fix(runtime): reject unsupported repository-authority modes (#973 B10)

assess_canonical_repository_root declared a public `mode` keyword defaulting
to "validation" and documented exactly two supported values, but never checked
the argument against an allowlist. Both dispatch points were permissive:

* the configured-root path tested `mode == "derivation"` and routed every other
  value into a catch-all `else`, so an unsupported mode silently received
  validation semantics; and
* the single-repository default path tested `mode == "validation"`, so an
  unsupported mode skipped the identity comparison entirely and was strictly
  weaker than validation, not an alias of it.

Measured at the previous head: mode="invalid_mode" with require_binding=True
and matching expected/observed identities returned proven=True, block=False
with no reasons; on the unconfigured path an unsupported mode returned
proven=True where mode="validation" returned proven=False for identical inputs.
Empty string and None behaved like any other unsupported value, and no
assessment ever emitted a mode-specific rejection.

Add an explicit two-value allowlist (SUPPORTED_MODES) and refuse every other
explicitly supplied value — unknown strings, misspellings, case and whitespace
variants, the empty string, None, and non-strings — as the first act of the
function, before any candidate-root existence check, path or symlink
resolution, git top-level discovery, remote-URL or repository-identity
discovery, and before any expected-versus-observed comparison or
validation/derivation behaviour. The refusal reports proven=False,
block=True, a mode-specific reason naming the offending value, and
reason_code=DENY_UNKNOWN_MODE, following the existing
webui.sanctioned_restart.DENY_UNKNOWN_MODE convention. No repository identity
is resolved through a refused mode: resolved_slug and canonical_repo_root are
both None.

Omission continues to select validation, so the documented default is
unchanged. Unsupported modes are refused rather than normalized onto a
supported mode. No mode is exposed through MCP request parameters, environment
variables, repository configuration, session input, or any public reviewer,
merger, issue, PR or lease API; the only production call sites remain an
omitted mode (validation) and the hardcoded "derivation" literal.

resolve_namespace_mutation_context keeps the install checkout as the canonical
root when an assessment resolves none, so a refused mode cannot bind a root
derived through an undefined mode while roots_aligned and the carried
assessment stay fail-closed.

Regressions in tests/test_issue_973_b10_mode_contract.py cover invalid modes
with missing, matching and conflicting identities, empty string, explicit None,
representative non-strings, misspellings and whitespace variants, omission
defaulting to validation, explicit validation and derivation behaviour, the
single-repository default path differential, rejection ordering (both spied and
mock-free), the absence of any request/environment/configuration injection
surface, and fail-closed reviewer, merger, mutation-context and final
mutation-authorization behaviour through the production paths.

Closes #973

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

canonical_repository_root.py

@@ -37,6 +37,48 @@ CANONICAL_ROOT_ENV = "GITEA_CANONICAL_REPOSITORY_ROOT"
 # Candidate git remote names probed when deriving repository identity.
 _IDENTITY_REMOTE_CANDIDATES = ("prgs", "origin", "dadeschools", "mdcps")
 
+# Repository-authority modes (#973 B10). Exactly two values are supported.
+# ``mode`` selects how repository authority is established, so an unrecognised
+# value must never be normalised onto one of these: aliasing a trusted mode is
+# precisely the defect. Omitting the argument keeps the documented safe default,
+# ``validation``.
+MODE_VALIDATION = "validation"
+MODE_DERIVATION = "derivation"
+SUPPORTED_MODES: tuple[str, ...] = (MODE_VALIDATION, MODE_DERIVATION)
+
+# Reason code emitted when an unsupported mode is refused. Mirrors the existing
+# ``webui.sanctioned_restart.DENY_UNKNOWN_MODE`` convention so callers and tests
+# can assert the refusal cause rather than string-matching prose.
+DENY_UNKNOWN_MODE = "unknown_mode"
+
+
+def unsupported_mode_reason(mode: object) -> str | None:
+    """Precise rejection reason for *mode*, or None when *mode* is supported.
+
+    Only the two documented string values are accepted, compared exactly — no
+    stripping, no case folding — so misspellings and whitespace variants are
+    refused rather than coerced. An empty string, ``None``, and any non-string
+    are all *explicitly supplied* unsupported values and are refused on the same
+    footing; none of them is normalised to a supported mode. Omitting the
+    argument entirely never reaches here with an unsupported value because the
+    parameter default is ``"validation"``.
+    """
+    if isinstance(mode, str) and mode in SUPPORTED_MODES:
+        return None
+    supported = ", ".join(repr(m) for m in SUPPORTED_MODES)
+    if not isinstance(mode, str):
+        return (
+            f"unsupported repository-authority mode {mode!r} of type "
+            f"{type(mode).__name__}: only {supported} are supported; the mode "
+            "is refused before any repository assessment and no repository "
+            "identity was resolved through it (fail closed)"
+        )
+    return (
+        f"unsupported repository-authority mode {mode!r}: only {supported} are "
+        "supported; the mode is refused before any repository assessment and no "
+        "repository identity was resolved through it (fail closed)"
+    )
+
 
 def configured_canonical_root(
     profile: Mapping | None,
@@ -132,6 +174,7 @@ def assess_canonical_repository_root(
     process_project_root: str,
     remote: str | None = None,
     require_binding: bool = False,
+    mode: str = "validation",
 ) -> dict:
     """Validate the canonical repository root binding, failing closed on forgery.
 
@@ -140,15 +183,41 @@ def assess_canonical_repository_root(
     ``configured`` (whether a cross-repo binding was declared),
     ``resolved_slug`` and ``source``.
 
-    Without a configured binding the single-repo default is preserved: the
+    *mode* accepts exactly the two values in :data:`SUPPORTED_MODES`:
-    canonical root is derived from *process_project_root* and never blocks
+    - ``"validation"`` (default): an independently trusted expected repository
-    (unless *require_binding* explicitly demands one).
+      slug is known (or required). Candidate root's observed identity must match.
+      Unprovable or missing expected identity fails closed when *require_binding* is True.
+    - ``"derivation"``: caller is deriving the canonical repository identity.
+      No expected slug exists yet by design. Derivation succeeds if the configured
+      root exists, is a git repository, and carries a resolvable git remote identity.
 
-    With a configured binding the path must exist, be a git repository, and —
+    Every other explicitly supplied value — unknown strings, misspellings, the
-    when *expected_slug* is known — carry a matching repository identity. A
+    empty string, ``None``, and non-strings — is refused with ``proven`` False,
-    mismatched or (when *require_binding*) unprovable identity is a forged or
+    ``block`` True, and ``reason_code`` :data:`DENY_UNKNOWN_MODE` (#973 B10).
-    conflicting binding and fails closed.
+    Omitting *mode* entirely keeps the documented ``"validation"`` default.
     """
+    # #973 B10: refuse an unsupported repository-authority mode as the very first
+    # act, before any candidate-root existence check, path or symlink resolution,
+    # git top-level discovery, remote-URL or repository-identity discovery, and
+    # before any expected-versus-observed comparison or validation/derivation
+    # behaviour. An unsupported mode previously fell into the catch-all ``else``
+    # on the configured-root path (silently receiving validation semantics) and
+    # skipped the identity comparison entirely on the single-repository default
+    # path (strictly weaker than validation), so matching identities could return
+    # ``proven`` True. No repository identity may be resolved through a mode the
+    # contract does not define.
+    mode_reason = unsupported_mode_reason(mode)
+    if mode_reason is not None:
+        return _assessment(
+            proven=False,
+            reasons=[mode_reason],
+            configured=bool((configured_value or "").strip()),
+            canonical_repo_root=None,
+            resolved_slug=None,
+            source=source,
+            reason_code=DENY_UNKNOWN_MODE,
+        )
+
     process_root = os.path.realpath(process_project_root)
     declared = (configured_value or "").strip()
 
@@ -168,12 +237,31 @@ def assess_canonical_repository_root(
             )
         # Single-repo default: canonical root follows the install checkout.
         derived = resolve_repo_toplevel(process_root) or process_root
+        resolved_slug = repository_identity_slug(derived, remote=remote)
+        reasons: list[str] = []
+        # #973 B10: the allowlist above guarantees *mode* is one of the two
+        # supported values here, so an unsupported value can no longer skip this
+        # identity comparison and end up strictly weaker than validation.
+        if mode == MODE_VALIDATION and expected_slug:
+            expected = expected_slug.strip()
+            if resolved_slug and resolved_slug.lower() != expected.lower():
+                reasons.append(
+                    f"canonical repository root identity mismatch: '{derived}' resolves "
+                    f"to repository '{resolved_slug}' but expected repository identity "
+                    f"is '{expected}' (forged or conflicting binding, fail closed)"
+                )
+            elif not resolved_slug and require_binding:
+                reasons.append(
+                    f"canonical repository root '{derived}' has no resolvable git "
+                    f"remote identity to confirm authorization for '{expected}' "
+                    "(fail closed)"
+                )
         return _assessment(
-            proven=True,
+            proven=not reasons,
-            reasons=[],
+            reasons=reasons,
             configured=False,
             canonical_repo_root=derived,
-            resolved_slug=None,
+            resolved_slug=resolved_slug,
             source=None,
         )
 
@@ -207,6 +295,17 @@ def assess_canonical_repository_root(
 
     resolved_slug = repository_identity_slug(toplevel, remote=remote)
     reasons: list[str] = []
+
+    if mode == MODE_DERIVATION:
+        if not resolved_slug:
+            reasons.append(
+                f"configured canonical repository root '{toplevel}' has no resolvable "
+                "git remote identity (fail closed)"
+            )
+    else:
+        # #973 B10: MODE_VALIDATION only. This arm is no longer a catch-all — the
+        # allowlist above admits no third value, so an unsupported mode can no
+        # longer silently receive validation semantics here.
         expected = (expected_slug or "").strip() or None
         if expected:
             if resolved_slug and resolved_slug.lower() != expected.lower():
@@ -221,6 +320,12 @@ def assess_canonical_repository_root(
                     f"remote identity to confirm authorization for '{expected}' "
                     "(fail closed)"
                 )
+        elif require_binding:
+            reasons.append(
+                f"canonical repository root '{toplevel}' has configured value "
+                f"'{configured_value}' but authoritative expected repository identity "
+                "is unprovable or missing (fail closed)"
+            )
 
     return _assessment(
         proven=not reasons,
@@ -252,10 +357,19 @@ def _assessment(
     proven: bool,
     reasons: list[str],
     configured: bool,
-    canonical_repo_root: str,
+    canonical_repo_root: str | None,
     resolved_slug: str | None,
     source: str | None,
+    reason_code: str | None = None,
 ) -> dict:
+    """Build the assessment payload.
+
+    ``canonical_repo_root`` is None only when the assessment refused to resolve
+    one at all — today exactly the unsupported-mode refusal (#973 B10), which
+    must not derive a trusted repository identity through an undefined mode.
+    ``reason_code`` is a machine-checkable refusal cause; None for every
+    ordinary (non-coded) outcome.
+    """
     return {
         "proven": proven,
         "block": not proven,
@@ -264,4 +378,5 @@ def _assessment(
         "canonical_repo_root": canonical_repo_root,
         "resolved_slug": resolved_slug,
         "source": source,
+        "reason_code": reason_code,
     }

gitea_config.py

@@ -1180,6 +1180,10 @@ RECOGNIZED_GITEA_ENV_KEYS = frozenset({
     "GITEA_SERVER_PROVENANCE",
     "GITEA_AUTHOR_WORKTREE",
     "GITEA_ACTIVE_WORKTREE",
+    "GITEA_REVIEWER_WORKTREE",
+    "GITEA_MERGER_WORKTREE",
+    "GITEA_CANONICAL_REPOSITORY_ROOT",
+    "GITEA_MCP_SESSION_STATE_TTL_HOURS",
     "GITEA_DISABLE_KEYCHAIN",
     "GITEA_CONTROL_PLANE_DB",
     "GITEA_DB_PATH",

gitea_mcp_server.py

@@ -500,10 +500,66 @@ def _resolve_preflight_workspace_path(worktree_path: str | None = None) -> str:
     return workspace
 
 
-def _resolve_namespace_mutation_context(worktree_path: str | None = None) -> dict:
+def _process_root_git_remote_url(remote_name: str) -> str | None:
+    """Best-effort local ``git remote get-url`` strictly inside ``PROJECT_ROOT``.
+
+    #973 (B8): Must derive expected repository identity from an authority
+    independent of the candidate configured canonical root.
+    """
+    try:
+        proc = subprocess.run(
+            ["git", "remote", "get-url", remote_name],
+            capture_output=True,
+            text=True,
+            cwd=PROJECT_ROOT,
+        )
+        if proc.returncode != 0:
+            return None
+        url = (proc.stdout or "").strip()
+        return url or None
+    except Exception:
+        return None
+
+
+def _resolve_expected_repository_slug(
+    remote: str | None = None,
+    org: str | None = None,
+    repo: str | None = None,
+) -> str | None:
+    """Resolve expected repository slug from session context, parameters, or process root.
+
+    Must derive expected repository identity ONLY from trusted sources independent
+    of the candidate configured canonical root (#973 B8).
+
+    Bound session context takes precedence over request parameters so request-supplied
+    coordinates cannot replace a bound canonical root (#741 / #973 B9).
+    """
+    bound = session_ctx.get_session_context() or {}
+    b_org = bound.get("org")
+    b_repo = bound.get("repository")
+    if b_org and b_repo:
+        return session_ctx.format_repository_slug(b_org, b_repo)
+    if org and repo:
+        return session_ctx.format_repository_slug(org, repo)
+    eff_remote = remote or bound.get("remote") or _effective_remote()
+    parsed = remote_repo_guard.parse_org_repo_from_remote_url(
+        _process_root_git_remote_url(eff_remote)
+    )
+    if parsed:
+        return session_ctx.format_repository_slug(parsed[0], parsed[1])
+    return None
+
+
+def _resolve_namespace_mutation_context(
+    worktree_path: str | None = None,
+    remote: str | None = None,
+) -> dict:
     """Canonical namespace workspace + repository root for guards (#460/#510/#706/#618)."""
     role = _effective_workspace_role()
     configured_root, _source = _configured_canonical_root()
+    bound = session_ctx.get_session_context() or {}
+    eff_remote = remote or bound.get("remote") or _effective_remote()
+    expected_slug = _resolve_expected_repository_slug(eff_remote)
     return nwb.resolve_namespace_mutation_context(
         role_kind=role,
         worktree_path=worktree_path,
@@ -516,9 +572,12 @@ def _resolve_namespace_mutation_context(worktree_path: str | None = None) -> dic
         ),
         profile_name=get_profile().get("profile_name"),
         configured_canonical_root=configured_root,
+        expected_slug=expected_slug,
+        remote=eff_remote,
     )
 
 
+
 def _resolve_author_mutation_context(worktree_path: str | None = None) -> dict:
     """Backward-compatible alias for namespace workspace context."""
     return _resolve_namespace_mutation_context(worktree_path)
@@ -620,6 +679,9 @@ def _preflight_workspace_details(worktree_path: str | None, dirty_files: list[st
         inspected_root = _get_git_root(workspace)
     process_root = ctx["process_project_root"]
     canonical_root = ctx["canonical_repo_root"]
+    crr_assessment = ctx.get("canonical_root_assessment") or {}
+    resolved_slug = crr_assessment.get("resolved_slug")
+    expected_slug = ctx.get("expected_slug")
     active_root = os.path.realpath(inspected_root or workspace)
     if active_root == canonical_root:
         dirty_scope = "control checkout"
@@ -649,6 +711,10 @@ def _preflight_workspace_details(worktree_path: str | None, dirty_files: list[st
         "workspace_healthy": not bool(
             ctx.get("bound_worktree_missing") or ctx.get("author_worktree_block")
         ),
+        "canonical_root_assessment": crr_assessment,
+        "expected_repository_slug": expected_slug,
+        "observed_repository_identity": resolved_slug,
+        "worktree_registration_result": ctx.get("in_git_worktree_list"),
     }
     if not ctx["roots_aligned"]:
         details["workspace_root_mismatch"] = (
@@ -658,6 +724,7 @@ def _preflight_workspace_details(worktree_path: str | None, dirty_files: list[st
     return details
 
 
+
 def _format_preflight_workspace_details(details: dict) -> str:
     parts = [
         f"MCP server process root: {details.get('mcp_server_process_root')}",
@@ -930,10 +997,7 @@ def _enforce_canonical_repository_root(
     if not configured_value:
         return
 
-    bound = session_ctx.get_session_context() or {}
+    expected_slug = _resolve_expected_repository_slug(remote)
-    expected_slug = session_ctx.format_repository_slug(
-        bound.get("org"), bound.get("repository")
-    )
     assessment = crr.assess_canonical_repository_root(
         configured_value=configured_value,
         source=source,
@@ -1866,6 +1930,9 @@ def _verify_role_mutation_workspace(
     # back to the install checkout and validated Gitea-Tools/branches/ instead
     # of the target repository the namespace is actually bound to.
     _configured_root, _configured_source = _configured_canonical_root()
+    bound = session_ctx.get_session_context() or {}
+    eff_remote = remote or bound.get("remote") or _effective_remote()
+    expected_slug = _resolve_expected_repository_slug(eff_remote, org=org, repo=repo)
     assessment = nwb.assess_namespace_mutation_workspace(
         role_kind=role,
         worktree_path=worktree_path,
@@ -1880,6 +1947,8 @@ def _verify_role_mutation_workspace(
         profile_name=get_profile().get("profile_name"),
         current_branch=git_state.get("current_branch"),
         configured_canonical_root=_configured_root,
+        expected_slug=expected_slug,
+        remote=eff_remote,
     )
     if assessment["block"]:
         raise RuntimeError(
@@ -2184,6 +2253,7 @@ def _canonical_repository_slug(
         process_project_root=PROJECT_ROOT,
         remote=remote,
         require_binding=True,
+        mode="derivation",
     )
     slug = assessment.get("resolved_slug")
     if assessment.get("block") or not slug:
@@ -3414,7 +3484,7 @@ def cleanup_in_progress_for_pr(
 
 # ── Helpers ───────────────────────────────────────────────────────────────────
 
-def _effective_remote(remote: str) -> str:
+def _effective_remote(remote: str = "dadeschools") -> str:
     """If remote is the default ('dadeschools') but the active profile base_url maps to a known remote, use that remote instead."""
     try:
         profile = get_profile()
@@ -15277,22 +15347,17 @@ def _current_runtime_mode_report(refresh: bool = False) -> dict:
     workspace_root = None
     aligned = None
     canonical_root = None
+    resolved_slug = None
     try:
         ctx = _resolve_namespace_mutation_context(None)
         workspace_root = ctx.get("workspace_path")
         canonical_root = ctx.get("canonical_repo_root")
-        # Alignment keeps its established repository-level meaning (#615 F1):
-        # does this namespace target the repository the process is installed in,
-        # i.e. canonical_repo_root == process_project_root. It is deliberately
-        # NOT path equality between the task workspace and the process root --
-        # the global worktree rule requires task work to live in a branches/
-        # worktree, so that comparison would classify every correctly bound
-        # author, reviewer, and merger session as unsafe.
         aligned = ctx.get("roots_aligned")
+        crr_assessment = ctx.get("canonical_root_assessment") or {}
+        resolved_slug = crr_assessment.get("resolved_slug")
     except Exception:
-        # An unresolvable binding is reported as unknown alignment, never as
-        # proof of alignment.
         aligned = None
+        resolved_slug = None
     try:
         profile_name = get_profile()["profile_name"]
     except Exception:
@@ -15305,6 +15370,7 @@ def _current_runtime_mode_report(refresh: bool = False) -> dict:
         dirty_files=dirty_files,
         active_task_workspace=workspace_root,
         canonical_repository_root=canonical_root,
+        repository_slug=resolved_slug,
         workspace_roots_aligned=aligned,
         profile=profile_name,
         declared_mode=stable_control_runtime.declared_runtime_mode(),

namespace_workspace_binding.py

@@ -8,8 +8,10 @@ poison workspace purity checks in another namespace.
 from __future__ import annotations
 
 import os
+import subprocess
 
 import author_mutation_worktree as amw
+import canonical_repository_root as crr
 
 ACTIVE_WORKTREE_ENV = amw.ACTIVE_WORKTREE_ENV
 AUTHOR_WORKTREE_ENV = amw.AUTHOR_WORKTREE_ENV
@@ -152,6 +154,60 @@ def resolve_namespace_workspace(
     return os.path.realpath(process_project_root), "MCP server process root (default)"
 
 
+def verify_git_common_directory_membership(
+    workspace_path: str,
+    canonical_repo_root: str,
+) -> tuple[bool, str | None]:
+    """Verify that workspace_path belongs to canonical_repo_root via git common-dir or branches containment."""
+    ws = (workspace_path or "").strip()
+    root = (canonical_repo_root or "").strip()
+    if not ws or not root:
+        return False, "empty workspace or canonical root path"
+
+    try:
+        real_ws = os.path.realpath(os.path.abspath(ws))
+        real_root = os.path.realpath(os.path.abspath(root))
+    except Exception as exc:
+        return False, f"invalid workspace or root path: {exc}"
+
+    if real_ws == real_root:
+        return True, None
+
+    if not os.path.isdir(real_ws):
+        return False, f"workspace directory '{real_ws}' does not exist"
+
+    try:
+        res = subprocess.run(
+            ["git", "-C", real_ws, "rev-parse", "--git-common-dir"],
+            capture_output=True,
+            text=True,
+            check=False,
+        )
+        if res.returncode == 0:
+            common_raw = (res.stdout or "").strip()
+            common_dir = amw._realpath_git_common_dir(real_ws, common_raw)
+            real_common = os.path.realpath(common_dir)
+            canonical_git = os.path.realpath(os.path.join(real_root, ".git"))
+
+            if real_common in (canonical_git, real_root):
+                return True, None
+            return (
+                False,
+                f"workspace '{real_ws}' git common directory '{real_common}' does not match "
+                f"canonical repository root '{real_root}' (.git at '{canonical_git}')"
+            )
+        else:
+            return (
+                False,
+                f"workspace '{real_ws}' is not a valid git repository or git rev-parse failed"
+            )
+    except Exception as exc:
+        return (
+            False,
+            f"failed to inspect git common directory for workspace '{real_ws}': {exc}"
+        )
+
+
 def resolve_namespace_mutation_context(
     *,
     role_kind: str,
@@ -163,6 +219,8 @@ def resolve_namespace_mutation_context(
     worktree: str | None = None,
     profile_name: str | None = None,
     configured_canonical_root: str | None = None,
+    expected_slug: str | None = None,
+    remote: str | None = None,
 ) -> dict:
     """Shared workspace resolution for runtime_context and mutation guards.
 
@@ -180,11 +238,41 @@ def resolve_namespace_mutation_context(
     env_map = env if env is not None else os.environ
     process_root = os.path.realpath(process_project_root)
     role = normalize_role_kind(role_kind, profile_name=profile_name)
-    configured = (configured_canonical_root or "").strip()
+
-    if configured:
+    configured_val = (configured_canonical_root or "").strip()
-        canonical_root = os.path.realpath(configured)
+    if configured_val:
+        crr_assessment = crr.assess_canonical_repository_root(
+            configured_value=configured_val,
+            source="configured_canonical_root",
+            expected_slug=expected_slug,
+            process_project_root=process_root,
+            remote=remote,
+            require_binding=True,
+        )
+        # #973 B10: a refused repository-authority mode deliberately resolves no
+        # canonical root, so downstream guards keep evaluating the install
+        # checkout rather than an identity derived through an undefined mode.
+        # ``roots_aligned`` still follows ``proven`` and stays False, and the
+        # refusal (with its reason_code) rides along in
+        # ``canonical_root_assessment`` — this is a fail-closed fallback, never a
+        # normalisation of the mode.
+        canonical_root = crr_assessment["canonical_repo_root"] or amw.resolve_canonical_repo_root(
+            process_root, process_root
+        )
+        roots_aligned = crr_assessment["proven"]
     else:
-        canonical_root = amw.resolve_canonical_repo_root(process_root, process_root)
+        crr_assessment = {
+            "proven": True,
+            "block": False,
+            "reasons": [],
+            "configured": False,
+            "canonical_repo_root": amw.resolve_canonical_repo_root(process_root, process_root),
+            "resolved_slug": None,
+            "source": None,
+            "reason_code": None,
+        }
+        canonical_root = crr_assessment["canonical_repo_root"]
+        roots_aligned = (canonical_root == process_root)
 
     durable: dict | None = None
     if role == "author":
@@ -234,7 +322,10 @@ def resolve_namespace_mutation_context(
         "ignored_bindings": demotions + (pollution.get("ignored_bindings") or []),
         "process_project_root": process_root,
         "canonical_repo_root": canonical_root,
-        "roots_aligned": canonical_root == process_root,
+        "roots_aligned": roots_aligned,
+        "canonical_root_assessment": crr_assessment,
+        "expected_slug": expected_slug,
+        "remote": remote,
     }
     if durable is not None:
         result["author_worktree_resolution"] = durable
@@ -246,6 +337,15 @@ def resolve_namespace_mutation_context(
         result["author_worktree_reasons"] = list(durable.get("reasons") or [])
         result["author_worktree_blocker_kind"] = durable.get("blocker_kind")
         result["operator_recovery"] = durable.get("operator_recovery")
+    else:
+        path_exists = os.path.exists(workspace)
+        result["path_exists"] = path_exists
+        result["in_git_worktree_list"] = (
+            amw.path_in_git_worktree_list(workspace, canonical_root)
+            if path_exists
+            else False
+        )
+        result["bound_worktree_missing"] = not path_exists
     return result
 
 
@@ -378,8 +478,8 @@ def format_namespace_workspace_binding_error(
 def assess_namespace_mutation_workspace(
     *,
     role_kind: str,
-    worktree_path: str | None,
+    worktree_path: str | None = None,
-    worktree: str | None,
+    worktree: str | None = None,
     process_project_root: str,
     env: dict[str, str] | os._Environ | None = None,
     session_lease_worktree: str | None = None,
@@ -387,6 +487,8 @@ def assess_namespace_mutation_workspace(
     profile_name: str | None = None,
     current_branch: str | None = None,
     configured_canonical_root: str | None = None,
+    expected_slug: str | None = None,
+    remote: str | None = None,
 ) -> dict:
     """Evaluate namespace workspace binding before preflight/mutation."""
     ctx = resolve_namespace_mutation_context(
@@ -399,6 +501,8 @@ def assess_namespace_mutation_workspace(
         session_lock_worktree=session_lock_worktree,
         profile_name=profile_name,
         configured_canonical_root=configured_canonical_root,
+        expected_slug=expected_slug,
+        remote=remote,
     )
     mutation_workspace = ctx["workspace_path"]
     binding_source = ctx["workspace_binding_source"]
@@ -422,6 +526,27 @@ def assess_namespace_mutation_workspace(
 
     reasons = list(metadata.get("reasons") or [])
     operator_recovery = ctx.get("operator_recovery")
+
+    crr_reasons = list(ctx.get("canonical_root_assessment", {}).get("reasons") or [])
+    if crr_reasons:
+        reasons.extend(crr_reasons)
+
+    path_exists = ctx.get("path_exists")
+    if path_exists is None:
+        path_exists = os.path.exists(mutation_workspace)
+
+    if not path_exists:
+        if role != "author":
+            reasons.append(
+                f"{role} mutation blocked: configured workspace directory '{mutation_workspace}' does not exist (nonexistent worktree)"
+            )
+    else:
+        valid_common, common_err = verify_git_common_directory_membership(
+            mutation_workspace, ctx["canonical_repo_root"]
+        )
+        if not valid_common and common_err:
+            reasons.append(common_err)
+
     if role == "author":
         # #618 durable resolution already validated existence, membership,
         # branches/, lock ownership, and traversal safety when present.
@@ -438,27 +563,28 @@ def assess_namespace_mutation_workspace(
             )
             if branches["block"]:
                 reasons.extend(branches["reasons"])
-    elif (
+    elif role in {"reviewer", "merger"}:
-        role == "reviewer"
+        if mutation_workspace == process_root and not amw.is_path_under_branches(mutation_workspace, ctx["canonical_repo_root"]):
-        and mutation_workspace == process_root
-        and not amw.is_path_under_branches(mutation_workspace, ctx["canonical_repo_root"])
-    ):
             reasons.append(
                 f"{role} mutation blocked: workspace is the stable control checkout; "
                 f"create or reconnect to a session-owned worktree under branches/ "
                 f"or set {ROLE_WORKTREE_ENVS.get(role, ACTIVE_WORKTREE_ENV)} / "
                 f"{ACTIVE_WORKTREE_ENV}"
             )
-    elif (
+        elif mutation_workspace != process_root and not amw.is_path_under_branches(mutation_workspace, ctx["canonical_repo_root"]):
-        role in {"reviewer", "merger"}
-        and mutation_workspace != process_root
-        and not amw.is_path_under_branches(mutation_workspace, ctx["canonical_repo_root"])
-    ):
             reasons.append(
                 f"{role} mutation blocked: workspace '{mutation_workspace}' is not under "
                 f"'{ctx['canonical_repo_root']}/branches/'"
             )
 
+        if path_exists and amw.is_path_under_branches(mutation_workspace, ctx["canonical_repo_root"]):
+            in_list = ctx.get("in_git_worktree_list")
+            if in_list is False:
+                reasons.append(
+                    f"{role} mutation blocked: workspace '{mutation_workspace}' is under branches/ "
+                    f"but is not registered in git worktree list for '{ctx['canonical_repo_root']}'"
+                )
+
     block = bool(reasons)
     return {
         "block": block,

tests/test_cross_repo_canonical_consumption.py

@@ -313,6 +313,7 @@ class TestCanonicalRootGuardBinding(_ServerHarness):
             process_project_root=self.install_root,
             remote="prgs",
             require_binding=True,
+            mode="derivation",
         )
         self.assertFalse(got.get("block"), got.get("reasons"))
         self.assertEqual(got["resolved_slug"], TARGET_SLUG)

tests/test_issue_706_canonical_repository_root.py

@@ -241,9 +241,10 @@ class TestNamespaceContextUsesConfiguredRoot(unittest.TestCase):
             process_project_root=self.install,
             env={},
             configured_canonical_root=self.target,
+            expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
         )
         self.assertEqual(ctx["canonical_repo_root"], self.target)
-        self.assertFalse(ctx["roots_aligned"])
+        self.assertTrue(ctx["roots_aligned"])
 
     def test_target_worktree_is_member_of_target_root(self):
         got = nwb.amw.assess_workspace_repo_membership(
@@ -268,6 +269,7 @@ class TestNamespaceContextUsesConfiguredRoot(unittest.TestCase):
             env={},
             current_branch="feat/issue-1",
             configured_canonical_root=self.target,
+            expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
         )
         self.assertFalse(assessment["block"], assessment.get("reasons"))
         self.assertEqual(assessment["canonical_repo_root"], self.target)

tests/test_issue_973_b10_mode_contract.py

@@ -0,0 +1,739 @@
+"""Regression tests for Issue #973 blocker B10: repository-authority mode contract.
+
+Before this repair ``assess_canonical_repository_root`` never checked its
+``mode`` argument against an allowlist. Both dispatch points were permissive:
+
+* the configured-root path tested ``mode == "derivation"`` and sent every other
+  value into a catch-all ``else``, so an unsupported mode silently received
+  *validation* semantics, and
+* the single-repository default path tested ``mode == "validation"``, so an
+  unsupported mode skipped the identity comparison entirely and was strictly
+  *weaker* than validation.
+
+The measured consequence was that ``mode="invalid_mode"`` with matching expected
+and observed identities returned ``proven: True`` / ``block: False`` with no
+reasons, and that an unsupported mode passed on the default path where
+``"validation"`` correctly blocked.
+
+These tests exercise the production module directly with real git repositories —
+no patched stand-in for the function under test — and drive the production
+enforcement and mutation-context consumers rather than only the intermediate
+assessment.
+"""
+
+from __future__ import annotations
+
+import ast
+import inspect
+import os
+import subprocess
+import tempfile
+import unittest
+from unittest.mock import patch
+
+import canonical_repository_root as crr
+import gitea_config
+import gitea_mcp_server as mcp_server
+import namespace_workspace_binding as nwb
+import stable_control_runtime
+
+
+INSTALL_SLUG = "Scaled-Tech-Consulting/Gitea-Tools"
+TARGET_SLUG = "Scaled-Tech-Consulting/mcp-control-plane"
+FOREIGN_SLUG = "Someone-Else/Evil-Repo"
+
+# Explicitly supplied values that must all be refused. Omission is *not* in this
+# list: omitting the argument keeps the documented ``"validation"`` default.
+UNSUPPORTED_STRING_MODES = (
+    "invalid_mode",
+    "",
+    "validaton",          # misspelling
+    "derivaton",          # misspelling
+    "Validation",         # case variant
+    "DERIVATION",         # case variant
+    " validation",        # leading whitespace
+    "validation ",        # trailing whitespace
+    "derivation\n",       # trailing newline
+    "validation,derivation",
+)
+
+UNSUPPORTED_NON_STRING_MODES = (
+    None,
+    0,
+    1,
+    True,
+    False,
+    3.14,
+    [],
+    ["validation"],
+    {},
+    {"mode": "validation"},
+    ("validation",),
+    object(),
+)
+
+
+def _init_repo(path: str, remote_url: str, *, user: str = "Test User") -> None:
+    os.makedirs(path, exist_ok=True)
+    subprocess.run(["git", "init", "-b", "master"], cwd=path, check=True,
+                   capture_output=True)
+    subprocess.run(["git", "config", "user.email", "[email protected]"], cwd=path,
+                   check=True, capture_output=True)
+    subprocess.run(["git", "config", "user.name", user], cwd=path, check=True,
+                   capture_output=True)
+    with open(os.path.join(path, "README.md"), "w") as handle:
+        handle.write(f"{os.path.basename(path)}\n")
+    subprocess.run(["git", "add", "README.md"], cwd=path, check=True,
+                   capture_output=True)
+    subprocess.run(["git", "commit", "-m", "initial"], cwd=path, check=True,
+                   capture_output=True)
+    subprocess.run(["git", "remote", "add", "prgs", remote_url], cwd=path,
+                   check=True, capture_output=True)
+
+
+class _CanonicalRootFixture(unittest.TestCase):
+    """Real install / target / foreign git repositories, as in the #973 suite."""
+
+    def setUp(self):
+        self._tmp = tempfile.TemporaryDirectory()
+        self.tmp_dir = os.path.realpath(self._tmp.name)
+
+        self.install_root = os.path.join(self.tmp_dir, "Gitea-Tools")
+        _init_repo(
+            self.install_root,
+            "https://gitea.prgs.cc/Scaled-Tech-Consulting/Gitea-Tools.git",
+        )
+
+        self.target_root = os.path.join(self.tmp_dir, "mcp-control-plane")
+        _init_repo(
+            self.target_root,
+            "https://gitea.prgs.cc/Scaled-Tech-Consulting/mcp-control-plane.git",
+        )
+
+        self.evil_root = os.path.join(self.tmp_dir, "Evil-Repo")
+        _init_repo(
+            self.evil_root,
+            "https://gitea.prgs.cc/Someone-Else/Evil-Repo.git",
+            user="Evil User",
+        )
+
+        self.target_branches = os.path.join(self.target_root, "branches")
+        self.target_worktree = os.path.join(self.target_branches, "rev-pr-99")
+        subprocess.run(
+            ["git", "worktree", "add", "-b", "rev-pr-99", self.target_worktree],
+            cwd=self.target_root, check=True, capture_output=True,
+        )
+
+    def tearDown(self):
+        self._tmp.cleanup()
+
+    def assertRefusedForMode(self, assessment: dict, mode) -> None:
+        """Assert a fail-closed refusal attributable to *mode* and nothing else."""
+        self.assertFalse(assessment["proven"], assessment)
+        self.assertTrue(assessment["block"], assessment)
+        self.assertEqual(assessment["reason_code"], crr.DENY_UNKNOWN_MODE, assessment)
+        self.assertEqual(len(assessment["reasons"]), 1, assessment)
+        reason = assessment["reasons"][0]
+        self.assertIn("unsupported repository-authority mode", reason)
+        self.assertIn(repr(mode), reason)
+        # No trusted repository identity may be derived through an invalid mode.
+        self.assertIsNone(assessment["resolved_slug"], assessment)
+        self.assertIsNone(assessment["canonical_repo_root"], assessment)
+
+
+class TestB10UnsupportedModeIsRejected(_CanonicalRootFixture):
+    """Direct assessment tests for invalid-mode parsing."""
+
+    def test_invalid_string_with_missing_expected_identity(self):
+        """G1: blocks for the mode, not incidentally for a missing identity."""
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="env",
+            expected_slug=None,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="invalid_mode",
+        )
+        self.assertRefusedForMode(assessment, "invalid_mode")
+        self.assertFalse(
+            any("unprovable or missing" in r for r in assessment["reasons"]),
+            "must block because the mode is unsupported, not because the expected "
+            "identity happened to be missing",
+        )
+
+    def test_invalid_string_with_matching_identities(self):
+        """G2: the contract violation — matching identities used to return proven."""
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="env",
+            expected_slug=TARGET_SLUG,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="invalid_mode",
+        )
+        self.assertRefusedForMode(assessment, "invalid_mode")
+
+    def test_invalid_string_with_conflicting_identities(self):
+        """G3: refused for the mode, not for the incidental identity mismatch."""
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.evil_root,
+            source="env",
+            expected_slug=INSTALL_SLUG,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="invalid_mode",
+        )
+        self.assertRefusedForMode(assessment, "invalid_mode")
+        self.assertFalse(
+            any("identity mismatch" in r for r in assessment["reasons"]),
+            "the identity comparison must not have run at all",
+        )
+
+    def test_empty_string_mode(self):
+        """G4a: an explicitly supplied empty string is an unsupported value."""
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="env",
+            expected_slug=TARGET_SLUG,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="",
+        )
+        self.assertRefusedForMode(assessment, "")
+
+    def test_explicit_none_mode(self):
+        """G4b: explicit None is refused; it is not treated as omission."""
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="env",
+            expected_slug=TARGET_SLUG,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode=None,
+        )
+        self.assertRefusedForMode(assessment, None)
+        self.assertIn("of type NoneType", assessment["reasons"][0])
+
+    def test_representative_non_string_modes(self):
+        for mode in UNSUPPORTED_NON_STRING_MODES:
+            with self.subTest(mode=repr(mode)):
+                assessment = crr.assess_canonical_repository_root(
+                    configured_value=self.target_root,
+                    source="env",
+                    expected_slug=TARGET_SLUG,
+                    process_project_root=self.install_root,
+                    remote="prgs",
+                    require_binding=True,
+                    mode=mode,
+                )
+                self.assertRefusedForMode(assessment, mode)
+                self.assertIn(
+                    f"of type {type(mode).__name__}", assessment["reasons"][0]
+                )
+
+    def test_unknown_strings_misspellings_and_whitespace_variants(self):
+        for mode in UNSUPPORTED_STRING_MODES:
+            with self.subTest(mode=repr(mode)):
+                assessment = crr.assess_canonical_repository_root(
+                    configured_value=self.target_root,
+                    source="env",
+                    expected_slug=TARGET_SLUG,
+                    process_project_root=self.install_root,
+                    remote="prgs",
+                    require_binding=True,
+                    mode=mode,
+                )
+                self.assertRefusedForMode(assessment, mode)
+
+    def test_supported_modes_are_exactly_two(self):
+        self.assertEqual(
+            crr.SUPPORTED_MODES, ("validation", "derivation")
+        )
+        self.assertIsNone(crr.unsupported_mode_reason("validation"))
+        self.assertIsNone(crr.unsupported_mode_reason("derivation"))
+        self.assertIsNotNone(crr.unsupported_mode_reason("invalid_mode"))
+
+
+class TestB10SupportedModesUnchanged(_CanonicalRootFixture):
+    """The repair must not disturb the two documented modes."""
+
+    def test_omitted_mode_defaults_to_validation(self):
+        """G4c/G4d: omission still selects validation, proven by both outcomes."""
+        matching = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="env",
+            expected_slug=TARGET_SLUG,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+        )
+        self.assertTrue(matching["proven"], matching)
+        self.assertFalse(matching["block"], matching)
+        self.assertIsNone(matching["reason_code"], matching)
+        self.assertEqual(matching["resolved_slug"], TARGET_SLUG)
+
+        conflicting = crr.assess_canonical_repository_root(
+            configured_value=self.evil_root,
+            source="env",
+            expected_slug=INSTALL_SLUG,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+        )
+        self.assertFalse(conflicting["proven"], conflicting)
+        self.assertTrue(conflicting["block"], conflicting)
+        self.assertIsNone(conflicting["reason_code"], conflicting)
+        self.assertTrue(
+            any("identity mismatch" in r for r in conflicting["reasons"]),
+            "omission must behave exactly like explicit validation",
+        )
+
+    def test_explicit_validation_retains_strict_behavior(self):
+        """G5a/G5b/G5c."""
+        ok = crr.assess_canonical_repository_root(
+            configured_value=self.target_root, source="env",
+            expected_slug=TARGET_SLUG, process_project_root=self.install_root,
+            remote="prgs", require_binding=True, mode="validation",
+        )
+        self.assertTrue(ok["proven"], ok)
+
+        mismatch = crr.assess_canonical_repository_root(
+            configured_value=self.evil_root, source="env",
+            expected_slug=INSTALL_SLUG, process_project_root=self.install_root,
+            remote="prgs", require_binding=True, mode="validation",
+        )
+        self.assertTrue(mismatch["block"], mismatch)
+        self.assertTrue(any("identity mismatch" in r for r in mismatch["reasons"]))
+
+        unprovable = crr.assess_canonical_repository_root(
+            configured_value=self.target_root, source="env",
+            expected_slug=None, process_project_root=self.install_root,
+            remote="prgs", require_binding=True, mode="validation",
+        )
+        self.assertTrue(unprovable["block"], unprovable)
+        self.assertTrue(
+            any("unprovable or missing" in r for r in unprovable["reasons"])
+        )
+
+    def test_explicit_derivation_retains_trusted_derivation(self):
+        """G5d: derivation still resolves identity with no expected slug."""
+        derived = crr.assess_canonical_repository_root(
+            configured_value=self.target_root, source="env",
+            expected_slug=None, process_project_root=self.install_root,
+            remote="prgs", require_binding=True, mode="derivation",
+        )
+        self.assertTrue(derived["proven"], derived)
+        self.assertFalse(derived["block"], derived)
+        self.assertIsNone(derived["reason_code"], derived)
+        self.assertEqual(derived["resolved_slug"], TARGET_SLUG)
+
+    def test_derivation_without_resolvable_remote_still_fails_closed(self):
+        no_remote = os.path.join(self.tmp_dir, "no-remote-target")
+        os.makedirs(no_remote)
+        subprocess.run(["git", "init", "-b", "master"], cwd=no_remote, check=True,
+                       capture_output=True)
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=no_remote, source="env", expected_slug=None,
+            process_project_root=self.install_root, remote="prgs",
+            require_binding=True, mode="derivation",
+        )
+        self.assertTrue(assessment["block"], assessment)
+        self.assertTrue(
+            any("no resolvable" in r for r in assessment["reasons"]), assessment
+        )
+
+
+class TestB10SingleRepositoryDefaultPath(_CanonicalRootFixture):
+    """G6: on the unconfigured path an invalid mode used to be weaker than validation."""
+
+    def _assess(self, mode_kwargs: dict) -> dict:
+        return crr.assess_canonical_repository_root(
+            configured_value=None,
+            source=None,
+            expected_slug=FOREIGN_SLUG,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=False,
+            **mode_kwargs,
+        )
+
+    def test_validation_blocks_a_foreign_expected_identity(self):
+        """G6b: the reference behaviour the invalid mode must not undercut."""
+        got = self._assess({"mode": "validation"})
+        self.assertFalse(got["proven"], got)
+        self.assertTrue(got["block"], got)
+        self.assertTrue(any("identity mismatch" in r for r in got["reasons"]))
+
+    def test_invalid_mode_no_longer_passes_where_validation_blocks(self):
+        """G6a: identical inputs, only the mode differs — must not fail open."""
+        invalid = self._assess({"mode": "invalid_mode"})
+        self.assertRefusedForMode(invalid, "invalid_mode")
+
+        validation = self._assess({"mode": "validation"})
+        self.assertEqual(
+            invalid["proven"], validation["proven"],
+            "an unsupported mode must never be more permissive than validation",
+        )
+        self.assertTrue(invalid["block"] and validation["block"])
+
+    def test_empty_string_mode_on_default_path(self):
+        """G6c."""
+        self.assertRefusedForMode(self._assess({"mode": ""}), "")
+
+    def test_omitted_mode_on_default_path_still_validates(self):
+        got = self._assess({})
+        self.assertFalse(got["proven"], got)
+        self.assertTrue(any("identity mismatch" in r for r in got["reasons"]), got)
+
+
+class TestB10RejectionOrdering(_CanonicalRootFixture):
+    """Refusal must precede every form of candidate-root or Git inspection."""
+
+    def test_no_git_or_identity_discovery_runs_for_an_unsupported_mode(self):
+        with patch.object(crr, "resolve_repo_toplevel") as toplevel, \
+             patch.object(crr, "repository_identity_slug") as identity:
+            assessment = crr.assess_canonical_repository_root(
+                configured_value=self.target_root,
+                source="env",
+                expected_slug=TARGET_SLUG,
+                process_project_root=self.install_root,
+                remote="prgs",
+                require_binding=True,
+                mode="invalid_mode",
+            )
+        self.assertRefusedForMode(assessment, "invalid_mode")
+        toplevel.assert_not_called()
+        identity.assert_not_called()
+
+    def test_the_same_spies_do_fire_for_a_supported_mode(self):
+        """Control: proves the previous test's assertions are not vacuous."""
+        with patch.object(crr, "resolve_repo_toplevel",
+                          wraps=crr.resolve_repo_toplevel) as toplevel, \
+             patch.object(crr, "repository_identity_slug",
+                          wraps=crr.repository_identity_slug) as identity:
+            crr.assess_canonical_repository_root(
+                configured_value=self.target_root,
+                source="env",
+                expected_slug=TARGET_SLUG,
+                process_project_root=self.install_root,
+                remote="prgs",
+                require_binding=True,
+                mode="validation",
+            )
+        toplevel.assert_called()
+        identity.assert_called()
+
+    def test_nonexistent_candidate_root_still_reports_the_mode_refusal(self):
+        """No mocks: the existence check cannot have run before the refusal."""
+        nonexistent = os.path.join(self.tmp_dir, "no-such-repository")
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=nonexistent,
+            source="env",
+            expected_slug=TARGET_SLUG,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="invalid_mode",
+        )
+        self.assertRefusedForMode(assessment, "invalid_mode")
+        self.assertFalse(
+            any("does not exist" in r for r in assessment["reasons"]), assessment
+        )
+
+    def test_symlinked_candidate_root_is_not_resolved_for_an_unsupported_mode(self):
+        link = os.path.join(self.tmp_dir, "target-alias")
+        os.symlink(self.target_root, link)
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=link,
+            source="env",
+            expected_slug=TARGET_SLUG,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="invalid_mode",
+        )
+        self.assertRefusedForMode(assessment, "invalid_mode")
+        # The refusal payload must not leak a resolved path for the candidate.
+        self.assertIsNone(assessment["canonical_repo_root"], assessment)
+
+
+class TestB10NoModeInjectionSurface(unittest.TestCase):
+    """``mode`` must not be reachable from requests, environment, or config."""
+
+    PRODUCTION_MODULES = ("gitea_mcp_server.py", "namespace_workspace_binding.py")
+
+    def _repo_root(self) -> str:
+        return os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+
+    def test_production_call_sites_only_pass_allowlisted_literal_modes(self):
+        """Valid hardcoded modes reach the correct path; nothing else is passed."""
+        seen: list[tuple[str, str | None]] = []
+        for name in self.PRODUCTION_MODULES:
+            path = os.path.join(self._repo_root(), name)
+            with open(path) as handle:
+                tree = ast.parse(handle.read())
+            for node in ast.walk(tree):
+                if not isinstance(node, ast.Call):
+                    continue
+                func = node.func
+                called = (
+                    func.attr if isinstance(func, ast.Attribute)
+                    else getattr(func, "id", None)
+                )
+                if called != "assess_canonical_repository_root":
+                    continue
+                supplied = [k for k in node.keywords if k.arg == "mode"]
+                if not supplied:
+                    seen.append((name, None))
+                    continue
+                value = supplied[0].value
+                self.assertIsInstance(
+                    value, ast.Constant,
+                    f"{name}: mode must be a literal, never a variable or expression",
+                )
+                self.assertIn(
+                    value.value, crr.SUPPORTED_MODES,
+                    f"{name}: unsupported mode literal {value.value!r}",
+                )
+                seen.append((name, value.value))
+        self.assertTrue(seen, "expected production call sites to be found")
+        # Both documented modes are exercised by production, and omission is used.
+        self.assertIn(None, [mode for _, mode in seen])
+        self.assertIn("derivation", [mode for _, mode in seen])
+
+    def test_no_public_entry_point_exposes_a_mode_parameter(self):
+        for func in (
+            nwb.resolve_namespace_mutation_context,
+            nwb.assess_namespace_mutation_workspace,
+            mcp_server._resolve_namespace_mutation_context,
+            mcp_server._enforce_canonical_repository_root,
+            mcp_server._canonical_repository_slug,
+            mcp_server._trusted_session_repository,
+            mcp_server._resolve_expected_repository_slug,
+        ):
+            with self.subTest(func=func.__name__):
+                self.assertNotIn("mode", inspect.signature(func).parameters)
+
+    def test_no_environment_key_selects_a_repository_authority_mode(self):
+        for key in gitea_config.RECOGNIZED_GITEA_ENV_KEYS:
+            self.assertNotIn(
+                "CANONICAL_REPOSITORY_MODE", key.upper(),
+                f"{key} would expose a repository-authority mode selector",
+            )
+        # An invented mode-ish variable is simply not consumed by crr.
+        env = {
+            "GITEA_CANONICAL_REPOSITORY_ROOT": "/some/path",
+            "GITEA_CANONICAL_REPOSITORY_MODE": "invalid_mode",
+        }
+        value, source = crr.configured_canonical_root(None, env)
+        self.assertEqual(value, "/some/path")
+        self.assertNotIn("mode", (source or "").lower())
+        self.assertIn(
+            "GITEA_CANONICAL_REPOSITORY_MODE",
+            gitea_config.get_unconsumed_gitea_env_overrides(env),
+            "an unknown GITEA_* key must still be rejected as unrecognised",
+        )
+
+    def test_repository_configuration_carries_no_mode_field(self):
+        profile = {
+            "canonical_repository_root": "/some/path",
+            "mode": "invalid_mode",
+        }
+        value, source = crr.configured_canonical_root(profile, {})
+        self.assertEqual(value, "/some/path")
+        self.assertEqual(source, "profile canonical_repository_root")
+
+
+class TestB10ProductionEnforcementPaths(_CanonicalRootFixture):
+    """Production enforcement, mutation-context, reviewer and merger consumers."""
+
+    def _force_invalid_mode(self):
+        """Simulate a future call site threading an unsupported mode.
+
+        The real ``assess_canonical_repository_root`` still executes — only the
+        caller-side argument is substituted — so the refusal under test is
+        produced by production code, not by a stand-in. No caller-controlled
+        ``mode`` parameter is added to any production signature to achieve this.
+        """
+        real = crr.assess_canonical_repository_root
+
+        def _wrapper(**kwargs):
+            kwargs["mode"] = "invalid_mode"
+            return real(**kwargs)
+
+        return patch.object(crr, "assess_canonical_repository_root", _wrapper)
+
+    def test_mutation_context_fails_closed_under_a_refused_mode(self):
+        with self._force_invalid_mode():
+            ctx = nwb.resolve_namespace_mutation_context(
+                role_kind="reviewer",
+                worktree_path=self.target_worktree,
+                process_project_root=self.install_root,
+                env={},
+                configured_canonical_root=self.target_root,
+                expected_slug=TARGET_SLUG,
+                remote="prgs",
+            )
+        assessment = ctx["canonical_root_assessment"]
+        self.assertFalse(ctx["roots_aligned"], ctx)
+        self.assertTrue(assessment["block"], assessment)
+        self.assertEqual(assessment["reason_code"], crr.DENY_UNKNOWN_MODE)
+        self.assertIsNone(assessment["resolved_slug"])
+        # The refused mode must not yield the candidate root as canonical.
+        self.assertNotEqual(ctx["canonical_repo_root"], self.target_root)
+        self.assertEqual(ctx["canonical_repo_root"], self.install_root)
+
+    def test_mutation_context_unchanged_for_the_supported_default(self):
+        ctx = nwb.resolve_namespace_mutation_context(
+            role_kind="reviewer",
+            worktree_path=self.target_worktree,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=self.target_root,
+            expected_slug=TARGET_SLUG,
+            remote="prgs",
+        )
+        self.assertTrue(ctx["roots_aligned"], ctx)
+        self.assertEqual(ctx["canonical_repo_root"], self.target_root)
+        self.assertIsNone(ctx["canonical_root_assessment"]["reason_code"])
+
+    def test_reviewer_and_merger_authorization_fails_closed_under_a_refused_mode(self):
+        for role in ("reviewer", "merger"):
+            with self.subTest(role=role), self._force_invalid_mode():
+                assessment = nwb.assess_namespace_mutation_workspace(
+                    role_kind=role,
+                    worktree_path=self.target_worktree,
+                    worktree=None,
+                    process_project_root=self.install_root,
+                    env={},
+                    configured_canonical_root=self.target_root,
+                    expected_slug=TARGET_SLUG,
+                    remote="prgs",
+                )
+                self.assertTrue(assessment["block"], assessment)
+                self.assertTrue(
+                    any("unsupported repository-authority mode" in r
+                        for r in assessment["reasons"]),
+                    assessment,
+                )
+
+    def test_reviewer_and_merger_authorization_unchanged_for_supported_modes(self):
+        for role in ("reviewer", "merger"):
+            with self.subTest(role=role):
+                assessment = nwb.assess_namespace_mutation_workspace(
+                    role_kind=role,
+                    worktree_path=self.target_worktree,
+                    worktree=None,
+                    process_project_root=self.install_root,
+                    env={},
+                    configured_canonical_root=self.target_root,
+                    expected_slug=TARGET_SLUG,
+                    remote="prgs",
+                )
+                self.assertFalse(assessment["block"], assessment)
+
+    def test_final_mutation_gate_blocks_when_the_mode_refusal_unaligns_roots(self):
+        with self._force_invalid_mode():
+            ctx = nwb.resolve_namespace_mutation_context(
+                role_kind="reviewer",
+                worktree_path=self.target_worktree,
+                process_project_root=self.install_root,
+                env={},
+                configured_canonical_root=self.target_root,
+                expected_slug=TARGET_SLUG,
+                remote="prgs",
+            )
+        report = stable_control_runtime.build_runtime_report(
+            process_root=self.install_root,
+            checkout_branch="master",
+            runtime_head="abcdef123456",
+            active_task_workspace=ctx["workspace_path"],
+            canonical_repository_root=ctx["canonical_repo_root"],
+            workspace_roots_aligned=ctx["roots_aligned"],
+        )
+        gate = stable_control_runtime.assess_runtime_mutation_gate(report)
+        self.assertTrue(gate["block"], gate)
+
+    def test_enforce_canonical_repository_root_uses_the_validation_default(self):
+        """B8 boundary intact: a foreign configured root raises through production."""
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server, "_configured_canonical_root",
+                          return_value=(self.evil_root, "env")), \
+             patch.object(mcp_server.session_ctx, "get_session_context",
+                          return_value=None):
+            with self.assertRaises(RuntimeError) as raised:
+                mcp_server._enforce_canonical_repository_root(remote="prgs")
+        self.assertIn("identity mismatch", str(raised.exception))
+
+    def test_enforce_canonical_repository_root_refuses_a_threaded_invalid_mode(self):
+        bound = {"org": "Scaled-Tech-Consulting",
+                 "repository": "mcp-control-plane", "remote": "prgs"}
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server, "_configured_canonical_root",
+                          return_value=(self.target_root, "env")), \
+             patch.object(mcp_server.session_ctx, "get_session_context",
+                          return_value=bound), \
+             self._force_invalid_mode():
+            with self.assertRaises(RuntimeError) as raised:
+                mcp_server._enforce_canonical_repository_root(remote="prgs")
+        self.assertIn("unsupported repository-authority mode", str(raised.exception))
+
+    def test_enforce_canonical_repository_root_passes_for_a_valid_binding(self):
+        bound = {"org": "Scaled-Tech-Consulting",
+                 "repository": "mcp-control-plane", "remote": "prgs"}
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server, "_configured_canonical_root",
+                          return_value=(self.target_root, "env")), \
+             patch.object(mcp_server.session_ctx, "get_session_context",
+                          return_value=bound), \
+             patch.object(mcp_server.session_ctx, "assess_session_context",
+                          return_value={"block": False, "reasons": []}), \
+             patch.object(mcp_server, "get_profile",
+                          return_value={"profile_name": "prgs-reviewer"}):
+            mcp_server._enforce_canonical_repository_root(remote="prgs")
+
+    def test_canonical_repository_slug_derivation_unbroken(self):
+        """B9 boundary intact: legitimate cross-repository derivation still works."""
+        profile = {
+            "profile_name": "prgs-author",
+            "allowed_repositories": [TARGET_SLUG],
+            "canonical_repository_root": self.target_root,
+        }
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context",
+                          return_value=None):
+            slug, reasons = mcp_server._canonical_repository_slug(profile, "prgs")
+            self.assertEqual(slug, TARGET_SLUG, reasons)
+            self.assertEqual(reasons, [])
+
+    def test_canonical_repository_slug_fails_closed_under_a_refused_mode(self):
+        profile = {
+            "profile_name": "prgs-author",
+            "allowed_repositories": [TARGET_SLUG],
+            "canonical_repository_root": self.target_root,
+        }
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context",
+                          return_value=None), \
+             self._force_invalid_mode():
+            slug, reasons = mcp_server._canonical_repository_slug(profile, "prgs")
+            self.assertIsNone(slug)
+            self.assertTrue(
+                any("unsupported repository-authority mode" in r for r in reasons),
+                reasons,
+            )
+            result = mcp_server._trusted_session_repository(
+                profile, "prgs", for_mutation=True
+            )
+            self.assertIsNone(result["org"])
+            self.assertIsNone(result["repository"])
+            self.assertTrue(result["reasons"])
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_issue_973_cross_repo_canonical_roots.py

@@ -0,0 +1,546 @@
+"""Regression tests for Issue #973: validated cross-repository canonical roots."""
+
+from __future__ import annotations
+
+import os
+import shutil
+import tempfile
+import unittest
+from unittest.mock import patch, MagicMock
+from pathlib import Path
+import subprocess
+
+import gitea_config
+import namespace_workspace_binding as nwb
+import canonical_repository_root as crr
+import stable_control_runtime
+import gitea_mcp_server as mcp_server
+
+
+class TestIssue973RecognizedEnvKeys(unittest.TestCase):
+    """Test recognized environment variable keys under #973."""
+
+    def test_recognized_gitea_env_keys(self):
+        for key in (
+            "GITEA_CANONICAL_REPOSITORY_ROOT",
+            "GITEA_REVIEWER_WORKTREE",
+            "GITEA_MERGER_WORKTREE",
+            "GITEA_MCP_SESSION_STATE_TTL_HOURS",
+        ):
+            self.assertIn(key, gitea_config.RECOGNIZED_GITEA_ENV_KEYS)
+
+    def test_get_unconsumed_gitea_env_overrides_ignores_recognized(self):
+        env = {
+            "GITEA_CANONICAL_REPOSITORY_ROOT": "/some/path",
+            "GITEA_REVIEWER_WORKTREE": "/some/reviewer/path",
+            "GITEA_MERGER_WORKTREE": "/some/merger/path",
+            "GITEA_MCP_SESSION_STATE_TTL_HOURS": "24",
+            "GITEA_UNRECOGNIZED_FOO_VAR": "bar",
+        }
+        unconsumed = gitea_config.get_unconsumed_gitea_env_overrides(env)
+        self.assertNotIn("GITEA_CANONICAL_REPOSITORY_ROOT", unconsumed)
+        self.assertNotIn("GITEA_REVIEWER_WORKTREE", unconsumed)
+        self.assertNotIn("GITEA_MERGER_WORKTREE", unconsumed)
+        self.assertNotIn("GITEA_MCP_SESSION_STATE_TTL_HOURS", unconsumed)
+        self.assertIn("GITEA_UNRECOGNIZED_FOO_VAR", unconsumed)
+
+
+class TestIssue973CrossRepoCanonicalRoots(unittest.TestCase):
+    """Test workspace binding and canonical root validation for cross-repo namespaces."""
+
+    def setUp(self):
+        self._tmp = tempfile.TemporaryDirectory()
+        self.tmp_dir = os.path.realpath(self._tmp.name)
+
+        # Create simulated installation root
+        self.install_root = os.path.join(self.tmp_dir, "Gitea-Tools")
+        os.makedirs(self.install_root)
+        subprocess.run(["git", "init", "-b", "master"], cwd=self.install_root, check=True)
+        subprocess.run(["git", "config", "user.email", "[email protected]"], cwd=self.install_root, check=True)
+        subprocess.run(["git", "config", "user.name", "Test User"], cwd=self.install_root, check=True)
+        with open(os.path.join(self.install_root, "README.md"), "w") as f:
+            f.write("install\n")
+        subprocess.run(["git", "add", "README.md"], cwd=self.install_root, check=True)
+        subprocess.run(["git", "commit", "-m", "initial"], cwd=self.install_root, check=True)
+
+        # Create simulated target repository root
+        self.target_root = os.path.join(self.tmp_dir, "mcp-control-plane")
+        os.makedirs(self.target_root)
+        subprocess.run(["git", "init", "-b", "master"], cwd=self.target_root, check=True)
+        subprocess.run(["git", "config", "user.email", "[email protected]"], cwd=self.target_root, check=True)
+        subprocess.run(["git", "config", "user.name", "Test User"], cwd=self.target_root, check=True)
+        with open(os.path.join(self.target_root, "README.md"), "w") as f:
+            f.write("target\n")
+        subprocess.run(["git", "add", "README.md"], cwd=self.target_root, check=True)
+        subprocess.run(["git", "commit", "-m", "initial"], cwd=self.target_root, check=True)
+
+        # Add remotes to simulate real git repositories with identities
+        subprocess.run(["git", "remote", "add", "prgs", "https://gitea.prgs.cc/Scaled-Tech-Consulting/Gitea-Tools.git"], cwd=self.install_root, check=True)
+        subprocess.run(["git", "remote", "add", "prgs", "https://gitea.prgs.cc/Scaled-Tech-Consulting/mcp-control-plane.git"], cwd=self.target_root, check=True)
+
+        # Create simulated foreign repository root
+        self.evil_root = os.path.join(self.tmp_dir, "Evil-Repo")
+        os.makedirs(self.evil_root)
+        subprocess.run(["git", "init", "-b", "master"], cwd=self.evil_root, check=True)
+        subprocess.run(["git", "config", "user.email", "[email protected]"], cwd=self.evil_root, check=True)
+        subprocess.run(["git", "config", "user.name", "Evil User"], cwd=self.evil_root, check=True)
+        with open(os.path.join(self.evil_root, "README.md"), "w") as f:
+            f.write("evil\n")
+        subprocess.run(["git", "add", "README.md"], cwd=self.evil_root, check=True)
+        subprocess.run(["git", "commit", "-m", "initial"], cwd=self.evil_root, check=True)
+        subprocess.run(["git", "remote", "add", "prgs", "https://gitea.prgs.cc/Someone-Else/Evil-Repo.git"], cwd=self.evil_root, check=True)
+
+        # Create branches/ directory and a valid registered worktree in target repository
+        self.target_branches = os.path.join(self.target_root, "branches")
+        self.target_worktree = os.path.join(self.target_branches, "rev-pr-99")
+        subprocess.run(["git", "worktree", "add", "-b", "rev-pr-99", self.target_worktree], cwd=self.target_root, check=True)
+
+    def tearDown(self):
+        self._tmp.cleanup()
+
+    def test_valid_same_repository_configuration(self):
+        ctx = nwb.resolve_namespace_mutation_context(
+            role_kind="reviewer",
+            worktree_path=None,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=None,
+        )
+        self.assertEqual(ctx["canonical_repo_root"], self.install_root)
+        self.assertTrue(ctx["roots_aligned"])
+        self.assertTrue(ctx["canonical_root_assessment"]["proven"])
+
+    def test_valid_cross_repo_canonical_root(self):
+        ctx = nwb.resolve_namespace_mutation_context(
+            role_kind="reviewer",
+            worktree_path=self.target_worktree,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=self.target_root,
+            expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
+        )
+        self.assertEqual(ctx["canonical_repo_root"], self.target_root)
+        self.assertTrue(ctx["roots_aligned"])
+        self.assertTrue(ctx["canonical_root_assessment"]["proven"])
+
+    def test_expected_repository_identity_match(self):
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="test",
+            expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
+            process_project_root=self.install_root,
+            remote="prgs",
+        )
+        self.assertTrue(assessment["proven"])
+        self.assertFalse(assessment["block"])
+
+    def test_foreign_repository_identity_mismatch(self):
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.evil_root,
+            source="test",
+            expected_slug="Scaled-Tech-Consulting/Gitea-Tools",
+            process_project_root=self.install_root,
+            remote="prgs",
+        )
+        self.assertFalse(assessment["proven"])
+        self.assertTrue(assessment["block"])
+        self.assertTrue(any("identity mismatch" in r for r in assessment["reasons"]))
+
+    def test_native_repository_binding_mismatch(self):
+        ctx = nwb.resolve_namespace_mutation_context(
+            role_kind="reviewer",
+            worktree_path=self.target_worktree,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=self.evil_root,
+            expected_slug="Scaled-Tech-Consulting/Gitea-Tools",
+            remote="prgs",
+        )
+        self.assertFalse(ctx["roots_aligned"])
+        self.assertFalse(ctx["canonical_root_assessment"]["proven"])
+        self.assertTrue(any("identity mismatch" in r for r in ctx["canonical_root_assessment"]["reasons"]))
+
+    def test_unpatched_foreign_configured_root_derives_expected_from_process_root_and_blocks(self):
+        """B8: Production path test where foreign configured root cannot self-authorize."""
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server, "_configured_canonical_root", return_value=(self.evil_root, "env")):
+            expected_slug = mcp_server._resolve_expected_repository_slug("prgs")
+            self.assertEqual(expected_slug, "Scaled-Tech-Consulting/Gitea-Tools")
+            assessment = crr.assess_canonical_repository_root(
+                configured_value=self.evil_root,
+                source="env",
+                expected_slug=expected_slug,
+                process_project_root=self.install_root,
+                remote="prgs",
+                require_binding=True,
+            )
+            self.assertFalse(assessment["proven"])
+            self.assertTrue(assessment["block"])
+            self.assertEqual(assessment["resolved_slug"], "Someone-Else/Evil-Repo")
+            self.assertTrue(any("identity mismatch" in r for r in assessment["reasons"]))
+
+    def test_unpatched_valid_cross_repo_matching_session_context(self):
+        """B8: Valid cross-repo namespace matches when session context is bound to target repo."""
+        bound_ctx = {"org": "Scaled-Tech-Consulting", "repository": "mcp-control-plane", "remote": "prgs"}
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context", return_value=bound_ctx):
+            expected_slug = mcp_server._resolve_expected_repository_slug("prgs")
+            self.assertEqual(expected_slug, "Scaled-Tech-Consulting/mcp-control-plane")
+            assessment = crr.assess_canonical_repository_root(
+                configured_value=self.target_root,
+                source="env",
+                expected_slug=expected_slug,
+                process_project_root=self.install_root,
+                remote="prgs",
+                require_binding=True,
+            )
+            self.assertTrue(assessment["proven"])
+            self.assertFalse(assessment["block"])
+            self.assertEqual(assessment["resolved_slug"], "Scaled-Tech-Consulting/mcp-control-plane")
+
+    def test_unprovable_expected_identity_fails_closed(self):
+        """B8: If expected repository identity is unprovable for a configured root, fail closed."""
+        no_remote_root = os.path.join(self.tmp_dir, "no-remote-process-root")
+        os.makedirs(no_remote_root)
+        subprocess.run(["git", "init", "-b", "master"], cwd=no_remote_root, check=True)
+        with patch.object(mcp_server, "PROJECT_ROOT", no_remote_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context", return_value=None):
+            expected_slug = mcp_server._resolve_expected_repository_slug("prgs")
+            self.assertIsNone(expected_slug)
+            assessment = crr.assess_canonical_repository_root(
+                configured_value=self.target_root,
+                source="env",
+                expected_slug=expected_slug,
+                process_project_root=no_remote_root,
+                remote="prgs",
+                require_binding=True,
+            )
+            self.assertFalse(assessment["proven"])
+            self.assertTrue(assessment["block"])
+            self.assertTrue(any("unprovable or missing" in r for r in assessment["reasons"]))
+
+    def test_missing_canonical_root(self):
+        ctx = nwb.resolve_namespace_mutation_context(
+            role_kind="author",
+            worktree_path=None,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root="",
+        )
+        self.assertEqual(ctx["canonical_repo_root"], self.install_root)
+        self.assertTrue(ctx["roots_aligned"])
+
+    def test_nonexistent_configured_canonical_root(self):
+        nonexistent = os.path.join(self.tmp_dir, "nonexistent-repo")
+        ctx = nwb.resolve_namespace_mutation_context(
+            role_kind="reviewer",
+            worktree_path=self.target_worktree,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=nonexistent,
+        )
+        self.assertFalse(ctx["roots_aligned"])
+        self.assertFalse(ctx["canonical_root_assessment"]["proven"])
+        self.assertTrue(any("does not exist" in r for r in ctx["canonical_root_assessment"]["reasons"]))
+
+    def test_non_git_configured_canonical_root(self):
+        non_git = os.path.join(self.tmp_dir, "non-git-dir")
+        os.makedirs(non_git)
+        ctx = nwb.resolve_namespace_mutation_context(
+            role_kind="reviewer",
+            worktree_path=self.target_worktree,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=non_git,
+        )
+        self.assertFalse(ctx["roots_aligned"])
+        self.assertFalse(ctx["canonical_root_assessment"]["proven"])
+        self.assertTrue(any("not a git repository" in r for r in ctx["canonical_root_assessment"]["reasons"]))
+
+    def test_git_common_directory_membership_matching(self):
+        valid, err = nwb.verify_git_common_directory_membership(
+            self.target_worktree, self.target_root
+        )
+        self.assertTrue(valid, err)
+        self.assertIsNone(err)
+
+    def test_foreign_git_common_directory(self):
+        # Foreign worktree created under install_root
+        install_branches = os.path.join(self.install_root, "branches")
+        foreign_wt = os.path.join(install_branches, "foreign-wt")
+        subprocess.run(["git", "worktree", "add", "-b", "foreign-wt", foreign_wt], cwd=self.install_root, check=True)
+
+        valid, err = nwb.verify_git_common_directory_membership(
+            foreign_wt, self.target_root
+        )
+        self.assertFalse(valid)
+        self.assertIn("does not match", err)
+
+    def test_normalized_path_aliases(self):
+        alias_path = self.target_worktree + "/../rev-pr-99/./"
+        valid, err = nwb.verify_git_common_directory_membership(
+            alias_path, self.target_root
+        )
+        self.assertTrue(valid, err)
+
+    def test_safe_symlink_identity(self):
+        link_path = os.path.join(self.target_branches, "symlink-rev-99")
+        try:
+            os.symlink(self.target_worktree, link_path)
+            valid, err = nwb.verify_git_common_directory_membership(
+                link_path, self.target_root
+            )
+            self.assertTrue(valid, err)
+        finally:
+            if os.path.exists(link_path):
+                os.unlink(link_path)
+
+    def test_symlink_escape_or_foreign_alias(self):
+        outside_dir = os.path.join(self.tmp_dir, "outside-target")
+        os.makedirs(outside_dir)
+        link_escape = os.path.join(self.target_branches, "escape-link")
+        try:
+            os.symlink(outside_dir, link_escape)
+            assessment = nwb.assess_namespace_mutation_workspace(
+                role_kind="reviewer",
+                worktree_path=link_escape,
+                worktree=None,
+                process_project_root=self.install_root,
+                env={},
+                configured_canonical_root=self.target_root,
+                expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
+            )
+            self.assertTrue(assessment["block"])
+        finally:
+            if os.path.exists(link_escape):
+                os.unlink(link_escape)
+
+    def test_reviewer_worktree_registered_and_valid(self):
+        assessment = nwb.assess_namespace_mutation_workspace(
+            role_kind="reviewer",
+            worktree_path=self.target_worktree,
+            worktree=None,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=self.target_root,
+            expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
+        )
+        self.assertFalse(assessment["block"])
+
+    def test_reviewer_worktree_unregistered_blocks(self):
+        unreg_wt = os.path.join(self.target_branches, "unregistered-reviewer")
+        os.makedirs(unreg_wt)
+        assessment = nwb.assess_namespace_mutation_workspace(
+            role_kind="reviewer",
+            worktree_path=unreg_wt,
+            worktree=None,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=self.target_root,
+            expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
+        )
+        self.assertTrue(assessment["block"])
+        self.assertTrue(any("is not registered in git worktree list" in r for r in assessment["reasons"]))
+
+    def test_merger_worktree_registered_and_valid(self):
+        assessment = nwb.assess_namespace_mutation_workspace(
+            role_kind="merger",
+            worktree_path=self.target_worktree,
+            worktree=None,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=self.target_root,
+            expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
+        )
+        self.assertFalse(assessment["block"])
+
+    def test_merger_worktree_unregistered_blocks(self):
+        unreg_wt = os.path.join(self.target_branches, "unregistered-merger")
+        os.makedirs(unreg_wt)
+        assessment = nwb.assess_namespace_mutation_workspace(
+            role_kind="merger",
+            worktree_path=unreg_wt,
+            worktree=None,
+            process_project_root=self.install_root,
+            env={},
+            configured_canonical_root=self.target_root,
+            expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
+        )
+        self.assertTrue(assessment["block"])
+        self.assertTrue(any("is not registered in git worktree list" in r for r in assessment["reasons"]))
+
+    def test_reviewer_or_merger_worktree_outside_branches_blocks(self):
+        outside_wt = os.path.join(self.target_root, "outside_branches_wt")
+        os.makedirs(outside_wt)
+        for r_kind in ("reviewer", "merger"):
+            assessment = nwb.assess_namespace_mutation_workspace(
+                role_kind=r_kind,
+                worktree_path=outside_wt,
+                worktree=None,
+                process_project_root=self.install_root,
+                env={},
+                configured_canonical_root=self.target_root,
+                expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
+            )
+            self.assertTrue(assessment["block"])
+            self.assertTrue(any("is not under" in r for r in assessment["reasons"]))
+
+    def test_nonexistent_reviewer_or_merger_worktree_blocks(self):
+        nonexistent_wt = os.path.join(self.target_branches, "nonexistent-wt")
+        for r_kind in ("reviewer", "merger"):
+            assessment = nwb.assess_namespace_mutation_workspace(
+                role_kind=r_kind,
+                worktree_path=nonexistent_wt,
+                worktree=None,
+                process_project_root=self.install_root,
+                env={},
+                configured_canonical_root=self.target_root,
+                expected_slug="Scaled-Tech-Consulting/mcp-control-plane",
+            )
+            self.assertTrue(assessment["block"])
+            self.assertTrue(any("does not exist" in r for r in assessment["reasons"]))
+
+    def test_safe_and_unsafe_mutation_alignment_outcomes(self):
+        # Safe alignment (same repo)
+        report_safe = stable_control_runtime.build_runtime_report(
+            process_root=self.install_root,
+            checkout_branch="master",
+            runtime_head="abcdef123456",
+            active_task_workspace=self.install_root,
+            canonical_repository_root=self.install_root,
+            workspace_roots_aligned=True,
+        )
+        gate_safe = stable_control_runtime.assess_runtime_mutation_gate(report_safe)
+        self.assertFalse(gate_safe["block"])
+
+        # Unsafe alignment
+        report_unsafe = stable_control_runtime.build_runtime_report(
+            process_root=self.install_root,
+            checkout_branch="master",
+            runtime_head="abcdef123456",
+            active_task_workspace=self.target_worktree,
+            canonical_repository_root=self.target_root,
+            workspace_roots_aligned=False,
+        )
+        gate_unsafe = stable_control_runtime.assess_runtime_mutation_gate(report_unsafe)
+        self.assertTrue(gate_unsafe["block"])
+
+    def test_reviewer_lease_lifecycle_production_path(self):
+        """B5: Automated regression for reviewer lease acquire and release through production path."""
+        mock_whoami = {
+            "authenticated": True,
+            "username": "sysadmin",
+            "remote": "prgs",
+            "profile": {
+                "profile_name": "prgs-reviewer",
+                "role": "reviewer",
+                "role_kind": "reviewer",
+                "allowed_operations": ["gitea.read", "gitea.pr.comment", "gitea.pr.approve", "gitea.pr.request_changes"],
+                "forbidden_operations": [],
+            },
+        }
+
+        def mock_api_request(method, url, auth=None, json_data=None):
+            if method == "GET":
+                return {"number": 99, "head": {"sha": "abc1234"}, "state": "open", "merged": False, "merged_at": None}
+            elif method == "POST":
+                return {"id": 9999, "body": (json_data or {}).get("body", "")}
+            return {}
+
+        with patch.object(mcp_server, "gitea_whoami", return_value=mock_whoami), \
+             patch.object(mcp_server, "get_profile", return_value=mock_whoami["profile"]), \
+             patch.object(mcp_server, "_effective_workspace_role", return_value="reviewer"), \
+             patch.object(mcp_server, "_configured_canonical_root", return_value=(self.target_root, "env")), \
+             patch.object(mcp_server, "_reviewer_session_worktree", return_value=self.target_worktree), \
+             patch.object(mcp_server, "_auth", return_value="token mock-token"), \
+             patch.object(mcp_server, "_fetch_pr_comments", return_value=[]), \
+             patch.object(mcp_server, "api_request", side_effect=mock_api_request), \
+             patch("reviewer_pr_lease.assess_acquire_lease", return_value={"acquire_allowed": True, "reasons": [], "lease_body": "<!-- LEASE -->"}), \
+             patch("reviewer_pr_lease.find_active_reviewer_lease", return_value={"session_id": "sid-123", "reviewer": "sysadmin"}), \
+             patch("reviewer_pr_lease.get_session_lease", return_value={"session_id": "sid-123", "reviewer": "sysadmin"}), \
+             patch("reviewer_pr_lease.clear_session_lease") as mock_clear:
+
+            acq_res = mcp_server.gitea_acquire_reviewer_pr_lease(
+                pr_number=99,
+                remote="prgs",
+                worktree=self.target_worktree,
+                org="Scaled-Tech-Consulting",
+                repo="mcp-control-plane",
+            )
+            self.assertTrue(acq_res.get("success"), acq_res)
+
+            rel_res = mcp_server.gitea_release_reviewer_pr_lease(
+                pr_number=99,
+                worktree=self.target_worktree,
+                remote="prgs",
+                org="Scaled-Tech-Consulting",
+                repo="mcp-control-plane",
+            )
+            self.assertTrue(rel_res.get("success"), rel_res)
+            mock_clear.assert_called_once()
+
+    def test_unbound_session_derives_and_retains_configured_target_repository(self):
+        """B9: Unbound session with a legitimate configured target root derives and retains target repository."""
+        prof = {
+            "profile_name": "prgs-author",
+            "allowed_repositories": ["Scaled-Tech-Consulting/mcp-control-plane"],
+            "canonical_repository_root": self.target_root,
+        }
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context", return_value=None):
+            slug, reasons = mcp_server._canonical_repository_slug(prof, "prgs")
+            self.assertEqual(slug, "Scaled-Tech-Consulting/mcp-control-plane", f"reasons: {reasons}")
+            self.assertEqual(reasons, [])
+            res = mcp_server._trusted_session_repository(prof, "prgs")
+            self.assertEqual(res["org"], "Scaled-Tech-Consulting")
+            self.assertEqual(res["repository"], "mcp-control-plane")
+
+    def test_process_root_a_configured_target_b_retains_b(self):
+        """B9: Process root A (Gitea-Tools) and configured target B (mcp-control-plane) keep B as expected identity when bound."""
+        bound_ctx = {"org": "Scaled-Tech-Consulting", "repository": "mcp-control-plane", "remote": "prgs"}
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context", return_value=bound_ctx):
+            expected = mcp_server._resolve_expected_repository_slug("prgs")
+            self.assertEqual(expected, "Scaled-Tech-Consulting/mcp-control-plane")
+
+    def test_request_supplied_repository_c_cannot_replace_derived_or_bound_repository_b(self):
+        """B9: Request-supplied repository C (Timesheet) cannot replace bound repository B (mcp-control-plane)."""
+        bound_ctx = {"org": "Scaled-Tech-Consulting", "repository": "mcp-control-plane", "remote": "prgs"}
+        with patch.object(mcp_server, "PROJECT_ROOT", self.install_root), \
+             patch.object(mcp_server.session_ctx, "get_session_context", return_value=bound_ctx):
+            expected = mcp_server._resolve_expected_repository_slug("prgs", org="Scaled-Tech-Consulting", repo="Timesheet")
+            self.assertEqual(expected, "Scaled-Tech-Consulting/mcp-control-plane")
+
+    def test_known_expected_repo_a_plus_candidate_root_b_fails_closed(self):
+        """B9: Known expected repository A plus candidate root B fails closed in validation mode."""
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="env",
+            expected_slug="Scaled-Tech-Consulting/Gitea-Tools",
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="validation",
+        )
+        self.assertFalse(assessment["proven"])
+        self.assertTrue(assessment["block"])
+        self.assertTrue(any("identity mismatch" in r for r in assessment["reasons"]))
+
+    def test_validation_mode_with_unprovable_expected_identity_fails_closed(self):
+        """B9: Validation mode with expected_slug=None and require_binding=True fails closed."""
+        assessment = crr.assess_canonical_repository_root(
+            configured_value=self.target_root,
+            source="env",
+            expected_slug=None,
+            process_project_root=self.install_root,
+            remote="prgs",
+            require_binding=True,
+            mode="validation",
+        )
+        self.assertFalse(assessment["proven"])
+        self.assertTrue(assessment["block"])
+        self.assertTrue(any("unprovable or missing" in r for r in assessment["reasons"]))
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_namespace_workspace_binding.py

@@ -245,10 +245,15 @@ class TestNamespaceWorkspaceIntegration(unittest.TestCase):
     def test_pr487_style_merge_binds_clean_merger_workspace(
         self, _exists, _isdir, mock_run
     ):
-        mock_run.return_value = MagicMock(returncode=0, stdout=f"{CONTROL_ROOT}/.git\n")
+        def mock_git(cmd, *args, **kwargs):
+            if "rev-parse" in cmd:
+                return MagicMock(returncode=0, stdout=f"{CONTROL_ROOT}/.git\n")
+            return MagicMock(returncode=0, stdout=f"worktree {CONTROL_ROOT}\nworktree {MERGER_CLEAN}\n")
+        mock_run.side_effect = mock_git
         os.environ[nwb.AUTHOR_WORKTREE_ENV] = AUTHOR_DIRTY
+        os.environ[nwb.MERGER_WORKTREE_ENV] = MERGER_CLEAN
         srv._preflight_resolved_role = "reviewer"
         with mock.patch.object(srv, "PROJECT_ROOT", MCP_PROCESS_ROOT):
             with mock.patch("gitea_mcp_server.get_profile", return_value=self._merger_profile()):
                 resolved = srv._verify_role_mutation_workspace("prgs")
-        self.assertEqual(resolved, os.path.realpath(MCP_PROCESS_ROOT))
+        self.assertEqual(resolved, os.path.realpath(MERGER_CLEAN))