From 50987d37b80299e1e8767510e8a60f4130db1c42 Mon Sep 17 00:00:00 2001
From: superbling <me@liukeliang.com>
Date: Sun, 10 May 2026 07:30:00 +0800
Subject: [PATCH] Fix /ctx error handling in interactive REPL

In REPL, parse_int() exits the process via exit(2) on invalid input,
which is correct for command-line parsing but kills the interactive
session, dropping the KV cache and conversation. Add parse_int_repl()
which prints the same error and returns false instead, so the REPL
can just prompt again.

repl_chat_set_ctx() freed the existing session before trying to
create the replacement. If creation failed (e.g. allocation error
for the new context size), the old session was already gone and
run_repl broke out of the loop. Drop the redundant pre-free;
repl_chat_create_session already keeps the old session intact on
failure, so /ctx can now report the error and keep the current
context.
---
 ds4_cli.c | 37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/ds4_cli.c b/ds4_cli.c
index ed53248..2562219 100644
--- a/ds4_cli.c
+++ b/ds4_cli.c
@@ -180,6 +180,17 @@ static int parse_int(const char *s, const char *opt) {
     return (int)v;
 }
 
+static bool parse_int_repl(const char *s, const char *opt, int *out) {
+    char *end = NULL;
+    long v = strtol(s, &end, 10);
+    if (s[0] == '\0' || *end != '\0' || v <= 0 || v > INT32_MAX) {
+        fprintf(stderr, "ds4: invalid value for %s: %s\n", opt, s);
+        return false;
+    }
+    *out = (int)v;
+    return true;
+}
+
 static uint64_t parse_u64(const char *s, const char *opt) {
     char *end = NULL;
     unsigned long long v = strtoull(s, &end, 10);
@@ -861,9 +872,6 @@ static void repl_chat_free(repl_chat *chat) {
 }
 
 static int repl_chat_set_ctx(ds4_engine *engine, repl_chat *chat, int ctx_size) {
-    ds4_session_free(chat->session);
-    chat->session = NULL;
-    chat->ctx_size = 0;
     return repl_chat_create_session(engine, chat, ctx_size);
 }
 
@@ -1057,17 +1065,20 @@ static int run_repl(ds4_engine *engine, cli_config *cfg) {
             if (!arg[0]) {
                 fprintf(stderr, "ds4: /ctx needs a positive integer\n");
             } else {
-                cfg->gen.ctx_size = parse_int(arg, "/ctx");
-                log_context_memory(cfg->engine.backend, cfg->gen.ctx_size);
-                rc = repl_chat_set_ctx(engine, &chat, cfg->gen.ctx_size);
-                if (rc != 0) {
-                    linenoiseFree(line);
-                    break;
+                int new_ctx;
+                if (parse_int_repl(arg, "/ctx", &new_ctx)) {
+                    log_context_memory(cfg->engine.backend, new_ctx);
+                    if (repl_chat_set_ctx(engine, &chat, new_ctx) == 0) {
+                        cfg->gen.ctx_size = new_ctx;
+                        bool active = ds4_think_mode_for_context(cfg->gen.think_mode,
+                                                                 chat.ctx_size) == DS4_THINK_MAX;
+                        repl_chat_apply_max_prefix(engine, &chat, active);
+                        cli_warn_think_max_downgraded(&cfg->gen, "/ctx");
+                    } else {
+                        fprintf(stderr, "ds4: /ctx %d failed; keeping current ctx %d\n",
+                                new_ctx, chat.ctx_size);
+                    }
                 }
-                bool active = ds4_think_mode_for_context(cfg->gen.think_mode,
-                                                         chat.ctx_size) == DS4_THINK_MAX;
-                repl_chat_apply_max_prefix(engine, &chat, active);
-                cli_warn_think_max_downgraded(&cfg->gen, "/ctx");
             }
         } else if (!strcmp(cmd, "/quit") || !strcmp(cmd, "/exit")) {
             linenoiseFree(line);