44 lines
1.8 KiB
Markdown
44 lines
1.8 KiB
Markdown
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# ADR-0002 — Out-of-process attachment
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**Status:** accepted · **Date:** 2026-09-04
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## Context
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A FLUID interface has to be able to wrap an existing API. The question is
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whether fluid-core is a library that API imports, or a process that sits in
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front of it.
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Blueprint §42 already answers this implicitly: `gateway`, `revision-router` and
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`adapter-r41`/`adapter-r42` are separate deployments. That is process-level
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integration, not library-level.
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## Decision
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fluid-core attaches out of process. The gateway and router run in front of
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adapter processes reached over the network. The target API contributes no code,
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imports no library, and may be written in any stack.
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An in-process SDK is explicitly deferred, not rejected. It would buy richer
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signal — call-sequence correlation and structured consumer feedback that a
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proxy cannot see from outside — at the cost of SDK versioning across languages.
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## Rationale
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Minimal conformance (`FluidAPIStandards.md` §36) requires a deterministic
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contract, revision identity, telemetry, declared intent, an evidence link,
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responsibility boundaries and deterministic security. Every one of those is
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observable from the proxy. Nothing in the conformance core needs to be inside
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the target process.
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The language-agnostic promise is only credible if the framework never asks for
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an import. Making the SDK optional from the start, rather than retrofitting the
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proxy later, is what keeps that true.
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## Consequences
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- The revision descriptor carries `runtime.upstream`: the adapter's address.
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- Interaction topology (Blueprint §6.4) is reconstructed from correlation IDs
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observed at the gateway, not reported by the consumer.
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- Explicit feedback (`FluidAPIStandards.md` §15) arrives over the wire as its
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own endpoint rather than through an SDK call.
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