api-config

name	api-config
description	Reference for core and server configuration in `@cyanheads/mcp-ts-core`. Covers env var tables with defaults, priority order, server-specific Zod schema pattern, and Workers lazy-parsing requirement.
metadata	{"author":"cyanheads","version":"1.16","audience":"external","type":"reference"}

Overview

Configuration has two layers: core config (managed by the framework, env-driven) and server config (your own Zod schema for domain-specific env vars). Never merge them.

Import: AppConfig, config, parseConfig, resetConfig, ConfigSchema from @cyanheads/mcp-ts-core/config.

---

Core config

Managed by @cyanheads/mcp-ts-core. Validated via Zod from environment variables. Uses a lazy proxy — parsing is deferred until the first property read.

Priority (highest to lowest):

1. name/version/title/websiteUrl/description/icons options passed to createApp() or createWorkerHandler()
2. Environment variables
3. package.json fields

Where package.json is read from: the application root — the nearest package.json at or above the process entry module (process.argv[1]), which is the served package on every launch path (npx, .mcpb, a client config naming dist/index.js), none of which run from the package root. The launching client's working directory is never the anchor: a stdio client starts the server from wherever it happens to be, so reading identity from there makes a server report a foreign project's name and version. When the entry module is a tool installed under the project's own node_modules and the process runs from that project — a test runner is the usual case — the project's manifest wins. With no manifest reachable, the framework's own identity is the fallback.

---

Identity

Env Var	AppConfig field	Default	Notes
MCP_SERVER_NAME	mcpServerName	package.json name	Overrides package name
MCP_SERVER_VERSION	mcpServerVersion	package.json version	Overrides package version
MCP_SERVER_DESCRIPTION	mcpServerDescription	package.json description	Optional; createApp({ description }) wins when set
PACKAGE_NAME	pkg.name	package.json name	Rarely needed
PACKAGE_VERSION	pkg.version	package.json version	Rarely needed

SDK identity fields (API-only, no env var equivalent — passed to createApp() / createWorkerHandler(), forwarded to initialize and /.well-known/mcp.json):

Option	Type	Notes
title	string?	Human-readable display name shown in client listings
websiteUrl	string?	Canonical homepage / repository URL
description	string?	One-line description; wins over MCP_SERVER_DESCRIPTION when set
icons	Implementation['icons']?	Array of icon objects: { src, mimeType?, sizes?: string[], theme?: 'light'|'dark' }
cacheHints	CacheHints?	Cache hints for the 2026-07-28 cacheable results, keyed by operation — see below

Cache hints (cacheHints)

API-only, no env var. Sets the ttlMs / cacheScope a client may cache a cacheable result for on protocol revision 2026-07-28. Keys are the closed set of cacheable operations: tools/list, prompts/list, resources/list, resources/templates/list, resources/read, server/discover.

await createApp({
  cacheHints: {
    'tools/list': { ttlMs: 3_600_000, cacheScope: 'public' },
    'resources/read': { ttlMs: 60_000 },
  },
});

• ttlMs — cache lifetime in milliseconds; must be a non-negative safe integer. An invalid value fails at startup with a ConfigurationError naming the field.
• cacheScope — 'private' (only the requesting client may cache) or 'public' (shared caches may too).
• A resource's own cacheHint overrides the resources/read entry for that resource, field by field — see the add-resource skill.
• Omitting a hint keeps the SDK defaults (ttlMs: 0, cacheScope: 'private'). Responses to 2025-era clients are never affected.

---

Environment & logging

Env Var	AppConfig field	Default	Notes
NODE_ENV	environment	development	Aliases: dev→development, prod→production, test→testing
MCP_LOG_LEVEL	logLevel	debug	Aliases: warn→warning, err→error, fatal/silent→emerg, trace→debug, information→info
LOGS_DIR	logsPath	<app-root>/logs	Node.js only; absolute paths are used verbatim, relative ones resolve against the application root (see Core config) — never the framework's install directory

Transport

Env Var	AppConfig field	Default	Notes
MCP_TRANSPORT_TYPE	mcpTransportType	stdio	stdio | http
MCP_HTTP_PORT	mcpHttpPort	3010	Port for HTTP transport
MCP_HTTP_HOST	mcpHttpHost	127.0.0.1	Bind address
MCP_HTTP_ENDPOINT_PATH	mcpHttpEndpointPath	/mcp	HTTP endpoint path
MCP_HTTP_MAX_BODY_BYTES	mcpHttpMaxBodyBytes	1048576 (1 MiB)	Max inbound JSON-RPC request body; oversized requests get 413 before per-request allocation. Does not cap upstream data staged into a canvas or response sizes. 0 disables (defer to runtime/proxy).
MCP_HTTP_MAX_PORT_RETRIES	mcpHttpMaxPortRetries	15	Rungs of the port ladder walked when a bind collides; each rung tries port + 1. See Port binding
MCP_HTTP_PORT_RETRY_DELAY_MS	mcpHttpPortRetryDelayMs	50	Delay between port retries (ms)
MCP_SESSION_MODE	mcpSessionMode	auto	stateless | stateful | auto; auto resolves to stateful. stateless also disables the 2025-era multi-round-trip shim, so v1 HTTP clients cannot answer a ctx.requestInput round — 2026-07-28 clients and stdio are unaffected
MCP_STATEFUL_SESSION_STALE_TIMEOUT_MS	mcpStatefulSessionStaleTimeoutMs	1800000	30 min; stale session eviction
MCP_HTTP_RESUMABILITY	mcpHttpResumability	true	SSE stream replay under stateful HTTP. On by default — selecting a session mode is the opt-in. Kill switch only; no effect on stateless serving or the session-less 2026-07-28 era
MCP_HTTP_RESUMABILITY_MAX_EVENTS	mcpHttpResumabilityMaxEvents	512	Events retained per session for replay; oldest evicted first. Lower it on a server whose tools return large results
MCP_HTTP_RESUMABILITY_TTL_MS	mcpHttpResumabilityTtlMs	300000	5 min; how long a retained event stays replayable
MCP_ALLOWED_ORIGINS	mcpAllowedOrigins	—	Comma-separated list; omit to allow all
MCP_SERVER_RESOURCE_IDENTIFIER	mcpServerResourceIdentifier	—	RFC 8707 resource indicator URL
MCP_PUBLIC_URL	mcpPublicUrl	—	Public-facing origin for reverse proxies (Cloudflare Tunnel, nginx, ALB) so emitted URLs carry the correct scheme
MCP_HEARTBEAT_INTERVAL_MS	mcpHeartbeatIntervalMs	0 (disabled)	Heartbeat ping interval; 0 disables
MCP_HEARTBEAT_MISS_THRESHOLD	mcpHeartbeatMissThreshold	3	Missed heartbeats before session is considered stale
MCP_GC_PRESSURE_INTERVAL_MS	mcpGcPressureIntervalMs	0 (disabled)	Bun-only opt-in forced GC loop for HTTP deployments with heap growth

Port binding

MCP_HTTP_PORT is where the HTTP transport starts, not necessarily where it ends up. Startup walks a ladder: bind MCP_HTTP_PORT, and on a collision wait MCP_HTTP_PORT_RETRY_DELAY_MS and try the next port, up to MCP_HTTP_MAX_PORT_RETRIES times. Read the bound port off the HTTP transport listening at … log line or the startup banner — with the defaults the server may be anywhere in 3010–3025. Pin the port by setting MCP_HTTP_MAX_PORT_RETRIES=0, which makes a collision a startup failure instead of a silent move.

• Startup resolves only once the server reports 'listening'. A bind failure arriving after the listen call — a collision the pre-bind probe could not see, because another process took the port in between — is routed to the ladder like any other, not reported as a successful start.
• A failure the ladder cannot clear rejects immediately. Each rung only changes the port, so EACCES (privileged port, typically <1024 as a non-root user) and EADDRNOTAVAIL (the MCP_HTTP_HOST address is not local to this machine) fail startup on the first attempt with the OS error as the rejection's cause, rather than burning every rung. Ladder exhaustion carries the last bind error as cause too, when a real bind attempt produced one.
• Runtime caveat: Bun reports a permission-denied bind as EADDRINUSE where Node reports EACCES. On Bun a privileged port therefore reads as an ordinary collision and walks the whole ladder before failing with Failed to bind to any port after N retries. — on Node the same port fails on the first attempt, naming EACCES.

---

Auth

Env Var	AppConfig field	Default	Notes
MCP_AUTH_MODE	mcpAuthMode	none	none | jwt | oauth
MCP_AUTH_SECRET_KEY	mcpAuthSecretKey	—	Required for jwt mode; min 32 chars
MCP_AUTH_DISABLE_SCOPE_CHECKS	mcpAuthDisableScopeChecks	false	When true, bypasses both withRequiredScopes (declared auth: [...]) and checkScopes (runtime/tenant scopes). Token validation (sig/aud/iss/exp) intact. Logs a WARNING at startup. See api-auth skill.
OAUTH_ISSUER_URL	oauthIssuerUrl	—	Required for oauth mode
OAUTH_AUDIENCE	oauthAudience	—	Required for oauth mode
OAUTH_JWKS_URI	oauthJwksUri	—	Override JWKS endpoint (otherwise derived from issuer)
OAUTH_JWKS_COOLDOWN_MS	oauthJwksCooldownMs	300000	5 min; min time between JWKS refetches
OAUTH_JWKS_TIMEOUT_MS	oauthJwksTimeoutMs	5000	JWKS fetch timeout (ms)
DEV_MCP_AUTH_BYPASS	devMcpAuthBypass	false	Skip auth in development; blocked in production
MCP_JWT_EXPECTED_ISSUER	mcpJwtExpectedIssuer	—	Optional issuer validation for JWT mode
MCP_JWT_EXPECTED_AUDIENCE	mcpJwtExpectedAudience	—	Optional audience validation for JWT mode
DEV_MCP_CLIENT_ID	devMcpClientId	—	Dev-only: override client ID
DEV_MCP_SCOPES	devMcpScopes	—	Dev-only: comma-separated scope overrides

---

Storage

Env Var	AppConfig field	Default	Notes
STORAGE_PROVIDER_TYPE	storage.providerType	in-memory	in-memory | filesystem | supabase | cloudflare-r2 | cloudflare-kv | cloudflare-d1; aliases: mem, fs
STORAGE_FILESYSTEM_PATH	storage.filesystemPath	./.storage	Used only when providerType is filesystem

---

Canvas (DataCanvas primitive — Tier 3, optional peer dep @duckdb/node-api)

Env Var	AppConfig field	Default	Notes
CANVAS_PROVIDER_TYPE	canvas.providerType	none	none | duckdb. Set to duckdb to enable core.canvas. Fails closed on Cloudflare Workers (DuckDB has no V8-isolate build).
CANVAS_DEFAULT_MEMORY_LIMIT_MB	canvas.defaultMemoryLimitMb	1024	Per-canvas DuckDB memory_limit PRAGMA value, in MB.
CANVAS_EXPORT_PATH	canvas.exportRootPath	./.canvas-exports	Sandbox root for path-targeted exports. Absolute paths and .. traversal are rejected.
CANVAS_TEMP_PATH	canvas.tempRootPath	<os.tmpdir()>/mcp-canvas	Scratch root: DuckDB's temp_directory for queries that spill past memory_limit, plus the transient files behind stream exports and the spillover round-trip. Never resolves to the process cwd — DuckDB's own cwd-relative .tmp default fails on a non-root or read-only container rootfs.
CANVAS_MAX_CANVASES_PER_TENANT	canvas.maxCanvasesPerTenant	100	Active canvas cap per tenant; throws RateLimited when exceeded.