feat(coverage): deterministic test-coverage gate on deploy-staging->deploy edge (ORCH-027)

Introduce a deterministic (no-LLM) coverage sub-gate that blocks coverage
degradation before a task branch merges into `main`. Existing gates judge only by
the FACT of passing (check_ci_green / check_tests_passed / merge-gate re-test), not
by completeness — so a batch autonomous run (ORCH-088) silently erodes coverage.

Pattern mirrors the security-gate (ORCH-022): leaf src/coverage_gate.py (never-raise)
+ thin check_coverage_gate in QG_CHECKS + _handle_coverage_gate splice in advance_stage,
run AFTER merge-gate (measured on the caught-up HEAD that lands in main) and BEFORE
image-freshness (fail before the expensive docker rebuild).

- measure_coverage: pytest --cov=src --cov-report=json in the per-branch worktree ->
  line coverage %; None on tool error -> fail-open + WARNING by default (FR-6).
- compute_coverage_verdict (pure): absolute | baseline | both + epsilon (NFR-4 anti-flap);
  baseline None -> bootstrap (absolute-only).
- coverage_baseline DB table (additive, CREATE TABLE IF NOT EXISTS) + ratchet-up in
  _handle_merge_verify (deploy->done): atomic compare-and-set under merge-lease, never
  decreases; bootstrap on first merge.
- Artefact 18-coverage-report.md (coverage_status: frontmatter, single source of truth);
  GET /queue `coverage` block; FAIL -> Telegram; optional POST /coverage/baseline override.
- Flags ORCH_COVERAGE_* (kill-switch + self-hosting-only scope) -> enduro untouched;
  STAGE_TRANSITIONS / existing check_* / verdict keys byte-for-byte unchanged (NFR-5/AC-8).
- pytest-cov==5.0.0 added to requirements.txt.

Tests: tests/test_coverage_gate.py (TC-01..TC-15). Frozen QG-registry anti-regress
tests + deploy-staging edge tests updated for the new sub-gate. Full suite green.

Docs: README / adr-0029 / PIPELINE_DOCS / 18-coverage-report.md template (architecture
stage) + CHANGELOG / CLAUDE.md / .env.example (this PR).

Refs: ORCH-027
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/config.py

@@ -259,6 +259,38 @@ class Settings(BaseSettings):
     security_dep_audit_fail_closed: bool = False
     security_secrets_block: bool = True
 
+    # ORCH-027: deterministic test-coverage gate on the deploy-staging -> deploy edge
+    # (AFTER the merge-gate, BEFORE image-freshness). Measures line coverage of src/
+    # under pytest-cov in the per-branch worktree, compares to an absolute floor and/or
+    # the ratchet baseline of `main`, and FAILs (rollback to development + developer
+    # retry) on degradation. Leaf src/coverage_gate.py (never-raise); machine verdict in
+    # 18-coverage-report.md frontmatter (coverage_status:). See ADR-001-coverage-gate.md.
+    #   coverage_gate_enabled     -> SINGLE kill-switch; False -> pipeline 1:1 as before
+    #                                ORCH-027 for everyone. Env ORCH_COVERAGE_GATE_ENABLED.
+    #   coverage_gate_repos       -> CSV of repos where the gate is REAL; empty -> only
+    #                                the self-hosting repo (orchestrator). Mirrors
+    #                                security_gate_repos / image_freshness_repos.
+    #   coverage_min_percent      -> absolute floor (% line coverage) for policy
+    #                                absolute/both. Default 0.0 -> safe rollout: the
+    #                                ratchet baseline drives no-regression, the floor
+    #                                never false-fails day one.
+    #   coverage_policy           -> absolute | baseline | both (default both): which
+    #                                condition(s) must hold (D3).
+    #   coverage_epsilon          -> small non-negative noise tolerance (%) so jitter at
+    #                                the boundary does not bounce a task (NFR-4).
+    #   coverage_tool_fail_closed -> strict mode: a coverage-tool error -> FAIL instead
+    #                                of the default fail-open + warning (FR-6). Default
+    #                                False (anti-loop, precedent ORCH-061/022).
+    #   coverage_run_timeout_s    -> wall-clock budget for the pytest --cov run (mirrors
+    #                                merge_retest_timeout_s / security_scan_timeout_s).
+    coverage_gate_enabled: bool = True
+    coverage_gate_repos: str = ""
+    coverage_min_percent: float = 0.0
+    coverage_policy: str = "both"
+    coverage_epsilon: float = 0.5
+    coverage_tool_fail_closed: bool = False
+    coverage_run_timeout_s: int = 900
+
     # ORCH-061: tolerate KNOWN sandbox-infra FAILs (C9a/C9b) in the staging suite.
     # The self-hosting deploy-staging stage looped because scripts/staging_check.py
     # exited non-zero on ANY failed check, so two infra-only failures (sandbox bot

src/coverage_gate.py

@@ -0,0 +1,616 @@
+"""Coverage-gate core (ORCH-027): deterministic test-coverage gate before merge.
+
+Background
+----------
+The orchestrator runs autonomous development: the ``developer`` agent writes code
+with no human filter, and on ``testing`` the ``tester`` agent decides for itself
+whether the tests are enough. The existing test gates judge only by the FACT of
+passing, never by COMPLETENESS: ``check_ci_green`` and ``check_tests_passed`` and
+the merge-gate re-test all look at a pytest exit code. None of them notices "300
+lines of new code, 0 tests". Across a batch autonomous run (ORCH-088) that means a
+monotonic erosion of coverage — every task shaves a corner on tests and the project
+silently loses testability.
+
+This module provides the deterministic (no-LLM) primitives that the quality-gate
+``check_coverage_gate`` (src/qg/checks.py) composes on the ``deploy-staging ->
+deploy`` edge — run **AFTER the merge-gate** (so coverage is measured on the
+caught-up HEAD that actually lands in ``main``) and **BEFORE image-freshness** (fail
+before the expensive docker rebuild), mirroring the security-gate (ORCH-022):
+
+  * ``measure_coverage``          -> run ``pytest --cov=src`` in the per-branch
+                                     worktree (offline) -> line coverage ``%`` or
+                                     ``None`` on tool error.
+  * ``compute_coverage_verdict``  -> pure: compare (measured, baseline, floor) under
+                                     a policy + epsilon -> ``(ok, reason)``.
+  * ``write_coverage_report`` / ``parse_coverage_status`` -> write the
+    ``18-coverage-report.md`` artefact and read its machine verdict back (single
+    source of truth: the gate returns exactly the frontmatter it wrote, AC-9).
+  * ``ratchet_baseline_on_merge`` -> on a CONFIRMED merge (``_handle_merge_verify``,
+    ``deploy -> done`` edge) raise the per-repo baseline UP from the merged branch's
+    measured coverage (atomic compare-and-set, never decreases — FR-4 / D5).
+  * ``check_coverage_gate``       -> the orchestrating entry the QG wrapper delegates
+                                     to.
+
+Invariants (ADR-001 §7, never broken):
+  * **Tool error -> fail-open + WARNING by default** (FR-6/AC-6): a coverage-tool
+    failure / unparseable metric degrades fail-open (anti-loop, precedent
+    ORCH-061/022 dep-audit); ``coverage_tool_fail_closed`` flips it to strict.
+  * **never-raise** (AC-7): any internal error is swallowed; an exception never
+    escapes into ``advance_stage``.
+  * **Baseline never decreases** (FR-4): the ratchet is an atomic SQL compare-and-set
+    under the held merge-lease (ORCH-043), so two parallel merges can never lower or
+    lose the value.
+  * **Self-hosting safety** (AC-7): the gate only measures / reads / writes the
+    artefact / decides. It never calls the deploy hook, never restarts the prod
+    container, never pushes / force-pushes ``main``.
+
+This module is a **leaf**: it imports only ``config`` / ``git_worktree`` and lazily
+``qg.checks.is_self_hosting_repo`` / ``db`` / ``notifications``; it never imports
+``stage_engine``.
+"""
+
+import json
+import logging
+import os
+import subprocess
+
+from .config import settings
+from .git_worktree import ensure_worktree, get_worktree_path
+
+logger = logging.getLogger("orchestrator.coverage_gate")
+
+
+# ---------------------------------------------------------------------------
+# Conditionality (mirrors security_gate_applies / _merge_gate_applies)
+# ---------------------------------------------------------------------------
+def coverage_gate_applies(repo: str) -> bool:
+    """Whether the coverage-gate is REAL for this repo (conditional rollout).
+
+    Mirrors the ORCH-22 / ORCH-43 / ORCH-58 pattern:
+      * ``coverage_gate_enabled=False`` -> always False (kill-switch; pipeline is
+        1:1 as before ORCH-027 for everyone).
+      * ``coverage_gate_repos`` (CSV) non-empty -> real only for the listed repos.
+      * empty CSV -> real ONLY for the self-hosting repo (``orchestrator``).
+    Never raises (AC-7): any error -> False (the safe no-op default).
+    """
+    try:
+        if not settings.coverage_gate_enabled:
+            return False
+        raw = (settings.coverage_gate_repos or "").strip()
+        if raw:
+            allowed = {r.strip().lower() for r in raw.split(",") if r.strip()}
+            return (repo or "").strip().lower() in allowed
+        # Lazy import keeps this module a leaf (no qg import at module load).
+        from .qg.checks import is_self_hosting_repo
+        return is_self_hosting_repo(repo)
+    except Exception as e:  # noqa: BLE001 - never-raise contract
+        logger.warning("coverage_gate_applies error for %s: %s", repo, e)
+        return False
+
+
+# ---------------------------------------------------------------------------
+# Measurement (pytest --cov=src in the per-branch worktree) — FR-1 / D2
+# ---------------------------------------------------------------------------
+def parse_coverage_percent(data) -> float | None:
+    """Pure: extract ``totals.percent_covered`` (line coverage ``%``) from a
+    coverage.py JSON dict. Returns ``None`` if the shape is missing / unparseable.
+    Never raises.
+    """
+    try:
+        if not isinstance(data, dict):
+            return None
+        totals = data.get("totals")
+        if not isinstance(totals, dict):
+            return None
+        pct = totals.get("percent_covered")
+        if pct is None:
+            return None
+        return float(pct)
+    except (TypeError, ValueError):
+        return None
+
+
+def measure_coverage(repo: str, branch: str) -> float | None:
+    """Run ``pytest --cov=src`` in the per-branch worktree -> line coverage ``%``.
+
+    Scope is ``src/`` only (the tests themselves are out of scope, BRD §«Вне
+    объёма»). Offline — coverage needs no network. The measurer is intentionally
+    encapsulated here so the pure decision logic and the baseline storage are
+    stack-agnostic (a future jest/jacoco measurer is a new ``measure_*`` branch,
+    BR-6).
+
+    The coverage metric is read from the ``--cov-report=json`` file regardless of
+    the pytest exit code: a non-zero exit because of *failing tests* is already
+    caught upstream (``check_ci_green`` / merge-gate re-test), and a partial run
+    still produces a meaningful coverage JSON. A genuine tool error (missing
+    plugin / timeout / no JSON / unparseable) -> ``None`` (the caller degrades
+    fail-open by default, FR-6). Never raises (AC-7).
+    """
+    try:
+        wt = ensure_worktree(repo, branch)
+    except Exception as e:  # noqa: BLE001 - never-raise contract
+        logger.warning("measure_coverage: worktree error for %s/%s: %s", repo, branch, e)
+        return None
+
+    cov_json = os.path.join(wt, ".coverage-report.json")
+    # Remove a stale report so we never read a previous pass's metric.
+    try:
+        if os.path.isfile(cov_json):
+            os.remove(cov_json)
+    except OSError:
+        pass
+
+    cmd = [
+        "python", "-m", "pytest", "tests/",
+        "--cov=src",
+        f"--cov-report=json:{cov_json}",
+        "--cov-report=",  # suppress the terminal cov report (json only)
+        "-q",
+    ]
+    timeout = settings.coverage_run_timeout_s
+    try:
+        subprocess.run(cmd, cwd=wt, capture_output=True, text=True, timeout=timeout)
+    except subprocess.TimeoutExpired:
+        logger.warning(
+            "measure_coverage: pytest --cov timed out after %ss for %s/%s",
+            timeout, repo, branch,
+        )
+        return None
+    except FileNotFoundError:
+        logger.warning(
+            "measure_coverage: pytest / pytest-cov not available for %s/%s", repo, branch
+        )
+        return None
+    except (subprocess.SubprocessError, OSError) as e:
+        logger.warning("measure_coverage: pytest --cov error for %s/%s: %s", repo, branch, e)
+        return None
+
+    data = None
+    try:
+        if not os.path.isfile(cov_json):
+            logger.warning(
+                "measure_coverage: no coverage json produced for %s/%s", repo, branch
+            )
+            return None
+        with open(cov_json, "r", encoding="utf-8") as f:
+            data = json.load(f)
+    except (OSError, ValueError) as e:
+        logger.warning(
+            "measure_coverage: cannot parse coverage json for %s/%s: %s", repo, branch, e
+        )
+        return None
+    finally:
+        try:
+            if os.path.isfile(cov_json):
+                os.remove(cov_json)
+        except OSError:
+            pass
+
+    return parse_coverage_percent(data)
+
+
+# ---------------------------------------------------------------------------
+# Pure decision (FR-2 / D3) — the core of the unit tests
+# ---------------------------------------------------------------------------
+def compute_coverage_verdict(measured, baseline, floor, policy, epsilon) -> tuple[bool, str]:
+    """Pure: decide PASS/FAIL from (measured, baseline, floor, policy, epsilon).
+
+    Deterministic, no LLM, no I/O. Returns ``(ok: bool, reason: str)``.
+
+      * ``policy = "absolute"`` -> PASS ⇔ ``measured >= floor - epsilon``.
+      * ``policy = "baseline"`` -> PASS ⇔ ``measured >= baseline - epsilon``.
+      * ``policy = "both"`` (default) -> PASS ⇔ BOTH conditions hold.
+      * ``baseline is None`` (no stored baseline / bootstrap) -> the baseline
+        condition does NOT apply (cannot regress against nothing); only the
+        absolute part decides. For ``policy = "baseline"`` with no baseline this is
+        a bootstrap PASS (the measured value seeds the baseline at merge, D5).
+      * ``epsilon`` — a small non-negative tolerance so jitter at the boundary does
+        not bounce a task (NFR-4).
+
+    Never raises: bad inputs -> ``(False, reason)`` (a verdict cannot be computed ->
+    conservative FAIL for the pure function; the orchestrating entry maps a *tool*
+    error to fail-open separately).
+    """
+    try:
+        pol = (policy or "both").strip().lower()
+        eps = max(0.0, float(epsilon if epsilon is not None else 0.0))
+        m = float(measured)
+    except (TypeError, ValueError) as e:
+        return False, f"coverage verdict: bad inputs ({e})"
+
+    abs_applicable = pol in ("absolute", "both")
+    base_applicable = pol in ("baseline", "both") and baseline is not None
+
+    checks: list[str] = []
+    ok = True
+
+    if abs_applicable:
+        try:
+            f = float(floor if floor is not None else 0.0)
+        except (TypeError, ValueError):
+            f = 0.0
+        abs_ok = m >= f - eps
+        checks.append(
+            f"absolute {m:.2f}% >= floor {f:.2f}%-eps{eps:.2f} -> "
+            f"{'PASS' if abs_ok else 'FAIL'}"
+        )
+        ok = ok and abs_ok
+
+    if base_applicable:
+        b = float(baseline)
+        base_ok = m >= b - eps
+        checks.append(
+            f"baseline {m:.2f}% >= base {b:.2f}%-eps{eps:.2f} -> "
+            f"{'PASS' if base_ok else 'FAIL'}"
+        )
+        ok = ok and base_ok
+    elif pol in ("baseline", "both") and baseline is None:
+        checks.append("baseline N/A (bootstrap — no stored baseline)")
+
+    body = "; ".join(checks) if checks else "no applicable condition (bootstrap) -> PASS"
+    reason = f"measured={m:.2f}% policy={pol} eps={eps:.2f}: {body}"
+    return ok, reason
+
+
+def compute_delta(measured, baseline, floor) -> float:
+    """Pure: signed ``measured - max(applicable references)`` (%, 2 decimals).
+
+    References are the present ones among ``baseline`` / ``floor``. With neither ->
+    ``0.0``. Never raises.
+    """
+    try:
+        m = float(measured)
+        refs = []
+        if baseline is not None:
+            refs.append(float(baseline))
+        if floor is not None:
+            refs.append(float(floor))
+        if not refs:
+            return 0.0
+        return round(m - max(refs), 2)
+    except (TypeError, ValueError):
+        return 0.0
+
+
+# ---------------------------------------------------------------------------
+# Artefact: write the report, read the machine verdict back (FR-7 / D7 / AC-9)
+# ---------------------------------------------------------------------------
+def _report_rel(work_item_id: str) -> str:
+    return f"docs/work-items/{work_item_id}/18-coverage-report.md"
+
+
+def _report_path(repo: str, work_item_id: str, branch: str) -> str:
+    """Absolute path of 18-coverage-report.md inside the task worktree."""
+    try:
+        wt = get_worktree_path(repo, branch)
+        if not os.path.isdir(wt):
+            wt = ensure_worktree(repo, branch)
+    except Exception:  # noqa: BLE001 - never-raise; fall back to shared clone
+        wt = os.path.join(settings.repos_dir, repo)
+    return os.path.join(wt, _report_rel(work_item_id))
+
+
+def _num(v) -> str:
+    """Render a numeric field with 2 decimals, or empty for None/unparseable."""
+    if v is None:
+        return ""
+    try:
+        return f"{float(v):.2f}"
+    except (TypeError, ValueError):
+        return ""
+
+
+def render_coverage_report(work_item_id: str, fields: dict) -> str:
+    """Pure: render the 18-coverage-report.md content (frontmatter + body).
+
+    The machine verdict lives ONLY in the YAML frontmatter ``coverage_status:``
+    (canon, regiser-sensitive); ``measured_coverage`` is the single source of truth
+    for the ratchet (D5). Never raises.
+    """
+    baseline = fields.get("baseline")
+    baseline_str = "" if baseline is None else _num(baseline)
+    return (
+        "---\n"
+        f"coverage_status: {fields.get('coverage_status', 'FAIL')}\n"
+        f"work_item: {work_item_id}\n"
+        f"measured_coverage: {_num(fields.get('measured_coverage'))}\n"
+        f"baseline: {baseline_str}\n"
+        f"floor: {_num(fields.get('floor'))}\n"
+        f"policy: {fields.get('policy', 'both')}\n"
+        f"epsilon: {_num(fields.get('epsilon'))}\n"
+        f"delta: {_num(fields.get('delta'))}\n"
+        "---\n"
+        f"# Coverage Report — {work_item_id}\n\n"
+        "Детерминированный гейт покрытия (ORCH-027) — под-гейт ребра "
+        "`deploy-staging→deploy` (ПОСЛЕ merge-gate, ДО image-freshness). Машинный "
+        "вердикт читается ТОЛЬКО из `coverage_status:` frontmatter выше.\n\n"
+        "## Verdict\n"
+        f"{fields.get('reason', '')}\n\n"
+        "## Measurement\n"
+        f"{fields.get('measurement', '')}\n\n"
+        "## Policy\n"
+        f"{fields.get('policy_detail', '')}\n"
+    )
+
+
+def write_coverage_report(repo: str, work_item_id: str, branch: str, fields: dict) -> str:
+    """Write 18-coverage-report.md into the task worktree; return its path.
+
+    Best-effort / never-raise: a write error is logged and the path is still
+    returned (the caller's read-back then fails closed)."""
+    path = _report_path(repo, work_item_id, branch)
+    try:
+        os.makedirs(os.path.dirname(path), exist_ok=True)
+        with open(path, "w", encoding="utf-8") as f:
+            f.write(render_coverage_report(work_item_id, fields))
+    except OSError as e:
+        logger.error("write_coverage_report error for %s/%s: %s", repo, work_item_id, e)
+    return path
+
+
+def parse_coverage_status(content: str) -> tuple[bool, str]:
+    """Map a 18-coverage-report.md body to a quality-gate verdict by reading ONLY
+    the machine-readable ``coverage_status:`` YAML frontmatter — never the prose.
+
+    Mirrors ``parse_security_status`` (canon: machine verdict only from frontmatter,
+    AC-9). The negative token (FAIL) is authoritative (checked first). Returns:
+      * ``coverage_status: PASS`` -> ``(True,  "Coverage status: PASS")``
+      * ``coverage_status: FAIL`` -> ``(False, "Coverage status: FAIL")``
+      * missing field / no frontmatter / bad YAML -> ``(False, <reason>)``.
+
+    Parse delegated to the unified ``frontmatter.parse_frontmatter`` primitive
+    (ORCH-052c single source of YAML-frontmatter logic).
+    """
+    from .frontmatter import parse_frontmatter
+
+    parse = parse_frontmatter(content)
+    if parse.yaml_error is not None:
+        return False, f"Invalid YAML frontmatter in coverage report: {parse.yaml_error}"
+    status = None
+    if parse.has_block and not parse.malformed:
+        status = str(parse.data.get("coverage_status", "")).upper().strip()
+    if status == "FAIL":
+        return False, "Coverage status: FAIL"
+    if status == "PASS":
+        return True, "Coverage status: PASS"
+    return False, f"No machine-readable coverage_status in frontmatter (got: {status!r})"
+
+
+def read_measured_coverage(content: str) -> float | None:
+    """Read ``measured_coverage`` (%, float) from a 18-coverage-report.md body via
+    the unified frontmatter parser. ``None`` when absent / unparseable (ratchet then
+    no-ops). Never raises.
+    """
+    try:
+        from .frontmatter import parse_frontmatter
+        parse = parse_frontmatter(content)
+        if not parse.has_block or parse.malformed:
+            return None
+        raw = parse.data.get("measured_coverage")
+        if raw is None or (isinstance(raw, str) and not raw.strip()):
+            return None
+        return float(raw)
+    except (TypeError, ValueError):
+        return None
+    except Exception as e:  # noqa: BLE001 - never-raise
+        logger.warning("read_measured_coverage error: %s", e)
+        return None
+
+
+def _error_fields(work_item_id, floor, policy, epsilon, baseline, *, fail_closed: bool) -> dict:
+    """Build the report fields for a tool-error pass (FR-6)."""
+    status = "FAIL" if fail_closed else "PASS"
+    mode = "fail-closed (FAIL)" if fail_closed else "fail-open (WARNING)"
+    return {
+        "coverage_status": status,
+        "measured_coverage": None,
+        "baseline": baseline,
+        "floor": floor,
+        "policy": policy,
+        "epsilon": epsilon,
+        "delta": None,
+        "reason": f"coverage measurement failed -> {mode}",
+        "measurement": (
+            "coverage tool error / unparseable metric "
+            f"(coverage_tool_fail_closed={fail_closed})"
+        ),
+        "policy_detail": f"policy={policy}, floor={floor}, baseline={baseline}, epsilon={epsilon}",
+    }
+
+
+# ---------------------------------------------------------------------------
+# Ratchet baseline UP on a confirmed merge (FR-4 / D5)
+# ---------------------------------------------------------------------------
+def ratchet_baseline_on_merge(repo: str, work_item_id: str, branch: str, sha: str | None = None) -> bool:
+    """Raise the per-repo coverage baseline UP from the merged branch's measured
+    coverage. Called from ``_handle_merge_verify`` (deploy -> done edge) AFTER the
+    merge is confirmed and BEFORE the task advances to ``done`` (D5).
+
+    Reads the measured value from ``18-coverage-report.md`` (single source of truth
+    — the exact metric the gate wrote on the deploy-staging->deploy edge) and applies
+    an atomic compare-and-set (``db.ratchet_coverage_baseline``) that never lowers
+    the baseline. Bootstrap: the first applicable merge seeds the baseline.
+
+    Returns True iff the baseline was inserted/raised. never-raise (AC-7): any error
+    -> False (observability best-effort; a ratchet failure must never break the
+    deploy->done path).
+    """
+    try:
+        if not coverage_gate_applies(repo):
+            return False
+        path = _report_path(repo, work_item_id, branch)
+        try:
+            with open(path, "r", encoding="utf-8") as f:
+                content = f.read()
+        except OSError as e:
+            logger.warning(
+                "ratchet: cannot read coverage report for %s/%s: %s", repo, work_item_id, e
+            )
+            return False
+        measured = read_measured_coverage(content)
+        if measured is None:
+            logger.warning(
+                "ratchet: no measured_coverage in report for %s/%s", repo, work_item_id
+            )
+            return False
+        from . import db
+        updated = db.ratchet_coverage_baseline(repo, measured, sha)
+        if updated:
+            logger.info(
+                "coverage baseline ratcheted for %s -> %.2f%% (sha=%s)", repo, measured, sha
+            )
+        else:
+            logger.info(
+                "coverage baseline unchanged for %s (measured %.2f%% not above current)",
+                repo, measured,
+            )
+        return updated
+    except Exception as e:  # noqa: BLE001 - never-raise contract
+        logger.error("ratchet_baseline_on_merge error for %s/%s: %s", repo, work_item_id, e)
+        return False
+
+
+# ---------------------------------------------------------------------------
+# Orchestrating entry — delegated to by qg.checks.check_coverage_gate
+# ---------------------------------------------------------------------------
+def check_coverage_gate(repo: str, work_item_id: str, branch: str) -> tuple[bool, str]:
+    """ORCH-027 coverage-gate on the deploy-staging -> deploy edge (after merge-gate).
+
+    Deterministic, no LLM. Algorithm (ADR-001 D1..D7):
+      1. Conditionality: ``coverage_gate_enabled=False`` -> ``(True, "...disabled")``;
+         a repo the gate is not real for -> ``(True, "coverage-gate N/A for <repo>")``.
+      2. ``measure_coverage`` (pytest --cov=src in the worktree). ``None`` (tool
+         error) -> fail-open + WARNING by default (``coverage_tool_fail_closed``
+         flips to FAIL), FR-6.
+      3. ``compute_coverage_verdict`` -> write ``18-coverage-report.md`` -> read the
+         verdict BACK via ``parse_coverage_status`` (single source of truth: the
+         returned verdict == the artefact frontmatter, AC-9).
+      4. FAIL -> ``(False, reason)`` (engine rolls back to ``development`` + releases
+         the merge lease); PASS -> ``(True, reason)`` (engine proceeds to
+         image-freshness).
+
+    Never-raise (AC-7): any internal error -> a (bool, reason) pair following the
+    fail-open default (so an unexpected fault never wedges the autonomous pipeline),
+    unless ``coverage_tool_fail_closed`` is set.
+    """
+    floor = getattr(settings, "coverage_min_percent", 0.0)
+    policy = getattr(settings, "coverage_policy", "both")
+    epsilon = getattr(settings, "coverage_epsilon", 0.5)
+    try:
+        if not settings.coverage_gate_enabled:
+            return True, "coverage-gate disabled"
+        if not coverage_gate_applies(repo):
+            return True, f"coverage-gate N/A for {repo}"
+
+        from . import db
+        try:
+            baseline = db.get_coverage_baseline(repo)
+        except Exception as e:  # noqa: BLE001 - baseline read best-effort
+            logger.warning("coverage-gate: baseline read error for %s: %s", repo, e)
+            baseline = None
+
+        measured = measure_coverage(repo, branch)
+        if measured is None:
+            fail_closed = bool(settings.coverage_tool_fail_closed)
+            fields = _error_fields(
+                work_item_id, floor, policy, epsilon, baseline, fail_closed=fail_closed
+            )
+            write_coverage_report(repo, work_item_id, branch, fields)
+            if fail_closed:
+                logger.warning(
+                    "coverage-gate %s/%s: measurement failed -> fail-CLOSED (FAIL)",
+                    repo, work_item_id,
+                )
+                return False, "coverage-gate fail-closed: measurement failed (tool error)"
+            logger.warning(
+                "coverage-gate %s/%s: measurement failed -> fail-OPEN + WARNING",
+                repo, work_item_id,
+            )
+            return True, "coverage-gate fail-open (WARNING): measurement failed (tool error)"
+
+        ok, reason = compute_coverage_verdict(measured, baseline, floor, policy, epsilon)
+        delta = compute_delta(measured, baseline, floor)
+        fields = {
+            "coverage_status": "PASS" if ok else "FAIL",
+            "measured_coverage": measured,
+            "baseline": baseline,
+            "floor": floor,
+            "policy": policy,
+            "epsilon": epsilon,
+            "delta": delta,
+            "reason": reason,
+            "measurement": f"pytest --cov=src: line coverage src/ = {measured:.2f}%",
+            "policy_detail": (
+                f"policy={policy}, floor={floor}%, "
+                f"baseline={'bootstrap' if baseline is None else f'{baseline:.2f}%'}, "
+                f"epsilon={epsilon}%"
+            ),
+        }
+        path = write_coverage_report(repo, work_item_id, branch, fields)
+
+        # Read the machine verdict back from the artefact we just wrote — so the
+        # returned (bool, reason) is guaranteed == the YAML frontmatter (AC-9).
+        try:
+            with open(path, "r", encoding="utf-8") as f:
+                content = f.read()
+        except OSError as e:
+            return False, f"cannot read coverage report (fail-closed): {e}"
+        verdict_ok, _v = parse_coverage_status(content)
+
+        if verdict_ok:
+            logger.info("coverage-gate passed for %s/%s: %s", repo, work_item_id, reason)
+            return True, f"coverage OK ({reason})"
+
+        # FAIL -> surface loudly (Telegram with the clickable issue number, FR-7).
+        try:
+            from .notifications import send_telegram, link_for
+            base_str = "n/a" if baseline is None else f"{baseline:.2f}%"
+            send_telegram(
+                f"\U0001f4c9 {link_for(work_item_id)}: coverage-гейт FAIL — измерено "
+                f"{measured:.2f}% (floor {floor}%, baseline {base_str}, "
+                f"delta {delta:+.2f}%). Откат на development для доработки тестов."
+            )
+        except Exception as e:  # noqa: BLE001 - telegram best-effort
+            logger.warning("coverage-gate FAIL telegram failed: %s", e)
+        return False, reason
+    except Exception as e:  # noqa: BLE001 - never-raise contract (AC-7)
+        logger.error("check_coverage_gate error for %s/%s: %s", repo, branch, e)
+        # An unexpected internal error follows the fail-open default (anti-loop): a
+        # coverage-tool/logic fault must not wedge the autonomous pipeline. The
+        # operator can flip coverage_tool_fail_closed to make it strict.
+        try:
+            if settings.coverage_tool_fail_closed:
+                return False, f"coverage-gate error (fail-closed): {e}"
+        except Exception:  # noqa: BLE001
+            pass
+        return True, f"coverage-gate error (fail-open): {e}"
+
+
+# ---------------------------------------------------------------------------
+# Observability snapshot for GET /queue (FR-7 / AC-9)
+# ---------------------------------------------------------------------------
+def snapshot() -> dict:
+    """Read-only coverage-gate summary for GET /queue (FR-7 / AC-9).
+
+    Additive block; existing /queue keys are untouched. never-raise: any error ->
+    a minimal dict with the flags.
+    """
+    try:
+        enabled = bool(settings.coverage_gate_enabled)
+    except Exception:  # noqa: BLE001
+        enabled = False
+    out = {
+        "enabled": enabled,
+        "repos": getattr(settings, "coverage_gate_repos", "") or "",
+        "policy": getattr(settings, "coverage_policy", "both"),
+        "floor": getattr(settings, "coverage_min_percent", 0.0),
+        "epsilon": getattr(settings, "coverage_epsilon", 0.5),
+        "fail_closed": bool(getattr(settings, "coverage_tool_fail_closed", False)),
+        "baselines": {},
+    }
+    try:
+        from . import db
+        out["baselines"] = db.all_coverage_baselines()
+    except Exception as e:  # noqa: BLE001 - never-raise -> empty baselines
+        logger.warning("coverage snapshot baselines error: %s", e)
+    return out

src/db.py

@@ -199,10 +199,138 @@ def init_db():
         CREATE INDEX IF NOT EXISTS idx_repo_freeze_active
             ON repo_freeze (repo, cleared_at);
     """)
+    # ORCH-027 (FR-4, ADR-001 D4): additive per-repo coverage baseline for the
+    # coverage-gate ratchet. One row per repo; the baseline is monotonically
+    # non-decreasing via ratchet_coverage_baseline (atomic compare-and-set). Purely
+    # ADDITIVE (CREATE TABLE IF NOT EXISTS, pattern repo_freeze/job_deps) ->
+    # idempotent, restart-safe on the shared prod DB; existing tables untouched
+    # (NFR-5). See docs/work-items/ORCH-027/08-data-requirements.md.
+    conn.executescript("""
+        CREATE TABLE IF NOT EXISTS coverage_baseline (
+            repo        TEXT PRIMARY KEY,
+            coverage    REAL NOT NULL,
+            source_sha  TEXT,
+            updated_at  TEXT NOT NULL DEFAULT (datetime('now'))
+        );
+    """)
     conn.commit()
     conn.close()
 
 
+def get_coverage_baseline(repo: str) -> float | None:
+    """ORCH-027: read the per-repo coverage baseline (%, line coverage).
+
+    Returns ``None`` when no baseline is stored yet (bootstrap mode — the gate then
+    decides on the absolute floor only, D3). Raises only on a real DB error (the
+    coverage_gate leaf caller wraps this in its never-raise contract).
+    """
+    if not repo:
+        return None
+    conn = get_db()
+    try:
+        row = conn.execute(
+            "SELECT coverage FROM coverage_baseline WHERE repo = ?", (repo,)
+        ).fetchone()
+    finally:
+        conn.close()
+    if row is None:
+        return None
+    try:
+        return float(row["coverage"])
+    except (TypeError, ValueError):
+        return None
+
+
+def ratchet_coverage_baseline(repo: str, coverage: float, sha: str | None = None) -> bool:
+    """ORCH-027 (FR-4, D5): raise the per-repo coverage baseline UP, never down.
+
+    Atomic compare-and-set: ``UPDATE ... WHERE coverage <= ?`` (the baseline never
+    decreases — an equal value is an idempotent no-harm re-stamp), or ``INSERT`` when
+    no row exists yet (bootstrap). Under the held merge-lease (ORCH-043) plus this
+    single-statement guard, two parallel merges can never lower or lose the value.
+    Returns True iff a row was inserted or raised.
+    """
+    if not repo:
+        return False
+    try:
+        cov = float(coverage)
+    except (TypeError, ValueError):
+        return False
+    conn = get_db()
+    try:
+        cur = conn.execute(
+            "UPDATE coverage_baseline "
+            "SET coverage = ?, source_sha = ?, updated_at = datetime('now') "
+            "WHERE repo = ? AND coverage <= ?",
+            (cov, sha, repo, cov),
+        )
+        changed = cur.rowcount or 0
+        if changed == 0:
+            # No row updated: either the row is absent (bootstrap INSERT) or the
+            # existing baseline is already higher (skip — never lower it).
+            exists = conn.execute(
+                "SELECT 1 FROM coverage_baseline WHERE repo = ?", (repo,)
+            ).fetchone()
+            if exists is None:
+                conn.execute(
+                    "INSERT INTO coverage_baseline (repo, coverage, source_sha, updated_at) "
+                    "VALUES (?, ?, ?, datetime('now'))",
+                    (repo, cov, sha),
+                )
+                changed = 1
+        conn.commit()
+        return bool(changed)
+    finally:
+        conn.close()
+
+
+def set_coverage_baseline(repo: str, coverage: float, sha: str | None = None) -> bool:
+    """ORCH-027 (D8): UNCONDITIONALLY set the per-repo coverage baseline.
+
+    For a legitimate one-off coverage drop (e.g. removing a large tested module) via
+    the manual ``POST /coverage/baseline`` override. Unlike ``ratchet_coverage_baseline``
+    this CAN lower the baseline. Returns True on success.
+    """
+    if not repo:
+        return False
+    try:
+        cov = float(coverage)
+    except (TypeError, ValueError):
+        return False
+    conn = get_db()
+    try:
+        conn.execute(
+            "INSERT INTO coverage_baseline (repo, coverage, source_sha, updated_at) "
+            "VALUES (?, ?, ?, datetime('now')) "
+            "ON CONFLICT(repo) DO UPDATE SET coverage = excluded.coverage, "
+            "source_sha = excluded.source_sha, updated_at = excluded.updated_at",
+            (repo, cov, sha),
+        )
+        conn.commit()
+        return True
+    finally:
+        conn.close()
+
+
+def all_coverage_baselines() -> dict:
+    """ORCH-027: all per-repo coverage baselines for the GET /queue snapshot."""
+    conn = get_db()
+    try:
+        rows = conn.execute(
+            "SELECT repo, coverage, source_sha, updated_at FROM coverage_baseline"
+        ).fetchall()
+    finally:
+        conn.close()
+    return {
+        r["repo"]: {
+            "coverage": r["coverage"],
+            "source_sha": r["source_sha"],
+            "updated_at": r["updated_at"],
+        }
+        for r in rows
+    }
+
+
 def _ensure_column(conn, table: str, column: str, decl: str):
     """Add a column to `table` if it does not already exist (idempotent migration)."""
     cols = [r[1] for r in conn.execute(f"PRAGMA table_info({table})").fetchall()]

src/main.py

@@ -170,6 +170,7 @@ async def queue():
     from . import merge_gate
     from . import task_deps
     from . import serial_gate
+    from . import coverage_gate
     from . import labels
     from . import cancel
     from .disk_watchdog import disk_watchdog
@@ -189,6 +190,9 @@ async def queue():
         # ORCH-088 (D9 / AC-10): per-repo serial-gate observability (read-only) —
         # active task, queued/waiting analyst-jobs, freeze state. Additive block.
         "serial_gate": serial_gate.snapshot(),
+        # ORCH-027 (FR-7 / AC-9): coverage-gate observability (read-only) —
+        # kill-switch, scope, policy/floor/epsilon, per-repo baselines. Additive block.
+        "coverage": coverage_gate.snapshot(),
         # ORCH-089 (D7): auto-mode-by-label observability (read-only) — kill-switch,
         # label names, scope. Additive block.
         "auto_labels": labels.snapshot(),
@@ -236,3 +240,23 @@ async def serial_gate_unfreeze(repo: str = ""):
         except Exception:
             pass
     return {"ok": True, "repo": repo, "cleared": cleared, "frozen": frozen}
+
+
+@app.post("/coverage/baseline")
+async def coverage_set_baseline(repo: str = "", value: float | None = None):
+    """ORCH-027 (D8): manually set/override the per-repo coverage baseline.
+
+    For a legitimate one-off coverage drop (e.g. removing a large tested module) the
+    operator sets the baseline directly here (by образцу ``POST /serial-gate/unfreeze``)
+    instead of waiting for the upward-only ratchet. Unlike the ratchet this CAN lower
+    the baseline. Alternative without this endpoint: temporarily flip
+    ``ORCH_COVERAGE_POLICY=absolute``.
+    """
+    from . import db
+    if not repo or not repo.strip():
+        return {"ok": False, "error": "missing 'repo'", "repo": repo}
+    if value is None:
+        return {"ok": False, "error": "missing 'value'", "repo": repo}
+    repo = repo.strip()
+    ok = db.set_coverage_baseline(repo, value, sha="manual-override")
+    return {"ok": ok, "repo": repo, "baseline": db.get_coverage_baseline(repo)}

src/qg/checks.py

@@ -755,6 +755,23 @@ def check_security_gate(repo: str, work_item_id: str, branch: str) -> tuple[bool
     return _impl(repo, work_item_id, branch)
 
 
+def check_coverage_gate(repo: str, work_item_id: str, branch: str) -> tuple[bool, str]:
+    """ORCH-027 coverage sub-gate (pytest --cov=src) on the deploy-staging -> deploy
+    edge, run AFTER the merge-gate (caught-up HEAD) and BEFORE image-freshness.
+
+    Thin registry wrapper that delegates to ``coverage_gate.check_coverage_gate``
+    (measure line coverage of src/, compare to floor/baseline under a policy, write/
+    read-back ``18-coverage-report.md``). The real logic lives in
+    ``src/coverage_gate.py`` (leaf module, never-raise, fail-open on a tool error by
+    default); importing it lazily here avoids an import cycle (coverage_gate imports
+    is_self_hosting_repo from this module). For non-self repos with an empty scope it
+    returns ``(True, "coverage-gate N/A for <repo>")`` so the deploy edge is unchanged
+    for them (AC-5).
+    """
+    from ..coverage_gate import check_coverage_gate as _impl
+    return _impl(repo, work_item_id, branch)
+
+
 # Registry for dynamic lookup by name
 QG_CHECKS = {
     "check_analysis_approved": check_analysis_approved,
@@ -770,4 +787,5 @@ QG_CHECKS = {
     "check_branch_mergeable": check_branch_mergeable,
     "check_staging_image_fresh": _check_staging_image_fresh,
     "check_security_gate": check_security_gate,
+    "check_coverage_gate": check_coverage_gate,
 }

src/stage_engine.py

@@ -322,6 +322,19 @@ def advance_stage(
             ):
                 return result
 
+            # --- ORCH-027 coverage sub-gate (deploy-staging -> deploy edge) ----
+            # AFTER the merge-gate (coverage measured on the caught-up HEAD that
+            # lands in `main`, so the metric matches landed code) and BEFORE the
+            # image-freshness rebuild (fail before the expensive docker rebuild).
+            # Deterministic (no LLM): pytest --cov=src -> line coverage % vs floor /
+            # ratchet baseline. FAIL -> rollback to development + release the merge
+            # lease (held by the merge-gate's PASS). It owns the outcome on
+            # intervention (mirrors the merge-gate / image-freshness).
+            if _handle_coverage_gate(
+                task_id, current_stage, repo, work_item_id, branch, agent, result
+            ):
+                return result
+
             # --- ORCH-058 freshness sub-gate (deploy-staging -> deploy edge) ---
             # AFTER the merge-gate finalised the validated HEAD and BEFORE Phase A.
             # Rebuilds the staging image from that validated commit + recreates 8501
@@ -1124,6 +1137,90 @@ def _handle_security_gate(
     return True
 
 
+# ---------------------------------------------------------------------------
+# ORCH-027: coverage sub-gate on the deploy-staging -> deploy edge
+# ---------------------------------------------------------------------------
+def _handle_coverage_gate(
+    task_id, current_stage, repo, work_item_id, branch, agent, result: AdvanceResult
+) -> bool:
+    """Run check_coverage_gate on the deploy-staging -> deploy edge (ORCH-027).
+
+    Runs AFTER the merge-gate (so coverage is measured on the rebased/caught-up HEAD
+    that actually lands in `main`) and BEFORE the image-freshness rebuild (fail before
+    the expensive docker rebuild). Deterministic (no LLM): pytest --cov=src in the
+    per-branch worktree -> line coverage % -> compute_coverage_verdict vs the absolute
+    floor and/or the ratchet baseline. The machine verdict lives in
+    18-coverage-report.md frontmatter. A coverage-tool error degrades fail-open +
+    WARNING by default (FR-6), so an infra hiccup never wedges the autonomous pipeline.
+
+    Returns True if the gate INTERVENED (the caller must return without advancing):
+      * FAIL (coverage below policy) -> ROLLBACK to development (+ developer retry,
+        capped by MAX_DEVELOPER_RETRIES) and RELEASE the merge lease (the merge-gate
+        held it on its PASS; coverage failed before the merge — mirrors the
+        image-freshness rollback, ADR-001 D1/TR-2).
+    Returns False when the gate PASSED (clean / fail-open / N/A) so advance_stage
+    proceeds to the image-freshness sub-gate. On a PASS the merge lease stays HELD
+    until the actual merge (released on done / rollback).
+    """
+    passed, reason = _run_qg("check_coverage_gate", repo, work_item_id, branch)
+    if passed:
+        logger.info(f"Task {task_id}: coverage-gate passed ({reason})")
+        return False
+
+    result.qg_name = "check_coverage_gate"
+    result.qg_passed = False
+    result.qg_reason = reason
+
+    update_task_stage(task_id, "development")
+    notify_stage_change(task_id, current_stage, "development")
+    plane_notify_stage(work_item_id, current_stage, "development")
+    result.rolled_back_to = "development"
+    set_issue_in_progress(work_item_id)
+    # The merge-gate held the lease on its PASS; coverage failed before the merge, so
+    # release it (holder-aware no-op if a different task already owns it). Mirrors the
+    # image-freshness rollback (ADR-001 D1/TR-2).
+    try:
+        merge_gate.release_merge_lease(repo, branch)
+    except Exception as e:  # noqa: BLE001 - defensive
+        logger.warning(f"Task {task_id}: merge-lease release on coverage fail failed: {e}")
+    notify_qg_failure(task_id, current_stage, "check_coverage_gate", reason)
+    plane_add_comment(
+        work_item_id,
+        f"❌ Coverage-гейт провален ({reason}). Откат на development. "
+        f"Developer нужен для добавления тестов (покрытие src/ просело).",
+        author="deployer",
+    )
+    retry_count = _developer_retry_count(task_id)
+    if retry_count < MAX_DEVELOPER_RETRIES:
+        report_ref = f"docs/work-items/{work_item_id}/18-coverage-report.md"
+        task_desc = (
+            f"Work item: {work_item_id}\nRepo: {repo}\nBranch: {branch}\n"
+            f"Stage: development\nNote: Coverage-гейт провален "
+            f"(attempt {retry_count + 1}/{MAX_DEVELOPER_RETRIES}). "
+            f"Причина: {reason}. Добавь тесты, чтобы покрытие src/ не падало ниже "
+            f"политики. Полный отчёт: {report_ref}"
+        )
+        new_job = enqueue_job("developer", repo, task_desc, task_id=task_id)
+        result.enqueued_agent = "developer"
+        result.enqueued_job_id = new_job
+        logger.info(
+            f"Task {task_id}: coverage-gate FAILED, enqueued developer (job_id={new_job})"
+        )
+    else:
+        set_issue_blocked(work_item_id)
+        send_telegram(
+            f"\U0001f6a8 {link_for(work_item_id)}: Coverage-гейт still failing after "
+            f"{MAX_DEVELOPER_RETRIES} developer retries ({reason}). "
+            f"Manual intervention needed."
+        )
+        result.alerted = True
+    logger.error(
+        f"Task {task_id}: coverage-gate FAILED, rolled back deploy-staging -> "
+        f"development ({reason})"
+    )
+    return True
+
+
 # ---------------------------------------------------------------------------
 # ORCH-058: staging-image freshness sub-gate on the deploy-staging -> deploy edge
 # ---------------------------------------------------------------------------
@@ -1546,6 +1643,17 @@ def _handle_merge_verify(task_id, repo, work_item_id, branch, result: AdvanceRes
                         task_id, repo, work_item_id, branch, guard_msg, result
                     )
 
+            # ORCH-027 (D5): ratchet the per-repo coverage baseline UP from this
+            # merged branch's measured coverage (single source of truth:
+            # 18-coverage-report.md). Atomic compare-and-set under the still-held
+            # merge-lease -> the baseline never decreases. never-raise (observability
+            # best-effort): a ratchet failure must never break the deploy->done path.
+            try:
+                from . import coverage_gate
+                coverage_gate.ratchet_baseline_on_merge(repo, work_item_id, branch, sha)
+            except Exception as e:  # noqa: BLE001 - observability best-effort
+                logger.warning(f"Task {task_id}: coverage baseline ratchet failed: {e}")
+
             merge_gate.note_merge_verified()
             try:
                 self_deploy.record_merged_to_main(repo, work_item_id, branch, True)