Errors

Every SDK exception inherits from AlterSDKError. Branching on the typed subclasses is the supported way to handle failure modes — never parse error message strings.

from alter_sdk import (
    AlterSDKError, AlterValueError,
    BackendError, ReAuthRequiredError,
    GrantExpiredError, GrantRevokedError, GrantDeletedError,
    GrantNotFoundError, AgentDelegationMissingError,
    GrantNotDelegableError, CredentialRevokedError,
    AmbiguousGrantError, GrantCandidate, NoDelegatedGrantError,
    PolicyViolationError, StepUpRequiredError, RedactDischargeFailedError,
    InsufficientScopeError,
    TokenRefreshInProgressError, QuotaExceededError, RateLimitError,
    ConnectFlowError, ConnectDeniedError, ConnectConfigError, ConnectTimeoutError,
    ProviderAPIError, ScopeReauthRequiredError, ProviderUnauthorizedError,
    NetworkError, TimeoutError,
    ApprovalError, ApprovalDeniedError, ApprovalExpiredError,
    ApprovalTimeoutError, ApprovalExecutionFailedError,
    AgentError, AgentNotFoundError, AgentNameExistsError,
    CallerAgentMismatchError, CallerAgentResolutionError,
    AgentConcurrentUpdateError,
    AgentInactiveError, AgentRevokedError,
    InvalidKeyError, KeyRevokedError, KeyExpiredError,
    KeyRotationExpiredError, KeyInactiveError, KeyAppNotFoundError,
    KeyAlreadyRevokedError,
    KeyNotFoundError, LastActiveKeyError, AgentKeyLimitError,
    MeRequiresAgentKeyError, AgentCannotMintSubagentsError,
    RestrictedGrantRequiresProxyError, SiblingLabelConflictError,
    IdempotencyKeyBodyMismatchError,
    IdempotencyKeyAgentRevokedError,
    IdempotencyKeyAgentInactiveError,
)

The full hierarchy and a per-error recovery playbook are documented at /reference/errors. This page is a short index of what’s exported from alter_sdk so you know what to import.

Catching by category

from alter_sdk import ReAuthRequiredError, BackendError

try:
    resp = await app.request("GET", url, provider="provider-id")
except ReAuthRequiredError:
    # GrantExpiredError, GrantRevokedError, CredentialRevokedError, GrantDeletedError
    # — user must re-authorize via Connect
    ...
except BackendError:
    # Any backend-origin failure not in the re-auth bucket
    ...

Common attributes

Every typed error carries .message and .details: dict[str, Any]. Specific subclasses add fields:

Exception	Extra attributes
GrantRevokedError, TokenRefreshInProgressError	grant_id
CredentialRevokedError	grant_id, provider_id, app_user_id
GrantExpiredError	provider_id, agent_id, app_user_id — populated only on the delegation-path expiry (a TTL-lapsed delegation chain); None on the root-path TTL expiry
GrantNotFoundError	provider_id, agent_id, app_user_id (no grant_id — the grant lookup is what failed)
AgentDelegationMissingError	subclass of GrantNotFoundError (same provider_id / agent_id / app_user_id fields) — raised on the agent path when a grant_id isn’t reachable by this agent; delegate via Connect or resolve by provider
GrantNotDelegableError	(subclass of BackendError) — raised by agent.delegate() when the held grant is not delegable, or a managed secret’s operator ceiling blocks re-delegable grants (HTTP 403 grant_not_delegable)
ScopeReauthRequiredError	grant_id, provider_id
AmbiguousGrantError	provider_id, account_identifiers, account_was_provided, app_user_ids, grant_ids, candidates
NoDelegatedGrantError	provider_id, agent_id, app_user_id
PolicyViolationError	policy_error
StepUpRequiredError	subclass of PolicyViolationError; policy_error="step_up_required" and max_session_age_seconds carries the session-freshness ceiling when supplied
RedactDischargeFailedError	subclass of PolicyViolationError; policy_error="redact_discharge_failed" and the request was denied because required redaction could not be applied
SiblingLabelConflictError	label — the sibling label already active on the credential
QuotaExceededError	retry_after — seconds until the quota window resets (prefers the Retry-After response header over the body value, so it can differ from details["retry_after"], and is capped at 2,678,400 seconds / 31 days — a quota window is a calendar period up to a month long, and the response reports the longest exhausted one); may be None. Raised on a request-quota policy denial; the SDK never auto-retries it
RateLimitError	retry_after — seconds to wait before retrying (prefers the Retry-After response header over the body value, so it can differ from details["retry_after"], and is capped at 3,600 seconds — one hour, above the platform’s legitimate retry guidance); scope ("ip", "api_key" or "organization") — which platform ceiling was hit (a plain str, not a closed enum, so a ceiling added later stays parseable; the known values are exported as RATE_LIMIT_SCOPE_VALUES, ordered outermost-first); limit; window_seconds. scope, limit and window_seconds may each be None — not every response carrying this error code supplies them, so branch on a missing value rather than assuming one. A transient throttle, not a denial: the same request succeeds once the reported wait elapses
InsufficientScopeError	required, granted, missing, scope_version, current_scope_version, scope_version_mismatch, documentation_url (aliases: required_scopes, granted_scopes, docs_url)
ProviderAPIError, ScopeReauthRequiredError, ProviderUnauthorizedError	status_code, response_body
ScopeReauthRequiredError	also missing_scopes (from WWW-Authenticate: Bearer error="insufficient_scope")
ProviderUnauthorizedError	grant_id, provider_id — provider returned 401 (credential rejected provider-side); re-authorize an OAuth grant via a new Connect session, or update the stored managed secret. A 401 whose WWW-Authenticate challenge carries error="insufficient_scope" (RFC 6750 — the credential is still valid, it just lacks a scope) surfaces as a generic ProviderAPIError instead
ConnectTimeoutError	details["reason"] is "poll_deadline_elapsed" when the local polling deadline wins, or "session_expired" when a session observed pending expires before Alter receives a callback. With no callback, an exact provider-side error is unknowable; the provider may have retained an error page, the browser may have closed, or the user may have abandoned the flow
ApprovalError (and subclasses)	approval_id
AgentError (and subclasses)	code, hint

GrantCandidate is a supporting dataclass, not an exception. Each item in AmbiguousGrantError.candidates has grant_id, label, account_identifier, and account_display_name; retry with the chosen grant_id, or with provider + label when a stable sibling address is preferable.

Recovery patterns

Identity-mode ambiguity — retry with account=:

from alter_sdk import AmbiguousGrantError

try:
    resp = await app.request("GET", url, provider="provider-id")
except AmbiguousGrantError as e:
    resp = await app.request(
        "GET",
        url,
        provider="provider-id",
        account=e.account_identifiers[0],
    )

Missing or broken credential — mint a recovery Connect session:

from alter_sdk import NoDelegatedGrantError, CredentialRevokedError

try:
    resp = await agent.request("GET", url, provider="provider-id")
except (NoDelegatedGrantError, CredentialRevokedError) as e:
    session = await agent.create_connect_session_for_error(e)
    redirect_to(session.connect_url)
    results = await agent.poll_connect_session(session.session_token)

Transient refresh conflict — exponential backoff:

import asyncio
from alter_sdk import TokenRefreshInProgressError

for attempt in range(3):
    try:
        resp = await app.request(...)
        break
    except TokenRefreshInProgressError:
        await asyncio.sleep(1 * (2 ** attempt))

Quota window exhausted — wait for the window to reset:

import asyncio
from alter_sdk import QuotaExceededError

try:
    resp = await app.request(...)
except QuotaExceededError as e:
    # A request-quota policy denial — the SDK never auto-retries it.
    await asyncio.sleep(e.retry_after if e.retry_after is not None else 60)
    resp = await app.request(...)

Insufficient scope at the version mismatch — rotate the key:

from alter_sdk import InsufficientScopeError

try:
    await app.agents.create(
        name="bot",
        scopes={"provider-id": ["resource:read"]},
    )
except InsufficientScopeError as e:
    if e.scope_version_mismatch:
        print(f"Key minted at v{e.scope_version}; server at v{e.current_scope_version}. Rotate.")
    else:
        print(f"Missing: {e.missing}. See {e.docs_url}")

See /reference/errors for the full hierarchy with descriptions and recovery guidance for every error.