The direct answer
Review the complete parent policy and iframe delegation together before treating an embedded voice widget as eligible for microphone access. A container or child declaration cannot broaden an ancestor’s denial. Keep effective browser support, user permission, current voice intent and later data-release authority as separate gates.
Start with one deliberately separate voice surface
A fictional console wants an independently reviewed voice-input widget from child origin O-W inside parent origin O-P. A developer has added a permissive-looking frame setting and expects the microphone prompt to appear. The useful question is which complete browser policy actually governs this child, before discussing any stream or later model request.
This worksheet selects one trusted, fixed cross-origin document and microphone-only eligibility. It excludes navigation, opaque origins, camera, recording, transmission and automatic reacquisition. The existing top-level microphone lifecycle remains unchanged. The untrusted HTML preview also stays restricted; this proposal does not turn generated content into trusted voice code.
Separate feature eligibility from a user grant
MDN’s Permissions Policy guide distinguishes document feature policy from user-granted permission. A named parent-header allowlist bounds delegation; an iframe also needs a matching grant. Parent denial cannot be reversed by descendants. The parent must itself have the feature enabled.
The microphone directive reference controls audio-input eligibility and gives its default allowlist as self. These facts do not establish an installed browser or a user’s choice. Both pages mark the feature experimental with limited availability; the guide was modified 23 October 2026 and the directive 4 July 2025.
The review therefore keeps three independent fields: effective policy eligibility, user-permission disposition and current application intent. A favorable value in the first field cannot fill the other two. Keep unknown outcomes explicit rather than presenting a combined green “microphone authorized” label.
Compute a small origin sheet before reviewing the adapter
Invent response plan H-A and container plan C-A. O-P, O-W and unrelated O-X are symbolic origin references, not URLs, headers or markup. H-A’s proposed set includes O-P and O-W; C-A’s proposed set includes O-W. Assume no additional ancestor restriction only for this paper calculation.
| Parent set | Container set | Child O-W result |
|---|---|---|
| O-P, O-W | O-W | Included by both. |
| O-P only | O-W | Excluded. |
| O-P, O-W | O-X only | Excluded. |
This table applies the documented combination rule to invented inputs. It is not a complete browser-policy evaluator. Real review must establish the whole ancestry, effective response, container and actual child association rather than substitute these two labels for observed policy.
Omission needs separate reasoning: the guide allows explicit delegation without a feature header, subject to parent eligibility; an unlisted iframe feature uses its default. For this cross-origin example, the default alone does not admit O-W. Our selected positive deliberately requires the explicit, reviewed H-A/C-A plan instead of relying on an unexplained omission.
Bind the calculation to an actual publisher and document
Create a protected review receipt identifying the owned parent release, independently admitted child release, intended origin association, complete policy evidence, supported browser profile and the local note purpose. Add separate references for user permission, active voice attempt, owned-resource lifecycle and current rights. Do not store audio, permission tokens or full device inventories merely to explain a decision.
The ordinary positive is only conditional eligibility for this fixed plan when every actual prerequisite is independently established. It claims no prompt, acquired stream, working capture, trusted transcript or successful model operation. The current child document and trusted code require evidence outside a matching origin label.
Actual publisher transformations, intermediary behavior, complete ancestry, effective policy composition, browser support and stable document association are unimplemented or unknown here. A template screenshot cannot settle those fields. Any missing prerequisite holds real admission; a compatibility problem does not authorize broadening the parent’s intended set.
Walk eight inert eligibility cards
| Invented condition | Proposed review disposition |
|---|---|
| 1. Complete H-A/C-A/O-W receipt and every independent prerequisite hold | Conditionally admit the declared eligibility plan only. |
| 2. The second worksheet row applies | Reject the proposed child use; do not treat its container as a repair. |
| 3. The third worksheet row applies | Reject that changed container plan. |
| 4. A child declaration tries to restore an ancestor’s denial | No restoration under the selected rule. |
| 5. A broad container is offered while H-A still excludes an unrelated origin | Do not expand the effective admitted set to that origin. |
| 6. The cross-origin child relies only on the default case discussed above | The selected explicit positive is unestablished. |
| 7. Browser, response, ancestry or current document evidence is unknown | Hold applicability rather than claim an enforced outcome. |
| 8. Policy fits but user permission, active intent or current rights fail | Deny the affected operation independently. |
Keep acquisition and later data use outside this calculation
The separate voice lifecycle must still handle abandoned attempts and late results under its own ownership contract. An eligible document must not inherit an unrelated attempt because a newer panel is visible. Likewise, a local note purpose does not approve forwarding audio, retaining a transcript or sending a model payload.
Keep this policy review separate from script provenance, sandbox tokens, inbound embedding restrictions and widget messages. Those existing contracts answer different questions and remain unchanged. No capability declaration establishes trustworthy child behavior, a correct user interface, physical device shutdown or erasure of previous copies.
No header, frame, DOM, permission prompt, audio object, stream, browser, policy fixture, API, network or model operation was constructed or run. Only the two declared documentation bodies were read. This article supplies no policy parser, capture adapter or browser compatibility fallback. Boundary remains prelaunch with planned request-path checks; its synthetic policy evidence does not implement this voice-widget controller.
Primary sources
Official references supporting the guidance. Examples in this guide are synthetic and are not reports of a production incident.