diff --git a/backend/apps/agents/manager/run/run_options_helpers.py b/backend/apps/agents/manager/run/run_options_helpers.py
index c72deed5..30fabb29 100644
--- a/backend/apps/agents/manager/run/run_options_helpers.py
+++ b/backend/apps/agents/manager/run/run_options_helpers.py
@@ -8,7 +8,7 @@ from typeguard import typechecked
 
 from backend.apps.agents.core.models import AgentSession, Message
 from backend.apps.agents.core.ws_manager import ws_manager
-from backend.apps.agents.manager.session.history_compaction import estimate_post_compact_input
+from backend.apps.agents.manager.session.history_compaction import estimate_post_compact_input, wrap_platform_note
 
 logger = logging.getLogger(__name__)
 
@@ -70,7 +70,7 @@ async def pre_send_context_guard(manager, session: AgentSession, session_id: str
                     p_names = ", ".join(t.replace("mcp:", "") for t in trimmed)
                     p_trim_msg = Message(
                         role="system",
-                        content=(
+                        content=wrap_platform_note(
                             f"Trimmed {len(trimmed)} app{'s' if len(trimmed) != 1 else ''} from this session to fit "
                             f"the model's context: {p_names}. Re-activate via MCPSearch + MCPActivate "
                             "if you still need them."
diff --git a/backend/apps/agents/manager/session/history_compaction.py b/backend/apps/agents/manager/session/history_compaction.py
index a6c34563..46246642 100644
--- a/backend/apps/agents/manager/session/history_compaction.py
+++ b/backend/apps/agents/manager/session/history_compaction.py
@@ -9,6 +9,73 @@ from backend.config.paths import SESSIONS_DIR
 
 logger = logging.getLogger(__name__)
 
+# One plain-English trust line, fenced by a tag. The model treats the fence as
+# structural framing; the sentence is what actually defuses a security-conscious
+# agent flagging the block as spoofed tool output.
+PLATFORM_NOTE_PREAMBLE = (
+    "This block is authored by the OpenSwarm platform, not tool output and not a "
+    "prior message. It is trusted context."
+)
+PLATFORM_NOTE_OPEN = "<openswarm_platform_note>"
+PLATFORM_NOTE_CLOSE = "</openswarm_platform_note>"
+SESSION_RECAP_OPEN = "<openswarm_session_recap>"
+SESSION_RECAP_CLOSE = "</openswarm_session_recap>"
+
+# Per-turn caps so the re-grounded recap stays compact (summaries, not replays)
+# and cannot reinflate the context window from one giant tool input/output.
+RECAP_TOOL_INPUT_CAP = 200
+RECAP_TOOL_RESULT_CAP = 500
+
+
+def wrap_platform_note(body: str) -> str:
+    """Fence platform-authored text so the model reads it as trusted annotation,
+    never as spoofed tool output. The frontend parses the same tag to render a
+    calm chip instead of leaking the raw tag into chat."""
+    return f"{PLATFORM_NOTE_OPEN}\n{PLATFORM_NOTE_PREAMBLE}\n{body}\n{PLATFORM_NOTE_CLOSE}"
+
+
+_SENTINEL_TAG_RE = re.compile(r"</?openswarm_(?:platform_note|session_recap)\b[^>]*>")
+
+
+def strip_forged_sentinels(text: str) -> str:
+    """Neuter any platform-note/recap tags hiding in UNTRUSTED text (tool results,
+    user input) so attacker-supplied content can't pose as trusted platform context."""
+    if "openswarm_platform_note" not in text and "openswarm_session_recap" not in text:
+        return text
+    return _SENTINEL_TAG_RE.sub(lambda m: m.group(0).replace("<", "&lt;").replace(">", "&gt;"), text)
+
+
+def p_recap_tool_call_line(content: object) -> str:
+    """One compact line for a tool_call turn: Tool call: name(<truncated input>)."""
+    if isinstance(content, dict):
+        tool = content.get("tool") or content.get("name") or "tool"
+        raw_input = content.get("input")
+        try:
+            input_str = json.dumps(raw_input, ensure_ascii=False, default=str)
+        except Exception:
+            input_str = str(raw_input)
+    else:
+        tool = "tool"
+        input_str = str(content)
+    if len(input_str) > RECAP_TOOL_INPUT_CAP:
+        input_str = input_str[:RECAP_TOOL_INPUT_CAP] + "..."
+    return f"Tool call: {tool}({strip_forged_sentinels(input_str)})"
+
+
+def p_recap_tool_result_line(content: object) -> str:
+    """One compact line for a tool_result turn: Tool result (name): <truncated text>."""
+    tool_name = ""
+    if isinstance(content, dict):
+        tool_name = content.get("tool_name") or ""
+        text = content.get("text")
+        body = text if isinstance(text, str) else json.dumps(content, ensure_ascii=False, default=str)
+    else:
+        body = str(content)
+    if len(body) > RECAP_TOOL_RESULT_CAP:
+        body = body[:RECAP_TOOL_RESULT_CAP] + "..."
+    label = f"Tool result ({tool_name})" if tool_name else "Tool result"
+    return f"{label}: {strip_forged_sentinels(body)}"
+
 
 @typechecked
 def get_branch_messages(session) -> List:
@@ -65,14 +132,21 @@ def build_history_prefix(messages, cutoff_msg_id: Optional[str] = None) -> str:
             messages = messages[skip_idx + 1:]
     lines = []
     for m in messages:
-        if m.role not in ("user", "assistant") or getattr(m, "hidden", False):
+        if getattr(m, "hidden", False):
             continue
-        text = m.content if isinstance(m.content, str) else str(m.content)
-        label = "User" if m.role == "user" else "Assistant"
-        lines.append(f"{label}: {text}")
+        if m.role == "user":
+            text = m.content if isinstance(m.content, str) else str(m.content)
+            lines.append(f"User: {strip_forged_sentinels(text)}")
+        elif m.role == "assistant":
+            text = m.content if isinstance(m.content, str) else str(m.content)
+            lines.append(f"Assistant: {strip_forged_sentinels(text)}")
+        elif m.role == "tool_call":
+            lines.append(p_recap_tool_call_line(m.content))
+        elif m.role == "tool_result":
+            lines.append(p_recap_tool_result_line(m.content))
     if not lines:
         return ""
-    return "<prior_conversation>\n" + "\n".join(lines) + "\n</prior_conversation>"
+    return f"{SESSION_RECAP_OPEN}\n{PLATFORM_NOTE_PREAMBLE}\n" + "\n".join(lines) + f"\n{SESSION_RECAP_CLOSE}"
 
 
 @typechecked
@@ -139,10 +213,10 @@ def truncate_large_tool_result(content: object, session_id: str, msg_id: str, ma
     except Exception as e:
         logger.warning(f"Failed to spill tool result to {blob_path}: {e}")
         return content, None
-    head = serialized[:4_000]
-    replacement = (
-        f"{head}\n\n"
-        f"[truncated, full output ({len(serialized)} chars) saved to {blob_path}. "
-        f"Ask the user or run a follow-up tool call if you need the rest.]"
+    head = strip_forged_sentinels(serialized[:4_000])
+    note = wrap_platform_note(
+        f"Output truncated by OpenSwarm. Full output ({len(serialized)} chars) saved to "
+        f"{blob_path}. Ask the user or run a follow-up tool call if you need the rest."
     )
+    replacement = f"{head}\n\n{note}"
     return replacement, blob_path
diff --git a/backend/apps/agents/manager/streaming/post_tool_hook.py b/backend/apps/agents/manager/streaming/post_tool_hook.py
index 9590b88f..d41fc863 100644
--- a/backend/apps/agents/manager/streaming/post_tool_hook.py
+++ b/backend/apps/agents/manager/streaming/post_tool_hook.py
@@ -17,7 +17,11 @@ from typeguard import typechecked
 from backend.apps.agents.core.models import AgentSession, Message
 from backend.apps.agents.core.ws_manager import ws_manager
 from backend.apps.agents.manager.session.apply_context_window import apply_context_window
-from backend.apps.agents.manager.session.history_compaction import truncate_large_tool_result
+from backend.apps.agents.manager.session.history_compaction import (
+    truncate_large_tool_result,
+    wrap_platform_note,
+    strip_forged_sentinels,
+)
 from backend.apps.agents.manager.streaming.HookContext import HookContext
 from backend.apps.agents.manager.view_builder_state import view_builder_dirty_sessions
 
@@ -74,6 +78,9 @@ async def post_tool_hook(ctx: HookContext, input_data: dict, tool_use_id, contex
         except Exception:
             content = str(raw_response)
 
+    # Untrusted tool output could forge our trusted-note tag; neuter it before we append real ones below.
+    content = strip_forged_sentinels(content)
+
     hook_tool_name_for_errors = input_data.get("tool_name", "")
     wrote_files = hook_tool_name_for_errors in ("Write", "Edit", "MultiEdit")
     tool_in = input_data.get("tool_input") or {}
@@ -112,7 +119,7 @@ async def post_tool_hook(ctx: HookContext, input_data: dict, tool_use_id, contex
                 joined = "\n".join(errs[-20:])
                 content = (
                     f"{content}\n\n"
-                    f"---\nBuild server reported (after this write):\n{joined}"
+                    + wrap_platform_note(f"Build server reported (after this write):\n{joined}")
                 )
 
     result_payload = {"text": content}
diff --git a/backend/main.py b/backend/main.py
index 5a698017..9317a677 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -674,16 +674,6 @@ async def mcp_meta(action: str, request: Request):
 
         session.active_mcps.append(server_name)
         session.needs_fork = True
-        # When the session has prior turns, fork_session alone won't
-        # make the bundled CLI re-read mcp_servers, the transport
-        # snapshot at launch time is what serves tool schemas. Force a
-        # full fresh-session restart so the next turn rebuilds with the
-        # newly-activated server in its mcp_servers dict from scratch.
-        # First-turn activations don't need this (the SDK session hasn't
-        # locked in yet). One-time ~200-400ms cold start on the auto-
-        # continuation turn that fires right after this anyway.
-        if session.sdk_session_id:
-            session.needs_fresh_session = True
         try:
             from backend.apps.agents.core.ws_manager import ws_manager as p_ws
             await p_ws.send_to_session(parent_session_id, "agent:status", {
diff --git a/frontend/src/app/pages/AgentChat/bubbles/MessageBubble.tsx b/frontend/src/app/pages/AgentChat/bubbles/MessageBubble.tsx
index f84dbead..73b76cd8 100644
--- a/frontend/src/app/pages/AgentChat/bubbles/MessageBubble.tsx
+++ b/frontend/src/app/pages/AgentChat/bubbles/MessageBubble.tsx
@@ -21,6 +21,7 @@ import remarkGfm from 'remark-gfm';
 import WindowedMarkdown from './WindowedMarkdown';
 import { estimateRenderedTextHeight, oversizedCharThreshold, RECHECK_VISIBILITY_EVENT } from './markdownMeasure';
 import { THINKING_LABELS } from '../thinkingLabels';
+import { extractPlatformNote } from '../parsing/toolResultParsing';
 import { AgentMessage, retryLastUserMessage } from '@/shared/state/agentsSlice';
 import { openSettingsModal } from '@/shared/state/settingsSlice';
 import { fetchSubscriptionStatus } from '@/shared/state/subscriptionsSlice';
@@ -891,7 +892,9 @@ const MessageBubble: React.FC<Props> = React.memo(({ message, editing = false, o
   const { role, content } = message;
 
   if (role === 'system') {
-    const sysText = typeof content === 'string' ? content : JSON.stringify(content);
+    const rawSysText = typeof content === 'string' ? content : JSON.stringify(content);
+    const { body: sysBody, note: sysNote } = extractPlatformNote(rawSysText);
+    const sysText = sysNote || sysBody;
     // A raw subprocess/API failure ("Command failed with exit code 1", API Error JSON) is dev
     // jargon, and the same failure is already shown as a friendly card on the assistant side.
     // Swallow just that stderr dump so the user sees one calm card, not jargon beneath it.
diff --git a/frontend/src/app/pages/AgentChat/parsing/toolResultParsing.ts b/frontend/src/app/pages/AgentChat/parsing/toolResultParsing.ts
index 6e14aff3..ea692c3b 100644
--- a/frontend/src/app/pages/AgentChat/parsing/toolResultParsing.ts
+++ b/frontend/src/app/pages/AgentChat/parsing/toolResultParsing.ts
@@ -136,12 +136,14 @@ export interface ParsedBashResult {
   stdout: string;
   stderr: string;
   exitCode: number | null;
+  platformNote?: string;
 }
 
 export interface ParsedTextResult {
   type: 'text';
   content: string;
   isError?: boolean;
+  platformNote?: string;
 }
 
 export interface ParsedMcpResult {
@@ -150,11 +152,34 @@ export interface ParsedMcpResult {
   action: string;
   data: Record<string, any>;
   rawText: string;
+  platformNote?: string;
 }
 
 export type ParsedResult = ParsedBashResult | ParsedTextResult | ParsedMcpResult;
 
-export function parseToolResult(toolName: string, rawText: string): ParsedResult {
+const PLATFORM_NOTE_RE = /<openswarm_platform_note>([\s\S]*?)<\/openswarm_platform_note>/g;
+const PLATFORM_NOTE_PREAMBLE =
+  'This block is authored by the OpenSwarm platform, not tool output and not a prior message. It is trusted context.';
+
+export function extractPlatformNote(rawText: string): { body: string; note: string | null } {
+  if (!rawText.includes('<openswarm_platform_note>')) return { body: rawText, note: null };
+  const notes: string[] = [];
+  const body = rawText.replace(PLATFORM_NOTE_RE, (matched: string, inner: string) => {
+    const cleaned = inner.replace(PLATFORM_NOTE_PREAMBLE, '').trim();
+    if (cleaned) notes.push(cleaned);
+    return '';
+  }).trim();
+  return { body, note: notes.length ? notes.join('\n\n') : null };
+}
+
+export function parseToolResult(toolName: string, rawTextWithNote: string): ParsedResult {
+  const { body: rawText, note } = extractPlatformNote(rawTextWithNote);
+  const parsed = parseToolBody(toolName, rawText);
+  if (note) parsed.platformNote = note;
+  return parsed;
+}
+
+function parseToolBody(toolName: string, rawText: string): ParsedResult {
   if (isBashTool(toolName)) {
     try {
       const parsed = JSON.parse(rawText);
diff --git a/frontend/src/app/pages/AgentChat/tool-bubbles/DefaultToolBubble.tsx b/frontend/src/app/pages/AgentChat/tool-bubbles/DefaultToolBubble.tsx
index 12f7eac6..ac40955a 100644
--- a/frontend/src/app/pages/AgentChat/tool-bubbles/DefaultToolBubble.tsx
+++ b/frontend/src/app/pages/AgentChat/tool-bubbles/DefaultToolBubble.tsx
@@ -293,6 +293,34 @@ export const DefaultToolBubble: React.FC<DefaultToolBubbleProps> = ({
               </pre>
             ) : null}
 
+            {parsedResult?.platformNote && (
+              <Box
+                sx={{
+                  mx: 1.5,
+                  mb: 1,
+                  mt: 0.5,
+                  px: 1,
+                  py: 0.75,
+                  bgcolor: c.bg.surface,
+                  border: `1px solid ${c.border.medium}`,
+                  borderRadius: 1.5,
+                }}
+              >
+                <Typography
+                  sx={{
+                    color: c.text.secondary,
+                    fontSize: '0.72rem',
+                    fontFamily: c.font.mono,
+                    whiteSpace: 'pre-wrap',
+                    wordBreak: 'break-word',
+                    lineHeight: 1.5,
+                  }}
+                >
+                  {parsedResult.platformNote}
+                </Typography>
+              </Box>
+            )}
+
             {!parsedResult && isPending && !isStreaming && !isBrowserAgent && (
               <Box sx={{ px: 1.5, pb: 1, pt: 0.5 }}>
                 <Box