feat: Ensure Toolkit doesn't connect to Deepnote backend (webapp)

[m1so]

closes BLU-4936

Summary by CodeRabbit

• New Features
  • Introduces a detached server startup mode that runs fully isolated without contacting backend services.
  • Disables automatic integration environment variable injection and post-start hooks when detached.
  • Preserves existing startup behavior (environment setup, dependency constraints, working directory, server launch, lock handling, timeouts) outside of the detached mode.
  • Ideal for offline or sandboxed sessions where external connectivity and automations should be suppressed.

[linear]

BLU-4936 Ensure there's no dependency if toolkit helpers on webapp when launched as CLI

This is related to all code for all integrations - ensure that they are usable independently from webapp. There are various places which request webapp directly and it should be handled in case it's configured to run in standalone mode, which should be default for CLI.

[coderabbitai]

📝 Walkthrough

Walkthrough

Introduces a new environment variable in Deepnote server startup: DETEPNOTE_RUNTIME__RUNNING_IN_DETACHED_MODE='true'. When set, the server runs in detached mode: no backend or proxy requests are made, integration environment variable injection is skipped, and post-start hooks are disabled. All other startup behaviors (virtualenv PATH/VIRTUAL_ENV handling, pip constraints, working directory, server launch, lockfile behavior, and timeouts) remain unchanged.

Sequence Diagram(s)

sequenceDiagram
    autonumber
    participant U as User/CLI
    participant S as DeepnoteServerStarter
    participant E as Environment
    participant P as Server Process
    participant B as Backend (Webapp)

    U->>S: start()
    S->>E: Set VIRTUAL_ENV/PATH, constraints, cwd
    S->>E: Set DETEPNOTE_RUNTIME__RUNNING_IN_DETACHED_MODE = "true"
    S->>P: Launch server

    alt Detached mode (flag = "true")
        Note over S,P: Skip integration env injection
        Note over S,P: Skip post-start hooks
        S--xB: Do not make backend/proxy requests
    else Normal mode
        S->>P: Inject integration env vars
        S->>P: Run post-start hooks
        P->>B: Optional backend/proxy requests
    end

    S->>S: Handle lockfile & timeouts (unchanged)

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Possibly related PRs

• feat: Prevent user from breaking Toolkit's dependencies #23: Also modifies server-startup environment variables in src/kernels/deepnote/deepnoteServerStarter.node.ts (adds DEEPNOTE_ENFORCE_PIP_CONSTRAINTS).

Suggested reviewers

• mfranczel

Pre-merge checks

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The title succinctly states the main purpose of the change—preventing the toolkit from connecting to the backend—and matches the code’s addition of a detached-mode flag without extraneous detail.
Linked Issues Check	✅ Passed	The new DETEPNOTE_RUNTIME__RUNNING_IN_DETACHED_MODE flag disables backend requests and integration hooks, directly fulfilling BLU-4936’s requirement to remove webapp dependencies and support standalone CLI mode.
Out of Scope Changes Check	✅ Passed	All modifications are confined to enabling a detached-mode flag in the server startup and do not introduce unrelated code or features outside the scope of disabling backend connections.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.

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[coderabbitai]

Actionable comments posted: 1

📜 Review details

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Reviewing files that changed from the base of the PR and between 8d67855 and b504eae.

📒 Files selected for processing (1)

• src/kernels/deepnote/deepnoteServerStarter.node.ts (1 hunks)

🧰 Additional context used

📓 Path-based instructions (3)

**/*.node.ts

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

Use *.node.ts for Desktop-specific implementations that require full file system access and Python environments

Files:

• src/kernels/deepnote/deepnoteServerStarter.node.ts

**/*.{ts,tsx}

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

**/*.{ts,tsx}: Inject interfaces, not concrete classes
Avoid circular dependencies
Use l10n.t() for user-facing strings
Use typed error classes from src/platform/errors/ when throwing or handling errors
Use the ILogger service instead of console.log
Preserve error details while scrubbing PII in messages and telemetry
Include the Microsoft copyright header in source files
Prefer async/await and handle cancellation with CancellationToken

**/*.{ts,tsx}: Order class members (methods, fields, properties) first by accessibility, then alphabetically
Separate third-party imports from local file imports

Files:

• src/kernels/deepnote/deepnoteServerStarter.node.ts

src/kernels/**/*.ts

📄 CodeRabbit inference engine (.github/instructions/kernel.instructions.md)

src/kernels/**/*.ts: Use event-driven updates (EventEmitter) for state changes
Monitor and dispose pending promises to prevent leaks during teardown
Use WeakRef/weak references for notebook/object backreferences to avoid memory leaks
Respect CancellationToken in all async operations

Files:

• src/kernels/deepnote/deepnoteServerStarter.node.ts

🧬 Code graph analysis (1)

src/kernels/deepnote/deepnoteServerStarter.node.ts (1)

.vscode-test.mjs (1)

• env (70-73)