Milestone 3.5.D.1 — Go gRPC Client for Context Assembly

Status: Planned
Goal: Track D — Proxy Integration
Phase: 3.5 — Extraction & Context Assembly
Estimated effort: 2 days
Track: Track D — Proxy Integration
Depends on: Milestone 3.5.C.6 (gRPC service skeleton)

Why This Milestone Exists

The proxy needs a thin, well-tested Go wrapper around the ContextAssemblyService gRPC contract — not raw grpc.ClientConn calls scattered in the handler. This mirrors the pattern already established for the auth gRPC client (fail-closed for auth, fail-open for context).

Orientation (indicative)

Named paths, package layouts, libraries, schemas, env vars, and commands anywhere on this page are rough sketches for orientation — inspiration and a baseline, not a required change list.

During implementation, expect to:

open the live tree and follow existing patterns before inventing new ones
research current constraints (latency, tenancy, deploy shape, libraries) more deeply than this page can
advance the design beyond the sketch where measurement or code reality says so
land work in different filenames, merged packages, deferred docs, or new surfaces when the situation calls for it

Prefer outcomes over matching any particular file tree or command sequence.

Areas that may be involved (situational — not a checklist):

Proxy service (HTTP, bootstrap, config)
Context assembly service
Workers / task runtime

Design

Assemble never returns a Go error to its caller — this is deliberate, matching applyDirectiveInjection's existing "missing context leaves messages unchanged" fail-open contract. A memory-quality degradation should never become an HTTP error.

// Illustrative — exact path may differ
func (c *Client) Assemble(ctx context.Context, req AssembleRequest) AssembleResult {
 ctx, cancel := context.WithTimeout(ctx, c.timeout) // default 45ms
 defer cancel()
 resp, err := c.stub.AssembleContext(ctx, req.toProto())
 if err != nil {
 return AssembleResult{Messages: req.OriginalMessages, Fallback: true}
 }
 return fromProto(resp)
}

Success signals

Outcome-oriented signals that the milestone is in good shape. Exact filenames, package layouts, and commands may differ from any sketches above.

Fully unit-tested with fault injection for all 4 degradation levels (exact path may differ)
Assemble never returns a Go error — always returns AssembleResult with Fallback flag
Default timeout 45ms, independent of server's internal 40ms budget
Tests for the new behavior pass
Repo guards / CI checks still pass

Prerequisites

Milestone 3.5.C.6 (gRPC service skeleton)