Document chat-lane idle exit and group_decrypt_shared

[jlucaso1]

Summary

Follow-up to whatsapp-rust#1389, a performance PR that shed resident per-chat memory and per-message copies. Most of that PR's changes are internal-only (no observable behavior change), but two touch content this repo already documents:

• advanced/state-management.mdx — "Session locks and message queues" described ChatLane as just enqueue_lock + queue_tx, and said lanes only exit on disconnect. #1389 adds a third field, worker_running, and makes a lane's worker exit after 60s of silence (LANE_IDLE_TIMEOUT) to stop pinning its ~9 KiB inbound-message future for chats that have gone quiet — bounded only by chat_lanes_capacity (5,000) previously, which could park tens of MiB in idle workers for an account active in many groups. The doc now shows the updated struct and explains the idle-exit/replacement lifecycle, including why enqueue_lock and worker_running are inherited by the replacement lane rather than re-minted.
• advanced/signal-protocol.mdx — "Group Decryption" quoted group_decrypt's signature and a stale line range. #1389 adds group_decrypt_shared (takes the skmsg as Bytes instead of &[u8], so a message the receive path already holds as Bytes is parsed in place instead of copied) and has group_decrypt forward to it. The doc now shows both signatures, the delegation, and why the zero-copy path exists.

No changelog entry added — per instructions, changelog entries are added by a human.

Test plan

• Docs-only change; no build/test required beyond visual review of the rendered MDX.

🤖 Generated with Claude Code

https://claude.ai/code/session_018WAJ2MALasTGSde9nrtbv2

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Generated by Claude Code

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Summary by cubic

Documents the two doc-relevant behavior changes from whatsapp-rust#1389: chat lanes now idle-exit after 60 seconds, and group decryption gained a zero-copy group_decrypt_shared path.

• Updated advanced/state-management.mdx and concepts/architecture.mdx to describe the new ChatLane worker_running field and the idle-exit/replacement lifecycle.
• Updated advanced/signal-protocol.mdx to show both group_decrypt and group_decrypt_shared signatures and why the zero-copy path exists.
• Updated api/bot.mdx so the chat_lanes_capacity config row mentions the idle-exit behavior.

^{Written for commit 4b4d02e. Summary will update on new commits.}

Summary by CodeRabbit

• Documentation
  • Updated Signal Protocol guidance with the shared group-decryption workflow, revised store mutability requirements, and clarified plaintext buffer sizing.
  • Expanded session-lock and message-queue documentation to describe worker idle timeouts, queue replacement, and preservation of message enqueue order.
  • Refreshed source references and processing steps to match the current implementation.

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📝 Walkthrough

Walkthrough

The pull request updates Signal Protocol documentation for shared group decryption and updates state-management documentation for chat-lane worker idle timeouts and replacement.

Changes

Signal Protocol documentation

Layer / File(s)	Summary
Shared group decryption flow advanced/signal-protocol.mdx	Documents group_decrypt_shared, the owned Bytes copy in group_decrypt, in-place SenderKeyMessage parsing, the mutable store parameter, and exact plaintext buffer sizing.

State management documentation

Layer / File(s)	Summary
Chat-lane worker lifecycle advanced/state-management.mdx	Documents worker_running, the 60-second LANE_IDLE_TIMEOUT, queue replacement, enqueue ordering, worker draining, and memory bounds. Updates the source location reference.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 63cfd

The PR only updates documentation to describe existing behavior. The remaining issue is limited to consistent active voice and second-person wording in two localized passages, with no product or runtime impact; it is mergeable after routine documentation cleanup, and no merge-blocking risk remains.

Poem

A rabbit reads each line,
The patch grows clear beneath the moon,
Small changes hop in place,
Tests guard the garden path,
Reviews bloom before the dawn.

🚥 Pre-merge checks | ✅ 5

✅ 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 clearly and concisely identifies both documented changes: chat-lane idle exit and the group_decrypt_shared entry point.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
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.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (2 skipped: 2 unsupported.)

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[greptile-apps]

Greptile Summary

This documentation update explains the 60-second idle lifecycle for per-chat workers and the shared-buffer group decryption API.

• Documents worker_running, idle queue closure, and replacement-worker coordination.
• Updates the architecture and cache references for idle chat-lane workers.
• Adds group_decrypt_shared and explains its zero-copy Bytes path.

Confidence Score: 5/5

The PR appears safe to merge because no blocking failure remains.

No blocking failure remains.

Important Files Changed

Filename	Overview
advanced/state-management.mdx	Documents the three-field ChatLane and its idle-exit and replacement lifecycle.
concepts/architecture.mdx	Synchronizes the per-chat lane architecture with worker-liveness locking and idle exit.
api/bot.mdx	Updates the cache configuration reference with the independent 60-second worker idle timeout.
advanced/signal-protocol.mdx	Documents mutable sender-key storage and the shared-buffer group decryption entry point.

_{Reviews (3): Last reviewed commit: "docs: tighten voice in the new group_dec..." | Re-trigger Greptile}

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Actionable comments posted: 1

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Inline comments:
In `@advanced/signal-protocol.mdx`:
- Line 642: Update the explanatory text around group_decrypt and
group_decrypt_shared to address the reader directly in second person, replacing
third-person caller descriptions with active “you” phrasing while preserving the
technical meaning.

Apply the same fix in `@advanced/state-management.mdx` at line 421: The same
documentation-style revision applies to the idle-exit and disconnect-cleanup
explanation.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

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Run ID: 116fad4a-eb57-4177-818a-1549b892de23

📥 Commits

Reviewing files that changed from the base of the PR and between f4875f1 and 63cfd90.

📒 Files selected for processing (2)

• advanced/signal-protocol.mdx
• advanced/state-management.mdx

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[cubic-dev-ai]

Review completed against the latest diff

<sub>Reply with feedback, questions, or to request a fix.

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Dismissed because a newer commit was pushed; Greptile will re-review the current head.

[cubic-dev-ai]

0 issues found across 4 files (changes from recent commits).

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

<sub>Auto-approved: Docs-only updates describing chat-lane idle-exit and the group_decrypt_shared zero-copy path from #1389; no runtime code, config, or public contract changes, so the risk is limited to documentation accuracy.

Re-trigger cubic</sub>