gitea_mcp_server.py

@@ -653,6 +653,10 @@ def verify_preflight_purity(
             f"'{task}' (fail closed)"
         )
 
+    # #671: block review/merge/close/completion mutations while the session is
+    # contaminated by a direct stable-branch push attempt (reconciler-exempt).
+    _enforce_stable_branch_contamination_gate(task, remote)
+
     ctx = _resolve_namespace_mutation_context(worktree_path)
     workspace = ctx["workspace_path"]
     canonical_root = ctx["canonical_repo_root"]
@@ -809,6 +813,80 @@ def _enforce_root_checkout_guard(worktree_path: str | None = None) -> None:
         raise RuntimeError(root_checkout_guard.format_root_checkout_guard_error(assessment))
 
 
+# ── stable-branch push contamination (#671) ──────────────────────────────────
+# A worker session that attempts a direct stable-branch push (or a
+# root-checkout local commit) is workflow-contaminated. The marker is durable
+# (survives daemon process pools like the other session proofs) and keyed per
+# profile identity. It fails closed on gated mutations until a reconciler
+# audits and clears it.
+
+def _stable_contamination_profile_identity() -> str:
+    return mcp_session_state.current_profile_identity(
+        profile_name=get_profile().get("profile_name"),
+    )
+
+
+def _load_stable_contamination_marker(remote: str | None = None) -> dict | None:
+    return mcp_session_state.load_state(
+        kind=mcp_session_state.KIND_STABLE_BRANCH_CONTAMINATION,
+        remote=remote,
+        profile_identity=_stable_contamination_profile_identity(),
+    )
+
+
+def _save_stable_contamination_marker(
+    record: dict,
+    *,
+    remote: str | None = None,
+) -> dict | None:
+    return mcp_session_state.save_state(
+        kind=mcp_session_state.KIND_STABLE_BRANCH_CONTAMINATION,
+        payload=record,
+        remote=remote,
+        profile_identity=_stable_contamination_profile_identity(),
+    )
+
+
+def _clear_stable_contamination_marker(
+    *,
+    remote: str | None = None,
+    profile_identity: str | None = None,
+) -> None:
+    mcp_session_state.clear_state(
+        kind=mcp_session_state.KIND_STABLE_BRANCH_CONTAMINATION,
+        remote=remote,
+        profile_identity=profile_identity or _stable_contamination_profile_identity(),
+    )
+
+
+def _enforce_stable_branch_contamination_gate(
+    task: str | None,
+    remote: str | None = None,
+) -> None:
+    """#671 AC4: fail closed on gated mutations while contaminated.
+
+    Reconciler role is exempt (the sanctioned audit/clear path). Non-gated
+    tasks (comment_issue, lock_issue) stay allowed so a contaminated worker can
+    still post the durable audit comment and hand off.
+    """
+    if _preflight_in_test_mode() and not os.environ.get(
+        "GITEA_TEST_FORCE_STABLE_CONTAMINATION"
+    ):
+        return
+    marker = _load_stable_contamination_marker(remote)
+    if not marker:
+        return
+    gate = stable_branch_push_guard.assess_contamination_gate(
+        marker,
+        task=task,
+        actual_role=_actual_profile_role(),
+    )
+    if gate["block"]:
+        raise RuntimeError(
+            stable_branch_push_guard.format_contamination_gate_error(gate)
+        )
+
+
 from mcp.server.fastmcp import FastMCP  # noqa: E402
 
 from gitea_auth import (  # noqa: E402
@@ -849,6 +927,7 @@ import merge_approval_gate  # noqa: E402
 import already_landed_reconcile  # noqa: E402
 import author_mutation_worktree  # noqa: E402
 import root_checkout_guard  # noqa: E402
+import stable_branch_push_guard  # noqa: E402
 import remote_repo_guard  # noqa: E402
 import issue_claim_heartbeat  # noqa: E402
 import issue_work_duplicate_gate  # noqa: E402
@@ -9273,6 +9352,160 @@ def gitea_diagnose_terminal(
     }
 
 
+@mcp.tool()
+def gitea_record_stable_branch_push_attempt(
+    command: str | None = None,
+    remote: str = "dadeschools",
+    ref: str | None = None,
+    session_id: str | None = None,
+    mark: bool = True,
+    current_branch: str | None = None,
+    head_sha: str | None = None,
+    remote_master_sha: str | None = None,
+    is_under_branches: bool | None = None,
+    ahead_count: int | None = None,
+) -> dict:
+    """Classify a proposed command for direct stable-branch push intent (#671).
+
+    Worker sessions must never publish stable branches (``master``/``main``/
+    ``dev``/...) directly. This tool detects ``git push <remote> master``
+    equivalents (refspecs, ``HEAD:master``, ``--force``, ``--dry-run`` no-op
+    intent, ``:master`` delete) and — separately — a root/control-checkout
+    local commit not carried by an issue feature branch.
+
+    When ``mark`` is true and contamination is detected, a durable
+    ``stable_branch_contamination`` marker is written for the active profile
+    identity. Subsequent review/merge/close/completion mutations then fail
+    closed (via the pre-flight gate) until a reconciler audits and clears it.
+    The stored command summary is redacted; secrets never persist.
+
+    Read-only when nothing is detected (or ``mark`` is false). Returns the
+    classification, any root-checkout assessment, and the marker state.
+    """
+    classification = stable_branch_push_guard.classify_push_command(command)
+
+    root_checkout = None
+    if any(v is not None for v in (current_branch, head_sha, remote_master_sha,
+                                   is_under_branches, ahead_count)):
+        root_checkout = stable_branch_push_guard.assess_root_checkout_local_commit(
+            current_branch=current_branch,
+            head_sha=head_sha,
+            remote_master_sha=remote_master_sha,
+            is_under_branches=bool(is_under_branches),
+            ahead_count=ahead_count,
+        )
+
+    push_contam = bool(classification.get("contamination"))
+    root_contam = bool(root_checkout and root_checkout.get("contamination"))
+    contaminated = push_contam or root_contam
+
+    marker = None
+    marked = False
+    if contaminated and mark:
+        if push_contam:
+            reason_class = "stable_branch_push"
+            command_redacted = classification.get("redacted_command")
+            detail = "; ".join(classification.get("reasons") or [])
+            resolved_ref = ref or (
+                (classification.get("stable_refs") or [None])[0]
+            )
+        else:
+            reason_class = "root_checkout_commit"
+            command_redacted = None
+            detail = "; ".join(root_checkout.get("reasons") or [])
+            resolved_ref = ref or root_checkout.get("current_branch")
+        record = stable_branch_push_guard.build_contamination_record(
+            reason_class=reason_class,
+            command_redacted=command_redacted,
+            session_id=session_id,
+            remote=remote,
+            ref=resolved_ref,
+            role=_actual_profile_role(),
+            detail=detail,
+        )
+        marker = _save_stable_contamination_marker(record, remote=remote)
+        marked = marker is not None
+
+    return {
+        "classification": classification,
+        "root_checkout": root_checkout,
+        "contaminated": contaminated,
+        "marked": marked,
+        "marker": marker,
+        "profile_identity": _stable_contamination_profile_identity(),
+        "remediation": stable_branch_push_guard.REMEDIATION if contaminated else None,
+    }
+
+
+@mcp.tool()
+def gitea_audit_stable_branch_contamination(
+    action: str = "inspect",
+    remote: str = "dadeschools",
+    profile_identity: str | None = None,
+) -> dict:
+    """Reconciler audit of a stable-branch contamination marker (#671).
+
+    ``action='inspect'`` (default, read-only) loads the durable marker for the
+    given ``profile_identity`` (or the active session's) and reports it.
+
+    ``action='clear'`` removes the marker so the contaminated session may
+    resume gated mutations. Clearing is the reconciler audit path and requires
+    an active reconciler profile — a worker session must never self-clear
+    (#671 security requirement). ``profile_identity`` targets the contaminated
+    worker's marker (a reconciler runs under its own identity).
+    """
+    act = (action or "inspect").strip().lower()
+    target_identity = (profile_identity or "").strip() or _stable_contamination_profile_identity()
+
+    marker = mcp_session_state.load_state(
+        kind=mcp_session_state.KIND_STABLE_BRANCH_CONTAMINATION,
+        remote=remote,
+        profile_identity=target_identity,
+    )
+
+    if act == "inspect":
+        return {
+            "action": "inspect",
+            "profile_identity": target_identity,
+            "contaminated": marker is not None,
+            "marker": marker,
+            "read_only": True,
+        }
+
+    if act == "clear":
+        role = _actual_profile_role()
+        if role != "reconciler":
+            return {
+                "action": "clear",
+                "success": False,
+                "performed": False,
+                "profile_identity": target_identity,
+                "reasons": [
+                    "stable-branch contamination may only be cleared by a "
+                    f"reconciler audit; active role is '{role}' (fail closed). "
+                    "The contaminated worker session must not self-clear."
+                ],
+            }
+        _clear_stable_contamination_marker(
+            remote=remote,
+            profile_identity=target_identity,
+        )
+        return {
+            "action": "clear",
+            "success": True,
+            "performed": True,
+            "profile_identity": target_identity,
+            "was_contaminated": marker is not None,
+        }
+
+    return {
+        "action": act,
+        "success": False,
+        "performed": False,
+        "reasons": [f"unknown action '{act}'; use 'inspect' or 'clear'"],
+    }
+
+
 @mcp.tool()
 def gitea_validate_review_final_report(
     report_text: str,

mcp_session_state.py

@@ -31,6 +31,11 @@ DEFAULT_TTL_HOURS = 4.0
 KIND_WORKFLOW_LOAD = "review_workflow_load"
 KIND_DECISION_LOCK = "review_decision_lock"
 KIND_REVIEW_DRAFT = "review_draft"
+# Durable marker set when a worker session attempts a direct stable-branch push
+# or a root-checkout local commit (#671). Keyed per profile identity like the
+# other session proofs; a contaminated session fails closed on gated mutations
+# until a reconciler audits and clears it.
+KIND_STABLE_BRANCH_CONTAMINATION = "stable_branch_contamination"
 
 
 

skills/llm-project-workflow/SKILL.md

@@ -32,6 +32,15 @@ workflow file.
   mutation.
 - A nearby capability does not count.
 - Do not self-review or self-merge.
+- **Never push a stable branch directly.** Worker sessions (author/reviewer/merger)
+  must never run `git push <remote> master` — or `main`/`dev`/other stable refs,
+  including refspecs (`HEAD:master`), `--force`, `--delete`, or `--dry-run` no-op
+  probes — and must never commit on the root/control checkout outside an issue
+  feature branch. Stable-branch updates land ONLY through sanctioned Gitea merge
+  tooling (`gitea_merge_pr`) or an explicitly authorized reconciler path. A
+  detected attempt marks the session workflow-contaminated (#671) and fails
+  closed on review/merge/close/completion until a reconciler audits and clears
+  it. `git fetch` / `git pull --ff-only` and feature-branch pushes stay allowed.
 - Do not mix modes in one run.
 - **BLOCKED + DIAGNOSE default rule (required):** If any required workflow step, skill, tool, capability, preflight, instruction, profile, worktree binding, or terminal/MCP operation cannot be performed or loaded (including the canonical ones listed in this skill and its loaded workflow), immediately enter `BLOCKED + DIAGNOSE`. Stop before any git or Gitea mutation. Diagnose using the standard template in [`templates/blocked-diagnose-report.md`](templates/blocked-diagnose-report.md). Attempt *only* safe non-mutating recovery. Report using the template. Do not continue, use fallbacks, or treat the missing requirement as harmless.
 - If the required workflow cannot be loaded, stop and produce a recovery handoff
@@ -48,6 +57,11 @@ workflow file.
 - wrong profile or role for the requested operation
 - dirty or misbound worktree (root checkout or non-branches/ path)
 - root checkout mutation risk
+- stable-branch push contamination (#671): a direct `git push <remote> master`
+  (or `main`/`dev`) equivalent, or a root/control-checkout commit not on an issue
+  feature branch, marks the session workflow-contaminated; review/merge/close/
+  completion mutations then fail closed until a reconciler audits and clears it
+  (`gitea_audit_stable_branch_contamination action=clear`, reconciler-only)
 - mutation guard failure (e.g. branches-only guard)
 - missing required MCP tool/schema or operation
 - stale or inconsistent runtime state (e.g. lease vs actual, dirty state disagreement)
@@ -118,6 +132,42 @@ The main project checkout is a stable control checkout on `master`, `main`, or
 If `cwd` is not inside `branches/`, stop before any file edit, test write,
 commit, merge, rebase, or cleanup. The main checkout is orchestration-only.
 
+## Stable Branch Push Protection (#671)
+
+Worker sessions must **never** publish a stable branch directly. This is the
+prevention hardening for the #670 incident (a bare direct-to-master commit
+`2fa97c26` and a PR #654 merger `git push prgs master` attempt).
+
+**Forbidden for author/reviewer/merger sessions:**
+
+- `git push <remote> master` (and `main`, `dev`, `develop`, `development`),
+  including refspecs (`HEAD:master`, `+refs/heads/x:refs/heads/master`),
+  `--force`, `--delete` / `:master`, and `--dry-run`/`-n` no-op probes (a
+  dry-run still proves intent and contaminates the session).
+- Local commits on the root/control checkout that are not carried by an issue
+  feature branch under `branches/`.
+
+**Allowed (never blocked):**
+
+- `git fetch` and `git pull --ff-only` of master into the control checkout when
+  authorized for sync.
+- Feature-branch pushes to non-stable refs (`git push <remote> fix/issue-N-...`).
+- Sanctioned merges via `gitea_merge_pr` / the Gitea API merge endpoint — the
+  **only** way stable branches advance.
+
+**What happens on a detected attempt:** the session is marked
+workflow-contaminated (durable `stable_branch_contamination` marker, redacted
+command summary + session id + remote + ref). While contaminated, all
+review / merge / close / issue-completion mutations fail closed. `comment_issue`
+and `lock_issue` remain allowed so the contaminated worker can post the durable
+audit comment and hand off. Contamination **cannot be self-cleared** — only a
+reconciler audit (`gitea_audit_stable_branch_contamination action=clear`) may
+clear it.
+
+Tooling: call `gitea_record_stable_branch_push_attempt` to classify/record a
+proposed push before running it; `gitea_audit_stable_branch_contamination` to
+inspect or (reconciler-only) clear the marker.
+
 ## Shell Spawn Hard-Stop Rule
 
 `exit_code: -1` with empty stdout/stderr means the shell failed to spawn — not a

stable_branch_push_guard.py

@@ -0,0 +1,478 @@
+"""Fail-closed guard against direct pushes to stable branches (#671).
+
+MCP workflow sessions must never publish to a stable branch (``master``,
+``main``, ``dev``, ...) directly. Stable-branch updates land only through
+sanctioned Gitea merge tooling or an explicitly authorized reconciler path.
+
+Incident origin (#670): a bare direct-to-master commit ``2fa97c26`` landed on
+``prgs/master`` without PR/review provenance, and a PR #654 merger run
+attempted ``git push prgs master`` (audited as a no-op, but the *intent* is the
+hazard). Partial protections already existed (``author_proofs.PROTECTED_BRANCHES``,
+``root_checkout_guard``, branch-push proofs) but did not detect shell push
+equivalents, mark the session contaminated after such an attempt, or fail
+closed on subsequent review/merge/close/completion mutations.
+
+This module is the detection + contamination-policy core. Like
+``author_proofs`` and ``root_checkout_guard`` it is **pure**: callers gather
+the raw facts (the proposed command line, git state, the durable contamination
+marker) and pass them in, so the same logic serves prompts, MCP gates, and
+tests. Nothing here performs git or network calls or reads durable state; the
+server wires these helpers to ``mcp_session_state`` and ``verify_preflight_purity``.
+
+Design rules honoured (from the #671 acceptance criteria):
+
+* Detect ``git push <remote> master`` shell equivalents, including refspecs
+  (``HEAD:master``, ``+refs/heads/x:refs/heads/master``), ``--force``,
+  ``--dry-run``/no-op intent, and delete refspecs (``:master``).
+* Never false-block a feature-branch push (``git push prgs fix/issue-671-...``).
+* Never treat ``git fetch`` / ``git pull --ff-only`` as a push.
+* Never treat sanctioned ``gitea_merge_pr`` / Gitea API merge as a push.
+* Fail closed on ambiguous targets that *may* resolve to a stable branch, but
+  surface ambiguity as its own signal rather than silently blocking feature work.
+* Contamination must not be clearable by the same worker session — only a
+  reconciler (audit) role may clear or bypass the gate.
+"""
+
+from __future__ import annotations
+
+import re
+from typing import Any, Iterable
+
+from author_proofs import PROTECTED_BRANCHES
+
+# Single source of truth for the stable branch set: the same protected set the
+# author branch-identity proofs already enforce (#177), so the two guards can
+# never drift apart.
+STABLE_BRANCHES = PROTECTED_BRANCHES
+
+# Mutations that must fail closed once the session is contaminated by a direct
+# stable-branch push attempt (#671 AC4: review, merge, close, completion).
+# ``comment_issue`` / ``lock_issue`` / ``create_issue`` are deliberately NOT
+# gated so a contaminated worker can still post the durable audit comment and
+# hand off. Only a reconciler (audit) role bypasses this set.
+CONTAMINATION_GATED_TASKS = frozenset({
+    "create_pr",
+    "commit_files",
+    "gitea_commit_files",
+    "close_pr",
+    "close_issue",
+    "review_pr",
+    "approve_pr",
+    "request_changes_pr",
+    "submit_pr_review",
+    "merge_pr",
+    "delete_branch",
+    "complete_issue",
+})
+
+CONTAMINATION_KIND = "stable_branch_push"
+
+REMEDIATION = (
+    "Direct stable-branch publication is forbidden for worker sessions. Stop, "
+    "leave the stable branch untouched, and route the change through sanctioned "
+    "Gitea merge tooling (gitea_merge_pr) or an explicitly authorized reconciler "
+    "audit. This session is workflow-contaminated until a reconciler audits it."
+)
+
+# ── command tokenising ────────────────────────────────────────────────────────
+
+# Split a compound command line into individual simple commands on shell
+# separators so ``a && git push prgs master`` is analysed segment by segment.
+_SEGMENT_SPLIT_RE = re.compile(r"(?:\|\||&&|\||;|\n)")
+
+_GIT_PUSH_RE = re.compile(r"\bgit\b[\w\s\-]*?\bpush\b", re.IGNORECASE)
+_GIT_FETCH_RE = re.compile(r"\bgit\b[\w\s\-]*?\b(?:fetch|pull)\b", re.IGNORECASE)
+
+# Flags that take a value argument in ``git push`` (so the following token is
+# consumed as the flag's value, not a refspec).
+_VALUE_FLAGS = frozenset({
+    "--repo",
+    "-o",
+    "--push-option",
+    "--receive-pack",
+    "--exec",
+})
+
+_FORCE_FLAGS = frozenset({"-f", "--force"})
+_DRY_RUN_FLAGS = frozenset({"-n", "--dry-run"})
+_DELETE_FLAGS = frozenset({"-d", "--delete"})
+
+
+def _clean(value: str | None) -> str:
+    return (value or "").strip()
+
+
+def _strip_ref_prefix(ref: str) -> str:
+    ref = ref.strip()
+    for prefix in ("refs/heads/", "heads/"):
+        if ref.startswith(prefix):
+            return ref[len(prefix):]
+    return ref
+
+
+def is_stable_ref(ref: str | None) -> bool:
+    """True when ``ref`` names a configured stable branch."""
+    name = _strip_ref_prefix(_clean(ref))
+    return bool(name) and name in STABLE_BRANCHES
+
+
+# ── redaction ─────────────────────────────────────────────────────────────────
+
+_URL_USERINFO_RE = re.compile(r"(https?://)[^/\s:@]+(?::[^/\s@]+)?@", re.IGNORECASE)
+_SECRET_ASSIGN_RE = re.compile(
+    r"\b((?:GITEA_)?(?:TOKEN|PASSWORD|PASS|PAT|SECRET|API_KEY|AUTH))\s*=\s*\S+",
+    re.IGNORECASE,
+)
+_BEARER_RE = re.compile(r"\b(Bearer|token)\s+[A-Za-z0-9._\-]{8,}", re.IGNORECASE)
+
+
+def redact_command(command: str | None) -> str:
+    """Strip credentials/URLs from a command line before logging it (#671).
+
+    Redacts URL userinfo (``https://user:tok@host`` → ``https://***@host``),
+    ``TOKEN=...`` style assignments, and bearer/token headers. Leaves the
+    structural parts (``git push <remote> master``) intact for audit value.
+    """
+    text = _clean(command)
+    if not text:
+        return ""
+    text = _URL_USERINFO_RE.sub(r"\1***@", text)
+    text = _SECRET_ASSIGN_RE.sub(lambda m: f"{m.group(1)}=***", text)
+    text = _BEARER_RE.sub(lambda m: f"{m.group(1)} ***", text)
+    return text
+
+
+# ── push classification ───────────────────────────────────────────────────────
+
+def _analyse_push_segment(segment: str) -> dict[str, Any]:
+    """Classify one ``git push ...`` command segment."""
+    tokens = segment.split()
+    # Drop everything up to and including the ``push`` verb.
+    try:
+        push_idx = next(
+            i for i, tok in enumerate(tokens)
+            if tok.lower() == "push"
+        )
+    except StopIteration:
+        push_idx = -1
+    args = tokens[push_idx + 1:] if push_idx >= 0 else []
+
+    is_force = False
+    is_dry_run = False
+    is_delete = False
+    positionals: list[str] = []
+
+    skip_next = False
+    for tok in args:
+        if skip_next:
+            skip_next = False
+            continue
+        if tok in _FORCE_FLAGS or tok.startswith("--force-with-lease") or tok.startswith("--force-if-includes"):
+            is_force = True
+            continue
+        if tok in _DRY_RUN_FLAGS:
+            is_dry_run = True
+            continue
+        if tok in _DELETE_FLAGS:
+            is_delete = True
+            continue
+        if tok in _VALUE_FLAGS:
+            skip_next = True
+            continue
+        if tok.startswith("--") and "=" in tok:
+            # e.g. --repo=... : self-contained, not a refspec.
+            continue
+        if tok.startswith("-"):
+            # Unknown/combined short flag; ignore for ref detection.
+            continue
+        positionals.append(tok)
+
+    # First positional after push is the remote (when any positional exists);
+    # the rest are refspecs / branch names.
+    remote = positionals[0] if positionals else None
+    refspecs = positionals[1:]
+
+    stable_refs: list[str] = []
+    force_to_stable = False
+    delete_stable = False
+    for spec in refspecs:
+        force_spec = spec.startswith("+")
+        body = spec[1:] if force_spec else spec
+        if ":" in body:
+            src, _, dst = body.partition(":")
+            dest = dst
+            if src == "" and dst:
+                # ``:master`` — delete refspec.
+                is_delete = True
+        else:
+            dest = body
+        if is_stable_ref(dest):
+            stable_refs.append(_strip_ref_prefix(dest))
+            if force_spec or is_force:
+                force_to_stable = True
+            if is_delete:
+                delete_stable = True
+
+    targets_stable = bool(stable_refs)
+    # Ambiguous: ``git push <remote>`` (or bare ``git push``) with no refspec —
+    # resolves to the current branch's upstream, which we cannot see from the
+    # command alone. Flag it, but do not assert stable (would false-block
+    # feature-branch pushes).
+    ambiguous = not refspecs
+
+    return {
+        "is_git_push": True,
+        "remote": remote,
+        "refspecs": refspecs,
+        "targets_stable": targets_stable,
+        "stable_refs": stable_refs,
+        "is_force": is_force or force_to_stable,
+        "is_dry_run": is_dry_run,
+        "is_delete": is_delete or delete_stable,
+        "ambiguous_target": ambiguous,
+    }
+
+
+def classify_push_command(command: str | None) -> dict[str, Any]:
+    """Classify a shell command line for direct stable-branch push intent (#671).
+
+    Returns a dict describing whether the command is a ``git push`` targeting a
+    stable branch. Fetch/pull are never pushes. A sanctioned Gitea merge (which
+    is not a ``git push`` at all) classifies as non-push. Dry-run and no-op
+    pushes still count as *intent* and are reported as contamination
+    (``proves_intent``) so a ``--dry-run`` cannot be used to probe the gate.
+    """
+    text = _clean(command)
+    result: dict[str, Any] = {
+        "command": text,
+        "redacted_command": redact_command(text),
+        "is_git_push": False,
+        "is_fetch_or_pull": False,
+        "targets_stable": False,
+        "stable_refs": [],
+        "is_force": False,
+        "is_dry_run": False,
+        "is_delete": False,
+        "ambiguous_target": False,
+        "contamination": False,
+        "proves_intent": False,
+        "reasons": [],
+    }
+    if not text:
+        return result
+
+    stable_refs: list[str] = []
+    saw_push = False
+    for segment in _SEGMENT_SPLIT_RE.split(text):
+        seg = segment.strip()
+        if not seg:
+            continue
+        if _GIT_FETCH_RE.search(seg) and not _GIT_PUSH_RE.search(seg):
+            result["is_fetch_or_pull"] = True
+            continue
+        if not _GIT_PUSH_RE.search(seg):
+            continue
+        saw_push = True
+        analysis = _analyse_push_segment(seg)
+        result["is_git_push"] = True
+        result["is_force"] = result["is_force"] or analysis["is_force"]
+        result["is_dry_run"] = result["is_dry_run"] or analysis["is_dry_run"]
+        result["is_delete"] = result["is_delete"] or analysis["is_delete"]
+        result["ambiguous_target"] = result["ambiguous_target"] or analysis["ambiguous_target"]
+        stable_refs.extend(analysis["stable_refs"])
+
+    result["stable_refs"] = sorted(set(stable_refs))
+    result["targets_stable"] = bool(stable_refs)
+
+    reasons: list[str] = []
+    if result["targets_stable"]:
+        refs = ", ".join(result["stable_refs"])
+        verb = "delete" if result["is_delete"] else ("force-push" if result["is_force"] else "push")
+        qualifier = " (dry-run/no-op still proves intent)" if result["is_dry_run"] else ""
+        reasons.append(
+            f"direct stable-branch {verb} detected targeting: {refs}{qualifier}; "
+            "worker sessions must never publish stable branches directly"
+        )
+        result["contamination"] = True
+        result["proves_intent"] = True
+    elif saw_push and result["ambiguous_target"]:
+        # Bare ``git push`` with no refspec: ambiguous. Report, but do not
+        # contaminate on the command alone — the root-checkout / branch-state
+        # detector resolves whether the current branch is stable.
+        reasons.append(
+            "ambiguous 'git push' with no refspec: resolve the current branch "
+            "before pushing; if it is a stable branch this is forbidden"
+        )
+
+    result["reasons"] = reasons
+    return result
+
+
+def detect_stable_push(commands: str | Iterable[str] | None) -> dict[str, Any]:
+    """Classify one command or an iterable of commands; contamination if any hit."""
+    if commands is None:
+        return classify_push_command(None)
+    if isinstance(commands, str):
+        return classify_push_command(commands)
+    worst: dict[str, Any] | None = None
+    for cmd in commands:
+        res = classify_push_command(cmd)
+        if res["contamination"]:
+            return res
+        if worst is None or (res["is_git_push"] and not worst["is_git_push"]):
+            worst = res
+    return worst or classify_push_command(None)
+
+
+# ── root/control checkout local-commit detection ──────────────────────────────
+
+def assess_root_checkout_local_commit(
+    *,
+    current_branch: str | None,
+    head_sha: str | None,
+    remote_master_sha: str | None,
+    is_under_branches: bool,
+    ahead_count: int | None = None,
+) -> dict[str, Any]:
+    """Detect a local commit on the root/control checkout not on a feature branch.
+
+    #671 AC2. An isolated ``branches/...`` worktree is exempt (that is where
+    feature work belongs). On the control checkout, a commit is illegitimate
+    when the checkout sits on a stable branch (or detached) and its HEAD has
+    advanced past the tracking ``prgs/master`` — i.e. a commit was made that is
+    not carried by an issue feature branch/PR.
+
+    Positive evidence only: missing state reports ``unknown`` rather than
+    asserting contamination, but an unreadable *branch* on the control checkout
+    (detached HEAD) with an advanced HEAD is still flagged.
+    """
+    branch = _clean(current_branch)
+    head = _clean(head_sha).lower()
+    master = _clean(remote_master_sha).lower()
+
+    if is_under_branches:
+        return {
+            "contamination": False,
+            "unknown": False,
+            "reasons": [],
+            "detail": "isolated branches/ worktree — feature commits are expected here",
+        }
+
+    reasons: list[str] = []
+    unknown = False
+
+    on_stable = (not branch) or (branch in STABLE_BRANCHES)
+    if not on_stable:
+        # Control checkout is on some non-stable branch: out of scope for this
+        # detector (root_checkout_guard #475 handles that contamination class).
+        return {
+            "contamination": False,
+            "unknown": False,
+            "reasons": [],
+            "detail": f"control checkout on non-stable branch '{branch}' — not this detector's class",
+        }
+
+    advanced = False
+    if ahead_count is not None and ahead_count > 0:
+        advanced = True
+    if head and master and head != master:
+        advanced = True
+    if (not head or not master) and ahead_count is None:
+        unknown = True
+
+    if advanced:
+        where = f"branch '{branch}'" if branch else "detached HEAD"
+        reasons.append(
+            f"control checkout ({where}) has local commits not on an issue "
+            "feature branch (HEAD advanced past prgs/master); worker sessions "
+            "must commit only on issue branches under branches/"
+        )
+
+    return {
+        "contamination": bool(reasons),
+        "unknown": unknown and not reasons,
+        "reasons": reasons,
+        "current_branch": branch or None,
+        "head_sha": head or None,
+        "remote_master_sha": master or None,
+    }
+
+
+# ── contamination record + gate ───────────────────────────────────────────────
+
+def build_contamination_record(
+    *,
+    reason_class: str,
+    command_redacted: str | None = None,
+    session_id: str | None = None,
+    remote: str | None = None,
+    ref: str | None = None,
+    role: str | None = None,
+    detail: str | None = None,
+) -> dict[str, Any]:
+    """Build the durable contamination marker payload (redacted, audit-safe).
+
+    ``reason_class`` is one of ``stable_branch_push`` / ``root_checkout_commit``.
+    The command is stored already-redacted; callers pass the raw line through
+    :func:`redact_command` (or this builder redacts a raw ``command`` for them).
+    """
+    return {
+        "kind": CONTAMINATION_KIND,
+        "reason_class": _clean(reason_class) or "stable_branch_push",
+        "command_summary": redact_command(command_redacted),
+        "session_id": _clean(session_id) or None,
+        "remote": _clean(remote) or None,
+        "ref": _clean(ref) or None,
+        "role": _clean(role) or None,
+        "detail": _clean(detail) or None,
+        "cleared_by_reconciler": False,
+    }
+
+
+def assess_contamination_gate(
+    marker: dict[str, Any] | None,
+    *,
+    task: str | None,
+    actual_role: str | None,
+) -> dict[str, Any]:
+    """Fail closed on gated mutations while a contamination marker is live (#671 AC4).
+
+    * No marker → allowed.
+    * Reconciler (audit) role → allowed (the sanctioned path to inspect/clear).
+    * Marker present + ``task`` in :data:`CONTAMINATION_GATED_TASKS` → blocked.
+    * Marker present + non-gated task (e.g. ``comment_issue``) → allowed, so the
+      worker can still post the durable audit/handoff comment.
+    """
+    if not marker or marker.get("cleared_by_reconciler"):
+        return {"block": False, "reasons": [], "task": task}
+
+    role = _clean(actual_role).lower()
+    if role == "reconciler":
+        return {
+            "block": False,
+            "reasons": [],
+            "task": task,
+            "detail": "reconciler audit path is exempt from the contamination gate",
+        }
+
+    task_name = _clean(task)
+    if task_name and task_name in CONTAMINATION_GATED_TASKS:
+        summary = marker.get("command_summary") or marker.get("detail") or "(no summary)"
+        reason_class = marker.get("reason_class") or "stable_branch_push"
+        return {
+            "block": True,
+            "reasons": [
+                f"session is workflow-contaminated ({reason_class}): {summary}. "
+                f"'{task_name}' is blocked until a reconciler audits and clears "
+                "the contamination. " + REMEDIATION
+            ],
+            "task": task_name,
+        }
+
+    return {"block": False, "reasons": [], "task": task_name or None}
+
+
+def format_contamination_gate_error(gate: dict[str, Any]) -> str:
+    """Single RuntimeError message for MCP mutation gates."""
+    reasons = "; ".join(gate.get("reasons") or ["session workflow-contaminated"])
+    return f"Stable-branch contamination gate (#671): {reasons}"

tests/test_stable_branch_contamination_server.py

@@ -0,0 +1,188 @@
+"""Server wiring for stable-branch push contamination (#671).
+
+Exercises the MCP tools and the pre-flight enforcement gate against the durable
+contamination marker (isolated per-test state dir from conftest).
+"""
+
+from __future__ import annotations
+
+import os
+from unittest.mock import patch
+
+import gitea_mcp_server as srv
+
+
+def _clear_marker(remote="prgs"):
+    srv._clear_stable_contamination_marker(remote=remote)
+
+
+def teardown_function():
+    _clear_marker()
+
+
+# ── record tool marks a real direct push ─────────────────────────────────────
+
+def test_record_tool_marks_direct_master_push():
+    _clear_marker()
+    res = srv.gitea_record_stable_branch_push_attempt(
+        command="git push prgs master", remote="prgs"
+    )
+    assert res["contaminated"] is True
+    assert res["marked"] is True
+    assert res["marker"] is not None
+    assert res["marker"]["reason_class"] == "stable_branch_push"
+    # loaded back through the durable store
+    loaded = srv._load_stable_contamination_marker("prgs")
+    assert loaded is not None
+    assert loaded["ref"] == "master"
+
+
+def test_record_tool_dry_run_still_marks():
+    _clear_marker()
+    res = srv.gitea_record_stable_branch_push_attempt(
+        command="git push --dry-run prgs master", remote="prgs"
+    )
+    assert res["contaminated"] is True
+    assert res["marked"] is True
+
+
+def test_record_tool_feature_branch_does_not_mark():
+    _clear_marker()
+    res = srv.gitea_record_stable_branch_push_attempt(
+        command="git push prgs fix/issue-671-block-stable-branch-push",
+        remote="prgs",
+    )
+    assert res["contaminated"] is False
+    assert res["marked"] is False
+    assert srv._load_stable_contamination_marker("prgs") is None
+
+
+def test_record_tool_fetch_only_does_not_mark():
+    _clear_marker()
+    res = srv.gitea_record_stable_branch_push_attempt(
+        command="git fetch prgs", remote="prgs"
+    )
+    assert res["contaminated"] is False
+    assert res["marked"] is False
+
+
+def test_record_tool_mark_false_is_readonly():
+    _clear_marker()
+    res = srv.gitea_record_stable_branch_push_attempt(
+        command="git push prgs master", remote="prgs", mark=False
+    )
+    assert res["contaminated"] is True
+    assert res["marked"] is False
+    assert srv._load_stable_contamination_marker("prgs") is None
+
+
+def test_record_tool_redacts_secret_in_marker():
+    _clear_marker()
+    res = srv.gitea_record_stable_branch_push_attempt(
+        command="git push https://u:supersecret@host/o/r.git master",
+        remote="prgs",
+    )
+    assert res["marked"] is True
+    assert "supersecret" not in res["marker"]["command_summary"]
+
+
+def test_record_tool_root_checkout_local_commit_marks():
+    _clear_marker()
+    res = srv.gitea_record_stable_branch_push_attempt(
+        command=None,
+        remote="prgs",
+        current_branch="master",
+        head_sha="a" * 40,
+        remote_master_sha="b" * 40,
+        is_under_branches=False,
+    )
+    assert res["contaminated"] is True
+    assert res["marked"] is True
+    assert res["marker"]["reason_class"] == "root_checkout_commit"
+
+
+# ── audit tool: inspect + reconciler-only clear ──────────────────────────────
+
+def test_audit_inspect_reports_marker():
+    _clear_marker()
+    srv.gitea_record_stable_branch_push_attempt(
+        command="git push prgs master", remote="prgs"
+    )
+    out = srv.gitea_audit_stable_branch_contamination(action="inspect", remote="prgs")
+    assert out["contaminated"] is True
+    assert out["read_only"] is True
+
+
+def test_audit_clear_refused_for_non_reconciler():
+    _clear_marker()
+    srv.gitea_record_stable_branch_push_attempt(
+        command="git push prgs master", remote="prgs"
+    )
+    with patch.object(srv, "_actual_profile_role", return_value="author"):
+        out = srv.gitea_audit_stable_branch_contamination(action="clear", remote="prgs")
+    assert out["success"] is False
+    assert out["reasons"]
+    # marker survives a refused clear
+    assert srv._load_stable_contamination_marker("prgs") is not None
+
+
+def test_audit_clear_allowed_for_reconciler():
+    _clear_marker()
+    srv.gitea_record_stable_branch_push_attempt(
+        command="git push prgs master", remote="prgs"
+    )
+    identity = srv._stable_contamination_profile_identity()
+    with patch.object(srv, "_actual_profile_role", return_value="reconciler"):
+        out = srv.gitea_audit_stable_branch_contamination(
+            action="clear", remote="prgs", profile_identity=identity
+        )
+    assert out["success"] is True
+    assert srv._load_stable_contamination_marker("prgs") is None
+
+
+# ── pre-flight enforcement gate ──────────────────────────────────────────────
+
+def _force_gate_env():
+    return patch.dict(os.environ, {"GITEA_TEST_FORCE_STABLE_CONTAMINATION": "1"})
+
+
+def test_gate_blocks_gated_mutation_when_contaminated():
+    _clear_marker()
+    srv.gitea_record_stable_branch_push_attempt(
+        command="git push prgs master", remote="prgs"
+    )
+    with _force_gate_env(), patch.object(srv, "_actual_profile_role", return_value="author"):
+        for task in ("merge_pr", "review_pr", "close_issue", "create_pr"):
+            try:
+                srv._enforce_stable_branch_contamination_gate(task, "prgs")
+                raised = False
+            except RuntimeError as exc:
+                raised = True
+                assert "#671" in str(exc)
+            assert raised, task
+
+
+def test_gate_allows_comment_for_handoff_when_contaminated():
+    _clear_marker()
+    srv.gitea_record_stable_branch_push_attempt(
+        command="git push prgs master", remote="prgs"
+    )
+    with _force_gate_env(), patch.object(srv, "_actual_profile_role", return_value="author"):
+        # must not raise — worker can still post the durable audit comment
+        srv._enforce_stable_branch_contamination_gate("comment_issue", "prgs")
+        srv._enforce_stable_branch_contamination_gate("lock_issue", "prgs")
+
+
+def test_gate_exempts_reconciler_when_contaminated():
+    _clear_marker()
+    srv.gitea_record_stable_branch_push_attempt(
+        command="git push prgs master", remote="prgs"
+    )
+    with _force_gate_env(), patch.object(srv, "_actual_profile_role", return_value="reconciler"):
+        srv._enforce_stable_branch_contamination_gate("merge_pr", "prgs")
+
+
+def test_gate_noop_when_not_contaminated():
+    _clear_marker()
+    with _force_gate_env(), patch.object(srv, "_actual_profile_role", return_value="author"):
+        srv._enforce_stable_branch_contamination_gate("merge_pr", "prgs")

tests/test_stable_branch_push_guard.py

@@ -0,0 +1,341 @@
+"""Tests for the direct stable-branch push guard (#671).
+
+Covers the acceptance criteria:
+1. detect shell ``git push <remote> master`` equivalents
+2. detect root/control-checkout local commits not on an issue branch
+3. contamination record shape
+4. fail-closed gate on review/merge/close/completion (reconciler-exempt)
+5. AC5 case matrix: no-op dry-run push, real direct push, sanctioned Gitea
+   merge, fetch-only, root-checkout local commit; plus feature-branch push
+   still allowed and sanctioned merge still allowed
+6. redaction of credentials in logged command summaries
+"""
+
+import stable_branch_push_guard as guard
+
+
+# ── AC1: detect direct stable-branch push equivalents ────────────────────────
+
+def test_plain_git_push_remote_master_is_contamination():
+    res = guard.classify_push_command("git push prgs master")
+    assert res["is_git_push"] is True
+    assert res["targets_stable"] is True
+    assert res["stable_refs"] == ["master"]
+    assert res["contamination"] is True
+    assert res["reasons"]
+
+
+def test_push_main_and_dev_detected():
+    for ref in ("main", "dev", "develop", "development"):
+        res = guard.classify_push_command(f"git push origin {ref}")
+        assert res["contamination"] is True, ref
+        assert res["stable_refs"] == [ref]
+
+
+def test_head_colon_master_refspec_detected():
+    res = guard.classify_push_command("git push prgs HEAD:master")
+    assert res["targets_stable"] is True
+    assert res["stable_refs"] == ["master"]
+    assert res["contamination"] is True
+
+
+def test_full_refspec_force_plus_detected():
+    res = guard.classify_push_command(
+        "git push prgs +refs/heads/tmp:refs/heads/master"
+    )
+    assert res["contamination"] is True
+    assert res["is_force"] is True
+    assert res["stable_refs"] == ["master"]
+
+
+def test_force_flag_to_master_detected():
+    res = guard.classify_push_command("git push --force prgs master")
+    assert res["contamination"] is True
+    assert res["is_force"] is True
+
+
+def test_delete_refspec_master_detected():
+    res = guard.classify_push_command("git push prgs :master")
+    assert res["contamination"] is True
+    assert res["is_delete"] is True
+
+
+def test_delete_flag_master_detected():
+    res = guard.classify_push_command("git push --delete prgs master")
+    assert res["contamination"] is True
+    assert res["is_delete"] is True
+
+
+def test_push_detected_inside_compound_command():
+    res = guard.classify_push_command("cd repo && git push prgs master && echo ok")
+    assert res["contamination"] is True
+    assert res["stable_refs"] == ["master"]
+
+
+# ── AC5: no-op / dry-run push still proves intent ────────────────────────────
+
+def test_dry_run_push_to_master_proves_intent():
+    res = guard.classify_push_command("git push --dry-run prgs master")
+    assert res["is_dry_run"] is True
+    assert res["contamination"] is True
+    assert res["proves_intent"] is True
+    assert "intent" in " ".join(res["reasons"]).lower()
+
+
+def test_short_dry_run_flag_n_detected():
+    res = guard.classify_push_command("git push -n prgs master")
+    assert res["is_dry_run"] is True
+    assert res["contamination"] is True
+
+
+# ── AC5 negative: feature-branch push still allowed ──────────────────────────
+
+def test_feature_branch_push_not_flagged():
+    res = guard.classify_push_command(
+        "git push prgs fix/issue-671-block-stable-branch-push"
+    )
+    assert res["is_git_push"] is True
+    assert res["targets_stable"] is False
+    assert res["contamination"] is False
+    assert res["reasons"] == []
+
+
+def test_feature_branch_head_refspec_not_flagged():
+    res = guard.classify_push_command(
+        "git push prgs HEAD:fix/issue-671-block-stable-branch-push"
+    )
+    assert res["contamination"] is False
+    assert res["targets_stable"] is False
+
+
+def test_branch_named_like_master_substring_not_flagged():
+    # 'master-notes' is not the stable 'master'.
+    res = guard.classify_push_command("git push prgs master-notes")
+    assert res["contamination"] is False
+    assert res["targets_stable"] is False
+
+
+# ── AC5 negative: fetch-only operations ──────────────────────────────────────
+
+def test_git_fetch_not_a_push():
+    res = guard.classify_push_command("git fetch prgs")
+    assert res["is_git_push"] is False
+    assert res["is_fetch_or_pull"] is True
+    assert res["contamination"] is False
+
+
+def test_git_pull_ff_only_master_not_a_push():
+    res = guard.classify_push_command("git pull --ff-only prgs master")
+    assert res["is_git_push"] is False
+    assert res["is_fetch_or_pull"] is True
+    assert res["contamination"] is False
+
+
+# ── AC5 negative: sanctioned Gitea merge is not a push ───────────────────────
+
+def test_gitea_merge_pr_tool_is_not_a_push():
+    res = guard.classify_push_command("gitea_merge_pr(pr_number=671, remote='prgs')")
+    assert res["is_git_push"] is False
+    assert res["contamination"] is False
+
+
+def test_gitea_api_merge_is_not_a_push():
+    res = guard.classify_push_command(
+        "curl -X POST https://gitea.example/api/v1/repos/o/r/pulls/671/merge"
+    )
+    assert res["is_git_push"] is False
+    assert res["contamination"] is False
+
+
+# ── ambiguous bare push: reported, not auto-contaminating ────────────────────
+
+def test_bare_push_is_ambiguous_not_contaminating():
+    res = guard.classify_push_command("git push prgs")
+    assert res["is_git_push"] is True
+    assert res["ambiguous_target"] is True
+    assert res["contamination"] is False
+    assert res["reasons"]  # surfaced as a warning
+
+
+# ── AC2: root/control-checkout local commit detection ────────────────────────
+
+def test_root_checkout_commit_ahead_of_master_flagged():
+    res = guard.assess_root_checkout_local_commit(
+        current_branch="master",
+        head_sha="a" * 40,
+        remote_master_sha="b" * 40,
+        is_under_branches=False,
+    )
+    assert res["contamination"] is True
+    assert res["reasons"]
+
+
+def test_root_checkout_clean_at_master_not_flagged():
+    sha = "c" * 40
+    res = guard.assess_root_checkout_local_commit(
+        current_branch="master",
+        head_sha=sha,
+        remote_master_sha=sha,
+        is_under_branches=False,
+    )
+    assert res["contamination"] is False
+    assert res["unknown"] is False
+
+
+def test_branches_worktree_commit_is_exempt():
+    res = guard.assess_root_checkout_local_commit(
+        current_branch="fix/issue-671-block-stable-branch-push",
+        head_sha="a" * 40,
+        remote_master_sha="b" * 40,
+        is_under_branches=True,
+    )
+    assert res["contamination"] is False
+
+
+def test_root_checkout_ahead_count_flagged():
+    res = guard.assess_root_checkout_local_commit(
+        current_branch="master",
+        head_sha="",
+        remote_master_sha="",
+        is_under_branches=False,
+        ahead_count=2,
+    )
+    assert res["contamination"] is True
+
+
+def test_root_checkout_unknown_when_state_missing():
+    res = guard.assess_root_checkout_local_commit(
+        current_branch="master",
+        head_sha="",
+        remote_master_sha="",
+        is_under_branches=False,
+    )
+    assert res["contamination"] is False
+    assert res["unknown"] is True
+
+
+def test_root_checkout_non_stable_branch_out_of_scope():
+    res = guard.assess_root_checkout_local_commit(
+        current_branch="feature/x",
+        head_sha="a" * 40,
+        remote_master_sha="b" * 40,
+        is_under_branches=False,
+    )
+    assert res["contamination"] is False
+
+
+# ── AC3: contamination record shape ──────────────────────────────────────────
+
+def test_build_contamination_record_shape_and_redaction():
+    rec = guard.build_contamination_record(
+        reason_class="stable_branch_push",
+        command_redacted="git push https://user:[email protected]/o/r.git master",
+        session_id="prgs-author-123",
+        remote="prgs",
+        ref="master",
+        role="author",
+    )
+    assert rec["kind"] == guard.CONTAMINATION_KIND
+    assert rec["reason_class"] == "stable_branch_push"
+    assert rec["remote"] == "prgs"
+    assert rec["ref"] == "master"
+    assert rec["cleared_by_reconciler"] is False
+    # secret must never survive into the durable record
+    assert "tok@" not in rec["command_summary"]
+    assert "***@" in rec["command_summary"]
+
+
+# ── AC4: fail-closed gate on gated mutations ─────────────────────────────────
+
+def _marker():
+    return guard.build_contamination_record(
+        reason_class="stable_branch_push",
+        command_redacted="git push prgs master",
+        remote="prgs",
+        ref="master",
+        role="author",
+    )
+
+
+def test_gate_blocks_gated_mutations_for_author():
+    marker = _marker()
+    for task in ("create_pr", "merge_pr", "close_issue", "review_pr",
+                 "submit_pr_review", "commit_files", "close_pr"):
+        gate = guard.assess_contamination_gate(marker, task=task, actual_role="author")
+        assert gate["block"] is True, task
+        assert gate["reasons"]
+
+
+def test_gate_allows_comment_and_lock_for_handoff():
+    marker = _marker()
+    for task in ("comment_issue", "lock_issue", "create_issue", "mark_issue"):
+        gate = guard.assess_contamination_gate(marker, task=task, actual_role="author")
+        assert gate["block"] is False, task
+
+
+def test_gate_exempts_reconciler_audit_path():
+    marker = _marker()
+    gate = guard.assess_contamination_gate(marker, task="close_pr", actual_role="reconciler")
+    assert gate["block"] is False
+
+
+def test_gate_no_marker_allows_everything():
+    gate = guard.assess_contamination_gate(None, task="merge_pr", actual_role="merger")
+    assert gate["block"] is False
+
+
+def test_gate_cleared_marker_allows_everything():
+    marker = _marker()
+    marker["cleared_by_reconciler"] = True
+    gate = guard.assess_contamination_gate(marker, task="merge_pr", actual_role="merger")
+    assert gate["block"] is False
+
+
+def test_same_worker_cannot_self_clear_by_role():
+    # A merger/reviewer/author role is still gated — only reconciler is exempt.
+    marker = _marker()
+    for role in ("author", "reviewer", "merger"):
+        gate = guard.assess_contamination_gate(marker, task="merge_pr", actual_role=role)
+        assert gate["block"] is True, role
+
+
+def test_format_gate_error_mentions_issue():
+    marker = _marker()
+    gate = guard.assess_contamination_gate(marker, task="merge_pr", actual_role="merger")
+    msg = guard.format_contamination_gate_error(gate)
+    assert "#671" in msg
+    assert "contaminat" in msg.lower()
+
+
+# ── redaction unit coverage ──────────────────────────────────────────────────
+
+def test_redact_url_userinfo():
+    out = guard.redact_command("git push https://bob:secretpat@host/o/r.git master")
+    assert "secretpat" not in out
+    assert "***@" in out
+    assert "master" in out  # structure preserved for audit
+
+
+def test_redact_token_assignment():
+    out = guard.redact_command("GITEA_TOKEN=abcdef123456 git push prgs master")
+    assert "abcdef123456" not in out
+    assert "GITEA_TOKEN=***" in out
+
+
+def test_redact_empty():
+    assert guard.redact_command(None) == ""
+    assert guard.redact_command("") == ""
+
+
+# ── detect_stable_push over iterables ────────────────────────────────────────
+
+def test_detect_stable_push_iterable_finds_first_contamination():
+    cmds = ["git status", "git push prgs master", "echo done"]
+    res = guard.detect_stable_push(cmds)
+    assert res["contamination"] is True
+
+
+def test_detect_stable_push_iterable_all_safe():
+    cmds = ["git status", "git push prgs feature/x", "git fetch prgs"]
+    res = guard.detect_stable_push(cmds)
+    assert res["contamination"] is False