openclaw-openclaw/docs/tools/diffs.md

summary, title, sidebarTitle, read_when

summary	title	sidebarTitle	read_when
Read-only diff viewer and file renderer for agents (optional plugin tool)	Diffs	Diffs	You want agents to show code or markdown edits as diffs You want a canvas-ready viewer URL or a rendered diff file You need controlled, temporary diff artifacts with secure defaults

diffs is an optional bundled plugin tool that turns before/after text or a unified patch into a read-only diff artifact. It also prepends short agent guidance into the system prompt and ships a companion skill for fuller instructions.

Input: before + after text, or a unified patch (mutually exclusive).

Output: a gateway viewer URL for canvas presentation, a rendered PNG/PDF file path for message delivery, or both.

Quick start

```bash openclaw plugins install diffs ``` ```json5 { plugins: { entries: { diffs: { enabled: true, }, }, }, } ``` Canvas-first flows: agents call `diffs` with `mode: "view"` and open `details.viewerUrl` with `canvas present`. Chat file delivery: agents call `diffs` with `mode: "file"` and send `details.filePath` with `message` using `path` or `filePath`. Combined (default): agents call `diffs` with `mode: "both"` to get both artifacts in one call.

Disable built-in system guidance

To keep the tool but drop the prepended system-prompt guidance, set plugins.entries.diffs.hooks.allowPromptInjection to false:

{
  plugins: {
    entries: {
      diffs: {
        enabled: true,
        hooks: {
          allowPromptInjection: false,
        },
      },
    },
  },
}

This blocks the plugin's before_prompt_build hook while keeping the tool and skill available. To disable both guidance and the tool, disable the plugin instead.

Tool input reference

All fields are optional unless noted.

Original text. Required with `after` when `patch` is omitted. Updated text. Required with `before` when `patch` is omitted. Unified diff text. Mutually exclusive with `before` and `after`. Display filename for before/after mode. Language override hint for before/after mode. Unknown values and languages outside the default viewer set fall back to plain text unless the Diff Viewer Language Pack plugin is installed. Viewer title override. Output mode. Defaults to plugin default `defaults.mode` (`both`). Deprecated alias: `"image"` behaves identically to `"file"`. Viewer theme. Defaults to plugin default `defaults.theme`. Diff layout. Defaults to plugin default `defaults.layout`. Expand unchanged sections when full context is available. Per-call option only (not a plugin default key). Rendered file format. Defaults to plugin default `defaults.fileFormat`. Quality preset for PNG/PDF rendering. Device scale override (`1`-`4`). Max render width in CSS pixels (`640`-`2400`). Artifact TTL in seconds for viewer and standalone file outputs. Max `21600`. Viewer URL origin override. Overrides plugin `viewerBaseUrl`. Must be `http` or `https`, no query/hash. Still accepted for backward compatibility:

- `format` -> `fileFormat`
- `imageFormat` -> `fileFormat`
- `imageQuality` -> `fileQuality`
- `imageScale` -> `fileScale`
- `imageMaxWidth` -> `fileMaxWidth`

- `before`/`after`: max 512 KiB each. - `patch`: max 2 MiB. - `path`: max 2048 bytes. - `lang`: max 128 bytes. - `title`: max 1024 bytes. - Patch complexity cap: max 128 files and 120000 total lines. - `patch` together with `before`/`after` is rejected. - Rendered file safety limits (PNG and PDF): - `fileQuality: "standard"`: max 8 MP (8,000,000 rendered pixels). - `fileQuality: "hq"`: max 14 MP. - `fileQuality: "print"`: max 24 MP. - PDF also caps at 50 pages.

Syntax highlighting

Built-in languages:

javascript, typescript, tsx, jsx, json, markdown, yaml, css, html, sh, python, go, rust, java, c, cpp, csharp, php, sql, docker, ruby, swift, kotlin, r, dart, lua, powershell, xml, and toml.

Common aliases (js, ts, bash, md, yml, c++, dockerfile, rb, kt, ps1, etc.) normalize to those languages.

Install the Diff Viewer Language Pack plugin for more languages (Astro, Vue, Svelte, MDX, GraphQL, Terraform/HCL, Nix, Clojure, Elixir, Haskell, OCaml, Scala, Zig, Solidity, Verilog/VHDL, Fortran, MATLAB, LaTeX, Mermaid, Sass/Less/SCSS, Nginx, Apache, CSV, dotenv, INI, diff, and more):

openclaw plugins install clawhub:@openclaw/diffs-language-pack

Without the pack, unsupported languages still render as readable plain text. See Diffs Language Pack plugin and Shiki languages for the upstream catalog.

Output details contract

- `artifactId` - `viewerUrl` - `viewerPath` - `title` - `expiresAt` - `inputKind` - `fileCount` - `mode` - `context` (`agentId`, `sessionId`, `messageChannel`, `agentAccountId` when available) - `artifactId` - `expiresAt` - `filePath` - `path` (same value as `filePath`, for message tool compatibility) - `fileBytes` - `fileFormat` - `fileQuality` - `fileScale` - `fileMaxWidth` - `format` (= `fileFormat`) - `imagePath` (= `filePath`) - `imageBytes` (= `fileBytes`) - `imageQuality` (= `fileQuality`) - `imageScale` (= `fileScale`) - `imageMaxWidth` (= `fileMaxWidth`)

Mode	Returns
"view"	Viewer fields only.
"file"	File fields only, no viewer artifact.
"both"	Viewer fields plus file fields. If file rendering fails, viewer still returns with fileError/imageError.

Collapsed unchanged sections

The viewer shows rows like N unmodified lines. Expand controls only appear when the rendered diff has expandable context data (typical for before/after input). Many unified patches omit context bodies in their hunks, so the row can appear without an expand control -- expected, not a bug. expandUnchanged only applies when expandable context exists.

Plugin defaults

Set plugin-wide defaults in ~/.openclaw/openclaw.json:

{
  plugins: {
    entries: {
      diffs: {
        enabled: true,
        config: {
          defaults: {
            fontFamily: "Fira Code",
            fontSize: 15,
            lineSpacing: 1.6,
            layout: "unified",
            showLineNumbers: true,
            diffIndicators: "bars",
            wordWrap: true,
            background: true,
            theme: "dark",
            fileFormat: "png",
            fileQuality: "standard",
            fileScale: 2,
            fileMaxWidth: 960,
            mode: "both",
            ttlSeconds: 21600,
          },
        },
      },
    },
  },
}

Supported defaults keys: fontFamily, fontSize, lineSpacing, layout, showLineNumbers, diffIndicators, wordWrap, background, theme, fileFormat, fileQuality, fileScale, fileMaxWidth, mode, ttlSeconds. Explicit tool call parameters override these.

Persistent viewer URL config

Plugin-owned fallback for returned viewer links when a tool call does not pass `baseUrl`. Must be `http` or `https`, no query/hash.

{
  plugins: {
    entries: {
      diffs: {
        enabled: true,
        config: {
          viewerBaseUrl: "https://gateway.example.com/openclaw",
        },
      },
    },
  },
}

Security config

`false`: non-loopback requests to viewer routes are denied. `true`: remote viewers are allowed if the tokenized path is valid.

{
  plugins: {
    entries: {
      diffs: {
        enabled: true,
        config: {
          security: {
            allowRemoteViewer: false,
          },
        },
      },
    },
  },
}

Artifact lifecycle and storage

• Artifacts live under $TMPDIR/openclaw-diffs.
• Viewer metadata stores a random 20-hex-char artifact ID, a random 48-hex-char token, createdAt/expiresAt, and the stored viewer.html path.
• Default artifact TTL: 30 minutes. Maximum accepted TTL: 6 hours.
• Cleanup runs opportunistically after each artifact create call; expired artifacts are deleted.
• Fallback sweep removes stale folders older than 24 hours when metadata is missing.

Viewer URL and network behavior

Viewer route: /plugins/diffs/view/{artifactId}/{token}

Viewer assets:

• /plugins/diffs/assets/viewer.js
• /plugins/diffs/assets/viewer-runtime.js
• /plugins/diffs-language-pack/assets/viewer.js (only when the diff uses a language pack language)

The viewer document resolves these assets relative to the viewer URL, so an optional baseUrl path prefix carries through to asset requests too.

URL resolution order: tool-call baseUrl (after strict validation) -> plugin viewerBaseUrl -> loopback 127.0.0.1 default. If gateway bind mode is custom and gateway.customBindHost is set, that host is used instead of loopback.

baseUrl rules: must be http:// or https://; query and hash are rejected; origin plus optional base path is allowed.

Security model

- Loopback-only by default. - Tokenized viewer paths with strict ID and token pattern validation. - Viewer response CSP: `default-src 'none'`; scripts/assets only from self; no outbound `connect-src`. - Remote miss throttling when remote access is enabled: 40 failures per 60 seconds triggers a 60-second lockout (`429 Too Many Requests`). - Screenshot browser request routing is deny-by-default. - Only local viewer assets from `http://127.0.0.1/plugins/diffs/assets/*` are allowed. - External network requests are blocked.

Browser requirements for file mode

mode: "file" and mode: "both" need a Chromium-compatible browser.

Resolution order:

`browser.executablePath` in OpenClaw config. - `OPENCLAW_BROWSER_EXECUTABLE_PATH` - `BROWSER_EXECUTABLE_PATH` - `PLAYWRIGHT_CHROMIUM_EXECUTABLE_PATH` Common install paths and `PATH` lookups for Chrome, Chromium, Edge, and Brave.

Common failure text: Diff PNG/PDF rendering requires a Chromium-compatible browser.... Fix by installing Chrome, Chromium, Edge, or Brave, or setting one of the executable path options above.

Troubleshooting

- `Provide patch or both before and after text.` -- include both `before` and `after`, or provide `patch`. - `Provide either patch or before/after input, not both.` -- do not mix input modes. - `Invalid baseUrl: ...` -- use an `http(s)` origin with optional path, no query/hash. - `{field} exceeds maximum size (...)` -- reduce payload size. - Large patch rejection -- reduce patch file count or total lines. - Viewer URL resolves to `127.0.0.1` by default. - For remote access, either set plugin `viewerBaseUrl`, pass `baseUrl` per call, or use `gateway.bind=custom` with `gateway.customBindHost`. - If `gateway.trustedProxies` includes loopback for a same-host proxy (for example Tailscale Serve), raw loopback viewer requests without forwarded client-IP headers fail closed by design. - For that proxy topology, prefer `mode: "file"`/`"both"` for an attachment, or intentionally enable `security.allowRemoteViewer` plus plugin `viewerBaseUrl`/a proxy `baseUrl` for a shareable viewer link. - Enable `security.allowRemoteViewer` only when external viewer access is intended. Expected for patch input that lacks expandable context; not a viewer failure. - Artifact expired due to TTL. - Token or path changed. - Cleanup removed stale data.

Operational guidance

• Prefer mode: "view" for local interactive reviews in canvas.
• Prefer mode: "file" for outbound chat channels that need an attachment.
• Keep allowRemoteViewer disabled unless your deployment requires remote viewer URLs.
• Set an explicit short ttlSeconds for sensitive diffs.
• Avoid sending secrets in diff input when not required.
• If your channel compresses images aggressively (for example Telegram or WhatsApp), prefer PDF output (fileFormat: "pdf").

Diff rendering engine powered by [Diffs](https://diffs.com).

Related

• Browser
• Plugins
• Tools overview