---
id: AGENTIC-WP-0009
type: workplan
title: "Coding Session Memory — Phase 4 (Measure: effectiveness + fleet trend)"
domain: helix_forge
repo: agentic-resources
status: finished
owner: codex
topic_slug: helix-forge
created: "2026-06-07"
updated: "2026-06-07"
state_hub_workstream_id: "99f1d836-3be0-40e5-9f17-63d3ecc5fcca"
---

# Coding Session Memory — Phase 4 (Measure)

Implements **Measure** (PRD §6.5, FR-M1–FR-M3) — the loop-closer. After patterns
are distributed (Phase 3) and changes land (e.g. the State Hub skill
[STATE-WP-0058] and the Read-before-Edit reflex
[AGENTIC-WP-0008](AGENTIC-WP-0008-read-before-edit-reflex.md)), Measure answers:
**did it actually help?**

Reuses what is already captured — WP-0005 tool buckets, WP-0006 error mining — so
this is computation over existing digests, not new capture.

## Baseline Metrics Module + Persisted Baseline

```task
id: AGENTIC-WP-0009-T01
status: done
priority: high
state_hub_task_id: "e5c2016a-2d51-4382-a013-7153e053e8ed"
```

`session_memory/measure/metrics.py`: compute fleet metrics over real sessions
(infra-overhead share, error rate, recurring-error count, schema-thrash, cost
percentiles) and persist a **timestamped baseline snapshot**. Reuses
`detect.signals.tool_bucket` and the digest `error_snippets`. Unit-tested.

## Before/After Per-Pattern Effectiveness

```task
id: AGENTIC-WP-0009-T02
status: done
priority: high
state_hub_task_id: "aa097a00-3462-41da-a137-67e1d61d8d33"
```

Given a change/pattern with an applied-at date, compare sessions **after** it
against the pre-change baseline (cost, error rate, infra-overhead, success) to
surface **per-pattern effectiveness** so ineffective patterns can be revised or
retired (FR-M1/FR-M2). Unit-tested.

## Fleet-Trend Report + Entrypoint + Tests

```task
id: AGENTIC-WP-0009-T03
status: done
priority: medium
state_hub_task_id: "f1147d59-2fb7-4d35-baec-b8f001bb9d62"
```

`python -m session_memory.measure`: fleet-level trend (is the median session
getting cheaper / more reliable over time, FR-M3) plus per-pattern effectiveness;
markdown + JSON. Document in `session_memory/README.md`. After updates, notify the
operator to run `make fix-consistency REPO=agentic-resources`.

[STATE-WP-0058]: handed off to the state-hub repo worker