diff --git a/README.md b/README.md
index 1fb861c..44e5503 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@ Start with:
 - `docs/evaluation-and-inspection.md`
 - `docs/reference-pilot-decision.md`
 - `docs/markitect-main-scope-assessment.md`
+- `docs/markitect-tool-adapter.md`
 - `docs/orthogonal-successor-roadmap.md`
 - `docs/legacy-infospace-feature-inventory.md`
 - `docs/successor-boundary-interface-map.md`
diff --git a/docs/markitect-tool-adapter.md b/docs/markitect-tool-adapter.md
new file mode 100644
index 0000000..228f7b1
--- /dev/null
+++ b/docs/markitect-tool-adapter.md
@@ -0,0 +1,68 @@
+# Markitect Tool Adapter
+
+Date: 2026-05-14
+
+## Purpose
+
+`infospace-bench` delegates Markdown syntax work to `markitect-tool` through a
+single narrow adapter:
+
+```text
+src/infospace_bench/markdown_adapter.py
+```
+
+This keeps the repos orthogonal:
+
+- `markitect-tool` parses and validates Markdown.
+- `infospace-bench` interprets parsed/validated artifacts as parts of concrete
+  infospaces.
+
+## Current Adapter Surface
+
+- `parse_markdown_artifact(path)`
+- `extract_section_text(parsed, heading)`
+- `validate_markdown_artifact(artifact_id, path, contract_path)`
+- `validate_infospace_artifacts(root)`
+
+The adapter normalizes `markitect-tool` diagnostics into
+`MarkdownDiagnostic`, preserving severity, code, message, source, contract,
+rule, guidance, and details.
+
+## Contract Selection
+
+`validate_infospace_artifacts()` reads `infospace.yaml` and uses the `schemas`
+mapping as artifact-kind contract references:
+
+```yaml
+schemas:
+  source: contracts/source.contract.md
+  generated: contracts/generated.contract.md
+```
+
+If no contract is configured for an artifact kind, validation skips that
+artifact. If a configured contract path is missing, validation raises a
+structured `InfospaceError`.
+
+## CLI
+
+```bash
+python3 -m infospace_bench validate infospaces/bootstrap-pilot
+```
+
+The command emits JSON:
+
+```json
+{
+  "valid": true,
+  "results": []
+}
+```
+
+It exits with `0` when all checked artifacts are valid and `1` when any checked
+artifact fails validation.
+
+## Boundary Rule
+
+Only `src/infospace_bench/markdown_adapter.py` should import `markitect_tool`.
+Other modules should consume adapter results so `infospace-bench` remains an
+application layer, not a Markdown toolkit.
diff --git a/pyproject.toml b/pyproject.toml
index 5196690..fb62221 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,11 +3,14 @@ name = "infospace-bench"
 version = "0.1.0"
 description = "Application-layer workspace for concrete structured knowledge spaces."
 requires-python = ">=3.11"
-dependencies = ["PyYAML>=6"]
+dependencies = [
+    "PyYAML>=6",
+    "markitect-tool @ file:///home/worsch/markitect-tool",
+]
 
 [project.scripts]
 infospace-bench = "infospace_bench.cli:main"
 
 [tool.pytest.ini_options]
-pythonpath = ["src"]
+pythonpath = ["src", "../markitect-tool/src"]
 testpaths = ["tests"]
diff --git a/src/infospace_bench/cli.py b/src/infospace_bench/cli.py
index 0b1be0b..d6377eb 100644
--- a/src/infospace_bench/cli.py
+++ b/src/infospace_bench/cli.py
@@ -7,6 +7,7 @@ from pathlib import Path
 
 from .errors import InfospaceError
 from .lifecycle import add_artifact, create_infospace, load_infospace
+from .markdown_adapter import validate_infospace_artifacts
 
 
 def build_parser() -> argparse.ArgumentParser:
@@ -31,6 +32,9 @@ def build_parser() -> argparse.ArgumentParser:
     export = sub.add_parser("export", help="Print the infospace representation")
     export.add_argument("root")
 
+    validate = sub.add_parser("validate", help="Validate infospace artifacts")
+    validate.add_argument("root")
+
     return parser
 
 
@@ -58,6 +62,16 @@ def main(argv: list[str] | None = None) -> int:
             _write_json({"artifact": artifact.to_dict()})
         elif args.command == "export":
             _write_json(load_infospace(Path(args.root)).to_dict())
+        elif args.command == "validate":
+            results = validate_infospace_artifacts(Path(args.root))
+            valid = all(result.valid for result in results)
+            _write_json(
+                {
+                    "valid": valid,
+                    "results": [result.to_dict() for result in results],
+                }
+            )
+            return 0 if valid else 1
         else:
             parser.error(f"Unhandled command: {args.command}")
     except InfospaceError as exc:
diff --git a/src/infospace_bench/markdown_adapter.py b/src/infospace_bench/markdown_adapter.py
new file mode 100644
index 0000000..2532c65
--- /dev/null
+++ b/src/infospace_bench/markdown_adapter.py
@@ -0,0 +1,169 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from pathlib import Path
+from typing import Any
+
+from markitect_tool import Heading, Section, parse_markdown_file
+from markitect_tool.contract import check_markdown_file
+
+from .errors import InfospaceError
+from .lifecycle import load_infospace
+
+
+@dataclass(frozen=True)
+class MarkdownDiagnostic:
+    severity: str
+    code: str
+    message: str
+    source: dict[str, Any] | None = None
+    contract: dict[str, Any] | None = None
+    rule_id: str | None = None
+    guidance: str | None = None
+    details: dict[str, Any] = field(default_factory=dict)
+
+    @classmethod
+    def from_markitect(cls, diagnostic: Any) -> "MarkdownDiagnostic":
+        data = diagnostic.to_dict()
+        return cls(
+            severity=str(data.get("severity") or ""),
+            code=str(data.get("code") or ""),
+            message=str(data.get("message") or ""),
+            source=data.get("source"),
+            contract=data.get("contract"),
+            rule_id=data.get("rule_id"),
+            guidance=data.get("guidance"),
+            details=dict(data.get("details") or {}),
+        )
+
+    def to_dict(self) -> dict[str, Any]:
+        data: dict[str, Any] = {
+            "severity": self.severity,
+            "code": self.code,
+            "message": self.message,
+        }
+        if self.source:
+            data["source"] = self.source
+        if self.contract:
+            data["contract"] = self.contract
+        if self.rule_id:
+            data["rule_id"] = self.rule_id
+        if self.guidance:
+            data["guidance"] = self.guidance
+        if self.details:
+            data["details"] = self.details
+        return data
+
+
+@dataclass(frozen=True)
+class ParsedMarkdownArtifact:
+    path: Path
+    frontmatter: dict[str, Any]
+    headings: list[Heading]
+    sections: list[Section]
+
+    def to_dict(self) -> dict[str, Any]:
+        return {
+            "path": str(self.path),
+            "frontmatter": self.frontmatter,
+            "headings": [heading.to_dict() for heading in self.headings],
+            "sections": [section.to_dict() for section in self.sections],
+        }
+
+
+@dataclass(frozen=True)
+class ArtifactValidationResult:
+    artifact_id: str
+    path: str
+    contract_path: str
+    valid: bool
+    diagnostics: list[MarkdownDiagnostic] = field(default_factory=list)
+    metrics: dict[str, Any] = field(default_factory=dict)
+
+    def to_dict(self) -> dict[str, Any]:
+        return {
+            "artifact_id": self.artifact_id,
+            "path": self.path,
+            "contract_path": self.contract_path,
+            "valid": self.valid,
+            "diagnostics": [diagnostic.to_dict() for diagnostic in self.diagnostics],
+            "metrics": self.metrics,
+        }
+
+
+def parse_markdown_artifact(path: str | Path) -> ParsedMarkdownArtifact:
+    artifact_path = Path(path)
+    document = parse_markdown_file(artifact_path)
+    return ParsedMarkdownArtifact(
+        path=artifact_path,
+        frontmatter=document.frontmatter,
+        headings=document.headings,
+        sections=document.sections,
+    )
+
+
+def extract_section_text(
+    parsed: ParsedMarkdownArtifact,
+    heading: str,
+) -> str:
+    expected = _normalize_heading(heading)
+    for section in parsed.sections:
+        if _normalize_heading(section.heading.text) == expected:
+            return "\n".join(block.text for block in section.blocks if block.text).strip()
+    return ""
+
+
+def validate_markdown_artifact(
+    artifact_id: str,
+    path: str | Path,
+    contract_path: str | Path,
+) -> ArtifactValidationResult:
+    artifact_path = Path(path)
+    contract = Path(contract_path)
+    result = check_markdown_file(artifact_path, contract)
+    return ArtifactValidationResult(
+        artifact_id=artifact_id,
+        path=str(artifact_path),
+        contract_path=str(contract),
+        valid=result.valid,
+        diagnostics=[
+            MarkdownDiagnostic.from_markitect(diagnostic)
+            for diagnostic in result.diagnostics
+        ],
+        metrics=result.metrics,
+    )
+
+
+def validate_infospace_artifacts(root: str | Path) -> list[ArtifactValidationResult]:
+    infospace = load_infospace(root)
+    results: list[ArtifactValidationResult] = []
+    for artifact in infospace.artifacts:
+        contract_ref = (
+            infospace.config.schemas.get(artifact.kind)
+            or infospace.config.schemas.get("artifact")
+        )
+        if not contract_ref:
+            continue
+        artifact_path = infospace.root / artifact.path
+        contract_path = infospace.root / contract_ref
+        if not contract_path.is_file():
+            raise InfospaceError(
+                "missing_contract",
+                f"Configured contract does not exist: {contract_path}",
+                {
+                    "artifact_id": artifact.id,
+                    "contract_path": str(contract_path),
+                },
+            )
+        results.append(
+            validate_markdown_artifact(
+                artifact.id,
+                artifact_path,
+                contract_path,
+            )
+        )
+    return results
+
+
+def _normalize_heading(value: str) -> str:
+    return " ".join(value.strip().lower().split())
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 9585ae2..ab50ad8 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -7,7 +7,7 @@ from pathlib import Path
 
 def run_cli(*args: str) -> subprocess.CompletedProcess[str]:
     env = os.environ.copy()
-    env["PYTHONPATH"] = "src"
+    env["PYTHONPATH"] = "src:/home/worsch/markitect-tool/src"
     return subprocess.run(
         [sys.executable, "-m", "infospace_bench", *args],
         check=False,
diff --git a/tests/test_markdown_adapter.py b/tests/test_markdown_adapter.py
new file mode 100644
index 0000000..4a0aaa8
--- /dev/null
+++ b/tests/test_markdown_adapter.py
@@ -0,0 +1,150 @@
+import json
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+from infospace_bench import add_artifact, create_infospace
+from infospace_bench.markdown_adapter import (
+    extract_section_text,
+    parse_markdown_artifact,
+    validate_infospace_artifacts,
+)
+
+
+CONTRACT = """# Source Artifact Contract
+
+```yaml contract
+id: source-artifact-v1
+document:
+  type: source-artifact
+sections:
+  - id: summary
+    title: Summary
+    presence: required
+    level: 2
+  - id: evidence
+    title: Evidence
+    presence: required
+    level: 2
+```
+"""
+
+
+VALID_SOURCE = """---
+document_type: source-artifact
+status: draft
+---
+
+# Source A
+
+## Summary
+
+This source describes the first artifact.
+
+## Evidence
+
+The required evidence section is present.
+"""
+
+
+INVALID_SOURCE = """---
+document_type: source-artifact
+---
+
+# Source B
+
+## Summary
+
+This source is missing evidence.
+"""
+
+
+def cli_env() -> dict[str, str]:
+    env = os.environ.copy()
+    env["PYTHONPATH"] = "src:/home/worsch/markitect-tool/src"
+    return env
+
+
+def test_parse_markdown_artifact_uses_markitect_tool_sections(tmp_path: Path) -> None:
+    source = tmp_path / "source.md"
+    source.write_text(VALID_SOURCE, encoding="utf-8")
+
+    parsed = parse_markdown_artifact(source)
+
+    assert parsed.frontmatter["document_type"] == "source-artifact"
+    assert [heading.text for heading in parsed.headings] == [
+        "Source A",
+        "Summary",
+        "Evidence",
+    ]
+    assert extract_section_text(parsed, "Summary") == (
+        "This source describes the first artifact."
+    )
+
+
+def test_validate_infospace_artifacts_uses_configured_contract(tmp_path: Path) -> None:
+    infospace = create_infospace(tmp_path, "pilot", name="Pilot")
+    contract = infospace.root / "contracts" / "source.contract.md"
+    contract.parent.mkdir()
+    contract.write_text(CONTRACT, encoding="utf-8")
+
+    config = infospace.root / "infospace.yaml"
+    config.write_text(
+        config.read_text(encoding="utf-8").replace(
+            "schemas: {}\n", "schemas:\n  source: contracts/source.contract.md\n"
+        ),
+        encoding="utf-8",
+    )
+
+    valid = tmp_path / "valid.md"
+    valid.write_text(VALID_SOURCE, encoding="utf-8")
+    invalid = tmp_path / "invalid.md"
+    invalid.write_text(INVALID_SOURCE, encoding="utf-8")
+    add_artifact(infospace.root, valid, kind="source", title="Valid")
+    add_artifact(infospace.root, invalid, kind="source", title="Invalid")
+
+    results = validate_infospace_artifacts(infospace.root)
+
+    by_id = {result.artifact_id: result for result in results}
+    assert by_id["source/valid.md"].valid is True
+    assert by_id["source/invalid.md"].valid is False
+    assert by_id["source/invalid.md"].diagnostics[0].code == "contract.section.missing"
+
+
+def test_cli_validate_outputs_json_results(tmp_path: Path) -> None:
+    infospace = create_infospace(tmp_path, "pilot", name="Pilot")
+    contract = infospace.root / "contracts" / "source.contract.md"
+    contract.parent.mkdir()
+    contract.write_text(CONTRACT, encoding="utf-8")
+    config = infospace.root / "infospace.yaml"
+    config.write_text(
+        config.read_text(encoding="utf-8").replace(
+            "schemas: {}\n", "schemas:\n  source: contracts/source.contract.md\n"
+        ),
+        encoding="utf-8",
+    )
+    source = tmp_path / "invalid.md"
+    source.write_text(INVALID_SOURCE, encoding="utf-8")
+    add_artifact(infospace.root, source, kind="source", title="Invalid")
+
+    result = subprocess.run(
+        [
+            sys.executable,
+            "-m",
+            "infospace_bench",
+            "validate",
+            str(infospace.root),
+        ],
+        check=False,
+        env=cli_env(),
+        text=True,
+        capture_output=True,
+    )
+
+    assert result.returncode == 1
+    payload = json.loads(result.stdout)
+    assert payload["valid"] is False
+    assert payload["results"][0]["diagnostics"][0]["code"] == (
+        "contract.section.missing"
+    )
diff --git a/workplans/IB-WP-0006-markitect-tool-adapter.md b/workplans/IB-WP-0006-markitect-tool-adapter.md
index ac6561d..5028587 100644
--- a/workplans/IB-WP-0006-markitect-tool-adapter.md
+++ b/workplans/IB-WP-0006-markitect-tool-adapter.md
@@ -4,7 +4,7 @@ type: workplan
 title: "Markitect Tool Adapter And Markdown Artifact Validation"
 domain: markitect
 repo: infospace-bench
-status: planned
+status: done
 owner: markitect
 topic_slug: markitect
 created: "2026-05-14"
@@ -26,7 +26,7 @@ a thin application adapter.
 
 ```task
 id: IB-WP-0006-T01
-status: todo
+status: done
 priority: high
 state_hub_task_id: "b438be61-6d2a-44f9-b235-2b415e9f4bca"
 ```
@@ -40,7 +40,7 @@ state_hub_task_id: "b438be61-6d2a-44f9-b235-2b415e9f4bca"
 
 ```task
 id: IB-WP-0006-T02
-status: todo
+status: done
 priority: high
 state_hub_task_id: "d37d6be3-ea04-4279-a113-086ab4fb617d"
 ```
@@ -54,7 +54,7 @@ state_hub_task_id: "d37d6be3-ea04-4279-a113-086ab4fb617d"
 
 ```task
 id: IB-WP-0006-T03
-status: todo
+status: done
 priority: high
 state_hub_task_id: "74a78679-4ef2-4b6b-a80c-b40119d9f90e"
 ```
@@ -67,7 +67,7 @@ state_hub_task_id: "74a78679-4ef2-4b6b-a80c-b40119d9f90e"
 
 ```task
 id: IB-WP-0006-T04
-status: todo
+status: done
 priority: medium
 state_hub_task_id: "99b4e2ca-d9be-40a5-8b10-0b0f3c18fb19"
 ```