Constant PLAN_V3_EXAMPLE 

pub const PLAN_V3_EXAMPLE: &str = "{\n  \"schema_version\": 3,\n  \"plan_rev\": 1,\n  \"intent_rev\": 3,\n  \"feature\": {\n    \"slug\": \"user-csv-export\",\n    \"source_branch\": \"main\",\n    \"integration_branch\": \"feat/user-csv-export\"\n  },\n  \"baseline\": {\n    \"ref\": \"feat/user-csv-export@fork\",\n    \"commit_oid\": \"3f2a1b0c9d8e7f6a5b4c3d2e1f0a9b8c7d6e5f40\",\n    \"toolchain\": \"rustc 1.97.1 (abcdef012 2026-06-01)\",\n    \"test_passlist_hash\": \"sha256:0000000000000000000000000000000000000000000000000000000000000000\",\n    \"clippy_warnings_hash\": \"sha256:1111111111111111111111111111111111111111111111111111111111111111\",\n    \"enumerated_targets_hash\": \"sha256:2222222222222222222222222222222222222222222222222222222222222222\"\n  },\n  \"acceptance\": [\n    {\n      \"kind\": \"check\",\n      \"desc\": \"signed-in user downloads their own data as CSV end-to-end\",\n      \"run\": \"cargo test --test e2e account_csv_export\"\n    },\n    {\n      \"kind\": \"assertion\",\n      \"desc\": \"the CSV contains exactly the user\'s own records and nothing else\"\n    }\n  ],\n  \"chunks\": [\n    {\n      \"id\": \"c1\",\n      \"title\": \"CSV serializer for a user record\",\n      \"deps\": [],\n      \"tier\": \"code\",\n      \"brief\": \"Turnkey, self-contained implementation brief; rich enough that a cheap model needs no architectural reasoning.\",\n      \"files_touched\": [\"src/export/csv.rs\", \"src/export/csv_test.rs\"],\n      \"checks\": [\n        { \"desc\": \"round-trips a representative record\", \"run\": \"cargo test export::csv::roundtrip\" },\n        { \"desc\": \"empty + unicode fields escaped\", \"run\": \"cargo test export::csv::escaping\" }\n      ],\n      \"assertions\": [\n        \"serializer API matches how the endpoint (c2) expects to call it\"\n      ],\n      \"requires_tests\": true\n    },\n    {\n      \"id\": \"c2\",\n      \"title\": \"Account-page export endpoint\",\n      \"deps\": [\"c1\"],\n      \"tier\": \"code\",\n      \"brief\": \"\u{2026}endpoint brief, referencing c1\'s serializer interface\u{2026}\",\n      \"files_touched\": [\"src/routes/account.rs\", \"src/routes/account_test.rs\"],\n      \"checks\": [\n        { \"desc\": \"GET /account/export returns text/csv for the session user\", \"run\": \"cargo test routes::account::export_ok\" },\n        { \"desc\": \"unauthenticated \u{2192} 401\", \"run\": \"cargo test routes::account::export_authn\" }\n      ],\n      \"assertions\": [],\n      \"requires_tests\": true\n    }\n  ]\n}\n";

The checked-in canonical plan.json v3 example (plan-schema.md sample), exposed so a spec-node prompt can show the model the exact target shape.