Durability: the 2026-07-21 fix stopped read routes writing the canonical
snapshot but left no save on ANY write path — every mutation lived in RAM
until a manual POST /api/save. Observed live: two restarts reverted the
store to a 17h-old snapshot, destroying same-day writes. persist_canonical()
now runs after node/edge create, knowledge capture, forget, strengthen, and
load-merge. ISE telemetry excluded deliberately (48h-pruned, loss-tolerant,
~2/min; snapshotting 28MB per heartbeat is waste).
Listing order: scan routes sort by salience with store-order ties, so
equal-salience telemetry (all ISEs are 0.3) returned OLDEST first — a
limited /api/nodes query silently returned a stale window, and a 41h-old
heartbeat series read as a live outage during this review. Ties now break
newest-first by created_at.
The old carry-over (weight *= 0.7 per engram_activate call) was call-rate-
dependent — carried context died in seconds under rapid curiosity scans and
lingered for hours under quiet loops — and a decayed scalar cannot represent
access frequency at all.
Now: k=10 access-timestamp ring + Petrov (2006) closed-form tail, d=0.5.
WM promotion and engram_strengthen record presentations; carry-over evicts
at base-level tau=-3.0 (Soar forgetting, ~403s single-touch) and shapes the
weight held at promotion (wm_anchor) with the ACT-R retrieval logistic
(s=0.4) — a pure function of wall-clock time, idempotent per call.
Persisted as access_ts/wm_anchor in snapshots; legacy nodes fall back to
the optimized form ln(n/(1-d)) - d*ln(L). base_level exposed in both node
serializers for observability.
Backing spec: 2026-07-21 integration brief (bl-b17facdd). Verified live:
carried weight ~anchor seconds after two disjoint activations (old code:
0.49x); frequency-hot nodes hold B=1.9 vs -0.14 single-touch.
Three fixes that existed elsewhere but never reached the runtime the engram
binary actually builds against:
- tokenized + ranked query matching (search/search_json/activate seeds/
goal_bias) ported from the el-compiler copy (e3dabe3, 2026-07-14) — the
production engram kept whole-query Ctrl-F for 5 days after the fix
'shipped'. Multi-word curiosity seeds went 0 -> 36 activated. Kept the
ISE seed exclusion the el-compiler copy dropped.
- Knowledge -> 0.20 WM threshold after tier checks (dev-line 4bf7716):
Semantic/Episodic Knowledge nodes fell to the 0.40 note default and only
entered WM via breakthrough.
- goal_bias: Knowledge in is_knowledge + curiosity-seed technical terms
(dev-line d53516b).
Also: seed_epoch was a running pairwise average, not the mean it claimed —
exponentially over-weighted later seeds in the temporal-proximity bonus.
Fixed to a true int64-sum mean. Stale INHIBITION_FACTOR comment corrected.
Root cause captured as knowledge: two runtime copies + branch-per-fix
without merge discipline stranded the entire dev semantic layer (cosine
activation, embeddings) out of production. Reconciliation planned as P1.
1. engram_neighbors_json (release runtime): BFS frontier/visited strings were
el_strdup'd (arena-tracked) but manually freed, so el_request_end()
double-freed every one — SIGABRT in http_worker under load (2 prod crashes
today via /api/neuron/session/begin and /api/neuron/graph; reproduced and
verified fixed with ASAN). Introduced when porting from the dev runtime,
which correctly uses plain strdup. Third instance of the
arena-vs-manual-free class (after EngramNode 07-15 and idmap keys 07-16).
2. server.el: let-in-if scoping sweep — defaults assigned inside if-blocks
never mutated the outer binding, so /api/search and /api/activate always
ran with q="", created nodes got node_type=""/salience=0.0, edges got
relation=""/weight=0.0, and save/load with no path hit engram_save("").
Rewritten to the let-if-else expression form. /api/activate now also
rejects empty queries instead of wiping carried WM weights.
3. engram_activate: retrieval reinforcement (ACT-R base-level learning) —
nodes promoted to WM that survive both capacity caps now get
last_activated/activation_count updated, so frequently retrieved memories
decay slower than abandoned ones. Scoped to promoted-only to avoid
flattening dampening across BFS fan-out.
Two independent investigations, one runtime, complementary halves:
1. Leak (Jul 2, this machine): JsonBuf buffers returned via el_wrap_str
were raw malloc, never arena-tracked — every engram_*_json call leaked
its output unconditionally. Added jb_finish() arena-tracking across all
~30 return sites. Plus el_arena_push/pop per-tick bracketing support
for the soul's awareness loop (the loop ran outside any request arena,
so even correctly-tracked allocations were permanent — 7.5GB RSS in
under a minute at 1s tick).
2. Corruption (Tim's container soak, docs findings/container-migration):
stored engram node/edge fields (content, node_type, label, tier, tags,
metadata, from/to ids) were arena el_strdup — freed at request end,
leaving dangling pointers that read back as recycled request-buffer
bytes one request later. This is the June corruption root cause and
the mechanism that grew snapshot.json to 18GB of empty-type junk
(21.6M nodes, 3,335 real). 39 sites switched to el_strdup_persist,
plus a latent double-free fix in engram_load metadata fixup.
Interaction note: fix 1's per-tick arena reclamation makes fix 2
mandatory — more aggressive arena recycling widens the use-after-free
window if stored fields still live in the arena. Apply as a pair, never
separately.
Verified live: soul + engram rebuilt from this runtime, booted against
the recovered real snapshot (3,335 nodes/40,146 edges), 5h stable at
<100MB RSS, write-then-next-request field-integrity test passes (the
June corruption fingerprint does not reproduce). engram/dist/engram
binary updated from this build.
Investigation credit: leak diagnosis this machine Jul 2-6; corruption
diagnosis + persist-fix patch by Tim's instance (docs PR #4).
Runtime now includes engram_load_merge — soul daemon awareness.el calls
this function during its periodic sync refresh cycle. Binary rebuilt from
server.el (unchanged source) + updated el_runtime.c.
Port critical WM fixes from self-review 2026-06-26 branch (f7bd99a) that were
never merged to HEAD. Running binary had these fixes; source did not — rebuild
would have silently regressed all three improvements.
1. ENGRAM_BREAKTHROUGH_WEIGHT 0.25→0.10
With 0.25, naturally-promoted nodes (threshold ≥0.15) decayed below the
breakthrough floor within one activation call and lost their WM slot to
fresh breakthrough candidates. All 524/525 WM nodes were at floor = useless.
Invariant: BREAKTHROUGH_WEIGHT < min(type_thresholds = 0.15 Canonical).
2. ENGRAM_WM_CAP=24 with Pass 4 (per-call) + Pass 5 (global) enforcement
Without cap, broad curiosity seeds promote 500+ nodes simultaneously.
wm_avg_weight collapses, goal-bias differentiation is lost. Verified:
"knowledge" query now promotes exactly 24 nodes (was 525). Cowan (2001)
cognitive basis: WM capacity ~4 chunks; 24 allows rich multi-topic context.
3. ISE exclusion from WM (Pass 2 guard)
InternalStateEvent JSON content ("knowledge", "memory", etc.) triggered
lexical seeding → suppression accumulation → breakthrough at floor. ISEs
are observability-only and must never surface in context compilation.
suppression_count cleared so ISEs never build toward breakthrough.
4. route_create_ise importance fix (0.5→0.3)
Corrects mismatch between HTTP route and awareness.el in-process fallback.
Also adds body comment clarifying auth-exempt rationale.
SYNAPSE (arXiv 2601.02744) validates WM cap design and ISE exclusion principle.
Next priority: cosine similarity seeding to complement lexical BFS.
el_strdup tracks pointers in the arena. The BFS arrays in
engram_neighbors_json are manually freed — using el_strdup caused a
double-free when the arena was later popped. Changed to plain strdup
for those allocations.
engram/dist/engram.c rebuilt from engram/src/server.el with current
elc (minor codegen diff: parenthesisation and _argc/_argv rename).
Dharma's EngramDB client calls /nodes/list to retrieve all nodes.
Add this as an alias for the existing /nodes (and /api/nodes) route
so downstream clients don't need to be updated when the API drifts.
Also update dist/engram.c to match server.el.
Engram is now a thin HTTP face over the El runtime's in-process graph
store. The C runtime owns the data; engram_*_json builtins serialize
results directly. There is no SQL, no SQLite, no db layer, no state
machine — the runtime IS the database.
src/server.el (348 lines, replacing 5797 lines across 15 legacy files):
GET /health
GET /api/stats
POST /api/nodes (auth required)
GET /api/nodes
GET /api/nodes/:id
DELETE /api/nodes/:id (auth required)
POST /api/edges (auth required)
GET /api/neighbors/:id
POST /api/activate
GET /api/activate
POST /api/search
GET /api/search
POST /api/strengthen (auth required)
POST /api/save (auth required)
POST /api/load (auth required)
Auth: ENGRAM_API_KEY in env. GET routes pass through (read-only).
Mutating routes require {"_auth": "<key>"} in the JSON body until
http_serve surfaces request headers and we can switch to Bearer.
Persistence: engram_save / engram_load via JSON snapshot at
$ENGRAM_DATA_DIR/snapshot.json. Loaded best-effort on startup.
Build: dist/platform/elc src/server.el > dist/engram.c
cc -std=c11 -O2 -I <runtime> -lcurl -lpthread -o dist/engram
dist/engram.c <runtime>/el_runtime.c
Live: native binary at dist/engram (113 KB), running under
~/Library/LaunchAgents/ai.neuron.engram.plist on :8742. Verified:
GET /api/stats returns counts; POST /api/nodes with auth creates
node with UUID; GET /api/search returns full node JSON; spreading
activation returns hop-decayed strengths (0.8 × edge × decay per
hop) with epistemic confidence filtering.
Legacy (5797 lines of SQLite-era src) sealed at
~/Archives/engram-src-legacy-20260430.tar.gz and removed from disk.
will.anderson
Will Anderson