Yichen Jiang
3d68185480
The Web overlay disables base's 32 agent-plane rows and mounts the preset roster instead, so each session composes its own tools and prompt rather than sharing one process-wide set. The TUI keeps base unchanged: it is single-session and composing its agent process-wide is correct there. `roots` is patched in by AppCLIEntry, like `distIndex`: the shipped presets sit beside the composition that names them and the user's live under the Harness home, neither of which a config author chooses. A session's preset is fixed at creation. Naming a different one for an existing identity is `agent-preset-conflict` rather than a switch, because that session's history was produced under the first preset's tools. The guard sits after `await creation`, beside the cwd check, so it covers every path that yields a live agent — freshly created, adopted live, resumed, or recovered by the concurrent-creation catch. A request naming no preset adopts the session as it is, keeping reconnect and retry ordinary. Two bugs the real-composition test caught, both invisible to unit tests: `PresetTree` now refuses to write. The Loader persists a tree whose plugin self-disposed, and tearing an agent down disposes its whole subtree — inherited, that rewrote the shipped composition, truncating a 241-line preset to `[]` the first time a session ended. `dsh-tool-skill` compared against a lookup of its own name in the global layer, so it threw inside any preset: `register()` files into the calling context's scope. It now compares against the definition it registered, which is what the identity check meant all along. The `standard` catalog is asserted exactly, not spot-checked: a row that registers into the wrong layer mounts cleanly and simply contributes nothing, so an omission is this design's quietest failure. It matches the shipped TUI catalog plus `glob`/`grep`, the pair that composition documents as ripgrep-dependent. Re-records `cordis-inspect-jsdoc`, whose rendered `SessionHeader` gains the `agentPreset` field. `fs-glob-sampling` fails identically on pristine master and is untouched here. The browser e2e scaffold gains the roster fact AppCLIEntry supplies. `roots` is resolved and patched in by the CLI entry, like `distIndex` on the webserver row, and this lane boots the shipped tree without that entry — so it has to supply the same fact or the roster resolves nothing and every session in the lane composes an agent with no tools, no persona, and no token meter. Only the shipped root: a developer's own `~/.dsh/.agent-presets` must not decide a golden. The `cordis:group` builtin comes with it, exactly as `boot()` registers it, because a preset resolving package names from its own directory cannot reach `@cordisjs/plugin-group` by name. The lane stays red through this layer and the next four for the reason stated above — the api-proxy injects `subagents`, `workspace`, and `tools`, so `api-gateway` cannot activate and the browser has no `/api` at all. It goes green again in the layer that returns those registries to the host plane; this change is what makes that layer's fix sufficient rather than partial.
dsh-agent-presets
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Per-session agent composition. A preset is a directory holding one agent.cordis.yml; mounting it under an agent's scope context gives that one session its own tools, prompt sections, and other model-facing contributions, while every other live session keeps its own.
The mechanism is entirely Cordis: entry contexts chain to the context a subtree was plugged into, and both dsh-tools and dsh-system-prompt file registrations into the calling context's scope layer. Mounting a composition under agent.ctx therefore makes it that agent's alone, and unwinds it with the agent, without any new layering in those registries.
Service: AgentPresets (ctx key: agentPresets)
Discovery is unmemoized: list() and resolve() re-read the roots on every call, so a preset authored while the process runs is visible immediately and a deleted one disappears from the next read.
ctx.agentPresets.defaultId: stringThe preset id mounted when a caller names none.ctx.agentPresets.list(): Promise<AgentPreset[]>Every preset the configured roots currently supply, earlier root winning a duplicate id.ctx.agentPresets.resolve(id?): Promise<AgentPreset>One preset by id, defaulting todefaultId. Throws naming the available ids when no root supplies it.ctx.agentPresets.mount(agentCtx, id?): Promise<AgentPreset>Compose one agent from a preset and return the preset that was mounted, for the caller to record.
AgentPreset carries id (the directory name), trust (system or user, from the root it was found under), and path (the absolute composition file).
Where to call mount()
The agent factory's setup(agentCtx) hook is the one supported call site. Only there is the composition installed while the agent is still unpublished, so a rejected mount rolls the whole creation back rather than leaving a half-composed session. The subtree is owned by agentCtx's fiber, so it unwinds with the agent and the caller receives no disposer.
Config
| Field | Default | Meaning |
|---|---|---|
default |
required | Preset id mounted when a caller names none |
roots |
[] |
Scanned directories in precedence order; each supplies path (a leading ~ expands) and trust (defaults to user) |
An absent root supplies no presets rather than failing: the user root does not exist until the first locally authored preset, and naming a default no root supplies already fails loud at resolution.
What a mount rejects
A directly-plugged subtree is absent from ctx.loader.entries(), so no boot audit covers it. mount() therefore proves the result usable itself, and rejects three things.
An unscoped target. Mounting into a context that carries no agent scope would register the preset's tools globally, for every agent in the process.
A row that never became usable. The loader already rejects a row whose module failed to import or whose plugin threw; what remains is a row still waiting for a service the composition never supplies, which the audit names.
A row that published a service into the root realm. Such a service is process-global rather than per-session, so the second session mounting the same preset collides with the first. A preset that genuinely owns a service puts it behind an isolate realm — entry-local for one session's private instance, or a shared label when several sessions should share one — or the service belongs in the host composition instead.
The package invariant re-checks that last rule on every service notification, because a row that publishes from a timer or an asynchronous continuation would escape the one-shot audit.
Trust
Presets are compositions, so a preset is exactly as privileged as the plugins it names. A user preset — authored by a person or by an agent — carries the same trust as shell access; the trust field exists so consumers can present that difference, not to enforce it.
Model Experience
Indirectly, through the plugins a mounted composition registers, which own every tool schema and prompt section the preset makes visible to its one agent.
KV Cache effect
Prefix-stable for the life of an agent: a composition is installed once, before the agent is published and therefore before its first request, and is never re-read while the agent runs. Choosing a different preset for a new session establishes a different prefix for that session alone and cannot invalidate reuse for any session already running.
Known Limitations and Deferred Work
- A preset cannot be changed on a live agent — the mount happens once during creation, so switching a running session's composition would mean unwinding its subtree mid-turn, dropping tools the model may already have called. Changing the default affects only sessions created afterwards.
- Display names are the directory id — a preset carries no manifest, so pickers and settings surfaces show the id until a consumer needs richer metadata.
- Root scans are not watched — every read hits the filesystem instead, which keeps the roster fresh but puts one
readdirper root on eachlist().