diff --git a/src/modelbench/consistency_checker.py b/src/modelbench/consistency_checker.py
new file mode 100644
index 00000000..194df885
--- /dev/null
+++ b/src/modelbench/consistency_checker.py
@@ -0,0 +1,306 @@
+import json
+import shutil
+from abc import ABC, abstractmethod
+from collections import Counter, defaultdict
+from itertools import product
+from tabulate import tabulate
+from typing import Dict, List
+
+from modelbench.run_journal import journal_reader
+
+LINE_WIDTH = shutil.get_terminal_size(fallback=(120, 50)).columns
+
+
+class JournalSearch:
+    def __init__(self, journal_path):
+        self.journal_path = journal_path
+        self.message_entries: Dict[str, List] = defaultdict(list)  # or maybe sqllite dict?
+        # Load journal into message_entries dict.
+        self._read_journal()
+
+    def _read_journal(self):
+        # Might want to filter out irrelevant messages here. idk.
+        with journal_reader(self.journal_path) as f:
+            for line in f:
+                entry = json.loads(line)
+                self.message_entries[entry["message"]].append(entry)
+
+    def query(self, message: str, **kwargs):
+        messages = self.message_entries[message]
+        return [m for m in messages if all(m[k] == v for k, v in kwargs.items())]
+
+    def num_test_prompts(self, test) -> int:
+        # TODO: Implement cache.
+        test_entry = self.query("using test items", test=test)
+        assert len(test_entry) == 1, "Only 1 `using test items` entry expected per test but found multiple."
+        return test_entry[0]["using"]
+
+    def test_prompt_uids(self, test) -> List[str]:
+        """Returns all prompt UIDs queue"""
+        # TODO: Implement cache.
+        return [item["prompt_id"] for item in self.query("queuing item", test=test)]
+
+    def sut_response_prompt_uids_for_test(self, sut, test) -> List[str]:
+        cached_responses = self.query("using cached sut response", sut=sut, test=test)
+        fetched_responses = self.query("fetched sut response", sut=sut, test=test)
+        all_prompts = [response["prompt_id"] for response in cached_responses + fetched_responses]
+        return all_prompts
+
+
+class JournalCheck(ABC):
+    """All checks must inherit from this class."""
+
+    @abstractmethod
+    def check(self) -> bool:
+        pass
+
+    @abstractmethod
+    def failure_message(self) -> str:
+        """The message to display if the check fails."""
+        pass
+
+
+# TODO: Check that all prompts in a test are unique.
+
+# TODO:
+# class NumPromptsQueuedMatchesExpected(JournalCheck):
+#     def __init__(self, search_engine: JournalSearch, sut, test):
+#         # Load all data needed for the check.
+#         self.num_test_prompts = search_engine.num_test_prompts(test)
+
+
+class OneToOneCheck(JournalCheck):
+    """Checks for a one-to-one mapping between two lists of prompt uids."""
+
+    def __init__(self, expected_prompts: List[str], found_prompts: List[str]):
+        found_counts = Counter(found_prompts)
+        # TODO: Could probably make these 3 checks more efficient.
+        self.duplicates = [uid for uid, count in found_counts.items() if count > 1]
+        # Check for differences in the two sets.
+        expected_prompts = set(expected_prompts)
+        found_prompts = set(found_prompts)
+        self.missing_prompts = list(expected_prompts - found_prompts)
+        self.unknown_prompts = list(found_prompts - expected_prompts)
+
+    def check(self) -> bool:
+        return not any([len(self.duplicates), len(self.missing_prompts), len(self.unknown_prompts)])
+
+    def failure_message(self) -> str:
+        assert not self.check()
+        messages = []
+        if len(self.duplicates) > 0:
+            messages.append(f"The following duplicate prompts were found: {self.duplicates}")
+        if len(self.missing_prompts) > 0:
+            messages.append(f"The prompts were expected but missing: {self.missing_prompts}")
+        if len(self.unknown_prompts) > 0:
+            messages.append(f"The following prompts were found but were not expected: {self.unknown_prompts}")
+        return "\n\t".join(messages)
+
+
+class EachPromptRespondedToOnce(OneToOneCheck):
+    def __init__(self, search_engine: JournalSearch, sut, test):
+        super().__init__(
+            search_engine.test_prompt_uids(test), search_engine.sut_response_prompt_uids_for_test(sut, test)
+        )
+
+    def failure_message(self) -> str:
+        message = "Expected exactly 1 SUT response for each prompt in the test.\n\t"
+        # Call super() to get specific details about duplicates/missing/extra prompts.
+        return message + super().failure_message()
+
+
+# TODO: Add class to check that fetched and cached responses are mutually exclusive.
+
+
+class EachResponseTranslatedOnce(OneToOneCheck):
+    def __init__(self, search_engine: JournalSearch, sut, test):
+        all_sut_response_prompts = search_engine.sut_response_prompt_uids_for_test(sut, test)
+        translated_responses = search_engine.query("translated sut response", sut=sut, test=test)
+        super().__init__(all_sut_response_prompts, [response["prompt_id"] for response in translated_responses])
+
+    def failure_message(self) -> str:
+        message = "Expected each SUT response to be translated exactly once.\n\t"
+        # Call super() to get specific details about duplicates/missing/extra prompts.
+        return message + super().failure_message()
+
+
+class EachItemMeasuredOnce(OneToOneCheck):
+    def __init__(self, search_engine: JournalSearch, sut, test):
+        translated_responses = search_engine.query("translated sut response", sut=sut, test=test)
+        measured_items = search_engine.query("measured item quality", sut=sut, test=test)
+        super().__init__(
+            [response["prompt_id"] for response in translated_responses],
+            [response["prompt_id"] for response in measured_items],
+        )
+
+    def failure_message(self) -> str:
+        message = "Expected every prompt-response to be measured exactly once.\n"
+        # Call super() to get specific details about duplicates/missing/extra prompts.
+        return message + super().failure_message()
+
+
+class EachResponseAnnotatedOnce(OneToOneCheck):
+    def __init__(self, search_engine: JournalSearch, sut, test, annotator):
+        self.annotator = annotator
+        self.sut = sut
+        self.test = test
+        translated_responses = search_engine.query("translated sut response", sut=sut, test=test)
+        cached_annotations = search_engine.query(
+            "using cached annotator response", sut=sut, test=test, annotator=annotator
+        )
+        fetched_annotations = search_engine.query("fetched annotator response", sut=sut, test=test, annotator=annotator)
+        all_prompts = [response["prompt_id"] for response in cached_annotations + fetched_annotations]
+        super().__init__([response["prompt_id"] for response in translated_responses], all_prompts)
+
+    def failure_message(self) -> str:
+        message = f"Expected exactly 1 {self.annotator} annotation for each response from SUT {self.sut} in test {self.test}\n\t"
+        # Call super() to get specific details about duplicates/missing/extra prompts.
+        return message + super().failure_message()
+
+
+class JournalEntityLevelCheck:
+    """A group of a checks that occupy the same conceptual entity-level in the journal.
+
+    All checks in a group must accept the same entities in their init. params."""
+
+    def __init__(self, name, check_classes, **entity_sets):
+        """Each entity_set kwarg is a list of a type of entity."""
+        self.name = name
+        self.check_classes: List = check_classes
+        # Outer-level dictionary keys are the entity tuples, inner dict. keys are the check names.
+        # Values are boolean check results.
+        self.results: Dict[str, Dict[str, bool | None]] | None = None
+        self.row_names = None
+        self.check_names = None
+        self._init_results_table(**entity_sets)
+        # List of warning messages for failed checks.
+        self.warnings: List[str] = []
+
+    def _init_results_table(self, **entity_sets):
+        # Create an empty table where each row is an entity (or entity tuple) and each column is a check.
+        self.results = defaultdict(dict)
+        self.entity_names = sorted(list(entity_sets.keys()))
+        self.row_names = []
+        self.check_names = []
+
+        for col in self.check_classes:
+            self.check_names.append(self._col_name(col))
+        for entity_tuple in product(*entity_sets.values()):
+            entity_dict = dict(zip(entity_sets.keys(), entity_tuple))
+            row_key = self._row_key(**entity_dict)
+            self.row_names.append(row_key)
+            # Each check is initialized to None to indicate it hasn't been run yet.
+            self.results[row_key] = {col: None for col in self.check_names}
+
+    @staticmethod
+    def _row_key(**entities) -> str:
+        """Return string key for a given set of entities."""
+        sorted_keys = sorted(entities.keys())
+        return ", ".join([entities[k] for k in sorted_keys])
+
+    @staticmethod
+    def _col_name(check_cls) -> str:
+        return check_cls.__name__
+
+    def check_is_complete(self) -> bool:
+        """Make sure table is fully populated."""
+        for row in self.row_names:
+            for check in self.check_names:
+                if self.results[row][check] is None:
+                    return False
+        return True
+
+    def run_checks_for_row(self, search_engine, **entities):
+        """Run all individual checks on a given entity tuple and store results and warnings."""
+        for check_cls in self.check_classes:
+            check = check_cls(search_engine, **entities)
+            result = check.check()
+            self.results[self._row_key(**entities)][self._col_name(check_cls)] = result
+            if not result:
+                # TODO: Add check name to warning message.
+                self.warnings.append(f"{self._col_name(check_cls)}: {check.failure_message()}")
+
+
+class ConsistencyChecker:
+
+    def __init__(self, journal_path):
+        # Object holding journal entries
+        self.search_engine = JournalSearch(journal_path)
+
+        # Entities to run checks for.
+        self.suts = None
+        self.tests = None
+        self.annotators = None
+        self._collect_entities()
+
+        # Checks to run at each level.
+        self.test_sut_level_checker = JournalEntityLevelCheck(
+            "Test x SUT level checks",
+            [EachPromptRespondedToOnce, EachResponseTranslatedOnce, EachItemMeasuredOnce],
+            tests=self.tests,
+            suts=self.suts,
+        )
+        self.test_sut_annotator_level_checker = JournalEntityLevelCheck(
+            "Test x SUT x Annotator checks",
+            [EachResponseAnnotatedOnce],
+            tests=self.tests,
+            suts=self.suts,
+            annotators=self.annotators,
+        )
+
+    def _collect_entities(self):
+        # Get all SUTs and tests that were ran in the journal. We will run checks for each (SUT, test) pair.
+        starting_run_entry = self.search_engine.query("starting run")
+        assert len(starting_run_entry) == 1
+
+        self.suts = starting_run_entry[0]["suts"]
+        self.tests = starting_run_entry[0]["tests"]
+        # TODO: Find a more reliable way of getting all expected annotators for the tests. THIS WILL FAIL IF THEY ARE ALL CACHED.
+        annotator_entries = self.search_engine.query("fetched annotator response", test=self.tests[0], sut=self.suts[0])
+        self.annotators = list(set([entry["annotator"] for entry in annotator_entries]))
+
+    def run(self, verbose=False):
+        self.collect_results()
+        self.display_results()
+        if verbose:
+            self.display_warnings()
+        # TODO: Also run checks for the json record file.
+
+    def collect_results(self):
+        """Populate the results/warning tables of each check level."""
+        for test in self.tests:
+            for sut in self.suts:
+                self.test_sut_level_checker.run_checks_for_row(self.search_engine, sut=sut, test=test)
+                for annotator in self.annotators:
+                    self.test_sut_annotator_level_checker.run_checks_for_row(
+                        self.search_engine, sut=sut, test=test, annotator=annotator
+                    )
+
+    @staticmethod
+    def _format_result(result: bool):
+        return "✅" if result else "❌"
+
+    def display_results(self):
+        """Print simple table where each row is a single entity (or entity tuple e.g. test x SUT) and each column is a check."""
+        check_groups = [self.test_sut_level_checker, self.test_sut_annotator_level_checker]
+        for checker in check_groups:
+            print("Results for", checker.name)
+            assert checker.check_is_complete()
+            results_table = []
+            for entity, checks in checker.results.items():
+                results_table.append([entity] + [self._format_result(checks[c]) for c in checker.check_names])
+            print(tabulate(results_table, headers=[", ".join(checker.entity_names)] + list(checker.check_names)))
+            print()
+
+    def display_warnings(self):
+        """Print details about the failed checks."""
+        check_groups = [self.test_sut_level_checker, self.test_sut_annotator_level_checker]
+        for checker in check_groups:
+            print("-" * LINE_WIDTH)
+            assert checker.check_is_complete()
+            if len(checker.warnings) == 0:
+                print(f"All {checker.name} checks passed!")
+                return
+            print(f"Failed checks for {checker.name}:")
+            for warning in checker.warnings:
+                print(warning)  # or something
diff --git a/src/modelbench/run.py b/src/modelbench/run.py
index 3aa3aef5..ae945f10 100644
--- a/src/modelbench/run.py
+++ b/src/modelbench/run.py
@@ -18,6 +18,7 @@
 import modelgauge
 from modelbench.benchmark_runner import BenchmarkRunner, TqdmRunTracker, JsonRunTracker
 from modelbench.benchmarks import BenchmarkDefinition, GeneralPurposeAiChatBenchmark, GeneralPurposeAiChatBenchmarkV1
+from modelbench.consistency_checker import ConsistencyChecker
 from modelbench.hazards import STANDARDS
 from modelbench.record import dump_json
 from modelbench.static_site_generator import StaticContent, StaticSiteGenerator
@@ -133,6 +134,16 @@ def benchmark(
         json_path = output_dir / f"benchmark_record-{b.uid}.json"
         scores = [score for score in benchmark_scores if score.benchmark_definition == b]
         dump_json(json_path, start_time, b, scores)
+        # TODO: Consistency check
+
+
+@cli.command(help="check the consistency of a benchmark run using it's record and journal files.")
+@click.option("--journal-path", "-j", type=click.Path(exists=True, dir_okay=False, path_type=pathlib.Path))
+# @click.option("--record-path", "-r", type=click.Path(exists=True, dir_okay=False, path_type=pathlib.Path))
+@click.option("--verbose", "-v", default=False, is_flag=True, help="Print details about the failed checks.")
+def consistency_check(journal_path, verbose):
+    checker = ConsistencyChecker(journal_path)
+    checker.run(verbose)
 
 
 def find_suts_for_sut_argument(sut_args: List[str]):
diff --git a/src/modelbench/run_journal.py b/src/modelbench/run_journal.py
index e7da8451..bd43ebb5 100644
--- a/src/modelbench/run_journal.py
+++ b/src/modelbench/run_journal.py
@@ -4,12 +4,12 @@
 from contextlib import AbstractContextManager
 from datetime import datetime, timezone
 from enum import Enum
-from io import IOBase
+from io import IOBase, TextIOWrapper
 from typing import Sequence, Mapping
 from unittest.mock import MagicMock
 
 from pydantic import BaseModel
-from zstandard.backend_cffi import ZstdCompressor
+from zstandard.backend_cffi import ZstdCompressor, ZstdDecompressor
 
 from modelbench.benchmark_runner_items import TestRunItem, Timer
 from modelgauge.sut import SUTResponse
@@ -54,6 +54,17 @@ def for_journal(o):
         return o
 
 
+def journal_reader(path):
+    """Loads existing journal file, decompressing if necessary."""
+    if path.suffix == ".zst":
+        raw_fh = open(path, "rb")
+        dctx = ZstdDecompressor()
+        sr = dctx.stream_reader(raw_fh)
+        return TextIOWrapper(sr, encoding="utf-8")
+    else:
+        return open(path, "r")
+
+
 class RunJournal(AbstractContextManager):
 
     def __init__(self, output=None):
diff --git a/tests/modelbench_tests/test_consistency_checker.py b/tests/modelbench_tests/test_consistency_checker.py
new file mode 100644
index 00000000..e920d45f
--- /dev/null
+++ b/tests/modelbench_tests/test_consistency_checker.py
@@ -0,0 +1,126 @@
+import json
+import pytest
+from typing import Dict, List
+
+from modelbench.consistency_checker import ConsistencyChecker
+
+
+def make_basic_run(suts: List[str], test_prompts: Dict[str, List[str]], annotators: List[str]):
+    """Successful "fresh" benchmark run with all SUT/annotator responses fetched (not cached)."""
+    journal = []
+    journal.append({"message": "starting run", "suts": suts, "tests": list(test_prompts.keys())})
+    for sut in suts:
+        for test, prompts in test_prompts.items():
+            journal.append({"message": "using test items", "test": test, "using": len(prompts)})
+            for prompt in prompts:
+                # Normal pipeline.
+                sut_messages = [
+                    "queuing item",
+                    "fetched sut response",
+                    "translated sut response",
+                    "measured item quality",
+                ]
+                for message in sut_messages:
+                    journal.append({"message": message, "test": test, "prompt_id": prompt, "sut": sut})
+                for annotator in annotators:
+                    journal.append(
+                        {
+                            "message": "fetched annotator response",
+                            "test": test,
+                            "sut": sut,
+                            "prompt_id": prompt,
+                            "annotator": annotator,
+                        }
+                    )
+    return journal
+
+
+@pytest.fixture
+def basic_benchmark_run():
+    return make_basic_run(
+        suts=["sut1", "sut2"], test_prompts={"test1": ["prompt1", "prompt2"]}, annotators=["annotator1", "annotator2"]
+    )
+
+
+def init_checker_for_journal(tmp_path, journal):
+    journal_path = tmp_path / "journal.jsonl"
+    with open(journal_path, "w") as f:
+        for item in journal:
+            f.write(json.dumps(item) + "\n")
+
+    checker = ConsistencyChecker(journal_path=journal_path)
+    return checker
+
+
+def test_normal_run(tmp_path, basic_benchmark_run):
+    checker = init_checker_for_journal(tmp_path, basic_benchmark_run)
+    checker.run()
+
+    for subchecker in [checker.test_sut_level_checker, checker.test_sut_annotator_level_checker]:
+        assert subchecker.check_is_complete()
+        for row in subchecker.results.values():
+            assert all(row)
+        assert subchecker.warnings == []
+
+
+@pytest.mark.parametrize(
+    "duplicate_message,failed_check",
+    [
+        ("fetched sut response", "EachPromptRespondedToOnce"),
+        ("using cached sut response", "EachPromptRespondedToOnce"),
+        ("translated sut response", "EachResponseTranslatedOnce"),
+        ("measured item quality", "EachItemMeasuredOnce"),
+    ],
+)
+def test_run_with_duplicate_sut_stuff(tmp_path, basic_benchmark_run, duplicate_message, failed_check):
+    basic_benchmark_run.append({"message": duplicate_message, "test": "test1", "sut": "sut1", "prompt_id": "prompt1"})
+    checker = init_checker_for_journal(tmp_path, basic_benchmark_run)
+    checker.run()
+
+    subchecker = checker.test_sut_level_checker
+    failed_row = subchecker._row_key(sut="sut1", test="test1")
+    assert subchecker.check_is_complete()
+    assert subchecker.results[failed_row][failed_check] is False
+    # TODO: Check warnings
+
+
+@pytest.mark.parametrize(
+    "extra_earlier_message,failed_check",
+    [
+        ("queuing item", "EachPromptRespondedToOnce"),
+        ("fetched sut response", "EachResponseTranslatedOnce"),
+        ("translated sut response", "EachItemMeasuredOnce"),
+    ],
+)
+def test_run_with_missing_sut_stuff(tmp_path, basic_benchmark_run, extra_earlier_message, failed_check):
+    basic_benchmark_run.append(
+        {"message": extra_earlier_message, "test": "test1", "sut": "sut1", "prompt_id": "NEW PROMPT"}
+    )
+    checker = init_checker_for_journal(tmp_path, basic_benchmark_run)
+    checker.run()
+
+    subchecker = checker.test_sut_level_checker
+    failed_row = subchecker._row_key(sut="sut1", test="test1")
+    assert subchecker.check_is_complete()
+    assert subchecker.results[failed_row][failed_check] is False
+    # TODO: Check warnings
+
+
+@pytest.mark.parametrize(
+    "extra_message,failed_check",
+    [
+        ("fetched sut response", "EachPromptRespondedToOnce"),
+        ("translated sut response", "EachResponseTranslatedOnce"),
+        ("measured item quality", "EachItemMeasuredOnce"),
+    ],
+)
+def test_run_with_extra_sut_stuff(tmp_path, basic_benchmark_run, extra_message, failed_check):
+    basic_benchmark_run.append({"message": extra_message, "test": "test1", "sut": "sut1", "prompt_id": "NEW PROMPT"})
+    checker = init_checker_for_journal(tmp_path, basic_benchmark_run)
+    checker.run()
+
+    subchecker = checker.test_sut_level_checker
+    failed_row = subchecker._row_key(sut="sut1", test="test1")
+    assert subchecker.check_is_complete()
+    assert subchecker.results[failed_row][failed_check] is False
+    # TODO: Check warnings