feat(push): PR-3a — wake the peer after a chat message

[grunch]

Summary

Phase 3, task T3.1 of docs/PUSH_NOTIFICATIONS.md (§7.3). Builds on PR-2 (#471, merged).

The chat envelope is p-tagged to pub(K_conv), an HKDF derivation of the two trade keys' ECDH secret. The push server's listener matches registrations by trade pubkey, so it can never match a chat message: a backgrounded peer learned of one only when they next opened the app. The sender now asks the server to ring the peer.

• wake_peer in api/push.rs, called from send_message and send_file once the chat envelope was accepted by at least one relay. It posts {"trade_pubkey": <peer's trade pubkey>} to /api/notify. The peer pubkey is the session's peer_pubkey, the counterparty's trade key from the reveal (Peer chat: the counterparty pubkey is never persisted, so the maker has no chat room and nobody can send after a restart #334), which is exactly what their device registers.
• No relay, no wake. send_event returns Ok even when every relay rejected the envelope, so publish_chat_payload reports delivery alongside the inner event and both callers gate the wake on it (peer_to_wake). Otherwise the peer would be rung for nothing and the debounce would swallow the wake of a retry that does land. publish_chat_payload_for keeps its signature, so the dispute path is unchanged.
• Not gated on this device's own push toggle. It is the peer's setting that decides what reaches them; the server answers 202 either way and reveals nothing.
• Debounced per peer, 10 s, recorded before the request, so messages sent while one is in flight do not each ring. A burst costs one wake and stays far under the server's 30/min per pubkey.
• Fire-and-forget: spawned, never awaited by the send, never retried, never a reason for the send to fail. A 400 is logged as a client bug.
• Scope limits, on purpose: the dispute channel does not ring its solver (not a push client), and the web build does not wake peers until the server answers CORS (mostro-push-server#44).
• Testable core notify_peer_with(server, memory, peer, now); under cargo test production paths talk to the unreachable stub, so the existing message tests never reach the network.
• Contracts: Peer wake in contracts/push.md (including "no relay, no wake"), a line in contracts/messages.md.
• Generated bindings regenerated after merging main (which now commits them): only the ignored-item comments in lib/src/rust/api/{messages,push}.dart change; no Dart API change.

Test plan

• 5 tests against the scripted fake server: one request then debounced then allowed again, the debounce is per peer, a non-pubkey is never sent, the peer is lowercased as the server matches it, a rejected wake is not retried and still debounces.
• 2 tests for the delivery gate shared by send_message and send_file: no relay accepted → no wake; some relay accepted → wake.
• cargo test, cargo clippy --all-targets (no new warnings), cargo check --target wasm32-unknown-unknown, ./scripts/frb-generate.sh (committed output matches), flutter analyze.

Manual testing

1. Check out the branch and run the app on two Android devices, A and B, both with push granted and in one active trade with the peer revealed.
2. On B, press Home so the app is backgrounded but alive.
3. On A, send a chat message. Expect the log line [push] peer wake: Sent at debug level on A, and on B a wake within seconds (with PR-3b, a "New message" notification; without it, the wake flag and a resync on resume).
4. On A, send five short messages within 3 seconds. Expect one wake request, then Debounced for the rest.
5. On A, send an image attachment. Expect a wake as for a text message.
6. Open a dispute on the trade and send a message in the dispute chat. Expect no wake request: the dispute channel does not ring.
7. On A, turn push off (or never grant it). Send a message again. Expect the wake to go out anyway: it is B's setting that matters.
8. On A, disable every relay (or cut network so all relays reject), then send a message. Expect no [push] peer wake line: nothing reached a relay, so nothing rings. Restore the relays, wait 10 s, send again: expect Sent.

🤖 Generated with Claude Code

https://claude.ai/code/session_01J19XhahRqfiW6PiHJS1GHp

Summary by CodeRabbit

• New Features

  • Peers can now receive push wake-ups after text messages and file attachments are successfully published.
  • Notifications are sent in the background and limited to avoid repeated alerts.
  • Notification failures do not prevent messages or attachments from being sent.

• Documentation

  • Added documentation describing peer wake-ups, timing limits, supported chat scenarios, and web-platform limitations.

[coderabbitai]

Walkthrough

The push client now supports debounced peer wake notifications. Successful text and file message publication triggers a fire-and-forget request to /api/notify. Contracts and tests document and verify the behavior.

Changes

Peer wake notifications

Layer / File(s)	Summary
Peer wake contract specs/004-mostro-p2p-client/contracts/messages.md, specs/004-mostro-p2p-client/contracts/push.md	The contracts define peer wake triggers, endpoint usage, debouncing, failure handling, chat-only scope, and web-build limits.
Push notification path rust/src/api/push.rs	The push client adds notify, peer-key validation, per-peer debouncing, outcome mapping, HTTP support, test-server support, and peer-wake tests.
Message send integration rust/src/api/messages.rs	Successful text and file message publication invokes peer wake. Other changes reformat existing code without changing behavior.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant ChatSend
  participant wake_peer
  participant notify_peer_with
  participant HttpPushServer
  ChatSend->>wake_peer: successful message publication
  wake_peer->>notify_peer_with: spawn peer wake
  notify_peer_with->>HttpPushServer: POST /api/notify
  HttpPushServer-->>notify_peer_with: ServerOutcome

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Suggested reviewers: forte11cuba

Merge Risk: 🔵 Low · up to 572f6

A peer may be notified about a message or attachment that was never delivered. The impact is bounded, but wake calls should be gated on relay success.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 68.75% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 32 functions across 2 files. (2 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
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.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the main peer-wake feature after chat messages. It does not mention file attachments, but the omission does not make the title misleading.

Full details: Docstring Coverage

Explanation

Docstring coverage is 68.75% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 32 functions across 2 files. (2 skipped: 2 unsupported.)

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-14T12:42:27.462770Z	572f669	PR opened

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Reviewed commit: 572f669202

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Actionable comments posted: 1

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Inline comments:
In `@rust/src/api/messages.rs`:
- Line 445: Update publish_chat_payload and its callers so relay-delivery
success is exposed separately from the shared result, and gate wake_peer in the
relevant success branches on at least one successful relay. Keep the existing
local-only fallback in send_message and send_file, and do not convert an empty
output.success result into an error because submit_evidence relies on
publish_chat_payload_for(...).await?. Add targeted text-message and attachment
tests covering empty output.success.

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📥 Commits

Reviewing files that changed from the base of the PR and between c7ef4f8 and 572f669.

📒 Files selected for processing (4)

• rust/src/api/messages.rs
• rust/src/api/push.rs
• specs/004-mostro-p2p-client/contracts/messages.md
• specs/004-mostro-p2p-client/contracts/push.md

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