diff --git a/.github/scripts/test_ci_workflow.py b/.github/scripts/test_ci_workflow.py
index 4f1971e..46de6f0 100644
--- a/.github/scripts/test_ci_workflow.py
+++ b/.github/scripts/test_ci_workflow.py
@@ -51,6 +51,7 @@ def test_ci_workflow_guard_is_run_by_ci(self) -> None:
         self.assertIn("python3 .github/scripts/test_execution_status.py", text)
         self.assertIn("python3 .github/scripts/test_roadmap_status.py", text)
         self.assertIn("python3 .github/scripts/test_milestone_b_closeout_record.py", text)
+        self.assertIn("python3 .github/scripts/test_milestone_b_exit_checklist.py", text)
 
 
 if __name__ == "__main__":
diff --git a/.github/scripts/test_milestone_b_exit_checklist.py b/.github/scripts/test_milestone_b_exit_checklist.py
new file mode 100644
index 0000000..07bc3f9
--- /dev/null
+++ b/.github/scripts/test_milestone_b_exit_checklist.py
@@ -0,0 +1,82 @@
+#!/usr/bin/env python3
+#
+# Copyright 2026 The Ethos maintainers
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+from __future__ import annotations
+
+import re
+import unittest
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[2]
+CHECKLIST = ROOT / "docs/milestone-b-exit-checklist.md"
+ROADMAP = ROOT / "docs/roadmap.md"
+
+
+def checklist_text() -> str:
+    return CHECKLIST.read_text(encoding="utf-8")
+
+
+def normalized_checklist_text() -> str:
+    return re.sub(r"\s+", " ", checklist_text())
+
+
+class MilestoneBExitChecklistTests(unittest.TestCase):
+    def test_roadmap_links_to_checklist(self) -> None:
+        text = ROADMAP.read_text(encoding="utf-8")
+
+        self.assertIn("[13-B exit checklist](milestone-b-exit-checklist.md)", text)
+
+    def test_checklist_names_current_validation_commands(self) -> None:
+        text = checklist_text()
+
+        self.assertIn("make milestone-b-internal-checks PYTHON=<jsonschema-venv>/bin/python", text)
+        self.assertIn("make verify-alpha", text)
+        self.assertIn("make layout-evaluator-alpha", text)
+        self.assertIn("make python-surface-test", text)
+
+    def test_checklist_covers_internal_b_lanes(self) -> None:
+        text = checklist_text()
+
+        for lane in [
+            "WS-VERIFY-ALPHA",
+            "WS-LAYOUT",
+            "WS-SURFACES",
+            "WS-HARNESS",
+            "DETERMINISM",
+        ]:
+            self.assertIn(lane, text)
+
+    def test_checklist_keeps_public_boundaries_explicit(self) -> None:
+        text = normalized_checklist_text()
+
+        self.assertIn("does not approve public benchmark reports", text)
+        self.assertIn("release artifacts", text)
+        self.assertIn("package publication", text)
+        self.assertIn("production positioning", text)
+        self.assertIn("Performance/quality/footprint claims remain blocked", text)
+        self.assertIn("Table-quality and parser-quality claims remain blocked", text)
+
+    def test_checklist_does_not_claim_broader_scope(self) -> None:
+        text = checklist_text()
+
+        self.assertIn("No semantic/arithmetic verification expansion is claimed.", text)
+        self.assertIn("No broader parser/table/OCR completion is claimed.", text)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/.github/scripts/test_milestone_b_internal_checks.py b/.github/scripts/test_milestone_b_internal_checks.py
index c91a6cd..776913b 100644
--- a/.github/scripts/test_milestone_b_internal_checks.py
+++ b/.github/scripts/test_milestone_b_internal_checks.py
@@ -63,6 +63,7 @@ def test_target_composes_current_internal_gates(self) -> None:
             "$(PYTHON) .github/scripts/test_execution_status.py",
             "$(PYTHON) .github/scripts/test_roadmap_status.py",
             "$(PYTHON) .github/scripts/test_milestone_b_closeout_record.py",
+            "$(PYTHON) .github/scripts/test_milestone_b_exit_checklist.py",
             "$(MAKE) verify-alpha PYTHON=$(PYTHON)",
             "$(MAKE) layout-evaluator-alpha PYTHON=$(PYTHON)",
             "$(MAKE) python-surface-test PYTHON=$(PYTHON)",
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ba22e3b..54a883c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -64,6 +64,8 @@ jobs:
         run: python3 .github/scripts/test_roadmap_status.py
       - name: Milestone B closeout validation record tests
         run: python3 .github/scripts/test_milestone_b_closeout_record.py
+      - name: Milestone B exit checklist tests
+        run: python3 .github/scripts/test_milestone_b_exit_checklist.py
       - name: Gate Zero harness tests
         run: python3 benchmarks/harness/test_run_gate_zero.py
       - name: same-platform double-parse byte-diff
diff --git a/Makefile b/Makefile
index 6c1b324..3788e4d 100644
--- a/Makefile
+++ b/Makefile
@@ -54,6 +54,7 @@ milestone-b-internal-checks:
 	$(PYTHON) .github/scripts/test_execution_status.py
 	$(PYTHON) .github/scripts/test_roadmap_status.py
 	$(PYTHON) .github/scripts/test_milestone_b_closeout_record.py
+	$(PYTHON) .github/scripts/test_milestone_b_exit_checklist.py
 	$(MAKE) verify-alpha PYTHON=$(PYTHON)
 	$(MAKE) layout-evaluator-alpha PYTHON=$(PYTHON)
 	$(MAKE) python-surface-test PYTHON=$(PYTHON)
diff --git a/docs/milestone-b-exit-checklist.md b/docs/milestone-b-exit-checklist.md
new file mode 100644
index 0000000..f896427
--- /dev/null
+++ b/docs/milestone-b-exit-checklist.md
@@ -0,0 +1,48 @@
+# Milestone B Internal Exit Checklist
+
+This checklist maps the current committed source tree to the Milestone B lanes in
+`docs/IMPLEMENTATION_PLAN.md` and the PRD's Milestone B section.
+
+Status: Internal Milestone B closeout validation is green for the current committed scope.
+Milestone exit remains a decider call. This checklist does not approve public benchmark reports,
+release artifacts, package publication, production positioning, or performance/quality/footprint
+claims.
+
+## Required Internal Validation
+
+Run the aggregate closeout target from a clean tree:
+
+```sh
+make milestone-b-internal-checks PYTHON=<jsonschema-venv>/bin/python
+```
+
+The target includes fixture validation, font-policy validation, status/roadmap/closeout-record
+guards, `make verify-alpha`, `make layout-evaluator-alpha`, `make python-surface-test`, claim
+language guardrails, public-readiness guardrails, and `git diff --check`.
+
+## Exit Evidence
+
+| Lane | Internal B criterion | Current evidence | Closeout status | Still outside scope |
+| --- | --- | --- | --- | --- |
+| WS-VERIFY-ALPHA | Alpha verification over native Ethos JSON and OpenDataLoader-style grounding sources, with deterministic evidence matching and capability-aware reports | `make verify-alpha`; native, synthetic OpenDataLoader-style, and pinned real OpenDataLoader fixtures; split-quote, stale-fingerprint, non-v1, capability-limited, malformed-input, and summary diagnostics coverage | Present for current v1 alpha policy | Future claim-kind expansion, `verify_citations` v1 hardening, broader adapter shapes, semantic/arithmetic verification |
+| WS-LAYOUT | Reading order, block grouping, heading/list alpha behavior, and Markdown/text export fixtures | `make layout-evaluator-alpha`; fixture metadata and committed extraction/layout/text/Markdown goldens | Present for current fixture-backed alpha scope | Broader table, nested-list, richer heading, OCR/image-only, and wider layout semantics |
+| WS-SURFACES | Internal Python surface scaffold for local CLI-backed parsing calls | `make python-surface-test`; stdlib tests with a fake caller-provided `ethos` command | Present as internal scaffold | Native bindings, wheel publication, package setup, public API stability |
+| WS-HARNESS | Internal validation path composes fixture, trust-loop, layout, surface, and policy guardrails | `make milestone-b-internal-checks`; `docs/validation/milestone-b-closeout-validation-2026-06-17.md` | Present for current source-tree validation | Public comparison report flow, claim-wording approval, release/package approval |
+| DETERMINISM | PR and nightly workflow guardrails cover current deterministic contracts, with Windows x64 preflight for core contracts | CI workflow static guards; `test_determinism_workflow.py`; same-platform checks in current internal validation paths | Present for current configured contracts | Windows PDFium runtime provisioning and broader cross-platform corpus validation |
+
+## Boundaries
+
+- This checklist is internal closeout evidence only.
+- Public benchmark reports remain blocked.
+- Release artifacts and package publication remain blocked.
+- Production positioning remains blocked.
+- Performance/quality/footprint claims remain blocked.
+- Table-quality and parser-quality claims remain blocked.
+- No semantic/arithmetic verification expansion is claimed.
+- No broader parser/table/OCR completion is claimed.
+
+## Next Milestone Hand-off
+
+Milestone C should start from the trust-loop and fixture/evaluator contracts already guarded here.
+The first C slice should choose a single lane, add fixture-backed behavior first, and update this
+checklist only if the Milestone B closeout contract itself changes.
diff --git a/docs/roadmap.md b/docs/roadmap.md
index f355f68..de46daf 100644
--- a/docs/roadmap.md
+++ b/docs/roadmap.md
@@ -19,7 +19,7 @@ performance/quality/footprint claims.
 | --- | --- | --- | --- |
 | Week 0 | pre-kickoff | ADRs, governance, corpus freeze, CI bootstrap, competitor pins | All 11 rows done; clock starts |
 | A | weeks 1-8 | Contracts (5 schemas, c14n, deterministic profile), trust-boundary artifacts (`GroundingSource`, verification schemas, OpenDataLoader adapter stub, `ethos verify` CLI stub), PDFium Phase 1 spike, harness + competitor adapters, CLI skeleton | **Gate Zero**: ADR-0005 is accepted as `PROCEED` for internal Milestone B continuation. This is not public benchmark, release, package, production, or claim approval. |
-| B | weeks 9-14 | **`ethos verify` alpha first**: native Ethos JSON + synthetic and pinned real OpenDataLoader verification demos, stale fingerprint checks, capability-limited reports, deterministic evidence matching including split-quote coverage, explicit unsupported non-v1 claim reporting, adapter structure diagnostics; then reading order, blocks, headings, lists, Markdown/text exporters, Python wheel scaffold, quality dashboard, Windows x64 nightly determinism | 13-B exit checklist |
+| B | weeks 9-14 | **`ethos verify` alpha first**: native Ethos JSON + synthetic and pinned real OpenDataLoader verification demos, stale fingerprint checks, capability-limited reports, deterministic evidence matching including split-quote coverage, explicit unsupported non-v1 claim reporting, adapter structure diagnostics; then reading order, blocks, headings, lists, Markdown/text exporters, Python wheel scaffold, quality dashboard, Windows x64 nightly determinism | [13-B exit checklist](milestone-b-exit-checklist.md) |
 | C | weeks 15-22 | Simple/bordered tables; RAG chunker + citations; non-text region coordinates; security report + default-chunk exclusion; debug overlay; internal benchmark snapshot | 13-C exit + first checkpoint |
 | D | weeks 23-30 | `verify_citations` v1; crop API; sandbox/subprocess backend; Node beta and MCP experimental only if staffed or accepted by release-scope ADR | 13-D exit |
 | E | weeks 31-40 | Public benchmark report (reproducible, labeled tiers); PDFium Phase 2 project-maintained builds; stable CLI/Python docs; proof-of-trust demos; **Public Beta** | Release 1 claim audit + public-beta checkpoint |