diff --git a/decnet/profiler/behave_shell/_features/__init__.py b/decnet/profiler/behave_shell/_features/__init__.py
index 906967d6..5ab5f170 100644
--- a/decnet/profiler/behave_shell/_features/__init__.py
+++ b/decnet/profiler/behave_shell/_features/__init__.py
@@ -14,6 +14,7 @@ from decnet.profiler.behave_shell._ctx import SessionContext
 from decnet.profiler.behave_shell._features.cognitive import (
     cognitive_load,
     command_branch_diversity,
+    error_resilience_frustration_typing,
     error_resilience_retry_tactic,
     exploration_style,
     feedback_loop_engagement,
@@ -55,4 +56,5 @@ FEATURES: tuple[FeatureFn, ...] = (
     planning_depth,
     tool_vocabulary,
     error_resilience_retry_tactic,
+    error_resilience_frustration_typing,
 )
diff --git a/decnet/profiler/behave_shell/_features/cognitive.py b/decnet/profiler/behave_shell/_features/cognitive.py
index 4264a183..8309ceef 100644
--- a/decnet/profiler/behave_shell/_features/cognitive.py
+++ b/decnet/profiler/behave_shell/_features/cognitive.py
@@ -25,6 +25,8 @@ from decnet.profiler.behave_shell._thresholds import (
     EXPLORATION_TARGETED_REP_MIN,
     FEEDBACK_CORRELATION_MIN,
     FEEDBACK_MIN_PAIRS,
+    FRUSTRATION_LOW_MAX,
+    FRUSTRATION_MODERATE_MAX,
     IKI_THINK_MAX_S,
     INTER_CMD_DELIBERATE_MAX,
     INTER_CMD_INSTANT_MAX,
@@ -186,6 +188,61 @@ def feedback_loop_engagement(ctx: SessionContext) -> Iterator[Observation]:
     )
 
 
+def error_resilience_frustration_typing(ctx: SessionContext) -> Iterator[Observation]:
+    """Emit ``cognitive.error_resilience.frustration_typing``.
+
+    Compares median within-command IAT for commands *following* an
+    errored command against the same statistic for commands following
+    a successful command. A large relative delta indicates the operator
+    typed differently after a failure — speed-up (rage / fluency) or
+    slowdown (caution); both are signs of arousal.
+
+    Skip emission when either group is empty (no errors, or every
+    command errored — no clean baseline). Sample-size honesty drops
+    confidence below the floor.
+    """
+    post_err: list[float] = []
+    post_ok: list[float] = []
+    cmds = ctx.commands
+    intra = ctx.intra_command_iats
+    if len(cmds) < 2 or len(intra) != len(cmds):
+        return
+    for i in range(1, len(cmds)):
+        cmd_iats = intra[i]
+        if not cmd_iats:
+            continue
+        m = statistics.median(cmd_iats)
+        if cmds[i - 1].errored:
+            post_err.append(m)
+        else:
+            post_ok.append(m)
+    if not post_err or not post_ok:
+        return
+    median_err = statistics.median(post_err)
+    median_ok = statistics.median(post_ok)
+    if median_ok <= 0.0:
+        return
+    delta = abs(median_err - median_ok) / median_ok
+
+    if delta < FRUSTRATION_LOW_MAX:
+        value = "low"
+    elif delta < FRUSTRATION_MODERATE_MAX:
+        value = "moderate"
+    else:
+        value = "high"
+
+    if len(post_err) < MIN_COMMANDS_FOR_FULL_CONFIDENCE:
+        confidence = 0.40
+    else:
+        confidence = 0.60
+    yield make_observation(
+        ctx,
+        primitive="cognitive.error_resilience.frustration_typing",
+        value=value,
+        confidence=confidence,
+    )
+
+
 def error_resilience_retry_tactic(ctx: SessionContext) -> Iterator[Observation]:
     """Emit ``cognitive.error_resilience.retry_tactic``.
 
diff --git a/decnet/profiler/behave_shell/_thresholds.py b/decnet/profiler/behave_shell/_thresholds.py
index 88a945e1..6249e296 100644
--- a/decnet/profiler/behave_shell/_thresholds.py
+++ b/decnet/profiler/behave_shell/_thresholds.py
@@ -155,6 +155,21 @@ PLANNING_REACTIVE_MIN: float = 0.50
 TOOL_VOCAB_NARROW_MAX: int = 3
 TOOL_VOCAB_BROAD_MIN: int = 10
 
+# ── cognitive.error_resilience.frustration_typing (Step D.6) ───────────────
+# Compare the median within-command IAT of commands *following* an
+# errored command against the same statistic for commands following a
+# successful command. The relative absolute delta:
+#
+#   delta = |median_post_error - median_post_success| / median_post_success
+#
+#   delta < FRUSTRATION_LOW_MAX        → low
+#   delta < FRUSTRATION_MODERATE_MAX   → moderate
+#   else                               → high
+#
+# v0.1; D.8 re-tunes.
+FRUSTRATION_LOW_MAX: float = 0.10
+FRUSTRATION_MODERATE_MAX: float = 0.30
+
 # ── motor.keystroke_cadence (Step B.1) ──────────────────────────────────────
 # Typing bursts split at gaps > IKI_THINK_MAX_S so think-pauses between
 # commands don't inflate the within-burst CV. Mirrors the prototype's
diff --git a/tests/profiler/behave_shell/test_cognitive_error_resilience_frustration_typing.py b/tests/profiler/behave_shell/test_cognitive_error_resilience_frustration_typing.py
new file mode 100644
index 00000000..5f98c487
--- /dev/null
+++ b/tests/profiler/behave_shell/test_cognitive_error_resilience_frustration_typing.py
@@ -0,0 +1,98 @@
+"""Step D.6: ``cognitive.error_resilience.frustration_typing``."""
+from __future__ import annotations
+
+from decnet.profiler.behave_shell import extract_session
+from decnet.profiler.behave_shell._parse import AsciinemaEvent
+
+
+PRIMITIVE = "cognitive.error_resilience.frustration_typing"
+
+
+def _of(observations: list, primitive: str):
+    obs = [o for o in observations if o.primitive == primitive]
+    assert len(obs) == 1, f"expected exactly one {primitive}, got {len(obs)}"
+    return obs[0]
+
+
+def _typed(text: str, t0: float, dt: float) -> list[AsciinemaEvent]:
+    return [(t0 + i * dt, "i", c) for i, c in enumerate(text)]
+
+
+def _build(blocks: list[tuple[str, bool, float]]) -> list[AsciinemaEvent]:
+    """Synthesise a session.
+
+    ``blocks`` is a list of (token, errored, dt) tuples. Each command
+    gets its own time slot 2s apart; ``dt`` is the within-command IAT.
+    """
+    events: list[AsciinemaEvent] = []
+    for i, (tok, errored, dt) in enumerate(blocks):
+        t0 = i * 2.0
+        events.extend(_typed(f"{tok}\r", t0=t0, dt=dt))
+        if errored:
+            cmd_end = t0 + len(tok) * dt
+            events.append((cmd_end + 0.10, "o", f"bash: {tok}: command not found\n"))
+        else:
+            cmd_end = t0 + len(tok) * dt
+            events.append((cmd_end + 0.10, "o", "ok\n"))
+    return events
+
+
+def test_no_errors_no_emission() -> None:
+    out = list(extract_session(_build([("ls", False, 0.05)] * 5), sid="ft-clean"))
+    assert [o for o in out if o.primitive == PRIMITIVE] == []
+
+
+def test_no_baseline_no_emission() -> None:
+    """Every command errored — no clean baseline → skip emission."""
+    out = list(extract_session(_build([("foo", True, 0.05)] * 5), sid="ft-allerr"))
+    assert [o for o in out if o.primitive == PRIMITIVE] == []
+
+
+def test_matching_speeds_emit_low() -> None:
+    """Same dt for post-error and post-success commands → delta ≈ 0 → low."""
+    blocks = [
+        ("ok", False, 0.05),
+        ("ok", False, 0.05),
+        ("foo", True, 0.05),
+        ("ok", False, 0.05),  # post-err: dt=0.05
+        ("ok", False, 0.05),  # post-ok:  dt=0.05
+        ("foo", True, 0.05),
+        ("ok", False, 0.05),  # post-err: dt=0.05
+        ("ok", False, 0.05),
+    ]
+    out = list(extract_session(_build(blocks), sid="ft-low"))
+    obs = _of(out, PRIMITIVE)
+    assert obs.value == "low"
+
+
+def test_huge_speed_change_emits_high() -> None:
+    """Post-error commands typed 4x slower than post-success → delta=3 → high."""
+    blocks = [
+        ("ok", False, 0.05),
+        ("ok", False, 0.05),  # post-ok: dt=0.05
+        ("foo", True, 0.05),
+        ("ok", False, 0.20),  # post-err: dt=0.20 (4x slower)
+        ("ok", False, 0.05),  # post-ok: dt=0.05
+        ("foo", True, 0.05),
+        ("ok", False, 0.20),
+        ("ok", False, 0.05),
+    ]
+    out = list(extract_session(_build(blocks), sid="ft-high"))
+    obs = _of(out, PRIMITIVE)
+    assert obs.value == "high"
+
+
+def test_low_post_error_count_reduces_confidence() -> None:
+    short = [
+        ("ok", False, 0.05),
+        ("foo", True, 0.05),
+        ("ok", False, 0.05),
+        ("ok", False, 0.05),
+    ]
+    full_blocks = [("ok", False, 0.05)]
+    for _ in range(6):
+        full_blocks.append(("foo", True, 0.05))
+        full_blocks.append(("ok", False, 0.05))
+    s = _of(list(extract_session(_build(short), sid="ft-short")), PRIMITIVE)
+    f = _of(list(extract_session(_build(full_blocks), sid="ft-full")), PRIMITIVE)
+    assert s.confidence < f.confidence