fix(message): preserve active chat lanes

[jlucaso1]

Closes #1039.

An active chat lane could be capacity-evicted after its worker dequeued a message. A later message for the same chat would then create a second worker, allowing post-decryption dispatch to run out of order.

This keeps the cached lane alive from enqueue through processing by carrying a clone of its existing lock with each queued message. The cache now skips lanes with live references, while idle lanes remain evictable on the next capacity check. The token is an Arc clone, so it adds no heap allocation.

The capacity-1 regression test reproduces the old eviction, verifies that consecutive messages stay on the original channel, and confirms the lane becomes evictable after processing.

Performance validation on 50,000-message ping-pong runs:

• median throughput: 4,747.92 -> 4,751.95 msg/s
• median client CPU: 3.33 -> 3.30 seconds
• zero lost or failed messages in all six runs
• DHAT: no additional allocation blocks; the wider queue slot accounts for 80,352 transient bytes across 10,000 messages (8.04 bytes/message), with nothing retained at exit

Validated with cargo fmt --all --check, cargo clippy --all --tests, the non-E2E workspace test suite, and the release WASM build.

[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Improved per-chat message queue handling by enqueueing a richer work item that keeps chat lanes active while messages are in-flight, preventing premature eviction.
  • Ensured capacity pressure retains active lanes so subsequent messages reuse the same processing queue.
  • Preserved existing redelivery behavior when message enqueueing fails.
• Tests
  • Added an integration test validating chat-lane retention under capacity pressure, reuse of the active worker/channel, and eviction after processing completes.

Walkthrough

Chat-lane queue entries now retain a per-lane guard while processing. Cache eviction checks that guard, message handlers use the new queue payload, and an integration test verifies active lanes survive capacity pressure before becoming evictable when idle.

Changes

Chat lane eviction protection

Layer / File(s)	Summary
Queued message contract src/client.rs	Introduces QueuedChatMessage, containing the node and lane guard, and adds ChatLane::try_enqueue.
Queue and worker integration src/handlers/message.rs	Routes enqueueing through try_enqueue and updates the chat worker to receive and release composite queue messages.
Eviction guard and capacity validation src/client/lifecycle.rs, src/client/tests.rs	Evicts lanes only when their enqueue-lock reference count is one, with coverage for active and idle lanes under capacity pressure.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• oxidezap/whatsapp-rust#485: Changes the per-chat message queue and worker pipeline.
• oxidezap/whatsapp-rust#1015: Modifies the message enqueue path around ChatLane.
• oxidezap/whatsapp-rust#991: Uses strong-reference-based cache eviction guards.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main fix: keeping active chat lanes alive.
Description check	✅ Passed	The description matches the code changes and explains the lane-preservation fix and test coverage.
Linked Issues check	✅ Passed	The PR satisfies #1039 by carrying the lane lock with each message, adding the eviction guard, and covering the capacity-1 case.
Out of Scope Changes check	✅ Passed	The changes stay focused on lane retention, eviction logic, and the related regression test.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/active-chat-lane-eviction

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[greptile-apps]

Greptile Summary

This PR fixes a race condition where a capacity-evicted chat_lanes entry could spawn a second worker for the same chat, allowing out-of-order post-decryption dispatch. The fix wraps each queued message in a QueuedChatMessage that carries an Arc clone of enqueue_lock as lane_liveness, and adds an evict_guard to the chat_lanes cache that skips entries with strong_count > 1.

• QueuedChatMessage bundles the node with a lane_liveness Arc clone; ChatLane::try_enqueue encapsulates creation so callers cannot bypass the guard.
• The evict_guard in lifecycle.rs mirrors the existing session_locks guard, blocking capacity eviction while any message is queued or in-flight; the lane becomes evictable again only after drop(lane_liveness) runs post-processing.
• A capacity-1 regression test in tests.rs exercises enqueue, in-flight protection, and post-processing evictability in sequence.

Confidence Score: 5/5

Safe to merge — the fix is a targeted, well-scoped addition that closes a real ordering race without altering any existing hot paths.

The evict_guard pattern is already proven by session_locks; applying it to chat_lanes via an Arc clone carried in QueuedChatMessage is a consistent extension. The strong-count check is race-free within the cache's write lock, explicit drop(lane_liveness) after processing is correctly positioned, and the regression test covers all key scenarios.

No files require special attention.

Important Files Changed

Filename	Overview
src/client.rs	Introduces QueuedChatMessage (node + lane_liveness Arc) and ChatLane::try_enqueue; cleanly encapsulates strong-count bump at enqueue time.
src/client/lifecycle.rs	Adds evict_guard to chat_lanes cache consistent with the existing session_locks guard; one-line change with no other side effects.
src/handlers/message.rs	Worker loop destructures QueuedChatMessage with an explicit lane_liveness binding and an explicit drop after processing; intent is anchored by a comment.
src/client/tests.rs	Adds active_chat_lane_survives_capacity_pressure regression test covering enqueue, in-flight eviction blocking, and post-processing evictability with a capacity-1 cache.

_{Reviews (3): Last reviewed commit: "refactor(message): make lane liveness ex..." | Re-trigger Greptile}

[coderabbitai]

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 `@src/handlers/message.rs`:
- Around line 88-92: Add a concise comment directly above or beside the
`lane_guard: _lane_guard` binding in the `QueuedChatMessage` destructuring
within the receive loop, documenting that the named binding must remain alive
through the worker body to preserve cache-eviction protection; do not change the
binding behavior.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI (base), Organization UI (inherited)

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 88529a47-20c0-4c1b-ae30-7dafcf4e844a

📥 Commits

Reviewing files that changed from the base of the PR and between 0e1f391 and 68e4dca.

📒 Files selected for processing (4)

• src/client.rs
• src/client/lifecycle.rs
• src/client/tests.rs
• src/handlers/message.rs

[github-actions]

📦 Binary size report

Metric	main	PR	Δ
bin size (stripped)	10.93 MiB	10.93 MiB	+768 B (+0.01%) 🔺
bin .text	8.91 MiB	8.91 MiB	+704 B (+0.01%) 🔺
bin allocated (text+data+bss)	10.93 MiB	10.93 MiB	-32 B (-0.00%) 🔽
llvm-lines wacore	514,458	514,458	0
llvm-lines wacore copies	17,564	17,564	0
llvm-lines whatsapp-rust lib	777,560	777,662	+102 (+0.01%) 🔺
llvm-lines whatsapp-rust lib copies	25,297	25,303	+6 (+0.02%) 🔺
deps crates (Cargo.lock)	472	472	0

.text per crate

Crate	main	PR	Δ
.text whatsapp_rust	1.69 MiB	1.69 MiB	+641 B (+0.04%) 🔺
.text wacore	537.22 KiB	537.22 KiB	0
.text wacore_binary	148.45 KiB	148.45 KiB	0
.text wacore_libsignal	203.49 KiB	203.49 KiB	0
.text wacore_appstate	158.31 KiB	158.31 KiB	0
.text wacore_noise	26.03 KiB	26.03 KiB	0
.text waproto	1.60 MiB	1.60 MiB	0
.text whatsapp_rust_sqlite_storage	513.08 KiB	513.08 KiB	0
.text whatsapp_rust_tokio_transport	43.79 KiB	43.79 KiB	0
.text whatsapp_rust_ureq_http_client	10.47 KiB	10.47 KiB	0
.text std	1.02 MiB	1.02 MiB	+19 B (+0.00%) 🔺
.text other deps	2.95 MiB	2.95 MiB	0

Baseline: 652d25de5 (latest main run) · Head: 4442470e6 · Graphs

[coderabbitai]

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 `@src/client.rs`:
- Around line 195-198: Add a Debug derive to the QueuedChatMessage struct while
preserving its existing fields and behavior.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI (base), Organization UI (inherited)

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 736042e1-242a-4bda-8a34-2aee162aeeaa

📥 Commits

Reviewing files that changed from the base of the PR and between 1ec3ba2 and 1a2a20b.

📒 Files selected for processing (4)

• src/client.rs
• src/client/lifecycle.rs
• src/client/tests.rs
• src/handlers/message.rs