---
title: Actions and sessions
description: Track AIP work and session context safely across queues, streams, and reconnects
kind: explanation
audience: developer
appliesTo: "1.x"
writingStandard: "aip-docs/1.0"
lastReviewedRevision: "97be86e9efedf07ecf1783b03800f683f107fb04"
---

# Actions and sessions

Use this page to understand how an AIP client identifies, observes, cancels,
and resumes work. It is for application and connector developers who need to
track an invocation beyond one request or transport connection.

An action is one requested capability invocation. A session is an optional
relationship between two principals that can group related messages and work.
They have different identities, lifecycles, and recovery rules.

This distinction matters when a request is queued, a stream reconnects, a
worker restarts, or a provider responds after the original transport has gone
away. The transport connection is not the identity of the work.

State-backed does not always mean process-durable: the reviewed runtime has
pluggable stores, including in-memory implementations. Deployment configuration
determines which state survives a process or host loss. The types and runtime
behavior on this page apply to AIP 1.0 at source revision
`97be86e9efedf07ecf1783b03800f683f107fb04`.

## Keep four identifiers separate

| Identifier | Scope | Use |
|---|---|---|
| `act_...` | One capability invocation | Submit, cancel, and query one unit of work |
| `sess_...` | A relationship between an initiator and responder | Group messages and resume session context |
| `msg_...` | One protocol envelope | Detect or correlate message delivery and replay |
| `corr_...` | A related request or trace flow | Associate messages without merging their identities |

These are the forms produced by the typed constructors and required by their
checked parsers. The identifier types use transparent serialization, so a
deserialization boundary must invoke a checked parser or an equivalent prefix
check; deserialization alone does not enforce the form.

An action can exist without a session. When a session is used, its ID is carried
by the enclosing `Envelope.session_id`; it is not a field of `Action`. The
runtime copies that trusted message context into its queued action record and
exposes it later in `ActionStatus`.

Do not substitute one identifier for another. Reusing an action ID for a
different capability, input, or principal is an identity conflict. Retrying the
same business intent is governed by the capability's idempotency contract and
key scope, not by inventing a new meaning for an existing action ID.

## What an action carries

An `Action` always contains an `id`, `capability_id`, and structured JSON
`input`. Every other field is optional or defaults to an empty collection:

| Field | Purpose | Important boundary |
|---|---|---|
| `mode` | Selects `sync`, `async`, or `streaming` | Omission is treated as `sync`; the capability contract must support the selected mode |
| `idempotency_key` | Identifies repeat business intent | Its required presence, collision behavior, scope, and retention come from the capability contract |
| `timeout_ms` | Supplies a caller timeout | The runtime combines it with the capability service-level contract and deployment behavior |
| `conversation` | Carries structured conversation context | It is not the AIP session lifecycle |
| `memory_context` | Carries application state or context | Runtime transport metadata is kept outside the caller-owned durable action contract |
| `delegation_chain` | Records delegated authorization hops | The path is checked for continuity and cycles; authority still comes from trusted context |
| `federation` | Describes cross-domain routing context | It does not authenticate a remote domain by itself |
| `callback` | Names an asynchronous delivery target and profile | Delivery state is tracked separately from action completion |
| `observability` | Carries trace, span, and diagnostic fields | It is correlation metadata, not authorization |
| `compliance` | Carries requested regimes and classification | Runtime policy remains authoritative |
| `identity` | Projects tenant, account, user, and credential references | The runtime replaces caller claims with resolved identity at the trusted ingress path |
| `approval` | References a decision authorizing this invocation | The decision must match the durable approval record and policy snapshot |
| `transaction` | Selects execute, plan, commit, reconcile, or recovery intent | Transaction admission and result state are separate from the action lifecycle |

After trusted identity and transaction normalization, the runtime retains the
durable action as the caller-facing work contract. Connector-facing enrichment,
queue leases, retry metadata, approval records, transaction records, receipts,
and stream chunks live in separate runtime state.

## One action has several status surfaces

AIP deliberately separates acceptance, execution observation, and result data.
Reading one surface as if it were another creates false completion claims.

### Acknowledgement

`Ack.status` has five wire values:

| Value | Meaning |
|---|---|
| `accepted` | Accepted for processing |
| `rejected` | Rejected before processing |
| `queued` | Accepted into a queue |
| `streaming` | Accepted and a stream will follow |
| `cached` | A prior idempotent result was selected |

An acknowledgement is not a successful business result. In the reviewed local
submission path, an asynchronous action that passes preflight is queued and
returns `queued`. A contract or credential violation, approval pause,
transaction preview, or resolved idempotent replay can instead return an
`ActionResult` immediately; other runtime failures can return a protocol error.

### Result

`ActionResult.status` is one of `completed`, `failed`, `cancelled`,
`pending_approval`, or `requires_human`. A result can also contain structured
output, user-facing message parts, memory updates, usage, a receipt reference,
or a typed protocol error.

Only `completed`, `failed`, and `cancelled` settle ordinary action execution.
`pending_approval` and `requires_human` preserve a governed pause; the runtime
projects both as `pending_approval` in the lifecycle view. A failed result must
carry a structured error.

### Lifecycle view

`ActionStatus` combines queue, result, transaction, approval, receipt, and
stream state into an operational read model. Its stable enum contains:

| State | Interpretation at the reviewed runtime |
|---|---|
| `unknown` | No visible queue record, result, or requested retained chunk was found |
| `accepted` | Reserved wire state; the current projection does not produce it |
| `queued` | A queue record is waiting for execution |
| `running` | A worker owns an executing queue record |
| `streaming` | No result exists and at least one retained chunk was requested and found |
| `pending_approval` | The result or queue state requires approval or human input |
| `cancelling` | Reserved wire state; the current projection does not produce it |
| `cancelled` | Cancellation is recorded as the action result or queue state |
| `completed` | A completed result or completed queue state exists |
| `failed` | A failed result or failed queue state exists |
| `expired` | Queue state expired under retention policy |
| `dead_lettered` | Retry processing parked the record with a dead-letter reason |

The runtime treats `cancelled`, `completed`, `failed`, `expired`, and
`dead_lettered` as terminal lifecycle states. `unknown` is a query outcome, not
an execution stage. The projection can change as separate records arrive, so a
client should retain the action ID and read the latest authorized view.

## Mode changes the response pattern

| Mode | Reviewed runtime path | Caller responsibility |
|---|---|---|
| Omitted or `sync` | Validates, authorizes, executes inline, and returns `ActionResult` | Bound the request and retain the action ID when the outcome is uncertain |
| `async` | Performs preflight, stores a queued record, and normally returns `Ack(queued)` | Persist the action ID and query status, result, or events |
| `streaming` | Executes through the non-async path, records chunks, and returns a final `ActionResult` | Consume ordered chunks and still use the result or lifecycle view as settlement authority |

The capability contract, not caller preference, decides which modes are
admitted. A long-running or approval-prone operation is normally easier to
recover when submitted asynchronously, but the provider's actual contract is
authoritative.

At the reviewed revision, asynchronous submission checks the contract,
credential context, authorization, approval, transaction preconditions,
idempotency, and handler presence before queueing. Capability input-schema
validation occurs when the worker enters the normal processing path, so a
queued acknowledgement is not proof that the input will execute.

## Stream chunks are ordered action records

Every `StreamChunk` contains an action ID, a monotonically increasing
`sequence`, a `kind`, and optional structured data or rich message content.
Kinds are `data`, `progress`, `tool`, `thought`, `preview`,
`pending_approval`, `error`, and `done`.

The reviewed lifecycle backend applies these rules atomically per action:

- the exact same sequence and content is classified as a replay and is not
  inserted twice;
- the same sequence with different content is rejected;
- a new sequence must be greater than every retained earlier sequence;
- no chunk may follow a retained `done` or `error` chunk;
- protocol-edge ingestion rejects chunks for an unknown or already settled
  action.

Action-event reads can return events and retained chunks behind one cursor.
Clients should checkpoint that cursor and chunk sequence, handle reconnects
idempotently, and treat the terminal action state as authoritative. These
storage checks do not create an exactly-once guarantee for every transport,
callback receiver, or external consumer.

## Cancellation stops runtime work, not committed history

`Cancel` can target either an action or a session. For an action, the reviewed
runtime authorizes write access, signals the active cancellation token, calls
the handler's cancellation path when the action is active, and records
cancellation in the lifecycle and queue stores. For a session, it performs an
authorized transition to `cancelled` when that transition is legal.

A cancelled AIP result proves what the runtime recorded. It does not prove that
an external provider reversed a side effect that had already committed.
Provider uncertainty belongs in transaction reconciliation and compensation;
blindly retrying a mutating action after a cancellation timeout can duplicate
work.

The `cancelling` enum value leaves room for an intermediate read state, but the
reviewed lifecycle projection does not currently emit it. Do not wait for that
state before reading the actual result and transaction evidence.

## Operational reads are authorization boundaries

The native read model supports four action operations:

| Operation | Selectors and optional data |
|---|---|
| Read status | Action ID, tenant boundary, result, receipt chain, and retained chunks |
| Read result | Action ID, tenant boundary, receipt metadata, and terminal event hints |
| List actions | Lifecycle, capability, session, principal, approval, transaction, tenant, cursor, and result or receipt inclusion |
| Read events | Action ID, tenant, cursor, kinds, retained chunks, and follow preference |

List and event limits are validated in the range 1–1000. Status and result
requests accept `wait_ms` only up to 30,000 milliseconds. At the reviewed
revision, the in-process runtime lookup is immediate and does not consume
`wait_ms`; callers should not infer long-poll behavior from the field alone.
The HTTP events binding implements follow mode separately through SSE.

These queries require transport-established identity and apply owner, delegated
scope, tenant, and sensitive-field policy. A caller that cannot see an action
must not use `unknown` or `not_found` to infer whether another tenant owns it.

## A session is optional negotiated context

The protocol `Session` stores five facts: `id`, lifecycle `state`,
`created_at`, `initiator`, and `responder`. `SessionView` adds the latest known
update time, an optional expiration, a count of non-terminal bound actions, and
operational links.

A native handshake requests profiles and optional capabilities. The reviewed
gateway requires the claimed client to match the transport-authenticated
principal, negotiates a shared profile, creates an `active` session, and returns
its ID plus an opaque resume token. If no profile matches, it rejects the
handshake and creates no session.

The `SessionState` transition model permits:

| Current state | Allowed next states |
|---|---|
| `new` | `active` |
| `active` | `queued`, `processing`, `cancelled` |
| `queued` | `processing`, `cancelled`, `failed` |
| `processing` | `streaming`, `waiting_for_human`, `completed`, `failed`, `cancelled` |
| `streaming` | `completed`, `failed`, `cancelled`, `waiting_for_human` |
| `waiting_for_human` | `processing`, `completed`, `cancelled`, `failed` |
| `completed`, `failed`, or `cancelled` | `settled` |
| `settled` | None |

This is the legal state graph, not a promise that action execution automatically
drives every session transition. The reviewed session manager creates sessions
directly as `active`; explicit runtime paths perform later transitions. Closing
a session transitions it to `cancelled`, so it can fail when the current state
does not permit that edge.

## Resume tokens are rotating credentials

The reviewed runtime returns a random resume token when creating a session. It
stores a SHA-256 hash, binds the token to the authenticated session owner, gives
it an expiration, and rotates it atomically after a resume credential passes
the owner, validity, and expiry checks. Reusing the old token is rejected.

A resume request supplies the session ID, current token, and optional last event
cursor. On success, the response contains the session view, session-scoped
events after the cursor, a next cursor, and the replacement token.

The reviewed runtime bounds one resume replay read to 100 events. Cancelled,
failed, and settled sessions cannot resume. Invalid, expired, and replayed credentials that
reach token verification collapse to `session.resume_rejected`; owner or scope
authorization can fail earlier. A non-resumable lifecycle state returns
`session.closed`.

The store rotates a valid token before the runtime rejects a closed lifecycle
state, and that error response does not expose the replacement. Do not attempt
resume on a session already known to be cancelled, failed, or settled.

Treat a resume token like a bearer credential:

- never put it in a URL, log, trace field, or analytics event;
- persist the replacement before discarding the previous response;
- serialize concurrent resume attempts so only one receives the next valid
  token;
- pair the token with transport authentication for the same owner;
- close the session, or use a deployment-owned revocation path when one is
  exposed, if continued resume access is no longer safe.

Session resume replays retained session events, not arbitrary application
memory or provider history. Retention and cross-process survival depend on the
configured event and session stores.

## Trust and data boundaries

- An action or session ID selects a record; it does not authorize access to it.
  The gateway and runtime use transport-established identity, owner, delegated
  scope, and verified tenant context for reads and mutations.
- `Action.input`, conversation context, memory, identity projections, results,
  chunks, and receipts can contain sensitive data. Inclusion flags do not
  bypass sensitive-field authorization or retention policy.
- The caller supplies business intent, but the trusted ingress replaces
  self-asserted action identity with resolved identity before execution.
- A resume token proves possession of one rotating session credential. It does
  not replace transport authentication or grant action access outside that
  owner's policy.
- AIP records describe runtime state. The external provider remains the source
  of truth for side effects whose completion is uncertain.

## Design choices and trade-offs

Keeping actions independent from sessions lets a client invoke one operation
without negotiating a long-lived relationship and lets many actions share one
session when continuity matters. The cost is that clients must preserve action,
session, message, and correlation identifiers explicitly instead of relying on
one connection-local handle.

Separate acknowledgement, result, and lifecycle types prevent queue admission
from masquerading as business completion. They also require clients to choose
the correct read surface and reconcile records that can arrive at different
times.

Pluggable stores make the runtime usable in tests, single-process deployments,
and persistent installations. They also make durability an explicit deployment
property. Rotating resume tokens limit replay, but require serialized resume
attempts and careful replacement-token persistence.

Stable enums include `accepted` and `cancelling` even though the reviewed
projection does not produce them. That preserves a vocabulary for other
bindings or later implementations, while requiring documentation to distinguish
wire capacity from observed implementation behavior.

## What these models do not guarantee

- An action ID does not make a non-idempotent provider call safe to retry.
- An acknowledgement does not prove execution or external commit.
- A `done` stream chunk does not replace the final action result.
- A session does not authenticate its participants without the transport and
  gateway trust path.
- Session grouping does not make multiple actions one atomic transaction.
- Cancellation does not compensate an already committed side effect.
- A lifecycle enum value does not prove the reviewed runtime currently emits
  that value.
- A state-backed record survives a restart only when its configured backend is
  persistent and correctly operated.

## Related pages

- [Capabilities and contracts](capabilities.md)
- [Approvals and policy](approvals-and-policy.md)
- [Transactions and compensation](transactions-and-compensation.md)
- [Identity and trust](identity-and-trust.md)
- [HTTP API](../reference/http-api.md)