[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
index_comp[il], err, errlen) != 0) return 1;
    }

    uint8_t *buf = xmalloc(DS4_SESSION_IO_CHUNK);
    int rc = 0;
    for (uint32_t il = 0; rc == 0 && il < DS4_N_LAYER; il++) {
        /* Write the raw ring in logical position order.  The file does not care
         * where the rows happened to live physically in the source graph. */
        const uint32_t raw_first = (uint32_t)s->checkpoint.len - raw_live;
        for (uint32_t r = 0; rc == 0 && r < raw_live; r++) {
            const uint32_t pos = raw_first + r;
            const uint32_t phys = pos % g->raw_cap;
            rc = payload_write_tensor_span(fp,
                                           g->layer_raw_cache[il],
                                           (uint64_t)phys * DS4_N_HEAD_DIM * sizeof(float),
                                           (uint64_t)DS4_N_HEAD_DIM * sizeof(float),
                                           buf,
                                           DS4_SESSION_IO_CHUNK,
                                           err,
                                           errlen);
        }
        const uint32_t ratio = ds4_layer_compress_ratio(il);
        if (rc != 0 || ratio == 0) continue;
        /* Compressed rows are append-only from row zero, so the live prefix is
         * contiguous.  The two compressor state tensors hold the partial window
         * that will become the next compressed row. */
        rc = payload_write_tensor_span(fp,
                                       g->layer_attn_comp_cache[il],
                                       0,
                                       (uint64_t)g->layer_n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                       buf,
                                       DS4_SESSION_IO_CHUNK,
                                       err,
                                       errlen);
        if (rc == 0) rc = payload_write_tensor_span(fp,
                                                    g->layer_attn_state_kv[il],
                                                    0,
                                                    layer_attn_state_bytes(ratio),
                                                    buf,
                                                    DS4_SESSION_IO_CHUNK,
                                                    err,
                                                    errlen);
        if (rc == 0) rc = payload_write_tensor_span(fp,
                                                    g->layer_attn_state_score[il],
                                                    0,
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
index_comp[il], err, errlen) != 0) return 1;
    }

    uint8_t *buf = xmalloc(DS4_SESSION_IO_CHUNK);
    int rc = 0;
    for (uint32_t il = 0; rc == 0 && il < DS4_N_LAYER; il++) {
        /* Write the raw ring in logical position order.  The file does not care
         * where the rows happened to live physically in the source graph. */
        const uint32_t raw_first = (uint32_t)s->checkpoint.len - raw_live;
        for (uint32_t r = 0; rc == 0 && r < raw_live; r++) {
            const uint32_t pos = raw_first + r;
            const uint32_t phys = pos % g->raw_cap;
            rc = payload_write_tensor_span(fp,
                                           g->layer_raw_cache[il],
                                           (uint64_t)phys * DS4_N_HEAD_DIM * sizeof(float),
                                           (uint64_t)DS4_N_HEAD_DIM * sizeof(float),
                                           buf,
                                           DS4_SESSION_IO_CHUNK,
                                           err,
                                           errlen);
        }
        const uint32_t ratio = ds4_layer_compress_ratio(il);
        if (rc != 0 || ratio == 0) continue;
        /* Compressed rows are append-only from row zero, so the live prefix is
         * contiguous.  The two compressor state tensors hold the partial window
         * that will become the next compressed row. */
        rc = payload_write_tensor_span(fp,
                                       g->layer_attn_comp_cache[il],
                                       0,
                                       (uint64_t)g->layer_n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                       buf,
                                       DS4_SESSION_IO_CHUNK,
                                       err,
                                       errlen);
        if (rc == 0) rc = payload_write_tensor_span(fp,
                                                    g->layer_attn_state_kv[il],
                                                    0,
                                                    layer_attn_state_bytes(ratio),
                                                    buf,
                                                    DS4_SESSION_IO_CHUNK,
                                                    err,
                                                    errlen);
        if (rc == 0) rc = payload_write_tensor_span(fp,
                                                    g->layer_attn_state_score[il],
                                                    0,
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
c == 0) rc = payload_write_tensor_span(fp,
                                                    g->layer_attn_state_score[il],
                                                    0,
                                                    layer_attn_state_bytes(ratio),
                                                    buf,
                                                    DS4_SESSION_IO_CHUNK,
                                                    err,
                                                    errlen);
        if (rc == 0 && ratio == 4) {
            rc = payload_write_tensor_span(fp,
                                           g->layer_index_comp_cache[il],
                                           0,
                                           (uint64_t)g->layer_n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                           buf,
                                           DS4_SESSION_IO_CHUNK,
                                           err,
                                           errlen);
            if (rc == 0) rc = payload_write_tensor_span(fp,
                                                        g->layer_index_state_kv[il],
                                                        0,
                                                        layer_index_state_bytes(ratio),
                                                        buf,
                                                        DS4_SESSION_IO_CHUNK,
                                                        err,
                                                        errlen);
            if (rc == 0) rc = payload_write_tensor_span(fp,
                                                        g->layer_index_state_score[il],
                                                        0,
                                                        layer_index_state_bytes(ratio),
                                                        buf,
                                                        DS4_SESSION_IO_CHUNK,
                                                        err,
                                                        errlen);
        }
    }
    free(buf);
    return rc;
#endif
}

int ds4_session_load_payload(ds4_session *s, FILE *fp, uint64_t payload_bytes, char *err, size_t errlen) {
    if (!s || !fp) {
        payload_set_err(err, errlen, "invalid session payload load");
        return 1;
    }
    uint64_t remaining = payload_bytes;
    uint32_t h[DS4_SESSION_PAYLOAD_U32_FIELDS];
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
c == 0) rc = payload_write_tensor_span(fp,
                                                    g->layer_attn_state_score[il],
                                                    0,
                                                    layer_attn_state_bytes(ratio),
                                                    buf,
                                                    DS4_SESSION_IO_CHUNK,
                                                    err,
                                                    errlen);
        if (rc == 0 && ratio == 4) {
            rc = payload_write_tensor_span(fp,
                                           g->layer_index_comp_cache[il],
                                           0,
                                           (uint64_t)g->layer_n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                           buf,
                                           DS4_SESSION_IO_CHUNK,
                                           err,
                                           errlen);
            if (rc == 0) rc = payload_write_tensor_span(fp,
                                                        g->layer_index_state_kv[il],
                                                        0,
                                                        layer_index_state_bytes(ratio),
                                                        buf,
                                                        DS4_SESSION_IO_CHUNK,
                                                        err,
                                                        errlen);
            if (rc == 0) rc = payload_write_tensor_span(fp,
                                                        g->layer_index_state_score[il],
                                                        0,
                                                        layer_index_state_bytes(ratio),
                                                        buf,
                                                        DS4_SESSION_IO_CHUNK,
                                                        err,
                                                        errlen);
        }
    }
    free(buf);
    return rc;
#endif
}

int ds4_session_load_payload(ds4_session *s, FILE *fp, uint64_t payload_bytes, char *err, size_t errlen) {
    if (!s || !fp) {
        payload_set_err(err, errlen, "invalid session payload load");
        return 1;
    }
    uint64_t remaining = payload_bytes;
    uint32_t h[DS4_SESSION_PAYLOAD_U32_FIELDS];
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
c == 0) rc = payload_write_tensor_span(fp,
                                                    g->layer_attn_state_score[il],
                                                    0,
                                                    layer_attn_state_bytes(ratio),
                                                    buf,
                                                    DS4_SESSION_IO_CHUNK,
                                                    err,
                                                    errlen);
        if (rc == 0 && ratio == 4) {
            rc = payload_write_tensor_span(fp,
                                           g->layer_index_comp_cache[il],
                                           0,
                                           (uint64_t)g->layer_n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                           buf,
                                           DS4_SESSION_IO_CHUNK,
                                           err,
                                           errlen);
            if (rc == 0) rc = payload_write_tensor_span(fp,
                                                        g->layer_index_state_kv[il],
                                                        0,
                                                        layer_index_state_bytes(ratio),
                                                        buf,
                                                        DS4_SESSION_IO_CHUNK,
                                                        err,
                                                        errlen);
            if (rc == 0) rc = payload_write_tensor_span(fp,
                                                        g->layer_index_state_score[il],
                                                        0,
                                                        layer_index_state_bytes(ratio),
                                                        buf,
                                                        DS4_SESSION_IO_CHUNK,
                                                        err,
                                                        errlen);
        }
    }
    free(buf);
    return rc;
#endif
}

int ds4_session_load_payload(ds4_session *s, FILE *fp, uint64_t payload_bytes, char *err, size_t errlen) {
    if (!s || !fp) {
        payload_set_err(err, errlen, "invalid session payload load");
        return 1;
    }
    uint64_t remaining = payload_bytes;
    uint32_t h[DS4_SESSION_PAYLOAD_U32_FIELDS];
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
c == 0) rc = payload_write_tensor_span(fp,
                                                    g->layer_attn_state_score[il],
                                                    0,
                                                    layer_attn_state_bytes(ratio),
                                                    buf,
                                                    DS4_SESSION_IO_CHUNK,
                                                    err,
                                                    errlen);
        if (rc == 0 && ratio == 4) {
            rc = payload_write_tensor_span(fp,
                                           g->layer_index_comp_cache[il],
                                           0,
                                           (uint64_t)g->layer_n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                           buf,
                                           DS4_SESSION_IO_CHUNK,
                                           err,
                                           errlen);
            if (rc == 0) rc = payload_write_tensor_span(fp,
                                                        g->layer_index_state_kv[il],
                                                        0,
                                                        layer_index_state_bytes(ratio),
                                                        buf,
                                                        DS4_SESSION_IO_CHUNK,
                                                        err,
                                                        errlen);
            if (rc == 0) rc = payload_write_tensor_span(fp,
                                                        g->layer_index_state_score[il],
                                                        0,
                                                        layer_index_state_bytes(ratio),
                                                        buf,
                                                        DS4_SESSION_IO_CHUNK,
                                                        err,
                                                        errlen);
        }
    }
    free(buf);
    return rc;
#endif
}

int ds4_session_load_payload(ds4_session *s, FILE *fp, uint64_t payload_bytes, char *err, size_t errlen) {
    if (!s || !fp) {
        payload_set_err(err, errlen, "invalid session payload load");
        return 1;
    }
    uint64_t remaining = payload_bytes;
    uint32_t h[DS4_SESSION_PAYLOAD_U32_FIELDS];
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
payload_set_err(err, errlen, "invalid session payload load");
        return 1;
    }
    uint64_t remaining = payload_bytes;
    uint32_t h[DS4_SESSION_PAYLOAD_U32_FIELDS];
    for (uint32_t i = 0; i < DS4_SESSION_PAYLOAD_U32_FIELDS; i++) {
        if (payload_read_u32(fp, &h[i], &remaining, err, errlen) != 0) return 1;
    }
    if (h[0] != DS4_SESSION_PAYLOAD_MAGIC || h[1] != DS4_SESSION_PAYLOAD_VERSION) {
        payload_set_err(err, errlen, "unsupported session payload version");
        return 1;
    }
    if (ds4_session_is_cpu(s)) {
        const uint32_t saved_ctx = h[2];
        const uint32_t saved_prefill_cap = h[3];
        const uint32_t saved_raw_cap = h[4];
        const uint32_t saved_raw_window = h[5];
        const uint32_t saved_comp_cap = h[6];
        const uint32_t saved_tokens = h[7];
        const uint32_t saved_raw_live = h[12];
        const uint32_t cpu_raw_cap = ds4_default_raw_cap((uint32_t)s->ctx_size);
        const uint32_t cpu_comp_cap = session_cpu_comp_cap(s);
        if (saved_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
            payload_set_err(err, errlen, "KV checkpoint does not fit current context");
            return 1;
        }
        if (h[8] != DS4_N_LAYER || h[9] != DS4_N_HEAD_DIM ||
            h[10] != DS4_N_INDEXER_HEAD_DIM || h[11] != DS4_N_VOCAB)
        {
            payload_set_err(err, errlen, "KV checkpoint was written for a different DS4 layout");
            return 1;
        }
        if (saved_prefill_cap != s->prefill_cap || saved_raw_window != cpu_raw_cap) {
            payload_set_err(err, errlen, "KV checkpoint graph chunk layout does not match current runtime");
            return 1;
        }
        const uint32_t expected_raw_live = saved_tokens < saved_raw_window ? saved_tokens : saved_raw_window;
        if (saved_raw_cap == 0 || saved_raw_live != expected_raw_live ||
            saved_raw_live > saved_raw_cap || saved_raw_live > cpu_raw_cap)
        {
            payload_set_err(err, errlen, "KV checkpoint raw ring layout does not match current context");
            return 1;
        }
        if (saved_comp_cap > cpu_comp_cap) {
            payload_set_err(err, errlen, "KV checkpoint compressed cache is larger than current context");
            return 1;
        }

        token_vec new_checkpoint = {0};
        for (uint32_t i = 0; i < saved_tokens; i++) {
            uint32_t tok = 0;
            if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
payload_set_err(err, errlen, "invalid session payload load");
        return 1;
    }
    uint64_t remaining = payload_bytes;
    uint32_t h[DS4_SESSION_PAYLOAD_U32_FIELDS];
    for (uint32_t i = 0; i < DS4_SESSION_PAYLOAD_U32_FIELDS; i++) {
        if (payload_read_u32(fp, &h[i], &remaining, err, errlen) != 0) return 1;
    }
    if (h[0] != DS4_SESSION_PAYLOAD_MAGIC || h[1] != DS4_SESSION_PAYLOAD_VERSION) {
        payload_set_err(err, errlen, "unsupported session payload version");
        return 1;
    }
    if (ds4_session_is_cpu(s)) {
        const uint32_t saved_ctx = h[2];
        const uint32_t saved_prefill_cap = h[3];
        const uint32_t saved_raw_cap = h[4];
        const uint32_t saved_raw_window = h[5];
        const uint32_t saved_comp_cap = h[6];
        const uint32_t saved_tokens = h[7];
        const uint32_t saved_raw_live = h[12];
        const uint32_t cpu_raw_cap = ds4_default_raw_cap((uint32_t)s->ctx_size);
        const uint32_t cpu_comp_cap = session_cpu_comp_cap(s);
        if (saved_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
            payload_set_err(err, errlen, "KV checkpoint does not fit current context");
            return 1;
        }
        if (h[8] != DS4_N_LAYER || h[9] != DS4_N_HEAD_DIM ||
            h[10] != DS4_N_INDEXER_HEAD_DIM || h[11] != DS4_N_VOCAB)
        {
            payload_set_err(err, errlen, "KV checkpoint was written for a different DS4 layout");
            return 1;
        }
        if (saved_prefill_cap != s->prefill_cap || saved_raw_window != cpu_raw_cap) {
            payload_set_err(err, errlen, "KV checkpoint graph chunk layout does not match current runtime");
            return 1;
        }
        const uint32_t expected_raw_live = saved_tokens < saved_raw_window ? saved_tokens : saved_raw_window;
        if (saved_raw_cap == 0 || saved_raw_live != expected_raw_live ||
            saved_raw_live > saved_raw_cap || saved_raw_live > cpu_raw_cap)
        {
            payload_set_err(err, errlen, "KV checkpoint raw ring layout does not match current context");
            return 1;
        }
        if (saved_comp_cap > cpu_comp_cap) {
            payload_set_err(err, errlen, "KV checkpoint compressed cache is larger than current context");
            return 1;
        }

        token_vec new_checkpoint = {0};
        for (uint32_t i = 0; i < saved_tokens; i++) {
            uint32_t tok = 0;
            if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
payload_set_err(err, errlen, "invalid session payload load");
        return 1;
    }
    uint64_t remaining = payload_bytes;
    uint32_t h[DS4_SESSION_PAYLOAD_U32_FIELDS];
    for (uint32_t i = 0; i < DS4_SESSION_PAYLOAD_U32_FIELDS; i++) {
        if (payload_read_u32(fp, &h[i], &remaining, err, errlen) != 0) return 1;
    }
    if (h[0] != DS4_SESSION_PAYLOAD_MAGIC || h[1] != DS4_SESSION_PAYLOAD_VERSION) {
        payload_set_err(err, errlen, "unsupported session payload version");
        return 1;
    }
    if (ds4_session_is_cpu(s)) {
        const uint32_t saved_ctx = h[2];
        const uint32_t saved_prefill_cap = h[3];
        const uint32_t saved_raw_cap = h[4];
        const uint32_t saved_raw_window = h[5];
        const uint32_t saved_comp_cap = h[6];
        const uint32_t saved_tokens = h[7];
        const uint32_t saved_raw_live = h[12];
        const uint32_t cpu_raw_cap = ds4_default_raw_cap((uint32_t)s->ctx_size);
        const uint32_t cpu_comp_cap = session_cpu_comp_cap(s);
        if (saved_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
            payload_set_err(err, errlen, "KV checkpoint does not fit current context");
            return 1;
        }
        if (h[8] != DS4_N_LAYER || h[9] != DS4_N_HEAD_DIM ||
            h[10] != DS4_N_INDEXER_HEAD_DIM || h[11] != DS4_N_VOCAB)
        {
            payload_set_err(err, errlen, "KV checkpoint was written for a different DS4 layout");
            return 1;
        }
        if (saved_prefill_cap != s->prefill_cap || saved_raw_window != cpu_raw_cap) {
            payload_set_err(err, errlen, "KV checkpoint graph chunk layout does not match current runtime");
            return 1;
        }
        const uint32_t expected_raw_live = saved_tokens < saved_raw_window ? saved_tokens : saved_raw_window;
        if (saved_raw_cap == 0 || saved_raw_live != expected_raw_live ||
            saved_raw_live > saved_raw_cap || saved_raw_live > cpu_raw_cap)
        {
            payload_set_err(err, errlen, "KV checkpoint raw ring layout does not match current context");
            return 1;
        }
        if (saved_comp_cap > cpu_comp_cap) {
            payload_set_err(err, errlen, "KV checkpoint compressed cache is larger than current context");
            return 1;
        }

        token_vec new_checkpoint = {0};
        for (uint32_t i = 0; i < saved_tokens; i++) {
            uint32_t tok = 0;
            if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
payload_set_err(err, errlen, "invalid session payload load");
        return 1;
    }
    uint64_t remaining = payload_bytes;
    uint32_t h[DS4_SESSION_PAYLOAD_U32_FIELDS];
    for (uint32_t i = 0; i < DS4_SESSION_PAYLOAD_U32_FIELDS; i++) {
        if (payload_read_u32(fp, &h[i], &remaining, err, errlen) != 0) return 1;
    }
    if (h[0] != DS4_SESSION_PAYLOAD_MAGIC || h[1] != DS4_SESSION_PAYLOAD_VERSION) {
        payload_set_err(err, errlen, "unsupported session payload version");
        return 1;
    }
    if (ds4_session_is_cpu(s)) {
        const uint32_t saved_ctx = h[2];
        const uint32_t saved_prefill_cap = h[3];
        const uint32_t saved_raw_cap = h[4];
        const uint32_t saved_raw_window = h[5];
        const uint32_t saved_comp_cap = h[6];
        const uint32_t saved_tokens = h[7];
        const uint32_t saved_raw_live = h[12];
        const uint32_t cpu_raw_cap = ds4_default_raw_cap((uint32_t)s->ctx_size);
        const uint32_t cpu_comp_cap = session_cpu_comp_cap(s);
        if (saved_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
            payload_set_err(err, errlen, "KV checkpoint does not fit current context");
            return 1;
        }
        if (h[8] != DS4_N_LAYER || h[9] != DS4_N_HEAD_DIM ||
            h[10] != DS4_N_INDEXER_HEAD_DIM || h[11] != DS4_N_VOCAB)
        {
            payload_set_err(err, errlen, "KV checkpoint was written for a different DS4 layout");
            return 1;
        }
        if (saved_prefill_cap != s->prefill_cap || saved_raw_window != cpu_raw_cap) {
            payload_set_err(err, errlen, "KV checkpoint graph chunk layout does not match current runtime");
            return 1;
        }
        const uint32_t expected_raw_live = saved_tokens < saved_raw_window ? saved_tokens : saved_raw_window;
        if (saved_raw_cap == 0 || saved_raw_live != expected_raw_live ||
            saved_raw_live > saved_raw_cap || saved_raw_live > cpu_raw_cap)
        {
            payload_set_err(err, errlen, "KV checkpoint raw ring layout does not match current context");
            return 1;
        }
        if (saved_comp_cap > cpu_comp_cap) {
            payload_set_err(err, errlen, "KV checkpoint compressed cache is larger than current context");
            return 1;
        }

        token_vec new_checkpoint = {0};
        for (uint32_t i = 0; i < saved_tokens; i++) {
            uint32_t tok = 0;
            if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
102, 231, 232, 105, 106, 235, 108, 237, 238, 111,
    240, 113, 114, 243, 116, 245, 246, 119, 120, 249, 250, 123, 252, 125, 126, 255,
};

static const uint64_t iq2xxs_grid[256] = {
    0x0808080808080808, 0x080808080808082b, 0x0808080808081919, 0x0808080808082b08,
    0x0808080808082b2b, 0x0808080808190819, 0x0808080808191908, 0x08080808082b0808,
    0x08080808082b082b, 0x08080808082b2b08, 0x08080808082b2b2b, 0x0808080819080819,
    0x0808080819081908, 0x0808080819190808, 0x0808080819192b08, 0x08080808192b0819,
    0x08080808192b1908, 0x080808082b080808, 0x080808082b08082b, 0x080808082b082b2b,
    0x080808082b2b082b, 0x0808081908080819, 0x0808081908081908, 0x0808081908190808,
    0x0808081908191919, 0x0808081919080808, 0x080808192b081908, 0x080808192b192b08,
    0x0808082b08080808, 0x0808082b0808082b, 0x0808082b082b082b, 0x0808082b2b08082b,
    0x0808190808080819, 0x0808190808081908, 0x0808190808190808, 0x08081908082b0819,
    0x08081908082b1908, 0x0808190819080808, 0x080819081908082b, 0x0808190819082b08,
    0x08081908192b0808, 0x080819082b080819, 0x080819082b081908, 0x080819082b190808,
    0x080819082b2b1908, 0x0808191908080808, 0x080819190808082b, 0x0808191908082b08,
    0x08081919082b0808, 0x080819191908192b, 0x08081919192b2b19, 0x080819192b080808,
    0x080819192b190819, 0x0808192b08082b19, 0x0808192b08190808, 0x0808192b19080808,
    0x0808192b2b081908, 0x0808192b2b2b1908, 0x08082b0808080808, 0x08082b0808081919,
    0x08082b0808082b08, 0x08082b0808191908, 0x08082b08082b2b08, 0x08082b0819080819,
    0x08082b0819081908, 0x08082b0819190808, 0x08082b081919082b, 0x08082b082b082b08,
    0x08082b1908081908, 0x08082b1919080808, 0x08082b2b0808082b, 0x08082b2b08191908,
    0x0819080808080819, 0x0819080808081908, 0x0819080808190808, 0x08190808082b0819,
    0x0819080819080808, 0x08190808192b0808, 0x081908082b081908, 0x081908082b190808,
    0x081908082b191919, 0x0819081908080808, 0x0819081908082b08, 0x08190819082b0808,
    0x0819081919190808, 0x0819081919192b2b, 0x081908192b080808, 0x0819082b082b1908,
    0x0819082b19081919, 0x0819190808080808, 0x0819190808082b08, 0x08191908082b0808,
    0x08191908082b1919, 0x0819190819082b19, 0x081919082b080808, 0x0819191908192b08,
    0x08191919192b082b, 0x0819192b08080808, 0x0819192b0819192b, 0x08192b0808080819,
    0x08192b0808081908, 0x08192b0808190808, 0x08192b0819080808, 0x08192b082b080819,
    0x08192b1908080808, 0x08192b1908081919, 0x08192b192b2b0808, 0x08192b2b19190819,
    0x082b080808080808, 0x082b08080808082b, 0x082b080808082b2b, 0x082b080819081908,
```


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
102, 231, 232, 105, 106, 235, 108, 237, 238, 111,
    240, 113, 114, 243, 116, 245, 246, 119, 120, 249, 250, 123, 252, 125, 126, 255,
};

static const uint64_t iq2xxs_grid[256] = {
    0x0808080808080808, 0x080808080808082b, 0x0808080808081919, 0x0808080808082b08,
    0x0808080808082b2b, 0x0808080808190819, 0x0808080808191908, 0x08080808082b0808,
    0x08080808082b082b, 0x08080808082b2b08, 0x08080808082b2b2b, 0x0808080819080819,
    0x0808080819081908, 0x0808080819190808, 0x0808080819192b08, 0x08080808192b0819,
    0x08080808192b1908, 0x080808082b080808, 0x080808082b08082b, 0x080808082b082b2b,
    0x080808082b2b082b, 0x0808081908080819, 0x0808081908081908, 0x0808081908190808,
    0x0808081908191919, 0x0808081919080808, 0x080808192b081908, 0x080808192b192b08,
    0x0808082b08080808, 0x0808082b0808082b, 0x0808082b082b082b, 0x0808082b2b08082b,
    0x0808190808080819, 0x0808190808081908, 0x0808190808190808, 0x08081908082b0819,
    0x08081908082b1908, 0x0808190819080808, 0x080819081908082b, 0x0808190819082b08,
    0x08081908192b0808, 0x080819082b080819, 0x080819082b081908, 0x080819082b190808,
    0x080819082b2b1908, 0x0808191908080808, 0x080819190808082b, 0x0808191908082b08,
    0x08081919082b0808, 0x080819191908192b, 0x08081919192b2b19, 0x080819192b080808,
    0x080819192b190819, 0x0808192b08082b19, 0x0808192b08190808, 0x0808192b19080808,
    0x0808192b2b081908, 0x0808192b2b2b1908, 0x08082b0808080808, 0x08082b0808081919,
    0x08082b0808082b08, 0x08082b0808191908, 0x08082b08082b2b08, 0x08082b0819080819,
    0x08082b0819081908, 0x08082b0819190808, 0x08082b081919082b, 0x08082b082b082b08,
    0x08082b1908081908, 0x08082b1919080808, 0x08082b2b0808082b, 0x08082b2b08191908,
    0x0819080808080819, 0x0819080808081908, 0x0819080808190808, 0x08190808082b0819,
    0x0819080819080808, 0x08190808192b0808, 0x081908082b081908, 0x081908082b190808,
    0x081908082b191919, 0x0819081908080808, 0x0819081908082b08, 0x08190819082b0808,
    0x0819081919190808, 0x0819081919192b2b, 0x081908192b080808, 0x0819082b082b1908,
    0x0819082b19081919, 0x0819190808080808, 0x0819190808082b08, 0x08191908082b0808,
    0x08191908082b1919, 0x0819190819082b19, 0x081919082b080808, 0x0819191908192b08,
    0x08191919192b082b, 0x0819192b08080808, 0x0819192b0819192b, 0x08192b0808080819,
    0x08192b0808081908, 0x08192b0808190808, 0x08192b0819080808, 0x08192b082b080819,
    0x08192b1908080808, 0x08192b1908081919, 0x08192b192b2b0808, 0x08192b2b19190819,
    0x082b080808080808, 0x082b08080808082b, 0x082b080808082b2b, 0x082b080819081908,
```


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
ds4_tensor *attn_compressor_gate;
    ds4_tensor *attn_compressor_norm;
    ds4_tensor *indexer_attn_q_b;
    ds4_tensor *indexer_proj;
    ds4_tensor *indexer_compressor_ape;
    ds4_tensor *indexer_compressor_kv;
    ds4_tensor *indexer_compressor_gate;
    ds4_tensor *indexer_compressor_norm;
    ds4_tensor *hc_ffn_fn;
    ds4_tensor *hc_ffn_scale;
    ds4_tensor *hc_ffn_base;
    ds4_tensor *ffn_norm;
    ds4_tensor *ffn_gate_tid2eid;
    ds4_tensor *ffn_gate_inp;
    ds4_tensor *ffn_exp_probs_b;
    ds4_tensor *ffn_gate_exps;
    ds4_tensor *ffn_up_exps;
    ds4_tensor *ffn_down_exps;
    ds4_tensor *ffn_gate_shexp;
    ds4_tensor *ffn_up_shexp;
    ds4_tensor *ffn_down_shexp;
} ds4_layer_weights;

typedef struct {
    ds4_tensor *token_embd;
    ds4_tensor *output_hc_base;
    ds4_tensor *output_hc_fn;
    ds4_tensor *output_hc_scale;
    ds4_tensor *output_norm;
    ds4_tensor *output;
    ds4_layer_weights layer[DS4_N_LAYER];
} ds4_weights;

typedef struct {
    ds4_tensor *e_proj;
    ds4_tensor *h_proj;
    ds4_tensor *enorm;
    ds4_tensor *hnorm;
    ds4_tensor *norm;
    ds4_tensor *hc_head_base;
    ds4_tensor *hc_head_fn;
    ds4_tensor *hc_head_scale;
    ds4_layer_weights block;
} ds4_mtp_weights;

/* =========================================================================
 * Fixed Weight Binding and Model Validation.
 * =========================================================================
 *
 * The GGUF tensor directory is converted into a DS4-specific pointer table.
 * After this section, the rest of the program addresses tensors by semantic
 * fields such as layer->attn_q_a or layer->ffn_gate_exps rather than by string
 * lookup.  Shape validation is intentionally strict.
 */

static uint32_t required_u32(const ds4_model *m, const char *key) {
    uint32_t v = 0;
    if (!model_get_u32(m, key, &v)) {
        fprintf(stderr, "ds4: required metadata key is missing: %s\n", key);
        exit(1);
    }
    return v;
}

static uint64_t required_u64(const ds4_model *m, const char *key) {
    ds4_kv *kv = model_find_kv(m, key);
    if (!kv) {
        fprintf(stderr, "ds4: required metadata key is missing: %s\n", key);
        exit(1);
    }

    ds4_cursor c = cursor_at(m, kv->value_pos);
    if (kv->type == GGUF_VALUE_UINT64) {
        uint64_t v = 0;
        if (!cursor_u64(&c, &v)) ds4_die(c.error);
        return v;
    }
    if (kv->type == GGUF_VALUE_UINT32) {
        uint32_t v = 0;
        if (!cursor_u32(&c, &v)) ds4_die(c.error);
        return v;
    }
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
ds4_tensor *attn_compressor_gate;
    ds4_tensor *attn_compressor_norm;
    ds4_tensor *indexer_attn_q_b;
    ds4_tensor *indexer_proj;
    ds4_tensor *indexer_compressor_ape;
    ds4_tensor *indexer_compressor_kv;
    ds4_tensor *indexer_compressor_gate;
    ds4_tensor *indexer_compressor_norm;
    ds4_tensor *hc_ffn_fn;
    ds4_tensor *hc_ffn_scale;
    ds4_tensor *hc_ffn_base;
    ds4_tensor *ffn_norm;
    ds4_tensor *ffn_gate_tid2eid;
    ds4_tensor *ffn_gate_inp;
    ds4_tensor *ffn_exp_probs_b;
    ds4_tensor *ffn_gate_exps;
    ds4_tensor *ffn_up_exps;
    ds4_tensor *ffn_down_exps;
    ds4_tensor *ffn_gate_shexp;
    ds4_tensor *ffn_up_shexp;
    ds4_tensor *ffn_down_shexp;
} ds4_layer_weights;

typedef struct {
    ds4_tensor *token_embd;
    ds4_tensor *output_hc_base;
    ds4_tensor *output_hc_fn;
    ds4_tensor *output_hc_scale;
    ds4_tensor *output_norm;
    ds4_tensor *output;
    ds4_layer_weights layer[DS4_N_LAYER];
} ds4_weights;

typedef struct {
    ds4_tensor *e_proj;
    ds4_tensor *h_proj;
    ds4_tensor *enorm;
    ds4_tensor *hnorm;
    ds4_tensor *norm;
    ds4_tensor *hc_head_base;
    ds4_tensor *hc_head_fn;
    ds4_tensor *hc_head_scale;
    ds4_layer_weights block;
} ds4_mtp_weights;

/* =========================================================================
 * Fixed Weight Binding and Model Validation.
 * =========================================================================
 *
 * The GGUF tensor directory is converted into a DS4-specific pointer table.
 * After this section, the rest of the program addresses tensors by semantic
 * fields such as layer->attn_q_a or layer->ffn_gate_exps rather than by string
 * lookup.  Shape validation is intentionally strict.
 */

static uint32_t required_u32(const ds4_model *m, const char *key) {
    uint32_t v = 0;
    if (!model_get_u32(m, key, &v)) {
        fprintf(stderr, "ds4: required metadata key is missing: %s\n", key);
        exit(1);
    }
    return v;
}

static uint64_t required_u64(const ds4_model *m, const char *key) {
    ds4_kv *kv = model_find_kv(m, key);
    if (!kv) {
        fprintf(stderr, "ds4: required metadata key is missing: %s\n", key);
        exit(1);
    }

    ds4_cursor c = cursor_at(m, kv->value_pos);
    if (kv->type == GGUF_VALUE_UINT64) {
        uint64_t v = 0;
        if (!cursor_u64(&c, &v)) ds4_die(c.error);
        return v;
    }
    if (kv->type == GGUF_VALUE_UINT32) {
        uint32_t v = 0;
        if (!cursor_u32(&c, &v)) ds4_die(c.error);
        return v;
    }
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
ds4_tensor *attn_compressor_gate;
    ds4_tensor *attn_compressor_norm;
    ds4_tensor *indexer_attn_q_b;
    ds4_tensor *indexer_proj;
    ds4_tensor *indexer_compressor_ape;
    ds4_tensor *indexer_compressor_kv;
    ds4_tensor *indexer_compressor_gate;
    ds4_tensor *indexer_compressor_norm;
    ds4_tensor *hc_ffn_fn;
    ds4_tensor *hc_ffn_scale;
    ds4_tensor *hc_ffn_base;
    ds4_tensor *ffn_norm;
    ds4_tensor *ffn_gate_tid2eid;
    ds4_tensor *ffn_gate_inp;
    ds4_tensor *ffn_exp_probs_b;
    ds4_tensor *ffn_gate_exps;
    ds4_tensor *ffn_up_exps;
    ds4_tensor *ffn_down_exps;
    ds4_tensor *ffn_gate_shexp;
    ds4_tensor *ffn_up_shexp;
    ds4_tensor *ffn_down_shexp;
} ds4_layer_weights;

typedef struct {
    ds4_tensor *token_embd;
    ds4_tensor *output_hc_base;
    ds4_tensor *output_hc_fn;
    ds4_tensor *output_hc_scale;
    ds4_tensor *output_norm;
    ds4_tensor *output;
    ds4_layer_weights layer[DS4_N_LAYER];
} ds4_weights;

typedef struct {
    ds4_tensor *e_proj;
    ds4_tensor *h_proj;
    ds4_tensor *enorm;
    ds4_tensor *hnorm;
    ds4_tensor *norm;
    ds4_tensor *hc_head_base;
    ds4_tensor *hc_head_fn;
    ds4_tensor *hc_head_scale;
    ds4_layer_weights block;
} ds4_mtp_weights;

/* =========================================================================
 * Fixed Weight Binding and Model Validation.
 * =========================================================================
 *
 * The GGUF tensor directory is converted into a DS4-specific pointer table.
 * After this section, the rest of the program addresses tensors by semantic
 * fields such as layer->attn_q_a or layer->ffn_gate_exps rather than by string
 * lookup.  Shape validation is intentionally strict.
 */

static uint32_t required_u32(const ds4_model *m, const char *key) {
    uint32_t v = 0;
    if (!model_get_u32(m, key, &v)) {
        fprintf(stderr, "ds4: required metadata key is missing: %s\n", key);
        exit(1);
    }
    return v;
}

static uint64_t required_u64(const ds4_model *m, const char *key) {
    ds4_kv *kv = model_find_kv(m, key);
    if (!kv) {
        fprintf(stderr, "ds4: required metadata key is missing: %s\n", key);
        exit(1);
    }

    ds4_cursor c = cursor_at(m, kv->value_pos);
    if (kv->type == GGUF_VALUE_UINT64) {
        uint64_t v = 0;
        if (!cursor_u64(&c, &v)) ds4_die(c.error);
        return v;
    }
    if (kv->type == GGUF_VALUE_UINT32) {
        uint32_t v = 0;
        if (!cursor_u32(&c, &v)) ds4_die(c.error);
        return v;
    }
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
ds4_tensor *attn_compressor_gate;
    ds4_tensor *attn_compressor_norm;
    ds4_tensor *indexer_attn_q_b;
    ds4_tensor *indexer_proj;
    ds4_tensor *indexer_compressor_ape;
    ds4_tensor *indexer_compressor_kv;
    ds4_tensor *indexer_compressor_gate;
    ds4_tensor *indexer_compressor_norm;
    ds4_tensor *hc_ffn_fn;
    ds4_tensor *hc_ffn_scale;
    ds4_tensor *hc_ffn_base;
    ds4_tensor *ffn_norm;
    ds4_tensor *ffn_gate_tid2eid;
    ds4_tensor *ffn_gate_inp;
    ds4_tensor *ffn_exp_probs_b;
    ds4_tensor *ffn_gate_exps;
    ds4_tensor *ffn_up_exps;
    ds4_tensor *ffn_down_exps;
    ds4_tensor *ffn_gate_shexp;
    ds4_tensor *ffn_up_shexp;
    ds4_tensor *ffn_down_shexp;
} ds4_layer_weights;

typedef struct {
    ds4_tensor *token_embd;
    ds4_tensor *output_hc_base;
    ds4_tensor *output_hc_fn;
    ds4_tensor *output_hc_scale;
    ds4_tensor *output_norm;
    ds4_tensor *output;
    ds4_layer_weights layer[DS4_N_LAYER];
} ds4_weights;

typedef struct {
    ds4_tensor *e_proj;
    ds4_tensor *h_proj;
    ds4_tensor *enorm;
    ds4_tensor *hnorm;
    ds4_tensor *norm;
    ds4_tensor *hc_head_base;
    ds4_tensor *hc_head_fn;
    ds4_tensor *hc_head_scale;
    ds4_layer_weights block;
} ds4_mtp_weights;

/* =========================================================================
 * Fixed Weight Binding and Model Validation.
 * =========================================================================
 *
 * The GGUF tensor directory is converted into a DS4-specific pointer table.
 * After this section, the rest of the program addresses tensors by semantic
 * fields such as layer->attn_q_a or layer->ffn_gate_exps rather than by string
 * lookup.  Shape validation is intentionally strict.
 */

static uint32_t required_u32(const ds4_model *m, const char *key) {
    uint32_t v = 0;
    if (!model_get_u32(m, key, &v)) {
        fprintf(stderr, "ds4: required metadata key is missing: %s\n", key);
        exit(1);
    }
    return v;
}

static uint64_t required_u64(const ds4_model *m, const char *key) {
    ds4_kv *kv = model_find_kv(m, key);
    if (!kv) {
        fprintf(stderr, "ds4: required metadata key is missing: %s\n", key);
        exit(1);
    }

    ds4_cursor c = cursor_at(m, kv->value_pos);
    if (kv->type == GGUF_VALUE_UINT64) {
        uint64_t v = 0;
        if (!cursor_u64(&c, &v)) ds4_die(c.error);
        return v;
    }
    if (kv->type == GGUF_VALUE_UINT32) {
        uint32_t v = 0;
        if (!cursor_u32(&c, &v)) ds4_die(c.error);
        return v;
    }
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
uint32_t tok = 0;
            if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            token_vec_push(&new_checkpoint, (int)tok);
        }
        if (payload_read_bytes(fp, s->logits, (uint64_t)DS4_N_VOCAB * sizeof(float),
                               &remaining, err, errlen) != 0)
        {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        uint32_t n_comp[DS4_N_LAYER];
        uint32_t n_index_comp[DS4_N_LAYER];
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            if (payload_read_u32(fp, &n_comp[il], &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (n_comp[il] > saved_comp_cap || n_comp[il] > cpu_comp_cap) {
                token_vec_free(&new_checkpoint);
                payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
                return 1;
            }
        }
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            if (payload_read_u32(fp, &n_index_comp[il], &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (n_index_comp[il] > saved_comp_cap || n_index_comp[il] > cpu_comp_cap) {
                token_vec_free(&new_checkpoint);
                payload_set_err(err, errlen, "KV checkpoint has invalid indexer row count");
                return 1;
            }
        }

        s->checkpoint_valid = false;
        s->mtp_draft_valid = false;
        session_cpu_reset_cache(s);
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            ds4_layer_cache *layer = &s->cpu_cache.layer[il];
            if (payload_read_bytes(fp,
                                   layer->raw_kv,
                                   (uint64_t)saved_raw_live * DS4_N_HEAD_DIM * sizeof(float),
                                   &remaining,
                                   err,
                                   errlen) != 0)
            {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            layer->n_raw = saved_raw_live;
            const uint32_t ratio = layer->compress_ratio;
            if (ratio == 0) continue;
            layer->n_comp = n_comp[il];
            layer->n_index_comp = n_index_comp[il];
            if (payload_read_bytes(fp,
                                   layer->attn_comp_kv,
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
uint32_t tok = 0;
            if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            token_vec_push(&new_checkpoint, (int)tok);
        }
        if (payload_read_bytes(fp, s->logits, (uint64_t)DS4_N_VOCAB * sizeof(float),
                               &remaining, err, errlen) != 0)
        {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        uint32_t n_comp[DS4_N_LAYER];
        uint32_t n_index_comp[DS4_N_LAYER];
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            if (payload_read_u32(fp, &n_comp[il], &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (n_comp[il] > saved_comp_cap || n_comp[il] > cpu_comp_cap) {
                token_vec_free(&new_checkpoint);
                payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
                return 1;
            }
        }
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            if (payload_read_u32(fp, &n_index_comp[il], &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (n_index_comp[il] > saved_comp_cap || n_index_comp[il] > cpu_comp_cap) {
                token_vec_free(&new_checkpoint);
                payload_set_err(err, errlen, "KV checkpoint has invalid indexer row count");
                return 1;
            }
        }

        s->checkpoint_valid = false;
        s->mtp_draft_valid = false;
        session_cpu_reset_cache(s);
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            ds4_layer_cache *layer = &s->cpu_cache.layer[il];
            if (payload_read_bytes(fp,
                                   layer->raw_kv,
                                   (uint64_t)saved_raw_live * DS4_N_HEAD_DIM * sizeof(float),
                                   &remaining,
                                   err,
                                   errlen) != 0)
            {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            layer->n_raw = saved_raw_live;
            const uint32_t ratio = layer->compress_ratio;
            if (ratio == 0) continue;
            layer->n_comp = n_comp[il];
            layer->n_index_comp = n_index_comp[il];
            if (payload_read_bytes(fp,
                                   layer->attn_comp_kv,
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
uint32_t tok = 0;
            if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            token_vec_push(&new_checkpoint, (int)tok);
        }
        if (payload_read_bytes(fp, s->logits, (uint64_t)DS4_N_VOCAB * sizeof(float),
                               &remaining, err, errlen) != 0)
        {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        uint32_t n_comp[DS4_N_LAYER];
        uint32_t n_index_comp[DS4_N_LAYER];
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            if (payload_read_u32(fp, &n_comp[il], &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (n_comp[il] > saved_comp_cap || n_comp[il] > cpu_comp_cap) {
                token_vec_free(&new_checkpoint);
                payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
                return 1;
            }
        }
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            if (payload_read_u32(fp, &n_index_comp[il], &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (n_index_comp[il] > saved_comp_cap || n_index_comp[il] > cpu_comp_cap) {
                token_vec_free(&new_checkpoint);
                payload_set_err(err, errlen, "KV checkpoint has invalid indexer row count");
                return 1;
            }
        }

        s->checkpoint_valid = false;
        s->mtp_draft_valid = false;
        session_cpu_reset_cache(s);
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            ds4_layer_cache *layer = &s->cpu_cache.layer[il];
            if (payload_read_bytes(fp,
                                   layer->raw_kv,
                                   (uint64_t)saved_raw_live * DS4_N_HEAD_DIM * sizeof(float),
                                   &remaining,
                                   err,
                                   errlen) != 0)
            {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            layer->n_raw = saved_raw_live;
            const uint32_t ratio = layer->compress_ratio;
            if (ratio == 0) continue;
            layer->n_comp = n_comp[il];
            layer->n_index_comp = n_index_comp[il];
            if (payload_read_bytes(fp,
                                   layer->attn_comp_kv,
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
uint32_t tok = 0;
            if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            token_vec_push(&new_checkpoint, (int)tok);
        }
        if (payload_read_bytes(fp, s->logits, (uint64_t)DS4_N_VOCAB * sizeof(float),
                               &remaining, err, errlen) != 0)
        {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        uint32_t n_comp[DS4_N_LAYER];
        uint32_t n_index_comp[DS4_N_LAYER];
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            if (payload_read_u32(fp, &n_comp[il], &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (n_comp[il] > saved_comp_cap || n_comp[il] > cpu_comp_cap) {
                token_vec_free(&new_checkpoint);
                payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
                return 1;
            }
        }
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            if (payload_read_u32(fp, &n_index_comp[il], &remaining, err, errlen) != 0) {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (n_index_comp[il] > saved_comp_cap || n_index_comp[il] > cpu_comp_cap) {
                token_vec_free(&new_checkpoint);
                payload_set_err(err, errlen, "KV checkpoint has invalid indexer row count");
                return 1;
            }
        }

        s->checkpoint_valid = false;
        s->mtp_draft_valid = false;
        session_cpu_reset_cache(s);
        for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
            ds4_layer_cache *layer = &s->cpu_cache.layer[il];
            if (payload_read_bytes(fp,
                                   layer->raw_kv,
                                   (uint64_t)saved_raw_live * DS4_N_HEAD_DIM * sizeof(float),
                                   &remaining,
                                   err,
                                   errlen) != 0)
            {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            layer->n_raw = saved_raw_live;
            const uint32_t ratio = layer->compress_ratio;
            if (ratio == 0) continue;
            layer->n_comp = n_comp[il];
            layer->n_index_comp = n_index_comp[il];
            if (payload_read_bytes(fp,
                                   layer->attn_comp_kv,
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
layer->n_comp = n_comp[il];
            layer->n_index_comp = n_index_comp[il];
            if (payload_read_bytes(fp,
                                   layer->attn_comp_kv,
                                   (uint64_t)n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                   &remaining,
                                   err,
                                   errlen) != 0 ||
                payload_read_bytes(fp, layer->attn_state_kv, layer_attn_state_bytes(ratio), &remaining, err, errlen) != 0 ||
                payload_read_bytes(fp, layer->attn_state_score, layer_attn_state_bytes(ratio), &remaining, err, errlen) != 0)
            {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (ratio == 4) {
                if (payload_read_bytes(fp,
                                       layer->index_comp_kv,
                                       (uint64_t)n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                       &remaining,
                                       err,
                                       errlen) != 0 ||
                    payload_read_bytes(fp, layer->index_state_kv, layer_index_state_bytes(ratio), &remaining, err, errlen) != 0 ||
                    payload_read_bytes(fp, layer->index_state_score, layer_index_state_bytes(ratio), &remaining, err, errlen) != 0)
                {
                    token_vec_free(&new_checkpoint);
                    return 1;
                }
            }
        }
        if (remaining != 0) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has trailing payload bytes");
            return 1;
        }
        token_vec_free(&s->checkpoint);
        s->checkpoint = new_checkpoint;
        s->checkpoint_valid = true;
        s->mtp_draft_valid = false;
        return 0;
    }
#ifdef DS4_NO_GPU
    payload_set_err(err, errlen, "graph backend support is not compiled in");
    return 1;
#else
    ds4_gpu_graph *g = &s->graph;
    const uint32_t saved_ctx = h[2];
    const uint32_t saved_prefill_cap = h[3];
    const uint32_t saved_raw_cap = h[4];
    const uint32_t saved_raw_window = h[5];
    const uint32_t saved_comp_cap = h[6];
    const uint32_t saved_tokens = h[7];
    const uint32_t saved_raw_live = h[12];
    if (saved_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
        payload_set_err(err, errlen, "KV checkpoint does not fit current context");
        return 1;
    }
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
layer->n_comp = n_comp[il];
            layer->n_index_comp = n_index_comp[il];
            if (payload_read_bytes(fp,
                                   layer->attn_comp_kv,
                                   (uint64_t)n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                   &remaining,
                                   err,
                                   errlen) != 0 ||
                payload_read_bytes(fp, layer->attn_state_kv, layer_attn_state_bytes(ratio), &remaining, err, errlen) != 0 ||
                payload_read_bytes(fp, layer->attn_state_score, layer_attn_state_bytes(ratio), &remaining, err, errlen) != 0)
            {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (ratio == 4) {
                if (payload_read_bytes(fp,
                                       layer->index_comp_kv,
                                       (uint64_t)n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                       &remaining,
                                       err,
                                       errlen) != 0 ||
                    payload_read_bytes(fp, layer->index_state_kv, layer_index_state_bytes(ratio), &remaining, err, errlen) != 0 ||
                    payload_read_bytes(fp, layer->index_state_score, layer_index_state_bytes(ratio), &remaining, err, errlen) != 0)
                {
                    token_vec_free(&new_checkpoint);
                    return 1;
                }
            }
        }
        if (remaining != 0) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has trailing payload bytes");
            return 1;
        }
        token_vec_free(&s->checkpoint);
        s->checkpoint = new_checkpoint;
        s->checkpoint_valid = true;
        s->mtp_draft_valid = false;
        return 0;
    }
#ifdef DS4_NO_GPU
    payload_set_err(err, errlen, "graph backend support is not compiled in");
    return 1;
#else
    ds4_gpu_graph *g = &s->graph;
    const uint32_t saved_ctx = h[2];
    const uint32_t saved_prefill_cap = h[3];
    const uint32_t saved_raw_cap = h[4];
    const uint32_t saved_raw_window = h[5];
    const uint32_t saved_comp_cap = h[6];
    const uint32_t saved_tokens = h[7];
    const uint32_t saved_raw_live = h[12];
    if (saved_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
        payload_set_err(err, errlen, "KV checkpoint does not fit current context");
        return 1;
    }
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
layer->n_comp = n_comp[il];
            layer->n_index_comp = n_index_comp[il];
            if (payload_read_bytes(fp,
                                   layer->attn_comp_kv,
                                   (uint64_t)n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                   &remaining,
                                   err,
                                   errlen) != 0 ||
                payload_read_bytes(fp, layer->attn_state_kv, layer_attn_state_bytes(ratio), &remaining, err, errlen) != 0 ||
                payload_read_bytes(fp, layer->attn_state_score, layer_attn_state_bytes(ratio), &remaining, err, errlen) != 0)
            {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (ratio == 4) {
                if (payload_read_bytes(fp,
                                       layer->index_comp_kv,
                                       (uint64_t)n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                       &remaining,
                                       err,
                                       errlen) != 0 ||
                    payload_read_bytes(fp, layer->index_state_kv, layer_index_state_bytes(ratio), &remaining, err, errlen) != 0 ||
                    payload_read_bytes(fp, layer->index_state_score, layer_index_state_bytes(ratio), &remaining, err, errlen) != 0)
                {
                    token_vec_free(&new_checkpoint);
                    return 1;
                }
            }
        }
        if (remaining != 0) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has trailing payload bytes");
            return 1;
        }
        token_vec_free(&s->checkpoint);
        s->checkpoint = new_checkpoint;
        s->checkpoint_valid = true;
        s->mtp_draft_valid = false;
        return 0;
    }
#ifdef DS4_NO_GPU
    payload_set_err(err, errlen, "graph backend support is not compiled in");
    return 1;
#else
    ds4_gpu_graph *g = &s->graph;
    const uint32_t saved_ctx = h[2];
    const uint32_t saved_prefill_cap = h[3];
    const uint32_t saved_raw_cap = h[4];
    const uint32_t saved_raw_window = h[5];
    const uint32_t saved_comp_cap = h[6];
    const uint32_t saved_tokens = h[7];
    const uint32_t saved_raw_live = h[12];
    if (saved_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
        payload_set_err(err, errlen, "KV checkpoint does not fit current context");
        return 1;
    }
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Suggest a minimal correctness-preserving optimization for this excerpt.

File: ds4.c

```c
layer->n_comp = n_comp[il];
            layer->n_index_comp = n_index_comp[il];
            if (payload_read_bytes(fp,
                                   layer->attn_comp_kv,
                                   (uint64_t)n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                   &remaining,
                                   err,
                                   errlen) != 0 ||
                payload_read_bytes(fp, layer->attn_state_kv, layer_attn_state_bytes(ratio), &remaining, err, errlen) != 0 ||
                payload_read_bytes(fp, layer->attn_state_score, layer_attn_state_bytes(ratio), &remaining, err, errlen) != 0)
            {
                token_vec_free(&new_checkpoint);
                return 1;
            }
            if (ratio == 4) {
                if (payload_read_bytes(fp,
                                       layer->index_comp_kv,
                                       (uint64_t)n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                       &remaining,
                                       err,
                                       errlen) != 0 ||
                    payload_read_bytes(fp, layer->index_state_kv, layer_index_state_bytes(ratio), &remaining, err, errlen) != 0 ||
                    payload_read_bytes(fp, layer->index_state_score, layer_index_state_bytes(ratio), &remaining, err, errlen) != 0)
                {
                    token_vec_free(&new_checkpoint);
                    return 1;
                }
            }
        }
        if (remaining != 0) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has trailing payload bytes");
            return 1;
        }
        token_vec_free(&s->checkpoint);
        s->checkpoint = new_checkpoint;
        s->checkpoint_valid = true;
        s->mtp_draft_valid = false;
        return 0;
    }
#ifdef DS4_NO_GPU
    payload_set_err(err, errlen, "graph backend support is not compiled in");
    return 1;
#else
    ds4_gpu_graph *g = &s->graph;
    const uint32_t saved_ctx = h[2];
    const uint32_t saved_prefill_cap = h[3];
    const uint32_t saved_raw_cap = h[4];
    const uint32_t saved_raw_window = h[5];
    const uint32_t saved_comp_cap = h[6];
    const uint32_t saved_tokens = h[7];
    const uint32_t saved_raw_live = h[12];
    if (saved_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
        payload_set_err(err, errlen, "KV checkpoint does not fit current context");
        return 1;
    }
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
        payload_set_err(err, errlen, "KV checkpoint does not fit current context");
        return 1;
    }
    if (h[8] != DS4_N_LAYER || h[9] != DS4_N_HEAD_DIM ||
        h[10] != DS4_N_INDEXER_HEAD_DIM || h[11] != DS4_N_VOCAB)
    {
        payload_set_err(err, errlen, "KV checkpoint was written for a different DS4 layout");
        return 1;
    }
    if (saved_prefill_cap != s->prefill_cap || saved_raw_window != g->raw_window) {
        payload_set_err(err, errlen, "KV checkpoint graph chunk layout does not match current runtime");
        return 1;
    }
    /* The raw rows in the file are logical rows.  We can restore them into any
     * current ring with enough capacity, but the saved live count must be exactly
     * the last window implied by the saved token count. */
    const uint32_t expected_raw_live = saved_tokens < saved_raw_window ? saved_tokens : saved_raw_window;
    if (saved_raw_cap == 0 || saved_raw_live != expected_raw_live ||
        saved_raw_live > saved_raw_cap || saved_raw_live > g->raw_cap)
    {
        payload_set_err(err, errlen, "KV checkpoint raw ring layout does not match current context");
        return 1;
    }
    if (saved_comp_cap > g->comp_cap) {
        payload_set_err(err, errlen, "KV checkpoint compressed cache is larger than current context");
        return 1;
    }

    token_vec new_checkpoint = {0};
    for (uint32_t i = 0; i < saved_tokens; i++) {
        uint32_t tok = 0;
        if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        token_vec_push(&new_checkpoint, (int)tok);
    }
    if (payload_read_bytes(fp, s->logits, (uint64_t)DS4_N_VOCAB * sizeof(float),
                           &remaining, err, errlen) != 0)
    {
        token_vec_free(&new_checkpoint);
        return 1;
    }
    uint32_t n_comp[DS4_N_LAYER];
    uint32_t n_index_comp[DS4_N_LAYER];
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        if (payload_read_u32(fp, &n_comp[il], &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        if (n_comp[il] > saved_comp_cap || n_comp[il] > g->layer_comp_cap[il]) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
            return 1;
        }
    }
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
        payload_set_err(err, errlen, "KV checkpoint does not fit current context");
        return 1;
    }
    if (h[8] != DS4_N_LAYER || h[9] != DS4_N_HEAD_DIM ||
        h[10] != DS4_N_INDEXER_HEAD_DIM || h[11] != DS4_N_VOCAB)
    {
        payload_set_err(err, errlen, "KV checkpoint was written for a different DS4 layout");
        return 1;
    }
    if (saved_prefill_cap != s->prefill_cap || saved_raw_window != g->raw_window) {
        payload_set_err(err, errlen, "KV checkpoint graph chunk layout does not match current runtime");
        return 1;
    }
    /* The raw rows in the file are logical rows.  We can restore them into any
     * current ring with enough capacity, but the saved live count must be exactly
     * the last window implied by the saved token count. */
    const uint32_t expected_raw_live = saved_tokens < saved_raw_window ? saved_tokens : saved_raw_window;
    if (saved_raw_cap == 0 || saved_raw_live != expected_raw_live ||
        saved_raw_live > saved_raw_cap || saved_raw_live > g->raw_cap)
    {
        payload_set_err(err, errlen, "KV checkpoint raw ring layout does not match current context");
        return 1;
    }
    if (saved_comp_cap > g->comp_cap) {
        payload_set_err(err, errlen, "KV checkpoint compressed cache is larger than current context");
        return 1;
    }

    token_vec new_checkpoint = {0};
    for (uint32_t i = 0; i < saved_tokens; i++) {
        uint32_t tok = 0;
        if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        token_vec_push(&new_checkpoint, (int)tok);
    }
    if (payload_read_bytes(fp, s->logits, (uint64_t)DS4_N_VOCAB * sizeof(float),
                           &remaining, err, errlen) != 0)
    {
        token_vec_free(&new_checkpoint);
        return 1;
    }
    uint32_t n_comp[DS4_N_LAYER];
    uint32_t n_index_comp[DS4_N_LAYER];
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        if (payload_read_u32(fp, &n_comp[il], &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        if (n_comp[il] > saved_comp_cap || n_comp[il] > g->layer_comp_cap[il]) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
            return 1;
        }
    }
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
        payload_set_err(err, errlen, "KV checkpoint does not fit current context");
        return 1;
    }
    if (h[8] != DS4_N_LAYER || h[9] != DS4_N_HEAD_DIM ||
        h[10] != DS4_N_INDEXER_HEAD_DIM || h[11] != DS4_N_VOCAB)
    {
        payload_set_err(err, errlen, "KV checkpoint was written for a different DS4 layout");
        return 1;
    }
    if (saved_prefill_cap != s->prefill_cap || saved_raw_window != g->raw_window) {
        payload_set_err(err, errlen, "KV checkpoint graph chunk layout does not match current runtime");
        return 1;
    }
    /* The raw rows in the file are logical rows.  We can restore them into any
     * current ring with enough capacity, but the saved live count must be exactly
     * the last window implied by the saved token count. */
    const uint32_t expected_raw_live = saved_tokens < saved_raw_window ? saved_tokens : saved_raw_window;
    if (saved_raw_cap == 0 || saved_raw_live != expected_raw_live ||
        saved_raw_live > saved_raw_cap || saved_raw_live > g->raw_cap)
    {
        payload_set_err(err, errlen, "KV checkpoint raw ring layout does not match current context");
        return 1;
    }
    if (saved_comp_cap > g->comp_cap) {
        payload_set_err(err, errlen, "KV checkpoint compressed cache is larger than current context");
        return 1;
    }

    token_vec new_checkpoint = {0};
    for (uint32_t i = 0; i < saved_tokens; i++) {
        uint32_t tok = 0;
        if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        token_vec_push(&new_checkpoint, (int)tok);
    }
    if (payload_read_bytes(fp, s->logits, (uint64_t)DS4_N_VOCAB * sizeof(float),
                           &remaining, err, errlen) != 0)
    {
        token_vec_free(&new_checkpoint);
        return 1;
    }
    uint32_t n_comp[DS4_N_LAYER];
    uint32_t n_index_comp[DS4_N_LAYER];
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        if (payload_read_u32(fp, &n_comp[il], &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        if (n_comp[il] > saved_comp_cap || n_comp[il] > g->layer_comp_cap[il]) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
            return 1;
        }
    }
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Trova bug sottili e spiega quali invarianti dell'inferenza possono rompersi.

File: ds4.c

```c
_ctx > (uint32_t)s->ctx_size || saved_tokens >= (uint32_t)s->ctx_size) {
        payload_set_err(err, errlen, "KV checkpoint does not fit current context");
        return 1;
    }
    if (h[8] != DS4_N_LAYER || h[9] != DS4_N_HEAD_DIM ||
        h[10] != DS4_N_INDEXER_HEAD_DIM || h[11] != DS4_N_VOCAB)
    {
        payload_set_err(err, errlen, "KV checkpoint was written for a different DS4 layout");
        return 1;
    }
    if (saved_prefill_cap != s->prefill_cap || saved_raw_window != g->raw_window) {
        payload_set_err(err, errlen, "KV checkpoint graph chunk layout does not match current runtime");
        return 1;
    }
    /* The raw rows in the file are logical rows.  We can restore them into any
     * current ring with enough capacity, but the saved live count must be exactly
     * the last window implied by the saved token count. */
    const uint32_t expected_raw_live = saved_tokens < saved_raw_window ? saved_tokens : saved_raw_window;
    if (saved_raw_cap == 0 || saved_raw_live != expected_raw_live ||
        saved_raw_live > saved_raw_cap || saved_raw_live > g->raw_cap)
    {
        payload_set_err(err, errlen, "KV checkpoint raw ring layout does not match current context");
        return 1;
    }
    if (saved_comp_cap > g->comp_cap) {
        payload_set_err(err, errlen, "KV checkpoint compressed cache is larger than current context");
        return 1;
    }

    token_vec new_checkpoint = {0};
    for (uint32_t i = 0; i < saved_tokens; i++) {
        uint32_t tok = 0;
        if (payload_read_u32(fp, &tok, &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        token_vec_push(&new_checkpoint, (int)tok);
    }
    if (payload_read_bytes(fp, s->logits, (uint64_t)DS4_N_VOCAB * sizeof(float),
                           &remaining, err, errlen) != 0)
    {
        token_vec_free(&new_checkpoint);
        return 1;
    }
    uint32_t n_comp[DS4_N_LAYER];
    uint32_t n_index_comp[DS4_N_LAYER];
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        if (payload_read_u32(fp, &n_comp[il], &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        if (n_comp[il] > saved_comp_cap || n_comp[il] > g->layer_comp_cap[il]) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
            return 1;
        }
    }
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
            return 1;
        }
    }
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        if (payload_read_u32(fp, &n_index_comp[il], &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        if (n_index_comp[il] > saved_comp_cap || n_index_comp[il] > g->layer_comp_cap[il]) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has invalid indexer row count");
            return 1;
        }
    }

    uint8_t *buf = xmalloc(DS4_SESSION_IO_CHUNK);
    int rc = 0;
    for (uint32_t il = 0; rc == 0 && il < DS4_N_LAYER; il++) {
        /* Rebuild the physical raw ring expected by the current graph.  This is
         * why the file stores rows in logical order instead of dumping bytes from
         * the old ring layout. */
        const uint32_t raw_first = saved_tokens - saved_raw_live;
        for (uint32_t r = 0; rc == 0 && r < saved_raw_live; r++) {
            const uint32_t pos = raw_first + r;
            const uint32_t phys = pos % g->raw_cap;
            rc = payload_read_tensor_span(fp,
                                          g->layer_raw_cache[il],
                                          (uint64_t)phys * DS4_N_HEAD_DIM * sizeof(float),
                                          (uint64_t)DS4_N_HEAD_DIM * sizeof(float),
                                          buf,
                                          DS4_SESSION_IO_CHUNK,
                                          &remaining,
                                          err,
                                          errlen);
        }
        const uint32_t ratio = ds4_layer_compress_ratio(il);
        if (rc != 0 || ratio == 0) continue;
        rc = payload_read_tensor_span(fp,
                                      g->layer_attn_comp_cache[il],
                                      0,
                                      (uint64_t)n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                      buf,
                                      DS4_SESSION_IO_CHUNK,
                                      &remaining,
                                      err,
                                      errlen);
        if (rc == 0) rc = payload_read_tensor_span(fp,
                                                   g->layer_attn_state_kv[il],
                                                   0,
                                                   layer_attn_state_bytes(ratio),
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
            return 1;
        }
    }
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        if (payload_read_u32(fp, &n_index_comp[il], &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        if (n_index_comp[il] > saved_comp_cap || n_index_comp[il] > g->layer_comp_cap[il]) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has invalid indexer row count");
            return 1;
        }
    }

    uint8_t *buf = xmalloc(DS4_SESSION_IO_CHUNK);
    int rc = 0;
    for (uint32_t il = 0; rc == 0 && il < DS4_N_LAYER; il++) {
        /* Rebuild the physical raw ring expected by the current graph.  This is
         * why the file stores rows in logical order instead of dumping bytes from
         * the old ring layout. */
        const uint32_t raw_first = saved_tokens - saved_raw_live;
        for (uint32_t r = 0; rc == 0 && r < saved_raw_live; r++) {
            const uint32_t pos = raw_first + r;
            const uint32_t phys = pos % g->raw_cap;
            rc = payload_read_tensor_span(fp,
                                          g->layer_raw_cache[il],
                                          (uint64_t)phys * DS4_N_HEAD_DIM * sizeof(float),
                                          (uint64_t)DS4_N_HEAD_DIM * sizeof(float),
                                          buf,
                                          DS4_SESSION_IO_CHUNK,
                                          &remaining,
                                          err,
                                          errlen);
        }
        const uint32_t ratio = ds4_layer_compress_ratio(il);
        if (rc != 0 || ratio == 0) continue;
        rc = payload_read_tensor_span(fp,
                                      g->layer_attn_comp_cache[il],
                                      0,
                                      (uint64_t)n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                      buf,
                                      DS4_SESSION_IO_CHUNK,
                                      &remaining,
                                      err,
                                      errlen);
        if (rc == 0) rc = payload_read_tensor_span(fp,
                                                   g->layer_attn_state_kv[il],
                                                   0,
                                                   layer_attn_state_bytes(ratio),
```<｜Assistant｜></think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
            return 1;
        }
    }
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        if (payload_read_u32(fp, &n_index_comp[il], &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        if (n_index_comp[il] > saved_comp_cap || n_index_comp[il] > g->layer_comp_cap[il]) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has invalid indexer row count");
            return 1;
        }
    }

    uint8_t *buf = xmalloc(DS4_SESSION_IO_CHUNK);
    int rc = 0;
    for (uint32_t il = 0; rc == 0 && il < DS4_N_LAYER; il++) {
        /* Rebuild the physical raw ring expected by the current graph.  This is
         * why the file stores rows in logical order instead of dumping bytes from
         * the old ring layout. */
        const uint32_t raw_first = saved_tokens - saved_raw_live;
        for (uint32_t r = 0; rc == 0 && r < saved_raw_live; r++) {
            const uint32_t pos = raw_first + r;
            const uint32_t phys = pos % g->raw_cap;
            rc = payload_read_tensor_span(fp,
                                          g->layer_raw_cache[il],
                                          (uint64_t)phys * DS4_N_HEAD_DIM * sizeof(float),
                                          (uint64_t)DS4_N_HEAD_DIM * sizeof(float),
                                          buf,
                                          DS4_SESSION_IO_CHUNK,
                                          &remaining,
                                          err,
                                          errlen);
        }
        const uint32_t ratio = ds4_layer_compress_ratio(il);
        if (rc != 0 || ratio == 0) continue;
        rc = payload_read_tensor_span(fp,
                                      g->layer_attn_comp_cache[il],
                                      0,
                                      (uint64_t)n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                      buf,
                                      DS4_SESSION_IO_CHUNK,
                                      &remaining,
                                      err,
                                      errlen);
        if (rc == 0) rc = payload_read_tensor_span(fp,
                                                   g->layer_attn_state_kv[il],
                                                   0,
                                                   layer_attn_state_bytes(ratio),
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Review this excerpt for correctness risks, memory lifetime issues, and performance bottlenecks.

File: ds4.c

```c
payload_set_err(err, errlen, "KV checkpoint has invalid compressed row count");
            return 1;
        }
    }
    for (uint32_t il = 0; il < DS4_N_LAYER; il++) {
        if (payload_read_u32(fp, &n_index_comp[il], &remaining, err, errlen) != 0) {
            token_vec_free(&new_checkpoint);
            return 1;
        }
        if (n_index_comp[il] > saved_comp_cap || n_index_comp[il] > g->layer_comp_cap[il]) {
            token_vec_free(&new_checkpoint);
            payload_set_err(err, errlen, "KV checkpoint has invalid indexer row count");
            return 1;
        }
    }

    uint8_t *buf = xmalloc(DS4_SESSION_IO_CHUNK);
    int rc = 0;
    for (uint32_t il = 0; rc == 0 && il < DS4_N_LAYER; il++) {
        /* Rebuild the physical raw ring expected by the current graph.  This is
         * why the file stores rows in logical order instead of dumping bytes from
         * the old ring layout. */
        const uint32_t raw_first = saved_tokens - saved_raw_live;
        for (uint32_t r = 0; rc == 0 && r < saved_raw_live; r++) {
            const uint32_t pos = raw_first + r;
            const uint32_t phys = pos % g->raw_cap;
            rc = payload_read_tensor_span(fp,
                                          g->layer_raw_cache[il],
                                          (uint64_t)phys * DS4_N_HEAD_DIM * sizeof(float),
                                          (uint64_t)DS4_N_HEAD_DIM * sizeof(float),
                                          buf,
                                          DS4_SESSION_IO_CHUNK,
                                          &remaining,
                                          err,
                                          errlen);
        }
        const uint32_t ratio = ds4_layer_compress_ratio(il);
        if (rc != 0 || ratio == 0) continue;
        rc = payload_read_tensor_span(fp,
                                      g->layer_attn_comp_cache[il],
                                      0,
                                      (uint64_t)n_comp[il] * DS4_N_HEAD_DIM * sizeof(float),
                                      buf,
                                      DS4_SESSION_IO_CHUNK,
                                      &remaining,
                                      err,
                                      errlen);
        if (rc == 0) rc = payload_read_tensor_span(fp,
                                                   g->layer_attn_state_kv[il],
                                                   0,
                                                   layer_attn_state_bytes(ratio),
```<｜Assistant｜><think>


[System] You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.

[User]
Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
g->layer_attn_state_kv[il],
                                                   0,
                                                   layer_attn_state_bytes(ratio),
                                                   buf,
                                                   DS4_SESSION_IO_CHUNK,
                                                   &remaining,
                                                   err,
                                                   errlen);
        if (rc == 0) rc = payload_read_tensor_span(fp,
                                                   g->layer_attn_state_score[il],
                                                   0,
                                                   layer_attn_state_bytes(ratio),
                                                   buf,
                                                   DS4_SESSION_IO_CHUNK,
                                                   &remaining,
                                                   err,
                                                   errlen);
        if (rc == 0 && ratio == 4) {
            rc = payload_read_tensor_span(fp,
                                          g->layer_index_comp_cache[il],
                                          0,
                                          (uint64_t)n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                          buf,
                                          DS4_SESSION_IO_CHUNK,
                                          &remaining,
                                          err,
                                          errlen);
            if (rc == 0) rc = payload_read_tensor_span(fp,
                                                       g->layer_index_state_kv[il],
                                                       0,
                                                       layer_index_state_bytes(ratio),
                                                       buf,
                                                       DS4_SESSION_IO_CHUNK,
                                                       &remaining,
                                                       err,
                                                       errlen);
            if (rc == 0) rc = payload_read_tensor_span(fp,
                                                       g->layer_index_state_score[il],
                                                       0,
                                                       layer_index_state_bytes(ratio),
```

<｜begin▁of▁sentence｜>You are DeepSeek V4 Flash running locally. Answer accurately, preserve technical details, and use tools only when the prompt asks for tool use.<｜User｜>Explain what this code does and identify the inference stage it belongs to.

File: ds4.c

```c
g->layer_attn_state_kv[il],
                                                   0,
                                                   layer_attn_state_bytes(ratio),
                                                   buf,
                                                   DS4_SESSION_IO_CHUNK,
                                                   &remaining,
                                                   err,
                                                   errlen);
        if (rc == 0) rc = payload_read_tensor_span(fp,
                                                   g->layer_attn_state_score[il],
                                                   0,
                                                   layer_attn_state_bytes(ratio),
                                                   buf,
                                                   DS4_SESSION_IO_CHUNK,
                                                   &remaining,
                                                   err,
                                                   errlen);
        if (rc == 0 && ratio == 4) {
            rc = payload_read_tensor_span(fp,
                                          g->layer_index_comp_cache[il],
                                          0,
                                          (uint64_t)n_index_comp[il] * DS4_N_INDEXER_HEAD_DIM * sizeof(float),
                                          buf,
                                          DS4_SESSION_IO_CHUNK,
                                          &remaining,
                                          err,
                                          errlen);
            if (rc == 0) rc = payload_read_tensor_span(fp,
                                                       g->layer_index_state_kv[il],
                                                       0,
                                                       layer_index_state_bytes(ratio),
                                                       buf,
                                                       DS4_SESSION_IO_CHUNK,
                                                       &remaining,
                                                       err,
                                                       errlen);
            if (rc == 0) rc = payload_read_tensor_span(fp,
                                                       g->layer_index_state_score[il],
                                                       0,
                                                       layer_index_state_bytes(ratio),
```<｜Assistant｜></think>