Proposed specificationSource-located exemplarH1 H3

Harness mimicry and service hosting

Preserve an interface while changing its implementation or host.

JOIN POINTexternal_harness_compatibilityRECORD STATUSCandidate · v0.1.0

UML class view

The proposed contract drawn as participant roles, received calls, and numbered dependencies.

Object interactions

The same roles and calls as a class collaboration and a numbered message sequence.

Object interaction diagram for Harness mimicry and service hosting, showing role collaboration and a numbered message sequence — FIG. P29 / OBJECT INTERACTIONS
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Pointcut

Where the mechanism applies. All four dimensions belong to the proposed match, not just its vocabulary.

Context: One harness exposes or consumes an external agent-client or service interface.
Trigger: A remote client invokes the adapter or a hosted backend is selected.
Structure: Protocol adapter, identity, capability mapping, and service boundary.
Effect: The external protocol is preserved while semantics and permissions are translated explicitly.

Protected contract

The obligation that clients, operators, and auditors should be able to rely on.

Requires: Protocol version and capability mapping are known.
Ensures: Requests, results, and errors satisfy the compatibility contract.
Invariant: Interface compatibility does not erase backend-specific authorization or effects.
Violation: Unsupported capabilities, disconnects, and translation errors are explicit.

Negative control

A similar function signature without protocol compatibility is insufficient.

Variation & lifecycle

The hot spot is admitted only where the protected semantics survive.

Permitted variation

ACP emulation, server hosting, transport adapter, and backend registry.

Test obligation

Test cross-backend parity, unsupported method, reconnect, and permission mapping.

Evolution question

Did harnesses evolve from mimicry toward hosted multi-backend services?

Prompt + code design

An illustrative prompt and a small design sketch for the proposed contract. Names and APIs are invented; this is not a repository excerpt.

PROMPT SKETCH

Expose the harness through a declared compatibility protocol. Map capabilities explicitly, return protocol-shaped errors, and reject requests that the backend cannot satisfy.

CODE DESIGN / PYTHON

def handle(request, backend, protocol):
    if not protocol.supports(request.method):
        return protocol.error("method_not_supported", request.id)
    try:
        result = backend.invoke(protocol.to_backend(request))
    except BackendError as error:
        return protocol.error(error.code, request.id, detail=error.detail)
    return protocol.from_backend(result)

Illustrative design sketch. Compatibility is a contract over requests, results, and errors, not a renamed endpoint. This example is a teaching aid, not implementation evidence or a conformance claim.

Detection & matching

The frozen rule that retrieves this record, the canonical source exemplar, and the control that should stay unmatched.

Join point: external_harness_compatibility
Source locator: See the source record.
Lexical cue: (?i)\b(?:mimic(?:ry)?|emulat(?:e|ion)|ACP[_-]?client|agent[_-]?client[_-]?protocol)\bFrozen expression, v0.1.0. A match is a retrieval cue, not a confirmed implementation.
Aliases: None
Canonical exemplar: OpenHands/software-agent-sdkopenhands-sdk/openhands/sdk/agent/acp_agent.py:1815Support: tests/sdk/agent/test_acp_agent.py:1
Negative control: A similar function signature without protocol compatibility is insufficient.

Scope-anchored review. pohe-agent analyze <repo> --pattern P29 anchors the cue to its enclosing declaration and checks a separate operational signature for all four pointcut dimensions. Missing roles and negative-control risks remain visible; a structural match is not E2/E3. Calibration report ↗

Repository files

Up to five public files retrieved by the frozen cue and pinned to the audited commit. A match is a place to inspect, not a confirmed implementation.

01OpenHands/software-agent-sdkopenhands-sdk/openhands/sdk/agent/acp_agent.py:1815CANONICAL SOURCE 02aaif-goose/goosecrates/goose/src/acp/common.rs:4RETRIEVAL CUE 03agno-agi/agnolibs/agno/agno/fs/base.py:150RETRIEVAL CUE 04anomalyco/opencodepackages/cli/src/acp/agent.ts:11RETRIEVAL CUE 05browser-use/browser-usebrowser_use/actor/page.py:22RETRIEVAL CUE

Evidence & provenance

Each layer answers a different question. Do not substitute retrieval for review.

Source-located exemplar

A concrete source anchor is available for this proposed record. It is one exemplar, not evidence that all repositories—or every contract field—conform.

Review boundary: this candidate and its specification come from an AI-assisted study. Independent human validation remains open.

ANY-EVIDENCE FAMILY COVERAGE29/36

80.6% of repository families in the frozen panel have at least one current cue, historical cue, or canonical source layer. This is not confirmed prevalence.

Current lexical-cue repositories: 31 / 41

Canonical source anchorOpenHands/software-agent-sdk 5c524ad65d81openhands-sdk/openhands/sdk/agent/acp_agent.py:1815

Supporting surfacetests/sdk/agent/test_acp_agent.py:1

ACP-compatible agent hosting and external harness adaptation.

Exploratory retrieval cue Regex / v0.1.0

(?i)\b(?:mimic(?:ry)?|emulat(?:e|ion)|ACP[_-]?client|agent[_-]?client[_-]?protocol)\b

This expression is a discovery instrument only. A match is a retrieval cue—not a confirmed implementation, pointcut match, or contract proof.