diff --git a/CHANGELOG.md b/CHANGELOG.md
index ee5d781..68e1773 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,18 @@
 
 All notable changes to this project will be documented in this file.
 
+## [Unreleased]
+
+### Fixed
+
+- **Hooks emitted invalid JSON, so Claude Code dropped their injected
+  context.** `outputWithContext()` wrote a `hookSpecificOutput` object
+  without the required `hookEventName` field; the harness rejected it
+  ("hookSpecificOutput is missing required field hookEventName") and
+  discarded the context the SessionStart, UserPromptSubmit, and PostToolUse
+  hooks tried to inject. The helper now takes the event name and every
+  caller passes its own (`SessionStart` / `UserPromptSubmit` / `PostToolUse`).
+
 ## [1.2.0] — 2026-05-01
 
 Research-paper-driven detector update. Implements operational findings from
diff --git a/hooks/scripts/lib.mjs b/hooks/scripts/lib.mjs
index a123590..1ddbdba 100644
--- a/hooks/scripts/lib.mjs
+++ b/hooks/scripts/lib.mjs
@@ -289,10 +289,11 @@ export function outputContinue() {
   process.stdout.write(JSON.stringify({ continue: true }) + '\n');
 }
 
-export function outputWithContext(message) {
+export function outputWithContext(message, hookEventName) {
   process.stdout.write(JSON.stringify({
     continue: true,
     hookSpecificOutput: {
+      hookEventName,
       additionalContext: message
     }
   }) + '\n');
diff --git a/hooks/scripts/prompt-analyzer.mjs b/hooks/scripts/prompt-analyzer.mjs
index da39fd6..2ad40a3 100644
--- a/hooks/scripts/prompt-analyzer.mjs
+++ b/hooks/scripts/prompt-analyzer.mjs
@@ -487,7 +487,7 @@ if (warnings.length > 0) {
     const freshState = readState();
     freshState.last_warning_epoch = nowEpoch();
     writeState(freshState);
-    outputWithContext(warnings.join(' '));
+    outputWithContext(warnings.join(' '), 'UserPromptSubmit');
   } else {
     outputContinue();
   }
diff --git a/hooks/scripts/session-start.mjs b/hooks/scripts/session-start.mjs
index 99f4335..fd98297 100644
--- a/hooks/scripts/session-start.mjs
+++ b/hooks/scripts/session-start.mjs
@@ -93,4 +93,4 @@ if (recent.length >= TIER2_SESSION_THRESHOLD) {
   }
 }
 
-outputWithContext(msg);
+outputWithContext(msg, 'SessionStart');
diff --git a/hooks/scripts/tool-tracker.mjs b/hooks/scripts/tool-tracker.mjs
index 7d67854..6b1a9ac 100644
--- a/hooks/scripts/tool-tracker.mjs
+++ b/hooks/scripts/tool-tracker.mjs
@@ -127,7 +127,7 @@ const late = isLateNight() ? ' Late-night session.' : '';
 // No warnings — just periodic reminder at modulo-25
 if (!level) {
   if (toolCount % 25 === 0) {
-    outputWithContext('REMINDER (Interaction Awareness): Check your next response against these rules — no unearned affirmations, no reformulating the user\'s words in stronger terms, no skipping counterarguments to stay agreeable. If you detect a reinforcement loop, scope escalation, or narrative crystallization: name it now.');
+    outputWithContext('REMINDER (Interaction Awareness): Check your next response against these rules — no unearned affirmations, no reformulating the user\'s words in stronger terms, no skipping counterarguments to stay agreeable. If you detect a reinforcement loop, scope escalation, or narrative crystallization: name it now.', 'PostToolUse');
   } else {
     outputContinue();
   }
@@ -141,7 +141,7 @@ const elapsed = nowTs - lastWarning;
 if (lastWarning > 0 && elapsed < cooldown) {
   // Still in cooldown — send periodic reminder instead if at modulo-25
   if (toolCount % 25 === 0) {
-    outputWithContext('REMINDER (Interaction Awareness): Check your next response against these rules — no unearned affirmations, no reformulating the user\'s words in stronger terms, no skipping counterarguments to stay agreeable.');
+    outputWithContext('REMINDER (Interaction Awareness): Check your next response against these rules — no unearned affirmations, no reformulating the user\'s words in stronger terms, no skipping counterarguments to stay agreeable.', 'PostToolUse');
   } else {
     outputContinue();
   }
@@ -163,4 +163,4 @@ state = readState();
 state.last_warning_epoch = nowTs;
 writeState(state);
 
-outputWithContext(warning);
+outputWithContext(warning, 'PostToolUse');
diff --git a/tests/prompt-analyzer.test.mjs b/tests/prompt-analyzer.test.mjs
index d68c5e2..0508423 100644
--- a/tests/prompt-analyzer.test.mjs
+++ b/tests/prompt-analyzer.test.mjs
@@ -273,6 +273,7 @@ describe('thresholds and cooldowns', () => {
     dir = setupTestDir();
     createStateFile(dir, 'p1', { ...freshState(), dep_flags: 1 });
     const out = runHook('prompt-analyzer.mjs', { session_id: 'p1', prompt: 'tell me what to do' }, dir);
+    assert.equal(out.hookSpecificOutput?.hookEventName, 'UserPromptSubmit');
     assert.ok(out.hookSpecificOutput?.additionalContext?.includes('Dependency language noticed'));
   });
 
diff --git a/tests/session-start.test.mjs b/tests/session-start.test.mjs
index a4efa57..bb8af98 100644
--- a/tests/session-start.test.mjs
+++ b/tests/session-start.test.mjs
@@ -12,6 +12,7 @@ describe('session-start', () => {
     dir = setupTestDir();
     const out = runHook('session-start.mjs', { session_id: 's1', cwd: '/tmp' }, dir);
     assert.equal(out.continue, true);
+    assert.equal(out.hookSpecificOutput.hookEventName, 'SessionStart');
     assert.ok(out.hookSpecificOutput.additionalContext.includes('Interaction Awareness is active'));
     const state = readState(dir, 's1');
     assert.ok(state);
diff --git a/tests/tool-tracker.test.mjs b/tests/tool-tracker.test.mjs
index ad20e3a..b1ab681 100644
--- a/tests/tool-tracker.test.mjs
+++ b/tests/tool-tracker.test.mjs
@@ -74,6 +74,7 @@ describe('tool-tracker', () => {
     dir = setupTestDir();
     createStateFile(dir, 't6', freshState({ tool_count: 24 }));
     const out = runHook('tool-tracker.mjs', { session_id: 't6', tool_name: 'Read' }, dir);
+    assert.equal(out.hookSpecificOutput?.hookEventName, 'PostToolUse');
     assert.ok(out.hookSpecificOutput?.additionalContext?.includes('REMINDER'));
   });