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feat(tokens): MCP tool-schema deferral check + CLI-over-MCP lever (v5.10 B4)

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By default Claude Code defers MCP tool schemas (names-only, ~120 tok; full
schemas on demand via tool search). CA-TOK-006 detects config-file signals that
force the FULL schemas into the always-loaded prefix every turn:
  - settings.json env.ENABLE_TOOL_SEARCH="false"          (high)
  - "ToolSearch" in permissions.deny                       (high)
  - configured model is a Haiku model                      (medium)
  - per-server .mcp.json alwaysLoad:true (CC v2.1.121+)    (high)
auto[:N] is threshold mode (info, not a trigger).

New engine lib/mcp-deferral.mjs: pure assessMcpDeferral({settings,mcpServers})
(unit-tested, no IO) + thin IO wrapper assessMcpDeferralForRepo shared by TOK and
GAP. Severity scales with aggregate forced-upfront tokens (medium-confidence
reasons cap at medium). feature-gap cliOverMcpLeverFinding fires only as a
companion to CA-TOK-006 (prefer gh/aws/gcloud over MCP for common ops).

Honest scoping (Verifiseringsplikt): triggers on config files ONLY — never
process.env shell vars. Vertex / custom ANTHROPIC_BASE_URL / runtime /model
switch are launch state (would flap snapshots machine-dependently), so they are
DISCLOSED in every finding, not triggered. Tool-level anthropic/alwaysLoad and
claude.ai connectors likewise disclosed. Mechanism verified 2026-06-23 against
code.claude.com/docs (context-window.md, mcp.md#configure-tool-search +
#exempt-a-server-from-deferral, costs.md); the prefix-cache invalidation claim
was NOT-CONFIRMED in docs and is not asserted.

alwaysLoad added to CA-MCP VALID_SERVER_FIELDS (no longer flagged as unknown).
active-config-reader surfaces per-server alwaysLoad. Byte-stable: CA-TOK-006
fires only on new conditions; frozen v5.0.0 + SC-5 snapshots untouched.
Tests 1215 -> 1239 (engine 16, integration 5, lever 2, mcp-field guard 1).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Kjell Tore Guttormsen 2026-06-23 19:59:14 +02:00
commit 8f7e196046
13 changed files with 692 additions and 2 deletions
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scanners/mcp-config-validator.mjs
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@ -18,6 +18,9 @@ const VALID_SERVER_TYPES = new Set(['stdio', 'http', 'sse']);
// not a per-server .mcp.json field. Verified against code.claude.com/docs 2026-06-18.
const VALID_SERVER_FIELDS = new Set([
'type', 'command', 'args', 'env', 'url', 'headers', 'timeout',
// alwaysLoad: exempt a server from MCP tool-schema deferral (CC v2.1.121+).
// Verified against code.claude.com/docs/en/mcp.md#exempt-a-server-from-deferral 2026-06-23.
'alwaysLoad',
]);
// Match only bare ${IDENTIFIER} references. POSIX expansions like ${VAR%pattern}