diff --git a/.changeset/init-json-envelope.md b/.changeset/init-json-envelope.md
new file mode 100644
index 00000000..5194f842
--- /dev/null
+++ b/.changeset/init-json-envelope.md
@@ -0,0 +1,13 @@
+---
+"@taskless/cli": patch
+---
+
+`init --json` now writes only the parseable envelope to stdout. Previously,
+the non-interactive install path (also reached from `init --no-interactive
+--json`) unconditionally logged human-readable prose — the "no tools
+detected" fallback notice and the per-target skill/command summary — to
+stdout ahead of the JSON envelope, so `taskless init --json | jq .` failed
+with a JSON parse error. That prose now goes to stderr, where it stays
+visible to a person watching the terminal without corrupting a machine
+consumer's view of stdout, matching how `verify`/`test` and the migration
+notice already behave under `--json`.
diff --git a/packages/cli/src/commands/init.ts b/packages/cli/src/commands/init.ts
index 58cd4c86..eb7f520c 100644
--- a/packages/cli/src/commands/init.ts
+++ b/packages/cli/src/commands/init.ts
@@ -94,7 +94,7 @@ export const initCommand = defineCommand({
       );
     }
 
-    const result = await runNonInteractive(cwd);
+    const result = await runNonInteractive(cwd, { json: args.json });
     if (args.json) {
       console.log(
         JSON.stringify({
@@ -245,11 +245,20 @@ export const updateCommand = defineCommand({
   },
 });
 
-async function runNonInteractive(cwd: string): Promise<{
+async function runNonInteractive(
+  cwd: string,
+  options: { json?: boolean } = {}
+): Promise<{
   commandsInstalled: boolean;
   reloadNotice: string | undefined;
   migrated: MigrationReport | undefined;
 }> {
+  // Under `--json`, stdout carries only the envelope printed by the caller.
+  // This per-target summary is not on that envelope (it is finer-grained than
+  // `migrated`/`commandsInstalled`), so rather than drop it, it goes to
+  // stderr — visible to a person watching the terminal, invisible to a
+  // machine consumer parsing stdout.
+  const log = options.json ? console.error : console.log;
   // Sampled BEFORE the directory is created, and that order is the whole
   // point. `ensureTasklessDirectory` mkdir -p's, so afterwards a pre-existing
   // project is indistinguishable from a fresh one.
@@ -263,7 +272,24 @@ async function runNonInteractive(cwd: string): Promise<{
   // can report what a migration moved. `check`, `verify` and `test` used to
   // carry this on their own envelopes and refuse rather than migrate now, so
   // the field followed the behaviour rather than being dropped.
-  const migrated = await ensureTasklessDirectory(cwd);
+  //
+  // The migration notice is suppressed entirely under `--json`, rather than
+  // moved to stderr like the per-target summary above: unlike that summary,
+  // this information IS already on the envelope, as `migrated`, so printing
+  // it a second time would just be noise. This is the actual `verify`/`test`
+  // convention (`verify.ts`'s `onNotice: (message) => { if (!json)
+  // console.error(message); }`), and the case `EnsureOptions.onNotice`'s own
+  // doc comment describes: "callers that emit `--json` should pass a
+  // callback that suppresses output under that flag: the same information is
+  // on the envelope's `migrated` field". Omitting `onNotice` here, as before,
+  // left it on the default fallback (unconditional `console.error`), which
+  // never corrupts stdout but doesn't suppress the duplicate under `--json`
+  // either — the gap a reviewer of this PR caught.
+  const migrated = await ensureTasklessDirectory(cwd, {
+    onNotice: (message: string) => {
+      if (!options.json) console.error(message);
+    },
+  });
   if (wasNewProject) {
     // A project this CLI just created has no entries to walk: everything the
     // ledger describes is already true of the scaffold it wrote.
@@ -291,7 +317,7 @@ async function runNonInteractive(cwd: string): Promise<{
   const reloadNotice = getReloadNotice({ previousCliVersion, cliVersion });
 
   if (detected.length === 0) {
-    console.log(`No tools detected. Using fallback: ${DEFAULT_SHIM_DIR}/`);
+    log(`No tools detected. Using fallback: ${DEFAULT_SHIM_DIR}/`);
   }
 
   const skillsByTarget = groupValuesByTarget(
@@ -332,33 +358,29 @@ async function runNonInteractive(cwd: string): Promise<{
       removedSkills.length === 0 &&
       removedCommands.length === 0
     ) {
-      console.log(`${target.label} (${target.dir}/): up to date`);
+      log(`${target.label} (${target.dir}/): up to date`);
       continue;
     }
 
-    console.log(
+    log(
       `${target.label} (${target.dir}/): wrote ${String(writtenSkills.length)} skill ${noun}(s)`
     );
     for (const name of writtenSkills) {
-      console.log(`  - ${name}`);
+      log(`  - ${name}`);
     }
     if (writtenCommands.length > 0) {
-      console.log(`  + ${String(writtenCommands.length)} command ${noun}(s)`);
+      log(`  + ${String(writtenCommands.length)} command ${noun}(s)`);
     }
     if (removedSkills.length > 0) {
-      console.log(
-        `  removed ${String(removedSkills.length)} obsolete skill(s):`
-      );
+      log(`  removed ${String(removedSkills.length)} obsolete skill(s):`);
       for (const name of removedSkills) {
-        console.log(`    - ${name}`);
+        log(`    - ${name}`);
       }
     }
     if (removedCommands.length > 0) {
-      console.log(
-        `  removed ${String(removedCommands.length)} obsolete command(s):`
-      );
+      log(`  removed ${String(removedCommands.length)} obsolete command(s):`);
       for (const name of removedCommands) {
-        console.log(`    - ${name}`);
+        log(`    - ${name}`);
       }
     }
   }
diff --git a/packages/cli/test/error-envelope.test.ts b/packages/cli/test/error-envelope.test.ts
index 55d56494..2c738b80 100644
--- a/packages/cli/test/error-envelope.test.ts
+++ b/packages/cli/test/error-envelope.test.ts
@@ -44,10 +44,7 @@ async function runCli(
 function parseEnvelope(stdout: string): ErrorEnvelope {
   // The envelope is the last JSON line in stdout. (Some commands also
   // print progress to stderr, so we ignore that.)
-  const lines = stdout.split("\n").filter((l) => l.trim().startsWith("{"));
-  expect(lines.length).toBeGreaterThan(0);
-  const last = lines.at(-1)!;
-  return JSON.parse(last) as ErrorEnvelope;
+  return JSON.parse(stdout.trim()) as ErrorEnvelope;
 }
 
 describe("standardized error envelope (--json)", () => {
diff --git a/packages/cli/test/migrated-envelope.test.ts b/packages/cli/test/migrated-envelope.test.ts
index e0e36a48..ae026e5d 100644
--- a/packages/cli/test/migrated-envelope.test.ts
+++ b/packages/cli/test/migrated-envelope.test.ts
@@ -36,9 +36,18 @@ async function runCli(
   }
 }
 
+/**
+ * Parse `--json` stdout as the WHOLE envelope, not just its last line.
+ *
+ * `stdout.trim().split("\n").at(-1)` was the earlier shape of this helper,
+ * and it is exactly why #279 (`init --json` printing prose ahead of the
+ * envelope) stayed invisible: a helper that only ever reads the last line
+ * cannot fail on anything printed before it. `JSON.parse` on the trimmed
+ * whole string fails loudly the moment stdout carries a second thing,
+ * whichever end it lands on.
+ */
 function parseEnvelope(stdout: string): Record<string, unknown> {
-  const line = stdout.trim().split("\n").at(-1) ?? "";
-  return JSON.parse(line) as Record<string, unknown>;
+  return JSON.parse(stdout.trim()) as Record<string, unknown>;
 }
 
 /** The versions a project seeded at 3 must be carried through. */
@@ -120,6 +129,26 @@ describe("who migrates, and who refuses", () => {
     expectSeededMigration(envelope.migrated);
   });
 
+  it("init --json reports the migration on stdout and stays silent about it on stderr", async () => {
+    // The migration notice duplicates the envelope's `migrated` field, so
+    // under `--json` it is suppressed rather than moved to stderr - unlike
+    // the per-target install summary, which stderr DOES carry under `--json`
+    // because that detail has no field of its own. Catches a regression that
+    // routes this notice back through the unconditional `console.error`
+    // fallback `ensureTasklessDirectory` uses when no `onNotice` is passed.
+    await seedVersion3();
+
+    const { stderr } = await runCli([
+      "init",
+      "--no-interactive",
+      "--json",
+      "-d",
+      temporaryDirectory,
+    ]);
+
+    expect(stderr).not.toContain("Migrat");
+  });
+
   it("init --json omits the field when nothing migrated", async () => {
     // Absence is the signal, so a consumer never reads empty arrays to decide.
     await seedVersion3();
diff --git a/packages/cli/test/no-implicit-migration.test.ts b/packages/cli/test/no-implicit-migration.test.ts
index d93d5097..0cf04bb2 100644
--- a/packages/cli/test/no-implicit-migration.test.ts
+++ b/packages/cli/test/no-implicit-migration.test.ts
@@ -57,6 +57,21 @@ async function runCli(
   }
 }
 
+/**
+ * Parse `--json` stdout as the WHOLE envelope, not just its last line.
+ *
+ * The earlier shape of every call site here was
+ * `JSON.parse(stdout.trim().split("\n").at(-1) ?? "{}")`, and that is exactly
+ * why `init --json` printing prose ahead of its envelope (#279) went
+ * undetected: a helper that only ever reads the last line cannot fail on
+ * anything printed before it. `JSON.parse` on the trimmed whole string fails
+ * loudly the moment stdout carries a second thing, whichever end it lands on
+ * — do not narrow this back to a last-line read.
+ */
+function parseEnvelope<T>(stdout: string): T {
+  return JSON.parse(stdout.trim()) as T;
+}
+
 const FLAT_RULE =
   "id: no-eval\nlanguage: TypeScript\nseverity: error\nmessage: no eval\nrule:\n  pattern: eval($A)\n";
 
@@ -114,10 +129,10 @@ describe("a reporting command never migrates", () => {
     "%s --json carries the code an agent branches on",
     async (command) => {
       const { stdout } = await runCli([command, "--json", "-d", directory]);
-      const envelope = JSON.parse(stdout.trim().split("\n").at(-1) ?? "{}") as {
+      const envelope = parseEnvelope<{
         ok?: boolean;
         code?: string;
-      };
+      }>(stdout);
       expect(envelope.ok).toBe(false);
       // Distinct from SCAFFOLD_VERSION_MISMATCH, which is the opposite
       // direction and asks the caller to upgrade the CLI instead.
@@ -231,9 +246,9 @@ describe("a reporting command never migrates", () => {
       directory,
     ]);
 
-    const envelope = JSON.parse(stdout.trim().split("\n").at(-1) ?? "{}") as {
+    const envelope = parseEnvelope<{
       migrated?: { from: number; to: number };
-    };
+    }>(stdout);
     expect(envelope.migrated?.from).toBe(3);
     expect(envelope.migrated?.to).toBe(LATEST_SCHEMA_VERSION);
     await expect(
@@ -278,11 +293,11 @@ describe("a manifest that cannot be parsed", () => {
     "%s --json reports the file, not a version it guessed",
     async (command) => {
       const { stdout } = await runCli([command, "--json", "-d", directory]);
-      const envelope = JSON.parse(stdout.trim().split("\n").at(-1) ?? "{}") as {
+      const envelope = parseEnvelope<{
         ok?: boolean;
         code?: string;
         message?: string;
-      };
+      }>(stdout);
       expect(envelope.ok).toBe(false);
       expect(envelope.code).toBe("SCAFFOLD_MANIFEST_UNREADABLE");
       expect(envelope.message).toContain("taskless.json");
@@ -331,9 +346,9 @@ describe("a manifest that cannot be parsed", () => {
         "-d",
         bare,
       ]);
-      const envelope = JSON.parse(stdout.trim().split("\n").at(-1) ?? "{}") as {
+      const envelope = parseEnvelope<{
         migrated?: { from: number; to: number };
-      };
+      }>(stdout);
       expect(envelope.migrated?.from).toBe(0);
       expect(envelope.migrated?.to).toBe(LATEST_SCHEMA_VERSION);
     } finally {