TL;DR. Ten tracks were live this week, all serving two deliverables: Paper A (the redundancy criterion + its positive instrument) and Paper 3 (the anatomy of beating PPO), both targeted at the late-July deadline. Headlines: the 3-task value-sufficiency grid reached n=4 (Cheetah strictly monotone 544/588/630/727 vs 855; Acrobot’s step-at-128 narrows to 78%; Walker lands tonight); the collection-mode × world-model double dissociation is confirmed at n=4 on the Walker side (full median 715.5 vs stripped 600.5, and the “bimodality” scare resolved into within-run eval volatility); Lean+ — target-EMA smoothing as a world-model substitute — returned a clean pre-registered null; and the graph-world-model line, reviewed here before its GPU box is retired, stays closed (its one legitimate follow-up is banked, post-deadline). Sources for every number: wm-redundancy-paper/bet2_null_results.md (commit hashes inline) and tdmpc-glass/docs/CHANGELOG.md.

Minimal shared context (60 seconds)

We study TD-MPC2, a model-based RL agent with three coupled parts: a latent world model (trained by a consistency loss to predict its own next latent), a value/policy head (two-hot cross-entropy critic, deterministic tanh-mean actor), and an MPPI planner (samples action sequences through the world model). Our stack is a JAX reimplementation (“our variant”) whose one deliberate deviation is documented in Part 16: it collects data with the policy, not the planner. The campaign’s core finding — the redundancy criterion — is that on several standard control tasks you can delete the world-model objective (“stripped”) and lose little or nothing, which makes many proposed abstraction objectives redundant. The open work this week: turn that negative into instruments and mechanisms (Paper A), and explain exactly what beats PPO and why (Paper 3). “n” always counts independent seeds; “vanilla” means the unmodified agent; “@5M/@2.5M” is environment steps.

Track 1 — Value-Sufficiency Bottleneck (VSB/VBN) grid: the positive instrument

What it is. A width-\(D\) bottleneck inserted between the latent and the value head: the critic may only read a \(D\)-dimensional slice. Sweeping \(D \in {16,32,64,128}\) against vanilla measures how much of the latent the value function actually needs — a valid replacement for the invalid decode-\(R^2\) probe Paper A already rejects.

Why it exists. Paper A’s arc ended deflating (“a valid probe is still open”). The VSB curve is the constructive answer, and its shape is a per-task fingerprint of value-information structure.

Status (n=4 on all three tasks as of tonight; final mppi evals, 5M steps).

  • CheetahRun: 544 / 588 / 630 / 727 vs vanilla 855 — 64→85%, strictly monotone (ledger 76c29ef). The “smooth information gradient” case: every doubling buys more, no width suffices.
  • AcrobotSwingup: 261 / 271 / 282 / 397 vs vanilla 511 — tight widths statistically flat at 51–55%, only D=128 recovers a large fraction (78%), and the step’s size is seed-heavy (3e3e312). The “least compressible” case.
  • WalkerRun: n=3 means 622 / 647 / 669 / 701 vs vanilla 727 (85–96%, flat-high — most compressible); the seed-53 arms complete tonight → n=4 (in flight, no numbers claimed).
  • Seed-54 arms for n=5 on Cheetah (all four widths) and Walker are already running.

Feeds: Paper A’s central positive figure (the three fingerprints), plus the cross-task compressibility ordering that matches Track 2.

Track 2 — Task-conditional sufficiency: how load-bearing is the world model?

What it is. The stripped-vs-full comparison (delete the consistency loss, keep everything else) run per task.

Why it exists. It quantifies the redundancy criterion task by task, and any candidate mechanism for “what the world model does” must reproduce its ordering.

Status (final, policy-collection, 5M). HopperHop 0% (n=8, removable) < WalkerRun −7.5% (n=4) < CheetahRun −23.8% (n=4) < AcrobotSwingup −44%. Stable all week; the V1 audit (Track 4) found the same ordering in the official-implementation deficits — independent corroboration.

Feeds: Papers A and 3 (it is the x-axis both papers’ mechanisms must explain).

Track 3 — Lean+: is the world model just a stabilizer? (pre-registered, closed today: NULL)

What it is. A “lightweight TD-MPC2” bet: if the world-model objective merely stabilizes value targets, then a slower target-EMA (\(\tau\) 0.01 → 0.003) should recover the stripped model’s losses on Cheetah — a two-line change instead of a world model.

Why it exists. The user asked for a lightweight variant; the honest way to build one is to test whether the WM’s role is replaceable by cheaper stabilization. Success and kill gates were pre-registered before launch (0af60bf).

Status (closed 07-12, n=3/arm, 5M, stripped Cheetah). Lean-on 596.9 (spread 21.5) vs lean-off control 607.1 (spread 48.2) — fails the pre-registered mean gate (≥620) without triggering the kill line; the only real effect is a halved seed variance (943819c). Verdict: the world model’s dense-task contribution is predictive structure, not mere target stabilization. The honest lightweight recipe remains: strip the WM only where Track 2 says it’s removable (Hopper-class).

Feeds: Paper A — sharpens the claim that the consistency loss carries irreplaceable predictive structure.

Track 4 — Reimplementation validity audit (V1): are we wrong at the very beginning?

What it is. A direct parity check of our JAX variant against the official TD-MPC2 (and official SAC), triggered by the user’s question once we noticed our stack never uses the planner to collect data.

Why it exists. Every claim in both papers is scoped by whether the reimplementation is faithful; this had never been tested head-to-head.

Status (closed, Part 16, 5a31517). Official hopper-hop 449 ≈ ours 420±113; official SAC’s Hopper failures match our SAC runs (the P1 result is not an artifact of our SAC). The official-minus-ours deficit is ordered exactly like Track 2’s WM-load ordering (Hop ≈0 < Cheetah < Walker < Acrobot ~23%) — the deviation costs performance precisely where the world model matters, which is what Track 5 then explained mechanistically. Consequence adopted campaign-wide: sample-efficiency claims are within-stack only.

Feeds: the scoping section of every paper; Part 16 (published) + Part 17, the from-scratch Handbook (shipped, with the co-design recipe the user asked for).

Track 5 — The collection-mode × world-model double dissociation (V2/V2W/V2X + extensions)

What it is. Rerun the stripped-vs-full contrast under planner-collection (the canonical mode, MPPI_COLLECT=1, 512 samples). Two pre-registered predictions: on Hopper (WM removable) stripping stays free; on Walker (WM load-bearing) stripping should start to hurt more, because the planner collects by rolling the model.

Why it exists. It is the cleanest mechanistic statement the campaign owns: the world model’s value is task-conditional, and collection mode modulates it in the predicted direction at both ends. It also retroactively explains Track 4’s deficit pattern.

Status.

  • Hopper: stripped ≈ full, +1.4%, n=3, tight (unchanged all week); seed-53 pair → n=4 in flight.
  • Walker (n=4, closed today, 377e319): full median 715.5 vs stripped 600.5 (−15.4%; means −10.4%). The mid-week scare — a seed-52 full arm at 455 suggesting bimodality — resolved when seed 53 finished at 744.7 and its live eval trajectory revealed the mechanism: the full arm’s evals swing ~250 points within a single late-training window (680→715→676→501→696→744) while stripped arms move ~30 points. Refined claim: under planner-collection the WM buys a higher-mean but higher-variance eval regime; seed 52’s 455 was an unlucky final draw, not a mode. Seed-54 pair → n=5 in flight (~tonight).
  • Cheetah (new, pre-registered 943819c, in flight): the third task joins the table; prediction: stripped degrades ≥15% under planner-collection; kill if <8% (that would falsify the “planner-collection amplifies WM importance” generalization). Verdict ~tonight.
  • Bonus finding retained: planner-collection roughly doubles Walker sample-efficiency in our stack (722@2.5M ≈ policy-collection@5M).

Feeds: Paper 3’s centerpiece table; Part 16 updates 1–3 (published).

Track 6 — P1, the entropy needle: why SAC fails Hopper

What it is. A full SAC entropy grid (auto-α, α=0.01, α=0.05; n=3 each) on HopperHop at 5M, against the planner-free TD-MPC2 core.

Why it exists. Paper 3 needs the mechanism of TD-MPC2’s Hopper advantage; the candidate was where stochasticity lives: in the objective (SAC) vs only in the data (TD-MPC2’s ε-noise collection).

Status (closed, 09fc2ab). Every SAC arm fails Hopper at 5M; the TD core is 8/8. With Track 4’s external validation (official SAC also fails), the “entropy needle” stands: stochasticity-in-objective vs exploration-in-data is a ≥4–8× sample-efficiency gap on this task, honestly capability-scoped.

Feeds: Paper 3, mechanism section.

Track 7 — H3, the margin-controlled Hopper wall

What it is. PPO on HopperHop with the reward re-shaped (product form, speed and margin knobs at 1.0) to test whether the PPO wall is a shaping artifact.

Why it exists. Closes Paper 3’s F3 audit caveat: is the wall the conjunctive reward itself, or our margin choice?

Status (closed, aa1a870). PPO still walls (2.8/3.6 @20M) with the margin held — the conjunction is the wall, de-confounded.

Feeds: Paper 3.

Track 8 — The graph-world-model (GWM) line: reviewed before the box is retired

What it is. The relational axis of the redundancy program: does giving the world model an explicit entity/graph structure (object nodes, interaction edges) buy anything a monolithic latent lacks? Run June 14–15 as iterations 34–36 plus a real-benchmark gate; its GPU box (the RTX 5070 Ti instance) has been idle since and is now being retired by the user.

Why it exists. The 2026 GWM survey (arXiv:2604.27895) named graph world models a paradigm; three deep-research reports converged that if headroom exists it is in contact-rich, compositional (held-out object-count) settings. Our smooth-spring synthetic could not have surfaced that, so a fair contact-world test was owed.

Status (closed June; reviewed 07-12; all numbers from tdmpc-glass/docs/CHANGELOG.md and docs/research/graph-world-model-plan.md). Four results, one honest asterisk:

  1. Iter-34 mechanism check (contact multi-disk world): the graph latent’s representation-level win was real — compositional-OOD value-\(R^2\) 0.57 vs fair param-matched monolithic 0.40 (gap 0.18 > pre-registered 0.15) — but the contact-conditioned-prediction criterion failed, and the control gate killed it: under random-shooting MPC, graph ≈ fair-mono ≈ random floor at every object count (graph−random +13, std ~110). Representation advantage did not convert to control.
  2. Iter-35 (SOLD, the official GWM): reproduced its released checkpoint at 100% success (30/30) vs paper 97.9%. Third-party corroboration from SOLD’s own Table 1: monolithic TD-MPC2 (97.6) ties SOLD (97.9) on the non-relational variant; SOLD’s wins are confined to the Distinct (relational) variants. The head-to-head on Distinct was blocked by hardware (15 GB replay memmap > box disk).
  3. Iter-36 (compositional-OOD control, on the 5070 Ti): uninformative, not a null — the GPU-vectorized contact env had a control-signal ceiling ~10% (no controller, including random, separated) plus BPTT NaNs.
  4. Paper-B gate on a real benchmark (ManiSkill PushCubeMulti): control signal passed (PPO 100% vs random 0%) but the headroom test failed — value-decodability stayed flat from 2→6 objects and the monolithic policy solved the OOD counts. Monolithic generalizes over passive distractors; the program folded into Paper A as its relational-axis closure.

Verdict on continuing (the user’s question). As a program: no — keep it closed. The one genuine positive (representation-level OOD advantage) failed to convert to control three separate ways, and the real-benchmark gate failed for the deeper reason that monolithic latents already generalize compositionally where objects don’t interact contingently. The redundancy criterion now spans state, temporal, and relational structure — that is the paper contribution. The one legitimately untested cell is a SOLD Fetch-Distinct head-to-head (active multi-object interaction, the regime where SOLD’s own table shows its only wins): a bounded reproduce-and-compare, ~2–3 box-days on a ≥30 GB-disk PyTorch box, banked as a post-deadline item — it either adds a third-party-anchored positive boundary to Paper A’s relational section or closes the last asterisk. It is not added to this week’s active plan (deadline math wins). Box retirement is safe: contact_entities.py, entity_wm.py, monolithic_wm.py, and value_coupling_probe.py are all preserved in the tdmpc-glass repo; iter-36 was already recorded as uninformative; nothing unique remains on the instance.

Feeds: Paper A (relational-axis closure section + one banked boundary experiment).

Track 9 — Parked from the Part-10 TODO: JEPA/SE cells and the taxonomy law

What it is (planned, unexecuted — labeled as such). The Part-10 worklist items that the revision campaign displaced: J0 anchor-strength A/B on nav H-JEPA, J1 SE-community vs uniformity/VICReg in the collapse regime (open cell #59, ~1 box-day), J2 SE-as-hierarchy (gated on J0/J1, ~2–3 box-days), J3 offline SE-JEPA probe, and Bet-B’s DOF-overlap monotonicity law (~2 box-days).

Why they exist. They are the next-paper pipeline (JEPA/SE line), deliberately paused because Papers A & 3 have a ~07-28 deadline and the audit (Tracks 4–5) was strictly more urgent.

Status. No runs this week; no numbers. Resume after paper assembly; J1/#59 first.

Feeds: the post-deadline JEPA/SE paper direction.

Track 10 — Assembly: the papers themselves

What it is. Fold everything above into Paper A (“When Is Explicit Abstraction Redundant”) and Paper 3 (“The Anatomy of Beating PPO”) per the Part-15 narrative plan: A gains the VSB instrument + 4-taxa closure + Lean+ sharpening + relational closure; 3 gains the wall mechanism (H3), the entropy needle (P1), the double dissociation (Track 5), and the within-stack scoping (Track 4).

Status. Planned; starts when tonight’s n=5/n=4 arms land (the last figure-feeding runs). Estimated 2–3 focused days of writing.

Feeds: both deliverables, deadline ~07-28.

Dependency map

  • Paper A ← Track 1 (VSB figure) ← Track 2 (ordering) ← Track 3 (Lean+ null) ← Track 8 (relational closure).
  • Paper 3 ← Track 5 (dissociation table) ← Track 4 (validity scoping) ← Track 6 (entropy needle) ← Track 7 (wall mechanism).
  • Docs/public record: Parts 16–17 (audit + Handbook, shipped), Part 15 live log (running), this notebook.
  • Post-deadline queue: Track 9 (JEPA/SE), Track 8’s banked SOLD-Distinct head-to-head.

Everything above is reproducible from the ledger (bet2_null_results.md, commits cited inline), the CHANGELOG, and the Part 15/16 live logs; in-flight tracks are stated without numbers on purpose.