test(sdk): the server knows its own name, and the tool never hears it

B4 asked whether this side gets server identity for free in tool names.
It does not. create_sdk_mcp_server emits the bare name; mcp__ appears in
0 of the package's 24 files, with create_sdk_mcp_server itself as the
positive control that the query can find. Identity lives on the config
and on Server.name, disjoint from anything the tool list carries.

The prefix does exist -- 178 times, inside the CLI bundled with the SDK.
But that was read off the artifact, not observed in a run, and observing
it would cost the one live query() this repo does not spend. So the
finding is scoped to the seam we can actually hang a recorder on, and
the note says so rather than claiming the wider thing.

Value-proved, not asserted: mutating the SDK to namespace at construction
time turns 3 of the 4 tests red, and the one that stays green is the
population control, which should. The SDK file was restored byte-identical.

Same answer as the MAF sibling, arrived at after 2026-08-09 -- so it is
recorded as a measurement, not as independent convergence.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/2026-08-18-funn-koeer-og-gater.md

@@ -44,10 +44,38 @@ kandidater, ikke som planlagt arbeid:
 - (a)/(i) `unquote_scalar`
 - `mandate.py`
 - A5 — TO halvdeler
-- B4 `ToolCallRecorder`
+- ~~B4 `ToolCallRecorder`~~ — **BESVART 2026-08-25, se under**
 
-**B4 spør OSS:** gir Claude-SDK-siden serveridentiteten gratis? MAF får verktøynavn UTEN
-server-prefiks. **Ikke målt — ikke gjett.** Åpent hos søskenet: MAF S3.4 (F10).
+**B4 spurte OSS:** gir Claude-SDK-siden serveridentiteten gratis? MAF får verktøynavn UTEN
+server-prefiks. Åpent hos søskenet: MAF S3.4 (F10).
+
+### B4 — svaret er NEI (målt 2026-08-25, offline, mot `claude-agent-sdk` 0.2.139)
+
+`create_sdk_mcp_server` emitterer det **bare** verktøynavnet. Serveridentiteten finnes — på
+`McpSdkServerConfig["name"]` og `Server.name` — men den er **disjunkt fra hvert navn
+verktøylista bærer**. Strengen `mcp__` forekommer i **0 av 24** Python-filer i pakken
+(positiv kontroll: `create_sdk_mcp_server` blir funnet av samme spørring, så spørringen KAN
+finne). Konstruksjonssiden namespacer altså ingenting: en `ToolCallRecorder` hengt der ser
+`record_call`, ikke `mcp__tool_call_recorder__record_call`, og må få servernavnet fortalt.
+Det er **samme pris som søskenet betaler**.
+
+**Ærlig grense — hva målingen IKKE sier.** Den navnerommede formen `mcp__<server>__<tool>`
+eksisterer: den bygges inne i CLI-en som følger med SDK-en (`_bundled/claude`, 178 literale
+`mcp__`-forekomster, konstruksjonen på formen `` `mcp__${…}__${…}` ``). Det er **lest av
+artefaktet, ikke observert i en kjøring hos oss** — å se den emittert krever en live
+`query()`, som både D6-kostnadsregelen og suitens offline-invariant forbyr. Funnet er derfor
+scopet til den sømmen vi faktisk kan bygge på: den in-process konstruksjonssiden. Prefikset
+finnes på et lag vi bevisst ikke kjører, og et lag vi ikke kjører er ikke en søm vi kan feste
+en recorder i.
+
+**Pinnet av** `tests/test_sdk_tool_namespace_loadbearing.py` (4 tester). Value-beviset er
+kjørt, ikke påstått: SDK-en ble mutert til å namespace ved konstruksjon (`"name":
+f"mcp__{name}__{tool_def.name}"`) — **grønn før, 3 av 4 røde etter**, og den ene som forble
+grønn er nettopp populasjons-kontrollen, som den skal. SDK-fila ble restaurert byte-identisk
+(sha256 verifisert begge veier).
+
+**Datering (D7-rammen):** dette er arbeid ETTER 2026-08-09 og skal **ikke** leses som
+uavhengig konvergens selv om svaret er identisk med søskenets.
 
 Rammen rundt køen: å lese søskenets kode er tillatt (`3bdf7f0`), men kopiering skal kun skje
 der det tjener løsningen, aldri som snarvei. **Uavhengighets-beviset er DATERT** t.o.m.

tests/test_sdk_tool_namespace_loadbearing.py

@@ -0,0 +1,128 @@
+"""B4: does the Claude Agent SDK hand us server identity for free in tool names?
+
+The D7 mirroring queue (``docs/2026-08-18-funn-koeer-og-gater.md § D7-speilingskøen``)
+asks one question of this side: when ``create_sdk_mcp_server`` emits a tool, does
+that tool's name carry the server it belongs to? The MAF sibling gets tool names
+WITHOUT a server prefix (their S3.4/F10), so a recorder there must carry server
+identity itself. Whether we pay the same price was never measured here.
+
+MEASURED 2026-08-25, offline, against claude-agent-sdk 0.2.139 (the version
+``tests/test_sdk_version_guard.py`` pins as read): **NO — not free.** The Python
+package emits the bare tool name; ``mcp__`` appears in ZERO of its 24 source files
+(positive control: ``create_sdk_mcp_server`` IS findable by the same query).
+Server identity lives on ``McpSdkServerConfig["name"]`` and ``Server.name``,
+disjoint from every name the tool list carries.
+
+HONEST LIMIT — what this does NOT say. The namespaced form ``mcp__<server>__<tool>``
+does exist: it is built inside the CLI bundled with the SDK (178 literal
+occurrences of ``mcp__`` in ``_bundled/claude``; the construction reads
+``` `mcp__${...}__${...}` ```). That was READ from the artifact, not observed in a
+run of ours — seeing it emitted would take a live ``query()``, which the D6 cost
+rule and this suite's offline invariant both forbid. So the finding is scoped to
+the seam we can actually build on: the in-process construction side. A recorder
+hung there sees the bare name and must be told which server it came from —
+the same shape the sibling pays for, arrived at after 2026-08-09 and therefore
+NOT readable as independent convergence.
+
+Offline-safe: constructing an SDK MCP server touches no network and needs no API
+key. Nothing here starts the bundled CLI.
+"""
+
+from __future__ import annotations
+
+import asyncio
+from typing import Any
+
+from claude_agent_sdk import McpSdkServerConfig, create_sdk_mcp_server, tool
+
+SERVER_NAME = "tool_call_recorder"
+BARE_TOOL_NAMES = ("record_call", "flush_calls")
+
+# What a "free" server identity would have to look like for B4 to be answered
+# YES. Kept as data so the assertions below read as the question, not as a
+# restatement of the answer.
+NAMESPACED_PREFIX = f"mcp__{SERVER_NAME}__"
+
+
+@tool("record_call", "Record one tool call", {"name": str})
+async def _record_call(args: dict[str, Any]) -> dict[str, Any]:
+    return {"content": [{"type": "text", "text": args["name"]}]}
+
+
+@tool("flush_calls", "Flush recorded calls", {})
+async def _flush_calls(args: dict[str, Any]) -> dict[str, Any]:
+    return {"content": [{"type": "text", "text": "flushed"}]}
+
+
+def _server(*, tools: list[Any] | None = None) -> McpSdkServerConfig:
+    return create_sdk_mcp_server(
+        name=SERVER_NAME,
+        version="1.0.0",
+        tools=[_record_call, _flush_calls] if tools is None else tools,
+    )
+
+
+def _emitted_tool_names(config: McpSdkServerConfig) -> list[str]:
+    """Read the tool names the server ACTUALLY emits.
+
+    Not a model of the emission — the registered ``tools/list`` handler is
+    invoked and its result read, because a check that models a tool instead of
+    reading it is green-but-dead (økt 28). The coupling that buys this is the
+    MCP lowlevel ``Server.request_handlers`` dispatch table; should its shape
+    change, the lookup below raises rather than quietly returning nothing, so
+    the failure mode is RED, not a false negative.
+    """
+    from mcp.types import ListToolsRequest
+
+    handler = config["instance"].request_handlers[ListToolsRequest]
+
+    async def _call() -> list[str]:
+        result = await handler(ListToolsRequest(method="tools/list"))
+        return [t.name for t in result.root.tools]
+
+    return asyncio.run(_call())
+
+
+class TestEmittedToolNamesCarryNoServerIdentity:
+    def test_the_emission_is_readable_and_the_population_is_two(self) -> None:
+        # POSITIVE CONTROL, and it runs FIRST: every negative below is worth
+        # exactly as much as this query's ability to find anything at all. An
+        # empty tool list would make "no name carries the prefix" vacuously
+        # true — so the denominator is asserted, not assumed.
+        names = _emitted_tool_names(_server())
+        assert len(names) == 2, f"emission unreadable or empty — measured {names!r}"
+        assert all(isinstance(n, str) and n for n in names)
+
+    def test_no_emitted_name_carries_the_server_prefix(self) -> None:
+        # THE B4 ANSWER, pinned. Red the day the SDK starts namespacing at
+        # construction time — which is the day this repo can stop carrying
+        # server identity by hand and the D7 queue note becomes wrong.
+        names = _emitted_tool_names(_server())
+        assert names == list(BARE_TOOL_NAMES)
+        assert not any(n.startswith("mcp__") for n in names), (
+            f"the SDK now namespaces at construction time — B4 flipped to YES: {names!r}"
+        )
+        assert not any(SERVER_NAME in n for n in names)
+
+    def test_the_name_is_passed_through_untouched(self) -> None:
+        # POSITIVE CONTROL FOR THE NEGATIVE. The assertion above only means
+        # something if a prefix WOULD have shown up had one been there. Feed
+        # the server a tool already wearing the namespaced form: it comes back
+        # verbatim. So the emission is pass-through, the query can see a
+        # prefix, and its absence above is a measurement — not a blind spot.
+        @tool(f"{NAMESPACED_PREFIX}record_call", "Pre-namespaced", {"name": str})
+        async def _prefixed(args: dict[str, Any]) -> dict[str, Any]:
+            return {"content": [{"type": "text", "text": args["name"]}]}
+
+        names = _emitted_tool_names(_server(tools=[_prefixed]))
+        assert names == [f"{NAMESPACED_PREFIX}record_call"]
+
+    def test_server_identity_exists_but_lives_off_the_tool_name(self) -> None:
+        # The disjointness is the whole finding: identity is AVAILABLE, just
+        # not on the tool. A recorder must join the two itself — this pins
+        # both halves so "free" cannot be assumed from either one alone.
+        config = _server()
+        assert config["type"] == "sdk"
+        assert config["name"] == SERVER_NAME
+        assert config["instance"].name == SERVER_NAME
+        assert SERVER_NAME not in "".join(_emitted_tool_names(config))