Chamber

Catches your AI agent quoting a number or a name that isn't in the note it cites. When Claude Code (or any MCP host) answers from your notes, it is told to run each claim through chamber_check first. Real output, trimmed:

2 claim(s): 1 supported · 1 terms absent · 0 nothing to check · 0 not judged

[TERMS_ABSENT] Q3 revenue was $420k, up 18% on Q2.
     the cited text does not contain: 420k
     checked: q3-review.md#p0
[SUPPORTED] Enterprise renewals moved to Dana Ortiz in August.
     every term Chamber recognises occurs in the cited text
     checked: q3-review.md#p0

The note says $240k. The agent wrote $420k. Edit the note afterwards and the same check returns STALE instead of a verdict, because what it is checking against has changed.

claude mcp add -s user chamber -- npx -y @bu7umaid/chamber mcp

No model, no account, no network: the check is deterministic string matching over node:sqlite and files on your disk. It checks numbers, capitalised names, domains, file names and counts. It does not check meaning, so a negated or reversed sentence built from the note's own words still passes. See what a verified citation does and does not prove.

Beyond the check: answers that cite their sources, and a daily job that tells you when a source changed underneath a conclusion you already trusted.

Run the check

The npx line above is all most people need. Two other ways in:

From a checkout (Node 23.6+). TypeScript runs straight from the repo, with no build step, config, model or network. try builds a throwaway workspace, runs the real code paths and deletes it.

git clone https://github.com/abm9111/chamber.git && cd chamber && npm ci && node --experimental-strip-types src/cli.ts try

If /mcp does not list chamber_check, the host started the server with a minimal PATH. Take the interpreter from command -v node in your own shell and point it at the published bin or at a checkout's src/mcp_server.ts. Those are different files:

# published bin: bin/chamber.js loads dist/. This is not src/mcp_server.ts.
claude mcp add -s user chamber -- "$(command -v node)" /path/to/node_modules/@bu7umaid/chamber/bin/chamber.js mcp

# checkout only. src/mcp_server.ts is not in the npm install.
claude mcp add -s user chamber -- "$(command -v node)" --experimental-strip-types /path/to/chamber/src/mcp_server.ts

Ingest and chamber_ask need config; the check does not. See for ingest and chamber_ask.

What people actually do

There is no public trail of Chamber users yet. These are the adjacent failures on X, which are the reason the check exists.

• Pointing Claude Code at an Obsidian folder reads files. It does not check the sentence. Richard Kovacs, 28 Sep 2026: Claude returns a list of sources and he checks them. The remaining failure he names is confirmation bias, and he treats that as discipline.
• A tool the agent must remember to call is not a gate. Saksham Arora, 2 Oct 2026: a shared-memory MCP only recalled a session if the other agent decided to search, so he put a hook before every message. chamber_check is the same shape. MCP instructions ask Claude to call it. Nothing blocks the turn if it skips. A Stop hook that requires a receipt is the missing piece; it is not in this repo yet.
• Viral vault posts (99.7% recall, thousands of links in minutes) are not measurements. The number in this repo is the 200-claim set in docs/KNOWN_LIMITATIONS.md §2: invented values mostly caught, negations not.

See it in two minutes

The checkout command above builds a throwaway workspace, runs the real code paths against it, and deletes it (--keep to look around). It does not open a database.

That recording is scripted from assets/demo.tape rather than hand-captured, so it is regenerated when the output changes instead of quietly showing a version of Chamber that no longer exists. Everything below is that checkout command's actual output, trimmed:

$ chamber believe belief "Customers may return any purchase within 30 days of delivery."
  committed blf_ddcf4f3c9b2e81b8
  an unsourced assertion is not refused — it mints citation debt.

$ chamber debts
  dbt_18bd1c1171cdbfcb  [pending]

$ chamber pay-debt
  proposed 2 source(s), 2 pinned; best=0.694

$ chamber verify
  blf_ddcf4f3c9b2e81b8  2/2 pins verified

That is the ordinary state: a belief standing on evidence that still holds. Then someone edits the note it was built on — 30 days becomes 14 days:

$ chamber ingest ./notes
  ingested 2 file(s) as 4 passage(s)

$ chamber verify
  blf_ddcf4f3c9b2e81b8  1/2 pins verified
    hash_mismatch: refunds.md#p0

Nobody asked it to re-examine that belief. The conclusion did not change; the ground under it did, and the exit code is non-zero, so a scheduled job can act on it. That is the whole product.

Four more scenarios — a rolled-back ledger caught by an outside anchor, a sandbox that refuses rather than degrade, a hostile tool catalogue rejected — are in demos/, and run in CI so they cannot drift from the code.

A dictionary for the words above

Everything Chamber does is rows in one SQLite file. Each term in the transcripts names a table or a hash:

| Word | What it actually is | |------|---------------------| | passage | one chunk of one markdown file. refunds.md#p0 is file path + chunk index. | | belief | a row in belief: one asserted sentence, linked to the passages it stands on. | | pin | a sha-256 of a cited passage's stored title, body and ref, taken at the moment of citation and kept in belief_source. | | verify | re-read every pinned passage, recompute the hash, compare. Any mismatch exits non-zero. No model involved. | | citation debt | a row in citation_debt, created when an assertion commits with no source. The same claim cannot commit again until the debt is paid. | | pay-debt | retrieval proposes passages for the indebted claim; accepting them pins them. | | APORIA | the verdict when no retrieved passage supports an answer. The reply is "I don't know", recorded as that. | | gate | a check and a write inside one SQLite transaction — both commit or neither does. | | audit log | append-only audit_event; each row's hash covers the previous row's hash, so editing history breaks every hash after it. | | anchor | the log's root hash stored outside the database, so truncating the log is detectable rather than silent. | | the scheduler | a launchd/systemd job running ingest + verify, notifying only on drift. |

None of it is hidden machinery: sqlite3 ~/.local/share/chamber/chamber.sqlite '.tables' shows the whole thing.

Answers that cite their sources

With a model configured, chamber ask judges every sentence on its own citations. Against the same two sample notes, on a local 30B:

$ chamber ask "summarise our refund policy"

Customers may return any purchase within 30 days of delivery [2]. Refunds
are issued to the original payment method, usually within five working days
of the returned item arriving at the warehouse [2]. However, perishable goods
and personalised items cannot be returned once dispatched [1].

  [ALLOWED] Customers may return any purchase within 30 days of delivery [2]. Refu
     sources: refunds.md#p0 — refunds › Refund policy, refunds.md#p1 — refunds › Refund policy › Exceptions

The model is shown [1]…[k] and never a document id or a hash, so it cannot fabricate a citation even in principle — the numbers are resolved back to files after the answer is written. A sentence that cites nothing is marked UNSUPPORTED: recorded, but not treated as load-bearing. A sentence whose numbers, names or domains are not in the passage it cites loses that citation too, and says which terms were missing (terms_absent) — a real passage is not evidence for a claim it does not contain. Headings in an answer print as [HEADING] and are not recorded.

Asking something the corpus cannot answer is the more important case:

$ chamber ask "what should a customer do if they want to return a perishable
               item after the office has closed?"

I don't know

  [APORIA] I don't know

Both notes are in the index and both are relevant. Neither answers the question, so nothing is composed from the pieces.

For ingest and chamber_ask, not for the check

npm link                 # puts `chamber` on your PATH
chamber init             # writes ~/.config/chamber/config.json

Then edit that config to add a notes folder and a model:

{
  "database": "~/.local/share/chamber/chamber.sqlite",
  "model": { "base": "http://127.0.0.1:8087/v1", "name": "your-model", "mode": "openai" },
  "ingest": [{ "root": "~/Notes", "exclude": ["transcripts", "attachments"] }]
}

model.base may name any OpenAI-compatible endpoint. A loopback address needs no API key; anything else reads CHAMBER_API_KEY from the environment, never from the file.

chamber ingest           # index every configured root
chamber ask "..."        # ask, with citations
chamber verify           # re-check stored pins against the corpus
chamber corpus           # what is actually in the index

Set your excludes before the first ingest. There is no default exclude list. Pointed at a folder of exported chat logs, Chamber will happily index all of them and answer from them — see chamber corpus and docs/KNOWN_LIMITATIONS.md entry 11. If the root is an Obsidian vault, exclude .obsidian, .trash, and *sync-conflict* before that first ingest. A symlinked folder is indexed under the link path and comes back STALE under the real path.

Use it as a CI drift gate

The same verify loop works on a repo: claims in docs pinned to passages of code or policy, chamber verify --json failing the build when the ground moves. One line in a workflow — this repo ships the action:

- uses: abm9111/chamber@v0.1.9

docs/CI_DRIFT_GATE.md is the one-page recipe; demos/06_ci_drift_gate.ts is the runnable transcript.

Run it daily

deploy/launchd/com.chamber.verify.plist (macOS) and deploy/systemd/ (Linux) run ingest and verify on a schedule, and raise a notification only when something drifted. A check that correctly reports nothing on most days is a check you stop reading, so it stays quiet until it isn't.

Render it in Obsidian

The companion plugin Chamber Drift renders verify --json's report as a vault sidebar panel and a per-note banner — nothing more. It never verifies and never writes; Chamber does both, on its own schedule, outside Obsidian. Setup, including the report-writing one-liner and the Obsidian Sync caveat: docs/OBSIDIAN.md.

Use it from an AI coding agent

An agent that reads your vault with its own tools can check what it is about to tell you. chamber_check takes the agent's claims and the notes it says they came from, and answers per claim (abridged):

[SUPPORTED] One NVIDIA A100 80GB or an L40S can serve about 1,000 users for code completion.
     found in: ai-coding-setups-march-2026.md#p25
[TERMS_ABSENT] One NVIDIA A100 80GB can serve about 2,000 users for code completion.
     the cited text does not contain: 2000

The check uses no model. It confirms the note is indexed, and unchanged on disk since it was indexed (STALE otherwise: the agent read one text and the index holds another, so neither verdict woul