mcp-ts-core MCP Server
Agent-native TypeScript framework for building MCP servers with declarative definitions.
Publisher claimed. No tool list reported, and Pod has not connected to this server.
Status
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Connect
Published as @cyanheads/mcp-ts-core on npm. Runs locally.
Known issues
331 problems reported by people outside the maintainer team. Issues filed by the project's own owners, members and collaborators are excluded — those are release checklists and internal refactors, not things that will go wrong for you. Showing 12.
Most discussed
bug(tool): error structuredContent fails strict SDK clients' output-schema validation on isError
When a tool declares an output schema, an isError: true response carrying structuredContent: { error: … } makes a validating MCP client throw -32602 "Structured content does not match the tool's output schema" instead of returning the isError result. The client validates the error envelope against the success schema, which it can never satisfy.
Exposure is every tool on every consuming server: output is required on ToolDefinition, so every tool advertises an outputSchema, an
Read the thread · 2026-06-18 · closed · 11 comments
feat(sdk): TypeScript SDK v2 / protocol 2026-07-28 — adoption impact audit
The framework pins @modelcontextprotocol/sdk ^1.29.0 (v1, current latest). Upstream has split v2 into @modelcontextprotocol/server / client / node (GA — 2.0.0, published 2026-07-27) and published the migration path for the 2026-07-28 protocol revision: support-2026-07-28.md (prerequisite: [upgrade-to-v2.md](https://gi
Read the thread · 2026-07-27 · closed · 7 comments
feat(canvas): prevent auth-none enumeration and capacity starvation
Use case
Related: #225, #275, #305
Under MCP_AUTH_MODE=none, every request intentionally resolves to the default tenant. A stateful HTTP session ID is not an authentication or tenant boundary, and two serving modes carry no session ID at all: stateless legacy HTTP, and every request under the per-request 2026-07-28 protocol revision. Session-derived tenancy therefore cannot promise confidentiality.
The collapsed tenant still creates two framework-level problems:
- **Ambient enumerat
Read the thread · 2026-07-02 · open · 7 comments
bug(transport): HTTP per-request McpServer cleanup leaks ~30 KB/req on heap
mcp-ts-core version
0.6.10 (reproduced against 0.6.16 — src/mcp-server/transports/http/httpTransport.ts cleanup path is unchanged between the two)
Runtime
Bun
Runtime version
Bun 1.3.2 (oven/bun:1 production image)
Transport
http (Streamable HTTP)
OS
Debian 13 (Docker container)
Description
The HTTP transport's per-request cleanup path — a fire-and-forget queueMicrotask calling transport.close() and server.close() after non-SSE responses — leaves ~30
Read the thread · 2026-04-24 · closed · 7 comments
Error-path parity: auto-mirror data.recovery.hint into error content[] text
Problem
The framework enforces parity on success responses via the format-parity linter rule: every field in output must appear in format()'s rendered content[], so structuredContent-readers and content[]-readers see the same data.
Errors have no equivalent guarantee. Handler-thrown errors are converted at src/mcp-server/tools/utils/toolHandlerFactory.ts:196–205:
return {
isError: true,
content: [{ type: 'text', text: `Error: ${mcpError.message}` }],
_meta: {
[Read the thread](https://github.com/cyanheads/mcp-ts-core/issues/84) · 2026-04-29 · closed · 6 comments
### Most recent
### feat(exports): advertisedOutputSchema is unreachable from any export subpath, so consumers cannot snapshot advertised wire shapes
Related: #241, #232
### Use case
[0.12.0](https://github.com/cyanheads/mcp-ts-core/blob/main/changelog/0.12.x/0.12.0.md) changed the bytes a tool advertises: `inputSchema` gained `additionalProperties: false`, the dialect moved to JSON Schema 2020-12, and `outputSchema` now declares the error envelope with success fields widened to optional. Its `agent-notes` tells downstream servers that "wire-shape snapshots need re-recording" as step 7 of the upgrade.
A consumer cannot actually do that. `a
[Read the thread](https://github.com/cyanheads/mcp-ts-core/issues/396) · 2026-08-25 · open · 0 comments
### bug(landing): connect card's curl snippet returns 400 — modern protocol header paired with a legacy initialize body
The landing page's `curl` tab publishes a request that fails on first paste. `connect.js` interpolates `manifest.protocol.latestVersion` into **both** the `MCP-Protocol-Version` header and the `initialize` body's `protocolVersion`. Now that `latestVersion` is `2026-07-28`, that pairs a modern header with a legacy handshake — a combination the transport explicitly rejects.
There is a second, independent defect in the same snippet: it omits `Accept`.
## Reproduction
Verified against a stock HTT
[Read the thread](https://github.com/cyanheads/mcp-ts-core/issues/395) · 2026-08-25 · open · 0 comments
### bug(tool): strictening a default-mode input silently discards its .meta(), dropping anyOf from the advertised inputSchema
### mcp-ts-core version
0.12.3
### Runtime
Bun
### Runtime version
1.4.0
### Transport
http
### Description
Related: #232
`tool()` applies `.strict()` to a default-mode input. Zod's `.strict()` returns a **fresh schema instance**, and that instance is not in the metadata registry, so anything attached with `.meta()` is silently lost. The advertised `inputSchema` loses the metadata with no error, no warning, and no lint finding.
The failure is invisible in the obvious place. Registrati
[Read the thread](https://github.com/cyanheads/mcp-ts-core/issues/394) · 2026-08-25 · open · 0 comments
### bug(skills): git-wrapup's version-sync list omits .claude-plugin/.codex-plugin plugin.json, so releases silently leave them behind
### mcp-ts-core version
0.12.3
### Runtime
Bun
### Runtime version
Bun 1.4.0
### Transport
N/A (release tooling)
### OS
macOS 15 (darwin arm64)
### Description
`skills/git-wrapup/SKILL.md` enumerates the files a release must re-version, and the list omits `.claude-plugin/plugin.json` and `.codex-plugin/plugin.json` — both of which declare a `version` that is expected to track `package.json`.
The list appears three times, consistently incomplete:
- the version-sync section names `pac
[Read the thread](https://github.com/cyanheads/mcp-ts-core/issues/393) · 2026-08-25 · open · 0 comments
### bug(templates): multi-arch Docker build fails on linux/amd64 under Bun 1.4.0
### Description
`templates/Dockerfile` runs its build stage on the target platform. Since the template moved to `oven/bun:1.4.0`, the `linux/amd64` leg of a multi-arch `docker buildx build` on an arm64 host aborts partway through `bun run build`: Bun's JavaScriptCore runs out of memory under QEMU x86_64 emulation and dies with SIGABRT.
The same Dockerfile shape built cleanly on `oven/bun:1.3.14`, so adopting the 1.4.0 pin is what exposes it. Any server that takes the template pin and publishes
[Read the thread](https://github.com/cyanheads/mcp-ts-core/issues/392) · 2026-08-25 · open · 1 comment
### bug(skills): field-test helper aborts on a stateless server — a missing Mcp-Session-Id is read as init failure
### mcp-ts-core version
0.12.3
### Runtime
Bun
### Runtime version
Bun 1.4.0
### Transport
http
### OS
macOS 15 (darwin arm64)
### Description
`skills/field-test/SKILL.md`'s `mcp_start` treats a missing `Mcp-Session-Id` response header as a fatal init failure:
```bash
local sid; sid=$(grep -i '^mcp-session-id:' "$hdr" | awk '{print $2}' | tr -d '\r\n')
if [ -z "$sid" ]; then
echo "init failed — HTTP $code, no Mcp-Session-Id header returned" >&2
A server running `MCP_SESSION_MO
Read the thread · 2026-08-25 · open · 0 comments
bug(devcheck): audit classifier splits paths on U+203A, but Bun 1.4 emits ASCII '>' — every transitive advisory reads as direct
mcp-ts-core version
0.12.3
Runtime
Bun
Runtime version
Bun 1.4.0
Transport
N/A (build tooling)
OS
macOS 15 (darwin arm64)
Description
classifyAuditVulns in scripts/devcheck.ts decides direct-vs-transitive by looking for › (U+203A) in each dependency path:
const isDirect = DIRECT_DEPS.has(pkgName) || paths.some((p) => !p.includes('›'));
Bun 1.4.0 emits ASCII > as the path separator, not ›. Every path therefore fails the includes check, `i
Read the thread · 2026-08-25 · open · 2 comments
See all 24 reports Pod holds for mcp-ts-core — of 331 qualified upstream.
Firsthand observations
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