
+    *,
+    catalog: Optional[list[dict[str, Any]]] = None,
+    api_key: Optional[str] = None,
+) -> str:
+    raw = str(model_id or "").strip()
+    if not raw:
+        return ""
+
+    catalog_ids = _copilot_catalog_ids(catalog=catalog, api_key=api_key)
+    alias = _COPILOT_MODEL_ALIASES.get(raw)
+    if alias:
+        return alias
+
+    candidates = [raw]
+    if "/" in raw:
+        candidates.append(raw.split("/", 1)[1].strip())
+
+    if raw.endswith("-mini"):
+        candidates.append(raw[:-5])
+    if raw.endswith("-nano"):
+        candidates.append(raw[:-5])
+    if raw.endswith("-chat"):
+        candidates.append(raw[:-5])
+
+    seen: set[str] = set()
+    for candidate in candidates:
+        if not candidate or candidate in seen:
+            continue
+        seen.add(candidate)
+        if candidate in _COPILOT_MODEL_ALIASES:
+            return _COPILOT_MODEL_ALIASES[candidate]
+        if candidate in catalog_ids:
+            return candidate
+
+    if "/" in raw:
+        return raw.split("/", 1)[1].strip()
+    return raw
+
+
+def _github_reasoning_efforts_for_model_id(model_id: str) -> list[str]:
+    raw = (model_id or "").strip().lower()
+    if raw.startswith(("openai/o1", "openai/o3", "openai/o4", "o1", "o3", "o4")):
+        return list(COPILOT_REASONING_EFFORTS_O_SERIES)
+    normalized = normalize_copilot_model_id(model_id).lower()
+    if normalized.startswith("gpt-5"):
+        return list(COPILOT_REASONING_EFFORTS_GPT5)
+    return []
+
+
+def copilot_model_api_mode(
+    model_id: Optional[str],
+    *,
+    catalog: Optional[list[dict[str, Any]]] = None,
+    api_key: Optional[str] = None,
+) -> str:
+    normalized = normalize_copilot_model_id(model_id, catalog=catalog, api_key=api_key)
+    if not normalized:
+        return "chat_completions"
+
+    if catalog is None and api_key:
+        catalog = fetch_github_model_catalog(api_key=api_key)
+
+    catalog_entry = None
+    if catalog:
+        catalog_entry = next((item for item in catalog if item.get("id") == normalized), None)
+
+    if isinstance(catalog_entry, dict):
+        supported_endpoints = {
+            str(endpoint).strip()
+            for endpoint in (catalog_entry.get("supported_endpoints") or [])
+            if str(endpoint).strip()
+        }
+        if "/chat/completions" in supported_endpoints:
+            return "chat_completions"
+        if "/responses" in supported_endpoints:
+            return "codex_responses"
+        if "/v1/messages" in supported_endpoints:
+            return "anthropic_messages"
+
+    if normalized.startswith(("gpt-5.4", "gpt-5.3-codex", "gpt-5.2-codex", "gpt-5.1-codex")):
+        return "codex_responses"
+    return "chat_completions"
+
+
+def github_model_reasoning_efforts(
+    model_id: Optional[str],
+    *,
+    catalog: Optional[list[dict[str, Any]]] = None,
+    api_key: Optional[str] = None,
+) -> list[str]:
+    """Return supported reasoning-effort levels for a Copilot-visible model."""
+    normalized = normalize_copilot_model_id(model_id, catalog=catalog, api_key=api_key)
+    if not normalized:
+        return []
+
+    catalog_entry = None
+    if catalog is not None:
+        catalog_entry = next((item for item in catalog if item.get("id") == normalized), None)
+    elif api_key:
+        fetched_catalog = fetch_github_model_catalog(api_key=api_key)
+        if fetched_catalog:
+            catalog_entry = next((item for item in fetched_catalog if item.get("id") == normalized), None)
+
+    if catalog_entry is not None:
+        capabilities = catalog_entry.get("capabilities")
+        if isinstance(capabilities, dict):
+            supports = capabilities.get("supports")
+            if isinstance(supports, dict):
+                efforts = supports.get("reasoning_effort")
+                if isinstance(efforts, list):
+                    normalized_efforts = [
+                        str(effort).strip().lower()
+                        for effort in efforts
+                        if str(effort).strip()
+                    ]
+                    return list(dict.fromkeys(normalized_efforts))
+            return []
+        legacy_capabilities = {
+            str(capability).strip().lower()
+            for capability in catalog_entry.get("capabilities", [])
+            if str(capability).strip()
+        }
+        if "reasoning" not in legacy_capabilities:
+            return []
+
+    return _github_reasoning_efforts_for_model_id(str(model_id or normalized))
+
+
 def probe_api_models(
     api_key: Optional[str],
     base_url: Optional[str],
@@ -561,6 +886,16 @@ def probe_api_models(
             "used_fallback": False,
         }
 
+    if _is_github_models_base_url(normalized):
+        models = _fetch_github_models(api_key=api_key, timeout=timeout)
+        return {
+            "models": models,
+            "probed_url": COPILOT_MODELS_URL,
+            "resolved_base_url": COPILOT_BASE_URL,
+            "suggested_base_url": None,
+            "used_fallback": False,
+        }
+
     if normalized.endswith("/v1"):
         alternate_base = normalized[:-3].rstrip("/")
     else:
@@ -574,6 +909,8 @@ def probe_api_models(
     headers: dict[str, str] = {}
     if api_key:
         headers["Authorization"] = f"Bearer {api_key}"
+    if normalized.startswith(COPILOT_BASE_URL):
+        headers.update(copilot_default_headers())
 
     for candidate_base, is_fallback in candidates:
         url = candidate_base.rstrip("/") + "/models"
@@ -664,6 +1001,12 @@ def validate_requested_model(
     normalized = normalize_provider(provider)
     if normalized == "openrouter" and base_url and "openrouter.ai" not in base_url:
         normalized = "custom"
+    requested_for_lookup = requested
+    if normalized == "copilot":
+        requested_for_lookup = normalize_copilot_model_id(
+            requested,
+            api_key=api_key,
+        ) or requested
 
     if not requested:
         return {
@@ -685,7 +1028,7 @@ def validate_requested_model(
         probe = probe_api_models(api_key, base_url)
         api_models = probe.get("models")
         if api_models is not None:
-            if requested in set(api_models):
+            if requested_for_lookup in set(api_models):
                 return {
                     "accepted": True,
                     "persist": True,
@@ -734,7 +1077,7 @@ def validate_requested_model(
     api_models = fetch_api_models(api_key, base_url)
 
     if api_models is not None:
-        if requested in set(api_models):
+        if requested_for_lookup in set(api_models):
             # API confirmed the model exists
             return {
                 "accepted": True,
diff --git a/hermes_cli/runtime_provider.py b/hermes_cli/runtime_provider.py
index 34ae43be8..ae3948da5 100644
--- a/hermes_cli/runtime_provider.py
+++ b/hermes_cli/runtime_provider.py
@@ -14,6 +14,7 @@ from hermes_cli.auth import (
     resolve_nous_runtime_credentials,
     resolve_codex_runtime_credentials,
     resolve_api_key_provider_credentials,
+    resolve_external_process_provider_credentials,
 )
 from hermes_cli.config import load_config
 from hermes_constants import OPENROUTER_BASE_URL
@@ -33,7 +34,24 @@ def _get_model_config() -> Dict[str, Any]:
     return {}
 
 
-_VALID_API_MODES = {"chat_completions", "codex_responses"}
+def _copilot_runtime_api_mode(model_cfg: Dict[str, Any], api_key: str) -> str:
+    configured_mode = _parse_api_mode(model_cfg.get("api_mode"))
+    if configured_mode:
+        return configured_mode
+
+    model_name = str(model_cfg.get("default") or "").strip()
+    if not model_name:
+        return "chat_completions"
+
+    try:
+        from hermes_cli.models import copilot_model_api_mode
+
+        return copilot_model_api_mode(model_name, api_key=api_key)
+    except Exception:
+        return "chat_completions"
+
+
+_VALID_API_MODES = {"chat_completions", "codex_responses", "anthropic_messages"}
 
 
 def _parse_api_mode(raw: Any) -> Optional[str]:
@@ -267,6 +285,19 @@ def resolve_runtime_provider(
             "requested_provider": requested_provider,
         }
 
+    if provider == "copilot-acp":
+        creds = resolve_external_process_provider_credentials(provider)
+        return {
+            "provider": "copilot-acp",
+            "api_mode": "chat_completions",
+            "base_url": creds.get("base_url", "").rstrip("/"),
+            "api_key": creds.get("api_key", ""),
+            "command": creds.get("command", ""),
+            "args": list(creds.get("args") or []),
+            "source": creds.get("source", "process"),
+            "requested_provider": requested_provider,
+        }
+
     # Anthropic (native Messages API)
     if provider == "anthropic":
         from agent.anthropic_adapter import resolve_anthropic_token
@@ -302,9 +333,13 @@ def resolve_runtime_provider(
     pconfig = PROVIDER_REGISTRY.get(provider)
     if pconfig and pconfig.auth_type == "api_key":
         creds = resolve_api_key_provider_credentials(provider)
+        model_cfg = _get_model_config()
+        api_mode = "chat_completions"
+        if provider == "copilot":
+            api_mode = _copilot_runtime_api_mode(model_cfg, creds.get("api_key", ""))
         return {
             "provider": provider,
-            "api_mode": "chat_completions",
+            "api_mode": api_mode,
             "base_url": creds.get("base_url", "").rstrip("/"),
             "api_key": creds.get("api_key", ""),
             "source": creds.get("source", "env"),
diff --git a/hermes_cli/setup.py b/hermes_cli/setup.py
index e3b5ed7d4..3264d7e47 100644
--- a/hermes_cli/setup.py
+++ b/hermes_cli/setup.py
@@ -55,6 +55,25 @@ def _set_default_model(config: Dict[str, Any], model_name: str) -> None:
 # Default model lists per provider — used as fallback when the live
 # /models endpoint can't be reached.
 _DEFAULT_PROVIDER_MODELS = {
+    "copilot-acp": [
+        "copilot-acp",
+    ],
+    "copilot": [
+        "gpt-5.4",
+        "gpt-5.4-mini",
+        "gpt-5-mini",
+        "gpt-5.3-codex",
+        "gpt-5.2-codex",
+        "gpt-4.1",
+        "gpt-4o",
+        "gpt-4o-mini",
+        "claude-opus-4.6",
+        "claude-sonnet-4.6",
+        "claude-sonnet-4.5",
+        "claude-haiku-4.5",
+        "gemini-2.5-pro",
+        "grok-code-fast-1",
+    ],
     "zai": ["glm-5", "glm-4.7", "glm-4.5", "glm-4.5-flash"],
     "kimi-coding": ["kimi-k2.5", "kimi-k2-thinking", "kimi-k2-turbo-preview"],
     "minimax": ["MiniMax-M2.5", "MiniMax-M2.5-highspeed", "MiniMax-M2.1"],
@@ -64,6 +83,59 @@ _DEFAULT_PROVIDER_MODELS = {
 }
 
 
+def _current_reasoning_effort(config: Dict[str, Any]) -> str:
+    agent_cfg = config.get("agent")
+    if isinstance(agent_cfg, dict):
+        return str(agent_cfg.get("reasoning_effort") or "").strip().lower()
+    return ""
+
+
+def _set_reasoning_effort(config: Dict[str, Any], effort: str) -> None:
+    agent_cfg = config.get("agent")
+    if not isinstance(agent_cfg, dict):
+        agent_cfg = {}
+        config["agent"] = agent_cfg
+    agent_cfg["reasoning_effort"] = effort
+
+
+def _setup_copilot_reasoning_selection(
+    config: Dict[str, Any],
+    model_id: str,
+    prompt_choice,
+    *,
+    catalog: Optional[list[dict[str, Any]]] = None,
+    api_key: str = "",
+) -> None:
+    from hermes_cli.models import github_model_reasoning_efforts, normalize_copilot_model_id
+
+    normalized_model = normalize_copilot_model_id(
+        model_id,
+        catalog=catalog,
+        api_key=api_key,
+    ) or model_id
+    efforts = github_model_reasoning_efforts(normalized_model, catalog=catalog, api_key=api_key)
+    if not efforts:
+        return
+
+    current_effort = _current_reasoning_effort(config)
+    choices = list(efforts) + ["Disable reasoning", f"Keep current ({current_effort or 'default'})"]
+
+    if current_effort == "none":
+        default_idx = len(efforts)
+    elif current_effort in efforts:
+        default_idx = efforts.index(current_effort)
+    elif "medium" in efforts:
+        default_idx = efforts.index("medium")
+    else:
+        default_idx = len(choices) - 1
+
+    effort_idx = prompt_choice("Select reasoning effort:", choices, default_idx)
+    if effort_idx < len(efforts):
+        _set_reasoning_effort(config, efforts[effort_idx])
+    elif effort_idx == len(efforts):
+        _set_reasoning_effort(config, "none")
+
+
 def _setup_provider_model_selection(config, provider_id, current_model, prompt_choice, prompt_fn):
     """Model selection for API-key providers with live /models detection.
 
@@ -71,29 +143,60 @@ def _setup_provider_model_selection(config, provider_id, current_model, prompt_c
     hardcoded default list with a warning if the endpoint is unreachable.
     Always offers a 'Custom model' escape hatch.
     """
-    from hermes_cli.auth import PROVIDER_REGISTRY
+    from hermes_cli.auth import PROVIDER_REGISTRY, resolve_api_key_provider_credentials
     from hermes_cli.config import get_env_value
-    from hermes_cli.models import fetch_api_models
+    from hermes_cli.models import (
+        copilot_model_api_mode,
+        fetch_api_models,
+        fetch_github_model_catalog,
+        normalize_copilot_model_id,
+    )
 
     pconfig = PROVIDER_REGISTRY[provider_id]
+    is_copilot_catalog_provider = provider_id in {"copilot", "copilot-acp"}
 
     # Resolve API key and base URL for the probe
-    api_key = ""
-    for ev in pconfig.api_key_env_vars:
-        api_key = get_env_value(ev) or os.getenv(ev, "")
-        if api_key:
-            break
-    base_url_env = pconfig.base_url_env_var or ""
-    base_url = (get_env_value(base_url_env) if base_url_env else "") or pconfig.inference_base_url
+    if is_copilot_catalog_provider:
+        api_key = ""
+        if provider_id == "copilot":
+            creds = resolve_api_key_provider_credentials(provider_id)
+            api_key = creds.get("api_key", "")
+            base_url = creds.get("base_url", "") or pconfig.inference_base_url
+        else:
+            try:
+                creds = resolve_api_key_provider_credentials("copilot")
+                api_key = creds.get("api_key", "")
+            except Exception:
+                pass
+            base_url = pconfig.inference_base_url
+        catalog = fetch_github_model_catalog(api_key)
+        current_model = normalize_copilot_model_id(
+            current_model,
+            catalog=catalog,
+            api_key=api_key,
+        ) or current_model
+    else:
+        api_key = ""
+        for ev in pconfig.api_key_env_vars:
+            api_key = get_env_value(ev) or os.getenv(ev, "")
+            if api_key:
+                break
+        base_url_env = pconfig.base_url_env_var or ""
+        base_url = (get_env_value(base_url_env) if base_url_env else "") or pconfig.inference_base_url
+        catalog = None
 
     # Try live /models endpoint
-    live_models = fetch_api_models(api_key, base_url)
+    if is_copilot_catalog_provider and catalog:
+        live_models = [item.get("id", "") for item in catalog if item.get("id")]
+    else:
+        live_models = fetch_api_models(api_key, base_url)
 
     if live_models:
         provider_models = live_models
         print_info(f"Found {len(live_models)} model(s) from {pconfig.name} API")
     else:
-        provider_models = _DEFAULT_PROVIDER_MODELS.get(provider_id, [])
+        fallback_provider_id = "copilot" if provider_id == "copilot-acp" else provider_id
+        provider_models = _DEFAULT_PROVIDER_MODELS.get(fallback_provider_id, [])
         if provider_models:
             print_warning(
                 f"Could not auto-detect models from {pconfig.name} API — showing defaults.\n"
@@ -107,12 +210,29 @@ def _setup_provider_model_selection(config, provider_id, current_model, prompt_c
     keep_idx = len(model_choices) - 1
     model_idx = prompt_choice("Select default model:", model_choices, keep_idx)
 
+    selected_model = current_model
+
     if model_idx < len(provider_models):
-        _set_default_model(config, provider_models[model_idx])
+        selected_model = provider_models[model_idx]
+        if is_copilot_catalog_provider:
+            selected_model = normalize_copilot_model_id(
+                selected_model,
+                catalog=catalog,
+                api_key=api_key,
+            ) or selected_model
+        _set_default_model(config, selected_model)
     elif model_idx == len(provider_models):
         custom = prompt_fn("Enter model name")
         if custom:
-            _set_default_model(config, custom)
+            if is_copilot_catalog_provider:
+                selected_model = normalize_copilot_model_id(
+                    custom,
+                    catalog=catalog,
+                    api_key=api_key,
+                ) or custom
+            else:
+                selected_model = custom
+            _set_default_model(config, selected_model)
     else:
         # "Keep current" selected — validate it's compatible with the new
         # provider.  OpenRouter-formatted names (containing "/") won't work
@@ -123,8 +243,25 @@ def _setup_provider_model_selection(config, provider_id, current_model, prompt_c
                 f"and won't work with {pconfig.name}. "
                 f"Switching to {provider_models[0]}."
             )
+            selected_model = provider_models[0]
             _set_default_model(config, provider_models[0])
 
+    if provider_id == "copilot" and selected_model:
+        model_cfg = _model_config_dict(config)
+        model_cfg["api_mode"] = copilot_model_api_mode(
+            selected_model,
+            catalog=catalog,
+            api_key=api_key,
+        )
+        config["model"] = model_cfg
+        _setup_copilot_reasoning_selection(
+            config,
+            selected_model,
+            prompt_choice,
+            catalog=catalog,
+            api_key=api_key,
+        )
+
 
 def _sync_model_from_disk(config: Dict[str, Any]) -> None:
     disk_model = load_config().get("model")
@@ -673,6 +810,8 @@ def setup_model_provider(config: dict):
         resolve_codex_runtime_credentials,
         DEFAULT_CODEX_BASE_URL,
         detect_external_credentials,
+        get_auth_status,
+        resolve_api_key_provider_credentials,
     )
 
     print_header("Inference Provider")
@@ -682,6 +821,8 @@ def setup_model_provider(config: dict):
     existing_or = get_env_value("OPENROUTER_API_KEY")
     active_oauth = get_active_provider()
     existing_custom = get_env_value("OPENAI_BASE_URL")
+    copilot_status = get_auth_status("copilot")
+    copilot_acp_status = get_auth_status("copilot-acp")
 
     model_cfg = config.get("model") if isinstance(config.get("model"), dict) else {}
     current_config_provider = str(model_cfg.get("provider") or "").strip().lower() or None
@@ -702,7 +843,12 @@ def setup_model_provider(config: dict):
 
     # Detect if any provider is already configured
     has_any_provider = bool(
-        current_config_provider or active_oauth or existing_custom or existing_or
+        current_config_provider
+        or active_oauth
+        or existing_custom
+        or existing_or
+        or copilot_status.get("logged_in")
+        or copilot_acp_status.get("logged_in")
     )
 
     # Build "keep current" label
@@ -741,6 +887,8 @@ def setup_model_provider(config: dict):
         "Alibaba Cloud / DashScope (Qwen models via Anthropic-compatible API)",
         "OpenCode Zen (35+ curated models, pay-as-you-go)",
         "OpenCode Go (open models, $10/month subscription)",
+        "GitHub Copilot (uses GITHUB_TOKEN or gh auth token)",
+        "GitHub Copilot ACP (spawns `copilot --acp --stdio`)",
     ]
     if keep_label:
         provider_choices.append(keep_label)
@@ -1412,7 +1560,56 @@ def setup_model_provider(config: dict):
         _set_model_provider(config, "opencode-go", pconfig.inference_base_url)
         selected_base_url = pconfig.inference_base_url
 
-    # else: provider_idx == 14 (Keep current) — only shown when a provider already exists
+    elif provider_idx == 14:  # GitHub Copilot
+        selected_provider = "copilot"
+        print()
+        print_header("GitHub Copilot")
+        pconfig = PROVIDER_REGISTRY["copilot"]
+        print_info("Hermes can use GITHUB_TOKEN, GH_TOKEN, or your gh CLI login.")
+        print_info(f"Base URL: {pconfig.inference_base_url}")
+        print()
+
+        copilot_creds = resolve_api_key_provider_credentials("copilot")
+        source = copilot_creds.get("source", "")
+        token = copilot_creds.get("api_key", "")
+        if token:
+            if source in ("GITHUB_TOKEN", "GH_TOKEN"):
+                print_info(f"Current: {token[:8]}... ({source})")
+            elif source == "gh auth token":
+                print_info("Current: authenticated via `gh auth token`")
+            else:
+                print_info("Current: GitHub token configured")
+        else:
+            api_key = prompt("  GitHub token", password=True)
+            if api_key:
+                save_env_value("GITHUB_TOKEN", api_key)
+                print_success("GitHub token saved")
+            else:
+                print_warning("Skipped - agent won't work without a GitHub token or gh auth login")
+
+        if existing_custom:
+            save_env_value("OPENAI_BASE_URL", "")
+            save_env_value("OPENAI_API_KEY", "")
+        _set_model_provider(config, "copilot", pconfig.inference_base_url)
+        selected_base_url = pconfig.inference_base_url
+
+    elif provider_idx == 15:  # GitHub Copilot ACP
+        selected_provider = "copilot-acp"
+        print()
+        print_header("GitHub Copilot ACP")
+        pconfig = PROVIDER_REGISTRY["copilot-acp"]
+        print_info("Hermes will start `copilot --acp --stdio` for each request.")
+        print_info("Use HERMES_COPILOT_ACP_COMMAND or COPILOT_CLI_PATH to override the command.")
+        print_info(f"Base marker: {pconfig.inference_base_url}")
+        print()
+
+        if existing_custom:
+            save_env_value("OPENAI_BASE_URL", "")
+            save_env_value("OPENAI_API_KEY", "")
+        _set_model_provider(config, "copilot-acp", pconfig.inference_base_url)
+        selected_base_url = pconfig.inference_base_url
+
+    # else: provider_idx == 16 (Keep current) — only shown when a provider already exists
     # Normalize "keep current" to an explicit provider so downstream logic
     # doesn't fall back to the generic OpenRouter/static-model path.
     if selected_provider is None:
@@ -1444,6 +1641,8 @@ def setup_model_provider(config: dict):
     if _vision_needs_setup:
         _prov_names = {
             "nous-api": "Nous Portal API key",
+            "copilot": "GitHub Copilot",
+            "copilot-acp": "GitHub Copilot ACP",
             "zai": "Z.AI / GLM",
             "kimi-coding": "Kimi / Moonshot",
             "minimax": "MiniMax",
@@ -1583,7 +1782,15 @@ def setup_model_provider(config: dict):
                     _set_default_model(config, custom)
             _update_config_for_provider("openai-codex", DEFAULT_CODEX_BASE_URL)
             _set_model_provider(config, "openai-codex", DEFAULT_CODEX_BASE_URL)
-        elif selected_provider in ("zai", "kimi-coding", "minimax", "minimax-cn", "kilocode", "ai-gateway"):
+        elif selected_provider == "copilot-acp":
+            _setup_provider_model_selection(
+                config, selected_provider, current_model,
+                prompt_choice, prompt,
+            )
+            model_cfg = _model_config_dict(config)
+            model_cfg["api_mode"] = "chat_completions"
+            config["model"] = model_cfg
+        elif selected_provider in ("copilot", "zai", "kimi-coding", "minimax", "minimax-cn", "kilocode", "ai-gateway"):
             _setup_provider_model_selection(
                 config, selected_provider, current_model,
                 prompt_choice, prompt,
@@ -1644,7 +1851,7 @@ def setup_model_provider(config: dict):
     # Write provider+base_url to config.yaml only after model selection is complete.
     # This prevents a race condition where the gateway picks up a new provider
     # before the model name has been updated to match.
-    if selected_provider in ("zai", "kimi-coding", "minimax", "minimax-cn", "kilocode", "anthropic") and selected_base_url is not None:
+    if selected_provider in ("copilot-acp", "copilot", "zai", "kimi-coding", "minimax", "minimax-cn", "kilocode", "anthropic") and selected_base_url is not None:
         _update_config_for_provider(selected_provider, selected_base_url)
 
     save_config(config)
diff --git a/pyproject.toml b/pyproject.toml
index 7e92f9078..79b8cdb95 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "hermes-agent"
-version = "0.3.0"
+version = "0.4.0"
 description = "The self-improving AI agent — creates skills from experience, improves them during use, and runs anywhere"
 readme = "README.md"
 requires-python = ">=3.11"
diff --git a/run_agent.py b/run_agent.py
index 210ab2d2b..348ec60d9 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -274,6 +274,10 @@ class AIAgent:
         api_key: str = None,
         provider: str = None,
         api_mode: str = None,
+        acp_command: str = None,
+        acp_args: list[str] | None = None,
+        command: str = None,
+        args: list[str] | None = None,
         model: str = "anthropic/claude-opus-4.6",  # OpenRouter format
         max_iterations: int = 90,  # Default tool-calling iterations (shared with subagents)
         tool_delay: float = 1.0,
@@ -379,6 +383,8 @@ class AIAgent:
         self.base_url = base_url or OPENROUTER_BASE_URL
         provider_name = provider.strip().lower() if isinstance(provider, str) and provider.strip() else None
         self.provider = provider_name or "openrouter"
+        self.acp_command = acp_command or command
+        self.acp_args = list(acp_args or args or [])
         if api_mode in {"chat_completions", "codex_responses", "anthropic_messages"}:
             self.api_mode = api_mode
         elif self.provider == "openai-codex":
@@ -572,6 +578,9 @@ class AIAgent:
                 # Explicit credentials from CLI/gateway — construct directly.
                 # The runtime provider resolver already handled auth for us.
                 client_kwargs = {"api_key": api_key, "base_url": base_url}
+                if self.provider == "copilot-acp":
+                    client_kwargs["command"] = self.acp_command
+                    client_kwargs["args"] = self.acp_args
                 effective_base = base_url
                 if "openrouter" in effective_base.lower():
                     client_kwargs["default_headers"] = {
@@ -579,6 +588,10 @@ class AIAgent:
                         "X-OpenRouter-Title": "Hermes Agent",
                         "X-OpenRouter-Categories": "productivity,cli-agent",
                     }
+                elif "api.githubcopilot.com" in effective_base.lower():
+                    from hermes_cli.models import copilot_default_headers
+
+                    client_kwargs["default_headers"] = copilot_default_headers()
                 elif "api.kimi.com" in effective_base.lower():
                     client_kwargs["default_headers"] = {
                         "User-Agent": "KimiCLI/1.3",
@@ -2685,10 +2698,23 @@ class AIAgent:
 
         if isinstance(client, Mock):
             return False
+        if bool(getattr(client, "is_closed", False)):
+            return True
         http_client = getattr(client, "_client", None)
         return bool(getattr(http_client, "is_closed", False))
 
     def _create_openai_client(self, client_kwargs: dict, *, reason: str, shared: bool) -> Any:
+        if self.provider == "copilot-acp" or str(client_kwargs.get("base_url", "")).startswith("acp://copilot"):
+            from agent.copilot_acp_client import CopilotACPClient
+
+            client = CopilotACPClient(**client_kwargs)
+            logger.info(
+                "Copilot ACP client created (%s, shared=%s) %s",
+                reason,
+                shared,
+                self._client_log_context(),
+            )
+            return client
         client = OpenAI(**client_kwargs)
         logger.info(
             "OpenAI client created (%s, shared=%s) %s",
@@ -3544,6 +3570,11 @@ class AIAgent:
             if not instructions:
                 instructions = DEFAULT_AGENT_IDENTITY
 
+            is_github_responses = (
+                "models.github.ai" in self.base_url.lower()
+                or "api.githubcopilot.com" in self.base_url.lower()
+            )
+
             # Resolve reasoning effort: config > default (medium)
             reasoning_effort = "medium"
             reasoning_enabled = True
@@ -3561,13 +3592,23 @@ class AIAgent:
                 "tool_choice": "auto",
                 "parallel_tool_calls": True,
                 "store": False,
-                "prompt_cache_key": self.session_id,
             }
 
+            if not is_github_responses:
+                kwargs["prompt_cache_key"] = self.session_id
+
             if reasoning_enabled:
-                kwargs["reasoning"] = {"effort": reasoning_effort, "summary": "auto"}
-                kwargs["include"] = ["reasoning.encrypted_content"]
-            else:
+                if is_github_responses:
+                    # Copilot's Responses route advertises reasoning-effort support,
+                    # but not OpenAI-specific prompt cache or encrypted reasoning
+                    # fields. Keep the payload to the documented subset.
+                    github_reasoning = self._github_models_reasoning_extra_body()
+                    if github_reasoning is not None:
+                        kwargs["reasoning"] = github_reasoning
+                else:
+                    kwargs["reasoning"] = {"effort": reasoning_effort, "summary": "auto"}
+                    kwargs["include"] = ["reasoning.encrypted_content"]
+            elif not is_github_responses:
                 kwargs["include"] = []
 
             if self.max_tokens is not None:
@@ -3638,6 +3679,10 @@ class AIAgent:
         extra_body = {}
 
         _is_openrouter = "openrouter" in self.base_url.lower()
+        _is_github_models = (
+            "models.github.ai" in self.base_url.lower()
+            or "api.githubcopilot.com" in self.base_url.lower()
+        )
 
         # Provider preferences (only, ignore, order, sort) are OpenRouter-
         # specific.  Only send to OpenRouter-compatible endpoints.
@@ -3648,19 +3693,24 @@ class AIAgent:
         _is_nous = "nousresearch" in self.base_url.lower()
 
         if self._supports_reasoning_extra_body():
-            if self.reasoning_config is not None:
-                rc = dict(self.reasoning_config)
-                # Nous Portal requires reasoning enabled — don't send
-                # enabled=false to it (would cause 400).
-                if _is_nous and rc.get("enabled") is False:
-                    pass  # omit reasoning entirely for Nous when disabled
-                else:
-                    extra_body["reasoning"] = rc
+            if _is_github_models:
+                github_reasoning = self._github_models_reasoning_extra_body()
+                if github_reasoning is not None:
+                    extra_body["reasoning"] = github_reasoning
             else:
-                extra_body["reasoning"] = {
-                    "enabled": True,
-                    "effort": "medium"
-                }
+                if self.reasoning_config is not None:
+                    rc = dict(self.reasoning_config)
+                    # Nous Portal requires reasoning enabled — don't send
+                    # enabled=false to it (would cause 400).
+                    if _is_nous and rc.get("enabled") is False:
+                        pass  # omit reasoning entirely for Nous when disabled
+                    else:
+                        extra_body["reasoning"] = rc
+                else:
+                    extra_body["reasoning"] = {
+                        "enabled": True,
+                        "effort": "medium"
+                    }
 
         # Nous Portal product attribution
         if _is_nous:
@@ -3683,6 +3733,13 @@ class AIAgent:
             return True
         if "ai-gateway.vercel.sh" in base_url:
             return True
+        if "models.github.ai" in base_url or "api.githubcopilot.com" in base_url:
+            try:
+                from hermes_cli.models import github_model_reasoning_efforts
+
+                return bool(github_model_reasoning_efforts(self.model))
+            except Exception:
+                return False
         if "openrouter" not in base_url:
             return False
         if "api.mistral.ai" in base_url:
@@ -3699,6 +3756,38 @@ class AIAgent:
         )
         return any(model.startswith(prefix) for prefix in reasoning_model_prefixes)
 
+    def _github_models_reasoning_extra_body(self) -> dict | None:
+        """Format reasoning payload for GitHub Models/OpenAI-compatible routes."""
+        try:
+            from hermes_cli.models import github_model_reasoning_efforts
+        except Exception:
+            return None
+
+        supported_efforts = github_model_reasoning_efforts(self.model)
+        if not supported_efforts:
+            return None
+
+        if self.reasoning_config and isinstance(self.reasoning_config, dict):
+            if self.reasoning_config.get("enabled") is False:
+                return None
+            requested_effort = str(
+                self.reasoning_config.get("effort", "medium")
+            ).strip().lower()
+        else:
+            requested_effort = "medium"
+
+        if requested_effort == "xhigh" and "high" in supported_efforts:
+            requested_effort = "high"
+        elif requested_effort not in supported_efforts:
+            if requested_effort == "minimal" and "low" in supported_efforts:
+                requested_effort = "low"
+            elif "medium" in supported_efforts:
+                requested_effort = "medium"
+            else:
+                requested_effort = supported_efforts[0]
+
+        return {"effort": requested_effort}
+
     def _build_assistant_message(self, assistant_message, finish_reason: str) -> dict:
         """Build a normalized assistant message dict from an API response message.
 
diff --git a/tests/agent/test_auxiliary_client.py b/tests/agent/test_auxiliary_client.py
index 760fd5845..0a396944a 100644
--- a/tests/agent/test_auxiliary_client.py
+++ b/tests/agent/test_auxiliary_client.py
@@ -248,6 +248,31 @@ class TestVisionClientFallback:
         assert client.__class__.__name__ == "AnthropicAuxiliaryClient"
         assert model == "claude-haiku-4-5-20251001"
 
+    def test_resolve_provider_client_copilot_uses_runtime_credentials(self, monkeypatch):
+        monkeypatch.delenv("GITHUB_TOKEN", raising=False)
+        monkeypatch.delenv("GH_TOKEN", raising=False)
+
+        with (
+            patch(
+                "hermes_cli.auth.resolve_api_key_provider_credentials",
+                return_value={
+                    "provider": "copilot",
+                    "api_key": "gh-cli-token",
+                    "base_url": "https://api.githubcopilot.com",
+                    "source": "gh auth token",
+                },
+            ),
+            patch("agent.auxiliary_client.OpenAI") as mock_openai,
+        ):
+            client, model = resolve_provider_client("copilot", model="gpt-5.4")
+
+        assert client is not None
+        assert model == "gpt-5.4"
+        call_kwargs = mock_openai.call_args.kwargs
+        assert call_kwargs["api_key"] == "gh-cli-token"
+        assert call_kwargs["base_url"] == "https://api.githubcopilot.com"
+        assert call_kwargs["default_headers"]["Editor-Version"]
+
     def test_vision_auto_uses_anthropic_when_no_higher_priority_backend(self, monkeypatch):
         monkeypatch.setenv("ANTHROPIC_API_KEY", "sk-ant-api03-key")
         with (
diff --git a/tests/hermes_cli/test_model_validation.py b/tests/hermes_cli/test_model_validation.py
index 59574c743..5f26e401f 100644
--- a/tests/hermes_cli/test_model_validation.py
+++ b/tests/hermes_cli/test_model_validation.py
@@ -3,8 +3,12 @@
 from unittest.mock import patch
 
 from hermes_cli.models import (
+    copilot_model_api_mode,
+    fetch_github_model_catalog,
     curated_models_for_provider,
     fetch_api_models,
+    github_model_reasoning_efforts,
+    normalize_copilot_model_id,
     normalize_provider,
     parse_model_input,
     probe_api_models,
@@ -116,6 +120,7 @@ class TestNormalizeProvider:
         assert normalize_provider("glm") == "zai"
         assert normalize_provider("kimi") == "kimi-coding"
         assert normalize_provider("moonshot") == "kimi-coding"
+        assert normalize_provider("github-copilot") == "copilot"
 
     def test_case_insensitive(self):
         assert normalize_provider("OpenRouter") == "openrouter"
@@ -125,6 +130,8 @@ class TestProviderLabel:
     def test_known_labels_and_auto(self):
         assert provider_label("anthropic") == "Anthropic"
         assert provider_label("kimi") == "Kimi / Moonshot"
+        assert provider_label("copilot") == "GitHub Copilot"
+        assert provider_label("copilot-acp") == "GitHub Copilot ACP"
         assert provider_label("auto") == "Auto"
 
     def test_unknown_provider_preserves_original_name(self):
@@ -145,6 +152,24 @@ class TestProviderModelIds:
     def test_zai_returns_glm_models(self):
         assert "glm-5" in provider_model_ids("zai")
 
+    def test_copilot_prefers_live_catalog(self):
+        with patch("hermes_cli.auth.resolve_api_key_provider_credentials", return_value={"api_key": "gh-token"}), \
+             patch("hermes_cli.models._fetch_github_models", return_value=["gpt-5.4", "claude-sonnet-4.6"]):
+            assert provider_model_ids("copilot") == ["gpt-5.4", "claude-sonnet-4.6"]
+
+    def test_copilot_acp_reuses_copilot_catalog(self):
+        with patch("hermes_cli.auth.resolve_api_key_provider_credentials", return_value={"api_key": "gh-token"}), \
+             patch("hermes_cli.models._fetch_github_models", return_value=["gpt-5.4", "claude-sonnet-4.6"]):
+            assert provider_model_ids("copilot-acp") == ["gpt-5.4", "claude-sonnet-4.6"]
+
+    def test_copilot_acp_falls_back_to_copilot_defaults(self):
+        with patch("hermes_cli.auth.resolve_api_key_provider_credentials", side_effect=Exception("no token")), \
+             patch("hermes_cli.models._fetch_github_models", return_value=None):
+            ids = provider_model_ids("copilot-acp")
+
+        assert "gpt-5.4" in ids
+        assert "copilot-acp" not in ids
+
 
 # -- fetch_api_models --------------------------------------------------------
 
@@ -183,6 +208,82 @@ class TestFetchApiModels:
         assert probe["resolved_base_url"] == "http://localhost:8000/v1"
         assert probe["used_fallback"] is True
 
+    def test_probe_api_models_uses_copilot_catalog(self):
+        class _Resp:
+            def __enter__(self):
+                return self
+
+            def __exit__(self, exc_type, exc, tb):
+                return False
+
+            def read(self):
+                return b'{"data": [{"id": "gpt-5.4", "model_picker_enabled": true, "supported_endpoints": ["/responses"], "capabilities": {"type": "chat", "supports": {"reasoning_effort": ["low", "medium", "high"]}}}, {"id": "claude-sonnet-4.6", "model_picker_enabled": true, "supported_endpoints": ["/chat/completions"], "capabilities": {"type": "chat", "supports": {"reasoning_effort": ["low", "medium", "high"]}}}, {"id": "text-embedding-3-small", "model_picker_enabled": true, "capabilities": {"type": "embedding"}}]}'
+
+        with patch("hermes_cli.models.urllib.request.urlopen", return_value=_Resp()) as mock_urlopen:
+            probe = probe_api_models("gh-token", "https://api.githubcopilot.com")
+
+        assert mock_urlopen.call_args[0][0].full_url == "https://api.githubcopilot.com/models"
+        assert probe["models"] == ["gpt-5.4", "claude-sonnet-4.6"]
+        assert probe["resolved_base_url"] == "https://api.githubcopilot.com"
+        assert probe["used_fallback"] is False
+
+    def test_fetch_github_model_catalog_filters_non_chat_models(self):
+        class _Resp:
+            def __enter__(self):
+                return self
+
+            def __exit__(self, exc_type, exc, tb):
+                return False
+
+            def read(self):
+                return b'{"data": [{"id": "gpt-5.4", "model_picker_enabled": true, "supported_endpoints": ["/responses"], "capabilities": {"type": "chat", "supports": {"reasoning_effort": ["low", "medium", "high"]}}}, {"id": "text-embedding-3-small", "model_picker_enabled": true, "capabilities": {"type": "embedding"}}]}'
+
+        with patch("hermes_cli.models.urllib.request.urlopen", return_value=_Resp()):
+            catalog = fetch_github_model_catalog("gh-token")
+
+        assert catalog is not None
+        assert [item["id"] for item in catalog] == ["gpt-5.4"]
+
+
+class TestGithubReasoningEfforts:
+    def test_gpt5_supports_minimal_to_high(self):
+        catalog = [{
+            "id": "gpt-5.4",
+            "capabilities": {"type": "chat", "supports": {"reasoning_effort": ["low", "medium", "high"]}},
+            "supported_endpoints": ["/responses"],
+        }]
+        assert github_model_reasoning_efforts("gpt-5.4", catalog=catalog) == [
+            "low",
+            "medium",
+            "high",
+        ]
+
+    def test_legacy_catalog_reasoning_still_supported(self):
+        catalog = [{"id": "openai/o3", "capabilities": ["reasoning"]}]
+        assert github_model_reasoning_efforts("openai/o3", catalog=catalog) == [
+            "low",
+            "medium",
+            "high",
+        ]
+
+    def test_non_reasoning_model_returns_empty(self):
+        catalog = [{"id": "gpt-4.1", "capabilities": {"type": "chat", "supports": {}}}]
+        assert github_model_reasoning_efforts("gpt-4.1", catalog=catalog) == []
+
+
+class TestCopilotNormalization:
+    def test_normalize_old_github_models_slug(self):
+        catalog = [{"id": "gpt-4.1"}, {"id": "gpt-5.4"}]
+        assert normalize_copilot_model_id("openai/gpt-4.1-mini", catalog=catalog) == "gpt-4.1"
+
+    def test_copilot_api_mode_prefers_responses(self):
+        catalog = [{
+            "id": "gpt-5.4",
+            "supported_endpoints": ["/responses"],
+            "capabilities": {"type": "chat"},
+        }]
+        assert copilot_model_api_mode("gpt-5.4", catalog=catalog) == "codex_responses"
+
 
 # -- validate — format checks -----------------------------------------------
 
diff --git a/tests/hermes_cli/test_setup_model_provider.py b/tests/hermes_cli/test_setup_model_provider.py
index 671bb9ba3..228d15240 100644
--- a/tests/hermes_cli/test_setup_model_provider.py
+++ b/tests/hermes_cli/test_setup_model_provider.py
@@ -32,6 +32,8 @@ def _clear_provider_env(monkeypatch):
         "OPENAI_BASE_URL",
         "OPENAI_API_KEY",
         "OPENROUTER_API_KEY",
+        "GITHUB_TOKEN",
+        "GH_TOKEN",
         "GLM_API_KEY",
         "KIMI_API_KEY",
         "MINIMAX_API_KEY",
@@ -231,6 +233,152 @@ def test_setup_keep_current_anthropic_can_configure_openai_vision_default(tmp_pa
     assert env.get("AUXILIARY_VISION_MODEL") == "gpt-4o-mini"
 
 
+def test_setup_copilot_uses_gh_auth_and_saves_provider(tmp_path, monkeypatch):
+    monkeypatch.setenv("HERMES_HOME", str(tmp_path))
+    _clear_provider_env(monkeypatch)
+
+    config = load_config()
+
+    def fake_prompt_choice(question, choices, default=0):
+        if question == "Select your inference provider:":
+            assert choices[14] == "GitHub Copilot (uses GITHUB_TOKEN or gh auth token)"
+            return 14
+        if question == "Select default model:":
+            assert "gpt-4.1" in choices
+            assert "gpt-5.4" in choices
+            return choices.index("gpt-5.4")
+        if question == "Select reasoning effort:":
+            assert "low" in choices
+            assert "high" in choices
+            return choices.index("high")
+        if question == "Configure vision:":
+            return len(choices) - 1
+        tts_idx = _maybe_keep_current_tts(question, choices)
+        if tts_idx is not None:
+            return tts_idx
+        raise AssertionError(f"Unexpected prompt_choice call: {question}")
+
+    def fake_prompt(message, *args, **kwargs):
+        raise AssertionError(f"Unexpected prompt call: {message}")
+
+    def fake_get_auth_status(provider_id):
+        if provider_id == "copilot":
+            return {"logged_in": True}
+        return {"logged_in": False}
+
+    monkeypatch.setattr("hermes_cli.setup.prompt_choice", fake_prompt_choice)
+    monkeypatch.setattr("hermes_cli.setup.prompt", fake_prompt)
+    monkeypatch.setattr("hermes_cli.setup.prompt_yes_no", lambda *args, **kwargs: False)
+    monkeypatch.setattr("hermes_cli.auth.get_active_provider", lambda: None)
+    monkeypatch.setattr("hermes_cli.auth.detect_external_credentials", lambda: [])
+    monkeypatch.setattr("hermes_cli.auth.get_auth_status", fake_get_auth_status)
+    monkeypatch.setattr(
+        "hermes_cli.auth.resolve_api_key_provider_credentials",
+        lambda provider_id: {
+            "provider": provider_id,
+            "api_key": "gh-cli-token",
+            "base_url": "https://api.githubcopilot.com",
+            "source": "gh auth token",
+        },
+    )
+    monkeypatch.setattr(
+        "hermes_cli.models.fetch_github_model_catalog",
+        lambda api_key: [
+            {
+                "id": "gpt-4.1",
+                "capabilities": {"type": "chat", "supports": {}},
+                "supported_endpoints": ["/chat/completions"],
+            },
+            {
+                "id": "gpt-5.4",
+                "capabilities": {"type": "chat", "supports": {"reasoning_effort": ["low", "medium", "high"]}},
+                "supported_endpoints": ["/responses"],
+            },
+        ],
+    )
+    monkeypatch.setattr("agent.auxiliary_client.get_available_vision_backends", lambda: [])
+
+    setup_model_provider(config)
+    save_config(config)
+
+    env = _read_env(tmp_path)
+    reloaded = load_config()
+
+    assert env.get("GITHUB_TOKEN") is None
+    assert reloaded["model"]["provider"] == "copilot"
+    assert reloaded["model"]["base_url"] == "https://api.githubcopilot.com"
+    assert reloaded["model"]["default"] == "gpt-5.4"
+    assert reloaded["model"]["api_mode"] == "codex_responses"
+    assert reloaded["agent"]["reasoning_effort"] == "high"
+
+
+def test_setup_copilot_acp_uses_model_picker_and_saves_provider(tmp_path, monkeypatch):
+    monkeypatch.setenv("HERMES_HOME", str(tmp_path))
+    _clear_provider_env(monkeypatch)
+
+    config = load_config()
+
+    def fake_prompt_choice(question, choices, default=0):
+        if question == "Select your inference provider:":
+            assert choices[15] == "GitHub Copilot ACP (spawns `copilot --acp --stdio`)"
+            return 15
+        if question == "Select default model:":
+            assert "gpt-4.1" in choices
+            assert "gpt-5.4" in choices
+            return choices.index("gpt-5.4")
+        if question == "Configure vision:":
+            return len(choices) - 1
+        tts_idx = _maybe_keep_current_tts(question, choices)
+        if tts_idx is not None:
+            return tts_idx
+        raise AssertionError(f"Unexpected prompt_choice call: {question}")
+
+    def fake_prompt(message, *args, **kwargs):
+        raise AssertionError(f"Unexpected prompt call: {message}")
+
+    monkeypatch.setattr("hermes_cli.setup.prompt_choice", fake_prompt_choice)
+    monkeypatch.setattr("hermes_cli.setup.prompt", fake_prompt)
+    monkeypatch.setattr("hermes_cli.setup.prompt_yes_no", lambda *args, **kwargs: False)
+    monkeypatch.setattr("hermes_cli.auth.get_active_provider", lambda: None)
+    monkeypatch.setattr("hermes_cli.auth.detect_external_credentials", lambda: [])
+    monkeypatch.setattr("hermes_cli.auth.get_auth_status", lambda provider_id: {"logged_in": provider_id == "copilot-acp"})
+    monkeypatch.setattr(
+        "hermes_cli.auth.resolve_api_key_provider_credentials",
+        lambda provider_id: {
+            "provider": "copilot",
+            "api_key": "gh-cli-token",
+            "base_url": "https://api.githubcopilot.com",
+            "source": "gh auth token",
+        },
+    )
+    monkeypatch.setattr(
+        "hermes_cli.models.fetch_github_model_catalog",
+        lambda api_key: [
+            {
+                "id": "gpt-4.1",
+                "capabilities": {"type": "chat", "supports": {}},
+                "supported_endpoints": ["/chat/completions"],
+            },
+            {
+                "id": "gpt-5.4",
+                "capabilities": {"type": "chat", "supports": {"reasoning_effort": ["low", "medium", "high"]}},
+                "supported_endpoints": ["/responses"],
+            },
+        ],
+    )
+    monkeypatch.setattr("agent.auxiliary_client.get_available_vision_backends", lambda: [])
+
+    setup_model_provider(config)
+    save_config(config)
+
+    reloaded = load_config()
+
+    assert reloaded["model"]["provider"] == "copilot-acp"
+    assert reloaded["model"]["base_url"] == "acp://copilot"
+    assert reloaded["model"]["default"] == "gpt-5.4"
+    assert reloaded["model"]["api_mode"] == "chat_completions"
+
+
 def test_setup_switch_custom_to_codex_clears_custom_endpoint_and_updates_config(tmp_path, monkeypatch):
     """Switching from custom to Codex should clear custom endpoint overrides."""
     monkeypatch.setenv("HERMES_HOME", str(tmp_path))
diff --git a/tests/test_api_key_providers.py b/tests/test_api_key_providers.py
index 98f27d103..631a7051c 100644
--- a/tests/test_api_key_providers.py
+++ b/tests/test_api_key_providers.py
@@ -18,9 +18,12 @@ from hermes_cli.auth import (
     resolve_provider,
     get_api_key_provider_status,
     resolve_api_key_provider_credentials,
+    get_external_process_provider_status,
+    resolve_external_process_provider_credentials,
     get_auth_status,
     AuthError,
     KIMI_CODE_BASE_URL,
+    _try_gh_cli_token,
     _resolve_kimi_base_url,
 )
 
@@ -33,6 +36,8 @@ class TestProviderRegistry:
     """Test that new providers are correctly registered."""
 
     @pytest.mark.parametrize("provider_id,name,auth_type", [
+        ("copilot-acp", "GitHub Copilot ACP", "external_process"),
+        ("copilot", "GitHub Copilot", "api_key"),
         ("zai", "Z.AI / GLM", "api_key"),
         ("kimi-coding", "Kimi / Moonshot", "api_key"),
         ("minimax", "MiniMax", "api_key"),
@@ -52,6 +57,11 @@ class TestProviderRegistry:
         assert pconfig.api_key_env_vars == ("GLM_API_KEY", "ZAI_API_KEY", "Z_AI_API_KEY")
         assert pconfig.base_url_env_var == "GLM_BASE_URL"
 
+    def test_copilot_env_vars(self):
+        pconfig = PROVIDER_REGISTRY["copilot"]
+        assert pconfig.api_key_env_vars == ("GITHUB_TOKEN", "GH_TOKEN")
+        assert pconfig.base_url_env_var == ""
+
     def test_kimi_env_vars(self):
         pconfig = PROVIDER_REGISTRY["kimi-coding"]
         assert pconfig.api_key_env_vars == ("KIMI_API_KEY",)
@@ -78,6 +88,8 @@ class TestProviderRegistry:
         assert pconfig.base_url_env_var == "KILOCODE_BASE_URL"
 
     def test_base_urls(self):
+        assert PROVIDER_REGISTRY["copilot"].inference_base_url == "https://api.githubcopilot.com"
+        assert PROVIDER_REGISTRY["copilot-acp"].inference_base_url == "acp://copilot"
         assert PROVIDER_REGISTRY["zai"].inference_base_url == "https://api.z.ai/api/paas/v4"
         assert PROVIDER_REGISTRY["kimi-coding"].inference_base_url == "https://api.moonshot.ai/v1"
         assert PROVIDER_REGISTRY["minimax"].inference_base_url == "https://api.minimax.io/v1"
@@ -105,8 +117,9 @@ PROVIDER_ENV_VARS = (
     "AI_GATEWAY_API_KEY", "AI_GATEWAY_BASE_URL",
     "KILOCODE_API_KEY", "KILOCODE_BASE_URL",
     "DASHSCOPE_API_KEY", "OPENCODE_ZEN_API_KEY", "OPENCODE_GO_API_KEY",
-    "NOUS_API_KEY",
-    "OPENAI_BASE_URL",
+    "NOUS_API_KEY", "GITHUB_TOKEN", "GH_TOKEN",
+    "OPENAI_BASE_URL", "HERMES_COPILOT_ACP_COMMAND", "COPILOT_CLI_PATH",
+    "HERMES_COPILOT_ACP_ARGS", "COPILOT_ACP_BASE_URL",
 )
 
 
@@ -176,6 +189,16 @@ class TestResolveProvider:
         assert resolve_provider("Z-AI") == "zai"
         assert resolve_provider("Kimi") == "kimi-coding"
 
+    def test_alias_github_copilot(self):
+        assert resolve_provider("github-copilot") == "copilot"
+
+    def test_alias_github_models(self):
+        assert resolve_provider("github-models") == "copilot"
+
+    def test_alias_github_copilot_acp(self):
+        assert resolve_provider("github-copilot-acp") == "copilot-acp"
+        assert resolve_provider("copilot-acp-agent") == "copilot-acp"
+
     def test_unknown_provider_raises(self):
         with pytest.raises(AuthError):
             resolve_provider("nonexistent-provider-xyz")
@@ -218,6 +241,10 @@ class TestResolveProvider:
         monkeypatch.setenv("GLM_API_KEY", "glm-key")
         assert resolve_provider("auto") == "openrouter"
 
+    def test_auto_does_not_select_copilot_from_github_token(self, monkeypatch):
+        monkeypatch.setenv("GITHUB_TOKEN", "gh-test-token")
+        assert resolve_provider("auto") == "openrouter"
+
 
 # =============================================================================
 # API Key Provider Status tests
@@ -251,12 +278,41 @@ class TestApiKeyProviderStatus:
         status = get_api_key_provider_status("kimi-coding")
         assert status["base_url"] == "https://custom.kimi.example/v1"
 
+    def test_copilot_status_uses_gh_cli_token(self, monkeypatch):
+        monkeypatch.setattr("hermes_cli.auth._try_gh_cli_token", lambda: "gh-cli-token")
+        status = get_api_key_provider_status("copilot")
+        assert status["configured"] is True
+        assert status["logged_in"] is True
+        assert status["key_source"] == "gh auth token"
+        assert status["base_url"] == "https://api.githubcopilot.com"
+
     def test_get_auth_status_dispatches_to_api_key(self, monkeypatch):
         monkeypatch.setenv("MINIMAX_API_KEY", "mm-key")
         status = get_auth_status("minimax")
         assert status["configured"] is True
         assert status["provider"] == "minimax"
 
+    def test_copilot_acp_status_detects_local_cli(self, monkeypatch):
+        monkeypatch.setenv("HERMES_COPILOT_ACP_ARGS", "--acp --stdio --debug")
+        monkeypatch.setattr("hermes_cli.auth.shutil.which", lambda command: f"/usr/local/bin/{command}")
+
+        status = get_external_process_provider_status("copilot-acp")
+
+        assert status["configured"] is True
+        assert status["logged_in"] is True
+        assert status["command"] == "copilot"
+        assert status["resolved_command"] == "/usr/local/bin/copilot"
+        assert status["args"] == ["--acp", "--stdio", "--debug"]
+        assert status["base_url"] == "acp://copilot"
+
+    def test_get_auth_status_dispatches_to_external_process(self, monkeypatch):
+        monkeypatch.setattr("hermes_cli.auth.shutil.which", lambda command: f"/opt/bin/{command}")
+
+        status = get_auth_status("copilot-acp")
+
+        assert status["configured"] is True
+        assert status["provider"] == "copilot-acp"
+
     def test_non_api_key_provider(self):
         status = get_api_key_provider_status("nous")
         assert status["configured"] is False
@@ -276,6 +332,61 @@ class TestResolveApiKeyProviderCredentials:
         assert creds["base_url"] == "https://api.z.ai/api/paas/v4"
         assert creds["source"] == "GLM_API_KEY"
 
+    def test_resolve_copilot_with_github_token(self, monkeypatch):
+        monkeypatch.setenv("GITHUB_TOKEN", "gh-env-secret")
+        creds = resolve_api_key_provider_credentials("copilot")
+        assert creds["provider"] == "copilot"
+        assert creds["api_key"] == "gh-env-secret"
+        assert creds["base_url"] == "https://api.githubcopilot.com"
+        assert creds["source"] == "GITHUB_TOKEN"
+
+    def test_resolve_copilot_with_gh_cli_fallback(self, monkeypatch):
+        monkeypatch.setattr("hermes_cli.auth._try_gh_cli_token", lambda: "gh-cli-secret")
+        creds = resolve_api_key_provider_credentials("copilot")
+        assert creds["provider"] == "copilot"
+        assert creds["api_key"] == "gh-cli-secret"
+        assert creds["base_url"] == "https://api.githubcopilot.com"
+        assert creds["source"] == "gh auth token"
+
+    def test_try_gh_cli_token_uses_homebrew_path_when_not_on_path(self, monkeypatch):
+        monkeypatch.setattr("hermes_cli.auth.shutil.which", lambda command: None)
+        monkeypatch.setattr(
+            "hermes_cli.auth.os.path.isfile",
+            lambda path: path == "/opt/homebrew/bin/gh",
+        )
+        monkeypatch.setattr(
+            "hermes_cli.auth.os.access",
+            lambda path, mode: path == "/opt/homebrew/bin/gh" and mode == os.X_OK,
+        )
+
+        calls = []
+
+        class _Result:
+            returncode = 0
+            stdout = "gh-cli-secret\n"
+
+        def _fake_run(cmd, capture_output, text, timeout):
+            calls.append(cmd)
+            return _Result()
+
+        monkeypatch.setattr("hermes_cli.auth.subprocess.run", _fake_run)
+
+        assert _try_gh_cli_token() == "gh-cli-secret"
+        assert calls == [["/opt/homebrew/bin/gh", "auth", "token"]]
+
+    def test_resolve_copilot_acp_with_local_cli(self, monkeypatch):
+        monkeypatch.setenv("HERMES_COPILOT_ACP_ARGS", "--acp --stdio")
+        monkeypatch.setattr("hermes_cli.auth.shutil.which", lambda command: f"/usr/local/bin/{command}")
+
+        creds = resolve_external_process_provider_credentials("copilot-acp")
+
+        assert creds["provider"] == "copilot-acp"
+        assert creds["api_key"] == "copilot-acp"
+        assert creds["base_url"] == "acp://copilot"
+        assert creds["command"] == "/usr/local/bin/copilot"
+        assert creds["args"] == ["--acp", "--stdio"]
+        assert creds["source"] == "process"
+
     def test_resolve_kimi_with_key(self, monkeypatch):
         monkeypatch.setenv("KIMI_API_KEY", "kimi-secret-key")
         creds = resolve_api_key_provider_credentials("kimi-coding")
@@ -403,6 +514,53 @@ class TestRuntimeProviderResolution:
         assert result["provider"] == "kimi-coding"
         assert result["api_key"] == "auto-kimi-key"
 
+    def test_runtime_copilot_uses_gh_cli_token(self, monkeypatch):
+        monkeypatch.setattr("hermes_cli.auth._try_gh_cli_token", lambda: "gh-cli-secret")
+        from hermes_cli.runtime_provider import resolve_runtime_provider
+        result = resolve_runtime_provider(requested="copilot")
+        assert result["provider"] == "copilot"
+        assert result["api_mode"] == "chat_completions"
+        assert result["api_key"] == "gh-cli-secret"
+        assert result["base_url"] == "https://api.githubcopilot.com"
+
+    def test_runtime_copilot_uses_responses_for_gpt_5_4(self, monkeypatch):
+        monkeypatch.setattr("hermes_cli.auth._try_gh_cli_token", lambda: "gh-cli-secret")
+        monkeypatch.setattr(
+            "hermes_cli.runtime_provider._get_model_config",
+            lambda: {"provider": "copilot", "default": "gpt-5.4"},
+        )
+        monkeypatch.setattr(
+            "hermes_cli.models.fetch_github_model_catalog",
+            lambda api_key=None, timeout=5.0: [
+                {
+                    "id": "gpt-5.4",
+                    "supported_endpoints": ["/responses"],
+                    "capabilities": {"type": "chat"},
+                }
+            ],
+        )
+        from hermes_cli.runtime_provider import resolve_runtime_provider
+
+        result = resolve_runtime_provider(requested="copilot")
+
+        assert result["provider"] == "copilot"
+        assert result["api_mode"] == "codex_responses"
+
+    def test_runtime_copilot_acp_uses_process_runtime(self, monkeypatch):
+        monkeypatch.setattr("hermes_cli.auth.shutil.which", lambda command: f"/usr/local/bin/{command}")
+        monkeypatch.setenv("HERMES_COPILOT_ACP_ARGS", "--acp --stdio --debug")
+
+        from hermes_cli.runtime_provider import resolve_runtime_provider
+
+        result = resolve_runtime_provider(requested="copilot-acp")
+
+        assert result["provider"] == "copilot-acp"
+        assert result["api_mode"] == "chat_completions"
+        assert result["api_key"] == "copilot-acp"
+        assert result["base_url"] == "acp://copilot"
+        assert result["command"] == "/usr/local/bin/copilot"
+        assert result["args"] == ["--acp", "--stdio", "--debug"]
+
 
 # =============================================================================
 # _has_any_provider_configured tests
@@ -430,6 +588,16 @@ class TestHasAnyProviderConfigured:
         from hermes_cli.main import _has_any_provider_configured
         assert _has_any_provider_configured() is True
 
+    def test_gh_cli_token_counts(self, monkeypatch, tmp_path):
+        from hermes_cli import config as config_module
+        monkeypatch.setattr("hermes_cli.auth._try_gh_cli_token", lambda: "gh-cli-secret")
+        hermes_home = tmp_path / ".hermes"
+        hermes_home.mkdir()
+        monkeypatch.setattr(config_module, "get_env_path", lambda: hermes_home / ".env")
+        monkeypatch.setattr(config_module, "get_hermes_home", lambda: hermes_home)
+        from hermes_cli.main import _has_any_provider_configured
+        assert _has_any_provider_configured() is True
+
 
 # =============================================================================
 # Kimi Code auto-detection tests
diff --git a/tests/test_model_provider_persistence.py b/tests/test_model_provider_persistence.py
index 026715bf2..d408a573a 100644
--- a/tests/test_model_provider_persistence.py
+++ b/tests/test_model_provider_persistence.py
@@ -27,6 +27,8 @@ def config_home(tmp_path, monkeypatch):
     monkeypatch.delenv("HERMES_MODEL", raising=False)
     monkeypatch.delenv("LLM_MODEL", raising=False)
     monkeypatch.delenv("HERMES_INFERENCE_PROVIDER", raising=False)
+    monkeypatch.delenv("GITHUB_TOKEN", raising=False)
+    monkeypatch.delenv("GH_TOKEN", raising=False)
     monkeypatch.delenv("OPENAI_BASE_URL", raising=False)
     monkeypatch.delenv("OPENAI_API_KEY", raising=False)
     monkeypatch.delenv("OPENROUTER_API_KEY", raising=False)
@@ -97,3 +99,114 @@ class TestProviderPersistsAfterModelSave:
             f"provider should be 'kimi-coding', got {model.get('provider')}"
         )
         assert model.get("default") == "kimi-k2.5"
+
+    def test_copilot_provider_saved_when_selected(self, config_home):
+        """_model_flow_copilot should persist provider/base_url/model together."""
+        from hermes_cli.main import _model_flow_copilot
+        from hermes_cli.config import load_config
+
+        with patch(
+            "hermes_cli.auth.resolve_api_key_provider_credentials",
+            return_value={
+                "provider": "copilot",
+                "api_key": "gh-cli-token",
+                "base_url": "https://api.githubcopilot.com",
+                "source": "gh auth token",
+            },
+        ), patch(
+            "hermes_cli.models.fetch_github_model_catalog",
+            return_value=[
+                {
+                    "id": "gpt-4.1",
+                    "capabilities": {"type": "chat", "supports": {}},
+                    "supported_endpoints": ["/chat/completions"],
+                },
+                {
+                    "id": "gpt-5.4",
+                    "capabilities": {"type": "chat", "supports": {"reasoning_effort": ["low", "medium", "high"]}},
+                    "supported_endpoints": ["/responses"],
+                },
+            ],
+        ), patch(
+            "hermes_cli.auth._prompt_model_selection",
+            return_value="gpt-5.4",
+        ), patch(
+            "hermes_cli.main._prompt_reasoning_effort_selection",
+            return_value="high",
+        ), patch(
+            "hermes_cli.auth.deactivate_provider",
+        ):
+            _model_flow_copilot(load_config(), "old-model")
+
+        import yaml
+
+        config = yaml.safe_load((config_home / "config.yaml").read_text()) or {}
+        model = config.get("model")
+        assert isinstance(model, dict), f"model should be dict, got {type(model)}"
+        assert model.get("provider") == "copilot"
+        assert model.get("base_url") == "https://api.githubcopilot.com"
+        assert model.get("default") == "gpt-5.4"
+        assert model.get("api_mode") == "codex_responses"
+        assert config["agent"]["reasoning_effort"] == "high"
+
+    def test_copilot_acp_provider_saved_when_selected(self, config_home):
+        """_model_flow_copilot_acp should persist provider/base_url/model together."""
+        from hermes_cli.main import _model_flow_copilot_acp
+        from hermes_cli.config import load_config
+
+        with patch(
+            "hermes_cli.auth.get_external_process_provider_status",
+            return_value={
+                "resolved_command": "/usr/local/bin/copilot",
+                "command": "copilot",
+                "base_url": "acp://copilot",
+            },
+        ), patch(
+            "hermes_cli.auth.resolve_external_process_provider_credentials",
+            return_value={
+                "provider": "copilot-acp",
+                "api_key": "copilot-acp",
+                "base_url": "acp://copilot",
+                "command": "/usr/local/bin/copilot",
+                "args": ["--acp", "--stdio"],
+                "source": "process",
+            },
+        ), patch(
+            "hermes_cli.auth.resolve_api_key_provider_credentials",
+            return_value={
+                "provider": "copilot",
+                "api_key": "gh-cli-token",
+                "base_url": "https://api.githubcopilot.com",
+                "source": "gh auth token",
+            },
+        ), patch(
+            "hermes_cli.models.fetch_github_model_catalog",
+            return_value=[
+                {
+                    "id": "gpt-4.1",
+                    "capabilities": {"type": "chat", "supports": {}},
+                    "supported_endpoints": ["/chat/completions"],
+                },
+                {
+                    "id": "gpt-5.4",
+                    "capabilities": {"type": "chat", "supports": {"reasoning_effort": ["low", "medium", "high"]}},
+                    "supported_endpoints": ["/responses"],
+                },
+            ],
+        ), patch(
+            "hermes_cli.auth._prompt_model_selection",
+            return_value="gpt-5.4",
+        ), patch(
+            "hermes_cli.auth.deactivate_provider",
+        ):
+            _model_flow_copilot_acp(load_config(), "old-model")
+
+        import yaml
+
+        config = yaml.safe_load((config_home / "config.yaml").read_text()) or {}
+        model = config.get("model")
+        assert isinstance(model, dict), f"model should be dict, got {type(model)}"
+        assert model.get("provider") == "copilot-acp"
+        assert model.get("base_url") == "acp://copilot"
+        assert model.get("default") == "gpt-5.4"
+        assert model.get("api_mode") == "chat_completions"
diff --git a/tests/test_run_agent.py b/tests/test_run_agent.py
index cfe8bab20..daa5f4a3a 100644
--- a/tests/test_run_agent.py
+++ b/tests/test_run_agent.py
@@ -631,6 +631,28 @@ class TestBuildApiKwargs:
         kwargs = agent._build_api_kwargs(messages)
         assert kwargs["extra_body"]["reasoning"]["effort"] == "medium"
 
+    def test_reasoning_sent_for_copilot_gpt5(self, agent):
+        agent.base_url = "https://api.githubcopilot.com"
+        agent.model = "gpt-5.4"
+        messages = [{"role": "user", "content": "hi"}]
+        kwargs = agent._build_api_kwargs(messages)
+        assert kwargs["extra_body"]["reasoning"] == {"effort": "medium"}
+
+    def test_reasoning_xhigh_normalized_for_copilot(self, agent):
+        agent.base_url = "https://api.githubcopilot.com"
+        agent.model = "gpt-5.4"
+        agent.reasoning_config = {"enabled": True, "effort": "xhigh"}
+        messages = [{"role": "user", "content": "hi"}]
+        kwargs = agent._build_api_kwargs(messages)
+        assert kwargs["extra_body"]["reasoning"] == {"effort": "high"}
+
+    def test_reasoning_omitted_for_non_reasoning_copilot_model(self, agent):
+        agent.base_url = "https://api.githubcopilot.com"
+        agent.model = "gpt-4.1"
+        messages = [{"role": "user", "content": "hi"}]
+        kwargs = agent._build_api_kwargs(messages)
+        assert "reasoning" not in kwargs.get("extra_body", {})
+
     def test_max_tokens_injected(self, agent):
         agent.max_tokens = 4096
         messages = [{"role": "user", "content": "hi"}]
@@ -2172,6 +2194,41 @@ class TestFallbackAnthropicProvider:
         assert agent.client is mock_client
 
 
+def test_aiagent_uses_copilot_acp_client():
+    with (
+        patch("run_agent.get_tool_definitions", return_value=_make_tool_defs("web_search")),
+        patch("run_agent.check_toolset_requirements", return_value={}),
+        patch("run_agent.OpenAI") as mock_openai,
+        patch("agent.copilot_acp_client.CopilotACPClient") as mock_acp_client,
+    ):
+        acp_client = MagicMock()
+        mock_acp_client.return_value = acp_client
+
+        agent = AIAgent(
+            api_key="copilot-acp",
+            base_url="acp://copilot",
+            provider="copilot-acp",
+            acp_command="/usr/local/bin/copilot",
+            acp_args=["--acp", "--stdio"],
+            quiet_mode=True,
+            skip_context_files=True,
+            skip_memory=True,
+        )
+
+    assert agent.client is acp_client
+    mock_openai.assert_not_called()
+    mock_acp_client.assert_called_once()
+    assert mock_acp_client.call_args.kwargs["base_url"] == "acp://copilot"
+    assert mock_acp_client.call_args.kwargs["api_key"] == "copilot-acp"
+    assert mock_acp_client.call_args.kwargs["command"] == "/usr/local/bin/copilot"
+    assert mock_acp_client.call_args.kwargs["args"] == ["--acp", "--stdio"]
+
+
+def test_is_openai_client_closed_honors_custom_client_flag():
+    assert AIAgent._is_openai_client_closed(SimpleNamespace(is_closed=True)) is True
+    assert AIAgent._is_openai_client_closed(SimpleNamespace(is_closed=False)) is False
+
+
 class TestAnthropicBaseUrlPassthrough:
     """Bug fix: base_url was filtered with 'anthropic in base_url', blocking proxies."""
 
diff --git a/tests/test_run_agent_codex_responses.py b/tests/test_run_agent_codex_responses.py
index 715074d90..42e41ec7b 100644
--- a/tests/test_run_agent_codex_responses.py
+++ b/tests/test_run_agent_codex_responses.py
@@ -49,6 +49,27 @@ def _build_agent(monkeypatch):
     return agent
 
 
+def _build_copilot_agent(monkeypatch, *, model="gpt-5.4"):
+    _patch_agent_bootstrap(monkeypatch)
+
+    agent = run_agent.AIAgent(
+        model=model,
+        provider="copilot",
+        api_mode="codex_responses",
+        base_url="https://api.githubcopilot.com",
+        api_key="gh-token",
+        quiet_mode=True,
+        max_iterations=4,
+        skip_context_files=True,
+        skip_memory=True,
+    )
+    agent._cleanup_task_resources = lambda task_id: None
+    agent._persist_session = lambda messages, history=None: None
+    agent._save_trajectory = lambda messages, user_message, completed: None
+    agent._save_session_log = lambda messages: None
+    return agent
+
+
 def _codex_message_response(text: str):
     return SimpleNamespace(
         output=[
@@ -244,6 +265,28 @@ def test_build_api_kwargs_codex(monkeypatch):
     assert "extra_body" not in kwargs
 
 
+def test_build_api_kwargs_copilot_responses_omits_openai_only_fields(monkeypatch):
+    agent = _build_copilot_agent(monkeypatch)
+    kwargs = agent._build_api_kwargs([{"role": "user", "content": "hi"}])
+
+    assert kwargs["model"] == "gpt-5.4"
+    assert kwargs["store"] is False
+    assert kwargs["tool_choice"] == "auto"
+    assert kwargs["parallel_tool_calls"] is True
+    assert kwargs["reasoning"] == {"effort": "medium"}
+    assert "prompt_cache_key" not in kwargs
+    assert "include" not in kwargs
+
+
+def test_build_api_kwargs_copilot_responses_omits_reasoning_for_non_reasoning_model(monkeypatch):
+    agent = _build_copilot_agent(monkeypatch, model="gpt-4.1")
+    kwargs = agent._build_api_kwargs([{"role": "user", "content": "hi"}])
+
+    assert "reasoning" not in kwargs
+    assert "include" not in kwargs
+    assert "prompt_cache_key" not in kwargs
+
+
 def test_run_codex_stream_retries_when_completed_event_missing(monkeypatch):
     agent = _build_agent(monkeypatch)
     calls = {"stream": 0}
diff --git a/tools/delegate_tool.py b/tools/delegate_tool.py
index 2a0e5b131..1d8ed9c04 100644
--- a/tools/delegate_tool.py
+++ b/tools/delegate_tool.py
@@ -205,6 +205,8 @@ def _build_child_agent(
     effective_base_url = override_base_url or parent_agent.base_url
     effective_api_key = override_api_key or parent_api_key
     effective_api_mode = override_api_mode or getattr(parent_agent, "api_mode", None)
+    effective_acp_command = getattr(parent_agent, "acp_command", None)
+    effective_acp_args = list(getattr(parent_agent, "acp_args", []) or [])
 
     child = AIAgent(
         base_url=effective_base_url,
@@ -212,6 +214,8 @@ def _build_child_agent(
         model=effective_model,
         provider=effective_provider,
         api_mode=effective_api_mode,
+        acp_command=effective_acp_command,
+        acp_args=effective_acp_args,
         max_iterations=max_iterations,
         max_tokens=getattr(parent_agent, "max_tokens", None),
         reasoning_config=getattr(parent_agent, "reasoning_config", None),
@@ -232,6 +236,7 @@ def _build_child_agent(
         tool_progress_callback=child_progress_cb,
         iteration_budget=shared_budget,
     )
+    child._delegate_saved_tool_names = list(_saved_tool_names)
 
     # Set delegation depth so children can't spawn grandchildren
     child._delegate_depth = getattr(parent_agent, '_delegate_depth', 0) + 1
@@ -372,7 +377,11 @@ def _run_single_child(
     finally:
         # Restore the parent's tool names so the process-global is correct
         # for any subsequent execute_code calls or other consumers.
-        model_tools._last_resolved_tool_names = _saved_tool_names
+        import model_tools
+
+        saved_tool_names = getattr(child, "_delegate_saved_tool_names", None)
+        if isinstance(saved_tool_names, list):
+            model_tools._last_resolved_tool_names = list(saved_tool_names)
 
         # Unregister child from interrupt propagation
         if hasattr(parent_agent, '_active_children'):
@@ -623,6 +632,8 @@ def _resolve_delegation_credentials(cfg: dict, parent_agent) -> dict:
         "base_url": runtime.get("base_url"),
         "api_key": api_key,
         "api_mode": runtime.get("api_mode"),
+        "command": runtime.get("command"),
+        "args": list(runtime.get("args") or []),
     }
 
 
diff --git a/website/docs/reference/cli-commands.md b/website/docs/reference/cli-commands.md
index d3f9a0ce3..effb13e5b 100644
--- a/website/docs/reference/cli-commands.md
+++ b/website/docs/reference/cli-commands.md
@@ -66,7 +66,7 @@ Common options:
 | `-q`, `--query "..."` | One-shot, non-interactive prompt. |
 | `-m`, `--model <model>` | Override the model for this run. |
 | `-t`, `--toolsets <csv>` | Enable a comma-separated set of toolsets. |
-| `--provider <provider>` | Force a provider: `auto`, `openrouter`, `nous`, `openai-codex`, `anthropic`, `zai`, `kimi-coding`, `minimax`, `minimax-cn`. |
+| `--provider <provider>` | Force a provider: `auto`, `openrouter`, `nous`, `openai-codex`, `copilot`, `anthropic`, `zai`, `kimi-coding`, `minimax`, `minimax-cn`. |
 | `-v`, `--verbose` | Verbose output. |
 | `-Q`, `--quiet` | Programmatic mode: suppress banner/spinner/tool previews. |
 | `--resume <session>` / `--continue [name]` | Resume a session directly from `chat`. |
diff --git a/website/docs/reference/environment-variables.md b/website/docs/reference/environment-variables.md
index c7ddfd1fa..3edf636ca 100644
--- a/website/docs/reference/environment-variables.md
+++ b/website/docs/reference/environment-variables.md
@@ -48,7 +48,7 @@ For native Anthropic auth, Hermes prefers Claude Code's own credential files whe
 
 | Variable | Description |
 |----------|-------------|
-| `HERMES_INFERENCE_PROVIDER` | Override provider selection: `auto`, `openrouter`, `nous`, `openai-codex`, `anthropic`, `zai`, `kimi-coding`, `minimax`, `minimax-cn`, `kilocode`, `alibaba` (default: `auto`) |
+| `HERMES_INFERENCE_PROVIDER` | Override provider selection: `auto`, `openrouter`, `nous`, `openai-codex`, `copilot`, `anthropic`, `zai`, `kimi-coding`, `minimax`, `minimax-cn`, `kilocode`, `alibaba` (default: `auto`) |
 | `HERMES_PORTAL_BASE_URL` | Override Nous Portal URL (for development/testing) |
 | `NOUS_INFERENCE_BASE_URL` | Override Nous inference API URL |
 | `HERMES_NOUS_MIN_KEY_TTL_SECONDS` | Min agent key TTL before re-mint (default: 1800 = 30min) |
diff --git a/website/docs/user-guide/configuration.md b/website/docs/user-guide/configuration.md
index 8ee4d3095..8f8a71217 100644
--- a/website/docs/user-guide/configuration.md
+++ b/website/docs/user-guide/configuration.md
@@ -63,6 +63,8 @@ You need at least one way to connect to an LLM. Use `hermes model` to switch pro
 |----------|-------|
 | **Nous Portal** | `hermes model` (OAuth, subscription-based) |
 | **OpenAI Codex** | `hermes model` (ChatGPT OAuth, uses Codex models) |
+| **GitHub Copilot ACP** | `hermes model` (spawns local `copilot --acp --stdio`) |
+| **GitHub Copilot** | `hermes model` (uses `GITHUB_TOKEN`, `GH_TOKEN`, or `gh auth token`) |
 | **Anthropic** | `hermes model` (Claude Pro/Max via Claude Code auth, Anthropic API key, or manual setup-token) |
 | **OpenRouter** | `OPENROUTER_API_KEY` in `~/.hermes/.env` |
 | **AI Gateway** | `AI_GATEWAY_API_KEY` in `~/.hermes/.env` (provider: `ai-gateway`) |
@@ -122,6 +124,15 @@ model:
 These providers have built-in support with dedicated provider IDs. Set the API key and use `--provider` to select:
 
 ```bash
+# GitHub Copilot ACP agent backend
+hermes chat --provider copilot-acp --model copilot-acp
+# Requires the GitHub Copilot CLI in PATH and an existing `copilot login`
+# session. Hermes starts `copilot --acp --stdio` for each request.
+
+# GitHub Copilot
+hermes chat --provider copilot --model gpt-5.4
+# Uses: GITHUB_TOKEN, GH_TOKEN, or `gh auth token`
+
 # z.ai / ZhipuAI GLM
 hermes chat --provider zai --model glm-4-plus
 # Requires: GLM_API_KEY in ~/.hermes/.env
@@ -146,11 +157,19 @@ hermes chat --provider alibaba --model qwen-plus
 Or set the provider permanently in `config.yaml`:
 ```yaml
 model:
-  provider: "zai"       # or: kimi-coding, minimax, minimax-cn, alibaba
-  default: "glm-4-plus"
+  provider: "copilot-acp"   # or: copilot, zai, kimi-coding, minimax, minimax-cn, alibaba
+  default: "copilot-acp"
 ```
 
-Base URLs can be overridden with `GLM_BASE_URL`, `KIMI_BASE_URL`, `MINIMAX_BASE_URL`, `MINIMAX_CN_BASE_URL`, or `DASHSCOPE_BASE_URL` environment variables.
+Or, for the direct Copilot premium API provider:
+
+```yaml
+model:
+  provider: "copilot"
+  default: "gpt-5.4"
+```
+
+Base URLs can be overridden with `GLM_BASE_URL`, `KIMI_BASE_URL`, `MINIMAX_BASE_URL`, `MINIMAX_CN_BASE_URL`, or `DASHSCOPE_BASE_URL` environment variables. The Copilot premium API provider uses the built-in GitHub Copilot API base URL automatically. The Copilot ACP backend can be pointed at a different executable with `HERMES_COPILOT_ACP_COMMAND`, `COPILOT_CLI_PATH`, and `HERMES_COPILOT_ACP_ARGS`.
 
 ## Custom & Self-Hosted LLM Providers
 
@@ -443,7 +462,7 @@ fallback_model:
 
 When activated, the fallback swaps the model and provider mid-session without losing your conversation. It fires **at most once** per session.
 
-Supported providers: `openrouter`, `nous`, `openai-codex`, `anthropic`, `zai`, `kimi-coding`, `minimax`, `minimax-cn`, `custom`.
+Supported providers: `openrouter`, `nous`, `openai-codex`, `copilot`, `anthropic`, `zai`, `kimi-coding`, `minimax`, `minimax-cn`, `custom`.
 
 :::tip
 Fallback is configured exclusively through `config.yaml` — there are no environment variables for it. For full details on when it triggers, supported providers, and how it interacts with auxiliary tasks and delegation, see [Fallback Providers](/docs/user-guide/features/fallback-providers).
@@ -766,7 +785,7 @@ Every model slot in Hermes — auxiliary tasks, compression, fallback — uses t
 
 When `base_url` is set, Hermes ignores the provider and calls that endpoint directly (using `api_key` or `OPENAI_API_KEY` for auth). When only `provider` is set, Hermes uses that provider's built-in auth and base URL.
 
-Available providers: `auto`, `openrouter`, `nous`, `codex`, `anthropic`, `main`, `zai`, `kimi-coding`, `minimax`, and any provider registered in the [provider registry](/docs/reference/environment-variables).
+Available providers: `auto`, `openrouter`, `nous`, `codex`, `copilot`, `anthropic`, `main`, `zai`, `kimi-coding`, `minimax`, and any provider registered in the [provider registry](/docs/reference/environment-variables).
 
 ### Full auxiliary config reference
 
@@ -1224,7 +1243,7 @@ delegation:
 
 **Direct endpoint override:** If you want the obvious custom-endpoint path, set `delegation.base_url`, `delegation.api_key`, and `delegation.model`. That sends subagents directly to that OpenAI-compatible endpoint and takes precedence over `delegation.provider`. If `delegation.api_key` is omitted, Hermes falls back to `OPENAI_API_KEY` only.
 
-The delegation provider uses the same credential resolution as CLI/gateway startup. All configured providers are supported: `openrouter`, `nous`, `zai`, `kimi-coding`, `minimax`, `minimax-cn`. When a provider is set, the system automatically resolves the correct base URL, API key, and API mode — no manual credential wiring needed.
+The delegation provider uses the same credential resolution as CLI/gateway startup. All configured providers are supported: `openrouter`, `nous`, `copilot`, `zai`, `kimi-coding`, `minimax`, `minimax-cn`. When a provider is set, the system automatically resolves the correct base URL, API key, and API mode — no manual credential wiring needed.
 
 **Precedence:** `delegation.base_url` in config → `delegation.provider` in config → parent provider (inherited). `delegation.model` in config → parent model (inherited). Setting just `model` without `provider` changes only the model name while keeping the parent's credentials (useful for switching models within the same provider like OpenRouter).