| **English** | [简体中文](adapter-contracts.zh-CN.md)
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| # Adapter capability contracts
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| These are discovery contracts. No implementation is bundled.
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| | Capability | Required input | Required receipt | Honest absence behavior |
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| | `agent.registry.read` | role/capability query, policy scope | candidates plus source revision | produce a packet for manual delivery; do not invent a recipient |
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| | `agent.spawn` | recipient ID and validated `bounded_subagent` packet | dispatch ID, recipient ID, timestamp, requested/effective mode | mark packet `undelivered` |
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| | `agent.task.create` | recipient ID and validated `independent_task` packet | dispatch ID, separately resumable task/thread ID, recipient ID, timestamp, authoritative workspace receipt | leave `undelivered`, or explicitly degrade only when the packet allows it and continuity is not required |
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| | `agent.message` | live dispatch ID and follow-up packet | message ID and timestamp | state that no follow-up mechanism was available |
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| | `workspace.authoritative.resolve` | stable root ID and task context | resolved real path plus resolution evidence | require a parent-supplied root and verify it from the parent filesystem; never substitute the current cwd |
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| | `collaboration.log.append` | structured event with redacted refs | exit code zero, event ID, append position/version | omit shared append; do not claim atomic logging |
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| | `agent.inbox.deliver` | recipient ID and directed message | delivery ID and destination ref | keep a copyable message and mark it undelivered |
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| Adapters may map these contracts to a specific Harness, but must not:
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| - promote optional capabilities to bundled features;
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| - alter safety or routing policy;
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| - expose secret values in packets or receipts;
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| - report `sent`, `spawned`, `followed_up`, or `appended` without provider evidence.
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| Provider-specific metadata belongs under a namespaced receipt field and must
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| not replace the required evidence. Validate neutral packet and receipt fields
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| against [`../contracts/`](../contracts/).
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| For a v1.3 durable chain, the validated handoff packet supplies `handoff_id`
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| and its persistence contract supplies `contract_id`. The dispatch adapter adds
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| its real `dispatch_id`. Every downstream return, closure receipt, and parent
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| verification repeats all three IDs. Reject a receipt when any ID belongs to a
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| different task, even when its fields and artifact paths otherwise look valid.
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| IDs are correlation labels, so each required target also carries a fresh
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| dispatcher-issued `evidence_nonce`. The adapter or parent combines it with the
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| real `dispatch_id` to produce the target's `evidence_anchor`. The file,
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| provider event, or board proposal must carry that anchor; the parent derives
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| it again from the saved dispatch receipt and contract instead of trusting
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| child-supplied labels alone.
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| Represent honest non-delivery with the `undelivered` branch in
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| `dispatch-receipt.schema.json`; it requires a reason and forbids invented
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| dispatch/task IDs or provider receipts.
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| `agent.task.create` means an independently identifiable, resumable task or
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| thread. A nested child that can only return to its parent does not satisfy this
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| contract. An adapter may report a degradation receipt only when it contains
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| both modes and a concrete reason.
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| Persistence does not choose the adapter. A `bounded_subagent` packet may carry
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| a required persistence contract and complete all four durable targets through
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| `agent.spawn`; that still remains bounded. Only a real, separately resumable
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| task/thread receipt from `agent.task.create` establishes `independent_task`.
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| For `independent_task`, compare the adapter's workspace receipt with the
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| persistence contract field by field: root ID, normalized resolved path, and
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| resolution evidence. Also compare a v1.3 return's declared mode with the
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| dispatch receipt's effective mode. A correct ID set does not excuse either
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| mismatch.
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| The selected log provider owns its atomicity guarantee. A thrown error, timeout,
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| missing receipt, malformed receipt, or nonzero exit means append failure. Do not
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| manufacture an event ID after failure.
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| The central board is not an append adapter. Configure one writer (normally the
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| parent/coordinator); children send proposals through their return packet. The
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| single writer serializes updates and re-reads the board after every merge.
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| ---
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| > Both language editions are maintained in sync. If they ever diverge, the **English edition** is authoritative — please open an [issue](https://github.com/LucioLiu/handoff-protocol/issues) if you spot one.
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