These limits apply to every workspace. A call or build that exceeds one fails with the error code shown, which caplo tool logs, test output or the build log reports.
| Limit |
Value |
| Runtime |
Node.js 24 (runtime: node24). Local caplo tool test and caplo tool dev also need Node 24. |
| Module format |
Your code is bundled into one ES module. Native .node addons are refused. |
| Forbidden imports |
child_process, cluster, worker_threads, inspector. |
| Environment |
No environment variables or secrets from the environment. Read secrets from the call context. |
| Memory |
Your workspace’s tools run in workers with a 256 MB JavaScript heap, shared by the packages loaded in that worker. Module-level state can persist between calls in the same worker. |
| Limit |
Value |
Error |
| Timeout per tool |
1 to 30 seconds, set by timeoutSeconds (remote MCP tools: set in review, 20 by default) |
tool_timeout |
| Result size |
256 KiB, after any files are taken out |
output_too_large |
| Structured result |
Must match the tool’s outputSchema, if it has one |
output_schema_violation |
| Files per result |
3, each up to the tool’s maxBytes, at most 10 MiB; JPEG, PNG, GIF, WebP or PDF |
output_file_invalid |
| Form questions |
3 per call; up to 12 declared fields |
|
| Concurrent calls |
Up to 16 of a workspace’s tool calls at a time |
tool_concurrency_exceeded |
| Write status checks |
Up to 8 per write |
|
| Limit |
Value |
Error |
| Package name |
2 to 40 characters: lowercase letters, digits and dashes, starting with a letter |
config_invalid |
| Tool name |
Up to 48 characters: lowercase letters, digits and underscores, starting with a letter |
tool_name_invalid |
Model name (<package>__<tool>) |
Up to 64 characters |
tool_name_invalid |
| Tools per MCP package |
64 |
config_invalid |
| Function package |
Exactly one tool |
schema_invalid |
| Description |
500 characters |
config_invalid |
| Files in a draft |
1,000, with paths up to 512 characters |
too_many_files |
| File size |
1 MiB per file; 10 MiB for a lockfile |
file_too_large |
| Draft size |
5 MiB in total, not counting lockfiles |
draft_too_large |
| Bundle size |
10 MiB |
bundle_too_large |
| Dependency install |
90 seconds |
install_timeout |
| Build |
120 seconds |
build_timeout |
| Limit |
Value |
| Egress hosts |
Up to 50 per package. No list means no network access. |
| Reachable addresses |
Public addresses only. Private, loopback, link-local and cloud metadata addresses are refused even when the host is listed. |
| Secrets |
Up to 50 names per package; names up to 64 characters. |
| Secret changes |
Live calls use a new, rotated or bound value within a minute. |
| Limit |
Value |
| Confirmation and receipt fields |
12 each |
| Labels and titles |
80 characters; action labels 20 |
list, table, cards |
20 items |
choices |
10 items |
comparison |
4 items |
timeline |
12 steps |
| Progress label |
3 to 40 characters; spoken line 3 to 90 |
| Limit |
Value |
| Retention |
Live invocations from the last hour, up to about the 1,000 most recent per package |
| Lines per invocation |
200; a line over 8 KiB is cut short |
caplo tool logs -n |
At most 200 invocations at a time |
