Agent Merge Conflict Arbiter

Agent Merge-Conflict Arbiter

Resolve a git merge conflict between two AGENTS' branches as an impartial third party. Agents resolving conflicts against a peer's work reliably either overwrite the peer or abandon their own change — they lack the peer's context and are biased toward their own side. This skill is the fix: a neutral reconciler that receives both diffs plus both sides' stated intents and produces a merged result, like a merge-queue arbiter.

When to Use

• Two agent branches/worktrees collide during a parallel campaign (kanban engineering pipeline, parallel-PR wave, multi-worktree refactor).
• git merge or git rebase halts on conflicts between two agents' work and neither original agent should self-adjudicate.
• Do NOT use for conflicts within a single agent's own work, or for trivial lockfile/generated-file conflicts (regenerate those instead).

Prerequisites

• A repo checkout containing the halted merge, or the two branch names plus permission to run the merge yourself.
• Both sides' intent sources: kanban completion summaries (terminal running hermes kanban show <task-id>), PR bodies, or at minimum each branch's commit messages.
• The project's build/test command, if one exists.

How to Run

Standalone — a human (or agent) invokes this skill inside the conflicted repo: load the skill, then follow the Procedure top to bottom.

Spawned neutral agent — the preferred shape in multi-agent campaigns:

• delegate_task: spawn a subagent whose task message contains the repo path, both branch names, and both sides' intent summaries verbatim, plus an instruction to follow this skill.
• Kanban-native: create a reconciliation card assigned to a third profile (not either worker's profile) with BOTH conflicted cards linked as parents — kanban_create(title="reconcile branch-a x branch-b", assignee="reconciler", parents=["t_a", "t_b"]). The parent links carry both sides' completion summaries into the reconciler's context automatically; the card body should name the repo path and the two branches.

Quick Reference

Impartiality contract: never favor the side that spawned you; touch ONLY conflicted regions (no drive-by edits); every design-question pick must appear explicitly in the hand-back summary.

Procedure

1. Gather both sides

• Run via terminal: git status (confirm the conflicted state and list conflicted files), git merge-base <A> <B>, then for each side git log --oneline <base>..<side> and git diff <base>..<side> -- <file> for every conflicted file. In a halted merge, HEAD is one side and MERGE_HEAD is the other.
• Collect each side's intent: hermes kanban show <task-id> for completion summaries/metadata, or the PR body, or the commit messages from the log above. Write down one sentence of intent per side before touching any file.
• Done when: you can state both intents in your own words and have both diffs for every conflicted file.

2. Classify every conflicted hunk

• Open each conflicted file with read_file and locate each <<<<<<</=======/>>>>>>> block.
• Assign each hunk exactly one class from the Quick Reference table, judging by the stated intents — not by which change looks nicer.
• If a single hunk contains multiple independent decisions (e.g., new logic that combines cleanly PLUS a styling/rounding choice both sides answered differently), decompose it into sub-decisions and classify each one.
• A single file often mixes classes: one hunk may be a design collision while a neighboring hunk is disjoint. Classify per hunk, not per file.
• Done when: every hunk has a written class and a one-line rationale.

3. Resolve under the impartiality contract

• Edit each hunk with patch (or write_file for whole-file rewrites):
  • disjoint-intent → merge both changes so each intent is fully served.
  • same-question-different-answer → pick the answer that best serves the STATED intents (e.g., an intent of "strict validation" beats "quick default" if the task required correctness). Never split the difference into a hybrid neither side asked for.
  • superseded → keep the surviving side; delete the dead premise.
• Never favor the side that spawned you. If intents genuinely tie, escalate (block the kanban card / report back) rather than guess.
• Change nothing outside conflict markers — no formatting, renames, or opportunistic fixes.
• git add each resolved file via terminal.
• Done when: search_files finds no <<<<<<< markers in the repo and every resolved file is staged.

4. Verify

• Run the project's build/tests via terminal; at minimum import/execute the touched modules. Both intents must be observable in the merged behavior (e.g., side A's new semantics AND side B's disjoint addition both present).
• Complete the merge: git commit (the default merge message plus a body listing hunk decisions is fine).
• Done when: verification passes and the merge commit exists.

5. Hand back

• Produce a completion summary naming EVERY hunk decision: file:lines — class — which side(s) kept — rationale. For every same-question-different-answer hunk, state the design question and the answer you picked so a human can veto it — never bury a design call.
• Kanban: kanban_complete(summary=...). Standalone: print the summary.
• Done when: the summary is delivered and lists all hunks.

Pitfalls

• Self-favoring: if you were spawned by one of the conflicting agents, you are structurally biased — state this and weigh the other side's intent deliberately. Prefer the third-profile shape so this never arises.
• Splitting the difference on a design collision produces a hybrid nobody designed; pick one answer and surface it.
• Per-file classification: files usually mix hunk classes; classifying a whole file as one class silently drops a disjoint change.
• Drive-by edits make the merge unreviewable and steal decisions from the original agents.
• Missing intents: commit messages alone can be thin; prefer kanban completion summaries or PR bodies. If neither side's intent is recoverable, escalate instead of guessing.
• Repeat offenders: repeated conflicts on the SAME file across rounds are a hotspot signal, not routine reconciliation work — flag it (e.g. a hotspot: <path> — <reason> kanban comment) so the orchestrator decomposes that file, rather than serially reconciling every new collision on it.

Verification

• git status shows a clean tree on the target branch with a merge commit.
• No conflict markers remain (search_files pattern <<<<<<<).
• Build/tests pass; both sides' intents are demonstrably present or the dropped one is explicitly named in the summary.
• The hand-back summary enumerates every hunk with class and rationale.