Merge commit from fork

* fix(security): stop API tokens reaching privileged agent tools

A bearer API token resolves to the human who minted it, and minting is admin-only, so every owner-keyed privilege check in the agent path answers "admin". A token issued for a narrow integration therefore reached bash and python with the authority of the account that created it.

Three independent routes to that sink, each closed here.

The token could answer its own tool-approval prompt. An approval records that a person authorized one dangerous action, and a token cannot make that statement, so /api/chat_stream now refuses an approval resume from a bearer caller.

The chat-session grant was reconstructable from caller-supplied message metadata. Two routes persist a metadata blob on the caller's behalf, so the shape of a resolved approval card could be written straight into a transcript and was then read back as authority. The server now signs the grant when it resolves an approval and verifies that signature when reading it back, binding it to the chat and the approval it was issued for. Both routes also drop server-owned keys from an inbound blob.

A run driven by a token inherited its owner's tool set. Such a run is now capped at the non-admin policy regardless of who minted the credential, which holds even where no approval is raised at all.

The human path is unchanged: a browser session still receives the prompt, still approves, and a granted chat-session scope still carries to later turns in that chat.

Scope enforcement across the wider route surface is a separate gap and is not addressed here.

* fix scoped chat delegation boundaries

* fix(auth): reject malformed chat approval signatures

---------

Co-authored-by: RaresKeY <158580472+RaresKeY@users.noreply.github.com>

src/tool_capabilities.py

@@ -15,7 +15,7 @@ from types import MappingProxyType
 from typing import Any, Iterable, Mapping
 
 from src.tool_approval_scopes import CHAT_SESSION_APPROVAL_CONTEXT_MARKER
-from src.tool_security import BUILTIN_EMAIL_TOOLS
+from src.tool_security import BUILTIN_EMAIL_TOOLS, is_public_blocked_tool
 
 
 class ToolEffect(str, Enum):
@@ -624,10 +624,21 @@ class ToolRunSecurityContext:
     # The bypass affects only this automatic gate; current tool policy, ownership,
     # workspace confinement, and execution/sandbox restrictions still apply.
     approval_gate_bypassed: bool = False
+    # Driven by a bearer API token, not a person at a browser. Privileged
+    # tools are refused outright and no approval can lift that.
+    delegated_credential: bool = False
 
     def observe_messages(self, messages: Iterable[dict]) -> None:
         """Apply server-owned chat scope and promote untrusted prompt context."""
         message_list = list(messages or ())
+        if self.delegated_credential:
+            # A delegated run has no human to grant chat-session scope, so a
+            # grant sitting in this chat's history (left by the owner's own
+            # browser) must not be picked up by a token driving the same chat.
+            self.approval_gate_bypassed = False
+            if messages_contain_external_untrusted_context(message_list):
+                self.external_untrusted_context_seen = True
+            return
         if any(
             isinstance(message, dict)
             and isinstance(message.get("metadata"), dict)
@@ -641,6 +652,17 @@ class ToolRunSecurityContext:
             self.external_untrusted_context_seen = True
 
     def decision_for(self, tool_name: Any, content: Any = None) -> ToolGateDecision:
+        # Checked before the bypasses below, because neither may lift it, and
+        # kept independent of external_untrusted_context_seen so it holds on a
+        # run where that gate never arms and raises no prompt to bypass.
+        if self.delegated_credential and is_public_blocked_tool(tool_name):
+            return ToolGateDecision(
+                False,
+                (
+                    f"Tool '{tool_name}' is not available to API-token callers. "
+                    "It requires an interactive session."
+                ),
+            )
         if self.approval_gate_bypassed:
             return ToolGateDecision(True)
         if not self.external_untrusted_context_seen: