diff --git a/docs/linuxcnc-porting.md b/docs/linuxcnc-porting.md
index ba5ecb1..9ba0aa1 100644
--- a/docs/linuxcnc-porting.md
+++ b/docs/linuxcnc-porting.md
@@ -215,6 +215,6 @@ This matrix tracks LinuxCNC feature coverage for the web/WASM simulator. A featu
 | Parameter expressions and operators | covered for parameter references, source-linked `mod`, `**`, logical, and relational operator precedence, plus LinuxCNC parameter-setting syntax, parameter index validation, named-parameter termination, real-number parsing, divide-by-zero, negative sqrt/power, infinity rejection, malformed `ATAN[]/[]`, unary operation syntax, `read_operation_unary()` unknown-word branches, `read_operation()` binary-operation prefix, unknown operation, and unclosed-expression error paths from `interp_read.cc`/`interp_execute.cc` | `tests/gcode/linuxcnc_parameter_expression_assignment.ngc`, `tests/gcode/linuxcnc_parameter_missing_equal_error.ngc`, `tests/gcode/linuxcnc_parameter_missing_value_error.ngc`, `tests/gcode/linuxcnc_parameter_number_out_of_range_error.ngc`, `tests/gcode/linuxcnc_parameter_reference_out_of_range_error.ngc`, `tests/gcode/linuxcnc_non_integer_parameter_index_error.ngc`, `tests/gcode/linuxcnc_named_parameter_not_terminated_error.ngc`, `tests/gcode/linuxcnc_no_real_value_error.ngc`, `tests/gcode/linuxcnc_bad_number_format_error.ngc`, `tests/gcode/linuxcnc_expression_operators.ngc`, `tests/gcode/linuxcnc_negative_sqrt_error.ngc`, `tests/gcode/linuxcnc_divide_by_zero_error.ngc`, `tests/gcode/linuxcnc_negative_power_error.ngc`, `tests/gcode/linuxcnc_infinite_expression_error.ngc`, `tests/gcode/linuxcnc_atan_missing_slash_error.ngc`, `tests/gcode/linuxcnc_atan_missing_bracket_error.ngc`, `tests/gcode/linuxcnc_unary_missing_bracket_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_word_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_c_word_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_e_word_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_f_word_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_l_word_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_r_word_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_s_word_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_t_word_error.ngc`, `tests/gcode/linuxcnc_unary_unknown_default_word_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_a_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_e_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_g_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_l_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_m_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_n_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_o_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_x_operation_error.ngc`, `tests/gcode/linuxcnc_binary_unknown_operation_error.ngc`, `tests/gcode/linuxcnc_unclosed_expression_error.ngc` |
 | Word reader validation | source-linked LinuxCNC reader errors covered for negative `F/G/H/L/M/S/T` values and repeated `A/B/C/D/E/F/H/I/J/K/L/P/Q/R/S/T/U/V/W/X/Y/Z` words from `interp_read.cc` | `tests/gcode/linuxcnc_negative_f_word_error.ngc`, `tests/gcode/linuxcnc_negative_g_code_error.ngc`, `tests/gcode/linuxcnc_negative_h_word_error.ngc`, `tests/gcode/linuxcnc_negative_l_word_error.ngc`, `tests/gcode/linuxcnc_negative_m_code_error.ngc`, `tests/gcode/linuxcnc_negative_s_word_error.ngc`, `tests/gcode/linuxcnc_negative_t_word_error.ngc`, `tests/gcode/linuxcnc_multiple_a_words_error.ngc`, `tests/gcode/linuxcnc_multiple_b_words_error.ngc`, `tests/gcode/linuxcnc_multiple_c_words_error.ngc`, `tests/gcode/linuxcnc_multiple_d_words_error.ngc`, `tests/gcode/linuxcnc_multiple_e_words_error.ngc`, `tests/gcode/linuxcnc_multiple_f_words_error.ngc`, `tests/gcode/linuxcnc_multiple_h_words_error.ngc`, `tests/gcode/linuxcnc_multiple_i_words_error.ngc`, `tests/gcode/linuxcnc_multiple_j_words_error.ngc`, `tests/gcode/linuxcnc_multiple_k_words_error.ngc`, `tests/gcode/linuxcnc_multiple_l_words_error.ngc`, `tests/gcode/linuxcnc_multiple_p_words_error.ngc`, `tests/gcode/linuxcnc_multiple_q_words_error.ngc`, `tests/gcode/linuxcnc_multiple_r_words_error.ngc`, `tests/gcode/linuxcnc_multiple_s_words_error.ngc`, `tests/gcode/linuxcnc_multiple_t_words_error.ngc`, `tests/gcode/linuxcnc_multiple_u_words_error.ngc`, `tests/gcode/linuxcnc_multiple_v_words_error.ngc`, `tests/gcode/linuxcnc_multiple_w_words_error.ngc`, `tests/gcode/linuxcnc_multiple_x_words_error.ngc`, `tests/gcode/linuxcnc_multiple_y_words_error.ngc`, `tests/gcode/linuxcnc_multiple_z_words_error.ngc` |
 | G/M reader validation | source-linked LinuxCNC `read_g()`/`read_m()` errors covered for range checks, unknown code tables, and same-modal-group conflicts from `interp_read.cc` and `interp_array.cc` | `tests/gcode/linuxcnc_g_code_out_of_range_error.ngc`, `tests/gcode/linuxcnc_unknown_g_code_error.ngc`, `tests/gcode/linuxcnc_two_g_codes_same_modal_group_error.ngc`, `tests/gcode/linuxcnc_m_code_greater_199_error.ngc`, `tests/gcode/linuxcnc_unknown_m_code_error.ngc`, `tests/gcode/linuxcnc_two_m_codes_same_modal_group_error.ngc` |
-| Block/item reader validation | source-linked LinuxCNC block reader errors covered for repeated `$`, bad item-start characters, middle-of-line `N` words, and too many M-codes from `interp_read.cc`, `interp_array.cc`, and `interp_check.cc` | `tests/gcode/linuxcnc_multiple_spindle_choice_words_error.ngc`, `tests/gcode/linuxcnc_bad_character_bang_error.ngc`, `tests/gcode/linuxcnc_bad_character_middle_n_word_error.ngc`, `tests/gcode/linuxcnc_too_many_m_codes_error.ngc` |
+| Block/item reader validation | source-linked LinuxCNC block reader errors covered for repeated `$`, bad item-start characters, middle-of-line `N` words, malformed leading `N` numbers, EOF/program-end file checks, overlong file lines, and too many M-codes from `interp_read.cc`, `interp_array.cc`, and `interp_check.cc` | `tests/gcode/linuxcnc_multiple_spindle_choice_words_error.ngc`, `tests/gcode/linuxcnc_bad_character_bang_error.ngc`, `tests/gcode/linuxcnc_bad_character_middle_n_word_error.ngc`, `tests/gcode/linuxcnc_bad_n_number_format_error.ngc`, `tests/gcode/linuxcnc_file_ended_no_program_end_error.ngc`, `tests/gcode/linuxcnc_file_ended_no_percent_error.ngc`, generated `linuxcnc_command_too_long_error.ngc`, `tests/gcode/linuxcnc_too_many_m_codes_error.ngc` |
 | Broader canned cycles `G73`, `G74`, `G82`-`G89` | partially covered: `G73`, `G74`, `G82`, `G83`, `G84`, `G85`, `G86`, `G87`, `G88`, `G89`; smoke parser maps supported cycles across `G17/G18/G19`, including LinuxCNC's special non-XY `G74/G84` tapping argument order and `G87` plane-specific `I/J/K` mapping; native/source regressions now check non-XY `G74/G84/G86/G87/G88` sequences | `tests/gcode/linuxcnc_canned_cycles_extended.ngc`, `tests/gcode/linuxcnc_canned_cycle_planes.ngc`, smoke API regression |
 | Full source-level wasm build | covered for the current wasm-safe RS274 source set, with remaining work focused on broadening browser-hostile dependency replacement and feature coverage | `./build-wasm.sh`, `test-linuxcnc-wasm-runtime-link.sh`, `test-web-wasm-node-smoke.sh`, `test-web-wasm-browser-smoke.sh` |
diff --git a/test-linuxcnc-source-link.sh b/test-linuxcnc-source-link.sh
index d07d8fe..780a110 100755
--- a/test-linuxcnc-source-link.sh
+++ b/test-linuxcnc-source-link.sh
@@ -893,6 +893,38 @@ for case in "${oword_reader_error_cases[@]}"; do
     fi
     grep -q "$expected" "$output_dir/cnc_sim_linuxcnc_source_$fixture.err"
 done
+# Source basis: LinuxCNC src/emc/rs274ngc/interp_read.cc read_text()
+# rejects EOF without the matching percent/program end and overlong file
+# lines; read_n_number() rejects malformed N-line numbers through
+# read_integer_unsigned().
+read_text_error_cases=(
+    "linuxcnc_file_ended_no_program_end_error|File ended with no percent sign"
+    "linuxcnc_file_ended_no_percent_error|File ended with no percent sign"
+    "linuxcnc_bad_n_number_format_error|Bad format unsigned integer"
+)
+for case in "${read_text_error_cases[@]}"; do
+    fixture=${case%%|*}
+    expected=${case#*|}
+    if CNC_SIM_RS274_FILE_MODE=1 CNC_SIM_RS274_VAR="$var_file" \
+        "$build_dir/linuxcnc_rs274_source_dump" "tests/gcode/$fixture.ngc" \
+        >"$output_dir/cnc_sim_linuxcnc_source_$fixture.json" 2>"$output_dir/cnc_sim_linuxcnc_source_$fixture.err"; then
+        echo "expected $fixture.ngc to fail" >&2
+        exit 1
+    fi
+    grep -q "$expected" "$output_dir/cnc_sim_linuxcnc_source_$fixture.err"
+done
+long_line_fixture="$output_dir/linuxcnc_command_too_long_error.ngc"
+printf 'G1 X' > "$long_line_fixture"
+printf '1%.0s' {1..260} >> "$long_line_fixture"
+printf '\n' >> "$long_line_fixture"
+if CNC_SIM_RS274_FILE_MODE=1 CNC_SIM_RS274_VAR="$var_file" \
+    "$build_dir/linuxcnc_rs274_source_dump" "$long_line_fixture" \
+    >"$output_dir/cnc_sim_linuxcnc_source_linuxcnc_command_too_long_error.json" 2>"$output_dir/cnc_sim_linuxcnc_source_linuxcnc_command_too_long_error.err"; then
+    echo "expected linuxcnc_command_too_long_error.ngc to fail" >&2
+    exit 1
+fi
+grep -q "Command too long" \
+    "$output_dir/cnc_sim_linuxcnc_source_linuxcnc_command_too_long_error.err"
 if CNC_SIM_RS274_FILE_MODE=1 CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_canned_cycle_reject_rotary_followup.ngc \
     >"$output_dir/cnc_sim_linuxcnc_source_canned_cycle_reject_rotary_followup.json" 2>"$output_dir/cnc_sim_linuxcnc_source_canned_cycle_reject_rotary_followup.err"; then
diff --git a/tests/gcode/linuxcnc_bad_n_number_format_error.ngc b/tests/gcode/linuxcnc_bad_n_number_format_error.ngc
new file mode 100644
index 0000000..ab68fb7
--- /dev/null
+++ b/tests/gcode/linuxcnc_bad_n_number_format_error.ngc
@@ -0,0 +1 @@
+N G1 X1 F100
diff --git a/tests/gcode/linuxcnc_file_ended_no_percent_error.ngc b/tests/gcode/linuxcnc_file_ended_no_percent_error.ngc
new file mode 100644
index 0000000..d124c0a
--- /dev/null
+++ b/tests/gcode/linuxcnc_file_ended_no_percent_error.ngc
@@ -0,0 +1,2 @@
+%
+G1 X1 F100
diff --git a/tests/gcode/linuxcnc_file_ended_no_program_end_error.ngc b/tests/gcode/linuxcnc_file_ended_no_program_end_error.ngc
new file mode 100644
index 0000000..a95b679
--- /dev/null
+++ b/tests/gcode/linuxcnc_file_ended_no_program_end_error.ngc
@@ -0,0 +1 @@
+G1 X1 F100