diff --git a/emrg/server/prompts/system.j2 b/emrg/server/prompts/system.j2
index e5132ad7..c247b714 100644
--- a/emrg/server/prompts/system.j2
+++ b/emrg/server/prompts/system.j2
@@ -60,7 +60,9 @@ A memory is frontmatter, then a Markdown body under a title; an existing entry s
 {% endif %}
 - **A write is two steps**: the file, then its row in the index. To retire one, set its `status`; never delete it.
 - **Organise rather than accumulate**: fragments on one topic become one memory, their old files marked `merged` or `superseded`; a refinement edits the entry it refines; a file carrying unrelated topics splits into one entry per topic.
-- **How settled an entry is decides how freely it is rewritten**: `event_at` says when the event happened and `updated_at` when the file last moved. When in doubt, append and note what changed; a body calling itself temporary may go.
+- **`event_at` says when the event happened and `updated_at` when the file last moved**; a body calling itself temporary may go.
+- **A refuted conclusion is replaced where it stands, never annotated**: delete the wrong sentence and write the right one in its place. A correction appended at the head or the tail leaves the falsehood holding the title and the opening — the two positions a reader actually reaches — and quotable by whoever reads no further; an entry already carrying such sections is rewritten whole, and one refuted as a whole takes `status: superseded` and leaves the active index, whose row follows the same rule as the body it points at.
+- **What a refutation keeps is the error and its discriminator**: what was thought, what is true, and the test that separates them — never the timeline or the effort, which the next round reads as fresh fact.
 - **Promotion**: a session memory worth keeping moves to the agent store, and both indexes learn of it.
 - **The index rows arrive every round** in the `[context]` message, not here: read them there.
 {% else %}
diff --git a/tests/test_memory_rewrite_prompt_reach.py b/tests/test_memory_rewrite_prompt_reach.py
new file mode 100644
index 00000000..031a2757
--- /dev/null
+++ b/tests/test_memory_rewrite_prompt_reach.py
@@ -0,0 +1,142 @@
+"""A refuted conclusion must be replaced where it stands, not annotated with a correction.
+
+Why this file exists
+--------------------
+A memory is read **index row → title → opening**, and those are the positions that decide what
+the next reader believes. The guidance that shipped in `system.j2`'s Memory section said the
+opposite of that: *"When in doubt, append and note what changed"*, with how *settled* an entry
+is framing appending as the safe default. A writer following it leaves a conclusion it has just
+disproved in the body — often in the opening, and in the index row that repeats it — and appends
+a section headed "void" / "expired" / "corrected" at the end. That is not a repair: a correction
+below the fold is read last or not read at all, so the falsehood keeps the two positions a reader
+actually reaches and stays quotable by whoever stops early, while the file grows a layer that the
+next writer has to read before learning one fact.
+
+What is asserted
+----------------
+Two legs, two questions, and neither implies the other: the **file** leg asks whether the source
+that ships states it, the **render** leg whether a session receives it — `system.j2` is a Jinja2
+template, so a block moved inside a false `{% if %}` keeps every character in the file and reaches
+nobody (the same pair `tests/test_plain_language_rule_reach.py` was written for).
+
+The removal is asserted as hard as the addition, and it is the half that decays silently: a test
+that only checks the new rule is present says nothing about the old instruction still standing
+beside it, and two contradictory sentences in one section are one instruction the reader picks
+from at random. So the file must carry the replace rule **and** no longer tell a writer to append.
+
+Both scopes are pinned together, because either alone over-corrects. "Replace the sentence" without
+"an entry refuted as a whole is superseded" turns a whole wrong memory into a rewritten one that
+is still wrong; "superseded" without "replace where it stands" retires a sound entry because two
+lines of it went stale.
+
+Named limit
+-----------
+This pins the guidance a session is given, not what any writer does with it afterwards. A session
+that reads the rule and appends a correction anyway is a model-behaviour failure this file cannot
+see — no test reads a memory and decides whether its shape came from a patch or a rewrite.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+SYSTEM_PROMPT = REPO_ROOT / "emrg" / "server" / "prompts" / "system.j2"
+
+#: The section that owns the subject. A second copy anywhere else in the template is a drift this
+#: file would not see, so the reading is taken from this block alone.
+MEMORY_HEADING = "## Memory"
+
+#: Load-bearing fragments, each a verbatim substring of the shipped wording: the rule, the repair it
+#: asks for, the "already patched" case, the whole-entry case, the index row, and the one thing a
+#: refutation keeps. They cannot drift away from the sentence they check without this file failing.
+REPLACE_TERMS = (
+    "A refuted conclusion is replaced where it stands, never annotated",
+    "delete the wrong sentence and write the right one in its place",
+    "an entry already carrying such sections is rewritten whole",
+    "takes `status: superseded` and leaves the active index",
+    "whose row follows the same rule as the body it points at",
+    "never the timeline or the effort",
+)
+
+#: The instruction this change removes. Its absence is the other half of the rule: leaving it in
+#: place would give one session two contradictory answers, and the older one is the shorter advice.
+GONE_TERMS = (
+    "When in doubt, append and note what changed",
+    "How settled an entry is decides how freely it is rewritten",
+)
+
+
+def _block_after(text: str, heading: str) -> str:
+    """The block starting at ``heading``, up to the next `## ` heading or EOF.
+
+    ``""`` when the heading is absent — the caller asserts, so a missing block reads as a failure
+    to measure rather than as a pass.
+    """
+    start = text.find(heading)
+    if start == -1:
+        return ""
+    rest = text[start + len(heading):]
+    end = rest.find("\n## ")
+    return rest if end == -1 else rest[:end]
+
+
+def _render_system_prompt() -> str:
+    """The prompt a session receives, rendered by the daemon's own Jinja environment.
+
+    The daemon's `_get_jinja_env` is what `_build_system_prompt` uses; a fresh `Environment` could
+    differ in `trim_blocks` / `lstrip_blocks` or in the loader path, and the prompt under test would
+    then be one nobody receives. `has_memories` is true because the rule sits in the branch that
+    speaks to a session which already holds memories — the only session a refutation can arise in.
+    """
+    from emrg.server.daemon import _get_jinja_env  # noqa: PLC0415
+
+    return _get_jinja_env().get_template("system.j2").render(
+        os_name="test",
+        config_dir="/nonexistent",
+        has_memories=True,
+        agent_memory_dir="/tmp/memory",
+        agent_memory_index_path="/tmp/memory/MEMORY.md",
+        session_memory_dir="/tmp/session-memory",
+        session_memory_index_path="/tmp/session-memory/MEMORY.md",
+        index_title_max_chars=512,
+        memory_index_row_cap=100,
+    )
+
+
+def test_the_shipped_prompt_replaces_a_refuted_conclusion() -> None:
+    block = _block_after(SYSTEM_PROMPT.read_text(encoding="utf-8"), MEMORY_HEADING)
+    assert block, (
+        "emrg/server/prompts/system.j2 must carry the Memory section — it is the only prompt every "
+        "session is rendered under, so a rule stated anywhere else reaches one agent and no other."
+    )
+    missing = [term for term in REPLACE_TERMS if term not in block]
+    assert not missing, f"the Memory section no longer states, or states differently: {missing}"
+
+
+def test_the_shipped_prompt_no_longer_instructs_an_append() -> None:
+    block = _block_after(SYSTEM_PROMPT.read_text(encoding="utf-8"), MEMORY_HEADING)
+    assert block
+    surviving = [term for term in GONE_TERMS if term in block]
+    assert not surviving, (
+        "the Memory section still carries the guidance this rule replaces, which leaves one session "
+        f"with two answers and the shorter one wins: {surviving}"
+    )
+
+
+def test_a_session_receives_the_replace_rule() -> None:
+    block = _block_after(_render_system_prompt(), MEMORY_HEADING)
+    assert "A refuted conclusion is replaced where it stands" in block, (
+        "the rule is in the template but not in the rendered prompt — a block moved behind a false "
+        "`{% if %}` keeps every character in the file and reaches no session."
+    )
+    assert "When in doubt, append and note what changed" not in block
+
+
+def test_the_render_carries_the_rule_and_not_the_append() -> None:
+    """One reading, both directions, on the artifact a session actually gets."""
+    block = _block_after(_render_system_prompt(), MEMORY_HEADING)
+    assert block
+    missing = [term for term in REPLACE_TERMS if term not in block]
+    surviving = [term for term in GONE_TERMS if term in block]
+    assert not missing and not surviving, f"missing={missing} surviving={surviving}"