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fix: preserve MCP request IDs in success and error responses #7

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Merged
veronica-agent merged 1 commit into from
Oct 5, 2026
Merged

fix: preserve MCP request IDs in success and error responses #7

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26 changes: 23 additions & 3 deletions src/json.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,6 @@ static char *dupn(const char *s, size_t n) {
static const char *parse_str(const char *s, char **out) {
if (*s != '"') return NULL;
s++;
const char *start = s;
char buf[4096];
size_t n = 0;
while (*s && *s != '"') {
Expand All @@ -38,13 +37,20 @@ static const char *parse_str(const char *s, char **out) {
if (c == 'n') c = '\n';
else if (c == 't') c = '\t';
else if (c == 'r') c = '\r';
else if (c == 'b') c = '\b';
else if (c == 'f') c = '\f';
else if (c == 'u') {
for (int i = 0; i < 4; i++) {
if (!isxdigit((unsigned char)s[i])) return NULL;
}
} else if (c != '"' && c != '\\' && c != '/') return NULL;
buf[n++] = c;
} else {
if ((unsigned char)*s < 0x20) return NULL;
buf[n++] = *s++;
}
}
if (*s != '"') return NULL;
(void)start;
*out = dupn(buf, n);
return *out ? s + 1 : NULL;
}
Expand All @@ -53,9 +59,17 @@ static const char *parse_num(const char *s, JVal *v) {
const char *b = s;
if (*s == '-') s++;
if (!isdigit((unsigned char)*s)) return NULL;
while (isdigit((unsigned char)*s)) s++;
if (*s == '0') s++;
else while (isdigit((unsigned char)*s)) s++;
if (*s == '.') {
s++;
if (!isdigit((unsigned char)*s)) return NULL;
while (isdigit((unsigned char)*s)) s++;
}
if (*s == 'e' || *s == 'E') {
s++;
if (*s == '+' || *s == '-') s++;
if (!isdigit((unsigned char)*s)) return NULL;
while (isdigit((unsigned char)*s)) s++;
}
v->s = dupn(b, (size_t)(s - b));
Expand Down Expand Up @@ -117,11 +131,16 @@ static const char *parse_arr(const char *s, JVal *v) {

static const char *parse_val(const char *s, JVal **out) {
s = skip(s);
const char *start = s;
JVal *v = NULL;
if (*s == '"') {
v = node(JSTR);
if (!v) return NULL;
s = parse_str(s, &v->s);
if (s) {
v->raw = dupn(start, (size_t)(s - start));
if (!v->raw) s = NULL;
}
} else if (*s == '{') {
v = node(JOBJ);
if (!v) return NULL;
Expand Down Expand Up @@ -178,6 +197,7 @@ void jfree(JVal *v) {
JVal *n = v->next;
jfree(v->head);
free(v->s);
free(v->raw);
free(v->k);
free(v);
v = n;
Expand Down
1 change: 1 addition & 0 deletions src/json.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ struct JVal {
JType t;
int b;
char *s; /* JSTR, and JNUM lexeme */
char *raw; /* owned JSTR JSON lexeme, for lossless protocol ID echo */
JVal *head; /* JARR/JOBJ children */
JVal *next;
char *k; /* object member key */
Expand Down
30 changes: 10 additions & 20 deletions src/mcp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,11 +37,14 @@ static void reply_ok(const char *id, const char *body) {
}

static void reply_err(const char *id, int code, const char *msg) {
char line[1024];
snprintf(line, sizeof(line),
size_t n = strlen(id) + strlen(msg) + 96;
char *line = malloc(n);
if (!line) return;
snprintf(line, n,
"{\"jsonrpc\":\"2.0\",\"id\":%s,\"error\":{\"code\":%d,\"message\":\"%s\"}}",
id, code, msg);
emit(line);
free(line);
}

static char *b64enc(const uint8_t *src, size_t n, size_t *outn) {
Expand Down Expand Up @@ -86,22 +89,10 @@ static void json_escape(const char *in, char *out, size_t n) {
out[i] = 0;
}

static void id_emit(const JVal *idv, char *out, size_t n) {
if (!idv || idv->t == JNULL) {
snprintf(out, n, "null");
return;
}
if (idv->t == JNUM && idv->s) {
snprintf(out, n, "%s", idv->s);
return;
}
if (idv->t == JSTR && idv->s) {
char esc[128];
json_escape(idv->s, esc, sizeof(esc));
snprintf(out, n, "\"%s\"", esc);
return;
}
snprintf(out, n, "null");
static const char *id_emit(const JVal *idv) {
if (idv && idv->t == JNUM && idv->s) return idv->s;
if (idv && idv->t == JSTR && idv->raw) return idv->raw;
return "null";
}

static void tool_text(const char *id, const char *text, int is_err) {
Expand Down Expand Up @@ -218,8 +209,7 @@ int gaze_mcp(uint16_t vid, uint16_t pid) {
reply_err("null", -32700, "parse error");
continue;
}
char id[64];
id_emit(jobj(root, "id"), id, sizeof(id));
const char *id = id_emit(jobj(root, "id"));
const char *method = jstr(jobj(root, "method"));
if (!method) {
if (jobj(root, "id")) reply_err(id, -32600, "no method");
Expand Down
47 changes: 47 additions & 0 deletions tests/test_protocol.py
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,53 @@ def call(self, method, params=None):


class Protocol(unittest.TestCase):
def test_request_ids_round_trip(self):
# Success and error responses must remain valid JSON and echo the full ID.
ids = [
"",
"request-" + "x" * 2000,
'quoted"\\request',
"line\nreturn\rtab\t",
"controls\b\f\x00\x1f",
"café-東京-🎥",
1234567890123456789012345678901234567890123456789012345678901234567890,
1.25e30,
-1.25e-30,
None,
]
mcp = Mcp()
try:
for request_id in ids:
for method in ("ping", "unknown-method", None):
with self.subTest(request_id=repr(request_id)[:80], method=method):
request = {"jsonrpc": "2.0", "id": request_id}
if method is not None:
request["method"] = method
reply = mcp.send(request)
self.assertEqual(reply["id"], request_id)
if method == "ping":
self.assertEqual(reply["result"], {})
else:
self.assertEqual(reply["error"]["code"],
-32600 if method is None else -32601)
self.assertEqual(mcp.call("ping")["result"], {})
finally:
mcp.close()

def test_invalid_id_tokens_are_parse_errors(self):
mcp = Mcp()
try:
for token in ('"\\q"', '"\\u12"', '"\\uZZZZ"', '"raw\tcontrol"',
'01', '-01', '1.', '1e', '1e+'):
with self.subTest(token=token):
reply = mcp.send('{"jsonrpc":"2.0","id":' + token +
',"method":"ping"}')
self.assertIsNone(reply["id"])
self.assertEqual(reply["error"]["code"], -32700)
self.assertEqual(mcp.call("ping")["result"], {})
finally:
mcp.close()

def test_version(self):
p = subprocess.run([str(GAZE), "--version"], capture_output=True, text=True)
self.assertEqual(p.returncode, 0)
Expand Down
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