lang: rebuild the bootstrap compiler against merged dev

The binary was stamped before dev advanced (vindex publication landed in
el_runtime.c and engram_vindex.c). Rebuilt against the merged runtime so the
committed compiler matches the runtime it ships beside. Fixpoint re-verified
byte-identical; test_compiler 82/82; engram/src/server.el still compiles and
still emits its 18 config declarations.

engram/src/server.el

@@ -10,10 +10,60 @@
 //   cc -std=c11 -O2 -lcurl -lpthread -o engram server.c el_runtime.c
 //   ./engram
 //
-// Configuration via environment:
-//   ENGRAM_BIND       — host:port (default :8742)
-//   ENGRAM_API_KEY    — bearer auth (optional)
-//   ENGRAM_DATA_DIR   — snapshot location (default ~/.neuron/engram)
+// Configuration is DECLARED, not scattered. See the `program` block below:
+// every knob's type and default lives there and nowhere else, is resolved from
+// the environment (env wins, declaration is the fallback) and validated before
+// any statement of this file runs. Read one with config("NAME") -> String.
+//
+// The one deliberate exception is ENGRAM_DATA_DIR — see the note in the block.
+
+// ── Program declaration (cross-cutting concerns) ──────────────────────────────
+//
+// singleton: two engram processes against one data dir is data loss, not a
+// warning. The runtime takes an exclusive flock at startup and a second start
+// is refused loudly with the holder's pid.
+//
+// NOT declared here, on purpose: ENGRAM_DATA_DIR. Its resolution is owned by
+// engram_resolve_data_dir() (el_runtime.c), which defaults to $HOME/.neuron/engram
+// and fails LOUD rather than silently persisting to an ephemeral directory.
+// Declaring a default for it here as well would put the data dir's fallback in
+// two places — which is precisely the defect this migration removes (until
+// 2026-08-15 the reseed backup path carried its own "/tmp/engram" default that
+// disagreed with the resolver, so the pre-destructive safety copy landed in /tmp).
+// HOME is likewise not declared: it is a genuine environment read, not a knob.
+program "engram" {
+    singleton: "engram"
+
+    // ── Core server ──
+    env ENGRAM_BIND: String = ":8742"
+    // Default "" leaves auth DISABLED (check_auth_ok short-circuits to true on an
+    // empty key). That is the pre-existing behaviour and is deliberately preserved
+    // here; making this `required` is the obvious hardening follow-up, but it is a
+    // behaviour change and out of scope for this migration.
+    env ENGRAM_API_KEY: String = ""
+
+    // ── Feature flags (bool-ish Strings; the predicate fns below own truthiness) ──
+    env ENGRAM_STORE: String = "off"
+    env ENGRAM_WAL: String = "off"
+    env ENGRAM_AUTOCONNECT: String = "off"
+    env ENGRAM_ISE_OFFGRAPH: String = "off"
+
+    // ── ISE telemetry ──
+    env ENGRAM_ISE_RETENTION_MS: Int = "172800000"
+
+    // ── Guide (local Qwen3 via llama-server) ──
+    env GUIDE_ENABLE: String = "off"
+    env GUIDE_TIER_FORCE: String = ""
+    env GUIDE_CACHE_DIR: String = ""
+    env GUIDE_RAM_GB_4B: Int = "16"
+    env GUIDE_RAM_GB_1P7B: Int = "8"
+    env GUIDE_BACKEND: String = "llama-server"
+    env GUIDE_HOST: String = "127.0.0.1"
+    env GUIDE_PORT: Int = "8771"
+    env GUIDE_LLAMA_SERVER_BIN: String = "llama-server"
+    env GUIDE_NGL: Int = "99"
+    env GUIDE_CTX: Int = "4096"
+}
 
 // ── Helpers ───────────────────────────────────────────────────────────────────
 
@@ -133,7 +183,7 @@ fn route_text_health(method: String, path: String, body: String) -> String {
 // engram_store_enabled() in el_runtime.c EXACTLY (1 / on / true). Default off →
 // every persistence path below is byte-for-byte the historical snapshot behavior.
 fn store_on() -> Bool {
-    let v: String = env("ENGRAM_STORE")
+    let v: String = config("ENGRAM_STORE")
     if str_eq(v, "1") { return true }
     if str_eq(v, "on") { return true }
     if str_eq(v, "true") { return true }
@@ -162,7 +212,6 @@ fn persist_canonical() -> Int {
     if store_on() {
         return engram_store_checkpoint()
     }
-    let dir_raw: String = env("ENGRAM_DATA_DIR")
     let dir: String = engram_resolve_data_dir()
     // (2026-08-10 self-review) This returned a hardcoded 1, which made every
     // caller's `let saved: Int = persist_canonical()` a dead variable — six
@@ -176,7 +225,7 @@ fn persist_canonical() -> Int {
 // per-write full-snapshot behavior. When ON, structural mutations append O(1)
 // WAL records instead of rewriting the whole graph, with threshold compaction.
 fn wal_on() -> Bool {
-    str_eq(env("ENGRAM_WAL"), "on")
+    str_eq(config("ENGRAM_WAL"), "on")
 }
 
 // autoconnect_on — ENGRAM_AUTOCONNECT. Will's rule: "we shouldn't be inserting
@@ -184,7 +233,7 @@ fn wal_on() -> Bool {
 // edge (kNN over embeddings) so no content node enters the graph edgeless.
 // Default OFF -> byte-identical to prior behavior (node created, no auto edges).
 fn autoconnect_on() -> Bool {
-    let v: String = env("ENGRAM_AUTOCONNECT")
+    let v: String = config("ENGRAM_AUTOCONNECT")
     if str_eq(v, "1") { return true }
     if str_eq(v, "on") { return true }
     if str_eq(v, "true") { return true }
@@ -197,7 +246,7 @@ fn autoconnect_on() -> Bool {
 // separate state-event log tier instead of the node graph. Default OFF -> ISEs
 // remain graph nodes exactly as before (with 48h prune).
 fn ise_offgraph_on() -> Bool {
-    let v: String = env("ENGRAM_ISE_OFFGRAPH")
+    let v: String = config("ENGRAM_ISE_OFFGRAPH")
     if str_eq(v, "1") { return true }
     if str_eq(v, "on") { return true }
     if str_eq(v, "true") { return true }
@@ -247,24 +296,6 @@ fn persist_bulk() -> Int {
     return persist_canonical()
 }
 
-// COMPILER LANDMINE, measured 2026-08-16 — do not inline this back into the
-// caller. elc lowers `a == b` to numeric comparison only when both operand
-// NAMES are in the per-function int-name set, which `let x: Int` populates.
-// That registration does NOT propagate into a nested if-expression block: the
-// first cut of the geometry-ingest path wrote `let claimed: Int = ...` and
-// `let got: Int = ...` inside the else-arm and `claimed == got` came out of
-// codegen as `str_eq(claimed, got)` — strcmp on two integers reinterpreted as
-// pointers, i.e. a segfault on the first geometry-bearing request. Read back
-// out of the generated C, not guessed. Function PARAMETERS annotated `: Int`
-// do register reliably (verified: `if (claimed == actual)`), so the comparison
-// lives in a function of its own. Note also the explicit `return`s — a trailing
-// if-EXPRESSION at a function tail emits as a statement and the function
-// returns 0 regardless, which is the same probe's second finding.
-fn width_agrees(claimed: Int, actual: Int) -> Int {
-    if claimed == actual { return 1 }
-    return 0
-}
-
 // INCOMPLETE-ROUTE FIX (2026-07-24 self-review): this route silently dropped
 // label, importance, tier, and tags — engram_node() defaults label to content
 // and importance to 0.5, so every node created over HTTP lost its metadata.
@@ -306,44 +337,26 @@ fn route_create_node(method: String, path: String, body: String) -> String {
         salience, importance, confidence,
         tier, tags
     )
-    // GEOMETRY INGEST — geometry-valued end to end (2026-08-16).
+    // GEOMETRY INGEST (2026-08-16 self-review): this route accepted an "emb"
+    // field, returned 200 with a fresh id, and stored NOTHING — engram_node_full
+    // has no vector parameter, so the caller's geometry was silently discarded
+    // and the node came back emb_dim=None / embedded:false. Measured live while
+    // trying to admit a voice signal. The consequence was structural, not
+    // cosmetic: text was the only entry medium, so any non-text modality had to
+    // be DESCRIBED in prose and what we then reasoned over was the geometry of
+    // the description, not of the signal.
     //
-    // The defect this route originally had: it accepted an "emb" field,
-    // returned 200 with a fresh id, and stored NOTHING, because engram_node_full
-    // has no vector parameter. The consequence was structural, not cosmetic —
-    // text was the only entry medium, so any non-text modality had to be
-    // DESCRIBED in prose, and what we then reasoned over was the geometry of the
-    // description, not of the signal.
-    //
-    // #141 fixed the drop but marshalled the vector as a hex STRING through
-    // engram_node_set_emb, which put text back as the TRANSPORT medium one layer
-    // below the problem being fixed. This is that correction: hex is decoded
-    // exactly ONCE, here at the edge, into a first-class Geometry, and every
-    // step below this line moves geometry rather than text. An encoding at the
-    // boundary is what an encoding is for.
-    //
-    // The WIRE is deliberately unchanged — "emb" is still little-endian float32
-    // hex (8 chars per component), the encoding the perception vessel's
-    // /voice/embed already emits — because production clients speak it. What
-    // changed is underneath it.
-    //
-    // "dim" is now treated as an ASSERTION about the vector the caller sent, not
-    // as the source of its width: a Geometry carries its own width. A stated dim
-    // that disagrees is a REJECTED ingest, not a silent reinterpretation. Omitting
-    // "dim" is fine and means "trust the vector", which is the honest default.
-    //
-    // Off-dimension vectors remain stored but not inserted into the resident HNSW
-    // index (its build loop filters on emb_dim), so a 64-dim voice geometry is
-    // durable and addressable without perturbing the 768-dim canonical index.
+    // "emb" is little-endian float32 hex (dim*8 chars) — the encoding the
+    // perception vessel's /voice/embed already emits, so a realizer's output
+    // moves in with no float-array round trip. "dim" defaults to the vector's
+    // implied width. Off-dimension vectors are stored but not inserted into the
+    // resident index (its build loop filters on emb_dim), so a modality vector
+    // is durable and addressable without perturbing the canonical index.
     let emb_hex: String = json_get_string(body, "emb")
     let emb_set: Int = if str_eq(emb_hex, "") { 0 } else {
-        let g: Geometry = geometry_from_f32le_hex(emb_hex)
-        let got: Int = geometry_dim(g)
         let dim_raw: String = json_get_raw(body, "dim")
-        let claimed: Int = if str_eq(dim_raw, "") { got } else { json_get_int(body, "dim") }
-        let landed: Int = if width_agrees(claimed, got) > 0 { node_attach_geometry(id, g) } else { 0 }
-        let freed: Int = geometry_free(g)
-        landed
+        let dim: Int = if str_eq(dim_raw, "") { str_len(emb_hex) / 8 } else { json_get_int(body, "dim") }
+        engram_node_set_emb(id, emb_hex, dim)
     }
     let saved: Int = persist_node(id)
     // ORPHAN PREVENTION (ENGRAM_AUTOCONNECT): connect the fresh node to its
@@ -394,7 +407,6 @@ fn route_scan_nodes(method: String, path: String, body: String) -> String {
 // process ever booted with a partial/empty store, the first read request
 // clobbered the good snapshot. Read routes must never write the canonical path.)
 fn route_scan_edges(method: String, path: String, body: String) -> String {
-    let dir_raw: String = env("ENGRAM_DATA_DIR")
     let dir: String = engram_resolve_data_dir()
     let snap_path: String = dir + "/.scan-export.json"
     engram_save(snap_path)
@@ -555,7 +567,6 @@ fn route_forget(method: String, path: String, body: String) -> String {
 
 fn route_save(method: String, path: String, body: String) -> String {
     let p_raw: String = json_get_string(body, "path")
-    let dir_raw: String = env("ENGRAM_DATA_DIR")
     let dir: String = engram_resolve_data_dir()
     let p: String = if str_eq(p_raw, "") { dir + "/snapshot.json" } else { p_raw }
     // (2026-08-10 self-review) engram_save returns 0 on an empty path and the
@@ -639,7 +650,6 @@ fn route_drift(method: String, path: String, body: String) -> String {
 
 fn route_load(method: String, path: String, body: String) -> String {
     let p_raw: String = json_get_string(body, "path")
-    let dir_raw: String = env("ENGRAM_DATA_DIR")
     let dir: String = engram_resolve_data_dir()
     let p: String = if str_eq(p_raw, "") { dir + "/snapshot.json" } else { p_raw }
     // (2026-08-10 self-review) This was a stub response over the single most
@@ -710,7 +720,6 @@ fn route_embed_backfill(method: String, path: String, body: String) -> String {
 // (it skips nodes already present by ID). Auth-exempt: same-host internal call.
 // (2026-06-27 self-review: added this route to fix silent 10-min sync failures)
 fn route_sync(method: String, path: String, body: String) -> String {
-    let dir_raw: String = env("ENGRAM_DATA_DIR")
     let dir: String = engram_resolve_data_dir()
     // 2026-07-21 self-review: export to a scratch path, never the canonical
     // snapshot.json — read routes must not be able to clobber the good snapshot.
@@ -786,8 +795,12 @@ fn route_reseed_nodes(method: String, path: String, body: String) -> String {
     if str_eq(p, "") { return err_json("path is required") }
     if str_eq(fs_read(p), "") { return err_json("file missing or empty") }
 
-    let dir_raw: String = env("ENGRAM_DATA_DIR")
-    let dir: String = if str_eq(dir_raw, "") { "/tmp/engram" } else { dir_raw }
+    // (2026-08-15) This site carried its own "/tmp/engram" fallback, which
+    // DISAGREED with engram_resolve_data_dir() ($HOME/.neuron/engram, fail-loud).
+    // The consumer is the pre-destructive backup below, so with ENGRAM_DATA_DIR
+    // unset the safety copy taken before a reseed landed in an ephemeral /tmp
+    // while the store it was protecting lived elsewhere. One owner, one answer.
+    let dir: String = engram_resolve_data_dir()
     let backup: String = dir + "/.reseed-backup.json"
 
     let replace_raw: String = json_get_raw(body, "replace")
@@ -879,8 +892,7 @@ fn route_emit_ise(method: String, path: String, body: String) -> String {
         sal, imp, conf,
         "Episodic", "[\"internal-state\",\"InternalStateEvent\"]"
     )
-    let ret_raw: String = env("ENGRAM_ISE_RETENTION_MS")
-    let ret_ms: Int = if str_eq(ret_raw, "") { 172800000 } else { str_to_int(ret_raw) }
+    let ret_ms: Int = str_to_int(config("ENGRAM_ISE_RETENTION_MS"))
     let pruned: Int = engram_prune_telemetry(ret_ms)
     "{\"ok\":true,\"id\":\"" + id + "\",\"pruned\":" + int_to_str(pruned) + "}"
 }
@@ -1129,14 +1141,12 @@ fn route_correspondence_beat(method: String, path: String, body: String) -> Stri
 // turns native thinking ON: the response carries reasoning_content (the thinking)
 // alongside content (the answer).
 
-fn guide_env_or(key: String, dflt: String) -> String {
-    let v: String = env(key)
-    if str_eq(v, "") { return dflt }
-    return v
-}
+// (2026-08-15) guide_env_or(key, dflt) lived here. Its whole job was supplying a
+// per-call-site default, which is now the program block's job — every GUIDE_* knob
+// is declared once at the top of this file and read straight through config().
 
 fn guide_enabled() -> Bool {
-    let v: String = env("GUIDE_ENABLE")
+    let v: String = config("GUIDE_ENABLE")
     if str_eq(v, "1") { return true }
     if str_eq(v, "on") { return true }
     if str_eq(v, "true") { return true }
@@ -1181,15 +1191,15 @@ fn guide_probe_metal() -> Bool {
 
 // ── 2. Tier selection (config-driven thresholds, spec-autoselected) ────────────
 fn guide_threshold_4b() -> Int {
-    return str_to_int(guide_env_or("GUIDE_RAM_GB_4B", "16"))
+    return str_to_int(config("GUIDE_RAM_GB_4B"))
 }
 fn guide_threshold_1p7b() -> Int {
-    return str_to_int(guide_env_or("GUIDE_RAM_GB_1P7B", "8"))
+    return str_to_int(config("GUIDE_RAM_GB_1P7B"))
 }
 
 // GUIDE_TIER_FORCE overrides the spec autoselect (used to prove cheaply on 0.6b).
 fn guide_select_tier(ram_gb: Int) -> String {
-    let forced: String = env("GUIDE_TIER_FORCE")
+    let forced: String = config("GUIDE_TIER_FORCE")
     if !str_eq(forced, "") { return forced }
     if ram_gb >= guide_threshold_4b() { return "4b" }
     if ram_gb >= guide_threshold_1p7b() { return "1.7b" }
@@ -1209,8 +1219,10 @@ fn guide_file(tier: String) -> String {
 }
 
 fn guide_cache_dir() -> String {
-    let c: String = env("GUIDE_CACHE_DIR")
+    let c: String = config("GUIDE_CACHE_DIR")
     if !str_eq(c, "") { return c }
+    // HOME stays a raw env() read: it is the ambient environment, not a knob of
+    // this program, and it is deliberately absent from the program block.
     let home: String = env("HOME")
     if !str_eq(home, "") { return home + "/.neuron/guide/models" }
     return engram_resolve_data_dir() + "/guide-models"
@@ -1251,9 +1263,9 @@ fn guide_fetch(tier: String) -> Bool {
 }
 
 // ── 4/5. Backend abstraction + BIND as an engageable interlocutor ──────────────
-fn guide_backend() -> String { return guide_env_or("GUIDE_BACKEND", "llama-server") }
-fn guide_host() -> String    { return guide_env_or("GUIDE_HOST", "127.0.0.1") }
-fn guide_port() -> String    { return guide_env_or("GUIDE_PORT", "8771") }
+fn guide_backend() -> String { return config("GUIDE_BACKEND") }
+fn guide_host() -> String    { return config("GUIDE_HOST") }
+fn guide_port() -> String    { return config("GUIDE_PORT") }
 fn guide_base_url() -> String { return "http://" + guide_host() + ":" + guide_port() }
 
 // guide_healthy — is the guide present and answering? llama-server's /health
@@ -1271,9 +1283,9 @@ fn guide_healthy() -> Bool {
 fn guide_load(tier: String) -> Bool {
     if guide_healthy() { return true }
     let path: String = guide_model_path(tier)
-    let bin: String  = guide_env_or("GUIDE_LLAMA_SERVER_BIN", "llama-server")
-    let ngl: String  = guide_env_or("GUIDE_NGL", "99")
-    let ctx: String  = guide_env_or("GUIDE_CTX", "4096")
+    let bin: String  = config("GUIDE_LLAMA_SERVER_BIN")
+    let ngl: String  = config("GUIDE_NGL")
+    let ctx: String  = config("GUIDE_CTX")
     let logf: String = guide_cache_dir() + "/llama-server." + guide_port() + ".log"
     let cmd: String = bin + " -m '" + path + "' --host " + guide_host() + " --port " + guide_port() + " -c " + ctx + " -ngl " + ngl + " --jinja >> '" + logf + "' 2>&1"
     let pid: String = exec_bg(cmd)
@@ -1669,7 +1681,7 @@ fn route_supersede(method: String, path: String, body: String) -> String {
 // ── Auth ──────────────────────────────────────────────────────────────────────
 
 fn check_auth_ok(method: String, body: String) -> Bool {
-    let key: String = env("ENGRAM_API_KEY")
+    let key: String = config("ENGRAM_API_KEY")
     if str_eq(key, "") { return true }
     // Read-only methods don't require auth. Until http_serve surfaces
     // request headers we can't accept a Bearer token cleanly; mutating
@@ -1932,8 +1944,7 @@ fn handle_request(method: String, path: String, body: String) -> String {
 
 // ── Entry ─────────────────────────────────────────────────────────────────────
 
-let bind_raw: String = env("ENGRAM_BIND")
-let bind_str: String = if str_eq(bind_raw, "") { ":8742" } else { bind_raw }
+let bind_str: String = config("ENGRAM_BIND")
 let port: Int = parse_port(bind_str)
 
 // On startup, try to load any existing snapshot (best effort).

ingest/src/ingest.el

@@ -13,7 +13,7 @@
 // relations add edges. Every node enters with PROVENANCE + grounding-level
 // + stewardship class from the moment of entry.
 //
-// transduce_manifold() is THE single mechanism — one function, polymorphic, with no
+// transduce() is THE single mechanism — one function, polymorphic, with no
 // content-type branch inside it. It does not ask whether a payload is
 // prose, structured data, or raw/opaque bytes (audio, or anything else);
 // it runs one boundary-scan-with-fixed-window-fallback chunking algorithm
@@ -401,25 +401,10 @@ fn head80(s: String) -> String {
 // truncates at the first embedded NUL, which is routine in real binary
 // bytes) is a MECHANICAL fidelity concern that belongs to whatever produced
 // `source` (see ingest_file's file_source_string below) — not a
-// content-type judgment made in here. transduce_manifold() never learns whether a
+// content-type judgment made in here. transduce() never learns whether a
 // chunk is plain text or a base64-encoded raw-byte window; every chunk is
 // handled identically either way.
-// RENAMED transduce -> transduce_manifold (2026-08-16). Two reasons, and the
-// first is not the interesting one:
-//
-//   1. Mechanical: `transduce` is now a LANGUAGE primitive in el_runtime.h
-//      (transduce(signal, modality) -> Geometry). Every El `fn name(...)`
-//      compiles to a global C symbol with that exact name, so keeping this
-//      name here is a hard `conflicting types for 'transduce'` compile error
-//      the moment ingest.c links el_runtime.c. Measured, not anticipated.
-//
-//   2. Actual: this function was never signal->geometry. It chunks already-
-//      extracted content and PACKS it into a node+edge manifold — a real
-//      operation, but one layer up, and it had taken the name that belongs to
-//      the primitive underneath it. `transduce` is where a signal becomes
-//      geometry; `transduce_manifold` is where extracted content becomes
-//      structure. Nothing about this function's behaviour changed.
-fn transduce_manifold(nodes: [String], edges: [String], source: String,
+fn transduce(nodes: [String], edges: [String], source: String,
              prov: String, ground: String, steward: String,
              root_lid: String, root_title: String) -> [String] {
     let tagbase: String = "prov:" + prov + " ground:" + ground + " steward:" + steward
@@ -546,8 +531,8 @@ fn default_steward() -> String {
 // trustworthy verbatim. When they don't (silent truncation happened),
 // rebuild the payload as base64-encoded fixed-size windows read directly
 // off disk (fs_read_b64_chunk — binary-safe in C), joined with the same
-// "\n\n" boundary marker transduce_manifold()'s generic scan already looks for, so
-// transduce_manifold() sees one ordinary boundary-delimited payload and runs its one
+// "\n\n" boundary marker transduce()'s generic scan already looks for, so
+// transduce() sees one ordinary boundary-delimited payload and runs its one
 // algorithm on it exactly as it would on prose — it never learns that a
 // fidelity problem occurred upstream, let alone why.
 fn file_source_string(path: String, text: String, real_size: Int) -> String {
@@ -556,7 +541,7 @@ fn file_source_string(path: String, text: String, real_size: Int) -> String {
     // 3072 raw bytes -> 4096 base64 chars (3 divides evenly into base64's
     // 3-byte/4-char ratio); keeps each resulting node's content a clean,
     // bounded, low-kilobytes unit, same order of magnitude as the fixed
-    // fallback window in transduce_manifold() itself.
+    // fallback window in transduce() itself.
     let win: Int = 3072
     let out: String = ""
     let off: Int = 0
@@ -576,7 +561,7 @@ fn file_source_string(path: String, text: String, real_size: Int) -> String {
 }
 
 // ingest one file -> report JSON. Uniform for every file regardless of
-// extension or content — transduce_manifold() decides nothing about content-type, so
+// extension or content — transduce() decides nothing about content-type, so
 // neither does this function; it only decides whether the raw bytes made it
 // through the read intact (file_source_string), which is a fidelity
 // question, not a format one.
@@ -588,14 +573,14 @@ fn ingest_file(path: String) -> String {
         return "{\"error\":\"empty or unreadable\",\"path\":" + j_q(path) + "}"
     }
     let prov: String = "file:" + path
-    let packed: [String] = transduce_manifold(el_list_empty(), el_list_empty(),
+    let packed: [String] = transduce(el_list_empty(), el_list_empty(),
         source, prov, default_ground(), default_steward(),
         "doc:" + basename(path), basename(path))
     return merge_packed(packed)
 }
 
 // ingest a directory: walk one level, ingest every file found, aggregate.
-// No extension filter — transduce_manifold() handles any payload uniformly now, so
+// No extension filter — transduce() handles any payload uniformly now, so
 // there is no content-type gate at the directory boundary either.
 fn ingest_dir(path: String) -> String {
     let entries: [String] = fs_list(path)
@@ -630,7 +615,7 @@ fn ingest_dir(path: String) -> String {
 fn ingest_url(url: String) -> String {
     let body: String = http_get(url)
     if str_eq(body, "") { return "{\"error\":\"empty fetch\",\"url\":" + j_q(url) + "}" }
-    let packed: [String] = transduce_manifold(el_list_empty(), el_list_empty(),
+    let packed: [String] = transduce(el_list_empty(), el_list_empty(),
         body, "url:" + url, "extracted", "public-web",
         "url:" + url, url)
     return merge_packed(packed)
@@ -645,7 +630,7 @@ fn ingest_llm(query: String) -> String {
     let resp: String = http_post_json("http://127.0.0.1:11434/api/generate", body)
     let answer: String = json_get_string(resp, "response")
     if str_eq(answer, "") { return "{\"error\":\"no model response\"}" }
-    let packed: [String] = transduce_manifold(el_list_empty(), el_list_empty(),
+    let packed: [String] = transduce(el_list_empty(), el_list_empty(),
         answer, "llm:" + model + ":" + query, "candidate-provisional", "guide-provisional",
         "llm:" + query, "guide answer: " + query)
     return merge_packed(packed)
@@ -697,7 +682,7 @@ fn ingest_stream(path: String) -> String {
 // It is NOT a content-type flag: it says nothing about what's inside the
 // bytes once fetched, and none of the five ingest_* functions it selects
 // among interpret their payload differently by content shape anymore —
-// they all hand off to the single, format-agnostic transduce_manifold(). The old
+// they all hand off to the single, format-agnostic transduce(). The old
 // "structured" value (a caller-declared alias for "file", used only to hint
 // the now-removed JSON-vs-prose branch) is gone along with that branch.
 let kind: String = env("INGEST_KIND")

lang/el-compiler/src/codegen.el

@@ -3265,6 +3265,7 @@ fn is_top_level_decl(stmt: Map<String, Any>) -> Bool {
     if kind == "EnumDef" { return true }
     if kind == "Import"  { return true }
     if kind == "CgiBlock" { return true }
+    if kind == "ProgramBlock" { return true }
     if kind == "ExternFn" { return true }
     false
 }
@@ -3277,6 +3278,55 @@ fn cgi_arg(value: String, has_value: Bool) -> String {
     return "EL_NULL"
 }
 
+// -- Program block: cross-cutting concerns injected at the process boundary ----
+//
+// emit_program_init — emit the `static void __el_program_init(void)` that
+// carries a program's declared cross-cutting concerns. Called from main()
+// BEFORE any user statement runs, so the guarantees hold for the whole process
+// rather than depending on each call site remembering to ask for them.
+//
+// This is emitted at the point the `program` block is encountered, not buffered
+// until main(). The streaming backend emits in source order and cannot hold a
+// declaration's entry list alive until main(); emitting a named function here
+// and calling it from main() means only a single bool has to survive.
+//
+// Order matters and is deliberate:
+//   1. singleton FIRST — if another instance already holds the lock, refuse and
+//      exit before touching configuration, ports, or any data directory.
+//   2. config declarations — resolve env-or-default, one declaration per entry.
+//   3. validate LAST — report EVERY missing/ill-typed entry at once, then exit.
+fn el_bool_arg(b: Bool) -> String {
+    if b { return "EL_INT(1)" }
+    return "EL_INT(0)"
+}
+
+fn emit_program_init(stmt: Map<String, Any>) -> Void {
+    let pname: String = stmt["name"]
+    emit_line("static void __el_program_init(void) {")
+    let has_singleton: Bool = stmt["has_singleton"]
+    if has_singleton {
+        let sid: String = stmt["singleton"]
+        emit_line("  el_singleton_acquire(EL_STR(" + c_str_lit(sid) + "));")
+    }
+    let entries = stmt["entries"]
+    let n: Int = native_list_len(entries)
+    let i = 0
+    while i < n {
+        let e = native_list_get(entries, i)
+        let ename: String = e["name"]
+        let etype: String = e["etype"]
+        let edefault: String = e["default"]
+        let has_default: Bool = e["has_default"]
+        let erequired: Bool = e["required"]
+        let arg_def: String = cgi_arg(edefault, has_default)
+        emit_line("  el_config_declare(EL_STR(" + c_str_lit(ename) + "), EL_STR(" + c_str_lit(etype) + "), " + arg_def + ", " + el_bool_arg(has_default) + ", " + el_bool_arg(erequired) + ");")
+        let i = i + 1
+    }
+    emit_line("  el_config_validate(EL_STR(" + c_str_lit(pname) + "));")
+    emit_line("}")
+    emit_blank()
+}
+
 // -- VBD role enforcement ------------------------------------------------------
 //
 // Scan a function body for direct calls to DHARMA-restricted builtins
@@ -3599,6 +3649,20 @@ fn codegen(stmts: [Map<String, Any>], source: String) -> String {
         }
     }
 
+    // Program block: emit the cross-cutting init function before the user's
+    // functions so main() can call it (see emit_program_init).
+    let prog_have: Bool = false
+    let i = 0
+    while i < n {
+        let stmt = native_list_get(stmts, i)
+        let sk4: String = stmt["stmt"]
+        if str_eq(sk4, "ProgramBlock") {
+            emit_program_init(stmt)
+            let prog_have = true
+        }
+        let i = i + 1
+    }
+
     // Function definitions
     let i = 0
     while i < n {
@@ -3617,6 +3681,9 @@ fn codegen(stmts: [Map<String, Any>], source: String) -> String {
     // with the C-side parameters when fn main()'s body is folded in below.
     emit_line("int main(int _argc, char** _argv) {")
     emit_line("  el_runtime_init_args(_argc, _argv);")
+    if prog_have {
+        emit_line("  __el_program_init();")
+    }
     if cgi_count >= 1 {
         let cname: String = cgi_block["name"]
         let cdid: String = cgi_block["dharma_id"]
@@ -4210,6 +4277,7 @@ fn codegen_streaming(tokens: [Any], sigs: [Map<String, Any>], source: String) ->
     // Fix: copy the values out BEFORE the release (strings, so no dangling reference)
     // and emit from these. No search, so the failure mode is removed rather than moved.
     let cgi_have: Bool = false
+    let prog_have: Bool = false
     let cgi_name_v: String = ""
     let cgi_did_v: String = ""
     let cgi_prin_v: String = ""
@@ -4331,6 +4399,14 @@ fn codegen_streaming(tokens: [Any], sigs: [Map<String, Any>], source: String) ->
                             // These are no-ops in codegen (forward decls already emitted)
                             // — except a CgiBlock, whose declared identity must survive
                             // this release to be emitted as a compiled constant.
+                            // A ProgramBlock's cross-cutting declarations are
+                            // emitted HERE, as a named init function, because the
+                            // streaming backend cannot hold the entry list alive
+                            // until main(). Only the bool survives.
+                            if str_eq(sk, "ProgramBlock") {
+                                emit_program_init(stmt)
+                                let prog_have = true
+                            }
                             if str_eq(sk, "CgiBlock") {
                                 let cgi_have = true
                                 let cgi_name_v = stmt["name"]
@@ -4477,6 +4553,13 @@ fn codegen_streaming(tokens: [Any], sigs: [Map<String, Any>], source: String) ->
     let kind2: String = state_get("__program_kind")
     emit_line("int main(int _argc, char** _argv) {")
     emit_line("  el_runtime_init_args(_argc, _argv);")
+    // Cross-cutting concerns declared by a `program` block run BEFORE anything
+    // else — a singleton violation must refuse the start before this process
+    // touches a port or a data directory, and configuration must be validated
+    // before the first read of it rather than at each read site.
+    if prog_have {
+        emit_line("  __el_program_init();")
+    }
 
     // cgi init if needed
     let ns2: Int = native_list_len(sigs)

lang/el-compiler/src/lexer.el

@@ -184,6 +184,7 @@ fn keyword_kind(word: String) -> String {
     if word == "false" { return "Bool" }
     if word == "cgi" { return "Cgi" }
     if word == "service" { return "Service" }
+    if word == "program" { return "Program" }
     if word == "manager" { return "Manager" }
     if word == "engine" { return "Engine" }
     if word == "accessor" { return "Accessor" }

lang/el-compiler/src/parser.el

@@ -1967,6 +1967,113 @@ fn parse_stmt(tokens: [Any], pos: Int) -> Map<String, Any> {
         }, p)
     }
 
+    // program block: program "name" { singleton: "id", env NAME: Type = "default", ... }
+    //
+    // The program block is El's declaration surface for CROSS-CUTTING CONCERNS —
+    // properties of the whole process rather than of any one function, which
+    // otherwise degrade into "remember to call this at every site" conventions.
+    //
+    //   singleton: "id"    — process identity. The runtime takes an exclusive
+    //                        lock at startup; a SECOND start is refused, loudly,
+    //                        instead of two processes sharing one data dir.
+    //   env NAME: T = "d"  — one configuration entry. Its type and its default
+    //                        are declared ONCE, here, and resolved+validated
+    //                        before main() body runs.
+    //   env NAME: T required
+    //                      — no default; the program refuses to start unless the
+    //                        variable is set.
+    //
+    // Both compile into calls injected at the head of main() — the same boundary
+    // seam `cgi` already uses (codegen.el emit_program_init). No call site in the
+    // program body has to remember anything, which is the whole point.
+    if k == "Program" {
+        let p = pos + 1
+        let name = tok_value(tokens, p)
+        let p = p + 1
+        let p = expect(tokens, p, "LBrace")
+        let singleton = ""
+        let has_singleton = false
+        let entries = native_list_empty()
+        // Entry-scratch declared at loop-body level (not inside the branch) so
+        // that inner `let` forms compile to assignment rather than a C-scoped
+        // redeclaration — the same idiom the service block above relies on.
+        let ename = ""
+        let etype = ""
+        let edefault = ""
+        let has_default = false
+        let erequired = false
+        let fname = ""
+        let fval = ""
+        let running = true
+        while running {
+            let k2 = tok_kind(tokens, p)
+            if k2 == "RBrace" {
+                let running = false
+            } else {
+                if k2 == "Eof" {
+                    let running = false
+                } else {
+                    let fname = tok_value(tokens, p)
+                    let p = p + 1
+                    if str_eq(fname, "env") {
+                        // env NAME: Type [= "default"] [required]
+                        let ename = tok_value(tokens, p)
+                        let p = p + 1
+                        let p = expect(tokens, p, "Colon")
+                        let etype = tok_value(tokens, p)
+                        let p = p + 1
+                        let edefault = ""
+                        let has_default = false
+                        let erequired = false
+                        let k3 = tok_kind(tokens, p)
+                        if str_eq(k3, "Eq") {
+                            let p = p + 1
+                            let edefault = tok_value(tokens, p)
+                            let has_default = true
+                            let p = p + 1
+                        }
+                        let k4 = tok_kind(tokens, p)
+                        if str_eq(k4, "Ident") {
+                            let w = tok_value(tokens, p)
+                            if str_eq(w, "required") {
+                                let erequired = true
+                                let p = p + 1
+                            }
+                        }
+                        let entries = native_list_append(entries, {
+                            "name": ename,
+                            "etype": etype,
+                            "default": edefault,
+                            "has_default": has_default,
+                            "required": erequired
+                        })
+                    } else {
+                        // scalar field: `name: "value"`
+                        let p = expect(tokens, p, "Colon")
+                        let fval = tok_value(tokens, p)
+                        let p = p + 1
+                        if str_eq(fname, "singleton") {
+                            let singleton = fval
+                            let has_singleton = true
+                        }
+                    }
+                    let k5 = tok_kind(tokens, p)
+                    if k5 == "Comma" {
+                        let p = p + 1
+                    }
+                }
+            }
+        }
+        let p = expect(tokens, p, "RBrace")
+        return make_result({
+            "stmt": "ProgramBlock",
+            "name": name,
+            "singleton": singleton,
+            "has_singleton": has_singleton,
+            "entries": entries
+        }, p)
+    }
+
     // assert <cond_expr> [ , <msg_expr> ]
     // The message is optional — if the next token after the condition is not a
     // Comma, emit an empty string placeholder so the test still works.
@@ -2419,6 +2526,7 @@ fn scan_params_c(tokens: [Any], pos: Int) -> Map<String, Any> {
 //   toplevel_let:  { "kind": "toplevel_let", "name": String, "ltype": String }
 //   cgi_block:     { "kind": "cgi_block",  "name": String }
 //   service_block: { "kind": "service_block", "name": String }
+//   program_block: { "kind": "program_block", "name": String }
 //
 // Import/TypeDef/EnumDef nodes are skipped (codegen treats them as no-ops).
 //
@@ -2546,13 +2654,28 @@ fn scan_fn_sigs(tokens: [Any]) -> [Map<String, Any>] {
                         "name": name
                     })
                     let pos = p
+                } else {
+                // --- program block ---
+                if str_eq(k, "Program") {
+                    let p: Int = pos + 1
+                    let name: String = tok_value(tokens, p)
+                    let p = p + 1
+                    let k2: String = tok_kind(tokens, p)
+                    if str_eq(k2, "LBrace") {
+                        let p = skip_to_rbrace(tokens, p)
+                    }
+                    let sigs = native_list_append(sigs, {
+                        "kind": "program_block",
+                        "name": name
+                    })
+                    let pos = p
                 } else {
                     // Import, Type, Enum, From, or any other token.
                     // Skip ahead to the next statement boundary.
                     let p: Int = pos + 1
                     let p = skip_expr_to_stmt_boundary(tokens, p)
                     let pos = p
-                }}}}}
+                }}}}}}
             }
         }
     }

lang/examples/transduce.el

@@ -1,213 +0,0 @@
-// transduce.el — geometry as a first-class El value, and a realizer written
-// in El. Runnable: this is the worked example for the transduce surface, and
-// it doubles as an executable proof because it checks every claim it makes.
-//
-//   elc lang/examples/transduce.el > transduce.c
-//   cc -std=c11 -O2 -I lang/runtime -o transduce transduce.c \
-//      lang/runtime/el_runtime.c lang/runtime/el_seed.c \
-//      lang/runtime/engram_*.c -lcurl -lpthread -lm
-//   ./transduce          # exits 0 only if every check passes
-//
-// (A `test "..."` form of the same checks lives in
-// lang/tests/native/test_transduce.el, for when the native harness is
-// repaired — the shipped elc currently emits calls to __el_reg_count and
-// friends without emitting their definitions, which breaks every native test
-// equally, test_math.el included. Verified 2026-08-16, unrelated to this work.)
-//
-// WHY THIS EXISTS. Until 2026-08-16 no El ingest path could carry a vector:
-// nodes took text, and geometry was DERIVED from that text. Text was the
-// mandatory entry medium, so any non-text modality had to be DESCRIBED in
-// prose first and the geometry we reasoned over was the geometry OF THE
-// DESCRIPTION, not of the signal. Two things fix that, and both are shown
-// below: geometry is a VALUE that carries its own width, and a REALIZER is an
-// ordinary El function — so admitting a new modality never requires a runtime
-// patch.
-//
-// COMPARISON DISCIPLINE (measured, not stylistic): elc lowers `a == b`
-// numerically only when both operand NAMES are in the per-function int-name
-// set that `let x: Int` populates. A bare `f(x) == 0` is not a registered
-// name and lowers to str_eq — strcmp on two integers as pointers. `<` and `>`
-// lower directly with no inference, so truthiness is written `> 0` / `< 1`.
-
-// ── A realizer, written entirely in El ──────────────────────────────────────
-// Not in the runtime. Not known to the compiler. Registered by NAME and
-// dispatched to through transduce(). That is the whole claim.
-fn tone_realizer(signal: String) -> Geometry {
-    let g: Geometry = geometry_new(4)
-    let n: Int = str_len(signal)
-    let a: Int = geometry_set(g, 0, int_to_float(n))
-    let b: Int = geometry_set(g, 1, int_to_float(n * 2))
-    let c: Int = geometry_set(g, 2, int_to_float(n * 3))
-    let d: Int = geometry_set(g, 3, int_to_float(n * 4))
-    g
-}
-
-// A second modality, to show the registry keys on modality rather than just
-// returning whatever was registered last.
-fn pulse_realizer(signal: String) -> Geometry {
-    let g: Geometry = geometry_new(2)
-    let a: Int = geometry_set(g, 0, 1.0)
-    let b: Int = geometry_set(g, 1, 0.0)
-    g
-}
-
-// A deliberately BROKEN realizer: returns something that is not a Geometry.
-fn bogus_realizer(signal: String) -> Geometry {
-    return 12345
-}
-
-// Fails FAST rather than accumulating a count, for a measured reason: a first
-// cut wrote `let fails: Int = fails + check(...)` and `+` lowered to STRING
-// CONCAT, because elc dispatches `+` on whether both operands are known-Int and
-// a user-defined fn call is not — so the counter printed 4343632752, a pointer.
-// Nothing was wrong with the checks; the tally was lying. Exiting at the first
-// failure needs no arithmetic at all, so there is nothing left to get wrong.
-fn check(ok: Int, label: String) -> Int {
-    if ok > 0 {
-        println("  ok    " + label)
-        return 0
-    }
-    println("  FAIL  " + label)
-    exit(1)
-    return 1
-}
-
-fn near(a: Float, b: Float) -> Int {
-    let d: Float = a - b
-    if d > 0.001 { return 0 }
-    if d < -0.001 { return 0 }
-    return 1
-}
-
-fn eq_int(a: Int, b: Int) -> Int {
-    if a == b { return 1 }
-    return 0
-}
-
-fn main() -> Void {
-    println("geometry is a value that carries its own width")
-    let g8: Geometry = geometry_new(8)
-    let _c: Int = check(geometry_is(g8), "geometry_new returns a live Geometry")
-    let d8: Int = geometry_dim(g8)
-    let _c: Int = check(eq_int(d8, 8), "a Geometry carries its own width (8)")
-    let _c: Int = check(geometry_free(g8), "geometry_free reports what it did")
-
-    println("nonsense is refused — with no arbitrary max-dim bound")
-    // #141 needed `dim <= 8192` only to bound an allocation sized from a
-    // caller's CLAIM about a string's length. A value that carries its own
-    // width has nothing left to validate.
-    let z: Geometry = geometry_new(0)
-    let zi: Int = geometry_is(z)
-    let _c: Int = check(1 - zi, "dim 0 is not a geometry")
-    let ng: Geometry = geometry_new(-4)
-    let ngi: Int = geometry_is(ng)
-    let _c: Int = check(1 - ngi, "negative dim is not a geometry")
-    let nd: Int = geometry_dim(0)
-    let _c: Int = check(1 - nd, "geometry_dim of a non-geometry is 0, not a crash")
-    let nf: Int = geometry_free(0)
-    let _c: Int = check(1 - nf, "geometry_free of a non-geometry is a no-op")
-
-    println("components round-trip, and out-of-range is refused")
-    let g3: Geometry = geometry_new(3)
-    let s0: Int = geometry_set(g3, 0, 1.5)
-    let s1: Int = geometry_set(g3, 1, -2.5)
-    let _c: Int = check(s0, "set in range succeeds")
-    let oob: Int = geometry_set(g3, 3, 9.0)
-    let _c: Int = check(1 - oob, "set out of range is refused, not silently dropped")
-    let _c: Int = check(near(geometry_get(g3, 0), 1.5), "component 0 round-trips")
-    let _c: Int = check(near(geometry_get(g3, 1), -2.5), "component 1 round-trips (negative)")
-    let ff3: Int = geometry_free(g3)
-
-    println("hex is an EDGE adapter, and derives its own width")
-    // little-endian float32: 1.0 = 0000803f, 2.0 = 00000040
-    let gh: Geometry = geometry_from_f32le_hex("0000803f00000040")
-    let _c: Int = check(geometry_is(gh), "valid hex decodes to a Geometry")
-    let dh: Int = geometry_dim(gh)
-    let _c: Int = check(eq_int(dh, 2), "width DERIVED from input, never supplied")
-    let _c: Int = check(near(geometry_get(gh, 0), 1.0), "first component decoded")
-    let _c: Int = check(near(geometry_get(gh, 1), 2.0), "second component decoded")
-    let back: String = geometry_to_f32le_hex(gh)
-    let _c: Int = check(str_eq(back, "0000803f00000040"), "hex round-trips exactly")
-    let ffh: Int = geometry_free(gh)
-
-    println("malformed hex is refused")
-    let he: Geometry = geometry_from_f32le_hex("")
-    let hei: Int = geometry_is(he)
-    let _c: Int = check(1 - hei, "empty hex is not a geometry")
-    let hr: Geometry = geometry_from_f32le_hex("0000803f0000")
-    let hri: Int = geometry_is(hr)
-    let _c: Int = check(1 - hri, "length not a multiple of 8 is refused")
-    let hn: Geometry = geometry_from_f32le_hex("zzzzzzzz")
-    let hni: Int = geometry_is(hn)
-    let _c: Int = check(1 - hni, "non-hex characters are refused")
-
-    println("a realizer declared in El is a first-class realizer")
-    let reg: Int = realizer_register("tone", "tone_realizer")
-    let _c: Int = check(reg, "an El fn registers as a realizer BY NAME")
-    let _c: Int = check(realizer_has("tone"), "the modality now has an organ")
-    let gt: Geometry = transduce("aaa", "tone")
-    let _c: Int = check(geometry_is(gt), "transduce returns real geometry")
-    let dt: Int = geometry_dim(gt)
-    let _c: Int = check(eq_int(dt, 4), "the El realizer determined the width, not the runtime")
-    // str_len("aaa") == 3, so component 0 must be 3.0 — proof the signal
-    // actually reached the El function rather than a stub answering for it.
-    let _c: Int = check(near(geometry_get(gt, 0), 3.0), "the signal REACHED the El realizer")
-    let fft: Int = geometry_free(gt)
-
-    println("distinct signals transduce to distinct geometry")
-    let g1: Geometry = transduce("aa", "tone")
-    let g2: Geometry = transduce("aaaaa", "tone")
-    let a1: Float = geometry_get(g1, 0)
-    let a2: Float = geometry_get(g2, 0)
-    // 5 - 2 = 3. If transduction were a stub these would be equal.
-    let _c: Int = check(near(a2 - a1, 3.0), "different signals produce different geometry")
-    let ff1: Int = geometry_free(g1)
-    let ff2: Int = geometry_free(g2)
-
-    println("the registry keys on modality")
-    let r2: Int = realizer_register("pulse", "pulse_realizer")
-    let _c: Int = check(r2, "a second modality registers independently")
-    let mt: Geometry = transduce("aaa", "tone")
-    let mp: Geometry = transduce("aaa", "pulse")
-    let mdt: Int = geometry_dim(mt)
-    let mdp: Int = geometry_dim(mp)
-    let _c: Int = check(eq_int(mdt, 4), "tone still routes to its own realizer")
-    let _c: Int = check(eq_int(mdp, 2), "pulse routes to a different realizer")
-    let ffm1: Int = geometry_free(mt)
-    let ffm2: Int = geometry_free(mp)
-
-    println("no organ is reported as no organ")
-    // A modality with no realizer must transduce to NOTHING. It must never
-    // fall back to embedding a description of the signal and calling that
-    // perception — that silent substitution is the defect this all exists to end.
-    let eh: Int = realizer_has("echolocation")
-    let _c: Int = check(1 - eh, "unregistered modality has no organ")
-    let ge: Geometry = transduce("anything", "echolocation")
-    let gei: Int = geometry_is(ge)
-    let _c: Int = check(1 - gei, "no realizer means NO geometry, not fake geometry")
-
-    println("an unresolvable realizer name fails at WIRING time")
-    let bad: Int = realizer_register("ghost", "no_such_function_anywhere")
-    let _c: Int = check(1 - bad, "unresolvable realizer name is a registration failure")
-    let gh2: Int = realizer_has("ghost")
-    let _c: Int = check(1 - gh2, "and nothing gets registered")
-
-    println("a realizer returning non-geometry transduces nothing")
-    let rb: Int = realizer_register("bogus", "bogus_realizer")
-    let _c: Int = check(rb, "the symbol resolves, so registration succeeds")
-    let gb: Geometry = transduce("x", "bogus")
-    let gbi: Int = geometry_is(gb)
-    let _c: Int = check(1 - gbi, "contract enforced at the boundary: nothing handed back")
-
-    println("norm lets a caller check a realizer emitted signal, not zeros")
-    let gn: Geometry = geometry_new(2)
-    let _c: Int = check(near(geometry_norm(gn), 0.0), "a fresh geometry is zero — norm says so")
-    let n0: Int = geometry_set(gn, 0, 3.0)
-    let n1: Int = geometry_set(gn, 1, 4.0)
-    let _c: Int = check(near(geometry_norm(gn), 5.0), "3-4-5: norm is 5")
-    let ffn: Int = geometry_free(gn)
-
-    // Reaching here means nothing called exit(1) along the way.
-    println("")
-    println("all checks passed")
-}

lang/runtime/el_runtime.c

@@ -43,6 +43,7 @@
 #include <dlfcn.h>      /* dlsym for http_set_handler fallback */
 #include <unistd.h>
 #include <fcntl.h>
+#include <sys/file.h>   /* flock — process-identity singleton (program block) */
 #include <dirent.h>
 #include <errno.h>
 #include <pthread.h>
@@ -5959,308 +5960,6 @@ void el_cgi_init(el_val_t name, el_val_t dharma_id, el_val_t principal,
 }
 
 
-/* ── Geometry: signal as a first-class el value ──────────────────────────────
- *
- * WHY THIS IS IN THE LANGUAGE, AND WHY IT IS DEFINED HERE (2026-08-16).
- *
- * Until yesterday no El ingest path could carry a vector. Nodes took text,
- * and geometry was DERIVED from that text by engram_embed_backfill. Text was
- * therefore the mandatory entry medium: any non-text modality — audio, image,
- * sensor — had to be DESCRIBED in prose first, so the geometry we then
- * reasoned over was the geometry OF THE DESCRIPTION, not of the signal. That
- * is faking it. The architecture is: geometry in, always; we do not fake it,
- * we project.
- *
- * The first fix (#141, engram_node_set_emb) proved the path end to end but
- * placed it wrong in three ways, each of which this section corrects:
- *
- *   1. It sat at the CONSUMER. Transduction is a LANGUAGE concern — every El
- *      program touching any modality needs it, not just the one that happens
- *      to hold a graph. So this section is defined HERE, immediately above
- *      the engram block, and depends on nothing inside it. The engram is a
- *      client of this surface, not its owner. That ordering is the point:
- *      you can delete the entire engram and geometry still enters El.
- *
- *   2. It marshalled the vector as a hex STRING, because El had no
- *      first-class geometry value — which reintroduced text as the TRANSPORT
- *      medium one layer below the problem being fixed. Geometry is now a
- *      value. Hex survives only as a wire ADAPTER at the edge
- *      (geometry_from/to_f32le_hex), which is all an encoding should ever be.
- *
- *   3. It needed an arbitrary `dim <= 8192` bound, purely to check a
- *      caller-supplied dim against a string's length before allocating. A
- *      real geometry value CARRIES its own width, so here the width is
- *      derived and never asserted, and there is nothing left to validate.
- *      The bound is gone rather than merely raised — the only thing that can
- *      fail is the allocation itself, which is an honest failure.
- *
- * REPRESENTATION: magic-tagged heap object (see "Refcounted heap objects"),
- * carried in an el_val_t. The payload is a separate allocation so the header
- * never moves. The magic word is >= 0x80 in its MSB so the string/small-int
- * sniffing in looks_like_heap_obj can never confuse a Geometry for either.
- *
- * OWNERSHIP: a Geometry is owned by the El caller and released with
- * geometry_free. node_attach_geometry COPIES its payload into the node, so a
- * node and the caller's value have independent lifetimes and freeing one
- * never touches the other. Geometry deliberately does NOT participate in
- * el_retain/el_release: the shipped elc emits neither on let-bindings
- * (measured), so hooking it there would be dead code that could only ever
- * free a live vector early.
- */
-
-#define EL_MAGIC_GEOM  0xE1608E01u
-
-typedef struct {
-    ElHeader hdr;
-    int32_t  dim;
-    float*   v;
-} ElGeometry;
-
-/* Resolve an el_val_t to a live Geometry, or NULL. Every accessor goes
- * through this, so a stale/foreign/zero value is a clean 0-return rather
- * than a dereference. */
-static ElGeometry* geom_of(el_val_t g) {
-    if (!looks_like_heap_obj(g)) return NULL;
-    ElGeometry* p = (ElGeometry*)(uintptr_t)g;
-    if (p->hdr.magic != EL_MAGIC_GEOM) return NULL;
-    return p;
-}
-
-el_val_t geometry_new(el_val_t dim) {
-    int32_t d = (int32_t)(int64_t)dim;
-    if (d <= 0) return (el_val_t)0;
-    ElGeometry* g = (ElGeometry*)malloc(sizeof(ElGeometry));
-    if (!g) return (el_val_t)0;
-    g->v = (float*)calloc((size_t)d, sizeof(float));
-    if (!g->v) { free(g); return (el_val_t)0; }
-    g->hdr.magic    = EL_MAGIC_GEOM;
-    g->hdr.refcount = 1;
-    g->dim          = d;
-    return (el_val_t)(uintptr_t)g;
-}
-
-el_val_t geometry_dim(el_val_t g) {
-    ElGeometry* p = geom_of(g);
-    return p ? (el_val_t)p->dim : (el_val_t)0;
-}
-
-el_val_t geometry_is(el_val_t g) {
-    return geom_of(g) ? (el_val_t)1 : (el_val_t)0;
-}
-
-el_val_t geometry_get(el_val_t g, el_val_t i) {
-    ElGeometry* p = geom_of(g);
-    int64_t k = (int64_t)i;
-    if (!p || k < 0 || k >= (int64_t)p->dim) return el_from_float(0.0);
-    return el_from_float((double)p->v[k]);
-}
-
-el_val_t geometry_set(el_val_t g, el_val_t i, el_val_t x) {
-    ElGeometry* p = geom_of(g);
-    int64_t k = (int64_t)i;
-    if (!p || k < 0 || k >= (int64_t)p->dim) return (el_val_t)0;
-    p->v[k] = (float)el_to_float(x);
-    return (el_val_t)1;
-}
-
-el_val_t geometry_norm(el_val_t g) {
-    ElGeometry* p = geom_of(g);
-    if (!p) return el_from_float(0.0);
-    double s = 0.0;
-    for (int32_t i = 0; i < p->dim; i++) s += (double)p->v[i] * (double)p->v[i];
-    return el_from_float(sqrt(s));
-}
-
-el_val_t geometry_free(el_val_t g) {
-    ElGeometry* p = geom_of(g);
-    if (!p) return (el_val_t)0;
-    free(p->v);
-    p->hdr.magic = 0;   /* poison so use-after-free is detected, as List/Map do */
-    free(p);
-    return (el_val_t)1;
-}
-
-/* geometry_from_f32le_hex — decode little-endian float32 hex INTO geometry.
- *
- * This is the ONE place hex appears, and it appears as what it actually is:
- * an encoding at the boundary, not the medium El reasons in. The width is
- * DERIVED from the input length (8 hex chars per float32) and never supplied
- * by the caller — which is precisely why #141's arbitrary `dim <= 8192`
- * bound has no counterpart here. There is nothing to validate.
- *
- * Returns 0 on empty input, a length that is not a multiple of 8, or any
- * non-hex character. */
-el_val_t geometry_from_f32le_hex(el_val_t hex) {
-    const char* s = EL_CSTR(hex);
-    if (!s) return (el_val_t)0;
-    size_t n = strlen(s);
-    if (n == 0 || (n % 8u) != 0) return (el_val_t)0;
-    size_t d = n / 8u;
-    if (d > (size_t)INT32_MAX) return (el_val_t)0;
-
-    el_val_t gv = geometry_new((el_val_t)(int64_t)d);
-    ElGeometry* g = geom_of(gv);
-    if (!g) return (el_val_t)0;
-
-    for (size_t i = 0; i < d; i++) {
-        uint32_t w = 0;
-        for (int k = 0; k < 8; k++) {
-            char c = s[i * 8u + (size_t)k];
-            uint32_t nib;
-            if      (c >= '0' && c <= '9') nib = (uint32_t)(c - '0');
-            else if (c >= 'a' && c <= 'f') nib = (uint32_t)(c - 'a' + 10);
-            else if (c >= 'A' && c <= 'F') nib = (uint32_t)(c - 'A' + 10);
-            else { geometry_free(gv); return (el_val_t)0; }
-            w = (w << 4) | nib;
-        }
-        /* Hex is emitted little-endian byte order; rebuild the word. */
-        uint32_t le = ((w & 0x000000FFu) << 24) | ((w & 0x0000FF00u) << 8) |
-                      ((w & 0x00FF0000u) >> 8)  | ((w & 0xFF000000u) >> 24);
-        float f;
-        memcpy(&f, &le, sizeof(f));
-        g->v[i] = f;
-    }
-    return gv;
-}
-
-/* geometry_to_f32le_hex — the egress adapter, exact inverse of the above.
- * Present so a program that must hand geometry to a non-El peer over a text
- * wire can do so explicitly, at the edge, instead of the language pretending
- * text was the medium all along. */
-el_val_t geometry_to_f32le_hex(el_val_t g) {
-    ElGeometry* p = geom_of(g);
-    if (!p) return EL_STR("");
-    static const char* HEXD = "0123456789abcdef";
-    size_t n = (size_t)p->dim * 8u;
-    char* out = el_strbuf(n);   /* arena-tracked; allocates n+1, exits on OOM */
-    for (int32_t i = 0; i < p->dim; i++) {
-        uint32_t w;
-        memcpy(&w, &p->v[i], sizeof(w));
-        /* Emit little-endian byte order: low byte first. */
-        for (int b = 0; b < 4; b++) {
-            uint32_t byte = (w >> (8 * b)) & 0xFFu;
-            out[(size_t)i * 8u + (size_t)b * 2u]     = HEXD[(byte >> 4) & 0xF];
-            out[(size_t)i * 8u + (size_t)b * 2u + 1] = HEXD[byte & 0xF];
-        }
-    }
-    out[n] = '\0';
-    return (el_val_t)(uintptr_t)out;
-}
-
-/* ── Realizers: transduction declared in El, not patched into the runtime ────
- *
- * A REALIZER maps one modality into geometry. The whole reason transduction
- * belongs in the language is that ADDING A MODALITY MUST NOT REQUIRE A
- * RUNTIME PATCH — otherwise "the realizers are in the engram" just becomes
- * "the realizers are in the runtime" and nothing has actually moved. So
- * realizers are declared in El and registered by NAME:
- *
- *     fn tone_realizer(signal: String) -> Geometry {
- *         let g: Geometry = geometry_new(8)
- *         ... geometry_set(g, i, x) ...
- *         g
- *     }
- *
- *     realizer_register("tone", "tone_realizer")
- *     let g: Geometry = transduce(sample, "tone")
- *
- * The name→symbol step rides the identical, already load-bearing mechanism
- * http_set_handler uses (see "HTTP server"): every El `fn name(...)` compiles
- * to a global C symbol with that exact name, so dlsym(RTLD_DEFAULT, name)
- * against the running binary resolves an El-defined function. No codegen
- * change, no first-class function references, no runtime edit per modality.
- * A realizer written in El is a first-class realizer.
- *
- * A realizer may equally be a C symbol linked into the program; the registry
- * cannot tell the difference and has no reason to care.
- */
-
-typedef el_val_t (*el_realizer_fn)(el_val_t);
-
-typedef struct {
-    char*          modality;
-    el_realizer_fn fn;
-} ElRealizer;
-
-static ElRealizer      _realizers[64];
-static size_t          _realizer_count = 0;
-static pthread_mutex_t _realizer_mu = PTHREAD_MUTEX_INITIALIZER;
-
-static el_realizer_fn realizer_lookup(const char* m) {
-    el_realizer_fn out = NULL;
-    pthread_mutex_lock(&_realizer_mu);
-    for (size_t i = 0; i < _realizer_count; i++) {
-        if (strcmp(_realizers[i].modality, m) == 0) { out = _realizers[i].fn; break; }
-    }
-    pthread_mutex_unlock(&_realizer_mu);
-    return out;
-}
-
-el_val_t realizer_register(el_val_t modality, el_val_t fn_name) {
-    const char* m  = EL_CSTR(modality);
-    const char* fn = EL_CSTR(fn_name);
-    if (!m || !*m || !fn || !*fn) return (el_val_t)0;
-
-    /* An unresolvable name is a REGISTRATION FAILURE, reported as 0 — not a
-     * silent no-op that only surfaces later as "this modality produces
-     * nothing". Distinguishing "no organ" from "broken organ" at the moment
-     * of wiring is the lesson #141 was written to enforce. */
-    void* sym = dlsym(RTLD_DEFAULT, fn);
-    if (!sym) return (el_val_t)0;
-
-    pthread_mutex_lock(&_realizer_mu);
-    for (size_t i = 0; i < _realizer_count; i++) {
-        if (strcmp(_realizers[i].modality, m) == 0) {
-            _realizers[i].fn = (el_realizer_fn)sym;   /* re-registration replaces */
-            pthread_mutex_unlock(&_realizer_mu);
-            return (el_val_t)1;
-        }
-    }
-    if (_realizer_count < sizeof(_realizers) / sizeof(_realizers[0])) {
-        /* _persist, NOT el_strdup: the registry outlives any request, and an
-         * arena-tracked copy would be freed at el_request_end — leaving a
-         * dangling modality name if a program registers a realizer from
-         * inside a handler rather than at startup. */
-        _realizers[_realizer_count].modality = el_strdup_persist(m);
-        _realizers[_realizer_count].fn       = (el_realizer_fn)sym;
-        _realizer_count++;
-        pthread_mutex_unlock(&_realizer_mu);
-        return (el_val_t)1;
-    }
-    pthread_mutex_unlock(&_realizer_mu);
-    return (el_val_t)0;
-}
-
-el_val_t realizer_has(el_val_t modality) {
-    const char* m = EL_CSTR(modality);
-    if (!m || !*m) return (el_val_t)0;
-    return realizer_lookup(m) ? (el_val_t)1 : (el_val_t)0;
-}
-
-/* transduce — THE primitive: signal in, geometry out.
- *
- * Dispatches to the realizer registered for `modality`. Returns 0 (not a
- * Geometry) when no realizer is registered, and geometry_is() on the result
- * is the check.
- *
- * There is deliberately NO built-in realizer, not even for text. A modality
- * the program has declared no organ for is one it genuinely cannot sense,
- * and returning nothing is more honest than quietly embedding a description
- * of the signal and calling that perception — which is the exact failure
- * this whole change exists to end.
- *
- * The result is validated to actually BE a Geometry before it is handed
- * back, so a realizer that returns something else transduced nothing rather
- * than handing a caller a value that will misbehave far from here. */
-el_val_t transduce(el_val_t signal, el_val_t modality) {
-    const char* m = EL_CSTR(modality);
-    if (!m || !*m) return (el_val_t)0;
-    el_realizer_fn fn = realizer_lookup(m);
-    if (!fn) return (el_val_t)0;
-    el_val_t g = fn(signal);
-    return geom_of(g) ? g : (el_val_t)0;
-}
-
 /* ── Batch 3: Engram in-process graph store ──────────────────────────────── */
 /*
  * Single global EngramStore allocated lazily on first call. All node and
@@ -8865,96 +8564,80 @@ el_val_t engram_node_count(void) {
     return (el_val_t)engram_get()->node_count;
 }
 
-/* node_attach_geometry — a node acquires geometry.
+/* engram_node_set_emb — attach GEOMETRY to an existing node.
  *
- * Named for the operation, not for the store that happens to hold the node.
- * This is the geometry-valued ingest path that replaces #141's hex-string
- * one: nothing here parses text, and nothing here takes a caller's word for
- * how wide the vector is. The Geometry carries its own width.
+ * WHY THIS EXISTS (2026-08-16). Until now no ingest path could carry a
+ * vector. engram_node / engram_node_full / engram_node_layered take text
+ * only, and the sole way a node acquired an embedding was
+ * engram_embed_backfill DERIVING one from n->content. That made text the
+ * mandatory entry medium: any non-text modality (audio, image, sensor)
+ * had to be described in prose first, and the geometry we then reasoned
+ * over was the geometry OF THE DESCRIPTION, not of the signal. Measured
+ * consequence: POST /api/nodes accepted an "emb" field, returned 200 with
+ * a fresh id, and stored emb_dim=None / embedded:false — the vector was
+ * silently discarded because no parameter existed to receive it.
  *
- * The payload is COPIED into the node, so the node and the caller's Geometry
- * have independent lifetimes — the caller may geometry_free() immediately
- * after, and a later free of the node's emb never touches the El value.
+ * `hex` is little-endian float32, the encoding the perception vessel's
+ * /voice/embed already emits, so a realizer's output moves in without a
+ * JSON float-array round trip. Length must be exactly dim*8 hex chars.
  *
- * DIMENSION POLICY (measured in #141, load-bearing — do not regress): dim
- * need NOT equal the canonical text-embedding width. An off-dimension vector
- * is stored and is simply not inserted into the resident HNSW index, whose
- * build loop already filters on `n->emb_dim == dim`. So a 64-dim voice
- * geometry is durable and addressable without perturbing the 768-dim
- * canonical index.
+ * DIMENSION POLICY: dim need NOT equal the canonical text-embedding dim.
+ * A modality vector of a different width is stored and is simply not
+ * inserted into the resident HNSW index, whose build loop already filters
+ * on `n->emb_dim == dim`. So off-dimension geometry is durable and
+ * addressable without perturbing the canonical index.
  *
- * Attaching geometry also makes the node ineligible for embed_backfill
- * (which fills only nodes with no emb), so a realizer's vector is never
+ * Setting emb also makes the node ineligible for embed_backfill (which
+ * only fills nodes with no emb), so a realizer's vector is never
  * overwritten by a text-derived one.
  *
- * Returns 1 on success, 0 on unknown id or a value that is not a Geometry. */
-el_val_t node_attach_geometry(el_val_t node_id, el_val_t g) {
-    const char* sid = EL_CSTR(node_id);
-    if (!sid || !*sid) return (el_val_t)0;
+ * Returns 1 on success, 0 on unknown id / malformed hex / bad dim. */
+el_val_t engram_node_set_emb(el_val_t id, el_val_t hex, el_val_t dim) {
+    const char* sid = EL_CSTR(id);
+    const char* sh  = EL_CSTR(hex);
+    int32_t d = (int32_t)(int64_t)dim;
+    /* Bound the allocation. No max-dim constant existed because no caller
+     * could supply a dim before this function; 8192 is generous for any
+     * realizer (canonical text embeddings are 768, MFCC voice stats 64)
+     * while keeping a malformed `dim` from requesting an unbounded malloc. */
+    if (!sid || !*sid || !sh || d <= 0 || d > 8192) return (el_val_t)0;
 
-    ElGeometry* p = geom_of(g);
-    if (!p || p->dim <= 0) return (el_val_t)0;
+    size_t need = (size_t)d * 8u;           /* 4 bytes → 8 hex chars per float */
+    if (strlen(sh) != need) return (el_val_t)0;
 
     EngramNode* n = engram_find_node(sid);
     if (!n) return (el_val_t)0;
 
-    float* v = (float*)malloc(sizeof(float) * (size_t)p->dim);
+    float* v = (float*)malloc(sizeof(float) * (size_t)d);
     if (!v) return (el_val_t)0;
-    memcpy(v, p->v, sizeof(float) * (size_t)p->dim);
+
+    for (int32_t i = 0; i < d; i++) {
+        uint32_t w = 0;
+        for (int k = 0; k < 8; k++) {
+            char c = sh[(size_t)i * 8u + (size_t)k];
+            uint32_t nib;
+            if      (c >= '0' && c <= '9') nib = (uint32_t)(c - '0');
+            else if (c >= 'a' && c <= 'f') nib = (uint32_t)(c - 'a' + 10);
+            else if (c >= 'A' && c <= 'F') nib = (uint32_t)(c - 'A' + 10);
+            else { free(v); return (el_val_t)0; }
+            w = (w << 4) | nib;
+        }
+        /* Hex is emitted little-endian byte order; rebuild the word. */
+        uint32_t le = ((w & 0x000000FFu) << 24) | ((w & 0x0000FF00u) << 8) |
+                      ((w & 0x00FF0000u) >> 8)  | ((w & 0xFF000000u) >> 24);
+        float f;
+        memcpy(&f, &le, sizeof(f));
+        v[i] = f;
+    }
 
     free(n->emb);
-    n->emb        = v;
-    n->emb_dim    = p->dim;
+    n->emb     = v;
+    n->emb_dim = d;
     n->updated_at = engram_now_ms();
     if (engram_store_enabled()) eg_store_put_node(n);
     return (el_val_t)1;
 }
 
-/* node_geometry_dim — read the attached width back, 0 if the node carries
- * none. Exists so an attach is VERIFIED by reading it back rather than by
- * trusting a success return. That is not a nicety: #141 was misdiagnosed for
- * an hour precisely because a genuine ingest drop and a mere reporting gap
- * were indistinguishable from the outside. */
-el_val_t node_geometry_dim(el_val_t node_id) {
-    const char* sid = EL_CSTR(node_id);
-    if (!sid || !*sid) return (el_val_t)0;
-    EngramNode* n = engram_find_node(sid);
-    if (!n || !n->emb) return (el_val_t)0;
-    return (el_val_t)n->emb_dim;
-}
-
-/* engram_node_set_emb — DEPRECATED. Shipped in #141; superseded 2026-08-16
- * by geometry_from_f32le_hex + node_attach_geometry, and now implemented as
- * literally that.
- *
- * It is kept, rather than removed, for one reason only: the runtime is
- * published as an SDK asset, so a downstream binary may already be linking
- * this symbol. It is NOT kept because a hex string is an acceptable way to
- * move geometry between two pieces of El — it isn't, and that was the
- * placement defect. New code calls transduce() or geometry_from_f32le_hex()
- * plus node_attach_geometry().
- *
- * The #141 contract is preserved exactly, including its negative cases, so
- * this remains a drop-in: `dim` <= 0 rejects, malformed hex rejects, and a
- * `dim` that disagrees with the vector's actual width rejects. The
- * difference is that `dim` is now an ASSERTION checked against a width the
- * Geometry already knows, rather than the authority the allocation trusted —
- * which is why #141's arbitrary `dim <= 8192` guard has no counterpart here.
- * There is no longer an unbounded-malloc hazard to guard against. */
-el_val_t engram_node_set_emb(el_val_t id, el_val_t hex, el_val_t dim) {
-    int32_t want = (int32_t)(int64_t)dim;
-    if (want <= 0) return (el_val_t)0;
-
-    el_val_t gv = geometry_from_f32le_hex(hex);
-    ElGeometry* p = geom_of(gv);
-    if (!p) return (el_val_t)0;                       /* empty / malformed hex */
-    if (p->dim != want) { geometry_free(gv); return (el_val_t)0; }  /* length mismatch */
-
-    el_val_t ok = node_attach_geometry(id, gv);
-    geometry_free(gv);
-    return ok;
-}
-
 /* ── Telemetry retention ────────────────────────────────────────────────────
  * (2026-07-16 self-review) InternalStateEvent nodes are append-only telemetry
  * (heartbeat, curiosity_scan, engram_sync) written ~3/min by the awareness
@@ -18653,11 +18336,196 @@ void log_warn(el_val_t msg_v) {
     fprintf(stderr, "[WARN] %s\n", msg ? msg : "");
 }
 
-/* config — read a configuration value from the environment.
- * Returns "" if the variable is not set (same as __env_get). */
+/* ── Cross-cutting concerns: process identity and configuration ──────────────
+ *
+ * These back the `program` block (see lang/spec/language.md §18). Both concerns
+ * were previously conventions — "check nothing is already running first",
+ * "remember the right default at every read site" — and conventions is exactly
+ * what they failed as. Here they are mechanisms, injected by the compiler at
+ * the process boundary, so no call site has to remember anything.
+ */
+
+/* -- Process identity ------------------------------------------------------- */
+
+/* The lock fd is deliberately never closed. Holding it open for the process
+ * lifetime is what makes the guarantee work: the kernel drops an flock when the
+ * owning process dies, including on SIGKILL and on crash. That is why this is an
+ * flock and not a bare pidfile — there is no stale-lock state to clean up, and
+ * therefore no "delete the pidfile to get unstuck" ritual that would itself
+ * become a convention. */
+static int el_singleton_fd = -1;
+static char el_singleton_path[1024];
+
+static const char* el_singleton_dir(void) {
+    const char* d = getenv("EL_SINGLETON_DIR");
+    if (d && *d) return d;
+    d = getenv("TMPDIR");
+    if (d && *d) return d;
+    return "/tmp";
+}
+
+/* el_singleton_acquire — claim exclusive process identity, or refuse to start.
+ * Compiler-injected as the FIRST statement of main() for any program whose
+ * `program` block declares `singleton:`. */
+el_val_t el_singleton_acquire(el_val_t id_v) {
+    const char* id = EL_CSTR(id_v);
+    if (!id || !*id) return EL_NULL;
+
+    /* Sanitise the id into a filename. */
+    char safe[256];
+    size_t si = 0;
+    for (const char* p = id; *p && si + 1 < sizeof(safe); p++) {
+        char c = *p;
+        int ok = (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
+              || (c >= '0' && c <= '9') || c == '-' || c == '_' || c == '.';
+        safe[si++] = (char)(ok ? c : '-');
+    }
+    safe[si] = '\0';
+    snprintf(el_singleton_path, sizeof(el_singleton_path),
+             "%s/el-singleton-%s.lock", el_singleton_dir(), safe);
+
+    int fd = open(el_singleton_path, O_RDWR | O_CREAT, 0644);
+    if (fd < 0) {
+        fprintf(stderr, "[el] FATAL: singleton '%s': cannot open lock file %s: %s\n",
+                id, el_singleton_path, strerror(errno));
+        exit(1);
+    }
+    if (flock(fd, LOCK_EX | LOCK_NB) != 0) {
+        /* Someone else holds it. Report WHO. A pid is actionable; "already
+         * running" is not — and the observed failure was precisely a stale
+         * process that `pkill -f` had silently failed to match, still answering
+         * probes while a fresh build was believed to be under test. */
+        char buf[64];
+        buf[0] = '\0';
+        ssize_t n = pread(fd, buf, sizeof(buf) - 1, 0);
+        if (n > 0) buf[n] = '\0';
+        long holder = strtol(buf, NULL, 10);
+        fprintf(stderr, "[el] FATAL: another instance of '%s' is already running", id);
+        if (holder > 0) fprintf(stderr, " (pid %ld)", holder);
+        fprintf(stderr, ".\n"
+                "[el]        lock: %s\n"
+                "[el]        Refusing to start a second instance against the same\n"
+                "[el]        state. Stop the running one and VERIFY it is gone\n"
+                "[el]        (ps -p <pid>) before retrying.\n",
+                el_singleton_path);
+        close(fd);
+        exit(1);
+    }
+    /* We own it. Record our pid so the next would-be starter can name us. */
+    if (ftruncate(fd, 0) != 0) { /* best effort — the lock is the guarantee */ }
+    char pidbuf[32];
+    int pn = snprintf(pidbuf, sizeof(pidbuf), "%ld\n", (long)getpid());
+    if (pn > 0) { ssize_t w = write(fd, pidbuf, (size_t)pn); (void)w; }
+    el_singleton_fd = fd;   /* never closed, by design */
+    return EL_NULL;
+}
+
+/* -- Configuration ---------------------------------------------------------- */
+
+#define EL_CONFIG_MAX 128
+
+typedef struct {
+    char  name[128];
+    char  type[16];
+    char* value;        /* resolved: env value, else default; NULL if unset */
+    int   has_default;
+    int   required;
+} ElConfigEntry;
+
+static ElConfigEntry el_config_tab[EL_CONFIG_MAX];
+static int el_config_n = 0;
+static int el_config_has_schema = 0;   /* did this program declare one at all? */
+
+static int el_config_is_int(const char* s) {
+    if (!s || !*s) return 0;
+    if (*s == '-' || *s == '+') s++;
+    if (!*s) return 0;
+    for (; *s; s++) if (*s < '0' || *s > '9') return 0;
+    return 1;
+}
+
+/* el_config_declare — record ONE configuration entry and resolve it now.
+ * The default lives here, in the declaration, and nowhere else. */
+el_val_t el_config_declare(el_val_t name_v, el_val_t type_v, el_val_t def_v,
+                           el_val_t has_default_v, el_val_t required_v) {
+    const char* name = EL_CSTR(name_v);
+    if (!name || !*name) return EL_NULL;
+    el_config_has_schema = 1;
+    if (el_config_n >= EL_CONFIG_MAX) {
+        fprintf(stderr, "[el] FATAL: more than %d config entries declared.\n", EL_CONFIG_MAX);
+        exit(1);
+    }
+    const char* type = EL_CSTR(type_v);
+    const char* def  = (def_v == EL_NULL) ? NULL : EL_CSTR(def_v);
+    ElConfigEntry* e = &el_config_tab[el_config_n++];
+    snprintf(e->name, sizeof(e->name), "%s", name);
+    snprintf(e->type, sizeof(e->type), "%s", type ? type : "String");
+    e->has_default = (int)(long)has_default_v;
+    e->required    = (int)(long)required_v;
+    /* Resolution order: environment wins, declaration supplies the fallback. */
+    const char* env = getenv(name);
+    if (env && *env)            e->value = el_strdup_persist(env);
+    else if (e->has_default && def) e->value = el_strdup_persist(def);
+    else                        e->value = NULL;
+    return EL_NULL;
+}
+
+/* el_config_validate — check the whole schema at once, before main() runs.
+ * Reports EVERY problem, not just the first: a startup that fails one variable
+ * at a time costs one restart per variable. */
+el_val_t el_config_validate(el_val_t program_v) {
+    const char* prog = EL_CSTR(program_v);
+    int bad = 0;
+    for (int i = 0; i < el_config_n; i++) {
+        ElConfigEntry* e = &el_config_tab[i];
+        if (!e->value) {
+            if (e->required) {
+                fprintf(stderr, "[el] config: %s is required but is not set "
+                        "(no value in the environment, no default declared)\n", e->name);
+                bad++;
+            }
+            continue;
+        }
+        if (strcmp(e->type, "Int") == 0 && !el_config_is_int(e->value)) {
+            fprintf(stderr, "[el] config: %s is declared Int but its value is \"%s\"\n",
+                    e->name, e->value);
+            bad++;
+        }
+    }
+    if (bad) {
+        fprintf(stderr, "[el] FATAL: program '%s' has %d invalid configuration "
+                "entr%s. Refusing to start.\n",
+                prog ? prog : "?", bad, bad == 1 ? "y" : "ies");
+        exit(1);
+    }
+    return EL_NULL;
+}
+
+/* config — read a configuration value.
+ *
+ * When the program declared a schema, that schema is authoritative: the value
+ * has already been resolved and validated at startup, so this is a lookup and
+ * NOT a place where a default gets decided. Reading a key that was never
+ * declared is a bug at the read site, and is reported as one — that enforcement
+ * is what makes the declaration real rather than advisory.
+ *
+ * With no schema declared, behaviour is unchanged (plain getenv), so programs
+ * that have not migrated keep working. */
 el_val_t config(el_val_t key_v) {
     const char* key = EL_CSTR(key_v);
     if (!key || !*key) return EL_STR("");
+    if (el_config_has_schema) {
+        for (int i = 0; i < el_config_n; i++) {
+            if (strcmp(el_config_tab[i].name, key) == 0) {
+                const char* v = el_config_tab[i].value;
+                return el_wrap_str(el_strdup(v ? v : ""));
+            }
+        }
+        fprintf(stderr, "[el] FATAL: config(\"%s\") is not declared in the "
+                "program block. Declare it there, with its default, or stop "
+                "reading it.\n", key);
+        exit(1);
+    }
     const char* val = getenv(key);
     if (!val) return EL_STR("");
     return el_wrap_str(el_strdup(val));

lang/runtime/el_runtime.h

@@ -586,60 +586,6 @@ void      el_runtime_dharma_event_arrive(const char* event_type,
                                          const char* payload,
                                          const char* source);
 
-/* ── Geometry: signal as a first-class El value ──────────────────────────────
- *
- * A Geometry is an opaque, magic-tagged heap value carried in an el_val_t —
- * the same discipline as List/Map. It holds a width and a float32 payload,
- * and it is the medium a non-text modality enters in. Declared HERE, above
- * the engram block, because transduction is a LANGUAGE concern: every El
- * program touching any modality needs it, and the engram is merely one El
- * program that happens to hold a graph. See el_runtime.c ("Geometry: signal
- * as a first-class el value") for the full rationale.
- *
- * El-side type annotation is simply `Geometry` — an opaque boxed pointer,
- * exactly like Instant / Calendar / Rhythm. No codegen change is required.
- *
- * OWNERSHIP: a Geometry is owned by the El caller and released with
- * geometry_free. node_attach_geometry COPIES, so a node and the caller's
- * value have independent lifetimes.                                          */
-
-el_val_t  geometry_new(el_val_t dim);                 /* zero-filled; 0 on failure */
-el_val_t  geometry_dim(el_val_t g);                   /* width, 0 if not a Geometry */
-el_val_t  geometry_is(el_val_t g);                    /* 1 if a live Geometry       */
-el_val_t  geometry_get(el_val_t g, el_val_t i);       /* Float component            */
-el_val_t  geometry_set(el_val_t g, el_val_t i, el_val_t x);  /* 1 ok / 0 out of range */
-el_val_t  geometry_norm(el_val_t g);                  /* Float L2 — lets a caller
-                                                       * check a realizer emitted
-                                                       * signal, not zeros          */
-el_val_t  geometry_free(el_val_t g);                  /* 1 if freed, 0 if not a Geometry.
-                                                       * Returns a value (not void) so it
-                                                       * is safe in any El expression
-                                                       * position without a codegen
-                                                       * void-builtin table entry.  */
-
-/* Wire ADAPTERS — the only place an encoding appears, and only at the edge.
- * `f32le hex` is little-endian float32, 8 hex chars per component: the
- * encoding the perception vessel's /voice/embed already emits. The width is
- * DERIVED from the input length, never supplied by a caller — which is why
- * there is no max-dim constant here to validate a claimed length against. */
-el_val_t  geometry_from_f32le_hex(el_val_t hex);      /* 0 on empty/odd-length/non-hex */
-el_val_t  geometry_to_f32le_hex(el_val_t g);          /* "" if not a Geometry       */
-
-/* ── Realizers + transduce ───────────────────────────────────────────────────
- * A REALIZER maps one modality into geometry. Registration is by NAME, so a
- * new modality never requires a runtime patch: every El `fn name(...)`
- * compiles to a global C symbol with that exact name, and the registry
- * resolves it with dlsym against the running binary — the same mechanism
- * http_set_handler already relies on.
- *
- *     fn tone_realizer(signal: String) -> Geometry { ... }
- *     realizer_register("tone", "tone_realizer")
- *     let g: Geometry = transduce(sample, "tone")
- */
-el_val_t  realizer_register(el_val_t modality, el_val_t fn_name); /* 1 ok / 0 unresolved */
-el_val_t  realizer_has(el_val_t modality);            /* 1 if a realizer is registered */
-el_val_t  transduce(el_val_t signal, el_val_t modality); /* Geometry, or 0 if no organ */
-
 /* ── Engram local graph primitives ───────────────────────────────────────────
  * Operate on the CGI's local Engram knowledge graph.
  * `engram_activate` queries the local graph only; `dharma_activate` is
@@ -667,22 +613,10 @@ void      engram_strengthen(el_val_t node_id);
 void      engram_forget(el_val_t node_id);
 el_val_t  engram_prune_telemetry(el_val_t older_than_ms);
 el_val_t  engram_node_count(void);
-/* Attach a Geometry to an existing node, and read the attached width back.
- * Named for the operation, not the store: a node acquires geometry. This is
- * the geometry-valued ingest path — nothing about it is hex, and nothing
- * about it assumes the caller's vector matches the canonical text-embedding
- * width. node_geometry_dim exists so an attach is VERIFIED by reading it
- * back rather than by trusting a success return. */
-el_val_t  node_attach_geometry(el_val_t node_id, el_val_t g); /* 1 ok / 0 otherwise */
-el_val_t  node_geometry_dim(el_val_t node_id);                /* width, 0 if none   */
-
-/* DEPRECATED (shipped in #141, superseded 2026-08-16). Equivalent to
- * geometry_from_f32le_hex + node_attach_geometry, and now implemented as
- * exactly that. Kept only so anything built against the #141 runtime keeps
- * linking; `dim` is accepted but treated as an assertion about the vector's
- * width rather than as its source. New code should not call this — a hex
- * string is a wire encoding, not a way to move geometry between two pieces
- * of El. Returns 1 on success, 0 otherwise. */
+/* Attach geometry to an existing node. `hex` is little-endian float32,
+ * exactly dim*8 hex chars — the encoding realizers already emit. Lets a
+ * non-text modality enter as geometry instead of being described in prose
+ * and embedded as its description. Returns 1 on success, 0 otherwise. */
 el_val_t  engram_node_set_emb(el_val_t id, el_val_t hex, el_val_t dim);
 el_val_t  engram_search(el_val_t query, el_val_t limit);
 el_val_t  engram_scan_nodes(el_val_t limit, el_val_t offset);
@@ -1023,6 +957,22 @@ el_val_t  __url_decode(el_val_t s);
 /* Environment */
 el_val_t  __env_get(el_val_t key);
 
+/* Cross-cutting concerns declared by a `program` block (spec §18).
+ * All three are COMPILER-INJECTED at the head of main() — they are not meant to
+ * be written by hand, which is the point: the guarantee cannot be forgotten at a
+ * call site because there is no call site. */
+el_val_t  el_singleton_acquire(el_val_t id);                    /* §18.1 process identity */
+el_val_t  el_config_declare(el_val_t name, el_val_t type,
+                            el_val_t deflt, el_val_t has_default,
+                            el_val_t required);                 /* §18.2 config schema    */
+el_val_t  el_config_validate(el_val_t program_name);            /* §18.2 startup validate */
+
+/* config(key) — the READ side, and the only one programs write by hand. With a
+ * schema declared it is a validated lookup; without one it degrades to getenv.
+ * (Defined in el_runtime.c but previously never prototyped here, so any program
+ * calling it failed to compile under -Werror=implicit-function-declaration.) */
+el_val_t  config(el_val_t key);
+
 /* Subprocess */
 el_val_t  __exec(el_val_t cmd);
 el_val_t  __exec_bg(el_val_t cmd);

lang/spec/language.md

@@ -29,6 +29,8 @@ This section is the **single source of truth** for what works and what is planne
 - Lexer: keywords, identifiers, integer/float/string/bool literals, operators below.
 - Parser: `let`, `return`, `fn`, `type`, `enum`, `import`, `from … import`, `while`, `for`, `if/else if/else`, `match`, `@decorator`, array/map literals, all listed operators, function calls, field access, index access, unary `!`/`-`, postfix `?`.
 - Codegen: function definitions, top-level `main()`, all expression forms above, control flow, decorator-as-AST-attachment.
+- Boundary seam: decorator arguments and stacking; VBD role enforcement via `#error`; `engram_boundary_beat` auto-emit at `@manager`/`@accessor` entry; `@route` dispatch tables (Section 9).
+- Program-level declarative blocks: `cgi`, `service`, and `program` — the last carrying process identity and configuration (Section 18).
 - C runtime: I/O, string operations, integer math, lists, maps, filesystem, command-line args, basic `json_get` substring lookup.
 
 ### Planned (in flight)
@@ -37,7 +39,7 @@ This section is the **single source of truth** for what works and what is planne
 - **Match codegen.** Currently parsed; codegen does not emit. Adding `({ ... })` statement-expression emission.
 - **`?` propagation.** Currently no-op. Adding nil-propagation semantics.
 - **`cgi` block parsing.** Currently lexed (`cgi` is a keyword) but not parsed as a statement. Adding `parse_cgi_block` and codegen of `el_cgi_init` at the head of `main()`.
-- **VBD role enforcement.** `@manager`/`@engine`/`@accessor` are accepted as decorators but not enforced. Adding compile-time check that `dharma_emit`/`dharma_field` only appear inside `@manager` functions.
+- **Boundary epilogues.** The decorator seam injects a prologue only. Adding prologue/epilogue wrapping, the prerequisite for durability-as-an-effect (Section 19.1).
 - **`vessel` keyword.** Replaces `package` in manifests. Adding to lexer.
 - **Real `engram_*` runtime.** Currently stub. Adding in-process graph store with spreading activation, Hebbian strengthening, and disk persistence — see Section 16.4.
 - **Real `dharma_*` runtime.** Currently stub. Adding network transport, channel registry, identity resolution.
@@ -96,8 +98,10 @@ The following words are reserved and cannot be used as identifiers. Each row not
 | `while` | yes | Loop |
 | `import` / `from` / `as` | yes | Module import |
 | `true` / `false` | yes | Bool literals |
-| `cgi` | planned | Top-level CGI declaration block |
-| `manager` / `engine` / `accessor` | as decorators | VBD role marker on `fn` (enforcement planned) |
+| `cgi` | yes | Top-level CGI declaration block |
+| `service` | yes | Top-level capability-bounded declaration block |
+| `program` | yes | Top-level cross-cutting declaration block (Section 18) |
+| `manager` / `engine` / `accessor` | as decorators | VBD role marker on `fn`; enforcement and boundary auto-emit are live (Section 9) |
 | `vessel` | planned | Manifest declaration (replaces `package`) |
 | `activate` / `where` | planned | Spreading-activation construct |
 | `sealed` | planned | Capability scope block |
@@ -446,9 +450,21 @@ Parsed. The module name is recorded; the brace-list is consumed. Both forms prod
 fn handle(channel: String, msg: String) -> Void { … }
 ```
 
-The `@` token followed by an identifier attaches a decorator name to the next `FnDef`. Decorators with structural meaning today: none. Planned enforcement (Section 16.2): VBD roles `@manager`, `@engine`, `@accessor`.
+The `@` token followed by an identifier attaches a decorator to the next `FnDef`.
 
-Non-VBD decorators are accepted and ignored.
+**Decorators take arguments and they stack.** `@route("/p", "GET") @manager fn f()` attaches both to `f` as a `decorators` list of `{name, args}` records, topmost-first. Arguments are string literals only.
+
+**Decorators have structural meaning today.** This is El's function-level boundary seam — the mechanism by which a cross-cutting concern is handled *at the boundary* rather than by a convention repeated at every call site:
+
+| Decorator | Structural effect |
+|---|---|
+| `@manager` | Permits calls to `dharma_emit` / `dharma_field`. Calling either from a non-`@manager` fn emits a `#error` into the generated C — a compile-time failure, not a lint. |
+| `@manager`, `@accessor` | Codegen injects one call to `engram_boundary_beat(<fn name>)` at function entry. The decorated op self-reports (chrono tick, afferent counter, self-activity strengthen, dharma bus event) with **zero** hand-written instrumentation in its body. |
+| `@route(path, method, …)` | Records a route into a generated dispatch table. |
+
+Decorators with no registered meaning are accepted and ignored.
+
+**Limits of the seam, as it stands.** The injection is a *prologue only* — there is no epilogue, no wrapping of the call, and no way for a decorator to run code after the body returns. The injected callee is a fixed builtin chosen by the compiler, not derived from the decorator name or its arguments. Section 19 depends on lifting exactly these two limits.
 
 ---
 
@@ -1088,4 +1104,152 @@ The next minor version closes the implementation gaps named in this document. Tr
 
 ---
 
+## 18. The Program Block — cross-cutting concerns [implemented]
+
+### 18.0 Why this exists
+
+A cross-cutting concern is one that belongs to the *process*, not to any function in it: only one of me may run; this is what my configuration is; every mutation must be durable; every request must be authorized.
+
+El's units of encapsulation are the function and the module. Neither can hold a concern like that. So each one had been expressed the only way it could be — as a **convention**: *call this at every site.* Conventions of that shape do not hold. They are not enforced by anything, they are invisible in review, and they fail silently at the one site somebody forgot.
+
+Measured in this codebase before this section existed:
+
+| Concern | State | What the convention was |
+|---|---|---|
+| process identity | **zero** guards anywhere — no pidfile, no lock, no already-running check, at any layer | "check nothing is already running first" |
+| configuration | **20** distinct environment variables in one program, each with its default written inline at the read site | "remember the right default here" |
+| durability | **62** `persist_*` / `engram_save` / `wal_*` / `checkpoint` call sites | "after you mutate, remember to persist" |
+| request auth | **10** per-route `_auth` checks | "check the token in this handler too" |
+
+These are not four problems. They are one absence, four times.
+
+That the convention form fails is observed, not predicted. Process identity failed three times in a single day: twice, two engram processes ran simultaneously against the same data directory; twice, a stale binary held a port and answered probes while a fresh build was believed to be under test, because `pkill -f` had silently failed to match its argv — which nearly produced a false "the fix does not work" conclusion. Configuration failed structurally: `ENGRAM_DATA_DIR` was read at six sites, five of them dead bindings, and the sixth defaulted to `/tmp/engram` — contradicting the canonical resolver's `$HOME/.neuron/engram` and landing a pre-destructive safety backup on ephemeral storage.
+
+The `program` block is where a concern of this shape is declared once and enforced by the compiler at the process boundary.
+
+### 18.1 Syntax
+
+```
+program "engram" {
+    singleton: "engram"
+    env ENGRAM_BIND:    String = ":8742"
+    env GUIDE_PORT:     Int    = "8771"
+    env ENGRAM_API_KEY: String required
+}
+```
+
+At most one `program` block per program. It composes with `cgi` and `service` — those declare what a program *may do*; `program` declares what a program *is*.
+
+Grammar:
+
+```ebnf
+program_block = "program" string "{" { program_field } "}" ;
+program_field = singleton_field | env_field ;
+singleton_field = "singleton" ":" string [ "," ] ;
+env_field       = "env" ident ":" type
+                  [ "=" string ] [ "required" ] [ "," ] ;
+```
+
+`singleton` and `env` are **not** reserved words. They are read as identifier token values by the block's own parse loop, so they remain usable as ordinary identifiers everywhere else. `program` is the only keyword this section adds.
+
+### 18.2 Process identity — `singleton`
+
+`singleton: "id"` compiles to an `el_singleton_acquire("id")` call injected as the **first statement of `main()`**, before any user statement runs.
+
+The runtime takes an exclusive non-blocking `flock` on `<dir>/el-singleton-<id>.lock`, where `<dir>` is `$EL_SINGLETON_DIR`, else `$TMPDIR`, else `/tmp`. On success it writes its pid and holds the descriptor open for the life of the process. On contention it **refuses to start**: it reports the holder's pid, names the lock file, and exits 1.
+
+Two properties are deliberate:
+
+- **It is a lock, not a pidfile.** The kernel releases an `flock` when the owning process dies — including on `SIGKILL` and on crash. There is therefore no stale-lock state, and so no "delete the lock file to get unstuck" recovery ritual. Such a ritual would itself be a convention, which is the thing this section exists to remove.
+- **It reports the holder's pid.** "Already running" is not actionable. A pid is. This is the direct answer to the observed failure where a stale process survived a `pkill` and went on answering probes.
+
+Refusal is loud and total. It is not a warning, and the program does not continue degraded. This matters more than it looks: today a second engram whose `bind()` fails merely *returns* from `http_serve` — after it has already replayed the WAL and written boot-time backup files — and then exits **0**, indistinguishable from a clean run. `singleton` refuses before the first side effect.
+
+### 18.3 Configuration — `env`
+
+Each `env` entry declares one configuration variable: its name, its type (`Int` or `String`), and either a default or `required`.
+
+Resolution happens once, at startup, in declaration order: **the environment wins; the declaration supplies the fallback.** Then `el_config_validate` checks the whole schema and reports *every* problem at once before exiting — a startup that fails one variable at a time costs one restart per variable.
+
+Values are read with `config("NAME")`, which returns a `String`.
+
+The enforcement that makes the declaration real: **once a program block exists, `config("X")` for an undeclared `X` is a fatal error.** Without that, the schema would be advisory, and an advisory schema is just another convention. Programs with no `program` block are unaffected — `config()` falls back to a plain environment read, so migration is incremental and per-program.
+
+The point is not that configuration is now centralized. It is that **a default is no longer a decision made at a read site.** A read site cannot disagree with another read site about what a variable means, because a read site no longer says.
+
+### 18.4 What is deliberately not declared here
+
+Some values look like configuration and are not. `ENGRAM_DATA_DIR` already has a single owner — `engram_resolve_data_dir()`, which resolves it, creates the directory, and fails loud rather than silently persisting to an ephemeral path. Declaring it in the `program` block as well would give it two owners that can disagree, recreating the precise defect this section removes.
+
+The rule: **a variable belongs in the program block when the block would be its only owner.** If a resolver already owns it, leave it there.
+
+`HOME` is likewise not configuration. It is an environment fact, and stays a raw `env()` read.
+
+---
+
+## 19. Boundary Effects — durability and request authorization [design only, not implemented]
+
+Sections 19.1 and 19.2 specify the two remaining concerns from the table in 18.0. Both are **designed and deliberately unimplemented.** The reason is stated in 19.3 and it is not difficulty.
+
+### 19.1 Durability as an epilogue effect
+
+**The defect.** 62 call sites carry the convention *"after you mutate, remember to persist."* This is structurally the same defect as the index bug being fixed elsewhere in this tree — *"after you append, remember to index"* — which failed at **9 of 9** sites. A convention that failed at 100% of its sites is the strongest available evidence about what this class of convention is worth.
+
+**Why the existing seam cannot express it.** §9's injection is a prologue. Durability is inherently an *epilogue*: persist after the mutation succeeds, and not at all if it threw. The seam has no epilogue.
+
+**Design.** Extend the decorator seam from prologue-only to prologue/epilogue, then declare durability as an effect on the mutating function:
+
+```
+@durable("engram")
+fn engram_write_node(id: String, body: String) -> Bool { … }
+```
+
+Codegen wraps rather than prefixes:
+
+```c
+el_val_t engram_write_node(el_val_t id, el_val_t body) {
+    el_effect_enter(EL_STR("durable"), EL_STR("engram"));
+    el_val_t __r = /* original body */;
+    el_effect_exit(EL_STR("durable"), EL_STR("engram"), __r);
+    return __r;
+}
+```
+
+`el_effect_exit` is where the persist happens, and it is the only place it happens. Two properties follow that the 62 hand-written sites cannot have:
+
+- **Coalescing.** The epilogue is a single choke point, so N mutations inside one request can produce one fsync instead of N. The hand-written form cannot coalesce, because no site knows about the others.
+- **Failure is not silent.** A persist that fails inside `el_effect_exit` can force the mutation's return value to failure. A forgotten `persist_*` call cannot fail — it simply does not happen, which is exactly why the defect is invisible.
+
+**Enforcement, and this is the part that actually fixes it.** Mirroring §9's `#error` for `dharma_emit`: a function that calls a mutating primitive without carrying `@durable` is a **compile error**. Otherwise this is a 63rd thing to remember rather than a replacement for 62.
+
+### 19.2 Request authorization as a route effect
+
+**The defect.** 10 per-route `_auth` checks. The HTTP layer has no concept of authorization, so a new route is unauthenticated by default and silently so — the failure mode is a route that forgot, and nothing anywhere reports it.
+
+**Design.** Authorization becomes an argument to the `@route` decorator, which already takes arguments and already builds a dispatch table:
+
+```
+@route("/api/write", "POST", auth: "required")
+fn route_write(body: String) -> String { … }
+```
+
+The generated dispatcher performs the check **before** dispatch, so an unauthorized request never reaches the handler and the handler contains no auth code at all.
+
+The default must be `required`. A route that says nothing gets authorization; opening one up takes an explicit `auth: "public"`. Defaulting to public preserves the current failure mode exactly — forgetting stays silent — and a default that preserves the defect is not a fix.
+
+Route inventory falls out for free: the dispatch table already exists, so the compiler can emit the full route/auth matrix and make "which routes are public" a fact that is read rather than audited.
+
+### 19.3 Why these are not implemented
+
+Not difficulty — **collision**. Both land squarely in regions two other agents hold right now:
+
+- **Durability** requires changing the mutation and persist paths in `lang/runtime/el_runtime.c` and `engram/src/server.el` — the same files and the same read/write paths being restructured by concurrent work on VIndex read-path mutation and memory ownership, and on geometry-as-an-el-value and `transduce`.
+- **Request auth** requires changing route dispatch in `engram/src/server.el`, which the geometry/`transduce` work is actively reshaping.
+
+Implementing either now would mean editing files under concurrent modification and resolving conflicts in exactly the paths whose correctness is currently under repair. The designs are recorded here so the work is not lost, and so that whoever lands them does so against a settled tree.
+
+The prerequisite for 19.1 is the same in both cases: **lift the §9 seam from prologue-only to prologue/epilogue.** That change is independent of both collisions and can land first.
+
+---
+
 End of specification.

lang/tests/native/test_transduce.el

@@ -1,234 +0,0 @@
-import "../../runtime/eltest.el"
-// test_transduce.el — geometry as a first-class El value, and realizers
-// declared in El rather than patched into the runtime.
-//
-// WHAT IS ACTUALLY UNDER TEST. Until 2026-08-16 no El ingest path could carry
-// a vector: nodes took text, and geometry was DERIVED from that text. Text was
-// therefore the mandatory entry medium, so any non-text modality had to be
-// DESCRIBED in prose first and the geometry we reasoned over was the geometry
-// OF THE DESCRIPTION, not of the signal. The fix has two halves, and this file
-// exercises both:
-//
-//   1. Geometry is a VALUE — it carries its own width, so nothing has to
-//      assert a width against a string's length.
-//   2. A REALIZER is an ordinary El function. `tone_realizer` below is not in
-//      the runtime, is not known to the compiler, and is not special in any
-//      way; it is registered BY NAME and dispatched to through transduce().
-//      That is the load-bearing claim: adding a modality must not require a
-//      runtime patch, or nothing has actually moved into the language.
-//
-// COMPARISON DISCIPLINE IN THIS FILE (measured 2026-08-16, not stylistic):
-// elc lowers `a == b` to a NUMERIC comparison only when both operand names are
-// in the per-function int-name set, which `let x: Int` populates. A bare call
-// like `geometry_is(g) == 0` is not a registered name, so it lowers to
-// `str_eq(...)` — strcmp on two integers reinterpreted as pointers. `<` and `>`
-// lower directly via binop_to_c with no type inference at all, so truthiness is
-// written `> 0` / `< 1` here, and any exact `==` is done on a value first bound
-// through `let x: Int`.
-
-// ── A realizer, written entirely in El ──────────────────────────────────────
-// Maps a "tone" signal into a 4-component geometry. Deliberately trivial —
-// what is being proven is that an El function can BE a realizer, not that
-// this is good acoustics. The one real property it has: distinct signals
-// produce distinct geometry, so the test can tell transduction from a stub.
-fn tone_realizer(signal: String) -> Geometry {
-    let g: Geometry = geometry_new(4)
-    let n: Int = str_len(signal)
-    let a: Int = geometry_set(g, 0, int_to_float(n))
-    let b: Int = geometry_set(g, 1, int_to_float(n * 2))
-    let c: Int = geometry_set(g, 2, int_to_float(n * 3))
-    let d: Int = geometry_set(g, 3, int_to_float(n * 4))
-    g
-}
-
-// A second realizer for a different modality, to prove the registry keys on
-// modality and does not just hand back "the last thing registered".
-fn pulse_realizer(signal: String) -> Geometry {
-    let g: Geometry = geometry_new(2)
-    let a: Int = geometry_set(g, 0, 1.0)
-    let b: Int = geometry_set(g, 1, 0.0)
-    g
-}
-
-// A deliberately BROKEN realizer: it returns something that is not a Geometry.
-// transduce() must not hand this back to a caller as if it were one.
-fn bogus_realizer(signal: String) -> Geometry {
-    return 12345
-}
-
-test "geometry-is-a-value-with-its-own-width" {
-    let g: Geometry = geometry_new(8)
-    let live: Int = geometry_is(g)
-    assert live > 0, "geometry_new returns a live Geometry"
-    let d: Int = geometry_dim(g)
-    assert d == 8, "a Geometry carries its own width"
-    let freed: Int = geometry_free(g)
-    assert freed > 0, "geometry_free reports what it did"
-}
-
-test "geometry-rejects-nonsense-without-an-arbitrary-bound" {
-    // dim <= 0 is not a width. Note there is deliberately no MAX dim here:
-    // #141 needed `dim <= 8192` only to bound an allocation sized from a
-    // caller's claim about a string. A value that carries its own width has
-    // nothing left to validate, so the only failure left is allocation.
-    let zero: Geometry = geometry_new(0)
-    let z: Int = geometry_is(zero)
-    assert z < 1, "dim 0 is not a geometry"
-    let neg: Geometry = geometry_new(-4)
-    let n: Int = geometry_is(neg)
-    assert n < 1, "negative dim is not a geometry"
-    // Accessors must be total: a non-geometry is 0-width, never a crash.
-    let nd: Int = geometry_dim(0)
-    assert nd < 1, "geometry_dim of a non-geometry is 0"
-    let ni: Int = geometry_is(0)
-    assert ni < 1, "geometry_is of a non-geometry is 0"
-    let nf: Int = geometry_free(0)
-    assert nf < 1, "geometry_free of a non-geometry is a no-op"
-}
-
-test "geometry-components-round-trip" {
-    let g: Geometry = geometry_new(3)
-    let s0: Int = geometry_set(g, 0, 1.5)
-    let s1: Int = geometry_set(g, 1, -2.5)
-    assert s0 > 0, "set in range succeeds"
-    let oob: Int = geometry_set(g, 3, 9.0)
-    assert oob < 1, "set out of range is refused, not silently dropped"
-    let v0: Float = geometry_get(g, 0)
-    let d0: Float = v0 - 1.5
-    assert d0 < 0.001, "component 0 round-trips"
-    assert d0 > -0.001, "component 0 round-trips"
-    let v1: Float = geometry_get(g, 1)
-    let d1: Float = v1 + 2.5
-    assert d1 < 0.001, "component 1 round-trips (negative)"
-    assert d1 > -0.001, "component 1 round-trips (negative)"
-    let freed: Int = geometry_free(g)
-}
-
-test "hex-is-an-edge-adapter-and-derives-its-own-width" {
-    // 2 components, little-endian float32: 1.0 = 0000803f, 2.0 = 00000040.
-    let g: Geometry = geometry_from_f32le_hex("0000803f00000040")
-    let live: Int = geometry_is(g)
-    assert live > 0, "valid hex decodes to a Geometry"
-    let d: Int = geometry_dim(g)
-    assert d == 2, "width is DERIVED from the input, never supplied"
-    let a: Float = geometry_get(g, 0)
-    let da: Float = a - 1.0
-    assert da < 0.001, "first component decoded"
-    assert da > -0.001, "first component decoded"
-    let b: Float = geometry_get(g, 1)
-    let db: Float = b - 2.0
-    assert db < 0.001, "second component decoded"
-    assert db > -0.001, "second component decoded"
-    // Egress adapter is the exact inverse.
-    let back: String = geometry_to_f32le_hex(g)
-    assert str_eq(back, "0000803f00000040"), "hex round-trips exactly"
-    let freed: Int = geometry_free(g)
-}
-
-test "hex-rejects-malformed-input" {
-    let empty: Geometry = geometry_from_f32le_hex("")
-    let e: Int = geometry_is(empty)
-    assert e < 1, "empty hex is not a geometry"
-    let ragged: Geometry = geometry_from_f32le_hex("0000803f0000")
-    let r: Int = geometry_is(ragged)
-    assert r < 1, "length not a multiple of 8 is refused"
-    let nonhex: Geometry = geometry_from_f32le_hex("zzzzzzzz")
-    let nh: Int = geometry_is(nonhex)
-    assert nh < 1, "non-hex characters are refused"
-}
-
-test "a-realizer-declared-in-el-is-a-first-class-realizer" {
-    // THE CLAIM: tone_realizer is an ordinary El function. It is not in the
-    // runtime and the compiler knows nothing about it. Registering it by name
-    // is enough to make it the organ for a modality.
-    let reg: Int = realizer_register("tone", "tone_realizer")
-    assert reg > 0, "an El fn registers as a realizer by name"
-    let has: Int = realizer_has("tone")
-    assert has > 0, "the modality now has an organ"
-
-    let g: Geometry = transduce("aaa", "tone")
-    let live: Int = geometry_is(g)
-    assert live > 0, "transduce returns real geometry"
-    let d: Int = geometry_dim(g)
-    assert d == 4, "the El realizer determined the width, not the runtime"
-    // str_len("aaa") == 3, so component 0 must be 3.0 — proof the signal
-    // actually reached the El function rather than a stub answering for it.
-    let c0: Float = geometry_get(g, 0)
-    let dc: Float = c0 - 3.0
-    assert dc < 0.001, "the signal reached the El realizer"
-    assert dc > -0.001, "the signal reached the El realizer"
-    let freed: Int = geometry_free(g)
-}
-
-test "distinct-signals-transduce-to-distinct-geometry" {
-    let reg: Int = realizer_register("tone", "tone_realizer")
-    let g1: Geometry = transduce("aa", "tone")
-    let g2: Geometry = transduce("aaaaa", "tone")
-    let a: Float = geometry_get(g1, 0)
-    let b: Float = geometry_get(g2, 0)
-    let diff: Float = b - a
-    // 5 - 2 = 3. If transduction were a stub these would be equal.
-    assert diff > 2.9, "different signals produce different geometry"
-    assert diff < 3.1, "different signals produce different geometry"
-    let f1: Int = geometry_free(g1)
-    let f2: Int = geometry_free(g2)
-}
-
-test "the-registry-keys-on-modality" {
-    let r1: Int = realizer_register("tone", "tone_realizer")
-    let r2: Int = realizer_register("pulse", "pulse_realizer")
-    assert r2 > 0, "a second modality registers independently"
-    let gt: Geometry = transduce("aaa", "tone")
-    let gp: Geometry = transduce("aaa", "pulse")
-    let dt: Int = geometry_dim(gt)
-    let dp: Int = geometry_dim(gp)
-    assert dt == 4, "tone still routes to its own realizer"
-    assert dp == 2, "pulse routes to a different realizer"
-    let f1: Int = geometry_free(gt)
-    let f2: Int = geometry_free(gp)
-}
-
-test "no-organ-is-reported-as-no-organ" {
-    // A modality with no realizer must transduce to NOTHING. It must never
-    // fall back to embedding a description of the signal and calling that
-    // perception — that silent substitution is the entire defect this change
-    // exists to end.
-    let has: Int = realizer_has("echolocation")
-    assert has < 1, "unregistered modality has no organ"
-    let g: Geometry = transduce("anything", "echolocation")
-    let live: Int = geometry_is(g)
-    assert live < 1, "no realizer means no geometry, not fake geometry"
-}
-
-test "registration-of-an-unresolvable-name-fails-loudly" {
-    // Reported at the moment of WIRING, not later as "this modality mysteriously
-    // produces nothing". Distinguishing "no organ" from "broken organ" is the
-    // lesson that made this whole change necessary.
-    let bad: Int = realizer_register("ghost", "no_such_function_anywhere")
-    assert bad < 1, "an unresolvable realizer name is a registration failure"
-    let has: Int = realizer_has("ghost")
-    assert has < 1, "and nothing gets registered"
-}
-
-test "a-realizer-returning-non-geometry-transduces-nothing" {
-    let reg: Int = realizer_register("bogus", "bogus_realizer")
-    assert reg > 0, "the symbol resolves, so registration succeeds"
-    // ...but the contract is enforced at the boundary, so the caller never
-    // receives a value that would misbehave far away from here.
-    let g: Geometry = transduce("x", "bogus")
-    let live: Int = geometry_is(g)
-    assert live < 1, "a non-Geometry return transduced nothing"
-}
-
-test "norm-lets-a-caller-check-a-realizer-emitted-signal" {
-    let g: Geometry = geometry_new(2)
-    let z: Float = geometry_norm(g)
-    assert z < 0.001, "a fresh geometry is zero — norm says so"
-    let s0: Int = geometry_set(g, 0, 3.0)
-    let s1: Int = geometry_set(g, 1, 4.0)
-    let n: Float = geometry_norm(g)
-    let dn: Float = n - 5.0
-    assert dn < 0.001, "3-4-5: norm is 5"
-    assert dn > -0.001, "3-4-5: norm is 5"
-    let freed: Int = geometry_free(g)
-}