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dsh-shift-router
A two-tier model router for DeepSeek Harness — automatic execution/judgment routing with an LLM Judge, multi-model fallback chains, exponential-backoff runtime failover, and task-level orchestration.
A DSH adaptation of pi-shift-router.
Ported from upstream v1.0.0; aligned with upstream v1.6.0 — see
ROADMAP.md for the per-version table and
SPEC.md for the contract.
Routine turns shouldn't cost flagship money. The turns that matter shouldn't be left to a cheap model.
Before every turn of a top-level agent, a small LLM Judge (running on your Fast-tier model chain) classifies the user's message as fast (routine) or smart (consequential). The chosen tier then drives the whole turn — thinking, tool calls, code edits — through the harness's own agent/request pipeline. The Judge only classifies; it never does the work.
🦾 [deepseek-v4-flash] → fix the failing test
🧭 judging…
🧠 [deepseek-v4-pro] ← "design the auth flow" → upgraded instantly
⚠️ deepseek-v4-flash 429 → cooldown, retrying on glm-5.2 — retry in 1m
🦾 [glm-5.2] ← same-tier failover
Features
- Expected-cost routing — the turn runs Smart iff
pSmart ≥ θ, with θ = 1/reworkPenalty: the bar is price-independent, so the one knob is how badly a wrong downgrade hurts. Upgrades are instant; coming back down needs downgradeMemory consecutive decisive fast turns. A Judge outage or an unsure verdict is a hold — the router keeps its position instead of guessing.
- Cache-aware routing — when Fast and Smart share a provider, the decision bar is divided by
sameFamilyPenalty (default 1.5) and downgrades are held off while the prompt cache is warm, so switching to a cheaper model never costs more than staying put.
- Runtime failover — 429 / 402 / 5xx / quota / usage-limit / unsupported-model failures put the model into exponential-backoff cooldown (1m → 4m → 16m → 1h04m → 4h16m → 6h cap; client-side limits start at 16m) and re-resolve the same tier to the next healthy model — same-turn retry, never cross-tier.
- Task-level orchestration — complex tasks run the Smart tier as a CTO that plans, delegates implementation to Fast engineer subagents via the harness's
subagent tool, reviews each result, and iterates. The hard caps are enforced by the plugin, not just prompted: each delegation counts a round, consecutive worker failures count an escalation, and once a cap is hit the subagent tool is denied outright and the system prompt switches to a "wrap up now" notice.
- Cost telemetry — per-tier token tracking and an optional USD pricing table (
/router status shows "what this session would have cost on the Smart model").
- Visible when it acts — a tier or model switch is written into the transcript as a
[shift-router] Fast → Smart · … notice (the harness has no status-bar seat for plugins), so an enabled router is never silently invisible. Set ux.routerLogVerbose to get one notice per judged turn, not just per switch.
- Zero-config startup — a no-op until you configure tiers; then routing just works. Configuration is editable live via the GUI settings panel and
/router config commands (persisted, no restart).
Install
This package is a DSH bundle: its cordis.patch.yml inserts the plugin row
into any profile that lists it. Every channel below ends in the same
dsh plugin --profile <name> add …, which forwards to pnpm inside the profile
directory.
From npm (recommended)
dsh plugin --profile web add dsh-shift-router
Installs the prebuilt artifact — no build script runs on your machine, so there
is nothing to authorize.
From a tarball
npm pack # or download the release tarball
dsh plugin --profile web add ./dsh-shift-router-0.6.0.tgz
Prebuilt as well, and the option to reach for when a registry is not available.
From git
dsh plugin --profile web add github:green-dalii/dsh-shift-router#v0.6.0
A git install fetches source, not artifacts, so the package's prepare
script builds dist/. pnpm ≥ 10 refuses a git dependency's prepare until you
allow it — if the first add fails, copy the exact key pnpm prints into the
profile's pnpm-workspace.yaml and re-run:
allowBuilds:
dsh-shift-router: true
This authorizes the package's code to execute on your machine at install time,
outside the agent sandbox. Pin a tag or commit (…#v0.6.0, …#<sha>) so a
later push cannot change what you actually run.
From a local checkout (development)
git clone https://github.com/green-dalii/dsh-shift-router.git
cd dsh-shift-router && npm install && npm run build
dsh plugin --profile web add /path/to/dsh-shift-router
Verify the layer landed
dsh --profile web --dump-config | grep -A3 'id: shift-router'
The plugin loads with no configuration at all (every default is safe); tier
models come from the settings card (SPEC §12) or from the profile's patch row.
Later layers win, and a patch replaces the target row's whole config value
— a row that overrides this one must restate every key it needs (SPEC §10).
Hot reload
DeepSeek Harness supports hot reload through @deepseek-ai/cordis-plugin-hmr, but two things are worth knowing:
-
The official Web bundle ships the shared HMR row disabled (packages/bundle/web-app/cordis.patch.yml has - id: hmr, disabled: true, upstream TODO: "Re-enable shared HMR for Web after its reload lifecycle is tested"). Re-enable it in your profile patch — this is the documented override mechanism:
# ~/.dsh/profiles/<name>/cordis.patch.yml
- id: hmr
disabled: false
-
What hot-reloads and what doesn't (verified against the current implementation):
- ✅ Configuration changes — editing this profile patch (or the home patch) re-runs the affected plugin's
apply() with the new config, no restart. The plugin's own config is also hot through the settings namespace (/router config set and the GUI card apply live without HMR at all).
- ❌ Module (code) changes — the HMR accepted-dependency graph currently covers the harness's own modules only; editing an external plugin's compiled files (e.g.
dist/index.js) does not trigger a reload in the current release, so code changes still require a restart. This is the untested "reload lifecycle" the upstream TODO refers to, not a limitation of this plugin.
- ❌ Client package metadata — the
dsh.client manifest and exports["./client"] are cached in-process; adding/fixing them requires a profile restart (only dist/client.js content changes ride the client HMR rebuild chain).
In practice: configure with /router config / the settings panel (always live), switch models by editing the patch (live once HMR is on), and restart only when you change plugin code.
Configuration
Configuration lives in the shift-router settings namespace: edit it in the GUI (Settings → Plugins → Plugin configuration — the "Shift-Router" card), with /router config commands, or via the profile patch row. All fields have safe defaults.
| Field | Default | Description |
|---|
enabled | true | Master switch |
tiers.fast.models | [] | Fast-tier chain (provider/model + priority); also the Judge's model chain |
tiers.smart.models | [] | Smart-tier chain |
routing.mode | auto | auto (default): judge + routing + failover + orchestration; manual: no judge, only explicit /route-force overrides; off: fully passive for model selection (commands/telemetry still work) |
routing.judgeTimeout | 5000 | Judge call timeout (ms) |
routing.judgeMaxTokens | 4000 | Max output tokens for a single Judge call |
routing.judgePromptCap | 6000 | Max prompt characters sent to the Judge (bounds Judge cost) |
routing.economics.reworkPenalty | 3 | R — how many price-deltas a wrong downgrade costs. The turn runs Smart iff pSmart ≥ θ, where θ = 1/R: higher R → lower θ → stickier on Smart |
routing.economics.downgradeMemory | 2 | Consecutive decisive fast turns required before Smart → Fast (a hold or a smart verdict resets the streak) |
routing.economics.mode | (unset) | Named gear preset, authoritative over reworkPenalty: eco (R=2, θ=0.5) / default (R=3, θ≈0.33) / sport (R=5, θ=0.2) |
routing.window.size | 5 | Decision-memory window size |
routing.window.threshold | (unset) | Legacy raw-θ override. The pre-EV default 0.6 is inert; only a different value is honoured (and flagged in ) |
All numeric fields are range-validated by the schema (e.g. window.minConfidence must be in [0,1], window.size a positive integer); invalid values are rejected at load / on set, never silently accepted.
Upgrading from v0.5.0: routing decisions change immediately with no config
edit — the decision rule went from counting window votes to weighing expected
cost, and two legacy knobs changed meaning. See
SPEC.md §15
and the [0.6.0] section of CHANGELOG.md.
GUI configuration card
The package ships a browser-side (client) module that registers a "Shift-Router" card in the GUI settings page:
- Where: Settings → Plugins → Plugin configuration (that page is provided by the official
dsh-client-ui-settings-plugins; the card registers into the settings.plugin.item slot).
- What: a form over every scalar leaf field (booleans, numbers, enums) plus the two tier model chains, grouped into seven sections (General / Models / Routing / Orchestration / Failover / Telemetry / Logs & UX) with sub-groups for the routing section (Judge / Decision window / Cache-aware). Scalar fields use the compact settings-row pattern — label + hint on the left, control right-aligned on the same line — so each field is one tight row instead of three stacked lines. Controls use the host-plane design tokens: toggle switches (contrast-safe in light and dark themes), a styled select for enums, unit suffixes inside numeric inputs (
ms, tokens, 0–1, …), and an ordered row editor for model chains — the row order is the in-tier fallback order, so the first available model wins and the rest are its fallbacks. The provider/model dropdowns are auto-loaded from DSH's runtime model catalog (llm.models — the same catalog the DSH settings surface reads): only providers with a currently advertised model list appear, no dormant-directory noise, and nothing is hardcoded, so the card works with any deployment's configured models. A "Custom…" escape covers values outside the catalog. Staged saving, per-field reset to default, and override markers work exactly like the official cards.
- Boundary: only
pricing (the optional USD cost table) stays with /router config and the profile patch; the tier model chains are editable in the card.
- Build:
npm run build emits both the host artifact (dist/index.js) and the client bundle (dist/client.js). The client module is discovered through the dsh.client manifest by dsh-client-modules, which requires the plugin to be mounted by package name (dsh-shift-router) — a source-checkout patch (name: '/path/dist/index.js') does not serve the card.
Legacy harnesses only: the Web settings whitelist (≤ 0.1.0-rc.x)
Harness builds up to 0.1.0-rc.x filtered a third-party settings namespace out of
the browser's settings.describe response unless it appeared in
WEB_SETTINGS_NAMESPACES — which is why scripts/expose-gui-settings.mjs exists: it
patches the profile's installed dsh-host-apiproxy (idempotent; re-run after a
dependency upgrade). From 0.1.5-rc.2, this project's baseline, that package and its
whitelist are gone and the namespace is exposed natively, so the script reports
"not needed" and exits 0. It is not part of the published package (files), so it is
only reachable from a source checkout.
Commands
| Command | Effect |
|---|
/router | Compact status |
/router status / /router stats | Full status: gear (R → θ), tiers, decision window (holds shown as h), the last decision and why, the model that actually ran vs the router's intent, worker delegation (Worker delegation:), transitions, cooldowns, tokens, cost telemetry |
/router on / /router off | Enable / disable (session-scoped) |
/router verbose / /router log | Toggle verbose router logging |
/router orchestrate auto|off | Orchestration mode |
/router allow-workers [on|off] | Authorise this plugin's Fast-tier routes in the harness subagent-model-selection allowlist, so workers can be pinned to Fast (off revokes, keeping the routes). Reports exactly what it wrote, or why it could not |
/router eco / /router default / /router sport | Gear presets: set routing.economics.mode (persisted) — cheaper ↔ stickier on Smart |
/router config | Interactive editor: numbered field list with current values + available providers + usage |
/router config get <N|path> | Show one field's current value, e.g. get 4 or get routing.judgeTimeout |
/router config set <N|path> <value> | Set one field (persisted), e.g. set 4 8000, set tiers.fast.models [...] (JSON values auto-parsed) |
/router config unset <N|path> | Clear a user override — the field reverts to its composition default |
/router config diff | List the overrides the user layer currently holds |
/router config set-fast <provider/model> | Replace the Fast tier chain with one model |
/router config set-smart <provider/model> | Replace the Smart tier chain with one model |
/router config reset | Restore the composition default |
How it works (DSH integration)
The mechanism-by-mechanism mapping is normative and lives in
SPEC.md §1.1. Two things are worth stating here because they are
not in that table:
- Throughput is deliberately absent. DSH renders
tok/s natively (chat footer, trajectory panel)
from decode time; the router owns routing decisions and spend, not rate display.
- Subagents are never routed. Workers spawned by the
subagent tool carry
session.header.origin === 'subagent' and keep their pinned model; the router drives top-level
agent turns only.
Orchestration and the DSH subagent tool
Upstream calls the per-worker model pin mandatory: without it a worker inherits the parent's
model — Smart mid-orchestration — and the economics collapse. In DSH that pin sits behind a
host-owned allowlist (subagent-model-selection, default off), so instead of asserting a
guarantee it cannot keep, the router:
- writes the Fast chain into that allowlist for you (
/router allow-workers — the one step it
cannot take at composition time);
- says so where you can read it when the allowlist is absent: a
Worker delegation: line in
/router status (the ctx.logger copy is visible only where a log exporter is mounted);
- tells the CTO, factually, where a worker's model comes from.
The caps (maxRounds, consecutive-failure escalation, maxSpendUsd) are enforced by the
router, not merely prompted: at the cap the subagent tool is denied and the prompt section
switches to a wrap-up notice, with live counters in /router status. A run that actually delegated
is also audited — deterministic checks always, one detached Fast-tier review when enabled, never
blocking a turn — surfacing as Last audit:. Contracts: SPEC §7.3, §7.4, §7.4.1.
Development
npm run build # tsc (host → dist/) + tsc client + tsdown (client bundle → dist/client.js)
npm test # vitest (336 tests across 18 files: EV routing / failover signatures / judge parsing + prompt contract / orchestration / config schema + migration / telemetry / route notices / config registries + GUI form model + card UX + model catalog / packaged-install contract)
npm run typecheck
End-to-end test (no credentials)
e2e/ contains a fake LLM adapter that registers the fake provider, so the whole routing pipeline can be exercised without any API key:
npm run test:e2e
That builds a throwaway DSH_HOME, installs this checkout as a bundle into a derived
headless profile, runs one turn through the fake adapter, and asserts:
ROUTER-E2E: turn ran on fake/fake-smart notice=yes — the Judge ran, the EV rule escalated,
the wire model was actually switched to the Smart tier, and the [shift-router] route notice
reached the model request (SPEC §13.1);- the same outcome under
e2e/legacy-config-overlay.yml, a profile patched with the
pre-alignment config (the legacy knobs at their old defaults plus the removed
requireSmartModel key) — i.e. the upgrade path, not just a fresh install;
- the same outcome under
e2e/orchestration-overlay.yml, which uses the plugin's
default orchestration mode (auto) and mounts the web-only
subagent-model-selection-settings row beside it — the composition that once aborted
the boot;
- the
shift-router settings namespace round-trips a write, and the Host model catalog
advertises the deployment's configured routes (e2e/settings-probe.mjs);
- a packed install (
npm pack → tarball → second scratch profile) boots with the
plugin loaded, its browser half offered to the client module loader, and no
@deepseek-ai/* copy installed into the profile — devDependencies are absent there, so a
runtime import that is not declared for the consumer fails in the e2e instead of in a
user's install.
It never touches your real DSH_HOME and cleans up after itself (--keep to inspect). To run
the same thing by hand, install the bundle into a scratch profile and apply the overlay:
DSH_HOME=/tmp/scratch dsh plugin --profile tmp add /path/to/dsh-shift-router
DSH_HOME=/tmp/scratch dsh --profile tmp --patch e2e/overlay.yml "design a migration plan"
Architecture
src/
├── index.ts # plugin entry: event wiring, per-agent state, judge, route notices
├── config.ts # Schemastery schema + deep-merge normalization
├── types.ts # shared types + defaults
├── router.ts # pure routing engine (upgrade/downgrade/window/cache-aware)
├── judge.ts # LLM Judge via ctx.llm.stream() + reply parsing
├── failover.ts # exponential-backoff cooldown state machine
├── tier.ts # tier model resolution + display
├── notice.ts # pure: route-notice text + summary (SPEC §13.1)
├── orchestrate.ts # orchestrator prompt + lifecycle + caps
├── audit.ts # non-blocking acceptance audit of delegated runs
├── stats.ts # telemetry snapshot (tokens / cost estimate / savings baseline)
├── commands.ts # /router and /route-force
└── client/ # browser half (GUI settings card)
├── index.tsx # client entry: registers into the settings.plugin.item slot
├── controller.ts # staged form → settings-scope writes (one per section)
├── form-model.ts # pure logic: field registry / draft parsing / save plan
├── card-ux.ts # pure logic: thresholds, chain problems, header summary
├── model-catalog.ts# Host model catalog → provider/model options
├── ShiftRouterCard.tsx # card component (DSW design tokens)
└── locales.ts # zh/en dictionaries
Pure logic (router / failover / judge parsing / orchestration / audit / route notices / the form model, card UX and catalog loader) is unit-tested in isolation. Wiring is tested in two layers: tests/plugin-load.test.ts loads the plugin through a real Cordis context and drives the real agent/pre-step waterfall (so an undeclared service read, an invalid prompt-section order, or a missing route notice fails fast), and the e2e boots scratch profiles — including the packed artifact and the plugin's default orchestration mode.
License
MIT © 2026 green-dalii and contributors.
