fix(bedrock): use non-whitespace placeholder for empty Converse content blocks

[taoxee]

Problem

Bedrock's Converse/ConverseStream API rejects text content blocks whose text is empty or whitespace-only:

ValidationException: ... The model returned the following errors:
messages: text content blocks must contain non-whitespace text

convert_messages_to_converse() (agent/bedrock_adapter.py) used a single space {"text": " "} as its placeholder for otherwise-empty content in six places, and appended empty/whitespace text blocks for system messages, list string parts, and tool results. A single space is whitespace-only, so it trips the exact error above.

The AnthropicBedrock SDK path tolerated these blocks, which is why this only surfaces on the Converse path — e.g. once bearer-token users route Claude through Converse (see #64857).

Fix

• Introduce a non-whitespace _EMPTY_TEXT_PLACEHOLDER = "(empty)" and use it for all empty-content fallbacks (replacing the six {"text": " "} spots).
• .strip()-guard every text-block append (list string parts, type:text parts, system-message list branch, tool-result content) so empty/whitespace blocks are dropped or replaced — never emitted.

Testing

• Unit: convert_messages_to_converse() on messages containing empty strings, whitespace-only strings, empty assistant content, and empty tool results produces zero whitespace-only text blocks.
• Integration: a real Converse call built from such messages returns content instead of raising ValidationException.

Note

Surfaces most directly on top of #64857 (which routes Claude through the Converse path for bearer-token auth). This fix is independent and correct on its own, but the two are best reviewed together; suggest merging #64857 first.

[teknium1]

Thanks for tracing the Converse-only validation path. The whitespace-content premise is present on current main: agent/bedrock_adapter.py:504-550, 586-600, and 637-668 can emit whitespace-only text blocks.

Problems

• No regression tests are included. Current tests/agent/test_bedrock_adapter.py:325-330 explicitly permits the single-space placeholder, despite the PR body claiming unit and integration coverage.
• The added text.strip() at the changed text-part path assumes part["text"] is a string. A None or other non-string value raises instead of being filtered; apply the same type guard in the new system-list branch.
• The bundled runtime-provider hunk is stale: current main already has bearer-token routing in hermes_cli/runtime_provider.py:1979-2008 from 5e6a0d9ee, covered by tests/agent/test_bedrock_adapter.py:1756-1796. Preserve that behavior when salvaging the whitespace fix.

Suggested changes

• Add recursive assertions that all emitted Converse text blocks, including nested tool results, are non-whitespace strings.
• Use isinstance(value, str) and value.strip() for text-part and system-part filtering.

Automated hermes-sweeper review.

[teknium1]

part.get("text", "") is not guaranteed to return a string; for example, a text part with "text": null reaches this line and raises AttributeError. Please use an isinstance(text, str) and text.strip() guard here and in the analogous system-message branch.

[taoxee]

Rebased onto current main and addressed the review:

• Dropped the stale runtime-provider hunk — this branch is now purely the whitespace-content fix (that routing change lives in fix(bedrock): honor api_mode=bedrock_converse so bearer-token auth works for Claude #64857).
• Type-guard bug fixed: added _nonblank_text(value) = isinstance(value, str) and value.strip(), and gate every text-block emit through it — the list type:text path, the system-message list branch, and the tool-result path. A None / non-string text is now filtered instead of raising on .strip().
• Regression tests added: updated the pre-existing TestEmptyTextBlockFix (and test_empty_content_gets_placeholder) that asserted the single-space placeholder to assert the non-whitespace invariant instead; added TestConverseNoWhitespaceOnlyTextBlocks with a recursive walk (_iter_converse_text_blocks) asserting no emitted text block — including nested toolResult content — is blank, plus a non-string text case that must be filtered rather than crash.

tests/agent/test_bedrock_adapter.py passes (143 tests).

[GottZ]

This was generated by AI during triage.

Summary

Fourteen PRs address or reference this three-issue complex. #9491 targets the Anthropic assistant-list cause of #9486; the Bedrock Converse variants replace invalid blank placeholders or sanitize additional system/list/tool-result paths for #39829 and #55092, with merged #67978 providing the recorded best fix for the latter two issues; #20366/#21202 instead concern response reasoning normalization.

Related pull requests

• fix(anthropic): filter empty text blocks from assistant messages #9491 [closed] best fix — (+11/-1) — n/a: Filters empty and whitespace-only assistant list-content blocks in the Anthropic adapter, directly matching the contributor-confirmed cause of [Bug]: Bedrock API 400 Error: "text content blocks must be non-empty" when using custom provider #9486 and the recorded best-fix verdict; although closed, it remains the reference fix, and its later keep_open review identifies current-code replay and regression-test salvage work rather than grounds to reopen this stale diff.
• fix(bedrock): preserve reasoningContent in normalized responses #20366 [closed] related — (+33/-2) — n/a: Preserves Bedrock reasoningContent in raw and streaming response normalization rather than changing outbound text blocks; although closed, it remains relevant as the source superseded by merged fix(bedrock): preserve reasoningContent in normalized responses #21202.
• fix(bedrock): preserve reasoningContent in normalized responses #21202 [merged] related — (+33/-2) — n/a: Merged reference implementation salvaged from fix(bedrock): preserve reasoningContent in normalized responses #20366, persisting reasoningContent through response normalization with tests; it is relevant for deduplicating fix(bedrock): preserve reasoningContent in normalized responses #20366 but addresses a different cause from the empty-text failures.
• fix(bedrock): sanitize empty text blocks for custom providers and dir… #24743 partial — (+60/-13) — n/a: Guards native tool results and attempts universal custom-proxy sanitization, but its single-space fallback remains invalid for [Bug]: Bedrock Converse rejects whitespace-only placeholder ('text content blocks must contain non-whitespace text'); breaks resuming assistant-first history #39829, while the keep_open maintainer-bot review documents nested-history mutation, valid-text stripping, and missing tests; only a copied outbound-only proxy sanitizer remains salvageable after fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978.
• fix(bedrock): replace whitespace-only ' ' placeholder with '(empty message)' in Converse adapter #39850 fixes — (+10/-9) — n/a: Replaces direct content and padding spaces with non-whitespace placeholders for [Bug]: Bedrock Converse rejects whitespace-only placeholder ('text content blocks must contain non-whitespace text'); breaks resuming assistant-first history #39829, but leaves list-string, system, and nested tool-result paths outside the diff and adds no tests; despite its keep_open contributor review, merged fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978 covers those cited omissions and supersedes it.
• fix(bedrock): replace whitespace-only placeholder text (#39829) #39871 fixes — (+104/-20) — n/a: Fixes principal placeholder, list-content, assistant-empty, and padding paths with regression tests, while its diff omits blank system and nested tool-result content; despite the keep_open maintainer-bot verdict, merged fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978 implements both missing paths and broader invariant tests.
• fix(bedrock): avoid whitespace-only converse placeholders #40075 [closed] fixes — (+65/-11) — n/a: Routes direct content and boundary placeholders through a nonblank helper with focused tests but does not sanitize system or tool-result text; although closed, it remains relevant as an earlier duplicate of fix(bedrock): replace whitespace-only placeholder text (#39829) #39871/fix(bedrock): replace whitespace-only ' ' placeholder with '(empty message)' in Converse adapter #39850 superseded by fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978.
• fix(bedrock): use non-whitespace placeholder for empty content blocks #41985 fixes — (+50/-17) — n/a: Replaces six whitespace placeholders and guards dictionary text parts, but raw string list items and nested tool results remain blank-capable; despite its keep_open contributor review and assistant-first E2E evidence, merged fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978 covers both the demonstrated trigger and those omissions.
• Guard empty Bedrock Converse tool results against empty text blocks #55093 partial — (+28/-0) — n/a: Narrowly guards empty or whitespace-only tool-result text and adds a targeted regression for Bedrock Converse: empty tool result produces an empty text block and 400s the request #55092, but substitutes another whitespace-only space; despite the high-salvageability keep_open maintainer-bot verdict, merged fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978 applies the same guard with a valid non-whitespace placeholder and dedicated nested-tool-result coverage.
• fix: strip empty text blocks from assistant content before Bedrock/Anthropic send #57985 partial — (+15/-1) — n/a: Filters blank assistant blocks in the normal Anthropic conversion tail, an adjacent [Bug]: Bedrock API 400 Error: "text content blocks must be non-empty" when using custom provider #9486 path rather than Bedrock Converse; consistent with its keep_open maintainer-bot verdict, salvage requires ordered-replay sanitization, cache-control-safe ordering, and regressions for both paths.
• fix(bedrock): reject whitespace-only text blocks in Converse conversion (fixes fallback-chain-killing ValidationException) #60628 duplicate — (+219/-18) — n/a: Enforces the Converse-wide non-whitespace invariant through direct guards and a recursive sweep covering system, message, padding, malformed-list, and nested tool-result content, with tests and the reviewed non-string regression fixed; despite its keep_open contributor review, merged fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978 now supplies the same root-cause coverage with a smaller shared helper.
• fix(bedrock): use non-whitespace placeholder for blank text blocks #63983 duplicate — (+164/-8) — n/a: Centralizes nonblank handling for message, list, system, padding, and tool-result paths with broad invariant tests, and the discussion records follow-up commit 01f07106a2 addressing the keep_open maintainer-bot review gaps; merged fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978 nevertheless already carries the overlapping fix.
• fix(bedrock): use non-whitespace placeholder for empty Converse content blocks #64858 fixes — (+190/-22) — n/a: Gates ordinary, system, padding, assistant, and tool-result text through type-safe nonblank checks and adds recursive payload tests; despite its keep_open contributor review, the shown rebase removes the stale runtime hunk and addresses the cited test and type-guard concerns, while merged fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978 already implements the same cause-level fix.
• fix(bedrock): non-whitespace placeholder for empty Converse text blocks (salvage #66167) #67978 [merged] best fix — (+185/-26) — n/a: Recorded best fix for [Bug]: Bedrock Converse rejects whitespace-only placeholder ('text content blocks must contain non-whitespace text'); breaks resuming assistant-first history #39829 and Bedrock Converse: empty tool result produces an empty text block and 400s the request #55092 and merged reference implementation: _safe_text() covers scalar/list/non-string content and nested tool results, blank system blocks are dropped, and assistant/padding fallbacks use a non-whitespace placeholder with dedicated regressions.

Duplicates

#39850, #39871, #40075, and #41985 are direct placeholder/padding variants; #60628, #63983, and #64858 are broader competing implementations superseded by merged #67978. #55093 and the native Bedrock portion of #24743 overlap subsets of #67978; #20366 is superseded by #21202, while #9491 and #57985 remain a separate Anthropic-path cluster.

Suggested consolidation

Close #39850, #39871, #41985, #55093, #60628, #63983, and #64858 as duplicates of merged #67978; #40075 is already closed in that chain. This departs from their visible keep_open reviews because #67978's merged diff covers the cited list-string, system, padding, non-string, and nested toolResult gaps with regression tests; for #24743, author action: rebase onto main and split out only the copied outbound-only custom-proxy sanitizer, while #57985 should keep open with a salvage path for ordered replay and cache-control-safe normalization.

Complex graph

flowchart LR
    classDef open fill:#dbeafe,stroke:#1d4ed8,color:#1e3a8a
    classDef merged fill:#dcfce7,stroke:#15803d,color:#14532d
    classDef closed fill:#e5e7eb,stroke:#6b7280,color:#1f2937
    classDef unverified fill:#f3f4f6,stroke:#9ca3af,color:#374151
    classDef best stroke-width:3px,stroke:#b45309
    classDef target stroke-width:3px,stroke:#4338ca
    I39829(["issue #39829 (open)"])
    I55092(["issue #55092 (open)"])
    subgraph Dup60628 ["PRs duplicating each other"]
        P60628["PR #60628 (open)"]
        P63983["PR #63983 (open)"]
        P64858["PR #64858 (open)"]
    end
    P64858 -->|fixes| I39829
    P64858 -->|fixes| I55092
    class I39829 open
    class I55092 open
    class P60628 open
    class P63983 open
    class P64858 open
    class P64858 target
    click I39829 "https://github.com/NousResearch/hermes-agent/issues/39829"
    click I55092 "https://github.com/NousResearch/hermes-agent/issues/55092"
    click P60628 "https://github.com/NousResearch/hermes-agent/pull/60628"
    click P63983 "https://github.com/NousResearch/hermes-agent/pull/63983"
    click P64858 "https://github.com/NousResearch/hermes-agent/pull/64858"

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Graph: solid arrow = fixes / best fix, dashed arrow = partial or unverified (see edge label); boxed group = PRs duplicating each other; amber border = best fix; indigo border = target; gray node = closed (state tag in the node label).

Cross-PR triage: Reviewed 14 pull requests and 3 issues in this complex. Each diff was read against this issue; Assessment working set: 103 kB of PR diffs, 35 kB of issue/PR text, 13 kB of discussion (19 comments), 26 verify verdicts. verdicts reflect diff content, not PR titles. Part of an automated triage batch.