G0 D6: gateway reverse proxy fronting all 4 backing services · 2 scrum fixes · G0 COMPLETE

Last day of Phase G0. Gateway promotes the D1 stub endpoints into
real reverse-proxies on :3110 fronting storaged + catalogd + ingestd
+ queryd. /v1 prefix lives at the edge — internal services route on
/storage, /catalog, /ingest, /sql, with the prefix stripped by a
custom Director per Kimi K2's D1-plan finding.

Routes:
  /v1/storage/*  → storaged
  /v1/catalog/*  → catalogd
  /v1/ingest     → ingestd
  /v1/sql        → queryd

Acceptance smoke 6/6 PASS — every assertion goes through :3110, none
direct to backing services. Full ingest → storage → catalog → query
round-trip verified end-to-end. The smoke's "rows[0].name=Alice"
assertion is the architectural payoff: five binaries, six HTTP
routes, one round-trip through one edge.

Cross-lineage scrum on shipped code:
  - Opus 4.7 (opencode):                      1 BLOCK + 2 WARN + 2 INFO
  - Kimi K2-0905 (openrouter):                1 BLOCK + 3 WARN + 1 INFO (3 false positives, all from one wrong TrimPrefix theory)
  - Qwen3-coder (openrouter):                 5 completion tokens — "No BLOCKs."

Fixed (2, both Opus single-reviewer):
  O-BLOCK: Director path stripping fails if upstream URL has a
    non-empty path. The default Director's singleJoiningSlash runs
    BEFORE the custom code, so an upstream like http://host/api
    produces /api/v1/storage/... after the join — then TrimPrefix("/v1")
    is a no-op because the string starts with /api. Fix: strip /v1
    BEFORE calling origDirector. New TestProxy_SubPathUpstream regression
    locks this in. Today: bare-host URLs only, dormant — but moving
    gateway behind a sub-path in prod would have silently 404'd.
  O-WARN2: url.Parse is permissive — typo "127.0.0.1:3211" (no scheme)
    parses fine, produces empty Host, every request 502s. mustParseUpstream
    fail-fast at startup with a clear message naming the offending
    config field.

Dismissed (3, all Kimi, same false TrimPrefix theory):
  K-BLOCK "TrimPrefix loops forever on //v1storage" — false, single
    check-and-trim, no loop
  K-WARN "no upper bound on repeated // removal" — same false theory
  K-WARN "goroutines leak if upstream parse fails while binaries
    running" — confused scope; binaries are separate OS processes
    launched by the smoke script

D1 smoke updated (post-D6): the 501 stub probes are gone (gateway no
longer stubs /v1/ingest and /v1/sql). Replaced with proxy probes that
verify gateway forwards malformed requests to ingestd and queryd. Launch
order changed from parallel to dep-ordered (storaged → catalogd →
ingestd → queryd → gateway) since catalogd's rehydrate now needs
storaged, queryd's initial Refresh needs catalogd.

All six G0 smokes (D1 through D6) PASS end-to-end after every fix
round. Phase G0 substrate is complete: 5 binaries, 6 routes, 25 fixes
applied across 6 days from cross-lineage review.

G1+ next: gRPC adapters, Lance/HNSW vector indices, Go MCP SDK port,
distillation rebuild, observer + Langfuse integration.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/shared/config.go

@@ -19,7 +19,7 @@ import (
 // the section it cares about, but they all share the same file so
 // operators have one place to look.
 type Config struct {
-	Gateway  ServiceConfig `toml:"gateway"`
+	Gateway  GatewayConfig `toml:"gateway"`
 	Storaged ServiceConfig `toml:"storaged"`
 	Catalogd CatalogConfig `toml:"catalogd"`
 	Ingestd  IngestConfig  `toml:"ingestd"`
@@ -37,6 +37,18 @@ type IngestConfig struct {
 	CatalogdURL string `toml:"catalogd_url"`
 }
 
+// GatewayConfig adds the upstream URLs the reverse proxy fronts.
+// Each route family (/v1/storage, /v1/catalog, /v1/ingest, /v1/sql)
+// has its own upstream so we can scale services independently or
+// move them to different boxes without touching gateway code.
+type GatewayConfig struct {
+	Bind        string `toml:"bind"`
+	StoragedURL string `toml:"storaged_url"`
+	CatalogdURL string `toml:"catalogd_url"`
+	IngestdURL  string `toml:"ingestd_url"`
+	QuerydURL   string `toml:"queryd_url"`
+}
+
 // QuerydConfig adds queryd-specific knobs. queryd talks DuckDB
 // directly to MinIO via DuckDB's httpfs extension (so no storaged
 // URL needed), and reads the catalog over HTTP for view registration.
@@ -84,7 +96,13 @@ type LogConfig struct {
 // during the migration. G5 cutover flips gateway back to 3100.
 func DefaultConfig() Config {
 	return Config{
-		Gateway:  ServiceConfig{Bind: "127.0.0.1:3110"},
+		Gateway: GatewayConfig{
+			Bind:        "127.0.0.1:3110",
+			StoragedURL: "http://127.0.0.1:3211",
+			CatalogdURL: "http://127.0.0.1:3212",
+			IngestdURL:  "http://127.0.0.1:3213",
+			QuerydURL:   "http://127.0.0.1:3214",
+		},
 		Storaged: ServiceConfig{Bind: "127.0.0.1:3211"},
 		Catalogd: CatalogConfig{Bind: "127.0.0.1:3212", StoragedURL: "http://127.0.0.1:3211"},
 		Ingestd: IngestConfig{