fix(oauth): keep the ChatGPT chain alive when the client echoes tool defaults

.claude/docs/oauth-continuation.md

@@ -552,11 +552,51 @@ transport-failure replay, although an OAuth 401 refresh can still start a new au
 **This policy can recover only while no model output has been exposed downstream**; replay after
 partial output could duplicate content or tool calls.
 
+### Schema defaults are filler on both sides
+
+When a tool call goes through Claude Code's permission path, the echoed call comes back with its zod
+defaults filled in: an `Edit` the model emitted without `replace_all` returns as `replace_all: false`.
+The head snapshot holds the model's raw arguments, so the strict-prefix comparison failed on every
+such call and re-sent the whole conversation (measured 2026-09-11 on one Luna session: 2 of 14 turns,
+~88k tokens each; 77.8% → 92.1% cached input with the fix).
+
+This is not a version change. `replace_all` carries the same `.default(false)` in 2.1.267 as in
+2.1.268, and captured echoes from both binaries agree: under `--dangerously-skip-permissions` the
+property is never filled, while `acceptEdits` and `--allowedTools` fill it in both versions. What
+fills it is `checkPermissions` writing `updatedInput` back to the transcript, so the trigger is the
+permission path, not a release.
+
+`toolSchemaDefaults(payload)` derives `{tool → {property → canonical default}}` from ONE request's
+`tools` array — namespaced tool groups included — and `normalizeToolCallJson` drops, from BOTH sides,
+any `arguments` property whose value equals its declared default. Compare-only: the outgoing payload
+is untouched. A value that differs from the default (`replace_all: true`) and a property with no
+declared default still diverge, as before.
+
+The map is per-request and pure, for the same reason `headRequiredToolProps` snapshots `required`
+from the head's own turn. A process-global map keyed only by tool name is last-writer-wins across
+every client, partition and session one `clodex server` handles. Independently, a request in the same
+partition can carry a different tool list — for example, a main-agent auxiliary request or a
+mid-session tool-list change — and populate a head memo under a map the next request no longer uses.
+An in-process subagent has its own partition because `responsesWebSocketPartitionKey` includes
+`x-claude-code-agent-id`, so it never scans its parent's heads. Without keyed invalidation,
+under-stripping costs a chain that should have continued and over-stripping can continue changed
+history. The two prefix memos and the in-flight `canonicalInput` memo are therefore keyed on a
+fingerprint of the defaults map they were built under and recomputed when it changes. While a
+request's tool defaults are unchanged, the fingerprint is stable and the memos still do their job;
+when the tool list changes, keyed invalidation recomputes them.
+
+Trade-off: a request whose `tools` omit a tool that appears in its own history gets no stripping for
+that tool, which is the pre-fix behaviour. Subagent histories never contain the parent's calls, so
+the residual is narrow.
+
 ### Mismatch diagnostics
 
 On a history mismatch the head-decision log includes `expected_hash`/`actual_hash` (SHA-256 of each
 side's canonical item bytes) whenever at least one side has an item at the divergent index, so
 same-kind mismatches are diagnosable without exposing content; `none` marks an unavailable side.
+The mismatch index, hashes, tool-argument gap check, and opt-in dump all use the same per-request
+tool-defaults map as head matching, so a default-stripped continuation records the full matched
+prefix instead of a misleading normalization gap.
 
 `CLODEX_MISMATCH_DUMP=1` additionally writes both divergent items' canonical bytes (capped per line,
 `(absent)` past a history's end) into the adapter debug log. **Privacy tradeoff:** the dump contains
@@ -574,9 +614,9 @@ genuine rewind or branch regenerates the call under a new one. These record
 `toolArgumentNormalizationGap` (`tool`, `equalAfterStrip`) on the head-decision diagnostic.
 
 - **Only `equalAfterStrip: true` warns on stderr**, deduplicated by tool and hard-capped (the
-  terminal is shared with Claude Code's UI). It means the two items are identical once the shared
-  filler-strip rule is applied to `arguments` — nothing but filler stood between the head and its
-  own echo.
+  terminal is shared with Claude Code's UI). It means the two items are identical once head
+  matching's schema-default normalization and the shared filler-strip rule are both applied to
+  `arguments` — nothing but filler stood between the head and its own echo.
 - **Coverage is narrower than it looks, in two directions.** It fires only when the divergent
   `function_call` is the *first* divergent item, with one alignment: a stored reasoning item Claude
   legitimately omitted (`continuationMatch`'s omitted-reasoning mode) shifts divergence onto a