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# DeepSeek Harness Architecture
This document describes the architecture of the DeepSeek Harness — the foundation of **DeepSeek Code**. The governing principle: **everything is a plugin**. The core is deliberately tiny — a handful of abstract services plus one concrete loop plugin (`dsh-agent-loop`) — and every product feature is a plugin against the extension surface described here, without modifying the loop. The stack is three tiers: plugins (the loop itself, seam implementations, model-facing tools, bridges) over interface/service packages (each owning one `ctx` key and its vocabulary) over the vendored Cordis kernel (`vendor/`).
The **DeepSeek Harness SDK** is an SDK for building agent harnesses using the Cordis framework. The governing principle is simple: **everything is a plugin**. For example, the shipped agent loop is just one plugin in the default bundle, not a privileged kernel.
This document covers **behavior**; type shapes live in [core-data-structures/](core-data-structures/core.md), the per-event/service reference in the generated [events](cordis-catalog/events.md) / [services](cordis-catalog/services.md) catalogs, visual relationship maps in the [documentation graph index](graph-atlas.md), and per-package contracts in the package READMEs ([map](../packages/README.md)).
Read this page as the system map before changing `packages/`. It explains how the runtime is shaped, how the default loop moves work, where state lives, and where extensions attach. Type shapes live in [core-data-structures/](core-data-structures/core.md); exact event and service signatures live in the generated [events](cordis-catalog/events.md) and [services](cordis-catalog/services.md) catalogs; package contracts live in the [package map](../packages/README.md); rationale lives in the [RFCs](rfc/README.md). If Cordis itself is new to you, start with the [Cordis primer](cordis-primer.md).
## Service map
## System Shape
The spine — the product API under `packages/core/`:
A running harness is one Cordis context. Packages contribute service keys, typed events, and disposable registrations to that context. Services are the stable call surfaces (`ctx.llm`, `ctx.tools`, `ctx.sessions`); events are interception and notification points (`agent/request`, `tools/pre-execute`, `session/event`); registrations install prompt sections, tool schemas, providers, adapters, and listeners.
The default distribution is a composition, not a hierarchy. `packages/core/` is a repository grouping for the default agent spine; capability seams around it are equally first-class plugins from a Cordis perspective.
### Default Service Spine
| ctx key | Package | Role |
|---|---|---|
| `ctx.sessions` | dsh-session | creates/holds event-sourced `Session`s |
| `ctx.systemPrompt` | dsh-system-prompt | ordered sections + tool schemas → `assemble()` |
| `ctx.tools` | dsh-tools | tool definitions; `execute()` through waterfall |
| `ctx.agents` | dsh-agent | live `Agent` handles + create/resume factory (returns `AgentHandle { agent, dispose() }`) |
| `ctx.agentLoop` | dsh-agent-loop | THE concrete loop plugin: creates and drives `ReactLoopAgent`s |
| `ctx.sessions` | `dsh-session` | in-memory event-sourced sessions |
| `ctx.systemPrompt` | `dsh-system-prompt` | ordered prompt sections plus tool schemas |
| `ctx.tools` | `dsh-tools` | tool registry and [execution pipeline](tool-execution-pipeline.md) |
| `ctx.agents` | `dsh-agent` | live agent registry, public `Agent` handle, `agent/*` vocabulary |
| `ctx.agentLoop` | `dsh-agent-loop` | shipped `ReactLoopAgent` driver |
The swappable capability seams:
### Capability Services
| ctx key | Package | Role |
| ctx key | Package family | Role |
|---|---|---|
| `ctx.llm` | dsh-llm | adapter registry; `stream()` |
| `ctx.sessionPersistence` | dsh-session-persistence | durable persistence: create/append/load/list |
| `ctx.bash` | dsh-bash | bash execution: foreground runs + background tasks |
| `ctx.fs` | dsh-fs | filesystem provider: read/stream, atomic writes/edits; owns the `fs/*` policy events |
| `ctx.compact` | dsh-compact | compaction: detect pressure, summarize an older range |
| `ctx.web` | dsh-web | search/fetch provider registries + `WebError` taxonomy |
| `ctx.subagents` | dsh-subagent | named provider registry for delegating to child agents |
| `ctx.llm` | [`llm/`](../packages/llm/README.md) | adapter registry and streaming model calls |
| `ctx.bash` | [`bash/`](../packages/bash/README.md) | foreground/background command execution |
| `ctx.fs` | [`fs/`](../packages/fs/README.md) | filesystem provider primitives and policy events |
| `ctx.web` | [`web/`](../packages/web/README.md) | search/fetch provider registries |
| `ctx.compact` | [`compact/`](../packages/compact/README.md) | session-surface compaction |
| `ctx.subagents` | [`subagent/`](../packages/subagent/README.md) | named delegation providers |
| `ctx.sessionPersistence` | [`session-persistence/`](../packages/session-persistence/README.md) | durable storage for session logs |
Dependency rule: plugins depend on these interfaces, never on `dsh-agent-loop` — the loop is swappable; the sanctioned exception is the composition bundle `dsh-agent-core`, whose job is assembling the concrete spine ([full rule + generated graph](../packages/README.md#dependencies)).
## Event Surface
All registrations go through `ctx.effect()` and return disposers, so hot-reload and fiber disposal clean up automatically (full service interfaces: the generated [services catalog](cordis-catalog/services.md)).
Events are the harness extension API. Each service owns the vocabulary for the behavior it controls, and the generated [events catalog](cordis-catalog/events.md) is the exhaustive reference. The [producer/consumer map](event-producer-consumer.md) shows which packages emit or listen to each event.
## Cordis waterfall semantics
### Event Domains
`ctx.waterfall` is **around-middleware**, not a value reducer. Each listener receives `(...args, next)`:
Use the event domain to decide where new behavior belongs:
- call `next()` to delegate to later listeners (and ultimately the core behavior), possibly wrapping it;
- return a value **without** calling `next()` to short-circuit (veto);
- listeners run in registration order; `prepend: true` jumps the queue.
- **Session events** are durable, replayable facts. Turn and step boundaries, user input, assistant output, tool calls, tool results, steering, compaction records, and tool-owned durable facts append to the session log and flow through `session/event`.
- **Agent events** are live runtime surfaces. They carry the live `Agent` handle for status, diagnostics, prompt admission, request mutation, result validation, and continuation policy.
- **Capability events** belong to the seam that owns the action. `tools/*`, `llm/*`, `system-prompt/*`, `fs/*`, and `subagent/*` let policy and adapters attach without importing the loop.
Composition caveat: values propagate through `next()`'s **return value** — a listener that returns a *new* object makes earlier listeners' mutations invisible downstream. Prefer mutate-then-`next()` for cooperative middleware; return a replacement only to take over the result.
### Interception Semantics
## Capability seams: interface / implementation / consumer
Waterfall events behave like around-middleware: a listener delegates by calling `next()` and vetoes or takes over by returning without it. The full rule lives in [Cordis waterfall semantics](cordis-primer.md#cordis-waterfall-semantics).
Swappable capabilities split into three packages — **interface** (abstract service + vocabulary, owns the ctx key), **implementation** (a concrete subclass loaded as a plugin), **consumer** (what the model and plugins program against) — so each evolves independently; the bash trio is the template ([capability seams RFC](rfc/implemented/architecture/2026-06-13-capability-seams.md)). Keep interface + consumer together when they are one concern (the LLM seam: `dsh-llm` carries both, adapters implement); don't split preemptively.
## Default Loop Lifecycle
Two seams bend the template deliberately:
The shipped loop drains queued work, assembles a request, streams a model answer, executes tools, decides whether to continue, and checkpoints durable state. The important architecture is where it pauses: each pause is a documented service call or event seam that another plugin can program against.
- **Filesystem** adds a policy layer as an **event gate**, not a method service: `dsh-tool-fs` (the `read`/`write`/`edit` tools AND executor) dispatches `fs/*` intent events that `dsh-fs-policy` decides, so dropping the policy plugin degrades to the bare provider instead of breaking an injection ([event-gate RFC](rfc/implemented/architecture/2026-06-26-file-context-as-event-gate.md)). Paths resolve against the caller's session cwd, matching bash ([per-session cwd RFC](rfc/implemented/architecture/2026-07-02-fs-per-session-cwd.md)).
- **Web** folds search and fetch onto one seam: `ctx.web` is a provider REGISTRY (`registerSearchProvider`/`registerFetchProvider`, registration-order-independent selection); providers register like LLM adapters, and `dsh-tool-web` is the single consumer owning the tool schemas ([web seam RFC](rfc/implemented/architecture/2026-06-24-web-capability-seam.md)).
A **session** is one agent's append-only event log. A **turn** drains one queued batch and runs until the model stops asking for tools and no plugin requests continuation. A **step** is one model request plus the tool executions caused by that response. In the flow below ([sequence companion](agent-lifecycle.md)), quoted names are durable session events and event names are extension seams.
> The seam pattern is plain Cordis services + `inject` (a consumer's fiber stays pending until the service exists). Despite the name, `@cordisjs/plugin-capability` is unrelated — a permission-security service (a candidate for the deferred permissions work), not a mechanism for swapping implementations.
### Turn Flow
## Content blocks and streaming (dsh-llm)
```text
create agent -> emit agent/session-start(source)
forever:
wait for queued messages
emit agent/status(running)
TURN:
'turn/start'
each queued message -> agent/prompt-submit
allowed prompt -> 'user/message' plus injected context
every prompt blocked -> 'turn/end'(rejected)
STEP loop:
drain steering
assemble system prompt and tool schemas
agent/pre-step
'step/start'
derive messages from the session log
agent/request -> llm/stream
'assistant/chunk'
agent/step-result
'assistant/message'
each tool call:
'tool/call'
tools/pre-execute -> dispatch -> tools/post-execute
'tool/result'
append post-tool context and steering
'step/end'
agent/turn-continuation
stop unless tools or continuation policy ask for another step
'turn/end'
checkpoint persistence and notify idle/running status
```
Messages are arrays of typed **content blocks** (`text`, `reasoning`, `tool-call`, `tool-result`); the union derives from the merge-extensible `ContentBlockMap`; the same pattern types `MessageSource`, `FinishReason`, `TurnTrigger`, `TurnEndReason`. The core set is limited to blocks every shipping path honors — multimodal content (images, audio, …) has no core block type; a feature that needs one adds it via the map in the same coordinated change that maps it in the adapters, surfaces it in the UI bridges, and prices it in compaction ([the drop-image RFC](rfc/implemented/simplification/2026-07-04-drop-image-content-block.md)). Streaming is a raw chunk protocol (`block-start` … `finish`) with `BlockAssembler` as the single shared chunk→block assembler; the loop logs raw chunks (replay fidelity) while assembling them. `LlmAdapter` is the provider seam: subclass, implement `stream()`, register via `ctx.llm.registerAdapter(models, adapter)`; `dsh-llm-deepseek` and `dsh-llm-pi-ai` implement the one contract as deliberate design twins ([twin RFC](rfc/implemented/architecture/2026-06-13-twin-llm-adapters.md)). The StreamChunk conventions (usage/finish ordering, raw-string tool arguments, the two sanctioned error paths) are pinned in `dsh-llm/src/types.ts` and [llm-streaming.md](core-data-structures/llm-streaming.md).
Post-tool context lands after all tool results so tool-call/result adjacency stays stable. Steering drains between steps; leftover steering after a turn is re-queued as ordinary input.
## Event-sourced sessions (dsh-session)
### Failure Boundaries
A `Session` is an append-only log of typed `SessionEvent`s — the single source of truth. The LLM message history is *derived* (`deriveMessages()`): user/assistant messages, tool results, and envelope-tagged context/steering messages come from their events in chronological order (raw `assistant/chunk` events are replay/UI data, skipped; the per-event mapping is in [session.md](core-data-structures/session.md)). Replay/fork = `ctx.sessions.create(id, { seed })`; trace/telemetry = listen to `session/event` ([event-sourcing RFC](rfc/implemented/architecture/2026-06-11-event-sourced-sessions.md)).
The turn is the containment boundary. A throwing listener, adapter error finish, or failed step ends the current turn with an error reason and reports live diagnostics through `agent/error`; it does not kill the driver loop. `cancel()` clears queued and steering work, aborts the active model/tool boundary when possible, and records the appropriate turn end. Disposal stops the loop, awaits quiescence, unregisters the agent, and lets service disposers drain.
**Durability**: `session/event` is a synchronous notification; persistence backends buffer write-behind and drain at the awaited `session/flush` checkpoint at every turn end. The abstract `SessionPersistence` seam defines create/append/load/list over `SessionEvent` (no parallel persisted type); metadata travels as `SessionHeader`; crash recovery preserves an interrupted turn by closing it with a synthetic `turn/end {interrupted}`. Two backends (JSONL, SQLite) pass one shared contract suite ([persistence RFC](rfc/implemented/architecture/2026-06-14-session-persistence.md), [write coordinator RFC](rfc/implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md)). Resume = `ctx.agents.resume({ resumeSessionId })`.
Every session event is turn-enclosed. Reloading a crashed session preserves the interrupted tail and closes it with a synthetic `interrupted` turn end. A failure after the durable turn has closed reports through `agent/error` only because no safe in-turn position remains. A turn ends with one `TurnEndReason` (`completed`, `aborted`, `error`, `disposed`, `max-tokens`, `rejected`, or `interrupted`); per-variant semantics are in [session.md § TurnEndReasonMap](core-data-structures/session.md#why-a-turn-ended-turnendreasonmap).
## Prompt assembly (dsh-system-prompt)
### Agent Handles
Plugins contribute `PromptSection`s (named, ordered, static or computed) and tool-schema providers; `assemble()` returns `PromptAssembly { sections, tools }` through the `system-prompt/assemble` waterfall. Tool schemas are deliberately part of the assembly — "what the model is told it can do" is one coherent thing — though adapters transmit them as the wire-level `tools` field ([RFC](rfc/implemented/architecture/2026-06-11-tool-schemas-in-prompt-assembly.md)).
`ctx.agents` owns live agents and returns an `AgentHandle { agent, dispose() }`. `Agent` is the surface other plugins drive: `send()` queues work, `steer()` injects mid-turn content, `inject()` appends context and opens a one-shot injection turn when idle, `cancel()` is the public stop primitive, and `whenIdle()` observes quiescence. Lifecycle owners tear down with `await dispose()`.
## State And Model Surface
### Session Log
The session log is the source of truth. `deriveMessages()` projects session events into the `Message[]` sent to the model; raw `assistant/chunk` events stay in the log for replay and UI fidelity. Replay, fork, resume, transcript rendering, telemetry, and persistence all derive from the same event stream.
Durability is a plugin concern. Persistence backends buffer synchronous `session/event` notifications and the loop awaits a turn-end checkpoint before moving on. The `SessionPersistence` seam stores `SessionEvent` directly, with metadata in `SessionHeader`; JSONL and SQLite share one contract suite.
### Model Content
Messages are arrays of typed content blocks (`text`, `reasoning`, `tool-call`, `tool-result`). The union derives from the merge-extensible `ContentBlockMap`; the same pattern types `MessageSource`, `FinishReason`, `TurnTrigger`, and `TurnEndReason`. New block types are coordinated across adapters, UI bridges, compaction pricing, and persistence, so block vocabulary remains a repo-wide contract.
Streaming is a raw chunk protocol (`block-start` through `finish`) with `BlockAssembler` as the shared chunk-to-block assembler. The loop logs raw chunks while assembling them for dispatch. `LlmAdapter` is the provider seam: subclass, implement `stream()`, and register with `ctx.llm.registerAdapter(models, adapter)`. StreamChunk conventions live in [llm-streaming.md](core-data-structures/llm-streaming.md).
## Extension And Composition
### Capability Pattern
A swappable capability usually splits into **interface / implementation / consumer**: the interface owns the `ctx` key and vocabulary; an implementation registers a backend; a consumer exposes model-facing behavior through `ctx.tools` or prompt assembly. The bash trio is the reference shape, and the [capability seam graph](capability-seams.md) shows the current package families.
Some seams bend the template deliberately. LLM keeps interface and consumer vocabulary together because adapters are the implementations. Filesystem adds policy as event gates around provider primitives. Web is one service with search and fetch provider registries, so provider swaps do not rename model tools. Subagents use a named provider registry because multiple delegation backends can coexist; `spawn` starts fresh, `fork` seeds from the parent's completed-turn prefix, and ACP can drive an out-of-process child ([subagent.md](core-data-structures/subagent.md)).
Prompt/context extension plugins that shape model inputs without owning a core service live under `packages/prompt/`. `dsh-project-instructions` is the reference case: it uses per-agent `agent/request` instead of global `ctx.systemPrompt.section()` for multi-cwd isolation, reads through `ctx.fs`, and observes successful `read`/`write`/`edit` calls via `tools/post-execute` to inject nested files as durable `context/message` entries. Shared filesystem path conventions such as the default DSH home live in the low-level `dsh-paths` utility package rather than in the prompt plugin.
## Tool pipeline (dsh-tools)
### Bundles And Apps
`ToolRegistry.register()` takes schema + `execute()`; schemas flow into the assembly automatically. `execute()` runs through a two-waterfall pipeline — `tools/pre-execute` (a `PreToolDecision`: allow/deny/ask) → core dispatch → `tools/post-execute` (a `PostToolDecision`: accept/block, replace content, attach context) — the seams where sandbox, permission, hook, and plan-mode plugins live. A thrown tool still reaches `post-execute` as an `isError` result.
`dsh-agent-core` is the default composition bundle: one plugin loading the providerless spine as code ([README](../packages/core/agent-core/README.md)). App packages compose it with a front door and own the boot `bin`: `dsh-stdio-agent` for the terminal REPL, and `dsh-acp-agent` for ACP over JSON-RPC stdio with no stdout logger ([ui/](../packages/ui/README.md)). A deployment is a thin `cordis.yml` leaf: swappable backends, one app entry, and optional product tools ([examples/](../examples/AGENTS.md), [runnable wirings](cookbook/extension-cookbook.md#runnable-wirings), [graph atlas](graph-atlas.md)).
## Agents (dsh-agent) and the loop (dsh-agent-loop)
### Where New Behavior Goes
`Agent` is the handle every plugin programs against: `send()` (queued), `steer()` (mid-turn injection, drained between steps), `inject()` (in-session context; a one-shot `injection` turn when idle), `cancel()` (the single public stop primitive: clears queued + steering work, aborts the in-flight step, drops a turn about to start), `whenIdle()` (quiescence observation, not teardown), plus `session`/`status`/`options`. A lifecycle owner tears down via `await AgentHandle.dispose()` — stop, await exit, unregister. Full semantics: [core.md](core-data-structures/core.md), [lifecycle RFC](rfc/implemented/architecture/2026-06-18-agent-lifecycle-and-ownership-seams.md).
New behavior should attach to a documented seam; changing the shipped loop requires updating this map.
**Subagents** are a seam, not a method on `Agent`: `ctx.subagents` is a named-provider registry (`spawn` starts fresh, `fork` seeds the child with the parent's completed-turn prefix, ACP drives an out-of-process child); children are ordinary `Agent`s. See [subagent.md](core-data-structures/subagent.md), [subagent RFC](rfc/implemented/feature/2026-06-21-subagent-capability-seam.md).
| Goal | Mechanism |
|---|---|
| Add a model provider | register an adapter on `ctx.llm` |
| Add a model-facing capability | register a tool on `ctx.tools`; schemas flow into prompt assembly |
| Add command execution | implement and register a `ctx.bash` backend |
| Add filesystem access or policy | implement a `ctx.fs` provider or listen on `fs/*` policy events |
| Intercept prompts, requests, tool use, or continuation | listen on the relevant `agent/*` or `tools/*` waterfall |
| Add UI or editor integration | drive `ctx.agents` and render from `session/event` |
| Add durable session state | add a `SessionEventMap` member and render/replay from the log |
### Loop lifecycle (session / turn / step)
- **Session**: the whole event log of one agent.
- **Turn**: ≥1 queued message; steps run until the model stops requesting tools and no plugin requests continuation.
- **Step**: one model request + its tool executions.
```
create agent → emit agent/session-start(source) ⟵ once, before turn 1 (startup|resume)
forever:
wait for queued messages (idle)
emit agent/status(running)
TURN (error-contained — a throwing plugin ends the turn, never the loop):
'turn/start' ⟵ durable turn boundary (no agent/* mirror)
each queued msg: waterfall agent/prompt-submit ⟵ allow (rewrite/+context) | block
allow → session('user/message'…); inject additionalContext
every prompt blocked → 'turn/end'(rejected), 0 steps ⟵ zero-step turn, model never called
STEP loop:
drain steering (late steering from previous step's listeners)
assembly = ctx.systemPrompt.assemble() ⟵ waterfall system-prompt/assemble
await ctx.serial('agent/pre-step') ⟵ surface mutation (compaction) OUTSIDE the step
session('step/start') ⟵ durable step boundary (no agent/* mirror)
req = {model, system, tools, messages: session.deriveMessages(), signal}
req = waterfall agent/request ⟵ hooks, model switch
stream ctx.llm.stream(req) ⟵ waterfall llm/stream (raw chunks)
session('assistant/chunk')
if assembler.finish is error/aborted: throw ⟵ adapter's in-band error path →
step error (turn ends error/aborted,
not a normal completed message)
msg = waterfall agent/step-result ⟵ runs BEFORE the log append, so the
session('assistant/message' {content, usage?}) log records what tool dispatch uses
each tool-call (sequential, abort-checked between calls):
session('tool/call'); ctx.tools.execute() ⟵ waterfall tools/pre-execute (allow/
deny/ask gate) → dispatch → tools/post-execute (accept/block, replace, +context)
tool execution may append tool-owned session events, e.g. `todo/write`
session('tool/result')
append buffered post-execute additionalContext → session('context/message')(s)
⟵ after ALL tool/results (adjacency)
drain steering → session('steering/message')
session('step/end') ⟵ durable step boundary (no agent/* mirror)
cont = waterfall agent/turn-continuation(default = {action: hadToolCalls||steered
? 'continue' : 'stop'}) → ContinuationDecision
a continue's reason is recorded as next-step steering (same turn); steering pending
also forces continue (continuation OR step/end listeners — the /goal pattern)
if action==stop: break
session('turn/end') ⟵ durable turn boundary (no agent/* mirror)
await ctx.parallel('session/flush', session) ⟵ durability checkpoint (failure
reported via agent/error, not fatal)
leftover steering re-enqueued as queued messages ⟵ steering is never stranded
emit agent/status(idle) unless more queued
```
Error containment: a throwing listener or broken step ends the **turn** (`turn/end { reason: { kind: 'error', step, … } }`), never the driver loop; live diagnostics fire via `agent/error`; an adapter's in-band error/aborted finish chunk becomes a step error. `cancel()` is honored mid-stream and between tool calls; disposal mid-turn ends the turn `disposed`. A post-`turn/end` failure (a rejecting `session/flush`) is reported via `agent/error` only — the turn stays balanced, the backend keeps its buffer.
A turn ends with one `TurnEndReason` — `completed`, `aborted`, `error`, `disposed`, `max-tokens`, `rejected`, or `interrupted`; per-variant semantics (and the max-tokens-wins rule) are in [session.md § TurnEndReasonMap](core-data-structures/session.md#why-a-turn-ended-turnendreasonmap).
**Turn-enclosure invariant**: every session event lives inside a turn, making the turn the single durability/replay boundary — anything after the last `turn/end` is an interrupted-crash tail. `dsh-invariants` enforces it in dev ([invariant RFC](rfc/implemented/architecture/2026-06-15-turn-enclosure-invariant.md)).
## Event taxonomy
The `agent/*` events are declared in `dsh-agent` (so nothing depends on the loop package); each other service declares its own (`tools/*`, `llm/*`, `system-prompt/*`, `session/*`). The full catalog — signatures, dispatch modes, prose — is generated from source and freshness-gated: [cordis-catalog/events.md](cordis-catalog/events.md). Domain semantics (session = the fact log, agent = the live surface): [the event-domain RFC](rfc/implemented/architecture/2026-06-30-event-domain-semantics.md).
## Extension guide
Plugin skeletons (tool, hook/permission gate, UI, protocol bridge) and the feature→mechanism map — which extension seam implements each product feature — live in [the extension cookbook](cookbook/extension-cookbook.md); step-by-step guides: [adding a package](cookbook/adding-a-package.md), [a tool](cookbook/adding-a-tool.md), [an LLM adapter](cookbook/adding-an-llm-adapter.md), [a vendored package](cookbook/adding-a-vendored-package.md).
## Deferred work (TODO)
Designed-for but not implemented: inter-agent channels beyond delegation (shared state, streaming output); the model-facing `/compact` consumer tool over `ctx.compact` ([compaction RFC](rfc/implemented/feature/2026-06-18-compaction-capability-seam.md)); parallel tool execution (concurrency-safety hints on `ToolDefinition`); session branching/tree if seed-based forking proves insufficient.
The [extension cookbook](cookbook/extension-cookbook.md) carries plugin skeletons and the feature-to-seam map; step-by-step guides cover [packages](cookbook/adding-a-package.md), [tools](cookbook/adding-a-tool.md), [LLM adapters](cookbook/adding-an-llm-adapter.md), and [vendored packages](cookbook/adding-a-vendored-package.md).