krita-codex-mcp 0.1.0

Windows-first local MCP bridge for reliable Krita control from Codex

Krita Codex MCP Server

Control Krita from OpenAI Codex through a secure local Model Context Protocol (MCP) server for Windows.

A Windows-first local MCP server that lets Codex inspect and control Krita through a small, authenticated bridge. The MCP process uses STDIO. The Krita Python plugin listens only on 127.0.0.1, validates a shared bearer token, and dispatches every Krita API call to Qt's main thread.

This repository is a Windows-first integration validated against Krita 5.3.2.1. It deliberately exposes a small set of cohesive tools instead of a large collection of micro-tools:

Tool	Purpose
krita_state	Active document, canvas/color space, recursive layer tree with UUIDs, active layer and current painting state
krita_preview	Whole-canvas or pixel-precise cropped PNG returned directly as MCP image content
krita_canvas	Sample colors; resize, scale, crop, rotate or flip; import editable raster layers
krita_edit	Create/refine/move selections; native copy, cut, paste, selection-to-layer, fill and clear
krita_document	List, create, open, activate, checkpoint-save and explicitly close documents
krita_layers	Read/edit the layer tree, safely reparent, and transform layers by stable UUID
krita_history	Read undo/redo state and execute bounded undo or redo steps
krita_brush	Read/set native brush state and search installed Krita presets
krita_paint_path	Pressure-aware line segments through Krita's native Node.paintLine API and active brush preset
krita_draw	Native preset-backed lines, open/closed paths, polygons, rectangles and ellipses
krita_color	KRA-backed project palettes, Krita palette swatches, color replacement and safe correction filters
krita_asset	Export layer PNGs plus Unity-oriented animation, tileset and named-region packages with direct previews
krita_save_export	Save KRA and export PNG beneath configured roots only

Codex -> local STDIO MCP process -> authenticated 127.0.0.1 HTTP bridge
      -> queued, timeout-aware Qt main-thread dispatch -> Krita Python API

The bridge has no arbitrary Python execution tool and no direct pixel painting fallback. Actual painting, shapes, replacement fills and correction filters go through native Krita actions or stroke APIs. If the installed Krita build lacks a required method, the operation fails closed.

Production workflow

Use this order for a real Krita session:

1. Run the wheel-bundled krita-codex-install install command with at least one explicit, narrow --allowed-root.
2. Enable Krita Codex Bridge in Krita's Python Plugin Manager.
3. Restart Krita so the installed plugin and shared protocol package are loaded together.
4. Run krita-codex-install check and require Ready for productive use.
5. Preview the checkout-free, exactly version-pinned uvx Codex block with krita-codex-install codex-config.
6. Apply it only after explicit confirmation, restart Codex, verify krita_state and krita_preview, and only then start normal work.

For a local wheel build, the initial installation looks like:

uvx --from .\dist\krita_codex_mcp-0.1.0-py3-none-any.whl `
  krita-codex-install install `
  --allowed-root "C:\Krita Work"

Once the same version is published, replace the wheel path with krita-codex-mcp==0.1.0. Install and update never close Krita. If the authenticated bridge is running, replacement is rejected before any installed files are changed and Krita must be closed manually. On Windows, safety is decided by an exclusive bind to every relevant old and new bridge port, not by a connection attempt. The installer holds those port reservations from before staging through journaled swaps, validation and cleanup. A failed reservation blocks replacement fail-closed and asks the user to close Krita or free the port.

For a personal installation, use the user-level C:\Users\<you>\.codex\config.toml. This is the recommended option because the server is then available to all local Codex tasks and Git worktrees. The generated block uses uvx, has no checkout cwd, and pins the same exact distribution version as the installed plugin. The installer only changes that file after showing the full preview and receiving explicit confirmation. Unmarked or conflicting Krita entries are never overwritten. Never commit personal configuration. See the Windows installation guide for details.

The preflight checks local configuration, the complete installed hash manifest, wheel/plugin/ protocol versions, loopback port, authentication and krita_state. The running plugin reports the distribution and protocol version loaded by Krita without adding an MCP tool. The check creates a disposable document, validates direct PNG preview bytes, exports a temporary PNG beneath an allowed root, closes the document and removes the file. It restores the previously active document and does not edit Codex configuration or contact an external service.

Current status

• The wheel now contains the complete Krita plugin, desktop descriptor and shared protocol, plus a Python-native transactional installer usable from a local wheel or an exactly pinned uvx invocation without a Git checkout.
• Installation manifests contain only relative managed paths, distribution/protocol versions and SHA-256 hashes. Configuration and bearer tokens remain outside the wheel and manifest.
• Package install, update, check and uninstall share one Python implementation. The PowerShell scripts are compatibility wrappers for trusted repository checkouts.
• Mutating commands hold a non-blocking process lock. A fsync-backed, atomically replaced journal records every target-to-backup and stage-to-target boundary. The next mutating command restores the previous installation after an interrupted install or uninstall before starting new work.
• Protocol, configuration, dual input/output path policy, bridge client and thirteen-tool MCP surface implemented.
• Krita plugin implements state, preview, persistent layer-tree editing, native path painting, KRA save and PNG export.
• Offline unit, functional HTTP and contract tests cover protocol, path escapes, authentication, request limits, timeout/busy serialization, input validation and the absence of pixel/arbitrary-code painting.
• Reliability contracts reject native draw calls that changed no pixels, verify layer reparenting with a recovery copy, synchronize projections before previews, and keep mutation responses compact unless the caller explicitly requests the full layer tree.
• A live Windows run on Krita 5.3.2.1 verified state, direct PNG previews, stable layer UUIDs, pressure-aware native painting, two undo steps for two segments, dialog-free KRA/PNG output, authentication failure and allowed-root enforcement.
• A real thirteen-tool MCP STDIO session created its own disposable document, used krita_draw and a KRA-backed project palette, verified direct metadata plus PNG ImageContent, and closed the document again.
• The expansion live run verified stable in-session document IDs, preset search and brush state, native painting, bounded undo/redo, layer duplication/grouping/reordering/translation/deletion, explicit targeting with two open documents, unsaved-close refusal, KRA/PNG output, an in-place KRA checkpoint, isolated transparent group export, and close/reopen with the saved layer structure intact.
• Frame-group animation export produces equal-size transparent frame PNGs, a deterministic spritesheet and a Unity-oriented JSON manifest in one managed package directory. Explicit frame order, canvas/common-union crops, timing, loop, padding, pivot and pixels-per-unit metadata are supported. Re-export preserves Unity .meta sidecars for stable generated filenames.
• Tileset-grid and explicit-region export produce an isolated full-canvas spritesheet, stable numeric region PNGs and a Unity-oriented manifest with Point-filter settings, hashes, pivots and both PNG-top-left and Unity-bottom-left rectangles. Re-export is transactional and keeps .meta sidecars untouched.
• The editing live run verified cropped nearest-neighbor previews, composited RGBA sampling, rectangular and opaque-pixel selections, native fill/clear with undo, anchored canvas resize, nearest-neighbor scaling, crop/rotate/flip, and an embedded editable raster import. The import survived source deletion plus a KRA save/close/reopen round trip with the same layer UUID.
• The creation live run verified native line/path/polygon/rectangle/ellipse painting, meaningful shape Undo/Redo, Krita-global clipboard actions, selection-to-layer workflows, exact RGBA color replacement through a temporary selection plus native fill, undoable filter strokes, and a document project palette that survived save/close/reopen. Free layer scale/rotate/shear/crop are not undoable in Krita 5.3.2.1's Python API, so each creates a hidden backup layer and returns its UUID. Because two direct node transforms in one open document crash that Krita build during teardown, a second is rejected until the KRA is saved, closed and reopened. Direct callers may set checkpoint_reopen=true to perform that bounded KRA round trip inside krita_layers and receive the replacement document/layer IDs. Native layer mirror remains one normal Undo step and does not count toward that guard.
• The transform-mask live run verified non-destructive scale, rotate and shear on one asymmetric transparent layer. Each operation created a native transformmask, changed the direct PNG preview, survived a KRA save/close/reopen round trip with stable UUIDs, and could then be removed to restore the original projection. Krita 5.3.2.1 is unstable when a mask is repeatedly mutated or removed before the first reopen, so the bridge allows at most three masks, blocks same-session mask mutation/removal, and refuses to mix mask and direct layer-transform backends until Krita is restarted.
• A direct Codex-to-Krita asset workflow created and reopened a layered transparent 128x128 pickup, preserved its project palette and stable layer UUIDs, and verified that whole-canvas previews retain transparent margins. Closing the final document now reports no stale active UUID.

Krita 5.3.2.1's Python binding requires integer QPoint values for Node.paintLine; incoming canvas coordinates are therefore rounded at the native API boundary. PNG export temporarily enables document batch mode so no format dialog can block the local bridge.

Timeouts and production guardrails

Timeouts are operation-specific across Codex, the MCP BridgeClient, the local HTTP bridge and Qt's main-thread dispatcher:

Operation class	Dispatcher timeout
Reads and normal edits	30 seconds
Document open and checkpoint save	120 seconds
KRA/PNG, layer, animation, tileset and region exports	180 seconds

The recommended Codex tool_timeout_sec is 210 seconds so the MCP client can receive the bridge's structured result. If a timed-out Qt operation is already running, operation_may_complete=true is preserved and later calls receive BRIDGE_BUSY until Krita actually finishes.

Keep allowed_roots as narrow as practical, keep ordinary versioned or manual KRA backups, and do not treat the bridge timeout as cancellation. The bridge is local-only and binds exactly to 127.0.0.1.

Before a release, run every live helper listed in the Krita E2E checklist against the supported Krita build. The offline CI does not start a Krita GUI.

See Windows installation, protocol, security, service mixin contracts, and the Krita E2E checklist.

Releases

Releases are built from stable vX.Y.Z tags that already belong to main. The release workflow repeats the complete Windows verification, publishes the exact verified wheel and sdist through PyPI Trusted Publishing, and creates the GitHub release only after the PyPI upload succeeds. It does not use a stored PyPI API token. See the release guide for the one-time publisher setup and the release checklist.

License

Released under the MIT License. Copyright (c) 2026 Nicklas Desens.

Plugin structure

The Qt-main-thread bridge keeps service.py as a small composition and dispatch entrypoint. Document, canvas, selection/editing, layer-tree operations, layer transforms, painting/drawing, palette handling, color adjustments, animation/region assets, managed packages, shared context and validation behavior live in focused sibling modules under krita-plugin/kritacodexbridge; the public bridge operations and error payloads do not depend on that internal split.

The STDIO side follows the same boundary: service.py is a compatibility facade, while core, editing, layer, drawing, color, asset and shared input validation live in focused modules under src/krita_codex_mcp. Tool registration is grouped into core, creation and asset modules, with server.py limited to composition and startup. This keeps the MCP schema stable without rebuilding another monolith.

Development

uv sync --all-groups --python 3.12
$env:PYTHONPATH = "src"
.\.venv\Scripts\python.exe -m unittest discover -s tests -v
.\.venv\Scripts\ruff.exe check .
.\.venv\Scripts\python.exe scripts\verify_release.py
.\.venv\Scripts\python.exe -m build

Inspect both wheel and sdist contents, build a wheel again from the sdist, and run the local-wheel uvx smoke before any release. Installation and development do not publish packages, commits or releases.