fix(simdrive): MCP auto-restart wedge + host-AX boundary diagnostics (1.0.0b11) - #166
Merged
mauricecarrier7 merged 1 commit intoJun 23, 2026
Merged
Conversation
…nostics (1.0.0b11) A live PP-4527/4531/4529 + PP-4632 validation campaign hit two sharp edges: the version-drift auto-restart desynced the MCP stdio transport, and the host-AX backend gave unhelpful errors at the WKWebView/SwiftUI boundaries. FIX 1 (run-breaker): never auto-restart while serving as an MCP stdio server. os.execv keeps the PID but tears down the client's initialized stdio session, so every later tool call failed `MCP error -32602` until a /mcp reconnect — strictly worse than the drift. Gate auto-restart on a new `_MCP_SERVER_MODE` flag set only in `_serve_async` (the one path that owns stdio). In that mode we surface a clear, actionable warning (reconnect /mcp) and schedule no re-exec. Safe self-restart is preserved for non-MCP (CLI/embedded) callers. `SIMDRIVE_NO_AUTO_RESTART=1` remains an explicit override everywhere. FIX 2: perform_accessibility_action now hints at the WKWebView/Readium host-AX boundary when ZERO custom actions exist anywhere in the target window — only then, not when a specific named action is merely absent. FIX 3: document set_text's UIKit-vs-SwiftUI boundary — AXValue commits UIKit (incl. UIAlertController) fields but not a SwiftUI @State-bound SecureField/ TextField; use tap + type_text/HID there. Docstring + MCP tool description. FIX 4: document SIMDRIVE_NO_AUTO_RESTART (README env-var table + drift text): set it for MCP-driver sessions to suppress the version-drift auto-restart. Tests: new test_b11_mcp_server_mode_no_restart.py (suppression in MCP mode, preserved restart outside it, actionable message) + WKWebView-hint and SwiftUI-docstring tests in test_ax_module.py. Version 1.0.0b10 -> 1.0.0b11 + CHANGELOG entry. **Scope:** docs + diagnostics + the MCP-mode restart gate only. No change to the actual AX value-setting behaviour (set_text still writes AXValue), no new SwiftUI/WKWebView code path, and no change to the on-device XCTest backend — this is the host-AX side plus the version-drift gating. The pre-existing test_e2e_testkit.py simulator-dependent tests are untouched. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
mauricecarrier7
added a commit
that referenced
this pull request
Jun 23, 2026
…nostics (1.0.0b11) (#166) A live internal-ticket/4531/4529 + internal-ticket validation campaign hit two sharp edges: the version-drift auto-restart desynced the MCP stdio transport, and the host-AX backend gave unhelpful errors at the WKWebView/SwiftUI boundaries. FIX 1 (run-breaker): never auto-restart while serving as an MCP stdio server. os.execv keeps the PID but tears down the client's initialized stdio session, so every later tool call failed `MCP error -32602` until a /mcp reconnect — strictly worse than the drift. Gate auto-restart on a new `_MCP_SERVER_MODE` flag set only in `_serve_async` (the one path that owns stdio). In that mode we surface a clear, actionable warning (reconnect /mcp) and schedule no re-exec. Safe self-restart is preserved for non-MCP (CLI/embedded) callers. `SIMDRIVE_NO_AUTO_RESTART=1` remains an explicit override everywhere. FIX 2: perform_accessibility_action now hints at the WKWebView/Readium host-AX boundary when ZERO custom actions exist anywhere in the target window — only then, not when a specific named action is merely absent. FIX 3: document set_text's UIKit-vs-SwiftUI boundary — AXValue commits UIKit (incl. UIAlertController) fields but not a SwiftUI @State-bound SecureField/ TextField; use tap + type_text/HID there. Docstring + MCP tool description. FIX 4: document SIMDRIVE_NO_AUTO_RESTART (README env-var table + drift text): set it for MCP-driver sessions to suppress the version-drift auto-restart. Tests: new test_b11_mcp_server_mode_no_restart.py (suppression in MCP mode, preserved restart outside it, actionable message) + WKWebView-hint and SwiftUI-docstring tests in test_ax_module.py. Version 1.0.0b10 -> 1.0.0b11 + CHANGELOG entry. **Scope:** docs + diagnostics + the MCP-mode restart gate only. No change to the actual AX value-setting behaviour (set_text still writes AXValue), no new SwiftUI/WKWebView code path, and no change to the on-device XCTest backend — this is the host-AX side plus the version-drift gating. The pre-existing test_e2e_testkit.py simulator-dependent tests are untouched. Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Four fixes surfaced by a live internal tickets iOS-validation campaign, which hit the MCP auto-restart wedge and the WKWebView host-AX boundary. Version bumped
1.0.0b10→1.0.0b11.FIX 1 (primary — run-breaker): MCP auto-restart wedge
When simdrive ran as an MCP stdio server and detected loaded-vs-disk version drift, it auto-restarted via
os.execv. That keeps the PID but tears down the client's initialized stdio session mid-stream, so every subsequent tool call failedMCP error -32602: Invalid request parameters— unrecoverable without a client/mcpreconnect. Strictly worse than the drift.Mode-detection mechanism: a module-level
_MCP_SERVER_MODEflag (helper_in_mcp_server_mode()) is flippedTrueonly inside_serve_async— the one code path that owns the stdio transport._maybe_handle_driftshort-circuits when it's set: it surfaces the drift warning, sets no_simdrive_action, and schedules no re-exec._check_version_driftreturns an actionable message naming the-32602hazard and the recovery (reconnect/mcp). Safe self-restart is preserved for non-MCP callers (CLI smokes, embedders, directcall_tool) where the flag staysFalse.SIMDRIVE_NO_AUTO_RESTART=1remains an explicit override everywhere.FIX 2: WKWebView host-AX diagnostic
perform_accessibility_actionnow appends a hint when zero custom actions are enumerated anywhere in the target window (new_window_has_any_custom_actionDFS): if it's a Readium/WKWebView reader, web-content a11y isn't bridged to host-AX on the simulator — use the on-device XCTest backend (runner/). Accuracy guard: the hint fires only on a genuinely empty window, not when a specific named action is simply absent among existing custom actions.FIX 3: set_text SwiftUI SecureField boundary (docs only)
Documented in both the
set_textMCP tool description (server.py) and theax.set_textdocstring:AXValuecommits UIKit fields (incl.UIAlertController) but does not reliably commit a SwiftUISecureField/TextFieldbound to@State(the field may display the text while@Statestays empty). Guidance: tap +type_text/HID for SwiftUI@State-bound fields. No behavior change.FIX 4: SIMDRIVE_NO_AUTO_RESTART docs
New "Environment variables" table in
simdrive/README.mddocuments the var (name matches what the code reads), plus the drift warning text now points to it: set it for MCP-driver sessions to suppress the version-drift auto-restart.Tests
tests/test_b11_mcp_server_mode_no_restart.py: drift in MCP-server mode does not schedule a restart and surfaces the-32602//mcpmessage (sync + async); restart is still scheduled outside MCP-server mode; helper reflects the flag.tests/test_ax_module.py:_window_has_any_custom_actiontrue/false; WKWebView hint added on empty window; hint NOT added when other custom actions exist; SwiftUI-boundary docstring assertion.tests/test_e2e_testkit.pyand are environmental — they fail at setup withno_device/first_booted(require a booted simulator), unrelated to this change.hypothesishad to be installed in the test env (it was missing) to collect 4 property-test modules; also a pre-existing environmental gap.Version + changelog
simdrive/pyproject.toml:1.0.0b10→1.0.0b11(single source of truth;__version__is read from package metadata).simdrive/CHANGELOG.md: added the[1.0.0b11]entry in the existing public-surface style.server.py/ax.pyare critical paths — architect + QA forge review still required before merge.🤖 Generated with Claude Code