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fix(agent): keep history that does not fit the summary #108

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45 changes: 37 additions & 8 deletions src/core/agent.c
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,25 @@ static int copy_printed_session_json(char *dst, size_t dst_size, char *printed,

static const char SUMMARIZE_SYSTEM[] = "Summarize the following conversation in one short paragraph. Output only the summary, no preamble.";

/** Summarize oldest messages when over max_ctx; replace with one summary + trailing. */
/** Append one "role: content" line, or roll back if the whole line does not fit. */
static int summary_source_append(char *buf, size_t cap, size_t *used,
const char *role, const char *content)
{
int n;
if (!buf || !used || *used >= cap - 1)
return 0;
n = snprintf(buf + *used, cap - *used, "%s: %s\n",
role ? role : "user", content ? content : "");
if (n < 0 || (size_t)n >= cap - *used) {
buf[*used] = '\0';
return 0;
}
*used += (size_t)n;
return 1;
}

/** Summarize oldest messages when over max_ctx; replace with one summary + trailing.
* Messages that do not fit in the summary source stay in the session. */
static int compact_session_via_llm(const char *session_id, char *session_buf, size_t session_buf_size,
int msg_count, int max_ctx, const provider_t *provider)
{
Expand All @@ -97,17 +115,27 @@ static int compact_session_via_llm(const char *session_id, char *session_buf, si
if (!source_buf) { cJSON_Delete(root); return -1; }
source_buf[0] = '\0';
size_t used = 0;
for (int i = 0; i < to_summarize_n && used < SUMMARY_SOURCE_MAX - 1; i++) {
int next_unsummarized = to_summarize_n;
for (int i = 0; i < to_summarize_n; i++) {
const cJSON *item = cJSON_GetArrayItem(root, i);
if (!item || !cJSON_IsObject(item)) continue;
const char *role = "user";
const char *content = "";
const cJSON *r = cJSON_GetObjectItem(item, "role");
const cJSON *c = cJSON_GetObjectItem(item, "content");
const cJSON *r;
const cJSON *c;
if (!item || !cJSON_IsObject(item)) continue;
r = cJSON_GetObjectItem(item, "role");
c = cJSON_GetObjectItem(item, "content");
if (cJSON_IsString(r)) role = r->valuestring;
if (cJSON_IsString(c)) content = c->valuestring;
int n = snprintf(source_buf + used, SUMMARY_SOURCE_MAX - used, "%s: %s\n", role, content ? content : "");
if (n > 0 && (size_t)n < SUMMARY_SOURCE_MAX - used) used += (size_t)n;
if (!summary_source_append(source_buf, SUMMARY_SOURCE_MAX, &used, role, content)) {
next_unsummarized = i;
break;
}
}
if (used == 0 || next_unsummarized == 0) {
free(source_buf);
cJSON_Delete(root);
return -1;
}
provider_message_t summ_msgs[2] = {
{ .role = "system", .content = SUMMARIZE_SYSTEM, .tool_calls = NULL, .tool_calls_count = 0, .tool_use_id = NULL },
Expand Down Expand Up @@ -136,7 +164,8 @@ static int compact_session_via_llm(const char *session_id, char *session_buf, si
cJSON_AddItemToArray(new_arr, summ_obj);
}
int keep = max_ctx - 1;
int start = msg_count - keep;
int start = (next_unsummarized < to_summarize_n)
? next_unsummarized : (msg_count - keep);
if (start < 0) start = 0;
for (int i = start; i < msg_count; i++) {
const cJSON *item = cJSON_GetArrayItem(root, i);
Expand Down
82 changes: 82 additions & 0 deletions tests/test_agent.c
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Original file line number Diff line number Diff line change
Expand Up @@ -452,6 +452,87 @@ static int test_context_compaction_when_history_exceeds_max(void)
return failed;
}

/* A message past the summary-source cap must stay in the session. The summarizer
* only receives lines that fit; deleting the rest loses history the model never saw. */
static int test_compaction_keeps_message_that_does_not_fit_summary(void)
{
enum { BIG = 65 * 1024, JSON_CAP = 96 * 1024, LOAD_CAP = 128 * 1024 };
int failed = 1;
config_t *cfg = NULL;
char *session_json = NULL;
char *loaded = NULL;
char *big = NULL;
const char *db_path = "build/test_agent_compact_fit.db";
const char *config_path = "build/test_agent_compact_fit.toml";
size_t off;
int i;
char response_buf[4096];
char errbuf[256];
FILE *cf;

memory_cleanup();
compaction_call_count = 0;
if (memory_init(db_path) != 0)
goto cleanup_early;
session_json = malloc(JSON_CAP);
big = malloc((size_t)BIG + 1);
loaded = malloc(LOAD_CAP);
if (!session_json || !big || !loaded)
goto cleanup;
memset(big, 'A', (size_t)BIG);
memcpy(big + BIG - 16, "BIG_MARKER_END!!", 16);
big[BIG] = '\0';
off = 0;
off += (size_t)snprintf(session_json + off, JSON_CAP - off, "[");
off += (size_t)snprintf(session_json + off, JSON_CAP - off,
"{\"role\":\"user\",\"content\":\"alpha_small\"}");
off += (size_t)snprintf(session_json + off, JSON_CAP - off,
",{\"role\":\"user\",\"content\":\"%s\"}", big);
for (i = 2; i < 6; i++) {
off += (size_t)snprintf(session_json + off, JSON_CAP - off,
",{\"role\":\"user\",\"content\":\"m%d\"}", i);
}
off += (size_t)snprintf(session_json + off, JSON_CAP - off, "]");
if (off >= JSON_CAP)
goto cleanup;
if (session_save("cli:compactfit", session_json) != 0)
goto cleanup;
cf = fopen(config_path, "w");
if (!cf)
goto cleanup;
fprintf(cf, "[agent]\nmodel = \"test\"\nmax_context_messages = 4\n[memory]\npath = \"%s\"\n",
db_path);
fclose(cf);
if (config_load(config_path, &cfg, errbuf, sizeof(errbuf)) != 0)
goto cleanup;
response_buf[0] = '\0';
if (agent_run(cfg, "cli:compactfit", "hi", &compaction_provider, NULL, 0,
response_buf, sizeof(response_buf)) != 0)
goto cleanup;
if (session_load("cli:compactfit", loaded, LOAD_CAP) != 0)
goto cleanup;
if (strstr(loaded, "BIG_MARKER_END!!") == NULL) {
fprintf(stderr,
"FAIL: compacted session dropped the message that did not fit the summary\n");
goto cleanup;
}
if (strstr(loaded, "Summary of earlier") == NULL) {
fprintf(stderr, "FAIL: expected a summary of the messages that did fit\n");
goto cleanup;
}
failed = 0;
cleanup:
config_free(cfg);
free(session_json);
free(big);
free(loaded);
cleanup_early:
remove(config_path);
remove(db_path);
memory_cleanup();
return failed;
}

static int test_local_offline_note_when_active_is_local(void)
{
const char *path = "build/test_agent_local_note.toml";
Expand Down Expand Up @@ -1186,6 +1267,7 @@ int main(void)
RUN(test_react_loop_preserves_prior_tool_results());
RUN(test_session_persisted_after_exchange());
RUN(test_context_compaction_when_history_exceeds_max());
RUN(test_compaction_keeps_message_that_does_not_fit_summary());
RUN(test_local_offline_note_when_active_is_local());
RUN(test_local_offline_note_skipped_for_non_local());
RUN(test_session_overflow_does_not_corrupt_history());
Expand Down
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