Root cause: two independent bugs in convert_messages_to_anthropic()
(agent/anthropic_adapter.py), the final conversion step before every
Anthropic messages.create() call, both producing HTTP 400 "text content
blocks must contain non-whitespace text":
1. _ensure_leading_user_turn() synthesized a filler user turn with
content [{"type": "text", "text": " "}] (a single space) whenever the
built payload didn't start with role=user (e.g. after context
compaction leaves a leading assistant summary). The space is itself
whitespace-only, so the guard traded a "leading assistant turn" 400
for the "text content blocks" 400 it now hits. Fixed to reuse the
existing non-blank _EMPTY_TEXT_PLACEHOLDER ("(empty)").
2. _convert_user_message() filtered blank text blocks from list-type
user content with an all-or-nothing check:
all(blank for b in blocks if b.type == "text"). This is vacuously
true when a message has zero text-type blocks (silently destroying
valid non-text blocks like images/documents it never inspected), and
false as soon as any single text block is non-blank — which let a
*sibling* blank text block sit untouched next to valid content and
reach Anthropic as-is. Replaced with per-block filtering (mirroring
the assistant-side logic already in _convert_assistant_message),
preserving all non-blank/non-text blocks and relocating any
cache_control marker carried by a dropped block.
Also added _scrub_blank_text_blocks(), a final defense-in-depth pass run
as the last step of convert_messages_to_anthropic() (after every other
transform, including nested tool_result content lists) so a blank text
block from any current or future producer never reaches the wire. It
logs only structural metadata (message index, role, content location,
block index/type) — never message text, tool arguments, tokens, or
credentials.
An earlier local patch to sanitize_api_messages() (agent_runtime_
helpers.py) attempted to fix this by rewriting blank assistant content
before the OpenAI->Anthropic conversion step, but the real leaks were
introduced downstream of that sanitizer, inside the Anthropic-specific
converter itself — the patch never touched the actual defect and has
been fully reverted (agent_runtime_helpers.py is back to its committed
state; verified via `git diff` showing no changes).
Verified against a real Telegram message end-to-end: the gateway no
longer produces the "text content blocks must contain non-whitespace
text" error on a fresh conversation turn.
Testing:
- 9 new end-to-end regression tests in test_anthropic_adapter.py
(TestFinalPayloadHasNoBlankTextBlocks) covering content="",
content=" ", content=[{"type":"text","text":""}], mixed blank+valid
text, blank text next to a valid tool block, an assistant tool-call
message with blank content, the leading-synthesized-user-turn case,
and a blank text block nested inside a tool_result's own content list.
- Fixed one pre-existing test that had asserted the broken " " filler
behavior as correct.
- Full tests/agent/ + tests/run_agent/ suite (4671 tests) run against
both the patched tree and a stashed pre-fix baseline: identical 148
pre-existing failures in both runs (unrelated subsystems — codex
app-server integration, credential-pool interrupt handling, OpenAI
client lifecycle), zero failures unique to either side.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
