⚡ Bolt: [performance improvement] Reduce eventqueue GC pressure

[matdev83]

The PendingEventQueue in internal/core/stream translates large wire chunks into many canonical events. Its compaction logic was reallocating an entire new slice with every shift if the queue capacity was over 32. Since these queues process rapidly arriving stream events, shifting head-to-tail down the existing array via copy is much cheaper than make+copy except when the array has bloated excessively (>1024 cap and <25% active).

This PR:
💡 What: Replaced the eager make reallocation in PendingEventQueue.compactIfNeeded with in-place copy slice shifting, only reallocating when the buffer is severely bloated.
🎯 Why: To reduce GC pressure and allocation overhead on the hot stream queue path.
📊 Impact: pushPop benchmark throughput improved ~35% (175k ns -> 126k ns) and allocations dropped from 13 to 9 per run.
🔬 Measurement: Run cd internal/core/stream && go test -bench=BenchmarkPendingEventQueue_pushPop -benchmem

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PR created automatically by Jules for task 8043453630250216761 started by @matdev83

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 73997caf-f8cc-4d48-8b70-a96bce06936f

📥 Commits

Reviewing files that changed from the base of the PR and between 6b89437 and ded6f70.

📒 Files selected for processing (2)

• internal/core/stream/eventqueue.go
• internal/core/stream/eventqueue_internal_test.go

📝 Walkthrough

Walkthrough

PendingEventQueue.compactIfNeeded is updated to prefer copying live elements in-place to the front of the existing buffer, restricting reallocation to buffers where capacity exceeds 1024 and fewer than one quarter of slots are alive. The .jules/bolt.md file records the change with benchmark figures.

Changes

PendingEventQueue Compaction Optimization

Layer / File(s)	Summary
compactIfNeeded: in-place slide default, shrink-only reallocation internal/core/stream/eventqueue.go, .jules/bolt.md	Replaces the old reallocation condition (alive <= cap/2 && cap > 32) with a narrow condition (cap > 1024 && alive < cap/4), reallocating at alive*2 only in that case and using copy-based in-place sliding otherwise. Documents the new strategy and benchmark results in .jules/bolt.md.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

🚥 Pre-merge checks | ✅ 8

✅ Passed checks (8 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly describes the main technical change (reducing GC pressure in eventqueue) with an appropriate performance-focused prefix, matching the changeset's optimization objective.
Description check	✅ Passed	The description provides comprehensive context about the change, explaining the problem, solution, and measured impact, all directly related to the changeset modifications.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
No Secrets	✅ Passed	PR modifies only .jules/bolt.md (documentation) and internal/core/stream/eventqueue.go (performance optimization). Comprehensive scanning for credentials, API keys, tokens, private keys, passwo...
Context Propagation	✅ Passed	The custom check for context propagation is not applicable. The changes modify only PendingEventQueue.compactIfNeeded, a private memory optimization method unrelated to context, cancellation, or...
No Accidental Public Api Break	✅ Passed	No public API breaks detected. The PR only modifies compactIfNeeded (private method) in internal/core/stream/eventqueue.go. All exported methods (Len, Push, PopFront, NewPendingEventQueue) remain u...

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@internal/core/stream/eventqueue.go`:
- Around line 96-97: The copy and reslice operation in the eventqueue compaction
logic leaves old entries in the truncated portion of the backing array, which
prevents garbage collection of popped events. After the reslice statement `q.buf
= q.buf[:alive]`, explicitly zero out the tail of the buffer from index alive to
the original length to clear the old event references and allow them to be
garbage collected.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: dfadfb1b-77b6-447e-a979-8d5925cd98f4

📥 Commits

Reviewing files that changed from the base of the PR and between ce359a8 and 6b89437.

📒 Files selected for processing (2)

• .jules/bolt.md
• internal/core/stream/eventqueue.go

📜 Review details

⏰ Context from checks skipped due to timeout. (1)

• GitHub Check: qa

🧰 Additional context used

📓 Path-based instructions (3)

internal/core/**/*.go

📄 CodeRabbit inference engine (AGENTS.md)

internal/core/**/*.go: Core packages must not import official provider SDKs
Core packages must not import concrete plugins
Return errors, do not panic in request paths
Keep core files small and cohesive
Do not mix frontend codec logic, routing policy, and backend invocation in one package
Prefer explicit construction and registration over DI containers, reflection, or global registries
No package-level mutable global state in core code
Capability mismatches must fail explicitly; never silently drop required semantics
Advanced request/response mutation belongs behind hook interfaces, not inside core business logic
Narrow interfaces, small files, simple control flow (keep the core boring)

Files:

• internal/core/stream/eventqueue.go

**/*.go

📄 CodeRabbit inference engine (AGENTS.md)

**/*.go: Use small interfaces defined where they are consumed
Every I/O boundary takes context.Context
Do not use Java-style interface prefixes; use idiomatic Go names such as Store, Router, Clock
Avoid any unless unavoidable at a protocol boundary
Wrap errors with %w and preserve classification metadata
Avoid circular imports by design
Prefer the standard library unless a dependency clearly reduces complexity
Use small interfaces defined where they are consumed
Slices in JSON and returned values should use explicit empty initialization (s := []T{} or make) to prevent null in JSON
Establish explicit ownership for goroutines, channels, buffers, and cancellation
Do not use Go's native plugin package in v1
Add package docs where the boundary is non-obvious
Line length ~120+ characters; break at semantic boundaries. Single long lines preferred for embedded JSON/SSE to preserve stream integrity

For server, CLI, worker, or network code, check that context.Context is propagated correctly, cancellation is respected, and new goroutines cannot leak indefinitely

Files:

• internal/core/stream/eventqueue.go

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⚙️ CodeRabbit configuration file

**/*.go: Review as production Go code. Prioritize correctness, race conditions, goroutine leaks, context cancellation, timeout handling, error wrapping, nil-pointer risks, resource cleanup, defer placement, API compatibility, interface design, dependency boundaries, and testability. Avoid generic style comments when gofmt/golangci-lint already covers the issue.

Files:

• internal/core/stream/eventqueue.go

internal/**

⚙️ CodeRabbit configuration file

internal/**: Focus on package boundaries, hidden coupling, unexported API design, concurrency safety, deterministic behavior, and whether logic belongs in this internal package.

Files:

• internal/core/stream/eventqueue.go

🪛 markdownlint-cli2 (0.22.1)

.jules/bolt.md

[warning] 1-1: Headings should be surrounded by blank lines
Expected: 1; Actual: 0; Below

(MD022, blanks-around-headings)

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[warning] 1-1: First line in a file should be a top-level heading

(MD041, first-line-heading, first-line-h1)

🔇 Additional comments (1)

.jules/bolt.md (1)

1-3: LGTM!