fix(rivetkit): copy Buffer to Uint8Array in ensureUint8Array to fix .slice() semantics

[NathanFlurry]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[railway-app]

🚅 Deployed to the rivet-pr-4506 environment in rivet-frontend

Service	Status	Web	Updated (UTC)
frontend-cloud	🕐 Queued (View Logs)	Web	Mar 25, 2026 at 8:04 pm
kitchen-sink	🕐 Queued (View Logs)	Web	Mar 25, 2026 at 8:04 pm
frontend-inspector	🕐 Queued (View Logs)	Web	Mar 25, 2026 at 8:04 pm
website	😴 Sleeping (View Logs)	Web	Mar 25, 2026 at 9:44 am
mcp-hub	✅ Success (View Logs)	Web	Mar 25, 2026 at 9:32 am
ladle	❌ Build Failed (View Logs)	Web	Mar 25, 2026 at 9:32 am

[NathanFlurry]

• fix(rivetkit): copy Buffer to Uint8Array in ensureUint8Array to fix .slice() semantics #4506 : 2 dependent PRs (#4502 , #4510 ) 👈 (View in Graphite)
• fix(rivetkit): setup database before lifecycle hooks for c.db availability #4494
• fix(rivetkit): remove drizzle-orm peer dep and add runtime version check #4492
• chore(skill): add version check to rivetkit skill #4491
• fix(rivetkit): prevent Turbopack from tracing sqlite-vfs dynamic import #4490
• fix(rivetkit): warn when manager port falls back to a different port #4489
• fix(rivetkit): clear connectableTs on actor sleep #4488
• fix(rivetkit): gate node:sqlite behind RIVETKIT_NODE_SQLITE env var #4487
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

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commit: bb97419

[claude]

PR Review: fix(rivetkit): copy Buffer to Uint8Array in ensureUint8Array

This is a correct and well-targeted bug fix. The root cause is real: Node.js Buffer extends Uint8Array but overrides .slice() to return a view instead of a copy, violating the Uint8Array spec. Libraries like vbare and cbor-x that depend on copy semantics can silently get aliased memory, causing subtle data corruption.

What looks good

• Comment quality: The comment at lines 219-223 clearly explains the why (spec violation, affected libraries) rather than just the what.
• Guard correctness: typeof Buffer !== "undefined" && Buffer.isBuffer(value) handles environments without Buffer (e.g. browsers, Deno) safely.
• Ordering: The Buffer.isBuffer check sits inside the instanceof Uint8Array branch, so it only runs when needed and correctly precedes the plain return value.
• Symmetry with normalizeParams: Input params go Uint8Array -> Buffer (line 45), output values now go Buffer -> Uint8Array. The round-trip is semantically correct.

Minor suggestions

Simpler copy idiom: The two-step copy is correct, but return new Uint8Array(value) achieves the same result in one line. The TypedArray constructor performs a copy when given another typed array. Either form is fine.

No test added: The driver test suite at src/driver-test-suite/tests/ has no coverage for the Buffer->Uint8Array copy path. A test that stores binary data, reads it back, and calls .slice() on the result to verify it returns a copy (not a view) would prevent a regression.

Other ArrayBufferView subtypes: The existing fallback at line 234-235 creates a view for non-Uint8Array ArrayBufferView inputs. This is fine for now since only Buffer is known to override .slice() semantics in practice.

Summary

The fix is correct and minimal. The suggestions above are optional — the change is mergeable as-is.

[NathanFlurry]

Merge activity

• Mar 25, 7:43 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Mar 25, 8:04 PM UTC: Graphite rebased this pull request as part of a merge.
• Mar 25, 8:05 PM UTC: @NathanFlurry merged this pull request with Graphite.