dsh-fastswitch

Makes switching Sessions in DeepSeek Harness fast. Two things, each independently switchable.

中文：README.zh.md

What it fixes

When you switch a Session, DSH asks the Host for the opening history page. That page has a hard-coded window — at least 50 messages — which on a long conversation arrives as a 2 MB frame. That frame is the wait you feel.

Separately, while the page shells itself, several components each fetch the same read-only catalogs on mount: session/modelCatalog 6 times, credentials/describe 7 times, agentPresets/list 6 times, cotTranslation/limits 3 times. No deduplication, no cache.

dsh-fastswitch makes one change for each, in the browser:

1. Configurable opening window — rewrites turnWindow.minMessages (50 → 20 by default) on the outgoing session/follow request. The Host validates 0 < minMessages <= maxMessages, so this is a supported request, not a patch. "Load earlier" pages (200 messages) are left untouched.
2. Read-only RPC dedupe + cache — wraps window.fetch, caching read-only catalog calls for 5 minutes and collapsing concurrent ones into a single flight.

Measured

Same machine, same page, same conversation:

	default	with dsh-fastswitch
Opening snapshot (one long Session)	2,040,432 B	1,054,070 B
session/modelCatalog	6 calls	1 call
credentials/describe	7 calls	1 call
agentPresets/list	6 calls	1 call
Total requests on first paint	52	33

These come from a single measurement; they depend on conversation length and browser cache state, and are not constants.

Install

Search fastswitch in the plugin market, or:

dsh plugin --profile web add github:guofug/dsh-fastswitch

Restart once (or let HMR reload) afterwards.

Configuration

All through localStorage — no config files:

Key	Default	Meaning
dsh-fastswitch	—	set to off to disable everything
dsh-fastswitch-window	20	opening window size; 0 leaves it alone
dsh-fastswitch-ttl	300000	cache TTL in ms; 0 disables caching
dsh-fastswitch-merge	800	concurrent-flight window in ms

localStorage.setItem('dsh-fastswitch-window', '10')   // more aggressive
localStorage.setItem('dsh-fastswitch', 'off')          // turn it all off

Checking that it works

window.__dshFastswitch
// { installed: true,
//   ws: { rewritten: 3, untouched: 40 },
//   fetch: { calls: 51, hits: 10, dedup: 8, bypass: 33 } }

• ws.rewritten should increment once per Session switch;
• fetch.hits + fetch.dedup is the number of requests saved.

Scope

• Browser only. Terminals, the SDK, ACP and other clients are unaffected.
• Modifies no DeepSeek Harness file and no Host behaviour. The window is a rewritten outgoing request; the cache is a browser-side fetch wrapper. Uninstall and everything is back to stock.
• No Session parking cache. Keeping opened Sessions in memory for instant switch-back would mean operating on Session lifecycle internals, which breaks across versions. Deliberately out of scope.
• Caching covers read-only catalogs only. No writes, no streaming responses, no auth endpoints.

Compatibility

• Targets dsh ^0.2.1-rc.2 (see engines.dsh).
• Both wrappers are idempotent, so HMR reloads do not stack wrappers.
• If either wrapper cannot be installed it is skipped; the page degrades to stock behaviour instead of breaking.

License

MIT