Stedi connector for AI agents

Tools your billing agent reaches for on Stedi, scoped per user.

CALL ANY TOOL

17 tools for insurance claims in Stedi: check eligibility, coordination of benefits, and claim status, search payers, validate and submit 837P claims, and read 277CA and 835 ERA reports.

stedi_check_claim_status

Check claim status

Send a real-time 276/277 claim status request to a payer through Stedi for a claim the payer has already accepted. Returns the payer's 277 response as JSON: a claims array where each matching claim has claimStatus (status category and codes, payer claim number, charge and paid amounts, dates) and serviceDetails, plus payer, providers, subscriber, errors and the raw X12. Use when a 277CA or 835 ERA has not arrived in the expected time. Use stedi_list_claims or stedi_get_claim_timeline to see what Stedi has already received. Works with production API keys only.

Parameters

Name

Type

Required

Description

providers

array

Required

The billing provider (exactly one) and optionally service providers on the claim. Each entry has providerType (BillingProvider or ServiceProvider), npi, and organizationName or firstName and lastName; tin is sometimes required by the payer. Example: [{"providerType": "BillingProvider", "npi": "1999999984", "organizationName": "Example Clinic"}].

subscriber

object

Required

The subscriber on the claim: memberId, firstName and lastName are required; add dateOfBirth (YYYYMMDD) and gender (M or F) when the subscriber is the patient. Example: {"memberId": "TEST12345", "firstName": "Test", "lastName": "Patient", "dateOfBirth": "19800101"}.

trading_partner_service_id

string

Required

The payer ID the claim was sent to (primary payer ID, Stedi payer ID or alias).

dependent

object

Optional

The patient, when the patient is a dependent on the subscriber's policy: firstName, lastName, dateOfBirth (YYYYMMDD) and gender (M or F). Example: {"firstName": "Test", "lastName": "Child", "dateOfBirth": "20150101"}.

encounter

object

Optional

Identifies the claim. Stedi recommends a date-of-service range (beginningDateOfService and endDateOfService, YYYYMMDD); you can also pass the payer's claim number (tradingPartnerClaimNumber), patientAccountNumber or submittedAmount. Sending too much detail can hide matches. Example: {"beginningDateOfService": "20260101", "endDateOfService": "20260107"}.

trading_partner_name

string

Optional

The payer's name, such as Cigna or Aetna. Optional.

stedi_check_coordination_of_benefits

Check coordination of benefits

stedi_check_eligibility

Check eligibility

Run a real-time 270/271 insurance eligibility and benefits check with a payer through Stedi. Returns the payer's 271 response as JSON: payer, provider and subscriber details, plans with their benefits (coverage status, copays, coinsurance, deductibles), errors and warnings, plus the raw X12. Use before a visit to confirm active coverage and patient responsibility. Use stedi_check_coordination_of_benefits to find other coverage; use stedi_search_payers first to get the payer ID.

Parameters

Name

Type

Required

Description

payer_id

string

Required

The payer ID to send the check to: the primary payer ID, Stedi payer ID or any payer ID alias from the Payer Network. Test API keys only accept Stedi's mock payer requests.

provider

object

Required

The provider requesting the check. It needs a name, given as an organization name or a person's first and last name, and usually the provider's 10-digit NPI. Tax ID and other identifiers are only needed when a payer asks for them. Example: {"name": {"organization": "Example Clinic"}, "npi": "1999999984"}.

subscriber

object

Required

The primary policyholder, or a dependent who has their own member ID. Send the member ID, the name as a person (firstName, lastName) and the date of birth (YYYY-MM-DD); payers match on these. Gender (MALE or FEMALE) and address are optional. Example: {"memberId": "TEST12345", "name": {"person": {"firstName": "Test", "lastName": "Patient"}}, "dateOfBirth": "1980-01-01"}.

dependent

object

Optional

A dependent to check, only when the patient is listed under the subscriber's policy and has no member ID of their own. One dependent per check. Give the name (person firstName and lastName), date of birth and relationship to the subscriber (SPOUSE, CHILD or OTHER_ADULT). Example: {"name": {"person": {"firstName": "Test", "lastName": "Child"}}, "dateOfBirth": "2015-01-01", "relationToSubscriber": "CHILD"}.

eligibility_search_id

string

Optional

Identifier that groups several eligibility checks for the same patient into one eligibility search record in the Stedi portal.

encounter

object

Optional

What benefits to ask about. List services as code system plus value: STC service type codes (for example 30 for general health plan coverage), CPT or HCPCS codes. Optionally add a service date or date range (dates.service); without one the payer uses today. Example: {"services": [{"system": "STC", "value": "30"}]}.

external_patient_id

string

Optional

Your own unique identifier for the patient. Stedi uses it to correlate past eligibility checks for the same person; recommended on every request.

payer_name

string

Optional

The payer's name, such as Cigna or Aetna. Optional and informational.

stedi_get_277ca_report

Get 277ca report

stedi_get_claim

Get claim

stedi_get_claim_timeline

Get claim timeline

stedi_get_era_report

Get era report

stedi_get_payer

Get payer

stedi_get_professional_claim_submission

Get professional claim submission

stedi_get_transaction

Get transaction

stedi_list_claims

List claims

stedi_list_payers

List payers

stedi_list_transactions

List transactions

List transactions Stedi has processed in the account, newest first, with optional filters such as transaction set (835 for ERAs, 277 for claim acknowledgments), direction, mode, status and date range. Returns items (each with transactionId, status, direction, mode, processedAt, x12 metadata including the transaction set, businessIdentifiers, partnership and artifacts with download URLs) and nextPageToken. Use to find ERAs or 277CAs and their transaction IDs. Use stedi_poll_transactions to fetch only transactions processed since a given time.

Parameters

Name

Type

Required

Description

business_identifier

string

Optional

Only return transactions containing a business identifier with this value, such as a patient control number or check number.

direction

string

Optional

INBOUND for transactions received from payers or partners, OUTBOUND for those you sent, or UNKNOWN. One of: `INBOUND`, `OUTBOUND`, `UNKNOWN`.

element_id

string

Optional

The X12 element ID the business identifier belongs to, such as 127 (Reference Identification). Only valid together with business_identifier.

from

string

Optional

Only return transactions created at or after this ISO 8601 timestamp.

mode

string

Optional

Only return test, production or other transactions. One of: `test`, `production`, `other`.

page_size

integer

Optional

Maximum number of transactions per page, up to 500. Stedi defaults to 100.

page_token

string

Optional

Opaque token from the nextPageToken field of a previous response, used to fetch the next page. Omit for the first page.

partnership_id

string

Optional

Only return transactions sent or received on this partnership.

status

string

Optional

Only return transactions Stedi processed successfully (succeeded) or not (failed). One of: `succeeded`, `failed`.

string

Optional

Only return transactions created up to and including this ISO 8601 timestamp.

transaction_set_id

string

Optional

Only return this type of transaction, as a 3-digit X12 transaction set code: 835 for ERAs, 277 for claim acknowledgments, 837 for claims, 270 or 271 for eligibility, 999 for implementation acknowledgments.

stedi_poll_transactions

Poll transactions

stedi_search_payers

Search payers

Search Stedi's Payer Network by payer name, payer ID or alias, with fuzzy matching, and optionally filter by supported transactions, coverage type, state or insurance program. Returns items ranked by relevance, each with the payer record (stediId, displayName, primaryPayerId, aliases, coverage types, supported transaction types and enrollment requirements), the matched text and a score, plus nextPageToken. Use to find the payer ID for an eligibility check, claim or claim status request. Use stedi_get_payer when you already have the Stedi payer ID, and stedi_list_payers to export the whole network.

Parameters

Name

Type

Required

Description

claim_payment

string

Optional

Filter payers by 835 Electronic Remittance Advice (ERA) support: SUPPORTED, NOT_SUPPORTED, ENROLLMENT_REQUIRED (supported once the provider is enrolled with the payer) or EITHER (supported with or without enrollment). When several transaction filters are set, a payer must match all of them. One of: `SUPPORTED`, `NOT_SUPPORTED`, `ENROLLMENT_REQUIRED`, `EITHER`.

claim_status

string

Optional

Filter payers by real-time 276/277 claim status support: SUPPORTED, NOT_SUPPORTED, ENROLLMENT_REQUIRED (supported once the provider is enrolled with the payer) or EITHER (supported with or without enrollment). When several transaction filters are set, a payer must match all of them. One of: `SUPPORTED`, `NOT_SUPPORTED`, `ENROLLMENT_REQUIRED`, `EITHER`.

coordination_of_benefits

string

Optional

Filter payers by coordination of benefits (COB) check support: SUPPORTED, NOT_SUPPORTED, ENROLLMENT_REQUIRED (supported once the provider is enrolled with the payer) or EITHER (supported with or without enrollment). When several transaction filters are set, a payer must match all of them. One of: `SUPPORTED`, `NOT_SUPPORTED`, `ENROLLMENT_REQUIRED`, `EITHER`.

coverage_types

array

Optional

Only return payers that support all of these coverage types: medical, dental and/or vision. Payers Stedi has not classified are excluded.

dental_claim_submission

string

Optional

Filter payers by 837D dental claim submission support: SUPPORTED, NOT_SUPPORTED, ENROLLMENT_REQUIRED (supported once the provider is enrolled with the payer) or EITHER (supported with or without enrollment). When several transaction filters are set, a payer must match all of them. One of: `SUPPORTED`, `NOT_SUPPORTED`, `ENROLLMENT_REQUIRED`, `EITHER`.

eligibility_check

string

Optional

Filter payers by real-time 270/271 eligibility check support: SUPPORTED, NOT_SUPPORTED, ENROLLMENT_REQUIRED (supported once the provider is enrolled with the payer) or EITHER (supported with or without enrollment). When several transaction filters are set, a payer must match all of them. One of: `SUPPORTED`, `NOT_SUPPORTED`, `ENROLLMENT_REQUIRED`, `EITHER`.

institutional_claim_submission

string

Optional

Filter payers by 837I institutional claim submission support: SUPPORTED, NOT_SUPPORTED, ENROLLMENT_REQUIRED (supported once the provider is enrolled with the payer) or EITHER (supported with or without enrollment). When several transaction filters are set, a payer must match all of them. One of: `SUPPORTED`, `NOT_SUPPORTED`, `ENROLLMENT_REQUIRED`, `EITHER`.

operating_states

array

Optional

Only return payers that operate in all of these two-letter US state or territory codes. Use NATIONAL for payers operating in all 50 states; territories such as PR must be listed explicitly. Payers without state classifications are excluded.

page_size

integer

Optional

Maximum number of payers to return per page. Stedi defaults to 20.

page_token

string

Optional

Opaque token from the nextPageToken field of a previous response, used to fetch the next page. Omit for the first page.

professional_claim_submission

string

Optional

Filter payers by 837P professional claim submission support: SUPPORTED, NOT_SUPPORTED, ENROLLMENT_REQUIRED (supported once the provider is enrolled with the payer) or EITHER (supported with or without enrollment). When several transaction filters are set, a payer must match all of them. One of: `SUPPORTED`, `NOT_SUPPORTED`, `ENROLLMENT_REQUIRED`, `EITHER`.

programs

array

Optional

Only return payers that participate in any of these insurance programs: AUTOMOBILE_MEDICAL, COMMERCIAL, DISABILITY, LIABILITY_MEDICAL, MEDICAID, MEDICARE, MEDICARE_ADVANTAGE, TITLE_V, TRICARE, VETERANS_AFFAIRS, WORKERS_COMPENSATION.

query

string

Optional

Text to search the Payer Network for: a payer name, payer ID or alias. Case-insensitive with fuzzy matching, so 'cig', '62308' and 'SX071' all find Cigna. If omitted, only the filters are applied.

stedi_submit_professional_claim

Submit professional claim

Submit an 837P professional claim to a payer through Stedi, using JSON fields laid out like the CMS-1500 form. Returns claimId and submissionId when the claim passes Stedi's edits; otherwise also an errors array, and the claim is stored as REJECTED (HTTP 201 either way). Use to bill a payer for professional services. Run stedi_validate_professional_claim first to catch errors without sending; track the result with stedi_get_claim and stedi_get_claim_timeline. With a test API key, set the payer id to STEDI.

Parameters

Name

Type

Required

Description

authorization

object

Required

Signature and assignment-of-benefits indicators (CMS-1500 boxes 12, 13, 27, 31). Example: {"patientReleasesMedicalInfo": "YES", "insuredAuthorizesAssignment": "YES", "providerAcceptsAssignment": "ASSIGNED", "providerSignature": "ON_FILE"}.

billing

object

Required

Billing details (CMS-1500 boxes 25, 26, 28, 32, 33): the billing provider (name, address, NPI and taxonomy code), the tax ID, your patientControlNumber and the totalCharge as a decimal string; optionally the service facility. Example: {"billingProvider": {"name": {"organization": "Example Clinic"}, "identifiers": {"npi": "1999999984", "taxonomyCode": "207Q00000X"}, "address": {"addressLine1": "123 Example St", "city": "Springfield", "state": "IL", "postalCode": "12345"}}, "taxId": {"ein": "123456789"}, "patientControlNumber": "TEST-001", "totalCharge": "100.00"}.

encounter

object

Required

Clinical details of the encounter: at least the primaryDiagnosisCode (ICD-10, without the dot), plus optional other diagnoses, referring or supervising providers, clinical dates, prior authorization and resubmission details. Example: {"primaryDiagnosisCode": "J0190"}.

insured

object

Required

The subscriber who holds the policy being billed (CMS-1500 boxes 1, 1a, 4, 7, 11). Required: name, insuranceType (MEDICARE, MEDICAID, TRICARE, CHAMPVA, FECA_BLK_LUNG or OTHER) and paymentResponsibilityLevelCode (PRIMARY). Also send the memberId, dateOfBirth (YYYY-MM-DD), gender and address. Example: {"memberId": "TEST12345", "name": {"person": {"firstName": "Test", "lastName": "Patient"}}, "dateOfBirth": "1980-01-01", "gender": "FEMALE", "insuranceType": "OTHER", "paymentResponsibilityLevelCode": "PRIMARY", "address": {"addressLine1": "1 Example Ave", "city": "Springfield", "state": "IL", "postalCode": "12345"}}.

payer

object

Required

The payer being billed: its payer ID and name. With a test API key, use STEDI as the payer ID. Example: {"id": "60054", "name": {"organization": "Aetna"}}.

purpose

string

Required

Why the claim is submitted: CHARGEABLE for a standard fee-for-service claim with at least one charge, REPORTING for an encounter report with no payment expected, SUBROGATION_DEMAND for a subrogation claim. One of: `CHARGEABLE`, `REPORTING`, `SUBROGATION_DEMAND`.

service_lines

array

Required

The services billed (CMS-1500 box 24), one object per line: datesOfService (start and end), procedureCode (code and optional modifiers), lineItemChargeAmount, units, placeOfService and the diagnosisCodes it relates to. Example: [{"datesOfService": {"start": "2026-01-15", "end": "2026-01-15"}, "procedureCode": {"code": "99213"}, "lineItemChargeAmount": "100.00", "units": "1", "placeOfService": "11", "diagnosisCodes": ["J0190"]}].

submitter

object

Required

The entity submitting the claim to Stedi: its name, a contact phone number or email, and its ETIN if one was assigned. Example: {"name": {"organization": "Example Billing"}, "contact": {"phoneNumber": "5555551234"}}.

idempotency_key

string

Optional

A unique string for this submission. Retrying with the same key within 24 hours returns the original result instead of submitting the claim twice.

other_insured

array

Optional

Other coverage the patient holds, for coordination of benefits (CMS-1500 boxes 9, 9a, 9d), one object per policy. Each needs memberId, name, otherPayer (payer ID and name), responsibilityLevel (PRIMARY, SECONDARY or TERTIARY), relationshipToInsured, claimFilingIndicator (such as COMMERCIAL_INSURANCE or BLUE_CROSS_BLUE_SHIELD) and authorization (insuredAuthorizesAssignment and patientReleasesMedicalInfo). Example: [{"memberId": "TEST67890", "name": {"person": {"firstName": "Test", "lastName": "Spouse"}}, "otherPayer": {"id": {"payerId": "00000"}, "name": {"organization": "Example Payer"}}, "responsibilityLevel": "SECONDARY", "relationshipToInsured": "SPOUSE", "claimFilingIndicator": "COMMERCIAL_INSURANCE", "authorization": {"insuredAuthorizesAssignment": "YES", "patientReleasesMedicalInfo": "YES"}}].

patient

object

Optional

The patient, only when they are not the insured. All of name, dateOfBirth (YYYY-MM-DD), gender, address and relationshipToInsured (for example CHILD or SPOUSE) are required. Example: {"name": {"person": {"firstName": "Test", "lastName": "Child"}}, "dateOfBirth": "2015-01-01", "gender": "MALE", "relationshipToInsured": "CHILD", "address": {"addressLine1": "1 Example Ave", "city": "Springfield", "state": "IL", "postalCode": "12345"}}.

stedi_validate_professional_claim

Validate professional claim

Validate an 837P professional claim (CMS-1500 JSON layout) against Stedi's payer checks, edits and mapping without sending it to the payer. Returns an empty object when the claim passes, or an errors array describing each failed edit. Use before stedi_submit_professional_claim, with the same inputs, to fix problems first. Nothing is submitted or stored.

Parameters

Name

Type

Required

Description

authorization

object

Required

billing

object

Required

encounter

object

Required

insured

object

Required

payer

object

Required

The payer being billed: its payer ID and name. With a test API key, use STEDI as the payer ID. Example: {"id": "60054", "name": {"organization": "Aetna"}}.

purpose

string

Required

service_lines

array

Required

submitter

object

Required

other_insured

array

Optional

patient

object

Optional

Build your Agent

Same auth pattern across LangChain, OpenAI, Anthropic, and Google ADK.

import { ScalekitClient } from "@scalekit-sdk/node";
import { createReactAgent } from "@langchain/langgraph/prebuilt";

const sk = new ScalekitClient(env.SCALEKIT_ENV_URL, env.SCALEKIT_CLIENT_ID, env.SCALEKIT_CLIENT_SECRET);

// Stedi tools scoped to this user
const { tools } = await sk.tools.listScopedTools("user_123", {
  filter: { connectionNames: ["stedi"], toolNames: [
    "stedi_check_eligibility",
    "stedi_list_claims",
    "stedi_get_claim_timeline"] },
  pageSize: 100,
});

const agent = createReactAgent({ llm, tools });
await agent.invoke({ messages: [{ role: "user", content: "Check eligibility for this patient and show the timeline of their last claim" }] });

import OpenAI from "openai";
import { ScalekitClient } from "@scalekit-sdk/node";

const sk = new ScalekitClient(env.SCALEKIT_ENV_URL, env.SCALEKIT_CLIENT_ID, env.SCALEKIT_CLIENT_SECRET);
const openai = new OpenAI();

const { tools } = await sk.tools.listScopedTools("user_123", {
  filter: { connectionNames: ["stedi"] }, pageSize: 100,
});

const res = await openai.chat.completions.create({
  model: "gpt-5",
  messages: [{ role: "user", content: "Check eligibility for this patient and show the timeline of their last claim" }],
  tools,
});

// Execute the tool call with the user's vaulted Stedi API key
await sk.tools.executeTool(res.choices[0].message.tool_calls[0], "user_123");

import Anthropic from "@anthropic-ai/sdk";
import { ScalekitClient } from "@scalekit-sdk/node";

const sk = new ScalekitClient(env.SCALEKIT_ENV_URL, env.SCALEKIT_CLIENT_ID, env.SCALEKIT_CLIENT_SECRET);
const anthropic = new Anthropic();

const { tools } = await sk.tools.listScopedTools("user_123", {
  filter: { connectionNames: ["stedi"] }, pageSize: 100,
});

const msg = await anthropic.messages.create({
  model: "claude-sonnet-5",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Check eligibility for this patient and show the timeline of their last claim" }],
  tools,
});

// Tool call runs with the user's vaulted Stedi API key
await sk.tools.executeTool(msg.content, "user_123");

import { Agent } from "@google/adk/agents";
import { ScalekitClient } from "@scalekit-sdk/node";

const sk = new ScalekitClient(env.SCALEKIT_ENV_URL, env.SCALEKIT_CLIENT_ID, env.SCALEKIT_CLIENT_SECRET);

const { tools } = await sk.tools.listScopedTools("user_123", {
  filter: { connectionNames: ["stedi"] }, pageSize: 100,
});

const agent = new Agent({
  name: "billing_agent",
  model: "gemini-2.5-pro",
  instruction: "Stedi tools scoped to this user",
  tools,
});

await agent.run("Check eligibility for this patient and show the timeline of their last claim");

Try these prompts

Copy any prompt into your agent. Each maps directly to a Stedi tool. Click to copy, paste into your agent, done.

Eligibility

Copy the prompt

Copied

Run an eligibility check for this patient with their payer for a routine office visit.

Copy the prompt

Copied

Check whether this patient has other active coverage and which payer is primary.

Copy the prompt

Copied

Find the Stedi payer ID for this payer by name.

Claims

Copy the prompt

Copied

Validate this 837P professional claim before we send it.

Copy the prompt

Copied

Submit this professional claim to the payer.

Copy the prompt

Copied

List claims submitted in the last 7 days and their status.

Status and payments

Copy the prompt

Copied

Check the claim status for patient control number PCN-20481 with the payer.

Copy the prompt

Copied

Show the timeline of claim PCN-20481, including acknowledgments and payments.

Copy the prompt

Copied

Get the 835 ERA for this transaction and summarize the paid amounts.

SEE HOW AUTH WORKS

Each user connects their own Stedi API key once, and Scalekit sends it with every call. Credentials stay vaulted, every call is scope checked, and every action is logged.

Authorize

Your user connects

Stedi

once. We tie it to their identity and the meetings they approved — no shared bot account, no org-wide access

Who:

user ‘A’

when:

Once per user

access:

Limited to user

Store

Their

Stedi

token lives in a vault scoped to them. User A's meetings are never reachable by an agent acting for user B, even on the same connection

vault:

encrypted

scope:

per-user

tokens:

auto-refreshed

Resolve

When your agent calls a

Stedi

tool, we fetch the right token server-side. It never touches your agent, never appears in the LLM context, never shows up in your logs

speed:

~40ms

check:

before every call

seen by:

nobody

Audit

Every

Stedi

tool call is logged — who triggered it, which meeting was fetched, what came back. 90 days of history, tied to the user who authorized it

history:

90 days

export:

SIEM-ready

logged:

every call

Test other agents

See the same per-user auth pattern across other healthcare connectors.

Support and Ops Teams

Support ticket automation agent

Fetches new Zendesk tickets, drafts a reply from Notion knowledge base articles, digests what it cannot answer to Slack, and archives the rest, acting as the support agent rather than a shared API key.

Engineering Teams

Slack triage

Polls Slack for new messages, classifies bugs and support requests with a LangGraph router, files GitHub issues or Zendesk tickets, and confirms in the thread.

Why Scalekit

Secure your agent's access. Connectors ship in minutes

01.

Shared tokens break per-user analytics

A shared Stedi API key looks fine in a demo. In production every claim submission looks like one service account, and you cannot tell which user triggered it. Scalekit resolves the credential of the actual user who triggered the agent, never a shared bot.

// shared key
audit → bot_service_account

// scalekit
audit → user_abc ✓

02.

Authentication is not authorization

03.

Multi-tenancy is architectural

04.

Stedi today. Ten connectors tomorrow.

“Our agents act across Salesforce, Gong, Google Drive, and more, on behalf of every customer. Scalekit behind the scenes meant we can keep adding tools without ever rebuilding how credentials or tool calling work.”

Venu Madhav Kattagoni

Head of Engineering / Von

FAQs

Frequently Asked Questions

Does the agent access Stedi as the user or through a shared key?

As the user. Each user connects their own Stedi API key once, and Scalekit sends it with every call. Every eligibility check and claim submission is attributed to that user in your audit trail, not a shared service account.

Where is the Stedi API key stored?

In Scalekit's managed AES-256 token vault, namespaced per tenant. To rotate it, the user reconnects with a new API key. Revocation is a single dashboard action. Credentials never appear in prompts, logs, or LLM context.

Can I limit what the agent does in Stedi?

Yes. Filter by tool name in listScopedTools to expose only what you want, for example the eligibility, claim status, and report tools without stedi_submit_professional_claim, the one tool that sends a claim to a payer. Scalekit also enforces scope checks before every API call.

What happens when a user revokes Stedi access?

The connection is invalidated on the next tool call. Subsequent requests for that user fail closed with a clear error. Other users in the tenant remain unaffected. The event is logged for audit.

Can the agent check a claim before submitting it?

Yes. stedi_validate_professional_claim runs an 837P claim through Stedi's payer checks, edits and mapping without sending it to the payer. stedi_submit_professional_claim then sends it, and stedi_get_claim_timeline tracks its 277CA acknowledgments and ERA payments.