diff --git a/.github/workflows/git-transport-boundaries.yml b/.github/workflows/git-transport-boundaries.yml
new file mode 100644
index 00000000..2f66e02b
--- /dev/null
+++ b/.github/workflows/git-transport-boundaries.yml
@@ -0,0 +1,75 @@
+name: Git transport boundary contracts
+on:
+  push:
+    branches: [fix/git-transport-boundaries-20260929]
+  workflow_dispatch:
+permissions:
+  contents: read
+concurrency:
+  group: git-transport-boundaries-${{ github.ref }}
+  cancel-in-progress: false
+jobs:
+  contracts:
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    services:
+      postgres:
+        image: postgres:16
+        env:
+          POSTGRES_USER: msgtest
+          POSTGRES_PASSWORD: msgtest
+          POSTGRES_DB: postgres
+        ports: ['5432:5432']
+        options: >-
+          --health-cmd "pg_isready -U msgtest"
+          --health-interval 5s --health-timeout 5s --health-retries 10
+      valkey:
+        image: valkey/valkey:9.0.6
+        ports: ['6379:6379']
+        options: >-
+          --health-cmd "valkey-cli ping"
+          --health-interval 5s --health-timeout 5s --health-retries 10
+    env:
+      MSG_TEST_POSTGRES_URL_TEMPLATE: postgresql://msgtest:msgtest@127.0.0.1:5432/{database}
+      MSG_TEST_VALKEY_URL: redis://127.0.0.1:6379/0
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+      - uses: actions/setup-python@v7
+        with:
+          python-version: '3.15'
+          allow-prereleases: true
+          cache: pip
+      - name: Install actual Git, LFS and cryptographic test tools
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y -qq age git-lfs
+          git --version
+          git lfs version
+          python -m pip install -e '.[dev]'
+      - name: Record exact source
+        env:
+          SOURCE_SHA: ${{ github.sha }}
+        run: |
+          mkdir -p artifacts
+          test "$(git rev-parse HEAD)" = "$SOURCE_SHA"
+          python - <<'PY'
+          import json,os,subprocess
+          from pathlib import Path
+          git=lambda *args:subprocess.check_output(['git',*args],text=True).strip()
+          Path('artifacts/source.json').write_text(json.dumps({'commit':git('rev-parse','HEAD'),
+              'tree':git('rev-parse','HEAD^{tree}'),'event_sha':os.environ['SOURCE_SHA'],
+              'dirty':bool(git('status','--porcelain'))},indent=2)+'\n')
+          PY
+      - name: Verify ownership and unchanged real Git reads
+        run: python -m pytest tests/test_git_transport_boundaries.py --junitxml=artifacts/git-boundaries.xml
+      - name: Preserve real HTTP, SSH, bundle, LFS and publication fences
+        run: |
+          python -m pytest tests/test_git_http_push.py tests/test_native_git_read_only.py tests/test_git_lfs.py tests/test_lfs_shared_gc_quota.py tests/test_ssh_rss.py tests/test_extensions.py tests/test_storage_layout.py tests/test_effect_completion_fencing.py tests/issue_78_80/test_lfs_integrity.py tests/issue_78_80/test_lfs_migration_contract.py --junitxml=artifacts/git-regressions.xml
+      - uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: git-transport-boundaries-${{ github.sha }}
+          path: artifacts/
+          if-no-files-found: error
diff --git a/docs/GIT_BOUNDARY_PROGRESS.md b/docs/GIT_BOUNDARY_PROGRESS.md
new file mode 100644
index 00000000..21aa088f
--- /dev/null
+++ b/docs/GIT_BOUNDARY_PROGRESS.md
@@ -0,0 +1,56 @@
+# Git transport boundary progress
+
+## Scope and coordination
+
+Issue #163. Branch `fix/git-transport-boundaries-20260929`. Base main
+`08c58928ee3f6c6cb350d9e9fba75d072bd78f08`, tree
+`8a62150d8273a2c75775872694749cb529835966` includes merged #165.
+Coordination: #163 comment5878830664 and #83 comment5878871933.
+No changes to parallel #166/#167/#169 executor/storage or #155 recovery branches.
+
+Main was compared with the inspected source baseline476e64f: only #165's eight
+files changed, none of the repository/SSH/HTTP modules under review. The source
+blobs remain repositories940a1a1bd987a2d97273734a8c0646097abf3c83,
+ssh_gitd6465ce37fd7e4743773942144e91e10a7c847af, and
+http_routes04a7de0431f1211893111e887ef87661ef877c0f.
+
+## Regression-first stage
+
+Nine new tests cover shared import isolation, actual store/adapter ownership,
+one shared publication implementation, shared HTTP-helper ownership, explicit
+composition and two existing-behavior characterizations (real Git public reads
+with unchanged database/refs, and bounded reference batch parsing).
+Production source is unchanged in the first commit. Obtain actual red cloud
+JUnit/source evidence before implementation; do not claim a result from intent.
+
+## Observed and intended boundaries
+
+NativeGitStore currently owns physical repositories and HTTP/LFS Request/Response
+handling; HTTP receive imports guarded_command from ssh_git, which imports the
+store back. The planned separation is:
+
+- NativeGitStore keeps repository/LFS paths, bounded store operations and physical
+  publication primitives, taking a snapshot of required settings rather than
+  retaining an Application service locator. Existing operation registration and
+  bundle worker behavior remain in their current module.
+- transports.git_http.GitHTTPAdapter composes a NativeGitStore and owns all HTTP
+  envelopes, streaming/spooling and signed/Basic protocol adaptation.
+- extensions.git_publication owns the existing ReferenceGuard and guarded Git
+  subprocess lifecycle. SSH and HTTP call this same implementation. Historical
+  ssh_git imports remain identical compatibility aliases, not duplicate wrappers.
+- transports.http_common owns the three existing body/JSON/error helpers and base
+  headers; HTTP routes and Git HTTP import it, avoiding a new router/adapter cycle.
+
+These are source ownership changes, not a new Git workflow/authorization engine.
+Original capacity limits, request IDs, signed envelopes, current-authority checks,
+reference-transaction phases, replay cache, uncertainty reporting, LFS digest and
+shared-volume constraints, and bundle job fences remain. No protocol version,
+database schema, receipt, real repository migration or deployment change.
+
+## Cloud acceptance
+
+The dedicated workflow runs real PostgreSQL/Valkey/Git/git-lfs and the existing
+HTTP/SSH/bundle/LFS/read-only and completion-fence tests. The full four-shard exact
+node-ID/conformance/build and applicable Recovery safety gates remain required on
+the final combined tree. No local project execution, skipped test, weakened
+assertion, production credentials, real funds/outbound delivery or recovery promotion.
diff --git a/tests/test_git_transport_boundaries.py b/tests/test_git_transport_boundaries.py
new file mode 100644
index 00000000..d5a9624d
--- /dev/null
+++ b/tests/test_git_transport_boundaries.py
@@ -0,0 +1,140 @@
+"""Git owns files/publication; protocol adapters own requests and responses."""
+from __future__ import annotations
+
+import ast
+import importlib
+from pathlib import Path
+import subprocess
+import sys
+
+import httpx
+import pytest
+
+from msg.core.errors import Failure
+from msg.core.codec import wire
+from msg.extensions.repositories import NativeGitStore
+from msg.extensions.ssh_git import ReferenceGuard
+from msg.transports.http import create_app
+from test_service import call, register
+from test_native_git_read_only import business_snapshot, refs_snapshot, seed_ref
+
+
+def dependencies(module):
+    tree=ast.parse(Path(importlib.import_module(module).__file__).read_text())
+    return [node.module or '' for node in ast.walk(tree) if isinstance(node,ast.ImportFrom)] + [
+        alias.name for node in ast.walk(tree) if isinstance(node,ast.Import) for alias in node.names]
+
+
+def test_shared_repository_module_does_not_import_http_or_ssh_adapters():
+    forbidden=('starlette','msg.transports.http','msg.transports.git_http','msg.extensions.ssh_git')
+    assert not [name for name in dependencies('msg.extensions.repositories')
+                if any(name==prefix or name.startswith(prefix+'.') for prefix in forbidden)]
+
+
+def test_repository_store_has_no_http_handlers_or_request_conversion_methods():
+    assert not {'http','http_push','http_lfs','_http_push_receive','_lfs_packet',
+                '_lfs_authorize','_lfs_preflight_publish','_repo_read_path','_job'}.intersection(vars(NativeGitStore))
+    assert {'path','lfs','lfs_capacity','create','refs','import_bundle','update_refs'}<=set(vars(NativeGitStore))
+
+
+def test_shared_publication_has_no_protocol_adapter_dependency():
+    module=importlib.import_module('msg.extensions.git_publication')
+    assert not hasattr(module,'receive_pack')
+    forbidden=('starlette','msg.transports.http','msg.transports.git_http','msg.extensions.ssh_git')
+    assert not [name for name in dependencies(module.__name__)
+                if any(name==prefix or name.startswith(prefix+'.') for prefix in forbidden)]
+
+
+def test_both_adapters_use_the_same_publication_implementation():
+    owner=importlib.import_module('msg.extensions.git_publication')
+    ssh=importlib.import_module('msg.extensions.ssh_git')
+    http=importlib.import_module('msg.transports.git_http')
+    for name in ('ReferenceGuard','hook_program','relay_bounded_stdin','guarded_command'):
+        assert getattr(ssh,name) is getattr(owner,name)
+        assert getattr(owner,name).__module__==owner.__name__
+    assert http.guarded_command is owner.guarded_command
+    assert 'msg.extensions.ssh_git' not in dependencies(http.__name__)
+
+
+def test_http_helpers_have_one_owner_without_a_router_import_cycle():
+    common=importlib.import_module('msg.transports.http_common')
+    routes=importlib.import_module('msg.transports.http_routes')
+    public=importlib.import_module('msg.transports.http')
+    git=importlib.import_module('msg.transports.git_http')
+    for name in ('body_bytes','json_response','error_status'):
+        assert getattr(common,name) is getattr(routes,name) is getattr(public,name) is getattr(git,name)
+        assert getattr(common,name).__module__==common.__name__
+    assert routes.BASE_HEADERS is common.BASE_HEADERS
+    assert not {'msg.transports.http','msg.transports.http_routes'}.intersection(dependencies(git.__name__))
+    assert not {'msg.transports.http','msg.transports.http_routes','msg.transports.git_http'}.intersection(dependencies(common.__name__))
+
+
+def test_git_storage_and_publication_import_without_loading_protocol_adapters():
+    code='''
+import importlib.abc,sys
+class NoAdapters(importlib.abc.MetaPathFinder):
+    def find_spec(self,fullname,path=None,target=None):
+        if any(fullname==name or fullname.startswith(name+'.') for name in
+               ('starlette','msg.transports.http','msg.transports.http_routes',
+                'msg.transports.git_http','msg.extensions.ssh_git')):
+            raise AssertionError('shared Git imported adapter '+fullname)
+sys.meta_path.insert(0,NoAdapters())
+from msg.extensions.repositories import NativeGitStore
+from msg.extensions.git_publication import ReferenceGuard,guarded_command
+'''
+    result=subprocess.run([sys.executable,'-c',code],capture_output=True,text=True)
+    assert result.returncode==0,result.stderr
+
+
+async def test_http_uses_explicit_store_composition_not_storage_inheritance(installed):
+    app,_=installed
+    adapter=importlib.import_module('msg.transports.git_http').GitHTTPAdapter
+    store=NativeGitStore(app)
+    assert not hasattr(store,'app')
+    assert store.root==app.settings.server.repositories_dir
+    assert store.blob_root==app.settings.server.blob_dir
+    http=adapter(app,store=store)
+    assert http.store is store and http.app is app
+    assert not isinstance(http,NativeGitStore)
+    assert '__getattr__' not in vars(adapter)
+
+
+async def test_public_git_read_and_rejected_push_preserve_all_business_state(installed):
+    app,_=installed
+    key,uid,_=await register(app,'git-boundary-read')
+    created=await call(app,'git.create',{'parent':'/@git-boundary-read','name':'code.git'},
+                       key=key,subject=uid)
+    assert created.status=='ok',wire(created)
+    rid=created.resources[0].id
+    repo=NativeGitStore(app).path(rid)
+    commit=seed_ref(repo)
+    before=await business_snapshot(app)
+    refs=refs_snapshot(repo)
+    async with httpx.AsyncClient(transport=httpx.ASGITransport(app=create_app(app)),
+                                 base_url=app.settings.service_url) as client:
+        path='/@git-boundary-read/code.git'
+        # Dumb HTTP HEAD is intentionally disabled by http.getanyfile=false.
+        # Exercise the supported smart fetch, not a new endpoint contract.
+        want=f'want {commit}\n'.encode()
+        packet=f'{len(want)+4:04x}'.encode()+want+b'00000009done\n'
+        fetched=await client.post(path+'/git-upload-pack',content=packet,
+            headers={'Content-Type':'application/x-git-upload-pack-request'})
+        assert fetched.status_code==200 and b'PACK' in fetched.content, fetched.text
+        advertised=await client.get(path+'/info/refs?service=git-upload-pack')
+        assert advertised.status_code==200 and b'git-upload-pack' in advertised.content
+        rejected=await client.post(path+'/git-receive-pack',content=b'0000')
+        assert rejected.status_code in {401,403,405}
+        unauthenticated=await client.get('/-/git/'+rid+'/info/refs?service=git-receive-pack')
+        assert unauthenticated.status_code==401
+    assert refs_snapshot(repo)==refs
+    assert await business_snapshot(app)==before
+
+
+def test_reference_batch_validation_preserves_exact_git_change_contract():
+    old,new='0'*40,'1'*40
+    rows=ReferenceGuard.validate_changes(f'{old} {new} refs/heads/main\n{old} {new} refs/tags/v1\n')
+    assert rows==[{'ref':'refs/heads/main','old':old,'new':new},
+                  {'ref':'refs/tags/v1','old':old,'new':new}]
+    for value in ('',f'{old} {new} refs/heads/main\n{old} {new} refs/heads/main',
+                  f'bad {new} refs/heads/main',f'{old} {new} refs/remotes/private'):
+        with pytest.raises(Failure):ReferenceGuard.validate_changes(value)