Add bimonthly index rebase to prevent structural decay by DavyMorgan · Pull Request #1 · y3zai/gp300

DavyMorgan · 2026-04-12T13:30:47Z

Summary

The GP 300 index has dropped from 1000 to 192 in one month due to structural decay: prediction markets inherently converge toward certainty (entropy → 0), and the fixed divisor can't counteract this. Without intervention, the index would approach zero.

This PR adds a periodic full rebase plus schedule changes to keep the index in a meaningful range.

Bimonthly rebase: Every 8 weeks, reset divisor so index = 1000 (no continuity at rebase points — intentional)
Schedule changes: Weekly reconstitution (Sunday) + daily rebalance (every midnight) replace the previous biweekly reconstitution + weekly rebalance
Chart updates: New "Period" range button (default), rebase markers (orange arrows), last_rebase field in /api/current

Backward compatible with existing D1 data — the state JSON blob adds a new last_rebase field that defaults to None for existing state, which triggers a rebase on the next Sunday reconstitution.

Test plan

Existing engine tests pass (pytest test_engine.py)
Verified rebase fires at 8-week boundary in isolated test
Verified rebase does NOT fire before 8 weeks
Deploy to production — next Sunday reconstitution should reset index from ~192 to 1000
Verify chart shows rebase marker and defaults to "Period" view after first rebase

🤖 Generated with Claude Code

The index decays structurally because prediction markets converge toward certainty (entropy → 0). This adds a full rebase every 8 weeks that resets the index to 1000, plus schedule changes for fresher data: - Engine: rebase logic resets divisor every 8 weekly reconstitutions - Worker: new cron schedule (daily rebalance, weekly reconstitution) - Chart: "Period" range button, rebase markers, default to current period - API: last_rebase field in /api/current response Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cloudflare-workers-and-pages · 2026-04-12T13:30:53Z

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	gp300	`66c3284`	Commit Preview URL Branch Preview URL	Apr 12 2026, 05:04 PM

Copilot

Pull request overview

Adds a periodic “rebase” mechanism and scheduling/UI updates to keep the GP 300 index in a meaningful range despite entropy-driven structural decay.

Changes:

Introduces an 8-week rebase (divisor reset so index returns to 1000) tracked via last_rebase and a rebased flag.
Updates cron schedule to weekly reconstitution (Sunday) plus daily rebalance (midnight), with 5-min updates skipping midnight.
Updates /api/current and the frontend chart to support a “Period” range and display rebase markers.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
`wrangler.toml`	Updates cron triggers to daily rebalance + weekly reconstitution.
`src/worker.py`	Persists/serves `last_rebase`, logs rebase adjustments, and updates scheduled cron routing.
`src/engine.py`	Adds rebase configuration/state fields and implements rebase logic during reconstitution.
`public/index.html`	Adds “Period” range selection and renders rebase markers on the chart.

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Copilot · 2026-04-12T13:35:32Z

+        # Check if a bimonthly rebase is due (only at reconstitution)
+        last_rebase = current_state.last_rebase
+        should_rebase = reconstitute and (
+            last_rebase is None
+            or (now - last_rebase).days >= config.rebase_interval_weeks * 7
+        )
+
+        if should_rebase and we > 0:
+            new_divisor = we / config.base_value
+            value = config.base_value
+            return IndexState(
+                value=value,
+                divisor=new_divisor,
+                weighted_entropy=we,
+                num_constituents=len(selected),
+                timestamp=now,
+                constituents=selected,
+                pre_adjustment_value=pre_val,
+                last_rebase=now,
+                rebased=True,
+            )


The new rebase path doesn’t appear to have unit test coverage. Given the engine already has targeted edge-case tests, please add tests that (1) assert a rebase triggers exactly at/after the configured 8-week interval on a reconstitution run, (2) does not trigger before the interval, and (3) confirms last_rebase and rebased are set as expected when the rebase happens.

Copilot · 2026-04-12T13:35:33Z

+        adj_data = {
+            "divisor_before": prev_state.divisor,
+            "divisor_after": state.divisor,
+            "index_before": round(prev_state.value, 2),


For the rebase adjustment log, index_before is taken from prev_state.value, which may be stale relative to the reconstitution timestamp (other adjustment events use state.pre_adjustment_value when available). If you want the audit trail to reflect the true pre-rebase level at current prices, consider logging state.pre_adjustment_value (or computing an equivalent) as index_before.

Suggested change

"index_before": round(prev_state.value, 2),

"index_before": round(state.pre_adjustment_value, 2)

if state.pre_adjustment_value is not None

else round(prev_state.value, 2),

Copilot · 2026-04-12T13:35:33Z

+      // Default to current rebase period if available, else 1M
+      if (currentData && currentData.last_rebase) {
+        activeRange = 'PERIOD';
+        document.querySelectorAll('.period-btn').forEach(b => b.classList.remove('active'));
+        const periodBtn = document.querySelector('.period-btn[data-range="PERIOD"]');
+        if (periodBtn) periodBtn.classList.add('active');
+      }


The comment says “Default to current rebase period if available, else 1M”, but activeRange is initialized to '1D' and is only changed when last_rebase is present. Either update the comment to match the actual default, or set activeRange to '1M' in the else branch if that’s the intended behavior.

Copilot · 2026-04-12T13:35:33Z

+      // Detect rebase points: where index jumps back to ~1000 from a much lower value
+      const rebases = [];
+      for (let i = 1; i < historyData.length; i++) {
+        const prev = historyData[i - 1].value;
+        const curr = historyData[i].value;
+        // Rebase: value jumps by >50% upward and lands near 1000
+        if (curr > prev * 1.5 && curr > 800) {


findRebaseTimestamps() uses a heuristic (curr > prev * 1.5 && curr > 800) that can misidentify large organic moves as a rebase. Since a rebase sets the index to the configured base (1000) deterministically, consider tightening detection to check that the post-jump value is near the base (e.g., within an epsilon of 1000) and that the prior value was materially below it, to avoid false positives in marker rendering.

Suggested change

// Detect rebase points: where index jumps back to ~1000 from a much lower value

const rebases = [];

for (let i = 1; i < historyData.length; i++) {

const prev = historyData[i - 1].value;

const curr = historyData[i].value;

// Rebase: value jumps by >50% upward and lands near 1000

if (curr > prev * 1.5 && curr > 800) {

// Detect rebase points: where index resets to the configured base from a materially lower value

const REBASE_BASE = 1000;

const REBASE_EPSILON = 25;

const MIN_PRE_REBASE_GAP = 100;

const rebases = [];

for (let i = 1; i < historyData.length; i++) {

const prev = historyData[i - 1].value;

const curr = historyData[i].value;

const landsNearBase = Math.abs(curr - REBASE_BASE) <= REBASE_EPSILON;

const prevMateriallyBelowBase = prev <= REBASE_BASE - MIN_PRE_REBASE_GAP;

// Rebase: value moves upward and lands back near the configured base

if (curr > prev && landsNearBase && prevMateriallyBelowBase) {

- worker: use state.pre_adjustment_value for rebase index_before (consistent with other adjustment events) - index.html: tighten rebase detection with explicit bounds (proximity to base + pre-rebase gap) to avoid false positives on organic moves - index.html: clarify default range comment - test: add coverage for rebase logic (triggers at 8 weeks, not before, skips on rebalance-only, sets fields correctly) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

DavyMorgan · 2026-04-12T17:03:57Z

@copilot to review again.

Copilot · 2026-04-12T17:05:37Z

@copilot to review again.

All four review items have been addressed in commit 66c3284:

Rebase unit tests — Added test_rebase_on_first_run, test_rebase_does_not_trigger_before_interval, test_rebase_triggers_at_interval, and test_rebase_skips_on_rebalance_only. All 11 tests pass.
index_before audit log — Now uses state.pre_adjustment_value (falling back to prev_state.value), consistent with other adjustment events.
findRebaseTimestamps() heuristic — Tightened to check landsNearBase (within ±25 of 1000) and prevMateriallyBelowBase (≥100 below base), eliminating false positives on large organic moves.
Comment accuracy — Updated to "else keep the HTML default (1D)" to match actual behavior.

Copilot AI review requested due to automatic review settings April 12, 2026 13:30

Copilot started reviewing on behalf of DavyMorgan April 12, 2026 13:31 View session

Copilot AI reviewed Apr 12, 2026

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Copilot started work on behalf of DavyMorgan April 12, 2026 17:04 View session

DavyMorgan merged commit b00e0c7 into main Apr 12, 2026
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Copilot stopped work on behalf of DavyMorgan due to an error April 12, 2026 17:06
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Add bimonthly index rebase to prevent structural decay#1

Add bimonthly index rebase to prevent structural decay#1
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-            "index_before": round(prev_state.value, 2),
+            "index_before": round(state.pre_adjustment_value, 2)
+            if state.pre_adjustment_value is not None
+            else round(prev_state.value, 2),

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DavyMorgan commented Apr 12, 2026

Summary

Test plan

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cloudflare-workers-and-pages Bot commented Apr 12, 2026 •

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