diff --git a/src/tests/AGENTS.md b/src/tests/AGENTS.md
index c0a91123..5488f62b 100644
--- a/src/tests/AGENTS.md
+++ b/src/tests/AGENTS.md
@@ -22,6 +22,8 @@ Top-level test harness and source-tree tests for ShellSpy/Punk. Tests here exerc
 - Tcltest files must finish with `tcltest::cleanupTests`; missing cleanup produces a `missing-cleanupTests` runner warning and only untrusted observed testcase events.
 - Agent-oriented runner output should use `-report compact -show-passes 0` for focused checks unless detailed Markdown pass lists are needed.
 - `-report json` emits a machine-readable final summary, but package-load warnings may still precede it on stdout/stderr.
+- ERROR-status failures now surface `errorInfo` (full Tcl error message/stack trace) in markdown, compact, and json reports. Compact mode truncates to a single line.
+- FAILED-status failures (result mismatch, not error) now surface `result_was` (actual) and `result_expected` (expected) in markdown, compact, and json reports. Compact mode truncates each to a single line.
 
 ## Work Guidance
 
@@ -34,6 +36,8 @@ Top-level test harness and source-tree tests for ShellSpy/Punk. Tests here exerc
 - Add `-slowest <n>` when timing outliers are relevant.
 - Add `-strict-exit 1` when a nonzero shell exit code is needed for failures or parser warnings.
 - Capture enough stderr or failure context to identify the failing command or assertion.
+- For ERROR-status failures, the markdown report's `errorInfo` block and compact `message=` field carry the full Tcl error message; use `-report markdown` for untruncated context.
+- For FAILED-status failures (result mismatch), the markdown report's `result_was`/`result_expected` blocks and compact `actual=`/`expected=` fields show the actual-vs-expected comparison; use `-report markdown` for full multi-line values.
 
 ## Verification
 
diff --git a/src/tests/runtests.tcl b/src/tests/runtests.tcl
index f8b56984..e77b9b57 100644
--- a/src/tests/runtests.tcl
+++ b/src/tests/runtests.tcl
@@ -155,6 +155,15 @@ proc runtests_failure_summaries {resultdict} {
         if {[dict exists $testdict errorcode]} {
             dict set failure errorcode [dict get $testdict errorcode]
         }
+        if {[dict exists $testdict errorinfo] && [dict get $testdict errorinfo] ne ""} {
+            dict set failure errorinfo [dict get $testdict errorinfo]
+        }
+        if {[dict exists $testdict result_was] && [dict get $testdict result_was] ne ""} {
+            dict set failure result_was [dict get $testdict result_was]
+        }
+        if {[dict exists $testdict result_expected] && [dict get $testdict result_expected] ne ""} {
+            dict set failure result_expected [dict get $testdict result_expected]
+        }
         lappend failures $failure
     }
     return $failures
@@ -193,6 +202,25 @@ proc runtests_print_failure_details {testfile_relative resultdict} {
         if {[dict get $testdict test_status] eq "ERROR"} {
             puts stdout "    returncode      : [dict get $testdict returncode]  "
             puts stdout "    errorcode       : [dict get $testdict errorcode]  "
+            if {[dict exists $testdict errorinfo] && [dict get $testdict errorinfo] ne ""} {
+                puts stdout "    errorInfo       :  "
+                puts stdout "    ```"
+                puts stdout "    [string trimright [dict get $testdict errorinfo]]"
+                puts stdout "    ```"
+            }
+        } elseif {[dict get $testdict test_status] eq "FAILED"} {
+            if {[dict exists $testdict result_was] && [dict get $testdict result_was] ne ""} {
+                puts stdout "    result_was      :  "
+                puts stdout "    ```"
+                puts stdout "    [string trimright [dict get $testdict result_was]]"
+                puts stdout "    ```"
+            }
+            if {[dict exists $testdict result_expected] && [dict get $testdict result_expected] ne ""} {
+                puts stdout "    result_expected :  "
+                puts stdout "    ```"
+                puts stdout "    [string trimright [dict get $testdict result_expected]]"
+                puts stdout "    ```"
+            }
         }
     }
 }
@@ -660,6 +688,30 @@ if {$report_compact} {
             if {[dict exists $failure errorcode] && [dict get $failure errorcode] ne ""} {
                 append line " errorcode=[dict get $failure errorcode]"
             }
+            if {[dict exists $failure errorinfo] && [dict get $failure errorinfo] ne ""} {
+                set msg [string trim [dict get $failure errorinfo]]
+                set first_line [lindex [split $msg \n] 0]
+                if {[string length $first_line] > 120} {
+                    set first_line "[string range $first_line 0 119]..."
+                }
+                append line " message=$first_line"
+            }
+            if {[dict exists $failure result_was] && [dict get $failure result_was] ne ""} {
+                set actual [string trim [dict get $failure result_was]]
+                set first_line [lindex [split $actual \n] 0]
+                if {[string length $first_line] > 80} {
+                    set first_line "[string range $first_line 0 79]..."
+                }
+                append line " actual=$first_line"
+            }
+            if {[dict exists $failure result_expected] && [dict get $failure result_expected] ne ""} {
+                set expected [string trim [dict get $failure result_expected]]
+                set first_line [lindex [split $expected \n] 0]
+                if {[string length $first_line] > 80} {
+                    set first_line "[string range $first_line 0 79]..."
+                }
+                append line " expected=$first_line"
+            }
             puts stdout $line
         }
     }