diff --git a/docs/research/experiments/windows-msal-account-metadata.md b/docs/research/experiments/windows-msal-account-metadata.md
index c5976466..891988ba 100644
--- a/docs/research/experiments/windows-msal-account-metadata.md
+++ b/docs/research/experiments/windows-msal-account-metadata.md
@@ -26,26 +26,22 @@ reuse, or all of RECHECK-007.
 There is no corporate-account comparison, resource write, PAT, registration/tenant
 administration, cache migration, plaintext cache, or fallback mechanism in this probe.
 
-## Current Advancement: Prepare, Then Wait for Operator Readiness
-
-The diagnostic sequence accepted by PR #48 and recorded by PR #49 stopped at the
-interactive process deadline, without an authentication result. The
-[diagnostic history](#diagnostic-subject-preparation-and-acquisition) retains its
-cancellation fields, changed account-match count, and missing detailed UI observations.
-That result does not identify the previous acquisition failure's cause.
-
-This amendment permits one preparation and one additional interactive attempt with the
-same nominated account/resource and unchanged authentication code and configuration.
-Its purpose is to observe that path with an explicitly ready operator. Finish all
-preparation before announcing readiness, then wait for the operator's explicit readiness
-response before launching any probe window. A general instruction to continue work is
-not desktop readiness. Preparation must not launch an account action to test readiness.
-
-The earlier nine Windows actions remain consumed. Only after this amendment is accepted
-may the additional preparation run. Its successful verification does not authorize an
-unattended interactive attempt. If interaction succeeds with the exact account and
-recognized Git discovery, the one previously unused silent slot may check later-process
-reuse during the same attended sequence. Any failure stops without another retry.
+## Current Disposition: Attended Broker Failure
+
+The preparation and attended interaction accepted by PR #50 have been executed. After
+preparation, the agent announced readiness and waited for the owner's explicit desktop
+readiness response before opening the probe. The interactive action found one exact
+account match but returned `unknown_broker_error`, broker status `Unexpected`, and code
+`2147786073` (`0x80049D59`) without an authentication result. The
+[attended history](#attended-preparation-and-structured-broker-failure) owns the exact
+observations, including the operator's brief possible-WAM UI observation.
+
+The sequence is stopped. All six preparations and three interactive attempts are
+consumed. The unused silent/resource slots require successful interaction and cannot be
+exercised. Do not retry, rebuild, change inputs, or expand diagnostics under this
+protocol. A new experiment requires another reviewed and accepted amendment, preserving
+prior consumption and the explicit readiness handoff. The procedure below preserves the
+executed sequence and its boundaries; it does not grant another execution.
 
 ## Subject and Environment
 
@@ -396,11 +392,11 @@ Cleanup, if later needed, is limited to verified experiment-owned files after ow
 processes have exited. Do not clear broker state, revoke consent, sign out, or modify an
 upstream installation as cleanup.
 
-Current consumption before the attended preparation: fetch 1/1, prepare 5/6, inspect 1/1,
-silent 1/2, interactive 2/3, discovery requests 1/3 (one anonymous, zero authenticated).
-Windows attempts 1 through 9 are complete. The next attempt is 10 (`prepare`); account
-actions remain blocked on the explicit readiness handoff after preparation. Historical
-sections preserve their actual outcomes and consumption at the time.
+Current consumption after the attended sequence: fetch 1/1, prepare 6/6, inspect 1/1,
+silent 1/2, interactive 3/3, discovery requests 1/3 (one anonymous, zero authenticated).
+Windows attempts 1 through 11 are complete; attempt 12 is absent. The sequence is stopped,
+and the remaining numeric slots do not authorize continuation. Historical sections
+preserve their actual outcomes and consumption at the time.
 
 ## Execution History
 
@@ -783,3 +779,113 @@ assumed reversed by failure. The sequence stopped without attempt 10 or another
 request. Totals are fetch 1/1, prepare 5/5, inspect 1/1, silent 1/2, interactive 2/2, and
 discovery 1/3; the conditional silent slot is unavailable because interaction did not
 succeed.
+
+### Attended Preparation and Structured Broker Failure
+
+Runtime observations on 2026-09-11 UTC under
+[PR #50](https://github.com/hcoona/microsoft-authentication-cli/pull/50), accepted protocol
+and source `facfec1aa86b88601a9a9e7835bf2d8b6fd7b727`. The merged tree matched the
+independently reviewed subject. Preflight recovered the nine completed Windows actions
+and the single fetch. Windows 11 25H2 build 26200.9445 AMD64, PowerShell 5.1.26100.9444,
+SDK 8.0.425, Core/Desktop runtime 8.0.31, and the declared WSL/kernel/Python versions
+still matched. The corporate-account session is owner-reported context, not a measured
+join/compliance result. Prior broker state remains incompletely known; it was not cleared.
+
+A new detached checkout supplied the five Windows files through `git archive`. Each
+copied file matched its accepted Git content, and the seven retained package archives
+matched their manifest. Only the launcher's cumulative limits differed from the previous
+subject; authentication, discovery, diagnostics, and self-check code were unchanged.
+Preparation reused the dedicated local feed/caches without another download or install.
+
+| Attempt | Action | Start UTC | End UTC | Outcome |
+| --- | --- | --- | --- | --- |
+| 10 | `prepare` | 2026-09-11 01:27:42.1974095 | 2026-09-11 01:27:48.2338358 | `prepared-and-self-checked`; launcher exit 0 |
+
+Release build completed in 3.32 seconds with zero warnings and errors. Restore resolved
+exactly the seven declared packages. The lock SHA-256 remains
+`6653224a1478ae1ef1a6d62c32c188b1408502ce4fcc2f4730f32673e23f3e77`;
+Core/Desktop runtime 8.0.31 and `rollForward: Disable` remain in the runtime configuration.
+The synthetic selector/URL/failure-output check returned `self-check-passed`.
+Preparation made no account, authentication, or resource call; its false/null result
+fields are unexecuted-path defaults. The launcher confirmed process completion and
+returned exit 0 with empty stdout/stderr. Build and restore stderr were also empty.
+
+| Prepared artifact under `bin/Release/net8.0-windows` | Bytes | SHA-256 |
+| --- | --- | --- |
+| `WindowsMsalProbe.exe` | 151,552 | `ada362907899479ec36f09a16b49b355952d50d4ffefe70f26a763ce428cdf32` |
+| `WindowsMsalProbe.dll` | 30,720 | `ca24373cbf19ef3642ec5e31ceccb11effb8a7f446e209b47de876fff01341d4` |
+
+Source, dependency, artifact, runtime, self-check, journal, and local launch-setup evidence
+was recorded and independently checked before the readiness announcement. No timing-test
+popup or account action ran during preparation. The agent then stopped before launch and
+waited for the owner's explicit readiness response. That response preceded this action;
+short preflight rechecked current authority, host, artifact/lock hashes, local input
+binding, and completed history. No rebuild, repeated self-check, account inspection, or
+pre-interaction silent action was performed.
+
+The same nominated personal account and single Git remote were bound locally without
+retaining either value. Client, authority, scope, broker options, and the existing Windows
+session were unchanged. The action used a fresh process with no application cache file.
+
+| Attempt | Action | Start UTC | End UTC | Probe result | Launcher exit |
+| --- | --- | --- | --- | --- | --- |
+| 11 | `interactive` | 2026-09-11 01:43:12.7868381 | 2026-09-11 01:43:33.3991836 | `acquisition-failed` | 2 |
+
+The probe reported broker availability, multiple visible accounts, exactly one email
+match, and no missing-email indication. This action used the real matched account through
+`WithAccount`, as in the first sequence. Attempt 9 had instead observed zero exact matches;
+the reason for the changing visibility is unknown. Neither observation establishes fresh
+state, account removal, or reliable discovery across hosts and registrations.
+
+Acquisition started but returned no `AuthenticationResult`. No authenticated resource
+request was made. Token, returned identity, tenant, scope, and expiry fields remained
+unobserved defaults; resource status was zero and resource outcome `not-observed`.
+
+| Structured failure field | Recorded value |
+| --- | --- |
+| `Kind` | `service-or-broker` |
+| `ErrorCode` | `unknown_broker_error` |
+| `BrokerStatus` | `Unexpected` |
+| `BrokerCode` | `2147786073` (`0x80049D59`) |
+| `ServiceStatusCode` | `0` |
+| `IsRetryable` | false |
+| `UiRequiredClassification` | null |
+
+Service status zero is the reported default, not an observed HTTP response. The
+[pinned MSAL default mapping](https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/blob/d5d7de6b103f0d9dd7bca9bf13cbb9f3da37bc9f/src/client/Microsoft.Identity.Client.Broker/WamAdapters.cs#L116-L120)
+accounts for this generic service-exception category. It does not identify the underlying
+cause of this broker code or establish remote identity-service rejection. No authoritative
+cause is established here. Matching the earlier exception category does not prove that
+attempt 7 had the same code or cause, since its finer fields were not retained.
+
+**Operator observation:** The owner saw the probe's email/HTTPS-address form, apparent
+automatic filling and submission, then a briefly visible surface that appeared to be WAM,
+after which the windows closed. The owner was uncertain about that brief surface's exact
+identity. No detailed sign-in, MFA, or consent steps were reported. The observation does
+not establish successful account choice, consent, sign-in, or a particular internal
+failure stage. The agent did not inspect authentication UI or capture a screenshot.
+
+One write-only input-automation operation filled the owned controls and started the
+action. Its worker and controller completed normally within their bounds, without retry;
+no WAM account choice, sign-in, unlock, MFA, or consent was automated. The launcher
+recorded `step-failed` and confirmed probe exit about 20.6 seconds after its start record,
+well before the process deadline. This action was not recorded as a timeout or
+cancellation. A later read-only check found no remaining probe, input worker, or
+controller. Source/artifact hashes still matched, and attempt 12 was absent. No shared
+broker was terminated; process completion does not prove reversal of platform session
+effects.
+
+**Bounded outcome:** The explicit readiness handoff was followed, exact account discovery
+worked in this existing state, and the probe retained a structured unexpected broker
+failure with the operator's UI observation. Token/result metadata, authenticated Git
+discovery, and later-process reuse remain unobserved. The underlying failure cause,
+registration eligibility, and intended external reuse remain unresolved; this result
+selects no Profile, product architecture, or supported platform.
+
+Retain the dedicated source/build/package and sanitized operational artifacts. No helper
+fallback, PAT, account switching, account/cache cleanup, sign-out, consent revocation,
+resource write, object/pack request, or installation change was performed. All six
+preparations and all three interactive attempts are consumed. Totals are fetch 1/1,
+prepare 6/6, inspect 1/1, silent 1/2, interactive 3/3, and discovery 1/3. The sequence
+stopped without a reuse follow-up or another resource request; unused conditional slots
+cannot be exercised.
diff --git a/docs/research/v1-public-contract-baseline.md b/docs/research/v1-public-contract-baseline.md
index 409856b6..164df8ca 100644
--- a/docs/research/v1-public-contract-baseline.md
+++ b/docs/research/v1-public-contract-baseline.md
@@ -1249,9 +1249,10 @@ and discovery at the single owner-designated Azure DevOps Git repository. It use
 managed/native dependency versions in a small research probe. The first sequence stopped
 without a token; the diagnostic sequence later timed out with structured cancellation
 fields, also without a token. Authentication configuration and selection logic were
-unchanged, but the observed exact-match count changed. Neither sequence establishes
-resource authorization, registration eligibility, or a Profile/support commitment, and
-no corporate-account comparison is performed.
+unchanged, but the observed exact-match count changed. A subsequent explicitly attended
+action returned an unexpected broker failure, also without a token. These observations
+do not establish resource authorization, registration eligibility, or a Profile/support
+commitment, and no corporate-account comparison is performed.
 
 The protocol's [execution history](experiments/windows-msal-account-metadata.md#execution-history)
 records the initial public-index and launcher failures, followed by successful Windows
@@ -1280,11 +1281,24 @@ explain the previous service-exception category. The cause of the changed accoun
 visibility and detailed operator UI steps remain unknown. The sequence is stopped; no
 reuse follow-up ran, and the evidence does not select a Profile or establish support.
 
-The subsequent [attended protocol amendment](experiments/windows-msal-account-metadata.md#operator-readiness-handoff)
-requires preparation to finish before a readiness announcement and an explicit operator
-response before any probe window opens. It prospectively permits one further interaction
-with unchanged authentication code and inputs. The handoff is an execution prerequisite,
-not evidence of a completed interaction or an explanation of either earlier outcome.
+The subsequent [attended sequence](experiments/windows-msal-account-metadata.md#attended-preparation-and-structured-broker-failure)
+completed preparation and the explicit readiness handoff, then again found one exact
+match and used the matched-account branch. It returned `unknown_broker_error`, broker
+status `Unexpected`, and code `2147786073` (`0x80049D59`) about 20.6 seconds after launch,
+with no authentication result or resource request. The owner reported the input form,
+apparent automatic fill/submission, and a brief possible WAM surface before the windows
+closed. The brief surface was not conclusively identified and no detailed sign-in/MFA/
+consent steps were reported. This adds structured failure and UI observations, not an
+explanation of the code, proof of the earlier failure's cause, or Profile eligibility.
+The sequence is stopped.
+
+**Source interpretation, checked 2026-09-11 UTC:** The same pinned
+[`WamAdapters` default branch](https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/blob/d5d7de6b103f0d9dd7bca9bf13cbb9f3da37bc9f/src/client/Microsoft.Identity.Client.Broker/WamAdapters.cs#L116-L120)
+returns a service exception with `UnknownBrokerError` for statuses outside its explicit
+cases. This supports the reported generic category for `Unexpected`, not a specific
+cause or identity-service rejection. Reported service status zero is not an observed
+HTTP response. The two failed matched-account actions need not share a cause; the first
+one lacks the finer fields needed to compare them.
 
 **Source interpretation, retrieved 2026-09-10 UTC:** The pinned MSAL
 [`WamAdapters` exception mapping](https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/blob/d5d7de6b103f0d9dd7bca9bf13cbb9f3da37bc9f/src/client/Microsoft.Identity.Client.Broker/WamAdapters.cs#L58-L120)
@@ -1338,7 +1352,7 @@ boundary; it selects no V2 WSL or Linux-broker implementation and transports no
 | RECHECK-003: [Issue #460](https://github.com/AzureAD/microsoft-authentication-cli/issues/460) | Open; `updated_at = 2026-05-13T17:25:51Z`. Its body proposes a Windows helper, trust/version/transport boundaries, and missing-helper/fallback handling. It is a proposal, not evidence of an upstream implemented bridge. This probe uses an exact local Windows executable and returns only flags. |
 | RECHECK-003/005: [current WSL guidance](https://learn.microsoft.com/en-us/entra/msal/dotnet/acquiring-tokens/desktop-mobile/linux-dotnet-sdk-wsl) | Documents native Linux broker packages, dependencies, and an unlocked keychain. It does not supply the Windows-helper protocol proposed by #460. This experiment uses native Windows WAM; it does not install or invoke that Linux broker. |
 | RECHECK-005: [PR #462](https://github.com/AzureAD/microsoft-authentication-cli/pull/462) | Open and unmerged; `updated_at = 2026-08-14T10:00:41Z`. The inspected diff adds Linux broker routing, a Linux redirect, and OS-account listing, while retaining an OS-default sentinel fallback. Its reported Ubuntu test is public author-reported experience, not a V2 support result or this experiment's implementation. |
-| RECHECK-007: [Azure DevOps guidance](https://learn.microsoft.com/en-us/azure/devops/integrate/get-started/authentication/entra-oauth?view=azure-devops) | Still states that ordinary Entra applications do not natively support MSA users for the Azure DevOps resource. The first Windows sequence found the requested account, required interaction, and ended in a coarse acquisition-failure category. The diagnostic sequence later observed zero exact matches and timed out with cancellation fields. Neither returned a token, and these observations do not identify the earlier failure cause; neither establishes categorical MSA incompatibility. Successful token/resource behavior and intended reuse remain unresolved; no Profile is selected. |
+| RECHECK-007: [Azure DevOps guidance](https://learn.microsoft.com/en-us/azure/devops/integrate/get-started/authentication/entra-oauth?view=azure-devops) | Still states that ordinary Entra applications do not natively support MSA users for the Azure DevOps resource. The first Windows sequence found the requested account, required interaction, and ended in a coarse acquisition-failure category. The diagnostic sequence later observed zero exact matches and timed out with cancellation fields. The later attended action found one exact match but returned an unexpected broker failure. No action returned a token, and these observations do not identify the earlier failure cause or establish categorical MSA incompatibility. Successful token/resource behavior and intended reuse remain unresolved; no Profile is selected. |
 
 RECHECK-001, RECHECK-002, and RECHECK-006 retain their bounded desk dispositions; this
 protocol does not amend product interaction, account, or cache requirements. RECHECK-004