Kairos

An astrology decision-support tool that gives you an honest answer, not a horoscope.

Ask a real decision or timing question, like "Will I get the job?", "Is now the right time to switch?", or "Will this come to fruition?". Kairos computes an astronomically accurate chart with the Swiss Ephemeris, then returns a calibrated verdict:

• a clear lean (favorable / unfavorable / uncertain),
• a confidence level (low / medium / high) tied to the actual weight of evidence,
• the specific classical signals behind it (the real testimonies, scored), and
• falsifiable caveats, including, up front, the outcome that would prove the read wrong.

Astrology is treated as one honest input, not destiny. No vague flattery, no unfalsifiable retrofits, no fake metrics. Just a lean you can act on and check against what actually happens.

For: anyone weighing a real choice who wants a structured, classical second opinion they can interrogate, and Claude Code users who want that opinion as a skill.

Install (Claude Code plugin):

/plugin marketplace add stardustxx/kairos
/plugin install kairos@stardustxx

See a real round-trip, question in and two-layer verdict out, in the worked example (a "Will I get the job?" horary that the engine scores favorable, medium confidence, +38).

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Kairos is available as:

• A Claude Code plugin (includes both the skill and the MCP server)
• A standalone MCP server (npx -y kairos-astrology mcp)
• A CLI tool (kairos compute, kairos memory, kairos geocode)
• A Docker image (fallback for Intel Mac, musl, and unprebuilt ABIs)

How it works

• engine/ is a TypeScript CLI that computes planetary positions, houses, aspects, and horary significators. Pure math, fully tested.
• .claude-plugin/ is a Claude Code plugin that bundles the MCP server and the skill. Install via Claude Code's plugin marketplace.
• skills/kairos/SKILL.md is the Claude Skill (bundled in the plugin): it classifies the question, calls the MCP tools, and interprets the result. Pure judgment, no math.

A 30-second example

Ask "Will I get the job?" in London on 8 June 2026 at 11:15. The 10th house signifies the job, so:

pnpm -s compute '{"kind":"horary","quesitedHouse":10,"moment":{"datetimeLocal":"2026-06-08T11:15:00","latitude":51.5074,"longitude":-0.1278,"timezone":"Europe/London"}}'

The engine returns the chart plus a scored verdict. The decisive part:

{
  "lean": "favorable",
  "confidence": "medium",
  "score": 38,
  "testimonies": [
    "No direct aspect between the significators (0)",
    "Moon (co-significator of querent) applies by trine to the quesited (+20)",
    "Translation of light by Moon (Mercury → Venus) (+18)"
  ]
}

The skill turns that into a two-layer answer. Layer 1 is the plain read; Layer 2 is the optional mechanics:

Leans yes, moderate confidence. The job is reachable, but it comes to you sideways rather than landing cleanly in your lap. Most likely: it comes through with help from a third party, such as a referral, a recruiter, or an introduction. What would prove this wrong: a flat, early "no" with no intermediary involved.

The chart detail, if you want it: you (the querent) are Mercury in Cancer 10.6° (dignity +1); the job is Venus in Cancer 24.1° (dignity +3). There is no direct aspect, but the Moon translates light from Mercury to Venus by trine (+18) and applies to Venus by trine (+20). That's the third party carrying it through. With no prohibition and the Moon not void, an outright "no" is the least likely outcome. Engine score +38.

Every number above comes from a real run. The full worked example walks through the complete two-layer reading; the same chart is also viewable in the web UI (web/index.html → Load Example).

More worked examples

The example gallery has five complete, reproducible round-trips. Each one includes the question, the exact command, the verbatim JSON verdict, and a two-layer reading built only from the real numbers:

Example	Kind	Real verdict
Career horary: "Will I get the job?"	horary (10th)	favorable / medium / +38
Relationship horary: "Will we get back together?"	horary (7th)	unfavorable / medium / −35
Relocation transit: born Seoul, living NYC	transit + relocation	11 placements change house; lord of year Mars
Electional window: "When should I launch?"	electional (10th)	117 moments, best +155
Money horary: "Will the money come through?"	horary (2nd)	favorable / medium / +35

These were not cherry-picked to all say yes; example 2 is an honest no. Every file ends with a copy-paste command, and since the Swiss Ephemeris is deterministic, you get the same chart and the same verdict.

Not sure what to ask? Sample questions has ready-to-use openers for every chart kind, including turned-chart questions about other people.

Calibration contract: Kairos keeps score

Here is the thing no generic astrology tool will do: keep score against itself.

Every directional verdict Kairos produces is falsifiable, and the tool is built to log it, remember it, and grade itself later:

1. Log on compute. Pass a journal field (or use the skill) and the engine records the question alongside the verdict it actually returned (kind, lean, confidence, score), captured from the engine itself so the track record can't drift from a hand-copied number. When the chart has a perfection date, it's stored as the expected-resolution date ("ask me later").
2. Resolve when ripe. kairos memory due surfaces the logged readings whose expected-resolution date has arrived. You tell it what happened: kairos memory outcome <id> happened (or did-not-happen / partial / unknown).
3. Read the scorecard. kairos memory calibration reports your hit-rate by confidence band. Does "high confidence" actually win more often than "low"?

The honest part: today that scorecard is empty. With no outcomes recorded yet, the real report is exactly this (verbatim):

// kairos memory calibration  (on a fresh install)
{
  "bands": [
    { "confidence": "low",    "resolved": 0, "correct": 0, "hitRate": null },
    { "confidence": "medium", "resolved": 0, "correct": 0, "hitRate": null },
    { "confidence": "high",   "resolved": 0, "correct": 0, "hitRate": null }
  ],
  "overall": { "resolved": 0, "correct": 0, "hitRate": null },
  "note": "Small samples are noisy — this is a personal pattern, not proof."
}

The --card view prints it plainly: "No resolved outcomes yet — here is how the track record grows." Kairos does not ship a fake hit-rate, and it does not claim its astrology is proven. It claims something narrower and more useful: it is the astrology tool that states a falsifiable verdict, remembers it, and will show you its own batting average as your outcomes accumulate, by confidence band, with the sample size always in view, and the standing caveat that a small personal sample is a pattern, not proof.

That reframes Kairos from "another ephemeris wrapper" to the one that keeps score.

Install

Primary: Claude Code Plugin

The easiest way to use Kairos in Claude Code:

/plugin marketplace add stardustxx/kairos
/plugin install kairos@stardustxx

This installs both the skill and the MCP server. The skill is automatically available as /kairos:kairos.

Alternative: Register the MCP Server Directly

If you already have Claude Code set up and want to just use the MCP tools without the full plugin:

# Start the server standalone
npx -y kairos-astrology mcp

# Or use the bundled MCP server via Claude Code's MCP configuration

The server prints a one-line ready notice to stderr and then nothing more, because stdout is reserved for the MCP protocol. An otherwise quiet terminal is success: point an MCP client at it and it is ready to accept tool calls.

Note: the raw MCP tools expose the ephemeris and verdict engine. The Claude Code plugin's skill layer adds the judgment discipline: question classification, the house-mapping table, two-layer output, falsifiability lines, and journal-by-default. If you are using the MCP server without the plugin, you are getting the engine without that calibration harness.

Alternative: skills CLI

If you manage agent skills with the skills CLI, it finds the Kairos skill in this repo, but you need BOTH commands. The skill is only the judgment layer; it calls MCP tools (compute, geocode, memory_*) that come from the engine, so installing the skill alone leaves it pointing at tools that do not exist:

npx skills add stardustxx/kairos                       # the skill (add -g for user-level)
claude mcp add kairos -- npx -y kairos-astrology mcp   # required: the engine it calls

Together these are equivalent to the plugin install above, which does both in one step.

Alternative: CLI Tool

For direct command-line access:

# Install globally
npm install -g kairos-astrology

# Or use npx without installation
npx -y kairos-astrology compute '{"kind":"horary","quesitedHouse":10,"moment":{"datetimeLocal":"2026-06-08T14:30:00","latitude":40.7128,"longitude":-74.0060}}'

# Geocode a location
npx -y kairos-astrology geocode 'Tokyo'

# Check past readings
npx -y kairos-astrology memory due

# Set birth profile
npx -y kairos-astrology memory profile set '{"birth":{"datetimeLocal":"1990-03-12T07:45:00","latitude":37.57,"longitude":126.98,"timezone":"Asia/Seoul","place":"Seoul"}}'

Cold install and the Intel-Mac caveat (read before npx)

Kairos's only native dependency is sweph (the Swiss Ephemeris bindings). It ships prebuilt binaries for:

Platform	Cold npx / install
macOS Apple Silicon (darwin-arm64)	prebuilt, installs with no compiler
Linux x64 / arm64 (glibc)	prebuilt, installs with no compiler
Windows x64 (win32-x64)	prebuilt, installs with no compiler
Intel macOS (darwin-x64)	no prebuild, compiles from source on first install
Alpine / musl Linux	no prebuild, compiles from source

On Intel macOS (and musl Linux), the first npx -y kairos-astrology … or npm install will compile sweph from source, which requires the Xcode Command Line Tools (xcode-select --install) on Mac, or build-base + python3 on Alpine. This is a one-time cost; once built, subsequent runs are fast. If the required toolchain is absent, the CLI and MCP server now fail with an actionable message naming the exact install command (xcode-select --install on Mac, apk add build-base python3 on Alpine, or the Docker fallback) rather than emitting an opaque node-gyp stack trace.

You do not need any ephemeris data files for this. Kairos defaults to Swiss Ephemeris Moshier mode, which computes positions analytically (sub-arcsecond for the modern era) with no .se1 downloads. The compile is only for the native addon, not for data.

If you can't (or don't want to) compile, the Docker image is the zero-build fallback. It bundles a working sweph for every platform:

docker build -t kairos:latest .
docker run --rm -i kairos:latest mcp     # stdio MCP server, forward to Claude Code
docker run --rm -i kairos:latest compute '{"kind":"horary","quesitedHouse":10,"moment":{"datetimeLocal":"2026-06-08T11:15:00","latitude":51.5074,"longitude":-0.1278,"timezone":"Europe/London"}}'

Development: Build from Source

git clone https://github.com/stardustxx/kairos.git
cd kairos
pnpm install
pnpm test                       # run the engine test suite

Try the engine directly

pnpm compute '{"kind":"horary","quesitedHouse":10,"moment":{"datetimeLocal":"2026-06-08T09:00:00","latitude":40.7128,"longitude":-74.006,"timezone":"America/New_York"}}'

Geocode a place (offline)

pnpm geocode:install            # one-time: download the GeoNames cities15000 set
pnpm -s geocode 'Tokyo'         # → [{ name, country, latitude, longitude, timezone, ... }]

When using the MCP server, the geocode_install MCP tool handles the one-time city-database download interactively with user consent, no shell command required.

Render a chart wheel

pnpm wheel '{"kind":"horary","quesitedHouse":10,"moment":{"datetimeLocal":"2026-06-08T09:00:00","latitude":40.7128,"longitude":-74.006,"timezone":"America/New_York"}}'

The UI also runs standalone: open web/index.html and paste any pnpm compute JSON (or click Load Example). See web/README.md.

Compute in the browser (no server)

The web app can also compute charts entirely in your browser. The same engine code runs against a WebAssembly build of the Swiss Ephemeris (swisseph-wasm, GPL-3.0-or-later), in the same Moshier mode as the Node default. A parity test pins the two backends to within 1e-6° and to identical horary verdicts. Everything stays in-page: no server, no telemetry, no data leaves the machine (the "use my location" button uses the browser's own geolocation API, locally).

From a clone, build the browser bundle once, then serve web/:

pnpm build:web                   # esbuild → web/engine.js + swisseph.{wasm,data}
python3 -m http.server -d web    # any static server; file:// can't load wasm modules

Fill in the compute form (kind, optional question, date/time, lat/lon, the matter's house) and the verdict panel + wheel render through the same path as pasted JSON. The npm tarball ships web/engine.js, web/swisseph.wasm, and web/swisseph.data prebuilt; in a git clone they are gitignored, so run pnpm build:web yourself. The in-browser mode covers horary and natal charts; journal/memory and the offline geocoder remain Node-only (enter lat/lon manually, or look them up with pnpm geocode).

Start the MCP server locally

pnpm mcp

Memory

Kairos keeps a small local memory so it can remember you and learn from its own track record:

• Profile stores your birth data (for transits/natal) and home/relocation location
• Multiple people: keep separate profiles per person you cast for (yourself, a partner, a friend)
• Journal: every verdict (question, kind, lean, confidence, score) is recorded
• Outcomes and calibration: record what actually happened and see hit-rate by confidence band

All memory is stored locally under ~/.kairos (one profiles/<slug>/ directory per person, plus a pooled journal.jsonl) and is never synced. Everyone's birth data and your reading history stay on this machine.

Conventions

• Western tropical zodiac.

• Houses: Placidus for natal/transit, Regiomontanus for horary

• Computation: Swiss Ephemeris Moshier mode by default. No data files, sub-arcsecond accuracy for the modern era. Opt into full SWIEPH precision:

  pnpm ephe:install            # download full .se1 data files
  

Distribution & Publishing

Kairos publishes to npm as kairos-astrology. The package ships:

• The compiled engine (dist/)
• The Claude skill and the plugin manifests (skills/, .claude-plugin/)
• The web UI (web/, minus the local last-result.json artifact)
• LICENSE, NOTICE, README.md, and the docs they link

Note: this package sets devEngines.packageManager: pnpm, so npm publish / npm pack are blocked with EBADDEVENGINES. Publish with pnpm (which the repo uses anyway). pnpm pack --dry prints the exact tarball contents.

Maintainer publish checklist

v1.1.0 is published: kairos-astrology on npm, the v1.1.0 tag is cut (release-check green on macOS, Linux, and Windows), and the MCP server is registered as io.github.stardustxx/kairos in the official MCP registry. The checklist below is the repeatable sequence for the next release; bump the versions first.

# 1. Verify green
pnpm install
pnpm lint && pnpm typecheck && pnpm test         # all must pass (321 tests today)

# 2. Build the publishable artifacts
pnpm build                                        # tsc -> dist/ (also runs as prepublishOnly)

# 3. Inspect what will ship (no last-result.json; dist + skills + .claude-plugin + web)
pnpm pack --dry

# 4. Confirm version is 1.1.0 everywhere it must match
grep -R '"version": "1.1.0"' package.json .claude-plugin/*.json

# 5. Publish (pnpm, not npm; see devEngines note above)
pnpm publish --access public                      # first publish of a public scoped/unscoped pkg

# 6. Prove the registry cold path from a scratch dir
cd "$(mktemp -d)"
npx -y [email protected] compute '{"kind":"horary","quesitedHouse":10,"moment":{"datetimeLocal":"2026-06-08T11:15:00","latitude":51.5074,"longitude":-0.1278,"timezone":"Europe/London"}}'
# expect: lean "favorable", score 38, confidence "medium"
# on Intel macOS this first run compiles sweph from source (needs Xcode CLT); see "Cold install" above

Follow-ups for each release: push the version tag (fires the release-check CI, a three-OS cold-install of the packed tarball) and re-publish server.json to the MCP registry with mcp-publisher publish (login via GitHub device flow).

License

Kairos is licensed under the GNU Affero General Public License v3.0 or later (AGPL-3.0-or-later). See LICENSE for details.

This means:

• You can use, modify, and distribute Kairos freely
• If you modify it and distribute the modified version, you must make your modifications available under the same license
• If you run a modified version as a service (including as part of Claude Code), you must offer the source code to users

See NOTICE for additional attribution.

Testing

pnpm test                       # run the engine test suite
pnpm typecheck                  # check TypeScript types
pnpm lint                       # lint the engine code

All 321 tests pass on the current build (37 files).

Technical Details

• Engine language: TypeScript
• MCP SDK: @modelcontextprotocol/sdk (Node.js)
• Native dependency: sweph (Swiss Ephemeris bindings; includes prebuilds for darwin-arm64, linux-x64, linux-arm64, win32-x64; Intel Mac and musl fall back to Docker or source compile)
• Data storage: ~/.kairos (profiles, journal, geocoder gazetteer)