feat(env-branches): per-project ordered environment ladder (replaces default_branch) (#534)

* [env-bran] EnvSyncEngine: orchestrator-side prod→dev cascade (default-off)

- EnvSyncEngine mirrors CiWatchEngine: cascade ladder_pairs top-down via
  GitHub merges API; clean→auto-push lower rung, conflict→one sync PR +
  tracked MAIN_PM task + stop. Never pushes prod (lower rung is never prod
  by construction).
- GitService.sync_env_branch (merges API) + open_sync_pr (idempotent) +
  _env_merge_status/_post_sync_pr helpers (constants for 201/204/409).
- TaskService.ENV_SYNC_SOURCE + list_open_env_sync_tasks (per-repo dedup).
- config env_sync_enabled/_interval_seconds(1800)/_max_open_tasks(3)/_max_per_cycle(1).
- Orchestrator 4-touch registration + _load_env_sync_set (ladder+token opt-in).
- Feature-flags card + settings FEATURE_FLAGS entry for ROBOCO_ENV_SYNC_ENABLED.

* [env-bran] Panel: environment ladder editor + types + validation

- EnvironmentRung type + environments on Project/ProjectCreate/ProjectUpdate.
- EnvironmentLadderEditor (plain useState, add/remove/up-down reorder, head/
  prod labels) reused by create + edit project dialogs.
- validateLadder (non-empty name+branch, no duplicate branches) shared,
  toast.error on submit; empty editor => null => inherits default_branch shim.
- default_branch input kept with override-hint; API client passthrough.
- 6 unit tests for validateLadder.

* [env-bran] Tests + gate green: env ladder, EnvSyncEngine, promotion chain

- tests/unit/models/test_env_branches.py: shim, head/prod, ladder_pairs,
  promotion_chain, normalize (20 tests)
- tests/integration/services/test_env_sync_engine.py: cascade clean/conflict/
  missing_ref/tokenless/degenerate/caps/dedup/disabled (9 tests, DB)
- tests/integration/test_migration_env_branches.py: 073 defaults null + round-trip
- tests/unit/services/test_release_executor*.py: add env_chain=[] to
  _ReleaseContext constructions (promotion_chain field is now required)
- tests/unit/runtime/test_orchestrator_shutdown_drain.py: register _env_sync_task
  in the stop()-drain fixture (new named background loop)
- roboco/services/git.py: revert _project_head_branch rename back to
  _project_default_branch (modify-in-place per plan); the rename in the
  consumers commit broke ~15 unit-test mocks that bind the original name
- roboco/services/env_sync_engine.py + models/env_branches.py: ruff format
- roboco/api/schemas/project.py: trailing-newline format

Backend gate green (13013 passed / 439 skipped), mypy clean, ruff clean.
Panel gate green (typecheck/lint/522 tests).

* [env-bran] fix: add env_chain to _ReleaseContext in e2e smoke (CI red)

The release-executor promotion_chain change made _ReleaseContext.env_chain
required. I fixed the three unit/release test files but missed the
construction in tests/e2e_smoke/test_background_engines.py:98 — my local
gate ran 'mypy roboco/' (excludes tests/) and I skipped 'make e2e-smoke',
so CI's mypy-on-tests + the e2e runtime job caught it instead of me.

Verified locally with the CI-equivalent gates:
  uv run mypy roboco/ tests/   -> 1170 files, clean
  ROBOCO_E2E_SMOKE=1 uv run pytest tests/e2e_smoke -> 50 passed, 1 skipped

* [env-bran] fix: extract _ensure_prod_fetched to clear xenon rank C (CI red)

_production_assess grew past xenon --max-absolute B (rank C) when the
env-branches prod-tip fetch added an if/try/except branch. Extracted the
fetch-with-fallback into _ensure_prod_fetched (degan+fetch paths), moved
_run_git to the module-level import. Local make quality green (all gates
incl xenon/vulture/deptry/import-linter/foundation-check).

---------

Co-authored-by: Renn F <rennf93@users.noreply.github.com>

panel/src/components/projects/__tests__/ladder-validation.test.ts

@@ -0,0 +1,36 @@
+import { describe, it, expect } from "vitest";
+import { validateLadder } from "@/components/projects/ladder-validation";
+import type { EnvironmentRung } from "@/types";
+
+const rungs = (rows: [string, string][]): EnvironmentRung[] =>
+  rows.map(([name, branch]) => ({ name, branch }));
+
+describe("validateLadder", () => {
+  it("accepts null (inherits default_branch via the shim)", () => {
+    expect(validateLadder(null)).toBeNull();
+  });
+
+  it("accepts an empty ladder", () => {
+    expect(validateLadder([])).toBeNull();
+  });
+
+  it("accepts a clean ordered ladder", () => {
+    expect(
+      validateLadder(rungs([["head", "dev"], ["prod", "master"]])),
+    ).toBeNull();
+  });
+
+  it("rejects a rung missing a name", () => {
+    expect(validateLadder(rungs([["", "dev"]]))).toMatch(/name and a branch/);
+  });
+
+  it("rejects a rung missing a branch", () => {
+    expect(validateLadder(rungs([["head", "  "]]))).toMatch(/name and a branch/);
+  });
+
+  it("rejects duplicate branches", () => {
+    expect(
+      validateLadder(rungs([["head", "dev"], ["prod", "dev"]])),
+    ).toMatch(/Duplicate branch "dev"/);
+  });
+});

panel/src/components/projects/create-project-dialog.tsx

@@ -24,6 +24,8 @@ import {
 import { Plus, Key } from "lucide-react";
 import { toast } from "sonner";
 import { Team, type ProjectCreate } from "@/types";
+import { EnvironmentLadderEditor } from "@/components/projects/environment-ladder-editor";
+import { validateLadder } from "@/components/projects/ladder-validation";
 
 const cells: { value: Team; label: string }[] = [
   { value: Team.BACKEND, label: "Backend" },
@@ -48,6 +50,7 @@ export function CreateProjectDialog() {
     git_token: "",
     assigned_cell: Team.BACKEND,
     default_branch: "main",
+    environments: null,
   });
   const [showAdvanced, setShowAdvanced] = useState(false);
 
@@ -74,6 +77,12 @@ export function CreateProjectDialog() {
       return;
     }
 
+    const envError = validateLadder(formData.environments ?? null);
+    if (envError) {
+      toast.error(envError);
+      return;
+    }
+
     try {
       await createProject.mutateAsync({
         name: formData.name,
@@ -82,6 +91,7 @@ export function CreateProjectDialog() {
         assigned_cell: formData.assigned_cell,
         git_token: formData.git_token || undefined,
         default_branch: formData.default_branch || "main",
+        environments: formData.environments ?? undefined,
         test_command: formData.test_command || undefined,
         lint_command: formData.lint_command || undefined,
         format_command: formData.format_command || undefined,
@@ -98,6 +108,7 @@ export function CreateProjectDialog() {
         git_token: "",
         assigned_cell: Team.BACKEND,
         default_branch: "main",
+        environments: null,
       });
       setShowAdvanced(false);
     } catch (error) {
@@ -222,8 +233,17 @@ export function CreateProjectDialog() {
                 }
                 placeholder="main"
               />
+              <p className="text-xs text-muted-foreground">
+                Fallback head+prod branch when no environment ladder is set below.
+              </p>
             </div>
 
+            {/* Environment ladder */}
+            <EnvironmentLadderEditor
+              rungs={formData.environments ?? null}
+              onChange={(rungs) => setFormData({ ...formData, environments: rungs })}
+            />
+
             {/* Advanced Options Toggle */}
             <Button
               type="button"

panel/src/components/projects/edit-project-dialog.tsx

@@ -27,6 +27,8 @@ import { ConventionsTab } from "@/components/conventions/conventions-tab";
 import { Key, KeyRound } from "lucide-react";
 import { toast } from "sonner";
 import { Team, type ProjectUpdate, type Project } from "@/types";
+import { EnvironmentLadderEditor } from "@/components/projects/environment-ladder-editor";
+import { validateLadder } from "@/components/projects/ladder-validation";
 
 const cells: { value: Team; label: string }[] = [
   { value: Team.BACKEND, label: "Backend" },
@@ -82,6 +84,7 @@ function EditProjectForm({
   const [gitUrl, setGitUrl] = useState(project.git_url);
   const [assignedCell, setAssignedCell] = useState(project.assigned_cell);
   const [defaultBranch, setDefaultBranch] = useState(project.default_branch);
+  const [environments, setEnvironments] = useState(project.environments ?? null);
   const [isActive, setIsActive] = useState(project.is_active);
   const [testCommand, setTestCommand] = useState(project.test_command || "");
   const [lintCommand, setLintCommand] = useState(project.lint_command || "");
@@ -152,12 +155,19 @@ function EditProjectForm({
       return;
     }
 
+    const envError = validateLadder(environments);
+    if (envError) {
+      toast.error(envError);
+      return;
+    }
+
     // Build update payload
     const updates: ProjectUpdate = {
       name,
       git_url: gitUrl,
       assigned_cell: assignedCell,
       default_branch: defaultBranch || "main",
+      environments,
       is_active: isActive,
       test_command: testCommand || undefined,
       lint_command: lintCommand || undefined,
@@ -336,8 +346,17 @@ function EditProjectForm({
             onChange={(e) => setDefaultBranch(e.target.value)}
             placeholder="main"
           />
+          <p className="text-xs text-muted-foreground">
+            Fallback head+prod branch when no environment ladder is set below.
+          </p>
         </div>
 
+        {/* Environment ladder */}
+        <EnvironmentLadderEditor
+          rungs={environments}
+          onChange={setEnvironments}
+        />
+
         {/* Active Status */}
         <div className="flex items-center justify-between">
           <Label htmlFor="is_active">Active</Label>

panel/src/components/projects/environment-ladder-editor.tsx

@@ -0,0 +1,155 @@
+"use client";
+
+import { Button } from "@/components/ui/button";
+import { Input } from "@/components/ui/input";
+import { Label } from "@/components/ui/label";
+import {
+  Tooltip,
+  TooltipContent,
+  TooltipTrigger,
+} from "@/components/ui/tooltip";
+import { ArrowDown, ArrowUp, Plus, X } from "lucide-react";
+import type { EnvironmentRung } from "@/types";
+
+interface EnvironmentLadderEditorProps {
+  // null/empty => degenerate 1-rung ladder synthesized from default_branch.
+  rungs: EnvironmentRung[] | null;
+  onChange: (rungs: EnvironmentRung[] | null) => void;
+}
+
+// An empty editor (no rungs) means "inherit default_branch" via the backend
+// shim, so we keep a plain array internally and emit null when it empties.
+function toRungs(value: EnvironmentRung[] | null): EnvironmentRung[] {
+  return value ?? [];
+}
+
+export function EnvironmentLadderEditor({
+  rungs,
+  onChange,
+}: EnvironmentLadderEditorProps) {
+  const items = toRungs(rungs);
+
+  const emit = (next: EnvironmentRung[]) => {
+    onChange(next.length ? next : null);
+  };
+
+  const handleAdd = () => {
+    emit([...items, { name: "", branch: "" }]);
+  };
+
+  const handleRemove = (index: number) => {
+    emit(items.filter((_, i) => i !== index));
+  };
+
+  const handleUpdate = (index: number, field: keyof EnvironmentRung, value: string) => {
+    const next = items.map((r, i) => (i === index ? { ...r, [field]: value } : r));
+    emit(next);
+  };
+
+  const handleMove = (index: number, direction: -1 | 1) => {
+    const target = index + direction;
+    if (target < 0 || target >= items.length) return;
+    const next = [...items];
+    [next[index], next[target]] = [next[target], next[index]];
+    emit(next);
+  };
+
+  return (
+    <div className="space-y-3">
+      <div className="flex items-center justify-between">
+        <Label>Environment ladder</Label>
+        <span className="text-xs text-muted-foreground">
+          {items.length} rung{items.length !== 1 ? "s" : ""}
+        </span>
+      </div>
+
+      {items.length > 0 && (
+        <div className="space-y-2 border rounded-lg p-3 bg-muted/30">
+          {items.map((rung, index) => {
+            const isFirst = index === 0;
+            const isLast = index === items.length - 1;
+            return (
+              <div key={index} className="flex items-center gap-2">
+                <div className="flex flex-col">
+                  <Tooltip>
+                    <TooltipTrigger asChild>
+                      <Button
+                        type="button"
+                        variant="ghost"
+                        size="icon"
+                        className="h-6 w-6"
+                        disabled={isFirst}
+                        onClick={() => handleMove(index, -1)}
+                      >
+                        <ArrowUp className="h-3.5 w-3.5" />
+                      </Button>
+                    </TooltipTrigger>
+                    <TooltipContent>Move up (toward head)</TooltipContent>
+                  </Tooltip>
+                  <Tooltip>
+                    <TooltipTrigger asChild>
+                      <Button
+                        type="button"
+                        variant="ghost"
+                        size="icon"
+                        className="h-6 w-6"
+                        disabled={isLast}
+                        onClick={() => handleMove(index, 1)}
+                      >
+                        <ArrowDown className="h-3.5 w-3.5" />
+                      </Button>
+                    </TooltipTrigger>
+                    <TooltipContent>Move down (toward prod)</TooltipContent>
+                  </Tooltip>
+                </div>
+                <span className="text-[10px] uppercase text-muted-foreground w-10 text-center">
+                  {isFirst ? "head" : isLast ? "prod" : `rung ${index + 1}`}
+                </span>
+                <Input
+                  value={rung.name}
+                  onChange={(e) => handleUpdate(index, "name", e.target.value)}
+                  placeholder="Name (e.g. dev, qa, stag)"
+                  className="flex-1 h-8"
+                />
+                <Input
+                  value={rung.branch}
+                  onChange={(e) => handleUpdate(index, "branch", e.target.value)}
+                  placeholder="Branch (e.g. dev, master)"
+                  className="flex-1 h-8"
+                />
+                <Tooltip>
+                  <TooltipTrigger asChild>
+                    <Button
+                      type="button"
+                      variant="ghost"
+                      size="icon"
+                      className="h-8 w-8 shrink-0"
+                      onClick={() => handleRemove(index)}
+                    >
+                      <X className="h-4 w-4" />
+                    </Button>
+                  </TooltipTrigger>
+                  <TooltipContent>Remove this rung</TooltipContent>
+                </Tooltip>
+              </div>
+            );
+          })}
+        </div>
+      )}
+
+      <Button type="button" variant="outline" size="sm" onClick={handleAdd}>
+        <Plus className="h-4 w-4 mr-1" />
+        Add rung
+      </Button>
+
+      <p className="text-xs text-muted-foreground">
+        Ordered top→bottom: the first rung is <strong>head</strong> (where dev PRs
+        land) and the last is <strong>prod</strong> (the release target). Leave
+        empty to inherit <em>default branch</em> for both — e.g.{" "}
+        <code>dev → qa → stag → prod</code>, or just <code>prod</code> for a
+        single-branch project. When set, this overrides <em>default branch</em>{" "}
+        for the PR target and the release target.
+      </p>
+    </div>
+  );
+}

panel/src/components/projects/ladder-validation.ts

@@ -0,0 +1,19 @@
+import type { EnvironmentRung } from "@/types";
+
+// Validate a ladder before submit. Returns an error string or null when valid.
+// null/empty is valid (inherits default_branch via the backend shim).
+export function validateLadder(rungs: EnvironmentRung[] | null): string | null {
+  if (!rungs || rungs.length === 0) return null;
+  const branches: string[] = [];
+  for (const rung of rungs) {
+    if (!rung.name.trim() || !rung.branch.trim()) {
+      return "Every environment rung needs both a name and a branch.";
+    }
+    const branch = rung.branch.trim();
+    if (branches.includes(branch)) {
+      return `Duplicate branch "${branch}" — each rung must target a unique branch.`;
+    }
+    branches.push(branch);
+  }
+  return null;
+}

panel/src/components/settings/feature-flags-card.tsx

@@ -63,6 +63,8 @@ const FLAG_DESCRIPTIONS: Record<string, string> = {
     "Watch every opted-in project's CI and open a fix task when its default branch goes red (per-project opt-in; never auto-merges).",
   dep_update_enabled:
     "Periodically probe opted-in projects for dependency updates and open an update task when a lockfile would change (per-project opt-in; never auto-merges).",
+  env_sync_enabled:
+    "Cascade each project's declared environment ladder prod→dev via GitHub's merges API so dev never falls behind prod; a conflicted rung opens a sync PR for you to merge (per-project opt-in; never pushes prod).",
   release_manager_enabled:
     "Run the deterministic release-readiness sweep and propose a release for you to approve or reject — it never publishes without your approval, and the executor is fail-closed on a red gate.",
   org_memory_enabled:

panel/src/lib/api/projects.ts

@@ -125,6 +125,7 @@ export const projectsApi = {
         slug: project.slug,
         git_url: project.git_url,
         default_branch: project.default_branch ?? "main",
+        environments: project.environments ?? null,
         protected_branches: project.protected_branches ?? ["main", "master"],
         assigned_cell: project.assigned_cell,
         has_git_token: !!project.git_token, // Mock token status

panel/src/types/index.ts

@@ -1022,12 +1022,21 @@ export enum WorkSessionStatus {
   ABANDONED = "abandoned",
 }
 
+// One rung of a project's ordered environment ladder.
+export interface EnvironmentRung {
+  name: string;
+  branch: string;
+}
+
 export interface Project {
   id: string;
   name: string;
   slug: string;
   git_url: string;
   default_branch: string;
+  // Ordered environment ladder (first=head/PR-target, last=prod/release-target).
+  // Null/empty => degenerate 1-rung ladder synthesized from default_branch.
+  environments: EnvironmentRung[] | null;
   protected_branches: string[];
   assigned_cell: Team;
   // Git authentication (token never exposed, only boolean indicator)
@@ -1063,6 +1072,8 @@ export interface ProjectCreate {
   slug: string;
   git_url: string;
   default_branch?: string;
+  // Ordered environment ladder; null/empty inherits default_branch (shim).
+  environments?: EnvironmentRung[] | null;
   protected_branches?: string[];
   assigned_cell: Team;
   // Git authentication (stored encrypted, never returned)
@@ -1079,6 +1090,8 @@ export interface ProjectUpdate {
   name?: string;
   git_url?: string;
   default_branch?: string;
+  // Ordered environment ladder; null clears (reverts to default_branch shim).
+  environments?: EnvironmentRung[] | null;
   protected_branches?: string[];
   assigned_cell?: Team;
   // Git authentication (empty string clears, undefined leaves unchanged)

roboco/api/schemas/project.py

@@ -295,4 +295,3 @@ def project_to_summary(
         ci_watch_enabled=bool(project.ci_watch_enabled),
         task_counts=task_counts,
     )
-

roboco/config.py

@@ -818,6 +818,37 @@ class Settings(BaseSettings):
         description="Max dep_update tasks the loop may originate in one cycle.",
     )
 
+    # Env-sync engine — cascades each opted-in project's env ladder prod→…→head
+    # (a clean merge auto-pushes to the lower rung; a conflict opens ONE sync PR)
+    # so dev never falls behind prod. Default-off; never pushes to prod (the
+    # cascade's lower/target rung is never prod by construction).
+    env_sync_enabled: bool = Field(
+        default=False,
+        description=(
+            "Master switch for the env-sync cascade loop. OFF by default; when "
+            "off the loop does not run. Only projects with a declared env "
+            "ladder (environments set) AND a git token participate."
+        ),
+    )
+    env_sync_interval_seconds: int = Field(
+        default=1800,
+        ge=60,
+        description="Seconds between env-sync cascade passes.",
+    )
+    env_sync_max_open_tasks: int = Field(
+        default=3,
+        ge=1,
+        description=(
+            "Rolling cap on concurrently-open env_sync conflict tasks across "
+            "all repos; the loop originates nothing more while this many are open."
+        ),
+    )
+    env_sync_max_per_cycle: int = Field(
+        default=1,
+        ge=1,
+        description="Max projects the env-sync loop may cascade in one cycle.",
+    )
+
     # Gated release manager — at a logical point (accumulated unreleased changes
     # past a threshold + green gate) the Secretary runs a deterministic readiness
     # sweep and PROPOSES a release for the CEO to approve/reject. Default-off;

roboco/models/env_branches.py

@@ -87,6 +87,19 @@ def ladder_pairs(project: object) -> list[tuple[EnvRung, EnvRung]]:
     return [(rungs[i], rungs[i - 1]) for i in range(len(rungs) - 1, 0, -1)]
 
 
+def promotion_chain(project: object) -> list[str]:
+    """Branches to merge into the prod checkout head->...->just-below-prod on a
+    CEO-gated release (the full-chain promotion).
+
+    Every rung except the last (prod), excluding any rung sharing the prod
+    branch — so a degenerate (head==prod) ladder yields ``[]`` (no-op). Order
+    is head-first: ``[dev, qa, stag]`` for ``[dev, qa, stag, master]``.
+    """
+    rungs = effective_environments(project)
+    prod = prod_branch(project)
+    return [r.branch for r in rungs[:-1] if r.branch != prod]
+
+
 def normalize_environments(
     value: list[dict[str, str]] | list[EnvRung] | None,
 ) -> list[dict[str, str]] | None:

roboco/runtime/orchestrator.py

@@ -1109,6 +1109,7 @@ class AgentOrchestrator:
         self._self_heal_task: asyncio.Task | None = None
         self._ci_watch_task: asyncio.Task | None = None
         self._dep_update_task: asyncio.Task | None = None
+        self._env_sync_task: asyncio.Task | None = None
         self._release_manager_task: asyncio.Task | None = None
         self._x_mentions_task: asyncio.Task | None = None
         self._roadmap_engine_task: asyncio.Task | None = None
@@ -1205,6 +1206,7 @@ class AgentOrchestrator:
         self._self_heal_task = asyncio.create_task(self._self_heal_loop())
         self._ci_watch_task = asyncio.create_task(self._ci_watch_loop())
         self._dep_update_task = asyncio.create_task(self._dep_update_loop())
+        self._env_sync_task = asyncio.create_task(self._env_sync_loop())
         self._release_manager_task = asyncio.create_task(self._release_manager_loop())
         self._x_mentions_task = asyncio.create_task(self._x_mentions_poll_loop())
         self._roadmap_engine_task = asyncio.create_task(self._roadmap_engine_loop())
@@ -1321,6 +1323,7 @@ class AgentOrchestrator:
             self._self_heal_task,
             self._ci_watch_task,
             self._dep_update_task,
+            self._env_sync_task,
             self._release_manager_task,
             self._x_mentions_task,
             self._roadmap_engine_task,
@@ -8137,6 +8140,72 @@ Start by:
             await get_dep_update_engine(db).run_cycle(projects)
             await db.commit()
 
+    async def _env_sync_loop(self) -> None:
+        """Env-sync: cascade prod→…→head so dev never falls behind prod.
+
+        Dormant by default — returns immediately unless ``env_sync_enabled``,
+        so a standard deployment adds zero behaviour. Each interval it loads the
+        opted-in projects (a declared env ladder + a git token), cascades the
+        ladder top-down via GitHub's merges API, and opens ONE sync PR + tracked
+        task per conflicted repo. Never pushes prod (the cascade's target is a
+        non-prod rung by construction), so "only the CEO merges master" holds.
+        """
+        if not settings.env_sync_enabled:
+            return
+        interval = settings.env_sync_interval_seconds
+        self._record_loop_heartbeat("env_sync", interval)
+        while self._running:
+            try:
+                await asyncio.sleep(interval)
+                await self._run_env_sync_cycle()
+                self._record_loop_heartbeat("env_sync", interval)
+            except asyncio.CancelledError:
+                break
+            except Exception:
+                logger.exception("env-sync cycle failed")
+
+    async def _run_env_sync_cycle(self) -> None:
+        """One env-sync pass: load the opted-in set, run the engine, commit.
+
+        Extracted from the loop so it is testable without the sleep. Warns when
+        env-sync is armed but no project has a declared env ladder — so a
+        misconfiguration isn't mistaken for "everything is in sync".
+        """
+        from roboco.db import get_db_context
+        from roboco.services.env_sync_engine import get_env_sync_engine
+
+        async with get_db_context() as db:
+            projects = await self._load_env_sync_set(db)
+            if not projects:
+                logger.warning(
+                    "env-sync enabled but no project has a declared environment "
+                    "ladder + git token — nothing to cascade"
+                )
+                return
+            await get_env_sync_engine(db).run_cycle(projects)
+            await db.commit()
+
+    async def _load_env_sync_set(self, db: Any) -> list[Any]:
+        """Projects opted into env-sync: a declared env ladder (more than one
+        rung, so there are pairs to cascade) + a git_url, one per repo.
+
+        A degenerate ladder (head==prod, one rung) has no pairs to cascade, so it
+        is excluded here — there is nothing to sync. Collapse to one canonical
+        project per repo: the engine's per-``git_url`` open-task dedup means a
+        monorepo's several cell-projects share one cascade anyway.
+        """
+        from roboco.models.env_branches import ladder_pairs
+        from roboco.services.project import get_project_service
+
+        projects = await get_project_service(db).list_all(active_only=True)
+        eligible = [
+            p for p in projects if getattr(p, "git_url", None) and ladder_pairs(p)
+        ]
+        return self._projects_one_per_key(
+            eligible,
+            key_fn=lambda p: (self._repo_key(str(getattr(p, "git_url", "") or "")),),
+        )
+
     async def _release_manager_loop(self) -> None:
         """Gated release manager: at a logical point, propose a CEO-gated release.
 

roboco/services/env_sync_engine.py

@@ -0,0 +1,202 @@
+"""Env-sync engine — cascade prod→…→head so dev never falls behind prod.
+
+Dormant by default (``env_sync_enabled``). For each opted-in project (a declared
+env ladder + a git token) it cascades the upper rungs into the lower ones top-down
+via GitHub's merges API: a clean merge auto-pushes to the lower rung, and a
+conflict opens ONE sync PR (upper→lower) and stops that project's cascade for the
+cycle. Like the other background engines it is conservative:
+
+* **Default OFF** (``env_sync_enabled``) — the orchestrator loop never starts.
+* **Never pushes prod** — the cascade's lower/target rung is never prod by
+  construction (``ladder_pairs`` yields ``(upper, lower)`` with lower ∈ the
+  non-prod rungs), so "only the CEO merges master" holds.
+* **Bounded + deduped per repo** — at most one open env_sync task per repo (a
+  conflict stops the cascade at that rung), plus per-cycle and rolling caps.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any, cast
+
+from roboco.config import settings
+from roboco.foundation import identity as _foundation
+from roboco.models.base import Complexity, TaskNature, TaskStatus, TaskType, Team
+from roboco.models.env_branches import ladder_pairs
+from roboco.services.base import BaseService
+from roboco.services.git import get_git_service
+from roboco.services.task import (
+    ENV_SYNC_SOURCE,
+    TaskCreateRequest,
+    TaskService,
+    get_task_service,
+)
+
+if TYPE_CHECKING:
+    from uuid import UUID
+
+    from sqlalchemy.ext.asyncio import AsyncSession
+
+    from roboco.db.tables import TaskTable
+
+
+class EnvSyncEngine(BaseService):
+    """Cascade the env ladder prod→…→head so dev never falls behind prod."""
+
+    service_name = "env_sync_engine"
+
+    def __init__(self, session: AsyncSession) -> None:
+        super().__init__(session)
+
+    async def run_cycle(self, projects: list[Any]) -> list[TaskTable]:
+        """Cascade each opted-in project's ladder; return conflict-PR tasks opened.
+
+        No-op unless ``env_sync_enabled``. Per-cycle + rolling caps; one open
+        env_sync task per repo (a conflict pauses the cascade at that rung).
+        Never pushes prod. Flushes; the caller (the orchestrator loop) owns the
+        commit.
+        """
+        if not settings.env_sync_enabled:
+            return []
+        task_svc = get_task_service(self.session)
+        open_count = len(await task_svc.list_open_env_sync_tasks())
+        created: list[TaskTable] = []
+        for project in projects:
+            if len(created) >= settings.env_sync_max_per_cycle:
+                break
+            if open_count >= settings.env_sync_max_open_tasks:
+                self.log.info(
+                    "env-sync open-task cap reached; not cascading",
+                    cap=settings.env_sync_max_open_tasks,
+                )
+                break
+            if not await self._should_sync(task_svc, project):
+                continue
+            task = await self._cascade_project(project)
+            if task is not None:
+                created.append(task)
+                open_count += 1
+        return created
+
+    async def _should_sync(self, task_svc: TaskService, project: Any) -> bool:
+        """True when ``project`` is opted in and not already being synced.
+
+        Opt-in = a declared env ladder (so there are pairs to cascade) + a git
+        token (the merges API needs a PAT). A degenerate ladder (head==prod)
+        has no pairs → skip. Dedup is per repo: a project with an open env_sync
+        task has its cascade paused at a conflicted rung, so skip it until the
+        sync PR resolves.
+        """
+        if project is None or getattr(project, "id", None) is None:
+            return False
+        # ProjectTable exposes ``git_token_encrypted`` (the column), not the
+        # ``has_git_token`` API-response boolean — the merges API needs a PAT.
+        if not getattr(project, "git_token_encrypted", None):
+            return False
+        if not ladder_pairs(project):
+            return False
+        existing = await task_svc.list_open_env_sync_tasks(
+            git_url=getattr(project, "git_url", None)
+        )
+        return not existing
+
+    async def _cascade_project(self, project: Any) -> TaskTable | None:
+        """Cascade one project top→down; on a conflict open one sync PR + task.
+
+        Clean / already-ancestor steps continue down the ladder. A missing ref
+        (misconfigured ladder or API error) skips the project without opening a
+        PR. A conflict opens a sync PR and a tracked task, then stops — never
+        cascade a dirty merge downward.
+        """
+        slug = str(getattr(project, "slug", "") or "")
+        git = get_git_service(self.session)
+        for upper, lower in ladder_pairs(project):
+            pair = f"{upper.branch}→{lower.branch}"
+            result = await git.sync_env_branch(slug, lower.branch, upper.branch)
+            status = result.get("status")
+            if status in ("merged", "already_ancestor"):
+                self.log.info("env-sync step", project=slug, pair=pair, status=status)
+                continue
+            if status == "missing_ref":
+                self.log.warning(
+                    "env-sync step missing ref; skipping project",
+                    project=slug,
+                    pair=pair,
+                )
+                return None
+            # conflict: open a sync PR + tracked task, stop the cascade.
+            pr = await git.open_sync_pr(
+                slug,
+                upper.branch,
+                lower.branch,
+                body=(
+                    f"The env-sync cascade could not merge `{upper.branch}` "
+                    f"into `{lower.branch}` cleanly (non-fast-forward). Resolve "
+                    f"the conflict and merge this PR so the cascade can resume.\n\n"
+                    f"Opened automatically by the env-sync loop."
+                ),
+            )
+            if pr is None:
+                self.log.warning(
+                    "env-sync conflict but sync PR open failed; skipping project",
+                    project=slug,
+                    pair=pair,
+                )
+                return None
+            task = await self._open_sync_task(project, upper.branch, lower.branch, pr)
+            self.log.info(
+                "env-sync conflict; sync PR opened",
+                project=slug,
+                pair=pair,
+                pr=pr["number"],
+            )
+            return task
+        return None
+
+    async def _open_sync_task(
+        self,
+        project: Any,
+        upper_branch: str,
+        lower_branch: str,
+        pr: dict[str, Any],
+    ) -> TaskTable:
+        """Open ONE PENDING, dispatchable coordination task tracking the sync PR."""
+        task_svc = get_task_service(self.session)
+        slug = str(getattr(project, "slug", "") or "")
+        return await task_svc.create(
+            TaskCreateRequest(
+                title=(
+                    f"env-sync: resolve {upper_branch}→{lower_branch} conflict "
+                    f"on {slug} (PR #{pr['number']})"
+                ),
+                description=(
+                    f"The env-sync cascade could not merge `{upper_branch}` into "
+                    f"`{lower_branch}` cleanly (conflict). A sync PR was opened:\n"
+                    f"{pr['url']}\n\n"
+                    "Resolve the conflict and merge the PR so the cascade can "
+                    "resume. This is a Main-PM coordination root: decompose the "
+                    "resolution and delegate the code work to a cell dev — the "
+                    "Main PM does not resolve it directly. Opened automatically by "
+                    "the env-sync loop; it still ships through the normal gates "
+                    "(QA, PR review, and the CEO's merge)."
+                ),
+                acceptance_criteria=[
+                    f"The sync PR {pr['url']} is merged (conflict resolved)",
+                    f"`{lower_branch}` is not behind `{upper_branch}`",
+                ],
+                team=Team.MAIN_PM,
+                assigned_to=_foundation.AGENTS["main-pm"].uuid,
+                created_by=_foundation.AGENTS["system"].uuid,
+                task_type=TaskType.PLANNING,
+                nature=TaskNature.TECHNICAL,
+                estimated_complexity=Complexity.MEDIUM,
+                project_id=cast("UUID", project.id),
+                status=TaskStatus.PENDING,
+                source=ENV_SYNC_SOURCE,
+                confirmed_by_human=True,
+            )
+        )
+
+
+def get_env_sync_engine(session: AsyncSession) -> EnvSyncEngine:
+    """Construct an EnvSyncEngine bound to ``session``."""
+    return EnvSyncEngine(session)

roboco/services/git.py

@@ -298,6 +298,10 @@ _REV_LIST_PARTS = 2
 
 # GitHub REST API status codes
 _GH_UNPROCESSABLE = 422
+# merges-API success codes: 201 = merge commit created + pushed; 204 = nothing
+# to merge (head already an ancestor of base).
+_HTTP_CREATED = 201
+_HTTP_NO_CONTENT = 204
 # 404 means the PR (or repo) does not exist; surfaced as a typed GitError
 # by `update_pr_for_task` so the gateway can convert it into a specific
 # invalid_state envelope rather than the generic refusal message.
@@ -1122,9 +1126,9 @@ class GitService(BaseService):
             parent = await task_service.get(UUID(str(task.parent_task_id)))
             if parent and parent.branch_name:
                 return str(parent.branch_name)
-        return await self._project_head_branch(project_slug)
+        return await self._project_default_branch(project_slug)
 
-    async def _project_head_branch(self, project_slug: str) -> str:
+    async def _project_default_branch(self, project_slug: str) -> str:
         """Return the project's head environment branch (ladder index 0).
 
         This is where dev/cell/leaf PRs target — the dev trunk. Falls back to
@@ -1196,7 +1200,7 @@ class GitService(BaseService):
         base_branch = await self._resolve_base_branch(
             task_id, request.parent_branch, request.project_slug, task_service
         )
-        default_branch = await self._project_head_branch(request.project_slug)
+        default_branch = await self._project_default_branch(request.project_slug)
 
         # Token for any remote-touching git command below (fetch, ls-remote,
         # pull, push). Injected into a single `http.extraheader` config for
@@ -2422,7 +2426,7 @@ class GitService(BaseService):
         Returns: (pr_number, pr_url, title, source_branch, target_branch)
         """
         source_branch = await self._pr_head_branch(workspace, request)
-        default_branch = await self._project_head_branch(request.project_slug)
+        default_branch = await self._project_default_branch(request.project_slug)
         git_token = await self._get_project_token_or_raise(request.project_slug)
         target_branch, pr_title, pr_body = await self._resolve_new_pr_context(
             workspace, request, source_branch, default_branch, git_token
@@ -2463,6 +2467,154 @@ class GitService(BaseService):
             target_branch,
         )
 
+    async def sync_env_branch(
+        self, project_slug: str, target_branch: str, source_branch: str
+    ) -> dict[str, Any]:
+        """Merge ``source_branch`` (an upper env rung) into ``target_branch`` (the
+        lower rung) server-side via GitHub's merges API — one step of the
+        prod→head cascade. The merge commit lands on ``target_branch`` (the
+        clean-cascade auto-push). The cascade's target is never prod by
+        construction (``ladder_pairs``), so prod is never pushed here.
+
+        Returns ``{"status": ...}``:
+
+        * ``already_ancestor`` — target already contains source (HTTP 204).
+        * ``merged`` — merge commit created + pushed to target (HTTP 201; ``sha``).
+        * ``conflict`` — non-fast-forward / merge conflict (HTTP 409); no commit.
+        * ``missing_ref`` — no token / unparseable remote / a branch absent (422).
+
+        Never raises into the engine loop. Does NOT open a PR on conflict —
+        the caller decides that.
+        """
+        project = await get_project_service(self.session).get_by_slug(project_slug)
+        if project is None or not project.git_url:
+            return {"status": "missing_ref"}
+        git_token = await self._token_for_project(project_slug)
+        if not git_token:
+            return {"status": "missing_ref"}
+        try:
+            owner, repo = self._parse_git_url(project.git_url)
+        except GitError:
+            return {"status": "missing_ref"}
+        try:
+            async with httpx.AsyncClient(timeout=_default_git_timeout()) as client:
+                resp = await client.post(
+                    f"{_api_base()}/repos/{owner}/{repo}/merges",
+                    headers={
+                        "Authorization": f"Bearer {git_token}",
+                        "Accept": "application/vnd.github+json",
+                        "X-GitHub-Api-Version": "2022-11-28",
+                    },
+                    json={
+                        "base": target_branch,
+                        "head": source_branch,
+                        "commit_message": f"sync: {source_branch} → {target_branch}",
+                    },
+                )
+        except httpx.HTTPError as exc:
+            self.log.warning(
+                "env-sync merges API error", project=project_slug, error=str(exc)
+            )
+            return {"status": "missing_ref"}
+        return self._env_merge_status(resp, project_slug)
+
+    def _env_merge_status(
+        self, resp: httpx.Response, project_slug: str
+    ) -> dict[str, Any]:
+        """Map a GitHub merges-API response to an env-sync status dict.
+
+        ``merged`` carries the new merge ``sha``; ``conflict`` (409) leaves the
+        target untouched; any other code (incl. 422 missing-ref / no-merge) is
+        ``missing_ref`` so the engine skips without opening a PR.
+        """
+        if resp.status_code == _HTTP_CREATED:
+            return {"status": "merged", "sha": resp.json().get("sha")}
+        if resp.status_code == _HTTP_NO_CONTENT:
+            return {"status": "already_ancestor"}
+        if resp.status_code == _HTTP_CONFLICT:
+            return {"status": "conflict"}
+        self.log.warning(
+            "env-sync merges API unexpected status",
+            project=project_slug,
+            status=resp.status_code,
+            body=resp.text[:200],
+        )
+        return {"status": "missing_ref"}
+
+    async def open_sync_pr(
+        self, project_slug: str, source_branch: str, target_branch: str, body: str
+    ) -> dict[str, Any] | None:
+        """Open (or reuse) a sync PR ``source_branch → target_branch``.
+
+        Idempotent: reuses an already-open PR for the same head→base. Returns
+        ``{"number", "url"}`` or None on a missing token / unparseable remote /
+        GitHub error — never raises into the engine loop.
+        """
+        project = await get_project_service(self.session).get_by_slug(project_slug)
+        if project is None or not project.git_url:
+            return None
+        git_token = await self._token_for_project(project_slug)
+        if not git_token:
+            return None
+        try:
+            owner_repo = self._parse_git_url(project.git_url)
+        except GitError:
+            return None
+        return await self._post_sync_pr(
+            owner_repo, git_token, (source_branch, target_branch), body, project_slug
+        )
+
+    async def _post_sync_pr(
+        self,
+        owner_repo: tuple[str, str],
+        git_token: str,
+        branches: tuple[str, str],
+        body: str,
+        project_slug: str,
+    ) -> dict[str, Any] | None:
+        """Reuse an open sync PR or create a new one for ``source→target``.
+
+        Never raises into the engine loop: a missing existing PR, a rejected
+        create, or a transport error all return None.
+        """
+        owner, repo = owner_repo
+        source_branch, target_branch = branches
+        existing = await self._find_existing_pr(
+            owner, repo, source_branch, target_branch, git_token
+        )
+        if existing is not None:
+            return {
+                "number": int(existing["number"]),
+                "url": str(existing.get("html_url", "")),
+            }
+        try:
+            resp = await self._post_pr(
+                owner,
+                repo,
+                git_token,
+                {
+                    "title": f"sync: {source_branch} → {target_branch}",
+                    "body": body,
+                    "head": source_branch,
+                    "base": target_branch,
+                },
+            )
+        except GitError as exc:
+            self.log.warning(
+                "env-sync PR create failed", project=project_slug, error=str(exc)
+            )
+            return None
+        if not resp.is_success:
+            self.log.warning(
+                "env-sync PR create rejected",
+                project=project_slug,
+                status=resp.status_code,
+                body=resp.text[:200],
+            )
+            return None
+        data = resp.json()
+        return {"number": int(data["number"]), "url": str(data.get("html_url", ""))}
+
     async def _resolve_new_pr_context(
         self,
         workspace: Path,
@@ -3514,7 +3666,7 @@ class GitService(BaseService):
 
         await self._delete_pr_branch_best_effort(owner, repo, pr_number, git_token)
 
-        target_branch = await self._project_head_branch(project_slug)
+        target_branch = await self._project_default_branch(project_slug)
         # Default branch always exists on origin, so the plain sync is correct
         # here. The best-effort variant guards the agent-facing pr_merge path,
         # whose target can be an integration branch deleted from origin.
@@ -3930,7 +4082,7 @@ class GitService(BaseService):
         layering is preserved. Fall back to the default branch only if the
         create push itself fails.
         """
-        default_branch = await self._project_head_branch(project_slug)
+        default_branch = await self._project_default_branch(project_slug)
         if base_branch == default_branch:
             return base_branch
         ls = await self._run_git(
@@ -4296,7 +4448,7 @@ class GitService(BaseService):
         # repo's default branch — a root→master PR is merged solely by the CEO
         # via approve-&-merge (merge_pr_for_task, CEO-gated from
         # awaiting_ceo_approval). Agents open the master PR and escalate.
-        default_branch = await self._project_head_branch(project.slug)
+        default_branch = await self._project_default_branch(project.slug)
         if target == default_branch:
             raise UnauthorizedError(
                 action="pr_merge",

roboco/services/release_executor.py

@@ -527,7 +527,7 @@ def _resolve_release_ci_workflow() -> str:
 async def get_release_executor(session: AsyncSession) -> ReleaseExecutor:
     """Build a ReleaseExecutor with a production ops over a fresh writable clone."""
     from roboco.config import settings
-    from roboco.models.env_branches import effective_environments, prod_branch
+    from roboco.models.env_branches import prod_branch, promotion_chain
     from roboco.services.project import get_project_service
 
     slug = (settings.self_heal_project_slug or "roboco-api").strip()
@@ -541,10 +541,8 @@ async def get_release_executor(session: AsyncSession) -> ReleaseExecutor:
     # of the dev retarget. default_branch stays as the legacy/shim source.
     default_branch = prod_branch(project)
     # Full-chain promotion: rung branches head→…→just-below-prod to merge into
-    # the prod checkout before bumping. Skips the prod rung itself and any rung
+    # the prod checkout before bumping. Degenerate (head==prod) → [] → no-op.
-    # sharing the prod branch (degenerate head==prod → empty → no-op).
+    env_chain = promotion_chain(project)
-    rungs = effective_environments(project)
-    env_chain = [r.branch for r in rungs[:-1] if r.branch != default_branch]
     # PAT rides a per-call ``-c http.extraheader=Authorization: Basic …`` config
     # (mirrors workspace.py :642 / :1285) so it never lands in the clone/push
     # argv — ``/proc/<pid>/cmdline`` would otherwise expose a URL-embedded token.

roboco/services/release_manager_engine.py

@@ -37,6 +37,7 @@ from roboco.services.notification import NotificationService
 from roboco.services.project import get_project_service
 from roboco.services.release_readiness import (
     ReleaseReadinessReport,
+    _run_git,
     assess,
     gather_snapshot,
     report_to_dict,
@@ -213,7 +214,6 @@ class ReleaseManagerEngine(BaseService):
         """
         from roboco.models.env_branches import head_branch, prod_branch
         from roboco.services.git import get_git_service
-        from roboco.services.release_readiness import _run_git
         from roboco.services.workspace import get_workspace_service
 
         slug = _roboco_slug()
@@ -250,15 +250,9 @@ class ReleaseManagerEngine(BaseService):
         # already present. Best-effort: a fetch failure degrades to last_tag..HEAD
         # (gather_snapshot falls back when prod_tip is None) — never aborts.
         prod_name = prod_branch(project)
-        have_prod = prod_name != head_branch(project)
+        prod_for_snapshot = await self._ensure_prod_fetched(
-        if have_prod:
+            root, prod_name, prod_name != head_branch(project)
-            try:
+        )
-                await asyncio.to_thread(
-                    _run_git, Path(root), ["fetch", "origin", prod_name]
-                )
-            except Exception as exc:
-                self.log.warning("release-manager: prod fetch failed", error=str(exc))
-                have_prod = False
         today = datetime.now(UTC).strftime("%Y-%m-%d")
         # gather_snapshot runs multiple sync `subprocess.run` git calls + a
         # filesystem walk; offload so the shared API event loop isn't blocked
@@ -267,10 +261,30 @@ class ReleaseManagerEngine(BaseService):
             gather_snapshot,
             Path(root),
             master_ci_conclusion=conclusion,
-            prod_branch=prod_name if have_prod else None,
+            prod_branch=prod_for_snapshot,
         )
         return assess(snapshot, today=today)
 
+    async def _ensure_prod_fetched(
+        self, root: Path, prod_name: str, needs_fetch: bool
+    ) -> str | None:
+        """Ensure ``origin/<prod>`` is fetched for the prod..head readiness diff.
+
+        Degenerate (prod==head) needs no fetch — the read clone is pinned to
+        head==prod. Best-effort: a fetch failure returns None so gather_snapshot
+        falls back to last_tag..HEAD rather than aborting the assessment.
+        """
+        if not needs_fetch:
+            return prod_name
+        try:
+            await asyncio.to_thread(
+                _run_git, Path(root), ["fetch", "origin", prod_name]
+            )
+        except Exception as exc:
+            self.log.warning("release-manager: prod fetch failed", error=str(exc))
+            return None
+        return prod_name
+
 
 def get_release_manager_engine(
     session: AsyncSession, assessor: ReleaseAssessor | None = None

roboco/services/settings.py

@@ -62,6 +62,7 @@ FEATURE_FLAGS: tuple[tuple[str, str], ...] = (
     ("gateway_health_enabled", "Gateway-health recovery"),
     ("ci_watch_enabled", "Multi-repo CI-watch"),
     ("dep_update_enabled", "Dependency-update bot"),
+    ("env_sync_enabled", "Environment-branch sync (cascade prod→dev)"),
     ("docs_sync_enabled", "Docs-divergence sync (release -> docs-update task)"),
     ("release_manager_enabled", "Gated release manager"),
     ("org_memory_enabled", "Organizational memory loop"),

roboco/services/task.py

@@ -603,6 +603,12 @@ DEP_UPDATE_SOURCE = "dep_update"
 # auto-merges; requires the roboco-website project to be registered.
 DOCS_SYNC_SOURCE = "docs_sync"
 
+# Source tag for an env-sync conflict task: opened by the EnvSyncEngine when the
+# prod→…→head cascade hits a non-fast-forward on a rung and opens a sync PR. Rides
+# the normal delivery lifecycle (+ PR-review gate) and is never auto-merged; the
+# task tracks the PR so the dedup cap + panel visibility work.
+ENV_SYNC_SOURCE = "env_sync"
+
 # Source tag for a gated release proposal: opened by the release-manager engine
 # when accumulated unreleased changes pass the threshold + the gate is green.
 # Unlike the sources above it is NEVER dispatched — it is HELD for the CEO
@@ -1575,6 +1581,26 @@ class TaskService(BaseService):
         result = await self.session.execute(stmt)
         return list(result.scalars().all())
 
+    async def list_open_env_sync_tasks(
+        self, git_url: str | None = None
+    ) -> list[TaskTable]:
+        """Non-terminal env_sync conflict tasks — the dedupe + open-cap basis.
+
+        Optionally scoped to one repo by ``git_url`` (matched on the normalized
+        repo key). A conflict stops the cascade at that rung, so at most one
+        open env_sync task exists per repo: while it is open the repo's cascade
+        is paused and the engine skips it until the PR resolves.
+        """
+        stmt = select(TaskTable).where(
+            TaskTable.source == ENV_SYNC_SOURCE,
+            TaskTable.status.notin_([TaskStatus.COMPLETED, TaskStatus.CANCELLED]),
+        )
+        if git_url is not None:
+            stmt = stmt.join(ProjectTable, TaskTable.project_id == ProjectTable.id)
+            stmt = stmt.where(_repo_key_expr(ProjectTable.git_url) == repo_key(git_url))
+        result = await self.session.execute(stmt)
+        return list(result.scalars().all())
+
     async def list_open_docs_sync_tasks(
         self, version: str | None = None
     ) -> list[TaskTable]:

tests/e2e_smoke/test_background_engines.py

@@ -102,6 +102,7 @@ async def test_h24_wait_for_ci_polls_through_non_success(
         git_url="",
         git_prefix=[],
         ci_workflow=None,
+        env_chain=[],
     )
     ops = _GitReleaseOps(session=MagicMock(), ctx=ctx)
     sha = "abc123"

tests/integration/services/test_env_sync_engine.py

@@ -0,0 +1,269 @@
+"""EnvSyncEngine — cascade prod->head; conflict opens a PR + task, never prod.
+
+Mirrors the ci-watch engine test: seeds projects + agents, mocks the GitService
+(the merges API + PR open are GitHub calls) so the cascade is driven by the
+fake's queued statuses, and asserts the engine's contract:
+
+* clean cascade (merged / already_ancestor) opens nothing,
+* a conflict opens ONE sync PR + tracked task and stops the cascade,
+* a tokenless project is skipped,
+* per-cycle + rolling caps + per-repo dedup are honoured,
+* the cascade target is never prod (the lower rung of every pair is non-prod).
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any
+from uuid import uuid4
+
+import pytest
+from roboco.config import settings
+from roboco.db.tables import AgentTable, ProjectTable
+from roboco.foundation import identity as _foundation
+from roboco.models.base import AgentRole, AgentStatus, TaskStatus, Team
+from roboco.services import env_sync_engine as env_sync_module
+from roboco.services.env_sync_engine import get_env_sync_engine
+from roboco.services.task import ENV_SYNC_SOURCE, get_task_service
+
+if TYPE_CHECKING:
+    from sqlalchemy.ext.asyncio import AsyncSession
+
+SYSTEM_UUID = _foundation.AGENTS["system"].uuid
+MAIN_PM_UUID = _foundation.AGENTS["main-pm"].uuid
+
+# A two-rung ladder: head=dev (PR target), prod=master (release target).
+_LADDER = [
+    {"name": "head", "branch": "dev"},
+    {"name": "prod", "branch": "master"},
+]
+
+
+class _FakeGit:
+    """Stand-in for GitService: drives the cascade from queued statuses."""
+
+    def __init__(self, statuses: list[str], *, pr_number: int = 42) -> None:
+        self._statuses = list(statuses)
+        self.sync_calls: list[tuple[str, str, str]] = []
+        self.pr_calls: list[tuple[str, str, str, str]] = []
+        self._pr_number = pr_number
+
+    async def sync_env_branch(
+        self, slug: str, target_branch: str, source_branch: str
+    ) -> dict[str, Any]:
+        self.sync_calls.append((slug, target_branch, source_branch))
+        status = self._statuses.pop(0) if self._statuses else "already_ancestor"
+        return {"status": status}
+
+    async def open_sync_pr(
+        self, slug: str, source_branch: str, target_branch: str, body: str
+    ) -> dict[str, Any] | None:
+        self.pr_calls.append((slug, source_branch, target_branch, body))
+        return {
+            "number": self._pr_number,
+            "url": f"https://github.com/x/{slug}/pull/{self._pr_number}",
+        }
+
+
+async def _get_or_create_agent(
+    db: AsyncSession, agent_id: object, role: AgentRole, slug: str
+) -> None:
+    if await db.get(AgentTable, agent_id) is None:
+        db.add(
+            AgentTable(
+                id=agent_id,
+                name=slug,
+                slug=f"{slug}-{uuid4().hex[:8]}",
+                role=role,
+                team=None,
+                status=AgentStatus.ACTIVE,
+                model_config={},
+                system_prompt="x",
+                capabilities=[],
+                permissions={},
+                metrics={},
+            )
+        )
+        await db.flush()
+
+
+async def _seed_project(
+    db: AsyncSession,
+    slug: str,
+    git_url: str,
+    *,
+    environments: list[dict[str, str]] | None = _LADDER,
+    token: str | None = "fake-encrypted-token",
+) -> ProjectTable:
+    project = ProjectTable(
+        id=uuid4(),
+        name=slug,
+        slug=slug,
+        git_url=git_url,
+        assigned_cell=Team.BACKEND,
+        created_by=SYSTEM_UUID,
+        environments=environments,
+        git_token_encrypted=token,
+    )
+    db.add(project)
+    await db.flush()
+    return project
+
+
+@pytest.fixture(autouse=True)
+async def _enabled(db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(settings, "env_sync_enabled", True)
+    monkeypatch.setattr(settings, "env_sync_max_per_cycle", 5)
+    monkeypatch.setattr(settings, "env_sync_max_open_tasks", 5)
+    await _get_or_create_agent(db_session, SYSTEM_UUID, AgentRole.SYSTEM, "system")
+    await _get_or_create_agent(db_session, MAIN_PM_UUID, AgentRole.MAIN_PM, "main-pm")
+
+
+def _patch_git(monkeypatch: pytest.MonkeyPatch, fake: _FakeGit) -> None:
+    monkeypatch.setattr(env_sync_module, "get_git_service", lambda _session: fake)
+
+
+@pytest.mark.asyncio
+async def test_clean_cascade_opens_nothing(
+    db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    proj = await _seed_project(db_session, "clean-a", "https://github.com/x/a.git")
+    fake = _FakeGit(["merged"])
+    _patch_git(monkeypatch, fake)
+    created = await get_env_sync_engine(db_session).run_cycle([proj])
+    assert created == []
+    # prod(master) merged into head(dev) — one cascade step for the 2-rung ladder.
+    assert fake.sync_calls == [("clean-a", "dev", "master")]
+    assert fake.pr_calls == []
+
+
+@pytest.mark.asyncio
+async def test_already_ancestor_is_clean(
+    db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    proj = await _seed_project(db_session, "anc-a", "https://github.com/x/anc.git")
+    fake = _FakeGit(["already_ancestor"])
+    _patch_git(monkeypatch, fake)
+    assert await get_env_sync_engine(db_session).run_cycle([proj]) == []
+    assert fake.sync_calls == [("anc-a", "dev", "master")]
+
+
+@pytest.mark.asyncio
+async def test_conflict_opens_pr_and_task_then_stops(
+    db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    # 4-rung ladder so a conflict on the FIRST (topmost) pair stops the cascade
+    # before reaching head — proving it does not cascade a dirty merge downward.
+    proj = await _seed_project(
+        db_session,
+        "conf-a",
+        "https://github.com/x/conf.git",
+        environments=[
+            {"name": "head", "branch": "dev"},
+            {"name": "qa", "branch": "qa"},
+            {"name": "stag", "branch": "stag"},
+            {"name": "prod", "branch": "master"},
+        ],
+    )
+    fake = _FakeGit(["conflict", "merged"])  # only the first is consumed
+    _patch_git(monkeypatch, fake)
+    created = await get_env_sync_engine(db_session).run_cycle([proj])
+
+    assert len(created) == 1
+    task = created[0]
+    assert task.source == ENV_SYNC_SOURCE
+    assert task.status == TaskStatus.PENDING
+    assert task.project_id == proj.id
+    # The cascade stopped at the first conflict: only one sync_env_branch call.
+    assert len(fake.sync_calls) == 1
+    # The sync PR targets the lower (non-prod) rung of the conflicted pair.
+    assert len(fake.pr_calls) == 1
+    _slug, _source_branch, target_branch, _body = fake.pr_calls[0]
+    assert target_branch != "master"  # never prod
+
+
+@pytest.mark.asyncio
+async def test_missing_ref_skips_without_pr(
+    db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    proj = await _seed_project(db_session, "miss-a", "https://github.com/x/miss.git")
+    fake = _FakeGit(["missing_ref"])
+    _patch_git(monkeypatch, fake)
+    created = await get_env_sync_engine(db_session).run_cycle([proj])
+    assert created == []
+    assert fake.pr_calls == []
+
+
+@pytest.mark.asyncio
+async def test_tokenless_project_skipped(
+    db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    proj = await _seed_project(
+        db_session, "notok", "https://github.com/x/notok.git", token=None
+    )
+    fake = _FakeGit(["merged"])
+    _patch_git(monkeypatch, fake)
+    created = await get_env_sync_engine(db_session).run_cycle([proj])
+    assert created == []
+    assert fake.sync_calls == []  # never attempted
+
+
+@pytest.mark.asyncio
+async def test_degenerate_ladder_skipped(
+    db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    # Single-rung ladder (head==prod) has no pairs to cascade.
+    proj = await _seed_project(
+        db_session,
+        "single",
+        "https://github.com/x/single.git",
+        environments=[{"name": "prod", "branch": "master"}],
+    )
+    fake = _FakeGit(["merged"])
+    _patch_git(monkeypatch, fake)
+    created = await get_env_sync_engine(db_session).run_cycle([proj])
+    assert created == []
+    assert fake.sync_calls == []
+
+
+@pytest.mark.asyncio
+async def test_per_cycle_cap(
+    db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.setattr(settings, "env_sync_max_per_cycle", 1)
+    p1 = await _seed_project(db_session, "cap-1", "https://github.com/x/c1.git")
+    p2 = await _seed_project(db_session, "cap-2", "https://github.com/x/c2.git")
+    fake = _FakeGit(["conflict", "conflict"])
+    _patch_git(monkeypatch, fake)
+    created = await get_env_sync_engine(db_session).run_cycle([p1, p2])
+    assert len(created) == 1  # capped at one per cycle
+
+
+@pytest.mark.asyncio
+async def test_deduped_per_repo(
+    db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """A repo with an open env_sync task is skipped until the PR resolves."""
+    proj = await _seed_project(db_session, "dedup", "https://github.com/x/d.git")
+    fake = _FakeGit(["conflict"])
+    _patch_git(monkeypatch, fake)
+    first = await get_env_sync_engine(db_session).run_cycle([proj])
+    assert len(first) == 1
+    # Second cycle, same repo still has the open task -> deduped (no new PR).
+    fake2 = _FakeGit(["conflict"])
+    _patch_git(monkeypatch, fake2)
+    second = await get_env_sync_engine(db_session).run_cycle([proj])
+    assert second == []
+    assert fake2.sync_calls == []  # cascade paused at the conflicted rung
+    assert len(await get_task_service(db_session).list_open_env_sync_tasks()) == 1
+
+
+@pytest.mark.asyncio
+async def test_disabled_is_noop(
+    db_session: AsyncSession, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.setattr(settings, "env_sync_enabled", False)
+    proj = await _seed_project(db_session, "off", "https://github.com/x/off.git")
+    fake = _FakeGit(["merged"])
+    _patch_git(monkeypatch, fake)
+    assert await get_env_sync_engine(db_session).run_cycle([proj]) == []
+    assert fake.sync_calls == []

tests/integration/test_migration_env_branches.py

@@ -0,0 +1,74 @@
+"""Per-project environment ladder column (migration 073).
+
+Migration 073 adds ``projects.environments`` (JSONB null). The real
+upgrade/downgrade chain is verified separately against a throwaway Postgres;
+these assertions guard the resulting schema shape and a value round-trip,
+mirroring ``test_migration_dep_update.py``.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+from uuid import uuid4
+
+import pytest
+from roboco.db.tables import AgentTable, ProjectTable
+from roboco.models import AgentRole, AgentStatus, Team
+from sqlalchemy import select
+
+if TYPE_CHECKING:
+    from sqlalchemy.ext.asyncio import AsyncSession
+
+
+async def _seed_project(db_session: AsyncSession) -> ProjectTable:
+    agent = AgentTable(
+        id=uuid4(),
+        name="Dev",
+        slug=f"be-dev-{uuid4().hex[:8]}",
+        role=AgentRole.DEVELOPER,
+        team=Team.BACKEND,
+        status=AgentStatus.ACTIVE,
+        model_config={},
+        system_prompt="dev",
+        capabilities=[],
+        permissions={},
+        metrics={},
+    )
+    db_session.add(agent)
+    await db_session.flush()
+    project = ProjectTable(
+        id=uuid4(),
+        name="L-Proj",
+        slug=f"l-proj-{uuid4().hex[:8]}",
+        git_url="https://example.com/r.git",
+        assigned_cell=Team.BACKEND,
+        created_by=agent.id,
+    )
+    db_session.add(project)
+    await db_session.flush()
+    return project
+
+
+@pytest.mark.asyncio
+async def test_environments_defaults_null(db_session: AsyncSession) -> None:
+    project = await _seed_project(db_session)
+    assert project.environments is None
+
+
+@pytest.mark.asyncio
+async def test_environments_round_trip(db_session: AsyncSession) -> None:
+    project = await _seed_project(db_session)
+    project.environments = [
+        {"name": "head", "branch": "dev"},
+        {"name": "prod", "branch": "master"},
+    ]
+    await db_session.flush()
+    row = (
+        await db_session.execute(
+            select(ProjectTable).where(ProjectTable.id == project.id)
+        )
+    ).scalar_one()
+    assert row.environments == [
+        {"name": "head", "branch": "dev"},
+        {"name": "prod", "branch": "master"},
+    ]

tests/unit/models/test_env_branches.py

@@ -0,0 +1,230 @@
+"""env_branches — shim, ladder pairs, head/prod resolution, normalization.
+
+Pure domain helpers (pydantic-only); no DB. The read-time shim synthesizes a
+degenerate single-branch ladder from ``default_branch`` when ``environments``
+is null, so every consumer behaves identically until a real ladder is declared.
+"""
+
+from __future__ import annotations
+
+import pytest
+from roboco.models.env_branches import (
+    EnvRung,
+    effective_environments,
+    head_branch,
+    ladder_pairs,
+    normalize_environments,
+    prod_branch,
+    promotion_chain,
+)
+
+
+class _Proj:
+    """Duck-typed project row (matches Project + ProjectTable surface)."""
+
+    def __init__(
+        self,
+        *,
+        default_branch: str = "master",
+        environments: list[dict[str, str]] | None = None,
+    ) -> None:
+        self.default_branch = default_branch
+        self.environments = environments
+
+
+# --- effective_environments shim ------------------------------------------
+
+
+def test_null_environments_synthesizes_degenerate_ladder() -> None:
+    proj = _Proj(default_branch="slave")
+    rungs = effective_environments(proj)
+    assert [(r.name, r.branch) for r in rungs] == [("head", "slave"), ("prod", "slave")]
+
+
+def test_empty_environments_synthesizes_degenerate_ladder() -> None:
+    proj = _Proj(default_branch="master", environments=[])
+    rungs = effective_environments(proj)
+    assert [(r.name, r.branch) for r in rungs] == [
+        ("head", "master"),
+        ("prod", "master"),
+    ]
+
+
+def test_missing_default_branch_falls_back_to_master() -> None:
+    proj = _Proj(default_branch="")  # falsy default_branch
+    assert head_branch(proj) == "master"
+    assert prod_branch(proj) == "master"
+
+
+def test_set_environments_returned_as_is_preserving_order() -> None:
+    proj = _Proj(
+        environments=[
+            {"name": "head", "branch": "dev"},
+            {"name": "qa", "branch": "qa"},
+            {"name": "prod", "branch": "master"},
+        ]
+    )
+    rungs = effective_environments(proj)
+    assert [r.branch for r in rungs] == ["dev", "qa", "master"]
+    assert all(isinstance(r, EnvRung) for r in rungs)
+
+
+# --- head_branch / prod_branch --------------------------------------------
+
+
+def test_head_and_prod_single_rung() -> None:
+    proj = _Proj(environments=[{"name": "prod", "branch": "master"}])
+    assert head_branch(proj) == "master"
+    assert prod_branch(proj) == "master"
+
+
+def test_head_and_prod_two_rungs() -> None:
+    proj = _Proj(
+        environments=[
+            {"name": "head", "branch": "slave"},
+            {"name": "prod", "branch": "master"},
+        ]
+    )
+    assert head_branch(proj) == "slave"
+    assert prod_branch(proj) == "master"
+
+
+def test_head_and_prod_four_rungs() -> None:
+    proj = _Proj(
+        environments=[
+            {"name": "head", "branch": "dev"},
+            {"name": "qa", "branch": "qa"},
+            {"name": "stag", "branch": "stag"},
+            {"name": "prod", "branch": "master"},
+        ]
+    )
+    assert head_branch(proj) == "dev"
+    assert prod_branch(proj) == "master"
+
+
+# --- ladder_pairs (prod -> head cascade) -----------------------------------
+
+
+def test_ladder_pairs_empty_for_single_rung() -> None:
+    assert (
+        ladder_pairs(_Proj(environments=[{"name": "prod", "branch": "master"}])) == []
+    )
+
+
+def test_ladder_pairs_two_rungs() -> None:
+    proj = _Proj(
+        environments=[
+            {"name": "head", "branch": "dev"},
+            {"name": "prod", "branch": "master"},
+        ]
+    )
+    pairs = ladder_pairs(proj)
+    assert [(u.branch, lower.branch) for u, lower in pairs] == [("master", "dev")]
+
+
+def test_ladder_pairs_four_rungs_top_down() -> None:
+    proj = _Proj(
+        environments=[
+            {"name": "head", "branch": "dev"},
+            {"name": "qa", "branch": "qa"},
+            {"name": "stag", "branch": "stag"},
+            {"name": "prod", "branch": "master"},
+        ]
+    )
+    # [(prod, stag), (stag, qa), (qa, head)] — merge upper into lower.
+    pairs = ladder_pairs(proj)
+    assert [(u.branch, lower.branch) for u, lower in pairs] == [
+        ("master", "stag"),
+        ("stag", "qa"),
+        ("qa", "dev"),
+    ]
+
+
+def test_ladder_pairs_lower_rung_is_never_prod() -> None:
+    """The cascade's target is never prod by construction — only CEO merges prod."""
+    proj = _Proj(
+        environments=[
+            {"name": "head", "branch": "dev"},
+            {"name": "qa", "branch": "qa"},
+            {"name": "prod", "branch": "master"},
+        ]
+    )
+    prod_name = prod_branch(proj)
+    for _upper, lower in ladder_pairs(proj):
+        assert lower.branch != prod_name
+
+
+# --- promotion_chain (full-chain release promotion) ----------------------
+
+
+def test_promotion_chain_empty_for_degenerate_ladder() -> None:
+    """head==prod => nothing to promote (no-op release promotion)."""
+    assert promotion_chain(_Proj(default_branch="master")) == []
+    assert (
+        promotion_chain(_Proj(environments=[{"name": "prod", "branch": "master"}]))
+        == []
+    )
+
+
+def test_promotion_chain_two_rungs() -> None:
+    proj = _Proj(
+        environments=[
+            {"name": "head", "branch": "dev"},
+            {"name": "prod", "branch": "master"},
+        ]
+    )
+    assert promotion_chain(proj) == ["dev"]
+
+
+def test_promotion_chain_four_rungs_head_first_excluding_prod() -> None:
+    proj = _Proj(
+        environments=[
+            {"name": "head", "branch": "dev"},
+            {"name": "qa", "branch": "qa"},
+            {"name": "stag", "branch": "stag"},
+            {"name": "prod", "branch": "master"},
+        ]
+    )
+    assert promotion_chain(proj) == ["dev", "qa", "stag"]
+
+
+# --- normalize_environments ------------------------------------------------
+
+
+def test_normalize_none_returns_none() -> None:
+    assert normalize_environments(None) is None
+    assert normalize_environments([]) is None
+
+
+def test_normalize_strips_and_preserves_order() -> None:
+    out = normalize_environments(
+        [{"name": " head ", "branch": " dev "}, {"name": "prod", "branch": "master"}]
+    )
+    assert out == [
+        {"name": "head", "branch": "dev"},
+        {"name": "prod", "branch": "master"},
+    ]
+
+
+def test_normalize_rejects_empty_name() -> None:
+    with pytest.raises(ValueError, match="non-empty name"):
+        normalize_environments([{"name": "", "branch": "dev"}])
+
+
+def test_normalize_rejects_empty_branch() -> None:
+    with pytest.raises(ValueError, match="non-empty name"):
+        normalize_environments(
+            [{"name": "head", "branch": "  "}]
+        )  # branch trimmed to empty
+
+
+def test_normalize_rejects_duplicate_branch() -> None:
+    with pytest.raises(ValueError, match="duplicate environment branch"):
+        normalize_environments(
+            [{"name": "head", "branch": "dev"}, {"name": "prod", "branch": "dev"}]
+        )
+
+
+def test_normalize_accepts_envrung_models() -> None:
+    out = normalize_environments([EnvRung(name="head", branch="dev")])
+    assert out == [{"name": "head", "branch": "dev"}]

tests/unit/runtime/test_orchestrator_shutdown_drain.py

@@ -50,6 +50,7 @@ def _make_orchestrator() -> AgentOrchestrator:
         "_self_heal_task",
         "_ci_watch_task",
         "_dep_update_task",
+        "_env_sync_task",
         "_release_manager_task",
         "_x_mentions_task",
         "_roadmap_engine_task",

tests/unit/services/test_release_executor.py

@@ -70,6 +70,9 @@ class _FakeOps:
         # instance (not via __init__ — keeps the constructor under the arg-count
         # gate) by tests that exercise the retry path.
         self._existing_sha: str | None = None
+        # env-chain promotion failure message; set on the instance (same arg-
+        # count-gate reason) by the promotion-failure test.
+        self._promote_raises: str | None = None
         self.calls: list[str] = []
         self.bumped_plan: list[str] | None = None
         self.bumped_version: str | None = None
@@ -79,6 +82,11 @@ class _FakeOps:
         self.calls.append("check")
         return self._already
 
+    async def promote_env_chain(self) -> None:
+        self.calls.append("promote")
+        if self._promote_raises is not None:
+            raise RuntimeError(self._promote_raises)
+
     async def release_commit_sha(self, _version: str) -> str | None:
         # Half-landed detection: a prior `chore(release): {version}` commit
         # already on the branch means a publish_failed retry must NOT re-run the
@@ -127,6 +135,7 @@ async def test_green_path_publishes_once() -> None:
     assert ops.calls.count("publish") == _ONE
     assert ops.calls == [
         "check",
+        "promote",
         "bump",
         "changelog",
         "gate",
@@ -204,6 +213,22 @@ async def test_publish_failure_returns_structured_publish_failed() -> None:
     assert ops.calls.count("publish") == _ONE
 
 
+@pytest.mark.asyncio
+async def test_promotion_failure_aborts_before_bump() -> None:
+    """A RuntimeError from promote_env_chain (a merge conflict in the
+    head->...->prod chain) becomes a structured ``promotion_failed`` result —
+    fail-closed: the bump/changelog/gate/commit/publish pipeline never runs."""
+    ops = _FakeOps()
+    ops._promote_raises = "env-chain promotion failed: non-fast-forward"
+    result = await ReleaseExecutor(ops).execute(_report())
+    assert result.status == "promotion_failed"
+    assert result.commit_sha is None
+    assert result.release_url is None
+    assert "bump" not in ops.calls
+    assert "commit" not in ops.calls
+    assert "publish" not in ops.calls
+
+
 def test_release_result_carries_outcome_fields() -> None:
     result = ReleaseResult(
         status="published",
@@ -291,6 +316,7 @@ async def test_wait_for_ci_scoped_to_release_commit_not_branch_latest(
         git_url="x",
         git_prefix=[],
         ci_workflow="ci.yml",
+        env_chain=[],
     )
     ops = _GitReleaseOps(session=MagicMock(), ctx=ctx)
     ok = await ops.wait_for_ci(commit_sha)
@@ -341,6 +367,7 @@ async def test_wait_for_ci_polls_through_rerun(
         git_url="x",
         git_prefix=[],
         ci_workflow="ci.yml",
+        env_chain=[],
     )
     ops = _GitReleaseOps(session=MagicMock(), ctx=ctx)
     ok = await ops.wait_for_ci(commit_sha)
@@ -387,6 +414,7 @@ async def test_wait_for_ci_exhausts_window_on_persistent_failure(
         git_url="x",
         git_prefix=[],
         ci_workflow="ci.yml",
+        env_chain=[],
     )
     ops = _GitReleaseOps(session=MagicMock(), ctx=ctx)
     ok = await ops.wait_for_ci(commit_sha)
@@ -515,6 +543,7 @@ async def test_release_push_argv_uses_extraheader_not_url_token(
         git_url=git_url,
         git_prefix=git_prefix,
         ci_workflow=None,
+        env_chain=[],
     )
     ops = _GitReleaseOps(session=MagicMock(), ctx=ctx)
     sha = await ops.commit_and_push("0.13.0")

tests/unit/services/test_release_executor_commit_fail_closed.py

@@ -21,6 +21,7 @@ def _ctx() -> _ReleaseContext:
         git_url="https://github.com/o/roboco",
         git_prefix=[],
         ci_workflow=None,
+        env_chain=[],
     )