fix(dapi): validate bounded request payloads

[QuantumExplorer]

Issue being fixed or feature implemented

Rejects semantically invalid public payloads before representation expansion or backend work. Covers internal review items 003, 004, 170, and 171.

What was done?

• Applied the active platform state-transition size limit before hashing and encoding.
• Enforced exact-width state-transition and Core block hashes before subscriptions or RPC work.
• Removed an avoidable broadcast payload clone and a temporary hash-string allocation.
• Added boundary regression coverage.

How Has This Been Tested?

• Full rs-dapi unit and documentation suite: 288 tests.
• Strict Clippy for rs-dapi across all targets.
• Workspace formatting check.

Breaking Changes

None for valid requests.

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have added "!" to the title and described breaking changes in the corresponding section if my code contains any
• I have made corresponding changes to the documentation if needed

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

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Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 285df24d-61bf-487b-b8fd-86a8f240d2f9

📥 Commits

Reviewing files that changed from the base of the PR and between fc05d62 and c40644b.

📒 Files selected for processing (5)

• packages/rs-dapi/src/services/platform_service/broadcast_state_transition.rs
• packages/rs-dapi/src/services/platform_service/wait_for_state_transition_result.rs
• packages/rs-dapi/src/services/streaming_service/block_header_stream.rs
• packages/rs-dapi/src/services/streaming_service/mod.rs
• packages/rs-dapi/src/services/streaming_service/transaction_stream.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/fix-dapi-input-bounds

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[thepastaclaw]

🕓 Ready for review — 39 ahead in queue (commit c40644b)
Queue position: 40/72 · 2 reviews active
ETA: start ~05:03 UTC · complete ~05:32 UTC (median 28m across 30 recent reviews; 2 slots)
Queued 12h 33m ago · Last checked: 2026-07-22 19:40 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.49%. Comparing base (fc05d62) to head (c40644b).
⚠️ Report is 266 commits behind head on v4.1-dev.

Additional details and impacted files

@@             Coverage Diff              @@
##           v4.1-dev    #4152      +/-   ##
============================================
+ Coverage     87.43%   87.49%   +0.06%     
============================================
  Files          2646     2663      +17     
  Lines        333981   336414    +2433     
============================================
+ Hits         292023   294354    +2331     
- Misses        41958    42060     +102     

Components	Coverage Δ
dpp	88.44% <ø> (-0.01%)	⬇️
drive	86.24% <ø> (+0.09%)	⬆️
drive-abci	89.55% <ø> (+0.04%)	⬆️
sdk	∅ <ø> (∅)
dapi-client	∅ <ø> (∅)
platform-version	∅ <ø> (∅)
platform-value	92.90% <ø> (+0.01%)	⬆️
platform-wallet	∅ <ø> (∅)
drive-proof-verifier	49.79% <ø> (+0.23%)	⬆️

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[QuantumExplorer]

Approved