> This document describes the architecture of the DeepSeek Harness — the foundation of **DeepSeek Code**. The governing principle, from the microkernel design discussion: **everything is a plugin**. The core is deliberately tiny — a handful of abstract services plus one concrete loop plugin (`dsh-agent-loop`) — and every product feature is a plugin against the extension surface described here, without modifying the loop.
> Dependency rule: extension plugins depend on interfaces, never on `dsh-agent-loop` (the loop is swappable); the sanctioned exception is the composition bundle `dsh-agent-spine-demo`, whose job is assembling the concrete spine.
> This document covers **behavior**; type shapes live in [core-data-structures/](../core-data-structures/core.md), the per-event/service reference in the [generated catalog](../cordis-catalog/events.md), per-package contracts in the package READMEs ([map](../../packages/README.md)).
> Hard-won bug-class rules: each pattern below is a class of defect that actually shipped or nearly shipped here, stated as the rule that prevents its recurrence. Read this before writing lifecycle, concurrency, subprocess, or teardown code.
> **Dispose must reach quiescence, not just request it** — A teardown that issues kills/aborts but returns before the work stops leaves orphans. Make cleanup async and await the children's exit (kill → await `done`), and close listener/notification registries BEFORE killing so late completions stay silent. Tests prove disposal waited (pid gone right after `await fiber.dispose()`), not merely that the process eventually dies.
> **Async state is not synchronous state** — `agent.followup()` does not flip status before returning; a background task's completion races turn boundaries; `reader.close()` fires for both EOF and disposal. Never gate control flow on a status you only just requested — drive lifecycle off the events/promises that actually fire (`agent/status`, `task.done`), and observe the transition (saw `running` THEN `idle`) instead of treating status as a per-follow-up result: several queued follow-ups run as consecutive turns under one `running` interval, while cancellation or disposal can discard unstarted items.
> **Coverage gate** (`pnpm run test:coverage`): the gating run, per-file 100% on `packages/*/*/src`. An uncovered line is often dead code the gate is correctly flagging for deletion, not a missing test to bolt on. Line coverage is necessary, never sufficient — it proves lines ran, not that the feature works as shipped.
覆盖率门禁（`pnpm run test:coverage`）：作为合入门禁校验，要求 `packages/*/*/src` 目录下每个文件行覆盖率达到 100%。未覆盖代码行大多是无用死代码，门禁标记这类代码是提示删除，而非单纯补充测试。行覆盖率是必要条件，但远不充分：它仅能证明代码被执行过，无法保证功能符合线上预期。
> We are DeepSeek — do not ration real-API tests. A no-key test proves the plumbing; only a with-key run proves the agent works against a real model. Write many: real prompts that write files, multi-turn conversations, tool use, cancellation mid-stream. Cheapest and highest-value are **smoke tests** that boot the real example, send one real prompt, and check the world — they catch the "green unit tests, broken product" class that mocks structurally cannot. The self-skip exists only so secretless CI and keyless contributors aren't blocked; it is not a cost signal.
> **Prefer the real implementation over a mock** — Mock only the genuinely expensive or non-deterministic boundary (the LLM adapter, the network, the clock); keep everything downstream real. A hand-rolled stand-in proves the bridge moves bytes, not that the shipping tool behaves as asserted — the two drift while the test stays green.
> Blob hashes, not commit hashes, so the record is computable for files edited in the same PR (`git hash-object foo.md`) and consistency is a pure content comparison. The recorded hash also recovers the exact last-confirmed text of either side (`git cat-file -p <hash>`), so an out-of-sync pair is updated by diffing the edited side against its last-confirmed state and patching the counterpart minimally — never by re-translating whole files.
> The gate's limit, stated plainly: a green gate means the pair was confirmed consistent at these exact contents, not that the confirmation was sound. It checks hashes and shape; it cannot judge whether the two sides actually say the same thing — that is the reviewer's half of the contract. A re-recorded pair with a sloppy counterpart passes the gate; it must not pass review.
> Comparing git timestamps of the pair (no record) — rejected: formatting-only edits would false-positive, and a counterpart committed after an unrelated edit would false-negative; content identity is the only signal that means what the gate claims.
> **Universal requirement**: every in-scope document merges as a complete bilingual pair. The manifest contains only explicit exclusions: it has no per-file rollout list, date cutoff, or README-specific policy class. […] Pairing is a continuing obligation: every later edit to either side updates the counterpart and consistency record in the same change.
