diff --git a/workspace/a2a_mcp_server.py b/workspace/a2a_mcp_server.py
index 22bbb682..e1d41a50 100644
--- a/workspace/a2a_mcp_server.py
+++ b/workspace/a2a_mcp_server.py
@@ -12,12 +12,14 @@ Environment variables (set by the workspace container):
   PLATFORM_URL  — platform API base URL (e.g. http://platform:8080)
 """
 
+import argparse
 import asyncio
 import json
 import logging
 import os
 import stat
 import sys
+import uuid
 from typing import Callable
 
 # Top-level (not inside main()) so the wheel rewriter expands this to
@@ -825,24 +827,163 @@ async def main():  # pragma: no cover
             break
 
 
-def cli_main() -> None:  # pragma: no cover
-    """Synchronous wrapper around the async MCP stdio loop.
+# --- HTTP/SSE Transport (for Hermes runtime) ---
+
+# Per-connection pending request queue.
+# Maps connection-id → asyncio.Queue of JSON-RPC responses.
+_http_connection_queues: dict[str, asyncio.Queue] = {}
+_http_connection_lock = asyncio.Lock()
+
+
+async def _handle_http_mcp(request) -> dict | None:
+    """Handle an incoming JSON-RPC request over HTTP. Returns the JSON-RPC response dict, or None for notifications."""
+    try:
+        body = await request.json()
+    except Exception:
+        return {"jsonrpc": "2.0", "id": None, "error": {"code": -32700, "message": "Parse error"}}
+
+    req_id = body.get("id")
+    method = body.get("method", "")
+
+    if method == "initialize":
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": _build_initialize_result(),
+        }
+    elif method == "notifications/initialized":
+        return None  # No response needed
+    elif method == "tools/list":
+        return {"jsonrpc": "2.0", "id": req_id, "result": {"tools": TOOLS}}
+    elif method == "tools/call":
+        params = body.get("params", {})
+        tool_name = params.get("name", "")
+        tool_args = params.get("arguments", {})
+        result_text = await handle_tool_call(tool_name, tool_args)
+        return {
+            "jsonrpc": "2.0",
+            "id": req_id,
+            "result": {"content": [{"type": "text", "text": result_text}]},
+        }
+    else:
+        return {"jsonrpc": "2.0", "id": req_id, "error": {"code": -32601, "message": f"Method not found: {method}"}}
+
+
+async def _run_http_server(port: int) -> None:
+    """Run MCP server over HTTP/SSE — compatible with Hermes MCP-native agents."""
+    try:
+        from starlette.applications import Starlette  # noqa: F401
+        from starlette.routing import Route  # noqa: F401
+        from starlette.responses import JSONResponse, Response, StreamingResponse  # noqa: F401
+    except ImportError:
+        logger.error("HTTP transport requires starlette — install with: pip install starlette uvicorn")
+        return
+
+    # Import uvicorn here so the stdio path (the common case) doesn't pay
+    # the import cost if starlette/uvicorn aren't installed.
+    import uvicorn  # noqa: F401
+
+    _http_connection_queues.clear()
+
+    async def mcp_handler(request):
+        """POST /mcp — receive and process JSON-RPC requests."""
+        conn_id = request.headers.get("x-mcp-conn-id", "default")
+        response = await _handle_http_mcp(request)
+        if response is None:
+            return Response(status_code=202)
+        async with _http_connection_lock:
+            queue = _http_connection_queues.get(conn_id)
+        if queue is not None and not queue.full():
+            await queue.put(response)
+            return Response(status_code=202)
+        # No SSE subscriber — return JSON directly
+        return JSONResponse(response)
+
+    async def sse_handler(request):
+        """GET /mcp/stream — SSE stream for push-based responses."""
+        conn_id = str(uuid.uuid4())
+        queue: asyncio.Queue = asyncio.Queue(maxsize=100)
+        async with _http_connection_lock:
+            _http_connection_queues[conn_id] = queue
+
+        async def event_stream():
+            yield f"event: connected\ndata: {json.dumps({'conn_id': conn_id})}\n\n"
+            try:
+                while True:
+                    response = await asyncio.wait_for(queue.get(), timeout=300)
+                    yield f"event: message\ndata: {json.dumps(response)}\n\n"
+                    if queue.empty():
+                        yield "event: heartbeat\ndata: null\n\n"
+            except asyncio.TimeoutError:
+                pass
+            finally:
+                async with _http_connection_lock:
+                    _http_connection_queues.pop(conn_id, None)
+
+        return StreamingResponse(
+            event_stream(),
+            media_type="text/event-stream",
+            headers={
+                "Cache-Control": "no-cache",
+                "Connection": "keep-alive",
+                "X-Accel-Buffering": "no",
+            },
+        )
+
+    async def health_handler(_request):
+        return JSONResponse({"ok": True, "transport": "http+sse", "port": port})
+
+    app = Starlette(
+        routes=[
+            Route("/mcp", mcp_handler, methods=["POST"]),
+            Route("/mcp/stream", sse_handler, methods=["GET"]),
+            Route("/health", health_handler),
+        ]
+    )
+    config = uvicorn.Config(app, host="127.0.0.1", port=port, log_level="warning")
+    server = uvicorn.Server(config)
+    logger.info(f"A2A MCP HTTP server listening on http://127.0.0.1:{port}/mcp")
+    await server.serve()
+
+
+def cli_main(transport: str = "stdio", port: int = 9100) -> None:  # pragma: no cover
+    """Synchronous wrapper — selects stdio or HTTP transport.
 
     Called by ``mcp_cli.main`` (the ``molecule-mcp`` console-script
     entry point in scripts/build_runtime_package.py) AFTER env
     validation and the standalone register + heartbeat thread setup.
     Direct callers (in-container code that already validated env and
-    runs heartbeat.py separately) can also invoke this — it's the
-    smallest possible "run the MCP stdio JSON-RPC loop" surface.
+    runs heartbeat.py separately) can also invoke this.
 
     Wheel-smoke gates in scripts/wheel_smoke.py pin the importability
     of this name (alongside ``mcp_cli.main``) so a silent rename can't
     break every external-runtime operator's MCP install — the 0.1.16
     ``main_sync`` rename incident is the cautionary precedent.
+
+    Args:
+        transport: "stdio" (default) or "http" (HTTP+SSE for Hermes).
+        port: TCP port for HTTP transport (default 9100).
     """
-    _warn_if_stdio_not_pipe()
-    asyncio.run(main())
+    if transport == "http":
+        asyncio.run(_run_http_server(port))
+    else:
+        _warn_if_stdio_not_pipe()
+        asyncio.run(main())
 
 
 if __name__ == "__main__":  # pragma: no cover
-    cli_main()
+    parser = argparse.ArgumentParser(description="A2A MCP Server")
+    parser.add_argument(
+        "--transport",
+        default="stdio",
+        choices=["stdio", "http"],
+        help="Transport mode: stdio (default) or http (HTTP+SSE for Hermes)",
+    )
+    parser.add_argument(
+        "--port",
+        type=int,
+        default=9100,
+        help="TCP port for HTTP transport (default 9100)",
+    )
+    args = parser.parse_args()
+    cli_main(transport=args.transport, port=args.port)
diff --git a/workspace/tests/test_a2a_mcp_server_http.py b/workspace/tests/test_a2a_mcp_server_http.py
new file mode 100644
index 00000000..4e844fb0
--- /dev/null
+++ b/workspace/tests/test_a2a_mcp_server_http.py
@@ -0,0 +1,671 @@
+"""Tests for the HTTP/SSE transport of a2a_mcp_server.
+
+Covers:
+- _handle_http_mcp: JSON-RPC request parsing and routing
+- Starlette app routes: POST /mcp, GET /mcp/stream, GET /health
+- cli_main argparse: --transport and --port flags
+"""
+
+from __future__ import annotations
+
+import asyncio
+import json
+import sys
+import types
+import uuid
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import httpx
+import pytest
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+class _DummyRequest:
+    """Minimal request duck-type for _handle_http_mcp."""
+
+    def __init__(self, body_json: dict, headers: dict | None = None):
+        self._body = body_json
+        self.headers = headers or {}
+
+    async def json(self) -> dict:
+        return self._body
+
+
+# ---------------------------------------------------------------------------
+# _handle_http_mcp — unit tests (no I/O)
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_initialize():
+    """initialize method returns protocol version, capabilities, and server info."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    req = _DummyRequest({"jsonrpc": "2.0", "id": 42, "method": "initialize", "params": {}})
+    resp = await _handle_http_mcp(req)
+
+    assert resp["jsonrpc"] == "2.0"
+    assert resp["id"] == 42
+    assert "protocolVersion" in resp["result"]
+    assert "capabilities" in resp["result"]
+    assert resp["result"]["serverInfo"]["name"] == "molecule"
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_notifications_initialized_returns_none():
+    """notifications/initialized is a notification (no response needed)."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    req = _DummyRequest({"jsonrpc": "2.0", "method": "notifications/initialized"})
+    resp = await _handle_http_mcp(req)
+
+    assert resp is None
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_tools_list():
+    """tools/list returns the TOOLS schema."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    req = _DummyRequest({"jsonrpc": "2.0", "id": 7, "method": "tools/list"})
+    resp = await _handle_http_mcp(req)
+
+    assert resp["jsonrpc"] == "2.0"
+    assert resp["id"] == 7
+    assert "tools" in resp["result"]
+    assert isinstance(resp["result"]["tools"], list)
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_unknown_method_returns_error():
+    """Unknown method returns -32601 Method not found."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    req = _DummyRequest({"jsonrpc": "2.0", "id": 3, "method": "foobar", "params": {}})
+    resp = await _handle_http_mcp(req)
+
+    assert resp["jsonrpc"] == "2.0"
+    assert resp["id"] == 3
+    assert resp["error"]["code"] == -32601
+    assert "Method not found" in resp["error"]["message"]
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_malformed_json_returns_parse_error():
+    """Request with bad JSON returns -32700 parse error."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    req = _DummyRequest.__new__(_DummyRequest)
+    req.headers = {}
+    req.json = AsyncMock(side_effect=ValueError("bad json"))
+
+    resp = await _handle_http_mcp(req)
+
+    assert resp["error"]["code"] == -32700
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_tools_call_with_get_workspace_info():
+    """tools/call for get_workspace_info returns workspace info (mocked platform call)."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    with patch("a2a_mcp_server.tool_get_workspace_info", AsyncMock(return_value="mocked info")):
+        req = _DummyRequest({
+            "jsonrpc": "2.0",
+            "id": 9,
+            "method": "tools/call",
+            "params": {"name": "get_workspace_info", "arguments": {}},
+        })
+        resp = await _handle_http_mcp(req)
+
+    assert resp["jsonrpc"] == "2.0"
+    assert resp["id"] == 9
+    assert resp["result"]["content"][0]["text"] == "mocked info"
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_tools_call_unknown_tool():
+    """tools/call for an unknown tool returns the handle_tool_call error text."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    req = _DummyRequest({
+        "jsonrpc": "2.0",
+        "id": 11,
+        "method": "tools/call",
+        "params": {"name": "not_a_real_tool", "arguments": {}},
+    })
+    resp = await _handle_http_mcp(req)
+
+    assert resp["jsonrpc"] == "2.0"
+    assert resp["id"] == 11
+    assert "Unknown tool" in resp["result"]["content"][0]["text"]
+
+
+# ---------------------------------------------------------------------------
+# Starlette app — integration tests with TestClient
+# ---------------------------------------------------------------------------
+
+
+@pytest.fixture()
+def _clear_http_globals():
+    """Reset module-level HTTP state before and after each test."""
+    import a2a_mcp_server
+
+    # Save and restore globals
+    saved_queues = a2a_mcp_server._http_connection_queues.copy()
+    saved_lock = a2a_mcp_server._http_connection_lock
+    a2a_mcp_server._http_connection_queues.clear()
+    yield
+    # Restore
+    a2a_mcp_server._http_connection_queues = saved_queues
+
+
+
+
+
+def _register_sse_queue():
+    """Register a queue for SSE push delivery (synchronous — callable from tests)."""
+    conn_id = str(uuid.uuid4())
+    queue = asyncio.Queue(maxsize=100)
+    import a2a_mcp_server
+    a2a_mcp_server._http_connection_queues[conn_id] = queue
+    return conn_id, queue
+
+
+def _build_test_app(port: int = 9100):
+    """Build the Starlette app for testing without starting a real server.
+
+    Mirrors the app construction inside _run_http_server, but returns
+    the app directly so TestClient can drive it without binding a port.
+    """
+    from starlette.applications import Starlette
+    from starlette.routing import Route
+
+    import a2a_mcp_server
+
+    async def mcp_handler(request):
+        conn_id = request.headers.get("x-mcp-conn-id", "default")
+        response = await a2a_mcp_server._handle_http_mcp(request)
+        if response is None:
+            from starlette.responses import Response
+            return Response(status_code=202)
+        async with a2a_mcp_server._http_connection_lock:
+            queue = a2a_mcp_server._http_connection_queues.get(conn_id)
+        if queue is not None and not queue.full():
+            await queue.put(response)
+            from starlette.responses import Response
+            return Response(status_code=202)
+        from starlette.responses import JSONResponse
+        return JSONResponse(response)
+
+    async def sse_handler(request):
+        conn_id, queue = _register_sse_queue()
+
+        import asyncio as _asyncio
+
+        async def event_stream():
+            import json as _json
+            yield f"event: connected\ndata: {_json.dumps({'conn_id': conn_id})}\n\n"
+            try:
+                while True:
+                    response = await _asyncio.wait_for(queue.get(), timeout=300)
+                    import json as _json
+                    yield f"event: message\ndata: {_json.dumps(response)}\n\n"
+                    if queue.empty():
+                        yield "event: heartbeat\ndata: null\n\n"
+            except _asyncio.TimeoutError:
+                pass
+            finally:
+                async with a2a_mcp_server._http_connection_lock:
+                    a2a_mcp_server._http_connection_queues.pop(conn_id, None)
+
+        from starlette.responses import StreamingResponse
+        return StreamingResponse(
+            event_stream(),
+            media_type="text/event-stream",
+            headers={
+                "Cache-Control": "no-cache",
+                "Connection": "keep-alive",
+                "X-Accel-Buffering": "no",
+            },
+        )
+
+    async def health_handler(_request):
+        from starlette.responses import JSONResponse
+        return JSONResponse({"ok": True, "transport": "http+sse", "port": port})
+
+    return Starlette(
+        routes=[
+            Route("/mcp", mcp_handler, methods=["POST"]),
+            Route("/mcp/stream", sse_handler, methods=["GET"]),
+            Route("/health", health_handler),
+        ]
+    )
+
+
+class TestHTTPAppRoutes:
+    """Integration tests using Starlette TestClient against the HTTP app.
+
+    Starlette TestClient uses the ASGI interface directly (no real HTTP server
+    or uvicorn needed), so no uvicorn mock is required.
+    """
+
+    def test_health_returns_ok_and_transport(self, _clear_http_globals):
+        from starlette.testclient import TestClient
+
+        app = _build_test_app(port=9100)
+        with TestClient(app) as client:
+            resp = client.get("/health")
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["ok"] is True
+        assert data["transport"] == "http+sse"
+        assert data["port"] == 9100
+
+    def test_health_accepts_different_port(self, _clear_http_globals):
+        from starlette.testclient import TestClient
+
+        app = _build_test_app(port=9999)
+        with TestClient(app) as client:
+            resp = client.get("/health")
+
+        assert resp.json()["port"] == 9999
+
+    def test_mcp_post_initialize(self, _clear_http_globals):
+        from starlette.testclient import TestClient
+
+        app = _build_test_app()
+        with TestClient(app) as client:
+            resp = client.post("/mcp", json={
+                "jsonrpc": "2.0",
+                "id": 1,
+                "method": "initialize",
+                "params": {},
+            })
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["id"] == 1
+        assert "protocolVersion" in data["result"]
+
+    def test_mcp_post_tools_list(self, _clear_http_globals):
+        from starlette.testclient import TestClient
+
+        app = _build_test_app()
+        with TestClient(app) as client:
+            resp = client.post("/mcp", json={
+                "jsonrpc": "2.0",
+                "id": 2,
+                "method": "tools/list",
+                "params": {},
+            })
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "tools" in data["result"]
+        assert len(data["result"]["tools"]) > 0
+
+    def test_mcp_post_notifications_initialized_returns_202(self, _clear_http_globals):
+        from starlette.testclient import TestClient
+
+        app = _build_test_app()
+        with TestClient(app) as client:
+            resp = client.post("/mcp", json={
+                "jsonrpc": "2.0",
+                "method": "notifications/initialized",
+            })
+
+        # Notifications return 202 with no body
+        assert resp.status_code == 202
+
+    def test_mcp_post_unknown_method_returns_200_with_error(self, _clear_http_globals):
+        from starlette.testclient import TestClient
+
+        app = _build_test_app()
+        with TestClient(app) as client:
+            resp = client.post("/mcp", json={
+                "jsonrpc": "2.0",
+                "id": 5,
+                "method": "no_such_method",
+                "params": {},
+            })
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["error"]["code"] == -32601
+
+    def test_mcp_post_malformed_json_returns_error(self, _clear_http_globals):
+        """Malformed JSON body returns a JSON-RPC parse-error response (HTTP 200)."""
+        from starlette.testclient import TestClient
+
+        app = _build_test_app()
+        with TestClient(app, raise_server_exceptions=False) as client:
+            resp = client.post(
+                "/mcp",
+                content=b"not json at all",
+                headers={"Content-Type": "application/json"},
+            )
+        # _handle_http_mcp catches ValueError from request.json() and returns
+        # a JSON-RPC parse-error response with HTTP 200.
+        assert resp.status_code == 200
+        assert resp.json()["error"]["code"] == -32700
+        assert "Parse error" in resp.json()["error"]["message"]
+
+    @pytest.mark.asyncio()
+    async def test_sse_stream_populates_queue(self, _clear_http_globals):
+        """_register_sse_queue adds a queue to _http_connection_queues before any async work."""
+        import a2a_mcp_server
+
+        conn_id, queue = _register_sse_queue()
+
+        # The queue is registered synchronously — no await needed, no cleanup ran yet.
+        assert conn_id in a2a_mcp_server._http_connection_queues
+        assert len(conn_id) == 36  # valid UUID format
+        assert not queue.full()
+
+    @pytest.mark.asyncio()
+    async def test_sse_queue_delivers_response(self, _clear_http_globals):
+        """POST /mcp with x-mcp-conn-id routes response into the SSE queue."""
+        import uuid
+
+        import a2a_mcp_server
+        from starlette.testclient import TestClient
+
+        # Pre-register an SSE queue to simulate an active SSE subscriber
+        conn_id = str(uuid.uuid4())
+        queue: asyncio.Queue = asyncio.Queue(maxsize=100)
+        async with a2a_mcp_server._http_connection_lock:
+            a2a_mcp_server._http_connection_queues[conn_id] = queue
+
+        # POST a tools/call with the conn_id header
+        with TestClient(_build_test_app()) as client:
+            with patch("a2a_mcp_server.tool_get_workspace_info", AsyncMock(return_value="test-ws-info")):
+                resp = client.post(
+                    "/mcp",
+                    headers={"x-mcp-conn-id": conn_id},
+                    json={
+                        "jsonrpc": "2.0",
+                        "id": 99,
+                        "method": "tools/call",
+                        "params": {"name": "get_workspace_info", "arguments": {}},
+                    },
+                )
+
+        # The handler returns 202 because the response was queued for SSE delivery
+        assert resp.status_code == 202
+
+        # Verify the response was placed in the SSE queue
+        result = await asyncio.wait_for(queue.get(), timeout=2.0)
+        assert result["id"] == 99
+        assert result["result"]["content"][0]["text"] == "test-ws-info"
+
+
+# ---------------------------------------------------------------------------
+# handle_tool_call — remaining tool branches
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_tools_call_send_message_to_user_with_mixed_attachments():
+    """attachments with non-string elements are filtered; the list branch is exercised."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    with patch("a2a_mcp_server.tool_send_message_to_user", AsyncMock(return_value="sent ok")) as mock_fn:
+        req = _DummyRequest({
+            "jsonrpc": "2.0",
+            "id": 21,
+            "method": "tools/call",
+            "params": {
+                "name": "send_message_to_user",
+                "arguments": {
+                    "message": "hello",
+                    # Mixed types: list contains a dict (non-string) and an empty string
+                    "attachments": [{"url": "http://x"}, "", "valid.zip", None],
+                },
+            },
+        })
+        resp = await _handle_http_mcp(req)
+
+    assert resp["result"]["content"][0]["text"] == "sent ok"
+    # Only string, non-empty values passed through
+    mock_fn.assert_called_once()
+    _, kwargs = mock_fn.call_args
+    assert kwargs["attachments"] == ["valid.zip"]
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_tools_call_wait_for_message():
+    """wait_for_message is dispatched and returns the wrapped result."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    with patch("a2a_mcp_server.tool_wait_for_message", AsyncMock(return_value="no messages")):
+        req = _DummyRequest({
+            "jsonrpc": "2.0",
+            "id": 22,
+            "method": "tools/call",
+            "params": {"name": "wait_for_message", "arguments": {"timeout_secs": 5.0}},
+        })
+        resp = await _handle_http_mcp(req)
+
+    assert resp["result"]["content"][0]["text"] == "no messages"
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_tools_call_inbox_peek():
+    """inbox_peek is dispatched with the limit argument."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    with patch("a2a_mcp_server.tool_inbox_peek", AsyncMock(return_value="2 items")):
+        req = _DummyRequest({
+            "jsonrpc": "2.0",
+            "id": 23,
+            "method": "tools/call",
+            "params": {"name": "inbox_peek", "arguments": {"limit": 5}},
+        })
+        resp = await _handle_http_mcp(req)
+
+    assert resp["result"]["content"][0]["text"] == "2 items"
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_tools_call_inbox_pop():
+    """inbox_pop is dispatched with the activity_id argument."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    with patch("a2a_mcp_server.tool_inbox_pop", AsyncMock(return_value="acked")):
+        req = _DummyRequest({
+            "jsonrpc": "2.0",
+            "id": 24,
+            "method": "tools/call",
+            "params": {"name": "inbox_pop", "arguments": {"activity_id": "abc-123"}},
+        })
+        resp = await _handle_http_mcp(req)
+
+    assert resp["result"]["content"][0]["text"] == "acked"
+
+
+@pytest.mark.asyncio()
+async def test_handle_http_mcp_tools_call_chat_history():
+    """chat_history is dispatched with peer_id, limit, and before_ts arguments."""
+    from a2a_mcp_server import _handle_http_mcp
+
+    with patch("a2a_mcp_server.tool_chat_history", AsyncMock(return_value="history")):
+        req = _DummyRequest({
+            "jsonrpc": "2.0",
+            "id": 25,
+            "method": "tools/call",
+            "params": {
+                "name": "chat_history",
+                "arguments": {"peer_id": "ws-peer-1", "limit": 10, "before_ts": ""},
+            },
+        })
+        resp = await _handle_http_mcp(req)
+
+    assert resp["result"]["content"][0]["text"] == "history"
+
+
+# ---------------------------------------------------------------------------
+# cli_main argparse — unit tests
+# ---------------------------------------------------------------------------
+
+
+def test_mcp_post_falls_back_to_json_when_sse_queue_is_full(_clear_http_globals):
+    """When the SSE queue is full (>100 pending), the handler returns JSON directly."""
+    import a2a_mcp_server
+    from starlette.testclient import TestClient
+
+    # Pre-register a queue and fill it to capacity
+    conn_id = str(uuid.uuid4())
+    queue: asyncio.Queue = asyncio.Queue(maxsize=2)  # small queue for testing
+
+    async def _setup():
+        async with a2a_mcp_server._http_connection_lock:
+            a2a_mcp_server._http_connection_queues[conn_id] = queue
+        queue.put_nowait({"id": 1})
+        queue.put_nowait({"id": 2})
+
+    _sync_run(_setup())
+    assert queue.full()
+
+    app = _build_test_app()
+    with TestClient(app) as client:
+        resp = client.post(
+            "/mcp",
+            headers={"x-mcp-conn-id": conn_id},
+            json={"jsonrpc": "2.0", "id": 99, "method": "initialize", "params": {}},
+        )
+
+    # With a full queue, the handler returns the response as JSON (not 202)
+    assert resp.status_code == 200
+    assert resp.json()["id"] == 99
+    assert "result" in resp.json()
+
+
+def _sync_run(coro):
+    """Run a coroutine synchronously for test isolation (no real event loop needed)."""
+    try:
+        loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(loop)
+        try:
+            return loop.run_until_complete(coro)
+        finally:
+            loop.close()
+    except Exception:
+        raise
+
+
+def test_cli_main_transport_stdio_calls_main(monkeypatch):
+    """cli_main(transport='stdio') calls asyncio.run(main) without HTTP."""
+    import a2a_mcp_server
+
+    run_calls: list = []
+
+    async def fake_main():
+        run_calls.append("called")
+
+    monkeypatch.setattr(a2a_mcp_server, "main", fake_main)
+    monkeypatch.setattr(a2a_mcp_server.asyncio, "run", _sync_run)
+    monkeypatch.setattr(a2a_mcp_server, "_assert_stdio_is_pipe_compatible", lambda: None)
+
+    a2a_mcp_server.cli_main(transport="stdio", port=9100)
+
+    assert "called" in run_calls
+
+
+def test_cli_main_transport_http_calls_run_http_server(monkeypatch):
+    """cli_main(transport='http') calls _run_http_server without stdio."""
+    import a2a_mcp_server
+
+    run_http_calls = []
+
+    async def fake_run_http(port):
+        run_http_calls.append(port)
+
+    # asyncio.run must execute the coroutine for _run_http_server to be called
+    monkeypatch.setattr(a2a_mcp_server.asyncio, "run", _sync_run)
+    monkeypatch.setattr(a2a_mcp_server, "_run_http_server", fake_run_http)
+    # stdio path must not be entered
+    monkeypatch.setattr(a2a_mcp_server, "_assert_stdio_is_pipe_compatible", lambda: None)
+
+    a2a_mcp_server.cli_main(transport="http", port=9102)
+
+    assert run_http_calls == [9102]
+
+
+def test_cli_main_http_skips_stdio_check(monkeypatch):
+    """When transport=http, _assert_stdio_is_pipe_compatible must NOT be called."""
+    import a2a_mcp_server
+
+    called = []
+
+    def fake_assert():
+        called.append("assert_called")
+
+    # Patch on the module object directly
+    monkeypatch.setattr(a2a_mcp_server, "_assert_stdio_is_pipe_compatible", fake_assert)
+    monkeypatch.setattr(a2a_mcp_server.asyncio, "run", lambda fn: None)
+
+    a2a_mcp_server.cli_main(transport="http", port=9100)
+
+    assert "assert_called" not in called
+
+
+def test_cli_main_default_transport_is_stdio(monkeypatch):
+    """cli_main() with no args defaults to stdio transport."""
+    import a2a_mcp_server
+
+    called_as: list = []
+
+    async def fake_main():
+        called_as.append("called")
+
+    monkeypatch.setattr(a2a_mcp_server, "main", fake_main)
+    monkeypatch.setattr(a2a_mcp_server.asyncio, "run", _sync_run)
+    monkeypatch.setattr(a2a_mcp_server, "_assert_stdio_is_pipe_compatible", lambda: None)
+
+    a2a_mcp_server.cli_main()  # No args — defaults to stdio
+
+    assert "called" in called_as
+
+
+def test_cli_main_main_raises_propagates(monkeypatch):
+    """If main() raises, cli_main() re-raises (doesn't swallow)."""
+    import a2a_mcp_server
+
+    async def fake_main():
+        raise RuntimeError("boom")
+
+    monkeypatch.setattr(a2a_mcp_server, "main", fake_main)
+    monkeypatch.setattr(a2a_mcp_server.asyncio, "run", _sync_run)
+    monkeypatch.setattr(a2a_mcp_server, "_assert_stdio_is_pipe_compatible", lambda: None)
+
+    with pytest.raises(RuntimeError, match="boom"):
+        a2a_mcp_server.cli_main(transport="stdio")
+
+
+# ---------------------------------------------------------------------------
+# uvicorn/starlette lazy-import
+# ---------------------------------------------------------------------------
+
+
+def test_run_http_server_is_coroutine_function():
+    """_run_http_server is a coroutine function accepting a port argument."""
+    import inspect
+    from a2a_mcp_server import _run_http_server
+
+    assert inspect.iscoroutinefunction(_run_http_server)
+
+
+def test_run_http_server_signature_port_int():
+    """_run_http_server accepts port as int."""
+    import inspect
+    from a2a_mcp_server import _run_http_server
+
+    sig = inspect.signature(_run_http_server)
+    assert "port" in sig.parameters
+    assert sig.parameters["port"].annotation == int
diff --git a/workspace/tests/test_builtin_security.py b/workspace/tests/test_builtin_security.py
new file mode 100644
index 00000000..334a44a4
--- /dev/null
+++ b/workspace/tests/test_builtin_security.py
@@ -0,0 +1,107 @@
+"""Test coverage for builtin_tools.security._redact_secrets().
+
+Issue #834 (C2): commit_memory must not persist API keys verbatim.
+
+Pre-commit hook blocks bare secret-like strings (ghp_, sk-ant-, etc.) to prevent
+accidental commits of real credentials.  These tests focus on the functional
+behaviour of the redaction logic: idempotency, contextual keyword=value patterns,
+boundary cases, and mixed content — without triggering the hook's length thresholds.
+The pre-commit hook itself is the primary guard for bare-pattern detection.
+"""
+from __future__ import annotations
+
+from builtin_tools.security import REDACTED, _redact_secrets
+
+
+class TestRedactContextual:
+    """Keyword=value patterns with high-entropy values (under pre-commit threshold)."""
+
+    def test_api_key_contextual(self):
+        """api_key=X where X ≥ 40 base64 chars → value replaced, keyword preserved."""
+        value = "A" * 40
+        assert _redact_secrets(f"api_key={value}") == f"api_key={REDACTED}"
+
+    def test_keyword_contextual(self):
+        """Generic 'key=' also matches."""
+        value = "B" * 45
+        assert _redact_secrets(f"key={value}") == f"key={REDACTED}"
+
+    def test_secret_contextual(self):
+        value = "C" * 50
+        assert _redact_secrets(f"secret= {value}") == f"secret= {REDACTED}"
+
+    def test_token_contextual(self):
+        value = "D" * 40
+        assert _redact_secrets(f"token={value}") == f"token={REDACTED}"
+
+    def test_password_contextual(self):
+        value = "E" * 50
+        assert _redact_secrets(f"password={value}") == f"password={REDACTED}"
+
+    def test_keyword_spacing_tolerated(self):
+        """Spaces around = are tolerated by the pattern."""
+        value = "F" * 40
+        assert _redact_secrets(f"key = {value}") == f"key = {REDACTED}"
+
+    def test_contextual_too_short_not_redacted(self):
+        """Value shorter than 40 chars is not redacted."""
+        short = "A" * 39
+        assert _redact_secrets(f"api_key={short}") == f"api_key={short}"
+
+    def test_case_insensitive_keyword(self):
+        """Keyword matching is case-insensitive."""
+        value = "G" * 40
+        assert _redact_secrets(f"API_KEY={value}") == f"API_KEY={REDACTED}"
+        assert _redact_secrets(f"Token={value}") == f"Token={REDACTED}"
+        assert _redact_secrets(f"SECRET={value}") == f"SECRET={REDACTED}"
+
+    def test_boundary_preserved(self):
+        """Contextual pattern preserves the keyword; only value is replaced."""
+        value = "H" * 40
+        result = _redact_secrets(f"api_key={value}")
+        assert result.startswith("api_key=")
+        assert result.endswith(REDACTED)
+        assert result == f"api_key={REDACTED}"
+
+    def test_base64_chars_in_value(self):
+        """Base64 alphabet chars (/ +) in value are covered by the charset."""
+        # 40-char string with base64 chars
+        value = "A" * 20 + "/+" + "A" * 18
+        result = _redact_secrets(f"api_key={value}")
+        assert result == f"api_key={REDACTED}"
+
+
+class TestRedactEdgeCases:
+    """Non-secret strings, idempotency, and boundary conditions."""
+
+    def test_idempotent(self):
+        """Calling redaction twice produces the same result."""
+        text = f"token={'A' * 40}"
+        first = _redact_secrets(text)
+        second = _redact_secrets(first)
+        assert second == first
+        assert REDACTED in first
+
+    def test_already_redacted_string(self):
+        """The [REDACTED] sentinel itself is not matched by any pattern."""
+        assert _redact_secrets(f"see {REDACTED} here") == f"see {REDACTED} here"
+
+    def test_no_match_passthrough(self):
+        """Normal prose passes through unchanged."""
+        assert _redact_secrets("The answer is 42.") == "The answer is 42."
+        assert _redact_secrets("Hello, world!") == "Hello, world!"
+        assert _redact_secrets("api_key short") == "api_key short"
+        assert _redact_secrets("") == ""
+
+    def test_empty_string(self):
+        assert _redact_secrets("") == ""
+
+    def test_short_value_not_secret(self):
+        """A short string after a keyword= prefix is not a secret."""
+        assert _redact_secrets("token=short") == "token=short"
+
+    def test_mixed_content(self):
+        """Real text with a secret-like prefix → only the secret is redacted."""
+        value = "A" * 40
+        result = _redact_secrets(f"found secret: api_key={value} in config")
+        assert result == f"found secret: api_key={REDACTED} in config"