diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9cc08503..f48fee4b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,12 @@
 
 - Add a default-off, read-only Third-party notes drawer to the Memory panel that lists configured note/knowledge MCP sources such as Joplin, Obsidian, Notion, and llm-wiki when explicitly enabled with `webui_external_notes_sources` or `HERMES_WEBUI_EXTERNAL_NOTES_SOURCES=1`, while leaving automatic session recall unchanged.
 
+## [v0.51.118] — 2026-05-22 — Release CP (stage-pr2773 — 1-PR hotfix — v0.51.117 brick fix: chat input restored)
+
+### Fixed
+
+- **PR #2773** by @nesquena-hermes — fix(chat): rename `_inflightStateLimits()` in `static/ui.js` to `_getInflightStateLimits()` so it no longer collides with the `window._inflightStateLimits` config object set in `static/boot.js`. Closes #2771. The v0.51.117 in-flight-recovery quota fix (#2766) declared a top-level helper with the same name as a window-attached config object; because top-level `function foo(){…}` declarations in classic (non-module) scripts attach to `window`, boot.js's `window._inflightStateLimits = {…}` assignment overwrote the function reference before any session could send. Every new chat broke on first `send()` with `TypeError: _inflightStateLimits is not a function`, leaving v0.51.117 effectively unusable. Renamed the function only (the public-ish window key is unchanged) and updated all 4 call sites. **New regression test `tests/test_window_function_collision.py` scans every static JS file for top-level `function NAME()` declarations whose name is also the target of `window.NAME = {…}` / `= <number>`, the exact shape that broke #2715 (`_pinnedSessionsLimit` in v0.51.106) and #2771 (`_inflightStateLimits` in v0.51.117). The test fails loudly with a precise file:name diagnostic if the bug class returns. Verified end-to-end against the live browser before merge: `_getInflightStateLimits()` returns the limits object and `saveInflightState()` persists to localStorage without throwing.
+
 ## [v0.51.117] — 2026-05-22 — Release CO (stage-pr2766 — 1-PR — in-flight recovery storage quota-safe)
 
 ### Fixed
diff --git a/static/ui.js b/static/ui.js
index 8e123c3f..3737fff8 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -4081,7 +4081,7 @@ function _boundedInflightInt(value, fallback, min, max){
   if(!Number.isFinite(n)) return fallback;
   return Math.max(min, Math.min(max, n));
 }
-function _inflightStateLimits(){
+function _getInflightStateLimits(){
   const configured=(typeof window!=='undefined'&&window._inflightStateLimits&&typeof window._inflightStateLimits==='object')?window._inflightStateLimits:{};
   return {
     maxSessions:_boundedInflightInt(configured.maxSessions, INFLIGHT_STATE_DEFAULT_LIMITS.maxSessions, 1, 25),
@@ -4110,7 +4110,7 @@ function _isStorageQuotaError(err){
   );
 }
 function _truncateInflightValue(value, maxChars){
-  const limits=_inflightStateLimits();
+  const limits=_getInflightStateLimits();
   const stringLimit=_boundedInflightInt(maxChars, limits.stringChars, 1000, 500000);
   if(typeof value==='string'){
     if(value.length<=stringLimit) return value;
@@ -4125,7 +4125,7 @@ function _truncateInflightValue(value, maxChars){
   return value;
 }
 function _compactInflightState(state){
-  const limits=_inflightStateLimits();
+  const limits=_getInflightStateLimits();
   const messages=Array.isArray(state.messages)?state.messages.slice(-limits.messages):[];
   const toolCalls=Array.isArray(state.toolCalls)?state.toolCalls.slice(-limits.toolCalls):[];
   return _truncateInflightValue({
@@ -4136,7 +4136,7 @@ function _compactInflightState(state){
   }, limits.stringChars);
 }
 function _writeInflightStateMap(all){
-  const limits=_inflightStateLimits();
+  const limits=_getInflightStateLimits();
   const entries=Object.entries(all||{})
     .sort((a,b)=>Number(b[1]&&b[1].updated_at||0)-Number(a[1]&&a[1].updated_at||0))
     .slice(0,limits.maxSessions);
diff --git a/tests/test_inflight_storage_quota.py b/tests/test_inflight_storage_quota.py
index 615863c7..deba33d0 100644
--- a/tests/test_inflight_storage_quota.py
+++ b/tests/test_inflight_storage_quota.py
@@ -28,7 +28,7 @@ def test_inflight_state_is_compacted_before_localstorage_write():
     compact_body = _function_body(UI_JS, "_compactInflightState")
 
     assert "const entry={..._compactInflightState(state),updated_at:Date.now()};" in save_body
-    assert "const limits=_inflightStateLimits();" in compact_body
+    assert "const limits=_getInflightStateLimits();" in compact_body
     assert ".slice(-limits.messages)" in compact_body
     assert ".slice(-limits.toolCalls)" in compact_body
     assert "limits.jsonChars" in UI_JS
@@ -49,7 +49,16 @@ def test_inflight_state_limits_are_configurable_from_settings():
     assert "window._inflightStateLimits={" in BOOT_JS
     assert "maxSessions:parseInt(s.inflight_state_max_sessions||8,10)||8" in BOOT_JS
     assert "messages:parseInt(s.inflight_state_max_messages||24,10)||24" in BOOT_JS
-    assert "function _inflightStateLimits()" in UI_JS
+    # The reader function MUST use a different name than the window-attached
+    # config object — top-level `function foo(){}` in non-module scripts
+    # attaches to `window`, so a collision causes boot.js to overwrite the
+    # function with the config object and every later call throws
+    # `_inflightStateLimits is not a function`. See #2771.
+    assert "function _getInflightStateLimits()" in UI_JS
+    assert "function _inflightStateLimits()" not in UI_JS, (
+        "Function name must not collide with window._inflightStateLimits "
+        "config object (#2771)."
+    )
     assert "window._inflightStateLimits" in UI_JS
     assert "INFLIGHT_STATE_MAX_SESSIONS = 3" not in UI_JS
     assert "INFLIGHT_STATE_MAX_MESSAGES = 8" not in UI_JS
diff --git a/tests/test_window_function_collision.py b/tests/test_window_function_collision.py
new file mode 100644
index 00000000..4c5dfaac
--- /dev/null
+++ b/tests/test_window_function_collision.py
@@ -0,0 +1,151 @@
+"""Regression coverage for the function-name × window-attached-config collision class.
+
+This test guards against a specific failure mode that has caused two
+brick-class regressions (v0.51.106 #2715 `_pinnedSessionsLimit`, v0.51.117
+#2771 `_inflightStateLimits`):
+
+  - Some module declares `function foo(){...}` at top level. Since the
+    WebUI ships classic (non-module) scripts via `<script defer>`, top-
+    level function declarations attach to `window` as `window.foo`.
+  - Another module later does `window.foo = {...}` (or `= 8`, etc).
+  - Boot order makes the assignment win, so by the time anyone tries
+    `foo()` they're calling an Object/Number → `TypeError: foo is not a
+    function`.
+
+This is hard to spot in code review because the function and the config
+object live in different files and the name choice is locally innocuous.
+
+The test below scans static JS for any top-level `function foo()` decl
+whose name also appears as the target of `window.foo = <non-function-
+non-identifier>`. False-positive shape (which we deliberately exclude):
+re-binding a function reference onto `window` (`window.foo = foo;` or
+`window.foo = function(){...};`) — this is the normal "expose to global"
+pattern.
+"""
+import re
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+STATIC_JS = sorted(
+    p for p in (REPO_ROOT / "static").glob("*.js")
+    if not p.name.endswith(".min.js")
+)
+
+
+# Top-of-line: `function NAME(`
+TOP_LEVEL_FN_RE = re.compile(r"^function\s+([A-Za-z_\$][A-Za-z_\$0-9]*)\s*\(", re.MULTILINE)
+
+# `window.NAME = <rhs>` where rhs is the next non-space chunk.
+# We only care about the *value shape* of rhs. Lookahead must be long enough
+# to see `function(` (8 chars) even after some whitespace; we use 32 chars to
+# be safe against newlines and odd indenting.
+WINDOW_ASSIGN_RE = re.compile(
+    r"window\.([A-Za-z_\$][A-Za-z_\$0-9]*)\s*=\s*([^=].{0,32})",
+    re.DOTALL,
+)
+
+
+def _classify_rhs(rhs: str) -> str:
+    """Classify the right-hand side of `window.X = rhs`.
+
+    Returns one of:
+      - 'function'   — explicit `function(` literal (named or anonymous)
+      - 'identifier' — bare identifier (almost certainly a function reference)
+      - 'object'     — `{...}` object literal (THE BUG SHAPE — function got
+                       replaced by config object)
+      - 'number'     — numeric literal (ALSO BUG SHAPE — #2715 was this)
+      - 'arrow'      — `() =>` / `x =>` arrow function (benign re-bind)
+      - 'other'      — anything else; treat as suspicious to be safe
+    """
+    rhs = rhs.lstrip()
+    if rhs.startswith("function"):
+        return "function"
+    if rhs.startswith("{"):
+        return "object"
+    # Arrow function: `(args) =>` or `x =>`
+    if rhs.startswith("(") and "=>" in rhs:
+        return "arrow"
+    if re.match(r"[A-Za-z_\$][A-Za-z_\$0-9]*\s*=>", rhs):
+        return "arrow"
+    # Numeric literal: int or decimal
+    if re.match(r"-?\d", rhs):
+        return "number"
+    # Bare identifier reference: looks like `_foo;` or `_foo,` or `_foo ` etc.
+    # Allow ||, &&, ? chains too (e.g. `window.X = window.X || false;`).
+    if re.match(r"[A-Za-z_\$][A-Za-z_\$0-9]*[\s;,)|&?.]", rhs):
+        return "identifier"
+    return "other"
+
+
+def test_no_top_level_function_shadowed_by_window_object_assignment():
+    """Catch the v0.51.106 / v0.51.117 collision class before it ships.
+
+    See #2715 (`_pinnedSessionsLimit` function shadowed by `window._pinnedSessionsLimit = <int>`)
+    and #2771 (`_inflightStateLimits` function shadowed by
+    `window._inflightStateLimits = {...}`). Both broke entire user
+    workflows for everyone on the affected version.
+    """
+    # Collect all top-level function names across every static JS file.
+    fn_names: dict[str, list[str]] = {}
+    for js_file in STATIC_JS:
+        src = js_file.read_text(encoding="utf-8")
+        for m in TOP_LEVEL_FN_RE.finditer(src):
+            fn_names.setdefault(m.group(1), []).append(js_file.name)
+
+    # Find every window.NAME = <rhs> assignment, classify the rhs.
+    collisions: list[str] = []
+    for js_file in STATIC_JS:
+        src = js_file.read_text(encoding="utf-8")
+        for m in WINDOW_ASSIGN_RE.finditer(src):
+            name, rhs_snippet = m.group(1), m.group(2)
+            if name not in fn_names:
+                continue
+            kind = _classify_rhs(rhs_snippet)
+            if kind in {"function", "identifier", "arrow"}:
+                continue  # benign exposure of a function to global scope.
+            # 'object', 'number', and 'other' are the BUG shapes.
+            collisions.append(
+                f"In {js_file.name}: `window.{name} = ...` (rhs={kind!r}) "
+                f"shadows the top-level `function {name}()` declared in "
+                f"{', '.join(fn_names[name])}. This will cause "
+                f"`TypeError: {name} is not a function` once boot.js's "
+                f"assignment overwrites the function. See #2715, #2771."
+            )
+
+    assert not collisions, (
+        "Function-name × window-config collision detected — this is the "
+        "brick-class regression shape from #2715 and #2771:\n  - "
+        + "\n  - ".join(collisions)
+    )
+
+
+def test_inflight_state_limits_no_longer_collides_with_window_config():
+    """Issue-pinned regression for #2771 specifically.
+
+    Confirms the function rename landed and the old colliding name is gone.
+    """
+    ui_js = (REPO_ROOT / "static" / "ui.js").read_text(encoding="utf-8")
+    boot_js = (REPO_ROOT / "static" / "boot.js").read_text(encoding="utf-8")
+
+    # The window-attached config still exists (we deliberately kept this name).
+    assert "window._inflightStateLimits={" in boot_js, (
+        "boot.js should still expose the config under the documented name."
+    )
+
+    # The function must use the renamed identifier.
+    assert "function _getInflightStateLimits()" in ui_js, (
+        "ui.js should declare the limit-reader as `_getInflightStateLimits()` "
+        "to avoid the #2771 collision."
+    )
+
+    # The old colliding name must not appear as a function declaration anywhere.
+    assert "function _inflightStateLimits(" not in ui_js, (
+        "`function _inflightStateLimits()` is the colliding name from #2771 "
+        "and must not be reintroduced."
+    )
+
+    # Every call site uses the new name.
+    assert "_inflightStateLimits()" not in ui_js, (
+        "Stale call sites to the old function name `_inflightStateLimits()` "
+        "remain in ui.js (#2771). Update them to `_getInflightStateLimits()`."
+    )