@@ -71,6 +71,14 @@ const HOOK_ZOD = resolve(SPEC_DIR, 'src/data/hook.zod.ts');
  * `src/`, so a probe can be written the way a hook author would actually type
  * it — import line included — instead of through relative paths no reader of
  * the docs would ever use.
+ *
+ * Diagnostics are asked of each PROBE file only, never of the whole program:
+ * every assertion below reads a probe's own diagnostics, and a whole-program
+ * request type-checks the body of every `packages/spec` source file the probes
+ * reach, for diagnostics a filter then discarded. A probe's diagnostics still
+ * reflect every type it reaches (the contract members, `HookContext`); only
+ * the bodies nobody reads are skipped. `shared/retired-key-tsc-diagnostic.test.ts`
+ * asks the same way.
  */
 function compileProbes(probes: Readonly<Record<string, string>>): Map<string, ts.Diagnostic[]> {
   const dir = resolve(SPEC_DIR, 'src/__scoped_context_probes__');
@@ -107,16 +115,49 @@ function compileProbes(probes: Readonly<Record<string, string>>): Map<string, ts
 
   const program = ts.createProgram([...paths.keys()], options, host);
   const out = new Map<string, ts.Diagnostic[]>();
-  for (const name of Object.keys(probes)) out.set(name, []);
-  for (const d of ts.getPreEmitDiagnostics(program)) {
-    const file = d.file?.fileName ? resolve(d.file.fileName) : undefined;
-    for (const name of Object.keys(probes)) {
-      if (file === resolve(dir, `${name}.ts`)) out.get(name)!.push(d);
-    }
+  for (const name of Object.keys(probes)) {
+    const path = resolve(dir, `${name}.ts`);
+    const file = program.getSourceFile(path);
+    if (file === undefined) throw new Error(`probe ${name} did not enter the program`);
+    out.set(name, ts.getPreEmitDiagnostics(program, file).filter((d) => d.file !== undefined && resolve(d.file.fileName) === path));
   }
   return out;
 }
 
+/**
+ * Every probe this file compiles, by name — registered while the describe
+ * blocks below are COLLECTED, and compiled together in ONE program the first
+ * time any case reads a result.
+ *
+ * Each probe is its own module (an `import` line opens every one), so a probe
+ * cannot see another's declarations and its diagnostics do not depend on which
+ * probes share the program; what four programs did here — each re-parsing and
+ * re-checking the same `HookContext` and contract types — one program does
+ * once. A name registered twice must carry the same text (the
+ * `harness-self-test` control is shared verbatim), and a case reading a probe
+ * the program never saw fails rather than reading an empty answer.
+ */
+const REGISTERED = new Map<string, string>();
+let compiled: Map<string, ts.Diagnostic[]> | undefined;
+
+function registerProbes(probes: Readonly<Record<string, string>>): () => Map<string, ts.Diagnostic[]> {
+  for (const [name, text] of Object.entries(probes)) {
+    const prior = REGISTERED.get(name);
+    if (prior !== undefined && prior !== text) throw new Error(`probe ${name} is registered twice with different text`);
+    REGISTERED.set(name, text);
+  }
+  return () => {
+    compiled ??= compileProbes(Object.fromEntries(REGISTERED));
+    const out = new Map<string, ts.Diagnostic[]>();
+    for (const name of Object.keys(probes)) {
+      const diagnostics = compiled.get(name);
+      if (diagnostics === undefined) throw new Error(`probe ${name} was registered after the program was built`);
+      out.set(name, diagnostics);
+    }
+    return out;
+  };
+}
+
 /** One diagnostic per line, `TS<code>: <message>`, for readable assertions. */
 function render(diagnostics: readonly ts.Diagnostic[]): string {
   return diagnostics
@@ -168,13 +209,15 @@ describe('the `HookContext.api` JSDoc example compiles', () => {
     expect(example.split('\n').length).toBeGreaterThanOrEqual(3);
   });
 
+  const compile = registerProbes({
+    'jsdoc-usage': hook(example),
+    // The harness's own control: a probe that MUST fail. A resolution failure
+    // reports zero diagnostics for every probe and reads as green.
+    'harness-self-test': hook("const x: number = ctx.api?.object('user');"),
+  });
+
   it('compiles verbatim, with zero diagnostics', () => {
-    const results = compileProbes({
-      'jsdoc-usage': hook(example),
-      // The harness's own control: a probe that MUST fail. A resolution failure
-      // reports zero diagnostics for every probe and reads as green.
-      'harness-self-test': hook("const x: number = ctx.api?.object('user');"),
-    });
+    const results = compile();
     expect(render(results.get('harness-self-test')!), 'the harness must be able to report an error')
       .toContain('TS2322');
     expect(render(results.get('jsdoc-usage')!), 'the JSDoc example must compile').toBe('');
@@ -215,12 +258,13 @@ describe('every corpus-measured call compiles', () => {
     'legal-transaction-info': 'await ctx.api?.transaction(async (_tx, info) => info.owned);',
   };
 
-  it('compiles all of them clean', () => {
-    const probes: Record<string, string> = {};
-    for (const [name, body] of Object.entries(legal)) probes[name] = hook(body);
-    probes['harness-self-test'] = hook("const x: number = ctx.api?.object('user');");
+  const probes: Record<string, string> = {};
+  for (const [name, body] of Object.entries(legal)) probes[name] = hook(body);
+  probes['harness-self-test'] = hook("const x: number = ctx.api?.object('user');");
+  const compile = registerProbes(probes);
 
-    const results = compileProbes(probes);
+  it('compiles all of them clean', () => {
+    const results = compile();
     expect(render(results.get('harness-self-test')!), 'the harness must be able to report an error')
       .toContain('TS2322');
 
@@ -259,20 +303,22 @@ describe('the evidence bar is enforced, not just documented', () => {
     'rejects-top-level-insert': ["await ctx.api?.insert('task', { title: 't' });", 'IScopedContext'],
   };
 
+  const probes: Record<string, string> = {};
+  for (const [name, [body]] of Object.entries(rejected)) {
+    probes[name] = name === 'rejects-invented-member'
+      ? [
+        "import type { HookContext } from '@objectstack/spec/data';",
+        "import type { IScopedContext } from '@objectstack/spec/contracts';",
+        'export const handler = async (ctx: HookContext) => {',
+        body,
+        '};',
+      ].join('\n')
+      : hook(body);
+  }
+  const compile = registerProbes(probes);
+
   it('reports TS2339 naming the contract type — not merely "some error"', () => {
-    const probes: Record<string, string> = {};
-    for (const [name, [body]] of Object.entries(rejected)) {
-      probes[name] = name === 'rejects-invented-member'
-        ? [
-          "import type { HookContext } from '@objectstack/spec/data';",
-          "import type { IScopedContext } from '@objectstack/spec/contracts';",
-          'export const handler = async (ctx: HookContext) => {',
-          body,
-          '};',
-        ].join('\n')
-        : hook(body);
-    }
-    const results = compileProbes(probes);
+    const results = compile();
 
     for (const [name, diagnostics] of results) {
       const text = render(diagnostics);
@@ -323,24 +369,26 @@ describe('`updateById` DECLARES its answer, and the declaration is enforced', ()
    * `update` sibling's wider `Record<string, any> | number | null`, so a
    * copy-paste of the wrong sibling's shape is caught too.
    */
+  const compile = registerProbes({
+    // The whole point of the declaration: a by-id update that matched no row
+    // answers `null`, and before this the call site was handed `any` and
+    // never asked.
+    'rejects-unnarrowed-updateById':
+      hook("const row: Record<string, any> = await ctx.api!.object('task').updateById('t1', { status: 'done' });"),
+    // Anti-vacuity twin: the CORRECT spelling must still compile clean, so
+    // the narrowing is a real answer shape and not a blanket refusal.
+    'legal-updateById-null-checked': hook([
+      "const row = await ctx.api!.object('task').updateById('t1', { status: 'done' });",
+      'if (row !== null) {',
+      '  const seen: unknown = row.status;',
+      '  void seen;',
+      '}',
+    ].join('\n')),
+    'harness-self-test': hook("const x: number = ctx.api?.object('user');"),
+  });
+
   it('the answer cannot enter a record slot unnarrowed, and the null-checked read compiles', () => {
-    const results = compileProbes({
-      // The whole point of the declaration: a by-id update that matched no row
-      // answers `null`, and before this the call site was handed `any` and
-      // never asked.
-      'rejects-unnarrowed-updateById':
-        hook("const row: Record<string, any> = await ctx.api!.object('task').updateById('t1', { status: 'done' });"),
-      // Anti-vacuity twin: the CORRECT spelling must still compile clean, so
-      // the narrowing is a real answer shape and not a blanket refusal.
-      'legal-updateById-null-checked': hook([
-        "const row = await ctx.api!.object('task').updateById('t1', { status: 'done' });",
-        'if (row !== null) {',
-        '  const seen: unknown = row.status;',
-        '  void seen;',
-        '}',
-      ].join('\n')),
-      'harness-self-test': hook("const x: number = ctx.api?.object('user');"),
-    });
+    const results = compile();
 
     expect(render(results.get('harness-self-test')!), 'the harness must be able to report an error')
       .toContain('TS2322');
 
@@ -86,6 +86,14 @@ const SYNC_ARCHITECTURE = resolve(SPEC_DIR, 'docs/SYNC_ARCHITECTURE.md');
  * gate's reason: a documentation snippet declares a `const` and stops, and
  * TS6133 is an opinion about the snippet's framing. Everything else runs at the
  * repo's real strictness (`strict: true`).
+ *
+ * Diagnostics are asked of each PROBE file only, never of the whole program:
+ * every assertion below reads a probe's own diagnostics, and a whole-program
+ * request type-checks the body of every `packages/spec` source file the probes
+ * reach, for diagnostics a filter then discarded. A probe's diagnostics still
+ * reflect every type it reaches (`Connector`, its tombstones, `ConnectorParsed`);
+ * only the bodies nobody reads are skipped.
+ * `shared/retired-key-tsc-diagnostic.test.ts` asks the same way.
  */
 function compileProbes(probes: Readonly<Record<string, string>>): Map<string, ts.Diagnostic[]> {
   const dir = resolve(SPEC_DIR, 'src/__connector_author_shape_probes__');
@@ -121,16 +129,48 @@ function compileProbes(probes: Readonly<Record<string, string>>): Map<string, ts
 
   const program = ts.createProgram([...paths.keys()], options, host);
   const out = new Map<string, ts.Diagnostic[]>();
-  for (const name of Object.keys(probes)) out.set(name, []);
-  for (const d of ts.getPreEmitDiagnostics(program)) {
-    const file = d.file?.fileName ? resolve(d.file.fileName) : undefined;
-    for (const [name] of Object.entries(probes)) {
-      if (file === resolve(dir, `${name}.ts`)) out.get(name)!.push(d);
-    }
+  for (const name of Object.keys(probes)) {
+    const path = resolve(dir, `${name}.ts`);
+    const file = program.getSourceFile(path);
+    if (file === undefined) throw new Error(`probe ${name} did not enter the program`);
+    out.set(name, ts.getPreEmitDiagnostics(program, file).filter((d) => d.file !== undefined && resolve(d.file.fileName) === path));
   }
   return out;
 }
 
+/**
+ * Every probe this file compiles, by name — registered while the describe
+ * blocks below are COLLECTED, and compiled together in ONE program the first
+ * time any case reads a result.
+ *
+ * Each probe is its own module (an `import` line opens every one), so a probe
+ * cannot see another's declarations and its diagnostics do not depend on which
+ * probes share the program; what three programs did here — each re-parsing and
+ * re-checking the same `Connector` types — one program does once. A name
+ * registered twice must carry the same text, and a case reading a probe the
+ * program never saw fails rather than reading an empty answer.
+ */
+const REGISTERED = new Map<string, string>();
+let compiled: Map<string, ts.Diagnostic[]> | undefined;
+
+function registerProbes(probes: Readonly<Record<string, string>>): () => Map<string, ts.Diagnostic[]> {
+  for (const [name, text] of Object.entries(probes)) {
+    const prior = REGISTERED.get(name);
+    if (prior !== undefined && prior !== text) throw new Error(`probe ${name} is registered twice with different text`);
+    REGISTERED.set(name, text);
+  }
+  return () => {
+    compiled ??= compileProbes(Object.fromEntries(REGISTERED));
+    const out = new Map<string, ts.Diagnostic[]>();
+    for (const name of Object.keys(probes)) {
+      const diagnostics = compiled.get(name);
+      if (diagnostics === undefined) throw new Error(`probe ${name} was registered after the program was built`);
+      out.set(name, diagnostics);
+    }
+    return out;
+  };
+}
+
 /** One diagnostic per line, `TS<code>: <message>`, for readable assertions. */
 function render(diagnostics: readonly ts.Diagnostic[]): string {
   return diagnostics
@@ -191,10 +231,24 @@ describe('SYNC_ARCHITECTURE.md L3 connector examples compile', () => {
     expect(markdown).not.toContain("```typescript\nimport type { ETLPipeline }");
   });
 
+  const probes: Record<string, string> = {};
+  compilable.forEach((block, i) => { probes[`doc-l3-connector-${i}`] = block; });
+  // The harness's own control: a probe that MUST fail. Without it a
+  // resolution failure (paths mapping wrong, host overlay not applied) would
+  // report zero diagnostics and read as a green example.
+  probes['harness-self-test'] = [
+    "import type { Connector } from '@objectstack/spec/integration';",
+    "const broken: Connector = { label: 'no name, no type' };",
+  ].join('\n');
+  const compile = registerProbes(probes);
+
   // This `it` carries its OWN timeout instead of the package's 60 s default
-  // (`vitest.config.ts`): it builds one `ts.createProgram` over the spec's types
-  // (both document examples plus the harness self-test probe, at `strict`), and
-  // that is more work than the default is sized for. CI readings, `Test Core
+  // (`vitest.config.ts`): it is the first case to read a compile result, so it
+  // builds the file's one `ts.createProgram` over the spec's types (every
+  // probe registered above and below, at `strict`), and that was more work
+  // than the default is sized for. The readings that follow are of the harness
+  // before it shared one program and asked only the probe files for
+  // diagnostics; the timeout is left where they put it. CI readings, `Test Core
   // (1/6)`: 55,680 ms on `main` (commit 85b4ac634e; the same figure appears at
   // 018b077fbf and eab7236ff7 because turbo replayed one cached run, so it is
   // one reading, not three) and 61,767 ms on a cold spec re-run (PR head
@@ -205,17 +259,7 @@ describe('SYNC_ARCHITECTURE.md L3 connector examples compile', () => {
   // import-everything `beforeAll`. Only this `it` is widened: raising the
   // global `testTimeout` would hide the next slow test as well.
   it('compiles every full connector example verbatim, import line included', () => {
-    const probes: Record<string, string> = {};
-    compilable.forEach((block, i) => { probes[`doc-l3-connector-${i}`] = block; });
-    // The harness's own control: a probe that MUST fail. Without it a
-    // resolution failure (paths mapping wrong, host overlay not applied) would
-    // report zero diagnostics and read as a green example.
-    probes['harness-self-test'] = [
-      "import type { Connector } from '@objectstack/spec/integration';",
-      "const broken: Connector = { label: 'no name, no type' };",
-    ].join('\n');
-
-    const results = compileProbes(probes);
+    const results = compile();
     expect(render(results.get('harness-self-test')!), 'the harness must be able to report an error')
       .toContain('TS2739');
     compilable.forEach((_, i) => {
@@ -279,7 +323,7 @@ describe('the spellings the example used to carry are rejected', () => {
     `,
   } as const;
 
-  const results = compileProbes(probes);
+  const compile = registerProbes(probes);
 
   // ⚠ Measured, not assumed — and it is the one place the two tombstone
   // channels are NOT equally good. `retiredKey()` types the key as its
@@ -291,6 +335,7 @@ describe('the spellings the example used to carry are rejected', () => {
   // channel (the runtime block below) carries the key's own prescription.
   for (const probe of ['field-mappings-retired', 'sync-config-retired', 'webhooks-retired'] as const) {
     it(`\`${probe}\`: the key no longer type-checks, whatever it holds`, () => {
+      const results = compile();
       const message = render(results.get(probe)!);
       expect(message).toMatch(/^TS(2741|2353): /);
       expect(message).toContain('[REMOVED]');
@@ -299,6 +344,7 @@ describe('the spellings the example used to carry are rejected', () => {
   }
 
   it('…while a live sibling key in the same literal compiles', () => {
+    const results = compile();
     expect(render(results.get('live-key-control')!)).toBe('');
   });
 });
@@ -382,13 +428,15 @@ describe('the bare `Connector` is the author shape; `ConnectorParsed` is the par
     `,
   } as const;
 
-  const results = compileProbes(probes);
+  const compile = registerProbes(probes);
 
   it('accepts the omitted defaults under the bare `Connector`', () => {
+    const results = compile();
     expect(render(results.get('author-connector')!)).toBe('');
   });
 
   it('rejects the same literal under `ConnectorParsed`, on the defaults it left out', () => {
+    const results = compile();
     const message = render(results.get('parsed-connector')!);
     expect(message).toMatch(/TS2739: .* is missing the following properties/);
     expect(message).toContain('enabled');