diff --git a/.changeset/sturdy-deer-frolic.md b/.changeset/sturdy-deer-frolic.md
new file mode 100644
index 000000000..8755d9aa5
--- /dev/null
+++ b/.changeset/sturdy-deer-frolic.md
@@ -0,0 +1,5 @@
+---
+type: Added
+pr: 3920
+---
+**Exit codes are now allocated from one registry instead of invented per module** — a generated table records every non-standard exit code with its meaning, owning module and authorizing decision, and the build fails if two modules claim the same number or a code lands in a range Node or the shell reserves. Nothing emits a registered code yet; this is the allocator the following phases draw from. (#3905)
diff --git a/CONTEXT.md b/CONTEXT.md
index 1656943c8..9fa3ca190 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -520,6 +520,9 @@ An injectable time abstraction accepted as an optional parameter by production c
 ### Process seam
 The single subprocess-spawning primitive test code uses (`tests/helpers/process-seam.cjs`, #3055): `runNode` / `runGit` / `runHook`, each returning one discriminated union `{ outcome, exitCode, stdout, stderr, timedOut, signal, killed, code }` where `outcome` is the frozen `OUTCOME` enum (`EXITED` / `KILLED` / `TIMED_OUT` / `BUFFER_OVERFLOW` / `SPAWN_FAILED`). Every call is timeout-bounded — there is no unbounded code path — and nothing throws for a child's exit code, kill, timeout, buffer overflow, or spawn failure; all five are data. KILLED is a child terminated by a signal the seam did not send (a genuine OOM kill): `spawnSync` reports no `error` for that case, so it must be distinguished from EXITED, and the `runGsdTools` adapter retries it exactly as the pre-seam `isKilled()` did. This is what makes `timedOut` and `signal` assertable, so a fail-open guard's degraded verdict can be tested instead of merely observing that the call did not throw. Discrimination order is forced by runtime behavior: a timeout and a maxBuffer overflow are identical on both `status` (`null`) and `signal` (`SIGTERM`) and differ only by `code` (`ETIMEDOUT` vs `ENOBUFS`), so overflow is classified first — but that ordering assumes `status === null`, which is checked ahead of it: at the exact timeout boundary `spawnSync` can report `error.code === 'ETIMEDOUT'` on a result that ALSO carries a real `status` (the child finished on its own just as the timer fired), so `status !== null` is classified EXITED before any error-code branch runs, keeping `exitCode` coherent with the reported outcome. Per-suite wrappers remain and bind fixtures (cwd, env, payload); only the spawn body delegates here. Deliberately **not** a fault-injection surface — it cannot distinguish an injected timeout from a genuine bench OOM and would retry it; injection is in-process via `deps` (#3056). `runGsdTools` is an adapter over it that preserves its own legacy `{ success, output, error, exitCode }` shape and retry-once-on-kill behavior.
 
+### Exit Code Registry Module
+Generated central allocator for this repo's process exit codes (ADR-3889, epic #3889 — "nothing fails with success"; Phase 1, #3905). Declaration source of truth: `gsd-core/bin/shared/exit-codes.json` (append-only entries: `code`, `name`, `meaning`, `owner`, `authorizedBy`); generated artifact `gsd-core/bin/lib/exit-code-registry.cjs` (`EXIT_CODES`, `exitCodeFor(name)`, `nameForExitCode(code)`) is produced by `scripts/gen-exit-code-registry.cjs --write` and byte-guarded by `npm run lint:generated-sync` — the same declaration → generator → `--check` gate pattern as the Capability Registry, the Model Catalog, and the ADR index. Band contract (ADR-3889 §1): `0` and `1` are free and never allocatable here; `2` is reserved to the Claude Code hook-adapter protocol (owner must be `hook-adapter`); `3`-`13` are Node-reserved; `64`-`78` are the generic band; `80`-`125` are the domain band; every other value (`14`-`63`, `79`, `126`+) sits outside every band and is rejected — so every registered code is non-zero by construction. The generator also enforces one-number-one-meaning and one-name-one-code across the whole declaration. This module is the ALLOCATOR only: nothing in the generator or the generated artifact emits a registered exit code itself — wiring real call sites onto the registry is later work that does not land until #3906.
+
 ### Git fixture wrapper
 The throw-preserving companion to the process seam (`tests/helpers/git-fixture.cjs`, #3143): `gitOrThrow(args, options)` runs `runGit` and returns `stdout` as a string on a clean exit, but throws on any other outcome. It exists because the seam **deliberately never throws** while `execSync` and `execFileSync` — the two forms 237 migrating call sites use — both throw on a non-zero exit. Migrating those mechanically onto `runGit` would convert a loud failure into a silent one: fixture setup that failed would return an empty string and surface as a baffling assertion failure further down. The thrown error carries `status` **and** `exitCode` as deliberate aliases (`status` is what the legacy `execSync` catch idiom reads, e.g. `tests/worktree-safety.test.cjs:1361`), plus `stdout`, `stderr`, `signal`, `timedOut` and `outcome`. Use `runGit` when every outcome is data you branch on; use `gitOrThrow` for fixture setup that must abort loudly. The seam module is **not** modified to add this — a throwing export would falsify the never-throws contract stated in its own header and in the `### Process seam` entry above. The module also exports `throwIfFailed(result, displayName)`, the single implementation of that throw shape: `gitOrThrow` itself is `throwIfFailed` specialized to `runGit`, so it routes through the same code path and the two cannot drift apart. Per-suite wrappers driving non-git targets — a node CLI via `runNode`, a bash snippet via `runHook` — call `throwIfFailed` directly rather than hand-rolling their own copy of this shape, which is exactly how five call sites had drifted from each other before this module exported it (#3144). It also exports `toLegacyResult(result)`, the non-throwing counterpart: a bare mapping onto the legacy `{ status, stdout, stderr }` shape (`status` aliasing the seam's `exitCode`) for call sites that already branch on exit status as data rather than wanting a throw — ~8 test files hand-rolled that identical three-line mapping before this module exported it too (#3147). Callers needing an extra field beyond that shape (e.g. a parsed-JSON body, a fixture-specific path) compose it — `{ ...toLegacyResult(result), extra }` — rather than folding the extra behavior into the shared helper.
 
diff --git a/docs/INVENTORY-MANIFEST.json b/docs/INVENTORY-MANIFEST.json
index 37dabf830..0af02c692 100644
--- a/docs/INVENTORY-MANIFEST.json
+++ b/docs/INVENTORY-MANIFEST.json
@@ -371,6 +371,7 @@
       "estimate-cli.cjs",
       "eval-command-router.cjs",
       "eval.cjs",
+      "exit-code-registry.cjs",
       "external-descriptor-trust.cjs",
       "external-job.cjs",
       "fallow-runner.cjs",
diff --git a/docs/INVENTORY.md b/docs/INVENTORY.md
index e20e1fe45..6521c8107 100644
--- a/docs/INVENTORY.md
+++ b/docs/INVENTORY.md
@@ -519,6 +519,7 @@ Full listing: `gsd-core/bin/lib/*.cjs`.
 | `eval-command-router.cjs` | Routes the `eval.score` verb (compiled from `src/eval-command-router.cts`, gitignored) — thin dispatcher into the eval scoring module (#1579) |
 | `eval.cjs` | Deterministic eval scoring (compiled from `src/eval.cts`, gitignored) — `computeEvalScore` (coverage*0.6 + infra*0.4, bands 80/60/40) + `cmdEvalScore` CLI domain guard; moves the gsd-eval-auditor's weighted arithmetic out of the prompt into code (#10 / #1579) |
 | `estimate-cli.cjs` | I/O seam over `phase-estimation.cjs` — the `estimate-check` and `estimate-calibration` query verbs; reads the `workflow.smart_zone_tokens` budget and `.planning/estimation-calibration.json`, both degrading to defaults rather than failing planning (#2630) |
+| `exit-code-registry.cjs` | Generated exit-code allocator — one number, one meaning table of registered process exit codes (band rules: `2` hook-adapter only, `64`-`78` generic, `80`-`125` domain); emitted by `scripts/gen-exit-code-registry.cjs --write` (ADR-3889 §1/§2); exports `EXIT_CODES` and the pure, total `exitCodeFor`/`nameForExitCode` |
 | `observability/event.cjs` | DispatchEvent shape factory for every Hub dispatch — traceId/parentTraceId/command/result/timestamp record consumed by DispatchLogger (#177, ADR-0174 P1.3/P1.4) |
 | `external-descriptor-trust.cjs` | Defense-in-depth path-containment check for third-party plugin descriptors (#1681) |
 | `external-job.cjs` | Produces scheduler manifests for asynchronous external jobs; SLURM is the first backend (#1164) |
diff --git a/gsd-core/bin/lib/exit-code-registry.cjs b/gsd-core/bin/lib/exit-code-registry.cjs
new file mode 100644
index 000000000..b0247b193
--- /dev/null
+++ b/gsd-core/bin/lib/exit-code-registry.cjs
@@ -0,0 +1,87 @@
+'use strict';
+
+// GENERATED FILE — DO NOT EDIT BY HAND.
+// Source of truth: gsd-core/bin/shared/exit-codes.json. Regenerate with:
+//   node scripts/gen-exit-code-registry.cjs --write
+// Byte-compared by `npm run lint:generated-sync` (#3905, ADR-3889 Phase 1).
+//
+// exitCodeFor(name) / nameForExitCode(code) are pure and total over this
+// closed table — each throws for anything not registered here.
+
+const EXIT_CODES = Object.freeze([
+  Object.freeze({
+    code: 2,
+    name: "HOOK_DENY",
+    meaning: "Claude Code hook protocol — deny the tool call",
+    owner: "hook-adapter",
+    authorizedBy: "ADR-3889",
+  }),
+  Object.freeze({
+    code: 64,
+    name: "USAGE",
+    meaning: "Caller error — bad argv, unknown subcommand, missing argument",
+    owner: "generic",
+    authorizedBy: "ADR-3889",
+  }),
+  Object.freeze({
+    code: 66,
+    name: "NO_INPUT",
+    meaning: "Ran; zero units were in scope, and that emptiness is known to be genuine",
+    owner: "generic",
+    authorizedBy: "ADR-3889",
+  }),
+  Object.freeze({
+    code: 69,
+    name: "UNAVAILABLE",
+    meaning: "Could not run — prerequisite absent, input unreadable, scope unestablished",
+    owner: "generic",
+    authorizedBy: "ADR-3889",
+  }),
+  Object.freeze({
+    code: 70,
+    name: "INTERNAL",
+    meaning: "Self-failure — crash, timeout, killed subprocess",
+    owner: "generic",
+    authorizedBy: "ADR-3889",
+  })
+]);
+
+const NAME_TO_CODE = new Map(EXIT_CODES.map((entry) => [entry.name, entry.code]));
+const CODE_TO_NAME = new Map(EXIT_CODES.map((entry) => [entry.code, entry.name]));
+
+/**
+ * Resolve the registered exit code for a symbolic name. Pure, total: throws
+ * for anything not an exact, registered, exact-case key — including
+ * non-strings, the empty string, untrimmed strings, wrong case, and
+ * prototype-chain names like `__proto__`/`constructor`/`toString` (a Map
+ * lookup never touches the prototype chain, so these are indistinguishable
+ * from any other unregistered name).
+ *
+ * @param {string} name
+ * @returns {number}
+ */
+function exitCodeFor(name) {
+  if (typeof name !== 'string' || name.length === 0) {
+    throw new Error(`exitCodeFor: name must be a non-empty string, received ${JSON.stringify(name)}`);
+  }
+  if (!NAME_TO_CODE.has(name)) {
+    throw new Error(`exitCodeFor: unregistered exit code name: ${JSON.stringify(name)}`);
+  }
+  return NAME_TO_CODE.get(name);
+}
+
+/**
+ * Reverse of exitCodeFor: resolve the symbolic name for a registered exit
+ * code. Pure, total: throws for anything not an exact, registered code.
+ *
+ * @param {number} code
+ * @returns {string}
+ */
+function nameForExitCode(code) {
+  if (!CODE_TO_NAME.has(code)) {
+    throw new Error(`nameForExitCode: unregistered exit code: ${JSON.stringify(code)}`);
+  }
+  return CODE_TO_NAME.get(code);
+}
+
+module.exports = { EXIT_CODES, exitCodeFor, nameForExitCode };
diff --git a/gsd-core/bin/shared/exit-codes.json b/gsd-core/bin/shared/exit-codes.json
new file mode 100644
index 000000000..279fe4dff
--- /dev/null
+++ b/gsd-core/bin/shared/exit-codes.json
@@ -0,0 +1,7 @@
+[
+  { "code": 2,  "name": "HOOK_DENY",   "meaning": "Claude Code hook protocol — deny the tool call", "owner": "hook-adapter", "authorizedBy": "ADR-3889" },
+  { "code": 64, "name": "USAGE",       "meaning": "Caller error — bad argv, unknown subcommand, missing argument", "owner": "generic", "authorizedBy": "ADR-3889" },
+  { "code": 66, "name": "NO_INPUT",    "meaning": "Ran; zero units were in scope, and that emptiness is known to be genuine", "owner": "generic", "authorizedBy": "ADR-3889" },
+  { "code": 69, "name": "UNAVAILABLE", "meaning": "Could not run — prerequisite absent, input unreadable, scope unestablished", "owner": "generic", "authorizedBy": "ADR-3889" },
+  { "code": 70, "name": "INTERNAL",    "meaning": "Self-failure — crash, timeout, killed subprocess", "owner": "generic", "authorizedBy": "ADR-3889" }
+]
diff --git a/package.json b/package.json
index 67f41bc96..635b5a8c4 100644
--- a/package.json
+++ b/package.json
@@ -108,7 +108,7 @@
     "gen:registry": "node scripts/gen-registry.cjs --write",
     "gen:install-tree": "node scripts/gen-install-tree-fixtures.cjs",
     "gen:section-manifest": "node scripts/gen-section-manifest.cjs --write",
-    "regen:derived": "npm run build && npm run gen:registry && node scripts/gen-adr-index.cjs --write && node scripts/gen-features.cjs --write && node scripts/gen-capability-matrix.cjs --write && node scripts/gen-inventory-manifest.cjs --write && node scripts/gen-context-index.cjs --write && node scripts/gen-state-md-docs.cjs --write && npm run gen:section-manifest && node scripts/sync-manifest-versions.cjs && npm run gen:install-tree && node scripts/gen-scripts-cli-exit.cjs --write",
+    "regen:derived": "npm run build && npm run gen:registry && node scripts/gen-adr-index.cjs --write && node scripts/gen-features.cjs --write && node scripts/gen-capability-matrix.cjs --write && node scripts/gen-inventory-manifest.cjs --write && node scripts/gen-context-index.cjs --write && node scripts/gen-state-md-docs.cjs --write && npm run gen:section-manifest && node scripts/sync-manifest-versions.cjs && npm run gen:install-tree && node scripts/gen-scripts-cli-exit.cjs --write && node scripts/gen-exit-code-registry.cjs --write",
     "validate:registry": "node scripts/validate-registry.cjs",
     "prepack": "npm run build:lib",
     "prepare": "npm run build:lib",
@@ -129,7 +129,7 @@
     "lint:test-file-count": "node scripts/lint-test-file-count.cjs",
     "lint:pr-checks": "node scripts/lint-pr-check-project-dir.cjs",
     "lint:changeset": "node scripts/changeset/lint.cjs",
-    "lint:generated-sync": "node scripts/gen-capability-registry.cjs --check && node scripts/gen-loop-host-contract.cjs --check && node scripts/gen-capability-matrix.cjs --check && node scripts/sync-manifest-versions.cjs --check && node scripts/gen-inventory-manifest.cjs --check && node scripts/generate-package-identity.cjs --check && node scripts/gen-plugin-skills.cjs --check && node scripts/gen-registry.cjs --check && node scripts/gen-adr-index.cjs --check && node scripts/gen-features.cjs --check && node scripts/check-glossary-refs.cjs --check && node scripts/lint-compiled-artifact-sync.cjs --check && node scripts/gen-context-index.cjs --check && node scripts/gen-section-manifest.cjs --check && node scripts/gen-health-docs.cjs --check && node scripts/gen-state-md-docs.cjs --check && node scripts/gen-scripts-cli-exit.cjs --check",
+    "lint:generated-sync": "node scripts/gen-capability-registry.cjs --check && node scripts/gen-loop-host-contract.cjs --check && node scripts/gen-capability-matrix.cjs --check && node scripts/sync-manifest-versions.cjs --check && node scripts/gen-inventory-manifest.cjs --check && node scripts/generate-package-identity.cjs --check && node scripts/gen-plugin-skills.cjs --check && node scripts/gen-registry.cjs --check && node scripts/gen-adr-index.cjs --check && node scripts/gen-features.cjs --check && node scripts/check-glossary-refs.cjs --check && node scripts/lint-compiled-artifact-sync.cjs --check && node scripts/gen-context-index.cjs --check && node scripts/gen-section-manifest.cjs --check && node scripts/gen-health-docs.cjs --check && node scripts/gen-state-md-docs.cjs --check && node scripts/gen-scripts-cli-exit.cjs --check && node scripts/gen-exit-code-registry.cjs --check",
     "lint:docs": "node scripts/lint-docs-required.cjs",
     "lint:qa-smells": "node scripts/qa-smell-ratchet.cjs",
     "lint:legacy-name": "node scripts/lint-legacy-dir-name.cjs",
diff --git a/scripts/gen-exit-code-registry.cjs b/scripts/gen-exit-code-registry.cjs
new file mode 100644
index 000000000..c3c2cdfc0
--- /dev/null
+++ b/scripts/gen-exit-code-registry.cjs
@@ -0,0 +1,519 @@
+#!/usr/bin/env node
+/**
+ * gen-exit-code-registry.cjs — generates gsd-core/bin/lib/exit-code-registry.cjs
+ * from the declaration at gsd-core/bin/shared/exit-codes.json.
+ *
+ * ADR-3889 ("One exit-code registry — 0 and 1 are free, everything else is
+ * allocated") Phase 1 (#3905): this script builds the ALLOCATOR. It owns
+ * validating the declaration (band rules, one-number-one-meaning, one-owner)
+ * and hand-serializing the generated lookup module — the same
+ * declaration -> generator -> `--check` gate pattern this repo already uses
+ * for capability-registry.cjs, the model catalog, and the ADR index.
+ *
+ * Nothing in this script emits a registered exit code itself; wiring
+ * consumers onto the registry is a later phase (#3906).
+ *
+ * Usage:
+ *   node scripts/gen-exit-code-registry.cjs                # same as --write
+ *   node scripts/gen-exit-code-registry.cjs --write         # write the artifact
+ *   node scripts/gen-exit-code-registry.cjs --check         # exit 1 if the committed artifact is stale
+ *   node scripts/gen-exit-code-registry.cjs --declaration <path> --out <path>   # override for tests
+ *   node scripts/gen-exit-code-registry.cjs --json          # emit ONE JSON report on stdout instead of human prose
+ */
+
+'use strict';
+
+const fs = require('node:fs');
+const path = require('node:path');
+
+const REPO_ROOT = path.resolve(__dirname, '..');
+const DEFAULT_DECLARATION_PATH = path.join(REPO_ROOT, 'gsd-core', 'bin', 'shared', 'exit-codes.json');
+const DEFAULT_OUTPUT_PATH = path.join(REPO_ROOT, 'gsd-core', 'bin', 'lib', 'exit-code-registry.cjs');
+
+/** Frozen reason codes so tests assert on structure, not prose. */
+const REASON = Object.freeze({
+  OK: 'ok_generated_sync',
+  DRIFTED: 'fail_generated_drifted',
+  USAGE: 'fail_usage',
+  MISSING_DECLARATION: 'fail_missing_declaration',
+  MALFORMED_DECLARATION: 'fail_malformed_declaration',
+  NOT_AN_ARRAY: 'fail_not_an_array',
+  EMPTY_DECLARATION: 'fail_empty_declaration',
+  INVALID_ENTRY: 'fail_invalid_entry',
+  DUPLICATE_CODE: 'fail_duplicate_code',
+  DUPLICATE_NAME: 'fail_duplicate_name',
+  RESERVED_CODE: 'fail_reserved_code',
+  FORBIDDEN_OWNER: 'fail_forbidden_owner',
+  MISSING_ARTIFACT: 'fail_missing_artifact',
+});
+
+const USAGE_MESSAGE = [
+  'Usage: node scripts/gen-exit-code-registry.cjs [--write|--check] [--declaration <path>] [--out <path>] [--json]',
+  '  (no flag)        same as --write',
+  '  --write          write the generated registry artifact',
+  '  --check          exit 1 if the committed artifact is stale',
+  '  --declaration    override the declaration path (default: gsd-core/bin/shared/exit-codes.json)',
+  '  --out            override the output artifact path (default: gsd-core/bin/lib/exit-code-registry.cjs)',
+  '  --json           emit ONE JSON report ({ok, reason, context, detail?}) on stdout instead of human-readable prose',
+].join('\n');
+
+/** SCREAMING_SNAKE_CASE: starts with a letter, only uppercase letters/digits/underscores. */
+const NAME_RE = /^[A-Z][A-Z0-9_]*$/;
+
+/** Fields every entry must carry as a non-empty, non-whitespace-only string. */
+const REQUIRED_STRING_FIELDS = ['meaning', 'owner', 'authorizedBy'];
+
+/**
+ * Bands, per ADR-3889 §1:
+ *   0, 1                 free (not allocatable here)
+ *   2                     hook-adapter only
+ *   3-13                  Node-reserved
+ *   14-63, 79, 126+        outside every band
+ *   64-78                 generic
+ *   80-125                domain
+ */
+function isAllocatableCode(code) {
+  if (code === 2) return true;
+  if (code >= 64 && code <= 78) return true;
+  if (code >= 80 && code <= 125) return true;
+  return false;
+}
+
+/**
+ * Label the non-allocatable band a rejected code falls into, per the same
+ * range boundaries documented on isAllocatableCode/ADR-3889 §1. Only called
+ * for codes that already failed isAllocatableCode, so 2 and 64-125 never
+ * reach here.
+ * @returns {string}
+ */
+function bandFor(code) {
+  if (code === 0 || code === 1) return 'free';
+  if (code >= 3 && code <= 13) return 'node-reserved';
+  if (code >= 126) return 'shell-signal';
+  return 'outside-every-band'; // 14-63, 79
+}
+
+/**
+ * Validate a single declaration entry's shape and band membership.
+ * @returns {{ok:true}|{ok:false,reason:string,message:string,context:object}}
+ */
+function validateEntry(entry, index) {
+  if (typeof entry !== 'object' || entry === null || Array.isArray(entry)) {
+    return {
+      ok: false,
+      reason: REASON.INVALID_ENTRY,
+      message: `entry[${index}] is not an object: ${JSON.stringify(entry)}`,
+      context: { field: 'entry', index },
+    };
+  }
+
+  const { code, name } = entry;
+  if (!Number.isInteger(code) || code < 0) {
+    return {
+      ok: false,
+      reason: REASON.INVALID_ENTRY,
+      message: `entry[${index}].code must be a non-negative integer (no coercion), received ${JSON.stringify(code)}`,
+      context: { field: 'code', index, code },
+    };
+  }
+
+  if (typeof name !== 'string' || name.trim() === '' || !NAME_RE.test(name)) {
+    return {
+      ok: false,
+      reason: REASON.INVALID_ENTRY,
+      message: `entry[${index}].name must be a non-empty SCREAMING_SNAKE_CASE string, received ${JSON.stringify(name)}`,
+      context: { field: 'name', index, code, name },
+    };
+  }
+
+  for (const field of REQUIRED_STRING_FIELDS) {
+    const value = entry[field];
+    if (typeof value !== 'string' || value.trim() === '') {
+      return {
+        ok: false,
+        reason: REASON.INVALID_ENTRY,
+        message: `entry[${index}] (${name}).${field} must be a non-empty string, received ${JSON.stringify(value)}`,
+        context: { field, index, code, name },
+      };
+    }
+  }
+
+  if (!isAllocatableCode(code)) {
+    return {
+      ok: false,
+      reason: REASON.RESERVED_CODE,
+      message: `entry[${index}] (${name}) declares code ${code}, which is outside every allocatable band ` +
+        `(2 hook-adapter only; 64-78 generic; 80-125 domain) — see ADR-3889 §1`,
+      context: { code, band: bandFor(code), index, name },
+    };
+  }
+
+  if (code === 2 && entry.owner !== 'hook-adapter') {
+    return {
+      ok: false,
+      reason: REASON.FORBIDDEN_OWNER,
+      message: `entry[${index}] (${name}) declares code 2 with owner "${entry.owner}" — code 2 is reserved to ` +
+        `the Claude Code hook protocol and may only be owned by "hook-adapter"`,
+      context: { code, owner: entry.owner, requiredOwner: 'hook-adapter', index, name },
+    };
+  }
+
+  return { ok: true };
+}
+
+/**
+ * Validate the whole declaration: every entry individually, then the
+ * cross-entry invariants (one number one meaning; one owner emits a given
+ * code — but the SAME owner may legitimately own several distinct codes).
+ * @returns {{ok:true}|{ok:false,reason:string,message:string,context:object}}
+ */
+function validateEntries(entries) {
+  for (let i = 0; i < entries.length; i++) {
+    const result = validateEntry(entries[i], i);
+    if (!result.ok) return result;
+  }
+
+  const byCode = new Map();
+  const byName = new Map();
+  for (const entry of entries) {
+    if (byCode.has(entry.code)) {
+      const other = byCode.get(entry.code);
+      return {
+        ok: false,
+        reason: REASON.DUPLICATE_CODE,
+        message: `code ${entry.code} is declared twice: "${other.name}" and "${entry.name}"`,
+        context: { code: entry.code, names: [other.name, entry.name] },
+      };
+    }
+    byCode.set(entry.code, entry);
+
+    if (byName.has(entry.name)) {
+      const other = byName.get(entry.name);
+      return {
+        ok: false,
+        reason: REASON.DUPLICATE_NAME,
+        message: `name "${entry.name}" is declared twice: code ${other.code} and code ${entry.code}`,
+        context: { name: entry.name, codes: [other.code, entry.code] },
+      };
+    }
+    byName.set(entry.name, entry);
+  }
+
+  return { ok: true };
+}
+
+/**
+ * Load and parse the declaration file.
+ * @returns {{ok:true,entries:Array}|{ok:false,reason:string,message:string}}
+ */
+function loadDeclaration(declarationPath) {
+  if (!fs.existsSync(declarationPath)) {
+    return {
+      ok: false,
+      reason: REASON.MISSING_DECLARATION,
+      message: `declaration not found at ${declarationPath}`,
+      context: { path: declarationPath },
+    };
+  }
+
+  let raw;
+  try {
+    raw = fs.readFileSync(declarationPath, 'utf8');
+  } catch (err) {
+    return {
+      ok: false,
+      reason: REASON.MISSING_DECLARATION,
+      message: `could not read ${declarationPath}: ${err.message}`,
+      context: { path: declarationPath },
+    };
+  }
+
+  let parsed;
+  try {
+    parsed = JSON.parse(raw);
+  } catch (err) {
+    return {
+      ok: false,
+      reason: REASON.MALFORMED_DECLARATION,
+      message: `${declarationPath} is not valid JSON: ${err.message}`,
+      context: { path: declarationPath },
+    };
+  }
+
+  if (!Array.isArray(parsed)) {
+    return {
+      ok: false,
+      reason: REASON.NOT_AN_ARRAY,
+      message: `${declarationPath} must be a JSON array, received ${parsed === null ? 'null' : typeof parsed}`,
+      context: { path: declarationPath },
+    };
+  }
+
+  if (parsed.length === 0) {
+    return {
+      ok: false,
+      reason: REASON.EMPTY_DECLARATION,
+      message: `${declarationPath} is an empty array — declare at least one exit code`,
+      context: { path: declarationPath },
+    };
+  }
+
+  return { ok: true, entries: parsed };
+}
+
+/**
+ * Hand-serialize the generated registry module (string concatenation, like
+ * gsd-core/bin/lib/capability-registry.cjs — no build step, no template
+ * engine, so the emitted bytes are exactly what `--check` re-derives).
+ */
+function serializeRegistry(entries, declarationPath) {
+  const relDeclaration = path.relative(REPO_ROOT, declarationPath).split(path.sep).join('/');
+  const banner = [
+    '\'use strict\';',
+    '',
+    '// GENERATED FILE — DO NOT EDIT BY HAND.',
+    `// Source of truth: ${relDeclaration}. Regenerate with:`,
+    '//   node scripts/gen-exit-code-registry.cjs --write',
+    '// Byte-compared by `npm run lint:generated-sync` (#3905, ADR-3889 Phase 1).',
+    '//',
+    '// exitCodeFor(name) / nameForExitCode(code) are pure and total over this',
+    '// closed table — each throws for anything not registered here.',
+    '',
+  ].join('\n');
+
+  const entryLiterals = entries.map((e) => {
+    return '  Object.freeze({\n'
+      + `    code: ${JSON.stringify(e.code)},\n`
+      + `    name: ${JSON.stringify(e.name)},\n`
+      + `    meaning: ${JSON.stringify(e.meaning)},\n`
+      + `    owner: ${JSON.stringify(e.owner)},\n`
+      + `    authorizedBy: ${JSON.stringify(e.authorizedBy)},\n`
+      + '  })';
+  }).join(',\n');
+
+  const body = [
+    'const EXIT_CODES = Object.freeze([',
+    entryLiterals,
+    ']);',
+    '',
+    'const NAME_TO_CODE = new Map(EXIT_CODES.map((entry) => [entry.name, entry.code]));',
+    'const CODE_TO_NAME = new Map(EXIT_CODES.map((entry) => [entry.code, entry.name]));',
+    '',
+    '/**',
+    ' * Resolve the registered exit code for a symbolic name. Pure, total: throws',
+    ' * for anything not an exact, registered, exact-case key — including',
+    ' * non-strings, the empty string, untrimmed strings, wrong case, and',
+    ' * prototype-chain names like `__proto__`/`constructor`/`toString` (a Map',
+    ' * lookup never touches the prototype chain, so these are indistinguishable',
+    ' * from any other unregistered name).',
+    ' *',
+    ' * @param {string} name',
+    ' * @returns {number}',
+    ' */',
+    'function exitCodeFor(name) {',
+    '  if (typeof name !== \'string\' || name.length === 0) {',
+    '    throw new Error(`exitCodeFor: name must be a non-empty string, received ${JSON.stringify(name)}`);',
+    '  }',
+    '  if (!NAME_TO_CODE.has(name)) {',
+    '    throw new Error(`exitCodeFor: unregistered exit code name: ${JSON.stringify(name)}`);',
+    '  }',
+    '  return NAME_TO_CODE.get(name);',
+    '}',
+    '',
+    '/**',
+    ' * Reverse of exitCodeFor: resolve the symbolic name for a registered exit',
+    ' * code. Pure, total: throws for anything not an exact, registered code.',
+    ' *',
+    ' * @param {number} code',
+    ' * @returns {string}',
+    ' */',
+    'function nameForExitCode(code) {',
+    '  if (!CODE_TO_NAME.has(code)) {',
+    '    throw new Error(`nameForExitCode: unregistered exit code: ${JSON.stringify(code)}`);',
+    '  }',
+    '  return CODE_TO_NAME.get(code);',
+    '}',
+    '',
+    'module.exports = { EXIT_CODES, exitCodeFor, nameForExitCode };',
+    '',
+  ].join('\n');
+
+  return banner + '\n' + body;
+}
+
+/**
+ * Load, validate, and serialize the declaration in one step.
+ * @returns {{ok:true,content:string}|{ok:false,reason:string,message:string}}
+ */
+function buildRegistryContent(declarationPath) {
+  const loaded = loadDeclaration(declarationPath);
+  if (!loaded.ok) return loaded;
+
+  const validated = validateEntries(loaded.entries);
+  if (!validated.ok) return validated;
+
+  return { ok: true, content: serializeRegistry(loaded.entries, declarationPath) };
+}
+
+function printFail(result) {
+  console.error(`FAIL gen-exit-code-registry: ${result.reason}`);
+  console.error(`  ${result.message}`);
+}
+
+/**
+ * Emit a failure outcome: structured JSON on stdout (and NO stderr prose)
+ * when `json` is set, otherwise the legacy human-readable stderr report.
+ * `context` carries the specifics (offending code/name/field/path) that the
+ * `detail` prose currently embeds, so a `--json` consumer never needs to
+ * parse prose to recover them — it defaults to `null` for reasons (USAGE,
+ * DRIFTED, MISSING_ARTIFACT) that carry no structured specifics.
+ * @param {{reason:string, message?:string, context?:object}} result
+ * @param {boolean} json
+ */
+function emitFail(result, json) {
+  if (json) {
+    process.stdout.write(JSON.stringify({ ok: false, reason: result.reason, context: result.context ?? null, detail: result.message }) + '\n');
+    return;
+  }
+  printFail(result);
+}
+
+/**
+ * Emit a success outcome: structured JSON on stdout when `json` is set,
+ * otherwise the legacy human-readable stdout line.
+ * @param {string} reason
+ * @param {string} humanMessage
+ * @param {boolean} json
+ */
+function emitOk(reason, humanMessage, json) {
+  if (json) {
+    process.stdout.write(JSON.stringify({ ok: true, reason }) + '\n');
+    return;
+  }
+  console.log(humanMessage);
+}
+
+function doWrite(declarationPath, outPath, json) {
+  const result = buildRegistryContent(declarationPath);
+  if (!result.ok) {
+    emitFail(result, json);
+    return 1;
+  }
+  fs.mkdirSync(path.dirname(outPath), { recursive: true });
+  fs.writeFileSync(outPath, result.content, 'utf8');
+  emitOk(REASON.OK, `ok gen-exit-code-registry: wrote ${outPath}`, json);
+  return 0;
+}
+
+function doCheck(declarationPath, outPath, json) {
+  const result = buildRegistryContent(declarationPath);
+  if (!result.ok) {
+    emitFail(result, json);
+    return 1;
+  }
+
+  if (!fs.existsSync(outPath)) {
+    emitFail(
+      {
+        reason: REASON.MISSING_ARTIFACT,
+        message: `${outPath} does not exist. Run:\n  node scripts/gen-exit-code-registry.cjs --write`,
+      },
+      json,
+    );
+    return 1;
+  }
+
+  const committed = fs.readFileSync(outPath, 'utf8');
+  if (committed !== result.content) {
+    emitFail(
+      {
+        reason: REASON.DRIFTED,
+        message:
+          `${outPath} (${committed.length} bytes) != freshly generated content (${result.content.length} bytes)\n\n`
+          + 'Regenerate with:\n  node scripts/gen-exit-code-registry.cjs --write',
+      },
+      json,
+    );
+    return 1;
+  }
+
+  emitOk(REASON.OK, `ok gen-exit-code-registry: ${outPath} matches ${declarationPath}`, json);
+  return 0;
+}
+
+/**
+ * @returns {{mode:'write'|'check', declarationPath:?string, outPath:?string, json:boolean}}
+ */
+function parseArgs(argv) {
+  let mode = null;
+  let declarationPath = null;
+  let outPath = null;
+  let json = false;
+
+  for (let i = 0; i < argv.length; i++) {
+    const arg = argv[i];
+    if (arg === '--write' || arg === '--check') {
+      if (mode !== null) {
+        throw new Error(`conflicting mode flags: --${mode} and ${arg}`);
+      }
+      mode = arg === '--write' ? 'write' : 'check';
+    } else if (arg === '--json') {
+      json = true;
+    } else if (arg === '--declaration') {
+      const value = argv[++i];
+      if (value === undefined) throw new Error('--declaration requires a value');
+      declarationPath = value;
+    } else if (arg.startsWith('--declaration=')) {
+      declarationPath = arg.slice('--declaration='.length);
+    } else if (arg === '--out') {
+      const value = argv[++i];
+      if (value === undefined) throw new Error('--out requires a value');
+      outPath = value;
+    } else if (arg.startsWith('--out=')) {
+      outPath = arg.slice('--out='.length);
+    } else {
+      throw new Error(`unrecognized argument: ${arg}`);
+    }
+  }
+
+  return { mode: mode || 'write', declarationPath, outPath, json };
+}
+
+function main() {
+  // --json must be honored even on a parse failure (e.g. an unrecognized
+  // flag alongside --json), so it is detected from the raw argv rather
+  // than from parseArgs's return value, which may never be produced.
+  const rawArgv = process.argv.slice(2);
+  const jsonRequested = rawArgv.includes('--json');
+
+  let args;
+  try {
+    args = parseArgs(rawArgv);
+  } catch (err) {
+    emitFail({ reason: REASON.USAGE, message: jsonRequested ? err.message : `${err.message}\n${USAGE_MESSAGE}` }, jsonRequested);
+    return 1;
+  }
+
+  const declarationPath = args.declarationPath || DEFAULT_DECLARATION_PATH;
+  const outPath = args.outPath || DEFAULT_OUTPUT_PATH;
+
+  return args.mode === 'check' ? doCheck(declarationPath, outPath, args.json) : doWrite(declarationPath, outPath, args.json);
+}
+
+if (require.main === module) process.exitCode = main();
+
+module.exports = {
+  REASON,
+  USAGE_MESSAGE,
+  DEFAULT_DECLARATION_PATH,
+  DEFAULT_OUTPUT_PATH,
+  isAllocatableCode,
+  bandFor,
+  validateEntry,
+  validateEntries,
+  loadDeclaration,
+  serializeRegistry,
+  buildRegistryContent,
+  parseArgs,
+  main,
+};
diff --git a/tests/exit-code-registry.test.cjs b/tests/exit-code-registry.test.cjs
new file mode 100644
index 000000000..d5a408631
--- /dev/null
+++ b/tests/exit-code-registry.test.cjs
@@ -0,0 +1,606 @@
+'use strict';
+
+/**
+ * tests/exit-code-registry.test.cjs
+ *
+ * ADR-3889 ("One exit-code registry — 0 and 1 are free, everything else is
+ * allocated") Phase 1 (#3905): behavioral tests for the allocator —
+ * gsd-core/bin/shared/exit-codes.json (declaration), scripts/gen-exit-code-registry.cjs
+ * (generator + validator), and the generated gsd-core/bin/lib/exit-code-registry.cjs
+ * artifact (`EXIT_CODES`, `exitCodeFor`, `nameForExitCode`).
+ *
+ * Every test that needs a mutated declaration or artifact operates on a
+ * temp-dir copy driven via --declaration/--out — the real repo files under
+ * gsd-core/bin/shared and gsd-core/bin/lib are never mutated, since test
+ * files in this repo run in parallel.
+ *
+ * fast-check is confirmed present in package.json devDependencies (^4.8.0);
+ * property tests below pin { seed: 2704, numRuns: 200 } per-call so a
+ * failure replays deterministically regardless of this suite's global fc
+ * default.
+ */
+
+const { test, describe, before, after } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const { runNode } = require('./helpers/process-seam.cjs');
+const { createTempDir, cleanup } = require('./helpers.cjs');
+const { PROBE_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
+const fc = require('./helpers/fast-check-setup.cjs');
+
+const REPO_ROOT = path.resolve(__dirname, '..');
+const GEN_SCRIPT = path.join(REPO_ROOT, 'scripts', 'gen-exit-code-registry.cjs');
+const REAL_DECLARATION_PATH = path.join(REPO_ROOT, 'gsd-core', 'bin', 'shared', 'exit-codes.json');
+const REAL_ARTIFACT_PATH = path.join(REPO_ROOT, 'gsd-core', 'bin', 'lib', 'exit-code-registry.cjs');
+
+const generator = require(GEN_SCRIPT);
+const registry = require(REAL_ARTIFACT_PATH);
+
+const REGISTERED_NAMES = new Set(registry.EXIT_CODES.map((e) => e.name));
+
+/** A minimal, otherwise-valid entry template, overridable per field. */
+function makeEntry(overrides) {
+  return {
+    code: 64,
+    name: 'T_ENTRY',
+    meaning: 'a test meaning',
+    owner: 'generic',
+    authorizedBy: 'ADR-3889',
+    ...overrides,
+  };
+}
+
+function runGen(args, opts = {}) {
+  return runNode([GEN_SCRIPT, ...args], { timeoutMs: PROBE_TIMEOUT_MS, ...opts });
+}
+
+/**
+ * Run the generator CLI with `--json` and parse its single stdout JSON
+ * report. Per CONTRIBUTING.md's "Prohibited: Raw Text Matching on Test
+ * Outputs", CLI-subprocess assertions in this suite key off this structured
+ * `{ok, reason, context, detail?}` report — never a regex against human-readable
+ * stdout/stderr prose.
+ * @returns {{result: object, report: {ok:boolean, reason:string, detail?:string}}}
+ */
+function runGenJson(args, opts = {}) {
+  const result = runGen(['--json', ...args], opts);
+  let report;
+  try {
+    report = JSON.parse(result.stdout);
+  } catch (err) {
+    throw new Error(`runGenJson: stdout did not parse as JSON: ${err.message}\nstdout: ${result.stdout}\nstderr: ${result.stderr}`);
+  }
+  return { result, report };
+}
+
+// ── exitCodeFor / nameForExitCode ─────────────────────────────────────────────
+describe('exit-code-registry: exitCodeFor', () => {
+  test('resolves each of the 5 registered names to its code', () => {
+    assert.equal(registry.exitCodeFor('HOOK_DENY'), 2);
+    assert.equal(registry.exitCodeFor('USAGE'), 64);
+    assert.equal(registry.exitCodeFor('NO_INPUT'), 66);
+    assert.equal(registry.exitCodeFor('UNAVAILABLE'), 69);
+    assert.equal(registry.exitCodeFor('INTERNAL'), 70);
+  });
+
+  const badNames = [
+    ['unknown name', 'NOT_A_REAL_NAME'],
+    ['empty string', ''],
+    ['null', null],
+    ['undefined', undefined],
+    ['number 0', 0],
+    ['plain object', {}],
+    ['array', []],
+    ['wrong case', 'usage'],
+    ['untrimmed', ' USAGE '],
+    ['__proto__', '__proto__'],
+    ['constructor', 'constructor'],
+    ['toString', 'toString'],
+  ];
+  for (const [label, value] of badNames) {
+    test(`throws for ${label}`, () => {
+      assert.throws(() => registry.exitCodeFor(value));
+    });
+  }
+});
+
+describe('exit-code-registry: nameForExitCode', () => {
+  test('resolves each of the 5 registered codes to its name', () => {
+    assert.equal(registry.nameForExitCode(2), 'HOOK_DENY');
+    assert.equal(registry.nameForExitCode(64), 'USAGE');
+    assert.equal(registry.nameForExitCode(66), 'NO_INPUT');
+    assert.equal(registry.nameForExitCode(69), 'UNAVAILABLE');
+    assert.equal(registry.nameForExitCode(70), 'INTERNAL');
+  });
+
+  const badCodes = [
+    ['unregistered code', 999],
+    ['0 (free, unregistered)', 0],
+    ['1 (free, unregistered)', 1],
+    ['negative', -1],
+    ['string', '64'],
+    ['null', null],
+    ['undefined', undefined],
+  ];
+  for (const [label, value] of badCodes) {
+    test(`throws for ${label}`, () => {
+      assert.throws(() => registry.nameForExitCode(value));
+    });
+  }
+});
+
+describe('exit-code-registry: shipped table invariants', () => {
+  test('EXIT_CODES is frozen and every entry is frozen', () => {
+    assert.ok(Object.isFrozen(registry.EXIT_CODES));
+    for (const entry of registry.EXIT_CODES) {
+      assert.ok(Object.isFrozen(entry), `entry ${JSON.stringify(entry)} must be frozen`);
+    }
+  });
+
+  test('every shipped code is non-zero and inside an allocatable band', () => {
+    assert.ok(registry.EXIT_CODES.length > 0);
+    for (const entry of registry.EXIT_CODES) {
+      assert.ok(Number.isInteger(entry.code));
+      assert.notEqual(entry.code, 0);
+      assert.ok(
+        generator.isAllocatableCode(entry.code),
+        `code ${entry.code} (${entry.name}) must be inside an allocatable band`,
+      );
+    }
+  });
+
+  test('code 2 is owned only by hook-adapter in the shipped table', () => {
+    const hookDeny = registry.EXIT_CODES.find((e) => e.code === 2);
+    assert.ok(hookDeny);
+    assert.equal(hookDeny.owner, 'hook-adapter');
+  });
+
+  test('generic owns four distinct codes in the shipped table (ACCEPTED negative-space case)', () => {
+    const genericCodes = registry.EXIT_CODES.filter((e) => e.owner === 'generic').map((e) => e.code);
+    assert.equal(genericCodes.length, 4);
+    assert.equal(new Set(genericCodes).size, 4);
+  });
+});
+
+// ── Generator: REASON ─────────────────────────────────────────────────────────
+describe('gen-exit-code-registry: REASON', () => {
+  const expectedKeys = [
+    'OK', 'DRIFTED', 'USAGE', 'MISSING_DECLARATION', 'MALFORMED_DECLARATION',
+    'NOT_AN_ARRAY', 'EMPTY_DECLARATION', 'INVALID_ENTRY', 'DUPLICATE_CODE',
+    'DUPLICATE_NAME', 'RESERVED_CODE', 'FORBIDDEN_OWNER', 'MISSING_ARTIFACT',
+  ];
+
+  test('is frozen', () => {
+    assert.ok(Object.isFrozen(generator.REASON));
+  });
+
+  test('key set matches exactly', () => {
+    assert.deepEqual(Object.keys(generator.REASON).sort(), [...expectedKeys].sort());
+  });
+});
+
+// ── Generator: per-entry band validation (limit-1/limit/limit+1 for every edge) ──
+describe('gen-exit-code-registry: band validation', () => {
+  const cases = [
+    [0, 'RESERVED_CODE'],
+    [1, 'RESERVED_CODE'],
+    [2, 'OK'],
+    [3, 'RESERVED_CODE'],
+    [13, 'RESERVED_CODE'],
+    [14, 'RESERVED_CODE'],
+    [63, 'RESERVED_CODE'],
+    [64, 'OK'],
+    [78, 'OK'],
+    [79, 'RESERVED_CODE'],
+    [80, 'OK'],
+    [125, 'OK'],
+    [126, 'RESERVED_CODE'],
+    [127, 'RESERVED_CODE'],
+    [128, 'RESERVED_CODE'],
+    [-1, 'INVALID_ENTRY'],
+    [1.5, 'INVALID_ENTRY'],
+    ['64', 'INVALID_ENTRY'],
+    [NaN, 'INVALID_ENTRY'],
+    [Infinity, 'INVALID_ENTRY'],
+  ];
+
+  for (const [code, expected] of cases) {
+    test(`code ${String(code)} -> ${expected}`, () => {
+      const entry = makeEntry({
+        code,
+        name: `T_${String(code).replace(/[^A-Za-z0-9]/g, '_').toUpperCase()}`,
+        // code 2 is only accepted with owner hook-adapter; every other
+        // fixture code here uses 'generic' and is unaffected by that rule.
+        owner: code === 2 ? 'hook-adapter' : 'generic',
+      });
+      const result = generator.validateEntry(entry, 0);
+      if (expected === 'OK') {
+        assert.deepEqual(result, { ok: true });
+      } else {
+        assert.equal(result.ok, false);
+        assert.equal(result.reason, generator.REASON[expected]);
+      }
+    });
+  }
+});
+
+describe('gen-exit-code-registry: forbidden owner for code 2', () => {
+  test('code 2 with owner "hook-adapter" is accepted', () => {
+    const result = generator.validateEntry(makeEntry({ code: 2, name: 'HOOK_DENY_2', owner: 'hook-adapter' }), 0);
+    assert.deepEqual(result, { ok: true });
+  });
+
+  test('code 2 with any other owner is FORBIDDEN_OWNER', () => {
+    const result = generator.validateEntry(makeEntry({ code: 2, name: 'HOOK_DENY_2', owner: 'generic' }), 0);
+    assert.equal(result.ok, false);
+    assert.equal(result.reason, generator.REASON.FORBIDDEN_OWNER);
+  });
+});
+
+describe('gen-exit-code-registry: required string fields', () => {
+  const fields = ['meaning', 'owner', 'authorizedBy'];
+  const badValues = [undefined, '', '   '];
+
+  for (const field of fields) {
+    for (const bad of badValues) {
+      test(`missing/empty/whitespace "${field}" (${JSON.stringify(bad)}) -> INVALID_ENTRY`, () => {
+        const entry = makeEntry({ [field]: bad });
+        const result = generator.validateEntry(entry, 0);
+        assert.equal(result.ok, false);
+        assert.equal(result.reason, generator.REASON.INVALID_ENTRY);
+      });
+    }
+  }
+
+  test('non-SCREAMING_SNAKE_CASE name -> INVALID_ENTRY', () => {
+    const result = generator.validateEntry(makeEntry({ name: 'not_screaming' }), 0);
+    assert.equal(result.ok, false);
+    assert.equal(result.reason, generator.REASON.INVALID_ENTRY);
+  });
+
+  test('empty name -> INVALID_ENTRY', () => {
+    const result = generator.validateEntry(makeEntry({ name: '' }), 0);
+    assert.equal(result.ok, false);
+    assert.equal(result.reason, generator.REASON.INVALID_ENTRY);
+  });
+});
+
+describe('gen-exit-code-registry: cross-entry invariants', () => {
+  test('duplicate code -> DUPLICATE_CODE, context carries the code and both names', () => {
+    const entries = [
+      makeEntry({ code: 64, name: 'FIRST_NAME' }),
+      makeEntry({ code: 64, name: 'SECOND_NAME' }),
+    ];
+    const result = generator.validateEntries(entries);
+    assert.equal(result.ok, false);
+    assert.equal(result.reason, generator.REASON.DUPLICATE_CODE);
+    assert.deepEqual(result.context, { code: 64, names: ['FIRST_NAME', 'SECOND_NAME'] });
+  });
+
+  test('duplicate name -> DUPLICATE_NAME, context carries the name and both codes', () => {
+    const entries = [
+      makeEntry({ code: 64, name: 'SAME_NAME' }),
+      makeEntry({ code: 70, name: 'SAME_NAME' }),
+    ];
+    const result = generator.validateEntries(entries);
+    assert.equal(result.ok, false);
+    assert.equal(result.reason, generator.REASON.DUPLICATE_NAME);
+    assert.deepEqual(result.context, { name: 'SAME_NAME', codes: [64, 70] });
+  });
+
+  test('same owner, different codes -> ACCEPTED', () => {
+    const entries = [
+      makeEntry({ code: 64, name: 'OWNER_A', owner: 'generic' }),
+      makeEntry({ code: 70, name: 'OWNER_B', owner: 'generic' }),
+    ];
+    const result = generator.validateEntries(entries);
+    assert.deepEqual(result, { ok: true });
+  });
+});
+
+// ── Generator: declaration-file handling (pure loadDeclaration, temp files) ──
+describe('gen-exit-code-registry: declaration file handling', () => {
+  let tmpDir;
+  before(() => {
+    tmpDir = createTempDir('gsd-exit-code-decl-');
+  });
+  after(() => {
+    cleanup(tmpDir);
+  });
+
+  test('absent declaration -> MISSING_DECLARATION', () => {
+    const missing = path.join(tmpDir, 'does-not-exist.json');
+    const result = generator.loadDeclaration(missing);
+    assert.equal(result.ok, false);
+    assert.equal(result.reason, generator.REASON.MISSING_DECLARATION);
+  });
+
+  test('unparseable JSON -> MALFORMED_DECLARATION', () => {
+    const bad = path.join(tmpDir, 'malformed.json');
+    fs.writeFileSync(bad, '{ this is not json', 'utf8');
+    const result = generator.loadDeclaration(bad);
+    assert.equal(result.ok, false);
+    assert.equal(result.reason, generator.REASON.MALFORMED_DECLARATION);
+  });
+
+  const notArrayCases = [
+    ['object', '{}'],
+    ['string', '"s"'],
+    ['number', '0'],
+    ['null', 'null'],
+  ];
+  for (const [label, json] of notArrayCases) {
+    test(`valid JSON but not an array (${label}) -> NOT_AN_ARRAY`, () => {
+      const p = path.join(tmpDir, `not-array-${label}.json`);
+      fs.writeFileSync(p, json, 'utf8');
+      const result = generator.loadDeclaration(p);
+      assert.equal(result.ok, false);
+      assert.equal(result.reason, generator.REASON.NOT_AN_ARRAY);
+    });
+  }
+
+  test('empty array -> EMPTY_DECLARATION', () => {
+    const p = path.join(tmpDir, 'empty.json');
+    fs.writeFileSync(p, '[]', 'utf8');
+    const result = generator.loadDeclaration(p);
+    assert.equal(result.ok, false);
+    assert.equal(result.reason, generator.REASON.EMPTY_DECLARATION);
+  });
+});
+
+// ── Generator CLI ──────────────────────────────────────────────────────────────
+describe('gen-exit-code-registry: CLI', () => {
+  let tmpDir;
+  before(() => {
+    tmpDir = createTempDir('gsd-exit-code-cli-');
+  });
+  after(() => {
+    cleanup(tmpDir);
+  });
+
+  function validDeclarationPath(dir, filename = 'exit-codes.json') {
+    const p = path.join(dir, filename);
+    fs.copyFileSync(REAL_DECLARATION_PATH, p);
+    return p;
+  }
+
+  test('--check is in sync against the real committed pair', () => {
+    const result = runGen(['--check']);
+    assert.equal(result.exitCode, 0, result.stderr);
+  });
+
+  test('--write then --check on temp paths both exit 0', () => {
+    const decl = validDeclarationPath(tmpDir, 'a-decl.json');
+    const out = path.join(tmpDir, 'a-out.cjs');
+    const write = runGen(['--write', '--declaration', decl, '--out', out]);
+    assert.equal(write.exitCode, 0, write.stderr);
+    const check = runGen(['--check', '--declaration', decl, '--out', out]);
+    assert.equal(check.exitCode, 0, check.stderr);
+  });
+
+  test('--write is idempotent (byte-identical on a second run)', () => {
+    const decl = validDeclarationPath(tmpDir, 'b-decl.json');
+    const out = path.join(tmpDir, 'b-out.cjs');
+    const first = runGen(['--write', '--declaration', decl, '--out', out]);
+    assert.equal(first.exitCode, 0, first.stderr);
+    const firstBytes = fs.readFileSync(out, 'utf8');
+    const second = runGen(['--write', '--declaration', decl, '--out', out]);
+    assert.equal(second.exitCode, 0, second.stderr);
+    const secondBytes = fs.readFileSync(out, 'utf8');
+    assert.equal(secondBytes, firstBytes);
+  });
+
+  test('--check on a hand-edited artifact -> DRIFTED', () => {
+    const decl = validDeclarationPath(tmpDir, 'c-decl.json');
+    const out = path.join(tmpDir, 'c-out.cjs');
+    assert.equal(runGen(['--write', '--declaration', decl, '--out', out]).exitCode, 0);
+    fs.appendFileSync(out, '\n// hand-edited, drifts from generated content\n');
+    const { result, report } = runGenJson(['--check', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.DRIFTED);
+  });
+
+  test('--check with a stale artifact (declaration changed after write) -> DRIFTED', () => {
+    const decl = validDeclarationPath(tmpDir, 'd-decl.json');
+    const out = path.join(tmpDir, 'd-out.cjs');
+    assert.equal(runGen(['--write', '--declaration', decl, '--out', out]).exitCode, 0);
+    const entries = JSON.parse(fs.readFileSync(decl, 'utf8'));
+    entries.push({ code: 80, name: 'DOMAIN_X', meaning: 'm', owner: 'domain-x', authorizedBy: 'ADR-3889' });
+    fs.writeFileSync(decl, JSON.stringify(entries, null, 2), 'utf8');
+    const { result, report } = runGenJson(['--check', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.DRIFTED);
+  });
+
+  test('--check with the artifact absent -> MISSING_ARTIFACT', () => {
+    const decl = validDeclarationPath(tmpDir, 'e-decl.json');
+    const out = path.join(tmpDir, 'e-out-absent.cjs');
+    const { result, report } = runGenJson(['--check', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.MISSING_ARTIFACT);
+    assert.equal(fs.existsSync(out), false);
+  });
+
+  test('unknown flag -> USAGE, exit 1, artifact unchanged on disk', () => {
+    const decl = validDeclarationPath(tmpDir, 'f-decl.json');
+    const out = path.join(tmpDir, 'f-out.cjs');
+    assert.equal(runGen(['--write', '--declaration', decl, '--out', out]).exitCode, 0);
+    const before = fs.readFileSync(out, 'utf8');
+    const { result, report } = runGenJson(['--bogus-flag', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.USAGE);
+    const after = fs.readFileSync(out, 'utf8');
+    assert.equal(after, before);
+  });
+
+  test('second positional argument -> USAGE', () => {
+    const decl = validDeclarationPath(tmpDir, 'g-decl.json');
+    const out = path.join(tmpDir, 'g-out.cjs');
+    const { result, report } = runGenJson(['--check', 'extra-positional', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.USAGE);
+  });
+
+  test('missing declaration -> MISSING_DECLARATION, exit 1', () => {
+    const decl = path.join(tmpDir, 'does-not-exist-h.json');
+    const out = path.join(tmpDir, 'h-out.cjs');
+    const { result, report } = runGenJson(['--write', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.MISSING_DECLARATION);
+  });
+
+  test('malformed JSON declaration -> MALFORMED_DECLARATION, exit 1', () => {
+    const decl = path.join(tmpDir, 'i-decl.json');
+    fs.writeFileSync(decl, '{ not json', 'utf8');
+    const out = path.join(tmpDir, 'i-out.cjs');
+    const { result, report } = runGenJson(['--write', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.MALFORMED_DECLARATION);
+  });
+
+  test('valid JSON, not an array -> NOT_AN_ARRAY, exit 1', () => {
+    const decl = path.join(tmpDir, 'j-decl.json');
+    fs.writeFileSync(decl, '{}', 'utf8');
+    const out = path.join(tmpDir, 'j-out.cjs');
+    const { result, report } = runGenJson(['--write', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.NOT_AN_ARRAY);
+  });
+
+  test('empty array declaration -> EMPTY_DECLARATION, exit 1', () => {
+    const decl = path.join(tmpDir, 'k-decl.json');
+    fs.writeFileSync(decl, '[]', 'utf8');
+    const out = path.join(tmpDir, 'k-out.cjs');
+    const { result, report } = runGenJson(['--write', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.EMPTY_DECLARATION);
+  });
+});
+
+// ── Generator CLI: positive controls (each guard actually FAILS the build) ────
+describe('gen-exit-code-registry: CLI positive controls for the ten guard rows', () => {
+  let tmpDir;
+  before(() => {
+    tmpDir = createTempDir('gsd-exit-code-positive-');
+  });
+  after(() => {
+    cleanup(tmpDir);
+  });
+
+  function writeFixture(name, entries) {
+    const decl = path.join(tmpDir, `${name}.json`);
+    fs.writeFileSync(decl, JSON.stringify(entries, null, 2), 'utf8');
+    return decl;
+  }
+
+  const validBase = () => ({ meaning: 'm', owner: 'generic', authorizedBy: 'ADR-3889' });
+
+  const rows = [
+    ['duplicate code', () => [
+      { ...validBase(), code: 64, name: 'DUP_A' },
+      { ...validBase(), code: 64, name: 'DUP_B' },
+    ], 'DUPLICATE_CODE'],
+    ['duplicate name', () => [
+      { ...validBase(), code: 64, name: 'SAME' },
+      { ...validBase(), code: 70, name: 'SAME' },
+    ], 'DUPLICATE_NAME'],
+    ['code 2 wrong owner', () => [
+      { ...validBase(), code: 2, name: 'HOOK_DENY', owner: 'not-hook-adapter' },
+    ], 'FORBIDDEN_OWNER'],
+    ['code 0', () => [{ ...validBase(), code: 0, name: 'ZERO' }], 'RESERVED_CODE'],
+    ['code 13', () => [{ ...validBase(), code: 13, name: 'THIRTEEN' }], 'RESERVED_CODE'],
+    ['code 79', () => [{ ...validBase(), code: 79, name: 'SEVENTYNINE' }], 'RESERVED_CODE'],
+    ['code 126', () => [{ ...validBase(), code: 126, name: 'ONETWENTYSIX' }], 'RESERVED_CODE'],
+    ['code "64" (string)', () => [{ ...validBase(), code: '64', name: 'STRCODE' }], 'INVALID_ENTRY'],
+    ['missing meaning', () => [{ code: 64, name: 'NO_MEANING', owner: 'generic', authorizedBy: 'ADR-3889' }], 'INVALID_ENTRY'],
+    ['[] empty declaration', () => [], 'EMPTY_DECLARATION'],
+  ];
+
+  for (const [label, buildEntries, expectedReasonKey] of rows) {
+    test(`${label} -> ${expectedReasonKey}, exit 1`, () => {
+      const decl = writeFixture(label.replace(/[^a-z0-9]+/gi, '-'), buildEntries());
+      const out = path.join(tmpDir, `${label.replace(/[^a-z0-9]+/gi, '-')}-out.cjs`);
+      const { result, report } = runGenJson(['--write', '--declaration', decl, '--out', out]);
+      assert.equal(result.exitCode, 1, `expected exit 1 for ${label}, got stderr: ${result.stderr}`);
+      assert.equal(report.ok, false);
+      assert.equal(report.reason, generator.REASON[expectedReasonKey]);
+    });
+  }
+
+  test('duplicate-code fixture: --json payload carries a structured context, not just the reason', () => {
+    const decl = writeFixture('json-duplicate-code', [
+      { ...validBase(), code: 64, name: 'DUP_A' },
+      { ...validBase(), code: 64, name: 'DUP_B' },
+    ]);
+    const out = path.join(tmpDir, 'json-duplicate-code-out.cjs');
+    const { result, report } = runGenJson(['--write', '--declaration', decl, '--out', out]);
+    assert.equal(result.exitCode, 1, result.stderr);
+    assert.equal(report.ok, false);
+    assert.equal(report.reason, generator.REASON.DUPLICATE_CODE);
+    // A --json consumer must be able to learn WHICH code collided and WHICH
+    // names collided without parsing the `detail` prose string.
+    assert.deepEqual(report.context, { code: 64, names: ['DUP_A', 'DUP_B'] });
+  });
+});
+
+// ── fast-check properties ─────────────────────────────────────────────────────
+describe('exit-code-registry: fast-check properties', () => {
+  test('nameForExitCode(exitCodeFor(name)) round-trips for every registered name', () => {
+    fc.assert(
+      fc.property(fc.constantFrom(...registry.EXIT_CODES.map((e) => e.name)), (name) => {
+        assert.equal(registry.nameForExitCode(registry.exitCodeFor(name)), name);
+      }),
+      { seed: 2704, numRuns: 200 },
+    );
+  });
+
+  test('exitCodeFor(nameForExitCode(code)) round-trips for every registered code', () => {
+    fc.assert(
+      fc.property(fc.constantFrom(...registry.EXIT_CODES.map((e) => e.code)), (code) => {
+        assert.equal(registry.exitCodeFor(registry.nameForExitCode(code)), code);
+      }),
+      { seed: 2704, numRuns: 200 },
+    );
+  });
+
+  test('exitCodeFor never resolves a code for an unregistered string', () => {
+    fc.assert(
+      fc.property(fc.string(), (s) => {
+        fc.pre(!REGISTERED_NAMES.has(s));
+        assert.throws(() => registry.exitCodeFor(s));
+      }),
+      { seed: 2704, numRuns: 200 },
+    );
+  });
+
+  // Unlike the two round-trip properties above (which replay only the 5
+  // shipped constants), this one explores the full integer domain —
+  // negatives, every band boundary, and values far outside every band —
+  // rather than a closed set of examples.
+  test('nameForExitCode(c) either throws or returns a name that round-trips to c, for any integer c', () => {
+    fc.assert(
+      fc.property(fc.integer(), (c) => {
+        let name;
+        try {
+          name = registry.nameForExitCode(c);
+        } catch {
+          return; // throwing for an unregistered code is a legal outcome
+        }
+        assert.notEqual(name, undefined);
+        assert.equal(registry.exitCodeFor(name), c);
+      }),
+      { seed: 2704, numRuns: 200 },
+    );
+  });
+});
diff --git a/tests/fixtures/install-tree/antigravity.json b/tests/fixtures/install-tree/antigravity.json
index e6354c6c5..930d84e4d 100644
--- a/tests/fixtures/install-tree/antigravity.json
+++ b/tests/fixtures/install-tree/antigravity.json
@@ -43,6 +43,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/augment.json b/tests/fixtures/install-tree/augment.json
index 30aa59c38..ed88f9acb 100644
--- a/tests/fixtures/install-tree/augment.json
+++ b/tests/fixtures/install-tree/augment.json
@@ -114,6 +114,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/claude-local.json b/tests/fixtures/install-tree/claude-local.json
index 2df5dd8e5..ba4533be8 100644
--- a/tests/fixtures/install-tree/claude-local.json
+++ b/tests/fixtures/install-tree/claude-local.json
@@ -114,6 +114,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/claude.json b/tests/fixtures/install-tree/claude.json
index 4e6aac011..962d51c75 100644
--- a/tests/fixtures/install-tree/claude.json
+++ b/tests/fixtures/install-tree/claude.json
@@ -43,6 +43,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/cline.json b/tests/fixtures/install-tree/cline.json
index ef603bb3b..5ad1f0f91 100644
--- a/tests/fixtures/install-tree/cline.json
+++ b/tests/fixtures/install-tree/cline.json
@@ -45,6 +45,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/codebuddy.json b/tests/fixtures/install-tree/codebuddy.json
index 591df36ec..eb9bc144d 100644
--- a/tests/fixtures/install-tree/codebuddy.json
+++ b/tests/fixtures/install-tree/codebuddy.json
@@ -114,6 +114,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/codex.json b/tests/fixtures/install-tree/codex.json
index 9e18368e0..0ea041be2 100644
--- a/tests/fixtures/install-tree/codex.json
+++ b/tests/fixtures/install-tree/codex.json
@@ -79,6 +79,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/copilot.json b/tests/fixtures/install-tree/copilot.json
index c9575d03b..1f1797858 100644
--- a/tests/fixtures/install-tree/copilot.json
+++ b/tests/fixtures/install-tree/copilot.json
@@ -44,6 +44,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/cursor.json b/tests/fixtures/install-tree/cursor.json
index 4ee95925b..6a941d73b 100644
--- a/tests/fixtures/install-tree/cursor.json
+++ b/tests/fixtures/install-tree/cursor.json
@@ -43,6 +43,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/hermes.json b/tests/fixtures/install-tree/hermes.json
index 0cfba059d..c846c9ddd 100644
--- a/tests/fixtures/install-tree/hermes.json
+++ b/tests/fixtures/install-tree/hermes.json
@@ -43,6 +43,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/kilo.json b/tests/fixtures/install-tree/kilo.json
index dffe3f5a8..6376113f4 100644
--- a/tests/fixtures/install-tree/kilo.json
+++ b/tests/fixtures/install-tree/kilo.json
@@ -114,6 +114,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/kimi-code.json b/tests/fixtures/install-tree/kimi-code.json
index 2baec4f3b..fc9f06d9e 100644
--- a/tests/fixtures/install-tree/kimi-code.json
+++ b/tests/fixtures/install-tree/kimi-code.json
@@ -44,6 +44,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/kimi.json b/tests/fixtures/install-tree/kimi.json
index 6f0f77f27..6e077cb1d 100644
--- a/tests/fixtures/install-tree/kimi.json
+++ b/tests/fixtures/install-tree/kimi.json
@@ -80,6 +80,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/opencode.json b/tests/fixtures/install-tree/opencode.json
index 26c0878f7..23ac2b5cf 100644
--- a/tests/fixtures/install-tree/opencode.json
+++ b/tests/fixtures/install-tree/opencode.json
@@ -114,6 +114,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/pi.json b/tests/fixtures/install-tree/pi.json
index 3381edb75..c348715ce 100644
--- a/tests/fixtures/install-tree/pi.json
+++ b/tests/fixtures/install-tree/pi.json
@@ -10,6 +10,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/qwen.json b/tests/fixtures/install-tree/qwen.json
index fd484e528..624f986cb 100644
--- a/tests/fixtures/install-tree/qwen.json
+++ b/tests/fixtures/install-tree/qwen.json
@@ -43,6 +43,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/trae.json b/tests/fixtures/install-tree/trae.json
index ff63fb203..e5ba00517 100644
--- a/tests/fixtures/install-tree/trae.json
+++ b/tests/fixtures/install-tree/trae.json
@@ -43,6 +43,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/windsurf.json b/tests/fixtures/install-tree/windsurf.json
index 5cb2ca335..74da4432a 100644
--- a/tests/fixtures/install-tree/windsurf.json
+++ b/tests/fixtures/install-tree/windsurf.json
@@ -43,6 +43,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",
diff --git a/tests/fixtures/install-tree/zcode.json b/tests/fixtures/install-tree/zcode.json
index 92572569a..43e1d9aca 100644
--- a/tests/fixtures/install-tree/zcode.json
+++ b/tests/fixtures/install-tree/zcode.json
@@ -114,6 +114,7 @@
   "gsd-core/bin/gsd_run",
   "gsd-core/bin/shared/config-defaults.manifest.json",
   "gsd-core/bin/shared/config-schema.manifest.json",
+  "gsd-core/bin/shared/exit-codes.json",
   "gsd-core/bin/shared/model-catalog.json",
   "gsd-core/bin/shared/runtime-aliases.manifest.json",
   "gsd-core/bin/verify-reapply-patches.cjs",