Fuse Workflow

FUSE Hybrid Workflows

This workflow is evolving. As we discover new dynamics, update this skill to capture them. Offer to do so when patterns emerge that aren't documented here.

What CF FUSE Does

Mounts a Common Fabric space as a local filesystem. Cells become files and directories. Reads and writes are bidirectional — edit a file, the cell updates; change a cell in the browser, the file updates within ~1 second.

Quick Start

# Prerequisites
brew install --cask fuse-t          # macOS only, requires sudo

# Identity (reuse existing, or create a unique one with `id new`)
ls cf.key || deno run -A packages/cli/mod.ts id new > cf.key

# Environment
export CF_API_URL=http://localhost:8000
export CF_IDENTITY=./cf.key

# Mount
deno task cf fuse mount /tmp/cf

# Explore a space (connects on demand — any name works)
ls /tmp/cf/home/pieces/
ls /tmp/cf/my-space/pieces/

# Unmount
deno task cf fuse unmount /tmp/cf

Filesystem Layout

/tmp/cf/
  <space>/                        # connected on first access
    pieces/
      <piece-name>/
        meta.json                 # read-only: id, entityId, name
        input.json                # full input cell as JSON
        input/                    # exploded input — each key is a file or dir
          title                   # raw text (no quotes): "My Title"
          count                   # raw text: "42"
        result.json               # full result cell as JSON
        result/
          items/
            0/
              text                # raw text: "Buy milk"
              done                # raw text: "false"
            0.json                # atomic: {"text":"Buy milk","done":false}
          addItem.handler         # write-only: send JSON to trigger handler
      .index.json                 # name → entity ID mapping
    entities/                     # access by entity ID (on demand)
    space.json                    # { did, name }
  .spaces.json                    # known spaces
  .status                         # connection state

Reading and Writing

# Read scalar
cat pieces/my-note/input/title           # => My Title

# Read JSON subtree
cat pieces/my-note/input.json            # => full input as JSON
cat pieces/my-note/result/items/0.json   # => single item as JSON

# Write scalar (type auto-detected: number, boolean, null, or string)
echo -n "New Title" > pieces/my-note/input/title

# Write JSON (atomic multi-field update)
echo '{"text":"Updated","done":true}' > pieces/my-note/result/items/0.json

# Trigger handler
echo '{"title":"New Item"}' > pieces/my-note/result/addItem.handler

# Create field
touch pieces/my-note/result/newField     # creates empty string
mkdir pieces/my-note/result/metadata     # creates empty object

# Delete field
rm pieces/my-note/result/oldField
rm -r pieces/my-note/result/items/0      # removes + re-indexes array

The Hybrid Workflow

The power is in combining FUSE, CLI, and browser simultaneously:

Deploy + Mount + Edit

# 1. Develop a pattern
deno task cf check packages/patterns/my-app/main.tsx --no-run

# 2. Run its automated pattern tests
deno task cf test packages/patterns/my-app/main.test.tsx

# 3. Deploy to a space with the tests attached
deno task cf piece new packages/patterns/my-app/main.tsx \
  --test packages/patterns/my-app/main.test.tsx -s my-space
# => Created piece bafyreia...

# 4. Mount and interact via filesystem
deno task cf fuse mount /tmp/cf
ls /tmp/cf/my-space/pieces/my-app/result/

# 5. Edit cells from terminal while viewing in browser
echo -n "Updated content" > /tmp/cf/my-space/pieces/my-app/input/title
# => Browser shows the change within ~1 second

# 6. Iterate on the pattern and retain its tests
deno task cf piece setsrc packages/patterns/my-app/main.tsx \
  --test packages/patterns/my-app/main.test.tsx --cell bafyreia...
# => Result updates in both browser AND filesystem

For multiple authored test entries, repeat --test. Run every entry locally before deployment and repeat the complete flag set on every setsrc.

Cross-Space Operations

# Copy data between spaces
cp /tmp/cf/space-a/pieces/notes/result/items.json /tmp/backup.json
cat /tmp/backup.json | jq '.' > /tmp/cf/space-b/pieces/notes/input/items.json

# Grep across an entire space
grep -r "TODO" /tmp/cf/my-space/pieces/*/result/content

# Diff two pieces
diff /tmp/cf/my-space/pieces/note-1/result/content \
     /tmp/cf/my-space/pieces/note-2/result/content

Agent Workflows

Multiple agents can read/write cells via the filesystem while a human works in the browser. Each agent sees the same live data:

# Agent reads a piece's state
cat /tmp/cf/my-space/pieces/assistant/result.json | jq '.messages'

# Agent writes to a handler
echo '{"message":"Hello from agent"}' > \
  /tmp/cf/my-space/pieces/assistant/result/sendMessage.handler

# Agent waits for a piece to reach a state. Resolve the entity ID once, then
# address the piece by it: a name gains a count suffix on every state change, so
# a pieces/<name>/... path goes stale on the very change being waited for. The
# entity ID is the piece ID, and it never changes.
ENTITY_ID=$(jq -r .entityId /tmp/cf/my-space/pieces/task/meta.json)

until [ "$(cat /tmp/cf/my-space/entities/$ENTITY_ID/result/status)" = "done" ]; do
  sleep 1
done

Wait on the condition and let the loop end when it holds, rather than printing on a while true loop. This polls because no change-notification surface through the mount is known to work — fswatch and watchman are untested against FUSE-T. The loop cannot detect a dead transport, which stalls it indefinitely; .status at the mount root reports connection.disconnected.

For a subscription rather than a poll, go through the runtime instead of the filesystem: cf piece render --cell <id> --watch subscribes to the cell and re-renders on each change. That surface renders UI, so it fits watching a piece render rather than reading a single scalar.

Pattern Development Loop

Combine pattern-dev with FUSE for a tight feedback loop:

# 1. Write pattern in packages/patterns/my-pattern/main.tsx
# 2. Type check
deno task cf check packages/patterns/my-pattern/main.tsx --no-run
# 3. Write and run automated pattern tests
deno task cf test packages/patterns/my-pattern/main.test.tsx
# 4. Deploy with every test entry attached
deno task cf piece new packages/patterns/my-pattern/main.tsx \
  --test packages/patterns/my-pattern/main.test.tsx -s dev-space
# 5. Mount
deno task cf fuse mount /tmp/cf
# 6. Set input via filesystem (faster than cf cell set for complex data)
cat test-data.json > /tmp/cf/dev-space/pieces/my-pattern/input.json
# 7. Read result
cat /tmp/cf/dev-space/pieces/my-pattern/result.json | jq '.'
# 8. Iterate: edit, run tests, then setsrc with every --test flag

Important Gotchas

Identity Mismatch

The CLI identity key creates a different space than the browser. If you deploy with cf.key but browse with your browser identity, you'll see different spaces.

Fix: Use the browser's space name when mounting:

# Find your browser space name from the URL or shell UI
ls /tmp/cf/2026-03-09-ben/pieces/   # connects on demand

No step Needed via FUSE

Unlike cf cell set which requires cf piece step to trigger recomputation, FUSE writes go through cell.set() directly, which triggers reactive updates automatically.

Writes Are Fire-and-Forget

FUSE returns success before the cell write completes. If toolshed is down or the transport has disconnected, writes silently fail. Check the browser or re-read the cell to confirm writes landed.

Diagnosing silent write failures: If writes succeed (no error) but values revert or stay empty, check the FUSE log for transport errors:

tail -20 /tmp/ct-fuse-<mount-name>.log
# Look for: "ConnectionError: memory/v2 transport closed"

If the transport is dead, the FUSE process is running but can't commit to the backend. Fix: unmount and remount:

cf fuse unmount /tmp/my-mount
cf fuse mount /tmp/my-mount --background

Long-running FUSE mounts (24h+) can lose their transport connection under sustained agent load. Remount before each experiment run to be safe.

FUSE-T Cache TTL

Changes from the browser appear in the filesystem within ~1 second (FUSE-T NFS cache). Not instant. If you need to force a re-read, cat the .json file (not the exploded directory).

FUSE-T mounts default to attrcache-timeout=1, which bounds all client-side staleness (attributes, negative name lookups, directory listings) at about one second — measured p99 read latency during daemon-side write storms is a few milliseconds, with sub-second transients while a subtree rebuilds. If a mount was created with --attrcache-timeout 0 (untuned), a path stat'd while absent can keep reporting NotFound for up to a minute and ls can be tens of seconds stale; remount with the default before debugging "missing" files. See packages/fuse/README.md "macOS: NFS client cache tuning".

Large Pieces

Pieces with large $UI trees or complex schemas produce huge result.json files (100KB+). Reading them works but is slow. Prefer reading specific fields via the exploded directory: cat result/title instead of cat result.json.

Mount Stability

The FUSE daemon can crash if patterns throw uncaught errors during reactive updates. If the mount stops responding but the process is still running:

pkill -f "packages/fuse/mod.ts"
umount /tmp/cf 2>/dev/null
# Remount
deno task cf fuse mount /tmp/cf

macOS Resource Forks

Finder and some macOS tools create ._ resource fork files. The FUSE mount rejects these with EACCES. Use CLI tools, not Finder, to browse mounted spaces.

Handler Invocation via FUSE

"MOUNT/SPACE/pieces/📝 Note Name/setTitle.handler" --value "New Title"

Void handlers can be invoked with no args:

"MOUNT/SPACE/pieces/Contact Book/result/onAddContact.handler"

Use --value null only if you specifically need the older explicit form.

After ANY handler call — re-read pieces.json immediately:

cat "MOUNT/SPACE/pieces/pieces.json"
# Piece names include count suffixes that update on every mutation:
# Reading List (0) → Reading List (1) → Reading List (2)
# All previously constructed FUSE paths are invalid after a mutation.

Writing to [FS] note pieces

Use Read/Write/Edit tools directly on index.md. Never use handler invocation for notes.

1. Read  "MOUNT/SPACE/pieces/📝 Note Name/index.md"  — capture frontmatter
2. Edit  targeted changes to body only, leaving frontmatter intact
   OR
   Write  full replacement — must include frontmatter (entityId + title from step 1)

Preserve the frontmatter. Losing entityId corrupts the piece.

Input cell writes (Python pattern)

For bulk writes to input cell arrays (e.g. populating a Contact Book):

import json

contacts = [
    {"name": "Alice", "email": "alice@example.com", "phone": "", "company": "",
     "tags": ["team"], "notes": "Context here", "createdAt": 1234567890000},
    # ...
]

try:
    open("MOUNT/SPACE/pieces/Contact Book/input/contacts.json", "w").write(
        json.dumps(contacts)
    )
except FileNotFoundError:
    pass  # FUSE close quirk — write succeeded despite the error

# Verify success:
import subprocess
result = subprocess.run(
    ["cat", "MOUNT/SPACE/pieces/Contact Book/result/contacts.json"],
    capture_output=True, text=True
)
data = json.loads(result.stdout)
print(f"{len(data)} contacts written")

input/ directory layout — two things coexist, only one is the write target:

• input/contacts.json — writable flat JSON array (correct write target)
• input/contacts/ — directory of individual cell-slot files (read-only view)
• Writing to input/contacts/N does not work as expected

Pattern Source: .src/ Directory

Every piece exposes its pattern source under .src/ in the FUSE mount. Read to understand how a piece works; write to modify it live.

MOUNT/SPACE/pieces/My Piece/
  .src/
    main.tsx       ← pattern source — readable and writable
    data/
      cities.json  ← an attached data file — readable and writable
    error.log      ← synthetic, read-only — pattern execution errors

Every file of the deployed source package appears here at its stored path: the entry, its imports, any attached test entries, and any attached data files.

Read source:

cat "MOUNT/SPACE/pieces/My Piece/.src/main.tsx"

Temporarily modify live source for diagnosis (use Python — shell redirect fails on FUSE):

path = "MOUNT/SPACE/pieces/My Piece/.src/main.tsx"
src = open(path).read()
# ... modify src ...
open(path, "w").write(modified_src)
# Write triggers setsrc automatically — no cf piece setsrc needed

FUSE preserves the existing attached test roots and data files during this write, but it does not run the tests and cannot change which entries are attached or which files are data. Editing a data file this way replaces its bytes and leaves it a data file. Treat the live edit as a diagnostic experiment. Before completing the change, make it in the repository checkout, run every test against that changed source, and deploy it with explicit cf piece setsrc plus the complete set of --test and --datafile flags.

Check for errors after modifying:

cat "MOUNT/SPACE/pieces/My Piece/.src/error.log"
# Empty = no errors; non-empty = compile or runtime error in new source

Reference

• packages/fuse/mod.ts — FUSE daemon entry point
• packages/fuse/cell-bridge.ts — cell-to-filesystem bridge
• packages/fuse/tree-builder.ts — JSON-to-tree conversion
• docs/specs/fuse-filesystem/ — 7-part specification
• Use the cf skill, or read skills/cf/SKILL.md, for CLI command reference
• Use the pattern-dev skill, or read skills/pattern-dev/SKILL.md, for pattern development