@@ -0,0 +1,134 @@
+# TypeSafe crosswalk transport through the vendor SDK
+
+Date: 2026-10-05. Scope: `tools/sota-convergence/gap_crosswalk.py::call()`.
+This serves the north-star research stack by maintaining the existing landscape
+gap judgments without duplicating the vendor's HTTP and retry implementation.
+It authorizes no new model run or reinterpretation of recorded judgments.
+
+## Decision and compatibility gates
+
+Use the published `typesafe-sdk==0.7.2` wheel, from
+`typesafe-ai/[email protected]`, commit
+`f078f1e208a0d885154dc758344ae4fce77ac168`, through its public
+`TypeSafeClient.system_one()` and `RetryPolicy`. The release was published on
+2026-09-26. Import it only inside `call()`, reached by `judge`; an absent or
+different SDK fails with the pinned `uv run --with typesafe-sdk==0.7.2` command.
+`build`, `build --check` and `score` retain their standard-library dependency
+boundary. The existing environment-only API-key consumer is unchanged.
+
+All three prerequisite gates pass by source review:
+
+1. Dict-shaped instructions and criteria are JSON content in
+   [ChoiceModel:39-49](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_core/question_types.py#L39).
+   [normalize_questions:10-23](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_core/questions.py#L10)
+   accepts the existing raw choice dictionaries; no prompt conversion is added.
+2. The response preserves
+   [usage:65-73](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_core/response_types.py#L65),
+   [choice probabilities:25-30](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_schemas/models.py#L25),
+   and [public raw HTTP metadata:81-94](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_core/schemas/base.py#L81).
+   Native `model_dump(mode="json")` supplies the existing `validate()` input.
+   Reading the raw header retains the prior optional request ID; the SDK's
+   stricter `request_id` property would reject a missing header.
+   A strict SDK schema now sits between the wire response and `validate()`
+   and the ledger. The [base schema:21](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_core/schemas/base.py#L21)
+   uses `extra="ignore"` and `strict=True`; the
+   [ChoiceAnswer schema:19-24](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_schemas/models.py#L19)
+   requires `confidence`. The
+   [response preparation:86-93](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_core/response_types.py#L86)
+   drops answers of unknown type from the parsed response. This loses nothing
+   on every retained successful recorded row:
+   [eval judgments](../../evidence/artifacts/gap-crosswalk-92bb279/typesafe-eval.json)
+   contain 315 rows / 1,039 answers and
+   [current judgments](../../evidence/artifacts/gap-crosswalk-92bb279/typesafe-current.json)
+   contain 380 rows / 1,215 answers. All 695 rows contain modeled usage fields
+   and all 2,254 answers contain exactly the four modeled Choice
+   fields, including confidence. This static artifact census is source review,
+   not a new SDK or model run. For a future response that does not match the
+   schema, the boundary can change acceptance and drops extra fields before our
+   unchanged validator and ledger. Raw HTTP data remains available through the
+   SDK, but the ledger receives its parsed model dump. This schema boundary was
+   omitted from the initial decision and is now explicit following cross-family
+   source review.
+3. [RetryPolicy:52-123](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_core/retry.py#L52)
+   supports both 429 and 529 and explicit backoff configuration.
+
+The published wheel's PyPI SHA256 is
+`0a961148187d52e18276ed7f2d02617cfac48e3b97673cb631a8749397d43d1e`;
+the distribution metadata is available at
+[PyPI 0.7.2](https://pypi.org/pypi/typesafe-sdk/0.7.2/json).
+Acceptance installs the published wheel in a private uv cache with source builds
+disabled. It does not install a new host-stack component.
+
+Dependency-resolution limitation: the install hint pins the SDK only, while its
+[dependency declarations:35-40](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/pyproject.toml#L35)
+allow dependency ranges. The tested environment used `httpx2==2.13.1`,
+`pydantic==2.13.5` and `tenacity==9.1.4`, as retained in
+`evidence/artifacts/typesafe-sdk-transport-20261005/checks.json`. Pinning that
+tested dependency set in the hint is deferred; another resolution may select
+versions outside this observed set. This task does not qualify every supported
+dependency resolution.
+
+## Retry and response metadata contract
+
+| Setting | Legacy urllib transport | SDK defaults | Selected SDK policy |
+| --- | --- | --- | --- |
+| Total attempts | 5 | 3 | 5 (`max_retries=4`) |
+| Retried statuses | 429, 529 | 408, 429, all 5xx | 429, 529 |
+| Delay before retries | 1, 2, 4, 8 seconds | Initial 0.5, cap 5, jitter 0.25 | 1, 2, 4, 8; no jitter |
+| Retry-After | Ignored | Honored | Ignored |
+| Connection/timeout retries | Disabled | Enabled | Disabled |
+| Overall retry budget | None | 30 seconds | None |
+| Per-attempt HTTP timeout | 60 seconds | SDK default | 60 seconds |
+
+The existing retry field remains the zero-based successful attempt number,
+obtained from the SDK's own
+[X-TypeSafe-Retry-Count:68-74](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_core/transport.py#L68)
+on the public originating request. Its absence on the first attempt means zero.
+
+Two transport details change explicitly. The SDK sets `User-Agent` to
+`typesafe-sdk/0.7.2`, replacing `agent-lab-gap-crosswalk/1 (python-urllib)`;
+its [header construction:116-127](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/src/typesafe_sdk/_core/transport.py#L116)
+overwrites a caller-supplied User-Agent. Accept the vendor's header contract.
+The latency field now uses the successful response's public `elapsed` HTTP
+exchange duration, excluding SDK decoding. The legacy timer also covered final
+JSON decoding. Both exclude earlier attempts and backoff; existing ledger bytes
+remain unchanged. The public dependency contract is
+[pydantic/[email protected], d426e2c4:_models.py:579-604](https://github.com/pydantic/httpx2/blob/d426e2c44d1247fcf3326ed1cb496e56353efa4a/src/httpx2/httpx2/_models.py#L579).
+
+## Alternatives and overturn condition
+
+Keeping the urllib loop duplicates the supported vendor implementation. Using
+SDK defaults changes the five-attempt retry contract. A wrapper or fork to
+override vendor headers or count retries adds unnecessary transport glue.
+Use the public client and its metadata directly.
+
+Keep the prior glue if a prerequisite fails at the selected pin. Revisit this
+decision if a future supported SDK cannot preserve structured questions,
+probabilities, usage, request metadata or the retry policy. A comparison through
+the upstream MockTransport seam must establish any proposed replacement before
+another transport change.
+
+## Acceptance boundary and completeness critic
+
+`tests/test_gap_crosswalk_sdk.py` uses the upstream
+[MockTransport seam:33](https://github.com/typesafe-ai/typesafe-sdk-python/blob/f078f1e208a0d885154dc758344ae4fce77ac168/tests/conftest.py#L33)
+and the vendor's unchanged parser and retry implementation. These are synthetic
+integration checks, not an unchanged upstream suite or a live judgment. They
+comprise six MockTransport tests plus three offline import and version checks.
+They cover structured questions, usage/probabilities/request metadata, both retry
+statuses, exhaustion, a non-retried 500, absent request ID and missing usage.
+Wrong probability keys still fail the unchanged validator. Streamed mock
+responses exercise the native client's HTTP elapsed metadata. The first fixture
+used preloaded responses without elapsed metadata and failed three tests; that
+failed attempt and the fixture correction are retained in
+`evidence/artifacts/typesafe-sdk-transport-20261005/checks.json`.
+Offline import checks cover absent and mismatched SDK installations. Independent
+review caught that an initial install hint omitted `judge`'s required `--set`
+and `--out` flags. The final hint asks users to prefix their original command,
+preserving those flags and their output path; the guard test checks that hint.
+
+The source review also checked the omitted contracts: optional metadata,
+retry-count provenance, per-attempt timing, fixed endpoint, SDK-owned headers
+and the offline CI build. Native service behavior remains unmeasured because
+this task authorizes no live judge run. `request_body()`, `validate()`, the
+threshold, ledger construction and recorded judgments are preserved.
@@ -0,0 +1,102 @@
+{
+  "id": "typesafe-sdk-transport-20261005",
+  "date": "2026-10-05",
+  "base_commit": "f946c6d4ca988a17b6fa4392ecb488909f147883",
+  "purpose": "Replace only the landscape crosswalk's transport and retry with the public vendor SDK after all compatibility gates pass.",
+  "sources": {
+    "repository": "https://github.com/typesafe-ai/typesafe-sdk-python",
+    "tag": "v0.7.2",
+    "commit": "f078f1e208a0d885154dc758344ae4fce77ac168",
+    "registry": "https://pypi.org/pypi/typesafe-sdk/0.7.2/json",
+    "wheel": "typesafe_sdk-0.7.2-py3-none-any.whl",
+    "published_sha256": "0a961148187d52e18276ed7f2d02617cfac48e3b97673cb631a8749397d43d1e",
+    "downloaded_sha256": "0a961148187d52e18276ed7f2d02617cfac48e3b97673cb631a8749397d43d1e",
+    "download_exit_code": 0,
+    "sha256sum_exit_code": 0,
+    "compatibility_gates": {
+      "structured_questions": "pass; src/typesafe_sdk/_core/question_types.py:39-49 and questions.py:10-23",
+      "response_metadata": "pass; src/typesafe_sdk/_core/response_types.py:65-120, schemas/base.py:81-94 and src/typesafe_sdk/_schemas/models.py:25-30",
+      "retry_policy": "pass; src/typesafe_sdk/_core/retry.py:52-123"
+    },
+    "evidence_class": "source_review"
+  },
+  "environment": {
+    "installation": "isolated uv --with environment; --no-build, --no-config and --no-env-file; scratch and cache outside /tmp",
+    "installed_packages": {
+      "typesafe-sdk": "0.7.2",
+      "httpx2": "2.13.1",
+      "httpcore2": "2.13.1",
+      "pydantic": "2.13.5",
+      "pydantic_core": "2.46.5",
+      "tenacity": "9.1.4",
+      "typing_extensions": "4.16.0",
+      "typing-inspection": "0.4.4",
+      "anyio": "4.15.1",
+      "h11": "0.16.0",
+      "annotated-types": "0.8.0",
+      "idna": "3.20",
+      "truststore": "0.10.4"
+    }
+  },
+  "checks": [
+    {
+      "command": "python3 tools/sota-convergence/gap_crosswalk.py build --check",
+      "phase": "baseline with SDK absent",
+      "exit_code": 0,
+      "returned_stdout": "crosswalk up to date\n",
+      "returned_stderr": "",
+      "evidence_class": "local_integration"
+    },
+    {
+      "command": "uv run --no-project --no-config --no-env-file --no-build --no-managed-python --no-python-downloads --default-index https://pypi.org/simple --with typesafe-sdk==0.7.2 python3 -m unittest discover -s tests -p test_gap_crosswalk_sdk.py -v",
+      "phase": "first stub fixture",
+      "exit_code": 1,
+      "returned_summary": "Ran 8 tests in 0.324s; FAILED (errors=3)",
+      "failure": "test_missing_request_id_stays_optional, test_missing_usage_remains_invalid, and test_structured_questions_metadata_and_final_attempt_retry_count failed at raw.elapsed: RuntimeError: '.elapsed' may only be accessed after the response has been read or closed.",
+      "correction": "The preloaded MockTransport fixture had no elapsed metadata. A subsequent explicit synthetic elapsed fixture passed all eight tests (exit 0). The final fixture instead streams its response through native ByteStream so the native client read/close sets elapsed; production transport code is unchanged by this correction.",
+      "evidence_class": "synthetic"
+    },
+    {
+      "command": "python3 -S tools/sota-convergence/gap_crosswalk.py build --check",
+      "phase": "changed transport with site packages disabled",
+      "exit_code": 0,
+      "returned_stdout": "crosswalk up to date\n",
+      "returned_stderr": "",
+      "evidence_class": "local_integration"
+    },
+    {
+      "command": "uv run --no-project --no-config --no-env-file --no-build --no-managed-python --no-python-downloads --offline --with typesafe-sdk==0.7.2 python3 -m unittest discover -s tests -p 'test_gap_crosswalk*.py' -v",
+      "phase": "final streamed SDK stub plus existing crosswalk and routing tests",
+      "exit_code": 0,
+      "returned_summary": "Ran 22 tests in 0.439s; OK",
+      "returned_output_path": "evidence/artifacts/typesafe-sdk-transport-20261005/unittest-output.txt",
+      "skipped": 0,
+      "new_sdk_tests": 9,
+      "evidence_class": "synthetic"
+    },
+    {
+      "command": "python3 tools/sota-convergence/gap_crosswalk.py build --check",
+      "phase": "changed transport with ordinary standard-library interpreter",
+      "exit_code": 0,
+      "returned_stdout": "crosswalk up to date\n",
+      "returned_stderr": "",
+      "evidence_class": "local_integration"
+    }
+  ],
+  "preservation": {
+    "byte_identical_functions": ["request_body", "validate", "judge", "build"],
+    "threshold": 0.3,
+    "recorded_judgments_changed": false,
+    "catalog_ledger_changed": false,
+    "user_agent": "SDK-owned typesafe-sdk/0.7.2; explicit authorized change from agent-lab-gap-crosswalk/1 (python-urllib)",
+    "latency_s": "Final successful HTTP exchange; excludes prior attempts, backoff and SDK decoding. Prior timer also included final JSON decoding."
+  },
+  "independent_review_correction": "The first missing-SDK hint omitted required judge --set/--out arguments. Final hint asks to prefix the original judge command, preserving its flags/output path; strengthened guard test passes.",
+  "limitations": [
+    "No live judge call, provider acceptance, credential value read or new judgment.",
+    "Stub tests are locally authored synthetic integration checks through the unchanged SDK implementation; they are not an unchanged upstream suite.",
+    "Stub timing does not establish live service latency.",
+    "Source gates establish compatibility at the selected pin, not live service correctness.",
+    "Repository validation checks integrity and declared consistency; its final exit code is reported in the draft PR and private lane status after the registry commit."
+  ]
+}
@@ -0,0 +1,27 @@
+test_build_check_is_up_to_date (test_gap_crosswalk.GapCrosswalkTests.test_build_check_is_up_to_date) ... ok
+test_build_rejects_candidates_outside_the_rule (test_gap_crosswalk.GapCrosswalkTests.test_build_rejects_candidates_outside_the_rule) ... ok
+test_build_rejects_receipt_content_changed_since_judging (test_gap_crosswalk.GapCrosswalkTests.test_build_rejects_receipt_content_changed_since_judging) ... ok
+test_every_gap_of_the_source_revision_is_covered (test_gap_crosswalk.GapCrosswalkTests.test_every_gap_of_the_source_revision_is_covered) ... ok
+test_every_layer_has_one_known_owner (test_gap_crosswalk.GapCrosswalkTests.test_every_layer_has_one_known_owner) ... ok
+test_judgment_and_review_files_match_their_recorded_hashes (test_gap_crosswalk.GapCrosswalkTests.test_judgment_and_review_files_match_their_recorded_hashes) ... ok
+test_no_host_paths_or_session_identifiers (test_gap_crosswalk.GapCrosswalkTests.test_no_host_paths_or_session_identifiers) ... ok
+test_status_follows_the_final_decisions (test_gap_crosswalk.GapCrosswalkTests.test_status_follows_the_final_decisions) ... ok
+test_a3_a_gap_with_a_digit_sends_every_pair_to_review (test_gap_crosswalk_routing.CrosswalkRoutingTests.test_a3_a_gap_with_a_digit_sends_every_pair_to_review) ... ok
+test_a7_a_gap_with_no_reviewed_pair_is_not_open (test_gap_crosswalk_routing.CrosswalkRoutingTests.test_a7_a_gap_with_no_reviewed_pair_is_not_open) ... ok
+test_a7_a_pair_no_reviewer_saw_has_no_final_decision (test_gap_crosswalk_routing.CrosswalkRoutingTests.test_a7_a_pair_no_reviewer_saw_has_no_final_decision) ... ok
+test_negative_control_the_2026_09_23_rule_fails_both_checks (test_gap_crosswalk_routing.CrosswalkRoutingTests.test_negative_control_the_2026_09_23_rule_fails_both_checks) ... ok
+test_each_rule_on_the_retained_inputs (test_gap_crosswalk_routing.RetainedLedgerRoutingTests.test_each_rule_on_the_retained_inputs) ... ok
+test_missing_sdk_fails_with_pinned_install_command (test_gap_crosswalk_sdk.OptionalSDKTests.test_missing_sdk_fails_with_pinned_install_command) ... ok
+test_module_import_does_not_load_sdk (test_gap_crosswalk_sdk.OptionalSDKTests.test_module_import_does_not_load_sdk) ... ok
+test_other_sdk_version_fails_before_transport (test_gap_crosswalk_sdk.OptionalSDKTests.test_other_sdk_version_fails_before_transport) ... ok
+test_missing_request_id_stays_optional (test_gap_crosswalk_sdk.SDKTransportTests.test_missing_request_id_stays_optional) ... ok
+test_missing_usage_remains_invalid (test_gap_crosswalk_sdk.SDKTransportTests.test_missing_usage_remains_invalid) ... ok
+test_non_retryable_status_stops_immediately (test_gap_crosswalk_sdk.SDKTransportTests.test_non_retryable_status_stops_immediately) ... ok
+test_retries_stop_after_five_attempts_with_legacy_backoff (test_gap_crosswalk_sdk.SDKTransportTests.test_retries_stop_after_five_attempts_with_legacy_backoff) ... ok
+test_structured_questions_metadata_and_final_attempt_retry_count (test_gap_crosswalk_sdk.SDKTransportTests.test_structured_questions_metadata_and_final_attempt_retry_count) ... ok
+test_wrong_probability_keys_remain_invalid (test_gap_crosswalk_sdk.SDKTransportTests.test_wrong_probability_keys_remain_invalid) ... ok
+
+----------------------------------------------------------------------
+Ran 22 tests in 0.439s
+
+OK
@@ -16682,6 +16682,11 @@
       "sha256": "d7698470de9eb7ed30f0764f8b1b17acd8a926298b08630829e1b955ba177dfe",
       "bytes": 23344
     },
+    {
+      "path": "docs/decisions/2026-10-05-typesafe-sdk-transport.md",
+      "sha256": "d197ab297186fe55e6c83624c78a06ead264e00d66a7fe2d5e62cfc1b653dbd6",
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+    },
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       "path": "docs/direct-results.md",
       "sha256": "12a511fee11f22c90b9b622701d5485be9c8247167102b5768d694244f939a5b",
@@ -49552,6 +49557,16 @@
       "sha256": "189a1b80b559e74fc12d0b7e73f6415e4829041bfe8f03d89ca5a18fb11be4f5",
       "bytes": 30252
     },
+    {
+      "path": "evidence/artifacts/typesafe-sdk-transport-20261005/checks.json",
+      "sha256": "0c2d0c3a40a5f4fdfbf707d30bc49a9d58cddbd01fdad8965fcb495248f312ac",
+      "bytes": 5642
+    },
+    {
+      "path": "evidence/artifacts/typesafe-sdk-transport-20261005/unittest-output.txt",
+      "sha256": "a2c5d1bde040183fcd96890e3ce1b5dce70197478942641dce45ca75976ddb15",
+      "bytes": 3275
+    },
     {
       "path": "evidence/artifacts/u11-part1-source-repair-20261001/integration-main-20261002.json",
       "sha256": "6382ce9bc43e18e5797b0e0c7df0f2b76f2485ca6a908e3b7aba13ec1c1eb638",
@@ -53677,6 +53692,11 @@
       "sha256": "3fee83f89033d101c71cbfcdb4eb2efb12166a459ae80f7c9a96cb58bb5937aa",
       "bytes": 13100
     },
+    {
+      "path": "tests/test_gap_crosswalk_sdk.py",
+      "sha256": "5bdf42e3dbd407909c1d21a1e8314d2f9d5b19623f26d8ee1d86689bf3184dda",
+      "bytes": 7316
+    },
     {
       "path": "tests/test_gap_resolution_ledger.py",
       "bytes": 5845,
@@ -54594,8 +54614,8 @@
     },
     {
       "path": "tools/sota-convergence/gap_crosswalk.py",
-      "sha256": "7545a9aa0a709aaca636e69b6ca7a1d6d9e317a53027098df7133e952d4f705f",
-      "bytes": 30150
+      "sha256": "77f9c58561e656dfa6b42a346ed6063d7a3716089c2900c84808e0527594c22c",
+      "bytes": 30850
     },
     {
       "path": "tools/sota-convergence/gap_wave_ledger.py",