IHMT — Infinite Hierarchical Memory Tree

Long-term memory for your AI coding agents. Tell your agent something once — a decision, how your setup works, a correction — and it remembers it in every future session, in any project, with any of your agents.

What IHMT does

• Remembers across sessions. Decisions and their reasons, your environment, your preferences, people and projects, corrections. Your agent searches the memory before answering and saves what lasts, so you stop repeating yourself.
• One memory for all your agents and models. Claude Code, Codex and opencode can share the same memory: what one saves, the others find. Tested with models from Anthropic, OpenAI, Google and Meta.
• Saves tokens. Instead of pasting your notes or re-explaining context every session, the agent retrieves only what the question needs — typically 200–900 tokens, whether the memory holds 50 entries or 50,000, because search walks a tree instead of reading everything. Honest numbers, including where it does not save.
• Understands time. When something changes ("I moved to Valencia", "staging is on PostgreSQL 17 now"), the old memory is kept as history, flagged OUTDATED, and searches answer with the current one first. Where you live, where you work and your stack are tracked automatically; any other correction is linked when the agent saves it with replaces. When a question is ambiguous ("Luis" — which one?), it asks instead of guessing.
• Portable. Your memory is one folder of plain text files. Copy it to another computer, back it up, or put it under version control — it works wherever you put it.
• Local, private and readable. No cloud, no database, no account: IHMT stores everything on your disk and sends nothing anywhere. (The memories your agent retrieves reach its model like any other context.) Every memory is a text file you can open, and each person who installs IHMT starts with their own, empty memory.

Compatibility. Officially supported: Claude Code. Also tested: Codex (CLI and the ChatGPT desktop app — setup) and opencode (setup). IHMT is a standard stdio MCP server, so any agent that supports local MCP servers should work — GitHub Copilot, Antigravity, Cursor, Windsurf, Gemini CLI, Claude Desktop… — and INSTALL.md knows how to configure them, but we have not tested those yet. All of them can share one memory.

Install

Before you start

Missing Python or git? Your AI agent installs them for you (it is instructed to ask you first). Python goes in your user folder, with no administrator password, so nothing system-wide changes. On a brand-new Mac, git may need one click: Apple shows a window asking to install its command-line tools.

On a Mac, note that the python3 that comes with macOS is version 3.9, which is too old — that is why your agent may say Python is missing even though python3 exists.

You do not need administrator rights, a database, an account, or any paid service beyond your agent. Tested on macOS and Linux (Ubuntu); on Windows the instructions are included but not tested yet. Details: GUIDE.md §3.

Let your AI agent install it

Paste this into the AI agent you want to give a memory to — Claude Code, Codex and opencode are tested; GitHub Copilot, Antigravity, Cursor, Windsurf, Gemini CLI, Claude Desktop and other MCP clients should work too:

Install the IHMT memory MCP server for me from https://github.com/gonzaroman/IHMT-MEMORY — follow the instructions in its INSTALL.md.

The agent follows INSTALL.md: it downloads IHMT to ~/IHMT-MEMORY, keeps your memory in ~/.ihmt, registers the server with itself only, adds the usage instructions, and tells you what it did. Then start a new session so the memory tools load.

Using several agents? Paste the same prompt in each one, whenever you want. If IHMT is already installed — say you have used it with Claude for months and now want it in Codex — the agent finds that installation, updates it if it safely can, and connects to the same memory, so it knows what you told the others from day one.

It needs an agent that can run terminal commands or edit files; chat-only assistants in a browser cannot install anything.

git clone https://github.com/gonzaroman/IHMT-MEMORY.git ~/IHMT-MEMORY
cd ~/IHMT-MEMORY
python3 -m venv .venv
.venv/bin/pip install -r requirements-mcp.txt
mkdir -p ~/.ihmt

claude mcp add ihmt-memory -s user -e IHMT_HOME="$HOME/.ihmt" -- "$PWD/.venv/bin/python" "$PWD/mcp_server.py"
claude mcp list                     # ihmt-memory … ✔ Connected

claude mcp add ihmt-memory -s user -- uvx ihmt-memory
claude mcp list                     # ihmt-memory … ✔ Connected
uvx ihmt-memory --instructions >> ~/.claude/CLAUDE.md

New here? Read GUIDE.md — everyday use, step by step, with real outputs. The rest of this README is the technical reference.

How it works

A universal, domain-agnostic long-term memory for LLMs, stored as a recursive tree of plain files on the local disk. No vector database, no server, no third-party dependencies — Python 3.10+ and the standard library.

Instead of embedding everything into one flat index and scanning it, IHMT organizes knowledge into a tree: raw text leaves at the bottom, recursive JSON summaries above them, and a single root.json trunk at the top. A query walks that tree — root → branch → branch → leaf — so the number of files opened grows with the depth of the tree (≈ beam × log_B(n)), not with the amount stored.

Quick start

python3 gui.py                       # graphical interface: set up, browse, inspect
python3 init_ihmt.py                 # or from the terminal: create ./ihmt_memory
python3 main.py demo                 # full walkthrough in ./demo_workspace
python3 -m unittest discover -v      # stdlib only; MCP tests skip without the SDK

Then use it on your own material:

python3 main.py ingest ~/notes ~/project/src/Main.java
python3 main.py consolidate --force
python3 main.py search "how did we handle stock reservations"
python3 main.py ask "Luis"                    # interactive clue loop
python3 main.py conflicts                     # what changed over time

As a library:

from ihmt import IHMT

memory = IHMT.initialize("./workspace")
memory.ingest_file("examples/InventoryService.java")
memory.ingest_file("examples/journal_personal.txt")
memory.flush()                                # close the tree up to the root

answer = memory.search("reserveStock soft hold")
print(answer.best.content)                    # the leaf
print(answer.best.path)                       # ['root', 'N1-software.java-…', 'L-software.java-…']
print(answer.node_reads)                      # how many branch files were opened

for notice in memory.notices():
    print(notice)   # "On 2024-03-11 you said user location = 'Madrid', but on 2026-02-03 you updated to 'Valencia'."

Graphical interface

python3 gui.py                       # opens a browser at 127.0.0.1
python3 gui.py --path ~/my-memory --port 8765 --no-browser

Still zero dependencies — the server is http.server from the standard library, it listens only on the loopback interface, and every /api/* call needs the random token carried in the URL it opens.

Four screens: Set up (pick the memory folder with the system dialog, create the store, choose between per-project and global registration, preview the exact command or JSON before anything is written), Explore (collapsible tree down to the stored text, with supersession notices), Diagnose (a search that reports confidence, files opened vs. total, and the descent path), and Timeline (active vs. historical values and the detected contradictions). The interface is bilingual (ES/EN) and read-only over the memory: it never deletes or edits a leaf.

Use it from Claude Code (MCP)

mcp_server.py exposes the tree to Claude Code as nine tools in three families: long-term memory, project indexes and session scratch memory. The core stays dependency-free; the SDK is an optional extra:

python3 -m venv .venv
.venv/bin/pip install -r requirements-mcp.txt        # mcp[cli]>=2.0

For a single project, copy .mcp.json.example to that project's .mcp.json and fill in the absolute paths; Claude Code asks you to approve it on the next session there (claude mcp list shows it as Pending approval until then):

{
  "mcpServers": {
    "ihmt-memory": {
      "command": "/absolute/path/to/IHMT-MEMORY/.venv/bin/python",
      "args": ["/absolute/path/to/IHMT-MEMORY/mcp_server.py"],
      "env": { "IHMT_HOME": "/absolute/path/to/IHMT-MEMORY" }
    }
  }
}

or in one command:

claude mcp add ihmt-memory --scope user \
  -e IHMT_HOME=/absolute/path/to/IHMT-MEMORY \
  -- /absolute/path/to/IHMT-MEMORY/.venv/bin/python /absolute/path/to/IHMT-MEMORY/mcp_server.py

IHMT_HOME selects the store ($IHMT_HOME/ihmt_memory), created on first use. Point every project at one shared directory for a single cross-project memory, or give each project its own.

Saving tokens inside a session

Long-term memory saves tokens between sessions. The project tools save them within one, where the cost is reading the same files again and again. ProjectIndex (ihmt/project_index.py) keeps a private store per project under $IHMT_PROJECTS_DIR (default $IHMT_HOME/ihmt_projects):

• one leaf per symbol — code_chunk_mode="symbol", so a lookup returns a method, not a file;
• checksum sync on every call — size and mtime first, SHA-256 only for what moved; changed files are re-ingested, removed ones deleted, and the branches rebuilt. Code is never served stale;
• path-ordered branches — each file is stamped with its rank in path order, so every branch covers neighbouring files and its summary stays meaningful for the descent;
• code-aware ranking — the navigator filters by scope/path_prefix from the catalog, prefers the file a query names, demotes tests unless asked and demotes import lines.

Measured on a 55-file Spring Boot project (8 typical questions): reading the files that hold the answers costs 3,613 tokens; find_code returns the exact method for all 8 in 1,071. The map of the project costs 660 tokens against 13,157 to read it whole.

Those savings are against an agent that reads whole files. In an A/B test with 22 real headless Claude Code sessions, Claude preferred batched grep/sed -n and never called the project tools on its own; forcing them made sessions 42–71 % more expensive. Keeping the server enabled costs about 460 tokens per conversation, since Claude Code loads MCP tools on demand. IHMT's main value is memory between sessions; treat the project tools as optional, and do not mandate them in CLAUDE.md.

The server transparently supports MCP SDK 2.x (MCPServer), 1.x (FastMCP) and the standalone fastmcp package.

The usage instructions in your ~/.claude/CLAUDE.md (template) tell Claude Code when to reach for each tool: search before answering anything that depends on earlier sessions, save durable facts with their date, never guess on AMBIGUOUS, always relay OUTDATED, and never store secrets.

Storage layout

Everything lives in one relocatable directory:

ihmt_memory/
  root.json                 # the trunk: domains, topics, top branches, counters
  layer_0/<domain>/*.txt    # the leaves: raw UTF-8 text + a strict JSON header
  layers/1/*.json           # branches: summaries of leaves
  layers/2..N/*.json        # branches: summaries of summaries
  state/catalog.json        # index: id -> path, domain, parent, timestamp
  state/facts.json          # the fact timeline
  ihmt.config.json          # branch factor, token budgets, backend

root.json lives inside ihmt_memory/ so the store is self-contained: copy the directory and the memory travels with it.

A leaf is a normal text file that describes itself, so it stays meaningful even if the catalog is lost:

<<<IHMT-META
{
  "leaf_id": "L-software.java-0001-84130ee123",
  "timestamp": "2026-09-09T17:45:00Z",
  "data_type": "CODE",
  "domain": "software.java",
  "tags": ["method:reserveStock", "class:InventoryService", "lang:java", "type:code"],
  "parent_id": "N1-software.java-5571a7baac",
  "span": {"start_line": 43, "end_line": 68},
  "checksum": "sha256:…",
  "extra": {"context": "public final class InventoryService {"}
}
IHMT-META>>>
    public Optional<String> reserveStock(Sku sku, int quantity) {
        …

A branch node embeds each child's title, excerpt and keywords. That is the detail that makes the descent cheap: a branch can be ranked without opening any of its children.

The five components

1. UniversalIngestor — detect, split, enrich, store

DomainDetector classifies each document by type (CODE, NARRATIVE, CLINICAL, PERSONAL, PROCESS, GENERIC) and domain (software.java, medicine.clinical, process.cooking, personal, …) from its extension plus lexical signatures in English and Spanish. Both can be overridden with --domain / --type.

The type selects the splitter, and every splitter obeys one invariant:

A logical block is never cut. If a single block exceeds max_tokens it is stored whole and flagged oversized. Correctness of the block beats hitting the token budget.

• Code (chunkers/code.py) — Python via the stdlib ast; Java/JS/TS/C/C++/C#/Go/Rust/Kotlin/ Swift/PHP via BraceScanner, a character-level scanner that tracks brace depth while skipping comments, string literals, char literals, template literals and preprocessor lines. Imports coalesce; each class/function is a block; an oversized class splits per member, and the enclosing class header travels in the leaf's extra.context rather than being spliced into the text. Concatenating a file's leaves reproduces the file byte for byte — asserted in the tests.
• Narrative — paragraph-atomic, with ***, ---, Chapter/Capítulo as hard boundaries. Only a paragraph larger than max_tokens is split, and then at sentence boundaries.
• Temporal (journals, chats, clinical records) — one dated entry is atomic and a change of date is a hard boundary, so a leaf never mixes two encounters. The date found in the text becomes the leaf's timestamp, which is what makes recency weighting mean when something was true rather than when it was ingested.
• Process (recipes, protocols, runbooks) — steps and ingredient lists stay attached to their heading.

Leaf ids are derived from (domain, source, position, content), so re-ingesting an unchanged document rewrites the same leaves instead of duplicating them.

2. RecursiveSummarizer — the Summarization Event

It watches layer 0. When branch_factor leaves of one domain have no parent, it fires a Summarization Event: they are condensed into a layer-1 node, the node is written, and only then are the children stamped with their parent_id — so an interrupted run re-processes a group instead of orphaning it. The same rule applies from layer 1 to layer 2, and so on, until the tree converges; then root.json is rewritten.

consolidate() is idempotent. flush() (--force) also promotes partial groups so the tree closes completely. Anything still unconsolidated is referenced directly by the trunk, so nothing in the store is ever unreachable from the root.

3. SemanticNavigator — descent and the Interactive Clue Loop

Ranking uses Okapi BM25 over each candidate's title, keywords, tags and excerpt, with field weights and document frequencies computed across the siblings of the current level — exactly the discrimination the descent needs, at no extra I/O cost. The walk keeps a beam of beam_width branches per level.

Confidence blends two independent signals:

confidence = 0.6 × coverage + 0.4 × margin

Coverage asks "does this leaf actually contain what was asked?"; margin asks "is it distinguishable from its rivals?". A common first name scores high on the first and near zero on the second — which is precisely when the system must not guess:

$ python main.py ask "Luis"

"Luis" is ambiguous (3 memories match this query equally well, confidence 0.62).
It could belong to any of these branches:
  1. [personal] journal_personal.txt · 2024-07-22 — Vacaciones en Benidorm con Luis, mi primo…
  2. [personal] journal_personal.txt · 2026-08-30 — Fin de semana en la playa de El Saler con Luis…
  3. [personal] journal_personal.txt · 2024-11-30 — Cierre de trimestre… Luis Marín revisó el pull request…
Give me a clue to narrow it down (e.g. a place, a date, a project):
> vacaciones en Benidorm

query: "Luis + vacaciones en Benidorm" · confidence 0.74 · 5 node reads, 3 leaf reads, depth 2
  1. [personal] journal_personal.txt · 2024-07-22
     path  root → N2-personal-ea34db33ae → N1-personal-59bf8bc291 → L-personal-0002-a17b3c8f35

The clue triggers a joint cross-reference: candidates matching both term groups are boosted (×1.6), candidates matching only one are demoted (×0.7). The loop runs up to max_clue_rounds times, stops early if the user declines, and never silently converts an ambiguous query into a confident answer.

clue_provider is any callable, so the loop works for a human at a terminal (input) or for an agent that lets the LLM supply its own follow-up.

4. ConflictResolver — recency weighting and the timeline

Facts are (subject, attribute, value, timestamp, source_leaf), recorded programmatically via record_fact() or extracted at ingest time by pattern rules (vivo en X / I live in X, mi stack es Y, trabajo en Z, Diagnóstico:, Tratamiento:, Medicación: …; extend with add_pattern).

Each (subject, attribute) keeps a dated timeline. The newest value is ACTIVE; every earlier one becomes HISTORICAL with superseded_by and a valid_from/valid_to interval. Nothing is deleted, so both questions stay answerable:

memory.resolver.active_state()["user::location"].value      # 'Valencia'  (now)
memory.resolver.state_at("2024-12-31")["user::location"].value  # 'Madrid'  (back then)

Repeating a value at a later date is a confirmation, not a contradiction. A genuine change produces a transparent notice — "On 2024-03-11 you said user location = 'Madrid', but on 2026-02-03 you updated to 'Valencia'." — and the superseded leaf is annotated, so retrieving outdated material always arrives with its correction attached (SearchResult.notices).

A leaf itself stays ACTIVE: what it says was true on its own date, and that remains the right answer to a historical question. What changes is that it can no longer be read as current.

5. Summarization backends

class SummarizerBackend(Protocol):
    name: str
    def summarize(self, children, *, domain: str, layer: int) -> NodeSummary: ...

• HeuristicSummarizer (default) — stdlib extractive summarization: TF term ranking with EN/ES stop words plus representative-sentence selection. Offline, deterministic, which is what lets the test suite assert on tree shape.
• AnthropicSummarizer (optional) — used only when selected and the anthropic package and ANTHROPIC_API_KEY are both present. Every failure path (missing SDK, missing key, network error, unparseable reply) falls back to the heuristic backend, so a consolidation is never lost because a model was unreachable.

python3 init_ihmt.py --backend anthropic     # model set by summarizer_model in ihmt.config.json

Any other model or local runtime plugs in by implementing the same protocol and passing it as IHMT(..., backend=MyBackend()).

CLI reference

--path selects the store directory and --json emits machine-readable output; both work before or after the subcommand.

Configuration

ihmt_memory/ihmt.config.json:

Small corpora deserve a small branch factor — the demo uses branch_factor=4, target_tokens=400 so a handful of documents still builds a genuine multi-layer tree.

Tests

python3 -m unittest discover -v          # from the project root

187 tests — 25 of them for the MCP server, skipped without the SDK — covering: byte-exact reconstruction and boundary-depth invariants for Java and Python, scene/date/section atomicity, oversized-block handling, leaf header round-trips, catalog recovery, summarization thresholds, upward propagation, idempotence, full reachability from the root, descent cost bounds, the clue loop, recency weighting, historical preservation, the project indexes, the MCP tools, the graphical interface and the CLI.

Design notes and limits

• Retrieval is a descent, not a scan. That is the whole point, and it means a branch pruned at the trunk is not revisited. Domain-level pruning only happens when a query has actual signal at the trunk; if it has none, every domain stays in play and the beam applies one level down. The clue loop is the recovery mechanism when the descent goes wide.
• Lexical, not semantic. Matching is BM25 over accent-folded, CamelCase-split tokens: it works in any language and needs no model, but it will not match a synonym. Plugging an embedding re-ranker into BM25Ranker is the natural upgrade; the tree structure does not change.
• Token counts are estimated at ~4 characters per token. Budgets only need to be consistent, not exact.
• Fact extraction is pattern-based. The bundled rules cover common English/Spanish phrasings and clinical headers; record_fact() is the reliable path, and add_pattern() extends the rules.
• Single-writer. Writes are atomic (tmp + os.replace) and catalog rebuilds take a lock file, but the store assumes one writer at a time.
• initialize(force=True) discards derived state only — branches, catalog, timeline — and detaches the surviving leaves so the next consolidation rebuilds the hierarchy. Leaf content is never deleted.

Layout

ihmt/
  api.py                    IHMT facade wiring everything together
  config.py                 IHMTConfig
  models.py                 MemoryLeaf, BranchNode, ChildRef, RootIndex, Fact, Contradiction
  storage.py                MemoryStore: atomic I/O, catalog, recovery
  textutils.py              tokenizing, keywords, entities, extractive summary, timestamps
  detectors.py              DomainDetector
  chunkers/                 base · code · narrative · temporal · process · generic
  summarizers.py            SummarizerBackend · Heuristic · Anthropic
  universal_ingestor.py     UniversalIngestor
  recursive_summarizer.py   RecursiveSummarizer
  semantic_navigator.py     SemanticNavigator, BM25Ranker, ClueRequest, scope/path filters
  project_index.py          ProjectIndex: per-project code cache with checksum sync
  conflict_resolver.py      ConflictResolver + timeline manager
ihmt_gui/                   local graphical interface (stdlib only)
mcp_server.py               MCP server: the nine tools
ihmt_launcher.py            the `ihmt-memory` command of the PyPI package (~/.ihmt by default)
pyproject.toml · server.json   PyPI package · MCP Registry entry
init_ihmt.py · main.py · gui.py · examples/ · tests/
GUIDE.md                    installation and usage guide
INSTALL.md                  installation instructions for AI agents
templates/                  memory-instructions.md: the usage rules agents append to CLAUDE.md / AGENTS.md

License

MIT © 2026 Gonzalo Román Márquez (gonzaroman)