tai42-skeleton

The open-source implementation of tai42-contract — the extended MCP server that hosts tools, agents, extensions, connectors, hooks, and storage for the TAI ecosystem. It provides the concrete TaiMCP server and the runtime engines (tool registry and adapters, the agent registry, the OAuth connector engine, the access-control middleware, the hooks router, the template/storage manager, the manifest loader, and the transport layer) that implement the protocols declared in tai42-contract.

Providers — OAuth connectors, storage backends, config providers, worker backends, monitoring — ship as separate plugins that register through the tai42_app contract handle when the manifest loads them; no plugin imports the skeleton.

Position in the ecosystem

TAI is an open-source runtime for MCP tools, agents, and workflows — the server that hosts a capability and supplies the operational layer around it (manifest loading, access control, OAuth connectors, background execution, monitoring, storage, and human-in-the-loop steps).

Four packages; each depends only on the ones to its left:

                     tai42-kit  <--.
                   /  (helpers)     \
tai42-contract  <-+                  +--  tai42-skeleton
  (interfaces)     \                /    (the server)
                     tai42-cli  <--'
               (the remote client)

tai42-skeleton is the server at the end of the chain: it depends on tai42-contract (the pure interface package), tai42-kit (generic leaf helpers), and tai42-cli (the terminal client whose tai command it extends). It is the runnable body every plugin plugs into.

Install

Requires Python 3.13+. Install from PyPI into the environment that runs the server:

uv add tai42-skeleton

Or from source:

git clone https://github.com/tai42ai/tai42
cd core/skeleton
uv venv --python 3.13
uv pip install --no-sources --editable .

Add the toolbox extra for batteries — it pulls in the tai42-toolbox contrib package, whose composition tool extensions (chain, batch) and generic tool collection load from the manifest (see examples/toolbox):

uv add "tai42-skeleton[toolbox]"                      # from PyPI
uv pip install --no-sources --editable ".[toolbox]"   # from a source checkout

Run it

The hello-world app in examples/hello registers one local greet tool and needs no services to stand up. From the repo root:

ACCESS_CONTROL_ENABLE=false \
PYTHONPATH=examples/hello \
uv run --no-sync tai serve --manifest-path examples/hello/manifest.yml --port 8765

The MCP endpoint is then http://127.0.0.1:8765/mcp, and it lists 94 tools, not one: alongside greet the server projects 93 operation tools from its own management operations, because the manifest's api_tools block is on by default. Set api_tools: {enabled: false} to switch that projection off and leave greet on its own. The server also polls the marketplace for security advisories on a timer — that is its one outbound call, and MARKETPLACE_ADVISORIES_POLL=false turns it off.

tai backend runs the agent/worker backend process and tai metrics serves the Prometheus endpoint; the full command surface is in the CLI reference below.

tai serve, tai backend, and tai metrics form one run family over a single shared Prometheus multiprocess directory (PROMETHEUS_MULTIPROC_DIR, default a fixed absolute path under the host temp dir; any override must be absolute). Point all three at the same directory and restart them together: tai serve clears the directory once at boot, so restarting it mid-run while a backend worker is still writing orphans that worker's counters until the whole family restarts. examples/README.md walks through the examples, and examples/manifest.yml is the commented manifest reference.

The worker bus

When a deployment runs more than one process — several tai serve workers, a tai backend runtime alongside the server, or multiple pods sharing one config — a manifest edit on one process must reach the others, or siblings serve stale state. The worker bus is how every process converges: each subscribes to one Redis channel at startup, a mutation applies locally and is then broadcast, and the response carries a per-origin report of how every worker fared.

The bus is internal app infrastructure, like the reload gate — it is NOT a plugin. Nothing about it is registrable, swappable, or user-selectable; there is exactly one bus and no manifest field chooses an implementation. It is configured only by environment: set TAI_BUS_REDIS_URL (plus the optional TAI_BUS_* knobs) to turn it on. A single-worker, file-mode, no-backend deployment needs no bus and runs on a no-op local variant; a multi-worker, backend-bearing, or k8s-mode boot refuses to start without one, naming TAI_BUS_REDIS_URL. On a shared Redis, TAI_BUS_NAMESPACE must diverge per stack — Redis pub/sub is server-global, so co-tenant deployments would otherwise cross-talk.

Conversations and person linking

The conversation bridge turns one inbound message — from an authed API caller (door=api) or a registered channel adapter (door=channel) — into an agent or tool turn whose answer is durably stored and delivered back. A route binds a door to a target: an agent run (threaded conversation memory) or a tool dispatch (stateless, one call per message). Routes are managed over POST /api/conversations/{route_name} (the tai conversations create CLI), and a thread reads over /api/conversations/{route_name}/threads and /transcript. An unlinked conversation keys its thread bridge:{route_name}:{address}.

One person who reaches a target on several channels can prove, by an explicit pair code, that those addresses are the same person — and the bridge then treats them as one person for that target. Nothing changes for anyone who never pairs: an unlinked conversation keeps its route-keyed thread byte-for-byte. Person linking is off by default and opted in per target.

Per-target conversation config

Each (target_kind, target_name) may carry a TargetConversationConfig:

greeting_template may reference only the {pairing_code} placeholder; any other {...} field is refused at write time so a typo cannot render literally. When the template references {pairing_code}, a fresh single-use code is minted at greeting time and substituted in. The greeting fires on first contact only — the first message the bridge admits from an address on that target; a later message from the same address carries no greeting. It also fires only on a multichannel: true target — the greeting lives inside the multichannel path, so a greeting set on a target with multichannel off stays inert until multichannel is enabled (the two fields are accepted independently).

Set it over the config API / CLI (config-set is an upsert and requires the agent or tool target to exist):

# PUT /api/conversation-configs/{target_kind}/{target_name}
tai conversations config-set agent assistant --multichannel \
  --greeting-template 'Hi! Pair another channel with {pairing_code}'
tai conversations config-list                  # GET /api/conversation-configs
tai conversations config-get agent assistant   # GET .../{target_kind}/{target_name}
tai conversations config-delete agent assistant # DELETE .../{target_kind}/{target_name}

Pairing protocol

On a target with multichannel: true, the bridge intercepts three exact things in the inbound text — everything else passes through unchanged to the target:

• /link (the whole trimmed message) — mints a fresh pair code and replies with it. /link extra is ordinary text, not a command.
• /unlink (the whole trimmed message) — detaches the sending address from its person; the rest of the person stays linked, and the detached address returns to its own route-keyed thread.
• a pair code anywhere in the text — LINK- followed by 8 [A-Z0-9] characters (matched as \bLINK-[A-Z0-9]{8}\b, so a code pasted inside a sentence still redeems). Redeeming merges the two conversations into one person.

A pair code is single-use and expires 15 minutes after it is minted. One code is open per conversation at a time: minting again rotates — a fresh code is issued and the previous one stops working (the newest code wins). The raw code exists only in flight and is never stored recoverably.

Merging is transitive: each redemption folds the two persons into one (the union of their addresses), so a chain of pairings across three or more channels always converges to a single person for that target.

Both doors join persons. On the channel door the address is the medium's (a phone number, a chat id, ...); on the api door it is the composed caller/end-user string. An API caller whose address belongs to a linked person reads the full merged person thread. Errors are uniform: an unknown, expired, or already-redeemed code all get the same refusal reply, so the wording reveals nothing about whether a code ever existed.

Person scope is per target: pairing on one (target_kind, target_name) never links addresses on any other target.

Known limits

• Histories are never merged. Linking two conversations does not stitch their two past transcripts together; the shared person thread starts at the pairing moment (agent targets — a tool target has no thread and shares identity only).
• Slack pairs the room. A Slack channel address is the room, not a user, so pairing on Slack links the room rather than one person in it.
• Web identity is a browser cookie. A web visitor who clears cookies or opens another browser/device is a new person until they pair again; an invite link re-pairs them in one load (see the channel-web plugin's invite links).

The get_pairing_code tool

get_pairing_code is a runtime-native builtin that mints a pair code for a live channel conversation, so an operator can compose an invite (a typed code, or a channel-web ?tai_pair= URL) around it. Opt the module in with a manifest tools[].module row:

tools:
  - title: get-pairing-code
    module: tai42_skeleton.tools.builtin.get_pairing_code

It returns {"code", "expires_at"} and nothing else — no link and no wording; the operator composes the invite text themselves. Calling it again rotates the conversation's open code (newest wins). Refusals are loud: a blank channel, our_identity, or sender raises; a null/absent argument — which the api door carries, having no channel identity — is refused by the typed signature before the tool body runs; and a resolved target with multichannel off is refused with no code minted.

Wiring it as a tool-target route. A tool route maps the inbound message to the tool's kwargs with a payload_expr (jq) and the result to the reply with a reply_expr (jq). The payload the expr runs over is {message, sender, our_identity, channel} — our_identity and channel are the route's, sender is the conversation address. Map those onto the tool's own parameter names and pull .code out of the result:

tai conversations create pair-mint --door channel --target-kind tool \
  --target-name get_pairing_code --execution-key svc \
  --channel telegram --identity <bot-id> \
  --payload-expr '{channel: .channel, our_identity: .our_identity, sender: .sender}' \
  --reply-expr '.code'

payload_expr must emit exactly one JSON object; reply_expr must emit null or a string — here the raw code — so the route replies with just the code. The tool mints for the conversation named by (channel, our_identity), whose resolved target must itself have multichannel on.

Development

Set up the dev venv and run the gates. --no-sources ignores the workspace-source overrides in [tool.uv.sources], so the dev deps come from PyPI and the clone stands alone; --no-sync runs each gate against that environment instead of re-resolving:

uv venv --python 3.13
uv pip install --no-sources --editable ".[dev]"
uv run --no-sync ruff check .
uv run --no-sync ruff format --check .
uv run --no-sync pyright
uv run --no-sync pytest --cov --cov-report=term-missing

See CONTRIBUTING.md for the rules.

Documentation

The whole platform — the quickstart, concepts, guides, and the generated reference — lives in the unified documentation site:

• Getting started & install: https://tai42.ai/getting-started/installation
• Quickstart: https://tai42.ai/getting-started/quickstart
• Concepts: https://tai42.ai/concepts
• Guides: https://tai42.ai/guides
• Built-in tools & extensions: https://tai42.ai/concepts/tools-and-extensions
• Reference (HTTP API, CLI, Python SDK): https://tai42.ai/reference/cli

License

Apache-2.0. See LICENSE and NOTICE.