Orchestration records intent and state without knowing which provider runs a thread. Provider protocols, account ownership, permissions, and capabilities belong at the adapter boundary. Normalize there instead of spreading provider checks through orchestration and clients.
A driver kind identifies an integration; an instance identifies one configuration and account lifecycle. Route work by instance, so two accounts using the same driver do not share mutable session or catalog state.
The opencode driver probes the installed version and runs the 1.x or 2.x runtime. OpenCode's MCP
registrations are directory-scoped, while T3's MCP connection is thread-scoped, so threads in one
directory must not share one T3 MCP entry.
- 1.x uses one T3-managed chat server per thread, so threads cannot replace each other's connection. Catalog and text-generation work can share the instance-owned helper, which closes after an idle period. See the 1.x adapter.
- 2.x serves every directory from one
server per instance. Each thread
registers its own
t3-code-<thread>MCP entry, and session permission rules deny every other thread's entry. See the 2.x adapter.
External OpenCode servers remain externally owned and can require an external restart to pick up
configuration changes. OpenCode stores "always" approval grants for the whole project. Automatic
full-access replies use once so they cannot widen a supervised thread's permissions on a shared
server. On 2.x, a session-wide approval also replies once and becomes T3's own rule on that session.
Pi runs the user's own pi install in RPC mode and owns native extension, package, and project
trust discovery. T3 injects only its namespaced MCP bridge, so a Pi session behaves as it does in
the Pi TUI. Pi session files back native resume, rollback, and same-instance thread forks.
Forks use Pi's CLI in the destination directory because RPC session switching retains the source
session's cwd. Provider switches still use portable handoff summaries.
See the adapter.
Antigravity separates account profiles per instance while sharing installed executables across the
environment. It forces file-based credential storage because the native macOS keychain entry would
otherwise be shared across instances. The launch environment removes ambient Google credentials,
so an instance cannot silently use another account or billing project. The agent also resolves
its user-global skill directories under that profile, so the profile links those two directories
back to the user's real ~/.gemini; MCP servers, hooks, and rules there stay out of the profile.
See profile isolation.
The Antigravity installer outlives client connections and provider-instance rebuilds. Releases are immutable, with an atomic pointer selecting the version for new processes. Running processes hold leases on their version. Updates and removal must respect those leases instead of replacing executables under a running agent.
Opening a provider session can start MCP servers, run hooks, or launch a login browser. Grok probes avoid authentication and session creation for this reason. Antigravity likewise reserves authenticated catalog sessions for explicit setup or model refresh; background checks use initialization only.
Devin probes are CLI-only —
devin version, devin auth status, devin models list --format json — and never spawn
devin acp. The Devin CLI reads its stored credentials automatically, so sending the advertised
devin-browser authenticate method would open a browser on every session spawn even for a
signed-in user. The runtime therefore
issues authenticate only when no ambient credential exists and the caller opted in to an
interactive login. Devin has no session/set_model; model selection rides the session's
category: "model" config option. devin acp advertises no HTTP/SSE MCP transports, so the
thread's T3 MCP endpoint reaches it through a
stdio bridge script the agent launches. An agent
that does advertise http gets the endpoint directly; the http entry also remains as a fallback
when the bridge script cannot be written.
Antigravity sign-in belongs to the initiating T3 auth session. The client carries the return URL back to the environment because the provider's loopback listener may be on another machine. Forward only the callback for the owned pending flow; a successful callback HTTP request is not proof that provider authentication finished. The native process owns token exchange and storage.
Managed ChatGPT sign-in for a remote environment can finish on a local primary. The primary handoff uses an ephemeral credential store and the destination's environment ID. It exchanges and verifies the code before transferring the issued client registration and tokens. Only the destination persists and refreshes that session; retaining a primary refresh session would race refresh-token rotation. Without a local primary, the client uses the remote callback completion flow.
Antigravity sign-out closes admission to new processes and stops existing processes before clearing account metadata. Otherwise a helper or resumed session could retain the old account. Cached model lists do not establish current access, and an authoritative empty catalog must clear the old list.
Antigravity text-generation helpers deny tool requests, but native hooks and MCP configuration can run before the prompt. They reject profiles with such configuration before launch. Prompt instructions and tool denial do not create a native sandbox. See helper constraints.
A one-click update is offered only when the resolved executable's path proves which installer owns
it. Homebrew and npm are proven by the real path (symlinks followed): a versioned keg or cask under
brew --prefix, or <prefix>/lib/node_modules/<pkg>/ (Windows: the shim beside node_modules).
Native installer layouts and the global bin directories of pnpm, Bun, and Vite+ may match on either
the resolved path or its real target, since those installers place real files or their own symlinks
there. Cursor and Grok are the exception: their only updater is the CLI itself, which detects its
own installer, so any resolved executable runs <binary> update. Anything unproven stays
manual-only but still reports the version gap. npm updates pin
--prefix because the npm on PATH can belong to a different Node than the one that owns the
provider. Homebrew
compares against brew info since casks trail npm by hours; native installs share npm's version
train, so the registry stays authoritative for them.
See the resolver.
Ownership is cached per instance and re-read immediately before an update runs. The runner refuses when the lock key changed since the advisory, and reports success only when the refreshed provider is still installed with a readable, current version.
Codex async questions arrive as notifications and are answered with a new user message. There is
no pending RPC response to send. The
adapter persists them as
user_input_request turn items and runtime requests with responseCapability: { type: "message" }.
Their execution nodes do not block the run. Web, desktop, and mobile use their normal question
panels, and requests remain pending after a turn finishes, a provider exits, or the server restarts.
runtime-request.respond reads the persisted request and question item, validates required
answers, and commits the resolution and a user message in one transaction. Repeating the same
command returns its receipt without posting the answer twice. The normal message path starts or
resumes a run, queues behind active work, or steers when the adapter supports it. Blocking questions
retain the provider's live response path. Do not infer that a request has disappeared merely because
it is outside the recent history window.
Capabilities must describe what the provider can actually do. Antigravity can capture workspace checkpoints but cannot roll back its conversation. The checkpoint boundary therefore rejects revert before touching files. Native permission and question option IDs must also survive normalization; a display label is not necessarily a valid reply.
Attachments live outside the project workspace. The attachment boundary validates and claims uploads for a thread; adapters choose native input formats for those environment-local files. A path in the prompt does not grant filesystem access. Keep provider sandbox and approval rules in force; copying uploads into the project to bypass them changes that boundary.
File attachments introduced a replay compatibility limit. Image-only clients cannot decode file-bearing messages, and an image-only server can fail the entire environment's startup when replaying one such event. Rollouts and downgrades must account for persisted history as well as current client support.
Native event logs retain lifecycle events, responses, and failures. Token deltas and duplicate raw frames are filtered before adapters copy or redact payloads. The filter accepts both legacy native events and v2 protocol envelopes; decode failures remain visible through diagnostic frames.
Log payloads have a 64 KiB encoded budget. Large or deeply nested payloads become structural summaries that retain routing identifiers, methods, status, and error fields. Traversal is bounded before redaction and serialization, so logging a large response does not require several full copies. These limits apply to diagnostics; provider event handling is unchanged.
Codex resumes with metadata-only reads when it needs a thread's identity and update time. Its
initialization capabilities opt out of turn/diff/updated: T3 derives diffs from checkpoints.
The logger filters those notifications before traversal when an older provider still sends them.
Model classification has its own manifest constraints. Assistant-reference handling is documented under citations.