Simon Willison’s Weblog

This alpha is a significant step on the road to a stable 1.0, finally extending the ?_extra= pattern I introduced in Datasette 1.0a3 to cover queries and rows in addition to tables. That pattern is also now documented!

I wrote a whole lot more about the new release on the Datasette project blog: Datasette 1.0a33 with JSON extras in the API.

Because API explorer tools are almost free to build now I had Claude Fable 5 in Claude Code (for the plan) and GPT-5.5 xhigh in Codex Desktop (for the implementation) build me this custom extras API explorer to help demonstrate the feature:

I built this utility library to support an asyncio dependency injection pattern a few years ago. I was using it with Datasette and Claude Fable 5 spotted some bugs in the dependency which it then fixed for me. It's a very proactive model!

Highlights from the release notes:

• Tools can now ask the user questions mid-execution. Tools that declare a context parameter receive a ToolContext object, and await context.ask_user(...) can ask a yes/no, multiple-choice (options=[...]) or free-text (free_text=True) question. While a question is unanswered the agent turn suspends: the question renders as a form in the chat UI and persists to the internal database, so suspended conversations survive a server restart. Once answered, the tool re-executes from the top with stored answers replayed, so call ask_user() before performing side effects. #20
• New built-in save_query tool: the agent can save SQL it has written as a Datasette stored query. Saving always requires human approval - the agent shows the full SQL plus the proposed name, database and visibility, and nothing is stored until you click Yes. #20

The ask_user() feature was enabled by the new LLM alpha I built yesterday with the help of Claude Fable 5.

Almost entirely written by the new Claude Fable 5, see my write-up for more details.

I'm planning several plugins for Datasette Agent which can make edits to existing pieces of text - things like collaborative Markdown editing, updating large SQL queries, and editing SVG files.

Agentic editing of text is a little tricky to get right. My favorite published design for this is for the Claude text editor, which implements the following tools:

• view - view sections of a file, with line numbers added to every line.
• str_replace - find an exact old_str and replace it with new_str - fail if the original string is not unique
• insert - insert the specified text after the specified line number

Rather than recreate these patterns for every plugin that needs them I decided to create this base plugin, datasette-agent-edit, which implements the core tools in a way that allows them to be adapted for other plugins.

I added a CLI to micropython-wasm (issue #7), inspired by the first draft of the blog entry when I realized it would be a great way to illustrate the Try it yourself section.

I want Datasette Agent to be able to generate and execute Python code safely. This alpha is looking promising so far. GPT-5.5 has so far failed to break out of the sandbox!

Fixes for some limitations that emerged while I was trying to use this to build datasette-agent-micropython.

My latest sandboxing experiment: This alpha package bundles a lightly customized WASM build of MicroPython with a wrapper to execute code in it via wasmtime.

A minor bugfix release. Fixes a bug with INSERT ... RETURNING queries via the new /db/-/execute-write endpoint and a bunch of base_url issues which showed up when I was experimenting with Service Workers yesterday.

Another significant alpha release, with two new headline features.

Datasette now offers users with the necessary permissions the ability to both execute write queries against their database and to save stored queries (renamed from "canned queries") both privately and for use by other members of their Datasette instance.

There's more detail in SQL write queries and stored queries in Datasette 1.0a31 on the Datasette blog, which now has three posts introducing new features since the blog launched two weeks ago.

Here's an animated demo from the blog post showing how the new execute query interface lets people get started with templated insert/update/delete queries from tables they have permission to edit:

• New model: Claude Opus 4.8 (claude-opus-4.8).
• New -o fast 1 option for fast mode, for organizations with that feature enabled on their account.
• Default max_tokens for each model now defaults to that model's maximum output rather than 8,192. #72

See also my notes on Opus 4.8 - I used this new release of llm-anthropic to generate the pelicans.

The big new feature in this alpha is a new customizable "Jump to..." menu, described in detail in The extensible "Jump to" menu in Datasette 1.0a30 on the Datasette blog. You can try it out by hitting / on latest.datasette.io - it looks like this:

The new jump_items_sql() plugin hook allows plugins to add their own items to the set that's searched by the plugin.

Taking advantage of the new makeJumpSections() JavaScript plugin hook added in Datasette 1.0a30, datasette-agent now presents this "Start a new agent chat" interface as part of the Jump to menu, any time you hit /:

You can try this out by signing into agent.datasette.io using your GitHub account.

One of the smaller features in Datasette 1.0a30 is this:

New documented datasette.fixtures.populate_fixture_database(conn) helper for creating the fixture database tables used by Datasette's own tests, intended for plugin test suites.

This new plugin takes advantage of that API. You can try it out using uvx without even installing Datasette like this:

uvx --prerelease=allow \
  --with datasette-fixtures datasette \
  --get /fixtures/roadside_attractions.json

Which outputs:

{
  "ok": true,
  "next": null,
  "rows": [
    {"pk": 1, "name": "The Mystery Spot", "address": "465 Mystery Spot Road, Santa Cruz, CA 95065", "url": "https://www.mysteryspot.com/", "latitude": 37.0167, "longitude": -122.0024},
    {"pk": 2, "name": "Winchester Mystery House", "address": "525 South Winchester Boulevard, San Jose, CA 95128", "url": "https://winchestermysteryhouse.com/", "latitude": 37.3184, "longitude": -121.9511},
    {"pk": 3, "name": "Burlingame Museum of PEZ Memorabilia", "address": "214 California Drive, Burlingame, CA 94010", "url": null, "latitude": 37.5793, "longitude": -122.3442},
    {"pk": 4, "name": "Bigfoot Discovery Museum", "address": "5497 Highway 9, Felton, CA 95018", "url": "https://www.bigfootdiscoveryproject.com/", "latitude": 37.0414, "longitude": -122.0725}
  ],
  "truncated": false
}

• Improved design of the /-/llm-limits page, now using the base template. #2
• Now shown in application menu for users with the datasette-llm-limits-view permission.

A Datasette Agent plugin for running commands in a Fly Sprites sandbox.

• "View SQL query" buttons below rendered charts.

• "View SQL query" buttons for both visible tables and collapsed SQL result tool calls.
• Don't display empty reasoning chunks
• Improved handling of truncated responses - table still displays to the user even if the SQL results were truncated when showing the agent.

See Datasette Agent, an extensible AI assistant for Datasette.

• More color! Bar and waffle charts without a color column are shaded by magnitude with a sequential color scheme; color columns holding text values use the observable10 categorical scheme. #2
• Now checks execute-sql permission before running the query to find the column names.
• Charts now display interactive tooltips.
• Fixed a bug where waffleY charts were not described to the agent.

• New model gemini-3.5-flash for Gemini 3.5 Flash.

See also my notes on Gemini 3.5 Flash, and the pelican I drew using this upgrade to the plugin.

• Fixed bug tracking chains of responses. Refs datasette-llm#7

• Compatible with llm>=0.32a0 alpha - adds the ability to stream reasoning tokens.

• Fix for bug where llm_prompt_context() hook did not fully collect chains of responses. #7

Part of the infrastructure I use for publishing my iNaturalist sightings on my blog. I've been running this in production for a few weeks now, inspiring some iterations on how it works, so I decided to ship a 0.1 release.

You can see an example of the output in this JSON file.

This plugin works in conjunction with datasette-llm and datasette-llm-accountant to let you configure a per-user (or global) spending limit for LLM usage inside of Datasette. Configuration looks something like this:

plugins:
  datasette-llm-limits:
    limits:
      per-user-daily:
        scope: actor
        window: rolling-24h
        amount_usd: 1.00

• Tool availability can now be attached to a required_permission. The default background agent tools now require the new datasette-agent-background permission. #10

• Now uses the execute-sql permission when deciding which tables to list to the user. #8

The datasette.io site was being hammered by poorly-behaved crawlers, so I had Codex (GPT-5.5 xhigh) build a configurable rate limiting plugin to block IPs that were hammering specific areas of the site too quickly.

Here's the production configuration I'm using on that site for the new plugin:

  datasette-ip-rate-limit:
    header: Fly-Client-IP
    max_keys: 10000
    exempt_paths:
    - "/static/*"
    - "/-/turnstile*"
    rules:
    - name: demo-databases
      paths:
      - "/global-power-plants/*"
      - "/legislators/*"
      window_seconds: 60
      max_requests: 60
      block_seconds: 20

• New TokenRestrictions.abbreviated(datasette) utility method for creating "_r" dictionaries. #2695
• Table headers and column options are now visible even if a table contains zero rows. #2701
• Fixed bug with display of column actions dialog on Mobile Safari. #2708
• Fixed bug where tests could crash with a segfault due to a race condition between Datasette.close() and Database.close(). #2709

That segfault bug was gnarly. I added a mechanism to Datasette recently that would automatically close connections at the end of each test, but it turned out that introduced a race condition where an in-flight query could sometimes be executing in a thread against a connection while it was being closed. I ended up solving that by having Codex CLI (with GPT-5.5 xhigh) create a minimal Dockerfile that recreated the bug.