diff --git a/src/main/java/dev/marcospaulo/canalhandia/Ai.java b/src/main/java/dev/marcospaulo/canalhandia/Ai.java
index 032431d..91d352f 100644
--- a/src/main/java/dev/marcospaulo/canalhandia/Ai.java
+++ b/src/main/java/dev/marcospaulo/canalhandia/Ai.java
@@ -66,16 +66,51 @@ final class Ai {
         return apiKey() != null;
     }
 
+    /**
+     * The first non-blank line of a key file or variable, with any control
+     * character removed. Null if there is nothing usable.
+     *
+     * <p>{@code trim()} alone leaves an <em>interior</em> newline — a key file
+     * with the key on line 1 and a comment on line 2 survives it. Such a key
+     * cannot go in an HTTP header, and the JDK's rejection of it quotes the
+     * whole header value, key included, into the exception message, which then
+     * reaches the server log. Cleaning at the source means that never happens;
+     * {@link HttpFetcher} checks again as a backstop.
+     *
+     * <p>Takes the first line rather than deleting the newline and joining, so
+     * a trailing comment line cannot be silently welded onto the key to make a
+     * different, wrong one — that would turn a readable failure into a puzzling
+     * authentication error.
+     */
+    static String cleanKey(String raw) {
+        if (raw == null) {
+            return null;
+        }
+        for (String line : raw.split("\\R")) {
+            StringBuilder out = new StringBuilder(line.length());
+            for (int i = 0; i < line.length(); i++) {
+                char c = line.charAt(i);
+                if (c >= 0x20 && c != 0x7F) {
+                    out.append(c);
+                }
+            }
+            String key = out.toString().trim();
+            if (!key.isEmpty()) {
+                return key;
+            }
+        }
+        return null;
+    }
+
     private String apiKey() {
         String fromEnv = System.getenv(KEY_ENV);
         if (fromEnv != null && !fromEnv.isBlank()) {
-            return fromEnv.trim();
+            return cleanKey(fromEnv);
         }
         Path file = plugin.getDataFolder().toPath().resolve(KEY_FILE);
         try {
             if (Files.isReadable(file)) {
-                String key = Files.readString(file, StandardCharsets.UTF_8).trim();
-                return key.isEmpty() ? null : key;
+                return cleanKey(Files.readString(file, StandardCharsets.UTF_8));
             }
         } catch (IOException e) {
             plugin.getLogger().warning("Não consegui ler " + KEY_FILE + ": " + e.getMessage());
diff --git a/src/main/java/dev/marcospaulo/canalhandia/HttpFetcher.java b/src/main/java/dev/marcospaulo/canalhandia/HttpFetcher.java
index 0ad6834..f3c9ba5 100644
--- a/src/main/java/dev/marcospaulo/canalhandia/HttpFetcher.java
+++ b/src/main/java/dev/marcospaulo/canalhandia/HttpFetcher.java
@@ -36,9 +36,38 @@ final class HttpFetcher implements Fetcher {
         return body(http.send(request, HttpResponse.BodyHandlers.ofString()));
     }
 
+    /**
+     * Rejects a bearer token that cannot go in a header, before it reaches one.
+     *
+     * <p>{@code HttpRequest.Builder.header()} validates the value itself, but
+     * its {@code IllegalArgumentException} quotes the offending value back —
+     * measured on temurin-25: {@code invalid header value: "Bearer sk-…"}. That
+     * throw happens before any I/O, so it reaches callers as an ordinary call
+     * failure and lands the credential in whatever log catches it. A key with a
+     * stray second line is enough to trigger it.
+     *
+     * <p>Checking here rather than at the call site means no future caller has
+     * to remember to redact. The message deliberately names only the position
+     * of the offending character, never any part of the key.
+     */
+    static void checkBearer(String bearer) throws IOException {
+        if (bearer == null || bearer.isEmpty()) {
+            throw new IOException("Chave de API vazia.");
+        }
+        for (int i = 0; i < bearer.length(); i++) {
+            char c = bearer.charAt(i);
+            if (c < 0x20 || c == 0x7F) {
+                throw new IOException("Chave de API inválida: caractere de controle na posição "
+                        + i + " (de " + bearer.length() + "). "
+                        + "Verifique se o arquivo da chave tem uma única linha, sem quebra de linha.");
+            }
+        }
+    }
+
     @Override
     public String postJson(String url, String json, String bearer)
             throws IOException, InterruptedException {
+        checkBearer(bearer);
         HttpRequest request = HttpRequest.newBuilder(URI.create(url))
                 .timeout(Duration.ofSeconds(timeoutSeconds))
                 .header("Content-Type", "application/json")
diff --git a/src/main/java/dev/marcospaulo/canalhandia/MiniMax.java b/src/main/java/dev/marcospaulo/canalhandia/MiniMax.java
index 9215daa..0431658 100644
--- a/src/main/java/dev/marcospaulo/canalhandia/MiniMax.java
+++ b/src/main/java/dev/marcospaulo/canalhandia/MiniMax.java
@@ -59,8 +59,15 @@ final class MiniMax {
      */
     private static final double TERM_TEMPERATURE = 0.0;
 
-    /** One message in the request. */
-    record Msg(String role, String content) {
+    /**
+     * One message in the request.
+     *
+     * <p>Named {@code Turn} and not {@code Msg} because the package already has
+     * a top-level {@link Msg}, the chat-formatting helper. A nested record of
+     * that name would shadow it inside this file, so a later {@code Msg.error}
+     * here would resolve to the record instead.
+     */
+    record Turn(String role, String content) {
     }
 
     private final Fetcher fetcher;
@@ -103,8 +110,8 @@ final class MiniMax {
      */
     String searchTerm(String key, String model, String question) {
         JsonObject body = base(model, List.of(
-                new Msg("system", "Você escolhe qual artigo da Minecraft Wiki consultar."),
-                new Msg("user", question)), TERM_TOKENS, TERM_TEMPERATURE);
+                new Turn("system", "Você escolhe qual artigo da Minecraft Wiki consultar."),
+                new Turn("user", question)), TERM_TOKENS, TERM_TEMPERATURE);
         body.add("tools", JsonParser.parseString(TOOLS).getAsJsonArray());
         body.add("tool_choice", JsonParser.parseString(TOOL_CHOICE).getAsJsonObject());
 
@@ -146,7 +153,7 @@ final class MiniMax {
      * spends the whole allowance thinking and returns nothing at all. Measured
      * twice at 400 tokens, which is why answers are given 1200.
      */
-    String answer(String key, String model, List<Msg> messages, int maxTokens, double temperature) {
+    String answer(String key, String model, List<Turn> messages, int maxTokens, double temperature) {
         JsonObject message = message(post(key, base(model, messages, maxTokens, temperature)));
         if (message == null) {
             return null;
@@ -160,9 +167,9 @@ final class MiniMax {
         return content.getAsString();
     }
 
-    private JsonObject base(String model, List<Msg> messages, int maxTokens, double temperature) {
+    private JsonObject base(String model, List<Turn> messages, int maxTokens, double temperature) {
         JsonArray array = new JsonArray();
-        for (Msg msg : messages) {
+        for (Turn msg : messages) {
             JsonObject object = new JsonObject();
             object.addProperty("role", msg.role());
             object.addProperty("content", msg.content());
diff --git a/src/test/java/dev/marcospaulo/canalhandia/AiKeyTest.java b/src/test/java/dev/marcospaulo/canalhandia/AiKeyTest.java
new file mode 100644
index 0000000..bae5bfe
--- /dev/null
+++ b/src/test/java/dev/marcospaulo/canalhandia/AiKeyTest.java
@@ -0,0 +1,78 @@
+package dev.marcospaulo.canalhandia;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * The key-cleaning half of {@link Ai}. The rest of that class needs a running
+ * server; {@code cleanKey} is pure and is where the credential is made safe to
+ * put in a header.
+ */
+class AiKeyTest {
+
+    private static final char LF = 10;
+    private static final char CR = 13;
+
+    @Test
+    void keepsAWellFormedKeyUnchanged() {
+        assertEquals("sk-abc123", Ai.cleanKey("sk-abc123"));
+    }
+
+    @Test
+    void stripsSurroundingWhitespaceAndTrailingNewline() {
+        assertEquals("sk-abc123", Ai.cleanKey("  sk-abc123 " + LF));
+        assertEquals("sk-abc123", Ai.cleanKey("sk-abc123" + CR + LF));
+    }
+
+    /** The case trim() misses: a second line in the key file. */
+    @Test
+    void takesTheFirstLineRatherThanWeldingTheSecondOn() {
+        assertEquals("sk-abc123", Ai.cleanKey("sk-abc123" + LF + "# comentário"));
+        assertEquals("sk-abc123", Ai.cleanKey("sk-abc123" + LF + LF + "lixo"));
+    }
+
+    @Test
+    void skipsLeadingBlankLines() {
+        assertEquals("sk-abc123", Ai.cleanKey(LF + "   " + LF + "sk-abc123"));
+    }
+
+    @Test
+    void removesControlCharactersFromWithinTheLine() {
+        assertEquals("sk-abc", Ai.cleanKey("sk-" + (char) 0 + "abc" + (char) 0x7F));
+    }
+
+    @Test
+    void nothingUsableIsNull() {
+        assertNull(Ai.cleanKey(null));
+        assertNull(Ai.cleanKey(""));
+        assertNull(Ai.cleanKey("   " + LF + "  "));
+    }
+
+    /**
+     * The contract that matters: whatever comes out is something
+     * {@link HttpFetcher} will accept, so the JDK never gets to quote it back.
+     */
+    /**
+     * The contract that matters, asserted end to end: anything {@code cleanKey}
+     * hands back is something {@link HttpFetcher} accepts, so a real key can
+     * never reach the JDK's header validator and be quoted back into a log.
+     */
+    @Test
+    void whateverSurvivesCleaningIsAcceptedAsABearer() {
+        String[] messy = {
+                "sk-abc123",
+                " sk-abc " + LF,
+                "sk-a" + LF + "b",
+                "sk" + (char) 9 + "-x",
+                "sk-x" + CR + LF + "# nota",
+                LF + "sk-y",
+        };
+        for (String raw : messy) {
+            String key = Ai.cleanKey(raw);
+            assertNotNull(key, "nothing survived cleaning of " + raw);
+            assertDoesNotThrow(() -> HttpFetcher.checkBearer(key),
+                    "HttpFetcher rejected a key cleanKey had approved");
+        }
+    }
+}
diff --git a/src/test/java/dev/marcospaulo/canalhandia/HttpFetcherTest.java b/src/test/java/dev/marcospaulo/canalhandia/HttpFetcherTest.java
new file mode 100644
index 0000000..f6274f9
--- /dev/null
+++ b/src/test/java/dev/marcospaulo/canalhandia/HttpFetcherTest.java
@@ -0,0 +1,63 @@
+package dev.marcospaulo.canalhandia;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Only the bearer check is exercised here. It runs before the request is built
+ * and before any I/O, so these tests reach no network: the URL below is a
+ * reserved-for-invalid TLD and would fail loudly if one were ever attempted.
+ */
+class HttpFetcherTest {
+
+    private static final String URL = "https://nunca.invalid/v1/chat";
+
+    /**
+     * A key file with a second line survives {@code trim()}. The resulting
+     * header value makes the JDK throw
+     * {@code invalid header value: "Bearer sk-…"} — the credential, in an
+     * exception message, in whatever log catches it.
+     */
+    @Test
+    void rejectsABearerWithANewlineBeforeBuildingTheRequest() {
+        String key = "sk-canalhandia-segredo" + (char) 10 + "# comentário";
+        IOException thrown = assertThrows(IOException.class,
+                () -> new HttpFetcher(5).postJson(URL, "{}", key));
+        assertFalse(thrown.getMessage().contains("segredo"),
+                "key leaked into the exception: " + thrown.getMessage());
+        assertTrue(thrown.getMessage().contains("controle"), thrown.getMessage());
+    }
+
+    @Test
+    void rejectsCarriageReturnAndNulAndDelete() {
+        for (char c : new char[]{13, 0, 0x7F, 9}) {
+            String key = "sk-segredo" + c + "x";
+            IOException thrown = assertThrows(IOException.class,
+                    () -> new HttpFetcher(5).postJson(URL, "{}", key),
+                    "accepted a bearer containing char " + (int) c);
+            assertFalse(thrown.getMessage().contains("segredo"), thrown.getMessage());
+        }
+    }
+
+    @Test
+    void rejectsAnEmptyOrNullBearer() {
+        assertThrows(IOException.class, () -> new HttpFetcher(5).postJson(URL, "{}", ""));
+        assertThrows(IOException.class, () -> new HttpFetcher(5).postJson(URL, "{}", null));
+    }
+
+    /**
+     * The message must be actionable without quoting the key, so it names the
+     * position and the likely cause instead.
+     */
+    @Test
+    void theMessageSaysWhereTheProblemIsWithoutQuotingTheKey() {
+        IOException thrown = assertThrows(IOException.class,
+                () -> new HttpFetcher(5).postJson(URL, "{}", "abc" + (char) 10 + "def"));
+        assertTrue(thrown.getMessage().contains("3"), thrown.getMessage());
+        assertFalse(thrown.getMessage().contains("abc"), thrown.getMessage());
+        assertFalse(thrown.getMessage().contains("def"), thrown.getMessage());
+    }
+}
diff --git a/src/test/java/dev/marcospaulo/canalhandia/MiniMaxTest.java b/src/test/java/dev/marcospaulo/canalhandia/MiniMaxTest.java
index a361901..b8d1fd3 100644
--- a/src/test/java/dev/marcospaulo/canalhandia/MiniMaxTest.java
+++ b/src/test/java/dev/marcospaulo/canalhandia/MiniMaxTest.java
@@ -119,7 +119,7 @@ class MiniMaxTest {
     void answerSendsNoToolsAndCarriesItsOwnBudget() {
         Recorder recorder = new Recorder("{\"choices\":[{\"message\":{\"content\":\"ok\"}}]}");
         new MiniMax(recorder).answer("k", "MiniMax-M2.7",
-                List.of(new MiniMax.Msg("system", "regras"), new MiniMax.Msg("user", "oi")),
+                List.of(new MiniMax.Turn("system", "regras"), new MiniMax.Turn("user", "oi")),
                 1200, 0.3);
 
         JsonObject body = JsonParser.parseString(recorder.json).getAsJsonObject();
@@ -203,7 +203,7 @@ class MiniMaxTest {
         Recorder recorder = new Recorder("{\"base_resp\":{\"status_code\":1004,"
                 + "\"status_msg\":\"invalid api key\"}}");
         MiniMax refused = new MiniMax(recorder, null, warnings::add);
-        assertNull(refused.answer(key, "m", List.of(new MiniMax.Msg("user", "oi")), 1200, 0.3));
+        assertNull(refused.answer(key, "m", List.of(new MiniMax.Turn("user", "oi")), 1200, 0.3));
         assertNull(refused.searchTerm(key, "m", "oi"));
 
         MiniMax broken = new MiniMax(new Fetcher() {