gigi-episodes

Change-point detection for time series. The "when did this break?" tool, as a portable Python library + CLI.

from gigi_episodes import find_changepoints

# Your latency over the last 1000 requests
latencies = [50.1, 49.8, 51.2, ..., 95.1, 96.3, 94.8, ...]

result = find_changepoints(latencies)
print(result.indices)   # [573]  — latency drift started around request 573
print(result.count)     # 1

$ gigi-episodes detect production.csv --column latency_p99
  source:      production.csv
  column:      latency_p99
  backend:     local
  threshold:   3.0
  min_segment: 10
  n_points:    1000
  changepoints: 1

  index    score   mean_before → mean_after
  -----    -----   ---------------------------
    573    12.83     50.247  →   95.103

What it's for

Anywhere you have a sequence of values and want to know when it changed:

• Ops — when did latency start drifting? When did error rate spike?
• Test flakiness — when did this test suite start failing?
• User behavior — when did retention break in this cohort?
• ML monitoring — when did model accuracy drop?
• Sensor data — when did the reading shift to a new regime?

gigi-episodes is intentionally narrow: change-point detection in 1-D value sequences, nothing else. Other "EPISODIC" features (multivariate, anisotropic, fiber-bundle native) live in the GIGI engine — gigi-episodes exposes one specific brain primitive as the smallest possible installable tool.

Install

pip install gigi-episodes

Optional: install with the GIGI backend (requires requests):

pip install "gigi-episodes[gigi]"

Quick start

from gigi_episodes import find_changepoints

values = [1, 1, 1, 1, 1, 1, 5, 5, 5, 5, 5, 5, 1, 1, 1, 1, 1, 1]
result = find_changepoints(values)

for cp in result.change_points:
    print(f"index {cp.index}: {cp.mean_before:.2f} → {cp.mean_after:.2f} (score {cp.score:.1f})")

# index 6: 1.00 → 5.00 (score 11.7)
# index 12: 5.00 → 1.00 (score 11.7)

CLI

# Detect in a CSV column
gigi-episodes detect data.csv --column latency_ms

# JSON output for piping into other tools
gigi-episodes detect data.csv --column latency_ms --json

# Tune sensitivity
gigi-episodes detect data.csv --column latency_ms --threshold 4.0 --min-segment 30

# Read from stdin
cat values.txt | gigi-episodes detect - --column 0

Tuning

Defaults are calibrated for clean operational data (latencies, counts, scores). For very noisy data, raise the threshold to 4.0 or 5.0. For long sequences with slow regime shifts, increase min_segment to 30+.

Two backends

LocalBackend (default) — pure numpy. No external services. Use this 99% of the time.

from gigi_episodes import LocalBackend, find_changepoints

result = find_changepoints(values, backend=LocalBackend())

GigiBackend — calls a running GIGI instance's /brain/episodic endpoint for higher-fidelity detection on multivariate or anisotropic data. Useful when you have data already in GIGI bundles and want the engine's full Kähler-aware Welford fit including L13.3 diagonal-Gaussian and L13.7 denominator-floor stability.

from gigi_episodes import GigiBackend, find_changepoints

backend = GigiBackend(
    url="http://localhost:3142",
    api_key="dev-local",
    bundle="latency_metrics",
    field="p99_ms",
)
result = find_changepoints(backend=backend)

The algorithm

gigi-episodes's local backend uses a windowed two-sample mean-difference test with global-scale floor:

1. For each candidate split point i, compute the mean of the segment so far (from the last change-point up to i) and the mean of the next window points.
2. Compute the standard error of the difference: SE = sqrt(var_before/n_before + var_after/n_after).
3. If |mean_after - mean_before| / SE > threshold, it's a change-point.
4. Both variances are floored by a global MAD-based sigma estimate, so locally-tiny variance (from short or smooth segments) can't blow up the test statistic.

This is the 1-D specialization of GIGI's /brain/episodic endpoint — one of twelve brain primitives unified by the Friston master equation on a Kähler bundle. gigi-episodes makes this single primitive portable; the eleven others live in GIGI.

License

MIT. Free for any use, commercial or otherwise. See LICENSE.

Related

• GIGI — the fiber-bundle database engine; gigi-episodes's GigiBackend calls it. EPISODIC is one of twelve brain primitives.
• DreamData — synthetic-data CLI using GIGI's DREAM primitive. Sibling project.
• gigi-mind — VS Code extension exposing all twelve brain primitives. Sibling project.

Status

v0.1.0 — stable for the documented surface (1-D LocalBackend + CLI + GigiBackend skeleton). API may evolve in 0.x; will stabilize at 1.0.