ADR 0010: Write-side single-threading

Status

Accepted

Context

Parallel autonomous writers collide on merges, violating determinism and bypassing coherent review narratives.

Decision

Parallelism is acceptable on read paths / research; writes that land in one branch must serialize through orchestration (Lead Engineer pattern) unless human explicitly forks work with merge policy.

Encoded in recursion limits and orchestration semantics (docs/concepts/10-subagent-strategy.md).

Consequences

• Positive: merges stay reviewable; fewer conflict-induced silent behaviour changes.
• Negative: throughput cap — tackled via batching orchestration waves, not uncontrolled agents.