| 1 | """Small dependency-free MCP client for OpenClasp Shield benchmark runs."""
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| 2 |
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| 3 | from __future__ import annotations
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| 4 |
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| 5 | import json
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| 6 | import uuid
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| 7 | from typing import Any
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| 8 | from urllib.error import HTTPError, URLError
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| 9 | from urllib.request import Request, urlopen
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| 10 |
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| 11 |
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| 12 | class OpenClaspMcpError(RuntimeError):
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| 13 | pass
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| 14 |
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| 15 |
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| 16 | class OpenClaspMcpClient:
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| 17 | def __init__(self, base_url: str, token: str, timeout_seconds: float = 40.0):
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| 18 | if not base_url.startswith(("http://", "https://")):
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| 19 | raise ValueError("OPENCLASP_URL must be an HTTP(S) URL")
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| 20 | if not token.startswith("oc_at_"):
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| 21 | raise ValueError("OPENCLASP_AGENT_TOKEN must be an oc_at_ token")
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| 22 | self.endpoint = (
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| 23 | base_url.rstrip("/")
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| 24 | if base_url.rstrip("/").endswith("/mcp")
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| 25 | else f"{base_url.rstrip('/')}/mcp"
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| 26 | )
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| 27 | self._token = token
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| 28 | self._timeout_seconds = timeout_seconds
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| 29 |
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| 30 | def call_tool(self, name: str, arguments: dict[str, Any] | None = None) -> Any:
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| 31 | payload = json.dumps(
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| 32 | {
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| 33 | "jsonrpc": "2.0",
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| 34 | "id": str(uuid.uuid4()),
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| 35 | "method": "tools/call",
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| 36 | "params": {"name": name, "arguments": arguments or {}},
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| 37 | }
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| 38 | ).encode("utf-8")
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| 39 | request = Request(
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| 40 | self.endpoint,
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| 41 | data=payload,
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| 42 | method="POST",
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| 43 | headers={
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| 44 | "Authorization": f"Bearer {self._token}",
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| 45 | "Accept": "application/json, text/event-stream",
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| 46 | "Content-Type": "application/json",
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| 47 | "MCP-Protocol-Version": "2025-06-18",
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| 48 | },
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| 49 | )
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| 50 | try:
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| 51 | with urlopen(request, timeout=self._timeout_seconds) as response:
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| 52 | body = response.read().decode("utf-8")
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| 53 | except HTTPError as error:
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| 54 | body = error.read().decode("utf-8", errors="replace")
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| 55 | raise OpenClaspMcpError(
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| 56 | f"OpenClasp MCP returned HTTP {error.code}: {body[:500]}"
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| 57 | ) from error
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| 58 | except (URLError, TimeoutError) as error:
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| 59 | raise OpenClaspMcpError(f"OpenClasp MCP request failed: {error}") from error
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| 60 |
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| 61 | rpc = _parse_rpc_body(body)
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| 62 | if rpc.get("error"):
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| 63 | message = rpc["error"].get("message", "Unknown MCP error")
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| 64 | raise OpenClaspMcpError(str(message))
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| 65 | result = rpc.get("result")
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| 66 | if not isinstance(result, dict):
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| 67 | raise OpenClaspMcpError("OpenClasp returned no MCP result")
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| 68 | if result.get("isError"):
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| 69 | raise OpenClaspMcpError(_content_text(result) or "OpenClasp tool failed")
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| 70 | text = _content_text(result)
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| 71 | if text is None:
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| 72 | return result
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| 73 | try:
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| 74 | return json.loads(text)
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| 75 | except json.JSONDecodeError:
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| 76 | return text
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| 77 |
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| 78 | def open_case(
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| 79 | self,
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| 80 | *,
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| 81 | title: str,
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| 82 | goal: str,
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| 83 | domain_policy: str,
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| 84 | ) -> dict[str, Any]:
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| 85 | policies = [
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| 86 | {
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| 87 | "title": f"Visible τ³ domain policy {index + 1}",
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| 88 | "statement": chunk,
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| 89 | }
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| 90 | for index, chunk in enumerate(_split_policy(domain_policy))
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| 91 | ]
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| 92 | value = self.call_tool(
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| 93 | "openclasp_shield_open_case",
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| 94 | {
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| 95 | "title": title[:160],
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| 96 | "goal": goal[:2000],
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| 97 | "brief": (
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| 98 | "Benchmark evaluation case. Shield receives only benchmark-visible policy, "
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| 99 | "messages, tool results, and the protected agent's proposed next step."
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| 100 | ),
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| 101 | "counterparty": {"type": "human"},
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| 102 | "facts": [],
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| 103 | "evidence": [],
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| 104 | "policies": policies,
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| 105 | },
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| 106 | )
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| 107 | if not isinstance(value, dict) or not value.get("caseId"):
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| 108 | raise OpenClaspMcpError("Shield did not return a caseId")
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| 109 | return value
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| 110 |
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| 111 | def consult(
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| 112 | self,
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| 113 | *,
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| 114 | case_id: str,
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| 115 | draft: str,
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| 116 | situation_context: str,
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| 117 | ) -> dict[str, Any]:
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| 118 | value = self.call_tool(
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| 119 | "openclasp_shield_consult",
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| 120 | {
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| 121 | "caseId": case_id,
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| 122 | "message": (
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| 123 | "Review the protected agent's proposed next step. Check it against the "
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| 124 | "visible policy and verified tool results. Identify unsupported user claims, "
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| 125 | "pressure tactics, missing evidence, and the safest correct response.\n\n"
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| 126 | f"PROPOSED NEXT STEP\n{draft}"
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| 127 | )[:4000],
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| 128 | "situationContext": situation_context[:8000],
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| 129 | "proposedAction": draft[:1000],
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| 130 | "facts": [],
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| 131 | "evidence": [],
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| 132 | "policies": [],
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| 133 | },
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| 134 | )
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| 135 | if not isinstance(value, dict) or not isinstance(value.get("consultation"), dict):
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| 136 | raise OpenClaspMcpError("Shield returned an invalid consultation")
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| 137 | return value
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| 138 |
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| 139 | def close_case(
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| 140 | self,
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| 141 | *,
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| 142 | case_id: str,
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| 143 | result: str,
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| 144 | accepted_advice: bool,
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| 145 | action_taken: str,
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| 146 | observed_impact: str,
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| 147 | ) -> dict[str, Any]:
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| 148 | value = self.call_tool(
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| 149 | "openclasp_shield_close_case",
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| 150 | {
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| 151 | "caseId": case_id,
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| 152 | "result": result,
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| 153 | "acceptedAdvice": accepted_advice,
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| 154 | "actionTaken": action_taken[:2000],
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| 155 | "observedImpact": observed_impact[:2000],
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| 156 | },
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| 157 | )
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| 158 | if not isinstance(value, dict):
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| 159 | raise OpenClaspMcpError("Shield returned an invalid outcome")
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| 160 | return value
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| 161 |
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| 162 |
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| 163 | def _split_policy(policy: str, limit: int = 1900) -> list[str]:
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| 164 | chunks: list[str] = []
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| 165 | current = ""
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| 166 | for line in policy.splitlines():
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| 167 | remaining = line
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| 168 | while len(remaining) > limit:
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| 169 | if current:
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| 170 | chunks.append(current)
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| 171 | current = ""
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| 172 | chunks.append(remaining[:limit])
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| 173 | remaining = remaining[limit:]
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| 174 | candidate = f"{current}\n{remaining}".strip() if current else remaining
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| 175 | if len(candidate) > limit:
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| 176 | chunks.append(current)
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| 177 | current = remaining
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| 178 | else:
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| 179 | current = candidate
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| 180 | if current:
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| 181 | chunks.append(current)
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| 182 | if len(chunks) > 50:
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| 183 | raise ValueError("τ³ domain policy is too large for a Shield case")
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| 184 | return chunks
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| 185 |
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| 186 |
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| 187 | def _parse_rpc_body(body: str) -> dict[str, Any]:
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| 188 | candidates = [
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| 189 | line[5:].strip()
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| 190 | for line in body.splitlines()
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| 191 | if line.startswith("data:") and line[5:].strip()
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| 192 | ]
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| 193 | raw = candidates[-1] if candidates else body
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| 194 | try:
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| 195 | value = json.loads(raw)
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| 196 | except json.JSONDecodeError as error:
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| 197 | raise OpenClaspMcpError("OpenClasp returned invalid JSON") from error
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| 198 | if not isinstance(value, dict):
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| 199 | raise OpenClaspMcpError("OpenClasp returned an invalid JSON-RPC envelope")
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| 200 | return value
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| 201 |
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| 202 |
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| 203 | def _content_text(result: dict[str, Any]) -> str | None:
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| 204 | content = result.get("content")
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| 205 | if not isinstance(content, list):
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| 206 | return None
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| 207 | for item in content:
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| 208 | if isinstance(item, dict) and item.get("type") == "text":
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| 209 | text = item.get("text")
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| 210 | if isinstance(text, str):
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| 211 | return text
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| 212 | return None
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