[Sehaan-1]

Closes #249

What changed

Collapse \orch frontier set\ from 3N + 2 subprocesses down to a flat 4 subprocesses:

• Replaced per-branch forge queries (--head\ down-walk and --base\ up-walk) with a single repo-wide PR query (\pr list --state all [--limit 300] --json ...) indexed into in-memory \�yHead\ and \openByBase\ lookup maps.
• Replaced per-branch \git rev-parse \ calls with one batched \git rev-parse ... \ parsed in argument order.
• Preserved byte-identical \rontier.json\ output, generation numbering, \lowestUnmerged\ semantics, pin validation, locking, and all \UserError\ messages.
• Updated fake forge in \orch.test.ts\ to single-command match with call counter, asserting exactly 1 forge call per \rontier.set.
• Added 7 behavior tests covering multi-PR head branches, non-linear stacks, base-chain loops (both walk directions), invalid forge rows, batched SHA ref failures, trunk short-circuit, and forge argv contracts.

Verification

• Bun tests, strict typecheck, static invariants, and plugin validation pass.
• The exact candidate is installed in every affected harness.
• The changed behavior passes from each real user surface.
• The \live-gate\ status on the final head links the evidence comment (installed version, surface, action, observed result).

Mergify does not queue a pull request without \live-gate\ on its exact head. Do not merge, tag, release, or roll out without it.

[mergify]

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• check-success=live-gate
• check-success=verify
• #review-threads-unresolved = 0
• -draft

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• -files~=^\.github/
• base = main

[greptile-apps]

[Medium impact] The change affects frontier setup in the orchestrator workflow.

Fix the repository-wide PR limit before merging so older stacks remain discoverable.

Findings

1.  Older stack PRs disappear ▶

Summary

Replaces per-branch forge queries with one repository-wide query and batches Git SHA lookups.

• Frontier setup makes two data calls for a non-trunk stack.

_{Reviews (1) · Last reviewed commit: "perf(orch): collapse frontier set to two..." · Reviewed by Greptile}