diff --git a/tests/ttp/test_tracing.py b/tests/ttp/test_tracing.py
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+"""E.2.14a — Observability tracing tests.
+
+Pins the OTEL span hierarchy from ``development/TTP_TAGGING.md``
+§"Observability". Spans are not optional decoration; they are a
+stated design property and the impl must produce them in the shape
+asserted here:
+
+* A single :meth:`RuleEngine.evaluate` call produces a ``ttp.eval``
+  span carrying ``attacker_uuid`` + ``identity_uuid`` attributes.
+* Within ``ttp.eval``, one ``ttp.lifter.{name}`` child span per
+  lifter that ran.
+* Within each lifter span, one ``ttp.rule.fire`` span per matched
+  rule, carrying ``rule_id`` + ``technique_id`` attributes.
+* :meth:`RuleStore.set_state` produces ``ttp.rule.state.change``
+  parent + ``ttp.store.write_state`` + ``ttp.rule.publish`` children.
+* **No-PII property.** Walk every emitted span attribute over a
+  battery of synthetic events containing tagged "PII canary" strings;
+  no attribute value contains any canary string. Catches accidental
+  attribute writes of raw command content / email body / fingerprint
+  bytes / payload bytes.
+
+The in-memory span exporter fixture lives in this module rather than
+``tests/ttp/conftest.py`` because no other ttp test currently needs
+OTEL plumbing; promoting it to ``conftest.py`` is a cheap follow-up
+once a second consumer arrives.
+
+Span-emission assertions xfail-gated behind the matching E.3 impl
+steps (E.3.7 engine; E.3.5/E.3.6 store; E.3.9–E.3.13 lifters).
+"""
+from __future__ import annotations
+
+from typing import Iterator
+
+import pytest
+
+from opentelemetry.sdk.trace import TracerProvider
+from opentelemetry.sdk.trace.export import SimpleSpanProcessor
+from opentelemetry.sdk.trace.export.in_memory_span_exporter import (
+    InMemorySpanExporter,
+)
+
+
+_PII_CANARIES: tuple[str, ...] = (
+    "CANARY_PII_DO_NOT_LEAK",
+    "CANARY_EMAIL_BODY",
+    "CANARY_PAYLOAD_BYTES",
+    "CANARY_COMMAND_RAW",
+    "CANARY_FINGERPRINT_BLOB",
+)
+
+
+@pytest.fixture
+def span_exporter() -> Iterator[tuple[InMemorySpanExporter, TracerProvider]]:
+    """Yield an :class:`InMemorySpanExporter` wired into a fresh
+    :class:`TracerProvider`.
+
+    OTEL forbids overriding the global tracer provider once set, so
+    we hand callers the provider directly — they call
+    ``provider.get_tracer(...)`` rather than the module-level
+    ``trace.get_tracer``. Production code under test that calls
+    ``trace.get_tracer`` will need to be patched (e.g. via
+    monkeypatch on ``decnet.telemetry.get_tracer``); the fixture
+    itself stays scoped.
+    """
+    exporter = InMemorySpanExporter()
+    provider = TracerProvider()
+    provider.add_span_processor(SimpleSpanProcessor(exporter))
+    try:
+        yield exporter, provider
+    finally:
+        provider.shutdown()
+
+
+# ── Eval span hierarchy (xfail until E.3.7) ─────────────────────────
+
+
+@pytest.mark.xfail(
+    strict=True,
+    reason="impl phase E.3.7 — RuleEngine.evaluate() emits no spans "
+    "today; ttp.eval span lands with the engine impl",
+)
+def test_eval_emits_top_level_span(span_exporter: tuple[InMemorySpanExporter, TracerProvider]) -> None:
+    """``evaluate()`` produces a ``ttp.eval`` span with
+    ``attacker_uuid`` and ``identity_uuid`` attributes."""
+    pytest.fail("ttp.eval span not yet emitted")
+
+
+@pytest.mark.xfail(
+    strict=True,
+    reason="impl phase E.3.9–E.3.13 — per-lifter ttp.lifter.{name} "
+    "child spans land with each lifter implementation",
+)
+def test_lifter_child_spans_emitted(span_exporter: tuple[InMemorySpanExporter, TracerProvider]) -> None:
+    """Within a ``ttp.eval``, every lifter that ran produces a
+    ``ttp.lifter.{name}`` child span."""
+    pytest.fail("per-lifter spans not yet emitted")
+
+
+@pytest.mark.xfail(
+    strict=True,
+    reason="impl phase E.3.7 — ttp.rule.fire spans with rule_id + "
+    "technique_id land with the engine impl",
+)
+def test_rule_fire_spans_carry_rule_and_technique_attrs(
+    span_exporter: tuple[InMemorySpanExporter, TracerProvider],
+) -> None:
+    """Each matched rule produces a ``ttp.rule.fire`` span with
+    ``rule_id`` and ``technique_id`` attributes set."""
+    pytest.fail("ttp.rule.fire spans not yet emitted")
+
+
+# ── set_state span hierarchy (xfail until E.3.5/E.3.6) ──────────────
+
+
+@pytest.mark.xfail(
+    strict=True,
+    reason="impl phase E.3.5/E.3.6 — set_state() span hierarchy lands "
+    "with the rule-store implementations",
+)
+def test_set_state_span_hierarchy(span_exporter: tuple[InMemorySpanExporter, TracerProvider]) -> None:
+    """``RuleStore.set_state`` produces a ``ttp.rule.state.change``
+    parent with ``ttp.store.write_state`` + ``ttp.rule.publish``
+    children — operator state changes are auditable."""
+    pytest.fail("set_state spans not yet emitted")
+
+
+# ── No-PII property (xfail until E.3.7+) ────────────────────────────
+
+
+@pytest.mark.xfail(
+    strict=True,
+    reason="impl phase E.3.7+ — span emission requires the engine + "
+    "lifter impls; the no-PII property is asserted across the "
+    "battery only once spans are actually being produced",
+)
+def test_no_pii_canary_in_span_attributes(
+    span_exporter: tuple[InMemorySpanExporter, TracerProvider],
+) -> None:
+    """Run a battery of synthetic events containing PII canary
+    strings (e.g. ``"CANARY_PII_DO_NOT_LEAK"`` in command bodies,
+    email bodies, fingerprint blobs, payload bytes). After eval,
+    walk every span attribute value and assert no canary string
+    appears anywhere.
+
+    Catches accidental attribute writes of raw command content,
+    email body, payload bytes, fingerprint blobs. Span attributes
+    leak to whatever OTEL backend is wired (Jaeger, Tempo, vendor
+    APM); a single PII leak there is a privacy incident, not a
+    bug.
+    """
+    pytest.fail("span emission not yet implemented")
+
+
+# ── Surface (GREEN today) ───────────────────────────────────────────
+
+
+def test_pii_canary_battery_is_non_empty() -> None:
+    """The canary battery itself is non-empty and consists of strings
+    a future contributor cannot accidentally write into a span.
+
+    Cheap meta-test so the no-PII assertion above can never silently
+    pass on an empty corpus.
+    """
+    assert len(_PII_CANARIES) >= 5
+    for canary in _PII_CANARIES:
+        assert canary.isupper()
+        assert "_" in canary
+
+
+def test_in_memory_exporter_fixture_works(
+    span_exporter: tuple[InMemorySpanExporter, TracerProvider],
+) -> None:
+    """Sanity: the fixture itself captures a synthetic span. If THIS
+    test breaks, every xfail above becomes meaningless.
+    """
+    exporter, provider = span_exporter
+    tracer = provider.get_tracer("decnet.tests.ttp.tracing")
+    with tracer.start_as_current_span("synthetic.span") as span:
+        span.set_attribute("test.key", "test.value")
+    spans = exporter.get_finished_spans()
+    assert any(s.name == "synthetic.span" for s in spans)