semvec 0.4.4

Semvec — patent-pending persistent semantic state engine

Semvec

Constant-cost semantic memory for LLM applications.

Semvec replaces unbounded conversation history with a fixed-size semantic state plus a tiered, content-aware memory. The cost of every LLM call stays constant — turn 10 and turn 10 000 carry the same input footprint — and the agent still has structured access to decisions, invariants, error patterns, and prior context across sessions.

Patent-pending technology — EP 25 188 105.8 - novelty acknowledged

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Table of contents

• What you get
• Installation
• Choose your use case
• Token-reduced LLM context
• Drop-in chat proxy
• Multi-agent coordination
• Coding-agent compaction
• REST API server
• Persistence
• Configuration & environment variables
• Error handling
• Licensing
• Limitations & non-goals
• FAQ
• Telemetry
• Support
• License

---

What you get

Capability	What it solves
Constant-size compressed context	Per-call LLM input cost stops growing with conversation length. ~76 % token reduction on 48-turn runs.
Tiered memory with selective forgetting	Three tiers (short / medium / long term) with retention scoring — frequently-accessed older memories outlive never-touched newer ones.
Domain anchors + resonance triggers	Bias retrieval toward known domains or specific keywords without re-training. Lifts precision@3 from 86 % → 91.7 % on mixed-domain workloads.
Drop-in chat proxy	Wrap any OpenAI-compatible LLM and get compressed context for free. Works with vLLM, LiteLLM, OpenRouter, Ollama out of the box.
Multi-agent coordination (Cortex)	Run several agents that share an aggregated view, vote on proposals, and exchange checksummed state vectors.
Coding-agent compaction	Persistent memory across coding sessions — design decisions, invariants, error patterns, code-pointer index, anti-resonance checks. MCP server for Claude Code & Cursor included.
REST API server	semvec serve exposes the full surface over FastAPI: sessions, clusters, regions, observer, network, literal cache, Prometheus metrics.
Compliance pack	Append-only event store, deterministic replay, GDPR Art. 17 forget with signed certificates, HMAC request signing, RS256 user JWTs.
Bring-your-own embedder	Anything exposing get_embedding(text) → np.ndarray and get_dimension() → int works. SentenceTransformers, OpenAI, ONNX int8 — see the embedders guide.
One wheel, all platforms	Python 3.10–3.14 via stable ABI. Pre-built wheels for Linux (x86_64 + aarch64), macOS (x86_64 + arm64), Windows (x86_64).

---

Installation

# Core only
pip install semvec

# With multi-agent coordination
pip install "semvec[cortex]"

# With coding-agent compaction (FastMCP server, Claude Code hooks)
pip install "semvec[coding]"

# Compliance pack (event store, retention, DSGVO forget, HMAC, RS256)
pip install "semvec[compliance]"
# When you also want the FastAPI compliance routes + middleware:
pip install "semvec[api,compliance]"

# REST API server
pip install "semvec[api]"
semvec serve --host 0.0.0.0 --port 8080

# Benchmark runners + optional Mem0 baseline
pip install "semvec[benchmarks,mem0]"

# Everything the developers use
pip install "semvec[cortex,coding,api,benchmarks,dev]"

Extra	Pulls in	When you need it
[cortex]	(marker only)	multi-agent coordination — primitives are always available; the extra marks intent
[coding]	fastmcp>=2.0	MCP server + Claude Code lifecycle hooks
[compliance]	cryptography>=42	Event store, retention sweeper, deletion certificate signer, HMAC + RS256 signing. FastAPI routes need [api] on top. See the Compliance guide.
[api]	fastapi, uvicorn[standard], slowapi, sqlalchemy, prometheus-client, pydantic	REST API server (semvec serve)
[benchmarks]	sentence-transformers>=3.0, datasets>=2.14, psutil>=5.9	running the LongMemEval harness or other benchmarks
[mem0]	mem0ai>=0.1, faiss-cpu>=1.7	head-to-head Mem0 comparison
[dev]	ruff, mypy, pre-commit, pytest, httpx	contributing

Embedder requirement

Semvec is embedder-agnostic and refuses silent hash-based fallbacks — you bring your own. Any object exposing get_embedding(text) → np.ndarray and get_dimension() → int works.

pip install sentence-transformers

Choose the embedder dimension carefully — Semvec's retrieval quality is bounded by what the embedder can separate. Measured on 80 mixed-domain notes:

Embedder	dimension	precision@3	usable for
all-MiniLM-L6-v2	384	66.67 %	English-only, tight-domain prototypes only
paraphrase-multilingual-mpnet-base-v2	768	86.11 %	German / multilingual mixed-domain (recommended)

The 384-dim MiniLM is the easy default but on multilingual or domain-mixed text it confuses generic terms (e.g. "filter" → coffee filter vs. data filter). For German content, mixed-domain corpora, or anything where you need ≥ 80 % precision@3, use multilingual mpnet 768 d minimum.

from sentence_transformers import SentenceTransformer

embedder = SentenceTransformer(
    "sentence-transformers/paraphrase-multilingual-mpnet-base-v2"
)

---

Choose your use case

You want to…	Jump to
Compress conversation history for any LLM	Token-reduced LLM context
Drop-in replacement for openai.chat.completions	Drop-in chat proxy
Coordinate many agents (analyst + planner + critic …)	Multi-agent coordination
Give Claude Code / Cursor persistent memory across sessions	Coding-agent compaction
Run as a service, talk to it over HTTP	REST API server
Process regulated data (GDPR, audit, retention)	Compliance pack

---

Token-reduced LLM context

The single most-used path: produce a compact system-prompt block from any conversation, regardless of length.

from semvec import SemvecState, SemvecConfig
from semvec.token_reduction import SemvecStateSerializer

state = SemvecState(config=SemvecConfig(dimension=768))

for text, embedding in conversation:
    state.update(embedding, text)

serializer = SemvecStateSerializer()
context = serializer.serialize(state, query_text="what did we decide about auth?")

response = openai.chat.completions.create(
    model="gpt-4o",
    messages=[
        {"role": "system", "content": context},
        {"role": "user",   "content": "what did we decide about auth?"},
    ],
)

Compared to raw history concatenation, the compressed context does not grow with conversation length — input cost converges to a constant. The serializer fits prior context into a 150–350-token block sized for a system prompt.

Lift retrieval quality with anchors and triggers

The passive ingest above gives you retrieval that already beats sliding-window concatenation. To bias retrieval toward known domains or specific cues, register anchors and resonance triggers:

from semvec import SemvecState, SemvecConfig

state = SemvecState(config=SemvecConfig(
    dimension=768,
    enable_topic_switch=True,
    auto_anchor_on_topic_switch=True,   # opt-in (default off)
))

# Anchors — bias retrieval toward your known domains.
for prototype in [
    "SAP Business One Service Layer OData REST API",
    "Python MCP Model Context Protocol Server",
    "italienische Kueche Kochen Pasta Pizza",
    "Kaffee Espresso Roesterei Brewing",
]:
    state.add_anchor(embed(prototype))

# Triggers — boost memories on a keyword OR vector match.
state.create_resonance_trigger(
    keyword="security review",
    embedding=embed("security audit threat model"),
    threshold=0.7,
)

for text, vec in conversation:
    state.update(vec, text)

# Retrieval is now anchor-biased: candidates aligned with one of
# your domain anchors win the tie-break against generic phrases.
top = state.memory.get_relevant_memories(embed("OData filter syntax"), top_k=3)

What each piece adds (measured on mpnet 768 d, 80 mixed German notes):

Variant	precision@3
passive update() only	86.11 %
+ 4 domain anchors	91.67 % (+ 5.56 pp)
+ 4 resonance triggers	86.11 %
anchors + triggers	91.67 %

Without anchors, the retrieval boost is a no-op — flipping these features on costs nothing if you do not need them. Anchors and triggers compete for the same boost slot (max(...), not addition), so redundant signals do not double-count.

Tuning rule of thumb: keep anchor_retrieval_boost ≥ trigger_retrieval_boost, both in the [0.1, 0.6] range. Pushing either past 0.7 mostly stops moving the needle — spend your budget on better anchor prototypes or sharper trigger thresholds rather than dialling the boosts higher.

---

Drop-in chat proxy

SemvecChatProxy wraps any callable LLM behind compressed context and tracks both compressed and full-history token counts per turn:

from semvec.token_reduction import SemvecChatProxy, create_llm_client

llm = create_llm_client("openai")  # reads OPENAI_BASE_URL/MODEL/API_KEY from env
proxy = SemvecChatProxy(
    llm_call=llm,
    system_prompt="You are a helpful assistant.",
    embedding_service=my_embedder,
)

for question in ["summarise Q3", "compare with Q2", "biggest miss?"]:
    result = proxy.chat(question)
    print(f"turn {result.turn_number}: {result.response}")
    print(f"  compressed tokens: {result.tokens.compressed}")
    print(f"  full-history tokens: {result.tokens.full_history}")

print(proxy.get_summary())

Built-in clients: OpenAIClient (works with the OpenAI API and any compatible endpoint such as vLLM, LiteLLM, OpenRouter), OllamaClient. You can pass any callable (list[ChatMessage]) -> str.

Break-even is around ten turns. The compressed prompt carries a constant ~110-token header. For very short conversations (≤ 5 turns) plain history concatenation is cheaper; from ~10 turns onward the proxy undercuts naive concatenation, and the gap widens linearly with conversation length. Measured on a 48-turn run: ~76 % token reduction vs. full-history.

---

Multi-agent coordination

Run several agents (analyst, planner, critic, …) that share an aggregated view, vote on proposals, and exchange checksummed state vectors.

from semvec.cortex import SemvecAgentNetwork, AttentionAggregation

network = SemvecAgentNetwork(
    aggregation_strategy=AttentionAggregation(dimension=768),
    dimension=768,
)
network.add_local_instance("analyst")
network.add_local_instance("planner")

network.process_input("analyst", "quarterly revenue is up 23%")
network.process_input("planner", "we should redirect Q4 spend to retention")

state = network.get_network_state()
print(f"active agents: {state['active_instances']}/{state['total_instances']}")

# Pull per-agent feedback for the next turn (consensus-aware)
feedback = network.get_feedback_for_agent("analyst")

Aggregation strategies: WeightedAverageAggregation, AttentionAggregation. ConsensusEngine adds proposal voting with five levels (SIMPLE_MAJORITY, QUALIFIED_MAJORITY, UNANIMOUS, WEIGHTED_VOTE, ADAPTIVE_THRESHOLD); quorum is measured against the registered voter pool, not just votes-cast-so-far. StateVectorPacket round-trips bit-exactly via serialize()/deserialize() and verify_integrity() confirms byte equality.

See the Cortex API reference for the full surface.

---

Coding-agent compaction

Persistent memory across coding sessions for Claude Code, Cursor, Aider — code pointers, anti-resonance error patterns, structured handoff context.

from semvec.coding import CodingEngine

engine = CodingEngine(state_dir="~/.semvec/project-x", embedder=my_embedder)
engine.ingest_transcript("path/to/claude_code_session.jsonl")

context = engine.get_compacted_context(
    "implement password reset flow",
    invariants=["never log plaintext passwords"],
)

Multi-session memory via LiteralCache

Below the high-level CodingEngine, state.literal_cache is a structured memory of design decisions, error patterns, invariants, and per-checkpoint test results — anything you want to survive across sessions verbatim:

import semvec

state = semvec.SemvecState(semvec.SemvecConfig(dimension=768))
cache = state.literal_cache

cache.record_decision("Use mpnet 768d for German content", checkpoint=1)
cache.record_error_pattern(
    pattern="catastrophic recency bias on blocked-domain ingest",
    example="500-note 4-domain blocked sequence",
    fix="raise long_term_size and use tier weights 1.0/0.95/0.9",
    checkpoint=1,
)
cache.add_invariant("State must round-trip via to_dict/from_dict")
cache.record_test_results(
    checkpoint=1,
    passed_tests=["test_a", "test_b", "test_c"],
    failed_tests=[],
)

# Build the LLM hand-off context for the next session
ctx = cache.build_handoff_context(next_checkpoint=2)
# ### INVARIANTS — Do NOT break these:
# - State must round-trip via to_dict/from_dict
#
# ### Test Status (CP1: 100%, 3/3)
#
# ### Known Error Patterns
# - `catastrophic recency bias on blocked-domain ingest` (x1): raise long_term_size...
#
# ### Design Decisions
# - [CP1] Use mpnet 768d for German content

# Persist + restore — round-trip preserves decisions, error_patterns,
# invariants, test_history, code_structures.
blob = state.to_bytes()
restored = semvec.SemvecState.from_bytes(blob)
assert restored.literal_cache.build_handoff_context(2) == ctx

build_handoff_context() produces a Markdown block ready for the system prompt of the next session. See the Coding API reference for the full surface.

Claude Code integration (MCP + hooks)

Wire it directly into Claude Code via the bundled FastMCP server and two lifecycle hooks. Add to .claude/settings.json:

{
  "mcpServers": {
    "semvec": {
      "command": "python",
      "args": ["-m", "semvec.coding.mcp_server"],
      "env": {
        "SEMVEC_STATE_DIR": ".semvec",
        "SEMVEC_EMBED_MODEL": "all-MiniLM-L6-v2"
      }
    }
  },
  "hooks": {
    "PreCompact":  [{"command": "python -m semvec.coding.hooks.pre_compact",  "timeout": 30000}],
    "SessionStart":[{"command": "python -m semvec.coding.hooks.session_start", "timeout": 10000}]
  }
}

The MCP server exposes six tools — pss_get_context, pss_update, pss_check_anti_resonance, pss_register_code, pss_record_error, pss_save. FastMCP is installed automatically via the [coding] extra.

The same FastMCP server plugs into Cursor via .cursor/mcp.json plus a Cursor Rule that replaces Claude Code's lifecycle hooks. Full step-by-step in the Cursor guide.

---

REST API server

pip install "semvec[api]"

# Dev mode — anonymous community-tier auth, in-memory SQLite
SEMVEC_ALLOW_ANONYMOUS=1 semvec serve --host 0.0.0.0 --port 8080

# Production — license JWT required, Postgres-backed metadata
export SEMVEC_LICENSE_KEY="eyJhbGciOiJFZERTQSI..."
export DATABASE_URL="postgresql://user:pw@host/semvec"
semvec serve --host 0.0.0.0 --port 8080

Talk HTTP:

# Health check (no auth)
curl http://localhost:8080/v1/health

# Single turn
curl -X POST http://localhost:8080/v1/run \
  -H "Authorization: Bearer $SEMVEC_LICENSE_KEY" \
  -H "Content-Type: application/json" \
  -d '{"session_id": "demo", "query": "what was the Q3 miss?"}'

# Retrieve compressed context
curl "http://localhost:8080/v1/state/context?session_id=demo&top_k=5" \
  -H "Authorization: Bearer $SEMVEC_LICENSE_KEY"

Endpoint groups: sessions (CRUD + run/store/context), session-control (resonance triggers, anchors, isolation, export/import/verify), clusters, regions (consensus-driven realignment), global observer (anomaly detection across regions), network (state transfer, user partitioning, trust-based consensus), literal cache, Prometheus /metrics.

Auth is via Authorization: Bearer <jwt> or X-API-Key: <jwt> — same Ed25519-signed JWT as the in-process licensing system.

See the REST API reference for every endpoint and the CLI reference for semvec serve flags.

---

Persistence

state.to_dict() is a JSON-safe checkpoint with embedded SHA-256 checksum — best when the snapshot has to round-trip through systems that only speak JSON.

state.to_bytes(compress=True) is the compact binary equivalent (gzip-compressed JSON, magic header, SHA-256 corruption check) — best for cold-storage checkpoints. state.to_bytes(compress=False) is the speed-optimised variant: same byte footprint as JSON, but kept as a self-describing binary blob with corruption check — best for hot-path persistence. Both paths preserve the full state on round-trip:

• the semantic state and its rolling histories
• all three memory tiers
• domain anchors and topic-switch history
• the complete LiteralCache: entities, decisions, error patterns, invariants, test history, code structures

Restore with SemvecState.from_bytes(blob); the version byte distinguishes the two to_bytes modes automatically.

Practical sizing on mpnet 768 d:

Memories	JSON	to_bytes(compress=True)	to_bytes(compress=False)
110 (small)	18 ms / 8.8 kB / memory	157 ms / 3.7 kB / memory	36 ms / 8.8 kB / memory
1 000 (extrapolated)	~ 0.2 s / 9 MB	~ 1.4 s / 3.7 MB	~ 0.3 s / 9 MB
100 000	~ 17 s / 1.7 GB	~ 2.5 min / 400 MB	~ 30 s / 1.7 GB

Pick the variant by use case:

• Cold-storage checkpoint (occasional, durability matters) → compress=True. ~ 2.4× smaller than JSON; pay the gzip cost once.
• Hot-path persistence (every-turn or per-request) → compress=False. Same size as JSON, only ~ 1.9× slower than json.dumps, but kept as a self-describing binary blob with corruption check.

For very large footprints (> 100 k memories) wrap your own NPZ/Parquet around the embedding payload to save another factor.

---

Configuration & environment variables

Variable	Default	Used by
SEMVEC_LICENSE_KEY	—	Pro/Enterprise gates; REST API auth
SEMVEC_ALLOW_ANONYMOUS	unset	REST API: bypass auth (dev only)
SEMVEC_STATE_DIR	.semvec	CodingEngine state persistence
SEMVEC_EMBED_MODEL	all-MiniLM-L6-v2	MCP server / hooks default embedder (consider overriding to paraphrase-multilingual-mpnet-base-v2 for German/multilingual)
SEMVEC_EMBED_DEVICE	cpu	MCP server / hooks: cpu or cuda
DATABASE_URL	sqlite:///semvec.db	REST API persistence (also accepts postgresql://…)
METRICS_USER / METRICS_PASSWORD	—	Basic Auth on Prometheus /metrics
OPENAI_BASE_URL, OPENAI_API_KEY, OPENAI_MODEL	—	OpenAIClient
OLLAMA_BASE_URL, OLLAMA_MODEL	http://localhost:11434, —	OllamaClient

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Error handling

import time
from semvec import RateLimitError, LicenseExpiredError, ConfigurationError

try:
    result = state.update(embedding, text)
except RateLimitError as e:
    # e.retry_after is a datetime.timedelta; e.upgrade_url is set
    time.sleep(e.retry_after.total_seconds())
    result = state.update(embedding, text)
except LicenseExpiredError as e:
    # Hard fail — re-import won't help. Renew at e.upgrade_url.
    logger.error("semvec license expired — renew at %s", e.upgrade_url)
    raise
except ConfigurationError as e:
    # Wrong dimension, missing embedder, malformed config, etc.
    raise

All Semvec exceptions inherit from SemvecError. License-related exceptions (RateLimitError, LicenseExpiredError, LicenseError) inherit from LicenseError → SemvecError.

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Licensing

Three tiers; Community works without a key, Pro and Enterprise require a signed Ed25519 JWT:

Tier	Rate limit	Retrieval modes
Community (no key)	5 QPS sustained / 50 burst	Base retrieval
Pro	200 / 2000 QPS	Extended
Enterprise	Unthrottled	All

JWTs have a 30-day TTL. Expiry is a hard fail — the next gated call raises LicenseExpiredError with the renewal URL in the message. Rate-limit exhaustion raises RateLimitError with a retry_after (a datetime.timedelta) and the upgrade URL.

export SEMVEC_LICENSE_KEY="eyJhbGciOiJFZERTQSI..."

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Limitations & non-goals

Honest list of what Semvec does not do:

• Not a vector database. Long-term memory is bounded; if you need recall over a million documents, run a dedicated vector store and treat Semvec as a conversational compressor on top.
• Not a drop-in for stateless completion. The whole point is persistent state; if you only do single-shot prompts, you do not need Semvec.
• No silent embedder fallback. If you do not pass an embedder, methods that need one raise a descriptive RuntimeError. Intentional — silent hash fallbacks gave surprising failure modes in earlier iterations.
• License gate is a licensing feature, not a hard security boundary. Use it to enforce subscription tiers, not to keep determined adversaries out.
• No mobile / WASM build today. abi3-py310 Linux/macOS/Windows only.
• REST API persistence is metadata-only. Hot semantic state lives in-memory per process; only session/cluster/member/region/audit metadata is persisted. Plan accordingly for restarts.

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FAQ

Is this RAG? Not in the usual sense. RAG retrieves documents at query time. Semvec compresses the conversation itself into a fixed-size state. They compose well — many users run Semvec for conversational signal + a vector DB for document retrieval.

Does the state ever grow? No, the state vector itself is fixed-size. The associated memory tiers are bounded by configured capacities — when full, the lowest-scoring entry is evicted (not the oldest).

Can I run it offline / air-gapped? Yes for Community tier. Pro/Enterprise tiers verify Ed25519 JWT signatures locally — no network call to a license server at runtime. Contact [e-mail] for offline-issued JWTs with custom TTLs.

How fast is it? Per-turn update() is sub-millisecond on a recent x86_64 CPU at dimension 384, dominated by NumPy/Rust matrix ops, not Python overhead. The whole point of the Rust port was to keep the math out of the GIL.

Is the source available? Compiled wheels are public on PyPI; the Rust source is held closed. Source access for Enterprise terms — contact [e-mail].

GPU support? Embedders run on whatever device you configure (cuda, mps, cpu); the Semvec core itself is CPU-only — the math is small enough that GPU offload would lose more in transfer than it gains.

---

Telemetry

Semvec sends one anonymous init ping per Python process — and nothing else. No heartbeat, no per-call event, no inference data, no licensing JWT contents. Default-on; opt out with SEMVEC_TELEMETRY=0.

The ping contains:

• the semvec version
• a pseudonymous machine identifier (no IP, no hostname)
• OS, architecture, Python version

The full schema and retention policy are documented at https://www.semvec.io/privacy.

Variable	Effect
(unset)	Telemetry is on, one ping on first import, stderr notice prints once
SEMVEC_TELEMETRY=0	Telemetry is off, no ping, no notice
SEMVEC_TELEMETRY_QUIET=1	Keep telemetry on but silence the stderr notice
SEMVEC_TELEMETRY_ENDPOINT=https://your.host/init	Route the ping to a self-hosted endpoint (air-gapped enterprise)

---

Support

• Documentation: https://semvec-docs.pages.dev
• Pricing & licensing: https://www.semvec.io
• Pro / Enterprise support: [e-mail] (priority response)
• Security disclosures: [e-mail] — please do not open public issues for vulnerabilities; coordinated disclosure with 48 h acknowledgement, fix-or-mitigation in 30 days for high-severity issues

License

Proprietary — all rights reserved. Commercial use requires a Pro or Enterprise license. The full license text ships inside the wheel as LICENSE; for procurement, see https://www.semvec.io.

Copyright © 2026 Michael Neuberger · Versino PsiOmega.