diff --git a/orchestrator/cli.py b/orchestrator/cli.py
index 9db68e4..bd10a1d 100644
--- a/orchestrator/cli.py
+++ b/orchestrator/cli.py
@@ -413,7 +413,7 @@ def _render_schema_markdown(schema: dict, *, artifact: str) -> str:
         lines.append("- `nous create-campaign --to ./campaign.yaml` — scaffold a heavily-commented starting point.")
         lines.append("- `nous run campaign.yaml` — run a campaign (default `--agent sdk`).")
         lines.append("- `nous run campaign.yaml --bundle ./bundle.yaml` — skip DESIGN with a pre-authored bundle (#188).")
-        lines.append("- `nous stop <target>` — ask a running campaign to halt at the next iteration boundary.")
+        lines.append("- `nous stop <target>` — ask a running campaign to halt at the next phase boundary (#198).")
         lines.append("- `nous status --watch <target>` — live progress, including a STUCK marker after 5 min of silence.")
     return "\n".join(lines)
 
@@ -879,7 +879,17 @@ def main():
     p_stop = subparsers.add_parser(
         "stop",
         help="Ask a running campaign to halt cleanly at the next "
-             "iteration boundary by writing a STOP sentinel.",
+             "phase boundary by writing a STOP sentinel (#198: honoured "
+             "at DESIGN / HUMAN_DESIGN_GATE / EXECUTE_ANALYZE / "
+             "HUMAN_FINDINGS_GATE transitions, not just between iterations).",
+        description=(
+            "Write a STOP sentinel that the running campaign honours at "
+            "the next phase boundary (#198). Phase boundaries are DESIGN, "
+            "HUMAN_DESIGN_GATE, EXECUTE_ANALYZE, and HUMAN_FINDINGS_GATE — "
+            "so the operator can halt cleanly without waiting for the "
+            "next iteration. Mid-phase interruption (a wedged BLIS "
+            "subprocess, a stuck SDK turn) is still SIGINT's job."
+        ),
     )
     p_stop.add_argument(
         "target",
diff --git a/orchestrator/schemas/campaign.schema.yaml b/orchestrator/schemas/campaign.schema.yaml
index 9c4a5a8..923224a 100644
--- a/orchestrator/schemas/campaign.schema.yaml
+++ b/orchestrator/schemas/campaign.schema.yaml
@@ -164,6 +164,21 @@ properties:
           Additional filenames allowed at the iter root (in addition to
           the global whitelist in orchestrator/validate.py). Names only,
           not paths — files in subdirectories are always allowed.
+      required_iter_root:
+        type: array
+        items:
+          type: string
+          minLength: 1
+        uniqueItems: true
+        description: >
+          Filenames that MUST exist at the iter root after EXECUTE_ANALYZE
+          completes (#199 v2). validate_execution emits a "required
+          iter-root file missing: X" error for each missing entry,
+          turning silent omissions into structured failures (sister to
+          #187's DesignIncompleteError and #200's
+          ExecuteAnalyzeIncompleteError). Required files are implicitly
+          allowed at the iter root — no need to also list them in
+          iter_root_extensions. Names only, not paths.
 
   max_turns:
     type: object
diff --git a/orchestrator/validate.py b/orchestrator/validate.py
index 33ea5ae..46f80d3 100644
--- a/orchestrator/validate.py
+++ b/orchestrator/validate.py
@@ -82,6 +82,40 @@ def _campaign_iter_root_extensions(campaign: dict | None) -> frozenset[str]:
     return frozenset(str(x) for x in extensions if x)
 
 
+def _campaign_required_iter_root(campaign: dict | None) -> frozenset[str]:
+    """Read ``campaign.validation.required_iter_root`` (#199 v2).
+
+    Files declared here are treated as MUST-EXIST at validate_execution
+    time. Required ⊆ allowed: a required file is also implicitly an
+    iter-root extension, so campaigns don't need to list it twice.
+    """
+    if not campaign:
+        return frozenset()
+    validation = campaign.get("validation") or {}
+    required = validation.get("required_iter_root") or []
+    return frozenset(str(x) for x in required if x)
+
+
+def _check_required_iter_root(
+    iter_dir: Path, required: set[str] | frozenset[str],
+) -> list[str]:
+    """Return one error per required iter-root file that's missing.
+
+    #199 v2: campaign.validation.required_iter_root declares files the
+    campaign promises to produce by EXECUTE_ANALYZE end. Missing entries
+    are surfaced with a clear "required iter-root file missing: X"
+    message so the operator (or a future incomplete-iteration diagnostic
+    in the spirit of #187 / #200) sees what the campaign committed to.
+    """
+    errors: list[str] = []
+    if not iter_dir.is_dir():
+        return errors
+    for name in sorted(required):
+        if not (iter_dir / name).exists():
+            errors.append(f"required iter-root file missing: {name}")
+    return errors
+
+
 def _validate_ground_truth_independence(bundle: dict) -> list[str]:
     """Cross-field check that the ground truth can disagree with the detector (issue #85).
 
@@ -279,9 +313,13 @@ def validate_design(iter_dir: Path, campaign: dict | None = None) -> dict:
     elif handoff_path.stat().st_size == 0:
         errors.append("handoff_snapshot.md is empty")
 
-    errors.extend(
-        _check_unexpected_files(iter_dir, _campaign_iter_root_extensions(campaign))
-    )
+    # #199 v2: required ⊆ allowed at design time too. We don't enforce
+    # required-presence here (most required files are written during
+    # EXECUTE, not DESIGN), but if the campaign agent does write one
+    # during DESIGN, the unexpected-file check must not reject it.
+    extensions = _campaign_iter_root_extensions(campaign)
+    required = _campaign_required_iter_root(campaign)
+    errors.extend(_check_unexpected_files(iter_dir, extensions | required))
 
     if errors:
         return {"status": "fail", "errors": errors}
@@ -399,9 +437,13 @@ def validate_execution(iter_dir: Path, campaign: dict | None = None) -> dict:
         except KeyError as exc:
             errors.append(f"bundle.yaml arm missing required field: {exc}")
 
-    errors.extend(
-        _check_unexpected_files(iter_dir, _campaign_iter_root_extensions(campaign))
-    )
+    # #199 v2: required ⊆ allowed (a required file is also implicitly
+    # allowed at iter-root, so campaigns don't have to declare it
+    # twice). Merge before the unexpected-file check.
+    extensions = _campaign_iter_root_extensions(campaign)
+    required = _campaign_required_iter_root(campaign)
+    errors.extend(_check_unexpected_files(iter_dir, extensions | required))
+    errors.extend(_check_required_iter_root(iter_dir, required))
 
     if errors:
         return {"status": "fail", "errors": errors}
diff --git a/tests/test_nous_stop.py b/tests/test_nous_stop.py
index ae90f0c..70dd4c1 100644
--- a/tests/test_nous_stop.py
+++ b/tests/test_nous_stop.py
@@ -395,3 +395,61 @@ def test_sentinel_after_design_halts_before_design_gate(
                 campaign, work_dir, iteration=1, agent="inline",
                 auto_approve=True,
             )
+
+
+# ─── Documentation parity (#198) ─────────────────────────────────────────
+#
+# The behavior of `nous stop` is honoured at every phase boundary
+# post-#198 (see TestEnterPhaseHonorsSentinel above). User-facing
+# documentation must reflect that — the legacy "iteration boundary"
+# wording lags the post-#198 reality and misleads operators.
+
+
+class TestStopDocumentationReflectsPhaseAwareness:
+    """#198: every user-facing surface must describe `nous stop` as
+    halting at a phase boundary, not an iteration boundary."""
+
+    def test_argparse_help_says_phase_boundary(
+        self, monkeypatch, capsys,
+    ) -> None:
+        """`nous stop --help` (the argparse text) must announce phase
+        boundary, not iteration boundary."""
+        import sys
+        from orchestrator.cli import main
+
+        monkeypatch.setattr(sys, "argv", ["nous", "stop", "--help"])
+        with pytest.raises(SystemExit):
+            main()  # --help triggers SystemExit(0)
+        out = capsys.readouterr().out
+        # argparse line-wraps long descriptions, so normalize whitespace
+        # before substring-matching.
+        normalized = " ".join(out.split())
+        assert "phase boundary" in normalized, (
+            f"#198: nous stop help must say 'phase boundary'; got: "
+            f"{normalized!r}"
+        )
+        assert "iteration boundary" not in normalized, (
+            f"#198: legacy 'iteration boundary' phrasing leaked into "
+            f"argparse help: {normalized!r}"
+        )
+
+    def test_schema_doc_render_says_phase_boundary(self, capsys) -> None:
+        """`nous schema` markdown render references `nous stop` in its
+        See-also section. That string must announce phase boundary too."""
+        from orchestrator.cli import _cmd_schema
+
+        ns = argparse.Namespace(artifact="campaign", format="md")
+        _cmd_schema(ns)
+        out = capsys.readouterr().out
+        stop_lines = [ln for ln in out.splitlines() if "`nous stop" in ln]
+        assert stop_lines, (
+            "schema doc render should describe `nous stop` in See-also"
+        )
+        joined = "\n".join(stop_lines)
+        assert "phase boundary" in joined, (
+            f"#198: schema doc must say 'phase boundary'; got: {joined!r}"
+        )
+        assert "iteration boundary" not in joined, (
+            f"#198: legacy 'iteration boundary' leaked into schema doc: "
+            f"{joined!r}"
+        )
diff --git a/tests/test_validate.py b/tests/test_validate.py
index 000c984..2f7cae1 100644
--- a/tests/test_validate.py
+++ b/tests/test_validate.py
@@ -453,3 +453,198 @@ def test_subdirectories_ignored(self, tmp_path: Path) -> None:
         (d / "results").mkdir()
         (d / "inputs").mkdir()
         assert _check_unexpected_files(d) == []
+
+
+# ─── #199 v2 — required_iter_root ────────────────────────────────────────
+#
+# Sister field to iter_root_extensions: campaigns can declare files that
+# MUST exist at the iter root after EXECUTE_ANALYZE completes. Missing
+# entries fail validate_execution. Mirrors the #187 / #200 pattern of
+# turning silent omissions into structured errors.
+
+
+class TestRequiredIterRoot:
+    """#199 v2: campaign.validation.required_iter_root makes campaign-
+    specific iter-root files mandatory at validate_execution time. The
+    validator fails with a clear ``required iter-root file missing: X``
+    error so operators see what the campaign promised to produce."""
+
+    def test_missing_required_file_fails_execution(
+        self, tmp_path: Path,
+    ) -> None:
+        d = tmp_path / "iter-1"
+        _setup_execution(d)
+        # No analysis_summary.json on disk.
+        campaign = {
+            "validation": {
+                "required_iter_root": ["analysis_summary.json"],
+                # Required files are also implicitly allowed (so a
+                # campaign doesn't have to list them in both blocks).
+            },
+        }
+        result = validate_execution(d, campaign=campaign)
+        assert result["status"] == "fail"
+        assert any(
+            "required iter-root file missing" in e
+            and "analysis_summary.json" in e
+            for e in result["errors"]
+        ), result["errors"]
+
+    def test_present_required_file_passes(self, tmp_path: Path) -> None:
+        d = tmp_path / "iter-1"
+        _setup_execution(d)
+        (d / "analysis_summary.json").write_text("{}")
+        campaign = {
+            "validation": {
+                "required_iter_root": ["analysis_summary.json"],
+            },
+        }
+        result = validate_execution(d, campaign=campaign)
+        assert result["status"] == "pass", result
+
+    def test_required_file_implicitly_allowed_at_iter_root(
+        self, tmp_path: Path,
+    ) -> None:
+        """A required file should NOT need to be listed in
+        iter_root_extensions to avoid the unexpected-file rejection.
+        Required ⊆ allowed — the validator merges them automatically."""
+        d = tmp_path / "iter-1"
+        _setup_execution(d)
+        (d / "probe_report.md").write_text("# Probe report\n")
+        campaign = {
+            "validation": {
+                "required_iter_root": ["probe_report.md"],
+                # Note: iter_root_extensions intentionally omitted.
+            },
+        }
+        result = validate_execution(d, campaign=campaign)
+        assert result["status"] == "pass", result
+        # Negative: the unexpected-file error must not have fired.
+        if result.get("errors"):
+            assert not any(
+                "unexpected file" in e and "probe_report.md" in e
+                for e in result["errors"]
+            ), result["errors"]
+
+    def test_missing_required_listed_alongside_other_errors(
+        self, tmp_path: Path,
+    ) -> None:
+        """Required-file check runs even when other errors exist —
+        validation collects all errors so the operator sees the full
+        picture in one pass."""
+        d = tmp_path / "iter-1"
+        _setup_execution(d)
+        (d / "findings.json").unlink()  # primary error
+        campaign = {
+            "validation": {
+                "required_iter_root": ["analysis_summary.json"],
+            },
+        }
+        result = validate_execution(d, campaign=campaign)
+        assert result["status"] == "fail"
+        joined = " | ".join(result["errors"])
+        assert "findings.json" in joined
+        assert "analysis_summary.json" in joined
+
+    def test_no_required_block_keeps_default_behavior(
+        self, tmp_path: Path,
+    ) -> None:
+        """Campaigns without required_iter_root behave exactly as
+        before this PR (backward-compat)."""
+        d = tmp_path / "iter-1"
+        _setup_execution(d)
+        # No analysis_summary.json on disk; no required_iter_root either.
+        result = validate_execution(d, campaign={})
+        assert result["status"] == "pass", result
+
+    def test_required_combined_with_extensions(
+        self, tmp_path: Path,
+    ) -> None:
+        """A campaign declares both required and optional iter-root
+        files; only the required one is enforced for presence."""
+        d = tmp_path / "iter-1"
+        _setup_execution(d)
+        (d / "analysis_summary.json").write_text("{}")  # required, present
+        # manifest.json is "extensions" (optional) and absent — no error.
+        campaign = {
+            "validation": {
+                "required_iter_root": ["analysis_summary.json"],
+                "iter_root_extensions": ["manifest.json"],
+            },
+        }
+        result = validate_execution(d, campaign=campaign)
+        assert result["status"] == "pass", result
+
+    def test_required_file_at_design_time_is_allowed_not_required(
+        self, tmp_path: Path,
+    ) -> None:
+        """validate_design merges required ⊆ allowed (so a campaign that
+        writes a required file during DESIGN doesn't get rejected by the
+        unexpected-file check), but does NOT enforce required-presence
+        at design time — most required artifacts are EXECUTE-phase
+        outputs (e.g. probe_report.md is written during EXECUTE for
+        paper-* campaigns).
+
+        Pins both invariants:
+          (a) present-during-design → no "unexpected file" rejection
+          (b) absent-during-design → still passes design (no required-presence enforcement)
+        """
+        campaign = {
+            "validation": {"required_iter_root": ["probe_report.md"]},
+        }
+
+        # (a) Present during DESIGN — required ⊆ allowed must let it through.
+        d1 = tmp_path / "iter-1"
+        _setup_design(d1)
+        (d1 / "probe_report.md").write_text("# Probe report\n")
+        result = validate_design(d1, campaign=campaign)
+        assert result["status"] == "pass", result
+
+        # (b) Absent during DESIGN — must still pass (only validate_execution
+        # enforces required-presence).
+        d2 = tmp_path / "iter-2"
+        _setup_design(d2)
+        result = validate_design(d2, campaign=campaign)
+        assert result["status"] == "pass", result
+
+    def test_required_overlapping_known_root_file_still_enforced(
+        self, tmp_path: Path,
+    ) -> None:
+        """A campaign may declare a file already in _KNOWN_ROOT_FILES
+        (e.g. findings.json) as required. The required-presence check
+        must still fire when the file is missing, even though the
+        unexpected-file check would never have flagged it.
+        """
+        d = tmp_path / "iter-1"
+        _setup_execution(d)
+        (d / "findings.json").unlink()  # in _KNOWN_ROOT_FILES, now absent.
+        campaign = {
+            "validation": {"required_iter_root": ["findings.json"]},
+        }
+        result = validate_execution(d, campaign=campaign)
+        assert result["status"] == "fail"
+        assert any(
+            "required iter-root file missing" in e and "findings.json" in e
+            for e in result["errors"]
+        ), result["errors"]
+
+    def test_schema_accepts_required_iter_root(self) -> None:
+        """The campaign.schema.yaml must accept the new field — without
+        a schema entry, jsonschema validation in nous run would reject
+        the campaign before the validator ever sees it."""
+        from orchestrator.validate import _load_yaml_schema
+        import jsonschema
+
+        schema = _load_yaml_schema("campaign.schema.yaml")
+        campaign = {
+            "research_question": "Does X work?",
+            "run_id": "demo",
+            "target_system": {"name": "T", "description": "d"},
+            "prompts": {"methodology_layer": "p"},
+            "validation": {
+                "required_iter_root": ["probe_report.md"],
+                "iter_root_extensions": ["analysis_summary.json"],
+            },
+        }
+        # Should not raise.
+        jsonschema.validate(campaign, schema)