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":"1.13","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

---

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	<project-root>/logs	Node.js only; absolute or relative to project root

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
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_RESPONSE_VERBOSITY	mcpResponseVerbosity	standard	minimal | standard | full
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

OAuth proxy (optional sub-object)

Activated when OAUTH_PROXY_AUTHORIZATION_URL or OAUTH_PROXY_TOKEN_URL is set.

Env Var	AppConfig field	Notes
OAUTH_PROXY_AUTHORIZATION_URL	oauthProxy.authorizationUrl	Proxy authorization endpoint
OAUTH_PROXY_TOKEN_URL	oauthProxy.tokenUrl	Proxy token endpoint
OAUTH_PROXY_REVOCATION_URL	oauthProxy.revocationUrl	Optional
OAUTH_PROXY_ISSUER_URL	oauthProxy.issuerUrl	Optional
OAUTH_PROXY_SERVICE_DOCUMENTATION_URL	oauthProxy.serviceDocumentationUrl	Optional
OAUTH_PROXY_DEFAULT_CLIENT_REDIRECT_URIS	oauthProxy.defaultClientRedirectUris	Comma-separated list

---

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.
CANVAS_TTL_MS	canvas.ttlMs	86400000	Sliding TTL (24 h). Every operation extends the expiry.
CANVAS_ABSOLUTE_CAP_MS	canvas.absoluteCapMs	604800000	Absolute cap from creation (7 d). Sliding window clamps to this.
CANVAS_SWEEPER_INTERVAL_MS	canvas.sweeperIntervalMs	60000	Background sweep interval. Set to 0 to disable.
CANVAS_DEFAULT_ROW_LIMIT	canvas.defaultRowLimit	10000	Default cap on rows materialized into a query response.
CANVAS_SCHEMA_SNIFF_ROWS	canvas.schemaSniffRows	100	Rows to materialize for schema inference when schema is omitted.

Platform support: Linux/macOS/Windows × x64 supported, Linux/macOS arm64 supported. Windows arm64 unsupported (DuckDB upstream). See api-canvas skill for the full DataCanvas reference.

Supabase (optional sub-object)

Activated when both SUPABASE_URL and SUPABASE_ANON_KEY are set.

Env Var	AppConfig field	Notes
SUPABASE_URL	supabase.url	Required to activate
SUPABASE_ANON_KEY	supabase.anonKey	Required to activate
SUPABASE_SERVICE_ROLE_KEY	supabase.serviceRoleKey	Optional; elevated access

---

LLM

Env Var	AppConfig field	Default	Notes
OPENROUTER_API_KEY	openrouterApiKey	—	Optional; enables LLM provider
OPENROUTER_APP_URL	openrouterAppUrl	http://localhost:3000	Reported to OpenRouter
OPENROUTER_APP_NAME	openrouterAppName	package.json name	Reported to OpenRouter
LLM_DEFAULT_MODEL	llmDefaultModel	google/gemini-2.5-flash-preview-05-20	OpenRouter model ID
LLM_DEFAULT_TEMPERATURE	llmDefaultTemperature	—	Float
LLM_DEFAULT_TOP_P	llmDefaultTopP	—	Float
LLM_DEFAULT_MAX_TOKENS	llmDefaultMaxTokens	—	Integer
LLM_DEFAULT_TOP_K	llmDefaultTopK	—	Integer
LLM_DEFAULT_MIN_P	llmDefaultMinP	—	Float

---

Telemetry

Env Var	AppConfig field	Default	Notes
OTEL_ENABLED	openTelemetry.enabled	false	Enable OpenTelemetry export
OTEL_SERVICE_NAME	openTelemetry.serviceName	createApp name → package.json name	Seeded from createApp({ name }) when unset; an env value wins
OTEL_SERVICE_VERSION	openTelemetry.serviceVersion	package.json version
OTEL_EXPORTER_OTLP_TRACES_ENDPOINT	openTelemetry.tracesEndpoint	—	OTLP traces endpoint URL
OTEL_EXPORTER_OTLP_METRICS_ENDPOINT	openTelemetry.metricsEndpoint	—	OTLP metrics endpoint URL
OTEL_TRACES_SAMPLER_ARG	openTelemetry.samplingRatio	1.0	0–1; fraction of traces to export
OTEL_LOG_LEVEL	openTelemetry.logLevel	INFO	OTel SDK internal log level: NONE | ERROR | WARN | INFO | DEBUG | VERBOSE | ALL

---

Speech (optional sub-object)

Activated when SPEECH_TTS_ENABLED or SPEECH_STT_ENABLED is set.

TTS (Text-to-Speech)

Env Var	AppConfig field	Default	Notes
SPEECH_TTS_ENABLED	speech.tts.enabled	false	Enable TTS
SPEECH_TTS_PROVIDER	speech.tts.provider	elevenlabs	Currently only elevenlabs
SPEECH_TTS_API_KEY	speech.tts.apiKey	—	Provider API key
SPEECH_TTS_BASE_URL	speech.tts.baseUrl	—	Override provider base URL
SPEECH_TTS_DEFAULT_VOICE_ID	speech.tts.defaultVoiceId	—	Default voice identifier
SPEECH_TTS_DEFAULT_MODEL_ID	speech.tts.defaultModelId	—	Default model identifier
SPEECH_TTS_TIMEOUT	speech.tts.timeout	—	Request timeout (ms)

STT (Speech-to-Text)

Env Var	AppConfig field	Default	Notes
SPEECH_STT_ENABLED	speech.stt.enabled	false	Enable STT
SPEECH_STT_PROVIDER	speech.stt.provider	openai-whisper	Currently only openai-whisper
SPEECH_STT_API_KEY	speech.stt.apiKey	—	Provider API key
SPEECH_STT_BASE_URL	speech.stt.baseUrl	—	Override provider base URL
SPEECH_STT_DEFAULT_MODEL_ID	speech.stt.defaultModelId	—	Default model identifier
SPEECH_STT_TIMEOUT	speech.stt.timeout	—	Request timeout (ms)

---

Server config (separate schema)

Define your own Zod schema for domain-specific env vars. Never merge with core's schema.

Use the lazy init/accessor pattern — do not parse process.env at module top-level.

// src/config/server-config.ts
import { z } from '@cyanheads/mcp-ts-core';
import { parseEnvConfig } from '@cyanheads/mcp-ts-core/config';

const ServerConfigSchema = z.object({
  apiKey: z.string().describe('External API key'),
  maxResults: z.coerce.number().default(100),
  verboseLogging: z.stringbool().default(false).describe('Enable verbose logging'),
});

export type ServerConfig = z.infer<typeof ServerConfigSchema>;

let _config: ServerConfig | undefined;

export function getServerConfig(): ServerConfig {
  _config ??= parseEnvConfig(ServerConfigSchema, {
    apiKey: 'MY_API_KEY',
    maxResults: 'MY_MAX_RESULTS',
    verboseLogging: 'MY_VERBOSE_LOGGING',
  });
  return _config;
}

Env booleans — use z.stringbool(), never z.coerce.boolean(). z.coerce.boolean() runs Boolean(value), so "false", "0", and "no" all coerce to true — the flag becomes impossible to disable through the environment except by omitting it entirely. z.stringbool() parses true/false/1/0/yes/no/on/off (case-insensitive) and rejects anything else, so MY_VERBOSE_LOGGING=false actually disables and a typo fails loudly at startup instead of silently coercing. Empty string and unset both fall through to .default().

Why parseEnvConfig? It maps Zod schema paths to env var names so validation errors name the actual variable at fault. A missing MY_API_KEY produces:

Server config validation failed:
  - MY_API_KEY (apiKey): Invalid input: expected string, received undefined

Instead of a raw ZodError dump at startup. The framework catches the resulting ConfigurationError and prints a clean banner (full stack behind DEBUG=true).

Direct ServerConfigSchema.parse(...) still works — the framework intercepts raw ZodError thrown from setup() and converts it — but error messages won't know about env var names, so they show the Zod path (apiKey) instead of the variable name (MY_API_KEY).

Workers: Do not parse process.env at module top-level. In Workers, env bindings are injected at request time via injectEnvVars(), after all static imports. Lazy parsing is required.