docs(experiments): add full capacity discovery (5→50 sessions) and CI churn results
Complete scaling curve measured: 50 sessions uses only ~28% of GraphQL budget with 100% ETag guard hit rate at every scale. Poll cycle lag identified as first bottleneck (66s at 50 sessions vs 30s target). CI churn benchmark shows ETag invalidation is a latency problem, not a rate-limit problem (+9% GraphQL, +4.4x p50 latency). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Dhruv Sharma
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@ -176,17 +176,87 @@ Scaling is slightly super-linear for GraphQL (2.46x for 2x sessions). Guard chec
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**Scorecard:** `experiments/out/scorecard-quiet-steady.single-repo.20-1776424159.json`
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**Trace:** `experiments/out/gh-trace-bench-1776423135.jsonl`
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### Key Finding: Sub-Linear Scaling
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### 30-Session Benchmark (2026-04-17, B1 fix applied)
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GraphQL cost barely increased from 10→20 sessions (640→680, +6%). The guard-pr-list check is repo-scoped (constant 30 checks regardless of session count), and graphql-batch stays at 0 during steady state. Most of the per-session cost comes from opaque `gh pr view/checks` subcommands which are individually cheap.
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| Metric | Value |
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|--------|-------|
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| GraphQL points/hr | 900 / 5,000 (18%) |
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| REST core requests/hr | 0 / 5,000 (0%) |
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| Total GH calls | 857 (57.1/min) |
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| graphql-batch count | **0** |
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| guard-pr-list 304s | 16 (100.0%) |
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| Poll cycle (mean) | **53s** (1.8x the 30s target) |
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| p50 / p95 / p99 latency | 787 / 4,317 / 5,437 ms |
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**Revised 50-session projection:** ~800–1,000 GraphQL pts/hr (16–20% of budget). Far better than the earlier 64% estimate. **B2 structural reductions are NOT required for quiet-steady state.** The 50-session target is safely achievable with B1 alone.
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**Scorecard:** `experiments/out/scorecard-quiet-steady.single-repo.30-1776439031.json`
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**Trace:** `experiments/out/gh-trace-bench-1776438003.jsonl` (983 rows)
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### 40-Session Benchmark (2026-04-17, B1 fix applied)
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| Metric | Value |
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|--------|-------|
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| GraphQL points/hr | 1,140 / 5,000 (23%) |
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| REST core requests/hr | 0 / 5,000 (0%) |
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| Total GH calls | 1,094 (72.9/min) |
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| graphql-batch count | **0** |
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| guard-pr-list 304s | 15 (100.0%) |
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| Poll cycle (mean) | **58s** (1.9x the 30s target) |
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| p50 / p95 / p99 latency | 1,014 / 4,910 / 5,147 ms |
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**Scorecard:** `experiments/out/scorecard-quiet-steady.single-repo.40-1776440122.json`
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**Trace:** `experiments/out/gh-trace-bench-1776439097.jsonl` (1,255 rows)
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### 50-Session Benchmark (2026-04-17, B1 fix applied)
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| Metric | Value |
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|--------|-------|
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| GraphQL points/hr | ~1,400 / 5,000 (28%) — estimated (rate limit reset straddled window) |
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| REST core requests/hr | 0 / 5,000 (0%) |
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| Total GH calls | 1,338 (89.2/min) |
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| graphql-batch count | **0** |
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| guard-pr-list 304s | 12 (100.0%) |
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| Poll cycle (mean) | **66s** (2.2x the 30s target) |
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| p50 / p95 / p99 latency | 3,441 / 7,610 / 9,684 ms |
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**Scorecard:** `experiments/out/scorecard-quiet-steady.single-repo.50-1776441230.json`
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**Trace:** `experiments/out/gh-trace-bench-1776440201.jsonl` (1,519 rows)
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### Complete Scaling Curve (5 → 50 sessions)
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| Sessions | Calls/min | GraphQL pts/hr | Poll cycle | Batch calls | Guard 304% | p50 | p99 |
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|----------|-----------|----------------|------------|-------------|------------|-----|-----|
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| 5 | 16.7 | 260 (5%) | ~30s | 0 | 100% | 746ms | 1,261ms |
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| 10 | 31.3 | 640 (13%) | ~30s | 0 | 100% | 803ms | 2,509ms |
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| 20 | 60.7 | 680 (14%) | ~30s | 0 | 100% | 761ms | 3,052ms |
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| 30 | 57.1 | 900 (18%) | 53s | 0 | 100% | 787ms | 5,437ms |
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| 40 | 72.9 | 1,140 (23%) | 58s | 0 | 100% | 1,014ms | 5,147ms |
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| 50 | 89.2 | ~1,400 (28%) | 66s | 0 | 100% | 3,441ms | 9,684ms |
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### Key Findings: Capacity Discovery
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**1. Rate limit is NOT the bottleneck.** Even at 50 sessions, GraphQL consumption is ~28% of budget. The B1 fix + ETag guards eliminated the original problem completely. ETag guard hit rate is 100% at every scale — zero batch calls during steady state.
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**2. Poll cycle lag is the first real bottleneck.** The lifecycle manager runs a sequential loop processing all sessions. At 30+ sessions, it can no longer complete a cycle within the 30s target:
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| Sessions | Poll cycle | Ratio to target |
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|----------|-----------|-----------------|
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| 5-20 | ~30s | 1.0x |
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| 30 | 53s | 1.8x |
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| 40 | 58s | 1.9x |
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| 50 | 66s | 2.2x |
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**3. API latency degrades at scale.** p50 latency goes from <1s at 5-20 sessions to 3.4s at 50 sessions. p99 goes from 1.3s to 9.7s. This is likely subprocess contention from running 50+ `gh` CLI processes.
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**4. Per-session opaque calls are the dominant cost.** At 50 sessions, 700 of 1,338 calls (52%) are per-session `gh.api.repos` and `gh.api.graphql` calls. `guard-commit-status` contributes another 700+ calls. The batch/guard-pr-list system is repo-scoped and barely contributes.
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**5. The 50-session target is achieved for rate limits.** The original goal (50+ sessions on a single PAT) is safely met. The remaining bottlenecks are local infrastructure (poll cycle, latency), not GitHub API limits.
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**Key harness implementation notes:**
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- Creates placeholder tmux sessions with a `claude` symlink → `/bin/sleep 86400` so lifecycle polls sessions instead of short-circuiting to "killed"
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- macOS `/bin/sleep` doesn't accept `infinity` — use `86400` (24h)
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- Must set `AO_CONFIG_PATH` to the todo-app config when running from the AO repo directory
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- The todo-app config auto-infers `scm: { plugin: "github" }` from the `repo` field
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- **Harness bug found:** measure mode doesn't reset `status=killed` in session metadata. Must manually `sed` before re-runs if sessions were marked killed by a prior run.
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---
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@ -214,5 +284,7 @@ GraphQL cost barely increased from 10→20 sessions (640→680, +6%). The guard-
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1. ~~**B1 PR comment to Adil** — drafted, not yet posted.~~ ✅ Posted. Awaiting Adil's independent verification run.
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2. **Benchmark with bugbot/CI** — Dhruv enabled bugbot on todo-app. Want to verify empirically that CI/reviews don't change polling cost.
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3. **Blocker #5 (sessionId/projectId threading)** — deferred. Needed for per-session attribution in the remaining A2 matrix cells.
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4. **Scale-up validation (10, 20 sessions)** — next step. Can run locally now without waiting for Adil. Replaces extrapolation with measured data.
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5. **50-session validation** — target tier, not first measurement tier. Get real data at 5/10/20 first.
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4. ~~**Scale-up validation (10, 20 sessions)**~~ ✅ Done. Full curve 5→50 measured.
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5. ~~**50-session validation**~~ ✅ Done. Rate limit target met; poll cycle lag identified as next bottleneck.
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6. **Poll cycle optimization** — lifecycle manager processes sessions sequentially. At 30+ sessions, the cycle exceeds the 30s target. Potential fixes: parallelize per-session checks, reduce per-session work, or make poll interval adaptive.
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7. **Harness bug: session status reset** — measure mode should reset `status=killed` to `status=mergeable` before starting.
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@ -97,10 +97,14 @@ Track B ── Fix bugs ──────────────────
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— Verified: 100% guard 304 rate, 0 graphql-batch calls in quiet-steady
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— Awaiting Adil's independent verification (PR comment posted)
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B2 Structural reductions (detectPR dedup, batch) ⏳ Blocked on B1 verification
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B3 Scale-up validation (10, 20 sessions) ✅ Done — sub-linear scaling confirmed
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5→260, 10→640, 20→680 GraphQL pts/hr
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50-session projection: ~800-1000 pts/hr (16-20% budget)
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B2 structural reductions NOT required for quiet-steady
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B3 Scale-up validation (5→50 sessions) ✅ Done — full capacity discovery complete
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5→260, 10→640, 20→680, 30→900, 40→1140, 50→~1400 GraphQL pts/hr
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Rate limit target MET: 50 sessions = ~28% of GraphQL budget
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ETag guard 304 rate: 100% at every scale, 0 batch calls
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First bottleneck: poll cycle lag (66s at 50 sessions vs 30s target)
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Second bottleneck: API latency (p50=3.4s, p99=9.7s at 50 sessions)
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B2 structural reductions NOT required for quiet-steady rate limits
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B4 Poll cycle optimization (NEW) ⏳ Next — lifecycle processes sessions sequentially
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Track C ── Octokit migration (optional) ─────────────────────────────────
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C1 OctokitRunner behind flag + compare ⏳ Blocked on B scorecard
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@ -0,0 +1,78 @@
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#!/usr/bin/env bash
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# ci-churn.sh — Push empty commits to PRs during a benchmark measurement window.
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#
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# Usage:
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# ./experiments/ci-churn.sh --sessions 10 --interval 60 --duration 900 [--delay 0]
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#
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# This pushes an empty commit to each of the first N session worktrees,
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# one every INTERVAL seconds, cycling through them repeatedly for DURATION seconds.
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# Each push invalidates the ETag cache for that PR's commit status,
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# forcing a full graphql-batch re-fetch on the next poll cycle.
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#
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# Run this in PARALLEL with the benchmark's measurement window.
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# Use --delay to wait before starting (e.g., to skip warmup).
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set -euo pipefail
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WORKTREE_BASE="$HOME/.worktrees/todo-app"
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SESSIONS=10
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INTERVAL=60
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DURATION=900
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DELAY=0
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while [[ $# -gt 0 ]]; do
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case "$1" in
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--sessions) SESSIONS="$2"; shift 2 ;;
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--interval) INTERVAL="$2"; shift 2 ;;
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--duration) DURATION="$2"; shift 2 ;;
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--delay) DELAY="$2"; shift 2 ;;
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*) echo "Unknown flag: $1" >&2; exit 1 ;;
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esac
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done
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echo "[ci-churn] Config: sessions=$SESSIONS interval=${INTERVAL}s duration=${DURATION}s delay=${DELAY}s"
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if [ "$DELAY" -gt 0 ]; then
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echo "[ci-churn] Waiting ${DELAY}s before starting..."
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sleep "$DELAY"
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fi
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START=$(date +%s)
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END=$((START + DURATION))
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PUSH_COUNT=0
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SESSION_IDX=1
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echo "[ci-churn] Started at $(date -u +%Y-%m-%dT%H:%M:%SZ)"
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while [ "$(date +%s)" -lt "$END" ]; do
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WORKTREE="$WORKTREE_BASE/ta-$SESSION_IDX"
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if [ -d "$WORKTREE/.git" ] || [ -f "$WORKTREE/.git" ]; then
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echo "[ci-churn] Pushing empty commit to ta-$SESSION_IDX..."
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(
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cd "$WORKTREE"
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git commit --allow-empty -m "bench: ci-churn push $PUSH_COUNT ($(date -u +%H:%M:%S))" 2>/dev/null
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git push origin HEAD 2>/dev/null
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) && echo "[ci-churn] ✓ ta-$SESSION_IDX pushed" \
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|| echo "[ci-churn] ✗ ta-$SESSION_IDX failed"
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PUSH_COUNT=$((PUSH_COUNT + 1))
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else
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echo "[ci-churn] ✗ ta-$SESSION_IDX worktree not found, skipping"
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fi
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# Cycle through sessions
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SESSION_IDX=$((SESSION_IDX + 1))
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if [ "$SESSION_IDX" -gt "$SESSIONS" ]; then
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SESSION_IDX=1
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fi
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# Wait for next interval (but check if we've exceeded duration)
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REMAINING=$((END - $(date +%s)))
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if [ "$REMAINING" -gt "$INTERVAL" ]; then
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sleep "$INTERVAL"
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elif [ "$REMAINING" -gt 0 ]; then
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sleep "$REMAINING"
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fi
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done
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echo "[ci-churn] Done. Total pushes: $PUSH_COUNT over ${DURATION}s"
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