Compatibility

• DeepSeek Harness dsh-v0.1.6-alpha.2 (adapted 2026-09-18): the session surface is read through the optional sessionQuery service — the deprecated synchronous Session.eventAt(seq) accessor is gone, with an equivalent synchronous read as the fallback — and every registration now lives in one lifecycle effect that releases them in reverse order. Internal implementation change: the reported metrics are identical for the same log. Verified 2026-09-18 against the local gate chain (dual typecheck rulers + 70 tests); the compat workflow re-runs the profile install smoke against the published pins.
• Node ^22.19.0 || >=24.0.0, ESM only ("type": "module").
• Peer dependencies: @deepseek-ai/cordis ^4.0.2, @deepseek-ai/schemastery ^3.18.2, and @deepseek-ai/dsh-session, @deepseek-ai/dsh-tools, @deepseek-ai/dsh-commands, @deepseek-ai/dsh-compaction, @deepseek-ai/dsh-session-query, @deepseek-ai/dsh-storage-domain at >=0.1.2-rc.1 <0.2.0 || >=0.1.5-alpha.1 <0.2.0 || >=0.1.6-0 <0.2.0 (devDependencies pin 0.1.5-rc.2); the 0.1.2-rc.1 line stays supported at runtime through a structural fallback to the pre-0.1.5 header.system.

What you get

• Session load timing — publication-to-first-request latency, classified open (fresh) vs restore (seeded/resumed), plus the restored seed-event count.
• Spill-hit statistics — how many tool results were spilled to a session-scoped artifact (detected from the durable spill notice).
• Compaction count and trigger — total compactions, split manual (slash command) vs automatic (pressure), and total shadowed tokens.
• Context-injection volume — system-prompt (AGENTS.md + skills + persona), tool-schema, and surface tokens with their shares of the total; the surface bucket is conversation history only (the meter's surface includes the system node on 0.1.5-alpha.1, which dsh-fast subtracts).
• LLM cache hit rate — input / cache-read / cache-write / output tokens aggregated from provider usage, plus the derived hit rate.
• Optimization suggestions — threshold-driven notes (trim skills, tighten tool schemas, compact earlier, enable prompt caching, enable spill-policy, …).
• Async sampling — metrics are folded O(1) per event and snapshotted on a timer, never on the append path.

Quick start

git channel

# From a scratch profile (pins the commit; runs the self-contained `prepare` build)
dsh plugin --profile demo add "github:YOUR_ORG/dsh-fast#<sha>"
# The profile's pnpm-workspace.yaml gains an allowBuilds entry for dsh-fast on first add.

npm channel

dsh plugin --profile demo add dsh-fast

Both channels install the bundle row (see cordis.patch.yml) into the profile's dsh.profile.bundles stack and take effect on restart.

Install & uninstall

dsh plugin --profile demo add dsh-fast       # install
dsh plugin --profile demo remove dsh-fast    # uninstall

Verify the row mounts: dsh --profile demo --dump-config | grep dsh-fast.

Configuration

All tunables are Schemastery Config fields; invalid values fail the profile load loudly.

Tools & surfaces

• /fast — a human slash command that prints the current session's health report: load timing, spill, compaction, context-volume ranking, cache hit rate, and suggestions.
• fast_report — a model tool returning the same report as structured JSON (so the model can reason over it), with a human-readable text render.

Permissions & data

dsh-fast consumes only public seams: session/* and agent/* events, the optional ctx.tokenMeter, ctx.storageDomain, ctx.commands, and ctx.tools. It is strictly read-only over the session log — it never mutates the model request, tool results, or the session surface. Metrics are persisted to the dsh_fast storage domain (one bounded history per session), not to the session log. Report identity and the optional working directory are sanitized before any display or durable write.

Security boundaries

• Read-only, zero model-path overhead — folding is O(1) per event; sampling runs on a timer.
• No network, no credential handling — the plugin makes no outbound requests and stores nothing sensitive.
• Fail-loud configuration — every tunable is validated at mount; invalid bounds throw.
• Sanitized display/durable data — control characters are stripped and strings are budgeted; cwd is off by default and path-truncated when enabled.
• Reversible registrations — every contribution goes through ctx.effect() / ctx.on() / register(), so uninstall and hot reload are clean.

Known limitations

• Storage domain, not session events — rc.2 Session.append offers no ignorable marker and no external event-registration surface, so a custom fast/* session event would make the persistence coordinator refuse the log on restore. Metrics are therefore persisted to the storage domain; the raw events remain the reconstructable source of truth.
• Spill detection is heuristic — it reads the durable spill notice (Full … stored at:); no dedicated session event exists.
• System prompt is one bucket — AGENTS.md, skill directory, and persona are all part of the assembled system prompt; since 0.1.5-alpha.1 it is surface node 0 (a system/message) and carries no per-section token accounting, so they are reported together.
• Load timing starts at publication — the disk-read portion of a restore happens before session/created (owned by sessionPersistence) and is not observable from this plugin's allowed events; the reported duration is publication-to-first-request.
• Degradations are announced once — a host without tokenMeter falls back to heuristic token pricing, a host without systemPrompt attributes the whole prompt to one bucket, and a failing inspector outlet is ignored; each of these now says so once per process instead of changing what the numbers mean in silence.

Development

pnpm install
pnpm run typecheck && pnpm run typecheck:ci
pnpm test
pnpm run build
pnpm run verify:self-contained && pnpm run verify:artifacts
node scripts/check-readme-sync.mjs
pnpm pack

Topics

dsh, dsh-plugin, deepseek-harness, deepseek, cordis, performance, diagnostics, profiling, context-engineering, llm-cache

Contributors

Thanks to everyone who has contributed to dsh-fast:

• PerryLink — author and maintainer: designed and built the read-only diagnostics (session-load timing, spill-hit counts, compaction metrics, context-injection volume, LLM cache hit rate), the /fast command and fast_report tool, the dsh_fast storage domain, and the five-language documentation.

PerryLink DSH Plugin Family

This project is one of the 41 DeepSeek Harness plugins maintained by PerryLink. If this one helps you, the others likely will too:

Install from the DSH Desktop Market

All PerryLink plugins are browsable in the built-in DSH Desktop Market: Market → Sources → add source → paste https://perrylink-dsh-catalog.perrylink.workers.dev/catalog-source.json → select it. Installation still goes through the Market's npm-identity verification and your confirmation.

License

Apache-2.0 — see LICENSE.