diff --git a/src/psyc/cli.py b/src/psyc/cli.py
index 12ecdfe..5a0615c 100644
--- a/src/psyc/cli.py
+++ b/src/psyc/cli.py
@@ -8,7 +8,7 @@ import typer
 import uvicorn
 
 from psyc import db, log
-from psyc.lines import classify, courier, route, scout, seal
+from psyc.lines import classify, courier, route, scout, seal, train
 from psyc.lines import map as map_line
 from psyc.models import Outcome
 from psyc.result import Err, Ok
@@ -204,6 +204,43 @@ def mock_cert_serve(host: str = "127.0.0.1", port: int = 8770) -> None:
     uvicorn.run("psyc.mock_cert:app", host=host, port=port)
 
 
+@app.command("train-build")
+def train_build(
+    task: str = typer.Option(..., "--task", "-t", help=f"one of: {', '.join(train.TASKS)}"),
+    limit: int = typer.Option(10_000, help="max cases to process"),
+) -> None:
+    if task not in train.TASKS:
+        typer.echo(f"unknown task: {task}; choices: {', '.join(train.TASKS)}", err=True)
+        raise typer.Exit(1)
+    cases = db.list_cases(limit=limit)
+    report = train.build(task, cases)
+    typer.echo(f"task: {report.task}")
+    typer.echo(f"path: {report.path}")
+    typer.echo(f"  written:           {report.written}")
+    typer.echo(f"  skipped (empty):   {report.skipped_empty}")
+    typer.echo(f"  skipped (tlp red): {report.skipped_tlp_red}")
+    typer.echo(f"  skipped (source):  {report.skipped_restricted_source}")
+    typer.echo(f"  skipped (quality): {report.skipped_quality}")
+
+
+@app.command("train-build-all")
+def train_build_all(limit: int = typer.Option(10_000, help="max cases per task")) -> None:
+    cases = db.list_cases(limit=limit)
+    for task in train.TASKS:
+        report = train.build(task, cases)
+        typer.echo(f"  {task}: wrote {report.written} → {report.path.name}")
+
+
+@app.command("train-list-datasets")
+def train_list_datasets() -> None:
+    rows = train.list_datasets()
+    if not rows:
+        typer.echo("(no datasets)")
+        return
+    for r in rows:
+        typer.echo(f"{r['name']:<40} {r['examples']:>6} examples  {int(r['size_bytes']):>8} B  {r['modified']}")
+
+
 @app.command("demo")
 def demo() -> None:
     db.init_db()
diff --git a/src/psyc/lines/train.py b/src/psyc/lines/train.py
new file mode 100644
index 0000000..14ecd55
--- /dev/null
+++ b/src/psyc/lines/train.py
@@ -0,0 +1,247 @@
+"""Trainline — ExampleBuilder + QualityGate + DatasetWriter.
+
+Reads reviewed cases from the DB, emits Alpaca-style JSONL training examples
+for the defensive task set defined in docs/dossier.md §intelminer:
+  - ioc_extraction
+  - severity_classification
+  - routing_decision
+  - tlp_assignment
+
+Outputs are versioned JSONL files under data/datasets/<task>-v<n>.jsonl.
+QualityGate enforces the dossier's training-data policy: never TLP:RED, never
+restricted source types, never empty input/output.
+"""
+
+from __future__ import annotations
+
+import json
+import re
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Callable, Dict, Iterable, List, Optional
+
+from pydantic import BaseModel, Field
+
+from psyc import DATA_DIR, log
+from psyc.lines import classify as classify_line
+from psyc.lines import route as route_line
+from psyc.models import Case, TLP
+
+
+_log = log.get(__name__)
+
+DATASETS_DIR = DATA_DIR / "datasets"
+
+TASKS = ("ioc_extraction", "severity_classification", "routing_decision", "tlp_assignment")
+
+RESTRICTED_SOURCE_TYPES = {"criminal_forum", "stolen_data_paste", "unauthorized_dump"}
+
+
+class Example(BaseModel):
+    instruction: str
+    input: str
+    output: str
+    task: str
+    case_id: str
+    tlp: str
+    meta: Dict[str, str] = Field(default_factory=dict)
+
+
+class DatasetReport(BaseModel):
+    task: str
+    path: Path
+    written: int
+    skipped_quality: int
+    skipped_tlp_red: int
+    skipped_restricted_source: int
+    skipped_empty: int
+
+
+# ---------- ExampleBuilder per task ---------------------------------------
+
+def _ex_ioc_extraction(case: Case) -> Optional[Example]:
+    obs = case.observables
+    if not (obs.urls or obs.domains or obs.ips or obs.hashes):
+        return None
+    summary_or_threat = case.summary or case.source_metadata.get("threat", "")
+    input_text = f"Advisory: {summary_or_threat}\nSource: {case.source_ref or case.source_type}"
+    output_obj = {
+        "urls": obs.urls,
+        "domains": obs.domains,
+        "ips": obs.ips,
+        "hashes": obs.hashes,
+        "cves": obs.cves,
+    }
+    return Example(
+        instruction="Extract all indicators of compromise (URLs, domains, IPs, hashes, CVEs) from the advisory. Return JSON with keys: urls, domains, ips, hashes, cves.",
+        input=input_text,
+        output=json.dumps(output_obj, ensure_ascii=False),
+        task="ioc_extraction",
+        case_id=case.case_id,
+        tlp=case.classification.tlp.value,
+    )
+
+
+def _ex_severity_classification(case: Case) -> Optional[Example]:
+    if case.classification.severity is None:
+        return None
+    input_obj = {
+        "summary": case.summary,
+        "source_type": case.source_type,
+        "incident_type": case.classification.incident_type.value if case.classification.incident_type else None,
+        "url_status": case.source_metadata.get("url_status", ""),
+        "victim_country": case.victim.country,
+        "critical_infrastructure": case.victim.critical_infrastructure,
+        "url_count": len(case.observables.urls),
+        "ip_count": len(case.observables.ips),
+    }
+    return Example(
+        instruction="Classify the defensive severity of this case as one of: low | medium | high | critical. Return only the label.",
+        input=json.dumps(input_obj, ensure_ascii=False),
+        output=case.classification.severity.value,
+        task="severity_classification",
+        case_id=case.case_id,
+        tlp=case.classification.tlp.value,
+    )
+
+
+def _ex_routing_decision(case: Case) -> Optional[Example]:
+    if case.classification.incident_type is None:
+        return None
+    routes, blocked = route_line.plan(case)
+    input_obj = {
+        "incident_type": case.classification.incident_type.value,
+        "tlp": case.classification.tlp.value,
+        "severity": case.classification.severity.value if case.classification.severity else None,
+        "victim_country": case.victim.country,
+        "critical_infrastructure": case.victim.critical_infrastructure,
+        "url_count": len(case.observables.urls),
+    }
+    output_obj = {
+        "allowed": [r.destination_name for r in routes],
+        "blocked": [{"destination": b.destination_name, "reason": b.reason} for b in blocked],
+    }
+    return Example(
+        instruction="Given the case, decide which destinations may receive a submission and which must be blocked. Return JSON with keys 'allowed' (destination names) and 'blocked' (objects with destination + reason).",
+        input=json.dumps(input_obj, ensure_ascii=False),
+        output=json.dumps(output_obj, ensure_ascii=False),
+        task="routing_decision",
+        case_id=case.case_id,
+        tlp=case.classification.tlp.value,
+    )
+
+
+def _ex_tlp_assignment(case: Case) -> Optional[Example]:
+    input_obj = {
+        "source_type": case.source_type,
+        "incident_type": case.classification.incident_type.value if case.classification.incident_type else None,
+        "victim_named": bool(case.victim.name),
+        "critical_infrastructure": case.victim.critical_infrastructure,
+        "summary": case.summary,
+    }
+    return Example(
+        instruction="Assign the Traffic Light Protocol (TLP) level for this case: RED | AMBER | GREEN | CLEAR. Return only the label.",
+        input=json.dumps(input_obj, ensure_ascii=False),
+        output=case.classification.tlp.value,
+        task="tlp_assignment",
+        case_id=case.case_id,
+        tlp=case.classification.tlp.value,
+    )
+
+
+_BUILDERS: Dict[str, Callable[[Case], Optional[Example]]] = {
+    "ioc_extraction": _ex_ioc_extraction,
+    "severity_classification": _ex_severity_classification,
+    "routing_decision": _ex_routing_decision,
+    "tlp_assignment": _ex_tlp_assignment,
+}
+
+
+# ---------- QualityGate ---------------------------------------------------
+
+class _Reject(BaseModel):
+    reason: str
+
+
+def quality_gate(example: Example, case: Case) -> Optional[str]:
+    if case.classification.tlp == TLP.RED:
+        return "tlp_red"
+    if case.source_type in RESTRICTED_SOURCE_TYPES:
+        return "restricted_source"
+    if not example.input.strip() or not example.output.strip():
+        return "empty"
+    if len(example.input) > 8000 or len(example.output) > 4000:
+        return "too_long"
+    if re.search(r"\b(password|api[_-]?key|secret|bearer)\b", example.input, re.IGNORECASE):
+        return "credential_leak_in_input"
+    return None
+
+
+# ---------- DatasetWriter -------------------------------------------------
+
+def _next_version(task: str) -> int:
+    DATASETS_DIR.mkdir(parents=True, exist_ok=True)
+    existing = list(DATASETS_DIR.glob(f"{task}-v*.jsonl"))
+    used = []
+    for p in existing:
+        m = re.search(rf"{re.escape(task)}-v(\d+)\.jsonl$", p.name)
+        if m:
+            used.append(int(m.group(1)))
+    return (max(used) + 1) if used else 1
+
+
+def build(task: str, cases: Iterable[Case]) -> DatasetReport:
+    if task not in _BUILDERS:
+        raise ValueError(f"unknown task: {task}; choices: {sorted(_BUILDERS)}")
+    builder = _BUILDERS[task]
+    version = _next_version(task)
+    path = DATASETS_DIR / f"{task}-v{version}.jsonl"
+    written = 0
+    skipped_quality = 0
+    skipped_tlp_red = 0
+    skipped_restricted = 0
+    skipped_empty = 0
+    with path.open("w", encoding="utf-8") as fh:
+        for case in cases:
+            example = builder(case)
+            if example is None:
+                skipped_empty += 1
+                continue
+            reject = quality_gate(example, case)
+            if reject == "tlp_red":
+                skipped_tlp_red += 1
+                continue
+            if reject == "restricted_source":
+                skipped_restricted += 1
+                continue
+            if reject is not None:
+                skipped_quality += 1
+                continue
+            fh.write(example.model_dump_json() + "\n")
+            written += 1
+    _log.info("train.dataset.built", task=task, version=version, written=written, path=str(path))
+    return DatasetReport(
+        task=task,
+        path=path,
+        written=written,
+        skipped_quality=skipped_quality,
+        skipped_tlp_red=skipped_tlp_red,
+        skipped_restricted_source=skipped_restricted,
+        skipped_empty=skipped_empty,
+    )
+
+
+def list_datasets() -> List[Dict[str, str]]:
+    if not DATASETS_DIR.exists():
+        return []
+    out: List[Dict[str, str]] = []
+    for p in sorted(DATASETS_DIR.glob("*.jsonl")):
+        line_count = sum(1 for _ in p.open("r", encoding="utf-8"))
+        out.append({
+            "name": p.name,
+            "path": str(p),
+            "examples": str(line_count),
+            "size_bytes": str(p.stat().st_size),
+            "modified": datetime.fromtimestamp(p.stat().st_mtime, tz=timezone.utc).isoformat(),
+        })
+    return out