feat(claude): add forward_host_credentials support

Reads the host's Claude OAuth session key from ~/.claude.json at launch
and forwards it only to the egress sidecar (never to the agent), placing
a placeholder CLAUDE_CODE_OAUTH_TOKEN in the agent env so Claude Code
starts without seeing the real credential.

Mirrors the existing Codex forward_host_credentials flow (PRD 0029).
Adds claude_auth.py to extract and validate the sessionKey, a
CLAUDE_HOST_CREDENTIAL_TOKEN_REF constant in egress.py, and updates
manifest_agent.py to allow the flag for both 'codex' and 'claude'
templates. Also adds a mutual-exclusion check that rejects setting
both auth_token and forward_host_credentials together.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bot_bottle/contrib/claude/agent_provider.py

@@ -23,8 +23,9 @@ from ...agent_provider import (
     provider_startup_args,
 )
 from ...backend.docker import util as docker_mod
-from ...egress import EgressRoute
+from ...egress import CLAUDE_HOST_CREDENTIAL_TOKEN_REF, EgressRoute
 from ...log import die, info, warn
+from .claude_auth import claude_host_access_token
 
 
 if TYPE_CHECKING:
@@ -115,7 +116,6 @@ class ClaudeAgentProvider(AgentProvider):
         color: str = "",
         provider_settings: dict[str, object] | None = None,
     ) -> AgentProvisionPlan:
-        del forward_host_credentials, host_env
         resolved_guest_env = dict(guest_env or {})
         startup_args = provider_startup_args(provider_settings)
         guest_home = self.guest_home
@@ -177,13 +177,24 @@ class ClaudeAgentProvider(AgentProvider):
                 claude_settings,
                 f"{guest_home}/.claude/settings.json",
             ))
+        provisioned_env: dict[str, str] = {}
+        if forward_host_credentials:
+            _host_env = host_env or dict(os.environ)
+            provisioned_env[CLAUDE_HOST_CREDENTIAL_TOKEN_REF] = (
+                claude_host_access_token(_host_env)
+            )
+
+        cred_token_ref = (
+            CLAUDE_HOST_CREDENTIAL_TOKEN_REF if forward_host_credentials
+            else auth_token
+        )
         egress_routes = (EgressRoute(
             host="api.anthropic.com",
-            auth_scheme="Bearer" if auth_token else "",
-            token_ref=auth_token,
+            auth_scheme="Bearer" if (auth_token or forward_host_credentials) else "",
+            token_ref=cred_token_ref,
         ),)
         hidden_env_names: frozenset[str] = frozenset()
-        if auth_token:
+        if auth_token or forward_host_credentials:
             env_vars["CLAUDE_CODE_OAUTH_TOKEN"] = "egress-placeholder"
             hidden_env_names = frozenset({"CLAUDE_CODE_OAUTH_TOKEN"})
 
@@ -205,6 +216,7 @@ class ClaudeAgentProvider(AgentProvider):
             files=tuple(files),
             egress_routes=egress_routes,
             hidden_env_names=hidden_env_names,
+            provisioned_env=provisioned_env,
         )
 
     def provision_skills(self, plan: "BottlePlan", bottle: "Bottle") -> None:

bot_bottle/contrib/claude/claude_auth.py

@@ -0,0 +1,76 @@
+"""Host Claude auth helpers.
+
+Reads the host's Claude Code auth state and returns only the
+session key needed by egress. Does not expose refresh tokens
+or raw auth payloads.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+from datetime import datetime, timezone
+from pathlib import Path
+
+from ...log import die
+
+
+def claude_auth_path(host_env: dict[str, str] | None = None) -> Path:
+    env = os.environ if host_env is None else host_env
+    home = env.get("HOME")
+    if home:
+        return Path(home) / ".claude.json"
+    return Path.home() / ".claude.json"
+
+
+def claude_host_access_token(
+    host_env: dict[str, str] | None = None,
+    *,
+    now: datetime | None = None,
+) -> str:
+    path = claude_auth_path(host_env)
+    if not path.is_file():
+        die(
+            f"claude host credentials: auth file missing at {path}. "
+            "Run `claude login` on the host or disable "
+            "agent_provider.forward_host_credentials."
+        )
+    try:
+        raw = json.loads(path.read_text())
+    except (OSError, json.JSONDecodeError) as e:
+        die(f"claude host credentials: could not read valid JSON at {path}: {e}")
+    if not isinstance(raw, dict):
+        die(f"claude host credentials: {path} must contain a JSON object")
+
+    oauth = raw.get("oauthAccount")
+    if not isinstance(oauth, dict):
+        die(
+            f"claude host credentials: {path} is missing oauthAccount. "
+            "Run `claude login` on the host or disable "
+            "agent_provider.forward_host_credentials."
+        )
+
+    session_key = oauth.get("sessionKey")
+    if not isinstance(session_key, str) or not session_key:
+        die(
+            f"claude host credentials: {path} oauthAccount.sessionKey is missing "
+            "or empty. Run `claude login` on the host and restart the bottle."
+        )
+
+    expires_at = oauth.get("expiresAt")
+    if isinstance(expires_at, (int, float)):
+        check_now = now or datetime.now(timezone.utc)
+        exp_dt = datetime.fromtimestamp(float(expires_at), timezone.utc)
+        if exp_dt <= check_now:
+            die(
+                "claude host credentials: host Claude session token is expired. "
+                "Run `claude login` on the host and restart the bottle."
+            )
+
+    return session_key
+
+
+__all__ = [
+    "claude_auth_path",
+    "claude_host_access_token",
+]