Chamber

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 judges the new text, and the result adds index is behind this file, because the index still holds the old copy.

In Claude Code, as a plugin. It asks for your notes folder and adds the server and a chamber-check skill:

/plugin install chamber --marketplace abm9111/chamber

On Claude Code before 2.1.275, run /plugin marketplace add abm9111/chamber first, then /plugin install chamber@chamber. The plugin takes one folder, as an absolute path or one that starts with ~/, and a comma-separated list of folders to skip (.obsidian,*sync-conflict*; a name cannot contain a comma). Change either with /plugin configure chamber@chamber. It runs the Chamber release its version pins, through a small launcher (plugin/launch.mjs) that starts npm's npx without a shell. A bare npx does not start on native Windows.

Claude Code does not update a third-party marketplace by itself. To get a newer pin, turn on auto-update (/plugin, the Marketplaces tab, chamber, Enable auto-update) or run claude plugin update chamber@chamber. If you also added the server by hand with claude mcp add, chamber_check is listed twice: keep the plugin's and run claude mcp remove chamber.

Or the server alone, in any MCP host:

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

{

"mcpServers": { "chamber": { "command": "npx", "args": ["-y", "@bu7umaid/chamber", "mcp", "--notes", "/absolute/path/to/Notes"] } } }

In Codex, the CLI, the IDE extension and the desktop app read one ~/.codex/config.toml. Add the server with the CLI:

codex mcp add chamber -- npx -y @bu7umaid/chamber mcp --notes /absolute/path/to/Notes

or by hand in that file. The first run downloads the package, which can take longer than the ten seconds Codex gives a server to start, so the table sets more:

[mcp_servers.chamber]

command = "npx" args = ["-y", "@bu7umaid/chamber", "mcp", "--notes", "/absolute/path/to/Notes"] startup_timeout_sec = 60

The format is from OpenAI's Codex MCP page: codex mcp add, the [mcp_servers. ] table with command and args, and startup_timeout_sec, which defaults to 10. Chamber has not been tested in Codex.

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. --exclude repeats after --notes. Config ingest roots and their excludes count too. Two other ways in:

From a checkout (Node 23.6+). TypeScript runs straight from the repo, with no build step. try builds a throwaway workspace, runs the real code paths and deletes it. The published package runs on Node 22 (measured 22.23.1, which prints Node's experimental-SQLite warning). Node 20.20.2 exits with ERR_UNKNOWN_BUILTIN_MODULE because node:sqlite is absent. Node 23.6 remains the floor for a checkout.

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 also reads config ingest roots when they are set. See config: ingest, chamber_ask, and the check.

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:

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.

Config: ingest, chamber_ask, and the check's config roots

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"] }] }

--exclude repeats after --notes; config ingest roots and their excludes also count as declared folders for the check, and an exclude that matches nothing refuses that folder. A root remembered only on an indexed row does not authorize readin