v0.8.53 — MCP Tasks-extension (SEP-1686) lifecycle guard

[0.8.53] - 2026-07-22 — "MCP Tasks-extension (SEP-1686) lifecycle guard"

Added

• feat(policy): MCP Tasks-extension (SEP-1686) lifecycle guard — bind task handle to
  issuing scope, refuse post-scope-change task ops. The MCP 2026-07-28 Tasks
  extension is call-now / fetch-later: a request returns a task handle, polled via
  tasks/get / tasks/update / tasks/cancel. A long-lived handle creates two lifecycle
  risks this preset closes, deny-by-default — it extends the MCP-2026-07-28 preset
  family (reuses the SEP-2350/2352 scope-change detector; the on-the-wire task schema is
  mcp_spec.tasks), it does not re-implement scope logic.
  • mcp_spec/tasks_lifecycle_guard.py — a caller-held registry of admitted handles.
    admit_task(registry, task_id, *, scopes, issuer, principal, expires_at=None) binds a
    handle at admission to the authorising scope set + principal. check_task_op(registry, method, task_id, *, live_scopes, live_issuer, principal, allow_scope_change=False, now=None) refuses a tasks/get/tasks/update/tasks/cancel when the caller's
    current scope set no longer covers the admission scope (reuses
    step_up_scope_guard.verify_scope_unchanged — scope broadening/narrowing and a
    different issuer are refused, RFC 9207 / SEP-2468) or the authorizing token expired;
    and — since tasks/list is spec-removed — refuses any op on a handle the principal was
    never admitted for, and tasks/list itself (deny-by-default, no cross-task
    enumeration). TaskLifecycleError carries a structured audit_event; every decision
    flows through observability.track_event.
  • policy_presets.mcp_tasks_lifecycle_2026_07_defaults() + MCP_TASKS_LIFECYCLE_2026_07
    (spec SEP-1686, owasp MCP07), discovered by list_active() (CLI / policy-compile
    exposure); top-level exported; wired into the OWASP MCP Top-10 MCP07 coverage row.
    Additive — no change to any existing preset. In-process (not a proxy), Pydantic-only,
    zero-dep core. SEP-1686 is a spec id, not a CVE.