diff --git a/eslint-rules/no-adhoc-timeout-literal.allowlist.json b/eslint-rules/no-adhoc-timeout-literal.allowlist.json
index c9878805c..0733f60d2 100644
--- a/eslint-rules/no-adhoc-timeout-literal.allowlist.json
+++ b/eslint-rules/no-adhoc-timeout-literal.allowlist.json
@@ -52,19 +52,12 @@
   "tests/plan-review-convergence.test.cjs",
   "tests/policy-160-route0-resume.test.cjs",
   "tests/prohibition-enforcement.test.cjs",
-  "tests/prompt-injection-scan.security.test.cjs",
   "tests/quick-batch.test.cjs",
-  "tests/read-injection-scanner.property.test.cjs",
-  "tests/read-injection-scanner.security.test.cjs",
   "tests/representative-corpus.test.cjs",
   "tests/review-lane-invocation.test.cjs",
   "tests/reviewer-manifest-body.test.cjs",
   "tests/reviewer-trust-disclosure.test.cjs",
   "tests/run-tests-temp-root.test.cjs",
-  "tests/secret-scan-lint.security.test.cjs",
-  "tests/security-prompt-injection.security.test.cjs",
-  "tests/security-scan.security.test.cjs",
-  "tests/security.test.cjs",
   "tests/shell-command-projection-dispatch.test.cjs",
   "tests/state-document.test.cjs",
   "tests/state-todos-render.test.cjs",
diff --git a/tests/helpers/timeouts.cjs b/tests/helpers/timeouts.cjs
index 39a9ad755..2133b616e 100644
--- a/tests/helpers/timeouts.cjs
+++ b/tests/helpers/timeouts.cjs
@@ -188,6 +188,42 @@ const STAGED_HOOK_SCRIPT_TIMEOUT_MS = 20000;
  */
 const LOOP_HOOK_POINT_CLI_TIMEOUT_MS = 60000;
 
+/**
+ * A security-scan shell script (secret-scan.sh, secret-scan-lint.sh,
+ * prompt-injection-scan.sh, base64-scan.sh) invoked with missing or invalid
+ * CLI arguments -- exits almost instantly with a usage error, no scan work
+ * performed at all. A distinct, lighter-weight class than a real scan of
+ * even a single tiny fixture (`QUICK_SPAWN_TIMEOUT_MS`, 10000ms) -- this is
+ * the fast-fail path, not the scan path.
+ *
+ * Deliberately a separate name from `MALFORMED_INPUT_HOOK_TIMEOUT_MS`, even
+ * though the two currently coincide at the same value: that constant bounds
+ * a Node hook script fed malformed input (a different runtime, a different
+ * failure shape), not a bash scan script given no arguments. Collapsing them
+ * would let a future, independent tune of either value silently move the
+ * other -- the same reasoning `SEAM_DEFAULT_TIMEOUT_MS` documents for its own
+ * coincidence with `HOOK_FANOUT_TIMEOUT_MS`.
+ *
+ * Shared across 2 files in batch #4519 of the ad hoc timeout literal
+ * migration, epic #4445 -- every site independently arrived at this exact
+ * value -- that is why it lives here rather than as a file-local constant.
+ */
+const SCAN_USAGE_ERROR_TIMEOUT_MS = 5000;
+
+/**
+ * A Node hook script (gsd-prompt-guard-hook.js, gsd-read-injection-scanner.js)
+ * spawned directly and fed malformed JSON on stdin -- expected to fail closed
+ * gracefully, no subprocess fan-out, no real scan work. A different operation
+ * family from `SCAN_USAGE_ERROR_TIMEOUT_MS` (a bash scan script given no
+ * arguments) despite the coincidentally-matching value -- see that constant's
+ * own doc comment for why the two are kept separate rather than merged.
+ *
+ * Shared across 2 files in batch #4519 of the ad hoc timeout literal
+ * migration, epic #4445 -- every site independently arrived at this exact
+ * value -- that is why it lives here rather than as a file-local constant.
+ */
+const MALFORMED_INPUT_HOOK_TIMEOUT_MS = 5000;
+
 module.exports = {
   PROBE_TIMEOUT_MS,
   HOOK_FANOUT_TIMEOUT_MS,
@@ -200,4 +236,6 @@ module.exports = {
   FIXTURE_HOOK_TIMEOUT_SECONDS,
   STAGED_HOOK_SCRIPT_TIMEOUT_MS,
   LOOP_HOOK_POINT_CLI_TIMEOUT_MS,
+  SCAN_USAGE_ERROR_TIMEOUT_MS,
+  MALFORMED_INPUT_HOOK_TIMEOUT_MS,
 };
diff --git a/tests/prompt-injection-scan.security.test.cjs b/tests/prompt-injection-scan.security.test.cjs
index 7c8d72327..87f70245f 100644
--- a/tests/prompt-injection-scan.security.test.cjs
+++ b/tests/prompt-injection-scan.security.test.cjs
@@ -32,6 +32,7 @@ const path = require('path');
 const { scanForInjection } = require('../gsd-core/bin/lib/security.cjs');
 const { runHook } = require('./helpers/process-seam.cjs');
 const { createTempDir, cleanup } = require('./helpers.cjs');
+const { QUICK_SPAWN_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
 // ─── Configuration ──────────────────────────────────────────────────────────
 
@@ -51,7 +52,7 @@ function scanContent(t, content) {
   t.after(() => cleanup(dir));
   const file = path.join(dir, 'fixture.txt');
   fs.writeFileSync(file, `${content}\n`);
-  const result = runHook(SCAN_SCRIPT, ['--file', file], { interpreter: 'bash', timeoutMs: 10_000 });
+  const result = runHook(SCAN_SCRIPT, ['--file', file], { interpreter: 'bash', timeoutMs: QUICK_SPAWN_TIMEOUT_MS });
   return result;
 }
 
diff --git a/tests/read-injection-scanner.property.test.cjs b/tests/read-injection-scanner.property.test.cjs
index bed64f101..3c5459046 100644
--- a/tests/read-injection-scanner.property.test.cjs
+++ b/tests/read-injection-scanner.property.test.cjs
@@ -32,6 +32,13 @@ const { runHook: runHookSeam } = require('./helpers/process-seam.cjs');
 
 const HOOK_PATH = path.join(__dirname, '..', 'hooks', 'gsd-read-injection-scanner.js');
 
+/**
+ * Safety-net ceiling for a single hook invocation — 6x the hook's own
+ * internal 5s timer. Never itself an assertion target; see the rationale
+ * in runHook()'s doc comment below.
+ */
+const READ_INJECTION_SCANNER_SAFETY_NET_TIMEOUT_MS = 30000;
+
 /**
  * Run the scanner hook with a payload and return its result.
  *
@@ -57,7 +64,10 @@ function runHook(payload) {
     return { exitCode: 0, stdout: '', skipped: true };
   }
 
-  const result = runHookSeam(HOOK_PATH, [], { input, timeoutMs: 30000 });
+  const result = runHookSeam(HOOK_PATH, [], {
+    input,
+    timeoutMs: READ_INJECTION_SCANNER_SAFETY_NET_TIMEOUT_MS,
+  });
 
   return {
     exitCode: result.exitCode ?? 1,
diff --git a/tests/read-injection-scanner.security.test.cjs b/tests/read-injection-scanner.security.test.cjs
index 09a5192ab..d9bee2c28 100644
--- a/tests/read-injection-scanner.security.test.cjs
+++ b/tests/read-injection-scanner.security.test.cjs
@@ -24,6 +24,7 @@ const { cleanup } = require('./helpers.cjs'); // #4020: fixture-tree removal
 const assert = require('node:assert/strict');
 const { execFileSync } = require('node:child_process');
 const { runHook: runHookSeam } = require('./helpers/process-seam.cjs');
+const { MALFORMED_INPUT_HOOK_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
 const HOOK_PATH = require('node:path').join(__dirname, '..', 'hooks', 'gsd-read-injection-scanner.js');
 
@@ -186,7 +187,7 @@ describe('gsd-read-injection-scanner: edge cases', () => {
     let signal = null;
     try {
       stdout = execFileSync(process.execPath, [HOOK_PATH], {
-        input, encoding: 'utf-8', timeout: 5000, stdio: ['pipe', 'pipe', 'pipe'],
+        input, encoding: 'utf-8', timeout: MALFORMED_INPUT_HOOK_TIMEOUT_MS, stdio: ['pipe', 'pipe', 'pipe'],
       }).trim();
     } catch (err) {
       exitCode = err.status ?? 0;
diff --git a/tests/secret-scan-lint.security.test.cjs b/tests/secret-scan-lint.security.test.cjs
index 49f551567..e3d7b18dd 100644
--- a/tests/secret-scan-lint.security.test.cjs
+++ b/tests/secret-scan-lint.security.test.cjs
@@ -39,6 +39,7 @@ const fs = require('fs');
 const os = require('os');
 const path = require('path');
 const { cleanup } = require('./helpers.cjs');
+const { QUICK_SPAWN_TIMEOUT_MS, SCAN_USAGE_ERROR_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
 const PROJECT_ROOT = path.join(__dirname, '..');
 const LINT_SCRIPT = path.join(PROJECT_ROOT, 'scripts', 'secret-scan-lint.sh');
@@ -62,7 +63,7 @@ function runLint(ignoreContent, extraArgs = []) {
     const args = ['--file', ignoreFile, ...extraArgs];
     const result = spawnSync(LINT_SCRIPT, args, {
       encoding: 'utf-8',
-      timeout: 10000,
+      timeout: QUICK_SPAWN_TIMEOUT_MS,
     });
     return {
       status: result.status !== null ? result.status : 1,
@@ -87,7 +88,7 @@ function runSecretScan(fileContent, extraArgs = []) {
     const args = ['--file', tmpFile, ...extraArgs];
     const result = spawnSync(SECRET_SCAN, args, {
       encoding: 'utf-8',
-      timeout: 10000,
+      timeout: QUICK_SPAWN_TIMEOUT_MS,
     });
     return {
       status: result.status !== null ? result.status : 1,
@@ -318,7 +319,7 @@ describe('lint: grandfathered entries (backward compat)', { skip: IS_WINDOWS },
       execFileSync(LINT_SCRIPT, [], {
         encoding: 'utf-8',
         stdio: ['pipe', 'pipe', 'pipe'],
-        timeout: 5000,
+        timeout: SCAN_USAGE_ERROR_TIMEOUT_MS,
       });
       assert.fail('Should have exited non-zero');
     } catch (err) {
@@ -339,7 +340,7 @@ describe('secret-scan.sh --strict: reduces effective exclusions', { skip: IS_WIN
     try {
       const result = spawnSync(SECRET_SCAN, ['--file', tmpFile, '--strict'], {
         encoding: 'utf-8',
-        timeout: 10000,
+        timeout: QUICK_SPAWN_TIMEOUT_MS,
         cwd: tmpDir,  // No .secretscanignore here — clean workspace
       });
       const status = result.status !== null ? result.status : 1;
@@ -384,7 +385,7 @@ describe('secret-scan.sh --strict: reduces effective exclusions', { skip: IS_WIN
       // Default mode: grandfathered entry IS honoured → file is excluded → exit 0
       const defaultResult = spawnSync(SECRET_SCAN, ['--file', relFile], {
         encoding: 'utf-8',
-        timeout: 10000,
+        timeout: QUICK_SPAWN_TIMEOUT_MS,
         cwd: tmpDir,  // CWD has .secretscanignore with the grandfathered entry
       });
       const defaultStatus = defaultResult.status !== null ? defaultResult.status : 1;
@@ -392,7 +393,7 @@ describe('secret-scan.sh --strict: reduces effective exclusions', { skip: IS_WIN
       // Strict mode: grandfathered entry NOT honoured → file is scanned → exit 1
       const strictResult = spawnSync(SECRET_SCAN, ['--file', relFile, '--strict'], {
         encoding: 'utf-8',
-        timeout: 10000,
+        timeout: QUICK_SPAWN_TIMEOUT_MS,
         cwd: tmpDir,  // Same CWD, same .secretscanignore
       });
       const strictStatus = strictResult.status !== null ? strictResult.status : 0;
@@ -426,7 +427,7 @@ describe('secret-scan.sh default mode: regression test', { skip: IS_WINDOWS }, (
     // .secretscanignore is found. Excluded → scanned 0 files → exit 0.
     const result = spawnSync(SECRET_SCAN, ['--file', 'gsd-core/workflows/plan-phase.md'], {
       encoding: 'utf-8',
-      timeout: 10000,
+      timeout: QUICK_SPAWN_TIMEOUT_MS,
       cwd: PROJECT_ROOT,
     });
     const status = result.status !== null ? result.status : 1;
diff --git a/tests/security-prompt-injection.security.test.cjs b/tests/security-prompt-injection.security.test.cjs
index f86cdb854..19287448b 100644
--- a/tests/security-prompt-injection.security.test.cjs
+++ b/tests/security-prompt-injection.security.test.cjs
@@ -85,6 +85,7 @@ const {
 } = require('./helpers.cjs');
 const { runCli } = require('./helpers/cli-negative.cjs');
 const { runHook: runHookSeam } = require('./helpers/process-seam.cjs');
+const { MALFORMED_INPUT_HOOK_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
 const REPO_ROOT = path.resolve(__dirname, '..');
 const PROMPT_GUARD_HOOK = path.join(REPO_ROOT, 'hooks', 'gsd-prompt-guard.js');
@@ -402,7 +403,7 @@ describe('gsd-prompt-guard: hostile .planning/ writes are advised, not blocked',
     const r = spawnSync(process.execPath, [PROMPT_GUARD_HOOK], {
       input: 'this is not json at all',
       encoding: 'utf-8',
-      timeout: 5000,
+      timeout: MALFORMED_INPUT_HOOK_TIMEOUT_MS,
     });
     assert.strictEqual(r.status, 0, 'hook must never propagate parser failure');
   });
@@ -493,7 +494,7 @@ describe('gsd-read-injection-scanner: hostile reads are flagged with severity',
     const r = spawnSync(process.execPath, [READ_SCANNER_HOOK], {
       input: '{not json',
       encoding: 'utf-8',
-      timeout: 5000,
+      timeout: MALFORMED_INPUT_HOOK_TIMEOUT_MS,
     });
     assert.strictEqual(r.status, 0,
       'hook must silent-fail on parser error — never block downstream tool');
diff --git a/tests/security-scan.security.test.cjs b/tests/security-scan.security.test.cjs
index cc718afac..370c63b97 100644
--- a/tests/security-scan.security.test.cjs
+++ b/tests/security-scan.security.test.cjs
@@ -42,7 +42,19 @@ const path = require('path');
 const { cleanup, createTempGitProject } = require('./helpers.cjs');
 const { runHook } = require('./helpers/process-seam.cjs');
 const { gitOrThrow, GIT_FIXTURE_TIMEOUT_MS } = require('./helpers/git-fixture.cjs');
-const { HOOK_FANOUT_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
+const {
+  HOOK_FANOUT_TIMEOUT_MS,
+  QUICK_SPAWN_TIMEOUT_MS,
+  SCAN_USAGE_ERROR_TIMEOUT_MS,
+} = require('./helpers/timeouts.cjs');
+
+// Bounds base64-scan.sh under the locale-regression scenario (see the
+// comment above the describe block below): a dir/file scan with non-UTF8
+// content under a non-C locale must complete cleanly within 30s. Numerically
+// coincides with timeouts.cjs's BUILD_TIMEOUT_MS (an unrelated
+// hooks-bundle-build operation) but matches neither that nor any other
+// existing shared constant, so it stays file-local.
+const BASE64_LOCALE_SCAN_TIMEOUT_MS = 30000;
 
 const PROJECT_ROOT = path.join(__dirname, '..');
 const SCRIPTS = {
@@ -68,7 +80,7 @@ function runScript(scriptPath, content, extraArgs) {
     const result = execFileSync(scriptPath, args, {
       encoding: 'utf-8',
       stdio: ['pipe', 'pipe', 'pipe'],
-      timeout: 10000,
+      timeout: QUICK_SPAWN_TIMEOUT_MS,
     });
     return { status: 0, stdout: result, stderr: '' };
   } catch (err) {
@@ -201,7 +213,7 @@ describe('prompt-injection-scan.sh', { skip: IS_WINDOWS }, () => {
       execFileSync(SCRIPTS.injection, [], {
         encoding: 'utf-8',
         stdio: ['pipe', 'pipe', 'pipe'],
-        timeout: 5000,
+        timeout: SCAN_USAGE_ERROR_TIMEOUT_MS,
       });
       assert.fail('Should have exited non-zero');
     } catch (err) {
@@ -218,7 +230,7 @@ describe('prompt-injection-scan.sh', { skip: IS_WINDOWS }, () => {
 function runScriptOnDir(scriptPath, dirPath, env) {
   const result = spawnSync('bash', [scriptPath, '--dir', dirPath], {
     encoding: 'utf-8',
-    timeout: 30000,
+    timeout: BASE64_LOCALE_SCAN_TIMEOUT_MS,
     env: { ...process.env, ...env },
   });
   return {
@@ -233,7 +245,7 @@ function runScriptOnDir(scriptPath, dirPath, env) {
 function runScriptOnFile(scriptPath, filePath, env) {
   const result = spawnSync('bash', [scriptPath, '--file', filePath], {
     encoding: 'utf-8',
-    timeout: 30000,
+    timeout: BASE64_LOCALE_SCAN_TIMEOUT_MS,
     env: { ...process.env, ...env },
   });
   return {
@@ -292,7 +304,7 @@ describe('base64-scan.sh', { skip: IS_WINDOWS }, () => {
       execFileSync(SCRIPTS.base64, [], {
         encoding: 'utf-8',
         stdio: ['pipe', 'pipe', 'pipe'],
-        timeout: 5000,
+        timeout: SCAN_USAGE_ERROR_TIMEOUT_MS,
       });
       assert.fail('Should have exited non-zero');
     } catch (err) {
@@ -504,7 +516,7 @@ describe('secret-scan.sh', { skip: IS_WINDOWS }, () => {
       execFileSync(SCRIPTS.secret, [], {
         encoding: 'utf-8',
         stdio: ['pipe', 'pipe', 'pipe'],
-        timeout: 5000,
+        timeout: SCAN_USAGE_ERROR_TIMEOUT_MS,
       });
       assert.fail('Should have exited non-zero');
     } catch (err) {
diff --git a/tests/security.test.cjs b/tests/security.test.cjs
index 7c64c66a5..e75f0944e 100644
--- a/tests/security.test.cjs
+++ b/tests/security.test.cjs
@@ -654,10 +654,19 @@ describe('validateFieldName', () => {
 
 const { runHook: runHookSeam } = require('./helpers/process-seam.cjs');
 
+// Bounds a single advisory hook invocation (gsd-context-monitor.js or
+// gsd-statusline.js) under a session_id path-traversal security test —
+// trivial synchronous work, no subprocess fan-out, expected near-instant
+// silent exit. The value (3000ms) is the tightest bound in this migration's
+// security-scanners batch and unique to this file/class; preserved exactly,
+// not widened to match any other existing norm. No fresh bench data
+// justifies a different number.
+const SESSION_ID_TRAVERSAL_HOOK_TIMEOUT_MS = 3000;
+
 function runHook(hookPath, inputJson) {
   const result = runHookSeam(hookPath, [], {
     input: JSON.stringify(inputJson),
-    timeoutMs: 3000,
+    timeoutMs: SESSION_ID_TRAVERSAL_HOOK_TIMEOUT_MS,
   });
   return { exitCode: result.exitCode, stdout: result.stdout, stderr: result.stderr };
 }