diff --git a/tests/agent/lsp/test_reporter.py b/tests/agent/lsp/test_reporter.py
index cd14c33ddf..4b15ca9d79 100644
--- a/tests/agent/lsp/test_reporter.py
+++ b/tests/agent/lsp/test_reporter.py
@@ -1,6 +1,7 @@
 """Tests for the diagnostic reporter (formatting layer)."""
 from __future__ import annotations
 
+from agent.compression_marker import _COMPRESSION_MARKER_RE
 from agent.lsp.reporter import (
     MAX_PER_FILE,
     format_diagnostic,
@@ -44,8 +45,7 @@ def test_truncate_above_limit_appends_marker():
     s = "x" * 10000
     out = truncate(s, limit=200)
     # Non-imitable elision marker (#121548), not the old bare truncation idiom.
-    assert "HERMES-CONTEXT-COMPRESSION" in out
-    assert out.endswith("⟫")
+    assert _COMPRESSION_MARKER_RE.search(out)
     assert len(out) <= 200
 
 
diff --git a/tests/agent/test_compression_marker.py b/tests/agent/test_compression_marker.py
index e35e63bb3f..84e67ec3c5 100644
--- a/tests/agent/test_compression_marker.py
+++ b/tests/agent/test_compression_marker.py
@@ -2,32 +2,28 @@
 
 The bare bracketed truncation idiom those renderers used to compose was imitated
 from replayed context into new durable writes (see #83435/#83714). All elision now
-routes through ``agent.compression_marker.elide`` / ``elide_middle``, and this file
-pins guard parity and the source-level invariant that the imitable idiom never
-returns to agent-facing strings.
+routes through ``agent.compression_marker.elide`` / ``elide_middle``; this file pins
+guard parity and that the real renderers emit a guard-visible marker, never the idiom.
 """
 from __future__ import annotations
 
-import pathlib
+import json
 import re
-import tokenize
 
 from agent.compression_marker import (
     _COMPRESSION_MARKER_RE,
     elide,
     elide_middle,
 )
-
-REPO_ROOT = pathlib.Path(__file__).resolve().parents[2]
-AGENT_ROOT = REPO_ROOT / "agent"
-# Agent-facing renderers outside agent/: Slack payload dumps and trajectory training data.
-SCANNED_PATHS = (
-    *sorted(AGENT_ROOT.rglob("*.py")),
-    *sorted((REPO_ROOT / "plugins" / "platforms" / "slack").rglob("*.py")),
-    REPO_ROOT / "trajectory_compressor.py",
+from agent.context_compressor import (
+    ContextCompressor,
+    _build_verbatim_user_section,
+    _compact_fallback_turn,
+    _summarize_tool_result,
 )
+
 # Any "...[<words> truncated]" variant, not just the bare one (e.g. "...[fallback summary truncated]").
-IMITABLE_MARKER_RE = re.compile(r"(?:\.\.\.|…)\s?\[[^\]\n]*truncated\]")
+IMITABLE_MARKER_RE = re.compile(r"(?:\.\.\.|…)\s?\[[^\]\n]*truncat")
 
 
 def test_minted_marker_is_caught_by_the_dispatch_boundary_guard():
@@ -36,19 +32,24 @@ def test_minted_marker_is_caught_by_the_dispatch_boundary_guard():
         assert _COMPRESSION_MARKER_RE.search(out)
 
 
-def test_no_imitable_truncation_marker_in_agent_strings():
-    """The imitable idiom must appear nowhere in agent/ strings — comments only.
+def test_real_renderers_emit_a_guard_visible_marker_never_the_imitable_idiom():
+    """Oversized input through the real renderers yields the guarded marker, not the idiom.
 
-    Regression for the open-coded renderers: the marker is minted by the shared
-    helpers now, so any such literal in a string token is a new imitation surface.
+    The active-task line quotes both apostrophes and double quotes so repr() cannot escape
+    the marker's own apostrophe out of the guard's reach.
     """
-    offenders = []
-    for path in SCANNED_PATHS:
-        with tokenize.open(str(path)) as fh:
-            for tok in tokenize.generate_tokens(fh.readline):
-                if tok.type != tokenize.STRING:
-                    continue
-                for match in IMITABLE_MARKER_RE.finditer(tok.string):
-                    rel = path.relative_to(REPO_ROOT)
-                    offenders.append(f"{rel}:{tok.start[0]}: {match.group()}")
-    assert not offenders, "imitable truncation markers in agent/ strings:\n" + "\n".join(offenders)
+    quoted = "a'b\"c " * 400
+    clarify = json.dumps({"user_response": "A" * 5000})
+    outputs = {
+        "clarify": _summarize_tool_result("clarify", "{}", clarify),
+        "fallback_turn": _compact_fallback_turn("z " * 5000),
+        "verbatim_user": _build_verbatim_user_section([{"role": "user", "content": "q" * 30000}]),
+        "record": ContextCompressor._bound_oversized_record("r" * 50000, 4000),
+        "active_task": ContextCompressor._latest_user_task_snapshot([{"role": "user", "content": quoted}]),
+    }
+    for name, out in outputs.items():
+        assert out and _COMPRESSION_MARKER_RE.search(out), (name, out[-300:] if out else out)
+        assert not IMITABLE_MARKER_RE.search(out), (name, out[-300:])
+    # A budget too small for marker + content skips the straddler instead of a marker-only quote.
+    fills_budget = [{"role": "user", "content": "u" * 3_998}] * 6  # 23,988 of the 24,000 budget
+    assert "chars omitted" not in _build_verbatim_user_section([{"role": "user", "content": "v" * 500}, *fills_budget])