Agent mode

lightpanda agent runs a browsing agent backed by Lightpanda's headless engine. It can act as:

an LLM agent that drives the browser with tool calls (--provider),
a scripted runner that replays a .panda script deterministically,
a dumb REPL for hand-driven Pandascript with no LLM at all,
a one-shot task runner that prints a single answer to stdout (--task).

All four modes share the same browser tools (goto, click, fill, tree, markdown, search, ...). The same set is exposed over MCP via lightpanda mcp, so an agent script and an MCP client see the same surface.

Quick start

# Interactive REPL with an LLM
./lightpanda agent --provider anthropic

# Dumb REPL (no API key, Pandascript only)
./lightpanda agent

# Replay a recorded script
./lightpanda agent session.panda

# Replay then continue interactively, appending new commands to the file
./lightpanda agent -i session.panda

# One-shot: ask a question, capture the answer on stdout
./lightpanda agent --provider gemini --task "what is on the front page of hn?"

Providers and API keys

Provider	Flag	API key env
Anthropic	`--provider anthropic`	`ANTHROPIC_API_KEY`
OpenAI	`--provider openai`	`OPENAI_API_KEY`
Gemini	`--provider gemini`	`GOOGLE_API_KEY` or `GEMINI_API_KEY`
Ollama	`--provider ollama`	none (local)

Defaults: --model falls back to a sensible per-provider default; --base-url overrides the API endpoint (Ollama defaults to http://localhost:11434/v1).

Without --provider, the REPL still works for Pandascript commands. Natural language, LOGIN, ACCEPT_COOKIES, and --self-heal all require a provider.

Pandascript

Pandascript is a tiny, line-oriented DSL for browser actions. Each line is one command. Comments start with #. Strings are quoted with ', ", or '''…''' for values that mix both quote styles. Quoting rules are content-aware so that recorded scripts round-trip through the parser.

Command	Form	Notes
`GOTO`	`GOTO <url>`	Navigate. URL is unquoted.
`CLICK`	`CLICK '<selector>'`	CSS selector.
`TYPE`	`TYPE '<selector>' '<value>'`	Fills an input. `$LP_*` env refs auto-resolve.
`WAIT`	`WAIT '<selector>'`	Wait for selector.
`SCROLL`	`SCROLL [x] [y]`	Default `(0, 0)`.
`HOVER`	`HOVER '<selector>'`
`SELECT`	`SELECT '<selector>' '<value>'`	`<select>` option by value.
`CHECK`	`CHECK '<selector>' [true\|false]`	Check / uncheck. Default `true`.
`EXTRACT`	`EXTRACT '<selector>'`	Returns text content.
`EVAL`	`EVAL '<js>'` or `EVAL '''…'''`	Triple-quote for multi-line JS.
`TREE`	`TREE`	Print the semantic tree (not recorded).
`MARKDOWN`	`MARKDOWN`	Print page as markdown (not recorded).
`LOGIN`	`LOGIN`	LLM-driven: fill `$LP_USERNAME` / `$LP_PASSWORD`.
`ACCEPT_COOKIES`	`ACCEPT_COOKIES`	LLM-driven: dismiss the consent banner.

In the REPL, anything that does not parse as a Pandascript command is sent to the LLM as natural language. To leave the REPL, use the /quit slash command.

Example script

# Log into the demo and grab the dashboard title.
GOTO https://demo-browser.lightpanda.io/
ACCEPT_COOKIES
TYPE '#email' '$LP_USERNAME'
TYPE '#password' '$LP_PASSWORD'
CLICK 'button[type="submit"]'
WAIT '.dashboard'
EXTRACT '.dashboard h1'

Recording

Interactive sessions can write back to a .panda file:

./lightpanda agent -i session.panda

State-mutating commands (GOTO, CLICK, TYPE, ...) are appended; read-only commands (TREE, MARKDOWN) and the natural-language turns that produced them are not. Natural-language turns are recorded as # <prompt> comments above the resulting tool calls so the script stays readable.

Replay and self-healing

./lightpanda agent script.panda replays without making any LLM call.

With --self-heal --provider <p>, a failed command (typically a stale selector after the page changed) triggers a short LLM turn that inspects the current page and emits a replacement command. The healed command runs, and the original script line is rewritten in place so the next replay succeeds deterministically.

Self-heal is constrained: at most one replacement per failure, capped LLM budget, no navigation away from the current page. It is meant to recover from selector drift, not to redesign the script.

REPL features

Tab completion: cycles through Pandascript keywords and /<tool> slash commands. The dim grey suffix shown after the cursor is the first match; pressing Tab accepts it.
Persistent history: stored in .lp-history in the working directory.
Slash commands: /<tool> [args] calls a browser tool directly without going through the LLM. /help lists tools, /help <tool> prints the JSON schema. Args accept either a single positional value (for tools with one required field), key=value pairs, or a raw {json} blob.
```
> /goto https://example.com
> /findElement role=button name=Submit
> /eval {"script": "document.title"}
```
Stdout vs stderr: the final assistant answer and data-producing commands (EXTRACT, EVAL, MARKDOWN, TREE) write to stdout. Tool calls, progress, and errors go to stderr, so lightpanda agent --task ... > out.txt captures a clean answer.

One-shot mode (`--task`)

./lightpanda agent --provider gemini \
  --task "what is the top story on news.ycombinator.com?"

--task runs a single user turn, prints the final answer on stdout, and exits. Combine with --task-attachment <path> (repeatable) to feed local files to providers that accept attachments.

Browser tools

The agent and MCP server share the tool set defined in src/browser/tools.zig. Highlights:

goto, search (Google with DuckDuckGo fallback on captcha)
tree, markdown, links, interactiveElements, structuredData, detectForms, nodeDetails, findElement
click, fill, hover, press, scroll, selectOption, setChecked, waitForSelector
eval, consoleLogs, getUrl, getCookies, getEnv

Selectors prefer CSS over backendNodeId for the click-family tools, since node IDs are invalidated by any DOM mutation. The system prompt enforces this for the LLM.

Security notes

The agent treats page content as untrusted data, not instructions. URLs surfaced by a page are not followed unless they match the user's task.
$LP_* environment variable references in TYPE / fill values are resolved at execution time, so credentials never enter the LLM context.
--obey-robots, --http-proxy, --user-agent, and the rest of the browser-level CLI flags apply to agent the same way they apply to serve, fetch, and mcp.

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