Architectural Decisions (synthesized from SPEC)

The SPEC Тз расширение фаза1.md does not formally label itself as ADR-set, but sections 2 ("Стек"), 7 ("Разрешения в manifest.json"), and 8 ("Важные ограничения и решения") encode binding technical choices that act as architectural decisions for Phase 1. Each decision below is reproduced from the SPEC verbatim where possible and tagged with its origin.

Status legend (synthesized, since SPEC has no formal ADR status field):

Accepted — SPEC §2/§7/§8 prescribed, no contradicting source
locked: false everywhere — SPEC is locked: false in classification, so these decisions can still be revised by a future ADR; today they are the authoritative baseline.

DEC-001: Chrome Extension Manifest V3

Source: Тз расширение фаза1.md §2 (Стек), §7 (Разрешения)
Status: Accepted
Locked: false
Scope: Extension platform / packaging
Decision: The extension MUST be implemented as a Chrome Extension targeting Manifest V3 (Service Worker background, no persistent background page).
Rationale (from SPEC): Required for modern Chrome compatibility; implied by every API used (chrome.tabCapture, chrome.downloads, chrome.tabs, chrome.alarms).
Confirming source: README.md §"Технический стек" — "Chrome Extension, Manifest V3".

DEC-002: Service Worker as Background Coordinator

Source: Тз расширение фаза1.md §2, §3 (Структура расширения), §8
Status: Accepted
Locked: false
Scope: Background execution model
Decision: Background logic runs in a Manifest V3 Service Worker (background/service-worker.js) that coordinates the video buffer and archive packaging.
Constraint binding: Service Worker is unloaded after ~30 s idle; keepalive MUST be maintained via chrome.alarms firing every 20 seconds (SPEC §8).
Confirming source: README.md §"Технический стек".

DEC-003: Tab Video Capture via `chrome.tabCapture`

Source: Тз расширение фаза1.md §2, §4.1, §7
Status: Accepted
Locked: false
Scope: Video acquisition
Decision: Active-tab video is captured via chrome.tabCapture.capture().
Codec/bitrate binding: video/webm; codecs=vp9 at 400 000 bps.
MediaRecorder chunk cadence: 2000 ms.
Activation constraint: tabCapture is tied to the active tab and requires a user gesture on first invocation; on tab switch the capture re-attaches.
Confirming source: README.md §"Технический стек".

DEC-004: DOM Capture via rrweb

Source: Тз расширение фаза1.md §2, §4.2
Status: Accepted
Locked: false
Scope: DOM recording
Decision: DOM events are captured via the rrweb npm library (rrweb.record()), running in the Content Script, with events forwarded to the Service Worker on archive-export request.
Sensitive-data binding: rrweb is configured with maskInputSelector to mask input[type=password] and [data-sensitive="true"].
Buffer cap binding: 5 000 rrweb events maximum; oldest dropped on overflow (SPEC §8).
Confirming source: README.md §"Технический стек", §"Особенности".

DEC-005: Archive Packaging via JSZip

Source: Тз расширение фаза1.md §2, §3, §6
Status: Accepted
Locked: false
Scope: Archive assembly
Decision: ZIP packaging uses the jszip npm library bundled as libs/jszip.min.js (or the Vite-bundled equivalent).
Archive layout binding: see REQ-archive-layout in requirements.md.
Confirming source: README.md §"Технический стек".

DEC-006: File Download via `chrome.downloads`

Source: Тз расширение фаза1.md §2, §5, §7
Status: Accepted
Locked: false
Scope: File delivery
Decision: The assembled ZIP is delivered to the user's "Downloads" folder via chrome.downloads.download(). No server upload in Phase 1.
Confirming source: README.md §"Технический стек".

DEC-007: In-Memory Buffers in Service Worker + Content Script

Source: Тз расширение фаза1.md §2, §4.1, §4.2, §4.3
Status: Accepted
Locked: false
Scope: Storage strategy
Decision: All recorded data (video chunks, rrweb events, user-event log) is held in memory only — video chunks in the Service Worker, rrweb events and user-event log in the Content Script. No chrome.storage / IndexedDB persistence for the rolling buffers in Phase 1.
Confirming source: README.md §"Технический стек" — "In-memory (Service Worker + Content Script)".

DEC-008: Screenshot via `chrome.tabs.captureVisibleTab`

Source: Тз расширение фаза1.md §4.4, §5
Status: Accepted
Locked: false
Scope: Screenshot capture
Decision: A single PNG screenshot is captured via chrome.tabs.captureVisibleTab() at the moment the user clicks "Save archive". The screenshot is bundled as screenshot.png inside the ZIP.

DEC-009: WebM Header Retention

Source: Тз расширение фаза1.md §4.1, §8
Status: Accepted
Locked: false
Scope: Video container integrity
Decision: The first chunk emitted by MediaRecorder (which contains the WebM container header) MUST be retained in the ring buffer indefinitely; only subsequent chunks rotate out by the 30-second TTL rule.
Rationale (from SPEC §8): WebM without its header is not playable.

DEC-010: Service Worker Keepalive via `chrome.alarms`

Source: Тз расширение фаза1.md §8
Status: Accepted
Locked: false
Scope: Service Worker lifecycle
Decision: To prevent the 30 s idle unload of MV3 Service Workers, a chrome.alarms alarm fires every 20 seconds to keep the worker alive.

DEC-011: Manifest Permissions Set

Source: Тз расширение фаза1.md §7
Status: Accepted
Locked: false
Scope: Manifest configuration
Decision: manifest.json requests exactly:
- permissions: tabCapture, activeTab, downloads, scripting, storage
- host_permissions: <all_urls>
Note: tabCapture requires explicit user gesture on first activation.

DEC-012: Vite + crxjs + TypeScript Build Toolchain

Source: README.md §"Технический стек"
Status: Accepted (DOC-level — not asserted by SPEC)
Locked: false
Scope: Build tooling
Decision: The extension is built with Vite + the crxjs plugin in TypeScript. The SPEC does not prescribe a build tool, so this is a DOC-level decision not contradicted by any higher-precedence source.
Provenance caveat: If a future ADR/SPEC selects a different toolchain, this DEC is auto-overridden.

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