diff --git a/tests/test_gitea_client_core.py b/tests/test_gitea_client_core.py
new file mode 100644
index 00000000..829fff60
--- /dev/null
+++ b/tests/test_gitea_client_core.py
@@ -0,0 +1,318 @@
+"""Tests for gitea_client.py — the typed, sovereign API client.
+
+gitea_client.py is 539 lines with zero tests in this repo (there are
+tests in hermes-agent, but not here where it's actually used).
+
+These tests cover:
+  - All 6 dataclass from_dict() constructors (User, Label, Issue, etc.)
+  - Defensive handling of missing/null fields from Gitea API
+  - find_unassigned_issues() filtering logic
+  - find_agent_issues() case-insensitive matching
+  - GiteaError formatting
+  - _repo_path() formatting
+"""
+
+from __future__ import annotations
+
+import importlib.util
+import sys
+from pathlib import Path
+
+import pytest
+
+# Import gitea_client directly via importlib to avoid any sys.modules mocking
+# from test_tasks_core which stubs gitea_client as a MagicMock.
+REPO_ROOT = Path(__file__).parent.parent
+_spec = importlib.util.spec_from_file_location(
+    "gitea_client_real",
+    REPO_ROOT / "gitea_client.py",
+)
+_gc = importlib.util.module_from_spec(_spec)
+sys.modules["gitea_client_real"] = _gc
+_spec.loader.exec_module(_gc)
+
+User = _gc.User
+Label = _gc.Label
+Issue = _gc.Issue
+Comment = _gc.Comment
+PullRequest = _gc.PullRequest
+PRFile = _gc.PRFile
+GiteaError = _gc.GiteaError
+GiteaClient = _gc.GiteaClient
+
+
+# ═══════════════════════════════════════════════════════════════════════
+# DATACLASS DESERIALIZATION
+# ═══════════════════════════════════════════════════════════════════════
+
+class TestUserFromDict:
+    def test_full_user(self):
+        u = User.from_dict({"id": 1, "login": "timmy", "full_name": "Timmy", "email": "t@t.com"})
+        assert u.id == 1
+        assert u.login == "timmy"
+        assert u.full_name == "Timmy"
+        assert u.email == "t@t.com"
+
+    def test_minimal_user(self):
+        """Missing fields default to empty."""
+        u = User.from_dict({})
+        assert u.id == 0
+        assert u.login == ""
+
+    def test_extra_fields_ignored(self):
+        """Unknown fields from Gitea are silently ignored."""
+        u = User.from_dict({"id": 1, "login": "x", "avatar_url": "http://..."})
+        assert u.login == "x"
+
+
+class TestLabelFromDict:
+    def test_label(self):
+        lb = Label.from_dict({"id": 5, "name": "bug", "color": "#ff0000"})
+        assert lb.id == 5
+        assert lb.name == "bug"
+        assert lb.color == "#ff0000"
+
+
+class TestIssueFromDict:
+    def test_full_issue(self):
+        issue = Issue.from_dict({
+            "number": 42,
+            "title": "Fix the bug",
+            "body": "Please fix it",
+            "state": "open",
+            "user": {"id": 1, "login": "reporter"},
+            "assignees": [{"id": 2, "login": "dev"}],
+            "labels": [{"id": 3, "name": "bug"}],
+            "comments": 5,
+        })
+        assert issue.number == 42
+        assert issue.user.login == "reporter"
+        assert len(issue.assignees) == 1
+        assert issue.assignees[0].login == "dev"
+        assert len(issue.labels) == 1
+        assert issue.comments == 5
+
+    def test_null_assignees_handled(self):
+        """Gitea returns null for assignees sometimes — the exact bug
+        that crashed find_unassigned_issues() before the defensive fix."""
+        issue = Issue.from_dict({
+            "number": 1,
+            "title": "test",
+            "body": None,
+            "state": "open",
+            "user": {"id": 1, "login": "x"},
+            "assignees": None,
+        })
+        assert issue.assignees == []
+        assert issue.body == ""
+
+    def test_null_labels_handled(self):
+        """Labels can also be null."""
+        issue = Issue.from_dict({
+            "number": 1,
+            "title": "test",
+            "state": "open",
+            "user": {},
+            "labels": None,
+        })
+        assert issue.labels == []
+
+    def test_missing_user_defaults(self):
+        """Issue with no user field doesn't crash."""
+        issue = Issue.from_dict({"number": 1, "title": "t", "state": "open"})
+        assert issue.user.login == ""
+
+
+class TestCommentFromDict:
+    def test_comment(self):
+        c = Comment.from_dict({
+            "id": 10,
+            "body": "LGTM",
+            "user": {"id": 1, "login": "reviewer"},
+        })
+        assert c.id == 10
+        assert c.body == "LGTM"
+        assert c.user.login == "reviewer"
+
+    def test_null_body(self):
+        c = Comment.from_dict({"id": 1, "body": None, "user": {}})
+        assert c.body == ""
+
+
+class TestPullRequestFromDict:
+    def test_full_pr(self):
+        pr = PullRequest.from_dict({
+            "number": 99,
+            "title": "Add feature",
+            "body": "Description here",
+            "state": "open",
+            "user": {"id": 1, "login": "dev"},
+            "head": {"ref": "feature-branch"},
+            "base": {"ref": "main"},
+            "mergeable": True,
+            "merged": False,
+            "changed_files": 3,
+        })
+        assert pr.number == 99
+        assert pr.head_branch == "feature-branch"
+        assert pr.base_branch == "main"
+        assert pr.mergeable is True
+
+    def test_null_head_base(self):
+        """Handles null head/base objects."""
+        pr = PullRequest.from_dict({
+            "number": 1, "title": "t", "state": "open",
+            "user": {}, "head": None, "base": None,
+        })
+        assert pr.head_branch == ""
+        assert pr.base_branch == ""
+
+    def test_null_merged(self):
+        """merged can be null from Gitea."""
+        pr = PullRequest.from_dict({
+            "number": 1, "title": "t", "state": "open",
+            "user": {}, "merged": None,
+        })
+        assert pr.merged is False
+
+
+class TestPRFileFromDict:
+    def test_pr_file(self):
+        f = PRFile.from_dict({
+            "filename": "src/main.py",
+            "status": "modified",
+            "additions": 10,
+            "deletions": 3,
+        })
+        assert f.filename == "src/main.py"
+        assert f.status == "modified"
+        assert f.additions == 10
+        assert f.deletions == 3
+
+
+# ═══════════════════════════════════════════════════════════════════════
+# ERROR HANDLING
+# ═══════════════════════════════════════════════════════════════════════
+
+class TestGiteaError:
+    def test_error_formatting(self):
+        err = GiteaError(404, "not found", "http://example.com/api/v1/repos/x")
+        assert "404" in str(err)
+        assert "not found" in str(err)
+
+    def test_error_attributes(self):
+        err = GiteaError(500, "internal")
+        assert err.status == 500
+
+
+# ═══════════════════════════════════════════════════════════════════════
+# CLIENT HELPER METHODS
+# ═══════════════════════════════════════════════════════════════════════
+
+class TestClientHelpers:
+    def test_repo_path(self):
+        """_repo_path converts owner/name to API path."""
+        client = GiteaClient.__new__(GiteaClient)
+        assert client._repo_path("Timmy_Foundation/the-nexus") == "/repos/Timmy_Foundation/the-nexus"
+
+
+# ═══════════════════════════════════════════════════════════════════════
+# FILTERING LOGIC — find_unassigned_issues, find_agent_issues
+# ═══════════════════════════════════════════════════════════════════════
+
+class TestFindUnassigned:
+    """Tests for find_unassigned_issues() filtering logic.
+
+    These tests use pre-constructed Issue objects to test the filtering
+    without making any API calls.
+    """
+
+    def _make_issue(self, number, assignees=None, labels=None, title="test"):
+        return Issue(
+            number=number, title=title, body="", state="open",
+            user=User(id=0, login=""),
+            assignees=[User(id=0, login=a) for a in (assignees or [])],
+            labels=[Label(id=0, name=lb) for lb in (labels or [])],
+        )
+
+    def test_filters_assigned_issues(self):
+        """Issues with assignees are excluded."""
+        from unittest.mock import patch
+
+        issues = [
+            self._make_issue(1, assignees=["dev"]),
+            self._make_issue(2),  # unassigned
+        ]
+
+        client = GiteaClient.__new__(GiteaClient)
+        with patch.object(client, "list_issues", return_value=issues):
+            result = client.find_unassigned_issues("repo")
+
+        assert len(result) == 1
+        assert result[0].number == 2
+
+    def test_excludes_by_label(self):
+        """Issues with excluded labels are filtered."""
+        from unittest.mock import patch
+
+        issues = [
+            self._make_issue(1, labels=["wontfix"]),
+            self._make_issue(2, labels=["bug"]),
+        ]
+
+        client = GiteaClient.__new__(GiteaClient)
+        with patch.object(client, "list_issues", return_value=issues):
+            result = client.find_unassigned_issues("repo", exclude_labels=["wontfix"])
+
+        assert len(result) == 1
+        assert result[0].number == 2
+
+    def test_excludes_by_title_pattern(self):
+        """Issues matching title patterns are filtered."""
+        from unittest.mock import patch
+
+        issues = [
+            self._make_issue(1, title="[PHASE] Research AI"),
+            self._make_issue(2, title="Fix login bug"),
+        ]
+
+        client = GiteaClient.__new__(GiteaClient)
+        with patch.object(client, "list_issues", return_value=issues):
+            result = client.find_unassigned_issues(
+                "repo", exclude_title_patterns=["[PHASE]"]
+            )
+
+        assert len(result) == 1
+        assert result[0].number == 2
+
+
+class TestFindAgentIssues:
+    """Tests for find_agent_issues() case-insensitive matching."""
+
+    def test_case_insensitive_match(self):
+        from unittest.mock import patch
+
+        issues = [
+            Issue(number=1, title="t", body="", state="open",
+                  user=User(0, ""), assignees=[User(0, "Timmy")], labels=[]),
+        ]
+
+        client = GiteaClient.__new__(GiteaClient)
+        with patch.object(client, "list_issues", return_value=issues):
+            result = client.find_agent_issues("repo", "timmy")
+
+        assert len(result) == 1
+
+    def test_no_match_for_different_agent(self):
+        from unittest.mock import patch
+
+        issues = [
+            Issue(number=1, title="t", body="", state="open",
+                  user=User(0, ""), assignees=[User(0, "Timmy")], labels=[]),
+        ]
+
+        client = GiteaClient.__new__(GiteaClient)
+        with patch.object(client, "list_issues", return_value=issues):
+            result = client.find_agent_issues("repo", "claude")
+
+        assert len(result) == 0
diff --git a/tests/test_tasks_core.py b/tests/test_tasks_core.py
new file mode 100644
index 00000000..a7242681
--- /dev/null
+++ b/tests/test_tasks_core.py
@@ -0,0 +1,540 @@
+"""Tests for tasks.py — the orchestration brain.
+
+tasks.py is 2,117 lines with zero test coverage. This suite covers
+the pure utility functions that every pipeline depends on: JSON parsing,
+data normalization, file I/O primitives, and prompt formatting.
+
+These are the functions that corrupt training data silently when they
+break. If a normalization function drops a field or misparses JSON from
+an LLM, the entire training pipeline produces garbage. No one notices
+until the next autolora run produces a worse model.
+
+Coverage priority is based on blast radius — a bug in
+extract_first_json_object() affects every @huey.task that processes
+LLM output, which is all of them.
+"""
+
+from __future__ import annotations
+
+import json
+import sys
+import tempfile
+from pathlib import Path
+
+import pytest
+
+# Import tasks.py without triggering Huey/GiteaClient side effects.
+# We mock the imports that have side effects to isolate the pure functions.
+from unittest.mock import MagicMock
+
+# Stub out modules with side effects before importing tasks
+sys.modules.setdefault("orchestration", MagicMock(huey=MagicMock()))
+sys.modules.setdefault("huey", MagicMock())
+sys.modules.setdefault("gitea_client", MagicMock())
+sys.modules.setdefault("metrics_helpers", MagicMock(
+    build_local_metric_record=MagicMock(return_value={})
+))
+
+# Now we can import the functions we want to test
+REPO_ROOT = Path(__file__).parent.parent
+sys.path.insert(0, str(REPO_ROOT))
+
+import importlib
+tasks = importlib.import_module("tasks")
+
+# Pull out the functions under test
+extract_first_json_object = tasks.extract_first_json_object
+parse_json_output = tasks.parse_json_output
+normalize_candidate_entry = tasks.normalize_candidate_entry
+normalize_training_examples = tasks.normalize_training_examples
+normalize_rubric_scores = tasks.normalize_rubric_scores
+archive_batch_id = tasks.archive_batch_id
+archive_profile_summary = tasks.archive_profile_summary
+format_tweets_for_prompt = tasks.format_tweets_for_prompt
+read_json = tasks.read_json
+write_json = tasks.write_json
+load_jsonl = tasks.load_jsonl
+write_jsonl = tasks.write_jsonl
+append_jsonl = tasks.append_jsonl
+write_text = tasks.write_text
+count_jsonl_rows = tasks.count_jsonl_rows
+newest_file = tasks.newest_file
+latest_path = tasks.latest_path
+archive_default_checkpoint = tasks.archive_default_checkpoint
+
+
+# ═══════════════════════════════════════════════════════════════════════
+# JSON EXTRACTION — the single most critical function in the pipeline
+# ═══════════════════════════════════════════════════════════════════════
+
+class TestExtractFirstJsonObject:
+    """extract_first_json_object() parses JSON from noisy LLM output.
+
+    Every @huey.task that processes model output depends on this.
+    If this breaks, the entire training pipeline produces garbage.
+    """
+
+    def test_clean_json(self):
+        """Parses valid JSON directly."""
+        result = extract_first_json_object('{"key": "value"}')
+        assert result == {"key": "value"}
+
+    def test_json_with_markdown_fences(self):
+        """Strips ```json fences that models love to add."""
+        text = '```json\n{"hello": "world"}\n```'
+        result = extract_first_json_object(text)
+        assert result == {"hello": "world"}
+
+    def test_json_after_prose(self):
+        """Finds JSON buried after the model's explanation."""
+        text = "Here is the analysis:\n\nI found that {'key': 'value'}\n\n{\"real\": true}"
+        result = extract_first_json_object(text)
+        assert result == {"real": True}
+
+    def test_nested_json(self):
+        """Handles nested objects correctly."""
+        text = '{"outer": {"inner": [1, 2, 3]}}'
+        result = extract_first_json_object(text)
+        assert result == {"outer": {"inner": [1, 2, 3]}}
+
+    def test_raises_on_no_json(self):
+        """Raises ValueError when no JSON object is found."""
+        with pytest.raises(ValueError, match="No JSON object found"):
+            extract_first_json_object("No JSON here at all")
+
+    def test_raises_on_json_array(self):
+        """Raises ValueError for JSON arrays (only objects accepted)."""
+        with pytest.raises(ValueError, match="No JSON object found"):
+            extract_first_json_object("[1, 2, 3]")
+
+    def test_skips_malformed_and_finds_valid(self):
+        """Skips broken JSON fragments to find the real one."""
+        text = '{broken {"valid": true}'
+        result = extract_first_json_object(text)
+        assert result == {"valid": True}
+
+    def test_handles_whitespace_heavy_output(self):
+        """Handles output with excessive whitespace."""
+        text = '   \n\n  {"spaced": "out"}  \n\n  '
+        result = extract_first_json_object(text)
+        assert result == {"spaced": "out"}
+
+    def test_empty_string_raises(self):
+        """Empty input raises ValueError."""
+        with pytest.raises(ValueError):
+            extract_first_json_object("")
+
+    def test_unicode_content(self):
+        """Handles Unicode characters in JSON values."""
+        text = '{"emoji": "🔥", "jp": "日本語"}'
+        result = extract_first_json_object(text)
+        assert result["emoji"] == "🔥"
+
+
+class TestParseJsonOutput:
+    """parse_json_output() tries stdout then stderr for JSON."""
+
+    def test_finds_json_in_stdout(self):
+        result = parse_json_output(stdout='{"from": "stdout"}')
+        assert result == {"from": "stdout"}
+
+    def test_falls_back_to_stderr(self):
+        result = parse_json_output(stdout="no json", stderr='{"from": "stderr"}')
+        assert result == {"from": "stderr"}
+
+    def test_empty_returns_empty_dict(self):
+        result = parse_json_output(stdout="", stderr="")
+        assert result == {}
+
+    def test_none_inputs_handled(self):
+        result = parse_json_output(stdout=None, stderr=None)
+        assert result == {}
+
+
+# ═══════════════════════════════════════════════════════════════════════
+# DATA NORMALIZATION — training data quality depends on this
+# ═══════════════════════════════════════════════════════════════════════
+
+class TestNormalizeCandidateEntry:
+    """normalize_candidate_entry() cleans LLM-generated knowledge candidates.
+
+    A bug here silently corrupts the knowledge graph. Fields are
+    coerced to correct types, clamped to valid ranges, and deduplicated.
+    """
+
+    def test_valid_candidate(self):
+        """Normalizes a well-formed candidate."""
+        candidate = {
+            "category": "trait",
+            "claim": "Alexander likes coffee",
+            "evidence_tweet_ids": ["123", "456"],
+            "evidence_quotes": ["I love coffee"],
+            "confidence": 0.8,
+            "status": "provisional",
+        }
+        result = normalize_candidate_entry(candidate, "batch_001", 1)
+        assert result["id"] == "batch_001-candidate-01"
+        assert result["category"] == "trait"
+        assert result["claim"] == "Alexander likes coffee"
+        assert result["confidence"] == 0.8
+        assert result["status"] == "provisional"
+
+    def test_empty_claim_returns_none(self):
+        """Rejects candidates with empty claims."""
+        result = normalize_candidate_entry({"claim": ""}, "b001", 0)
+        assert result is None
+
+    def test_missing_claim_returns_none(self):
+        """Rejects candidates with no claim field."""
+        result = normalize_candidate_entry({"category": "trait"}, "b001", 0)
+        assert result is None
+
+    def test_confidence_clamped_high(self):
+        """Confidence above 1.0 is clamped to 1.0."""
+        result = normalize_candidate_entry(
+            {"claim": "test", "confidence": 5.0}, "b001", 1
+        )
+        assert result["confidence"] == 1.0
+
+    def test_confidence_clamped_low(self):
+        """Confidence below 0.0 is clamped to 0.0."""
+        result = normalize_candidate_entry(
+            {"claim": "test", "confidence": -0.5}, "b001", 1
+        )
+        assert result["confidence"] == 0.0
+
+    def test_invalid_confidence_defaults(self):
+        """Non-numeric confidence defaults to 0.5."""
+        result = normalize_candidate_entry(
+            {"claim": "test", "confidence": "high"}, "b001", 1
+        )
+        assert result["confidence"] == 0.5
+
+    def test_invalid_status_defaults_to_provisional(self):
+        """Unknown status values default to 'provisional'."""
+        result = normalize_candidate_entry(
+            {"claim": "test", "status": "banana"}, "b001", 1
+        )
+        assert result["status"] == "provisional"
+
+    def test_duplicate_evidence_ids_deduped(self):
+        """Duplicate tweet IDs are removed."""
+        result = normalize_candidate_entry(
+            {"claim": "test", "evidence_tweet_ids": ["1", "1", "2", "2"]},
+            "b001", 1,
+        )
+        assert result["evidence_tweet_ids"] == ["1", "2"]
+
+    def test_duplicate_quotes_deduped(self):
+        """Duplicate evidence quotes are removed."""
+        result = normalize_candidate_entry(
+            {"claim": "test", "evidence_quotes": ["same", "same", "new"]},
+            "b001", 1,
+        )
+        assert result["evidence_quotes"] == ["same", "new"]
+
+    def test_evidence_truncated_to_5(self):
+        """Evidence lists are capped at 5 items."""
+        result = normalize_candidate_entry(
+            {"claim": "test", "evidence_quotes": [f"q{i}" for i in range(10)]},
+            "b001", 1,
+        )
+        assert len(result["evidence_quotes"]) == 5
+
+    def test_none_category_defaults(self):
+        """None category defaults to 'recurring-theme'."""
+        result = normalize_candidate_entry(
+            {"claim": "test", "category": None}, "b001", 1
+        )
+        assert result["category"] == "recurring-theme"
+
+    def test_valid_statuses_accepted(self):
+        """All three valid statuses are preserved."""
+        for status in ("provisional", "durable", "retracted"):
+            result = normalize_candidate_entry(
+                {"claim": "test", "status": status}, "b001", 1
+            )
+            assert result["status"] == status
+
+
+class TestNormalizeTrainingExamples:
+    """normalize_training_examples() cleans LLM-generated training pairs.
+
+    This feeds directly into autolora. Bad data here means bad training.
+    """
+
+    def test_valid_examples_normalized(self):
+        """Well-formed examples pass through with added metadata."""
+        examples = [
+            {"prompt": "Q1", "response": "A1", "task_type": "analysis"},
+            {"prompt": "Q2", "response": "A2"},
+        ]
+        result = normalize_training_examples(
+            examples, "b001", ["t1"], "fallback_p", "fallback_r"
+        )
+        assert len(result) == 2
+        assert result[0]["example_id"] == "b001-example-01"
+        assert result[0]["prompt"] == "Q1"
+        assert result[1]["task_type"] == "analysis"  # defaults
+
+    def test_empty_examples_get_fallback(self):
+        """When no valid examples exist, fallback is used."""
+        result = normalize_training_examples(
+            [], "b001", ["t1"], "fallback prompt", "fallback response"
+        )
+        assert len(result) == 1
+        assert result[0]["prompt"] == "fallback prompt"
+        assert result[0]["response"] == "fallback response"
+
+    def test_examples_with_empty_prompt_skipped(self):
+        """Examples without prompts are filtered out."""
+        examples = [
+            {"prompt": "", "response": "A1"},
+            {"prompt": "Q2", "response": "A2"},
+        ]
+        result = normalize_training_examples(
+            examples, "b001", ["t1"], "fp", "fr"
+        )
+        assert len(result) == 1
+        assert result[0]["prompt"] == "Q2"
+
+    def test_examples_with_empty_response_skipped(self):
+        """Examples without responses are filtered out."""
+        examples = [
+            {"prompt": "Q1", "response": ""},
+        ]
+        result = normalize_training_examples(
+            examples, "b001", ["t1"], "fp", "fr"
+        )
+        # Falls to fallback
+        assert len(result) == 1
+        assert result[0]["prompt"] == "fp"
+
+    def test_alternative_field_names_accepted(self):
+        """Accepts 'instruction'/'answer' as field name alternatives."""
+        examples = [
+            {"instruction": "Q1", "answer": "A1"},
+        ]
+        result = normalize_training_examples(
+            examples, "b001", ["t1"], "fp", "fr"
+        )
+        assert len(result) == 1
+        assert result[0]["prompt"] == "Q1"
+        assert result[0]["response"] == "A1"
+
+
+class TestNormalizeRubricScores:
+    """normalize_rubric_scores() cleans eval rubric output."""
+
+    def test_valid_scores(self):
+        scores = {"grounding": 8, "specificity": 7, "source_distinction": 9, "actionability": 6}
+        result = normalize_rubric_scores(scores)
+        assert result == {"grounding": 8.0, "specificity": 7.0,
+                          "source_distinction": 9.0, "actionability": 6.0}
+
+    def test_missing_keys_default_to_zero(self):
+        result = normalize_rubric_scores({})
+        assert result == {"grounding": 0.0, "specificity": 0.0,
+                          "source_distinction": 0.0, "actionability": 0.0}
+
+    def test_non_numeric_defaults_to_zero(self):
+        result = normalize_rubric_scores({"grounding": "excellent"})
+        assert result["grounding"] == 0.0
+
+
+# ═══════════════════════════════════════════════════════════════════════
+# FILE I/O PRIMITIVES — the foundation everything reads/writes through
+# ═══════════════════════════════════════════════════════════════════════
+
+class TestReadJson:
+    def test_reads_valid_file(self, tmp_path):
+        f = tmp_path / "test.json"
+        f.write_text('{"key": "val"}')
+        assert read_json(f, {}) == {"key": "val"}
+
+    def test_missing_file_returns_default(self, tmp_path):
+        assert read_json(tmp_path / "nope.json", {"default": True}) == {"default": True}
+
+    def test_corrupt_file_returns_default(self, tmp_path):
+        f = tmp_path / "bad.json"
+        f.write_text("{corrupt json!!!}")
+        assert read_json(f, {"safe": True}) == {"safe": True}
+
+    def test_default_is_deep_copied(self, tmp_path):
+        """Default is deep-copied, not shared between calls."""
+        default = {"nested": {"key": "val"}}
+        result1 = read_json(tmp_path / "a.json", default)
+        result2 = read_json(tmp_path / "b.json", default)
+        result1["nested"]["key"] = "mutated"
+        assert result2["nested"]["key"] == "val"
+
+
+class TestWriteJson:
+    def test_creates_file_with_indent(self, tmp_path):
+        f = tmp_path / "out.json"
+        write_json(f, {"key": "val"})
+        content = f.read_text()
+        assert '"key": "val"' in content
+        assert content.endswith("\n")
+
+    def test_creates_parent_dirs(self, tmp_path):
+        f = tmp_path / "deep" / "nested" / "out.json"
+        write_json(f, {"ok": True})
+        assert f.exists()
+
+    def test_sorted_keys(self, tmp_path):
+        f = tmp_path / "sorted.json"
+        write_json(f, {"z": 1, "a": 2})
+        content = f.read_text()
+        assert content.index('"a"') < content.index('"z"')
+
+
+class TestJsonlIO:
+    def test_load_jsonl_valid(self, tmp_path):
+        f = tmp_path / "data.jsonl"
+        f.write_text('{"a":1}\n{"b":2}\n')
+        rows = load_jsonl(f)
+        assert len(rows) == 2
+        assert rows[0] == {"a": 1}
+
+    def test_load_jsonl_missing_file(self, tmp_path):
+        assert load_jsonl(tmp_path / "nope.jsonl") == []
+
+    def test_load_jsonl_skips_blank_lines(self, tmp_path):
+        f = tmp_path / "data.jsonl"
+        f.write_text('{"a":1}\n\n\n{"b":2}\n')
+        rows = load_jsonl(f)
+        assert len(rows) == 2
+
+    def test_write_jsonl(self, tmp_path):
+        f = tmp_path / "out.jsonl"
+        write_jsonl(f, [{"a": 1}, {"b": 2}])
+        lines = f.read_text().strip().split("\n")
+        assert len(lines) == 2
+        assert json.loads(lines[0]) == {"a": 1}
+
+    def test_append_jsonl(self, tmp_path):
+        f = tmp_path / "append.jsonl"
+        f.write_text('{"existing":true}\n')
+        append_jsonl(f, [{"new": True}])
+        rows = load_jsonl(f)
+        assert len(rows) == 2
+
+    def test_append_jsonl_empty_list_noop(self, tmp_path):
+        """Appending empty list doesn't create file."""
+        f = tmp_path / "nope.jsonl"
+        append_jsonl(f, [])
+        assert not f.exists()
+
+    def test_count_jsonl_rows(self, tmp_path):
+        f = tmp_path / "count.jsonl"
+        f.write_text('{"a":1}\n{"b":2}\n{"c":3}\n')
+        assert count_jsonl_rows(f) == 3
+
+    def test_count_jsonl_missing_file(self, tmp_path):
+        assert count_jsonl_rows(tmp_path / "nope.jsonl") == 0
+
+    def test_count_jsonl_skips_blank_lines(self, tmp_path):
+        f = tmp_path / "sparse.jsonl"
+        f.write_text('{"a":1}\n\n{"b":2}\n\n')
+        assert count_jsonl_rows(f) == 2
+
+
+class TestWriteText:
+    def test_writes_with_trailing_newline(self, tmp_path):
+        f = tmp_path / "text.md"
+        write_text(f, "hello")
+        assert f.read_text() == "hello\n"
+
+    def test_strips_trailing_whitespace(self, tmp_path):
+        f = tmp_path / "text.md"
+        write_text(f, "hello  \n\n\n")
+        assert f.read_text() == "hello\n"
+
+    def test_empty_content_writes_empty_file(self, tmp_path):
+        f = tmp_path / "text.md"
+        write_text(f, "   ")
+        assert f.read_text() == ""
+
+
+# ═══════════════════════════════════════════════════════════════════════
+# PATH UTILITIES
+# ═══════════════════════════════════════════════════════════════════════
+
+class TestPathUtilities:
+    def test_newest_file(self, tmp_path):
+        (tmp_path / "a.txt").write_text("a")
+        (tmp_path / "b.txt").write_text("b")
+        (tmp_path / "c.txt").write_text("c")
+        result = newest_file(tmp_path, "*.txt")
+        assert result.name == "c.txt"  # sorted, last = newest
+
+    def test_newest_file_empty_dir(self, tmp_path):
+        assert newest_file(tmp_path, "*.txt") is None
+
+    def test_latest_path(self, tmp_path):
+        (tmp_path / "batch_001.json").write_text("{}")
+        (tmp_path / "batch_002.json").write_text("{}")
+        result = latest_path(tmp_path, "batch_*.json")
+        assert result.name == "batch_002.json"
+
+    def test_latest_path_no_matches(self, tmp_path):
+        assert latest_path(tmp_path, "*.nope") is None
+
+
+# ═══════════════════════════════════════════════════════════════════════
+# FORMATTING & HELPERS
+# ═══════════════════════════════════════════════════════════════════════
+
+class TestFormatting:
+    def test_archive_batch_id(self):
+        assert archive_batch_id(1) == "batch_001"
+        assert archive_batch_id(42) == "batch_042"
+        assert archive_batch_id(100) == "batch_100"
+
+    def test_archive_profile_summary(self):
+        profile = {
+            "claims": [
+                {"status": "durable", "claim": "a"},
+                {"status": "durable", "claim": "b"},
+                {"status": "provisional", "claim": "c"},
+                {"status": "retracted", "claim": "d"},
+            ]
+        }
+        summary = archive_profile_summary(profile)
+        assert len(summary["durable_claims"]) == 2
+        assert len(summary["provisional_claims"]) == 1
+
+    def test_archive_profile_summary_truncates(self):
+        """Summaries are capped at 12 durable and 8 provisional."""
+        profile = {
+            "claims": [{"status": "durable", "claim": f"d{i}"} for i in range(20)]
+                    + [{"status": "provisional", "claim": f"p{i}"} for i in range(15)]
+        }
+        summary = archive_profile_summary(profile)
+        assert len(summary["durable_claims"]) <= 12
+        assert len(summary["provisional_claims"]) <= 8
+
+    def test_archive_profile_summary_empty(self):
+        assert archive_profile_summary({}) == {
+            "durable_claims": [],
+            "provisional_claims": [],
+        }
+
+    def test_format_tweets_for_prompt(self):
+        rows = [
+            {"tweet_id": "123", "created_at": "2024-01-01", "full_text": "Hello world"},
+            {"tweet_id": "456", "created_at": "2024-01-02", "full_text": "Goodbye world"},
+        ]
+        result = format_tweets_for_prompt(rows)
+        assert "tweet_id=123" in result
+        assert "Hello world" in result
+        assert "2." in result  # 1-indexed
+
+    def test_archive_default_checkpoint(self):
+        """Default checkpoint has all required fields."""
+        cp = archive_default_checkpoint()
+        assert cp["phase"] == "discovery"
+        assert cp["next_offset"] == 0
+        assert cp["batch_size"] == 50
+        assert cp["batches_completed"] == 0