fix(core): accept markdown strings in portableText fields over MCP by officialasishkumar · Pull Request #1164 · emdash-cms/emdash

officialasishkumar · 2026-05-25T02:16:17Z

What does this PR do?

Fixes the MCP content_create and content_update tools rejecting a markdown string in a portableText field with [VALIDATION_ERROR] content: Invalid input: expected array, received string.

The emdash CLI client already converts markdown to Portable Text via convertDataForWrite() before sending (packages/core/src/client/index.ts), but the MCP server passed args.data straight to handleContentCreate/handleContentUpdate without that step. Since LLM callers reliably produce markdown but not valid Portable Text JSON (unique _keys, resolved markDefs, correct block shapes), this effectively blocked writing rich text over MCP — the documented workaround was to fall back to the CLI.

The MCP server now performs the same conversion before the data reaches the handlers, so a portableText field accepts either a Portable Text array or a markdown string. Existing Portable Text arrays pass through unchanged.

Closes #1005

Type of change

Checklist

I have read CONTRIBUTING.md
pnpm typecheck passes
pnpm lint passes
pnpm test passes (or targeted tests for my change)
pnpm format has been run
I have added/updated tests for my changes (if applicable)
User-visible strings in the admin UI are wrapped for translation (if applicable). Do not include messages.po changes except in translation PRs — a workflow extracts catalogs on merge to main.
I have added a changeset (if this PR changes a published package)
New features link to an approved Discussion: https://github.com/emdash-cms/emdash/discussions/...

AI-generated code disclosure

This PR includes AI-generated code — model/tool:

Root cause

convertDataForWrite() (packages/core/src/client/portable-text.ts) maps markdown strings to Portable Text for any field declared as portableText. The CLI client calls it before every create/update:

// packages/core/src/client/index.ts
const fields = await this.getFieldSchemas(collection);
const data = convertDataForWrite(input.data, fields);

The MCP server did not — packages/core/src/mcp/server.ts passed args.data directly:

await emdash.handleContentCreate(args.collection, { data: args.data, ... });

A portableText field's generated Zod schema expects an array, so a markdown string is rejected at validation time before the write happens.

Fix

Add a small helper that resolves the collection's field types via SchemaRegistry and runs the same convertDataForWrite() the CLI uses, then call it in both MCP tools before the handlers:

async function convertContentDataForWrite(emdash, collection, data) {
  const { SchemaRegistry } = await import("../schema/index.js");
  const def = await new SchemaRegistry(emdash.db).getCollectionWithFields(collection);
  if (!def) return data; // unknown collection -> let the handler raise the real error
  return convertDataForWrite(data, def.fields);
}

content_create converts args.data; content_update converts it when present. The content_create tool description is updated to note that portableText fields accept markdown.

How to test

Added packages/core/tests/integration/mcp/content-portabletext-markdown.test.ts, which drives the real MCP client/server harness against a real SQLite runtime and verifies:

content_create with content: "## Heading\n\nSome **bold** text." succeeds and stores a Portable Text array (_type: "block", style: "h2");
content_update with a markdown string for content succeeds and stores Portable Text;
an existing Portable Text array passed to content_create is stored unchanged.

The first two reproduce the bug — on main the create/update fail validation; with this change they succeed.

The conversion itself (markdown → blocks/spans with marks, markDefs, and unique _keys, plus array pass-through) is exercised directly by convertDataForWrite, which this change reuses rather than reimplements.

The MCP content_create and content_update tools passed `args.data` straight to the write handlers, so a markdown string in a `portableText` field failed schema validation with 'expected array, received string'. The emdash CLI client already converts markdown to Portable Text via convertDataForWrite before sending; the MCP server skipped that step. LLM callers reliably produce markdown but not valid Portable Text JSON (unique _key values, markDefs, block shapes), so this effectively blocked writing rich text over MCP. Convert markdown to Portable Text in the MCP server before the data reaches the handlers, resolving the collection's field types via SchemaRegistry — the same conversion the CLI performs. Existing Portable Text arrays pass through unchanged. Closes emdash-cms#1005

changeset-bot · 2026-05-25T02:16:22Z

🦋 Changeset detected

Latest commit: 1676290

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 14 packages

Name	Type
emdash	Patch
@emdash-cms/cloudflare	Patch
@emdash-cms/sandbox-workerd	Patch
@emdash-cms/fixture-perf-site	Patch
@emdash-cms/perf-demo-site	Patch
@emdash-cms/cache-demo-site	Patch
@emdash-cms/admin	Patch
@emdash-cms/auth	Patch
@emdash-cms/blocks	Patch
@emdash-cms/gutenberg-to-portable-text	Patch
@emdash-cms/x402	Patch
create-emdash	Patch
@emdash-cms/auth-atproto	Patch
@emdash-cms/plugin-embeds	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

github-actions · 2026-05-25T02:16:28Z

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

Copilot

Pull request overview

Fixes MCP content_create / content_update rejecting markdown strings in portableText fields by converting markdown → Portable Text in the MCP server before schema validation, matching the emdash CLI client behavior (closes #1005).

Changes:

Add convertContentDataForWrite() in the MCP server and apply it to content_create and content_update payloads.
Update the content_create MCP tool description to document markdown acceptance for portableText.
Add an MCP integration regression test covering create/update markdown conversion and PT-array passthrough; add a patch changeset.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
`packages/core/src/mcp/server.ts`	Converts markdown strings in `portableText` fields to Portable Text before invoking content write handlers; updates `content_create` tool docs.
`packages/core/tests/integration/mcp/content-portabletext-markdown.test.ts`	Adds end-to-end MCP regression coverage for markdown → Portable Text conversion on create/update and passthrough behavior for PT arrays.
`.changeset/fix-mcp-portabletext-markdown.md`	Publishes the MCP behavior fix as a patch release note for `emdash`.

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 			const resolvedId = extractContentId(existing.data) ?? args.id;
+			const data =
+				args.data === undefined
+					? undefined
+					: await convertContentDataForWrite(emdash, args.collection, args.data);



officialasishkumar · 2026-05-25T02:29:44Z

recheck

Copilot AI review requested due to automatic review settings May 25, 2026 02:16

github-actions Bot added area/core size/M labels May 25, 2026

github-actions Bot added the cla: needed label May 25, 2026

style: format

1676290

Copilot started reviewing on behalf of officialasishkumar May 25, 2026 02:16 View session

Copilot AI reviewed May 25, 2026

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Comment thread packages/core/src/mcp/server.ts

Comment on lines 727 to 732

const resolvedId = extractContentId(existing.data) ?? args.id;

const data =

args.data === undefined

? undefined

: await convertContentDataForWrite(emdash, args.collection, args.data);

github-actions Bot added cla: signed and removed cla: needed labels May 25, 2026

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fix(core): accept markdown strings in portableText fields over MCP#1164

fix(core): accept markdown strings in portableText fields over MCP#1164
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officialasishkumar commented May 25, 2026

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Pull request overview

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