diff --git a/Cargo.lock b/Cargo.lock
index 269c2418..66984c6b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -291,7 +291,6 @@ dependencies = [
  "rustyline",
  "serde",
  "serde_json",
- "serde_yaml",
  "sha2",
  "signal-hook",
  "tempfile",
@@ -301,6 +300,7 @@ dependencies = [
  "unicode-width",
  "url",
  "uuid",
+ "yaml_serde",
 ]
 
 [[package]]
@@ -842,6 +842,12 @@ version = "0.2.186"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "68ab91017fe16c622486840e4c83c9a37afeff978bd239b5293d61ece587de66"
 
+[[package]]
+name = "libyaml-rs"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2e126dda6f34391ab7b444f9922055facc83c07a910da3eb16f1e4d9c45dc777"
+
 [[package]]
 name = "linux-raw-sys"
 version = "0.4.15"
@@ -1409,19 +1415,6 @@ dependencies = [
  "serde",
 ]
 
-[[package]]
-name = "serde_yaml"
-version = "0.9.34+deprecated"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a8b1a1a2ebf674015cc02edccce75287f1a0130d394307b36743c2f5d504b47"
-dependencies = [
- "indexmap",
- "itoa",
- "ryu",
- "serde",
- "unsafe-libyaml",
-]
-
 [[package]]
 name = "sha2"
 version = "0.10.9"
@@ -1783,12 +1776,6 @@ version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7dd6e30e90baa6f72411720665d41d89b9a3d039dc45b8faea1ddd07f617f6af"
 
-[[package]]
-name = "unsafe-libyaml"
-version = "0.2.11"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "673aac59facbab8a9007c7f6108d11f63b603f7cabff99fabf650fea5c32b861"
-
 [[package]]
 name = "untrusted"
 version = "0.9.0"
@@ -2156,6 +2143,19 @@ version = "0.6.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1ffae5123b2d3fc086436f8834ae3ab053a283cfac8fe0a0b8eaae044768a4c4"
 
+[[package]]
+name = "yaml_serde"
+version = "0.10.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "33b729a08a9a6be689bbad3e2bf8015926db54b6622cc89c3a5f7dc174b9e918"
+dependencies = [
+ "indexmap",
+ "itoa",
+ "libyaml-rs",
+ "ryu",
+ "serde",
+]
+
 [[package]]
 name = "yoke"
 version = "0.8.3"
diff --git a/Cargo.toml b/Cargo.toml
index 80157253..d4266b9d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -40,7 +40,7 @@ reqwest = { version = "0.12", features = ["blocking", "rustls-tls", "json"], def
 rustyline = { version = "14", default-features = false, features = ["custom-bindings", "with-file-history"] }
 serde = { version = "1", features = ["derive"] }
 serde_json = { version = "1", features = ["raw_value"] }
-serde_yaml = "0.9"
+serde_yaml = { package = "yaml_serde", version = "0.10.7" }
 sha2 = "0.10"
 signal-hook = "0.3"
 tempfile = "3"
diff --git a/deny.toml b/deny.toml
index 3439831d..7b96ae71 100644
--- a/deny.toml
+++ b/deny.toml
@@ -11,13 +11,7 @@
 [advisories]
 # A new advisory must fail the check; add an entry here only with a written
 # reason and a link to the tracking Issue.
-ignore = [
-  # unsafe-libyaml is unmaintained (published 2026-10). It reaches us only
-  # through serde_yaml 0.9, which has no safe upgrade. Temporary, approved by
-  # the user 2026-10-13: remove this entry in the PR that migrates off
-  # serde_yaml (https://github.com/Kewton/CommandAgent/issues/530).
-  { id = "RUSTSEC-2024-0449", reason = "unsafe-libyaml via serde_yaml 0.9; migration tracked in #530" },
-]
+ignore = []
 
 [licenses]
 # Curated allow list matching the current dependency graph. BSL-1.0 is required
diff --git a/tests/corpus/apps/issue530-yaml-migration/expectations.toml b/tests/corpus/apps/issue530-yaml-migration/expectations.toml
new file mode 100644
index 00000000..df92988e
--- /dev/null
+++ b/tests/corpus/apps/issue530-yaml-migration/expectations.toml
@@ -0,0 +1,31 @@
+case_id = "issue530-yaml-migration"
+source = "Issue #530: serde_yaml 0.9 (unsafe-libyaml, RUSTSEC-2024-0449) migrated to yaml_serde 0.10.7 (libyaml-rs); pre-migration measurements are recorded in the fixture and reproduced through the public API"
+required_paths = []
+verify_commands = []
+required_capabilities = []
+required_evidence = []
+required_obligations = []
+deferred_verify_requirements = []
+evidence_hint_tokens = []
+
+[route_closure]
+include = []
+exclude = []
+
+[weak_evidence]
+contains = []
+
+[diagnostics]
+contains = []
+
+[compile]
+expect = "not_checked"
+
+[fixture_contains]
+fixtures/compatibility.json = [
+  "\"migrated_from\": \"serde_yaml 0.9.34+deprecated\"",
+  "\"migrated_to\": \"yaml_serde 0.10.7\"",
+  "\"id\": \"anchor-alias-rejected\"",
+  "\"schema_accepts\": false",
+  "\"parser_accepts\": true"
+]
diff --git a/tests/corpus/apps/issue530-yaml-migration/fixtures/compatibility.json b/tests/corpus/apps/issue530-yaml-migration/fixtures/compatibility.json
new file mode 100644
index 00000000..a7247a2a
--- /dev/null
+++ b/tests/corpus/apps/issue530-yaml-migration/fixtures/compatibility.json
@@ -0,0 +1,219 @@
+{
+  "issue": 530,
+  "migrated_from": "serde_yaml 0.9.34+deprecated",
+  "migrated_to": "yaml_serde 0.10.7",
+  "parser_dependency_from": "unsafe-libyaml 0.2.11 (RUSTSEC-2024-0449, unmaintained)",
+  "parser_dependency_to": "libyaml-rs 0.3.0",
+  "baseline": "Measured on the pre-migration develop export; yaml_serde 0.10.7 reproduces accept/reject, type, value, tag, arbitrary-key, serialization, and diagnostic line/column identically.",
+  "pack_cases": [
+    {
+      "id": "valid-assist-accepted",
+      "document": "schema_version: commandagent.pack.assist/v0\npack:\n  id: ingest-default\n  version: 1.0.0\n  profile: ingest\n  intent: create\ninject:\n  - point: declare-ingest-inspection\n    source: ingest_snapshot_structure_injected\n    required: true\n    params:\n      max_files: 8\nliterals:\n  - gate: ingest_source_binding\n    example:\n      format: json\n      value: '{\"date\":\"2026-08-03\"}'\nvocabulary:\n  - point: implement-ingest-delivery\n    source: ingest_candidate_ids_injected\n    mode: verbatim\n    required: true\n    params: {}\n",
+      "parser_accepts": true,
+      "schema_accepts": true
+    },
+    {
+      "id": "unknown-field-rejected",
+      "document": "schema_version: commandagent.pack.assist/v0\npack:\n  id: ingest-default\n  version: 1.0.0\n  profile: ingest\n  intent: create\ninvented: true\ninject:\n  - point: declare-ingest-inspection\n    source: ingest_snapshot_structure_injected\n    required: true\n    params:\n      max_files: 8\nliterals:\n  - gate: ingest_source_binding\n    example:\n      format: json\n      value: '{\"date\":\"2026-08-03\"}'\nvocabulary:\n  - point: implement-ingest-delivery\n    source: ingest_candidate_ids_injected\n    mode: verbatim\n    required: true\n    params: {}\n",
+      "parser_accepts": true,
+      "schema_accepts": false,
+      "schema_error": "unknown field `invented`, expected one of `schema_version`, `pack`, `inject`, `literals`, `vocabulary` at line 7 column 1"
+    },
+    {
+      "id": "duplicate-key-rejected",
+      "document": "schema_version: commandagent.pack.assist/v0\npack:\n  id: ingest-default\n  id: duplicate\n  version: 1.0.0\n  profile: ingest\n  intent: create\ninject:\n  - point: declare-ingest-inspection\n    source: ingest_snapshot_structure_injected\n    required: true\n    params:\n      max_files: 8\nliterals:\n  - gate: ingest_source_binding\n    example:\n      format: json\n      value: '{\"date\":\"2026-08-03\"}'\nvocabulary:\n  - point: implement-ingest-delivery\n    source: ingest_candidate_ids_injected\n    mode: verbatim\n    required: true\n    params: {}\n",
+      "parser_accepts": false,
+      "schema_accepts": false,
+      "schema_error": "duplicate YAML key `id` at line 3 column 3"
+    },
+    {
+      "id": "anchor-alias-rejected",
+      "document": "schema_version: commandagent.pack.assist/v0\npack:\n  id: ingest-default\n  version: 1.0.0\n  profile: ingest\n  intent: create\ninject:\n  - point: declare-ingest-inspection\n    source: ingest_snapshot_structure_injected\n    required: true\n    params:\n      max_files: 8\nliterals:\n  - gate: ingest_source_binding\n    example:\n      format: json\n      value: '{\"date\":\"2026-08-03\"}'\nvocabulary:\n  - point: implement-ingest-delivery\n    source: ingest_candidate_ids_injected\n    mode: verbatim\n    required: true\n    params: {}\nnote: &n hello\nref: *n\n",
+      "parser_accepts": true,
+      "schema_accepts": false,
+      "schema_error": "YAML anchors are forbidden at line 24"
+    },
+    {
+      "id": "tag-rejected",
+      "document": "schema_version: commandagent.pack.assist/v0\npack:\n  id: ingest-default\n  version: 1.0.0\n  profile: ingest\n  intent: create\ninject:\n  - point: declare-ingest-inspection\n    source: ingest_snapshot_structure_injected\n    required: true\n    params:\n      max_files: 8\nliterals:\n  - gate: ingest_source_binding\n    example:\n      format: json\n      value: '{\"date\":\"2026-08-03\"}'\nvocabulary:\n  - point: implement-ingest-delivery\n    source: ingest_candidate_ids_injected\n    mode: verbatim\n    required: true\n    params: {}\nnote: !custom hello\n",
+      "parser_accepts": true,
+      "schema_accepts": false,
+      "schema_error": "YAML tags are forbidden at line 24"
+    },
+    {
+      "id": "merge-key-rejected",
+      "document": "schema_version: commandagent.pack.assist/v0\npack:\n  id: ingest-default\n  version: 1.0.0\n  profile: ingest\n  intent: create\nextra:\n  <<: {a: 1}\ninject:\n  - point: declare-ingest-inspection\n    source: ingest_snapshot_structure_injected\n    required: true\n    params:\n      max_files: 8\nliterals:\n  - gate: ingest_source_binding\n    example:\n      format: json\n      value: '{\"date\":\"2026-08-03\"}'\nvocabulary:\n  - point: implement-ingest-delivery\n    source: ingest_candidate_ids_injected\n    mode: verbatim\n    required: true\n    params: {}\n",
+      "parser_accepts": true,
+      "schema_accepts": false,
+      "schema_error": "YAML merge keys are forbidden at line 8"
+    },
+    {
+      "id": "multi-document-rejected",
+      "document": "schema_version: commandagent.pack.assist/v0\npack:\n  id: ingest-default\n  version: 1.0.0\n  profile: ingest\n  intent: create\ninject:\n  - point: declare-ingest-inspection\n    source: ingest_snapshot_structure_injected\n    required: true\n    params:\n      max_files: 8\nliterals:\n  - gate: ingest_source_binding\n    example:\n      format: json\n      value: '{\"date\":\"2026-08-03\"}'\nvocabulary:\n  - point: implement-ingest-delivery\n    source: ingest_candidate_ids_injected\n    mode: verbatim\n    required: true\n    params: {}\n---\nschema_version: other\n",
+      "parser_accepts": false,
+      "schema_accepts": false,
+      "schema_error": "deserializing from YAML containing more than one document is not supported"
+    },
+    {
+      "id": "non-string-key-rejected",
+      "document": "1: x\nschema_version: commandagent.pack.assist/v0\npack:\n  id: ingest-default\n  version: 1.0.0\n  profile: ingest\n  intent: create\ninject:\n  - point: declare-ingest-inspection\n    source: ingest_snapshot_structure_injected\n    required: true\n    params:\n      max_files: 8\nliterals:\n  - gate: ingest_source_binding\n    example:\n      format: json\n      value: '{\"date\":\"2026-08-03\"}'\nvocabulary:\n  - point: implement-ingest-delivery\n    source: ingest_candidate_ids_injected\n    mode: verbatim\n    required: true\n    params: {}\n",
+      "parser_accepts": true,
+      "schema_accepts": false,
+      "schema_error": "unknown field `1`, expected one of `schema_version`, `pack`, `inject`, `literals`, `vocabulary`"
+    }
+  ],
+  "plan_cases": [
+    {
+      "id": "valid-step-plan-accepted",
+      "document": "goal: Update the plan YAML guide\nsteps:\n  - id: update-guide\n    kind: implement\n    expected_result: pass\n    instruction: Update docs/guide/en/plan-yaml.md with editing guidance.\n    expected_paths:\n      - docs/guide/en/plan-yaml.md\n",
+      "accepts": true
+    },
+    {
+      "id": "valid-ultra-plan-accepted",
+      "document": "recovery_schema_version: '1'\ngoal: recover\nprofile: generic\nstyle: recovery\nintent: recover\nphases:\n  - id: repair\n    prompt: Repair.\n  - id: verify\n    prompt: Verify.\n",
+      "accepts": true
+    },
+    {
+      "id": "syntax-error-keeps-line-and-column",
+      "document": "goal: x\nsteps:\n  - id: bad\n    instruction: [\n",
+      "accepts": false,
+      "error_contains": "did not find expected node content",
+      "line": 5,
+      "column": 1
+    },
+    {
+      "id": "type-error-keeps-line-and-column",
+      "document": "goal: docs\nsteps:\n  - id: update-guide\n    kind: implement\n    expected_result: pass\n    instruction: [not, a, string]\n",
+      "accepts": false,
+      "error_contains": "invalid type: sequence, expected a string",
+      "line": 6,
+      "column": 18
+    },
+    {
+      "id": "both-steps-and-phases-rejected",
+      "document": "goal: x\nsteps:\n  - id: s1\n    instruction: a\nphases:\n  - id: p1\n    prompt: b\n",
+      "accepts": false,
+      "error_contains": "plan cannot contain both `steps` and `phases`",
+      "line": 5,
+      "column": 1
+    },
+    {
+      "id": "neither-steps-nor-phases-rejected",
+      "document": "goal: x\n",
+      "accepts": false,
+      "error_contains": "plan must contain either a `steps` list or a `phases` list",
+      "line": 1,
+      "column": 1
+    },
+    {
+      "id": "contract-error-keeps-line-and-column",
+      "document": "goal: test\nsteps:\n  - id: verify\n    kind: verify\n    expected_result: pass\n    instruction: Run tests.\n    verify:\n      - \"cargo test | cargo clippy\"\n",
+      "accepts": false,
+      "error_contains": "verify command may not use shell control syntax",
+      "line": 8,
+      "column": 10
+    }
+  ],
+  "workflow_versions": [
+    {
+      "id": "numeric-0",
+      "document": "workflow: recovery-circle-data\nversion: 0\nentry: create\nnodes:\n  create: {intent: create, profile: generic}\nroutes: []\nterminal: {}\n",
+      "accepts": true
+    },
+    {
+      "id": "numeric-0.1",
+      "document": "workflow: recovery-circle-data\nversion: 0.1\nentry: create\nnodes:\n  create: {intent: create, profile: generic}\nroutes: []\nterminal: {}\n",
+      "accepts": true
+    },
+    {
+      "id": "numeric-0.2",
+      "document": "workflow: recovery-circle-data\nversion: 0.2\nentry: create\nnodes:\n  create: {intent: create, profile: generic}\nroutes: []\nterminal: {}\n",
+      "accepts": true
+    },
+    {
+      "id": "numeric-0.3-rejected",
+      "document": "workflow: recovery-circle-data\nversion: 0.3\nentry: create\nnodes:\n  create: {intent: create, profile: generic}\nroutes: []\nterminal: {}\n",
+      "accepts": false,
+      "error_contains": "workflow version must be 0, 0.1, or 0.2"
+    },
+    {
+      "id": "string-zero-rejected",
+      "document": "workflow: recovery-circle-data\nversion: \"0\"\nentry: create\nnodes:\n  create: {intent: create, profile: generic}\nroutes: []\nterminal: {}\n",
+      "accepts": false,
+      "error_contains": "workflow version must be 0, 0.1, or 0.2"
+    }
+  ],
+  "scrub_cases": [
+    {
+      "id": "tagged-keys-keep-element-count",
+      "register_plain": [
+        "SECRET-AAA-111",
+        "SECRET-BBB-222"
+      ],
+      "document": "!t SECRET-AAA-111: 1\n!t SECRET-BBB-222: 2\n!t keep-me: 3\n",
+      "mapping_len": 3,
+      "absent": [
+        "SECRET-AAA-111",
+        "SECRET-BBB-222"
+      ],
+      "serialized_contains": [
+        "!t keep-me: 3"
+      ]
+    },
+    {
+      "id": "compound-mapping-keys-keep-element-count",
+      "register_plain": [
+        "SECRET-AAA-111",
+        "SECRET-BBB-222"
+      ],
+      "document": "? {a: SECRET-AAA-111}\n: 1\n? {a: SECRET-BBB-222}\n: 2\n",
+      "mapping_len": 2,
+      "absent": [
+        "SECRET-AAA-111",
+        "SECRET-BBB-222"
+      ]
+    },
+    {
+      "id": "numeric-secret-becomes-marker-string",
+      "register_plain": [
+        "8675309012345"
+      ],
+      "document": "port: 8675309012345\nplain: 42\n",
+      "mapping_len": 2,
+      "absent": [
+        "8675309012345"
+      ],
+      "string_value": {
+        "port": "<redacted>"
+      },
+      "number_value": {
+        "plain": 42
+      }
+    },
+    {
+      "id": "key-collision-keeps-existing-value",
+      "register_plain": [
+        "SECRET-AAA-111"
+      ],
+      "document": "SECRET-AAA-111: keep\n<redacted>: existing\n",
+      "mapping_len": 2,
+      "absent": [
+        "SECRET-AAA-111"
+      ],
+      "string_value": {
+        "<redacted>": "existing",
+        "<redacted>#1": "keep"
+      }
+    }
+  ],
+  "boundary": {
+    "max_file_bytes": 262144,
+    "file_error": "file exceeds 262144 bytes",
+    "max_depth": 16,
+    "depth_error": "YAML nesting exceeds 16",
+    "max_sequence": 256,
+    "sequence_error": "YAML sequence exceeds 256 entries",
+    "max_scalar_bytes": 65536,
+    "scalar_error": "YAML scalar exceeds 65536 bytes"
+  }
+}
diff --git a/tests/issue530_yaml_migration.rs b/tests/issue530_yaml_migration.rs
new file mode 100644
index 00000000..3be2f16b
--- /dev/null
+++ b/tests/issue530_yaml_migration.rs
@@ -0,0 +1,278 @@
+//! Issue #530 — the YAML parser migration compatibility corpus.
+//!
+//! `serde_yaml` was migrated from the unmaintained 0.9 (which pulled in
+//! `unsafe-libyaml` and RUSTSEC-2024-0449) to the maintained `yaml_serde`
+//! 0.10.7 (`libyaml-rs`). Because the crate name stays `serde_yaml`, no
+//! production source changed. This integration test drives the public API over
+//! the pre-migration measurements recorded in `fixtures/compatibility.json` and
+//! requires the same accept/reject decisions, types, tags, mapping element
+//! counts, and diagnostic line/column.
+//!
+//! The corpus fixture lives under `tests/corpus/apps/` so the generated-app
+//! corpus regression discovers it; `expectations.toml` pins the fixture tokens.
+
+use std::collections::BTreeMap;
+use std::io::Write;
+use std::path::Path;
+
+use commandagent::planner::pack::parse_bytes;
+use commandagent::planner::plan::validate_plan_file;
+use commandagent::sensitive_data::{REDACTED, SecretCatalog};
+use commandagent::workflow::schema::Workflow;
+use serde::Deserialize;
+
+#[derive(Debug, Deserialize)]
+struct Compatibility {
+    pack_cases: Vec<PackCase>,
+    plan_cases: Vec<PlanCase>,
+    workflow_versions: Vec<WorkflowCase>,
+    scrub_cases: Vec<ScrubCase>,
+    boundary: Boundary,
+}
+
+#[derive(Debug, Deserialize)]
+struct PackCase {
+    id: String,
+    document: String,
+    parser_accepts: bool,
+    schema_accepts: bool,
+    #[serde(default)]
+    schema_error: Option<String>,
+}
+
+#[derive(Debug, Deserialize)]
+struct PlanCase {
+    id: String,
+    document: String,
+    accepts: bool,
+    #[serde(default)]
+    error_contains: Option<String>,
+    #[serde(default)]
+    line: Option<usize>,
+    #[serde(default)]
+    column: Option<usize>,
+}
+
+#[derive(Debug, Deserialize)]
+struct WorkflowCase {
+    id: String,
+    document: String,
+    accepts: bool,
+    #[serde(default)]
+    error_contains: Option<String>,
+}
+
+#[derive(Debug, Deserialize)]
+struct ScrubCase {
+    id: String,
+    register_plain: Vec<String>,
+    document: String,
+    mapping_len: usize,
+    #[serde(default)]
+    absent: Vec<String>,
+    #[serde(default)]
+    serialized_contains: Vec<String>,
+    #[serde(default)]
+    string_value: BTreeMap<String, String>,
+    #[serde(default)]
+    number_value: BTreeMap<String, i64>,
+}
+
+#[derive(Debug, Deserialize)]
+struct Boundary {
+    max_file_bytes: usize,
+    file_error: String,
+    max_depth: usize,
+    depth_error: String,
+    max_sequence: usize,
+    sequence_error: String,
+    max_scalar_bytes: usize,
+    scalar_error: String,
+}
+
+fn fixture() -> Compatibility {
+    let path = Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/corpus/apps/issue530-yaml-migration/fixtures/compatibility.json");
+    let text = std::fs::read_to_string(&path)
+        .unwrap_or_else(|error| panic!("failed to read {}: {error}", path.display()));
+    serde_json::from_str(&text)
+        .unwrap_or_else(|error| panic!("invalid {}: {error}", path.display()))
+}
+
+/// The business schema must keep rejecting exactly what the YAML parser itself
+/// may (or may not) accept; the two decisions are recorded separately and must
+/// not collapse into one.
+#[test]
+fn pack_acceptance_keeps_parser_and_schema_decisions_separate() {
+    let compatibility = fixture();
+    assert!(
+        !compatibility.pack_cases.is_empty(),
+        "no pack cases recorded"
+    );
+    for case in &compatibility.pack_cases {
+        let parser = serde_yaml::from_str::<serde_yaml::Value>(&case.document);
+        assert_eq!(
+            parser.is_ok(),
+            case.parser_accepts,
+            "{}: YAML parser accept/reject changed; error={:?}",
+            case.id,
+            parser.err().map(|error| error.to_string())
+        );
+
+        let schema = parse_bytes(Some(case.document.as_bytes()), None);
+        assert_eq!(
+            schema.is_ok(),
+            case.schema_accepts,
+            "{}: pack schema accept/reject changed; error={:?}",
+            case.id,
+            schema.as_ref().err().map(ToString::to_string)
+        );
+
+        if let Some(expected) = &case.schema_error {
+            let error = schema.expect_err("negative case must reject").to_string();
+            assert!(error.contains(expected), "{}: got {error}", case.id);
+        }
+    }
+}
+
+#[test]
+fn plan_diagnostics_keep_reason_and_position() {
+    let compatibility = fixture();
+    for case in &compatibility.plan_cases {
+        let workspace = tempfile::tempdir().unwrap();
+        let path = workspace.path().join("plan.yaml");
+        std::fs::File::create(&path)
+            .and_then(|mut file| file.write_all(case.document.as_bytes()))
+            .unwrap();
+
+        let result = validate_plan_file(&path, workspace.path());
+        assert_eq!(
+            result.is_ok(),
+            case.accepts,
+            "{}: plan accept/reject changed",
+            case.id
+        );
+        let Err(error) = result else {
+            continue;
+        };
+        let error = error.to_string();
+        assert!(
+            error.contains(&format!(
+                ":{}:{}:",
+                case.line.expect("rejected case must record a line"),
+                case.column.expect("rejected case must record a column")
+            )),
+            "{}: diagnostic position lost; {error}",
+            case.id
+        );
+        let expected = case
+            .error_contains
+            .as_deref()
+            .expect("rejected case reason");
+        assert!(error.contains(expected), "{}: got {error}", case.id);
+    }
+}
+
+#[test]
+fn workflow_versions_keep_the_numeric_value_contract() {
+    let compatibility = fixture();
+    for case in &compatibility.workflow_versions {
+        let result = Workflow::parse(&case.document);
+        assert_eq!(result.is_ok(), case.accepts, "{}", case.id);
+        if let Some(expected) = &case.error_contains {
+            let error = result.expect_err("negative case must reject").to_string();
+            assert!(error.contains(expected), "{}: got {error}", case.id);
+        }
+    }
+}
+
+#[test]
+fn scrub_contract_keeps_type_and_mapping_element_count() {
+    let compatibility = fixture();
+    assert!(
+        !compatibility.scrub_cases.is_empty(),
+        "no scrub cases recorded"
+    );
+    for case in &compatibility.scrub_cases {
+        let mut catalog = SecretCatalog::new();
+        for value in &case.register_plain {
+            catalog.register_plain(value).unwrap();
+        }
+        let mut value: serde_yaml::Value = serde_yaml::from_str(&case.document)
+            .unwrap_or_else(|error| panic!("{}: {error}", case.id));
+        catalog.scrub_yaml(&mut value);
+
+        let mapping = value.as_mapping().unwrap();
+        assert_eq!(
+            mapping.len(),
+            case.mapping_len,
+            "{}: element count",
+            case.id
+        );
+
+        let serialized = serde_yaml::to_string(&value).unwrap();
+        for absent in &case.absent {
+            assert!(!serialized.contains(absent), "{}: leaked {absent}", case.id);
+        }
+        for expected in &case.serialized_contains {
+            assert!(
+                serialized.contains(expected),
+                "{}: missing {expected}; serialized={serialized}",
+                case.id
+            );
+        }
+        for (key, expected) in &case.string_value {
+            assert_eq!(
+                value[key.as_str()].as_str(),
+                Some(expected.as_str()),
+                "{}: string value {key}",
+                case.id
+            );
+        }
+        for (key, expected) in &case.number_value {
+            assert_eq!(
+                value[key.as_str()].as_i64(),
+                Some(*expected),
+                "{}: number value {key}",
+                case.id
+            );
+        }
+    }
+    assert_eq!(REDACTED, "<redacted>");
+}
+
+#[test]
+fn boundary_limits_keep_their_recorded_errors() {
+    let boundary = fixture().boundary;
+
+    let oversized = format!("#{}\n", "x".repeat(boundary.max_file_bytes + 64));
+    let error = parse_bytes(Some(oversized.as_bytes()), None)
+        .unwrap_err()
+        .to_string();
+    assert!(error.contains(&boundary.file_error), "{error}");
+
+    let mut deep = String::from("a:\n");
+    for level in 1..=boundary.max_depth + 2 {
+        deep.push_str(&" ".repeat(level * 2));
+        deep.push_str("a:\n");
+    }
+    let error = parse_bytes(Some(deep.as_bytes()), None)
+        .unwrap_err()
+        .to_string();
+    assert!(error.contains(&boundary.depth_error), "{error}");
+
+    let mut sequence = String::from("a:\n");
+    for _ in 0..boundary.max_sequence + 8 {
+        sequence.push_str("  - x\n");
+    }
+    let error = parse_bytes(Some(sequence.as_bytes()), None)
+        .unwrap_err()
+        .to_string();
+    assert!(error.contains(&boundary.sequence_error), "{error}");
+
+    let scalar = format!("a: {}\n", "x".repeat(boundary.max_scalar_bytes + 16));
+    let error = parse_bytes(Some(scalar.as_bytes()), None)
+        .unwrap_err()
+        .to_string();
+    assert!(error.contains(&boundary.scalar_error), "{error}");
+}