|
| 1 | +# Multi-Model Routing, Refinement & Panel Deliberation — Design |
| 2 | + |
| 3 | +**Status:** Design for a future release, scope confirmed (build all three tracks |
| 4 | +plus a combined `auto` mode). No implementation code written yet. |
| 5 | +**Date:** 2026-07-05 |
| 6 | + |
| 7 | +## 1. The ask |
| 8 | + |
| 9 | +Route different parts of an agent session to different models based on which |
| 10 | +model is good at that kind of work, for two payoffs at once: lower cost and |
| 11 | +higher per-task quality. Two products were named as inspiration — |
| 12 | +OpenRouter's "Fusion" and Sakana AI's multi-model work — plus the |
| 13 | +cost-focused academic pattern (RouteLLM/FrugalGPT). Decision: build all |
| 14 | +three, composed into one adaptive `auto` mode rather than three disconnected |
| 15 | +toggles. |
| 16 | + |
| 17 | +## 2. What the named prior art actually does |
| 18 | + |
| 19 | +### OpenRouter Fusion — deliberation, not routing |
| 20 | +`openrouter/fusion` sends one prompt to a **panel** of models in parallel, |
| 21 | +then a **judge** model reads every panel response, identifies consensus, |
| 22 | +contradictions, and blind spots, and produces one synthesized answer. |
| 23 | +OpenRouter's own docs scope it to "scenarios where accuracy and thoroughness |
| 24 | +are critical and the cost of being wrong outweighs the higher latency and |
| 25 | +cost," and call it "overkill for simple, tactical prompts." Billing is the |
| 26 | +**sum** of every panel completion plus the judge — strictly more expensive |
| 27 | +than one model call. Quality-maximizing, not cost-saving. |
| 28 | + |
| 29 | +### Sakana AI — Multi-LLM AB-MCTS / "Fugu" |
| 30 | +Treats several frontier models as a collaborative pool and runs Monte Carlo |
| 31 | +Tree Search with adaptive branching: at each node, go "wider" (try a |
| 32 | +different model for a fresh candidate) or "deeper" (refine the current |
| 33 | +candidate using external feedback, e.g. execute code and check the result), |
| 34 | +balanced via Thompson sampling. Explicitly an inference-time-scaling |
| 35 | +technique — spends more compute per query for a better answer on hard, |
| 36 | +scorable benchmarks (SWE-bench-class). Productized as "Sakana Fugu," a |
| 37 | +single endpoint that conducts/routes/verifies/synthesizes internally. |
| 38 | +[reported per sakana.ai and third-party coverage, not independently |
| 39 | +re-verified against a primary paper] |
| 40 | + |
| 41 | +Full MCTS assumes many rollouts scored against a numeric reward — that setup |
| 42 | +fits competitive-programming/math-style tasks with a clean pass/fail signal. |
| 43 | +Most day-to-day dev tasks either have a *weaker* verifiable signal (tests, |
| 44 | +build, lint — binary-ish, not a smooth reward) or *no* verifiable signal at |
| 45 | +all (design judgment calls). The design below adapts the wider/deeper |
| 46 | +**idea** without building literal MCTS. |
| 47 | + |
| 48 | +### RouteLLM / FrugalGPT — the actual cost-saving pattern |
| 49 | +RouteLLM trains a classifier on preference data to predict whether a "weak" |
| 50 | +model matches a "strong" model on a given query and routes accordingly. |
| 51 | +FrugalGPT cascades: cheap model first, a judge/verifier checks the answer, |
| 52 | +escalate to a stronger model only on failure. Both are reported to cut cost |
| 53 | +40–85% while retaining roughly 95% of frontier-model quality. |
| 54 | + |
| 55 | +Both of Sakana/OpenRouter's patterns spend *more* for a *better* answer; |
| 56 | +RouteLLM/FrugalGPT spend *less* by not over-using frontier models. They are |
| 57 | +opposite levers — the design below keeps them as separate mechanisms and |
| 58 | +lets a third policy (`auto`) decide when to use which, rather than merging |
| 59 | +them into one setting. |
| 60 | + |
| 61 | +## 3. Zero's existing substrate (grounds every "reuse" claim below) |
| 62 | + |
| 63 | +| Piece | File | Relevance | |
| 64 | +|---|---|---| |
| 65 | +| Per-specialist model override, wired end-to-end | `internal/specialist/manifest.go:30` (`Metadata.Model`), applied in `internal/specialist/exec.go:693-705` (`appendModelArgs`) | Direct substrate for **Route**. Empty inherits parent; set value is passed to the spawned subprocess today. | |
| 66 | +| Per-swarm-member model override | `internal/swarm/definition.go:33`, resolved in `internal/swarm/team.go:209-214` | Same override pattern, swarm side. | |
| 67 | +| Coarse manual mode presets | `internal/modelregistry/modes.go:30-63` | `smart`/`deep`/`fast`/`large`/`precise`. **`smart` stays as-is — do not repurpose or rename.** | |
| 68 | +| Tiered, cache-aware cost computation | `internal/modelregistry/cost.go` | Feeds `zero usage`; reused as-is for Route's savings telemetry. | |
| 69 | +| Live pricing/context-limit catalog | `internal/modelregistry/modelsdev.go` | Keeps routing cost data fresh without hardcoding. | |
| 70 | +| Model-family prompt tuning | `internal/agent/system_prompt_models.go` | Precedent for "different models get different treatment," at the prompt layer. | |
| 71 | +| **Post-edit verify + corrective feedback loop, already shipped** | `internal/agent/selfcorrect.go` (`SelfCorrector.AfterEdit`, `Outcome` enum: `Disabled`/`Passed`/`Correcting`/`Reported`/`Aborted`) | This **is** the "deeper" half of Refine. Runs LSP diagnostics + `verify.Run`, synthesizes feedback, retries same-model, bounded at `defaultSelfCorrectMaxAttempts = 3`. | |
| 72 | +| **The exact gap**, precisely located | `internal/agent/loop.go:602`: `if feedback, _ := options.SelfCorrect.AfterEdit(ctx, ...); feedback != "" { … }` | The `Outcome` return value is discarded. `OutcomeAborted` (still failing after budget) currently just... ends up wherever the run's normal stop condition takes it. No escalation policy reads this signal today. **This is the hook point for "wider."** | |
| 73 | +| No fan-one-task-to-N-models primitive | Checked `internal/swarm/coordinator.go` | Confirmed absent. Swarm decomposes into distinct per-member sub-tasks; it does not broadcast one identical task to N members. **Panel needs new dispatch code**, though it can reuse `exec.go`'s subprocess-launch-with-model-override underneath. | |
| 74 | + |
| 75 | +## 4. Design: three mechanisms plus one policy that composes them |
| 76 | + |
| 77 | +### Naming |
| 78 | +`modelregistry.Mode`'s existing `"smart"` preset (fixed `claude-sonnet-4.5`, |
| 79 | +balanced daily driver) is unchanged — renaming or repurposing it would |
| 80 | +silently change behavior for anyone currently running `/mode smart`. The new |
| 81 | +adaptive/combined mode is named **`auto`**: it more precisely says "the |
| 82 | +system is choosing for you" than "smart" would, and it doesn't collide. |
| 83 | + |
| 84 | +### 4.1 Route (cost-saving — RouteLLM/FrugalGPT pattern) |
| 85 | + |
| 86 | +- New `modelRouting.roles` config block (user or project config): role name |
| 87 | + → model id/alias, e.g. `{"roles": {"explorer": "haiku-4.5", "code-review": |
| 88 | + "gpt-5.5", "worker": ""}}` (empty = inherit, matching existing manifest |
| 89 | + semantics). Resolved through the existing `modelregistry.Resolve` — same |
| 90 | + resolver every other model input already goes through, so aliases and |
| 91 | + deprecation fallbacks are handled for free. |
| 92 | +- Ship sensible defaults directly on the three builtins in |
| 93 | + `internal/specialist/builtin.go`: `explorer` (read-only enumeration) to a |
| 94 | + small/fast tier, `code-review` to a strong reasoning tier, `worker` stays |
| 95 | + inherit/balanced. This is close to a one-line-per-specialist change given |
| 96 | + the field and its wiring already exist. |
| 97 | +- Classification signal: the specialist/role name at the `Task` call site. |
| 98 | + This is a free, reliable signal — Zero already knows which role is being |
| 99 | + invoked because the calling model names it explicitly. No text classifier |
| 100 | + needed, which sidesteps RouteLLM's hardest problem (it has no such label |
| 101 | + in a raw chat stream; Zero's architecture already segments work by role). |
| 102 | +- Savings telemetry: extend `zero usage` with a comparison line — "routing |
| 103 | + saved $X vs. running every call on your primary model" — by reusing |
| 104 | + `internal/usage`'s existing per-model `CostBreakdown` aggregation. |
| 105 | + |
| 106 | +### 4.2 Refine + Escalate (Sakana-inspired "wider vs. deeper," pragmatic) |
| 107 | + |
| 108 | +**Deeper (already shipped, no new work required):** `SelfCorrector.AfterEdit` |
| 109 | +verifies, synthesizes feedback, retries the same model, gives up after 3 |
| 110 | +attempts (`OutcomeAborted`). |
| 111 | + |
| 112 | +**Wider (new):** |
| 113 | +1. Stop discarding the `Outcome` at `loop.go:602`; branch on it. |
| 114 | +2. On `OutcomeAborted`, for a **verifiable** task (tests/build/lint exist to |
| 115 | + check against): |
| 116 | + - Simplest correct version: retry once more on a stronger single model |
| 117 | + (classic FrugalGPT-style cascade escalation), carrying the same |
| 118 | + corrective feedback `SelfCorrector` already synthesized. |
| 119 | + - Stronger version (follow-up, not required for first ship): fan the |
| 120 | + still-failing task to a small panel (2 models) and let the *existing |
| 121 | + verifier* pick whichever candidate actually passes — cheap because the |
| 122 | + test suite is the judge; no extra judge-model call needed. |
| 123 | +3. For an **unverifiable** task with no tests/build to check against, Refine |
| 124 | + has nothing to referee an escalation with — hand off to Panel instead |
| 125 | + (§4.3), don't try to force a verify-loop where none is meaningful. |
| 126 | + |
| 127 | +This keeps "deeper" exactly as it already works and adds "wider" as a |
| 128 | +genuinely new but narrowly-scoped escalation policy sitting on top of an |
| 129 | +existing, tested signal. |
| 130 | + |
| 131 | +### 4.3 Panel (quality-maximizing — OpenRouter Fusion pattern) |
| 132 | + |
| 133 | +- New dispatch primitive: fan one prompt to N diverse models in parallel |
| 134 | + (reusing `exec.go`'s subprocess-launch-with-model-override underneath), |
| 135 | + collect N responses, synthesize with a judge call that surfaces consensus, |
| 136 | + contradictions, and blind spots (mirroring Fusion's actual synthesis |
| 137 | + shape, not just picking one response). |
| 138 | +- Explicit opt-in only: a `/panel <question>` command, or a `panel: true` |
| 139 | + flag on a `Task` call. Never automatic or default — it's billed as the sum |
| 140 | + of every panel completion plus the judge, same cost shape OpenRouter |
| 141 | + itself documents. |
| 142 | +- Primary use: unverifiable, high-stakes, or ambiguous judgment calls — |
| 143 | + architecture decisions, "should I use X or Y," irreversible/security- |
| 144 | + sensitive changes — where being wrong is expensive enough to justify |
| 145 | + paying for multiple opinions up front. |
| 146 | + |
| 147 | +### 4.4 `auto` mode — the combination |
| 148 | + |
| 149 | +A policy, not a fourth execution mechanism. Sequences the three above: |
| 150 | + |
| 151 | +1. **Route** picks the cheapest-sufficient model for the task's role. |
| 152 | +2. Mutating edits run through **Refine**'s existing verify-loop unchanged. |
| 153 | +3. On `OutcomeAborted`: if verifiable, escalate **wider** (stronger model, |
| 154 | + or verifier-arbitrated mini-panel). If unverifiable and either |
| 155 | + low-confidence or explicitly flagged high-stakes, escalate straight to |
| 156 | + **Panel**. |
| 157 | +4. Otherwise, stay on the cheap path. |
| 158 | + |
| 159 | +Net effect: the cheap model absorbs the routine majority of turns (where |
| 160 | +most token volume actually sits); Panel's multi-model cost is only paid on |
| 161 | +the minority of cases that demonstrably need it. This is the concrete |
| 162 | +mechanism behind "both at once" — cost savings and quality aren't competing |
| 163 | +settings, they're different rungs of one cascade. |
| 164 | + |
| 165 | +## 5. Build sequencing |
| 166 | + |
| 167 | +Route and Panel do not depend on each other and can be built in parallel; |
| 168 | +`auto` depends on all three existing first. |
| 169 | + |
| 170 | +1. **Route** — foundational, lowest risk, mostly config + defaults on |
| 171 | + already-wired plumbing. Also required as `auto`'s first tier regardless |
| 172 | + of sequencing. |
| 173 | +2. **Wire the discarded `Outcome`** at `loop.go:602` and define the |
| 174 | + escalation-policy interface — small, mechanical, unlocks the extension |
| 175 | + point cleanly before the escalation mechanics themselves exist. |
| 176 | +3. **Refine's "wider" escalation** for verifiable tasks — ship the |
| 177 | + stronger-single-model fallback first; verifier-arbitrated mini-panel is a |
| 178 | + follow-up enhancement, not required for first ship. |
| 179 | +4. **Panel** — new fan-out dispatch + judge synthesis, its own opt-in |
| 180 | + command; independent of step 3, can proceed in parallel. |
| 181 | +5. **`auto` mode** — composes 1+3+4 once all three exist. Pure policy/config, |
| 182 | + no new execution machinery of its own. |
| 183 | + |
| 184 | +## 6. Risks |
| 185 | + |
| 186 | +- **Silent quality regression on Route.** A cheap model can silently |
| 187 | + underperform on a harder-than-expected task. Mitigated by Refine's |
| 188 | + escalate-wider path once §4.2/step 2-3 exist — don't ship Route's defaults |
| 189 | + as a dead end with no escalation path for long. |
| 190 | +- **Surprise.** A session should not silently feel like multiple different |
| 191 | + models without the user knowing. Surface "ran on {model}" per specialist |
| 192 | + call in the TUI (`internal/tui` already renders specialist tool-call |
| 193 | + dispatch — this is a display change, not new infra). |
| 194 | +- **Provider/quota sprawl.** Routing across more of the 25+ supported |
| 195 | + providers within one session raises concurrent auth/rate-limit surface. |
| 196 | + Not a new problem class (credstore already handles multi-provider auth), |
| 197 | + but exercise it under real routing load before shipping. |
| 198 | +- **Panel cost blowup if scope creeps.** The single biggest risk to the |
| 199 | + whole feature paying off is letting Panel's per-query cost multiplier leak |
| 200 | + into default behavior. Keep it opt-in-only, and keep `auto`'s escalation |
| 201 | + criteria to Panel deliberately narrow (unverifiable + low-confidence, or |
| 202 | + explicitly flagged high-stakes) — not "whenever unsure." |
| 203 | +- **`OutcomeAborted` today has no escalation consumer.** Until step 2 of the |
| 204 | + build sequence lands, `SelfCorrector` exhausting its budget is a dead end |
| 205 | + that surfaces `abortedSelfCorrectNotice` and stops. Refine's value only |
| 206 | + materializes once wider-escalation is wired — don't consider Refine |
| 207 | + "shipped" with only the deeper half. |
0 commit comments