fix(files): stop a cached collab snapshot resurrecting blank lines

[waleedlatif1]

Summary

• A collaborative markdown file's cold-start seed can come from a cached Yjs snapshot (workspace_file_collab_state.doc_state) instead of a fresh markdown re-parse. That snapshot is a raw CRDT binary, so it preserves top-level empty paragraphs that parseMarkdownToDoc → stripEmptyParagraphs strips from every parse target.
• The static placeholder always re-parses (clean); a warm seed replays the snapshot verbatim, so a stray blank line appears once the doc settles — and only intermittently, because a stale/cold cache falls through to the clean re-parse.
• Proven from production data: decoded the persisted snapshot for the reported staging file and found two consecutive len=0 paragraphs sitting exactly between the description paragraph and the bullet list (plus one more before the trailing link) — the reported "two spaces."
• This is the warm-seed repair explicitly flagged as owed when the parse-side collapse fix (fix(files): collapse blank-line runs to markdown standard (no empty-paragraph explosion / reflow) #6198) shipped — now self-healing at seed time, so no data migration is needed.

Changes

• lib/collab-doc/normalize.ts — stripEmptyTopLevelParagraphs(doc) shared pure-Yjs helper enforcing the same no-top-level-empty-paragraph invariant on the CRDT side.
• lib/collab-doc/seed.ts — repair the cached snapshot on read (self-heals legacy snapshots, preserving CRDT client ids; returns original bytes untouched when already clean).
• lib/collab-doc/persist.ts — normalize before caching so new snapshots are clean by construction.

Type of Change

• Bug fix

Testing

• normalize.test.ts: 5 tests (production repro, idempotency, no-op-when-clean, nested-untouched, encode/decode preserves config + CRDT ids). Verified they go red when the helper is neutralized.
• Full lib/collab-doc suite (24 tests) green; type-check clean.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Aug 5, 2026 8:26pm

[cursor]

PR Summary

Low Risk
Collab doc normalization only; no auth or durable markdown semantics change beyond aligning cached CRDT state with existing parse rules.

Overview
Fixes intermittent stray blank lines when a collaborative file cold-starts from a cached Yjs snapshot instead of a fresh markdown re-parse. Raw CRDT binaries can keep top-level empty paragraph nodes that parseMarkdownToDoc / stripEmptyParagraphs already drop, so the warm seed diverges from the static placeholder once the doc settles.

Adds stripEmptyTopLevelParagraphs in normalize.ts (shared with COLLAB_DOC_FIELD moved there from converter.ts) to enforce the same invariant on the Yjs body fragment. Seed repairs legacy cached snapshots on read via normalizeSeedUpdate (re-encode only when needed). Persist strips empties before writing the collab cache so new snapshots stay clean. normalize.test.ts covers the production repro, idempotency, nested paragraphs, and encode/decode round-trips.

^{Reviewed by Cursor Bugbot for commit 72c1a4a. Configure here.}

[greptile-apps]

Greptile Summary

The PR normalizes cached collaborative Yjs documents when they are seeded and persisted, preventing legacy empty top-level paragraphs from resurfacing.

• Adds a shared top-level paragraph normalization helper and focused tests.
• Repairs cached snapshots during room seeding and stores normalized snapshots during persistence.
• Centralizes the collaborative document field name for conversion and normalization.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
apps/sim/lib/collab-doc/normalize.ts	Adds the shared Yjs fragment constant and an idempotent helper that removes empty top-level paragraphs.
apps/sim/lib/collab-doc/seed.ts	Repairs legacy cached snapshots before using them to seed collaborative rooms.
apps/sim/lib/collab-doc/persist.ts	Normalizes the Yjs document before deriving markdown and caching its snapshot.
apps/sim/lib/collab-doc/normalize.test.ts	Covers production-shaped normalization, idempotency, nested content, clean no-ops, and snapshot metadata preservation.
apps/sim/lib/collab-doc/converter.ts	Reuses the canonical collaborative document field constant.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
Cache[Cached Yjs snapshot] --> Seed[Seed-time normalization]
Live[Live Yjs document] --> Persist[Persist-time normalization]
Seed --> Room[Collaborative room]
Persist --> Markdown[Durable markdown]
Persist --> CleanCache[Normalized cached snapshot]

Loading

_{Reviews (2): Last reviewed commit: "refactor(collab-doc): make COLLAB_DOC_FI..." | Re-trigger Greptile}

[waleedlatif1]

@greptile

[waleedlatif1]

@cursor review

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 72c1a4a. Configure here.}