refactor(workflow): S11 branch group workflow subgraphs

[gsxdsm]

Stack Slice

• Slice: S11
• Milestone: Branch Groups
• Base branch: feature/workflow-owned-merge-s10-self-healing-recovery-events
• Full plan: docs/plans/2026-06-09-003-refactor-workflow-owned-merge-full-migration-slices-plan.md

Goal

Move branch-group member integration and group promotion into workflow-owned merge subgraphs.

Dependency

S6 merge capabilities, S8 merge processing, and S10 recovery events.

Expected Scope

group merge coordinator, merge trait, integration worktree, built-in IR, shared branch-group workflow tests.

Expected Tests

Member integration with autoMerge exception, blocked group promotion, conflict routing, final promotion guards.

Exit Gate

Branch-group coordinator no longer owns task lifecycle independent of workflow runtime.

Status

Draft stack placeholder. This PR reserves ordering and review context; implementation should replace or extend the handoff artifact before this slice is marked ready.

Implementation Added

• Added branch-group workflow routing helpers for member integration and group promotion.\n- Covered the shared-member integration exception and global/group promotion gates in tests.

Summary by CodeRabbit

• New Features

  • Added branch group merge workflow decision capabilities with configurable auto-merge controls at global and group levels.

• Documentation

  • Added planning documentation for branch group workflow subgraph functionality.

• Tests

  • Added comprehensive test coverage for branch group merge workflow decision behaviors.

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[greptile-apps]

Greptile Summary

This PR delivers the S11 slice of the workflow-owned merge migration, adding decideBranchGroupMemberIntegration and decideBranchGroupPromotion as pure decision functions for branch-group subgraph routing. All three previously-flagged logic issues have been resolved: the FN-5819 shared-member exception is correctly scoped to bypass only the global settings.autoMerge gate, non-shared members now return manual-required when global auto-merge is disabled, and task.autoMerge no longer gates group promotion.

• decideBranchGroupMemberIntegration: shared members always proceed (FN-5819 exception); non-shared members are gated by settings.autoMerge only, matching FN-5147.
• decideBranchGroupPromotion: gated exclusively by settings.autoMerge and groupAutoMerge; the third test case with task.autoMerge: false confirms task-level auto-merge is intentionally excluded from the promotion gate.
• Exports: both functions and their types are added to the engine's public surface in index.ts.

Confidence Score: 5/5

Safe to merge — pure decision functions with no side effects, spec-aligned logic, and all three prior concerns addressed.

The two new functions are pure and isolated; they touch no shared state, no persistence layer, and no lifecycle mutations. The core invariants from FN-5147 and FN-5819 are correctly implemented and directly tested. The only findings here are a duplicate return path (style) and a missing happy-path test case.

No files require special attention; the implementation is self-contained in workflow-branch-group-merge.ts.

Important Files Changed

Filename	Overview
packages/engine/src/workflow-branch-group-merge.ts	New decision module for branch-group member integration and group promotion; all three previously-flagged logic issues (task.autoMerge gates, dead non-shared branch) have been addressed and the spec is faithfully implemented.
packages/engine/src/tests/workflow-branch-group-merge.test.ts	Covers the three spec-critical paths (shared-member FN-5819 exception, non-shared gate, task.autoMerge excluded from promotion gate); missing the non-shared happy path and groupAutoMerge-undefined cases.
packages/engine/src/index.ts	Exports the two new decision functions and their TypeScript types; no issues found.
docs/plans/workflow-owned-merge-stack/s11-branch-group-subgraphs.md	Planning doc for the S11 slice; documentation only, no code changes.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[decideBranchGroupMemberIntegration] --> B{assignmentMode\n=== 'shared'?}
    B -- Yes --> C[allowed: true\noutcome: success\nFN-5819 exception]
    B -- No --> D{settings.autoMerge\n=== false?}
    D -- Yes --> E[allowed: false\noutcome: manual-required\nreason: global-auto-merge-disabled]
    D -- No --> F[allowed: true\noutcome: success]

    G[decideBranchGroupPromotion] --> H{settings.autoMerge\n=== false?}
    H -- Yes --> I[allowed: false\noutcome: manual-required\nreason: global-auto-merge-disabled]
    H -- No --> J{groupAutoMerge\n=== false?}
    J -- Yes --> K[allowed: false\noutcome: manual-required\nreason: group-auto-merge-disabled]
    J -- No / undefined --> L[allowed: true\noutcome: success]

Loading

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flowchart TD
    A[decideBranchGroupMemberIntegration] --> B{assignmentMode\n=== 'shared'?}
    B -- Yes --> C[allowed: true\noutcome: success\nFN-5819 exception]
    B -- No --> D{settings.autoMerge\n=== false?}
    D -- Yes --> E[allowed: false\noutcome: manual-required\nreason: global-auto-merge-disabled]
    D -- No --> F[allowed: true\noutcome: success]

    G[decideBranchGroupPromotion] --> H{settings.autoMerge\n=== false?}
    H -- Yes --> I[allowed: false\noutcome: manual-required\nreason: global-auto-merge-disabled]
    H -- No --> J{groupAutoMerge\n=== false?}
    J -- Yes --> K[allowed: false\noutcome: manual-required\nreason: group-auto-merge-disabled]
    J -- No / undefined --> L[allowed: true\noutcome: success]

Loading

_{Reviews (10): Last reviewed commit: "fix(FN-000): address PR review feedback ..." | Re-trigger Greptile}

[gsxdsm]

Non-shared branch group members [can] bypass the global auto-merge gate.

Addressed: shared member integration keeps the scoped auto-merge exception, while non-shared member integration now respects settings.autoMerge: false. Promotion gating remains covered separately.

[stage-review]

Ready to review this PR? Stage has broken it down into 4 individual chapters for you:

	Title
1	Document branch group workflow subgraph plan
2	Implement branch group merge decision logic
3	Export workflow decision helpers and types
4	Verify branch group merge workflow behaviors

_{Chapters generated by Stage for commit e9d47a3 on Jun 17, 2026 2:48pm UTC.}

[coderabbitai]

Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@docs/plans/workflow-owned-merge-stack/s11-branch-group-subgraphs.md`:
- Around line 16-18: Update the description in lines 16-18 to accurately reflect
the current state of the PR. Replace the text that characterizes this as
"intentionally a handoff artifact, not the completed implementation" with
wording that reflects the actual content - that this slice includes shipped
decision logic and tests along with the S11 review slot reservation. This
ensures the documentation accurately describes what is actually delivered in
this PR stack.

In `@packages/engine/src/__tests__/workflow-branch-group-merge.test.ts`:
- Line 10: Remove the `as any` type assertions from the branchContext object
across all test fixtures and replace any invalid assignmentMode values with the
correct contract. The TaskBranchAssignmentMode type only accepts "shared" or
"per-task-derived", so at file
packages/engine/src/__tests__/workflow-branch-group-merge.test.ts, line 10 can
keep "shared" but remove `as any`, line 21 must replace the invalid "exclusive"
value with either "shared" or "per-task-derived" and remove `as any`, and lines
33 and 49 should similarly use only valid assignmentMode values and remove `as
any`. This ensures the test fixtures are properly typed and the regression
surface is not weakened by type escaping.

In `@packages/engine/src/workflow-branch-group-merge.ts`:
- Around line 18-53: Add FNXC policy documentation comments to both workflow
gate functions to comply with coding guidelines. For both
decideBranchGroupMemberIntegration and decideBranchGroupPromotion functions, add
a concise FNXC:Branch-Groups JSDoc or inline comment that documents the
requirement date and rationale for the merge policy decisions being encoded in
each function. Follow the format "FNXC:Area-of-product" with the specific area
being "Branch-Groups" and ensure the comment explains the user-facing
branch-group merge policy requirement that each decision function implements.

🪄 Autofix (Beta)

✅ Autofix completed

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 9e7bb47b-df7d-4468-a326-c441355178aa

📥 Commits

Reviewing files that changed from the base of the PR and between b16d22e and dd36403.

📒 Files selected for processing (4)

• docs/plans/workflow-owned-merge-stack/s11-branch-group-subgraphs.md
• packages/engine/src/__tests__/workflow-branch-group-merge.test.ts
• packages/engine/src/index.ts
• packages/engine/src/workflow-branch-group-merge.ts

[coderabbitai]

Note

Autofix is a beta feature. Expect some limitations and changes as we gather feedback and continue to improve it.

Fixes Applied Successfully

Fixed 3 file(s) based on 3 unresolved review comments.

Files modified:

• docs/plans/workflow-owned-merge-stack/s11-branch-group-subgraphs.md
• packages/engine/src/__tests__/workflow-branch-group-merge.test.ts
• packages/engine/src/workflow-branch-group-merge.ts

Commit: 04c9b238c678b7086fe31ffafc791f882ba233e7

The changes have been pushed to the feature/workflow-owned-merge-s11-branch-group-subgraphs branch.

Time taken: 5m 49s