Pass cwd to agents from backend

[Light2Dark]

📝 Summary

Previously, the agent would not know the absolute filepath, this led to errors when an agent is instantiated outside of the current directory. This fix ensures current working directory is passed from the backend on-mount, and subsequently passed to the agent.

🔍 Description of Changes

📋 Checklist

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• For large changes, or changes that affect the public API: this change was discussed or approved through an issue, on Discord, or the community discussions (Please provide a link if applicable).
• Tests have been added for the changes made.
• Documentation has been updated where applicable, including docstrings for API changes.
• Pull request title is a good summary of the changes - it will be used in the release notes.

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Error		Mar 3, 2026 7:37pm

[mscolnick]

it's unfortunate to have to pass filename and filepath. can these be merged? I thought filename was absolute? should we force it?

Another option is to call the /files api which gives you the root iirc

[Light2Dark]

it's unfortunate to have to pass filename and filepath. can these be merged? I thought filename was absolute? should we force it?

Another option is to call the /files api which gives you the root iirc

It's a bit tricky, we started passing the relative paths instead of absolute path for filename (where possible). #7722 Not sure if I want to touch this.

The other option, I think we could use files_details endpoint from file_explorer, but this will fetch contents of the file as well. Maybe can create another light endpoint to get absolute path

[mscolnick]

@Light2Dark got it, this is just for home mode? maybe we could just make those absolute URLs. @dmadisetti do you see any issue with that? that does help with consistency, but maybe folks used "home mode" in order to avoid absolute paths.

separately, right now for Agents we use basedir(filename) as the CWD. we don't need to do this now, but maybe it would be better to actually use the CWD, in which the better long-term approach would be to pass that down instead of filepath.

[manzt]

Similar comment to @mscolnick. Is trying to think if there is a way we can require/use one attribute instead of two that could get out of sync.

[manzt]

I think I like the idea of cwd

[Copilot]

Pull request overview

This PR ensures the frontend agent receives a correct working directory (cwd) derived from the backend’s absolute notebook filepath, preventing path-resolution errors when notebooks are mounted from outside the current directory.

Changes:

• Add cwd to the server-generated mount config (derived from filepath) and thread it into the notebook/static templates.
• Introduce a cwdAtom on the frontend, parse cwd at mount-time, and use it to initialize agent sessions / compute absolute notebook paths for agent resources.
• Update template tests and export HTML snapshots to include the new cwd field.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
marimo/_server/templates/templates.py	Adds cwd to mount config and derives it from filepath for notebook pages.
frontend/src/mount.tsx	Extends mount options schema to accept cwd and stores it in state.
frontend/src/core/saving/file-state.ts	Adds cwdAtom to store the notebook working directory.
frontend/src/components/chat/acp/agent-panel.tsx	Uses cwdAtom to set agent session cwd and build an absolute filename for agent resources.
tests/_server/templates/test_templates.py	Adds assertions for cwd and a new filepath-driven test case.
tests/_server/templates/snapshots/export1.txt	Snapshot update to include "cwd": "" in mount config.
tests/_server/templates/snapshots/export2.txt	Snapshot update to include "cwd": "" in mount config.
tests/_server/templates/snapshots/export3.txt	Snapshot update to include "cwd": "" in mount config.
tests/_server/templates/snapshots/export4.txt	Snapshot update to include "cwd": "" in mount config.
tests/_server/templates/snapshots/export5.txt	Snapshot update to include "cwd": "" in mount config.
tests/_server/templates/snapshots/export6.txt	Snapshot update to include "cwd": "" in mount config.

Comments suppressed due to low confidence (3)

marimo/_server/templates/templates.py:71

• cwd is derived from filepath (an absolute server-side path) and embedded into window.__MARIMO_MOUNT_CONFIG__, which is sent to the browser. This can unintentionally disclose server filesystem layout (especially when filename is made relative for directory mode). Consider limiting exposure (e.g., only include cwd when running in a trusted/local mode or when the agent feature is enabled), or pass a server-resolvable identifier instead of an absolute path and have the backend resolve paths for agent operations.

    options: dict[str, Any] = {
        "filename": filename or "",
        "cwd": cwd or "",
        "mode": mode,
        "version": version or get_version(),
        "server_token": str(server_token),
        "user_config": user_config,

tests/_server/templates/test_templates.py:101

• This assertion is not portable on Windows: the rendered JSON will escape backslashes (e.g., C:\\...), so f'"cwd": "{expected_cwd}"' won’t match. Consider asserting against json.dumps(expected_cwd) (or parsing the mount config JSON and comparing the cwd field) so the test is robust across path separators/escaping.

        )

        assert self.filename.name in result
        assert f'"cwd": "{expected_cwd}"' in result
        _assert_no_leftover_replacements(result)

frontend/src/mount.tsx:153

• The schema/docs say cwd is an absolute working directory, but the backend currently emits an empty string when unknown. Consider normalizing "" to null in the schema/transform (or updating the doc comment to explicitly state it may be empty/unknown) to avoid downstream code treating an empty string as a valid absolute path.

  /**
   * absolute working directory of the notebook
   */
  cwd: z.string().nullish().default(null),
  /**

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[dmadisetti]

No issues passing the data, assuming our permissions work

[dmadisetti]

The windows failure might be real (file path issues)

[Light2Dark]

I pushed a fix but not showing up here. I think its a test issue, it's escaping \ with \ so shows up as \\