Model Switch

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Choose one explicit route for Main, Subagents, Web Search, image generation, the active conversation, and Plan execution in DeepSeek Harness. Model Switch uses public DSH services and provider-owned adapters; it does not patch DSH Core or manage provider credentials.

Routes

Route	Behavior
Main model	Default provider, model, and optional effort for newly created sessions. Existing sessions are not migrated.
Subagent	Follow the active parent route, or use a fixed provider/model/effort. Workflow overrides remain authoritative.
Composer Picker	Changes only the active session and submits the exact catalog model id. Main defaults are preserved.
Plan Review	Chooses the execution model before the Plan approval response is sent.
Web Search	Keeps the official web_search tool and routes it through the selected Codex search adapter.
Image generation	Provides one stable generate_image tool routed through a selected Codex or Grok adapter.

Invalid, unavailable, or unsupported routes fail explicitly. Model Switch never silently falls back to another provider or model.

Configure Main and Subagents

Open Settings → Model Switch. Main changes affect new sessions only. Subagents may follow Main or use a fixed provider, model, and effort.

Follow Main resolves the active parent request first, then the configured Main default. A fixed route is injected before the official Subagent descriptor is created. On DSH 0.1.1-rc.2, child effort falls back to the provider default because that runtime cannot carry the alpha.1 effort field.

How custom models appear in the Picker

Model Switch does not turn an arbitrary string in its own settings into a model. A provider plugin must publish the model to the official DSH model catalog first:

Provider configuration
→ provider publishes model rows to the DSH catalog
→ the active session Model Directory exposes provider/model metadata
→ Model Switch groups those catalog rows
→ the Picker submits the original provider id and model id

The catalog supplies the provider name, model id/name, reasoning efforts, and default effort. A saved route that is no longer present remains visible as unavailable in Settings; the Picker does not pretend it is routable.

Variant id grammar

Model Switch groups catalog rows by provider and by the model id after peeling these suffixes:

Catalog model id	Picker variant
acme-v1	Standard row
acme-v1-fast	Fast
acme-v1-128k	Context 128K
acme-v1-1m	Context 1M
acme-v1-1m-fast	Context 1M + Fast

Rules:

• -fast creates the Fast axis.
• -<n>k and -<n>m create Context tiers; suffixes may be combined with -fast in either order.
• reasoning.efforts creates the Effort choices; reasoning.defaultEffort selects the initial value.
• Reasoning metadata marks a catalog row as Thinking-capable.
• Unrecognized ids remain independent model families; Model Switch never drops them.

To support a combined selection, the provider must publish the combined row. Publishing only acme-v1-fast and acme-v1-1m cannot represent Fast + 1M; publish acme-v1-1m-fast as well. The Picker never synthesizes a model id that the provider did not publish.

Plan Review

Plan Review owns an execution-model draft separate from Main. Confirm first commits that model to the active session, then answers the pending Plan review. A failed model commit leaves the review pending and retryable. Reject and Discuss in chat do not execute the Plan.

What Model Switch does not change

• web_fetch and its configured provider
• Vision routing, read_image, and ordinary chat attachments
• Provider login, credentials, or provider settings cards
• Official Agent Presets
• Existing provider-specific image tools
• Existing sessions when the Main default changes

Installation

Install Model Switch and only the provider adapters you use. These versions are validated with DSH 0.1.2-alpha.1:

DSH_HOME=~/.dsh dsh plugin --profile web add github:NOirBRight/dsh-llm-codex#v0.3.3
DSH_HOME=~/.dsh dsh plugin --profile web add github:NOirBRight/dsh-llm-grok#v0.3.3
DSH_HOME=~/.dsh dsh plugin --profile web add github:NOirBRight/dsh-model-switch#v0.4.1

For routed Web Search, set the existing Web plugin's searchProvider to model-switch and preserve its current fetchProvider. Model Switch never replaces web_fetch.

If dsh-composer-picker is installed, remove it from the profile before enabling Model Switch. Model Switch already owns the Composer Picker and Plan Review seat; two owners produce duplicate or competing UI.

Production profiles must use released GitHub tags rather than workspace-local dependencies. Restart the selected DSH profile after installation or route changes.

Compatibility

Model Switch v0.4.1 supports DSH 0.1.1-rc.2 and DSH 0.1.2-alpha.1 through plugin-owned compatibility adapters. Alpha.1 adds fixed Subagent effort transport and replaces the removed monolithic client runtime with public Cordis/client services. No DSH Core patch is required.

Development

Requires Node 22.19+ and pnpm.

pnpm install
pnpm run check

check builds Host and Client artifacts, runs unit and Cordis/Settings composition tests, validates the extracted package, and verifies reproducible bundles. Product scope is defined in PRODUCT.md; implementation constraints live in IMPLEMENTATION_PLAN.md.