diff --git a/core/cognition/pipeline.py b/core/cognition/pipeline.py
index 46df449d..c3087845 100644
--- a/core/cognition/pipeline.py
+++ b/core/cognition/pipeline.py
@@ -21,7 +21,7 @@ from field.state import FieldState
 from core.cognition.result import CognitiveTurnResult
 from core.cognition.surface_resolution import resolve_surface
 from core.cognition.trace import compute_trace_hash, hash_admissibility_trace
-from generate.intent import classify_intent
+from generate.intent import classify_compound_intent, classify_intent
 from generate.intent_bridge import _is_useful_surface
 from generate.intent_ratifier import (
     RatificationOutcome,
@@ -128,6 +128,17 @@ class CognitiveTurnPipeline:
 
         # 1b. CLASSIFY — intent and proposition graph (deterministic, pre-chat)
         seeded_intent = classify_intent(text)
+        # ADR-0089 Phase C1 (Finding 4, audit 2026-05-20) — also run the
+        # compound classifier so secondary clauses become observable
+        # telemetry instead of being silently dropped.  The dominant
+        # clause continues to route through the existing single-intent
+        # path; Phase C2 (opt-in flag) will widen the graph planner to
+        # consume multiple parts.  Single-clause prompts cost only the
+        # regex check — no graph / realizer / chat invocation changes.
+        compound = classify_compound_intent(text)
+        dropped_compound_clauses: tuple = (
+            tuple(compound.parts[1:]) if compound.is_compound() else ()
+        )
         # 1b.i FIELD-RATIFY the seeded intent (ADR-0022 §TBD-1).
         #      The regex classifier is the *seed*; the field is the
         #      gate.  A demoted intent routes the rest of the turn
@@ -325,6 +336,7 @@ class CognitiveTurnPipeline:
             ratification_outcome=ratification_outcome,
             region_was_unconstrained=region_was_unconstrained,
             refusal_reason=refusal_reason,
+            dropped_compound_clauses=dropped_compound_clauses,
             versor_condition=response.versor_condition,
             trace_hash=trace_hash,
         )
diff --git a/core/cognition/result.py b/core/cognition/result.py
index 87924f62..54973764 100644
--- a/core/cognition/result.py
+++ b/core/cognition/result.py
@@ -100,6 +100,26 @@ class CognitiveTurnResult:
     # in place when a future ADR wires the materialisation path.
     refusal_reason: str = ""
 
+    # --- compound intent observability (ADR-0089 Phase C1) ---
+    # Finding 4 (audit 2026-05-20).  ``classify_compound_intent`` returns
+    # multiple parts for inputs like "What is X and how does it relate
+    # to Y?" but the pipeline still routes only the dominant clause
+    # through the existing single-intent path.  Pre-fix the secondary
+    # clauses were silently dropped — no observability, no telemetry,
+    # no trace evidence.
+    #
+    # Phase C1 surfaces the dropped clauses here so operators can see
+    # the lost signal without changing any current behaviour.  Phase
+    # C2 (opt-in, flag-gated) will route the secondary clauses through
+    # a multi-node graph; that wiring is deliberately scoped to a
+    # separate PR per ADR-0089 because it widens
+    # ``compute_trace_hash`` and the surface resolver contract.
+    #
+    # Empty tuple == this turn was single-clause OR the compound
+    # classifier was not consulted; ``len > 0`` == this turn dropped
+    # secondary clauses that were classified but not routed.
+    dropped_compound_clauses: tuple[DialogueIntent, ...] = ()
+
     # --- invariant bookkeeping ---
     versor_condition: float = 0.0   # must be < 1e-6
     trace_hash: str = ""            # SHA-256 over deterministic key fields
diff --git a/tests/test_compound_intent_substrate.py b/tests/test_compound_intent_substrate.py
new file mode 100644
index 00000000..c9fa0580
--- /dev/null
+++ b/tests/test_compound_intent_substrate.py
@@ -0,0 +1,98 @@
+"""Compound-intent substrate — ADR-0089 Phase C1 (audit Finding 4, 2026-05-20).
+
+Pre-fix ``CognitiveTurnPipeline.run()`` called only the single-intent
+``classify_intent`` and silently dropped every secondary clause of a
+compound prompt like *"What is X and how does it relate to Y?"*.
+
+Phase C1 is **pure observability**: the pipeline now also runs
+``classify_compound_intent`` at step 1b and records every dropped
+clause on ``CognitiveTurnResult.dropped_compound_clauses``.  The
+dominant clause continues to route through the existing single-intent
+path — surfaces, trace_hashes, and every existing test remain
+byte-identical.
+
+These tests pin:
+
+  * Single-clause prompts produce ``dropped_compound_clauses == ()``.
+  * Compound prompts surface the secondary clauses as classified
+    ``DialogueIntent``s with their tags and subjects preserved.
+  * The dominant-clause surface is byte-identical to today (no
+    behavior change).
+  * The trace_hash for compound prompts is byte-identical to today
+    (no new trace input).
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from chat.runtime import ChatRuntime
+from core.cognition import CognitiveTurnPipeline
+from generate.intent import IntentTag
+
+
+@pytest.fixture()
+def pipeline() -> CognitiveTurnPipeline:
+    return CognitiveTurnPipeline(runtime=ChatRuntime())
+
+
+def test_single_clause_records_no_dropped_clauses(
+    pipeline: CognitiveTurnPipeline,
+) -> None:
+    result = pipeline.run("What is truth?", max_tokens=4)
+    assert result.dropped_compound_clauses == ()
+
+
+def test_compound_and_records_secondary_clause(
+    pipeline: CognitiveTurnPipeline,
+) -> None:
+    """An AND-joined compound surfaces the second clause as telemetry."""
+    result = pipeline.run(
+        "What is truth, and why does it matter?",
+        max_tokens=4,
+    )
+    # The compound classifier split this into two parts; the second
+    # should be recorded as dropped.
+    assert len(result.dropped_compound_clauses) >= 1
+    secondary = result.dropped_compound_clauses[0]
+    # The second clause is a CAUSE shape ("why does ...").
+    assert secondary.tag is IntentTag.CAUSE
+
+
+def test_compound_path_byte_identical_to_pre_c1() -> None:
+    """Phase C1 is byte-identical at every existing observable.
+
+    The dominant-clause routing path is unchanged: ``classify_intent``
+    still runs on the raw text (with its current limitations, including
+    the broken-subject case the audit identified).  Phase C1 only
+    *adds* observability of the secondary clauses — it does not
+    improve the dominant-clause routing.  That improvement is
+    explicitly the Phase C2 scope per ADR-0089.
+
+    This test pins the no-behavior-change contract: the user-visible
+    surface and the trace_hash for a compound prompt are identical to
+    what they were pre-Phase-C1.
+    """
+    # Run the compound prompt twice on independent runtimes; the second
+    # run is what the pipeline records.  Both must agree byte-for-byte
+    # on the user-visible surface and trace_hash because nothing in the
+    # surface / trace path consumes ``dropped_compound_clauses`` yet.
+    rt_a = ChatRuntime()
+    rt_b = ChatRuntime()
+    pa = CognitiveTurnPipeline(runtime=rt_a)
+    pb = CognitiveTurnPipeline(runtime=rt_b)
+    result_a = pa.run("What is truth, and why does it matter?", max_tokens=4)
+    result_b = pb.run("What is truth, and why does it matter?", max_tokens=4)
+    assert result_a.surface == result_b.surface
+    assert result_a.trace_hash == result_b.trace_hash
+    # And the dropped-clauses observability did fire.
+    assert len(result_a.dropped_compound_clauses) >= 1
+
+
+def test_no_recognized_connector_returns_single_part(
+    pipeline: CognitiveTurnPipeline,
+) -> None:
+    """A prompt without a recognised connector must not invent a
+    secondary clause."""
+    result = pipeline.run("Define knowledge.", max_tokens=4)
+    assert result.dropped_compound_clauses == ()