> ## Documentation Index > Fetch the complete documentation index at: https://checkfu.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Lookup tables > The facts you look up mid-integration: headers, versions, limits, identifiers, and where each canonical table lives. One page for the facts you need mid-integration. Where a canonical table already exists elsewhere, this page links it rather than restating it. The linked section is the source of truth. ## Request headers | Header | Required | Rule | | --------------------------------- | --------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- | | `Authorization: Bearer ` | Always | Server-side only; missing/revoked → `401 auth.invalid_key` | | `Checkfu-Version: 2026-08-27` | Always | Dated wire contract; missing/unsupported → `400 validation.malformed` | | `Idempotency-Key` | Mutating POSTs (where the contract allows it) | Same key + same body replays the first result; same key + different body conflicts. Semantics: [HTTP overview](/reference/overview) | | `Content-Type: application/json` | Requests with a body | | | `Last-Event-ID` | SSE reconnect | Resume a dropped stream: [Resume a stream](/guides/resume-a-stream) | ## Wire versions Only **`2026-08-27`** is currently supported. D257 authorizes pre-launch hard cuts backed by fresh storage; the policy lives in [Authentication and versions](/reference/authentication#dated-wire-versions). ## Throttling and refusals Checkfu does not publish anonymous rate-limit numbers; work is refused by **named gates**, each with a typed error you can dispatch on: | Refusal | Error | What to do | | ------------------------------------------------------------- | ------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------- | | A limit you configured (Budget, quota, or API-key rate limit) | `429 budget.exceeded` | Clears only when the limit does. Back off substantially or raise the limit; surface "limit reached" to end users without distinguishing which limit | | Organization entitlement exhausted | `402 billing.usage_limit_reached` | An Organization administrator raises the plan or adds credits | | Account not in good standing | `402 billing.payment_required` | An Organization administrator fixes billing | | Platform-supplied model capacity exhausted | `503 model.platform_capacity_reached` | Retry later, or bring your own provider key | Whether an error is worth retrying is a per-error property. The [error registry](/reference/errors) has a retry-safety column for the whole catalog. A `429` in particular clears only when its underlying limit does, so immediate retries buy nothing. ## Request and payload limits Every ceiling below is enforced before the work happens, and each one has a typed refusal. A byte limit crossed while the body streams in is `413 validation.payload_too_large`; a count or size the schema rejects after the body arrives is `400 validation.malformed`. | Payload | Ceiling | On breach | | ------------------------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------- | | Any `/v1` request body with a method other than `GET` or `HEAD`, unless a row below overrides it | 4 MiB | `413 validation.payload_too_large` | | `POST /v1/files` upload | 64 MiB of file content; the multipart envelope allows a further 64 KiB for part framing | `413 validation.payload_too_large` | | The JSON body of a Project tree route (`POST /v1/projects`, `…/revisions`, `…/push`) | A computed envelope over the tree budget in the next two rows (base64 expansion plus per-file path and structure) rather than the 4 MiB default | `413 validation.payload_too_large` | | An uploaded Project revision | 1,024 files, 10 MiB per decoded file, 20 MiB per decoded revision | `400 validation.malformed` | | A Git push manifest (`POST /v1/projects/{id}/push`) | 64 files; the per-file and per-revision byte budget is unchanged | `400 validation.malformed` | | An Agent directory archive (`application/x-tar`) | 2 MiB per archive, 1 MiB per file, 256 files | `400 validation.malformed` | | A Skill (`POST /v1/skills`, `POST /v1/skills/import`) | 1 MiB of instructions, 256 files, 1 MiB per file, 2 MiB across files; an imported tar archive is additionally capped at 4 MiB | `400 validation.malformed` | | An Automation webhook delivery body (`POST /v1/ingest/automations/{id}`) | 1 MiB | `413 validation.payload_too_large` | | That delivery's JSON structure, checked after the signature verifies | 64 levels of nesting, 100,000 nodes | `400 validation.malformed` | | An Automation prompt, both as authored and after `{{event}}` expands | 64 KiB encoded as UTF-8 | `400 validation.malformed` | | A MemoryStore document body | 100 kB | `400 validation.malformed` | ## Canonical tables and where they live | You need | Go to | | ----------------------------------------------------- | ---------------------------------------------------------------------- | | Every error, with retry safety | [Errors](/reference/errors) | | Session statuses and every legal transition | [Sessions reference](/reference/sessions#session-status) | | The complete event catalog and envelope | [Events](/reference/events) | | The freeze rule (what changes when) | [Two freeze horizons](/concepts/sessions-and-runs#two-freeze-horizons) | | PermissionAssignment/ActionPolicy decision algorithm | [Tenancy and governance](/concepts/tenancy-and-governance) | | Pagination and streaming conventions | [HTTP overview](/reference/overview) | | Identifier prefixes (`wrkspc_`, `agent_`, `sess_`, …) | [HTTP overview → Identifiers](/reference/overview#identifiers) |