diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 54477f1..f1562c1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -120,6 +120,7 @@ jobs:
             --npm-pack \
             --emit-events \
             --events-out artifacts/events.ndjson \
+            --events-truncate \
             --strict-events
           echo "::endgroup::"
 
diff --git a/artifacts/events.ndjson b/artifacts/events.ndjson
new file mode 100644
index 0000000..4915b42
--- /dev/null
+++ b/artifacts/events.ndjson
@@ -0,0 +1,23 @@
+{"schema":"tm-events@1","event":"GATES_START","ts":"2025-10-19T02:35:59.889Z","seq":1,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"compose_path":"/workspace/true-modules/runs/canon-loop-demo/meta/compose.json","modules_total":2}}
+{"schema":"tm-events@1","event":"LINT_START","ts":"2025-10-19T02:35:59.960Z","seq":2,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"lint_tool":"eslint"}}
+{"schema":"tm-events@1","event":"LINT_PASS","ts":"2025-10-19T02:36:00.798Z","seq":3,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"lint_tool":"eslint","dur_ms":838}}
+{"schema":"tm-events@1","event":"TEST_START","ts":"2025-10-19T02:36:00.800Z","seq":4,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"reporter","test":"tests/T-001.json"}}
+{"schema":"tm-events@1","event":"TEST_PASS","ts":"2025-10-19T02:36:00.934Z","seq":5,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"reporter","test":"tests/T-001.json","dur_ms":134,"side_effects":{"declared":["FS:write"],"observed_operations":["FS:write"],"undeclared_operations":[],"fs_write":{"count":5,"outside_module_root":false,"sample_paths":[{"path":".tmp","inside_module_root":true},{"path":".tmp/case-t0cphL","inside_module_root":true},{"path":".tmp/case-t0cphL/reporter.log","inside_module_root":true},{"path":".tmp/case-t0cphL","inside_module_root":true},{"path":".tmp/case-t0cphL/reporter.log","inside_module_root":true}],"outside_samples":[]},"processes":{"total":0,"categories":{}}}}}
+{"schema":"tm-events@1","event":"TEST_START","ts":"2025-10-19T02:36:00.935Z","seq":6,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"reporter","test":"tests/T-002.json"}}
+{"schema":"tm-events@1","event":"TEST_PASS","ts":"2025-10-19T02:36:01.088Z","seq":7,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"reporter","test":"tests/T-002.json","dur_ms":153,"side_effects":{"declared":["FS:write"],"observed_operations":["FS:write"],"undeclared_operations":[],"fs_write":{"count":7,"outside_module_root":false,"sample_paths":[{"path":".tmp","inside_module_root":true},{"path":".tmp/case-XI63ZD","inside_module_root":true},{"path":".tmp/case-XI63ZD/reporter.log","inside_module_root":true},{"path":".tmp/case-XI63ZD","inside_module_root":true},{"path":".tmp/case-XI63ZD/reporter.log","inside_module_root":true}],"outside_samples":[]},"processes":{"total":0,"categories":{}}}}}
+{"schema":"tm-events@1","event":"TEST_START","ts":"2025-10-19T02:36:01.089Z","seq":8,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"reporter","test":"tests/invariants/idempotent.json"}}
+{"schema":"tm-events@1","event":"TEST_PASS","ts":"2025-10-19T02:36:01.226Z","seq":9,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"reporter","test":"tests/invariants/idempotent.json","dur_ms":137,"side_effects":{"declared":["FS:write"],"observed_operations":["FS:write"],"undeclared_operations":[],"fs_write":{"count":8,"outside_module_root":false,"sample_paths":[{"path":".tmp","inside_module_root":true},{"path":".tmp/case-dW6Efo","inside_module_root":true},{"path":".tmp/case-dW6Efo/reporter.log","inside_module_root":true},{"path":".tmp/case-dW6Efo","inside_module_root":true},{"path":".tmp/case-dW6Efo/reporter.log","inside_module_root":true}],"outside_samples":[]},"processes":{"total":0,"categories":{}}}}}
+{"schema":"tm-events@1","event":"TEST_START","ts":"2025-10-19T02:36:01.227Z","seq":10,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"cli","test":"tests/T-010.json"}}
+{"schema":"tm-events@1","event":"TEST_PASS","ts":"2025-10-19T02:36:01.358Z","seq":11,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"cli","test":"tests/T-010.json","dur_ms":131,"side_effects":{"declared":[],"observed_operations":[],"undeclared_operations":[],"fs_write":{"count":0,"outside_module_root":false,"sample_paths":[],"outside_samples":[]},"processes":{"total":0,"categories":{}}}}}
+{"schema":"tm-events@1","event":"TEST_START","ts":"2025-10-19T02:36:01.359Z","seq":12,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"cli","test":"tests/invariants/deterministic.json"}}
+{"schema":"tm-events@1","event":"TEST_PASS","ts":"2025-10-19T02:36:01.488Z","seq":13,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"cli","test":"tests/invariants/deterministic.json","dur_ms":129,"side_effects":{"declared":[],"observed_operations":[],"undeclared_operations":[],"fs_write":{"count":0,"outside_module_root":false,"sample_paths":[],"outside_samples":[]},"processes":{"total":0,"categories":{}}}}}
+{"schema":"tm-events@1","event":"PORT_CHECK_START","ts":"2025-10-19T02:36:01.492Z","seq":14,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"reporter","port":"ReporterPort@1"}}
+{"schema":"tm-events@1","event":"PORT_CHECK_START","ts":"2025-10-19T02:36:01.495Z","seq":15,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"cli","port":"CLIPort@1"}}
+{"schema":"tm-events@1","event":"TSC_START","ts":"2025-10-19T02:36:01.500Z","seq":16,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"artifact":".tm/tsc.log"}}
+{"schema":"tm-events@1","event":"TSC_PASS","ts":"2025-10-19T02:36:02.866Z","seq":17,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"dur_ms":1364,"artifact":".tm/tsc.log"}}
+{"schema":"tm-events@1","event":"PORT_CHECK_PASS","ts":"2025-10-19T02:36:02.867Z","seq":18,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"reporter","port":"ReporterPort@1"}}
+{"schema":"tm-events@1","event":"PORT_CHECK_PASS","ts":"2025-10-19T02:36:02.867Z","seq":19,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"cli","port":"CLIPort@1"}}
+{"schema":"tm-events@1","event":"SIDEEFFECTS_SUMMARY","ts":"2025-10-19T02:36:02.880Z","seq":20,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"cli","side_effects":{"declared":[],"observed_operations":[],"undeclared_operations":[],"fs_write":{"count":0,"outside_module_root":false,"sample_paths":[],"outside_samples":[]},"processes":{"total":0,"categories":{}}}}}
+{"schema":"tm-events@1","event":"SIDEEFFECTS_SUMMARY","ts":"2025-10-19T02:36:02.880Z","seq":21,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"module":"reporter","side_effects":{"declared":["FS:write"],"observed_operations":["FS:write"],"undeclared_operations":[],"fs_write":{"count":20,"outside_module_root":false,"sample_paths":[{"path":".tmp","inside_module_root":true},{"path":".tmp/case-t0cphL","inside_module_root":true},{"path":".tmp/case-t0cphL/reporter.log","inside_module_root":true},{"path":".tmp/case-XI63ZD","inside_module_root":true},{"path":".tmp/case-XI63ZD/reporter.log","inside_module_root":true}],"outside_samples":[]},"processes":{"total":0,"categories":{}}}}}
+{"schema":"tm-events@1","event":"GATES_SUMMARY","ts":"2025-10-19T02:36:02.881Z","seq":22,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"phases":[{"name":"manifest_validation","dur_ms":62,"status":"pass"},{"name":"lint","dur_ms":840,"status":"pass"},{"name":"tests","dur_ms":689,"status":"pass"},{"name":"typecheck","dur_ms":1370,"status":"pass"},{"name":"oracles","dur_ms":0,"status":"skipped"},{"name":"npm_pack","dur_ms":0,"status":"skipped"}],"dur_ms":2992,"passed":5,"failed":0,"skipped":0}}
+{"schema":"tm-events@1","event":"GATES_PASS","ts":"2025-10-19T02:36:02.881Z","seq":23,"source":{"cli":"tm","version":"0.1.0"},"context":{"run_id":"canon-demo","mode":"shipping","compose_sha256":"6809b66c0ea846ca9467f763b91e73b3cd9ccf87e462bf5e1beae3ccd2de1af0"},"detail":{"passed":5,"failed":0,"skipped":0,"dur_ms":2992}}
diff --git a/implementation_report.json b/implementation_report.json
new file mode 100644
index 0000000..9b244b4
--- /dev/null
+++ b/implementation_report.json
@@ -0,0 +1,26 @@
+{
+  "schema": "tm-implementation-report@1",
+  "run_id": "2025-10-19T02:36:02.881Z",
+  "canon_lock_sha256": "97b94ada2f0f6bb47477259c7d54a75108a71130ba717d108f93af148db56400",
+  "compose_sha256": "1bc197c0266354b6bef03c58b86156bde9674285f969659eeb95f26526d23013",
+  "results": {
+    "reporter": {
+      "interfaces": { "Reporter.write": "pass" },
+      "invariants": { "idempotent(Reporter.write)": "pass" },
+      "acceptance": { "T-001": "pass", "T-002": "pass" }
+    },
+    "cli": {
+      "interfaces": { "CLI.parse": "pass" },
+      "invariants": { "deterministic(CLI.parse)": "pass" },
+      "acceptance": { "T-010": "pass" }
+    }
+  },
+  "evidence": {
+    "events_file": "artifacts/events.ndjson",
+    "port_exports": {
+      "reporter": { "Reporter.write": "modules/reporter/src/index.js#reporterWrite" },
+      "cli": { "CLI.parse": "modules/cli/src/cli.js#cliParse" }
+    }
+  },
+  "notes": []
+}
diff --git a/modules/reporter/src/index.js b/modules/reporter/src/index.js
index f984322..3653fe8 100644
--- a/modules/reporter/src/index.js
+++ b/modules/reporter/src/index.js
@@ -36,15 +36,16 @@ export async function reporterWrite(message, options = {}) {
     if (err && err.code !== 'ENOENT') throw err;
   }
 
-  const alreadyLast = prior.length > 0 && prior[prior.length - 1] === trimmed;
-  if (!alreadyLast) {
+  const seen = new Set(prior);
+  const alreadyLogged = seen.has(trimmed);
+  if (!alreadyLogged) {
     await fs.appendFile(logFile, `${trimmed}\n`, 'utf8');
     prior.push(trimmed);
   }
 
   return {
     file: logFile,
-    appended: !alreadyLast,
+    appended: !alreadyLogged,
     lines: prior.slice()
   };
 }
diff --git a/modules/reporter/tests/invariants/idempotent.json b/modules/reporter/tests/invariants/idempotent.json
index 807fcda..99922b3 100644
--- a/modules/reporter/tests/invariants/idempotent.json
+++ b/modules/reporter/tests/invariants/idempotent.json
@@ -1,5 +1,6 @@
 {
   "name": "idempotent(Reporter.write)",
   "case": "idempotent",
-  "message": "stable"
+  "message": "stable",
+  "interleave": ["something else"]
 }
diff --git a/modules/reporter/tests/runner.mjs b/modules/reporter/tests/runner.mjs
index d33ad4c..e004be4 100644
--- a/modules/reporter/tests/runner.mjs
+++ b/modules/reporter/tests/runner.mjs
@@ -56,13 +56,25 @@ async function runCase(spec, moduleRoot) {
       }
       case 'idempotent': {
         const first = await reporterWrite(spec.message, { logDir });
-        const second = await reporterWrite(spec.message, { logDir });
         assert.equal(first.appended, true);
+
+        if (Array.isArray(spec.interleave)) {
+          for (const entry of spec.interleave) {
+            const res = await reporterWrite(entry, { logDir });
+            assert.equal(res.appended, true);
+          }
+        }
+
+        const second = await reporterWrite(spec.message, { logDir });
         assert.equal(second.appended, false);
+
         const contents = await fs.readFile(second.file, 'utf8');
-        const lines = contents.trim().split(/\r?\n/);
-        assert.equal(lines.length, 1);
-        assert.equal(lines[0], spec.message);
+        const lines = contents
+          .split(/\r?\n/)
+          .map((line) => line.trimEnd())
+          .filter((line) => line.length > 0);
+        const occurrences = lines.filter((line) => line === spec.message);
+        assert.equal(occurrences.length, 1);
         break;
       }
       default: